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medical history comprises hpi and pmh. medications ( rx ) : what drugs the patient takes including prescribed, over - the - counter, and home remedies, as well as alternative and herbal medicines or remedies. allergies are also recorded. past medical history ( pmh / pmhx ) : concurrent medical problems, past hospitalizations and operations, injuries, past infectious diseases or vaccinations, history of known allergies. review of systems ( ros ) or systems inquiry : a set of additional questions to ask, which may be missed on hpi : a general enquiry ( have you noticed any weight loss, change in sleep quality, fevers, lumps and bumps? etc. ), followed by questions on the body ' s main organ systems ( heart, lungs, digestive tract, urinary tract, etc. ). social history ( sh ) : birthplace, residences, marital history, social and economic status, habits ( including diet, medications, tobacco, alcohol ). the physical examination is the examination of the patient for medical signs of disease that are objective and observable, in contrast to symptoms that are volunteered by the patient and are not necessarily objectively observable. the healthcare provider uses sight, hearing, touch, and sometimes smell ( e. g., in infection, uremia, diabetic ketoacidosis ). four actions are the basis of physical examination : inspection, palpation ( feel ), percussion ( tap to determine resonance characteristics ), and auscultation ( listen ), generally in that order, although auscultation occurs prior to percussion and palpation for abdominal assessments. the clinical examination involves the study of : abdomen and rectum cardiovascular ( heart and blood vessels ) general appearance of the patient and specific indicators of disease ( nutritional status, presence of jaundice, pallor or clubbing ) genitalia ( and pregnancy if the patient is or could be pregnant ) head, eye, ear, nose, and throat ( heent ) musculoskeletal ( including spine and extremities ) neurological ( consciousness, awareness, brain, vision, cranial nerves, spinal cord and peripheral nerves ) psychiatric ( orientation, mental state, mood, evidence of abnormal perception or thought ). respiratory ( large airways and lungs ) skin vital signs including height, weight, body temperature, blood pressure, pulse, respiration rate, and hemoglobin oxygen saturation it is to likely focus on
##ate flux which is the volumetric flow rate per unit of membrane area. the solute sieving coefficient and hydraulic permeability allow the quick assessment of the synthetic membrane performance. = = membrane separation processes = = membrane separation processes have a very important role in the separation industry. nevertheless, they were not considered technically important until the mid - 1970s. membrane separation processes differ based on separation mechanisms and size of the separated particles. the widely used membrane processes include microfiltration, ultrafiltration, nanofiltration, reverse osmosis, electrolysis, dialysis, electrodialysis, gas separation, vapor permeation, pervaporation, membrane distillation, and membrane contactors. all processes except for pervaporation involve no phase change. all processes except electrodialysis are pressure driven. microfiltration and ultrafiltration is widely used in food and beverage processing ( beer microfiltration, apple juice ultrafiltration ), biotechnological applications and pharmaceutical industry ( antibiotic production, protein purification ), water purification and wastewater treatment, the microelectronics industry, and others. nanofiltration and reverse osmosis membranes are mainly used for water purification purposes. dense membranes are utilized for gas separations ( removal of co2 from natural gas, separating n2 from air, organic vapor removal from air or a nitrogen stream ) and sometimes in membrane distillation. the later process helps in the separation of azeotropic compositions reducing the costs of distillation processes. = = pore size and selectivity = = the pore sizes of technical membranes are specified differently depending on the manufacturer. one common distinction is by nominal pore size. it describes the maximum pore size distribution and gives only vague information about the retention capacity of a membrane. the exclusion limit or " cut - off " of the membrane is usually specified in the form of nmwc ( nominal molecular weight cut - off, or mwco, molecular weight cut off, with units in dalton ). it is defined as the minimum molecular weight of a globular molecule that is retained to 90 % by the membrane. the cut - off, depending on the method, can by converted to so - called d90, which is then expressed in a metric unit. in practice the mwco of the membrane should be at least 20 % lower than the molecular weight of the molecule that is to be separated. using track etched mica membranes beck and schultz demonstrated that hindered diffusion of molecules in pores can be described by the rankin equation. filter membranes are divided into four
the most puzzling issue in the foundations of quantum mechanics is perhaps that of the status of the wave function of a system in a quantum universe. is the wave function objective or subjective? does it represent the physical state of the system or merely our information about the system? and if the former, does it provide a complete description of the system or only a partial description? we shall address these questions here mainly from a bohmian perspective, and shall argue that part of the difficulty in ascertaining the status of the wave function in quantum mechanics arises from the fact that there are two different sorts of wave functions involved. the most fundamental wave function is that of the universe. from it, together with the configuration of the universe, one can define the wave function of a subsystem. we argue that the fundamental wave function, the wave function of the universe, has a law - like character.
much of their work in hospitals. formerly, many internists were not subspecialized ; such general physicians would see any complex nonsurgical problem ; this style of practice has become much less common. in modern urban practice, most internists are subspecialists : that is, they generally limit their medical practice to problems of one organ system or to one particular area of medical knowledge. for example, gastroenterologists and nephrologists specialize respectively in diseases of the gut and the kidneys. in the commonwealth of nations and some other countries, specialist pediatricians and geriatricians are also described as specialist physicians ( or internists ) who have subspecialized by age of patient rather than by organ system. elsewhere, especially in north america, general pediatrics is often a form of primary care. there are many subspecialities ( or subdisciplines ) of internal medicine : training in internal medicine ( as opposed to surgical training ), varies considerably across the world : see the articles on medical education for more details. in north america, it requires at least three years of residency training after medical school, which can then be followed by a one - to three - year fellowship in the subspecialties listed above. in general, resident work hours in medicine are less than those in surgery, averaging about 60 hours per week in the us. this difference does not apply in the uk where all doctors are now required by law to work less than 48 hours per week on average. = = = = diagnostic specialties = = = = clinical laboratory sciences are the clinical diagnostic services that apply laboratory techniques to diagnosis and management of patients. in the united states, these services are supervised by a pathologist. the personnel that work in these medical laboratory departments are technically trained staff who do not hold medical degrees, but who usually hold an undergraduate medical technology degree, who actually perform the tests, assays, and procedures needed for providing the specific services. subspecialties include transfusion medicine, cellular pathology, clinical chemistry, hematology, clinical microbiology and clinical immunology. clinical neurophysiology is concerned with testing the physiology or function of the central and peripheral aspects of the nervous system. these kinds of tests can be divided into recordings of : ( 1 ) spontaneous or continuously running electrical activity, or ( 2 ) stimulus evoked responses. subspecialties include electroencephalography, electromyography, evoked potential, nerve conduction study and polysomnography. sometimes
often called physicians. these terms, internist or physician ( in the narrow sense, common outside north america ), generally exclude practitioners of gynecology and obstetrics, pathology, psychiatry, and especially surgery and its subspecialities. because their patients are often seriously ill or require complex investigations, internists do much of their work in hospitals. formerly, many internists were not subspecialized ; such general physicians would see any complex nonsurgical problem ; this style of practice has become much less common. in modern urban practice, most internists are subspecialists : that is, they generally limit their medical practice to problems of one organ system or to one particular area of medical knowledge. for example, gastroenterologists and nephrologists specialize respectively in diseases of the gut and the kidneys. in the commonwealth of nations and some other countries, specialist pediatricians and geriatricians are also described as specialist physicians ( or internists ) who have subspecialized by age of patient rather than by organ system. elsewhere, especially in north america, general pediatrics is often a form of primary care. there are many subspecialities ( or subdisciplines ) of internal medicine : training in internal medicine ( as opposed to surgical training ), varies considerably across the world : see the articles on medical education for more details. in north america, it requires at least three years of residency training after medical school, which can then be followed by a one - to three - year fellowship in the subspecialties listed above. in general, resident work hours in medicine are less than those in surgery, averaging about 60 hours per week in the us. this difference does not apply in the uk where all doctors are now required by law to work less than 48 hours per week on average. = = = = diagnostic specialties = = = = clinical laboratory sciences are the clinical diagnostic services that apply laboratory techniques to diagnosis and management of patients. in the united states, these services are supervised by a pathologist. the personnel that work in these medical laboratory departments are technically trained staff who do not hold medical degrees, but who usually hold an undergraduate medical technology degree, who actually perform the tests, assays, and procedures needed for providing the specific services. subspecialties include transfusion medicine, cellular pathology, clinical chemistry, hematology, clinical microbiology and clinical immunology. clinical neurophysiology is concerned with testing the physiology or function of the central and peripheral aspects of
functions of the human body, if necessary, through the use of technology. modern medicine can replace several of the body ' s functions through the use of artificial organs and can significantly alter the function of the human body through artificial devices such as, for example, brain implants and pacemakers. the fields of bionics and medical bionics are dedicated to the study of synthetic implants pertaining to natural systems. conversely, some engineering disciplines view the human body as a biological machine worth studying and are dedicated to emulating many of its functions by replacing biology with technology. this has led to fields such as artificial intelligence, neural networks, fuzzy logic, and robotics. there are also substantial interdisciplinary interactions between engineering and medicine. both fields provide solutions to real world problems. this often requires moving forward before phenomena are completely understood in a more rigorous scientific sense and therefore experimentation and empirical knowledge is an integral part of both. medicine, in part, studies the function of the human body. the human body, as a biological machine, has many functions that can be modeled using engineering methods. the heart for example functions much like a pump, the skeleton is like a linked structure with levers, the brain produces electrical signals etc. these similarities as well as the increasing importance and application of engineering principles in medicine, led to the development of the field of biomedical engineering that uses concepts developed in both disciplines. newly emerging branches of science, such as systems biology, are adapting analytical tools traditionally used for engineering, such as systems modeling and computational analysis, to the description of biological systems. = = = art = = = there are connections between engineering and art, for example, architecture, landscape architecture and industrial design ( even to the extent that these disciplines may sometimes be included in a university ' s faculty of engineering ). the art institute of chicago, for instance, held an exhibition about the art of nasa ' s aerospace design. robert maillart ' s bridge design is perceived by some to have been deliberately artistic. at the university of south florida, an engineering professor, through a grant with the national science foundation, has developed a course that connects art and engineering. among famous historical figures, leonardo da vinci is a well - known renaissance artist and engineer, and a prime example of the nexus between art and engineering. = = = business = = = business engineering deals with the relationship between professional engineering, it systems, business administration and change management. engineering management or " management engineering " is a specialized field of management concerned with engineering practice or the engineering industry sector. the demand for management
) : concurrent medical problems, past hospitalizations and operations, injuries, past infectious diseases or vaccinations, history of known allergies. review of systems ( ros ) or systems inquiry : a set of additional questions to ask, which may be missed on hpi : a general enquiry ( have you noticed any weight loss, change in sleep quality, fevers, lumps and bumps? etc. ), followed by questions on the body ' s main organ systems ( heart, lungs, digestive tract, urinary tract, etc. ). social history ( sh ) : birthplace, residences, marital history, social and economic status, habits ( including diet, medications, tobacco, alcohol ). the physical examination is the examination of the patient for medical signs of disease that are objective and observable, in contrast to symptoms that are volunteered by the patient and are not necessarily objectively observable. the healthcare provider uses sight, hearing, touch, and sometimes smell ( e. g., in infection, uremia, diabetic ketoacidosis ). four actions are the basis of physical examination : inspection, palpation ( feel ), percussion ( tap to determine resonance characteristics ), and auscultation ( listen ), generally in that order, although auscultation occurs prior to percussion and palpation for abdominal assessments. the clinical examination involves the study of : abdomen and rectum cardiovascular ( heart and blood vessels ) general appearance of the patient and specific indicators of disease ( nutritional status, presence of jaundice, pallor or clubbing ) genitalia ( and pregnancy if the patient is or could be pregnant ) head, eye, ear, nose, and throat ( heent ) musculoskeletal ( including spine and extremities ) neurological ( consciousness, awareness, brain, vision, cranial nerves, spinal cord and peripheral nerves ) psychiatric ( orientation, mental state, mood, evidence of abnormal perception or thought ). respiratory ( large airways and lungs ) skin vital signs including height, weight, body temperature, blood pressure, pulse, respiration rate, and hemoglobin oxygen saturation it is to likely focus on areas of interest highlighted in the medical history and may not include everything listed above. the treatment plan may include ordering additional medical laboratory tests and medical imaging studies, starting therapy, referral to a specialist, or watchful observation. a follow - up may be advised. depending upon the health insurance plan and the managed care system
, characterizing organs as predominantly yin or yang, and understood the relationship between the pulse, the heart, and the flow of blood in the body centuries before it became accepted in the west. little evidence survives of how ancient indian cultures around the indus river understood nature, but some of their perspectives may be reflected in the vedas, a set of sacred hindu texts. they reveal a conception of the universe as ever - expanding and constantly being recycled and reformed. surgeons in the ayurvedic tradition saw health and illness as a combination of three humors : wind, bile and phlegm. a healthy life resulted from a balance among these humors. in ayurvedic thought, the body consisted of five elements : earth, water, fire, wind, and space. ayurvedic surgeons performed complex surgeries and developed a detailed understanding of human anatomy. pre - socratic philosophers in ancient greek culture brought natural philosophy a step closer to direct inquiry about cause and effect in nature between 600 and 400 bc. however, an element of magic and mythology remained. natural phenomena such as earthquakes and eclipses were explained increasingly in the context of nature itself instead of being attributed to angry gods. thales of miletus, an early philosopher who lived from 625 to 546 bc, explained earthquakes by theorizing that the world floated on water and that water was the fundamental element in nature. in the 5th century bc, leucippus was an early exponent of atomism, the idea that the world is made up of fundamental indivisible particles. pythagoras applied greek innovations in mathematics to astronomy and suggested that the earth was spherical. = = = aristotelian natural philosophy ( 400 bc β 1100 ad ) = = = later socratic and platonic thought focused on ethics, morals, and art and did not attempt an investigation of the physical world ; plato criticized pre - socratic thinkers as materialists and anti - religionists. aristotle, however, a student of plato who lived from 384 to 322 bc, paid closer attention to the natural world in his philosophy. in his history of animals, he described the inner workings of 110 species, including the stingray, catfish and bee. he investigated chick embryos by breaking open eggs and observing them at various stages of development. aristotle ' s works were influential through the 16th century, and he is considered to be the father of biology for his pioneering work in that science. he also presented philosophies about physics, nature, and astronomy using
you noticed any weight loss, change in sleep quality, fevers, lumps and bumps? etc. ), followed by questions on the body ' s main organ systems ( heart, lungs, digestive tract, urinary tract, etc. ). social history ( sh ) : birthplace, residences, marital history, social and economic status, habits ( including diet, medications, tobacco, alcohol ). the physical examination is the examination of the patient for medical signs of disease that are objective and observable, in contrast to symptoms that are volunteered by the patient and are not necessarily objectively observable. the healthcare provider uses sight, hearing, touch, and sometimes smell ( e. g., in infection, uremia, diabetic ketoacidosis ). four actions are the basis of physical examination : inspection, palpation ( feel ), percussion ( tap to determine resonance characteristics ), and auscultation ( listen ), generally in that order, although auscultation occurs prior to percussion and palpation for abdominal assessments. the clinical examination involves the study of : abdomen and rectum cardiovascular ( heart and blood vessels ) general appearance of the patient and specific indicators of disease ( nutritional status, presence of jaundice, pallor or clubbing ) genitalia ( and pregnancy if the patient is or could be pregnant ) head, eye, ear, nose, and throat ( heent ) musculoskeletal ( including spine and extremities ) neurological ( consciousness, awareness, brain, vision, cranial nerves, spinal cord and peripheral nerves ) psychiatric ( orientation, mental state, mood, evidence of abnormal perception or thought ). respiratory ( large airways and lungs ) skin vital signs including height, weight, body temperature, blood pressure, pulse, respiration rate, and hemoglobin oxygen saturation it is to likely focus on areas of interest highlighted in the medical history and may not include everything listed above. the treatment plan may include ordering additional medical laboratory tests and medical imaging studies, starting therapy, referral to a specialist, or watchful observation. a follow - up may be advised. depending upon the health insurance plan and the managed care system, various forms of " utilization review ", such as prior authorization of tests, may place barriers on accessing expensive services. the medical decision - making ( mdm ) process includes the analysis and synthesis of all the above data to come up with a list of possible diagnoses ( the differential diagnoses ),
automatically assigns frequency channels to user groups. walkie - talkie β a battery - powered portable handheld half - duplex two - way radio, used in land mobile radio systems. airband β half - duplex radio system used by aircraft pilots to talk to other aircraft and ground - based air traffic controllers. this vital system is the main communication channel for air traffic control. for most communication in overland flights in air corridors a vhf - am system using channels between 108 and 137 mhz in the vhf band is used. this system has a typical transmission range of 200 miles ( 320 km ) for aircraft flying at cruising altitude. for flights in more remote areas, such as transoceanic airline flights, aircraft use the hf band or channels on the inmarsat or iridium satphone satellites. military aircraft also use a dedicated uhf - am band from 225. 0 to 399. 95 mhz. marine radio β medium - range transceivers on ships, used for ship - to - ship, ship - to - air, and ship - to - shore communication with harbormasters they use fm channels between 156 and 174 mhz in the vhf band with up to 25 watts power, giving them a range of about 60 miles ( 97 km ). some channels are half - duplex and some are full - duplex, to be compatible with the telephone network, to allow users to make telephone calls through a marine operator. amateur radio β long - range half - duplex two - way radio used by hobbyists for non - commercial purposes : recreational radio contacts with other amateurs, volunteer emergency communication during disasters, contests, and experimentation. radio amateurs must hold an amateur radio license and are given a unique callsign that must be used as an identifier in transmissions. amateur radio is restricted to small frequency bands, the amateur radio bands, spaced throughout the radio spectrum starting at 136 khz. within these bands, amateurs are allowed the freedom to transmit on any frequency using a wide variety of voice modulation methods, along with other forms of communication, such as slow - scan television ( sstv ), and radioteletype ( rtty ). additionally, amateurs are among the only radio operators still using morse code radiotelegraphy. = = = = one - way voice communication = = = = one way, unidirectional radio transmission is called simplex. baby monitor β a crib - side appliance for parents of infants that transmits the baby ' s sounds to a receiver carried by the parent, so they can monitor the
Question: The lungs, kidneys, skin, and large intestine are all part of what organ system?
A) respiratory
B) sensory
C) digestive
D) excretory
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D) excretory
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Context:
. species boundaries in plants may be weaker than in animals, and cross species hybrids are often possible. a familiar example is peppermint, mentha Γ piperita, a sterile hybrid between mentha aquatica and spearmint, mentha spicata. the many cultivated varieties of wheat are the result of multiple inter - and intra - specific crosses between wild species and their hybrids. angiosperms with monoecious flowers often have self - incompatibility mechanisms that operate between the pollen and stigma so that the pollen either fails to reach the stigma or fails to germinate and produce male gametes. this is one of several methods used by plants to promote outcrossing. in many land plants the male and female gametes are produced by separate individuals. these species are said to be dioecious when referring to vascular plant sporophytes and dioicous when referring to bryophyte gametophytes. charles darwin in his 1878 book the effects of cross and self - fertilization in the vegetable kingdom at the start of chapter xii noted " the first and most important of the conclusions which may be drawn from the observations given in this volume, is that generally cross - fertilisation is beneficial and self - fertilisation often injurious, at least with the plants on which i experimented. " an important adaptive benefit of outcrossing is that it allows the masking of deleterious mutations in the genome of progeny. this beneficial effect is also known as hybrid vigor or heterosis. once outcrossing is established, subsequent switching to inbreeding becomes disadvantageous since it allows expression of the previously masked deleterious recessive mutations, commonly referred to as inbreeding depression. unlike in higher animals, where parthenogenesis is rare, asexual reproduction may occur in plants by several different mechanisms. the formation of stem tubers in potato is one example. particularly in arctic or alpine habitats, where opportunities for fertilisation of flowers by animals are rare, plantlets or bulbs, may develop instead of flowers, replacing sexual reproduction with asexual reproduction and giving rise to clonal populations genetically identical to the parent. this is one of several types of apomixis that occur in plants. apomixis can also happen in a seed, producing a seed that contains an embryo genetically identical to the parent. most sexually reproducing organisms are diploid, with paired chromosomes, but doubling of their chromosome number may occur due to errors in
men ' s sports include baseball, basketball, cross country, football, golf, swimming & diving, cheerleading, tennis and track & field ; while women ' s sports include basketball, cross country, softball, swimming and diving, tennis, track & field, cheerleading, and volleyball. their cheerleading squad has, in the past, only competed the national cheerleaders & dance association ( nca & nda ) college nationals along with buzz and the goldrush dance team competing here as well. however, in the 2022 season, goldrush competed at the universal cheerleaders & dance association ( uca & uda ) college nationals for the first time and in 2023 the cheer team will compete here for the first time as well. the institute mascots are buzz and the ramblin ' wreck. the institute ' s traditional football rival is the university of georgia ; the rivalry is considered one of the fiercest in college football. the rivalry is commonly referred to as clean, old - fashioned hate, which is also the title of a book about the subject. there is also a long - standing rivalry with clemson. tech has eighteen varsity sports : football, women ' s and men ' s basketball, baseball, softball, volleyball, golf, men ' s and women ' s tennis, men ' s and women ' s swimming and diving, men ' s and women ' s track and field, men ' s and women ' s cross country, and coed cheerleading. four georgia tech football teams were selected as national champions in news polls : 1917, 1928, 1952, and 1990. in may 2007, the women ' s tennis team won the ncaa national championship with a 4 β 2 victory over ucla, the first ever national title granted by the ncaa to tech. = = = fight songs = = = tech ' s fight song " i ' m a ramblin ' wreck from georgia tech " is known worldwide. first published in the 1908 blue print, it was adapted from an old drinking song ( " son of a gambolier " ) and embellished with trumpet flourishes by frank roman. then - vice president richard nixon and soviet premier nikita khrushchev sang the song together when they met in moscow in 1958 to reduce the tension between them. as the story goes, nixon did not know any russian songs, but khrushchev knew that one american song as it had been sung on the ed sullivan show. " i ' m a ramblin ' wreck " has had many other notable moments in its history
inherited traits such as shape in pisum sativum ( peas ). what mendel learned from studying plants has had far - reaching benefits outside of botany. similarly, " jumping genes " were discovered by barbara mcclintock while she was studying maize. nevertheless, there are some distinctive genetic differences between plants and other organisms. species boundaries in plants may be weaker than in animals, and cross species hybrids are often possible. a familiar example is peppermint, mentha Γ piperita, a sterile hybrid between mentha aquatica and spearmint, mentha spicata. the many cultivated varieties of wheat are the result of multiple inter - and intra - specific crosses between wild species and their hybrids. angiosperms with monoecious flowers often have self - incompatibility mechanisms that operate between the pollen and stigma so that the pollen either fails to reach the stigma or fails to germinate and produce male gametes. this is one of several methods used by plants to promote outcrossing. in many land plants the male and female gametes are produced by separate individuals. these species are said to be dioecious when referring to vascular plant sporophytes and dioicous when referring to bryophyte gametophytes. charles darwin in his 1878 book the effects of cross and self - fertilization in the vegetable kingdom at the start of chapter xii noted " the first and most important of the conclusions which may be drawn from the observations given in this volume, is that generally cross - fertilisation is beneficial and self - fertilisation often injurious, at least with the plants on which i experimented. " an important adaptive benefit of outcrossing is that it allows the masking of deleterious mutations in the genome of progeny. this beneficial effect is also known as hybrid vigor or heterosis. once outcrossing is established, subsequent switching to inbreeding becomes disadvantageous since it allows expression of the previously masked deleterious recessive mutations, commonly referred to as inbreeding depression. unlike in higher animals, where parthenogenesis is rare, asexual reproduction may occur in plants by several different mechanisms. the formation of stem tubers in potato is one example. particularly in arctic or alpine habitats, where opportunities for fertilisation of flowers by animals are rare, plantlets or bulbs, may develop instead of flowers, replacing sexual reproduction with asexual reproduction and giving rise to clonal populations genetically identical to the parent. this is one
of several methods used by plants to promote outcrossing. in many land plants the male and female gametes are produced by separate individuals. these species are said to be dioecious when referring to vascular plant sporophytes and dioicous when referring to bryophyte gametophytes. charles darwin in his 1878 book the effects of cross and self - fertilization in the vegetable kingdom at the start of chapter xii noted " the first and most important of the conclusions which may be drawn from the observations given in this volume, is that generally cross - fertilisation is beneficial and self - fertilisation often injurious, at least with the plants on which i experimented. " an important adaptive benefit of outcrossing is that it allows the masking of deleterious mutations in the genome of progeny. this beneficial effect is also known as hybrid vigor or heterosis. once outcrossing is established, subsequent switching to inbreeding becomes disadvantageous since it allows expression of the previously masked deleterious recessive mutations, commonly referred to as inbreeding depression. unlike in higher animals, where parthenogenesis is rare, asexual reproduction may occur in plants by several different mechanisms. the formation of stem tubers in potato is one example. particularly in arctic or alpine habitats, where opportunities for fertilisation of flowers by animals are rare, plantlets or bulbs, may develop instead of flowers, replacing sexual reproduction with asexual reproduction and giving rise to clonal populations genetically identical to the parent. this is one of several types of apomixis that occur in plants. apomixis can also happen in a seed, producing a seed that contains an embryo genetically identical to the parent. most sexually reproducing organisms are diploid, with paired chromosomes, but doubling of their chromosome number may occur due to errors in cytokinesis. this can occur early in development to produce an autopolyploid or partly autopolyploid organism, or during normal processes of cellular differentiation to produce some cell types that are polyploid ( endopolyploidy ), or during gamete formation. an allopolyploid plant may result from a hybridisation event between two different species. both autopolyploid and allopolyploid plants can often reproduce normally, but may be unable to cross - breed successfully with the parent population because there is a mismatch in chromosome numbers. these plants that are reproductively isolated from the parent
nintendo ' s super smash bros. melee fighting game can be emulated on modern hardware allowing us to inspect internal memory states, such as character positions. we created an ai that avoids being hit by training using these internal memory states and outputting controller button presses. after training on a month ' s worth of melee matches, our best agent learned to avoid the toughest ai built into the game for a full minute 74. 6 % of the time.
is the scientific study of inheritance. mendelian inheritance, specifically, is the process by which genes and traits are passed on from parents to offspring. it has several principles. the first is that genetic characteristics, alleles, are discrete and have alternate forms ( e. g., purple vs. white or tall vs. dwarf ), each inherited from one of two parents. based on the law of dominance and uniformity, which states that some alleles are dominant while others are recessive ; an organism with at least one dominant allele will display the phenotype of that dominant allele. during gamete formation, the alleles for each gene segregate, so that each gamete carries only one allele for each gene. heterozygotic individuals produce gametes with an equal frequency of two alleles. finally, the law of independent assortment, states that genes of different traits can segregate independently during the formation of gametes, i. e., genes are unlinked. an exception to this rule would include traits that are sex - linked. test crosses can be performed to experimentally determine the underlying genotype of an organism with a dominant phenotype. a punnett square can be used to predict the results of a test cross. the chromosome theory of inheritance, which states that genes are found on chromosomes, was supported by thomas morgans ' s experiments with fruit flies, which established the sex linkage between eye color and sex in these insects. = = = genes and dna = = = a gene is a unit of heredity that corresponds to a region of deoxyribonucleic acid ( dna ) that carries genetic information that controls form or function of an organism. dna is composed of two polynucleotide chains that coil around each other to form a double helix. it is found as linear chromosomes in eukaryotes, and circular chromosomes in prokaryotes. the set of chromosomes in a cell is collectively known as its genome. in eukaryotes, dna is mainly in the cell nucleus. in prokaryotes, the dna is held within the nucleoid. the genetic information is held within genes, and the complete assemblage in an organism is called its genotype. dna replication is a semiconservative process whereby each strand serves as a template for a new strand of dna. mutations are heritable changes in dna. they can arise spontaneously as a result of replication errors that were not corrected by proofreading or can
##logous in nature, and can be used in a myriad of ways, from helping repair skeletal tissue to replenishing beta cells in diabetic patients. allogenic : cells are obtained from the body of a donor of the same species as the recipient. while there are some ethical constraints to the use of human cells for in vitro studies ( i. e. human brain tissue chimera development ), the employment of dermal fibroblasts from human foreskin demonstrates an immunologically safe and thus a viable choice for allogenic tissue engineering of the skin. xenogenic : these cells are derived isolated cells from alternate species from the recipient. a notable example of xenogeneic tissue utilization is cardiovascular implant construction via animal cells. chimeric human - animal farming raises ethical concerns around the potential for improved consciousness from implanting human organs in animals. syngeneic or isogenic : these cells describe those borne from identical genetic code. this imparts an immunologic benefit similar to autologous cell lines ( see above ). autologous cells can be considered syngenic, but the classification also extends to non - autologously derived cells such as those from an identical twin, from genetically identical ( cloned ) research models, or induced stem cells ( isc ) as related to the donor. = = = stem cells = = = stem cells are undifferentiated cells with the ability to divide in culture and give rise to different forms of specialized cells. stem cells are divided into " adult " and " embryonic " stem cells according to their source. while there is still a large ethical debate related to the use of embryonic stem cells, it is thought that another alternative source β induced pluripotent stem cells β may be useful for the repair of diseased or damaged tissues, or may be used to grow new organs. totipotent cells are stem cells which can divide into further stem cells or differentiate into any cell type in the body, including extra - embryonic tissue. pluripotent cells are stem cells which can differentiate into any cell type in the body except extra - embryonic tissue. induced pluripotent stem cells ( ipscs ) are subclass of pluripotent stem cells resembling embryonic stem cells ( escs ) that have been derived from adult differentiated cells. ipscs are created by altering the expression of transcriptional factors in adult cells until they become like embryonic stem cells. multipotent stem cells can be differentiated into any cell
cortisol, corticosterone and aldosterone activate full - length glucocorticoid receptor ( gr ) from elephant shark, a cartilaginous fish belonging to the oldest group of jawed vertebrates. activation by aldosterone a mineralocorticoid, indicates partial divergence of elephant shark gr from the mr. progesterone activates elephant shark mr, but not elephant shark gr. progesterone inhibits steroid binding to elephant shark gr, but not to human gr. deletion of the n - terminal domain ( ntd ) from elephant shark gr ( truncated gr ) reduced the response to corticosteroids, while truncated and full - length elephant shark mr had similar responses to corticosteroids. chimeras of elephant shark gr ntd fused to mr dbd + lbd had increased activation by corticosteroids and progesterone compared to full - length elephant shark mr. elephant shark mr ntd fused to gr dbd + lbd had similar activation as full - length elephant shark mr, indicating that activation of human gr by the ntd evolved early in gr divergence from the mr.
for the most up - to - date version please visit http : / / www. cis. upenn. edu / ~ brautbar / ccgame. pdf
usability engineering, it ' s important target and identify human errors when interacting with the product of interest because if a user is expected to engage with a product, interface, or service in some way, the very introduction of a human in that engagement increases the potential of encountering human error. error should be reduced as much as possible in order to avoid frustration or injury. there are two main types of human errors which are categorized as slips and mistakes. slips are a very common kind of error involving automatic behaviors ( i. e. typos, hitting the wrong menu item ). when we experience slips, we have the correct goal in mind, but execute the wrong action. mistakes on the other hand involve conscious deliberation that result in the incorrect conclusion. when we experience mistakes, we have the wrong goal in mind and thereby execute the wrong action. even though slips are the more common type of error, they are no less dangerous. a certain type of slip error, a mode error, can be especially dangerous if a user is executing a high - risk task. for instance, if a user is operating a vehicle and does not realize they are in the wrong mode ( i. e. reverse ), they might step on the gas intending to drive, but instead accelerate into a garage wall or another car. in order to avoid modal errors, designers often employ modeless states in which users do not have to choose a mode at all, or they must execute a continuous action while intending to execute a certain mode ( i. e. pressing a key continuously in order to activate " lasso " mode in photoshop ). = = evaluation methods = = usability engineers conduct usability evaluations of existing or proposed interfaces and their findings are fed back to the designer for use in design or redesign. common usability evaluation methods include : card sorting cognitive task analysis cognitive walkthroughs contextual inquiry focus groups heuristic evaluations interviews questionnaires rite method surveys think aloud protocol usability testing = = software applications and development tools = = there are a variety of online resources that make the job of a usability engineer a little easier. online tools are only a useful tool, and do not substitute for a complete usability engineering analysis. some examples of these include : = = = the web metrics tool suite = = = this is a product of the national institute of standards and technology. this toolkit is focused on evaluating the html of a website versus a wide range of usability guidelines and includes : web static analyzer tool
Question: What is the male gamete called in humans?
A) testes
B) dna
C) egg
D) sperm
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D) sperm
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Context:
liver glycogen. during recovery, when oxygen becomes available, nad + attaches to hydrogen from lactate to form atp. in yeast, the waste products are ethanol and carbon dioxide. this type of fermentation is known as alcoholic or ethanol fermentation. the atp generated in this process is made by substrate - level phosphorylation, which does not require oxygen. = = = photosynthesis = = = photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organism ' s metabolic activities via cellular respiration. this chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. in most cases, oxygen is released as a waste product. most plants, algae, and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of the earth ' s atmosphere, and supplies most of the energy necessary for life on earth. photosynthesis has four stages : light absorption, electron transport, atp synthesis, and carbon fixation. light absorption is the initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to proteins in the thylakoid membranes. the absorbed light energy is used to remove electrons from a donor ( water ) to a primary electron acceptor, a quinone designated as q. in the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach a final electron acceptor, which is usually the oxidized form of nadp +, which is reduced to nadph, a process that takes place in a protein complex called photosystem i ( psi ). the transport of electrons is coupled to the movement of protons ( or hydrogen ) from the stroma to the thylakoid membrane, which forms a ph gradient across the membrane as hydrogen becomes more concentrated in the lumen than in the stroma. this is analogous to the proton - motive force generated across the inner mitochondrial membrane in aerobic respiration. during the third stage of photosynthesis, the movement of protons down their concentration gradients from the thylakoid lumen to the stroma through the atp synthase is coupled to the synthesis of atp by that same atp synthase. the nadph and atps generated by the light - dependent reactions in the second and third stages, respectively, provide the energy and
a process of fermentation. the pyruvate is not transported into the mitochondrion but remains in the cytoplasm, where it is converted to waste products that may be removed from the cell. this serves the purpose of oxidizing the electron carriers so that they can perform glycolysis again and removing the excess pyruvate. fermentation oxidizes nadh to nad + so it can be re - used in glycolysis. in the absence of oxygen, fermentation prevents the buildup of nadh in the cytoplasm and provides nad + for glycolysis. this waste product varies depending on the organism. in skeletal muscles, the waste product is lactic acid. this type of fermentation is called lactic acid fermentation. in strenuous exercise, when energy demands exceed energy supply, the respiratory chain cannot process all of the hydrogen atoms joined by nadh. during anaerobic glycolysis, nad + regenerates when pairs of hydrogen combine with pyruvate to form lactate. lactate formation is catalyzed by lactate dehydrogenase in a reversible reaction. lactate can also be used as an indirect precursor for liver glycogen. during recovery, when oxygen becomes available, nad + attaches to hydrogen from lactate to form atp. in yeast, the waste products are ethanol and carbon dioxide. this type of fermentation is known as alcoholic or ethanol fermentation. the atp generated in this process is made by substrate - level phosphorylation, which does not require oxygen. = = = photosynthesis = = = photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organism ' s metabolic activities via cellular respiration. this chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. in most cases, oxygen is released as a waste product. most plants, algae, and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of the earth ' s atmosphere, and supplies most of the energy necessary for life on earth. photosynthesis has four stages : light absorption, electron transport, atp synthesis, and carbon fixation. light absorption is the initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to
of these cellular components. the different stages of mitosis all together define the mitotic phase of an animal cell cycle β the division of the mother cell into two genetically identical daughter cells. the cell cycle is a vital process by which a single - celled fertilized egg develops into a mature organism, as well as the process by which hair, skin, blood cells, and some internal organs are renewed. after cell division, each of the daughter cells begin the interphase of a new cycle. in contrast to mitosis, meiosis results in four haploid daughter cells by undergoing one round of dna replication followed by two divisions. homologous chromosomes are separated in the first division ( meiosis i ), and sister chromatids are separated in the second division ( meiosis ii ). both of these cell division cycles are used in the process of sexual reproduction at some point in their life cycle. both are believed to be present in the last eukaryotic common ancestor. prokaryotes ( i. e., archaea and bacteria ) can also undergo cell division ( or binary fission ). unlike the processes of mitosis and meiosis in eukaryotes, binary fission in prokaryotes takes place without the formation of a spindle apparatus on the cell. before binary fission, dna in the bacterium is tightly coiled. after it has uncoiled and duplicated, it is pulled to the separate poles of the bacterium as it increases the size to prepare for splitting. growth of a new cell wall begins to separate the bacterium ( triggered by ftsz polymerization and " z - ring " formation ). the new cell wall ( septum ) fully develops, resulting in the complete split of the bacterium. the new daughter cells have tightly coiled dna rods, ribosomes, and plasmids. = = = sexual reproduction and meiosis = = = meiosis is a central feature of sexual reproduction in eukaryotes, and the most fundamental function of meiosis appears to be conservation of the integrity of the genome that is passed on to progeny by parents. two aspects of sexual reproduction, meiotic recombination and outcrossing, are likely maintained respectively by the adaptive advantages of recombinational repair of genomic dna damage and genetic complementation which masks the expression of deleterious recessive mutations. the beneficial effect of genetic complementation, derived from outcrossing ( cross - fertilization ) is also referred to as hybrid vigor or heterosis. charles
the process by which hair, skin, blood cells, and some internal organs are renewed. after cell division, each of the daughter cells begin the interphase of a new cycle. in contrast to mitosis, meiosis results in four haploid daughter cells by undergoing one round of dna replication followed by two divisions. homologous chromosomes are separated in the first division ( meiosis i ), and sister chromatids are separated in the second division ( meiosis ii ). both of these cell division cycles are used in the process of sexual reproduction at some point in their life cycle. both are believed to be present in the last eukaryotic common ancestor. prokaryotes ( i. e., archaea and bacteria ) can also undergo cell division ( or binary fission ). unlike the processes of mitosis and meiosis in eukaryotes, binary fission in prokaryotes takes place without the formation of a spindle apparatus on the cell. before binary fission, dna in the bacterium is tightly coiled. after it has uncoiled and duplicated, it is pulled to the separate poles of the bacterium as it increases the size to prepare for splitting. growth of a new cell wall begins to separate the bacterium ( triggered by ftsz polymerization and " z - ring " formation ). the new cell wall ( septum ) fully develops, resulting in the complete split of the bacterium. the new daughter cells have tightly coiled dna rods, ribosomes, and plasmids. = = = sexual reproduction and meiosis = = = meiosis is a central feature of sexual reproduction in eukaryotes, and the most fundamental function of meiosis appears to be conservation of the integrity of the genome that is passed on to progeny by parents. two aspects of sexual reproduction, meiotic recombination and outcrossing, are likely maintained respectively by the adaptive advantages of recombinational repair of genomic dna damage and genetic complementation which masks the expression of deleterious recessive mutations. the beneficial effect of genetic complementation, derived from outcrossing ( cross - fertilization ) is also referred to as hybrid vigor or heterosis. charles darwin in his 1878 book the effects of cross and self - fertilization in the vegetable kingdom at the start of chapter xii noted β the first and most important of the conclusions which may be drawn from the observations given in this volume, is that generally cross - fertilisation is beneficial and self - fertilis
. throughout the history of agriculture, farmers have inadvertently altered the genetics of their crops through introducing them to new environments and breeding them with other plants β one of the first forms of biotechnology. these processes also were included in early fermentation of beer. these processes were introduced in early mesopotamia, egypt, china and india, and still use the same basic biological methods. in brewing, malted grains ( containing enzymes ) convert starch from grains into sugar and then adding specific yeasts to produce beer. in this process, carbohydrates in the grains broke down into alcohols, such as ethanol. later, other cultures produced the process of lactic acid fermentation, which produced other preserved foods, such as soy sauce. fermentation was also used in this time period to produce leavened bread. although the process of fermentation was not fully understood until louis pasteur ' s work in 1857, it is still the first use of biotechnology to convert a food source into another form. before the time of charles darwin ' s work and life, animal and plant scientists had already used selective breeding. darwin added to that body of work with his scientific observations about the ability of science to change species. these accounts contributed to darwin ' s theory of natural selection. for thousands of years, humans have used selective breeding to improve the production of crops and livestock to use them for food. in selective breeding, organisms with desirable characteristics are mated to produce offspring with the same characteristics. for example, this technique was used with corn to produce the largest and sweetest crops. in the early twentieth century scientists gained a greater understanding of microbiology and explored ways of manufacturing specific products. in 1917, chaim weizmann first used a pure microbiological culture in an industrial process, that of manufacturing corn starch using clostridium acetobutylicum, to produce acetone, which the united kingdom desperately needed to manufacture explosives during world war i. biotechnology has also led to the development of antibiotics. in 1928, alexander fleming discovered the mold penicillium. his work led to the purification of the antibiotic formed by the mold by howard florey, ernst boris chain and norman heatley β to form what we today know as penicillin. in 1940, penicillin became available for medicinal use to treat bacterial infections in humans. the field of modern biotechnology is generally thought of as having been born in 1971 when paul berg ' s ( stanford ) experiments in gene splicing had early success. herbert w. boyer
and still use the same basic biological methods. in brewing, malted grains ( containing enzymes ) convert starch from grains into sugar and then adding specific yeasts to produce beer. in this process, carbohydrates in the grains broke down into alcohols, such as ethanol. later, other cultures produced the process of lactic acid fermentation, which produced other preserved foods, such as soy sauce. fermentation was also used in this time period to produce leavened bread. although the process of fermentation was not fully understood until louis pasteur ' s work in 1857, it is still the first use of biotechnology to convert a food source into another form. before the time of charles darwin ' s work and life, animal and plant scientists had already used selective breeding. darwin added to that body of work with his scientific observations about the ability of science to change species. these accounts contributed to darwin ' s theory of natural selection. for thousands of years, humans have used selective breeding to improve the production of crops and livestock to use them for food. in selective breeding, organisms with desirable characteristics are mated to produce offspring with the same characteristics. for example, this technique was used with corn to produce the largest and sweetest crops. in the early twentieth century scientists gained a greater understanding of microbiology and explored ways of manufacturing specific products. in 1917, chaim weizmann first used a pure microbiological culture in an industrial process, that of manufacturing corn starch using clostridium acetobutylicum, to produce acetone, which the united kingdom desperately needed to manufacture explosives during world war i. biotechnology has also led to the development of antibiotics. in 1928, alexander fleming discovered the mold penicillium. his work led to the purification of the antibiotic formed by the mold by howard florey, ernst boris chain and norman heatley β to form what we today know as penicillin. in 1940, penicillin became available for medicinal use to treat bacterial infections in humans. the field of modern biotechnology is generally thought of as having been born in 1971 when paul berg ' s ( stanford ) experiments in gene splicing had early success. herbert w. boyer ( univ. calif. at san francisco ) and stanley n. cohen ( stanford ) significantly advanced the new technology in 1972 by transferring genetic material into a bacterium, such that the imported material would be reproduced. the commercial viability of a biotechnology industry was significantly expanded on june 16, 1980, when the united states
the broad definition of " utilizing a biotechnological system to make products ". indeed, the cultivation of plants may be viewed as the earliest biotechnological enterprise. agriculture has been theorized to have become the dominant way of producing food since the neolithic revolution. through early biotechnology, the earliest farmers selected and bred the best - suited crops ( e. g., those with the highest yields ) to produce enough food to support a growing population. as crops and fields became increasingly large and difficult to maintain, it was discovered that specific organisms and their by - products could effectively fertilize, restore nitrogen, and control pests. throughout the history of agriculture, farmers have inadvertently altered the genetics of their crops through introducing them to new environments and breeding them with other plants β one of the first forms of biotechnology. these processes also were included in early fermentation of beer. these processes were introduced in early mesopotamia, egypt, china and india, and still use the same basic biological methods. in brewing, malted grains ( containing enzymes ) convert starch from grains into sugar and then adding specific yeasts to produce beer. in this process, carbohydrates in the grains broke down into alcohols, such as ethanol. later, other cultures produced the process of lactic acid fermentation, which produced other preserved foods, such as soy sauce. fermentation was also used in this time period to produce leavened bread. although the process of fermentation was not fully understood until louis pasteur ' s work in 1857, it is still the first use of biotechnology to convert a food source into another form. before the time of charles darwin ' s work and life, animal and plant scientists had already used selective breeding. darwin added to that body of work with his scientific observations about the ability of science to change species. these accounts contributed to darwin ' s theory of natural selection. for thousands of years, humans have used selective breeding to improve the production of crops and livestock to use them for food. in selective breeding, organisms with desirable characteristics are mated to produce offspring with the same characteristics. for example, this technique was used with corn to produce the largest and sweetest crops. in the early twentieth century scientists gained a greater understanding of microbiology and explored ways of manufacturing specific products. in 1917, chaim weizmann first used a pure microbiological culture in an industrial process, that of manufacturing corn starch using clostridium acetobutylicum, to produce acetone, which the united
from the proton motive force drives the enzyme atp synthase to synthesize more atps by phosphorylating adps. the transfer of electrons terminates with molecular oxygen being the final electron acceptor. if oxygen were not present, pyruvate would not be metabolized by cellular respiration but undergoes a process of fermentation. the pyruvate is not transported into the mitochondrion but remains in the cytoplasm, where it is converted to waste products that may be removed from the cell. this serves the purpose of oxidizing the electron carriers so that they can perform glycolysis again and removing the excess pyruvate. fermentation oxidizes nadh to nad + so it can be re - used in glycolysis. in the absence of oxygen, fermentation prevents the buildup of nadh in the cytoplasm and provides nad + for glycolysis. this waste product varies depending on the organism. in skeletal muscles, the waste product is lactic acid. this type of fermentation is called lactic acid fermentation. in strenuous exercise, when energy demands exceed energy supply, the respiratory chain cannot process all of the hydrogen atoms joined by nadh. during anaerobic glycolysis, nad + regenerates when pairs of hydrogen combine with pyruvate to form lactate. lactate formation is catalyzed by lactate dehydrogenase in a reversible reaction. lactate can also be used as an indirect precursor for liver glycogen. during recovery, when oxygen becomes available, nad + attaches to hydrogen from lactate to form atp. in yeast, the waste products are ethanol and carbon dioxide. this type of fermentation is known as alcoholic or ethanol fermentation. the atp generated in this process is made by substrate - level phosphorylation, which does not require oxygen. = = = photosynthesis = = = photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organism ' s metabolic activities via cellular respiration. this chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. in most cases, oxygen is released as a waste product. most plants, algae, and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of
, fungi ( mycology ) β including lichen - forming fungi ( lichenology ), non - chlorophyte algae ( phycology ), and viruses ( virology ). however, attention is still given to these groups by botanists, and fungi ( including lichens ) and photosynthetic protists are usually covered in introductory botany courses. palaeobotanists study ancient plants in the fossil record to provide information about the evolutionary history of plants. cyanobacteria, the first oxygen - releasing photosynthetic organisms on earth, are thought to have given rise to the ancestor of plants by entering into an endosymbiotic relationship with an early eukaryote, ultimately becoming the chloroplasts in plant cells. the new photosynthetic plants ( along with their algal relatives ) accelerated the rise in atmospheric oxygen started by the cyanobacteria, changing the ancient oxygen - free, reducing, atmosphere to one in which free oxygen has been abundant for more than 2 billion years. among the important botanical questions of the 21st century are the role of plants as primary producers in the global cycling of life ' s basic ingredients : energy, carbon, oxygen, nitrogen and water, and ways that our plant stewardship can help address the global environmental issues of resource management, conservation, human food security, biologically invasive organisms, carbon sequestration, climate change, and sustainability. = = = human nutrition = = = virtually all staple foods come either directly from primary production by plants, or indirectly from animals that eat them. plants and other photosynthetic organisms are at the base of most food chains because they use the energy from the sun and nutrients from the soil and atmosphere, converting them into a form that can be used by animals. this is what ecologists call the first trophic level. the modern forms of the major staple foods, such as hemp, teff, maize, rice, wheat and other cereal grasses, pulses, bananas and plantains, as well as hemp, flax and cotton grown for their fibres, are the outcome of prehistoric selection over thousands of years from among wild ancestral plants with the most desirable characteristics. botanists study how plants produce food and how to increase yields, for example through plant breeding, making their work important to humanity ' s ability to feed the world and provide food security for future generations. botanists also study weeds, which are a considerable problem in agriculture, and the biology and control of plant
this article has been withdrown by the author.
Question: The lifecycle of an ascomycete is characterized by the production of what during the sexual phase?
A) abaci
B) cerci
C) flageli
D) asci
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D) asci
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Context:
wave, carrying an information signal, occupies a range of frequencies. the information in a radio signal is usually concentrated in narrow frequency bands called sidebands ( sb ) just above and below the carrier frequency. the width in hertz of the frequency range that the radio signal occupies, the highest frequency minus the lowest frequency, is called its bandwidth ( bw ). for any given signal - to - noise ratio, a given bandwidth can carry the same amount of information regardless of where in the radio frequency spectrum it is located ; bandwidth is a measure of information - carrying capacity. the bandwidth required by a radio transmission depends on the data rate of the information being sent, and the spectral efficiency of the modulation method used ; how much data it can transmit in each unit of bandwidth. different types of information signals carried by radio have different data rates. for example, a television signal has a greater data rate than an audio signal. the radio spectrum, the total range of radio frequencies that can be used for communication in a given area, is a limited resource. each radio transmission occupies a portion of the total bandwidth available. radio bandwidth is regarded as an economic good which has a monetary cost and is in increasing demand. in some parts of the radio spectrum, the right to use a frequency band or even a single radio channel is bought and sold for millions of dollars. so there is an incentive to employ technology to minimize the bandwidth used by radio services. a slow transition from analog to digital radio transmission technologies began in the late 1990s. part of the reason for this is that digital modulation can often transmit more information ( a greater data rate ) in a given bandwidth than analog modulation, by using data compression algorithms, which reduce redundancy in the data to be sent, and more efficient modulation. other reasons for the transition is that digital modulation has greater noise immunity than analog, digital signal processing chips have more power and flexibility than analog circuits, and a wide variety of types of information can be transmitted using the same digital modulation. because it is a fixed resource which is in demand by an increasing number of users, the radio spectrum has become increasingly congested in recent decades, and the need to use it more effectively is driving many additional radio innovations such as trunked radio systems, spread spectrum ( ultra - wideband ) transmission, frequency reuse, dynamic spectrum management, frequency pooling, and cognitive radio. = = = itu frequency bands = = = the itu arbitrarily divides the radio spectrum into 12 bands, each beginning at a wavelength which is a power
or a base, as is evident in the history of this concept. acid strength is commonly measured by two methods. one measurement, based on the arrhenius definition of acidity, is ph, which is a measurement of the hydronium ion concentration in a solution, as expressed on a negative logarithmic scale. thus, solutions that have a low ph have a high hydronium ion concentration and can be said to be more acidic. the other measurement, based on the brΓΈnsted β lowry definition, is the acid dissociation constant ( ka ), which measures the relative ability of a substance to act as an acid under the brΓΈnsted β lowry definition of an acid. that is, substances with a higher ka are more likely to donate hydrogen ions in chemical reactions than those with lower ka values. = = = redox = = = redox ( reduction - oxidation ) reactions include all chemical reactions in which atoms have their oxidation state changed by either gaining electrons ( reduction ) or losing electrons ( oxidation ). substances that have the ability to oxidize other substances are said to be oxidative and are known as oxidizing agents, oxidants or oxidizers. an oxidant removes electrons from another substance. similarly, substances that have the ability to reduce other substances are said to be reductive and are known as reducing agents, reductants, or reducers. a reductant transfers electrons to another substance and is thus oxidized itself. and because it " donates " electrons it is also called an electron donor. oxidation and reduction properly refer to a change in oxidation number β the actual transfer of electrons may never occur. thus, oxidation is better defined as an increase in oxidation number, and reduction as a decrease in oxidation number. = = = equilibrium = = = although the concept of equilibrium is widely used across sciences, in the context of chemistry, it arises whenever a number of different states of the chemical composition are possible, as for example, in a mixture of several chemical compounds that can react with one another, or when a substance can be present in more than one kind of phase. a system of chemical substances at equilibrium, even though having an unchanging composition, is most often not static ; molecules of the substances continue to react with one another thus giving rise to a dynamic equilibrium. thus the concept describes the state in which the parameters such as chemical composition remain unchanged over time. = = = chemical laws = = = chemical reactions are governed by certain laws
= = when 0 is said to be neither positive nor negative, the following phrases may refer to the sign of a number : a number is positive if it is greater than zero. a number is negative if it is less than zero. a number is non - negative if it is greater than or equal to zero. a number is non - positive if it is less than or equal to zero. when 0 is said to be both positive and negative, modified phrases are used to refer to the sign of a number : a number is strictly positive if it is greater than zero. a number is strictly negative if it is less than zero. a number is positive if it is greater than or equal to zero. a number is negative if it is less than or equal to zero. for example, the absolute value of a real number is always " non - negative ", but is not necessarily " positive " in the first interpretation, whereas in the second interpretation, it is called " positive " β though not necessarily " strictly positive ". the same terminology is sometimes used for functions that yield real or other signed values. for example, a function would be called a positive function if its values are positive for all arguments of its domain, or a non - negative function if all of its values are non - negative. = = = complex numbers = = = complex numbers are impossible to order, so they cannot carry the structure of an ordered ring, and, accordingly, cannot be partitioned into positive and negative complex numbers. they do, however, share an attribute with the reals, which is called absolute value or magnitude. magnitudes are always non - negative real numbers, and to any non - zero number there belongs a positive real number, its absolute value. for example, the absolute value of β3 and the absolute value of 3 are both equal to 3. this is written in symbols as | β3 | = 3 and | 3 | = 3. in general, any arbitrary real value can be specified by its magnitude and its sign. using the standard encoding, any real value is given by the product of the magnitude and the sign in standard encoding. this relation can be generalized to define a sign for complex numbers. since the real and complex numbers both form a field and contain the positive reals, they also contain the reciprocals of the magnitudes of all non - zero numbers. this means that any non - zero number may be multiplied with the reciprocal of its magnitude, that is, divided by its magnitude. it is immediate that the quotient
is called its bandwidth ( bw ). for any given signal - to - noise ratio, a given bandwidth can carry the same amount of information regardless of where in the radio frequency spectrum it is located ; bandwidth is a measure of information - carrying capacity. the bandwidth required by a radio transmission depends on the data rate of the information being sent, and the spectral efficiency of the modulation method used ; how much data it can transmit in each unit of bandwidth. different types of information signals carried by radio have different data rates. for example, a television signal has a greater data rate than an audio signal. the radio spectrum, the total range of radio frequencies that can be used for communication in a given area, is a limited resource. each radio transmission occupies a portion of the total bandwidth available. radio bandwidth is regarded as an economic good which has a monetary cost and is in increasing demand. in some parts of the radio spectrum, the right to use a frequency band or even a single radio channel is bought and sold for millions of dollars. so there is an incentive to employ technology to minimize the bandwidth used by radio services. a slow transition from analog to digital radio transmission technologies began in the late 1990s. part of the reason for this is that digital modulation can often transmit more information ( a greater data rate ) in a given bandwidth than analog modulation, by using data compression algorithms, which reduce redundancy in the data to be sent, and more efficient modulation. other reasons for the transition is that digital modulation has greater noise immunity than analog, digital signal processing chips have more power and flexibility than analog circuits, and a wide variety of types of information can be transmitted using the same digital modulation. because it is a fixed resource which is in demand by an increasing number of users, the radio spectrum has become increasingly congested in recent decades, and the need to use it more effectively is driving many additional radio innovations such as trunked radio systems, spread spectrum ( ultra - wideband ) transmission, frequency reuse, dynamic spectrum management, frequency pooling, and cognitive radio. = = = itu frequency bands = = = the itu arbitrarily divides the radio spectrum into 12 bands, each beginning at a wavelength which is a power of ten ( 10n ) metres, with corresponding frequency of 3 times a power of ten, and each covering a decade of frequency or wavelength. each of these bands has a traditional name : it can be seen that the bandwidth, the range of frequencies, contained in each band is not equal but increases exponentially as the
scale. thus, solutions that have a low ph have a high hydronium ion concentration and can be said to be more acidic. the other measurement, based on the brΓΈnsted β lowry definition, is the acid dissociation constant ( ka ), which measures the relative ability of a substance to act as an acid under the brΓΈnsted β lowry definition of an acid. that is, substances with a higher ka are more likely to donate hydrogen ions in chemical reactions than those with lower ka values. = = = redox = = = redox ( reduction - oxidation ) reactions include all chemical reactions in which atoms have their oxidation state changed by either gaining electrons ( reduction ) or losing electrons ( oxidation ). substances that have the ability to oxidize other substances are said to be oxidative and are known as oxidizing agents, oxidants or oxidizers. an oxidant removes electrons from another substance. similarly, substances that have the ability to reduce other substances are said to be reductive and are known as reducing agents, reductants, or reducers. a reductant transfers electrons to another substance and is thus oxidized itself. and because it " donates " electrons it is also called an electron donor. oxidation and reduction properly refer to a change in oxidation number β the actual transfer of electrons may never occur. thus, oxidation is better defined as an increase in oxidation number, and reduction as a decrease in oxidation number. = = = equilibrium = = = although the concept of equilibrium is widely used across sciences, in the context of chemistry, it arises whenever a number of different states of the chemical composition are possible, as for example, in a mixture of several chemical compounds that can react with one another, or when a substance can be present in more than one kind of phase. a system of chemical substances at equilibrium, even though having an unchanging composition, is most often not static ; molecules of the substances continue to react with one another thus giving rise to a dynamic equilibrium. thus the concept describes the state in which the parameters such as chemical composition remain unchanged over time. = = = chemical laws = = = chemical reactions are governed by certain laws, which have become fundamental concepts in chemistry. some of them are : = = history = = the history of chemistry spans a period from the ancient past to the present. since several millennia bc, civilizations were using technologies that would eventually form the basis of the various branches of chemistry. examples include extracting metals from ores
the manufacturer. one common distinction is by nominal pore size. it describes the maximum pore size distribution and gives only vague information about the retention capacity of a membrane. the exclusion limit or " cut - off " of the membrane is usually specified in the form of nmwc ( nominal molecular weight cut - off, or mwco, molecular weight cut off, with units in dalton ). it is defined as the minimum molecular weight of a globular molecule that is retained to 90 % by the membrane. the cut - off, depending on the method, can by converted to so - called d90, which is then expressed in a metric unit. in practice the mwco of the membrane should be at least 20 % lower than the molecular weight of the molecule that is to be separated. using track etched mica membranes beck and schultz demonstrated that hindered diffusion of molecules in pores can be described by the rankin equation. filter membranes are divided into four classes according to pore size : the form and shape of the membrane pores are highly dependent on the manufacturing process and are often difficult to specify. therefore, for characterization, test filtrations are carried out and the pore diameter refers to the diameter of the smallest particles which could not pass through the membrane. the rejection can be determined in various ways and provides an indirect measurement of the pore size. one possibility is the filtration of macromolecules ( often dextran, polyethylene glycol or albumin ), another is measurement of the cut - off by gel permeation chromatography. these methods are used mainly to measure membranes for ultrafiltration applications. another testing method is the filtration of particles with defined size and their measurement with a particle sizer or by laser induced breakdown spectroscopy ( libs ). a vivid characterization is to measure the rejection of dextran blue or other colored molecules. the retention of bacteriophage and bacteria, the so - called " bacteria challenge test ", can also provide information about the pore size. to determine the pore diameter, physical methods such as porosimeter ( mercury, liquid - liquid porosimeter and bubble point test ) are also used, but a certain form of the pores ( such as cylindrical or concatenated spherical holes ) is assumed. such methods are used for membranes whose pore geometry does not match the ideal, and we get " nominal " pore diameter, which characterizes the membrane, but does not necessarily reflect its actual filt
of measurement that denotes an amount of substance ( also called chemical amount ). one mole is defined to contain exactly 6. 02214076Γ1023 particles ( atoms, molecules, ions, or electrons ), where the number of particles per mole is known as the avogadro constant. molar concentration is the amount of a particular substance per volume of solution, and is commonly reported in mol / dm3. = = = phase = = = in addition to the specific chemical properties that distinguish different chemical classifications, chemicals can exist in several phases. for the most part, the chemical classifications are independent of these bulk phase classifications ; however, some more exotic phases are incompatible with certain chemical properties. a phase is a set of states of a chemical system that have similar bulk structural properties, over a range of conditions, such as pressure or temperature. physical properties, such as density and refractive index tend to fall within values characteristic of the phase. the phase of matter is defined by the phase transition, which is when energy put into or taken out of the system goes into rearranging the structure of the system, instead of changing the bulk conditions. sometimes the distinction between phases can be continuous instead of having a discrete boundary ; in this case the matter is considered to be in a supercritical state. when three states meet based on the conditions, it is known as a triple point and since this is invariant, it is a convenient way to define a set of conditions. the most familiar examples of phases are solids, liquids, and gases. many substances exhibit multiple solid phases. for example, there are three phases of solid iron ( alpha, gamma, and delta ) that vary based on temperature and pressure. a principal difference between solid phases is the crystal structure, or arrangement, of the atoms. another phase commonly encountered in the study of chemistry is the aqueous phase, which is the state of substances dissolved in aqueous solution ( that is, in water ). less familiar phases include plasmas, bose β einstein condensates and fermionic condensates and the paramagnetic and ferromagnetic phases of magnetic materials. while most familiar phases deal with three - dimensional systems, it is also possible to define analogs in two - dimensional systems, which has received attention for its relevance to systems in biology. = = = bonding = = = atoms sticking together in molecules or crystals are said to be bonded with one another. a chemical bond may be visualized as the multipole balance between the positive
missiles, ships, vehicles, and also to map weather patterns and terrain. a radar set consists of a transmitter and receiver. the transmitter emits a narrow beam of radio waves which is swept around the surrounding space. when the beam strikes a target object, radio waves are reflected back to the receiver. the direction of the beam reveals the object ' s location. since radio waves travel at a constant speed close to the speed of light, by measuring the brief time delay between the outgoing pulse and the received " echo ", the range to the target can be calculated. the targets are often displayed graphically on a map display called a radar screen. doppler radar can measure a moving object ' s velocity, by measuring the change in frequency of the return radio waves due to the doppler effect. radar sets mainly use high frequencies in the microwave bands, because these frequencies create strong reflections from objects the size of vehicles and can be focused into narrow beams with compact antennas. parabolic ( dish ) antennas are widely used. in most radars the transmitting antenna also serves as the receiving antenna ; this is called a monostatic radar. a radar which uses separate transmitting and receiving antennas is called a bistatic radar. airport surveillance radar β in aviation, radar is the main tool of air traffic control. a rotating dish antenna sweeps a vertical fan - shaped beam of microwaves around the airspace and the radar set shows the location of aircraft as " blips " of light on a display called a radar screen. airport radar operates at 2. 7 β 2. 9 ghz in the microwave s band. in large airports the radar image is displayed on multiple screens in an operations room called the tracon ( terminal radar approach control ), where air traffic controllers direct the aircraft by radio to maintain safe aircraft separation. secondary surveillance radar β aircraft carry radar transponders, transceivers which when triggered by the incoming radar signal transmit a return microwave signal. this causes the aircraft to show up more strongly on the radar screen. the radar which triggers the transponder and receives the return beam, usually mounted on top of the primary radar dish, is called the secondary surveillance radar. since radar cannot measure an aircraft ' s altitude with any accuracy, the transponder also transmits back the aircraft ' s altitude measured by its altimeter, and an id number identifying the aircraft, which is displayed on the radar screen. electronic countermeasures ( ecm ) β military defensive electronic systems designed to degrade enemy radar effectiveness, or deceive it
as subjects perceive the sensory world, different stimuli elicit a number of neural representations. here, a subjective distance between stimuli is defined, measuring the degree of similarity between the underlying representations. as an example, the subjective distance between different locations in space is calculated from the activity of rodent hippocampal place cells, and lateral septal cells. such a distance is compared to the real distance, between locations. as the number of sampled neurons increases, the subjective distance shows a tendency to resemble the metrics of real space.
other thing ". this tradition can be traced back to at least 350 bc by aristotle : in his categories, he defines the notion of quantity in terms of a more primitive equality ( distinct from identity or similarity ), stating : the most distinctive mark of quantity is that equality and inequality are predicated of it. each of the aforesaid quantities is said to be equal or unequal. for instance, one solid is said to be equal or unequal to another ; number, too, and time can have these terms applied to them, indeed can all those kinds of quantity that have been mentioned. that which is not a quantity can by no means, it would seem, be termed equal or unequal to anything else. one particular disposition or one particular quality, such as whiteness, is by no means compared with another in terms of equality and inequality but rather in terms of similarity. thus it is the distinctive mark of quantity that it can be called equal and unequal. β ( translated by e. m. edghill ) aristotle had separate categories for quantities ( number, length, volume ) and qualities ( temperature, density, pressure ), now called intensive and extensive properties. the scholastics, particularly richard swineshead and other oxford calculators in the 14th century, began seriously thinking about kinematics and quantitative treatment of qualities. for example, two flames have the same heat - intensity if they produce the same effect on water ( e. g, warming vs boiling ). since two intensities could be shown to be equal, and equality was considered the defining feature of quantities, it meant those intensities were quantifiable. around the 19th century, with the growth of modern logic, it became necessary to have a more concrete description of equality. with the rise of predicate logic due to the work of gottlob frege, logic shifted from being focused on classes of objects to being property - based. this was followed by a movement for describing mathematics in logical foundations, called logicism. this trend lead to the axiomatization of equality through the law of identity and the substitution property especially in mathematical logic and analytic philosophy. the precursor to the substitution property of equality was first formulated by gottfried leibniz in his discourse on metaphysics ( 1686 ), stating, roughly, that " no two distinct things can have all properties in common. " this has since broken into two principles, the substitution property ( if x = y, { \ displaystyle x = y, } then any property of x
Question: What does the concentration of a solution represent?
A) percentage of solute
B) the percentage of contaminates
C) spending of solute
D) the darkness
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A) percentage of solute
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Context:
a legal document in many jurisdictions. follow - ups may be shorter but follow the same general procedure, and specialists follow a similar process. the diagnosis and treatment may take only a few minutes or a few weeks, depending on the complexity of the issue. the components of the medical interview and encounter are : chief complaint ( cc ) : the reason for the current medical visit. these are the symptoms. they are in the patient ' s own words and are recorded along with the duration of each one. also called chief concern or presenting complaint. current activity : occupation, hobbies, what the patient actually does. family history ( fh ) : listing of diseases in the family that may impact the patient. a family tree is sometimes used. history of present illness ( hpi ) : the chronological order of events of symptoms and further clarification of each symptom. distinguishable from history of previous illness, often called past medical history ( pmh ). medical history comprises hpi and pmh. medications ( rx ) : what drugs the patient takes including prescribed, over - the - counter, and home remedies, as well as alternative and herbal medicines or remedies. allergies are also recorded. past medical history ( pmh / pmhx ) : concurrent medical problems, past hospitalizations and operations, injuries, past infectious diseases or vaccinations, history of known allergies. review of systems ( ros ) or systems inquiry : a set of additional questions to ask, which may be missed on hpi : a general enquiry ( have you noticed any weight loss, change in sleep quality, fevers, lumps and bumps? etc. ), followed by questions on the body ' s main organ systems ( heart, lungs, digestive tract, urinary tract, etc. ). social history ( sh ) : birthplace, residences, marital history, social and economic status, habits ( including diet, medications, tobacco, alcohol ). the physical examination is the examination of the patient for medical signs of disease that are objective and observable, in contrast to symptoms that are volunteered by the patient and are not necessarily objectively observable. the healthcare provider uses sight, hearing, touch, and sometimes smell ( e. g., in infection, uremia, diabetic ketoacidosis ). four actions are the basis of physical examination : inspection, palpation ( feel ), percussion ( tap to determine resonance characteristics ), and auscultation (
, or prescribe pharmaceutical drugs or other therapies. differential diagnosis methods help to rule out conditions based on the information provided. during the encounter, properly informing the patient of all relevant facts is an important part of the relationship and the development of trust. the medical encounter is then documented in the medical record, which is a legal document in many jurisdictions. follow - ups may be shorter but follow the same general procedure, and specialists follow a similar process. the diagnosis and treatment may take only a few minutes or a few weeks, depending on the complexity of the issue. the components of the medical interview and encounter are : chief complaint ( cc ) : the reason for the current medical visit. these are the symptoms. they are in the patient ' s own words and are recorded along with the duration of each one. also called chief concern or presenting complaint. current activity : occupation, hobbies, what the patient actually does. family history ( fh ) : listing of diseases in the family that may impact the patient. a family tree is sometimes used. history of present illness ( hpi ) : the chronological order of events of symptoms and further clarification of each symptom. distinguishable from history of previous illness, often called past medical history ( pmh ). medical history comprises hpi and pmh. medications ( rx ) : what drugs the patient takes including prescribed, over - the - counter, and home remedies, as well as alternative and herbal medicines or remedies. allergies are also recorded. past medical history ( pmh / pmhx ) : concurrent medical problems, past hospitalizations and operations, injuries, past infectious diseases or vaccinations, history of known allergies. review of systems ( ros ) or systems inquiry : a set of additional questions to ask, which may be missed on hpi : a general enquiry ( have you noticed any weight loss, change in sleep quality, fevers, lumps and bumps? etc. ), followed by questions on the body ' s main organ systems ( heart, lungs, digestive tract, urinary tract, etc. ). social history ( sh ) : birthplace, residences, marital history, social and economic status, habits ( including diet, medications, tobacco, alcohol ). the physical examination is the examination of the patient for medical signs of disease that are objective and observable, in contrast to symptoms that are volunteered by the patient and are not necessarily objectively observable. the healthcare provider uses
is not present ( e. g., litter in a parking lot or readings on an electric meter ). behavioral observations involve the direct witnessing of the actor engaging in the behavior ( e. g., watching how close a person sits next to another person ). behavioral choices are when a person selects between two or more options ( e. g., voting behavior, choice of a punishment for another participant ). reaction time. the time between the presentation of a stimulus and an appropriate response can indicate differences between two cognitive processes, and can indicate some things about their nature. for example, if in a search task the reaction times vary proportionally with the number of elements, then it is evident that this cognitive process of searching involves serial instead of parallel processing. psychophysical responses. psychophysical experiments are an old psychological technique, which has been adopted by cognitive psychology. they typically involve making judgments of some physical property, e. g. the loudness of a sound. correlation of subjective scales between individuals can show cognitive or sensory biases as compared to actual physical measurements. some examples include : sameness judgments for colors, tones, textures, etc. threshold differences for colors, tones, textures, etc. eye tracking. this methodology is used to study a variety of cognitive processes, most notably visual perception and language processing. the fixation point of the eyes is linked to an individual ' s focus of attention. thus, by monitoring eye movements, we can study what information is being processed at a given time. eye tracking allows us to study cognitive processes on extremely short time scales. eye movements reflect online decision making during a task, and they provide us with some insight into the ways in which those decisions may be processed. = = = brain imaging = = = brain imaging involves analyzing activity within the brain while performing various tasks. this allows us to link behavior and brain function to help understand how information is processed. different types of imaging techniques vary in their temporal ( time - based ) and spatial ( location - based ) resolution. brain imaging is often used in cognitive neuroscience. single - photon emission computed tomography and positron emission tomography. spect and pet use radioactive isotopes, which are injected into the subject ' s bloodstream and taken up by the brain. by observing which areas of the brain take up the radioactive isotope, we can see which areas of the brain are more active than other areas. pet has similar spatial resolution to fmri, but it has extremely poor temporal resolution. electroencephalography. eeg measures the electrical fields
behavioral responses to different stimuli, one can understand something about how those stimuli are processed. lewandowski & strohmetz ( 2009 ) reviewed a collection of innovative uses of behavioral measurement in psychology including behavioral traces, behavioral observations, and behavioral choice. behavioral traces are pieces of evidence that indicate behavior occurred, but the actor is not present ( e. g., litter in a parking lot or readings on an electric meter ). behavioral observations involve the direct witnessing of the actor engaging in the behavior ( e. g., watching how close a person sits next to another person ). behavioral choices are when a person selects between two or more options ( e. g., voting behavior, choice of a punishment for another participant ). reaction time. the time between the presentation of a stimulus and an appropriate response can indicate differences between two cognitive processes, and can indicate some things about their nature. for example, if in a search task the reaction times vary proportionally with the number of elements, then it is evident that this cognitive process of searching involves serial instead of parallel processing. psychophysical responses. psychophysical experiments are an old psychological technique, which has been adopted by cognitive psychology. they typically involve making judgments of some physical property, e. g. the loudness of a sound. correlation of subjective scales between individuals can show cognitive or sensory biases as compared to actual physical measurements. some examples include : sameness judgments for colors, tones, textures, etc. threshold differences for colors, tones, textures, etc. eye tracking. this methodology is used to study a variety of cognitive processes, most notably visual perception and language processing. the fixation point of the eyes is linked to an individual ' s focus of attention. thus, by monitoring eye movements, we can study what information is being processed at a given time. eye tracking allows us to study cognitive processes on extremely short time scales. eye movements reflect online decision making during a task, and they provide us with some insight into the ways in which those decisions may be processed. = = = brain imaging = = = brain imaging involves analyzing activity within the brain while performing various tasks. this allows us to link behavior and brain function to help understand how information is processed. different types of imaging techniques vary in their temporal ( time - based ) and spatial ( location - based ) resolution. brain imaging is often used in cognitive neuroscience. single - photon emission computed tomography and positron emission tomography. spect and pet use radioactive isotopes, which are injected into the subject ' s bloodstream
as possible in order to avoid frustration or injury. there are two main types of human errors which are categorized as slips and mistakes. slips are a very common kind of error involving automatic behaviors ( i. e. typos, hitting the wrong menu item ). when we experience slips, we have the correct goal in mind, but execute the wrong action. mistakes on the other hand involve conscious deliberation that result in the incorrect conclusion. when we experience mistakes, we have the wrong goal in mind and thereby execute the wrong action. even though slips are the more common type of error, they are no less dangerous. a certain type of slip error, a mode error, can be especially dangerous if a user is executing a high - risk task. for instance, if a user is operating a vehicle and does not realize they are in the wrong mode ( i. e. reverse ), they might step on the gas intending to drive, but instead accelerate into a garage wall or another car. in order to avoid modal errors, designers often employ modeless states in which users do not have to choose a mode at all, or they must execute a continuous action while intending to execute a certain mode ( i. e. pressing a key continuously in order to activate " lasso " mode in photoshop ). = = evaluation methods = = usability engineers conduct usability evaluations of existing or proposed interfaces and their findings are fed back to the designer for use in design or redesign. common usability evaluation methods include : card sorting cognitive task analysis cognitive walkthroughs contextual inquiry focus groups heuristic evaluations interviews questionnaires rite method surveys think aloud protocol usability testing = = software applications and development tools = = there are a variety of online resources that make the job of a usability engineer a little easier. online tools are only a useful tool, and do not substitute for a complete usability engineering analysis. some examples of these include : = = = the web metrics tool suite = = = this is a product of the national institute of standards and technology. this toolkit is focused on evaluating the html of a website versus a wide range of usability guidelines and includes : web static analyzer tool ( websat ) β checks web page html against typical usability guidelines web category analysis tool ( webcat ) β lets the usability engineer construct and conduct a web category analysis web variable instrumenter program ( webvip ) β instruments a website to capture a log of user interaction framework for logging usability data ( flu
usability engineering, it ' s important target and identify human errors when interacting with the product of interest because if a user is expected to engage with a product, interface, or service in some way, the very introduction of a human in that engagement increases the potential of encountering human error. error should be reduced as much as possible in order to avoid frustration or injury. there are two main types of human errors which are categorized as slips and mistakes. slips are a very common kind of error involving automatic behaviors ( i. e. typos, hitting the wrong menu item ). when we experience slips, we have the correct goal in mind, but execute the wrong action. mistakes on the other hand involve conscious deliberation that result in the incorrect conclusion. when we experience mistakes, we have the wrong goal in mind and thereby execute the wrong action. even though slips are the more common type of error, they are no less dangerous. a certain type of slip error, a mode error, can be especially dangerous if a user is executing a high - risk task. for instance, if a user is operating a vehicle and does not realize they are in the wrong mode ( i. e. reverse ), they might step on the gas intending to drive, but instead accelerate into a garage wall or another car. in order to avoid modal errors, designers often employ modeless states in which users do not have to choose a mode at all, or they must execute a continuous action while intending to execute a certain mode ( i. e. pressing a key continuously in order to activate " lasso " mode in photoshop ). = = evaluation methods = = usability engineers conduct usability evaluations of existing or proposed interfaces and their findings are fed back to the designer for use in design or redesign. common usability evaluation methods include : card sorting cognitive task analysis cognitive walkthroughs contextual inquiry focus groups heuristic evaluations interviews questionnaires rite method surveys think aloud protocol usability testing = = software applications and development tools = = there are a variety of online resources that make the job of a usability engineer a little easier. online tools are only a useful tool, and do not substitute for a complete usability engineering analysis. some examples of these include : = = = the web metrics tool suite = = = this is a product of the national institute of standards and technology. this toolkit is focused on evaluating the html of a website versus a wide range of usability guidelines and includes : web static analyzer tool
. long - term memory allows us to store information over prolonged periods ( days, weeks, years ). we do not yet know the practical limit of long - term memory capacity. short - term memory allows us to store information over short time scales ( seconds or minutes ). memory is also often grouped into declarative and procedural forms. declarative memory β grouped into subsets of semantic and episodic forms of memory β refers to our memory for facts and specific knowledge, specific meanings, and specific experiences ( e. g. " are apples food? ", or " what did i eat for breakfast four days ago? " ). procedural memory allows us to remember actions and motor sequences ( e. g. how to ride a bicycle ) and is often dubbed implicit knowledge or memory. cognitive scientists study memory just as psychologists do, but tend to focus more on how memory bears on cognitive processes, and the interrelationship between cognition and memory. one example of this could be, what mental processes does a person go through to retrieve a long - lost memory? or, what differentiates between the cognitive process of recognition ( seeing hints of something before remembering it, or memory in context ) and recall ( retrieving a memory, as in " fill - in - the - blank " )? = = = perception and action = = = perception is the ability to take in information via the senses, and process it in some way. vision and hearing are two dominant senses that allow us to perceive the environment. some questions in the study of visual perception, for example, include : ( 1 ) how are we able to recognize objects?, ( 2 ) why do we perceive a continuous visual environment, even though we only see small bits of it at any one time? one tool for studying visual perception is by looking at how people process optical illusions. the image on the right of a necker cube is an example of a bistable percept, that is, the cube can be interpreted as being oriented in two different directions. the study of haptic ( tactile ), olfactory, and gustatory stimuli also fall into the domain of perception. action is taken to refer to the output of a system. in humans, this is accomplished through motor responses. spatial planning and movement, speech production, and complex motor movements are all aspects of action. = = = consciousness = = = = = research methods = = many different methodologies are used to study cognitive science. as the field is highly interdisciplinary, research often cuts across
, followed by a medical interview and a physical examination. basic diagnostic medical devices ( e. g., stethoscope, tongue depressor ) are typically used. after examining for signs and interviewing for symptoms, the doctor may order medical tests ( e. g., blood tests ), take a biopsy, or prescribe pharmaceutical drugs or other therapies. differential diagnosis methods help to rule out conditions based on the information provided. during the encounter, properly informing the patient of all relevant facts is an important part of the relationship and the development of trust. the medical encounter is then documented in the medical record, which is a legal document in many jurisdictions. follow - ups may be shorter but follow the same general procedure, and specialists follow a similar process. the diagnosis and treatment may take only a few minutes or a few weeks, depending on the complexity of the issue. the components of the medical interview and encounter are : chief complaint ( cc ) : the reason for the current medical visit. these are the symptoms. they are in the patient ' s own words and are recorded along with the duration of each one. also called chief concern or presenting complaint. current activity : occupation, hobbies, what the patient actually does. family history ( fh ) : listing of diseases in the family that may impact the patient. a family tree is sometimes used. history of present illness ( hpi ) : the chronological order of events of symptoms and further clarification of each symptom. distinguishable from history of previous illness, often called past medical history ( pmh ). medical history comprises hpi and pmh. medications ( rx ) : what drugs the patient takes including prescribed, over - the - counter, and home remedies, as well as alternative and herbal medicines or remedies. allergies are also recorded. past medical history ( pmh / pmhx ) : concurrent medical problems, past hospitalizations and operations, injuries, past infectious diseases or vaccinations, history of known allergies. review of systems ( ros ) or systems inquiry : a set of additional questions to ask, which may be missed on hpi : a general enquiry ( have you noticed any weight loss, change in sleep quality, fevers, lumps and bumps? etc. ), followed by questions on the body ' s main organ systems ( heart, lungs, digestive tract, urinary tract, etc. ). social history ( sh ) : birthplace, residences, marital history
) : the reason for the current medical visit. these are the symptoms. they are in the patient ' s own words and are recorded along with the duration of each one. also called chief concern or presenting complaint. current activity : occupation, hobbies, what the patient actually does. family history ( fh ) : listing of diseases in the family that may impact the patient. a family tree is sometimes used. history of present illness ( hpi ) : the chronological order of events of symptoms and further clarification of each symptom. distinguishable from history of previous illness, often called past medical history ( pmh ). medical history comprises hpi and pmh. medications ( rx ) : what drugs the patient takes including prescribed, over - the - counter, and home remedies, as well as alternative and herbal medicines or remedies. allergies are also recorded. past medical history ( pmh / pmhx ) : concurrent medical problems, past hospitalizations and operations, injuries, past infectious diseases or vaccinations, history of known allergies. review of systems ( ros ) or systems inquiry : a set of additional questions to ask, which may be missed on hpi : a general enquiry ( have you noticed any weight loss, change in sleep quality, fevers, lumps and bumps? etc. ), followed by questions on the body ' s main organ systems ( heart, lungs, digestive tract, urinary tract, etc. ). social history ( sh ) : birthplace, residences, marital history, social and economic status, habits ( including diet, medications, tobacco, alcohol ). the physical examination is the examination of the patient for medical signs of disease that are objective and observable, in contrast to symptoms that are volunteered by the patient and are not necessarily objectively observable. the healthcare provider uses sight, hearing, touch, and sometimes smell ( e. g., in infection, uremia, diabetic ketoacidosis ). four actions are the basis of physical examination : inspection, palpation ( feel ), percussion ( tap to determine resonance characteristics ), and auscultation ( listen ), generally in that order, although auscultation occurs prior to percussion and palpation for abdominal assessments. the clinical examination involves the study of : abdomen and rectum cardiovascular ( heart and blood vessels ) general appearance of the patient and specific indicators of disease ( nutritional status, presence of jaundice,
options ( e. g., voting behavior, choice of a punishment for another participant ). reaction time. the time between the presentation of a stimulus and an appropriate response can indicate differences between two cognitive processes, and can indicate some things about their nature. for example, if in a search task the reaction times vary proportionally with the number of elements, then it is evident that this cognitive process of searching involves serial instead of parallel processing. psychophysical responses. psychophysical experiments are an old psychological technique, which has been adopted by cognitive psychology. they typically involve making judgments of some physical property, e. g. the loudness of a sound. correlation of subjective scales between individuals can show cognitive or sensory biases as compared to actual physical measurements. some examples include : sameness judgments for colors, tones, textures, etc. threshold differences for colors, tones, textures, etc. eye tracking. this methodology is used to study a variety of cognitive processes, most notably visual perception and language processing. the fixation point of the eyes is linked to an individual ' s focus of attention. thus, by monitoring eye movements, we can study what information is being processed at a given time. eye tracking allows us to study cognitive processes on extremely short time scales. eye movements reflect online decision making during a task, and they provide us with some insight into the ways in which those decisions may be processed. = = = brain imaging = = = brain imaging involves analyzing activity within the brain while performing various tasks. this allows us to link behavior and brain function to help understand how information is processed. different types of imaging techniques vary in their temporal ( time - based ) and spatial ( location - based ) resolution. brain imaging is often used in cognitive neuroscience. single - photon emission computed tomography and positron emission tomography. spect and pet use radioactive isotopes, which are injected into the subject ' s bloodstream and taken up by the brain. by observing which areas of the brain take up the radioactive isotope, we can see which areas of the brain are more active than other areas. pet has similar spatial resolution to fmri, but it has extremely poor temporal resolution. electroencephalography. eeg measures the electrical fields generated by large populations of neurons in the cortex by placing a series of electrodes on the scalp of the subject. this technique has an extremely high temporal resolution, but a relatively poor spatial resolution. functional magnetic resonance imaging. fmri measures the relative amount of oxygenated blood flowing to different parts of the brain. more oxygen
Question: What is the term for any behavior that occurs only after experience or practice?
A) learned behavior
B) practiced behavior
C) saved behavior
D) studied behavior
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A) learned behavior
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Context:
the large scale pattern in the arrival directions of extragalactic cosmic rays that reach the earth is different from that of the flux arriving to the halo of the galaxy as a result of the propagation through the galactic magnetic field. two different effects are relevant in this process : deflections of trajectories and ( de ) acceleration by the electric field component due to the galactic rotation. the deflection of the cosmic ray trajectories makes the flux intensity arriving to the halo from some direction to appear reaching the earth from another direction. this applies to any intrinsic anisotropy in the extragalactic distribution or, even in the absence of intrinsic anisotropies, to the dipolar compton - getting anisotropy induced when the observer is moving with respect to the cosmic rays rest frame. for an observer moving with the solar system, cosmic rays traveling through far away regions of the galaxy also experience an electric force coming from the relative motion ( due to the rotation of the galaxy ) of the local system in which the field can be considered as being purely magnetic. this produces small changes in the particles momentum that can originate large scale anisotropies even for an isotropic extragalactic flux.
release the energy they contain, essentially the opposite of photosynthesis. molecules are moved within plants by transport processes that operate at a variety of spatial scales. subcellular transport of ions, electrons and molecules such as water and enzymes occurs across cell membranes. minerals and water are transported from roots to other parts of the plant in the transpiration stream. diffusion, osmosis, and active transport and mass flow are all different ways transport can occur. examples of elements that plants need to transport are nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. in vascular plants, these elements are extracted from the soil as soluble ions by the roots and transported throughout the plant in the xylem. most of the elements required for plant nutrition come from the chemical breakdown of soil minerals. sucrose produced by photosynthesis is transported from the leaves to other parts of the plant in the phloem and plant hormones are transported by a variety of processes. = = = plant hormones = = = plants are not passive, but respond to external signals such as light, touch, and injury by moving or growing towards or away from the stimulus, as appropriate. tangible evidence of touch sensitivity is the almost instantaneous collapse of leaflets of mimosa pudica, the insect traps of venus flytrap and bladderworts, and the pollinia of orchids. the hypothesis that plant growth and development is coordinated by plant hormones or plant growth regulators first emerged in the late 19th century. darwin experimented on the movements of plant shoots and roots towards light and gravity, and concluded " it is hardly an exaggeration to say that the tip of the radicle.. acts like the brain of one of the lower animals.. directing the several movements ". about the same time, the role of auxins ( from the greek auxein, to grow ) in control of plant growth was first outlined by the dutch scientist frits went. the first known auxin, indole - 3 - acetic acid ( iaa ), which promotes cell growth, was only isolated from plants about 50 years later. this compound mediates the tropic responses of shoots and roots towards light and gravity. the finding in 1939 that plant callus could be maintained in culture containing iaa, followed by the observation in 1947 that it could be induced to form roots and shoots by controlling the concentration of growth hormones were key steps in the development of plant biotechnology and genetic modification. cytokinins are a class of plant hormones named for their control of cell division ( especially
big data dictate their requirements to the hardware and software. simple migration to the cloud data processing, while solving the problem of increasing computational capabilities, however creates some issues : the need to ensure the safety, the need to control the quality during data transmission, the need to optimize requests. computational cloud does not simply provide scalable resources but also requires network infrastructure, unknown routes and the number of user requests. in addition, during functioning situation can occur, in which you need to change the architecture of the application - part of the data needs to be placed in a private cloud, part in a public cloud, part stays on the client.
depends on the extent of the continent in which it is situated, its position in relation to the hilly regions in which rivers generally arise and the sea into which they flow, and the distance between the source and the outlet into the sea of the river draining it. the rate of flow of rivers depends mainly upon their fall, also known as the gradient or slope. when two rivers of different sizes have the same fall, the larger river has the quicker flow, as its retardation by friction against its bed and banks is less in proportion to its volume than is the case with the smaller river. the fall available in a section of a river approximately corresponds to the slope of the country it traverses ; as rivers rise close to the highest part of their basins, generally in hilly regions, their fall is rapid near their source and gradually diminishes, with occasional irregularities, until, in traversing plains along the latter part of their course, their fall usually becomes quite gentle. accordingly, in large basins, rivers in most cases begin as torrents with a variable flow, and end as gently flowing rivers with a comparatively regular discharge. the irregular flow of rivers throughout their course forms one of the main difficulties in devising works for mitigating inundations or for increasing the navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform
oxygen ion migration in li2mno3 was systematically studied by first - principles calculations. hole polaron is found effective to lower the migration barrier of oxygen ion.
this third part of the lecture series deals with the question : who will pay for your retirement? for western europe the answer may be ` ` nobody ' ', but for algeria the demography looks more promising.
the possible dynamics of an ecosystem with three interconnected patches among which one population can migrate are investigated, paying attention to the consequences that possible disruption in the communicating paths can cause.
a novel effect of population transfer in a five - level system is analyzed. this population transfer effect is found to be a version of a raman process, which is facilitated and assisted by coherence effects, acting to close other available decay channels.
device connectivity. 5g is still a fairly new type of networking and is still being spread across nations. moving forward, 5g is going to set the standard of cellular service around the whole globe. corporations such as at & t, verizon, and t - mobile are some of the notorious cellular companies that are rolling out 5g services across the us. 5g started being deployed at the beginning of 2020 and has been growing ever since. according to the gsm association, by 2025, approximately 1. 7 billion subscribers will have a subscription with 5g service. 5g wireless signals are transmitted through large numbers of small cell stations located in places like light poles or building roofs. in the past, 4g networking had to rely on large cell towers in order to transmit signals over large distances. with the introduction of 5g networking, it is imperative that small cell stations are used because the mm wave spectrum, which is the specific type of band used in 5g services, strictly travels over short distances. if the distances between cell stations were longer, signals may suffer from interference from inclimate weather, or other objects such as houses, buildings, trees, and much more. in 5g networking, there are 3 main kinds of 5g : low - band, mid - band, and high - band. low - band frequencies operate below 2 ghz, mid - band frequencies operate between 2 β 10 ghz, and high - band frequencies operate between 20 and 100 ghz. verizon have seen outrageous numbers on their high - band 5g service, which they deem " ultraband ", which hit speeds of over 3 gbit / s. the main advantage of 5g networks is that the data transmission rate is much higher than the previous cellular network, up to 10 gbit / s, which is faster than the current wired internet and 100 times faster than the previous 4g lte cellular network. another advantage is lower network latency ( faster response time ), less than 1 millisecond, and 4g is 30 - 70 milliseconds. the peak rate needs to reach the gbit / s standard to meet the high data volume of high - definition video, virtual reality and so on. the air interface delay level needs to be around 1ms, which meets real - time applications such as autonomous driving and telemedicine. large network capacity, providing the connection capacity of 100 billion devices to meet iot communication. the spectrum efficiency is 10 times higher than lte. with continuous wide area coverage and
have to move to track it. in a satellite ground station a microwave transmitter and large satellite dish antenna transmit a microwave uplink beam to the satellite. the uplink signal carries many channels of telecommunications traffic, such as long - distance telephone calls, television programs, and internet signals, using a technique called frequency - division multiplexing ( fdm ). on the satellite, a transponder receives the signal, translates it to a different downlink frequency to avoid interfering with the uplink signal, and retransmits it down to another ground station, which may be widely separated from the first. there the downlink signal is demodulated and the telecommunications traffic it carries is sent to its local destinations through landlines. communication satellites typically have several dozen transponders on different frequencies, which are leased by different users. direct broadcast satellite β a geostationary communication satellite that transmits retail programming directly to receivers in subscriber ' s homes and vehicles on earth, in satellite radio and tv systems. it uses a higher transmitter power than other communication satellites, to allow the signal to be received by consumers with a small unobtrusive antenna. for example, satellite television uses downlink frequencies from 12. 2 to 12. 7 ghz in the ku band transmitted at 100 to 250 watts, which can be received by relatively small 43 β 80 cm ( 17 β 31 in ) satellite dishes mounted on the outside of buildings. = = = other applications = = = = = = = radar = = = = radar is a radiolocation method used to locate and track aircraft, spacecraft, missiles, ships, vehicles, and also to map weather patterns and terrain. a radar set consists of a transmitter and receiver. the transmitter emits a narrow beam of radio waves which is swept around the surrounding space. when the beam strikes a target object, radio waves are reflected back to the receiver. the direction of the beam reveals the object ' s location. since radio waves travel at a constant speed close to the speed of light, by measuring the brief time delay between the outgoing pulse and the received " echo ", the range to the target can be calculated. the targets are often displayed graphically on a map display called a radar screen. doppler radar can measure a moving object ' s velocity, by measuring the change in frequency of the return radio waves due to the doppler effect. radar sets mainly use high frequencies in the microwave bands, because these frequencies create strong reflections from objects the size of vehicles and can be focused into narrow beams with
Question: What do we call the movement of individuals into a population from other areas?
A) nomadic
B) pilgrimage
C) assimilation
D) immigration
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D) immigration
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Context:
), electron transport chain, and oxidative phosphorylation. glycolysis is a metabolic process that occurs in the cytoplasm whereby glucose is converted into two pyruvates, with two net molecules of atp being produced at the same time. each pyruvate is then oxidized into acetyl - coa by the pyruvate dehydrogenase complex, which also generates nadh and carbon dioxide. acetyl - coa enters the citric acid cycle, which takes places inside the mitochondrial matrix. at the end of the cycle, the total yield from 1 glucose ( or 2 pyruvates ) is 6 nadh, 2 fadh2, and 2 atp molecules. finally, the next stage is oxidative phosphorylation, which in eukaryotes, occurs in the mitochondrial cristae. oxidative phosphorylation comprises the electron transport chain, which is a series of four protein complexes that transfer electrons from one complex to another, thereby releasing energy from nadh and fadh2 that is coupled to the pumping of protons ( hydrogen ions ) across the inner mitochondrial membrane ( chemiosmosis ), which generates a proton motive force. energy from the proton motive force drives the enzyme atp synthase to synthesize more atps by phosphorylating adps. the transfer of electrons terminates with molecular oxygen being the final electron acceptor. if oxygen were not present, pyruvate would not be metabolized by cellular respiration but undergoes a process of fermentation. the pyruvate is not transported into the mitochondrion but remains in the cytoplasm, where it is converted to waste products that may be removed from the cell. this serves the purpose of oxidizing the electron carriers so that they can perform glycolysis again and removing the excess pyruvate. fermentation oxidizes nadh to nad + so it can be re - used in glycolysis. in the absence of oxygen, fermentation prevents the buildup of nadh in the cytoplasm and provides nad + for glycolysis. this waste product varies depending on the organism. in skeletal muscles, the waste product is lactic acid. this type of fermentation is called lactic acid fermentation. in strenuous exercise, when energy demands exceed energy supply, the respiratory chain cannot process all of the hydrogen atoms joined by
transport chain, which is a series of four protein complexes that transfer electrons from one complex to another, thereby releasing energy from nadh and fadh2 that is coupled to the pumping of protons ( hydrogen ions ) across the inner mitochondrial membrane ( chemiosmosis ), which generates a proton motive force. energy from the proton motive force drives the enzyme atp synthase to synthesize more atps by phosphorylating adps. the transfer of electrons terminates with molecular oxygen being the final electron acceptor. if oxygen were not present, pyruvate would not be metabolized by cellular respiration but undergoes a process of fermentation. the pyruvate is not transported into the mitochondrion but remains in the cytoplasm, where it is converted to waste products that may be removed from the cell. this serves the purpose of oxidizing the electron carriers so that they can perform glycolysis again and removing the excess pyruvate. fermentation oxidizes nadh to nad + so it can be re - used in glycolysis. in the absence of oxygen, fermentation prevents the buildup of nadh in the cytoplasm and provides nad + for glycolysis. this waste product varies depending on the organism. in skeletal muscles, the waste product is lactic acid. this type of fermentation is called lactic acid fermentation. in strenuous exercise, when energy demands exceed energy supply, the respiratory chain cannot process all of the hydrogen atoms joined by nadh. during anaerobic glycolysis, nad + regenerates when pairs of hydrogen combine with pyruvate to form lactate. lactate formation is catalyzed by lactate dehydrogenase in a reversible reaction. lactate can also be used as an indirect precursor for liver glycogen. during recovery, when oxygen becomes available, nad + attaches to hydrogen from lactate to form atp. in yeast, the waste products are ethanol and carbon dioxide. this type of fermentation is known as alcoholic or ethanol fermentation. the atp generated in this process is made by substrate - level phosphorylation, which does not require oxygen. = = = photosynthesis = = = photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organism ' s metabolic activities via cellular respiration. this chemical energy
from the proton motive force drives the enzyme atp synthase to synthesize more atps by phosphorylating adps. the transfer of electrons terminates with molecular oxygen being the final electron acceptor. if oxygen were not present, pyruvate would not be metabolized by cellular respiration but undergoes a process of fermentation. the pyruvate is not transported into the mitochondrion but remains in the cytoplasm, where it is converted to waste products that may be removed from the cell. this serves the purpose of oxidizing the electron carriers so that they can perform glycolysis again and removing the excess pyruvate. fermentation oxidizes nadh to nad + so it can be re - used in glycolysis. in the absence of oxygen, fermentation prevents the buildup of nadh in the cytoplasm and provides nad + for glycolysis. this waste product varies depending on the organism. in skeletal muscles, the waste product is lactic acid. this type of fermentation is called lactic acid fermentation. in strenuous exercise, when energy demands exceed energy supply, the respiratory chain cannot process all of the hydrogen atoms joined by nadh. during anaerobic glycolysis, nad + regenerates when pairs of hydrogen combine with pyruvate to form lactate. lactate formation is catalyzed by lactate dehydrogenase in a reversible reaction. lactate can also be used as an indirect precursor for liver glycogen. during recovery, when oxygen becomes available, nad + attaches to hydrogen from lactate to form atp. in yeast, the waste products are ethanol and carbon dioxide. this type of fermentation is known as alcoholic or ethanol fermentation. the atp generated in this process is made by substrate - level phosphorylation, which does not require oxygen. = = = photosynthesis = = = photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organism ' s metabolic activities via cellular respiration. this chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. in most cases, oxygen is released as a waste product. most plants, algae, and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of
oxidized into acetyl - coa by the pyruvate dehydrogenase complex, which also generates nadh and carbon dioxide. acetyl - coa enters the citric acid cycle, which takes places inside the mitochondrial matrix. at the end of the cycle, the total yield from 1 glucose ( or 2 pyruvates ) is 6 nadh, 2 fadh2, and 2 atp molecules. finally, the next stage is oxidative phosphorylation, which in eukaryotes, occurs in the mitochondrial cristae. oxidative phosphorylation comprises the electron transport chain, which is a series of four protein complexes that transfer electrons from one complex to another, thereby releasing energy from nadh and fadh2 that is coupled to the pumping of protons ( hydrogen ions ) across the inner mitochondrial membrane ( chemiosmosis ), which generates a proton motive force. energy from the proton motive force drives the enzyme atp synthase to synthesize more atps by phosphorylating adps. the transfer of electrons terminates with molecular oxygen being the final electron acceptor. if oxygen were not present, pyruvate would not be metabolized by cellular respiration but undergoes a process of fermentation. the pyruvate is not transported into the mitochondrion but remains in the cytoplasm, where it is converted to waste products that may be removed from the cell. this serves the purpose of oxidizing the electron carriers so that they can perform glycolysis again and removing the excess pyruvate. fermentation oxidizes nadh to nad + so it can be re - used in glycolysis. in the absence of oxygen, fermentation prevents the buildup of nadh in the cytoplasm and provides nad + for glycolysis. this waste product varies depending on the organism. in skeletal muscles, the waste product is lactic acid. this type of fermentation is called lactic acid fermentation. in strenuous exercise, when energy demands exceed energy supply, the respiratory chain cannot process all of the hydrogen atoms joined by nadh. during anaerobic glycolysis, nad + regenerates when pairs of hydrogen combine with pyruvate to form lactate. lactate formation is catalyzed by lactate dehydrogenase in a reversible reaction. lactate can also be used as an indirect precursor for
cell. in juxtacrine signaling, there is direct contact between the signaling and responding cells. finally, hormones are ligands that travel through the circulatory systems of animals or vascular systems of plants to reach their target cells. once a ligand binds with a receptor, it can influence the behavior of another cell, depending on the type of receptor. for instance, neurotransmitters that bind with an inotropic receptor can alter the excitability of a target cell. other types of receptors include protein kinase receptors ( e. g., receptor for the hormone insulin ) and g protein - coupled receptors. activation of g protein - coupled receptors can initiate second messenger cascades. the process by which a chemical or physical signal is transmitted through a cell as a series of molecular events is called signal transduction. = = = cell cycle = = = the cell cycle is a series of events that take place in a cell that cause it to divide into two daughter cells. these events include the duplication of its dna and some of its organelles, and the subsequent partitioning of its cytoplasm into two daughter cells in a process called cell division. in eukaryotes ( i. e., animal, plant, fungal, and protist cells ), there are two distinct types of cell division : mitosis and meiosis. mitosis is part of the cell cycle, in which replicated chromosomes are separated into two new nuclei. cell division gives rise to genetically identical cells in which the total number of chromosomes is maintained. in general, mitosis ( division of the nucleus ) is preceded by the s stage of interphase ( during which the dna is replicated ) and is often followed by telophase and cytokinesis ; which divides the cytoplasm, organelles and cell membrane of one cell into two new cells containing roughly equal shares of these cellular components. the different stages of mitosis all together define the mitotic phase of an animal cell cycle β the division of the mother cell into two genetically identical daughter cells. the cell cycle is a vital process by which a single - celled fertilized egg develops into a mature organism, as well as the process by which hair, skin, blood cells, and some internal organs are renewed. after cell division, each of the daughter cells begin the interphase of a new cycle. in contrast to mitosis, meiosis results in four haploid daughter cells by undergoing one round of dna replication followed by two divisions
protons down their concentration gradients from the thylakoid lumen to the stroma through the atp synthase is coupled to the synthesis of atp by that same atp synthase. the nadph and atps generated by the light - dependent reactions in the second and third stages, respectively, provide the energy and electrons to drive the synthesis of glucose by fixing atmospheric carbon dioxide into existing organic carbon compounds, such as ribulose bisphosphate ( rubp ) in a sequence of light - independent ( or dark ) reactions called the calvin cycle. = = = cell signaling = = = cell signaling ( or communication ) is the ability of cells to receive, process, and transmit signals with its environment and with itself. signals can be non - chemical such as light, electrical impulses, and heat, or chemical signals ( or ligands ) that interact with receptors, which can be found embedded in the cell membrane of another cell or located deep inside a cell. there are generally four types of chemical signals : autocrine, paracrine, juxtacrine, and hormones. in autocrine signaling, the ligand affects the same cell that releases it. tumor cells, for example, can reproduce uncontrollably because they release signals that initiate their own self - division. in paracrine signaling, the ligand diffuses to nearby cells and affects them. for example, brain cells called neurons release ligands called neurotransmitters that diffuse across a synaptic cleft to bind with a receptor on an adjacent cell such as another neuron or muscle cell. in juxtacrine signaling, there is direct contact between the signaling and responding cells. finally, hormones are ligands that travel through the circulatory systems of animals or vascular systems of plants to reach their target cells. once a ligand binds with a receptor, it can influence the behavior of another cell, depending on the type of receptor. for instance, neurotransmitters that bind with an inotropic receptor can alter the excitability of a target cell. other types of receptors include protein kinase receptors ( e. g., receptor for the hormone insulin ) and g protein - coupled receptors. activation of g protein - coupled receptors can initiate second messenger cascades. the process by which a chemical or physical signal is transmitted through a cell as a series of molecular events is called signal transduction. = = = cell cycle = = = the cell cycle is a series of events that take place in a cell that cause
or 2 pyruvates ) is 6 nadh, 2 fadh2, and 2 atp molecules. finally, the next stage is oxidative phosphorylation, which in eukaryotes, occurs in the mitochondrial cristae. oxidative phosphorylation comprises the electron transport chain, which is a series of four protein complexes that transfer electrons from one complex to another, thereby releasing energy from nadh and fadh2 that is coupled to the pumping of protons ( hydrogen ions ) across the inner mitochondrial membrane ( chemiosmosis ), which generates a proton motive force. energy from the proton motive force drives the enzyme atp synthase to synthesize more atps by phosphorylating adps. the transfer of electrons terminates with molecular oxygen being the final electron acceptor. if oxygen were not present, pyruvate would not be metabolized by cellular respiration but undergoes a process of fermentation. the pyruvate is not transported into the mitochondrion but remains in the cytoplasm, where it is converted to waste products that may be removed from the cell. this serves the purpose of oxidizing the electron carriers so that they can perform glycolysis again and removing the excess pyruvate. fermentation oxidizes nadh to nad + so it can be re - used in glycolysis. in the absence of oxygen, fermentation prevents the buildup of nadh in the cytoplasm and provides nad + for glycolysis. this waste product varies depending on the organism. in skeletal muscles, the waste product is lactic acid. this type of fermentation is called lactic acid fermentation. in strenuous exercise, when energy demands exceed energy supply, the respiratory chain cannot process all of the hydrogen atoms joined by nadh. during anaerobic glycolysis, nad + regenerates when pairs of hydrogen combine with pyruvate to form lactate. lactate formation is catalyzed by lactate dehydrogenase in a reversible reaction. lactate can also be used as an indirect precursor for liver glycogen. during recovery, when oxygen becomes available, nad + attaches to hydrogen from lactate to form atp. in yeast, the waste products are ethanol and carbon dioxide. this type of fermentation is known as alcoholic or ethanol fermentation. the atp generated in this process is made by
nadh. during anaerobic glycolysis, nad + regenerates when pairs of hydrogen combine with pyruvate to form lactate. lactate formation is catalyzed by lactate dehydrogenase in a reversible reaction. lactate can also be used as an indirect precursor for liver glycogen. during recovery, when oxygen becomes available, nad + attaches to hydrogen from lactate to form atp. in yeast, the waste products are ethanol and carbon dioxide. this type of fermentation is known as alcoholic or ethanol fermentation. the atp generated in this process is made by substrate - level phosphorylation, which does not require oxygen. = = = photosynthesis = = = photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organism ' s metabolic activities via cellular respiration. this chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. in most cases, oxygen is released as a waste product. most plants, algae, and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of the earth ' s atmosphere, and supplies most of the energy necessary for life on earth. photosynthesis has four stages : light absorption, electron transport, atp synthesis, and carbon fixation. light absorption is the initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to proteins in the thylakoid membranes. the absorbed light energy is used to remove electrons from a donor ( water ) to a primary electron acceptor, a quinone designated as q. in the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach a final electron acceptor, which is usually the oxidized form of nadp +, which is reduced to nadph, a process that takes place in a protein complex called photosystem i ( psi ). the transport of electrons is coupled to the movement of protons ( or hydrogen ) from the stroma to the thylakoid membrane, which forms a ph gradient across the membrane as hydrogen becomes more concentrated in the lumen than in the stroma. this is analogous to the proton - motive force generated across the inner mitochondrial membrane in aerobic respiration. during the third stage of photosynthesis, the movement of
the elimination of metabolic wastes. these enzyme - catalyzed reactions allow organisms to grow and reproduce, maintain their structures, and respond to their environments. metabolic reactions may be categorized as catabolic β the breaking down of compounds ( for example, the breaking down of glucose to pyruvate by cellular respiration ) ; or anabolic β the building up ( synthesis ) of compounds ( such as proteins, carbohydrates, lipids, and nucleic acids ). usually, catabolism releases energy, and anabolism consumes energy. the chemical reactions of metabolism are organized into metabolic pathways, in which one chemical is transformed through a series of steps into another chemical, each step being facilitated by a specific enzyme. enzymes are crucial to metabolism because they allow organisms to drive desirable reactions that require energy that will not occur by themselves, by coupling them to spontaneous reactions that release energy. enzymes act as catalysts β they allow a reaction to proceed more rapidly without being consumed by it β by reducing the amount of activation energy needed to convert reactants into products. enzymes also allow the regulation of the rate of a metabolic reaction, for example in response to changes in the cell ' s environment or to signals from other cells. = = = cellular respiration = = = cellular respiration is a set of metabolic reactions and processes that take place in cells to convert chemical energy from nutrients into adenosine triphosphate ( atp ), and then release waste products. the reactions involved in respiration are catabolic reactions, which break large molecules into smaller ones, releasing energy. respiration is one of the key ways a cell releases chemical energy to fuel cellular activity. the overall reaction occurs in a series of biochemical steps, some of which are redox reactions. although cellular respiration is technically a combustion reaction, it clearly does not resemble one when it occurs in a cell because of the slow, controlled release of energy from the series of reactions. sugar in the form of glucose is the main nutrient used by animal and plant cells in respiration. cellular respiration involving oxygen is called aerobic respiration, which has four stages : glycolysis, citric acid cycle ( or krebs cycle ), electron transport chain, and oxidative phosphorylation. glycolysis is a metabolic process that occurs in the cytoplasm whereby glucose is converted into two pyruvates, with two net molecules of atp being produced at the same time. each pyruvate is then
a process of fermentation. the pyruvate is not transported into the mitochondrion but remains in the cytoplasm, where it is converted to waste products that may be removed from the cell. this serves the purpose of oxidizing the electron carriers so that they can perform glycolysis again and removing the excess pyruvate. fermentation oxidizes nadh to nad + so it can be re - used in glycolysis. in the absence of oxygen, fermentation prevents the buildup of nadh in the cytoplasm and provides nad + for glycolysis. this waste product varies depending on the organism. in skeletal muscles, the waste product is lactic acid. this type of fermentation is called lactic acid fermentation. in strenuous exercise, when energy demands exceed energy supply, the respiratory chain cannot process all of the hydrogen atoms joined by nadh. during anaerobic glycolysis, nad + regenerates when pairs of hydrogen combine with pyruvate to form lactate. lactate formation is catalyzed by lactate dehydrogenase in a reversible reaction. lactate can also be used as an indirect precursor for liver glycogen. during recovery, when oxygen becomes available, nad + attaches to hydrogen from lactate to form atp. in yeast, the waste products are ethanol and carbon dioxide. this type of fermentation is known as alcoholic or ethanol fermentation. the atp generated in this process is made by substrate - level phosphorylation, which does not require oxygen. = = = photosynthesis = = = photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organism ' s metabolic activities via cellular respiration. this chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. in most cases, oxygen is released as a waste product. most plants, algae, and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of the earth ' s atmosphere, and supplies most of the energy necessary for life on earth. photosynthesis has four stages : light absorption, electron transport, atp synthesis, and carbon fixation. light absorption is the initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to
Question: Enzymes, proteins, electron carriers, and pumps that play roles in glycolysis, the citric acid cycle, and the electron transport chain tend to catalyze reactions that are what?
A) reversible
B) non-reversible
C) changeable
D) continuous
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B) non-reversible
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Context:
use less energy than conventional thermal separation processes such as distillation, sublimation or crystallization. the separation process is purely physical and both fractions ( permeate and retentate ) can be obtained as useful products. cold separation using membrane technology is widely used in the food technology, biotechnology and pharmaceutical industries. furthermore, using membranes enables separations to take place that would be impossible using thermal separation methods. for example, it is impossible to separate the constituents of azeotropic liquids or solutes which form isomorphic crystals by distillation or recrystallization but such separations can be achieved using membrane technology. depending on the type of membrane, the selective separation of certain individual substances or substance mixtures is possible. important technical applications include the production of drinking water by reverse osmosis. in waste water treatment, membrane technology is becoming increasingly important. ultra / microfiltration can be very effective in removing colloids and macromolecules from wastewater. this is needed if wastewater is discharged into sensitive waters especially those designated for contact water sports and recreation. about half of the market is in medical applications such as artificial kidneys to remove toxic substances by hemodialysis and as artificial lung for bubble - free supply of oxygen in the blood. the importance of membrane technology is growing in the field of environmental protection ( nano - mem - pro ippc database ). even in modern energy recovery techniques, membranes are increasingly used, for example in fuel cells and in osmotic power plants. = = mass transfer = = two basic models can be distinguished for mass transfer through the membrane : the solution - diffusion model and the hydrodynamic model. in real membranes, these two transport mechanisms certainly occur side by side, especially during ultra - filtration. = = = solution - diffusion model = = = in the solution - diffusion model, transport occurs only by diffusion. the component that needs to be transported must first be dissolved in the membrane. the general approach of the solution - diffusion model is to assume that the chemical potential of the feed and permeate fluids are in equilibrium with the adjacent membrane surfaces such that appropriate expressions for the chemical potential in the fluid and membrane phases can be equated at the solution - membrane interface. this principle is more important for dense membranes without natural pores such as those used for reverse osmosis and in fuel cells. during the filtration process a boundary layer forms on the membrane. this concentration gradient is created by molecules which cannot pass through the membrane. the
remediation include ; soil contamination, hazardous waste, groundwater contamination, oil, gas and chemical spills. there are three most common types of environmental remediation. these include soil, water, and sediment remediation. soil remediation consists of removing contaminants in soil, as these pose great risks to humans and the ecosystem. some examples of this are heavy metals, pesticides, and radioactive materials. depending on the contaminant the remedial processes can be physical, chemical, thermal, or biological. water remediation is one of the most important considering water is an essential natural resource. depending on the source of water there will be different contaminants. surface water contamination mainly consists of agricultural, animal, and industrial waste, as well as acid mine drainage. there has been a rise in the need for water remediation due to the increased discharge of industrial waste, leading to a demand for sustainable water solutions. the market for water remediation is expected to consistently increase to $ 19. 6 billion by 2030. sediment remediation consists of removing contaminated sediments. is it almost similar to soil remediation except it is often more sophisticated as it involves additional contaminants. to reduce the contaminants it is likely to use physical, chemical, and biological processes that help with source control, but if these processes are executed correctly, there ' s a risk of contamination resurfacing. = = = solid waste management = = = solid waste management is the purification, consumption, reuse, disposal, and treatment of solid waste that is undertaken by the government or the ruling bodies of a city / town. it refers to the collection, treatment, and disposal of non - soluble, solid waste material. solid waste is associated with both industrial, institutional, commercial and residential activities. hazardous solid waste, when improperly disposed can encourage the infestation of insects and rodents, contributing to the spread of diseases. some of the most common types of solid waste management include ; landfills, vermicomposting, composting, recycling, and incineration. however, a major barrier for solid waste management practices is the high costs associated with recycling and the risks of creating more pollution. = = = e - waste recycling = = = the recycling of electronic waste ( e - waste ) has seen significant technological advancements due to increasing environmental concerns and the growing volume of electronic product disposals. traditional e - waste recycling methods, which often involve manual disassemb
the surface of the membrane, retentate is removed from the same side further downstream, whereas the permeate flow is tracked on the other side. in dead - end filtration, the direction of the fluid flow is normal to the membrane surface. both flow geometries offer some advantages and disadvantages. generally, dead - end filtration is used for feasibility studies on a laboratory scale. the dead - end membranes are relatively easy to fabricate which reduces the cost of the separation process. the dead - end membrane separation process is easy to implement and the process is usually cheaper than cross - flow membrane filtration. the dead - end filtration process is usually a batch - type process, where the filtering solution is loaded ( or slowly fed ) into the membrane device, which then allows passage of some particles subject to the driving force. the main disadvantage of dead - end filtration is the extensive membrane fouling and concentration polarization. the fouling is usually induced faster at higher driving forces. membrane fouling and particle retention in a feed solution also builds up a concentration gradients and particle backflow ( concentration polarization ). the tangential flow devices are more cost and labor - intensive, but they are less susceptible to fouling due to the sweeping effects and high shear rates of the passing flow. the most commonly used synthetic membrane devices ( modules ) are flat sheets / plates, spiral wounds, and hollow fibers. flat membranes used in filtration and separation processes can be enhanced with surface patterning, where microscopic structures are introduced to improve performance. these patterns increase surface area, optimize water flow, and reduce fouling, leading to higher permeability and longer membrane lifespan. research has shown that such modifications can significantly enhance efficiency in water purification, energy applications, and industrial separations. flat plates are usually constructed as circular thin flat membrane surfaces to be used in dead - end geometry modules. spiral wounds are constructed from similar flat membranes but in the form of a " pocket " containing two membrane sheets separated by a highly porous support plate. several such pockets are then wound around a tube to create a tangential flow geometry and to reduce membrane fouling. hollow fiber modules consist of an assembly of self - supporting fibers with dense skin separation layers, and a more open matrix helping to withstand pressure gradients and maintain structural integrity. the hollow fiber modules can contain up to 10, 000 fibers ranging from 200 to 2500 ΞΌm in diameter ; the main advantage of hollow fiber modules is the very large surface area within
= = = = = = environmental remediation = = = environmental remediation is the process through which contaminants or pollutants in soil, water and other media are removed to improve environmental quality. the main focus is the reduction of hazardous substances within the environment. some of the areas involved in environmental remediation include ; soil contamination, hazardous waste, groundwater contamination, oil, gas and chemical spills. there are three most common types of environmental remediation. these include soil, water, and sediment remediation. soil remediation consists of removing contaminants in soil, as these pose great risks to humans and the ecosystem. some examples of this are heavy metals, pesticides, and radioactive materials. depending on the contaminant the remedial processes can be physical, chemical, thermal, or biological. water remediation is one of the most important considering water is an essential natural resource. depending on the source of water there will be different contaminants. surface water contamination mainly consists of agricultural, animal, and industrial waste, as well as acid mine drainage. there has been a rise in the need for water remediation due to the increased discharge of industrial waste, leading to a demand for sustainable water solutions. the market for water remediation is expected to consistently increase to $ 19. 6 billion by 2030. sediment remediation consists of removing contaminated sediments. is it almost similar to soil remediation except it is often more sophisticated as it involves additional contaminants. to reduce the contaminants it is likely to use physical, chemical, and biological processes that help with source control, but if these processes are executed correctly, there ' s a risk of contamination resurfacing. = = = solid waste management = = = solid waste management is the purification, consumption, reuse, disposal, and treatment of solid waste that is undertaken by the government or the ruling bodies of a city / town. it refers to the collection, treatment, and disposal of non - soluble, solid waste material. solid waste is associated with both industrial, institutional, commercial and residential activities. hazardous solid waste, when improperly disposed can encourage the infestation of insects and rodents, contributing to the spread of diseases. some of the most common types of solid waste management include ; landfills, vermicomposting, composting, recycling, and incineration. however, a major barrier for solid waste management practices is the high costs associated with recycling
generally, dead - end filtration is used for feasibility studies on a laboratory scale. the dead - end membranes are relatively easy to fabricate which reduces the cost of the separation process. the dead - end membrane separation process is easy to implement and the process is usually cheaper than cross - flow membrane filtration. the dead - end filtration process is usually a batch - type process, where the filtering solution is loaded ( or slowly fed ) into the membrane device, which then allows passage of some particles subject to the driving force. the main disadvantage of dead - end filtration is the extensive membrane fouling and concentration polarization. the fouling is usually induced faster at higher driving forces. membrane fouling and particle retention in a feed solution also builds up a concentration gradients and particle backflow ( concentration polarization ). the tangential flow devices are more cost and labor - intensive, but they are less susceptible to fouling due to the sweeping effects and high shear rates of the passing flow. the most commonly used synthetic membrane devices ( modules ) are flat sheets / plates, spiral wounds, and hollow fibers. flat membranes used in filtration and separation processes can be enhanced with surface patterning, where microscopic structures are introduced to improve performance. these patterns increase surface area, optimize water flow, and reduce fouling, leading to higher permeability and longer membrane lifespan. research has shown that such modifications can significantly enhance efficiency in water purification, energy applications, and industrial separations. flat plates are usually constructed as circular thin flat membrane surfaces to be used in dead - end geometry modules. spiral wounds are constructed from similar flat membranes but in the form of a " pocket " containing two membrane sheets separated by a highly porous support plate. several such pockets are then wound around a tube to create a tangential flow geometry and to reduce membrane fouling. hollow fiber modules consist of an assembly of self - supporting fibers with dense skin separation layers, and a more open matrix helping to withstand pressure gradients and maintain structural integrity. the hollow fiber modules can contain up to 10, 000 fibers ranging from 200 to 2500 ΞΌm in diameter ; the main advantage of hollow fiber modules is the very large surface area within an enclosed volume, increasing the efficiency of the separation process. the disc tube module uses a cross - flow geometry and consists of a pressure tube and hydraulic discs, which are held by a central tension rod, and membrane cushions that lie between two discs. = = membrane performance and governing equations = = the selection of synthetic membranes
soft interactions are not easily disentangled from hard ones. in an operational definition of soft and hard processes one finds that at presently analyzed scales there is an interplay of soft and hard processes. as the scale increases, so does the amount of hard processes. so far, nothing is as soft nor as hard as we would like.
##g mills. wet mixing generally involves the same equipment. forming is making the mixed material into shapes, ranging from toilet bowls to spark plug insulators. forming can involve : ( 1 ) extrusion, such as extruding " slugs " to make bricks, ( 2 ) pressing to make shaped parts, ( 3 ) slip casting, as in making toilet bowls, wash basins and ornamentals like ceramic statues. forming produces a " green " part, ready for drying. green parts are soft, pliable, and over time will lose shape. handling the green product will change its shape. for example, a green brick can be " squeezed ", and after squeezing it will stay that way. drying is removing the water or binder from the formed material. spray drying is widely used to prepare powder for pressing operations. other dryers are tunnel dryers and periodic dryers. controlled heat is applied in this two - stage process. first, heat removes water. this step needs careful control, as rapid heating causes cracks and surface defects. the dried part is smaller than the green part, and is brittle, necessitating careful handling, since a small impact will cause crumbling and breaking. sintering is where the dried parts pass through a controlled heating process, and the oxides are chemically changed to cause bonding and densification. the fired part will be smaller than the dried part. = = forming methods = = ceramic forming techniques include throwing, slipcasting, tape casting, freeze - casting, injection molding, dry pressing, isostatic pressing, hot isostatic pressing ( hip ), 3d printing and others. methods for forming ceramic powders into complex shapes are desirable in many areas of technology. such methods are required for producing advanced, high - temperature structural parts such as heat engine components and turbines. materials other than ceramics which are used in these processes may include : wood, metal, water, plaster and epoxy β most of which will be eliminated upon firing. a ceramic - filled epoxy, such as martyte, is sometimes used to protect structural steel under conditions of rocket exhaust impingement. these forming techniques are well known for providing tools and other components with dimensional stability, surface quality, high ( near theoretical ) density and microstructural uniformity. the increasing use and diversity of specialty forms of ceramics adds to the diversity of process technologies to be used. thus, reinforcing fibers and filaments are mainly made by polymer, sol - gel, or cvd processes, but melt
. batching is the process of weighing the oxides according to recipes, and preparing them for mixing and drying. mixing occurs after batching and is performed with various machines, such as dry mixing ribbon mixers ( a type of cement mixer ), resonantacoustic mixers, mueller mixers, and pug mills. wet mixing generally involves the same equipment. forming is making the mixed material into shapes, ranging from toilet bowls to spark plug insulators. forming can involve : ( 1 ) extrusion, such as extruding " slugs " to make bricks, ( 2 ) pressing to make shaped parts, ( 3 ) slip casting, as in making toilet bowls, wash basins and ornamentals like ceramic statues. forming produces a " green " part, ready for drying. green parts are soft, pliable, and over time will lose shape. handling the green product will change its shape. for example, a green brick can be " squeezed ", and after squeezing it will stay that way. drying is removing the water or binder from the formed material. spray drying is widely used to prepare powder for pressing operations. other dryers are tunnel dryers and periodic dryers. controlled heat is applied in this two - stage process. first, heat removes water. this step needs careful control, as rapid heating causes cracks and surface defects. the dried part is smaller than the green part, and is brittle, necessitating careful handling, since a small impact will cause crumbling and breaking. sintering is where the dried parts pass through a controlled heating process, and the oxides are chemically changed to cause bonding and densification. the fired part will be smaller than the dried part. = = forming methods = = ceramic forming techniques include throwing, slipcasting, tape casting, freeze - casting, injection molding, dry pressing, isostatic pressing, hot isostatic pressing ( hip ), 3d printing and others. methods for forming ceramic powders into complex shapes are desirable in many areas of technology. such methods are required for producing advanced, high - temperature structural parts such as heat engine components and turbines. materials other than ceramics which are used in these processes may include : wood, metal, water, plaster and epoxy β most of which will be eliminated upon firing. a ceramic - filled epoxy, such as martyte, is sometimes used to protect structural steel under conditions of rocket exhaust impingement. these forming techniques are well known for providing tools and other components with dimensional stability, surface quality
becomes quite gentle. accordingly, in large basins, rivers in most cases begin as torrents with a variable flow, and end as gently flowing rivers with a comparatively regular discharge. the irregular flow of rivers throughout their course forms one of the main difficulties in devising works for mitigating inundations or for increasing the navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with a rapid fall near the sources of rivers can carry down rocks, boulders and large stones, which are by degrees ground by attrition in their onward course into slate, gravel, sand and silt, simultaneously with the gradual reduction in fall, and, consequently, in the transporting force of the current. accordingly, under
which applies a forces that results in fracturing ), and impact ( which employs a milling medium or the particles themselves to cause fracturing ). attrition milling equipment includes the wet scrubber ( also called the planetary mill or wet attrition mill ), which has paddles in water creating vortexes in which the material collides and break up. compression mills include the jaw crusher, roller crusher and cone crusher. impact mills include the ball mill, which has media that tumble and fracture the material, or the resonantacoustic mixer. shaft impactors cause particle - to particle attrition and compression. batching is the process of weighing the oxides according to recipes, and preparing them for mixing and drying. mixing occurs after batching and is performed with various machines, such as dry mixing ribbon mixers ( a type of cement mixer ), resonantacoustic mixers, mueller mixers, and pug mills. wet mixing generally involves the same equipment. forming is making the mixed material into shapes, ranging from toilet bowls to spark plug insulators. forming can involve : ( 1 ) extrusion, such as extruding " slugs " to make bricks, ( 2 ) pressing to make shaped parts, ( 3 ) slip casting, as in making toilet bowls, wash basins and ornamentals like ceramic statues. forming produces a " green " part, ready for drying. green parts are soft, pliable, and over time will lose shape. handling the green product will change its shape. for example, a green brick can be " squeezed ", and after squeezing it will stay that way. drying is removing the water or binder from the formed material. spray drying is widely used to prepare powder for pressing operations. other dryers are tunnel dryers and periodic dryers. controlled heat is applied in this two - stage process. first, heat removes water. this step needs careful control, as rapid heating causes cracks and surface defects. the dried part is smaller than the green part, and is brittle, necessitating careful handling, since a small impact will cause crumbling and breaking. sintering is where the dried parts pass through a controlled heating process, and the oxides are chemically changed to cause bonding and densification. the fired part will be smaller than the dried part. = = forming methods = = ceramic forming techniques include throwing, slipcasting, tape casting, freeze - casting, injection molding, dry pressing, isostatic pressing, hot isostatic pressing
Question: Is purifying water a simple or complicated process?
A) simple
B) impossible
C) expensive
D) complicated
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D) complicated
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Context:
a graviton laser works, in principle, by the stimulated emission of coherent gravitons from a lasing medium. for significant amplification, we must have a very long path length and / or very high densities. black holes and the existence of weakly interacting sub - ev dark matter particles ( wisps ) solve both of these obstacles. orbiting trajectories for massless particles around black holes are well understood \ cite { mtw } and allow for arbitrarily long graviton path lengths. superradiance from kerr black holes of wisps can provide the sufficiently high density \ cite { abh }. this suggests that black holes can act as efficient graviton lasers. thus directed graviton laser beams have been emitted since the beginning of the universe and give rise to new sources of gravitational wave signals. to be in the path of particularly harmfully amplified graviton death rays will not be pleasant.
listen ), generally in that order, although auscultation occurs prior to percussion and palpation for abdominal assessments. the clinical examination involves the study of : abdomen and rectum cardiovascular ( heart and blood vessels ) general appearance of the patient and specific indicators of disease ( nutritional status, presence of jaundice, pallor or clubbing ) genitalia ( and pregnancy if the patient is or could be pregnant ) head, eye, ear, nose, and throat ( heent ) musculoskeletal ( including spine and extremities ) neurological ( consciousness, awareness, brain, vision, cranial nerves, spinal cord and peripheral nerves ) psychiatric ( orientation, mental state, mood, evidence of abnormal perception or thought ). respiratory ( large airways and lungs ) skin vital signs including height, weight, body temperature, blood pressure, pulse, respiration rate, and hemoglobin oxygen saturation it is to likely focus on areas of interest highlighted in the medical history and may not include everything listed above. the treatment plan may include ordering additional medical laboratory tests and medical imaging studies, starting therapy, referral to a specialist, or watchful observation. a follow - up may be advised. depending upon the health insurance plan and the managed care system, various forms of " utilization review ", such as prior authorization of tests, may place barriers on accessing expensive services. the medical decision - making ( mdm ) process includes the analysis and synthesis of all the above data to come up with a list of possible diagnoses ( the differential diagnoses ), along with an idea of what needs to be done to obtain a definitive diagnosis that would explain the patient ' s problem. on subsequent visits, the process may be repeated in an abbreviated manner to obtain any new history, symptoms, physical findings, lab or imaging results, or specialist consultations. = = institutions = = contemporary medicine is, in general, conducted within health care systems. legal, credentialing, and financing frameworks are established by individual governments, augmented on occasion by international organizations, such as churches. the characteristics of any given health care system have a significant impact on the way medical care is provided. from ancient times, christian emphasis on practical charity gave rise to the development of systematic nursing and hospitals, and the catholic church today remains the largest non - government provider of medical services in the world. advanced industrial countries ( with the exception of the united states ) and many developing countries provide medical services through a system of universal health care that aims to
, characterizing organs as predominantly yin or yang, and understood the relationship between the pulse, the heart, and the flow of blood in the body centuries before it became accepted in the west. little evidence survives of how ancient indian cultures around the indus river understood nature, but some of their perspectives may be reflected in the vedas, a set of sacred hindu texts. they reveal a conception of the universe as ever - expanding and constantly being recycled and reformed. surgeons in the ayurvedic tradition saw health and illness as a combination of three humors : wind, bile and phlegm. a healthy life resulted from a balance among these humors. in ayurvedic thought, the body consisted of five elements : earth, water, fire, wind, and space. ayurvedic surgeons performed complex surgeries and developed a detailed understanding of human anatomy. pre - socratic philosophers in ancient greek culture brought natural philosophy a step closer to direct inquiry about cause and effect in nature between 600 and 400 bc. however, an element of magic and mythology remained. natural phenomena such as earthquakes and eclipses were explained increasingly in the context of nature itself instead of being attributed to angry gods. thales of miletus, an early philosopher who lived from 625 to 546 bc, explained earthquakes by theorizing that the world floated on water and that water was the fundamental element in nature. in the 5th century bc, leucippus was an early exponent of atomism, the idea that the world is made up of fundamental indivisible particles. pythagoras applied greek innovations in mathematics to astronomy and suggested that the earth was spherical. = = = aristotelian natural philosophy ( 400 bc β 1100 ad ) = = = later socratic and platonic thought focused on ethics, morals, and art and did not attempt an investigation of the physical world ; plato criticized pre - socratic thinkers as materialists and anti - religionists. aristotle, however, a student of plato who lived from 384 to 322 bc, paid closer attention to the natural world in his philosophy. in his history of animals, he described the inner workings of 110 species, including the stingray, catfish and bee. he investigated chick embryos by breaking open eggs and observing them at various stages of development. aristotle ' s works were influential through the 16th century, and he is considered to be the father of biology for his pioneering work in that science. he also presented philosophies about physics, nature, and astronomy using
both a monomorphism and an epimorphism. a retraction if it has a right inverse, i. e. if there exists a morphism g : b β a with fg = 1b. a section if it has a left inverse, i. e. if there exists a morphism g : b β a with gf = 1a. an isomorphism if it has an inverse, i. e. if there exists a morphism g : b β a with fg = 1b and gf = 1a. an endomorphism if a = b. the class of endomorphisms of a is denoted end ( a ). for locally small categories, end ( a ) is a set and forms a monoid under morphism composition. an automorphism if f is both an endomorphism and an isomorphism. the class of automorphisms of a is denoted aut ( a ). for locally small categories, it forms a group under morphism composition called the automorphism group of a. every retraction is an epimorphism. every section is a monomorphism. the following three statements are equivalent : f is a monomorphism and a retraction ; f is an epimorphism and a section ; f is an isomorphism. relations among morphisms ( such as fg = h ) can most conveniently be represented with commutative diagrams, where the objects are represented as points and the morphisms as arrows. = = types of categories = = in many categories, e. g. ab or vectk, the hom - sets hom ( a, b ) are not just sets but actually abelian groups, and the composition of morphisms is compatible with these group structures ; i. e. is bilinear. such a category is called preadditive. if, furthermore, the category has all finite products and coproducts, it is called an additive category. if all morphisms have a kernel and a cokernel, and all epimorphisms are cokernels and all monomorphisms are kernels, then we speak of an abelian category. a typical example of an abelian category is the category of abelian groups. a category is called complete if all small limits exist in it. the categories of sets, abelian groups and topological spaces are complete. a category is called cartesian closed if it has finite direct products and a morphism
beam reveals the object ' s location. since radio waves travel at a constant speed close to the speed of light, by measuring the brief time delay between the outgoing pulse and the received " echo ", the range to the target can be calculated. the targets are often displayed graphically on a map display called a radar screen. doppler radar can measure a moving object ' s velocity, by measuring the change in frequency of the return radio waves due to the doppler effect. radar sets mainly use high frequencies in the microwave bands, because these frequencies create strong reflections from objects the size of vehicles and can be focused into narrow beams with compact antennas. parabolic ( dish ) antennas are widely used. in most radars the transmitting antenna also serves as the receiving antenna ; this is called a monostatic radar. a radar which uses separate transmitting and receiving antennas is called a bistatic radar. airport surveillance radar β in aviation, radar is the main tool of air traffic control. a rotating dish antenna sweeps a vertical fan - shaped beam of microwaves around the airspace and the radar set shows the location of aircraft as " blips " of light on a display called a radar screen. airport radar operates at 2. 7 β 2. 9 ghz in the microwave s band. in large airports the radar image is displayed on multiple screens in an operations room called the tracon ( terminal radar approach control ), where air traffic controllers direct the aircraft by radio to maintain safe aircraft separation. secondary surveillance radar β aircraft carry radar transponders, transceivers which when triggered by the incoming radar signal transmit a return microwave signal. this causes the aircraft to show up more strongly on the radar screen. the radar which triggers the transponder and receives the return beam, usually mounted on top of the primary radar dish, is called the secondary surveillance radar. since radar cannot measure an aircraft ' s altitude with any accuracy, the transponder also transmits back the aircraft ' s altitude measured by its altimeter, and an id number identifying the aircraft, which is displayed on the radar screen. electronic countermeasures ( ecm ) β military defensive electronic systems designed to degrade enemy radar effectiveness, or deceive it with false information, to prevent enemies from locating local forces. it often consists of powerful microwave transmitters that can mimic enemy radar signals to create false target indications on the enemy radar screens. marine radar β an s or x band radar on ships used to detect nearby ships and obstructions like bridges. a rotating antenna sweeps a vertical
be at most one morphism between any two objects. the existence of identity morphisms and the composability of the morphisms are guaranteed by the reflexivity and the transitivity of the preorder. by the same argument, any partially ordered set and any equivalence relation can be seen as a small category. any ordinal number can be seen as a category when viewed as an ordered set. any monoid ( any algebraic structure with a single associative binary operation and an identity element ) forms a small category with a single object x. ( here, x is any fixed set. ) the morphisms from x to x are precisely the elements of the monoid, the identity morphism of x is the identity of the monoid, and the categorical composition of morphisms is given by the monoid operation. several definitions and theorems about monoids may be generalized for categories. similarly any group can be seen as a category with a single object in which every morphism is invertible, that is, for every morphism f there is a morphism g that is both left and right inverse to f under composition. a morphism that is invertible in this sense is called an isomorphism. a groupoid is a category in which every morphism is an isomorphism. groupoids are generalizations of groups, group actions and equivalence relations. actually, in the view of category the only difference between groupoid and group is that a groupoid may have more than one object but the group must have only one. consider a topological space x and fix a base point x 0 { \ displaystyle x _ { 0 } } of x, then Ο 1 ( x, x 0 ) { \ displaystyle \ pi _ { 1 } ( x, x _ { 0 } ) } is the fundamental group of the topological space x and the base point x 0 { \ displaystyle x _ { 0 } }, and as a set it has the structure of group ; if then let the base point x 0 { \ displaystyle x _ { 0 } } runs over all points of x, and take the union of all Ο 1 ( x, x 0 ) { \ displaystyle \ pi _ { 1 } ( x, x _ { 0 } ) }, then the set we get has only the structure of groupoid ( which is called as the fundamental groupoid of x ) : two loops ( under equivalence relation of homotopy ) may
subject. electronics engineers typically possess an academic degree with a major in electronics engineering. the length of study for such a degree is usually three or four years and the completed degree may be designated as a bachelor of engineering, bachelor of science, bachelor of applied science, or bachelor of technology depending upon the university. many uk universities also offer master of engineering ( meng ) degrees at the graduate level. some electronics engineers also choose to pursue a postgraduate degree such as a master of science, doctor of philosophy in engineering, or an engineering doctorate. the master ' s degree is being introduced in some european and american universities as a first degree and the differentiation of an engineer with graduate and postgraduate studies is often difficult. in these cases, experience is taken into account. the master ' s degree may consist of either research, coursework or a mixture of the two. the doctor of philosophy consists of a significant research component and is often viewed as the entry point to academia. in most countries, a bachelor ' s degree in engineering represents the first step towards certification and the degree program itself is certified by a professional body. certification allows engineers to legally sign off on plans for projects affecting public safety. after completing a certified degree program, the engineer must satisfy a range of requirements, including work experience requirements, before being certified. once certified the engineer is designated the title of professional engineer ( in the united states, canada, and south africa ), chartered engineer or incorporated engineer ( in the united kingdom, ireland, india, and zimbabwe ), chartered professional engineer ( in australia and new zealand ) or european engineer ( in much of the european union ). a degree in electronics generally includes units covering physics, chemistry, mathematics, project management and specific topics in electrical engineering. initially, such topics cover most, if not all, of the subfields of electronics engineering. students then choose to specialize in one or more subfields towards the end of the degree. fundamental to the discipline are the sciences of physics and mathematics as these help to obtain both a qualitative and quantitative description of how such systems will work. today, most engineering work involves the use of computers and it is commonplace to use computer - aided design and simulation software programs when designing electronic systems. although most electronic engineers will understand basic circuit theory, the theories employed by engineers generally depend upon the work they do. for example, quantum mechanics and solid - state physics might be relevant to an engineer working on vlsi but are largely irrelevant to engineers working with embedded systems. apart from electromagnetics and network theory, other items in the
defective body parts. inside the body, artificial heart valves are in common use with artificial hearts and lungs seeing less common use but under active technology development. other medical devices and aids that can be considered prosthetics include hearing aids, artificial eyes, palatal obturator, gastric bands, and dentures. prostheses are specifically not orthoses, although given certain circumstances a prosthesis might end up performing some or all of the same functionary benefits as an orthosis. prostheses are technically the complete finished item. for instance, a c - leg knee alone is not a prosthesis, but only a prosthetic component. the complete prosthesis would consist of the attachment system to the residual limb β usually a " socket ", and all the attachment hardware components all the way down to and including the terminal device. despite the technical difference, the terms are often used interchangeably. the terms " prosthetic " and " orthotic " are adjectives used to describe devices such as a prosthetic knee. the terms " prosthetics " and " orthotics " are used to describe the respective allied health fields. an occupational therapist ' s role in prosthetics include therapy, training and evaluations. prosthetic training includes orientation to prosthetics components and terminology, donning and doffing, wearing schedule, and how to care for residual limb and the prosthesis. = = = exoskeletons = = = a powered exoskeleton is a wearable mobile machine that is powered by a system of electric motors, pneumatics, levers, hydraulics, or a combination of technologies that allow for limb movement with increased strength and endurance. its design aims to provide back support, sense the user ' s motion, and send a signal to motors which manage the gears. the exoskeleton supports the shoulder, waist and thigh, and assists movement for lifting and holding heavy items, while lowering back stress. = = = adaptive seating and positioning = = = people with balance and motor function challenges often need specialized equipment to sit or stand safely and securely. this equipment is frequently specialized for specific settings such as in a classroom or nursing home. positioning is often important in seating arrangements to ensure that user ' s body pressure is distributed equally without inhibiting movement in a desired way. positioning devices have been developed to aid in allowing people to stand and bear weight on their legs without risk of a fall.
hand axes emerged. this early stone age is described as the lower paleolithic. the middle paleolithic, approximately 300, 000 years ago, saw the introduction of the prepared - core technique, where multiple blades could be rapidly formed from a single core stone. the upper paleolithic, beginning approximately 40, 000 years ago, saw the introduction of pressure flaking, where a wood, bone, or antler punch could be used to shape a stone very finely. the end of the last ice age about 10, 000 years ago is taken as the end point of the upper paleolithic and the beginning of the epipaleolithic / mesolithic. the mesolithic technology included the use of microliths as composite stone tools, along with wood, bone, and antler tools. the later stone age, during which the rudiments of agricultural technology were developed, is called the neolithic period. during this period, polished stone tools were made from a variety of hard rocks such as flint, jade, jadeite, and greenstone, largely by working exposures as quarries, but later the valuable rocks were pursued by tunneling underground, the first steps in mining technology. the polished axes were used for forest clearance and the establishment of crop farming and were so effective as to remain in use when bronze and iron appeared. these stone axes were used alongside a continued use of stone tools such as a range of projectiles, knives, and scrapers, as well as tools, made from organic materials such as wood, bone, and antler. stone age cultures developed music and engaged in organized warfare. stone age humans developed ocean - worthy outrigger canoe technology, leading to migration across the malay archipelago, across the indian ocean to madagascar and also across the pacific ocean, which required knowledge of the ocean currents, weather patterns, sailing, and celestial navigation. although paleolithic cultures left no written records, the shift from nomadic life to settlement and agriculture can be inferred from a range of archaeological evidence. such evidence includes ancient tools, cave paintings, and other prehistoric art, such as the venus of willendorf. human remains also provide direct evidence, both through the examination of bones, and the study of mummies. scientists and historians have been able to form significant inferences about the lifestyle and culture of various prehistoric peoples, and especially their technology. = = = ancient = = = = = = = copper and bronze ages = = = = metallic copper occurs on the surface of weathered copper ore deposits and copper
often called physicians. these terms, internist or physician ( in the narrow sense, common outside north america ), generally exclude practitioners of gynecology and obstetrics, pathology, psychiatry, and especially surgery and its subspecialities. because their patients are often seriously ill or require complex investigations, internists do much of their work in hospitals. formerly, many internists were not subspecialized ; such general physicians would see any complex nonsurgical problem ; this style of practice has become much less common. in modern urban practice, most internists are subspecialists : that is, they generally limit their medical practice to problems of one organ system or to one particular area of medical knowledge. for example, gastroenterologists and nephrologists specialize respectively in diseases of the gut and the kidneys. in the commonwealth of nations and some other countries, specialist pediatricians and geriatricians are also described as specialist physicians ( or internists ) who have subspecialized by age of patient rather than by organ system. elsewhere, especially in north america, general pediatrics is often a form of primary care. there are many subspecialities ( or subdisciplines ) of internal medicine : training in internal medicine ( as opposed to surgical training ), varies considerably across the world : see the articles on medical education for more details. in north america, it requires at least three years of residency training after medical school, which can then be followed by a one - to three - year fellowship in the subspecialties listed above. in general, resident work hours in medicine are less than those in surgery, averaging about 60 hours per week in the us. this difference does not apply in the uk where all doctors are now required by law to work less than 48 hours per week on average. = = = = diagnostic specialties = = = = clinical laboratory sciences are the clinical diagnostic services that apply laboratory techniques to diagnosis and management of patients. in the united states, these services are supervised by a pathologist. the personnel that work in these medical laboratory departments are technically trained staff who do not hold medical degrees, but who usually hold an undergraduate medical technology degree, who actually perform the tests, assays, and procedures needed for providing the specific services. subspecialties include transfusion medicine, cellular pathology, clinical chemistry, hematology, clinical microbiology and clinical immunology. clinical neurophysiology is concerned with testing the physiology or function of the central and peripheral aspects of
Question: What is a sac-like organ at the end of the esophagus?
A) appendix
B) larynx
C) the stomach
D) spleen
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C) the stomach
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Context:
electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature. = = = = substance and mixture = = = = a chemical substance is a kind of matter with a definite composition and set of properties. a collection of substances is called a mixture. examples of mixtures are air and alloys. = = = = mole and amount of substance = = = = the mole is a unit of measurement that denotes an amount of substance ( also called chemical amount ). one mole is defined to contain exactly 6. 02214076Γ1023 particles ( atoms, molecules, ions, or electrons ), where the number of particles per mole is known as the avogadro constant. molar concentration is the amount of a particular substance per volume of solution, and is commonly reported in mol / dm3. = = = phase = = = in addition to the specific chemical properties that distinguish different chemical classifications, chemicals can exist in several phases. for the most part, the chemical classifications are independent of these bulk phase
, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature. = = = = substance and mixture = = = = a chemical substance is a kind of matter with a definite composition and set of properties. a collection of substances is called a mixture. examples of mixtures are air and alloys. = = = = mole and amount of substance = = = = the mole is a unit of measurement that denotes an amount of substance ( also called chemical amount ). one mole is defined to contain exactly 6. 02214076Γ1023 particles ( atoms, molecules, ions, or electrons ), where the number of particles per mole is known as the avogadro constant. molar concentration is the amount of a particular substance per volume of solution, and is commonly reported in mol / dm3. = = = phase = = = in addition to the specific chemical properties that distinguish different chemical classifications, chemicals can exist in several phases. for the most part, the chemical classifications are independent of these bulk phase classifications ; however, some more exotic phases are incompatible with certain chemical properties. a phase is a set of states of a chemical system that have similar bulk structural properties, over a range of conditions, such as pressure or temperature. physical properties, such as density and refractive index tend to fall within values characteristic of the phase
that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature. = = = = substance and mixture = = = = a chemical substance is a kind of matter with a definite composition and set of properties. a collection of substances is called a mixture. examples of mixtures are air and alloys. = = = = mole and amount of substance = = = = the mole is a unit of measurement that denotes an amount of substance ( also called chemical amount ). one mole is defined to contain exactly 6. 02214076Γ1023 particles ( atoms, molecules, ions, or electrons ), where the number of particles per mole is known as the avogadro constant. molar concentration is
set of chemical reactions with other substances. however, this definition only works well for substances that are composed of molecules, which is not true of many substances ( see below ). molecules are typically a set of atoms bound together by covalent bonds, such that the structure is electrically neutral and all valence electrons are paired with other electrons either in bonds or in lone pairs. thus, molecules exist as electrically neutral units, unlike ions. when this rule is broken, giving the " molecule " a charge, the result is sometimes named a molecular ion or a polyatomic ion. however, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature.
index chemical substances. in this scheme each chemical substance is identifiable by a number known as its cas registry number. = = = = molecule = = = = a molecule is the smallest indivisible portion of a pure chemical substance that has its unique set of chemical properties, that is, its potential to undergo a certain set of chemical reactions with other substances. however, this definition only works well for substances that are composed of molecules, which is not true of many substances ( see below ). molecules are typically a set of atoms bound together by covalent bonds, such that the structure is electrically neutral and all valence electrons are paired with other electrons either in bonds or in lone pairs. thus, molecules exist as electrically neutral units, unlike ions. when this rule is broken, giving the " molecule " a charge, the result is sometimes named a molecular ion or a polyatomic ion. however, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry
other electrons either in bonds or in lone pairs. thus, molecules exist as electrically neutral units, unlike ions. when this rule is broken, giving the " molecule " a charge, the result is sometimes named a molecular ion or a polyatomic ion. however, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature. = = = = substance and mixture = = = = a chemical substance is a kind of matter with a definite composition and set of properties. a collection of substances is called a mixture. examples of mixtures are air and alloys. = = = = mole and amount of substance = = = = the mole is a unit
of measurement that denotes an amount of substance ( also called chemical amount ). one mole is defined to contain exactly 6. 02214076Γ1023 particles ( atoms, molecules, ions, or electrons ), where the number of particles per mole is known as the avogadro constant. molar concentration is the amount of a particular substance per volume of solution, and is commonly reported in mol / dm3. = = = phase = = = in addition to the specific chemical properties that distinguish different chemical classifications, chemicals can exist in several phases. for the most part, the chemical classifications are independent of these bulk phase classifications ; however, some more exotic phases are incompatible with certain chemical properties. a phase is a set of states of a chemical system that have similar bulk structural properties, over a range of conditions, such as pressure or temperature. physical properties, such as density and refractive index tend to fall within values characteristic of the phase. the phase of matter is defined by the phase transition, which is when energy put into or taken out of the system goes into rearranging the structure of the system, instead of changing the bulk conditions. sometimes the distinction between phases can be continuous instead of having a discrete boundary ; in this case the matter is considered to be in a supercritical state. when three states meet based on the conditions, it is known as a triple point and since this is invariant, it is a convenient way to define a set of conditions. the most familiar examples of phases are solids, liquids, and gases. many substances exhibit multiple solid phases. for example, there are three phases of solid iron ( alpha, gamma, and delta ) that vary based on temperature and pressure. a principal difference between solid phases is the crystal structure, or arrangement, of the atoms. another phase commonly encountered in the study of chemistry is the aqueous phase, which is the state of substances dissolved in aqueous solution ( that is, in water ). less familiar phases include plasmas, bose β einstein condensates and fermionic condensates and the paramagnetic and ferromagnetic phases of magnetic materials. while most familiar phases deal with three - dimensional systems, it is also possible to define analogs in two - dimensional systems, which has received attention for its relevance to systems in biology. = = = bonding = = = atoms sticking together in molecules or crystals are said to be bonded with one another. a chemical bond may be visualized as the multipole balance between the positive
the thickness and the density of the material to be measured. the method is used for containers of liquids or of grainy substances thickness gauges : if the material is of constant density, the signal measured by the radiation detector depends on the thickness of the material. this is useful for continuous production, like of paper, rubber, etc. electrostatic control - to avoid the build - up of static electricity in production of paper, plastics, synthetic textiles, etc., a ribbon - shaped source of the alpha emitter 241am can be placed close to the material at the end of the production line. the source ionizes the air to remove electric charges on the material. radioactive tracers - since radioactive isotopes behave, chemically, mostly like the inactive element, the behavior of a certain chemical substance can be followed by tracing the radioactivity. examples : adding a gamma tracer to a gas or liquid in a closed system makes it possible to find a hole in a tube. adding a tracer to the surface of the component of a motor makes it possible to measure wear by measuring the activity of the lubricating oil. oil and gas exploration - nuclear well logging is used to help predict the commercial viability of new or existing wells. the technology involves the use of a neutron or gamma - ray source and a radiation detector which are lowered into boreholes to determine the properties of the surrounding rock such as porosity and lithography. [ 1 ] road construction - nuclear moisture / density gauges are used to determine the density of soils, asphalt, and concrete. typically a cesium - 137 source is used. = = = commercial applications = = = radioluminescence tritium illumination : tritium is used with phosphor in rifle sights to increase nighttime firing accuracy. some runway markers and building exit signs use the same technology, to remain illuminated during blackouts. betavoltaics. smoke detector : an ionization smoke detector includes a tiny mass of radioactive americium - 241, which is a source of alpha radiation. two ionisation chambers are placed next to each other. both contain a small source of 241am that gives rise to a small constant current. one is closed and serves for comparison, the other is open to ambient air ; it has a gridded electrode. when smoke enters the open chamber, the current is disrupted as the smoke particles attach to the charged ions and restore them to a neutral electrical state. this reduces the current in the open chamber. when the current drops below a certain threshold, the
based on 1 / 10 and 1 / 100 weight percentages of the carbon and other alloying elements they contain. thus, the extracting and purifying methods used to extract iron in a blast furnace can affect the quality of steel that is produced. solid materials are generally grouped into three basic classifications : ceramics, metals, and polymers. this broad classification is based on the empirical makeup and atomic structure of the solid materials, and most solids fall into one of these broad categories. an item that is often made from each of these materials types is the beverage container. the material types used for beverage containers accordingly provide different advantages and disadvantages, depending on the material used. ceramic ( glass ) containers are optically transparent, impervious to the passage of carbon dioxide, relatively inexpensive, and are easily recycled, but are also heavy and fracture easily. metal ( aluminum alloy ) is relatively strong, is a good barrier to the diffusion of carbon dioxide, and is easily recycled. however, the cans are opaque, expensive to produce, and are easily dented and punctured. polymers ( polyethylene plastic ) are relatively strong, can be optically transparent, are inexpensive and lightweight, and can be recyclable, but are not as impervious to the passage of carbon dioxide as aluminum and glass. = = = ceramics and glasses = = = another application of materials science is the study of ceramics and glasses, typically the most brittle materials with industrial relevance. many ceramics and glasses exhibit covalent or ionic - covalent bonding with sio2 ( silica ) as a fundamental building block. ceramics β not to be confused with raw, unfired clay β are usually seen in crystalline form. the vast majority of commercial glasses contain a metal oxide fused with silica. at the high temperatures used to prepare glass, the material is a viscous liquid which solidifies into a disordered state upon cooling. windowpanes and eyeglasses are important examples. fibers of glass are also used for long - range telecommunication and optical transmission. scratch resistant corning gorilla glass is a well - known example of the application of materials science to drastically improve the properties of common components. engineering ceramics are known for their stiffness and stability under high temperatures, compression and electrical stress. alumina, silicon carbide, and tungsten carbide are made from a fine powder of their constituents in a process of sintering with a binder. hot pressing provides higher density material. chemical vapor deposition can place a film of a ceramic on another
the motion of celestial bodies through a higher power such as god. aristotle did not have the technological advancements that would have explained the motion of celestial bodies. in addition, aristotle had many views on the elements. he believed that everything was derived of the elements earth, water, air, fire, and lastly the aether. the aether was a celestial element, and therefore made up the matter of the celestial bodies. the elements of earth, water, air and fire were derived of a combination of two of the characteristics of hot, wet, cold, and dry, and all had their inevitable place and motion. the motion of these elements begins with earth being the closest to " the earth, " then water, air, fire, and finally aether. in addition to the makeup of all things, aristotle came up with theories as to why things did not return to their natural motion. he understood that water sits above earth, air above water, and fire above air in their natural state. he explained that although all elements must return to their natural state, the human body and other living things have a constraint on the elements β thus not allowing the elements making one who they are to return to their natural state. the important legacy of this period included substantial advances in factual knowledge, especially in anatomy, zoology, botany, mineralogy, geography, mathematics and astronomy ; an awareness of the importance of certain scientific problems, especially those related to the problem of change and its causes ; and a recognition of the methodological importance of applying mathematics to natural phenomena and of undertaking empirical research. in the hellenistic age scholars frequently employed the principles developed in earlier greek thought : the application of mathematics and deliberate empirical research, in their scientific investigations. thus, clear unbroken lines of influence lead from ancient greek and hellenistic philosophers, to medieval muslim philosophers and scientists, to the european renaissance and enlightenment, to the secular sciences of the modern day. neither reason nor inquiry began with the ancient greeks, but the socratic method did, along with the idea of forms, give great advances in geometry, logic, and the natural sciences. according to benjamin farrington, former professor of classics at swansea university : " men were weighing for thousands of years before archimedes worked out the laws of equilibrium ; they must have had practical and intuitional knowledge of the principals involved. what archimedes did was to sort out the theoretical implications of this practical knowledge and present the resulting body of knowledge as a logically coherent system. " and again : " with astonishment we find ourselves on the threshold of modern science
Question: Substances may be either elements or what?
A) pure chemicals
B) pure compounds
C) fundamental compounds
D) existent compounds
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B) pure compounds
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Context:
pigment chlorophyll a. chlorophyll a ( as well as its plant and green algal - specific cousin chlorophyll b ) absorbs light in the blue - violet and orange / red parts of the spectrum while reflecting and transmitting the green light that we see as the characteristic colour of these organisms. the energy in the red and blue light that these pigments absorb is used by chloroplasts to make energy - rich carbon compounds from carbon dioxide and water by oxygenic photosynthesis, a process that generates molecular oxygen ( o2 ) as a by - product. the light energy captured by chlorophyll a is initially in the form of electrons ( and later a proton gradient ) that is used to make molecules of atp and nadph which temporarily store and transport energy. their energy is used in the light - independent reactions of the calvin cycle by the enzyme rubisco to produce molecules of the 3 - carbon sugar glyceraldehyde 3 - phosphate ( g3p ). glyceraldehyde 3 - phosphate is the first product of photosynthesis and the raw material from which glucose and almost all other organic molecules of biological origin are synthesised. some of the glucose is converted to starch which is stored in the chloroplast. starch is the characteristic energy store of most land plants and algae, while inulin, a polymer of fructose is used for the same purpose in the sunflower family asteraceae. some of the glucose is converted to sucrose ( common table sugar ) for export to the rest of the plant. unlike in animals ( which lack chloroplasts ), plants and their eukaryote relatives have delegated many biochemical roles to their chloroplasts, including synthesising all their fatty acids, and most amino acids. the fatty acids that chloroplasts make are used for many things, such as providing material to build cell membranes out of and making the polymer cutin which is found in the plant cuticle that protects land plants from drying out. plants synthesise a number of unique polymers like the polysaccharide molecules cellulose, pectin and xyloglucan from which the land plant cell wall is constructed. vascular land plants make lignin, a polymer used to strengthen the secondary cell walls of xylem tracheids and vessels to keep them from collapsing when a plant sucks water through them under water stress. lignin
of these organisms. the energy in the red and blue light that these pigments absorb is used by chloroplasts to make energy - rich carbon compounds from carbon dioxide and water by oxygenic photosynthesis, a process that generates molecular oxygen ( o2 ) as a by - product. the light energy captured by chlorophyll a is initially in the form of electrons ( and later a proton gradient ) that is used to make molecules of atp and nadph which temporarily store and transport energy. their energy is used in the light - independent reactions of the calvin cycle by the enzyme rubisco to produce molecules of the 3 - carbon sugar glyceraldehyde 3 - phosphate ( g3p ). glyceraldehyde 3 - phosphate is the first product of photosynthesis and the raw material from which glucose and almost all other organic molecules of biological origin are synthesised. some of the glucose is converted to starch which is stored in the chloroplast. starch is the characteristic energy store of most land plants and algae, while inulin, a polymer of fructose is used for the same purpose in the sunflower family asteraceae. some of the glucose is converted to sucrose ( common table sugar ) for export to the rest of the plant. unlike in animals ( which lack chloroplasts ), plants and their eukaryote relatives have delegated many biochemical roles to their chloroplasts, including synthesising all their fatty acids, and most amino acids. the fatty acids that chloroplasts make are used for many things, such as providing material to build cell membranes out of and making the polymer cutin which is found in the plant cuticle that protects land plants from drying out. plants synthesise a number of unique polymers like the polysaccharide molecules cellulose, pectin and xyloglucan from which the land plant cell wall is constructed. vascular land plants make lignin, a polymer used to strengthen the secondary cell walls of xylem tracheids and vessels to keep them from collapsing when a plant sucks water through them under water stress. lignin is also used in other cell types like sclerenchyma fibres that provide structural support for a plant and is a major constituent of wood. sporopollenin is a chemically resistant polymer found in the outer cell walls of spores and pollen of land plants responsible for the survival of early land plant spores and
known as " algae " have unique organelles known as chloroplasts. chloroplasts are thought to be descended from cyanobacteria that formed endosymbiotic relationships with ancient plant and algal ancestors. chloroplasts and cyanobacteria contain the blue - green pigment chlorophyll a. chlorophyll a ( as well as its plant and green algal - specific cousin chlorophyll b ) absorbs light in the blue - violet and orange / red parts of the spectrum while reflecting and transmitting the green light that we see as the characteristic colour of these organisms. the energy in the red and blue light that these pigments absorb is used by chloroplasts to make energy - rich carbon compounds from carbon dioxide and water by oxygenic photosynthesis, a process that generates molecular oxygen ( o2 ) as a by - product. the light energy captured by chlorophyll a is initially in the form of electrons ( and later a proton gradient ) that is used to make molecules of atp and nadph which temporarily store and transport energy. their energy is used in the light - independent reactions of the calvin cycle by the enzyme rubisco to produce molecules of the 3 - carbon sugar glyceraldehyde 3 - phosphate ( g3p ). glyceraldehyde 3 - phosphate is the first product of photosynthesis and the raw material from which glucose and almost all other organic molecules of biological origin are synthesised. some of the glucose is converted to starch which is stored in the chloroplast. starch is the characteristic energy store of most land plants and algae, while inulin, a polymer of fructose is used for the same purpose in the sunflower family asteraceae. some of the glucose is converted to sucrose ( common table sugar ) for export to the rest of the plant. unlike in animals ( which lack chloroplasts ), plants and their eukaryote relatives have delegated many biochemical roles to their chloroplasts, including synthesising all their fatty acids, and most amino acids. the fatty acids that chloroplasts make are used for many things, such as providing material to build cell membranes out of and making the polymer cutin which is found in the plant cuticle that protects land plants from drying out. plants synthesise a number of unique polymers like the polysaccharide molecules cellulose,
used by pharmaceutical companies as a way of drug discovery. plants can synthesise coloured dyes and pigments such as the anthocyanins responsible for the red colour of red wine, yellow weld and blue woad used together to produce lincoln green, indoxyl, source of the blue dye indigo traditionally used to dye denim and the artist ' s pigments gamboge and rose madder. sugar, starch, cotton, linen, hemp, some types of rope, wood and particle boards, papyrus and paper, vegetable oils, wax, and natural rubber are examples of commercially important materials made from plant tissues or their secondary products. charcoal, a pure form of carbon made by pyrolysis of wood, has a long history as a metal - smelting fuel, as a filter material and adsorbent and as an artist ' s material and is one of the three ingredients of gunpowder. cellulose, the world ' s most abundant organic polymer, can be converted into energy, fuels, materials and chemical feedstock. products made from cellulose include rayon and cellophane, wallpaper paste, biobutanol and gun cotton. sugarcane, rapeseed and soy are some of the plants with a highly fermentable sugar or oil content that are used as sources of biofuels, important alternatives to fossil fuels, such as biodiesel. sweetgrass was used by native americans to ward off bugs like mosquitoes. these bug repelling properties of sweetgrass were later found by the american chemical society in the molecules phytol and coumarin. = = plant ecology = = plant ecology is the science of the functional relationships between plants and their habitats β the environments where they complete their life cycles. plant ecologists study the composition of local and regional floras, their biodiversity, genetic diversity and fitness, the adaptation of plants to their environment, and their competitive or mutualistic interactions with other species. some ecologists even rely on empirical data from indigenous people that is gathered by ethnobotanists. this information can relay a great deal of information on how the land once was thousands of years ago and how it has changed over that time. the goals of plant ecology are to understand the causes of their distribution patterns, productivity, environmental impact, evolution, and responses to environmental change. plants depend on certain edaphic ( soil ) and climatic factors in their environment but can modify these factors too. for example, they can change their environment ' s albedo, increase runoff interception
the status of the theory of color confinemnt is discussed.
reflectometer ), which takes measurements in the visible region ( and a little beyond ) of a given color sample. if the custom of taking readings at 10 nanometer increments is followed, the visible light range of 400 β 700 nm will yield 31 readings. these readings are typically used to draw the sample ' s spectral reflectance curve ( how much it reflects, as a function of wavelength ) β the most accurate data that can be provided regarding its characteristics. the readings by themselves are typically not as useful as their tristimulus values, which can be converted into chromaticity co - ordinates and manipulated through color space transformations. for this purpose, a spectrocolorimeter may be used. a spectrocolorimeter is simply a spectrophotometer that can estimate tristimulus values by numerical integration ( of the color matching functions ' inner product with the illuminant ' s spectral power distribution ). one benefit of spectrocolorimeters over tristimulus colorimeters is that they do not have optical filters, which are subject to manufacturing variance, and have a fixed spectral transmittance curve β until they age. on the other hand, tristimulus colorimeters are purpose - built, cheaper, and easier to use. the cie ( international commission on illumination ) recommends using measurement intervals under 5 nm, even for smooth spectra. sparser measurements fail to accurately characterize spiky emission spectra, such as that of the red phosphor of a crt display, depicted aside. = = = color temperature meter = = = photographers and cinematographers use information provided by these meters to decide what color balancing should be done to make different light sources appear to have the same color temperature. if the user enters the reference color temperature, the meter can calculate the mired difference between the measurement and the reference, enabling the user to choose a corrective color gel or photographic filter with the closest mired factor. internally the meter is typically a silicon photodiode tristimulus colorimeter. the correlated color temperature can be calculated from the tristimulus values by first calculating the chromaticity co - ordinates in the cie 1960 color space, then finding the closest point on the planckian locus. = = see also = = color science photometry radiometry = = references = = = = further reading = = schanda, janos d. ( 1997 ). " colorimetry " ( pdf ). in casimer decusatis ( ed. ). handbook
their primary metabolism like the photosynthetic calvin cycle and crassulacean acid metabolism. others make specialised materials like the cellulose and lignin used to build their bodies, and secondary products like resins and aroma compounds. plants and various other groups of photosynthetic eukaryotes collectively known as " algae " have unique organelles known as chloroplasts. chloroplasts are thought to be descended from cyanobacteria that formed endosymbiotic relationships with ancient plant and algal ancestors. chloroplasts and cyanobacteria contain the blue - green pigment chlorophyll a. chlorophyll a ( as well as its plant and green algal - specific cousin chlorophyll b ) absorbs light in the blue - violet and orange / red parts of the spectrum while reflecting and transmitting the green light that we see as the characteristic colour of these organisms. the energy in the red and blue light that these pigments absorb is used by chloroplasts to make energy - rich carbon compounds from carbon dioxide and water by oxygenic photosynthesis, a process that generates molecular oxygen ( o2 ) as a by - product. the light energy captured by chlorophyll a is initially in the form of electrons ( and later a proton gradient ) that is used to make molecules of atp and nadph which temporarily store and transport energy. their energy is used in the light - independent reactions of the calvin cycle by the enzyme rubisco to produce molecules of the 3 - carbon sugar glyceraldehyde 3 - phosphate ( g3p ). glyceraldehyde 3 - phosphate is the first product of photosynthesis and the raw material from which glucose and almost all other organic molecules of biological origin are synthesised. some of the glucose is converted to starch which is stored in the chloroplast. starch is the characteristic energy store of most land plants and algae, while inulin, a polymer of fructose is used for the same purpose in the sunflower family asteraceae. some of the glucose is converted to sucrose ( common table sugar ) for export to the rest of the plant. unlike in animals ( which lack chloroplasts ), plants and their eukaryote relatives have delegated many biochemical roles to their chloroplasts, including synthesising all their fatty acids, and most amino acids. the fatty acids that
##physical processes which take place in human beings as they make sense of information received through the visual system. the subject of the image. when developing an imaging system, designers must consider the observables associated with the subjects which will be imaged. these observables generally take the form of emitted or reflected energy, such as electromagnetic energy or mechanical energy. the capture device. once the observables associated with the subject are characterized, designers can then identify and integrate the technologies needed to capture those observables. for example, in the case of consumer digital cameras, those technologies include optics for collecting energy in the visible portion of the electromagnetic spectrum, and electronic detectors for converting the electromagnetic energy into an electronic signal. the processor. for all digital imaging systems, the electronic signals produced by the capture device must be manipulated by an algorithm which formats the signals so they can be displayed as an image. in practice, there are often multiple processors involved in the creation of a digital image. the display. the display takes the electronic signals which have been manipulated by the processor and renders them on some visual medium. examples include paper ( for printed, or " hard copy " images ), television, computer monitor, or projector. note that some imaging scientists will include additional " links " in their description of the imaging chain. for example, some will include the " source " of the energy which " illuminates " or interacts with the subject of the image. others will include storage and / or transmission systems. = = subfields = = subfields within imaging science include : image processing, computer vision, 3d computer graphics, animations, atmospheric optics, astronomical imaging, biological imaging, digital image restoration, digital imaging, color science, digital photography, holography, magnetic resonance imaging, medical imaging, microdensitometry, optics, photography, remote sensing, radar imaging, radiometry, silver halide, ultrasound imaging, photoacoustic imaging, thermal imaging, visual perception, and various printing technologies. = = methodologies = = acoustic imaging coherent imaging uses an active coherent illumination source, such as in radar, synthetic aperture radar ( sar ), medical ultrasound and optical coherence tomography ; non - coherent imaging systems include fluorescent microscopes, optical microscopes, and telescopes. chemical imaging, the simultaneous measurement of spectra and pictures digital imaging, creating digital images, generally by scanning or through digital photography disk image, a file which contains the exact content of a data storage medium document imaging, replicating documents commonly
of a light source can be measured with a spectroradiometer, which works by optically collecting the light, then passing it through a monochromator before reading it in narrow bands of wavelength. reflected color can be measured using a spectrophotometer ( also called spectroreflectometer or reflectometer ), which takes measurements in the visible region ( and a little beyond ) of a given color sample. if the custom of taking readings at 10 nanometer increments is followed, the visible light range of 400 β 700 nm will yield 31 readings. these readings are typically used to draw the sample ' s spectral reflectance curve ( how much it reflects, as a function of wavelength ) β the most accurate data that can be provided regarding its characteristics. the readings by themselves are typically not as useful as their tristimulus values, which can be converted into chromaticity co - ordinates and manipulated through color space transformations. for this purpose, a spectrocolorimeter may be used. a spectrocolorimeter is simply a spectrophotometer that can estimate tristimulus values by numerical integration ( of the color matching functions ' inner product with the illuminant ' s spectral power distribution ). one benefit of spectrocolorimeters over tristimulus colorimeters is that they do not have optical filters, which are subject to manufacturing variance, and have a fixed spectral transmittance curve β until they age. on the other hand, tristimulus colorimeters are purpose - built, cheaper, and easier to use. the cie ( international commission on illumination ) recommends using measurement intervals under 5 nm, even for smooth spectra. sparser measurements fail to accurately characterize spiky emission spectra, such as that of the red phosphor of a crt display, depicted aside. = = = color temperature meter = = = photographers and cinematographers use information provided by these meters to decide what color balancing should be done to make different light sources appear to have the same color temperature. if the user enters the reference color temperature, the meter can calculate the mired difference between the measurement and the reference, enabling the user to choose a corrective color gel or photographic filter with the closest mired factor. internally the meter is typically a silicon photodiode tristimulus colorimeter. the correlated color temperature can be calculated from the tristimulus values by first calculating the chromaticity co - ordinates in the cie 1960 color space, then finding the closest
the first observations of saturn ' s visible - wavelength aurora were made by the cassini camera. the aurora was observed between 2006 and 2013 in the northern and southern hemispheres. the color of the aurora changes from pink at a few hundred km above the horizon to purple at 1000 - 1500 km above the horizon. the spectrum observed in 9 filters spanning wavelengths from 250 nm to 1000 nm has a prominent h - alpha line and roughly agrees with laboratory simulated auroras. auroras in both hemispheres vary dramatically with longitude. auroras form bright arcs between 70 and 80 degree latitude north and between 65 and 80 degree latitude south, which sometimes spiral around the pole, and sometimes form double arcs. a large 10, 000 - km - scale longitudinal brightness structure persists for more than 100 hours. this structure rotates approximately together with saturn. on top of the large steady structure, the auroras brighten suddenly on the timescales of a few minutes. these brightenings repeat with a period of about 1 hour. smaller, 1000 - km - scale structures may move faster or lag behind saturn ' s rotation on timescales of tens of minutes. the persistence of nearly - corotating large bright longitudinal structure in the auroral oval seen in two movies spanning 8 and 11 rotations gives an estimate on the period of 10. 65 $ \ pm $ 0. 15 h for 2009 in the northern oval and 10. 8 $ \ pm $ 0. 1 h for 2012 in the southern oval. the 2009 north aurora period is close to the north branch of saturn kilometric radiation ( skr ) detected at that time.
Question: Visible light can be split into colors with the use of a what?
A) kaleidoscope
B) spectrum
C) prism
D) convex lenses
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C) prism
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Context:
are the stone - paved streets of the city - state of ur, dating to c. 4, 000 bce, and timber roads leading through the swamps of glastonbury, england, dating to around the same period. the first long - distance road, which came into use around 3, 500 bce, spanned 2, 400 km from the persian gulf to the mediterranean sea, but was not paved and was only partially maintained. in around 2, 000 bce, the minoans on the greek island of crete built a 50 km road leading from the palace of gortyn on the south side of the island, through the mountains, to the palace of knossos on the north side of the island. unlike the earlier road, the minoan road was completely paved. ancient minoan private homes had running water. a bathtub virtually identical to modern ones was unearthed at the palace of knossos. several minoan private homes also had toilets, which could be flushed by pouring water down the drain. the ancient romans had many public flush toilets, which emptied into an extensive sewage system. the primary sewer in rome was the cloaca maxima ; construction began on it in the sixth century bce and it is still in use today. the ancient romans also had a complex system of aqueducts, which were used to transport water across long distances. the first roman aqueduct was built in 312 bce. the eleventh and final ancient roman aqueduct was built in 226 ce. put together, the roman aqueducts extended over 450 km, but less than 70 km of this was above ground and supported by arches. = = = pre - modern = = = innovations continued through the middle ages with the introduction of silk production ( in asia and later europe ), the horse collar, and horseshoes. simple machines ( such as the lever, the screw, and the pulley ) were combined into more complicated tools, such as the wheelbarrow, windmills, and clocks. a system of universities developed and spread scientific ideas and practices, including oxford and cambridge. the renaissance era produced many innovations, including the introduction of the movable type printing press to europe, which facilitated the communication of knowledge. technology became increasingly influenced by science, beginning a cycle of mutual advancement. = = = modern = = = starting in the united kingdom in the 18th century, the discovery of steam power set off the industrial revolution, which saw wide - ranging technological discoveries, particularly in the areas of agriculture, manufacturing, mining, metallurgy, and transport, and the
equalizing the flow at these places, produces a lowering of the river above the rapids by facilitating the efflux, which may result in the appearance of fresh shoals at the low stage of the river. where, however, narrow rocky reefs or other hard shoals stretch across the bottom of a river and present obstacles to the erosion by the current of the soft materials forming the bed of the river above and below, their removal may result in permanent improvement by enabling the river to deepen its bed by natural scour. the capability of a river to provide a waterway for navigation during the summer or throughout the dry season depends on the depth that can be secured in the channel at the lowest stage. the problem in the dry season is the small discharge and deficiency in scour during this period. a typical solution is to restrict the width of the low - water channel, concentrate all of the flow in it, and also to fix its position so that it is scoured out every year by the floods which follow the deepest part of the bed along the line of the strongest current. this can be effected by closing subsidiary low - water channels with dikes across them, and narrowing the channel at the low stage by low - dipping cross dikes extending from the river banks down the slope and pointing slightly up - stream so as to direct the water flowing over them into a central channel. = = estuarine works = = the needs of navigation may also require that a stable, continuous, navigable channel is prolonged from the navigable river to deep water at the mouth of the estuary. the interaction of river flow and tide needs to be modeled by computer or using scale models, moulded to the configuration of the estuary under consideration and reproducing in miniature the tidal ebb and flow and fresh - water discharge over a bed of fine sand, in which various lines of training walls can be successively inserted. the models should be capable of furnishing valuable indications of the respective effects and comparative merits of the different schemes proposed for works. = = see also = = bridge scour flood control = = references = = = = external links = = u. s. army corps of engineers β civil works program river morphology and stream restoration references - wildland hydrology at the library of congress web archives ( archived 2002 - 08 - 13 )
also known as the gradient or slope. when two rivers of different sizes have the same fall, the larger river has the quicker flow, as its retardation by friction against its bed and banks is less in proportion to its volume than is the case with the smaller river. the fall available in a section of a river approximately corresponds to the slope of the country it traverses ; as rivers rise close to the highest part of their basins, generally in hilly regions, their fall is rapid near their source and gradually diminishes, with occasional irregularities, until, in traversing plains along the latter part of their course, their fall usually becomes quite gentle. accordingly, in large basins, rivers in most cases begin as torrents with a variable flow, and end as gently flowing rivers with a comparatively regular discharge. the irregular flow of rivers throughout their course forms one of the main difficulties in devising works for mitigating inundations or for increasing the navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in
the injuries of the inundations they have been designed to prevent, as the escape of floods from the raised river must occur sooner or later. inadequate planning controls which have permitted development on floodplains have been blamed for the flooding of domestic properties. channelization was done under the auspices or overall direction of engineers employed by the local authority or the national government. one of the most heavily channelized areas in the united states is west tennessee, where every major stream with one exception ( the hatchie river ) has been partially or completely channelized. channelization of a stream may be undertaken for several reasons. one is to make a stream more suitable for navigation or for navigation by larger vessels with deep draughts. another is to restrict water to a certain area of a stream ' s natural bottom lands so that the bulk of such lands can be made available for agriculture. a third reason is flood control, with the idea of giving a stream a sufficiently large and deep channel so that flooding beyond those limits will be minimal or nonexistent, at least on a routine basis. one major reason is to reduce natural erosion ; as a natural waterway curves back and forth, it usually deposits sand and gravel on the inside of the corners where the water flows slowly, and cuts sand, gravel, subsoil, and precious topsoil from the outside corners where it flows rapidly due to a change in direction. unlike sand and gravel, the topsoil that is eroded does not get deposited on the inside of the next corner of the river. it simply washes away. = = loss of wetlands = = channelization has several predictable and negative effects. one of them is loss of wetlands. wetlands are an excellent habitat for multiple forms of wildlife, and additionally serve as a " filter " for much of the world ' s surface fresh water. another is the fact that channelized streams are almost invariably straightened. for example, the channelization of florida ' s kissimmee river has been cited as a cause contributing to the loss of wetlands. this straightening causes the streams to flow more rapidly, which can, in some instances, vastly increase soil erosion. it can also increase flooding downstream from the channelized area, as larger volumes of water traveling more rapidly than normal can reach choke points over a shorter period of time than they otherwise would, with a net effect of flood control in one area coming at the expense of aggravated flooding in another. in addition, studies have shown that stream channelization results in declines of river fish populations. : 3 - 1ff a
becomes quite gentle. accordingly, in large basins, rivers in most cases begin as torrents with a variable flow, and end as gently flowing rivers with a comparatively regular discharge. the irregular flow of rivers throughout their course forms one of the main difficulties in devising works for mitigating inundations or for increasing the navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with a rapid fall near the sources of rivers can carry down rocks, boulders and large stones, which are by degrees ground by attrition in their onward course into slate, gravel, sand and silt, simultaneously with the gradual reduction in fall, and, consequently, in the transporting force of the current. accordingly, under
approximately corresponds to the slope of the country it traverses ; as rivers rise close to the highest part of their basins, generally in hilly regions, their fall is rapid near their source and gradually diminishes, with occasional irregularities, until, in traversing plains along the latter part of their course, their fall usually becomes quite gentle. accordingly, in large basins, rivers in most cases begin as torrents with a variable flow, and end as gently flowing rivers with a comparatively regular discharge. the irregular flow of rivers throughout their course forms one of the main difficulties in devising works for mitigating inundations or for increasing the navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with
river - beds ), but not for where there may be large obstructions in the ground. an open caisson that is used in soft grounds or high water tables, where open trench excavations are impractical, can also be used to install deep manholes, pump stations and reception / launch pits for microtunnelling, pipe jacking and other operations. a caisson is sunk by self - weight, concrete or water ballast placed on top, or by hydraulic jacks. the leading edge ( or cutting shoe ) of the caisson is sloped out at a sharp angle to aid sinking in a vertical manner ; it is usually made of steel. the shoe is generally wider than the caisson to reduce friction, and the leading edge may be supplied with pressurised bentonite slurry, which swells in water, stabilizing settlement by filling depressions and voids. an open caisson may fill with water during sinking. the material is excavated by clamshell excavator bucket on crane. the formation level subsoil may still not be suitable for excavation or bearing capacity. the water in the caisson ( due to a high water table ) balances the upthrust forces of the soft soils underneath. if dewatered, the base may " pipe " or " boil ", causing the caisson to sink. to combat this problem, piles may be driven from the surface to act as : load - bearing walls, in that they transmit loads to deeper soils. anchors, in that they resist flotation because of the friction at the interface between their surfaces and the surrounding earth into which they have been driven. h - beam sections ( typical column sections, due to resistance to bending in all axis ) may be driven at angles " raked " to rock or other firmer soils ; the h - beams are left extended above the base. a reinforced concrete plug may be placed under the water, a process known as tremie concrete placement. when the caisson is dewatered, this plug acts as a pile cap, resisting the upward forces of the subsoil. = = = monolithic = = = a monolithic caisson ( or simply a monolith ) is larger than the other types of caisson, but similar to open caissons. such caissons are often found in quay walls, where resistance to impact from ships is required. = = = pneumatic = = = shallow caissons may be open to the air, whereas pneumatic caisson
navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with a rapid fall near the sources of rivers can carry down rocks, boulders and large stones, which are by degrees ground by attrition in their onward course into slate, gravel, sand and silt, simultaneously with the gradual reduction in fall, and, consequently, in the transporting force of the current. accordingly, under ordinary conditions, most of the materials brought down from the high lands by torrential water courses are carried forward by the main river to the sea, or partially strewn over flat alluvial plains during floods ; the size of the materials forming the bed of the river or borne along by the stream is gradually reduced on proceeding sea
##ructing the channel depends on the nature of the shoals. a soft shoal in the bed of a river is due to deposit from a diminution in velocity of flow, produced by a reduction in fall and by a widening of the channel, or to a loss in concentration of the scour of the main current in passing over from one concave bank to the next on the opposite side. the lowering of such a shoal by dredging merely effects a temporary deepening, for it soon forms again from the causes which produced it. the removal, moreover, of the rocky obstructions at rapids, though increasing the depth and equalizing the flow at these places, produces a lowering of the river above the rapids by facilitating the efflux, which may result in the appearance of fresh shoals at the low stage of the river. where, however, narrow rocky reefs or other hard shoals stretch across the bottom of a river and present obstacles to the erosion by the current of the soft materials forming the bed of the river above and below, their removal may result in permanent improvement by enabling the river to deepen its bed by natural scour. the capability of a river to provide a waterway for navigation during the summer or throughout the dry season depends on the depth that can be secured in the channel at the lowest stage. the problem in the dry season is the small discharge and deficiency in scour during this period. a typical solution is to restrict the width of the low - water channel, concentrate all of the flow in it, and also to fix its position so that it is scoured out every year by the floods which follow the deepest part of the bed along the line of the strongest current. this can be effected by closing subsidiary low - water channels with dikes across them, and narrowing the channel at the low stage by low - dipping cross dikes extending from the river banks down the slope and pointing slightly up - stream so as to direct the water flowing over them into a central channel. = = estuarine works = = the needs of navigation may also require that a stable, continuous, navigable channel is prolonged from the navigable river to deep water at the mouth of the estuary. the interaction of river flow and tide needs to be modeled by computer or using scale models, moulded to the configuration of the estuary under consideration and reproducing in miniature the tidal ebb and flow and fresh - water discharge over a bed of fine sand, in which various lines of training walls can be successively inserted. the models
made of steel. the shoe is generally wider than the caisson to reduce friction, and the leading edge may be supplied with pressurised bentonite slurry, which swells in water, stabilizing settlement by filling depressions and voids. an open caisson may fill with water during sinking. the material is excavated by clamshell excavator bucket on crane. the formation level subsoil may still not be suitable for excavation or bearing capacity. the water in the caisson ( due to a high water table ) balances the upthrust forces of the soft soils underneath. if dewatered, the base may " pipe " or " boil ", causing the caisson to sink. to combat this problem, piles may be driven from the surface to act as : load - bearing walls, in that they transmit loads to deeper soils. anchors, in that they resist flotation because of the friction at the interface between their surfaces and the surrounding earth into which they have been driven. h - beam sections ( typical column sections, due to resistance to bending in all axis ) may be driven at angles " raked " to rock or other firmer soils ; the h - beams are left extended above the base. a reinforced concrete plug may be placed under the water, a process known as tremie concrete placement. when the caisson is dewatered, this plug acts as a pile cap, resisting the upward forces of the subsoil. = = = monolithic = = = a monolithic caisson ( or simply a monolith ) is larger than the other types of caisson, but similar to open caissons. such caissons are often found in quay walls, where resistance to impact from ships is required. = = = pneumatic = = = shallow caissons may be open to the air, whereas pneumatic caissons ( sometimes called pressurized caissons ), which penetrate soft mud, are bottomless boxes sealed at the top and filled with compressed air to keep water and mud out at depth. an airlock allows access to the chamber. workers, called sandhogs in american english, move mud and rock debris ( called muck ) from the edge of the workspace to a water - filled pit, connected by a tube ( called the muck tube ) to the surface. a crane at the surface removes the soil with a clamshell bucket. the water pressure in the tube balances the air pressure, with excess air escaping up
Question: Marshes, swamps, and bogs are types of what?
A) wetlands
B) ponds
C) grasslands
D) rivers
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A) wetlands
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Context:
are the stone - paved streets of the city - state of ur, dating to c. 4, 000 bce, and timber roads leading through the swamps of glastonbury, england, dating to around the same period. the first long - distance road, which came into use around 3, 500 bce, spanned 2, 400 km from the persian gulf to the mediterranean sea, but was not paved and was only partially maintained. in around 2, 000 bce, the minoans on the greek island of crete built a 50 km road leading from the palace of gortyn on the south side of the island, through the mountains, to the palace of knossos on the north side of the island. unlike the earlier road, the minoan road was completely paved. ancient minoan private homes had running water. a bathtub virtually identical to modern ones was unearthed at the palace of knossos. several minoan private homes also had toilets, which could be flushed by pouring water down the drain. the ancient romans had many public flush toilets, which emptied into an extensive sewage system. the primary sewer in rome was the cloaca maxima ; construction began on it in the sixth century bce and it is still in use today. the ancient romans also had a complex system of aqueducts, which were used to transport water across long distances. the first roman aqueduct was built in 312 bce. the eleventh and final ancient roman aqueduct was built in 226 ce. put together, the roman aqueducts extended over 450 km, but less than 70 km of this was above ground and supported by arches. = = = pre - modern = = = innovations continued through the middle ages with the introduction of silk production ( in asia and later europe ), the horse collar, and horseshoes. simple machines ( such as the lever, the screw, and the pulley ) were combined into more complicated tools, such as the wheelbarrow, windmills, and clocks. a system of universities developed and spread scientific ideas and practices, including oxford and cambridge. the renaissance era produced many innovations, including the introduction of the movable type printing press to europe, which facilitated the communication of knowledge. technology became increasingly influenced by science, beginning a cycle of mutual advancement. = = = modern = = = starting in the united kingdom in the 18th century, the discovery of steam power set off the industrial revolution, which saw wide - ranging technological discoveries, particularly in the areas of agriculture, manufacturing, mining, metallurgy, and transport, and the
, 400 km from the persian gulf to the mediterranean sea, but was not paved and was only partially maintained. in around 2, 000 bce, the minoans on the greek island of crete built a 50 km road leading from the palace of gortyn on the south side of the island, through the mountains, to the palace of knossos on the north side of the island. unlike the earlier road, the minoan road was completely paved. ancient minoan private homes had running water. a bathtub virtually identical to modern ones was unearthed at the palace of knossos. several minoan private homes also had toilets, which could be flushed by pouring water down the drain. the ancient romans had many public flush toilets, which emptied into an extensive sewage system. the primary sewer in rome was the cloaca maxima ; construction began on it in the sixth century bce and it is still in use today. the ancient romans also had a complex system of aqueducts, which were used to transport water across long distances. the first roman aqueduct was built in 312 bce. the eleventh and final ancient roman aqueduct was built in 226 ce. put together, the roman aqueducts extended over 450 km, but less than 70 km of this was above ground and supported by arches. = = = pre - modern = = = innovations continued through the middle ages with the introduction of silk production ( in asia and later europe ), the horse collar, and horseshoes. simple machines ( such as the lever, the screw, and the pulley ) were combined into more complicated tools, such as the wheelbarrow, windmills, and clocks. a system of universities developed and spread scientific ideas and practices, including oxford and cambridge. the renaissance era produced many innovations, including the introduction of the movable type printing press to europe, which facilitated the communication of knowledge. technology became increasingly influenced by science, beginning a cycle of mutual advancement. = = = modern = = = starting in the united kingdom in the 18th century, the discovery of steam power set off the industrial revolution, which saw wide - ranging technological discoveries, particularly in the areas of agriculture, manufacturing, mining, metallurgy, and transport, and the widespread application of the factory system. this was followed a century later by the second industrial revolution which led to rapid scientific discovery, standardization, and mass production. new technologies were developed, including sewage systems, electricity, light bulbs, electric motors, railroads, automobiles, and airplanes. these technological advances led to significant developments in medicine
you noticed any weight loss, change in sleep quality, fevers, lumps and bumps? etc. ), followed by questions on the body ' s main organ systems ( heart, lungs, digestive tract, urinary tract, etc. ). social history ( sh ) : birthplace, residences, marital history, social and economic status, habits ( including diet, medications, tobacco, alcohol ). the physical examination is the examination of the patient for medical signs of disease that are objective and observable, in contrast to symptoms that are volunteered by the patient and are not necessarily objectively observable. the healthcare provider uses sight, hearing, touch, and sometimes smell ( e. g., in infection, uremia, diabetic ketoacidosis ). four actions are the basis of physical examination : inspection, palpation ( feel ), percussion ( tap to determine resonance characteristics ), and auscultation ( listen ), generally in that order, although auscultation occurs prior to percussion and palpation for abdominal assessments. the clinical examination involves the study of : abdomen and rectum cardiovascular ( heart and blood vessels ) general appearance of the patient and specific indicators of disease ( nutritional status, presence of jaundice, pallor or clubbing ) genitalia ( and pregnancy if the patient is or could be pregnant ) head, eye, ear, nose, and throat ( heent ) musculoskeletal ( including spine and extremities ) neurological ( consciousness, awareness, brain, vision, cranial nerves, spinal cord and peripheral nerves ) psychiatric ( orientation, mental state, mood, evidence of abnormal perception or thought ). respiratory ( large airways and lungs ) skin vital signs including height, weight, body temperature, blood pressure, pulse, respiration rate, and hemoglobin oxygen saturation it is to likely focus on areas of interest highlighted in the medical history and may not include everything listed above. the treatment plan may include ordering additional medical laboratory tests and medical imaging studies, starting therapy, referral to a specialist, or watchful observation. a follow - up may be advised. depending upon the health insurance plan and the managed care system, various forms of " utilization review ", such as prior authorization of tests, may place barriers on accessing expensive services. the medical decision - making ( mdm ) process includes the analysis and synthesis of all the above data to come up with a list of possible diagnoses ( the differential diagnoses ),
known as anaesthetics ) : concerned with the perioperative management of the surgical patient. the anesthesiologist ' s role during surgery is to prevent derangement in the vital organs ' ( i. e. brain, heart, kidneys ) functions and postoperative pain. outside of the operating room, the anesthesiology physician also serves the same function in the labor and delivery ward, and some are specialized in critical medicine. emergency medicine is concerned with the diagnosis and treatment of acute or life - threatening conditions, including trauma, surgical, medical, pediatric, and psychiatric emergencies. family medicine, family practice, general practice or primary care is, in many countries, the first port - of - call for patients with non - emergency medical problems. family physicians often provide services across a broad range of settings including office based practices, emergency department coverage, inpatient care, and nursing home care. medical genetics is concerned with the diagnosis and management of hereditary disorders. neurology is concerned with diseases of the nervous system. in the uk, neurology is a subspecialty of general medicine. obstetrics and gynecology ( often abbreviated as ob / gyn ( american english ) or obs & gynae ( british english ) ) are concerned respectively with childbirth and the female reproductive and associated organs. reproductive medicine and fertility medicine are generally practiced by gynecological specialists. pediatrics ( ae ) or paediatrics ( be ) is devoted to the care of infants, children, and adolescents. like internal medicine, there are many pediatric subspecialties for specific age ranges, organ systems, disease classes, and sites of care delivery. pharmaceutical medicine is the medical scientific discipline concerned with the discovery, development, evaluation, registration, monitoring and medical aspects of marketing of medicines for the benefit of patients and public health. physical medicine and rehabilitation ( or physiatry ) is concerned with functional improvement after injury, illness, or congenital disorders. podiatric medicine is the study of, diagnosis, and medical and surgical treatment of disorders of the foot, ankle, lower limb, hip and lower back. preventive medicine is the branch of medicine concerned with preventing disease. community health or public health is an aspect of health services concerned with threats to the overall health of a community based on population health analysis. psychiatry is the branch of medicine concerned with the bio - psycho - social study of the etiology, diagnosis, treatment and prevention of cognitive, perceptual, emotional and behavioral disorders.
kidneys and the majority of those currently in use are extracorporeal, such as with hemodialysis, which filters blood directly, or peritoneal dialysis, which filters via a fluid in the abdomen. in order to contribute to the biological functions of a kidney such as producing metabolic factors or hormones, some artificial kidneys incorporate renal cells. there has been progress in the way of making these devices smaller and more transportable, or even implantable. one challenge still to be faced in these smaller devices is countering the limited volume and therefore limited filtering capabilities. bioscaffolds have also been introduced to provide a framework upon which normal kidney tissue can be regenerated. these scaffolds encompass natural scaffolds ( e. g., decellularized kidneys, collagen hydrogel, or silk fibroin ), synthetic scaffolds ( e. g., poly [ lactic - co - glycolic acid ] or other polymers ), or a combination of two or more natural and synthetic scaffolds. these scaffolds can be implanted into the body either without cell treatment or after a period of stem cell seeding and incubation. in vitro and in vivo studies are being conducted to compare and optimize the type of scaffold and to assess whether cell seeding prior to implantation adds to the viability, regeneration and effective function of the kidneys. a recent systematic review and meta - analysis compared the results of published animal studies and identified that improved outcomes are reported with the use of hybrid ( mixed ) scaffolds and cell seeding ; however, the meta - analysis of these results were not in agreement with the evaluation of descriptive results from the review. therefore, further studies involving larger animals and novel scaffolds, and more transparent reproduction of previous studies are advisable. = = = biomimetics = = = biomimetics is a field that aims to produce materials and systems that replicate those present in nature. in the context of tissue engineering, this is a common approach used by engineers to create materials for these applications that are comparable to native tissues in terms of their structure, properties, and biocompatibility. material properties are largely dependent on physical, structural, and chemical characteristics of that material. subsequently, a biomimetic approach to system design will become significant in material integration, and a sufficient understanding of biological processes and interactions will be necessary. replication of biological systems and
this is a thesis submitted for the degree of doctor philosophiae at s. i. s. s. a. / i. s. a. s.
practice, general practice or primary care is, in many countries, the first port - of - call for patients with non - emergency medical problems. family physicians often provide services across a broad range of settings including office based practices, emergency department coverage, inpatient care, and nursing home care. medical genetics is concerned with the diagnosis and management of hereditary disorders. neurology is concerned with diseases of the nervous system. in the uk, neurology is a subspecialty of general medicine. obstetrics and gynecology ( often abbreviated as ob / gyn ( american english ) or obs & gynae ( british english ) ) are concerned respectively with childbirth and the female reproductive and associated organs. reproductive medicine and fertility medicine are generally practiced by gynecological specialists. pediatrics ( ae ) or paediatrics ( be ) is devoted to the care of infants, children, and adolescents. like internal medicine, there are many pediatric subspecialties for specific age ranges, organ systems, disease classes, and sites of care delivery. pharmaceutical medicine is the medical scientific discipline concerned with the discovery, development, evaluation, registration, monitoring and medical aspects of marketing of medicines for the benefit of patients and public health. physical medicine and rehabilitation ( or physiatry ) is concerned with functional improvement after injury, illness, or congenital disorders. podiatric medicine is the study of, diagnosis, and medical and surgical treatment of disorders of the foot, ankle, lower limb, hip and lower back. preventive medicine is the branch of medicine concerned with preventing disease. community health or public health is an aspect of health services concerned with threats to the overall health of a community based on population health analysis. psychiatry is the branch of medicine concerned with the bio - psycho - social study of the etiology, diagnosis, treatment and prevention of cognitive, perceptual, emotional and behavioral disorders. related fields include psychotherapy and clinical psychology. = = = interdisciplinary fields = = = some interdisciplinary sub - specialties of medicine include : addiction medicine deals with the treatment of addiction. aerospace medicine deals with medical problems related to flying and space travel. biomedical engineering is a field dealing with the application of engineering principles to medical practice. clinical pharmacology is concerned with how systems of therapeutics interact with patients. conservation medicine studies the relationship between human and non - human animal health, and environmental conditions. also known as ecological medicine, environmental medicine, or medical geology. disaster medicine deals with medical aspects of emergency preparedness, disaster mitigation
english ) ) are concerned respectively with childbirth and the female reproductive and associated organs. reproductive medicine and fertility medicine are generally practiced by gynecological specialists. pediatrics ( ae ) or paediatrics ( be ) is devoted to the care of infants, children, and adolescents. like internal medicine, there are many pediatric subspecialties for specific age ranges, organ systems, disease classes, and sites of care delivery. pharmaceutical medicine is the medical scientific discipline concerned with the discovery, development, evaluation, registration, monitoring and medical aspects of marketing of medicines for the benefit of patients and public health. physical medicine and rehabilitation ( or physiatry ) is concerned with functional improvement after injury, illness, or congenital disorders. podiatric medicine is the study of, diagnosis, and medical and surgical treatment of disorders of the foot, ankle, lower limb, hip and lower back. preventive medicine is the branch of medicine concerned with preventing disease. community health or public health is an aspect of health services concerned with threats to the overall health of a community based on population health analysis. psychiatry is the branch of medicine concerned with the bio - psycho - social study of the etiology, diagnosis, treatment and prevention of cognitive, perceptual, emotional and behavioral disorders. related fields include psychotherapy and clinical psychology. = = = interdisciplinary fields = = = some interdisciplinary sub - specialties of medicine include : addiction medicine deals with the treatment of addiction. aerospace medicine deals with medical problems related to flying and space travel. biomedical engineering is a field dealing with the application of engineering principles to medical practice. clinical pharmacology is concerned with how systems of therapeutics interact with patients. conservation medicine studies the relationship between human and non - human animal health, and environmental conditions. also known as ecological medicine, environmental medicine, or medical geology. disaster medicine deals with medical aspects of emergency preparedness, disaster mitigation and management. diving medicine ( or hyperbaric medicine ) is the prevention and treatment of diving - related problems. evolutionary medicine is a perspective on medicine derived through applying evolutionary theory. forensic medicine deals with medical questions in legal context, such as determination of the time and cause of death, type of weapon used to inflict trauma, reconstruction of the facial features using remains of deceased ( skull ) thus aiding identification. gender - based medicine studies the biological and physiological differences between the human sexes and how that affects differences in disease. health informatics is a relatively recent field that deal with the application of computers and information technology to medicine. hospice and pal
often called physicians. these terms, internist or physician ( in the narrow sense, common outside north america ), generally exclude practitioners of gynecology and obstetrics, pathology, psychiatry, and especially surgery and its subspecialities. because their patients are often seriously ill or require complex investigations, internists do much of their work in hospitals. formerly, many internists were not subspecialized ; such general physicians would see any complex nonsurgical problem ; this style of practice has become much less common. in modern urban practice, most internists are subspecialists : that is, they generally limit their medical practice to problems of one organ system or to one particular area of medical knowledge. for example, gastroenterologists and nephrologists specialize respectively in diseases of the gut and the kidneys. in the commonwealth of nations and some other countries, specialist pediatricians and geriatricians are also described as specialist physicians ( or internists ) who have subspecialized by age of patient rather than by organ system. elsewhere, especially in north america, general pediatrics is often a form of primary care. there are many subspecialities ( or subdisciplines ) of internal medicine : training in internal medicine ( as opposed to surgical training ), varies considerably across the world : see the articles on medical education for more details. in north america, it requires at least three years of residency training after medical school, which can then be followed by a one - to three - year fellowship in the subspecialties listed above. in general, resident work hours in medicine are less than those in surgery, averaging about 60 hours per week in the us. this difference does not apply in the uk where all doctors are now required by law to work less than 48 hours per week on average. = = = = diagnostic specialties = = = = clinical laboratory sciences are the clinical diagnostic services that apply laboratory techniques to diagnosis and management of patients. in the united states, these services are supervised by a pathologist. the personnel that work in these medical laboratory departments are technically trained staff who do not hold medical degrees, but who usually hold an undergraduate medical technology degree, who actually perform the tests, assays, and procedures needed for providing the specific services. subspecialties include transfusion medicine, cellular pathology, clinical chemistry, hematology, clinical microbiology and clinical immunology. clinical neurophysiology is concerned with testing the physiology or function of the central and peripheral aspects of
this is an experimentalist ' s list of questions concerning the physics of the charmed baryon sector which have no satisfactory answer.
Question: What is the chief organ of the urinary system?
A) lung
B) liver
C) kidney
D) bladder
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C) kidney
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Context:
winds from agn and quasars will form large amounts of dust, as the cool gas in these winds passes through the ( pressure, temperature ) region where dust is formed in agb stars. conditions in the gas are benign to dust at these radii. as a result quasar winds may be a major source of dust at high redshifts, obviating a difficulty with current observations, and requiring far less dust to exist at early epochs.
, lightning strikes, tornadoes, building fires, wildfires, and mass shootings disabling most of the system if not the entirety of it. geographic redundancy locations can be more than 621 miles ( 999 km ) continental, more than 62 miles apart and less than 93 miles ( 150 km ) apart, less than 62 miles apart, but not on the same campus, or different buildings that are more than 300 feet ( 91 m ) apart on the same campus. the following methods can reduce the risks of damage by a fire conflagration : large buildings at least 80 feet ( 24 m ) to 110 feet ( 34 m ) apart, but sometimes a minimum of 210 feet ( 64 m ) apart. : 9 high - rise buildings at least 82 feet ( 25 m ) apart : 12 open spaces clear of flammable vegetation within 200 feet ( 61 m ) on each side of objects different wings on the same building, in rooms that are separated by more than 300 feet ( 91 m ) different floors on the same wing of a building in rooms that are horizontally offset by a minimum of 70 feet ( 21 m ) with fire walls between the rooms that are on different floors two rooms separated by another room, leaving at least a 70 - foot gap between the two rooms there should be a minimum of two separated fire walls and on opposite sides of a corridor geographic redundancy is used by amazon web services ( aws ), google cloud platform ( gcp ), microsoft azure, netflix, dropbox, salesforce, linkedin, paypal, twitter, facebook, apple icloud, cisco meraki, and many others to provide geographic redundancy, high availability, fault tolerance and to ensure availability and reliability for their cloud services. as another example, to minimize risk of damage from severe windstorms or water damage, buildings can be located at least 2 miles ( 3. 2 km ) away from the shore, with an elevation of at least 5 feet ( 1. 5 m ) above sea level. for additional protection, they can be located at least 100 feet ( 30 m ) away from flood plain areas. = = functions of redundancy = = the two functions of redundancy are passive redundancy and active redundancy. both functions prevent performance decline from exceeding specification limits without human intervention using extra capacity. passive redundancy uses excess capacity to reduce the impact of component failures. one common form of passive redundancy is the extra strength of cabling and struts used in bridges.
the transition of our energy system to renewable energies is necessary in order not to heat up the climate any further and to achieve climate neutrality. the use of wind energy plays an important role in this transition in germany. but how much wind energy can be used and what are the possible consequences for the atmosphere if more and more wind energy is used?
current in passing over from one concave bank to the next on the opposite side. the lowering of such a shoal by dredging merely effects a temporary deepening, for it soon forms again from the causes which produced it. the removal, moreover, of the rocky obstructions at rapids, though increasing the depth and equalizing the flow at these places, produces a lowering of the river above the rapids by facilitating the efflux, which may result in the appearance of fresh shoals at the low stage of the river. where, however, narrow rocky reefs or other hard shoals stretch across the bottom of a river and present obstacles to the erosion by the current of the soft materials forming the bed of the river above and below, their removal may result in permanent improvement by enabling the river to deepen its bed by natural scour. the capability of a river to provide a waterway for navigation during the summer or throughout the dry season depends on the depth that can be secured in the channel at the lowest stage. the problem in the dry season is the small discharge and deficiency in scour during this period. a typical solution is to restrict the width of the low - water channel, concentrate all of the flow in it, and also to fix its position so that it is scoured out every year by the floods which follow the deepest part of the bed along the line of the strongest current. this can be effected by closing subsidiary low - water channels with dikes across them, and narrowing the channel at the low stage by low - dipping cross dikes extending from the river banks down the slope and pointing slightly up - stream so as to direct the water flowing over them into a central channel. = = estuarine works = = the needs of navigation may also require that a stable, continuous, navigable channel is prolonged from the navigable river to deep water at the mouth of the estuary. the interaction of river flow and tide needs to be modeled by computer or using scale models, moulded to the configuration of the estuary under consideration and reproducing in miniature the tidal ebb and flow and fresh - water discharge over a bed of fine sand, in which various lines of training walls can be successively inserted. the models should be capable of furnishing valuable indications of the respective effects and comparative merits of the different schemes proposed for works. = = see also = = bridge scour flood control = = references = = = = external links = = u. s. army corps of engineers β civil works program river morphology and stream restoration references
##ediment to up - stream navigation, and there are generally variations in water level, and when the discharge becomes small in the dry season. it is impossible to maintain a sufficient depth of water in the low - water channel. the possibility to secure uniformity of depth in a river by lowering the shoals obstructing the channel depends on the nature of the shoals. a soft shoal in the bed of a river is due to deposit from a diminution in velocity of flow, produced by a reduction in fall and by a widening of the channel, or to a loss in concentration of the scour of the main current in passing over from one concave bank to the next on the opposite side. the lowering of such a shoal by dredging merely effects a temporary deepening, for it soon forms again from the causes which produced it. the removal, moreover, of the rocky obstructions at rapids, though increasing the depth and equalizing the flow at these places, produces a lowering of the river above the rapids by facilitating the efflux, which may result in the appearance of fresh shoals at the low stage of the river. where, however, narrow rocky reefs or other hard shoals stretch across the bottom of a river and present obstacles to the erosion by the current of the soft materials forming the bed of the river above and below, their removal may result in permanent improvement by enabling the river to deepen its bed by natural scour. the capability of a river to provide a waterway for navigation during the summer or throughout the dry season depends on the depth that can be secured in the channel at the lowest stage. the problem in the dry season is the small discharge and deficiency in scour during this period. a typical solution is to restrict the width of the low - water channel, concentrate all of the flow in it, and also to fix its position so that it is scoured out every year by the floods which follow the deepest part of the bed along the line of the strongest current. this can be effected by closing subsidiary low - water channels with dikes across them, and narrowing the channel at the low stage by low - dipping cross dikes extending from the river banks down the slope and pointing slightly up - stream so as to direct the water flowing over them into a central channel. = = estuarine works = = the needs of navigation may also require that a stable, continuous, navigable channel is prolonged from the navigable river to deep water at the mouth of the estuary. the interaction of river
becomes quite gentle. accordingly, in large basins, rivers in most cases begin as torrents with a variable flow, and end as gently flowing rivers with a comparatively regular discharge. the irregular flow of rivers throughout their course forms one of the main difficulties in devising works for mitigating inundations or for increasing the navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with a rapid fall near the sources of rivers can carry down rocks, boulders and large stones, which are by degrees ground by attrition in their onward course into slate, gravel, sand and silt, simultaneously with the gradual reduction in fall, and, consequently, in the transporting force of the current. accordingly, under
approximately corresponds to the slope of the country it traverses ; as rivers rise close to the highest part of their basins, generally in hilly regions, their fall is rapid near their source and gradually diminishes, with occasional irregularities, until, in traversing plains along the latter part of their course, their fall usually becomes quite gentle. accordingly, in large basins, rivers in most cases begin as torrents with a variable flow, and end as gently flowing rivers with a comparatively regular discharge. the irregular flow of rivers throughout their course forms one of the main difficulties in devising works for mitigating inundations or for increasing the navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with
equalizing the flow at these places, produces a lowering of the river above the rapids by facilitating the efflux, which may result in the appearance of fresh shoals at the low stage of the river. where, however, narrow rocky reefs or other hard shoals stretch across the bottom of a river and present obstacles to the erosion by the current of the soft materials forming the bed of the river above and below, their removal may result in permanent improvement by enabling the river to deepen its bed by natural scour. the capability of a river to provide a waterway for navigation during the summer or throughout the dry season depends on the depth that can be secured in the channel at the lowest stage. the problem in the dry season is the small discharge and deficiency in scour during this period. a typical solution is to restrict the width of the low - water channel, concentrate all of the flow in it, and also to fix its position so that it is scoured out every year by the floods which follow the deepest part of the bed along the line of the strongest current. this can be effected by closing subsidiary low - water channels with dikes across them, and narrowing the channel at the low stage by low - dipping cross dikes extending from the river banks down the slope and pointing slightly up - stream so as to direct the water flowing over them into a central channel. = = estuarine works = = the needs of navigation may also require that a stable, continuous, navigable channel is prolonged from the navigable river to deep water at the mouth of the estuary. the interaction of river flow and tide needs to be modeled by computer or using scale models, moulded to the configuration of the estuary under consideration and reproducing in miniature the tidal ebb and flow and fresh - water discharge over a bed of fine sand, in which various lines of training walls can be successively inserted. the models should be capable of furnishing valuable indications of the respective effects and comparative merits of the different schemes proposed for works. = = see also = = bridge scour flood control = = references = = = = external links = = u. s. army corps of engineers β civil works program river morphology and stream restoration references - wildland hydrology at the library of congress web archives ( archived 2002 - 08 - 13 )
fluid dynamics video demonstrating the evolution of dynamic stall on a wind turbine blade.
ambient air ( see lockheed f - 117 nighthawk, rectangular nozzles on the lockheed martin f - 22 raptor, and serrated nozzle flaps on the lockheed martin f - 35 lightning ). often, cool air is deliberately injected into the exhaust flow to boost this process ( see ryan aqm - 91 firefly and northrop b - 2 spirit ). the stefan β boltzmann law shows how this results in less energy ( thermal radiation in infrared spectrum ) being released and thus reduces the heat signature. in some aircraft, the jet exhaust is vented above the wing surface to shield it from observers below, as in the lockheed f - 117 nighthawk, and the unstealthy fairchild republic a - 10 thunderbolt ii. to achieve infrared stealth, the exhaust gas is cooled to the temperatures where the brightest wavelengths it radiates are absorbed by atmospheric carbon dioxide and water vapor, greatly reducing the infrared visibility of the exhaust plume. another way to reduce the exhaust temperature is to circulate coolant fluids such as fuel inside the exhaust pipe, where the fuel tanks serve as heat sinks cooled by the flow of air along the wings. ground combat includes the use of both active and passive infrared sensors. thus, the united states marine corps ( usmc ) ground combat uniform requirements document specifies infrared reflective quality standards. = = reducing radio frequency ( rf ) emissions = = in addition to reducing infrared and acoustic emissions, a stealth vehicle must avoid radiating any other detectable energy, such as from onboard radars, communications systems, or rf leakage from electronics enclosures. the f - 117 uses passive infrared and low light level television sensor systems to aim its weapons and the f - 22 raptor has an advanced lpi radar which can illuminate enemy aircraft without triggering a radar warning receiver response. = = measuring = = the size of a target ' s image on radar is measured by the rcs, often represented by the symbol Ο and expressed in square meters. this does not equal geometric area. a perfectly conducting sphere of projected cross sectional area 1 m2 ( i. e. a diameter of 1. 13 m ) will have an rcs of 1 m2. note that for radar wavelengths much less than the diameter of the sphere, rcs is independent of frequency. conversely, a square flat plate of area 1 m2 will have an rcs of Ο = 4Ο a2 / Ξ»2 ( where a = area, Ξ» = wavelength ), or 13, 982 m2 at 10 ghz if the radar is perpendicular to the flat
Question: What type of winds blow over a limited area?
A) trade winds
B) hurricanes
C) local winds
D) gales
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C) local winds
|
Context:
sight, hearing, touch, and sometimes smell ( e. g., in infection, uremia, diabetic ketoacidosis ). four actions are the basis of physical examination : inspection, palpation ( feel ), percussion ( tap to determine resonance characteristics ), and auscultation ( listen ), generally in that order, although auscultation occurs prior to percussion and palpation for abdominal assessments. the clinical examination involves the study of : abdomen and rectum cardiovascular ( heart and blood vessels ) general appearance of the patient and specific indicators of disease ( nutritional status, presence of jaundice, pallor or clubbing ) genitalia ( and pregnancy if the patient is or could be pregnant ) head, eye, ear, nose, and throat ( heent ) musculoskeletal ( including spine and extremities ) neurological ( consciousness, awareness, brain, vision, cranial nerves, spinal cord and peripheral nerves ) psychiatric ( orientation, mental state, mood, evidence of abnormal perception or thought ). respiratory ( large airways and lungs ) skin vital signs including height, weight, body temperature, blood pressure, pulse, respiration rate, and hemoglobin oxygen saturation it is to likely focus on areas of interest highlighted in the medical history and may not include everything listed above. the treatment plan may include ordering additional medical laboratory tests and medical imaging studies, starting therapy, referral to a specialist, or watchful observation. a follow - up may be advised. depending upon the health insurance plan and the managed care system, various forms of " utilization review ", such as prior authorization of tests, may place barriers on accessing expensive services. the medical decision - making ( mdm ) process includes the analysis and synthesis of all the above data to come up with a list of possible diagnoses ( the differential diagnoses ), along with an idea of what needs to be done to obtain a definitive diagnosis that would explain the patient ' s problem. on subsequent visits, the process may be repeated in an abbreviated manner to obtain any new history, symptoms, physical findings, lab or imaging results, or specialist consultations. = = institutions = = contemporary medicine is, in general, conducted within health care systems. legal, credentialing, and financing frameworks are established by individual governments, augmented on occasion by international organizations, such as churches. the characteristics of any given health care system have a significant impact on the way medical care is provided. from ancient times,
scientists look through telescopes, study images on electronic screens, record meter readings, and so on. generally, on a basic level, they can agree on what they see, e. g., the thermometer shows 37. 9 degrees c. but, if these scientists have different ideas about the theories that have been developed to explain these basic observations, they may disagree about what they are observing. for example, before albert einstein ' s general theory of relativity, observers would have likely interpreted an image of the einstein cross as five different objects in space. in light of that theory, however, astronomers will tell you that there are actually only two objects, one in the center and four different images of a second object around the sides. alternatively, if other scientists suspect that something is wrong with the telescope and only one object is actually being observed, they are operating under yet another theory. observations that cannot be separated from theoretical interpretation are said to be theory - laden. all observation involves both perception and cognition. that is, one does not make an observation passively, but rather is actively engaged in distinguishing the phenomenon being observed from surrounding sensory data. therefore, observations are affected by one ' s underlying understanding of the way in which the world functions, and that understanding may influence what is perceived, noticed, or deemed worthy of consideration. in this sense, it can be argued that all observation is theory - laden. = = = the purpose of science = = = should science aim to determine ultimate truth, or are there questions that science cannot answer? scientific realists claim that science aims at truth and that one ought to regard scientific theories as true, approximately true, or likely true. conversely, scientific anti - realists argue that science does not aim ( or at least does not succeed ) at truth, especially truth about unobservables like electrons or other universes. instrumentalists argue that scientific theories should only be evaluated on whether they are useful. in their view, whether theories are true or not is beside the point, because the purpose of science is to make predictions and enable effective technology. realists often point to the success of recent scientific theories as evidence for the truth ( or near truth ) of current theories. antirealists point to either the many false theories in the history of science, epistemic morals, the success of false modeling assumptions, or widely termed postmodern criticisms of objectivity as evidence against scientific realism. antirealists attempt to explain the success of scientific theories without reference to truth. some antirealists claim that scientific
, social and economic status, habits ( including diet, medications, tobacco, alcohol ). the physical examination is the examination of the patient for medical signs of disease that are objective and observable, in contrast to symptoms that are volunteered by the patient and are not necessarily objectively observable. the healthcare provider uses sight, hearing, touch, and sometimes smell ( e. g., in infection, uremia, diabetic ketoacidosis ). four actions are the basis of physical examination : inspection, palpation ( feel ), percussion ( tap to determine resonance characteristics ), and auscultation ( listen ), generally in that order, although auscultation occurs prior to percussion and palpation for abdominal assessments. the clinical examination involves the study of : abdomen and rectum cardiovascular ( heart and blood vessels ) general appearance of the patient and specific indicators of disease ( nutritional status, presence of jaundice, pallor or clubbing ) genitalia ( and pregnancy if the patient is or could be pregnant ) head, eye, ear, nose, and throat ( heent ) musculoskeletal ( including spine and extremities ) neurological ( consciousness, awareness, brain, vision, cranial nerves, spinal cord and peripheral nerves ) psychiatric ( orientation, mental state, mood, evidence of abnormal perception or thought ). respiratory ( large airways and lungs ) skin vital signs including height, weight, body temperature, blood pressure, pulse, respiration rate, and hemoglobin oxygen saturation it is to likely focus on areas of interest highlighted in the medical history and may not include everything listed above. the treatment plan may include ordering additional medical laboratory tests and medical imaging studies, starting therapy, referral to a specialist, or watchful observation. a follow - up may be advised. depending upon the health insurance plan and the managed care system, various forms of " utilization review ", such as prior authorization of tests, may place barriers on accessing expensive services. the medical decision - making ( mdm ) process includes the analysis and synthesis of all the above data to come up with a list of possible diagnoses ( the differential diagnoses ), along with an idea of what needs to be done to obtain a definitive diagnosis that would explain the patient ' s problem. on subsequent visits, the process may be repeated in an abbreviated manner to obtain any new history, symptoms, physical findings, lab or imaging results, or specialist consultations. = = institutions = = contemporary
is not present ( e. g., litter in a parking lot or readings on an electric meter ). behavioral observations involve the direct witnessing of the actor engaging in the behavior ( e. g., watching how close a person sits next to another person ). behavioral choices are when a person selects between two or more options ( e. g., voting behavior, choice of a punishment for another participant ). reaction time. the time between the presentation of a stimulus and an appropriate response can indicate differences between two cognitive processes, and can indicate some things about their nature. for example, if in a search task the reaction times vary proportionally with the number of elements, then it is evident that this cognitive process of searching involves serial instead of parallel processing. psychophysical responses. psychophysical experiments are an old psychological technique, which has been adopted by cognitive psychology. they typically involve making judgments of some physical property, e. g. the loudness of a sound. correlation of subjective scales between individuals can show cognitive or sensory biases as compared to actual physical measurements. some examples include : sameness judgments for colors, tones, textures, etc. threshold differences for colors, tones, textures, etc. eye tracking. this methodology is used to study a variety of cognitive processes, most notably visual perception and language processing. the fixation point of the eyes is linked to an individual ' s focus of attention. thus, by monitoring eye movements, we can study what information is being processed at a given time. eye tracking allows us to study cognitive processes on extremely short time scales. eye movements reflect online decision making during a task, and they provide us with some insight into the ways in which those decisions may be processed. = = = brain imaging = = = brain imaging involves analyzing activity within the brain while performing various tasks. this allows us to link behavior and brain function to help understand how information is processed. different types of imaging techniques vary in their temporal ( time - based ) and spatial ( location - based ) resolution. brain imaging is often used in cognitive neuroscience. single - photon emission computed tomography and positron emission tomography. spect and pet use radioactive isotopes, which are injected into the subject ' s bloodstream and taken up by the brain. by observing which areas of the brain take up the radioactive isotope, we can see which areas of the brain are more active than other areas. pet has similar spatial resolution to fmri, but it has extremely poor temporal resolution. electroencephalography. eeg measures the electrical fields
the nervous system. these kinds of tests can be divided into recordings of : ( 1 ) spontaneous or continuously running electrical activity, or ( 2 ) stimulus evoked responses. subspecialties include electroencephalography, electromyography, evoked potential, nerve conduction study and polysomnography. sometimes these tests are performed by techs without a medical degree, but the interpretation of these tests is done by a medical professional. diagnostic radiology is concerned with imaging of the body, e. g. by x - rays, x - ray computed tomography, ultrasonography, and nuclear magnetic resonance tomography. interventional radiologists can access areas in the body under imaging for an intervention or diagnostic sampling. nuclear medicine is concerned with studying human organ systems by administering radiolabelled substances ( radiopharmaceuticals ) to the body, which can then be imaged outside the body by a gamma camera or a pet scanner. each radiopharmaceutical consists of two parts : a tracer that is specific for the function under study ( e. g., neurotransmitter pathway, metabolic pathway, blood flow, or other ), and a radionuclide ( usually either a gamma - emitter or a positron emitter ). there is a degree of overlap between nuclear medicine and radiology, as evidenced by the emergence of combined devices such as the pet / ct scanner. pathology as a medical specialty is the branch of medicine that deals with the study of diseases and the morphologic, physiologic changes produced by them. as a diagnostic specialty, pathology can be considered the basis of modern scientific medical knowledge and plays a large role in evidence - based medicine. many modern molecular tests such as flow cytometry, polymerase chain reaction ( pcr ), immunohistochemistry, cytogenetics, gene rearrangements studies and fluorescent in situ hybridization ( fish ) fall within the territory of pathology. = = = = other major specialties = = = = the following are some major medical specialties that do not directly fit into any of the above - mentioned groups : anesthesiology ( also known as anaesthetics ) : concerned with the perioperative management of the surgical patient. the anesthesiologist ' s role during surgery is to prevent derangement in the vital organs ' ( i. e. brain, heart, kidneys ) functions and postoperative pain. outside of
as subjects perceive the sensory world, different stimuli elicit a number of neural representations. here, a subjective distance between stimuli is defined, measuring the degree of similarity between the underlying representations. as an example, the subjective distance between different locations in space is calculated from the activity of rodent hippocampal place cells, and lateral septal cells. such a distance is compared to the real distance, between locations. as the number of sampled neurons increases, the subjective distance shows a tendency to resemble the metrics of real space.
behavioral responses to different stimuli, one can understand something about how those stimuli are processed. lewandowski & strohmetz ( 2009 ) reviewed a collection of innovative uses of behavioral measurement in psychology including behavioral traces, behavioral observations, and behavioral choice. behavioral traces are pieces of evidence that indicate behavior occurred, but the actor is not present ( e. g., litter in a parking lot or readings on an electric meter ). behavioral observations involve the direct witnessing of the actor engaging in the behavior ( e. g., watching how close a person sits next to another person ). behavioral choices are when a person selects between two or more options ( e. g., voting behavior, choice of a punishment for another participant ). reaction time. the time between the presentation of a stimulus and an appropriate response can indicate differences between two cognitive processes, and can indicate some things about their nature. for example, if in a search task the reaction times vary proportionally with the number of elements, then it is evident that this cognitive process of searching involves serial instead of parallel processing. psychophysical responses. psychophysical experiments are an old psychological technique, which has been adopted by cognitive psychology. they typically involve making judgments of some physical property, e. g. the loudness of a sound. correlation of subjective scales between individuals can show cognitive or sensory biases as compared to actual physical measurements. some examples include : sameness judgments for colors, tones, textures, etc. threshold differences for colors, tones, textures, etc. eye tracking. this methodology is used to study a variety of cognitive processes, most notably visual perception and language processing. the fixation point of the eyes is linked to an individual ' s focus of attention. thus, by monitoring eye movements, we can study what information is being processed at a given time. eye tracking allows us to study cognitive processes on extremely short time scales. eye movements reflect online decision making during a task, and they provide us with some insight into the ways in which those decisions may be processed. = = = brain imaging = = = brain imaging involves analyzing activity within the brain while performing various tasks. this allows us to link behavior and brain function to help understand how information is processed. different types of imaging techniques vary in their temporal ( time - based ) and spatial ( location - based ) resolution. brain imaging is often used in cognitive neuroscience. single - photon emission computed tomography and positron emission tomography. spect and pet use radioactive isotopes, which are injected into the subject ' s bloodstream
##physical processes which take place in human beings as they make sense of information received through the visual system. the subject of the image. when developing an imaging system, designers must consider the observables associated with the subjects which will be imaged. these observables generally take the form of emitted or reflected energy, such as electromagnetic energy or mechanical energy. the capture device. once the observables associated with the subject are characterized, designers can then identify and integrate the technologies needed to capture those observables. for example, in the case of consumer digital cameras, those technologies include optics for collecting energy in the visible portion of the electromagnetic spectrum, and electronic detectors for converting the electromagnetic energy into an electronic signal. the processor. for all digital imaging systems, the electronic signals produced by the capture device must be manipulated by an algorithm which formats the signals so they can be displayed as an image. in practice, there are often multiple processors involved in the creation of a digital image. the display. the display takes the electronic signals which have been manipulated by the processor and renders them on some visual medium. examples include paper ( for printed, or " hard copy " images ), television, computer monitor, or projector. note that some imaging scientists will include additional " links " in their description of the imaging chain. for example, some will include the " source " of the energy which " illuminates " or interacts with the subject of the image. others will include storage and / or transmission systems. = = subfields = = subfields within imaging science include : image processing, computer vision, 3d computer graphics, animations, atmospheric optics, astronomical imaging, biological imaging, digital image restoration, digital imaging, color science, digital photography, holography, magnetic resonance imaging, medical imaging, microdensitometry, optics, photography, remote sensing, radar imaging, radiometry, silver halide, ultrasound imaging, photoacoustic imaging, thermal imaging, visual perception, and various printing technologies. = = methodologies = = acoustic imaging coherent imaging uses an active coherent illumination source, such as in radar, synthetic aperture radar ( sar ), medical ultrasound and optical coherence tomography ; non - coherent imaging systems include fluorescent microscopes, optical microscopes, and telescopes. chemical imaging, the simultaneous measurement of spectra and pictures digital imaging, creating digital images, generally by scanning or through digital photography disk image, a file which contains the exact content of a data storage medium document imaging, replicating documents commonly
you noticed any weight loss, change in sleep quality, fevers, lumps and bumps? etc. ), followed by questions on the body ' s main organ systems ( heart, lungs, digestive tract, urinary tract, etc. ). social history ( sh ) : birthplace, residences, marital history, social and economic status, habits ( including diet, medications, tobacco, alcohol ). the physical examination is the examination of the patient for medical signs of disease that are objective and observable, in contrast to symptoms that are volunteered by the patient and are not necessarily objectively observable. the healthcare provider uses sight, hearing, touch, and sometimes smell ( e. g., in infection, uremia, diabetic ketoacidosis ). four actions are the basis of physical examination : inspection, palpation ( feel ), percussion ( tap to determine resonance characteristics ), and auscultation ( listen ), generally in that order, although auscultation occurs prior to percussion and palpation for abdominal assessments. the clinical examination involves the study of : abdomen and rectum cardiovascular ( heart and blood vessels ) general appearance of the patient and specific indicators of disease ( nutritional status, presence of jaundice, pallor or clubbing ) genitalia ( and pregnancy if the patient is or could be pregnant ) head, eye, ear, nose, and throat ( heent ) musculoskeletal ( including spine and extremities ) neurological ( consciousness, awareness, brain, vision, cranial nerves, spinal cord and peripheral nerves ) psychiatric ( orientation, mental state, mood, evidence of abnormal perception or thought ). respiratory ( large airways and lungs ) skin vital signs including height, weight, body temperature, blood pressure, pulse, respiration rate, and hemoglobin oxygen saturation it is to likely focus on areas of interest highlighted in the medical history and may not include everything listed above. the treatment plan may include ordering additional medical laboratory tests and medical imaging studies, starting therapy, referral to a specialist, or watchful observation. a follow - up may be advised. depending upon the health insurance plan and the managed care system, various forms of " utilization review ", such as prior authorization of tests, may place barriers on accessing expensive services. the medical decision - making ( mdm ) process includes the analysis and synthesis of all the above data to come up with a list of possible diagnoses ( the differential diagnoses ),
options ( e. g., voting behavior, choice of a punishment for another participant ). reaction time. the time between the presentation of a stimulus and an appropriate response can indicate differences between two cognitive processes, and can indicate some things about their nature. for example, if in a search task the reaction times vary proportionally with the number of elements, then it is evident that this cognitive process of searching involves serial instead of parallel processing. psychophysical responses. psychophysical experiments are an old psychological technique, which has been adopted by cognitive psychology. they typically involve making judgments of some physical property, e. g. the loudness of a sound. correlation of subjective scales between individuals can show cognitive or sensory biases as compared to actual physical measurements. some examples include : sameness judgments for colors, tones, textures, etc. threshold differences for colors, tones, textures, etc. eye tracking. this methodology is used to study a variety of cognitive processes, most notably visual perception and language processing. the fixation point of the eyes is linked to an individual ' s focus of attention. thus, by monitoring eye movements, we can study what information is being processed at a given time. eye tracking allows us to study cognitive processes on extremely short time scales. eye movements reflect online decision making during a task, and they provide us with some insight into the ways in which those decisions may be processed. = = = brain imaging = = = brain imaging involves analyzing activity within the brain while performing various tasks. this allows us to link behavior and brain function to help understand how information is processed. different types of imaging techniques vary in their temporal ( time - based ) and spatial ( location - based ) resolution. brain imaging is often used in cognitive neuroscience. single - photon emission computed tomography and positron emission tomography. spect and pet use radioactive isotopes, which are injected into the subject ' s bloodstream and taken up by the brain. by observing which areas of the brain take up the radioactive isotope, we can see which areas of the brain are more active than other areas. pet has similar spatial resolution to fmri, but it has extremely poor temporal resolution. electroencephalography. eeg measures the electrical fields generated by large populations of neurons in the cortex by placing a series of electrodes on the scalp of the subject. this technique has an extremely high temporal resolution, but a relatively poor spatial resolution. functional magnetic resonance imaging. fmri measures the relative amount of oxygenated blood flowing to different parts of the brain. more oxygen
Question: In terms of scientific investigation, things you notice about an environment using your five senses are called what?
A) behaviors
B) observations
C) evidence
D) patterns
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B) observations
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Context:
by chlorophyll a is initially in the form of electrons ( and later a proton gradient ) that is used to make molecules of atp and nadph which temporarily store and transport energy. their energy is used in the light - independent reactions of the calvin cycle by the enzyme rubisco to produce molecules of the 3 - carbon sugar glyceraldehyde 3 - phosphate ( g3p ). glyceraldehyde 3 - phosphate is the first product of photosynthesis and the raw material from which glucose and almost all other organic molecules of biological origin are synthesised. some of the glucose is converted to starch which is stored in the chloroplast. starch is the characteristic energy store of most land plants and algae, while inulin, a polymer of fructose is used for the same purpose in the sunflower family asteraceae. some of the glucose is converted to sucrose ( common table sugar ) for export to the rest of the plant. unlike in animals ( which lack chloroplasts ), plants and their eukaryote relatives have delegated many biochemical roles to their chloroplasts, including synthesising all their fatty acids, and most amino acids. the fatty acids that chloroplasts make are used for many things, such as providing material to build cell membranes out of and making the polymer cutin which is found in the plant cuticle that protects land plants from drying out. plants synthesise a number of unique polymers like the polysaccharide molecules cellulose, pectin and xyloglucan from which the land plant cell wall is constructed. vascular land plants make lignin, a polymer used to strengthen the secondary cell walls of xylem tracheids and vessels to keep them from collapsing when a plant sucks water through them under water stress. lignin is also used in other cell types like sclerenchyma fibres that provide structural support for a plant and is a major constituent of wood. sporopollenin is a chemically resistant polymer found in the outer cell walls of spores and pollen of land plants responsible for the survival of early land plant spores and the pollen of seed plants in the fossil record. it is widely regarded as a marker for the start of land plant evolution during the ordovician period. the concentration of carbon dioxide in the atmosphere today is much lower than it was when plants emerged onto land during the ordovician and silurian periods.
of these organisms. the energy in the red and blue light that these pigments absorb is used by chloroplasts to make energy - rich carbon compounds from carbon dioxide and water by oxygenic photosynthesis, a process that generates molecular oxygen ( o2 ) as a by - product. the light energy captured by chlorophyll a is initially in the form of electrons ( and later a proton gradient ) that is used to make molecules of atp and nadph which temporarily store and transport energy. their energy is used in the light - independent reactions of the calvin cycle by the enzyme rubisco to produce molecules of the 3 - carbon sugar glyceraldehyde 3 - phosphate ( g3p ). glyceraldehyde 3 - phosphate is the first product of photosynthesis and the raw material from which glucose and almost all other organic molecules of biological origin are synthesised. some of the glucose is converted to starch which is stored in the chloroplast. starch is the characteristic energy store of most land plants and algae, while inulin, a polymer of fructose is used for the same purpose in the sunflower family asteraceae. some of the glucose is converted to sucrose ( common table sugar ) for export to the rest of the plant. unlike in animals ( which lack chloroplasts ), plants and their eukaryote relatives have delegated many biochemical roles to their chloroplasts, including synthesising all their fatty acids, and most amino acids. the fatty acids that chloroplasts make are used for many things, such as providing material to build cell membranes out of and making the polymer cutin which is found in the plant cuticle that protects land plants from drying out. plants synthesise a number of unique polymers like the polysaccharide molecules cellulose, pectin and xyloglucan from which the land plant cell wall is constructed. vascular land plants make lignin, a polymer used to strengthen the secondary cell walls of xylem tracheids and vessels to keep them from collapsing when a plant sucks water through them under water stress. lignin is also used in other cell types like sclerenchyma fibres that provide structural support for a plant and is a major constituent of wood. sporopollenin is a chemically resistant polymer found in the outer cell walls of spores and pollen of land plants responsible for the survival of early land plant spores and
is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. in most cases, oxygen is released as a waste product. most plants, algae, and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of the earth ' s atmosphere, and supplies most of the energy necessary for life on earth. photosynthesis has four stages : light absorption, electron transport, atp synthesis, and carbon fixation. light absorption is the initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to proteins in the thylakoid membranes. the absorbed light energy is used to remove electrons from a donor ( water ) to a primary electron acceptor, a quinone designated as q. in the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach a final electron acceptor, which is usually the oxidized form of nadp +, which is reduced to nadph, a process that takes place in a protein complex called photosystem i ( psi ). the transport of electrons is coupled to the movement of protons ( or hydrogen ) from the stroma to the thylakoid membrane, which forms a ph gradient across the membrane as hydrogen becomes more concentrated in the lumen than in the stroma. this is analogous to the proton - motive force generated across the inner mitochondrial membrane in aerobic respiration. during the third stage of photosynthesis, the movement of protons down their concentration gradients from the thylakoid lumen to the stroma through the atp synthase is coupled to the synthesis of atp by that same atp synthase. the nadph and atps generated by the light - dependent reactions in the second and third stages, respectively, provide the energy and electrons to drive the synthesis of glucose by fixing atmospheric carbon dioxide into existing organic carbon compounds, such as ribulose bisphosphate ( rubp ) in a sequence of light - independent ( or dark ) reactions called the calvin cycle. = = = cell signaling = = = cell signaling ( or communication ) is the ability of cells to receive, process, and transmit signals with its environment and with itself. signals can be non - chemical such as light, electrical impulses, and heat, or chemical signals ( or ligands ) that interact with receptors, which can be found embedded in the cell membrane of another cell or located deep inside
their primary metabolism like the photosynthetic calvin cycle and crassulacean acid metabolism. others make specialised materials like the cellulose and lignin used to build their bodies, and secondary products like resins and aroma compounds. plants and various other groups of photosynthetic eukaryotes collectively known as " algae " have unique organelles known as chloroplasts. chloroplasts are thought to be descended from cyanobacteria that formed endosymbiotic relationships with ancient plant and algal ancestors. chloroplasts and cyanobacteria contain the blue - green pigment chlorophyll a. chlorophyll a ( as well as its plant and green algal - specific cousin chlorophyll b ) absorbs light in the blue - violet and orange / red parts of the spectrum while reflecting and transmitting the green light that we see as the characteristic colour of these organisms. the energy in the red and blue light that these pigments absorb is used by chloroplasts to make energy - rich carbon compounds from carbon dioxide and water by oxygenic photosynthesis, a process that generates molecular oxygen ( o2 ) as a by - product. the light energy captured by chlorophyll a is initially in the form of electrons ( and later a proton gradient ) that is used to make molecules of atp and nadph which temporarily store and transport energy. their energy is used in the light - independent reactions of the calvin cycle by the enzyme rubisco to produce molecules of the 3 - carbon sugar glyceraldehyde 3 - phosphate ( g3p ). glyceraldehyde 3 - phosphate is the first product of photosynthesis and the raw material from which glucose and almost all other organic molecules of biological origin are synthesised. some of the glucose is converted to starch which is stored in the chloroplast. starch is the characteristic energy store of most land plants and algae, while inulin, a polymer of fructose is used for the same purpose in the sunflower family asteraceae. some of the glucose is converted to sucrose ( common table sugar ) for export to the rest of the plant. unlike in animals ( which lack chloroplasts ), plants and their eukaryote relatives have delegated many biochemical roles to their chloroplasts, including synthesising all their fatty acids, and most amino acids. the fatty acids that
pigment chlorophyll a. chlorophyll a ( as well as its plant and green algal - specific cousin chlorophyll b ) absorbs light in the blue - violet and orange / red parts of the spectrum while reflecting and transmitting the green light that we see as the characteristic colour of these organisms. the energy in the red and blue light that these pigments absorb is used by chloroplasts to make energy - rich carbon compounds from carbon dioxide and water by oxygenic photosynthesis, a process that generates molecular oxygen ( o2 ) as a by - product. the light energy captured by chlorophyll a is initially in the form of electrons ( and later a proton gradient ) that is used to make molecules of atp and nadph which temporarily store and transport energy. their energy is used in the light - independent reactions of the calvin cycle by the enzyme rubisco to produce molecules of the 3 - carbon sugar glyceraldehyde 3 - phosphate ( g3p ). glyceraldehyde 3 - phosphate is the first product of photosynthesis and the raw material from which glucose and almost all other organic molecules of biological origin are synthesised. some of the glucose is converted to starch which is stored in the chloroplast. starch is the characteristic energy store of most land plants and algae, while inulin, a polymer of fructose is used for the same purpose in the sunflower family asteraceae. some of the glucose is converted to sucrose ( common table sugar ) for export to the rest of the plant. unlike in animals ( which lack chloroplasts ), plants and their eukaryote relatives have delegated many biochemical roles to their chloroplasts, including synthesising all their fatty acids, and most amino acids. the fatty acids that chloroplasts make are used for many things, such as providing material to build cell membranes out of and making the polymer cutin which is found in the plant cuticle that protects land plants from drying out. plants synthesise a number of unique polymers like the polysaccharide molecules cellulose, pectin and xyloglucan from which the land plant cell wall is constructed. vascular land plants make lignin, a polymer used to strengthen the secondary cell walls of xylem tracheids and vessels to keep them from collapsing when a plant sucks water through them under water stress. lignin
3 - carbon sugar glyceraldehyde 3 - phosphate ( g3p ). glyceraldehyde 3 - phosphate is the first product of photosynthesis and the raw material from which glucose and almost all other organic molecules of biological origin are synthesised. some of the glucose is converted to starch which is stored in the chloroplast. starch is the characteristic energy store of most land plants and algae, while inulin, a polymer of fructose is used for the same purpose in the sunflower family asteraceae. some of the glucose is converted to sucrose ( common table sugar ) for export to the rest of the plant. unlike in animals ( which lack chloroplasts ), plants and their eukaryote relatives have delegated many biochemical roles to their chloroplasts, including synthesising all their fatty acids, and most amino acids. the fatty acids that chloroplasts make are used for many things, such as providing material to build cell membranes out of and making the polymer cutin which is found in the plant cuticle that protects land plants from drying out. plants synthesise a number of unique polymers like the polysaccharide molecules cellulose, pectin and xyloglucan from which the land plant cell wall is constructed. vascular land plants make lignin, a polymer used to strengthen the secondary cell walls of xylem tracheids and vessels to keep them from collapsing when a plant sucks water through them under water stress. lignin is also used in other cell types like sclerenchyma fibres that provide structural support for a plant and is a major constituent of wood. sporopollenin is a chemically resistant polymer found in the outer cell walls of spores and pollen of land plants responsible for the survival of early land plant spores and the pollen of seed plants in the fossil record. it is widely regarded as a marker for the start of land plant evolution during the ordovician period. the concentration of carbon dioxide in the atmosphere today is much lower than it was when plants emerged onto land during the ordovician and silurian periods. many monocots like maize and the pineapple and some dicots like the asteraceae have since independently evolved pathways like crassulacean acid metabolism and the c4 carbon fixation pathway for photosynthesis which avoid the losses resulting from photorespiration in the more common c3 carbon fixation pathway
liver glycogen. during recovery, when oxygen becomes available, nad + attaches to hydrogen from lactate to form atp. in yeast, the waste products are ethanol and carbon dioxide. this type of fermentation is known as alcoholic or ethanol fermentation. the atp generated in this process is made by substrate - level phosphorylation, which does not require oxygen. = = = photosynthesis = = = photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organism ' s metabolic activities via cellular respiration. this chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. in most cases, oxygen is released as a waste product. most plants, algae, and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of the earth ' s atmosphere, and supplies most of the energy necessary for life on earth. photosynthesis has four stages : light absorption, electron transport, atp synthesis, and carbon fixation. light absorption is the initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to proteins in the thylakoid membranes. the absorbed light energy is used to remove electrons from a donor ( water ) to a primary electron acceptor, a quinone designated as q. in the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach a final electron acceptor, which is usually the oxidized form of nadp +, which is reduced to nadph, a process that takes place in a protein complex called photosystem i ( psi ). the transport of electrons is coupled to the movement of protons ( or hydrogen ) from the stroma to the thylakoid membrane, which forms a ph gradient across the membrane as hydrogen becomes more concentrated in the lumen than in the stroma. this is analogous to the proton - motive force generated across the inner mitochondrial membrane in aerobic respiration. during the third stage of photosynthesis, the movement of protons down their concentration gradients from the thylakoid lumen to the stroma through the atp synthase is coupled to the synthesis of atp by that same atp synthase. the nadph and atps generated by the light - dependent reactions in the second and third stages, respectively, provide the energy and
from the proton motive force drives the enzyme atp synthase to synthesize more atps by phosphorylating adps. the transfer of electrons terminates with molecular oxygen being the final electron acceptor. if oxygen were not present, pyruvate would not be metabolized by cellular respiration but undergoes a process of fermentation. the pyruvate is not transported into the mitochondrion but remains in the cytoplasm, where it is converted to waste products that may be removed from the cell. this serves the purpose of oxidizing the electron carriers so that they can perform glycolysis again and removing the excess pyruvate. fermentation oxidizes nadh to nad + so it can be re - used in glycolysis. in the absence of oxygen, fermentation prevents the buildup of nadh in the cytoplasm and provides nad + for glycolysis. this waste product varies depending on the organism. in skeletal muscles, the waste product is lactic acid. this type of fermentation is called lactic acid fermentation. in strenuous exercise, when energy demands exceed energy supply, the respiratory chain cannot process all of the hydrogen atoms joined by nadh. during anaerobic glycolysis, nad + regenerates when pairs of hydrogen combine with pyruvate to form lactate. lactate formation is catalyzed by lactate dehydrogenase in a reversible reaction. lactate can also be used as an indirect precursor for liver glycogen. during recovery, when oxygen becomes available, nad + attaches to hydrogen from lactate to form atp. in yeast, the waste products are ethanol and carbon dioxide. this type of fermentation is known as alcoholic or ethanol fermentation. the atp generated in this process is made by substrate - level phosphorylation, which does not require oxygen. = = = photosynthesis = = = photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organism ' s metabolic activities via cellular respiration. this chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. in most cases, oxygen is released as a waste product. most plants, algae, and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of
substrate - level phosphorylation, which does not require oxygen. = = = photosynthesis = = = photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organism ' s metabolic activities via cellular respiration. this chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. in most cases, oxygen is released as a waste product. most plants, algae, and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of the earth ' s atmosphere, and supplies most of the energy necessary for life on earth. photosynthesis has four stages : light absorption, electron transport, atp synthesis, and carbon fixation. light absorption is the initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to proteins in the thylakoid membranes. the absorbed light energy is used to remove electrons from a donor ( water ) to a primary electron acceptor, a quinone designated as q. in the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach a final electron acceptor, which is usually the oxidized form of nadp +, which is reduced to nadph, a process that takes place in a protein complex called photosystem i ( psi ). the transport of electrons is coupled to the movement of protons ( or hydrogen ) from the stroma to the thylakoid membrane, which forms a ph gradient across the membrane as hydrogen becomes more concentrated in the lumen than in the stroma. this is analogous to the proton - motive force generated across the inner mitochondrial membrane in aerobic respiration. during the third stage of photosynthesis, the movement of protons down their concentration gradients from the thylakoid lumen to the stroma through the atp synthase is coupled to the synthesis of atp by that same atp synthase. the nadph and atps generated by the light - dependent reactions in the second and third stages, respectively, provide the energy and electrons to drive the synthesis of glucose by fixing atmospheric carbon dioxide into existing organic carbon compounds, such as ribulose bisphosphate ( rubp ) in a sequence of light - independent ( or dark ) reactions called the calvin cycle. = = = cell signaling = = = cell signaling ( or communication ) is the
and still use the same basic biological methods. in brewing, malted grains ( containing enzymes ) convert starch from grains into sugar and then adding specific yeasts to produce beer. in this process, carbohydrates in the grains broke down into alcohols, such as ethanol. later, other cultures produced the process of lactic acid fermentation, which produced other preserved foods, such as soy sauce. fermentation was also used in this time period to produce leavened bread. although the process of fermentation was not fully understood until louis pasteur ' s work in 1857, it is still the first use of biotechnology to convert a food source into another form. before the time of charles darwin ' s work and life, animal and plant scientists had already used selective breeding. darwin added to that body of work with his scientific observations about the ability of science to change species. these accounts contributed to darwin ' s theory of natural selection. for thousands of years, humans have used selective breeding to improve the production of crops and livestock to use them for food. in selective breeding, organisms with desirable characteristics are mated to produce offspring with the same characteristics. for example, this technique was used with corn to produce the largest and sweetest crops. in the early twentieth century scientists gained a greater understanding of microbiology and explored ways of manufacturing specific products. in 1917, chaim weizmann first used a pure microbiological culture in an industrial process, that of manufacturing corn starch using clostridium acetobutylicum, to produce acetone, which the united kingdom desperately needed to manufacture explosives during world war i. biotechnology has also led to the development of antibiotics. in 1928, alexander fleming discovered the mold penicillium. his work led to the purification of the antibiotic formed by the mold by howard florey, ernst boris chain and norman heatley β to form what we today know as penicillin. in 1940, penicillin became available for medicinal use to treat bacterial infections in humans. the field of modern biotechnology is generally thought of as having been born in 1971 when paul berg ' s ( stanford ) experiments in gene splicing had early success. herbert w. boyer ( univ. calif. at san francisco ) and stanley n. cohen ( stanford ) significantly advanced the new technology in 1972 by transferring genetic material into a bacterium, such that the imported material would be reproduced. the commercial viability of a biotechnology industry was significantly expanded on june 16, 1980, when the united states
Question: What is the final product of the calvin cycle?
A) chloride
B) insulin
C) glucose
D) energy
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C) glucose
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Context:
##idermal electronics mirror those of skin to allow them to perform in this same way. like skin, epidermal electronics are ultrathin ( h < 100 ΞΌm ), low - modulus ( e β70 kpa ), and lightweight ( < 10 mg / cm2 ), enabling them to conform to the skin without applying strain. conformal contact and proper adhesion enable the device to bend and stretch without delaminating, deforming or failing, thereby eliminating the challenges with conventional, bulky wearables, including measurement artifacts, hysteresis, and motion - induced irritation to the skin. with this inherent ability to take the shape of skin, epidermal electronics can accurately acquire data without altering the natural motion or behavior of skin. the thin, soft, flexible design of epidermal electronics resembles that of temporary tattoos laminated on the skin. essentially, these devices are " mechanically invisible " to the wearer. epidermal electronics devices may adhere to the skin via van der waals forces or elastomeric substrates. with only van der waals forces, an epidermal device has the same thermal mass per unit area ( 150 mj / cm2k ) as skin, when the skin ' s thickness is < 500 nm. along with van der waals forces, the low values of e and thickness are effective in maximizing adhesion because they prevent deformation - induced detachment due to tension or compression. introducing an elastomeric substrate can improve adhesion but will raise the thermal mass per unit area slightly. several materials have been studied to produce these skin - like properties, including photolithography patterned serpentine gold nanofilm and patterned doping of silicon nanomembranes. = = = foot - worn = = = smart shoes are an example of wearable technology that incorporate smart features into shoes. smart shoes often work with smartphone applications to support tasks cannot be done with standard footwear. the uses include vibrating of the smart phone to tell users when and where to turn to reach their destination via google maps or self - lacing. self - lacing sneaker technology, similar to the nike mag in back to the future part ii, is another use of the smart shoe. in 2019 german footwear company puma was recognized as one of the " 100 best inventions of 2019 " by time for its fi laceless shoe that uses micro - motors to adjust the fit from an iphone. nike also introduced a smart shoe in 2019 known as adapt bb. the shoe featured buttons on the
the skin without applying strain. conformal contact and proper adhesion enable the device to bend and stretch without delaminating, deforming or failing, thereby eliminating the challenges with conventional, bulky wearables, including measurement artifacts, hysteresis, and motion - induced irritation to the skin. with this inherent ability to take the shape of skin, epidermal electronics can accurately acquire data without altering the natural motion or behavior of skin. the thin, soft, flexible design of epidermal electronics resembles that of temporary tattoos laminated on the skin. essentially, these devices are " mechanically invisible " to the wearer. epidermal electronics devices may adhere to the skin via van der waals forces or elastomeric substrates. with only van der waals forces, an epidermal device has the same thermal mass per unit area ( 150 mj / cm2k ) as skin, when the skin ' s thickness is < 500 nm. along with van der waals forces, the low values of e and thickness are effective in maximizing adhesion because they prevent deformation - induced detachment due to tension or compression. introducing an elastomeric substrate can improve adhesion but will raise the thermal mass per unit area slightly. several materials have been studied to produce these skin - like properties, including photolithography patterned serpentine gold nanofilm and patterned doping of silicon nanomembranes. = = = foot - worn = = = smart shoes are an example of wearable technology that incorporate smart features into shoes. smart shoes often work with smartphone applications to support tasks cannot be done with standard footwear. the uses include vibrating of the smart phone to tell users when and where to turn to reach their destination via google maps or self - lacing. self - lacing sneaker technology, similar to the nike mag in back to the future part ii, is another use of the smart shoe. in 2019 german footwear company puma was recognized as one of the " 100 best inventions of 2019 " by time for its fi laceless shoe that uses micro - motors to adjust the fit from an iphone. nike also introduced a smart shoe in 2019 known as adapt bb. the shoe featured buttons on the side to loosen or tighten the fit with a custom motor and gear, which could also be controlled by a smartphone. = = modern technologies = = on april 16, 2013, google invited " glass explorers " who had pre - ordered its wearable glasses at the 2012 google i / o conference to pick up their devices.
directly on the skin is currently available as a sole study source. the significance of epidermal electronics involves their mechanical properties, which resemble those of skin. the skin can be modeled as bilayer, composed of an epidermis having young ' s modulus ( e ) of 2 - 80 kpa and thickness of 0. 3 β 3 mm and a dermis having e of 140 - 600 kpa and thickness of 0. 05 - 1. 5 mm. together this bilayer responds plastically to tensile strains β₯ 30 %, below which the skin ' s surface stretches and wrinkles without deforming. properties of epidermal electronics mirror those of skin to allow them to perform in this same way. like skin, epidermal electronics are ultrathin ( h < 100 ΞΌm ), low - modulus ( e β70 kpa ), and lightweight ( < 10 mg / cm2 ), enabling them to conform to the skin without applying strain. conformal contact and proper adhesion enable the device to bend and stretch without delaminating, deforming or failing, thereby eliminating the challenges with conventional, bulky wearables, including measurement artifacts, hysteresis, and motion - induced irritation to the skin. with this inherent ability to take the shape of skin, epidermal electronics can accurately acquire data without altering the natural motion or behavior of skin. the thin, soft, flexible design of epidermal electronics resembles that of temporary tattoos laminated on the skin. essentially, these devices are " mechanically invisible " to the wearer. epidermal electronics devices may adhere to the skin via van der waals forces or elastomeric substrates. with only van der waals forces, an epidermal device has the same thermal mass per unit area ( 150 mj / cm2k ) as skin, when the skin ' s thickness is < 500 nm. along with van der waals forces, the low values of e and thickness are effective in maximizing adhesion because they prevent deformation - induced detachment due to tension or compression. introducing an elastomeric substrate can improve adhesion but will raise the thermal mass per unit area slightly. several materials have been studied to produce these skin - like properties, including photolithography patterned serpentine gold nanofilm and patterned doping of silicon nanomembranes. = = = foot - worn = = = smart shoes are an example of wearable technology that incorporate smart features into shoes. smart shoes often work with smartphone applications to support
layer of the skin. these wearables are mounted directly onto the skin to continuously monitor physiological and metabolic processes, both dermal and subdermal. wireless capability is typically achieved through battery, bluetooth or nfc, making these devices convenient and portable as a type of wearable technology. currently, epidermal electronics are being developed in the fields of fitness and medical monitoring. current usage of epidermal technology is limited by existing fabrication processes. its current application relies on various sophisticated fabrication techniques such as by lithography or by directly printing on a carrier substrate before attaching directly to the body. research into printing epidermal electronics directly on the skin is currently available as a sole study source. the significance of epidermal electronics involves their mechanical properties, which resemble those of skin. the skin can be modeled as bilayer, composed of an epidermis having young ' s modulus ( e ) of 2 - 80 kpa and thickness of 0. 3 β 3 mm and a dermis having e of 140 - 600 kpa and thickness of 0. 05 - 1. 5 mm. together this bilayer responds plastically to tensile strains β₯ 30 %, below which the skin ' s surface stretches and wrinkles without deforming. properties of epidermal electronics mirror those of skin to allow them to perform in this same way. like skin, epidermal electronics are ultrathin ( h < 100 ΞΌm ), low - modulus ( e β70 kpa ), and lightweight ( < 10 mg / cm2 ), enabling them to conform to the skin without applying strain. conformal contact and proper adhesion enable the device to bend and stretch without delaminating, deforming or failing, thereby eliminating the challenges with conventional, bulky wearables, including measurement artifacts, hysteresis, and motion - induced irritation to the skin. with this inherent ability to take the shape of skin, epidermal electronics can accurately acquire data without altering the natural motion or behavior of skin. the thin, soft, flexible design of epidermal electronics resembles that of temporary tattoos laminated on the skin. essentially, these devices are " mechanically invisible " to the wearer. epidermal electronics devices may adhere to the skin via van der waals forces or elastomeric substrates. with only van der waals forces, an epidermal device has the same thermal mass per unit area ( 150 mj / cm2k ) as skin, when the skin ' s thickness is < 500
0. 3 β 3 mm and a dermis having e of 140 - 600 kpa and thickness of 0. 05 - 1. 5 mm. together this bilayer responds plastically to tensile strains β₯ 30 %, below which the skin ' s surface stretches and wrinkles without deforming. properties of epidermal electronics mirror those of skin to allow them to perform in this same way. like skin, epidermal electronics are ultrathin ( h < 100 ΞΌm ), low - modulus ( e β70 kpa ), and lightweight ( < 10 mg / cm2 ), enabling them to conform to the skin without applying strain. conformal contact and proper adhesion enable the device to bend and stretch without delaminating, deforming or failing, thereby eliminating the challenges with conventional, bulky wearables, including measurement artifacts, hysteresis, and motion - induced irritation to the skin. with this inherent ability to take the shape of skin, epidermal electronics can accurately acquire data without altering the natural motion or behavior of skin. the thin, soft, flexible design of epidermal electronics resembles that of temporary tattoos laminated on the skin. essentially, these devices are " mechanically invisible " to the wearer. epidermal electronics devices may adhere to the skin via van der waals forces or elastomeric substrates. with only van der waals forces, an epidermal device has the same thermal mass per unit area ( 150 mj / cm2k ) as skin, when the skin ' s thickness is < 500 nm. along with van der waals forces, the low values of e and thickness are effective in maximizing adhesion because they prevent deformation - induced detachment due to tension or compression. introducing an elastomeric substrate can improve adhesion but will raise the thermal mass per unit area slightly. several materials have been studied to produce these skin - like properties, including photolithography patterned serpentine gold nanofilm and patterned doping of silicon nanomembranes. = = = foot - worn = = = smart shoes are an example of wearable technology that incorporate smart features into shoes. smart shoes often work with smartphone applications to support tasks cannot be done with standard footwear. the uses include vibrating of the smart phone to tell users when and where to turn to reach their destination via google maps or self - lacing. self - lacing sneaker technology, similar to the nike mag in back to the future part ii, is another use of the
bear ' ) was conspicuous on radar. it is now known that propellers and jet turbine blades produce a bright radar image ; the bear has four pairs of large 18 - foot ( 5. 6 m ) diameter contra - rotating propellers. another important factor is internal construction. some stealth aircraft have skin that is radar transparent or absorbing, behind which are structures termed reentrant triangles. radar waves penetrating the skin get trapped in these structures, reflecting off the internal faces and losing energy. this method was first used on the blackbird series : a - 12, yf - 12a, lockheed sr - 71 blackbird. the most efficient way to reflect radar waves back to the emitting radar is with orthogonal metal plates, forming a corner reflector consisting of either a dihedral ( two plates ) or a trihedral ( three orthogonal plates ). this configuration occurs in the tail of a conventional aircraft, where the vertical and horizontal components of the tail are set at right angles. stealth aircraft such as the f - 117 use a different arrangement, tilting the tail surfaces to reduce corner reflections formed between them. a more radical method is to omit the tail, as in the b - 2 spirit. the b - 2 ' s clean, low - drag flying wing configuration gives it exceptional range and reduces its radar profile. the flying wing design most closely resembles a so - called infinite flat plate ( as vertical control surfaces dramatically increase rcs ), the perfect stealth shape, as it would have no angles to reflect back radar waves. in addition to altering the tail, stealth design must bury the engines within the wing or fuselage, or in some cases where stealth is applied to an extant aircraft, install baffles in the air intakes, so that the compressor blades are not visible to radar. a stealthy shape must be devoid of complex bumps or protrusions of any kind, meaning that weapons, fuel tanks, and other stores must not be carried externally. any stealthy vehicle becomes un - stealthy when a door or hatch opens. parallel alignment of edges or even surfaces is also often used in stealth designs. the technique involves using a small number of edge orientations in the shape of the structure. for example, on the f - 22a raptor, the leading edges of the wing and the tail planes are set at the same angle. other smaller structures, such as the air intake bypass doors and the air refueling aperture, also use the same angles. the effect of this is to return a narrow radar signal in a very specific direction away from the radar
water, plaster and epoxy β most of which will be eliminated upon firing. a ceramic - filled epoxy, such as martyte, is sometimes used to protect structural steel under conditions of rocket exhaust impingement. these forming techniques are well known for providing tools and other components with dimensional stability, surface quality, high ( near theoretical ) density and microstructural uniformity. the increasing use and diversity of specialty forms of ceramics adds to the diversity of process technologies to be used. thus, reinforcing fibers and filaments are mainly made by polymer, sol - gel, or cvd processes, but melt processing also has applicability. the most widely used specialty form is layered structures, with tape casting for electronic substrates and packages being pre - eminent. photo - lithography is of increasing interest for precise patterning of conductors and other components for such packaging. tape casting or forming processes are also of increasing interest for other applications, ranging from open structures such as fuel cells to ceramic composites. the other major layer structure is coating, where thermal spraying is very important, but chemical and physical vapor deposition and chemical ( e. g., sol - gel and polymer pyrolysis ) methods are all seeing increased use. besides open structures from formed tape, extruded structures, such as honeycomb catalyst supports, and highly porous structures, including various foams, for example, reticulated foam, are of increasing use. densification of consolidated powder bodies continues to be achieved predominantly by ( pressureless ) sintering. however, the use of pressure sintering by hot pressing is increasing, especially for non - oxides and parts of simple shapes where higher quality ( mainly microstructural homogeneity ) is needed, and larger size or multiple parts per pressing can be an advantage. = = the sintering process = = the principles of sintering - based methods are simple ( " sinter " has roots in the english " cinder " ). the firing is done at a temperature below the melting point of the ceramic. once a roughly - held - together object called a " green body " is made, it is fired in a kiln, where atomic and molecular diffusion processes give rise to significant changes in the primary microstructural features. this includes the gradual elimination of porosity, which is typically accompanied by a net shrinkage and overall densification of the component. thus, the pores in the object may close up, resulting in a denser product of
any two generating systems of the fundamental group of a closed surface are nielsen equivalent.
, behind which are structures termed reentrant triangles. radar waves penetrating the skin get trapped in these structures, reflecting off the internal faces and losing energy. this method was first used on the blackbird series : a - 12, yf - 12a, lockheed sr - 71 blackbird. the most efficient way to reflect radar waves back to the emitting radar is with orthogonal metal plates, forming a corner reflector consisting of either a dihedral ( two plates ) or a trihedral ( three orthogonal plates ). this configuration occurs in the tail of a conventional aircraft, where the vertical and horizontal components of the tail are set at right angles. stealth aircraft such as the f - 117 use a different arrangement, tilting the tail surfaces to reduce corner reflections formed between them. a more radical method is to omit the tail, as in the b - 2 spirit. the b - 2 ' s clean, low - drag flying wing configuration gives it exceptional range and reduces its radar profile. the flying wing design most closely resembles a so - called infinite flat plate ( as vertical control surfaces dramatically increase rcs ), the perfect stealth shape, as it would have no angles to reflect back radar waves. in addition to altering the tail, stealth design must bury the engines within the wing or fuselage, or in some cases where stealth is applied to an extant aircraft, install baffles in the air intakes, so that the compressor blades are not visible to radar. a stealthy shape must be devoid of complex bumps or protrusions of any kind, meaning that weapons, fuel tanks, and other stores must not be carried externally. any stealthy vehicle becomes un - stealthy when a door or hatch opens. parallel alignment of edges or even surfaces is also often used in stealth designs. the technique involves using a small number of edge orientations in the shape of the structure. for example, on the f - 22a raptor, the leading edges of the wing and the tail planes are set at the same angle. other smaller structures, such as the air intake bypass doors and the air refueling aperture, also use the same angles. the effect of this is to return a narrow radar signal in a very specific direction away from the radar emitter rather than returning a diffuse signal detectable at many angles. the effect is sometimes called " glitter " after the very brief signal seen when the reflected beam passes across a detector. it can be difficult for the radar operator to distinguish between a glitter event and a digital glitch in the processing system. stealth air
reflect radar waves back to the emitting radar is with orthogonal metal plates, forming a corner reflector consisting of either a dihedral ( two plates ) or a trihedral ( three orthogonal plates ). this configuration occurs in the tail of a conventional aircraft, where the vertical and horizontal components of the tail are set at right angles. stealth aircraft such as the f - 117 use a different arrangement, tilting the tail surfaces to reduce corner reflections formed between them. a more radical method is to omit the tail, as in the b - 2 spirit. the b - 2 ' s clean, low - drag flying wing configuration gives it exceptional range and reduces its radar profile. the flying wing design most closely resembles a so - called infinite flat plate ( as vertical control surfaces dramatically increase rcs ), the perfect stealth shape, as it would have no angles to reflect back radar waves. in addition to altering the tail, stealth design must bury the engines within the wing or fuselage, or in some cases where stealth is applied to an extant aircraft, install baffles in the air intakes, so that the compressor blades are not visible to radar. a stealthy shape must be devoid of complex bumps or protrusions of any kind, meaning that weapons, fuel tanks, and other stores must not be carried externally. any stealthy vehicle becomes un - stealthy when a door or hatch opens. parallel alignment of edges or even surfaces is also often used in stealth designs. the technique involves using a small number of edge orientations in the shape of the structure. for example, on the f - 22a raptor, the leading edges of the wing and the tail planes are set at the same angle. other smaller structures, such as the air intake bypass doors and the air refueling aperture, also use the same angles. the effect of this is to return a narrow radar signal in a very specific direction away from the radar emitter rather than returning a diffuse signal detectable at many angles. the effect is sometimes called " glitter " after the very brief signal seen when the reflected beam passes across a detector. it can be difficult for the radar operator to distinguish between a glitter event and a digital glitch in the processing system. stealth airframes sometimes display distinctive serrations on some exposed edges, such as the engine ports. the yf - 23 has such serrations on the exhaust ports. this is another example in the parallel alignment of features, this time on the external airframe. the shaping requirements detracted greatly from the f - 117 '
Question: The nail bed is a specialized structure of the epidermis that is found at the tips of our what?
A) only fingers
B) fingers, nails, and scalp
C) only nails
D) fingers and toes
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D) fingers and toes
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Context:
or lipids ( elaioplasts ). uniquely, streptophyte cells and those of the green algal order trentepohliales divide by construction of a phragmoplast as a template for building a cell plate late in cell division. the bodies of vascular plants including clubmosses, ferns and seed plants ( gymnosperms and angiosperms ) generally have aerial and subterranean subsystems. the shoots consist of stems bearing green photosynthesising leaves and reproductive structures. the underground vascularised roots bear root hairs at their tips and generally lack chlorophyll. non - vascular plants, the liverworts, hornworts and mosses do not produce ground - penetrating vascular roots and most of the plant participates in photosynthesis. the sporophyte generation is nonphotosynthetic in liverworts but may be able to contribute part of its energy needs by photosynthesis in mosses and hornworts. the root system and the shoot system are interdependent β the usually nonphotosynthetic root system depends on the shoot system for food, and the usually photosynthetic shoot system depends on water and minerals from the root system. cells in each system are capable of creating cells of the other and producing adventitious shoots or roots. stolons and tubers are examples of shoots that can grow roots. roots that spread out close to the surface, such as those of willows, can produce shoots and ultimately new plants. in the event that one of the systems is lost, the other can often regrow it. in fact it is possible to grow an entire plant from a single leaf, as is the case with plants in streptocarpus sect. saintpaulia, or even a single cell β which can dedifferentiate into a callus ( a mass of unspecialised cells ) that can grow into a new plant. in vascular plants, the xylem and phloem are the conductive tissues that transport resources between shoots and roots. roots are often adapted to store food such as sugars or starch, as in sugar beets and carrots. stems mainly provide support to the leaves and reproductive structures, but can store water in succulent plants such as cacti, food as in potato tubers, or reproduce vegetatively as in the stolons of strawberry plants or in the process of layering. leaves gather sunlight and carry out photosyn
earth. it emphasizes the study of how humans use and interact with freshwater supplies. study of water ' s movement is closely related to geomorphology and other branches of earth science. applied hydrology involves engineering to maintain aquatic environments and distribute water supplies. subdisciplines of hydrology include oceanography, hydrogeology, ecohydrology, and glaciology. oceanography is the study of oceans. hydrogeology is the study of groundwater. it includes the mapping of groundwater supplies and the analysis of groundwater contaminants. applied hydrogeology seeks to prevent contamination of groundwater and mineral springs and make it available as drinking water. the earliest exploitation of groundwater resources dates back to 3000 bc, and hydrogeology as a science was developed by hydrologists beginning in the 17th century. ecohydrology is the study of ecological systems in the hydrosphere. it can be divided into the physical study of aquatic ecosystems and the biological study of aquatic organisms. ecohydrology includes the effects that organisms and aquatic ecosystems have on one another as well as how these ecoystems are affected by humans. glaciology is the study of the cryosphere, including glaciers and coverage of the earth by ice and snow. concerns of glaciology include access to glacial freshwater, mitigation of glacial hazards, obtaining resources that exist beneath frozen land, and addressing the effects of climate change on the cryosphere. = = ecology = = ecology is the study of the biosphere. this includes the study of nature and of how living things interact with the earth and one another and the consequences of that. it considers how living things use resources such as oxygen, water, and nutrients from the earth to sustain themselves. it also considers how humans and other living creatures cause changes to nature. = = physical geography = = physical geography is the study of earth ' s systems and how they interact with one another as part of a single self - contained system. it incorporates astronomy, mathematical geography, meteorology, climatology, geology, geomorphology, biology, biogeography, pedology, and soils geography. physical geography is distinct from human geography, which studies the human populations on earth, though it does include human effects on the environment. = = methodology = = methodologies vary depending on the nature of the subjects being studied. studies typically fall into one of three categories : observational, experimental, or theoretical. earth scientists often conduct sophisticated computer analysis or visit an interesting location to study earth phenomena (
their mechanical properties. = = tissue culture = = in many cases, creation of functional tissues and biological structures in vitro requires extensive culturing to promote survival, growth and inducement of functionality. in general, the basic requirements of cells must be maintained in culture, which include oxygen, ph, humidity, temperature, nutrients and osmotic pressure maintenance. tissue engineered cultures also present additional problems in maintaining culture conditions. in standard cell culture, diffusion is often the sole means of nutrient and metabolite transport. however, as a culture becomes larger and more complex, such as the case with engineered organs and whole tissues, other mechanisms must be employed to maintain the culture, such as the creation of capillary networks within the tissue. another issue with tissue culture is introducing the proper factors or stimuli required to induce functionality. in many cases, simple maintenance culture is not sufficient. growth factors, hormones, specific metabolites or nutrients, chemical and physical stimuli are sometimes required. for example, certain cells respond to changes in oxygen tension as part of their normal development, such as chondrocytes, which must adapt to low oxygen conditions or hypoxia during skeletal development. others, such as endothelial cells, respond to shear stress from fluid flow, which is encountered in blood vessels. mechanical stimuli, such as pressure pulses seem to be beneficial to all kind of cardiovascular tissue such as heart valves, blood vessels or pericardium. = = = bioreactors = = = in tissue engineering, a bioreactor is a device that attempts to simulate a physiological environment in order to promote cell or tissue growth in vitro. a physiological environment can consist of many different parameters such as temperature, pressure, oxygen or carbon dioxide concentration, or osmolality of fluid environment, and it can extend to all kinds of biological, chemical or mechanical stimuli. therefore, there are systems that may include the application of forces such as electromagnetic forces, mechanical pressures, or fluid pressures to the tissue. these systems can be two - or three - dimensional setups. bioreactors can be used in both academic and industry applications. general - use and application - specific bioreactors are also commercially available, which may provide static chemical stimulation or a combination of chemical and mechanical stimulation. cell proliferation and differentiation are largely influenced by mechanical and biochemical cues in the surrounding extracellular matrix environment. bioreactors are typically developed to replicate the specific physiological environment of the tissue being grown ( e. g., flex and fluid shearing for heart tissue growth ). this can
the following purposes : allowing cell attachment and migration, delivering and retaining cells and biochemical factors, enabling diffusion of vital cell nutrients and expressed products, and exerting certain mechanical and biological influences to modify the behaviour of the cell phase. in 2009, an interdisciplinary team led by the thoracic surgeon thorsten walles implanted the first bioartificial transplant that provides an innate vascular network for post - transplant graft supply successfully into a patient awaiting tracheal reconstruction. to achieve the goal of tissue reconstruction, scaffolds must meet some specific requirements. high porosity and adequate pore size are necessary to facilitate cell seeding and diffusion throughout the whole structure of both cells and nutrients. biodegradability is often an essential factor since scaffolds should preferably be absorbed by the surrounding tissues without the necessity of surgical removal. the rate at which degradation occurs has to coincide as much as possible with the rate of tissue formation : this means that while cells are fabricating their own natural matrix structure around themselves, the scaffold is able to provide structural integrity within the body and eventually it will break down leaving the newly formed tissue which will take over the mechanical load. injectability is also important for clinical uses. recent research on organ printing is showing how crucial a good control of the 3d environment is to ensure reproducibility of experiments and offer better results. = = = materials = = = material selection is an essential aspect of producing a scaffold. the materials utilized can be natural or synthetic and can be biodegradable or non - biodegradable. additionally, they must be biocompatible, meaning that they do not cause any adverse effects to cells. silicone, for example, is a synthetic, non - biodegradable material commonly used as a drug delivery material, while gelatin is a biodegradable, natural material commonly used in cell - culture scaffolds the material needed for each application is different, and dependent on the desired mechanical properties of the material. tissue engineering of long bone defects for example, will require a rigid scaffold with a compressive strength similar to that of cortical bone ( 100 - 150 mpa ), which is much higher compared to a scaffold for skin regeneration. there are a few versatile synthetic materials used for many different scaffold applications. one of these commonly used materials is polylactic acid ( pla ), a synthetic polymer. pla β polylactic acid. this is a polyester which
##lling, pipe jacking and other operations. a caisson is sunk by self - weight, concrete or water ballast placed on top, or by hydraulic jacks. the leading edge ( or cutting shoe ) of the caisson is sloped out at a sharp angle to aid sinking in a vertical manner ; it is usually made of steel. the shoe is generally wider than the caisson to reduce friction, and the leading edge may be supplied with pressurised bentonite slurry, which swells in water, stabilizing settlement by filling depressions and voids. an open caisson may fill with water during sinking. the material is excavated by clamshell excavator bucket on crane. the formation level subsoil may still not be suitable for excavation or bearing capacity. the water in the caisson ( due to a high water table ) balances the upthrust forces of the soft soils underneath. if dewatered, the base may " pipe " or " boil ", causing the caisson to sink. to combat this problem, piles may be driven from the surface to act as : load - bearing walls, in that they transmit loads to deeper soils. anchors, in that they resist flotation because of the friction at the interface between their surfaces and the surrounding earth into which they have been driven. h - beam sections ( typical column sections, due to resistance to bending in all axis ) may be driven at angles " raked " to rock or other firmer soils ; the h - beams are left extended above the base. a reinforced concrete plug may be placed under the water, a process known as tremie concrete placement. when the caisson is dewatered, this plug acts as a pile cap, resisting the upward forces of the subsoil. = = = monolithic = = = a monolithic caisson ( or simply a monolith ) is larger than the other types of caisson, but similar to open caissons. such caissons are often found in quay walls, where resistance to impact from ships is required. = = = pneumatic = = = shallow caissons may be open to the air, whereas pneumatic caissons ( sometimes called pressurized caissons ), which penetrate soft mud, are bottomless boxes sealed at the top and filled with compressed air to keep water and mud out at depth. an airlock allows access to the chamber. workers, called sandhogs in american english, move mud and rock debris ( called
in the year 1598 philipp uffenbach published a printed diptych sundial, which is a forerunner of franz ritters horizantal sundial. uffenbach ' s sundial contains apart from the usual information on a sundial ascending signs of the zodiac, several brigthest stars, an almucantar and most important the oldest gnomonic world map known so far. the sundial is constructed for the polar height of 50 1 / 6 degrees, the height of frankfurt / main the town of his citizenship.
water content and the internal evolution of terrestrial planets and icy bodies are closely linked. the distribution of water in planetary systems is controlled by the temperature structure in the protoplanetary disk and dynamics and migration of planetesimals and planetary embryos. this results in the formation of planetesimals and planetary embryos with a great variety of compositions, water contents and degrees of oxidation. the internal evolution and especially the formation time of planetesimals relative to the timescale of radiogenic heating by short - lived 26al decay may govern the amount of hydrous silicates and leftover rock - ice mixtures available in the late stages of their evolution. in turn, water content may affect the early internal evolution of the planetesimals and in particular metal - silicate separation processes. moreover, water content may contribute to an increase of oxygen fugacity and thus affect the concentrations of siderophile elements within the silicate reservoirs of solar system objects. finally, the water content strongly influences the differentiation rate of the icy moons, controls their internal evolution and governs the alteration processes occurring in their deep interiors.
, dendrology is the study of woody plants. many divisions of biology have botanical subfields. these are commonly denoted by prefixing the word plant ( e. g. plant taxonomy, plant ecology, plant anatomy, plant morphology, plant systematics ), or prefixing or substituting the prefix phyto - ( e. g. phytochemistry, phytogeography ). the study of fossil plants is called palaeobotany. other fields are denoted by adding or substituting the word botany ( e. g. systematic botany ). phytosociology is a subfield of plant ecology that classifies and studies communities of plants. the intersection of fields from the above pair of categories gives rise to fields such as bryogeography, the study of the distribution of mosses. different parts of plants also give rise to their own subfields, including xylology, carpology ( or fructology ), and palynology, these being the study of wood, fruit and pollen / spores respectively. botany also overlaps on the one hand with agriculture, horticulture and silviculture, and on the other hand with medicine and pharmacology, giving rise to fields such as agronomy, horticultural botany, phytopathology, and phytopharmacology. = = scope and importance = = the study of plants is vital because they underpin almost all animal life on earth by generating a large proportion of the oxygen and food that provide humans and other organisms with aerobic respiration with the chemical energy they need to exist. plants, algae and cyanobacteria are the major groups of organisms that carry out photosynthesis, a process that uses the energy of sunlight to convert water and carbon dioxide into sugars that can be used both as a source of chemical energy and of organic molecules that are used in the structural components of cells. as a by - product of photosynthesis, plants release oxygen into the atmosphere, a gas that is required by nearly all living things to carry out cellular respiration. in addition, they are influential in the global carbon and water cycles and plant roots bind and stabilise soils, preventing soil erosion. plants are crucial to the future of human society as they provide food, oxygen, biochemicals, and products for people, as well as creating and preserving soil. historically, all living things were classified as either animals or plants and botany covered the study of all organisms not considered animals. botanists examine both
medical purposes. cells are often ' seeded ' into these structures capable of supporting three - dimensional tissue formation. scaffolds mimic the extracellular matrix of the native tissue, recapitulating the in vivo milieu and allowing cells to influence their own microenvironments. they usually serve at least one of the following purposes : allowing cell attachment and migration, delivering and retaining cells and biochemical factors, enabling diffusion of vital cell nutrients and expressed products, and exerting certain mechanical and biological influences to modify the behaviour of the cell phase. in 2009, an interdisciplinary team led by the thoracic surgeon thorsten walles implanted the first bioartificial transplant that provides an innate vascular network for post - transplant graft supply successfully into a patient awaiting tracheal reconstruction. to achieve the goal of tissue reconstruction, scaffolds must meet some specific requirements. high porosity and adequate pore size are necessary to facilitate cell seeding and diffusion throughout the whole structure of both cells and nutrients. biodegradability is often an essential factor since scaffolds should preferably be absorbed by the surrounding tissues without the necessity of surgical removal. the rate at which degradation occurs has to coincide as much as possible with the rate of tissue formation : this means that while cells are fabricating their own natural matrix structure around themselves, the scaffold is able to provide structural integrity within the body and eventually it will break down leaving the newly formed tissue which will take over the mechanical load. injectability is also important for clinical uses. recent research on organ printing is showing how crucial a good control of the 3d environment is to ensure reproducibility of experiments and offer better results. = = = materials = = = material selection is an essential aspect of producing a scaffold. the materials utilized can be natural or synthetic and can be biodegradable or non - biodegradable. additionally, they must be biocompatible, meaning that they do not cause any adverse effects to cells. silicone, for example, is a synthetic, non - biodegradable material commonly used as a drug delivery material, while gelatin is a biodegradable, natural material commonly used in cell - culture scaffolds the material needed for each application is different, and dependent on the desired mechanical properties of the material. tissue engineering of long bone defects for example, will require a rigid scaffold with a compressive strength similar to that of cortical bone ( 100 - 150 mpa ),
made of steel. the shoe is generally wider than the caisson to reduce friction, and the leading edge may be supplied with pressurised bentonite slurry, which swells in water, stabilizing settlement by filling depressions and voids. an open caisson may fill with water during sinking. the material is excavated by clamshell excavator bucket on crane. the formation level subsoil may still not be suitable for excavation or bearing capacity. the water in the caisson ( due to a high water table ) balances the upthrust forces of the soft soils underneath. if dewatered, the base may " pipe " or " boil ", causing the caisson to sink. to combat this problem, piles may be driven from the surface to act as : load - bearing walls, in that they transmit loads to deeper soils. anchors, in that they resist flotation because of the friction at the interface between their surfaces and the surrounding earth into which they have been driven. h - beam sections ( typical column sections, due to resistance to bending in all axis ) may be driven at angles " raked " to rock or other firmer soils ; the h - beams are left extended above the base. a reinforced concrete plug may be placed under the water, a process known as tremie concrete placement. when the caisson is dewatered, this plug acts as a pile cap, resisting the upward forces of the subsoil. = = = monolithic = = = a monolithic caisson ( or simply a monolith ) is larger than the other types of caisson, but similar to open caissons. such caissons are often found in quay walls, where resistance to impact from ships is required. = = = pneumatic = = = shallow caissons may be open to the air, whereas pneumatic caissons ( sometimes called pressurized caissons ), which penetrate soft mud, are bottomless boxes sealed at the top and filled with compressed air to keep water and mud out at depth. an airlock allows access to the chamber. workers, called sandhogs in american english, move mud and rock debris ( called muck ) from the edge of the workspace to a water - filled pit, connected by a tube ( called the muck tube ) to the surface. a crane at the surface removes the soil with a clamshell bucket. the water pressure in the tube balances the air pressure, with excess air escaping up
Question: The anatomical arrangement of capillaries and alveoli emphasizes the structural and functional relationship of what systems?
A) endocrine and renal
B) respiratory and circulatory
C) digestive and respiratory
D) nervous and lymphatic
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B) respiratory and circulatory
|
Context:
cross. the chromosome theory of inheritance, which states that genes are found on chromosomes, was supported by thomas morgans ' s experiments with fruit flies, which established the sex linkage between eye color and sex in these insects. = = = genes and dna = = = a gene is a unit of heredity that corresponds to a region of deoxyribonucleic acid ( dna ) that carries genetic information that controls form or function of an organism. dna is composed of two polynucleotide chains that coil around each other to form a double helix. it is found as linear chromosomes in eukaryotes, and circular chromosomes in prokaryotes. the set of chromosomes in a cell is collectively known as its genome. in eukaryotes, dna is mainly in the cell nucleus. in prokaryotes, the dna is held within the nucleoid. the genetic information is held within genes, and the complete assemblage in an organism is called its genotype. dna replication is a semiconservative process whereby each strand serves as a template for a new strand of dna. mutations are heritable changes in dna. they can arise spontaneously as a result of replication errors that were not corrected by proofreading or can be induced by an environmental mutagen such as a chemical ( e. g., nitrous acid, benzopyrene ) or radiation ( e. g., x - ray, gamma ray, ultraviolet radiation, particles emitted by unstable isotopes ). mutations can lead to phenotypic effects such as loss - of - function, gain - of - function, and conditional mutations. some mutations are beneficial, as they are a source of genetic variation for evolution. others are harmful if they were to result in a loss of function of genes needed for survival. = = = gene expression = = = gene expression is the molecular process by which a genotype encoded in dna gives rise to an observable phenotype in the proteins of an organism ' s body. this process is summarized by the central dogma of molecular biology, which was formulated by francis crick in 1958. according to the central dogma, genetic information flows from dna to rna to protein. there are two gene expression processes : transcription ( dna to rna ) and translation ( rna to protein ). = = = gene regulation = = = the regulation of gene expression by environmental factors and during different stages of development can occur at each step of the process such as transcription, rna splicing
of several types of apomixis that occur in plants. apomixis can also happen in a seed, producing a seed that contains an embryo genetically identical to the parent. most sexually reproducing organisms are diploid, with paired chromosomes, but doubling of their chromosome number may occur due to errors in cytokinesis. this can occur early in development to produce an autopolyploid or partly autopolyploid organism, or during normal processes of cellular differentiation to produce some cell types that are polyploid ( endopolyploidy ), or during gamete formation. an allopolyploid plant may result from a hybridisation event between two different species. both autopolyploid and allopolyploid plants can often reproduce normally, but may be unable to cross - breed successfully with the parent population because there is a mismatch in chromosome numbers. these plants that are reproductively isolated from the parent species but live within the same geographical area, may be sufficiently successful to form a new species. some otherwise sterile plant polyploids can still reproduce vegetatively or by seed apomixis, forming clonal populations of identical individuals. durum wheat is a fertile tetraploid allopolyploid, while bread wheat is a fertile hexaploid. the commercial banana is an example of a sterile, seedless triploid hybrid. common dandelion is a triploid that produces viable seeds by apomictic seed. as in other eukaryotes, the inheritance of endosymbiotic organelles like mitochondria and chloroplasts in plants is non - mendelian. chloroplasts are inherited through the male parent in gymnosperms but often through the female parent in flowering plants. = = = molecular genetics = = = a considerable amount of new knowledge about plant function comes from studies of the molecular genetics of model plants such as the thale cress, arabidopsis thaliana, a weedy species in the mustard family ( brassicaceae ). the genome or hereditary information contained in the genes of this species is encoded by about 135 million base pairs of dna, forming one of the smallest genomes among flowering plants. arabidopsis was the first plant to have its genome sequenced, in 2000. the sequencing of some other relatively small genomes, of rice ( oryza sativa ) and brachypodium distachyon, has made them important model species for understanding the genetics,
tubers in potato is one example. particularly in arctic or alpine habitats, where opportunities for fertilisation of flowers by animals are rare, plantlets or bulbs, may develop instead of flowers, replacing sexual reproduction with asexual reproduction and giving rise to clonal populations genetically identical to the parent. this is one of several types of apomixis that occur in plants. apomixis can also happen in a seed, producing a seed that contains an embryo genetically identical to the parent. most sexually reproducing organisms are diploid, with paired chromosomes, but doubling of their chromosome number may occur due to errors in cytokinesis. this can occur early in development to produce an autopolyploid or partly autopolyploid organism, or during normal processes of cellular differentiation to produce some cell types that are polyploid ( endopolyploidy ), or during gamete formation. an allopolyploid plant may result from a hybridisation event between two different species. both autopolyploid and allopolyploid plants can often reproduce normally, but may be unable to cross - breed successfully with the parent population because there is a mismatch in chromosome numbers. these plants that are reproductively isolated from the parent species but live within the same geographical area, may be sufficiently successful to form a new species. some otherwise sterile plant polyploids can still reproduce vegetatively or by seed apomixis, forming clonal populations of identical individuals. durum wheat is a fertile tetraploid allopolyploid, while bread wheat is a fertile hexaploid. the commercial banana is an example of a sterile, seedless triploid hybrid. common dandelion is a triploid that produces viable seeds by apomictic seed. as in other eukaryotes, the inheritance of endosymbiotic organelles like mitochondria and chloroplasts in plants is non - mendelian. chloroplasts are inherited through the male parent in gymnosperms but often through the female parent in flowering plants. = = = molecular genetics = = = a considerable amount of new knowledge about plant function comes from studies of the molecular genetics of model plants such as the thale cress, arabidopsis thaliana, a weedy species in the mustard family ( brassicaceae ). the genome or hereditary information contained in the genes of this species is encoded by about 135 million base pairs of dna, forming one of the
cytokinesis. this can occur early in development to produce an autopolyploid or partly autopolyploid organism, or during normal processes of cellular differentiation to produce some cell types that are polyploid ( endopolyploidy ), or during gamete formation. an allopolyploid plant may result from a hybridisation event between two different species. both autopolyploid and allopolyploid plants can often reproduce normally, but may be unable to cross - breed successfully with the parent population because there is a mismatch in chromosome numbers. these plants that are reproductively isolated from the parent species but live within the same geographical area, may be sufficiently successful to form a new species. some otherwise sterile plant polyploids can still reproduce vegetatively or by seed apomixis, forming clonal populations of identical individuals. durum wheat is a fertile tetraploid allopolyploid, while bread wheat is a fertile hexaploid. the commercial banana is an example of a sterile, seedless triploid hybrid. common dandelion is a triploid that produces viable seeds by apomictic seed. as in other eukaryotes, the inheritance of endosymbiotic organelles like mitochondria and chloroplasts in plants is non - mendelian. chloroplasts are inherited through the male parent in gymnosperms but often through the female parent in flowering plants. = = = molecular genetics = = = a considerable amount of new knowledge about plant function comes from studies of the molecular genetics of model plants such as the thale cress, arabidopsis thaliana, a weedy species in the mustard family ( brassicaceae ). the genome or hereditary information contained in the genes of this species is encoded by about 135 million base pairs of dna, forming one of the smallest genomes among flowering plants. arabidopsis was the first plant to have its genome sequenced, in 2000. the sequencing of some other relatively small genomes, of rice ( oryza sativa ) and brachypodium distachyon, has made them important model species for understanding the genetics, cellular and molecular biology of cereals, grasses and monocots generally. model plants such as arabidopsis thaliana are used for studying the molecular biology of plant cells and the chloroplast. ideally, these organisms have small genomes that are well known or completely sequenced, small stature and short
##tes, i. e., genes are unlinked. an exception to this rule would include traits that are sex - linked. test crosses can be performed to experimentally determine the underlying genotype of an organism with a dominant phenotype. a punnett square can be used to predict the results of a test cross. the chromosome theory of inheritance, which states that genes are found on chromosomes, was supported by thomas morgans ' s experiments with fruit flies, which established the sex linkage between eye color and sex in these insects. = = = genes and dna = = = a gene is a unit of heredity that corresponds to a region of deoxyribonucleic acid ( dna ) that carries genetic information that controls form or function of an organism. dna is composed of two polynucleotide chains that coil around each other to form a double helix. it is found as linear chromosomes in eukaryotes, and circular chromosomes in prokaryotes. the set of chromosomes in a cell is collectively known as its genome. in eukaryotes, dna is mainly in the cell nucleus. in prokaryotes, the dna is held within the nucleoid. the genetic information is held within genes, and the complete assemblage in an organism is called its genotype. dna replication is a semiconservative process whereby each strand serves as a template for a new strand of dna. mutations are heritable changes in dna. they can arise spontaneously as a result of replication errors that were not corrected by proofreading or can be induced by an environmental mutagen such as a chemical ( e. g., nitrous acid, benzopyrene ) or radiation ( e. g., x - ray, gamma ray, ultraviolet radiation, particles emitted by unstable isotopes ). mutations can lead to phenotypic effects such as loss - of - function, gain - of - function, and conditional mutations. some mutations are beneficial, as they are a source of genetic variation for evolution. others are harmful if they were to result in a loss of function of genes needed for survival. = = = gene expression = = = gene expression is the molecular process by which a genotype encoded in dna gives rise to an observable phenotype in the proteins of an organism ' s body. this process is summarized by the central dogma of molecular biology, which was formulated by francis crick in 1958. according to the central dogma, genetic information flows from dna
, subsequent switching to inbreeding becomes disadvantageous since it allows expression of the previously masked deleterious recessive mutations, commonly referred to as inbreeding depression. unlike in higher animals, where parthenogenesis is rare, asexual reproduction may occur in plants by several different mechanisms. the formation of stem tubers in potato is one example. particularly in arctic or alpine habitats, where opportunities for fertilisation of flowers by animals are rare, plantlets or bulbs, may develop instead of flowers, replacing sexual reproduction with asexual reproduction and giving rise to clonal populations genetically identical to the parent. this is one of several types of apomixis that occur in plants. apomixis can also happen in a seed, producing a seed that contains an embryo genetically identical to the parent. most sexually reproducing organisms are diploid, with paired chromosomes, but doubling of their chromosome number may occur due to errors in cytokinesis. this can occur early in development to produce an autopolyploid or partly autopolyploid organism, or during normal processes of cellular differentiation to produce some cell types that are polyploid ( endopolyploidy ), or during gamete formation. an allopolyploid plant may result from a hybridisation event between two different species. both autopolyploid and allopolyploid plants can often reproduce normally, but may be unable to cross - breed successfully with the parent population because there is a mismatch in chromosome numbers. these plants that are reproductively isolated from the parent species but live within the same geographical area, may be sufficiently successful to form a new species. some otherwise sterile plant polyploids can still reproduce vegetatively or by seed apomixis, forming clonal populations of identical individuals. durum wheat is a fertile tetraploid allopolyploid, while bread wheat is a fertile hexaploid. the commercial banana is an example of a sterile, seedless triploid hybrid. common dandelion is a triploid that produces viable seeds by apomictic seed. as in other eukaryotes, the inheritance of endosymbiotic organelles like mitochondria and chloroplasts in plants is non - mendelian. chloroplasts are inherited through the male parent in gymnosperms but often through the female parent in flowering plants. = = = molecular genetics = = = a considerable amount of new knowledge about plant function comes from
. species boundaries in plants may be weaker than in animals, and cross species hybrids are often possible. a familiar example is peppermint, mentha Γ piperita, a sterile hybrid between mentha aquatica and spearmint, mentha spicata. the many cultivated varieties of wheat are the result of multiple inter - and intra - specific crosses between wild species and their hybrids. angiosperms with monoecious flowers often have self - incompatibility mechanisms that operate between the pollen and stigma so that the pollen either fails to reach the stigma or fails to germinate and produce male gametes. this is one of several methods used by plants to promote outcrossing. in many land plants the male and female gametes are produced by separate individuals. these species are said to be dioecious when referring to vascular plant sporophytes and dioicous when referring to bryophyte gametophytes. charles darwin in his 1878 book the effects of cross and self - fertilization in the vegetable kingdom at the start of chapter xii noted " the first and most important of the conclusions which may be drawn from the observations given in this volume, is that generally cross - fertilisation is beneficial and self - fertilisation often injurious, at least with the plants on which i experimented. " an important adaptive benefit of outcrossing is that it allows the masking of deleterious mutations in the genome of progeny. this beneficial effect is also known as hybrid vigor or heterosis. once outcrossing is established, subsequent switching to inbreeding becomes disadvantageous since it allows expression of the previously masked deleterious recessive mutations, commonly referred to as inbreeding depression. unlike in higher animals, where parthenogenesis is rare, asexual reproduction may occur in plants by several different mechanisms. the formation of stem tubers in potato is one example. particularly in arctic or alpine habitats, where opportunities for fertilisation of flowers by animals are rare, plantlets or bulbs, may develop instead of flowers, replacing sexual reproduction with asexual reproduction and giving rise to clonal populations genetically identical to the parent. this is one of several types of apomixis that occur in plants. apomixis can also happen in a seed, producing a seed that contains an embryo genetically identical to the parent. most sexually reproducing organisms are diploid, with paired chromosomes, but doubling of their chromosome number may occur due to errors in
often injurious, at least with the plants on which i experimented. " an important adaptive benefit of outcrossing is that it allows the masking of deleterious mutations in the genome of progeny. this beneficial effect is also known as hybrid vigor or heterosis. once outcrossing is established, subsequent switching to inbreeding becomes disadvantageous since it allows expression of the previously masked deleterious recessive mutations, commonly referred to as inbreeding depression. unlike in higher animals, where parthenogenesis is rare, asexual reproduction may occur in plants by several different mechanisms. the formation of stem tubers in potato is one example. particularly in arctic or alpine habitats, where opportunities for fertilisation of flowers by animals are rare, plantlets or bulbs, may develop instead of flowers, replacing sexual reproduction with asexual reproduction and giving rise to clonal populations genetically identical to the parent. this is one of several types of apomixis that occur in plants. apomixis can also happen in a seed, producing a seed that contains an embryo genetically identical to the parent. most sexually reproducing organisms are diploid, with paired chromosomes, but doubling of their chromosome number may occur due to errors in cytokinesis. this can occur early in development to produce an autopolyploid or partly autopolyploid organism, or during normal processes of cellular differentiation to produce some cell types that are polyploid ( endopolyploidy ), or during gamete formation. an allopolyploid plant may result from a hybridisation event between two different species. both autopolyploid and allopolyploid plants can often reproduce normally, but may be unable to cross - breed successfully with the parent population because there is a mismatch in chromosome numbers. these plants that are reproductively isolated from the parent species but live within the same geographical area, may be sufficiently successful to form a new species. some otherwise sterile plant polyploids can still reproduce vegetatively or by seed apomixis, forming clonal populations of identical individuals. durum wheat is a fertile tetraploid allopolyploid, while bread wheat is a fertile hexaploid. the commercial banana is an example of a sterile, seedless triploid hybrid. common dandelion is a triploid that produces viable seeds by apomictic seed. as in other eukaryotes, the inheritance of endosymbiotic organelles like
the strictest definition of " plant " includes only the " land plants " or embryophytes, which include seed plants ( gymnosperms, including the pines, and flowering plants ) and the free - sporing cryptogams including ferns, clubmosses, liverworts, hornworts and mosses. embryophytes are multicellular eukaryotes descended from an ancestor that obtained its energy from sunlight by photosynthesis. they have life cycles with alternating haploid and diploid phases. the sexual haploid phase of embryophytes, known as the gametophyte, nurtures the developing diploid embryo sporophyte within its tissues for at least part of its life, even in the seed plants, where the gametophyte itself is nurtured by its parent sporophyte. other groups of organisms that were previously studied by botanists include bacteria ( now studied in bacteriology ), fungi ( mycology ) β including lichen - forming fungi ( lichenology ), non - chlorophyte algae ( phycology ), and viruses ( virology ). however, attention is still given to these groups by botanists, and fungi ( including lichens ) and photosynthetic protists are usually covered in introductory botany courses. palaeobotanists study ancient plants in the fossil record to provide information about the evolutionary history of plants. cyanobacteria, the first oxygen - releasing photosynthetic organisms on earth, are thought to have given rise to the ancestor of plants by entering into an endosymbiotic relationship with an early eukaryote, ultimately becoming the chloroplasts in plant cells. the new photosynthetic plants ( along with their algal relatives ) accelerated the rise in atmospheric oxygen started by the cyanobacteria, changing the ancient oxygen - free, reducing, atmosphere to one in which free oxygen has been abundant for more than 2 billion years. among the important botanical questions of the 21st century are the role of plants as primary producers in the global cycling of life ' s basic ingredients : energy, carbon, oxygen, nitrogen and water, and ways that our plant stewardship can help address the global environmental issues of resource management, conservation, human food security, biologically invasive organisms, carbon sequestration, climate change, and sustainability. = = = human nutrition = = = virtually all staple foods come either directly from primary production by plants, or indirectly from animals that
are independent of x define constant functions and are therefore called constant. for example, a constant of integration is an arbitrary constant function that is added to a particular antiderivative to obtain the other antiderivatives. because of the strong relationship between polynomials and polynomial functions, the term " constant " is often used to denote the coefficients of a polynomial, which are constant functions of the indeterminates. other specific names for variables are : an unknown is a variable in an equation which has to be solved for. an indeterminate is a symbol, commonly called variable, that appears in a polynomial or a formal power series. formally speaking, an indeterminate is not a variable, but a constant in the polynomial ring or the ring of formal power series. however, because of the strong relationship between polynomials or power series and the functions that they define, many authors consider indeterminates as a special kind of variables. a parameter is a quantity ( usually a number ) which is a part of the input of a problem, and remains constant during the whole solution of this problem. for example, in mechanics the mass and the size of a solid body are parameters for the study of its movement. in computer science, parameter has a different meaning and denotes an argument of a function. free variables and bound variables a random variable is a kind of variable that is used in probability theory and its applications. all these denominations of variables are of semantic nature, and the way of computing with them ( syntax ) is the same for all. = = = dependent and independent variables = = = in calculus and its application to physics and other sciences, it is rather common to consider a variable, say y, whose possible values depend on the value of another variable, say x. in mathematical terms, the dependent variable y represents the value of a function of x. to simplify formulas, it is often useful to use the same symbol for the dependent variable y and the function mapping x onto y. for example, the state of a physical system depends on measurable quantities such as the pressure, the temperature, the spatial position,..., and all these quantities vary when the system evolves, that is, they are function of the time. in the formulas describing the system, these quantities are represented by variables which are dependent on the time, and thus considered implicitly as functions of the time. therefore, in a formula, a dependent variable is a variable that is implicitly a function of another ( or several other ) variables. an independent variable
Question: What term describes all but the sex chromosomes?
A) autsomes
B) lysosomes
C) sporozoans
D) telomeres
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A) autsomes
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Context:
so mars below means blood and war ", is a false cause fallacy. : 26 many astrologers claim that astrology is scientific. if one were to attempt to try to explain it scientifically, there are only four fundamental forces ( conventionally ), limiting the choice of possible natural mechanisms. : 65 some astrologers have proposed conventional causal agents such as electromagnetism and gravity. the strength of these forces drops off with distance. : 65 scientists reject these proposed mechanisms as implausible since, for example, the magnetic field, when measured from earth, of a large but distant planet such as jupiter is far smaller than that produced by ordinary household appliances. astronomer phil plait noted that in terms of magnitude, the sun is the only object with an electromagnetic field of note, but astrology isn ' t based just off the sun alone. : 65 while astrologers could try to suggest a fifth force, this is inconsistent with the trends in physics with the unification of electromagnetism and the weak force into the electroweak force. if the astrologer insisted on being inconsistent with the current understanding and evidential basis of physics, that would be an extraordinary claim. : 65 it would also be inconsistent with the other forces which drop off with distance. : 65 if distance is irrelevant, then, logically, all objects in space should be taken into account. : 66 carl jung sought to invoke synchronicity, the claim that two events have some sort of acausal connection, to explain the lack of statistically significant results on astrology from a single study he conducted. however, synchronicity itself is considered neither testable nor falsifiable. the study was subsequently heavily criticised for its non - random sample and its use of statistics and also its lack of consistency with astrology. = = psychology = = psychological studies have not found any robust relationship between astrological signs and life outcomes. for example, a study showed that zodiac signs are no more effective than random numbers in predicting subjective well - being and quality of life. it has also been shown that confirmation bias is a psychological factor that contributes to belief in astrology. : 344 : 180 β 181 : 42 β 48 confirmation bias is a form of cognitive bias. : 553 from the literature, astrology believers often tend to selectively remember those predictions that turned out to be true and do not remember those that turned out false. another, separate, form of confirmation bias also plays a role, where believers often fail to
the scientific revolution. aristotle also contributed to theories of the elements and the cosmos. he believed that the celestial bodies ( such as the planets and the sun ) had something called an unmoved mover that put the celestial bodies in motion. aristotle tried to explain everything through mathematics and physics, but sometimes explained things such as the motion of celestial bodies through a higher power such as god. aristotle did not have the technological advancements that would have explained the motion of celestial bodies. in addition, aristotle had many views on the elements. he believed that everything was derived of the elements earth, water, air, fire, and lastly the aether. the aether was a celestial element, and therefore made up the matter of the celestial bodies. the elements of earth, water, air and fire were derived of a combination of two of the characteristics of hot, wet, cold, and dry, and all had their inevitable place and motion. the motion of these elements begins with earth being the closest to " the earth, " then water, air, fire, and finally aether. in addition to the makeup of all things, aristotle came up with theories as to why things did not return to their natural motion. he understood that water sits above earth, air above water, and fire above air in their natural state. he explained that although all elements must return to their natural state, the human body and other living things have a constraint on the elements β thus not allowing the elements making one who they are to return to their natural state. the important legacy of this period included substantial advances in factual knowledge, especially in anatomy, zoology, botany, mineralogy, geography, mathematics and astronomy ; an awareness of the importance of certain scientific problems, especially those related to the problem of change and its causes ; and a recognition of the methodological importance of applying mathematics to natural phenomena and of undertaking empirical research. in the hellenistic age scholars frequently employed the principles developed in earlier greek thought : the application of mathematics and deliberate empirical research, in their scientific investigations. thus, clear unbroken lines of influence lead from ancient greek and hellenistic philosophers, to medieval muslim philosophers and scientists, to the european renaissance and enlightenment, to the secular sciences of the modern day. neither reason nor inquiry began with the ancient greeks, but the socratic method did, along with the idea of forms, give great advances in geometry, logic, and the natural sciences. according to benjamin farrington, former professor of classics at swansea university : " men were weighing for thousands of years before archimedes worked out the
einstein, when he began working on the general theory of relativity, believed that energy of any kind is the source of the gravitational field. therefore, the energy of gravity, like any energy, must be the source of the field. it was previously discovered that the energy - momentum tensor of the gravitational field is already contained in the ricci tensor. this hypothesis is used to construct a new equation of the gravitational field.
the motion of celestial bodies through a higher power such as god. aristotle did not have the technological advancements that would have explained the motion of celestial bodies. in addition, aristotle had many views on the elements. he believed that everything was derived of the elements earth, water, air, fire, and lastly the aether. the aether was a celestial element, and therefore made up the matter of the celestial bodies. the elements of earth, water, air and fire were derived of a combination of two of the characteristics of hot, wet, cold, and dry, and all had their inevitable place and motion. the motion of these elements begins with earth being the closest to " the earth, " then water, air, fire, and finally aether. in addition to the makeup of all things, aristotle came up with theories as to why things did not return to their natural motion. he understood that water sits above earth, air above water, and fire above air in their natural state. he explained that although all elements must return to their natural state, the human body and other living things have a constraint on the elements β thus not allowing the elements making one who they are to return to their natural state. the important legacy of this period included substantial advances in factual knowledge, especially in anatomy, zoology, botany, mineralogy, geography, mathematics and astronomy ; an awareness of the importance of certain scientific problems, especially those related to the problem of change and its causes ; and a recognition of the methodological importance of applying mathematics to natural phenomena and of undertaking empirical research. in the hellenistic age scholars frequently employed the principles developed in earlier greek thought : the application of mathematics and deliberate empirical research, in their scientific investigations. thus, clear unbroken lines of influence lead from ancient greek and hellenistic philosophers, to medieval muslim philosophers and scientists, to the european renaissance and enlightenment, to the secular sciences of the modern day. neither reason nor inquiry began with the ancient greeks, but the socratic method did, along with the idea of forms, give great advances in geometry, logic, and the natural sciences. according to benjamin farrington, former professor of classics at swansea university : " men were weighing for thousands of years before archimedes worked out the laws of equilibrium ; they must have had practical and intuitional knowledge of the principals involved. what archimedes did was to sort out the theoretical implications of this practical knowledge and present the resulting body of knowledge as a logically coherent system. " and again : " with astonishment we find ourselves on the threshold of modern science
oscillations of the sun have been used to understand its interior structure. the extension of similar studies to more distant stars has raised many difficulties despite the strong efforts of the international community over the past decades. the corot ( convection rotation and planetary transits ) satellite, launched in december 2006, has now measured oscillations and the stellar granulation signature in three main sequence stars that are noticeably hotter than the sun. the oscillation amplitudes are about 1. 5 times as large as those in the sun ; the stellar granulation is up to three times as high. the stellar amplitudes are about 25 % below the theoretic values, providing a measurement of the nonadiabaticity of the process ruling the oscillations in the outer layers of the stars.
excess lightweight products of slow neutron capture in the photosphere, over the mass range of 25 to 207 amu, confirm the solar mass separation recorded by excess lightweight isotopes in the solar wind, over the mass range of 3 to 136 amu [ solar abundance of the elements, meteoritics, volume 18, 1983, pages 209 to 222 ]. both measurements show that major elements inside the sun are fe, o, ni, si and s, like those in rocky planets.
the gravitational poynting vector provides a mechanism for the transfer of gravitational energy to a system of falling objects. in the following we will show that the gravitational poynting vector together with the gravitational larmor theorem also provides a mechanism to explain how massive bodies acquire rotational kinetic energy when external mechanical forces are applied on them.
has rest mass and volume ( it takes up space ) and is made up of particles. the particles that make up matter have rest mass as well β not all particles have rest mass, such as the photon. matter can be a pure chemical substance or a mixture of substances. = = = = atom = = = = the atom is the basic unit of chemistry. it consists of a dense core called the atomic nucleus surrounded by a space occupied by an electron cloud. the nucleus is made up of positively charged protons and uncharged neutrons ( together called nucleons ), while the electron cloud consists of negatively charged electrons which orbit the nucleus. in a neutral atom, the negatively charged electrons balance out the positive charge of the protons. the nucleus is dense ; the mass of a nucleon is approximately 1, 836 times that of an electron, yet the radius of an atom is about 10, 000 times that of its nucleus. the atom is also the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state ( s ), coordination number, and preferred types of bonds to form ( e. g., metallic, ionic, covalent ). = = = = element = = = = a chemical element is a pure substance which is composed of a single type of atom, characterized by its particular number of protons in the nuclei of its atoms, known as the atomic number and represented by the symbol z. the mass number is the sum of the number of protons and neutrons in a nucleus. although all the nuclei of all atoms belonging to one element will have the same atomic number, they may not necessarily have the same mass number ; atoms of an element which have different mass numbers are known as isotopes. for example, all atoms with 6 protons in their nuclei are atoms of the chemical element carbon, but atoms of carbon may have mass numbers of 12 or 13. the standard presentation of the chemical elements is in the periodic table, which orders elements by atomic number. the periodic table is arranged in groups, or columns, and periods, or rows. the periodic table is useful in identifying periodic trends. = = = = compound = = = = a compound is a pure chemical substance composed of more than one element. the properties of a compound bear little similarity to those of its elements. the standard nomenclature of compounds is set by the international union of pure and applied chemistry ( iupac ). organic compounds are named
we bring you, as usual, the sun and moon and stars, plus some galaxies and a new section on astrobiology. some highlights are short ( the newly identified class of gamma - ray bursts, and the deep impact on comet 9p / tempel 1 ), some long ( the age of the universe, which will be found to have the earth at its center ), and a few metonymic, for instance the term " down - sizing " to describe the evolution of star formation rates with redshift.
in the year 1598 philipp uffenbach published a printed diptych sundial, which is a forerunner of franz ritters horizantal sundial. uffenbach ' s sundial contains apart from the usual information on a sundial ascending signs of the zodiac, several brigthest stars, an almucantar and most important the oldest gnomonic world map known so far. the sundial is constructed for the polar height of 50 1 / 6 degrees, the height of frankfurt / main the town of his citizenship.
Question: The sun and all objects held by it's gravity make up the?
A) milky way
B) atmosphere
C) planet
D) solar system
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D) solar system
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Context:
practice, general practice or primary care is, in many countries, the first port - of - call for patients with non - emergency medical problems. family physicians often provide services across a broad range of settings including office based practices, emergency department coverage, inpatient care, and nursing home care. medical genetics is concerned with the diagnosis and management of hereditary disorders. neurology is concerned with diseases of the nervous system. in the uk, neurology is a subspecialty of general medicine. obstetrics and gynecology ( often abbreviated as ob / gyn ( american english ) or obs & gynae ( british english ) ) are concerned respectively with childbirth and the female reproductive and associated organs. reproductive medicine and fertility medicine are generally practiced by gynecological specialists. pediatrics ( ae ) or paediatrics ( be ) is devoted to the care of infants, children, and adolescents. like internal medicine, there are many pediatric subspecialties for specific age ranges, organ systems, disease classes, and sites of care delivery. pharmaceutical medicine is the medical scientific discipline concerned with the discovery, development, evaluation, registration, monitoring and medical aspects of marketing of medicines for the benefit of patients and public health. physical medicine and rehabilitation ( or physiatry ) is concerned with functional improvement after injury, illness, or congenital disorders. podiatric medicine is the study of, diagnosis, and medical and surgical treatment of disorders of the foot, ankle, lower limb, hip and lower back. preventive medicine is the branch of medicine concerned with preventing disease. community health or public health is an aspect of health services concerned with threats to the overall health of a community based on population health analysis. psychiatry is the branch of medicine concerned with the bio - psycho - social study of the etiology, diagnosis, treatment and prevention of cognitive, perceptual, emotional and behavioral disorders. related fields include psychotherapy and clinical psychology. = = = interdisciplinary fields = = = some interdisciplinary sub - specialties of medicine include : addiction medicine deals with the treatment of addiction. aerospace medicine deals with medical problems related to flying and space travel. biomedical engineering is a field dealing with the application of engineering principles to medical practice. clinical pharmacology is concerned with how systems of therapeutics interact with patients. conservation medicine studies the relationship between human and non - human animal health, and environmental conditions. also known as ecological medicine, environmental medicine, or medical geology. disaster medicine deals with medical aspects of emergency preparedness, disaster mitigation
in a voltaic cell, positive ( negative ) ions flow from the low ( high ) potential electrode to the high ( low ) potential electrode, driven by an ` electromotive force ' which points in opposite direction and overcomes the electric force. similarly in a superconductor charge flows in direction opposite to that dictated by the faraday electric field as the magnetic field is expelled in the meissner effect. the puzzle is the same in both cases : what drives electric charges against electromagnetic forces? i propose that the answer is also the same in both cases : kinetic energy lowering, or ` quantum pressure '.
power to watermills and water - raising machines. many of these technologies were transferred to medieval europe. wind - powered machines used to grind grain and pump water, the windmill and wind pump, first appeared in what are now iran, afghanistan and pakistan by the 9th century. they were used to grind grains and draw up water, and used in the gristmilling and sugarcane industries. sugar mills first appeared in the medieval islamic world. they were first driven by watermills, and then windmills from the 9th and 10th centuries in what are today afghanistan, pakistan and iran. crops such as almonds and citrus fruit were brought to europe through al - andalus, and sugar cultivation was gradually adopted across europe. arab merchants dominated trade in the indian ocean until the arrival of the portuguese in the 16th century. the muslim world adopted papermaking from china. the earliest paper mills appeared in abbasid - era baghdad during 794 β 795. the knowledge of gunpowder was also transmitted from china via predominantly islamic countries, where formulas for pure potassium nitrate were developed. the spinning wheel was invented in the islamic world by the early 11th century. it was later widely adopted in europe, where it was adapted into the spinning jenny, a key device during the industrial revolution. the crankshaft was invented by al - jazari in 1206, and is central to modern machinery such as the steam engine, internal combustion engine and automatic controls. the camshaft was also first described by al - jazari in 1206. early programmable machines were also invented in the muslim world. the first music sequencer, a programmable musical instrument, was an automated flute player invented by the banu musa brothers, described in their book of ingenious devices, in the 9th century. in 1206, al - jazari invented programmable automata / robots. he described four automaton musicians, including two drummers operated by a programmable drum machine, where the drummer could be made to play different rhythms and different drum patterns. the castle clock, a hydropowered mechanical astronomical clock invented by al - jazari, was an early programmable analog computer. in the ottoman empire, a practical impulse steam turbine was invented in 1551 by taqi ad - din muhammad ibn ma ' ruf in ottoman egypt. he described a method for rotating a spit by means of a jet of steam playing on rotary vanes around the periphery of a wheel. known as a steam jack, a similar device for rotating a spit was also later described by john
water, and used in the gristmilling and sugarcane industries. sugar mills first appeared in the medieval islamic world. they were first driven by watermills, and then windmills from the 9th and 10th centuries in what are today afghanistan, pakistan and iran. crops such as almonds and citrus fruit were brought to europe through al - andalus, and sugar cultivation was gradually adopted across europe. arab merchants dominated trade in the indian ocean until the arrival of the portuguese in the 16th century. the muslim world adopted papermaking from china. the earliest paper mills appeared in abbasid - era baghdad during 794 β 795. the knowledge of gunpowder was also transmitted from china via predominantly islamic countries, where formulas for pure potassium nitrate were developed. the spinning wheel was invented in the islamic world by the early 11th century. it was later widely adopted in europe, where it was adapted into the spinning jenny, a key device during the industrial revolution. the crankshaft was invented by al - jazari in 1206, and is central to modern machinery such as the steam engine, internal combustion engine and automatic controls. the camshaft was also first described by al - jazari in 1206. early programmable machines were also invented in the muslim world. the first music sequencer, a programmable musical instrument, was an automated flute player invented by the banu musa brothers, described in their book of ingenious devices, in the 9th century. in 1206, al - jazari invented programmable automata / robots. he described four automaton musicians, including two drummers operated by a programmable drum machine, where the drummer could be made to play different rhythms and different drum patterns. the castle clock, a hydropowered mechanical astronomical clock invented by al - jazari, was an early programmable analog computer. in the ottoman empire, a practical impulse steam turbine was invented in 1551 by taqi ad - din muhammad ibn ma ' ruf in ottoman egypt. he described a method for rotating a spit by means of a jet of steam playing on rotary vanes around the periphery of a wheel. known as a steam jack, a similar device for rotating a spit was also later described by john wilkins in 1648. = = = = medieval europe = = = = while medieval technology has been long depicted as a step backward in the evolution of western technology, a generation of medievalists ( like the american historian of science lynn white ) stressed from the 1940s onwards the innovative character of many medieval techniques. genuine medieval contributions include
earth. each satellite has an onboard atomic clock and transmits a continuous radio signal containing a precise time signal as well as its current position. two frequencies are used, 1. 2276 and 1. 57542 ghz. since the velocity of radio waves is virtually constant, the delay of the radio signal from a satellite is proportional to the distance of the receiver from the satellite. by receiving the signals from at least four satellites a gps receiver can calculate its position on earth by comparing the arrival time of the radio signals. since each satellite ' s position is known precisely at any given time, from the delay the position of the receiver can be calculated by a microprocessor in the receiver. the position can be displayed as latitude and longitude, or as a marker on an electronic map. gps receivers are incorporated in almost all cellphones and in vehicles such as automobiles, aircraft, and ships, and are used to guide drones, missiles, cruise missiles, and even artillery shells to their target, and handheld gps receivers are produced for hikers and the military. radio beacon β a fixed location terrestrial radio transmitter which transmits a continuous radio signal used by aircraft and ships for navigation. the locations of beacons are plotted on navigational maps used by aircraft and ships. vhf omnidirectional range ( vor ) β a worldwide aircraft radio navigation system consisting of fixed ground radio beacons transmitting between 108. 00 and 117. 95 mhz in the very high frequency ( vhf ) band. an automated navigational instrument on the aircraft displays a bearing to a nearby vor transmitter. a vor beacon transmits two signals simultaneously on different frequencies. a directional antenna transmits a beam of radio waves that rotates like a lighthouse at a fixed rate, 30 times per second. when the directional beam is facing north, an omnidirectional antenna transmits a pulse. by measuring the difference in phase of these two signals, an aircraft can determine its bearing ( or " radial " ) from the station accurately. by taking a bearing on two vor beacons an aircraft can determine its position ( called a " fix " ) to an accuracy of about 90 metres ( 300 ft ). most vor beacons also have a distance measuring capability, called distance measuring equipment ( dme ) ; these are called vor / dme ' s. the aircraft transmits a radio signal to the vor / dme beacon and a transponder transmits a return signal. from the propagation delay between the transmitted and received signal the aircraft can calculate
the european union ' s galileo. global positioning system ( gps ) β the most widely used satellite navigation system, maintained by the us air force, which uses a constellation of 31 satellites in low earth orbit. the orbits of the satellites are distributed so at any time at least four satellites are above the horizon over each point on earth. each satellite has an onboard atomic clock and transmits a continuous radio signal containing a precise time signal as well as its current position. two frequencies are used, 1. 2276 and 1. 57542 ghz. since the velocity of radio waves is virtually constant, the delay of the radio signal from a satellite is proportional to the distance of the receiver from the satellite. by receiving the signals from at least four satellites a gps receiver can calculate its position on earth by comparing the arrival time of the radio signals. since each satellite ' s position is known precisely at any given time, from the delay the position of the receiver can be calculated by a microprocessor in the receiver. the position can be displayed as latitude and longitude, or as a marker on an electronic map. gps receivers are incorporated in almost all cellphones and in vehicles such as automobiles, aircraft, and ships, and are used to guide drones, missiles, cruise missiles, and even artillery shells to their target, and handheld gps receivers are produced for hikers and the military. radio beacon β a fixed location terrestrial radio transmitter which transmits a continuous radio signal used by aircraft and ships for navigation. the locations of beacons are plotted on navigational maps used by aircraft and ships. vhf omnidirectional range ( vor ) β a worldwide aircraft radio navigation system consisting of fixed ground radio beacons transmitting between 108. 00 and 117. 95 mhz in the very high frequency ( vhf ) band. an automated navigational instrument on the aircraft displays a bearing to a nearby vor transmitter. a vor beacon transmits two signals simultaneously on different frequencies. a directional antenna transmits a beam of radio waves that rotates like a lighthouse at a fixed rate, 30 times per second. when the directional beam is facing north, an omnidirectional antenna transmits a pulse. by measuring the difference in phase of these two signals, an aircraft can determine its bearing ( or " radial " ) from the station accurately. by taking a bearing on two vor beacons an aircraft can determine its position ( called a " fix " ) to an accuracy of about 90 metres ( 300 ft ). most vor beacons also have a
of the desired gene has been altered to make it non - functional. embryonic stem cells incorporate the altered gene, which replaces the already present functional copy. these stem cells are injected into blastocysts, which are implanted into surrogate mothers. this allows the experimenter to analyse the defects caused by this mutation and thereby determine the role of particular genes. it is used especially frequently in developmental biology. when this is done by creating a library of genes with point mutations at every position in the area of interest, or even every position in the whole gene, this is called " scanning mutagenesis ". the simplest method, and the first to be used, is " alanine scanning ", where every position in turn is mutated to the unreactive amino acid alanine. gain of function experiments, the logical counterpart of knockouts. these are sometimes performed in conjunction with knockout experiments to more finely establish the function of the desired gene. the process is much the same as that in knockout engineering, except that the construct is designed to increase the function of the gene, usually by providing extra copies of the gene or inducing synthesis of the protein more frequently. gain of function is used to tell whether or not a protein is sufficient for a function, but does not always mean it is required, especially when dealing with genetic or functional redundancy. tracking experiments, which seek to gain information about the localisation and interaction of the desired protein. one way to do this is to replace the wild - type gene with a ' fusion ' gene, which is a juxtaposition of the wild - type gene with a reporting element such as green fluorescent protein ( gfp ) that will allow easy visualisation of the products of the genetic modification. while this is a useful technique, the manipulation can destroy the function of the gene, creating secondary effects and possibly calling into question the results of the experiment. more sophisticated techniques are now in development that can track protein products without mitigating their function, such as the addition of small sequences that will serve as binding motifs to monoclonal antibodies. expression studies aim to discover where and when specific proteins are produced. in these experiments, the dna sequence before the dna that codes for a protein, known as a gene ' s promoter, is reintroduced into an organism with the protein coding region replaced by a reporter gene such as gfp or an enzyme that catalyses the production of a dye. thus the time and place where a particular protein is produced can be observed. expression studies can be taken a
adaptation of crops and techniques from and to regions outside it. advances were made in animal husbandry, irrigation, and farming, with the help of new technology such as the windmill. these changes made agriculture much more productive, supporting population growth, urbanisation, and increased stratification of society. muslim engineers in the islamic world made wide use of hydropower, along with early uses of tidal power, wind power, fossil fuels such as petroleum, and large factory complexes ( tiraz in arabic ). a variety of industrial mills were employed in the islamic world, including fulling mills, gristmills, hullers, sawmills, ship mills, stamp mills, steel mills, and tide mills. by the 11th century, every province throughout the islamic world had these industrial mills in operation. muslim engineers also employed water turbines and gears in mills and water - raising machines, and pioneered the use of dams as a source of water power, used to provide additional power to watermills and water - raising machines. many of these technologies were transferred to medieval europe. wind - powered machines used to grind grain and pump water, the windmill and wind pump, first appeared in what are now iran, afghanistan and pakistan by the 9th century. they were used to grind grains and draw up water, and used in the gristmilling and sugarcane industries. sugar mills first appeared in the medieval islamic world. they were first driven by watermills, and then windmills from the 9th and 10th centuries in what are today afghanistan, pakistan and iran. crops such as almonds and citrus fruit were brought to europe through al - andalus, and sugar cultivation was gradually adopted across europe. arab merchants dominated trade in the indian ocean until the arrival of the portuguese in the 16th century. the muslim world adopted papermaking from china. the earliest paper mills appeared in abbasid - era baghdad during 794 β 795. the knowledge of gunpowder was also transmitted from china via predominantly islamic countries, where formulas for pure potassium nitrate were developed. the spinning wheel was invented in the islamic world by the early 11th century. it was later widely adopted in europe, where it was adapted into the spinning jenny, a key device during the industrial revolution. the crankshaft was invented by al - jazari in 1206, and is central to modern machinery such as the steam engine, internal combustion engine and automatic controls. the camshaft was also first described by al - jazari in 1206. early programmable machines were also invented in the muslim world. the first music
in an imaginary conversation with guido altarelli, i express my views on the status of particle physics beyond the standard model and its future prospects.
is proportional to the distance of the receiver from the satellite. by receiving the signals from at least four satellites a gps receiver can calculate its position on earth by comparing the arrival time of the radio signals. since each satellite ' s position is known precisely at any given time, from the delay the position of the receiver can be calculated by a microprocessor in the receiver. the position can be displayed as latitude and longitude, or as a marker on an electronic map. gps receivers are incorporated in almost all cellphones and in vehicles such as automobiles, aircraft, and ships, and are used to guide drones, missiles, cruise missiles, and even artillery shells to their target, and handheld gps receivers are produced for hikers and the military. radio beacon β a fixed location terrestrial radio transmitter which transmits a continuous radio signal used by aircraft and ships for navigation. the locations of beacons are plotted on navigational maps used by aircraft and ships. vhf omnidirectional range ( vor ) β a worldwide aircraft radio navigation system consisting of fixed ground radio beacons transmitting between 108. 00 and 117. 95 mhz in the very high frequency ( vhf ) band. an automated navigational instrument on the aircraft displays a bearing to a nearby vor transmitter. a vor beacon transmits two signals simultaneously on different frequencies. a directional antenna transmits a beam of radio waves that rotates like a lighthouse at a fixed rate, 30 times per second. when the directional beam is facing north, an omnidirectional antenna transmits a pulse. by measuring the difference in phase of these two signals, an aircraft can determine its bearing ( or " radial " ) from the station accurately. by taking a bearing on two vor beacons an aircraft can determine its position ( called a " fix " ) to an accuracy of about 90 metres ( 300 ft ). most vor beacons also have a distance measuring capability, called distance measuring equipment ( dme ) ; these are called vor / dme ' s. the aircraft transmits a radio signal to the vor / dme beacon and a transponder transmits a return signal. from the propagation delay between the transmitted and received signal the aircraft can calculate its distance from the beacon. this allows an aircraft to determine its location " fix " from only one vor beacon. since line - of - sight vhf frequencies are used vor beacons have a range of about 200 miles for aircraft at cruising altitude. tacan is a similar military radio beacon system which transmits in
Question: From the uterus, where do sperm travel next?
A) vagina
B) fallopian tubes
C) urinary tract
D) ovaries
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B) fallopian tubes
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the thickness and the density of the material to be measured. the method is used for containers of liquids or of grainy substances thickness gauges : if the material is of constant density, the signal measured by the radiation detector depends on the thickness of the material. this is useful for continuous production, like of paper, rubber, etc. electrostatic control - to avoid the build - up of static electricity in production of paper, plastics, synthetic textiles, etc., a ribbon - shaped source of the alpha emitter 241am can be placed close to the material at the end of the production line. the source ionizes the air to remove electric charges on the material. radioactive tracers - since radioactive isotopes behave, chemically, mostly like the inactive element, the behavior of a certain chemical substance can be followed by tracing the radioactivity. examples : adding a gamma tracer to a gas or liquid in a closed system makes it possible to find a hole in a tube. adding a tracer to the surface of the component of a motor makes it possible to measure wear by measuring the activity of the lubricating oil. oil and gas exploration - nuclear well logging is used to help predict the commercial viability of new or existing wells. the technology involves the use of a neutron or gamma - ray source and a radiation detector which are lowered into boreholes to determine the properties of the surrounding rock such as porosity and lithography. [ 1 ] road construction - nuclear moisture / density gauges are used to determine the density of soils, asphalt, and concrete. typically a cesium - 137 source is used. = = = commercial applications = = = radioluminescence tritium illumination : tritium is used with phosphor in rifle sights to increase nighttime firing accuracy. some runway markers and building exit signs use the same technology, to remain illuminated during blackouts. betavoltaics. smoke detector : an ionization smoke detector includes a tiny mass of radioactive americium - 241, which is a source of alpha radiation. two ionisation chambers are placed next to each other. both contain a small source of 241am that gives rise to a small constant current. one is closed and serves for comparison, the other is open to ambient air ; it has a gridded electrode. when smoke enters the open chamber, the current is disrupted as the smoke particles attach to the charged ions and restore them to a neutral electrical state. this reduces the current in the open chamber. when the current drops below a certain threshold, the
delay of ripening, increase of juice yield, and improvement of re - hydration. irradiation is a more general term of deliberate exposure of materials to radiation to achieve a technical goal ( in this context ' ionizing radiation ' is implied ). as such it is also used on non - food items, such as medical hardware, plastics, tubes for gas - pipelines, hoses for floor - heating, shrink - foils for food packaging, automobile parts, wires and cables ( isolation ), tires, and even gemstones. compared to the amount of food irradiated, the volume of those every - day applications is huge but not noticed by the consumer. the genuine effect of processing food by ionizing radiation relates to damages to the dna, the basic genetic information for life. microorganisms can no longer proliferate and continue their malignant or pathogenic activities. spoilage causing micro - organisms cannot continue their activities. insects do not survive or become incapable of procreation. plants cannot continue the natural ripening or aging process. all these effects are beneficial to the consumer and the food industry, likewise. the amount of energy imparted for effective food irradiation is low compared to cooking the same ; even at a typical dose of 10 kgy most food, which is ( with regard to warming ) physically equivalent to water, would warm by only about 2. 5 Β°c ( 4. 5 Β°f ). the specialty of processing food by ionizing radiation is the fact, that the energy density per atomic transition is very high, it can cleave molecules and induce ionization ( hence the name ) which cannot be achieved by mere heating. this is the reason for new beneficial effects, however at the same time, for new concerns. the treatment of solid food by ionizing radiation can provide an effect similar to heat pasteurization of liquids, such as milk. however, the use of the term, cold pasteurization, to describe irradiated foods is controversial, because pasteurization and irradiation are fundamentally different processes, although the intended end results can in some cases be similar. detractors of food irradiation have concerns about the health hazards of induced radioactivity. a report for the industry advocacy group american council on science and health entitled " irradiated foods " states : " the types of radiation sources approved for the treatment of foods have specific energy levels well below that which would cause any element in food to become radioactive. food undergoing irradiation does not become any more
the surface of the membrane, retentate is removed from the same side further downstream, whereas the permeate flow is tracked on the other side. in dead - end filtration, the direction of the fluid flow is normal to the membrane surface. both flow geometries offer some advantages and disadvantages. generally, dead - end filtration is used for feasibility studies on a laboratory scale. the dead - end membranes are relatively easy to fabricate which reduces the cost of the separation process. the dead - end membrane separation process is easy to implement and the process is usually cheaper than cross - flow membrane filtration. the dead - end filtration process is usually a batch - type process, where the filtering solution is loaded ( or slowly fed ) into the membrane device, which then allows passage of some particles subject to the driving force. the main disadvantage of dead - end filtration is the extensive membrane fouling and concentration polarization. the fouling is usually induced faster at higher driving forces. membrane fouling and particle retention in a feed solution also builds up a concentration gradients and particle backflow ( concentration polarization ). the tangential flow devices are more cost and labor - intensive, but they are less susceptible to fouling due to the sweeping effects and high shear rates of the passing flow. the most commonly used synthetic membrane devices ( modules ) are flat sheets / plates, spiral wounds, and hollow fibers. flat membranes used in filtration and separation processes can be enhanced with surface patterning, where microscopic structures are introduced to improve performance. these patterns increase surface area, optimize water flow, and reduce fouling, leading to higher permeability and longer membrane lifespan. research has shown that such modifications can significantly enhance efficiency in water purification, energy applications, and industrial separations. flat plates are usually constructed as circular thin flat membrane surfaces to be used in dead - end geometry modules. spiral wounds are constructed from similar flat membranes but in the form of a " pocket " containing two membrane sheets separated by a highly porous support plate. several such pockets are then wound around a tube to create a tangential flow geometry and to reduce membrane fouling. hollow fiber modules consist of an assembly of self - supporting fibers with dense skin separation layers, and a more open matrix helping to withstand pressure gradients and maintain structural integrity. the hollow fiber modules can contain up to 10, 000 fibers ranging from 200 to 2500 ΞΌm in diameter ; the main advantage of hollow fiber modules is the very large surface area within
generally, dead - end filtration is used for feasibility studies on a laboratory scale. the dead - end membranes are relatively easy to fabricate which reduces the cost of the separation process. the dead - end membrane separation process is easy to implement and the process is usually cheaper than cross - flow membrane filtration. the dead - end filtration process is usually a batch - type process, where the filtering solution is loaded ( or slowly fed ) into the membrane device, which then allows passage of some particles subject to the driving force. the main disadvantage of dead - end filtration is the extensive membrane fouling and concentration polarization. the fouling is usually induced faster at higher driving forces. membrane fouling and particle retention in a feed solution also builds up a concentration gradients and particle backflow ( concentration polarization ). the tangential flow devices are more cost and labor - intensive, but they are less susceptible to fouling due to the sweeping effects and high shear rates of the passing flow. the most commonly used synthetic membrane devices ( modules ) are flat sheets / plates, spiral wounds, and hollow fibers. flat membranes used in filtration and separation processes can be enhanced with surface patterning, where microscopic structures are introduced to improve performance. these patterns increase surface area, optimize water flow, and reduce fouling, leading to higher permeability and longer membrane lifespan. research has shown that such modifications can significantly enhance efficiency in water purification, energy applications, and industrial separations. flat plates are usually constructed as circular thin flat membrane surfaces to be used in dead - end geometry modules. spiral wounds are constructed from similar flat membranes but in the form of a " pocket " containing two membrane sheets separated by a highly porous support plate. several such pockets are then wound around a tube to create a tangential flow geometry and to reduce membrane fouling. hollow fiber modules consist of an assembly of self - supporting fibers with dense skin separation layers, and a more open matrix helping to withstand pressure gradients and maintain structural integrity. the hollow fiber modules can contain up to 10, 000 fibers ranging from 200 to 2500 ΞΌm in diameter ; the main advantage of hollow fiber modules is the very large surface area within an enclosed volume, increasing the efficiency of the separation process. the disc tube module uses a cross - flow geometry and consists of a pressure tube and hydraulic discs, which are held by a central tension rod, and membrane cushions that lie between two discs. = = membrane performance and governing equations = = the selection of synthetic membranes
##physical processes which take place in human beings as they make sense of information received through the visual system. the subject of the image. when developing an imaging system, designers must consider the observables associated with the subjects which will be imaged. these observables generally take the form of emitted or reflected energy, such as electromagnetic energy or mechanical energy. the capture device. once the observables associated with the subject are characterized, designers can then identify and integrate the technologies needed to capture those observables. for example, in the case of consumer digital cameras, those technologies include optics for collecting energy in the visible portion of the electromagnetic spectrum, and electronic detectors for converting the electromagnetic energy into an electronic signal. the processor. for all digital imaging systems, the electronic signals produced by the capture device must be manipulated by an algorithm which formats the signals so they can be displayed as an image. in practice, there are often multiple processors involved in the creation of a digital image. the display. the display takes the electronic signals which have been manipulated by the processor and renders them on some visual medium. examples include paper ( for printed, or " hard copy " images ), television, computer monitor, or projector. note that some imaging scientists will include additional " links " in their description of the imaging chain. for example, some will include the " source " of the energy which " illuminates " or interacts with the subject of the image. others will include storage and / or transmission systems. = = subfields = = subfields within imaging science include : image processing, computer vision, 3d computer graphics, animations, atmospheric optics, astronomical imaging, biological imaging, digital image restoration, digital imaging, color science, digital photography, holography, magnetic resonance imaging, medical imaging, microdensitometry, optics, photography, remote sensing, radar imaging, radiometry, silver halide, ultrasound imaging, photoacoustic imaging, thermal imaging, visual perception, and various printing technologies. = = methodologies = = acoustic imaging coherent imaging uses an active coherent illumination source, such as in radar, synthetic aperture radar ( sar ), medical ultrasound and optical coherence tomography ; non - coherent imaging systems include fluorescent microscopes, optical microscopes, and telescopes. chemical imaging, the simultaneous measurement of spectra and pictures digital imaging, creating digital images, generally by scanning or through digital photography disk image, a file which contains the exact content of a data storage medium document imaging, replicating documents commonly
usability engineering, it ' s important target and identify human errors when interacting with the product of interest because if a user is expected to engage with a product, interface, or service in some way, the very introduction of a human in that engagement increases the potential of encountering human error. error should be reduced as much as possible in order to avoid frustration or injury. there are two main types of human errors which are categorized as slips and mistakes. slips are a very common kind of error involving automatic behaviors ( i. e. typos, hitting the wrong menu item ). when we experience slips, we have the correct goal in mind, but execute the wrong action. mistakes on the other hand involve conscious deliberation that result in the incorrect conclusion. when we experience mistakes, we have the wrong goal in mind and thereby execute the wrong action. even though slips are the more common type of error, they are no less dangerous. a certain type of slip error, a mode error, can be especially dangerous if a user is executing a high - risk task. for instance, if a user is operating a vehicle and does not realize they are in the wrong mode ( i. e. reverse ), they might step on the gas intending to drive, but instead accelerate into a garage wall or another car. in order to avoid modal errors, designers often employ modeless states in which users do not have to choose a mode at all, or they must execute a continuous action while intending to execute a certain mode ( i. e. pressing a key continuously in order to activate " lasso " mode in photoshop ). = = evaluation methods = = usability engineers conduct usability evaluations of existing or proposed interfaces and their findings are fed back to the designer for use in design or redesign. common usability evaluation methods include : card sorting cognitive task analysis cognitive walkthroughs contextual inquiry focus groups heuristic evaluations interviews questionnaires rite method surveys think aloud protocol usability testing = = software applications and development tools = = there are a variety of online resources that make the job of a usability engineer a little easier. online tools are only a useful tool, and do not substitute for a complete usability engineering analysis. some examples of these include : = = = the web metrics tool suite = = = this is a product of the national institute of standards and technology. this toolkit is focused on evaluating the html of a website versus a wide range of usability guidelines and includes : web static analyzer tool
##iation is the process of exposing food to ionizing radiation in order to destroy microorganisms, bacteria, viruses, or insects that might be present in the food. the radiation sources used include radioisotope gamma ray sources, x - ray generators and electron accelerators. further applications include sprout inhibition, delay of ripening, increase of juice yield, and improvement of re - hydration. irradiation is a more general term of deliberate exposure of materials to radiation to achieve a technical goal ( in this context ' ionizing radiation ' is implied ). as such it is also used on non - food items, such as medical hardware, plastics, tubes for gas - pipelines, hoses for floor - heating, shrink - foils for food packaging, automobile parts, wires and cables ( isolation ), tires, and even gemstones. compared to the amount of food irradiated, the volume of those every - day applications is huge but not noticed by the consumer. the genuine effect of processing food by ionizing radiation relates to damages to the dna, the basic genetic information for life. microorganisms can no longer proliferate and continue their malignant or pathogenic activities. spoilage causing micro - organisms cannot continue their activities. insects do not survive or become incapable of procreation. plants cannot continue the natural ripening or aging process. all these effects are beneficial to the consumer and the food industry, likewise. the amount of energy imparted for effective food irradiation is low compared to cooking the same ; even at a typical dose of 10 kgy most food, which is ( with regard to warming ) physically equivalent to water, would warm by only about 2. 5 Β°c ( 4. 5 Β°f ). the specialty of processing food by ionizing radiation is the fact, that the energy density per atomic transition is very high, it can cleave molecules and induce ionization ( hence the name ) which cannot be achieved by mere heating. this is the reason for new beneficial effects, however at the same time, for new concerns. the treatment of solid food by ionizing radiation can provide an effect similar to heat pasteurization of liquids, such as milk. however, the use of the term, cold pasteurization, to describe irradiated foods is controversial, because pasteurization and irradiation are fundamentally different processes, although the intended end results can in some cases be similar. detractors of food irradiation have concerns about the health hazards of induced radioact
= = = = = = environmental remediation = = = environmental remediation is the process through which contaminants or pollutants in soil, water and other media are removed to improve environmental quality. the main focus is the reduction of hazardous substances within the environment. some of the areas involved in environmental remediation include ; soil contamination, hazardous waste, groundwater contamination, oil, gas and chemical spills. there are three most common types of environmental remediation. these include soil, water, and sediment remediation. soil remediation consists of removing contaminants in soil, as these pose great risks to humans and the ecosystem. some examples of this are heavy metals, pesticides, and radioactive materials. depending on the contaminant the remedial processes can be physical, chemical, thermal, or biological. water remediation is one of the most important considering water is an essential natural resource. depending on the source of water there will be different contaminants. surface water contamination mainly consists of agricultural, animal, and industrial waste, as well as acid mine drainage. there has been a rise in the need for water remediation due to the increased discharge of industrial waste, leading to a demand for sustainable water solutions. the market for water remediation is expected to consistently increase to $ 19. 6 billion by 2030. sediment remediation consists of removing contaminated sediments. is it almost similar to soil remediation except it is often more sophisticated as it involves additional contaminants. to reduce the contaminants it is likely to use physical, chemical, and biological processes that help with source control, but if these processes are executed correctly, there ' s a risk of contamination resurfacing. = = = solid waste management = = = solid waste management is the purification, consumption, reuse, disposal, and treatment of solid waste that is undertaken by the government or the ruling bodies of a city / town. it refers to the collection, treatment, and disposal of non - soluble, solid waste material. solid waste is associated with both industrial, institutional, commercial and residential activities. hazardous solid waste, when improperly disposed can encourage the infestation of insects and rodents, contributing to the spread of diseases. some of the most common types of solid waste management include ; landfills, vermicomposting, composting, recycling, and incineration. however, a major barrier for solid waste management practices is the high costs associated with recycling
". = = extraction = = extractive metallurgy is the practice of removing valuable metals from an ore and refining the extracted raw metals into a purer form. in order to convert a metal oxide or sulphide to a purer metal, the ore must be reduced physically, chemically, or electrolytically. extractive metallurgists are interested in three primary streams : feed, concentrate ( metal oxide / sulphide ) and tailings ( waste ). after mining, large pieces of the ore feed are broken through crushing or grinding in order to obtain particles small enough, where each particle is either mostly valuable or mostly waste. concentrating the particles of value in a form supporting separation enables the desired metal to be removed from waste products. mining may not be necessary, if the ore body and physical environment are conducive to leaching. leaching dissolves minerals in an ore body and results in an enriched solution. the solution is collected and processed to extract valuable metals. ore bodies often contain more than one valuable metal. tailings of a previous process may be used as a feed in another process to extract a secondary product from the original ore. additionally, a concentrate may contain more than one valuable metal. that concentrate would then be processed to separate the valuable metals into individual constituents. = = metal and its alloys = = much effort has been placed on understanding iron β carbon alloy system, which includes steels and cast irons. plain carbon steels ( those that contain essentially only carbon as an alloying element ) are used in low - cost, high - strength applications, where neither weight nor corrosion are a major concern. cast irons, including ductile iron, are also part of the iron - carbon system. iron - manganese - chromium alloys ( hadfield - type steels ) are also used in non - magnetic applications such as directional drilling. other engineering metals include aluminium, chromium, copper, magnesium, nickel, titanium, zinc, and silicon. these metals are most often used as alloys with the noted exception of silicon, which is not a metal. other forms include : stainless steel, particularly austenitic stainless steels, galvanized steel, nickel alloys, titanium alloys, or occasionally copper alloys are used, where resistance to corrosion is important. aluminium alloys and magnesium alloys are commonly used, when a lightweight strong part is required such as in automotive and aerospace applications. copper - nickel alloys ( such as monel ) are used in highly corrosive environments and for non - magnetic applications
the elimination of metabolic wastes. these enzyme - catalyzed reactions allow organisms to grow and reproduce, maintain their structures, and respond to their environments. metabolic reactions may be categorized as catabolic β the breaking down of compounds ( for example, the breaking down of glucose to pyruvate by cellular respiration ) ; or anabolic β the building up ( synthesis ) of compounds ( such as proteins, carbohydrates, lipids, and nucleic acids ). usually, catabolism releases energy, and anabolism consumes energy. the chemical reactions of metabolism are organized into metabolic pathways, in which one chemical is transformed through a series of steps into another chemical, each step being facilitated by a specific enzyme. enzymes are crucial to metabolism because they allow organisms to drive desirable reactions that require energy that will not occur by themselves, by coupling them to spontaneous reactions that release energy. enzymes act as catalysts β they allow a reaction to proceed more rapidly without being consumed by it β by reducing the amount of activation energy needed to convert reactants into products. enzymes also allow the regulation of the rate of a metabolic reaction, for example in response to changes in the cell ' s environment or to signals from other cells. = = = cellular respiration = = = cellular respiration is a set of metabolic reactions and processes that take place in cells to convert chemical energy from nutrients into adenosine triphosphate ( atp ), and then release waste products. the reactions involved in respiration are catabolic reactions, which break large molecules into smaller ones, releasing energy. respiration is one of the key ways a cell releases chemical energy to fuel cellular activity. the overall reaction occurs in a series of biochemical steps, some of which are redox reactions. although cellular respiration is technically a combustion reaction, it clearly does not resemble one when it occurs in a cell because of the slow, controlled release of energy from the series of reactions. sugar in the form of glucose is the main nutrient used by animal and plant cells in respiration. cellular respiration involving oxygen is called aerobic respiration, which has four stages : glycolysis, citric acid cycle ( or krebs cycle ), electron transport chain, and oxidative phosphorylation. glycolysis is a metabolic process that occurs in the cytoplasm whereby glucose is converted into two pyruvates, with two net molecules of atp being produced at the same time. each pyruvate is then
Question: What completes the process as undigested material passes out of the digestive system?
A) elimination
B) accumulation
C) culmination
D) reaction
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A) elimination
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Context:
enough to rise to the surface β giving birth to volcanoes. = = atmospheric science = = atmospheric science initially developed in the late - 19th century as a means to forecast the weather through meteorology, the study of weather. atmospheric chemistry was developed in the 20th century to measure air pollution and expanded in the 1970s in response to acid rain. climatology studies the climate and climate change. the troposphere, stratosphere, mesosphere, thermosphere, and exosphere are the five layers which make up earth ' s atmosphere. 75 % of the mass in the atmosphere is located within the troposphere, the lowest layer. in all, the atmosphere is made up of about 78. 0 % nitrogen, 20. 9 % oxygen, and 0. 92 % argon, and small amounts of other gases including co2 and water vapor. water vapor and co2 cause the earth ' s atmosphere to catch and hold the sun ' s energy through the greenhouse effect. this makes earth ' s surface warm enough for liquid water and life. in addition to trapping heat, the atmosphere also protects living organisms by shielding the earth ' s surface from cosmic rays. the magnetic field β created by the internal motions of the core β produces the magnetosphere which protects earth ' s atmosphere from the solar wind. as the earth is 4. 5 billion years old, it would have lost its atmosphere by now if there were no protective magnetosphere. = = earth ' s magnetic field = = = = hydrology = = hydrology is the study of the hydrosphere and the movement of water on earth. it emphasizes the study of how humans use and interact with freshwater supplies. study of water ' s movement is closely related to geomorphology and other branches of earth science. applied hydrology involves engineering to maintain aquatic environments and distribute water supplies. subdisciplines of hydrology include oceanography, hydrogeology, ecohydrology, and glaciology. oceanography is the study of oceans. hydrogeology is the study of groundwater. it includes the mapping of groundwater supplies and the analysis of groundwater contaminants. applied hydrogeology seeks to prevent contamination of groundwater and mineral springs and make it available as drinking water. the earliest exploitation of groundwater resources dates back to 3000 bc, and hydrogeology as a science was developed by hydrologists beginning in the 17th century. ecohydrology is the study of ecological systems in the hydrosphere. it can be divided into the physical study of aquatic ecosystems and the
cools and solidifies. through subduction, oceanic crust and lithosphere vehemently returns to the convecting mantle. volcanoes result primarily from the melting of subducted crust material. crust material that is forced into the asthenosphere melts, and some portion of the melted material becomes light enough to rise to the surface β giving birth to volcanoes. = = atmospheric science = = atmospheric science initially developed in the late - 19th century as a means to forecast the weather through meteorology, the study of weather. atmospheric chemistry was developed in the 20th century to measure air pollution and expanded in the 1970s in response to acid rain. climatology studies the climate and climate change. the troposphere, stratosphere, mesosphere, thermosphere, and exosphere are the five layers which make up earth ' s atmosphere. 75 % of the mass in the atmosphere is located within the troposphere, the lowest layer. in all, the atmosphere is made up of about 78. 0 % nitrogen, 20. 9 % oxygen, and 0. 92 % argon, and small amounts of other gases including co2 and water vapor. water vapor and co2 cause the earth ' s atmosphere to catch and hold the sun ' s energy through the greenhouse effect. this makes earth ' s surface warm enough for liquid water and life. in addition to trapping heat, the atmosphere also protects living organisms by shielding the earth ' s surface from cosmic rays. the magnetic field β created by the internal motions of the core β produces the magnetosphere which protects earth ' s atmosphere from the solar wind. as the earth is 4. 5 billion years old, it would have lost its atmosphere by now if there were no protective magnetosphere. = = earth ' s magnetic field = = = = hydrology = = hydrology is the study of the hydrosphere and the movement of water on earth. it emphasizes the study of how humans use and interact with freshwater supplies. study of water ' s movement is closely related to geomorphology and other branches of earth science. applied hydrology involves engineering to maintain aquatic environments and distribute water supplies. subdisciplines of hydrology include oceanography, hydrogeology, ecohydrology, and glaciology. oceanography is the study of oceans. hydrogeology is the study of groundwater. it includes the mapping of groundwater supplies and the analysis of groundwater contaminants. applied hydrogeology seeks to prevent contamination of groundwater and mineral springs and make
, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature. = = = = substance and mixture = = = = a chemical substance is a kind of matter with a definite composition and set of properties. a collection of substances is called a mixture. examples of mixtures are air and alloys. = = = = mole and amount of substance = = = = the mole is a unit of measurement that denotes an amount of substance ( also called chemical amount ). one mole is defined to contain exactly 6. 02214076Γ1023 particles ( atoms, molecules, ions, or electrons ), where the number of particles per mole is known as the avogadro constant. molar concentration is the amount of a particular substance per volume of solution, and is commonly reported in mol / dm3. = = = phase = = = in addition to the specific chemical properties that distinguish different chemical classifications, chemicals can exist in several phases. for the most part, the chemical classifications are independent of these bulk phase classifications ; however, some more exotic phases are incompatible with certain chemical properties. a phase is a set of states of a chemical system that have similar bulk structural properties, over a range of conditions, such as pressure or temperature. physical properties, such as density and refractive index tend to fall within values characteristic of the phase
consisting of several distinct layers, often referred to as spheres : the lithosphere, the hydrosphere, the atmosphere, and the biosphere, this concept of spheres is a useful tool for understanding the earth ' s surface and its various processes these correspond to rocks, water, air and life. also included by some are the cryosphere ( corresponding to ice ) as a distinct portion of the hydrosphere and the pedosphere ( corresponding to soil ) as an active and intermixed sphere. the following fields of science are generally categorized within the earth sciences : geology describes the rocky parts of the earth ' s crust ( or lithosphere ) and its historic development. major subdisciplines are mineralogy and petrology, geomorphology, paleontology, stratigraphy, structural geology, engineering geology, and sedimentology. physical geography focuses on geography as an earth science. physical geography is the study of earth ' s seasons, climate, atmosphere, soil, streams, landforms, and oceans. physical geography can be divided into several branches or related fields, as follows : geomorphology, biogeography, environmental geography, palaeogeography, climatology, meteorology, coastal geography, hydrology, ecology, glaciology. geophysics and geodesy investigate the shape of the earth, its reaction to forces and its magnetic and gravity fields. geophysicists explore the earth ' s core and mantle as well as the tectonic and seismic activity of the lithosphere. geophysics is commonly used to supplement the work of geologists in developing a comprehensive understanding of crustal geology, particularly in mineral and petroleum exploration. seismologists use geophysics to understand plate tectonic movement, as well as predict seismic activity. geochemistry studies the processes that control the abundance, composition, and distribution of chemical compounds and isotopes in geologic environments. geochemists use the tools and principles of chemistry to study the earth ' s composition, structure, processes, and other physical aspects. major subdisciplines are aqueous geochemistry, cosmochemistry, isotope geochemistry and biogeochemistry. soil science covers the outermost layer of the earth ' s crust that is subject to soil formation processes ( or pedosphere ). major subdivisions in this field of study include edaphology and pedology. ecology covers the interactions between organisms and their environment. this field of study differentiates the study of earth
all christian authors held that the earth was round. athenagoras, an eastern christian writing around the year 175 ad, said that the earth was spherical. methodius ( c. 290 ad ), an eastern christian writing against " the theory of the chaldeans and the egyptians " said : " let us first lay bare... the theory of the chaldeans and the egyptians. they say that the circumference of the universe is likened to the turnings of a well - rounded globe, the earth being a central point. they say that since its outline is spherical,... the earth should be the center of the universe, around which the heaven is whirling. " arnobius, another eastern christian writing sometime around 305 ad, described the round earth : " in the first place, indeed, the world itself is neither right nor left. it has neither upper nor lower regions, nor front nor back. for whatever is round and bounded on every side by the circumference of a solid sphere, has no beginning or end... " other advocates of a round earth included eusebius, hilary of poitiers, irenaeus, hippolytus of rome, firmicus maternus, ambrose, jerome, prudentius, favonius eulogius, and others. the only exceptions to this consensus up until the mid - fourth century were theophilus of antioch and lactantius, both of whom held anti - hellenistic views and associated the round - earth view with pagan cosmology. lactantius, a western christian writer and advisor to the first christian roman emperor, constantine, writing sometime between 304 and 313 ad, ridiculed the notion of antipodes and the philosophers who fancied that " the universe is round like a ball. they also thought that heaven revolves in accordance with the motion of the heavenly bodies.... for that reason, they constructed brass globes, as though after the figure of the universe. " the influential theologian and philosopher saint augustine, one of the four great church fathers of the western church, similarly objected to the " fable " of antipodes : but as to the fable that there are antipodes, that is to say, men on the opposite side of the earth, where the sun rises when it sets to us, men who walk with their feet opposite ours that is on no ground credible. and, indeed, it is not affirmed that this has been learned by historical knowledge, but by scientific conjecture
, crystal structure, hazards associated with minerals, and the physical and chemical properties of minerals. petrology is the study of rocks, including the formation and composition of rocks. petrography is a branch of petrology that studies the typology and classification of rocks. = = earth ' s interior = = plate tectonics, mountain ranges, volcanoes, and earthquakes are geological phenomena that can be explained in terms of physical and chemical processes in the earth ' s crust. beneath the earth ' s crust lies the mantle which is heated by the radioactive decay of heavy elements. the mantle is not quite solid and consists of magma which is in a state of semi - perpetual convection. this convection process causes the lithospheric plates to move, albeit slowly. the resulting process is known as plate tectonics. areas of the crust where new crust is created are called divergent boundaries, those where it is brought back into the earth are convergent boundaries and those where plates slide past each other, but no new lithospheric material is created or destroyed, are referred to as transform ( or conservative ) boundaries. earthquakes result from the movement of the lithospheric plates, and they often occur near convergent boundaries where parts of the crust are forced into the earth as part of subduction. plate tectonics might be thought of as the process by which the earth is resurfaced. as the result of seafloor spreading, new crust and lithosphere is created by the flow of magma from the mantle to the near surface, through fissures, where it cools and solidifies. through subduction, oceanic crust and lithosphere vehemently returns to the convecting mantle. volcanoes result primarily from the melting of subducted crust material. crust material that is forced into the asthenosphere melts, and some portion of the melted material becomes light enough to rise to the surface β giving birth to volcanoes. = = atmospheric science = = atmospheric science initially developed in the late - 19th century as a means to forecast the weather through meteorology, the study of weather. atmospheric chemistry was developed in the 20th century to measure air pollution and expanded in the 1970s in response to acid rain. climatology studies the climate and climate change. the troposphere, stratosphere, mesosphere, thermosphere, and exosphere are the five layers which make up earth ' s atmosphere. 75 % of the mass in the atmosphere is located within the troposphere, the lowest
higher concentrations of atmospheric nitrous oxide ( n2o ) are expected to slightly warm earth ' s surface because of increases in radiative forcing. radiative forcing is the difference in the net upward thermal radiation flux from the earth through a transparent atmosphere and radiation through an otherwise identical atmosphere with greenhouse gases. radiative forcing, normally measured in w / m ^ 2, depends on latitude, longitude and altitude, but it is often quoted for the tropopause, about 11 km of altitude for temperate latitudes, or for the top of the atmosphere at around 90 km. for current concentrations of greenhouse gases, the radiative forcing per added n2o molecule is about 230 times larger than the forcing per added carbon dioxide ( co2 ) molecule. this is due to the heavy saturation of the absorption band of the relatively abundant greenhouse gas, co2, compared to the much smaller saturation of the absorption bands of the trace greenhouse gas n2o. but the rate of increase of co2 molecules, about 2. 5 ppm / year ( ppm = part per million by mole ), is about 3000 times larger than the rate of increase of n2o molecules, which has held steady at around 0. 00085 ppm / year since 1985. so, the contribution of nitrous oxide to the annual increase in forcing is 230 / 3000 or about 1 / 13 that of co2. if the main greenhouse gases, co2, ch4 and n2o have contributed about 0. 1 c / decade of the warming observed over the past few decades, this would correspond to about 0. 00064 k per year or 0. 064 k per century of warming from n2o. proposals to place harsh restrictions on nitrous oxide emissions because of warming fears are not justified by these facts. restrictions would cause serious harm ; for example, by jeopardizing world food supplies.
earth science or geoscience includes all fields of natural science related to the planet earth. this is a branch of science dealing with the physical, chemical, and biological complex constitutions and synergistic linkages of earth ' s four spheres : the biosphere, hydrosphere / cryosphere, atmosphere, and geosphere ( or lithosphere ). earth science can be considered to be a branch of planetary science but with a much older history. = = geology = = geology is broadly the study of earth ' s structure, substance, and processes. geology is largely the study of the lithosphere, or earth ' s surface, including the crust and rocks. it includes the physical characteristics and processes that occur in the lithosphere as well as how they are affected by geothermal energy. it incorporates aspects of chemistry, physics, and biology as elements of geology interact. historical geology is the application of geology to interpret earth history and how it has changed over time. geochemistry studies the chemical components and processes of the earth. geophysics studies the physical properties of the earth. paleontology studies fossilized biological material in the lithosphere. planetary geology studies geoscience as it pertains to extraterrestrial bodies. geomorphology studies the origin of landscapes. structural geology studies the deformation of rocks to produce mountains and lowlands. resource geology studies how energy resources can be obtained from minerals. environmental geology studies how pollution and contaminants affect soil and rock. mineralogy is the study of minerals and includes the study of mineral formation, crystal structure, hazards associated with minerals, and the physical and chemical properties of minerals. petrology is the study of rocks, including the formation and composition of rocks. petrography is a branch of petrology that studies the typology and classification of rocks. = = earth ' s interior = = plate tectonics, mountain ranges, volcanoes, and earthquakes are geological phenomena that can be explained in terms of physical and chemical processes in the earth ' s crust. beneath the earth ' s crust lies the mantle which is heated by the radioactive decay of heavy elements. the mantle is not quite solid and consists of magma which is in a state of semi - perpetual convection. this convection process causes the lithospheric plates to move, albeit slowly. the resulting process is known as plate tectonics. areas of the crust where new crust is created are called divergent boundaries, those where it is brought back into the earth are convergent boundaries and
are the cryosphere ( corresponding to ice ) as a distinct portion of the hydrosphere and the pedosphere ( corresponding to soil ) as an active and intermixed sphere. the following fields of science are generally categorized within the earth sciences : geology describes the rocky parts of the earth ' s crust ( or lithosphere ) and its historic development. major subdisciplines are mineralogy and petrology, geomorphology, paleontology, stratigraphy, structural geology, engineering geology, and sedimentology. physical geography focuses on geography as an earth science. physical geography is the study of earth ' s seasons, climate, atmosphere, soil, streams, landforms, and oceans. physical geography can be divided into several branches or related fields, as follows : geomorphology, biogeography, environmental geography, palaeogeography, climatology, meteorology, coastal geography, hydrology, ecology, glaciology. geophysics and geodesy investigate the shape of the earth, its reaction to forces and its magnetic and gravity fields. geophysicists explore the earth ' s core and mantle as well as the tectonic and seismic activity of the lithosphere. geophysics is commonly used to supplement the work of geologists in developing a comprehensive understanding of crustal geology, particularly in mineral and petroleum exploration. seismologists use geophysics to understand plate tectonic movement, as well as predict seismic activity. geochemistry studies the processes that control the abundance, composition, and distribution of chemical compounds and isotopes in geologic environments. geochemists use the tools and principles of chemistry to study the earth ' s composition, structure, processes, and other physical aspects. major subdisciplines are aqueous geochemistry, cosmochemistry, isotope geochemistry and biogeochemistry. soil science covers the outermost layer of the earth ' s crust that is subject to soil formation processes ( or pedosphere ). major subdivisions in this field of study include edaphology and pedology. ecology covers the interactions between organisms and their environment. this field of study differentiates the study of earth from other planets in the solar system, earth being the only planet teeming with life. hydrology, oceanography and limnology are studies which focus on the movement, distribution, and quality of the water and involve all the components of the hydrologic cycle on the earth and its atmosphere ( or hydrosphere ). "
, glaciology. geophysics and geodesy investigate the shape of the earth, its reaction to forces and its magnetic and gravity fields. geophysicists explore the earth ' s core and mantle as well as the tectonic and seismic activity of the lithosphere. geophysics is commonly used to supplement the work of geologists in developing a comprehensive understanding of crustal geology, particularly in mineral and petroleum exploration. seismologists use geophysics to understand plate tectonic movement, as well as predict seismic activity. geochemistry studies the processes that control the abundance, composition, and distribution of chemical compounds and isotopes in geologic environments. geochemists use the tools and principles of chemistry to study the earth ' s composition, structure, processes, and other physical aspects. major subdisciplines are aqueous geochemistry, cosmochemistry, isotope geochemistry and biogeochemistry. soil science covers the outermost layer of the earth ' s crust that is subject to soil formation processes ( or pedosphere ). major subdivisions in this field of study include edaphology and pedology. ecology covers the interactions between organisms and their environment. this field of study differentiates the study of earth from other planets in the solar system, earth being the only planet teeming with life. hydrology, oceanography and limnology are studies which focus on the movement, distribution, and quality of the water and involve all the components of the hydrologic cycle on the earth and its atmosphere ( or hydrosphere ). " sub - disciplines of hydrology include hydrometeorology, surface water hydrology, hydrogeology, watershed science, forest hydrology, and water chemistry. " glaciology covers the icy parts of the earth ( or cryosphere ). atmospheric sciences cover the gaseous parts of the earth ( or atmosphere ) between the surface and the exosphere ( about 1000 km ). major subdisciplines include meteorology, climatology, atmospheric chemistry, and atmospheric physics. = = = earth science breakup = = = = = see also = = = = references = = = = = sources = = = = = further reading = = = = external links = = earth science picture of the day, a service of universities space research association, sponsored by nasa goddard space flight center. geoethics in planetary and space exploration. geology buzz : earth science archived 2021 - 11 - 04 at the wayback machine
Question: What is a thin layer of gas that surrounds earth called?
A) the wind cycle
B) the cloud cover
C) the dioxide
D) the atmosphere
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D) the atmosphere
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Context:
has rest mass and volume ( it takes up space ) and is made up of particles. the particles that make up matter have rest mass as well β not all particles have rest mass, such as the photon. matter can be a pure chemical substance or a mixture of substances. = = = = atom = = = = the atom is the basic unit of chemistry. it consists of a dense core called the atomic nucleus surrounded by a space occupied by an electron cloud. the nucleus is made up of positively charged protons and uncharged neutrons ( together called nucleons ), while the electron cloud consists of negatively charged electrons which orbit the nucleus. in a neutral atom, the negatively charged electrons balance out the positive charge of the protons. the nucleus is dense ; the mass of a nucleon is approximately 1, 836 times that of an electron, yet the radius of an atom is about 10, 000 times that of its nucleus. the atom is also the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state ( s ), coordination number, and preferred types of bonds to form ( e. g., metallic, ionic, covalent ). = = = = element = = = = a chemical element is a pure substance which is composed of a single type of atom, characterized by its particular number of protons in the nuclei of its atoms, known as the atomic number and represented by the symbol z. the mass number is the sum of the number of protons and neutrons in a nucleus. although all the nuclei of all atoms belonging to one element will have the same atomic number, they may not necessarily have the same mass number ; atoms of an element which have different mass numbers are known as isotopes. for example, all atoms with 6 protons in their nuclei are atoms of the chemical element carbon, but atoms of carbon may have mass numbers of 12 or 13. the standard presentation of the chemical elements is in the periodic table, which orders elements by atomic number. the periodic table is arranged in groups, or columns, and periods, or rows. the periodic table is useful in identifying periodic trends. = = = = compound = = = = a compound is a pure chemical substance composed of more than one element. the properties of a compound bear little similarity to those of its elements. the standard nomenclature of compounds is set by the international union of pure and applied chemistry ( iupac ). organic compounds are named
that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature. = = = = substance and mixture = = = = a chemical substance is a kind of matter with a definite composition and set of properties. a collection of substances is called a mixture. examples of mixtures are air and alloys. = = = = mole and amount of substance = = = = the mole is a unit of measurement that denotes an amount of substance ( also called chemical amount ). one mole is defined to contain exactly 6. 02214076Γ1023 particles ( atoms, molecules, ions, or electrons ), where the number of particles per mole is known as the avogadro constant. molar concentration is
, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature. = = = = substance and mixture = = = = a chemical substance is a kind of matter with a definite composition and set of properties. a collection of substances is called a mixture. examples of mixtures are air and alloys. = = = = mole and amount of substance = = = = the mole is a unit of measurement that denotes an amount of substance ( also called chemical amount ). one mole is defined to contain exactly 6. 02214076Γ1023 particles ( atoms, molecules, ions, or electrons ), where the number of particles per mole is known as the avogadro constant. molar concentration is the amount of a particular substance per volume of solution, and is commonly reported in mol / dm3. = = = phase = = = in addition to the specific chemical properties that distinguish different chemical classifications, chemicals can exist in several phases. for the most part, the chemical classifications are independent of these bulk phase classifications ; however, some more exotic phases are incompatible with certain chemical properties. a phase is a set of states of a chemical system that have similar bulk structural properties, over a range of conditions, such as pressure or temperature. physical properties, such as density and refractive index tend to fall within values characteristic of the phase
other electrons either in bonds or in lone pairs. thus, molecules exist as electrically neutral units, unlike ions. when this rule is broken, giving the " molecule " a charge, the result is sometimes named a molecular ion or a polyatomic ion. however, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature. = = = = substance and mixture = = = = a chemical substance is a kind of matter with a definite composition and set of properties. a collection of substances is called a mixture. examples of mixtures are air and alloys. = = = = mole and amount of substance = = = = the mole is a unit
set of chemical reactions with other substances. however, this definition only works well for substances that are composed of molecules, which is not true of many substances ( see below ). molecules are typically a set of atoms bound together by covalent bonds, such that the structure is electrically neutral and all valence electrons are paired with other electrons either in bonds or in lone pairs. thus, molecules exist as electrically neutral units, unlike ions. when this rule is broken, giving the " molecule " a charge, the result is sometimes named a molecular ion or a polyatomic ion. however, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature.
electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature. = = = = substance and mixture = = = = a chemical substance is a kind of matter with a definite composition and set of properties. a collection of substances is called a mixture. examples of mixtures are air and alloys. = = = = mole and amount of substance = = = = the mole is a unit of measurement that denotes an amount of substance ( also called chemical amount ). one mole is defined to contain exactly 6. 02214076Γ1023 particles ( atoms, molecules, ions, or electrons ), where the number of particles per mole is known as the avogadro constant. molar concentration is the amount of a particular substance per volume of solution, and is commonly reported in mol / dm3. = = = phase = = = in addition to the specific chemical properties that distinguish different chemical classifications, chemicals can exist in several phases. for the most part, the chemical classifications are independent of these bulk phase
g. spectroscopy and chromatography. scientists engaged in chemical research are known as chemists. most chemists specialize in one or more sub - disciplines. several concepts are essential for the study of chemistry ; some of them are : = = = matter = = = in chemistry, matter is defined as anything that has rest mass and volume ( it takes up space ) and is made up of particles. the particles that make up matter have rest mass as well β not all particles have rest mass, such as the photon. matter can be a pure chemical substance or a mixture of substances. = = = = atom = = = = the atom is the basic unit of chemistry. it consists of a dense core called the atomic nucleus surrounded by a space occupied by an electron cloud. the nucleus is made up of positively charged protons and uncharged neutrons ( together called nucleons ), while the electron cloud consists of negatively charged electrons which orbit the nucleus. in a neutral atom, the negatively charged electrons balance out the positive charge of the protons. the nucleus is dense ; the mass of a nucleon is approximately 1, 836 times that of an electron, yet the radius of an atom is about 10, 000 times that of its nucleus. the atom is also the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state ( s ), coordination number, and preferred types of bonds to form ( e. g., metallic, ionic, covalent ). = = = = element = = = = a chemical element is a pure substance which is composed of a single type of atom, characterized by its particular number of protons in the nuclei of its atoms, known as the atomic number and represented by the symbol z. the mass number is the sum of the number of protons and neutrons in a nucleus. although all the nuclei of all atoms belonging to one element will have the same atomic number, they may not necessarily have the same mass number ; atoms of an element which have different mass numbers are known as isotopes. for example, all atoms with 6 protons in their nuclei are atoms of the chemical element carbon, but atoms of carbon may have mass numbers of 12 or 13. the standard presentation of the chemical elements is in the periodic table, which orders elements by atomic number. the periodic table is arranged in groups, or columns, and periods, or rows. the periodic table is useful in identifying periodic trends
chemistry is the scientific study of the properties and behavior of matter. it is a physical science within the natural sciences that studies the chemical elements that make up matter and compounds made of atoms, molecules and ions : their composition, structure, properties, behavior and the changes they undergo during reactions with other substances. chemistry also addresses the nature of chemical bonds in chemical compounds. in the scope of its subject, chemistry occupies an intermediate position between physics and biology. it is sometimes called the central science because it provides a foundation for understanding both basic and applied scientific disciplines at a fundamental level. for example, chemistry explains aspects of plant growth ( botany ), the formation of igneous rocks ( geology ), how atmospheric ozone is formed and how environmental pollutants are degraded ( ecology ), the properties of the soil on the moon ( cosmochemistry ), how medications work ( pharmacology ), and how to collect dna evidence at a crime scene ( forensics ). chemistry has existed under various names since ancient times. it has evolved, and now chemistry encompasses various areas of specialisation, or subdisciplines, that continue to increase in number and interrelate to create further interdisciplinary fields of study. the applications of various fields of chemistry are used frequently for economic purposes in the chemical industry. = = etymology = = the word chemistry comes from a modification during the renaissance of the word alchemy, which referred to an earlier set of practices that encompassed elements of chemistry, metallurgy, philosophy, astrology, astronomy, mysticism, and medicine. alchemy is often associated with the quest to turn lead or other base metals into gold, though alchemists were also interested in many of the questions of modern chemistry. the modern word alchemy in turn is derived from the arabic word al - kimia ( Ψ§ΩΩΫΩ
ΫΨ§Ψ‘ ). this may have egyptian origins since al - kimia is derived from the ancient greek ΟΞ·ΞΌΞΉΞ±, which is in turn derived from the word kemet, which is the ancient name of egypt in the egyptian language. alternately, al - kimia may derive from ΟημΡια ' cast together '. = = modern principles = = the current model of atomic structure is the quantum mechanical model. traditional chemistry starts with the study of elementary particles, atoms, molecules, substances, metals, crystals and other aggregates of matter. matter can be studied in solid, liquid, gas and plasma states, in isolation or in combination. the interactions, reactions and transformations that
of measurement that denotes an amount of substance ( also called chemical amount ). one mole is defined to contain exactly 6. 02214076Γ1023 particles ( atoms, molecules, ions, or electrons ), where the number of particles per mole is known as the avogadro constant. molar concentration is the amount of a particular substance per volume of solution, and is commonly reported in mol / dm3. = = = phase = = = in addition to the specific chemical properties that distinguish different chemical classifications, chemicals can exist in several phases. for the most part, the chemical classifications are independent of these bulk phase classifications ; however, some more exotic phases are incompatible with certain chemical properties. a phase is a set of states of a chemical system that have similar bulk structural properties, over a range of conditions, such as pressure or temperature. physical properties, such as density and refractive index tend to fall within values characteristic of the phase. the phase of matter is defined by the phase transition, which is when energy put into or taken out of the system goes into rearranging the structure of the system, instead of changing the bulk conditions. sometimes the distinction between phases can be continuous instead of having a discrete boundary ; in this case the matter is considered to be in a supercritical state. when three states meet based on the conditions, it is known as a triple point and since this is invariant, it is a convenient way to define a set of conditions. the most familiar examples of phases are solids, liquids, and gases. many substances exhibit multiple solid phases. for example, there are three phases of solid iron ( alpha, gamma, and delta ) that vary based on temperature and pressure. a principal difference between solid phases is the crystal structure, or arrangement, of the atoms. another phase commonly encountered in the study of chemistry is the aqueous phase, which is the state of substances dissolved in aqueous solution ( that is, in water ). less familiar phases include plasmas, bose β einstein condensates and fermionic condensates and the paramagnetic and ferromagnetic phases of magnetic materials. while most familiar phases deal with three - dimensional systems, it is also possible to define analogs in two - dimensional systems, which has received attention for its relevance to systems in biology. = = = bonding = = = atoms sticking together in molecules or crystals are said to be bonded with one another. a chemical bond may be visualized as the multipole balance between the positive
quantum mechanics is interpreted by the adjacent vacuum that behaves as a virtual particle to be absorbed and emitted by its matter. as described in the vacuum universe model, the adjacent vacuum is derived from the pre - inflationary universe in which the pre - adjacent vacuum is absorbed by the pre - matter. this absorbed pre - adjacent vacuum is emitted to become the added space for the inflation in the inflationary universe whose space - time is separated from the pre - inflationary universe. this added space is the adjacent vacuum. the absorption of the adjacent vacuum as the added space results in the adjacent zero space ( no space ), quantum mechanics is the interaction between matter and the three different types of vacuum : the adjacent vacuum, the adjacent zero space, and the empty space. the absorption of the adjacent vacuum results in the empty space superimposed with the adjacent zero space, confining the matter in the form of particle. when the absorbed vacuum is emitted, the adjacent vacuum can be anywhere instantly in the empty space superimposed with the adjacent zero space where any point can be the starting point ( zero point ) of space - time. consequently, the matter that expands into the adjacent vacuum has the probability to be anywhere instantly in the form of wavefunction. in the vacuum universe model, the universe not only gains its existence from the vacuum but also fattens itself with the vacuum. during the inflation, the adjacent vacuum also generates the periodic table of elementary particles to account for all elementary particles and their masses in a good agreement with the observed values.
Question: What does all matter consist of?
A) atoms
B) carbon
C) oxygen
D) helium
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A) atoms
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Context:
planetary systems can evolve dynamically even after the full growth of the planets themselves. there is actually circumstantial evidence that most planetary systems become unstable after the disappearance of gas from the protoplanetary disk. these instabilities can be due to the original system being too crowded and too closely packed or to external perturbations such as tides, planetesimal scattering, or torques from distant stellar companions. the solar system was not exceptional in this sense. in its inner part, a crowded system of planetary embryos became unstable, leading to a series of mutual impacts that built the terrestrial planets on a timescale of ~ 100 my. in its outer part, the giant planets became temporarily unstable and their orbital configuration expanded under the effect of mutual encounters. a planet might have been ejected in this phase. thus, the orbital distributions of planetary systems that we observe today, both solar and extrasolar ones, can be different from the those emerging from the formation process and it is important to consider possible long - term evolutionary effects to connect the two.
outer satellites of the planets have distant, eccentric orbits that can be highly inclined or even retrograde relative to the equatorial planes of their planets. these irregular orbits cannot have formed by circumplanetary accretion and are likely products of early capture from heliocentric orbit. the irregular satellites may be the only small bodies remaining which are still relatively near their formation locations within the giant planet region. the study of the irregular satellites provides a unique window on processes operating in the young solar system and allows us to probe possible planet formation mechanisms and the composition of the solar nebula between the rocky objects in the main asteroid belt and the very volatile rich objects in the kuiper belt. the gas and ice giant planets all appear to have very similar irregular satellite systems irrespective of their mass or formation timescales and mechanisms. water ice has been detected on some of the outer satellites of saturn and neptune whereas none has been observed on jupiter ' s outer satellites.
two planetary nebulae are shown to belong to the sagittarius dwarf galaxy, on the basis of their radial velocities. this is only the second dwarf spheroidal galaxy, after fornax, found to contain planetary nebulae. their existence confirms that this galaxy is at least as massive as the fornax dwarf spheroidal which has a single planetary nebula, and suggests a mass of a few times 10 * * 7 solar masses. the two planetary nebulae are located along the major axis of the galaxy, near the base of the tidal tail. there is a further candidate, situated at a very large distance along the direction of the tidal tail, for which no velocity measurement is available. the location of the planetary nebulae and globular clusters of the sagittarius dwarf galaxy suggests that a significant fraction of its mass is contained within the tidal tail.
the gas giant planets in the solar system have a retinue of icy moons, and we expect giant exoplanets to have similar satellite systems. if a jupiter - like planet were to migrate toward its parent star the icy moons orbiting it would evaporate, creating atmospheres and possible habitable surface oceans. here, we examine how long the surface ice and possible oceans would last before being hydrodynamically lost to space. the hydrodynamic loss rate from the moons is determined, in large part, by the stellar flux available for absorption, which increases as the giant planet and icy moons migrate closer to the star. at some planet - star distance the stellar flux incident on the icy moons becomes so great that they enter a runaway greenhouse state. this runaway greenhouse state rapidly transfers all available surface water to the atmosphere as vapor, where it is easily lost from the small moons. however, for icy moons of ganymede ' s size around a sun - like star we found that surface water ( either ice or liquid ) can persist indefinitely outside the runaway greenhouse orbital distance. in contrast, the surface water on smaller moons of europa ' s size will only persist on timescales greater than 1 gyr at distances ranging 1. 49 to 0. 74 au around a sun - like star for bond albedos of 0. 2 and 0. 8, where the lower albedo becomes relevant if ice melts. consequently, small moons can lose their icy shells, which would create a torus of h atoms around their host planet that might be detectable in future observations.
armed with an astrolabe and kepler ' s laws one can arrive at accurate estimates of the orbits of planets.
recent surveys have revealed a lack of close - in planets around evolved stars more massive than 1. 2 msun. such planets are common around solar - mass stars. we have calculated the orbital evolution of planets around stars with a range of initial masses, and have shown how planetary orbits are affected by the evolution of the stars all the way to the tip of the red giant branch ( rgb ). we find that tidal interaction can lead to the engulfment of close - in planets by evolved stars. the engulfment is more efficient for more - massive planets and less - massive stars. these results may explain the observed semi - major axis distribution of planets around evolved stars with masses larger than 1. 5 msun. our results also suggest that massive planets may form more efficiently around intermediate - mass stars.
three planets with minimum masses less than 10 earth masses orbit the star hd 40307, suggesting these planets may be rocky. however, with only radial velocity data, it is impossible to determine if these planets are rocky or gaseous. here we exploit various dynamical features of the system in order to assess the physical properties of the planets. observations allow for circular orbits, but a numerical integration shows that the eccentricities must be at least 0. 0001. also, planets b and c are so close to the star that tidal effects are significant. if planet b has tidal parameters similar to the terrestrial planets in the solar system and a remnant eccentricity larger than 0. 001, then, going back in time, the system would have been unstable within the lifetime of the star ( which we estimate to be 6. 1 + / - 1. 6 gyr ). moreover, if the eccentricities are that large and the inner planet is rocky, then its tidal heating may be an order of magnitude greater than extremely volcanic io, on a per unit surface area basis. if planet b is not terrestrial, e. g. neptune - like, these physical constraints would not apply. this analysis suggests the planets are not terrestrial - like, and are more like our giant planets. in either case, we find that the planets probably formed at larger radii and migrated early - on ( via disk interactions ) into their current orbits. this study demonstrates how the orbital and dynamical properties of exoplanet systems may be used to constrain the planets ' physical properties.
a 4mj planet with a 15. 8day orbital period has been detected from very precise radial velocity measurements with the coralie echelle spectrograph. a second remote and more massive companion has also been detected. all the planetary companions so far detected in orbit closer than 0. 08 au have a parent star with a statistically higher metal content compared to the metallicity distribution of other stars with planets. different processes occuring during their formation may provide a possible explanation for this observation.
light and cold extrasolar planets such as ogle 2005 - blg - 390lb, a 5. 5 earth - mass planet detected via microlensing, could be frequent in the galaxy according to some preliminary results from microlensing experiments. these planets can be frozen rocky - or ocean - planets, situated beyond the snow line and, therefore, beyond the habitable zone of their system. they can nonetheless host a layer of liquid water, heated by radiogenic energy, underneath an ice shell surface for billions of years, before freezing completely. these results suggest that oceans under ice, like those suspected to be present on icy moons in the solar system, could be a common feature of cold low - mass extrasolar planets.
three major planets, venus, earth, and mercury formed out of the solar nebula. a fourth planetesimal, theia, also formed near earth where it collided in a giant impact, rebounding as the planet mars. during this impact earth lost $ { \ approx } 4 $ \ % of its crust and mantle that is now is found on mars and the moon. at the antipode of the giant impact, $ \ approx $ 60 \ % of earth ' s crust, atmosphere, and a large amount of mantle were ejected into space forming the moon. the lost crust never reformed and became the earth ' s ocean basins. the theia impact site corresponds to indian ocean gravitational anomaly on earth and the hellas basin on mars. the dynamics of the giant impact are consistent with the rotational rates and axial tilts of both earth and mars. the giant impact removed sufficient co $ _ 2 $ from earth ' s atmosphere to avoid a runaway greenhouse effect, initiated plate tectonics, and gave life time to form near geothermal vents at the continental margins. mercury formed near venus where on a close approach it was slingshot into the sun ' s convective zone losing 94 \ % of its mass, much of which remains there today. black carbon, from co $ _ 2 $ decomposed by the intense heat, is still found on the surface of mercury. arriving at 616 km / s, mercury dramatically altered the sun ' s rotational energy, explaining both its anomalously slow rotation rate and axial tilt. these results are quantitatively supported by mass balances, the current locations of the terrestrial planets, and the orientations of their major orbital axes.
Question: What do you call a system that has one or more planets orbiting one or more stars?
A) solar system
B) galaxy
C) atom
D) molecular system
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A) solar system
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Context:
high speed photometry of kuv 01584 - 0939 ( alias cet3 ) shows that is has a period of 620. 26 s. combined with its hydrogen - deficient spectrum, this implies that it is an am cvn star. the optical modulation is probably a superhump, in which case the orbital period will be slightly shorter than what we have observed.
variation in total solar irradiance is thought to have little effect on the earth ' s surface temperature because of the thermal time constant - - the characteristic response time of the earth ' s global surface temperature to changes in forcing. this time constant is large enough to smooth annual variations but not necessarily variations having a longer period such as those due to solar inertial motion ; the magnitude of these surface temperature variations is estimated.
the first observations of saturn ' s visible - wavelength aurora were made by the cassini camera. the aurora was observed between 2006 and 2013 in the northern and southern hemispheres. the color of the aurora changes from pink at a few hundred km above the horizon to purple at 1000 - 1500 km above the horizon. the spectrum observed in 9 filters spanning wavelengths from 250 nm to 1000 nm has a prominent h - alpha line and roughly agrees with laboratory simulated auroras. auroras in both hemispheres vary dramatically with longitude. auroras form bright arcs between 70 and 80 degree latitude north and between 65 and 80 degree latitude south, which sometimes spiral around the pole, and sometimes form double arcs. a large 10, 000 - km - scale longitudinal brightness structure persists for more than 100 hours. this structure rotates approximately together with saturn. on top of the large steady structure, the auroras brighten suddenly on the timescales of a few minutes. these brightenings repeat with a period of about 1 hour. smaller, 1000 - km - scale structures may move faster or lag behind saturn ' s rotation on timescales of tens of minutes. the persistence of nearly - corotating large bright longitudinal structure in the auroral oval seen in two movies spanning 8 and 11 rotations gives an estimate on the period of 10. 65 $ \ pm $ 0. 15 h for 2009 in the northern oval and 10. 8 $ \ pm $ 0. 1 h for 2012 in the southern oval. the 2009 north aurora period is close to the north branch of saturn kilometric radiation ( skr ) detected at that time.
the purpose of this article is to view the penrose kite from the perspective of symplectic geometry.
it was the best of times ; it was the worst of times is the way dickens begins the tale of two cities. the line is appropriate to our time in particle physics. it is the best of times because we are in the midst of a revolution in understanding, the third to occur during my career. it is the worst of times because accelerator facilities are shutting down before new ones are opening, restricting the opportunity for experiments, and because of great uncertainty about future funding. my task today is to give you a view of the most important opportunities for our field under a scenario that is constrained by a tight budget. it is a time when we cannot afford the merely good, but must give first priority to the really important.
becomes quite gentle. accordingly, in large basins, rivers in most cases begin as torrents with a variable flow, and end as gently flowing rivers with a comparatively regular discharge. the irregular flow of rivers throughout their course forms one of the main difficulties in devising works for mitigating inundations or for increasing the navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with a rapid fall near the sources of rivers can carry down rocks, boulders and large stones, which are by degrees ground by attrition in their onward course into slate, gravel, sand and silt, simultaneously with the gradual reduction in fall, and, consequently, in the transporting force of the current. accordingly, under
navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with a rapid fall near the sources of rivers can carry down rocks, boulders and large stones, which are by degrees ground by attrition in their onward course into slate, gravel, sand and silt, simultaneously with the gradual reduction in fall, and, consequently, in the transporting force of the current. accordingly, under ordinary conditions, most of the materials brought down from the high lands by torrential water courses are carried forward by the main river to the sea, or partially strewn over flat alluvial plains during floods ; the size of the materials forming the bed of the river or borne along by the stream is gradually reduced on proceeding sea
chapter prepared for the book " astrophysics ", isbn 979 - 953 - 307 - 389 - 6, intech publishers ( in press ).
weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with a rapid fall near the sources of rivers can carry down rocks, boulders and large stones, which are by degrees ground by attrition in their onward course into slate, gravel, sand and silt, simultaneously with the gradual reduction in fall, and, consequently, in the transporting force of the current. accordingly, under ordinary conditions, most of the materials brought down from the high lands by torrential water courses are carried forward by the main river to the sea, or partially strewn over flat alluvial plains during floods ; the size of the materials forming the bed of the river or borne along by the stream is gradually reduced on proceeding seawards, so that in the po river in italy, for instance, pebbles and gravel are found for about 140 miles below turin, sand along the next 100 miles, and silt and mud in the last 110 miles ( 176 km ). = = channelization = = the removal of obstructions, natural or artificial
the lorentz covariant tempered disributions with the supports in the product of the closed upper light cones are described.
Question: The longest period of daylight hours occurs at the beginning of what season?
A) autumn
B) summer
C) winter
D) spring
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B) summer
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Context:
or solid as is the case with water ( h2o ) ; a liquid at room temperature because its molecules are bound by hydrogen bonds. whereas hydrogen sulfide ( h2s ) is a gas at room temperature and standard pressure, as its molecules are bound by weaker dipole β dipole interactions. the transfer of energy from one chemical substance to another depends on the size of energy quanta emitted from one substance. however, heat energy is often transferred more easily from almost any substance to another because the phonons responsible for vibrational and rotational energy levels in a substance have much less energy than photons invoked for the electronic energy transfer. thus, because vibrational and rotational energy levels are more closely spaced than electronic energy levels, heat is more easily transferred between substances relative to light or other forms of electronic energy. for example, ultraviolet electromagnetic radiation is not transferred with as much efficacy from one substance to another as thermal or electrical energy. the existence of characteristic energy levels for different chemical substances is useful for their identification by the analysis of spectral lines. different kinds of spectra are often used in chemical spectroscopy, e. g. ir, microwave, nmr, esr, etc. spectroscopy is also used to identify the composition of remote objects β like stars and distant galaxies β by analyzing their radiation spectra. the term chemical energy is often used to indicate the potential of a chemical substance to undergo a transformation through a chemical reaction or to transform other chemical substances. = = = reaction = = = when a chemical substance is transformed as a result of its interaction with another substance or with energy, a chemical reaction is said to have occurred. a chemical reaction is therefore a concept related to the " reaction " of a substance when it comes in close contact with another, whether as a mixture or a solution ; exposure to some form of energy, or both. it results in some energy exchange between the constituents of the reaction as well as with the system environment, which may be designed vessels β often laboratory glassware. chemical reactions can result in the formation or dissociation of molecules, that is, molecules breaking apart to form two or more molecules or rearrangement of atoms within or across molecules. chemical reactions usually involve the making or breaking of chemical bonds. oxidation, reduction, dissociation, acid β base neutralization and molecular rearrangement are some examples of common chemical reactions. a chemical reaction can be symbolically depicted through a chemical equation. while in a non - nuclear chemical reaction the number and kind of atoms on both sides of the equation are equal, for
another and therefore take part in chemical reactions that sustain life. in terms of its molecular structure, water is a small polar molecule with a bent shape formed by the polar covalent bonds of two hydrogen ( h ) atoms to one oxygen ( o ) atom ( h2o ). because the o β h bonds are polar, the oxygen atom has a slight negative charge and the two hydrogen atoms have a slight positive charge. this polar property of water allows it to attract other water molecules via hydrogen bonds, which makes water cohesive. surface tension results from the cohesive force due to the attraction between molecules at the surface of the liquid. water is also adhesive as it is able to adhere to the surface of any polar or charged non - water molecules. water is denser as a liquid than it is as a solid ( or ice ). this unique property of water allows ice to float above liquid water such as ponds, lakes, and oceans, thereby insulating the liquid below from the cold air above. water has the capacity to absorb energy, giving it a higher specific heat capacity than other solvents such as ethanol. thus, a large amount of energy is needed to break the hydrogen bonds between water molecules to convert liquid water into water vapor. as a molecule, water is not completely stable as each water molecule continuously dissociates into hydrogen and hydroxyl ions before reforming into a water molecule again. in pure water, the number of hydrogen ions balances ( or equals ) the number of hydroxyl ions, resulting in a ph that is neutral. = = = organic compounds = = = organic compounds are molecules that contain carbon bonded to another element such as hydrogen. with the exception of water, nearly all the molecules that make up each organism contain carbon. carbon can form covalent bonds with up to four other atoms, enabling it to form diverse, large, and complex molecules. for example, a single carbon atom can form four single covalent bonds such as in methane, two double covalent bonds such as in carbon dioxide ( co2 ), or a triple covalent bond such as in carbon monoxide ( co ). moreover, carbon can form very long chains of interconnecting carbon β carbon bonds such as octane or ring - like structures such as glucose. the simplest form of an organic molecule is the hydrocarbon, which is a large family of organic compounds that are composed of hydrogen atoms bonded to a chain of carbon atoms. a hydrocarbon backbone can be substituted by other elements such as oxygen ( o ), hydrogen
liver glycogen. during recovery, when oxygen becomes available, nad + attaches to hydrogen from lactate to form atp. in yeast, the waste products are ethanol and carbon dioxide. this type of fermentation is known as alcoholic or ethanol fermentation. the atp generated in this process is made by substrate - level phosphorylation, which does not require oxygen. = = = photosynthesis = = = photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organism ' s metabolic activities via cellular respiration. this chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. in most cases, oxygen is released as a waste product. most plants, algae, and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of the earth ' s atmosphere, and supplies most of the energy necessary for life on earth. photosynthesis has four stages : light absorption, electron transport, atp synthesis, and carbon fixation. light absorption is the initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to proteins in the thylakoid membranes. the absorbed light energy is used to remove electrons from a donor ( water ) to a primary electron acceptor, a quinone designated as q. in the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach a final electron acceptor, which is usually the oxidized form of nadp +, which is reduced to nadph, a process that takes place in a protein complex called photosystem i ( psi ). the transport of electrons is coupled to the movement of protons ( or hydrogen ) from the stroma to the thylakoid membrane, which forms a ph gradient across the membrane as hydrogen becomes more concentrated in the lumen than in the stroma. this is analogous to the proton - motive force generated across the inner mitochondrial membrane in aerobic respiration. during the third stage of photosynthesis, the movement of protons down their concentration gradients from the thylakoid lumen to the stroma through the atp synthase is coupled to the synthesis of atp by that same atp synthase. the nadph and atps generated by the light - dependent reactions in the second and third stages, respectively, provide the energy and
) of the mass of all organisms, with calcium, phosphorus, sulfur, sodium, chlorine, and magnesium constituting essentially all the remainder. different elements can combine to form compounds such as water, which is fundamental to life. biochemistry is the study of chemical processes within and relating to living organisms. molecular biology is the branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including molecular synthesis, modification, mechanisms, and interactions. = = = water = = = life arose from the earth ' s first ocean, which formed some 3. 8 billion years ago. since then, water continues to be the most abundant molecule in every organism. water is important to life because it is an effective solvent, capable of dissolving solutes such as sodium and chloride ions or other small molecules to form an aqueous solution. once dissolved in water, these solutes are more likely to come in contact with one another and therefore take part in chemical reactions that sustain life. in terms of its molecular structure, water is a small polar molecule with a bent shape formed by the polar covalent bonds of two hydrogen ( h ) atoms to one oxygen ( o ) atom ( h2o ). because the o β h bonds are polar, the oxygen atom has a slight negative charge and the two hydrogen atoms have a slight positive charge. this polar property of water allows it to attract other water molecules via hydrogen bonds, which makes water cohesive. surface tension results from the cohesive force due to the attraction between molecules at the surface of the liquid. water is also adhesive as it is able to adhere to the surface of any polar or charged non - water molecules. water is denser as a liquid than it is as a solid ( or ice ). this unique property of water allows ice to float above liquid water such as ponds, lakes, and oceans, thereby insulating the liquid below from the cold air above. water has the capacity to absorb energy, giving it a higher specific heat capacity than other solvents such as ethanol. thus, a large amount of energy is needed to break the hydrogen bonds between water molecules to convert liquid water into water vapor. as a molecule, water is not completely stable as each water molecule continuously dissociates into hydrogen and hydroxyl ions before reforming into a water molecule again. in pure water, the number of hydrogen ions balances ( or equals ) the number of hydroxyl ions, resulting in a ph that is neutral. = = = organic compounds =
a letter to the editor shortly summing up ten or so years of research into the h - index.
substrate - level phosphorylation, which does not require oxygen. = = = photosynthesis = = = photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organism ' s metabolic activities via cellular respiration. this chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. in most cases, oxygen is released as a waste product. most plants, algae, and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of the earth ' s atmosphere, and supplies most of the energy necessary for life on earth. photosynthesis has four stages : light absorption, electron transport, atp synthesis, and carbon fixation. light absorption is the initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to proteins in the thylakoid membranes. the absorbed light energy is used to remove electrons from a donor ( water ) to a primary electron acceptor, a quinone designated as q. in the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach a final electron acceptor, which is usually the oxidized form of nadp +, which is reduced to nadph, a process that takes place in a protein complex called photosystem i ( psi ). the transport of electrons is coupled to the movement of protons ( or hydrogen ) from the stroma to the thylakoid membrane, which forms a ph gradient across the membrane as hydrogen becomes more concentrated in the lumen than in the stroma. this is analogous to the proton - motive force generated across the inner mitochondrial membrane in aerobic respiration. during the third stage of photosynthesis, the movement of protons down their concentration gradients from the thylakoid lumen to the stroma through the atp synthase is coupled to the synthesis of atp by that same atp synthase. the nadph and atps generated by the light - dependent reactions in the second and third stages, respectively, provide the energy and electrons to drive the synthesis of glucose by fixing atmospheric carbon dioxide into existing organic carbon compounds, such as ribulose bisphosphate ( rubp ) in a sequence of light - independent ( or dark ) reactions called the calvin cycle. = = = cell signaling = = = cell signaling ( or communication ) is the
single carbon atom can form four single covalent bonds such as in methane, two double covalent bonds such as in carbon dioxide ( co2 ), or a triple covalent bond such as in carbon monoxide ( co ). moreover, carbon can form very long chains of interconnecting carbon β carbon bonds such as octane or ring - like structures such as glucose. the simplest form of an organic molecule is the hydrocarbon, which is a large family of organic compounds that are composed of hydrogen atoms bonded to a chain of carbon atoms. a hydrocarbon backbone can be substituted by other elements such as oxygen ( o ), hydrogen ( h ), phosphorus ( p ), and sulfur ( s ), which can change the chemical behavior of that compound. groups of atoms that contain these elements ( o -, h -, p -, and s - ) and are bonded to a central carbon atom or skeleton are called functional groups. there are six prominent functional groups that can be found in organisms : amino group, carboxyl group, carbonyl group, hydroxyl group, phosphate group, and sulfhydryl group. in 1953, the miller β urey experiment showed that organic compounds could be synthesized abiotically within a closed system mimicking the conditions of early earth, thus suggesting that complex organic molecules could have arisen spontaneously in early earth ( see abiogenesis ). = = = macromolecules = = = macromolecules are large molecules made up of smaller subunits or monomers. monomers include sugars, amino acids, and nucleotides. carbohydrates include monomers and polymers of sugars. lipids are the only class of macromolecules that are not made up of polymers. they include steroids, phospholipids, and fats, largely nonpolar and hydrophobic ( water - repelling ) substances. proteins are the most diverse of the macromolecules. they include enzymes, transport proteins, large signaling molecules, antibodies, and structural proteins. the basic unit ( or monomer ) of a protein is an amino acid. twenty amino acids are used in proteins. nucleic acids are polymers of nucleotides. their function is to store, transmit, and express hereditary information. = = cells = = cell theory states that cells are the fundamental units of life, that all living things are composed of one or more cells, and that all cells arise from preexisting cells through cell division
during aqueous corrosion, atoms in the solid react chemically with oxygen, leading either to the formation of an oxide film or to the dissolution of the host material. commonly, the first step in corrosion involves an oxygen atom from the dissociated water that reacts with the surface atoms and breaks near surface bonds. in contrast, hydrogen on the surface often functions as a passivating species. here, we discovered that the roles of o and h are reversed in the early corrosion stages on a si terminated sic surface. o forms stable species on the surface, and chemical attack occurs by h that breaks the si - c bonds. this so - called hydrogen scission reaction is enabled by a newly discovered metastable bridging hydroxyl group that can form during water dissociation. the si atom that is displaced from the surface during water attack subsequently forms h2sio3, which is a known precursor to the formation of silica and silicic acid. this study suggests that the roles of h and o in oxidation need to be reconsidered.
polyatomic ions that do not split up during acid β base reactions are hydroxide ( ohβ ) and phosphate ( po43β ). plasma is composed of gaseous matter that has been completely ionized, usually through high temperature. = = = acidity and basicity = = = a substance can often be classified as an acid or a base. there are several different theories which explain acid β base behavior. the simplest is arrhenius theory, which states that an acid is a substance that produces hydronium ions when it is dissolved in water, and a base is one that produces hydroxide ions when dissolved in water. according to brΓΈnsted β lowry acid β base theory, acids are substances that donate a positive hydrogen ion to another substance in a chemical reaction ; by extension, a base is the substance which receives that hydrogen ion. a third common theory is lewis acid β base theory, which is based on the formation of new chemical bonds. lewis theory explains that an acid is a substance which is capable of accepting a pair of electrons from another substance during the process of bond formation, while a base is a substance which can provide a pair of electrons to form a new bond. there are several other ways in which a substance may be classified as an acid or a base, as is evident in the history of this concept. acid strength is commonly measured by two methods. one measurement, based on the arrhenius definition of acidity, is ph, which is a measurement of the hydronium ion concentration in a solution, as expressed on a negative logarithmic scale. thus, solutions that have a low ph have a high hydronium ion concentration and can be said to be more acidic. the other measurement, based on the brΓΈnsted β lowry definition, is the acid dissociation constant ( ka ), which measures the relative ability of a substance to act as an acid under the brΓΈnsted β lowry definition of an acid. that is, substances with a higher ka are more likely to donate hydrogen ions in chemical reactions than those with lower ka values. = = = redox = = = redox ( reduction - oxidation ) reactions include all chemical reactions in which atoms have their oxidation state changed by either gaining electrons ( reduction ) or losing electrons ( oxidation ). substances that have the ability to oxidize other substances are said to be oxidative and are known as oxidizing agents, oxidants or oxidizers. an oxidant removes electrons from another substance. similarly,
analyzing their radiation spectra. the term chemical energy is often used to indicate the potential of a chemical substance to undergo a transformation through a chemical reaction or to transform other chemical substances. = = = reaction = = = when a chemical substance is transformed as a result of its interaction with another substance or with energy, a chemical reaction is said to have occurred. a chemical reaction is therefore a concept related to the " reaction " of a substance when it comes in close contact with another, whether as a mixture or a solution ; exposure to some form of energy, or both. it results in some energy exchange between the constituents of the reaction as well as with the system environment, which may be designed vessels β often laboratory glassware. chemical reactions can result in the formation or dissociation of molecules, that is, molecules breaking apart to form two or more molecules or rearrangement of atoms within or across molecules. chemical reactions usually involve the making or breaking of chemical bonds. oxidation, reduction, dissociation, acid β base neutralization and molecular rearrangement are some examples of common chemical reactions. a chemical reaction can be symbolically depicted through a chemical equation. while in a non - nuclear chemical reaction the number and kind of atoms on both sides of the equation are equal, for a nuclear reaction this holds true only for the nuclear particles viz. protons and neutrons. the sequence of steps in which the reorganization of chemical bonds may be taking place in the course of a chemical reaction is called its mechanism. a chemical reaction can be envisioned to take place in a number of steps, each of which may have a different speed. many reaction intermediates with variable stability can thus be envisaged during the course of a reaction. reaction mechanisms are proposed to explain the kinetics and the relative product mix of a reaction. many physical chemists specialize in exploring and proposing the mechanisms of various chemical reactions. several empirical rules, like the woodward β hoffmann rules often come in handy while proposing a mechanism for a chemical reaction. according to the iupac gold book, a chemical reaction is " a process that results in the interconversion of chemical species. " accordingly, a chemical reaction may be an elementary reaction or a stepwise reaction. an additional caveat is made, in that this definition includes cases where the interconversion of conformers is experimentally observable. such detectable chemical reactions normally involve sets of molecular entities as indicated by this definition, but it is often conceptually convenient to use the term also for changes involving single molecular entities (
Question: H2o is the chemical formula for what?
A) water
B) glass
C) salt
D) smog
|
A) water
|
Context:
the earth ' s atmosphere, and supplies most of the energy necessary for life on earth. photosynthesis has four stages : light absorption, electron transport, atp synthesis, and carbon fixation. light absorption is the initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to proteins in the thylakoid membranes. the absorbed light energy is used to remove electrons from a donor ( water ) to a primary electron acceptor, a quinone designated as q. in the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach a final electron acceptor, which is usually the oxidized form of nadp +, which is reduced to nadph, a process that takes place in a protein complex called photosystem i ( psi ). the transport of electrons is coupled to the movement of protons ( or hydrogen ) from the stroma to the thylakoid membrane, which forms a ph gradient across the membrane as hydrogen becomes more concentrated in the lumen than in the stroma. this is analogous to the proton - motive force generated across the inner mitochondrial membrane in aerobic respiration. during the third stage of photosynthesis, the movement of protons down their concentration gradients from the thylakoid lumen to the stroma through the atp synthase is coupled to the synthesis of atp by that same atp synthase. the nadph and atps generated by the light - dependent reactions in the second and third stages, respectively, provide the energy and electrons to drive the synthesis of glucose by fixing atmospheric carbon dioxide into existing organic carbon compounds, such as ribulose bisphosphate ( rubp ) in a sequence of light - independent ( or dark ) reactions called the calvin cycle. = = = cell signaling = = = cell signaling ( or communication ) is the ability of cells to receive, process, and transmit signals with its environment and with itself. signals can be non - chemical such as light, electrical impulses, and heat, or chemical signals ( or ligands ) that interact with receptors, which can be found embedded in the cell membrane of another cell or located deep inside a cell. there are generally four types of chemical signals : autocrine, paracrine, juxtacrine, and hormones. in autocrine signaling, the ligand affects the same cell that releases it. tumor cells, for example, can reproduce uncontrollably because they release signals that initiate their
enough to rise to the surface β giving birth to volcanoes. = = atmospheric science = = atmospheric science initially developed in the late - 19th century as a means to forecast the weather through meteorology, the study of weather. atmospheric chemistry was developed in the 20th century to measure air pollution and expanded in the 1970s in response to acid rain. climatology studies the climate and climate change. the troposphere, stratosphere, mesosphere, thermosphere, and exosphere are the five layers which make up earth ' s atmosphere. 75 % of the mass in the atmosphere is located within the troposphere, the lowest layer. in all, the atmosphere is made up of about 78. 0 % nitrogen, 20. 9 % oxygen, and 0. 92 % argon, and small amounts of other gases including co2 and water vapor. water vapor and co2 cause the earth ' s atmosphere to catch and hold the sun ' s energy through the greenhouse effect. this makes earth ' s surface warm enough for liquid water and life. in addition to trapping heat, the atmosphere also protects living organisms by shielding the earth ' s surface from cosmic rays. the magnetic field β created by the internal motions of the core β produces the magnetosphere which protects earth ' s atmosphere from the solar wind. as the earth is 4. 5 billion years old, it would have lost its atmosphere by now if there were no protective magnetosphere. = = earth ' s magnetic field = = = = hydrology = = hydrology is the study of the hydrosphere and the movement of water on earth. it emphasizes the study of how humans use and interact with freshwater supplies. study of water ' s movement is closely related to geomorphology and other branches of earth science. applied hydrology involves engineering to maintain aquatic environments and distribute water supplies. subdisciplines of hydrology include oceanography, hydrogeology, ecohydrology, and glaciology. oceanography is the study of oceans. hydrogeology is the study of groundwater. it includes the mapping of groundwater supplies and the analysis of groundwater contaminants. applied hydrogeology seeks to prevent contamination of groundwater and mineral springs and make it available as drinking water. the earliest exploitation of groundwater resources dates back to 3000 bc, and hydrogeology as a science was developed by hydrologists beginning in the 17th century. ecohydrology is the study of ecological systems in the hydrosphere. it can be divided into the physical study of aquatic ecosystems and the
is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. in most cases, oxygen is released as a waste product. most plants, algae, and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of the earth ' s atmosphere, and supplies most of the energy necessary for life on earth. photosynthesis has four stages : light absorption, electron transport, atp synthesis, and carbon fixation. light absorption is the initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to proteins in the thylakoid membranes. the absorbed light energy is used to remove electrons from a donor ( water ) to a primary electron acceptor, a quinone designated as q. in the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach a final electron acceptor, which is usually the oxidized form of nadp +, which is reduced to nadph, a process that takes place in a protein complex called photosystem i ( psi ). the transport of electrons is coupled to the movement of protons ( or hydrogen ) from the stroma to the thylakoid membrane, which forms a ph gradient across the membrane as hydrogen becomes more concentrated in the lumen than in the stroma. this is analogous to the proton - motive force generated across the inner mitochondrial membrane in aerobic respiration. during the third stage of photosynthesis, the movement of protons down their concentration gradients from the thylakoid lumen to the stroma through the atp synthase is coupled to the synthesis of atp by that same atp synthase. the nadph and atps generated by the light - dependent reactions in the second and third stages, respectively, provide the energy and electrons to drive the synthesis of glucose by fixing atmospheric carbon dioxide into existing organic carbon compounds, such as ribulose bisphosphate ( rubp ) in a sequence of light - independent ( or dark ) reactions called the calvin cycle. = = = cell signaling = = = cell signaling ( or communication ) is the ability of cells to receive, process, and transmit signals with its environment and with itself. signals can be non - chemical such as light, electrical impulses, and heat, or chemical signals ( or ligands ) that interact with receptors, which can be found embedded in the cell membrane of another cell or located deep inside
pigment chlorophyll a. chlorophyll a ( as well as its plant and green algal - specific cousin chlorophyll b ) absorbs light in the blue - violet and orange / red parts of the spectrum while reflecting and transmitting the green light that we see as the characteristic colour of these organisms. the energy in the red and blue light that these pigments absorb is used by chloroplasts to make energy - rich carbon compounds from carbon dioxide and water by oxygenic photosynthesis, a process that generates molecular oxygen ( o2 ) as a by - product. the light energy captured by chlorophyll a is initially in the form of electrons ( and later a proton gradient ) that is used to make molecules of atp and nadph which temporarily store and transport energy. their energy is used in the light - independent reactions of the calvin cycle by the enzyme rubisco to produce molecules of the 3 - carbon sugar glyceraldehyde 3 - phosphate ( g3p ). glyceraldehyde 3 - phosphate is the first product of photosynthesis and the raw material from which glucose and almost all other organic molecules of biological origin are synthesised. some of the glucose is converted to starch which is stored in the chloroplast. starch is the characteristic energy store of most land plants and algae, while inulin, a polymer of fructose is used for the same purpose in the sunflower family asteraceae. some of the glucose is converted to sucrose ( common table sugar ) for export to the rest of the plant. unlike in animals ( which lack chloroplasts ), plants and their eukaryote relatives have delegated many biochemical roles to their chloroplasts, including synthesising all their fatty acids, and most amino acids. the fatty acids that chloroplasts make are used for many things, such as providing material to build cell membranes out of and making the polymer cutin which is found in the plant cuticle that protects land plants from drying out. plants synthesise a number of unique polymers like the polysaccharide molecules cellulose, pectin and xyloglucan from which the land plant cell wall is constructed. vascular land plants make lignin, a polymer used to strengthen the secondary cell walls of xylem tracheids and vessels to keep them from collapsing when a plant sucks water through them under water stress. lignin
a minimum atmospheric temperature, or tropopause, occurs at a pressure of around 0. 1 bar in the atmospheres of earth, titan, jupiter, saturn, uranus and neptune, despite great differences in atmospheric composition, gravity, internal heat and sunlight. in all these bodies, the tropopause separates a stratosphere with a temperature profile that is controlled by the absorption of shortwave solar radiation, from a region below characterised by convection, weather, and clouds. however, it is not obvious why the tropopause occurs at the specific pressure near 0. 1 bar. here we use a physically - based model to demonstrate that, at atmospheric pressures lower than 0. 1 bar, transparency to thermal radiation allows shortwave heating to dominate, creating a stratosphere. at higher pressures, atmospheres become opaque to thermal radiation, causing temperatures to increase with depth and convection to ensue. a common dependence of infrared opacity on pressure, arising from the shared physics of molecular absorption, sets the 0. 1 bar tropopause. we hypothesize that a tropopause at a pressure of approximately 0. 1 bar is characteristic of many thick atmospheres, including exoplanets and exomoons in our galaxy and beyond. judicious use of this rule could help constrain the atmospheric structure, and thus the surface environments and habitability, of exoplanets.
the motion of celestial bodies through a higher power such as god. aristotle did not have the technological advancements that would have explained the motion of celestial bodies. in addition, aristotle had many views on the elements. he believed that everything was derived of the elements earth, water, air, fire, and lastly the aether. the aether was a celestial element, and therefore made up the matter of the celestial bodies. the elements of earth, water, air and fire were derived of a combination of two of the characteristics of hot, wet, cold, and dry, and all had their inevitable place and motion. the motion of these elements begins with earth being the closest to " the earth, " then water, air, fire, and finally aether. in addition to the makeup of all things, aristotle came up with theories as to why things did not return to their natural motion. he understood that water sits above earth, air above water, and fire above air in their natural state. he explained that although all elements must return to their natural state, the human body and other living things have a constraint on the elements β thus not allowing the elements making one who they are to return to their natural state. the important legacy of this period included substantial advances in factual knowledge, especially in anatomy, zoology, botany, mineralogy, geography, mathematics and astronomy ; an awareness of the importance of certain scientific problems, especially those related to the problem of change and its causes ; and a recognition of the methodological importance of applying mathematics to natural phenomena and of undertaking empirical research. in the hellenistic age scholars frequently employed the principles developed in earlier greek thought : the application of mathematics and deliberate empirical research, in their scientific investigations. thus, clear unbroken lines of influence lead from ancient greek and hellenistic philosophers, to medieval muslim philosophers and scientists, to the european renaissance and enlightenment, to the secular sciences of the modern day. neither reason nor inquiry began with the ancient greeks, but the socratic method did, along with the idea of forms, give great advances in geometry, logic, and the natural sciences. according to benjamin farrington, former professor of classics at swansea university : " men were weighing for thousands of years before archimedes worked out the laws of equilibrium ; they must have had practical and intuitional knowledge of the principals involved. what archimedes did was to sort out the theoretical implications of this practical knowledge and present the resulting body of knowledge as a logically coherent system. " and again : " with astonishment we find ourselves on the threshold of modern science
nanodust, which undergoes stochastic heating by single starlight photons in the interstellar medium, ranges from angstrom - sized large molecules containing tens to thousands of atoms ( e. g. polycyclic aromatic hydrocarbon molecules ) to grains of a couple tens of nanometers. the presence of nanograins in astrophysical environments has been revealed by a variety of interstellar phenomena : the optical luminescence, the near - and mid - infrared emission, the galactic foreground microwave emission, and the ultraviolet extinction which are ubiquitously seen in the interstellar medium of the milky way and beyond. nanograins ( e. g. nanodiamonds ) have also been identified as presolar in primitive meteorites based on their isotopically anomalous composition. considering the very processes that lead to the detection of nanodust in the ism for the nanodust in the solar system shows that the observation of solar system nanodust by these processes is less likely.
substrate - level phosphorylation, which does not require oxygen. = = = photosynthesis = = = photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organism ' s metabolic activities via cellular respiration. this chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. in most cases, oxygen is released as a waste product. most plants, algae, and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of the earth ' s atmosphere, and supplies most of the energy necessary for life on earth. photosynthesis has four stages : light absorption, electron transport, atp synthesis, and carbon fixation. light absorption is the initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to proteins in the thylakoid membranes. the absorbed light energy is used to remove electrons from a donor ( water ) to a primary electron acceptor, a quinone designated as q. in the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach a final electron acceptor, which is usually the oxidized form of nadp +, which is reduced to nadph, a process that takes place in a protein complex called photosystem i ( psi ). the transport of electrons is coupled to the movement of protons ( or hydrogen ) from the stroma to the thylakoid membrane, which forms a ph gradient across the membrane as hydrogen becomes more concentrated in the lumen than in the stroma. this is analogous to the proton - motive force generated across the inner mitochondrial membrane in aerobic respiration. during the third stage of photosynthesis, the movement of protons down their concentration gradients from the thylakoid lumen to the stroma through the atp synthase is coupled to the synthesis of atp by that same atp synthase. the nadph and atps generated by the light - dependent reactions in the second and third stages, respectively, provide the energy and electrons to drive the synthesis of glucose by fixing atmospheric carbon dioxide into existing organic carbon compounds, such as ribulose bisphosphate ( rubp ) in a sequence of light - independent ( or dark ) reactions called the calvin cycle. = = = cell signaling = = = cell signaling ( or communication ) is the
parts of australia have been privileged to see dazzling lights in the night sky as the aurora australis ( known as the southern lights ) puts on a show this year. aurorae are significant in australian indigenous astronomical traditions. aboriginal people associate aurorae with fire, death, blood, and omens, sharing many similarities with native american communities.
higher concentrations of atmospheric nitrous oxide ( n2o ) are expected to slightly warm earth ' s surface because of increases in radiative forcing. radiative forcing is the difference in the net upward thermal radiation flux from the earth through a transparent atmosphere and radiation through an otherwise identical atmosphere with greenhouse gases. radiative forcing, normally measured in w / m ^ 2, depends on latitude, longitude and altitude, but it is often quoted for the tropopause, about 11 km of altitude for temperate latitudes, or for the top of the atmosphere at around 90 km. for current concentrations of greenhouse gases, the radiative forcing per added n2o molecule is about 230 times larger than the forcing per added carbon dioxide ( co2 ) molecule. this is due to the heavy saturation of the absorption band of the relatively abundant greenhouse gas, co2, compared to the much smaller saturation of the absorption bands of the trace greenhouse gas n2o. but the rate of increase of co2 molecules, about 2. 5 ppm / year ( ppm = part per million by mole ), is about 3000 times larger than the rate of increase of n2o molecules, which has held steady at around 0. 00085 ppm / year since 1985. so, the contribution of nitrous oxide to the annual increase in forcing is 230 / 3000 or about 1 / 13 that of co2. if the main greenhouse gases, co2, ch4 and n2o have contributed about 0. 1 c / decade of the warming observed over the past few decades, this would correspond to about 0. 00064 k per year or 0. 064 k per century of warming from n2o. proposals to place harsh restrictions on nitrous oxide emissions because of warming fears are not justified by these facts. restrictions would cause serious harm ; for example, by jeopardizing world food supplies.
Question: What occurs when light interacts with our atmosphere?
A) rayleigh scattering
B) eclipse
C) rainbow formation
D) prism effect
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A) rayleigh scattering
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Context:
##logous in nature, and can be used in a myriad of ways, from helping repair skeletal tissue to replenishing beta cells in diabetic patients. allogenic : cells are obtained from the body of a donor of the same species as the recipient. while there are some ethical constraints to the use of human cells for in vitro studies ( i. e. human brain tissue chimera development ), the employment of dermal fibroblasts from human foreskin demonstrates an immunologically safe and thus a viable choice for allogenic tissue engineering of the skin. xenogenic : these cells are derived isolated cells from alternate species from the recipient. a notable example of xenogeneic tissue utilization is cardiovascular implant construction via animal cells. chimeric human - animal farming raises ethical concerns around the potential for improved consciousness from implanting human organs in animals. syngeneic or isogenic : these cells describe those borne from identical genetic code. this imparts an immunologic benefit similar to autologous cell lines ( see above ). autologous cells can be considered syngenic, but the classification also extends to non - autologously derived cells such as those from an identical twin, from genetically identical ( cloned ) research models, or induced stem cells ( isc ) as related to the donor. = = = stem cells = = = stem cells are undifferentiated cells with the ability to divide in culture and give rise to different forms of specialized cells. stem cells are divided into " adult " and " embryonic " stem cells according to their source. while there is still a large ethical debate related to the use of embryonic stem cells, it is thought that another alternative source β induced pluripotent stem cells β may be useful for the repair of diseased or damaged tissues, or may be used to grow new organs. totipotent cells are stem cells which can divide into further stem cells or differentiate into any cell type in the body, including extra - embryonic tissue. pluripotent cells are stem cells which can differentiate into any cell type in the body except extra - embryonic tissue. induced pluripotent stem cells ( ipscs ) are subclass of pluripotent stem cells resembling embryonic stem cells ( escs ) that have been derived from adult differentiated cells. ipscs are created by altering the expression of transcriptional factors in adult cells until they become like embryonic stem cells. multipotent stem cells can be differentiated into any cell
of cells = = = autologous : the donor and the recipient of the cells are the same individual. cells are harvested, cultured or stored, and then reintroduced to the host. as a result of the host ' s own cells being reintroduced, an antigenic response is not elicited. the body ' s immune system recognizes these re - implanted cells as its own, and does not target them for attack. autologous cell dependence on host cell health and donor site morbidity may be deterrents to their use. adipose - derived and bone marrow - derived mesenchymal stem cells are commonly autologous in nature, and can be used in a myriad of ways, from helping repair skeletal tissue to replenishing beta cells in diabetic patients. allogenic : cells are obtained from the body of a donor of the same species as the recipient. while there are some ethical constraints to the use of human cells for in vitro studies ( i. e. human brain tissue chimera development ), the employment of dermal fibroblasts from human foreskin demonstrates an immunologically safe and thus a viable choice for allogenic tissue engineering of the skin. xenogenic : these cells are derived isolated cells from alternate species from the recipient. a notable example of xenogeneic tissue utilization is cardiovascular implant construction via animal cells. chimeric human - animal farming raises ethical concerns around the potential for improved consciousness from implanting human organs in animals. syngeneic or isogenic : these cells describe those borne from identical genetic code. this imparts an immunologic benefit similar to autologous cell lines ( see above ). autologous cells can be considered syngenic, but the classification also extends to non - autologously derived cells such as those from an identical twin, from genetically identical ( cloned ) research models, or induced stem cells ( isc ) as related to the donor. = = = stem cells = = = stem cells are undifferentiated cells with the ability to divide in culture and give rise to different forms of specialized cells. stem cells are divided into " adult " and " embryonic " stem cells according to their source. while there is still a large ethical debate related to the use of embryonic stem cells, it is thought that another alternative source β induced pluripotent stem cells β may be useful for the repair of diseased or damaged tissues, or may be used to grow new organs. totipotent cells
the following purposes : allowing cell attachment and migration, delivering and retaining cells and biochemical factors, enabling diffusion of vital cell nutrients and expressed products, and exerting certain mechanical and biological influences to modify the behaviour of the cell phase. in 2009, an interdisciplinary team led by the thoracic surgeon thorsten walles implanted the first bioartificial transplant that provides an innate vascular network for post - transplant graft supply successfully into a patient awaiting tracheal reconstruction. to achieve the goal of tissue reconstruction, scaffolds must meet some specific requirements. high porosity and adequate pore size are necessary to facilitate cell seeding and diffusion throughout the whole structure of both cells and nutrients. biodegradability is often an essential factor since scaffolds should preferably be absorbed by the surrounding tissues without the necessity of surgical removal. the rate at which degradation occurs has to coincide as much as possible with the rate of tissue formation : this means that while cells are fabricating their own natural matrix structure around themselves, the scaffold is able to provide structural integrity within the body and eventually it will break down leaving the newly formed tissue which will take over the mechanical load. injectability is also important for clinical uses. recent research on organ printing is showing how crucial a good control of the 3d environment is to ensure reproducibility of experiments and offer better results. = = = materials = = = material selection is an essential aspect of producing a scaffold. the materials utilized can be natural or synthetic and can be biodegradable or non - biodegradable. additionally, they must be biocompatible, meaning that they do not cause any adverse effects to cells. silicone, for example, is a synthetic, non - biodegradable material commonly used as a drug delivery material, while gelatin is a biodegradable, natural material commonly used in cell - culture scaffolds the material needed for each application is different, and dependent on the desired mechanical properties of the material. tissue engineering of long bone defects for example, will require a rigid scaffold with a compressive strength similar to that of cortical bone ( 100 - 150 mpa ), which is much higher compared to a scaffold for skin regeneration. there are a few versatile synthetic materials used for many different scaffold applications. one of these commonly used materials is polylactic acid ( pla ), a synthetic polymer. pla β polylactic acid. this is a polyester which
induced stem cells ( isc ) as related to the donor. = = = stem cells = = = stem cells are undifferentiated cells with the ability to divide in culture and give rise to different forms of specialized cells. stem cells are divided into " adult " and " embryonic " stem cells according to their source. while there is still a large ethical debate related to the use of embryonic stem cells, it is thought that another alternative source β induced pluripotent stem cells β may be useful for the repair of diseased or damaged tissues, or may be used to grow new organs. totipotent cells are stem cells which can divide into further stem cells or differentiate into any cell type in the body, including extra - embryonic tissue. pluripotent cells are stem cells which can differentiate into any cell type in the body except extra - embryonic tissue. induced pluripotent stem cells ( ipscs ) are subclass of pluripotent stem cells resembling embryonic stem cells ( escs ) that have been derived from adult differentiated cells. ipscs are created by altering the expression of transcriptional factors in adult cells until they become like embryonic stem cells. multipotent stem cells can be differentiated into any cell within the same class, such as blood or bone. a common example of multipotent cells is mesenchymal stem cells ( mscs ). = = scaffolds = = scaffolds are materials that have been engineered to cause desirable cellular interactions to contribute to the formation of new functional tissues for medical purposes. cells are often ' seeded ' into these structures capable of supporting three - dimensional tissue formation. scaffolds mimic the extracellular matrix of the native tissue, recapitulating the in vivo milieu and allowing cells to influence their own microenvironments. they usually serve at least one of the following purposes : allowing cell attachment and migration, delivering and retaining cells and biochemical factors, enabling diffusion of vital cell nutrients and expressed products, and exerting certain mechanical and biological influences to modify the behaviour of the cell phase. in 2009, an interdisciplinary team led by the thoracic surgeon thorsten walles implanted the first bioartificial transplant that provides an innate vascular network for post - transplant graft supply successfully into a patient awaiting tracheal reconstruction. to achieve the goal of tissue reconstruction, scaffolds must meet some specific requirements. high porosity and adequate pore size are necessary to facilitate cell seed
animal cells using microinjection, where it can be injected through the cell ' s nuclear envelope directly into the nucleus, or through the use of viral vectors. plant genomes can be engineered by physical methods or by use of agrobacterium for the delivery of sequences hosted in t - dna binary vectors. in plants the dna is often inserted using agrobacterium - mediated transformation, taking advantage of the agrobacteriums t - dna sequence that allows natural insertion of genetic material into plant cells. other methods include biolistics, where particles of gold or tungsten are coated with dna and then shot into young plant cells, and electroporation, which involves using an electric shock to make the cell membrane permeable to plasmid dna. as only a single cell is transformed with genetic material, the organism must be regenerated from that single cell. in plants this is accomplished through the use of tissue culture. in animals it is necessary to ensure that the inserted dna is present in the embryonic stem cells. bacteria consist of a single cell and reproduce clonally so regeneration is not necessary. selectable markers are used to easily differentiate transformed from untransformed cells. these markers are usually present in the transgenic organism, although a number of strategies have been developed that can remove the selectable marker from the mature transgenic plant. further testing using pcr, southern hybridization, and dna sequencing is conducted to confirm that an organism contains the new gene. these tests can also confirm the chromosomal location and copy number of the inserted gene. the presence of the gene does not guarantee it will be expressed at appropriate levels in the target tissue so methods that look for and measure the gene products ( rna and protein ) are also used. these include northern hybridisation, quantitative rt - pcr, western blot, immunofluorescence, elisa and phenotypic analysis. the new genetic material can be inserted randomly within the host genome or targeted to a specific location. the technique of gene targeting uses homologous recombination to make desired changes to a specific endogenous gene. this tends to occur at a relatively low frequency in plants and animals and generally requires the use of selectable markers. the frequency of gene targeting can be greatly enhanced through genome editing. genome editing uses artificially engineered nucleases that create specific double - stranded breaks at desired locations in the genome, and use the cell ' s endogenous mechanisms to repair the induced break by the natural processes
allow specialized cell lines to thrive in cultures replicating their native environments, but it also makes bioreactors attractive tools for culturing stem cells. a successful stem - cell - based bioreactor is effective at expanding stem cells with uniform properties and / or promoting controlled, reproducible differentiation into selected mature cell types. there are a variety of bioreactors designed for 3d cell cultures. there are small plastic cylindrical chambers, as well as glass chambers, with regulated internal humidity and moisture specifically engineered for the purpose of growing cells in three dimensions. the bioreactor uses bioactive synthetic materials such as polyethylene terephthalate membranes to surround the spheroid cells in an environment that maintains high levels of nutrients. they are easy to open and close, so that cell spheroids can be removed for testing, yet the chamber is able to maintain 100 % humidity throughout. this humidity is important to achieve maximum cell growth and function. the bioreactor chamber is part of a larger device that rotates to ensure equal cell growth in each direction across three dimensions. quinxell technologies now under quintech life sciences from singapore has developed a bioreactor known as the tisxell biaxial bioreactor which is specially designed for the purpose of tissue engineering. it is the first bioreactor in the world to have a spherical glass chamber with biaxial rotation ; specifically to mimic the rotation of the fetus in the womb ; which provides a conducive environment for the growth of tissues. multiple forms of mechanical stimulation have also been combined into a single bioreactor. using gene expression analysis, one academic study found that applying a combination of cyclic strain and ultrasound stimulation to pre - osteoblast cells in a bioreactor accelerated matrix maturation and differentiation. the technology of this combined stimulation bioreactor could be used to grow bone cells more quickly and effectively in future clinical stem cell therapies. mc2 biotek has also developed a bioreactor known as prototissue that uses gas exchange to maintain high oxygen levels within the cell chamber ; improving upon previous bioreactors, since the higher oxygen levels help the cell grow and undergo normal cell respiration. active areas of research on bioreactors includes increasing production scale and refining the physiological environment, both of which could improve the efficiency and efficacy of bioreactors in research or clinical use. bioreactors are currently used to study, among other things, cell and tissue level therapies, cell and tissue response to specific physiological
young plant cells, and electroporation, which involves using an electric shock to make the cell membrane permeable to plasmid dna. as only a single cell is transformed with genetic material, the organism must be regenerated from that single cell. in plants this is accomplished through the use of tissue culture. in animals it is necessary to ensure that the inserted dna is present in the embryonic stem cells. bacteria consist of a single cell and reproduce clonally so regeneration is not necessary. selectable markers are used to easily differentiate transformed from untransformed cells. these markers are usually present in the transgenic organism, although a number of strategies have been developed that can remove the selectable marker from the mature transgenic plant. further testing using pcr, southern hybridization, and dna sequencing is conducted to confirm that an organism contains the new gene. these tests can also confirm the chromosomal location and copy number of the inserted gene. the presence of the gene does not guarantee it will be expressed at appropriate levels in the target tissue so methods that look for and measure the gene products ( rna and protein ) are also used. these include northern hybridisation, quantitative rt - pcr, western blot, immunofluorescence, elisa and phenotypic analysis. the new genetic material can be inserted randomly within the host genome or targeted to a specific location. the technique of gene targeting uses homologous recombination to make desired changes to a specific endogenous gene. this tends to occur at a relatively low frequency in plants and animals and generally requires the use of selectable markers. the frequency of gene targeting can be greatly enhanced through genome editing. genome editing uses artificially engineered nucleases that create specific double - stranded breaks at desired locations in the genome, and use the cell ' s endogenous mechanisms to repair the induced break by the natural processes of homologous recombination and nonhomologous end - joining. there are four families of engineered nucleases : meganucleases, zinc finger nucleases, transcription activator - like effector nucleases ( talens ), and the cas9 - guiderna system ( adapted from crispr ). talen and crispr are the two most commonly used and each has its own advantages. talens have greater target specificity, while crispr is easier to design and more efficient. in addition to enhancing gene targeting, engineered nucleases can be used to introduce mutations
medical purposes. cells are often ' seeded ' into these structures capable of supporting three - dimensional tissue formation. scaffolds mimic the extracellular matrix of the native tissue, recapitulating the in vivo milieu and allowing cells to influence their own microenvironments. they usually serve at least one of the following purposes : allowing cell attachment and migration, delivering and retaining cells and biochemical factors, enabling diffusion of vital cell nutrients and expressed products, and exerting certain mechanical and biological influences to modify the behaviour of the cell phase. in 2009, an interdisciplinary team led by the thoracic surgeon thorsten walles implanted the first bioartificial transplant that provides an innate vascular network for post - transplant graft supply successfully into a patient awaiting tracheal reconstruction. to achieve the goal of tissue reconstruction, scaffolds must meet some specific requirements. high porosity and adequate pore size are necessary to facilitate cell seeding and diffusion throughout the whole structure of both cells and nutrients. biodegradability is often an essential factor since scaffolds should preferably be absorbed by the surrounding tissues without the necessity of surgical removal. the rate at which degradation occurs has to coincide as much as possible with the rate of tissue formation : this means that while cells are fabricating their own natural matrix structure around themselves, the scaffold is able to provide structural integrity within the body and eventually it will break down leaving the newly formed tissue which will take over the mechanical load. injectability is also important for clinical uses. recent research on organ printing is showing how crucial a good control of the 3d environment is to ensure reproducibility of experiments and offer better results. = = = materials = = = material selection is an essential aspect of producing a scaffold. the materials utilized can be natural or synthetic and can be biodegradable or non - biodegradable. additionally, they must be biocompatible, meaning that they do not cause any adverse effects to cells. silicone, for example, is a synthetic, non - biodegradable material commonly used as a drug delivery material, while gelatin is a biodegradable, natural material commonly used in cell - culture scaffolds the material needed for each application is different, and dependent on the desired mechanical properties of the material. tissue engineering of long bone defects for example, will require a rigid scaffold with a compressive strength similar to that of cortical bone ( 100 - 150 mpa ),
and then graft healthy skin onto 80 percent of the boy ' s body which was affected by the illness. germline gene therapy would result in any change being inheritable, which has raised concerns within the scientific community. in 2015, crispr was used to edit the dna of non - viable human embryos, leading scientists of major world academies to call for a moratorium on inheritable human genome edits. there are also concerns that the technology could be used not just for treatment, but for enhancement, modification or alteration of a human beings ' appearance, adaptability, intelligence, character or behavior. the distinction between cure and enhancement can also be difficult to establish. in november 2018, he jiankui announced that he had edited the genomes of two human embryos, to attempt to disable the ccr5 gene, which codes for a receptor that hiv uses to enter cells. the work was widely condemned as unethical, dangerous, and premature. currently, germline modification is banned in 40 countries. scientists that do this type of research will often let embryos grow for a few days without allowing it to develop into a baby. researchers are altering the genome of pigs to induce the growth of human organs, with the aim of increasing the success of pig to human organ transplantation. scientists are creating " gene drives ", changing the genomes of mosquitoes to make them immune to malaria, and then looking to spread the genetically altered mosquitoes throughout the mosquito population in the hopes of eliminating the disease. = = = research = = = genetic engineering is an important tool for natural scientists, with the creation of transgenic organisms one of the most important tools for analysis of gene function. genes and other genetic information from a wide range of organisms can be inserted into bacteria for storage and modification, creating genetically modified bacteria in the process. bacteria are cheap, easy to grow, clonal, multiply quickly, relatively easy to transform and can be stored at - 80 Β°c almost indefinitely. once a gene is isolated it can be stored inside the bacteria providing an unlimited supply for research. organisms are genetically engineered to discover the functions of certain genes. this could be the effect on the phenotype of the organism, where the gene is expressed or what other genes it interacts with. these experiments generally involve loss of function, gain of function, tracking and expression. loss of function experiments, such as in a gene knockout experiment, in which an organism is engineered to lack the activity of one or more genes. in a simple knockout a copy
##s can be tested against these mouse models. gene therapy is the genetic engineering of humans, generally by replacing defective genes with effective ones. clinical research using somatic gene therapy has been conducted with several diseases, including x - linked scid, chronic lymphocytic leukemia ( cll ), and parkinson ' s disease. in 2012, alipogene tiparvovec became the first gene therapy treatment to be approved for clinical use. in 2015 a virus was used to insert a healthy gene into the skin cells of a boy suffering from a rare skin disease, epidermolysis bullosa, in order to grow, and then graft healthy skin onto 80 percent of the boy ' s body which was affected by the illness. germline gene therapy would result in any change being inheritable, which has raised concerns within the scientific community. in 2015, crispr was used to edit the dna of non - viable human embryos, leading scientists of major world academies to call for a moratorium on inheritable human genome edits. there are also concerns that the technology could be used not just for treatment, but for enhancement, modification or alteration of a human beings ' appearance, adaptability, intelligence, character or behavior. the distinction between cure and enhancement can also be difficult to establish. in november 2018, he jiankui announced that he had edited the genomes of two human embryos, to attempt to disable the ccr5 gene, which codes for a receptor that hiv uses to enter cells. the work was widely condemned as unethical, dangerous, and premature. currently, germline modification is banned in 40 countries. scientists that do this type of research will often let embryos grow for a few days without allowing it to develop into a baby. researchers are altering the genome of pigs to induce the growth of human organs, with the aim of increasing the success of pig to human organ transplantation. scientists are creating " gene drives ", changing the genomes of mosquitoes to make them immune to malaria, and then looking to spread the genetically altered mosquitoes throughout the mosquito population in the hopes of eliminating the disease. = = = research = = = genetic engineering is an important tool for natural scientists, with the creation of transgenic organisms one of the most important tools for analysis of gene function. genes and other genetic information from a wide range of organisms can be inserted into bacteria for storage and modification, creating genetically modified bacteria in the process. bacteria are cheap, easy to grow, clonal, multi
Question: Layers of placental transfer cells help transport nutrients to the embryos as they develop into what?
A) kinesins
B) fibroblasts
C) sporophytes
D) keratinocytes
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C) sporophytes
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Context:
current in passing over from one concave bank to the next on the opposite side. the lowering of such a shoal by dredging merely effects a temporary deepening, for it soon forms again from the causes which produced it. the removal, moreover, of the rocky obstructions at rapids, though increasing the depth and equalizing the flow at these places, produces a lowering of the river above the rapids by facilitating the efflux, which may result in the appearance of fresh shoals at the low stage of the river. where, however, narrow rocky reefs or other hard shoals stretch across the bottom of a river and present obstacles to the erosion by the current of the soft materials forming the bed of the river above and below, their removal may result in permanent improvement by enabling the river to deepen its bed by natural scour. the capability of a river to provide a waterway for navigation during the summer or throughout the dry season depends on the depth that can be secured in the channel at the lowest stage. the problem in the dry season is the small discharge and deficiency in scour during this period. a typical solution is to restrict the width of the low - water channel, concentrate all of the flow in it, and also to fix its position so that it is scoured out every year by the floods which follow the deepest part of the bed along the line of the strongest current. this can be effected by closing subsidiary low - water channels with dikes across them, and narrowing the channel at the low stage by low - dipping cross dikes extending from the river banks down the slope and pointing slightly up - stream so as to direct the water flowing over them into a central channel. = = estuarine works = = the needs of navigation may also require that a stable, continuous, navigable channel is prolonged from the navigable river to deep water at the mouth of the estuary. the interaction of river flow and tide needs to be modeled by computer or using scale models, moulded to the configuration of the estuary under consideration and reproducing in miniature the tidal ebb and flow and fresh - water discharge over a bed of fine sand, in which various lines of training walls can be successively inserted. the models should be capable of furnishing valuable indications of the respective effects and comparative merits of the different schemes proposed for works. = = see also = = bridge scour flood control = = references = = = = external links = = u. s. army corps of engineers β civil works program river morphology and stream restoration references
equalizing the flow at these places, produces a lowering of the river above the rapids by facilitating the efflux, which may result in the appearance of fresh shoals at the low stage of the river. where, however, narrow rocky reefs or other hard shoals stretch across the bottom of a river and present obstacles to the erosion by the current of the soft materials forming the bed of the river above and below, their removal may result in permanent improvement by enabling the river to deepen its bed by natural scour. the capability of a river to provide a waterway for navigation during the summer or throughout the dry season depends on the depth that can be secured in the channel at the lowest stage. the problem in the dry season is the small discharge and deficiency in scour during this period. a typical solution is to restrict the width of the low - water channel, concentrate all of the flow in it, and also to fix its position so that it is scoured out every year by the floods which follow the deepest part of the bed along the line of the strongest current. this can be effected by closing subsidiary low - water channels with dikes across them, and narrowing the channel at the low stage by low - dipping cross dikes extending from the river banks down the slope and pointing slightly up - stream so as to direct the water flowing over them into a central channel. = = estuarine works = = the needs of navigation may also require that a stable, continuous, navigable channel is prolonged from the navigable river to deep water at the mouth of the estuary. the interaction of river flow and tide needs to be modeled by computer or using scale models, moulded to the configuration of the estuary under consideration and reproducing in miniature the tidal ebb and flow and fresh - water discharge over a bed of fine sand, in which various lines of training walls can be successively inserted. the models should be capable of furnishing valuable indications of the respective effects and comparative merits of the different schemes proposed for works. = = see also = = bridge scour flood control = = references = = = = external links = = u. s. army corps of engineers β civil works program river morphology and stream restoration references - wildland hydrology at the library of congress web archives ( archived 2002 - 08 - 13 )
fluid dynamics video demonstrating the evolution of dynamic stall on a wind turbine blade.
##ediment to up - stream navigation, and there are generally variations in water level, and when the discharge becomes small in the dry season. it is impossible to maintain a sufficient depth of water in the low - water channel. the possibility to secure uniformity of depth in a river by lowering the shoals obstructing the channel depends on the nature of the shoals. a soft shoal in the bed of a river is due to deposit from a diminution in velocity of flow, produced by a reduction in fall and by a widening of the channel, or to a loss in concentration of the scour of the main current in passing over from one concave bank to the next on the opposite side. the lowering of such a shoal by dredging merely effects a temporary deepening, for it soon forms again from the causes which produced it. the removal, moreover, of the rocky obstructions at rapids, though increasing the depth and equalizing the flow at these places, produces a lowering of the river above the rapids by facilitating the efflux, which may result in the appearance of fresh shoals at the low stage of the river. where, however, narrow rocky reefs or other hard shoals stretch across the bottom of a river and present obstacles to the erosion by the current of the soft materials forming the bed of the river above and below, their removal may result in permanent improvement by enabling the river to deepen its bed by natural scour. the capability of a river to provide a waterway for navigation during the summer or throughout the dry season depends on the depth that can be secured in the channel at the lowest stage. the problem in the dry season is the small discharge and deficiency in scour during this period. a typical solution is to restrict the width of the low - water channel, concentrate all of the flow in it, and also to fix its position so that it is scoured out every year by the floods which follow the deepest part of the bed along the line of the strongest current. this can be effected by closing subsidiary low - water channels with dikes across them, and narrowing the channel at the low stage by low - dipping cross dikes extending from the river banks down the slope and pointing slightly up - stream so as to direct the water flowing over them into a central channel. = = estuarine works = = the needs of navigation may also require that a stable, continuous, navigable channel is prolonged from the navigable river to deep water at the mouth of the estuary. the interaction of river
river - beds ), but not for where there may be large obstructions in the ground. an open caisson that is used in soft grounds or high water tables, where open trench excavations are impractical, can also be used to install deep manholes, pump stations and reception / launch pits for microtunnelling, pipe jacking and other operations. a caisson is sunk by self - weight, concrete or water ballast placed on top, or by hydraulic jacks. the leading edge ( or cutting shoe ) of the caisson is sloped out at a sharp angle to aid sinking in a vertical manner ; it is usually made of steel. the shoe is generally wider than the caisson to reduce friction, and the leading edge may be supplied with pressurised bentonite slurry, which swells in water, stabilizing settlement by filling depressions and voids. an open caisson may fill with water during sinking. the material is excavated by clamshell excavator bucket on crane. the formation level subsoil may still not be suitable for excavation or bearing capacity. the water in the caisson ( due to a high water table ) balances the upthrust forces of the soft soils underneath. if dewatered, the base may " pipe " or " boil ", causing the caisson to sink. to combat this problem, piles may be driven from the surface to act as : load - bearing walls, in that they transmit loads to deeper soils. anchors, in that they resist flotation because of the friction at the interface between their surfaces and the surrounding earth into which they have been driven. h - beam sections ( typical column sections, due to resistance to bending in all axis ) may be driven at angles " raked " to rock or other firmer soils ; the h - beams are left extended above the base. a reinforced concrete plug may be placed under the water, a process known as tremie concrete placement. when the caisson is dewatered, this plug acts as a pile cap, resisting the upward forces of the subsoil. = = = monolithic = = = a monolithic caisson ( or simply a monolith ) is larger than the other types of caisson, but similar to open caissons. such caissons are often found in quay walls, where resistance to impact from ships is required. = = = pneumatic = = = shallow caissons may be open to the air, whereas pneumatic caisson
contains a unique number that when added with any number leaves the latter unchanged. this unique number is known as the system ' s additive identity element. for example, the integers has the structure of an ordered ring. this number is generally denoted as 0. because of the total order in this ring, there are numbers greater than zero, called the positive numbers. another property required for a ring to be ordered is that, for each positive number, there exists a unique corresponding number less than 0 whose sum with the original positive number is 0. these numbers less than 0 are called the negative numbers. the numbers in each such pair are their respective additive inverses. this attribute of a number, being exclusively either zero ( 0 ), positive ( + ), or negative ( β ), is called its sign, and is often encoded to the real numbers 0, 1, and β1, respectively ( similar to the way the sign function is defined ). since rational and real numbers are also ordered rings ( in fact ordered fields ), the sign attribute also applies to these number systems. when a minus sign is used in between two numbers, it represents the binary operation of subtraction. when a minus sign is written before a single number, it represents the unary operation of yielding the additive inverse ( sometimes called negation ) of the operand. abstractly then, the difference of two number is the sum of the minuend with the additive inverse of the subtrahend. while 0 is its own additive inverse ( β0 = 0 ), the additive inverse of a positive number is negative, and the additive inverse of a negative number is positive. a double application of this operation is written as β ( β3 ) = 3. the plus sign is predominantly used in algebra to denote the binary operation of addition, and only rarely to emphasize the positivity of an expression. in common numeral notation ( used in arithmetic and elsewhere ), the sign of a number is often made explicit by placing a plus or a minus sign before the number. for example, + 3 denotes " positive three ", and β3 denotes " negative three " ( algebraically : the additive inverse of 3 ). without specific context ( or when no explicit sign is given ), a number is interpreted per default as positive. this notation establishes a strong association of the minus sign " β " with negative numbers, and the plus sign " + " with positive numbers. = = = sign of zero = = = within the convention of zero being neither positive nor negative,
or, and not. vectors can be added and subtracted. rotations can be combined using the function composition operation, performing the first rotation and then the second. operations on sets include the binary operations union and intersection and the unary operation of complementation. operations on functions include composition and convolution. operations may not be defined for every possible value of its domain. for example, in the real numbers one cannot divide by zero or take square roots of negative numbers. the values for which an operation is defined form a set called its domain of definition or active domain. the set which contains the values produced is called the codomain, but the set of actual values attained by the operation is its codomain of definition, active codomain, image or range. for example, in the real numbers, the squaring operation only produces non - negative numbers ; the codomain is the set of real numbers, but the range is the non - negative numbers. operations can involve dissimilar objects : a vector can be multiplied by a scalar to form another vector ( an operation known as scalar multiplication ), and the inner product operation on two vectors produces a quantity that is scalar. an operation may or may not have certain properties, for example it may be associative, commutative, anticommutative, idempotent, and so on. the values combined are called operands, arguments, or inputs, and the value produced is called the value, result, or output. operations can have fewer or more than two inputs ( including the case of zero input and infinitely many inputs ). an operator is similar to an operation in that it refers to the symbol or the process used to denote the operation. hence, their point of view is different. for instance, one often speaks of " the operation of addition " or " the addition operation, " when focusing on the operands and result, but one switch to " addition operator " ( rarely " operator of addition " ), when focusing on the process, or from the more symbolic viewpoint, the function + : x Γ x β x ( where x is a set such as the set of real numbers ). = = definition = = an n - ary operation Ο on a set x is a function Ο : xn β x. the set xn is called the domain of the operation, the output set is called the codomain of the operation, and the fixed non - negative integer n ( the number of opera
the injuries of the inundations they have been designed to prevent, as the escape of floods from the raised river must occur sooner or later. inadequate planning controls which have permitted development on floodplains have been blamed for the flooding of domestic properties. channelization was done under the auspices or overall direction of engineers employed by the local authority or the national government. one of the most heavily channelized areas in the united states is west tennessee, where every major stream with one exception ( the hatchie river ) has been partially or completely channelized. channelization of a stream may be undertaken for several reasons. one is to make a stream more suitable for navigation or for navigation by larger vessels with deep draughts. another is to restrict water to a certain area of a stream ' s natural bottom lands so that the bulk of such lands can be made available for agriculture. a third reason is flood control, with the idea of giving a stream a sufficiently large and deep channel so that flooding beyond those limits will be minimal or nonexistent, at least on a routine basis. one major reason is to reduce natural erosion ; as a natural waterway curves back and forth, it usually deposits sand and gravel on the inside of the corners where the water flows slowly, and cuts sand, gravel, subsoil, and precious topsoil from the outside corners where it flows rapidly due to a change in direction. unlike sand and gravel, the topsoil that is eroded does not get deposited on the inside of the next corner of the river. it simply washes away. = = loss of wetlands = = channelization has several predictable and negative effects. one of them is loss of wetlands. wetlands are an excellent habitat for multiple forms of wildlife, and additionally serve as a " filter " for much of the world ' s surface fresh water. another is the fact that channelized streams are almost invariably straightened. for example, the channelization of florida ' s kissimmee river has been cited as a cause contributing to the loss of wetlands. this straightening causes the streams to flow more rapidly, which can, in some instances, vastly increase soil erosion. it can also increase flooding downstream from the channelized area, as larger volumes of water traveling more rapidly than normal can reach choke points over a shorter period of time than they otherwise would, with a net effect of flood control in one area coming at the expense of aggravated flooding in another. in addition, studies have shown that stream channelization results in declines of river fish populations. : 3 - 1ff a
to increase as far as practicable the navigable depth at the lowest stage of the water level. engineering works to increase the navigability of rivers can only be advantageously undertaken in large rivers with a moderate fall and a fair discharge at their lowest stage, for with a large fall the current presents a great impediment to up - stream navigation, and there are generally variations in water level, and when the discharge becomes small in the dry season. it is impossible to maintain a sufficient depth of water in the low - water channel. the possibility to secure uniformity of depth in a river by lowering the shoals obstructing the channel depends on the nature of the shoals. a soft shoal in the bed of a river is due to deposit from a diminution in velocity of flow, produced by a reduction in fall and by a widening of the channel, or to a loss in concentration of the scour of the main current in passing over from one concave bank to the next on the opposite side. the lowering of such a shoal by dredging merely effects a temporary deepening, for it soon forms again from the causes which produced it. the removal, moreover, of the rocky obstructions at rapids, though increasing the depth and equalizing the flow at these places, produces a lowering of the river above the rapids by facilitating the efflux, which may result in the appearance of fresh shoals at the low stage of the river. where, however, narrow rocky reefs or other hard shoals stretch across the bottom of a river and present obstacles to the erosion by the current of the soft materials forming the bed of the river above and below, their removal may result in permanent improvement by enabling the river to deepen its bed by natural scour. the capability of a river to provide a waterway for navigation during the summer or throughout the dry season depends on the depth that can be secured in the channel at the lowest stage. the problem in the dry season is the small discharge and deficiency in scour during this period. a typical solution is to restrict the width of the low - water channel, concentrate all of the flow in it, and also to fix its position so that it is scoured out every year by the floods which follow the deepest part of the bed along the line of the strongest current. this can be effected by closing subsidiary low - water channels with dikes across them, and narrowing the channel at the low stage by low - dipping cross dikes extending from the river banks down the
for inland navigation in the lower portion of their course, as, for instance, the rhine, the danube and the mississippi. river engineering works are only required to prevent changes in the course of the stream, to regulate its depth, and especially to fix the low - water channel and concentrate the flow in it, so as to increase as far as practicable the navigable depth at the lowest stage of the water level. engineering works to increase the navigability of rivers can only be advantageously undertaken in large rivers with a moderate fall and a fair discharge at their lowest stage, for with a large fall the current presents a great impediment to up - stream navigation, and there are generally variations in water level, and when the discharge becomes small in the dry season. it is impossible to maintain a sufficient depth of water in the low - water channel. the possibility to secure uniformity of depth in a river by lowering the shoals obstructing the channel depends on the nature of the shoals. a soft shoal in the bed of a river is due to deposit from a diminution in velocity of flow, produced by a reduction in fall and by a widening of the channel, or to a loss in concentration of the scour of the main current in passing over from one concave bank to the next on the opposite side. the lowering of such a shoal by dredging merely effects a temporary deepening, for it soon forms again from the causes which produced it. the removal, moreover, of the rocky obstructions at rapids, though increasing the depth and equalizing the flow at these places, produces a lowering of the river above the rapids by facilitating the efflux, which may result in the appearance of fresh shoals at the low stage of the river. where, however, narrow rocky reefs or other hard shoals stretch across the bottom of a river and present obstacles to the erosion by the current of the soft materials forming the bed of the river above and below, their removal may result in permanent improvement by enabling the river to deepen its bed by natural scour. the capability of a river to provide a waterway for navigation during the summer or throughout the dry season depends on the depth that can be secured in the channel at the lowest stage. the problem in the dry season is the small discharge and deficiency in scour during this period. a typical solution is to restrict the width of the low - water channel, concentrate all of the flow in it, and also to fix its position so that it is
Question: The kayakβs motion in the water is an example of classical addition of what?
A) momentum
B) force
C) acceleration
D) velocities
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D) velocities
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Context:
, and includes, but is not limited to, the study of epidemics. genetics is the study of genes, and their role in biological inheritance. gynecology is the study of female reproductive system. histology is the study of the structures of biological tissues by light microscopy, electron microscopy and immunohistochemistry. immunology is the study of the immune system, which includes the innate and adaptive immune system in humans, for example. lifestyle medicine is the study of the chronic conditions, and how to prevent, treat and reverse them. medical physics is the study of the applications of physics principles in medicine. microbiology is the study of microorganisms, including protozoa, bacteria, fungi, and viruses. molecular biology is the study of molecular underpinnings of the process of replication, transcription and translation of the genetic material. neuroscience includes those disciplines of science that are related to the study of the nervous system. a main focus of neuroscience is the biology and physiology of the human brain and spinal cord. some related clinical specialties include neurology, neurosurgery and psychiatry. nutrition science ( theoretical focus ) and dietetics ( practical focus ) is the study of the relationship of food and drink to health and disease, especially in determining an optimal diet. medical nutrition therapy is done by dietitians and is prescribed for diabetes, cardiovascular diseases, weight and eating disorders, allergies, malnutrition, and neoplastic diseases. pathology as a science is the study of disease β the causes, course, progression and resolution thereof. pharmacology is the study of drugs and their actions. photobiology is the study of the interactions between non - ionizing radiation and living organisms. physiology is the study of the normal functioning of the body and the underlying regulatory mechanisms. radiobiology is the study of the interactions between ionizing radiation and living organisms. toxicology is the study of hazardous effects of drugs and poisons. = = = specialties = = = in the broadest meaning of " medicine ", there are many different specialties. in the uk, most specialities have their own body or college, which has its own entrance examination. these are collectively known as the royal colleges, although not all currently use the term " royal ". the development of a speciality is often driven by new technology ( such as the development of effective anaesthetics ) or ways of working ( such as emergency departments ) ; the new specialty leads to the formation of a unifying body of
for the treatment of diabetes, was previously extracted from the pancreas of abattoir animals ( cattle or pigs ). the genetically engineered bacteria are able to produce large quantities of synthetic human insulin at relatively low cost. biotechnology has also enabled emerging therapeutics like gene therapy. the application of biotechnology to basic science ( for example through the human genome project ) has also dramatically improved our understanding of biology and as our scientific knowledge of normal and disease biology has increased, our ability to develop new medicines to treat previously untreatable diseases has increased as well. genetic testing allows the genetic diagnosis of vulnerabilities to inherited diseases, and can also be used to determine a child ' s parentage ( genetic mother and father ) or in general a person ' s ancestry. in addition to studying chromosomes to the level of individual genes, genetic testing in a broader sense includes biochemical tests for the possible presence of genetic diseases, or mutant forms of genes associated with increased risk of developing genetic disorders. genetic testing identifies changes in chromosomes, genes, or proteins. most of the time, testing is used to find changes that are associated with inherited disorders. the results of a genetic test can confirm or rule out a suspected genetic condition or help determine a person ' s chance of developing or passing on a genetic disorder. as of 2011 several hundred genetic tests were in use. since genetic testing may open up ethical or psychological problems, genetic testing is often accompanied by genetic counseling. = = = agriculture = = = genetically modified crops ( " gm crops ", or " biotech crops " ) are plants used in agriculture, the dna of which has been modified with genetic engineering techniques. in most cases, the main aim is to introduce a new trait that does not occur naturally in the species. biotechnology firms can contribute to future food security by improving the nutrition and viability of urban agriculture. furthermore, the protection of intellectual property rights encourages private sector investment in agrobiotechnology. examples in food crops include resistance to certain pests, diseases, stressful environmental conditions, resistance to chemical treatments ( e. g. resistance to a herbicide ), reduction of spoilage, or improving the nutrient profile of the crop. examples in non - food crops include production of pharmaceutical agents, biofuels, and other industrially useful goods, as well as for bioremediation. farmers have widely adopted gm technology. between 1996 and 2011, the total surface area of land cultivated with gm crops had increased by a factor of 94, from 17, 000 to 1, 600, 000 square
to epidemiology and evidence - based medicine. cytology is the microscopic study of individual cells. embryology is the study of the early development of organisms. endocrinology is the study of hormones and their effect throughout the body of animals. epidemiology is the study of the demographics of disease processes, and includes, but is not limited to, the study of epidemics. genetics is the study of genes, and their role in biological inheritance. gynecology is the study of female reproductive system. histology is the study of the structures of biological tissues by light microscopy, electron microscopy and immunohistochemistry. immunology is the study of the immune system, which includes the innate and adaptive immune system in humans, for example. lifestyle medicine is the study of the chronic conditions, and how to prevent, treat and reverse them. medical physics is the study of the applications of physics principles in medicine. microbiology is the study of microorganisms, including protozoa, bacteria, fungi, and viruses. molecular biology is the study of molecular underpinnings of the process of replication, transcription and translation of the genetic material. neuroscience includes those disciplines of science that are related to the study of the nervous system. a main focus of neuroscience is the biology and physiology of the human brain and spinal cord. some related clinical specialties include neurology, neurosurgery and psychiatry. nutrition science ( theoretical focus ) and dietetics ( practical focus ) is the study of the relationship of food and drink to health and disease, especially in determining an optimal diet. medical nutrition therapy is done by dietitians and is prescribed for diabetes, cardiovascular diseases, weight and eating disorders, allergies, malnutrition, and neoplastic diseases. pathology as a science is the study of disease β the causes, course, progression and resolution thereof. pharmacology is the study of drugs and their actions. photobiology is the study of the interactions between non - ionizing radiation and living organisms. physiology is the study of the normal functioning of the body and the underlying regulatory mechanisms. radiobiology is the study of the interactions between ionizing radiation and living organisms. toxicology is the study of hazardous effects of drugs and poisons. = = = specialties = = = in the broadest meaning of " medicine ", there are many different specialties. in the uk, most specialities have their own body or college, which has its own entrance examination. these are collectively known
is the scientific study of inheritance. mendelian inheritance, specifically, is the process by which genes and traits are passed on from parents to offspring. it has several principles. the first is that genetic characteristics, alleles, are discrete and have alternate forms ( e. g., purple vs. white or tall vs. dwarf ), each inherited from one of two parents. based on the law of dominance and uniformity, which states that some alleles are dominant while others are recessive ; an organism with at least one dominant allele will display the phenotype of that dominant allele. during gamete formation, the alleles for each gene segregate, so that each gamete carries only one allele for each gene. heterozygotic individuals produce gametes with an equal frequency of two alleles. finally, the law of independent assortment, states that genes of different traits can segregate independently during the formation of gametes, i. e., genes are unlinked. an exception to this rule would include traits that are sex - linked. test crosses can be performed to experimentally determine the underlying genotype of an organism with a dominant phenotype. a punnett square can be used to predict the results of a test cross. the chromosome theory of inheritance, which states that genes are found on chromosomes, was supported by thomas morgans ' s experiments with fruit flies, which established the sex linkage between eye color and sex in these insects. = = = genes and dna = = = a gene is a unit of heredity that corresponds to a region of deoxyribonucleic acid ( dna ) that carries genetic information that controls form or function of an organism. dna is composed of two polynucleotide chains that coil around each other to form a double helix. it is found as linear chromosomes in eukaryotes, and circular chromosomes in prokaryotes. the set of chromosomes in a cell is collectively known as its genome. in eukaryotes, dna is mainly in the cell nucleus. in prokaryotes, the dna is held within the nucleoid. the genetic information is held within genes, and the complete assemblage in an organism is called its genotype. dna replication is a semiconservative process whereby each strand serves as a template for a new strand of dna. mutations are heritable changes in dna. they can arise spontaneously as a result of replication errors that were not corrected by proofreading or can
the study of microorganisms, including protozoa, bacteria, fungi, and viruses. molecular biology is the study of molecular underpinnings of the process of replication, transcription and translation of the genetic material. neuroscience includes those disciplines of science that are related to the study of the nervous system. a main focus of neuroscience is the biology and physiology of the human brain and spinal cord. some related clinical specialties include neurology, neurosurgery and psychiatry. nutrition science ( theoretical focus ) and dietetics ( practical focus ) is the study of the relationship of food and drink to health and disease, especially in determining an optimal diet. medical nutrition therapy is done by dietitians and is prescribed for diabetes, cardiovascular diseases, weight and eating disorders, allergies, malnutrition, and neoplastic diseases. pathology as a science is the study of disease β the causes, course, progression and resolution thereof. pharmacology is the study of drugs and their actions. photobiology is the study of the interactions between non - ionizing radiation and living organisms. physiology is the study of the normal functioning of the body and the underlying regulatory mechanisms. radiobiology is the study of the interactions between ionizing radiation and living organisms. toxicology is the study of hazardous effects of drugs and poisons. = = = specialties = = = in the broadest meaning of " medicine ", there are many different specialties. in the uk, most specialities have their own body or college, which has its own entrance examination. these are collectively known as the royal colleges, although not all currently use the term " royal ". the development of a speciality is often driven by new technology ( such as the development of effective anaesthetics ) or ways of working ( such as emergency departments ) ; the new specialty leads to the formation of a unifying body of doctors and the prestige of administering their own examination. within medical circles, specialities usually fit into one of two broad categories : " medicine " and " surgery ". " medicine " refers to the practice of non - operative medicine, and most of its subspecialties require preliminary training in internal medicine. in the uk, this was traditionally evidenced by passing the examination for the membership of the royal college of physicians ( mrcp ) or the equivalent college in scotland or ireland. " surgery " refers to the practice of operative medicine, and most subspecialties in this area require preliminary training in general surgery, which in the uk leads to
. biophysics is an interdisciplinary science that uses the methods of physics and physical chemistry to study biological systems. biostatistics is the application of statistics to biological fields in the broadest sense. a knowledge of biostatistics is essential in the planning, evaluation, and interpretation of medical research. it is also fundamental to epidemiology and evidence - based medicine. cytology is the microscopic study of individual cells. embryology is the study of the early development of organisms. endocrinology is the study of hormones and their effect throughout the body of animals. epidemiology is the study of the demographics of disease processes, and includes, but is not limited to, the study of epidemics. genetics is the study of genes, and their role in biological inheritance. gynecology is the study of female reproductive system. histology is the study of the structures of biological tissues by light microscopy, electron microscopy and immunohistochemistry. immunology is the study of the immune system, which includes the innate and adaptive immune system in humans, for example. lifestyle medicine is the study of the chronic conditions, and how to prevent, treat and reverse them. medical physics is the study of the applications of physics principles in medicine. microbiology is the study of microorganisms, including protozoa, bacteria, fungi, and viruses. molecular biology is the study of molecular underpinnings of the process of replication, transcription and translation of the genetic material. neuroscience includes those disciplines of science that are related to the study of the nervous system. a main focus of neuroscience is the biology and physiology of the human brain and spinal cord. some related clinical specialties include neurology, neurosurgery and psychiatry. nutrition science ( theoretical focus ) and dietetics ( practical focus ) is the study of the relationship of food and drink to health and disease, especially in determining an optimal diet. medical nutrition therapy is done by dietitians and is prescribed for diabetes, cardiovascular diseases, weight and eating disorders, allergies, malnutrition, and neoplastic diseases. pathology as a science is the study of disease β the causes, course, progression and resolution thereof. pharmacology is the study of drugs and their actions. photobiology is the study of the interactions between non - ionizing radiation and living organisms. physiology is the study of the normal functioning of the body and the underlying regulatory mechanisms. radiobiology is the study of the interactions between ionizing radiation and living organisms.
##ry. immunology is the study of the immune system, which includes the innate and adaptive immune system in humans, for example. lifestyle medicine is the study of the chronic conditions, and how to prevent, treat and reverse them. medical physics is the study of the applications of physics principles in medicine. microbiology is the study of microorganisms, including protozoa, bacteria, fungi, and viruses. molecular biology is the study of molecular underpinnings of the process of replication, transcription and translation of the genetic material. neuroscience includes those disciplines of science that are related to the study of the nervous system. a main focus of neuroscience is the biology and physiology of the human brain and spinal cord. some related clinical specialties include neurology, neurosurgery and psychiatry. nutrition science ( theoretical focus ) and dietetics ( practical focus ) is the study of the relationship of food and drink to health and disease, especially in determining an optimal diet. medical nutrition therapy is done by dietitians and is prescribed for diabetes, cardiovascular diseases, weight and eating disorders, allergies, malnutrition, and neoplastic diseases. pathology as a science is the study of disease β the causes, course, progression and resolution thereof. pharmacology is the study of drugs and their actions. photobiology is the study of the interactions between non - ionizing radiation and living organisms. physiology is the study of the normal functioning of the body and the underlying regulatory mechanisms. radiobiology is the study of the interactions between ionizing radiation and living organisms. toxicology is the study of hazardous effects of drugs and poisons. = = = specialties = = = in the broadest meaning of " medicine ", there are many different specialties. in the uk, most specialities have their own body or college, which has its own entrance examination. these are collectively known as the royal colleges, although not all currently use the term " royal ". the development of a speciality is often driven by new technology ( such as the development of effective anaesthetics ) or ways of working ( such as emergency departments ) ; the new specialty leads to the formation of a unifying body of doctors and the prestige of administering their own examination. within medical circles, specialities usually fit into one of two broad categories : " medicine " and " surgery ". " medicine " refers to the practice of non - operative medicine, and most of its subspecialties require preliminary training in internal medicine. in the uk
##tes, i. e., genes are unlinked. an exception to this rule would include traits that are sex - linked. test crosses can be performed to experimentally determine the underlying genotype of an organism with a dominant phenotype. a punnett square can be used to predict the results of a test cross. the chromosome theory of inheritance, which states that genes are found on chromosomes, was supported by thomas morgans ' s experiments with fruit flies, which established the sex linkage between eye color and sex in these insects. = = = genes and dna = = = a gene is a unit of heredity that corresponds to a region of deoxyribonucleic acid ( dna ) that carries genetic information that controls form or function of an organism. dna is composed of two polynucleotide chains that coil around each other to form a double helix. it is found as linear chromosomes in eukaryotes, and circular chromosomes in prokaryotes. the set of chromosomes in a cell is collectively known as its genome. in eukaryotes, dna is mainly in the cell nucleus. in prokaryotes, the dna is held within the nucleoid. the genetic information is held within genes, and the complete assemblage in an organism is called its genotype. dna replication is a semiconservative process whereby each strand serves as a template for a new strand of dna. mutations are heritable changes in dna. they can arise spontaneously as a result of replication errors that were not corrected by proofreading or can be induced by an environmental mutagen such as a chemical ( e. g., nitrous acid, benzopyrene ) or radiation ( e. g., x - ray, gamma ray, ultraviolet radiation, particles emitted by unstable isotopes ). mutations can lead to phenotypic effects such as loss - of - function, gain - of - function, and conditional mutations. some mutations are beneficial, as they are a source of genetic variation for evolution. others are harmful if they were to result in a loss of function of genes needed for survival. = = = gene expression = = = gene expression is the molecular process by which a genotype encoded in dna gives rise to an observable phenotype in the proteins of an organism ' s body. this process is summarized by the central dogma of molecular biology, which was formulated by francis crick in 1958. according to the central dogma, genetic information flows from dna
studies of the molecular genetics of model plants such as the thale cress, arabidopsis thaliana, a weedy species in the mustard family ( brassicaceae ). the genome or hereditary information contained in the genes of this species is encoded by about 135 million base pairs of dna, forming one of the smallest genomes among flowering plants. arabidopsis was the first plant to have its genome sequenced, in 2000. the sequencing of some other relatively small genomes, of rice ( oryza sativa ) and brachypodium distachyon, has made them important model species for understanding the genetics, cellular and molecular biology of cereals, grasses and monocots generally. model plants such as arabidopsis thaliana are used for studying the molecular biology of plant cells and the chloroplast. ideally, these organisms have small genomes that are well known or completely sequenced, small stature and short generation times. corn has been used to study mechanisms of photosynthesis and phloem loading of sugar in c4 plants. the single celled green alga chlamydomonas reinhardtii, while not an embryophyte itself, contains a green - pigmented chloroplast related to that of land plants, making it useful for study. a red alga cyanidioschyzon merolae has also been used to study some basic chloroplast functions. spinach, peas, soybeans and a moss physcomitrella patens are commonly used to study plant cell biology. agrobacterium tumefaciens, a soil rhizosphere bacterium, can attach to plant cells and infect them with a callus - inducing ti plasmid by horizontal gene transfer, causing a callus infection called crown gall disease. schell and van montagu ( 1977 ) hypothesised that the ti plasmid could be a natural vector for introducing the nif gene responsible for nitrogen fixation in the root nodules of legumes and other plant species. today, genetic modification of the ti plasmid is one of the main techniques for introduction of transgenes to plants and the creation of genetically modified crops. = = = epigenetics = = = epigenetics is the study of heritable changes in gene function that cannot be explained by changes in the underlying dna sequence but cause the organism ' s genes to behave ( or " express themselves " ) differently. one example
genetic engineering takes the gene directly from one organism and delivers it to the other. this is much faster, can be used to insert any genes from any organism ( even ones from different domains ) and prevents other undesirable genes from also being added. genetic engineering could potentially fix severe genetic disorders in humans by replacing the defective gene with a functioning one. it is an important tool in research that allows the function of specific genes to be studied. drugs, vaccines and other products have been harvested from organisms engineered to produce them. crops have been developed that aid food security by increasing yield, nutritional value and tolerance to environmental stresses. the dna can be introduced directly into the host organism or into a cell that is then fused or hybridised with the host. this relies on recombinant nucleic acid techniques to form new combinations of heritable genetic material followed by the incorporation of that material either indirectly through a vector system or directly through micro - injection, macro - injection or micro - encapsulation. genetic engineering does not normally include traditional breeding, in vitro fertilisation, induction of polyploidy, mutagenesis and cell fusion techniques that do not use recombinant nucleic acids or a genetically modified organism in the process. however, some broad definitions of genetic engineering include selective breeding. cloning and stem cell research, although not considered genetic engineering, are closely related and genetic engineering can be used within them. synthetic biology is an emerging discipline that takes genetic engineering a step further by introducing artificially synthesised material into an organism. plants, animals or microorganisms that have been changed through genetic engineering are termed genetically modified organisms or gmos. if genetic material from another species is added to the host, the resulting organism is called transgenic. if genetic material from the same species or a species that can naturally breed with the host is used the resulting organism is called cisgenic. if genetic engineering is used to remove genetic material from the target organism the resulting organism is termed a knockout organism. in europe genetic modification is synonymous with genetic engineering while within the united states of america and canada genetic modification can also be used to refer to more conventional breeding methods. = = history = = humans have altered the genomes of species for thousands of years through selective breeding, or artificial selection : 1 : 1 as contrasted with natural selection. more recently, mutation breeding has used exposure to chemicals or radiation to produce a high frequency of random mutations, for selective breeding purposes. genetic engineering as the direct manipulation of dna by humans outside breeding and
Question: Introduction genetics is the study of what?
A) obesity
B) variability
C) heredity
D) biology
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C) heredity
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Context:
biotechnology is a multidisciplinary field that involves the integration of natural sciences and engineering sciences in order to achieve the application of organisms and parts thereof for products and services. specialists in the field are known as biotechnologists. the term biotechnology was first used by karoly ereky in 1919 to refer to the production of products from raw materials with the aid of living organisms. the core principle of biotechnology involves harnessing biological systems and organisms, such as bacteria, yeast, and plants, to perform specific tasks or produce valuable substances. biotechnology had a significant impact on many areas of society, from medicine to agriculture to environmental science. one of the key techniques used in biotechnology is genetic engineering, which allows scientists to modify the genetic makeup of organisms to achieve desired outcomes. this can involve inserting genes from one organism into another, and consequently, create new traits or modifying existing ones. other important techniques used in biotechnology include tissue culture, which allows researchers to grow cells and tissues in the lab for research and medical purposes, and fermentation, which is used to produce a wide range of products such as beer, wine, and cheese. the applications of biotechnology are diverse and have led to the development of products like life - saving drugs, biofuels, genetically modified crops, and innovative materials. it has also been used to address environmental challenges, such as developing biodegradable plastics and using microorganisms to clean up contaminated sites. biotechnology is a rapidly evolving field with significant potential to address pressing global challenges and improve the quality of life for people around the world ; however, despite its numerous benefits, it also poses ethical and societal challenges, such as questions around genetic modification and intellectual property rights. as a result, there is ongoing debate and regulation surrounding the use and application of biotechnology in various industries and fields. = = definition = = the concept of biotechnology encompasses a wide range of procedures for modifying living organisms for human purposes, going back to domestication of animals, cultivation of plants, and " improvements " to these through breeding programs that employ artificial selection and hybridization. modern usage also includes genetic engineering, as well as cell and tissue culture technologies. the american chemical society defines biotechnology as the application of biological organisms, systems, or processes by various industries to learning about the science of life and the improvement of the value of materials and organisms, such as pharmaceuticals, crops, and livestock. as per the european federation of biotechnology, biotechnology is the integration of natural science and organisms, cells, parts thereof, and molecular analogues for products and
biology is the scientific study of life and living organisms. it is a broad natural science that encompasses a wide range of fields and unifying principles that explain the structure, function, growth, origin, evolution, and distribution of life. central to biology are five fundamental themes : the cell as the basic unit of life, genes and heredity as the basis of inheritance, evolution as the driver of biological diversity, energy transformation for sustaining life processes, and the maintenance of internal stability ( homeostasis ). biology examines life across multiple levels of organization, from molecules and cells to organisms, populations, and ecosystems. subdisciplines include molecular biology, physiology, ecology, evolutionary biology, developmental biology, and systematics, among others. each of these fields applies a range of methods to investigate biological phenomena, including observation, experimentation, and mathematical modeling. modern biology is grounded in the theory of evolution by natural selection, first articulated by charles darwin, and in the molecular understanding of genes encoded in dna. the discovery of the structure of dna and advances in molecular genetics have transformed many areas of biology, leading to applications in medicine, agriculture, biotechnology, and environmental science. life on earth is believed to have originated over 3. 7 billion years ago. today, it includes a vast diversity of organisms β from single - celled archaea and bacteria to complex multicellular plants, fungi, and animals. biologists classify organisms based on shared characteristics and evolutionary relationships, using taxonomic and phylogenetic frameworks. these organisms interact with each other and with their environments in ecosystems, where they play roles in energy flow and nutrient cycling. as a constantly evolving field, biology incorporates new discoveries and technologies that enhance the understanding of life and its processes, while contributing to solutions for challenges such as disease, climate change, and biodiversity loss. = = history = = the earliest of roots of science, which included medicine, can be traced to ancient egypt and mesopotamia in around 3000 to 1200 bce. their contributions shaped ancient greek natural philosophy. ancient greek philosophers such as aristotle ( 384 β 322 bce ) contributed extensively to the development of biological knowledge. he explored biological causation and the diversity of life. his successor, theophrastus, began the scientific study of plants. scholars of the medieval islamic world who wrote on biology included al - jahiz ( 781 β 869 ), al - dinawari ( 828 β 896 ), who wrote on botany, and rhazes ( 865 β 925 ) who wrote on anatomy and physiology. medicine was especially well
cellular and molecular biology of cereals, grasses and monocots generally. model plants such as arabidopsis thaliana are used for studying the molecular biology of plant cells and the chloroplast. ideally, these organisms have small genomes that are well known or completely sequenced, small stature and short generation times. corn has been used to study mechanisms of photosynthesis and phloem loading of sugar in c4 plants. the single celled green alga chlamydomonas reinhardtii, while not an embryophyte itself, contains a green - pigmented chloroplast related to that of land plants, making it useful for study. a red alga cyanidioschyzon merolae has also been used to study some basic chloroplast functions. spinach, peas, soybeans and a moss physcomitrella patens are commonly used to study plant cell biology. agrobacterium tumefaciens, a soil rhizosphere bacterium, can attach to plant cells and infect them with a callus - inducing ti plasmid by horizontal gene transfer, causing a callus infection called crown gall disease. schell and van montagu ( 1977 ) hypothesised that the ti plasmid could be a natural vector for introducing the nif gene responsible for nitrogen fixation in the root nodules of legumes and other plant species. today, genetic modification of the ti plasmid is one of the main techniques for introduction of transgenes to plants and the creation of genetically modified crops. = = = epigenetics = = = epigenetics is the study of heritable changes in gene function that cannot be explained by changes in the underlying dna sequence but cause the organism ' s genes to behave ( or " express themselves " ) differently. one example of epigenetic change is the marking of the genes by dna methylation which determines whether they will be expressed or not. gene expression can also be controlled by repressor proteins that attach to silencer regions of the dna and prevent that region of the dna code from being expressed. epigenetic marks may be added or removed from the dna during programmed stages of development of the plant, and are responsible, for example, for the differences between anthers, petals and normal leaves, despite the fact that they all have the same underlying genetic code. epigenetic changes may be temporary or may remain through successive cell divisions for the remainder of
soil erosion. plants are crucial to the future of human society as they provide food, oxygen, biochemicals, and products for people, as well as creating and preserving soil. historically, all living things were classified as either animals or plants and botany covered the study of all organisms not considered animals. botanists examine both the internal functions and processes within plant organelles, cells, tissues, whole plants, plant populations and plant communities. at each of these levels, a botanist may be concerned with the classification ( taxonomy ), phylogeny and evolution, structure ( anatomy and morphology ), or function ( physiology ) of plant life. the strictest definition of " plant " includes only the " land plants " or embryophytes, which include seed plants ( gymnosperms, including the pines, and flowering plants ) and the free - sporing cryptogams including ferns, clubmosses, liverworts, hornworts and mosses. embryophytes are multicellular eukaryotes descended from an ancestor that obtained its energy from sunlight by photosynthesis. they have life cycles with alternating haploid and diploid phases. the sexual haploid phase of embryophytes, known as the gametophyte, nurtures the developing diploid embryo sporophyte within its tissues for at least part of its life, even in the seed plants, where the gametophyte itself is nurtured by its parent sporophyte. other groups of organisms that were previously studied by botanists include bacteria ( now studied in bacteriology ), fungi ( mycology ) β including lichen - forming fungi ( lichenology ), non - chlorophyte algae ( phycology ), and viruses ( virology ). however, attention is still given to these groups by botanists, and fungi ( including lichens ) and photosynthetic protists are usually covered in introductory botany courses. palaeobotanists study ancient plants in the fossil record to provide information about the evolutionary history of plants. cyanobacteria, the first oxygen - releasing photosynthetic organisms on earth, are thought to have given rise to the ancestor of plants by entering into an endosymbiotic relationship with an early eukaryote, ultimately becoming the chloroplasts in plant cells. the new photosynthetic plants ( along with their algal relatives ) accelerated the rise in atmospheric oxygen started by the cyanobacteria, changing the
. an example of this would be bt corn. whether or not green biotechnology products such as this are ultimately more environmentally friendly is a topic of considerable debate. it is commonly considered as the next phase of green revolution, which can be seen as a platform to eradicate world hunger by using technologies which enable the production of more fertile and resistant, towards biotic and abiotic stress, plants and ensures application of environmentally friendly fertilizers and the use of biopesticides, it is mainly focused on the development of agriculture. on the other hand, some of the uses of green biotechnology involve microorganisms to clean and reduce waste. red biotechnology is the use of biotechnology in the medical and pharmaceutical industries, and health preservation. this branch involves the production of vaccines and antibiotics, regenerative therapies, creation of artificial organs and new diagnostics of diseases. as well as the development of hormones, stem cells, antibodies, sirna and diagnostic tests. white biotechnology, also known as industrial biotechnology, is biotechnology applied to industrial processes. an example is the designing of an organism to produce a useful chemical. another example is the using of enzymes as industrial catalysts to either produce valuable chemicals or destroy hazardous / polluting chemicals. white biotechnology tends to consume less in resources than traditional processes used to produce industrial goods. yellow biotechnology refers to the use of biotechnology in food production ( food industry ), for example in making wine ( winemaking ), cheese ( cheesemaking ), and beer ( brewing ) by fermentation. it has also been used to refer to biotechnology applied to insects. this includes biotechnology - based approaches for the control of harmful insects, the characterisation and utilisation of active ingredients or genes of insects for research, or application in agriculture and medicine and various other approaches. gray biotechnology is dedicated to environmental applications, and focused on the maintenance of biodiversity and the remotion of pollutants. brown biotechnology is related to the management of arid lands and deserts. one application is the creation of enhanced seeds that resist extreme environmental conditions of arid regions, which is related to the innovation, creation of agriculture techniques and management of resources. violet biotechnology is related to law, ethical and philosophical issues around biotechnology. microbial biotechnology has been proposed for the rapidly emerging area of biotechnology applications in space and microgravity ( space bioeconomy ) dark biotechnology is the color associated with bioterrorism or biological weapons and biowarfare which uses microorganisms, and toxins to cause diseases and death in humans, livestock and
what violations of bell inequalities teach us is that the world is quantum mechanical, i. e., nonclassical. assertions that they imply the world is nonlocal arise from ignoring differences between quantum and classical physics.
. biophysics is an interdisciplinary science that uses the methods of physics and physical chemistry to study biological systems. biostatistics is the application of statistics to biological fields in the broadest sense. a knowledge of biostatistics is essential in the planning, evaluation, and interpretation of medical research. it is also fundamental to epidemiology and evidence - based medicine. cytology is the microscopic study of individual cells. embryology is the study of the early development of organisms. endocrinology is the study of hormones and their effect throughout the body of animals. epidemiology is the study of the demographics of disease processes, and includes, but is not limited to, the study of epidemics. genetics is the study of genes, and their role in biological inheritance. gynecology is the study of female reproductive system. histology is the study of the structures of biological tissues by light microscopy, electron microscopy and immunohistochemistry. immunology is the study of the immune system, which includes the innate and adaptive immune system in humans, for example. lifestyle medicine is the study of the chronic conditions, and how to prevent, treat and reverse them. medical physics is the study of the applications of physics principles in medicine. microbiology is the study of microorganisms, including protozoa, bacteria, fungi, and viruses. molecular biology is the study of molecular underpinnings of the process of replication, transcription and translation of the genetic material. neuroscience includes those disciplines of science that are related to the study of the nervous system. a main focus of neuroscience is the biology and physiology of the human brain and spinal cord. some related clinical specialties include neurology, neurosurgery and psychiatry. nutrition science ( theoretical focus ) and dietetics ( practical focus ) is the study of the relationship of food and drink to health and disease, especially in determining an optimal diet. medical nutrition therapy is done by dietitians and is prescribed for diabetes, cardiovascular diseases, weight and eating disorders, allergies, malnutrition, and neoplastic diseases. pathology as a science is the study of disease β the causes, course, progression and resolution thereof. pharmacology is the study of drugs and their actions. photobiology is the study of the interactions between non - ionizing radiation and living organisms. physiology is the study of the normal functioning of the body and the underlying regulatory mechanisms. radiobiology is the study of the interactions between ionizing radiation and living organisms.
there are no limits for the speeds of light and particles in general relativity ( gr ). four examples illustrate this basic result, which is too often neglected.
on biological causation and the diversity of life. he made countless observations of nature, especially the habits and attributes of plants and animals on lesbos, classified more than 540 animal species, and dissected at least 50. aristotle ' s writings profoundly influenced subsequent islamic and european scholarship, though they were eventually superseded in the scientific revolution. aristotle also contributed to theories of the elements and the cosmos. he believed that the celestial bodies ( such as the planets and the sun ) had something called an unmoved mover that put the celestial bodies in motion. aristotle tried to explain everything through mathematics and physics, but sometimes explained things such as the motion of celestial bodies through a higher power such as god. aristotle did not have the technological advancements that would have explained the motion of celestial bodies. in addition, aristotle had many views on the elements. he believed that everything was derived of the elements earth, water, air, fire, and lastly the aether. the aether was a celestial element, and therefore made up the matter of the celestial bodies. the elements of earth, water, air and fire were derived of a combination of two of the characteristics of hot, wet, cold, and dry, and all had their inevitable place and motion. the motion of these elements begins with earth being the closest to " the earth, " then water, air, fire, and finally aether. in addition to the makeup of all things, aristotle came up with theories as to why things did not return to their natural motion. he understood that water sits above earth, air above water, and fire above air in their natural state. he explained that although all elements must return to their natural state, the human body and other living things have a constraint on the elements β thus not allowing the elements making one who they are to return to their natural state. the important legacy of this period included substantial advances in factual knowledge, especially in anatomy, zoology, botany, mineralogy, geography, mathematics and astronomy ; an awareness of the importance of certain scientific problems, especially those related to the problem of change and its causes ; and a recognition of the methodological importance of applying mathematics to natural phenomena and of undertaking empirical research. in the hellenistic age scholars frequently employed the principles developed in earlier greek thought : the application of mathematics and deliberate empirical research, in their scientific investigations. thus, clear unbroken lines of influence lead from ancient greek and hellenistic philosophers, to medieval muslim philosophers and scientists, to the european renaissance and enlightenment, to the secular sciences of the modern day. neither reason
of embryophytes ( land plants ) is called phytology. bryology is the study of mosses ( and in the broader sense also liverworts and hornworts ). pteridology ( or filicology ) is the study of ferns and allied plants. a number of other taxa of ranks varying from family to subgenus have terms for their study, including agrostology ( or graminology ) for the study of grasses, synantherology for the study of composites, and batology for the study of brambles. study can also be divided by guild rather than clade or grade. for example, dendrology is the study of woody plants. many divisions of biology have botanical subfields. these are commonly denoted by prefixing the word plant ( e. g. plant taxonomy, plant ecology, plant anatomy, plant morphology, plant systematics ), or prefixing or substituting the prefix phyto - ( e. g. phytochemistry, phytogeography ). the study of fossil plants is called palaeobotany. other fields are denoted by adding or substituting the word botany ( e. g. systematic botany ). phytosociology is a subfield of plant ecology that classifies and studies communities of plants. the intersection of fields from the above pair of categories gives rise to fields such as bryogeography, the study of the distribution of mosses. different parts of plants also give rise to their own subfields, including xylology, carpology ( or fructology ), and palynology, these being the study of wood, fruit and pollen / spores respectively. botany also overlaps on the one hand with agriculture, horticulture and silviculture, and on the other hand with medicine and pharmacology, giving rise to fields such as agronomy, horticultural botany, phytopathology, and phytopharmacology. = = scope and importance = = the study of plants is vital because they underpin almost all animal life on earth by generating a large proportion of the oxygen and food that provide humans and other organisms with aerobic respiration with the chemical energy they need to exist. plants, algae and cyanobacteria are the major groups of organisms that carry out photosynthesis, a process that uses the energy of sunlight to convert water and carbon dioxide into sugars that can be used both as a source of chemical energy and of organic molecules that are used in
Question: A _______ of biology is a fundamental concept that is just as true for a bee or a sunflower as it is for us.
A) principle
B) theory
C) hypothesis
D) notion
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A) principle
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Context:
in steady state, the fuel cycle of a fusion plasma requires inward particle fluxes of fuel ions. these particle flows are also accompanied by heating. in the case of classical transport in a rotating cylindrical plasma, this heating can proceed through several distinct channels depending on the physical mechanisms involved. some channels directly heat the fuel ions themselves, whereas others heat electrons. which channel dominates depends, in general, on the details of the temperature, density, and rotation profiles of the plasma constituents. however, remarkably, under relatively few assumptions concerning these profiles, if the alpha particles, the byproducts of the fusion reaction, can be removed directly by other means, a hot - ion mode tends to emerge naturally.
10 kgy most food, which is ( with regard to warming ) physically equivalent to water, would warm by only about 2. 5 Β°c ( 4. 5 Β°f ). the specialty of processing food by ionizing radiation is the fact, that the energy density per atomic transition is very high, it can cleave molecules and induce ionization ( hence the name ) which cannot be achieved by mere heating. this is the reason for new beneficial effects, however at the same time, for new concerns. the treatment of solid food by ionizing radiation can provide an effect similar to heat pasteurization of liquids, such as milk. however, the use of the term, cold pasteurization, to describe irradiated foods is controversial, because pasteurization and irradiation are fundamentally different processes, although the intended end results can in some cases be similar. detractors of food irradiation have concerns about the health hazards of induced radioactivity. a report for the industry advocacy group american council on science and health entitled " irradiated foods " states : " the types of radiation sources approved for the treatment of foods have specific energy levels well below that which would cause any element in food to become radioactive. food undergoing irradiation does not become any more radioactive than luggage passing through an airport x - ray scanner or teeth that have been x - rayed. " food irradiation is currently permitted by over 40 countries and volumes are estimated to exceed 500, 000 metric tons ( 490, 000 long tons ; 550, 000 short tons ) annually worldwide. food irradiation is essentially a non - nuclear technology ; it relies on the use of ionizing radiation which may be generated by accelerators for electrons and conversion into bremsstrahlung, but which may use also gamma - rays from nuclear decay. there is a worldwide industry for processing by ionizing radiation, the majority by number and by processing power using accelerators. food irradiation is only a niche application compared to medical supplies, plastic materials, raw materials, gemstones, cables and wires, etc. = = accidents = = nuclear accidents, because of the powerful forces involved, are often very dangerous. historically, the first incidents involved fatal radiation exposure. marie curie died from aplastic anemia which resulted from her high levels of exposure. two scientists, an american and canadian respectively, harry daghlian and louis slotin, died after mishandling the same plutonium mass. unlike conventional weapons, the intense light, heat, and explosive force is
which constitutes anywhere from 30 % [ m / m ] to 90 % [ m / m ] of its composition by volume, yielding an array of materials with interesting thermomechanical properties. in the processing of glass - ceramics, molten glass is cooled down gradually before reheating and annealing. in this heat treatment the glass partly crystallizes. in many cases, so - called ' nucleation agents ' are added in order to regulate and control the crystallization process. because there is usually no pressing and sintering, glass - ceramics do not contain the volume fraction of porosity typically present in sintered ceramics. the term mainly refers to a mix of lithium and aluminosilicates which yields an array of materials with interesting thermomechanical properties. the most commercially important of these have the distinction of being impervious to thermal shock. thus, glass - ceramics have become extremely useful for countertop cooking. the negative thermal expansion coefficient ( tec ) of the crystalline ceramic phase can be balanced with the positive tec of the glassy phase. at a certain point ( ~ 70 % crystalline ) the glass - ceramic has a net tec near zero. this type of glass - ceramic exhibits excellent mechanical properties and can sustain repeated and quick temperature changes up to 1000 Β°c. = = processing steps = = the traditional ceramic process generally follows this sequence : milling β batching β mixing β forming β drying β firing β assembly. milling is the process by which materials are reduced from a large size to a smaller size. milling may involve breaking up cemented material ( in which case individual particles retain their shape ) or pulverization ( which involves grinding the particles themselves to a smaller size ). milling is generally done by mechanical means, including attrition ( which is particle - to - particle collision that results in agglomerate break up or particle shearing ), compression ( which applies a forces that results in fracturing ), and impact ( which employs a milling medium or the particles themselves to cause fracturing ). attrition milling equipment includes the wet scrubber ( also called the planetary mill or wet attrition mill ), which has paddles in water creating vortexes in which the material collides and break up. compression mills include the jaw crusher, roller crusher and cone crusher. impact mills include the ball mill, which has media that tumble and fracture the material, or the resonantacoustic mixer. shaft impactors cause particle - to particle attrition and compression
the attenuation length and refractive index of liquid xenon for intrinsic scintillation light ( 178nm ) have been measured in a single experiment. the value obtained for attenuation length is 364 + - 18 mm. the refractive index is found to be 1. 69 + - 0. 02. both values were measured at a temperature of 170 + - 1 k.
the responds of different common alkali halide crystals to alpha - rays and gamma - rays are tested in our research. it is found that only csi ( na ) crystals have significantly different waveforms between alpha and gamma scintillations, while others have not this phenomena. it is suggested that the fast light of csi ( na ) crystals arises from the recombination of free electrons with self - trapped holes of the host crystal csi. self - absorption limits the emission of fast light of csi ( tl ) and nai ( tl ) crystals.
building block. ceramics β not to be confused with raw, unfired clay β are usually seen in crystalline form. the vast majority of commercial glasses contain a metal oxide fused with silica. at the high temperatures used to prepare glass, the material is a viscous liquid which solidifies into a disordered state upon cooling. windowpanes and eyeglasses are important examples. fibers of glass are also used for long - range telecommunication and optical transmission. scratch resistant corning gorilla glass is a well - known example of the application of materials science to drastically improve the properties of common components. engineering ceramics are known for their stiffness and stability under high temperatures, compression and electrical stress. alumina, silicon carbide, and tungsten carbide are made from a fine powder of their constituents in a process of sintering with a binder. hot pressing provides higher density material. chemical vapor deposition can place a film of a ceramic on another material. cermets are ceramic particles containing some metals. the wear resistance of tools is derived from cemented carbides with the metal phase of cobalt and nickel typically added to modify properties. ceramics can be significantly strengthened for engineering applications using the principle of crack deflection. this process involves the strategic addition of second - phase particles within a ceramic matrix, optimizing their shape, size, and distribution to direct and control crack propagation. this approach enhances fracture toughness, paving the way for the creation of advanced, high - performance ceramics in various industries. = = = composites = = = another application of materials science in industry is making composite materials. these are structured materials composed of two or more macroscopic phases. applications range from structural elements such as steel - reinforced concrete, to the thermal insulating tiles, which play a key and integral role in nasa ' s space shuttle thermal protection system, which is used to protect the surface of the shuttle from the heat of re - entry into the earth ' s atmosphere. one example is reinforced carbon - carbon ( rcc ), the light gray material, which withstands re - entry temperatures up to 1, 510 Β°c ( 2, 750 Β°f ) and protects the space shuttle ' s wing leading edges and nose cap. rcc is a laminated composite material made from graphite rayon cloth and impregnated with a phenolic resin. after curing at high temperature in an autoclave, the laminate is pyrolized to convert the resin to carbon, impregnated with furfuryl alcohol in a
i build a melting temperature database that contains approximately 10, 000 materials. based on the database, i build a machine learning model that predicts melting temperature in seconds. the model features graph neural network and residual neural network architecture. the root - mean - square errors of melting temperature are 90 and 160k for training and testing, respectively. the model is deployed online and is publicly available.
superdielectric behavior was observed in pastes made of high surface area alumina filled to the level of incipient wetness with water containing dissolved sodium chloride ( table salt ). in some cases the dielectric constants were greater than 10 ^ 10.
the graphane with chemically bonded alkali metals ( li, na, k ) was considered as potential material for hydrogen storage. the ab initio calculations show that such material can adsorb as many as 4 hydrogen molecules per li, na and k metal atoms. these values correspond to 12. 20 wt %, 10. 33 wt % and 8. 56 wt % of hydrogen, respectively and exceed the doe requirements. the thermodynamic analysis shows that li - graphane complex is the most promising for hydrogen storage with ability to adsorb 3 hydrogen molecules per metal atom at 300 k and pressure in the range from 5 to 250 atm.
various mechanisms of thermal photon production are reviewed and their implications for heavy ion collisions are briefly sketched.
Question: Ionic liquids heating a salt to its melting point produces a what?
A) table salt
B) plasma
C) gas
D) molten salt
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D) molten salt
|
Context:
. the phase of matter is defined by the phase transition, which is when energy put into or taken out of the system goes into rearranging the structure of the system, instead of changing the bulk conditions. sometimes the distinction between phases can be continuous instead of having a discrete boundary ; in this case the matter is considered to be in a supercritical state. when three states meet based on the conditions, it is known as a triple point and since this is invariant, it is a convenient way to define a set of conditions. the most familiar examples of phases are solids, liquids, and gases. many substances exhibit multiple solid phases. for example, there are three phases of solid iron ( alpha, gamma, and delta ) that vary based on temperature and pressure. a principal difference between solid phases is the crystal structure, or arrangement, of the atoms. another phase commonly encountered in the study of chemistry is the aqueous phase, which is the state of substances dissolved in aqueous solution ( that is, in water ). less familiar phases include plasmas, bose β einstein condensates and fermionic condensates and the paramagnetic and ferromagnetic phases of magnetic materials. while most familiar phases deal with three - dimensional systems, it is also possible to define analogs in two - dimensional systems, which has received attention for its relevance to systems in biology. = = = bonding = = = atoms sticking together in molecules or crystals are said to be bonded with one another. a chemical bond may be visualized as the multipole balance between the positive charges in the nuclei and the negative charges oscillating about them. more than simple attraction and repulsion, the energies and distributions characterize the availability of an electron to bond to another atom. the chemical bond can be a covalent bond, an ionic bond, a hydrogen bond or just because of van der waals force. each of these kinds of bonds is ascribed to some potential. these potentials create the interactions which hold atoms together in molecules or crystals. in many simple compounds, valence bond theory, the valence shell electron pair repulsion model ( vsepr ), and the concept of oxidation number can be used to explain molecular structure and composition. an ionic bond is formed when a metal loses one or more of its electrons, becoming a positively charged cation, and the electrons are then gained by the non - metal atom, becoming a negatively charged anion. the two oppositely charged ions attract one another, and the ionic bond
classifications ; however, some more exotic phases are incompatible with certain chemical properties. a phase is a set of states of a chemical system that have similar bulk structural properties, over a range of conditions, such as pressure or temperature. physical properties, such as density and refractive index tend to fall within values characteristic of the phase. the phase of matter is defined by the phase transition, which is when energy put into or taken out of the system goes into rearranging the structure of the system, instead of changing the bulk conditions. sometimes the distinction between phases can be continuous instead of having a discrete boundary ; in this case the matter is considered to be in a supercritical state. when three states meet based on the conditions, it is known as a triple point and since this is invariant, it is a convenient way to define a set of conditions. the most familiar examples of phases are solids, liquids, and gases. many substances exhibit multiple solid phases. for example, there are three phases of solid iron ( alpha, gamma, and delta ) that vary based on temperature and pressure. a principal difference between solid phases is the crystal structure, or arrangement, of the atoms. another phase commonly encountered in the study of chemistry is the aqueous phase, which is the state of substances dissolved in aqueous solution ( that is, in water ). less familiar phases include plasmas, bose β einstein condensates and fermionic condensates and the paramagnetic and ferromagnetic phases of magnetic materials. while most familiar phases deal with three - dimensional systems, it is also possible to define analogs in two - dimensional systems, which has received attention for its relevance to systems in biology. = = = bonding = = = atoms sticking together in molecules or crystals are said to be bonded with one another. a chemical bond may be visualized as the multipole balance between the positive charges in the nuclei and the negative charges oscillating about them. more than simple attraction and repulsion, the energies and distributions characterize the availability of an electron to bond to another atom. the chemical bond can be a covalent bond, an ionic bond, a hydrogen bond or just because of van der waals force. each of these kinds of bonds is ascribed to some potential. these potentials create the interactions which hold atoms together in molecules or crystals. in many simple compounds, valence bond theory, the valence shell electron pair repulsion model ( vsepr ), and the concept of oxidation number can be used
or solid as is the case with water ( h2o ) ; a liquid at room temperature because its molecules are bound by hydrogen bonds. whereas hydrogen sulfide ( h2s ) is a gas at room temperature and standard pressure, as its molecules are bound by weaker dipole β dipole interactions. the transfer of energy from one chemical substance to another depends on the size of energy quanta emitted from one substance. however, heat energy is often transferred more easily from almost any substance to another because the phonons responsible for vibrational and rotational energy levels in a substance have much less energy than photons invoked for the electronic energy transfer. thus, because vibrational and rotational energy levels are more closely spaced than electronic energy levels, heat is more easily transferred between substances relative to light or other forms of electronic energy. for example, ultraviolet electromagnetic radiation is not transferred with as much efficacy from one substance to another as thermal or electrical energy. the existence of characteristic energy levels for different chemical substances is useful for their identification by the analysis of spectral lines. different kinds of spectra are often used in chemical spectroscopy, e. g. ir, microwave, nmr, esr, etc. spectroscopy is also used to identify the composition of remote objects β like stars and distant galaxies β by analyzing their radiation spectra. the term chemical energy is often used to indicate the potential of a chemical substance to undergo a transformation through a chemical reaction or to transform other chemical substances. = = = reaction = = = when a chemical substance is transformed as a result of its interaction with another substance or with energy, a chemical reaction is said to have occurred. a chemical reaction is therefore a concept related to the " reaction " of a substance when it comes in close contact with another, whether as a mixture or a solution ; exposure to some form of energy, or both. it results in some energy exchange between the constituents of the reaction as well as with the system environment, which may be designed vessels β often laboratory glassware. chemical reactions can result in the formation or dissociation of molecules, that is, molecules breaking apart to form two or more molecules or rearrangement of atoms within or across molecules. chemical reactions usually involve the making or breaking of chemical bonds. oxidation, reduction, dissociation, acid β base neutralization and molecular rearrangement are some examples of common chemical reactions. a chemical reaction can be symbolically depicted through a chemical equation. while in a non - nuclear chemical reaction the number and kind of atoms on both sides of the equation are equal, for
; that is, more amenable to chemical reactions. the phase of a substance is invariably determined by its energy and the energy of its surroundings. when the intermolecular forces of a substance are such that the energy of the surroundings is not sufficient to overcome them, it occurs in a more ordered phase like liquid or solid as is the case with water ( h2o ) ; a liquid at room temperature because its molecules are bound by hydrogen bonds. whereas hydrogen sulfide ( h2s ) is a gas at room temperature and standard pressure, as its molecules are bound by weaker dipole β dipole interactions. the transfer of energy from one chemical substance to another depends on the size of energy quanta emitted from one substance. however, heat energy is often transferred more easily from almost any substance to another because the phonons responsible for vibrational and rotational energy levels in a substance have much less energy than photons invoked for the electronic energy transfer. thus, because vibrational and rotational energy levels are more closely spaced than electronic energy levels, heat is more easily transferred between substances relative to light or other forms of electronic energy. for example, ultraviolet electromagnetic radiation is not transferred with as much efficacy from one substance to another as thermal or electrical energy. the existence of characteristic energy levels for different chemical substances is useful for their identification by the analysis of spectral lines. different kinds of spectra are often used in chemical spectroscopy, e. g. ir, microwave, nmr, esr, etc. spectroscopy is also used to identify the composition of remote objects β like stars and distant galaxies β by analyzing their radiation spectra. the term chemical energy is often used to indicate the potential of a chemical substance to undergo a transformation through a chemical reaction or to transform other chemical substances. = = = reaction = = = when a chemical substance is transformed as a result of its interaction with another substance or with energy, a chemical reaction is said to have occurred. a chemical reaction is therefore a concept related to the " reaction " of a substance when it comes in close contact with another, whether as a mixture or a solution ; exposure to some form of energy, or both. it results in some energy exchange between the constituents of the reaction as well as with the system environment, which may be designed vessels β often laboratory glassware. chemical reactions can result in the formation or dissociation of molecules, that is, molecules breaking apart to form two or more molecules or rearrangement of atoms within or across molecules. chemical reactions usually involve the making or breaking of chemical bonds
building block. ceramics β not to be confused with raw, unfired clay β are usually seen in crystalline form. the vast majority of commercial glasses contain a metal oxide fused with silica. at the high temperatures used to prepare glass, the material is a viscous liquid which solidifies into a disordered state upon cooling. windowpanes and eyeglasses are important examples. fibers of glass are also used for long - range telecommunication and optical transmission. scratch resistant corning gorilla glass is a well - known example of the application of materials science to drastically improve the properties of common components. engineering ceramics are known for their stiffness and stability under high temperatures, compression and electrical stress. alumina, silicon carbide, and tungsten carbide are made from a fine powder of their constituents in a process of sintering with a binder. hot pressing provides higher density material. chemical vapor deposition can place a film of a ceramic on another material. cermets are ceramic particles containing some metals. the wear resistance of tools is derived from cemented carbides with the metal phase of cobalt and nickel typically added to modify properties. ceramics can be significantly strengthened for engineering applications using the principle of crack deflection. this process involves the strategic addition of second - phase particles within a ceramic matrix, optimizing their shape, size, and distribution to direct and control crack propagation. this approach enhances fracture toughness, paving the way for the creation of advanced, high - performance ceramics in various industries. = = = composites = = = another application of materials science in industry is making composite materials. these are structured materials composed of two or more macroscopic phases. applications range from structural elements such as steel - reinforced concrete, to the thermal insulating tiles, which play a key and integral role in nasa ' s space shuttle thermal protection system, which is used to protect the surface of the shuttle from the heat of re - entry into the earth ' s atmosphere. one example is reinforced carbon - carbon ( rcc ), the light gray material, which withstands re - entry temperatures up to 1, 510 Β°c ( 2, 750 Β°f ) and protects the space shuttle ' s wing leading edges and nose cap. rcc is a laminated composite material made from graphite rayon cloth and impregnated with a phenolic resin. after curing at high temperature in an autoclave, the laminate is pyrolized to convert the resin to carbon, impregnated with furfuryl alcohol in a
casting, also called the lost wax process, die casting, centrifugal casting, both vertical and horizontal, and continuous castings. each of these forms has advantages for certain metals and applications considering factors like magnetism and corrosion. forging β a red - hot billet is hammered into shape. rolling β a billet is passed through successively narrower rollers to create a sheet. extrusion β a hot and malleable metal is forced under pressure through a die, which shapes it before it cools. machining β lathes, milling machines and drills cut the cold metal to shape. sintering β a powdered metal is heated in a non - oxidizing environment after being compressed into a die. fabrication β sheets of metal are cut with guillotines or gas cutters and bent and welded into structural shape. laser cladding β metallic powder is blown through a movable laser beam ( e. g. mounted on a nc 5 - axis machine ). the resulting melted metal reaches a substrate to form a melt pool. by moving the laser head, it is possible to stack the tracks and build up a three - dimensional piece. 3d printing β sintering or melting amorphous powder metal in a 3d space to make any object to shape. cold - working processes, in which the product ' s shape is altered by rolling, fabrication or other processes, while the product is cold, can increase the strength of the product by a process called work hardening. work hardening creates microscopic defects in the metal, which resist further changes of shape. = = = heat treatment = = = metals can be heat - treated to alter the properties of strength, ductility, toughness, hardness and resistance to corrosion. common heat treatment processes include annealing, precipitation strengthening, quenching, and tempering : annealing process softens the metal by heating it and then allowing it to cool very slowly, which gets rid of stresses in the metal and makes the grain structure large and soft - edged so that, when the metal is hit or stressed it dents or perhaps bends, rather than breaking ; it is also easier to sand, grind, or cut annealed metal. quenching is the process of cooling metal very quickly after heating, thus " freezing " the metal ' s molecules in the very hard martensite form, which makes the metal harder. tempering relieves stresses in the metal that were caused by the hardening process ; tempering makes the metal less hard while making it better able to sustain
the recent report on laser cooling of liquid may contradict the law of energy conservation.
temperature changes up to 1000 Β°c. = = processing steps = = the traditional ceramic process generally follows this sequence : milling β batching β mixing β forming β drying β firing β assembly. milling is the process by which materials are reduced from a large size to a smaller size. milling may involve breaking up cemented material ( in which case individual particles retain their shape ) or pulverization ( which involves grinding the particles themselves to a smaller size ). milling is generally done by mechanical means, including attrition ( which is particle - to - particle collision that results in agglomerate break up or particle shearing ), compression ( which applies a forces that results in fracturing ), and impact ( which employs a milling medium or the particles themselves to cause fracturing ). attrition milling equipment includes the wet scrubber ( also called the planetary mill or wet attrition mill ), which has paddles in water creating vortexes in which the material collides and break up. compression mills include the jaw crusher, roller crusher and cone crusher. impact mills include the ball mill, which has media that tumble and fracture the material, or the resonantacoustic mixer. shaft impactors cause particle - to particle attrition and compression. batching is the process of weighing the oxides according to recipes, and preparing them for mixing and drying. mixing occurs after batching and is performed with various machines, such as dry mixing ribbon mixers ( a type of cement mixer ), resonantacoustic mixers, mueller mixers, and pug mills. wet mixing generally involves the same equipment. forming is making the mixed material into shapes, ranging from toilet bowls to spark plug insulators. forming can involve : ( 1 ) extrusion, such as extruding " slugs " to make bricks, ( 2 ) pressing to make shaped parts, ( 3 ) slip casting, as in making toilet bowls, wash basins and ornamentals like ceramic statues. forming produces a " green " part, ready for drying. green parts are soft, pliable, and over time will lose shape. handling the green product will change its shape. for example, a green brick can be " squeezed ", and after squeezing it will stay that way. drying is removing the water or binder from the formed material. spray drying is widely used to prepare powder for pressing operations. other dryers are tunnel dryers and periodic dryers. controlled heat is applied in this two - stage process. first,
##tering - based methods are simple ( " sinter " has roots in the english " cinder " ). the firing is done at a temperature below the melting point of the ceramic. once a roughly - held - together object called a " green body " is made, it is fired in a kiln, where atomic and molecular diffusion processes give rise to significant changes in the primary microstructural features. this includes the gradual elimination of porosity, which is typically accompanied by a net shrinkage and overall densification of the component. thus, the pores in the object may close up, resulting in a denser product of significantly greater strength and fracture toughness. another major change in the body during the firing or sintering process will be the establishment of the polycrystalline nature of the solid. significant grain growth tends to occur during sintering, with this growth depending on temperature and duration of the sintering process. the growth of grains will result in some form of grain size distribution, which will have a significant impact on the ultimate physical properties of the material. in particular, abnormal grain growth in which certain grains grow very large in a matrix of finer grains will significantly alter the physical and mechanical properties of the obtained ceramic. in the sintered body, grain sizes are a product of the thermal processing parameters as well as the initial particle size, or possibly the sizes of aggregates or particle clusters which arise during the initial stages of processing. the ultimate microstructure ( and thus the physical properties ) of the final product will be limited by and subject to the form of the structural template or precursor which is created in the initial stages of chemical synthesis and physical forming. hence the importance of chemical powder and polymer processing as it pertains to the synthesis of industrial ceramics, glasses and glass - ceramics. there are numerous possible refinements of the sintering process. some of the most common involve pressing the green body to give the densification a head start and reduce the sintering time needed. sometimes organic binders such as polyvinyl alcohol are added to hold the green body together ; these burn out during the firing ( at 200 β 350 Β°c ). sometimes organic lubricants are added during pressing to increase densification. it is common to combine these, and add binders and lubricants to a powder, then press. ( the formulation of these organic chemical additives is an art in itself. this is particularly important in the manufacture of high performance ceramics such as those used by the billions for
10 kgy most food, which is ( with regard to warming ) physically equivalent to water, would warm by only about 2. 5 Β°c ( 4. 5 Β°f ). the specialty of processing food by ionizing radiation is the fact, that the energy density per atomic transition is very high, it can cleave molecules and induce ionization ( hence the name ) which cannot be achieved by mere heating. this is the reason for new beneficial effects, however at the same time, for new concerns. the treatment of solid food by ionizing radiation can provide an effect similar to heat pasteurization of liquids, such as milk. however, the use of the term, cold pasteurization, to describe irradiated foods is controversial, because pasteurization and irradiation are fundamentally different processes, although the intended end results can in some cases be similar. detractors of food irradiation have concerns about the health hazards of induced radioactivity. a report for the industry advocacy group american council on science and health entitled " irradiated foods " states : " the types of radiation sources approved for the treatment of foods have specific energy levels well below that which would cause any element in food to become radioactive. food undergoing irradiation does not become any more radioactive than luggage passing through an airport x - ray scanner or teeth that have been x - rayed. " food irradiation is currently permitted by over 40 countries and volumes are estimated to exceed 500, 000 metric tons ( 490, 000 long tons ; 550, 000 short tons ) annually worldwide. food irradiation is essentially a non - nuclear technology ; it relies on the use of ionizing radiation which may be generated by accelerators for electrons and conversion into bremsstrahlung, but which may use also gamma - rays from nuclear decay. there is a worldwide industry for processing by ionizing radiation, the majority by number and by processing power using accelerators. food irradiation is only a niche application compared to medical supplies, plastic materials, raw materials, gemstones, cables and wires, etc. = = accidents = = nuclear accidents, because of the powerful forces involved, are often very dangerous. historically, the first incidents involved fatal radiation exposure. marie curie died from aplastic anemia which resulted from her high levels of exposure. two scientists, an american and canadian respectively, harry daghlian and louis slotin, died after mishandling the same plutonium mass. unlike conventional weapons, the intense light, heat, and explosive force is
Question: What is the term for the temperature at which a solid changes into a liquid?
A) the pressure point
B) the mixture point
C) the melting point
D) the starting point
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C) the melting point
|
Context:
), electron transport chain, and oxidative phosphorylation. glycolysis is a metabolic process that occurs in the cytoplasm whereby glucose is converted into two pyruvates, with two net molecules of atp being produced at the same time. each pyruvate is then oxidized into acetyl - coa by the pyruvate dehydrogenase complex, which also generates nadh and carbon dioxide. acetyl - coa enters the citric acid cycle, which takes places inside the mitochondrial matrix. at the end of the cycle, the total yield from 1 glucose ( or 2 pyruvates ) is 6 nadh, 2 fadh2, and 2 atp molecules. finally, the next stage is oxidative phosphorylation, which in eukaryotes, occurs in the mitochondrial cristae. oxidative phosphorylation comprises the electron transport chain, which is a series of four protein complexes that transfer electrons from one complex to another, thereby releasing energy from nadh and fadh2 that is coupled to the pumping of protons ( hydrogen ions ) across the inner mitochondrial membrane ( chemiosmosis ), which generates a proton motive force. energy from the proton motive force drives the enzyme atp synthase to synthesize more atps by phosphorylating adps. the transfer of electrons terminates with molecular oxygen being the final electron acceptor. if oxygen were not present, pyruvate would not be metabolized by cellular respiration but undergoes a process of fermentation. the pyruvate is not transported into the mitochondrion but remains in the cytoplasm, where it is converted to waste products that may be removed from the cell. this serves the purpose of oxidizing the electron carriers so that they can perform glycolysis again and removing the excess pyruvate. fermentation oxidizes nadh to nad + so it can be re - used in glycolysis. in the absence of oxygen, fermentation prevents the buildup of nadh in the cytoplasm and provides nad + for glycolysis. this waste product varies depending on the organism. in skeletal muscles, the waste product is lactic acid. this type of fermentation is called lactic acid fermentation. in strenuous exercise, when energy demands exceed energy supply, the respiratory chain cannot process all of the hydrogen atoms joined by
slow, controlled release of energy from the series of reactions. sugar in the form of glucose is the main nutrient used by animal and plant cells in respiration. cellular respiration involving oxygen is called aerobic respiration, which has four stages : glycolysis, citric acid cycle ( or krebs cycle ), electron transport chain, and oxidative phosphorylation. glycolysis is a metabolic process that occurs in the cytoplasm whereby glucose is converted into two pyruvates, with two net molecules of atp being produced at the same time. each pyruvate is then oxidized into acetyl - coa by the pyruvate dehydrogenase complex, which also generates nadh and carbon dioxide. acetyl - coa enters the citric acid cycle, which takes places inside the mitochondrial matrix. at the end of the cycle, the total yield from 1 glucose ( or 2 pyruvates ) is 6 nadh, 2 fadh2, and 2 atp molecules. finally, the next stage is oxidative phosphorylation, which in eukaryotes, occurs in the mitochondrial cristae. oxidative phosphorylation comprises the electron transport chain, which is a series of four protein complexes that transfer electrons from one complex to another, thereby releasing energy from nadh and fadh2 that is coupled to the pumping of protons ( hydrogen ions ) across the inner mitochondrial membrane ( chemiosmosis ), which generates a proton motive force. energy from the proton motive force drives the enzyme atp synthase to synthesize more atps by phosphorylating adps. the transfer of electrons terminates with molecular oxygen being the final electron acceptor. if oxygen were not present, pyruvate would not be metabolized by cellular respiration but undergoes a process of fermentation. the pyruvate is not transported into the mitochondrion but remains in the cytoplasm, where it is converted to waste products that may be removed from the cell. this serves the purpose of oxidizing the electron carriers so that they can perform glycolysis again and removing the excess pyruvate. fermentation oxidizes nadh to nad + so it can be re - used in glycolysis. in the absence of oxygen, fermentation prevents the buildup of nadh in the cytoplasm and provides nad + for gly
liver glycogen. during recovery, when oxygen becomes available, nad + attaches to hydrogen from lactate to form atp. in yeast, the waste products are ethanol and carbon dioxide. this type of fermentation is known as alcoholic or ethanol fermentation. the atp generated in this process is made by substrate - level phosphorylation, which does not require oxygen. = = = photosynthesis = = = photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organism ' s metabolic activities via cellular respiration. this chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. in most cases, oxygen is released as a waste product. most plants, algae, and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of the earth ' s atmosphere, and supplies most of the energy necessary for life on earth. photosynthesis has four stages : light absorption, electron transport, atp synthesis, and carbon fixation. light absorption is the initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to proteins in the thylakoid membranes. the absorbed light energy is used to remove electrons from a donor ( water ) to a primary electron acceptor, a quinone designated as q. in the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach a final electron acceptor, which is usually the oxidized form of nadp +, which is reduced to nadph, a process that takes place in a protein complex called photosystem i ( psi ). the transport of electrons is coupled to the movement of protons ( or hydrogen ) from the stroma to the thylakoid membrane, which forms a ph gradient across the membrane as hydrogen becomes more concentrated in the lumen than in the stroma. this is analogous to the proton - motive force generated across the inner mitochondrial membrane in aerobic respiration. during the third stage of photosynthesis, the movement of protons down their concentration gradients from the thylakoid lumen to the stroma through the atp synthase is coupled to the synthesis of atp by that same atp synthase. the nadph and atps generated by the light - dependent reactions in the second and third stages, respectively, provide the energy and
##ysis again and removing the excess pyruvate. fermentation oxidizes nadh to nad + so it can be re - used in glycolysis. in the absence of oxygen, fermentation prevents the buildup of nadh in the cytoplasm and provides nad + for glycolysis. this waste product varies depending on the organism. in skeletal muscles, the waste product is lactic acid. this type of fermentation is called lactic acid fermentation. in strenuous exercise, when energy demands exceed energy supply, the respiratory chain cannot process all of the hydrogen atoms joined by nadh. during anaerobic glycolysis, nad + regenerates when pairs of hydrogen combine with pyruvate to form lactate. lactate formation is catalyzed by lactate dehydrogenase in a reversible reaction. lactate can also be used as an indirect precursor for liver glycogen. during recovery, when oxygen becomes available, nad + attaches to hydrogen from lactate to form atp. in yeast, the waste products are ethanol and carbon dioxide. this type of fermentation is known as alcoholic or ethanol fermentation. the atp generated in this process is made by substrate - level phosphorylation, which does not require oxygen. = = = photosynthesis = = = photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organism ' s metabolic activities via cellular respiration. this chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. in most cases, oxygen is released as a waste product. most plants, algae, and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of the earth ' s atmosphere, and supplies most of the energy necessary for life on earth. photosynthesis has four stages : light absorption, electron transport, atp synthesis, and carbon fixation. light absorption is the initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to proteins in the thylakoid membranes. the absorbed light energy is used to remove electrons from a donor ( water ) to a primary electron acceptor, a quinone designated as q. in the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach a
. respiration is one of the key ways a cell releases chemical energy to fuel cellular activity. the overall reaction occurs in a series of biochemical steps, some of which are redox reactions. although cellular respiration is technically a combustion reaction, it clearly does not resemble one when it occurs in a cell because of the slow, controlled release of energy from the series of reactions. sugar in the form of glucose is the main nutrient used by animal and plant cells in respiration. cellular respiration involving oxygen is called aerobic respiration, which has four stages : glycolysis, citric acid cycle ( or krebs cycle ), electron transport chain, and oxidative phosphorylation. glycolysis is a metabolic process that occurs in the cytoplasm whereby glucose is converted into two pyruvates, with two net molecules of atp being produced at the same time. each pyruvate is then oxidized into acetyl - coa by the pyruvate dehydrogenase complex, which also generates nadh and carbon dioxide. acetyl - coa enters the citric acid cycle, which takes places inside the mitochondrial matrix. at the end of the cycle, the total yield from 1 glucose ( or 2 pyruvates ) is 6 nadh, 2 fadh2, and 2 atp molecules. finally, the next stage is oxidative phosphorylation, which in eukaryotes, occurs in the mitochondrial cristae. oxidative phosphorylation comprises the electron transport chain, which is a series of four protein complexes that transfer electrons from one complex to another, thereby releasing energy from nadh and fadh2 that is coupled to the pumping of protons ( hydrogen ions ) across the inner mitochondrial membrane ( chemiosmosis ), which generates a proton motive force. energy from the proton motive force drives the enzyme atp synthase to synthesize more atps by phosphorylating adps. the transfer of electrons terminates with molecular oxygen being the final electron acceptor. if oxygen were not present, pyruvate would not be metabolized by cellular respiration but undergoes a process of fermentation. the pyruvate is not transported into the mitochondrion but remains in the cytoplasm, where it is converted to waste products that may be removed from the cell. this serves the purpose of oxidizing the electron carriers so that they can perform glycol
an oscillation with a period of around 500 kb in guanine and cytosine content ( gc % ) is observed in the dna sequence of human chromosome 21. this oscillation is localized in the rightmost one - eighth region of the chromosome, from 43. 5 mb to 46. 5 mb. five cycles of oscillation are observed in this region with six gc - rich peaks and five gc - poor valleys. the gc - poor valleys comprise regions with low density of cpg islands and, alternating between the two dna strands, low gene density regions. consequently, the long - range oscillation of gc % result in spacing patterns of both cpg island density, and to a lesser extent, gene densities.
and myelomas can be made to fuse by chemical protocols, most often using polyethylene glycol. the myeloma cells are selected beforehand to ensure they are not secreting antibody themselves and that they lack the hypoxanthine - guanine phosphoribosyltransferase ( hgprt ) gene, making them sensitive ( or vulnerable ) to the hat medium ( see below ). fused cells are incubated in hat medium ( hypoxanthine - aminopterin - thymidine medium ) for roughly 10 to 14 days. aminopterin blocks the pathway that allows for nucleotide synthesis. hence, unfused myeloma cells die, as they cannot produce nucleotides by the de novo or salvage pathways because they lack hgprt. removal of the unfused myeloma cells is necessary because they have the potential to outgrow other cells, especially weakly established hybridomas. unfused b cells die as they have a short life span. in this way, only the b cell - myeloma hybrids survive, since the hgprt gene coming from the b cells is functional. these cells produce antibodies ( a property of b cells ) and are immortal ( a property of myeloma cells ). the incubated medium is then diluted into multi - well plates to such an extent that each well contains only one cell. since the antibodies in a well are produced by the same b cell, they will be directed towards the same epitope, and are thus monoclonal antibodies. the next stage is a rapid primary screening process, which identifies and selects only those hybridomas that produce antibodies of appropriate specificity. the first screening technique used is called elisa. the hybridoma culture supernatant, secondary enzyme labeled conjugate, and chromogenic substrate, are then incubated, and the formation of a colored product indicates a positive hybridoma. alternatively, immunocytochemical, western blot, and immunoprecipitation - mass spectrometry. unlike western blot assays, immunoprecipitation - mass spectrometry facilitates screening and ranking of clones which bind to the native ( non - denaturated ) forms of antigen proteins. flow cytometry screening has been used for primary screening of a large number ( ~ 1000 ) of hybridoma clones recognizing the native form of the antigen on the cell surface. in the flow
a process of fermentation. the pyruvate is not transported into the mitochondrion but remains in the cytoplasm, where it is converted to waste products that may be removed from the cell. this serves the purpose of oxidizing the electron carriers so that they can perform glycolysis again and removing the excess pyruvate. fermentation oxidizes nadh to nad + so it can be re - used in glycolysis. in the absence of oxygen, fermentation prevents the buildup of nadh in the cytoplasm and provides nad + for glycolysis. this waste product varies depending on the organism. in skeletal muscles, the waste product is lactic acid. this type of fermentation is called lactic acid fermentation. in strenuous exercise, when energy demands exceed energy supply, the respiratory chain cannot process all of the hydrogen atoms joined by nadh. during anaerobic glycolysis, nad + regenerates when pairs of hydrogen combine with pyruvate to form lactate. lactate formation is catalyzed by lactate dehydrogenase in a reversible reaction. lactate can also be used as an indirect precursor for liver glycogen. during recovery, when oxygen becomes available, nad + attaches to hydrogen from lactate to form atp. in yeast, the waste products are ethanol and carbon dioxide. this type of fermentation is known as alcoholic or ethanol fermentation. the atp generated in this process is made by substrate - level phosphorylation, which does not require oxygen. = = = photosynthesis = = = photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organism ' s metabolic activities via cellular respiration. this chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. in most cases, oxygen is released as a waste product. most plants, algae, and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of the earth ' s atmosphere, and supplies most of the energy necessary for life on earth. photosynthesis has four stages : light absorption, electron transport, atp synthesis, and carbon fixation. light absorption is the initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to
kidneys and the majority of those currently in use are extracorporeal, such as with hemodialysis, which filters blood directly, or peritoneal dialysis, which filters via a fluid in the abdomen. in order to contribute to the biological functions of a kidney such as producing metabolic factors or hormones, some artificial kidneys incorporate renal cells. there has been progress in the way of making these devices smaller and more transportable, or even implantable. one challenge still to be faced in these smaller devices is countering the limited volume and therefore limited filtering capabilities. bioscaffolds have also been introduced to provide a framework upon which normal kidney tissue can be regenerated. these scaffolds encompass natural scaffolds ( e. g., decellularized kidneys, collagen hydrogel, or silk fibroin ), synthetic scaffolds ( e. g., poly [ lactic - co - glycolic acid ] or other polymers ), or a combination of two or more natural and synthetic scaffolds. these scaffolds can be implanted into the body either without cell treatment or after a period of stem cell seeding and incubation. in vitro and in vivo studies are being conducted to compare and optimize the type of scaffold and to assess whether cell seeding prior to implantation adds to the viability, regeneration and effective function of the kidneys. a recent systematic review and meta - analysis compared the results of published animal studies and identified that improved outcomes are reported with the use of hybrid ( mixed ) scaffolds and cell seeding ; however, the meta - analysis of these results were not in agreement with the evaluation of descriptive results from the review. therefore, further studies involving larger animals and novel scaffolds, and more transparent reproduction of previous studies are advisable. = = = biomimetics = = = biomimetics is a field that aims to produce materials and systems that replicate those present in nature. in the context of tissue engineering, this is a common approach used by engineers to create materials for these applications that are comparable to native tissues in terms of their structure, properties, and biocompatibility. material properties are largely dependent on physical, structural, and chemical characteristics of that material. subsequently, a biomimetic approach to system design will become significant in material integration, and a sufficient understanding of biological processes and interactions will be necessary. replication of biological systems and
the best - suited crops ( e. g., those with the highest yields ) to produce enough food to support a growing population. as crops and fields became increasingly large and difficult to maintain, it was discovered that specific organisms and their by - products could effectively fertilize, restore nitrogen, and control pests. throughout the history of agriculture, farmers have inadvertently altered the genetics of their crops through introducing them to new environments and breeding them with other plants β one of the first forms of biotechnology. these processes also were included in early fermentation of beer. these processes were introduced in early mesopotamia, egypt, china and india, and still use the same basic biological methods. in brewing, malted grains ( containing enzymes ) convert starch from grains into sugar and then adding specific yeasts to produce beer. in this process, carbohydrates in the grains broke down into alcohols, such as ethanol. later, other cultures produced the process of lactic acid fermentation, which produced other preserved foods, such as soy sauce. fermentation was also used in this time period to produce leavened bread. although the process of fermentation was not fully understood until louis pasteur ' s work in 1857, it is still the first use of biotechnology to convert a food source into another form. before the time of charles darwin ' s work and life, animal and plant scientists had already used selective breeding. darwin added to that body of work with his scientific observations about the ability of science to change species. these accounts contributed to darwin ' s theory of natural selection. for thousands of years, humans have used selective breeding to improve the production of crops and livestock to use them for food. in selective breeding, organisms with desirable characteristics are mated to produce offspring with the same characteristics. for example, this technique was used with corn to produce the largest and sweetest crops. in the early twentieth century scientists gained a greater understanding of microbiology and explored ways of manufacturing specific products. in 1917, chaim weizmann first used a pure microbiological culture in an industrial process, that of manufacturing corn starch using clostridium acetobutylicum, to produce acetone, which the united kingdom desperately needed to manufacture explosives during world war i. biotechnology has also led to the development of antibiotics. in 1928, alexander fleming discovered the mold penicillium. his work led to the purification of the antibiotic formed by the mold by howard florey, ernst boris chain and norman heatley β to form
Question: What does glycolysis generate in phase ii?
A) atp
B) adp
C) dna
D) amino acids
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A) atp
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Context:
oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions. cell membranes also contain membrane proteins, including integral membrane proteins that go across the membrane serving as membrane transporters, and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes shaping the cell. cell membranes are involved in various cellular processes such as cell adhesion, storing electrical energy, and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall, glycocalyx, and cytoskeleton. within the cytoplasm of a cell, there are many biomolecules such as proteins and nucleic acids. in addition to biomolecules, eukaryotic cells have specialized structures called organelles that have their own lipid bilayers or are spatially units. these organelles include the cell nucleus, which contains most of the cell ' s dna, or mitochondria, which generate adenosine triphosphate ( atp ) to power cellular processes. other organelles such as endoplasmic reticulum and golgi apparatus play a role in the synthesis and packaging of proteins, respectively. biomolecules such as proteins can be engulfed by lysosomes, another specialized organelle. plant cells have additional organelles that distinguish them from animal cells such as a cell wall that provides support for the plant cell, chloroplasts that harvest sunlight energy to produce sugar, and vacuoles that provide storage and structural support as well as being involved in reproduction and breakdown of plant seeds. eukaryotic cells also have cytoskeleton that is made up of microtubules, intermediate filaments, and microfilaments, all of which provide support for the cell and are involved in the movement of the cell and its organelles. in terms of their structural composition, the microtubules are made up of tubulin ( e. g., Ξ± - tubulin and Ξ² - tubulin ) whereas intermediate filaments are made up of fibrous proteins. microfilaments are made up of actin molecules that interact with other strands of proteins. = = = metabolism = = = all cells require energy to sustain cellular processes. metabolism is the set of chemical reactions in an organism. the three main purposes of metabolism are : the conversion of food to energy to run cellular processes ; the conversion of food / fuel to monomer building blocks ; and
the paper erroneously assumed that the normal carriers giving rise to the backflow could be either electrons or holes.
cytokinesis ). the natural cytokinin zeatin was discovered in corn, zea mays, and is a derivative of the purine adenine. zeatin is produced in roots and transported to shoots in the xylem where it promotes cell division, bud development, and the greening of chloroplasts. the gibberelins, such as gibberelic acid are diterpenes synthesised from acetyl coa via the mevalonate pathway. they are involved in the promotion of germination and dormancy - breaking in seeds, in regulation of plant height by controlling stem elongation and the control of flowering. abscisic acid ( aba ) occurs in all land plants except liverworts, and is synthesised from carotenoids in the chloroplasts and other plastids. it inhibits cell division, promotes seed maturation, and dormancy, and promotes stomatal closure. it was so named because it was originally thought to control abscission. ethylene is a gaseous hormone that is produced in all higher plant tissues from methionine. it is now known to be the hormone that stimulates or regulates fruit ripening and abscission, and it, or the synthetic growth regulator ethephon which is rapidly metabolised to produce ethylene, are used on industrial scale to promote ripening of cotton, pineapples and other climacteric crops. another class of phytohormones is the jasmonates, first isolated from the oil of jasminum grandiflorum which regulates wound responses in plants by unblocking the expression of genes required in the systemic acquired resistance response to pathogen attack. in addition to being the primary energy source for plants, light functions as a signalling device, providing information to the plant, such as how much sunlight the plant receives each day. this can result in adaptive changes in a process known as photomorphogenesis. phytochromes are the photoreceptors in a plant that are sensitive to light. = = plant anatomy and morphology = = plant anatomy is the study of the structure of plant cells and tissues, whereas plant morphology is the study of their external form. all plants are multicellular eukaryotes, their dna stored in nuclei. the characteristic features of plant cells that distinguish them from those of animals and fungi include a primary cell wall composed of the polysaccharides cellulose,
the cell ' s dna, or mitochondria, which generate adenosine triphosphate ( atp ) to power cellular processes. other organelles such as endoplasmic reticulum and golgi apparatus play a role in the synthesis and packaging of proteins, respectively. biomolecules such as proteins can be engulfed by lysosomes, another specialized organelle. plant cells have additional organelles that distinguish them from animal cells such as a cell wall that provides support for the plant cell, chloroplasts that harvest sunlight energy to produce sugar, and vacuoles that provide storage and structural support as well as being involved in reproduction and breakdown of plant seeds. eukaryotic cells also have cytoskeleton that is made up of microtubules, intermediate filaments, and microfilaments, all of which provide support for the cell and are involved in the movement of the cell and its organelles. in terms of their structural composition, the microtubules are made up of tubulin ( e. g., Ξ± - tubulin and Ξ² - tubulin ) whereas intermediate filaments are made up of fibrous proteins. microfilaments are made up of actin molecules that interact with other strands of proteins. = = = metabolism = = = all cells require energy to sustain cellular processes. metabolism is the set of chemical reactions in an organism. the three main purposes of metabolism are : the conversion of food to energy to run cellular processes ; the conversion of food / fuel to monomer building blocks ; and the elimination of metabolic wastes. these enzyme - catalyzed reactions allow organisms to grow and reproduce, maintain their structures, and respond to their environments. metabolic reactions may be categorized as catabolic β the breaking down of compounds ( for example, the breaking down of glucose to pyruvate by cellular respiration ) ; or anabolic β the building up ( synthesis ) of compounds ( such as proteins, carbohydrates, lipids, and nucleic acids ). usually, catabolism releases energy, and anabolism consumes energy. the chemical reactions of metabolism are organized into metabolic pathways, in which one chemical is transformed through a series of steps into another chemical, each step being facilitated by a specific enzyme. enzymes are crucial to metabolism because they allow organisms to drive desirable reactions that require energy that will not occur by themselves, by coupling them to spontaneous reactions that release energy. enzymes act as catalysts β they allow a
in a voltaic cell, positive ( negative ) ions flow from the low ( high ) potential electrode to the high ( low ) potential electrode, driven by an ` electromotive force ' which points in opposite direction and overcomes the electric force. similarly in a superconductor charge flows in direction opposite to that dictated by the faraday electric field as the magnetic field is expelled in the meissner effect. the puzzle is the same in both cases : what drives electric charges against electromagnetic forces? i propose that the answer is also the same in both cases : kinetic energy lowering, or ` quantum pressure '.
much sunlight the plant receives each day. this can result in adaptive changes in a process known as photomorphogenesis. phytochromes are the photoreceptors in a plant that are sensitive to light. = = plant anatomy and morphology = = plant anatomy is the study of the structure of plant cells and tissues, whereas plant morphology is the study of their external form. all plants are multicellular eukaryotes, their dna stored in nuclei. the characteristic features of plant cells that distinguish them from those of animals and fungi include a primary cell wall composed of the polysaccharides cellulose, hemicellulose and pectin, larger vacuoles than in animal cells and the presence of plastids with unique photosynthetic and biosynthetic functions as in the chloroplasts. other plastids contain storage products such as starch ( amyloplasts ) or lipids ( elaioplasts ). uniquely, streptophyte cells and those of the green algal order trentepohliales divide by construction of a phragmoplast as a template for building a cell plate late in cell division. the bodies of vascular plants including clubmosses, ferns and seed plants ( gymnosperms and angiosperms ) generally have aerial and subterranean subsystems. the shoots consist of stems bearing green photosynthesising leaves and reproductive structures. the underground vascularised roots bear root hairs at their tips and generally lack chlorophyll. non - vascular plants, the liverworts, hornworts and mosses do not produce ground - penetrating vascular roots and most of the plant participates in photosynthesis. the sporophyte generation is nonphotosynthetic in liverworts but may be able to contribute part of its energy needs by photosynthesis in mosses and hornworts. the root system and the shoot system are interdependent β the usually nonphotosynthetic root system depends on the shoot system for food, and the usually photosynthetic shoot system depends on water and minerals from the root system. cells in each system are capable of creating cells of the other and producing adventitious shoots or roots. stolons and tubers are examples of shoots that can grow roots. roots that spread out close to the surface, such as those of willows, can produce shoots and ultimately new plants. in the event that one of the systems is lost
cell. in juxtacrine signaling, there is direct contact between the signaling and responding cells. finally, hormones are ligands that travel through the circulatory systems of animals or vascular systems of plants to reach their target cells. once a ligand binds with a receptor, it can influence the behavior of another cell, depending on the type of receptor. for instance, neurotransmitters that bind with an inotropic receptor can alter the excitability of a target cell. other types of receptors include protein kinase receptors ( e. g., receptor for the hormone insulin ) and g protein - coupled receptors. activation of g protein - coupled receptors can initiate second messenger cascades. the process by which a chemical or physical signal is transmitted through a cell as a series of molecular events is called signal transduction. = = = cell cycle = = = the cell cycle is a series of events that take place in a cell that cause it to divide into two daughter cells. these events include the duplication of its dna and some of its organelles, and the subsequent partitioning of its cytoplasm into two daughter cells in a process called cell division. in eukaryotes ( i. e., animal, plant, fungal, and protist cells ), there are two distinct types of cell division : mitosis and meiosis. mitosis is part of the cell cycle, in which replicated chromosomes are separated into two new nuclei. cell division gives rise to genetically identical cells in which the total number of chromosomes is maintained. in general, mitosis ( division of the nucleus ) is preceded by the s stage of interphase ( during which the dna is replicated ) and is often followed by telophase and cytokinesis ; which divides the cytoplasm, organelles and cell membrane of one cell into two new cells containing roughly equal shares of these cellular components. the different stages of mitosis all together define the mitotic phase of an animal cell cycle β the division of the mother cell into two genetically identical daughter cells. the cell cycle is a vital process by which a single - celled fertilized egg develops into a mature organism, as well as the process by which hair, skin, blood cells, and some internal organs are renewed. after cell division, each of the daughter cells begin the interphase of a new cycle. in contrast to mitosis, meiosis results in four haploid daughter cells by undergoing one round of dna replication followed by two divisions
, the other can often regrow it. in fact it is possible to grow an entire plant from a single leaf, as is the case with plants in streptocarpus sect. saintpaulia, or even a single cell β which can dedifferentiate into a callus ( a mass of unspecialised cells ) that can grow into a new plant. in vascular plants, the xylem and phloem are the conductive tissues that transport resources between shoots and roots. roots are often adapted to store food such as sugars or starch, as in sugar beets and carrots. stems mainly provide support to the leaves and reproductive structures, but can store water in succulent plants such as cacti, food as in potato tubers, or reproduce vegetatively as in the stolons of strawberry plants or in the process of layering. leaves gather sunlight and carry out photosynthesis. large, flat, flexible, green leaves are called foliage leaves. gymnosperms, such as conifers, cycads, ginkgo, and gnetophytes are seed - producing plants with open seeds. angiosperms are seed - producing plants that produce flowers and have enclosed seeds. woody plants, such as azaleas and oaks, undergo a secondary growth phase resulting in two additional types of tissues : wood ( secondary xylem ) and bark ( secondary phloem and cork ). all gymnosperms and many angiosperms are woody plants. some plants reproduce sexually, some asexually, and some via both means. although reference to major morphological categories such as root, stem, leaf, and trichome are useful, one has to keep in mind that these categories are linked through intermediate forms so that a continuum between the categories results. furthermore, structures can be seen as processes, that is, process combinations. = = systematic botany = = systematic botany is part of systematic biology, which is concerned with the range and diversity of organisms and their relationships, particularly as determined by their evolutionary history. it involves, or is related to, biological classification, scientific taxonomy and phylogenetics. biological classification is the method by which botanists group organisms into categories such as genera or species. biological classification is a form of scientific taxonomy. modern taxonomy is rooted in the work of carl linnaeus, who grouped species according to shared physical characteristics. these groupings have since been revised to align better with the darwinian principle of common descent β grouping organisms
hemicellulose and pectin, larger vacuoles than in animal cells and the presence of plastids with unique photosynthetic and biosynthetic functions as in the chloroplasts. other plastids contain storage products such as starch ( amyloplasts ) or lipids ( elaioplasts ). uniquely, streptophyte cells and those of the green algal order trentepohliales divide by construction of a phragmoplast as a template for building a cell plate late in cell division. the bodies of vascular plants including clubmosses, ferns and seed plants ( gymnosperms and angiosperms ) generally have aerial and subterranean subsystems. the shoots consist of stems bearing green photosynthesising leaves and reproductive structures. the underground vascularised roots bear root hairs at their tips and generally lack chlorophyll. non - vascular plants, the liverworts, hornworts and mosses do not produce ground - penetrating vascular roots and most of the plant participates in photosynthesis. the sporophyte generation is nonphotosynthetic in liverworts but may be able to contribute part of its energy needs by photosynthesis in mosses and hornworts. the root system and the shoot system are interdependent β the usually nonphotosynthetic root system depends on the shoot system for food, and the usually photosynthetic shoot system depends on water and minerals from the root system. cells in each system are capable of creating cells of the other and producing adventitious shoots or roots. stolons and tubers are examples of shoots that can grow roots. roots that spread out close to the surface, such as those of willows, can produce shoots and ultimately new plants. in the event that one of the systems is lost, the other can often regrow it. in fact it is possible to grow an entire plant from a single leaf, as is the case with plants in streptocarpus sect. saintpaulia, or even a single cell β which can dedifferentiate into a callus ( a mass of unspecialised cells ) that can grow into a new plant. in vascular plants, the xylem and phloem are the conductive tissues that transport resources between shoots and roots. roots are often adapted to store food such as sugars or starch, as in sugar beets and carrots.
, 400 km from the persian gulf to the mediterranean sea, but was not paved and was only partially maintained. in around 2, 000 bce, the minoans on the greek island of crete built a 50 km road leading from the palace of gortyn on the south side of the island, through the mountains, to the palace of knossos on the north side of the island. unlike the earlier road, the minoan road was completely paved. ancient minoan private homes had running water. a bathtub virtually identical to modern ones was unearthed at the palace of knossos. several minoan private homes also had toilets, which could be flushed by pouring water down the drain. the ancient romans had many public flush toilets, which emptied into an extensive sewage system. the primary sewer in rome was the cloaca maxima ; construction began on it in the sixth century bce and it is still in use today. the ancient romans also had a complex system of aqueducts, which were used to transport water across long distances. the first roman aqueduct was built in 312 bce. the eleventh and final ancient roman aqueduct was built in 226 ce. put together, the roman aqueducts extended over 450 km, but less than 70 km of this was above ground and supported by arches. = = = pre - modern = = = innovations continued through the middle ages with the introduction of silk production ( in asia and later europe ), the horse collar, and horseshoes. simple machines ( such as the lever, the screw, and the pulley ) were combined into more complicated tools, such as the wheelbarrow, windmills, and clocks. a system of universities developed and spread scientific ideas and practices, including oxford and cambridge. the renaissance era produced many innovations, including the introduction of the movable type printing press to europe, which facilitated the communication of knowledge. technology became increasingly influenced by science, beginning a cycle of mutual advancement. = = = modern = = = starting in the united kingdom in the 18th century, the discovery of steam power set off the industrial revolution, which saw wide - ranging technological discoveries, particularly in the areas of agriculture, manufacturing, mining, metallurgy, and transport, and the widespread application of the factory system. this was followed a century later by the second industrial revolution which led to rapid scientific discovery, standardization, and mass production. new technologies were developed, including sewage systems, electricity, light bulbs, electric motors, railroads, automobiles, and airplanes. these technological advances led to significant developments in medicine
Question: These vacuoles take water from the cytoplasm and excrete it from the cell to avoid bursting due to what?
A) impervious pressure
B) static pressure
C) osmotic pressure
D) apoptotic pressure
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C) osmotic pressure
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Context:
known as " algae " have unique organelles known as chloroplasts. chloroplasts are thought to be descended from cyanobacteria that formed endosymbiotic relationships with ancient plant and algal ancestors. chloroplasts and cyanobacteria contain the blue - green pigment chlorophyll a. chlorophyll a ( as well as its plant and green algal - specific cousin chlorophyll b ) absorbs light in the blue - violet and orange / red parts of the spectrum while reflecting and transmitting the green light that we see as the characteristic colour of these organisms. the energy in the red and blue light that these pigments absorb is used by chloroplasts to make energy - rich carbon compounds from carbon dioxide and water by oxygenic photosynthesis, a process that generates molecular oxygen ( o2 ) as a by - product. the light energy captured by chlorophyll a is initially in the form of electrons ( and later a proton gradient ) that is used to make molecules of atp and nadph which temporarily store and transport energy. their energy is used in the light - independent reactions of the calvin cycle by the enzyme rubisco to produce molecules of the 3 - carbon sugar glyceraldehyde 3 - phosphate ( g3p ). glyceraldehyde 3 - phosphate is the first product of photosynthesis and the raw material from which glucose and almost all other organic molecules of biological origin are synthesised. some of the glucose is converted to starch which is stored in the chloroplast. starch is the characteristic energy store of most land plants and algae, while inulin, a polymer of fructose is used for the same purpose in the sunflower family asteraceae. some of the glucose is converted to sucrose ( common table sugar ) for export to the rest of the plant. unlike in animals ( which lack chloroplasts ), plants and their eukaryote relatives have delegated many biochemical roles to their chloroplasts, including synthesising all their fatty acids, and most amino acids. the fatty acids that chloroplasts make are used for many things, such as providing material to build cell membranes out of and making the polymer cutin which is found in the plant cuticle that protects land plants from drying out. plants synthesise a number of unique polymers like the polysaccharide molecules cellulose,
used by pharmaceutical companies as a way of drug discovery. plants can synthesise coloured dyes and pigments such as the anthocyanins responsible for the red colour of red wine, yellow weld and blue woad used together to produce lincoln green, indoxyl, source of the blue dye indigo traditionally used to dye denim and the artist ' s pigments gamboge and rose madder. sugar, starch, cotton, linen, hemp, some types of rope, wood and particle boards, papyrus and paper, vegetable oils, wax, and natural rubber are examples of commercially important materials made from plant tissues or their secondary products. charcoal, a pure form of carbon made by pyrolysis of wood, has a long history as a metal - smelting fuel, as a filter material and adsorbent and as an artist ' s material and is one of the three ingredients of gunpowder. cellulose, the world ' s most abundant organic polymer, can be converted into energy, fuels, materials and chemical feedstock. products made from cellulose include rayon and cellophane, wallpaper paste, biobutanol and gun cotton. sugarcane, rapeseed and soy are some of the plants with a highly fermentable sugar or oil content that are used as sources of biofuels, important alternatives to fossil fuels, such as biodiesel. sweetgrass was used by native americans to ward off bugs like mosquitoes. these bug repelling properties of sweetgrass were later found by the american chemical society in the molecules phytol and coumarin. = = plant ecology = = plant ecology is the science of the functional relationships between plants and their habitats β the environments where they complete their life cycles. plant ecologists study the composition of local and regional floras, their biodiversity, genetic diversity and fitness, the adaptation of plants to their environment, and their competitive or mutualistic interactions with other species. some ecologists even rely on empirical data from indigenous people that is gathered by ethnobotanists. this information can relay a great deal of information on how the land once was thousands of years ago and how it has changed over that time. the goals of plant ecology are to understand the causes of their distribution patterns, productivity, environmental impact, evolution, and responses to environmental change. plants depend on certain edaphic ( soil ) and climatic factors in their environment but can modify these factors too. for example, they can change their environment ' s albedo, increase runoff interception
pigment chlorophyll a. chlorophyll a ( as well as its plant and green algal - specific cousin chlorophyll b ) absorbs light in the blue - violet and orange / red parts of the spectrum while reflecting and transmitting the green light that we see as the characteristic colour of these organisms. the energy in the red and blue light that these pigments absorb is used by chloroplasts to make energy - rich carbon compounds from carbon dioxide and water by oxygenic photosynthesis, a process that generates molecular oxygen ( o2 ) as a by - product. the light energy captured by chlorophyll a is initially in the form of electrons ( and later a proton gradient ) that is used to make molecules of atp and nadph which temporarily store and transport energy. their energy is used in the light - independent reactions of the calvin cycle by the enzyme rubisco to produce molecules of the 3 - carbon sugar glyceraldehyde 3 - phosphate ( g3p ). glyceraldehyde 3 - phosphate is the first product of photosynthesis and the raw material from which glucose and almost all other organic molecules of biological origin are synthesised. some of the glucose is converted to starch which is stored in the chloroplast. starch is the characteristic energy store of most land plants and algae, while inulin, a polymer of fructose is used for the same purpose in the sunflower family asteraceae. some of the glucose is converted to sucrose ( common table sugar ) for export to the rest of the plant. unlike in animals ( which lack chloroplasts ), plants and their eukaryote relatives have delegated many biochemical roles to their chloroplasts, including synthesising all their fatty acids, and most amino acids. the fatty acids that chloroplasts make are used for many things, such as providing material to build cell membranes out of and making the polymer cutin which is found in the plant cuticle that protects land plants from drying out. plants synthesise a number of unique polymers like the polysaccharide molecules cellulose, pectin and xyloglucan from which the land plant cell wall is constructed. vascular land plants make lignin, a polymer used to strengthen the secondary cell walls of xylem tracheids and vessels to keep them from collapsing when a plant sucks water through them under water stress. lignin
their primary metabolism like the photosynthetic calvin cycle and crassulacean acid metabolism. others make specialised materials like the cellulose and lignin used to build their bodies, and secondary products like resins and aroma compounds. plants and various other groups of photosynthetic eukaryotes collectively known as " algae " have unique organelles known as chloroplasts. chloroplasts are thought to be descended from cyanobacteria that formed endosymbiotic relationships with ancient plant and algal ancestors. chloroplasts and cyanobacteria contain the blue - green pigment chlorophyll a. chlorophyll a ( as well as its plant and green algal - specific cousin chlorophyll b ) absorbs light in the blue - violet and orange / red parts of the spectrum while reflecting and transmitting the green light that we see as the characteristic colour of these organisms. the energy in the red and blue light that these pigments absorb is used by chloroplasts to make energy - rich carbon compounds from carbon dioxide and water by oxygenic photosynthesis, a process that generates molecular oxygen ( o2 ) as a by - product. the light energy captured by chlorophyll a is initially in the form of electrons ( and later a proton gradient ) that is used to make molecules of atp and nadph which temporarily store and transport energy. their energy is used in the light - independent reactions of the calvin cycle by the enzyme rubisco to produce molecules of the 3 - carbon sugar glyceraldehyde 3 - phosphate ( g3p ). glyceraldehyde 3 - phosphate is the first product of photosynthesis and the raw material from which glucose and almost all other organic molecules of biological origin are synthesised. some of the glucose is converted to starch which is stored in the chloroplast. starch is the characteristic energy store of most land plants and algae, while inulin, a polymer of fructose is used for the same purpose in the sunflower family asteraceae. some of the glucose is converted to sucrose ( common table sugar ) for export to the rest of the plant. unlike in animals ( which lack chloroplasts ), plants and their eukaryote relatives have delegated many biochemical roles to their chloroplasts, including synthesising all their fatty acids, and most amino acids. the fatty acids that
prehistory. the oldest gold treasure in the world, dating from 4, 600 bc to 4, 200 bc, was discovered at the site. the gold piece dating from 4, 500 bc, found in 2019 in durankulak, near varna is another important example. other signs of early metals are found from the third millennium bc in palmela, portugal, los millares, spain, and stonehenge, united kingdom. the precise beginnings, however, have not be clearly ascertained and new discoveries are both continuous and ongoing. in approximately 1900 bc, ancient iron smelting sites existed in tamil nadu. in the near east, about 3, 500 bc, it was discovered that by combining copper and tin, a superior metal could be made, an alloy called bronze. this represented a major technological shift known as the bronze age. the extraction of iron from its ore into a workable metal is much more difficult than for copper or tin. the process appears to have been invented by the hittites in about 1200 bc, beginning the iron age. the secret of extracting and working iron was a key factor in the success of the philistines. historical developments in ferrous metallurgy can be found in a wide variety of past cultures and civilizations. this includes the ancient and medieval kingdoms and empires of the middle east and near east, ancient iran, ancient egypt, ancient nubia, and anatolia in present - day turkey, ancient nok, carthage, the celts, greeks and romans of ancient europe, medieval europe, ancient and medieval china, ancient and medieval india, ancient and medieval japan, amongst others. a 16th century book by georg agricola, de re metallica, describes the highly developed and complex processes of mining metal ores, metal extraction, and metallurgy of the time. agricola has been described as the " father of metallurgy ". = = extraction = = extractive metallurgy is the practice of removing valuable metals from an ore and refining the extracted raw metals into a purer form. in order to convert a metal oxide or sulphide to a purer metal, the ore must be reduced physically, chemically, or electrolytically. extractive metallurgists are interested in three primary streams : feed, concentrate ( metal oxide / sulphide ) and tailings ( waste ). after mining, large pieces of the ore feed are broken through crushing or grinding in order to obtain particles small enough, where each particle is either mostly valuable or
the third millennium bc in palmela, portugal, los millares, spain, and stonehenge, united kingdom. the precise beginnings, however, have not be clearly ascertained and new discoveries are both continuous and ongoing. in approximately 1900 bc, ancient iron smelting sites existed in tamil nadu. in the near east, about 3, 500 bc, it was discovered that by combining copper and tin, a superior metal could be made, an alloy called bronze. this represented a major technological shift known as the bronze age. the extraction of iron from its ore into a workable metal is much more difficult than for copper or tin. the process appears to have been invented by the hittites in about 1200 bc, beginning the iron age. the secret of extracting and working iron was a key factor in the success of the philistines. historical developments in ferrous metallurgy can be found in a wide variety of past cultures and civilizations. this includes the ancient and medieval kingdoms and empires of the middle east and near east, ancient iran, ancient egypt, ancient nubia, and anatolia in present - day turkey, ancient nok, carthage, the celts, greeks and romans of ancient europe, medieval europe, ancient and medieval china, ancient and medieval india, ancient and medieval japan, amongst others. a 16th century book by georg agricola, de re metallica, describes the highly developed and complex processes of mining metal ores, metal extraction, and metallurgy of the time. agricola has been described as the " father of metallurgy ". = = extraction = = extractive metallurgy is the practice of removing valuable metals from an ore and refining the extracted raw metals into a purer form. in order to convert a metal oxide or sulphide to a purer metal, the ore must be reduced physically, chemically, or electrolytically. extractive metallurgists are interested in three primary streams : feed, concentrate ( metal oxide / sulphide ) and tailings ( waste ). after mining, large pieces of the ore feed are broken through crushing or grinding in order to obtain particles small enough, where each particle is either mostly valuable or mostly waste. concentrating the particles of value in a form supporting separation enables the desired metal to be removed from waste products. mining may not be necessary, if the ore body and physical environment are conducive to leaching. leaching dissolves minerals in an ore body and results in an enriched solution. the solution
was used before copper smelting was known. copper smelting is believed to have originated when the technology of pottery kilns allowed sufficiently high temperatures. the concentration of various elements such as arsenic increase with depth in copper ore deposits and smelting of these ores yields arsenical bronze, which can be sufficiently work hardened to be suitable for making tools. bronze is an alloy of copper with tin ; the latter being found in relatively few deposits globally caused a long time to elapse before true tin bronze became widespread. ( see : tin sources and trade in ancient times ) bronze was a major advancement over stone as a material for making tools, both because of its mechanical properties like strength and ductility and because it could be cast in molds to make intricately shaped objects. bronze significantly advanced shipbuilding technology with better tools and bronze nails. bronze nails replaced the old method of attaching boards of the hull with cord woven through drilled holes. better ships enabled long - distance trade and the advance of civilization. this technological trend apparently began in the fertile crescent and spread outward over time. these developments were not, and still are not, universal. the three - age system does not accurately describe the technology history of groups outside of eurasia, and does not apply at all in the case of some isolated populations, such as the spinifex people, the sentinelese, and various amazonian tribes, which still make use of stone age technology, and have not developed agricultural or metal technology. these villages preserve traditional customs in the face of global modernity, exhibiting a remarkable resistance to the rapid advancement of technology. = = = = iron age = = = = before iron smelting was developed the only iron was obtained from meteorites and is usually identified by having nickel content. meteoric iron was rare and valuable, but was sometimes used to make tools and other implements, such as fish hooks. the iron age involved the adoption of iron smelting technology. it generally replaced bronze and made it possible to produce tools which were stronger, lighter and cheaper to make than bronze equivalents. the raw materials to make iron, such as ore and limestone, are far more abundant than copper and especially tin ores. consequently, iron was produced in many areas. it was not possible to mass manufacture steel or pure iron because of the high temperatures required. furnaces could reach melting temperature but the crucibles and molds needed for melting and casting had not been developed. steel could be produced by forging bloomery iron to reduce the carbon content in a
building block. ceramics β not to be confused with raw, unfired clay β are usually seen in crystalline form. the vast majority of commercial glasses contain a metal oxide fused with silica. at the high temperatures used to prepare glass, the material is a viscous liquid which solidifies into a disordered state upon cooling. windowpanes and eyeglasses are important examples. fibers of glass are also used for long - range telecommunication and optical transmission. scratch resistant corning gorilla glass is a well - known example of the application of materials science to drastically improve the properties of common components. engineering ceramics are known for their stiffness and stability under high temperatures, compression and electrical stress. alumina, silicon carbide, and tungsten carbide are made from a fine powder of their constituents in a process of sintering with a binder. hot pressing provides higher density material. chemical vapor deposition can place a film of a ceramic on another material. cermets are ceramic particles containing some metals. the wear resistance of tools is derived from cemented carbides with the metal phase of cobalt and nickel typically added to modify properties. ceramics can be significantly strengthened for engineering applications using the principle of crack deflection. this process involves the strategic addition of second - phase particles within a ceramic matrix, optimizing their shape, size, and distribution to direct and control crack propagation. this approach enhances fracture toughness, paving the way for the creation of advanced, high - performance ceramics in various industries. = = = composites = = = another application of materials science in industry is making composite materials. these are structured materials composed of two or more macroscopic phases. applications range from structural elements such as steel - reinforced concrete, to the thermal insulating tiles, which play a key and integral role in nasa ' s space shuttle thermal protection system, which is used to protect the surface of the shuttle from the heat of re - entry into the earth ' s atmosphere. one example is reinforced carbon - carbon ( rcc ), the light gray material, which withstands re - entry temperatures up to 1, 510 Β°c ( 2, 750 Β°f ) and protects the space shuttle ' s wing leading edges and nose cap. rcc is a laminated composite material made from graphite rayon cloth and impregnated with a phenolic resin. after curing at high temperature in an autoclave, the laminate is pyrolized to convert the resin to carbon, impregnated with furfuryl alcohol in a
as dental implants and synthetic bones. hydroxyapatite, the natural mineral component of bone, has been made synthetically from a number of biological and chemical sources and can be formed into ceramic materials. orthopedic implants made from these materials bond readily to bone and other tissues in the body without rejection or inflammatory reactions. because of this, they are of great interest for gene delivery and tissue engineering scaffolds. most hydroxyapatite ceramics are very porous and lack mechanical strength and are used to coat metal orthopedic devices to aid in forming a bond to bone or as bone fillers. they are also used as fillers for orthopedic plastic screws to aid in reducing the inflammation and increase absorption of these plastic materials. work is being done to make strong, fully dense nano crystalline hydroxyapatite ceramic materials for orthopedic weight bearing devices, replacing foreign metal and plastic orthopedic materials with a synthetic, but naturally occurring, bone mineral. ultimately these ceramic materials may be used as bone replacements or with the incorporation of protein collagens, synthetic bones. durable actinide - containing ceramic materials have many applications such as in nuclear fuels for burning excess pu and in chemically - inert sources of alpha irradiation for power supply of unmanned space vehicles or to produce electricity for microelectronic devices. both use and disposal of radioactive actinides require their immobilization in a durable host material. nuclear waste long - lived radionuclides such as actinides are immobilized using chemically - durable crystalline materials based on polycrystalline ceramics and large single crystals. alumina ceramics are widely utilized in the chemical industry due to their excellent chemical stability and high resistance to corrosion. it is used as acid - resistant pump impellers and pump bodies, ensuring long - lasting performance in transferring aggressive fluids. they are also used in acid - carrying pipe linings to prevent contamination and maintain fluid purity, which is crucial in industries like pharmaceuticals and food processing. valves made from alumina ceramics demonstrate exceptional durability and resistance to chemical attack, making them reliable for controlling the flow of corrosive liquids. = = glass - ceramics = = glass - ceramic materials share many properties with both glasses and ceramics. glass - ceramics have an amorphous phase and one or more crystalline phases and are produced by a so - called " controlled crystallization ", which is typically avoided in glass manufacturing. glass - ceramics often contain a crystalline phase
near east, about 3, 500 bc, it was discovered that by combining copper and tin, a superior metal could be made, an alloy called bronze. this represented a major technological shift known as the bronze age. the extraction of iron from its ore into a workable metal is much more difficult than for copper or tin. the process appears to have been invented by the hittites in about 1200 bc, beginning the iron age. the secret of extracting and working iron was a key factor in the success of the philistines. historical developments in ferrous metallurgy can be found in a wide variety of past cultures and civilizations. this includes the ancient and medieval kingdoms and empires of the middle east and near east, ancient iran, ancient egypt, ancient nubia, and anatolia in present - day turkey, ancient nok, carthage, the celts, greeks and romans of ancient europe, medieval europe, ancient and medieval china, ancient and medieval india, ancient and medieval japan, amongst others. a 16th century book by georg agricola, de re metallica, describes the highly developed and complex processes of mining metal ores, metal extraction, and metallurgy of the time. agricola has been described as the " father of metallurgy ". = = extraction = = extractive metallurgy is the practice of removing valuable metals from an ore and refining the extracted raw metals into a purer form. in order to convert a metal oxide or sulphide to a purer metal, the ore must be reduced physically, chemically, or electrolytically. extractive metallurgists are interested in three primary streams : feed, concentrate ( metal oxide / sulphide ) and tailings ( waste ). after mining, large pieces of the ore feed are broken through crushing or grinding in order to obtain particles small enough, where each particle is either mostly valuable or mostly waste. concentrating the particles of value in a form supporting separation enables the desired metal to be removed from waste products. mining may not be necessary, if the ore body and physical environment are conducive to leaching. leaching dissolves minerals in an ore body and results in an enriched solution. the solution is collected and processed to extract valuable metals. ore bodies often contain more than one valuable metal. tailings of a previous process may be used as a feed in another process to extract a secondary product from the original ore. additionally, a concentrate may contain more than one valuable metal. that concentrate would then be processed to separate
Question: Where does the purple color in quartz come from?
A) dirt
B) bronze
C) iron
D) aluminum
|
C) iron
|
Context:
and taken up by the brain. by observing which areas of the brain take up the radioactive isotope, we can see which areas of the brain are more active than other areas. pet has similar spatial resolution to fmri, but it has extremely poor temporal resolution. electroencephalography. eeg measures the electrical fields generated by large populations of neurons in the cortex by placing a series of electrodes on the scalp of the subject. this technique has an extremely high temporal resolution, but a relatively poor spatial resolution. functional magnetic resonance imaging. fmri measures the relative amount of oxygenated blood flowing to different parts of the brain. more oxygenated blood in a particular region is assumed to correlate with an increase in neural activity in that part of the brain. this allows us to localize particular functions within different brain regions. fmri has moderate spatial and temporal resolution. optical imaging. this technique uses infrared transmitters and receivers to measure the amount of light reflectance by blood near different areas of the brain. since oxygenated and deoxygenated blood reflects light by different amounts, we can study which areas are more active ( i. e., those that have more oxygenated blood ). optical imaging has moderate temporal resolution, but poor spatial resolution. it also has the advantage that it is extremely safe and can be used to study infants ' brains. magnetoencephalography. meg measures magnetic fields resulting from cortical activity. it is similar to eeg, except that it has improved spatial resolution since the magnetic fields it measures are not as blurred or attenuated by the scalp, meninges and so forth as the electrical activity measured in eeg is. meg uses squid sensors to detect tiny magnetic fields. = = = computational modeling = = = computational models require a mathematically and logically formal representation of a problem. computer models are used in the simulation and experimental verification of different specific and general properties of intelligence. computational modeling can help us understand the functional organization of a particular cognitive phenomenon. approaches to cognitive modeling can be categorized as : ( 1 ) symbolic, on abstract mental functions of an intelligent mind by means of symbols ; ( 2 ) subsymbolic, on the neural and associative properties of the human brain ; and ( 3 ) across the symbolic β subsymbolic border, including hybrid. symbolic modeling evolved from the computer science paradigms using the technologies of knowledge - based systems, as well as a philosophical perspective ( e. g. " good old - fashioned artificial intelligence " ( gofa
generated by large populations of neurons in the cortex by placing a series of electrodes on the scalp of the subject. this technique has an extremely high temporal resolution, but a relatively poor spatial resolution. functional magnetic resonance imaging. fmri measures the relative amount of oxygenated blood flowing to different parts of the brain. more oxygenated blood in a particular region is assumed to correlate with an increase in neural activity in that part of the brain. this allows us to localize particular functions within different brain regions. fmri has moderate spatial and temporal resolution. optical imaging. this technique uses infrared transmitters and receivers to measure the amount of light reflectance by blood near different areas of the brain. since oxygenated and deoxygenated blood reflects light by different amounts, we can study which areas are more active ( i. e., those that have more oxygenated blood ). optical imaging has moderate temporal resolution, but poor spatial resolution. it also has the advantage that it is extremely safe and can be used to study infants ' brains. magnetoencephalography. meg measures magnetic fields resulting from cortical activity. it is similar to eeg, except that it has improved spatial resolution since the magnetic fields it measures are not as blurred or attenuated by the scalp, meninges and so forth as the electrical activity measured in eeg is. meg uses squid sensors to detect tiny magnetic fields. = = = computational modeling = = = computational models require a mathematically and logically formal representation of a problem. computer models are used in the simulation and experimental verification of different specific and general properties of intelligence. computational modeling can help us understand the functional organization of a particular cognitive phenomenon. approaches to cognitive modeling can be categorized as : ( 1 ) symbolic, on abstract mental functions of an intelligent mind by means of symbols ; ( 2 ) subsymbolic, on the neural and associative properties of the human brain ; and ( 3 ) across the symbolic β subsymbolic border, including hybrid. symbolic modeling evolved from the computer science paradigms using the technologies of knowledge - based systems, as well as a philosophical perspective ( e. g. " good old - fashioned artificial intelligence " ( gofai ) ). they were developed by the first cognitive researchers and later used in information engineering for expert systems. since the early 1990s it was generalized in systemics for the investigation of functional human - like intelligence models, such as personoids, and, in parallel, developed as the soar environment. recently, especially in
of imaging techniques vary in their temporal ( time - based ) and spatial ( location - based ) resolution. brain imaging is often used in cognitive neuroscience. single - photon emission computed tomography and positron emission tomography. spect and pet use radioactive isotopes, which are injected into the subject ' s bloodstream and taken up by the brain. by observing which areas of the brain take up the radioactive isotope, we can see which areas of the brain are more active than other areas. pet has similar spatial resolution to fmri, but it has extremely poor temporal resolution. electroencephalography. eeg measures the electrical fields generated by large populations of neurons in the cortex by placing a series of electrodes on the scalp of the subject. this technique has an extremely high temporal resolution, but a relatively poor spatial resolution. functional magnetic resonance imaging. fmri measures the relative amount of oxygenated blood flowing to different parts of the brain. more oxygenated blood in a particular region is assumed to correlate with an increase in neural activity in that part of the brain. this allows us to localize particular functions within different brain regions. fmri has moderate spatial and temporal resolution. optical imaging. this technique uses infrared transmitters and receivers to measure the amount of light reflectance by blood near different areas of the brain. since oxygenated and deoxygenated blood reflects light by different amounts, we can study which areas are more active ( i. e., those that have more oxygenated blood ). optical imaging has moderate temporal resolution, but poor spatial resolution. it also has the advantage that it is extremely safe and can be used to study infants ' brains. magnetoencephalography. meg measures magnetic fields resulting from cortical activity. it is similar to eeg, except that it has improved spatial resolution since the magnetic fields it measures are not as blurred or attenuated by the scalp, meninges and so forth as the electrical activity measured in eeg is. meg uses squid sensors to detect tiny magnetic fields. = = = computational modeling = = = computational models require a mathematically and logically formal representation of a problem. computer models are used in the simulation and experimental verification of different specific and general properties of intelligence. computational modeling can help us understand the functional organization of a particular cognitive phenomenon. approaches to cognitive modeling can be categorized as : ( 1 ) symbolic, on abstract mental functions of an intelligent mind by means of symbols ; ( 2 ) subsymbolic, on the neural and associa
and child health in boston, said of the digital generation, " their brains are rewarded not for staying on task, but for jumping to the next thing. the worry is we ' re raising a generation of kids in front of screens whose brains are going to be wired differently. " students have always faced distractions ; computers and cell phones are a particular challenge because the stream of data can interfere with focusing and learning. although these technologies affect adults too, young people may be more influenced by it as their developing brains can easily become habituated to switching tasks and become unaccustomed to sustaining attention. too much information, coming too rapidly, can overwhelm thinking. technology is " rapidly and profoundly altering our brains. " high exposure levels stimulate brain cell alteration and release neurotransmitters, which causes the strengthening of some neural pathways and the weakening of others. this leads to heightened stress levels on the brain that, at first, boost energy levels, but, over time, actually augment memory, impair cognition, lead to depression, and alter the neural circuitry of the hippocampus, amygdala and prefrontal cortex. these are the brain regions that control mood and thought. if unchecked, the underlying structure of the brain could be altered. overstimulation due to technology may begin too young. when children are exposed before the age of seven, important developmental tasks may be delayed, and bad learning habits might develop, which " deprives children of the exploration and play that they need to develop. " media psychology is an emerging specialty field that embraces electronic devices and the sensory behaviors occurring from the use of educational technology in learning. = = = sociocultural criticism = = = according to lai, " the learning environment is a complex system where the interplay and interactions of many things impact the outcome of learning. " when technology is brought into an educational setting, the pedagogical setting changes in that technology - driven teaching can change the entire meaning of an activity without adequate research validation. if technology monopolizes an activity, students can begin to develop the sense that " life would scarcely be thinkable without technology. " leo marx considered the word " technology " itself as problematic, susceptible to reification and " phantom objectivity ", which conceals its fundamental nature as something that is only valuable insofar as it benefits the human condition. technology ultimately comes down to affecting the relations between people, but this notion is obfuscated when technology is treated as an abstract notion devoid of
and cell phones are a particular challenge because the stream of data can interfere with focusing and learning. although these technologies affect adults too, young people may be more influenced by it as their developing brains can easily become habituated to switching tasks and become unaccustomed to sustaining attention. too much information, coming too rapidly, can overwhelm thinking. technology is " rapidly and profoundly altering our brains. " high exposure levels stimulate brain cell alteration and release neurotransmitters, which causes the strengthening of some neural pathways and the weakening of others. this leads to heightened stress levels on the brain that, at first, boost energy levels, but, over time, actually augment memory, impair cognition, lead to depression, and alter the neural circuitry of the hippocampus, amygdala and prefrontal cortex. these are the brain regions that control mood and thought. if unchecked, the underlying structure of the brain could be altered. overstimulation due to technology may begin too young. when children are exposed before the age of seven, important developmental tasks may be delayed, and bad learning habits might develop, which " deprives children of the exploration and play that they need to develop. " media psychology is an emerging specialty field that embraces electronic devices and the sensory behaviors occurring from the use of educational technology in learning. = = = sociocultural criticism = = = according to lai, " the learning environment is a complex system where the interplay and interactions of many things impact the outcome of learning. " when technology is brought into an educational setting, the pedagogical setting changes in that technology - driven teaching can change the entire meaning of an activity without adequate research validation. if technology monopolizes an activity, students can begin to develop the sense that " life would scarcely be thinkable without technology. " leo marx considered the word " technology " itself as problematic, susceptible to reification and " phantom objectivity ", which conceals its fundamental nature as something that is only valuable insofar as it benefits the human condition. technology ultimately comes down to affecting the relations between people, but this notion is obfuscated when technology is treated as an abstract notion devoid of good and evil. langdon winner makes a similar point by arguing that the underdevelopment of the philosophy of technology leaves us with an overly simplistic reduction in our discourse to the supposedly dichotomous notions of the " making " versus the " uses " of new technologies and that a narrow focus on " use
decision making during a task, and they provide us with some insight into the ways in which those decisions may be processed. = = = brain imaging = = = brain imaging involves analyzing activity within the brain while performing various tasks. this allows us to link behavior and brain function to help understand how information is processed. different types of imaging techniques vary in their temporal ( time - based ) and spatial ( location - based ) resolution. brain imaging is often used in cognitive neuroscience. single - photon emission computed tomography and positron emission tomography. spect and pet use radioactive isotopes, which are injected into the subject ' s bloodstream and taken up by the brain. by observing which areas of the brain take up the radioactive isotope, we can see which areas of the brain are more active than other areas. pet has similar spatial resolution to fmri, but it has extremely poor temporal resolution. electroencephalography. eeg measures the electrical fields generated by large populations of neurons in the cortex by placing a series of electrodes on the scalp of the subject. this technique has an extremely high temporal resolution, but a relatively poor spatial resolution. functional magnetic resonance imaging. fmri measures the relative amount of oxygenated blood flowing to different parts of the brain. more oxygenated blood in a particular region is assumed to correlate with an increase in neural activity in that part of the brain. this allows us to localize particular functions within different brain regions. fmri has moderate spatial and temporal resolution. optical imaging. this technique uses infrared transmitters and receivers to measure the amount of light reflectance by blood near different areas of the brain. since oxygenated and deoxygenated blood reflects light by different amounts, we can study which areas are more active ( i. e., those that have more oxygenated blood ). optical imaging has moderate temporal resolution, but poor spatial resolution. it also has the advantage that it is extremely safe and can be used to study infants ' brains. magnetoencephalography. meg measures magnetic fields resulting from cortical activity. it is similar to eeg, except that it has improved spatial resolution since the magnetic fields it measures are not as blurred or attenuated by the scalp, meninges and so forth as the electrical activity measured in eeg is. meg uses squid sensors to detect tiny magnetic fields. = = = computational modeling = = = computational models require a mathematically and logically formal representation of a problem. computer models are used in the simulation and experimental verification of different
considered the father of modern neuroscience. from new zealand and australia came maurice wilkins, howard florey, and frank macfarlane burnet. others that did significant work include william williams keen, william coley, james d. watson ( united states ) ; salvador luria ( italy ) ; alexandre yersin ( switzerland ) ; kitasato shibasaburo ( japan ) ; jean - martin charcot, claude bernard, paul broca ( france ) ; adolfo lutz ( brazil ) ; nikolai korotkov ( russia ) ; sir william osler ( canada ) ; and harvey cushing ( united states ). as science and technology developed, medicine became more reliant upon medications. throughout history and in europe right until the late 18th century, not only plant products were used as medicine, but also animal ( including human ) body parts and fluids. pharmacology developed in part from herbalism and some drugs are still derived from plants ( atropine, ephedrine, warfarin, aspirin, digoxin, vinca alkaloids, taxol, hyoscine, etc. ). vaccines were discovered by edward jenner and louis pasteur. the first antibiotic was arsphenamine ( salvarsan ) discovered by paul ehrlich in 1908 after he observed that bacteria took up toxic dyes that human cells did not. the first major class of antibiotics was the sulfa drugs, derived by german chemists originally from azo dyes. pharmacology has become increasingly sophisticated ; modern biotechnology allows drugs targeted towards specific physiological processes to be developed, sometimes designed for compatibility with the body to reduce side - effects. genomics and knowledge of human genetics and human evolution is having increasingly significant influence on medicine, as the causative genes of most monogenic genetic disorders have now been identified, and the development of techniques in molecular biology, evolution, and genetics are influencing medical technology, practice and decision - making. evidence - based medicine is a contemporary movement to establish the most effective algorithms of practice ( ways of doing things ) through the use of systematic reviews and meta - analysis. the movement is facilitated by modern global information science, which allows as much of the available evidence as possible to be collected and analyzed according to standard protocols that are then disseminated to healthcare providers. the cochrane collaboration leads this movement. a 2001 review of 160 cochrane systematic reviews revealed that, according to two readers, 21. 3 % of the reviews concluded insufficient evidence, 20 % concluded evidence of no effect,
cross - fertilization that takes place among the various fields. psychology differs from biology and neuroscience in that it is primarily concerned with the interaction of mental processes and behaviour, and of the overall processes of a system, and not simply the biological or neural processes themselves, though the subfield of neuropsychology combines the study of the actual neural processes with the study of the mental effects they have subjectively produced. many people associate psychology with clinical psychology, which focuses on assessment and treatment of problems in living and psychopathology. in reality, psychology has myriad specialties including social psychology, developmental psychology, cognitive psychology, educational psychology, industrial - organizational psychology, mathematical psychology, neuropsychology, and quantitative analysis of behaviour. psychology is a very broad science that is rarely tackled as a whole, major block. although some subfields encompass a natural science base and a social science application, others can be clearly distinguished as having little to do with the social sciences or having a lot to do with the social sciences. for example, biological psychology is considered a natural science with a social scientific application ( as is clinical medicine ), social and occupational psychology are, generally speaking, purely social sciences, whereas neuropsychology is a natural science that lacks application out of the scientific tradition entirely. in british universities, emphasis on what tenet of psychology a student has studied and / or concentrated is communicated through the degree conferred : bpsy indicates a balance between natural and social sciences, bsc indicates a strong ( or entire ) scientific concentration, whereas a ba underlines a majority of social science credits. this is not always necessarily the case however, and in many uk institutions students studying the bpsy, bsc, and ba follow the same curriculum as outlined by the british psychological society and have the same options of specialism open to them regardless of whether they choose a balance, a heavy science basis, or heavy social science basis to their degree. if they applied to read the ba. for example, but specialized in heavily science - based modules, then they will still generally be awarded the ba. = = = sociology = = = sociology is the systematic study of society, individuals ' relationship to their societies, the consequences of difference, and other aspects of human social action. the meaning of the word comes from the suffix - logy, which means " study of ", derived from ancient greek, and the stem soci -, which is from the latin word socius, meaning " companion ", or society in general. auguste comte ( 1798 β 1857 ) coined
? if the latter, an important question is how the internal experiences of others can be measured. self - reports of feelings and beliefs may not be reliable because, even in cases in which there is no apparent incentive for subjects to intentionally deceive in their answers, self - deception or selective memory may affect their responses. then even in the case of accurate self - reports, how can responses be compared across individuals? even if two individuals respond with the same answer on a likert scale, they may be experiencing very different things. other issues in philosophy of psychology are philosophical questions about the nature of mind, brain, and cognition, and are perhaps more commonly thought of as part of cognitive science, or philosophy of mind. for example, are humans rational creatures? is there any sense in which they have free will, and how does that relate to the experience of making choices? philosophy of psychology also closely monitors contemporary work conducted in cognitive neuroscience, psycholinguistics, and artificial intelligence, questioning what they can and cannot explain in psychology. philosophy of psychology is a relatively young field, because psychology only became a discipline of its own in the late 1800s. in particular, neurophilosophy has just recently become its own field with the works of paul churchland and patricia churchland. philosophy of mind, by contrast, has been a well - established discipline since before psychology was a field of study at all. it is concerned with questions about the very nature of mind, the qualities of experience, and particular issues like the debate between dualism and monism. = = = philosophy of social science = = = the philosophy of social science is the study of the logic and method of the social sciences, such as sociology and cultural anthropology. philosophers of social science are concerned with the differences and similarities between the social and the natural sciences, causal relationships between social phenomena, the possible existence of social laws, and the ontological significance of structure and agency. the french philosopher, auguste comte ( 1798 β 1857 ), established the epistemological perspective of positivism in the course in positivist philosophy, a series of texts published between 1830 and 1842. the first three volumes of the course dealt chiefly with the natural sciences already in existence ( geoscience, astronomy, physics, chemistry, biology ), whereas the latter two emphasised the inevitable coming of social science : " sociologie ". for comte, the natural sciences had to necessarily arrive first, before humanity could adequately channel its efforts into the most challenging and complex " queen science " of human society
three of what is called the six simple machines, from which all machines are based. these machines are the inclined plane, the wedge, and the lever, which allowed the ancient egyptians to move millions of limestone blocks which weighed approximately 3. 5 tons ( 7, 000 lbs. ) each into place to create structures like the great pyramid of giza, which is 481 feet ( 147 meters ) high. they also made writing medium similar to paper from papyrus, which joshua mark states is the foundation for modern paper. papyrus is a plant ( cyperus papyrus ) which grew in plentiful amounts in the egyptian delta and throughout the nile river valley during ancient times. the papyrus was harvested by field workers and brought to processing centers where it was cut into thin strips. the strips were then laid - out side by side and covered in plant resin. the second layer of strips was laid on perpendicularly, then both pressed together until the sheet was dry. the sheets were then joined to form a roll and later used for writing. egyptian society made several significant advances during dynastic periods in many areas of technology. according to hossam elanzeery, they were the first civilization to use timekeeping devices such as sundials, shadow clocks, and obelisks and successfully leveraged their knowledge of astronomy to create a calendar model that society still uses today. they developed shipbuilding technology that saw them progress from papyrus reed vessels to cedar wood ships while also pioneering the use of rope trusses and stem - mounted rudders. the egyptians also used their knowledge of anatomy to lay the foundation for many modern medical techniques and practiced the earliest known version of neuroscience. elanzeery also states that they used and furthered mathematical science, as evidenced in the building of the pyramids. ancient egyptians also invented and pioneered many food technologies that have become the basis of modern food technology processes. based on paintings and reliefs found in tombs, as well as archaeological artifacts, scholars like paul t nicholson believe that the ancient egyptians established systematic farming practices, engaged in cereal processing, brewed beer and baked bread, processed meat, practiced viticulture and created the basis for modern wine production, and created condiments to complement, preserve and mask the flavors of their food. = = = = indus valley = = = = the indus valley civilization, situated in a resource - rich area ( in modern pakistan and northwestern india ), is notable for its early application of city planning, sanitation technologies, and plumbing. indus valley construction and architecture, called ' vaastu
Question: What is the largest part of the brain?
A) hypothalamus
B) cerebrum
C) pituitary gland
D) temporal lobe
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B) cerebrum
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Context:
##rozoic eon that began 539 million years ago being subdivided into paleozoic, mesozoic, and cenozoic eras. these three eras together comprise eleven periods ( cambrian, ordovician, silurian, devonian, carboniferous, permian, triassic, jurassic, cretaceous, tertiary, and quaternary ). the similarities among all known present - day species indicate that they have diverged through the process of evolution from their common ancestor. biologists regard the ubiquity of the genetic code as evidence of universal common descent for all bacteria, archaea, and eukaryotes. microbial mats of coexisting bacteria and archaea were the dominant form of life in the early archean eon and many of the major steps in early evolution are thought to have taken place in this environment. the earliest evidence of eukaryotes dates from 1. 85 billion years ago, and while they may have been present earlier, their diversification accelerated when they started using oxygen in their metabolism. later, around 1. 7 billion years ago, multicellular organisms began to appear, with differentiated cells performing specialised functions. algae - like multicellular land plants are dated back to about 1 billion years ago, although evidence suggests that microorganisms formed the earliest terrestrial ecosystems, at least 2. 7 billion years ago. microorganisms are thought to have paved the way for the inception of land plants in the ordovician period. land plants were so successful that they are thought to have contributed to the late devonian extinction event. ediacara biota appear during the ediacaran period, while vertebrates, along with most other modern phyla originated about 525 million years ago during the cambrian explosion. during the permian period, synapsids, including the ancestors of mammals, dominated the land, but most of this group became extinct in the permian β triassic extinction event 252 million years ago. during the recovery from this catastrophe, archosaurs became the most abundant land vertebrates ; one archosaur group, the dinosaurs, dominated the jurassic and cretaceous periods. after the cretaceous β paleogene extinction event 66 million years ago killed off the non - avian dinosaurs, mammals increased rapidly in size and diversity. such mass extinctions may have accelerated evolution by providing opportunities for new groups of organisms to diversify. = = diversity = = = = = bacteria and archaea = = = bacteria are a type of cell that constitute a large domain of prokar
have evolved from the earliest emergence of life to present day. earth formed about 4. 5 billion years ago and all life on earth, both living and extinct, descended from a last universal common ancestor that lived about 3. 5 billion years ago. geologists have developed a geologic time scale that divides the history of the earth into major divisions, starting with four eons ( hadean, archean, proterozoic, and phanerozoic ), the first three of which are collectively known as the precambrian, which lasted approximately 4 billion years. each eon can be divided into eras, with the phanerozoic eon that began 539 million years ago being subdivided into paleozoic, mesozoic, and cenozoic eras. these three eras together comprise eleven periods ( cambrian, ordovician, silurian, devonian, carboniferous, permian, triassic, jurassic, cretaceous, tertiary, and quaternary ). the similarities among all known present - day species indicate that they have diverged through the process of evolution from their common ancestor. biologists regard the ubiquity of the genetic code as evidence of universal common descent for all bacteria, archaea, and eukaryotes. microbial mats of coexisting bacteria and archaea were the dominant form of life in the early archean eon and many of the major steps in early evolution are thought to have taken place in this environment. the earliest evidence of eukaryotes dates from 1. 85 billion years ago, and while they may have been present earlier, their diversification accelerated when they started using oxygen in their metabolism. later, around 1. 7 billion years ago, multicellular organisms began to appear, with differentiated cells performing specialised functions. algae - like multicellular land plants are dated back to about 1 billion years ago, although evidence suggests that microorganisms formed the earliest terrestrial ecosystems, at least 2. 7 billion years ago. microorganisms are thought to have paved the way for the inception of land plants in the ordovician period. land plants were so successful that they are thought to have contributed to the late devonian extinction event. ediacara biota appear during the ediacaran period, while vertebrates, along with most other modern phyla originated about 525 million years ago during the cambrian explosion. during the permian period, synapsids, including the ancestors of mammals, dominated the land, but most of this group became
##ning an animal for its hide, and even forming other tools out of softer materials such as bone and wood. the earliest stone tools were irrelevant, being little more than a fractured rock. in the acheulian era, beginning approximately 1. 65 million years ago, methods of working these stones into specific shapes, such as hand axes emerged. this early stone age is described as the lower paleolithic. the middle paleolithic, approximately 300, 000 years ago, saw the introduction of the prepared - core technique, where multiple blades could be rapidly formed from a single core stone. the upper paleolithic, beginning approximately 40, 000 years ago, saw the introduction of pressure flaking, where a wood, bone, or antler punch could be used to shape a stone very finely. the end of the last ice age about 10, 000 years ago is taken as the end point of the upper paleolithic and the beginning of the epipaleolithic / mesolithic. the mesolithic technology included the use of microliths as composite stone tools, along with wood, bone, and antler tools. the later stone age, during which the rudiments of agricultural technology were developed, is called the neolithic period. during this period, polished stone tools were made from a variety of hard rocks such as flint, jade, jadeite, and greenstone, largely by working exposures as quarries, but later the valuable rocks were pursued by tunneling underground, the first steps in mining technology. the polished axes were used for forest clearance and the establishment of crop farming and were so effective as to remain in use when bronze and iron appeared. these stone axes were used alongside a continued use of stone tools such as a range of projectiles, knives, and scrapers, as well as tools, made from organic materials such as wood, bone, and antler. stone age cultures developed music and engaged in organized warfare. stone age humans developed ocean - worthy outrigger canoe technology, leading to migration across the malay archipelago, across the indian ocean to madagascar and also across the pacific ocean, which required knowledge of the ocean currents, weather patterns, sailing, and celestial navigation. although paleolithic cultures left no written records, the shift from nomadic life to settlement and agriculture can be inferred from a range of archaeological evidence. such evidence includes ancient tools, cave paintings, and other prehistoric art, such as the venus of willendorf. human remains also provide direct evidence, both through the examination of bones, and
##wi, turkana, dating from 3. 3 million years ago. stone tools diversified through the pleistocene period, which ended ~ 12, 000 years ago. the earliest evidence of warfare between two groups is recorded at the site of nataruk in turkana, kenya, where human skeletons with major traumatic injuries to the head, neck, ribs, knees and hands, including an embedded obsidian bladelet on a skull, are evidence of inter - group conflict between groups of nomadic hunter - gatherers 10, 000 years ago. humans entered the bronze age as they learned to smelt copper into an alloy with tin to make weapons. in asia where copper - tin ores are rare, this development was delayed until trading in bronze began in the third millennium bce. in the middle east and southern european regions, the bronze age follows the neolithic period, but in other parts of the world, the copper age is a transition from neolithic to the bronze age. although the iron age generally follows the bronze age, in some areas the iron age intrudes directly on the neolithic from outside the region, with the exception of sub - saharan africa where it was developed independently. the first large - scale use of iron weapons began in asia minor around the 14th century bce and in central europe around the 11th century bce followed by the middle east ( about 1000 bce ) and india and china. the assyrians are credited with the introduction of horse cavalry in warfare and the extensive use of iron weapons by 1100 bce. assyrians were also the first to use iron - tipped arrows. = = = post - classical technology = = = the wujing zongyao ( essentials of the military arts ), written by zeng gongliang, ding du, and others at the order of emperor renzong around 1043 during the song dynasty illustrate the eras focus on advancing intellectual issues and military technology due to the significance of warfare between the song and the liao, jin, and yuan to their north. the book covers topics of military strategy, training, and the production and employment of advanced weaponry. advances in military technology aided the song dynasty in its defense against hostile neighbors to the north. the flamethrower found its origins in byzantine - era greece, employing greek fire ( a chemically complex, highly flammable petrol fluid ) in a device with a siphon hose by the 7th century. : 77 the earliest reference to greek fire in china was made in 917, written by wu renchen in his spring and autumn annals of the ten kingdoms. : 80 in 91
. the first major technologies were tied to survival, hunting, and food preparation. stone tools and weapons, fire, and clothing were technological developments of major importance during this period. human ancestors have been using stone and other tools since long before the emergence of homo sapiens approximately 300, 000 years ago. the earliest direct evidence of tool usage was found in ethiopia within the great rift valley, dating back to 2. 5 million years ago. the earliest methods of stone tool making, known as the oldowan " industry ", date back to at least 2. 3 million years ago. this era of stone tool use is called the paleolithic, or " old stone age ", and spans all of human history up to the development of agriculture approximately 12, 000 years ago. to make a stone tool, a " core " of hard stone with specific flaking properties ( such as flint ) was struck with a hammerstone. this flaking produced sharp edges which could be used as tools, primarily in the form of choppers or scrapers. these tools greatly aided the early humans in their hunter - gatherer lifestyle to perform a variety of tasks including butchering carcasses ( and breaking bones to get at the marrow ) ; chopping wood ; cracking open nuts ; skinning an animal for its hide, and even forming other tools out of softer materials such as bone and wood. the earliest stone tools were irrelevant, being little more than a fractured rock. in the acheulian era, beginning approximately 1. 65 million years ago, methods of working these stones into specific shapes, such as hand axes emerged. this early stone age is described as the lower paleolithic. the middle paleolithic, approximately 300, 000 years ago, saw the introduction of the prepared - core technique, where multiple blades could be rapidly formed from a single core stone. the upper paleolithic, beginning approximately 40, 000 years ago, saw the introduction of pressure flaking, where a wood, bone, or antler punch could be used to shape a stone very finely. the end of the last ice age about 10, 000 years ago is taken as the end point of the upper paleolithic and the beginning of the epipaleolithic / mesolithic. the mesolithic technology included the use of microliths as composite stone tools, along with wood, bone, and antler tools. the later stone age, during which the rudiments of agricultural technology were developed, is called the neolithic period. during this period,
diploid embryo sporophyte within its tissues for at least part of its life, even in the seed plants, where the gametophyte itself is nurtured by its parent sporophyte. other groups of organisms that were previously studied by botanists include bacteria ( now studied in bacteriology ), fungi ( mycology ) β including lichen - forming fungi ( lichenology ), non - chlorophyte algae ( phycology ), and viruses ( virology ). however, attention is still given to these groups by botanists, and fungi ( including lichens ) and photosynthetic protists are usually covered in introductory botany courses. palaeobotanists study ancient plants in the fossil record to provide information about the evolutionary history of plants. cyanobacteria, the first oxygen - releasing photosynthetic organisms on earth, are thought to have given rise to the ancestor of plants by entering into an endosymbiotic relationship with an early eukaryote, ultimately becoming the chloroplasts in plant cells. the new photosynthetic plants ( along with their algal relatives ) accelerated the rise in atmospheric oxygen started by the cyanobacteria, changing the ancient oxygen - free, reducing, atmosphere to one in which free oxygen has been abundant for more than 2 billion years. among the important botanical questions of the 21st century are the role of plants as primary producers in the global cycling of life ' s basic ingredients : energy, carbon, oxygen, nitrogen and water, and ways that our plant stewardship can help address the global environmental issues of resource management, conservation, human food security, biologically invasive organisms, carbon sequestration, climate change, and sustainability. = = = human nutrition = = = virtually all staple foods come either directly from primary production by plants, or indirectly from animals that eat them. plants and other photosynthetic organisms are at the base of most food chains because they use the energy from the sun and nutrients from the soil and atmosphere, converting them into a form that can be used by animals. this is what ecologists call the first trophic level. the modern forms of the major staple foods, such as hemp, teff, maize, rice, wheat and other cereal grasses, pulses, bananas and plantains, as well as hemp, flax and cotton grown for their fibres, are the outcome of prehistoric selection over thousands of years from among wild ancestral plants with the most
into major divisions, starting with four eons ( hadean, archean, proterozoic, and phanerozoic ), the first three of which are collectively known as the precambrian, which lasted approximately 4 billion years. each eon can be divided into eras, with the phanerozoic eon that began 539 million years ago being subdivided into paleozoic, mesozoic, and cenozoic eras. these three eras together comprise eleven periods ( cambrian, ordovician, silurian, devonian, carboniferous, permian, triassic, jurassic, cretaceous, tertiary, and quaternary ). the similarities among all known present - day species indicate that they have diverged through the process of evolution from their common ancestor. biologists regard the ubiquity of the genetic code as evidence of universal common descent for all bacteria, archaea, and eukaryotes. microbial mats of coexisting bacteria and archaea were the dominant form of life in the early archean eon and many of the major steps in early evolution are thought to have taken place in this environment. the earliest evidence of eukaryotes dates from 1. 85 billion years ago, and while they may have been present earlier, their diversification accelerated when they started using oxygen in their metabolism. later, around 1. 7 billion years ago, multicellular organisms began to appear, with differentiated cells performing specialised functions. algae - like multicellular land plants are dated back to about 1 billion years ago, although evidence suggests that microorganisms formed the earliest terrestrial ecosystems, at least 2. 7 billion years ago. microorganisms are thought to have paved the way for the inception of land plants in the ordovician period. land plants were so successful that they are thought to have contributed to the late devonian extinction event. ediacara biota appear during the ediacaran period, while vertebrates, along with most other modern phyla originated about 525 million years ago during the cambrian explosion. during the permian period, synapsids, including the ancestors of mammals, dominated the land, but most of this group became extinct in the permian β triassic extinction event 252 million years ago. during the recovery from this catastrophe, archosaurs became the most abundant land vertebrates ; one archosaur group, the dinosaurs, dominated the jurassic and cretaceous periods. after the cretaceous β paleogene extinction event 66 million years ago killed off
hand axes emerged. this early stone age is described as the lower paleolithic. the middle paleolithic, approximately 300, 000 years ago, saw the introduction of the prepared - core technique, where multiple blades could be rapidly formed from a single core stone. the upper paleolithic, beginning approximately 40, 000 years ago, saw the introduction of pressure flaking, where a wood, bone, or antler punch could be used to shape a stone very finely. the end of the last ice age about 10, 000 years ago is taken as the end point of the upper paleolithic and the beginning of the epipaleolithic / mesolithic. the mesolithic technology included the use of microliths as composite stone tools, along with wood, bone, and antler tools. the later stone age, during which the rudiments of agricultural technology were developed, is called the neolithic period. during this period, polished stone tools were made from a variety of hard rocks such as flint, jade, jadeite, and greenstone, largely by working exposures as quarries, but later the valuable rocks were pursued by tunneling underground, the first steps in mining technology. the polished axes were used for forest clearance and the establishment of crop farming and were so effective as to remain in use when bronze and iron appeared. these stone axes were used alongside a continued use of stone tools such as a range of projectiles, knives, and scrapers, as well as tools, made from organic materials such as wood, bone, and antler. stone age cultures developed music and engaged in organized warfare. stone age humans developed ocean - worthy outrigger canoe technology, leading to migration across the malay archipelago, across the indian ocean to madagascar and also across the pacific ocean, which required knowledge of the ocean currents, weather patterns, sailing, and celestial navigation. although paleolithic cultures left no written records, the shift from nomadic life to settlement and agriculture can be inferred from a range of archaeological evidence. such evidence includes ancient tools, cave paintings, and other prehistoric art, such as the venus of willendorf. human remains also provide direct evidence, both through the examination of bones, and the study of mummies. scientists and historians have been able to form significant inferences about the lifestyle and culture of various prehistoric peoples, and especially their technology. = = = ancient = = = = = = = copper and bronze ages = = = = metallic copper occurs on the surface of weathered copper ore deposits and copper
they may have been present earlier, their diversification accelerated when they started using oxygen in their metabolism. later, around 1. 7 billion years ago, multicellular organisms began to appear, with differentiated cells performing specialised functions. algae - like multicellular land plants are dated back to about 1 billion years ago, although evidence suggests that microorganisms formed the earliest terrestrial ecosystems, at least 2. 7 billion years ago. microorganisms are thought to have paved the way for the inception of land plants in the ordovician period. land plants were so successful that they are thought to have contributed to the late devonian extinction event. ediacara biota appear during the ediacaran period, while vertebrates, along with most other modern phyla originated about 525 million years ago during the cambrian explosion. during the permian period, synapsids, including the ancestors of mammals, dominated the land, but most of this group became extinct in the permian β triassic extinction event 252 million years ago. during the recovery from this catastrophe, archosaurs became the most abundant land vertebrates ; one archosaur group, the dinosaurs, dominated the jurassic and cretaceous periods. after the cretaceous β paleogene extinction event 66 million years ago killed off the non - avian dinosaurs, mammals increased rapidly in size and diversity. such mass extinctions may have accelerated evolution by providing opportunities for new groups of organisms to diversify. = = diversity = = = = = bacteria and archaea = = = bacteria are a type of cell that constitute a large domain of prokaryotic microorganisms. typically a few micrometers in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. bacteria were among the first life forms to appear on earth, and are present in most of its habitats. bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep biosphere of the earth ' s crust. bacteria also live in symbiotic and parasitic relationships with plants and animals. most bacteria have not been characterised, and only about 27 percent of the bacterial phyla have species that can be grown in the laboratory. archaea constitute the other domain of prokaryotic cells and were initially classified as bacteria, receiving the name archaebacteria ( in the archaebacteria kingdom ), a term that has fallen out of use. archaeal cells have unique properties separating them from the other two domains, bacteria and eukaryota. archaea
, tertiary, and quaternary ). the similarities among all known present - day species indicate that they have diverged through the process of evolution from their common ancestor. biologists regard the ubiquity of the genetic code as evidence of universal common descent for all bacteria, archaea, and eukaryotes. microbial mats of coexisting bacteria and archaea were the dominant form of life in the early archean eon and many of the major steps in early evolution are thought to have taken place in this environment. the earliest evidence of eukaryotes dates from 1. 85 billion years ago, and while they may have been present earlier, their diversification accelerated when they started using oxygen in their metabolism. later, around 1. 7 billion years ago, multicellular organisms began to appear, with differentiated cells performing specialised functions. algae - like multicellular land plants are dated back to about 1 billion years ago, although evidence suggests that microorganisms formed the earliest terrestrial ecosystems, at least 2. 7 billion years ago. microorganisms are thought to have paved the way for the inception of land plants in the ordovician period. land plants were so successful that they are thought to have contributed to the late devonian extinction event. ediacara biota appear during the ediacaran period, while vertebrates, along with most other modern phyla originated about 525 million years ago during the cambrian explosion. during the permian period, synapsids, including the ancestors of mammals, dominated the land, but most of this group became extinct in the permian β triassic extinction event 252 million years ago. during the recovery from this catastrophe, archosaurs became the most abundant land vertebrates ; one archosaur group, the dinosaurs, dominated the jurassic and cretaceous periods. after the cretaceous β paleogene extinction event 66 million years ago killed off the non - avian dinosaurs, mammals increased rapidly in size and diversity. such mass extinctions may have accelerated evolution by providing opportunities for new groups of organisms to diversify. = = diversity = = = = = bacteria and archaea = = = bacteria are a type of cell that constitute a large domain of prokaryotic microorganisms. typically a few micrometers in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. bacteria were among the first life forms to appear on earth, and are present in most of its habitats. bacteria inhabit soil, water, acidic hot springs, radioactive
Question: Data from paleontology offer insights into the early evolution of what?
A) fungi
B) acids
C) neurons
D) cells
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A) fungi
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Context:
building block. ceramics β not to be confused with raw, unfired clay β are usually seen in crystalline form. the vast majority of commercial glasses contain a metal oxide fused with silica. at the high temperatures used to prepare glass, the material is a viscous liquid which solidifies into a disordered state upon cooling. windowpanes and eyeglasses are important examples. fibers of glass are also used for long - range telecommunication and optical transmission. scratch resistant corning gorilla glass is a well - known example of the application of materials science to drastically improve the properties of common components. engineering ceramics are known for their stiffness and stability under high temperatures, compression and electrical stress. alumina, silicon carbide, and tungsten carbide are made from a fine powder of their constituents in a process of sintering with a binder. hot pressing provides higher density material. chemical vapor deposition can place a film of a ceramic on another material. cermets are ceramic particles containing some metals. the wear resistance of tools is derived from cemented carbides with the metal phase of cobalt and nickel typically added to modify properties. ceramics can be significantly strengthened for engineering applications using the principle of crack deflection. this process involves the strategic addition of second - phase particles within a ceramic matrix, optimizing their shape, size, and distribution to direct and control crack propagation. this approach enhances fracture toughness, paving the way for the creation of advanced, high - performance ceramics in various industries. = = = composites = = = another application of materials science in industry is making composite materials. these are structured materials composed of two or more macroscopic phases. applications range from structural elements such as steel - reinforced concrete, to the thermal insulating tiles, which play a key and integral role in nasa ' s space shuttle thermal protection system, which is used to protect the surface of the shuttle from the heat of re - entry into the earth ' s atmosphere. one example is reinforced carbon - carbon ( rcc ), the light gray material, which withstands re - entry temperatures up to 1, 510 Β°c ( 2, 750 Β°f ) and protects the space shuttle ' s wing leading edges and nose cap. rcc is a laminated composite material made from graphite rayon cloth and impregnated with a phenolic resin. after curing at high temperature in an autoclave, the laminate is pyrolized to convert the resin to carbon, impregnated with furfuryl alcohol in a
which constitutes anywhere from 30 % [ m / m ] to 90 % [ m / m ] of its composition by volume, yielding an array of materials with interesting thermomechanical properties. in the processing of glass - ceramics, molten glass is cooled down gradually before reheating and annealing. in this heat treatment the glass partly crystallizes. in many cases, so - called ' nucleation agents ' are added in order to regulate and control the crystallization process. because there is usually no pressing and sintering, glass - ceramics do not contain the volume fraction of porosity typically present in sintered ceramics. the term mainly refers to a mix of lithium and aluminosilicates which yields an array of materials with interesting thermomechanical properties. the most commercially important of these have the distinction of being impervious to thermal shock. thus, glass - ceramics have become extremely useful for countertop cooking. the negative thermal expansion coefficient ( tec ) of the crystalline ceramic phase can be balanced with the positive tec of the glassy phase. at a certain point ( ~ 70 % crystalline ) the glass - ceramic has a net tec near zero. this type of glass - ceramic exhibits excellent mechanical properties and can sustain repeated and quick temperature changes up to 1000 Β°c. = = processing steps = = the traditional ceramic process generally follows this sequence : milling β batching β mixing β forming β drying β firing β assembly. milling is the process by which materials are reduced from a large size to a smaller size. milling may involve breaking up cemented material ( in which case individual particles retain their shape ) or pulverization ( which involves grinding the particles themselves to a smaller size ). milling is generally done by mechanical means, including attrition ( which is particle - to - particle collision that results in agglomerate break up or particle shearing ), compression ( which applies a forces that results in fracturing ), and impact ( which employs a milling medium or the particles themselves to cause fracturing ). attrition milling equipment includes the wet scrubber ( also called the planetary mill or wet attrition mill ), which has paddles in water creating vortexes in which the material collides and break up. compression mills include the jaw crusher, roller crusher and cone crusher. impact mills include the ball mill, which has media that tumble and fracture the material, or the resonantacoustic mixer. shaft impactors cause particle - to particle attrition and compression
material includes the unit cell, which is the smallest unit of a crystal lattice ( space lattice ) that repeats to make up the macroscopic crystal structure. most common structural materials include parallelpiped and hexagonal lattice types. in single crystals, the effects of the crystalline arrangement of atoms is often easy to see macroscopically, because the natural shapes of crystals reflect the atomic structure. further, physical properties are often controlled by crystalline defects. the understanding of crystal structures is an important prerequisite for understanding crystallographic defects. examples of crystal defects consist of dislocations including edges, screws, vacancies, self inter - stitials, and more that are linear, planar, and three dimensional types of defects. new and advanced materials that are being developed include nanomaterials, biomaterials. mostly, materials do not occur as a single crystal, but in polycrystalline form, as an aggregate of small crystals or grains with different orientations. because of this, the powder diffraction method, which uses diffraction patterns of polycrystalline samples with a large number of crystals, plays an important role in structural determination. most materials have a crystalline structure, but some important materials do not exhibit regular crystal structure. polymers display varying degrees of crystallinity, and many are completely non - crystalline. glass, some ceramics, and many natural materials are amorphous, not possessing any long - range order in their atomic arrangements. the study of polymers combines elements of chemical and statistical thermodynamics to give thermodynamic and mechanical descriptions of physical properties. = = = = nanostructure = = = = materials, which atoms and molecules form constituents in the nanoscale ( i. e., they form nanostructures ) are called nanomaterials. nanomaterials are the subject of intense research in the materials science community due to the unique properties that they exhibit. nanostructure deals with objects and structures that are in the 1 β 100 nm range. in many materials, atoms or molecules agglomerate to form objects at the nanoscale. this causes many interesting electrical, magnetic, optical, and mechanical properties. in describing nanostructures, it is necessary to differentiate between the number of dimensions on the nanoscale. nanotextured surfaces have one dimension on the nanoscale, i. e., only the thickness of the surface of an object is between 0. 1 and 100 nm
as dental implants and synthetic bones. hydroxyapatite, the natural mineral component of bone, has been made synthetically from a number of biological and chemical sources and can be formed into ceramic materials. orthopedic implants made from these materials bond readily to bone and other tissues in the body without rejection or inflammatory reactions. because of this, they are of great interest for gene delivery and tissue engineering scaffolds. most hydroxyapatite ceramics are very porous and lack mechanical strength and are used to coat metal orthopedic devices to aid in forming a bond to bone or as bone fillers. they are also used as fillers for orthopedic plastic screws to aid in reducing the inflammation and increase absorption of these plastic materials. work is being done to make strong, fully dense nano crystalline hydroxyapatite ceramic materials for orthopedic weight bearing devices, replacing foreign metal and plastic orthopedic materials with a synthetic, but naturally occurring, bone mineral. ultimately these ceramic materials may be used as bone replacements or with the incorporation of protein collagens, synthetic bones. durable actinide - containing ceramic materials have many applications such as in nuclear fuels for burning excess pu and in chemically - inert sources of alpha irradiation for power supply of unmanned space vehicles or to produce electricity for microelectronic devices. both use and disposal of radioactive actinides require their immobilization in a durable host material. nuclear waste long - lived radionuclides such as actinides are immobilized using chemically - durable crystalline materials based on polycrystalline ceramics and large single crystals. alumina ceramics are widely utilized in the chemical industry due to their excellent chemical stability and high resistance to corrosion. it is used as acid - resistant pump impellers and pump bodies, ensuring long - lasting performance in transferring aggressive fluids. they are also used in acid - carrying pipe linings to prevent contamination and maintain fluid purity, which is crucial in industries like pharmaceuticals and food processing. valves made from alumina ceramics demonstrate exceptional durability and resistance to chemical attack, making them reliable for controlling the flow of corrosive liquids. = = glass - ceramics = = glass - ceramic materials share many properties with both glasses and ceramics. glass - ceramics have an amorphous phase and one or more crystalline phases and are produced by a so - called " controlled crystallization ", which is typically avoided in glass manufacturing. glass - ceramics often contain a crystalline phase
= glass - ceramics = = glass - ceramic materials share many properties with both glasses and ceramics. glass - ceramics have an amorphous phase and one or more crystalline phases and are produced by a so - called " controlled crystallization ", which is typically avoided in glass manufacturing. glass - ceramics often contain a crystalline phase which constitutes anywhere from 30 % [ m / m ] to 90 % [ m / m ] of its composition by volume, yielding an array of materials with interesting thermomechanical properties. in the processing of glass - ceramics, molten glass is cooled down gradually before reheating and annealing. in this heat treatment the glass partly crystallizes. in many cases, so - called ' nucleation agents ' are added in order to regulate and control the crystallization process. because there is usually no pressing and sintering, glass - ceramics do not contain the volume fraction of porosity typically present in sintered ceramics. the term mainly refers to a mix of lithium and aluminosilicates which yields an array of materials with interesting thermomechanical properties. the most commercially important of these have the distinction of being impervious to thermal shock. thus, glass - ceramics have become extremely useful for countertop cooking. the negative thermal expansion coefficient ( tec ) of the crystalline ceramic phase can be balanced with the positive tec of the glassy phase. at a certain point ( ~ 70 % crystalline ) the glass - ceramic has a net tec near zero. this type of glass - ceramic exhibits excellent mechanical properties and can sustain repeated and quick temperature changes up to 1000 Β°c. = = processing steps = = the traditional ceramic process generally follows this sequence : milling β batching β mixing β forming β drying β firing β assembly. milling is the process by which materials are reduced from a large size to a smaller size. milling may involve breaking up cemented material ( in which case individual particles retain their shape ) or pulverization ( which involves grinding the particles themselves to a smaller size ). milling is generally done by mechanical means, including attrition ( which is particle - to - particle collision that results in agglomerate break up or particle shearing ), compression ( which applies a forces that results in fracturing ), and impact ( which employs a milling medium or the particles themselves to cause fracturing ). attrition milling equipment includes the wet scrubber ( also called the planetary mill or wet attrition mill ), which has paddles in water creating vortexes in which
passage of carbon dioxide as aluminum and glass. = = = ceramics and glasses = = = another application of materials science is the study of ceramics and glasses, typically the most brittle materials with industrial relevance. many ceramics and glasses exhibit covalent or ionic - covalent bonding with sio2 ( silica ) as a fundamental building block. ceramics β not to be confused with raw, unfired clay β are usually seen in crystalline form. the vast majority of commercial glasses contain a metal oxide fused with silica. at the high temperatures used to prepare glass, the material is a viscous liquid which solidifies into a disordered state upon cooling. windowpanes and eyeglasses are important examples. fibers of glass are also used for long - range telecommunication and optical transmission. scratch resistant corning gorilla glass is a well - known example of the application of materials science to drastically improve the properties of common components. engineering ceramics are known for their stiffness and stability under high temperatures, compression and electrical stress. alumina, silicon carbide, and tungsten carbide are made from a fine powder of their constituents in a process of sintering with a binder. hot pressing provides higher density material. chemical vapor deposition can place a film of a ceramic on another material. cermets are ceramic particles containing some metals. the wear resistance of tools is derived from cemented carbides with the metal phase of cobalt and nickel typically added to modify properties. ceramics can be significantly strengthened for engineering applications using the principle of crack deflection. this process involves the strategic addition of second - phase particles within a ceramic matrix, optimizing their shape, size, and distribution to direct and control crack propagation. this approach enhances fracture toughness, paving the way for the creation of advanced, high - performance ceramics in various industries. = = = composites = = = another application of materials science in industry is making composite materials. these are structured materials composed of two or more macroscopic phases. applications range from structural elements such as steel - reinforced concrete, to the thermal insulating tiles, which play a key and integral role in nasa ' s space shuttle thermal protection system, which is used to protect the surface of the shuttle from the heat of re - entry into the earth ' s atmosphere. one example is reinforced carbon - carbon ( rcc ), the light gray material, which withstands re - entry temperatures up to 1, 510 Β°c ( 2, 750 Β°f ) and protects the space shuttle ' s wing leading edges and nose cap
##ally, because the natural shapes of crystals reflect the atomic structure. further, physical properties are often controlled by crystalline defects. the understanding of crystal structures is an important prerequisite for understanding crystallographic defects. examples of crystal defects consist of dislocations including edges, screws, vacancies, self inter - stitials, and more that are linear, planar, and three dimensional types of defects. new and advanced materials that are being developed include nanomaterials, biomaterials. mostly, materials do not occur as a single crystal, but in polycrystalline form, as an aggregate of small crystals or grains with different orientations. because of this, the powder diffraction method, which uses diffraction patterns of polycrystalline samples with a large number of crystals, plays an important role in structural determination. most materials have a crystalline structure, but some important materials do not exhibit regular crystal structure. polymers display varying degrees of crystallinity, and many are completely non - crystalline. glass, some ceramics, and many natural materials are amorphous, not possessing any long - range order in their atomic arrangements. the study of polymers combines elements of chemical and statistical thermodynamics to give thermodynamic and mechanical descriptions of physical properties. = = = = nanostructure = = = = materials, which atoms and molecules form constituents in the nanoscale ( i. e., they form nanostructures ) are called nanomaterials. nanomaterials are the subject of intense research in the materials science community due to the unique properties that they exhibit. nanostructure deals with objects and structures that are in the 1 β 100 nm range. in many materials, atoms or molecules agglomerate to form objects at the nanoscale. this causes many interesting electrical, magnetic, optical, and mechanical properties. in describing nanostructures, it is necessary to differentiate between the number of dimensions on the nanoscale. nanotextured surfaces have one dimension on the nanoscale, i. e., only the thickness of the surface of an object is between 0. 1 and 100 nm. nanotubes have two dimensions on the nanoscale, i. e., the diameter of the tube is between 0. 1 and 100 nm ; its length could be much greater. finally, spherical nanoparticles have three dimensions on the nanoscale, i. e., the particle is between
of ceramic parts in the requisite precision and durability is difficult. imperfection in the ceramic leads to cracks, which can lead to potentially dangerous equipment failure. such engines are possible in laboratory settings, but mass - production is not feasible with current technology. work is being done in developing ceramic parts for gas turbine engines. currently, even blades made of advanced metal alloys used in the engines ' hot section require cooling and careful limiting of operating temperatures. turbine engines made with ceramics could operate more efficiently, giving aircraft greater range and payload for a set amount of fuel. recently, there have been advances in ceramics which include bio - ceramics, such as dental implants and synthetic bones. hydroxyapatite, the natural mineral component of bone, has been made synthetically from a number of biological and chemical sources and can be formed into ceramic materials. orthopedic implants made from these materials bond readily to bone and other tissues in the body without rejection or inflammatory reactions. because of this, they are of great interest for gene delivery and tissue engineering scaffolds. most hydroxyapatite ceramics are very porous and lack mechanical strength and are used to coat metal orthopedic devices to aid in forming a bond to bone or as bone fillers. they are also used as fillers for orthopedic plastic screws to aid in reducing the inflammation and increase absorption of these plastic materials. work is being done to make strong, fully dense nano crystalline hydroxyapatite ceramic materials for orthopedic weight bearing devices, replacing foreign metal and plastic orthopedic materials with a synthetic, but naturally occurring, bone mineral. ultimately these ceramic materials may be used as bone replacements or with the incorporation of protein collagens, synthetic bones. durable actinide - containing ceramic materials have many applications such as in nuclear fuels for burning excess pu and in chemically - inert sources of alpha irradiation for power supply of unmanned space vehicles or to produce electricity for microelectronic devices. both use and disposal of radioactive actinides require their immobilization in a durable host material. nuclear waste long - lived radionuclides such as actinides are immobilized using chemically - durable crystalline materials based on polycrystalline ceramics and large single crystals. alumina ceramics are widely utilized in the chemical industry due to their excellent chemical stability and high resistance to corrosion. it is used as acid - resistant pump impellers and pump bodies, ensuring long - lasting performance in transferring aggressive
product of ceramic manufacture, or as an adjective. ceramics is the making of things out of ceramic materials. ceramic engineering, like many sciences, evolved from a different discipline by today ' s standards. materials science engineering is grouped with ceramics engineering to this day. abraham darby first used coke in 1709 in shropshire, england, to improve the yield of a smelting process. coke is now widely used to produce carbide ceramics. potter josiah wedgwood opened the first modern ceramics factory in stoke - on - trent, england, in 1759. austrian chemist carl josef bayer, working for the textile industry in russia, developed a process to separate alumina from bauxite ore in 1888. the bayer process is still used to purify alumina for the ceramic and aluminium industries. brothers pierre and jacques curie discovered piezoelectricity in rochelle salt c. 1880. piezoelectricity is one of the key properties of electroceramics. e. g. acheson heated a mixture of coke and clay in 1893, and invented carborundum, or synthetic silicon carbide. henri moissan also synthesized sic and tungsten carbide in his electric arc furnace in paris about the same time as acheson. karl schroter used liquid - phase sintering to bond or " cement " moissan ' s tungsten carbide particles with cobalt in 1923 in germany. cemented ( metal - bonded ) carbide edges greatly increase the durability of hardened steel cutting tools. w. h. nernst developed cubic - stabilized zirconia in the 1920s in berlin. this material is used as an oxygen sensor in exhaust systems. the main limitation on the use of ceramics in engineering is brittleness. = = = military = = = the military requirements of world war ii encouraged developments, which created a need for high - performance materials and helped speed the development of ceramic science and engineering. throughout the 1960s and 1970s, new types of ceramics were developed in response to advances in atomic energy, electronics, communications, and space travel. the discovery of ceramic superconductors in 1986 has spurred intense research to develop superconducting ceramic parts for electronic devices, electric motors, and transportation equipment. there is an increasing need in the military sector for high - strength, robust materials which have the capability to transmit light around the visible ( 0. 4 β 0. 7 micrometers ) and mid - infrared ( 1 β 5 micrometers ) regions of the spectrum. these materials
. currently, even blades made of advanced metal alloys used in the engines ' hot section require cooling and careful limiting of operating temperatures. turbine engines made with ceramics could operate more efficiently, giving aircraft greater range and payload for a set amount of fuel. recently, there have been advances in ceramics which include bio - ceramics, such as dental implants and synthetic bones. hydroxyapatite, the natural mineral component of bone, has been made synthetically from a number of biological and chemical sources and can be formed into ceramic materials. orthopedic implants made from these materials bond readily to bone and other tissues in the body without rejection or inflammatory reactions. because of this, they are of great interest for gene delivery and tissue engineering scaffolds. most hydroxyapatite ceramics are very porous and lack mechanical strength and are used to coat metal orthopedic devices to aid in forming a bond to bone or as bone fillers. they are also used as fillers for orthopedic plastic screws to aid in reducing the inflammation and increase absorption of these plastic materials. work is being done to make strong, fully dense nano crystalline hydroxyapatite ceramic materials for orthopedic weight bearing devices, replacing foreign metal and plastic orthopedic materials with a synthetic, but naturally occurring, bone mineral. ultimately these ceramic materials may be used as bone replacements or with the incorporation of protein collagens, synthetic bones. durable actinide - containing ceramic materials have many applications such as in nuclear fuels for burning excess pu and in chemically - inert sources of alpha irradiation for power supply of unmanned space vehicles or to produce electricity for microelectronic devices. both use and disposal of radioactive actinides require their immobilization in a durable host material. nuclear waste long - lived radionuclides such as actinides are immobilized using chemically - durable crystalline materials based on polycrystalline ceramics and large single crystals. alumina ceramics are widely utilized in the chemical industry due to their excellent chemical stability and high resistance to corrosion. it is used as acid - resistant pump impellers and pump bodies, ensuring long - lasting performance in transferring aggressive fluids. they are also used in acid - carrying pipe linings to prevent contamination and maintain fluid purity, which is crucial in industries like pharmaceuticals and food processing. valves made from alumina ceramics demonstrate exceptional durability and resistance to chemical attack, making them reliable for controlling the flow of corrosive liquids. =
Question: One crystalline form of calcium carbonate is the mineral sold as what?
A) quartz
B) calcite
C) basalt
D) salt
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B) calcite
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Context:
the world is changing at an ever - increasing pace. and it has changed in a much more fundamental way than one would think, primarily because it has become more connected and interdependent than in our entire history. every new product, every new invention can be combined with those that existed before, thereby creating an explosion of complexity : structural complexity, dynamic complexity, functional complexity, and algorithmic complexity. how to respond to this challenge? and what are the costs?
fluid dynamics video demonstrating the evolution of dynamic stall on a wind turbine blade.
, tertiary, and quaternary ). the similarities among all known present - day species indicate that they have diverged through the process of evolution from their common ancestor. biologists regard the ubiquity of the genetic code as evidence of universal common descent for all bacteria, archaea, and eukaryotes. microbial mats of coexisting bacteria and archaea were the dominant form of life in the early archean eon and many of the major steps in early evolution are thought to have taken place in this environment. the earliest evidence of eukaryotes dates from 1. 85 billion years ago, and while they may have been present earlier, their diversification accelerated when they started using oxygen in their metabolism. later, around 1. 7 billion years ago, multicellular organisms began to appear, with differentiated cells performing specialised functions. algae - like multicellular land plants are dated back to about 1 billion years ago, although evidence suggests that microorganisms formed the earliest terrestrial ecosystems, at least 2. 7 billion years ago. microorganisms are thought to have paved the way for the inception of land plants in the ordovician period. land plants were so successful that they are thought to have contributed to the late devonian extinction event. ediacara biota appear during the ediacaran period, while vertebrates, along with most other modern phyla originated about 525 million years ago during the cambrian explosion. during the permian period, synapsids, including the ancestors of mammals, dominated the land, but most of this group became extinct in the permian β triassic extinction event 252 million years ago. during the recovery from this catastrophe, archosaurs became the most abundant land vertebrates ; one archosaur group, the dinosaurs, dominated the jurassic and cretaceous periods. after the cretaceous β paleogene extinction event 66 million years ago killed off the non - avian dinosaurs, mammals increased rapidly in size and diversity. such mass extinctions may have accelerated evolution by providing opportunities for new groups of organisms to diversify. = = diversity = = = = = bacteria and archaea = = = bacteria are a type of cell that constitute a large domain of prokaryotic microorganisms. typically a few micrometers in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. bacteria were among the first life forms to appear on earth, and are present in most of its habitats. bacteria inhabit soil, water, acidic hot springs, radioactive
have evolved from the earliest emergence of life to present day. earth formed about 4. 5 billion years ago and all life on earth, both living and extinct, descended from a last universal common ancestor that lived about 3. 5 billion years ago. geologists have developed a geologic time scale that divides the history of the earth into major divisions, starting with four eons ( hadean, archean, proterozoic, and phanerozoic ), the first three of which are collectively known as the precambrian, which lasted approximately 4 billion years. each eon can be divided into eras, with the phanerozoic eon that began 539 million years ago being subdivided into paleozoic, mesozoic, and cenozoic eras. these three eras together comprise eleven periods ( cambrian, ordovician, silurian, devonian, carboniferous, permian, triassic, jurassic, cretaceous, tertiary, and quaternary ). the similarities among all known present - day species indicate that they have diverged through the process of evolution from their common ancestor. biologists regard the ubiquity of the genetic code as evidence of universal common descent for all bacteria, archaea, and eukaryotes. microbial mats of coexisting bacteria and archaea were the dominant form of life in the early archean eon and many of the major steps in early evolution are thought to have taken place in this environment. the earliest evidence of eukaryotes dates from 1. 85 billion years ago, and while they may have been present earlier, their diversification accelerated when they started using oxygen in their metabolism. later, around 1. 7 billion years ago, multicellular organisms began to appear, with differentiated cells performing specialised functions. algae - like multicellular land plants are dated back to about 1 billion years ago, although evidence suggests that microorganisms formed the earliest terrestrial ecosystems, at least 2. 7 billion years ago. microorganisms are thought to have paved the way for the inception of land plants in the ordovician period. land plants were so successful that they are thought to have contributed to the late devonian extinction event. ediacara biota appear during the ediacaran period, while vertebrates, along with most other modern phyla originated about 525 million years ago during the cambrian explosion. during the permian period, synapsids, including the ancestors of mammals, dominated the land, but most of this group became
##rozoic eon that began 539 million years ago being subdivided into paleozoic, mesozoic, and cenozoic eras. these three eras together comprise eleven periods ( cambrian, ordovician, silurian, devonian, carboniferous, permian, triassic, jurassic, cretaceous, tertiary, and quaternary ). the similarities among all known present - day species indicate that they have diverged through the process of evolution from their common ancestor. biologists regard the ubiquity of the genetic code as evidence of universal common descent for all bacteria, archaea, and eukaryotes. microbial mats of coexisting bacteria and archaea were the dominant form of life in the early archean eon and many of the major steps in early evolution are thought to have taken place in this environment. the earliest evidence of eukaryotes dates from 1. 85 billion years ago, and while they may have been present earlier, their diversification accelerated when they started using oxygen in their metabolism. later, around 1. 7 billion years ago, multicellular organisms began to appear, with differentiated cells performing specialised functions. algae - like multicellular land plants are dated back to about 1 billion years ago, although evidence suggests that microorganisms formed the earliest terrestrial ecosystems, at least 2. 7 billion years ago. microorganisms are thought to have paved the way for the inception of land plants in the ordovician period. land plants were so successful that they are thought to have contributed to the late devonian extinction event. ediacara biota appear during the ediacaran period, while vertebrates, along with most other modern phyla originated about 525 million years ago during the cambrian explosion. during the permian period, synapsids, including the ancestors of mammals, dominated the land, but most of this group became extinct in the permian β triassic extinction event 252 million years ago. during the recovery from this catastrophe, archosaurs became the most abundant land vertebrates ; one archosaur group, the dinosaurs, dominated the jurassic and cretaceous periods. after the cretaceous β paleogene extinction event 66 million years ago killed off the non - avian dinosaurs, mammals increased rapidly in size and diversity. such mass extinctions may have accelerated evolution by providing opportunities for new groups of organisms to diversify. = = diversity = = = = = bacteria and archaea = = = bacteria are a type of cell that constitute a large domain of prokar
to chromatin, which is a complex of dna and protein found in eukaryotic cells. = = = genes, development, and evolution = = = development is the process by which a multicellular organism ( plant or animal ) goes through a series of changes, starting from a single cell, and taking on various forms that are characteristic of its life cycle. there are four key processes that underlie development : determination, differentiation, morphogenesis, and growth. determination sets the developmental fate of a cell, which becomes more restrictive during development. differentiation is the process by which specialized cells arise from less specialized cells such as stem cells. stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. cellular differentiation dramatically changes a cell ' s size, shape, membrane potential, metabolic activity, and responsiveness to signals, which are largely due to highly controlled modifications in gene expression and epigenetics. with a few exceptions, cellular differentiation almost never involves a change in the dna sequence itself. thus, different cells can have very different physical characteristics despite having the same genome. morphogenesis, or the development of body form, is the result of spatial differences in gene expression. a small fraction of the genes in an organism ' s genome called the developmental - genetic toolkit control the development of that organism. these toolkit genes are highly conserved among phyla, meaning that they are ancient and very similar in widely separated groups of animals. differences in deployment of toolkit genes affect the body plan and the number, identity, and pattern of body parts. among the most important toolkit genes are the hox genes. hox genes determine where repeating parts, such as the many vertebrae of snakes, will grow in a developing embryo or larva. = = evolution = = = = = evolutionary processes = = = evolution is a central organizing concept in biology. it is the change in heritable characteristics of populations over successive generations. in artificial selection, animals were selectively bred for specific traits. given that traits are inherited, populations contain a varied mix of traits, and reproduction is able to increase any population, darwin argued that in the natural world, it was nature that played the role of humans in selecting for specific traits. darwin inferred that individuals who possessed heritable traits better adapted to their environments are more likely to survive and produce more offspring than other individuals. he further inferred that this would lead to the
dynamical evolution of spiral galaxies is strongly dependent on non - axisymmetric patterns that develop from gravitational instabilities, either spontaneously or externally triggered. some evolutionary sequences are described through which a galaxy could possibly concentrate mass and build bulges, how external gas accretion from cosmic filaments could be funneled to the galaxy disks, and intermittently driven to the galaxy center, to form nuclear starbursts and fuel an active nucleus. the frequency of both bars and lopsidedness can be used to constrain the gas accretion rate.
into major divisions, starting with four eons ( hadean, archean, proterozoic, and phanerozoic ), the first three of which are collectively known as the precambrian, which lasted approximately 4 billion years. each eon can be divided into eras, with the phanerozoic eon that began 539 million years ago being subdivided into paleozoic, mesozoic, and cenozoic eras. these three eras together comprise eleven periods ( cambrian, ordovician, silurian, devonian, carboniferous, permian, triassic, jurassic, cretaceous, tertiary, and quaternary ). the similarities among all known present - day species indicate that they have diverged through the process of evolution from their common ancestor. biologists regard the ubiquity of the genetic code as evidence of universal common descent for all bacteria, archaea, and eukaryotes. microbial mats of coexisting bacteria and archaea were the dominant form of life in the early archean eon and many of the major steps in early evolution are thought to have taken place in this environment. the earliest evidence of eukaryotes dates from 1. 85 billion years ago, and while they may have been present earlier, their diversification accelerated when they started using oxygen in their metabolism. later, around 1. 7 billion years ago, multicellular organisms began to appear, with differentiated cells performing specialised functions. algae - like multicellular land plants are dated back to about 1 billion years ago, although evidence suggests that microorganisms formed the earliest terrestrial ecosystems, at least 2. 7 billion years ago. microorganisms are thought to have paved the way for the inception of land plants in the ordovician period. land plants were so successful that they are thought to have contributed to the late devonian extinction event. ediacara biota appear during the ediacaran period, while vertebrates, along with most other modern phyla originated about 525 million years ago during the cambrian explosion. during the permian period, synapsids, including the ancestors of mammals, dominated the land, but most of this group became extinct in the permian β triassic extinction event 252 million years ago. during the recovery from this catastrophe, archosaurs became the most abundant land vertebrates ; one archosaur group, the dinosaurs, dominated the jurassic and cretaceous periods. after the cretaceous β paleogene extinction event 66 million years ago killed off
this paper has been withdrawn by the authors until some changes are made.
or removed from the dna during programmed stages of development of the plant, and are responsible, for example, for the differences between anthers, petals and normal leaves, despite the fact that they all have the same underlying genetic code. epigenetic changes may be temporary or may remain through successive cell divisions for the remainder of the cell ' s life. some epigenetic changes have been shown to be heritable, while others are reset in the germ cells. epigenetic changes in eukaryotic biology serve to regulate the process of cellular differentiation. during morphogenesis, totipotent stem cells become the various pluripotent cell lines of the embryo, which in turn become fully differentiated cells. a single fertilised egg cell, the zygote, gives rise to the many different plant cell types including parenchyma, xylem vessel elements, phloem sieve tubes, guard cells of the epidermis, etc. as it continues to divide. the process results from the epigenetic activation of some genes and inhibition of others. unlike animals, many plant cells, particularly those of the parenchyma, do not terminally differentiate, remaining totipotent with the ability to give rise to a new individual plant. exceptions include highly lignified cells, the sclerenchyma and xylem which are dead at maturity, and the phloem sieve tubes which lack nuclei. while plants use many of the same epigenetic mechanisms as animals, such as chromatin remodelling, an alternative hypothesis is that plants set their gene expression patterns using positional information from the environment and surrounding cells to determine their developmental fate. epigenetic changes can lead to paramutations, which do not follow the mendelian heritage rules. these epigenetic marks are carried from one generation to the next, with one allele inducing a change on the other. = = plant evolution = = the chloroplasts of plants have a number of biochemical, structural and genetic similarities to cyanobacteria, ( commonly but incorrectly known as " blue - green algae " ) and are thought to be derived from an ancient endosymbiotic relationship between an ancestral eukaryotic cell and a cyanobacterial resident. the algae are a polyphyletic group and are placed in various divisions, some more closely related to plants than others. there are many differences between them in features such as cell wall composition, biochemistry,
Question: Human evolution shows that evolutionary changes typically occur at what pace?
A) slow
B) sudden
C) uneven
D) rapid
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A) slow
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Context:
##yotic microorganisms. typically a few micrometers in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. bacteria were among the first life forms to appear on earth, and are present in most of its habitats. bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep biosphere of the earth ' s crust. bacteria also live in symbiotic and parasitic relationships with plants and animals. most bacteria have not been characterised, and only about 27 percent of the bacterial phyla have species that can be grown in the laboratory. archaea constitute the other domain of prokaryotic cells and were initially classified as bacteria, receiving the name archaebacteria ( in the archaebacteria kingdom ), a term that has fallen out of use. archaeal cells have unique properties separating them from the other two domains, bacteria and eukaryota. archaea are further divided into multiple recognized phyla. archaea and bacteria are generally similar in size and shape, although a few archaea have very different shapes, such as the flat and square cells of haloquadratum walsbyi. despite this morphological similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes, notably for the enzymes involved in transcription and translation. other aspects of archaeal biochemistry are unique, such as their reliance on ether lipids in their cell membranes, including archaeols. archaea use more energy sources than eukaryotes : these range from organic compounds, such as sugars, to ammonia, metal ions or even hydrogen gas. salt - tolerant archaea ( the haloarchaea ) use sunlight as an energy source, and other species of archaea fix carbon, but unlike plants and cyanobacteria, no known species of archaea does both. archaea reproduce asexually by binary fission, fragmentation, or budding ; unlike bacteria, no known species of archaea form endospores. the first observed archaea were extremophiles, living in extreme environments, such as hot springs and salt lakes with no other organisms. improved molecular detection tools led to the discovery of archaea in almost every habitat, including soil, oceans, and marshlands. archaea are particularly numerous in the oceans, and the archaea in plankton may be one of the most abundant groups of organisms on the planet. archaea are a major part of earth ' s life.
, tertiary, and quaternary ). the similarities among all known present - day species indicate that they have diverged through the process of evolution from their common ancestor. biologists regard the ubiquity of the genetic code as evidence of universal common descent for all bacteria, archaea, and eukaryotes. microbial mats of coexisting bacteria and archaea were the dominant form of life in the early archean eon and many of the major steps in early evolution are thought to have taken place in this environment. the earliest evidence of eukaryotes dates from 1. 85 billion years ago, and while they may have been present earlier, their diversification accelerated when they started using oxygen in their metabolism. later, around 1. 7 billion years ago, multicellular organisms began to appear, with differentiated cells performing specialised functions. algae - like multicellular land plants are dated back to about 1 billion years ago, although evidence suggests that microorganisms formed the earliest terrestrial ecosystems, at least 2. 7 billion years ago. microorganisms are thought to have paved the way for the inception of land plants in the ordovician period. land plants were so successful that they are thought to have contributed to the late devonian extinction event. ediacara biota appear during the ediacaran period, while vertebrates, along with most other modern phyla originated about 525 million years ago during the cambrian explosion. during the permian period, synapsids, including the ancestors of mammals, dominated the land, but most of this group became extinct in the permian β triassic extinction event 252 million years ago. during the recovery from this catastrophe, archosaurs became the most abundant land vertebrates ; one archosaur group, the dinosaurs, dominated the jurassic and cretaceous periods. after the cretaceous β paleogene extinction event 66 million years ago killed off the non - avian dinosaurs, mammals increased rapidly in size and diversity. such mass extinctions may have accelerated evolution by providing opportunities for new groups of organisms to diversify. = = diversity = = = = = bacteria and archaea = = = bacteria are a type of cell that constitute a large domain of prokaryotic microorganisms. typically a few micrometers in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. bacteria were among the first life forms to appear on earth, and are present in most of its habitats. bacteria inhabit soil, water, acidic hot springs, radioactive
urinary tract infection ( utis ) is referred as one of the most common infection in medical sectors worldwide and antimicrobial resistance ( amr ) is also a global threat to human that is related with many diseases. as antibiotics used for the treatment of infectious diseases, the rate of resistance is increasing day by day. gram positive pathogens are commonly found in urine sample collected from different age groups of people, associated with uti. the study was conducted in a diagnostic center in dhaka, bangladesh with total 1308 urine samples from november 2021 to april 2022. gram positive pathogens were isolated and antimicrobial susceptibility tests were done. from total 121 samples of gram positive bacteria the highest prevalence rate of utis was found in age group of 21 - 30 year. mostly enterococcus spp. ( 33. 05 % ) staphylococcus aureus ( 27. 27 % ), streptococcus spp. ( 20. 66 % ), beta - hemolytic streptococci ( 19. 00 % ) were found as causative agents of uti compared to others. the majority of isolates have been detected as multi - drug resistant ( mdr ). the higher percentage of antibiotic resistance were found against azithromycin ( 75 % ), and cefixime ( 64. 46 % ). this research focused on the regular basis of surveillance for the gram - positive bacteria antibiotic susceptibility to increase awareness about the use of proper antibiotic thus minimize the drug resistance.
for natural scientists, with the creation of transgenic organisms one of the most important tools for analysis of gene function. genes and other genetic information from a wide range of organisms can be inserted into bacteria for storage and modification, creating genetically modified bacteria in the process. bacteria are cheap, easy to grow, clonal, multiply quickly, relatively easy to transform and can be stored at - 80 Β°c almost indefinitely. once a gene is isolated it can be stored inside the bacteria providing an unlimited supply for research. organisms are genetically engineered to discover the functions of certain genes. this could be the effect on the phenotype of the organism, where the gene is expressed or what other genes it interacts with. these experiments generally involve loss of function, gain of function, tracking and expression. loss of function experiments, such as in a gene knockout experiment, in which an organism is engineered to lack the activity of one or more genes. in a simple knockout a copy of the desired gene has been altered to make it non - functional. embryonic stem cells incorporate the altered gene, which replaces the already present functional copy. these stem cells are injected into blastocysts, which are implanted into surrogate mothers. this allows the experimenter to analyse the defects caused by this mutation and thereby determine the role of particular genes. it is used especially frequently in developmental biology. when this is done by creating a library of genes with point mutations at every position in the area of interest, or even every position in the whole gene, this is called " scanning mutagenesis ". the simplest method, and the first to be used, is " alanine scanning ", where every position in turn is mutated to the unreactive amino acid alanine. gain of function experiments, the logical counterpart of knockouts. these are sometimes performed in conjunction with knockout experiments to more finely establish the function of the desired gene. the process is much the same as that in knockout engineering, except that the construct is designed to increase the function of the gene, usually by providing extra copies of the gene or inducing synthesis of the protein more frequently. gain of function is used to tell whether or not a protein is sufficient for a function, but does not always mean it is required, especially when dealing with genetic or functional redundancy. tracking experiments, which seek to gain information about the localisation and interaction of the desired protein. one way to do this is to replace the wild - type gene with a ' fusion ' gene, which is a juxtaposition
is opened and the dna is purified. the gene is separated by using restriction enzymes to cut the dna into fragments or polymerase chain reaction ( pcr ) to amplify up the gene segment. these segments can then be extracted through gel electrophoresis. if the chosen gene or the donor organism ' s genome has been well studied it may already be accessible from a genetic library. if the dna sequence is known, but no copies of the gene are available, it can also be artificially synthesised. once isolated the gene is ligated into a plasmid that is then inserted into a bacterium. the plasmid is replicated when the bacteria divide, ensuring unlimited copies of the gene are available. the rk2 plasmid is notable for its ability to replicate in a wide variety of single - celled organisms, which makes it suitable as a genetic engineering tool. before the gene is inserted into the target organism it must be combined with other genetic elements. these include a promoter and terminator region, which initiate and end transcription. a selectable marker gene is added, which in most cases confers antibiotic resistance, so researchers can easily determine which cells have been successfully transformed. the gene can also be modified at this stage for better expression or effectiveness. these manipulations are carried out using recombinant dna techniques, such as restriction digests, ligations and molecular cloning. = = = inserting dna into the host genome = = = there are a number of techniques used to insert genetic material into the host genome. some bacteria can naturally take up foreign dna. this ability can be induced in other bacteria via stress ( e. g. thermal or electric shock ), which increases the cell membrane ' s permeability to dna ; up - taken dna can either integrate with the genome or exist as extrachromosomal dna. dna is generally inserted into animal cells using microinjection, where it can be injected through the cell ' s nuclear envelope directly into the nucleus, or through the use of viral vectors. plant genomes can be engineered by physical methods or by use of agrobacterium for the delivery of sequences hosted in t - dna binary vectors. in plants the dna is often inserted using agrobacterium - mediated transformation, taking advantage of the agrobacteriums t - dna sequence that allows natural insertion of genetic material into plant cells. other methods include biolistics, where particles of gold or tungsten are coated with dna and then shot into
in star wars episode v, we see luke skywalker being repaired by a surgical robot. in the context of the movie, this doesn ' t seem surprising or disturbing. after all, it is a long, long time ago, in a galaxy far, far away. it would never happen here. or could it? would we accept a robot as our doctor, our surgeon, or our in - home care specialist? imagine walking into an operating room and no one was there. you are instructed to lie down on the operating table, and the or system takes over. would you feel comfortable with this possible future world?
the non - avian dinosaurs, mammals increased rapidly in size and diversity. such mass extinctions may have accelerated evolution by providing opportunities for new groups of organisms to diversify. = = diversity = = = = = bacteria and archaea = = = bacteria are a type of cell that constitute a large domain of prokaryotic microorganisms. typically a few micrometers in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. bacteria were among the first life forms to appear on earth, and are present in most of its habitats. bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep biosphere of the earth ' s crust. bacteria also live in symbiotic and parasitic relationships with plants and animals. most bacteria have not been characterised, and only about 27 percent of the bacterial phyla have species that can be grown in the laboratory. archaea constitute the other domain of prokaryotic cells and were initially classified as bacteria, receiving the name archaebacteria ( in the archaebacteria kingdom ), a term that has fallen out of use. archaeal cells have unique properties separating them from the other two domains, bacteria and eukaryota. archaea are further divided into multiple recognized phyla. archaea and bacteria are generally similar in size and shape, although a few archaea have very different shapes, such as the flat and square cells of haloquadratum walsbyi. despite this morphological similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes, notably for the enzymes involved in transcription and translation. other aspects of archaeal biochemistry are unique, such as their reliance on ether lipids in their cell membranes, including archaeols. archaea use more energy sources than eukaryotes : these range from organic compounds, such as sugars, to ammonia, metal ions or even hydrogen gas. salt - tolerant archaea ( the haloarchaea ) use sunlight as an energy source, and other species of archaea fix carbon, but unlike plants and cyanobacteria, no known species of archaea does both. archaea reproduce asexually by binary fission, fragmentation, or budding ; unlike bacteria, no known species of archaea form endospores. the first observed archaea were extremophiles, living in extreme environments, such as hot springs and salt lakes with no other organisms. improved molecular detection
becomes quite gentle. accordingly, in large basins, rivers in most cases begin as torrents with a variable flow, and end as gently flowing rivers with a comparatively regular discharge. the irregular flow of rivers throughout their course forms one of the main difficulties in devising works for mitigating inundations or for increasing the navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with a rapid fall near the sources of rivers can carry down rocks, boulders and large stones, which are by degrees ground by attrition in their onward course into slate, gravel, sand and silt, simultaneously with the gradual reduction in fall, and, consequently, in the transporting force of the current. accordingly, under
##rozoic eon that began 539 million years ago being subdivided into paleozoic, mesozoic, and cenozoic eras. these three eras together comprise eleven periods ( cambrian, ordovician, silurian, devonian, carboniferous, permian, triassic, jurassic, cretaceous, tertiary, and quaternary ). the similarities among all known present - day species indicate that they have diverged through the process of evolution from their common ancestor. biologists regard the ubiquity of the genetic code as evidence of universal common descent for all bacteria, archaea, and eukaryotes. microbial mats of coexisting bacteria and archaea were the dominant form of life in the early archean eon and many of the major steps in early evolution are thought to have taken place in this environment. the earliest evidence of eukaryotes dates from 1. 85 billion years ago, and while they may have been present earlier, their diversification accelerated when they started using oxygen in their metabolism. later, around 1. 7 billion years ago, multicellular organisms began to appear, with differentiated cells performing specialised functions. algae - like multicellular land plants are dated back to about 1 billion years ago, although evidence suggests that microorganisms formed the earliest terrestrial ecosystems, at least 2. 7 billion years ago. microorganisms are thought to have paved the way for the inception of land plants in the ordovician period. land plants were so successful that they are thought to have contributed to the late devonian extinction event. ediacara biota appear during the ediacaran period, while vertebrates, along with most other modern phyla originated about 525 million years ago during the cambrian explosion. during the permian period, synapsids, including the ancestors of mammals, dominated the land, but most of this group became extinct in the permian β triassic extinction event 252 million years ago. during the recovery from this catastrophe, archosaurs became the most abundant land vertebrates ; one archosaur group, the dinosaurs, dominated the jurassic and cretaceous periods. after the cretaceous β paleogene extinction event 66 million years ago killed off the non - avian dinosaurs, mammals increased rapidly in size and diversity. such mass extinctions may have accelerated evolution by providing opportunities for new groups of organisms to diversify. = = diversity = = = = = bacteria and archaea = = = bacteria are a type of cell that constitute a large domain of prokar
waste, and the deep biosphere of the earth ' s crust. bacteria also live in symbiotic and parasitic relationships with plants and animals. most bacteria have not been characterised, and only about 27 percent of the bacterial phyla have species that can be grown in the laboratory. archaea constitute the other domain of prokaryotic cells and were initially classified as bacteria, receiving the name archaebacteria ( in the archaebacteria kingdom ), a term that has fallen out of use. archaeal cells have unique properties separating them from the other two domains, bacteria and eukaryota. archaea are further divided into multiple recognized phyla. archaea and bacteria are generally similar in size and shape, although a few archaea have very different shapes, such as the flat and square cells of haloquadratum walsbyi. despite this morphological similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes, notably for the enzymes involved in transcription and translation. other aspects of archaeal biochemistry are unique, such as their reliance on ether lipids in their cell membranes, including archaeols. archaea use more energy sources than eukaryotes : these range from organic compounds, such as sugars, to ammonia, metal ions or even hydrogen gas. salt - tolerant archaea ( the haloarchaea ) use sunlight as an energy source, and other species of archaea fix carbon, but unlike plants and cyanobacteria, no known species of archaea does both. archaea reproduce asexually by binary fission, fragmentation, or budding ; unlike bacteria, no known species of archaea form endospores. the first observed archaea were extremophiles, living in extreme environments, such as hot springs and salt lakes with no other organisms. improved molecular detection tools led to the discovery of archaea in almost every habitat, including soil, oceans, and marshlands. archaea are particularly numerous in the oceans, and the archaea in plankton may be one of the most abundant groups of organisms on the planet. archaea are a major part of earth ' s life. they are part of the microbiota of all organisms. in the human microbiome, they are important in the gut, mouth, and on the skin. their morphological, metabolic, and geographical diversity permits them to play multiple ecological roles : carbon fixation ; nitrogen cycling ; organic compound turnover ; and maintaining microbial
Question: When bacteria enter the bloodstream, the result is what condition?
A) hypoxia
B) septicemia
C) diarrhea
D) hypertension
|
B) septicemia
|
Context:
, calorimetry, nuclear microscopy ( hefib ), rutherford backscattering, neutron diffraction, small - angle x - ray scattering ( saxs ), etc. ). besides material characterization, the material scientist or engineer also deals with extracting materials and converting them into useful forms. thus ingot casting, foundry methods, blast furnace extraction, and electrolytic extraction are all part of the required knowledge of a materials engineer. often the presence, absence, or variation of minute quantities of secondary elements and compounds in a bulk material will greatly affect the final properties of the materials produced. for example, steels are classified based on 1 / 10 and 1 / 100 weight percentages of the carbon and other alloying elements they contain. thus, the extracting and purifying methods used to extract iron in a blast furnace can affect the quality of steel that is produced. solid materials are generally grouped into three basic classifications : ceramics, metals, and polymers. this broad classification is based on the empirical makeup and atomic structure of the solid materials, and most solids fall into one of these broad categories. an item that is often made from each of these materials types is the beverage container. the material types used for beverage containers accordingly provide different advantages and disadvantages, depending on the material used. ceramic ( glass ) containers are optically transparent, impervious to the passage of carbon dioxide, relatively inexpensive, and are easily recycled, but are also heavy and fracture easily. metal ( aluminum alloy ) is relatively strong, is a good barrier to the diffusion of carbon dioxide, and is easily recycled. however, the cans are opaque, expensive to produce, and are easily dented and punctured. polymers ( polyethylene plastic ) are relatively strong, can be optically transparent, are inexpensive and lightweight, and can be recyclable, but are not as impervious to the passage of carbon dioxide as aluminum and glass. = = = ceramics and glasses = = = another application of materials science is the study of ceramics and glasses, typically the most brittle materials with industrial relevance. many ceramics and glasses exhibit covalent or ionic - covalent bonding with sio2 ( silica ) as a fundamental building block. ceramics β not to be confused with raw, unfired clay β are usually seen in crystalline form. the vast majority of commercial glasses contain a metal oxide fused with silica. at the high temperatures used to prepare glass, the material is a viscous liquid which solidifies into a disordered state upon
include materials design, cost - benefit tradeoffs in industrial production of materials, processing methods ( casting, rolling, welding, ion implantation, crystal growth, thin - film deposition, sintering, glassblowing, etc. ), and analytic methods ( characterization methods such as electron microscopy, x - ray diffraction, calorimetry, nuclear microscopy ( hefib ), rutherford backscattering, neutron diffraction, small - angle x - ray scattering ( saxs ), etc. ). besides material characterization, the material scientist or engineer also deals with extracting materials and converting them into useful forms. thus ingot casting, foundry methods, blast furnace extraction, and electrolytic extraction are all part of the required knowledge of a materials engineer. often the presence, absence, or variation of minute quantities of secondary elements and compounds in a bulk material will greatly affect the final properties of the materials produced. for example, steels are classified based on 1 / 10 and 1 / 100 weight percentages of the carbon and other alloying elements they contain. thus, the extracting and purifying methods used to extract iron in a blast furnace can affect the quality of steel that is produced. solid materials are generally grouped into three basic classifications : ceramics, metals, and polymers. this broad classification is based on the empirical makeup and atomic structure of the solid materials, and most solids fall into one of these broad categories. an item that is often made from each of these materials types is the beverage container. the material types used for beverage containers accordingly provide different advantages and disadvantages, depending on the material used. ceramic ( glass ) containers are optically transparent, impervious to the passage of carbon dioxide, relatively inexpensive, and are easily recycled, but are also heavy and fracture easily. metal ( aluminum alloy ) is relatively strong, is a good barrier to the diffusion of carbon dioxide, and is easily recycled. however, the cans are opaque, expensive to produce, and are easily dented and punctured. polymers ( polyethylene plastic ) are relatively strong, can be optically transparent, are inexpensive and lightweight, and can be recyclable, but are not as impervious to the passage of carbon dioxide as aluminum and glass. = = = ceramics and glasses = = = another application of materials science is the study of ceramics and glasses, typically the most brittle materials with industrial relevance. many ceramics and glasses exhibit covalent or ionic - covalent bonding with sio2 ( silica ) as a fundamental
of measuring methods. x - rays and gamma rays are used in industrial radiography to make images of the inside of solid products, as a means of nondestructive testing and inspection. the piece to be radiographed is placed between the source and a photographic film in a cassette. after a certain exposure time, the film is developed and it shows any internal defects of the material. gauges - gauges use the exponential absorption law of gamma rays level indicators : source and detector are placed at opposite sides of a container, indicating the presence or absence of material in the horizontal radiation path. beta or gamma sources are used, depending on the thickness and the density of the material to be measured. the method is used for containers of liquids or of grainy substances thickness gauges : if the material is of constant density, the signal measured by the radiation detector depends on the thickness of the material. this is useful for continuous production, like of paper, rubber, etc. electrostatic control - to avoid the build - up of static electricity in production of paper, plastics, synthetic textiles, etc., a ribbon - shaped source of the alpha emitter 241am can be placed close to the material at the end of the production line. the source ionizes the air to remove electric charges on the material. radioactive tracers - since radioactive isotopes behave, chemically, mostly like the inactive element, the behavior of a certain chemical substance can be followed by tracing the radioactivity. examples : adding a gamma tracer to a gas or liquid in a closed system makes it possible to find a hole in a tube. adding a tracer to the surface of the component of a motor makes it possible to measure wear by measuring the activity of the lubricating oil. oil and gas exploration - nuclear well logging is used to help predict the commercial viability of new or existing wells. the technology involves the use of a neutron or gamma - ray source and a radiation detector which are lowered into boreholes to determine the properties of the surrounding rock such as porosity and lithography. [ 1 ] road construction - nuclear moisture / density gauges are used to determine the density of soils, asphalt, and concrete. typically a cesium - 137 source is used. = = = commercial applications = = = radioluminescence tritium illumination : tritium is used with phosphor in rifle sights to increase nighttime firing accuracy. some runway markers and building exit signs use the same technology, to remain illuminated during blackouts. betavoltaics
##physical processes which take place in human beings as they make sense of information received through the visual system. the subject of the image. when developing an imaging system, designers must consider the observables associated with the subjects which will be imaged. these observables generally take the form of emitted or reflected energy, such as electromagnetic energy or mechanical energy. the capture device. once the observables associated with the subject are characterized, designers can then identify and integrate the technologies needed to capture those observables. for example, in the case of consumer digital cameras, those technologies include optics for collecting energy in the visible portion of the electromagnetic spectrum, and electronic detectors for converting the electromagnetic energy into an electronic signal. the processor. for all digital imaging systems, the electronic signals produced by the capture device must be manipulated by an algorithm which formats the signals so they can be displayed as an image. in practice, there are often multiple processors involved in the creation of a digital image. the display. the display takes the electronic signals which have been manipulated by the processor and renders them on some visual medium. examples include paper ( for printed, or " hard copy " images ), television, computer monitor, or projector. note that some imaging scientists will include additional " links " in their description of the imaging chain. for example, some will include the " source " of the energy which " illuminates " or interacts with the subject of the image. others will include storage and / or transmission systems. = = subfields = = subfields within imaging science include : image processing, computer vision, 3d computer graphics, animations, atmospheric optics, astronomical imaging, biological imaging, digital image restoration, digital imaging, color science, digital photography, holography, magnetic resonance imaging, medical imaging, microdensitometry, optics, photography, remote sensing, radar imaging, radiometry, silver halide, ultrasound imaging, photoacoustic imaging, thermal imaging, visual perception, and various printing technologies. = = methodologies = = acoustic imaging coherent imaging uses an active coherent illumination source, such as in radar, synthetic aperture radar ( sar ), medical ultrasound and optical coherence tomography ; non - coherent imaging systems include fluorescent microscopes, optical microscopes, and telescopes. chemical imaging, the simultaneous measurement of spectra and pictures digital imaging, creating digital images, generally by scanning or through digital photography disk image, a file which contains the exact content of a data storage medium document imaging, replicating documents commonly
it is stronger, then demodulates it, extracting the original modulation signal from the modulated carrier wave. the modulation signal is converted by a transducer back to a human - usable form : an audio signal is converted to sound waves by a loudspeaker or earphones, a video signal is converted to images by a display, while a digital signal is applied to a computer or microprocessor, which interacts with human users. the radio waves from many transmitters pass through the air simultaneously without interfering with each other because each transmitter ' s radio waves oscillate at a different frequency, measured in hertz ( hz ), kilohertz ( khz ), megahertz ( mhz ) or gigahertz ( ghz ). the receiving antenna typically picks up the radio signals of many transmitters. the receiver uses tuned circuits to select the radio signal desired out of all the signals picked up by the antenna and reject the others. a tuned circuit acts like a resonator, similar to a tuning fork. it has a natural resonant frequency at which it oscillates. the resonant frequency of the receiver ' s tuned circuit is adjusted by the user to the frequency of the desired radio station ; this is called tuning. the oscillating radio signal from the desired station causes the tuned circuit to oscillate in sympathy, and it passes the signal on to the rest of the receiver. radio signals at other frequencies are blocked by the tuned circuit and not passed on. = = = bandwidth = = = a modulated radio wave, carrying an information signal, occupies a range of frequencies. the information in a radio signal is usually concentrated in narrow frequency bands called sidebands ( sb ) just above and below the carrier frequency. the width in hertz of the frequency range that the radio signal occupies, the highest frequency minus the lowest frequency, is called its bandwidth ( bw ). for any given signal - to - noise ratio, a given bandwidth can carry the same amount of information regardless of where in the radio frequency spectrum it is located ; bandwidth is a measure of information - carrying capacity. the bandwidth required by a radio transmission depends on the data rate of the information being sent, and the spectral efficiency of the modulation method used ; how much data it can transmit in each unit of bandwidth. different types of information signals carried by radio have different data rates. for example, a television signal has a greater data rate than an audio signal. the radio spectrum, the total range of
##hography is quite small, large area patterns must be created by stitching together the small fields. ion track technology is a deep cutting tool with a resolution limit around 8 nm applicable to radiation resistant minerals, glasses and polymers. it is capable of generating holes in thin films without any development process. structural depth can be defined either by ion range or by material thickness. aspect ratios up to several 104 can be reached. the technique can shape and texture materials at a defined inclination angle. random pattern, single - ion track structures and an aimed pattern consisting of individual single tracks can be generated. x - ray lithography is a process used in the electronic industry to selectively remove parts of a thin film. it uses x - rays to transfer a geometric pattern from a mask to a light - sensitive chemical photoresist, or simply " resist ", on the substrate. a series of chemical treatments then engraves the produced pattern into the material underneath the photoresist. diamond patterning is a method of forming diamond mems. it is achieved by the lithographic application of diamond films to a substrate such as silicon. the patterns can be formed by selective deposition through a silicon dioxide mask, or by deposition followed by micromachining or focused ion beam milling. = = = etching processes = = = there are two basic categories of etching processes : wet etching and dry etching. in the former, the material is dissolved when immersed in a chemical solution. in the latter, the material is sputtered or dissolved using reactive ions or a vapor phase etchant. = = = = wet etching = = = = wet chemical etching consists of the selective removal of material by dipping a substrate into a solution that dissolves it. the chemical nature of this etching process provides good selectivity, which means the etching rate of the target material is considerably higher than the mask material if selected carefully. wet etching can be performed using either isotropic wet etchants or anisotropic wet etchants. isotropic wet etchant etch in all directions of the crystalline silicon at approximately equal rates. anisotropic wet etchants preferably etch along certain crystal planes at faster rates than other planes, thereby allowing more complicated 3 - d microstructures to be implemented. wet anisotropic etchants are often used in conjunction with boron etch stops wherein the surface of the silicon is heavily doped with boron resulting in a silicon material layer that is
= glass - ceramics = = glass - ceramic materials share many properties with both glasses and ceramics. glass - ceramics have an amorphous phase and one or more crystalline phases and are produced by a so - called " controlled crystallization ", which is typically avoided in glass manufacturing. glass - ceramics often contain a crystalline phase which constitutes anywhere from 30 % [ m / m ] to 90 % [ m / m ] of its composition by volume, yielding an array of materials with interesting thermomechanical properties. in the processing of glass - ceramics, molten glass is cooled down gradually before reheating and annealing. in this heat treatment the glass partly crystallizes. in many cases, so - called ' nucleation agents ' are added in order to regulate and control the crystallization process. because there is usually no pressing and sintering, glass - ceramics do not contain the volume fraction of porosity typically present in sintered ceramics. the term mainly refers to a mix of lithium and aluminosilicates which yields an array of materials with interesting thermomechanical properties. the most commercially important of these have the distinction of being impervious to thermal shock. thus, glass - ceramics have become extremely useful for countertop cooking. the negative thermal expansion coefficient ( tec ) of the crystalline ceramic phase can be balanced with the positive tec of the glassy phase. at a certain point ( ~ 70 % crystalline ) the glass - ceramic has a net tec near zero. this type of glass - ceramic exhibits excellent mechanical properties and can sustain repeated and quick temperature changes up to 1000 Β°c. = = processing steps = = the traditional ceramic process generally follows this sequence : milling β batching β mixing β forming β drying β firing β assembly. milling is the process by which materials are reduced from a large size to a smaller size. milling may involve breaking up cemented material ( in which case individual particles retain their shape ) or pulverization ( which involves grinding the particles themselves to a smaller size ). milling is generally done by mechanical means, including attrition ( which is particle - to - particle collision that results in agglomerate break up or particle shearing ), compression ( which applies a forces that results in fracturing ), and impact ( which employs a milling medium or the particles themselves to cause fracturing ). attrition milling equipment includes the wet scrubber ( also called the planetary mill or wet attrition mill ), which has paddles in water creating vortexes in which
molecules and induce ionization ( hence the name ) which cannot be achieved by mere heating. this is the reason for new beneficial effects, however at the same time, for new concerns. the treatment of solid food by ionizing radiation can provide an effect similar to heat pasteurization of liquids, such as milk. however, the use of the term, cold pasteurization, to describe irradiated foods is controversial, because pasteurization and irradiation are fundamentally different processes, although the intended end results can in some cases be similar. detractors of food irradiation have concerns about the health hazards of induced radioactivity. a report for the industry advocacy group american council on science and health entitled " irradiated foods " states : " the types of radiation sources approved for the treatment of foods have specific energy levels well below that which would cause any element in food to become radioactive. food undergoing irradiation does not become any more radioactive than luggage passing through an airport x - ray scanner or teeth that have been x - rayed. " food irradiation is currently permitted by over 40 countries and volumes are estimated to exceed 500, 000 metric tons ( 490, 000 long tons ; 550, 000 short tons ) annually worldwide. food irradiation is essentially a non - nuclear technology ; it relies on the use of ionizing radiation which may be generated by accelerators for electrons and conversion into bremsstrahlung, but which may use also gamma - rays from nuclear decay. there is a worldwide industry for processing by ionizing radiation, the majority by number and by processing power using accelerators. food irradiation is only a niche application compared to medical supplies, plastic materials, raw materials, gemstones, cables and wires, etc. = = accidents = = nuclear accidents, because of the powerful forces involved, are often very dangerous. historically, the first incidents involved fatal radiation exposure. marie curie died from aplastic anemia which resulted from her high levels of exposure. two scientists, an american and canadian respectively, harry daghlian and louis slotin, died after mishandling the same plutonium mass. unlike conventional weapons, the intense light, heat, and explosive force is not the only deadly component to a nuclear weapon. approximately half of the deaths from hiroshima and nagasaki died two to five years afterward from radiation exposure. civilian nuclear and radiological accidents primarily involve nuclear power plants. most common are nuclear leaks that expose workers to hazardous material. a nuclear meltdown refers to the more serious hazard of
radio waves. the radio waves carry the information to the receiver location. at the receiver, the radio wave induces a tiny oscillating voltage in the receiving antenna β a weaker replica of the current in the transmitting antenna. this voltage is applied to the radio receiver, which amplifies the weak radio signal so it is stronger, then demodulates it, extracting the original modulation signal from the modulated carrier wave. the modulation signal is converted by a transducer back to a human - usable form : an audio signal is converted to sound waves by a loudspeaker or earphones, a video signal is converted to images by a display, while a digital signal is applied to a computer or microprocessor, which interacts with human users. the radio waves from many transmitters pass through the air simultaneously without interfering with each other because each transmitter ' s radio waves oscillate at a different frequency, measured in hertz ( hz ), kilohertz ( khz ), megahertz ( mhz ) or gigahertz ( ghz ). the receiving antenna typically picks up the radio signals of many transmitters. the receiver uses tuned circuits to select the radio signal desired out of all the signals picked up by the antenna and reject the others. a tuned circuit acts like a resonator, similar to a tuning fork. it has a natural resonant frequency at which it oscillates. the resonant frequency of the receiver ' s tuned circuit is adjusted by the user to the frequency of the desired radio station ; this is called tuning. the oscillating radio signal from the desired station causes the tuned circuit to oscillate in sympathy, and it passes the signal on to the rest of the receiver. radio signals at other frequencies are blocked by the tuned circuit and not passed on. = = = bandwidth = = = a modulated radio wave, carrying an information signal, occupies a range of frequencies. the information in a radio signal is usually concentrated in narrow frequency bands called sidebands ( sb ) just above and below the carrier frequency. the width in hertz of the frequency range that the radio signal occupies, the highest frequency minus the lowest frequency, is called its bandwidth ( bw ). for any given signal - to - noise ratio, a given bandwidth can carry the same amount of information regardless of where in the radio frequency spectrum it is located ; bandwidth is a measure of information - carrying capacity. the bandwidth required by a radio transmission depends on the data rate of
of cells = = = autologous : the donor and the recipient of the cells are the same individual. cells are harvested, cultured or stored, and then reintroduced to the host. as a result of the host ' s own cells being reintroduced, an antigenic response is not elicited. the body ' s immune system recognizes these re - implanted cells as its own, and does not target them for attack. autologous cell dependence on host cell health and donor site morbidity may be deterrents to their use. adipose - derived and bone marrow - derived mesenchymal stem cells are commonly autologous in nature, and can be used in a myriad of ways, from helping repair skeletal tissue to replenishing beta cells in diabetic patients. allogenic : cells are obtained from the body of a donor of the same species as the recipient. while there are some ethical constraints to the use of human cells for in vitro studies ( i. e. human brain tissue chimera development ), the employment of dermal fibroblasts from human foreskin demonstrates an immunologically safe and thus a viable choice for allogenic tissue engineering of the skin. xenogenic : these cells are derived isolated cells from alternate species from the recipient. a notable example of xenogeneic tissue utilization is cardiovascular implant construction via animal cells. chimeric human - animal farming raises ethical concerns around the potential for improved consciousness from implanting human organs in animals. syngeneic or isogenic : these cells describe those borne from identical genetic code. this imparts an immunologic benefit similar to autologous cell lines ( see above ). autologous cells can be considered syngenic, but the classification also extends to non - autologously derived cells such as those from an identical twin, from genetically identical ( cloned ) research models, or induced stem cells ( isc ) as related to the donor. = = = stem cells = = = stem cells are undifferentiated cells with the ability to divide in culture and give rise to different forms of specialized cells. stem cells are divided into " adult " and " embryonic " stem cells according to their source. while there is still a large ethical debate related to the use of embryonic stem cells, it is thought that another alternative source β induced pluripotent stem cells β may be useful for the repair of diseased or damaged tissues, or may be used to grow new organs. totipotent cells
Question: Solid-state radiation detectors convert ionization produced in a semiconductor (like those found in computer chips) directly into what?
A) thermal energy
B) isotopes
C) electrical signal
D) microwaves
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C) electrical signal
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Context:
they may have been present earlier, their diversification accelerated when they started using oxygen in their metabolism. later, around 1. 7 billion years ago, multicellular organisms began to appear, with differentiated cells performing specialised functions. algae - like multicellular land plants are dated back to about 1 billion years ago, although evidence suggests that microorganisms formed the earliest terrestrial ecosystems, at least 2. 7 billion years ago. microorganisms are thought to have paved the way for the inception of land plants in the ordovician period. land plants were so successful that they are thought to have contributed to the late devonian extinction event. ediacara biota appear during the ediacaran period, while vertebrates, along with most other modern phyla originated about 525 million years ago during the cambrian explosion. during the permian period, synapsids, including the ancestors of mammals, dominated the land, but most of this group became extinct in the permian β triassic extinction event 252 million years ago. during the recovery from this catastrophe, archosaurs became the most abundant land vertebrates ; one archosaur group, the dinosaurs, dominated the jurassic and cretaceous periods. after the cretaceous β paleogene extinction event 66 million years ago killed off the non - avian dinosaurs, mammals increased rapidly in size and diversity. such mass extinctions may have accelerated evolution by providing opportunities for new groups of organisms to diversify. = = diversity = = = = = bacteria and archaea = = = bacteria are a type of cell that constitute a large domain of prokaryotic microorganisms. typically a few micrometers in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. bacteria were among the first life forms to appear on earth, and are present in most of its habitats. bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep biosphere of the earth ' s crust. bacteria also live in symbiotic and parasitic relationships with plants and animals. most bacteria have not been characterised, and only about 27 percent of the bacterial phyla have species that can be grown in the laboratory. archaea constitute the other domain of prokaryotic cells and were initially classified as bacteria, receiving the name archaebacteria ( in the archaebacteria kingdom ), a term that has fallen out of use. archaeal cells have unique properties separating them from the other two domains, bacteria and eukaryota. archaea
have evolved from the earliest emergence of life to present day. earth formed about 4. 5 billion years ago and all life on earth, both living and extinct, descended from a last universal common ancestor that lived about 3. 5 billion years ago. geologists have developed a geologic time scale that divides the history of the earth into major divisions, starting with four eons ( hadean, archean, proterozoic, and phanerozoic ), the first three of which are collectively known as the precambrian, which lasted approximately 4 billion years. each eon can be divided into eras, with the phanerozoic eon that began 539 million years ago being subdivided into paleozoic, mesozoic, and cenozoic eras. these three eras together comprise eleven periods ( cambrian, ordovician, silurian, devonian, carboniferous, permian, triassic, jurassic, cretaceous, tertiary, and quaternary ). the similarities among all known present - day species indicate that they have diverged through the process of evolution from their common ancestor. biologists regard the ubiquity of the genetic code as evidence of universal common descent for all bacteria, archaea, and eukaryotes. microbial mats of coexisting bacteria and archaea were the dominant form of life in the early archean eon and many of the major steps in early evolution are thought to have taken place in this environment. the earliest evidence of eukaryotes dates from 1. 85 billion years ago, and while they may have been present earlier, their diversification accelerated when they started using oxygen in their metabolism. later, around 1. 7 billion years ago, multicellular organisms began to appear, with differentiated cells performing specialised functions. algae - like multicellular land plants are dated back to about 1 billion years ago, although evidence suggests that microorganisms formed the earliest terrestrial ecosystems, at least 2. 7 billion years ago. microorganisms are thought to have paved the way for the inception of land plants in the ordovician period. land plants were so successful that they are thought to have contributed to the late devonian extinction event. ediacara biota appear during the ediacaran period, while vertebrates, along with most other modern phyla originated about 525 million years ago during the cambrian explosion. during the permian period, synapsids, including the ancestors of mammals, dominated the land, but most of this group became
. microbial mats of coexisting bacteria and archaea were the dominant form of life in the early archean eon and many of the major steps in early evolution are thought to have taken place in this environment. the earliest evidence of eukaryotes dates from 1. 85 billion years ago, and while they may have been present earlier, their diversification accelerated when they started using oxygen in their metabolism. later, around 1. 7 billion years ago, multicellular organisms began to appear, with differentiated cells performing specialised functions. algae - like multicellular land plants are dated back to about 1 billion years ago, although evidence suggests that microorganisms formed the earliest terrestrial ecosystems, at least 2. 7 billion years ago. microorganisms are thought to have paved the way for the inception of land plants in the ordovician period. land plants were so successful that they are thought to have contributed to the late devonian extinction event. ediacara biota appear during the ediacaran period, while vertebrates, along with most other modern phyla originated about 525 million years ago during the cambrian explosion. during the permian period, synapsids, including the ancestors of mammals, dominated the land, but most of this group became extinct in the permian β triassic extinction event 252 million years ago. during the recovery from this catastrophe, archosaurs became the most abundant land vertebrates ; one archosaur group, the dinosaurs, dominated the jurassic and cretaceous periods. after the cretaceous β paleogene extinction event 66 million years ago killed off the non - avian dinosaurs, mammals increased rapidly in size and diversity. such mass extinctions may have accelerated evolution by providing opportunities for new groups of organisms to diversify. = = diversity = = = = = bacteria and archaea = = = bacteria are a type of cell that constitute a large domain of prokaryotic microorganisms. typically a few micrometers in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. bacteria were among the first life forms to appear on earth, and are present in most of its habitats. bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep biosphere of the earth ' s crust. bacteria also live in symbiotic and parasitic relationships with plants and animals. most bacteria have not been characterised, and only about 27 percent of the bacterial phyla have species that can be grown in the laboratory. archaea constitute the other domain of
##rozoic eon that began 539 million years ago being subdivided into paleozoic, mesozoic, and cenozoic eras. these three eras together comprise eleven periods ( cambrian, ordovician, silurian, devonian, carboniferous, permian, triassic, jurassic, cretaceous, tertiary, and quaternary ). the similarities among all known present - day species indicate that they have diverged through the process of evolution from their common ancestor. biologists regard the ubiquity of the genetic code as evidence of universal common descent for all bacteria, archaea, and eukaryotes. microbial mats of coexisting bacteria and archaea were the dominant form of life in the early archean eon and many of the major steps in early evolution are thought to have taken place in this environment. the earliest evidence of eukaryotes dates from 1. 85 billion years ago, and while they may have been present earlier, their diversification accelerated when they started using oxygen in their metabolism. later, around 1. 7 billion years ago, multicellular organisms began to appear, with differentiated cells performing specialised functions. algae - like multicellular land plants are dated back to about 1 billion years ago, although evidence suggests that microorganisms formed the earliest terrestrial ecosystems, at least 2. 7 billion years ago. microorganisms are thought to have paved the way for the inception of land plants in the ordovician period. land plants were so successful that they are thought to have contributed to the late devonian extinction event. ediacara biota appear during the ediacaran period, while vertebrates, along with most other modern phyla originated about 525 million years ago during the cambrian explosion. during the permian period, synapsids, including the ancestors of mammals, dominated the land, but most of this group became extinct in the permian β triassic extinction event 252 million years ago. during the recovery from this catastrophe, archosaurs became the most abundant land vertebrates ; one archosaur group, the dinosaurs, dominated the jurassic and cretaceous periods. after the cretaceous β paleogene extinction event 66 million years ago killed off the non - avian dinosaurs, mammals increased rapidly in size and diversity. such mass extinctions may have accelerated evolution by providing opportunities for new groups of organisms to diversify. = = diversity = = = = = bacteria and archaea = = = bacteria are a type of cell that constitute a large domain of prokar
into major divisions, starting with four eons ( hadean, archean, proterozoic, and phanerozoic ), the first three of which are collectively known as the precambrian, which lasted approximately 4 billion years. each eon can be divided into eras, with the phanerozoic eon that began 539 million years ago being subdivided into paleozoic, mesozoic, and cenozoic eras. these three eras together comprise eleven periods ( cambrian, ordovician, silurian, devonian, carboniferous, permian, triassic, jurassic, cretaceous, tertiary, and quaternary ). the similarities among all known present - day species indicate that they have diverged through the process of evolution from their common ancestor. biologists regard the ubiquity of the genetic code as evidence of universal common descent for all bacteria, archaea, and eukaryotes. microbial mats of coexisting bacteria and archaea were the dominant form of life in the early archean eon and many of the major steps in early evolution are thought to have taken place in this environment. the earliest evidence of eukaryotes dates from 1. 85 billion years ago, and while they may have been present earlier, their diversification accelerated when they started using oxygen in their metabolism. later, around 1. 7 billion years ago, multicellular organisms began to appear, with differentiated cells performing specialised functions. algae - like multicellular land plants are dated back to about 1 billion years ago, although evidence suggests that microorganisms formed the earliest terrestrial ecosystems, at least 2. 7 billion years ago. microorganisms are thought to have paved the way for the inception of land plants in the ordovician period. land plants were so successful that they are thought to have contributed to the late devonian extinction event. ediacara biota appear during the ediacaran period, while vertebrates, along with most other modern phyla originated about 525 million years ago during the cambrian explosion. during the permian period, synapsids, including the ancestors of mammals, dominated the land, but most of this group became extinct in the permian β triassic extinction event 252 million years ago. during the recovery from this catastrophe, archosaurs became the most abundant land vertebrates ; one archosaur group, the dinosaurs, dominated the jurassic and cretaceous periods. after the cretaceous β paleogene extinction event 66 million years ago killed off
, tertiary, and quaternary ). the similarities among all known present - day species indicate that they have diverged through the process of evolution from their common ancestor. biologists regard the ubiquity of the genetic code as evidence of universal common descent for all bacteria, archaea, and eukaryotes. microbial mats of coexisting bacteria and archaea were the dominant form of life in the early archean eon and many of the major steps in early evolution are thought to have taken place in this environment. the earliest evidence of eukaryotes dates from 1. 85 billion years ago, and while they may have been present earlier, their diversification accelerated when they started using oxygen in their metabolism. later, around 1. 7 billion years ago, multicellular organisms began to appear, with differentiated cells performing specialised functions. algae - like multicellular land plants are dated back to about 1 billion years ago, although evidence suggests that microorganisms formed the earliest terrestrial ecosystems, at least 2. 7 billion years ago. microorganisms are thought to have paved the way for the inception of land plants in the ordovician period. land plants were so successful that they are thought to have contributed to the late devonian extinction event. ediacara biota appear during the ediacaran period, while vertebrates, along with most other modern phyla originated about 525 million years ago during the cambrian explosion. during the permian period, synapsids, including the ancestors of mammals, dominated the land, but most of this group became extinct in the permian β triassic extinction event 252 million years ago. during the recovery from this catastrophe, archosaurs became the most abundant land vertebrates ; one archosaur group, the dinosaurs, dominated the jurassic and cretaceous periods. after the cretaceous β paleogene extinction event 66 million years ago killed off the non - avian dinosaurs, mammals increased rapidly in size and diversity. such mass extinctions may have accelerated evolution by providing opportunities for new groups of organisms to diversify. = = diversity = = = = = bacteria and archaea = = = bacteria are a type of cell that constitute a large domain of prokaryotic microorganisms. typically a few micrometers in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. bacteria were among the first life forms to appear on earth, and are present in most of its habitats. bacteria inhabit soil, water, acidic hot springs, radioactive
pigmentation, chloroplast structure and nutrient reserves. the algal division charophyta, sister to the green algal division chlorophyta, is considered to contain the ancestor of true plants. the charophyte class charophyceae and the land plant sub - kingdom embryophyta together form the monophyletic group or clade streptophytina. nonvascular land plants are embryophytes that lack the vascular tissues xylem and phloem. they include mosses, liverworts and hornworts. pteridophytic vascular plants with true xylem and phloem that reproduced by spores germinating into free - living gametophytes evolved during the silurian period and diversified into several lineages during the late silurian and early devonian. representatives of the lycopods have survived to the present day. by the end of the devonian period, several groups, including the lycopods, sphenophylls and progymnosperms, had independently evolved " megaspory " β their spores were of two distinct sizes, larger megaspores and smaller microspores. their reduced gametophytes developed from megaspores retained within the spore - producing organs ( megasporangia ) of the sporophyte, a condition known as endospory. seeds consist of an endosporic megasporangium surrounded by one or two sheathing layers ( integuments ). the young sporophyte develops within the seed, which on germination splits to release it. the earliest known seed plants date from the latest devonian famennian stage. following the evolution of the seed habit, seed plants diversified, giving rise to a number of now - extinct groups, including seed ferns, as well as the modern gymnosperms and angiosperms. gymnosperms produce " naked seeds " not fully enclosed in an ovary ; modern representatives include conifers, cycads, ginkgo, and gnetales. angiosperms produce seeds enclosed in a structure such as a carpel or an ovary. ongoing research on the molecular phylogenetics of living plants appears to show that the angiosperms are a sister clade to the gymnosperms. = = plant physiology = = plant physiology encompasses all the internal chemical and physical activities of plants associated with life. chemicals obtained from the air, soil and water form
##ta together form the monophyletic group or clade streptophytina. nonvascular land plants are embryophytes that lack the vascular tissues xylem and phloem. they include mosses, liverworts and hornworts. pteridophytic vascular plants with true xylem and phloem that reproduced by spores germinating into free - living gametophytes evolved during the silurian period and diversified into several lineages during the late silurian and early devonian. representatives of the lycopods have survived to the present day. by the end of the devonian period, several groups, including the lycopods, sphenophylls and progymnosperms, had independently evolved " megaspory " β their spores were of two distinct sizes, larger megaspores and smaller microspores. their reduced gametophytes developed from megaspores retained within the spore - producing organs ( megasporangia ) of the sporophyte, a condition known as endospory. seeds consist of an endosporic megasporangium surrounded by one or two sheathing layers ( integuments ). the young sporophyte develops within the seed, which on germination splits to release it. the earliest known seed plants date from the latest devonian famennian stage. following the evolution of the seed habit, seed plants diversified, giving rise to a number of now - extinct groups, including seed ferns, as well as the modern gymnosperms and angiosperms. gymnosperms produce " naked seeds " not fully enclosed in an ovary ; modern representatives include conifers, cycads, ginkgo, and gnetales. angiosperms produce seeds enclosed in a structure such as a carpel or an ovary. ongoing research on the molecular phylogenetics of living plants appears to show that the angiosperms are a sister clade to the gymnosperms. = = plant physiology = = plant physiology encompasses all the internal chemical and physical activities of plants associated with life. chemicals obtained from the air, soil and water form the basis of all plant metabolism. the energy of sunlight, captured by oxygenic photosynthesis and released by cellular respiration, is the basis of almost all life. photoautotrophs, including all green plants, algae and cyanobacteria gather energy directly from sunlight by photosynthesis. hetero
##ochondria and chloroplasts, both of which are now part of modern - day eukaryotic cells. the major lineages of eukaryotes diversified in the precambrian about 1. 5 billion years ago and can be classified into eight major clades : alveolates, excavates, stramenopiles, plants, rhizarians, amoebozoans, fungi, and animals. five of these clades are collectively known as protists, which are mostly microscopic eukaryotic organisms that are not plants, fungi, or animals. while it is likely that protists share a common ancestor ( the last eukaryotic common ancestor ), protists by themselves do not constitute a separate clade as some protists may be more closely related to plants, fungi, or animals than they are to other protists. like groupings such as algae, invertebrates, or protozoans, the protist grouping is not a formal taxonomic group but is used for convenience. most protists are unicellular ; these are called microbial eukaryotes. plants are mainly multicellular organisms, predominantly photosynthetic eukaryotes of the kingdom plantae, which would exclude fungi and some algae. plant cells were derived by endosymbiosis of a cyanobacterium into an early eukaryote about one billion years ago, which gave rise to chloroplasts. the first several clades that emerged following primary endosymbiosis were aquatic and most of the aquatic photosynthetic eukaryotic organisms are collectively described as algae, which is a term of convenience as not all algae are closely related. algae comprise several distinct clades such as glaucophytes, which are microscopic freshwater algae that may have resembled in form to the early unicellular ancestor of plantae. unlike glaucophytes, the other algal clades such as red and green algae are multicellular. green algae comprise three major clades : chlorophytes, coleochaetophytes, and stoneworts. fungi are eukaryotes that digest foods outside their bodies, secreting digestive enzymes that break down large food molecules before absorbing them through their cell membranes. many fungi are also saprobes, feeding on dead organic matter, making them important decomposers in ecological systems. animals are multicellular eukaryotes. with few exceptions, animals
##ning an animal for its hide, and even forming other tools out of softer materials such as bone and wood. the earliest stone tools were irrelevant, being little more than a fractured rock. in the acheulian era, beginning approximately 1. 65 million years ago, methods of working these stones into specific shapes, such as hand axes emerged. this early stone age is described as the lower paleolithic. the middle paleolithic, approximately 300, 000 years ago, saw the introduction of the prepared - core technique, where multiple blades could be rapidly formed from a single core stone. the upper paleolithic, beginning approximately 40, 000 years ago, saw the introduction of pressure flaking, where a wood, bone, or antler punch could be used to shape a stone very finely. the end of the last ice age about 10, 000 years ago is taken as the end point of the upper paleolithic and the beginning of the epipaleolithic / mesolithic. the mesolithic technology included the use of microliths as composite stone tools, along with wood, bone, and antler tools. the later stone age, during which the rudiments of agricultural technology were developed, is called the neolithic period. during this period, polished stone tools were made from a variety of hard rocks such as flint, jade, jadeite, and greenstone, largely by working exposures as quarries, but later the valuable rocks were pursued by tunneling underground, the first steps in mining technology. the polished axes were used for forest clearance and the establishment of crop farming and were so effective as to remain in use when bronze and iron appeared. these stone axes were used alongside a continued use of stone tools such as a range of projectiles, knives, and scrapers, as well as tools, made from organic materials such as wood, bone, and antler. stone age cultures developed music and engaged in organized warfare. stone age humans developed ocean - worthy outrigger canoe technology, leading to migration across the malay archipelago, across the indian ocean to madagascar and also across the pacific ocean, which required knowledge of the ocean currents, weather patterns, sailing, and celestial navigation. although paleolithic cultures left no written records, the shift from nomadic life to settlement and agriculture can be inferred from a range of archaeological evidence. such evidence includes ancient tools, cave paintings, and other prehistoric art, such as the venus of willendorf. human remains also provide direct evidence, both through the examination of bones, and
Question: Most, if not all, of the extant animal phyla today evolved during the cambrian period, yet many of what devastating events have taken place since then?
A) starvations
B) mass extinctions
C) life extinctions
D) earthquakes
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B) mass extinctions
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Context:
activation energy necessary for a chemical reaction to occur can be in the form of heat, light, electricity or mechanical force in the form of ultrasound. a related concept free energy, which also incorporates entropy considerations, is a very useful means for predicting the feasibility of a reaction and determining the state of equilibrium of a chemical reaction, in chemical thermodynamics. a reaction is feasible only if the total change in the gibbs free energy is negative, Ξ΄ g β€ 0 { \ displaystyle \ delta g \ leq 0 \, } ; if it is equal to zero the chemical reaction is said to be at equilibrium. there exist only limited possible states of energy for electrons, atoms and molecules. these are determined by the rules of quantum mechanics, which require quantization of energy of a bound system. the atoms / molecules in a higher energy state are said to be excited. the molecules / atoms of substance in an excited energy state are often much more reactive ; that is, more amenable to chemical reactions. the phase of a substance is invariably determined by its energy and the energy of its surroundings. when the intermolecular forces of a substance are such that the energy of the surroundings is not sufficient to overcome them, it occurs in a more ordered phase like liquid or solid as is the case with water ( h2o ) ; a liquid at room temperature because its molecules are bound by hydrogen bonds. whereas hydrogen sulfide ( h2s ) is a gas at room temperature and standard pressure, as its molecules are bound by weaker dipole β dipole interactions. the transfer of energy from one chemical substance to another depends on the size of energy quanta emitted from one substance. however, heat energy is often transferred more easily from almost any substance to another because the phonons responsible for vibrational and rotational energy levels in a substance have much less energy than photons invoked for the electronic energy transfer. thus, because vibrational and rotational energy levels are more closely spaced than electronic energy levels, heat is more easily transferred between substances relative to light or other forms of electronic energy. for example, ultraviolet electromagnetic radiation is not transferred with as much efficacy from one substance to another as thermal or electrical energy. the existence of characteristic energy levels for different chemical substances is useful for their identification by the analysis of spectral lines. different kinds of spectra are often used in chemical spectroscopy, e. g. ir, microwave, nmr, esr, etc. spectroscopy is also used to identify the composition of remote objects β like stars and distant galaxies β by
set of chemical reactions with other substances. however, this definition only works well for substances that are composed of molecules, which is not true of many substances ( see below ). molecules are typically a set of atoms bound together by covalent bonds, such that the structure is electrically neutral and all valence electrons are paired with other electrons either in bonds or in lone pairs. thus, molecules exist as electrically neutral units, unlike ions. when this rule is broken, giving the " molecule " a charge, the result is sometimes named a molecular ion or a polyatomic ion. however, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature.
ion or cation. when an atom gains an electron and thus has more electrons than protons, the atom is a negatively charged ion or anion. cations and anions can form a crystalline lattice of neutral salts, such as the na + and clβ ions forming sodium chloride, or nacl. examples of polyatomic ions that do not split up during acid β base reactions are hydroxide ( ohβ ) and phosphate ( po43β ). plasma is composed of gaseous matter that has been completely ionized, usually through high temperature. = = = acidity and basicity = = = a substance can often be classified as an acid or a base. there are several different theories which explain acid β base behavior. the simplest is arrhenius theory, which states that an acid is a substance that produces hydronium ions when it is dissolved in water, and a base is one that produces hydroxide ions when dissolved in water. according to brΓΈnsted β lowry acid β base theory, acids are substances that donate a positive hydrogen ion to another substance in a chemical reaction ; by extension, a base is the substance which receives that hydrogen ion. a third common theory is lewis acid β base theory, which is based on the formation of new chemical bonds. lewis theory explains that an acid is a substance which is capable of accepting a pair of electrons from another substance during the process of bond formation, while a base is a substance which can provide a pair of electrons to form a new bond. there are several other ways in which a substance may be classified as an acid or a base, as is evident in the history of this concept. acid strength is commonly measured by two methods. one measurement, based on the arrhenius definition of acidity, is ph, which is a measurement of the hydronium ion concentration in a solution, as expressed on a negative logarithmic scale. thus, solutions that have a low ph have a high hydronium ion concentration and can be said to be more acidic. the other measurement, based on the brΓΈnsted β lowry definition, is the acid dissociation constant ( ka ), which measures the relative ability of a substance to act as an acid under the brΓΈnsted β lowry definition of an acid. that is, substances with a higher ka are more likely to donate hydrogen ions in chemical reactions than those with lower ka values. = = = redox = = = redox ( reduction - oxidation ) reactions include all chemical reactions in which atoms have their
factor e β e / k t { \ displaystyle e ^ { - e / kt } } β that is the probability of a molecule to have energy greater than or equal to e at the given temperature t. this exponential dependence of a reaction rate on temperature is known as the arrhenius equation. the activation energy necessary for a chemical reaction to occur can be in the form of heat, light, electricity or mechanical force in the form of ultrasound. a related concept free energy, which also incorporates entropy considerations, is a very useful means for predicting the feasibility of a reaction and determining the state of equilibrium of a chemical reaction, in chemical thermodynamics. a reaction is feasible only if the total change in the gibbs free energy is negative, Ξ΄ g β€ 0 { \ displaystyle \ delta g \ leq 0 \, } ; if it is equal to zero the chemical reaction is said to be at equilibrium. there exist only limited possible states of energy for electrons, atoms and molecules. these are determined by the rules of quantum mechanics, which require quantization of energy of a bound system. the atoms / molecules in a higher energy state are said to be excited. the molecules / atoms of substance in an excited energy state are often much more reactive ; that is, more amenable to chemical reactions. the phase of a substance is invariably determined by its energy and the energy of its surroundings. when the intermolecular forces of a substance are such that the energy of the surroundings is not sufficient to overcome them, it occurs in a more ordered phase like liquid or solid as is the case with water ( h2o ) ; a liquid at room temperature because its molecules are bound by hydrogen bonds. whereas hydrogen sulfide ( h2s ) is a gas at room temperature and standard pressure, as its molecules are bound by weaker dipole β dipole interactions. the transfer of energy from one chemical substance to another depends on the size of energy quanta emitted from one substance. however, heat energy is often transferred more easily from almost any substance to another because the phonons responsible for vibrational and rotational energy levels in a substance have much less energy than photons invoked for the electronic energy transfer. thus, because vibrational and rotational energy levels are more closely spaced than electronic energy levels, heat is more easily transferred between substances relative to light or other forms of electronic energy. for example, ultraviolet electromagnetic radiation is not transferred with as much efficacy from one substance to another as thermal or electrical energy. the existence of characteristic
has rest mass and volume ( it takes up space ) and is made up of particles. the particles that make up matter have rest mass as well β not all particles have rest mass, such as the photon. matter can be a pure chemical substance or a mixture of substances. = = = = atom = = = = the atom is the basic unit of chemistry. it consists of a dense core called the atomic nucleus surrounded by a space occupied by an electron cloud. the nucleus is made up of positively charged protons and uncharged neutrons ( together called nucleons ), while the electron cloud consists of negatively charged electrons which orbit the nucleus. in a neutral atom, the negatively charged electrons balance out the positive charge of the protons. the nucleus is dense ; the mass of a nucleon is approximately 1, 836 times that of an electron, yet the radius of an atom is about 10, 000 times that of its nucleus. the atom is also the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state ( s ), coordination number, and preferred types of bonds to form ( e. g., metallic, ionic, covalent ). = = = = element = = = = a chemical element is a pure substance which is composed of a single type of atom, characterized by its particular number of protons in the nuclei of its atoms, known as the atomic number and represented by the symbol z. the mass number is the sum of the number of protons and neutrons in a nucleus. although all the nuclei of all atoms belonging to one element will have the same atomic number, they may not necessarily have the same mass number ; atoms of an element which have different mass numbers are known as isotopes. for example, all atoms with 6 protons in their nuclei are atoms of the chemical element carbon, but atoms of carbon may have mass numbers of 12 or 13. the standard presentation of the chemical elements is in the periodic table, which orders elements by atomic number. the periodic table is arranged in groups, or columns, and periods, or rows. the periodic table is useful in identifying periodic trends. = = = = compound = = = = a compound is a pure chemical substance composed of more than one element. the properties of a compound bear little similarity to those of its elements. the standard nomenclature of compounds is set by the international union of pure and applied chemistry ( iupac ). organic compounds are named
index chemical substances. in this scheme each chemical substance is identifiable by a number known as its cas registry number. = = = = molecule = = = = a molecule is the smallest indivisible portion of a pure chemical substance that has its unique set of chemical properties, that is, its potential to undergo a certain set of chemical reactions with other substances. however, this definition only works well for substances that are composed of molecules, which is not true of many substances ( see below ). molecules are typically a set of atoms bound together by covalent bonds, such that the structure is electrically neutral and all valence electrons are paired with other electrons either in bonds or in lone pairs. thus, molecules exist as electrically neutral units, unlike ions. when this rule is broken, giving the " molecule " a charge, the result is sometimes named a molecular ion or a polyatomic ion. however, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry
##ting the principle of conservation of mass and developing a new system of chemical nomenclature used to this day. english scientist john dalton proposed the modern theory of atoms ; that all substances are composed of indivisible ' atoms ' of matter and that different atoms have varying atomic weights. the development of the electrochemical theory of chemical combinations occurred in the early 19th century as the result of the work of two scientists in particular, jons jacob berzelius and humphry davy, made possible by the prior invention of the voltaic pile by alessandro volta. davy discovered nine new elements including the alkali metals by extracting them from their oxides with electric current. british william prout first proposed ordering all the elements by their atomic weight as all atoms had a weight that was an exact multiple of the atomic weight of hydrogen. j. a. r. newlands devised an early table of elements, which was then developed into the modern periodic table of elements in the 1860s by dmitri mendeleev and independently by several other scientists including julius lothar meyer. the inert gases, later called the noble gases were discovered by william ramsay in collaboration with lord rayleigh at the end of the century, thereby filling in the basic structure of the table. organic chemistry was developed by justus von liebig and others, following friedrich wohler ' s synthesis of urea. other crucial 19th century advances were ; an understanding of valence bonding ( edward frankland in 1852 ) and the application of thermodynamics to chemistry ( j. w. gibbs and svante arrhenius in the 1870s ). at the turn of the twentieth century the theoretical underpinnings of chemistry were finally understood due to a series of remarkable discoveries that succeeded in probing and discovering the very nature of the internal structure of atoms. in 1897, j. j. thomson of the university of cambridge discovered the electron and soon after the french scientist becquerel as well as the couple pierre and marie curie investigated the phenomenon of radioactivity. in a series of pioneering scattering experiments ernest rutherford at the university of manchester discovered the internal structure of the atom and the existence of the proton, classified and explained the different types of radioactivity and successfully transmuted the first element by bombarding nitrogen with alpha particles. his work on atomic structure was improved on by his students, the danish physicist niels bohr, the englishman henry moseley and the german otto hahn, who went on to father the emerging nuclear chemistry and discovered nuclear fission. the electronic theory
i. e. ' microscopic chemical events ' ). = = = ions and salts = = = an ion is a charged species, an atom or a molecule, that has lost or gained one or more electrons. when an atom loses an electron and thus has more protons than electrons, the atom is a positively charged ion or cation. when an atom gains an electron and thus has more electrons than protons, the atom is a negatively charged ion or anion. cations and anions can form a crystalline lattice of neutral salts, such as the na + and clβ ions forming sodium chloride, or nacl. examples of polyatomic ions that do not split up during acid β base reactions are hydroxide ( ohβ ) and phosphate ( po43β ). plasma is composed of gaseous matter that has been completely ionized, usually through high temperature. = = = acidity and basicity = = = a substance can often be classified as an acid or a base. there are several different theories which explain acid β base behavior. the simplest is arrhenius theory, which states that an acid is a substance that produces hydronium ions when it is dissolved in water, and a base is one that produces hydroxide ions when dissolved in water. according to brΓΈnsted β lowry acid β base theory, acids are substances that donate a positive hydrogen ion to another substance in a chemical reaction ; by extension, a base is the substance which receives that hydrogen ion. a third common theory is lewis acid β base theory, which is based on the formation of new chemical bonds. lewis theory explains that an acid is a substance which is capable of accepting a pair of electrons from another substance during the process of bond formation, while a base is a substance which can provide a pair of electrons to form a new bond. there are several other ways in which a substance may be classified as an acid or a base, as is evident in the history of this concept. acid strength is commonly measured by two methods. one measurement, based on the arrhenius definition of acidity, is ph, which is a measurement of the hydronium ion concentration in a solution, as expressed on a negative logarithmic scale. thus, solutions that have a low ph have a high hydronium ion concentration and can be said to be more acidic. the other measurement, based on the brΓΈnsted β lowry definition, is the acid dissociation constant ( ka ), which measures the relative ability of a substance to act as an
g. spectroscopy and chromatography. scientists engaged in chemical research are known as chemists. most chemists specialize in one or more sub - disciplines. several concepts are essential for the study of chemistry ; some of them are : = = = matter = = = in chemistry, matter is defined as anything that has rest mass and volume ( it takes up space ) and is made up of particles. the particles that make up matter have rest mass as well β not all particles have rest mass, such as the photon. matter can be a pure chemical substance or a mixture of substances. = = = = atom = = = = the atom is the basic unit of chemistry. it consists of a dense core called the atomic nucleus surrounded by a space occupied by an electron cloud. the nucleus is made up of positively charged protons and uncharged neutrons ( together called nucleons ), while the electron cloud consists of negatively charged electrons which orbit the nucleus. in a neutral atom, the negatively charged electrons balance out the positive charge of the protons. the nucleus is dense ; the mass of a nucleon is approximately 1, 836 times that of an electron, yet the radius of an atom is about 10, 000 times that of its nucleus. the atom is also the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state ( s ), coordination number, and preferred types of bonds to form ( e. g., metallic, ionic, covalent ). = = = = element = = = = a chemical element is a pure substance which is composed of a single type of atom, characterized by its particular number of protons in the nuclei of its atoms, known as the atomic number and represented by the symbol z. the mass number is the sum of the number of protons and neutrons in a nucleus. although all the nuclei of all atoms belonging to one element will have the same atomic number, they may not necessarily have the same mass number ; atoms of an element which have different mass numbers are known as isotopes. for example, all atoms with 6 protons in their nuclei are atoms of the chemical element carbon, but atoms of carbon may have mass numbers of 12 or 13. the standard presentation of the chemical elements is in the periodic table, which orders elements by atomic number. the periodic table is arranged in groups, or columns, and periods, or rows. the periodic table is useful in identifying periodic trends
forming another gaseous material. this is known as the chemical part of reactive ion etching. there is also a physical part, which is similar to the sputtering deposition process. if the ions have high enough energy, they can knock atoms out of the material to be etched without a chemical reaction. it is a very complex task to develop dry etch processes that balance chemical and physical etching, since there are many parameters to adjust. by changing the balance it is possible to influence the anisotropy of the etching, since the chemical part is isotropic and the physical part highly anisotropic the combination can form sidewalls that have shapes from rounded to vertical. deep reactive ion etching ( drie ) is a special subclass of rie that is growing in popularity. in this process, etch depths of hundreds of micrometers are achieved with almost vertical sidewalls. the primary technology is based on the so - called " bosch process ", named after the german company robert bosch, which filed the original patent, where two different gas compositions alternate in the reactor. currently, there are two variations of the drie. the first variation consists of three distinct steps ( the original bosch process ) while the second variation only consists of two steps. in the first variation, the etch cycle is as follows : ( i ) sf6 isotropic etch ; ( ii ) c4f8 passivation ; ( iii ) sf6 anisotropic etch for floor cleaning. in the 2nd variation, steps ( i ) and ( iii ) are combined. both variations operate similarly. the c4f8 creates a polymer on the surface of the substrate, and the second gas composition ( sf6 and o2 ) etches the substrate. the polymer is immediately sputtered away by the physical part of the etching, but only on the horizontal surfaces and not the sidewalls. since the polymer only dissolves very slowly in the chemical part of the etching, it builds up on the sidewalls and protects them from etching. as a result, etching aspect ratios of 50 to 1 can be achieved. the process can easily be used to etch completely through a silicon substrate, and etch rates are 3 β 6 times higher than wet etching. after preparing a large number of mems devices on a silicon wafer, individual dies have to be separated, which is called die preparation in semiconductor technology. for some applications, the separation is preceded by wafer backgrin
Question: What is the name for the energy required for an electron to be added to a neutral atom in its gaseous form?
A) photon affinity
B) neutron affinity
C) electron affinity
D) mass affinity
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C) electron affinity
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Context:
, they can fission as well, leading to a chain reaction. the average number of neutrons released per nucleus that go on to fission another nucleus is referred to as k. values of k larger than 1 mean that the fission reaction is releasing more neutrons than it absorbs, and therefore is referred to as a self - sustaining chain reaction. a mass of fissile material large enough ( and in a suitable configuration ) to induce a self - sustaining chain reaction is called a critical mass. when a neutron is captured by a suitable nucleus, fission may occur immediately, or the nucleus may persist in an unstable state for a short time. if there are enough immediate decays to carry on the chain reaction, the mass is said to be prompt critical, and the energy release will grow rapidly and uncontrollably, usually leading to an explosion. when discovered on the eve of world war ii, this insight led multiple countries to begin programs investigating the possibility of constructing an atomic bomb β a weapon which utilized fission reactions to generate far more energy than could be created with chemical explosives. the manhattan project, run by the united states with the help of the united kingdom and canada, developed multiple fission weapons which were used against japan in 1945 at hiroshima and nagasaki. during the project, the first fission reactors were developed as well, though they were primarily for weapons manufacture and did not generate electricity. in 1951, the first nuclear fission power plant was the first to produce electricity at the experimental breeder reactor no. 1 ( ebr - 1 ), in arco, idaho, ushering in the " atomic age " of more intensive human energy use. however, if the mass is critical only when the delayed neutrons are included, then the reaction can be controlled, for example by the introduction or removal of neutron absorbers. this is what allows nuclear reactors to be built. fast neutrons are not easily captured by nuclei ; they must be slowed ( slow neutrons ), generally by collision with the nuclei of a neutron moderator, before they can be easily captured. today, this type of fission is commonly used to generate electricity. = = = nuclear fusion = = = if nuclei are forced to collide, they can undergo nuclear fusion. this process may release or absorb energy. when the resulting nucleus is lighter than that of iron, energy is normally released ; when the nucleus is heavier than that of iron, energy is generally absorbed. this process of fusion occurs in stars, which derive their energy from hydrogen and helium. they form, through stellar nucleos
has rest mass and volume ( it takes up space ) and is made up of particles. the particles that make up matter have rest mass as well β not all particles have rest mass, such as the photon. matter can be a pure chemical substance or a mixture of substances. = = = = atom = = = = the atom is the basic unit of chemistry. it consists of a dense core called the atomic nucleus surrounded by a space occupied by an electron cloud. the nucleus is made up of positively charged protons and uncharged neutrons ( together called nucleons ), while the electron cloud consists of negatively charged electrons which orbit the nucleus. in a neutral atom, the negatively charged electrons balance out the positive charge of the protons. the nucleus is dense ; the mass of a nucleon is approximately 1, 836 times that of an electron, yet the radius of an atom is about 10, 000 times that of its nucleus. the atom is also the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state ( s ), coordination number, and preferred types of bonds to form ( e. g., metallic, ionic, covalent ). = = = = element = = = = a chemical element is a pure substance which is composed of a single type of atom, characterized by its particular number of protons in the nuclei of its atoms, known as the atomic number and represented by the symbol z. the mass number is the sum of the number of protons and neutrons in a nucleus. although all the nuclei of all atoms belonging to one element will have the same atomic number, they may not necessarily have the same mass number ; atoms of an element which have different mass numbers are known as isotopes. for example, all atoms with 6 protons in their nuclei are atoms of the chemical element carbon, but atoms of carbon may have mass numbers of 12 or 13. the standard presentation of the chemical elements is in the periodic table, which orders elements by atomic number. the periodic table is arranged in groups, or columns, and periods, or rows. the periodic table is useful in identifying periodic trends. = = = = compound = = = = a compound is a pure chemical substance composed of more than one element. the properties of a compound bear little similarity to those of its elements. the standard nomenclature of compounds is set by the international union of pure and applied chemistry ( iupac ). organic compounds are named
g. spectroscopy and chromatography. scientists engaged in chemical research are known as chemists. most chemists specialize in one or more sub - disciplines. several concepts are essential for the study of chemistry ; some of them are : = = = matter = = = in chemistry, matter is defined as anything that has rest mass and volume ( it takes up space ) and is made up of particles. the particles that make up matter have rest mass as well β not all particles have rest mass, such as the photon. matter can be a pure chemical substance or a mixture of substances. = = = = atom = = = = the atom is the basic unit of chemistry. it consists of a dense core called the atomic nucleus surrounded by a space occupied by an electron cloud. the nucleus is made up of positively charged protons and uncharged neutrons ( together called nucleons ), while the electron cloud consists of negatively charged electrons which orbit the nucleus. in a neutral atom, the negatively charged electrons balance out the positive charge of the protons. the nucleus is dense ; the mass of a nucleon is approximately 1, 836 times that of an electron, yet the radius of an atom is about 10, 000 times that of its nucleus. the atom is also the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state ( s ), coordination number, and preferred types of bonds to form ( e. g., metallic, ionic, covalent ). = = = = element = = = = a chemical element is a pure substance which is composed of a single type of atom, characterized by its particular number of protons in the nuclei of its atoms, known as the atomic number and represented by the symbol z. the mass number is the sum of the number of protons and neutrons in a nucleus. although all the nuclei of all atoms belonging to one element will have the same atomic number, they may not necessarily have the same mass number ; atoms of an element which have different mass numbers are known as isotopes. for example, all atoms with 6 protons in their nuclei are atoms of the chemical element carbon, but atoms of carbon may have mass numbers of 12 or 13. the standard presentation of the chemical elements is in the periodic table, which orders elements by atomic number. the periodic table is arranged in groups, or columns, and periods, or rows. the periodic table is useful in identifying periodic trends
to block. all three types of radiation occur naturally in certain elements. it has also become clear that the ultimate source of most terrestrial energy is nuclear, either through radiation from the sun caused by stellar thermonuclear reactions or by radioactive decay of uranium within the earth, the principal source of geothermal energy. = = = nuclear fission = = = in natural nuclear radiation, the byproducts are very small compared to the nuclei from which they originate. nuclear fission is the process of splitting a nucleus into roughly equal parts, and releasing energy and neutrons in the process. if these neutrons are captured by another unstable nucleus, they can fission as well, leading to a chain reaction. the average number of neutrons released per nucleus that go on to fission another nucleus is referred to as k. values of k larger than 1 mean that the fission reaction is releasing more neutrons than it absorbs, and therefore is referred to as a self - sustaining chain reaction. a mass of fissile material large enough ( and in a suitable configuration ) to induce a self - sustaining chain reaction is called a critical mass. when a neutron is captured by a suitable nucleus, fission may occur immediately, or the nucleus may persist in an unstable state for a short time. if there are enough immediate decays to carry on the chain reaction, the mass is said to be prompt critical, and the energy release will grow rapidly and uncontrollably, usually leading to an explosion. when discovered on the eve of world war ii, this insight led multiple countries to begin programs investigating the possibility of constructing an atomic bomb β a weapon which utilized fission reactions to generate far more energy than could be created with chemical explosives. the manhattan project, run by the united states with the help of the united kingdom and canada, developed multiple fission weapons which were used against japan in 1945 at hiroshima and nagasaki. during the project, the first fission reactors were developed as well, though they were primarily for weapons manufacture and did not generate electricity. in 1951, the first nuclear fission power plant was the first to produce electricity at the experimental breeder reactor no. 1 ( ebr - 1 ), in arco, idaho, ushering in the " atomic age " of more intensive human energy use. however, if the mass is critical only when the delayed neutrons are included, then the reaction can be controlled, for example by the introduction or removal of neutron absorbers. this is what allows nuclear reactors to be built. fast neutrons are not easily captured by nuclei
two neutrons, equivalent to a helium nucleus. beta decay is the release of a beta particle, a high - energy electron. gamma decay releases gamma rays, which unlike alpha and beta radiation are not matter but electromagnetic radiation of very high frequency, and therefore energy. this type of radiation is the most dangerous and most difficult to block. all three types of radiation occur naturally in certain elements. it has also become clear that the ultimate source of most terrestrial energy is nuclear, either through radiation from the sun caused by stellar thermonuclear reactions or by radioactive decay of uranium within the earth, the principal source of geothermal energy. = = = nuclear fission = = = in natural nuclear radiation, the byproducts are very small compared to the nuclei from which they originate. nuclear fission is the process of splitting a nucleus into roughly equal parts, and releasing energy and neutrons in the process. if these neutrons are captured by another unstable nucleus, they can fission as well, leading to a chain reaction. the average number of neutrons released per nucleus that go on to fission another nucleus is referred to as k. values of k larger than 1 mean that the fission reaction is releasing more neutrons than it absorbs, and therefore is referred to as a self - sustaining chain reaction. a mass of fissile material large enough ( and in a suitable configuration ) to induce a self - sustaining chain reaction is called a critical mass. when a neutron is captured by a suitable nucleus, fission may occur immediately, or the nucleus may persist in an unstable state for a short time. if there are enough immediate decays to carry on the chain reaction, the mass is said to be prompt critical, and the energy release will grow rapidly and uncontrollably, usually leading to an explosion. when discovered on the eve of world war ii, this insight led multiple countries to begin programs investigating the possibility of constructing an atomic bomb β a weapon which utilized fission reactions to generate far more energy than could be created with chemical explosives. the manhattan project, run by the united states with the help of the united kingdom and canada, developed multiple fission weapons which were used against japan in 1945 at hiroshima and nagasaki. during the project, the first fission reactors were developed as well, though they were primarily for weapons manufacture and did not generate electricity. in 1951, the first nuclear fission power plant was the first to produce electricity at the experimental breeder reactor no. 1 ( ebr - 1 ), in arco, idaho, ushering in the "
single carbon atom can form four single covalent bonds such as in methane, two double covalent bonds such as in carbon dioxide ( co2 ), or a triple covalent bond such as in carbon monoxide ( co ). moreover, carbon can form very long chains of interconnecting carbon β carbon bonds such as octane or ring - like structures such as glucose. the simplest form of an organic molecule is the hydrocarbon, which is a large family of organic compounds that are composed of hydrogen atoms bonded to a chain of carbon atoms. a hydrocarbon backbone can be substituted by other elements such as oxygen ( o ), hydrogen ( h ), phosphorus ( p ), and sulfur ( s ), which can change the chemical behavior of that compound. groups of atoms that contain these elements ( o -, h -, p -, and s - ) and are bonded to a central carbon atom or skeleton are called functional groups. there are six prominent functional groups that can be found in organisms : amino group, carboxyl group, carbonyl group, hydroxyl group, phosphate group, and sulfhydryl group. in 1953, the miller β urey experiment showed that organic compounds could be synthesized abiotically within a closed system mimicking the conditions of early earth, thus suggesting that complex organic molecules could have arisen spontaneously in early earth ( see abiogenesis ). = = = macromolecules = = = macromolecules are large molecules made up of smaller subunits or monomers. monomers include sugars, amino acids, and nucleotides. carbohydrates include monomers and polymers of sugars. lipids are the only class of macromolecules that are not made up of polymers. they include steroids, phospholipids, and fats, largely nonpolar and hydrophobic ( water - repelling ) substances. proteins are the most diverse of the macromolecules. they include enzymes, transport proteins, large signaling molecules, antibodies, and structural proteins. the basic unit ( or monomer ) of a protein is an amino acid. twenty amino acids are used in proteins. nucleic acids are polymers of nucleotides. their function is to store, transmit, and express hereditary information. = = cells = = cell theory states that cells are the fundamental units of life, that all living things are composed of one or more cells, and that all cells arise from preexisting cells through cell division
( create a critical mass ) for detonation. it also is quite difficult to ensure that such a chain reaction consumes a significant fraction of the fuel before the device flies apart. the procurement of a nuclear fuel is also more difficult than it might seem, since sufficiently unstable substances for this process do not currently occur naturally on earth in suitable amounts. one isotope of uranium, namely uranium - 235, is naturally occurring and sufficiently unstable, but it is always found mixed with the more stable isotope uranium - 238. the latter accounts for more than 99 % of the weight of natural uranium. therefore, some method of isotope separation based on the weight of three neutrons must be performed to enrich ( isolate ) uranium - 235. alternatively, the element plutonium possesses an isotope that is sufficiently unstable for this process to be usable. terrestrial plutonium does not currently occur naturally in sufficient quantities for such use, so it must be manufactured in a nuclear reactor. ultimately, the manhattan project manufactured nuclear weapons based on each of these elements. they detonated the first nuclear weapon in a test code - named " trinity ", near alamogordo, new mexico, on july 16, 1945. the test was conducted to ensure that the implosion method of detonation would work, which it did. a uranium bomb, little boy, was dropped on the japanese city hiroshima on august 6, 1945, followed three days later by the plutonium - based fat man on nagasaki. in the wake of unprecedented devastation and casualties from a single weapon, the japanese government soon surrendered, ending world war ii. since these bombings, no nuclear weapons have been deployed offensively. nevertheless, they prompted an arms race to develop increasingly destructive bombs to provide a nuclear deterrent. just over four years later, on august 29, 1949, the soviet union detonated its first fission weapon. the united kingdom followed on october 2, 1952 ; france, on february 13, 1960 ; and china component to a nuclear weapon. approximately half of the deaths from hiroshima and nagasaki died two to five years afterward from radiation exposure. a radiological weapon is a type of nuclear weapon designed to distribute hazardous nuclear material in enemy areas. such a weapon would not have the explosive capability of a fission or fusion bomb, but would kill many people and contaminate a large area. a radiological weapon has never been deployed. while considered useless by a conventional military, such a weapon raises concerns over nuclear terrorism. there have been over 2, 000 nuclear tests conducted since 1945. in 1963, all nuclear and many non -
it is believed that there may have been a large number of black holes formed in the very early universe. these would have quantised masses. a charged ` ` elementary black hole ' ' ( with the minimum possible mass ) can capture electrons, protons and other charged particles to form a ` ` black hole atom ' '. we find the spectrum of such an object with a view to laboratory and astronomical observation of them, and estimate the lifetime of the bound states. there is no limit to the charge of the black hole, which gives us the possibility of observing z > 137 bound states and transitions at the lower continuum. negatively charged black holes can capture protons. for z > 1, the orbiting protons will coalesce to form a nucleus ( after beta - decay of some protons to neutrons ), with a stability curve different to that of free nuclei. in this system there is also the distinct possibility of single quark capture. this leads to the formation of a coloured black hole that plays the role of an extremely heavy quark interacting strongly with the other two quarks. finally we consider atoms formed with much larger black holes.
the r - process of nucleosynthesis requires a large neutron - to - seed nucleus ratio. this does not, however, that there be an excess of neutrons over protons. if the expansion of the material is sufficiently rapid and the entropy per nucleon is sufficiently high, the nucleosynthesis enters a heavy - element synthesis regime heretofore unexplored. in this extreme regime, characterized by a persistent disequilibrium between free nucleons and the abundant alpha particles, heavy r - process nuclei can form even in matter with more protons than neutrons. this observation bears on the issue of the site of the r - process, on the variability of abundance yields from r - process events, and on cnstraints on neutrino physics derived from nucleosynthesis. it also clarifies the difference between nucleosynthesis in the early universe and that in less extreme stellar explosive environments.
on earth in suitable amounts. one isotope of uranium, namely uranium - 235, is naturally occurring and sufficiently unstable, but it is always found mixed with the more stable isotope uranium - 238. the latter accounts for more than 99 % of the weight of natural uranium. therefore, some method of isotope separation based on the weight of three neutrons must be performed to enrich ( isolate ) uranium - 235. alternatively, the element plutonium possesses an isotope that is sufficiently unstable for this process to be usable. terrestrial plutonium does not currently occur naturally in sufficient quantities for such use, so it must be manufactured in a nuclear reactor. ultimately, the manhattan project manufactured nuclear weapons based on each of these elements. they detonated the first nuclear weapon in a test code - named " trinity ", near alamogordo, new mexico, on july 16, 1945. the test was conducted to ensure that the implosion method of detonation would work, which it did. a uranium bomb, little boy, was dropped on the japanese city hiroshima on august 6, 1945, followed three days later by the plutonium - based fat man on nagasaki. in the wake of unprecedented devastation and casualties from a single weapon, the japanese government soon surrendered, ending world war ii. since these bombings, no nuclear weapons have been deployed offensively. nevertheless, they prompted an arms race to develop increasingly destructive bombs to provide a nuclear deterrent. just over four years later, on august 29, 1949, the soviet union detonated its first fission weapon. the united kingdom followed on october 2, 1952 ; france, on february 13, 1960 ; and china component to a nuclear weapon. approximately half of the deaths from hiroshima and nagasaki died two to five years afterward from radiation exposure. a radiological weapon is a type of nuclear weapon designed to distribute hazardous nuclear material in enemy areas. such a weapon would not have the explosive capability of a fission or fusion bomb, but would kill many people and contaminate a large area. a radiological weapon has never been deployed. while considered useless by a conventional military, such a weapon raises concerns over nuclear terrorism. there have been over 2, 000 nuclear tests conducted since 1945. in 1963, all nuclear and many non - nuclear states signed the limited test ban treaty, pledging to refrain from testing nuclear weapons in the atmosphere, underwater, or in outer space. the treaty permitted underground nuclear testing. france continued atmospheric testing until 1974, while china continued up until 1980. the last underground test by the united states was in 1992, the soviet union
Question: Carbon atoms have six neutrons as well as how many protons?
A) two
B) six
C) ten
D) four
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B) six
|
Context:
set of chemical reactions with other substances. however, this definition only works well for substances that are composed of molecules, which is not true of many substances ( see below ). molecules are typically a set of atoms bound together by covalent bonds, such that the structure is electrically neutral and all valence electrons are paired with other electrons either in bonds or in lone pairs. thus, molecules exist as electrically neutral units, unlike ions. when this rule is broken, giving the " molecule " a charge, the result is sometimes named a molecular ion or a polyatomic ion. however, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature.
other electrons either in bonds or in lone pairs. thus, molecules exist as electrically neutral units, unlike ions. when this rule is broken, giving the " molecule " a charge, the result is sometimes named a molecular ion or a polyatomic ion. however, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature. = = = = substance and mixture = = = = a chemical substance is a kind of matter with a definite composition and set of properties. a collection of substances is called a mixture. examples of mixtures are air and alloys. = = = = mole and amount of substance = = = = the mole is a unit
that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature. = = = = substance and mixture = = = = a chemical substance is a kind of matter with a definite composition and set of properties. a collection of substances is called a mixture. examples of mixtures are air and alloys. = = = = mole and amount of substance = = = = the mole is a unit of measurement that denotes an amount of substance ( also called chemical amount ). one mole is defined to contain exactly 6. 02214076Γ1023 particles ( atoms, molecules, ions, or electrons ), where the number of particles per mole is known as the avogadro constant. molar concentration is
the thickness and the density of the material to be measured. the method is used for containers of liquids or of grainy substances thickness gauges : if the material is of constant density, the signal measured by the radiation detector depends on the thickness of the material. this is useful for continuous production, like of paper, rubber, etc. electrostatic control - to avoid the build - up of static electricity in production of paper, plastics, synthetic textiles, etc., a ribbon - shaped source of the alpha emitter 241am can be placed close to the material at the end of the production line. the source ionizes the air to remove electric charges on the material. radioactive tracers - since radioactive isotopes behave, chemically, mostly like the inactive element, the behavior of a certain chemical substance can be followed by tracing the radioactivity. examples : adding a gamma tracer to a gas or liquid in a closed system makes it possible to find a hole in a tube. adding a tracer to the surface of the component of a motor makes it possible to measure wear by measuring the activity of the lubricating oil. oil and gas exploration - nuclear well logging is used to help predict the commercial viability of new or existing wells. the technology involves the use of a neutron or gamma - ray source and a radiation detector which are lowered into boreholes to determine the properties of the surrounding rock such as porosity and lithography. [ 1 ] road construction - nuclear moisture / density gauges are used to determine the density of soils, asphalt, and concrete. typically a cesium - 137 source is used. = = = commercial applications = = = radioluminescence tritium illumination : tritium is used with phosphor in rifle sights to increase nighttime firing accuracy. some runway markers and building exit signs use the same technology, to remain illuminated during blackouts. betavoltaics. smoke detector : an ionization smoke detector includes a tiny mass of radioactive americium - 241, which is a source of alpha radiation. two ionisation chambers are placed next to each other. both contain a small source of 241am that gives rise to a small constant current. one is closed and serves for comparison, the other is open to ambient air ; it has a gridded electrode. when smoke enters the open chamber, the current is disrupted as the smoke particles attach to the charged ions and restore them to a neutral electrical state. this reduces the current in the open chamber. when the current drops below a certain threshold, the
classes according to pore size : the form and shape of the membrane pores are highly dependent on the manufacturing process and are often difficult to specify. therefore, for characterization, test filtrations are carried out and the pore diameter refers to the diameter of the smallest particles which could not pass through the membrane. the rejection can be determined in various ways and provides an indirect measurement of the pore size. one possibility is the filtration of macromolecules ( often dextran, polyethylene glycol or albumin ), another is measurement of the cut - off by gel permeation chromatography. these methods are used mainly to measure membranes for ultrafiltration applications. another testing method is the filtration of particles with defined size and their measurement with a particle sizer or by laser induced breakdown spectroscopy ( libs ). a vivid characterization is to measure the rejection of dextran blue or other colored molecules. the retention of bacteriophage and bacteria, the so - called " bacteria challenge test ", can also provide information about the pore size. to determine the pore diameter, physical methods such as porosimeter ( mercury, liquid - liquid porosimeter and bubble point test ) are also used, but a certain form of the pores ( such as cylindrical or concatenated spherical holes ) is assumed. such methods are used for membranes whose pore geometry does not match the ideal, and we get " nominal " pore diameter, which characterizes the membrane, but does not necessarily reflect its actual filtration behavior and selectivity. the selectivity is highly dependent on the separation process, the composition of the membrane and its electrochemical properties in addition to the pore size. with high selectivity, isotopes can be enriched ( uranium enrichment ) in nuclear engineering or industrial gases like nitrogen can be recovered ( gas separation ). ideally, even racemics can be enriched with a suitable membrane. when choosing membranes selectivity has priority over a high permeability, as low flows can easily be offset by increasing the filter surface with a modular structure. in gas phase filtration different deposition mechanisms are operative, so that particles having sizes below the pore size of the membrane can be retained as well. = = membrane classification = = bio - membrane is classified in two categories, synthetic membrane and natural membrane. synthetic membranes further classified in organic and inorganic membranes. organic membrane sub classified polymeric membranes and inorganic membrane sub classified ceramic polymers. = = synthesis of biomass membrane
intense research in the materials science community due to the unique properties that they exhibit. nanostructure deals with objects and structures that are in the 1 β 100 nm range. in many materials, atoms or molecules agglomerate to form objects at the nanoscale. this causes many interesting electrical, magnetic, optical, and mechanical properties. in describing nanostructures, it is necessary to differentiate between the number of dimensions on the nanoscale. nanotextured surfaces have one dimension on the nanoscale, i. e., only the thickness of the surface of an object is between 0. 1 and 100 nm. nanotubes have two dimensions on the nanoscale, i. e., the diameter of the tube is between 0. 1 and 100 nm ; its length could be much greater. finally, spherical nanoparticles have three dimensions on the nanoscale, i. e., the particle is between 0. 1 and 100 nm in each spatial dimension. the terms nanoparticles and ultrafine particles ( ufp ) often are used synonymously although ufp can reach into the micrometre range. the term ' nanostructure ' is often used, when referring to magnetic technology. nanoscale structure in biology is often called ultrastructure. = = = = microstructure = = = = microstructure is defined as the structure of a prepared surface or thin foil of material as revealed by a microscope above 25Γ magnification. it deals with objects from 100 nm to a few cm. the microstructure of a material ( which can be broadly classified into metallic, polymeric, ceramic and composite ) can strongly influence physical properties such as strength, toughness, ductility, hardness, corrosion resistance, high / low temperature behavior, wear resistance, and so on. most of the traditional materials ( such as metals and ceramics ) are microstructured. the manufacture of a perfect crystal of a material is physically impossible. for example, any crystalline material will contain defects such as precipitates, grain boundaries ( hall β petch relationship ), vacancies, interstitial atoms or substitutional atoms. the microstructure of materials reveals these larger defects and advances in simulation have allowed an increased understanding of how defects can be used to enhance material properties. = = = = macrostructure = = = = macrostructure is the appearance of a material in the scale millimeters to meters, it is the structure of
another and therefore take part in chemical reactions that sustain life. in terms of its molecular structure, water is a small polar molecule with a bent shape formed by the polar covalent bonds of two hydrogen ( h ) atoms to one oxygen ( o ) atom ( h2o ). because the o β h bonds are polar, the oxygen atom has a slight negative charge and the two hydrogen atoms have a slight positive charge. this polar property of water allows it to attract other water molecules via hydrogen bonds, which makes water cohesive. surface tension results from the cohesive force due to the attraction between molecules at the surface of the liquid. water is also adhesive as it is able to adhere to the surface of any polar or charged non - water molecules. water is denser as a liquid than it is as a solid ( or ice ). this unique property of water allows ice to float above liquid water such as ponds, lakes, and oceans, thereby insulating the liquid below from the cold air above. water has the capacity to absorb energy, giving it a higher specific heat capacity than other solvents such as ethanol. thus, a large amount of energy is needed to break the hydrogen bonds between water molecules to convert liquid water into water vapor. as a molecule, water is not completely stable as each water molecule continuously dissociates into hydrogen and hydroxyl ions before reforming into a water molecule again. in pure water, the number of hydrogen ions balances ( or equals ) the number of hydroxyl ions, resulting in a ph that is neutral. = = = organic compounds = = = organic compounds are molecules that contain carbon bonded to another element such as hydrogen. with the exception of water, nearly all the molecules that make up each organism contain carbon. carbon can form covalent bonds with up to four other atoms, enabling it to form diverse, large, and complex molecules. for example, a single carbon atom can form four single covalent bonds such as in methane, two double covalent bonds such as in carbon dioxide ( co2 ), or a triple covalent bond such as in carbon monoxide ( co ). moreover, carbon can form very long chains of interconnecting carbon β carbon bonds such as octane or ring - like structures such as glucose. the simplest form of an organic molecule is the hydrocarbon, which is a large family of organic compounds that are composed of hydrogen atoms bonded to a chain of carbon atoms. a hydrocarbon backbone can be substituted by other elements such as oxygen ( o ), hydrogen
index chemical substances. in this scheme each chemical substance is identifiable by a number known as its cas registry number. = = = = molecule = = = = a molecule is the smallest indivisible portion of a pure chemical substance that has its unique set of chemical properties, that is, its potential to undergo a certain set of chemical reactions with other substances. however, this definition only works well for substances that are composed of molecules, which is not true of many substances ( see below ). molecules are typically a set of atoms bound together by covalent bonds, such that the structure is electrically neutral and all valence electrons are paired with other electrons either in bonds or in lone pairs. thus, molecules exist as electrically neutral units, unlike ions. when this rule is broken, giving the " molecule " a charge, the result is sometimes named a molecular ion or a polyatomic ion. however, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry
lithography is throughput, i. e., the very long time it takes to expose an entire silicon wafer or glass substrate. a long exposure time leaves the user vulnerable to beam drift or instability which may occur during the exposure. also, the turn - around time for reworking or re - design is lengthened unnecessarily if the pattern is not being changed the second time. it is known that focused - ion beam lithography has the capability of writing extremely fine lines ( less than 50 nm line and space has been achieved ) without proximity effect. however, because the writing field in ion - beam lithography is quite small, large area patterns must be created by stitching together the small fields. ion track technology is a deep cutting tool with a resolution limit around 8 nm applicable to radiation resistant minerals, glasses and polymers. it is capable of generating holes in thin films without any development process. structural depth can be defined either by ion range or by material thickness. aspect ratios up to several 104 can be reached. the technique can shape and texture materials at a defined inclination angle. random pattern, single - ion track structures and an aimed pattern consisting of individual single tracks can be generated. x - ray lithography is a process used in the electronic industry to selectively remove parts of a thin film. it uses x - rays to transfer a geometric pattern from a mask to a light - sensitive chemical photoresist, or simply " resist ", on the substrate. a series of chemical treatments then engraves the produced pattern into the material underneath the photoresist. diamond patterning is a method of forming diamond mems. it is achieved by the lithographic application of diamond films to a substrate such as silicon. the patterns can be formed by selective deposition through a silicon dioxide mask, or by deposition followed by micromachining or focused ion beam milling. = = = etching processes = = = there are two basic categories of etching processes : wet etching and dry etching. in the former, the material is dissolved when immersed in a chemical solution. in the latter, the material is sputtered or dissolved using reactive ions or a vapor phase etchant. = = = = wet etching = = = = wet chemical etching consists of the selective removal of material by dipping a substrate into a solution that dissolves it. the chemical nature of this etching process provides good selectivity, which means the etching rate of the target material is considerably higher than the mask material if
the film is developed and it shows any internal defects of the material. gauges - gauges use the exponential absorption law of gamma rays level indicators : source and detector are placed at opposite sides of a container, indicating the presence or absence of material in the horizontal radiation path. beta or gamma sources are used, depending on the thickness and the density of the material to be measured. the method is used for containers of liquids or of grainy substances thickness gauges : if the material is of constant density, the signal measured by the radiation detector depends on the thickness of the material. this is useful for continuous production, like of paper, rubber, etc. electrostatic control - to avoid the build - up of static electricity in production of paper, plastics, synthetic textiles, etc., a ribbon - shaped source of the alpha emitter 241am can be placed close to the material at the end of the production line. the source ionizes the air to remove electric charges on the material. radioactive tracers - since radioactive isotopes behave, chemically, mostly like the inactive element, the behavior of a certain chemical substance can be followed by tracing the radioactivity. examples : adding a gamma tracer to a gas or liquid in a closed system makes it possible to find a hole in a tube. adding a tracer to the surface of the component of a motor makes it possible to measure wear by measuring the activity of the lubricating oil. oil and gas exploration - nuclear well logging is used to help predict the commercial viability of new or existing wells. the technology involves the use of a neutron or gamma - ray source and a radiation detector which are lowered into boreholes to determine the properties of the surrounding rock such as porosity and lithography. [ 1 ] road construction - nuclear moisture / density gauges are used to determine the density of soils, asphalt, and concrete. typically a cesium - 137 source is used. = = = commercial applications = = = radioluminescence tritium illumination : tritium is used with phosphor in rifle sights to increase nighttime firing accuracy. some runway markers and building exit signs use the same technology, to remain illuminated during blackouts. betavoltaics. smoke detector : an ionization smoke detector includes a tiny mass of radioactive americium - 241, which is a source of alpha radiation. two ionisation chambers are placed next to each other. both contain a small source of 241am that gives rise to a small constant current. one is closed and serves for comparison
Question: What term means that only molecules or ions of a certain size, shape, polarity or charge are capable of passing through the material?
A) induced permeation
B) selective permeation
C) radiation permeation
D) classic permeation
|
B) selective permeation
|
Context:
and nucleotides. carbohydrates include monomers and polymers of sugars. lipids are the only class of macromolecules that are not made up of polymers. they include steroids, phospholipids, and fats, largely nonpolar and hydrophobic ( water - repelling ) substances. proteins are the most diverse of the macromolecules. they include enzymes, transport proteins, large signaling molecules, antibodies, and structural proteins. the basic unit ( or monomer ) of a protein is an amino acid. twenty amino acids are used in proteins. nucleic acids are polymers of nucleotides. their function is to store, transmit, and express hereditary information. = = cells = = cell theory states that cells are the fundamental units of life, that all living things are composed of one or more cells, and that all cells arise from preexisting cells through cell division. most cells are very small, with diameters ranging from 1 to 100 micrometers and are therefore only visible under a light or electron microscope. there are generally two types of cells : eukaryotic cells, which contain a nucleus, and prokaryotic cells, which do not. prokaryotes are single - celled organisms such as bacteria, whereas eukaryotes can be single - celled or multicellular. in multicellular organisms, every cell in the organism ' s body is derived ultimately from a single cell in a fertilized egg. = = = cell structure = = = every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions. cell membranes also contain membrane proteins, including integral membrane proteins that go across the membrane serving as membrane transporters, and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes shaping the cell. cell membranes are involved in various cellular processes such as cell adhesion, storing electrical energy, and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall, glycocalyx, and cytoskeleton. within the cytoplasm of a cell
set of chemical reactions with other substances. however, this definition only works well for substances that are composed of molecules, which is not true of many substances ( see below ). molecules are typically a set of atoms bound together by covalent bonds, such that the structure is electrically neutral and all valence electrons are paired with other electrons either in bonds or in lone pairs. thus, molecules exist as electrically neutral units, unlike ions. when this rule is broken, giving the " molecule " a charge, the result is sometimes named a molecular ion or a polyatomic ion. however, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature.
to a region of deoxyribonucleic acid ( dna ) that carries genetic information that controls form or function of an organism. dna is composed of two polynucleotide chains that coil around each other to form a double helix. it is found as linear chromosomes in eukaryotes, and circular chromosomes in prokaryotes. the set of chromosomes in a cell is collectively known as its genome. in eukaryotes, dna is mainly in the cell nucleus. in prokaryotes, the dna is held within the nucleoid. the genetic information is held within genes, and the complete assemblage in an organism is called its genotype. dna replication is a semiconservative process whereby each strand serves as a template for a new strand of dna. mutations are heritable changes in dna. they can arise spontaneously as a result of replication errors that were not corrected by proofreading or can be induced by an environmental mutagen such as a chemical ( e. g., nitrous acid, benzopyrene ) or radiation ( e. g., x - ray, gamma ray, ultraviolet radiation, particles emitted by unstable isotopes ). mutations can lead to phenotypic effects such as loss - of - function, gain - of - function, and conditional mutations. some mutations are beneficial, as they are a source of genetic variation for evolution. others are harmful if they were to result in a loss of function of genes needed for survival. = = = gene expression = = = gene expression is the molecular process by which a genotype encoded in dna gives rise to an observable phenotype in the proteins of an organism ' s body. this process is summarized by the central dogma of molecular biology, which was formulated by francis crick in 1958. according to the central dogma, genetic information flows from dna to rna to protein. there are two gene expression processes : transcription ( dna to rna ) and translation ( rna to protein ). = = = gene regulation = = = the regulation of gene expression by environmental factors and during different stages of development can occur at each step of the process such as transcription, rna splicing, translation, and post - translational modification of a protein. gene expression can be influenced by positive or negative regulation, depending on which of the two types of regulatory proteins called transcription factors bind to the dna sequence close to or at a promoter. a cluster of genes that share the same promoter is called an operon,
other electrons either in bonds or in lone pairs. thus, molecules exist as electrically neutral units, unlike ions. when this rule is broken, giving the " molecule " a charge, the result is sometimes named a molecular ion or a polyatomic ion. however, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature. = = = = substance and mixture = = = = a chemical substance is a kind of matter with a definite composition and set of properties. a collection of substances is called a mixture. examples of mixtures are air and alloys. = = = = mole and amount of substance = = = = the mole is a unit
index chemical substances. in this scheme each chemical substance is identifiable by a number known as its cas registry number. = = = = molecule = = = = a molecule is the smallest indivisible portion of a pure chemical substance that has its unique set of chemical properties, that is, its potential to undergo a certain set of chemical reactions with other substances. however, this definition only works well for substances that are composed of molecules, which is not true of many substances ( see below ). molecules are typically a set of atoms bound together by covalent bonds, such that the structure is electrically neutral and all valence electrons are paired with other electrons either in bonds or in lone pairs. thus, molecules exist as electrically neutral units, unlike ions. when this rule is broken, giving the " molecule " a charge, the result is sometimes named a molecular ion or a polyatomic ion. however, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry
prominent functional groups that can be found in organisms : amino group, carboxyl group, carbonyl group, hydroxyl group, phosphate group, and sulfhydryl group. in 1953, the miller β urey experiment showed that organic compounds could be synthesized abiotically within a closed system mimicking the conditions of early earth, thus suggesting that complex organic molecules could have arisen spontaneously in early earth ( see abiogenesis ). = = = macromolecules = = = macromolecules are large molecules made up of smaller subunits or monomers. monomers include sugars, amino acids, and nucleotides. carbohydrates include monomers and polymers of sugars. lipids are the only class of macromolecules that are not made up of polymers. they include steroids, phospholipids, and fats, largely nonpolar and hydrophobic ( water - repelling ) substances. proteins are the most diverse of the macromolecules. they include enzymes, transport proteins, large signaling molecules, antibodies, and structural proteins. the basic unit ( or monomer ) of a protein is an amino acid. twenty amino acids are used in proteins. nucleic acids are polymers of nucleotides. their function is to store, transmit, and express hereditary information. = = cells = = cell theory states that cells are the fundamental units of life, that all living things are composed of one or more cells, and that all cells arise from preexisting cells through cell division. most cells are very small, with diameters ranging from 1 to 100 micrometers and are therefore only visible under a light or electron microscope. there are generally two types of cells : eukaryotic cells, which contain a nucleus, and prokaryotic cells, which do not. prokaryotes are single - celled organisms such as bacteria, whereas eukaryotes can be single - celled or multicellular. in multicellular organisms, every cell in the organism ' s body is derived ultimately from a single cell in a fertilized egg. = = = cell structure = = = every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as
that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature. = = = = substance and mixture = = = = a chemical substance is a kind of matter with a definite composition and set of properties. a collection of substances is called a mixture. examples of mixtures are air and alloys. = = = = mole and amount of substance = = = = the mole is a unit of measurement that denotes an amount of substance ( also called chemical amount ). one mole is defined to contain exactly 6. 02214076Γ1023 particles ( atoms, molecules, ions, or electrons ), where the number of particles per mole is known as the avogadro constant. molar concentration is
the r - process of nucleosynthesis requires a large neutron - to - seed nucleus ratio. this does not, however, that there be an excess of neutrons over protons. if the expansion of the material is sufficiently rapid and the entropy per nucleon is sufficiently high, the nucleosynthesis enters a heavy - element synthesis regime heretofore unexplored. in this extreme regime, characterized by a persistent disequilibrium between free nucleons and the abundant alpha particles, heavy r - process nuclei can form even in matter with more protons than neutrons. this observation bears on the issue of the site of the r - process, on the variability of abundance yields from r - process events, and on cnstraints on neutrino physics derived from nucleosynthesis. it also clarifies the difference between nucleosynthesis in the early universe and that in less extreme stellar explosive environments.
g. spectroscopy and chromatography. scientists engaged in chemical research are known as chemists. most chemists specialize in one or more sub - disciplines. several concepts are essential for the study of chemistry ; some of them are : = = = matter = = = in chemistry, matter is defined as anything that has rest mass and volume ( it takes up space ) and is made up of particles. the particles that make up matter have rest mass as well β not all particles have rest mass, such as the photon. matter can be a pure chemical substance or a mixture of substances. = = = = atom = = = = the atom is the basic unit of chemistry. it consists of a dense core called the atomic nucleus surrounded by a space occupied by an electron cloud. the nucleus is made up of positively charged protons and uncharged neutrons ( together called nucleons ), while the electron cloud consists of negatively charged electrons which orbit the nucleus. in a neutral atom, the negatively charged electrons balance out the positive charge of the protons. the nucleus is dense ; the mass of a nucleon is approximately 1, 836 times that of an electron, yet the radius of an atom is about 10, 000 times that of its nucleus. the atom is also the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state ( s ), coordination number, and preferred types of bonds to form ( e. g., metallic, ionic, covalent ). = = = = element = = = = a chemical element is a pure substance which is composed of a single type of atom, characterized by its particular number of protons in the nuclei of its atoms, known as the atomic number and represented by the symbol z. the mass number is the sum of the number of protons and neutrons in a nucleus. although all the nuclei of all atoms belonging to one element will have the same atomic number, they may not necessarily have the same mass number ; atoms of an element which have different mass numbers are known as isotopes. for example, all atoms with 6 protons in their nuclei are atoms of the chemical element carbon, but atoms of carbon may have mass numbers of 12 or 13. the standard presentation of the chemical elements is in the periodic table, which orders elements by atomic number. the periodic table is arranged in groups, or columns, and periods, or rows. the periodic table is useful in identifying periodic trends
= = organic compounds are molecules that contain carbon bonded to another element such as hydrogen. with the exception of water, nearly all the molecules that make up each organism contain carbon. carbon can form covalent bonds with up to four other atoms, enabling it to form diverse, large, and complex molecules. for example, a single carbon atom can form four single covalent bonds such as in methane, two double covalent bonds such as in carbon dioxide ( co2 ), or a triple covalent bond such as in carbon monoxide ( co ). moreover, carbon can form very long chains of interconnecting carbon β carbon bonds such as octane or ring - like structures such as glucose. the simplest form of an organic molecule is the hydrocarbon, which is a large family of organic compounds that are composed of hydrogen atoms bonded to a chain of carbon atoms. a hydrocarbon backbone can be substituted by other elements such as oxygen ( o ), hydrogen ( h ), phosphorus ( p ), and sulfur ( s ), which can change the chemical behavior of that compound. groups of atoms that contain these elements ( o -, h -, p -, and s - ) and are bonded to a central carbon atom or skeleton are called functional groups. there are six prominent functional groups that can be found in organisms : amino group, carboxyl group, carbonyl group, hydroxyl group, phosphate group, and sulfhydryl group. in 1953, the miller β urey experiment showed that organic compounds could be synthesized abiotically within a closed system mimicking the conditions of early earth, thus suggesting that complex organic molecules could have arisen spontaneously in early earth ( see abiogenesis ). = = = macromolecules = = = macromolecules are large molecules made up of smaller subunits or monomers. monomers include sugars, amino acids, and nucleotides. carbohydrates include monomers and polymers of sugars. lipids are the only class of macromolecules that are not made up of polymers. they include steroids, phospholipids, and fats, largely nonpolar and hydrophobic ( water - repelling ) substances. proteins are the most diverse of the macromolecules. they include enzymes, transport proteins, large signaling molecules, antibodies, and structural proteins. the basic unit ( or monomer ) of a protein is an amino acid. twenty amino acids are used in proteins. nucleic acids
Question: What holds together the small molecules called nucleotides which make up nucleic acids?
A) dissonance bonds
B) covalent bonds
C) curvature bonds
D) permanent bonds
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B) covalent bonds
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Context:
. most cells are very small, with diameters ranging from 1 to 100 micrometers and are therefore only visible under a light or electron microscope. there are generally two types of cells : eukaryotic cells, which contain a nucleus, and prokaryotic cells, which do not. prokaryotes are single - celled organisms such as bacteria, whereas eukaryotes can be single - celled or multicellular. in multicellular organisms, every cell in the organism ' s body is derived ultimately from a single cell in a fertilized egg. = = = cell structure = = = every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions. cell membranes also contain membrane proteins, including integral membrane proteins that go across the membrane serving as membrane transporters, and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes shaping the cell. cell membranes are involved in various cellular processes such as cell adhesion, storing electrical energy, and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall, glycocalyx, and cytoskeleton. within the cytoplasm of a cell, there are many biomolecules such as proteins and nucleic acids. in addition to biomolecules, eukaryotic cells have specialized structures called organelles that have their own lipid bilayers or are spatially units. these organelles include the cell nucleus, which contains most of the cell ' s dna, or mitochondria, which generate adenosine triphosphate ( atp ) to power cellular processes. other organelles such as endoplasmic reticulum and golgi apparatus play a role in the synthesis and packaging of proteins, respectively. biomolecules such as proteins can be engulfed by lysosomes, another specialized organelle. plant cells have additional organelles that distinguish them from animal cells such as a cell wall that provides support for the plant cell, chloroplasts that harvest sunlight energy to produce sugar, and vacuoles that provide storage and structural support
, there are many biomolecules such as proteins and nucleic acids. in addition to biomolecules, eukaryotic cells have specialized structures called organelles that have their own lipid bilayers or are spatially units. these organelles include the cell nucleus, which contains most of the cell ' s dna, or mitochondria, which generate adenosine triphosphate ( atp ) to power cellular processes. other organelles such as endoplasmic reticulum and golgi apparatus play a role in the synthesis and packaging of proteins, respectively. biomolecules such as proteins can be engulfed by lysosomes, another specialized organelle. plant cells have additional organelles that distinguish them from animal cells such as a cell wall that provides support for the plant cell, chloroplasts that harvest sunlight energy to produce sugar, and vacuoles that provide storage and structural support as well as being involved in reproduction and breakdown of plant seeds. eukaryotic cells also have cytoskeleton that is made up of microtubules, intermediate filaments, and microfilaments, all of which provide support for the cell and are involved in the movement of the cell and its organelles. in terms of their structural composition, the microtubules are made up of tubulin ( e. g., Ξ± - tubulin and Ξ² - tubulin ) whereas intermediate filaments are made up of fibrous proteins. microfilaments are made up of actin molecules that interact with other strands of proteins. = = = metabolism = = = all cells require energy to sustain cellular processes. metabolism is the set of chemical reactions in an organism. the three main purposes of metabolism are : the conversion of food to energy to run cellular processes ; the conversion of food / fuel to monomer building blocks ; and the elimination of metabolic wastes. these enzyme - catalyzed reactions allow organisms to grow and reproduce, maintain their structures, and respond to their environments. metabolic reactions may be categorized as catabolic β the breaking down of compounds ( for example, the breaking down of glucose to pyruvate by cellular respiration ) ; or anabolic β the building up ( synthesis ) of compounds ( such as proteins, carbohydrates, lipids, and nucleic acids ). usually, catabolism releases energy, and anabolism consumes energy. the chemical reactions of metabolism are organized into metabolic pathways, in which
plant cells and tissues, whereas plant morphology is the study of their external form. all plants are multicellular eukaryotes, their dna stored in nuclei. the characteristic features of plant cells that distinguish them from those of animals and fungi include a primary cell wall composed of the polysaccharides cellulose, hemicellulose and pectin, larger vacuoles than in animal cells and the presence of plastids with unique photosynthetic and biosynthetic functions as in the chloroplasts. other plastids contain storage products such as starch ( amyloplasts ) or lipids ( elaioplasts ). uniquely, streptophyte cells and those of the green algal order trentepohliales divide by construction of a phragmoplast as a template for building a cell plate late in cell division. the bodies of vascular plants including clubmosses, ferns and seed plants ( gymnosperms and angiosperms ) generally have aerial and subterranean subsystems. the shoots consist of stems bearing green photosynthesising leaves and reproductive structures. the underground vascularised roots bear root hairs at their tips and generally lack chlorophyll. non - vascular plants, the liverworts, hornworts and mosses do not produce ground - penetrating vascular roots and most of the plant participates in photosynthesis. the sporophyte generation is nonphotosynthetic in liverworts but may be able to contribute part of its energy needs by photosynthesis in mosses and hornworts. the root system and the shoot system are interdependent β the usually nonphotosynthetic root system depends on the shoot system for food, and the usually photosynthetic shoot system depends on water and minerals from the root system. cells in each system are capable of creating cells of the other and producing adventitious shoots or roots. stolons and tubers are examples of shoots that can grow roots. roots that spread out close to the surface, such as those of willows, can produce shoots and ultimately new plants. in the event that one of the systems is lost, the other can often regrow it. in fact it is possible to grow an entire plant from a single leaf, as is the case with plants in streptocarpus sect. saintpaulia, or even a single cell β which can dedifferentiate into a callus ( a mass of
cross. the chromosome theory of inheritance, which states that genes are found on chromosomes, was supported by thomas morgans ' s experiments with fruit flies, which established the sex linkage between eye color and sex in these insects. = = = genes and dna = = = a gene is a unit of heredity that corresponds to a region of deoxyribonucleic acid ( dna ) that carries genetic information that controls form or function of an organism. dna is composed of two polynucleotide chains that coil around each other to form a double helix. it is found as linear chromosomes in eukaryotes, and circular chromosomes in prokaryotes. the set of chromosomes in a cell is collectively known as its genome. in eukaryotes, dna is mainly in the cell nucleus. in prokaryotes, the dna is held within the nucleoid. the genetic information is held within genes, and the complete assemblage in an organism is called its genotype. dna replication is a semiconservative process whereby each strand serves as a template for a new strand of dna. mutations are heritable changes in dna. they can arise spontaneously as a result of replication errors that were not corrected by proofreading or can be induced by an environmental mutagen such as a chemical ( e. g., nitrous acid, benzopyrene ) or radiation ( e. g., x - ray, gamma ray, ultraviolet radiation, particles emitted by unstable isotopes ). mutations can lead to phenotypic effects such as loss - of - function, gain - of - function, and conditional mutations. some mutations are beneficial, as they are a source of genetic variation for evolution. others are harmful if they were to result in a loss of function of genes needed for survival. = = = gene expression = = = gene expression is the molecular process by which a genotype encoded in dna gives rise to an observable phenotype in the proteins of an organism ' s body. this process is summarized by the central dogma of molecular biology, which was formulated by francis crick in 1958. according to the central dogma, genetic information flows from dna to rna to protein. there are two gene expression processes : transcription ( dna to rna ) and translation ( rna to protein ). = = = gene regulation = = = the regulation of gene expression by environmental factors and during different stages of development can occur at each step of the process such as transcription, rna splicing
oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions. cell membranes also contain membrane proteins, including integral membrane proteins that go across the membrane serving as membrane transporters, and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes shaping the cell. cell membranes are involved in various cellular processes such as cell adhesion, storing electrical energy, and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall, glycocalyx, and cytoskeleton. within the cytoplasm of a cell, there are many biomolecules such as proteins and nucleic acids. in addition to biomolecules, eukaryotic cells have specialized structures called organelles that have their own lipid bilayers or are spatially units. these organelles include the cell nucleus, which contains most of the cell ' s dna, or mitochondria, which generate adenosine triphosphate ( atp ) to power cellular processes. other organelles such as endoplasmic reticulum and golgi apparatus play a role in the synthesis and packaging of proteins, respectively. biomolecules such as proteins can be engulfed by lysosomes, another specialized organelle. plant cells have additional organelles that distinguish them from animal cells such as a cell wall that provides support for the plant cell, chloroplasts that harvest sunlight energy to produce sugar, and vacuoles that provide storage and structural support as well as being involved in reproduction and breakdown of plant seeds. eukaryotic cells also have cytoskeleton that is made up of microtubules, intermediate filaments, and microfilaments, all of which provide support for the cell and are involved in the movement of the cell and its organelles. in terms of their structural composition, the microtubules are made up of tubulin ( e. g., Ξ± - tubulin and Ξ² - tubulin ) whereas intermediate filaments are made up of fibrous proteins. microfilaments are made up of actin molecules that interact with other strands of proteins. = = = metabolism = = = all cells require energy to sustain cellular processes. metabolism is the set of chemical reactions in an organism. the three main purposes of metabolism are : the conversion of food to energy to run cellular processes ; the conversion of food / fuel to monomer building blocks ; and
shaping the cell. cell membranes are involved in various cellular processes such as cell adhesion, storing electrical energy, and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall, glycocalyx, and cytoskeleton. within the cytoplasm of a cell, there are many biomolecules such as proteins and nucleic acids. in addition to biomolecules, eukaryotic cells have specialized structures called organelles that have their own lipid bilayers or are spatially units. these organelles include the cell nucleus, which contains most of the cell ' s dna, or mitochondria, which generate adenosine triphosphate ( atp ) to power cellular processes. other organelles such as endoplasmic reticulum and golgi apparatus play a role in the synthesis and packaging of proteins, respectively. biomolecules such as proteins can be engulfed by lysosomes, another specialized organelle. plant cells have additional organelles that distinguish them from animal cells such as a cell wall that provides support for the plant cell, chloroplasts that harvest sunlight energy to produce sugar, and vacuoles that provide storage and structural support as well as being involved in reproduction and breakdown of plant seeds. eukaryotic cells also have cytoskeleton that is made up of microtubules, intermediate filaments, and microfilaments, all of which provide support for the cell and are involved in the movement of the cell and its organelles. in terms of their structural composition, the microtubules are made up of tubulin ( e. g., Ξ± - tubulin and Ξ² - tubulin ) whereas intermediate filaments are made up of fibrous proteins. microfilaments are made up of actin molecules that interact with other strands of proteins. = = = metabolism = = = all cells require energy to sustain cellular processes. metabolism is the set of chemical reactions in an organism. the three main purposes of metabolism are : the conversion of food to energy to run cellular processes ; the conversion of food / fuel to monomer building blocks ; and the elimination of metabolic wastes. these enzyme - catalyzed reactions allow organisms to grow and reproduce, maintain their structures, and respond to their environments. metabolic reactions may be categorized as catabolic β the breaking down of compounds ( for example, the breaking down of glucose to pyruvate by cellular respiration
the cell ' s dna, or mitochondria, which generate adenosine triphosphate ( atp ) to power cellular processes. other organelles such as endoplasmic reticulum and golgi apparatus play a role in the synthesis and packaging of proteins, respectively. biomolecules such as proteins can be engulfed by lysosomes, another specialized organelle. plant cells have additional organelles that distinguish them from animal cells such as a cell wall that provides support for the plant cell, chloroplasts that harvest sunlight energy to produce sugar, and vacuoles that provide storage and structural support as well as being involved in reproduction and breakdown of plant seeds. eukaryotic cells also have cytoskeleton that is made up of microtubules, intermediate filaments, and microfilaments, all of which provide support for the cell and are involved in the movement of the cell and its organelles. in terms of their structural composition, the microtubules are made up of tubulin ( e. g., Ξ± - tubulin and Ξ² - tubulin ) whereas intermediate filaments are made up of fibrous proteins. microfilaments are made up of actin molecules that interact with other strands of proteins. = = = metabolism = = = all cells require energy to sustain cellular processes. metabolism is the set of chemical reactions in an organism. the three main purposes of metabolism are : the conversion of food to energy to run cellular processes ; the conversion of food / fuel to monomer building blocks ; and the elimination of metabolic wastes. these enzyme - catalyzed reactions allow organisms to grow and reproduce, maintain their structures, and respond to their environments. metabolic reactions may be categorized as catabolic β the breaking down of compounds ( for example, the breaking down of glucose to pyruvate by cellular respiration ) ; or anabolic β the building up ( synthesis ) of compounds ( such as proteins, carbohydrates, lipids, and nucleic acids ). usually, catabolism releases energy, and anabolism consumes energy. the chemical reactions of metabolism are organized into metabolic pathways, in which one chemical is transformed through a series of steps into another chemical, each step being facilitated by a specific enzyme. enzymes are crucial to metabolism because they allow organisms to drive desirable reactions that require energy that will not occur by themselves, by coupling them to spontaneous reactions that release energy. enzymes act as catalysts β they allow a
to a region of deoxyribonucleic acid ( dna ) that carries genetic information that controls form or function of an organism. dna is composed of two polynucleotide chains that coil around each other to form a double helix. it is found as linear chromosomes in eukaryotes, and circular chromosomes in prokaryotes. the set of chromosomes in a cell is collectively known as its genome. in eukaryotes, dna is mainly in the cell nucleus. in prokaryotes, the dna is held within the nucleoid. the genetic information is held within genes, and the complete assemblage in an organism is called its genotype. dna replication is a semiconservative process whereby each strand serves as a template for a new strand of dna. mutations are heritable changes in dna. they can arise spontaneously as a result of replication errors that were not corrected by proofreading or can be induced by an environmental mutagen such as a chemical ( e. g., nitrous acid, benzopyrene ) or radiation ( e. g., x - ray, gamma ray, ultraviolet radiation, particles emitted by unstable isotopes ). mutations can lead to phenotypic effects such as loss - of - function, gain - of - function, and conditional mutations. some mutations are beneficial, as they are a source of genetic variation for evolution. others are harmful if they were to result in a loss of function of genes needed for survival. = = = gene expression = = = gene expression is the molecular process by which a genotype encoded in dna gives rise to an observable phenotype in the proteins of an organism ' s body. this process is summarized by the central dogma of molecular biology, which was formulated by francis crick in 1958. according to the central dogma, genetic information flows from dna to rna to protein. there are two gene expression processes : transcription ( dna to rna ) and translation ( rna to protein ). = = = gene regulation = = = the regulation of gene expression by environmental factors and during different stages of development can occur at each step of the process such as transcription, rna splicing, translation, and post - translational modification of a protein. gene expression can be influenced by positive or negative regulation, depending on which of the two types of regulatory proteins called transcription factors bind to the dna sequence close to or at a promoter. a cluster of genes that share the same promoter is called an operon,
and nucleotides. carbohydrates include monomers and polymers of sugars. lipids are the only class of macromolecules that are not made up of polymers. they include steroids, phospholipids, and fats, largely nonpolar and hydrophobic ( water - repelling ) substances. proteins are the most diverse of the macromolecules. they include enzymes, transport proteins, large signaling molecules, antibodies, and structural proteins. the basic unit ( or monomer ) of a protein is an amino acid. twenty amino acids are used in proteins. nucleic acids are polymers of nucleotides. their function is to store, transmit, and express hereditary information. = = cells = = cell theory states that cells are the fundamental units of life, that all living things are composed of one or more cells, and that all cells arise from preexisting cells through cell division. most cells are very small, with diameters ranging from 1 to 100 micrometers and are therefore only visible under a light or electron microscope. there are generally two types of cells : eukaryotic cells, which contain a nucleus, and prokaryotic cells, which do not. prokaryotes are single - celled organisms such as bacteria, whereas eukaryotes can be single - celled or multicellular. in multicellular organisms, every cell in the organism ' s body is derived ultimately from a single cell in a fertilized egg. = = = cell structure = = = every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions. cell membranes also contain membrane proteins, including integral membrane proteins that go across the membrane serving as membrane transporters, and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes shaping the cell. cell membranes are involved in various cellular processes such as cell adhesion, storing electrical energy, and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall, glycocalyx, and cytoskeleton. within the cytoplasm of a cell
has rest mass and volume ( it takes up space ) and is made up of particles. the particles that make up matter have rest mass as well β not all particles have rest mass, such as the photon. matter can be a pure chemical substance or a mixture of substances. = = = = atom = = = = the atom is the basic unit of chemistry. it consists of a dense core called the atomic nucleus surrounded by a space occupied by an electron cloud. the nucleus is made up of positively charged protons and uncharged neutrons ( together called nucleons ), while the electron cloud consists of negatively charged electrons which orbit the nucleus. in a neutral atom, the negatively charged electrons balance out the positive charge of the protons. the nucleus is dense ; the mass of a nucleon is approximately 1, 836 times that of an electron, yet the radius of an atom is about 10, 000 times that of its nucleus. the atom is also the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state ( s ), coordination number, and preferred types of bonds to form ( e. g., metallic, ionic, covalent ). = = = = element = = = = a chemical element is a pure substance which is composed of a single type of atom, characterized by its particular number of protons in the nuclei of its atoms, known as the atomic number and represented by the symbol z. the mass number is the sum of the number of protons and neutrons in a nucleus. although all the nuclei of all atoms belonging to one element will have the same atomic number, they may not necessarily have the same mass number ; atoms of an element which have different mass numbers are known as isotopes. for example, all atoms with 6 protons in their nuclei are atoms of the chemical element carbon, but atoms of carbon may have mass numbers of 12 or 13. the standard presentation of the chemical elements is in the periodic table, which orders elements by atomic number. the periodic table is arranged in groups, or columns, and periods, or rows. the periodic table is useful in identifying periodic trends. = = = = compound = = = = a compound is a pure chemical substance composed of more than one element. the properties of a compound bear little similarity to those of its elements. the standard nomenclature of compounds is set by the international union of pure and applied chemistry ( iupac ). organic compounds are named
Question: What type of cell contains a nucleus?
A) endogenous cell
B) chloroplasts cell
C) candid cell
D) eukaryotic cell
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D) eukaryotic cell
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Context:
by ancestry rather than superficial characteristics. while scientists do not always agree on how to classify organisms, molecular phylogenetics, which uses dna sequences as data, has driven many recent revisions along evolutionary lines and is likely to continue to do so. the dominant classification system is called linnaean taxonomy. it includes ranks and binomial nomenclature. the nomenclature of botanical organisms is codified in the international code of nomenclature for algae, fungi, and plants ( icn ) and administered by the international botanical congress. kingdom plantae belongs to domain eukaryota and is broken down recursively until each species is separately classified. the order is : kingdom ; phylum ( or division ) ; class ; order ; family ; genus ( plural genera ) ; species. the scientific name of a plant represents its genus and its species within the genus, resulting in a single worldwide name for each organism. for example, the tiger lily is lilium columbianum. lilium is the genus, and columbianum the specific epithet. the combination is the name of the species. when writing the scientific name of an organism, it is proper to capitalise the first letter in the genus and put all of the specific epithet in lowercase. additionally, the entire term is ordinarily italicised ( or underlined when italics are not available ). the evolutionary relationships and heredity of a group of organisms is called its phylogeny. phylogenetic studies attempt to discover phylogenies. the basic approach is to use similarities based on shared inheritance to determine relationships. as an example, species of pereskia are trees or bushes with prominent leaves. they do not obviously resemble a typical leafless cactus such as an echinocactus. however, both pereskia and echinocactus have spines produced from areoles ( highly specialised pad - like structures ) suggesting that the two genera are indeed related. judging relationships based on shared characters requires care, since plants may resemble one another through convergent evolution in which characters have arisen independently. some euphorbias have leafless, rounded bodies adapted to water conservation similar to those of globular cacti, but characters such as the structure of their flowers make it clear that the two groups are not closely related. the cladistic method takes a systematic approach to characters, distinguishing between those that carry no information about shared evolutionary history β such as those evolved separately in different groups ( homoplasies ) or those left over from ancestors ( plesiomorphies ) β and derived characters, which
by which botanists group organisms into categories such as genera or species. biological classification is a form of scientific taxonomy. modern taxonomy is rooted in the work of carl linnaeus, who grouped species according to shared physical characteristics. these groupings have since been revised to align better with the darwinian principle of common descent β grouping organisms by ancestry rather than superficial characteristics. while scientists do not always agree on how to classify organisms, molecular phylogenetics, which uses dna sequences as data, has driven many recent revisions along evolutionary lines and is likely to continue to do so. the dominant classification system is called linnaean taxonomy. it includes ranks and binomial nomenclature. the nomenclature of botanical organisms is codified in the international code of nomenclature for algae, fungi, and plants ( icn ) and administered by the international botanical congress. kingdom plantae belongs to domain eukaryota and is broken down recursively until each species is separately classified. the order is : kingdom ; phylum ( or division ) ; class ; order ; family ; genus ( plural genera ) ; species. the scientific name of a plant represents its genus and its species within the genus, resulting in a single worldwide name for each organism. for example, the tiger lily is lilium columbianum. lilium is the genus, and columbianum the specific epithet. the combination is the name of the species. when writing the scientific name of an organism, it is proper to capitalise the first letter in the genus and put all of the specific epithet in lowercase. additionally, the entire term is ordinarily italicised ( or underlined when italics are not available ). the evolutionary relationships and heredity of a group of organisms is called its phylogeny. phylogenetic studies attempt to discover phylogenies. the basic approach is to use similarities based on shared inheritance to determine relationships. as an example, species of pereskia are trees or bushes with prominent leaves. they do not obviously resemble a typical leafless cactus such as an echinocactus. however, both pereskia and echinocactus have spines produced from areoles ( highly specialised pad - like structures ) suggesting that the two genera are indeed related. judging relationships based on shared characters requires care, since plants may resemble one another through convergent evolution in which characters have arisen independently. some euphorbias have leafless, rounded bodies adapted to water conservation similar to those of globular cacti, but characters such as the structure of their flowers make it clear that the
##al nomenclature. the nomenclature of botanical organisms is codified in the international code of nomenclature for algae, fungi, and plants ( icn ) and administered by the international botanical congress. kingdom plantae belongs to domain eukaryota and is broken down recursively until each species is separately classified. the order is : kingdom ; phylum ( or division ) ; class ; order ; family ; genus ( plural genera ) ; species. the scientific name of a plant represents its genus and its species within the genus, resulting in a single worldwide name for each organism. for example, the tiger lily is lilium columbianum. lilium is the genus, and columbianum the specific epithet. the combination is the name of the species. when writing the scientific name of an organism, it is proper to capitalise the first letter in the genus and put all of the specific epithet in lowercase. additionally, the entire term is ordinarily italicised ( or underlined when italics are not available ). the evolutionary relationships and heredity of a group of organisms is called its phylogeny. phylogenetic studies attempt to discover phylogenies. the basic approach is to use similarities based on shared inheritance to determine relationships. as an example, species of pereskia are trees or bushes with prominent leaves. they do not obviously resemble a typical leafless cactus such as an echinocactus. however, both pereskia and echinocactus have spines produced from areoles ( highly specialised pad - like structures ) suggesting that the two genera are indeed related. judging relationships based on shared characters requires care, since plants may resemble one another through convergent evolution in which characters have arisen independently. some euphorbias have leafless, rounded bodies adapted to water conservation similar to those of globular cacti, but characters such as the structure of their flowers make it clear that the two groups are not closely related. the cladistic method takes a systematic approach to characters, distinguishing between those that carry no information about shared evolutionary history β such as those evolved separately in different groups ( homoplasies ) or those left over from ancestors ( plesiomorphies ) β and derived characters, which have been passed down from innovations in a shared ancestor ( apomorphies ). only derived characters, such as the spine - producing areoles of cacti, provide evidence for descent from a common ancestor. the results of cladistic analyses are expressed as cladograms : tree - like diagrams showing the
sciences are the clinical diagnostic services that apply laboratory techniques to diagnosis and management of patients. in the united states, these services are supervised by a pathologist. the personnel that work in these medical laboratory departments are technically trained staff who do not hold medical degrees, but who usually hold an undergraduate medical technology degree, who actually perform the tests, assays, and procedures needed for providing the specific services. subspecialties include transfusion medicine, cellular pathology, clinical chemistry, hematology, clinical microbiology and clinical immunology. clinical neurophysiology is concerned with testing the physiology or function of the central and peripheral aspects of the nervous system. these kinds of tests can be divided into recordings of : ( 1 ) spontaneous or continuously running electrical activity, or ( 2 ) stimulus evoked responses. subspecialties include electroencephalography, electromyography, evoked potential, nerve conduction study and polysomnography. sometimes these tests are performed by techs without a medical degree, but the interpretation of these tests is done by a medical professional. diagnostic radiology is concerned with imaging of the body, e. g. by x - rays, x - ray computed tomography, ultrasonography, and nuclear magnetic resonance tomography. interventional radiologists can access areas in the body under imaging for an intervention or diagnostic sampling. nuclear medicine is concerned with studying human organ systems by administering radiolabelled substances ( radiopharmaceuticals ) to the body, which can then be imaged outside the body by a gamma camera or a pet scanner. each radiopharmaceutical consists of two parts : a tracer that is specific for the function under study ( e. g., neurotransmitter pathway, metabolic pathway, blood flow, or other ), and a radionuclide ( usually either a gamma - emitter or a positron emitter ). there is a degree of overlap between nuclear medicine and radiology, as evidenced by the emergence of combined devices such as the pet / ct scanner. pathology as a medical specialty is the branch of medicine that deals with the study of diseases and the morphologic, physiologic changes produced by them. as a diagnostic specialty, pathology can be considered the basis of modern scientific medical knowledge and plays a large role in evidence - based medicine. many modern molecular tests such as flow cytometry, polymerase chain reaction ( pcr ), immunohistochemistry, cytogenetic
ranks varying from family to subgenus have terms for their study, including agrostology ( or graminology ) for the study of grasses, synantherology for the study of composites, and batology for the study of brambles. study can also be divided by guild rather than clade or grade. for example, dendrology is the study of woody plants. many divisions of biology have botanical subfields. these are commonly denoted by prefixing the word plant ( e. g. plant taxonomy, plant ecology, plant anatomy, plant morphology, plant systematics ), or prefixing or substituting the prefix phyto - ( e. g. phytochemistry, phytogeography ). the study of fossil plants is called palaeobotany. other fields are denoted by adding or substituting the word botany ( e. g. systematic botany ). phytosociology is a subfield of plant ecology that classifies and studies communities of plants. the intersection of fields from the above pair of categories gives rise to fields such as bryogeography, the study of the distribution of mosses. different parts of plants also give rise to their own subfields, including xylology, carpology ( or fructology ), and palynology, these being the study of wood, fruit and pollen / spores respectively. botany also overlaps on the one hand with agriculture, horticulture and silviculture, and on the other hand with medicine and pharmacology, giving rise to fields such as agronomy, horticultural botany, phytopathology, and phytopharmacology. = = scope and importance = = the study of plants is vital because they underpin almost all animal life on earth by generating a large proportion of the oxygen and food that provide humans and other organisms with aerobic respiration with the chemical energy they need to exist. plants, algae and cyanobacteria are the major groups of organisms that carry out photosynthesis, a process that uses the energy of sunlight to convert water and carbon dioxide into sugars that can be used both as a source of chemical energy and of organic molecules that are used in the structural components of cells. as a by - product of photosynthesis, plants release oxygen into the atmosphere, a gas that is required by nearly all living things to carry out cellular respiration. in addition, they are influential in the global carbon and water cycles and plant roots bind and stabilise soils, preventing
is opened and the dna is purified. the gene is separated by using restriction enzymes to cut the dna into fragments or polymerase chain reaction ( pcr ) to amplify up the gene segment. these segments can then be extracted through gel electrophoresis. if the chosen gene or the donor organism ' s genome has been well studied it may already be accessible from a genetic library. if the dna sequence is known, but no copies of the gene are available, it can also be artificially synthesised. once isolated the gene is ligated into a plasmid that is then inserted into a bacterium. the plasmid is replicated when the bacteria divide, ensuring unlimited copies of the gene are available. the rk2 plasmid is notable for its ability to replicate in a wide variety of single - celled organisms, which makes it suitable as a genetic engineering tool. before the gene is inserted into the target organism it must be combined with other genetic elements. these include a promoter and terminator region, which initiate and end transcription. a selectable marker gene is added, which in most cases confers antibiotic resistance, so researchers can easily determine which cells have been successfully transformed. the gene can also be modified at this stage for better expression or effectiveness. these manipulations are carried out using recombinant dna techniques, such as restriction digests, ligations and molecular cloning. = = = inserting dna into the host genome = = = there are a number of techniques used to insert genetic material into the host genome. some bacteria can naturally take up foreign dna. this ability can be induced in other bacteria via stress ( e. g. thermal or electric shock ), which increases the cell membrane ' s permeability to dna ; up - taken dna can either integrate with the genome or exist as extrachromosomal dna. dna is generally inserted into animal cells using microinjection, where it can be injected through the cell ' s nuclear envelope directly into the nucleus, or through the use of viral vectors. plant genomes can be engineered by physical methods or by use of agrobacterium for the delivery of sequences hosted in t - dna binary vectors. in plants the dna is often inserted using agrobacterium - mediated transformation, taking advantage of the agrobacteriums t - dna sequence that allows natural insertion of genetic material into plant cells. other methods include biolistics, where particles of gold or tungsten are coated with dna and then shot into
not always mean it is required, especially when dealing with genetic or functional redundancy. tracking experiments, which seek to gain information about the localisation and interaction of the desired protein. one way to do this is to replace the wild - type gene with a ' fusion ' gene, which is a juxtaposition of the wild - type gene with a reporting element such as green fluorescent protein ( gfp ) that will allow easy visualisation of the products of the genetic modification. while this is a useful technique, the manipulation can destroy the function of the gene, creating secondary effects and possibly calling into question the results of the experiment. more sophisticated techniques are now in development that can track protein products without mitigating their function, such as the addition of small sequences that will serve as binding motifs to monoclonal antibodies. expression studies aim to discover where and when specific proteins are produced. in these experiments, the dna sequence before the dna that codes for a protein, known as a gene ' s promoter, is reintroduced into an organism with the protein coding region replaced by a reporter gene such as gfp or an enzyme that catalyses the production of a dye. thus the time and place where a particular protein is produced can be observed. expression studies can be taken a step further by altering the promoter to find which pieces are crucial for the proper expression of the gene and are actually bound by transcription factor proteins ; this process is known as promoter bashing. = = = industrial = = = organisms can have their cells transformed with a gene coding for a useful protein, such as an enzyme, so that they will overexpress the desired protein. mass quantities of the protein can then be manufactured by growing the transformed organism in bioreactor equipment using industrial fermentation, and then purifying the protein. some genes do not work well in bacteria, so yeast, insect cells or mammalian cells can also be used. these techniques are used to produce medicines such as insulin, human growth hormone, and vaccines, supplements such as tryptophan, aid in the production of food ( chymosin in cheese making ) and fuels. other applications with genetically engineered bacteria could involve making them perform tasks outside their natural cycle, such as making biofuels, cleaning up oil spills, carbon and other toxic waste and detecting arsenic in drinking water. certain genetically modified microbes can also be used in biomining and bioremediation, due to their ability to extract heavy metals from their environment and incorporate them into compounds that are more easily recover
is the genus, and columbianum the specific epithet. the combination is the name of the species. when writing the scientific name of an organism, it is proper to capitalise the first letter in the genus and put all of the specific epithet in lowercase. additionally, the entire term is ordinarily italicised ( or underlined when italics are not available ). the evolutionary relationships and heredity of a group of organisms is called its phylogeny. phylogenetic studies attempt to discover phylogenies. the basic approach is to use similarities based on shared inheritance to determine relationships. as an example, species of pereskia are trees or bushes with prominent leaves. they do not obviously resemble a typical leafless cactus such as an echinocactus. however, both pereskia and echinocactus have spines produced from areoles ( highly specialised pad - like structures ) suggesting that the two genera are indeed related. judging relationships based on shared characters requires care, since plants may resemble one another through convergent evolution in which characters have arisen independently. some euphorbias have leafless, rounded bodies adapted to water conservation similar to those of globular cacti, but characters such as the structure of their flowers make it clear that the two groups are not closely related. the cladistic method takes a systematic approach to characters, distinguishing between those that carry no information about shared evolutionary history β such as those evolved separately in different groups ( homoplasies ) or those left over from ancestors ( plesiomorphies ) β and derived characters, which have been passed down from innovations in a shared ancestor ( apomorphies ). only derived characters, such as the spine - producing areoles of cacti, provide evidence for descent from a common ancestor. the results of cladistic analyses are expressed as cladograms : tree - like diagrams showing the pattern of evolutionary branching and descent. from the 1990s onwards, the predominant approach to constructing phylogenies for living plants has been molecular phylogenetics, which uses molecular characters, particularly dna sequences, rather than morphological characters like the presence or absence of spines and areoles. the difference is that the genetic code itself is used to decide evolutionary relationships, instead of being used indirectly via the characters it gives rise to. clive stace describes this as having " direct access to the genetic basis of evolution. " as a simple example, prior to the use of genetic evidence, fungi were thought either to be plants or to be more closely related to plants
. forensic histopathology is the application of histological techniques and examination to forensic pathology practice. forensic limnology is the analysis of evidence collected from crime scenes in or around fresh - water sources. examination of biological organisms, in particular diatoms, can be useful in connecting suspects with victims. forensic linguistics deals with issues in the legal system that requires linguistic expertise. forensic meteorology is a site - specific analysis of past weather conditions for a point of loss. forensic metrology is the application of metrology to assess the reliability of scientific evidence obtained through measurements forensic microbiology is the study of the necrobiome. forensic nursing is the application of nursing sciences to abusive crimes, like child abuse, or sexual abuse. categorization of wounds and traumas, collection of bodily fluids and emotional support are some of the duties of forensic nurses. forensic odontology is the study of the uniqueness of dentition, better known as the study of teeth. forensic optometry is the study of glasses and other eyewear relating to crime scenes and criminal investigations. forensic pathology is a field in which the principles of medicine and pathology are applied to determine a cause of death or injury in the context of a legal inquiry. forensic podiatry is an application of the study of feet footprint or footwear and their traces to analyze scene of crime and to establish personal identity in forensic examinations. forensic psychiatry is a specialized branch of psychiatry as applied to and based on scientific criminology. forensic psychology is the study of the mind of an individual, using forensic methods. usually it determines the circumstances behind a criminal ' s behavior. forensic seismology is the study of techniques to distinguish the seismic signals generated by underground nuclear explosions from those generated by earthquakes. forensic serology is the study of the body fluids. forensic social work is the specialist study of social work theories and their applications to a clinical, criminal justice or psychiatric setting. practitioners of forensic social work connected with the criminal justice system are often termed social supervisors, whilst the remaining use the interchangeable titles forensic social worker, approved mental health professional or forensic practitioner and they conduct specialist assessments of risk, care planning and act as an officer of the court. forensic toxicology is the study of the effect of drugs and poisons on / in the human body. forensic video analysis is the scientific examination, comparison and evaluation of video in legal matters. mobile device forensics is the scientific examination and evaluation of evidence found in mobile phones, e. g. call history and deleted sms, and includes sim card forensics
##hography is quite small, large area patterns must be created by stitching together the small fields. ion track technology is a deep cutting tool with a resolution limit around 8 nm applicable to radiation resistant minerals, glasses and polymers. it is capable of generating holes in thin films without any development process. structural depth can be defined either by ion range or by material thickness. aspect ratios up to several 104 can be reached. the technique can shape and texture materials at a defined inclination angle. random pattern, single - ion track structures and an aimed pattern consisting of individual single tracks can be generated. x - ray lithography is a process used in the electronic industry to selectively remove parts of a thin film. it uses x - rays to transfer a geometric pattern from a mask to a light - sensitive chemical photoresist, or simply " resist ", on the substrate. a series of chemical treatments then engraves the produced pattern into the material underneath the photoresist. diamond patterning is a method of forming diamond mems. it is achieved by the lithographic application of diamond films to a substrate such as silicon. the patterns can be formed by selective deposition through a silicon dioxide mask, or by deposition followed by micromachining or focused ion beam milling. = = = etching processes = = = there are two basic categories of etching processes : wet etching and dry etching. in the former, the material is dissolved when immersed in a chemical solution. in the latter, the material is sputtered or dissolved using reactive ions or a vapor phase etchant. = = = = wet etching = = = = wet chemical etching consists of the selective removal of material by dipping a substrate into a solution that dissolves it. the chemical nature of this etching process provides good selectivity, which means the etching rate of the target material is considerably higher than the mask material if selected carefully. wet etching can be performed using either isotropic wet etchants or anisotropic wet etchants. isotropic wet etchant etch in all directions of the crystalline silicon at approximately equal rates. anisotropic wet etchants preferably etch along certain crystal planes at faster rates than other planes, thereby allowing more complicated 3 - d microstructures to be implemented. wet anisotropic etchants are often used in conjunction with boron etch stops wherein the surface of the silicon is heavily doped with boron resulting in a silicon material layer that is
Question: What method uses a retailer's coding method to catalog biological specimens in museums?
A) structure barcoding
B) dna barcoding
C) content barcoding
D) metallic barcoding
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B) dna barcoding
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Context:
higher concentrations of atmospheric nitrous oxide ( n2o ) are expected to slightly warm earth ' s surface because of increases in radiative forcing. radiative forcing is the difference in the net upward thermal radiation flux from the earth through a transparent atmosphere and radiation through an otherwise identical atmosphere with greenhouse gases. radiative forcing, normally measured in w / m ^ 2, depends on latitude, longitude and altitude, but it is often quoted for the tropopause, about 11 km of altitude for temperate latitudes, or for the top of the atmosphere at around 90 km. for current concentrations of greenhouse gases, the radiative forcing per added n2o molecule is about 230 times larger than the forcing per added carbon dioxide ( co2 ) molecule. this is due to the heavy saturation of the absorption band of the relatively abundant greenhouse gas, co2, compared to the much smaller saturation of the absorption bands of the trace greenhouse gas n2o. but the rate of increase of co2 molecules, about 2. 5 ppm / year ( ppm = part per million by mole ), is about 3000 times larger than the rate of increase of n2o molecules, which has held steady at around 0. 00085 ppm / year since 1985. so, the contribution of nitrous oxide to the annual increase in forcing is 230 / 3000 or about 1 / 13 that of co2. if the main greenhouse gases, co2, ch4 and n2o have contributed about 0. 1 c / decade of the warming observed over the past few decades, this would correspond to about 0. 00064 k per year or 0. 064 k per century of warming from n2o. proposals to place harsh restrictions on nitrous oxide emissions because of warming fears are not justified by these facts. restrictions would cause serious harm ; for example, by jeopardizing world food supplies.
enough to rise to the surface β giving birth to volcanoes. = = atmospheric science = = atmospheric science initially developed in the late - 19th century as a means to forecast the weather through meteorology, the study of weather. atmospheric chemistry was developed in the 20th century to measure air pollution and expanded in the 1970s in response to acid rain. climatology studies the climate and climate change. the troposphere, stratosphere, mesosphere, thermosphere, and exosphere are the five layers which make up earth ' s atmosphere. 75 % of the mass in the atmosphere is located within the troposphere, the lowest layer. in all, the atmosphere is made up of about 78. 0 % nitrogen, 20. 9 % oxygen, and 0. 92 % argon, and small amounts of other gases including co2 and water vapor. water vapor and co2 cause the earth ' s atmosphere to catch and hold the sun ' s energy through the greenhouse effect. this makes earth ' s surface warm enough for liquid water and life. in addition to trapping heat, the atmosphere also protects living organisms by shielding the earth ' s surface from cosmic rays. the magnetic field β created by the internal motions of the core β produces the magnetosphere which protects earth ' s atmosphere from the solar wind. as the earth is 4. 5 billion years old, it would have lost its atmosphere by now if there were no protective magnetosphere. = = earth ' s magnetic field = = = = hydrology = = hydrology is the study of the hydrosphere and the movement of water on earth. it emphasizes the study of how humans use and interact with freshwater supplies. study of water ' s movement is closely related to geomorphology and other branches of earth science. applied hydrology involves engineering to maintain aquatic environments and distribute water supplies. subdisciplines of hydrology include oceanography, hydrogeology, ecohydrology, and glaciology. oceanography is the study of oceans. hydrogeology is the study of groundwater. it includes the mapping of groundwater supplies and the analysis of groundwater contaminants. applied hydrogeology seeks to prevent contamination of groundwater and mineral springs and make it available as drinking water. the earliest exploitation of groundwater resources dates back to 3000 bc, and hydrogeology as a science was developed by hydrologists beginning in the 17th century. ecohydrology is the study of ecological systems in the hydrosphere. it can be divided into the physical study of aquatic ecosystems and the
cell or tissue growth in vitro. a physiological environment can consist of many different parameters such as temperature, pressure, oxygen or carbon dioxide concentration, or osmolality of fluid environment, and it can extend to all kinds of biological, chemical or mechanical stimuli. therefore, there are systems that may include the application of forces such as electromagnetic forces, mechanical pressures, or fluid pressures to the tissue. these systems can be two - or three - dimensional setups. bioreactors can be used in both academic and industry applications. general - use and application - specific bioreactors are also commercially available, which may provide static chemical stimulation or a combination of chemical and mechanical stimulation. cell proliferation and differentiation are largely influenced by mechanical and biochemical cues in the surrounding extracellular matrix environment. bioreactors are typically developed to replicate the specific physiological environment of the tissue being grown ( e. g., flex and fluid shearing for heart tissue growth ). this can allow specialized cell lines to thrive in cultures replicating their native environments, but it also makes bioreactors attractive tools for culturing stem cells. a successful stem - cell - based bioreactor is effective at expanding stem cells with uniform properties and / or promoting controlled, reproducible differentiation into selected mature cell types. there are a variety of bioreactors designed for 3d cell cultures. there are small plastic cylindrical chambers, as well as glass chambers, with regulated internal humidity and moisture specifically engineered for the purpose of growing cells in three dimensions. the bioreactor uses bioactive synthetic materials such as polyethylene terephthalate membranes to surround the spheroid cells in an environment that maintains high levels of nutrients. they are easy to open and close, so that cell spheroids can be removed for testing, yet the chamber is able to maintain 100 % humidity throughout. this humidity is important to achieve maximum cell growth and function. the bioreactor chamber is part of a larger device that rotates to ensure equal cell growth in each direction across three dimensions. quinxell technologies now under quintech life sciences from singapore has developed a bioreactor known as the tisxell biaxial bioreactor which is specially designed for the purpose of tissue engineering. it is the first bioreactor in the world to have a spherical glass chamber with biaxial rotation ; specifically to mimic the rotation of the fetus in the womb ; which provides a conducive environment for the growth of tissues. multiple forms of mechanical stimulation have also been combined into a single
blood vessels. mechanical stimuli, such as pressure pulses seem to be beneficial to all kind of cardiovascular tissue such as heart valves, blood vessels or pericardium. = = = bioreactors = = = in tissue engineering, a bioreactor is a device that attempts to simulate a physiological environment in order to promote cell or tissue growth in vitro. a physiological environment can consist of many different parameters such as temperature, pressure, oxygen or carbon dioxide concentration, or osmolality of fluid environment, and it can extend to all kinds of biological, chemical or mechanical stimuli. therefore, there are systems that may include the application of forces such as electromagnetic forces, mechanical pressures, or fluid pressures to the tissue. these systems can be two - or three - dimensional setups. bioreactors can be used in both academic and industry applications. general - use and application - specific bioreactors are also commercially available, which may provide static chemical stimulation or a combination of chemical and mechanical stimulation. cell proliferation and differentiation are largely influenced by mechanical and biochemical cues in the surrounding extracellular matrix environment. bioreactors are typically developed to replicate the specific physiological environment of the tissue being grown ( e. g., flex and fluid shearing for heart tissue growth ). this can allow specialized cell lines to thrive in cultures replicating their native environments, but it also makes bioreactors attractive tools for culturing stem cells. a successful stem - cell - based bioreactor is effective at expanding stem cells with uniform properties and / or promoting controlled, reproducible differentiation into selected mature cell types. there are a variety of bioreactors designed for 3d cell cultures. there are small plastic cylindrical chambers, as well as glass chambers, with regulated internal humidity and moisture specifically engineered for the purpose of growing cells in three dimensions. the bioreactor uses bioactive synthetic materials such as polyethylene terephthalate membranes to surround the spheroid cells in an environment that maintains high levels of nutrients. they are easy to open and close, so that cell spheroids can be removed for testing, yet the chamber is able to maintain 100 % humidity throughout. this humidity is important to achieve maximum cell growth and function. the bioreactor chamber is part of a larger device that rotates to ensure equal cell growth in each direction across three dimensions. quinxell technologies now under quintech life sciences from singapore has developed a bioreactor known as the tisxell biaxial bioreactor which is specially designed for the purpose of
graphene oxide ( go ) is one of the important functional materials. large - scale synthesis of it is very challenging. following a simple cost - effective route, large - scale go was produced by mechanical ( ball ) milling, in air, of carbon nanoparticles ( cnps ) present in carbon soot in the present study. the thickness of the go layer was seen to decrease with an increase in milling time. ball milling provided the required energy to acquire the in - plane graphitic order in the cnps reducing the disorders in it. as the surface area of the layered structure became more and more with the increase in milling time, more and more oxygen of air got attached to the carbon in graphene leading to the formation of go. an increase in the time of the ball mill up to 5 hours leads to a significant increase in the content of go. thus ball milling can be useful to produce large - scale two - dimensional go for a short time.
single carbon atom can form four single covalent bonds such as in methane, two double covalent bonds such as in carbon dioxide ( co2 ), or a triple covalent bond such as in carbon monoxide ( co ). moreover, carbon can form very long chains of interconnecting carbon β carbon bonds such as octane or ring - like structures such as glucose. the simplest form of an organic molecule is the hydrocarbon, which is a large family of organic compounds that are composed of hydrogen atoms bonded to a chain of carbon atoms. a hydrocarbon backbone can be substituted by other elements such as oxygen ( o ), hydrogen ( h ), phosphorus ( p ), and sulfur ( s ), which can change the chemical behavior of that compound. groups of atoms that contain these elements ( o -, h -, p -, and s - ) and are bonded to a central carbon atom or skeleton are called functional groups. there are six prominent functional groups that can be found in organisms : amino group, carboxyl group, carbonyl group, hydroxyl group, phosphate group, and sulfhydryl group. in 1953, the miller β urey experiment showed that organic compounds could be synthesized abiotically within a closed system mimicking the conditions of early earth, thus suggesting that complex organic molecules could have arisen spontaneously in early earth ( see abiogenesis ). = = = macromolecules = = = macromolecules are large molecules made up of smaller subunits or monomers. monomers include sugars, amino acids, and nucleotides. carbohydrates include monomers and polymers of sugars. lipids are the only class of macromolecules that are not made up of polymers. they include steroids, phospholipids, and fats, largely nonpolar and hydrophobic ( water - repelling ) substances. proteins are the most diverse of the macromolecules. they include enzymes, transport proteins, large signaling molecules, antibodies, and structural proteins. the basic unit ( or monomer ) of a protein is an amino acid. twenty amino acids are used in proteins. nucleic acids are polymers of nucleotides. their function is to store, transmit, and express hereditary information. = = cells = = cell theory states that cells are the fundamental units of life, that all living things are composed of one or more cells, and that all cells arise from preexisting cells through cell division
uniaxial pressure applied in the b crystallographic direction perpendicular to spontaneous magnetization in heavy fermion ferromagnet urhge strongly stimulates superconductivity in this compound. the phenomenological approach allows point out two mechanisms of superconducting temperature raising. they originates from stimulation by the uniaxial stress both intraband and interband amplitudes of triplet cooper pairing. the phenomenon of reentrant superconductivity under magnetic field along b - axis is also strongly sensitive to the uniaxial stress in the same direction. the uniaxial stress accelerates suppression the curie temperature by the transversal magnetic field. the emergence of the first order transition to the paramagnetic state occurs at much lower field than in the absence of uniaxial stress.
required. for example, certain cells respond to changes in oxygen tension as part of their normal development, such as chondrocytes, which must adapt to low oxygen conditions or hypoxia during skeletal development. others, such as endothelial cells, respond to shear stress from fluid flow, which is encountered in blood vessels. mechanical stimuli, such as pressure pulses seem to be beneficial to all kind of cardiovascular tissue such as heart valves, blood vessels or pericardium. = = = bioreactors = = = in tissue engineering, a bioreactor is a device that attempts to simulate a physiological environment in order to promote cell or tissue growth in vitro. a physiological environment can consist of many different parameters such as temperature, pressure, oxygen or carbon dioxide concentration, or osmolality of fluid environment, and it can extend to all kinds of biological, chemical or mechanical stimuli. therefore, there are systems that may include the application of forces such as electromagnetic forces, mechanical pressures, or fluid pressures to the tissue. these systems can be two - or three - dimensional setups. bioreactors can be used in both academic and industry applications. general - use and application - specific bioreactors are also commercially available, which may provide static chemical stimulation or a combination of chemical and mechanical stimulation. cell proliferation and differentiation are largely influenced by mechanical and biochemical cues in the surrounding extracellular matrix environment. bioreactors are typically developed to replicate the specific physiological environment of the tissue being grown ( e. g., flex and fluid shearing for heart tissue growth ). this can allow specialized cell lines to thrive in cultures replicating their native environments, but it also makes bioreactors attractive tools for culturing stem cells. a successful stem - cell - based bioreactor is effective at expanding stem cells with uniform properties and / or promoting controlled, reproducible differentiation into selected mature cell types. there are a variety of bioreactors designed for 3d cell cultures. there are small plastic cylindrical chambers, as well as glass chambers, with regulated internal humidity and moisture specifically engineered for the purpose of growing cells in three dimensions. the bioreactor uses bioactive synthetic materials such as polyethylene terephthalate membranes to surround the spheroid cells in an environment that maintains high levels of nutrients. they are easy to open and close, so that cell spheroids can be removed for testing, yet the chamber is able to maintain 100 % humidity throughout. this humidity is important to achieve maximum cell growth and function. the
the results of the quantitative investigations of the renormalization of the absorption edge of different compounds by the isotope effect are described.
the planetary nebulae he 2 - 436 and wray 16 - 423 in the sagittarius dwarf galaxy appear to result from nearly twin stars, except that third - dredge - up carbon is more abundant in he 2 - 436. a thorough photoionization - model analysis implies that ratios ne / o, s / o and ar / o are significantly smaller in he 2 - 436, indicative of third - dredge - up oxygen enrichment. the enrichment of oxygen with respect to carbon is ( 7 + / - 4 ) %. excess nitrogen in wray 16 - 423 suggests third dredge - up of late cn - cycle products even in these low - mass, intermediate - metallicity stars.
Question: The level of carbon dioxide in the atmosphere is greatly influenced by the reservoir of carbon where?
A) in the oceans
B) in the earth
C) after the oceans
D) before the oceans
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A) in the oceans
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Context:
time - dependent distribution of the global extinction of megafauna is compared with the growth of human population. there is no correlation between the two processes. furthermore, the size of human population and its growth rate were far too small to have any significant impact on the environment and on the life of megafauna.
participates as a consumer, resource, or both in consumer β resource interactions, which form the core of food chains or food webs. there are different trophic levels within any food web, with the lowest level being the primary producers ( or autotrophs ) such as plants and algae that convert energy and inorganic material into organic compounds, which can then be used by the rest of the community. at the next level are the heterotrophs, which are the species that obtain energy by breaking apart organic compounds from other organisms. heterotrophs that consume plants are primary consumers ( or herbivores ) whereas heterotrophs that consume herbivores are secondary consumers ( or carnivores ). and those that eat secondary consumers are tertiary consumers and so on. omnivorous heterotrophs are able to consume at multiple levels. finally, there are decomposers that feed on the waste products or dead bodies of organisms. on average, the total amount of energy incorporated into the biomass of a trophic level per unit of time is about one - tenth of the energy of the trophic level that it consumes. waste and dead material used by decomposers as well as heat lost from metabolism make up the other ninety percent of energy that is not consumed by the next trophic level. = = = biosphere = = = in the global ecosystem or biosphere, matter exists as different interacting compartments, which can be biotic or abiotic as well as accessible or inaccessible, depending on their forms and locations. for example, matter from terrestrial autotrophs are both biotic and accessible to other organisms whereas the matter in rocks and minerals are abiotic and inaccessible. a biogeochemical cycle is a pathway by which specific elements of matter are turned over or moved through the biotic ( biosphere ) and the abiotic ( lithosphere, atmosphere, and hydrosphere ) compartments of earth. there are biogeochemical cycles for nitrogen, carbon, and water. = = = conservation = = = conservation biology is the study of the conservation of earth ' s biodiversity with the aim of protecting species, their habitats, and ecosystems from excessive rates of extinction and the erosion of biotic interactions. it is concerned with factors that influence the maintenance, loss, and restoration of biodiversity and the science of sustaining evolutionary processes that engender genetic, population, species, and ecosystem diversity. the concern stems from estimates suggesting that up to 50 % of all species on the planet
alarm is triggered. = = = food processing and agriculture = = = in biology and agriculture, radiation is used to induce mutations to produce new or improved species, such as in atomic gardening. another use in insect control is the sterile insect technique, where male insects are sterilized by radiation and released, so they have no offspring, to reduce the population. in industrial and food applications, radiation is used for sterilization of tools and equipment. an advantage is that the object may be sealed in plastic before sterilization. an emerging use in food production is the sterilization of food using food irradiation. food irradiation is the process of exposing food to ionizing radiation in order to destroy microorganisms, bacteria, viruses, or insects that might be present in the food. the radiation sources used include radioisotope gamma ray sources, x - ray generators and electron accelerators. further applications include sprout inhibition, delay of ripening, increase of juice yield, and improvement of re - hydration. irradiation is a more general term of deliberate exposure of materials to radiation to achieve a technical goal ( in this context ' ionizing radiation ' is implied ). as such it is also used on non - food items, such as medical hardware, plastics, tubes for gas - pipelines, hoses for floor - heating, shrink - foils for food packaging, automobile parts, wires and cables ( isolation ), tires, and even gemstones. compared to the amount of food irradiated, the volume of those every - day applications is huge but not noticed by the consumer. the genuine effect of processing food by ionizing radiation relates to damages to the dna, the basic genetic information for life. microorganisms can no longer proliferate and continue their malignant or pathogenic activities. spoilage causing micro - organisms cannot continue their activities. insects do not survive or become incapable of procreation. plants cannot continue the natural ripening or aging process. all these effects are beneficial to the consumer and the food industry, likewise. the amount of energy imparted for effective food irradiation is low compared to cooking the same ; even at a typical dose of 10 kgy most food, which is ( with regard to warming ) physically equivalent to water, would warm by only about 2. 5 Β°c ( 4. 5 Β°f ). the specialty of processing food by ionizing radiation is the fact, that the energy density per atomic transition is very high, it can cleave
consume organic material, breathe oxygen, are able to move, can reproduce sexually, and grow from a hollow sphere of cells, the blastula, during embryonic development. over 1. 5 million living animal species have been described β of which around 1 million are insects β but it has been estimated there are over 7 million animal species in total. they have complex interactions with each other and their environments, forming intricate food webs. = = = viruses = = = viruses are submicroscopic infectious agents that replicate inside the cells of organisms. viruses infect all types of life forms, from animals and plants to microorganisms, including bacteria and archaea. more than 6, 000 virus species have been described in detail. viruses are found in almost every ecosystem on earth and are the most numerous type of biological entity. the origins of viruses in the evolutionary history of life are unclear : some may have evolved from plasmids β pieces of dna that can move between cells β while others may have evolved from bacteria. in evolution, viruses are an important means of horizontal gene transfer, which increases genetic diversity in a way analogous to sexual reproduction. because viruses possess some but not all characteristics of life, they have been described as " organisms at the edge of life ", and as self - replicators. = = ecology = = ecology is the study of the distribution and abundance of life, the interaction between organisms and their environment. = = = ecosystems = = = the community of living ( biotic ) organisms in conjunction with the nonliving ( abiotic ) components ( e. g., water, light, radiation, temperature, humidity, atmosphere, acidity, and soil ) of their environment is called an ecosystem. these biotic and abiotic components are linked together through nutrient cycles and energy flows. energy from the sun enters the system through photosynthesis and is incorporated into plant tissue. by feeding on plants and on one another, animals move matter and energy through the system. they also influence the quantity of plant and microbial biomass present. by breaking down dead organic matter, decomposers release carbon back to the atmosphere and facilitate nutrient cycling by converting nutrients stored in dead biomass back to a form that can be readily used by plants and other microbes. = = = populations = = = a population is the group of organisms of the same species that occupies an area and reproduce from generation to generation. population size can be estimated by multiplying population density by the area or volume. the carrying capacity of an environment
kilometers ( 4, 200, 000 to 395, 400, 000 acres ). 10 % of the world ' s crop lands were planted with gm crops in 2010. as of 2011, 11 different transgenic crops were grown commercially on 395 million acres ( 160 million hectares ) in 29 countries such as the us, brazil, argentina, india, canada, china, paraguay, pakistan, south africa, uruguay, bolivia, australia, philippines, myanmar, burkina faso, mexico and spain. genetically modified foods are foods produced from organisms that have had specific changes introduced into their dna with the methods of genetic engineering. these techniques have allowed for the introduction of new crop traits as well as a far greater control over a food ' s genetic structure than previously afforded by methods such as selective breeding and mutation breeding. commercial sale of genetically modified foods began in 1994, when calgene first marketed its flavr savr delayed ripening tomato. to date most genetic modification of foods have primarily focused on cash crops in high demand by farmers such as soybean, corn, canola, and cotton seed oil. these have been engineered for resistance to pathogens and herbicides and better nutrient profiles. gm livestock have also been experimentally developed ; in november 2013 none were available on the market, but in 2015 the fda approved the first gm salmon for commercial production and consumption. there is a scientific consensus that currently available food derived from gm crops poses no greater risk to human health than conventional food, but that each gm food needs to be tested on a case - by - case basis before introduction. nonetheless, members of the public are much less likely than scientists to perceive gm foods as safe. the legal and regulatory status of gm foods varies by country, with some nations banning or restricting them, and others permitting them with widely differing degrees of regulation. gm crops also provide a number of ecological benefits, if not used in excess. insect - resistant crops have proven to lower pesticide usage, therefore reducing the environmental impact of pesticides as a whole. however, opponents have objected to gm crops per se on several grounds, including environmental concerns, whether food produced from gm crops is safe, whether gm crops are needed to address the world ' s food needs, and economic concerns raised by the fact these organisms are subject to intellectual property law. biotechnology has several applications in the realm of food security. crops like golden rice are engineered to have higher nutritional content, and there is potential for food products with longer shelf lives. though not a form of agricultural biotechnology, vaccines can help prevent diseases found in
new crop traits as well as a far greater control over a food ' s genetic structure than previously afforded by methods such as selective breeding and mutation breeding. commercial sale of genetically modified foods began in 1994, when calgene first marketed its flavr savr delayed ripening tomato. to date most genetic modification of foods have primarily focused on cash crops in high demand by farmers such as soybean, corn, canola, and cotton seed oil. these have been engineered for resistance to pathogens and herbicides and better nutrient profiles. gm livestock have also been experimentally developed ; in november 2013 none were available on the market, but in 2015 the fda approved the first gm salmon for commercial production and consumption. there is a scientific consensus that currently available food derived from gm crops poses no greater risk to human health than conventional food, but that each gm food needs to be tested on a case - by - case basis before introduction. nonetheless, members of the public are much less likely than scientists to perceive gm foods as safe. the legal and regulatory status of gm foods varies by country, with some nations banning or restricting them, and others permitting them with widely differing degrees of regulation. gm crops also provide a number of ecological benefits, if not used in excess. insect - resistant crops have proven to lower pesticide usage, therefore reducing the environmental impact of pesticides as a whole. however, opponents have objected to gm crops per se on several grounds, including environmental concerns, whether food produced from gm crops is safe, whether gm crops are needed to address the world ' s food needs, and economic concerns raised by the fact these organisms are subject to intellectual property law. biotechnology has several applications in the realm of food security. crops like golden rice are engineered to have higher nutritional content, and there is potential for food products with longer shelf lives. though not a form of agricultural biotechnology, vaccines can help prevent diseases found in animal agriculture. additionally, agricultural biotechnology can expedite breeding processes in order to yield faster results and provide greater quantities of food. transgenic biofortification in cereals has been considered as a promising method to combat malnutrition in india and other countries. = = = industrial = = = industrial biotechnology ( known mainly in europe as white biotechnology ) is the application of biotechnology for industrial purposes, including industrial fermentation. it includes the practice of using cells such as microorganisms, or components of cells like enzymes, to generate industrially useful products in sectors such as chemicals, food and feed, detergents, paper
the prevalence of sexual reproduction ( " sex " ) in eukaryotes is an enigma of evolutionary biology. sex increases genetic variation only tells its long - term superiority in essence. the accumulation of harmful mutations causes an immediate and ubiquitous pressure for organisms. contrary to the common sense, our theoretical model suggests that reproductive rate can influence initiatively the accumulation of harmful mutations. the interaction of reproductive rate and the integrated harm of mutations causes a critical reproductive rate r *. a population will become irreversibly extinct once the reproductive rate reduces to lower than r *. a sexual population has a r * lower than 1 and an asexual population has a r * higher than 1. the mean reproductive rate of a population reached to the carrying capacity has to reduce to 1. that explains the widespread sex as well as the persistence of facultative and asexual organisms. computer simulations support significantly our conclusion.
one might ask why is it important to know the mechanism of fracture in leaves when mother nature is doing her job perfectly. i could list the following reasons to address that question : ( a ) leaves are natural composite structures, during millions of years of evolution, they have adapted themselves to their surrounding environment and their design is optimized, one can apply the knowledge gained from studying the fracture mechanism of leaves to the development of new composite materials ; ( b ) other soft tissues like skin and blood vessel have similar structure at some scales and may possess the same fracture mechanism. the gained knowledge can also be applied to these materials ; ( c ) global need for food is skyrocketing. there are few countries, including the united states, that have all the potentials ( i. e. water, soil, sunlight, and manpower ) to play a major role in the future world food supplying market. if we can increase the output of our farms and forests, by means of protecting them against herbivores [ beck 1965 ], pathogens [ campbell et al. 1980 ], and other physical damages, our share of the future market will be higher. it will also enforce our national food security because we will not be dependent on food import. we do not yet know how much of our farms and forests output can be saved if we can genetically design tougher materials, but the whole idea does worth to be studied.
species occupying the same geographical area at the same time. a biological interaction is the effect that a pair of organisms living together in a community have on each other. they can be either of the same species ( intraspecific interactions ), or of different species ( interspecific interactions ). these effects may be short - term, like pollination and predation, or long - term ; both often strongly influence the evolution of the species involved. a long - term interaction is called a symbiosis. symbioses range from mutualism, beneficial to both partners, to competition, harmful to both partners. every species participates as a consumer, resource, or both in consumer β resource interactions, which form the core of food chains or food webs. there are different trophic levels within any food web, with the lowest level being the primary producers ( or autotrophs ) such as plants and algae that convert energy and inorganic material into organic compounds, which can then be used by the rest of the community. at the next level are the heterotrophs, which are the species that obtain energy by breaking apart organic compounds from other organisms. heterotrophs that consume plants are primary consumers ( or herbivores ) whereas heterotrophs that consume herbivores are secondary consumers ( or carnivores ). and those that eat secondary consumers are tertiary consumers and so on. omnivorous heterotrophs are able to consume at multiple levels. finally, there are decomposers that feed on the waste products or dead bodies of organisms. on average, the total amount of energy incorporated into the biomass of a trophic level per unit of time is about one - tenth of the energy of the trophic level that it consumes. waste and dead material used by decomposers as well as heat lost from metabolism make up the other ninety percent of energy that is not consumed by the next trophic level. = = = biosphere = = = in the global ecosystem or biosphere, matter exists as different interacting compartments, which can be biotic or abiotic as well as accessible or inaccessible, depending on their forms and locations. for example, matter from terrestrial autotrophs are both biotic and accessible to other organisms whereas the matter in rocks and minerals are abiotic and inaccessible. a biogeochemical cycle is a pathway by which specific elements of matter are turned over or moved through the biotic ( biosphere ) and the abiotic ( lithos
this third part of the lecture series deals with the question : who will pay for your retirement? for western europe the answer may be ` ` nobody ' ', but for algeria the demography looks more promising.
Question: Who controls prey population?
A) parasites
B) predators
C) ecosystems
D) bees
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B) predators
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Context:
, characterizing organs as predominantly yin or yang, and understood the relationship between the pulse, the heart, and the flow of blood in the body centuries before it became accepted in the west. little evidence survives of how ancient indian cultures around the indus river understood nature, but some of their perspectives may be reflected in the vedas, a set of sacred hindu texts. they reveal a conception of the universe as ever - expanding and constantly being recycled and reformed. surgeons in the ayurvedic tradition saw health and illness as a combination of three humors : wind, bile and phlegm. a healthy life resulted from a balance among these humors. in ayurvedic thought, the body consisted of five elements : earth, water, fire, wind, and space. ayurvedic surgeons performed complex surgeries and developed a detailed understanding of human anatomy. pre - socratic philosophers in ancient greek culture brought natural philosophy a step closer to direct inquiry about cause and effect in nature between 600 and 400 bc. however, an element of magic and mythology remained. natural phenomena such as earthquakes and eclipses were explained increasingly in the context of nature itself instead of being attributed to angry gods. thales of miletus, an early philosopher who lived from 625 to 546 bc, explained earthquakes by theorizing that the world floated on water and that water was the fundamental element in nature. in the 5th century bc, leucippus was an early exponent of atomism, the idea that the world is made up of fundamental indivisible particles. pythagoras applied greek innovations in mathematics to astronomy and suggested that the earth was spherical. = = = aristotelian natural philosophy ( 400 bc β 1100 ad ) = = = later socratic and platonic thought focused on ethics, morals, and art and did not attempt an investigation of the physical world ; plato criticized pre - socratic thinkers as materialists and anti - religionists. aristotle, however, a student of plato who lived from 384 to 322 bc, paid closer attention to the natural world in his philosophy. in his history of animals, he described the inner workings of 110 species, including the stingray, catfish and bee. he investigated chick embryos by breaking open eggs and observing them at various stages of development. aristotle ' s works were influential through the 16th century, and he is considered to be the father of biology for his pioneering work in that science. he also presented philosophies about physics, nature, and astronomy using
oxygen ion migration in li2mno3 was systematically studied by first - principles calculations. hole polaron is found effective to lower the migration barrier of oxygen ion.
required. for example, certain cells respond to changes in oxygen tension as part of their normal development, such as chondrocytes, which must adapt to low oxygen conditions or hypoxia during skeletal development. others, such as endothelial cells, respond to shear stress from fluid flow, which is encountered in blood vessels. mechanical stimuli, such as pressure pulses seem to be beneficial to all kind of cardiovascular tissue such as heart valves, blood vessels or pericardium. = = = bioreactors = = = in tissue engineering, a bioreactor is a device that attempts to simulate a physiological environment in order to promote cell or tissue growth in vitro. a physiological environment can consist of many different parameters such as temperature, pressure, oxygen or carbon dioxide concentration, or osmolality of fluid environment, and it can extend to all kinds of biological, chemical or mechanical stimuli. therefore, there are systems that may include the application of forces such as electromagnetic forces, mechanical pressures, or fluid pressures to the tissue. these systems can be two - or three - dimensional setups. bioreactors can be used in both academic and industry applications. general - use and application - specific bioreactors are also commercially available, which may provide static chemical stimulation or a combination of chemical and mechanical stimulation. cell proliferation and differentiation are largely influenced by mechanical and biochemical cues in the surrounding extracellular matrix environment. bioreactors are typically developed to replicate the specific physiological environment of the tissue being grown ( e. g., flex and fluid shearing for heart tissue growth ). this can allow specialized cell lines to thrive in cultures replicating their native environments, but it also makes bioreactors attractive tools for culturing stem cells. a successful stem - cell - based bioreactor is effective at expanding stem cells with uniform properties and / or promoting controlled, reproducible differentiation into selected mature cell types. there are a variety of bioreactors designed for 3d cell cultures. there are small plastic cylindrical chambers, as well as glass chambers, with regulated internal humidity and moisture specifically engineered for the purpose of growing cells in three dimensions. the bioreactor uses bioactive synthetic materials such as polyethylene terephthalate membranes to surround the spheroid cells in an environment that maintains high levels of nutrients. they are easy to open and close, so that cell spheroids can be removed for testing, yet the chamber is able to maintain 100 % humidity throughout. this humidity is important to achieve maximum cell growth and function. the
) another aspect of the development engineer ' s job is a trade - off process required to deliver all of the automobile attributes at a certain acceptable level. an example of this is the trade - off between engine performance and fuel economy. while some customers are looking for maximum power from their engine, the automobile is still required to deliver an acceptable level of fuel economy. from the engine ' s perspective, these are opposing requirements. engine performance is looking for maximum displacement ( bigger, more power ), while fuel economy is looking for a smaller displacement engine ( ex : 1. 4 l vs. 5. 4 l ). the engine size however, is not the only contributing factor to fuel economy and automobile performance. different values come into play. other attributes that involve trade - offs include : automobile weight, aerodynamic drag, transmission gearing, emission control devices, handling / roadholding, ride quality, and tires. the development engineer is also responsible for organizing automobile level testing, validation, and certification. components and systems are designed and tested individually by the product engineer. the final evaluation is to be conducted at the automobile level to evaluate system to system interactions. as an example, the audio system ( radio ) needs to be evaluated at the automobile level. interaction with other electronic components can cause interference. heat dissipation of the system and ergonomic placement of the controls need to be evaluated. sound quality in all seating positions needs to be provided at acceptable levels. = = = manufacturing engineer = = = manufacturing engineers are responsible for ensuring proper production of the automotive components or complete vehicles. while the development engineers are responsible for the function of the vehicle, manufacturing engineers are responsible for the safe and effective production of the vehicle. this group of engineers consist of process engineers, logistic coordinators, tooling engineers, robotics engineers, and assembly planners. in the automotive industry manufacturers are playing a larger role in the development stages of automotive components to ensure that the products are easy to manufacture. design for manufacturability in the automotive world is crucial to make certain whichever design is developed in the research and development stage of automotive design. once the design is established, the manufacturing engineers take over. they design the machinery and tooling necessary to build the automotive components or vehicle and establish the methods of how to mass - produce the product. it is the manufacturing engineers job to increase the efficiency of the automotive plant and to implement lean manufacturing techniques such as six sigma and kaizen. = = = other automotive engineering roles = = = other automotive engineers include those listed below : aerodynamic
gas load and pumping determine the quality of vacuum systems. in particle accelerators, once leaks are excluded, outgassing of materials is an important source of gas together with degassing induced by particle beams. understanding, predicting, and measuring gas release from materials in vacuum are among the fundamental tasks of ultrahigh - vacuum experts. the knowledge of outgassing phenomena is essential for the choice of materials and their treatments so that the required gas density is achieved in such demanding and expensive scientific instruments. this note provides the background to understand outgassing in vacuum and gives references for further study.
this document aims at specifying the requirements and capturing the needs of users for building a softbody simulation system. this system has different applications ranging from computer games to surgery training which facilitates the creation and visualization of a certain softbody object. it also allows users to interact with created object at real time. a softbody or deformable object is an object whose shape changes due to an external force. deformation type varies depending on the amount of object deformation. each object can have multiple layers and each layer can have its own properties. so layers can be different in pressure, density and motion.
we have detected extremely wide ( 1100 km / s ) co ( 1 - 0 ) emission from ngc 1144, an interacting, luminous infrared galaxy that is the dominant component of the arp 118 system. the observations show that ngc 1144 is one of the most co luminous galaxies in the local universe, with a co luminosity twice that of arp 220. maps with the iram interferometer show that the co is not in or very near the seyfert 2 nucleus, but in the 20 kpc diameter ring that extends halfway between ngc 1144 and the elliptical galaxy ngc 1143. the greatest gas concentration, with 40 % of the co luminosity, is in the southern part of the ring, in ngc 1144. another 15 % of the co luminosity comes from the dominant 10 $ \ mu $ m source, a giant extranuclear hii region. the ring of molecular gas, the off - center nucleus, the ring extending halfway to the intruder, and the velocity of the intruder nearly equal to the escape velocity all show that arp 118 is a ring galaxy produced by a collision of a massive spiral with an elliptical. the most spectacular property is the velocity range, which in arp 118 is 2 to 3 times higher than in a typical ring galaxy. arp 118 is a rare example of a very luminous extended starburst with a scale of about 5 - 10 kpc, and a luminosity of 3 $ \ times 10 ^ { 11 } l _ { \ odot } $.
human blood primarily comprises plasma, red blood cells, white blood cells, and platelets. it plays a vital role in transporting nutrients to different organs, where it stores essential health - related data about the human body. blood cells are utilized to defend the body against diverse infections, including fungi, viruses, and bacteria. hence, blood analysis can help physicians assess an individual ' s physiological condition. blood cells have been sub - classified into eight groups : neutrophils, eosinophils, basophils, lymphocytes, monocytes, immature granulocytes ( promyelocytes, myelocytes, and metamyelocytes ), erythroblasts, and platelets or thrombocytes on the basis of their nucleus, shape, and cytoplasm. traditionally, pathologists and hematologists in laboratories have examined these blood cells using a microscope before manually classifying them. the manual approach is slower and more prone to human error. therefore, it is essential to automate this process. in our paper, transfer learning with cnn pre - trained models. vgg16, vgg19, resnet - 50, resnet - 101, resnet - 152, inceptionv3, mobilenetv2, and densenet - 20 applied to the pbc dataset ' s normal dib. the overall accuracy achieved with these models lies between 91. 375 and 94. 72 %. hence, inspired by these pre - trained architectures, a model has been proposed to automatically classify the ten types of blood cells with increased accuracy. a novel cnn - based framework has been presented to improve accuracy. the proposed cnn model has been tested on the pbc dataset normal dib. the outcomes of the experiments demonstrate that our cnn - based framework designed for blood cell classification attains an accuracy of 99. 91 % on the pbc dataset. our proposed convolutional neural network model performs competitively when compared to earlier results reported in the literature.
the modular neutron array ( mona ) was used in conjunction with a large - gap dipole magnet ( sweeper ) to measure neutron - unbound states in oxygen isotopes close to the neutron dripline. while no excited states were observed in 24o, a resonance at 45 ( 2 ) kev above the neutron separation energy was observed in 23o.
numerical algorithm for direct simulation of the gas flow in the holweck pump is developed. the results illustrating the important features of the flow in the pump are reported. an attention is paid to the problem of the pump design optimization.
Question: In which organs does gas exchange take place between blood and air?
A) lungs
B) esophagus and larynx
C) kidneys
D) liver and spleen
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A) lungs
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Context:
it is stronger, then demodulates it, extracting the original modulation signal from the modulated carrier wave. the modulation signal is converted by a transducer back to a human - usable form : an audio signal is converted to sound waves by a loudspeaker or earphones, a video signal is converted to images by a display, while a digital signal is applied to a computer or microprocessor, which interacts with human users. the radio waves from many transmitters pass through the air simultaneously without interfering with each other because each transmitter ' s radio waves oscillate at a different frequency, measured in hertz ( hz ), kilohertz ( khz ), megahertz ( mhz ) or gigahertz ( ghz ). the receiving antenna typically picks up the radio signals of many transmitters. the receiver uses tuned circuits to select the radio signal desired out of all the signals picked up by the antenna and reject the others. a tuned circuit acts like a resonator, similar to a tuning fork. it has a natural resonant frequency at which it oscillates. the resonant frequency of the receiver ' s tuned circuit is adjusted by the user to the frequency of the desired radio station ; this is called tuning. the oscillating radio signal from the desired station causes the tuned circuit to oscillate in sympathy, and it passes the signal on to the rest of the receiver. radio signals at other frequencies are blocked by the tuned circuit and not passed on. = = = bandwidth = = = a modulated radio wave, carrying an information signal, occupies a range of frequencies. the information in a radio signal is usually concentrated in narrow frequency bands called sidebands ( sb ) just above and below the carrier frequency. the width in hertz of the frequency range that the radio signal occupies, the highest frequency minus the lowest frequency, is called its bandwidth ( bw ). for any given signal - to - noise ratio, a given bandwidth can carry the same amount of information regardless of where in the radio frequency spectrum it is located ; bandwidth is a measure of information - carrying capacity. the bandwidth required by a radio transmission depends on the data rate of the information being sent, and the spectral efficiency of the modulation method used ; how much data it can transmit in each unit of bandwidth. different types of information signals carried by radio have different data rates. for example, a television signal has a greater data rate than an audio signal. the radio spectrum, the total range of
an important question of theoretical physics is whether sound is able to propagate in vacuums at all and if this is the case, then it must lead to the reinterpretation of one zero - restmass particle which corresponds to vacuum - sound waves. taking the electron - neutrino as the corresponding particle, its observed non - vanishing rest - energy may only appear for neutrino - propagation inside material media. the idea may also influence the physics of dense matter, restricting the maximum speed of sound, both in vacuums and in matter to the speed of light.
subsea engineering and the ability to detect, track and destroy submarines ( anti - submarine warfare ) required the parallel development of a host of marine scientific instrumentation and sensors. visible light is not transferred far underwater, so the medium for transmission of data is primarily acoustic. high - frequency sound is used to measure the depth of the ocean, determine the nature of the seafloor, and detect submerged objects. the higher the frequency, the higher the definition of the data that is returned. sound navigation and ranging or sonar was developed during the first world war to detect submarines, and has been greatly refined through to the present day. submarines similarly use sonar equipment to detect and target other submarines and surface ships, and to detect submerged obstacles such as seamounts that pose a navigational obstacle. simple echo - sounders point straight down and can give an accurate reading of ocean depth ( or look up at the underside of sea - ice ). more advanced echo sounders use a fan - shaped beam or sound, or multiple beams to derive highly detailed images of the ocean floor. high power systems can penetrate the soil and seabed rocks to give information about the geology of the seafloor, and are widely used in geophysics for the discovery of hydrocarbons, or for engineering survey. for close - range underwater communications, optical transmission is possible, mainly using blue lasers. these have a high bandwidth compared with acoustic systems, but the range is usually only a few tens of metres, and ideally at night. as well as acoustic communications and navigation, sensors have been developed to measure ocean parameters such as temperature, salinity, oxygen levels and other properties including nitrate levels, levels of trace chemicals and environmental dna. the industry trend has been towards smaller, more accurate and more affordable systems so that they can be purchased and used by university departments and small companies as well as large corporations, research organisations and governments. the sensors and instruments are fitted to autonomous and remotely - operated systems as well as ships, and are enabling these systems to take on tasks that hitherto required an expensive human - crewed platform. manufacture of marine sensors and instruments mainly takes place in asia, europe and north america. products are advertised in specialist journals, and through trade shows such as oceanology international and ocean business which help raise awareness of the products. = = = environmental engineering = = = in every coastal and offshore project, environmental sustainability is an important consideration for the preservation of ocean ecosystems and natural resources. instances in which marine engineers benefit from knowledge of environmental engineering include creation of fisheries, clean
beacon transmits two signals simultaneously on different frequencies. a directional antenna transmits a beam of radio waves that rotates like a lighthouse at a fixed rate, 30 times per second. when the directional beam is facing north, an omnidirectional antenna transmits a pulse. by measuring the difference in phase of these two signals, an aircraft can determine its bearing ( or " radial " ) from the station accurately. by taking a bearing on two vor beacons an aircraft can determine its position ( called a " fix " ) to an accuracy of about 90 metres ( 300 ft ). most vor beacons also have a distance measuring capability, called distance measuring equipment ( dme ) ; these are called vor / dme ' s. the aircraft transmits a radio signal to the vor / dme beacon and a transponder transmits a return signal. from the propagation delay between the transmitted and received signal the aircraft can calculate its distance from the beacon. this allows an aircraft to determine its location " fix " from only one vor beacon. since line - of - sight vhf frequencies are used vor beacons have a range of about 200 miles for aircraft at cruising altitude. tacan is a similar military radio beacon system which transmits in 962 β 1213 mhz, and a combined vor and tacan beacon is called a vortac. the number of vor beacons is declining as aviation switches to the rnav system that relies on global positioning system satellite navigation. instrument landing system ( ils ) - a short range radio navigation aid at airports which guides aircraft landing in low visibility conditions. it consists of multiple antennas at the end of each runway that radiate two beams of radio waves along the approach to the runway : the localizer ( 108 to 111. 95 mhz frequency ), which provides horizontal guidance, a heading line to keep the aircraft centered on the runway, and the glideslope ( 329. 15 to 335 mhz ) for vertical guidance, to keep the aircraft descending at the proper rate for a smooth touchdown at the correct point on the runway. each aircraft has a receiver instrument and antenna which receives the beams, with an indicator to tell the pilot whether he is on the correct horizontal and vertical approach. the ils beams are receivable for at least 15 miles, and have a radiated power of 25 watts. ils systems at airports are being replaced by systems that use satellite navigation. non - directional beacon ( ndb ) β legacy fixed radio beacons used before the vo
##directional range ( vor ) β a worldwide aircraft radio navigation system consisting of fixed ground radio beacons transmitting between 108. 00 and 117. 95 mhz in the very high frequency ( vhf ) band. an automated navigational instrument on the aircraft displays a bearing to a nearby vor transmitter. a vor beacon transmits two signals simultaneously on different frequencies. a directional antenna transmits a beam of radio waves that rotates like a lighthouse at a fixed rate, 30 times per second. when the directional beam is facing north, an omnidirectional antenna transmits a pulse. by measuring the difference in phase of these two signals, an aircraft can determine its bearing ( or " radial " ) from the station accurately. by taking a bearing on two vor beacons an aircraft can determine its position ( called a " fix " ) to an accuracy of about 90 metres ( 300 ft ). most vor beacons also have a distance measuring capability, called distance measuring equipment ( dme ) ; these are called vor / dme ' s. the aircraft transmits a radio signal to the vor / dme beacon and a transponder transmits a return signal. from the propagation delay between the transmitted and received signal the aircraft can calculate its distance from the beacon. this allows an aircraft to determine its location " fix " from only one vor beacon. since line - of - sight vhf frequencies are used vor beacons have a range of about 200 miles for aircraft at cruising altitude. tacan is a similar military radio beacon system which transmits in 962 β 1213 mhz, and a combined vor and tacan beacon is called a vortac. the number of vor beacons is declining as aviation switches to the rnav system that relies on global positioning system satellite navigation. instrument landing system ( ils ) - a short range radio navigation aid at airports which guides aircraft landing in low visibility conditions. it consists of multiple antennas at the end of each runway that radiate two beams of radio waves along the approach to the runway : the localizer ( 108 to 111. 95 mhz frequency ), which provides horizontal guidance, a heading line to keep the aircraft centered on the runway, and the glideslope ( 329. 15 to 335 mhz ) for vertical guidance, to keep the aircraft descending at the proper rate for a smooth touchdown at the correct point on the runway. each aircraft has a receiver instrument and antenna which receives the beams, with an indicator to tell the pilot whether he is
missiles, ships, vehicles, and also to map weather patterns and terrain. a radar set consists of a transmitter and receiver. the transmitter emits a narrow beam of radio waves which is swept around the surrounding space. when the beam strikes a target object, radio waves are reflected back to the receiver. the direction of the beam reveals the object ' s location. since radio waves travel at a constant speed close to the speed of light, by measuring the brief time delay between the outgoing pulse and the received " echo ", the range to the target can be calculated. the targets are often displayed graphically on a map display called a radar screen. doppler radar can measure a moving object ' s velocity, by measuring the change in frequency of the return radio waves due to the doppler effect. radar sets mainly use high frequencies in the microwave bands, because these frequencies create strong reflections from objects the size of vehicles and can be focused into narrow beams with compact antennas. parabolic ( dish ) antennas are widely used. in most radars the transmitting antenna also serves as the receiving antenna ; this is called a monostatic radar. a radar which uses separate transmitting and receiving antennas is called a bistatic radar. airport surveillance radar β in aviation, radar is the main tool of air traffic control. a rotating dish antenna sweeps a vertical fan - shaped beam of microwaves around the airspace and the radar set shows the location of aircraft as " blips " of light on a display called a radar screen. airport radar operates at 2. 7 β 2. 9 ghz in the microwave s band. in large airports the radar image is displayed on multiple screens in an operations room called the tracon ( terminal radar approach control ), where air traffic controllers direct the aircraft by radio to maintain safe aircraft separation. secondary surveillance radar β aircraft carry radar transponders, transceivers which when triggered by the incoming radar signal transmit a return microwave signal. this causes the aircraft to show up more strongly on the radar screen. the radar which triggers the transponder and receives the return beam, usually mounted on top of the primary radar dish, is called the secondary surveillance radar. since radar cannot measure an aircraft ' s altitude with any accuracy, the transponder also transmits back the aircraft ' s altitude measured by its altimeter, and an id number identifying the aircraft, which is displayed on the radar screen. electronic countermeasures ( ecm ) β military defensive electronic systems designed to degrade enemy radar effectiveness, or deceive it
when fast radio burst ( frb ) waves propagate through the local ( < 1 pc ) environment of the frb source, electrons in the plasma undergo large - amplitude oscillations. the finite - amplitude effects cause the effective plasma frequency and cyclotron frequency to be dependent on the wave strength. the dispersion measure and rotation measure should therefore vary slightly from burst to burst for a repeating source, depending on the luminosity and frequency of the individual burst. furthermore, free - free absorption of strong waves is suppressed due to the accelerated electrons ' reduced energy exchange in coulomb collisions. this allows bright low - frequency bursts to propagate through an environment that would be optically thick to low - amplitude waves. given a large sample of bursts from a repeating source, it would be possible to use the deficit of low - frequency and low - luminosity bursts to infer the emission measure of the local intervening plasma and its distance from the source. information about the local environment will shed light on the nature of frb sources.
wave, carrying an information signal, occupies a range of frequencies. the information in a radio signal is usually concentrated in narrow frequency bands called sidebands ( sb ) just above and below the carrier frequency. the width in hertz of the frequency range that the radio signal occupies, the highest frequency minus the lowest frequency, is called its bandwidth ( bw ). for any given signal - to - noise ratio, a given bandwidth can carry the same amount of information regardless of where in the radio frequency spectrum it is located ; bandwidth is a measure of information - carrying capacity. the bandwidth required by a radio transmission depends on the data rate of the information being sent, and the spectral efficiency of the modulation method used ; how much data it can transmit in each unit of bandwidth. different types of information signals carried by radio have different data rates. for example, a television signal has a greater data rate than an audio signal. the radio spectrum, the total range of radio frequencies that can be used for communication in a given area, is a limited resource. each radio transmission occupies a portion of the total bandwidth available. radio bandwidth is regarded as an economic good which has a monetary cost and is in increasing demand. in some parts of the radio spectrum, the right to use a frequency band or even a single radio channel is bought and sold for millions of dollars. so there is an incentive to employ technology to minimize the bandwidth used by radio services. a slow transition from analog to digital radio transmission technologies began in the late 1990s. part of the reason for this is that digital modulation can often transmit more information ( a greater data rate ) in a given bandwidth than analog modulation, by using data compression algorithms, which reduce redundancy in the data to be sent, and more efficient modulation. other reasons for the transition is that digital modulation has greater noise immunity than analog, digital signal processing chips have more power and flexibility than analog circuits, and a wide variety of types of information can be transmitted using the same digital modulation. because it is a fixed resource which is in demand by an increasing number of users, the radio spectrum has become increasingly congested in recent decades, and the need to use it more effectively is driving many additional radio innovations such as trunked radio systems, spread spectrum ( ultra - wideband ) transmission, frequency reuse, dynamic spectrum management, frequency pooling, and cognitive radio. = = = itu frequency bands = = = the itu arbitrarily divides the radio spectrum into 12 bands, each beginning at a wavelength which is a power
the attenuation length and refractive index of liquid xenon for intrinsic scintillation light ( 178nm ) have been measured in a single experiment. the value obtained for attenuation length is 364 + - 18 mm. the refractive index is found to be 1. 69 + - 0. 02. both values were measured at a temperature of 170 + - 1 k.
ocean, determine the nature of the seafloor, and detect submerged objects. the higher the frequency, the higher the definition of the data that is returned. sound navigation and ranging or sonar was developed during the first world war to detect submarines, and has been greatly refined through to the present day. submarines similarly use sonar equipment to detect and target other submarines and surface ships, and to detect submerged obstacles such as seamounts that pose a navigational obstacle. simple echo - sounders point straight down and can give an accurate reading of ocean depth ( or look up at the underside of sea - ice ). more advanced echo sounders use a fan - shaped beam or sound, or multiple beams to derive highly detailed images of the ocean floor. high power systems can penetrate the soil and seabed rocks to give information about the geology of the seafloor, and are widely used in geophysics for the discovery of hydrocarbons, or for engineering survey. for close - range underwater communications, optical transmission is possible, mainly using blue lasers. these have a high bandwidth compared with acoustic systems, but the range is usually only a few tens of metres, and ideally at night. as well as acoustic communications and navigation, sensors have been developed to measure ocean parameters such as temperature, salinity, oxygen levels and other properties including nitrate levels, levels of trace chemicals and environmental dna. the industry trend has been towards smaller, more accurate and more affordable systems so that they can be purchased and used by university departments and small companies as well as large corporations, research organisations and governments. the sensors and instruments are fitted to autonomous and remotely - operated systems as well as ships, and are enabling these systems to take on tasks that hitherto required an expensive human - crewed platform. manufacture of marine sensors and instruments mainly takes place in asia, europe and north america. products are advertised in specialist journals, and through trade shows such as oceanology international and ocean business which help raise awareness of the products. = = = environmental engineering = = = in every coastal and offshore project, environmental sustainability is an important consideration for the preservation of ocean ecosystems and natural resources. instances in which marine engineers benefit from knowledge of environmental engineering include creation of fisheries, clean - up of oil spills, and creation of coastal solutions. = = = offshore systems = = = a number of systems designed fully or in part by marine engineers are used offshore - far away from coastlines. = = = = offshore oil platforms = = = = the design of offshore oil platforms involves a number of
Question: The frequency of sound waves is measured in what unit?
A) decibel
B) watt
C) rads
D) hertz
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D) hertz
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Context:
in one or more of these kinds of structures, it is invariably accompanied by an increase or decrease of energy of the substances involved. some energy is transferred between the surroundings and the reactants of the reaction in the form of heat or light ; thus the products of a reaction may have more or less energy than the reactants. a reaction is said to be exergonic if the final state is lower on the energy scale than the initial state ; in the case of endergonic reactions the situation is the reverse. a reaction is said to be exothermic if the reaction releases heat to the surroundings ; in the case of endothermic reactions, the reaction absorbs heat from the surroundings. chemical reactions are invariably not possible unless the reactants surmount an energy barrier known as the activation energy. the speed of a chemical reaction ( at given temperature t ) is related to the activation energy e, by the boltzmann ' s population factor e β e / k t { \ displaystyle e ^ { - e / kt } } β that is the probability of a molecule to have energy greater than or equal to e at the given temperature t. this exponential dependence of a reaction rate on temperature is known as the arrhenius equation. the activation energy necessary for a chemical reaction to occur can be in the form of heat, light, electricity or mechanical force in the form of ultrasound. a related concept free energy, which also incorporates entropy considerations, is a very useful means for predicting the feasibility of a reaction and determining the state of equilibrium of a chemical reaction, in chemical thermodynamics. a reaction is feasible only if the total change in the gibbs free energy is negative, Ξ΄ g β€ 0 { \ displaystyle \ delta g \ leq 0 \, } ; if it is equal to zero the chemical reaction is said to be at equilibrium. there exist only limited possible states of energy for electrons, atoms and molecules. these are determined by the rules of quantum mechanics, which require quantization of energy of a bound system. the atoms / molecules in a higher energy state are said to be excited. the molecules / atoms of substance in an excited energy state are often much more reactive ; that is, more amenable to chemical reactions. the phase of a substance is invariably determined by its energy and the energy of its surroundings. when the intermolecular forces of a substance are such that the energy of the surroundings is not sufficient to overcome them, it occurs in a more ordered phase like liquid
10 kgy most food, which is ( with regard to warming ) physically equivalent to water, would warm by only about 2. 5 Β°c ( 4. 5 Β°f ). the specialty of processing food by ionizing radiation is the fact, that the energy density per atomic transition is very high, it can cleave molecules and induce ionization ( hence the name ) which cannot be achieved by mere heating. this is the reason for new beneficial effects, however at the same time, for new concerns. the treatment of solid food by ionizing radiation can provide an effect similar to heat pasteurization of liquids, such as milk. however, the use of the term, cold pasteurization, to describe irradiated foods is controversial, because pasteurization and irradiation are fundamentally different processes, although the intended end results can in some cases be similar. detractors of food irradiation have concerns about the health hazards of induced radioactivity. a report for the industry advocacy group american council on science and health entitled " irradiated foods " states : " the types of radiation sources approved for the treatment of foods have specific energy levels well below that which would cause any element in food to become radioactive. food undergoing irradiation does not become any more radioactive than luggage passing through an airport x - ray scanner or teeth that have been x - rayed. " food irradiation is currently permitted by over 40 countries and volumes are estimated to exceed 500, 000 metric tons ( 490, 000 long tons ; 550, 000 short tons ) annually worldwide. food irradiation is essentially a non - nuclear technology ; it relies on the use of ionizing radiation which may be generated by accelerators for electrons and conversion into bremsstrahlung, but which may use also gamma - rays from nuclear decay. there is a worldwide industry for processing by ionizing radiation, the majority by number and by processing power using accelerators. food irradiation is only a niche application compared to medical supplies, plastic materials, raw materials, gemstones, cables and wires, etc. = = accidents = = nuclear accidents, because of the powerful forces involved, are often very dangerous. historically, the first incidents involved fatal radiation exposure. marie curie died from aplastic anemia which resulted from her high levels of exposure. two scientists, an american and canadian respectively, harry daghlian and louis slotin, died after mishandling the same plutonium mass. unlike conventional weapons, the intense light, heat, and explosive force is
variation in total solar irradiance is thought to have little effect on the earth ' s surface temperature because of the thermal time constant - - the characteristic response time of the earth ' s global surface temperature to changes in forcing. this time constant is large enough to smooth annual variations but not necessarily variations having a longer period such as those due to solar inertial motion ; the magnitude of these surface temperature variations is estimated.
do not survive or become incapable of procreation. plants cannot continue the natural ripening or aging process. all these effects are beneficial to the consumer and the food industry, likewise. the amount of energy imparted for effective food irradiation is low compared to cooking the same ; even at a typical dose of 10 kgy most food, which is ( with regard to warming ) physically equivalent to water, would warm by only about 2. 5 Β°c ( 4. 5 Β°f ). the specialty of processing food by ionizing radiation is the fact, that the energy density per atomic transition is very high, it can cleave molecules and induce ionization ( hence the name ) which cannot be achieved by mere heating. this is the reason for new beneficial effects, however at the same time, for new concerns. the treatment of solid food by ionizing radiation can provide an effect similar to heat pasteurization of liquids, such as milk. however, the use of the term, cold pasteurization, to describe irradiated foods is controversial, because pasteurization and irradiation are fundamentally different processes, although the intended end results can in some cases be similar. detractors of food irradiation have concerns about the health hazards of induced radioactivity. a report for the industry advocacy group american council on science and health entitled " irradiated foods " states : " the types of radiation sources approved for the treatment of foods have specific energy levels well below that which would cause any element in food to become radioactive. food undergoing irradiation does not become any more radioactive than luggage passing through an airport x - ray scanner or teeth that have been x - rayed. " food irradiation is currently permitted by over 40 countries and volumes are estimated to exceed 500, 000 metric tons ( 490, 000 long tons ; 550, 000 short tons ) annually worldwide. food irradiation is essentially a non - nuclear technology ; it relies on the use of ionizing radiation which may be generated by accelerators for electrons and conversion into bremsstrahlung, but which may use also gamma - rays from nuclear decay. there is a worldwide industry for processing by ionizing radiation, the majority by number and by processing power using accelerators. food irradiation is only a niche application compared to medical supplies, plastic materials, raw materials, gemstones, cables and wires, etc. = = accidents = = nuclear accidents, because of the powerful forces involved, are often very dangerous. historically, the first incidents involved fatal
temperature changes up to 1000 Β°c. = = processing steps = = the traditional ceramic process generally follows this sequence : milling β batching β mixing β forming β drying β firing β assembly. milling is the process by which materials are reduced from a large size to a smaller size. milling may involve breaking up cemented material ( in which case individual particles retain their shape ) or pulverization ( which involves grinding the particles themselves to a smaller size ). milling is generally done by mechanical means, including attrition ( which is particle - to - particle collision that results in agglomerate break up or particle shearing ), compression ( which applies a forces that results in fracturing ), and impact ( which employs a milling medium or the particles themselves to cause fracturing ). attrition milling equipment includes the wet scrubber ( also called the planetary mill or wet attrition mill ), which has paddles in water creating vortexes in which the material collides and break up. compression mills include the jaw crusher, roller crusher and cone crusher. impact mills include the ball mill, which has media that tumble and fracture the material, or the resonantacoustic mixer. shaft impactors cause particle - to particle attrition and compression. batching is the process of weighing the oxides according to recipes, and preparing them for mixing and drying. mixing occurs after batching and is performed with various machines, such as dry mixing ribbon mixers ( a type of cement mixer ), resonantacoustic mixers, mueller mixers, and pug mills. wet mixing generally involves the same equipment. forming is making the mixed material into shapes, ranging from toilet bowls to spark plug insulators. forming can involve : ( 1 ) extrusion, such as extruding " slugs " to make bricks, ( 2 ) pressing to make shaped parts, ( 3 ) slip casting, as in making toilet bowls, wash basins and ornamentals like ceramic statues. forming produces a " green " part, ready for drying. green parts are soft, pliable, and over time will lose shape. handling the green product will change its shape. for example, a green brick can be " squeezed ", and after squeezing it will stay that way. drying is removing the water or binder from the formed material. spray drying is widely used to prepare powder for pressing operations. other dryers are tunnel dryers and periodic dryers. controlled heat is applied in this two - stage process. first,
##tering - based methods are simple ( " sinter " has roots in the english " cinder " ). the firing is done at a temperature below the melting point of the ceramic. once a roughly - held - together object called a " green body " is made, it is fired in a kiln, where atomic and molecular diffusion processes give rise to significant changes in the primary microstructural features. this includes the gradual elimination of porosity, which is typically accompanied by a net shrinkage and overall densification of the component. thus, the pores in the object may close up, resulting in a denser product of significantly greater strength and fracture toughness. another major change in the body during the firing or sintering process will be the establishment of the polycrystalline nature of the solid. significant grain growth tends to occur during sintering, with this growth depending on temperature and duration of the sintering process. the growth of grains will result in some form of grain size distribution, which will have a significant impact on the ultimate physical properties of the material. in particular, abnormal grain growth in which certain grains grow very large in a matrix of finer grains will significantly alter the physical and mechanical properties of the obtained ceramic. in the sintered body, grain sizes are a product of the thermal processing parameters as well as the initial particle size, or possibly the sizes of aggregates or particle clusters which arise during the initial stages of processing. the ultimate microstructure ( and thus the physical properties ) of the final product will be limited by and subject to the form of the structural template or precursor which is created in the initial stages of chemical synthesis and physical forming. hence the importance of chemical powder and polymer processing as it pertains to the synthesis of industrial ceramics, glasses and glass - ceramics. there are numerous possible refinements of the sintering process. some of the most common involve pressing the green body to give the densification a head start and reduce the sintering time needed. sometimes organic binders such as polyvinyl alcohol are added to hold the green body together ; these burn out during the firing ( at 200 β 350 Β°c ). sometimes organic lubricants are added during pressing to increase densification. it is common to combine these, and add binders and lubricants to a powder, then press. ( the formulation of these organic chemical additives is an art in itself. this is particularly important in the manufacture of high performance ceramics such as those used by the billions for
molecular diffusion processes give rise to significant changes in the primary microstructural features. this includes the gradual elimination of porosity, which is typically accompanied by a net shrinkage and overall densification of the component. thus, the pores in the object may close up, resulting in a denser product of significantly greater strength and fracture toughness. another major change in the body during the firing or sintering process will be the establishment of the polycrystalline nature of the solid. significant grain growth tends to occur during sintering, with this growth depending on temperature and duration of the sintering process. the growth of grains will result in some form of grain size distribution, which will have a significant impact on the ultimate physical properties of the material. in particular, abnormal grain growth in which certain grains grow very large in a matrix of finer grains will significantly alter the physical and mechanical properties of the obtained ceramic. in the sintered body, grain sizes are a product of the thermal processing parameters as well as the initial particle size, or possibly the sizes of aggregates or particle clusters which arise during the initial stages of processing. the ultimate microstructure ( and thus the physical properties ) of the final product will be limited by and subject to the form of the structural template or precursor which is created in the initial stages of chemical synthesis and physical forming. hence the importance of chemical powder and polymer processing as it pertains to the synthesis of industrial ceramics, glasses and glass - ceramics. there are numerous possible refinements of the sintering process. some of the most common involve pressing the green body to give the densification a head start and reduce the sintering time needed. sometimes organic binders such as polyvinyl alcohol are added to hold the green body together ; these burn out during the firing ( at 200 β 350 Β°c ). sometimes organic lubricants are added during pressing to increase densification. it is common to combine these, and add binders and lubricants to a powder, then press. ( the formulation of these organic chemical additives is an art in itself. this is particularly important in the manufacture of high performance ceramics such as those used by the billions for electronics, in capacitors, inductors, sensors, etc. ) a slurry can be used in place of a powder, and then cast into a desired shape, dried and then sintered. indeed, traditional pottery is done with this type of method, using a plastic mixture worked with the hands.
. a reaction is said to be exergonic if the final state is lower on the energy scale than the initial state ; in the case of endergonic reactions the situation is the reverse. a reaction is said to be exothermic if the reaction releases heat to the surroundings ; in the case of endothermic reactions, the reaction absorbs heat from the surroundings. chemical reactions are invariably not possible unless the reactants surmount an energy barrier known as the activation energy. the speed of a chemical reaction ( at given temperature t ) is related to the activation energy e, by the boltzmann ' s population factor e β e / k t { \ displaystyle e ^ { - e / kt } } β that is the probability of a molecule to have energy greater than or equal to e at the given temperature t. this exponential dependence of a reaction rate on temperature is known as the arrhenius equation. the activation energy necessary for a chemical reaction to occur can be in the form of heat, light, electricity or mechanical force in the form of ultrasound. a related concept free energy, which also incorporates entropy considerations, is a very useful means for predicting the feasibility of a reaction and determining the state of equilibrium of a chemical reaction, in chemical thermodynamics. a reaction is feasible only if the total change in the gibbs free energy is negative, Ξ΄ g β€ 0 { \ displaystyle \ delta g \ leq 0 \, } ; if it is equal to zero the chemical reaction is said to be at equilibrium. there exist only limited possible states of energy for electrons, atoms and molecules. these are determined by the rules of quantum mechanics, which require quantization of energy of a bound system. the atoms / molecules in a higher energy state are said to be excited. the molecules / atoms of substance in an excited energy state are often much more reactive ; that is, more amenable to chemical reactions. the phase of a substance is invariably determined by its energy and the energy of its surroundings. when the intermolecular forces of a substance are such that the energy of the surroundings is not sufficient to overcome them, it occurs in a more ordered phase like liquid or solid as is the case with water ( h2o ) ; a liquid at room temperature because its molecules are bound by hydrogen bonds. whereas hydrogen sulfide ( h2s ) is a gas at room temperature and standard pressure, as its molecules are bound by weaker dipole β dipole interactions. the transfer of
is also higher at high temperature, as shown by carnot ' s theorem. in a conventional metallic engine, much of the energy released from the fuel must be dissipated as waste heat in order to prevent a meltdown of the metallic parts. despite all of these desirable properties, such engines are not in production because the manufacturing of ceramic parts in the requisite precision and durability is difficult. imperfection in the ceramic leads to cracks, which can lead to potentially dangerous equipment failure. such engines are possible in laboratory settings, but mass - production is not feasible with current technology. work is being done in developing ceramic parts for gas turbine engines. currently, even blades made of advanced metal alloys used in the engines ' hot section require cooling and careful limiting of operating temperatures. turbine engines made with ceramics could operate more efficiently, giving aircraft greater range and payload for a set amount of fuel. recently, there have been advances in ceramics which include bio - ceramics, such as dental implants and synthetic bones. hydroxyapatite, the natural mineral component of bone, has been made synthetically from a number of biological and chemical sources and can be formed into ceramic materials. orthopedic implants made from these materials bond readily to bone and other tissues in the body without rejection or inflammatory reactions. because of this, they are of great interest for gene delivery and tissue engineering scaffolds. most hydroxyapatite ceramics are very porous and lack mechanical strength and are used to coat metal orthopedic devices to aid in forming a bond to bone or as bone fillers. they are also used as fillers for orthopedic plastic screws to aid in reducing the inflammation and increase absorption of these plastic materials. work is being done to make strong, fully dense nano crystalline hydroxyapatite ceramic materials for orthopedic weight bearing devices, replacing foreign metal and plastic orthopedic materials with a synthetic, but naturally occurring, bone mineral. ultimately these ceramic materials may be used as bone replacements or with the incorporation of protein collagens, synthetic bones. durable actinide - containing ceramic materials have many applications such as in nuclear fuels for burning excess pu and in chemically - inert sources of alpha irradiation for power supply of unmanned space vehicles or to produce electricity for microelectronic devices. both use and disposal of radioactive actinides require their immobilization in a durable host material. nuclear waste long - lived radionuclides such as actinides are immobilized using chemical
material. silicon nitride parts are used in ceramic ball bearings. their higher hardness means that they are much less susceptible to wear and can offer more than triple lifetimes. they also deform less under load meaning they have less contact with the bearing retainer walls and can roll faster. in very high speed applications, heat from friction during rolling can cause problems for metal bearings ; problems which are reduced by the use of ceramics. ceramics are also more chemically resistant and can be used in wet environments where steel bearings would rust. the major drawback to using ceramics is a significantly higher cost. in many cases their electrically insulating properties may also be valuable in bearings. in the early 1980s, toyota researched production of an adiabatic ceramic engine which can run at a temperature of over 6000 Β°f ( 3300 Β°c ). ceramic engines do not require a cooling system and hence allow a major weight reduction and therefore greater fuel efficiency. fuel efficiency of the engine is also higher at high temperature, as shown by carnot ' s theorem. in a conventional metallic engine, much of the energy released from the fuel must be dissipated as waste heat in order to prevent a meltdown of the metallic parts. despite all of these desirable properties, such engines are not in production because the manufacturing of ceramic parts in the requisite precision and durability is difficult. imperfection in the ceramic leads to cracks, which can lead to potentially dangerous equipment failure. such engines are possible in laboratory settings, but mass - production is not feasible with current technology. work is being done in developing ceramic parts for gas turbine engines. currently, even blades made of advanced metal alloys used in the engines ' hot section require cooling and careful limiting of operating temperatures. turbine engines made with ceramics could operate more efficiently, giving aircraft greater range and payload for a set amount of fuel. recently, there have been advances in ceramics which include bio - ceramics, such as dental implants and synthetic bones. hydroxyapatite, the natural mineral component of bone, has been made synthetically from a number of biological and chemical sources and can be formed into ceramic materials. orthopedic implants made from these materials bond readily to bone and other tissues in the body without rejection or inflammatory reactions. because of this, they are of great interest for gene delivery and tissue engineering scaffolds. most hydroxyapatite ceramics are very porous and lack mechanical strength and are used to coat metal orthopedic devices to aid in forming a bond to bone or as bone fillers. they are
Question: Does an increase in temperature speed up or slow down reactions?
A) speed up
B) end reaction
C) slow down
D) remain the same
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A) speed up
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Context:
the extremely small probability of tunneling through an almost classical potential barrier may become not small under the action of the specially adapted non - stationary signal which selects the certain particle energy e _ r. for particle energies close to this value, the tunneling rate is not small during a finite interval of time and has a very sharp peak at the energy e _ r. after entering inside the barrier, the particle emits electromagnetic quanta and exits the barrier with a lower energy. the signal amplitude can be much less compared to the field of the static barrier. this phenomenon can be called the euclidean resonance since the under - barrier motion occurs in imaginary time. the resonance may stimulate chemical and biochemical reactions in a selective way by adapting the signal to a certain particular chemical bond. the resonance may be used in search of the soft alpha - decay for which a conventional observation is impossible due to an extremely small decay rate.
, lightning strikes, tornadoes, building fires, wildfires, and mass shootings disabling most of the system if not the entirety of it. geographic redundancy locations can be more than 621 miles ( 999 km ) continental, more than 62 miles apart and less than 93 miles ( 150 km ) apart, less than 62 miles apart, but not on the same campus, or different buildings that are more than 300 feet ( 91 m ) apart on the same campus. the following methods can reduce the risks of damage by a fire conflagration : large buildings at least 80 feet ( 24 m ) to 110 feet ( 34 m ) apart, but sometimes a minimum of 210 feet ( 64 m ) apart. : 9 high - rise buildings at least 82 feet ( 25 m ) apart : 12 open spaces clear of flammable vegetation within 200 feet ( 61 m ) on each side of objects different wings on the same building, in rooms that are separated by more than 300 feet ( 91 m ) different floors on the same wing of a building in rooms that are horizontally offset by a minimum of 70 feet ( 21 m ) with fire walls between the rooms that are on different floors two rooms separated by another room, leaving at least a 70 - foot gap between the two rooms there should be a minimum of two separated fire walls and on opposite sides of a corridor geographic redundancy is used by amazon web services ( aws ), google cloud platform ( gcp ), microsoft azure, netflix, dropbox, salesforce, linkedin, paypal, twitter, facebook, apple icloud, cisco meraki, and many others to provide geographic redundancy, high availability, fault tolerance and to ensure availability and reliability for their cloud services. as another example, to minimize risk of damage from severe windstorms or water damage, buildings can be located at least 2 miles ( 3. 2 km ) away from the shore, with an elevation of at least 5 feet ( 1. 5 m ) above sea level. for additional protection, they can be located at least 100 feet ( 30 m ) away from flood plain areas. = = functions of redundancy = = the two functions of redundancy are passive redundancy and active redundancy. both functions prevent performance decline from exceeding specification limits without human intervention using extra capacity. passive redundancy uses excess capacity to reduce the impact of component failures. one common form of passive redundancy is the extra strength of cabling and struts used in bridges.
current in passing over from one concave bank to the next on the opposite side. the lowering of such a shoal by dredging merely effects a temporary deepening, for it soon forms again from the causes which produced it. the removal, moreover, of the rocky obstructions at rapids, though increasing the depth and equalizing the flow at these places, produces a lowering of the river above the rapids by facilitating the efflux, which may result in the appearance of fresh shoals at the low stage of the river. where, however, narrow rocky reefs or other hard shoals stretch across the bottom of a river and present obstacles to the erosion by the current of the soft materials forming the bed of the river above and below, their removal may result in permanent improvement by enabling the river to deepen its bed by natural scour. the capability of a river to provide a waterway for navigation during the summer or throughout the dry season depends on the depth that can be secured in the channel at the lowest stage. the problem in the dry season is the small discharge and deficiency in scour during this period. a typical solution is to restrict the width of the low - water channel, concentrate all of the flow in it, and also to fix its position so that it is scoured out every year by the floods which follow the deepest part of the bed along the line of the strongest current. this can be effected by closing subsidiary low - water channels with dikes across them, and narrowing the channel at the low stage by low - dipping cross dikes extending from the river banks down the slope and pointing slightly up - stream so as to direct the water flowing over them into a central channel. = = estuarine works = = the needs of navigation may also require that a stable, continuous, navigable channel is prolonged from the navigable river to deep water at the mouth of the estuary. the interaction of river flow and tide needs to be modeled by computer or using scale models, moulded to the configuration of the estuary under consideration and reproducing in miniature the tidal ebb and flow and fresh - water discharge over a bed of fine sand, in which various lines of training walls can be successively inserted. the models should be capable of furnishing valuable indications of the respective effects and comparative merits of the different schemes proposed for works. = = see also = = bridge scour flood control = = references = = = = external links = = u. s. army corps of engineers β civil works program river morphology and stream restoration references
##ediment to up - stream navigation, and there are generally variations in water level, and when the discharge becomes small in the dry season. it is impossible to maintain a sufficient depth of water in the low - water channel. the possibility to secure uniformity of depth in a river by lowering the shoals obstructing the channel depends on the nature of the shoals. a soft shoal in the bed of a river is due to deposit from a diminution in velocity of flow, produced by a reduction in fall and by a widening of the channel, or to a loss in concentration of the scour of the main current in passing over from one concave bank to the next on the opposite side. the lowering of such a shoal by dredging merely effects a temporary deepening, for it soon forms again from the causes which produced it. the removal, moreover, of the rocky obstructions at rapids, though increasing the depth and equalizing the flow at these places, produces a lowering of the river above the rapids by facilitating the efflux, which may result in the appearance of fresh shoals at the low stage of the river. where, however, narrow rocky reefs or other hard shoals stretch across the bottom of a river and present obstacles to the erosion by the current of the soft materials forming the bed of the river above and below, their removal may result in permanent improvement by enabling the river to deepen its bed by natural scour. the capability of a river to provide a waterway for navigation during the summer or throughout the dry season depends on the depth that can be secured in the channel at the lowest stage. the problem in the dry season is the small discharge and deficiency in scour during this period. a typical solution is to restrict the width of the low - water channel, concentrate all of the flow in it, and also to fix its position so that it is scoured out every year by the floods which follow the deepest part of the bed along the line of the strongest current. this can be effected by closing subsidiary low - water channels with dikes across them, and narrowing the channel at the low stage by low - dipping cross dikes extending from the river banks down the slope and pointing slightly up - stream so as to direct the water flowing over them into a central channel. = = estuarine works = = the needs of navigation may also require that a stable, continuous, navigable channel is prolonged from the navigable river to deep water at the mouth of the estuary. the interaction of river
one phenomenological explanation of superluminal propagation of neutrinos, which may have been observed by opera and minos, is that neutrinos travel faster inside of matter than in vacuum. if so neutrinos exhibit refraction inside matter and should exhibit other manifestations of refraction, such as deflection and reflection. such refraction would be easily detectable through the momentum imparted to appropriately shaped refractive material inserted into the neutrino beam. for numi this could be as large as ~ 10g cm / s. if these effect were found, they would provide new ways of manipulating and detecting neutrinos. reasons why this scenario seems implausible are given, however it is still worthwhile to conduct simple searches for differential refraction of neutrinos.
for inland navigation in the lower portion of their course, as, for instance, the rhine, the danube and the mississippi. river engineering works are only required to prevent changes in the course of the stream, to regulate its depth, and especially to fix the low - water channel and concentrate the flow in it, so as to increase as far as practicable the navigable depth at the lowest stage of the water level. engineering works to increase the navigability of rivers can only be advantageously undertaken in large rivers with a moderate fall and a fair discharge at their lowest stage, for with a large fall the current presents a great impediment to up - stream navigation, and there are generally variations in water level, and when the discharge becomes small in the dry season. it is impossible to maintain a sufficient depth of water in the low - water channel. the possibility to secure uniformity of depth in a river by lowering the shoals obstructing the channel depends on the nature of the shoals. a soft shoal in the bed of a river is due to deposit from a diminution in velocity of flow, produced by a reduction in fall and by a widening of the channel, or to a loss in concentration of the scour of the main current in passing over from one concave bank to the next on the opposite side. the lowering of such a shoal by dredging merely effects a temporary deepening, for it soon forms again from the causes which produced it. the removal, moreover, of the rocky obstructions at rapids, though increasing the depth and equalizing the flow at these places, produces a lowering of the river above the rapids by facilitating the efflux, which may result in the appearance of fresh shoals at the low stage of the river. where, however, narrow rocky reefs or other hard shoals stretch across the bottom of a river and present obstacles to the erosion by the current of the soft materials forming the bed of the river above and below, their removal may result in permanent improvement by enabling the river to deepen its bed by natural scour. the capability of a river to provide a waterway for navigation during the summer or throughout the dry season depends on the depth that can be secured in the channel at the lowest stage. the problem in the dry season is the small discharge and deficiency in scour during this period. a typical solution is to restrict the width of the low - water channel, concentrate all of the flow in it, and also to fix its position so that it is
equalizing the flow at these places, produces a lowering of the river above the rapids by facilitating the efflux, which may result in the appearance of fresh shoals at the low stage of the river. where, however, narrow rocky reefs or other hard shoals stretch across the bottom of a river and present obstacles to the erosion by the current of the soft materials forming the bed of the river above and below, their removal may result in permanent improvement by enabling the river to deepen its bed by natural scour. the capability of a river to provide a waterway for navigation during the summer or throughout the dry season depends on the depth that can be secured in the channel at the lowest stage. the problem in the dry season is the small discharge and deficiency in scour during this period. a typical solution is to restrict the width of the low - water channel, concentrate all of the flow in it, and also to fix its position so that it is scoured out every year by the floods which follow the deepest part of the bed along the line of the strongest current. this can be effected by closing subsidiary low - water channels with dikes across them, and narrowing the channel at the low stage by low - dipping cross dikes extending from the river banks down the slope and pointing slightly up - stream so as to direct the water flowing over them into a central channel. = = estuarine works = = the needs of navigation may also require that a stable, continuous, navigable channel is prolonged from the navigable river to deep water at the mouth of the estuary. the interaction of river flow and tide needs to be modeled by computer or using scale models, moulded to the configuration of the estuary under consideration and reproducing in miniature the tidal ebb and flow and fresh - water discharge over a bed of fine sand, in which various lines of training walls can be successively inserted. the models should be capable of furnishing valuable indications of the respective effects and comparative merits of the different schemes proposed for works. = = see also = = bridge scour flood control = = references = = = = external links = = u. s. army corps of engineers β civil works program river morphology and stream restoration references - wildland hydrology at the library of congress web archives ( archived 2002 - 08 - 13 )
emitter rather than returning a diffuse signal detectable at many angles. the effect is sometimes called " glitter " after the very brief signal seen when the reflected beam passes across a detector. it can be difficult for the radar operator to distinguish between a glitter event and a digital glitch in the processing system. stealth airframes sometimes display distinctive serrations on some exposed edges, such as the engine ports. the yf - 23 has such serrations on the exhaust ports. this is another example in the parallel alignment of features, this time on the external airframe. the shaping requirements detracted greatly from the f - 117 ' s aerodynamic properties. it is inherently unstable, and cannot be flown without a fly - by - wire control system. similarly, coating the cockpit canopy with a thin film transparent conductor ( vapor - deposited gold or indium tin oxide ) helps to reduce the aircraft ' s radar profile, because radar waves would normally enter the cockpit, reflect off objects ( the inside of a cockpit has a complex shape, with a pilot helmet alone forming a sizeable return ), and possibly return to the radar, but the conductive coating creates a controlled shape that deflects the incoming radar waves away from the radar. the coating is thin enough that it has no adverse effect on pilot vision. = = = = ships = = = = ships have also adopted similar methods. though the earlier american arleigh burke - class destroyers incorporated some signature - reduction features. the norwegian skjold - class corvettes was the first coastal defence and the french la fayette - class frigates the first ocean - going stealth ships to enter service. other examples are the dutch de zeven provincien - class frigates, the taiwanese tuo chiang - class corvettes, german sachsen - class frigates, the swedish visby - class corvette, the american san antonio - class amphibious transport docks, and most modern warship designs. = = = materials = = = = = = = non - metallic airframe = = = = dielectric composite materials are more transparent to radar, whereas electrically conductive materials such as metals and carbon fibers reflect electromagnetic energy incident on the material ' s surface. composites may also contain ferrites to optimize the dielectric and magnetic properties of a material for its application. = = = = radar - absorbent material = = = = radiation - absorbent material ( ram ), often as paints, are used especially on the edges of metal surfaces. while the material and thickness of ram coatings can
to increase as far as practicable the navigable depth at the lowest stage of the water level. engineering works to increase the navigability of rivers can only be advantageously undertaken in large rivers with a moderate fall and a fair discharge at their lowest stage, for with a large fall the current presents a great impediment to up - stream navigation, and there are generally variations in water level, and when the discharge becomes small in the dry season. it is impossible to maintain a sufficient depth of water in the low - water channel. the possibility to secure uniformity of depth in a river by lowering the shoals obstructing the channel depends on the nature of the shoals. a soft shoal in the bed of a river is due to deposit from a diminution in velocity of flow, produced by a reduction in fall and by a widening of the channel, or to a loss in concentration of the scour of the main current in passing over from one concave bank to the next on the opposite side. the lowering of such a shoal by dredging merely effects a temporary deepening, for it soon forms again from the causes which produced it. the removal, moreover, of the rocky obstructions at rapids, though increasing the depth and equalizing the flow at these places, produces a lowering of the river above the rapids by facilitating the efflux, which may result in the appearance of fresh shoals at the low stage of the river. where, however, narrow rocky reefs or other hard shoals stretch across the bottom of a river and present obstacles to the erosion by the current of the soft materials forming the bed of the river above and below, their removal may result in permanent improvement by enabling the river to deepen its bed by natural scour. the capability of a river to provide a waterway for navigation during the summer or throughout the dry season depends on the depth that can be secured in the channel at the lowest stage. the problem in the dry season is the small discharge and deficiency in scour during this period. a typical solution is to restrict the width of the low - water channel, concentrate all of the flow in it, and also to fix its position so that it is scoured out every year by the floods which follow the deepest part of the bed along the line of the strongest current. this can be effected by closing subsidiary low - water channels with dikes across them, and narrowing the channel at the low stage by low - dipping cross dikes extending from the river banks down the
when fast radio burst ( frb ) waves propagate through the local ( < 1 pc ) environment of the frb source, electrons in the plasma undergo large - amplitude oscillations. the finite - amplitude effects cause the effective plasma frequency and cyclotron frequency to be dependent on the wave strength. the dispersion measure and rotation measure should therefore vary slightly from burst to burst for a repeating source, depending on the luminosity and frequency of the individual burst. furthermore, free - free absorption of strong waves is suppressed due to the accelerated electrons ' reduced energy exchange in coulomb collisions. this allows bright low - frequency bursts to propagate through an environment that would be optically thick to low - amplitude waves. given a large sample of bursts from a repeating source, it would be possible to use the deficit of low - frequency and low - luminosity bursts to infer the emission measure of the local intervening plasma and its distance from the source. information about the local environment will shed light on the nature of frb sources.
Question: An obstacle or opening that is shorter than the wavelength causes greater diffraction of what?
A) waves
B) particles
C) ranges
D) tides
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A) waves
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Context:
three of what is called the six simple machines, from which all machines are based. these machines are the inclined plane, the wedge, and the lever, which allowed the ancient egyptians to move millions of limestone blocks which weighed approximately 3. 5 tons ( 7, 000 lbs. ) each into place to create structures like the great pyramid of giza, which is 481 feet ( 147 meters ) high. they also made writing medium similar to paper from papyrus, which joshua mark states is the foundation for modern paper. papyrus is a plant ( cyperus papyrus ) which grew in plentiful amounts in the egyptian delta and throughout the nile river valley during ancient times. the papyrus was harvested by field workers and brought to processing centers where it was cut into thin strips. the strips were then laid - out side by side and covered in plant resin. the second layer of strips was laid on perpendicularly, then both pressed together until the sheet was dry. the sheets were then joined to form a roll and later used for writing. egyptian society made several significant advances during dynastic periods in many areas of technology. according to hossam elanzeery, they were the first civilization to use timekeeping devices such as sundials, shadow clocks, and obelisks and successfully leveraged their knowledge of astronomy to create a calendar model that society still uses today. they developed shipbuilding technology that saw them progress from papyrus reed vessels to cedar wood ships while also pioneering the use of rope trusses and stem - mounted rudders. the egyptians also used their knowledge of anatomy to lay the foundation for many modern medical techniques and practiced the earliest known version of neuroscience. elanzeery also states that they used and furthered mathematical science, as evidenced in the building of the pyramids. ancient egyptians also invented and pioneered many food technologies that have become the basis of modern food technology processes. based on paintings and reliefs found in tombs, as well as archaeological artifacts, scholars like paul t nicholson believe that the ancient egyptians established systematic farming practices, engaged in cereal processing, brewed beer and baked bread, processed meat, practiced viticulture and created the basis for modern wine production, and created condiments to complement, preserve and mask the flavors of their food. = = = = indus valley = = = = the indus valley civilization, situated in a resource - rich area ( in modern pakistan and northwestern india ), is notable for its early application of city planning, sanitation technologies, and plumbing. indus valley construction and architecture, called ' vaastu
reference to recent papers and experimental feasibility are added. the paper will not be published in a hard - copy journal.
some references for the breaking strength of fused silica fibers compiled in 1999.
symbiotic and syntrophic communities, for example. = = = eukaryotes = = = eukaryotes are hypothesized to have split from archaea, which was followed by their endosymbioses with bacteria ( or symbiogenesis ) that gave rise to mitochondria and chloroplasts, both of which are now part of modern - day eukaryotic cells. the major lineages of eukaryotes diversified in the precambrian about 1. 5 billion years ago and can be classified into eight major clades : alveolates, excavates, stramenopiles, plants, rhizarians, amoebozoans, fungi, and animals. five of these clades are collectively known as protists, which are mostly microscopic eukaryotic organisms that are not plants, fungi, or animals. while it is likely that protists share a common ancestor ( the last eukaryotic common ancestor ), protists by themselves do not constitute a separate clade as some protists may be more closely related to plants, fungi, or animals than they are to other protists. like groupings such as algae, invertebrates, or protozoans, the protist grouping is not a formal taxonomic group but is used for convenience. most protists are unicellular ; these are called microbial eukaryotes. plants are mainly multicellular organisms, predominantly photosynthetic eukaryotes of the kingdom plantae, which would exclude fungi and some algae. plant cells were derived by endosymbiosis of a cyanobacterium into an early eukaryote about one billion years ago, which gave rise to chloroplasts. the first several clades that emerged following primary endosymbiosis were aquatic and most of the aquatic photosynthetic eukaryotic organisms are collectively described as algae, which is a term of convenience as not all algae are closely related. algae comprise several distinct clades such as glaucophytes, which are microscopic freshwater algae that may have resembled in form to the early unicellular ancestor of plantae. unlike glaucophytes, the other algal clades such as red and green algae are multicellular. green algae comprise three major clades : chlorophytes, coleochaetophytes, and stoneworts. fungi are eukaryotes that
with one allele inducing a change on the other. = = plant evolution = = the chloroplasts of plants have a number of biochemical, structural and genetic similarities to cyanobacteria, ( commonly but incorrectly known as " blue - green algae " ) and are thought to be derived from an ancient endosymbiotic relationship between an ancestral eukaryotic cell and a cyanobacterial resident. the algae are a polyphyletic group and are placed in various divisions, some more closely related to plants than others. there are many differences between them in features such as cell wall composition, biochemistry, pigmentation, chloroplast structure and nutrient reserves. the algal division charophyta, sister to the green algal division chlorophyta, is considered to contain the ancestor of true plants. the charophyte class charophyceae and the land plant sub - kingdom embryophyta together form the monophyletic group or clade streptophytina. nonvascular land plants are embryophytes that lack the vascular tissues xylem and phloem. they include mosses, liverworts and hornworts. pteridophytic vascular plants with true xylem and phloem that reproduced by spores germinating into free - living gametophytes evolved during the silurian period and diversified into several lineages during the late silurian and early devonian. representatives of the lycopods have survived to the present day. by the end of the devonian period, several groups, including the lycopods, sphenophylls and progymnosperms, had independently evolved " megaspory " β their spores were of two distinct sizes, larger megaspores and smaller microspores. their reduced gametophytes developed from megaspores retained within the spore - producing organs ( megasporangia ) of the sporophyte, a condition known as endospory. seeds consist of an endosporic megasporangium surrounded by one or two sheathing layers ( integuments ). the young sporophyte develops within the seed, which on germination splits to release it. the earliest known seed plants date from the latest devonian famennian stage. following the evolution of the seed habit, seed plants diversified, giving rise to a number of now - extinct groups, including seed ferns, as well as the modern gym
maya were great, even by today ' s standards. an example of this exceptional engineering is the use of pieces weighing upwards of one ton in their stonework placed together so that not even a blade can fit into the cracks. inca villages used irrigation canals and drainage systems, making agriculture very efficient. while some claim that the incas were the first inventors of hydroponics, their agricultural technology was still soil based, if advanced. though the maya civilization did not incorporate metallurgy or wheel technology in their architectural constructions, they developed complex writing and astronomical systems, and created beautiful sculptural works in stone and flint. like the inca, the maya also had command of fairly advanced agricultural and construction technology. the maya are also responsible for creating the first pressurized water system in mesoamerica, located in the maya site of palenque. the main contribution of the aztec rule was a system of communications between the conquered cities and the ubiquity of the ingenious agricultural technology of chinampas. in mesoamerica, without draft animals for transport ( nor, as a result, wheeled vehicles ), the roads were designed for travel on foot, just as in the inca and mayan civilizations. the aztec, subsequently to the maya, inherited many of the technologies and intellectual advancements of their predecessors : the olmec ( see native american inventions and innovations ). = = = medieval to early modern = = = one of the most significant developments of the medieval were economies in which water and wind power were more significant than animal and human muscle power. : 38 most water and wind power was used for milling grain. water power was also used for blowing air in blast furnace, pulping rags for paper making and for felting wool. the domesday book recorded 5, 624 water mills in great britain in 1086, being about one per thirty families. = = = = east asia = = = = = = = = indian subcontinent = = = = = = = = islamic world = = = = the muslim caliphates united in trade large areas that had previously traded little, including the middle east, north africa, central asia, the iberian peninsula, and parts of the indian subcontinent. the science and technology of previous empires in the region, including the mesopotamian, egyptian, persian, hellenistic and roman empires, were inherited by the muslim world, where arabic replaced syriac, persian and greek as the lingua franca of the region. significant advances were made in the region during the islamic golden age ( 8th β 16th centuries
inflammatory reactions. because of this, they are of great interest for gene delivery and tissue engineering scaffolds. most hydroxyapatite ceramics are very porous and lack mechanical strength and are used to coat metal orthopedic devices to aid in forming a bond to bone or as bone fillers. they are also used as fillers for orthopedic plastic screws to aid in reducing the inflammation and increase absorption of these plastic materials. work is being done to make strong, fully dense nano crystalline hydroxyapatite ceramic materials for orthopedic weight bearing devices, replacing foreign metal and plastic orthopedic materials with a synthetic, but naturally occurring, bone mineral. ultimately these ceramic materials may be used as bone replacements or with the incorporation of protein collagens, synthetic bones. durable actinide - containing ceramic materials have many applications such as in nuclear fuels for burning excess pu and in chemically - inert sources of alpha irradiation for power supply of unmanned space vehicles or to produce electricity for microelectronic devices. both use and disposal of radioactive actinides require their immobilization in a durable host material. nuclear waste long - lived radionuclides such as actinides are immobilized using chemically - durable crystalline materials based on polycrystalline ceramics and large single crystals. alumina ceramics are widely utilized in the chemical industry due to their excellent chemical stability and high resistance to corrosion. it is used as acid - resistant pump impellers and pump bodies, ensuring long - lasting performance in transferring aggressive fluids. they are also used in acid - carrying pipe linings to prevent contamination and maintain fluid purity, which is crucial in industries like pharmaceuticals and food processing. valves made from alumina ceramics demonstrate exceptional durability and resistance to chemical attack, making them reliable for controlling the flow of corrosive liquids. = = glass - ceramics = = glass - ceramic materials share many properties with both glasses and ceramics. glass - ceramics have an amorphous phase and one or more crystalline phases and are produced by a so - called " controlled crystallization ", which is typically avoided in glass manufacturing. glass - ceramics often contain a crystalline phase which constitutes anywhere from 30 % [ m / m ] to 90 % [ m / m ] of its composition by volume, yielding an array of materials with interesting thermomechanical properties. in the processing of glass - ceramics, molten glass is cooled down gradually before reheating and annealing. in this heat
required. for example, certain cells respond to changes in oxygen tension as part of their normal development, such as chondrocytes, which must adapt to low oxygen conditions or hypoxia during skeletal development. others, such as endothelial cells, respond to shear stress from fluid flow, which is encountered in blood vessels. mechanical stimuli, such as pressure pulses seem to be beneficial to all kind of cardiovascular tissue such as heart valves, blood vessels or pericardium. = = = bioreactors = = = in tissue engineering, a bioreactor is a device that attempts to simulate a physiological environment in order to promote cell or tissue growth in vitro. a physiological environment can consist of many different parameters such as temperature, pressure, oxygen or carbon dioxide concentration, or osmolality of fluid environment, and it can extend to all kinds of biological, chemical or mechanical stimuli. therefore, there are systems that may include the application of forces such as electromagnetic forces, mechanical pressures, or fluid pressures to the tissue. these systems can be two - or three - dimensional setups. bioreactors can be used in both academic and industry applications. general - use and application - specific bioreactors are also commercially available, which may provide static chemical stimulation or a combination of chemical and mechanical stimulation. cell proliferation and differentiation are largely influenced by mechanical and biochemical cues in the surrounding extracellular matrix environment. bioreactors are typically developed to replicate the specific physiological environment of the tissue being grown ( e. g., flex and fluid shearing for heart tissue growth ). this can allow specialized cell lines to thrive in cultures replicating their native environments, but it also makes bioreactors attractive tools for culturing stem cells. a successful stem - cell - based bioreactor is effective at expanding stem cells with uniform properties and / or promoting controlled, reproducible differentiation into selected mature cell types. there are a variety of bioreactors designed for 3d cell cultures. there are small plastic cylindrical chambers, as well as glass chambers, with regulated internal humidity and moisture specifically engineered for the purpose of growing cells in three dimensions. the bioreactor uses bioactive synthetic materials such as polyethylene terephthalate membranes to surround the spheroid cells in an environment that maintains high levels of nutrients. they are easy to open and close, so that cell spheroids can be removed for testing, yet the chamber is able to maintain 100 % humidity throughout. this humidity is important to achieve maximum cell growth and function. the
given invariant percolation on a regular tree, where the probability of an edge to be open equals $ p $, is it always possible to find an infinite self - avoiding path along which the density of open edges is bigger then $ p $?
onset of electro - chemical corrosion. similar problems are encountered in coastal and offshore structures. = = = anti - fouling = = = anti - fouling is the process of eliminating obstructive organisms from essential components of seawater systems. depending on the nature and location of marine growth, this process is performed in a number of different ways : marine organisms may grow and attach to the surfaces of the outboard suction inlets used to obtain water for cooling systems. electro - chlorination involves running high electrical current through sea water, altering the water ' s chemical composition to create sodium hypochlorite, purging any bio - matter. an electrolytic method of anti - fouling involves running electrical current through two anodes ( scardino, 2009 ). these anodes typically consist of copper and aluminum ( or alternatively, iron ). the first metal, copper anode, releases its ion into the water, creating an environment that is too toxic for bio - matter. the second metal, aluminum, coats the inside of the pipes to prevent corrosion. other forms of marine growth such as mussels and algae may attach themselves to the bottom of a ship ' s hull. this growth interferes with the smoothness and uniformity of the ship ' s hull, causing the ship to have a less hydrodynamic shape that causes it to be slower and less fuel - efficient. marine growth on the hull can be remedied by using special paint that prevents the growth of such organisms. = = = pollution control = = = = = = = sulfur emission = = = = the burning of marine fuels releases harmful pollutants into the atmosphere. ships burn marine diesel in addition to heavy fuel oil. heavy fuel oil, being the heaviest of refined oils, releases sulfur dioxide when burned. sulfur dioxide emissions have the potential to raise atmospheric and ocean acidity causing harm to marine life. however, heavy fuel oil may only be burned in international waters due to the pollution created. it is commercially advantageous due to the cost effectiveness compared to other marine fuels. it is prospected that heavy fuel oil will be phased out of commercial use by the year 2020 ( smith, 2018 ). = = = = oil and water discharge = = = = water, oil, and other substances collect at the bottom of the ship in what is known as the bilge. bilge water is pumped overboard, but must pass a pollution threshold test of 15 ppm ( parts per million ) of oil to be discharged. water is tested
Question: Corals build hard exoskeletons that grow to become coral what?
A) beds
B) crystals
C) reefs
D) layers
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C) reefs
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g. spectroscopy and chromatography. scientists engaged in chemical research are known as chemists. most chemists specialize in one or more sub - disciplines. several concepts are essential for the study of chemistry ; some of them are : = = = matter = = = in chemistry, matter is defined as anything that has rest mass and volume ( it takes up space ) and is made up of particles. the particles that make up matter have rest mass as well β not all particles have rest mass, such as the photon. matter can be a pure chemical substance or a mixture of substances. = = = = atom = = = = the atom is the basic unit of chemistry. it consists of a dense core called the atomic nucleus surrounded by a space occupied by an electron cloud. the nucleus is made up of positively charged protons and uncharged neutrons ( together called nucleons ), while the electron cloud consists of negatively charged electrons which orbit the nucleus. in a neutral atom, the negatively charged electrons balance out the positive charge of the protons. the nucleus is dense ; the mass of a nucleon is approximately 1, 836 times that of an electron, yet the radius of an atom is about 10, 000 times that of its nucleus. the atom is also the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state ( s ), coordination number, and preferred types of bonds to form ( e. g., metallic, ionic, covalent ). = = = = element = = = = a chemical element is a pure substance which is composed of a single type of atom, characterized by its particular number of protons in the nuclei of its atoms, known as the atomic number and represented by the symbol z. the mass number is the sum of the number of protons and neutrons in a nucleus. although all the nuclei of all atoms belonging to one element will have the same atomic number, they may not necessarily have the same mass number ; atoms of an element which have different mass numbers are known as isotopes. for example, all atoms with 6 protons in their nuclei are atoms of the chemical element carbon, but atoms of carbon may have mass numbers of 12 or 13. the standard presentation of the chemical elements is in the periodic table, which orders elements by atomic number. the periodic table is arranged in groups, or columns, and periods, or rows. the periodic table is useful in identifying periodic trends
the thickness and the density of the material to be measured. the method is used for containers of liquids or of grainy substances thickness gauges : if the material is of constant density, the signal measured by the radiation detector depends on the thickness of the material. this is useful for continuous production, like of paper, rubber, etc. electrostatic control - to avoid the build - up of static electricity in production of paper, plastics, synthetic textiles, etc., a ribbon - shaped source of the alpha emitter 241am can be placed close to the material at the end of the production line. the source ionizes the air to remove electric charges on the material. radioactive tracers - since radioactive isotopes behave, chemically, mostly like the inactive element, the behavior of a certain chemical substance can be followed by tracing the radioactivity. examples : adding a gamma tracer to a gas or liquid in a closed system makes it possible to find a hole in a tube. adding a tracer to the surface of the component of a motor makes it possible to measure wear by measuring the activity of the lubricating oil. oil and gas exploration - nuclear well logging is used to help predict the commercial viability of new or existing wells. the technology involves the use of a neutron or gamma - ray source and a radiation detector which are lowered into boreholes to determine the properties of the surrounding rock such as porosity and lithography. [ 1 ] road construction - nuclear moisture / density gauges are used to determine the density of soils, asphalt, and concrete. typically a cesium - 137 source is used. = = = commercial applications = = = radioluminescence tritium illumination : tritium is used with phosphor in rifle sights to increase nighttime firing accuracy. some runway markers and building exit signs use the same technology, to remain illuminated during blackouts. betavoltaics. smoke detector : an ionization smoke detector includes a tiny mass of radioactive americium - 241, which is a source of alpha radiation. two ionisation chambers are placed next to each other. both contain a small source of 241am that gives rise to a small constant current. one is closed and serves for comparison, the other is open to ambient air ; it has a gridded electrode. when smoke enters the open chamber, the current is disrupted as the smoke particles attach to the charged ions and restore them to a neutral electrical state. this reduces the current in the open chamber. when the current drops below a certain threshold, the
the walls of a victim ' s stomach. toxicology, a subfield of forensic chemistry, focuses on detecting and identifying drugs, poisons, and other toxic substances in biological samples. forensic toxicologists work on cases involving drug overdoses, poisoning, and substance abuse. their work is critical in determining whether harmful substances play a role in a person β s death or impairment. read more james marsh was the first to apply this new science to the art of forensics. he was called by the prosecution in a murder trial to give evidence as a chemist in 1832. the defendant, john bodle, was accused of poisoning his grandfather with arsenic - laced coffee. marsh performed the standard test by mixing a suspected sample with hydrogen sulfide and hydrochloric acid. while he was able to detect arsenic as yellow arsenic trisulfide, when it was shown to the jury it had deteriorated, allowing the suspect to be acquitted due to reasonable doubt. annoyed by that, marsh developed a much better test. he combined a sample containing arsenic with sulfuric acid and arsenic - free zinc, resulting in arsine gas. the gas was ignited, and it decomposed to pure metallic arsenic, which, when passed to a cold surface, would appear as a silvery - black deposit. so sensitive was the test, known formally as the marsh test, that it could detect as little as one - fiftieth of a milligram of arsenic. he first described this test in the edinburgh philosophical journal in 1836. = = = ballistics and firearms = = = ballistics is " the science of the motion of projectiles in flight ". in forensic science, analysts examine the patterns left on bullets and cartridge casings after being ejected from a weapon. when fired, a bullet is left with indentations and markings that are unique to the barrel and firing pin of the firearm that ejected the bullet. this examination can help scientists identify possible makes and models of weapons connected to a crime. henry goddard at scotland yard pioneered the use of bullet comparison in 1835. he noticed a flaw in the bullet that killed the victim and was able to trace this back to the mold that was used in the manufacturing process. = = = anthropometry = = = the french police officer alphonse bertillon was the first to apply the anthropological technique of anthropometry to law enforcement, thereby creating an identification system based on physical measurements. before that time, criminals could be identified only by name or photograph. dissatisfied with the ad hoc methods used to identify captured
modifying the nervous system. nuclear chemistry is the study of how subatomic particles come together and make nuclei. modern transmutation is a large component of nuclear chemistry, and the table of nuclides is an important result and tool for this field. in addition to medical applications, nuclear chemistry encompasses nuclear engineering which explores the topic of using nuclear power sources for generating energy. organic chemistry is the study of the structure, properties, composition, mechanisms, and reactions of organic compounds. an organic compound is defined as any compound based on a carbon skeleton. organic compounds can be classified, organized and understood in reactions by their functional groups, unit atoms or molecules that show characteristic chemical properties in a compound. physical chemistry is the study of the physical and fundamental basis of chemical systems and processes. in particular, the energetics and dynamics of such systems and processes are of interest to physical chemists. important areas of study include chemical thermodynamics, chemical kinetics, electrochemistry, statistical mechanics, spectroscopy, and more recently, astrochemistry. physical chemistry has large overlap with molecular physics. physical chemistry involves the use of infinitesimal calculus in deriving equations. it is usually associated with quantum chemistry and theoretical chemistry. physical chemistry is a distinct discipline from chemical physics, but again, there is very strong overlap. theoretical chemistry is the study of chemistry via fundamental theoretical reasoning ( usually within mathematics or physics ). in particular the application of quantum mechanics to chemistry is called quantum chemistry. since the end of the second world war, the development of computers has allowed a systematic development of computational chemistry, which is the art of developing and applying computer programs for solving chemical problems. theoretical chemistry has large overlap with ( theoretical and experimental ) condensed matter physics and molecular physics. other subdivisions include electrochemistry, femtochemistry, flavor chemistry, flow chemistry, immunohistochemistry, hydrogenation chemistry, mathematical chemistry, molecular mechanics, natural product chemistry, organometallic chemistry, petrochemistry, photochemistry, physical organic chemistry, polymer chemistry, radiochemistry, sonochemistry, supramolecular chemistry, synthetic chemistry, and many others. = = = interdisciplinary = = = interdisciplinary fields include agrochemistry, astrochemistry ( and cosmochemistry ), atmospheric chemistry, chemical engineering, chemical biology, chemo - informatics, environmental chemistry, geochemistry, green chemistry, immunochemistry, marine chemistry, materials science, mechanochemistry, medicinal chemistry, molecular biology,
, calorimetry, nuclear microscopy ( hefib ), rutherford backscattering, neutron diffraction, small - angle x - ray scattering ( saxs ), etc. ). besides material characterization, the material scientist or engineer also deals with extracting materials and converting them into useful forms. thus ingot casting, foundry methods, blast furnace extraction, and electrolytic extraction are all part of the required knowledge of a materials engineer. often the presence, absence, or variation of minute quantities of secondary elements and compounds in a bulk material will greatly affect the final properties of the materials produced. for example, steels are classified based on 1 / 10 and 1 / 100 weight percentages of the carbon and other alloying elements they contain. thus, the extracting and purifying methods used to extract iron in a blast furnace can affect the quality of steel that is produced. solid materials are generally grouped into three basic classifications : ceramics, metals, and polymers. this broad classification is based on the empirical makeup and atomic structure of the solid materials, and most solids fall into one of these broad categories. an item that is often made from each of these materials types is the beverage container. the material types used for beverage containers accordingly provide different advantages and disadvantages, depending on the material used. ceramic ( glass ) containers are optically transparent, impervious to the passage of carbon dioxide, relatively inexpensive, and are easily recycled, but are also heavy and fracture easily. metal ( aluminum alloy ) is relatively strong, is a good barrier to the diffusion of carbon dioxide, and is easily recycled. however, the cans are opaque, expensive to produce, and are easily dented and punctured. polymers ( polyethylene plastic ) are relatively strong, can be optically transparent, are inexpensive and lightweight, and can be recyclable, but are not as impervious to the passage of carbon dioxide as aluminum and glass. = = = ceramics and glasses = = = another application of materials science is the study of ceramics and glasses, typically the most brittle materials with industrial relevance. many ceramics and glasses exhibit covalent or ionic - covalent bonding with sio2 ( silica ) as a fundamental building block. ceramics β not to be confused with raw, unfired clay β are usually seen in crystalline form. the vast majority of commercial glasses contain a metal oxide fused with silica. at the high temperatures used to prepare glass, the material is a viscous liquid which solidifies into a disordered state upon
casting, foundry methods, blast furnace extraction, and electrolytic extraction are all part of the required knowledge of a materials engineer. often the presence, absence, or variation of minute quantities of secondary elements and compounds in a bulk material will greatly affect the final properties of the materials produced. for example, steels are classified based on 1 / 10 and 1 / 100 weight percentages of the carbon and other alloying elements they contain. thus, the extracting and purifying methods used to extract iron in a blast furnace can affect the quality of steel that is produced. solid materials are generally grouped into three basic classifications : ceramics, metals, and polymers. this broad classification is based on the empirical makeup and atomic structure of the solid materials, and most solids fall into one of these broad categories. an item that is often made from each of these materials types is the beverage container. the material types used for beverage containers accordingly provide different advantages and disadvantages, depending on the material used. ceramic ( glass ) containers are optically transparent, impervious to the passage of carbon dioxide, relatively inexpensive, and are easily recycled, but are also heavy and fracture easily. metal ( aluminum alloy ) is relatively strong, is a good barrier to the diffusion of carbon dioxide, and is easily recycled. however, the cans are opaque, expensive to produce, and are easily dented and punctured. polymers ( polyethylene plastic ) are relatively strong, can be optically transparent, are inexpensive and lightweight, and can be recyclable, but are not as impervious to the passage of carbon dioxide as aluminum and glass. = = = ceramics and glasses = = = another application of materials science is the study of ceramics and glasses, typically the most brittle materials with industrial relevance. many ceramics and glasses exhibit covalent or ionic - covalent bonding with sio2 ( silica ) as a fundamental building block. ceramics β not to be confused with raw, unfired clay β are usually seen in crystalline form. the vast majority of commercial glasses contain a metal oxide fused with silica. at the high temperatures used to prepare glass, the material is a viscous liquid which solidifies into a disordered state upon cooling. windowpanes and eyeglasses are important examples. fibers of glass are also used for long - range telecommunication and optical transmission. scratch resistant corning gorilla glass is a well - known example of the application of materials science to drastically improve the properties of common components. engineering ceramics are known for their stiffness and
these samples by using specific research instruments. the instruments used for data collection must be valid and reliable. analysis of data : involves breaking down the individual pieces of data to draw conclusions about it. data interpretation : this can be represented through tables, figures, and pictures, and then described in words. test, revising of hypothesis conclusion, reiteration if necessary a common misconception is that a hypothesis will be proven ( see, rather, null hypothesis ). generally, a hypothesis is used to make predictions that can be tested by observing the outcome of an experiment. if the outcome is inconsistent with the hypothesis, then the hypothesis is rejected ( see falsifiability ). however, if the outcome is consistent with the hypothesis, the experiment is said to support the hypothesis. this careful language is used because researchers recognize that alternative hypotheses may also be consistent with the observations. in this sense, a hypothesis can never be proven, but rather only supported by surviving rounds of scientific testing and, eventually, becoming widely thought of as true. a useful hypothesis allows prediction and within the accuracy of observation of the time, the prediction will be verified. as the accuracy of observation improves with time, the hypothesis may no longer provide an accurate prediction. in this case, a new hypothesis will arise to challenge the old, and to the extent that the new hypothesis makes more accurate predictions than the old, the new will supplant it. researchers can also use a null hypothesis, which states no relationship or difference between the independent or dependent variables. = = = research in the humanities = = = research in the humanities involves different methods such as for example hermeneutics and semiotics. humanities scholars usually do not search for the ultimate correct answer to a question, but instead, explore the issues and details that surround it. context is always important, and context can be social, historical, political, cultural, or ethnic. an example of research in the humanities is historical research, which is embodied in historical method. historians use primary sources and other evidence to systematically investigate a topic, and then to write histories in the form of accounts of the past. other studies aim to merely examine the occurrence of behaviours in societies and communities, without particularly looking for reasons or motivations to explain these. these studies may be qualitative or quantitative, and can use a variety of approaches, such as queer theory or feminist theory. = = = artistic research = = = artistic research, also seen as ' practice - based research ', can take form when
frequent itemsets form a polytope and can be found and analyzed with linear programming.
of measuring methods. x - rays and gamma rays are used in industrial radiography to make images of the inside of solid products, as a means of nondestructive testing and inspection. the piece to be radiographed is placed between the source and a photographic film in a cassette. after a certain exposure time, the film is developed and it shows any internal defects of the material. gauges - gauges use the exponential absorption law of gamma rays level indicators : source and detector are placed at opposite sides of a container, indicating the presence or absence of material in the horizontal radiation path. beta or gamma sources are used, depending on the thickness and the density of the material to be measured. the method is used for containers of liquids or of grainy substances thickness gauges : if the material is of constant density, the signal measured by the radiation detector depends on the thickness of the material. this is useful for continuous production, like of paper, rubber, etc. electrostatic control - to avoid the build - up of static electricity in production of paper, plastics, synthetic textiles, etc., a ribbon - shaped source of the alpha emitter 241am can be placed close to the material at the end of the production line. the source ionizes the air to remove electric charges on the material. radioactive tracers - since radioactive isotopes behave, chemically, mostly like the inactive element, the behavior of a certain chemical substance can be followed by tracing the radioactivity. examples : adding a gamma tracer to a gas or liquid in a closed system makes it possible to find a hole in a tube. adding a tracer to the surface of the component of a motor makes it possible to measure wear by measuring the activity of the lubricating oil. oil and gas exploration - nuclear well logging is used to help predict the commercial viability of new or existing wells. the technology involves the use of a neutron or gamma - ray source and a radiation detector which are lowered into boreholes to determine the properties of the surrounding rock such as porosity and lithography. [ 1 ] road construction - nuclear moisture / density gauges are used to determine the density of soils, asphalt, and concrete. typically a cesium - 137 source is used. = = = commercial applications = = = radioluminescence tritium illumination : tritium is used with phosphor in rifle sights to increase nighttime firing accuracy. some runway markers and building exit signs use the same technology, to remain illuminated during blackouts. betavoltaics
( create a critical mass ) for detonation. it also is quite difficult to ensure that such a chain reaction consumes a significant fraction of the fuel before the device flies apart. the procurement of a nuclear fuel is also more difficult than it might seem, since sufficiently unstable substances for this process do not currently occur naturally on earth in suitable amounts. one isotope of uranium, namely uranium - 235, is naturally occurring and sufficiently unstable, but it is always found mixed with the more stable isotope uranium - 238. the latter accounts for more than 99 % of the weight of natural uranium. therefore, some method of isotope separation based on the weight of three neutrons must be performed to enrich ( isolate ) uranium - 235. alternatively, the element plutonium possesses an isotope that is sufficiently unstable for this process to be usable. terrestrial plutonium does not currently occur naturally in sufficient quantities for such use, so it must be manufactured in a nuclear reactor. ultimately, the manhattan project manufactured nuclear weapons based on each of these elements. they detonated the first nuclear weapon in a test code - named " trinity ", near alamogordo, new mexico, on july 16, 1945. the test was conducted to ensure that the implosion method of detonation would work, which it did. a uranium bomb, little boy, was dropped on the japanese city hiroshima on august 6, 1945, followed three days later by the plutonium - based fat man on nagasaki. in the wake of unprecedented devastation and casualties from a single weapon, the japanese government soon surrendered, ending world war ii. since these bombings, no nuclear weapons have been deployed offensively. nevertheless, they prompted an arms race to develop increasingly destructive bombs to provide a nuclear deterrent. just over four years later, on august 29, 1949, the soviet union detonated its first fission weapon. the united kingdom followed on october 2, 1952 ; france, on february 13, 1960 ; and china component to a nuclear weapon. approximately half of the deaths from hiroshima and nagasaki died two to five years afterward from radiation exposure. a radiological weapon is a type of nuclear weapon designed to distribute hazardous nuclear material in enemy areas. such a weapon would not have the explosive capability of a fission or fusion bomb, but would kill many people and contaminate a large area. a radiological weapon has never been deployed. while considered useless by a conventional military, such a weapon raises concerns over nuclear terrorism. there have been over 2, 000 nuclear tests conducted since 1945. in 1963, all nuclear and many non -
Question: What is the name of the procedure where an unknown compound can be analyzed in the laboratory in order to determine the percentages of each element contained within it?
A) gaseous analysis
B) elemental analysis
C) electrical analysis
D) chemical analysis
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B) elemental analysis
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Context:
cytokinesis. this can occur early in development to produce an autopolyploid or partly autopolyploid organism, or during normal processes of cellular differentiation to produce some cell types that are polyploid ( endopolyploidy ), or during gamete formation. an allopolyploid plant may result from a hybridisation event between two different species. both autopolyploid and allopolyploid plants can often reproduce normally, but may be unable to cross - breed successfully with the parent population because there is a mismatch in chromosome numbers. these plants that are reproductively isolated from the parent species but live within the same geographical area, may be sufficiently successful to form a new species. some otherwise sterile plant polyploids can still reproduce vegetatively or by seed apomixis, forming clonal populations of identical individuals. durum wheat is a fertile tetraploid allopolyploid, while bread wheat is a fertile hexaploid. the commercial banana is an example of a sterile, seedless triploid hybrid. common dandelion is a triploid that produces viable seeds by apomictic seed. as in other eukaryotes, the inheritance of endosymbiotic organelles like mitochondria and chloroplasts in plants is non - mendelian. chloroplasts are inherited through the male parent in gymnosperms but often through the female parent in flowering plants. = = = molecular genetics = = = a considerable amount of new knowledge about plant function comes from studies of the molecular genetics of model plants such as the thale cress, arabidopsis thaliana, a weedy species in the mustard family ( brassicaceae ). the genome or hereditary information contained in the genes of this species is encoded by about 135 million base pairs of dna, forming one of the smallest genomes among flowering plants. arabidopsis was the first plant to have its genome sequenced, in 2000. the sequencing of some other relatively small genomes, of rice ( oryza sativa ) and brachypodium distachyon, has made them important model species for understanding the genetics, cellular and molecular biology of cereals, grasses and monocots generally. model plants such as arabidopsis thaliana are used for studying the molecular biology of plant cells and the chloroplast. ideally, these organisms have small genomes that are well known or completely sequenced, small stature and short
of several types of apomixis that occur in plants. apomixis can also happen in a seed, producing a seed that contains an embryo genetically identical to the parent. most sexually reproducing organisms are diploid, with paired chromosomes, but doubling of their chromosome number may occur due to errors in cytokinesis. this can occur early in development to produce an autopolyploid or partly autopolyploid organism, or during normal processes of cellular differentiation to produce some cell types that are polyploid ( endopolyploidy ), or during gamete formation. an allopolyploid plant may result from a hybridisation event between two different species. both autopolyploid and allopolyploid plants can often reproduce normally, but may be unable to cross - breed successfully with the parent population because there is a mismatch in chromosome numbers. these plants that are reproductively isolated from the parent species but live within the same geographical area, may be sufficiently successful to form a new species. some otherwise sterile plant polyploids can still reproduce vegetatively or by seed apomixis, forming clonal populations of identical individuals. durum wheat is a fertile tetraploid allopolyploid, while bread wheat is a fertile hexaploid. the commercial banana is an example of a sterile, seedless triploid hybrid. common dandelion is a triploid that produces viable seeds by apomictic seed. as in other eukaryotes, the inheritance of endosymbiotic organelles like mitochondria and chloroplasts in plants is non - mendelian. chloroplasts are inherited through the male parent in gymnosperms but often through the female parent in flowering plants. = = = molecular genetics = = = a considerable amount of new knowledge about plant function comes from studies of the molecular genetics of model plants such as the thale cress, arabidopsis thaliana, a weedy species in the mustard family ( brassicaceae ). the genome or hereditary information contained in the genes of this species is encoded by about 135 million base pairs of dna, forming one of the smallest genomes among flowering plants. arabidopsis was the first plant to have its genome sequenced, in 2000. the sequencing of some other relatively small genomes, of rice ( oryza sativa ) and brachypodium distachyon, has made them important model species for understanding the genetics,
tubers in potato is one example. particularly in arctic or alpine habitats, where opportunities for fertilisation of flowers by animals are rare, plantlets or bulbs, may develop instead of flowers, replacing sexual reproduction with asexual reproduction and giving rise to clonal populations genetically identical to the parent. this is one of several types of apomixis that occur in plants. apomixis can also happen in a seed, producing a seed that contains an embryo genetically identical to the parent. most sexually reproducing organisms are diploid, with paired chromosomes, but doubling of their chromosome number may occur due to errors in cytokinesis. this can occur early in development to produce an autopolyploid or partly autopolyploid organism, or during normal processes of cellular differentiation to produce some cell types that are polyploid ( endopolyploidy ), or during gamete formation. an allopolyploid plant may result from a hybridisation event between two different species. both autopolyploid and allopolyploid plants can often reproduce normally, but may be unable to cross - breed successfully with the parent population because there is a mismatch in chromosome numbers. these plants that are reproductively isolated from the parent species but live within the same geographical area, may be sufficiently successful to form a new species. some otherwise sterile plant polyploids can still reproduce vegetatively or by seed apomixis, forming clonal populations of identical individuals. durum wheat is a fertile tetraploid allopolyploid, while bread wheat is a fertile hexaploid. the commercial banana is an example of a sterile, seedless triploid hybrid. common dandelion is a triploid that produces viable seeds by apomictic seed. as in other eukaryotes, the inheritance of endosymbiotic organelles like mitochondria and chloroplasts in plants is non - mendelian. chloroplasts are inherited through the male parent in gymnosperms but often through the female parent in flowering plants. = = = molecular genetics = = = a considerable amount of new knowledge about plant function comes from studies of the molecular genetics of model plants such as the thale cress, arabidopsis thaliana, a weedy species in the mustard family ( brassicaceae ). the genome or hereditary information contained in the genes of this species is encoded by about 135 million base pairs of dna, forming one of the
##es. embryophytes are multicellular eukaryotes descended from an ancestor that obtained its energy from sunlight by photosynthesis. they have life cycles with alternating haploid and diploid phases. the sexual haploid phase of embryophytes, known as the gametophyte, nurtures the developing diploid embryo sporophyte within its tissues for at least part of its life, even in the seed plants, where the gametophyte itself is nurtured by its parent sporophyte. other groups of organisms that were previously studied by botanists include bacteria ( now studied in bacteriology ), fungi ( mycology ) β including lichen - forming fungi ( lichenology ), non - chlorophyte algae ( phycology ), and viruses ( virology ). however, attention is still given to these groups by botanists, and fungi ( including lichens ) and photosynthetic protists are usually covered in introductory botany courses. palaeobotanists study ancient plants in the fossil record to provide information about the evolutionary history of plants. cyanobacteria, the first oxygen - releasing photosynthetic organisms on earth, are thought to have given rise to the ancestor of plants by entering into an endosymbiotic relationship with an early eukaryote, ultimately becoming the chloroplasts in plant cells. the new photosynthetic plants ( along with their algal relatives ) accelerated the rise in atmospheric oxygen started by the cyanobacteria, changing the ancient oxygen - free, reducing, atmosphere to one in which free oxygen has been abundant for more than 2 billion years. among the important botanical questions of the 21st century are the role of plants as primary producers in the global cycling of life ' s basic ingredients : energy, carbon, oxygen, nitrogen and water, and ways that our plant stewardship can help address the global environmental issues of resource management, conservation, human food security, biologically invasive organisms, carbon sequestration, climate change, and sustainability. = = = human nutrition = = = virtually all staple foods come either directly from primary production by plants, or indirectly from animals that eat them. plants and other photosynthetic organisms are at the base of most food chains because they use the energy from the sun and nutrients from the soil and atmosphere, converting them into a form that can be used by animals. this is what ecologists call the first trophic level. the modern forms of
the strictest definition of " plant " includes only the " land plants " or embryophytes, which include seed plants ( gymnosperms, including the pines, and flowering plants ) and the free - sporing cryptogams including ferns, clubmosses, liverworts, hornworts and mosses. embryophytes are multicellular eukaryotes descended from an ancestor that obtained its energy from sunlight by photosynthesis. they have life cycles with alternating haploid and diploid phases. the sexual haploid phase of embryophytes, known as the gametophyte, nurtures the developing diploid embryo sporophyte within its tissues for at least part of its life, even in the seed plants, where the gametophyte itself is nurtured by its parent sporophyte. other groups of organisms that were previously studied by botanists include bacteria ( now studied in bacteriology ), fungi ( mycology ) β including lichen - forming fungi ( lichenology ), non - chlorophyte algae ( phycology ), and viruses ( virology ). however, attention is still given to these groups by botanists, and fungi ( including lichens ) and photosynthetic protists are usually covered in introductory botany courses. palaeobotanists study ancient plants in the fossil record to provide information about the evolutionary history of plants. cyanobacteria, the first oxygen - releasing photosynthetic organisms on earth, are thought to have given rise to the ancestor of plants by entering into an endosymbiotic relationship with an early eukaryote, ultimately becoming the chloroplasts in plant cells. the new photosynthetic plants ( along with their algal relatives ) accelerated the rise in atmospheric oxygen started by the cyanobacteria, changing the ancient oxygen - free, reducing, atmosphere to one in which free oxygen has been abundant for more than 2 billion years. among the important botanical questions of the 21st century are the role of plants as primary producers in the global cycling of life ' s basic ingredients : energy, carbon, oxygen, nitrogen and water, and ways that our plant stewardship can help address the global environmental issues of resource management, conservation, human food security, biologically invasive organisms, carbon sequestration, climate change, and sustainability. = = = human nutrition = = = virtually all staple foods come either directly from primary production by plants, or indirectly from animals that
, subsequent switching to inbreeding becomes disadvantageous since it allows expression of the previously masked deleterious recessive mutations, commonly referred to as inbreeding depression. unlike in higher animals, where parthenogenesis is rare, asexual reproduction may occur in plants by several different mechanisms. the formation of stem tubers in potato is one example. particularly in arctic or alpine habitats, where opportunities for fertilisation of flowers by animals are rare, plantlets or bulbs, may develop instead of flowers, replacing sexual reproduction with asexual reproduction and giving rise to clonal populations genetically identical to the parent. this is one of several types of apomixis that occur in plants. apomixis can also happen in a seed, producing a seed that contains an embryo genetically identical to the parent. most sexually reproducing organisms are diploid, with paired chromosomes, but doubling of their chromosome number may occur due to errors in cytokinesis. this can occur early in development to produce an autopolyploid or partly autopolyploid organism, or during normal processes of cellular differentiation to produce some cell types that are polyploid ( endopolyploidy ), or during gamete formation. an allopolyploid plant may result from a hybridisation event between two different species. both autopolyploid and allopolyploid plants can often reproduce normally, but may be unable to cross - breed successfully with the parent population because there is a mismatch in chromosome numbers. these plants that are reproductively isolated from the parent species but live within the same geographical area, may be sufficiently successful to form a new species. some otherwise sterile plant polyploids can still reproduce vegetatively or by seed apomixis, forming clonal populations of identical individuals. durum wheat is a fertile tetraploid allopolyploid, while bread wheat is a fertile hexaploid. the commercial banana is an example of a sterile, seedless triploid hybrid. common dandelion is a triploid that produces viable seeds by apomictic seed. as in other eukaryotes, the inheritance of endosymbiotic organelles like mitochondria and chloroplasts in plants is non - mendelian. chloroplasts are inherited through the male parent in gymnosperms but often through the female parent in flowering plants. = = = molecular genetics = = = a considerable amount of new knowledge about plant function comes from
for nucleotide synthesis. hence, unfused myeloma cells die, as they cannot produce nucleotides by the de novo or salvage pathways because they lack hgprt. removal of the unfused myeloma cells is necessary because they have the potential to outgrow other cells, especially weakly established hybridomas. unfused b cells die as they have a short life span. in this way, only the b cell - myeloma hybrids survive, since the hgprt gene coming from the b cells is functional. these cells produce antibodies ( a property of b cells ) and are immortal ( a property of myeloma cells ). the incubated medium is then diluted into multi - well plates to such an extent that each well contains only one cell. since the antibodies in a well are produced by the same b cell, they will be directed towards the same epitope, and are thus monoclonal antibodies. the next stage is a rapid primary screening process, which identifies and selects only those hybridomas that produce antibodies of appropriate specificity. the first screening technique used is called elisa. the hybridoma culture supernatant, secondary enzyme labeled conjugate, and chromogenic substrate, are then incubated, and the formation of a colored product indicates a positive hybridoma. alternatively, immunocytochemical, western blot, and immunoprecipitation - mass spectrometry. unlike western blot assays, immunoprecipitation - mass spectrometry facilitates screening and ranking of clones which bind to the native ( non - denaturated ) forms of antigen proteins. flow cytometry screening has been used for primary screening of a large number ( ~ 1000 ) of hybridoma clones recognizing the native form of the antigen on the cell surface. in the flow cytometry - based screening, a mixture of antigen - negative cells and antigen - positive cells is used as the antigen to be tested for each hybridoma supernatant sample. the b cell that produces the desired antibodies can be cloned to produce many identical daughter clones. supplemental media containing interleukin - 6 ( such as briclone ) are essential for this step. once a hybridoma colony is established, it will continually grow in culture medium like rpmi - 1640 ( with antibiotics and fetal bovine serum ) and produce antibodies. multiwell plates are used initially to grow the hybridomas, and after selection,
( division of the nucleus ) is preceded by the s stage of interphase ( during which the dna is replicated ) and is often followed by telophase and cytokinesis ; which divides the cytoplasm, organelles and cell membrane of one cell into two new cells containing roughly equal shares of these cellular components. the different stages of mitosis all together define the mitotic phase of an animal cell cycle β the division of the mother cell into two genetically identical daughter cells. the cell cycle is a vital process by which a single - celled fertilized egg develops into a mature organism, as well as the process by which hair, skin, blood cells, and some internal organs are renewed. after cell division, each of the daughter cells begin the interphase of a new cycle. in contrast to mitosis, meiosis results in four haploid daughter cells by undergoing one round of dna replication followed by two divisions. homologous chromosomes are separated in the first division ( meiosis i ), and sister chromatids are separated in the second division ( meiosis ii ). both of these cell division cycles are used in the process of sexual reproduction at some point in their life cycle. both are believed to be present in the last eukaryotic common ancestor. prokaryotes ( i. e., archaea and bacteria ) can also undergo cell division ( or binary fission ). unlike the processes of mitosis and meiosis in eukaryotes, binary fission in prokaryotes takes place without the formation of a spindle apparatus on the cell. before binary fission, dna in the bacterium is tightly coiled. after it has uncoiled and duplicated, it is pulled to the separate poles of the bacterium as it increases the size to prepare for splitting. growth of a new cell wall begins to separate the bacterium ( triggered by ftsz polymerization and " z - ring " formation ). the new cell wall ( septum ) fully develops, resulting in the complete split of the bacterium. the new daughter cells have tightly coiled dna rods, ribosomes, and plasmids. = = = sexual reproduction and meiosis = = = meiosis is a central feature of sexual reproduction in eukaryotes, and the most fundamental function of meiosis appears to be conservation of the integrity of the genome that is passed on to progeny by parents. two aspects of sexual reproduction, meiotic recombination and outcrossing, are likely maintained respectively by
weakly established hybridomas. unfused b cells die as they have a short life span. in this way, only the b cell - myeloma hybrids survive, since the hgprt gene coming from the b cells is functional. these cells produce antibodies ( a property of b cells ) and are immortal ( a property of myeloma cells ). the incubated medium is then diluted into multi - well plates to such an extent that each well contains only one cell. since the antibodies in a well are produced by the same b cell, they will be directed towards the same epitope, and are thus monoclonal antibodies. the next stage is a rapid primary screening process, which identifies and selects only those hybridomas that produce antibodies of appropriate specificity. the first screening technique used is called elisa. the hybridoma culture supernatant, secondary enzyme labeled conjugate, and chromogenic substrate, are then incubated, and the formation of a colored product indicates a positive hybridoma. alternatively, immunocytochemical, western blot, and immunoprecipitation - mass spectrometry. unlike western blot assays, immunoprecipitation - mass spectrometry facilitates screening and ranking of clones which bind to the native ( non - denaturated ) forms of antigen proteins. flow cytometry screening has been used for primary screening of a large number ( ~ 1000 ) of hybridoma clones recognizing the native form of the antigen on the cell surface. in the flow cytometry - based screening, a mixture of antigen - negative cells and antigen - positive cells is used as the antigen to be tested for each hybridoma supernatant sample. the b cell that produces the desired antibodies can be cloned to produce many identical daughter clones. supplemental media containing interleukin - 6 ( such as briclone ) are essential for this step. once a hybridoma colony is established, it will continually grow in culture medium like rpmi - 1640 ( with antibiotics and fetal bovine serum ) and produce antibodies. multiwell plates are used initially to grow the hybridomas, and after selection, are changed to larger tissue culture flasks. this maintains the well - being of the hybridomas and provides enough cells for cryopreservation and supernatant for subsequent investigations. the culture supernatant can yield 1 to 60 ΞΌg / ml of monoclonal antibody, which is maintained at -
of these cellular components. the different stages of mitosis all together define the mitotic phase of an animal cell cycle β the division of the mother cell into two genetically identical daughter cells. the cell cycle is a vital process by which a single - celled fertilized egg develops into a mature organism, as well as the process by which hair, skin, blood cells, and some internal organs are renewed. after cell division, each of the daughter cells begin the interphase of a new cycle. in contrast to mitosis, meiosis results in four haploid daughter cells by undergoing one round of dna replication followed by two divisions. homologous chromosomes are separated in the first division ( meiosis i ), and sister chromatids are separated in the second division ( meiosis ii ). both of these cell division cycles are used in the process of sexual reproduction at some point in their life cycle. both are believed to be present in the last eukaryotic common ancestor. prokaryotes ( i. e., archaea and bacteria ) can also undergo cell division ( or binary fission ). unlike the processes of mitosis and meiosis in eukaryotes, binary fission in prokaryotes takes place without the formation of a spindle apparatus on the cell. before binary fission, dna in the bacterium is tightly coiled. after it has uncoiled and duplicated, it is pulled to the separate poles of the bacterium as it increases the size to prepare for splitting. growth of a new cell wall begins to separate the bacterium ( triggered by ftsz polymerization and " z - ring " formation ). the new cell wall ( septum ) fully develops, resulting in the complete split of the bacterium. the new daughter cells have tightly coiled dna rods, ribosomes, and plasmids. = = = sexual reproduction and meiosis = = = meiosis is a central feature of sexual reproduction in eukaryotes, and the most fundamental function of meiosis appears to be conservation of the integrity of the genome that is passed on to progeny by parents. two aspects of sexual reproduction, meiotic recombination and outcrossing, are likely maintained respectively by the adaptive advantages of recombinational repair of genomic dna damage and genetic complementation which masks the expression of deleterious recessive mutations. the beneficial effect of genetic complementation, derived from outcrossing ( cross - fertilization ) is also referred to as hybrid vigor or heterosis. charles
Question: While spermatogenesis produces four haploid sperm cells, oogenesis produces one mature what?
A) egg
B) semen
C) datum
D) ovum
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D) ovum
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Context:
while the modern stellar imf shows a rapid decline with increasing mass, theoretical investigations suggest that very massive stars ( > 100 solar masses ) may have been abundant in the early universe. other calculations also indicate that, lacking metals, these same stars reach their late evolutionary stages without appreciable mass loss. after central helium burning, they encounter the electron - positron pair instability, collapse, and burn oxygen and silicon explosively. if sufficient energy is released by the burning, these stars explode as brilliant supernovae with energies up to 100 times that of an ordinary core collapse supernova. they also eject up to 50 solar masses of radioactive ni56. stars less massive than 140 solar masses or more massive than 260 solar masses should collapse into black holes instead of exploding, thus bounding the pair - creation supernovae with regions of stellar mass that are nucleosynthetically sterile. pair - instability supernovae might be detectable in the near infrared out to redshifts of 20 or more and their ashes should leave a distinctive nucleosynthetic pattern.
oscillations of the sun have been used to understand its interior structure. the extension of similar studies to more distant stars has raised many difficulties despite the strong efforts of the international community over the past decades. the corot ( convection rotation and planetary transits ) satellite, launched in december 2006, has now measured oscillations and the stellar granulation signature in three main sequence stars that are noticeably hotter than the sun. the oscillation amplitudes are about 1. 5 times as large as those in the sun ; the stellar granulation is up to three times as high. the stellar amplitudes are about 25 % below the theoretic values, providing a measurement of the nonadiabaticity of the process ruling the oscillations in the outer layers of the stars.
i will discuss the presence of massive star clusters in starburst galaxies with an emphasis on low mass galaxies outside the local group. i will show that such galaxies, with respect to their mass and luminosity, may be very rich in young luminous clusters.
two types of stars are known to have strong, large scale magnetic fields : the main sequence ap stars and the magnetic white dwarfs. this suggest that the former might be the progenitors of the latter. in order to test this idea, i have carried out a search for large scale magnetic fields in stars with evolutionary states which are intermediate, i. e. in horizontal branch stars and in hot subdwarfs.
we bring you, as usual, the sun and moon and stars, plus some galaxies and a new section on astrobiology. some highlights are short ( the newly identified class of gamma - ray bursts, and the deep impact on comet 9p / tempel 1 ), some long ( the age of the universe, which will be found to have the earth at its center ), and a few metonymic, for instance the term " down - sizing " to describe the evolution of star formation rates with redshift.
galactic nuclei are unique laboratories for the study of processes connected with the accretion of gas onto supermassive black holes. at the same time, they represent challenging environments from the point of view of stellar dynamics due to their extreme densities and masses involved. there is a growing evidence about the importance of the mutual interaction of stars with gas in galactic nuclei. gas rich environment may lead to stellar formation which, on the other hand, may regulate accretion onto the central mass. gas in the form of massive torus or accretion disc further influences stellar dynamics in the central parsec either via gravitational or hydrodynamical interaction. eccentricity oscillations on one hand and energy dissipation on the other hand lead to increased rate of infall of stars into the supermassive black hole. last, but not least, processes related to the stellar dynamics may be detectable with forthcoming gravitational waves detectors.
so mars below means blood and war ", is a false cause fallacy. : 26 many astrologers claim that astrology is scientific. if one were to attempt to try to explain it scientifically, there are only four fundamental forces ( conventionally ), limiting the choice of possible natural mechanisms. : 65 some astrologers have proposed conventional causal agents such as electromagnetism and gravity. the strength of these forces drops off with distance. : 65 scientists reject these proposed mechanisms as implausible since, for example, the magnetic field, when measured from earth, of a large but distant planet such as jupiter is far smaller than that produced by ordinary household appliances. astronomer phil plait noted that in terms of magnitude, the sun is the only object with an electromagnetic field of note, but astrology isn ' t based just off the sun alone. : 65 while astrologers could try to suggest a fifth force, this is inconsistent with the trends in physics with the unification of electromagnetism and the weak force into the electroweak force. if the astrologer insisted on being inconsistent with the current understanding and evidential basis of physics, that would be an extraordinary claim. : 65 it would also be inconsistent with the other forces which drop off with distance. : 65 if distance is irrelevant, then, logically, all objects in space should be taken into account. : 66 carl jung sought to invoke synchronicity, the claim that two events have some sort of acausal connection, to explain the lack of statistically significant results on astrology from a single study he conducted. however, synchronicity itself is considered neither testable nor falsifiable. the study was subsequently heavily criticised for its non - random sample and its use of statistics and also its lack of consistency with astrology. = = psychology = = psychological studies have not found any robust relationship between astrological signs and life outcomes. for example, a study showed that zodiac signs are no more effective than random numbers in predicting subjective well - being and quality of life. it has also been shown that confirmation bias is a psychological factor that contributes to belief in astrology. : 344 : 180 β 181 : 42 β 48 confirmation bias is a form of cognitive bias. : 553 from the literature, astrology believers often tend to selectively remember those predictions that turned out to be true and do not remember those that turned out false. another, separate, form of confirmation bias also plays a role, where believers often fail to
. this, he argued, would have been more persuasive and would have produced less controversy. the use of poetic imagery based on the concepts of the macrocosm and microcosm, " as above so below " to decide meaning such as edward w. james ' example of " mars above is red, so mars below means blood and war ", is a false cause fallacy. : 26 many astrologers claim that astrology is scientific. if one were to attempt to try to explain it scientifically, there are only four fundamental forces ( conventionally ), limiting the choice of possible natural mechanisms. : 65 some astrologers have proposed conventional causal agents such as electromagnetism and gravity. the strength of these forces drops off with distance. : 65 scientists reject these proposed mechanisms as implausible since, for example, the magnetic field, when measured from earth, of a large but distant planet such as jupiter is far smaller than that produced by ordinary household appliances. astronomer phil plait noted that in terms of magnitude, the sun is the only object with an electromagnetic field of note, but astrology isn ' t based just off the sun alone. : 65 while astrologers could try to suggest a fifth force, this is inconsistent with the trends in physics with the unification of electromagnetism and the weak force into the electroweak force. if the astrologer insisted on being inconsistent with the current understanding and evidential basis of physics, that would be an extraordinary claim. : 65 it would also be inconsistent with the other forces which drop off with distance. : 65 if distance is irrelevant, then, logically, all objects in space should be taken into account. : 66 carl jung sought to invoke synchronicity, the claim that two events have some sort of acausal connection, to explain the lack of statistically significant results on astrology from a single study he conducted. however, synchronicity itself is considered neither testable nor falsifiable. the study was subsequently heavily criticised for its non - random sample and its use of statistics and also its lack of consistency with astrology. = = psychology = = psychological studies have not found any robust relationship between astrological signs and life outcomes. for example, a study showed that zodiac signs are no more effective than random numbers in predicting subjective well - being and quality of life. it has also been shown that confirmation bias is a psychological factor that contributes to belief in astrology. : 344 : 180 β 181 :
there are a few different mechanisms that can cause white dwarf stars to vary in brightness, providing opportunities to probe the physics, structures, and formation of these compact stellar remnants. the observational characteristics of the three most common types of white dwarf variability are summarized : stellar pulsations, rotation, and ellipsoidal variations from tidal distortion in binary systems. stellar pulsations are emphasized as the most complex type of variability, which also has the greatest potential to reveal the conditions of white dwarf interiors.
v735 sgr was known as an enigmatic star with rapid brightness variations. long - term ogle photometry, brightness measurements in infrared bands, and recently obtained moderate resolution spectrum from the 6. 5 - m magellan telescope show that this star is an active young stellar object of herbig ae / be type.
Question: What are groups of tens to hundreds of thousands of stars held tightly together by gravity called?
A) elongated clusters
B) galaxy
C) globular clusters
D) elliptical clusters
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C) globular clusters
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Context:
a discontinuity of a turbulent ideal fluid is considered. it is supposed to be split and dispersed, or spread in the stochastic environment forming a gas without hydrostatic pressure. two equal - mass fragments of a discontinuity are indistinguishable from each other. a gas, that possesses such properties, must behave itself as the madelung medium.
which applies a forces that results in fracturing ), and impact ( which employs a milling medium or the particles themselves to cause fracturing ). attrition milling equipment includes the wet scrubber ( also called the planetary mill or wet attrition mill ), which has paddles in water creating vortexes in which the material collides and break up. compression mills include the jaw crusher, roller crusher and cone crusher. impact mills include the ball mill, which has media that tumble and fracture the material, or the resonantacoustic mixer. shaft impactors cause particle - to particle attrition and compression. batching is the process of weighing the oxides according to recipes, and preparing them for mixing and drying. mixing occurs after batching and is performed with various machines, such as dry mixing ribbon mixers ( a type of cement mixer ), resonantacoustic mixers, mueller mixers, and pug mills. wet mixing generally involves the same equipment. forming is making the mixed material into shapes, ranging from toilet bowls to spark plug insulators. forming can involve : ( 1 ) extrusion, such as extruding " slugs " to make bricks, ( 2 ) pressing to make shaped parts, ( 3 ) slip casting, as in making toilet bowls, wash basins and ornamentals like ceramic statues. forming produces a " green " part, ready for drying. green parts are soft, pliable, and over time will lose shape. handling the green product will change its shape. for example, a green brick can be " squeezed ", and after squeezing it will stay that way. drying is removing the water or binder from the formed material. spray drying is widely used to prepare powder for pressing operations. other dryers are tunnel dryers and periodic dryers. controlled heat is applied in this two - stage process. first, heat removes water. this step needs careful control, as rapid heating causes cracks and surface defects. the dried part is smaller than the green part, and is brittle, necessitating careful handling, since a small impact will cause crumbling and breaking. sintering is where the dried parts pass through a controlled heating process, and the oxides are chemically changed to cause bonding and densification. the fired part will be smaller than the dried part. = = forming methods = = ceramic forming techniques include throwing, slipcasting, tape casting, freeze - casting, injection molding, dry pressing, isostatic pressing, hot isostatic pressing
. batching is the process of weighing the oxides according to recipes, and preparing them for mixing and drying. mixing occurs after batching and is performed with various machines, such as dry mixing ribbon mixers ( a type of cement mixer ), resonantacoustic mixers, mueller mixers, and pug mills. wet mixing generally involves the same equipment. forming is making the mixed material into shapes, ranging from toilet bowls to spark plug insulators. forming can involve : ( 1 ) extrusion, such as extruding " slugs " to make bricks, ( 2 ) pressing to make shaped parts, ( 3 ) slip casting, as in making toilet bowls, wash basins and ornamentals like ceramic statues. forming produces a " green " part, ready for drying. green parts are soft, pliable, and over time will lose shape. handling the green product will change its shape. for example, a green brick can be " squeezed ", and after squeezing it will stay that way. drying is removing the water or binder from the formed material. spray drying is widely used to prepare powder for pressing operations. other dryers are tunnel dryers and periodic dryers. controlled heat is applied in this two - stage process. first, heat removes water. this step needs careful control, as rapid heating causes cracks and surface defects. the dried part is smaller than the green part, and is brittle, necessitating careful handling, since a small impact will cause crumbling and breaking. sintering is where the dried parts pass through a controlled heating process, and the oxides are chemically changed to cause bonding and densification. the fired part will be smaller than the dried part. = = forming methods = = ceramic forming techniques include throwing, slipcasting, tape casting, freeze - casting, injection molding, dry pressing, isostatic pressing, hot isostatic pressing ( hip ), 3d printing and others. methods for forming ceramic powders into complex shapes are desirable in many areas of technology. such methods are required for producing advanced, high - temperature structural parts such as heat engine components and turbines. materials other than ceramics which are used in these processes may include : wood, metal, water, plaster and epoxy β most of which will be eliminated upon firing. a ceramic - filled epoxy, such as martyte, is sometimes used to protect structural steel under conditions of rocket exhaust impingement. these forming techniques are well known for providing tools and other components with dimensional stability, surface quality
mixes of multi - track recordings. it is common to record a commercial record at one studio and have it mixed by different engineers in other studios. mastering engineer β the person who masters the final mixed stereo tracks ( or sometimes a series of audio stems, which consists in a mix of the main sections ) that the mix engineer produces. the mastering engineer makes any final adjustments to the overall sound of the record in the final step before commercial duplication. mastering engineers use principles of equalization, compression and limiting to fine - tune the sound timbre and dynamics and to achieve a louder recording. sound designer β broadly an artist who produces soundtracks or sound effects content for media. live sound engineer front of house ( foh ) engineer, or a1. β a person dealing with live sound reinforcement. this usually includes planning and installation of loudspeakers, cabling and equipment and mixing sound during the show. this may or may not include running the foldback sound. a live / sound reinforcement engineer hears source material and tries to correlate that sonic experience with system performance. wireless microphone engineer, or a2. this position is responsible for wireless microphones during a theatre production, a sports event or a corporate event. foldback or monitor engineer β a person running foldback sound during a live event. the term foldback comes from the old practice of folding back audio signals from the front of house ( foh ) mixing console to the stage so musicians can hear themselves while performing. monitor engineers usually have a separate audio system from the foh engineer and manipulate audio signals independently from what the audience hears so they can satisfy the requirements of each performer on stage. in - ear systems, digital and analog mixing consoles, and a variety of speaker enclosures are typically used by monitor engineers. in addition, most monitor engineers must be familiar with wireless or rf ( radio - frequency ) equipment and often must communicate personally with the artist ( s ) during each performance. systems engineer β responsible for the design setup of modern pa systems, which are often very complex. a systems engineer is usually also referred to as a crew chief on tour and is responsible for the performance and day - to - day job requirements of the audio crew as a whole along with the foh audio system. this is a sound - only position concerned with implementation, not to be confused with the interdisciplinary field of system engineering, which typically requires a college degree. re - recording mixer β a person in post - production who mixes audio tracks for feature films or television programs. = = equipment = = an audio engineer is
the material collides and break up. compression mills include the jaw crusher, roller crusher and cone crusher. impact mills include the ball mill, which has media that tumble and fracture the material, or the resonantacoustic mixer. shaft impactors cause particle - to particle attrition and compression. batching is the process of weighing the oxides according to recipes, and preparing them for mixing and drying. mixing occurs after batching and is performed with various machines, such as dry mixing ribbon mixers ( a type of cement mixer ), resonantacoustic mixers, mueller mixers, and pug mills. wet mixing generally involves the same equipment. forming is making the mixed material into shapes, ranging from toilet bowls to spark plug insulators. forming can involve : ( 1 ) extrusion, such as extruding " slugs " to make bricks, ( 2 ) pressing to make shaped parts, ( 3 ) slip casting, as in making toilet bowls, wash basins and ornamentals like ceramic statues. forming produces a " green " part, ready for drying. green parts are soft, pliable, and over time will lose shape. handling the green product will change its shape. for example, a green brick can be " squeezed ", and after squeezing it will stay that way. drying is removing the water or binder from the formed material. spray drying is widely used to prepare powder for pressing operations. other dryers are tunnel dryers and periodic dryers. controlled heat is applied in this two - stage process. first, heat removes water. this step needs careful control, as rapid heating causes cracks and surface defects. the dried part is smaller than the green part, and is brittle, necessitating careful handling, since a small impact will cause crumbling and breaking. sintering is where the dried parts pass through a controlled heating process, and the oxides are chemically changed to cause bonding and densification. the fired part will be smaller than the dried part. = = forming methods = = ceramic forming techniques include throwing, slipcasting, tape casting, freeze - casting, injection molding, dry pressing, isostatic pressing, hot isostatic pressing ( hip ), 3d printing and others. methods for forming ceramic powders into complex shapes are desirable in many areas of technology. such methods are required for producing advanced, high - temperature structural parts such as heat engine components and turbines. materials other than ceramics which are used in these processes may include : wood, metal,
##g mills. wet mixing generally involves the same equipment. forming is making the mixed material into shapes, ranging from toilet bowls to spark plug insulators. forming can involve : ( 1 ) extrusion, such as extruding " slugs " to make bricks, ( 2 ) pressing to make shaped parts, ( 3 ) slip casting, as in making toilet bowls, wash basins and ornamentals like ceramic statues. forming produces a " green " part, ready for drying. green parts are soft, pliable, and over time will lose shape. handling the green product will change its shape. for example, a green brick can be " squeezed ", and after squeezing it will stay that way. drying is removing the water or binder from the formed material. spray drying is widely used to prepare powder for pressing operations. other dryers are tunnel dryers and periodic dryers. controlled heat is applied in this two - stage process. first, heat removes water. this step needs careful control, as rapid heating causes cracks and surface defects. the dried part is smaller than the green part, and is brittle, necessitating careful handling, since a small impact will cause crumbling and breaking. sintering is where the dried parts pass through a controlled heating process, and the oxides are chemically changed to cause bonding and densification. the fired part will be smaller than the dried part. = = forming methods = = ceramic forming techniques include throwing, slipcasting, tape casting, freeze - casting, injection molding, dry pressing, isostatic pressing, hot isostatic pressing ( hip ), 3d printing and others. methods for forming ceramic powders into complex shapes are desirable in many areas of technology. such methods are required for producing advanced, high - temperature structural parts such as heat engine components and turbines. materials other than ceramics which are used in these processes may include : wood, metal, water, plaster and epoxy β most of which will be eliminated upon firing. a ceramic - filled epoxy, such as martyte, is sometimes used to protect structural steel under conditions of rocket exhaust impingement. these forming techniques are well known for providing tools and other components with dimensional stability, surface quality, high ( near theoretical ) density and microstructural uniformity. the increasing use and diversity of specialty forms of ceramics adds to the diversity of process technologies to be used. thus, reinforcing fibers and filaments are mainly made by polymer, sol - gel, or cvd processes, but melt
wrought, which itself is the original past passive participle of the word work, now superseded by the weak verb forms worker and worked respectively. ) blacksmithing and the various related smithing and metal - crafts. folk music played on acoustic instruments. mathematics ( particularly, pure mathematics ) organic farming and animal husbandry ( i. e. ; agriculture as practiced by all american farmers prior to world war ii ). milling in the sense of operating hand - constructed equipment with the intent to either grind grain, or the reduction of timber to lumber as practiced in a saw - mill. fulling, felting, drop spindle spinning, hand knitting, crochet, & similar textile preparation. the production of charcoal by the collier, for use in home heating, foundry operations, smelting, the various smithing trades, and for brushing ones teeth as in colonial america. glass - blowing. various subskills of food preservation : smoking salting pickling drying note : home canning is a counter example of a low technology since some of the supplies needed to pursue this skill rely on a global trade network and an existing manufacturing infrastructure. the production of various alcoholic beverages : wine : poorly preserved fruit juice. beer : a way to preserve the calories of grain products from decay. whiskey : an improved ( distilled ) form of beer. flint - knapping masonry as used in castles, cathedrals, and root cellars. = = = domestic or consumer = = = ( non exhaustive ) list of low - tech in a westerner ' s everyday life : getting around by bike, and repairing it with second - hand materials using a cargo bike to carry loads ( rather than a gasoline vehicle ) drying clothes on a clothesline or on a drying rack washing clothes by hand, or in a human - powered washing machine cooling one ' s home with a fan or an air expander ( rather than electrical appliances such as air conditioners ) using a bell as door bell a cellar, " desert fridge ", or icebox ( rather than a fridge or freezer ) long - distance travel by sailing boat ( rather than by plane ) a wicker bag or a tote bag ( rather than a plastic bag ) to carry things swedish lighter ( rather than disposable lighter or matches ) a hand drill, instead of an electric one lighting with sunlight or candles hemp textiles to water plants with drip irrigation paper sheets for note - taking to clean with a broom ( rather than a vacuum cleaner ) to find one ' s way with map
the most abundant molecule in every organism. water is important to life because it is an effective solvent, capable of dissolving solutes such as sodium and chloride ions or other small molecules to form an aqueous solution. once dissolved in water, these solutes are more likely to come in contact with one another and therefore take part in chemical reactions that sustain life. in terms of its molecular structure, water is a small polar molecule with a bent shape formed by the polar covalent bonds of two hydrogen ( h ) atoms to one oxygen ( o ) atom ( h2o ). because the o β h bonds are polar, the oxygen atom has a slight negative charge and the two hydrogen atoms have a slight positive charge. this polar property of water allows it to attract other water molecules via hydrogen bonds, which makes water cohesive. surface tension results from the cohesive force due to the attraction between molecules at the surface of the liquid. water is also adhesive as it is able to adhere to the surface of any polar or charged non - water molecules. water is denser as a liquid than it is as a solid ( or ice ). this unique property of water allows ice to float above liquid water such as ponds, lakes, and oceans, thereby insulating the liquid below from the cold air above. water has the capacity to absorb energy, giving it a higher specific heat capacity than other solvents such as ethanol. thus, a large amount of energy is needed to break the hydrogen bonds between water molecules to convert liquid water into water vapor. as a molecule, water is not completely stable as each water molecule continuously dissociates into hydrogen and hydroxyl ions before reforming into a water molecule again. in pure water, the number of hydrogen ions balances ( or equals ) the number of hydroxyl ions, resulting in a ph that is neutral. = = = organic compounds = = = organic compounds are molecules that contain carbon bonded to another element such as hydrogen. with the exception of water, nearly all the molecules that make up each organism contain carbon. carbon can form covalent bonds with up to four other atoms, enabling it to form diverse, large, and complex molecules. for example, a single carbon atom can form four single covalent bonds such as in methane, two double covalent bonds such as in carbon dioxide ( co2 ), or a triple covalent bond such as in carbon monoxide ( co ). moreover, carbon can form very long chains of interconnecting carbon β carbon bonds such
= = = = substance and mixture = = = = a chemical substance is a kind of matter with a definite composition and set of properties. a collection of substances is called a mixture. examples of mixtures are air and alloys. = = = = mole and amount of substance = = = = the mole is a unit of measurement that denotes an amount of substance ( also called chemical amount ). one mole is defined to contain exactly 6. 02214076Γ1023 particles ( atoms, molecules, ions, or electrons ), where the number of particles per mole is known as the avogadro constant. molar concentration is the amount of a particular substance per volume of solution, and is commonly reported in mol / dm3. = = = phase = = = in addition to the specific chemical properties that distinguish different chemical classifications, chemicals can exist in several phases. for the most part, the chemical classifications are independent of these bulk phase classifications ; however, some more exotic phases are incompatible with certain chemical properties. a phase is a set of states of a chemical system that have similar bulk structural properties, over a range of conditions, such as pressure or temperature. physical properties, such as density and refractive index tend to fall within values characteristic of the phase. the phase of matter is defined by the phase transition, which is when energy put into or taken out of the system goes into rearranging the structure of the system, instead of changing the bulk conditions. sometimes the distinction between phases can be continuous instead of having a discrete boundary ; in this case the matter is considered to be in a supercritical state. when three states meet based on the conditions, it is known as a triple point and since this is invariant, it is a convenient way to define a set of conditions. the most familiar examples of phases are solids, liquids, and gases. many substances exhibit multiple solid phases. for example, there are three phases of solid iron ( alpha, gamma, and delta ) that vary based on temperature and pressure. a principal difference between solid phases is the crystal structure, or arrangement, of the atoms. another phase commonly encountered in the study of chemistry is the aqueous phase, which is the state of substances dissolved in aqueous solution ( that is, in water ). less familiar phases include plasmas, bose β einstein condensates and fermionic condensates and the paramagnetic and ferromagnetic phases of magnetic materials. while most familiar phases deal with three - dimensional systems,
this is an expository paper about the topics listed in the title.
Question: What is the general name for the homogeneous mixture that is formed when a solute dissolves in a solvent?
A) Reaction
B) Dissolvant
C) solution
D) Combination
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C) solution
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Context:
energy they need to exist. plants, algae and cyanobacteria are the major groups of organisms that carry out photosynthesis, a process that uses the energy of sunlight to convert water and carbon dioxide into sugars that can be used both as a source of chemical energy and of organic molecules that are used in the structural components of cells. as a by - product of photosynthesis, plants release oxygen into the atmosphere, a gas that is required by nearly all living things to carry out cellular respiration. in addition, they are influential in the global carbon and water cycles and plant roots bind and stabilise soils, preventing soil erosion. plants are crucial to the future of human society as they provide food, oxygen, biochemicals, and products for people, as well as creating and preserving soil. historically, all living things were classified as either animals or plants and botany covered the study of all organisms not considered animals. botanists examine both the internal functions and processes within plant organelles, cells, tissues, whole plants, plant populations and plant communities. at each of these levels, a botanist may be concerned with the classification ( taxonomy ), phylogeny and evolution, structure ( anatomy and morphology ), or function ( physiology ) of plant life. the strictest definition of " plant " includes only the " land plants " or embryophytes, which include seed plants ( gymnosperms, including the pines, and flowering plants ) and the free - sporing cryptogams including ferns, clubmosses, liverworts, hornworts and mosses. embryophytes are multicellular eukaryotes descended from an ancestor that obtained its energy from sunlight by photosynthesis. they have life cycles with alternating haploid and diploid phases. the sexual haploid phase of embryophytes, known as the gametophyte, nurtures the developing diploid embryo sporophyte within its tissues for at least part of its life, even in the seed plants, where the gametophyte itself is nurtured by its parent sporophyte. other groups of organisms that were previously studied by botanists include bacteria ( now studied in bacteriology ), fungi ( mycology ) β including lichen - forming fungi ( lichenology ), non - chlorophyte algae ( phycology ), and viruses ( virology ). however, attention is still given to these groups by botanists, and fungi ( including lichens ) and photos
substrate - level phosphorylation, which does not require oxygen. = = = photosynthesis = = = photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organism ' s metabolic activities via cellular respiration. this chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. in most cases, oxygen is released as a waste product. most plants, algae, and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of the earth ' s atmosphere, and supplies most of the energy necessary for life on earth. photosynthesis has four stages : light absorption, electron transport, atp synthesis, and carbon fixation. light absorption is the initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to proteins in the thylakoid membranes. the absorbed light energy is used to remove electrons from a donor ( water ) to a primary electron acceptor, a quinone designated as q. in the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach a final electron acceptor, which is usually the oxidized form of nadp +, which is reduced to nadph, a process that takes place in a protein complex called photosystem i ( psi ). the transport of electrons is coupled to the movement of protons ( or hydrogen ) from the stroma to the thylakoid membrane, which forms a ph gradient across the membrane as hydrogen becomes more concentrated in the lumen than in the stroma. this is analogous to the proton - motive force generated across the inner mitochondrial membrane in aerobic respiration. during the third stage of photosynthesis, the movement of protons down their concentration gradients from the thylakoid lumen to the stroma through the atp synthase is coupled to the synthesis of atp by that same atp synthase. the nadph and atps generated by the light - dependent reactions in the second and third stages, respectively, provide the energy and electrons to drive the synthesis of glucose by fixing atmospheric carbon dioxide into existing organic carbon compounds, such as ribulose bisphosphate ( rubp ) in a sequence of light - independent ( or dark ) reactions called the calvin cycle. = = = cell signaling = = = cell signaling ( or communication ) is the
##vary. ongoing research on the molecular phylogenetics of living plants appears to show that the angiosperms are a sister clade to the gymnosperms. = = plant physiology = = plant physiology encompasses all the internal chemical and physical activities of plants associated with life. chemicals obtained from the air, soil and water form the basis of all plant metabolism. the energy of sunlight, captured by oxygenic photosynthesis and released by cellular respiration, is the basis of almost all life. photoautotrophs, including all green plants, algae and cyanobacteria gather energy directly from sunlight by photosynthesis. heterotrophs including all animals, all fungi, all completely parasitic plants, and non - photosynthetic bacteria take in organic molecules produced by photoautotrophs and respire them or use them in the construction of cells and tissues. respiration is the oxidation of carbon compounds by breaking them down into simpler structures to release the energy they contain, essentially the opposite of photosynthesis. molecules are moved within plants by transport processes that operate at a variety of spatial scales. subcellular transport of ions, electrons and molecules such as water and enzymes occurs across cell membranes. minerals and water are transported from roots to other parts of the plant in the transpiration stream. diffusion, osmosis, and active transport and mass flow are all different ways transport can occur. examples of elements that plants need to transport are nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. in vascular plants, these elements are extracted from the soil as soluble ions by the roots and transported throughout the plant in the xylem. most of the elements required for plant nutrition come from the chemical breakdown of soil minerals. sucrose produced by photosynthesis is transported from the leaves to other parts of the plant in the phloem and plant hormones are transported by a variety of processes. = = = plant hormones = = = plants are not passive, but respond to external signals such as light, touch, and injury by moving or growing towards or away from the stimulus, as appropriate. tangible evidence of touch sensitivity is the almost instantaneous collapse of leaflets of mimosa pudica, the insect traps of venus flytrap and bladderworts, and the pollinia of orchids. the hypothesis that plant growth and development is coordinated by plant hormones or plant growth regulators first emerged in the late 19th century. darwin experimented on the movements of plant shoots and roots towards light and gravity, and concluded " it is hardly an ex
the earth ' s atmosphere, and supplies most of the energy necessary for life on earth. photosynthesis has four stages : light absorption, electron transport, atp synthesis, and carbon fixation. light absorption is the initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to proteins in the thylakoid membranes. the absorbed light energy is used to remove electrons from a donor ( water ) to a primary electron acceptor, a quinone designated as q. in the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach a final electron acceptor, which is usually the oxidized form of nadp +, which is reduced to nadph, a process that takes place in a protein complex called photosystem i ( psi ). the transport of electrons is coupled to the movement of protons ( or hydrogen ) from the stroma to the thylakoid membrane, which forms a ph gradient across the membrane as hydrogen becomes more concentrated in the lumen than in the stroma. this is analogous to the proton - motive force generated across the inner mitochondrial membrane in aerobic respiration. during the third stage of photosynthesis, the movement of protons down their concentration gradients from the thylakoid lumen to the stroma through the atp synthase is coupled to the synthesis of atp by that same atp synthase. the nadph and atps generated by the light - dependent reactions in the second and third stages, respectively, provide the energy and electrons to drive the synthesis of glucose by fixing atmospheric carbon dioxide into existing organic carbon compounds, such as ribulose bisphosphate ( rubp ) in a sequence of light - independent ( or dark ) reactions called the calvin cycle. = = = cell signaling = = = cell signaling ( or communication ) is the ability of cells to receive, process, and transmit signals with its environment and with itself. signals can be non - chemical such as light, electrical impulses, and heat, or chemical signals ( or ligands ) that interact with receptors, which can be found embedded in the cell membrane of another cell or located deep inside a cell. there are generally four types of chemical signals : autocrine, paracrine, juxtacrine, and hormones. in autocrine signaling, the ligand affects the same cell that releases it. tumor cells, for example, can reproduce uncontrollably because they release signals that initiate their
the basis of all plant metabolism. the energy of sunlight, captured by oxygenic photosynthesis and released by cellular respiration, is the basis of almost all life. photoautotrophs, including all green plants, algae and cyanobacteria gather energy directly from sunlight by photosynthesis. heterotrophs including all animals, all fungi, all completely parasitic plants, and non - photosynthetic bacteria take in organic molecules produced by photoautotrophs and respire them or use them in the construction of cells and tissues. respiration is the oxidation of carbon compounds by breaking them down into simpler structures to release the energy they contain, essentially the opposite of photosynthesis. molecules are moved within plants by transport processes that operate at a variety of spatial scales. subcellular transport of ions, electrons and molecules such as water and enzymes occurs across cell membranes. minerals and water are transported from roots to other parts of the plant in the transpiration stream. diffusion, osmosis, and active transport and mass flow are all different ways transport can occur. examples of elements that plants need to transport are nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. in vascular plants, these elements are extracted from the soil as soluble ions by the roots and transported throughout the plant in the xylem. most of the elements required for plant nutrition come from the chemical breakdown of soil minerals. sucrose produced by photosynthesis is transported from the leaves to other parts of the plant in the phloem and plant hormones are transported by a variety of processes. = = = plant hormones = = = plants are not passive, but respond to external signals such as light, touch, and injury by moving or growing towards or away from the stimulus, as appropriate. tangible evidence of touch sensitivity is the almost instantaneous collapse of leaflets of mimosa pudica, the insect traps of venus flytrap and bladderworts, and the pollinia of orchids. the hypothesis that plant growth and development is coordinated by plant hormones or plant growth regulators first emerged in the late 19th century. darwin experimented on the movements of plant shoots and roots towards light and gravity, and concluded " it is hardly an exaggeration to say that the tip of the radicle.. acts like the brain of one of the lower animals.. directing the several movements ". about the same time, the role of auxins ( from the greek auxein, to grow ) in control of plant growth was first outlined by the dutch scientist
the structural components of cells. as a by - product of photosynthesis, plants release oxygen into the atmosphere, a gas that is required by nearly all living things to carry out cellular respiration. in addition, they are influential in the global carbon and water cycles and plant roots bind and stabilise soils, preventing soil erosion. plants are crucial to the future of human society as they provide food, oxygen, biochemicals, and products for people, as well as creating and preserving soil. historically, all living things were classified as either animals or plants and botany covered the study of all organisms not considered animals. botanists examine both the internal functions and processes within plant organelles, cells, tissues, whole plants, plant populations and plant communities. at each of these levels, a botanist may be concerned with the classification ( taxonomy ), phylogeny and evolution, structure ( anatomy and morphology ), or function ( physiology ) of plant life. the strictest definition of " plant " includes only the " land plants " or embryophytes, which include seed plants ( gymnosperms, including the pines, and flowering plants ) and the free - sporing cryptogams including ferns, clubmosses, liverworts, hornworts and mosses. embryophytes are multicellular eukaryotes descended from an ancestor that obtained its energy from sunlight by photosynthesis. they have life cycles with alternating haploid and diploid phases. the sexual haploid phase of embryophytes, known as the gametophyte, nurtures the developing diploid embryo sporophyte within its tissues for at least part of its life, even in the seed plants, where the gametophyte itself is nurtured by its parent sporophyte. other groups of organisms that were previously studied by botanists include bacteria ( now studied in bacteriology ), fungi ( mycology ) β including lichen - forming fungi ( lichenology ), non - chlorophyte algae ( phycology ), and viruses ( virology ). however, attention is still given to these groups by botanists, and fungi ( including lichens ) and photosynthetic protists are usually covered in introductory botany courses. palaeobotanists study ancient plants in the fossil record to provide information about the evolutionary history of plants. cyanobacteria, the first oxygen - releasing photosynthetic organisms on earth, are thought to have given rise to the
is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. in most cases, oxygen is released as a waste product. most plants, algae, and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of the earth ' s atmosphere, and supplies most of the energy necessary for life on earth. photosynthesis has four stages : light absorption, electron transport, atp synthesis, and carbon fixation. light absorption is the initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to proteins in the thylakoid membranes. the absorbed light energy is used to remove electrons from a donor ( water ) to a primary electron acceptor, a quinone designated as q. in the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach a final electron acceptor, which is usually the oxidized form of nadp +, which is reduced to nadph, a process that takes place in a protein complex called photosystem i ( psi ). the transport of electrons is coupled to the movement of protons ( or hydrogen ) from the stroma to the thylakoid membrane, which forms a ph gradient across the membrane as hydrogen becomes more concentrated in the lumen than in the stroma. this is analogous to the proton - motive force generated across the inner mitochondrial membrane in aerobic respiration. during the third stage of photosynthesis, the movement of protons down their concentration gradients from the thylakoid lumen to the stroma through the atp synthase is coupled to the synthesis of atp by that same atp synthase. the nadph and atps generated by the light - dependent reactions in the second and third stages, respectively, provide the energy and electrons to drive the synthesis of glucose by fixing atmospheric carbon dioxide into existing organic carbon compounds, such as ribulose bisphosphate ( rubp ) in a sequence of light - independent ( or dark ) reactions called the calvin cycle. = = = cell signaling = = = cell signaling ( or communication ) is the ability of cells to receive, process, and transmit signals with its environment and with itself. signals can be non - chemical such as light, electrical impulses, and heat, or chemical signals ( or ligands ) that interact with receptors, which can be found embedded in the cell membrane of another cell or located deep inside
the internal functions and processes within plant organelles, cells, tissues, whole plants, plant populations and plant communities. at each of these levels, a botanist may be concerned with the classification ( taxonomy ), phylogeny and evolution, structure ( anatomy and morphology ), or function ( physiology ) of plant life. the strictest definition of " plant " includes only the " land plants " or embryophytes, which include seed plants ( gymnosperms, including the pines, and flowering plants ) and the free - sporing cryptogams including ferns, clubmosses, liverworts, hornworts and mosses. embryophytes are multicellular eukaryotes descended from an ancestor that obtained its energy from sunlight by photosynthesis. they have life cycles with alternating haploid and diploid phases. the sexual haploid phase of embryophytes, known as the gametophyte, nurtures the developing diploid embryo sporophyte within its tissues for at least part of its life, even in the seed plants, where the gametophyte itself is nurtured by its parent sporophyte. other groups of organisms that were previously studied by botanists include bacteria ( now studied in bacteriology ), fungi ( mycology ) β including lichen - forming fungi ( lichenology ), non - chlorophyte algae ( phycology ), and viruses ( virology ). however, attention is still given to these groups by botanists, and fungi ( including lichens ) and photosynthetic protists are usually covered in introductory botany courses. palaeobotanists study ancient plants in the fossil record to provide information about the evolutionary history of plants. cyanobacteria, the first oxygen - releasing photosynthetic organisms on earth, are thought to have given rise to the ancestor of plants by entering into an endosymbiotic relationship with an early eukaryote, ultimately becoming the chloroplasts in plant cells. the new photosynthetic plants ( along with their algal relatives ) accelerated the rise in atmospheric oxygen started by the cyanobacteria, changing the ancient oxygen - free, reducing, atmosphere to one in which free oxygen has been abundant for more than 2 billion years. among the important botanical questions of the 21st century are the role of plants as primary producers in the global cycling of life ' s basic ingredients : energy, carbon, oxygen, nitrogen and water, and ways
liver glycogen. during recovery, when oxygen becomes available, nad + attaches to hydrogen from lactate to form atp. in yeast, the waste products are ethanol and carbon dioxide. this type of fermentation is known as alcoholic or ethanol fermentation. the atp generated in this process is made by substrate - level phosphorylation, which does not require oxygen. = = = photosynthesis = = = photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organism ' s metabolic activities via cellular respiration. this chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. in most cases, oxygen is released as a waste product. most plants, algae, and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of the earth ' s atmosphere, and supplies most of the energy necessary for life on earth. photosynthesis has four stages : light absorption, electron transport, atp synthesis, and carbon fixation. light absorption is the initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to proteins in the thylakoid membranes. the absorbed light energy is used to remove electrons from a donor ( water ) to a primary electron acceptor, a quinone designated as q. in the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach a final electron acceptor, which is usually the oxidized form of nadp +, which is reduced to nadph, a process that takes place in a protein complex called photosystem i ( psi ). the transport of electrons is coupled to the movement of protons ( or hydrogen ) from the stroma to the thylakoid membrane, which forms a ph gradient across the membrane as hydrogen becomes more concentrated in the lumen than in the stroma. this is analogous to the proton - motive force generated across the inner mitochondrial membrane in aerobic respiration. during the third stage of photosynthesis, the movement of protons down their concentration gradients from the thylakoid lumen to the stroma through the atp synthase is coupled to the synthesis of atp by that same atp synthase. the nadph and atps generated by the light - dependent reactions in the second and third stages, respectively, provide the energy and
##nosperms and angiosperms. gymnosperms produce " naked seeds " not fully enclosed in an ovary ; modern representatives include conifers, cycads, ginkgo, and gnetales. angiosperms produce seeds enclosed in a structure such as a carpel or an ovary. ongoing research on the molecular phylogenetics of living plants appears to show that the angiosperms are a sister clade to the gymnosperms. = = plant physiology = = plant physiology encompasses all the internal chemical and physical activities of plants associated with life. chemicals obtained from the air, soil and water form the basis of all plant metabolism. the energy of sunlight, captured by oxygenic photosynthesis and released by cellular respiration, is the basis of almost all life. photoautotrophs, including all green plants, algae and cyanobacteria gather energy directly from sunlight by photosynthesis. heterotrophs including all animals, all fungi, all completely parasitic plants, and non - photosynthetic bacteria take in organic molecules produced by photoautotrophs and respire them or use them in the construction of cells and tissues. respiration is the oxidation of carbon compounds by breaking them down into simpler structures to release the energy they contain, essentially the opposite of photosynthesis. molecules are moved within plants by transport processes that operate at a variety of spatial scales. subcellular transport of ions, electrons and molecules such as water and enzymes occurs across cell membranes. minerals and water are transported from roots to other parts of the plant in the transpiration stream. diffusion, osmosis, and active transport and mass flow are all different ways transport can occur. examples of elements that plants need to transport are nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. in vascular plants, these elements are extracted from the soil as soluble ions by the roots and transported throughout the plant in the xylem. most of the elements required for plant nutrition come from the chemical breakdown of soil minerals. sucrose produced by photosynthesis is transported from the leaves to other parts of the plant in the phloem and plant hormones are transported by a variety of processes. = = = plant hormones = = = plants are not passive, but respond to external signals such as light, touch, and injury by moving or growing towards or away from the stimulus, as appropriate. tangible evidence of touch sensitivity is the almost instantaneous collapse of leaflets of mimosa pudica, the insect traps of
Question: Life itself could not exist without what energy, which plays a vital role in photosynthesis?
A) spin energy
B) magnetic energy
C) time energy
D) light energy
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D) light energy
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Context:
energy is no doubt an intuitive concept. following a previous analysis on the nature of elementary particles and associated elementary quantum fields, the peculiar status and role of energy is scrutinised further at elementary and larger scales. energy physical characterisation shows that it is a primordial component of reality highlighting the quantum fields natural tendencies to interact, the elementary particles natural tendency to constitute complex bodies and every material thing natural tendency to actualise and be active. energy therefore is a primordial notion in need of a proper assessment.
##physical processes which take place in human beings as they make sense of information received through the visual system. the subject of the image. when developing an imaging system, designers must consider the observables associated with the subjects which will be imaged. these observables generally take the form of emitted or reflected energy, such as electromagnetic energy or mechanical energy. the capture device. once the observables associated with the subject are characterized, designers can then identify and integrate the technologies needed to capture those observables. for example, in the case of consumer digital cameras, those technologies include optics for collecting energy in the visible portion of the electromagnetic spectrum, and electronic detectors for converting the electromagnetic energy into an electronic signal. the processor. for all digital imaging systems, the electronic signals produced by the capture device must be manipulated by an algorithm which formats the signals so they can be displayed as an image. in practice, there are often multiple processors involved in the creation of a digital image. the display. the display takes the electronic signals which have been manipulated by the processor and renders them on some visual medium. examples include paper ( for printed, or " hard copy " images ), television, computer monitor, or projector. note that some imaging scientists will include additional " links " in their description of the imaging chain. for example, some will include the " source " of the energy which " illuminates " or interacts with the subject of the image. others will include storage and / or transmission systems. = = subfields = = subfields within imaging science include : image processing, computer vision, 3d computer graphics, animations, atmospheric optics, astronomical imaging, biological imaging, digital image restoration, digital imaging, color science, digital photography, holography, magnetic resonance imaging, medical imaging, microdensitometry, optics, photography, remote sensing, radar imaging, radiometry, silver halide, ultrasound imaging, photoacoustic imaging, thermal imaging, visual perception, and various printing technologies. = = methodologies = = acoustic imaging coherent imaging uses an active coherent illumination source, such as in radar, synthetic aperture radar ( sar ), medical ultrasound and optical coherence tomography ; non - coherent imaging systems include fluorescent microscopes, optical microscopes, and telescopes. chemical imaging, the simultaneous measurement of spectra and pictures digital imaging, creating digital images, generally by scanning or through digital photography disk image, a file which contains the exact content of a data storage medium document imaging, replicating documents commonly
einstein, when he began working on the general theory of relativity, believed that energy of any kind is the source of the gravitational field. therefore, the energy of gravity, like any energy, must be the source of the field. it was previously discovered that the energy - momentum tensor of the gravitational field is already contained in the ricci tensor. this hypothesis is used to construct a new equation of the gravitational field.
activation energy necessary for a chemical reaction to occur can be in the form of heat, light, electricity or mechanical force in the form of ultrasound. a related concept free energy, which also incorporates entropy considerations, is a very useful means for predicting the feasibility of a reaction and determining the state of equilibrium of a chemical reaction, in chemical thermodynamics. a reaction is feasible only if the total change in the gibbs free energy is negative, Ξ΄ g β€ 0 { \ displaystyle \ delta g \ leq 0 \, } ; if it is equal to zero the chemical reaction is said to be at equilibrium. there exist only limited possible states of energy for electrons, atoms and molecules. these are determined by the rules of quantum mechanics, which require quantization of energy of a bound system. the atoms / molecules in a higher energy state are said to be excited. the molecules / atoms of substance in an excited energy state are often much more reactive ; that is, more amenable to chemical reactions. the phase of a substance is invariably determined by its energy and the energy of its surroundings. when the intermolecular forces of a substance are such that the energy of the surroundings is not sufficient to overcome them, it occurs in a more ordered phase like liquid or solid as is the case with water ( h2o ) ; a liquid at room temperature because its molecules are bound by hydrogen bonds. whereas hydrogen sulfide ( h2s ) is a gas at room temperature and standard pressure, as its molecules are bound by weaker dipole β dipole interactions. the transfer of energy from one chemical substance to another depends on the size of energy quanta emitted from one substance. however, heat energy is often transferred more easily from almost any substance to another because the phonons responsible for vibrational and rotational energy levels in a substance have much less energy than photons invoked for the electronic energy transfer. thus, because vibrational and rotational energy levels are more closely spaced than electronic energy levels, heat is more easily transferred between substances relative to light or other forms of electronic energy. for example, ultraviolet electromagnetic radiation is not transferred with as much efficacy from one substance to another as thermal or electrical energy. the existence of characteristic energy levels for different chemical substances is useful for their identification by the analysis of spectral lines. different kinds of spectra are often used in chemical spectroscopy, e. g. ir, microwave, nmr, esr, etc. spectroscopy is also used to identify the composition of remote objects β like stars and distant galaxies β by
factor e β e / k t { \ displaystyle e ^ { - e / kt } } β that is the probability of a molecule to have energy greater than or equal to e at the given temperature t. this exponential dependence of a reaction rate on temperature is known as the arrhenius equation. the activation energy necessary for a chemical reaction to occur can be in the form of heat, light, electricity or mechanical force in the form of ultrasound. a related concept free energy, which also incorporates entropy considerations, is a very useful means for predicting the feasibility of a reaction and determining the state of equilibrium of a chemical reaction, in chemical thermodynamics. a reaction is feasible only if the total change in the gibbs free energy is negative, Ξ΄ g β€ 0 { \ displaystyle \ delta g \ leq 0 \, } ; if it is equal to zero the chemical reaction is said to be at equilibrium. there exist only limited possible states of energy for electrons, atoms and molecules. these are determined by the rules of quantum mechanics, which require quantization of energy of a bound system. the atoms / molecules in a higher energy state are said to be excited. the molecules / atoms of substance in an excited energy state are often much more reactive ; that is, more amenable to chemical reactions. the phase of a substance is invariably determined by its energy and the energy of its surroundings. when the intermolecular forces of a substance are such that the energy of the surroundings is not sufficient to overcome them, it occurs in a more ordered phase like liquid or solid as is the case with water ( h2o ) ; a liquid at room temperature because its molecules are bound by hydrogen bonds. whereas hydrogen sulfide ( h2s ) is a gas at room temperature and standard pressure, as its molecules are bound by weaker dipole β dipole interactions. the transfer of energy from one chemical substance to another depends on the size of energy quanta emitted from one substance. however, heat energy is often transferred more easily from almost any substance to another because the phonons responsible for vibrational and rotational energy levels in a substance have much less energy than photons invoked for the electronic energy transfer. thus, because vibrational and rotational energy levels are more closely spaced than electronic energy levels, heat is more easily transferred between substances relative to light or other forms of electronic energy. for example, ultraviolet electromagnetic radiation is not transferred with as much efficacy from one substance to another as thermal or electrical energy. the existence of characteristic
energy they need to exist. plants, algae and cyanobacteria are the major groups of organisms that carry out photosynthesis, a process that uses the energy of sunlight to convert water and carbon dioxide into sugars that can be used both as a source of chemical energy and of organic molecules that are used in the structural components of cells. as a by - product of photosynthesis, plants release oxygen into the atmosphere, a gas that is required by nearly all living things to carry out cellular respiration. in addition, they are influential in the global carbon and water cycles and plant roots bind and stabilise soils, preventing soil erosion. plants are crucial to the future of human society as they provide food, oxygen, biochemicals, and products for people, as well as creating and preserving soil. historically, all living things were classified as either animals or plants and botany covered the study of all organisms not considered animals. botanists examine both the internal functions and processes within plant organelles, cells, tissues, whole plants, plant populations and plant communities. at each of these levels, a botanist may be concerned with the classification ( taxonomy ), phylogeny and evolution, structure ( anatomy and morphology ), or function ( physiology ) of plant life. the strictest definition of " plant " includes only the " land plants " or embryophytes, which include seed plants ( gymnosperms, including the pines, and flowering plants ) and the free - sporing cryptogams including ferns, clubmosses, liverworts, hornworts and mosses. embryophytes are multicellular eukaryotes descended from an ancestor that obtained its energy from sunlight by photosynthesis. they have life cycles with alternating haploid and diploid phases. the sexual haploid phase of embryophytes, known as the gametophyte, nurtures the developing diploid embryo sporophyte within its tissues for at least part of its life, even in the seed plants, where the gametophyte itself is nurtured by its parent sporophyte. other groups of organisms that were previously studied by botanists include bacteria ( now studied in bacteriology ), fungi ( mycology ) β including lichen - forming fungi ( lichenology ), non - chlorophyte algae ( phycology ), and viruses ( virology ). however, attention is still given to these groups by botanists, and fungi ( including lichens ) and photos
doing research is fighting, what any other thing the human being could do? fight against powers or to get powers, that depends on us. science can be a revolution or deadlocked idleness. still waters, without hitting the stones along their history, trend to form bogs.
this process may release or absorb energy. when the resulting nucleus is lighter than that of iron, energy is normally released ; when the nucleus is heavier than that of iron, energy is generally absorbed. this process of fusion occurs in stars, which derive their energy from hydrogen and helium. they form, through stellar nucleosynthesis, the light elements ( lithium to calcium ) as well as some of the heavy elements ( beyond iron and nickel, via the s - process ). the remaining abundance of heavy elements, from nickel to uranium and beyond, is due to supernova nucleosynthesis, the r - process. of course, these natural processes of astrophysics are not examples of nuclear " technology ". because of the very strong repulsion of nuclei, fusion is difficult to achieve in a controlled fashion. hydrogen bombs, formally known as thermonuclear weapons, obtain their enormous destructive power from fusion, but their energy cannot be controlled. controlled fusion is achieved in particle accelerators ; this is how many synthetic elements are produced. a fusor can also produce controlled fusion and is a useful neutron source. however, both of these devices operate at a net energy loss. controlled, viable fusion power has proven elusive, despite the occasional hoax. technical and theoretical difficulties have hindered the development of working civilian fusion technology, though research continues to this day around the world. nuclear fusion was initially pursued only in theoretical stages during world war ii, when scientists on the manhattan project ( led by edward teller ) investigated it as a method to build a bomb. the project abandoned fusion after concluding that it would require a fission reaction to detonate. it took until 1952 for the first full hydrogen bomb to be detonated, so - called because it used reactions between deuterium and tritium. fusion reactions are much more energetic per unit mass of fuel than fission reactions, but starting the fusion chain reaction is much more difficult. = = nuclear weapons = = a nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or a combination of fission and fusion. both reactions release vast quantities of energy from relatively small amounts of matter. even small nuclear devices can devastate a city by blast, fire and radiation. nuclear weapons are considered weapons of mass destruction, and their use and control has been a major aspect of international policy since their debut. the design of a nuclear weapon is more complicated than it might seem. such a weapon must hold one or more subcritical fissile masses stable for deployment, then induce criticality
the recent report on laser cooling of liquid may contradict the law of energy conservation.
not only is the bekenstein expression for the entropy of a black hole a convex function of the energy, rather than being a concave function as it must be, it predicts a final equilibrium temperature given by the harmonic mean. this violates the third law, and the principle of maximum work. the property that means are monotonically increasing functions of their argument underscores the error of transferring from temperature means to means in the internal energy when the energy is not a monotonically increasing function of temperature. whereas the former leads to an increase in entropy, the latter lead to a decrease in entropy thereby violating the second law. the internal energy cannot increase at a slower rate than the temperature itself.
Question: What does power imply is happening to energy?
A) being created
B) being destroyed
C) is expanding
D) being transferred
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D) being transferred
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Context:
has rest mass and volume ( it takes up space ) and is made up of particles. the particles that make up matter have rest mass as well β not all particles have rest mass, such as the photon. matter can be a pure chemical substance or a mixture of substances. = = = = atom = = = = the atom is the basic unit of chemistry. it consists of a dense core called the atomic nucleus surrounded by a space occupied by an electron cloud. the nucleus is made up of positively charged protons and uncharged neutrons ( together called nucleons ), while the electron cloud consists of negatively charged electrons which orbit the nucleus. in a neutral atom, the negatively charged electrons balance out the positive charge of the protons. the nucleus is dense ; the mass of a nucleon is approximately 1, 836 times that of an electron, yet the radius of an atom is about 10, 000 times that of its nucleus. the atom is also the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state ( s ), coordination number, and preferred types of bonds to form ( e. g., metallic, ionic, covalent ). = = = = element = = = = a chemical element is a pure substance which is composed of a single type of atom, characterized by its particular number of protons in the nuclei of its atoms, known as the atomic number and represented by the symbol z. the mass number is the sum of the number of protons and neutrons in a nucleus. although all the nuclei of all atoms belonging to one element will have the same atomic number, they may not necessarily have the same mass number ; atoms of an element which have different mass numbers are known as isotopes. for example, all atoms with 6 protons in their nuclei are atoms of the chemical element carbon, but atoms of carbon may have mass numbers of 12 or 13. the standard presentation of the chemical elements is in the periodic table, which orders elements by atomic number. the periodic table is arranged in groups, or columns, and periods, or rows. the periodic table is useful in identifying periodic trends. = = = = compound = = = = a compound is a pure chemical substance composed of more than one element. the properties of a compound bear little similarity to those of its elements. the standard nomenclature of compounds is set by the international union of pure and applied chemistry ( iupac ). organic compounds are named
other electrons either in bonds or in lone pairs. thus, molecules exist as electrically neutral units, unlike ions. when this rule is broken, giving the " molecule " a charge, the result is sometimes named a molecular ion or a polyatomic ion. however, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature. = = = = substance and mixture = = = = a chemical substance is a kind of matter with a definite composition and set of properties. a collection of substances is called a mixture. examples of mixtures are air and alloys. = = = = mole and amount of substance = = = = the mole is a unit
it is believed that there may have been a large number of black holes formed in the very early universe. these would have quantised masses. a charged ` ` elementary black hole ' ' ( with the minimum possible mass ) can capture electrons, protons and other charged particles to form a ` ` black hole atom ' '. we find the spectrum of such an object with a view to laboratory and astronomical observation of them, and estimate the lifetime of the bound states. there is no limit to the charge of the black hole, which gives us the possibility of observing z > 137 bound states and transitions at the lower continuum. negatively charged black holes can capture protons. for z > 1, the orbiting protons will coalesce to form a nucleus ( after beta - decay of some protons to neutrons ), with a stability curve different to that of free nuclei. in this system there is also the distinct possibility of single quark capture. this leads to the formation of a coloured black hole that plays the role of an extremely heavy quark interacting strongly with the other two quarks. finally we consider atoms formed with much larger black holes.
set of chemical reactions with other substances. however, this definition only works well for substances that are composed of molecules, which is not true of many substances ( see below ). molecules are typically a set of atoms bound together by covalent bonds, such that the structure is electrically neutral and all valence electrons are paired with other electrons either in bonds or in lone pairs. thus, molecules exist as electrically neutral units, unlike ions. when this rule is broken, giving the " molecule " a charge, the result is sometimes named a molecular ion or a polyatomic ion. however, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature.
this proceeding explores some of the questions that connect the lhc and neutrino experiments : what is the origin of mass? what is the meaning of flavor? is there direct evidence of new forces or particles? the neutrino program investigating these questions is large and diverse. the strategy here, to narrow the discussion, is to focus on relatively new ideas for experiments that may be less known within the lhc community.
g. spectroscopy and chromatography. scientists engaged in chemical research are known as chemists. most chemists specialize in one or more sub - disciplines. several concepts are essential for the study of chemistry ; some of them are : = = = matter = = = in chemistry, matter is defined as anything that has rest mass and volume ( it takes up space ) and is made up of particles. the particles that make up matter have rest mass as well β not all particles have rest mass, such as the photon. matter can be a pure chemical substance or a mixture of substances. = = = = atom = = = = the atom is the basic unit of chemistry. it consists of a dense core called the atomic nucleus surrounded by a space occupied by an electron cloud. the nucleus is made up of positively charged protons and uncharged neutrons ( together called nucleons ), while the electron cloud consists of negatively charged electrons which orbit the nucleus. in a neutral atom, the negatively charged electrons balance out the positive charge of the protons. the nucleus is dense ; the mass of a nucleon is approximately 1, 836 times that of an electron, yet the radius of an atom is about 10, 000 times that of its nucleus. the atom is also the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state ( s ), coordination number, and preferred types of bonds to form ( e. g., metallic, ionic, covalent ). = = = = element = = = = a chemical element is a pure substance which is composed of a single type of atom, characterized by its particular number of protons in the nuclei of its atoms, known as the atomic number and represented by the symbol z. the mass number is the sum of the number of protons and neutrons in a nucleus. although all the nuclei of all atoms belonging to one element will have the same atomic number, they may not necessarily have the same mass number ; atoms of an element which have different mass numbers are known as isotopes. for example, all atoms with 6 protons in their nuclei are atoms of the chemical element carbon, but atoms of carbon may have mass numbers of 12 or 13. the standard presentation of the chemical elements is in the periodic table, which orders elements by atomic number. the periodic table is arranged in groups, or columns, and periods, or rows. the periodic table is useful in identifying periodic trends
the united rest mass and charge of a particle correspond to the two forms of the same regularity of the unified nature of its ultimate structure. each of them contains the electric, weak, strong and the gravitational contributions. as a consequence, the force of an attraction among the two neutrinos and force of their repulsion must be defined from the point of view of any of the existing types of the actions. therefore, to understand the nature of the micro world interaction at the fundamental level, one must use the fact that each of the four types of well known forces includes both a kind of the newton and a kind of the coulomb components. the opinion has been spoken that the existence of the gravitational parts of the united rest mass and charge would imply the availability of such a fifth force which come forwards in the system as a unified whole.
there are four puzzling questions about by the magnitudes of neutrino mixings and mass splittings. a brief sketch is given of the various kinds of models of neutrino masses and how they answer these questions. special attention is given to so - called " lopsided " models.
that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature. = = = = substance and mixture = = = = a chemical substance is a kind of matter with a definite composition and set of properties. a collection of substances is called a mixture. examples of mixtures are air and alloys. = = = = mole and amount of substance = = = = the mole is a unit of measurement that denotes an amount of substance ( also called chemical amount ). one mole is defined to contain exactly 6. 02214076Γ1023 particles ( atoms, molecules, ions, or electrons ), where the number of particles per mole is known as the avogadro constant. molar concentration is
classes according to pore size : the form and shape of the membrane pores are highly dependent on the manufacturing process and are often difficult to specify. therefore, for characterization, test filtrations are carried out and the pore diameter refers to the diameter of the smallest particles which could not pass through the membrane. the rejection can be determined in various ways and provides an indirect measurement of the pore size. one possibility is the filtration of macromolecules ( often dextran, polyethylene glycol or albumin ), another is measurement of the cut - off by gel permeation chromatography. these methods are used mainly to measure membranes for ultrafiltration applications. another testing method is the filtration of particles with defined size and their measurement with a particle sizer or by laser induced breakdown spectroscopy ( libs ). a vivid characterization is to measure the rejection of dextran blue or other colored molecules. the retention of bacteriophage and bacteria, the so - called " bacteria challenge test ", can also provide information about the pore size. to determine the pore diameter, physical methods such as porosimeter ( mercury, liquid - liquid porosimeter and bubble point test ) are also used, but a certain form of the pores ( such as cylindrical or concatenated spherical holes ) is assumed. such methods are used for membranes whose pore geometry does not match the ideal, and we get " nominal " pore diameter, which characterizes the membrane, but does not necessarily reflect its actual filtration behavior and selectivity. the selectivity is highly dependent on the separation process, the composition of the membrane and its electrochemical properties in addition to the pore size. with high selectivity, isotopes can be enriched ( uranium enrichment ) in nuclear engineering or industrial gases like nitrogen can be recovered ( gas separation ). ideally, even racemics can be enriched with a suitable membrane. when choosing membranes selectivity has priority over a high permeability, as low flows can easily be offset by increasing the filter surface with a modular structure. in gas phase filtration different deposition mechanisms are operative, so that particles having sizes below the pore size of the membrane can be retained as well. = = membrane classification = = bio - membrane is classified in two categories, synthetic membrane and natural membrane. synthetic membranes further classified in organic and inorganic membranes. organic membrane sub classified polymeric membranes and inorganic membrane sub classified ceramic polymers. = = synthesis of biomass membrane
Question: Because the masses of subatomic particles are so small, a new unit, called what, was defined?
A) nuclear mass unit
B) atomic mass unit
C) particle mass unit
D) atomic volume unit
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B) atomic mass unit
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Context:
scale. thus, solutions that have a low ph have a high hydronium ion concentration and can be said to be more acidic. the other measurement, based on the brΓΈnsted β lowry definition, is the acid dissociation constant ( ka ), which measures the relative ability of a substance to act as an acid under the brΓΈnsted β lowry definition of an acid. that is, substances with a higher ka are more likely to donate hydrogen ions in chemical reactions than those with lower ka values. = = = redox = = = redox ( reduction - oxidation ) reactions include all chemical reactions in which atoms have their oxidation state changed by either gaining electrons ( reduction ) or losing electrons ( oxidation ). substances that have the ability to oxidize other substances are said to be oxidative and are known as oxidizing agents, oxidants or oxidizers. an oxidant removes electrons from another substance. similarly, substances that have the ability to reduce other substances are said to be reductive and are known as reducing agents, reductants, or reducers. a reductant transfers electrons to another substance and is thus oxidized itself. and because it " donates " electrons it is also called an electron donor. oxidation and reduction properly refer to a change in oxidation number β the actual transfer of electrons may never occur. thus, oxidation is better defined as an increase in oxidation number, and reduction as a decrease in oxidation number. = = = equilibrium = = = although the concept of equilibrium is widely used across sciences, in the context of chemistry, it arises whenever a number of different states of the chemical composition are possible, as for example, in a mixture of several chemical compounds that can react with one another, or when a substance can be present in more than one kind of phase. a system of chemical substances at equilibrium, even though having an unchanging composition, is most often not static ; molecules of the substances continue to react with one another thus giving rise to a dynamic equilibrium. thus the concept describes the state in which the parameters such as chemical composition remain unchanged over time. = = = chemical laws = = = chemical reactions are governed by certain laws, which have become fundamental concepts in chemistry. some of them are : = = history = = the history of chemistry spans a period from the ancient past to the present. since several millennia bc, civilizations were using technologies that would eventually form the basis of the various branches of chemistry. examples include extracting metals from ores
the walls of a victim ' s stomach. toxicology, a subfield of forensic chemistry, focuses on detecting and identifying drugs, poisons, and other toxic substances in biological samples. forensic toxicologists work on cases involving drug overdoses, poisoning, and substance abuse. their work is critical in determining whether harmful substances play a role in a person β s death or impairment. read more james marsh was the first to apply this new science to the art of forensics. he was called by the prosecution in a murder trial to give evidence as a chemist in 1832. the defendant, john bodle, was accused of poisoning his grandfather with arsenic - laced coffee. marsh performed the standard test by mixing a suspected sample with hydrogen sulfide and hydrochloric acid. while he was able to detect arsenic as yellow arsenic trisulfide, when it was shown to the jury it had deteriorated, allowing the suspect to be acquitted due to reasonable doubt. annoyed by that, marsh developed a much better test. he combined a sample containing arsenic with sulfuric acid and arsenic - free zinc, resulting in arsine gas. the gas was ignited, and it decomposed to pure metallic arsenic, which, when passed to a cold surface, would appear as a silvery - black deposit. so sensitive was the test, known formally as the marsh test, that it could detect as little as one - fiftieth of a milligram of arsenic. he first described this test in the edinburgh philosophical journal in 1836. = = = ballistics and firearms = = = ballistics is " the science of the motion of projectiles in flight ". in forensic science, analysts examine the patterns left on bullets and cartridge casings after being ejected from a weapon. when fired, a bullet is left with indentations and markings that are unique to the barrel and firing pin of the firearm that ejected the bullet. this examination can help scientists identify possible makes and models of weapons connected to a crime. henry goddard at scotland yard pioneered the use of bullet comparison in 1835. he noticed a flaw in the bullet that killed the victim and was able to trace this back to the mold that was used in the manufacturing process. = = = anthropometry = = = the french police officer alphonse bertillon was the first to apply the anthropological technique of anthropometry to law enforcement, thereby creating an identification system based on physical measurements. before that time, criminals could be identified only by name or photograph. dissatisfied with the ad hoc methods used to identify captured
some references for the breaking strength of fused silica fibers compiled in 1999.
what kind of new physics, if any, we expect to discover at the lhc? i will try to address this formidable question by re - formulating it as follows : is the breaking of the electroweak symmetry strong or weak?
prominent functional groups that can be found in organisms : amino group, carboxyl group, carbonyl group, hydroxyl group, phosphate group, and sulfhydryl group. in 1953, the miller β urey experiment showed that organic compounds could be synthesized abiotically within a closed system mimicking the conditions of early earth, thus suggesting that complex organic molecules could have arisen spontaneously in early earth ( see abiogenesis ). = = = macromolecules = = = macromolecules are large molecules made up of smaller subunits or monomers. monomers include sugars, amino acids, and nucleotides. carbohydrates include monomers and polymers of sugars. lipids are the only class of macromolecules that are not made up of polymers. they include steroids, phospholipids, and fats, largely nonpolar and hydrophobic ( water - repelling ) substances. proteins are the most diverse of the macromolecules. they include enzymes, transport proteins, large signaling molecules, antibodies, and structural proteins. the basic unit ( or monomer ) of a protein is an amino acid. twenty amino acids are used in proteins. nucleic acids are polymers of nucleotides. their function is to store, transmit, and express hereditary information. = = cells = = cell theory states that cells are the fundamental units of life, that all living things are composed of one or more cells, and that all cells arise from preexisting cells through cell division. most cells are very small, with diameters ranging from 1 to 100 micrometers and are therefore only visible under a light or electron microscope. there are generally two types of cells : eukaryotic cells, which contain a nucleus, and prokaryotic cells, which do not. prokaryotes are single - celled organisms such as bacteria, whereas eukaryotes can be single - celled or multicellular. in multicellular organisms, every cell in the organism ' s body is derived ultimately from a single cell in a fertilized egg. = = = cell structure = = = every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as
or a base, as is evident in the history of this concept. acid strength is commonly measured by two methods. one measurement, based on the arrhenius definition of acidity, is ph, which is a measurement of the hydronium ion concentration in a solution, as expressed on a negative logarithmic scale. thus, solutions that have a low ph have a high hydronium ion concentration and can be said to be more acidic. the other measurement, based on the brΓΈnsted β lowry definition, is the acid dissociation constant ( ka ), which measures the relative ability of a substance to act as an acid under the brΓΈnsted β lowry definition of an acid. that is, substances with a higher ka are more likely to donate hydrogen ions in chemical reactions than those with lower ka values. = = = redox = = = redox ( reduction - oxidation ) reactions include all chemical reactions in which atoms have their oxidation state changed by either gaining electrons ( reduction ) or losing electrons ( oxidation ). substances that have the ability to oxidize other substances are said to be oxidative and are known as oxidizing agents, oxidants or oxidizers. an oxidant removes electrons from another substance. similarly, substances that have the ability to reduce other substances are said to be reductive and are known as reducing agents, reductants, or reducers. a reductant transfers electrons to another substance and is thus oxidized itself. and because it " donates " electrons it is also called an electron donor. oxidation and reduction properly refer to a change in oxidation number β the actual transfer of electrons may never occur. thus, oxidation is better defined as an increase in oxidation number, and reduction as a decrease in oxidation number. = = = equilibrium = = = although the concept of equilibrium is widely used across sciences, in the context of chemistry, it arises whenever a number of different states of the chemical composition are possible, as for example, in a mixture of several chemical compounds that can react with one another, or when a substance can be present in more than one kind of phase. a system of chemical substances at equilibrium, even though having an unchanging composition, is most often not static ; molecules of the substances continue to react with one another thus giving rise to a dynamic equilibrium. thus the concept describes the state in which the parameters such as chemical composition remain unchanged over time. = = = chemical laws = = = chemical reactions are governed by certain laws
, characterizing organs as predominantly yin or yang, and understood the relationship between the pulse, the heart, and the flow of blood in the body centuries before it became accepted in the west. little evidence survives of how ancient indian cultures around the indus river understood nature, but some of their perspectives may be reflected in the vedas, a set of sacred hindu texts. they reveal a conception of the universe as ever - expanding and constantly being recycled and reformed. surgeons in the ayurvedic tradition saw health and illness as a combination of three humors : wind, bile and phlegm. a healthy life resulted from a balance among these humors. in ayurvedic thought, the body consisted of five elements : earth, water, fire, wind, and space. ayurvedic surgeons performed complex surgeries and developed a detailed understanding of human anatomy. pre - socratic philosophers in ancient greek culture brought natural philosophy a step closer to direct inquiry about cause and effect in nature between 600 and 400 bc. however, an element of magic and mythology remained. natural phenomena such as earthquakes and eclipses were explained increasingly in the context of nature itself instead of being attributed to angry gods. thales of miletus, an early philosopher who lived from 625 to 546 bc, explained earthquakes by theorizing that the world floated on water and that water was the fundamental element in nature. in the 5th century bc, leucippus was an early exponent of atomism, the idea that the world is made up of fundamental indivisible particles. pythagoras applied greek innovations in mathematics to astronomy and suggested that the earth was spherical. = = = aristotelian natural philosophy ( 400 bc β 1100 ad ) = = = later socratic and platonic thought focused on ethics, morals, and art and did not attempt an investigation of the physical world ; plato criticized pre - socratic thinkers as materialists and anti - religionists. aristotle, however, a student of plato who lived from 384 to 322 bc, paid closer attention to the natural world in his philosophy. in his history of animals, he described the inner workings of 110 species, including the stingray, catfish and bee. he investigated chick embryos by breaking open eggs and observing them at various stages of development. aristotle ' s works were influential through the 16th century, and he is considered to be the father of biology for his pioneering work in that science. he also presented philosophies about physics, nature, and astronomy using
men. well - known spiritual systems include animism ( the notion of inanimate objects having spirits ), spiritualism ( an appeal to gods or communion with ancestor spirits ) ; shamanism ( the vesting of an individual with mystic powers ) ; and divination ( magically obtaining the truth ). the field of medical anthropology examines the ways in which culture and society are organized around or impacted by issues of health, health care and related issues. the earliest known medical texts in the world were found in the ancient syrian city of ebla and date back to 2500 bce. other early records on medicine have been discovered from ancient egyptian medicine, babylonian medicine, ayurvedic medicine ( in the indian subcontinent ), classical chinese medicine ( alternative medicine ) predecessor to the modern traditional chinese medicine ), and ancient greek medicine and roman medicine. in egypt, imhotep ( 3rd millennium bce ) is the first physician in history known by name. the oldest egyptian medical text is the kahun gynaecological papyrus from around 2000 bce, which describes gynaecological diseases. the edwin smith papyrus dating back to 1600 bce is an early work on surgery, while the ebers papyrus dating back to 1500 bce is akin to a textbook on medicine. in china, archaeological evidence of medicine in chinese dates back to the bronze age shang dynasty, based on seeds for herbalism and tools presumed to have been used for surgery. the huangdi neijing, the progenitor of chinese medicine, is a medical text written beginning in the 2nd century bce and compiled in the 3rd century. in india, the surgeon sushruta described numerous surgical operations, including the earliest forms of plastic surgery. earliest records of dedicated hospitals come from mihintale in sri lanka where evidence of dedicated medicinal treatment facilities for patients are found. in greece, the ancient greek physician hippocrates, the " father of modern medicine ", laid the foundation for a rational approach to medicine. hippocrates introduced the hippocratic oath for physicians, which is still relevant and in use today, and was the first to categorize illnesses as acute, chronic, endemic and epidemic, and use terms such as, " exacerbation, relapse, resolution, crisis, paroxysm, peak, and convalescence ". the greek physician galen was also one of the greatest surgeons of the ancient world and performed many audacious operations, including brain and eye surgeries. after the fall of the western roman empire and the onset of
water - repelling ) substances. proteins are the most diverse of the macromolecules. they include enzymes, transport proteins, large signaling molecules, antibodies, and structural proteins. the basic unit ( or monomer ) of a protein is an amino acid. twenty amino acids are used in proteins. nucleic acids are polymers of nucleotides. their function is to store, transmit, and express hereditary information. = = cells = = cell theory states that cells are the fundamental units of life, that all living things are composed of one or more cells, and that all cells arise from preexisting cells through cell division. most cells are very small, with diameters ranging from 1 to 100 micrometers and are therefore only visible under a light or electron microscope. there are generally two types of cells : eukaryotic cells, which contain a nucleus, and prokaryotic cells, which do not. prokaryotes are single - celled organisms such as bacteria, whereas eukaryotes can be single - celled or multicellular. in multicellular organisms, every cell in the organism ' s body is derived ultimately from a single cell in a fertilized egg. = = = cell structure = = = every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions. cell membranes also contain membrane proteins, including integral membrane proteins that go across the membrane serving as membrane transporters, and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes shaping the cell. cell membranes are involved in various cellular processes such as cell adhesion, storing electrical energy, and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall, glycocalyx, and cytoskeleton. within the cytoplasm of a cell, there are many biomolecules such as proteins and nucleic acids. in addition to biomolecules, eukaryotic cells have specialized structures called organelles that have their own lipid bilayers or are spatially units. these organelles include the cell nucleus, which contains most of
conditions of early earth, thus suggesting that complex organic molecules could have arisen spontaneously in early earth ( see abiogenesis ). = = = macromolecules = = = macromolecules are large molecules made up of smaller subunits or monomers. monomers include sugars, amino acids, and nucleotides. carbohydrates include monomers and polymers of sugars. lipids are the only class of macromolecules that are not made up of polymers. they include steroids, phospholipids, and fats, largely nonpolar and hydrophobic ( water - repelling ) substances. proteins are the most diverse of the macromolecules. they include enzymes, transport proteins, large signaling molecules, antibodies, and structural proteins. the basic unit ( or monomer ) of a protein is an amino acid. twenty amino acids are used in proteins. nucleic acids are polymers of nucleotides. their function is to store, transmit, and express hereditary information. = = cells = = cell theory states that cells are the fundamental units of life, that all living things are composed of one or more cells, and that all cells arise from preexisting cells through cell division. most cells are very small, with diameters ranging from 1 to 100 micrometers and are therefore only visible under a light or electron microscope. there are generally two types of cells : eukaryotic cells, which contain a nucleus, and prokaryotic cells, which do not. prokaryotes are single - celled organisms such as bacteria, whereas eukaryotes can be single - celled or multicellular. in multicellular organisms, every cell in the organism ' s body is derived ultimately from a single cell in a fertilized egg. = = = cell structure = = = every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions. cell membranes also contain membrane proteins, including integral membrane proteins that go across the membrane serving as membrane transporters, and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes
Question: Which organ breaks down amino acids and toxins that are in the blood?
A) liver
B) kidney
C) small intestine
D) skin
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A) liver
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Context:
charges in the nuclei and the negative charges oscillating about them. more than simple attraction and repulsion, the energies and distributions characterize the availability of an electron to bond to another atom. the chemical bond can be a covalent bond, an ionic bond, a hydrogen bond or just because of van der waals force. each of these kinds of bonds is ascribed to some potential. these potentials create the interactions which hold atoms together in molecules or crystals. in many simple compounds, valence bond theory, the valence shell electron pair repulsion model ( vsepr ), and the concept of oxidation number can be used to explain molecular structure and composition. an ionic bond is formed when a metal loses one or more of its electrons, becoming a positively charged cation, and the electrons are then gained by the non - metal atom, becoming a negatively charged anion. the two oppositely charged ions attract one another, and the ionic bond is the electrostatic force of attraction between them. for example, sodium ( na ), a metal, loses one electron to become an na + cation while chlorine ( cl ), a non - metal, gains this electron to become clβ. the ions are held together due to electrostatic attraction, and that compound sodium chloride ( nacl ), or common table salt, is formed. in a covalent bond, one or more pairs of valence electrons are shared by two atoms : the resulting electrically neutral group of bonded atoms is termed a molecule. atoms will share valence electrons in such a way as to create a noble gas electron configuration ( eight electrons in their outermost shell ) for each atom. atoms that tend to combine in such a way that they each have eight electrons in their valence shell are said to follow the octet rule. however, some elements like hydrogen and lithium need only two electrons in their outermost shell to attain this stable configuration ; these atoms are said to follow the duet rule, and in this way they are reaching the electron configuration of the noble gas helium, which has two electrons in its outer shell. similarly, theories from classical physics can be used to predict many ionic structures. with more complicated compounds, such as metal complexes, valence bond theory is less applicable and alternative approaches, such as the molecular orbital theory, are generally used. = = = energy = = = in the context of chemistry, energy is an attribute of a substance as a consequence of its atomic, molecular or aggregate structure. since a chemical transformation is accompanied by a change
set of chemical reactions with other substances. however, this definition only works well for substances that are composed of molecules, which is not true of many substances ( see below ). molecules are typically a set of atoms bound together by covalent bonds, such that the structure is electrically neutral and all valence electrons are paired with other electrons either in bonds or in lone pairs. thus, molecules exist as electrically neutral units, unlike ions. when this rule is broken, giving the " molecule " a charge, the result is sometimes named a molecular ion or a polyatomic ion. however, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature.
other electrons either in bonds or in lone pairs. thus, molecules exist as electrically neutral units, unlike ions. when this rule is broken, giving the " molecule " a charge, the result is sometimes named a molecular ion or a polyatomic ion. however, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature. = = = = substance and mixture = = = = a chemical substance is a kind of matter with a definite composition and set of properties. a collection of substances is called a mixture. examples of mixtures are air and alloys. = = = = mole and amount of substance = = = = the mole is a unit
##als force. each of these kinds of bonds is ascribed to some potential. these potentials create the interactions which hold atoms together in molecules or crystals. in many simple compounds, valence bond theory, the valence shell electron pair repulsion model ( vsepr ), and the concept of oxidation number can be used to explain molecular structure and composition. an ionic bond is formed when a metal loses one or more of its electrons, becoming a positively charged cation, and the electrons are then gained by the non - metal atom, becoming a negatively charged anion. the two oppositely charged ions attract one another, and the ionic bond is the electrostatic force of attraction between them. for example, sodium ( na ), a metal, loses one electron to become an na + cation while chlorine ( cl ), a non - metal, gains this electron to become clβ. the ions are held together due to electrostatic attraction, and that compound sodium chloride ( nacl ), or common table salt, is formed. in a covalent bond, one or more pairs of valence electrons are shared by two atoms : the resulting electrically neutral group of bonded atoms is termed a molecule. atoms will share valence electrons in such a way as to create a noble gas electron configuration ( eight electrons in their outermost shell ) for each atom. atoms that tend to combine in such a way that they each have eight electrons in their valence shell are said to follow the octet rule. however, some elements like hydrogen and lithium need only two electrons in their outermost shell to attain this stable configuration ; these atoms are said to follow the duet rule, and in this way they are reaching the electron configuration of the noble gas helium, which has two electrons in its outer shell. similarly, theories from classical physics can be used to predict many ionic structures. with more complicated compounds, such as metal complexes, valence bond theory is less applicable and alternative approaches, such as the molecular orbital theory, are generally used. = = = energy = = = in the context of chemistry, energy is an attribute of a substance as a consequence of its atomic, molecular or aggregate structure. since a chemical transformation is accompanied by a change in one or more of these kinds of structures, it is invariably accompanied by an increase or decrease of energy of the substances involved. some energy is transferred between the surroundings and the reactants of the reaction in the form of heat or light ; thus the products of a reaction may have more or less energy than the reactants
to explain molecular structure and composition. an ionic bond is formed when a metal loses one or more of its electrons, becoming a positively charged cation, and the electrons are then gained by the non - metal atom, becoming a negatively charged anion. the two oppositely charged ions attract one another, and the ionic bond is the electrostatic force of attraction between them. for example, sodium ( na ), a metal, loses one electron to become an na + cation while chlorine ( cl ), a non - metal, gains this electron to become clβ. the ions are held together due to electrostatic attraction, and that compound sodium chloride ( nacl ), or common table salt, is formed. in a covalent bond, one or more pairs of valence electrons are shared by two atoms : the resulting electrically neutral group of bonded atoms is termed a molecule. atoms will share valence electrons in such a way as to create a noble gas electron configuration ( eight electrons in their outermost shell ) for each atom. atoms that tend to combine in such a way that they each have eight electrons in their valence shell are said to follow the octet rule. however, some elements like hydrogen and lithium need only two electrons in their outermost shell to attain this stable configuration ; these atoms are said to follow the duet rule, and in this way they are reaching the electron configuration of the noble gas helium, which has two electrons in its outer shell. similarly, theories from classical physics can be used to predict many ionic structures. with more complicated compounds, such as metal complexes, valence bond theory is less applicable and alternative approaches, such as the molecular orbital theory, are generally used. = = = energy = = = in the context of chemistry, energy is an attribute of a substance as a consequence of its atomic, molecular or aggregate structure. since a chemical transformation is accompanied by a change in one or more of these kinds of structures, it is invariably accompanied by an increase or decrease of energy of the substances involved. some energy is transferred between the surroundings and the reactants of the reaction in the form of heat or light ; thus the products of a reaction may have more or less energy than the reactants. a reaction is said to be exergonic if the final state is lower on the energy scale than the initial state ; in the case of endergonic reactions the situation is the reverse. a reaction is said to be exothermic if the reaction releases heat to the surroundings ; in the case of
octet hyperon charge radii are calculated in a chiral constituent quark model including electromagnetic exchange currents between quarks. in impulse approximation one observes a decrease of the hyperon charge radii with increasing strangeness. this effect is reduced by exchange currents. due to exchange currents, the charge radius of the negatively charged hyperons are close to the proton charge radius.
the united rest mass and charge of a particle correspond to the two forms of the same regularity of the unified nature of its ultimate structure. each of them contains the electric, weak, strong and the gravitational contributions. as a consequence, the force of an attraction among the two neutrinos and force of their repulsion must be defined from the point of view of any of the existing types of the actions. therefore, to understand the nature of the micro world interaction at the fundamental level, one must use the fact that each of the four types of well known forces includes both a kind of the newton and a kind of the coulomb components. the opinion has been spoken that the existence of the gravitational parts of the united rest mass and charge would imply the availability of such a fifth force which come forwards in the system as a unified whole.
= = when 0 is said to be neither positive nor negative, the following phrases may refer to the sign of a number : a number is positive if it is greater than zero. a number is negative if it is less than zero. a number is non - negative if it is greater than or equal to zero. a number is non - positive if it is less than or equal to zero. when 0 is said to be both positive and negative, modified phrases are used to refer to the sign of a number : a number is strictly positive if it is greater than zero. a number is strictly negative if it is less than zero. a number is positive if it is greater than or equal to zero. a number is negative if it is less than or equal to zero. for example, the absolute value of a real number is always " non - negative ", but is not necessarily " positive " in the first interpretation, whereas in the second interpretation, it is called " positive " β though not necessarily " strictly positive ". the same terminology is sometimes used for functions that yield real or other signed values. for example, a function would be called a positive function if its values are positive for all arguments of its domain, or a non - negative function if all of its values are non - negative. = = = complex numbers = = = complex numbers are impossible to order, so they cannot carry the structure of an ordered ring, and, accordingly, cannot be partitioned into positive and negative complex numbers. they do, however, share an attribute with the reals, which is called absolute value or magnitude. magnitudes are always non - negative real numbers, and to any non - zero number there belongs a positive real number, its absolute value. for example, the absolute value of β3 and the absolute value of 3 are both equal to 3. this is written in symbols as | β3 | = 3 and | 3 | = 3. in general, any arbitrary real value can be specified by its magnitude and its sign. using the standard encoding, any real value is given by the product of the magnitude and the sign in standard encoding. this relation can be generalized to define a sign for complex numbers. since the real and complex numbers both form a field and contain the positive reals, they also contain the reciprocals of the magnitudes of all non - zero numbers. this means that any non - zero number may be multiplied with the reciprocal of its magnitude, that is, divided by its magnitude. it is immediate that the quotient
in a voltaic cell, positive ( negative ) ions flow from the low ( high ) potential electrode to the high ( low ) potential electrode, driven by an ` electromotive force ' which points in opposite direction and overcomes the electric force. similarly in a superconductor charge flows in direction opposite to that dictated by the faraday electric field as the magnetic field is expelled in the meissner effect. the puzzle is the same in both cases : what drives electric charges against electromagnetic forces? i propose that the answer is also the same in both cases : kinetic energy lowering, or ` quantum pressure '.
the value of excess charge in the kernel of massive body ( and the opposite in sign excess charge at the surface ) caused by the influence of gravitational forces is determined.
Question: Which compound has positively and negatively charged ends?
A) non-polar compound
B) tumultuous compound
C) polar compound
D) real compound
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C) polar compound
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Context:
to epidemiology and evidence - based medicine. cytology is the microscopic study of individual cells. embryology is the study of the early development of organisms. endocrinology is the study of hormones and their effect throughout the body of animals. epidemiology is the study of the demographics of disease processes, and includes, but is not limited to, the study of epidemics. genetics is the study of genes, and their role in biological inheritance. gynecology is the study of female reproductive system. histology is the study of the structures of biological tissues by light microscopy, electron microscopy and immunohistochemistry. immunology is the study of the immune system, which includes the innate and adaptive immune system in humans, for example. lifestyle medicine is the study of the chronic conditions, and how to prevent, treat and reverse them. medical physics is the study of the applications of physics principles in medicine. microbiology is the study of microorganisms, including protozoa, bacteria, fungi, and viruses. molecular biology is the study of molecular underpinnings of the process of replication, transcription and translation of the genetic material. neuroscience includes those disciplines of science that are related to the study of the nervous system. a main focus of neuroscience is the biology and physiology of the human brain and spinal cord. some related clinical specialties include neurology, neurosurgery and psychiatry. nutrition science ( theoretical focus ) and dietetics ( practical focus ) is the study of the relationship of food and drink to health and disease, especially in determining an optimal diet. medical nutrition therapy is done by dietitians and is prescribed for diabetes, cardiovascular diseases, weight and eating disorders, allergies, malnutrition, and neoplastic diseases. pathology as a science is the study of disease β the causes, course, progression and resolution thereof. pharmacology is the study of drugs and their actions. photobiology is the study of the interactions between non - ionizing radiation and living organisms. physiology is the study of the normal functioning of the body and the underlying regulatory mechanisms. radiobiology is the study of the interactions between ionizing radiation and living organisms. toxicology is the study of hazardous effects of drugs and poisons. = = = specialties = = = in the broadest meaning of " medicine ", there are many different specialties. in the uk, most specialities have their own body or college, which has its own entrance examination. these are collectively known
could be maintained in culture containing iaa, followed by the observation in 1947 that it could be induced to form roots and shoots by controlling the concentration of growth hormones were key steps in the development of plant biotechnology and genetic modification. cytokinins are a class of plant hormones named for their control of cell division ( especially cytokinesis ). the natural cytokinin zeatin was discovered in corn, zea mays, and is a derivative of the purine adenine. zeatin is produced in roots and transported to shoots in the xylem where it promotes cell division, bud development, and the greening of chloroplasts. the gibberelins, such as gibberelic acid are diterpenes synthesised from acetyl coa via the mevalonate pathway. they are involved in the promotion of germination and dormancy - breaking in seeds, in regulation of plant height by controlling stem elongation and the control of flowering. abscisic acid ( aba ) occurs in all land plants except liverworts, and is synthesised from carotenoids in the chloroplasts and other plastids. it inhibits cell division, promotes seed maturation, and dormancy, and promotes stomatal closure. it was so named because it was originally thought to control abscission. ethylene is a gaseous hormone that is produced in all higher plant tissues from methionine. it is now known to be the hormone that stimulates or regulates fruit ripening and abscission, and it, or the synthetic growth regulator ethephon which is rapidly metabolised to produce ethylene, are used on industrial scale to promote ripening of cotton, pineapples and other climacteric crops. another class of phytohormones is the jasmonates, first isolated from the oil of jasminum grandiflorum which regulates wound responses in plants by unblocking the expression of genes required in the systemic acquired resistance response to pathogen attack. in addition to being the primary energy source for plants, light functions as a signalling device, providing information to the plant, such as how much sunlight the plant receives each day. this can result in adaptive changes in a process known as photomorphogenesis. phytochromes are the photoreceptors in a plant that are sensitive to light. = = plant anatomy and morphology = = plant anatomy is the study of the structure of
venus flytrap and bladderworts, and the pollinia of orchids. the hypothesis that plant growth and development is coordinated by plant hormones or plant growth regulators first emerged in the late 19th century. darwin experimented on the movements of plant shoots and roots towards light and gravity, and concluded " it is hardly an exaggeration to say that the tip of the radicle.. acts like the brain of one of the lower animals.. directing the several movements ". about the same time, the role of auxins ( from the greek auxein, to grow ) in control of plant growth was first outlined by the dutch scientist frits went. the first known auxin, indole - 3 - acetic acid ( iaa ), which promotes cell growth, was only isolated from plants about 50 years later. this compound mediates the tropic responses of shoots and roots towards light and gravity. the finding in 1939 that plant callus could be maintained in culture containing iaa, followed by the observation in 1947 that it could be induced to form roots and shoots by controlling the concentration of growth hormones were key steps in the development of plant biotechnology and genetic modification. cytokinins are a class of plant hormones named for their control of cell division ( especially cytokinesis ). the natural cytokinin zeatin was discovered in corn, zea mays, and is a derivative of the purine adenine. zeatin is produced in roots and transported to shoots in the xylem where it promotes cell division, bud development, and the greening of chloroplasts. the gibberelins, such as gibberelic acid are diterpenes synthesised from acetyl coa via the mevalonate pathway. they are involved in the promotion of germination and dormancy - breaking in seeds, in regulation of plant height by controlling stem elongation and the control of flowering. abscisic acid ( aba ) occurs in all land plants except liverworts, and is synthesised from carotenoids in the chloroplasts and other plastids. it inhibits cell division, promotes seed maturation, and dormancy, and promotes stomatal closure. it was so named because it was originally thought to control abscission. ethylene is a gaseous hormone that is produced in all higher plant tissues from methionine. it is now known to be the hormone that stimulates or regulates fruit ripening and abscission,
other strands of proteins. = = = metabolism = = = all cells require energy to sustain cellular processes. metabolism is the set of chemical reactions in an organism. the three main purposes of metabolism are : the conversion of food to energy to run cellular processes ; the conversion of food / fuel to monomer building blocks ; and the elimination of metabolic wastes. these enzyme - catalyzed reactions allow organisms to grow and reproduce, maintain their structures, and respond to their environments. metabolic reactions may be categorized as catabolic β the breaking down of compounds ( for example, the breaking down of glucose to pyruvate by cellular respiration ) ; or anabolic β the building up ( synthesis ) of compounds ( such as proteins, carbohydrates, lipids, and nucleic acids ). usually, catabolism releases energy, and anabolism consumes energy. the chemical reactions of metabolism are organized into metabolic pathways, in which one chemical is transformed through a series of steps into another chemical, each step being facilitated by a specific enzyme. enzymes are crucial to metabolism because they allow organisms to drive desirable reactions that require energy that will not occur by themselves, by coupling them to spontaneous reactions that release energy. enzymes act as catalysts β they allow a reaction to proceed more rapidly without being consumed by it β by reducing the amount of activation energy needed to convert reactants into products. enzymes also allow the regulation of the rate of a metabolic reaction, for example in response to changes in the cell ' s environment or to signals from other cells. = = = cellular respiration = = = cellular respiration is a set of metabolic reactions and processes that take place in cells to convert chemical energy from nutrients into adenosine triphosphate ( atp ), and then release waste products. the reactions involved in respiration are catabolic reactions, which break large molecules into smaller ones, releasing energy. respiration is one of the key ways a cell releases chemical energy to fuel cellular activity. the overall reaction occurs in a series of biochemical steps, some of which are redox reactions. although cellular respiration is technically a combustion reaction, it clearly does not resemble one when it occurs in a cell because of the slow, controlled release of energy from the series of reactions. sugar in the form of glucose is the main nutrient used by animal and plant cells in respiration. cellular respiration involving oxygen is called aerobic respiration, which has four stages : glycolysis, citric acid cycle ( or krebs cycle
chloroplasts. the gibberelins, such as gibberelic acid are diterpenes synthesised from acetyl coa via the mevalonate pathway. they are involved in the promotion of germination and dormancy - breaking in seeds, in regulation of plant height by controlling stem elongation and the control of flowering. abscisic acid ( aba ) occurs in all land plants except liverworts, and is synthesised from carotenoids in the chloroplasts and other plastids. it inhibits cell division, promotes seed maturation, and dormancy, and promotes stomatal closure. it was so named because it was originally thought to control abscission. ethylene is a gaseous hormone that is produced in all higher plant tissues from methionine. it is now known to be the hormone that stimulates or regulates fruit ripening and abscission, and it, or the synthetic growth regulator ethephon which is rapidly metabolised to produce ethylene, are used on industrial scale to promote ripening of cotton, pineapples and other climacteric crops. another class of phytohormones is the jasmonates, first isolated from the oil of jasminum grandiflorum which regulates wound responses in plants by unblocking the expression of genes required in the systemic acquired resistance response to pathogen attack. in addition to being the primary energy source for plants, light functions as a signalling device, providing information to the plant, such as how much sunlight the plant receives each day. this can result in adaptive changes in a process known as photomorphogenesis. phytochromes are the photoreceptors in a plant that are sensitive to light. = = plant anatomy and morphology = = plant anatomy is the study of the structure of plant cells and tissues, whereas plant morphology is the study of their external form. all plants are multicellular eukaryotes, their dna stored in nuclei. the characteristic features of plant cells that distinguish them from those of animals and fungi include a primary cell wall composed of the polysaccharides cellulose, hemicellulose and pectin, larger vacuoles than in animal cells and the presence of plastids with unique photosynthetic and biosynthetic functions as in the chloroplasts. other plastids contain storage products such as starch ( amyloplasts )
the broad definition of " utilizing a biotechnological system to make products ". indeed, the cultivation of plants may be viewed as the earliest biotechnological enterprise. agriculture has been theorized to have become the dominant way of producing food since the neolithic revolution. through early biotechnology, the earliest farmers selected and bred the best - suited crops ( e. g., those with the highest yields ) to produce enough food to support a growing population. as crops and fields became increasingly large and difficult to maintain, it was discovered that specific organisms and their by - products could effectively fertilize, restore nitrogen, and control pests. throughout the history of agriculture, farmers have inadvertently altered the genetics of their crops through introducing them to new environments and breeding them with other plants β one of the first forms of biotechnology. these processes also were included in early fermentation of beer. these processes were introduced in early mesopotamia, egypt, china and india, and still use the same basic biological methods. in brewing, malted grains ( containing enzymes ) convert starch from grains into sugar and then adding specific yeasts to produce beer. in this process, carbohydrates in the grains broke down into alcohols, such as ethanol. later, other cultures produced the process of lactic acid fermentation, which produced other preserved foods, such as soy sauce. fermentation was also used in this time period to produce leavened bread. although the process of fermentation was not fully understood until louis pasteur ' s work in 1857, it is still the first use of biotechnology to convert a food source into another form. before the time of charles darwin ' s work and life, animal and plant scientists had already used selective breeding. darwin added to that body of work with his scientific observations about the ability of science to change species. these accounts contributed to darwin ' s theory of natural selection. for thousands of years, humans have used selective breeding to improve the production of crops and livestock to use them for food. in selective breeding, organisms with desirable characteristics are mated to produce offspring with the same characteristics. for example, this technique was used with corn to produce the largest and sweetest crops. in the early twentieth century scientists gained a greater understanding of microbiology and explored ways of manufacturing specific products. in 1917, chaim weizmann first used a pure microbiological culture in an industrial process, that of manufacturing corn starch using clostridium acetobutylicum, to produce acetone, which the united
occurs when another transcription factor called a repressor binds to a dna sequence called an operator, which is part of an operon, to prevent transcription. repressors can be inhibited by compounds called inducers ( e. g., allolactose ), thereby allowing transcription to occur. specific genes that can be activated by inducers are called inducible genes, in contrast to constitutive genes that are almost constantly active. in contrast to both, structural genes encode proteins that are not involved in gene regulation. in addition to regulatory events involving the promoter, gene expression can also be regulated by epigenetic changes to chromatin, which is a complex of dna and protein found in eukaryotic cells. = = = genes, development, and evolution = = = development is the process by which a multicellular organism ( plant or animal ) goes through a series of changes, starting from a single cell, and taking on various forms that are characteristic of its life cycle. there are four key processes that underlie development : determination, differentiation, morphogenesis, and growth. determination sets the developmental fate of a cell, which becomes more restrictive during development. differentiation is the process by which specialized cells arise from less specialized cells such as stem cells. stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. cellular differentiation dramatically changes a cell ' s size, shape, membrane potential, metabolic activity, and responsiveness to signals, which are largely due to highly controlled modifications in gene expression and epigenetics. with a few exceptions, cellular differentiation almost never involves a change in the dna sequence itself. thus, different cells can have very different physical characteristics despite having the same genome. morphogenesis, or the development of body form, is the result of spatial differences in gene expression. a small fraction of the genes in an organism ' s genome called the developmental - genetic toolkit control the development of that organism. these toolkit genes are highly conserved among phyla, meaning that they are ancient and very similar in widely separated groups of animals. differences in deployment of toolkit genes affect the body plan and the number, identity, and pattern of body parts. among the most important toolkit genes are the hox genes. hox genes determine where repeating parts, such as the many vertebrae of snakes, will grow in a developing embryo or larva. = = evolution = = = = = evolutionary
founded in 1976 and started the production of human proteins. genetically engineered human insulin was produced in 1978 and insulin - producing bacteria were commercialised in 1982. genetically modified food has been sold since 1994, with the release of the flavr savr tomato. the flavr savr was engineered to have a longer shelf life, but most current gm crops are modified to increase resistance to insects and herbicides. glofish, the first gmo designed as a pet, was sold in the united states in december 2003. in 2016 salmon modified with a growth hormone were sold. genetic engineering has been applied in numerous fields including research, medicine, industrial biotechnology and agriculture. in research, gmos are used to study gene function and expression through loss of function, gain of function, tracking and expression experiments. by knocking out genes responsible for certain conditions it is possible to create animal model organisms of human diseases. as well as producing hormones, vaccines and other drugs, genetic engineering has the potential to cure genetic diseases through gene therapy. chinese hamster ovary ( cho ) cells are used in industrial genetic engineering. additionally mrna vaccines are made through genetic engineering to prevent infections by viruses such as covid - 19. the same techniques that are used to produce drugs can also have industrial applications such as producing enzymes for laundry detergent, cheeses and other products. the rise of commercialised genetically modified crops has provided economic benefit to farmers in many different countries, but has also been the source of most of the controversy surrounding the technology. this has been present since its early use ; the first field trials were destroyed by anti - gm activists. although there is a scientific consensus that currently available food derived from gm crops poses no greater risk to human health than conventional food, critics consider gm food safety a leading concern. gene flow, impact on non - target organisms, control of the food supply and intellectual property rights have also been raised as potential issues. these concerns have led to the development of a regulatory framework, which started in 1975. it has led to an international treaty, the cartagena protocol on biosafety, that was adopted in 2000. individual countries have developed their own regulatory systems regarding gmos, with the most marked differences occurring between the united states and europe. = = overview = = genetic engineering is a process that alters the genetic structure of an organism by either removing or introducing dna, or modifying existing genetic material in situ. unlike traditional animal and plant breeding, which involves doing multiple crosses and then selecting for the organism with the desired phenotype,
promotes stomatal closure. it was so named because it was originally thought to control abscission. ethylene is a gaseous hormone that is produced in all higher plant tissues from methionine. it is now known to be the hormone that stimulates or regulates fruit ripening and abscission, and it, or the synthetic growth regulator ethephon which is rapidly metabolised to produce ethylene, are used on industrial scale to promote ripening of cotton, pineapples and other climacteric crops. another class of phytohormones is the jasmonates, first isolated from the oil of jasminum grandiflorum which regulates wound responses in plants by unblocking the expression of genes required in the systemic acquired resistance response to pathogen attack. in addition to being the primary energy source for plants, light functions as a signalling device, providing information to the plant, such as how much sunlight the plant receives each day. this can result in adaptive changes in a process known as photomorphogenesis. phytochromes are the photoreceptors in a plant that are sensitive to light. = = plant anatomy and morphology = = plant anatomy is the study of the structure of plant cells and tissues, whereas plant morphology is the study of their external form. all plants are multicellular eukaryotes, their dna stored in nuclei. the characteristic features of plant cells that distinguish them from those of animals and fungi include a primary cell wall composed of the polysaccharides cellulose, hemicellulose and pectin, larger vacuoles than in animal cells and the presence of plastids with unique photosynthetic and biosynthetic functions as in the chloroplasts. other plastids contain storage products such as starch ( amyloplasts ) or lipids ( elaioplasts ). uniquely, streptophyte cells and those of the green algal order trentepohliales divide by construction of a phragmoplast as a template for building a cell plate late in cell division. the bodies of vascular plants including clubmosses, ferns and seed plants ( gymnosperms and angiosperms ) generally have aerial and subterranean subsystems. the shoots consist of stems bearing green photosynthesising leaves and reproductive structures. the underground vascularised roots bear root hairs at their tips and generally lack chlorophyll. non - vascular
two neutrons, equivalent to a helium nucleus. beta decay is the release of a beta particle, a high - energy electron. gamma decay releases gamma rays, which unlike alpha and beta radiation are not matter but electromagnetic radiation of very high frequency, and therefore energy. this type of radiation is the most dangerous and most difficult to block. all three types of radiation occur naturally in certain elements. it has also become clear that the ultimate source of most terrestrial energy is nuclear, either through radiation from the sun caused by stellar thermonuclear reactions or by radioactive decay of uranium within the earth, the principal source of geothermal energy. = = = nuclear fission = = = in natural nuclear radiation, the byproducts are very small compared to the nuclei from which they originate. nuclear fission is the process of splitting a nucleus into roughly equal parts, and releasing energy and neutrons in the process. if these neutrons are captured by another unstable nucleus, they can fission as well, leading to a chain reaction. the average number of neutrons released per nucleus that go on to fission another nucleus is referred to as k. values of k larger than 1 mean that the fission reaction is releasing more neutrons than it absorbs, and therefore is referred to as a self - sustaining chain reaction. a mass of fissile material large enough ( and in a suitable configuration ) to induce a self - sustaining chain reaction is called a critical mass. when a neutron is captured by a suitable nucleus, fission may occur immediately, or the nucleus may persist in an unstable state for a short time. if there are enough immediate decays to carry on the chain reaction, the mass is said to be prompt critical, and the energy release will grow rapidly and uncontrollably, usually leading to an explosion. when discovered on the eve of world war ii, this insight led multiple countries to begin programs investigating the possibility of constructing an atomic bomb β a weapon which utilized fission reactions to generate far more energy than could be created with chemical explosives. the manhattan project, run by the united states with the help of the united kingdom and canada, developed multiple fission weapons which were used against japan in 1945 at hiroshima and nagasaki. during the project, the first fission reactors were developed as well, though they were primarily for weapons manufacture and did not generate electricity. in 1951, the first nuclear fission power plant was the first to produce electricity at the experimental breeder reactor no. 1 ( ebr - 1 ), in arco, idaho, ushering in the "
Question: What system of the body is responsible for producing hormones?
A) nervous system
B) regulatory system
C) endocrine system
D) homeostasis system
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C) endocrine system
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Context:
building block. ceramics β not to be confused with raw, unfired clay β are usually seen in crystalline form. the vast majority of commercial glasses contain a metal oxide fused with silica. at the high temperatures used to prepare glass, the material is a viscous liquid which solidifies into a disordered state upon cooling. windowpanes and eyeglasses are important examples. fibers of glass are also used for long - range telecommunication and optical transmission. scratch resistant corning gorilla glass is a well - known example of the application of materials science to drastically improve the properties of common components. engineering ceramics are known for their stiffness and stability under high temperatures, compression and electrical stress. alumina, silicon carbide, and tungsten carbide are made from a fine powder of their constituents in a process of sintering with a binder. hot pressing provides higher density material. chemical vapor deposition can place a film of a ceramic on another material. cermets are ceramic particles containing some metals. the wear resistance of tools is derived from cemented carbides with the metal phase of cobalt and nickel typically added to modify properties. ceramics can be significantly strengthened for engineering applications using the principle of crack deflection. this process involves the strategic addition of second - phase particles within a ceramic matrix, optimizing their shape, size, and distribution to direct and control crack propagation. this approach enhances fracture toughness, paving the way for the creation of advanced, high - performance ceramics in various industries. = = = composites = = = another application of materials science in industry is making composite materials. these are structured materials composed of two or more macroscopic phases. applications range from structural elements such as steel - reinforced concrete, to the thermal insulating tiles, which play a key and integral role in nasa ' s space shuttle thermal protection system, which is used to protect the surface of the shuttle from the heat of re - entry into the earth ' s atmosphere. one example is reinforced carbon - carbon ( rcc ), the light gray material, which withstands re - entry temperatures up to 1, 510 Β°c ( 2, 750 Β°f ) and protects the space shuttle ' s wing leading edges and nose cap. rcc is a laminated composite material made from graphite rayon cloth and impregnated with a phenolic resin. after curing at high temperature in an autoclave, the laminate is pyrolized to convert the resin to carbon, impregnated with furfuryl alcohol in a
to investigate the affinity of acetylated wood for organic liquids, yezo spruce wood specimens were acetylated with acetic anhydride, and their swelling in various liquids were compared to those of untreated specimens. the acetylated wood was rapidly and remarkably swollen in aprotic organic liquids such as benzene and toluene in which the untreated wood was swollen only slightly and / or very slowly. on the other hand, the swelling of wood in water, ethylene glycol and alcohols remained unchanged or decreased by the acetylation. consequently the maximum volume of wood swollen in organic liquids was always larger than that in water. the effect of acetylation on the maximum swollen volume of wood was greater in liquids having smaller solubility parameters. the easier penetration of aprotic organic liquids into the acetylated wood was considered to be due to the scission of hydrogen bonds among the amorphous wood constituents by the substitution of hydroxyl groups with hydrophobic acetyl groups.
; that is, more amenable to chemical reactions. the phase of a substance is invariably determined by its energy and the energy of its surroundings. when the intermolecular forces of a substance are such that the energy of the surroundings is not sufficient to overcome them, it occurs in a more ordered phase like liquid or solid as is the case with water ( h2o ) ; a liquid at room temperature because its molecules are bound by hydrogen bonds. whereas hydrogen sulfide ( h2s ) is a gas at room temperature and standard pressure, as its molecules are bound by weaker dipole β dipole interactions. the transfer of energy from one chemical substance to another depends on the size of energy quanta emitted from one substance. however, heat energy is often transferred more easily from almost any substance to another because the phonons responsible for vibrational and rotational energy levels in a substance have much less energy than photons invoked for the electronic energy transfer. thus, because vibrational and rotational energy levels are more closely spaced than electronic energy levels, heat is more easily transferred between substances relative to light or other forms of electronic energy. for example, ultraviolet electromagnetic radiation is not transferred with as much efficacy from one substance to another as thermal or electrical energy. the existence of characteristic energy levels for different chemical substances is useful for their identification by the analysis of spectral lines. different kinds of spectra are often used in chemical spectroscopy, e. g. ir, microwave, nmr, esr, etc. spectroscopy is also used to identify the composition of remote objects β like stars and distant galaxies β by analyzing their radiation spectra. the term chemical energy is often used to indicate the potential of a chemical substance to undergo a transformation through a chemical reaction or to transform other chemical substances. = = = reaction = = = when a chemical substance is transformed as a result of its interaction with another substance or with energy, a chemical reaction is said to have occurred. a chemical reaction is therefore a concept related to the " reaction " of a substance when it comes in close contact with another, whether as a mixture or a solution ; exposure to some form of energy, or both. it results in some energy exchange between the constituents of the reaction as well as with the system environment, which may be designed vessels β often laboratory glassware. chemical reactions can result in the formation or dissociation of molecules, that is, molecules breaking apart to form two or more molecules or rearrangement of atoms within or across molecules. chemical reactions usually involve the making or breaking of chemical bonds
. the phase of matter is defined by the phase transition, which is when energy put into or taken out of the system goes into rearranging the structure of the system, instead of changing the bulk conditions. sometimes the distinction between phases can be continuous instead of having a discrete boundary ; in this case the matter is considered to be in a supercritical state. when three states meet based on the conditions, it is known as a triple point and since this is invariant, it is a convenient way to define a set of conditions. the most familiar examples of phases are solids, liquids, and gases. many substances exhibit multiple solid phases. for example, there are three phases of solid iron ( alpha, gamma, and delta ) that vary based on temperature and pressure. a principal difference between solid phases is the crystal structure, or arrangement, of the atoms. another phase commonly encountered in the study of chemistry is the aqueous phase, which is the state of substances dissolved in aqueous solution ( that is, in water ). less familiar phases include plasmas, bose β einstein condensates and fermionic condensates and the paramagnetic and ferromagnetic phases of magnetic materials. while most familiar phases deal with three - dimensional systems, it is also possible to define analogs in two - dimensional systems, which has received attention for its relevance to systems in biology. = = = bonding = = = atoms sticking together in molecules or crystals are said to be bonded with one another. a chemical bond may be visualized as the multipole balance between the positive charges in the nuclei and the negative charges oscillating about them. more than simple attraction and repulsion, the energies and distributions characterize the availability of an electron to bond to another atom. the chemical bond can be a covalent bond, an ionic bond, a hydrogen bond or just because of van der waals force. each of these kinds of bonds is ascribed to some potential. these potentials create the interactions which hold atoms together in molecules or crystals. in many simple compounds, valence bond theory, the valence shell electron pair repulsion model ( vsepr ), and the concept of oxidation number can be used to explain molecular structure and composition. an ionic bond is formed when a metal loses one or more of its electrons, becoming a positively charged cation, and the electrons are then gained by the non - metal atom, becoming a negatively charged anion. the two oppositely charged ions attract one another, and the ionic bond
or solid as is the case with water ( h2o ) ; a liquid at room temperature because its molecules are bound by hydrogen bonds. whereas hydrogen sulfide ( h2s ) is a gas at room temperature and standard pressure, as its molecules are bound by weaker dipole β dipole interactions. the transfer of energy from one chemical substance to another depends on the size of energy quanta emitted from one substance. however, heat energy is often transferred more easily from almost any substance to another because the phonons responsible for vibrational and rotational energy levels in a substance have much less energy than photons invoked for the electronic energy transfer. thus, because vibrational and rotational energy levels are more closely spaced than electronic energy levels, heat is more easily transferred between substances relative to light or other forms of electronic energy. for example, ultraviolet electromagnetic radiation is not transferred with as much efficacy from one substance to another as thermal or electrical energy. the existence of characteristic energy levels for different chemical substances is useful for their identification by the analysis of spectral lines. different kinds of spectra are often used in chemical spectroscopy, e. g. ir, microwave, nmr, esr, etc. spectroscopy is also used to identify the composition of remote objects β like stars and distant galaxies β by analyzing their radiation spectra. the term chemical energy is often used to indicate the potential of a chemical substance to undergo a transformation through a chemical reaction or to transform other chemical substances. = = = reaction = = = when a chemical substance is transformed as a result of its interaction with another substance or with energy, a chemical reaction is said to have occurred. a chemical reaction is therefore a concept related to the " reaction " of a substance when it comes in close contact with another, whether as a mixture or a solution ; exposure to some form of energy, or both. it results in some energy exchange between the constituents of the reaction as well as with the system environment, which may be designed vessels β often laboratory glassware. chemical reactions can result in the formation or dissociation of molecules, that is, molecules breaking apart to form two or more molecules or rearrangement of atoms within or across molecules. chemical reactions usually involve the making or breaking of chemical bonds. oxidation, reduction, dissociation, acid β base neutralization and molecular rearrangement are some examples of common chemical reactions. a chemical reaction can be symbolically depicted through a chemical equation. while in a non - nuclear chemical reaction the number and kind of atoms on both sides of the equation are equal, for
a discontinuity of a turbulent ideal fluid is considered. it is supposed to be split and dispersed, or spread in the stochastic environment forming a gas without hydrostatic pressure. two equal - mass fragments of a discontinuity are indistinguishable from each other. a gas, that possesses such properties, must behave itself as the madelung medium.
eremets and troyan ( nature mater. 10, 927 - 931 ( 2011 ) ) claim that they produced the conducting liquid hydrogen state at 270 gpa and 295 k. their evidence consists of disappearance of raman signals, visual observations, and measurements of electrical conductivity in diamond anvil cells ( dac ). however, there is no proof that the reported observations are due to transformations in hydrogen.
##ulating the liquid below from the cold air above. water has the capacity to absorb energy, giving it a higher specific heat capacity than other solvents such as ethanol. thus, a large amount of energy is needed to break the hydrogen bonds between water molecules to convert liquid water into water vapor. as a molecule, water is not completely stable as each water molecule continuously dissociates into hydrogen and hydroxyl ions before reforming into a water molecule again. in pure water, the number of hydrogen ions balances ( or equals ) the number of hydroxyl ions, resulting in a ph that is neutral. = = = organic compounds = = = organic compounds are molecules that contain carbon bonded to another element such as hydrogen. with the exception of water, nearly all the molecules that make up each organism contain carbon. carbon can form covalent bonds with up to four other atoms, enabling it to form diverse, large, and complex molecules. for example, a single carbon atom can form four single covalent bonds such as in methane, two double covalent bonds such as in carbon dioxide ( co2 ), or a triple covalent bond such as in carbon monoxide ( co ). moreover, carbon can form very long chains of interconnecting carbon β carbon bonds such as octane or ring - like structures such as glucose. the simplest form of an organic molecule is the hydrocarbon, which is a large family of organic compounds that are composed of hydrogen atoms bonded to a chain of carbon atoms. a hydrocarbon backbone can be substituted by other elements such as oxygen ( o ), hydrogen ( h ), phosphorus ( p ), and sulfur ( s ), which can change the chemical behavior of that compound. groups of atoms that contain these elements ( o -, h -, p -, and s - ) and are bonded to a central carbon atom or skeleton are called functional groups. there are six prominent functional groups that can be found in organisms : amino group, carboxyl group, carbonyl group, hydroxyl group, phosphate group, and sulfhydryl group. in 1953, the miller β urey experiment showed that organic compounds could be synthesized abiotically within a closed system mimicking the conditions of early earth, thus suggesting that complex organic molecules could have arisen spontaneously in early earth ( see abiogenesis ). = = = macromolecules = = = macromolecules are large molecules made up of smaller subunits or monomers. monomers include sugars, amino acids,
classifications ; however, some more exotic phases are incompatible with certain chemical properties. a phase is a set of states of a chemical system that have similar bulk structural properties, over a range of conditions, such as pressure or temperature. physical properties, such as density and refractive index tend to fall within values characteristic of the phase. the phase of matter is defined by the phase transition, which is when energy put into or taken out of the system goes into rearranging the structure of the system, instead of changing the bulk conditions. sometimes the distinction between phases can be continuous instead of having a discrete boundary ; in this case the matter is considered to be in a supercritical state. when three states meet based on the conditions, it is known as a triple point and since this is invariant, it is a convenient way to define a set of conditions. the most familiar examples of phases are solids, liquids, and gases. many substances exhibit multiple solid phases. for example, there are three phases of solid iron ( alpha, gamma, and delta ) that vary based on temperature and pressure. a principal difference between solid phases is the crystal structure, or arrangement, of the atoms. another phase commonly encountered in the study of chemistry is the aqueous phase, which is the state of substances dissolved in aqueous solution ( that is, in water ). less familiar phases include plasmas, bose β einstein condensates and fermionic condensates and the paramagnetic and ferromagnetic phases of magnetic materials. while most familiar phases deal with three - dimensional systems, it is also possible to define analogs in two - dimensional systems, which has received attention for its relevance to systems in biology. = = = bonding = = = atoms sticking together in molecules or crystals are said to be bonded with one another. a chemical bond may be visualized as the multipole balance between the positive charges in the nuclei and the negative charges oscillating about them. more than simple attraction and repulsion, the energies and distributions characterize the availability of an electron to bond to another atom. the chemical bond can be a covalent bond, an ionic bond, a hydrogen bond or just because of van der waals force. each of these kinds of bonds is ascribed to some potential. these potentials create the interactions which hold atoms together in molecules or crystals. in many simple compounds, valence bond theory, the valence shell electron pair repulsion model ( vsepr ), and the concept of oxidation number can be used
the thickness and the density of the material to be measured. the method is used for containers of liquids or of grainy substances thickness gauges : if the material is of constant density, the signal measured by the radiation detector depends on the thickness of the material. this is useful for continuous production, like of paper, rubber, etc. electrostatic control - to avoid the build - up of static electricity in production of paper, plastics, synthetic textiles, etc., a ribbon - shaped source of the alpha emitter 241am can be placed close to the material at the end of the production line. the source ionizes the air to remove electric charges on the material. radioactive tracers - since radioactive isotopes behave, chemically, mostly like the inactive element, the behavior of a certain chemical substance can be followed by tracing the radioactivity. examples : adding a gamma tracer to a gas or liquid in a closed system makes it possible to find a hole in a tube. adding a tracer to the surface of the component of a motor makes it possible to measure wear by measuring the activity of the lubricating oil. oil and gas exploration - nuclear well logging is used to help predict the commercial viability of new or existing wells. the technology involves the use of a neutron or gamma - ray source and a radiation detector which are lowered into boreholes to determine the properties of the surrounding rock such as porosity and lithography. [ 1 ] road construction - nuclear moisture / density gauges are used to determine the density of soils, asphalt, and concrete. typically a cesium - 137 source is used. = = = commercial applications = = = radioluminescence tritium illumination : tritium is used with phosphor in rifle sights to increase nighttime firing accuracy. some runway markers and building exit signs use the same technology, to remain illuminated during blackouts. betavoltaics. smoke detector : an ionization smoke detector includes a tiny mass of radioactive americium - 241, which is a source of alpha radiation. two ionisation chambers are placed next to each other. both contain a small source of 241am that gives rise to a small constant current. one is closed and serves for comparison, the other is open to ambient air ; it has a gridded electrode. when smoke enters the open chamber, the current is disrupted as the smoke particles attach to the charged ions and restore them to a neutral electrical state. this reduces the current in the open chamber. when the current drops below a certain threshold, the
Question: What happens to a substance in a liquid state when the temperate is lowed?
A) it melts
B) it dissipates
C) it evaporates
D) it solidifies
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D) it solidifies
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Context:
##hthalmology and dermatology, but are not considered surgical sub - specialties per se. surgical training in the u. s. requires a minimum of five years of residency after medical school. sub - specialties of surgery often require seven or more years. in addition, fellowships can last an additional one to three years. because post - residency fellowships can be competitive, many trainees devote two additional years to research. thus in some cases surgical training will not finish until more than a decade after medical school. furthermore, surgical training can be very difficult and time - consuming. surgical subspecialties include those a physician may specialize in after undergoing general surgery residency training as well as several surgical fields with separate residency training. surgical subspecialties that one may pursue following general surgery residency training : bariatric surgery cardiovascular surgery β may also be pursued through a separate cardiovascular surgery residency track colorectal surgery endocrine surgery general surgery hand surgery hepatico - pancreatico - biliary surgery minimally invasive surgery pediatric surgery plastic surgery β may also be pursued through a separate plastic surgery residency track surgical critical care surgical oncology transplant surgery trauma surgery vascular surgery β may also be pursued through a separate vascular surgery residency track other surgical specialties within medicine with their own individual residency training : dermatology neurosurgery ophthalmology oral and maxillofacial surgery orthopedic surgery otorhinolaryngology podiatric surgery β do not undergo medical school training, but rather separate training in podiatry school urology = = = = internal medicine specialty = = = = internal medicine is the medical specialty dealing with the prevention, diagnosis, and treatment of adult diseases. according to some sources, an emphasis on internal structures is implied. in north america, specialists in internal medicine are commonly called " internists ". elsewhere, especially in commonwealth nations, such specialists are often called physicians. these terms, internist or physician ( in the narrow sense, common outside north america ), generally exclude practitioners of gynecology and obstetrics, pathology, psychiatry, and especially surgery and its subspecialities. because their patients are often seriously ill or require complex investigations, internists do much of their work in hospitals. formerly, many internists were not subspecialized ; such general physicians would see any complex nonsurgical problem ; this style of practice has become much less common. in modern urban practice, most internists are subspecialists : that is, they generally limit their medical practice
molecular diffusion processes give rise to significant changes in the primary microstructural features. this includes the gradual elimination of porosity, which is typically accompanied by a net shrinkage and overall densification of the component. thus, the pores in the object may close up, resulting in a denser product of significantly greater strength and fracture toughness. another major change in the body during the firing or sintering process will be the establishment of the polycrystalline nature of the solid. significant grain growth tends to occur during sintering, with this growth depending on temperature and duration of the sintering process. the growth of grains will result in some form of grain size distribution, which will have a significant impact on the ultimate physical properties of the material. in particular, abnormal grain growth in which certain grains grow very large in a matrix of finer grains will significantly alter the physical and mechanical properties of the obtained ceramic. in the sintered body, grain sizes are a product of the thermal processing parameters as well as the initial particle size, or possibly the sizes of aggregates or particle clusters which arise during the initial stages of processing. the ultimate microstructure ( and thus the physical properties ) of the final product will be limited by and subject to the form of the structural template or precursor which is created in the initial stages of chemical synthesis and physical forming. hence the importance of chemical powder and polymer processing as it pertains to the synthesis of industrial ceramics, glasses and glass - ceramics. there are numerous possible refinements of the sintering process. some of the most common involve pressing the green body to give the densification a head start and reduce the sintering time needed. sometimes organic binders such as polyvinyl alcohol are added to hold the green body together ; these burn out during the firing ( at 200 β 350 Β°c ). sometimes organic lubricants are added during pressing to increase densification. it is common to combine these, and add binders and lubricants to a powder, then press. ( the formulation of these organic chemical additives is an art in itself. this is particularly important in the manufacture of high performance ceramics such as those used by the billions for electronics, in capacitors, inductors, sensors, etc. ) a slurry can be used in place of a powder, and then cast into a desired shape, dried and then sintered. indeed, traditional pottery is done with this type of method, using a plastic mixture worked with the hands.
. the phase of matter is defined by the phase transition, which is when energy put into or taken out of the system goes into rearranging the structure of the system, instead of changing the bulk conditions. sometimes the distinction between phases can be continuous instead of having a discrete boundary ; in this case the matter is considered to be in a supercritical state. when three states meet based on the conditions, it is known as a triple point and since this is invariant, it is a convenient way to define a set of conditions. the most familiar examples of phases are solids, liquids, and gases. many substances exhibit multiple solid phases. for example, there are three phases of solid iron ( alpha, gamma, and delta ) that vary based on temperature and pressure. a principal difference between solid phases is the crystal structure, or arrangement, of the atoms. another phase commonly encountered in the study of chemistry is the aqueous phase, which is the state of substances dissolved in aqueous solution ( that is, in water ). less familiar phases include plasmas, bose β einstein condensates and fermionic condensates and the paramagnetic and ferromagnetic phases of magnetic materials. while most familiar phases deal with three - dimensional systems, it is also possible to define analogs in two - dimensional systems, which has received attention for its relevance to systems in biology. = = = bonding = = = atoms sticking together in molecules or crystals are said to be bonded with one another. a chemical bond may be visualized as the multipole balance between the positive charges in the nuclei and the negative charges oscillating about them. more than simple attraction and repulsion, the energies and distributions characterize the availability of an electron to bond to another atom. the chemical bond can be a covalent bond, an ionic bond, a hydrogen bond or just because of van der waals force. each of these kinds of bonds is ascribed to some potential. these potentials create the interactions which hold atoms together in molecules or crystals. in many simple compounds, valence bond theory, the valence shell electron pair repulsion model ( vsepr ), and the concept of oxidation number can be used to explain molecular structure and composition. an ionic bond is formed when a metal loses one or more of its electrons, becoming a positively charged cation, and the electrons are then gained by the non - metal atom, becoming a negatively charged anion. the two oppositely charged ions attract one another, and the ionic bond
high machining costs. there is a possibility for melt casting to be used for many of these approaches. potentially even more desirable is using melt - derived particles. in this method, quenching is done in a solid solution or in a fine eutectic structure, in which the particles are then processed by more typical ceramic powder processing methods into a useful body. there have also been preliminary attempts to use melt spraying as a means of forming composites by introducing the dispersed particulate, whisker, or fiber phase in conjunction with the melt spraying process. other methods besides melt infiltration to manufacture ceramic composites with long fiber reinforcement are chemical vapor infiltration and the infiltration of fiber preforms with organic precursor, which after pyrolysis yield an amorphous ceramic matrix, initially with a low density. with repeated cycles of infiltration and pyrolysis one of those types of ceramic matrix composites is produced. chemical vapor infiltration is used to manufacture carbon / carbon and silicon carbide reinforced with carbon or silicon carbide fibers. besides many process improvements, the first of two major needs for fiber composites is lower fiber costs. the second major need is fiber compositions or coatings, or composite processing, to reduce degradation that results from high - temperature composite exposure under oxidizing conditions. = = applications = = the products of technical ceramics include tiles used in the space shuttle program, gas burner nozzles, ballistic protection, nuclear fuel uranium oxide pellets, bio - medical implants, jet engine turbine blades, and missile nose cones. its products are often made from materials other than clay, chosen for their particular physical properties. these may be classified as follows : oxides : silica, alumina, zirconia non - oxides : carbides, borides, nitrides, silicides composites : particulate or whisker reinforced matrices, combinations of oxides and non - oxides ( e. g. polymers ). ceramics can be used in many technological industries. one application is the ceramic tiles on nasa ' s space shuttle, used to protect it and the future supersonic space planes from the searing heat of re - entry into the earth ' s atmosphere. they are also used widely in electronics and optics. in addition to the applications listed here, ceramics are also used as a coating in various engineering cases. an example would be a ceramic bearing coating over a titanium frame used for an aircraft. recently the field has come to include the studies of single
lower limits are found for the disorder resistivity of solid neutron - star matter in the neutron - drip region which is amorphous and heterogeneous in nuclear charge. this temperature - independent resistivity, large compared with that produced by phonon scattering, has direct consequences for theories of neutron - star magnetic field generation and evolution.
building block. ceramics β not to be confused with raw, unfired clay β are usually seen in crystalline form. the vast majority of commercial glasses contain a metal oxide fused with silica. at the high temperatures used to prepare glass, the material is a viscous liquid which solidifies into a disordered state upon cooling. windowpanes and eyeglasses are important examples. fibers of glass are also used for long - range telecommunication and optical transmission. scratch resistant corning gorilla glass is a well - known example of the application of materials science to drastically improve the properties of common components. engineering ceramics are known for their stiffness and stability under high temperatures, compression and electrical stress. alumina, silicon carbide, and tungsten carbide are made from a fine powder of their constituents in a process of sintering with a binder. hot pressing provides higher density material. chemical vapor deposition can place a film of a ceramic on another material. cermets are ceramic particles containing some metals. the wear resistance of tools is derived from cemented carbides with the metal phase of cobalt and nickel typically added to modify properties. ceramics can be significantly strengthened for engineering applications using the principle of crack deflection. this process involves the strategic addition of second - phase particles within a ceramic matrix, optimizing their shape, size, and distribution to direct and control crack propagation. this approach enhances fracture toughness, paving the way for the creation of advanced, high - performance ceramics in various industries. = = = composites = = = another application of materials science in industry is making composite materials. these are structured materials composed of two or more macroscopic phases. applications range from structural elements such as steel - reinforced concrete, to the thermal insulating tiles, which play a key and integral role in nasa ' s space shuttle thermal protection system, which is used to protect the surface of the shuttle from the heat of re - entry into the earth ' s atmosphere. one example is reinforced carbon - carbon ( rcc ), the light gray material, which withstands re - entry temperatures up to 1, 510 Β°c ( 2, 750 Β°f ) and protects the space shuttle ' s wing leading edges and nose cap. rcc is a laminated composite material made from graphite rayon cloth and impregnated with a phenolic resin. after curing at high temperature in an autoclave, the laminate is pyrolized to convert the resin to carbon, impregnated with furfuryl alcohol in a
billet is passed through successively narrower rollers to create a sheet. extrusion β a hot and malleable metal is forced under pressure through a die, which shapes it before it cools. machining β lathes, milling machines and drills cut the cold metal to shape. sintering β a powdered metal is heated in a non - oxidizing environment after being compressed into a die. fabrication β sheets of metal are cut with guillotines or gas cutters and bent and welded into structural shape. laser cladding β metallic powder is blown through a movable laser beam ( e. g. mounted on a nc 5 - axis machine ). the resulting melted metal reaches a substrate to form a melt pool. by moving the laser head, it is possible to stack the tracks and build up a three - dimensional piece. 3d printing β sintering or melting amorphous powder metal in a 3d space to make any object to shape. cold - working processes, in which the product ' s shape is altered by rolling, fabrication or other processes, while the product is cold, can increase the strength of the product by a process called work hardening. work hardening creates microscopic defects in the metal, which resist further changes of shape. = = = heat treatment = = = metals can be heat - treated to alter the properties of strength, ductility, toughness, hardness and resistance to corrosion. common heat treatment processes include annealing, precipitation strengthening, quenching, and tempering : annealing process softens the metal by heating it and then allowing it to cool very slowly, which gets rid of stresses in the metal and makes the grain structure large and soft - edged so that, when the metal is hit or stressed it dents or perhaps bends, rather than breaking ; it is also easier to sand, grind, or cut annealed metal. quenching is the process of cooling metal very quickly after heating, thus " freezing " the metal ' s molecules in the very hard martensite form, which makes the metal harder. tempering relieves stresses in the metal that were caused by the hardening process ; tempering makes the metal less hard while making it better able to sustain impacts without breaking. often, mechanical and thermal treatments are combined in what are known as thermo - mechanical treatments for better properties and more efficient processing of materials. these processes are common to high - alloy special steels, superalloys and titanium alloys. = = = plating = = = electroplating is
as for precipitation - toughened, partially stabilized zirconia. similarly, it is known that one can directionally solidify ceramic eutectic mixtures and hence obtain uniaxially aligned fiber composites. such composite processing has typically been limited to very simple shapes and thus suffers from serious economic problems due to high machining costs. there is a possibility for melt casting to be used for many of these approaches. potentially even more desirable is using melt - derived particles. in this method, quenching is done in a solid solution or in a fine eutectic structure, in which the particles are then processed by more typical ceramic powder processing methods into a useful body. there have also been preliminary attempts to use melt spraying as a means of forming composites by introducing the dispersed particulate, whisker, or fiber phase in conjunction with the melt spraying process. other methods besides melt infiltration to manufacture ceramic composites with long fiber reinforcement are chemical vapor infiltration and the infiltration of fiber preforms with organic precursor, which after pyrolysis yield an amorphous ceramic matrix, initially with a low density. with repeated cycles of infiltration and pyrolysis one of those types of ceramic matrix composites is produced. chemical vapor infiltration is used to manufacture carbon / carbon and silicon carbide reinforced with carbon or silicon carbide fibers. besides many process improvements, the first of two major needs for fiber composites is lower fiber costs. the second major need is fiber compositions or coatings, or composite processing, to reduce degradation that results from high - temperature composite exposure under oxidizing conditions. = = applications = = the products of technical ceramics include tiles used in the space shuttle program, gas burner nozzles, ballistic protection, nuclear fuel uranium oxide pellets, bio - medical implants, jet engine turbine blades, and missile nose cones. its products are often made from materials other than clay, chosen for their particular physical properties. these may be classified as follows : oxides : silica, alumina, zirconia non - oxides : carbides, borides, nitrides, silicides composites : particulate or whisker reinforced matrices, combinations of oxides and non - oxides ( e. g. polymers ). ceramics can be used in many technological industries. one application is the ceramic tiles on nasa ' s space shuttle, used to protect it and the future supersonic space planes from the searing heat of re - entry into
the structural template or precursor which is created in the initial stages of chemical synthesis and physical forming. hence the importance of chemical powder and polymer processing as it pertains to the synthesis of industrial ceramics, glasses and glass - ceramics. there are numerous possible refinements of the sintering process. some of the most common involve pressing the green body to give the densification a head start and reduce the sintering time needed. sometimes organic binders such as polyvinyl alcohol are added to hold the green body together ; these burn out during the firing ( at 200 β 350 Β°c ). sometimes organic lubricants are added during pressing to increase densification. it is common to combine these, and add binders and lubricants to a powder, then press. ( the formulation of these organic chemical additives is an art in itself. this is particularly important in the manufacture of high performance ceramics such as those used by the billions for electronics, in capacitors, inductors, sensors, etc. ) a slurry can be used in place of a powder, and then cast into a desired shape, dried and then sintered. indeed, traditional pottery is done with this type of method, using a plastic mixture worked with the hands. if a mixture of different materials is used together in a ceramic, the sintering temperature is sometimes above the melting point of one minor component β a liquid phase sintering. this results in shorter sintering times compared to solid state sintering. such liquid phase sintering involves in faster diffusion processes and may result in abnormal grain growth. = = strength of ceramics = = a material ' s strength is dependent on its microstructure. the engineering processes to which a material is subjected can alter its microstructure. the variety of strengthening mechanisms that alter the strength of a material include the mechanism of grain boundary strengthening. thus, although yield strength is maximized with decreasing grain size, ultimately, very small grain sizes make the material brittle. considered in tandem with the fact that the yield strength is the parameter that predicts plastic deformation in the material, one can make informed decisions on how to increase the strength of a material depending on its microstructural properties and the desired end effect. the relation between yield stress and grain size is described mathematically by the hall - petch equation which is Ο y = Ο 0 + k y d { \ displaystyle \ sigma _ { y } = \ sigma _ { 0 } + { k _ { y } \ over {
casting, also called the lost wax process, die casting, centrifugal casting, both vertical and horizontal, and continuous castings. each of these forms has advantages for certain metals and applications considering factors like magnetism and corrosion. forging β a red - hot billet is hammered into shape. rolling β a billet is passed through successively narrower rollers to create a sheet. extrusion β a hot and malleable metal is forced under pressure through a die, which shapes it before it cools. machining β lathes, milling machines and drills cut the cold metal to shape. sintering β a powdered metal is heated in a non - oxidizing environment after being compressed into a die. fabrication β sheets of metal are cut with guillotines or gas cutters and bent and welded into structural shape. laser cladding β metallic powder is blown through a movable laser beam ( e. g. mounted on a nc 5 - axis machine ). the resulting melted metal reaches a substrate to form a melt pool. by moving the laser head, it is possible to stack the tracks and build up a three - dimensional piece. 3d printing β sintering or melting amorphous powder metal in a 3d space to make any object to shape. cold - working processes, in which the product ' s shape is altered by rolling, fabrication or other processes, while the product is cold, can increase the strength of the product by a process called work hardening. work hardening creates microscopic defects in the metal, which resist further changes of shape. = = = heat treatment = = = metals can be heat - treated to alter the properties of strength, ductility, toughness, hardness and resistance to corrosion. common heat treatment processes include annealing, precipitation strengthening, quenching, and tempering : annealing process softens the metal by heating it and then allowing it to cool very slowly, which gets rid of stresses in the metal and makes the grain structure large and soft - edged so that, when the metal is hit or stressed it dents or perhaps bends, rather than breaking ; it is also easier to sand, grind, or cut annealed metal. quenching is the process of cooling metal very quickly after heating, thus " freezing " the metal ' s molecules in the very hard martensite form, which makes the metal harder. tempering relieves stresses in the metal that were caused by the hardening process ; tempering makes the metal less hard while making it better able to sustain
Question: Sublimation and deposition involve direct transitions between solid and gas without going through which state?
A) carbon
B) chemical
C) homeostasis
D) liquid
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D) liquid
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Context:
##aggeration to say that the tip of the radicle.. acts like the brain of one of the lower animals.. directing the several movements ". about the same time, the role of auxins ( from the greek auxein, to grow ) in control of plant growth was first outlined by the dutch scientist frits went. the first known auxin, indole - 3 - acetic acid ( iaa ), which promotes cell growth, was only isolated from plants about 50 years later. this compound mediates the tropic responses of shoots and roots towards light and gravity. the finding in 1939 that plant callus could be maintained in culture containing iaa, followed by the observation in 1947 that it could be induced to form roots and shoots by controlling the concentration of growth hormones were key steps in the development of plant biotechnology and genetic modification. cytokinins are a class of plant hormones named for their control of cell division ( especially cytokinesis ). the natural cytokinin zeatin was discovered in corn, zea mays, and is a derivative of the purine adenine. zeatin is produced in roots and transported to shoots in the xylem where it promotes cell division, bud development, and the greening of chloroplasts. the gibberelins, such as gibberelic acid are diterpenes synthesised from acetyl coa via the mevalonate pathway. they are involved in the promotion of germination and dormancy - breaking in seeds, in regulation of plant height by controlling stem elongation and the control of flowering. abscisic acid ( aba ) occurs in all land plants except liverworts, and is synthesised from carotenoids in the chloroplasts and other plastids. it inhibits cell division, promotes seed maturation, and dormancy, and promotes stomatal closure. it was so named because it was originally thought to control abscission. ethylene is a gaseous hormone that is produced in all higher plant tissues from methionine. it is now known to be the hormone that stimulates or regulates fruit ripening and abscission, and it, or the synthetic growth regulator ethephon which is rapidly metabolised to produce ethylene, are used on industrial scale to promote ripening of cotton, pineapples and other climacteric crops. another class of phytohormones is the jasmonates, first isolated
on a large scale provided protection from insect pests or tolerance to herbicides. fungal and virus resistant crops have also been developed or are in development. this makes the insect and weed management of crops easier and can indirectly increase crop yield. gm crops that directly improve yield by accelerating growth or making the plant more hardy ( by improving salt, cold or drought tolerance ) are also under development. in 2016 salmon have been genetically modified with growth hormones to reach normal adult size much faster. gmos have been developed that modify the quality of produce by increasing the nutritional value or providing more industrially useful qualities or quantities. the amflora potato produces a more industrially useful blend of starches. soybeans and canola have been genetically modified to produce more healthy oils. the first commercialised gm food was a tomato that had delayed ripening, increasing its shelf life. plants and animals have been engineered to produce materials they do not normally make. pharming uses crops and animals as bioreactors to produce vaccines, drug intermediates, or the drugs themselves ; the useful product is purified from the harvest and then used in the standard pharmaceutical production process. cows and goats have been engineered to express drugs and other proteins in their milk, and in 2009 the fda approved a drug produced in goat milk. = = = other applications = = = genetic engineering has potential applications in conservation and natural area management. gene transfer through viral vectors has been proposed as a means of controlling invasive species as well as vaccinating threatened fauna from disease. transgenic trees have been suggested as a way to confer resistance to pathogens in wild populations. with the increasing risks of maladaptation in organisms as a result of climate change and other perturbations, facilitated adaptation through gene tweaking could be one solution to reducing extinction risks. applications of genetic engineering in conservation are thus far mostly theoretical and have yet to be put into practice. genetic engineering is also being used to create microbial art. some bacteria have been genetically engineered to create black and white photographs. novelty items such as lavender - colored carnations, blue roses, and glowing fish, have also been produced through genetic engineering. = = regulation = = the regulation of genetic engineering concerns the approaches taken by governments to assess and manage the risks associated with the development and release of gmos. the development of a regulatory framework began in 1975, at asilomar, california. the asilomar meeting recommended a set of voluntary guidelines regarding the use of recombinant technology. as the technology improved
significantly greater strength and fracture toughness. another major change in the body during the firing or sintering process will be the establishment of the polycrystalline nature of the solid. significant grain growth tends to occur during sintering, with this growth depending on temperature and duration of the sintering process. the growth of grains will result in some form of grain size distribution, which will have a significant impact on the ultimate physical properties of the material. in particular, abnormal grain growth in which certain grains grow very large in a matrix of finer grains will significantly alter the physical and mechanical properties of the obtained ceramic. in the sintered body, grain sizes are a product of the thermal processing parameters as well as the initial particle size, or possibly the sizes of aggregates or particle clusters which arise during the initial stages of processing. the ultimate microstructure ( and thus the physical properties ) of the final product will be limited by and subject to the form of the structural template or precursor which is created in the initial stages of chemical synthesis and physical forming. hence the importance of chemical powder and polymer processing as it pertains to the synthesis of industrial ceramics, glasses and glass - ceramics. there are numerous possible refinements of the sintering process. some of the most common involve pressing the green body to give the densification a head start and reduce the sintering time needed. sometimes organic binders such as polyvinyl alcohol are added to hold the green body together ; these burn out during the firing ( at 200 β 350 Β°c ). sometimes organic lubricants are added during pressing to increase densification. it is common to combine these, and add binders and lubricants to a powder, then press. ( the formulation of these organic chemical additives is an art in itself. this is particularly important in the manufacture of high performance ceramics such as those used by the billions for electronics, in capacitors, inductors, sensors, etc. ) a slurry can be used in place of a powder, and then cast into a desired shape, dried and then sintered. indeed, traditional pottery is done with this type of method, using a plastic mixture worked with the hands. if a mixture of different materials is used together in a ceramic, the sintering temperature is sometimes above the melting point of one minor component β a liquid phase sintering. this results in shorter sintering times compared to solid state sintering. such liquid phase sintering involves in faster diffusion processes and may result in abnormal grain
venus flytrap and bladderworts, and the pollinia of orchids. the hypothesis that plant growth and development is coordinated by plant hormones or plant growth regulators first emerged in the late 19th century. darwin experimented on the movements of plant shoots and roots towards light and gravity, and concluded " it is hardly an exaggeration to say that the tip of the radicle.. acts like the brain of one of the lower animals.. directing the several movements ". about the same time, the role of auxins ( from the greek auxein, to grow ) in control of plant growth was first outlined by the dutch scientist frits went. the first known auxin, indole - 3 - acetic acid ( iaa ), which promotes cell growth, was only isolated from plants about 50 years later. this compound mediates the tropic responses of shoots and roots towards light and gravity. the finding in 1939 that plant callus could be maintained in culture containing iaa, followed by the observation in 1947 that it could be induced to form roots and shoots by controlling the concentration of growth hormones were key steps in the development of plant biotechnology and genetic modification. cytokinins are a class of plant hormones named for their control of cell division ( especially cytokinesis ). the natural cytokinin zeatin was discovered in corn, zea mays, and is a derivative of the purine adenine. zeatin is produced in roots and transported to shoots in the xylem where it promotes cell division, bud development, and the greening of chloroplasts. the gibberelins, such as gibberelic acid are diterpenes synthesised from acetyl coa via the mevalonate pathway. they are involved in the promotion of germination and dormancy - breaking in seeds, in regulation of plant height by controlling stem elongation and the control of flowering. abscisic acid ( aba ) occurs in all land plants except liverworts, and is synthesised from carotenoids in the chloroplasts and other plastids. it inhibits cell division, promotes seed maturation, and dormancy, and promotes stomatal closure. it was so named because it was originally thought to control abscission. ethylene is a gaseous hormone that is produced in all higher plant tissues from methionine. it is now known to be the hormone that stimulates or regulates fruit ripening and abscission,
much sunlight the plant receives each day. this can result in adaptive changes in a process known as photomorphogenesis. phytochromes are the photoreceptors in a plant that are sensitive to light. = = plant anatomy and morphology = = plant anatomy is the study of the structure of plant cells and tissues, whereas plant morphology is the study of their external form. all plants are multicellular eukaryotes, their dna stored in nuclei. the characteristic features of plant cells that distinguish them from those of animals and fungi include a primary cell wall composed of the polysaccharides cellulose, hemicellulose and pectin, larger vacuoles than in animal cells and the presence of plastids with unique photosynthetic and biosynthetic functions as in the chloroplasts. other plastids contain storage products such as starch ( amyloplasts ) or lipids ( elaioplasts ). uniquely, streptophyte cells and those of the green algal order trentepohliales divide by construction of a phragmoplast as a template for building a cell plate late in cell division. the bodies of vascular plants including clubmosses, ferns and seed plants ( gymnosperms and angiosperms ) generally have aerial and subterranean subsystems. the shoots consist of stems bearing green photosynthesising leaves and reproductive structures. the underground vascularised roots bear root hairs at their tips and generally lack chlorophyll. non - vascular plants, the liverworts, hornworts and mosses do not produce ground - penetrating vascular roots and most of the plant participates in photosynthesis. the sporophyte generation is nonphotosynthetic in liverworts but may be able to contribute part of its energy needs by photosynthesis in mosses and hornworts. the root system and the shoot system are interdependent β the usually nonphotosynthetic root system depends on the shoot system for food, and the usually photosynthetic shoot system depends on water and minerals from the root system. cells in each system are capable of creating cells of the other and producing adventitious shoots or roots. stolons and tubers are examples of shoots that can grow roots. roots that spread out close to the surface, such as those of willows, can produce shoots and ultimately new plants. in the event that one of the systems is lost
, dendrology is the study of woody plants. many divisions of biology have botanical subfields. these are commonly denoted by prefixing the word plant ( e. g. plant taxonomy, plant ecology, plant anatomy, plant morphology, plant systematics ), or prefixing or substituting the prefix phyto - ( e. g. phytochemistry, phytogeography ). the study of fossil plants is called palaeobotany. other fields are denoted by adding or substituting the word botany ( e. g. systematic botany ). phytosociology is a subfield of plant ecology that classifies and studies communities of plants. the intersection of fields from the above pair of categories gives rise to fields such as bryogeography, the study of the distribution of mosses. different parts of plants also give rise to their own subfields, including xylology, carpology ( or fructology ), and palynology, these being the study of wood, fruit and pollen / spores respectively. botany also overlaps on the one hand with agriculture, horticulture and silviculture, and on the other hand with medicine and pharmacology, giving rise to fields such as agronomy, horticultural botany, phytopathology, and phytopharmacology. = = scope and importance = = the study of plants is vital because they underpin almost all animal life on earth by generating a large proportion of the oxygen and food that provide humans and other organisms with aerobic respiration with the chemical energy they need to exist. plants, algae and cyanobacteria are the major groups of organisms that carry out photosynthesis, a process that uses the energy of sunlight to convert water and carbon dioxide into sugars that can be used both as a source of chemical energy and of organic molecules that are used in the structural components of cells. as a by - product of photosynthesis, plants release oxygen into the atmosphere, a gas that is required by nearly all living things to carry out cellular respiration. in addition, they are influential in the global carbon and water cycles and plant roots bind and stabilise soils, preventing soil erosion. plants are crucial to the future of human society as they provide food, oxygen, biochemicals, and products for people, as well as creating and preserving soil. historically, all living things were classified as either animals or plants and botany covered the study of all organisms not considered animals. botanists examine both
grains will result in some form of grain size distribution, which will have a significant impact on the ultimate physical properties of the material. in particular, abnormal grain growth in which certain grains grow very large in a matrix of finer grains will significantly alter the physical and mechanical properties of the obtained ceramic. in the sintered body, grain sizes are a product of the thermal processing parameters as well as the initial particle size, or possibly the sizes of aggregates or particle clusters which arise during the initial stages of processing. the ultimate microstructure ( and thus the physical properties ) of the final product will be limited by and subject to the form of the structural template or precursor which is created in the initial stages of chemical synthesis and physical forming. hence the importance of chemical powder and polymer processing as it pertains to the synthesis of industrial ceramics, glasses and glass - ceramics. there are numerous possible refinements of the sintering process. some of the most common involve pressing the green body to give the densification a head start and reduce the sintering time needed. sometimes organic binders such as polyvinyl alcohol are added to hold the green body together ; these burn out during the firing ( at 200 β 350 Β°c ). sometimes organic lubricants are added during pressing to increase densification. it is common to combine these, and add binders and lubricants to a powder, then press. ( the formulation of these organic chemical additives is an art in itself. this is particularly important in the manufacture of high performance ceramics such as those used by the billions for electronics, in capacitors, inductors, sensors, etc. ) a slurry can be used in place of a powder, and then cast into a desired shape, dried and then sintered. indeed, traditional pottery is done with this type of method, using a plastic mixture worked with the hands. if a mixture of different materials is used together in a ceramic, the sintering temperature is sometimes above the melting point of one minor component β a liquid phase sintering. this results in shorter sintering times compared to solid state sintering. such liquid phase sintering involves in faster diffusion processes and may result in abnormal grain growth. = = strength of ceramics = = a material ' s strength is dependent on its microstructure. the engineering processes to which a material is subjected can alter its microstructure. the variety of strengthening mechanisms that alter the strength of a material include the mechanism of grain boundary strengthening. thus, although yield
molecular diffusion processes give rise to significant changes in the primary microstructural features. this includes the gradual elimination of porosity, which is typically accompanied by a net shrinkage and overall densification of the component. thus, the pores in the object may close up, resulting in a denser product of significantly greater strength and fracture toughness. another major change in the body during the firing or sintering process will be the establishment of the polycrystalline nature of the solid. significant grain growth tends to occur during sintering, with this growth depending on temperature and duration of the sintering process. the growth of grains will result in some form of grain size distribution, which will have a significant impact on the ultimate physical properties of the material. in particular, abnormal grain growth in which certain grains grow very large in a matrix of finer grains will significantly alter the physical and mechanical properties of the obtained ceramic. in the sintered body, grain sizes are a product of the thermal processing parameters as well as the initial particle size, or possibly the sizes of aggregates or particle clusters which arise during the initial stages of processing. the ultimate microstructure ( and thus the physical properties ) of the final product will be limited by and subject to the form of the structural template or precursor which is created in the initial stages of chemical synthesis and physical forming. hence the importance of chemical powder and polymer processing as it pertains to the synthesis of industrial ceramics, glasses and glass - ceramics. there are numerous possible refinements of the sintering process. some of the most common involve pressing the green body to give the densification a head start and reduce the sintering time needed. sometimes organic binders such as polyvinyl alcohol are added to hold the green body together ; these burn out during the firing ( at 200 β 350 Β°c ). sometimes organic lubricants are added during pressing to increase densification. it is common to combine these, and add binders and lubricants to a powder, then press. ( the formulation of these organic chemical additives is an art in itself. this is particularly important in the manufacture of high performance ceramics such as those used by the billions for electronics, in capacitors, inductors, sensors, etc. ) a slurry can be used in place of a powder, and then cast into a desired shape, dried and then sintered. indeed, traditional pottery is done with this type of method, using a plastic mixture worked with the hands.
animal cells using microinjection, where it can be injected through the cell ' s nuclear envelope directly into the nucleus, or through the use of viral vectors. plant genomes can be engineered by physical methods or by use of agrobacterium for the delivery of sequences hosted in t - dna binary vectors. in plants the dna is often inserted using agrobacterium - mediated transformation, taking advantage of the agrobacteriums t - dna sequence that allows natural insertion of genetic material into plant cells. other methods include biolistics, where particles of gold or tungsten are coated with dna and then shot into young plant cells, and electroporation, which involves using an electric shock to make the cell membrane permeable to plasmid dna. as only a single cell is transformed with genetic material, the organism must be regenerated from that single cell. in plants this is accomplished through the use of tissue culture. in animals it is necessary to ensure that the inserted dna is present in the embryonic stem cells. bacteria consist of a single cell and reproduce clonally so regeneration is not necessary. selectable markers are used to easily differentiate transformed from untransformed cells. these markers are usually present in the transgenic organism, although a number of strategies have been developed that can remove the selectable marker from the mature transgenic plant. further testing using pcr, southern hybridization, and dna sequencing is conducted to confirm that an organism contains the new gene. these tests can also confirm the chromosomal location and copy number of the inserted gene. the presence of the gene does not guarantee it will be expressed at appropriate levels in the target tissue so methods that look for and measure the gene products ( rna and protein ) are also used. these include northern hybridisation, quantitative rt - pcr, western blot, immunofluorescence, elisa and phenotypic analysis. the new genetic material can be inserted randomly within the host genome or targeted to a specific location. the technique of gene targeting uses homologous recombination to make desired changes to a specific endogenous gene. this tends to occur at a relatively low frequency in plants and animals and generally requires the use of selectable markers. the frequency of gene targeting can be greatly enhanced through genome editing. genome editing uses artificially engineered nucleases that create specific double - stranded breaks at desired locations in the genome, and use the cell ' s endogenous mechanisms to repair the induced break by the natural processes
eat them. plants and other photosynthetic organisms are at the base of most food chains because they use the energy from the sun and nutrients from the soil and atmosphere, converting them into a form that can be used by animals. this is what ecologists call the first trophic level. the modern forms of the major staple foods, such as hemp, teff, maize, rice, wheat and other cereal grasses, pulses, bananas and plantains, as well as hemp, flax and cotton grown for their fibres, are the outcome of prehistoric selection over thousands of years from among wild ancestral plants with the most desirable characteristics. botanists study how plants produce food and how to increase yields, for example through plant breeding, making their work important to humanity ' s ability to feed the world and provide food security for future generations. botanists also study weeds, which are a considerable problem in agriculture, and the biology and control of plant pathogens in agriculture and natural ecosystems. ethnobotany is the study of the relationships between plants and people. when applied to the investigation of historical plant β people relationships ethnobotany may be referred to as archaeobotany or palaeoethnobotany. some of the earliest plant - people relationships arose between the indigenous people of canada in identifying edible plants from inedible plants. this relationship the indigenous people had with plants was recorded by ethnobotanists. = = plant biochemistry = = plant biochemistry is the study of the chemical processes used by plants. some of these processes are used in their primary metabolism like the photosynthetic calvin cycle and crassulacean acid metabolism. others make specialised materials like the cellulose and lignin used to build their bodies, and secondary products like resins and aroma compounds. plants and various other groups of photosynthetic eukaryotes collectively known as " algae " have unique organelles known as chloroplasts. chloroplasts are thought to be descended from cyanobacteria that formed endosymbiotic relationships with ancient plant and algal ancestors. chloroplasts and cyanobacteria contain the blue - green pigment chlorophyll a. chlorophyll a ( as well as its plant and green algal - specific cousin chlorophyll b ) absorbs light in the blue - violet and orange / red parts of the spectrum while reflecting and transmitting the green light that we see as the characteristic colour
Question: What is the process by which plants and animals increase in size?
A) reproduction
B) splicing
C) grafting
D) growth
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D) growth
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Context:
kidneys and the majority of those currently in use are extracorporeal, such as with hemodialysis, which filters blood directly, or peritoneal dialysis, which filters via a fluid in the abdomen. in order to contribute to the biological functions of a kidney such as producing metabolic factors or hormones, some artificial kidneys incorporate renal cells. there has been progress in the way of making these devices smaller and more transportable, or even implantable. one challenge still to be faced in these smaller devices is countering the limited volume and therefore limited filtering capabilities. bioscaffolds have also been introduced to provide a framework upon which normal kidney tissue can be regenerated. these scaffolds encompass natural scaffolds ( e. g., decellularized kidneys, collagen hydrogel, or silk fibroin ), synthetic scaffolds ( e. g., poly [ lactic - co - glycolic acid ] or other polymers ), or a combination of two or more natural and synthetic scaffolds. these scaffolds can be implanted into the body either without cell treatment or after a period of stem cell seeding and incubation. in vitro and in vivo studies are being conducted to compare and optimize the type of scaffold and to assess whether cell seeding prior to implantation adds to the viability, regeneration and effective function of the kidneys. a recent systematic review and meta - analysis compared the results of published animal studies and identified that improved outcomes are reported with the use of hybrid ( mixed ) scaffolds and cell seeding ; however, the meta - analysis of these results were not in agreement with the evaluation of descriptive results from the review. therefore, further studies involving larger animals and novel scaffolds, and more transparent reproduction of previous studies are advisable. = = = biomimetics = = = biomimetics is a field that aims to produce materials and systems that replicate those present in nature. in the context of tissue engineering, this is a common approach used by engineers to create materials for these applications that are comparable to native tissues in terms of their structure, properties, and biocompatibility. material properties are largely dependent on physical, structural, and chemical characteristics of that material. subsequently, a biomimetic approach to system design will become significant in material integration, and a sufficient understanding of biological processes and interactions will be necessary. replication of biological systems and
, 400 km from the persian gulf to the mediterranean sea, but was not paved and was only partially maintained. in around 2, 000 bce, the minoans on the greek island of crete built a 50 km road leading from the palace of gortyn on the south side of the island, through the mountains, to the palace of knossos on the north side of the island. unlike the earlier road, the minoan road was completely paved. ancient minoan private homes had running water. a bathtub virtually identical to modern ones was unearthed at the palace of knossos. several minoan private homes also had toilets, which could be flushed by pouring water down the drain. the ancient romans had many public flush toilets, which emptied into an extensive sewage system. the primary sewer in rome was the cloaca maxima ; construction began on it in the sixth century bce and it is still in use today. the ancient romans also had a complex system of aqueducts, which were used to transport water across long distances. the first roman aqueduct was built in 312 bce. the eleventh and final ancient roman aqueduct was built in 226 ce. put together, the roman aqueducts extended over 450 km, but less than 70 km of this was above ground and supported by arches. = = = pre - modern = = = innovations continued through the middle ages with the introduction of silk production ( in asia and later europe ), the horse collar, and horseshoes. simple machines ( such as the lever, the screw, and the pulley ) were combined into more complicated tools, such as the wheelbarrow, windmills, and clocks. a system of universities developed and spread scientific ideas and practices, including oxford and cambridge. the renaissance era produced many innovations, including the introduction of the movable type printing press to europe, which facilitated the communication of knowledge. technology became increasingly influenced by science, beginning a cycle of mutual advancement. = = = modern = = = starting in the united kingdom in the 18th century, the discovery of steam power set off the industrial revolution, which saw wide - ranging technological discoveries, particularly in the areas of agriculture, manufacturing, mining, metallurgy, and transport, and the widespread application of the factory system. this was followed a century later by the second industrial revolution which led to rapid scientific discovery, standardization, and mass production. new technologies were developed, including sewage systems, electricity, light bulbs, electric motors, railroads, automobiles, and airplanes. these technological advances led to significant developments in medicine
often called physicians. these terms, internist or physician ( in the narrow sense, common outside north america ), generally exclude practitioners of gynecology and obstetrics, pathology, psychiatry, and especially surgery and its subspecialities. because their patients are often seriously ill or require complex investigations, internists do much of their work in hospitals. formerly, many internists were not subspecialized ; such general physicians would see any complex nonsurgical problem ; this style of practice has become much less common. in modern urban practice, most internists are subspecialists : that is, they generally limit their medical practice to problems of one organ system or to one particular area of medical knowledge. for example, gastroenterologists and nephrologists specialize respectively in diseases of the gut and the kidneys. in the commonwealth of nations and some other countries, specialist pediatricians and geriatricians are also described as specialist physicians ( or internists ) who have subspecialized by age of patient rather than by organ system. elsewhere, especially in north america, general pediatrics is often a form of primary care. there are many subspecialities ( or subdisciplines ) of internal medicine : training in internal medicine ( as opposed to surgical training ), varies considerably across the world : see the articles on medical education for more details. in north america, it requires at least three years of residency training after medical school, which can then be followed by a one - to three - year fellowship in the subspecialties listed above. in general, resident work hours in medicine are less than those in surgery, averaging about 60 hours per week in the us. this difference does not apply in the uk where all doctors are now required by law to work less than 48 hours per week on average. = = = = diagnostic specialties = = = = clinical laboratory sciences are the clinical diagnostic services that apply laboratory techniques to diagnosis and management of patients. in the united states, these services are supervised by a pathologist. the personnel that work in these medical laboratory departments are technically trained staff who do not hold medical degrees, but who usually hold an undergraduate medical technology degree, who actually perform the tests, assays, and procedures needed for providing the specific services. subspecialties include transfusion medicine, cellular pathology, clinical chemistry, hematology, clinical microbiology and clinical immunology. clinical neurophysiology is concerned with testing the physiology or function of the central and peripheral aspects of
as subjects perceive the sensory world, different stimuli elicit a number of neural representations. here, a subjective distance between stimuli is defined, measuring the degree of similarity between the underlying representations. as an example, the subjective distance between different locations in space is calculated from the activity of rodent hippocampal place cells, and lateral septal cells. such a distance is compared to the real distance, between locations. as the number of sampled neurons increases, the subjective distance shows a tendency to resemble the metrics of real space.
men. well - known spiritual systems include animism ( the notion of inanimate objects having spirits ), spiritualism ( an appeal to gods or communion with ancestor spirits ) ; shamanism ( the vesting of an individual with mystic powers ) ; and divination ( magically obtaining the truth ). the field of medical anthropology examines the ways in which culture and society are organized around or impacted by issues of health, health care and related issues. the earliest known medical texts in the world were found in the ancient syrian city of ebla and date back to 2500 bce. other early records on medicine have been discovered from ancient egyptian medicine, babylonian medicine, ayurvedic medicine ( in the indian subcontinent ), classical chinese medicine ( alternative medicine ) predecessor to the modern traditional chinese medicine ), and ancient greek medicine and roman medicine. in egypt, imhotep ( 3rd millennium bce ) is the first physician in history known by name. the oldest egyptian medical text is the kahun gynaecological papyrus from around 2000 bce, which describes gynaecological diseases. the edwin smith papyrus dating back to 1600 bce is an early work on surgery, while the ebers papyrus dating back to 1500 bce is akin to a textbook on medicine. in china, archaeological evidence of medicine in chinese dates back to the bronze age shang dynasty, based on seeds for herbalism and tools presumed to have been used for surgery. the huangdi neijing, the progenitor of chinese medicine, is a medical text written beginning in the 2nd century bce and compiled in the 3rd century. in india, the surgeon sushruta described numerous surgical operations, including the earliest forms of plastic surgery. earliest records of dedicated hospitals come from mihintale in sri lanka where evidence of dedicated medicinal treatment facilities for patients are found. in greece, the ancient greek physician hippocrates, the " father of modern medicine ", laid the foundation for a rational approach to medicine. hippocrates introduced the hippocratic oath for physicians, which is still relevant and in use today, and was the first to categorize illnesses as acute, chronic, endemic and epidemic, and use terms such as, " exacerbation, relapse, resolution, crisis, paroxysm, peak, and convalescence ". the greek physician galen was also one of the greatest surgeons of the ancient world and performed many audacious operations, including brain and eye surgeries. after the fall of the western roman empire and the onset of
medical history comprises hpi and pmh. medications ( rx ) : what drugs the patient takes including prescribed, over - the - counter, and home remedies, as well as alternative and herbal medicines or remedies. allergies are also recorded. past medical history ( pmh / pmhx ) : concurrent medical problems, past hospitalizations and operations, injuries, past infectious diseases or vaccinations, history of known allergies. review of systems ( ros ) or systems inquiry : a set of additional questions to ask, which may be missed on hpi : a general enquiry ( have you noticed any weight loss, change in sleep quality, fevers, lumps and bumps? etc. ), followed by questions on the body ' s main organ systems ( heart, lungs, digestive tract, urinary tract, etc. ). social history ( sh ) : birthplace, residences, marital history, social and economic status, habits ( including diet, medications, tobacco, alcohol ). the physical examination is the examination of the patient for medical signs of disease that are objective and observable, in contrast to symptoms that are volunteered by the patient and are not necessarily objectively observable. the healthcare provider uses sight, hearing, touch, and sometimes smell ( e. g., in infection, uremia, diabetic ketoacidosis ). four actions are the basis of physical examination : inspection, palpation ( feel ), percussion ( tap to determine resonance characteristics ), and auscultation ( listen ), generally in that order, although auscultation occurs prior to percussion and palpation for abdominal assessments. the clinical examination involves the study of : abdomen and rectum cardiovascular ( heart and blood vessels ) general appearance of the patient and specific indicators of disease ( nutritional status, presence of jaundice, pallor or clubbing ) genitalia ( and pregnancy if the patient is or could be pregnant ) head, eye, ear, nose, and throat ( heent ) musculoskeletal ( including spine and extremities ) neurological ( consciousness, awareness, brain, vision, cranial nerves, spinal cord and peripheral nerves ) psychiatric ( orientation, mental state, mood, evidence of abnormal perception or thought ). respiratory ( large airways and lungs ) skin vital signs including height, weight, body temperature, blood pressure, pulse, respiration rate, and hemoglobin oxygen saturation it is to likely focus on
observed solar neutrino fluxes are employed to constrain the interior composition of the sun. including the effects of neutrino flavor mixing, the results from homestake, sudbury, and gallium experiments constrain the mg, si, and fe abundances in the solar interior to be within a factor 0. 89 to 1. 34 of the surface values with 68 % confidence. if the o and / or ne abundances are increased in the interior to resolve helioseismic discrepancies with recent standard solar models, then the nominal interior mg, si, and fe abundances are constrained to a range of 0. 83 to 1. 24 relative to the surface. additional research is needed to determine whether the sun ' s interior is metal poor relative to its surface.
as iss expeditions. expedition crew members typically spend approximately six months on the iss. the initial expedition crew size was three, temporarily decreased to two following the columbia disaster. between may 2009 and until the retirement of the space shuttle, the expedition crew size has been six crew members. as of 2024, though the commercial program ' s crew capsules can allow a crew of up to seven, expeditions using them typically consist of a crew of four. the iss has been continuously occupied for the past 24 years and 202 days, having exceeded the previous record held by mir ; and has been visited by astronauts and cosmonauts from 15 different nations. the station can be seen from the earth with the naked eye and, as of 2025, is the largest artificial satellite in earth orbit with a mass and volume greater than that of any previous space station. the russian soyuz and american dragon and starliner spacecraft are used to send astronauts to and from the iss. several uncrewed cargo spacecraft provide service to the iss ; they are the russian progress spacecraft which has done so since 2000, the european automated transfer vehicle ( atv ) since 2008, the japanese h - ii transfer vehicle ( htv ) since 2009, the ( uncrewed ) dragon since 2012, and the american cygnus spacecraft since 2013. the space shuttle, before its retirement, was also used for cargo transfer and would often switch out expedition crew members, although it did not have the capability to remain docked for the duration of their stay. between the retirement of the shuttle in 2011 and the commencement of crewed dragon flights in 2020, american astronauts exclusively used the soyuz for crew transport to and from the iss the highest number of people occupying the iss has been thirteen ; this occurred three times during the late shuttle iss assembly missions. the iss program is expected to continue until 2030, after which the space station will be retired and destroyed in a controlled de - orbit. = = = = commercial resupply services ( 2008 β present ) = = = = commercial resupply services ( crs ) are a contract solution to deliver cargo and supplies to the international space station on a commercial basis by private companies. nasa signed its first crs contracts in 2008 and awarded $ 1. 6 billion to spacex for twelve cargo dragon and $ 1. 9 billion to orbital sciences for eight cygnus flights, covering deliveries until 2016. both companies evolved or created their launch vehicle products to launch the spacecrafts ( spacex with the falcon 9 and orbital with the antares ). spacex flew its
, no patient, no matter, no illness, no one to heal, no substance, no person, no thing and no place that needs to be influenced. this is what the practitioner must first be clear about. christian scientists avoid almost all medical treatment, relying instead on christian science prayer. this consists of silently arguing with oneself ; there are no appeals to a personal god, and no set words. caroline fraser wrote in 1999 that the practitioner might repeat : " the allness of god using eddy ' s seven synonyms β life, truth, love, spirit, soul, principle and mind, " then that " spirit, substance, is the only mind, and man is its image and likeness ; that mind is intelligence ; that spirit is substance ; that love is wholeness ; that life, truth, and love are the only reality. " she might deny other religions, the existence of evil, mesmerism, astrology, numerology, and the symptoms of whatever the illness is. she concludes, fraser writes, by asserting that disease is a lie, that this is the word of god, and that it has the power to heal. christian science practitioners are certified by the church of christ, scientist, to charge a fee for christian science prayer. there were 1, 249 practitioners worldwide in 2015 ; in the united states in 2010 they charged $ 25 β $ 50 for an e - mail, telephone or face - to - face consultation. their training is a two - week, 12 - lesson course called " primary class ", based on the recapitulation chapter of science and health. practitioners wanting to teach primary class take a six - day " normal class ", held in boston once every three years, and become christian science teachers. there are also christian science nursing homes. they offer no medical services ; the nurses are christian scientists who have completed a course of religious study and training in basic skills, such as feeding and bathing. the christian science journal and christian science sentinel publish anecdotal healing testimonials ( they published 53, 900 between 1900 and april 1989 ), which must be accompanied by statements from three verifiers : " people who know [ the testifier ] well and have either witnessed the healing or can vouch for [ the testifier ' s ] integrity in sharing it ". philosopher margaret p. battin wrote in 1999 that the seriousness with which these testimonials are treated by christian scientists ignores factors such as false positives caused by self - limiting conditions. because no negative accounts
the tests, assays, and procedures needed for providing the specific services. subspecialties include transfusion medicine, cellular pathology, clinical chemistry, hematology, clinical microbiology and clinical immunology. clinical neurophysiology is concerned with testing the physiology or function of the central and peripheral aspects of the nervous system. these kinds of tests can be divided into recordings of : ( 1 ) spontaneous or continuously running electrical activity, or ( 2 ) stimulus evoked responses. subspecialties include electroencephalography, electromyography, evoked potential, nerve conduction study and polysomnography. sometimes these tests are performed by techs without a medical degree, but the interpretation of these tests is done by a medical professional. diagnostic radiology is concerned with imaging of the body, e. g. by x - rays, x - ray computed tomography, ultrasonography, and nuclear magnetic resonance tomography. interventional radiologists can access areas in the body under imaging for an intervention or diagnostic sampling. nuclear medicine is concerned with studying human organ systems by administering radiolabelled substances ( radiopharmaceuticals ) to the body, which can then be imaged outside the body by a gamma camera or a pet scanner. each radiopharmaceutical consists of two parts : a tracer that is specific for the function under study ( e. g., neurotransmitter pathway, metabolic pathway, blood flow, or other ), and a radionuclide ( usually either a gamma - emitter or a positron emitter ). there is a degree of overlap between nuclear medicine and radiology, as evidenced by the emergence of combined devices such as the pet / ct scanner. pathology as a medical specialty is the branch of medicine that deals with the study of diseases and the morphologic, physiologic changes produced by them. as a diagnostic specialty, pathology can be considered the basis of modern scientific medical knowledge and plays a large role in evidence - based medicine. many modern molecular tests such as flow cytometry, polymerase chain reaction ( pcr ), immunohistochemistry, cytogenetics, gene rearrangements studies and fluorescent in situ hybridization ( fish ) fall within the territory of pathology. = = = = other major specialties = = = = the following are some major medical specialties that do not directly fit into any of the above - mentioned groups : anesthesiology ( also
Question: Which glands sit atop the kidneys and are composed of an outer cortex and an inner medulla, all surrounded by a connective tissue capsule?
A) adrenal
B) gonads
C) thyroid glands
D) salivary
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A) adrenal
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Context:
within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions. cell membranes also contain membrane proteins, including integral membrane proteins that go across the membrane serving as membrane transporters, and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes shaping the cell. cell membranes are involved in various cellular processes such as cell adhesion, storing electrical energy, and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall, glycocalyx, and cytoskeleton. within the cytoplasm of a cell, there are many biomolecules such as proteins and nucleic acids. in addition to biomolecules, eukaryotic cells have specialized structures called organelles that have their own lipid bilayers or are spatially units. these organelles include the cell nucleus, which contains most of the cell ' s dna, or mitochondria, which generate adenosine triphosphate ( atp ) to power cellular processes. other organelles such as endoplasmic reticulum and golgi apparatus play a role in the synthesis and packaging of proteins, respectively. biomolecules such as proteins can be engulfed by lysosomes, another specialized organelle. plant cells have additional organelles that distinguish them from animal cells such as a cell wall that provides support for the plant cell, chloroplasts that harvest sunlight energy to produce sugar, and vacuoles that provide storage and structural support as well as being involved in reproduction and breakdown of plant seeds. eukaryotic cells also have cytoskeleton that is made up of microtubules, intermediate filaments, and microfilaments, all of which provide support for the cell and are involved in the movement of the cell and its organelles. in terms of their structural composition, the microtubules are made up of tubulin ( e. g., Ξ± - tubulin and Ξ² - tubulin ) whereas intermediate filaments are made up of fibrous proteins. microfilaments are made up of actin molecules that interact with
. most cells are very small, with diameters ranging from 1 to 100 micrometers and are therefore only visible under a light or electron microscope. there are generally two types of cells : eukaryotic cells, which contain a nucleus, and prokaryotic cells, which do not. prokaryotes are single - celled organisms such as bacteria, whereas eukaryotes can be single - celled or multicellular. in multicellular organisms, every cell in the organism ' s body is derived ultimately from a single cell in a fertilized egg. = = = cell structure = = = every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions. cell membranes also contain membrane proteins, including integral membrane proteins that go across the membrane serving as membrane transporters, and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes shaping the cell. cell membranes are involved in various cellular processes such as cell adhesion, storing electrical energy, and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall, glycocalyx, and cytoskeleton. within the cytoplasm of a cell, there are many biomolecules such as proteins and nucleic acids. in addition to biomolecules, eukaryotic cells have specialized structures called organelles that have their own lipid bilayers or are spatially units. these organelles include the cell nucleus, which contains most of the cell ' s dna, or mitochondria, which generate adenosine triphosphate ( atp ) to power cellular processes. other organelles such as endoplasmic reticulum and golgi apparatus play a role in the synthesis and packaging of proteins, respectively. biomolecules such as proteins can be engulfed by lysosomes, another specialized organelle. plant cells have additional organelles that distinguish them from animal cells such as a cell wall that provides support for the plant cell, chloroplasts that harvest sunlight energy to produce sugar, and vacuoles that provide storage and structural support
shaping the cell. cell membranes are involved in various cellular processes such as cell adhesion, storing electrical energy, and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall, glycocalyx, and cytoskeleton. within the cytoplasm of a cell, there are many biomolecules such as proteins and nucleic acids. in addition to biomolecules, eukaryotic cells have specialized structures called organelles that have their own lipid bilayers or are spatially units. these organelles include the cell nucleus, which contains most of the cell ' s dna, or mitochondria, which generate adenosine triphosphate ( atp ) to power cellular processes. other organelles such as endoplasmic reticulum and golgi apparatus play a role in the synthesis and packaging of proteins, respectively. biomolecules such as proteins can be engulfed by lysosomes, another specialized organelle. plant cells have additional organelles that distinguish them from animal cells such as a cell wall that provides support for the plant cell, chloroplasts that harvest sunlight energy to produce sugar, and vacuoles that provide storage and structural support as well as being involved in reproduction and breakdown of plant seeds. eukaryotic cells also have cytoskeleton that is made up of microtubules, intermediate filaments, and microfilaments, all of which provide support for the cell and are involved in the movement of the cell and its organelles. in terms of their structural composition, the microtubules are made up of tubulin ( e. g., Ξ± - tubulin and Ξ² - tubulin ) whereas intermediate filaments are made up of fibrous proteins. microfilaments are made up of actin molecules that interact with other strands of proteins. = = = metabolism = = = all cells require energy to sustain cellular processes. metabolism is the set of chemical reactions in an organism. the three main purposes of metabolism are : the conversion of food to energy to run cellular processes ; the conversion of food / fuel to monomer building blocks ; and the elimination of metabolic wastes. these enzyme - catalyzed reactions allow organisms to grow and reproduce, maintain their structures, and respond to their environments. metabolic reactions may be categorized as catabolic β the breaking down of compounds ( for example, the breaking down of glucose to pyruvate by cellular respiration
are single - celled organisms such as bacteria, whereas eukaryotes can be single - celled or multicellular. in multicellular organisms, every cell in the organism ' s body is derived ultimately from a single cell in a fertilized egg. = = = cell structure = = = every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions. cell membranes also contain membrane proteins, including integral membrane proteins that go across the membrane serving as membrane transporters, and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes shaping the cell. cell membranes are involved in various cellular processes such as cell adhesion, storing electrical energy, and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall, glycocalyx, and cytoskeleton. within the cytoplasm of a cell, there are many biomolecules such as proteins and nucleic acids. in addition to biomolecules, eukaryotic cells have specialized structures called organelles that have their own lipid bilayers or are spatially units. these organelles include the cell nucleus, which contains most of the cell ' s dna, or mitochondria, which generate adenosine triphosphate ( atp ) to power cellular processes. other organelles such as endoplasmic reticulum and golgi apparatus play a role in the synthesis and packaging of proteins, respectively. biomolecules such as proteins can be engulfed by lysosomes, another specialized organelle. plant cells have additional organelles that distinguish them from animal cells such as a cell wall that provides support for the plant cell, chloroplasts that harvest sunlight energy to produce sugar, and vacuoles that provide storage and structural support as well as being involved in reproduction and breakdown of plant seeds. eukaryotic cells also have cytoskeleton that is made up of microtubules, intermediate filaments, and microfilaments, all of which provide support for the cell and are involved in the movement of the cell and its
oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions. cell membranes also contain membrane proteins, including integral membrane proteins that go across the membrane serving as membrane transporters, and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes shaping the cell. cell membranes are involved in various cellular processes such as cell adhesion, storing electrical energy, and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall, glycocalyx, and cytoskeleton. within the cytoplasm of a cell, there are many biomolecules such as proteins and nucleic acids. in addition to biomolecules, eukaryotic cells have specialized structures called organelles that have their own lipid bilayers or are spatially units. these organelles include the cell nucleus, which contains most of the cell ' s dna, or mitochondria, which generate adenosine triphosphate ( atp ) to power cellular processes. other organelles such as endoplasmic reticulum and golgi apparatus play a role in the synthesis and packaging of proteins, respectively. biomolecules such as proteins can be engulfed by lysosomes, another specialized organelle. plant cells have additional organelles that distinguish them from animal cells such as a cell wall that provides support for the plant cell, chloroplasts that harvest sunlight energy to produce sugar, and vacuoles that provide storage and structural support as well as being involved in reproduction and breakdown of plant seeds. eukaryotic cells also have cytoskeleton that is made up of microtubules, intermediate filaments, and microfilaments, all of which provide support for the cell and are involved in the movement of the cell and its organelles. in terms of their structural composition, the microtubules are made up of tubulin ( e. g., Ξ± - tubulin and Ξ² - tubulin ) whereas intermediate filaments are made up of fibrous proteins. microfilaments are made up of actin molecules that interact with other strands of proteins. = = = metabolism = = = all cells require energy to sustain cellular processes. metabolism is the set of chemical reactions in an organism. the three main purposes of metabolism are : the conversion of food to energy to run cellular processes ; the conversion of food / fuel to monomer building blocks ; and
plant cells and tissues, whereas plant morphology is the study of their external form. all plants are multicellular eukaryotes, their dna stored in nuclei. the characteristic features of plant cells that distinguish them from those of animals and fungi include a primary cell wall composed of the polysaccharides cellulose, hemicellulose and pectin, larger vacuoles than in animal cells and the presence of plastids with unique photosynthetic and biosynthetic functions as in the chloroplasts. other plastids contain storage products such as starch ( amyloplasts ) or lipids ( elaioplasts ). uniquely, streptophyte cells and those of the green algal order trentepohliales divide by construction of a phragmoplast as a template for building a cell plate late in cell division. the bodies of vascular plants including clubmosses, ferns and seed plants ( gymnosperms and angiosperms ) generally have aerial and subterranean subsystems. the shoots consist of stems bearing green photosynthesising leaves and reproductive structures. the underground vascularised roots bear root hairs at their tips and generally lack chlorophyll. non - vascular plants, the liverworts, hornworts and mosses do not produce ground - penetrating vascular roots and most of the plant participates in photosynthesis. the sporophyte generation is nonphotosynthetic in liverworts but may be able to contribute part of its energy needs by photosynthesis in mosses and hornworts. the root system and the shoot system are interdependent β the usually nonphotosynthetic root system depends on the shoot system for food, and the usually photosynthetic shoot system depends on water and minerals from the root system. cells in each system are capable of creating cells of the other and producing adventitious shoots or roots. stolons and tubers are examples of shoots that can grow roots. roots that spread out close to the surface, such as those of willows, can produce shoots and ultimately new plants. in the event that one of the systems is lost, the other can often regrow it. in fact it is possible to grow an entire plant from a single leaf, as is the case with plants in streptocarpus sect. saintpaulia, or even a single cell β which can dedifferentiate into a callus ( a mass of
ability of cells to receive, process, and transmit signals with its environment and with itself. signals can be non - chemical such as light, electrical impulses, and heat, or chemical signals ( or ligands ) that interact with receptors, which can be found embedded in the cell membrane of another cell or located deep inside a cell. there are generally four types of chemical signals : autocrine, paracrine, juxtacrine, and hormones. in autocrine signaling, the ligand affects the same cell that releases it. tumor cells, for example, can reproduce uncontrollably because they release signals that initiate their own self - division. in paracrine signaling, the ligand diffuses to nearby cells and affects them. for example, brain cells called neurons release ligands called neurotransmitters that diffuse across a synaptic cleft to bind with a receptor on an adjacent cell such as another neuron or muscle cell. in juxtacrine signaling, there is direct contact between the signaling and responding cells. finally, hormones are ligands that travel through the circulatory systems of animals or vascular systems of plants to reach their target cells. once a ligand binds with a receptor, it can influence the behavior of another cell, depending on the type of receptor. for instance, neurotransmitters that bind with an inotropic receptor can alter the excitability of a target cell. other types of receptors include protein kinase receptors ( e. g., receptor for the hormone insulin ) and g protein - coupled receptors. activation of g protein - coupled receptors can initiate second messenger cascades. the process by which a chemical or physical signal is transmitted through a cell as a series of molecular events is called signal transduction. = = = cell cycle = = = the cell cycle is a series of events that take place in a cell that cause it to divide into two daughter cells. these events include the duplication of its dna and some of its organelles, and the subsequent partitioning of its cytoplasm into two daughter cells in a process called cell division. in eukaryotes ( i. e., animal, plant, fungal, and protist cells ), there are two distinct types of cell division : mitosis and meiosis. mitosis is part of the cell cycle, in which replicated chromosomes are separated into two new nuclei. cell division gives rise to genetically identical cells in which the total number of chromosomes is maintained. in general, mitosis
combination of chemical and mechanical stimulation. cell proliferation and differentiation are largely influenced by mechanical and biochemical cues in the surrounding extracellular matrix environment. bioreactors are typically developed to replicate the specific physiological environment of the tissue being grown ( e. g., flex and fluid shearing for heart tissue growth ). this can allow specialized cell lines to thrive in cultures replicating their native environments, but it also makes bioreactors attractive tools for culturing stem cells. a successful stem - cell - based bioreactor is effective at expanding stem cells with uniform properties and / or promoting controlled, reproducible differentiation into selected mature cell types. there are a variety of bioreactors designed for 3d cell cultures. there are small plastic cylindrical chambers, as well as glass chambers, with regulated internal humidity and moisture specifically engineered for the purpose of growing cells in three dimensions. the bioreactor uses bioactive synthetic materials such as polyethylene terephthalate membranes to surround the spheroid cells in an environment that maintains high levels of nutrients. they are easy to open and close, so that cell spheroids can be removed for testing, yet the chamber is able to maintain 100 % humidity throughout. this humidity is important to achieve maximum cell growth and function. the bioreactor chamber is part of a larger device that rotates to ensure equal cell growth in each direction across three dimensions. quinxell technologies now under quintech life sciences from singapore has developed a bioreactor known as the tisxell biaxial bioreactor which is specially designed for the purpose of tissue engineering. it is the first bioreactor in the world to have a spherical glass chamber with biaxial rotation ; specifically to mimic the rotation of the fetus in the womb ; which provides a conducive environment for the growth of tissues. multiple forms of mechanical stimulation have also been combined into a single bioreactor. using gene expression analysis, one academic study found that applying a combination of cyclic strain and ultrasound stimulation to pre - osteoblast cells in a bioreactor accelerated matrix maturation and differentiation. the technology of this combined stimulation bioreactor could be used to grow bone cells more quickly and effectively in future clinical stem cell therapies. mc2 biotek has also developed a bioreactor known as prototissue that uses gas exchange to maintain high oxygen levels within the cell chamber ; improving upon previous bioreactors, since the higher oxygen levels help the cell grow and undergo normal cell respiration. active
medical purposes. cells are often ' seeded ' into these structures capable of supporting three - dimensional tissue formation. scaffolds mimic the extracellular matrix of the native tissue, recapitulating the in vivo milieu and allowing cells to influence their own microenvironments. they usually serve at least one of the following purposes : allowing cell attachment and migration, delivering and retaining cells and biochemical factors, enabling diffusion of vital cell nutrients and expressed products, and exerting certain mechanical and biological influences to modify the behaviour of the cell phase. in 2009, an interdisciplinary team led by the thoracic surgeon thorsten walles implanted the first bioartificial transplant that provides an innate vascular network for post - transplant graft supply successfully into a patient awaiting tracheal reconstruction. to achieve the goal of tissue reconstruction, scaffolds must meet some specific requirements. high porosity and adequate pore size are necessary to facilitate cell seeding and diffusion throughout the whole structure of both cells and nutrients. biodegradability is often an essential factor since scaffolds should preferably be absorbed by the surrounding tissues without the necessity of surgical removal. the rate at which degradation occurs has to coincide as much as possible with the rate of tissue formation : this means that while cells are fabricating their own natural matrix structure around themselves, the scaffold is able to provide structural integrity within the body and eventually it will break down leaving the newly formed tissue which will take over the mechanical load. injectability is also important for clinical uses. recent research on organ printing is showing how crucial a good control of the 3d environment is to ensure reproducibility of experiments and offer better results. = = = materials = = = material selection is an essential aspect of producing a scaffold. the materials utilized can be natural or synthetic and can be biodegradable or non - biodegradable. additionally, they must be biocompatible, meaning that they do not cause any adverse effects to cells. silicone, for example, is a synthetic, non - biodegradable material commonly used as a drug delivery material, while gelatin is a biodegradable, natural material commonly used in cell - culture scaffolds the material needed for each application is different, and dependent on the desired mechanical properties of the material. tissue engineering of long bone defects for example, will require a rigid scaffold with a compressive strength similar to that of cortical bone ( 100 - 150 mpa ),
there are a variety of bioreactors designed for 3d cell cultures. there are small plastic cylindrical chambers, as well as glass chambers, with regulated internal humidity and moisture specifically engineered for the purpose of growing cells in three dimensions. the bioreactor uses bioactive synthetic materials such as polyethylene terephthalate membranes to surround the spheroid cells in an environment that maintains high levels of nutrients. they are easy to open and close, so that cell spheroids can be removed for testing, yet the chamber is able to maintain 100 % humidity throughout. this humidity is important to achieve maximum cell growth and function. the bioreactor chamber is part of a larger device that rotates to ensure equal cell growth in each direction across three dimensions. quinxell technologies now under quintech life sciences from singapore has developed a bioreactor known as the tisxell biaxial bioreactor which is specially designed for the purpose of tissue engineering. it is the first bioreactor in the world to have a spherical glass chamber with biaxial rotation ; specifically to mimic the rotation of the fetus in the womb ; which provides a conducive environment for the growth of tissues. multiple forms of mechanical stimulation have also been combined into a single bioreactor. using gene expression analysis, one academic study found that applying a combination of cyclic strain and ultrasound stimulation to pre - osteoblast cells in a bioreactor accelerated matrix maturation and differentiation. the technology of this combined stimulation bioreactor could be used to grow bone cells more quickly and effectively in future clinical stem cell therapies. mc2 biotek has also developed a bioreactor known as prototissue that uses gas exchange to maintain high oxygen levels within the cell chamber ; improving upon previous bioreactors, since the higher oxygen levels help the cell grow and undergo normal cell respiration. active areas of research on bioreactors includes increasing production scale and refining the physiological environment, both of which could improve the efficiency and efficacy of bioreactors in research or clinical use. bioreactors are currently used to study, among other things, cell and tissue level therapies, cell and tissue response to specific physiological environment changes, and development of disease and injury. = = = long fiber generation = = = in 2013, a group from the university of tokyo developed cell laden fibers up to a meter in length and on the order of 100 ΞΌm in size. these fibers were created using a microfluidic device that forms a
Question: What is it that surrounds cells and serve to keep the insides separated from the outsides?
A) inner membranes
B) abundant membranes
C) biological membranes
D) similar membranes
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C) biological membranes
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Context:
##rates and peripheral blood, further development of this method is necessary before it can be used routinely. one major drawback of immuno - cytochemistry is that only tumor - associated and not tumor - specific monoclonal antibodies are used, and as a result, some cross - reaction with normal cells can occur. in order to effectively stage breast cancer and assess the efficacy of purging regimens prior to autologous stem cell infusion, it is important to detect even small quantities of breast cancer cells. immuno - histochemical methods are ideal for this purpose because they are simple, sensitive, and quite specific. franklin et al. performed a sensitive immuno - cytochemical assay by using a combination of four monoclonal antibodies ( 260f9, 520c9, 317g5 and bre - 3 ) against tumor cell surface glycoproteins to identify breast tumour cells in bone marrow and peripheral blood. they concluded from the results that immuno - cytochemical staining of bone marrow and peripheral blood is a sensitive and simple way to detect and quantify breast cancer cells. one of the main reasons for metastatic relapse in patients with solid tumours is the early dissemination of malignant cells. the use of monoclonal antibodies ( mabs ) specific for cytokeratins can identify disseminated individual epithelial tumor cells in the bone marrow. one study reports on having developed an immuno - cytochemical procedure for simultaneous labeling of cytokeratin component no. 18 ( ck18 ) and prostate specific antigen ( psa ). this would help in the further characterization of disseminated individual epithelial tumor cells in patients with prostate cancer. the twelve control aspirates from patients with benign prostatic hyperplasia showed negative staining, which further supports the specificity of ck18 in detecting epithelial tumour cells in bone marrow. in most cases of malignant disease complicated by effusion, neoplastic cells can be easily recognized. however, in some cases, malignant cells are not so easily seen or their presence is too doubtful to call it a positive report. the use of immuno - cytochemical techniques increases diagnostic accuracy in these cases. ghosh, mason and spriggs analysed 53 samples of pleural or peritoneal fluid from 41 patients with malignant disease. conventional cytological examination had not revealed any neoplastic cells. three monocl
. in order to effectively stage breast cancer and assess the efficacy of purging regimens prior to autologous stem cell infusion, it is important to detect even small quantities of breast cancer cells. immuno - histochemical methods are ideal for this purpose because they are simple, sensitive, and quite specific. franklin et al. performed a sensitive immuno - cytochemical assay by using a combination of four monoclonal antibodies ( 260f9, 520c9, 317g5 and bre - 3 ) against tumor cell surface glycoproteins to identify breast tumour cells in bone marrow and peripheral blood. they concluded from the results that immuno - cytochemical staining of bone marrow and peripheral blood is a sensitive and simple way to detect and quantify breast cancer cells. one of the main reasons for metastatic relapse in patients with solid tumours is the early dissemination of malignant cells. the use of monoclonal antibodies ( mabs ) specific for cytokeratins can identify disseminated individual epithelial tumor cells in the bone marrow. one study reports on having developed an immuno - cytochemical procedure for simultaneous labeling of cytokeratin component no. 18 ( ck18 ) and prostate specific antigen ( psa ). this would help in the further characterization of disseminated individual epithelial tumor cells in patients with prostate cancer. the twelve control aspirates from patients with benign prostatic hyperplasia showed negative staining, which further supports the specificity of ck18 in detecting epithelial tumour cells in bone marrow. in most cases of malignant disease complicated by effusion, neoplastic cells can be easily recognized. however, in some cases, malignant cells are not so easily seen or their presence is too doubtful to call it a positive report. the use of immuno - cytochemical techniques increases diagnostic accuracy in these cases. ghosh, mason and spriggs analysed 53 samples of pleural or peritoneal fluid from 41 patients with malignant disease. conventional cytological examination had not revealed any neoplastic cells. three monoclonal antibodies ( anti - cea, ca 1 and hmfg - 2 ) were used to search for malignant cells. immunocytochemical labelling was performed on unstained smears, which had been stored at - 20 Β°c up to 18 months. twelve of the forty - one cases
##tase, human chorionic gonadotrophin, Ξ± - fetoprotein and others are organ - associated antigens and the production of monoclonal antibodies against these antigens helps in determining the nature of a primary tumor. monoclonal antibodies are especially useful in distinguishing morphologically similar lesions, like pleural and peritoneal mesothelioma, adenocarcinoma, and in the determination of the organ or tissue origin of undifferentiated metastases. selected monoclonal antibodies help in the detection of occult metastases ( cancer of unknown primary origin ) by immuno - cytological analysis of bone marrow, other tissue aspirates, as well as lymph nodes and other tissues and can have increased sensitivity over normal histopathological staining. one study performed a sensitive immuno - histochemical assay on bone marrow aspirates of 20 patients with localized prostate cancer. three monoclonal antibodies ( t16, c26, and ae - 1 ), capable of recognizing membrane and cytoskeletal antigens expressed by epithelial cells to detect tumour cells, were used in the assay. bone marrow aspirates of 22 % of patients with localized prostate cancer ( stage b, 0 / 5 ; stage c, 2 / 4 ), and 36 % patients with metastatic prostate cancer ( stage d1, 0 / 7 patients ; stage d2, 4 / 4 patients ) had antigen - positive cells in their bone marrow. it was concluded that immuno - histochemical staining of bone marrow aspirates are very useful to detect occult bone marrow metastases in patients with apparently localized prostate cancer. although immuno - cytochemistry using tumor - associated monoclonal antibodies has led to an improved ability to detect occult breast cancer cells in bone marrow aspirates and peripheral blood, further development of this method is necessary before it can be used routinely. one major drawback of immuno - cytochemistry is that only tumor - associated and not tumor - specific monoclonal antibodies are used, and as a result, some cross - reaction with normal cells can occur. in order to effectively stage breast cancer and assess the efficacy of purging regimens prior to autologous stem cell infusion, it is important to detect even small quantities of breast cancer cells. immuno - histochemical methods are ideal for this purpose because they are simple, sensitive, and quite specific
histochemical staining of bone marrow aspirates are very useful to detect occult bone marrow metastases in patients with apparently localized prostate cancer. although immuno - cytochemistry using tumor - associated monoclonal antibodies has led to an improved ability to detect occult breast cancer cells in bone marrow aspirates and peripheral blood, further development of this method is necessary before it can be used routinely. one major drawback of immuno - cytochemistry is that only tumor - associated and not tumor - specific monoclonal antibodies are used, and as a result, some cross - reaction with normal cells can occur. in order to effectively stage breast cancer and assess the efficacy of purging regimens prior to autologous stem cell infusion, it is important to detect even small quantities of breast cancer cells. immuno - histochemical methods are ideal for this purpose because they are simple, sensitive, and quite specific. franklin et al. performed a sensitive immuno - cytochemical assay by using a combination of four monoclonal antibodies ( 260f9, 520c9, 317g5 and bre - 3 ) against tumor cell surface glycoproteins to identify breast tumour cells in bone marrow and peripheral blood. they concluded from the results that immuno - cytochemical staining of bone marrow and peripheral blood is a sensitive and simple way to detect and quantify breast cancer cells. one of the main reasons for metastatic relapse in patients with solid tumours is the early dissemination of malignant cells. the use of monoclonal antibodies ( mabs ) specific for cytokeratins can identify disseminated individual epithelial tumor cells in the bone marrow. one study reports on having developed an immuno - cytochemical procedure for simultaneous labeling of cytokeratin component no. 18 ( ck18 ) and prostate specific antigen ( psa ). this would help in the further characterization of disseminated individual epithelial tumor cells in patients with prostate cancer. the twelve control aspirates from patients with benign prostatic hyperplasia showed negative staining, which further supports the specificity of ck18 in detecting epithelial tumour cells in bone marrow. in most cases of malignant disease complicated by effusion, neoplastic cells can be easily recognized. however, in some cases, malignant cells are not so easily seen or their presence is too doubtful to call it a positive report. the use
we review our expectations in the last year before the lhc commissioning.
prostate cancer ( stage b, 0 / 5 ; stage c, 2 / 4 ), and 36 % patients with metastatic prostate cancer ( stage d1, 0 / 7 patients ; stage d2, 4 / 4 patients ) had antigen - positive cells in their bone marrow. it was concluded that immuno - histochemical staining of bone marrow aspirates are very useful to detect occult bone marrow metastases in patients with apparently localized prostate cancer. although immuno - cytochemistry using tumor - associated monoclonal antibodies has led to an improved ability to detect occult breast cancer cells in bone marrow aspirates and peripheral blood, further development of this method is necessary before it can be used routinely. one major drawback of immuno - cytochemistry is that only tumor - associated and not tumor - specific monoclonal antibodies are used, and as a result, some cross - reaction with normal cells can occur. in order to effectively stage breast cancer and assess the efficacy of purging regimens prior to autologous stem cell infusion, it is important to detect even small quantities of breast cancer cells. immuno - histochemical methods are ideal for this purpose because they are simple, sensitive, and quite specific. franklin et al. performed a sensitive immuno - cytochemical assay by using a combination of four monoclonal antibodies ( 260f9, 520c9, 317g5 and bre - 3 ) against tumor cell surface glycoproteins to identify breast tumour cells in bone marrow and peripheral blood. they concluded from the results that immuno - cytochemical staining of bone marrow and peripheral blood is a sensitive and simple way to detect and quantify breast cancer cells. one of the main reasons for metastatic relapse in patients with solid tumours is the early dissemination of malignant cells. the use of monoclonal antibodies ( mabs ) specific for cytokeratins can identify disseminated individual epithelial tumor cells in the bone marrow. one study reports on having developed an immuno - cytochemical procedure for simultaneous labeling of cytokeratin component no. 18 ( ck18 ) and prostate specific antigen ( psa ). this would help in the further characterization of disseminated individual epithelial tumor cells in patients with prostate cancer. the twelve control aspirates from patients with benign prostatic hyperplasia showed negative staining, which further supports the specificity of ck
this scaffold and cells were placed in a bioreactor, where it matured to become a partially or fully transplantable organ. the work was called a " landmark ". the lab first stripped the cells away from a rat heart ( a process called " decellularization " ) and then injected rat stem cells into the decellularized rat heart. tissue - engineered blood vessels : blood vessels that have been grown in a lab and can be used to repair damaged blood vessels without eliciting an immune response. tissue engineered blood vessels have been developed by many different approaches. they could be implanted as pre - seeded cellularized blood vessels, as acellular vascular grafts made with decellularized vessels or synthetic vascular grafts. artificial skin constructed from human skin cells embedded in a hydrogel, such as in the case of bio - printed constructs for battlefield burn repairs. artificial bone marrow : bone marrow cultured in vitro to be transplanted serves as a " just cells " approach to tissue engineering. tissue engineered bone : a structural matrix can be composed of metals such as titanium, polymers of varying degradation rates, or certain types of ceramics. materials are often chosen to recruit osteoblasts to aid in reforming the bone and returning biological function. various types of cells can be added directly into the matrix to expedite the process. laboratory - grown penis : decellularized scaffolds of rabbit penises were recellularised with smooth muscle and endothelial cells. the organ was then transplanted to live rabbits and functioned comparably to the native organ, suggesting potential as treatment for genital trauma. oral mucosa tissue engineering uses a cells and scaffold approach to replicate the 3 dimensional structure and function of oral mucosa. = = cells as building blocks = = cells are one of the main components for the success of tissue engineering approaches. tissue engineering uses cells as strategies for creation / replacement of new tissue. examples include fibroblasts used for skin repair or renewal, chondrocytes used for cartilage repair ( maci β fda approved product ), and hepatocytes used in liver support systems cells can be used alone or with support matrices for tissue engineering applications. an adequate environment for promoting cell growth, differentiation, and integration with the existing tissue is a critical factor for cell - based building blocks. manipulation of any of these cell processes create alternative avenues for the development of new tissue ( e. g., cell reprogramming - somatic
prostate cancer. three monoclonal antibodies ( t16, c26, and ae - 1 ), capable of recognizing membrane and cytoskeletal antigens expressed by epithelial cells to detect tumour cells, were used in the assay. bone marrow aspirates of 22 % of patients with localized prostate cancer ( stage b, 0 / 5 ; stage c, 2 / 4 ), and 36 % patients with metastatic prostate cancer ( stage d1, 0 / 7 patients ; stage d2, 4 / 4 patients ) had antigen - positive cells in their bone marrow. it was concluded that immuno - histochemical staining of bone marrow aspirates are very useful to detect occult bone marrow metastases in patients with apparently localized prostate cancer. although immuno - cytochemistry using tumor - associated monoclonal antibodies has led to an improved ability to detect occult breast cancer cells in bone marrow aspirates and peripheral blood, further development of this method is necessary before it can be used routinely. one major drawback of immuno - cytochemistry is that only tumor - associated and not tumor - specific monoclonal antibodies are used, and as a result, some cross - reaction with normal cells can occur. in order to effectively stage breast cancer and assess the efficacy of purging regimens prior to autologous stem cell infusion, it is important to detect even small quantities of breast cancer cells. immuno - histochemical methods are ideal for this purpose because they are simple, sensitive, and quite specific. franklin et al. performed a sensitive immuno - cytochemical assay by using a combination of four monoclonal antibodies ( 260f9, 520c9, 317g5 and bre - 3 ) against tumor cell surface glycoproteins to identify breast tumour cells in bone marrow and peripheral blood. they concluded from the results that immuno - cytochemical staining of bone marrow and peripheral blood is a sensitive and simple way to detect and quantify breast cancer cells. one of the main reasons for metastatic relapse in patients with solid tumours is the early dissemination of malignant cells. the use of monoclonal antibodies ( mabs ) specific for cytokeratins can identify disseminated individual epithelial tumor cells in the bone marrow. one study reports on having developed an immuno - cytochemical procedure for simultaneous labeling of cytokeratin component no. 18
trauma, reconstruction of the facial features using remains of deceased ( skull ) thus aiding identification. gender - based medicine studies the biological and physiological differences between the human sexes and how that affects differences in disease. health informatics is a relatively recent field that deal with the application of computers and information technology to medicine. hospice and palliative medicine is a relatively modern branch of clinical medicine that deals with pain and symptom relief and emotional support in patients with terminal illnesses including cancer and heart failure. hospital medicine is the general medical care of hospitalized patients. physicians whose primary professional focus is hospital medicine are called hospitalists in the united states and canada. the term most responsible physician ( mrp ) or attending physician is also used interchangeably to describe this role. laser medicine involves the use of lasers in the diagnostics or treatment of various conditions. many other health science fields, e. g. dietetics medical ethics deals with ethical and moral principles that apply values and judgments to the practice of medicine. medical humanities includes the humanities ( literature, philosophy, ethics, history and religion ), social science ( anthropology, cultural studies, psychology, sociology ), and the arts ( literature, theater, film, and visual arts ) and their application to medical education and practice. nosokinetics is the science / subject of measuring and modelling the process of care in health and social care systems. nosology is the classification of diseases for various purposes. occupational medicine is the provision of health advice to organizations and individuals to ensure that the highest standards of health and safety at work can be achieved and maintained. pain management ( also called pain medicine, or algiatry ) is the medical discipline concerned with the relief of pain. pharmacogenomics is a form of individualized medicine. podiatric medicine is the study of, diagnosis, and medical treatment of disorders of the foot, ankle, lower limb, hip and lower back. sexual medicine is concerned with diagnosing, assessing and treating all disorders related to sexuality. sports medicine deals with the treatment and prevention and rehabilitation of sports / exercise injuries such as muscle spasms, muscle tears, injuries to ligaments ( ligament tears or ruptures ) and their repair in athletes, amateur and professional. therapeutics is the field, more commonly referenced in earlier periods of history, of the various remedies that can be used to treat disease and promote health. travel medicine or emporiatrics deals with health problems of international travelers or travelers across highly different environments. tropical medicine deals with the prevention and treatment of tropical diseases
men. well - known spiritual systems include animism ( the notion of inanimate objects having spirits ), spiritualism ( an appeal to gods or communion with ancestor spirits ) ; shamanism ( the vesting of an individual with mystic powers ) ; and divination ( magically obtaining the truth ). the field of medical anthropology examines the ways in which culture and society are organized around or impacted by issues of health, health care and related issues. the earliest known medical texts in the world were found in the ancient syrian city of ebla and date back to 2500 bce. other early records on medicine have been discovered from ancient egyptian medicine, babylonian medicine, ayurvedic medicine ( in the indian subcontinent ), classical chinese medicine ( alternative medicine ) predecessor to the modern traditional chinese medicine ), and ancient greek medicine and roman medicine. in egypt, imhotep ( 3rd millennium bce ) is the first physician in history known by name. the oldest egyptian medical text is the kahun gynaecological papyrus from around 2000 bce, which describes gynaecological diseases. the edwin smith papyrus dating back to 1600 bce is an early work on surgery, while the ebers papyrus dating back to 1500 bce is akin to a textbook on medicine. in china, archaeological evidence of medicine in chinese dates back to the bronze age shang dynasty, based on seeds for herbalism and tools presumed to have been used for surgery. the huangdi neijing, the progenitor of chinese medicine, is a medical text written beginning in the 2nd century bce and compiled in the 3rd century. in india, the surgeon sushruta described numerous surgical operations, including the earliest forms of plastic surgery. earliest records of dedicated hospitals come from mihintale in sri lanka where evidence of dedicated medicinal treatment facilities for patients are found. in greece, the ancient greek physician hippocrates, the " father of modern medicine ", laid the foundation for a rational approach to medicine. hippocrates introduced the hippocratic oath for physicians, which is still relevant and in use today, and was the first to categorize illnesses as acute, chronic, endemic and epidemic, and use terms such as, " exacerbation, relapse, resolution, crisis, paroxysm, peak, and convalescence ". the greek physician galen was also one of the greatest surgeons of the ancient world and performed many audacious operations, including brain and eye surgeries. after the fall of the western roman empire and the onset of
Question: What is the gland in the chest behind the breast bone that stores some types of lymphocytes while they mature?
A) thymus
B) Montgomery
C) pineal
D) lumbar
|
A) thymus
|
Context:
could be maintained in culture containing iaa, followed by the observation in 1947 that it could be induced to form roots and shoots by controlling the concentration of growth hormones were key steps in the development of plant biotechnology and genetic modification. cytokinins are a class of plant hormones named for their control of cell division ( especially cytokinesis ). the natural cytokinin zeatin was discovered in corn, zea mays, and is a derivative of the purine adenine. zeatin is produced in roots and transported to shoots in the xylem where it promotes cell division, bud development, and the greening of chloroplasts. the gibberelins, such as gibberelic acid are diterpenes synthesised from acetyl coa via the mevalonate pathway. they are involved in the promotion of germination and dormancy - breaking in seeds, in regulation of plant height by controlling stem elongation and the control of flowering. abscisic acid ( aba ) occurs in all land plants except liverworts, and is synthesised from carotenoids in the chloroplasts and other plastids. it inhibits cell division, promotes seed maturation, and dormancy, and promotes stomatal closure. it was so named because it was originally thought to control abscission. ethylene is a gaseous hormone that is produced in all higher plant tissues from methionine. it is now known to be the hormone that stimulates or regulates fruit ripening and abscission, and it, or the synthetic growth regulator ethephon which is rapidly metabolised to produce ethylene, are used on industrial scale to promote ripening of cotton, pineapples and other climacteric crops. another class of phytohormones is the jasmonates, first isolated from the oil of jasminum grandiflorum which regulates wound responses in plants by unblocking the expression of genes required in the systemic acquired resistance response to pathogen attack. in addition to being the primary energy source for plants, light functions as a signalling device, providing information to the plant, such as how much sunlight the plant receives each day. this can result in adaptive changes in a process known as photomorphogenesis. phytochromes are the photoreceptors in a plant that are sensitive to light. = = plant anatomy and morphology = = plant anatomy is the study of the structure of
frits went. the first known auxin, indole - 3 - acetic acid ( iaa ), which promotes cell growth, was only isolated from plants about 50 years later. this compound mediates the tropic responses of shoots and roots towards light and gravity. the finding in 1939 that plant callus could be maintained in culture containing iaa, followed by the observation in 1947 that it could be induced to form roots and shoots by controlling the concentration of growth hormones were key steps in the development of plant biotechnology and genetic modification. cytokinins are a class of plant hormones named for their control of cell division ( especially cytokinesis ). the natural cytokinin zeatin was discovered in corn, zea mays, and is a derivative of the purine adenine. zeatin is produced in roots and transported to shoots in the xylem where it promotes cell division, bud development, and the greening of chloroplasts. the gibberelins, such as gibberelic acid are diterpenes synthesised from acetyl coa via the mevalonate pathway. they are involved in the promotion of germination and dormancy - breaking in seeds, in regulation of plant height by controlling stem elongation and the control of flowering. abscisic acid ( aba ) occurs in all land plants except liverworts, and is synthesised from carotenoids in the chloroplasts and other plastids. it inhibits cell division, promotes seed maturation, and dormancy, and promotes stomatal closure. it was so named because it was originally thought to control abscission. ethylene is a gaseous hormone that is produced in all higher plant tissues from methionine. it is now known to be the hormone that stimulates or regulates fruit ripening and abscission, and it, or the synthetic growth regulator ethephon which is rapidly metabolised to produce ethylene, are used on industrial scale to promote ripening of cotton, pineapples and other climacteric crops. another class of phytohormones is the jasmonates, first isolated from the oil of jasminum grandiflorum which regulates wound responses in plants by unblocking the expression of genes required in the systemic acquired resistance response to pathogen attack. in addition to being the primary energy source for plants, light functions as a signalling device, providing information to the plant, such as how
their mechanical properties. = = tissue culture = = in many cases, creation of functional tissues and biological structures in vitro requires extensive culturing to promote survival, growth and inducement of functionality. in general, the basic requirements of cells must be maintained in culture, which include oxygen, ph, humidity, temperature, nutrients and osmotic pressure maintenance. tissue engineered cultures also present additional problems in maintaining culture conditions. in standard cell culture, diffusion is often the sole means of nutrient and metabolite transport. however, as a culture becomes larger and more complex, such as the case with engineered organs and whole tissues, other mechanisms must be employed to maintain the culture, such as the creation of capillary networks within the tissue. another issue with tissue culture is introducing the proper factors or stimuli required to induce functionality. in many cases, simple maintenance culture is not sufficient. growth factors, hormones, specific metabolites or nutrients, chemical and physical stimuli are sometimes required. for example, certain cells respond to changes in oxygen tension as part of their normal development, such as chondrocytes, which must adapt to low oxygen conditions or hypoxia during skeletal development. others, such as endothelial cells, respond to shear stress from fluid flow, which is encountered in blood vessels. mechanical stimuli, such as pressure pulses seem to be beneficial to all kind of cardiovascular tissue such as heart valves, blood vessels or pericardium. = = = bioreactors = = = in tissue engineering, a bioreactor is a device that attempts to simulate a physiological environment in order to promote cell or tissue growth in vitro. a physiological environment can consist of many different parameters such as temperature, pressure, oxygen or carbon dioxide concentration, or osmolality of fluid environment, and it can extend to all kinds of biological, chemical or mechanical stimuli. therefore, there are systems that may include the application of forces such as electromagnetic forces, mechanical pressures, or fluid pressures to the tissue. these systems can be two - or three - dimensional setups. bioreactors can be used in both academic and industry applications. general - use and application - specific bioreactors are also commercially available, which may provide static chemical stimulation or a combination of chemical and mechanical stimulation. cell proliferation and differentiation are largely influenced by mechanical and biochemical cues in the surrounding extracellular matrix environment. bioreactors are typically developed to replicate the specific physiological environment of the tissue being grown ( e. g., flex and fluid shearing for heart tissue growth ). this can
cytokinesis ). the natural cytokinin zeatin was discovered in corn, zea mays, and is a derivative of the purine adenine. zeatin is produced in roots and transported to shoots in the xylem where it promotes cell division, bud development, and the greening of chloroplasts. the gibberelins, such as gibberelic acid are diterpenes synthesised from acetyl coa via the mevalonate pathway. they are involved in the promotion of germination and dormancy - breaking in seeds, in regulation of plant height by controlling stem elongation and the control of flowering. abscisic acid ( aba ) occurs in all land plants except liverworts, and is synthesised from carotenoids in the chloroplasts and other plastids. it inhibits cell division, promotes seed maturation, and dormancy, and promotes stomatal closure. it was so named because it was originally thought to control abscission. ethylene is a gaseous hormone that is produced in all higher plant tissues from methionine. it is now known to be the hormone that stimulates or regulates fruit ripening and abscission, and it, or the synthetic growth regulator ethephon which is rapidly metabolised to produce ethylene, are used on industrial scale to promote ripening of cotton, pineapples and other climacteric crops. another class of phytohormones is the jasmonates, first isolated from the oil of jasminum grandiflorum which regulates wound responses in plants by unblocking the expression of genes required in the systemic acquired resistance response to pathogen attack. in addition to being the primary energy source for plants, light functions as a signalling device, providing information to the plant, such as how much sunlight the plant receives each day. this can result in adaptive changes in a process known as photomorphogenesis. phytochromes are the photoreceptors in a plant that are sensitive to light. = = plant anatomy and morphology = = plant anatomy is the study of the structure of plant cells and tissues, whereas plant morphology is the study of their external form. all plants are multicellular eukaryotes, their dna stored in nuclei. the characteristic features of plant cells that distinguish them from those of animals and fungi include a primary cell wall composed of the polysaccharides cellulose,
##aggeration to say that the tip of the radicle.. acts like the brain of one of the lower animals.. directing the several movements ". about the same time, the role of auxins ( from the greek auxein, to grow ) in control of plant growth was first outlined by the dutch scientist frits went. the first known auxin, indole - 3 - acetic acid ( iaa ), which promotes cell growth, was only isolated from plants about 50 years later. this compound mediates the tropic responses of shoots and roots towards light and gravity. the finding in 1939 that plant callus could be maintained in culture containing iaa, followed by the observation in 1947 that it could be induced to form roots and shoots by controlling the concentration of growth hormones were key steps in the development of plant biotechnology and genetic modification. cytokinins are a class of plant hormones named for their control of cell division ( especially cytokinesis ). the natural cytokinin zeatin was discovered in corn, zea mays, and is a derivative of the purine adenine. zeatin is produced in roots and transported to shoots in the xylem where it promotes cell division, bud development, and the greening of chloroplasts. the gibberelins, such as gibberelic acid are diterpenes synthesised from acetyl coa via the mevalonate pathway. they are involved in the promotion of germination and dormancy - breaking in seeds, in regulation of plant height by controlling stem elongation and the control of flowering. abscisic acid ( aba ) occurs in all land plants except liverworts, and is synthesised from carotenoids in the chloroplasts and other plastids. it inhibits cell division, promotes seed maturation, and dormancy, and promotes stomatal closure. it was so named because it was originally thought to control abscission. ethylene is a gaseous hormone that is produced in all higher plant tissues from methionine. it is now known to be the hormone that stimulates or regulates fruit ripening and abscission, and it, or the synthetic growth regulator ethephon which is rapidly metabolised to produce ethylene, are used on industrial scale to promote ripening of cotton, pineapples and other climacteric crops. another class of phytohormones is the jasmonates, first isolated
elongation and the control of flowering. abscisic acid ( aba ) occurs in all land plants except liverworts, and is synthesised from carotenoids in the chloroplasts and other plastids. it inhibits cell division, promotes seed maturation, and dormancy, and promotes stomatal closure. it was so named because it was originally thought to control abscission. ethylene is a gaseous hormone that is produced in all higher plant tissues from methionine. it is now known to be the hormone that stimulates or regulates fruit ripening and abscission, and it, or the synthetic growth regulator ethephon which is rapidly metabolised to produce ethylene, are used on industrial scale to promote ripening of cotton, pineapples and other climacteric crops. another class of phytohormones is the jasmonates, first isolated from the oil of jasminum grandiflorum which regulates wound responses in plants by unblocking the expression of genes required in the systemic acquired resistance response to pathogen attack. in addition to being the primary energy source for plants, light functions as a signalling device, providing information to the plant, such as how much sunlight the plant receives each day. this can result in adaptive changes in a process known as photomorphogenesis. phytochromes are the photoreceptors in a plant that are sensitive to light. = = plant anatomy and morphology = = plant anatomy is the study of the structure of plant cells and tissues, whereas plant morphology is the study of their external form. all plants are multicellular eukaryotes, their dna stored in nuclei. the characteristic features of plant cells that distinguish them from those of animals and fungi include a primary cell wall composed of the polysaccharides cellulose, hemicellulose and pectin, larger vacuoles than in animal cells and the presence of plastids with unique photosynthetic and biosynthetic functions as in the chloroplasts. other plastids contain storage products such as starch ( amyloplasts ) or lipids ( elaioplasts ). uniquely, streptophyte cells and those of the green algal order trentepohliales divide by construction of a phragmoplast as a template for building a cell plate late in cell division. the bodies of vascular plants including clubmos
the process by which hair, skin, blood cells, and some internal organs are renewed. after cell division, each of the daughter cells begin the interphase of a new cycle. in contrast to mitosis, meiosis results in four haploid daughter cells by undergoing one round of dna replication followed by two divisions. homologous chromosomes are separated in the first division ( meiosis i ), and sister chromatids are separated in the second division ( meiosis ii ). both of these cell division cycles are used in the process of sexual reproduction at some point in their life cycle. both are believed to be present in the last eukaryotic common ancestor. prokaryotes ( i. e., archaea and bacteria ) can also undergo cell division ( or binary fission ). unlike the processes of mitosis and meiosis in eukaryotes, binary fission in prokaryotes takes place without the formation of a spindle apparatus on the cell. before binary fission, dna in the bacterium is tightly coiled. after it has uncoiled and duplicated, it is pulled to the separate poles of the bacterium as it increases the size to prepare for splitting. growth of a new cell wall begins to separate the bacterium ( triggered by ftsz polymerization and " z - ring " formation ). the new cell wall ( septum ) fully develops, resulting in the complete split of the bacterium. the new daughter cells have tightly coiled dna rods, ribosomes, and plasmids. = = = sexual reproduction and meiosis = = = meiosis is a central feature of sexual reproduction in eukaryotes, and the most fundamental function of meiosis appears to be conservation of the integrity of the genome that is passed on to progeny by parents. two aspects of sexual reproduction, meiotic recombination and outcrossing, are likely maintained respectively by the adaptive advantages of recombinational repair of genomic dna damage and genetic complementation which masks the expression of deleterious recessive mutations. the beneficial effect of genetic complementation, derived from outcrossing ( cross - fertilization ) is also referred to as hybrid vigor or heterosis. charles darwin in his 1878 book the effects of cross and self - fertilization in the vegetable kingdom at the start of chapter xii noted β the first and most important of the conclusions which may be drawn from the observations given in this volume, is that generally cross - fertilisation is beneficial and self - fertilis
it to divide into two daughter cells. these events include the duplication of its dna and some of its organelles, and the subsequent partitioning of its cytoplasm into two daughter cells in a process called cell division. in eukaryotes ( i. e., animal, plant, fungal, and protist cells ), there are two distinct types of cell division : mitosis and meiosis. mitosis is part of the cell cycle, in which replicated chromosomes are separated into two new nuclei. cell division gives rise to genetically identical cells in which the total number of chromosomes is maintained. in general, mitosis ( division of the nucleus ) is preceded by the s stage of interphase ( during which the dna is replicated ) and is often followed by telophase and cytokinesis ; which divides the cytoplasm, organelles and cell membrane of one cell into two new cells containing roughly equal shares of these cellular components. the different stages of mitosis all together define the mitotic phase of an animal cell cycle β the division of the mother cell into two genetically identical daughter cells. the cell cycle is a vital process by which a single - celled fertilized egg develops into a mature organism, as well as the process by which hair, skin, blood cells, and some internal organs are renewed. after cell division, each of the daughter cells begin the interphase of a new cycle. in contrast to mitosis, meiosis results in four haploid daughter cells by undergoing one round of dna replication followed by two divisions. homologous chromosomes are separated in the first division ( meiosis i ), and sister chromatids are separated in the second division ( meiosis ii ). both of these cell division cycles are used in the process of sexual reproduction at some point in their life cycle. both are believed to be present in the last eukaryotic common ancestor. prokaryotes ( i. e., archaea and bacteria ) can also undergo cell division ( or binary fission ). unlike the processes of mitosis and meiosis in eukaryotes, binary fission in prokaryotes takes place without the formation of a spindle apparatus on the cell. before binary fission, dna in the bacterium is tightly coiled. after it has uncoiled and duplicated, it is pulled to the separate poles of the bacterium as it increases the size to prepare for splitting. growth of a new cell wall begins to separate the bacterium ( triggered by ft
or removed from the dna during programmed stages of development of the plant, and are responsible, for example, for the differences between anthers, petals and normal leaves, despite the fact that they all have the same underlying genetic code. epigenetic changes may be temporary or may remain through successive cell divisions for the remainder of the cell ' s life. some epigenetic changes have been shown to be heritable, while others are reset in the germ cells. epigenetic changes in eukaryotic biology serve to regulate the process of cellular differentiation. during morphogenesis, totipotent stem cells become the various pluripotent cell lines of the embryo, which in turn become fully differentiated cells. a single fertilised egg cell, the zygote, gives rise to the many different plant cell types including parenchyma, xylem vessel elements, phloem sieve tubes, guard cells of the epidermis, etc. as it continues to divide. the process results from the epigenetic activation of some genes and inhibition of others. unlike animals, many plant cells, particularly those of the parenchyma, do not terminally differentiate, remaining totipotent with the ability to give rise to a new individual plant. exceptions include highly lignified cells, the sclerenchyma and xylem which are dead at maturity, and the phloem sieve tubes which lack nuclei. while plants use many of the same epigenetic mechanisms as animals, such as chromatin remodelling, an alternative hypothesis is that plants set their gene expression patterns using positional information from the environment and surrounding cells to determine their developmental fate. epigenetic changes can lead to paramutations, which do not follow the mendelian heritage rules. these epigenetic marks are carried from one generation to the next, with one allele inducing a change on the other. = = plant evolution = = the chloroplasts of plants have a number of biochemical, structural and genetic similarities to cyanobacteria, ( commonly but incorrectly known as " blue - green algae " ) and are thought to be derived from an ancient endosymbiotic relationship between an ancestral eukaryotic cell and a cyanobacterial resident. the algae are a polyphyletic group and are placed in various divisions, some more closely related to plants than others. there are many differences between them in features such as cell wall composition, biochemistry,
the cell ' s life. some epigenetic changes have been shown to be heritable, while others are reset in the germ cells. epigenetic changes in eukaryotic biology serve to regulate the process of cellular differentiation. during morphogenesis, totipotent stem cells become the various pluripotent cell lines of the embryo, which in turn become fully differentiated cells. a single fertilised egg cell, the zygote, gives rise to the many different plant cell types including parenchyma, xylem vessel elements, phloem sieve tubes, guard cells of the epidermis, etc. as it continues to divide. the process results from the epigenetic activation of some genes and inhibition of others. unlike animals, many plant cells, particularly those of the parenchyma, do not terminally differentiate, remaining totipotent with the ability to give rise to a new individual plant. exceptions include highly lignified cells, the sclerenchyma and xylem which are dead at maturity, and the phloem sieve tubes which lack nuclei. while plants use many of the same epigenetic mechanisms as animals, such as chromatin remodelling, an alternative hypothesis is that plants set their gene expression patterns using positional information from the environment and surrounding cells to determine their developmental fate. epigenetic changes can lead to paramutations, which do not follow the mendelian heritage rules. these epigenetic marks are carried from one generation to the next, with one allele inducing a change on the other. = = plant evolution = = the chloroplasts of plants have a number of biochemical, structural and genetic similarities to cyanobacteria, ( commonly but incorrectly known as " blue - green algae " ) and are thought to be derived from an ancient endosymbiotic relationship between an ancestral eukaryotic cell and a cyanobacterial resident. the algae are a polyphyletic group and are placed in various divisions, some more closely related to plants than others. there are many differences between them in features such as cell wall composition, biochemistry, pigmentation, chloroplast structure and nutrient reserves. the algal division charophyta, sister to the green algal division chlorophyta, is considered to contain the ancestor of true plants. the charophyte class charophyceae and the land plant sub - kingdom embryophy
Question: What promotes cell division and are necessary for growing plants in tissue culture?
A) mitochondria
B) auxins
C) polyamines
D) cytokinins
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D) cytokinins
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Context:
cross. the chromosome theory of inheritance, which states that genes are found on chromosomes, was supported by thomas morgans ' s experiments with fruit flies, which established the sex linkage between eye color and sex in these insects. = = = genes and dna = = = a gene is a unit of heredity that corresponds to a region of deoxyribonucleic acid ( dna ) that carries genetic information that controls form or function of an organism. dna is composed of two polynucleotide chains that coil around each other to form a double helix. it is found as linear chromosomes in eukaryotes, and circular chromosomes in prokaryotes. the set of chromosomes in a cell is collectively known as its genome. in eukaryotes, dna is mainly in the cell nucleus. in prokaryotes, the dna is held within the nucleoid. the genetic information is held within genes, and the complete assemblage in an organism is called its genotype. dna replication is a semiconservative process whereby each strand serves as a template for a new strand of dna. mutations are heritable changes in dna. they can arise spontaneously as a result of replication errors that were not corrected by proofreading or can be induced by an environmental mutagen such as a chemical ( e. g., nitrous acid, benzopyrene ) or radiation ( e. g., x - ray, gamma ray, ultraviolet radiation, particles emitted by unstable isotopes ). mutations can lead to phenotypic effects such as loss - of - function, gain - of - function, and conditional mutations. some mutations are beneficial, as they are a source of genetic variation for evolution. others are harmful if they were to result in a loss of function of genes needed for survival. = = = gene expression = = = gene expression is the molecular process by which a genotype encoded in dna gives rise to an observable phenotype in the proteins of an organism ' s body. this process is summarized by the central dogma of molecular biology, which was formulated by francis crick in 1958. according to the central dogma, genetic information flows from dna to rna to protein. there are two gene expression processes : transcription ( dna to rna ) and translation ( rna to protein ). = = = gene regulation = = = the regulation of gene expression by environmental factors and during different stages of development can occur at each step of the process such as transcription, rna splicing
to a region of deoxyribonucleic acid ( dna ) that carries genetic information that controls form or function of an organism. dna is composed of two polynucleotide chains that coil around each other to form a double helix. it is found as linear chromosomes in eukaryotes, and circular chromosomes in prokaryotes. the set of chromosomes in a cell is collectively known as its genome. in eukaryotes, dna is mainly in the cell nucleus. in prokaryotes, the dna is held within the nucleoid. the genetic information is held within genes, and the complete assemblage in an organism is called its genotype. dna replication is a semiconservative process whereby each strand serves as a template for a new strand of dna. mutations are heritable changes in dna. they can arise spontaneously as a result of replication errors that were not corrected by proofreading or can be induced by an environmental mutagen such as a chemical ( e. g., nitrous acid, benzopyrene ) or radiation ( e. g., x - ray, gamma ray, ultraviolet radiation, particles emitted by unstable isotopes ). mutations can lead to phenotypic effects such as loss - of - function, gain - of - function, and conditional mutations. some mutations are beneficial, as they are a source of genetic variation for evolution. others are harmful if they were to result in a loss of function of genes needed for survival. = = = gene expression = = = gene expression is the molecular process by which a genotype encoded in dna gives rise to an observable phenotype in the proteins of an organism ' s body. this process is summarized by the central dogma of molecular biology, which was formulated by francis crick in 1958. according to the central dogma, genetic information flows from dna to rna to protein. there are two gene expression processes : transcription ( dna to rna ) and translation ( rna to protein ). = = = gene regulation = = = the regulation of gene expression by environmental factors and during different stages of development can occur at each step of the process such as transcription, rna splicing, translation, and post - translational modification of a protein. gene expression can be influenced by positive or negative regulation, depending on which of the two types of regulatory proteins called transcription factors bind to the dna sequence close to or at a promoter. a cluster of genes that share the same promoter is called an operon,
an oscillation with a period of around 500 kb in guanine and cytosine content ( gc % ) is observed in the dna sequence of human chromosome 21. this oscillation is localized in the rightmost one - eighth region of the chromosome, from 43. 5 mb to 46. 5 mb. five cycles of oscillation are observed in this region with six gc - rich peaks and five gc - poor valleys. the gc - poor valleys comprise regions with low density of cpg islands and, alternating between the two dna strands, low gene density regions. consequently, the long - range oscillation of gc % result in spacing patterns of both cpg island density, and to a lesser extent, gene densities.
##tes, i. e., genes are unlinked. an exception to this rule would include traits that are sex - linked. test crosses can be performed to experimentally determine the underlying genotype of an organism with a dominant phenotype. a punnett square can be used to predict the results of a test cross. the chromosome theory of inheritance, which states that genes are found on chromosomes, was supported by thomas morgans ' s experiments with fruit flies, which established the sex linkage between eye color and sex in these insects. = = = genes and dna = = = a gene is a unit of heredity that corresponds to a region of deoxyribonucleic acid ( dna ) that carries genetic information that controls form or function of an organism. dna is composed of two polynucleotide chains that coil around each other to form a double helix. it is found as linear chromosomes in eukaryotes, and circular chromosomes in prokaryotes. the set of chromosomes in a cell is collectively known as its genome. in eukaryotes, dna is mainly in the cell nucleus. in prokaryotes, the dna is held within the nucleoid. the genetic information is held within genes, and the complete assemblage in an organism is called its genotype. dna replication is a semiconservative process whereby each strand serves as a template for a new strand of dna. mutations are heritable changes in dna. they can arise spontaneously as a result of replication errors that were not corrected by proofreading or can be induced by an environmental mutagen such as a chemical ( e. g., nitrous acid, benzopyrene ) or radiation ( e. g., x - ray, gamma ray, ultraviolet radiation, particles emitted by unstable isotopes ). mutations can lead to phenotypic effects such as loss - of - function, gain - of - function, and conditional mutations. some mutations are beneficial, as they are a source of genetic variation for evolution. others are harmful if they were to result in a loss of function of genes needed for survival. = = = gene expression = = = gene expression is the molecular process by which a genotype encoded in dna gives rise to an observable phenotype in the proteins of an organism ' s body. this process is summarized by the central dogma of molecular biology, which was formulated by francis crick in 1958. according to the central dogma, genetic information flows from dna
of epigenetic change is the marking of the genes by dna methylation which determines whether they will be expressed or not. gene expression can also be controlled by repressor proteins that attach to silencer regions of the dna and prevent that region of the dna code from being expressed. epigenetic marks may be added or removed from the dna during programmed stages of development of the plant, and are responsible, for example, for the differences between anthers, petals and normal leaves, despite the fact that they all have the same underlying genetic code. epigenetic changes may be temporary or may remain through successive cell divisions for the remainder of the cell ' s life. some epigenetic changes have been shown to be heritable, while others are reset in the germ cells. epigenetic changes in eukaryotic biology serve to regulate the process of cellular differentiation. during morphogenesis, totipotent stem cells become the various pluripotent cell lines of the embryo, which in turn become fully differentiated cells. a single fertilised egg cell, the zygote, gives rise to the many different plant cell types including parenchyma, xylem vessel elements, phloem sieve tubes, guard cells of the epidermis, etc. as it continues to divide. the process results from the epigenetic activation of some genes and inhibition of others. unlike animals, many plant cells, particularly those of the parenchyma, do not terminally differentiate, remaining totipotent with the ability to give rise to a new individual plant. exceptions include highly lignified cells, the sclerenchyma and xylem which are dead at maturity, and the phloem sieve tubes which lack nuclei. while plants use many of the same epigenetic mechanisms as animals, such as chromatin remodelling, an alternative hypothesis is that plants set their gene expression patterns using positional information from the environment and surrounding cells to determine their developmental fate. epigenetic changes can lead to paramutations, which do not follow the mendelian heritage rules. these epigenetic marks are carried from one generation to the next, with one allele inducing a change on the other. = = plant evolution = = the chloroplasts of plants have a number of biochemical, structural and genetic similarities to cyanobacteria, ( commonly but incorrectly known as " blue - green algae " ) and are thought to be derived from an
and the creation of genetically modified crops. = = = epigenetics = = = epigenetics is the study of heritable changes in gene function that cannot be explained by changes in the underlying dna sequence but cause the organism ' s genes to behave ( or " express themselves " ) differently. one example of epigenetic change is the marking of the genes by dna methylation which determines whether they will be expressed or not. gene expression can also be controlled by repressor proteins that attach to silencer regions of the dna and prevent that region of the dna code from being expressed. epigenetic marks may be added or removed from the dna during programmed stages of development of the plant, and are responsible, for example, for the differences between anthers, petals and normal leaves, despite the fact that they all have the same underlying genetic code. epigenetic changes may be temporary or may remain through successive cell divisions for the remainder of the cell ' s life. some epigenetic changes have been shown to be heritable, while others are reset in the germ cells. epigenetic changes in eukaryotic biology serve to regulate the process of cellular differentiation. during morphogenesis, totipotent stem cells become the various pluripotent cell lines of the embryo, which in turn become fully differentiated cells. a single fertilised egg cell, the zygote, gives rise to the many different plant cell types including parenchyma, xylem vessel elements, phloem sieve tubes, guard cells of the epidermis, etc. as it continues to divide. the process results from the epigenetic activation of some genes and inhibition of others. unlike animals, many plant cells, particularly those of the parenchyma, do not terminally differentiate, remaining totipotent with the ability to give rise to a new individual plant. exceptions include highly lignified cells, the sclerenchyma and xylem which are dead at maturity, and the phloem sieve tubes which lack nuclei. while plants use many of the same epigenetic mechanisms as animals, such as chromatin remodelling, an alternative hypothesis is that plants set their gene expression patterns using positional information from the environment and surrounding cells to determine their developmental fate. epigenetic changes can lead to paramutations, which do not follow the mendelian heritage rules. these epigenetic marks are carried from one generation to the next,
not always mean it is required, especially when dealing with genetic or functional redundancy. tracking experiments, which seek to gain information about the localisation and interaction of the desired protein. one way to do this is to replace the wild - type gene with a ' fusion ' gene, which is a juxtaposition of the wild - type gene with a reporting element such as green fluorescent protein ( gfp ) that will allow easy visualisation of the products of the genetic modification. while this is a useful technique, the manipulation can destroy the function of the gene, creating secondary effects and possibly calling into question the results of the experiment. more sophisticated techniques are now in development that can track protein products without mitigating their function, such as the addition of small sequences that will serve as binding motifs to monoclonal antibodies. expression studies aim to discover where and when specific proteins are produced. in these experiments, the dna sequence before the dna that codes for a protein, known as a gene ' s promoter, is reintroduced into an organism with the protein coding region replaced by a reporter gene such as gfp or an enzyme that catalyses the production of a dye. thus the time and place where a particular protein is produced can be observed. expression studies can be taken a step further by altering the promoter to find which pieces are crucial for the proper expression of the gene and are actually bound by transcription factor proteins ; this process is known as promoter bashing. = = = industrial = = = organisms can have their cells transformed with a gene coding for a useful protein, such as an enzyme, so that they will overexpress the desired protein. mass quantities of the protein can then be manufactured by growing the transformed organism in bioreactor equipment using industrial fermentation, and then purifying the protein. some genes do not work well in bacteria, so yeast, insect cells or mammalian cells can also be used. these techniques are used to produce medicines such as insulin, human growth hormone, and vaccines, supplements such as tryptophan, aid in the production of food ( chymosin in cheese making ) and fuels. other applications with genetically engineered bacteria could involve making them perform tasks outside their natural cycle, such as making biofuels, cleaning up oil spills, carbon and other toxic waste and detecting arsenic in drinking water. certain genetically modified microbes can also be used in biomining and bioremediation, due to their ability to extract heavy metals from their environment and incorporate them into compounds that are more easily recover
is opened and the dna is purified. the gene is separated by using restriction enzymes to cut the dna into fragments or polymerase chain reaction ( pcr ) to amplify up the gene segment. these segments can then be extracted through gel electrophoresis. if the chosen gene or the donor organism ' s genome has been well studied it may already be accessible from a genetic library. if the dna sequence is known, but no copies of the gene are available, it can also be artificially synthesised. once isolated the gene is ligated into a plasmid that is then inserted into a bacterium. the plasmid is replicated when the bacteria divide, ensuring unlimited copies of the gene are available. the rk2 plasmid is notable for its ability to replicate in a wide variety of single - celled organisms, which makes it suitable as a genetic engineering tool. before the gene is inserted into the target organism it must be combined with other genetic elements. these include a promoter and terminator region, which initiate and end transcription. a selectable marker gene is added, which in most cases confers antibiotic resistance, so researchers can easily determine which cells have been successfully transformed. the gene can also be modified at this stage for better expression or effectiveness. these manipulations are carried out using recombinant dna techniques, such as restriction digests, ligations and molecular cloning. = = = inserting dna into the host genome = = = there are a number of techniques used to insert genetic material into the host genome. some bacteria can naturally take up foreign dna. this ability can be induced in other bacteria via stress ( e. g. thermal or electric shock ), which increases the cell membrane ' s permeability to dna ; up - taken dna can either integrate with the genome or exist as extrachromosomal dna. dna is generally inserted into animal cells using microinjection, where it can be injected through the cell ' s nuclear envelope directly into the nucleus, or through the use of viral vectors. plant genomes can be engineered by physical methods or by use of agrobacterium for the delivery of sequences hosted in t - dna binary vectors. in plants the dna is often inserted using agrobacterium - mediated transformation, taking advantage of the agrobacteriums t - dna sequence that allows natural insertion of genetic material into plant cells. other methods include biolistics, where particles of gold or tungsten are coated with dna and then shot into
the gene is expressed or what other genes it interacts with. these experiments generally involve loss of function, gain of function, tracking and expression. loss of function experiments, such as in a gene knockout experiment, in which an organism is engineered to lack the activity of one or more genes. in a simple knockout a copy of the desired gene has been altered to make it non - functional. embryonic stem cells incorporate the altered gene, which replaces the already present functional copy. these stem cells are injected into blastocysts, which are implanted into surrogate mothers. this allows the experimenter to analyse the defects caused by this mutation and thereby determine the role of particular genes. it is used especially frequently in developmental biology. when this is done by creating a library of genes with point mutations at every position in the area of interest, or even every position in the whole gene, this is called " scanning mutagenesis ". the simplest method, and the first to be used, is " alanine scanning ", where every position in turn is mutated to the unreactive amino acid alanine. gain of function experiments, the logical counterpart of knockouts. these are sometimes performed in conjunction with knockout experiments to more finely establish the function of the desired gene. the process is much the same as that in knockout engineering, except that the construct is designed to increase the function of the gene, usually by providing extra copies of the gene or inducing synthesis of the protein more frequently. gain of function is used to tell whether or not a protein is sufficient for a function, but does not always mean it is required, especially when dealing with genetic or functional redundancy. tracking experiments, which seek to gain information about the localisation and interaction of the desired protein. one way to do this is to replace the wild - type gene with a ' fusion ' gene, which is a juxtaposition of the wild - type gene with a reporting element such as green fluorescent protein ( gfp ) that will allow easy visualisation of the products of the genetic modification. while this is a useful technique, the manipulation can destroy the function of the gene, creating secondary effects and possibly calling into question the results of the experiment. more sophisticated techniques are now in development that can track protein products without mitigating their function, such as the addition of small sequences that will serve as binding motifs to monoclonal antibodies. expression studies aim to discover where and when specific proteins are produced. in these experiments, the dna sequence before the dna that codes for
studies of the molecular genetics of model plants such as the thale cress, arabidopsis thaliana, a weedy species in the mustard family ( brassicaceae ). the genome or hereditary information contained in the genes of this species is encoded by about 135 million base pairs of dna, forming one of the smallest genomes among flowering plants. arabidopsis was the first plant to have its genome sequenced, in 2000. the sequencing of some other relatively small genomes, of rice ( oryza sativa ) and brachypodium distachyon, has made them important model species for understanding the genetics, cellular and molecular biology of cereals, grasses and monocots generally. model plants such as arabidopsis thaliana are used for studying the molecular biology of plant cells and the chloroplast. ideally, these organisms have small genomes that are well known or completely sequenced, small stature and short generation times. corn has been used to study mechanisms of photosynthesis and phloem loading of sugar in c4 plants. the single celled green alga chlamydomonas reinhardtii, while not an embryophyte itself, contains a green - pigmented chloroplast related to that of land plants, making it useful for study. a red alga cyanidioschyzon merolae has also been used to study some basic chloroplast functions. spinach, peas, soybeans and a moss physcomitrella patens are commonly used to study plant cell biology. agrobacterium tumefaciens, a soil rhizosphere bacterium, can attach to plant cells and infect them with a callus - inducing ti plasmid by horizontal gene transfer, causing a callus infection called crown gall disease. schell and van montagu ( 1977 ) hypothesised that the ti plasmid could be a natural vector for introducing the nif gene responsible for nitrogen fixation in the root nodules of legumes and other plant species. today, genetic modification of the ti plasmid is one of the main techniques for introduction of transgenes to plants and the creation of genetically modified crops. = = = epigenetics = = = epigenetics is the study of heritable changes in gene function that cannot be explained by changes in the underlying dna sequence but cause the organism ' s genes to behave ( or " express themselves " ) differently. one example
Question: What map shows the locations of several genes on the x chromosome?
A) the linkage map
B) the component map
C) The allelic map
D) The genomic map
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A) the linkage map
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Context:
and their competitive or mutualistic interactions with other species. some ecologists even rely on empirical data from indigenous people that is gathered by ethnobotanists. this information can relay a great deal of information on how the land once was thousands of years ago and how it has changed over that time. the goals of plant ecology are to understand the causes of their distribution patterns, productivity, environmental impact, evolution, and responses to environmental change. plants depend on certain edaphic ( soil ) and climatic factors in their environment but can modify these factors too. for example, they can change their environment ' s albedo, increase runoff interception, stabilise mineral soils and develop their organic content, and affect local temperature. plants compete with other organisms in their ecosystem for resources. they interact with their neighbours at a variety of spatial scales in groups, populations and communities that collectively constitute vegetation. regions with characteristic vegetation types and dominant plants as well as similar abiotic and biotic factors, climate, and geography make up biomes like tundra or tropical rainforest. herbivores eat plants, but plants can defend themselves and some species are parasitic or even carnivorous. other organisms form mutually beneficial relationships with plants. for example, mycorrhizal fungi and rhizobia provide plants with nutrients in exchange for food, ants are recruited by ant plants to provide protection, honey bees, bats and other animals pollinate flowers and humans and other animals act as dispersal vectors to spread spores and seeds. = = = plants, climate and environmental change = = = plant responses to climate and other environmental changes can inform our understanding of how these changes affect ecosystem function and productivity. for example, plant phenology can be a useful proxy for temperature in historical climatology, and the biological impact of climate change and global warming. palynology, the analysis of fossil pollen deposits in sediments from thousands or millions of years ago allows the reconstruction of past climates. estimates of atmospheric co2 concentrations since the palaeozoic have been obtained from stomatal densities and the leaf shapes and sizes of ancient land plants. ozone depletion can expose plants to higher levels of ultraviolet radiation - b ( uv - b ), resulting in lower growth rates. moreover, information from studies of community ecology, plant systematics, and taxonomy is essential to understanding vegetation change, habitat destruction and species extinction. = = genetics = = inheritance in plants follows the same fundamental principles of genetics as in other multicellular organisms. gregor mendel discovered the genetic laws of inheritance by studying
species occupying the same geographical area at the same time. a biological interaction is the effect that a pair of organisms living together in a community have on each other. they can be either of the same species ( intraspecific interactions ), or of different species ( interspecific interactions ). these effects may be short - term, like pollination and predation, or long - term ; both often strongly influence the evolution of the species involved. a long - term interaction is called a symbiosis. symbioses range from mutualism, beneficial to both partners, to competition, harmful to both partners. every species participates as a consumer, resource, or both in consumer β resource interactions, which form the core of food chains or food webs. there are different trophic levels within any food web, with the lowest level being the primary producers ( or autotrophs ) such as plants and algae that convert energy and inorganic material into organic compounds, which can then be used by the rest of the community. at the next level are the heterotrophs, which are the species that obtain energy by breaking apart organic compounds from other organisms. heterotrophs that consume plants are primary consumers ( or herbivores ) whereas heterotrophs that consume herbivores are secondary consumers ( or carnivores ). and those that eat secondary consumers are tertiary consumers and so on. omnivorous heterotrophs are able to consume at multiple levels. finally, there are decomposers that feed on the waste products or dead bodies of organisms. on average, the total amount of energy incorporated into the biomass of a trophic level per unit of time is about one - tenth of the energy of the trophic level that it consumes. waste and dead material used by decomposers as well as heat lost from metabolism make up the other ninety percent of energy that is not consumed by the next trophic level. = = = biosphere = = = in the global ecosystem or biosphere, matter exists as different interacting compartments, which can be biotic or abiotic as well as accessible or inaccessible, depending on their forms and locations. for example, matter from terrestrial autotrophs are both biotic and accessible to other organisms whereas the matter in rocks and minerals are abiotic and inaccessible. a biogeochemical cycle is a pathway by which specific elements of matter are turned over or moved through the biotic ( biosphere ) and the abiotic ( lithos
pathogens in agriculture and natural ecosystems. ethnobotany is the study of the relationships between plants and people. when applied to the investigation of historical plant β people relationships ethnobotany may be referred to as archaeobotany or palaeoethnobotany. some of the earliest plant - people relationships arose between the indigenous people of canada in identifying edible plants from inedible plants. this relationship the indigenous people had with plants was recorded by ethnobotanists. = = plant biochemistry = = plant biochemistry is the study of the chemical processes used by plants. some of these processes are used in their primary metabolism like the photosynthetic calvin cycle and crassulacean acid metabolism. others make specialised materials like the cellulose and lignin used to build their bodies, and secondary products like resins and aroma compounds. plants and various other groups of photosynthetic eukaryotes collectively known as " algae " have unique organelles known as chloroplasts. chloroplasts are thought to be descended from cyanobacteria that formed endosymbiotic relationships with ancient plant and algal ancestors. chloroplasts and cyanobacteria contain the blue - green pigment chlorophyll a. chlorophyll a ( as well as its plant and green algal - specific cousin chlorophyll b ) absorbs light in the blue - violet and orange / red parts of the spectrum while reflecting and transmitting the green light that we see as the characteristic colour of these organisms. the energy in the red and blue light that these pigments absorb is used by chloroplasts to make energy - rich carbon compounds from carbon dioxide and water by oxygenic photosynthesis, a process that generates molecular oxygen ( o2 ) as a by - product. the light energy captured by chlorophyll a is initially in the form of electrons ( and later a proton gradient ) that is used to make molecules of atp and nadph which temporarily store and transport energy. their energy is used in the light - independent reactions of the calvin cycle by the enzyme rubisco to produce molecules of the 3 - carbon sugar glyceraldehyde 3 - phosphate ( g3p ). glyceraldehyde 3 - phosphate is the first product of photosynthesis and the raw material from which glucose and almost all other organic molecules of biological origin are synthesised. some of the glucose is converted to star
navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with a rapid fall near the sources of rivers can carry down rocks, boulders and large stones, which are by degrees ground by attrition in their onward course into slate, gravel, sand and silt, simultaneously with the gradual reduction in fall, and, consequently, in the transporting force of the current. accordingly, under ordinary conditions, most of the materials brought down from the high lands by torrential water courses are carried forward by the main river to the sea, or partially strewn over flat alluvial plains during floods ; the size of the materials forming the bed of the river or borne along by the stream is gradually reduced on proceeding sea
approximately corresponds to the slope of the country it traverses ; as rivers rise close to the highest part of their basins, generally in hilly regions, their fall is rapid near their source and gradually diminishes, with occasional irregularities, until, in traversing plains along the latter part of their course, their fall usually becomes quite gentle. accordingly, in large basins, rivers in most cases begin as torrents with a variable flow, and end as gently flowing rivers with a comparatively regular discharge. the irregular flow of rivers throughout their course forms one of the main difficulties in devising works for mitigating inundations or for increasing the navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with
with one allele inducing a change on the other. = = plant evolution = = the chloroplasts of plants have a number of biochemical, structural and genetic similarities to cyanobacteria, ( commonly but incorrectly known as " blue - green algae " ) and are thought to be derived from an ancient endosymbiotic relationship between an ancestral eukaryotic cell and a cyanobacterial resident. the algae are a polyphyletic group and are placed in various divisions, some more closely related to plants than others. there are many differences between them in features such as cell wall composition, biochemistry, pigmentation, chloroplast structure and nutrient reserves. the algal division charophyta, sister to the green algal division chlorophyta, is considered to contain the ancestor of true plants. the charophyte class charophyceae and the land plant sub - kingdom embryophyta together form the monophyletic group or clade streptophytina. nonvascular land plants are embryophytes that lack the vascular tissues xylem and phloem. they include mosses, liverworts and hornworts. pteridophytic vascular plants with true xylem and phloem that reproduced by spores germinating into free - living gametophytes evolved during the silurian period and diversified into several lineages during the late silurian and early devonian. representatives of the lycopods have survived to the present day. by the end of the devonian period, several groups, including the lycopods, sphenophylls and progymnosperms, had independently evolved " megaspory " β their spores were of two distinct sizes, larger megaspores and smaller microspores. their reduced gametophytes developed from megaspores retained within the spore - producing organs ( megasporangia ) of the sporophyte, a condition known as endospory. seeds consist of an endosporic megasporangium surrounded by one or two sheathing layers ( integuments ). the young sporophyte develops within the seed, which on germination splits to release it. the earliest known seed plants date from the latest devonian famennian stage. following the evolution of the seed habit, seed plants diversified, giving rise to a number of now - extinct groups, including seed ferns, as well as the modern gym
. species boundaries in plants may be weaker than in animals, and cross species hybrids are often possible. a familiar example is peppermint, mentha Γ piperita, a sterile hybrid between mentha aquatica and spearmint, mentha spicata. the many cultivated varieties of wheat are the result of multiple inter - and intra - specific crosses between wild species and their hybrids. angiosperms with monoecious flowers often have self - incompatibility mechanisms that operate between the pollen and stigma so that the pollen either fails to reach the stigma or fails to germinate and produce male gametes. this is one of several methods used by plants to promote outcrossing. in many land plants the male and female gametes are produced by separate individuals. these species are said to be dioecious when referring to vascular plant sporophytes and dioicous when referring to bryophyte gametophytes. charles darwin in his 1878 book the effects of cross and self - fertilization in the vegetable kingdom at the start of chapter xii noted " the first and most important of the conclusions which may be drawn from the observations given in this volume, is that generally cross - fertilisation is beneficial and self - fertilisation often injurious, at least with the plants on which i experimented. " an important adaptive benefit of outcrossing is that it allows the masking of deleterious mutations in the genome of progeny. this beneficial effect is also known as hybrid vigor or heterosis. once outcrossing is established, subsequent switching to inbreeding becomes disadvantageous since it allows expression of the previously masked deleterious recessive mutations, commonly referred to as inbreeding depression. unlike in higher animals, where parthenogenesis is rare, asexual reproduction may occur in plants by several different mechanisms. the formation of stem tubers in potato is one example. particularly in arctic or alpine habitats, where opportunities for fertilisation of flowers by animals are rare, plantlets or bulbs, may develop instead of flowers, replacing sexual reproduction with asexual reproduction and giving rise to clonal populations genetically identical to the parent. this is one of several types of apomixis that occur in plants. apomixis can also happen in a seed, producing a seed that contains an embryo genetically identical to the parent. most sexually reproducing organisms are diploid, with paired chromosomes, but doubling of their chromosome number may occur due to errors in
##nts from the air to reduce the potential adverse effects on humans and the environment. the process of air purification may be performed using methods such as mechanical filtration, ionization, activated carbon adsorption, photocatalytic oxidation, and ultraviolet light germicidal irradiation. = = = sewage treatment = = = = = = environmental remediation = = = environmental remediation is the process through which contaminants or pollutants in soil, water and other media are removed to improve environmental quality. the main focus is the reduction of hazardous substances within the environment. some of the areas involved in environmental remediation include ; soil contamination, hazardous waste, groundwater contamination, oil, gas and chemical spills. there are three most common types of environmental remediation. these include soil, water, and sediment remediation. soil remediation consists of removing contaminants in soil, as these pose great risks to humans and the ecosystem. some examples of this are heavy metals, pesticides, and radioactive materials. depending on the contaminant the remedial processes can be physical, chemical, thermal, or biological. water remediation is one of the most important considering water is an essential natural resource. depending on the source of water there will be different contaminants. surface water contamination mainly consists of agricultural, animal, and industrial waste, as well as acid mine drainage. there has been a rise in the need for water remediation due to the increased discharge of industrial waste, leading to a demand for sustainable water solutions. the market for water remediation is expected to consistently increase to $ 19. 6 billion by 2030. sediment remediation consists of removing contaminated sediments. is it almost similar to soil remediation except it is often more sophisticated as it involves additional contaminants. to reduce the contaminants it is likely to use physical, chemical, and biological processes that help with source control, but if these processes are executed correctly, there ' s a risk of contamination resurfacing. = = = solid waste management = = = solid waste management is the purification, consumption, reuse, disposal, and treatment of solid waste that is undertaken by the government or the ruling bodies of a city / town. it refers to the collection, treatment, and disposal of non - soluble, solid waste material. solid waste is associated with both industrial, institutional, commercial and residential activities. hazardous solid waste, when improperly disposed can encourage the
equalizing the flow at these places, produces a lowering of the river above the rapids by facilitating the efflux, which may result in the appearance of fresh shoals at the low stage of the river. where, however, narrow rocky reefs or other hard shoals stretch across the bottom of a river and present obstacles to the erosion by the current of the soft materials forming the bed of the river above and below, their removal may result in permanent improvement by enabling the river to deepen its bed by natural scour. the capability of a river to provide a waterway for navigation during the summer or throughout the dry season depends on the depth that can be secured in the channel at the lowest stage. the problem in the dry season is the small discharge and deficiency in scour during this period. a typical solution is to restrict the width of the low - water channel, concentrate all of the flow in it, and also to fix its position so that it is scoured out every year by the floods which follow the deepest part of the bed along the line of the strongest current. this can be effected by closing subsidiary low - water channels with dikes across them, and narrowing the channel at the low stage by low - dipping cross dikes extending from the river banks down the slope and pointing slightly up - stream so as to direct the water flowing over them into a central channel. = = estuarine works = = the needs of navigation may also require that a stable, continuous, navigable channel is prolonged from the navigable river to deep water at the mouth of the estuary. the interaction of river flow and tide needs to be modeled by computer or using scale models, moulded to the configuration of the estuary under consideration and reproducing in miniature the tidal ebb and flow and fresh - water discharge over a bed of fine sand, in which various lines of training walls can be successively inserted. the models should be capable of furnishing valuable indications of the respective effects and comparative merits of the different schemes proposed for works. = = see also = = bridge scour flood control = = references = = = = external links = = u. s. army corps of engineers β civil works program river morphology and stream restoration references - wildland hydrology at the library of congress web archives ( archived 2002 - 08 - 13 )
##ta together form the monophyletic group or clade streptophytina. nonvascular land plants are embryophytes that lack the vascular tissues xylem and phloem. they include mosses, liverworts and hornworts. pteridophytic vascular plants with true xylem and phloem that reproduced by spores germinating into free - living gametophytes evolved during the silurian period and diversified into several lineages during the late silurian and early devonian. representatives of the lycopods have survived to the present day. by the end of the devonian period, several groups, including the lycopods, sphenophylls and progymnosperms, had independently evolved " megaspory " β their spores were of two distinct sizes, larger megaspores and smaller microspores. their reduced gametophytes developed from megaspores retained within the spore - producing organs ( megasporangia ) of the sporophyte, a condition known as endospory. seeds consist of an endosporic megasporangium surrounded by one or two sheathing layers ( integuments ). the young sporophyte develops within the seed, which on germination splits to release it. the earliest known seed plants date from the latest devonian famennian stage. following the evolution of the seed habit, seed plants diversified, giving rise to a number of now - extinct groups, including seed ferns, as well as the modern gymnosperms and angiosperms. gymnosperms produce " naked seeds " not fully enclosed in an ovary ; modern representatives include conifers, cycads, ginkgo, and gnetales. angiosperms produce seeds enclosed in a structure such as a carpel or an ovary. ongoing research on the molecular phylogenetics of living plants appears to show that the angiosperms are a sister clade to the gymnosperms. = = plant physiology = = plant physiology encompasses all the internal chemical and physical activities of plants associated with life. chemicals obtained from the air, soil and water form the basis of all plant metabolism. the energy of sunlight, captured by oxygenic photosynthesis and released by cellular respiration, is the basis of almost all life. photoautotrophs, including all green plants, algae and cyanobacteria gather energy directly from sunlight by photosynthesis. hetero
Question: Although they are as different as deserts and wetlands, all of these ecosystem units have populations of interacting species?
A) continents
B) zoos
C) biomes
D) corals
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C) biomes
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Context:
. currently, even blades made of advanced metal alloys used in the engines ' hot section require cooling and careful limiting of operating temperatures. turbine engines made with ceramics could operate more efficiently, giving aircraft greater range and payload for a set amount of fuel. recently, there have been advances in ceramics which include bio - ceramics, such as dental implants and synthetic bones. hydroxyapatite, the natural mineral component of bone, has been made synthetically from a number of biological and chemical sources and can be formed into ceramic materials. orthopedic implants made from these materials bond readily to bone and other tissues in the body without rejection or inflammatory reactions. because of this, they are of great interest for gene delivery and tissue engineering scaffolds. most hydroxyapatite ceramics are very porous and lack mechanical strength and are used to coat metal orthopedic devices to aid in forming a bond to bone or as bone fillers. they are also used as fillers for orthopedic plastic screws to aid in reducing the inflammation and increase absorption of these plastic materials. work is being done to make strong, fully dense nano crystalline hydroxyapatite ceramic materials for orthopedic weight bearing devices, replacing foreign metal and plastic orthopedic materials with a synthetic, but naturally occurring, bone mineral. ultimately these ceramic materials may be used as bone replacements or with the incorporation of protein collagens, synthetic bones. durable actinide - containing ceramic materials have many applications such as in nuclear fuels for burning excess pu and in chemically - inert sources of alpha irradiation for power supply of unmanned space vehicles or to produce electricity for microelectronic devices. both use and disposal of radioactive actinides require their immobilization in a durable host material. nuclear waste long - lived radionuclides such as actinides are immobilized using chemically - durable crystalline materials based on polycrystalline ceramics and large single crystals. alumina ceramics are widely utilized in the chemical industry due to their excellent chemical stability and high resistance to corrosion. it is used as acid - resistant pump impellers and pump bodies, ensuring long - lasting performance in transferring aggressive fluids. they are also used in acid - carrying pipe linings to prevent contamination and maintain fluid purity, which is crucial in industries like pharmaceuticals and food processing. valves made from alumina ceramics demonstrate exceptional durability and resistance to chemical attack, making them reliable for controlling the flow of corrosive liquids. =
as dental implants and synthetic bones. hydroxyapatite, the natural mineral component of bone, has been made synthetically from a number of biological and chemical sources and can be formed into ceramic materials. orthopedic implants made from these materials bond readily to bone and other tissues in the body without rejection or inflammatory reactions. because of this, they are of great interest for gene delivery and tissue engineering scaffolds. most hydroxyapatite ceramics are very porous and lack mechanical strength and are used to coat metal orthopedic devices to aid in forming a bond to bone or as bone fillers. they are also used as fillers for orthopedic plastic screws to aid in reducing the inflammation and increase absorption of these plastic materials. work is being done to make strong, fully dense nano crystalline hydroxyapatite ceramic materials for orthopedic weight bearing devices, replacing foreign metal and plastic orthopedic materials with a synthetic, but naturally occurring, bone mineral. ultimately these ceramic materials may be used as bone replacements or with the incorporation of protein collagens, synthetic bones. durable actinide - containing ceramic materials have many applications such as in nuclear fuels for burning excess pu and in chemically - inert sources of alpha irradiation for power supply of unmanned space vehicles or to produce electricity for microelectronic devices. both use and disposal of radioactive actinides require their immobilization in a durable host material. nuclear waste long - lived radionuclides such as actinides are immobilized using chemically - durable crystalline materials based on polycrystalline ceramics and large single crystals. alumina ceramics are widely utilized in the chemical industry due to their excellent chemical stability and high resistance to corrosion. it is used as acid - resistant pump impellers and pump bodies, ensuring long - lasting performance in transferring aggressive fluids. they are also used in acid - carrying pipe linings to prevent contamination and maintain fluid purity, which is crucial in industries like pharmaceuticals and food processing. valves made from alumina ceramics demonstrate exceptional durability and resistance to chemical attack, making them reliable for controlling the flow of corrosive liquids. = = glass - ceramics = = glass - ceramic materials share many properties with both glasses and ceramics. glass - ceramics have an amorphous phase and one or more crystalline phases and are produced by a so - called " controlled crystallization ", which is typically avoided in glass manufacturing. glass - ceramics often contain a crystalline phase
this scaffold and cells were placed in a bioreactor, where it matured to become a partially or fully transplantable organ. the work was called a " landmark ". the lab first stripped the cells away from a rat heart ( a process called " decellularization " ) and then injected rat stem cells into the decellularized rat heart. tissue - engineered blood vessels : blood vessels that have been grown in a lab and can be used to repair damaged blood vessels without eliciting an immune response. tissue engineered blood vessels have been developed by many different approaches. they could be implanted as pre - seeded cellularized blood vessels, as acellular vascular grafts made with decellularized vessels or synthetic vascular grafts. artificial skin constructed from human skin cells embedded in a hydrogel, such as in the case of bio - printed constructs for battlefield burn repairs. artificial bone marrow : bone marrow cultured in vitro to be transplanted serves as a " just cells " approach to tissue engineering. tissue engineered bone : a structural matrix can be composed of metals such as titanium, polymers of varying degradation rates, or certain types of ceramics. materials are often chosen to recruit osteoblasts to aid in reforming the bone and returning biological function. various types of cells can be added directly into the matrix to expedite the process. laboratory - grown penis : decellularized scaffolds of rabbit penises were recellularised with smooth muscle and endothelial cells. the organ was then transplanted to live rabbits and functioned comparably to the native organ, suggesting potential as treatment for genital trauma. oral mucosa tissue engineering uses a cells and scaffold approach to replicate the 3 dimensional structure and function of oral mucosa. = = cells as building blocks = = cells are one of the main components for the success of tissue engineering approaches. tissue engineering uses cells as strategies for creation / replacement of new tissue. examples include fibroblasts used for skin repair or renewal, chondrocytes used for cartilage repair ( maci β fda approved product ), and hepatocytes used in liver support systems cells can be used alone or with support matrices for tissue engineering applications. an adequate environment for promoting cell growth, differentiation, and integration with the existing tissue is a critical factor for cell - based building blocks. manipulation of any of these cell processes create alternative avenues for the development of new tissue ( e. g., cell reprogramming - somatic
##ning an animal for its hide, and even forming other tools out of softer materials such as bone and wood. the earliest stone tools were irrelevant, being little more than a fractured rock. in the acheulian era, beginning approximately 1. 65 million years ago, methods of working these stones into specific shapes, such as hand axes emerged. this early stone age is described as the lower paleolithic. the middle paleolithic, approximately 300, 000 years ago, saw the introduction of the prepared - core technique, where multiple blades could be rapidly formed from a single core stone. the upper paleolithic, beginning approximately 40, 000 years ago, saw the introduction of pressure flaking, where a wood, bone, or antler punch could be used to shape a stone very finely. the end of the last ice age about 10, 000 years ago is taken as the end point of the upper paleolithic and the beginning of the epipaleolithic / mesolithic. the mesolithic technology included the use of microliths as composite stone tools, along with wood, bone, and antler tools. the later stone age, during which the rudiments of agricultural technology were developed, is called the neolithic period. during this period, polished stone tools were made from a variety of hard rocks such as flint, jade, jadeite, and greenstone, largely by working exposures as quarries, but later the valuable rocks were pursued by tunneling underground, the first steps in mining technology. the polished axes were used for forest clearance and the establishment of crop farming and were so effective as to remain in use when bronze and iron appeared. these stone axes were used alongside a continued use of stone tools such as a range of projectiles, knives, and scrapers, as well as tools, made from organic materials such as wood, bone, and antler. stone age cultures developed music and engaged in organized warfare. stone age humans developed ocean - worthy outrigger canoe technology, leading to migration across the malay archipelago, across the indian ocean to madagascar and also across the pacific ocean, which required knowledge of the ocean currents, weather patterns, sailing, and celestial navigation. although paleolithic cultures left no written records, the shift from nomadic life to settlement and agriculture can be inferred from a range of archaeological evidence. such evidence includes ancient tools, cave paintings, and other prehistoric art, such as the venus of willendorf. human remains also provide direct evidence, both through the examination of bones, and
reflect radar waves back to the emitting radar is with orthogonal metal plates, forming a corner reflector consisting of either a dihedral ( two plates ) or a trihedral ( three orthogonal plates ). this configuration occurs in the tail of a conventional aircraft, where the vertical and horizontal components of the tail are set at right angles. stealth aircraft such as the f - 117 use a different arrangement, tilting the tail surfaces to reduce corner reflections formed between them. a more radical method is to omit the tail, as in the b - 2 spirit. the b - 2 ' s clean, low - drag flying wing configuration gives it exceptional range and reduces its radar profile. the flying wing design most closely resembles a so - called infinite flat plate ( as vertical control surfaces dramatically increase rcs ), the perfect stealth shape, as it would have no angles to reflect back radar waves. in addition to altering the tail, stealth design must bury the engines within the wing or fuselage, or in some cases where stealth is applied to an extant aircraft, install baffles in the air intakes, so that the compressor blades are not visible to radar. a stealthy shape must be devoid of complex bumps or protrusions of any kind, meaning that weapons, fuel tanks, and other stores must not be carried externally. any stealthy vehicle becomes un - stealthy when a door or hatch opens. parallel alignment of edges or even surfaces is also often used in stealth designs. the technique involves using a small number of edge orientations in the shape of the structure. for example, on the f - 22a raptor, the leading edges of the wing and the tail planes are set at the same angle. other smaller structures, such as the air intake bypass doors and the air refueling aperture, also use the same angles. the effect of this is to return a narrow radar signal in a very specific direction away from the radar emitter rather than returning a diffuse signal detectable at many angles. the effect is sometimes called " glitter " after the very brief signal seen when the reflected beam passes across a detector. it can be difficult for the radar operator to distinguish between a glitter event and a digital glitch in the processing system. stealth airframes sometimes display distinctive serrations on some exposed edges, such as the engine ports. the yf - 23 has such serrations on the exhaust ports. this is another example in the parallel alignment of features, this time on the external airframe. the shaping requirements detracted greatly from the f - 117 '
casting, also called the lost wax process, die casting, centrifugal casting, both vertical and horizontal, and continuous castings. each of these forms has advantages for certain metals and applications considering factors like magnetism and corrosion. forging β a red - hot billet is hammered into shape. rolling β a billet is passed through successively narrower rollers to create a sheet. extrusion β a hot and malleable metal is forced under pressure through a die, which shapes it before it cools. machining β lathes, milling machines and drills cut the cold metal to shape. sintering β a powdered metal is heated in a non - oxidizing environment after being compressed into a die. fabrication β sheets of metal are cut with guillotines or gas cutters and bent and welded into structural shape. laser cladding β metallic powder is blown through a movable laser beam ( e. g. mounted on a nc 5 - axis machine ). the resulting melted metal reaches a substrate to form a melt pool. by moving the laser head, it is possible to stack the tracks and build up a three - dimensional piece. 3d printing β sintering or melting amorphous powder metal in a 3d space to make any object to shape. cold - working processes, in which the product ' s shape is altered by rolling, fabrication or other processes, while the product is cold, can increase the strength of the product by a process called work hardening. work hardening creates microscopic defects in the metal, which resist further changes of shape. = = = heat treatment = = = metals can be heat - treated to alter the properties of strength, ductility, toughness, hardness and resistance to corrosion. common heat treatment processes include annealing, precipitation strengthening, quenching, and tempering : annealing process softens the metal by heating it and then allowing it to cool very slowly, which gets rid of stresses in the metal and makes the grain structure large and soft - edged so that, when the metal is hit or stressed it dents or perhaps bends, rather than breaking ; it is also easier to sand, grind, or cut annealed metal. quenching is the process of cooling metal very quickly after heating, thus " freezing " the metal ' s molecules in the very hard martensite form, which makes the metal harder. tempering relieves stresses in the metal that were caused by the hardening process ; tempering makes the metal less hard while making it better able to sustain
bear ' ) was conspicuous on radar. it is now known that propellers and jet turbine blades produce a bright radar image ; the bear has four pairs of large 18 - foot ( 5. 6 m ) diameter contra - rotating propellers. another important factor is internal construction. some stealth aircraft have skin that is radar transparent or absorbing, behind which are structures termed reentrant triangles. radar waves penetrating the skin get trapped in these structures, reflecting off the internal faces and losing energy. this method was first used on the blackbird series : a - 12, yf - 12a, lockheed sr - 71 blackbird. the most efficient way to reflect radar waves back to the emitting radar is with orthogonal metal plates, forming a corner reflector consisting of either a dihedral ( two plates ) or a trihedral ( three orthogonal plates ). this configuration occurs in the tail of a conventional aircraft, where the vertical and horizontal components of the tail are set at right angles. stealth aircraft such as the f - 117 use a different arrangement, tilting the tail surfaces to reduce corner reflections formed between them. a more radical method is to omit the tail, as in the b - 2 spirit. the b - 2 ' s clean, low - drag flying wing configuration gives it exceptional range and reduces its radar profile. the flying wing design most closely resembles a so - called infinite flat plate ( as vertical control surfaces dramatically increase rcs ), the perfect stealth shape, as it would have no angles to reflect back radar waves. in addition to altering the tail, stealth design must bury the engines within the wing or fuselage, or in some cases where stealth is applied to an extant aircraft, install baffles in the air intakes, so that the compressor blades are not visible to radar. a stealthy shape must be devoid of complex bumps or protrusions of any kind, meaning that weapons, fuel tanks, and other stores must not be carried externally. any stealthy vehicle becomes un - stealthy when a door or hatch opens. parallel alignment of edges or even surfaces is also often used in stealth designs. the technique involves using a small number of edge orientations in the shape of the structure. for example, on the f - 22a raptor, the leading edges of the wing and the tail planes are set at the same angle. other smaller structures, such as the air intake bypass doors and the air refueling aperture, also use the same angles. the effect of this is to return a narrow radar signal in a very specific direction away from the radar
s immune system recognizes these re - implanted cells as its own, and does not target them for attack. autologous cell dependence on host cell health and donor site morbidity may be deterrents to their use. adipose - derived and bone marrow - derived mesenchymal stem cells are commonly autologous in nature, and can be used in a myriad of ways, from helping repair skeletal tissue to replenishing beta cells in diabetic patients. allogenic : cells are obtained from the body of a donor of the same species as the recipient. while there are some ethical constraints to the use of human cells for in vitro studies ( i. e. human brain tissue chimera development ), the employment of dermal fibroblasts from human foreskin demonstrates an immunologically safe and thus a viable choice for allogenic tissue engineering of the skin. xenogenic : these cells are derived isolated cells from alternate species from the recipient. a notable example of xenogeneic tissue utilization is cardiovascular implant construction via animal cells. chimeric human - animal farming raises ethical concerns around the potential for improved consciousness from implanting human organs in animals. syngeneic or isogenic : these cells describe those borne from identical genetic code. this imparts an immunologic benefit similar to autologous cell lines ( see above ). autologous cells can be considered syngenic, but the classification also extends to non - autologously derived cells such as those from an identical twin, from genetically identical ( cloned ) research models, or induced stem cells ( isc ) as related to the donor. = = = stem cells = = = stem cells are undifferentiated cells with the ability to divide in culture and give rise to different forms of specialized cells. stem cells are divided into " adult " and " embryonic " stem cells according to their source. while there is still a large ethical debate related to the use of embryonic stem cells, it is thought that another alternative source β induced pluripotent stem cells β may be useful for the repair of diseased or damaged tissues, or may be used to grow new organs. totipotent cells are stem cells which can divide into further stem cells or differentiate into any cell type in the body, including extra - embryonic tissue. pluripotent cells are stem cells which can differentiate into any cell type in the body except extra - embryonic tissue. induced pluripotent stem cells ( ipscs )
and reduces its radar profile. the flying wing design most closely resembles a so - called infinite flat plate ( as vertical control surfaces dramatically increase rcs ), the perfect stealth shape, as it would have no angles to reflect back radar waves. in addition to altering the tail, stealth design must bury the engines within the wing or fuselage, or in some cases where stealth is applied to an extant aircraft, install baffles in the air intakes, so that the compressor blades are not visible to radar. a stealthy shape must be devoid of complex bumps or protrusions of any kind, meaning that weapons, fuel tanks, and other stores must not be carried externally. any stealthy vehicle becomes un - stealthy when a door or hatch opens. parallel alignment of edges or even surfaces is also often used in stealth designs. the technique involves using a small number of edge orientations in the shape of the structure. for example, on the f - 22a raptor, the leading edges of the wing and the tail planes are set at the same angle. other smaller structures, such as the air intake bypass doors and the air refueling aperture, also use the same angles. the effect of this is to return a narrow radar signal in a very specific direction away from the radar emitter rather than returning a diffuse signal detectable at many angles. the effect is sometimes called " glitter " after the very brief signal seen when the reflected beam passes across a detector. it can be difficult for the radar operator to distinguish between a glitter event and a digital glitch in the processing system. stealth airframes sometimes display distinctive serrations on some exposed edges, such as the engine ports. the yf - 23 has such serrations on the exhaust ports. this is another example in the parallel alignment of features, this time on the external airframe. the shaping requirements detracted greatly from the f - 117 ' s aerodynamic properties. it is inherently unstable, and cannot be flown without a fly - by - wire control system. similarly, coating the cockpit canopy with a thin film transparent conductor ( vapor - deposited gold or indium tin oxide ) helps to reduce the aircraft ' s radar profile, because radar waves would normally enter the cockpit, reflect off objects ( the inside of a cockpit has a complex shape, with a pilot helmet alone forming a sizeable return ), and possibly return to the radar, but the conductive coating creates a controlled shape that deflects the incoming radar waves away from the radar. the coating is thin enough that it has
inflammatory reactions. because of this, they are of great interest for gene delivery and tissue engineering scaffolds. most hydroxyapatite ceramics are very porous and lack mechanical strength and are used to coat metal orthopedic devices to aid in forming a bond to bone or as bone fillers. they are also used as fillers for orthopedic plastic screws to aid in reducing the inflammation and increase absorption of these plastic materials. work is being done to make strong, fully dense nano crystalline hydroxyapatite ceramic materials for orthopedic weight bearing devices, replacing foreign metal and plastic orthopedic materials with a synthetic, but naturally occurring, bone mineral. ultimately these ceramic materials may be used as bone replacements or with the incorporation of protein collagens, synthetic bones. durable actinide - containing ceramic materials have many applications such as in nuclear fuels for burning excess pu and in chemically - inert sources of alpha irradiation for power supply of unmanned space vehicles or to produce electricity for microelectronic devices. both use and disposal of radioactive actinides require their immobilization in a durable host material. nuclear waste long - lived radionuclides such as actinides are immobilized using chemically - durable crystalline materials based on polycrystalline ceramics and large single crystals. alumina ceramics are widely utilized in the chemical industry due to their excellent chemical stability and high resistance to corrosion. it is used as acid - resistant pump impellers and pump bodies, ensuring long - lasting performance in transferring aggressive fluids. they are also used in acid - carrying pipe linings to prevent contamination and maintain fluid purity, which is crucial in industries like pharmaceuticals and food processing. valves made from alumina ceramics demonstrate exceptional durability and resistance to chemical attack, making them reliable for controlling the flow of corrosive liquids. = = glass - ceramics = = glass - ceramic materials share many properties with both glasses and ceramics. glass - ceramics have an amorphous phase and one or more crystalline phases and are produced by a so - called " controlled crystallization ", which is typically avoided in glass manufacturing. glass - ceramics often contain a crystalline phase which constitutes anywhere from 30 % [ m / m ] to 90 % [ m / m ] of its composition by volume, yielding an array of materials with interesting thermomechanical properties. in the processing of glass - ceramics, molten glass is cooled down gradually before reheating and annealing. in this heat
Question: What is the name of the bone that forms the forehead?
A) high bone
B) frontal bone
C) forebone
D) upper bone
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B) frontal bone
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Context:
set of chemical reactions with other substances. however, this definition only works well for substances that are composed of molecules, which is not true of many substances ( see below ). molecules are typically a set of atoms bound together by covalent bonds, such that the structure is electrically neutral and all valence electrons are paired with other electrons either in bonds or in lone pairs. thus, molecules exist as electrically neutral units, unlike ions. when this rule is broken, giving the " molecule " a charge, the result is sometimes named a molecular ion or a polyatomic ion. however, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature.
it is also possible to define analogs in two - dimensional systems, which has received attention for its relevance to systems in biology. = = = bonding = = = atoms sticking together in molecules or crystals are said to be bonded with one another. a chemical bond may be visualized as the multipole balance between the positive charges in the nuclei and the negative charges oscillating about them. more than simple attraction and repulsion, the energies and distributions characterize the availability of an electron to bond to another atom. the chemical bond can be a covalent bond, an ionic bond, a hydrogen bond or just because of van der waals force. each of these kinds of bonds is ascribed to some potential. these potentials create the interactions which hold atoms together in molecules or crystals. in many simple compounds, valence bond theory, the valence shell electron pair repulsion model ( vsepr ), and the concept of oxidation number can be used to explain molecular structure and composition. an ionic bond is formed when a metal loses one or more of its electrons, becoming a positively charged cation, and the electrons are then gained by the non - metal atom, becoming a negatively charged anion. the two oppositely charged ions attract one another, and the ionic bond is the electrostatic force of attraction between them. for example, sodium ( na ), a metal, loses one electron to become an na + cation while chlorine ( cl ), a non - metal, gains this electron to become clβ. the ions are held together due to electrostatic attraction, and that compound sodium chloride ( nacl ), or common table salt, is formed. in a covalent bond, one or more pairs of valence electrons are shared by two atoms : the resulting electrically neutral group of bonded atoms is termed a molecule. atoms will share valence electrons in such a way as to create a noble gas electron configuration ( eight electrons in their outermost shell ) for each atom. atoms that tend to combine in such a way that they each have eight electrons in their valence shell are said to follow the octet rule. however, some elements like hydrogen and lithium need only two electrons in their outermost shell to attain this stable configuration ; these atoms are said to follow the duet rule, and in this way they are reaching the electron configuration of the noble gas helium, which has two electrons in its outer shell. similarly, theories from classical physics can be used to predict many ionic structures. with more complicated compounds, such as metal complexes
single carbon atom can form four single covalent bonds such as in methane, two double covalent bonds such as in carbon dioxide ( co2 ), or a triple covalent bond such as in carbon monoxide ( co ). moreover, carbon can form very long chains of interconnecting carbon β carbon bonds such as octane or ring - like structures such as glucose. the simplest form of an organic molecule is the hydrocarbon, which is a large family of organic compounds that are composed of hydrogen atoms bonded to a chain of carbon atoms. a hydrocarbon backbone can be substituted by other elements such as oxygen ( o ), hydrogen ( h ), phosphorus ( p ), and sulfur ( s ), which can change the chemical behavior of that compound. groups of atoms that contain these elements ( o -, h -, p -, and s - ) and are bonded to a central carbon atom or skeleton are called functional groups. there are six prominent functional groups that can be found in organisms : amino group, carboxyl group, carbonyl group, hydroxyl group, phosphate group, and sulfhydryl group. in 1953, the miller β urey experiment showed that organic compounds could be synthesized abiotically within a closed system mimicking the conditions of early earth, thus suggesting that complex organic molecules could have arisen spontaneously in early earth ( see abiogenesis ). = = = macromolecules = = = macromolecules are large molecules made up of smaller subunits or monomers. monomers include sugars, amino acids, and nucleotides. carbohydrates include monomers and polymers of sugars. lipids are the only class of macromolecules that are not made up of polymers. they include steroids, phospholipids, and fats, largely nonpolar and hydrophobic ( water - repelling ) substances. proteins are the most diverse of the macromolecules. they include enzymes, transport proteins, large signaling molecules, antibodies, and structural proteins. the basic unit ( or monomer ) of a protein is an amino acid. twenty amino acids are used in proteins. nucleic acids are polymers of nucleotides. their function is to store, transmit, and express hereditary information. = = cells = = cell theory states that cells are the fundamental units of life, that all living things are composed of one or more cells, and that all cells arise from preexisting cells through cell division
other electrons either in bonds or in lone pairs. thus, molecules exist as electrically neutral units, unlike ions. when this rule is broken, giving the " molecule " a charge, the result is sometimes named a molecular ion or a polyatomic ion. however, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature. = = = = substance and mixture = = = = a chemical substance is a kind of matter with a definite composition and set of properties. a collection of substances is called a mixture. examples of mixtures are air and alloys. = = = = mole and amount of substance = = = = the mole is a unit
= = organic compounds are molecules that contain carbon bonded to another element such as hydrogen. with the exception of water, nearly all the molecules that make up each organism contain carbon. carbon can form covalent bonds with up to four other atoms, enabling it to form diverse, large, and complex molecules. for example, a single carbon atom can form four single covalent bonds such as in methane, two double covalent bonds such as in carbon dioxide ( co2 ), or a triple covalent bond such as in carbon monoxide ( co ). moreover, carbon can form very long chains of interconnecting carbon β carbon bonds such as octane or ring - like structures such as glucose. the simplest form of an organic molecule is the hydrocarbon, which is a large family of organic compounds that are composed of hydrogen atoms bonded to a chain of carbon atoms. a hydrocarbon backbone can be substituted by other elements such as oxygen ( o ), hydrogen ( h ), phosphorus ( p ), and sulfur ( s ), which can change the chemical behavior of that compound. groups of atoms that contain these elements ( o -, h -, p -, and s - ) and are bonded to a central carbon atom or skeleton are called functional groups. there are six prominent functional groups that can be found in organisms : amino group, carboxyl group, carbonyl group, hydroxyl group, phosphate group, and sulfhydryl group. in 1953, the miller β urey experiment showed that organic compounds could be synthesized abiotically within a closed system mimicking the conditions of early earth, thus suggesting that complex organic molecules could have arisen spontaneously in early earth ( see abiogenesis ). = = = macromolecules = = = macromolecules are large molecules made up of smaller subunits or monomers. monomers include sugars, amino acids, and nucleotides. carbohydrates include monomers and polymers of sugars. lipids are the only class of macromolecules that are not made up of polymers. they include steroids, phospholipids, and fats, largely nonpolar and hydrophobic ( water - repelling ) substances. proteins are the most diverse of the macromolecules. they include enzymes, transport proteins, large signaling molecules, antibodies, and structural proteins. the basic unit ( or monomer ) of a protein is an amino acid. twenty amino acids are used in proteins. nucleic acids
possible states of energy for electrons, atoms and molecules. these are determined by the rules of quantum mechanics, which require quantization of energy of a bound system. the atoms / molecules in a higher energy state are said to be excited. the molecules / atoms of substance in an excited energy state are often much more reactive ; that is, more amenable to chemical reactions. the phase of a substance is invariably determined by its energy and the energy of its surroundings. when the intermolecular forces of a substance are such that the energy of the surroundings is not sufficient to overcome them, it occurs in a more ordered phase like liquid or solid as is the case with water ( h2o ) ; a liquid at room temperature because its molecules are bound by hydrogen bonds. whereas hydrogen sulfide ( h2s ) is a gas at room temperature and standard pressure, as its molecules are bound by weaker dipole β dipole interactions. the transfer of energy from one chemical substance to another depends on the size of energy quanta emitted from one substance. however, heat energy is often transferred more easily from almost any substance to another because the phonons responsible for vibrational and rotational energy levels in a substance have much less energy than photons invoked for the electronic energy transfer. thus, because vibrational and rotational energy levels are more closely spaced than electronic energy levels, heat is more easily transferred between substances relative to light or other forms of electronic energy. for example, ultraviolet electromagnetic radiation is not transferred with as much efficacy from one substance to another as thermal or electrical energy. the existence of characteristic energy levels for different chemical substances is useful for their identification by the analysis of spectral lines. different kinds of spectra are often used in chemical spectroscopy, e. g. ir, microwave, nmr, esr, etc. spectroscopy is also used to identify the composition of remote objects β like stars and distant galaxies β by analyzing their radiation spectra. the term chemical energy is often used to indicate the potential of a chemical substance to undergo a transformation through a chemical reaction or to transform other chemical substances. = = = reaction = = = when a chemical substance is transformed as a result of its interaction with another substance or with energy, a chemical reaction is said to have occurred. a chemical reaction is therefore a concept related to the " reaction " of a substance when it comes in close contact with another, whether as a mixture or a solution ; exposure to some form of energy, or both. it results in some energy exchange between the constituents of the reaction as well as
, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature. = = = = substance and mixture = = = = a chemical substance is a kind of matter with a definite composition and set of properties. a collection of substances is called a mixture. examples of mixtures are air and alloys. = = = = mole and amount of substance = = = = the mole is a unit of measurement that denotes an amount of substance ( also called chemical amount ). one mole is defined to contain exactly 6. 02214076Γ1023 particles ( atoms, molecules, ions, or electrons ), where the number of particles per mole is known as the avogadro constant. molar concentration is the amount of a particular substance per volume of solution, and is commonly reported in mol / dm3. = = = phase = = = in addition to the specific chemical properties that distinguish different chemical classifications, chemicals can exist in several phases. for the most part, the chemical classifications are independent of these bulk phase classifications ; however, some more exotic phases are incompatible with certain chemical properties. a phase is a set of states of a chemical system that have similar bulk structural properties, over a range of conditions, such as pressure or temperature. physical properties, such as density and refractive index tend to fall within values characteristic of the phase
or molecules that show characteristic chemical properties in a compound. physical chemistry is the study of the physical and fundamental basis of chemical systems and processes. in particular, the energetics and dynamics of such systems and processes are of interest to physical chemists. important areas of study include chemical thermodynamics, chemical kinetics, electrochemistry, statistical mechanics, spectroscopy, and more recently, astrochemistry. physical chemistry has large overlap with molecular physics. physical chemistry involves the use of infinitesimal calculus in deriving equations. it is usually associated with quantum chemistry and theoretical chemistry. physical chemistry is a distinct discipline from chemical physics, but again, there is very strong overlap. theoretical chemistry is the study of chemistry via fundamental theoretical reasoning ( usually within mathematics or physics ). in particular the application of quantum mechanics to chemistry is called quantum chemistry. since the end of the second world war, the development of computers has allowed a systematic development of computational chemistry, which is the art of developing and applying computer programs for solving chemical problems. theoretical chemistry has large overlap with ( theoretical and experimental ) condensed matter physics and molecular physics. other subdivisions include electrochemistry, femtochemistry, flavor chemistry, flow chemistry, immunohistochemistry, hydrogenation chemistry, mathematical chemistry, molecular mechanics, natural product chemistry, organometallic chemistry, petrochemistry, photochemistry, physical organic chemistry, polymer chemistry, radiochemistry, sonochemistry, supramolecular chemistry, synthetic chemistry, and many others. = = = interdisciplinary = = = interdisciplinary fields include agrochemistry, astrochemistry ( and cosmochemistry ), atmospheric chemistry, chemical engineering, chemical biology, chemo - informatics, environmental chemistry, geochemistry, green chemistry, immunochemistry, marine chemistry, materials science, mechanochemistry, medicinal chemistry, molecular biology, nanotechnology, oenology, pharmacology, phytochemistry, solid - state chemistry, surface science, thermochemistry, and many others. = = = industry = = = the chemical industry represents an important economic activity worldwide. the global top 50 chemical producers in 2013 had sales of us $ 980. 5 billion with a profit margin of 10. 3 %. = = = professional societies = = = = = see also = = = = references = = = = bibliography = = = = further reading = = popular reading atkins, p. w. galileo ' s finger ( oxford university press )
with the system environment, which may be designed vessels β often laboratory glassware. chemical reactions can result in the formation or dissociation of molecules, that is, molecules breaking apart to form two or more molecules or rearrangement of atoms within or across molecules. chemical reactions usually involve the making or breaking of chemical bonds. oxidation, reduction, dissociation, acid β base neutralization and molecular rearrangement are some examples of common chemical reactions. a chemical reaction can be symbolically depicted through a chemical equation. while in a non - nuclear chemical reaction the number and kind of atoms on both sides of the equation are equal, for a nuclear reaction this holds true only for the nuclear particles viz. protons and neutrons. the sequence of steps in which the reorganization of chemical bonds may be taking place in the course of a chemical reaction is called its mechanism. a chemical reaction can be envisioned to take place in a number of steps, each of which may have a different speed. many reaction intermediates with variable stability can thus be envisaged during the course of a reaction. reaction mechanisms are proposed to explain the kinetics and the relative product mix of a reaction. many physical chemists specialize in exploring and proposing the mechanisms of various chemical reactions. several empirical rules, like the woodward β hoffmann rules often come in handy while proposing a mechanism for a chemical reaction. according to the iupac gold book, a chemical reaction is " a process that results in the interconversion of chemical species. " accordingly, a chemical reaction may be an elementary reaction or a stepwise reaction. an additional caveat is made, in that this definition includes cases where the interconversion of conformers is experimentally observable. such detectable chemical reactions normally involve sets of molecular entities as indicated by this definition, but it is often conceptually convenient to use the term also for changes involving single molecular entities ( i. e. ' microscopic chemical events ' ). = = = ions and salts = = = an ion is a charged species, an atom or a molecule, that has lost or gained one or more electrons. when an atom loses an electron and thus has more protons than electrons, the atom is a positively charged ion or cation. when an atom gains an electron and thus has more electrons than protons, the atom is a negatively charged ion or anion. cations and anions can form a crystalline lattice of neutral salts, such as the na + and clβ ions forming sodium chloride, or nacl. examples of
modifying the nervous system. nuclear chemistry is the study of how subatomic particles come together and make nuclei. modern transmutation is a large component of nuclear chemistry, and the table of nuclides is an important result and tool for this field. in addition to medical applications, nuclear chemistry encompasses nuclear engineering which explores the topic of using nuclear power sources for generating energy. organic chemistry is the study of the structure, properties, composition, mechanisms, and reactions of organic compounds. an organic compound is defined as any compound based on a carbon skeleton. organic compounds can be classified, organized and understood in reactions by their functional groups, unit atoms or molecules that show characteristic chemical properties in a compound. physical chemistry is the study of the physical and fundamental basis of chemical systems and processes. in particular, the energetics and dynamics of such systems and processes are of interest to physical chemists. important areas of study include chemical thermodynamics, chemical kinetics, electrochemistry, statistical mechanics, spectroscopy, and more recently, astrochemistry. physical chemistry has large overlap with molecular physics. physical chemistry involves the use of infinitesimal calculus in deriving equations. it is usually associated with quantum chemistry and theoretical chemistry. physical chemistry is a distinct discipline from chemical physics, but again, there is very strong overlap. theoretical chemistry is the study of chemistry via fundamental theoretical reasoning ( usually within mathematics or physics ). in particular the application of quantum mechanics to chemistry is called quantum chemistry. since the end of the second world war, the development of computers has allowed a systematic development of computational chemistry, which is the art of developing and applying computer programs for solving chemical problems. theoretical chemistry has large overlap with ( theoretical and experimental ) condensed matter physics and molecular physics. other subdivisions include electrochemistry, femtochemistry, flavor chemistry, flow chemistry, immunohistochemistry, hydrogenation chemistry, mathematical chemistry, molecular mechanics, natural product chemistry, organometallic chemistry, petrochemistry, photochemistry, physical organic chemistry, polymer chemistry, radiochemistry, sonochemistry, supramolecular chemistry, synthetic chemistry, and many others. = = = interdisciplinary = = = interdisciplinary fields include agrochemistry, astrochemistry ( and cosmochemistry ), atmospheric chemistry, chemical engineering, chemical biology, chemo - informatics, environmental chemistry, geochemistry, green chemistry, immunochemistry, marine chemistry, materials science, mechanochemistry, medicinal chemistry, molecular biology,
Question: What is the name for a molecule with two atoms?
A) ionized
B) hydrostatic
C) diatomic
D) covalent
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C) diatomic
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Context:
electric motors, servo - mechanisms, and other electrical systems in conjunction with special software. a common example of a mechatronics system is a cd - rom drive. mechanical systems open and close the drive, spin the cd and move the laser, while an optical system reads the data on the cd and converts it to bits. integrated software controls the process and communicates the contents of the cd to the computer. robotics is the application of mechatronics to create robots, which are often used in industry to perform tasks that are dangerous, unpleasant, or repetitive. these robots may be of any shape and size, but all are preprogrammed and interact physically with the world. to create a robot, an engineer typically employs kinematics ( to determine the robot ' s range of motion ) and mechanics ( to determine the stresses within the robot ). robots are used extensively in industrial automation engineering. they allow businesses to save money on labor, perform tasks that are either too dangerous or too precise for humans to perform them economically, and to ensure better quality. many companies employ assembly lines of robots, especially in automotive industries and some factories are so robotized that they can run by themselves. outside the factory, robots have been employed in bomb disposal, space exploration, and many other fields. robots are also sold for various residential applications, from recreation to domestic applications. = = = structural analysis = = = structural analysis is the branch of mechanical engineering ( and also civil engineering ) devoted to examining why and how objects fail and to fix the objects and their performance. structural failures occur in two general modes : static failure, and fatigue failure. static structural failure occurs when, upon being loaded ( having a force applied ) the object being analyzed either breaks or is deformed plastically, depending on the criterion for failure. fatigue failure occurs when an object fails after a number of repeated loading and unloading cycles. fatigue failure occurs because of imperfections in the object : a microscopic crack on the surface of the object, for instance, will grow slightly with each cycle ( propagation ) until the crack is large enough to cause ultimate failure. failure is not simply defined as when a part breaks, however ; it is defined as when a part does not operate as intended. some systems, such as the perforated top sections of some plastic bags, are designed to break. if these systems do not break, failure analysis might be employed to determine the cause. structural analysis is often used by mechanical engineers after a failure has occurred, or when designing to prevent failure
actions of a device at a remote location. remote control systems may also include telemetry channels in the other direction, used to transmit real - time information on the state of the device back to the control station. uncrewed spacecraft are an example of remote - controlled machines, controlled by commands transmitted by satellite ground stations. most handheld remote controls used to control consumer electronics products like televisions or dvd players actually operate by infrared light rather than radio waves, so are not examples of radio remote control. a security concern with remote control systems is spoofing, in which an unauthorized person transmits an imitation of the control signal to take control of the device. examples of radio remote control : unmanned aerial vehicle ( uav, drone ) β a drone is an aircraft without an onboard pilot, flown by remote control by a pilot in another location, usually in a piloting station on the ground. they are used by the military for reconnaissance and ground attack, and more recently by the civilian world for news reporting and aerial photography. the pilot uses aircraft controls like a joystick or steering wheel, which create control signals which are transmitted to the drone by radio to control the flight surfaces and engine. a telemetry system transmits back a video image from a camera in the drone to allow the pilot to see where the aircraft is going, and data from a gps receiver giving the real - time position of the aircraft. uavs have sophisticated onboard automatic pilot systems that maintain stable flight and only require manual control to change directions. keyless entry system β a short - range handheld battery powered key fob transmitter, included with most modern cars, which can lock and unlock the doors of a vehicle from outside, eliminating the need to use a key. when a button is pressed, the transmitter sends a coded radio signal to a receiver in the vehicle, operating the locks. the fob must be close to the vehicle, typically within 5 to 20 meters. north america and japan use a frequency of 315 mhz, while europe uses 433. 92 and 868 mhz. some models can also remotely start the engine, to warm up the car. a security concern with all keyless entry systems is a replay attack, in which a thief uses a special receiver ( " code grabber " ) to record the radio signal during opening, which can later be replayed to open the door. to prevent this, keyless systems use a rolling code system in which a pseudorandom number generator in the remote control generates a different random key each time it is used. to prevent
used for tools, weapons and monumental statuary. by 1200 bc they could cast objects 5 m long in a single piece. several of the six classic simple machines were invented in mesopotamia. mesopotamians have been credited with the invention of the wheel. the wheel and axle mechanism first appeared with the potter ' s wheel, invented in mesopotamia ( modern iraq ) during the 5th millennium bc. this led to the invention of the wheeled vehicle in mesopotamia during the early 4th millennium bc. depictions of wheeled wagons found on clay tablet pictographs at the eanna district of uruk are dated between 3700 and 3500 bc. the lever was used in the shadoof water - lifting device, the first crane machine, which appeared in mesopotamia circa 3000 bc, and then in ancient egyptian technology circa 2000 bc. the earliest evidence of pulleys date back to mesopotamia in the early 2nd millennium bc. the screw, the last of the simple machines to be invented, first appeared in mesopotamia during the neo - assyrian period ( 911 β 609 ) bc. the assyrian king sennacherib ( 704 β 681 bc ) claims to have invented automatic sluices and to have been the first to use water screw pumps, of up to 30 tons weight, which were cast using two - part clay molds rather than by the ' lost wax ' process. the jerwan aqueduct ( c. 688 bc ) is made with stone arches and lined with waterproof concrete. the babylonian astronomical diaries spanned 800 years. they enabled meticulous astronomers to plot the motions of the planets and to predict eclipses. the earliest evidence of water wheels and watermills date back to the ancient near east in the 4th century bc, specifically in the persian empire before 350 bc, in the regions of mesopotamia ( iraq ) and persia ( iran ). this pioneering use of water power constituted the first human - devised motive force not to rely on muscle power ( besides the sail ). = = = = egypt = = = = the egyptians, known for building pyramids centuries before the creation of modern tools, invented and used many simple machines, such as the ramp to aid construction processes. historians and archaeologists have found evidence that the pyramids were built using three of what is called the six simple machines, from which all machines are based. these machines are the inclined plane, the wedge, and the lever, which allowed the ancient egyptians to move millions of limestone blocks which weighed approximately 3. 5 tons ( 7, 000 lbs. ) each into place to create structures like the
wrought, which itself is the original past passive participle of the word work, now superseded by the weak verb forms worker and worked respectively. ) blacksmithing and the various related smithing and metal - crafts. folk music played on acoustic instruments. mathematics ( particularly, pure mathematics ) organic farming and animal husbandry ( i. e. ; agriculture as practiced by all american farmers prior to world war ii ). milling in the sense of operating hand - constructed equipment with the intent to either grind grain, or the reduction of timber to lumber as practiced in a saw - mill. fulling, felting, drop spindle spinning, hand knitting, crochet, & similar textile preparation. the production of charcoal by the collier, for use in home heating, foundry operations, smelting, the various smithing trades, and for brushing ones teeth as in colonial america. glass - blowing. various subskills of food preservation : smoking salting pickling drying note : home canning is a counter example of a low technology since some of the supplies needed to pursue this skill rely on a global trade network and an existing manufacturing infrastructure. the production of various alcoholic beverages : wine : poorly preserved fruit juice. beer : a way to preserve the calories of grain products from decay. whiskey : an improved ( distilled ) form of beer. flint - knapping masonry as used in castles, cathedrals, and root cellars. = = = domestic or consumer = = = ( non exhaustive ) list of low - tech in a westerner ' s everyday life : getting around by bike, and repairing it with second - hand materials using a cargo bike to carry loads ( rather than a gasoline vehicle ) drying clothes on a clothesline or on a drying rack washing clothes by hand, or in a human - powered washing machine cooling one ' s home with a fan or an air expander ( rather than electrical appliances such as air conditioners ) using a bell as door bell a cellar, " desert fridge ", or icebox ( rather than a fridge or freezer ) long - distance travel by sailing boat ( rather than by plane ) a wicker bag or a tote bag ( rather than a plastic bag ) to carry things swedish lighter ( rather than disposable lighter or matches ) a hand drill, instead of an electric one lighting with sunlight or candles hemp textiles to water plants with drip irrigation paper sheets for note - taking to clean with a broom ( rather than a vacuum cleaner ) to find one ' s way with map
. most handheld remote controls used to control consumer electronics products like televisions or dvd players actually operate by infrared light rather than radio waves, so are not examples of radio remote control. a security concern with remote control systems is spoofing, in which an unauthorized person transmits an imitation of the control signal to take control of the device. examples of radio remote control : unmanned aerial vehicle ( uav, drone ) β a drone is an aircraft without an onboard pilot, flown by remote control by a pilot in another location, usually in a piloting station on the ground. they are used by the military for reconnaissance and ground attack, and more recently by the civilian world for news reporting and aerial photography. the pilot uses aircraft controls like a joystick or steering wheel, which create control signals which are transmitted to the drone by radio to control the flight surfaces and engine. a telemetry system transmits back a video image from a camera in the drone to allow the pilot to see where the aircraft is going, and data from a gps receiver giving the real - time position of the aircraft. uavs have sophisticated onboard automatic pilot systems that maintain stable flight and only require manual control to change directions. keyless entry system β a short - range handheld battery powered key fob transmitter, included with most modern cars, which can lock and unlock the doors of a vehicle from outside, eliminating the need to use a key. when a button is pressed, the transmitter sends a coded radio signal to a receiver in the vehicle, operating the locks. the fob must be close to the vehicle, typically within 5 to 20 meters. north america and japan use a frequency of 315 mhz, while europe uses 433. 92 and 868 mhz. some models can also remotely start the engine, to warm up the car. a security concern with all keyless entry systems is a replay attack, in which a thief uses a special receiver ( " code grabber " ) to record the radio signal during opening, which can later be replayed to open the door. to prevent this, keyless systems use a rolling code system in which a pseudorandom number generator in the remote control generates a different random key each time it is used. to prevent thieves from simulating the pseudorandom generator to calculate the next key, the radio signal is also encrypted. garage door opener β a short - range handheld transmitter which can open or close a building ' s electrically operated garage door from outside, so the owner can open the door upon arrival, and close it
wearable technology is any technology that is designed to be used while worn. common types of wearable technology include smartwatches, fitness trackers, and smartglasses. wearable electronic devices are often close to or on the surface of the skin, where they detect, analyze, and transmit information such as vital signs, and / or ambient data and which allow in some cases immediate biofeedback to the wearer. wearable devices collect vast amounts of data from users making use of different behavioral and physiological sensors, which monitor their health status and activity levels. wrist - worn devices include smartwatches with a touchscreen display, while wristbands are mainly used for fitness tracking but do not contain a touchscreen display. wearable devices such as activity trackers are an example of the internet of things, since " things " such as electronics, software, sensors, and connectivity are effectors that enable objects to exchange data ( including data quality ) through the internet with a manufacturer, operator, and / or other connected devices, without requiring human intervention. wearable technology offers a wide range of possible uses, from communication and entertainment to improving health and fitness, however, there are worries about privacy and security because wearable devices have the ability to collect personal data. wearable technology has a variety of use cases which is growing as the technology is developed and the market expands. it can be used to encourage individuals to be more active and improve their lifestyle choices. healthy behavior is encouraged by tracking activity levels and providing useful feedback to enable goal setting. this can be shared with interested stakeholders such as healthcare providers. wearables are popular in consumer electronics, most commonly in the form factors of smartwatches, smart rings, and implants. apart from commercial uses, wearable technology is being incorporated into navigation systems, advanced textiles ( e - textiles ), and healthcare. as wearable technology is being proposed for use in critical applications, like other technology, it is vetted for its reliability and security properties. = = history = = in the 1500s, german inventor peter henlein ( 1485 β 1542 ) created small watches that were worn as necklaces. a century later, pocket watches grew in popularity as waistcoats became fashionable for men. wristwatches were created in the late 1600s but were worn mostly by women as bracelets. pedometers were developed around the same time as pocket watches. the concept of a pedometer was described by leonardo da vinci around 1500, and the germanic national museum in nuremberg has a
##tronics, the science of using mechanical devices with human muscular, musculoskeletal, and nervous systems to assist or enhance motor control lost by trauma, disease, or defect. prostheses are typically used to replace parts lost by injury ( traumatic ) or missing from birth ( congenital ) or to supplement defective body parts. inside the body, artificial heart valves are in common use with artificial hearts and lungs seeing less common use but under active technology development. other medical devices and aids that can be considered prosthetics include hearing aids, artificial eyes, palatal obturator, gastric bands, and dentures. prostheses are specifically not orthoses, although given certain circumstances a prosthesis might end up performing some or all of the same functionary benefits as an orthosis. prostheses are technically the complete finished item. for instance, a c - leg knee alone is not a prosthesis, but only a prosthetic component. the complete prosthesis would consist of the attachment system to the residual limb β usually a " socket ", and all the attachment hardware components all the way down to and including the terminal device. despite the technical difference, the terms are often used interchangeably. the terms " prosthetic " and " orthotic " are adjectives used to describe devices such as a prosthetic knee. the terms " prosthetics " and " orthotics " are used to describe the respective allied health fields. an occupational therapist ' s role in prosthetics include therapy, training and evaluations. prosthetic training includes orientation to prosthetics components and terminology, donning and doffing, wearing schedule, and how to care for residual limb and the prosthesis. = = = exoskeletons = = = a powered exoskeleton is a wearable mobile machine that is powered by a system of electric motors, pneumatics, levers, hydraulics, or a combination of technologies that allow for limb movement with increased strength and endurance. its design aims to provide back support, sense the user ' s motion, and send a signal to motors which manage the gears. the exoskeleton supports the shoulder, waist and thigh, and assists movement for lifting and holding heavy items, while lowering back stress. = = = adaptive seating and positioning = = = people with balance and motor function challenges often need specialized equipment to sit or stand safely and securely. this equipment is frequently
world made wide use of hydropower, along with early uses of tidal power, wind power, fossil fuels such as petroleum, and large factory complexes ( tiraz in arabic ). a variety of industrial mills were employed in the islamic world, including fulling mills, gristmills, hullers, sawmills, ship mills, stamp mills, steel mills, and tide mills. by the 11th century, every province throughout the islamic world had these industrial mills in operation. muslim engineers also employed water turbines and gears in mills and water - raising machines, and pioneered the use of dams as a source of water power, used to provide additional power to watermills and water - raising machines. many of these technologies were transferred to medieval europe. wind - powered machines used to grind grain and pump water, the windmill and wind pump, first appeared in what are now iran, afghanistan and pakistan by the 9th century. they were used to grind grains and draw up water, and used in the gristmilling and sugarcane industries. sugar mills first appeared in the medieval islamic world. they were first driven by watermills, and then windmills from the 9th and 10th centuries in what are today afghanistan, pakistan and iran. crops such as almonds and citrus fruit were brought to europe through al - andalus, and sugar cultivation was gradually adopted across europe. arab merchants dominated trade in the indian ocean until the arrival of the portuguese in the 16th century. the muslim world adopted papermaking from china. the earliest paper mills appeared in abbasid - era baghdad during 794 β 795. the knowledge of gunpowder was also transmitted from china via predominantly islamic countries, where formulas for pure potassium nitrate were developed. the spinning wheel was invented in the islamic world by the early 11th century. it was later widely adopted in europe, where it was adapted into the spinning jenny, a key device during the industrial revolution. the crankshaft was invented by al - jazari in 1206, and is central to modern machinery such as the steam engine, internal combustion engine and automatic controls. the camshaft was also first described by al - jazari in 1206. early programmable machines were also invented in the muslim world. the first music sequencer, a programmable musical instrument, was an automated flute player invented by the banu musa brothers, described in their book of ingenious devices, in the 9th century. in 1206, al - jazari invented programmable automata / robots. he described four automaton musicians, including two
of the device. examples of radio remote control : unmanned aerial vehicle ( uav, drone ) β a drone is an aircraft without an onboard pilot, flown by remote control by a pilot in another location, usually in a piloting station on the ground. they are used by the military for reconnaissance and ground attack, and more recently by the civilian world for news reporting and aerial photography. the pilot uses aircraft controls like a joystick or steering wheel, which create control signals which are transmitted to the drone by radio to control the flight surfaces and engine. a telemetry system transmits back a video image from a camera in the drone to allow the pilot to see where the aircraft is going, and data from a gps receiver giving the real - time position of the aircraft. uavs have sophisticated onboard automatic pilot systems that maintain stable flight and only require manual control to change directions. keyless entry system β a short - range handheld battery powered key fob transmitter, included with most modern cars, which can lock and unlock the doors of a vehicle from outside, eliminating the need to use a key. when a button is pressed, the transmitter sends a coded radio signal to a receiver in the vehicle, operating the locks. the fob must be close to the vehicle, typically within 5 to 20 meters. north america and japan use a frequency of 315 mhz, while europe uses 433. 92 and 868 mhz. some models can also remotely start the engine, to warm up the car. a security concern with all keyless entry systems is a replay attack, in which a thief uses a special receiver ( " code grabber " ) to record the radio signal during opening, which can later be replayed to open the door. to prevent this, keyless systems use a rolling code system in which a pseudorandom number generator in the remote control generates a different random key each time it is used. to prevent thieves from simulating the pseudorandom generator to calculate the next key, the radio signal is also encrypted. garage door opener β a short - range handheld transmitter which can open or close a building ' s electrically operated garage door from outside, so the owner can open the door upon arrival, and close it after departure. when a button is pressed the control transmits a coded fsk radio signal to a receiver in the opener, raising or lowering the door. modern openers use 310, 315 or 390 mhz. to prevent a thief using a replay attack, modern openers use a rolling code system. radio - controlled models
like it, assist physical therapists by providing task - specific practice of walking in people following neurological injury. = = = prosthesis = = = a prosthesis, prosthetic, or prosthetic limb is a device that replaces a missing body part. it is part of the field of biomechatronics, the science of using mechanical devices with human muscular, musculoskeletal, and nervous systems to assist or enhance motor control lost by trauma, disease, or defect. prostheses are typically used to replace parts lost by injury ( traumatic ) or missing from birth ( congenital ) or to supplement defective body parts. inside the body, artificial heart valves are in common use with artificial hearts and lungs seeing less common use but under active technology development. other medical devices and aids that can be considered prosthetics include hearing aids, artificial eyes, palatal obturator, gastric bands, and dentures. prostheses are specifically not orthoses, although given certain circumstances a prosthesis might end up performing some or all of the same functionary benefits as an orthosis. prostheses are technically the complete finished item. for instance, a c - leg knee alone is not a prosthesis, but only a prosthetic component. the complete prosthesis would consist of the attachment system to the residual limb β usually a " socket ", and all the attachment hardware components all the way down to and including the terminal device. despite the technical difference, the terms are often used interchangeably. the terms " prosthetic " and " orthotic " are adjectives used to describe devices such as a prosthetic knee. the terms " prosthetics " and " orthotics " are used to describe the respective allied health fields. an occupational therapist ' s role in prosthetics include therapy, training and evaluations. prosthetic training includes orientation to prosthetics components and terminology, donning and doffing, wearing schedule, and how to care for residual limb and the prosthesis. = = = exoskeletons = = = a powered exoskeleton is a wearable mobile machine that is powered by a system of electric motors, pneumatics, levers, hydraulics, or a combination of technologies that allow for limb movement with increased strength and endurance. its design aims to provide back support, sense the user ' s motion, and send a signal to motors which manage the
Question: What type of motor is used in most household devices with moving parts?
A) thermal motors
B) cooling motors
C) vacuum motors
D) electric motors
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D) electric motors
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to a region of deoxyribonucleic acid ( dna ) that carries genetic information that controls form or function of an organism. dna is composed of two polynucleotide chains that coil around each other to form a double helix. it is found as linear chromosomes in eukaryotes, and circular chromosomes in prokaryotes. the set of chromosomes in a cell is collectively known as its genome. in eukaryotes, dna is mainly in the cell nucleus. in prokaryotes, the dna is held within the nucleoid. the genetic information is held within genes, and the complete assemblage in an organism is called its genotype. dna replication is a semiconservative process whereby each strand serves as a template for a new strand of dna. mutations are heritable changes in dna. they can arise spontaneously as a result of replication errors that were not corrected by proofreading or can be induced by an environmental mutagen such as a chemical ( e. g., nitrous acid, benzopyrene ) or radiation ( e. g., x - ray, gamma ray, ultraviolet radiation, particles emitted by unstable isotopes ). mutations can lead to phenotypic effects such as loss - of - function, gain - of - function, and conditional mutations. some mutations are beneficial, as they are a source of genetic variation for evolution. others are harmful if they were to result in a loss of function of genes needed for survival. = = = gene expression = = = gene expression is the molecular process by which a genotype encoded in dna gives rise to an observable phenotype in the proteins of an organism ' s body. this process is summarized by the central dogma of molecular biology, which was formulated by francis crick in 1958. according to the central dogma, genetic information flows from dna to rna to protein. there are two gene expression processes : transcription ( dna to rna ) and translation ( rna to protein ). = = = gene regulation = = = the regulation of gene expression by environmental factors and during different stages of development can occur at each step of the process such as transcription, rna splicing, translation, and post - translational modification of a protein. gene expression can be influenced by positive or negative regulation, depending on which of the two types of regulatory proteins called transcription factors bind to the dna sequence close to or at a promoter. a cluster of genes that share the same promoter is called an operon,
to chromatin, which is a complex of dna and protein found in eukaryotic cells. = = = genes, development, and evolution = = = development is the process by which a multicellular organism ( plant or animal ) goes through a series of changes, starting from a single cell, and taking on various forms that are characteristic of its life cycle. there are four key processes that underlie development : determination, differentiation, morphogenesis, and growth. determination sets the developmental fate of a cell, which becomes more restrictive during development. differentiation is the process by which specialized cells arise from less specialized cells such as stem cells. stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. cellular differentiation dramatically changes a cell ' s size, shape, membrane potential, metabolic activity, and responsiveness to signals, which are largely due to highly controlled modifications in gene expression and epigenetics. with a few exceptions, cellular differentiation almost never involves a change in the dna sequence itself. thus, different cells can have very different physical characteristics despite having the same genome. morphogenesis, or the development of body form, is the result of spatial differences in gene expression. a small fraction of the genes in an organism ' s genome called the developmental - genetic toolkit control the development of that organism. these toolkit genes are highly conserved among phyla, meaning that they are ancient and very similar in widely separated groups of animals. differences in deployment of toolkit genes affect the body plan and the number, identity, and pattern of body parts. among the most important toolkit genes are the hox genes. hox genes determine where repeating parts, such as the many vertebrae of snakes, will grow in a developing embryo or larva. = = evolution = = = = = evolutionary processes = = = evolution is a central organizing concept in biology. it is the change in heritable characteristics of populations over successive generations. in artificial selection, animals were selectively bred for specific traits. given that traits are inherited, populations contain a varied mix of traits, and reproduction is able to increase any population, darwin argued that in the natural world, it was nature that played the role of humans in selecting for specific traits. darwin inferred that individuals who possessed heritable traits better adapted to their environments are more likely to survive and produce more offspring than other individuals. he further inferred that this would lead to the
studies of the molecular genetics of model plants such as the thale cress, arabidopsis thaliana, a weedy species in the mustard family ( brassicaceae ). the genome or hereditary information contained in the genes of this species is encoded by about 135 million base pairs of dna, forming one of the smallest genomes among flowering plants. arabidopsis was the first plant to have its genome sequenced, in 2000. the sequencing of some other relatively small genomes, of rice ( oryza sativa ) and brachypodium distachyon, has made them important model species for understanding the genetics, cellular and molecular biology of cereals, grasses and monocots generally. model plants such as arabidopsis thaliana are used for studying the molecular biology of plant cells and the chloroplast. ideally, these organisms have small genomes that are well known or completely sequenced, small stature and short generation times. corn has been used to study mechanisms of photosynthesis and phloem loading of sugar in c4 plants. the single celled green alga chlamydomonas reinhardtii, while not an embryophyte itself, contains a green - pigmented chloroplast related to that of land plants, making it useful for study. a red alga cyanidioschyzon merolae has also been used to study some basic chloroplast functions. spinach, peas, soybeans and a moss physcomitrella patens are commonly used to study plant cell biology. agrobacterium tumefaciens, a soil rhizosphere bacterium, can attach to plant cells and infect them with a callus - inducing ti plasmid by horizontal gene transfer, causing a callus infection called crown gall disease. schell and van montagu ( 1977 ) hypothesised that the ti plasmid could be a natural vector for introducing the nif gene responsible for nitrogen fixation in the root nodules of legumes and other plant species. today, genetic modification of the ti plasmid is one of the main techniques for introduction of transgenes to plants and the creation of genetically modified crops. = = = epigenetics = = = epigenetics is the study of heritable changes in gene function that cannot be explained by changes in the underlying dna sequence but cause the organism ' s genes to behave ( or " express themselves " ) differently. one example
cross. the chromosome theory of inheritance, which states that genes are found on chromosomes, was supported by thomas morgans ' s experiments with fruit flies, which established the sex linkage between eye color and sex in these insects. = = = genes and dna = = = a gene is a unit of heredity that corresponds to a region of deoxyribonucleic acid ( dna ) that carries genetic information that controls form or function of an organism. dna is composed of two polynucleotide chains that coil around each other to form a double helix. it is found as linear chromosomes in eukaryotes, and circular chromosomes in prokaryotes. the set of chromosomes in a cell is collectively known as its genome. in eukaryotes, dna is mainly in the cell nucleus. in prokaryotes, the dna is held within the nucleoid. the genetic information is held within genes, and the complete assemblage in an organism is called its genotype. dna replication is a semiconservative process whereby each strand serves as a template for a new strand of dna. mutations are heritable changes in dna. they can arise spontaneously as a result of replication errors that were not corrected by proofreading or can be induced by an environmental mutagen such as a chemical ( e. g., nitrous acid, benzopyrene ) or radiation ( e. g., x - ray, gamma ray, ultraviolet radiation, particles emitted by unstable isotopes ). mutations can lead to phenotypic effects such as loss - of - function, gain - of - function, and conditional mutations. some mutations are beneficial, as they are a source of genetic variation for evolution. others are harmful if they were to result in a loss of function of genes needed for survival. = = = gene expression = = = gene expression is the molecular process by which a genotype encoded in dna gives rise to an observable phenotype in the proteins of an organism ' s body. this process is summarized by the central dogma of molecular biology, which was formulated by francis crick in 1958. according to the central dogma, genetic information flows from dna to rna to protein. there are two gene expression processes : transcription ( dna to rna ) and translation ( rna to protein ). = = = gene regulation = = = the regulation of gene expression by environmental factors and during different stages of development can occur at each step of the process such as transcription, rna splicing
is opened and the dna is purified. the gene is separated by using restriction enzymes to cut the dna into fragments or polymerase chain reaction ( pcr ) to amplify up the gene segment. these segments can then be extracted through gel electrophoresis. if the chosen gene or the donor organism ' s genome has been well studied it may already be accessible from a genetic library. if the dna sequence is known, but no copies of the gene are available, it can also be artificially synthesised. once isolated the gene is ligated into a plasmid that is then inserted into a bacterium. the plasmid is replicated when the bacteria divide, ensuring unlimited copies of the gene are available. the rk2 plasmid is notable for its ability to replicate in a wide variety of single - celled organisms, which makes it suitable as a genetic engineering tool. before the gene is inserted into the target organism it must be combined with other genetic elements. these include a promoter and terminator region, which initiate and end transcription. a selectable marker gene is added, which in most cases confers antibiotic resistance, so researchers can easily determine which cells have been successfully transformed. the gene can also be modified at this stage for better expression or effectiveness. these manipulations are carried out using recombinant dna techniques, such as restriction digests, ligations and molecular cloning. = = = inserting dna into the host genome = = = there are a number of techniques used to insert genetic material into the host genome. some bacteria can naturally take up foreign dna. this ability can be induced in other bacteria via stress ( e. g. thermal or electric shock ), which increases the cell membrane ' s permeability to dna ; up - taken dna can either integrate with the genome or exist as extrachromosomal dna. dna is generally inserted into animal cells using microinjection, where it can be injected through the cell ' s nuclear envelope directly into the nucleus, or through the use of viral vectors. plant genomes can be engineered by physical methods or by use of agrobacterium for the delivery of sequences hosted in t - dna binary vectors. in plants the dna is often inserted using agrobacterium - mediated transformation, taking advantage of the agrobacteriums t - dna sequence that allows natural insertion of genetic material into plant cells. other methods include biolistics, where particles of gold or tungsten are coated with dna and then shot into
an oscillation with a period of around 500 kb in guanine and cytosine content ( gc % ) is observed in the dna sequence of human chromosome 21. this oscillation is localized in the rightmost one - eighth region of the chromosome, from 43. 5 mb to 46. 5 mb. five cycles of oscillation are observed in this region with six gc - rich peaks and five gc - poor valleys. the gc - poor valleys comprise regions with low density of cpg islands and, alternating between the two dna strands, low gene density regions. consequently, the long - range oscillation of gc % result in spacing patterns of both cpg island density, and to a lesser extent, gene densities.
in plants the dna is often inserted using agrobacterium - mediated transformation, taking advantage of the agrobacteriums t - dna sequence that allows natural insertion of genetic material into plant cells. other methods include biolistics, where particles of gold or tungsten are coated with dna and then shot into young plant cells, and electroporation, which involves using an electric shock to make the cell membrane permeable to plasmid dna. as only a single cell is transformed with genetic material, the organism must be regenerated from that single cell. in plants this is accomplished through the use of tissue culture. in animals it is necessary to ensure that the inserted dna is present in the embryonic stem cells. bacteria consist of a single cell and reproduce clonally so regeneration is not necessary. selectable markers are used to easily differentiate transformed from untransformed cells. these markers are usually present in the transgenic organism, although a number of strategies have been developed that can remove the selectable marker from the mature transgenic plant. further testing using pcr, southern hybridization, and dna sequencing is conducted to confirm that an organism contains the new gene. these tests can also confirm the chromosomal location and copy number of the inserted gene. the presence of the gene does not guarantee it will be expressed at appropriate levels in the target tissue so methods that look for and measure the gene products ( rna and protein ) are also used. these include northern hybridisation, quantitative rt - pcr, western blot, immunofluorescence, elisa and phenotypic analysis. the new genetic material can be inserted randomly within the host genome or targeted to a specific location. the technique of gene targeting uses homologous recombination to make desired changes to a specific endogenous gene. this tends to occur at a relatively low frequency in plants and animals and generally requires the use of selectable markers. the frequency of gene targeting can be greatly enhanced through genome editing. genome editing uses artificially engineered nucleases that create specific double - stranded breaks at desired locations in the genome, and use the cell ' s endogenous mechanisms to repair the induced break by the natural processes of homologous recombination and nonhomologous end - joining. there are four families of engineered nucleases : meganucleases, zinc finger nucleases, transcription activator - like effector nucleases ( talens ), and the cas9 - guide
occurs when another transcription factor called a repressor binds to a dna sequence called an operator, which is part of an operon, to prevent transcription. repressors can be inhibited by compounds called inducers ( e. g., allolactose ), thereby allowing transcription to occur. specific genes that can be activated by inducers are called inducible genes, in contrast to constitutive genes that are almost constantly active. in contrast to both, structural genes encode proteins that are not involved in gene regulation. in addition to regulatory events involving the promoter, gene expression can also be regulated by epigenetic changes to chromatin, which is a complex of dna and protein found in eukaryotic cells. = = = genes, development, and evolution = = = development is the process by which a multicellular organism ( plant or animal ) goes through a series of changes, starting from a single cell, and taking on various forms that are characteristic of its life cycle. there are four key processes that underlie development : determination, differentiation, morphogenesis, and growth. determination sets the developmental fate of a cell, which becomes more restrictive during development. differentiation is the process by which specialized cells arise from less specialized cells such as stem cells. stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. cellular differentiation dramatically changes a cell ' s size, shape, membrane potential, metabolic activity, and responsiveness to signals, which are largely due to highly controlled modifications in gene expression and epigenetics. with a few exceptions, cellular differentiation almost never involves a change in the dna sequence itself. thus, different cells can have very different physical characteristics despite having the same genome. morphogenesis, or the development of body form, is the result of spatial differences in gene expression. a small fraction of the genes in an organism ' s genome called the developmental - genetic toolkit control the development of that organism. these toolkit genes are highly conserved among phyla, meaning that they are ancient and very similar in widely separated groups of animals. differences in deployment of toolkit genes affect the body plan and the number, identity, and pattern of body parts. among the most important toolkit genes are the hox genes. hox genes determine where repeating parts, such as the many vertebrae of snakes, will grow in a developing embryo or larva. = = evolution = = = = = evolutionary
can be activated by inducers are called inducible genes, in contrast to constitutive genes that are almost constantly active. in contrast to both, structural genes encode proteins that are not involved in gene regulation. in addition to regulatory events involving the promoter, gene expression can also be regulated by epigenetic changes to chromatin, which is a complex of dna and protein found in eukaryotic cells. = = = genes, development, and evolution = = = development is the process by which a multicellular organism ( plant or animal ) goes through a series of changes, starting from a single cell, and taking on various forms that are characteristic of its life cycle. there are four key processes that underlie development : determination, differentiation, morphogenesis, and growth. determination sets the developmental fate of a cell, which becomes more restrictive during development. differentiation is the process by which specialized cells arise from less specialized cells such as stem cells. stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. cellular differentiation dramatically changes a cell ' s size, shape, membrane potential, metabolic activity, and responsiveness to signals, which are largely due to highly controlled modifications in gene expression and epigenetics. with a few exceptions, cellular differentiation almost never involves a change in the dna sequence itself. thus, different cells can have very different physical characteristics despite having the same genome. morphogenesis, or the development of body form, is the result of spatial differences in gene expression. a small fraction of the genes in an organism ' s genome called the developmental - genetic toolkit control the development of that organism. these toolkit genes are highly conserved among phyla, meaning that they are ancient and very similar in widely separated groups of animals. differences in deployment of toolkit genes affect the body plan and the number, identity, and pattern of body parts. among the most important toolkit genes are the hox genes. hox genes determine where repeating parts, such as the many vertebrae of snakes, will grow in a developing embryo or larva. = = evolution = = = = = evolutionary processes = = = evolution is a central organizing concept in biology. it is the change in heritable characteristics of populations over successive generations. in artificial selection, animals were selectively bred for specific traits. given that traits are inherited, populations contain a varied mix of traits, and reproduction is able to increase any population,
young plant cells, and electroporation, which involves using an electric shock to make the cell membrane permeable to plasmid dna. as only a single cell is transformed with genetic material, the organism must be regenerated from that single cell. in plants this is accomplished through the use of tissue culture. in animals it is necessary to ensure that the inserted dna is present in the embryonic stem cells. bacteria consist of a single cell and reproduce clonally so regeneration is not necessary. selectable markers are used to easily differentiate transformed from untransformed cells. these markers are usually present in the transgenic organism, although a number of strategies have been developed that can remove the selectable marker from the mature transgenic plant. further testing using pcr, southern hybridization, and dna sequencing is conducted to confirm that an organism contains the new gene. these tests can also confirm the chromosomal location and copy number of the inserted gene. the presence of the gene does not guarantee it will be expressed at appropriate levels in the target tissue so methods that look for and measure the gene products ( rna and protein ) are also used. these include northern hybridisation, quantitative rt - pcr, western blot, immunofluorescence, elisa and phenotypic analysis. the new genetic material can be inserted randomly within the host genome or targeted to a specific location. the technique of gene targeting uses homologous recombination to make desired changes to a specific endogenous gene. this tends to occur at a relatively low frequency in plants and animals and generally requires the use of selectable markers. the frequency of gene targeting can be greatly enhanced through genome editing. genome editing uses artificially engineered nucleases that create specific double - stranded breaks at desired locations in the genome, and use the cell ' s endogenous mechanisms to repair the induced break by the natural processes of homologous recombination and nonhomologous end - joining. there are four families of engineered nucleases : meganucleases, zinc finger nucleases, transcription activator - like effector nucleases ( talens ), and the cas9 - guiderna system ( adapted from crispr ). talen and crispr are the two most commonly used and each has its own advantages. talens have greater target specificity, while crispr is easier to design and more efficient. in addition to enhancing gene targeting, engineered nucleases can be used to introduce mutations
Question: What process determines the dna sequence of an entire genome?
A) dna replication
B) genetic factorization
C) chromosomal counting
D) whole-genome sequencing
|
D) whole-genome sequencing
|
Context:
so mars below means blood and war ", is a false cause fallacy. : 26 many astrologers claim that astrology is scientific. if one were to attempt to try to explain it scientifically, there are only four fundamental forces ( conventionally ), limiting the choice of possible natural mechanisms. : 65 some astrologers have proposed conventional causal agents such as electromagnetism and gravity. the strength of these forces drops off with distance. : 65 scientists reject these proposed mechanisms as implausible since, for example, the magnetic field, when measured from earth, of a large but distant planet such as jupiter is far smaller than that produced by ordinary household appliances. astronomer phil plait noted that in terms of magnitude, the sun is the only object with an electromagnetic field of note, but astrology isn ' t based just off the sun alone. : 65 while astrologers could try to suggest a fifth force, this is inconsistent with the trends in physics with the unification of electromagnetism and the weak force into the electroweak force. if the astrologer insisted on being inconsistent with the current understanding and evidential basis of physics, that would be an extraordinary claim. : 65 it would also be inconsistent with the other forces which drop off with distance. : 65 if distance is irrelevant, then, logically, all objects in space should be taken into account. : 66 carl jung sought to invoke synchronicity, the claim that two events have some sort of acausal connection, to explain the lack of statistically significant results on astrology from a single study he conducted. however, synchronicity itself is considered neither testable nor falsifiable. the study was subsequently heavily criticised for its non - random sample and its use of statistics and also its lack of consistency with astrology. = = psychology = = psychological studies have not found any robust relationship between astrological signs and life outcomes. for example, a study showed that zodiac signs are no more effective than random numbers in predicting subjective well - being and quality of life. it has also been shown that confirmation bias is a psychological factor that contributes to belief in astrology. : 344 : 180 β 181 : 42 β 48 confirmation bias is a form of cognitive bias. : 553 from the literature, astrology believers often tend to selectively remember those predictions that turned out to be true and do not remember those that turned out false. another, separate, form of confirmation bias also plays a role, where believers often fail to
the first three greek letters. some of these kinds of radiation could pass through ordinary matter, and all of them could be harmful in large amounts. all of the early researchers received various radiation burns, much like sunburn, and thought little of it. the new phenomenon of radioactivity was seized upon by the manufacturers of quack medicine ( as had the discoveries of electricity and magnetism, earlier ), and a number of patent medicines and treatments involving radioactivity were put forward. gradually it was realized that the radiation produced by radioactive decay was ionizing radiation, and that even quantities too small to burn could pose a severe long - term hazard. many of the scientists working on radioactivity died of cancer as a result of their exposure. radioactive patent medicines mostly disappeared, but other applications of radioactive materials persisted, such as the use of radium salts to produce glowing dials on meters. as the atom came to be better understood, the nature of radioactivity became clearer. some larger atomic nuclei are unstable, and so decay ( release matter or energy ) after a random interval. the three forms of radiation that becquerel and the curies discovered are also more fully understood. alpha decay is when a nucleus releases an alpha particle, which is two protons and two neutrons, equivalent to a helium nucleus. beta decay is the release of a beta particle, a high - energy electron. gamma decay releases gamma rays, which unlike alpha and beta radiation are not matter but electromagnetic radiation of very high frequency, and therefore energy. this type of radiation is the most dangerous and most difficult to block. all three types of radiation occur naturally in certain elements. it has also become clear that the ultimate source of most terrestrial energy is nuclear, either through radiation from the sun caused by stellar thermonuclear reactions or by radioactive decay of uranium within the earth, the principal source of geothermal energy. = = = nuclear fission = = = in natural nuclear radiation, the byproducts are very small compared to the nuclei from which they originate. nuclear fission is the process of splitting a nucleus into roughly equal parts, and releasing energy and neutrons in the process. if these neutrons are captured by another unstable nucleus, they can fission as well, leading to a chain reaction. the average number of neutrons released per nucleus that go on to fission another nucleus is referred to as k. values of k larger than 1 mean that the fission reaction is releasing more neutrons than it absorbs, and therefore is referred to as a self
, heat from friction during rolling can cause problems for metal bearings ; problems which are reduced by the use of ceramics. ceramics are also more chemically resistant and can be used in wet environments where steel bearings would rust. the major drawback to using ceramics is a significantly higher cost. in many cases their electrically insulating properties may also be valuable in bearings. in the early 1980s, toyota researched production of an adiabatic ceramic engine which can run at a temperature of over 6000 Β°f ( 3300 Β°c ). ceramic engines do not require a cooling system and hence allow a major weight reduction and therefore greater fuel efficiency. fuel efficiency of the engine is also higher at high temperature, as shown by carnot ' s theorem. in a conventional metallic engine, much of the energy released from the fuel must be dissipated as waste heat in order to prevent a meltdown of the metallic parts. despite all of these desirable properties, such engines are not in production because the manufacturing of ceramic parts in the requisite precision and durability is difficult. imperfection in the ceramic leads to cracks, which can lead to potentially dangerous equipment failure. such engines are possible in laboratory settings, but mass - production is not feasible with current technology. work is being done in developing ceramic parts for gas turbine engines. currently, even blades made of advanced metal alloys used in the engines ' hot section require cooling and careful limiting of operating temperatures. turbine engines made with ceramics could operate more efficiently, giving aircraft greater range and payload for a set amount of fuel. recently, there have been advances in ceramics which include bio - ceramics, such as dental implants and synthetic bones. hydroxyapatite, the natural mineral component of bone, has been made synthetically from a number of biological and chemical sources and can be formed into ceramic materials. orthopedic implants made from these materials bond readily to bone and other tissues in the body without rejection or inflammatory reactions. because of this, they are of great interest for gene delivery and tissue engineering scaffolds. most hydroxyapatite ceramics are very porous and lack mechanical strength and are used to coat metal orthopedic devices to aid in forming a bond to bone or as bone fillers. they are also used as fillers for orthopedic plastic screws to aid in reducing the inflammation and increase absorption of these plastic materials. work is being done to make strong, fully dense nano crystalline hydroxyapatite ceramic materials for orthopedic weight bearing devices, replacing foreign metal and plastic orthopedic materials
and cell phones are a particular challenge because the stream of data can interfere with focusing and learning. although these technologies affect adults too, young people may be more influenced by it as their developing brains can easily become habituated to switching tasks and become unaccustomed to sustaining attention. too much information, coming too rapidly, can overwhelm thinking. technology is " rapidly and profoundly altering our brains. " high exposure levels stimulate brain cell alteration and release neurotransmitters, which causes the strengthening of some neural pathways and the weakening of others. this leads to heightened stress levels on the brain that, at first, boost energy levels, but, over time, actually augment memory, impair cognition, lead to depression, and alter the neural circuitry of the hippocampus, amygdala and prefrontal cortex. these are the brain regions that control mood and thought. if unchecked, the underlying structure of the brain could be altered. overstimulation due to technology may begin too young. when children are exposed before the age of seven, important developmental tasks may be delayed, and bad learning habits might develop, which " deprives children of the exploration and play that they need to develop. " media psychology is an emerging specialty field that embraces electronic devices and the sensory behaviors occurring from the use of educational technology in learning. = = = sociocultural criticism = = = according to lai, " the learning environment is a complex system where the interplay and interactions of many things impact the outcome of learning. " when technology is brought into an educational setting, the pedagogical setting changes in that technology - driven teaching can change the entire meaning of an activity without adequate research validation. if technology monopolizes an activity, students can begin to develop the sense that " life would scarcely be thinkable without technology. " leo marx considered the word " technology " itself as problematic, susceptible to reification and " phantom objectivity ", which conceals its fundamental nature as something that is only valuable insofar as it benefits the human condition. technology ultimately comes down to affecting the relations between people, but this notion is obfuscated when technology is treated as an abstract notion devoid of good and evil. langdon winner makes a similar point by arguing that the underdevelopment of the philosophy of technology leaves us with an overly simplistic reduction in our discourse to the supposedly dichotomous notions of the " making " versus the " uses " of new technologies and that a narrow focus on " use
. this, he argued, would have been more persuasive and would have produced less controversy. the use of poetic imagery based on the concepts of the macrocosm and microcosm, " as above so below " to decide meaning such as edward w. james ' example of " mars above is red, so mars below means blood and war ", is a false cause fallacy. : 26 many astrologers claim that astrology is scientific. if one were to attempt to try to explain it scientifically, there are only four fundamental forces ( conventionally ), limiting the choice of possible natural mechanisms. : 65 some astrologers have proposed conventional causal agents such as electromagnetism and gravity. the strength of these forces drops off with distance. : 65 scientists reject these proposed mechanisms as implausible since, for example, the magnetic field, when measured from earth, of a large but distant planet such as jupiter is far smaller than that produced by ordinary household appliances. astronomer phil plait noted that in terms of magnitude, the sun is the only object with an electromagnetic field of note, but astrology isn ' t based just off the sun alone. : 65 while astrologers could try to suggest a fifth force, this is inconsistent with the trends in physics with the unification of electromagnetism and the weak force into the electroweak force. if the astrologer insisted on being inconsistent with the current understanding and evidential basis of physics, that would be an extraordinary claim. : 65 it would also be inconsistent with the other forces which drop off with distance. : 65 if distance is irrelevant, then, logically, all objects in space should be taken into account. : 66 carl jung sought to invoke synchronicity, the claim that two events have some sort of acausal connection, to explain the lack of statistically significant results on astrology from a single study he conducted. however, synchronicity itself is considered neither testable nor falsifiable. the study was subsequently heavily criticised for its non - random sample and its use of statistics and also its lack of consistency with astrology. = = psychology = = psychological studies have not found any robust relationship between astrological signs and life outcomes. for example, a study showed that zodiac signs are no more effective than random numbers in predicting subjective well - being and quality of life. it has also been shown that confirmation bias is a psychological factor that contributes to belief in astrology. : 344 : 180 β 181 :
their mechanical properties. = = tissue culture = = in many cases, creation of functional tissues and biological structures in vitro requires extensive culturing to promote survival, growth and inducement of functionality. in general, the basic requirements of cells must be maintained in culture, which include oxygen, ph, humidity, temperature, nutrients and osmotic pressure maintenance. tissue engineered cultures also present additional problems in maintaining culture conditions. in standard cell culture, diffusion is often the sole means of nutrient and metabolite transport. however, as a culture becomes larger and more complex, such as the case with engineered organs and whole tissues, other mechanisms must be employed to maintain the culture, such as the creation of capillary networks within the tissue. another issue with tissue culture is introducing the proper factors or stimuli required to induce functionality. in many cases, simple maintenance culture is not sufficient. growth factors, hormones, specific metabolites or nutrients, chemical and physical stimuli are sometimes required. for example, certain cells respond to changes in oxygen tension as part of their normal development, such as chondrocytes, which must adapt to low oxygen conditions or hypoxia during skeletal development. others, such as endothelial cells, respond to shear stress from fluid flow, which is encountered in blood vessels. mechanical stimuli, such as pressure pulses seem to be beneficial to all kind of cardiovascular tissue such as heart valves, blood vessels or pericardium. = = = bioreactors = = = in tissue engineering, a bioreactor is a device that attempts to simulate a physiological environment in order to promote cell or tissue growth in vitro. a physiological environment can consist of many different parameters such as temperature, pressure, oxygen or carbon dioxide concentration, or osmolality of fluid environment, and it can extend to all kinds of biological, chemical or mechanical stimuli. therefore, there are systems that may include the application of forces such as electromagnetic forces, mechanical pressures, or fluid pressures to the tissue. these systems can be two - or three - dimensional setups. bioreactors can be used in both academic and industry applications. general - use and application - specific bioreactors are also commercially available, which may provide static chemical stimulation or a combination of chemical and mechanical stimulation. cell proliferation and differentiation are largely influenced by mechanical and biochemical cues in the surrounding extracellular matrix environment. bioreactors are typically developed to replicate the specific physiological environment of the tissue being grown ( e. g., flex and fluid shearing for heart tissue growth ). this can
lithography is throughput, i. e., the very long time it takes to expose an entire silicon wafer or glass substrate. a long exposure time leaves the user vulnerable to beam drift or instability which may occur during the exposure. also, the turn - around time for reworking or re - design is lengthened unnecessarily if the pattern is not being changed the second time. it is known that focused - ion beam lithography has the capability of writing extremely fine lines ( less than 50 nm line and space has been achieved ) without proximity effect. however, because the writing field in ion - beam lithography is quite small, large area patterns must be created by stitching together the small fields. ion track technology is a deep cutting tool with a resolution limit around 8 nm applicable to radiation resistant minerals, glasses and polymers. it is capable of generating holes in thin films without any development process. structural depth can be defined either by ion range or by material thickness. aspect ratios up to several 104 can be reached. the technique can shape and texture materials at a defined inclination angle. random pattern, single - ion track structures and an aimed pattern consisting of individual single tracks can be generated. x - ray lithography is a process used in the electronic industry to selectively remove parts of a thin film. it uses x - rays to transfer a geometric pattern from a mask to a light - sensitive chemical photoresist, or simply " resist ", on the substrate. a series of chemical treatments then engraves the produced pattern into the material underneath the photoresist. diamond patterning is a method of forming diamond mems. it is achieved by the lithographic application of diamond films to a substrate such as silicon. the patterns can be formed by selective deposition through a silicon dioxide mask, or by deposition followed by micromachining or focused ion beam milling. = = = etching processes = = = there are two basic categories of etching processes : wet etching and dry etching. in the former, the material is dissolved when immersed in a chemical solution. in the latter, the material is sputtered or dissolved using reactive ions or a vapor phase etchant. = = = = wet etching = = = = wet chemical etching consists of the selective removal of material by dipping a substrate into a solution that dissolves it. the chemical nature of this etching process provides good selectivity, which means the etching rate of the target material is considerably higher than the mask material if
the energy conditions of classical einstein gravity fail once quantum effects are introduced. these quantum violations of the energy conditions are not subtle high - energy planck scale effects. rather the quantum violations of the energy conditions already occur in semiclassical quantum gravity and are first - order o ( \ hbar ) effects. quantum violations of the energy conditions are widespread, albeit small.
is also higher at high temperature, as shown by carnot ' s theorem. in a conventional metallic engine, much of the energy released from the fuel must be dissipated as waste heat in order to prevent a meltdown of the metallic parts. despite all of these desirable properties, such engines are not in production because the manufacturing of ceramic parts in the requisite precision and durability is difficult. imperfection in the ceramic leads to cracks, which can lead to potentially dangerous equipment failure. such engines are possible in laboratory settings, but mass - production is not feasible with current technology. work is being done in developing ceramic parts for gas turbine engines. currently, even blades made of advanced metal alloys used in the engines ' hot section require cooling and careful limiting of operating temperatures. turbine engines made with ceramics could operate more efficiently, giving aircraft greater range and payload for a set amount of fuel. recently, there have been advances in ceramics which include bio - ceramics, such as dental implants and synthetic bones. hydroxyapatite, the natural mineral component of bone, has been made synthetically from a number of biological and chemical sources and can be formed into ceramic materials. orthopedic implants made from these materials bond readily to bone and other tissues in the body without rejection or inflammatory reactions. because of this, they are of great interest for gene delivery and tissue engineering scaffolds. most hydroxyapatite ceramics are very porous and lack mechanical strength and are used to coat metal orthopedic devices to aid in forming a bond to bone or as bone fillers. they are also used as fillers for orthopedic plastic screws to aid in reducing the inflammation and increase absorption of these plastic materials. work is being done to make strong, fully dense nano crystalline hydroxyapatite ceramic materials for orthopedic weight bearing devices, replacing foreign metal and plastic orthopedic materials with a synthetic, but naturally occurring, bone mineral. ultimately these ceramic materials may be used as bone replacements or with the incorporation of protein collagens, synthetic bones. durable actinide - containing ceramic materials have many applications such as in nuclear fuels for burning excess pu and in chemically - inert sources of alpha irradiation for power supply of unmanned space vehicles or to produce electricity for microelectronic devices. both use and disposal of radioactive actinides require their immobilization in a durable host material. nuclear waste long - lived radionuclides such as actinides are immobilized using chemical
the ways to beat the diffraction limit of light and make features in the nanometer range. this form of maskless lithography has found wide usage in photomask - making used in photolithography, low - volume production of semiconductor components, and research & development. the key limitation of electron beam lithography is throughput, i. e., the very long time it takes to expose an entire silicon wafer or glass substrate. a long exposure time leaves the user vulnerable to beam drift or instability which may occur during the exposure. also, the turn - around time for reworking or re - design is lengthened unnecessarily if the pattern is not being changed the second time. it is known that focused - ion beam lithography has the capability of writing extremely fine lines ( less than 50 nm line and space has been achieved ) without proximity effect. however, because the writing field in ion - beam lithography is quite small, large area patterns must be created by stitching together the small fields. ion track technology is a deep cutting tool with a resolution limit around 8 nm applicable to radiation resistant minerals, glasses and polymers. it is capable of generating holes in thin films without any development process. structural depth can be defined either by ion range or by material thickness. aspect ratios up to several 104 can be reached. the technique can shape and texture materials at a defined inclination angle. random pattern, single - ion track structures and an aimed pattern consisting of individual single tracks can be generated. x - ray lithography is a process used in the electronic industry to selectively remove parts of a thin film. it uses x - rays to transfer a geometric pattern from a mask to a light - sensitive chemical photoresist, or simply " resist ", on the substrate. a series of chemical treatments then engraves the produced pattern into the material underneath the photoresist. diamond patterning is a method of forming diamond mems. it is achieved by the lithographic application of diamond films to a substrate such as silicon. the patterns can be formed by selective deposition through a silicon dioxide mask, or by deposition followed by micromachining or focused ion beam milling. = = = etching processes = = = there are two basic categories of etching processes : wet etching and dry etching. in the former, the material is dissolved when immersed in a chemical solution. in the latter, the material is sputtered or dissolved using reactive ions or a vapor phase etchant. =
Question: What disease can too little calcium cause?
A) arthritis
B) psoriasis
C) osteoporosis
D) anemia
|
C) osteoporosis
|
Context:
the nervous system. these kinds of tests can be divided into recordings of : ( 1 ) spontaneous or continuously running electrical activity, or ( 2 ) stimulus evoked responses. subspecialties include electroencephalography, electromyography, evoked potential, nerve conduction study and polysomnography. sometimes these tests are performed by techs without a medical degree, but the interpretation of these tests is done by a medical professional. diagnostic radiology is concerned with imaging of the body, e. g. by x - rays, x - ray computed tomography, ultrasonography, and nuclear magnetic resonance tomography. interventional radiologists can access areas in the body under imaging for an intervention or diagnostic sampling. nuclear medicine is concerned with studying human organ systems by administering radiolabelled substances ( radiopharmaceuticals ) to the body, which can then be imaged outside the body by a gamma camera or a pet scanner. each radiopharmaceutical consists of two parts : a tracer that is specific for the function under study ( e. g., neurotransmitter pathway, metabolic pathway, blood flow, or other ), and a radionuclide ( usually either a gamma - emitter or a positron emitter ). there is a degree of overlap between nuclear medicine and radiology, as evidenced by the emergence of combined devices such as the pet / ct scanner. pathology as a medical specialty is the branch of medicine that deals with the study of diseases and the morphologic, physiologic changes produced by them. as a diagnostic specialty, pathology can be considered the basis of modern scientific medical knowledge and plays a large role in evidence - based medicine. many modern molecular tests such as flow cytometry, polymerase chain reaction ( pcr ), immunohistochemistry, cytogenetics, gene rearrangements studies and fluorescent in situ hybridization ( fish ) fall within the territory of pathology. = = = = other major specialties = = = = the following are some major medical specialties that do not directly fit into any of the above - mentioned groups : anesthesiology ( also known as anaesthetics ) : concerned with the perioperative management of the surgical patient. the anesthesiologist ' s role during surgery is to prevent derangement in the vital organs ' ( i. e. brain, heart, kidneys ) functions and postoperative pain. outside of
is not present ( e. g., litter in a parking lot or readings on an electric meter ). behavioral observations involve the direct witnessing of the actor engaging in the behavior ( e. g., watching how close a person sits next to another person ). behavioral choices are when a person selects between two or more options ( e. g., voting behavior, choice of a punishment for another participant ). reaction time. the time between the presentation of a stimulus and an appropriate response can indicate differences between two cognitive processes, and can indicate some things about their nature. for example, if in a search task the reaction times vary proportionally with the number of elements, then it is evident that this cognitive process of searching involves serial instead of parallel processing. psychophysical responses. psychophysical experiments are an old psychological technique, which has been adopted by cognitive psychology. they typically involve making judgments of some physical property, e. g. the loudness of a sound. correlation of subjective scales between individuals can show cognitive or sensory biases as compared to actual physical measurements. some examples include : sameness judgments for colors, tones, textures, etc. threshold differences for colors, tones, textures, etc. eye tracking. this methodology is used to study a variety of cognitive processes, most notably visual perception and language processing. the fixation point of the eyes is linked to an individual ' s focus of attention. thus, by monitoring eye movements, we can study what information is being processed at a given time. eye tracking allows us to study cognitive processes on extremely short time scales. eye movements reflect online decision making during a task, and they provide us with some insight into the ways in which those decisions may be processed. = = = brain imaging = = = brain imaging involves analyzing activity within the brain while performing various tasks. this allows us to link behavior and brain function to help understand how information is processed. different types of imaging techniques vary in their temporal ( time - based ) and spatial ( location - based ) resolution. brain imaging is often used in cognitive neuroscience. single - photon emission computed tomography and positron emission tomography. spect and pet use radioactive isotopes, which are injected into the subject ' s bloodstream and taken up by the brain. by observing which areas of the brain take up the radioactive isotope, we can see which areas of the brain are more active than other areas. pet has similar spatial resolution to fmri, but it has extremely poor temporal resolution. electroencephalography. eeg measures the electrical fields
, followed by a medical interview and a physical examination. basic diagnostic medical devices ( e. g., stethoscope, tongue depressor ) are typically used. after examining for signs and interviewing for symptoms, the doctor may order medical tests ( e. g., blood tests ), take a biopsy, or prescribe pharmaceutical drugs or other therapies. differential diagnosis methods help to rule out conditions based on the information provided. during the encounter, properly informing the patient of all relevant facts is an important part of the relationship and the development of trust. the medical encounter is then documented in the medical record, which is a legal document in many jurisdictions. follow - ups may be shorter but follow the same general procedure, and specialists follow a similar process. the diagnosis and treatment may take only a few minutes or a few weeks, depending on the complexity of the issue. the components of the medical interview and encounter are : chief complaint ( cc ) : the reason for the current medical visit. these are the symptoms. they are in the patient ' s own words and are recorded along with the duration of each one. also called chief concern or presenting complaint. current activity : occupation, hobbies, what the patient actually does. family history ( fh ) : listing of diseases in the family that may impact the patient. a family tree is sometimes used. history of present illness ( hpi ) : the chronological order of events of symptoms and further clarification of each symptom. distinguishable from history of previous illness, often called past medical history ( pmh ). medical history comprises hpi and pmh. medications ( rx ) : what drugs the patient takes including prescribed, over - the - counter, and home remedies, as well as alternative and herbal medicines or remedies. allergies are also recorded. past medical history ( pmh / pmhx ) : concurrent medical problems, past hospitalizations and operations, injuries, past infectious diseases or vaccinations, history of known allergies. review of systems ( ros ) or systems inquiry : a set of additional questions to ask, which may be missed on hpi : a general enquiry ( have you noticed any weight loss, change in sleep quality, fevers, lumps and bumps? etc. ), followed by questions on the body ' s main organ systems ( heart, lungs, digestive tract, urinary tract, etc. ). social history ( sh ) : birthplace, residences, marital history
scientists look through telescopes, study images on electronic screens, record meter readings, and so on. generally, on a basic level, they can agree on what they see, e. g., the thermometer shows 37. 9 degrees c. but, if these scientists have different ideas about the theories that have been developed to explain these basic observations, they may disagree about what they are observing. for example, before albert einstein ' s general theory of relativity, observers would have likely interpreted an image of the einstein cross as five different objects in space. in light of that theory, however, astronomers will tell you that there are actually only two objects, one in the center and four different images of a second object around the sides. alternatively, if other scientists suspect that something is wrong with the telescope and only one object is actually being observed, they are operating under yet another theory. observations that cannot be separated from theoretical interpretation are said to be theory - laden. all observation involves both perception and cognition. that is, one does not make an observation passively, but rather is actively engaged in distinguishing the phenomenon being observed from surrounding sensory data. therefore, observations are affected by one ' s underlying understanding of the way in which the world functions, and that understanding may influence what is perceived, noticed, or deemed worthy of consideration. in this sense, it can be argued that all observation is theory - laden. = = = the purpose of science = = = should science aim to determine ultimate truth, or are there questions that science cannot answer? scientific realists claim that science aims at truth and that one ought to regard scientific theories as true, approximately true, or likely true. conversely, scientific anti - realists argue that science does not aim ( or at least does not succeed ) at truth, especially truth about unobservables like electrons or other universes. instrumentalists argue that scientific theories should only be evaluated on whether they are useful. in their view, whether theories are true or not is beside the point, because the purpose of science is to make predictions and enable effective technology. realists often point to the success of recent scientific theories as evidence for the truth ( or near truth ) of current theories. antirealists point to either the many false theories in the history of science, epistemic morals, the success of false modeling assumptions, or widely termed postmodern criticisms of objectivity as evidence against scientific realism. antirealists attempt to explain the success of scientific theories without reference to truth. some antirealists claim that scientific
##physical processes which take place in human beings as they make sense of information received through the visual system. the subject of the image. when developing an imaging system, designers must consider the observables associated with the subjects which will be imaged. these observables generally take the form of emitted or reflected energy, such as electromagnetic energy or mechanical energy. the capture device. once the observables associated with the subject are characterized, designers can then identify and integrate the technologies needed to capture those observables. for example, in the case of consumer digital cameras, those technologies include optics for collecting energy in the visible portion of the electromagnetic spectrum, and electronic detectors for converting the electromagnetic energy into an electronic signal. the processor. for all digital imaging systems, the electronic signals produced by the capture device must be manipulated by an algorithm which formats the signals so they can be displayed as an image. in practice, there are often multiple processors involved in the creation of a digital image. the display. the display takes the electronic signals which have been manipulated by the processor and renders them on some visual medium. examples include paper ( for printed, or " hard copy " images ), television, computer monitor, or projector. note that some imaging scientists will include additional " links " in their description of the imaging chain. for example, some will include the " source " of the energy which " illuminates " or interacts with the subject of the image. others will include storage and / or transmission systems. = = subfields = = subfields within imaging science include : image processing, computer vision, 3d computer graphics, animations, atmospheric optics, astronomical imaging, biological imaging, digital image restoration, digital imaging, color science, digital photography, holography, magnetic resonance imaging, medical imaging, microdensitometry, optics, photography, remote sensing, radar imaging, radiometry, silver halide, ultrasound imaging, photoacoustic imaging, thermal imaging, visual perception, and various printing technologies. = = methodologies = = acoustic imaging coherent imaging uses an active coherent illumination source, such as in radar, synthetic aperture radar ( sar ), medical ultrasound and optical coherence tomography ; non - coherent imaging systems include fluorescent microscopes, optical microscopes, and telescopes. chemical imaging, the simultaneous measurement of spectra and pictures digital imaging, creating digital images, generally by scanning or through digital photography disk image, a file which contains the exact content of a data storage medium document imaging, replicating documents commonly
options ( e. g., voting behavior, choice of a punishment for another participant ). reaction time. the time between the presentation of a stimulus and an appropriate response can indicate differences between two cognitive processes, and can indicate some things about their nature. for example, if in a search task the reaction times vary proportionally with the number of elements, then it is evident that this cognitive process of searching involves serial instead of parallel processing. psychophysical responses. psychophysical experiments are an old psychological technique, which has been adopted by cognitive psychology. they typically involve making judgments of some physical property, e. g. the loudness of a sound. correlation of subjective scales between individuals can show cognitive or sensory biases as compared to actual physical measurements. some examples include : sameness judgments for colors, tones, textures, etc. threshold differences for colors, tones, textures, etc. eye tracking. this methodology is used to study a variety of cognitive processes, most notably visual perception and language processing. the fixation point of the eyes is linked to an individual ' s focus of attention. thus, by monitoring eye movements, we can study what information is being processed at a given time. eye tracking allows us to study cognitive processes on extremely short time scales. eye movements reflect online decision making during a task, and they provide us with some insight into the ways in which those decisions may be processed. = = = brain imaging = = = brain imaging involves analyzing activity within the brain while performing various tasks. this allows us to link behavior and brain function to help understand how information is processed. different types of imaging techniques vary in their temporal ( time - based ) and spatial ( location - based ) resolution. brain imaging is often used in cognitive neuroscience. single - photon emission computed tomography and positron emission tomography. spect and pet use radioactive isotopes, which are injected into the subject ' s bloodstream and taken up by the brain. by observing which areas of the brain take up the radioactive isotope, we can see which areas of the brain are more active than other areas. pet has similar spatial resolution to fmri, but it has extremely poor temporal resolution. electroencephalography. eeg measures the electrical fields generated by large populations of neurons in the cortex by placing a series of electrodes on the scalp of the subject. this technique has an extremely high temporal resolution, but a relatively poor spatial resolution. functional magnetic resonance imaging. fmri measures the relative amount of oxygenated blood flowing to different parts of the brain. more oxygen
behavioral responses to different stimuli, one can understand something about how those stimuli are processed. lewandowski & strohmetz ( 2009 ) reviewed a collection of innovative uses of behavioral measurement in psychology including behavioral traces, behavioral observations, and behavioral choice. behavioral traces are pieces of evidence that indicate behavior occurred, but the actor is not present ( e. g., litter in a parking lot or readings on an electric meter ). behavioral observations involve the direct witnessing of the actor engaging in the behavior ( e. g., watching how close a person sits next to another person ). behavioral choices are when a person selects between two or more options ( e. g., voting behavior, choice of a punishment for another participant ). reaction time. the time between the presentation of a stimulus and an appropriate response can indicate differences between two cognitive processes, and can indicate some things about their nature. for example, if in a search task the reaction times vary proportionally with the number of elements, then it is evident that this cognitive process of searching involves serial instead of parallel processing. psychophysical responses. psychophysical experiments are an old psychological technique, which has been adopted by cognitive psychology. they typically involve making judgments of some physical property, e. g. the loudness of a sound. correlation of subjective scales between individuals can show cognitive or sensory biases as compared to actual physical measurements. some examples include : sameness judgments for colors, tones, textures, etc. threshold differences for colors, tones, textures, etc. eye tracking. this methodology is used to study a variety of cognitive processes, most notably visual perception and language processing. the fixation point of the eyes is linked to an individual ' s focus of attention. thus, by monitoring eye movements, we can study what information is being processed at a given time. eye tracking allows us to study cognitive processes on extremely short time scales. eye movements reflect online decision making during a task, and they provide us with some insight into the ways in which those decisions may be processed. = = = brain imaging = = = brain imaging involves analyzing activity within the brain while performing various tasks. this allows us to link behavior and brain function to help understand how information is processed. different types of imaging techniques vary in their temporal ( time - based ) and spatial ( location - based ) resolution. brain imaging is often used in cognitive neuroscience. single - photon emission computed tomography and positron emission tomography. spect and pet use radioactive isotopes, which are injected into the subject ' s bloodstream
the tests, assays, and procedures needed for providing the specific services. subspecialties include transfusion medicine, cellular pathology, clinical chemistry, hematology, clinical microbiology and clinical immunology. clinical neurophysiology is concerned with testing the physiology or function of the central and peripheral aspects of the nervous system. these kinds of tests can be divided into recordings of : ( 1 ) spontaneous or continuously running electrical activity, or ( 2 ) stimulus evoked responses. subspecialties include electroencephalography, electromyography, evoked potential, nerve conduction study and polysomnography. sometimes these tests are performed by techs without a medical degree, but the interpretation of these tests is done by a medical professional. diagnostic radiology is concerned with imaging of the body, e. g. by x - rays, x - ray computed tomography, ultrasonography, and nuclear magnetic resonance tomography. interventional radiologists can access areas in the body under imaging for an intervention or diagnostic sampling. nuclear medicine is concerned with studying human organ systems by administering radiolabelled substances ( radiopharmaceuticals ) to the body, which can then be imaged outside the body by a gamma camera or a pet scanner. each radiopharmaceutical consists of two parts : a tracer that is specific for the function under study ( e. g., neurotransmitter pathway, metabolic pathway, blood flow, or other ), and a radionuclide ( usually either a gamma - emitter or a positron emitter ). there is a degree of overlap between nuclear medicine and radiology, as evidenced by the emergence of combined devices such as the pet / ct scanner. pathology as a medical specialty is the branch of medicine that deals with the study of diseases and the morphologic, physiologic changes produced by them. as a diagnostic specialty, pathology can be considered the basis of modern scientific medical knowledge and plays a large role in evidence - based medicine. many modern molecular tests such as flow cytometry, polymerase chain reaction ( pcr ), immunohistochemistry, cytogenetics, gene rearrangements studies and fluorescent in situ hybridization ( fish ) fall within the territory of pathology. = = = = other major specialties = = = = the following are some major medical specialties that do not directly fit into any of the above - mentioned groups : anesthesiology ( also
sciences are the clinical diagnostic services that apply laboratory techniques to diagnosis and management of patients. in the united states, these services are supervised by a pathologist. the personnel that work in these medical laboratory departments are technically trained staff who do not hold medical degrees, but who usually hold an undergraduate medical technology degree, who actually perform the tests, assays, and procedures needed for providing the specific services. subspecialties include transfusion medicine, cellular pathology, clinical chemistry, hematology, clinical microbiology and clinical immunology. clinical neurophysiology is concerned with testing the physiology or function of the central and peripheral aspects of the nervous system. these kinds of tests can be divided into recordings of : ( 1 ) spontaneous or continuously running electrical activity, or ( 2 ) stimulus evoked responses. subspecialties include electroencephalography, electromyography, evoked potential, nerve conduction study and polysomnography. sometimes these tests are performed by techs without a medical degree, but the interpretation of these tests is done by a medical professional. diagnostic radiology is concerned with imaging of the body, e. g. by x - rays, x - ray computed tomography, ultrasonography, and nuclear magnetic resonance tomography. interventional radiologists can access areas in the body under imaging for an intervention or diagnostic sampling. nuclear medicine is concerned with studying human organ systems by administering radiolabelled substances ( radiopharmaceuticals ) to the body, which can then be imaged outside the body by a gamma camera or a pet scanner. each radiopharmaceutical consists of two parts : a tracer that is specific for the function under study ( e. g., neurotransmitter pathway, metabolic pathway, blood flow, or other ), and a radionuclide ( usually either a gamma - emitter or a positron emitter ). there is a degree of overlap between nuclear medicine and radiology, as evidenced by the emergence of combined devices such as the pet / ct scanner. pathology as a medical specialty is the branch of medicine that deals with the study of diseases and the morphologic, physiologic changes produced by them. as a diagnostic specialty, pathology can be considered the basis of modern scientific medical knowledge and plays a large role in evidence - based medicine. many modern molecular tests such as flow cytometry, polymerase chain reaction ( pcr ), immunohistochemistry, cytogenetic
of measuring methods. x - rays and gamma rays are used in industrial radiography to make images of the inside of solid products, as a means of nondestructive testing and inspection. the piece to be radiographed is placed between the source and a photographic film in a cassette. after a certain exposure time, the film is developed and it shows any internal defects of the material. gauges - gauges use the exponential absorption law of gamma rays level indicators : source and detector are placed at opposite sides of a container, indicating the presence or absence of material in the horizontal radiation path. beta or gamma sources are used, depending on the thickness and the density of the material to be measured. the method is used for containers of liquids or of grainy substances thickness gauges : if the material is of constant density, the signal measured by the radiation detector depends on the thickness of the material. this is useful for continuous production, like of paper, rubber, etc. electrostatic control - to avoid the build - up of static electricity in production of paper, plastics, synthetic textiles, etc., a ribbon - shaped source of the alpha emitter 241am can be placed close to the material at the end of the production line. the source ionizes the air to remove electric charges on the material. radioactive tracers - since radioactive isotopes behave, chemically, mostly like the inactive element, the behavior of a certain chemical substance can be followed by tracing the radioactivity. examples : adding a gamma tracer to a gas or liquid in a closed system makes it possible to find a hole in a tube. adding a tracer to the surface of the component of a motor makes it possible to measure wear by measuring the activity of the lubricating oil. oil and gas exploration - nuclear well logging is used to help predict the commercial viability of new or existing wells. the technology involves the use of a neutron or gamma - ray source and a radiation detector which are lowered into boreholes to determine the properties of the surrounding rock such as porosity and lithography. [ 1 ] road construction - nuclear moisture / density gauges are used to determine the density of soils, asphalt, and concrete. typically a cesium - 137 source is used. = = = commercial applications = = = radioluminescence tritium illumination : tritium is used with phosphor in rifle sights to increase nighttime firing accuracy. some runway markers and building exit signs use the same technology, to remain illuminated during blackouts. betavoltaics
Question: In a scientific investigation, what do you call a direct, physical observation of something or a process?
A) sighting
B) reason
C) declaration
D) evidence
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D) evidence
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Context:
blood vessels. mechanical stimuli, such as pressure pulses seem to be beneficial to all kind of cardiovascular tissue such as heart valves, blood vessels or pericardium. = = = bioreactors = = = in tissue engineering, a bioreactor is a device that attempts to simulate a physiological environment in order to promote cell or tissue growth in vitro. a physiological environment can consist of many different parameters such as temperature, pressure, oxygen or carbon dioxide concentration, or osmolality of fluid environment, and it can extend to all kinds of biological, chemical or mechanical stimuli. therefore, there are systems that may include the application of forces such as electromagnetic forces, mechanical pressures, or fluid pressures to the tissue. these systems can be two - or three - dimensional setups. bioreactors can be used in both academic and industry applications. general - use and application - specific bioreactors are also commercially available, which may provide static chemical stimulation or a combination of chemical and mechanical stimulation. cell proliferation and differentiation are largely influenced by mechanical and biochemical cues in the surrounding extracellular matrix environment. bioreactors are typically developed to replicate the specific physiological environment of the tissue being grown ( e. g., flex and fluid shearing for heart tissue growth ). this can allow specialized cell lines to thrive in cultures replicating their native environments, but it also makes bioreactors attractive tools for culturing stem cells. a successful stem - cell - based bioreactor is effective at expanding stem cells with uniform properties and / or promoting controlled, reproducible differentiation into selected mature cell types. there are a variety of bioreactors designed for 3d cell cultures. there are small plastic cylindrical chambers, as well as glass chambers, with regulated internal humidity and moisture specifically engineered for the purpose of growing cells in three dimensions. the bioreactor uses bioactive synthetic materials such as polyethylene terephthalate membranes to surround the spheroid cells in an environment that maintains high levels of nutrients. they are easy to open and close, so that cell spheroids can be removed for testing, yet the chamber is able to maintain 100 % humidity throughout. this humidity is important to achieve maximum cell growth and function. the bioreactor chamber is part of a larger device that rotates to ensure equal cell growth in each direction across three dimensions. quinxell technologies now under quintech life sciences from singapore has developed a bioreactor known as the tisxell biaxial bioreactor which is specially designed for the purpose of
such as electromagnetic forces, mechanical pressures, or fluid pressures to the tissue. these systems can be two - or three - dimensional setups. bioreactors can be used in both academic and industry applications. general - use and application - specific bioreactors are also commercially available, which may provide static chemical stimulation or a combination of chemical and mechanical stimulation. cell proliferation and differentiation are largely influenced by mechanical and biochemical cues in the surrounding extracellular matrix environment. bioreactors are typically developed to replicate the specific physiological environment of the tissue being grown ( e. g., flex and fluid shearing for heart tissue growth ). this can allow specialized cell lines to thrive in cultures replicating their native environments, but it also makes bioreactors attractive tools for culturing stem cells. a successful stem - cell - based bioreactor is effective at expanding stem cells with uniform properties and / or promoting controlled, reproducible differentiation into selected mature cell types. there are a variety of bioreactors designed for 3d cell cultures. there are small plastic cylindrical chambers, as well as glass chambers, with regulated internal humidity and moisture specifically engineered for the purpose of growing cells in three dimensions. the bioreactor uses bioactive synthetic materials such as polyethylene terephthalate membranes to surround the spheroid cells in an environment that maintains high levels of nutrients. they are easy to open and close, so that cell spheroids can be removed for testing, yet the chamber is able to maintain 100 % humidity throughout. this humidity is important to achieve maximum cell growth and function. the bioreactor chamber is part of a larger device that rotates to ensure equal cell growth in each direction across three dimensions. quinxell technologies now under quintech life sciences from singapore has developed a bioreactor known as the tisxell biaxial bioreactor which is specially designed for the purpose of tissue engineering. it is the first bioreactor in the world to have a spherical glass chamber with biaxial rotation ; specifically to mimic the rotation of the fetus in the womb ; which provides a conducive environment for the growth of tissues. multiple forms of mechanical stimulation have also been combined into a single bioreactor. using gene expression analysis, one academic study found that applying a combination of cyclic strain and ultrasound stimulation to pre - osteoblast cells in a bioreactor accelerated matrix maturation and differentiation. the technology of this combined stimulation bioreactor could be used to grow bone cells more quickly and effectively
required. for example, certain cells respond to changes in oxygen tension as part of their normal development, such as chondrocytes, which must adapt to low oxygen conditions or hypoxia during skeletal development. others, such as endothelial cells, respond to shear stress from fluid flow, which is encountered in blood vessels. mechanical stimuli, such as pressure pulses seem to be beneficial to all kind of cardiovascular tissue such as heart valves, blood vessels or pericardium. = = = bioreactors = = = in tissue engineering, a bioreactor is a device that attempts to simulate a physiological environment in order to promote cell or tissue growth in vitro. a physiological environment can consist of many different parameters such as temperature, pressure, oxygen or carbon dioxide concentration, or osmolality of fluid environment, and it can extend to all kinds of biological, chemical or mechanical stimuli. therefore, there are systems that may include the application of forces such as electromagnetic forces, mechanical pressures, or fluid pressures to the tissue. these systems can be two - or three - dimensional setups. bioreactors can be used in both academic and industry applications. general - use and application - specific bioreactors are also commercially available, which may provide static chemical stimulation or a combination of chemical and mechanical stimulation. cell proliferation and differentiation are largely influenced by mechanical and biochemical cues in the surrounding extracellular matrix environment. bioreactors are typically developed to replicate the specific physiological environment of the tissue being grown ( e. g., flex and fluid shearing for heart tissue growth ). this can allow specialized cell lines to thrive in cultures replicating their native environments, but it also makes bioreactors attractive tools for culturing stem cells. a successful stem - cell - based bioreactor is effective at expanding stem cells with uniform properties and / or promoting controlled, reproducible differentiation into selected mature cell types. there are a variety of bioreactors designed for 3d cell cultures. there are small plastic cylindrical chambers, as well as glass chambers, with regulated internal humidity and moisture specifically engineered for the purpose of growing cells in three dimensions. the bioreactor uses bioactive synthetic materials such as polyethylene terephthalate membranes to surround the spheroid cells in an environment that maintains high levels of nutrients. they are easy to open and close, so that cell spheroids can be removed for testing, yet the chamber is able to maintain 100 % humidity throughout. this humidity is important to achieve maximum cell growth and function. the
unitary recordings in freely - moving pulse weakly electric fish suggest spike timing encoding of electrosensory signals
the heart beat data recorded from samples before and during meditation are analyzed using two different scaling analysis methods. these analyses revealed that mediation severely affects the long range correlation of heart beat of a normal heart. moreover, it is found that meditation induces periodic behavior in the heart beat. the complexity of the heart rate variability is quantified using multiscale entropy analysis and recurrence analysis. the complexity of the heart beat during mediation is found to be more.
to maintain the culture, such as the creation of capillary networks within the tissue. another issue with tissue culture is introducing the proper factors or stimuli required to induce functionality. in many cases, simple maintenance culture is not sufficient. growth factors, hormones, specific metabolites or nutrients, chemical and physical stimuli are sometimes required. for example, certain cells respond to changes in oxygen tension as part of their normal development, such as chondrocytes, which must adapt to low oxygen conditions or hypoxia during skeletal development. others, such as endothelial cells, respond to shear stress from fluid flow, which is encountered in blood vessels. mechanical stimuli, such as pressure pulses seem to be beneficial to all kind of cardiovascular tissue such as heart valves, blood vessels or pericardium. = = = bioreactors = = = in tissue engineering, a bioreactor is a device that attempts to simulate a physiological environment in order to promote cell or tissue growth in vitro. a physiological environment can consist of many different parameters such as temperature, pressure, oxygen or carbon dioxide concentration, or osmolality of fluid environment, and it can extend to all kinds of biological, chemical or mechanical stimuli. therefore, there are systems that may include the application of forces such as electromagnetic forces, mechanical pressures, or fluid pressures to the tissue. these systems can be two - or three - dimensional setups. bioreactors can be used in both academic and industry applications. general - use and application - specific bioreactors are also commercially available, which may provide static chemical stimulation or a combination of chemical and mechanical stimulation. cell proliferation and differentiation are largely influenced by mechanical and biochemical cues in the surrounding extracellular matrix environment. bioreactors are typically developed to replicate the specific physiological environment of the tissue being grown ( e. g., flex and fluid shearing for heart tissue growth ). this can allow specialized cell lines to thrive in cultures replicating their native environments, but it also makes bioreactors attractive tools for culturing stem cells. a successful stem - cell - based bioreactor is effective at expanding stem cells with uniform properties and / or promoting controlled, reproducible differentiation into selected mature cell types. there are a variety of bioreactors designed for 3d cell cultures. there are small plastic cylindrical chambers, as well as glass chambers, with regulated internal humidity and moisture specifically engineered for the purpose of growing cells in three dimensions. the bioreactor uses bioactive synthetic materials such as polyethylene terephthala
cell or tissue growth in vitro. a physiological environment can consist of many different parameters such as temperature, pressure, oxygen or carbon dioxide concentration, or osmolality of fluid environment, and it can extend to all kinds of biological, chemical or mechanical stimuli. therefore, there are systems that may include the application of forces such as electromagnetic forces, mechanical pressures, or fluid pressures to the tissue. these systems can be two - or three - dimensional setups. bioreactors can be used in both academic and industry applications. general - use and application - specific bioreactors are also commercially available, which may provide static chemical stimulation or a combination of chemical and mechanical stimulation. cell proliferation and differentiation are largely influenced by mechanical and biochemical cues in the surrounding extracellular matrix environment. bioreactors are typically developed to replicate the specific physiological environment of the tissue being grown ( e. g., flex and fluid shearing for heart tissue growth ). this can allow specialized cell lines to thrive in cultures replicating their native environments, but it also makes bioreactors attractive tools for culturing stem cells. a successful stem - cell - based bioreactor is effective at expanding stem cells with uniform properties and / or promoting controlled, reproducible differentiation into selected mature cell types. there are a variety of bioreactors designed for 3d cell cultures. there are small plastic cylindrical chambers, as well as glass chambers, with regulated internal humidity and moisture specifically engineered for the purpose of growing cells in three dimensions. the bioreactor uses bioactive synthetic materials such as polyethylene terephthalate membranes to surround the spheroid cells in an environment that maintains high levels of nutrients. they are easy to open and close, so that cell spheroids can be removed for testing, yet the chamber is able to maintain 100 % humidity throughout. this humidity is important to achieve maximum cell growth and function. the bioreactor chamber is part of a larger device that rotates to ensure equal cell growth in each direction across three dimensions. quinxell technologies now under quintech life sciences from singapore has developed a bioreactor known as the tisxell biaxial bioreactor which is specially designed for the purpose of tissue engineering. it is the first bioreactor in the world to have a spherical glass chamber with biaxial rotation ; specifically to mimic the rotation of the fetus in the womb ; which provides a conducive environment for the growth of tissues. multiple forms of mechanical stimulation have also been combined into a single
tissue engineering. it is the first bioreactor in the world to have a spherical glass chamber with biaxial rotation ; specifically to mimic the rotation of the fetus in the womb ; which provides a conducive environment for the growth of tissues. multiple forms of mechanical stimulation have also been combined into a single bioreactor. using gene expression analysis, one academic study found that applying a combination of cyclic strain and ultrasound stimulation to pre - osteoblast cells in a bioreactor accelerated matrix maturation and differentiation. the technology of this combined stimulation bioreactor could be used to grow bone cells more quickly and effectively in future clinical stem cell therapies. mc2 biotek has also developed a bioreactor known as prototissue that uses gas exchange to maintain high oxygen levels within the cell chamber ; improving upon previous bioreactors, since the higher oxygen levels help the cell grow and undergo normal cell respiration. active areas of research on bioreactors includes increasing production scale and refining the physiological environment, both of which could improve the efficiency and efficacy of bioreactors in research or clinical use. bioreactors are currently used to study, among other things, cell and tissue level therapies, cell and tissue response to specific physiological environment changes, and development of disease and injury. = = = long fiber generation = = = in 2013, a group from the university of tokyo developed cell laden fibers up to a meter in length and on the order of 100 ΞΌm in size. these fibers were created using a microfluidic device that forms a double coaxial laminar flow. each ' layer ' of the microfluidic device ( cells seeded in ecm, a hydrogel sheath, and finally a calcium chloride solution ). the seeded cells culture within the hydrogel sheath for several days, and then the sheath is removed with viable cell fibers. various cell types were inserted into the ecm core, including myocytes, endothelial cells, nerve cell fibers, and epithelial cell fibers. this group then showed that these fibers can be woven together to fabricate tissues or organs in a mechanism similar to textile weaving. fibrous morphologies are advantageous in that they provide an alternative to traditional scaffold design, and many organs ( such as muscle ) are composed of fibrous cells. = = = bioartificial organs = = = an artificial organ is an engineered device that can be extra corporeal or implanted to support impaired or failing organ
we cut the volume of surface code s gates by 25 % by omitting a hadamard gate.
numerical model of the peripheral circulation and dynamical model of the large vessels and the heart are discussed in this paper. they combined together into the global model of blood circulation. some results of numerical simulations concerning matter transport through the human organism and heart diseases are represented in the end.
Question: The volume of blood each ventricle pumps per minute is called what?
A) trauma output
B) brain output
C) blood output
D) cardiac output
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D) cardiac output
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Context:
also called pain medicine, or algiatry ) is the medical discipline concerned with the relief of pain. pharmacogenomics is a form of individualized medicine. podiatric medicine is the study of, diagnosis, and medical treatment of disorders of the foot, ankle, lower limb, hip and lower back. sexual medicine is concerned with diagnosing, assessing and treating all disorders related to sexuality. sports medicine deals with the treatment and prevention and rehabilitation of sports / exercise injuries such as muscle spasms, muscle tears, injuries to ligaments ( ligament tears or ruptures ) and their repair in athletes, amateur and professional. therapeutics is the field, more commonly referenced in earlier periods of history, of the various remedies that can be used to treat disease and promote health. travel medicine or emporiatrics deals with health problems of international travelers or travelers across highly different environments. tropical medicine deals with the prevention and treatment of tropical diseases. it is studied separately in temperate climates where those diseases are quite unfamiliar to medical practitioners and their local clinical needs. urgent care focuses on delivery of unscheduled, walk - in care outside of the hospital emergency department for injuries and illnesses that are not severe enough to require care in an emergency department. in some jurisdictions this function is combined with the emergency department. veterinary medicine ; veterinarians apply similar techniques as physicians to the care of non - human animals. wilderness medicine entails the practice of medicine in the wild, where conventional medical facilities may not be available. = = education and legal controls = = medical education and training varies around the world. it typically involves entry level education at a university medical school, followed by a period of supervised practice or internship, or residency. this can be followed by postgraduate vocational training. a variety of teaching methods have been employed in medical education, still itself a focus of active research. in canada and the united states of america, a doctor of medicine degree, often abbreviated m. d., or a doctor of osteopathic medicine degree, often abbreviated as d. o. and unique to the united states, must be completed in and delivered from a recognized university. since knowledge, techniques, and medical technology continue to evolve at a rapid rate, many regulatory authorities require continuing medical education. medical practitioners upgrade their knowledge in various ways, including medical journals, seminars, conferences, and online programs. a database of objectives covering medical knowledge, as suggested by national societies across the united states, can be searched at http : / / data. medobjectives
##ry. immunology is the study of the immune system, which includes the innate and adaptive immune system in humans, for example. lifestyle medicine is the study of the chronic conditions, and how to prevent, treat and reverse them. medical physics is the study of the applications of physics principles in medicine. microbiology is the study of microorganisms, including protozoa, bacteria, fungi, and viruses. molecular biology is the study of molecular underpinnings of the process of replication, transcription and translation of the genetic material. neuroscience includes those disciplines of science that are related to the study of the nervous system. a main focus of neuroscience is the biology and physiology of the human brain and spinal cord. some related clinical specialties include neurology, neurosurgery and psychiatry. nutrition science ( theoretical focus ) and dietetics ( practical focus ) is the study of the relationship of food and drink to health and disease, especially in determining an optimal diet. medical nutrition therapy is done by dietitians and is prescribed for diabetes, cardiovascular diseases, weight and eating disorders, allergies, malnutrition, and neoplastic diseases. pathology as a science is the study of disease β the causes, course, progression and resolution thereof. pharmacology is the study of drugs and their actions. photobiology is the study of the interactions between non - ionizing radiation and living organisms. physiology is the study of the normal functioning of the body and the underlying regulatory mechanisms. radiobiology is the study of the interactions between ionizing radiation and living organisms. toxicology is the study of hazardous effects of drugs and poisons. = = = specialties = = = in the broadest meaning of " medicine ", there are many different specialties. in the uk, most specialities have their own body or college, which has its own entrance examination. these are collectively known as the royal colleges, although not all currently use the term " royal ". the development of a speciality is often driven by new technology ( such as the development of effective anaesthetics ) or ways of working ( such as emergency departments ) ; the new specialty leads to the formation of a unifying body of doctors and the prestige of administering their own examination. within medical circles, specialities usually fit into one of two broad categories : " medicine " and " surgery ". " medicine " refers to the practice of non - operative medicine, and most of its subspecialties require preliminary training in internal medicine. in the uk
the study of microorganisms, including protozoa, bacteria, fungi, and viruses. molecular biology is the study of molecular underpinnings of the process of replication, transcription and translation of the genetic material. neuroscience includes those disciplines of science that are related to the study of the nervous system. a main focus of neuroscience is the biology and physiology of the human brain and spinal cord. some related clinical specialties include neurology, neurosurgery and psychiatry. nutrition science ( theoretical focus ) and dietetics ( practical focus ) is the study of the relationship of food and drink to health and disease, especially in determining an optimal diet. medical nutrition therapy is done by dietitians and is prescribed for diabetes, cardiovascular diseases, weight and eating disorders, allergies, malnutrition, and neoplastic diseases. pathology as a science is the study of disease β the causes, course, progression and resolution thereof. pharmacology is the study of drugs and their actions. photobiology is the study of the interactions between non - ionizing radiation and living organisms. physiology is the study of the normal functioning of the body and the underlying regulatory mechanisms. radiobiology is the study of the interactions between ionizing radiation and living organisms. toxicology is the study of hazardous effects of drugs and poisons. = = = specialties = = = in the broadest meaning of " medicine ", there are many different specialties. in the uk, most specialities have their own body or college, which has its own entrance examination. these are collectively known as the royal colleges, although not all currently use the term " royal ". the development of a speciality is often driven by new technology ( such as the development of effective anaesthetics ) or ways of working ( such as emergency departments ) ; the new specialty leads to the formation of a unifying body of doctors and the prestige of administering their own examination. within medical circles, specialities usually fit into one of two broad categories : " medicine " and " surgery ". " medicine " refers to the practice of non - operative medicine, and most of its subspecialties require preliminary training in internal medicine. in the uk, this was traditionally evidenced by passing the examination for the membership of the royal college of physicians ( mrcp ) or the equivalent college in scotland or ireland. " surgery " refers to the practice of operative medicine, and most subspecialties in this area require preliminary training in general surgery, which in the uk leads to
more recently by the civilian world for news reporting and aerial photography. the pilot uses aircraft controls like a joystick or steering wheel, which create control signals which are transmitted to the drone by radio to control the flight surfaces and engine. a telemetry system transmits back a video image from a camera in the drone to allow the pilot to see where the aircraft is going, and data from a gps receiver giving the real - time position of the aircraft. uavs have sophisticated onboard automatic pilot systems that maintain stable flight and only require manual control to change directions. keyless entry system β a short - range handheld battery powered key fob transmitter, included with most modern cars, which can lock and unlock the doors of a vehicle from outside, eliminating the need to use a key. when a button is pressed, the transmitter sends a coded radio signal to a receiver in the vehicle, operating the locks. the fob must be close to the vehicle, typically within 5 to 20 meters. north america and japan use a frequency of 315 mhz, while europe uses 433. 92 and 868 mhz. some models can also remotely start the engine, to warm up the car. a security concern with all keyless entry systems is a replay attack, in which a thief uses a special receiver ( " code grabber " ) to record the radio signal during opening, which can later be replayed to open the door. to prevent this, keyless systems use a rolling code system in which a pseudorandom number generator in the remote control generates a different random key each time it is used. to prevent thieves from simulating the pseudorandom generator to calculate the next key, the radio signal is also encrypted. garage door opener β a short - range handheld transmitter which can open or close a building ' s electrically operated garage door from outside, so the owner can open the door upon arrival, and close it after departure. when a button is pressed the control transmits a coded fsk radio signal to a receiver in the opener, raising or lowering the door. modern openers use 310, 315 or 390 mhz. to prevent a thief using a replay attack, modern openers use a rolling code system. radio - controlled models β a popular hobby is playing with radio - controlled model boats, cars, airplanes, and helicopters ( quadcopters ) which are controlled by radio signals from a handheld console with a joystick. most recent transmitters use the 2. 4 ghz ism band with multiple control channels modulated with pwm, pc
known as anaesthetics ) : concerned with the perioperative management of the surgical patient. the anesthesiologist ' s role during surgery is to prevent derangement in the vital organs ' ( i. e. brain, heart, kidneys ) functions and postoperative pain. outside of the operating room, the anesthesiology physician also serves the same function in the labor and delivery ward, and some are specialized in critical medicine. emergency medicine is concerned with the diagnosis and treatment of acute or life - threatening conditions, including trauma, surgical, medical, pediatric, and psychiatric emergencies. family medicine, family practice, general practice or primary care is, in many countries, the first port - of - call for patients with non - emergency medical problems. family physicians often provide services across a broad range of settings including office based practices, emergency department coverage, inpatient care, and nursing home care. medical genetics is concerned with the diagnosis and management of hereditary disorders. neurology is concerned with diseases of the nervous system. in the uk, neurology is a subspecialty of general medicine. obstetrics and gynecology ( often abbreviated as ob / gyn ( american english ) or obs & gynae ( british english ) ) are concerned respectively with childbirth and the female reproductive and associated organs. reproductive medicine and fertility medicine are generally practiced by gynecological specialists. pediatrics ( ae ) or paediatrics ( be ) is devoted to the care of infants, children, and adolescents. like internal medicine, there are many pediatric subspecialties for specific age ranges, organ systems, disease classes, and sites of care delivery. pharmaceutical medicine is the medical scientific discipline concerned with the discovery, development, evaluation, registration, monitoring and medical aspects of marketing of medicines for the benefit of patients and public health. physical medicine and rehabilitation ( or physiatry ) is concerned with functional improvement after injury, illness, or congenital disorders. podiatric medicine is the study of, diagnosis, and medical and surgical treatment of disorders of the foot, ankle, lower limb, hip and lower back. preventive medicine is the branch of medicine concerned with preventing disease. community health or public health is an aspect of health services concerned with threats to the overall health of a community based on population health analysis. psychiatry is the branch of medicine concerned with the bio - psycho - social study of the etiology, diagnosis, treatment and prevention of cognitive, perceptual, emotional and behavioral disorders.
used to manufacture existing medicines relatively easily and cheaply. the first genetically engineered products were medicines designed to treat human diseases. to cite one example, in 1978 genentech developed synthetic humanized insulin by joining its gene with a plasmid vector inserted into the bacterium escherichia coli. insulin, widely used for the treatment of diabetes, was previously extracted from the pancreas of abattoir animals ( cattle or pigs ). the genetically engineered bacteria are able to produce large quantities of synthetic human insulin at relatively low cost. biotechnology has also enabled emerging therapeutics like gene therapy. the application of biotechnology to basic science ( for example through the human genome project ) has also dramatically improved our understanding of biology and as our scientific knowledge of normal and disease biology has increased, our ability to develop new medicines to treat previously untreatable diseases has increased as well. genetic testing allows the genetic diagnosis of vulnerabilities to inherited diseases, and can also be used to determine a child ' s parentage ( genetic mother and father ) or in general a person ' s ancestry. in addition to studying chromosomes to the level of individual genes, genetic testing in a broader sense includes biochemical tests for the possible presence of genetic diseases, or mutant forms of genes associated with increased risk of developing genetic disorders. genetic testing identifies changes in chromosomes, genes, or proteins. most of the time, testing is used to find changes that are associated with inherited disorders. the results of a genetic test can confirm or rule out a suspected genetic condition or help determine a person ' s chance of developing or passing on a genetic disorder. as of 2011 several hundred genetic tests were in use. since genetic testing may open up ethical or psychological problems, genetic testing is often accompanied by genetic counseling. = = = agriculture = = = genetically modified crops ( " gm crops ", or " biotech crops " ) are plants used in agriculture, the dna of which has been modified with genetic engineering techniques. in most cases, the main aim is to introduce a new trait that does not occur naturally in the species. biotechnology firms can contribute to future food security by improving the nutrition and viability of urban agriculture. furthermore, the protection of intellectual property rights encourages private sector investment in agrobiotechnology. examples in food crops include resistance to certain pests, diseases, stressful environmental conditions, resistance to chemical treatments ( e. g. resistance to a herbicide ), reduction of spoilage, or improving the nutrient profile of the crop. examples in non - food crops include production of
##artificial liver device, " temporary liver ", extracorporeal liver assist device ( elad ) : the human hepatocyte cell line ( c3a line ) in a hollow fiber bioreactor can mimic the hepatic function of the liver for acute instances of liver failure. a fully capable elad would temporarily function as an individual ' s liver, thus avoiding transplantation and allowing regeneration of their own liver. artificial pancreas : research involves using islet cells to regulate the body ' s blood sugar, particularly in cases of diabetes. biochemical factors may be used to cause human pluripotent stem cells to differentiate ( turn into ) cells that function similarly to beta cells, which are in an islet cell in charge of producing insulin. artificial bladders : anthony atala ( wake forest university ) has successfully implanted artificial bladders, constructed of cultured cells seeded onto a bladder - shaped scaffold, into seven out of approximately 20 human test subjects as part of a long - term experiment. cartilage : lab - grown cartilage, cultured in vitro on a scaffold, was successfully used as an autologous transplant to repair patients ' knees. scaffold - free cartilage : cartilage generated without the use of exogenous scaffold material. in this methodology, all material in the construct is cellular produced directly by the cells. bioartificial heart : doris taylor ' s lab constructed a biocompatible rat heart by re - cellularising a de - cellularised rat heart. this scaffold and cells were placed in a bioreactor, where it matured to become a partially or fully transplantable organ. the work was called a " landmark ". the lab first stripped the cells away from a rat heart ( a process called " decellularization " ) and then injected rat stem cells into the decellularized rat heart. tissue - engineered blood vessels : blood vessels that have been grown in a lab and can be used to repair damaged blood vessels without eliciting an immune response. tissue engineered blood vessels have been developed by many different approaches. they could be implanted as pre - seeded cellularized blood vessels, as acellular vascular grafts made with decellularized vessels or synthetic vascular grafts. artificial skin constructed from human skin cells embedded in a hydrogel, such as in the case of bio - printed constructs for battlefield burn repairs. artificial bone marrow : bone marrow cultured in vitro to
listen ), generally in that order, although auscultation occurs prior to percussion and palpation for abdominal assessments. the clinical examination involves the study of : abdomen and rectum cardiovascular ( heart and blood vessels ) general appearance of the patient and specific indicators of disease ( nutritional status, presence of jaundice, pallor or clubbing ) genitalia ( and pregnancy if the patient is or could be pregnant ) head, eye, ear, nose, and throat ( heent ) musculoskeletal ( including spine and extremities ) neurological ( consciousness, awareness, brain, vision, cranial nerves, spinal cord and peripheral nerves ) psychiatric ( orientation, mental state, mood, evidence of abnormal perception or thought ). respiratory ( large airways and lungs ) skin vital signs including height, weight, body temperature, blood pressure, pulse, respiration rate, and hemoglobin oxygen saturation it is to likely focus on areas of interest highlighted in the medical history and may not include everything listed above. the treatment plan may include ordering additional medical laboratory tests and medical imaging studies, starting therapy, referral to a specialist, or watchful observation. a follow - up may be advised. depending upon the health insurance plan and the managed care system, various forms of " utilization review ", such as prior authorization of tests, may place barriers on accessing expensive services. the medical decision - making ( mdm ) process includes the analysis and synthesis of all the above data to come up with a list of possible diagnoses ( the differential diagnoses ), along with an idea of what needs to be done to obtain a definitive diagnosis that would explain the patient ' s problem. on subsequent visits, the process may be repeated in an abbreviated manner to obtain any new history, symptoms, physical findings, lab or imaging results, or specialist consultations. = = institutions = = contemporary medicine is, in general, conducted within health care systems. legal, credentialing, and financing frameworks are established by individual governments, augmented on occasion by international organizations, such as churches. the characteristics of any given health care system have a significant impact on the way medical care is provided. from ancient times, christian emphasis on practical charity gave rise to the development of systematic nursing and hospitals, and the catholic church today remains the largest non - government provider of medical services in the world. advanced industrial countries ( with the exception of the united states ) and many developing countries provide medical services through a system of universal health care that aims to
judgments to the practice of medicine. medical humanities includes the humanities ( literature, philosophy, ethics, history and religion ), social science ( anthropology, cultural studies, psychology, sociology ), and the arts ( literature, theater, film, and visual arts ) and their application to medical education and practice. nosokinetics is the science / subject of measuring and modelling the process of care in health and social care systems. nosology is the classification of diseases for various purposes. occupational medicine is the provision of health advice to organizations and individuals to ensure that the highest standards of health and safety at work can be achieved and maintained. pain management ( also called pain medicine, or algiatry ) is the medical discipline concerned with the relief of pain. pharmacogenomics is a form of individualized medicine. podiatric medicine is the study of, diagnosis, and medical treatment of disorders of the foot, ankle, lower limb, hip and lower back. sexual medicine is concerned with diagnosing, assessing and treating all disorders related to sexuality. sports medicine deals with the treatment and prevention and rehabilitation of sports / exercise injuries such as muscle spasms, muscle tears, injuries to ligaments ( ligament tears or ruptures ) and their repair in athletes, amateur and professional. therapeutics is the field, more commonly referenced in earlier periods of history, of the various remedies that can be used to treat disease and promote health. travel medicine or emporiatrics deals with health problems of international travelers or travelers across highly different environments. tropical medicine deals with the prevention and treatment of tropical diseases. it is studied separately in temperate climates where those diseases are quite unfamiliar to medical practitioners and their local clinical needs. urgent care focuses on delivery of unscheduled, walk - in care outside of the hospital emergency department for injuries and illnesses that are not severe enough to require care in an emergency department. in some jurisdictions this function is combined with the emergency department. veterinary medicine ; veterinarians apply similar techniques as physicians to the care of non - human animals. wilderness medicine entails the practice of medicine in the wild, where conventional medical facilities may not be available. = = education and legal controls = = medical education and training varies around the world. it typically involves entry level education at a university medical school, followed by a period of supervised practice or internship, or residency. this can be followed by postgraduate vocational training. a variety of teaching methods have been employed in medical education, still itself a focus of active research. in canada and the united states of
, characterizing organs as predominantly yin or yang, and understood the relationship between the pulse, the heart, and the flow of blood in the body centuries before it became accepted in the west. little evidence survives of how ancient indian cultures around the indus river understood nature, but some of their perspectives may be reflected in the vedas, a set of sacred hindu texts. they reveal a conception of the universe as ever - expanding and constantly being recycled and reformed. surgeons in the ayurvedic tradition saw health and illness as a combination of three humors : wind, bile and phlegm. a healthy life resulted from a balance among these humors. in ayurvedic thought, the body consisted of five elements : earth, water, fire, wind, and space. ayurvedic surgeons performed complex surgeries and developed a detailed understanding of human anatomy. pre - socratic philosophers in ancient greek culture brought natural philosophy a step closer to direct inquiry about cause and effect in nature between 600 and 400 bc. however, an element of magic and mythology remained. natural phenomena such as earthquakes and eclipses were explained increasingly in the context of nature itself instead of being attributed to angry gods. thales of miletus, an early philosopher who lived from 625 to 546 bc, explained earthquakes by theorizing that the world floated on water and that water was the fundamental element in nature. in the 5th century bc, leucippus was an early exponent of atomism, the idea that the world is made up of fundamental indivisible particles. pythagoras applied greek innovations in mathematics to astronomy and suggested that the earth was spherical. = = = aristotelian natural philosophy ( 400 bc β 1100 ad ) = = = later socratic and platonic thought focused on ethics, morals, and art and did not attempt an investigation of the physical world ; plato criticized pre - socratic thinkers as materialists and anti - religionists. aristotle, however, a student of plato who lived from 384 to 322 bc, paid closer attention to the natural world in his philosophy. in his history of animals, he described the inner workings of 110 species, including the stingray, catfish and bee. he investigated chick embryos by breaking open eggs and observing them at various stages of development. aristotle ' s works were influential through the 16th century, and he is considered to be the father of biology for his pioneering work in that science. he also presented philosophies about physics, nature, and astronomy using
Question: How does consuming enterobactin help our body?
A) builds excess iron
B) eliminates excess iron
C) eliminates excess fat
D) eliminates excess oxygen
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B) eliminates excess iron
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Context:
known as " algae " have unique organelles known as chloroplasts. chloroplasts are thought to be descended from cyanobacteria that formed endosymbiotic relationships with ancient plant and algal ancestors. chloroplasts and cyanobacteria contain the blue - green pigment chlorophyll a. chlorophyll a ( as well as its plant and green algal - specific cousin chlorophyll b ) absorbs light in the blue - violet and orange / red parts of the spectrum while reflecting and transmitting the green light that we see as the characteristic colour of these organisms. the energy in the red and blue light that these pigments absorb is used by chloroplasts to make energy - rich carbon compounds from carbon dioxide and water by oxygenic photosynthesis, a process that generates molecular oxygen ( o2 ) as a by - product. the light energy captured by chlorophyll a is initially in the form of electrons ( and later a proton gradient ) that is used to make molecules of atp and nadph which temporarily store and transport energy. their energy is used in the light - independent reactions of the calvin cycle by the enzyme rubisco to produce molecules of the 3 - carbon sugar glyceraldehyde 3 - phosphate ( g3p ). glyceraldehyde 3 - phosphate is the first product of photosynthesis and the raw material from which glucose and almost all other organic molecules of biological origin are synthesised. some of the glucose is converted to starch which is stored in the chloroplast. starch is the characteristic energy store of most land plants and algae, while inulin, a polymer of fructose is used for the same purpose in the sunflower family asteraceae. some of the glucose is converted to sucrose ( common table sugar ) for export to the rest of the plant. unlike in animals ( which lack chloroplasts ), plants and their eukaryote relatives have delegated many biochemical roles to their chloroplasts, including synthesising all their fatty acids, and most amino acids. the fatty acids that chloroplasts make are used for many things, such as providing material to build cell membranes out of and making the polymer cutin which is found in the plant cuticle that protects land plants from drying out. plants synthesise a number of unique polymers like the polysaccharide molecules cellulose,
their primary metabolism like the photosynthetic calvin cycle and crassulacean acid metabolism. others make specialised materials like the cellulose and lignin used to build their bodies, and secondary products like resins and aroma compounds. plants and various other groups of photosynthetic eukaryotes collectively known as " algae " have unique organelles known as chloroplasts. chloroplasts are thought to be descended from cyanobacteria that formed endosymbiotic relationships with ancient plant and algal ancestors. chloroplasts and cyanobacteria contain the blue - green pigment chlorophyll a. chlorophyll a ( as well as its plant and green algal - specific cousin chlorophyll b ) absorbs light in the blue - violet and orange / red parts of the spectrum while reflecting and transmitting the green light that we see as the characteristic colour of these organisms. the energy in the red and blue light that these pigments absorb is used by chloroplasts to make energy - rich carbon compounds from carbon dioxide and water by oxygenic photosynthesis, a process that generates molecular oxygen ( o2 ) as a by - product. the light energy captured by chlorophyll a is initially in the form of electrons ( and later a proton gradient ) that is used to make molecules of atp and nadph which temporarily store and transport energy. their energy is used in the light - independent reactions of the calvin cycle by the enzyme rubisco to produce molecules of the 3 - carbon sugar glyceraldehyde 3 - phosphate ( g3p ). glyceraldehyde 3 - phosphate is the first product of photosynthesis and the raw material from which glucose and almost all other organic molecules of biological origin are synthesised. some of the glucose is converted to starch which is stored in the chloroplast. starch is the characteristic energy store of most land plants and algae, while inulin, a polymer of fructose is used for the same purpose in the sunflower family asteraceae. some of the glucose is converted to sucrose ( common table sugar ) for export to the rest of the plant. unlike in animals ( which lack chloroplasts ), plants and their eukaryote relatives have delegated many biochemical roles to their chloroplasts, including synthesising all their fatty acids, and most amino acids. the fatty acids that
, which would exclude fungi and some algae. plant cells were derived by endosymbiosis of a cyanobacterium into an early eukaryote about one billion years ago, which gave rise to chloroplasts. the first several clades that emerged following primary endosymbiosis were aquatic and most of the aquatic photosynthetic eukaryotic organisms are collectively described as algae, which is a term of convenience as not all algae are closely related. algae comprise several distinct clades such as glaucophytes, which are microscopic freshwater algae that may have resembled in form to the early unicellular ancestor of plantae. unlike glaucophytes, the other algal clades such as red and green algae are multicellular. green algae comprise three major clades : chlorophytes, coleochaetophytes, and stoneworts. fungi are eukaryotes that digest foods outside their bodies, secreting digestive enzymes that break down large food molecules before absorbing them through their cell membranes. many fungi are also saprobes, feeding on dead organic matter, making them important decomposers in ecological systems. animals are multicellular eukaryotes. with few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and grow from a hollow sphere of cells, the blastula, during embryonic development. over 1. 5 million living animal species have been described β of which around 1 million are insects β but it has been estimated there are over 7 million animal species in total. they have complex interactions with each other and their environments, forming intricate food webs. = = = viruses = = = viruses are submicroscopic infectious agents that replicate inside the cells of organisms. viruses infect all types of life forms, from animals and plants to microorganisms, including bacteria and archaea. more than 6, 000 virus species have been described in detail. viruses are found in almost every ecosystem on earth and are the most numerous type of biological entity. the origins of viruses in the evolutionary history of life are unclear : some may have evolved from plasmids β pieces of dna that can move between cells β while others may have evolved from bacteria. in evolution, viruses are an important means of horizontal gene transfer, which increases genetic diversity in a way analogous to sexual reproduction. because viruses possess some but not all characteristics of life, they have been described as " organisms at the edge of life ",
is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. in most cases, oxygen is released as a waste product. most plants, algae, and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of the earth ' s atmosphere, and supplies most of the energy necessary for life on earth. photosynthesis has four stages : light absorption, electron transport, atp synthesis, and carbon fixation. light absorption is the initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to proteins in the thylakoid membranes. the absorbed light energy is used to remove electrons from a donor ( water ) to a primary electron acceptor, a quinone designated as q. in the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach a final electron acceptor, which is usually the oxidized form of nadp +, which is reduced to nadph, a process that takes place in a protein complex called photosystem i ( psi ). the transport of electrons is coupled to the movement of protons ( or hydrogen ) from the stroma to the thylakoid membrane, which forms a ph gradient across the membrane as hydrogen becomes more concentrated in the lumen than in the stroma. this is analogous to the proton - motive force generated across the inner mitochondrial membrane in aerobic respiration. during the third stage of photosynthesis, the movement of protons down their concentration gradients from the thylakoid lumen to the stroma through the atp synthase is coupled to the synthesis of atp by that same atp synthase. the nadph and atps generated by the light - dependent reactions in the second and third stages, respectively, provide the energy and electrons to drive the synthesis of glucose by fixing atmospheric carbon dioxide into existing organic carbon compounds, such as ribulose bisphosphate ( rubp ) in a sequence of light - independent ( or dark ) reactions called the calvin cycle. = = = cell signaling = = = cell signaling ( or communication ) is the ability of cells to receive, process, and transmit signals with its environment and with itself. signals can be non - chemical such as light, electrical impulses, and heat, or chemical signals ( or ligands ) that interact with receptors, which can be found embedded in the cell membrane of another cell or located deep inside
pigment chlorophyll a. chlorophyll a ( as well as its plant and green algal - specific cousin chlorophyll b ) absorbs light in the blue - violet and orange / red parts of the spectrum while reflecting and transmitting the green light that we see as the characteristic colour of these organisms. the energy in the red and blue light that these pigments absorb is used by chloroplasts to make energy - rich carbon compounds from carbon dioxide and water by oxygenic photosynthesis, a process that generates molecular oxygen ( o2 ) as a by - product. the light energy captured by chlorophyll a is initially in the form of electrons ( and later a proton gradient ) that is used to make molecules of atp and nadph which temporarily store and transport energy. their energy is used in the light - independent reactions of the calvin cycle by the enzyme rubisco to produce molecules of the 3 - carbon sugar glyceraldehyde 3 - phosphate ( g3p ). glyceraldehyde 3 - phosphate is the first product of photosynthesis and the raw material from which glucose and almost all other organic molecules of biological origin are synthesised. some of the glucose is converted to starch which is stored in the chloroplast. starch is the characteristic energy store of most land plants and algae, while inulin, a polymer of fructose is used for the same purpose in the sunflower family asteraceae. some of the glucose is converted to sucrose ( common table sugar ) for export to the rest of the plant. unlike in animals ( which lack chloroplasts ), plants and their eukaryote relatives have delegated many biochemical roles to their chloroplasts, including synthesising all their fatty acids, and most amino acids. the fatty acids that chloroplasts make are used for many things, such as providing material to build cell membranes out of and making the polymer cutin which is found in the plant cuticle that protects land plants from drying out. plants synthesise a number of unique polymers like the polysaccharide molecules cellulose, pectin and xyloglucan from which the land plant cell wall is constructed. vascular land plants make lignin, a polymer used to strengthen the secondary cell walls of xylem tracheids and vessels to keep them from collapsing when a plant sucks water through them under water stress. lignin
- people relationships arose between the indigenous people of canada in identifying edible plants from inedible plants. this relationship the indigenous people had with plants was recorded by ethnobotanists. = = plant biochemistry = = plant biochemistry is the study of the chemical processes used by plants. some of these processes are used in their primary metabolism like the photosynthetic calvin cycle and crassulacean acid metabolism. others make specialised materials like the cellulose and lignin used to build their bodies, and secondary products like resins and aroma compounds. plants and various other groups of photosynthetic eukaryotes collectively known as " algae " have unique organelles known as chloroplasts. chloroplasts are thought to be descended from cyanobacteria that formed endosymbiotic relationships with ancient plant and algal ancestors. chloroplasts and cyanobacteria contain the blue - green pigment chlorophyll a. chlorophyll a ( as well as its plant and green algal - specific cousin chlorophyll b ) absorbs light in the blue - violet and orange / red parts of the spectrum while reflecting and transmitting the green light that we see as the characteristic colour of these organisms. the energy in the red and blue light that these pigments absorb is used by chloroplasts to make energy - rich carbon compounds from carbon dioxide and water by oxygenic photosynthesis, a process that generates molecular oxygen ( o2 ) as a by - product. the light energy captured by chlorophyll a is initially in the form of electrons ( and later a proton gradient ) that is used to make molecules of atp and nadph which temporarily store and transport energy. their energy is used in the light - independent reactions of the calvin cycle by the enzyme rubisco to produce molecules of the 3 - carbon sugar glyceraldehyde 3 - phosphate ( g3p ). glyceraldehyde 3 - phosphate is the first product of photosynthesis and the raw material from which glucose and almost all other organic molecules of biological origin are synthesised. some of the glucose is converted to starch which is stored in the chloroplast. starch is the characteristic energy store of most land plants and algae, while inulin, a polymer of fructose is used for the same purpose in the sunflower family asteraceae. some of the glucose is converted to sucrose ( common table
substrate - level phosphorylation, which does not require oxygen. = = = photosynthesis = = = photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organism ' s metabolic activities via cellular respiration. this chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. in most cases, oxygen is released as a waste product. most plants, algae, and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of the earth ' s atmosphere, and supplies most of the energy necessary for life on earth. photosynthesis has four stages : light absorption, electron transport, atp synthesis, and carbon fixation. light absorption is the initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to proteins in the thylakoid membranes. the absorbed light energy is used to remove electrons from a donor ( water ) to a primary electron acceptor, a quinone designated as q. in the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach a final electron acceptor, which is usually the oxidized form of nadp +, which is reduced to nadph, a process that takes place in a protein complex called photosystem i ( psi ). the transport of electrons is coupled to the movement of protons ( or hydrogen ) from the stroma to the thylakoid membrane, which forms a ph gradient across the membrane as hydrogen becomes more concentrated in the lumen than in the stroma. this is analogous to the proton - motive force generated across the inner mitochondrial membrane in aerobic respiration. during the third stage of photosynthesis, the movement of protons down their concentration gradients from the thylakoid lumen to the stroma through the atp synthase is coupled to the synthesis of atp by that same atp synthase. the nadph and atps generated by the light - dependent reactions in the second and third stages, respectively, provide the energy and electrons to drive the synthesis of glucose by fixing atmospheric carbon dioxide into existing organic carbon compounds, such as ribulose bisphosphate ( rubp ) in a sequence of light - independent ( or dark ) reactions called the calvin cycle. = = = cell signaling = = = cell signaling ( or communication ) is the
aquatic and most of the aquatic photosynthetic eukaryotic organisms are collectively described as algae, which is a term of convenience as not all algae are closely related. algae comprise several distinct clades such as glaucophytes, which are microscopic freshwater algae that may have resembled in form to the early unicellular ancestor of plantae. unlike glaucophytes, the other algal clades such as red and green algae are multicellular. green algae comprise three major clades : chlorophytes, coleochaetophytes, and stoneworts. fungi are eukaryotes that digest foods outside their bodies, secreting digestive enzymes that break down large food molecules before absorbing them through their cell membranes. many fungi are also saprobes, feeding on dead organic matter, making them important decomposers in ecological systems. animals are multicellular eukaryotes. with few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and grow from a hollow sphere of cells, the blastula, during embryonic development. over 1. 5 million living animal species have been described β of which around 1 million are insects β but it has been estimated there are over 7 million animal species in total. they have complex interactions with each other and their environments, forming intricate food webs. = = = viruses = = = viruses are submicroscopic infectious agents that replicate inside the cells of organisms. viruses infect all types of life forms, from animals and plants to microorganisms, including bacteria and archaea. more than 6, 000 virus species have been described in detail. viruses are found in almost every ecosystem on earth and are the most numerous type of biological entity. the origins of viruses in the evolutionary history of life are unclear : some may have evolved from plasmids β pieces of dna that can move between cells β while others may have evolved from bacteria. in evolution, viruses are an important means of horizontal gene transfer, which increases genetic diversity in a way analogous to sexual reproduction. because viruses possess some but not all characteristics of life, they have been described as " organisms at the edge of life ", and as self - replicators. = = ecology = = ecology is the study of the distribution and abundance of life, the interaction between organisms and their environment. = = = ecosystems = = = the community of living ( biotic ) organisms in conjunction with the nonliving ( abiotic ) components ( e.
industrial applications. this branch of biotechnology is the most used for the industries of refining and combustion principally on the production of bio - oils with photosynthetic micro - algae. green biotechnology is biotechnology applied to agricultural processes. an example would be the selection and domestication of plants via micropropagation. another example is the designing of transgenic plants to grow under specific environments in the presence ( or absence ) of chemicals. one hope is that green biotechnology might produce more environmentally friendly solutions than traditional industrial agriculture. an example of this is the engineering of a plant to express a pesticide, thereby ending the need of external application of pesticides. an example of this would be bt corn. whether or not green biotechnology products such as this are ultimately more environmentally friendly is a topic of considerable debate. it is commonly considered as the next phase of green revolution, which can be seen as a platform to eradicate world hunger by using technologies which enable the production of more fertile and resistant, towards biotic and abiotic stress, plants and ensures application of environmentally friendly fertilizers and the use of biopesticides, it is mainly focused on the development of agriculture. on the other hand, some of the uses of green biotechnology involve microorganisms to clean and reduce waste. red biotechnology is the use of biotechnology in the medical and pharmaceutical industries, and health preservation. this branch involves the production of vaccines and antibiotics, regenerative therapies, creation of artificial organs and new diagnostics of diseases. as well as the development of hormones, stem cells, antibodies, sirna and diagnostic tests. white biotechnology, also known as industrial biotechnology, is biotechnology applied to industrial processes. an example is the designing of an organism to produce a useful chemical. another example is the using of enzymes as industrial catalysts to either produce valuable chemicals or destroy hazardous / polluting chemicals. white biotechnology tends to consume less in resources than traditional processes used to produce industrial goods. yellow biotechnology refers to the use of biotechnology in food production ( food industry ), for example in making wine ( winemaking ), cheese ( cheesemaking ), and beer ( brewing ) by fermentation. it has also been used to refer to biotechnology applied to insects. this includes biotechnology - based approaches for the control of harmful insects, the characterisation and utilisation of active ingredients or genes of insects for research, or application in agriculture and medicine and various other approaches. gray biotechnology is dedicated to environmental applications, and focused on the maintenance of biodiversity and the remotion of poll
pathogens in agriculture and natural ecosystems. ethnobotany is the study of the relationships between plants and people. when applied to the investigation of historical plant β people relationships ethnobotany may be referred to as archaeobotany or palaeoethnobotany. some of the earliest plant - people relationships arose between the indigenous people of canada in identifying edible plants from inedible plants. this relationship the indigenous people had with plants was recorded by ethnobotanists. = = plant biochemistry = = plant biochemistry is the study of the chemical processes used by plants. some of these processes are used in their primary metabolism like the photosynthetic calvin cycle and crassulacean acid metabolism. others make specialised materials like the cellulose and lignin used to build their bodies, and secondary products like resins and aroma compounds. plants and various other groups of photosynthetic eukaryotes collectively known as " algae " have unique organelles known as chloroplasts. chloroplasts are thought to be descended from cyanobacteria that formed endosymbiotic relationships with ancient plant and algal ancestors. chloroplasts and cyanobacteria contain the blue - green pigment chlorophyll a. chlorophyll a ( as well as its plant and green algal - specific cousin chlorophyll b ) absorbs light in the blue - violet and orange / red parts of the spectrum while reflecting and transmitting the green light that we see as the characteristic colour of these organisms. the energy in the red and blue light that these pigments absorb is used by chloroplasts to make energy - rich carbon compounds from carbon dioxide and water by oxygenic photosynthesis, a process that generates molecular oxygen ( o2 ) as a by - product. the light energy captured by chlorophyll a is initially in the form of electrons ( and later a proton gradient ) that is used to make molecules of atp and nadph which temporarily store and transport energy. their energy is used in the light - independent reactions of the calvin cycle by the enzyme rubisco to produce molecules of the 3 - carbon sugar glyceraldehyde 3 - phosphate ( g3p ). glyceraldehyde 3 - phosphate is the first product of photosynthesis and the raw material from which glucose and almost all other organic molecules of biological origin are synthesised. some of the glucose is converted to star
Question: Green cyanobacteria on a lake produce food through what process?
A) glycolysis
B) reverse transferase
C) photosynthesis
D) spermatogenesis
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C) photosynthesis
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Context:
##ulating the liquid below from the cold air above. water has the capacity to absorb energy, giving it a higher specific heat capacity than other solvents such as ethanol. thus, a large amount of energy is needed to break the hydrogen bonds between water molecules to convert liquid water into water vapor. as a molecule, water is not completely stable as each water molecule continuously dissociates into hydrogen and hydroxyl ions before reforming into a water molecule again. in pure water, the number of hydrogen ions balances ( or equals ) the number of hydroxyl ions, resulting in a ph that is neutral. = = = organic compounds = = = organic compounds are molecules that contain carbon bonded to another element such as hydrogen. with the exception of water, nearly all the molecules that make up each organism contain carbon. carbon can form covalent bonds with up to four other atoms, enabling it to form diverse, large, and complex molecules. for example, a single carbon atom can form four single covalent bonds such as in methane, two double covalent bonds such as in carbon dioxide ( co2 ), or a triple covalent bond such as in carbon monoxide ( co ). moreover, carbon can form very long chains of interconnecting carbon β carbon bonds such as octane or ring - like structures such as glucose. the simplest form of an organic molecule is the hydrocarbon, which is a large family of organic compounds that are composed of hydrogen atoms bonded to a chain of carbon atoms. a hydrocarbon backbone can be substituted by other elements such as oxygen ( o ), hydrogen ( h ), phosphorus ( p ), and sulfur ( s ), which can change the chemical behavior of that compound. groups of atoms that contain these elements ( o -, h -, p -, and s - ) and are bonded to a central carbon atom or skeleton are called functional groups. there are six prominent functional groups that can be found in organisms : amino group, carboxyl group, carbonyl group, hydroxyl group, phosphate group, and sulfhydryl group. in 1953, the miller β urey experiment showed that organic compounds could be synthesized abiotically within a closed system mimicking the conditions of early earth, thus suggesting that complex organic molecules could have arisen spontaneously in early earth ( see abiogenesis ). = = = macromolecules = = = macromolecules are large molecules made up of smaller subunits or monomers. monomers include sugars, amino acids,
10 kgy most food, which is ( with regard to warming ) physically equivalent to water, would warm by only about 2. 5 Β°c ( 4. 5 Β°f ). the specialty of processing food by ionizing radiation is the fact, that the energy density per atomic transition is very high, it can cleave molecules and induce ionization ( hence the name ) which cannot be achieved by mere heating. this is the reason for new beneficial effects, however at the same time, for new concerns. the treatment of solid food by ionizing radiation can provide an effect similar to heat pasteurization of liquids, such as milk. however, the use of the term, cold pasteurization, to describe irradiated foods is controversial, because pasteurization and irradiation are fundamentally different processes, although the intended end results can in some cases be similar. detractors of food irradiation have concerns about the health hazards of induced radioactivity. a report for the industry advocacy group american council on science and health entitled " irradiated foods " states : " the types of radiation sources approved for the treatment of foods have specific energy levels well below that which would cause any element in food to become radioactive. food undergoing irradiation does not become any more radioactive than luggage passing through an airport x - ray scanner or teeth that have been x - rayed. " food irradiation is currently permitted by over 40 countries and volumes are estimated to exceed 500, 000 metric tons ( 490, 000 long tons ; 550, 000 short tons ) annually worldwide. food irradiation is essentially a non - nuclear technology ; it relies on the use of ionizing radiation which may be generated by accelerators for electrons and conversion into bremsstrahlung, but which may use also gamma - rays from nuclear decay. there is a worldwide industry for processing by ionizing radiation, the majority by number and by processing power using accelerators. food irradiation is only a niche application compared to medical supplies, plastic materials, raw materials, gemstones, cables and wires, etc. = = accidents = = nuclear accidents, because of the powerful forces involved, are often very dangerous. historically, the first incidents involved fatal radiation exposure. marie curie died from aplastic anemia which resulted from her high levels of exposure. two scientists, an american and canadian respectively, harry daghlian and louis slotin, died after mishandling the same plutonium mass. unlike conventional weapons, the intense light, heat, and explosive force is
or solid as is the case with water ( h2o ) ; a liquid at room temperature because its molecules are bound by hydrogen bonds. whereas hydrogen sulfide ( h2s ) is a gas at room temperature and standard pressure, as its molecules are bound by weaker dipole β dipole interactions. the transfer of energy from one chemical substance to another depends on the size of energy quanta emitted from one substance. however, heat energy is often transferred more easily from almost any substance to another because the phonons responsible for vibrational and rotational energy levels in a substance have much less energy than photons invoked for the electronic energy transfer. thus, because vibrational and rotational energy levels are more closely spaced than electronic energy levels, heat is more easily transferred between substances relative to light or other forms of electronic energy. for example, ultraviolet electromagnetic radiation is not transferred with as much efficacy from one substance to another as thermal or electrical energy. the existence of characteristic energy levels for different chemical substances is useful for their identification by the analysis of spectral lines. different kinds of spectra are often used in chemical spectroscopy, e. g. ir, microwave, nmr, esr, etc. spectroscopy is also used to identify the composition of remote objects β like stars and distant galaxies β by analyzing their radiation spectra. the term chemical energy is often used to indicate the potential of a chemical substance to undergo a transformation through a chemical reaction or to transform other chemical substances. = = = reaction = = = when a chemical substance is transformed as a result of its interaction with another substance or with energy, a chemical reaction is said to have occurred. a chemical reaction is therefore a concept related to the " reaction " of a substance when it comes in close contact with another, whether as a mixture or a solution ; exposure to some form of energy, or both. it results in some energy exchange between the constituents of the reaction as well as with the system environment, which may be designed vessels β often laboratory glassware. chemical reactions can result in the formation or dissociation of molecules, that is, molecules breaking apart to form two or more molecules or rearrangement of atoms within or across molecules. chemical reactions usually involve the making or breaking of chemical bonds. oxidation, reduction, dissociation, acid β base neutralization and molecular rearrangement are some examples of common chemical reactions. a chemical reaction can be symbolically depicted through a chemical equation. while in a non - nuclear chemical reaction the number and kind of atoms on both sides of the equation are equal, for
is also higher at high temperature, as shown by carnot ' s theorem. in a conventional metallic engine, much of the energy released from the fuel must be dissipated as waste heat in order to prevent a meltdown of the metallic parts. despite all of these desirable properties, such engines are not in production because the manufacturing of ceramic parts in the requisite precision and durability is difficult. imperfection in the ceramic leads to cracks, which can lead to potentially dangerous equipment failure. such engines are possible in laboratory settings, but mass - production is not feasible with current technology. work is being done in developing ceramic parts for gas turbine engines. currently, even blades made of advanced metal alloys used in the engines ' hot section require cooling and careful limiting of operating temperatures. turbine engines made with ceramics could operate more efficiently, giving aircraft greater range and payload for a set amount of fuel. recently, there have been advances in ceramics which include bio - ceramics, such as dental implants and synthetic bones. hydroxyapatite, the natural mineral component of bone, has been made synthetically from a number of biological and chemical sources and can be formed into ceramic materials. orthopedic implants made from these materials bond readily to bone and other tissues in the body without rejection or inflammatory reactions. because of this, they are of great interest for gene delivery and tissue engineering scaffolds. most hydroxyapatite ceramics are very porous and lack mechanical strength and are used to coat metal orthopedic devices to aid in forming a bond to bone or as bone fillers. they are also used as fillers for orthopedic plastic screws to aid in reducing the inflammation and increase absorption of these plastic materials. work is being done to make strong, fully dense nano crystalline hydroxyapatite ceramic materials for orthopedic weight bearing devices, replacing foreign metal and plastic orthopedic materials with a synthetic, but naturally occurring, bone mineral. ultimately these ceramic materials may be used as bone replacements or with the incorporation of protein collagens, synthetic bones. durable actinide - containing ceramic materials have many applications such as in nuclear fuels for burning excess pu and in chemically - inert sources of alpha irradiation for power supply of unmanned space vehicles or to produce electricity for microelectronic devices. both use and disposal of radioactive actinides require their immobilization in a durable host material. nuclear waste long - lived radionuclides such as actinides are immobilized using chemical
and then graft healthy skin onto 80 percent of the boy ' s body which was affected by the illness. germline gene therapy would result in any change being inheritable, which has raised concerns within the scientific community. in 2015, crispr was used to edit the dna of non - viable human embryos, leading scientists of major world academies to call for a moratorium on inheritable human genome edits. there are also concerns that the technology could be used not just for treatment, but for enhancement, modification or alteration of a human beings ' appearance, adaptability, intelligence, character or behavior. the distinction between cure and enhancement can also be difficult to establish. in november 2018, he jiankui announced that he had edited the genomes of two human embryos, to attempt to disable the ccr5 gene, which codes for a receptor that hiv uses to enter cells. the work was widely condemned as unethical, dangerous, and premature. currently, germline modification is banned in 40 countries. scientists that do this type of research will often let embryos grow for a few days without allowing it to develop into a baby. researchers are altering the genome of pigs to induce the growth of human organs, with the aim of increasing the success of pig to human organ transplantation. scientists are creating " gene drives ", changing the genomes of mosquitoes to make them immune to malaria, and then looking to spread the genetically altered mosquitoes throughout the mosquito population in the hopes of eliminating the disease. = = = research = = = genetic engineering is an important tool for natural scientists, with the creation of transgenic organisms one of the most important tools for analysis of gene function. genes and other genetic information from a wide range of organisms can be inserted into bacteria for storage and modification, creating genetically modified bacteria in the process. bacteria are cheap, easy to grow, clonal, multiply quickly, relatively easy to transform and can be stored at - 80 Β°c almost indefinitely. once a gene is isolated it can be stored inside the bacteria providing an unlimited supply for research. organisms are genetically engineered to discover the functions of certain genes. this could be the effect on the phenotype of the organism, where the gene is expressed or what other genes it interacts with. these experiments generally involve loss of function, gain of function, tracking and expression. loss of function experiments, such as in a gene knockout experiment, in which an organism is engineered to lack the activity of one or more genes. in a simple knockout a copy
while co - coculturing epithelial and adipocyte cells. the hystem kit is another 3 - d platform containing ecm components and hyaluronic acid that has been used for cancer research. additionally, hydrogel constituents can be chemically modified to assist in crosslinking and enhance their mechanical properties. = = tissue culture = = in many cases, creation of functional tissues and biological structures in vitro requires extensive culturing to promote survival, growth and inducement of functionality. in general, the basic requirements of cells must be maintained in culture, which include oxygen, ph, humidity, temperature, nutrients and osmotic pressure maintenance. tissue engineered cultures also present additional problems in maintaining culture conditions. in standard cell culture, diffusion is often the sole means of nutrient and metabolite transport. however, as a culture becomes larger and more complex, such as the case with engineered organs and whole tissues, other mechanisms must be employed to maintain the culture, such as the creation of capillary networks within the tissue. another issue with tissue culture is introducing the proper factors or stimuli required to induce functionality. in many cases, simple maintenance culture is not sufficient. growth factors, hormones, specific metabolites or nutrients, chemical and physical stimuli are sometimes required. for example, certain cells respond to changes in oxygen tension as part of their normal development, such as chondrocytes, which must adapt to low oxygen conditions or hypoxia during skeletal development. others, such as endothelial cells, respond to shear stress from fluid flow, which is encountered in blood vessels. mechanical stimuli, such as pressure pulses seem to be beneficial to all kind of cardiovascular tissue such as heart valves, blood vessels or pericardium. = = = bioreactors = = = in tissue engineering, a bioreactor is a device that attempts to simulate a physiological environment in order to promote cell or tissue growth in vitro. a physiological environment can consist of many different parameters such as temperature, pressure, oxygen or carbon dioxide concentration, or osmolality of fluid environment, and it can extend to all kinds of biological, chemical or mechanical stimuli. therefore, there are systems that may include the application of forces such as electromagnetic forces, mechanical pressures, or fluid pressures to the tissue. these systems can be two - or three - dimensional setups. bioreactors can be used in both academic and industry applications. general - use and application - specific bioreactors are also commercially available, which may provide static chemical stimulation or a
a comparison of the sensitivities of methods which allow us to determine the coordinates of a moving hot body is made.
, the oxygen atom has a slight negative charge and the two hydrogen atoms have a slight positive charge. this polar property of water allows it to attract other water molecules via hydrogen bonds, which makes water cohesive. surface tension results from the cohesive force due to the attraction between molecules at the surface of the liquid. water is also adhesive as it is able to adhere to the surface of any polar or charged non - water molecules. water is denser as a liquid than it is as a solid ( or ice ). this unique property of water allows ice to float above liquid water such as ponds, lakes, and oceans, thereby insulating the liquid below from the cold air above. water has the capacity to absorb energy, giving it a higher specific heat capacity than other solvents such as ethanol. thus, a large amount of energy is needed to break the hydrogen bonds between water molecules to convert liquid water into water vapor. as a molecule, water is not completely stable as each water molecule continuously dissociates into hydrogen and hydroxyl ions before reforming into a water molecule again. in pure water, the number of hydrogen ions balances ( or equals ) the number of hydroxyl ions, resulting in a ph that is neutral. = = = organic compounds = = = organic compounds are molecules that contain carbon bonded to another element such as hydrogen. with the exception of water, nearly all the molecules that make up each organism contain carbon. carbon can form covalent bonds with up to four other atoms, enabling it to form diverse, large, and complex molecules. for example, a single carbon atom can form four single covalent bonds such as in methane, two double covalent bonds such as in carbon dioxide ( co2 ), or a triple covalent bond such as in carbon monoxide ( co ). moreover, carbon can form very long chains of interconnecting carbon β carbon bonds such as octane or ring - like structures such as glucose. the simplest form of an organic molecule is the hydrocarbon, which is a large family of organic compounds that are composed of hydrogen atoms bonded to a chain of carbon atoms. a hydrocarbon backbone can be substituted by other elements such as oxygen ( o ), hydrogen ( h ), phosphorus ( p ), and sulfur ( s ), which can change the chemical behavior of that compound. groups of atoms that contain these elements ( o -, h -, p -, and s - ) and are bonded to a central carbon atom or skeleton are called functional groups. there are six
use less energy than conventional thermal separation processes such as distillation, sublimation or crystallization. the separation process is purely physical and both fractions ( permeate and retentate ) can be obtained as useful products. cold separation using membrane technology is widely used in the food technology, biotechnology and pharmaceutical industries. furthermore, using membranes enables separations to take place that would be impossible using thermal separation methods. for example, it is impossible to separate the constituents of azeotropic liquids or solutes which form isomorphic crystals by distillation or recrystallization but such separations can be achieved using membrane technology. depending on the type of membrane, the selective separation of certain individual substances or substance mixtures is possible. important technical applications include the production of drinking water by reverse osmosis. in waste water treatment, membrane technology is becoming increasingly important. ultra / microfiltration can be very effective in removing colloids and macromolecules from wastewater. this is needed if wastewater is discharged into sensitive waters especially those designated for contact water sports and recreation. about half of the market is in medical applications such as artificial kidneys to remove toxic substances by hemodialysis and as artificial lung for bubble - free supply of oxygen in the blood. the importance of membrane technology is growing in the field of environmental protection ( nano - mem - pro ippc database ). even in modern energy recovery techniques, membranes are increasingly used, for example in fuel cells and in osmotic power plants. = = mass transfer = = two basic models can be distinguished for mass transfer through the membrane : the solution - diffusion model and the hydrodynamic model. in real membranes, these two transport mechanisms certainly occur side by side, especially during ultra - filtration. = = = solution - diffusion model = = = in the solution - diffusion model, transport occurs only by diffusion. the component that needs to be transported must first be dissolved in the membrane. the general approach of the solution - diffusion model is to assume that the chemical potential of the feed and permeate fluids are in equilibrium with the adjacent membrane surfaces such that appropriate expressions for the chemical potential in the fluid and membrane phases can be equated at the solution - membrane interface. this principle is more important for dense membranes without natural pores such as those used for reverse osmosis and in fuel cells. during the filtration process a boundary layer forms on the membrane. this concentration gradient is created by molecules which cannot pass through the membrane. the
water content and the internal evolution of terrestrial planets and icy bodies are closely linked. the distribution of water in planetary systems is controlled by the temperature structure in the protoplanetary disk and dynamics and migration of planetesimals and planetary embryos. this results in the formation of planetesimals and planetary embryos with a great variety of compositions, water contents and degrees of oxidation. the internal evolution and especially the formation time of planetesimals relative to the timescale of radiogenic heating by short - lived 26al decay may govern the amount of hydrous silicates and leftover rock - ice mixtures available in the late stages of their evolution. in turn, water content may affect the early internal evolution of the planetesimals and in particular metal - silicate separation processes. moreover, water content may contribute to an increase of oxygen fugacity and thus affect the concentrations of siderophile elements within the silicate reservoirs of solar system objects. finally, the water content strongly influences the differentiation rate of the icy moons, controls their internal evolution and governs the alteration processes occurring in their deep interiors.
Question: Because the human body is about 70% water by mass, and liquid water has high specific heat, a great deal of what is required to change its temperature?
A) energy
B) work
C) digestion
D) power
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A) energy
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Context:
commonly called plastics and rubber. plastics and rubber are the final product, created after one or more polymers or additives have been added to a resin during processing, which is then shaped into a final form. plastics in former and in current widespread use include polyethylene, polypropylene, polyvinyl chloride ( pvc ), polystyrene, nylons, polyesters, acrylics, polyurethanes, and polycarbonates. rubbers include natural rubber, styrene - butadiene rubber, chloroprene, and butadiene rubber. plastics are generally classified as commodity, specialty and engineering plastics. polyvinyl chloride ( pvc ) is widely used, inexpensive, and annual production quantities are large. it lends itself to a vast array of applications, from artificial leather to electrical insulation and cabling, packaging, and containers. its fabrication and processing are simple and well - established. the versatility of pvc is due to the wide range of plasticisers and other additives that it accepts. the term " additives " in polymer science refers to the chemicals and compounds added to the polymer base to modify its material properties. polycarbonate would be normally considered an engineering plastic ( other examples include peek, abs ). such plastics are valued for their superior strengths and other special material properties. they are usually not used for disposable applications, unlike commodity plastics. specialty plastics are materials with unique characteristics, such as ultra - high strength, electrical conductivity, electro - fluorescence, high thermal stability, etc. the dividing lines between the various types of plastics is not based on material but rather on their properties and applications. for example, polyethylene ( pe ) is a cheap, low friction polymer commonly used to make disposable bags for shopping and trash, and is considered a commodity plastic, whereas medium - density polyethylene ( mdpe ) is used for underground gas and water pipes, and another variety called ultra - high - molecular - weight polyethylene ( uhmwpe ) is an engineering plastic which is used extensively as the glide rails for industrial equipment and the low - friction socket in implanted hip joints. = = = metal alloys = = = the alloys of iron ( steel, stainless steel, cast iron, tool steel, alloy steels ) make up the largest proportion of metals today both by quantity and commercial value. iron alloyed with various proportions of carbon gives low, mid and high carbon steels. an
so on. these plastic casings are usually a composite material made up of a thermoplastic matrix such as acrylonitrile butadiene styrene ( abs ) in which calcium carbonate chalk, talc, glass fibers or carbon fibers have been added for added strength, bulk, or electrostatic dispersion. these additions may be termed reinforcing fibers, or dispersants, depending on their purpose. = = = polymers = = = polymers are chemical compounds made up of a large number of identical components linked together like chains. polymers are the raw materials ( the resins ) used to make what are commonly called plastics and rubber. plastics and rubber are the final product, created after one or more polymers or additives have been added to a resin during processing, which is then shaped into a final form. plastics in former and in current widespread use include polyethylene, polypropylene, polyvinyl chloride ( pvc ), polystyrene, nylons, polyesters, acrylics, polyurethanes, and polycarbonates. rubbers include natural rubber, styrene - butadiene rubber, chloroprene, and butadiene rubber. plastics are generally classified as commodity, specialty and engineering plastics. polyvinyl chloride ( pvc ) is widely used, inexpensive, and annual production quantities are large. it lends itself to a vast array of applications, from artificial leather to electrical insulation and cabling, packaging, and containers. its fabrication and processing are simple and well - established. the versatility of pvc is due to the wide range of plasticisers and other additives that it accepts. the term " additives " in polymer science refers to the chemicals and compounds added to the polymer base to modify its material properties. polycarbonate would be normally considered an engineering plastic ( other examples include peek, abs ). such plastics are valued for their superior strengths and other special material properties. they are usually not used for disposable applications, unlike commodity plastics. specialty plastics are materials with unique characteristics, such as ultra - high strength, electrical conductivity, electro - fluorescence, high thermal stability, etc. the dividing lines between the various types of plastics is not based on material but rather on their properties and applications. for example, polyethylene ( pe ) is a cheap, low friction polymer commonly used to make disposable bags for shopping and trash, and is considered a commodity plastic, whereas medium -
chloroplasts make are used for many things, such as providing material to build cell membranes out of and making the polymer cutin which is found in the plant cuticle that protects land plants from drying out. plants synthesise a number of unique polymers like the polysaccharide molecules cellulose, pectin and xyloglucan from which the land plant cell wall is constructed. vascular land plants make lignin, a polymer used to strengthen the secondary cell walls of xylem tracheids and vessels to keep them from collapsing when a plant sucks water through them under water stress. lignin is also used in other cell types like sclerenchyma fibres that provide structural support for a plant and is a major constituent of wood. sporopollenin is a chemically resistant polymer found in the outer cell walls of spores and pollen of land plants responsible for the survival of early land plant spores and the pollen of seed plants in the fossil record. it is widely regarded as a marker for the start of land plant evolution during the ordovician period. the concentration of carbon dioxide in the atmosphere today is much lower than it was when plants emerged onto land during the ordovician and silurian periods. many monocots like maize and the pineapple and some dicots like the asteraceae have since independently evolved pathways like crassulacean acid metabolism and the c4 carbon fixation pathway for photosynthesis which avoid the losses resulting from photorespiration in the more common c3 carbon fixation pathway. these biochemical strategies are unique to land plants. = = = medicine and materials = = = phytochemistry is a branch of plant biochemistry primarily concerned with the chemical substances produced by plants during secondary metabolism. some of these compounds are toxins such as the alkaloid coniine from hemlock. others, such as the essential oils peppermint oil and lemon oil are useful for their aroma, as flavourings and spices ( e. g., capsaicin ), and in medicine as pharmaceuticals as in opium from opium poppies. many medicinal and recreational drugs, such as tetrahydrocannabinol ( active ingredient in cannabis ), caffeine, morphine and nicotine come directly from plants. others are simple derivatives of botanical natural products. for example, the pain killer aspirin is the acetyl ester of salicylic acid, originally isolated from the bark of willow trees, and
the structural template or precursor which is created in the initial stages of chemical synthesis and physical forming. hence the importance of chemical powder and polymer processing as it pertains to the synthesis of industrial ceramics, glasses and glass - ceramics. there are numerous possible refinements of the sintering process. some of the most common involve pressing the green body to give the densification a head start and reduce the sintering time needed. sometimes organic binders such as polyvinyl alcohol are added to hold the green body together ; these burn out during the firing ( at 200 β 350 Β°c ). sometimes organic lubricants are added during pressing to increase densification. it is common to combine these, and add binders and lubricants to a powder, then press. ( the formulation of these organic chemical additives is an art in itself. this is particularly important in the manufacture of high performance ceramics such as those used by the billions for electronics, in capacitors, inductors, sensors, etc. ) a slurry can be used in place of a powder, and then cast into a desired shape, dried and then sintered. indeed, traditional pottery is done with this type of method, using a plastic mixture worked with the hands. if a mixture of different materials is used together in a ceramic, the sintering temperature is sometimes above the melting point of one minor component β a liquid phase sintering. this results in shorter sintering times compared to solid state sintering. such liquid phase sintering involves in faster diffusion processes and may result in abnormal grain growth. = = strength of ceramics = = a material ' s strength is dependent on its microstructure. the engineering processes to which a material is subjected can alter its microstructure. the variety of strengthening mechanisms that alter the strength of a material include the mechanism of grain boundary strengthening. thus, although yield strength is maximized with decreasing grain size, ultimately, very small grain sizes make the material brittle. considered in tandem with the fact that the yield strength is the parameter that predicts plastic deformation in the material, one can make informed decisions on how to increase the strength of a material depending on its microstructural properties and the desired end effect. the relation between yield stress and grain size is described mathematically by the hall - petch equation which is Ο y = Ο 0 + k y d { \ displaystyle \ sigma _ { y } = \ sigma _ { 0 } + { k _ { y } \ over {
, specialty and engineering plastics. polyvinyl chloride ( pvc ) is widely used, inexpensive, and annual production quantities are large. it lends itself to a vast array of applications, from artificial leather to electrical insulation and cabling, packaging, and containers. its fabrication and processing are simple and well - established. the versatility of pvc is due to the wide range of plasticisers and other additives that it accepts. the term " additives " in polymer science refers to the chemicals and compounds added to the polymer base to modify its material properties. polycarbonate would be normally considered an engineering plastic ( other examples include peek, abs ). such plastics are valued for their superior strengths and other special material properties. they are usually not used for disposable applications, unlike commodity plastics. specialty plastics are materials with unique characteristics, such as ultra - high strength, electrical conductivity, electro - fluorescence, high thermal stability, etc. the dividing lines between the various types of plastics is not based on material but rather on their properties and applications. for example, polyethylene ( pe ) is a cheap, low friction polymer commonly used to make disposable bags for shopping and trash, and is considered a commodity plastic, whereas medium - density polyethylene ( mdpe ) is used for underground gas and water pipes, and another variety called ultra - high - molecular - weight polyethylene ( uhmwpe ) is an engineering plastic which is used extensively as the glide rails for industrial equipment and the low - friction socket in implanted hip joints. = = = metal alloys = = = the alloys of iron ( steel, stainless steel, cast iron, tool steel, alloy steels ) make up the largest proportion of metals today both by quantity and commercial value. iron alloyed with various proportions of carbon gives low, mid and high carbon steels. an iron - carbon alloy is only considered steel if the carbon level is between 0. 01 % and 2. 00 % by weight. for steels, the hardness and tensile strength of the steel is related to the amount of carbon present, with increasing carbon levels also leading to lower ductility and toughness. heat treatment processes such as quenching and tempering can significantly change these properties, however. in contrast, certain metal alloys exhibit unique properties where their size and density remain unchanged across a range of temperatures. cast iron is defined as an iron β carbon alloy with more than 2. 00 %, but less than 6. 67 %
( pvc ), polystyrene, nylons, polyesters, acrylics, polyurethanes, and polycarbonates. rubbers include natural rubber, styrene - butadiene rubber, chloroprene, and butadiene rubber. plastics are generally classified as commodity, specialty and engineering plastics. polyvinyl chloride ( pvc ) is widely used, inexpensive, and annual production quantities are large. it lends itself to a vast array of applications, from artificial leather to electrical insulation and cabling, packaging, and containers. its fabrication and processing are simple and well - established. the versatility of pvc is due to the wide range of plasticisers and other additives that it accepts. the term " additives " in polymer science refers to the chemicals and compounds added to the polymer base to modify its material properties. polycarbonate would be normally considered an engineering plastic ( other examples include peek, abs ). such plastics are valued for their superior strengths and other special material properties. they are usually not used for disposable applications, unlike commodity plastics. specialty plastics are materials with unique characteristics, such as ultra - high strength, electrical conductivity, electro - fluorescence, high thermal stability, etc. the dividing lines between the various types of plastics is not based on material but rather on their properties and applications. for example, polyethylene ( pe ) is a cheap, low friction polymer commonly used to make disposable bags for shopping and trash, and is considered a commodity plastic, whereas medium - density polyethylene ( mdpe ) is used for underground gas and water pipes, and another variety called ultra - high - molecular - weight polyethylene ( uhmwpe ) is an engineering plastic which is used extensively as the glide rails for industrial equipment and the low - friction socket in implanted hip joints. = = = metal alloys = = = the alloys of iron ( steel, stainless steel, cast iron, tool steel, alloy steels ) make up the largest proportion of metals today both by quantity and commercial value. iron alloyed with various proportions of carbon gives low, mid and high carbon steels. an iron - carbon alloy is only considered steel if the carbon level is between 0. 01 % and 2. 00 % by weight. for steels, the hardness and tensile strength of the steel is related to the amount of carbon present, with increasing carbon levels also leading to lower ductility and toughness. heat treatment
##spersion. these additions may be termed reinforcing fibers, or dispersants, depending on their purpose. = = = polymers = = = polymers are chemical compounds made up of a large number of identical components linked together like chains. polymers are the raw materials ( the resins ) used to make what are commonly called plastics and rubber. plastics and rubber are the final product, created after one or more polymers or additives have been added to a resin during processing, which is then shaped into a final form. plastics in former and in current widespread use include polyethylene, polypropylene, polyvinyl chloride ( pvc ), polystyrene, nylons, polyesters, acrylics, polyurethanes, and polycarbonates. rubbers include natural rubber, styrene - butadiene rubber, chloroprene, and butadiene rubber. plastics are generally classified as commodity, specialty and engineering plastics. polyvinyl chloride ( pvc ) is widely used, inexpensive, and annual production quantities are large. it lends itself to a vast array of applications, from artificial leather to electrical insulation and cabling, packaging, and containers. its fabrication and processing are simple and well - established. the versatility of pvc is due to the wide range of plasticisers and other additives that it accepts. the term " additives " in polymer science refers to the chemicals and compounds added to the polymer base to modify its material properties. polycarbonate would be normally considered an engineering plastic ( other examples include peek, abs ). such plastics are valued for their superior strengths and other special material properties. they are usually not used for disposable applications, unlike commodity plastics. specialty plastics are materials with unique characteristics, such as ultra - high strength, electrical conductivity, electro - fluorescence, high thermal stability, etc. the dividing lines between the various types of plastics is not based on material but rather on their properties and applications. for example, polyethylene ( pe ) is a cheap, low friction polymer commonly used to make disposable bags for shopping and trash, and is considered a commodity plastic, whereas medium - density polyethylene ( mdpe ) is used for underground gas and water pipes, and another variety called ultra - high - molecular - weight polyethylene ( uhmwpe ) is an engineering plastic which is used extensively as the glide rails for industrial equipment and the low - friction socket in implanted hip
. batching is the process of weighing the oxides according to recipes, and preparing them for mixing and drying. mixing occurs after batching and is performed with various machines, such as dry mixing ribbon mixers ( a type of cement mixer ), resonantacoustic mixers, mueller mixers, and pug mills. wet mixing generally involves the same equipment. forming is making the mixed material into shapes, ranging from toilet bowls to spark plug insulators. forming can involve : ( 1 ) extrusion, such as extruding " slugs " to make bricks, ( 2 ) pressing to make shaped parts, ( 3 ) slip casting, as in making toilet bowls, wash basins and ornamentals like ceramic statues. forming produces a " green " part, ready for drying. green parts are soft, pliable, and over time will lose shape. handling the green product will change its shape. for example, a green brick can be " squeezed ", and after squeezing it will stay that way. drying is removing the water or binder from the formed material. spray drying is widely used to prepare powder for pressing operations. other dryers are tunnel dryers and periodic dryers. controlled heat is applied in this two - stage process. first, heat removes water. this step needs careful control, as rapid heating causes cracks and surface defects. the dried part is smaller than the green part, and is brittle, necessitating careful handling, since a small impact will cause crumbling and breaking. sintering is where the dried parts pass through a controlled heating process, and the oxides are chemically changed to cause bonding and densification. the fired part will be smaller than the dried part. = = forming methods = = ceramic forming techniques include throwing, slipcasting, tape casting, freeze - casting, injection molding, dry pressing, isostatic pressing, hot isostatic pressing ( hip ), 3d printing and others. methods for forming ceramic powders into complex shapes are desirable in many areas of technology. such methods are required for producing advanced, high - temperature structural parts such as heat engine components and turbines. materials other than ceramics which are used in these processes may include : wood, metal, water, plaster and epoxy β most of which will be eliminated upon firing. a ceramic - filled epoxy, such as martyte, is sometimes used to protect structural steel under conditions of rocket exhaust impingement. these forming techniques are well known for providing tools and other components with dimensional stability, surface quality
grain sizes are a product of the thermal processing parameters as well as the initial particle size, or possibly the sizes of aggregates or particle clusters which arise during the initial stages of processing. the ultimate microstructure ( and thus the physical properties ) of the final product will be limited by and subject to the form of the structural template or precursor which is created in the initial stages of chemical synthesis and physical forming. hence the importance of chemical powder and polymer processing as it pertains to the synthesis of industrial ceramics, glasses and glass - ceramics. there are numerous possible refinements of the sintering process. some of the most common involve pressing the green body to give the densification a head start and reduce the sintering time needed. sometimes organic binders such as polyvinyl alcohol are added to hold the green body together ; these burn out during the firing ( at 200 β 350 Β°c ). sometimes organic lubricants are added during pressing to increase densification. it is common to combine these, and add binders and lubricants to a powder, then press. ( the formulation of these organic chemical additives is an art in itself. this is particularly important in the manufacture of high performance ceramics such as those used by the billions for electronics, in capacitors, inductors, sensors, etc. ) a slurry can be used in place of a powder, and then cast into a desired shape, dried and then sintered. indeed, traditional pottery is done with this type of method, using a plastic mixture worked with the hands. if a mixture of different materials is used together in a ceramic, the sintering temperature is sometimes above the melting point of one minor component β a liquid phase sintering. this results in shorter sintering times compared to solid state sintering. such liquid phase sintering involves in faster diffusion processes and may result in abnormal grain growth. = = strength of ceramics = = a material ' s strength is dependent on its microstructure. the engineering processes to which a material is subjected can alter its microstructure. the variety of strengthening mechanisms that alter the strength of a material include the mechanism of grain boundary strengthening. thus, although yield strength is maximized with decreasing grain size, ultimately, very small grain sizes make the material brittle. considered in tandem with the fact that the yield strength is the parameter that predicts plastic deformation in the material, one can make informed decisions on how to increase the strength of a material depending on its microstructural
sugar ) for export to the rest of the plant. unlike in animals ( which lack chloroplasts ), plants and their eukaryote relatives have delegated many biochemical roles to their chloroplasts, including synthesising all their fatty acids, and most amino acids. the fatty acids that chloroplasts make are used for many things, such as providing material to build cell membranes out of and making the polymer cutin which is found in the plant cuticle that protects land plants from drying out. plants synthesise a number of unique polymers like the polysaccharide molecules cellulose, pectin and xyloglucan from which the land plant cell wall is constructed. vascular land plants make lignin, a polymer used to strengthen the secondary cell walls of xylem tracheids and vessels to keep them from collapsing when a plant sucks water through them under water stress. lignin is also used in other cell types like sclerenchyma fibres that provide structural support for a plant and is a major constituent of wood. sporopollenin is a chemically resistant polymer found in the outer cell walls of spores and pollen of land plants responsible for the survival of early land plant spores and the pollen of seed plants in the fossil record. it is widely regarded as a marker for the start of land plant evolution during the ordovician period. the concentration of carbon dioxide in the atmosphere today is much lower than it was when plants emerged onto land during the ordovician and silurian periods. many monocots like maize and the pineapple and some dicots like the asteraceae have since independently evolved pathways like crassulacean acid metabolism and the c4 carbon fixation pathway for photosynthesis which avoid the losses resulting from photorespiration in the more common c3 carbon fixation pathway. these biochemical strategies are unique to land plants. = = = medicine and materials = = = phytochemistry is a branch of plant biochemistry primarily concerned with the chemical substances produced by plants during secondary metabolism. some of these compounds are toxins such as the alkaloid coniine from hemlock. others, such as the essential oils peppermint oil and lemon oil are useful for their aroma, as flavourings and spices ( e. g., capsaicin ), and in medicine as pharmaceuticals as in opium from opium poppies. many medicinal and recreational drugs, such as tetrahydrocannabino
Question: The process of making a polymer is called what?
A) fermentation
B) memorization
C) polymerization
D) reaction
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C) polymerization
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Context:
sumerians in mesopotamia used a complex system of canals and levees to divert water from the tigris and euphrates rivers for irrigation. archaeologists estimate that the wheel was invented independently and concurrently in mesopotamia ( in present - day iraq ), the northern caucasus ( maykop culture ), and central europe. time estimates range from 5, 500 to 3, 000 bce with most experts putting it closer to 4, 000 bce. the oldest artifacts with drawings depicting wheeled carts date from about 3, 500 bce. more recently, the oldest - known wooden wheel in the world as of 2024 was found in the ljubljana marsh of slovenia ; austrian experts have established that the wheel is between 5, 100 and 5, 350 years old. the invention of the wheel revolutionized trade and war. it did not take long to discover that wheeled wagons could be used to carry heavy loads. the ancient sumerians used a potter ' s wheel and may have invented it. a stone pottery wheel found in the city - state of ur dates to around 3, 429 bce, and even older fragments of wheel - thrown pottery have been found in the same area. fast ( rotary ) potters ' wheels enabled early mass production of pottery, but it was the use of the wheel as a transformer of energy ( through water wheels, windmills, and even treadmills ) that revolutionized the application of nonhuman power sources. the first two - wheeled carts were derived from travois and were first used in mesopotamia and iran in around 3, 000 bce. the oldest known constructed roadways are the stone - paved streets of the city - state of ur, dating to c. 4, 000 bce, and timber roads leading through the swamps of glastonbury, england, dating to around the same period. the first long - distance road, which came into use around 3, 500 bce, spanned 2, 400 km from the persian gulf to the mediterranean sea, but was not paved and was only partially maintained. in around 2, 000 bce, the minoans on the greek island of crete built a 50 km road leading from the palace of gortyn on the south side of the island, through the mountains, to the palace of knossos on the north side of the island. unlike the earlier road, the minoan road was completely paved. ancient minoan private homes had running water. a bathtub virtually identical to modern ones was unearthed at the palace of knossos. several minoan private homes also
earliest record of a ship under sail is that of a nile boat dating to around 7, 000 bce. from prehistoric times, egyptians likely used the power of the annual flooding of the nile to irrigate their lands, gradually learning to regulate much of it through purposely built irrigation channels and " catch " basins. the ancient sumerians in mesopotamia used a complex system of canals and levees to divert water from the tigris and euphrates rivers for irrigation. archaeologists estimate that the wheel was invented independently and concurrently in mesopotamia ( in present - day iraq ), the northern caucasus ( maykop culture ), and central europe. time estimates range from 5, 500 to 3, 000 bce with most experts putting it closer to 4, 000 bce. the oldest artifacts with drawings depicting wheeled carts date from about 3, 500 bce. more recently, the oldest - known wooden wheel in the world as of 2024 was found in the ljubljana marsh of slovenia ; austrian experts have established that the wheel is between 5, 100 and 5, 350 years old. the invention of the wheel revolutionized trade and war. it did not take long to discover that wheeled wagons could be used to carry heavy loads. the ancient sumerians used a potter ' s wheel and may have invented it. a stone pottery wheel found in the city - state of ur dates to around 3, 429 bce, and even older fragments of wheel - thrown pottery have been found in the same area. fast ( rotary ) potters ' wheels enabled early mass production of pottery, but it was the use of the wheel as a transformer of energy ( through water wheels, windmills, and even treadmills ) that revolutionized the application of nonhuman power sources. the first two - wheeled carts were derived from travois and were first used in mesopotamia and iran in around 3, 000 bce. the oldest known constructed roadways are the stone - paved streets of the city - state of ur, dating to c. 4, 000 bce, and timber roads leading through the swamps of glastonbury, england, dating to around the same period. the first long - distance road, which came into use around 3, 500 bce, spanned 2, 400 km from the persian gulf to the mediterranean sea, but was not paved and was only partially maintained. in around 2, 000 bce, the minoans on the greek island of crete built a 50 km road leading from the palace of gortyn on the south side of the island, through the mountains,
made of steel. the shoe is generally wider than the caisson to reduce friction, and the leading edge may be supplied with pressurised bentonite slurry, which swells in water, stabilizing settlement by filling depressions and voids. an open caisson may fill with water during sinking. the material is excavated by clamshell excavator bucket on crane. the formation level subsoil may still not be suitable for excavation or bearing capacity. the water in the caisson ( due to a high water table ) balances the upthrust forces of the soft soils underneath. if dewatered, the base may " pipe " or " boil ", causing the caisson to sink. to combat this problem, piles may be driven from the surface to act as : load - bearing walls, in that they transmit loads to deeper soils. anchors, in that they resist flotation because of the friction at the interface between their surfaces and the surrounding earth into which they have been driven. h - beam sections ( typical column sections, due to resistance to bending in all axis ) may be driven at angles " raked " to rock or other firmer soils ; the h - beams are left extended above the base. a reinforced concrete plug may be placed under the water, a process known as tremie concrete placement. when the caisson is dewatered, this plug acts as a pile cap, resisting the upward forces of the subsoil. = = = monolithic = = = a monolithic caisson ( or simply a monolith ) is larger than the other types of caisson, but similar to open caissons. such caissons are often found in quay walls, where resistance to impact from ships is required. = = = pneumatic = = = shallow caissons may be open to the air, whereas pneumatic caissons ( sometimes called pressurized caissons ), which penetrate soft mud, are bottomless boxes sealed at the top and filled with compressed air to keep water and mud out at depth. an airlock allows access to the chamber. workers, called sandhogs in american english, move mud and rock debris ( called muck ) from the edge of the workspace to a water - filled pit, connected by a tube ( called the muck tube ) to the surface. a crane at the surface removes the soil with a clamshell bucket. the water pressure in the tube balances the air pressure, with excess air escaping up
three of what is called the six simple machines, from which all machines are based. these machines are the inclined plane, the wedge, and the lever, which allowed the ancient egyptians to move millions of limestone blocks which weighed approximately 3. 5 tons ( 7, 000 lbs. ) each into place to create structures like the great pyramid of giza, which is 481 feet ( 147 meters ) high. they also made writing medium similar to paper from papyrus, which joshua mark states is the foundation for modern paper. papyrus is a plant ( cyperus papyrus ) which grew in plentiful amounts in the egyptian delta and throughout the nile river valley during ancient times. the papyrus was harvested by field workers and brought to processing centers where it was cut into thin strips. the strips were then laid - out side by side and covered in plant resin. the second layer of strips was laid on perpendicularly, then both pressed together until the sheet was dry. the sheets were then joined to form a roll and later used for writing. egyptian society made several significant advances during dynastic periods in many areas of technology. according to hossam elanzeery, they were the first civilization to use timekeeping devices such as sundials, shadow clocks, and obelisks and successfully leveraged their knowledge of astronomy to create a calendar model that society still uses today. they developed shipbuilding technology that saw them progress from papyrus reed vessels to cedar wood ships while also pioneering the use of rope trusses and stem - mounted rudders. the egyptians also used their knowledge of anatomy to lay the foundation for many modern medical techniques and practiced the earliest known version of neuroscience. elanzeery also states that they used and furthered mathematical science, as evidenced in the building of the pyramids. ancient egyptians also invented and pioneered many food technologies that have become the basis of modern food technology processes. based on paintings and reliefs found in tombs, as well as archaeological artifacts, scholars like paul t nicholson believe that the ancient egyptians established systematic farming practices, engaged in cereal processing, brewed beer and baked bread, processed meat, practiced viticulture and created the basis for modern wine production, and created condiments to complement, preserve and mask the flavors of their food. = = = = indus valley = = = = the indus valley civilization, situated in a resource - rich area ( in modern pakistan and northwestern india ), is notable for its early application of city planning, sanitation technologies, and plumbing. indus valley construction and architecture, called ' vaastu
##lling, pipe jacking and other operations. a caisson is sunk by self - weight, concrete or water ballast placed on top, or by hydraulic jacks. the leading edge ( or cutting shoe ) of the caisson is sloped out at a sharp angle to aid sinking in a vertical manner ; it is usually made of steel. the shoe is generally wider than the caisson to reduce friction, and the leading edge may be supplied with pressurised bentonite slurry, which swells in water, stabilizing settlement by filling depressions and voids. an open caisson may fill with water during sinking. the material is excavated by clamshell excavator bucket on crane. the formation level subsoil may still not be suitable for excavation or bearing capacity. the water in the caisson ( due to a high water table ) balances the upthrust forces of the soft soils underneath. if dewatered, the base may " pipe " or " boil ", causing the caisson to sink. to combat this problem, piles may be driven from the surface to act as : load - bearing walls, in that they transmit loads to deeper soils. anchors, in that they resist flotation because of the friction at the interface between their surfaces and the surrounding earth into which they have been driven. h - beam sections ( typical column sections, due to resistance to bending in all axis ) may be driven at angles " raked " to rock or other firmer soils ; the h - beams are left extended above the base. a reinforced concrete plug may be placed under the water, a process known as tremie concrete placement. when the caisson is dewatered, this plug acts as a pile cap, resisting the upward forces of the subsoil. = = = monolithic = = = a monolithic caisson ( or simply a monolith ) is larger than the other types of caisson, but similar to open caissons. such caissons are often found in quay walls, where resistance to impact from ships is required. = = = pneumatic = = = shallow caissons may be open to the air, whereas pneumatic caissons ( sometimes called pressurized caissons ), which penetrate soft mud, are bottomless boxes sealed at the top and filled with compressed air to keep water and mud out at depth. an airlock allows access to the chamber. workers, called sandhogs in american english, move mud and rock debris ( called
used for tools, weapons and monumental statuary. by 1200 bc they could cast objects 5 m long in a single piece. several of the six classic simple machines were invented in mesopotamia. mesopotamians have been credited with the invention of the wheel. the wheel and axle mechanism first appeared with the potter ' s wheel, invented in mesopotamia ( modern iraq ) during the 5th millennium bc. this led to the invention of the wheeled vehicle in mesopotamia during the early 4th millennium bc. depictions of wheeled wagons found on clay tablet pictographs at the eanna district of uruk are dated between 3700 and 3500 bc. the lever was used in the shadoof water - lifting device, the first crane machine, which appeared in mesopotamia circa 3000 bc, and then in ancient egyptian technology circa 2000 bc. the earliest evidence of pulleys date back to mesopotamia in the early 2nd millennium bc. the screw, the last of the simple machines to be invented, first appeared in mesopotamia during the neo - assyrian period ( 911 β 609 ) bc. the assyrian king sennacherib ( 704 β 681 bc ) claims to have invented automatic sluices and to have been the first to use water screw pumps, of up to 30 tons weight, which were cast using two - part clay molds rather than by the ' lost wax ' process. the jerwan aqueduct ( c. 688 bc ) is made with stone arches and lined with waterproof concrete. the babylonian astronomical diaries spanned 800 years. they enabled meticulous astronomers to plot the motions of the planets and to predict eclipses. the earliest evidence of water wheels and watermills date back to the ancient near east in the 4th century bc, specifically in the persian empire before 350 bc, in the regions of mesopotamia ( iraq ) and persia ( iran ). this pioneering use of water power constituted the first human - devised motive force not to rely on muscle power ( besides the sail ). = = = = egypt = = = = the egyptians, known for building pyramids centuries before the creation of modern tools, invented and used many simple machines, such as the ramp to aid construction processes. historians and archaeologists have found evidence that the pyramids were built using three of what is called the six simple machines, from which all machines are based. these machines are the inclined plane, the wedge, and the lever, which allowed the ancient egyptians to move millions of limestone blocks which weighed approximately 3. 5 tons ( 7, 000 lbs. ) each into place to create structures like the
##s ( sometimes called pressurized caissons ), which penetrate soft mud, are bottomless boxes sealed at the top and filled with compressed air to keep water and mud out at depth. an airlock allows access to the chamber. workers, called sandhogs in american english, move mud and rock debris ( called muck ) from the edge of the workspace to a water - filled pit, connected by a tube ( called the muck tube ) to the surface. a crane at the surface removes the soil with a clamshell bucket. the water pressure in the tube balances the air pressure, with excess air escaping up the muck tube. the pressurized air flow must be constant to ensure regular air changes for the workers and prevent excessive inflow of mud or water at the base of the caisson. when the caisson hits bedrock, the sandhogs exit through the airlock and fill the box with concrete, forming a solid foundation pier. a pneumatic ( compressed - air ) caisson has the advantage of providing dry working conditions, which is better for placing concrete. it is also well suited for foundations for which other methods might cause settlement of adjacent structures. construction workers who leave the pressurized environment of the caisson must decompress at a rate that allows symptom - free release of inert gases dissolved in the body tissues if they are to avoid decompression sickness, a condition first identified in caisson workers, and originally named " caisson disease " in recognition of the occupational hazard. construction of the brooklyn bridge, which was built with the help of pressurised caissons, resulted in numerous workers being either killed or permanently injured by caisson disease during its construction. barotrauma of the ears, sinus cavities and lungs and dysbaric osteonecrosis are other risks. = = other uses = = caissons have also been used in the installation of hydraulic elevators where a single - stage ram is installed below the ground level. caissons, codenamed phoenix, were an integral part of the mulberry harbours used during the world war ii allied invasion of normandy. = = other meanings = = boat lift caissons : the word caisson is also used as a synonym for the moving trough part of caisson locks, canal lifts and inclines in which boats and ships rest while being lifted from one canal elevation to another ; the water is retained on the inside of the caisson, or excluded from the caisson
, and finally large gunpowder - propelled arrows and rocket weaponry. : 220 β 221 eventually, perishable bamboo was replaced with hollow tubes of cast iron, and so too did the terminology of this new weapon change, from ' fire - spear ' huo qiang to ' fire - tube ' huo tong. : 221 this ancestor to the gun was complemented by the ancestor to the cannon, what the chinese referred to since the 13th century as the ' multiple bullets magazine erupter ' bai zu lian zhu pao, a tube of bronze or cast iron that was filled with about 100 lead balls. : 263 β 264 the earliest known depiction of a gun is a sculpture from a cave in sichuan, dating to 1128, that portrays a figure carrying a vase - shaped bombard, firing flames and a cannonball. however, the oldest existent archaeological discovery of a metal barrel handgun is from the chinese heilongjiang excavation, dated to 1288. : 293 the chinese also discovered the explosive potential of packing hollowed cannonball shells with gunpowder. written later by jiao yu in his huolongjing ( mid - 14th century ), this manuscript recorded an earlier song - era cast - iron cannon known as the ' flying - cloud thunderclap eruptor ' ( fei yun pi - li pao ). the manuscript stated that : as noted before, the change in terminology for these new weapons during the song period were gradual. the early song cannons were at first termed the same way as the chinese trebuchet catapult. a later ming dynasty scholar known as mao yuanyi would explain this use of terminology and true origins of the cannon in his text of the wubei zhi, written in 1628 : the 14th - century huolongjing was also one of the first chinese texts to carefully describe to the use of explosive land mines, which had been used by the late song chinese against the mongols in 1277, and employed by the yuan dynasty afterwards. the innovation of the detonated land mine was accredited to one luo qianxia in the campaign of defense against the mongol invasion by kublai khan, : 192 later chinese texts revealed that the chinese land mine employed either a rip cord or a motion booby trap of a pin releasing falling weights that rotated a steel flint wheel, which in turn created sparks that ignited the train of fuses for the land mines. : 199 furthermore, the song employed the earliest known gunpowder - propelled rockets in warfare during the late 13th century, : 477 its earliest form being
bear ' ) was conspicuous on radar. it is now known that propellers and jet turbine blades produce a bright radar image ; the bear has four pairs of large 18 - foot ( 5. 6 m ) diameter contra - rotating propellers. another important factor is internal construction. some stealth aircraft have skin that is radar transparent or absorbing, behind which are structures termed reentrant triangles. radar waves penetrating the skin get trapped in these structures, reflecting off the internal faces and losing energy. this method was first used on the blackbird series : a - 12, yf - 12a, lockheed sr - 71 blackbird. the most efficient way to reflect radar waves back to the emitting radar is with orthogonal metal plates, forming a corner reflector consisting of either a dihedral ( two plates ) or a trihedral ( three orthogonal plates ). this configuration occurs in the tail of a conventional aircraft, where the vertical and horizontal components of the tail are set at right angles. stealth aircraft such as the f - 117 use a different arrangement, tilting the tail surfaces to reduce corner reflections formed between them. a more radical method is to omit the tail, as in the b - 2 spirit. the b - 2 ' s clean, low - drag flying wing configuration gives it exceptional range and reduces its radar profile. the flying wing design most closely resembles a so - called infinite flat plate ( as vertical control surfaces dramatically increase rcs ), the perfect stealth shape, as it would have no angles to reflect back radar waves. in addition to altering the tail, stealth design must bury the engines within the wing or fuselage, or in some cases where stealth is applied to an extant aircraft, install baffles in the air intakes, so that the compressor blades are not visible to radar. a stealthy shape must be devoid of complex bumps or protrusions of any kind, meaning that weapons, fuel tanks, and other stores must not be carried externally. any stealthy vehicle becomes un - stealthy when a door or hatch opens. parallel alignment of edges or even surfaces is also often used in stealth designs. the technique involves using a small number of edge orientations in the shape of the structure. for example, on the f - 22a raptor, the leading edges of the wing and the tail planes are set at the same angle. other smaller structures, such as the air intake bypass doors and the air refueling aperture, also use the same angles. the effect of this is to return a narrow radar signal in a very specific direction away from the radar
and irrigation in the alluvial south, and catchment systems stretching for tens of kilometers in the hilly north. their palaces had sophisticated drainage systems. writing was invented in mesopotamia, using the cuneiform script. many records on clay tablets and stone inscriptions have survived. these civilizations were early adopters of bronze technologies which they used for tools, weapons and monumental statuary. by 1200 bc they could cast objects 5 m long in a single piece. several of the six classic simple machines were invented in mesopotamia. mesopotamians have been credited with the invention of the wheel. the wheel and axle mechanism first appeared with the potter ' s wheel, invented in mesopotamia ( modern iraq ) during the 5th millennium bc. this led to the invention of the wheeled vehicle in mesopotamia during the early 4th millennium bc. depictions of wheeled wagons found on clay tablet pictographs at the eanna district of uruk are dated between 3700 and 3500 bc. the lever was used in the shadoof water - lifting device, the first crane machine, which appeared in mesopotamia circa 3000 bc, and then in ancient egyptian technology circa 2000 bc. the earliest evidence of pulleys date back to mesopotamia in the early 2nd millennium bc. the screw, the last of the simple machines to be invented, first appeared in mesopotamia during the neo - assyrian period ( 911 β 609 ) bc. the assyrian king sennacherib ( 704 β 681 bc ) claims to have invented automatic sluices and to have been the first to use water screw pumps, of up to 30 tons weight, which were cast using two - part clay molds rather than by the ' lost wax ' process. the jerwan aqueduct ( c. 688 bc ) is made with stone arches and lined with waterproof concrete. the babylonian astronomical diaries spanned 800 years. they enabled meticulous astronomers to plot the motions of the planets and to predict eclipses. the earliest evidence of water wheels and watermills date back to the ancient near east in the 4th century bc, specifically in the persian empire before 350 bc, in the regions of mesopotamia ( iraq ) and persia ( iran ). this pioneering use of water power constituted the first human - devised motive force not to rely on muscle power ( besides the sail ). = = = = egypt = = = = the egyptians, known for building pyramids centuries before the creation of modern tools, invented and used many simple machines, such as the ramp to aid construction processes. historians and archaeologists have found evidence that the pyramids were built using
Question: Behind a ship, what is the giant rectangular bucket that is dragged along from the behind called?
A) prop
B) wig
C) dredge
D) trousers
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C) dredge
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Context:
, lightning strikes, tornadoes, building fires, wildfires, and mass shootings disabling most of the system if not the entirety of it. geographic redundancy locations can be more than 621 miles ( 999 km ) continental, more than 62 miles apart and less than 93 miles ( 150 km ) apart, less than 62 miles apart, but not on the same campus, or different buildings that are more than 300 feet ( 91 m ) apart on the same campus. the following methods can reduce the risks of damage by a fire conflagration : large buildings at least 80 feet ( 24 m ) to 110 feet ( 34 m ) apart, but sometimes a minimum of 210 feet ( 64 m ) apart. : 9 high - rise buildings at least 82 feet ( 25 m ) apart : 12 open spaces clear of flammable vegetation within 200 feet ( 61 m ) on each side of objects different wings on the same building, in rooms that are separated by more than 300 feet ( 91 m ) different floors on the same wing of a building in rooms that are horizontally offset by a minimum of 70 feet ( 21 m ) with fire walls between the rooms that are on different floors two rooms separated by another room, leaving at least a 70 - foot gap between the two rooms there should be a minimum of two separated fire walls and on opposite sides of a corridor geographic redundancy is used by amazon web services ( aws ), google cloud platform ( gcp ), microsoft azure, netflix, dropbox, salesforce, linkedin, paypal, twitter, facebook, apple icloud, cisco meraki, and many others to provide geographic redundancy, high availability, fault tolerance and to ensure availability and reliability for their cloud services. as another example, to minimize risk of damage from severe windstorms or water damage, buildings can be located at least 2 miles ( 3. 2 km ) away from the shore, with an elevation of at least 5 feet ( 1. 5 m ) above sea level. for additional protection, they can be located at least 100 feet ( 30 m ) away from flood plain areas. = = functions of redundancy = = the two functions of redundancy are passive redundancy and active redundancy. both functions prevent performance decline from exceeding specification limits without human intervention using extra capacity. passive redundancy uses excess capacity to reduce the impact of component failures. one common form of passive redundancy is the extra strength of cabling and struts used in bridges.
this extra strength allows some structural components to fail without bridge collapse. the extra strength used in the design is called the margin of safety. eyes and ears provide working examples of passive redundancy. vision loss in one eye does not cause blindness but depth perception is impaired. hearing loss in one ear does not cause deafness but directionality is lost. performance decline is commonly associated with passive redundancy when a limited number of failures occur. active redundancy eliminates performance declines by monitoring the performance of individual devices, and this monitoring is used in voting logic. the voting logic is linked to switching that automatically reconfigures the components. error detection and correction and the global positioning system ( gps ) are two examples of active redundancy. electrical power distribution provides an example of active redundancy. several power lines connect each generation facility with customers. each power line includes monitors that detect overload. each power line also includes circuit breakers. the combination of power lines provides excess capacity. circuit breakers disconnect a power line when monitors detect an overload. power is redistributed across the remaining lines. at the toronto airport, there are 4 redundant electrical lines. each of the 4 lines supply enough power for the entire airport. a spot network substation uses reverse current relays to open breakers to lines that fail, but lets power continue to flow the airport. electrical power systems use power scheduling to reconfigure active redundancy. computing systems adjust the production output of each generating facility when other generating facilities are suddenly lost. this prevents blackout conditions during major events such as an earthquake. = = disadvantages = = charles perrow, author of normal accidents, has said that sometimes redundancies backfire and produce less, not more reliability. this may happen in three ways : first, redundant safety devices result in a more complex system, more prone to errors and accidents. second, redundancy may lead to shirking of responsibility among workers. third, redundancy may lead to increased production pressures, resulting in a system that operates at higher speeds, but less safely. = = voting logic = = voting logic uses performance monitoring to determine how to reconfigure individual components so that operation continues without violating specification limitations of the overall system. voting logic often involves computers, but systems composed of items other than computers may be reconfigured using voting logic. circuit breakers are an example of a form of non - computer voting logic. the simplest voting logic in computing systems involves two components :
a binary 1 - error - correcting code can always be embedded in a 1 - perfect code of some larger length
radiation exposure. marie curie died from aplastic anemia which resulted from her high levels of exposure. two scientists, an american and canadian respectively, harry daghlian and louis slotin, died after mishandling the same plutonium mass. unlike conventional weapons, the intense light, heat, and explosive force is not the only deadly component to a nuclear weapon. approximately half of the deaths from hiroshima and nagasaki died two to five years afterward from radiation exposure. civilian nuclear and radiological accidents primarily involve nuclear power plants. most common are nuclear leaks that expose workers to hazardous material. a nuclear meltdown refers to the more serious hazard of releasing nuclear material into the surrounding environment. the most significant meltdowns occurred at three mile island in pennsylvania and chernobyl in the soviet ukraine. the earthquake and tsunami on march 11, 2011 caused serious damage to three nuclear reactors and a spent fuel storage pond at the fukushima daiichi nuclear power plant in japan. military reactors that experienced similar accidents were windscale in the united kingdom and sl - 1 in the united states. military accidents usually involve the loss or unexpected detonation of nuclear weapons. the castle bravo test in 1954 produced a larger yield than expected, which contaminated nearby islands, a japanese fishing boat ( with one fatality ), and raised concerns about contaminated fish in japan. in the 1950s through 1970s, several nuclear bombs were lost from submarines and aircraft, some of which have never been recovered. the last twenty years have seen a marked decline in such accidents. = = examples of environmental benefits = = proponents of nuclear energy note that annually, nuclear - generated electricity reduces 470 million metric tons of carbon dioxide emissions that would otherwise come from fossil fuels. additionally, the amount of comparatively low waste that nuclear energy does create is safely disposed of by the large scale nuclear energy production facilities or it is repurposed / recycled for other energy uses. proponents of nuclear energy also bring to attention the opportunity cost of utilizing other forms of electricity. for example, the environmental protection agency estimates that coal kills 30, 000 people a year, as a result of its environmental impact, while 60 people died in the chernobyl disaster. a real world example of impact provided by proponents of nuclear energy is the 650, 000 ton increase in carbon emissions in the two months following the closure of the vermont yankee nuclear plant. = = see also = = atomic age lists of nuclear disasters and radioactive incidents nuclear power debate outline of nuclear technology radiology = = references = = = = external links = = nuclear energy institute β beneficial uses
in engineering and systems theory, redundancy is the intentional duplication of critical components or functions of a system with the goal of increasing reliability of the system, usually in the form of a backup or fail - safe, or to improve actual system performance, such as in the case of gnss receivers, or multi - threaded computer processing. in many safety - critical systems, such as fly - by - wire and hydraulic systems in aircraft, some parts of the control system may be triplicated, which is formally termed triple modular redundancy ( tmr ). an error in one component may then be out - voted by the other two. in a triply redundant system, the system has three sub components, all three of which must fail before the system fails. since each one rarely fails, and the sub components are designed to preclude common failure modes ( which can then be modelled as independent failure ), the probability of all three failing is calculated to be extraordinarily small ; it is often outweighed by other risk factors, such as human error. electrical surges arising from lightning strikes are an example of a failure mode which is difficult to fully isolate, unless the components are powered from independent power busses and have no direct electrical pathway in their interconnect ( communication by some means is required for voting ). redundancy may also be known by the terms " majority voting systems " or " voting logic ". redundancy sometimes produces less, instead of greater reliability β it creates a more complex system which is prone to various issues, it may lead to human neglect of duty, and may lead to higher production demands which by overstressing the system may make it less safe. redundancy is one form of robustness as practiced in computer science. geographic redundancy has become important in the data center industry, to safeguard data against natural disasters and political instability ( see below ). = = forms of redundancy = = in computer science, there are four major forms of redundancy : hardware redundancy, such as dual modular redundancy and triple modular redundancy information redundancy, such as error detection and correction methods time redundancy, performing the same operation multiple times such as multiple executions of a program or multiple copies of data transmitted software redundancy such as n - version programming a modified form of software redundancy, applied to hardware may be : distinct functional redundancy, such as both mechanical and hydraulic braking in a car. applied in the
usability engineering, it ' s important target and identify human errors when interacting with the product of interest because if a user is expected to engage with a product, interface, or service in some way, the very introduction of a human in that engagement increases the potential of encountering human error. error should be reduced as much as possible in order to avoid frustration or injury. there are two main types of human errors which are categorized as slips and mistakes. slips are a very common kind of error involving automatic behaviors ( i. e. typos, hitting the wrong menu item ). when we experience slips, we have the correct goal in mind, but execute the wrong action. mistakes on the other hand involve conscious deliberation that result in the incorrect conclusion. when we experience mistakes, we have the wrong goal in mind and thereby execute the wrong action. even though slips are the more common type of error, they are no less dangerous. a certain type of slip error, a mode error, can be especially dangerous if a user is executing a high - risk task. for instance, if a user is operating a vehicle and does not realize they are in the wrong mode ( i. e. reverse ), they might step on the gas intending to drive, but instead accelerate into a garage wall or another car. in order to avoid modal errors, designers often employ modeless states in which users do not have to choose a mode at all, or they must execute a continuous action while intending to execute a certain mode ( i. e. pressing a key continuously in order to activate " lasso " mode in photoshop ). = = evaluation methods = = usability engineers conduct usability evaluations of existing or proposed interfaces and their findings are fed back to the designer for use in design or redesign. common usability evaluation methods include : card sorting cognitive task analysis cognitive walkthroughs contextual inquiry focus groups heuristic evaluations interviews questionnaires rite method surveys think aloud protocol usability testing = = software applications and development tools = = there are a variety of online resources that make the job of a usability engineer a little easier. online tools are only a useful tool, and do not substitute for a complete usability engineering analysis. some examples of these include : = = = the web metrics tool suite = = = this is a product of the national institute of standards and technology. this toolkit is focused on evaluating the html of a website versus a wide range of usability guidelines and includes : web static analyzer tool
- threaded computer processing. in many safety - critical systems, such as fly - by - wire and hydraulic systems in aircraft, some parts of the control system may be triplicated, which is formally termed triple modular redundancy ( tmr ). an error in one component may then be out - voted by the other two. in a triply redundant system, the system has three sub components, all three of which must fail before the system fails. since each one rarely fails, and the sub components are designed to preclude common failure modes ( which can then be modelled as independent failure ), the probability of all three failing is calculated to be extraordinarily small ; it is often outweighed by other risk factors, such as human error. electrical surges arising from lightning strikes are an example of a failure mode which is difficult to fully isolate, unless the components are powered from independent power busses and have no direct electrical pathway in their interconnect ( communication by some means is required for voting ). redundancy may also be known by the terms " majority voting systems " or " voting logic ". redundancy sometimes produces less, instead of greater reliability β it creates a more complex system which is prone to various issues, it may lead to human neglect of duty, and may lead to higher production demands which by overstressing the system may make it less safe. redundancy is one form of robustness as practiced in computer science. geographic redundancy has become important in the data center industry, to safeguard data against natural disasters and political instability ( see below ). = = forms of redundancy = = in computer science, there are four major forms of redundancy : hardware redundancy, such as dual modular redundancy and triple modular redundancy information redundancy, such as error detection and correction methods time redundancy, performing the same operation multiple times such as multiple executions of a program or multiple copies of data transmitted software redundancy such as n - version programming a modified form of software redundancy, applied to hardware may be : distinct functional redundancy, such as both mechanical and hydraulic braking in a car. applied in the case of software, code written independently and distinctly different but producing the same results for the same inputs. structures are usually designed with redundant parts as well, ensuring that if one part fails, the entire structure will not collapse. a structure without redundancy is called fracture - critical, meaning that a single broken component can cause
the other two. in a triply redundant system, the system has three sub components, all three of which must fail before the system fails. since each one rarely fails, and the sub components are designed to preclude common failure modes ( which can then be modelled as independent failure ), the probability of all three failing is calculated to be extraordinarily small ; it is often outweighed by other risk factors, such as human error. electrical surges arising from lightning strikes are an example of a failure mode which is difficult to fully isolate, unless the components are powered from independent power busses and have no direct electrical pathway in their interconnect ( communication by some means is required for voting ). redundancy may also be known by the terms " majority voting systems " or " voting logic ". redundancy sometimes produces less, instead of greater reliability β it creates a more complex system which is prone to various issues, it may lead to human neglect of duty, and may lead to higher production demands which by overstressing the system may make it less safe. redundancy is one form of robustness as practiced in computer science. geographic redundancy has become important in the data center industry, to safeguard data against natural disasters and political instability ( see below ). = = forms of redundancy = = in computer science, there are four major forms of redundancy : hardware redundancy, such as dual modular redundancy and triple modular redundancy information redundancy, such as error detection and correction methods time redundancy, performing the same operation multiple times such as multiple executions of a program or multiple copies of data transmitted software redundancy such as n - version programming a modified form of software redundancy, applied to hardware may be : distinct functional redundancy, such as both mechanical and hydraulic braking in a car. applied in the case of software, code written independently and distinctly different but producing the same results for the same inputs. structures are usually designed with redundant parts as well, ensuring that if one part fails, the entire structure will not collapse. a structure without redundancy is called fracture - critical, meaning that a single broken component can cause the collapse of the entire structure. bridges that failed due to lack of redundancy include the silver bridge and the interstate 5 bridge over the skagit river. parallel and combined systems demonstrate different level of redundancy. the models are subject of studies in reliability and safety engineering. = = = dissimilar red
beacon transmits two signals simultaneously on different frequencies. a directional antenna transmits a beam of radio waves that rotates like a lighthouse at a fixed rate, 30 times per second. when the directional beam is facing north, an omnidirectional antenna transmits a pulse. by measuring the difference in phase of these two signals, an aircraft can determine its bearing ( or " radial " ) from the station accurately. by taking a bearing on two vor beacons an aircraft can determine its position ( called a " fix " ) to an accuracy of about 90 metres ( 300 ft ). most vor beacons also have a distance measuring capability, called distance measuring equipment ( dme ) ; these are called vor / dme ' s. the aircraft transmits a radio signal to the vor / dme beacon and a transponder transmits a return signal. from the propagation delay between the transmitted and received signal the aircraft can calculate its distance from the beacon. this allows an aircraft to determine its location " fix " from only one vor beacon. since line - of - sight vhf frequencies are used vor beacons have a range of about 200 miles for aircraft at cruising altitude. tacan is a similar military radio beacon system which transmits in 962 β 1213 mhz, and a combined vor and tacan beacon is called a vortac. the number of vor beacons is declining as aviation switches to the rnav system that relies on global positioning system satellite navigation. instrument landing system ( ils ) - a short range radio navigation aid at airports which guides aircraft landing in low visibility conditions. it consists of multiple antennas at the end of each runway that radiate two beams of radio waves along the approach to the runway : the localizer ( 108 to 111. 95 mhz frequency ), which provides horizontal guidance, a heading line to keep the aircraft centered on the runway, and the glideslope ( 329. 15 to 335 mhz ) for vertical guidance, to keep the aircraft descending at the proper rate for a smooth touchdown at the correct point on the runway. each aircraft has a receiver instrument and antenna which receives the beams, with an indicator to tell the pilot whether he is on the correct horizontal and vertical approach. the ils beams are receivable for at least 15 miles, and have a radiated power of 25 watts. ils systems at airports are being replaced by systems that use satellite navigation. non - directional beacon ( ndb ) β legacy fixed radio beacons used before the vo
general modes : static failure, and fatigue failure. static structural failure occurs when, upon being loaded ( having a force applied ) the object being analyzed either breaks or is deformed plastically, depending on the criterion for failure. fatigue failure occurs when an object fails after a number of repeated loading and unloading cycles. fatigue failure occurs because of imperfections in the object : a microscopic crack on the surface of the object, for instance, will grow slightly with each cycle ( propagation ) until the crack is large enough to cause ultimate failure. failure is not simply defined as when a part breaks, however ; it is defined as when a part does not operate as intended. some systems, such as the perforated top sections of some plastic bags, are designed to break. if these systems do not break, failure analysis might be employed to determine the cause. structural analysis is often used by mechanical engineers after a failure has occurred, or when designing to prevent failure. engineers often use online documents and books such as those published by asm to aid them in determining the type of failure and possible causes. once theory is applied to a mechanical design, physical testing is often performed to verify calculated results. structural analysis may be used in an office when designing parts, in the field to analyze failed parts, or in laboratories where parts might undergo controlled failure tests. = = = thermodynamics and thermo - science = = = thermodynamics is an applied science used in several branches of engineering, including mechanical and chemical engineering. at its simplest, thermodynamics is the study of energy, its use and transformation through a system. typically, engineering thermodynamics is concerned with changing energy from one form to another. as an example, automotive engines convert chemical energy ( enthalpy ) from the fuel into heat, and then into mechanical work that eventually turns the wheels. thermodynamics principles are used by mechanical engineers in the fields of heat transfer, thermofluids, and energy conversion. mechanical engineers use thermo - science to design engines and power plants, heating, ventilation, and air - conditioning ( hvac ) systems, heat exchangers, heat sinks, radiators, refrigeration, insulation, and others. = = = design and drafting = = = drafting or technical drawing is the means by which mechanical engineers design products and create instructions for manufacturing parts. a technical drawing can be a computer model or hand - drawn schematic showing all the dimensions necessary to manufacture a
Question: What is it called when multiple faults are located in close proximity to one another?
A) crystal zone
B) solid zone
C) fault zone
D) fog zone
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C) fault zone
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Context:
cortisol, corticosterone and aldosterone activate full - length glucocorticoid receptor ( gr ) from elephant shark, a cartilaginous fish belonging to the oldest group of jawed vertebrates. activation by aldosterone a mineralocorticoid, indicates partial divergence of elephant shark gr from the mr. progesterone activates elephant shark mr, but not elephant shark gr. progesterone inhibits steroid binding to elephant shark gr, but not to human gr. deletion of the n - terminal domain ( ntd ) from elephant shark gr ( truncated gr ) reduced the response to corticosteroids, while truncated and full - length elephant shark mr had similar responses to corticosteroids. chimeras of elephant shark gr ntd fused to mr dbd + lbd had increased activation by corticosteroids and progesterone compared to full - length elephant shark mr. elephant shark mr ntd fused to gr dbd + lbd had similar activation as full - length elephant shark mr, indicating that activation of human gr by the ntd evolved early in gr divergence from the mr.
a cell. there are generally four types of chemical signals : autocrine, paracrine, juxtacrine, and hormones. in autocrine signaling, the ligand affects the same cell that releases it. tumor cells, for example, can reproduce uncontrollably because they release signals that initiate their own self - division. in paracrine signaling, the ligand diffuses to nearby cells and affects them. for example, brain cells called neurons release ligands called neurotransmitters that diffuse across a synaptic cleft to bind with a receptor on an adjacent cell such as another neuron or muscle cell. in juxtacrine signaling, there is direct contact between the signaling and responding cells. finally, hormones are ligands that travel through the circulatory systems of animals or vascular systems of plants to reach their target cells. once a ligand binds with a receptor, it can influence the behavior of another cell, depending on the type of receptor. for instance, neurotransmitters that bind with an inotropic receptor can alter the excitability of a target cell. other types of receptors include protein kinase receptors ( e. g., receptor for the hormone insulin ) and g protein - coupled receptors. activation of g protein - coupled receptors can initiate second messenger cascades. the process by which a chemical or physical signal is transmitted through a cell as a series of molecular events is called signal transduction. = = = cell cycle = = = the cell cycle is a series of events that take place in a cell that cause it to divide into two daughter cells. these events include the duplication of its dna and some of its organelles, and the subsequent partitioning of its cytoplasm into two daughter cells in a process called cell division. in eukaryotes ( i. e., animal, plant, fungal, and protist cells ), there are two distinct types of cell division : mitosis and meiosis. mitosis is part of the cell cycle, in which replicated chromosomes are separated into two new nuclei. cell division gives rise to genetically identical cells in which the total number of chromosomes is maintained. in general, mitosis ( division of the nucleus ) is preceded by the s stage of interphase ( during which the dna is replicated ) and is often followed by telophase and cytokinesis ; which divides the cytoplasm, organelles and cell membrane of one cell into two new cells containing roughly equal shares
cell. in juxtacrine signaling, there is direct contact between the signaling and responding cells. finally, hormones are ligands that travel through the circulatory systems of animals or vascular systems of plants to reach their target cells. once a ligand binds with a receptor, it can influence the behavior of another cell, depending on the type of receptor. for instance, neurotransmitters that bind with an inotropic receptor can alter the excitability of a target cell. other types of receptors include protein kinase receptors ( e. g., receptor for the hormone insulin ) and g protein - coupled receptors. activation of g protein - coupled receptors can initiate second messenger cascades. the process by which a chemical or physical signal is transmitted through a cell as a series of molecular events is called signal transduction. = = = cell cycle = = = the cell cycle is a series of events that take place in a cell that cause it to divide into two daughter cells. these events include the duplication of its dna and some of its organelles, and the subsequent partitioning of its cytoplasm into two daughter cells in a process called cell division. in eukaryotes ( i. e., animal, plant, fungal, and protist cells ), there are two distinct types of cell division : mitosis and meiosis. mitosis is part of the cell cycle, in which replicated chromosomes are separated into two new nuclei. cell division gives rise to genetically identical cells in which the total number of chromosomes is maintained. in general, mitosis ( division of the nucleus ) is preceded by the s stage of interphase ( during which the dna is replicated ) and is often followed by telophase and cytokinesis ; which divides the cytoplasm, organelles and cell membrane of one cell into two new cells containing roughly equal shares of these cellular components. the different stages of mitosis all together define the mitotic phase of an animal cell cycle β the division of the mother cell into two genetically identical daughter cells. the cell cycle is a vital process by which a single - celled fertilized egg develops into a mature organism, as well as the process by which hair, skin, blood cells, and some internal organs are renewed. after cell division, each of the daughter cells begin the interphase of a new cycle. in contrast to mitosis, meiosis results in four haploid daughter cells by undergoing one round of dna replication followed by two divisions
to investigate the affinity of acetylated wood for organic liquids, yezo spruce wood specimens were acetylated with acetic anhydride, and their swelling in various liquids were compared to those of untreated specimens. the acetylated wood was rapidly and remarkably swollen in aprotic organic liquids such as benzene and toluene in which the untreated wood was swollen only slightly and / or very slowly. on the other hand, the swelling of wood in water, ethylene glycol and alcohols remained unchanged or decreased by the acetylation. consequently the maximum volume of wood swollen in organic liquids was always larger than that in water. the effect of acetylation on the maximum swollen volume of wood was greater in liquids having smaller solubility parameters. the easier penetration of aprotic organic liquids into the acetylated wood was considered to be due to the scission of hydrogen bonds among the amorphous wood constituents by the substitution of hydroxyl groups with hydrophobic acetyl groups.
electrons to drive the synthesis of glucose by fixing atmospheric carbon dioxide into existing organic carbon compounds, such as ribulose bisphosphate ( rubp ) in a sequence of light - independent ( or dark ) reactions called the calvin cycle. = = = cell signaling = = = cell signaling ( or communication ) is the ability of cells to receive, process, and transmit signals with its environment and with itself. signals can be non - chemical such as light, electrical impulses, and heat, or chemical signals ( or ligands ) that interact with receptors, which can be found embedded in the cell membrane of another cell or located deep inside a cell. there are generally four types of chemical signals : autocrine, paracrine, juxtacrine, and hormones. in autocrine signaling, the ligand affects the same cell that releases it. tumor cells, for example, can reproduce uncontrollably because they release signals that initiate their own self - division. in paracrine signaling, the ligand diffuses to nearby cells and affects them. for example, brain cells called neurons release ligands called neurotransmitters that diffuse across a synaptic cleft to bind with a receptor on an adjacent cell such as another neuron or muscle cell. in juxtacrine signaling, there is direct contact between the signaling and responding cells. finally, hormones are ligands that travel through the circulatory systems of animals or vascular systems of plants to reach their target cells. once a ligand binds with a receptor, it can influence the behavior of another cell, depending on the type of receptor. for instance, neurotransmitters that bind with an inotropic receptor can alter the excitability of a target cell. other types of receptors include protein kinase receptors ( e. g., receptor for the hormone insulin ) and g protein - coupled receptors. activation of g protein - coupled receptors can initiate second messenger cascades. the process by which a chemical or physical signal is transmitted through a cell as a series of molecular events is called signal transduction. = = = cell cycle = = = the cell cycle is a series of events that take place in a cell that cause it to divide into two daughter cells. these events include the duplication of its dna and some of its organelles, and the subsequent partitioning of its cytoplasm into two daughter cells in a process called cell division. in eukaryotes ( i. e., animal, plant, fungal, and
own self - division. in paracrine signaling, the ligand diffuses to nearby cells and affects them. for example, brain cells called neurons release ligands called neurotransmitters that diffuse across a synaptic cleft to bind with a receptor on an adjacent cell such as another neuron or muscle cell. in juxtacrine signaling, there is direct contact between the signaling and responding cells. finally, hormones are ligands that travel through the circulatory systems of animals or vascular systems of plants to reach their target cells. once a ligand binds with a receptor, it can influence the behavior of another cell, depending on the type of receptor. for instance, neurotransmitters that bind with an inotropic receptor can alter the excitability of a target cell. other types of receptors include protein kinase receptors ( e. g., receptor for the hormone insulin ) and g protein - coupled receptors. activation of g protein - coupled receptors can initiate second messenger cascades. the process by which a chemical or physical signal is transmitted through a cell as a series of molecular events is called signal transduction. = = = cell cycle = = = the cell cycle is a series of events that take place in a cell that cause it to divide into two daughter cells. these events include the duplication of its dna and some of its organelles, and the subsequent partitioning of its cytoplasm into two daughter cells in a process called cell division. in eukaryotes ( i. e., animal, plant, fungal, and protist cells ), there are two distinct types of cell division : mitosis and meiosis. mitosis is part of the cell cycle, in which replicated chromosomes are separated into two new nuclei. cell division gives rise to genetically identical cells in which the total number of chromosomes is maintained. in general, mitosis ( division of the nucleus ) is preceded by the s stage of interphase ( during which the dna is replicated ) and is often followed by telophase and cytokinesis ; which divides the cytoplasm, organelles and cell membrane of one cell into two new cells containing roughly equal shares of these cellular components. the different stages of mitosis all together define the mitotic phase of an animal cell cycle β the division of the mother cell into two genetically identical daughter cells. the cell cycle is a vital process by which a single - celled fertilized egg develops into a mature organism, as well as
the action potential is widely considered a purely electrical phenomenon. however, one also finds mechanical and thermal changes that can be observed experimentally. in particular, nerve membranes become thicker and axons contract. the spatial length of the action potential can be quite large, ranging from millimeters to many centimeters. this suggests to employ macroscopic thermodynamics methods to understand its properties. the pulse length is several orders of magnitude larger than the synaptic gap, larger than the distance of the nodes of ranvier, and even larger than the size of many neurons such as pyramidal cells or brain stem motor neurons. here, we review the mechanical changes in nerves, theoretical possibilities to explain them, and implications of a mechanical nerve pulse for the neuron and for the brain. in particular, the contraction of nerves gives rise to the possibility of fast mechanical synapses.
in building up composite structures using carbon nanotube ( cnt ) fibers, the fiber - to - matrix interfacial shear strength ( ifss ) is one of the most important issues. originating from the assembly characteristics of cnt fiber, the ifss strongly depends on the fiber ' s twisting level and densification level. furthermore, there are rich ways to modify the fiber surface and thus enhance the ifss, including the physical and chemical modification on fiber surface, the infiltration of matrix resin into cnt fiber, and the introduction of silane coupling agent. a new feature differing from carbon fibers is that all these treatments either change the fiber ' s surface structure or form a several - hundreds - nm - thick interphase inside rather than around the fiber. these " generalized " treatments obviously extend the common concept of surface sizing and can be used for various forms of cnt assembly structures.
if a fintie group g acts topologically and faithfully on r ^ 3, then g is a subgroup of o ( 3 )
this paper has been withdrawn, see the replacement arxiv : 1302. 6670.
Question: Binding of acetylcholine to receptors on the muscle fiber leads to a?
A) excitation
B) repolarization
C) depolarization
D) conduction
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C) depolarization
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Context:
onset of electro - chemical corrosion. similar problems are encountered in coastal and offshore structures. = = = anti - fouling = = = anti - fouling is the process of eliminating obstructive organisms from essential components of seawater systems. depending on the nature and location of marine growth, this process is performed in a number of different ways : marine organisms may grow and attach to the surfaces of the outboard suction inlets used to obtain water for cooling systems. electro - chlorination involves running high electrical current through sea water, altering the water ' s chemical composition to create sodium hypochlorite, purging any bio - matter. an electrolytic method of anti - fouling involves running electrical current through two anodes ( scardino, 2009 ). these anodes typically consist of copper and aluminum ( or alternatively, iron ). the first metal, copper anode, releases its ion into the water, creating an environment that is too toxic for bio - matter. the second metal, aluminum, coats the inside of the pipes to prevent corrosion. other forms of marine growth such as mussels and algae may attach themselves to the bottom of a ship ' s hull. this growth interferes with the smoothness and uniformity of the ship ' s hull, causing the ship to have a less hydrodynamic shape that causes it to be slower and less fuel - efficient. marine growth on the hull can be remedied by using special paint that prevents the growth of such organisms. = = = pollution control = = = = = = = sulfur emission = = = = the burning of marine fuels releases harmful pollutants into the atmosphere. ships burn marine diesel in addition to heavy fuel oil. heavy fuel oil, being the heaviest of refined oils, releases sulfur dioxide when burned. sulfur dioxide emissions have the potential to raise atmospheric and ocean acidity causing harm to marine life. however, heavy fuel oil may only be burned in international waters due to the pollution created. it is commercially advantageous due to the cost effectiveness compared to other marine fuels. it is prospected that heavy fuel oil will be phased out of commercial use by the year 2020 ( smith, 2018 ). = = = = oil and water discharge = = = = water, oil, and other substances collect at the bottom of the ship in what is known as the bilge. bilge water is pumped overboard, but must pass a pollution threshold test of 15 ppm ( parts per million ) of oil to be discharged. water is tested
are continuous lines used to depict edges directly visible from a particular angle. hidden β are short - dashed lines that may be used to represent edges that are not directly visible. center β are alternately long - and short - dashed lines that may be used to represent the axes of circular features. cutting plane β are thin, medium - dashed lines, or thick alternately long - and double short - dashed that may be used to define sections for section views. section β are thin lines in a pattern ( pattern determined by the material being " cut " or " sectioned " ) used to indicate surfaces in section views resulting from " cutting ". section lines are commonly referred to as " cross - hatching ". phantom β ( not shown ) are alternately long - and double short - dashed thin lines used to represent a feature or component that is not part of the specified part or assembly. e. g. billet ends that may be used for testing, or the machined product that is the focus of a tooling drawing. lines can also be classified by a letter classification in which each line is given a letter. type a lines show the outline of the feature of an object. they are the thickest lines on a drawing and done with a pencil softer than hb. type b lines are dimension lines and are used for dimensioning, projecting, extending, or leaders. a harder pencil should be used, such as a 2h pencil. type c lines are used for breaks when the whole object is not shown. these are freehand drawn and only for short breaks. 2h pencil type d lines are similar to type c, except these are zigzagged and only for longer breaks. 2h pencil type e lines indicate hidden outlines of internal features of an object. these are dotted lines. 2h pencil type f lines are type e lines, except these are used for drawings in electrotechnology. 2h pencil type g lines are used for centre lines. these are dotted lines, but a long line of 10 β 20 mm, then a 1 mm gap, then a small line of 2 mm. 2h pencil type h lines are the same as type g, except that every second long line is thicker. these indicate the cutting plane of an object. 2h pencil type k lines indicate the alternate positions of an object and the line taken by that object. these are drawn with a long line of 10 β 20 mm, then a small gap, then a small line of 2 mm, then a gap, then another small line. 2h
frequent itemsets form a polytope and can be found and analyzed with linear programming.
- dashed lines, or thick alternately long - and double short - dashed that may be used to define sections for section views. section β are thin lines in a pattern ( pattern determined by the material being " cut " or " sectioned " ) used to indicate surfaces in section views resulting from " cutting ". section lines are commonly referred to as " cross - hatching ". phantom β ( not shown ) are alternately long - and double short - dashed thin lines used to represent a feature or component that is not part of the specified part or assembly. e. g. billet ends that may be used for testing, or the machined product that is the focus of a tooling drawing. lines can also be classified by a letter classification in which each line is given a letter. type a lines show the outline of the feature of an object. they are the thickest lines on a drawing and done with a pencil softer than hb. type b lines are dimension lines and are used for dimensioning, projecting, extending, or leaders. a harder pencil should be used, such as a 2h pencil. type c lines are used for breaks when the whole object is not shown. these are freehand drawn and only for short breaks. 2h pencil type d lines are similar to type c, except these are zigzagged and only for longer breaks. 2h pencil type e lines indicate hidden outlines of internal features of an object. these are dotted lines. 2h pencil type f lines are type e lines, except these are used for drawings in electrotechnology. 2h pencil type g lines are used for centre lines. these are dotted lines, but a long line of 10 β 20 mm, then a 1 mm gap, then a small line of 2 mm. 2h pencil type h lines are the same as type g, except that every second long line is thicker. these indicate the cutting plane of an object. 2h pencil type k lines indicate the alternate positions of an object and the line taken by that object. these are drawn with a long line of 10 β 20 mm, then a small gap, then a small line of 2 mm, then a gap, then another small line. 2h pencil. = = = multiple views and projections = = = in most cases, a single view is not sufficient to show all necessary features, and several views are used. types of views include the following : = = = = multiview projection = = = = a multiview projection is a type of orthographic projection
subsea engineering and the ability to detect, track and destroy submarines ( anti - submarine warfare ) required the parallel development of a host of marine scientific instrumentation and sensors. visible light is not transferred far underwater, so the medium for transmission of data is primarily acoustic. high - frequency sound is used to measure the depth of the ocean, determine the nature of the seafloor, and detect submerged objects. the higher the frequency, the higher the definition of the data that is returned. sound navigation and ranging or sonar was developed during the first world war to detect submarines, and has been greatly refined through to the present day. submarines similarly use sonar equipment to detect and target other submarines and surface ships, and to detect submerged obstacles such as seamounts that pose a navigational obstacle. simple echo - sounders point straight down and can give an accurate reading of ocean depth ( or look up at the underside of sea - ice ). more advanced echo sounders use a fan - shaped beam or sound, or multiple beams to derive highly detailed images of the ocean floor. high power systems can penetrate the soil and seabed rocks to give information about the geology of the seafloor, and are widely used in geophysics for the discovery of hydrocarbons, or for engineering survey. for close - range underwater communications, optical transmission is possible, mainly using blue lasers. these have a high bandwidth compared with acoustic systems, but the range is usually only a few tens of metres, and ideally at night. as well as acoustic communications and navigation, sensors have been developed to measure ocean parameters such as temperature, salinity, oxygen levels and other properties including nitrate levels, levels of trace chemicals and environmental dna. the industry trend has been towards smaller, more accurate and more affordable systems so that they can be purchased and used by university departments and small companies as well as large corporations, research organisations and governments. the sensors and instruments are fitted to autonomous and remotely - operated systems as well as ships, and are enabling these systems to take on tasks that hitherto required an expensive human - crewed platform. manufacture of marine sensors and instruments mainly takes place in asia, europe and north america. products are advertised in specialist journals, and through trade shows such as oceanology international and ocean business which help raise awareness of the products. = = = environmental engineering = = = in every coastal and offshore project, environmental sustainability is an important consideration for the preservation of ocean ecosystems and natural resources. instances in which marine engineers benefit from knowledge of environmental engineering include creation of fisheries, clean
= = = the ancient norse and germanic peoples believed in a flat - earth cosmography with the earth surrounded by an ocean, with the axis mundi, a world tree ( yggdrasil ), or pillar ( irminsul ) in the centre. in the world - encircling ocean sat a snake called jormungandr. the norse creation account preserved in gylfaginning ( viii ) states that during the creation of the earth, an impassable sea was placed around it : and jafnharr said : " of the blood, which ran and welled forth freely out of his wounds, they made the sea, when they had formed and made firm the earth together, and laid the sea in a ring round. about her ; and it may well seem a hard thing to most men to cross over it. " the late norse konungs skuggsja, on the other hand, explains earth ' s shape as a sphere : if you take a lighted candle and set it in a room, you may expect it to light up the entire interior, unless something should hinder, though the room be quite large. but if you take an apple and hang it close to the flame, so near that it is heated, the apple will darken nearly half the room or even more. however, if you hang the apple near the wall, it will not get hot ; the candle will light up the whole house ; and the shadow on the wall where the apple hangs will be scarcely half as large as the apple itself. from this you may infer that the earth - circle is round like a ball and not equally near the sun at every point. but where the curved surface lies nearest the sun ' s path, there will the greatest heat be ; and some of the lands that lie continuously under the unbroken rays cannot be inhabited. = = = = east asia = = = = in ancient china, the prevailing belief was that the earth was flat and square, while the heavens were round, an assumption virtually unquestioned until the introduction of european astronomy in the 17th century. the english sinologist cullen emphasizes the point that there was no concept of a round earth in ancient chinese astronomy : chinese thought on the form of the earth remained almost unchanged from early times until the first contacts with modern science through the medium of jesuit missionaries in the seventeenth century. while the heavens were variously described as being like an umbrella covering the earth ( the kai tian theory ), or like a sphere surrounding it (
river - beds ), but not for where there may be large obstructions in the ground. an open caisson that is used in soft grounds or high water tables, where open trench excavations are impractical, can also be used to install deep manholes, pump stations and reception / launch pits for microtunnelling, pipe jacking and other operations. a caisson is sunk by self - weight, concrete or water ballast placed on top, or by hydraulic jacks. the leading edge ( or cutting shoe ) of the caisson is sloped out at a sharp angle to aid sinking in a vertical manner ; it is usually made of steel. the shoe is generally wider than the caisson to reduce friction, and the leading edge may be supplied with pressurised bentonite slurry, which swells in water, stabilizing settlement by filling depressions and voids. an open caisson may fill with water during sinking. the material is excavated by clamshell excavator bucket on crane. the formation level subsoil may still not be suitable for excavation or bearing capacity. the water in the caisson ( due to a high water table ) balances the upthrust forces of the soft soils underneath. if dewatered, the base may " pipe " or " boil ", causing the caisson to sink. to combat this problem, piles may be driven from the surface to act as : load - bearing walls, in that they transmit loads to deeper soils. anchors, in that they resist flotation because of the friction at the interface between their surfaces and the surrounding earth into which they have been driven. h - beam sections ( typical column sections, due to resistance to bending in all axis ) may be driven at angles " raked " to rock or other firmer soils ; the h - beams are left extended above the base. a reinforced concrete plug may be placed under the water, a process known as tremie concrete placement. when the caisson is dewatered, this plug acts as a pile cap, resisting the upward forces of the subsoil. = = = monolithic = = = a monolithic caisson ( or simply a monolith ) is larger than the other types of caisson, but similar to open caissons. such caissons are often found in quay walls, where resistance to impact from ships is required. = = = pneumatic = = = shallow caissons may be open to the air, whereas pneumatic caisson
planets less massive than about 10 mearth are expected to have no massive h - he atmosphere and a cometary composition ( 50 % rocks, 50 % water, by mass ) provided they formed beyond the snowline of protoplanetary disks. due to inward migration, such planets could be found at any distance between their formation site and the star. if migration stops within the habitable zone, this will produce a new kind of planets, called ocean - planets. ocean - planets typically consist in a silicate core, surrounded by a thick ice mantle, itself covered by a 100 km deep ocean. the existence of ocean - planets raises important astrobiological questions : can life originate on such body, in the absence of continent and ocean - silicate interfaces? what would be the nature of the atmosphere and the geochemical cycles? in this work, we address the fate of hot ocean - planets produced when migration ends at a closer distance. in this case the liquid / gas interface can disappear, and the hot h2o envelope is made of a supercritical fluid. although we do not expect these bodies to harbor life, their detection and identification as water - rich planets would give us insight as to the abundance of hot and, by extrapolation, cool ocean - planets.
assuming that the e ( 38 ) boson candidate recently observed at the jinr nuclotron is produced in a bremsstrahlung - like manner and decays only to two photons, its coupling constant to light quarks is estimated to be $ \ sim 10 ^ { - 4 } $.
the goal of project gauss is to return samples from the dwarf planet ceres. ceres is the most accessible ocean world candidate and the largest reservoir of water in the inner solar system. it shows active cryovolcanism and hydrothermal activities in recent history that resulted in minerals not found in any other planets to date except for earth ' s upper crust. the possible occurrence of recent subsurface ocean on ceres and the complex geochemistry suggest possible past habitability and even the potential for ongoing habitability. aiming to answer a broad spectrum of questions about the origin and evolution of ceres and its potential habitability, gauss will return samples from this possible ocean world for the first time. the project will address the following top - level scientific questions : 1 ) what is the origin of ceres and the origin and transfer of water and other volatiles in the inner solar system? 2 ) what are the physical properties and internal structure of ceres? what do they tell us about the evolutionary and aqueous alteration history of icy dwarf planets? 3 ) what are the astrobiological implications of ceres? was it habitable in the past and is it still today? 4 ) what are the mineralogical connections between ceres and our current collections of primitive meteorites? gauss will first perform a high - resolution global remote sensing investigation, characterizing the geophysical and geochemical properties of ceres. candidate sampling sites will then be identified, and observation campaigns will be run for an in - depth assessment of the candidate sites. once the sampling site is selected, a lander will be deployed on the surface to collect samples and return them to earth in cryogenic conditions that preserves the volatile and organic composition as well as the original physical status as much as possible.
Question: Most tunicates live a sessile existence in shallow ocean waters and are suspension feeders. the primary foods of tunicates are plankton and this?
A) bacteria
B) detritus
C) crustaceans
D) debris
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B) detritus
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Context:
stems mainly provide support to the leaves and reproductive structures, but can store water in succulent plants such as cacti, food as in potato tubers, or reproduce vegetatively as in the stolons of strawberry plants or in the process of layering. leaves gather sunlight and carry out photosynthesis. large, flat, flexible, green leaves are called foliage leaves. gymnosperms, such as conifers, cycads, ginkgo, and gnetophytes are seed - producing plants with open seeds. angiosperms are seed - producing plants that produce flowers and have enclosed seeds. woody plants, such as azaleas and oaks, undergo a secondary growth phase resulting in two additional types of tissues : wood ( secondary xylem ) and bark ( secondary phloem and cork ). all gymnosperms and many angiosperms are woody plants. some plants reproduce sexually, some asexually, and some via both means. although reference to major morphological categories such as root, stem, leaf, and trichome are useful, one has to keep in mind that these categories are linked through intermediate forms so that a continuum between the categories results. furthermore, structures can be seen as processes, that is, process combinations. = = systematic botany = = systematic botany is part of systematic biology, which is concerned with the range and diversity of organisms and their relationships, particularly as determined by their evolutionary history. it involves, or is related to, biological classification, scientific taxonomy and phylogenetics. biological classification is the method by which botanists group organisms into categories such as genera or species. biological classification is a form of scientific taxonomy. modern taxonomy is rooted in the work of carl linnaeus, who grouped species according to shared physical characteristics. these groupings have since been revised to align better with the darwinian principle of common descent β grouping organisms by ancestry rather than superficial characteristics. while scientists do not always agree on how to classify organisms, molecular phylogenetics, which uses dna sequences as data, has driven many recent revisions along evolutionary lines and is likely to continue to do so. the dominant classification system is called linnaean taxonomy. it includes ranks and binomial nomenclature. the nomenclature of botanical organisms is codified in the international code of nomenclature for algae, fungi, and plants ( icn ) and administered by the international botanical congress. kingdom plantae belongs to domain eukaryota and is broken down recursively until each species is separately classified. the order is :
##nosperms and angiosperms. gymnosperms produce " naked seeds " not fully enclosed in an ovary ; modern representatives include conifers, cycads, ginkgo, and gnetales. angiosperms produce seeds enclosed in a structure such as a carpel or an ovary. ongoing research on the molecular phylogenetics of living plants appears to show that the angiosperms are a sister clade to the gymnosperms. = = plant physiology = = plant physiology encompasses all the internal chemical and physical activities of plants associated with life. chemicals obtained from the air, soil and water form the basis of all plant metabolism. the energy of sunlight, captured by oxygenic photosynthesis and released by cellular respiration, is the basis of almost all life. photoautotrophs, including all green plants, algae and cyanobacteria gather energy directly from sunlight by photosynthesis. heterotrophs including all animals, all fungi, all completely parasitic plants, and non - photosynthetic bacteria take in organic molecules produced by photoautotrophs and respire them or use them in the construction of cells and tissues. respiration is the oxidation of carbon compounds by breaking them down into simpler structures to release the energy they contain, essentially the opposite of photosynthesis. molecules are moved within plants by transport processes that operate at a variety of spatial scales. subcellular transport of ions, electrons and molecules such as water and enzymes occurs across cell membranes. minerals and water are transported from roots to other parts of the plant in the transpiration stream. diffusion, osmosis, and active transport and mass flow are all different ways transport can occur. examples of elements that plants need to transport are nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. in vascular plants, these elements are extracted from the soil as soluble ions by the roots and transported throughout the plant in the xylem. most of the elements required for plant nutrition come from the chemical breakdown of soil minerals. sucrose produced by photosynthesis is transported from the leaves to other parts of the plant in the phloem and plant hormones are transported by a variety of processes. = = = plant hormones = = = plants are not passive, but respond to external signals such as light, touch, and injury by moving or growing towards or away from the stimulus, as appropriate. tangible evidence of touch sensitivity is the almost instantaneous collapse of leaflets of mimosa pudica, the insect traps of
the strictest definition of " plant " includes only the " land plants " or embryophytes, which include seed plants ( gymnosperms, including the pines, and flowering plants ) and the free - sporing cryptogams including ferns, clubmosses, liverworts, hornworts and mosses. embryophytes are multicellular eukaryotes descended from an ancestor that obtained its energy from sunlight by photosynthesis. they have life cycles with alternating haploid and diploid phases. the sexual haploid phase of embryophytes, known as the gametophyte, nurtures the developing diploid embryo sporophyte within its tissues for at least part of its life, even in the seed plants, where the gametophyte itself is nurtured by its parent sporophyte. other groups of organisms that were previously studied by botanists include bacteria ( now studied in bacteriology ), fungi ( mycology ) β including lichen - forming fungi ( lichenology ), non - chlorophyte algae ( phycology ), and viruses ( virology ). however, attention is still given to these groups by botanists, and fungi ( including lichens ) and photosynthetic protists are usually covered in introductory botany courses. palaeobotanists study ancient plants in the fossil record to provide information about the evolutionary history of plants. cyanobacteria, the first oxygen - releasing photosynthetic organisms on earth, are thought to have given rise to the ancestor of plants by entering into an endosymbiotic relationship with an early eukaryote, ultimately becoming the chloroplasts in plant cells. the new photosynthetic plants ( along with their algal relatives ) accelerated the rise in atmospheric oxygen started by the cyanobacteria, changing the ancient oxygen - free, reducing, atmosphere to one in which free oxygen has been abundant for more than 2 billion years. among the important botanical questions of the 21st century are the role of plants as primary producers in the global cycling of life ' s basic ingredients : energy, carbon, oxygen, nitrogen and water, and ways that our plant stewardship can help address the global environmental issues of resource management, conservation, human food security, biologically invasive organisms, carbon sequestration, climate change, and sustainability. = = = human nutrition = = = virtually all staple foods come either directly from primary production by plants, or indirectly from animals that
unspecialised cells ) that can grow into a new plant. in vascular plants, the xylem and phloem are the conductive tissues that transport resources between shoots and roots. roots are often adapted to store food such as sugars or starch, as in sugar beets and carrots. stems mainly provide support to the leaves and reproductive structures, but can store water in succulent plants such as cacti, food as in potato tubers, or reproduce vegetatively as in the stolons of strawberry plants or in the process of layering. leaves gather sunlight and carry out photosynthesis. large, flat, flexible, green leaves are called foliage leaves. gymnosperms, such as conifers, cycads, ginkgo, and gnetophytes are seed - producing plants with open seeds. angiosperms are seed - producing plants that produce flowers and have enclosed seeds. woody plants, such as azaleas and oaks, undergo a secondary growth phase resulting in two additional types of tissues : wood ( secondary xylem ) and bark ( secondary phloem and cork ). all gymnosperms and many angiosperms are woody plants. some plants reproduce sexually, some asexually, and some via both means. although reference to major morphological categories such as root, stem, leaf, and trichome are useful, one has to keep in mind that these categories are linked through intermediate forms so that a continuum between the categories results. furthermore, structures can be seen as processes, that is, process combinations. = = systematic botany = = systematic botany is part of systematic biology, which is concerned with the range and diversity of organisms and their relationships, particularly as determined by their evolutionary history. it involves, or is related to, biological classification, scientific taxonomy and phylogenetics. biological classification is the method by which botanists group organisms into categories such as genera or species. biological classification is a form of scientific taxonomy. modern taxonomy is rooted in the work of carl linnaeus, who grouped species according to shared physical characteristics. these groupings have since been revised to align better with the darwinian principle of common descent β grouping organisms by ancestry rather than superficial characteristics. while scientists do not always agree on how to classify organisms, molecular phylogenetics, which uses dna sequences as data, has driven many recent revisions along evolutionary lines and is likely to continue to do so. the dominant classification system is called linnaean taxonomy. it includes ranks and binomi
, dendrology is the study of woody plants. many divisions of biology have botanical subfields. these are commonly denoted by prefixing the word plant ( e. g. plant taxonomy, plant ecology, plant anatomy, plant morphology, plant systematics ), or prefixing or substituting the prefix phyto - ( e. g. phytochemistry, phytogeography ). the study of fossil plants is called palaeobotany. other fields are denoted by adding or substituting the word botany ( e. g. systematic botany ). phytosociology is a subfield of plant ecology that classifies and studies communities of plants. the intersection of fields from the above pair of categories gives rise to fields such as bryogeography, the study of the distribution of mosses. different parts of plants also give rise to their own subfields, including xylology, carpology ( or fructology ), and palynology, these being the study of wood, fruit and pollen / spores respectively. botany also overlaps on the one hand with agriculture, horticulture and silviculture, and on the other hand with medicine and pharmacology, giving rise to fields such as agronomy, horticultural botany, phytopathology, and phytopharmacology. = = scope and importance = = the study of plants is vital because they underpin almost all animal life on earth by generating a large proportion of the oxygen and food that provide humans and other organisms with aerobic respiration with the chemical energy they need to exist. plants, algae and cyanobacteria are the major groups of organisms that carry out photosynthesis, a process that uses the energy of sunlight to convert water and carbon dioxide into sugars that can be used both as a source of chemical energy and of organic molecules that are used in the structural components of cells. as a by - product of photosynthesis, plants release oxygen into the atmosphere, a gas that is required by nearly all living things to carry out cellular respiration. in addition, they are influential in the global carbon and water cycles and plant roots bind and stabilise soils, preventing soil erosion. plants are crucial to the future of human society as they provide food, oxygen, biochemicals, and products for people, as well as creating and preserving soil. historically, all living things were classified as either animals or plants and botany covered the study of all organisms not considered animals. botanists examine both
##ian period, several groups, including the lycopods, sphenophylls and progymnosperms, had independently evolved " megaspory " β their spores were of two distinct sizes, larger megaspores and smaller microspores. their reduced gametophytes developed from megaspores retained within the spore - producing organs ( megasporangia ) of the sporophyte, a condition known as endospory. seeds consist of an endosporic megasporangium surrounded by one or two sheathing layers ( integuments ). the young sporophyte develops within the seed, which on germination splits to release it. the earliest known seed plants date from the latest devonian famennian stage. following the evolution of the seed habit, seed plants diversified, giving rise to a number of now - extinct groups, including seed ferns, as well as the modern gymnosperms and angiosperms. gymnosperms produce " naked seeds " not fully enclosed in an ovary ; modern representatives include conifers, cycads, ginkgo, and gnetales. angiosperms produce seeds enclosed in a structure such as a carpel or an ovary. ongoing research on the molecular phylogenetics of living plants appears to show that the angiosperms are a sister clade to the gymnosperms. = = plant physiology = = plant physiology encompasses all the internal chemical and physical activities of plants associated with life. chemicals obtained from the air, soil and water form the basis of all plant metabolism. the energy of sunlight, captured by oxygenic photosynthesis and released by cellular respiration, is the basis of almost all life. photoautotrophs, including all green plants, algae and cyanobacteria gather energy directly from sunlight by photosynthesis. heterotrophs including all animals, all fungi, all completely parasitic plants, and non - photosynthetic bacteria take in organic molecules produced by photoautotrophs and respire them or use them in the construction of cells and tissues. respiration is the oxidation of carbon compounds by breaking them down into simpler structures to release the energy they contain, essentially the opposite of photosynthesis. molecules are moved within plants by transport processes that operate at a variety of spatial scales. subcellular transport of ions, electrons and molecules such as water and enzymes occurs across cell membranes. minerals and water are transported from roots to other parts of the plant in
diploid embryo sporophyte within its tissues for at least part of its life, even in the seed plants, where the gametophyte itself is nurtured by its parent sporophyte. other groups of organisms that were previously studied by botanists include bacteria ( now studied in bacteriology ), fungi ( mycology ) β including lichen - forming fungi ( lichenology ), non - chlorophyte algae ( phycology ), and viruses ( virology ). however, attention is still given to these groups by botanists, and fungi ( including lichens ) and photosynthetic protists are usually covered in introductory botany courses. palaeobotanists study ancient plants in the fossil record to provide information about the evolutionary history of plants. cyanobacteria, the first oxygen - releasing photosynthetic organisms on earth, are thought to have given rise to the ancestor of plants by entering into an endosymbiotic relationship with an early eukaryote, ultimately becoming the chloroplasts in plant cells. the new photosynthetic plants ( along with their algal relatives ) accelerated the rise in atmospheric oxygen started by the cyanobacteria, changing the ancient oxygen - free, reducing, atmosphere to one in which free oxygen has been abundant for more than 2 billion years. among the important botanical questions of the 21st century are the role of plants as primary producers in the global cycling of life ' s basic ingredients : energy, carbon, oxygen, nitrogen and water, and ways that our plant stewardship can help address the global environmental issues of resource management, conservation, human food security, biologically invasive organisms, carbon sequestration, climate change, and sustainability. = = = human nutrition = = = virtually all staple foods come either directly from primary production by plants, or indirectly from animals that eat them. plants and other photosynthetic organisms are at the base of most food chains because they use the energy from the sun and nutrients from the soil and atmosphere, converting them into a form that can be used by animals. this is what ecologists call the first trophic level. the modern forms of the major staple foods, such as hemp, teff, maize, rice, wheat and other cereal grasses, pulses, bananas and plantains, as well as hemp, flax and cotton grown for their fibres, are the outcome of prehistoric selection over thousands of years from among wild ancestral plants with the most
ranks varying from family to subgenus have terms for their study, including agrostology ( or graminology ) for the study of grasses, synantherology for the study of composites, and batology for the study of brambles. study can also be divided by guild rather than clade or grade. for example, dendrology is the study of woody plants. many divisions of biology have botanical subfields. these are commonly denoted by prefixing the word plant ( e. g. plant taxonomy, plant ecology, plant anatomy, plant morphology, plant systematics ), or prefixing or substituting the prefix phyto - ( e. g. phytochemistry, phytogeography ). the study of fossil plants is called palaeobotany. other fields are denoted by adding or substituting the word botany ( e. g. systematic botany ). phytosociology is a subfield of plant ecology that classifies and studies communities of plants. the intersection of fields from the above pair of categories gives rise to fields such as bryogeography, the study of the distribution of mosses. different parts of plants also give rise to their own subfields, including xylology, carpology ( or fructology ), and palynology, these being the study of wood, fruit and pollen / spores respectively. botany also overlaps on the one hand with agriculture, horticulture and silviculture, and on the other hand with medicine and pharmacology, giving rise to fields such as agronomy, horticultural botany, phytopathology, and phytopharmacology. = = scope and importance = = the study of plants is vital because they underpin almost all animal life on earth by generating a large proportion of the oxygen and food that provide humans and other organisms with aerobic respiration with the chemical energy they need to exist. plants, algae and cyanobacteria are the major groups of organisms that carry out photosynthesis, a process that uses the energy of sunlight to convert water and carbon dioxide into sugars that can be used both as a source of chemical energy and of organic molecules that are used in the structural components of cells. as a by - product of photosynthesis, plants release oxygen into the atmosphere, a gas that is required by nearly all living things to carry out cellular respiration. in addition, they are influential in the global carbon and water cycles and plant roots bind and stabilise soils, preventing
the internal functions and processes within plant organelles, cells, tissues, whole plants, plant populations and plant communities. at each of these levels, a botanist may be concerned with the classification ( taxonomy ), phylogeny and evolution, structure ( anatomy and morphology ), or function ( physiology ) of plant life. the strictest definition of " plant " includes only the " land plants " or embryophytes, which include seed plants ( gymnosperms, including the pines, and flowering plants ) and the free - sporing cryptogams including ferns, clubmosses, liverworts, hornworts and mosses. embryophytes are multicellular eukaryotes descended from an ancestor that obtained its energy from sunlight by photosynthesis. they have life cycles with alternating haploid and diploid phases. the sexual haploid phase of embryophytes, known as the gametophyte, nurtures the developing diploid embryo sporophyte within its tissues for at least part of its life, even in the seed plants, where the gametophyte itself is nurtured by its parent sporophyte. other groups of organisms that were previously studied by botanists include bacteria ( now studied in bacteriology ), fungi ( mycology ) β including lichen - forming fungi ( lichenology ), non - chlorophyte algae ( phycology ), and viruses ( virology ). however, attention is still given to these groups by botanists, and fungi ( including lichens ) and photosynthetic protists are usually covered in introductory botany courses. palaeobotanists study ancient plants in the fossil record to provide information about the evolutionary history of plants. cyanobacteria, the first oxygen - releasing photosynthetic organisms on earth, are thought to have given rise to the ancestor of plants by entering into an endosymbiotic relationship with an early eukaryote, ultimately becoming the chloroplasts in plant cells. the new photosynthetic plants ( along with their algal relatives ) accelerated the rise in atmospheric oxygen started by the cyanobacteria, changing the ancient oxygen - free, reducing, atmosphere to one in which free oxygen has been abundant for more than 2 billion years. among the important botanical questions of the 21st century are the role of plants as primary producers in the global cycling of life ' s basic ingredients : energy, carbon, oxygen, nitrogen and water, and ways
, fungi ( mycology ) β including lichen - forming fungi ( lichenology ), non - chlorophyte algae ( phycology ), and viruses ( virology ). however, attention is still given to these groups by botanists, and fungi ( including lichens ) and photosynthetic protists are usually covered in introductory botany courses. palaeobotanists study ancient plants in the fossil record to provide information about the evolutionary history of plants. cyanobacteria, the first oxygen - releasing photosynthetic organisms on earth, are thought to have given rise to the ancestor of plants by entering into an endosymbiotic relationship with an early eukaryote, ultimately becoming the chloroplasts in plant cells. the new photosynthetic plants ( along with their algal relatives ) accelerated the rise in atmospheric oxygen started by the cyanobacteria, changing the ancient oxygen - free, reducing, atmosphere to one in which free oxygen has been abundant for more than 2 billion years. among the important botanical questions of the 21st century are the role of plants as primary producers in the global cycling of life ' s basic ingredients : energy, carbon, oxygen, nitrogen and water, and ways that our plant stewardship can help address the global environmental issues of resource management, conservation, human food security, biologically invasive organisms, carbon sequestration, climate change, and sustainability. = = = human nutrition = = = virtually all staple foods come either directly from primary production by plants, or indirectly from animals that eat them. plants and other photosynthetic organisms are at the base of most food chains because they use the energy from the sun and nutrients from the soil and atmosphere, converting them into a form that can be used by animals. this is what ecologists call the first trophic level. the modern forms of the major staple foods, such as hemp, teff, maize, rice, wheat and other cereal grasses, pulses, bananas and plantains, as well as hemp, flax and cotton grown for their fibres, are the outcome of prehistoric selection over thousands of years from among wild ancestral plants with the most desirable characteristics. botanists study how plants produce food and how to increase yields, for example through plant breeding, making their work important to humanity ' s ability to feed the world and provide food security for future generations. botanists also study weeds, which are a considerable problem in agriculture, and the biology and control of plant
Question: Ginkgo trees are gymnosperms with broad?
A) leaves
B) fruits
C) trunks
D) roots
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A) leaves
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Context:
use less energy than conventional thermal separation processes such as distillation, sublimation or crystallization. the separation process is purely physical and both fractions ( permeate and retentate ) can be obtained as useful products. cold separation using membrane technology is widely used in the food technology, biotechnology and pharmaceutical industries. furthermore, using membranes enables separations to take place that would be impossible using thermal separation methods. for example, it is impossible to separate the constituents of azeotropic liquids or solutes which form isomorphic crystals by distillation or recrystallization but such separations can be achieved using membrane technology. depending on the type of membrane, the selective separation of certain individual substances or substance mixtures is possible. important technical applications include the production of drinking water by reverse osmosis. in waste water treatment, membrane technology is becoming increasingly important. ultra / microfiltration can be very effective in removing colloids and macromolecules from wastewater. this is needed if wastewater is discharged into sensitive waters especially those designated for contact water sports and recreation. about half of the market is in medical applications such as artificial kidneys to remove toxic substances by hemodialysis and as artificial lung for bubble - free supply of oxygen in the blood. the importance of membrane technology is growing in the field of environmental protection ( nano - mem - pro ippc database ). even in modern energy recovery techniques, membranes are increasingly used, for example in fuel cells and in osmotic power plants. = = mass transfer = = two basic models can be distinguished for mass transfer through the membrane : the solution - diffusion model and the hydrodynamic model. in real membranes, these two transport mechanisms certainly occur side by side, especially during ultra - filtration. = = = solution - diffusion model = = = in the solution - diffusion model, transport occurs only by diffusion. the component that needs to be transported must first be dissolved in the membrane. the general approach of the solution - diffusion model is to assume that the chemical potential of the feed and permeate fluids are in equilibrium with the adjacent membrane surfaces such that appropriate expressions for the chemical potential in the fluid and membrane phases can be equated at the solution - membrane interface. this principle is more important for dense membranes without natural pores such as those used for reverse osmosis and in fuel cells. during the filtration process a boundary layer forms on the membrane. this concentration gradient is created by molecules which cannot pass through the membrane. the
= = = = = = environmental remediation = = = environmental remediation is the process through which contaminants or pollutants in soil, water and other media are removed to improve environmental quality. the main focus is the reduction of hazardous substances within the environment. some of the areas involved in environmental remediation include ; soil contamination, hazardous waste, groundwater contamination, oil, gas and chemical spills. there are three most common types of environmental remediation. these include soil, water, and sediment remediation. soil remediation consists of removing contaminants in soil, as these pose great risks to humans and the ecosystem. some examples of this are heavy metals, pesticides, and radioactive materials. depending on the contaminant the remedial processes can be physical, chemical, thermal, or biological. water remediation is one of the most important considering water is an essential natural resource. depending on the source of water there will be different contaminants. surface water contamination mainly consists of agricultural, animal, and industrial waste, as well as acid mine drainage. there has been a rise in the need for water remediation due to the increased discharge of industrial waste, leading to a demand for sustainable water solutions. the market for water remediation is expected to consistently increase to $ 19. 6 billion by 2030. sediment remediation consists of removing contaminated sediments. is it almost similar to soil remediation except it is often more sophisticated as it involves additional contaminants. to reduce the contaminants it is likely to use physical, chemical, and biological processes that help with source control, but if these processes are executed correctly, there ' s a risk of contamination resurfacing. = = = solid waste management = = = solid waste management is the purification, consumption, reuse, disposal, and treatment of solid waste that is undertaken by the government or the ruling bodies of a city / town. it refers to the collection, treatment, and disposal of non - soluble, solid waste material. solid waste is associated with both industrial, institutional, commercial and residential activities. hazardous solid waste, when improperly disposed can encourage the infestation of insects and rodents, contributing to the spread of diseases. some of the most common types of solid waste management include ; landfills, vermicomposting, composting, recycling, and incineration. however, a major barrier for solid waste management practices is the high costs associated with recycling
remediation include ; soil contamination, hazardous waste, groundwater contamination, oil, gas and chemical spills. there are three most common types of environmental remediation. these include soil, water, and sediment remediation. soil remediation consists of removing contaminants in soil, as these pose great risks to humans and the ecosystem. some examples of this are heavy metals, pesticides, and radioactive materials. depending on the contaminant the remedial processes can be physical, chemical, thermal, or biological. water remediation is one of the most important considering water is an essential natural resource. depending on the source of water there will be different contaminants. surface water contamination mainly consists of agricultural, animal, and industrial waste, as well as acid mine drainage. there has been a rise in the need for water remediation due to the increased discharge of industrial waste, leading to a demand for sustainable water solutions. the market for water remediation is expected to consistently increase to $ 19. 6 billion by 2030. sediment remediation consists of removing contaminated sediments. is it almost similar to soil remediation except it is often more sophisticated as it involves additional contaminants. to reduce the contaminants it is likely to use physical, chemical, and biological processes that help with source control, but if these processes are executed correctly, there ' s a risk of contamination resurfacing. = = = solid waste management = = = solid waste management is the purification, consumption, reuse, disposal, and treatment of solid waste that is undertaken by the government or the ruling bodies of a city / town. it refers to the collection, treatment, and disposal of non - soluble, solid waste material. solid waste is associated with both industrial, institutional, commercial and residential activities. hazardous solid waste, when improperly disposed can encourage the infestation of insects and rodents, contributing to the spread of diseases. some of the most common types of solid waste management include ; landfills, vermicomposting, composting, recycling, and incineration. however, a major barrier for solid waste management practices is the high costs associated with recycling and the risks of creating more pollution. = = = e - waste recycling = = = the recycling of electronic waste ( e - waste ) has seen significant technological advancements due to increasing environmental concerns and the growing volume of electronic product disposals. traditional e - waste recycling methods, which often involve manual disassemb
the designing of transgenic plants to grow under specific environments in the presence ( or absence ) of chemicals. one hope is that green biotechnology might produce more environmentally friendly solutions than traditional industrial agriculture. an example of this is the engineering of a plant to express a pesticide, thereby ending the need of external application of pesticides. an example of this would be bt corn. whether or not green biotechnology products such as this are ultimately more environmentally friendly is a topic of considerable debate. it is commonly considered as the next phase of green revolution, which can be seen as a platform to eradicate world hunger by using technologies which enable the production of more fertile and resistant, towards biotic and abiotic stress, plants and ensures application of environmentally friendly fertilizers and the use of biopesticides, it is mainly focused on the development of agriculture. on the other hand, some of the uses of green biotechnology involve microorganisms to clean and reduce waste. red biotechnology is the use of biotechnology in the medical and pharmaceutical industries, and health preservation. this branch involves the production of vaccines and antibiotics, regenerative therapies, creation of artificial organs and new diagnostics of diseases. as well as the development of hormones, stem cells, antibodies, sirna and diagnostic tests. white biotechnology, also known as industrial biotechnology, is biotechnology applied to industrial processes. an example is the designing of an organism to produce a useful chemical. another example is the using of enzymes as industrial catalysts to either produce valuable chemicals or destroy hazardous / polluting chemicals. white biotechnology tends to consume less in resources than traditional processes used to produce industrial goods. yellow biotechnology refers to the use of biotechnology in food production ( food industry ), for example in making wine ( winemaking ), cheese ( cheesemaking ), and beer ( brewing ) by fermentation. it has also been used to refer to biotechnology applied to insects. this includes biotechnology - based approaches for the control of harmful insects, the characterisation and utilisation of active ingredients or genes of insects for research, or application in agriculture and medicine and various other approaches. gray biotechnology is dedicated to environmental applications, and focused on the maintenance of biodiversity and the remotion of pollutants. brown biotechnology is related to the management of arid lands and deserts. one application is the creation of enhanced seeds that resist extreme environmental conditions of arid regions, which is related to the innovation, creation of agriculture techniques and management of resources. violet biotechnology is related to law, ethical and philosophical issues around biotechnology. micro
genetic engineering, also called genetic modification or genetic manipulation, is the modification and manipulation of an organism ' s genes using technology. it is a set of technologies used to change the genetic makeup of cells, including the transfer of genes within and across species boundaries to produce improved or novel organisms. new dna is obtained by either isolating and copying the genetic material of interest using recombinant dna methods or by artificially synthesising the dna. a construct is usually created and used to insert this dna into the host organism. the first recombinant dna molecule was made by paul berg in 1972 by combining dna from the monkey virus sv40 with the lambda virus. as well as inserting genes, the process can be used to remove, or " knock out ", genes. the new dna can be inserted randomly, or targeted to a specific part of the genome. an organism that is generated through genetic engineering is considered to be genetically modified ( gm ) and the resulting entity is a genetically modified organism ( gmo ). the first gmo was a bacterium generated by herbert boyer and stanley cohen in 1973. rudolf jaenisch created the first gm animal when he inserted foreign dna into a mouse in 1974. the first company to focus on genetic engineering, genentech, was founded in 1976 and started the production of human proteins. genetically engineered human insulin was produced in 1978 and insulin - producing bacteria were commercialised in 1982. genetically modified food has been sold since 1994, with the release of the flavr savr tomato. the flavr savr was engineered to have a longer shelf life, but most current gm crops are modified to increase resistance to insects and herbicides. glofish, the first gmo designed as a pet, was sold in the united states in december 2003. in 2016 salmon modified with a growth hormone were sold. genetic engineering has been applied in numerous fields including research, medicine, industrial biotechnology and agriculture. in research, gmos are used to study gene function and expression through loss of function, gain of function, tracking and expression experiments. by knocking out genes responsible for certain conditions it is possible to create animal model organisms of human diseases. as well as producing hormones, vaccines and other drugs, genetic engineering has the potential to cure genetic diseases through gene therapy. chinese hamster ovary ( cho ) cells are used in industrial genetic engineering. additionally mrna vaccines are made through genetic engineering to prevent infections by viruses such as covid - 19. the same techniques that are used to produce drugs can also have industrial applications such
reaction to proceed more rapidly without being consumed by it β by reducing the amount of activation energy needed to convert reactants into products. enzymes also allow the regulation of the rate of a metabolic reaction, for example in response to changes in the cell ' s environment or to signals from other cells. = = = cellular respiration = = = cellular respiration is a set of metabolic reactions and processes that take place in cells to convert chemical energy from nutrients into adenosine triphosphate ( atp ), and then release waste products. the reactions involved in respiration are catabolic reactions, which break large molecules into smaller ones, releasing energy. respiration is one of the key ways a cell releases chemical energy to fuel cellular activity. the overall reaction occurs in a series of biochemical steps, some of which are redox reactions. although cellular respiration is technically a combustion reaction, it clearly does not resemble one when it occurs in a cell because of the slow, controlled release of energy from the series of reactions. sugar in the form of glucose is the main nutrient used by animal and plant cells in respiration. cellular respiration involving oxygen is called aerobic respiration, which has four stages : glycolysis, citric acid cycle ( or krebs cycle ), electron transport chain, and oxidative phosphorylation. glycolysis is a metabolic process that occurs in the cytoplasm whereby glucose is converted into two pyruvates, with two net molecules of atp being produced at the same time. each pyruvate is then oxidized into acetyl - coa by the pyruvate dehydrogenase complex, which also generates nadh and carbon dioxide. acetyl - coa enters the citric acid cycle, which takes places inside the mitochondrial matrix. at the end of the cycle, the total yield from 1 glucose ( or 2 pyruvates ) is 6 nadh, 2 fadh2, and 2 atp molecules. finally, the next stage is oxidative phosphorylation, which in eukaryotes, occurs in the mitochondrial cristae. oxidative phosphorylation comprises the electron transport chain, which is a series of four protein complexes that transfer electrons from one complex to another, thereby releasing energy from nadh and fadh2 that is coupled to the pumping of protons ( hydrogen ions ) across the inner mitochondrial membrane ( chemiosmosis ), which generates a proton motive force. energy
. an example of this would be bt corn. whether or not green biotechnology products such as this are ultimately more environmentally friendly is a topic of considerable debate. it is commonly considered as the next phase of green revolution, which can be seen as a platform to eradicate world hunger by using technologies which enable the production of more fertile and resistant, towards biotic and abiotic stress, plants and ensures application of environmentally friendly fertilizers and the use of biopesticides, it is mainly focused on the development of agriculture. on the other hand, some of the uses of green biotechnology involve microorganisms to clean and reduce waste. red biotechnology is the use of biotechnology in the medical and pharmaceutical industries, and health preservation. this branch involves the production of vaccines and antibiotics, regenerative therapies, creation of artificial organs and new diagnostics of diseases. as well as the development of hormones, stem cells, antibodies, sirna and diagnostic tests. white biotechnology, also known as industrial biotechnology, is biotechnology applied to industrial processes. an example is the designing of an organism to produce a useful chemical. another example is the using of enzymes as industrial catalysts to either produce valuable chemicals or destroy hazardous / polluting chemicals. white biotechnology tends to consume less in resources than traditional processes used to produce industrial goods. yellow biotechnology refers to the use of biotechnology in food production ( food industry ), for example in making wine ( winemaking ), cheese ( cheesemaking ), and beer ( brewing ) by fermentation. it has also been used to refer to biotechnology applied to insects. this includes biotechnology - based approaches for the control of harmful insects, the characterisation and utilisation of active ingredients or genes of insects for research, or application in agriculture and medicine and various other approaches. gray biotechnology is dedicated to environmental applications, and focused on the maintenance of biodiversity and the remotion of pollutants. brown biotechnology is related to the management of arid lands and deserts. one application is the creation of enhanced seeds that resist extreme environmental conditions of arid regions, which is related to the innovation, creation of agriculture techniques and management of resources. violet biotechnology is related to law, ethical and philosophical issues around biotechnology. microbial biotechnology has been proposed for the rapidly emerging area of biotechnology applications in space and microgravity ( space bioeconomy ) dark biotechnology is the color associated with bioterrorism or biological weapons and biowarfare which uses microorganisms, and toxins to cause diseases and death in humans, livestock and
product of ceramic manufacture, or as an adjective. ceramics is the making of things out of ceramic materials. ceramic engineering, like many sciences, evolved from a different discipline by today ' s standards. materials science engineering is grouped with ceramics engineering to this day. abraham darby first used coke in 1709 in shropshire, england, to improve the yield of a smelting process. coke is now widely used to produce carbide ceramics. potter josiah wedgwood opened the first modern ceramics factory in stoke - on - trent, england, in 1759. austrian chemist carl josef bayer, working for the textile industry in russia, developed a process to separate alumina from bauxite ore in 1888. the bayer process is still used to purify alumina for the ceramic and aluminium industries. brothers pierre and jacques curie discovered piezoelectricity in rochelle salt c. 1880. piezoelectricity is one of the key properties of electroceramics. e. g. acheson heated a mixture of coke and clay in 1893, and invented carborundum, or synthetic silicon carbide. henri moissan also synthesized sic and tungsten carbide in his electric arc furnace in paris about the same time as acheson. karl schroter used liquid - phase sintering to bond or " cement " moissan ' s tungsten carbide particles with cobalt in 1923 in germany. cemented ( metal - bonded ) carbide edges greatly increase the durability of hardened steel cutting tools. w. h. nernst developed cubic - stabilized zirconia in the 1920s in berlin. this material is used as an oxygen sensor in exhaust systems. the main limitation on the use of ceramics in engineering is brittleness. = = = military = = = the military requirements of world war ii encouraged developments, which created a need for high - performance materials and helped speed the development of ceramic science and engineering. throughout the 1960s and 1970s, new types of ceramics were developed in response to advances in atomic energy, electronics, communications, and space travel. the discovery of ceramic superconductors in 1986 has spurred intense research to develop superconducting ceramic parts for electronic devices, electric motors, and transportation equipment. there is an increasing need in the military sector for high - strength, robust materials which have the capability to transmit light around the visible ( 0. 4 β 0. 7 micrometers ) and mid - infrared ( 1 β 5 micrometers ) regions of the spectrum. these materials
industrial applications. this branch of biotechnology is the most used for the industries of refining and combustion principally on the production of bio - oils with photosynthetic micro - algae. green biotechnology is biotechnology applied to agricultural processes. an example would be the selection and domestication of plants via micropropagation. another example is the designing of transgenic plants to grow under specific environments in the presence ( or absence ) of chemicals. one hope is that green biotechnology might produce more environmentally friendly solutions than traditional industrial agriculture. an example of this is the engineering of a plant to express a pesticide, thereby ending the need of external application of pesticides. an example of this would be bt corn. whether or not green biotechnology products such as this are ultimately more environmentally friendly is a topic of considerable debate. it is commonly considered as the next phase of green revolution, which can be seen as a platform to eradicate world hunger by using technologies which enable the production of more fertile and resistant, towards biotic and abiotic stress, plants and ensures application of environmentally friendly fertilizers and the use of biopesticides, it is mainly focused on the development of agriculture. on the other hand, some of the uses of green biotechnology involve microorganisms to clean and reduce waste. red biotechnology is the use of biotechnology in the medical and pharmaceutical industries, and health preservation. this branch involves the production of vaccines and antibiotics, regenerative therapies, creation of artificial organs and new diagnostics of diseases. as well as the development of hormones, stem cells, antibodies, sirna and diagnostic tests. white biotechnology, also known as industrial biotechnology, is biotechnology applied to industrial processes. an example is the designing of an organism to produce a useful chemical. another example is the using of enzymes as industrial catalysts to either produce valuable chemicals or destroy hazardous / polluting chemicals. white biotechnology tends to consume less in resources than traditional processes used to produce industrial goods. yellow biotechnology refers to the use of biotechnology in food production ( food industry ), for example in making wine ( winemaking ), cheese ( cheesemaking ), and beer ( brewing ) by fermentation. it has also been used to refer to biotechnology applied to insects. this includes biotechnology - based approaches for the control of harmful insects, the characterisation and utilisation of active ingredients or genes of insects for research, or application in agriculture and medicine and various other approaches. gray biotechnology is dedicated to environmental applications, and focused on the maintenance of biodiversity and the remotion of poll
be introduced directly into the host organism or into a cell that is then fused or hybridised with the host. this relies on recombinant nucleic acid techniques to form new combinations of heritable genetic material followed by the incorporation of that material either indirectly through a vector system or directly through micro - injection, macro - injection or micro - encapsulation. genetic engineering does not normally include traditional breeding, in vitro fertilisation, induction of polyploidy, mutagenesis and cell fusion techniques that do not use recombinant nucleic acids or a genetically modified organism in the process. however, some broad definitions of genetic engineering include selective breeding. cloning and stem cell research, although not considered genetic engineering, are closely related and genetic engineering can be used within them. synthetic biology is an emerging discipline that takes genetic engineering a step further by introducing artificially synthesised material into an organism. plants, animals or microorganisms that have been changed through genetic engineering are termed genetically modified organisms or gmos. if genetic material from another species is added to the host, the resulting organism is called transgenic. if genetic material from the same species or a species that can naturally breed with the host is used the resulting organism is called cisgenic. if genetic engineering is used to remove genetic material from the target organism the resulting organism is termed a knockout organism. in europe genetic modification is synonymous with genetic engineering while within the united states of america and canada genetic modification can also be used to refer to more conventional breeding methods. = = history = = humans have altered the genomes of species for thousands of years through selective breeding, or artificial selection : 1 : 1 as contrasted with natural selection. more recently, mutation breeding has used exposure to chemicals or radiation to produce a high frequency of random mutations, for selective breeding purposes. genetic engineering as the direct manipulation of dna by humans outside breeding and mutations has only existed since the 1970s. the term " genetic engineering " was coined by the russian - born geneticist nikolay timofeev - ressovsky in his 1934 paper " the experimental production of mutations ", published in the british journal biological reviews. jack williamson used the term in his science fiction novel dragon ' s island, published in 1951 β one year before dna ' s role in heredity was confirmed by alfred hershey and martha chase, and two years before james watson and francis crick showed that the dna molecule has a double - helix structure β though the general concept of direct genetic manipulation was explored in rudimentary form
Question: Recrystallization is a process that can remove what, which result when compounds are synthesized?
A) minerals
B) chemicals
C) contaminants
D) substances
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C) contaminants
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Context:
. these biochemical strategies are unique to land plants. = = = medicine and materials = = = phytochemistry is a branch of plant biochemistry primarily concerned with the chemical substances produced by plants during secondary metabolism. some of these compounds are toxins such as the alkaloid coniine from hemlock. others, such as the essential oils peppermint oil and lemon oil are useful for their aroma, as flavourings and spices ( e. g., capsaicin ), and in medicine as pharmaceuticals as in opium from opium poppies. many medicinal and recreational drugs, such as tetrahydrocannabinol ( active ingredient in cannabis ), caffeine, morphine and nicotine come directly from plants. others are simple derivatives of botanical natural products. for example, the pain killer aspirin is the acetyl ester of salicylic acid, originally isolated from the bark of willow trees, and a wide range of opiate painkillers like heroin are obtained by chemical modification of morphine obtained from the opium poppy. popular stimulants come from plants, such as caffeine from coffee, tea and chocolate, and nicotine from tobacco. most alcoholic beverages come from fermentation of carbohydrate - rich plant products such as barley ( beer ), rice ( sake ) and grapes ( wine ). native americans have used various plants as ways of treating illness or disease for thousands of years. this knowledge native americans have on plants has been recorded by enthnobotanists and then in turn has been used by pharmaceutical companies as a way of drug discovery. plants can synthesise coloured dyes and pigments such as the anthocyanins responsible for the red colour of red wine, yellow weld and blue woad used together to produce lincoln green, indoxyl, source of the blue dye indigo traditionally used to dye denim and the artist ' s pigments gamboge and rose madder. sugar, starch, cotton, linen, hemp, some types of rope, wood and particle boards, papyrus and paper, vegetable oils, wax, and natural rubber are examples of commercially important materials made from plant tissues or their secondary products. charcoal, a pure form of carbon made by pyrolysis of wood, has a long history as a metal - smelting fuel, as a filter material and adsorbent and as an artist ' s material and is one of the three ingredients of gunpowder. cellulose, the world
##l ( active ingredient in cannabis ), caffeine, morphine and nicotine come directly from plants. others are simple derivatives of botanical natural products. for example, the pain killer aspirin is the acetyl ester of salicylic acid, originally isolated from the bark of willow trees, and a wide range of opiate painkillers like heroin are obtained by chemical modification of morphine obtained from the opium poppy. popular stimulants come from plants, such as caffeine from coffee, tea and chocolate, and nicotine from tobacco. most alcoholic beverages come from fermentation of carbohydrate - rich plant products such as barley ( beer ), rice ( sake ) and grapes ( wine ). native americans have used various plants as ways of treating illness or disease for thousands of years. this knowledge native americans have on plants has been recorded by enthnobotanists and then in turn has been used by pharmaceutical companies as a way of drug discovery. plants can synthesise coloured dyes and pigments such as the anthocyanins responsible for the red colour of red wine, yellow weld and blue woad used together to produce lincoln green, indoxyl, source of the blue dye indigo traditionally used to dye denim and the artist ' s pigments gamboge and rose madder. sugar, starch, cotton, linen, hemp, some types of rope, wood and particle boards, papyrus and paper, vegetable oils, wax, and natural rubber are examples of commercially important materials made from plant tissues or their secondary products. charcoal, a pure form of carbon made by pyrolysis of wood, has a long history as a metal - smelting fuel, as a filter material and adsorbent and as an artist ' s material and is one of the three ingredients of gunpowder. cellulose, the world ' s most abundant organic polymer, can be converted into energy, fuels, materials and chemical feedstock. products made from cellulose include rayon and cellophane, wallpaper paste, biobutanol and gun cotton. sugarcane, rapeseed and soy are some of the plants with a highly fermentable sugar or oil content that are used as sources of biofuels, important alternatives to fossil fuels, such as biodiesel. sweetgrass was used by native americans to ward off bugs like mosquitoes. these bug repelling properties of sweetgrass were later found by the american chemical society in the molecules phytol
used by pharmaceutical companies as a way of drug discovery. plants can synthesise coloured dyes and pigments such as the anthocyanins responsible for the red colour of red wine, yellow weld and blue woad used together to produce lincoln green, indoxyl, source of the blue dye indigo traditionally used to dye denim and the artist ' s pigments gamboge and rose madder. sugar, starch, cotton, linen, hemp, some types of rope, wood and particle boards, papyrus and paper, vegetable oils, wax, and natural rubber are examples of commercially important materials made from plant tissues or their secondary products. charcoal, a pure form of carbon made by pyrolysis of wood, has a long history as a metal - smelting fuel, as a filter material and adsorbent and as an artist ' s material and is one of the three ingredients of gunpowder. cellulose, the world ' s most abundant organic polymer, can be converted into energy, fuels, materials and chemical feedstock. products made from cellulose include rayon and cellophane, wallpaper paste, biobutanol and gun cotton. sugarcane, rapeseed and soy are some of the plants with a highly fermentable sugar or oil content that are used as sources of biofuels, important alternatives to fossil fuels, such as biodiesel. sweetgrass was used by native americans to ward off bugs like mosquitoes. these bug repelling properties of sweetgrass were later found by the american chemical society in the molecules phytol and coumarin. = = plant ecology = = plant ecology is the science of the functional relationships between plants and their habitats β the environments where they complete their life cycles. plant ecologists study the composition of local and regional floras, their biodiversity, genetic diversity and fitness, the adaptation of plants to their environment, and their competitive or mutualistic interactions with other species. some ecologists even rely on empirical data from indigenous people that is gathered by ethnobotanists. this information can relay a great deal of information on how the land once was thousands of years ago and how it has changed over that time. the goals of plant ecology are to understand the causes of their distribution patterns, productivity, environmental impact, evolution, and responses to environmental change. plants depend on certain edaphic ( soil ) and climatic factors in their environment but can modify these factors too. for example, they can change their environment ' s albedo, increase runoff interception
a wide range of opiate painkillers like heroin are obtained by chemical modification of morphine obtained from the opium poppy. popular stimulants come from plants, such as caffeine from coffee, tea and chocolate, and nicotine from tobacco. most alcoholic beverages come from fermentation of carbohydrate - rich plant products such as barley ( beer ), rice ( sake ) and grapes ( wine ). native americans have used various plants as ways of treating illness or disease for thousands of years. this knowledge native americans have on plants has been recorded by enthnobotanists and then in turn has been used by pharmaceutical companies as a way of drug discovery. plants can synthesise coloured dyes and pigments such as the anthocyanins responsible for the red colour of red wine, yellow weld and blue woad used together to produce lincoln green, indoxyl, source of the blue dye indigo traditionally used to dye denim and the artist ' s pigments gamboge and rose madder. sugar, starch, cotton, linen, hemp, some types of rope, wood and particle boards, papyrus and paper, vegetable oils, wax, and natural rubber are examples of commercially important materials made from plant tissues or their secondary products. charcoal, a pure form of carbon made by pyrolysis of wood, has a long history as a metal - smelting fuel, as a filter material and adsorbent and as an artist ' s material and is one of the three ingredients of gunpowder. cellulose, the world ' s most abundant organic polymer, can be converted into energy, fuels, materials and chemical feedstock. products made from cellulose include rayon and cellophane, wallpaper paste, biobutanol and gun cotton. sugarcane, rapeseed and soy are some of the plants with a highly fermentable sugar or oil content that are used as sources of biofuels, important alternatives to fossil fuels, such as biodiesel. sweetgrass was used by native americans to ward off bugs like mosquitoes. these bug repelling properties of sweetgrass were later found by the american chemical society in the molecules phytol and coumarin. = = plant ecology = = plant ecology is the science of the functional relationships between plants and their habitats β the environments where they complete their life cycles. plant ecologists study the composition of local and regional floras, their biodiversity, genetic diversity and fitness, the adaptation of plants to their environment,
##drate - rich plant products such as barley ( beer ), rice ( sake ) and grapes ( wine ). native americans have used various plants as ways of treating illness or disease for thousands of years. this knowledge native americans have on plants has been recorded by enthnobotanists and then in turn has been used by pharmaceutical companies as a way of drug discovery. plants can synthesise coloured dyes and pigments such as the anthocyanins responsible for the red colour of red wine, yellow weld and blue woad used together to produce lincoln green, indoxyl, source of the blue dye indigo traditionally used to dye denim and the artist ' s pigments gamboge and rose madder. sugar, starch, cotton, linen, hemp, some types of rope, wood and particle boards, papyrus and paper, vegetable oils, wax, and natural rubber are examples of commercially important materials made from plant tissues or their secondary products. charcoal, a pure form of carbon made by pyrolysis of wood, has a long history as a metal - smelting fuel, as a filter material and adsorbent and as an artist ' s material and is one of the three ingredients of gunpowder. cellulose, the world ' s most abundant organic polymer, can be converted into energy, fuels, materials and chemical feedstock. products made from cellulose include rayon and cellophane, wallpaper paste, biobutanol and gun cotton. sugarcane, rapeseed and soy are some of the plants with a highly fermentable sugar or oil content that are used as sources of biofuels, important alternatives to fossil fuels, such as biodiesel. sweetgrass was used by native americans to ward off bugs like mosquitoes. these bug repelling properties of sweetgrass were later found by the american chemical society in the molecules phytol and coumarin. = = plant ecology = = plant ecology is the science of the functional relationships between plants and their habitats β the environments where they complete their life cycles. plant ecologists study the composition of local and regional floras, their biodiversity, genetic diversity and fitness, the adaptation of plants to their environment, and their competitive or mutualistic interactions with other species. some ecologists even rely on empirical data from indigenous people that is gathered by ethnobotanists. this information can relay a great deal of information on how the land once was thousands of years ago and how it has changed over that time. the goals of
##vary. ongoing research on the molecular phylogenetics of living plants appears to show that the angiosperms are a sister clade to the gymnosperms. = = plant physiology = = plant physiology encompasses all the internal chemical and physical activities of plants associated with life. chemicals obtained from the air, soil and water form the basis of all plant metabolism. the energy of sunlight, captured by oxygenic photosynthesis and released by cellular respiration, is the basis of almost all life. photoautotrophs, including all green plants, algae and cyanobacteria gather energy directly from sunlight by photosynthesis. heterotrophs including all animals, all fungi, all completely parasitic plants, and non - photosynthetic bacteria take in organic molecules produced by photoautotrophs and respire them or use them in the construction of cells and tissues. respiration is the oxidation of carbon compounds by breaking them down into simpler structures to release the energy they contain, essentially the opposite of photosynthesis. molecules are moved within plants by transport processes that operate at a variety of spatial scales. subcellular transport of ions, electrons and molecules such as water and enzymes occurs across cell membranes. minerals and water are transported from roots to other parts of the plant in the transpiration stream. diffusion, osmosis, and active transport and mass flow are all different ways transport can occur. examples of elements that plants need to transport are nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. in vascular plants, these elements are extracted from the soil as soluble ions by the roots and transported throughout the plant in the xylem. most of the elements required for plant nutrition come from the chemical breakdown of soil minerals. sucrose produced by photosynthesis is transported from the leaves to other parts of the plant in the phloem and plant hormones are transported by a variety of processes. = = = plant hormones = = = plants are not passive, but respond to external signals such as light, touch, and injury by moving or growing towards or away from the stimulus, as appropriate. tangible evidence of touch sensitivity is the almost instantaneous collapse of leaflets of mimosa pudica, the insect traps of venus flytrap and bladderworts, and the pollinia of orchids. the hypothesis that plant growth and development is coordinated by plant hormones or plant growth regulators first emerged in the late 19th century. darwin experimented on the movements of plant shoots and roots towards light and gravity, and concluded " it is hardly an ex
others, such as the essential oils peppermint oil and lemon oil are useful for their aroma, as flavourings and spices ( e. g., capsaicin ), and in medicine as pharmaceuticals as in opium from opium poppies. many medicinal and recreational drugs, such as tetrahydrocannabinol ( active ingredient in cannabis ), caffeine, morphine and nicotine come directly from plants. others are simple derivatives of botanical natural products. for example, the pain killer aspirin is the acetyl ester of salicylic acid, originally isolated from the bark of willow trees, and a wide range of opiate painkillers like heroin are obtained by chemical modification of morphine obtained from the opium poppy. popular stimulants come from plants, such as caffeine from coffee, tea and chocolate, and nicotine from tobacco. most alcoholic beverages come from fermentation of carbohydrate - rich plant products such as barley ( beer ), rice ( sake ) and grapes ( wine ). native americans have used various plants as ways of treating illness or disease for thousands of years. this knowledge native americans have on plants has been recorded by enthnobotanists and then in turn has been used by pharmaceutical companies as a way of drug discovery. plants can synthesise coloured dyes and pigments such as the anthocyanins responsible for the red colour of red wine, yellow weld and blue woad used together to produce lincoln green, indoxyl, source of the blue dye indigo traditionally used to dye denim and the artist ' s pigments gamboge and rose madder. sugar, starch, cotton, linen, hemp, some types of rope, wood and particle boards, papyrus and paper, vegetable oils, wax, and natural rubber are examples of commercially important materials made from plant tissues or their secondary products. charcoal, a pure form of carbon made by pyrolysis of wood, has a long history as a metal - smelting fuel, as a filter material and adsorbent and as an artist ' s material and is one of the three ingredients of gunpowder. cellulose, the world ' s most abundant organic polymer, can be converted into energy, fuels, materials and chemical feedstock. products made from cellulose include rayon and cellophane, wallpaper paste, biobutanol and gun cotton. sugarcane, rapeseed and soy are some of the plants with a highly ferment
##al nomenclature. the nomenclature of botanical organisms is codified in the international code of nomenclature for algae, fungi, and plants ( icn ) and administered by the international botanical congress. kingdom plantae belongs to domain eukaryota and is broken down recursively until each species is separately classified. the order is : kingdom ; phylum ( or division ) ; class ; order ; family ; genus ( plural genera ) ; species. the scientific name of a plant represents its genus and its species within the genus, resulting in a single worldwide name for each organism. for example, the tiger lily is lilium columbianum. lilium is the genus, and columbianum the specific epithet. the combination is the name of the species. when writing the scientific name of an organism, it is proper to capitalise the first letter in the genus and put all of the specific epithet in lowercase. additionally, the entire term is ordinarily italicised ( or underlined when italics are not available ). the evolutionary relationships and heredity of a group of organisms is called its phylogeny. phylogenetic studies attempt to discover phylogenies. the basic approach is to use similarities based on shared inheritance to determine relationships. as an example, species of pereskia are trees or bushes with prominent leaves. they do not obviously resemble a typical leafless cactus such as an echinocactus. however, both pereskia and echinocactus have spines produced from areoles ( highly specialised pad - like structures ) suggesting that the two genera are indeed related. judging relationships based on shared characters requires care, since plants may resemble one another through convergent evolution in which characters have arisen independently. some euphorbias have leafless, rounded bodies adapted to water conservation similar to those of globular cacti, but characters such as the structure of their flowers make it clear that the two groups are not closely related. the cladistic method takes a systematic approach to characters, distinguishing between those that carry no information about shared evolutionary history β such as those evolved separately in different groups ( homoplasies ) or those left over from ancestors ( plesiomorphies ) β and derived characters, which have been passed down from innovations in a shared ancestor ( apomorphies ). only derived characters, such as the spine - producing areoles of cacti, provide evidence for descent from a common ancestor. the results of cladistic analyses are expressed as cladograms : tree - like diagrams showing the
- people relationships arose between the indigenous people of canada in identifying edible plants from inedible plants. this relationship the indigenous people had with plants was recorded by ethnobotanists. = = plant biochemistry = = plant biochemistry is the study of the chemical processes used by plants. some of these processes are used in their primary metabolism like the photosynthetic calvin cycle and crassulacean acid metabolism. others make specialised materials like the cellulose and lignin used to build their bodies, and secondary products like resins and aroma compounds. plants and various other groups of photosynthetic eukaryotes collectively known as " algae " have unique organelles known as chloroplasts. chloroplasts are thought to be descended from cyanobacteria that formed endosymbiotic relationships with ancient plant and algal ancestors. chloroplasts and cyanobacteria contain the blue - green pigment chlorophyll a. chlorophyll a ( as well as its plant and green algal - specific cousin chlorophyll b ) absorbs light in the blue - violet and orange / red parts of the spectrum while reflecting and transmitting the green light that we see as the characteristic colour of these organisms. the energy in the red and blue light that these pigments absorb is used by chloroplasts to make energy - rich carbon compounds from carbon dioxide and water by oxygenic photosynthesis, a process that generates molecular oxygen ( o2 ) as a by - product. the light energy captured by chlorophyll a is initially in the form of electrons ( and later a proton gradient ) that is used to make molecules of atp and nadph which temporarily store and transport energy. their energy is used in the light - independent reactions of the calvin cycle by the enzyme rubisco to produce molecules of the 3 - carbon sugar glyceraldehyde 3 - phosphate ( g3p ). glyceraldehyde 3 - phosphate is the first product of photosynthesis and the raw material from which glucose and almost all other organic molecules of biological origin are synthesised. some of the glucose is converted to starch which is stored in the chloroplast. starch is the characteristic energy store of most land plants and algae, while inulin, a polymer of fructose is used for the same purpose in the sunflower family asteraceae. some of the glucose is converted to sucrose ( common table
) of the mass of all organisms, with calcium, phosphorus, sulfur, sodium, chlorine, and magnesium constituting essentially all the remainder. different elements can combine to form compounds such as water, which is fundamental to life. biochemistry is the study of chemical processes within and relating to living organisms. molecular biology is the branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including molecular synthesis, modification, mechanisms, and interactions. = = = water = = = life arose from the earth ' s first ocean, which formed some 3. 8 billion years ago. since then, water continues to be the most abundant molecule in every organism. water is important to life because it is an effective solvent, capable of dissolving solutes such as sodium and chloride ions or other small molecules to form an aqueous solution. once dissolved in water, these solutes are more likely to come in contact with one another and therefore take part in chemical reactions that sustain life. in terms of its molecular structure, water is a small polar molecule with a bent shape formed by the polar covalent bonds of two hydrogen ( h ) atoms to one oxygen ( o ) atom ( h2o ). because the o β h bonds are polar, the oxygen atom has a slight negative charge and the two hydrogen atoms have a slight positive charge. this polar property of water allows it to attract other water molecules via hydrogen bonds, which makes water cohesive. surface tension results from the cohesive force due to the attraction between molecules at the surface of the liquid. water is also adhesive as it is able to adhere to the surface of any polar or charged non - water molecules. water is denser as a liquid than it is as a solid ( or ice ). this unique property of water allows ice to float above liquid water such as ponds, lakes, and oceans, thereby insulating the liquid below from the cold air above. water has the capacity to absorb energy, giving it a higher specific heat capacity than other solvents such as ethanol. thus, a large amount of energy is needed to break the hydrogen bonds between water molecules to convert liquid water into water vapor. as a molecule, water is not completely stable as each water molecule continuously dissociates into hydrogen and hydroxyl ions before reforming into a water molecule again. in pure water, the number of hydrogen ions balances ( or equals ) the number of hydroxyl ions, resulting in a ph that is neutral. = = = organic compounds =
Question: What is one of the most common biochemical compounds on earth and is found in all plants?
A) cellulose
B) sulfur
C) carbon dioxide
D) hydrogen
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A) cellulose
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Context:
outer satellites of the planets have distant, eccentric orbits that can be highly inclined or even retrograde relative to the equatorial planes of their planets. these irregular orbits cannot have formed by circumplanetary accretion and are likely products of early capture from heliocentric orbit. the irregular satellites may be the only small bodies remaining which are still relatively near their formation locations within the giant planet region. the study of the irregular satellites provides a unique window on processes operating in the young solar system and allows us to probe possible planet formation mechanisms and the composition of the solar nebula between the rocky objects in the main asteroid belt and the very volatile rich objects in the kuiper belt. the gas and ice giant planets all appear to have very similar irregular satellite systems irrespective of their mass or formation timescales and mechanisms. water ice has been detected on some of the outer satellites of saturn and neptune whereas none has been observed on jupiter ' s outer satellites.
planetary systems can evolve dynamically even after the full growth of the planets themselves. there is actually circumstantial evidence that most planetary systems become unstable after the disappearance of gas from the protoplanetary disk. these instabilities can be due to the original system being too crowded and too closely packed or to external perturbations such as tides, planetesimal scattering, or torques from distant stellar companions. the solar system was not exceptional in this sense. in its inner part, a crowded system of planetary embryos became unstable, leading to a series of mutual impacts that built the terrestrial planets on a timescale of ~ 100 my. in its outer part, the giant planets became temporarily unstable and their orbital configuration expanded under the effect of mutual encounters. a planet might have been ejected in this phase. thus, the orbital distributions of planetary systems that we observe today, both solar and extrasolar ones, can be different from the those emerging from the formation process and it is important to consider possible long - term evolutionary effects to connect the two.
also launched missions to mercury in 2004, with the messenger probe demonstrating as the first use of a solar sail. nasa also launched probes to the outer solar system starting in the 1960s. pioneer 10 was the first probe to the outer planets, flying by jupiter, while pioneer 11 provided the first close up view of the planet. both probes became the first objects to leave the solar system. the voyager program launched in 1977, conducting flybys of jupiter and saturn, neptune, and uranus on a trajectory to leave the solar system. the galileo spacecraft, deployed from the space shuttle flight sts - 34, was the first spacecraft to orbit jupiter, discovering evidence of subsurface oceans on the europa and observed that the moon may hold ice or liquid water. a joint nasa - european space agency - italian space agency mission, cassini β huygens, was sent to saturn ' s moon titan, which, along with mars and europa, are the only celestial bodies in the solar system suspected of being capable of harboring life. cassini discovered three new moons of saturn and the huygens probe entered titan ' s atmosphere. the mission discovered evidence of liquid hydrocarbon lakes on titan and subsurface water oceans on the moon of enceladus, which could harbor life. finally launched in 2006, the new horizons mission was the first spacecraft to visit pluto and the kuiper belt. beyond interplanetary probes, nasa has launched many space telescopes. launched in the 1960s, the orbiting astronomical observatory were nasa ' s first orbital telescopes, providing ultraviolet, gamma - ray, x - ray, and infrared observations. nasa launched the orbiting geophysical observatory in the 1960s and 1970s to look down at earth and observe its interactions with the sun. the uhuru satellite was the first dedicated x - ray telescope, mapping 85 % of the sky and discovering a large number of black holes. launched in the 1990s and early 2000s, the great observatories program are among nasa ' s most powerful telescopes. the hubble space telescope was launched in 1990 on sts - 31 from the discovery and could view galaxies 15 billion light years away. a major defect in the telescope ' s mirror could have crippled the program, had nasa not used computer enhancement to compensate for the imperfection and launched five space shuttle servicing flights to replace the damaged components. the compton gamma ray observatory was launched from the atlantis on sts - 37 in 1991, discovering a possible source of antimatter at the center of the milky way and observing that the majority of gamma - ray bursts
armed with an astrolabe and kepler ' s laws one can arrive at accurate estimates of the orbits of planets.
three major planets, venus, earth, and mercury formed out of the solar nebula. a fourth planetesimal, theia, also formed near earth where it collided in a giant impact, rebounding as the planet mars. during this impact earth lost $ { \ approx } 4 $ \ % of its crust and mantle that is now is found on mars and the moon. at the antipode of the giant impact, $ \ approx $ 60 \ % of earth ' s crust, atmosphere, and a large amount of mantle were ejected into space forming the moon. the lost crust never reformed and became the earth ' s ocean basins. the theia impact site corresponds to indian ocean gravitational anomaly on earth and the hellas basin on mars. the dynamics of the giant impact are consistent with the rotational rates and axial tilts of both earth and mars. the giant impact removed sufficient co $ _ 2 $ from earth ' s atmosphere to avoid a runaway greenhouse effect, initiated plate tectonics, and gave life time to form near geothermal vents at the continental margins. mercury formed near venus where on a close approach it was slingshot into the sun ' s convective zone losing 94 \ % of its mass, much of which remains there today. black carbon, from co $ _ 2 $ decomposed by the intense heat, is still found on the surface of mercury. arriving at 616 km / s, mercury dramatically altered the sun ' s rotational energy, explaining both its anomalously slow rotation rate and axial tilt. these results are quantitatively supported by mass balances, the current locations of the terrestrial planets, and the orientations of their major orbital axes.
the d68 ringlet is the innermost narrow feature in saturn ' s rings. prior to 2014, the brightness of this ringlet did not vary much with longitude, but sometime in 2014 or 2015 a series of bright clumps appeared within d68. these clumps were up to four times brighter than the typical ringlet, occurred within a span of ~ 120 degrees in corotating longitude, and moved at an average rate of 1751. 7 degrees / day during the last year of the cassini mission. the slow evolution and relative motions of these clumps suggest that they are composed of particles with a narrow ( sub - kilometer ) spread in semi - major axis. the clumps therefore probably consist of fine material released by collisions among larger ( up to 20 meters wide ) objects orbiting close to d68. the event that triggered the formation of these bright clumps is still unclear, but it could have some connection to the material observed when the cassini spacecraft passed between the planet and the rings.
the gas giant planets in the solar system have a retinue of icy moons, and we expect giant exoplanets to have similar satellite systems. if a jupiter - like planet were to migrate toward its parent star the icy moons orbiting it would evaporate, creating atmospheres and possible habitable surface oceans. here, we examine how long the surface ice and possible oceans would last before being hydrodynamically lost to space. the hydrodynamic loss rate from the moons is determined, in large part, by the stellar flux available for absorption, which increases as the giant planet and icy moons migrate closer to the star. at some planet - star distance the stellar flux incident on the icy moons becomes so great that they enter a runaway greenhouse state. this runaway greenhouse state rapidly transfers all available surface water to the atmosphere as vapor, where it is easily lost from the small moons. however, for icy moons of ganymede ' s size around a sun - like star we found that surface water ( either ice or liquid ) can persist indefinitely outside the runaway greenhouse orbital distance. in contrast, the surface water on smaller moons of europa ' s size will only persist on timescales greater than 1 gyr at distances ranging 1. 49 to 0. 74 au around a sun - like star for bond albedos of 0. 2 and 0. 8, where the lower albedo becomes relevant if ice melts. consequently, small moons can lose their icy shells, which would create a torus of h atoms around their host planet that might be detectable in future observations.
a 4mj planet with a 15. 8day orbital period has been detected from very precise radial velocity measurements with the coralie echelle spectrograph. a second remote and more massive companion has also been detected. all the planetary companions so far detected in orbit closer than 0. 08 au have a parent star with a statistically higher metal content compared to the metallicity distribution of other stars with planets. different processes occuring during their formation may provide a possible explanation for this observation.
three planets with minimum masses less than 10 earth masses orbit the star hd 40307, suggesting these planets may be rocky. however, with only radial velocity data, it is impossible to determine if these planets are rocky or gaseous. here we exploit various dynamical features of the system in order to assess the physical properties of the planets. observations allow for circular orbits, but a numerical integration shows that the eccentricities must be at least 0. 0001. also, planets b and c are so close to the star that tidal effects are significant. if planet b has tidal parameters similar to the terrestrial planets in the solar system and a remnant eccentricity larger than 0. 001, then, going back in time, the system would have been unstable within the lifetime of the star ( which we estimate to be 6. 1 + / - 1. 6 gyr ). moreover, if the eccentricities are that large and the inner planet is rocky, then its tidal heating may be an order of magnitude greater than extremely volcanic io, on a per unit surface area basis. if planet b is not terrestrial, e. g. neptune - like, these physical constraints would not apply. this analysis suggests the planets are not terrestrial - like, and are more like our giant planets. in either case, we find that the planets probably formed at larger radii and migrated early - on ( via disk interactions ) into their current orbits. this study demonstrates how the orbital and dynamical properties of exoplanet systems may be used to constrain the planets ' physical properties.
water content and the internal evolution of terrestrial planets and icy bodies are closely linked. the distribution of water in planetary systems is controlled by the temperature structure in the protoplanetary disk and dynamics and migration of planetesimals and planetary embryos. this results in the formation of planetesimals and planetary embryos with a great variety of compositions, water contents and degrees of oxidation. the internal evolution and especially the formation time of planetesimals relative to the timescale of radiogenic heating by short - lived 26al decay may govern the amount of hydrous silicates and leftover rock - ice mixtures available in the late stages of their evolution. in turn, water content may affect the early internal evolution of the planetesimals and in particular metal - silicate separation processes. moreover, water content may contribute to an increase of oxygen fugacity and thus affect the concentrations of siderophile elements within the silicate reservoirs of solar system objects. finally, the water content strongly influences the differentiation rate of the icy moons, controls their internal evolution and governs the alteration processes occurring in their deep interiors.
Question: What man-made structures orbit all of the inner planets as well as jupiter and saturn?
A) satellites
B) moons
C) space shuttles
D) comets
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A) satellites
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Context:
the structural components of cells. as a by - product of photosynthesis, plants release oxygen into the atmosphere, a gas that is required by nearly all living things to carry out cellular respiration. in addition, they are influential in the global carbon and water cycles and plant roots bind and stabilise soils, preventing soil erosion. plants are crucial to the future of human society as they provide food, oxygen, biochemicals, and products for people, as well as creating and preserving soil. historically, all living things were classified as either animals or plants and botany covered the study of all organisms not considered animals. botanists examine both the internal functions and processes within plant organelles, cells, tissues, whole plants, plant populations and plant communities. at each of these levels, a botanist may be concerned with the classification ( taxonomy ), phylogeny and evolution, structure ( anatomy and morphology ), or function ( physiology ) of plant life. the strictest definition of " plant " includes only the " land plants " or embryophytes, which include seed plants ( gymnosperms, including the pines, and flowering plants ) and the free - sporing cryptogams including ferns, clubmosses, liverworts, hornworts and mosses. embryophytes are multicellular eukaryotes descended from an ancestor that obtained its energy from sunlight by photosynthesis. they have life cycles with alternating haploid and diploid phases. the sexual haploid phase of embryophytes, known as the gametophyte, nurtures the developing diploid embryo sporophyte within its tissues for at least part of its life, even in the seed plants, where the gametophyte itself is nurtured by its parent sporophyte. other groups of organisms that were previously studied by botanists include bacteria ( now studied in bacteriology ), fungi ( mycology ) β including lichen - forming fungi ( lichenology ), non - chlorophyte algae ( phycology ), and viruses ( virology ). however, attention is still given to these groups by botanists, and fungi ( including lichens ) and photosynthetic protists are usually covered in introductory botany courses. palaeobotanists study ancient plants in the fossil record to provide information about the evolutionary history of plants. cyanobacteria, the first oxygen - releasing photosynthetic organisms on earth, are thought to have given rise to the
, there are many biomolecules such as proteins and nucleic acids. in addition to biomolecules, eukaryotic cells have specialized structures called organelles that have their own lipid bilayers or are spatially units. these organelles include the cell nucleus, which contains most of the cell ' s dna, or mitochondria, which generate adenosine triphosphate ( atp ) to power cellular processes. other organelles such as endoplasmic reticulum and golgi apparatus play a role in the synthesis and packaging of proteins, respectively. biomolecules such as proteins can be engulfed by lysosomes, another specialized organelle. plant cells have additional organelles that distinguish them from animal cells such as a cell wall that provides support for the plant cell, chloroplasts that harvest sunlight energy to produce sugar, and vacuoles that provide storage and structural support as well as being involved in reproduction and breakdown of plant seeds. eukaryotic cells also have cytoskeleton that is made up of microtubules, intermediate filaments, and microfilaments, all of which provide support for the cell and are involved in the movement of the cell and its organelles. in terms of their structural composition, the microtubules are made up of tubulin ( e. g., Ξ± - tubulin and Ξ² - tubulin ) whereas intermediate filaments are made up of fibrous proteins. microfilaments are made up of actin molecules that interact with other strands of proteins. = = = metabolism = = = all cells require energy to sustain cellular processes. metabolism is the set of chemical reactions in an organism. the three main purposes of metabolism are : the conversion of food to energy to run cellular processes ; the conversion of food / fuel to monomer building blocks ; and the elimination of metabolic wastes. these enzyme - catalyzed reactions allow organisms to grow and reproduce, maintain their structures, and respond to their environments. metabolic reactions may be categorized as catabolic β the breaking down of compounds ( for example, the breaking down of glucose to pyruvate by cellular respiration ) ; or anabolic β the building up ( synthesis ) of compounds ( such as proteins, carbohydrates, lipids, and nucleic acids ). usually, catabolism releases energy, and anabolism consumes energy. the chemical reactions of metabolism are organized into metabolic pathways, in which
to be separated conceptually from geology and crop production and treated as a whole. as a founding father of soil science, fallou has primacy in time. fallou was working on the origins of soil before dokuchaev was born ; however dokuchaev ' s work was more extensive and is considered to be the more significant to modern soil theory than fallou ' s. previously, soil had been considered a product of chemical transformations of rocks, a dead substrate from which plants derive nutritious elements. soil and bedrock were in fact equated. dokuchaev considers the soil as a natural body having its own genesis and its own history of development, a body with complex and multiform processes taking place within it. the soil is considered as different from bedrock. the latter becomes soil under the influence of a series of soil - formation factors ( climate, vegetation, country, relief and age ). according to him, soil should be called the " daily " or outward horizons of rocks regardless of the type ; they are changed naturally by the common effect of water, air and various kinds of living and dead organisms. a 1914 encyclopedic definition : " the different forms of earth on the surface of the rocks, formed by the breaking down or weathering of rocks ". serves to illustrate the historic view of soil which persisted from the 19th century. dokuchaev ' s late 19th century soil concept developed in the 20th century to one of soil as earthy material that has been altered by living processes. a corollary concept is that soil without a living component is simply a part of earth ' s outer layer. further refinement of the soil concept is occurring in view of an appreciation of energy transport and transformation within soil. the term is popularly applied to the material on the surface of the earth ' s moon and mars, a usage acceptable within a portion of the scientific community. accurate to this modern understanding of soil is nikiforoff ' s 1959 definition of soil as the " excited skin of the sub aerial part of the earth ' s crust ". = = areas of practice = = academically, soil scientists tend to be drawn to one of five areas of specialization : microbiology, pedology, edaphology, physics, or chemistry. yet the work specifics are very much dictated by the challenges facing our civilization ' s desire to sustain the land that supports it, and the distinctions between the sub - disciplines of soil science often blur in the process. soil science professionals commonly stay current
from the oil of jasminum grandiflorum which regulates wound responses in plants by unblocking the expression of genes required in the systemic acquired resistance response to pathogen attack. in addition to being the primary energy source for plants, light functions as a signalling device, providing information to the plant, such as how much sunlight the plant receives each day. this can result in adaptive changes in a process known as photomorphogenesis. phytochromes are the photoreceptors in a plant that are sensitive to light. = = plant anatomy and morphology = = plant anatomy is the study of the structure of plant cells and tissues, whereas plant morphology is the study of their external form. all plants are multicellular eukaryotes, their dna stored in nuclei. the characteristic features of plant cells that distinguish them from those of animals and fungi include a primary cell wall composed of the polysaccharides cellulose, hemicellulose and pectin, larger vacuoles than in animal cells and the presence of plastids with unique photosynthetic and biosynthetic functions as in the chloroplasts. other plastids contain storage products such as starch ( amyloplasts ) or lipids ( elaioplasts ). uniquely, streptophyte cells and those of the green algal order trentepohliales divide by construction of a phragmoplast as a template for building a cell plate late in cell division. the bodies of vascular plants including clubmosses, ferns and seed plants ( gymnosperms and angiosperms ) generally have aerial and subterranean subsystems. the shoots consist of stems bearing green photosynthesising leaves and reproductive structures. the underground vascularised roots bear root hairs at their tips and generally lack chlorophyll. non - vascular plants, the liverworts, hornworts and mosses do not produce ground - penetrating vascular roots and most of the plant participates in photosynthesis. the sporophyte generation is nonphotosynthetic in liverworts but may be able to contribute part of its energy needs by photosynthesis in mosses and hornworts. the root system and the shoot system are interdependent β the usually nonphotosynthetic root system depends on the shoot system for food, and the usually photosynthetic shoot system depends on water and minerals from the root system. cells in each system are capable
soil erosion. plants are crucial to the future of human society as they provide food, oxygen, biochemicals, and products for people, as well as creating and preserving soil. historically, all living things were classified as either animals or plants and botany covered the study of all organisms not considered animals. botanists examine both the internal functions and processes within plant organelles, cells, tissues, whole plants, plant populations and plant communities. at each of these levels, a botanist may be concerned with the classification ( taxonomy ), phylogeny and evolution, structure ( anatomy and morphology ), or function ( physiology ) of plant life. the strictest definition of " plant " includes only the " land plants " or embryophytes, which include seed plants ( gymnosperms, including the pines, and flowering plants ) and the free - sporing cryptogams including ferns, clubmosses, liverworts, hornworts and mosses. embryophytes are multicellular eukaryotes descended from an ancestor that obtained its energy from sunlight by photosynthesis. they have life cycles with alternating haploid and diploid phases. the sexual haploid phase of embryophytes, known as the gametophyte, nurtures the developing diploid embryo sporophyte within its tissues for at least part of its life, even in the seed plants, where the gametophyte itself is nurtured by its parent sporophyte. other groups of organisms that were previously studied by botanists include bacteria ( now studied in bacteriology ), fungi ( mycology ) β including lichen - forming fungi ( lichenology ), non - chlorophyte algae ( phycology ), and viruses ( virology ). however, attention is still given to these groups by botanists, and fungi ( including lichens ) and photosynthetic protists are usually covered in introductory botany courses. palaeobotanists study ancient plants in the fossil record to provide information about the evolutionary history of plants. cyanobacteria, the first oxygen - releasing photosynthetic organisms on earth, are thought to have given rise to the ancestor of plants by entering into an endosymbiotic relationship with an early eukaryote, ultimately becoming the chloroplasts in plant cells. the new photosynthetic plants ( along with their algal relatives ) accelerated the rise in atmospheric oxygen started by the cyanobacteria, changing the
be the more significant to modern soil theory than fallou ' s. previously, soil had been considered a product of chemical transformations of rocks, a dead substrate from which plants derive nutritious elements. soil and bedrock were in fact equated. dokuchaev considers the soil as a natural body having its own genesis and its own history of development, a body with complex and multiform processes taking place within it. the soil is considered as different from bedrock. the latter becomes soil under the influence of a series of soil - formation factors ( climate, vegetation, country, relief and age ). according to him, soil should be called the " daily " or outward horizons of rocks regardless of the type ; they are changed naturally by the common effect of water, air and various kinds of living and dead organisms. a 1914 encyclopedic definition : " the different forms of earth on the surface of the rocks, formed by the breaking down or weathering of rocks ". serves to illustrate the historic view of soil which persisted from the 19th century. dokuchaev ' s late 19th century soil concept developed in the 20th century to one of soil as earthy material that has been altered by living processes. a corollary concept is that soil without a living component is simply a part of earth ' s outer layer. further refinement of the soil concept is occurring in view of an appreciation of energy transport and transformation within soil. the term is popularly applied to the material on the surface of the earth ' s moon and mars, a usage acceptable within a portion of the scientific community. accurate to this modern understanding of soil is nikiforoff ' s 1959 definition of soil as the " excited skin of the sub aerial part of the earth ' s crust ". = = areas of practice = = academically, soil scientists tend to be drawn to one of five areas of specialization : microbiology, pedology, edaphology, physics, or chemistry. yet the work specifics are very much dictated by the challenges facing our civilization ' s desire to sustain the land that supports it, and the distinctions between the sub - disciplines of soil science often blur in the process. soil science professionals commonly stay current in soil chemistry, soil physics, soil microbiology, pedology, and applied soil science in related disciplines. one exciting effort drawing in soil scientists in the u. s. as of 2004 is the soil quality initiative. central to the soil quality initiative is developing indices of soil health and then monitoring them in a way
pectin and xyloglucan from which the land plant cell wall is constructed. vascular land plants make lignin, a polymer used to strengthen the secondary cell walls of xylem tracheids and vessels to keep them from collapsing when a plant sucks water through them under water stress. lignin is also used in other cell types like sclerenchyma fibres that provide structural support for a plant and is a major constituent of wood. sporopollenin is a chemically resistant polymer found in the outer cell walls of spores and pollen of land plants responsible for the survival of early land plant spores and the pollen of seed plants in the fossil record. it is widely regarded as a marker for the start of land plant evolution during the ordovician period. the concentration of carbon dioxide in the atmosphere today is much lower than it was when plants emerged onto land during the ordovician and silurian periods. many monocots like maize and the pineapple and some dicots like the asteraceae have since independently evolved pathways like crassulacean acid metabolism and the c4 carbon fixation pathway for photosynthesis which avoid the losses resulting from photorespiration in the more common c3 carbon fixation pathway. these biochemical strategies are unique to land plants. = = = medicine and materials = = = phytochemistry is a branch of plant biochemistry primarily concerned with the chemical substances produced by plants during secondary metabolism. some of these compounds are toxins such as the alkaloid coniine from hemlock. others, such as the essential oils peppermint oil and lemon oil are useful for their aroma, as flavourings and spices ( e. g., capsaicin ), and in medicine as pharmaceuticals as in opium from opium poppies. many medicinal and recreational drugs, such as tetrahydrocannabinol ( active ingredient in cannabis ), caffeine, morphine and nicotine come directly from plants. others are simple derivatives of botanical natural products. for example, the pain killer aspirin is the acetyl ester of salicylic acid, originally isolated from the bark of willow trees, and a wide range of opiate painkillers like heroin are obtained by chemical modification of morphine obtained from the opium poppy. popular stimulants come from plants, such as caffeine from coffee, tea and chocolate, and nicotine from tobacco. most alcoholic beverages come from fermentation of carbohy
and their competitive or mutualistic interactions with other species. some ecologists even rely on empirical data from indigenous people that is gathered by ethnobotanists. this information can relay a great deal of information on how the land once was thousands of years ago and how it has changed over that time. the goals of plant ecology are to understand the causes of their distribution patterns, productivity, environmental impact, evolution, and responses to environmental change. plants depend on certain edaphic ( soil ) and climatic factors in their environment but can modify these factors too. for example, they can change their environment ' s albedo, increase runoff interception, stabilise mineral soils and develop their organic content, and affect local temperature. plants compete with other organisms in their ecosystem for resources. they interact with their neighbours at a variety of spatial scales in groups, populations and communities that collectively constitute vegetation. regions with characteristic vegetation types and dominant plants as well as similar abiotic and biotic factors, climate, and geography make up biomes like tundra or tropical rainforest. herbivores eat plants, but plants can defend themselves and some species are parasitic or even carnivorous. other organisms form mutually beneficial relationships with plants. for example, mycorrhizal fungi and rhizobia provide plants with nutrients in exchange for food, ants are recruited by ant plants to provide protection, honey bees, bats and other animals pollinate flowers and humans and other animals act as dispersal vectors to spread spores and seeds. = = = plants, climate and environmental change = = = plant responses to climate and other environmental changes can inform our understanding of how these changes affect ecosystem function and productivity. for example, plant phenology can be a useful proxy for temperature in historical climatology, and the biological impact of climate change and global warming. palynology, the analysis of fossil pollen deposits in sediments from thousands or millions of years ago allows the reconstruction of past climates. estimates of atmospheric co2 concentrations since the palaeozoic have been obtained from stomatal densities and the leaf shapes and sizes of ancient land plants. ozone depletion can expose plants to higher levels of ultraviolet radiation - b ( uv - b ), resulting in lower growth rates. moreover, information from studies of community ecology, plant systematics, and taxonomy is essential to understanding vegetation change, habitat destruction and species extinction. = = genetics = = inheritance in plants follows the same fundamental principles of genetics as in other multicellular organisms. gregor mendel discovered the genetic laws of inheritance by studying
stems mainly provide support to the leaves and reproductive structures, but can store water in succulent plants such as cacti, food as in potato tubers, or reproduce vegetatively as in the stolons of strawberry plants or in the process of layering. leaves gather sunlight and carry out photosynthesis. large, flat, flexible, green leaves are called foliage leaves. gymnosperms, such as conifers, cycads, ginkgo, and gnetophytes are seed - producing plants with open seeds. angiosperms are seed - producing plants that produce flowers and have enclosed seeds. woody plants, such as azaleas and oaks, undergo a secondary growth phase resulting in two additional types of tissues : wood ( secondary xylem ) and bark ( secondary phloem and cork ). all gymnosperms and many angiosperms are woody plants. some plants reproduce sexually, some asexually, and some via both means. although reference to major morphological categories such as root, stem, leaf, and trichome are useful, one has to keep in mind that these categories are linked through intermediate forms so that a continuum between the categories results. furthermore, structures can be seen as processes, that is, process combinations. = = systematic botany = = systematic botany is part of systematic biology, which is concerned with the range and diversity of organisms and their relationships, particularly as determined by their evolutionary history. it involves, or is related to, biological classification, scientific taxonomy and phylogenetics. biological classification is the method by which botanists group organisms into categories such as genera or species. biological classification is a form of scientific taxonomy. modern taxonomy is rooted in the work of carl linnaeus, who grouped species according to shared physical characteristics. these groupings have since been revised to align better with the darwinian principle of common descent β grouping organisms by ancestry rather than superficial characteristics. while scientists do not always agree on how to classify organisms, molecular phylogenetics, which uses dna sequences as data, has driven many recent revisions along evolutionary lines and is likely to continue to do so. the dominant classification system is called linnaean taxonomy. it includes ranks and binomial nomenclature. the nomenclature of botanical organisms is codified in the international code of nomenclature for algae, fungi, and plants ( icn ) and administered by the international botanical congress. kingdom plantae belongs to domain eukaryota and is broken down recursively until each species is separately classified. the order is :
eat them. plants and other photosynthetic organisms are at the base of most food chains because they use the energy from the sun and nutrients from the soil and atmosphere, converting them into a form that can be used by animals. this is what ecologists call the first trophic level. the modern forms of the major staple foods, such as hemp, teff, maize, rice, wheat and other cereal grasses, pulses, bananas and plantains, as well as hemp, flax and cotton grown for their fibres, are the outcome of prehistoric selection over thousands of years from among wild ancestral plants with the most desirable characteristics. botanists study how plants produce food and how to increase yields, for example through plant breeding, making their work important to humanity ' s ability to feed the world and provide food security for future generations. botanists also study weeds, which are a considerable problem in agriculture, and the biology and control of plant pathogens in agriculture and natural ecosystems. ethnobotany is the study of the relationships between plants and people. when applied to the investigation of historical plant β people relationships ethnobotany may be referred to as archaeobotany or palaeoethnobotany. some of the earliest plant - people relationships arose between the indigenous people of canada in identifying edible plants from inedible plants. this relationship the indigenous people had with plants was recorded by ethnobotanists. = = plant biochemistry = = plant biochemistry is the study of the chemical processes used by plants. some of these processes are used in their primary metabolism like the photosynthetic calvin cycle and crassulacean acid metabolism. others make specialised materials like the cellulose and lignin used to build their bodies, and secondary products like resins and aroma compounds. plants and various other groups of photosynthetic eukaryotes collectively known as " algae " have unique organelles known as chloroplasts. chloroplasts are thought to be descended from cyanobacteria that formed endosymbiotic relationships with ancient plant and algal ancestors. chloroplasts and cyanobacteria contain the blue - green pigment chlorophyll a. chlorophyll a ( as well as its plant and green algal - specific cousin chlorophyll b ) absorbs light in the blue - violet and orange / red parts of the spectrum while reflecting and transmitting the green light that we see as the characteristic colour
Question: What basic structures take in nutrients from the soil and help the plant survive?
A) tissues
B) stems
C) leaves
D) roots
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D) roots
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Context:
weakly established hybridomas. unfused b cells die as they have a short life span. in this way, only the b cell - myeloma hybrids survive, since the hgprt gene coming from the b cells is functional. these cells produce antibodies ( a property of b cells ) and are immortal ( a property of myeloma cells ). the incubated medium is then diluted into multi - well plates to such an extent that each well contains only one cell. since the antibodies in a well are produced by the same b cell, they will be directed towards the same epitope, and are thus monoclonal antibodies. the next stage is a rapid primary screening process, which identifies and selects only those hybridomas that produce antibodies of appropriate specificity. the first screening technique used is called elisa. the hybridoma culture supernatant, secondary enzyme labeled conjugate, and chromogenic substrate, are then incubated, and the formation of a colored product indicates a positive hybridoma. alternatively, immunocytochemical, western blot, and immunoprecipitation - mass spectrometry. unlike western blot assays, immunoprecipitation - mass spectrometry facilitates screening and ranking of clones which bind to the native ( non - denaturated ) forms of antigen proteins. flow cytometry screening has been used for primary screening of a large number ( ~ 1000 ) of hybridoma clones recognizing the native form of the antigen on the cell surface. in the flow cytometry - based screening, a mixture of antigen - negative cells and antigen - positive cells is used as the antigen to be tested for each hybridoma supernatant sample. the b cell that produces the desired antibodies can be cloned to produce many identical daughter clones. supplemental media containing interleukin - 6 ( such as briclone ) are essential for this step. once a hybridoma colony is established, it will continually grow in culture medium like rpmi - 1640 ( with antibiotics and fetal bovine serum ) and produce antibodies. multiwell plates are used initially to grow the hybridomas, and after selection, are changed to larger tissue culture flasks. this maintains the well - being of the hybridomas and provides enough cells for cryopreservation and supernatant for subsequent investigations. the culture supernatant can yield 1 to 60 ΞΌg / ml of monoclonal antibody, which is maintained at -
##se ( hgprt ) gene, making them sensitive ( or vulnerable ) to the hat medium ( see below ). fused cells are incubated in hat medium ( hypoxanthine - aminopterin - thymidine medium ) for roughly 10 to 14 days. aminopterin blocks the pathway that allows for nucleotide synthesis. hence, unfused myeloma cells die, as they cannot produce nucleotides by the de novo or salvage pathways because they lack hgprt. removal of the unfused myeloma cells is necessary because they have the potential to outgrow other cells, especially weakly established hybridomas. unfused b cells die as they have a short life span. in this way, only the b cell - myeloma hybrids survive, since the hgprt gene coming from the b cells is functional. these cells produce antibodies ( a property of b cells ) and are immortal ( a property of myeloma cells ). the incubated medium is then diluted into multi - well plates to such an extent that each well contains only one cell. since the antibodies in a well are produced by the same b cell, they will be directed towards the same epitope, and are thus monoclonal antibodies. the next stage is a rapid primary screening process, which identifies and selects only those hybridomas that produce antibodies of appropriate specificity. the first screening technique used is called elisa. the hybridoma culture supernatant, secondary enzyme labeled conjugate, and chromogenic substrate, are then incubated, and the formation of a colored product indicates a positive hybridoma. alternatively, immunocytochemical, western blot, and immunoprecipitation - mass spectrometry. unlike western blot assays, immunoprecipitation - mass spectrometry facilitates screening and ranking of clones which bind to the native ( non - denaturated ) forms of antigen proteins. flow cytometry screening has been used for primary screening of a large number ( ~ 1000 ) of hybridoma clones recognizing the native form of the antigen on the cell surface. in the flow cytometry - based screening, a mixture of antigen - negative cells and antigen - positive cells is used as the antigen to be tested for each hybridoma supernatant sample. the b cell that produces the desired antibodies can be cloned to produce many identical daughter clones. supplemental media containing interleukin -
small ubiquitin - related modifier ( sumo ) proteins are widely expressed in eukaryotic cells, which are reversibly coupled to their substrates by motif recognition, called sumoylation. two interesting questions are 1 ) how many potential sumo substrates may be included in mammalian proteomes, such as human and mouse, 2 ) and given a sumo substrate, can we recognize its sumoylation sites? to answer these two questions, previous prediction systems of sumo substrates mainly adopted the pattern recognition methods, which could get high sensitivity with relatively too many potential false positives. so we use phylogenetic conservation between mouse and human to reduce the number of potential false positives.
for nucleotide synthesis. hence, unfused myeloma cells die, as they cannot produce nucleotides by the de novo or salvage pathways because they lack hgprt. removal of the unfused myeloma cells is necessary because they have the potential to outgrow other cells, especially weakly established hybridomas. unfused b cells die as they have a short life span. in this way, only the b cell - myeloma hybrids survive, since the hgprt gene coming from the b cells is functional. these cells produce antibodies ( a property of b cells ) and are immortal ( a property of myeloma cells ). the incubated medium is then diluted into multi - well plates to such an extent that each well contains only one cell. since the antibodies in a well are produced by the same b cell, they will be directed towards the same epitope, and are thus monoclonal antibodies. the next stage is a rapid primary screening process, which identifies and selects only those hybridomas that produce antibodies of appropriate specificity. the first screening technique used is called elisa. the hybridoma culture supernatant, secondary enzyme labeled conjugate, and chromogenic substrate, are then incubated, and the formation of a colored product indicates a positive hybridoma. alternatively, immunocytochemical, western blot, and immunoprecipitation - mass spectrometry. unlike western blot assays, immunoprecipitation - mass spectrometry facilitates screening and ranking of clones which bind to the native ( non - denaturated ) forms of antigen proteins. flow cytometry screening has been used for primary screening of a large number ( ~ 1000 ) of hybridoma clones recognizing the native form of the antigen on the cell surface. in the flow cytometry - based screening, a mixture of antigen - negative cells and antigen - positive cells is used as the antigen to be tested for each hybridoma supernatant sample. the b cell that produces the desired antibodies can be cloned to produce many identical daughter clones. supplemental media containing interleukin - 6 ( such as briclone ) are essential for this step. once a hybridoma colony is established, it will continually grow in culture medium like rpmi - 1640 ( with antibiotics and fetal bovine serum ) and produce antibodies. multiwell plates are used initially to grow the hybridomas, and after selection,
into major divisions, starting with four eons ( hadean, archean, proterozoic, and phanerozoic ), the first three of which are collectively known as the precambrian, which lasted approximately 4 billion years. each eon can be divided into eras, with the phanerozoic eon that began 539 million years ago being subdivided into paleozoic, mesozoic, and cenozoic eras. these three eras together comprise eleven periods ( cambrian, ordovician, silurian, devonian, carboniferous, permian, triassic, jurassic, cretaceous, tertiary, and quaternary ). the similarities among all known present - day species indicate that they have diverged through the process of evolution from their common ancestor. biologists regard the ubiquity of the genetic code as evidence of universal common descent for all bacteria, archaea, and eukaryotes. microbial mats of coexisting bacteria and archaea were the dominant form of life in the early archean eon and many of the major steps in early evolution are thought to have taken place in this environment. the earliest evidence of eukaryotes dates from 1. 85 billion years ago, and while they may have been present earlier, their diversification accelerated when they started using oxygen in their metabolism. later, around 1. 7 billion years ago, multicellular organisms began to appear, with differentiated cells performing specialised functions. algae - like multicellular land plants are dated back to about 1 billion years ago, although evidence suggests that microorganisms formed the earliest terrestrial ecosystems, at least 2. 7 billion years ago. microorganisms are thought to have paved the way for the inception of land plants in the ordovician period. land plants were so successful that they are thought to have contributed to the late devonian extinction event. ediacara biota appear during the ediacaran period, while vertebrates, along with most other modern phyla originated about 525 million years ago during the cambrian explosion. during the permian period, synapsids, including the ancestors of mammals, dominated the land, but most of this group became extinct in the permian β triassic extinction event 252 million years ago. during the recovery from this catastrophe, archosaurs became the most abundant land vertebrates ; one archosaur group, the dinosaurs, dominated the jurassic and cretaceous periods. after the cretaceous β paleogene extinction event 66 million years ago killed off
a letter to the editor shortly summing up ten or so years of research into the h - index.
, tertiary, and quaternary ). the similarities among all known present - day species indicate that they have diverged through the process of evolution from their common ancestor. biologists regard the ubiquity of the genetic code as evidence of universal common descent for all bacteria, archaea, and eukaryotes. microbial mats of coexisting bacteria and archaea were the dominant form of life in the early archean eon and many of the major steps in early evolution are thought to have taken place in this environment. the earliest evidence of eukaryotes dates from 1. 85 billion years ago, and while they may have been present earlier, their diversification accelerated when they started using oxygen in their metabolism. later, around 1. 7 billion years ago, multicellular organisms began to appear, with differentiated cells performing specialised functions. algae - like multicellular land plants are dated back to about 1 billion years ago, although evidence suggests that microorganisms formed the earliest terrestrial ecosystems, at least 2. 7 billion years ago. microorganisms are thought to have paved the way for the inception of land plants in the ordovician period. land plants were so successful that they are thought to have contributed to the late devonian extinction event. ediacara biota appear during the ediacaran period, while vertebrates, along with most other modern phyla originated about 525 million years ago during the cambrian explosion. during the permian period, synapsids, including the ancestors of mammals, dominated the land, but most of this group became extinct in the permian β triassic extinction event 252 million years ago. during the recovery from this catastrophe, archosaurs became the most abundant land vertebrates ; one archosaur group, the dinosaurs, dominated the jurassic and cretaceous periods. after the cretaceous β paleogene extinction event 66 million years ago killed off the non - avian dinosaurs, mammals increased rapidly in size and diversity. such mass extinctions may have accelerated evolution by providing opportunities for new groups of organisms to diversify. = = diversity = = = = = bacteria and archaea = = = bacteria are a type of cell that constitute a large domain of prokaryotic microorganisms. typically a few micrometers in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. bacteria were among the first life forms to appear on earth, and are present in most of its habitats. bacteria inhabit soil, water, acidic hot springs, radioactive
technology developed, medicine became more reliant upon medications. throughout history and in europe right until the late 18th century, not only plant products were used as medicine, but also animal ( including human ) body parts and fluids. pharmacology developed in part from herbalism and some drugs are still derived from plants ( atropine, ephedrine, warfarin, aspirin, digoxin, vinca alkaloids, taxol, hyoscine, etc. ). vaccines were discovered by edward jenner and louis pasteur. the first antibiotic was arsphenamine ( salvarsan ) discovered by paul ehrlich in 1908 after he observed that bacteria took up toxic dyes that human cells did not. the first major class of antibiotics was the sulfa drugs, derived by german chemists originally from azo dyes. pharmacology has become increasingly sophisticated ; modern biotechnology allows drugs targeted towards specific physiological processes to be developed, sometimes designed for compatibility with the body to reduce side - effects. genomics and knowledge of human genetics and human evolution is having increasingly significant influence on medicine, as the causative genes of most monogenic genetic disorders have now been identified, and the development of techniques in molecular biology, evolution, and genetics are influencing medical technology, practice and decision - making. evidence - based medicine is a contemporary movement to establish the most effective algorithms of practice ( ways of doing things ) through the use of systematic reviews and meta - analysis. the movement is facilitated by modern global information science, which allows as much of the available evidence as possible to be collected and analyzed according to standard protocols that are then disseminated to healthcare providers. the cochrane collaboration leads this movement. a 2001 review of 160 cochrane systematic reviews revealed that, according to two readers, 21. 3 % of the reviews concluded insufficient evidence, 20 % concluded evidence of no effect, and 22. 5 % concluded positive effect. = = quality, efficiency, and access = = evidence - based medicine, prevention of medical error ( and other " iatrogenesis " ), and avoidance of unnecessary health care are a priority in modern medical systems. these topics generate significant political and public policy attention, particularly in the united states where healthcare is regarded as excessively costly but population health metrics lag similar nations. globally, many developing countries lack access to care and access to medicines. as of 2015, most wealthy developed countries provide health care to all citizens, with a few exceptions such as the united states where lack of health insurance
water - repelling ) substances. proteins are the most diverse of the macromolecules. they include enzymes, transport proteins, large signaling molecules, antibodies, and structural proteins. the basic unit ( or monomer ) of a protein is an amino acid. twenty amino acids are used in proteins. nucleic acids are polymers of nucleotides. their function is to store, transmit, and express hereditary information. = = cells = = cell theory states that cells are the fundamental units of life, that all living things are composed of one or more cells, and that all cells arise from preexisting cells through cell division. most cells are very small, with diameters ranging from 1 to 100 micrometers and are therefore only visible under a light or electron microscope. there are generally two types of cells : eukaryotic cells, which contain a nucleus, and prokaryotic cells, which do not. prokaryotes are single - celled organisms such as bacteria, whereas eukaryotes can be single - celled or multicellular. in multicellular organisms, every cell in the organism ' s body is derived ultimately from a single cell in a fertilized egg. = = = cell structure = = = every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions. cell membranes also contain membrane proteins, including integral membrane proteins that go across the membrane serving as membrane transporters, and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes shaping the cell. cell membranes are involved in various cellular processes such as cell adhesion, storing electrical energy, and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall, glycocalyx, and cytoskeleton. within the cytoplasm of a cell, there are many biomolecules such as proteins and nucleic acids. in addition to biomolecules, eukaryotic cells have specialized structures called organelles that have their own lipid bilayers or are spatially units. these organelles include the cell nucleus, which contains most of
founded in 1976 and started the production of human proteins. genetically engineered human insulin was produced in 1978 and insulin - producing bacteria were commercialised in 1982. genetically modified food has been sold since 1994, with the release of the flavr savr tomato. the flavr savr was engineered to have a longer shelf life, but most current gm crops are modified to increase resistance to insects and herbicides. glofish, the first gmo designed as a pet, was sold in the united states in december 2003. in 2016 salmon modified with a growth hormone were sold. genetic engineering has been applied in numerous fields including research, medicine, industrial biotechnology and agriculture. in research, gmos are used to study gene function and expression through loss of function, gain of function, tracking and expression experiments. by knocking out genes responsible for certain conditions it is possible to create animal model organisms of human diseases. as well as producing hormones, vaccines and other drugs, genetic engineering has the potential to cure genetic diseases through gene therapy. chinese hamster ovary ( cho ) cells are used in industrial genetic engineering. additionally mrna vaccines are made through genetic engineering to prevent infections by viruses such as covid - 19. the same techniques that are used to produce drugs can also have industrial applications such as producing enzymes for laundry detergent, cheeses and other products. the rise of commercialised genetically modified crops has provided economic benefit to farmers in many different countries, but has also been the source of most of the controversy surrounding the technology. this has been present since its early use ; the first field trials were destroyed by anti - gm activists. although there is a scientific consensus that currently available food derived from gm crops poses no greater risk to human health than conventional food, critics consider gm food safety a leading concern. gene flow, impact on non - target organisms, control of the food supply and intellectual property rights have also been raised as potential issues. these concerns have led to the development of a regulatory framework, which started in 1975. it has led to an international treaty, the cartagena protocol on biosafety, that was adopted in 2000. individual countries have developed their own regulatory systems regarding gmos, with the most marked differences occurring between the united states and europe. = = overview = = genetic engineering is a process that alters the genetic structure of an organism by either removing or introducing dna, or modifying existing genetic material in situ. unlike traditional animal and plant breeding, which involves doing multiple crosses and then selecting for the organism with the desired phenotype,
Question: What does ubiquitin indicate about a protein's lifespan?
A) completion
B) reaction ratio
C) initiation
D) transaction
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A) completion
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Context:
the value of excess charge in the kernel of massive body ( and the opposite in sign excess charge at the surface ) caused by the influence of gravitational forces is determined.
the manufacturer. one common distinction is by nominal pore size. it describes the maximum pore size distribution and gives only vague information about the retention capacity of a membrane. the exclusion limit or " cut - off " of the membrane is usually specified in the form of nmwc ( nominal molecular weight cut - off, or mwco, molecular weight cut off, with units in dalton ). it is defined as the minimum molecular weight of a globular molecule that is retained to 90 % by the membrane. the cut - off, depending on the method, can by converted to so - called d90, which is then expressed in a metric unit. in practice the mwco of the membrane should be at least 20 % lower than the molecular weight of the molecule that is to be separated. using track etched mica membranes beck and schultz demonstrated that hindered diffusion of molecules in pores can be described by the rankin equation. filter membranes are divided into four classes according to pore size : the form and shape of the membrane pores are highly dependent on the manufacturing process and are often difficult to specify. therefore, for characterization, test filtrations are carried out and the pore diameter refers to the diameter of the smallest particles which could not pass through the membrane. the rejection can be determined in various ways and provides an indirect measurement of the pore size. one possibility is the filtration of macromolecules ( often dextran, polyethylene glycol or albumin ), another is measurement of the cut - off by gel permeation chromatography. these methods are used mainly to measure membranes for ultrafiltration applications. another testing method is the filtration of particles with defined size and their measurement with a particle sizer or by laser induced breakdown spectroscopy ( libs ). a vivid characterization is to measure the rejection of dextran blue or other colored molecules. the retention of bacteriophage and bacteria, the so - called " bacteria challenge test ", can also provide information about the pore size. to determine the pore diameter, physical methods such as porosimeter ( mercury, liquid - liquid porosimeter and bubble point test ) are also used, but a certain form of the pores ( such as cylindrical or concatenated spherical holes ) is assumed. such methods are used for membranes whose pore geometry does not match the ideal, and we get " nominal " pore diameter, which characterizes the membrane, but does not necessarily reflect its actual filt
the spectrum of doubly heavy baryons, hadrons made up of two heavy quarks and one light quark, is computed through a potential model with relativistic kinematics. the expression for the $ q \ bar q $ potential comes from the ads / qcd correspondence.
excess lightweight products of slow neutron capture in the photosphere, over the mass range of 25 to 207 amu, confirm the solar mass separation recorded by excess lightweight isotopes in the solar wind, over the mass range of 3 to 136 amu [ solar abundance of the elements, meteoritics, volume 18, 1983, pages 209 to 222 ]. both measurements show that major elements inside the sun are fe, o, ni, si and s, like those in rocky planets.
the electric dipole strength in 120sn has been extracted from proton inelastic scattering experiments at e _ p = 295 mev and at forward angles including 0 degree. below neutron threshoild it differs from the results of a 120sn ( gamma, gamma ' ) experiment and peaks at an excitation energy of 8. 3 mev. the total strength corresponds to 2. 3 ( 2 ) % of the energy - weighted sum rule and is more than three times larger than what is observed with the ( gamma, gamma ' ) reaction. this implies a strong fragmentation of the e1 strength and / or small ground state branching ratios of the excited 1 - states.
listen ), generally in that order, although auscultation occurs prior to percussion and palpation for abdominal assessments. the clinical examination involves the study of : abdomen and rectum cardiovascular ( heart and blood vessels ) general appearance of the patient and specific indicators of disease ( nutritional status, presence of jaundice, pallor or clubbing ) genitalia ( and pregnancy if the patient is or could be pregnant ) head, eye, ear, nose, and throat ( heent ) musculoskeletal ( including spine and extremities ) neurological ( consciousness, awareness, brain, vision, cranial nerves, spinal cord and peripheral nerves ) psychiatric ( orientation, mental state, mood, evidence of abnormal perception or thought ). respiratory ( large airways and lungs ) skin vital signs including height, weight, body temperature, blood pressure, pulse, respiration rate, and hemoglobin oxygen saturation it is to likely focus on areas of interest highlighted in the medical history and may not include everything listed above. the treatment plan may include ordering additional medical laboratory tests and medical imaging studies, starting therapy, referral to a specialist, or watchful observation. a follow - up may be advised. depending upon the health insurance plan and the managed care system, various forms of " utilization review ", such as prior authorization of tests, may place barriers on accessing expensive services. the medical decision - making ( mdm ) process includes the analysis and synthesis of all the above data to come up with a list of possible diagnoses ( the differential diagnoses ), along with an idea of what needs to be done to obtain a definitive diagnosis that would explain the patient ' s problem. on subsequent visits, the process may be repeated in an abbreviated manner to obtain any new history, symptoms, physical findings, lab or imaging results, or specialist consultations. = = institutions = = contemporary medicine is, in general, conducted within health care systems. legal, credentialing, and financing frameworks are established by individual governments, augmented on occasion by international organizations, such as churches. the characteristics of any given health care system have a significant impact on the way medical care is provided. from ancient times, christian emphasis on practical charity gave rise to the development of systematic nursing and hospitals, and the catholic church today remains the largest non - government provider of medical services in the world. advanced industrial countries ( with the exception of the united states ) and many developing countries provide medical services through a system of universal health care that aims to
. additionally, there are more sophisticated vr systems being developed which allow the user to use their entire body in their recovery. it also has sophisticated sensors that would allow medical professionals to collect data on muscle engagement and tension. it uses electrical impedance tomography, a form of noninvasive imaging to view muscle usage. another concern is the lack of major funding by big companies and the government into the field. many of these vr sets are off the shelf items, and not properly made for medical use. external add - ones are usually 3d printed or made from spare parts from other electronics. this lack of support means that patients who want to try this method have to be technically savvy, which is unlikely as many ailments only appear later in life. additionally, certain parts of vr like haptic feedback and tracking are still not advanced enough to be used reliably in a medical setting. another issue is the amount of vr devices that are available for purchase. while this does increase the options available, the differences between vr systems could impact patient recovery. the vast number of vr devices also makes it difficult for medical professionals to give and interpret information, as they might not have had practice with the specific model, which could lead to faulty advice being given out. = = = applications = = = currently other applications within healthcare are being explored, such as : applications for monitoring of glucose, alcohol, and lactate or blood oxygen, breath monitoring, heartbeat, heart rate and its variability, electromyography ( emg ), electrocardiogram ( ecg ) and electroencephalogram ( eeg ), body temperature, pressure ( e. g. in shoes ), sweat rate or sweat loss, levels of uric acid and ions β e. g. for preventing fatigue or injuries or for optimizing training patterns, including via " human - integrated electronics " forecasting changes in mood, stress, and health measuring blood alcohol content measuring athletic performance monitoring how sick the user is detecting early signs of infection long - term monitoring of patients with heart and circulatory problems that records an electrocardiogram and is self - moistening health risk assessment applications, including measures of frailty and risks of age - dependent diseases automatic documentation of care activities days - long continuous imaging of diverse organs via a wearable bioadhesive stretchable high - resolution ultrasound imaging patch or e. g. a wearable continuous heart ultrasound imager. ( potential novel diagnostic and monitoring tools ) sleep tracking cortisol monitoring for measuring stress measuring relaxation or alert
is called its bandwidth ( bw ). for any given signal - to - noise ratio, a given bandwidth can carry the same amount of information regardless of where in the radio frequency spectrum it is located ; bandwidth is a measure of information - carrying capacity. the bandwidth required by a radio transmission depends on the data rate of the information being sent, and the spectral efficiency of the modulation method used ; how much data it can transmit in each unit of bandwidth. different types of information signals carried by radio have different data rates. for example, a television signal has a greater data rate than an audio signal. the radio spectrum, the total range of radio frequencies that can be used for communication in a given area, is a limited resource. each radio transmission occupies a portion of the total bandwidth available. radio bandwidth is regarded as an economic good which has a monetary cost and is in increasing demand. in some parts of the radio spectrum, the right to use a frequency band or even a single radio channel is bought and sold for millions of dollars. so there is an incentive to employ technology to minimize the bandwidth used by radio services. a slow transition from analog to digital radio transmission technologies began in the late 1990s. part of the reason for this is that digital modulation can often transmit more information ( a greater data rate ) in a given bandwidth than analog modulation, by using data compression algorithms, which reduce redundancy in the data to be sent, and more efficient modulation. other reasons for the transition is that digital modulation has greater noise immunity than analog, digital signal processing chips have more power and flexibility than analog circuits, and a wide variety of types of information can be transmitted using the same digital modulation. because it is a fixed resource which is in demand by an increasing number of users, the radio spectrum has become increasingly congested in recent decades, and the need to use it more effectively is driving many additional radio innovations such as trunked radio systems, spread spectrum ( ultra - wideband ) transmission, frequency reuse, dynamic spectrum management, frequency pooling, and cognitive radio. = = = itu frequency bands = = = the itu arbitrarily divides the radio spectrum into 12 bands, each beginning at a wavelength which is a power of ten ( 10n ) metres, with corresponding frequency of 3 times a power of ten, and each covering a decade of frequency or wavelength. each of these bands has a traditional name : it can be seen that the bandwidth, the range of frequencies, contained in each band is not equal but increases exponentially as the
##nik, in present - day serbia. the site of plocnik has produced a smelted copper axe dating from 5, 500 bc, belonging to the vinca culture. the balkans and adjacent carpathian region were the location of major chalcolithic cultures including vinca, varna, karanovo, gumelnita and hamangia, which are often grouped together under the name of ' old europe '. with the carpatho - balkan region described as the ' earliest metallurgical province in eurasia ', its scale and technical quality of metal production in the 6th β 5th millennia bc totally overshadowed that of any other contemporary production centre. the earliest documented use of lead ( possibly native or smelted ) in the near east dates from the 6th millennium bc, is from the late neolithic settlements of yarim tepe and arpachiyah in iraq. the artifacts suggest that lead smelting may have predated copper smelting. metallurgy of lead has also been found in the balkans during the same period. copper smelting is documented at sites in anatolia and at the site of tal - i iblis in southeastern iran from c. 5000 bc. copper smelting is first documented in the delta region of northern egypt in c. 4000 bc, associated with the maadi culture. this represents the earliest evidence for smelting in africa. the varna necropolis, bulgaria, is a burial site located in the western industrial zone of varna, approximately 4 km from the city centre, internationally considered one of the key archaeological sites in world prehistory. the oldest gold treasure in the world, dating from 4, 600 bc to 4, 200 bc, was discovered at the site. the gold piece dating from 4, 500 bc, found in 2019 in durankulak, near varna is another important example. other signs of early metals are found from the third millennium bc in palmela, portugal, los millares, spain, and stonehenge, united kingdom. the precise beginnings, however, have not be clearly ascertained and new discoveries are both continuous and ongoing. in approximately 1900 bc, ancient iron smelting sites existed in tamil nadu. in the near east, about 3, 500 bc, it was discovered that by combining copper and tin, a superior metal could be made, an alloy called bronze. this represented a major technological shift known as the bronze age. the extraction of iron from its ore into a workable metal is much more difficult than for copper or tin
of a point on the object, including whole - body translations and rotations ( rigid transformations ). deformation are changes in the relative position between internals points on the object, excluding rigid transformations, causing the body to change shape or size. strain is the relative internal deformation, the dimensionless change in shape of an infinitesimal cube of material relative to a reference configuration. mechanical strains are caused by mechanical stress, see stress - strain curve. the relationship between stress and strain is generally linear and reversible up until the yield point and the deformation is elastic. elasticity in materials occurs when applied stress does not surpass the energy required to break molecular bonds, allowing the material to deform reversibly and return to its original shape once the stress is removed. the linear relationship for a material is known as young ' s modulus. above the yield point, some degree of permanent distortion remains after unloading and is termed plastic deformation. the determination of the stress and strain throughout a solid object is given by the field of strength of materials and for a structure by structural analysis. in the above figure, it can be seen that the compressive loading ( indicated by the arrow ) has caused deformation in the cylinder so that the original shape ( dashed lines ) has changed ( deformed ) into one with bulging sides. the sides bulge because the material, although strong enough to not crack or otherwise fail, is not strong enough to support the load without change. as a result, the material is forced out laterally. internal forces ( in this case at right angles to the deformation ) resist the applied load. = = types of deformation = = depending on the type of material, size and geometry of the object, and the forces applied, various types of deformation may result. the image to the right shows the engineering stress vs. strain diagram for a typical ductile material such as steel. different deformation modes may occur under different conditions, as can be depicted using a deformation mechanism map. permanent deformation is irreversible ; the deformation stays even after removal of the applied forces, while the temporary deformation is recoverable as it disappears after the removal of applied forces. temporary deformation is also called elastic deformation, while the permanent deformation is called plastic deformation. = = = elastic deformation = = = the study of temporary or elastic deformation in the case of engineering strain is applied to materials used in mechanical and structural engineering, such as concrete and steel, which are subjected to very small deformations. engineering strain is modeled by infinitesimal strain theory, also called
Question: Which vertebrae carry the greatest amount of body weight and are thus characterized by the large size and thickness of the vertebral body?
A) invertebrae
B) artery vertebrae
C) thickness vertebrae
D) lumbar vertebrae
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D) lumbar vertebrae
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Context:
material includes the unit cell, which is the smallest unit of a crystal lattice ( space lattice ) that repeats to make up the macroscopic crystal structure. most common structural materials include parallelpiped and hexagonal lattice types. in single crystals, the effects of the crystalline arrangement of atoms is often easy to see macroscopically, because the natural shapes of crystals reflect the atomic structure. further, physical properties are often controlled by crystalline defects. the understanding of crystal structures is an important prerequisite for understanding crystallographic defects. examples of crystal defects consist of dislocations including edges, screws, vacancies, self inter - stitials, and more that are linear, planar, and three dimensional types of defects. new and advanced materials that are being developed include nanomaterials, biomaterials. mostly, materials do not occur as a single crystal, but in polycrystalline form, as an aggregate of small crystals or grains with different orientations. because of this, the powder diffraction method, which uses diffraction patterns of polycrystalline samples with a large number of crystals, plays an important role in structural determination. most materials have a crystalline structure, but some important materials do not exhibit regular crystal structure. polymers display varying degrees of crystallinity, and many are completely non - crystalline. glass, some ceramics, and many natural materials are amorphous, not possessing any long - range order in their atomic arrangements. the study of polymers combines elements of chemical and statistical thermodynamics to give thermodynamic and mechanical descriptions of physical properties. = = = = nanostructure = = = = materials, which atoms and molecules form constituents in the nanoscale ( i. e., they form nanostructures ) are called nanomaterials. nanomaterials are the subject of intense research in the materials science community due to the unique properties that they exhibit. nanostructure deals with objects and structures that are in the 1 β 100 nm range. in many materials, atoms or molecules agglomerate to form objects at the nanoscale. this causes many interesting electrical, magnetic, optical, and mechanical properties. in describing nanostructures, it is necessary to differentiate between the number of dimensions on the nanoscale. nanotextured surfaces have one dimension on the nanoscale, i. e., only the thickness of the surface of an object is between 0. 1 and 100 nm
, behind which are structures termed reentrant triangles. radar waves penetrating the skin get trapped in these structures, reflecting off the internal faces and losing energy. this method was first used on the blackbird series : a - 12, yf - 12a, lockheed sr - 71 blackbird. the most efficient way to reflect radar waves back to the emitting radar is with orthogonal metal plates, forming a corner reflector consisting of either a dihedral ( two plates ) or a trihedral ( three orthogonal plates ). this configuration occurs in the tail of a conventional aircraft, where the vertical and horizontal components of the tail are set at right angles. stealth aircraft such as the f - 117 use a different arrangement, tilting the tail surfaces to reduce corner reflections formed between them. a more radical method is to omit the tail, as in the b - 2 spirit. the b - 2 ' s clean, low - drag flying wing configuration gives it exceptional range and reduces its radar profile. the flying wing design most closely resembles a so - called infinite flat plate ( as vertical control surfaces dramatically increase rcs ), the perfect stealth shape, as it would have no angles to reflect back radar waves. in addition to altering the tail, stealth design must bury the engines within the wing or fuselage, or in some cases where stealth is applied to an extant aircraft, install baffles in the air intakes, so that the compressor blades are not visible to radar. a stealthy shape must be devoid of complex bumps or protrusions of any kind, meaning that weapons, fuel tanks, and other stores must not be carried externally. any stealthy vehicle becomes un - stealthy when a door or hatch opens. parallel alignment of edges or even surfaces is also often used in stealth designs. the technique involves using a small number of edge orientations in the shape of the structure. for example, on the f - 22a raptor, the leading edges of the wing and the tail planes are set at the same angle. other smaller structures, such as the air intake bypass doors and the air refueling aperture, also use the same angles. the effect of this is to return a narrow radar signal in a very specific direction away from the radar emitter rather than returning a diffuse signal detectable at many angles. the effect is sometimes called " glitter " after the very brief signal seen when the reflected beam passes across a detector. it can be difficult for the radar operator to distinguish between a glitter event and a digital glitch in the processing system. stealth air
' t there. charles darwin a mathematician, like a painter or poet, is a maker of patterns. if his patterns are more permanent than theirs, it is because they are made with ideas. g. h. hardy, 1940 mathematics is the art of giving the same name to different things. henri poincare mathematics is the science of skillful operations with concepts and rules invented just for this purpose. [ this purpose being the skillful operation.... ] eugene wigner mathematics is not a book confined within a cover and bound between brazen clasps, whose contents it needs only patience to ransack ; it is not a mine, whose treasures may take long to reduce into possession, but which fill only a limited number of veins and lodes ; it is not a soil, whose fertility can be exhausted by the yield of successive harvests ; it is not a continent or an ocean, whose area can be mapped out and its contour defined : it is limitless as that space which it finds too narrow for its aspirations ; its possibilities are as infinite as the worlds which are forever crowding in and multiplying upon the astronomer ' s gaze ; it is as incapable of being restricted within assigned boundaries or being reduced to definitions of permanent validity, as the consciousness of life, which seems to slumber in each monad, in every atom of matter, in each leaf and bud cell, and is forever ready to burst forth into new forms of vegetable and animal existence. james joseph sylvester what is mathematics? what is it for? what are mathematicians doing nowadays? wasn ' t it all finished long ago? how many new numbers can you invent anyway? is today ' s mathematics just a matter of huge calculations, with the mathematician as a kind of zookeeper, making sure the precious computers are fed and watered? if it ' s not, what is it other than the incomprehensible outpourings of superpowered brainboxes with their heads in the clouds and their feet dangling from the lofty balconies of their ivory towers? mathematics is all of these, and none. mostly, it ' s just different. it ' s not what you expect it to be, you turn your back for a moment and it ' s changed. it ' s certainly not just a fixed body of knowledge, its growth is not confined to inventing new numbers, and its hidden tendrils pervade every aspect of modern life. ian stewart = = see also = = philosophy of mathematics foundations of mathematics = = references =
##hography is quite small, large area patterns must be created by stitching together the small fields. ion track technology is a deep cutting tool with a resolution limit around 8 nm applicable to radiation resistant minerals, glasses and polymers. it is capable of generating holes in thin films without any development process. structural depth can be defined either by ion range or by material thickness. aspect ratios up to several 104 can be reached. the technique can shape and texture materials at a defined inclination angle. random pattern, single - ion track structures and an aimed pattern consisting of individual single tracks can be generated. x - ray lithography is a process used in the electronic industry to selectively remove parts of a thin film. it uses x - rays to transfer a geometric pattern from a mask to a light - sensitive chemical photoresist, or simply " resist ", on the substrate. a series of chemical treatments then engraves the produced pattern into the material underneath the photoresist. diamond patterning is a method of forming diamond mems. it is achieved by the lithographic application of diamond films to a substrate such as silicon. the patterns can be formed by selective deposition through a silicon dioxide mask, or by deposition followed by micromachining or focused ion beam milling. = = = etching processes = = = there are two basic categories of etching processes : wet etching and dry etching. in the former, the material is dissolved when immersed in a chemical solution. in the latter, the material is sputtered or dissolved using reactive ions or a vapor phase etchant. = = = = wet etching = = = = wet chemical etching consists of the selective removal of material by dipping a substrate into a solution that dissolves it. the chemical nature of this etching process provides good selectivity, which means the etching rate of the target material is considerably higher than the mask material if selected carefully. wet etching can be performed using either isotropic wet etchants or anisotropic wet etchants. isotropic wet etchant etch in all directions of the crystalline silicon at approximately equal rates. anisotropic wet etchants preferably etch along certain crystal planes at faster rates than other planes, thereby allowing more complicated 3 - d microstructures to be implemented. wet anisotropic etchants are often used in conjunction with boron etch stops wherein the surface of the silicon is heavily doped with boron resulting in a silicon material layer that is
by reference to undefined terms : the subject in which we never know what we are talking about, nor whether what we are saying is true. bertrand russell 1901 many other attempts to characterize mathematics have led to humor or poetic prose : a mathematician is a blind man in a dark room looking for a black cat which isn ' t there. charles darwin a mathematician, like a painter or poet, is a maker of patterns. if his patterns are more permanent than theirs, it is because they are made with ideas. g. h. hardy, 1940 mathematics is the art of giving the same name to different things. henri poincare mathematics is the science of skillful operations with concepts and rules invented just for this purpose. [ this purpose being the skillful operation.... ] eugene wigner mathematics is not a book confined within a cover and bound between brazen clasps, whose contents it needs only patience to ransack ; it is not a mine, whose treasures may take long to reduce into possession, but which fill only a limited number of veins and lodes ; it is not a soil, whose fertility can be exhausted by the yield of successive harvests ; it is not a continent or an ocean, whose area can be mapped out and its contour defined : it is limitless as that space which it finds too narrow for its aspirations ; its possibilities are as infinite as the worlds which are forever crowding in and multiplying upon the astronomer ' s gaze ; it is as incapable of being restricted within assigned boundaries or being reduced to definitions of permanent validity, as the consciousness of life, which seems to slumber in each monad, in every atom of matter, in each leaf and bud cell, and is forever ready to burst forth into new forms of vegetable and animal existence. james joseph sylvester what is mathematics? what is it for? what are mathematicians doing nowadays? wasn ' t it all finished long ago? how many new numbers can you invent anyway? is today ' s mathematics just a matter of huge calculations, with the mathematician as a kind of zookeeper, making sure the precious computers are fed and watered? if it ' s not, what is it other than the incomprehensible outpourings of superpowered brainboxes with their heads in the clouds and their feet dangling from the lofty balconies of their ivory towers? mathematics is all of these, and none. mostly, it ' s just different. it ' s not what you expect it to be, you turn your back for
is the scientific study of inheritance. mendelian inheritance, specifically, is the process by which genes and traits are passed on from parents to offspring. it has several principles. the first is that genetic characteristics, alleles, are discrete and have alternate forms ( e. g., purple vs. white or tall vs. dwarf ), each inherited from one of two parents. based on the law of dominance and uniformity, which states that some alleles are dominant while others are recessive ; an organism with at least one dominant allele will display the phenotype of that dominant allele. during gamete formation, the alleles for each gene segregate, so that each gamete carries only one allele for each gene. heterozygotic individuals produce gametes with an equal frequency of two alleles. finally, the law of independent assortment, states that genes of different traits can segregate independently during the formation of gametes, i. e., genes are unlinked. an exception to this rule would include traits that are sex - linked. test crosses can be performed to experimentally determine the underlying genotype of an organism with a dominant phenotype. a punnett square can be used to predict the results of a test cross. the chromosome theory of inheritance, which states that genes are found on chromosomes, was supported by thomas morgans ' s experiments with fruit flies, which established the sex linkage between eye color and sex in these insects. = = = genes and dna = = = a gene is a unit of heredity that corresponds to a region of deoxyribonucleic acid ( dna ) that carries genetic information that controls form or function of an organism. dna is composed of two polynucleotide chains that coil around each other to form a double helix. it is found as linear chromosomes in eukaryotes, and circular chromosomes in prokaryotes. the set of chromosomes in a cell is collectively known as its genome. in eukaryotes, dna is mainly in the cell nucleus. in prokaryotes, the dna is held within the nucleoid. the genetic information is held within genes, and the complete assemblage in an organism is called its genotype. dna replication is a semiconservative process whereby each strand serves as a template for a new strand of dna. mutations are heritable changes in dna. they can arise spontaneously as a result of replication errors that were not corrected by proofreading or can
so - called " bosch process ", named after the german company robert bosch, which filed the original patent, where two different gas compositions alternate in the reactor. currently, there are two variations of the drie. the first variation consists of three distinct steps ( the original bosch process ) while the second variation only consists of two steps. in the first variation, the etch cycle is as follows : ( i ) sf6 isotropic etch ; ( ii ) c4f8 passivation ; ( iii ) sf6 anisotropic etch for floor cleaning. in the 2nd variation, steps ( i ) and ( iii ) are combined. both variations operate similarly. the c4f8 creates a polymer on the surface of the substrate, and the second gas composition ( sf6 and o2 ) etches the substrate. the polymer is immediately sputtered away by the physical part of the etching, but only on the horizontal surfaces and not the sidewalls. since the polymer only dissolves very slowly in the chemical part of the etching, it builds up on the sidewalls and protects them from etching. as a result, etching aspect ratios of 50 to 1 can be achieved. the process can easily be used to etch completely through a silicon substrate, and etch rates are 3 β 6 times higher than wet etching. after preparing a large number of mems devices on a silicon wafer, individual dies have to be separated, which is called die preparation in semiconductor technology. for some applications, the separation is preceded by wafer backgrinding in order to reduce the wafer thickness. wafer dicing may then be performed either by sawing using a cooling liquid or a dry laser process called stealth dicing. = = manufacturing technologies = = bulk micromachining is the oldest paradigm of silicon - based mems. the whole thickness of a silicon wafer is used for building the micro - mechanical structures. silicon is machined using various etching processes. bulk micromachining has been essential in enabling high performance pressure sensors and accelerometers that changed the sensor industry in the 1980s and 1990s. surface micromachining uses layers deposited on the surface of a substrate as the structural materials, rather than using the substrate itself. surface micromachining was created in the late 1980s to render micromachining of silicon more compatible with planar integrated circuit technology, with the goal of combining mems and integrated circuits on the same silicon wafer. the original surface micro
reflect radar waves back to the emitting radar is with orthogonal metal plates, forming a corner reflector consisting of either a dihedral ( two plates ) or a trihedral ( three orthogonal plates ). this configuration occurs in the tail of a conventional aircraft, where the vertical and horizontal components of the tail are set at right angles. stealth aircraft such as the f - 117 use a different arrangement, tilting the tail surfaces to reduce corner reflections formed between them. a more radical method is to omit the tail, as in the b - 2 spirit. the b - 2 ' s clean, low - drag flying wing configuration gives it exceptional range and reduces its radar profile. the flying wing design most closely resembles a so - called infinite flat plate ( as vertical control surfaces dramatically increase rcs ), the perfect stealth shape, as it would have no angles to reflect back radar waves. in addition to altering the tail, stealth design must bury the engines within the wing or fuselage, or in some cases where stealth is applied to an extant aircraft, install baffles in the air intakes, so that the compressor blades are not visible to radar. a stealthy shape must be devoid of complex bumps or protrusions of any kind, meaning that weapons, fuel tanks, and other stores must not be carried externally. any stealthy vehicle becomes un - stealthy when a door or hatch opens. parallel alignment of edges or even surfaces is also often used in stealth designs. the technique involves using a small number of edge orientations in the shape of the structure. for example, on the f - 22a raptor, the leading edges of the wing and the tail planes are set at the same angle. other smaller structures, such as the air intake bypass doors and the air refueling aperture, also use the same angles. the effect of this is to return a narrow radar signal in a very specific direction away from the radar emitter rather than returning a diffuse signal detectable at many angles. the effect is sometimes called " glitter " after the very brief signal seen when the reflected beam passes across a detector. it can be difficult for the radar operator to distinguish between a glitter event and a digital glitch in the processing system. stealth airframes sometimes display distinctive serrations on some exposed edges, such as the engine ports. the yf - 23 has such serrations on the exhaust ports. this is another example in the parallel alignment of features, this time on the external airframe. the shaping requirements detracted greatly from the f - 117 '
##as sutra chhandah - sutra ), a sanskrit treatise on prosody. pingala ' s work also contains the basic ideas of fibonacci numbers ( called maatraameru ). although the chandah sutra hasn ' t survived in its entirety, a 10th - century commentary on it by halayudha has. halayudha, who refers to the pascal triangle as meru - prastara ( literally " the staircase to mount meru " ), has this to say : draw a square. beginning at half the square, draw two other similar squares below it ; below these two, three other squares, and so on. the marking should be started by putting 1 in the first square. put 1 in each of the two squares of the second line. in the third line put 1 in the two squares at the ends and, in the middle square, the sum of the digits in the two squares lying above it. in the fourth line put 1 in the two squares at the ends. in the middle ones put the sum of the digits in the two squares above each. proceed in this way. of these lines, the second gives the combinations with one syllable, the third the combinations with two syllables,... the text also indicates that pingala was aware of the combinatorial identity : ( n 0 ) + ( n 1 ) + ( n 2 ) + [UNK] + ( n n β 1 ) + ( n n ) = 2 n { \ displaystyle { n \ choose 0 } + { n \ choose 1 } + { n \ choose 2 } + \ cdots + { n \ choose n - 1 } + { n \ choose n } = 2 ^ { n } } katyayana katyayana ( c. 3rd century bce ) is notable for being the last of the vedic mathematicians. he wrote the katyayana sulba sutra, which presented much geometry, including the general pythagorean theorem and a computation of the square root of 2 correct to five decimal places. = = jain mathematics ( 400 bce β 200 ce ) = = although jainism as a religion and philosophy predates its most famous exponent, the great mahaviraswami ( 6th century bce ), most jain texts on mathematical topics were composed after the 6th century bce. jain mathematicians are important historically as crucial links between the mathematics of the vedic period and that of the " classical period. " a significant historical contribution of jain mathematicians lay in their freeing indian mathematics from its religious and ritualistic
patterned surface approximately the same as its downward etch rate, or can be anisotropic, i. e., exhibiting a smaller lateral undercut rate than its downward etch rate. such anisotropy is maximized in deep reactive ion etching. the use of the term anisotropy for plasma etching should not be conflated with the use of the same term when referring to orientation - dependent etching. the source gas for the plasma usually contains small molecules rich in chlorine or fluorine. for instance, carbon tetrachloride ( ccl4 ) etches silicon and aluminium, and trifluoromethane etches silicon dioxide and silicon nitride. a plasma containing oxygen is used to oxidize ( " ash " ) photoresist and facilitate its removal. ion milling, or sputter etching, uses lower pressures, often as low as 10β4 torr ( 10 mpa ). it bombards the wafer with energetic ions of noble gases, often ar +, which knock atoms from the substrate by transferring momentum. because the etching is performed by ions, which approach the wafer approximately from one direction, this process is highly anisotropic. on the other hand, it tends to display poor selectivity. reactive - ion etching ( rie ) operates under conditions intermediate between sputter and plasma etching ( between 10β3 and 10β1 torr ). deep reactive - ion etching ( drie ) modifies the rie technique to produce deep, narrow features. in reactive - ion etching ( rie ), the substrate is placed inside a reactor, and several gases are introduced. a plasma is struck in the gas mixture using an rf power source, which breaks the gas molecules into ions. the ions accelerate towards, and react with, the surface of the material being etched, forming another gaseous material. this is known as the chemical part of reactive ion etching. there is also a physical part, which is similar to the sputtering deposition process. if the ions have high enough energy, they can knock atoms out of the material to be etched without a chemical reaction. it is a very complex task to develop dry etch processes that balance chemical and physical etching, since there are many parameters to adjust. by changing the balance it is possible to influence the anisotropy of the etching, since the chemical part is isotropic and the physical part highly anisotropic the combination can
Question: Because of it's repeating pattern, what is mendeleev's table of the elements called?
A) periodic table
B) cycles table
C) serial chart
D) phases table
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A) periodic table
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Context:
proteins in the thylakoid membranes. the absorbed light energy is used to remove electrons from a donor ( water ) to a primary electron acceptor, a quinone designated as q. in the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach a final electron acceptor, which is usually the oxidized form of nadp +, which is reduced to nadph, a process that takes place in a protein complex called photosystem i ( psi ). the transport of electrons is coupled to the movement of protons ( or hydrogen ) from the stroma to the thylakoid membrane, which forms a ph gradient across the membrane as hydrogen becomes more concentrated in the lumen than in the stroma. this is analogous to the proton - motive force generated across the inner mitochondrial membrane in aerobic respiration. during the third stage of photosynthesis, the movement of protons down their concentration gradients from the thylakoid lumen to the stroma through the atp synthase is coupled to the synthesis of atp by that same atp synthase. the nadph and atps generated by the light - dependent reactions in the second and third stages, respectively, provide the energy and electrons to drive the synthesis of glucose by fixing atmospheric carbon dioxide into existing organic carbon compounds, such as ribulose bisphosphate ( rubp ) in a sequence of light - independent ( or dark ) reactions called the calvin cycle. = = = cell signaling = = = cell signaling ( or communication ) is the ability of cells to receive, process, and transmit signals with its environment and with itself. signals can be non - chemical such as light, electrical impulses, and heat, or chemical signals ( or ligands ) that interact with receptors, which can be found embedded in the cell membrane of another cell or located deep inside a cell. there are generally four types of chemical signals : autocrine, paracrine, juxtacrine, and hormones. in autocrine signaling, the ligand affects the same cell that releases it. tumor cells, for example, can reproduce uncontrollably because they release signals that initiate their own self - division. in paracrine signaling, the ligand diffuses to nearby cells and affects them. for example, brain cells called neurons release ligands called neurotransmitters that diffuse across a synaptic cleft to bind with a receptor on an adjacent cell such as another neuron or muscle
the earth ' s atmosphere, and supplies most of the energy necessary for life on earth. photosynthesis has four stages : light absorption, electron transport, atp synthesis, and carbon fixation. light absorption is the initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to proteins in the thylakoid membranes. the absorbed light energy is used to remove electrons from a donor ( water ) to a primary electron acceptor, a quinone designated as q. in the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach a final electron acceptor, which is usually the oxidized form of nadp +, which is reduced to nadph, a process that takes place in a protein complex called photosystem i ( psi ). the transport of electrons is coupled to the movement of protons ( or hydrogen ) from the stroma to the thylakoid membrane, which forms a ph gradient across the membrane as hydrogen becomes more concentrated in the lumen than in the stroma. this is analogous to the proton - motive force generated across the inner mitochondrial membrane in aerobic respiration. during the third stage of photosynthesis, the movement of protons down their concentration gradients from the thylakoid lumen to the stroma through the atp synthase is coupled to the synthesis of atp by that same atp synthase. the nadph and atps generated by the light - dependent reactions in the second and third stages, respectively, provide the energy and electrons to drive the synthesis of glucose by fixing atmospheric carbon dioxide into existing organic carbon compounds, such as ribulose bisphosphate ( rubp ) in a sequence of light - independent ( or dark ) reactions called the calvin cycle. = = = cell signaling = = = cell signaling ( or communication ) is the ability of cells to receive, process, and transmit signals with its environment and with itself. signals can be non - chemical such as light, electrical impulses, and heat, or chemical signals ( or ligands ) that interact with receptors, which can be found embedded in the cell membrane of another cell or located deep inside a cell. there are generally four types of chemical signals : autocrine, paracrine, juxtacrine, and hormones. in autocrine signaling, the ligand affects the same cell that releases it. tumor cells, for example, can reproduce uncontrollably because they release signals that initiate their
the cross section of elastic electron - proton scattering taking place in an electron gas is calculated within the closed time path method. it is found to be the sum of two terms, one being the expression in the vacuum except that it involves dressing due to the electron gas. the other term is due to the scattering particles - electron gas entanglement. this term dominates the usual one when the exchange energy is in the vicinity of the fermi energy. furthermore it makes the trajectories of the colliding particles more consistent and the collision more irreversible, rendering the scattering more classical in this regime.
is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. in most cases, oxygen is released as a waste product. most plants, algae, and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of the earth ' s atmosphere, and supplies most of the energy necessary for life on earth. photosynthesis has four stages : light absorption, electron transport, atp synthesis, and carbon fixation. light absorption is the initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to proteins in the thylakoid membranes. the absorbed light energy is used to remove electrons from a donor ( water ) to a primary electron acceptor, a quinone designated as q. in the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach a final electron acceptor, which is usually the oxidized form of nadp +, which is reduced to nadph, a process that takes place in a protein complex called photosystem i ( psi ). the transport of electrons is coupled to the movement of protons ( or hydrogen ) from the stroma to the thylakoid membrane, which forms a ph gradient across the membrane as hydrogen becomes more concentrated in the lumen than in the stroma. this is analogous to the proton - motive force generated across the inner mitochondrial membrane in aerobic respiration. during the third stage of photosynthesis, the movement of protons down their concentration gradients from the thylakoid lumen to the stroma through the atp synthase is coupled to the synthesis of atp by that same atp synthase. the nadph and atps generated by the light - dependent reactions in the second and third stages, respectively, provide the energy and electrons to drive the synthesis of glucose by fixing atmospheric carbon dioxide into existing organic carbon compounds, such as ribulose bisphosphate ( rubp ) in a sequence of light - independent ( or dark ) reactions called the calvin cycle. = = = cell signaling = = = cell signaling ( or communication ) is the ability of cells to receive, process, and transmit signals with its environment and with itself. signals can be non - chemical such as light, electrical impulses, and heat, or chemical signals ( or ligands ) that interact with receptors, which can be found embedded in the cell membrane of another cell or located deep inside
endothermic reactions, the reaction absorbs heat from the surroundings. chemical reactions are invariably not possible unless the reactants surmount an energy barrier known as the activation energy. the speed of a chemical reaction ( at given temperature t ) is related to the activation energy e, by the boltzmann ' s population factor e β e / k t { \ displaystyle e ^ { - e / kt } } β that is the probability of a molecule to have energy greater than or equal to e at the given temperature t. this exponential dependence of a reaction rate on temperature is known as the arrhenius equation. the activation energy necessary for a chemical reaction to occur can be in the form of heat, light, electricity or mechanical force in the form of ultrasound. a related concept free energy, which also incorporates entropy considerations, is a very useful means for predicting the feasibility of a reaction and determining the state of equilibrium of a chemical reaction, in chemical thermodynamics. a reaction is feasible only if the total change in the gibbs free energy is negative, Ξ΄ g β€ 0 { \ displaystyle \ delta g \ leq 0 \, } ; if it is equal to zero the chemical reaction is said to be at equilibrium. there exist only limited possible states of energy for electrons, atoms and molecules. these are determined by the rules of quantum mechanics, which require quantization of energy of a bound system. the atoms / molecules in a higher energy state are said to be excited. the molecules / atoms of substance in an excited energy state are often much more reactive ; that is, more amenable to chemical reactions. the phase of a substance is invariably determined by its energy and the energy of its surroundings. when the intermolecular forces of a substance are such that the energy of the surroundings is not sufficient to overcome them, it occurs in a more ordered phase like liquid or solid as is the case with water ( h2o ) ; a liquid at room temperature because its molecules are bound by hydrogen bonds. whereas hydrogen sulfide ( h2s ) is a gas at room temperature and standard pressure, as its molecules are bound by weaker dipole β dipole interactions. the transfer of energy from one chemical substance to another depends on the size of energy quanta emitted from one substance. however, heat energy is often transferred more easily from almost any substance to another because the phonons responsible for vibrational and rotational energy levels in a substance have much less energy than photons invoked for the electronic energy transfer
the motion and photon emission of electrons in a superlattice may be described as in an undulator. therefore, there is a close analogy between ballistic electrons in a superlattice and electrons in a free electron laser ( fel ). touching upon this analogy the intensity of photon emission in the ir region and the gain are calculated. it is shown that the amplification can be significant, reaching tens of percent.
the connection between the quantum frequency of radiation by the transition of the electron from orbit n to orbit k and frequencies of circling of electron in these orbits for the atom of hydrogen is determined.
##physical processes which take place in human beings as they make sense of information received through the visual system. the subject of the image. when developing an imaging system, designers must consider the observables associated with the subjects which will be imaged. these observables generally take the form of emitted or reflected energy, such as electromagnetic energy or mechanical energy. the capture device. once the observables associated with the subject are characterized, designers can then identify and integrate the technologies needed to capture those observables. for example, in the case of consumer digital cameras, those technologies include optics for collecting energy in the visible portion of the electromagnetic spectrum, and electronic detectors for converting the electromagnetic energy into an electronic signal. the processor. for all digital imaging systems, the electronic signals produced by the capture device must be manipulated by an algorithm which formats the signals so they can be displayed as an image. in practice, there are often multiple processors involved in the creation of a digital image. the display. the display takes the electronic signals which have been manipulated by the processor and renders them on some visual medium. examples include paper ( for printed, or " hard copy " images ), television, computer monitor, or projector. note that some imaging scientists will include additional " links " in their description of the imaging chain. for example, some will include the " source " of the energy which " illuminates " or interacts with the subject of the image. others will include storage and / or transmission systems. = = subfields = = subfields within imaging science include : image processing, computer vision, 3d computer graphics, animations, atmospheric optics, astronomical imaging, biological imaging, digital image restoration, digital imaging, color science, digital photography, holography, magnetic resonance imaging, medical imaging, microdensitometry, optics, photography, remote sensing, radar imaging, radiometry, silver halide, ultrasound imaging, photoacoustic imaging, thermal imaging, visual perception, and various printing technologies. = = methodologies = = acoustic imaging coherent imaging uses an active coherent illumination source, such as in radar, synthetic aperture radar ( sar ), medical ultrasound and optical coherence tomography ; non - coherent imaging systems include fluorescent microscopes, optical microscopes, and telescopes. chemical imaging, the simultaneous measurement of spectra and pictures digital imaging, creating digital images, generally by scanning or through digital photography disk image, a file which contains the exact content of a data storage medium document imaging, replicating documents commonly
in one or more of these kinds of structures, it is invariably accompanied by an increase or decrease of energy of the substances involved. some energy is transferred between the surroundings and the reactants of the reaction in the form of heat or light ; thus the products of a reaction may have more or less energy than the reactants. a reaction is said to be exergonic if the final state is lower on the energy scale than the initial state ; in the case of endergonic reactions the situation is the reverse. a reaction is said to be exothermic if the reaction releases heat to the surroundings ; in the case of endothermic reactions, the reaction absorbs heat from the surroundings. chemical reactions are invariably not possible unless the reactants surmount an energy barrier known as the activation energy. the speed of a chemical reaction ( at given temperature t ) is related to the activation energy e, by the boltzmann ' s population factor e β e / k t { \ displaystyle e ^ { - e / kt } } β that is the probability of a molecule to have energy greater than or equal to e at the given temperature t. this exponential dependence of a reaction rate on temperature is known as the arrhenius equation. the activation energy necessary for a chemical reaction to occur can be in the form of heat, light, electricity or mechanical force in the form of ultrasound. a related concept free energy, which also incorporates entropy considerations, is a very useful means for predicting the feasibility of a reaction and determining the state of equilibrium of a chemical reaction, in chemical thermodynamics. a reaction is feasible only if the total change in the gibbs free energy is negative, Ξ΄ g β€ 0 { \ displaystyle \ delta g \ leq 0 \, } ; if it is equal to zero the chemical reaction is said to be at equilibrium. there exist only limited possible states of energy for electrons, atoms and molecules. these are determined by the rules of quantum mechanics, which require quantization of energy of a bound system. the atoms / molecules in a higher energy state are said to be excited. the molecules / atoms of substance in an excited energy state are often much more reactive ; that is, more amenable to chemical reactions. the phase of a substance is invariably determined by its energy and the energy of its surroundings. when the intermolecular forces of a substance are such that the energy of the surroundings is not sufficient to overcome them, it occurs in a more ordered phase like liquid
a rydberg gas of no entrained in a supersonic molecular beam releases electrons as it evolves to form an ultracold plasma. the size of this signal, compared with that extracted by the subsequent application of a pulsed electric field, determines the absolute magnitude of the plasma charge. this information, combined with the number density of ions, supports a simple thermochemical model that explains the evolution of the plasma to an ultracold electron temperature.
Question: Where does an electron move to after it absorbs energy?
A) another electron
B) atomic orbit
C) a shell farther from the nucleus
D) a shell closer to the nucleus
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C) a shell farther from the nucleus
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