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covid - 19, also known as novel coronavirus disease, is a highly contagious disease that first surfaced in china in late 2019. sars - cov - 2 is a coronavirus that belongs to the vast family of coronaviruses that causes this disease. the sickness originally appeared in wuhan, china in december 2019 and quickly spread to over 213 nations, becoming a global pandemic. fever, dry cough, and tiredness are the most typical covid - 19 symptoms. aches, pains, and difficulty breathing are some of the other symptoms that patients may face. the majority of these symptoms are indicators of respiratory infections and lung abnormalities, which radiologists can identify. chest x - rays of covid - 19 patients seem similar, with patchy and hazy lungs rather than clear and healthy lungs. on x - rays, however, pneumonia and other chronic lung disorders can resemble covid - 19. trained radiologists must be able to distinguish between covid - 19 and an illness that is less contagious. our ai algorithm seeks to give doctors a quantitative estimate of the risk of deterioration. so that patients at high risk of deterioration can be triaged and treated efficiently. the method could be particularly useful in pandemic hotspots when screening upon admission is important for allocating limited resources like hospital beds.
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
) : 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,
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.
a stack of tensionless membranes with nonlinear curvature energy and vertical harmonic interaction is studied. at low temperatures, the system forms a lamellar phase. at a critical temperature, the stack disorders vertically in a melting - like transition.
we predict the upper bound on the dissociation temperatures of different quarkonium states.
background : african swine fever is among the most devastating viral diseases of pigs. despite nearly a century of research, there is still no safe and effective vaccine available. the current situation is that either vaccines are safe but not effective, or they are effective but not safe. findings : the asf vaccine prepared using the inactivation method with propiolactone provided 98. 6 % protection within 100 days after three intranasal immunizations, spaced 7 days apart. conclusions : an inactivated vaccine made from complete african swine fever virus particles using propiolactone is safe and effective for controlling asf through mucosal immunity.
multi - strain diseases are diseases that consist of several strains, or serotypes. the serotypes may interact by antibody - dependent enhancement ( ade ), in which infection with a single serotype is asymptomatic, but infection with a second serotype leads to serious illness accompanied by greater infectivity. it has been observed from serotype data of dengue hemorrhagic fever that outbreaks of the four serotypes occur asynchronously. both autonomous and seasonally driven outbreaks were studied in a model containing ade. for sufficiently small ade, the number of infectives of each serotype synchronizes, with outbreaks occurring in phase. when the ade increases past a threshold, the system becomes chaotic, and infectives of each serotype desynchronize. however, certain groupings of the primary and second ary infectives remain synchronized even in the chaotic regime.
the recursion operator and bi - hamiltonian formulation of the drinfeld - sokolov system are given
we discuss the recent development of effective field theories for quarkonium at finite temperature.
Question: Which factor will most likely cause a person to develop a fever?
A) a leg muscle relaxing after exercise
B) a bacterial population in the bloodstream
C) several viral particles on the skin
D) carbohydrates being digested in the stomach
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B) a bacterial population in the bloodstream
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Context:
, 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 ",
, 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
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.
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 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
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
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,
- 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
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
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 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 o
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
Question: Lichens are symbiotic organisms made of green algae and fungi. What do the green algae supply to the fungi in this symbiotic relationship?
A) carbon dioxide
B) food
C) protection
D) water
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B) food
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Context:
in order to obtain the keys in this system, a key must be inserted and turned ( like the key at the bottom of the system of the picture ). once the key is turned, the operator may retrieve the remaining keys that will be used to open other doors. once all keys are returned, then the operator will be allowed to take out the original key from the beginning. the key will not turn unless the remaining keys are put back in place. another example is an electric kiln. to prevent access to the inside of an electric kiln, a trapped key system may be used to interlock a disconnecting switch and the kiln door. while the switch is turned on, the key is held by the interlock attached to the disconnecting switch. to open the kiln door, the switch is first opened, which releases the key. the key can then be used to unlock the kiln door. while the key is removed from the switch interlock, a plunger from the interlock mechanically prevents the switch from closing. power cannot be re - applied to the kiln until the kiln door is locked, releasing the key, and the key is then returned to the disconnecting switch interlock. a similar two - part interlock system can be used anywhere it is necessary to ensure the energy supply to a machine is interrupted before the machine is entered for adjustment or maintenance. = = mechanical = = interlocks may be strictly mechanical. an example of a mechanical interlock is a steering wheel of a car. in modern days, most cars have an anti - theft feature that restricts the turning of the steering wheel if the key is not inserted in the ignition. this prevents an individual from pushing the car since the mechanical interlock restricts the directional motion of the front wheels of the car. in the operation of a device such as a press or cutter that is hand fed or the workpiece hand removed, the use of two buttons to actuate the device, one for each hand, greatly reduces the possibility of operation endangering the operator. no such system is fool - proof, and such systems are often augmented by the use of cable β pulled gloves worn by the operator ; these are retracted away from the danger area by the stroke of the machine. a major problem in engineering operator safety is the tendency of operators to ignore safety precautions or even outright disabling forced interlocks due to work pressure and other factors. therefore, such safeties require and perhaps must facilitate operator cooperation. = = electrical =
in a predetermined sequence. after the control or power has been isolated, a key is released that can be used to grant access to individual or multiple doors. below is an example of what a trapped key interlock transfer block would look like. this is a part of a trapped key interlocking system. in order to obtain the keys in this system, a key must be inserted and turned ( like the key at the bottom of the system of the picture ). once the key is turned, the operator may retrieve the remaining keys that will be used to open other doors. once all keys are returned, then the operator will be allowed to take out the original key from the beginning. the key will not turn unless the remaining keys are put back in place. another example is an electric kiln. to prevent access to the inside of an electric kiln, a trapped key system may be used to interlock a disconnecting switch and the kiln door. while the switch is turned on, the key is held by the interlock attached to the disconnecting switch. to open the kiln door, the switch is first opened, which releases the key. the key can then be used to unlock the kiln door. while the key is removed from the switch interlock, a plunger from the interlock mechanically prevents the switch from closing. power cannot be re - applied to the kiln until the kiln door is locked, releasing the key, and the key is then returned to the disconnecting switch interlock. a similar two - part interlock system can be used anywhere it is necessary to ensure the energy supply to a machine is interrupted before the machine is entered for adjustment or maintenance. = = mechanical = = interlocks may be strictly mechanical. an example of a mechanical interlock is a steering wheel of a car. in modern days, most cars have an anti - theft feature that restricts the turning of the steering wheel if the key is not inserted in the ignition. this prevents an individual from pushing the car since the mechanical interlock restricts the directional motion of the front wheels of the car. in the operation of a device such as a press or cutter that is hand fed or the workpiece hand removed, the use of two buttons to actuate the device, one for each hand, greatly reduces the possibility of operation endangering the operator. no such system is fool - proof, and such systems are often augmented by the use of cable β pulled gloves worn by the operator ; these are
##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
which offer more ergonomic layouts of the keys. assistive technology devices have been created to enable disabled people to use modern touch screen mobile computers such as the ipad, iphone and ipod touch. the pererro is a plug and play adapter for ios devices which uses the built in apple voiceover feature in combination with a basic switch. this brings touch screen technology to those who were previously unable to use it. apple, with the release of ios 7 had introduced the ability to navigate apps using switch control. switch access could be activated either through an external bluetooth connected switch, single touch of the screen, or use of right and left head turns using the device ' s camera. additional accessibility features include the use of assistive touch which allows a user to access multi - touch gestures through pre - programmed onscreen buttons. for users with physical disabilities a large variety of switches are available and customizable to the user ' s needs varying in size, shape, or amount of pressure required for activation. switch access may be placed near any area of the body which has consistent and reliable mobility and less subject to fatigue. common sites include the hands, head, and feet. eye gaze and head mouse systems can also be used as an alternative mouse navigation. a user may use single or multiple switch sites and the process often involves a scanning through items on a screen and activating the switch once the desired object is highlighted. = = home automation = = the form of home automation called assistive domotics focuses on making it possible for elderly and disabled people to live independently. home automation is becoming a viable option for the elderly and disabled who would prefer to stay in their own homes rather than move to a healthcare facility. this field uses much of the same technology and equipment as home automation for security, entertainment, and energy conservation but tailors it towards elderly and disabled users. for example, automated prompts and reminders use motion sensors and pre - recorded audio messages ; an automated prompt in the kitchen may remind the resident to turn off the oven, and one by the front door may remind the resident to lock the door. = = assistive technology and innovation = = innovation is happening in assistive technology either through improvements to existing devices or the creation of new products. in the wipo published 2021 report on technology trends, assistive products are grouped into either conventional or emerging technologies. conventional assisting technology tracks innovation within well - established assistive products, whereas emerging assistive technology refers to more advanced products. these identified advanced assistive products are distinguished from the
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
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, pcm or fsk. wireless doorbell β a residential doorbell that uses wireless technology to eliminate the need to run wires through the building walls. it consists of a doorbell button beside the door containing a small battery powered transmitter. when the doorbell is pressed it sends a signal to a receiver inside the house with a speaker that sounds chimes to indicate someone is at the door. they usually use the 2. 4 ghz ism band. the frequency channel used can usually be changed by the owner in case another nearby doorbell is using the same channel. = = = = scientific research = = = = radio astronomy is the scientific study of radio waves emitted by astronomical objects. radio astronomers use radio telescopes, large radio antennas and receivers, to receive and study the radio waves from astronomical radio sources. since astronomical radio sources are so far away, the radio waves from them are extremely weak, requiring extremely sensitive receivers, and radio telescopes are the most sensitive radio receivers in existence. they use
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
##rs in their design. from that time on transistors were almost exclusively used for computer logic circuits and peripheral devices. however, early junction transistors were relatively bulky devices that were difficult to manufacture on a mass - production basis, which limited them to a number of specialised applications. the mosfet was invented at bell labs between 1955 and 1960. it was the first truly compact transistor that could be miniaturised and mass - produced for a wide range of uses. its advantages include high scalability, affordability, low power consumption, and high density. it revolutionized the electronics industry, becoming the most widely used electronic device in the world. the mosfet is the basic element in most modern electronic equipment. as the complexity of circuits grew, problems arose. one problem was the size of the circuit. a complex circuit like a computer was dependent on speed. if the components were large, the wires interconnecting them must be long. the electric signals took time to go through the circuit, thus slowing the computer. the invention of the integrated circuit by jack kilby and robert noyce solved this problem by making all the components and the chip out of the same block ( monolith ) of semiconductor material. the circuits could be made smaller, and the manufacturing process could be automated. this led to the idea of integrating all components on a single - crystal silicon wafer, which led to small - scale integration ( ssi ) in the early 1960s, and then medium - scale integration ( msi ) in the late 1960s, followed by vlsi. in 2008, billion - transistor processors became commercially available. = = subfields = = = = devices and components = = an electronic component is any component in an electronic system either active or passive. components are connected together, usually by being soldered to a printed circuit board ( pcb ), to create an electronic circuit with a particular function. components may be packaged singly, or in more complex groups as integrated circuits. passive electronic components are capacitors, inductors, resistors, whilst active components are such as semiconductor devices ; transistors and thyristors, which control current flow at electron level. = = types of circuits = = electronic circuit functions can be divided into two function groups : analog and digital. a particular device may consist of circuitry that has either or a mix of the two types. analog circuits are becoming less common, as many of their functions are being digitized. = = = analog circuits = =
this paper deals with a problem in which two players share a previously sliced pizza and try to eat as much amount of pizza as they can. it takes time to eat each piece of pizza and both players eat pizza at the same rate. one is allowed to take a next piece only after the person has finished eating the piece on hand. also, after the first piece is taken, one can only take a piece which is adjacent to already - taken piece. this paper shows that, in this real time setting, the starting player can always eat at least two - fifth of the total size of the pizza. however, this may not be the best possible amount the starting player can eat. it is a modified problem from an original one where two players takes piece alternatively instead.
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.
Question: When a switch is used in an electrical circuit, the switch can
A) cause the charge to build.
B) increase and decrease the voltage.
C) cause the current to change direction.
D) stop and start the flow of current.
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D) stop and start the flow of current.
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Context:
##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
which offer more ergonomic layouts of the keys. assistive technology devices have been created to enable disabled people to use modern touch screen mobile computers such as the ipad, iphone and ipod touch. the pererro is a plug and play adapter for ios devices which uses the built in apple voiceover feature in combination with a basic switch. this brings touch screen technology to those who were previously unable to use it. apple, with the release of ios 7 had introduced the ability to navigate apps using switch control. switch access could be activated either through an external bluetooth connected switch, single touch of the screen, or use of right and left head turns using the device ' s camera. additional accessibility features include the use of assistive touch which allows a user to access multi - touch gestures through pre - programmed onscreen buttons. for users with physical disabilities a large variety of switches are available and customizable to the user ' s needs varying in size, shape, or amount of pressure required for activation. switch access may be placed near any area of the body which has consistent and reliable mobility and less subject to fatigue. common sites include the hands, head, and feet. eye gaze and head mouse systems can also be used as an alternative mouse navigation. a user may use single or multiple switch sites and the process often involves a scanning through items on a screen and activating the switch once the desired object is highlighted. = = home automation = = the form of home automation called assistive domotics focuses on making it possible for elderly and disabled people to live independently. home automation is becoming a viable option for the elderly and disabled who would prefer to stay in their own homes rather than move to a healthcare facility. this field uses much of the same technology and equipment as home automation for security, entertainment, and energy conservation but tailors it towards elderly and disabled users. for example, automated prompts and reminders use motion sensors and pre - recorded audio messages ; an automated prompt in the kitchen may remind the resident to turn off the oven, and one by the front door may remind the resident to lock the door. = = assistive technology and innovation = = innovation is happening in assistive technology either through improvements to existing devices or the creation of new products. in the wipo published 2021 report on technology trends, assistive products are grouped into either conventional or emerging technologies. conventional assisting technology tracks innovation within well - established assistive products, whereas emerging assistive technology refers to more advanced products. these identified advanced assistive products are distinguished from 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.
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
in the old age, few people need special care if they are suffering from specific diseases as they can get stroke while they are in normal life routine. also patients of any age, who are not able to walk, need to be taken care of personally but for this, either they have to be in hospital or someone like nurse should be with them for better care. this is costly in terms of money and man power. a person is needed for 24x7 care of these people. to help in this aspect we purposes a vision based system which will take input from the patient and will provide information to the specified person, who is currently may not in the patient room. this will reduce the need of man power, also a continuous monitoring would not be needed. the system is using ms kinect for gesture detection for better accuracy and this system can be installed at home or hospital easily. the system provides gui for simple usage and gives visual and audio feedback to user. this system work on natural hand interaction and need no training before using and also no need to wear any glove or color strip.
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
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
. 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
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
as a traditional tool of external assistance, crutches play an important role in society. they have a wide range of applications to help either the elderly and disabled to walk or to treat certain illnesses or for post - operative rehabilitation. but there are many different types of crutches, including shoulder crutches and elbow crutches. how to choose has become an issue that deserves to be debated. because while crutches help people walk, they also have an impact on the body. inappropriate choice of crutches or long - term misuse can lead to problems such as scoliosis. previous studies were mainly experimental measurements or the construction of dynamic models to calculate the load on joints with crutches. these studies focus only on the level of the joints, ignoring the role that muscles play in this process. although some also take into account the degree of muscle activation, there is still a lack of quantitative analysis. the traditional dynamic model can be used to calculate the load on each joint. however, due to the activation of the muscle, this situation only causes part of the load transmitted to the joint, and the work of the chair will compensate the other part of the load. analysis at the muscle level allows a better understanding of the impact of crutches on the body. by comparing the levels of activation of the trunk muscles, it was found that the use of crutches for walking, especially a single crutch, can cause a large difference in the activation of the back muscles on the left and right sides, and this difference will cause muscle degeneration for a long time, leading to scoliosis. in this article taking scoliosis as an example, by analyzing the muscles around the spine, we can better understand the pathology and can better prevent diseases. the objective of this article is to analyze normal walking compared to walking with one or two crutches using opensim software to obtain the degree of activation of different muscles in order to analyze the impact of crutches on the body.
Question: Which of the following is an example of an assistive device?
A) contact lens
B) motorcycle
C) raincoat
D) coffee pot
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A) contact lens
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Context:
, 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
##morphology 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 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
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 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
##sphere ( 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 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
##hosphere ) 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 ). " 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
all simple weight modules with finite dimensional weight spaces over affine lie algebras are classified.
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 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
an orthotropic metamaterial is composed of elements arrayed periodically in space. the element includes two cuboid structures. the first structure is the basic structure of the element, and the second structure is the transformation of the first structure of the element. the first structure of the element is a cuboid structure composed of 24 bars connected by 8 nodes, and the second structure of the element is a cuboid structure composed of 36 bars connected by 14 nodes. this metamaterial has 6 independent elastic constants, so there is a large degree of freedom in material design. using a simple universal design method, a metamaterial with tailored elastic constants can be designed. therefore, it has great application value in the fields of mechanical metamaterials, elastic wave metamaterials, acoustic metamaterials, and seismic metamaterials, and has also laid the foundation for realizing the dream of controlling elastic waves, acoustic waves and vibrations.
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 ). " 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 = = = = =
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
Question: Rocks are classified as igneous, metamorphic, or sedimentary according to
A) their color
B) their shape
C) how they formed
D) the minerals they contain
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C) how they formed
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Context:
##able. 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 degrades within the human body to form lactic acid, a naturally occurring chemical which is easily removed from the body. similar materials are polyglycolic acid ( pga ) and polycaprolactone ( pcl ) : their degradation mechanism is similar to that of pla, but pcl degrades slower and pga degrades faster. pla is commonly combined with pga to create poly - lactic - co - glycolic acid ( plga ). this is especially useful because the degradation of plga can be tailored by altering the weight percentages of pla and pga : more pla β slower degradation, more pga β faster degradation. this tunability, along with its biocompatibility, makes it an extremely useful material for scaffold creation. scaffolds may also be constructed from natural materials : in particular different derivatives of the extracellular matrix have been studied to evaluate their ability to support cell growth. protein based materials β such as collagen, or fibrin, and polysaccharidic materials - like chitosan or glycosaminoglycans ( gags ), have all proved suitable in terms of cell compatibility. among gags, hyaluronic acid, possibly in combination with cross linking agents ( e. g. glutaraldehyde, water - soluble carbodiimide, etc. ), is one of the possible choices as scaffold material. due to the covalent attachment of thiol groups to these polymers, they can crosslink via disulfide bond
applications continue to expand as researchers develop new kinds of ceramics to serve different purposes. zirconium dioxide ceramics are used in the manufacture of knives. the blade of the ceramic knife will stay sharp for much longer than that of a steel knife, although it is more brittle and can be snapped by dropping it on a hard surface. ceramics such as alumina, boron carbide and silicon carbide have been used in bulletproof vests to repel small arms rifle fire. such plates are known commonly as ballistic plates. similar material is used to protect cockpits of some military aircraft, because of the low weight of the 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
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
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
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
, 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
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
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 - 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.
##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
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
Question: A chewable calcium carbonate tablet is a common treatment for stomach discomfort. Calcium carbonate is most likely used as this type of medicine because calcium carbonate
A) has a pleasant flavor.
B) is inexpensive to produce.
C) neutralizes digestive acid.
D) occurs naturally in the body.
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C) neutralizes digestive acid.
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Context:
grasping an object is a matter of first moving a prehensile organ at some position in the world, and then managing the contact relationship between the prehensile organ and the object. once the contact relationship has been established and made stable, the object is part of the body and it can move in the world. as any action, the action of grasping is ontologically anchored in the physical space while the correlative movement originates in the space of the body. evolution has found amazing solutions that allow organisms to rapidly and efficiently manage the relationship between their body and the world. it is then natural that roboticists consider taking inspiration of these natural solutions, while contributing to better understand their origin.
affect static bodies dynamics, the study of how forces affect moving bodies. dynamics includes kinematics ( about movement, velocity, and acceleration ) and kinetics ( about forces and resulting accelerations ). mechanics of materials, the study of how different materials deform under various types of stress fluid mechanics, the study of how fluids react to forces kinematics, the study of the motion of bodies ( objects ) and systems ( groups of objects ), while ignoring the forces that cause the motion. kinematics is often used in the design and analysis of mechanisms. continuum mechanics, a method of applying mechanics that assumes that objects are continuous ( rather than discrete ) mechanical engineers typically use mechanics in the design or analysis phases of engineering. if the engineering project were the design of a vehicle, statics might be employed to design the frame of the vehicle, in order to evaluate where the stresses will be most intense. dynamics might be used when designing the car ' s engine, to evaluate the forces in the pistons and cams as the engine cycles. mechanics of materials might be used to choose appropriate materials for the frame and engine. fluid mechanics might be used to design a ventilation system for the vehicle ( see hvac ), or to design the intake system for the engine. = = = mechatronics and robotics = = = mechatronics is a combination of mechanics and electronics. it is an interdisciplinary branch of mechanical engineering, electrical engineering and software engineering that is concerned with integrating electrical and mechanical engineering to create hybrid automation systems. in this way, machines can be automated through the use of 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,
a comparison of the sensitivities of methods which allow us to determine the coordinates of a moving hot body is made.
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 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.
the classical and the quantum motion of a massive body in the rotating tube is considered. photon is included. the spin motion described by the bargmann - michel - telegdi equation is considered in the rotation tube and rotating system.
forces and their effect upon matter. typically, engineering mechanics is used to analyze and predict the acceleration and deformation ( both elastic and plastic ) of objects under known forces ( also called loads ) or stresses. subdisciplines of mechanics include statics, the study of non - moving bodies under known loads, how forces affect static bodies dynamics, the study of how forces affect moving bodies. dynamics includes kinematics ( about movement, velocity, and acceleration ) and kinetics ( about forces and resulting accelerations ). mechanics of materials, the study of how different materials deform under various types of stress fluid mechanics, the study of how fluids react to forces kinematics, the study of the motion of bodies ( objects ) and systems ( groups of objects ), while ignoring the forces that cause the motion. kinematics is often used in the design and analysis of mechanisms. continuum mechanics, a method of applying mechanics that assumes that objects are continuous ( rather than discrete ) mechanical engineers typically use mechanics in the design or analysis phases of engineering. if the engineering project were the design of a vehicle, statics might be employed to design the frame of the vehicle, in order to evaluate where the stresses will be most intense. dynamics might be used when designing the car ' s engine, to evaluate the forces in the pistons and cams as the engine cycles. mechanics of materials might be used to choose appropriate materials for the frame and engine. fluid mechanics might be used to design a ventilation system for the vehicle ( see hvac ), or to design the intake system for the engine. = = = mechatronics and robotics = = = mechatronics is a combination of mechanics and electronics. it is an interdisciplinary branch of mechanical engineering, electrical engineering and software engineering that is concerned with integrating electrical and mechanical engineering to create hybrid automation systems. in this way, machines can be automated through the use of 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
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.
##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
unitary recordings in freely - moving pulse weakly electric fish suggest spike timing encoding of electrosensory signals
Question: Which two body systems are directly involved in movement?
A) muscular and skeletal
B) digestive and muscular
C) skeletal and respiratory
D) respiratory and digestive
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A) muscular and skeletal
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Context:
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, 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
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,
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
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 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.
. 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 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
to that of a flat crack through the plain matrix. the magnitude of the toughening is determined by the mismatch strain caused by thermal contraction incompatibility and the microfracture resistance of the particle / matrix interface. the toughening becomes noticeable with a narrow size distribution of appropriately sized particles, and researchers typically accept that deflection effects in materials with roughly equiaxial grains may increase the fracture toughness by about twice the grain boundary value. the model reveals that the increase in toughness is dependent on particle shape and the volume fraction of the second phase, with the most effective morphology being the rod of high aspect ratio, which can account for a fourfold increase in fracture toughness. the toughening arises primarily from the twist of the crack front between particles, as indicated by deflection profiles. disc - shaped particles and spheres are less effective in toughening. fracture toughness, regardless of morphology, is determined by the twist of the crack front at its most severe configuration, rather than the initial tilt of the crack front. only for disc - shaped particles does the initial tilting of the crack front provide significant toughening ; however, the twist component still overrides the tilt - derived toughening. additional important features of the deflection analysis include the appearance of asymptotic toughening for the three morphologies at volume fractions in excess of 0. 2. it is also noted that a significant influence on the toughening by spherical particles is exerted by the interparticle spacing distribution ; greater toughening is afforded when spheres are nearly contacting such that twist angles approach Ο / 2. these predictions provide the basis for the design of high - toughness two - phase ceramic materials. the ideal second phase, in addition to maintaining chemical compatibility, should be present in amounts of 10 to 20 volume percent. greater amounts may diminish the toughness increase due to overlapping particles. particles with high aspect ratios, especially those with rod - shaped morphologies, are most suitable for maximum toughening. this model is often used to determine the factors that contribute to the increase in fracture toughness in ceramics which is ultimately useful in the development of advanced ceramic materials with improved performance. = = theory of chemical processing = = = = = microstructural uniformity = = = in the processing of fine ceramics, the irregular particle sizes and shapes in a typical powder often lead to non - uniform packing morphologies that result in packing density variations in the powder compact. uncontrolled aggl
gravity induced condensation takes the form of momentum alignment in an ensemble of identical particles. use is made of a one - dimensional ising model to calculate the alignment per particle and the correlation length as a function of the temperature. these parameters indicate that momentum alignment is possible in the proximity of some astrophysical objects and in earth, or near earth laboratories. momenta oscillations behave as known spin oscillations and obey identical dispersion relations.
the robot ' s objective is to rehabilitate the pipe joints of fresh water supply systems by crawling into water canals and applying a restoration material to repair the pipes. the robot ' s structure consists of six wheeled - legs, three on the front separated 120 { \ deg } and three on the back in the same configuration, supporting the structure along the centre of the pipe. in this configuration the robot is able to clean and seal with a rotating tool, similar to a cylindrical robot, covering the entire 3d in - pipe space.
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.
various charge pairings in strongly correlated electron systems are interpreted as quantum entanglement of a composite system. particles in the intermediate phase have a tendency to form the coherent superposition state of the localized state and the itinerant state, which induces the entanglement of both particles in the bipartite subsystems for increasing the entropy of the system. the correction to the entropic coulomb force becomes an immediate cause of charge pairing.
Question: Which change in the state of water particles causes the particles to become arranged in a fixed position?
A) boiling
B) melting
C) freezing
D) evaporating
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C) freezing
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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
##sphere ( 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 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
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 vacuum chamber, and cured - pyrolized to convert the furfuryl alcohol to carbon. to provide oxidation resistance for reusability, the outer layers of the rcc are converted to silicon carbide. other examples can be seen in the " plastic " casings of television sets, cell - phones and 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
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
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
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 that gives us long - term ( decade - to - decade ) feedback on our performance as stewards of the planet. the effort includes understanding the functions of soil microbiotic crusts and exploring the potential to sequester atmospheric carbon in soil organic matter. relating the concept of agriculture to soil quality, however, has not
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
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 ). "
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
Question: Earth's core is primarily composed of which of the following materials?
A) basalt
B) iron
C) magma
D) quartz
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B) iron
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Context:
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
, 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
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
. 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
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 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
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 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
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
i summarise the experimental results presented during the hadronic session of the xxxivth rencontre de moriond.
a letter to the editor shortly summing up ten or so years of research into the h - index.
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 at endogenous genes that generate a gene knockout. = = applications = = genetic engineering has applications in medicine, research, industry and agriculture and can be used on a wide range of plants, animals and microorganisms. bacteria, the first organisms to be genetically modified, can have plasmid dna inserted containing new genes that code for medicines or enzymes that process food and other substrates. plants have been modified for insect protection, herbicide resistance, virus resistance, enhanced nutrition, tolerance to environmental pressures and the production of edible vaccines. most commercialised gmos are insect resistant or herbicide tolerant crop plants. genetically modified animals have been used for research, model animals and the production of agricultural or pharmaceutical products. the genetically modified animals include animals with genes knocked out, increased susceptibility to disease, hormones for extra growth and the ability to express proteins in their milk. = = = medicine = = = genetic engineering has many applications to medicine that include the manufacturing of drugs, creation of model animals that mimic human conditions and gene therapy. one of the earliest uses of genetic engineering was to mass - produce human insulin in bacteria. this application has now been applied to human growth hormones, follicle stimulating hormones ( for treating infertility ), human albumin,
Question: Which of the following events during meiosis contributes most to the variation within a species?
A) pairing of chromosomes
B) creation of haploid gametes
C) segregation of alleles
D) separation of chromatids
|
C) segregation of alleles
|
Context:
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
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
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
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
; 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 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
. 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
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
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
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. 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
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: Which of the following was probably most important in the formation of dark, fertile soil that is good for farming?
A) plant decomposition
B) radioactive decay
C) water erosion
D) wind erosion
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A) plant decomposition
|
Context:
##morphology 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 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
, 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
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
this paper has been withdrawn by the authors until some changes are made.
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 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
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 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
##sphere ( 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 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
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 that gives us long - term ( decade - to - decade ) feedback on our performance as stewards of the planet. the effort includes understanding the functions of soil microbiotic crusts and exploring the potential to sequester atmospheric carbon in soil organic matter. relating the concept of agriculture to soil quality, however, has not
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
##thic, 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, 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
Question: When igneous rock is changed into metamorphic rock, which form of energy is this process?
A) heat
B) chemical
C) magnetic
D) light
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A) heat
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Context:
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
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
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
##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
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
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, 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
it is hard for us humans to recognize things in nature until we have invented them ourselves. for image - forming optics, nature has made virtually every kind of lens humans have devised. but what about lensless " imaging "? recently, we showed that a bare array of sensors on a curved substrate could achieve resolution not limited by diffraction - without any lens at all provided that the objects imaged conform to our a priori assumptions. is it possible that somewhere in nature we will find this kind of vision system? we think so and provide examples that seem to make no sense whatever unless they are using something like our lensless imaging work.
. 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
also called projection lines ) differs, as explained below. in first - angle projection, the parallel projectors originate as if radiated from behind the viewer and pass through the 3d object to project a 2d image onto the orthogonal plane behind it. the 3d object is projected into 2d " paper " space as if you were looking at a radiograph of the object : the top view is under the front view, the right view is at the left of the front view. first - angle projection is the iso standard and is primarily used in europe. in third - angle projection, the parallel projectors originate as if radiated from the far side of the object and pass through the 3d object to project a 2d image onto the orthogonal plane in front of it. the views of the 3d object are like the panels of a box that envelopes the object, and the panels pivot as they open up flat into the plane of the drawing. thus the left view is placed on the left and the top view on the top ; and the features closest to the front of the 3d object will appear closest to the front view in the drawing. third - angle projection is primarily used in the united states and canada, where it is the default projection system according to asme standard asme y14. 3m. until the late 19th century, first - angle projection was the norm in north america as well as europe ; but circa the 1890s, third - angle projection spread throughout the north american engineering and manufacturing communities to the point of becoming a widely followed convention, and it was an asa standard by the 1950s. circa world war i, british practice was frequently mixing the use of both projection methods. as shown above, the determination of what surface constitutes the front, back, top, and bottom varies depending on the projection method used. not all views are necessarily used. generally only as many views are used as are necessary to convey all needed information clearly and economically. the front, top, and right - side views are commonly considered the core group of views included by default, but any combination of views may be used depending on the needs of the particular design. in addition to the six principal views ( front, back, top, bottom, right side, left side ), any auxiliary views or sections may be included as serve the purposes of part definition and its communication. view lines or section lines ( lines with arrows marked " a - a ", " b - b ", etc. ) define the direction and location of viewing or sectioning. sometimes a note tells the reader in which zone
the carbon - based biosphere has generated a system ( humans ) capable of creating technology that will result in a comparable evolutionary transition. the digital information created by humans has reached a similar magnitude to biological information in the biosphere. since the 1980s, the quantity of digital information stored has doubled about every 2. 5 years, reaching about 5 zettabytes in 2014 ( 5Γ1021 bytes ). in biological terms, there are 7. 2 billion humans on the planet, each having a genome of 6. 2 billion nucleotides. since one byte can encode four nucleotide pairs, the individual genomes of every human on the planet could be encoded by approximately 1Γ1019 bytes. the digital realm stored 500 times more information than this in 2014 ( see figure ). the total amount of dna contained in all of the cells on earth is estimated to be about 5. 3Γ1037 base pairs, equivalent to 1. 325Γ1037 bytes of information. if growth in digital storage continues at its current rate of 30 β 38 % compound annual growth per year, it will rival the total information content contained in all of the dna in all of the cells on earth in about 110 years. this would represent a doubling of the amount of information stored in the biosphere across a total time period of just 150 years ". = = = implications for human society = = = in february 2009, under the auspices of the association for the advancement of artificial intelligence ( aaai ), eric horvitz chaired a meeting of leading computer scientists, artificial intelligence researchers and roboticists at the asilomar conference center in pacific grove, california. the goal was to discuss the potential impact of the hypothetical possibility that robots could become self - sufficient and able to make their own decisions. they discussed the extent to which computers and robots might be able to acquire autonomy, and to what degree they could use such abilities to pose threats or hazards. some machines are programmed with various forms of semi - autonomy, including the ability to locate their own power sources and choose targets to attack with weapons. also, some computer viruses can evade elimination and, according to scientists in attendance, could therefore be said to have reached a " cockroach " stage of machine intelligence. the conference attendees noted that self - awareness as depicted in science - fiction is probably unlikely, but that other potential hazards and pitfalls exist. frank s. robinson predicts that once humans achieve a machine with the intelligence of a human, scientific and technological problems will be tackled and solved with
Question: In humans, the digestion process begins in
A) the intestine, with squeezing.
B) the mouth, with chewing and saliva.
C) the stomach, with churning and acid.
D) the esophagus, with pushing towards the stomach.
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B) the mouth, with chewing and saliva.
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Context:
necessary and sufficient conditions for a term to apply to an object. for example : " a platonic solid is a convex, regular polyhedron in three - dimensional euclidean space. " an extensional definition instead lists all objects where the term applies. for example : " a platonic solid is one of the following : tetrahedron, cube, octahedron, dodecahedron, or icosahedron. " in logic, the extension of a predicate is the set of all objects for which the predicate is true. further, the logical principle of extensionality judges two objects to objects to be equal if they satisfy the same external properties. since, by the axiom, two sets are defined to be equal if they satisfy membership, sets are extentional. jose ferreiros credits richard dedekind for being the first to explicitly state the principle, although he does not assert it as a definition : it very frequently happens that different things a, b, c... considered for any reason under a common point of view, are collected together in the mind, and one then says that they form a system s ; one calls the things a, b, c... the elements of the system s, they are contained in s ; conversely, s consists of these elements. such a system s ( or a collection, a manifold, a totality ), as an object of our thought, is likewise a thing ; it is completely determined when, for every thing, it is determined whether it is an element of s or not. = = = background = = = around the turn of the 20th century, mathematics faced several paradoxes and counter - intuitive results. for example, russell ' s paradox showed a contradiction of naive set theory, it was shown that the parallel postulate cannot be proved, the existence of mathematical objects that cannot be computed or explicitly described, and the existence of theorems of arithmetic that cannot be proved with peano arithmetic. the result was a foundational crisis of mathematics. the resolution of this crisis involved the rise of a new mathematical discipline called mathematical logic, which studies formal logic within mathematics. subsequent discoveries in the 20th century then stabilized the foundations of mathematics into a coherent framework valid for all mathematics. this framework is based on a systematic use of axiomatic method and on set theory, specifically zermelo β fraenkel set theory, developed by ernst zermelo and abraham fraenkel. this set theory ( and set theory in general ) is now considered the most common foundation of mathematics
here are discussed some problems concerning quant - ph / 0208006.
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 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
##trahedron, cube, octahedron, dodecahedron, or icosahedron. " in logic, the extension of a predicate is the set of all objects for which the predicate is true. further, the logical principle of extensionality judges two objects to objects to be equal if they satisfy the same external properties. since, by the axiom, two sets are defined to be equal if they satisfy membership, sets are extentional. jose ferreiros credits richard dedekind for being the first to explicitly state the principle, although he does not assert it as a definition : it very frequently happens that different things a, b, c... considered for any reason under a common point of view, are collected together in the mind, and one then says that they form a system s ; one calls the things a, b, c... the elements of the system s, they are contained in s ; conversely, s consists of these elements. such a system s ( or a collection, a manifold, a totality ), as an object of our thought, is likewise a thing ; it is completely determined when, for every thing, it is determined whether it is an element of s or not. = = = background = = = around the turn of the 20th century, mathematics faced several paradoxes and counter - intuitive results. for example, russell ' s paradox showed a contradiction of naive set theory, it was shown that the parallel postulate cannot be proved, the existence of mathematical objects that cannot be computed or explicitly described, and the existence of theorems of arithmetic that cannot be proved with peano arithmetic. the result was a foundational crisis of mathematics. the resolution of this crisis involved the rise of a new mathematical discipline called mathematical logic, which studies formal logic within mathematics. subsequent discoveries in the 20th century then stabilized the foundations of mathematics into a coherent framework valid for all mathematics. this framework is based on a systematic use of axiomatic method and on set theory, specifically zermelo β fraenkel set theory, developed by ernst zermelo and abraham fraenkel. this set theory ( and set theory in general ) is now considered the most common foundation of mathematics. = = = set equality based on first - order logic with equality = = = in first - order logic with equality ( see Β§ axioms ), the axiom of extensionality states that two sets that contain the same elements are the same set. logic axiom : x = y [UNK] [UNK] z, ( z
i state some open problems coming from joint work with paul erd \ h { o } s
be only either positive, negative, or zero. the word " sign " is also often used to indicate binary aspects of mathematical or scientific objects, such as odd and even ( sign of a permutation ), sense of orientation or rotation ( cw / ccw ), one sided limits, and other concepts described in Β§ other meanings below. = = sign of a number = = numbers from various number systems, like integers, rationals, complex numbers, quaternions, octonions,... may have multiple attributes, that fix certain properties of a number. a number system that bears the structure of an ordered ring 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 (
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. nickel - based superalloys like inconel are used in high - temperature applications such as gas turbines, turbochargers, pressure vessels, and heat exchangers. for extremely high temperatures, single crystal alloys are used to minimize creep. in modern electronics, high purity single crystal silicon is essential for metal - oxide - silicon transistors ( mos ) and integrated circuits. = = production = = in production engineering, metallurgy is concerned with the production of metallic components for use in consumer or engineering products. this involves production of alloys, shaping, heat treatment and surface treatment of product. the task of the metallurgist is to achieve balance between material properties, such as cost, weight, strength, toughness, hardness, corrosion, fatigue resistance and performance in temperature extremes. to achieve this goal, the operating environment must be carefully considered. determining the hardness of the metal using the rockwell, vickers, and brinell hardness scales
ceramic constituents, the greatest attention is on composites in which all constituents are ceramic. these typically comprise two ceramic constituents : a continuous matrix, and a dispersed phase of ceramic particles, whiskers, or short ( chopped ) or continuous ceramic fibers. the challenge, as in wet chemical processing, is to obtain a uniform or homogeneous distribution of the dispersed particle or fiber phase. consider first the processing of particulate composites. the particulate phase of greatest interest is tetragonal zirconia because of the toughening that can be achieved from the phase transformation from the metastable tetragonal to the monoclinic crystalline phase, aka transformation toughening. there is also substantial interest in dispersion of hard, non - oxide phases such as sic, tib, tic, boron, carbon and especially oxide matrices like alumina and mullite. there is also interest too incorporating other ceramic particulates, especially those of highly anisotropic thermal expansion. examples include al2o3, tio2, graphite, and boron nitride. in processing particulate composites, the issue is not only homogeneity of the size and spatial distribution of the dispersed and matrix phases, but also control of the matrix grain size. however, there is some built - in self - control due to inhibition of matrix grain growth by the dispersed phase. particulate composites, though generally offer increased resistance to damage, failure, or both, are still quite sensitive to inhomogeneities of composition as well as other processing defects such as pores. thus they need good processing to be effective. particulate composites have been made on a commercial basis by simply mixing powders of the two constituents. although this approach is inherently limited in the homogeneity that can be achieved, it is the most readily adaptable for existing ceramic production technology. however, other approaches are of interest. from the technological standpoint, a particularly desirable approach to fabricating particulate composites is to coat the matrix or its precursor onto fine particles of the dispersed phase with good control of the starting dispersed particle size and the resultant matrix coating thickness. one should in principle be able to achieve the ultimate in homogeneity of distribution and thereby optimize composite performance. this can also have other ramifications, such as allowing more useful composite performance to be achieved in a body having porosity, which might be desired for other factors, such as limiting thermal conductivity. there are also some opportunities to
wireless communication ( or just wireless, when the context allows ) is the transfer of information ( telecommunication ) between two or more points without the use of an electrical conductor, optical fiber or other continuous guided medium for the transfer. the most common wireless technologies use radio waves. with radio waves, intended distances can be short, such as a few meters for bluetooth, or as far as millions of kilometers for deep - space radio communications. it encompasses various types of fixed, mobile, and portable applications, including two - way radios, cellular telephones, personal digital assistants ( pdas ), and wireless networking. other examples of applications of radio wireless technology include gps units, garage door openers, wireless computer mouse, keyboards and headsets, headphones, radio receivers, satellite television, broadcast television and cordless telephones. somewhat less common methods of achieving wireless communications involve other electromagnetic phenomena, such as light and magnetic or electric fields, or the use of sound. the term wireless has been used twice in communications history, with slightly different meanings. it was initially used from about 1890 for the first radio transmitting and receiving technology, as in wireless telegraphy, until the new word radio replaced it around 1920. radio sets in the uk and the english - speaking world that were not portable continued to be referred to as wireless sets into the 1960s. the term wireless was revived in the 1980s and 1990s mainly to distinguish digital devices that communicate without wires, such as the examples listed in the previous paragraph, from those that require wires or cables. this became its primary usage in the 2000s, due to the advent of technologies such as mobile broadband, wi - fi, and bluetooth. wireless operations permit services, such as mobile and interplanetary communications, that are impossible or impractical to implement with the use of wires. the term is commonly used in the telecommunications industry to refer to telecommunications systems ( e. g. radio transmitters and receivers, remote controls, etc. ) that use some form of energy ( e. g. radio waves and acoustic energy ) to transfer information without the use of wires. information is transferred in this manner over both short and long distances. = = history = = = = = photophone = = = the first wireless telephone conversation occurred in 1880 when alexander graham bell and charles sumner tainter invented the photophone, a telephone that sent audio over a beam of light. the photophone required sunlight to operate, and a clear line of sight between the transmitter and receiver, which greatly decreased the viability of the photophone in any practical use
the hun tian theory ), or as being without substance while the heavenly bodies float freely ( the hsuan yeh theory ), the earth was at all times flat, although perhaps bulging up slightly. the model of an egg was often used by chinese astronomers such as zhang heng ( 78 β 139 ad ) to describe the heavens as spherical : the heavens are like a hen ' s egg and as round as a crossbow bullet ; the earth is like the yolk of the egg, and lies in the centre. this analogy with a curved egg led some modern historians, notably joseph needham, to conjecture that chinese astronomers were, after all, aware of the earth ' s sphericity. the egg reference, however, was rather meant to clarify the relative position of the flat earth to the heavens : in a passage of zhang heng ' s cosmogony not translated by needham, zhang himself says : " heaven takes its body from the yang, so it is round and in motion. earth takes its body from the yin, so it is flat and quiescent ". the point of the egg analogy is simply to stress that the earth is completely enclosed by heaven, rather than merely covered from above as the kai tian describes. chinese astronomers, many of them brilliant men by any standards, continued to think in flat - earth terms until the seventeenth century ; this surprising fact might be the starting - point for a re - examination of the apparent facility with which the idea of a spherical earth found acceptance in fifth - century bc greece. further examples cited by needham supposed to demonstrate dissenting voices from the ancient chinese consensus actually refer without exception to the earth being square, not to it being flat. accordingly, the 13th - century scholar li ye, who argued that the movements of the round heaven would be hindered by a square earth, did not advocate a spherical earth, but rather that its edge should be rounded off so as to be circular. however, needham disagrees, affirming that li ye believed the earth to be spherical, similar in shape to the heavens but much smaller. this was preconceived by the 4th - century scholar yu xi, who argued for the infinity of outer space surrounding the earth and that the latter could be either square or round, in accordance to the shape of the heavens. when chinese geographers of the 17th century, influenced by european cartography and astronomy, showed the earth as a sphere that could be circumnavigated by sailing around the globe, they
Question: Which of these items contains only a solution?
A) a jar of pickles
B) a bottle of juice
C) a bag of peanuts
D) a can of mixed fruit
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B) a bottle of juice
|
Context:
##morphology 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 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
, 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
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
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
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
. historically, metallurgy has predominately focused on the production of metals. metal production begins with the processing of ores to extract the metal, and includes the mixture of metals to make alloys. metal alloys are often a blend of at least two different metallic elements. however, non - metallic elements are often added to alloys in order to achieve properties suitable for an application. the study of metal production is subdivided into ferrous metallurgy ( also known as black metallurgy ) and non - ferrous metallurgy, also known as colored metallurgy. ferrous metallurgy involves processes and alloys based on iron, while non - ferrous metallurgy involves processes and alloys based on other metals. the production of ferrous metals accounts for 95 % of world metal production. modern metallurgists work in both emerging and traditional areas as part of an interdisciplinary team alongside material scientists and other engineers. some traditional areas include mineral processing, metal production, heat treatment, failure analysis, and the joining of metals ( including welding, brazing, and soldering ). emerging areas for metallurgists include nanotechnology, superconductors, composites, biomedical materials, electronic materials ( semiconductors ) and surface engineering. = = etymology and pronunciation = = metallurgy derives from the ancient greek ΞΌΞ΅ΟαλλοΟ
ΟΞ³ΞΏΟ, metallourgos, " worker in metal ", from ΞΌΞ΅Οαλλον, metallon, " mine, metal " + Ξ΅ΟΞ³ΞΏΞ½, ergon, " work " the word was originally an alchemist ' s term for the extraction of metals from minerals, the ending - urgy signifying a process, especially manufacturing : it was discussed in this sense in the 1797 encyclopΓ¦dia britannica. in the late 19th century, metallurgy ' s definition was extended to the more general scientific study of metals, alloys, and related processes. in english, the pronunciation is the more common one in the united kingdom. the pronunciation is the more common one in the us and is the first - listed variant in various american dictionaries, including merriam - webster collegiate and american heritage. = = history = = the earliest metal employed by humans appears to be gold, which can be found " native ". small amounts of natural gold, dating to the late paleolithic period, 40, 000 bc, have been found in spanish caves. silver, copper, tin and meteoric iron
##sphere ( 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 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
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 that gives us long - term ( decade - to - decade ) feedback on our performance as stewards of the planet. the effort includes understanding the functions of soil microbiotic crusts and exploring the potential to sequester atmospheric carbon in soil organic matter. relating the concept of agriculture to soil quality, however, has not
##chemistry, and chemical degradation ( corrosion ). in contrast, physical metallurgy focuses on the mechanical properties of metals, the physical properties of metals, and the physical performance of metals. topics studied in physical metallurgy include crystallography, material characterization, mechanical metallurgy, phase transformations, and failure mechanisms. historically, metallurgy has predominately focused on the production of metals. metal production begins with the processing of ores to extract the metal, and includes the mixture of metals to make alloys. metal alloys are often a blend of at least two different metallic elements. however, non - metallic elements are often added to alloys in order to achieve properties suitable for an application. the study of metal production is subdivided into ferrous metallurgy ( also known as black metallurgy ) and non - ferrous metallurgy, also known as colored metallurgy. ferrous metallurgy involves processes and alloys based on iron, while non - ferrous metallurgy involves processes and alloys based on other metals. the production of ferrous metals accounts for 95 % of world metal production. modern metallurgists work in both emerging and traditional areas as part of an interdisciplinary team alongside material scientists and other engineers. some traditional areas include mineral processing, metal production, heat treatment, failure analysis, and the joining of metals ( including welding, brazing, and soldering ). emerging areas for metallurgists include nanotechnology, superconductors, composites, biomedical materials, electronic materials ( semiconductors ) and surface engineering. = = etymology and pronunciation = = metallurgy derives from the ancient greek ΞΌΞ΅ΟαλλοΟ
ΟΞ³ΞΏΟ, metallourgos, " worker in metal ", from ΞΌΞ΅Οαλλον, metallon, " mine, metal " + Ξ΅ΟΞ³ΞΏΞ½, ergon, " work " the word was originally an alchemist ' s term for the extraction of metals from minerals, the ending - urgy signifying a process, especially manufacturing : it was discussed in this sense in the 1797 encyclopΓ¦dia britannica. in the late 19th century, metallurgy ' s definition was extended to the more general scientific study of metals, alloys, and related processes. in english, the pronunciation is the more common one in the united kingdom. the pronunciation is the more common one in the us and is the first - listed variant in various american dictionaries, including merriam - webster collegiate
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 % carbon. stainless steel is defined as a regular steel alloy with greater than 10 % by weight alloying content of chromium. nickel and molybdenum are typically also added in stainless steels. other significant metallic alloys are those of aluminium, titanium, copper and magnesium. copper alloys have been known for a long time ( since the bronze age ), while the alloys of the other three metals have been relatively recently developed. due to the chemical reactivity of these metals, the electrolytic extraction processes required were only developed relatively recently. the alloys of aluminium, titanium and magnesium are also known and valued for their high strength to weight ratios and, in the case of magnesium, their ability to provide electromagnetic shielding. these materials are ideal for situations where high strength to weight ratios are more important than bulk cost, such as in the aerospace industry and certain automotive engineering applications. = = = semiconductors = = = a semiconductor is a material that has a resistivity between a conductor and insulator. modern day electronics run on semiconductors, and the industry had an estimated us $ 530 billion market in 2021. its electronic properties can be greatly altered through intentionally introducing impurities in a process referred to as doping. semiconductor materials are used to build diodes, transistors, light - emitting diodes ( leds ), and analog and digital electric circuits, among their many uses. semiconductor devices have replaced thermionic devices like vacuum tubes in most applications. semiconductor devices are manufactured both as single discrete devices and as integrated circuits ( ics ), which consist of a number β from a
Question: Many natural rock formations change color over time. In Utah, for example, iron oxidized and formed red, orange, and yellow rock. Which of the following is the cause of this change?
A) chemical weathering
B) mechanical weathering
C) water erosion
D) wind erosion
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A) chemical weathering
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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
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
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
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 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
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
above any tidal limit and their average freshwater discharge are proportionate to the extent of their basins and the amount of rain which, after falling over these basins, reaches the river channels in the bottom of the valleys, by which it is conveyed to the sea. the drainage basin of a river is the expanse of country bounded by a watershed ( called a " divide " in north america ) over which rainfall flows down towards the river traversing the lowest part of the valley, whereas the rain falling on the far slope of the watershed flows away to another river draining an adjacent basin. river basins vary in extent according to the configuration of the country, ranging from the insignificant drainage areas of streams rising on high ground near the coast and flowing straight down into the sea, up to immense tracts of continents, where rivers rising on the slopes of mountain ranges far inland have to traverse vast stretches of valleys and plains before reaching the ocean. the size of the largest river basin of any country 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
in a diagram of metallicity ( \ ~ z ) vs. luminosity ( m $ _ b $ ), the different types of nearby ( z $ < 0. 05 $ ) starburst galaxies seem to follow the same linear relationship as the normal spiral and irregular galaxies. however, for comparable luminosities the more massive starburst nucleus galaxies ( sbngs ) show a slight metallic defficiency as compared to the giant spiral galaxies. furthermore, the sbngs do not seem to follow the same relationship between \ ~ z and hubble type ( t ) than the normal galaxies. the early - type sbngs are metal poor as compared to normal galaxies. it may suggests that the chemical evolution of a majority of the nearby starbursts galaxies is not completely over and that the present burst represent an important phase of this process.
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
the rapidly developing research field of organic analogue sensors aims to replace traditional semiconductors with naturally occurring materials. photosensors, or photodetectors, change their electrical properties in response to the light levels they are exposed to. organic photosensors can be functionalised to respond to specific wavelengths, from ultra - violet to red light. performing cyclic voltammetry on fungal mycelium and fruiting bodies under different lighting conditions shows no appreciable response to changes in lighting condition. however, functionalising the specimen using pedot : pss yields in a photosensor that produces large, instantaneous current spikes when the light conditions change. future works would look at interfacing this organic photosensor with an appropriate digital back - end for interpreting and processing the response.
Question: A population of small, plant-eating beetles lives in a forest. About half of the beetles are light brown and the others are dark green. If years of drought cause the area to become dry with few trees, what would the beetle population most likely look like after several generations?
A) It would be mostly light brown beetles.
B) It would be mostly dark green beetles.
C) It would be mostly carnivorous beetles.
D) It would be mostly very large beetles.
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A) It would be mostly light brown beetles.
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Context:
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
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
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
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
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 )
##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
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,
from the insignificant drainage areas of streams rising on high ground near the coast and flowing straight down into the sea, up to immense tracts of continents, where rivers rising on the slopes of mountain ranges far inland have to traverse vast stretches of valleys and plains before reaching the ocean. the size of the largest river basin of any country 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
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 (
Question: A scientist wanting to document a change in a river's flow pattern should observe a river over a period of
A) days.
B) weeks.
C) months.
D) years.
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D) years.
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Context:
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
, 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
vehicle crashes. fuel economy / emissions : fuel economy is the measured fuel efficiency of the vehicle in miles per gallon or kilometers per liter. emissions - testing covers the measurement of vehicle emissions, including hydrocarbons, nitrogen oxides ( nox ), carbon monoxide ( co ), carbon dioxide ( co2 ), and evaporative emissions. nvh engineering ( noise, vibration, and harshness ) : nvh involves customer feedback ( both tactile [ felt ] and audible [ heard ] ) concerning a vehicle. while sound can be interpreted as a rattle, squeal, or hot, a tactile response can be seat vibration or a buzz in the steering wheel. this feedback is generated by components either rubbing, vibrating, or rotating. nvh response can be classified in various ways : powertrain nvh, road noise, wind noise, component noise, and squeak and rattle. note, there are both good and bad nvh qualities. the nvh engineer works to either eliminate bad nvh or change the " bad nvh " to good ( i. e., exhaust tones ). vehicle electronics : automotive electronics is an increasingly important aspect of automotive engineering. modern vehicles employ dozens of electronic systems. these systems are responsible for operational controls such as the throttle, brake and steering controls ; as well as many comfort - and - convenience systems such as the hvac, infotainment, and lighting systems. it would not be possible for automobiles to meet modern safety and fuel - economy requirements without electronic controls. performance : performance is a measurable and testable value of a vehicle ' s ability to perform in various conditions. performance can be considered in a wide variety of tasks, but it generally considers how quickly a car can accelerate ( e. g. standing start 1 / 4 mile elapsed time, 0 β 60 mph, etc. ), its top speed, how short and quickly a car can come to a complete stop from a set speed ( e. g. 70 - 0 mph ), how much g - force a car can generate without losing grip, recorded lap - times, cornering speed, brake fade, etc. performance can also reflect the amount of control in inclement weather ( snow, ice, rain ). shift quality : shift quality is the driver ' s perception of the vehicle to an automatic transmission shift event. this is influenced by the powertrain ( internal combustion engine, transmission ), and the vehicle ( driveline, suspension, engine and power
and bad nvh qualities. the nvh engineer works to either eliminate bad nvh or change the " bad nvh " to good ( i. e., exhaust tones ). vehicle electronics : automotive electronics is an increasingly important aspect of automotive engineering. modern vehicles employ dozens of electronic systems. these systems are responsible for operational controls such as the throttle, brake and steering controls ; as well as many comfort - and - convenience systems such as the hvac, infotainment, and lighting systems. it would not be possible for automobiles to meet modern safety and fuel - economy requirements without electronic controls. performance : performance is a measurable and testable value of a vehicle ' s ability to perform in various conditions. performance can be considered in a wide variety of tasks, but it generally considers how quickly a car can accelerate ( e. g. standing start 1 / 4 mile elapsed time, 0 β 60 mph, etc. ), its top speed, how short and quickly a car can come to a complete stop from a set speed ( e. g. 70 - 0 mph ), how much g - force a car can generate without losing grip, recorded lap - times, cornering speed, brake fade, etc. performance can also reflect the amount of control in inclement weather ( snow, ice, rain ). shift quality : shift quality is the driver ' s perception of the vehicle to an automatic transmission shift event. this is influenced by the powertrain ( internal combustion engine, transmission ), and the vehicle ( driveline, suspension, engine and powertrain mounts, etc. ) shift feel is both a tactile ( felt ) and audible ( heard ) response of the vehicle. shift quality is experienced as various events : transmission shifts are felt as an upshift at acceleration ( 1 β 2 ), or a downshift maneuver in passing ( 4 β 2 ). shift engagements of the vehicle are also evaluated, as in park to reverse, etc. durability / corrosion engineering : durability and corrosion engineering is the evaluation testing of a vehicle for its useful life. tests include mileage accumulation, severe driving conditions, and corrosive salt baths. drivability : drivability is the vehicle ' s response to general driving conditions. cold starts and stalls, rpm dips, idle response, launch hesitations and stumbles, and performance levels all contribute to the overall drivability of any given vehicle. cost : the cost of a vehicle program is typically split into the effect
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
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 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
pumping. steam engines were too powerful for leather bellows, so cast iron blowing cylinders were developed in 1768. steam powered blast furnaces achieved higher temperatures, allowing the use of more lime in iron blast furnace feed. ( lime rich slag was not free - flowing at the previously used temperatures. ) with a sufficient lime ratio, sulfur from coal or coke fuel reacts with the slag so that the sulfur does not contaminate the iron. coal and coke were cheaper and more abundant fuel. as a result, iron production rose significantly during the last decades of the 18th century. coal converted to coke fueled higher temperature blast furnaces and produced cast iron in much larger amounts than before, allowing the creation of a range of structures such as the iron bridge. cheap coal meant that industry was no longer constrained by water resources driving the mills, although it continued as a valuable source of power. the steam engine helped drain the mines, so more coal reserves could be accessed, and the output of coal increased. the development of the high - pressure steam engine made locomotives possible, and a transport revolution followed. the steam engine which had existed since the early 18th century, was practically applied to both steamboat and railway transportation. the liverpool and manchester railway, the first purpose - built railway line, opened in 1830, the rocket locomotive of robert stephenson being one of its first working locomotives used. manufacture of ships ' pulley blocks by all - metal machines at the portsmouth block mills in 1803 instigated the age of sustained mass production. machine tools used by engineers to manufacture parts began in the first decade of the century, notably by richard roberts and joseph whitworth. the development of interchangeable parts through what is now called the american system of manufacturing began in the firearms industry at the u. s. federal arsenals in the early 19th century, and became widely used by the end of the century. until the enlightenment era, little progress was made in water supply and sanitation and the engineering skills of the romans were largely neglected throughout europe. the first documented use of sand filters to purify the water supply dates to 1804, when the owner of a bleachery in paisley, scotland, john gibb, installed an experimental filter, selling his unwanted surplus to the public. the first treated public water supply in the world was installed by engineer james simpson for the chelsea waterworks company in london in 1829. the first screw - down water tap was patented in 1845 by guest and chrimes, a brass foundry in rotherham. the practice of water treatment soon became mainstream,
the utility of jet spectroscopy at the lhc is compromised by the existence of multiple interactions within a bunch crossing. the energy deposits from these interactions at the design luminosity of the lhc may degrade the dijet mass resolution unless great care is taken. energy clusters making up the jet can be required to have an energy flow with respect to the jet axis which resembles qcd. in addition, subsidiary information such as the jet mass or the out of jet cone mass or transverse momentum can be deployed so as to alleviate the adverse effects of pileup.
high quality thread. the power loom was invented by edmund cartwright in 1787. in the mid - 1750s, the steam engine was applied to the water power - constrained iron, copper and lead industries for powering blast bellows. these industries were located near the mines, some of which were using steam engines for mine pumping. steam engines were too powerful for leather bellows, so cast iron blowing cylinders were developed in 1768. steam powered blast furnaces achieved higher temperatures, allowing the use of more lime in iron blast furnace feed. ( lime rich slag was not free - flowing at the previously used temperatures. ) with a sufficient lime ratio, sulfur from coal or coke fuel reacts with the slag so that the sulfur does not contaminate the iron. coal and coke were cheaper and more abundant fuel. as a result, iron production rose significantly during the last decades of the 18th century. coal converted to coke fueled higher temperature blast furnaces and produced cast iron in much larger amounts than before, allowing the creation of a range of structures such as the iron bridge. cheap coal meant that industry was no longer constrained by water resources driving the mills, although it continued as a valuable source of power. the steam engine helped drain the mines, so more coal reserves could be accessed, and the output of coal increased. the development of the high - pressure steam engine made locomotives possible, and a transport revolution followed. the steam engine which had existed since the early 18th century, was practically applied to both steamboat and railway transportation. the liverpool and manchester railway, the first purpose - built railway line, opened in 1830, the rocket locomotive of robert stephenson being one of its first working locomotives used. manufacture of ships ' pulley blocks by all - metal machines at the portsmouth block mills in 1803 instigated the age of sustained mass production. machine tools used by engineers to manufacture parts began in the first decade of the century, notably by richard roberts and joseph whitworth. the development of interchangeable parts through what is now called the american system of manufacturing began in the firearms industry at the u. s. federal arsenals in the early 19th century, and became widely used by the end of the century. until the enlightenment era, little progress was made in water supply and sanitation and the engineering skills of the romans were largely neglected throughout europe. the first documented use of sand filters to purify the water supply dates to 1804, when the owner of a bleachery in paisley, scotland, john gibb, installed an experimental filter, selling his unwanted
of the u. k. an unnamed third country is helping as well. according to a report, russia has provided critical help in the project. india ' s main defence - industrial partner is russia, which has carried out considerable research into hypersonic propulsion. the 1 - metric - ton, 5. 6 - meter - long ( 18 ft ) air vehicle under construction features a flattened octagonal cross section with mid - body stub - wings and raked tail fins and a 3. 7 - meter rectangular section air intake. the scramjet engine is located under the mid - body, with the aftbody serving as part of the exhaust nozzle. development work on the engine is also in progress. two parallel fences in the forebody are meant to reduce spillage and increase thrust. part span flaps are provided at the trailing edge of the wings for roll control. a deflectable nozzle cowl at the combustor end can deflect up to 25Β° to ensure satisfactory performance during power - off and power - on phases. surfaces of the airframe ' s bottom, wings and tail are made of titanium alloy, while aluminum alloy comprises the top surface. the inner surface of the double - wall engine is niobium alloy and the outer surface is nimonic alloy. due to technology denial of material for the scramjet engine, a new program was initiated and the materials were developed in - house. this led to self - sufficiency in the area and the scramjet engine was ground tested successfully for 20s instead of the initial 3s. in the 12 june 2019 test, the cruise vehicle was mounted on an agni - i solid rocket motor to take it to the required altitude. after the required altitude was reached and the mach was achieved, the cruise vehicle was ejected out of the launch vehicle. mid - air the scramjet engine was auto - ignited, and propelled the cruise vehicle at mach 6. drdo spent $ 30 million during design and development phase while $ 4. 5 million was spent on hstdv prototype development. = = testing = = = = = wind tunnel testing = = = a 1 : 16 scale model of the vehicle was tested at a hypersonic wind tunnel operated by israel aerospace industries. the isolated intake has been tested at a trisonic wind tunnel at india ' s national aerospace laboratory ( nal ) in bangalore. during the lab testing the scramjet engine was tested twice for 20s. a total of five to six tests are required before the test flight. the test flight was
Question: Automobile engines built today are designed to be gas efficient. Gas-efficient engines most likely affect a city by reducing
A) air pollution.
B) heat pollution.
C) noise pollution.
D) light pollution.
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A) air pollution.
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Context:
in this article i explain in detail a method for making small amounts of liquid oxygen in the classroom if there is no access to a cylinder of compressed oxygen gas. i also discuss two methods for identifying the fact that it is liquid oxygen as opposed to liquid nitrogen.
the motion of a pendulum is described as simple harmonic motion ( shm ) in case the initial displacement given is small. if we relax this condition then we observe the deviation from the shm. the equation of motion is non - linear and thus difficult to explain to under - graduate students. this manuscript tries to simplify things.
the qcd instanton can be observed at relatively low energies at nica collider by studying the spin - spin correlations between the incoming proton and the produced hyperons.
honorable rector, honorable professors, and students of this university : in these times of political and economic struggle and nationalistic fragmentation, it is a particular joy for me to see people assembling here to give their attention exclusively to the highest values that are common to us all. i am glad to be in this blessed land before a small circle of people who are interested in topics of science to speak on those issues that, in essence, are the subject of my own meditations.. [ abridged ].
, 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. it is reportedly the first school song to have been played in space. gregory peck sang the song while strumming a ukulele in the movie the man in the gray flannel suit. john wayne whistled it in the high and the mighty. tim holt ' s character sings a few bars of it in
language is a method by which individuals express their thoughts. each language has its own set of alphabetic and numeric characters. people can communicate with one another through either oral or written communication. however, each language has a sign language counterpart. individuals who are deaf and / or mute communicate through sign language. the bangla language also has a sign language, which is called bdsl. the dataset is about bangla hand sign images. the collection contains 49 individual bangla alphabet images in sign language. bdsl49 is a dataset that consists of 29, 490 images with 49 labels. images of 14 different adult individuals, each with a distinct background and appearance, have been recorded during data collection. several strategies have been used to eliminate noise from datasets during preparation. this dataset is available to researchers for free. they can develop automated systems using machine learning, computer vision, and deep learning techniques. in addition, two models were used in this dataset. the first is for detection, while the second is for recognition.
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
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 in 1990, the united kingdom in 1991, and both france and china continued testing until 1996. after signing the comprehensive test ban treaty in 1996 ( which had as of 2011 not entered into force ), all of these states have pledged to discontinue all nuclear testing. non - signatories india and pakistan last tested nuclear weapons in 1998. nuclear weapons are the most destructive weapons known - the archetypal weapons of mass destruction. throughout the cold war, the opposing powers had huge nuclear arsenals, sufficient to kill hundreds of millions of people. generations of people grew up under the shadow of nuclear devastation, portrayed in films such as dr. strangelove and the atomic cafe. however, the tremendous energy release in the detonation of a nuclear weapon also suggested the possibility of a new energy source. = = civilian uses = = = = = nuclear power = = = nuclear power is a type of nuclear technology involving the controlled use of nuclear fission to release energy for work including propulsion, heat, and the generation of electricity. nuclear energy is produced by a controlled nuclear chain reaction which creates heat β and which is used to boil water, produce steam, and drive a steam turbine. the turbine is used to generate electricity and / or to do mechanical work. currently nuclear power provides approximately 15. 7 % of the world ' s electricity ( in 2004 ) and is used to propel aircraft carriers, icebreakers and submarines ( so far economics and fears in some ports have prevented the use of nuclear power in transport ships ). all nuclear power plants use fission. no man - made fusion reaction has resulted in a viable source of electricity. = = = medical applications = = = the medical applications of nuclear technology are divided into diagnostics and radiation treatment. imaging - the largest use of ionizing radiation in medicine is in medical radiography to make images of the inside of the human body using x - rays. this
i have been asked to write brief, gentle introduction to the basic idea behind the field of " quantum gravity " in 1500 words or less. doing so appears to be almost as great a challenge as coming up with a consistent theory of quantum gravity. however, i will try. disclaimer : \ emph { the views expressed in this article are my own and do not represent the consensus of the quantum gravity community }.
some topics which can be easily explained to undergraduate students are presented, with elementary derivations. for a more systematic treatment of heavy - quark physics, see the textbook by manohar and wise.
Question: A student in an empty classroom shouts, "Hello!" Which best explains what the student hears after the shout?
A) an increased loudness of sound
B) a reflection of sound
C) an increased frequency of sound
D) a refraction of sound
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B) a reflection of sound
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Context:
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
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
, 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
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, 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
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
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
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
. 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. =
= = = 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 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
vehicle crashes. fuel economy / emissions : fuel economy is the measured fuel efficiency of the vehicle in miles per gallon or kilometers per liter. emissions - testing covers the measurement of vehicle emissions, including hydrocarbons, nitrogen oxides ( nox ), carbon monoxide ( co ), carbon dioxide ( co2 ), and evaporative emissions. nvh engineering ( noise, vibration, and harshness ) : nvh involves customer feedback ( both tactile [ felt ] and audible [ heard ] ) concerning a vehicle. while sound can be interpreted as a rattle, squeal, or hot, a tactile response can be seat vibration or a buzz in the steering wheel. this feedback is generated by components either rubbing, vibrating, or rotating. nvh response can be classified in various ways : powertrain nvh, road noise, wind noise, component noise, and squeak and rattle. note, there are both good and bad nvh qualities. the nvh engineer works to either eliminate bad nvh or change the " bad nvh " to good ( i. e., exhaust tones ). vehicle electronics : automotive electronics is an increasingly important aspect of automotive engineering. modern vehicles employ dozens of electronic systems. these systems are responsible for operational controls such as the throttle, brake and steering controls ; as well as many comfort - and - convenience systems such as the hvac, infotainment, and lighting systems. it would not be possible for automobiles to meet modern safety and fuel - economy requirements without electronic controls. performance : performance is a measurable and testable value of a vehicle ' s ability to perform in various conditions. performance can be considered in a wide variety of tasks, but it generally considers how quickly a car can accelerate ( e. g. standing start 1 / 4 mile elapsed time, 0 β 60 mph, etc. ), its top speed, how short and quickly a car can come to a complete stop from a set speed ( e. g. 70 - 0 mph ), how much g - force a car can generate without losing grip, recorded lap - times, cornering speed, brake fade, etc. performance can also reflect the amount of control in inclement weather ( snow, ice, rain ). shift quality : shift quality is the driver ' s perception of the vehicle to an automatic transmission shift event. this is influenced by the powertrain ( internal combustion engine, transmission ), and the vehicle ( driveline, suspension, engine and power
Question: Which type of energy in gasoline is transformed into mechanical energy in a motorcycle engine?
A) chemical
B) nuclear
C) magnetic
D) electrical
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A) chemical
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Context:
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
by charles darwin as " possibly the greatest ever made by man ". archaeological, dietary, and social evidence point to " continuous [ human ] fire - use " at least 1. 5 mya. fire, fueled with wood and charcoal, allowed early humans to cook their food to increase its digestibility, improving its nutrient value and broadening the number of foods that could be eaten. the cooking hypothesis proposes that the ability to cook promoted an increase in hominid brain size, though some researchers find the evidence inconclusive. archaeological evidence of hearths was dated to 790 kya ; researchers believe this is likely to have intensified human socialization and may have contributed to the emergence of language. other technological advances made during the paleolithic era include clothing and shelter. no consensus exists on the approximate time of adoption of either technology, but archaeologists have found archaeological evidence of clothing 90 - 120 kya and shelter 450 kya. as the paleolithic era progressed, dwellings became more sophisticated and more elaborate ; as early as 380 kya, humans were constructing temporary wood huts. clothing, adapted from the fur and hides of hunted animals, helped humanity expand into colder regions ; humans began to migrate out of africa around 200 kya, initially moving to eurasia. = = = neolithic = = = the neolithic revolution ( or first agricultural revolution ) brought about an acceleration of technological innovation, and a consequent increase in social complexity. the invention of the polished stone axe was a major advance that allowed large - scale forest clearance and farming. this use of polished stone axes increased greatly in the neolithic but was originally used in the preceding mesolithic in some areas such as ireland. agriculture fed larger populations, and the transition to sedentism allowed for the simultaneous raising of more children, as infants no longer needed to be carried around by nomads. additionally, children could contribute labor to the raising of crops more readily than they could participate in hunter - gatherer activities. with this increase in population and availability of labor came an increase in labor specialization. what triggered the progression from early neolithic villages to the first cities, such as uruk, and the first civilizations, such as sumer, is not specifically known ; however, the emergence of increasingly hierarchical social structures and specialized labor, of trade and war among adjacent cultures, and the need for collective action to overcome environmental challenges such as irrigation, are all thought to have played a role. the invention of writing led to the spread of cultural knowledge and became the basis for history, libraries, schools,
pumping. steam engines were too powerful for leather bellows, so cast iron blowing cylinders were developed in 1768. steam powered blast furnaces achieved higher temperatures, allowing the use of more lime in iron blast furnace feed. ( lime rich slag was not free - flowing at the previously used temperatures. ) with a sufficient lime ratio, sulfur from coal or coke fuel reacts with the slag so that the sulfur does not contaminate the iron. coal and coke were cheaper and more abundant fuel. as a result, iron production rose significantly during the last decades of the 18th century. coal converted to coke fueled higher temperature blast furnaces and produced cast iron in much larger amounts than before, allowing the creation of a range of structures such as the iron bridge. cheap coal meant that industry was no longer constrained by water resources driving the mills, although it continued as a valuable source of power. the steam engine helped drain the mines, so more coal reserves could be accessed, and the output of coal increased. the development of the high - pressure steam engine made locomotives possible, and a transport revolution followed. the steam engine which had existed since the early 18th century, was practically applied to both steamboat and railway transportation. the liverpool and manchester railway, the first purpose - built railway line, opened in 1830, the rocket locomotive of robert stephenson being one of its first working locomotives used. manufacture of ships ' pulley blocks by all - metal machines at the portsmouth block mills in 1803 instigated the age of sustained mass production. machine tools used by engineers to manufacture parts began in the first decade of the century, notably by richard roberts and joseph whitworth. the development of interchangeable parts through what is now called the american system of manufacturing began in the firearms industry at the u. s. federal arsenals in the early 19th century, and became widely used by the end of the century. until the enlightenment era, little progress was made in water supply and sanitation and the engineering skills of the romans were largely neglected throughout europe. the first documented use of sand filters to purify the water supply dates to 1804, when the owner of a bleachery in paisley, scotland, john gibb, installed an experimental filter, selling his unwanted surplus to the public. the first treated public water supply in the world was installed by engineer james simpson for the chelsea waterworks company in london in 1829. the first screw - down water tap was patented in 1845 by guest and chrimes, a brass foundry in rotherham. the practice of water treatment soon became mainstream,
igniting cornstarch powder is a classic physics demonstration that showcases the rapid conduction of heat for a material in which the surface area is greater than the volume of its constituent particles. including such a demonstration in a physics " magic show " for the general public presents certain challenges such as reproducibility and consistent crowd appeal. a simple but effective design for widely scattering cornstarch dust over a flame breaches these challenges and always results in consistently large, crowd - pleasing fireballs ; so much so that the resulting demonstration has been dubbed the " cornstarch flamethrower. " a small - scale version may also be used effectively for classroom instruction.
and error. around 2 mya ( million years ago ), they learned to make the first stone tools by hammering flakes off a pebble, forming a sharp hand axe. this practice was refined 75 kya ( thousand years ago ) into pressure flaking, enabling much finer work. the discovery of fire was described by charles darwin as " possibly the greatest ever made by man ". archaeological, dietary, and social evidence point to " continuous [ human ] fire - use " at least 1. 5 mya. fire, fueled with wood and charcoal, allowed early humans to cook their food to increase its digestibility, improving its nutrient value and broadening the number of foods that could be eaten. the cooking hypothesis proposes that the ability to cook promoted an increase in hominid brain size, though some researchers find the evidence inconclusive. archaeological evidence of hearths was dated to 790 kya ; researchers believe this is likely to have intensified human socialization and may have contributed to the emergence of language. other technological advances made during the paleolithic era include clothing and shelter. no consensus exists on the approximate time of adoption of either technology, but archaeologists have found archaeological evidence of clothing 90 - 120 kya and shelter 450 kya. as the paleolithic era progressed, dwellings became more sophisticated and more elaborate ; as early as 380 kya, humans were constructing temporary wood huts. clothing, adapted from the fur and hides of hunted animals, helped humanity expand into colder regions ; humans began to migrate out of africa around 200 kya, initially moving to eurasia. = = = neolithic = = = the neolithic revolution ( or first agricultural revolution ) brought about an acceleration of technological innovation, and a consequent increase in social complexity. the invention of the polished stone axe was a major advance that allowed large - scale forest clearance and farming. this use of polished stone axes increased greatly in the neolithic but was originally used in the preceding mesolithic in some areas such as ireland. agriculture fed larger populations, and the transition to sedentism allowed for the simultaneous raising of more children, as infants no longer needed to be carried around by nomads. additionally, children could contribute labor to the raising of crops more readily than they could participate in hunter - gatherer activities. with this increase in population and availability of labor came an increase in labor specialization. what triggered the progression from early neolithic villages to the first cities, such as uruk, and the first civilizations, such as sumer, is not specifically known ; however,
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
masculinity and warmth. the five phases β fire, earth, metal, wood, and water β described a cycle of transformations in nature. the water turned into wood, which turned into the fire when it burned. the ashes left by fire were earth. using these principles, chinese philosophers and doctors explored human anatomy, 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
ratio, sulfur from coal or coke fuel reacts with the slag so that the sulfur does not contaminate the iron. coal and coke were cheaper and more abundant fuel. as a result, iron production rose significantly during the last decades of the 18th century. coal converted to coke fueled higher temperature blast furnaces and produced cast iron in much larger amounts than before, allowing the creation of a range of structures such as the iron bridge. cheap coal meant that industry was no longer constrained by water resources driving the mills, although it continued as a valuable source of power. the steam engine helped drain the mines, so more coal reserves could be accessed, and the output of coal increased. the development of the high - pressure steam engine made locomotives possible, and a transport revolution followed. the steam engine which had existed since the early 18th century, was practically applied to both steamboat and railway transportation. the liverpool and manchester railway, the first purpose - built railway line, opened in 1830, the rocket locomotive of robert stephenson being one of its first working locomotives used. manufacture of ships ' pulley blocks by all - metal machines at the portsmouth block mills in 1803 instigated the age of sustained mass production. machine tools used by engineers to manufacture parts began in the first decade of the century, notably by richard roberts and joseph whitworth. the development of interchangeable parts through what is now called the american system of manufacturing began in the firearms industry at the u. s. federal arsenals in the early 19th century, and became widely used by the end of the century. until the enlightenment era, little progress was made in water supply and sanitation and the engineering skills of the romans were largely neglected throughout europe. the first documented use of sand filters to purify the water supply dates to 1804, when the owner of a bleachery in paisley, scotland, john gibb, installed an experimental filter, selling his unwanted surplus to the public. the first treated public water supply in the world was installed by engineer james simpson for the chelsea waterworks company in london in 1829. the first screw - down water tap was patented in 1845 by guest and chrimes, a brass foundry in rotherham. the practice of water treatment soon became mainstream, and the virtues of the system were made starkly apparent after the investigations of the physician john snow during the 1854 broad street cholera outbreak demonstrated the role of the water supply in spreading the cholera epidemic. = = = second industrial revolution ( 1860s β 1914 ) = = = the 19th century saw astonishing developments in transportation, construction,
within protogalaxies, thermal instability leads to the formation of a population of cool fragments, confined by the pressure of residual hot gas. the hot gas remains in quasi - hydrostatic equilibrium, at approximately the virial temperature of the dark matter halo. it is heated by compression and shock dissipation and is cooled by bremsstrahlung emission and conductive losses into the cool clouds. the cool fragments are photoionized and heated by the extragalactic uv background and nearby massive stars. the smallest clouds are evaporated due to conductive heat transfer from the hot gas. all are subject to disruption due to hydrodynamic instabilities. they also gain mass due to collisions and mergers and condensation from the hot gas due to conduction. the size distribution of the fragments in turn determines the rate and efficiency of star formation during the early phase of galactic evolution. we have performed one - dimensional hydrodynamic simulations of the evolution of the hot and cool gas. the cool clouds are assumed to follow a power - law size distribution, and fall into the galactic potential, subject to drag from the hot gas. the relative amounts of the hot and cool gas is determined by the processes discussed above, and star formation occurs at a rate sufficient to maintain the cool clouds at 10 $ ^ 4 $ k. we present density distributions for the two phases and also for the stars for several cases, parametrized by the circular speeds of the potentials. under some conditions, primarily low densities of the hot gas, conduction is more efficient than radiative processes at cooling the hot gas, limiting the x - ray radiation from the halo gas.
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 919, the siphon projector - pump was used to spread the ' fierce fire oil ' that could not be doused with water, as recorded by lin yu in his wuyue beishi, hence the first credible chinese reference to the flamethrower employing the chemical solution of greek fire ( see also pen huo qi ). : 81 lin yu mentioned also that the ' fierce fire oil ' derived ultimately from one of china ' s maritime contacts in the ' southern seas ', arabia dashiguo. : 82 in the battle of langshan jiang in 919, the naval fleet of the wenmu king from wuyue defeated a huainan army from the wu state ; wenmu ' s success was facilitated by the use of ' fire oil ' ( ' huoyou ' ) to burn their fleet, signifying the first chinese use of gunpowder in a battle. : 81 β 83 the chinese applied the use of double - piston bellows to pump petrol out of a single cylinder ( with an upstroke and downstroke ), lit at the end by a slow - burning gunpowder match to fire a continuous stream of flame. : 82 this device was featured in description and illustration of the wujing zongyao military manuscript of 1044. : 82 in the suppression of the southern tang state by 976, early song naval forces confronted them on the yangtze river in 975. southern tang forces attempted to use flamethrowers against the song navy, but were accidentally consumed by their own fire when violent winds swept in their direction. : 89 although the destructive effects of gunpowder were described in the earlier tang dynasty by a daoist alchemist, the earliest developments of the gun barrel and the projectile - fire cannon were found in late song china. the first art depiction of the chinese ' fire lance ' ( a combination of a temporary - fire flamethrower and gun ) was from a buddhist mural painting of dunhuang, dated circa 950. these ' fire - lances ' were widespread in use by the early 12th century, featuring hollowed bamboo poles as tubes to fire sand particles ( to blind and choke ), lead pellets, bits of sharp metal and pottery shards
Question: A student standing near a campfire feels warmer as the fire grows. Which process most likely transfers heat from the campfire to the student?
A) conduction
B) convection
C) radiation
D) transformation
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C) radiation
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Context:
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
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
. 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
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,
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
, 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
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
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,
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 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 o
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,
Question: In snapdragon plants, red flowers are dominant to white flowers. When red-flowered plants are crossed with white-flowered plants, pink flowers are produced. If a researcher wants to produce plants with only white flowers, what color should the parent plants be?
A) both red
B) both white
C) one red and one white
D) one white and one pink
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B) both white
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Context:
a detailed analysis of primordial nucleosynthesis predictions for light element abundances is performed. contents : 1. the standard cosmology : an overview. 2. primordial nucleosynthesis. 3. the born rates for n < - > p reactions. 4. finite nucleon mass corrections. 5. qed thermal radiative corrections. 6. calculations of big bang nucleosynthesis. results.
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.
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
we throw a brief glance at galois ' life, on the occasion of his 200th anniversary ( written in german ).
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
, 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
##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
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.
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.
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
Question: Scientists use the term "light year" to describe
A) how fast light travels in space.
B) the distance light travels in one year.
C) how large the diameters of different stars are.
D) the time it takes the Sun to move through the galaxy.
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B) the distance light travels in one year.
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Context:
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 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 '
##ctonics, 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 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
, 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
##morphology 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 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
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 ). "
##hosphere ) 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 ). " 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
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.
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 ). " 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 = = = = =
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
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: Plate movement can form different features on Earth. The movement of tectonic plates can be both a constructive and a destructive force. At which type of plate boundary is new crust formed?
A) convergent
B) subduction
C) transform
D) divergent
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D) divergent
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Context:
, 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
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
. 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
##ply 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 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.
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 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
##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
( 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. 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
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
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
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: Which group of organisms can show significant trait changes in the shortest period of time?
A) bacteria
B) birds
C) fish
D) reptiles
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A) bacteria
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Context:
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
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,
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 :
##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
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,
. 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
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
, 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. it is reportedly the first school song to have been played in space. gregory peck sang the song while strumming a ukulele in the movie the man in the gray flannel suit. john wayne whistled it in the high and the mighty. tim holt ' s character sings a few bars of it in
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
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
Question: Peach trees have sweet-smelling blossoms and produce rich fruit. What is the main purpose of the flowers of a peach tree?
A) to attract bees for pollination
B) to create flower arrangements
C) to protect the tree from disease
D) to feed migratory birds
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A) to attract bees for pollination
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Context:
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
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
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
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
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
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
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 ). " 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 = = = = =
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.
##hosphere ) 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 ). " 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
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
Question: A group of students are researching changes in climate in their region. Which of these would best provide evidence of changes in temperature and rainfall over a period of years?
A) tree rings
B) pollen samples
C) harvest production
D) carbon dating
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A) tree rings
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Context:
1975. skin tissue - engineered skin is a type of bioartificial organ that is often used to treat burns, diabetic foot ulcers, or other large wounds that cannot heal well on their own. artificial skin can be made from autografts, allografts, and xenografts. autografted skin comes from a patient ' s own skin, which allows the dermis to have a faster healing rate, and the donor site can be re - harvested a few times. allograft skin often comes from cadaver skin and is mostly used to treat burn victims. lastly, xenografted skin comes from animals and provides a temporary healing structure for the skin. they assist in dermal regeneration, but cannot become part of the host skin. tissue - engineered skin is now available in commercial products. integra, originally used to only treat burns, consists of a collagen matrix and chondroitin sulfate that can be used as a skin replacement. the chondroitin sulfate functions as a component of proteoglycans, which helps to form the extracellular matrix. integra can be repopulated and revascularized while maintaining its dermal collagen architecture, making it a bioartificial organ dermagraft, another commercial - made tissue - engineered skin product, is made out of living fibroblasts. these fibroblasts proliferate and produce growth factors, collagen, and ecm proteins, that help build granulation tissue. = = = = heart = = = = since the number of patients awaiting a heart transplant is continuously increasing over time, and the number of patients on the waiting list surpasses the organ availability, artificial organs used as replacement therapy for terminal heart failure would help alleviate this difficulty. artificial hearts are usually used to bridge the heart transplantation or can be applied as replacement therapy for terminal heart malfunction. the total artificial heart ( tah ), first introduced by dr. vladimir p. demikhov in 1937, emerged as an ideal alternative. since then it has been developed and improved as a mechanical pump that provides long - term circulatory support and replaces diseased or damaged heart ventricles that cannot properly pump the blood, restoring thus the pulmonary and systemic flow. some of the current tahs include abiocor, an fda - approved device that comprises two artificial ventricles and their valves, and does not require subcutaneous connections, and is indicated for
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, 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
applications continue to expand as researchers develop new kinds of ceramics to serve different purposes. zirconium dioxide ceramics are used in the manufacture of knives. the blade of the ceramic knife will stay sharp for much longer than that of a steel knife, although it is more brittle and can be snapped by dropping it on a hard surface. ceramics such as alumina, boron carbide and silicon carbide have been used in bulletproof vests to repel small arms rifle fire. such plates are known commonly as ballistic plates. similar material is used to protect cockpits of some military aircraft, because of the low weight of the 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
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
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
surface. ceramics such as alumina, boron carbide and silicon carbide have been used in bulletproof vests to repel small arms rifle fire. such plates are known commonly as ballistic plates. similar material is used to protect cockpits of some military aircraft, because of the low weight of the 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
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, 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
computer networking. coaxial cable is widely used for cable television systems, office buildings, and other work - sites for local area networks. transmission speed ranges from 200 million bits per second to more than 500 million bits per second. itu - t g. hn technology uses existing home wiring ( coaxial cable, phone lines and power lines ) to create a high - speed local area network. twisted pair cabling is used for wired ethernet and other standards. it typically consists of 4 pairs of copper cabling that can be utilized for both voice and data transmission. the use of two wires twisted together helps to reduce crosstalk and electromagnetic induction. the transmission speed ranges from 2 mbit / s to 10 gbit / s. twisted pair cabling comes in two forms : unshielded twisted pair ( utp ) and shielded twisted - pair ( stp ). each form comes in several category ratings, designed for use in various scenarios. an optical fiber is a glass fiber. it carries pulses of light that represent data via lasers and optical amplifiers. some advantages of optical fibers over metal wires are very low transmission loss and immunity to electrical interference. using dense wave division multiplexing, optical fibers can simultaneously carry multiple streams of data on different wavelengths of light, which greatly increases the rate that data can be sent to up to trillions of bits per second. optic fibers can be used for long runs of cable carrying very high data rates, and are used for undersea communications cables to interconnect continents. there are two basic types of fiber optics, single - mode optical fiber ( smf ) and multi - mode optical fiber ( mmf ). single - mode fiber has the advantage of being able to sustain a coherent signal for dozens or even a hundred kilometers. multimode fiber is cheaper to terminate but is limited to a few hundred or even only a few dozens of meters, depending on the data rate and cable grade. = = = wireless = = = network connections can be established wirelessly using radio or other electromagnetic means of communication. terrestrial microwave β terrestrial microwave communication uses earth - based transmitters and receivers resembling satellite dishes. terrestrial microwaves are in the low gigahertz range, which limits all communications to line - of - sight. relay stations are spaced approximately 40 miles ( 64 km ) apart. communications satellites β satellites also communicate via microwave. the satellites are stationed in space, typically in geosynchronous orbit 35, 400 km ( 22, 000 mi ) above the equator. these earth - orbiting systems are
, biomedical research, genetics, and medical technology to diagnose, treat, and prevent injury and disease, typically through pharmaceuticals or surgery, but also through therapies as diverse as psychotherapy, external splints and traction, medical devices, biologics, and ionizing radiation, amongst others. medicine has been practiced since prehistoric times, and for most of this time it was an art ( an area of creativity and skill ), frequently having connections to the religious and philosophical beliefs of local culture. for example, a medicine man would apply herbs and say prayers for healing, or an ancient philosopher and physician would apply bloodletting according to the theories of humorism. in recent centuries, since the advent of modern science, most medicine has become a combination of art and science ( both basic and applied, under the umbrella of medical science ). for example, while stitching technique for sutures is an art learned through practice, knowledge of what happens at the cellular and molecular level in the tissues being stitched arises through science. prescientific forms of medicine, now known as traditional medicine or folk medicine, remain commonly used in the absence of scientific medicine and are thus called alternative medicine. alternative treatments outside of scientific medicine with ethical, safety and efficacy concerns are termed quackery. = = etymology = = medicine ( uk :, us : ) is the science and practice of the diagnosis, prognosis, treatment, and prevention of disease. the word " medicine " is derived from latin medicus, meaning " a physician ". the word " physic " itself, from which " physician " derives, was the old word for what is now called a medicine, and also the field of medicine. = = clinical practice = = medical availability and clinical practice vary across the world due to regional differences in culture and technology. modern scientific medicine is highly developed in the western world, while in developing countries such as parts of africa or asia, the population may rely more heavily on traditional medicine with limited evidence and efficacy and no required formal training for practitioners. in the developed world, evidence - based medicine is not universally used in clinical practice ; for example, a 2007 survey of literature reviews found that about 49 % of the interventions lacked sufficient evidence to support either benefit or harm. in modern clinical practice, physicians and physician assistants personally assess patients to diagnose, prognose, treat, and prevent disease using clinical judgment. the doctor - patient relationship typically begins with an interaction with an examination of the patient ' s medical history and medical record
, phone lines and power lines ) to create a high - speed local area network. twisted pair cabling is used for wired ethernet and other standards. it typically consists of 4 pairs of copper cabling that can be utilized for both voice and data transmission. the use of two wires twisted together helps to reduce crosstalk and electromagnetic induction. the transmission speed ranges from 2 mbit / s to 10 gbit / s. twisted pair cabling comes in two forms : unshielded twisted pair ( utp ) and shielded twisted - pair ( stp ). each form comes in several category ratings, designed for use in various scenarios. an optical fiber is a glass fiber. it carries pulses of light that represent data via lasers and optical amplifiers. some advantages of optical fibers over metal wires are very low transmission loss and immunity to electrical interference. using dense wave division multiplexing, optical fibers can simultaneously carry multiple streams of data on different wavelengths of light, which greatly increases the rate that data can be sent to up to trillions of bits per second. optic fibers can be used for long runs of cable carrying very high data rates, and are used for undersea communications cables to interconnect continents. there are two basic types of fiber optics, single - mode optical fiber ( smf ) and multi - mode optical fiber ( mmf ). single - mode fiber has the advantage of being able to sustain a coherent signal for dozens or even a hundred kilometers. multimode fiber is cheaper to terminate but is limited to a few hundred or even only a few dozens of meters, depending on the data rate and cable grade. = = = wireless = = = network connections can be established wirelessly using radio or other electromagnetic means of communication. terrestrial microwave β terrestrial microwave communication uses earth - based transmitters and receivers resembling satellite dishes. terrestrial microwaves are in the low gigahertz range, which limits all communications to line - of - sight. relay stations are spaced approximately 40 miles ( 64 km ) apart. communications satellites β satellites also communicate via microwave. the satellites are stationed in space, typically in geosynchronous orbit 35, 400 km ( 22, 000 mi ) above the equator. these earth - orbiting systems are capable of receiving and relaying voice, data, and tv signals. cellular networks use several radio communications technologies. the systems divide the region covered into multiple geographic areas. each area is served by a low - power transceiver. radio and spread spectrum technologies β wireless lans use a high - frequency radio technology similar to
Question: Which of these would help to prevent infections from occurring in small cuts and scrapes?
A) apply a cold ice pack
B) raise the injured area
C) apply pressure to stop bleeding
D) wash the area with warm, soapy water
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D) wash the area with warm, soapy water
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Context:
a review of mhd dynamos and turbulence.
fluid dynamics video demonstrating the evolution of dynamic stall on a wind turbine blade.
masculinity and warmth. the five phases β fire, earth, metal, wood, and water β described a cycle of transformations in nature. the water turned into wood, which turned into the fire when it burned. the ashes left by fire were earth. using these principles, chinese philosophers and doctors explored human anatomy, 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
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 )
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
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
the purpose of this article is to view the penrose kite from the perspective of symplectic geometry.
a qualitative understanding of the day - night asymmetry for solar neutrinos is provided. the greater night flux in nu _ e is seen to be a consequence of the fact that the matter effect in the sun and that in the earth have the same sign. it is shown in the adiabatic approximation for the sun that for all values of the mixing angle theta _ v between 0 and pi / 2, the night flux of neutrinos is greater than the day flux. only for small values of theta _ v where the adiabatic approximation badly fails does the sign of the day - night asymmetry reverse.
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
Question: Which best describes why winds at the beach change direction between day and night?
A) because the temperatures over land and over water change
B) because warm air over land sinks and stays in place over land
C) because cool air rises and is replaced by warm air from the ocean
D) because cool air sinks and stays in place over land
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A) because the temperatures over land and over water change
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Context:
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
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
= = = = = = 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
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 )
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
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
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
##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
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
Question: Soil erosion can be best prevented by
A) removing grass from the steepest slope.
B) building terraces into the sides of a slope.
C) heavily watering the vegetation on the slope.
D) increasing the slope of the land by adding more soil.
|
B) building terraces into the sides of a slope.
|
Context:
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
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
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
##morphology 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 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
, 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
, 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 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
, 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
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
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. nickel - based superalloys like inconel are used in high - temperature applications such as gas turbines, turbochargers, pressure vessels, and heat exchangers. for extremely high temperatures, single crystal alloys are used to minimize creep. in modern electronics, high purity single crystal silicon is essential for metal - oxide - silicon transistors ( mos ) and integrated circuits. = = production = = in production engineering, metallurgy is concerned with the production of metallic components for use in consumer or engineering products. this involves production of alloys, shaping, heat treatment and surface treatment of product. the task of the metallurgist is to achieve balance between material properties, such as cost, weight, strength, toughness, hardness, corrosion, fatigue resistance and performance in temperature extremes. to achieve this goal, the operating environment must be carefully considered. determining the hardness of the metal using the rockwell, vickers, and brinell hardness scales
Question: Which of the following properties provides the BEST way to identify a mineral?
A) hardness
B) shape
C) size
D) temperature
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A) hardness
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Context:
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 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
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
##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
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,
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
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
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
, 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
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
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 :
Question: Which sequence represents the order of development for many plants?
A) seed develops inside fruit -> seed is dispersed -> seed germinates -> plant grows
B) seed is dispersed -> seed develops inside fruit -> seed germinates -> plant grows
C) seed germinates -> plant grows -> seed is dispersed -> seed develops inside fruit
D) seed is dispersed -> plant grows -> seed germinates -> seed develops inside fruit
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A) seed develops inside fruit -> seed is dispersed -> seed germinates -> plant grows
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the paper is withdrawn by the author because it is superseded by cond - mat / 0303357.
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
uv ice photodesorption is an important non - thermal desorption pathway in many interstellar environments that has been invoked to explain observations of cold molecules in disks, clouds and cloud cores. systematic laboratory studies of the photodesorption rates, between 7 and 14 ev, from co : n2 binary ices, have been performed at the desirs vacuum uv beamline of the synchrotron facility soleil. the photodesorption spectral analysis demonstrates that the photodesorption process is indirect, i. e. the desorption is induced by a photon absorption in sub - surface molecular layers, while only surface molecules are actually desorbing. the photodesorption spectra of co and n2 in binary ices therefore depend on the absorption spectra of the dominant species in the subsurface ice layer, which implies that the photodesorption efficiency and energy dependence are dramatically different for mixed and layered ices compared to pure ices. in particular, a thin ( 1 - 2 ml ) n2 ice layer on top of co will effectively quench co photodesorption, while enhancing n2 photodesorption by a factors of a few ( compared to the pure ices ) when the ice is exposed to a typical dark cloud uv field, which may help to explain the different distributions of co and n2h + in molecular cloud cores. this indirect photodesorption mechanism may also explain observations of small amounts of complex organics in cold interstellar environments.
, even if the idempotence property is lost. an everyday example of a projection is the casting of shadows onto a plane ( sheet of paper ) : the projection of a point is its shadow on the sheet of paper, and the projection ( shadow ) of a point on the sheet of paper is that point itself ( idempotency ). the shadow of a three - dimensional sphere is a disk. originally, the notion of projection was introduced in euclidean geometry to denote the projection of the three - dimensional euclidean space onto a plane in it, like the shadow example. the two main projections of this kind are : the projection from a point onto a plane or central projection : if c is a point, called the center of projection, then the projection of a point p different from c onto a plane that does not contain c is the intersection of the line cp with the plane. the points p such that the line cp is parallel to the plane does not have any image by the projection, but one often says that they project to a point at infinity of the plane ( see projective geometry for a formalization of this terminology ). the projection of the point c itself is not defined. the projection parallel to a direction d, onto a plane or parallel projection : the image of a point p is the intersection of the plane with the line parallel to d passing through p. see affine space Β§ projection for an accurate definition, generalized to any dimension. the concept of projection in mathematics is a very old one, and most likely has its roots in the phenomenon of the shadows cast by real - world objects on the ground. this rudimentary idea was refined and abstracted, first in a geometric context and later in other branches of mathematics. over time different versions of the concept developed, but today, in a sufficiently abstract setting, we can unify these variations. in cartography, a map projection is a map of a part of the surface of the earth onto a plane, which, in some cases, but not always, is the restriction of a projection in the above meaning. the 3d projections are also at the basis of the theory of perspective. the need for unifying the two kinds of projections and of defining the image by a central projection of any point different of the center of projection are at the origin of projective geometry. = = definition = = generally, a mapping where the domain and codomain are the same set ( or mathematical structure ) is a projection if the mapping is idempotent, which means that a projection is
necessary and sufficient conditions for a term to apply to an object. for example : " a platonic solid is a convex, regular polyhedron in three - dimensional euclidean space. " an extensional definition instead lists all objects where the term applies. for example : " a platonic solid is one of the following : tetrahedron, cube, octahedron, dodecahedron, or icosahedron. " in logic, the extension of a predicate is the set of all objects for which the predicate is true. further, the logical principle of extensionality judges two objects to objects to be equal if they satisfy the same external properties. since, by the axiom, two sets are defined to be equal if they satisfy membership, sets are extentional. jose ferreiros credits richard dedekind for being the first to explicitly state the principle, although he does not assert it as a definition : it very frequently happens that different things a, b, c... considered for any reason under a common point of view, are collected together in the mind, and one then says that they form a system s ; one calls the things a, b, c... the elements of the system s, they are contained in s ; conversely, s consists of these elements. such a system s ( or a collection, a manifold, a totality ), as an object of our thought, is likewise a thing ; it is completely determined when, for every thing, it is determined whether it is an element of s or not. = = = background = = = around the turn of the 20th century, mathematics faced several paradoxes and counter - intuitive results. for example, russell ' s paradox showed a contradiction of naive set theory, it was shown that the parallel postulate cannot be proved, the existence of mathematical objects that cannot be computed or explicitly described, and the existence of theorems of arithmetic that cannot be proved with peano arithmetic. the result was a foundational crisis of mathematics. the resolution of this crisis involved the rise of a new mathematical discipline called mathematical logic, which studies formal logic within mathematics. subsequent discoveries in the 20th century then stabilized the foundations of mathematics into a coherent framework valid for all mathematics. this framework is based on a systematic use of axiomatic method and on set theory, specifically zermelo β fraenkel set theory, developed by ernst zermelo and abraham fraenkel. this set theory ( and set theory in general ) is now considered the most common foundation of mathematics
basic properties of black holes are explained in terms of trapping horizons. it is shown that matter and information will escape from an evaporating black hole. a general scenario is outlined whereby a black hole evaporates completely without singularity, event horizon or loss of energy or information.
offended athenian audiences ; in this play, he speculated that the titular sorceress medea killed her own children, as opposed to their being killed by other corinthians after her departure. in historiography, what is now called speculative fiction has previously been termed historical invention, historical fiction, and similar names. these terms have been extensively applied in literary criticism to the works of william shakespeare. for example, in a midsummer night ' s dream, he places several characters from different locations and times into the fairyland of the fictional merovingian germanic sovereign oberon ; these characters include the athenian duke theseus, the amazonian queen hippolyta, the english fairy puck, and the roman god cupid. in mythography, the concept of speculative fiction has been termed mythopoesis or mythopoeia. this process involves the creative design and development of lore and mythology for works of fiction. the term ' s definition comes from use by j. r. r. tolkien ; his series of novels, the lord of the rings, shows an application of the process. themes common in mythopoeia, such as the supernatural, alternate history, and sexuality, continue to be explored in works produced in modern speculative fiction. speculative fiction in the general sense of hypothetical history, explanation, or ahistorical storytelling has been attributed to authors in ostensibly non - fiction modes since herodotus of halicarnassus ( fl. 5th century bce ) with his histories ; it was already both created and edited out by early encyclopedic writers such sima qian ( c. 145 or 135 bce β 86 bce ), author of shiji. these examples highlight a caveat β many works that are now viewed as speculative fiction long predated the labelling of the genre. in the broadest sense, the genre ' s concept does two things : it captures both conscious and unconscious aspects of human psychology in making sense of the world, and it responds to the world by creating imaginative, inventive, and artistic expressions. such expressions can contribute to practical societal progress through interpersonal influences ; social and cultural movements ; scientific research and advances ; and the philosophy of science. in english - language usage in arts and literature since the mid 20th century, the term speculative fiction has often been attributed to robert a. heinlein, who first used it in an editorial in the saturday evening post ( on 8 february 1947 ). in the article, heinlein used speculative fiction as a synonym for science fiction ; in
be reduced to three propositions : existence : there are mathematical objects. abstractness : mathematical objects are abstract. independence : mathematical objects are independent of intelligent agents and their language, thought, and practices. it is again not clear the extent to which plato held to these views himself but they were associated with the platonist school. nevertheless, this was a significant progression in the ideas of mathematicism. markus gabriel refers to plato in his fields of sense : a new realist ontology, and in so doing provides a definition for mathematicism. he says : ultimately, set - theoretical ontology is a remainder of platonic mathematicism. let mathematicism from here on be the view that everything that exists can be studied mathematically either directly or indirectly. it is an instance of theory - reduction, that is, a claim to the effect that every vocabulary can be translated into that of mathematics such that this reduction grounds all derivative vocabulary and helps us understand it significantly better. he goes on, however, to show that the term need not be applied merely to the set - theroetical ontology that he takes issue with, but for other mathematical ontologies. set - theoretical ontology is just one instance of mathematicism. depending on one ' s preferred candidate for the most fundamental theory of quantifiable structure, one can wind up with a graphtheoretical mathematicism, a set - theoretical, category - theoretical, or some other ( maybe hybrid ) form of mathematicism. however, mathematicism is metaphysics, and metaphysics need not be associated with ontology. = = rene descartes = = although mathematical methods of investigation have been used to establish meaning and analyse the world since pythagoras, it was descartes who pioneered the subject as epistemology, setting out rules for the direction of the mind. he proposed that method, rather than intuition, should direct the mind, saying : so blind is the curiosity with which mortals are possessed that they often direct their minds down untrodden paths, in the groundless hope that they will chance upon what they are seeking, rather like someone who is consumed with such a senseless desire to discover treasure that he continually roams the streets to see if he can find any that a passerby might have dropped [... ] by ' a method ' i mean reliable rules which are easy to apply, and such that if one follows them exactly, one will never take what
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, making pottery and glazes, fermenting beer and wine, extracting chemicals from plants for medicine and perfume, rendering fat into soap, making glass, and making alloys like bronze. chemistry was preceded by its protoscience, alchemy, which operated a non - scientific approach to understanding the constituents of matter and their interactions. despite being unsuccessful in explaining the nature of matter and its transformations, alchemists set the stage for modern chemistry by performing experiments and recording the results. robert boyle, although skeptical of elements and convinced of alchemy, played a key part in elevating the " sacred art " as an
various versions of club are shown to be different. a question of soukup, fuchino and juhasz, is it consistent to have a stick without club, is answered as a consequence. the more detailed version of the paper, which is coming up, also answers a question of galvin.
Question: When ice cream is left out of a freezer, the ice cream changes from a ___.
A) solid to a gas
B) gas to a liquid
C) solid to a liquid
D) liquid to a gas
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C) solid to a liquid
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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. nickel - based superalloys like inconel are used in high - temperature applications such as gas turbines, turbochargers, pressure vessels, and heat exchangers. for extremely high temperatures, single crystal alloys are used to minimize creep. in modern electronics, high purity single crystal silicon is essential for metal - oxide - silicon transistors ( mos ) and integrated circuits. = = production = = in production engineering, metallurgy is concerned with the production of metallic components for use in consumer or engineering products. this involves production of alloys, shaping, heat treatment and surface treatment of product. the task of the metallurgist is to achieve balance between material properties, such as cost, weight, strength, toughness, hardness, corrosion, fatigue resistance and performance in temperature extremes. to achieve this goal, the operating environment must be carefully considered. determining the hardness of the metal using the rockwell, vickers, and brinell hardness scales
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
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 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,
. historically, metallurgy has predominately focused on the production of metals. metal production begins with the processing of ores to extract the metal, and includes the mixture of metals to make alloys. metal alloys are often a blend of at least two different metallic elements. however, non - metallic elements are often added to alloys in order to achieve properties suitable for an application. the study of metal production is subdivided into ferrous metallurgy ( also known as black metallurgy ) and non - ferrous metallurgy, also known as colored metallurgy. ferrous metallurgy involves processes and alloys based on iron, while non - ferrous metallurgy involves processes and alloys based on other metals. the production of ferrous metals accounts for 95 % of world metal production. modern metallurgists work in both emerging and traditional areas as part of an interdisciplinary team alongside material scientists and other engineers. some traditional areas include mineral processing, metal production, heat treatment, failure analysis, and the joining of metals ( including welding, brazing, and soldering ). emerging areas for metallurgists include nanotechnology, superconductors, composites, biomedical materials, electronic materials ( semiconductors ) and surface engineering. = = etymology and pronunciation = = metallurgy derives from the ancient greek ΞΌΞ΅ΟαλλοΟ
ΟΞ³ΞΏΟ, metallourgos, " worker in metal ", from ΞΌΞ΅Οαλλον, metallon, " mine, metal " + Ξ΅ΟΞ³ΞΏΞ½, ergon, " work " the word was originally an alchemist ' s term for the extraction of metals from minerals, the ending - urgy signifying a process, especially manufacturing : it was discussed in this sense in the 1797 encyclopΓ¦dia britannica. in the late 19th century, metallurgy ' s definition was extended to the more general scientific study of metals, alloys, and related processes. in english, the pronunciation is the more common one in the united kingdom. the pronunciation is the more common one in the us and is the first - listed variant in various american dictionaries, including merriam - webster collegiate and american heritage. = = history = = the earliest metal employed by humans appears to be gold, which can be found " native ". small amounts of natural gold, dating to the late paleolithic period, 40, 000 bc, have been found in spanish caves. silver, copper, tin and meteoric iron
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
". = = 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
, 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
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. nickel - based superalloys like inconel are used in high - temperature applications such as gas turbines, turbochargers, pressure vessels, and heat exchangers. for extremely high temperatures, single crystal alloys are used to minimize creep. in modern electronics, high purity single crystal silicon is essential for metal - oxide - silicon transistors ( mos ) and integrated circuits. = = production = = in production engineering, metallurgy is concerned with the production of metallic components for use in consumer or engineering products. this involves production of alloys, shaping, heat treatment and surface treatment of product. the task of the metallurgist is to achieve balance between material properties, such as cost, weight, strength, toughness, hardness, corrosion, fatigue resistance and performance in temperature extremes. to achieve this goal, the operating environment must be carefully considered. determining the hardness of the metal using the rockwell, vickers, and brinell hardness scales is a commonly used practice that helps better understand the metal ' s elasticity and plasticity for different applications and production processes. in a saltwater environment, most ferrous metals and some non - ferrous alloys corrode quickly. metals exposed to cold or cryogenic conditions may undergo a ductile to brittle
##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
Question: Which equipment will best separate a mixture of iron filings and black pepper?
A) magnet
B) filter paper
C) triple-beam balance
D) voltmeter
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A) magnet
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Context:
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
##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
. 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
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
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
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
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. 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
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
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 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,
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: Which characteristic is shared by all cells?
A) They need energy.
B) They reproduce sexually.
C) They make their own food.
D) They move from place to place.
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A) They need energy.
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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.
in a diagram of metallicity ( \ ~ z ) vs. luminosity ( m $ _ b $ ), the different types of nearby ( z $ < 0. 05 $ ) starburst galaxies seem to follow the same linear relationship as the normal spiral and irregular galaxies. however, for comparable luminosities the more massive starburst nucleus galaxies ( sbngs ) show a slight metallic defficiency as compared to the giant spiral galaxies. furthermore, the sbngs do not seem to follow the same relationship between \ ~ z and hubble type ( t ) than the normal galaxies. the early - type sbngs are metal poor as compared to normal galaxies. it may suggests that the chemical evolution of a majority of the nearby starbursts galaxies is not completely over and that the present burst represent an important phase of this process.
##m 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. 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
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
##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
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,
accept that deflection effects in materials with roughly equiaxial grains may increase the fracture toughness by about twice the grain boundary value. the model reveals that the increase in toughness is dependent on particle shape and the volume fraction of the second phase, with the most effective morphology being the rod of high aspect ratio, which can account for a fourfold increase in fracture toughness. the toughening arises primarily from the twist of the crack front between particles, as indicated by deflection profiles. disc - shaped particles and spheres are less effective in toughening. fracture toughness, regardless of morphology, is determined by the twist of the crack front at its most severe configuration, rather than the initial tilt of the crack front. only for disc - shaped particles does the initial tilting of the crack front provide significant toughening ; however, the twist component still overrides the tilt - derived toughening. additional important features of the deflection analysis include the appearance of asymptotic toughening for the three morphologies at volume fractions in excess of 0. 2. it is also noted that a significant influence on the toughening by spherical particles is exerted by the interparticle spacing distribution ; greater toughening is afforded when spheres are nearly contacting such that twist angles approach Ο / 2. these predictions provide the basis for the design of high - toughness two - phase ceramic materials. the ideal second phase, in addition to maintaining chemical compatibility, should be present in amounts of 10 to 20 volume percent. greater amounts may diminish the toughness increase due to overlapping particles. particles with high aspect ratios, especially those with rod - shaped morphologies, are most suitable for maximum toughening. this model is often used to determine the factors that contribute to the increase in fracture toughness in ceramics which is ultimately useful in the development of advanced ceramic materials with improved performance. = = theory of chemical processing = = = = = microstructural uniformity = = = in the processing of fine ceramics, the irregular particle sizes and shapes in a typical powder often lead to non - uniform packing morphologies that result in packing density variations in the powder compact. uncontrolled agglomeration of powders due to attractive van der waals forces can also give rise to in microstructural inhomogeneities. differential stresses that develop as a result of non - uniform drying shrinkage are directly related to the rate at which the solvent can be removed, and thus highly dependent upon the
the magellanic clouds were known before magellan ' s voyage exactly 500 years ago, and were not given that name by magellan himself or his chronicler antonio pigafetta. they were, of course, already known by local populations in south america, such as the mapuche and tupi - guaranis. the portuguese called them clouds of the cape, and scientific circles had long used the name of nubecula minor and major. we trace how and when the name magellanic clouds came into common usage by following the history of exploration of the southern hemisphere and the southern sky by european explorers. while the name of magellan was quickly associated to the strait he discovered ( within about 20 years only ), the clouds got their final scientific name only at the end of the 19th century, when scientists finally abandoned latin as their communication language.
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.
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.
Question: On a small, isolated island, a hurricane destroyed all the trees that produced a large, hard-shelled nut. Which bird population would most likely decrease?
A) birds with long, probing beaks
B) birds with thick, strong beaks
C) birds with thin, short beaks
D) birds with large, pouch beaks
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B) birds with thick, strong beaks
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Context:
##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
( 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 than animals. genetic evidence suggests that the true evolutionary relationship of multicelled organisms is as shown in the cladogram below β fungi are more closely related to animals than to plants. in 1998, the angiosperm phylogeny group published a phylogeny for flowering plants based on an analysis of
interaction between tannin and bovine serum albumin ( bsa ) was examined by the fluorescent quenching. the process of elimination between bsa and tannin was the one of a stationary state, and the coupling coefficient was one. the working strength between the tannin and the beef serum was hydrophobic one.
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
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 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,
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
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
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 % carbon. stainless steel is defined as a regular steel alloy with greater than 10 % by weight alloying content of chromium. nickel and molybdenum are typically also added in stainless steels. other significant metallic alloys are those of aluminium, titanium, copper and magnesium. copper alloys have been known for a long time ( since the bronze age ), while the alloys of the other three metals have been relatively recently developed. due to the chemical reactivity of these metals, the electrolytic extraction processes required were only developed relatively recently. the alloys of aluminium, titanium and magnesium are also known and valued for their high strength to weight ratios and, in the case of magnesium, their ability to provide electromagnetic shielding. these materials are ideal for situations where high strength to weight ratios are more important than bulk cost, such as in the aerospace industry and certain automotive engineering applications. = = = semiconductors = = = a semiconductor is a material that has a resistivity between a conductor and insulator. modern day electronics run on semiconductors, and the industry had an estimated us $ 530 billion market in 2021. its electronic properties can be greatly altered through intentionally introducing impurities in a process referred to as doping. semiconductor materials are used to build diodes, transistors, light - emitting diodes ( leds ), and analog and digital electric circuits, among their many uses. semiconductor devices have replaced thermionic devices like vacuum tubes in most applications. semiconductor devices are manufactured both as single discrete devices and as integrated circuits ( ics ), which consist of a number β from a
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
time interval between the incident and scattered photon in raman effect and absorption of photon and emission of electron in photoelectric effect has not been determined till now. this is because there is no such high level instrument discovered till now to detect time interval to such a small level. but this can be calculated theoretically by applying a basic principle of physics like impulse is equal to the change in momentum. considering the collision between electron and photon as perfect inelastic collision in photoelectric effect, elastic and inelastic collision in raman effect and elastic collision in plane mirror reflection and the interaction between electron and photon as strong gravitational interaction we calculate the required time interval. during these phenomena there is lattice vibration which can be quantized as phonon particles.
Question: A cow and a frog have similar bone structures in their forelimbs. Both have phalanges, radius, ulna, and humerus bones. However, the cow and frog are animals with very different life cycles from each other. Which most likely describes why the body structures of these animals are so similar?
A) Both have undergone similar mutations.
B) Both descended from a common ancestor.
C) Both reacted similarly to environmental pressures.
D) Both spread out from the same geographical region.
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B) Both descended from a common ancestor.
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Context:
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
= = = 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 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
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
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
. 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
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
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
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
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
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 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 '
Question: A cell that is unable to import substances required to process chemical energy is most likely a result of a malfunctioning
A) cell membrane.
B) endoplasmic reticulum.
C) Golgi body.
D) nuclear envelope.
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A) cell membrane.
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Context:
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 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
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.
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
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 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
. 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
, 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 ",
##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.
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 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,
, 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
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
Question: Which best describes all unicellular organisms?
A) Every cell is round.
B) Every cell can make food.
C) Every cell can move on its own.
D) Every cell performs all life functions.
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D) Every cell performs all life functions.
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Context:
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.
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.
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
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.
the relations among the components of the exit momenta of ultrarelativistic electrons scattered on a strong electromagnetic wave of a low ( optical ) frequency and linear polarization are established using the exact solutions to the equations of motion with radiation reaction included ( the landau - lifshitz equation ). it is found that the momentum components of the electrons traversed the electromagnetic wave depend weakly on the initial values of the momenta. these electrons are mostly scattered at the small angles to the direction of propagation of the electromagnetic wave. the maximum lorentz factor of the electrons crossed the electromagnetic wave is proportional to the work done by the electromagnetic field and is independent of the initial momenta. the momentum component parallel to the electric field strength vector of the electromagnetic wave is determined only by the diameter of the laser beam measured in the units of the classical electron radius. as for the reflected electrons, they for the most part lose the energy, but remain relativistic. there is a reflection law for these electrons that relates the incident and the reflection angles and is independent of any parameters.
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
, 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
are combined in the proper order into one bitstream. many other types of modulation are also used. in some types, the carrier wave is suppressed, and only one or both modulation sidebands are transmitted. the modulated carrier is amplified in the transmitter and applied to a transmitting antenna which radiates the energy as 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,
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
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: When a transverse wave passes from right to left through a medium, what happens to the particles of the medium?
A) Particles travel from right to left along the wave.
B) Particles travel from left to right along the wave.
C) Particles move back and forth parallel to the wave.
D) Particles move back and forth perpendicular to the wave.
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D) Particles move back and forth perpendicular to the wave.
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Context:
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.
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.
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.
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.
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.
one of the greatest discoveries of modern times is that of the expanding universe, almost invariably attributed to hubble ( 1929 ). what is not widely known is that the original treatise by lemaitre ( 1927 ) contained a rich fusion of both theory and of observation. stiglers law of eponymy is yet again affirmed : no scientific discovery is named after its original discoverer ( merton, 1957 ). an appeal is made for a lemaitre telescope, to honour the discoverer of the expanding universe.
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.
the origin of the arc - shaped stellar complexes in the lmc4 region is still unknown. these perfect arcs could not have been formed by o - stars and sne in their centers ; the strong arguments exist also against the possibility of their formation from infalling gas clouds. the origin from microquasars / grb jets is not excluded, because there is the strong concentration of x - ray binaries in the same region and the massive old cluster ngc 1978, probable site of formation of binaries with compact components, is there also. the last possibility is that the source of energy for formation of the stellar arcs and the lmc4 supershell might be the the giant jet from the nucleus of the milky way, which might be active a dozen myr ago.
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.
Question: Which characteristic below most likely accounts for our limited knowledge of galaxies?
A) their tiny size
B) their magnetic cores
C) their inability to produce light
D) their great distance from Earth
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D) their great distance from Earth
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Context:
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
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
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 crops. = = = medicine = = = in medicine, modern biotechnology has many applications in areas such as pharmaceutical drug discoveries and production, pharmacogenomics, and genetic testing ( or genetic screening ). in 2021, nearly 40 % of the total company value of pharmaceutical biotech companies worldwide were active in oncology
anticommutative engel algebras of the first five degeneration levels are classified. all algebras appearing in this classification are nilpotent malcev algebras.
the decomposition theorem is deduced from local purity.
##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
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
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
= = = = = = 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
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. 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
Question: Decomposers increase the fertility of the soil and prevent dead organisms from building up in the environment. In which way do decomposers make the soil more fertile?
A) by adding carbon
B) by adding nitrogen
C) by removing excess water
D) by removing excess minerals
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B) by adding nitrogen
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Context:
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,
= = 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
ammonium hydrosulphide has long since been postulated to exist at least in certain layers of the giant planets. its radiation products may be the reason for the red colour seen on jupiter. several ammonium salts, the products of nh3 and an acid, have previously been detected at comet 67p / churyumov - gerasimenko. the acid h2s is the fifth most abundant molecule in the coma of 67p followed by nh3. in order to look for the salt nh4 + sh -, we analysed in situ measurements from the rosetta / rosina double focusing mass spectrometer during the rosetta mission. nh3 and h2s appear to be independent of each other when sublimating directly from the nucleus. however, we observe a strong correlation between the two species during dust impacts, clearly pointing to the salt. we find that nh4 + sh - is by far the most abundant salt, more abundant in the dust impacts than even water. we also find all previously detected ammonium salts and for the first time ammonium fluoride. the amount of ammonia and acids balance each other, confirming that ammonia is mostly in the form of salt embedded into dust grains. allotropes s2 and s3 are strongly enhanced in the impacts, while h2s2 and its fragment hs2 are not detected, which is most probably the result of radiolysis of nh4 + sh -. this makes a prestellar origin of the salt likely. our findings may explain the apparent depletion of nitrogen in comets and maybe help to solve the riddle of the missing sulphur in star forming regions.
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, 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
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, 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 (
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
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.
##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
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, 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
Question: When oxygen combines with hydrogen, which substance is formed?
A) water
B) vinegar
C) hydrochloric acid
D) hydrogen dioxide
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A) water
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Context:
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
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
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
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
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.
= = = 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 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
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
. 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
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
Question: When plants undergo photosynthesis, a reaction produces sugar, oxygen, and water. During respiration, stored energy from the products of photosynthesis is converted to usable energy. In what form is the energy stored prior to use in respiration?
A) chemical energy
B) kinetic energy
C) light energy
D) heat energy
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A) chemical energy
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Context:
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 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
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.
. 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
are dreidels fair? in other words, does the average dreidel have an equal chance of turning up any one of its four sides? to explore this hypothesis, three different dreidels were each spun hundreds of times with the number of occurrences of each side recorded. it was found that all three dreidels tested - - a cheap plastic dreidel, an old wooden dreidel, and a dreidel that came embossed with a picture of santa claus - - were not fair. statistically, for each dreidel, some sides came up significantly more often than others. although an unfair dreidel does not necessarily make the game itself unfair, it is conjectured that hundreds of pounds of chocolate have been distributed during chanukah under false pretenses.
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 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
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
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 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,
the gravitational waves are non - physical sinuosities generated, in the last analysis, by undulating reference frames.
##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.
, 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 ",
Question: Which of the following is a typical example of a unicellular organism?
A) earthworm
B) bacteria
C) fungi
D) green algae
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B) bacteria
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Context:
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.
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 ). "
##hosphere ) 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 ). " 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
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
from the insignificant drainage areas of streams rising on high ground near the coast and flowing straight down into the sea, up to immense tracts of continents, where rivers rising on the slopes of mountain ranges far inland have to traverse vast stretches of valleys and plains before reaching the ocean. the size of the largest river basin of any country 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
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
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 ). " 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 = = = = =
##sphere ( 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 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
above any tidal limit and their average freshwater discharge are proportionate to the extent of their basins and the amount of rain which, after falling over these basins, reaches the river channels in the bottom of the valleys, by which it is conveyed to the sea. the drainage basin of a river is the expanse of country bounded by a watershed ( called a " divide " in north america ) over which rainfall flows down towards the river traversing the lowest part of the valley, whereas the rain falling on the far slope of the watershed flows away to another river draining an adjacent basin. river basins vary in extent according to the configuration of the country, ranging from the insignificant drainage areas of streams rising on high ground near the coast and flowing straight down into the sea, up to immense tracts of continents, where rivers rising on the slopes of mountain ranges far inland have to traverse vast stretches of valleys and plains before reaching the ocean. the size of the largest river basin of any country 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
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?
Question: Over geologic time, global mean sea level has varied significantly. Which change is most likely responsible for an increase in global mean sea level?
A) erosion of sediment from a mountain range
B) mass extinction of marine organisms
C) formation of an ocean trench
D) melting of polar ice caps
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D) melting of polar ice caps
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Context:
= = = = = = 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
##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
". = = 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
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
( 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 -
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
, 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
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 "
porosimetry are utilized. = = introduction = = membrane technology covers all engineering approaches for the transport of substances between two fractions with the help of semi - permeable membranes. in general, mechanical separation processes for separating gaseous or liquid streams use membrane technology. in recent years, different methods have been used to remove environmental pollutants, like adsorption, oxidation, and membrane separation. different pollution occurs in the environment like air pollution, waste water pollution etc. as per industry requirement to prevent industrial pollution because more than 70 % of environmental pollution occurs due to industries. it is their responsibility to follow government rules of the air pollution control & prevention act 1981 to maintain and prevent the harmful chemical release into the environment. make sure to do prevention & safety processes after that industries are able to release their waste in the environment. biomass - based membrane technology is one of the most promising technologies for use as a pollutants removal weapon because it has low cost, more efficiency, & lack of secondary pollutants. typically polysulfone, polyvinylidene fluoride, and polypropylene are used in the membrane preparation process. these membrane materials are non - renewable and non - biodegradable which create harmful environmental pollution. researchers are trying to find a solution to synthesize an eco - friendly membrane which avoids environmental pollution. synthesis of biodegradable material with the help of naturally available material such as biomass - based membrane synthesis can be used to remove pollutants. = = = membrane overview = = = membrane separation processes operate without heating and therefore 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 macro
Question: Which body system is most responsible for the removal of waste?
A) skeletal system
B) nervous system
C) muscular system
D) excretory system
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D) excretory system
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Context:
the status of the theory of color confinemnt is discussed.
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 vacuum chamber, and cured - pyrolized to convert the furfuryl alcohol to carbon. to provide oxidation resistance for reusability, the outer layers of the rcc are converted to silicon carbide. other examples can be seen in the " plastic " casings of television sets, cell - phones and 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.
an extended polya urn model with two colors, black and white, is studied with some slln and clt on the proportion of white balls.
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
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 vacuum chamber, and cured - pyrolized to convert the furfuryl alcohol to carbon. to provide oxidation resistance for reusability, the outer layers of the rcc are converted to silicon carbide. other examples can be seen in the " plastic " casings of television sets, cell - phones and 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
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, 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 abiot
the influence of a neutrinoless electron to positron conversion on a cooling of strongly magnetized iron white dwarfs is studied.
the creation of your own reality and your own world. the metaphor i used was humans being like magic markers. for so long, they painted black and white pictures in their life because that ' s all they thought they could do. but they can paint with a different color and make a very vibrant and beautiful picture if they take control. on the single " new skin ", he further elaborated : in " new skin ", i attribute a scab to the present state of society. the way the scab looks in its worst state is gross and chaotic and horrible, that ' s now, but when it breaks away, there ' s a brand new piece of skin that ' s stronger than before. it ' s like creation out of chaos. the song " favorite things ", according to boyd, related to the topic of religion : " my favorite things " is my personal beliefs about religion and how it oppresses the things i enjoy the most. unfortunately, the simplest things, such as thinking for myself, creating my own reality and being whatever the hell i want to be each day of my life, are a sin. to be a good christian basically means to give up the reigns of your life and let some unseen force do it for you. " favorite things " also includes a sample of the 1959 track " flamenco fantasy ", by easy listening group the 101 strings orchestra. the song has a similar title to " my favorite things ", from the mary poppins musical and film, with both songs repeatedly mentioning their titles in the lyrics. however, it does not musically reference " my favorite things ". the single " a certain shade of green " has been described as being a song about procrastination. the line " are you gonna stand around till 2012 a. d.? " is a reference to an interpretation of the mayan calendar which dictated that the world would end on december 21, 2012. boyd did not believe this to be true, but it was on his mind as his mother was researching it for a book called maya memory : the glory that was palenque. while recording " nebula ", boyd said in 1997, " we found out what it ' s like to actually plug a phaser pedal into the wall while it ' s on. it sounds like a laser gun, and that ' s the first sound you hear in ' nebula '. " he added that for the song, " we used these walkie - talkies for children that have this slinky - like coil between them. when
the status of our understanding of the mechanisms of color confinement is reviewed, in particular the results of numerical simulations on the lattice.
the luminescence properties of the colloidal hybrid si - ni nanoparticles system fabricated in the pure water by pulsed laser ablation is considered. the red - shifted photoluminescence of this system because of the stark effect in the coulomb field of the charged ni nanoparticles has been registered in the blue range of the spectrum.
Question: In which environment is white fur color an advantage for survival?
A) desert
B) grassland
C) arctic tundra
D) temperate forest
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C) arctic tundra
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Context:
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. nickel - based superalloys like inconel are used in high - temperature applications such as gas turbines, turbochargers, pressure vessels, and heat exchangers. for extremely high temperatures, single crystal alloys are used to minimize creep. in modern electronics, high purity single crystal silicon is essential for metal - oxide - silicon transistors ( mos ) and integrated circuits. = = production = = in production engineering, metallurgy is concerned with the production of metallic components for use in consumer or engineering products. this involves production of alloys, shaping, heat treatment and surface treatment of product. the task of the metallurgist is to achieve balance between material properties, such as cost, weight, strength, toughness, hardness, corrosion, fatigue resistance and performance in temperature extremes. to achieve this goal, the operating environment must be carefully considered. determining the hardness of the metal using the rockwell, vickers, and brinell hardness scales
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
##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
". = = 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
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
some references for the breaking strength of fused silica fibers compiled in 1999.
various versions of club are shown to be different. a question of soukup, fuchino and juhasz, is it consistent to have a stick without club, is answered as a consequence. the more detailed version of the paper, which is coming up, also answers a question of galvin.
, 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
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
##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: Which of these will best separate iron filings from sand?
A) water
B) a magnifying glass
C) a magnet
D) rubbing alcohol
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C) a magnet
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Context:
is further subdivided into two broad categories : chemical metallurgy and physical metallurgy. chemical metallurgy is chiefly concerned with the reduction and oxidation of metals, and the chemical performance of metals. subjects of study in chemical metallurgy include mineral processing, the extraction of metals, thermodynamics, electrochemistry, and chemical degradation ( corrosion ). in contrast, physical metallurgy focuses on the mechanical properties of metals, the physical properties of metals, and the physical performance of metals. topics studied in physical metallurgy include crystallography, material characterization, mechanical metallurgy, phase transformations, and failure mechanisms. historically, metallurgy has predominately focused on the production of metals. metal production begins with the processing of ores to extract the metal, and includes the mixture of metals to make alloys. metal alloys are often a blend of at least two different metallic elements. however, non - metallic elements are often added to alloys in order to achieve properties suitable for an application. the study of metal production is subdivided into ferrous metallurgy ( also known as black metallurgy ) and non - ferrous metallurgy, also known as colored metallurgy. ferrous metallurgy involves processes and alloys based on iron, while non - ferrous metallurgy involves processes and alloys based on other metals. the production of ferrous metals accounts for 95 % of world metal production. modern metallurgists work in both emerging and traditional areas as part of an interdisciplinary team alongside material scientists and other engineers. some traditional areas include mineral processing, metal production, heat treatment, failure analysis, and the joining of metals ( including welding, brazing, and soldering ). emerging areas for metallurgists include nanotechnology, superconductors, composites, biomedical materials, electronic materials ( semiconductors ) and surface engineering. = = etymology and pronunciation = = metallurgy derives from the ancient greek ΞΌΞ΅ΟαλλοΟ
ΟΞ³ΞΏΟ, metallourgos, " worker in metal ", from ΞΌΞ΅Οαλλον, metallon, " mine, metal " + Ξ΅ΟΞ³ΞΏΞ½, ergon, " work " the word was originally an alchemist ' s term for the extraction of metals from minerals, the ending - urgy signifying a process, especially manufacturing : it was discussed in this sense in the 1797 encyclopΓ¦dia britannica. in the late 19th century, metallurgy '
in products for both consumers and manufacturers. metallurgy is distinct from the craft of metalworking. metalworking relies on metallurgy in a similar manner to how medicine relies on medical science for technical advancement. a specialist practitioner of metallurgy is known as a metallurgist. the science of metallurgy is further subdivided into two broad categories : chemical metallurgy and physical metallurgy. chemical metallurgy is chiefly concerned with the reduction and oxidation of metals, and the chemical performance of metals. subjects of study in chemical metallurgy include mineral processing, the extraction of metals, thermodynamics, electrochemistry, and chemical degradation ( corrosion ). in contrast, physical metallurgy focuses on the mechanical properties of metals, the physical properties of metals, and the physical performance of metals. topics studied in physical metallurgy include crystallography, material characterization, mechanical metallurgy, phase transformations, and failure mechanisms. historically, metallurgy has predominately focused on the production of metals. metal production begins with the processing of ores to extract the metal, and includes the mixture of metals to make alloys. metal alloys are often a blend of at least two different metallic elements. however, non - metallic elements are often added to alloys in order to achieve properties suitable for an application. the study of metal production is subdivided into ferrous metallurgy ( also known as black metallurgy ) and non - ferrous metallurgy, also known as colored metallurgy. ferrous metallurgy involves processes and alloys based on iron, while non - ferrous metallurgy involves processes and alloys based on other metals. the production of ferrous metals accounts for 95 % of world metal production. modern metallurgists work in both emerging and traditional areas as part of an interdisciplinary team alongside material scientists and other engineers. some traditional areas include mineral processing, metal production, heat treatment, failure analysis, and the joining of metals ( including welding, brazing, and soldering ). emerging areas for metallurgists include nanotechnology, superconductors, composites, biomedical materials, electronic materials ( semiconductors ) and surface engineering. = = etymology and pronunciation = = metallurgy derives from the ancient greek ΞΌΞ΅ΟαλλοΟ
ΟΞ³ΞΏΟ, metallourgos, " worker in metal ", from ΞΌΞ΅Οαλλον, metallon, " mine, metal " + Ξ΅ΟΞ³ΞΏΞ½, ergon
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. nickel - based superalloys like inconel are used in high - temperature applications such as gas turbines, turbochargers, pressure vessels, and heat exchangers. for extremely high temperatures, single crystal alloys are used to minimize creep. in modern electronics, high purity single crystal silicon is essential for metal - oxide - silicon transistors ( mos ) and integrated circuits. = = production = = in production engineering, metallurgy is concerned with the production of metallic components for use in consumer or engineering products. this involves production of alloys, shaping, heat treatment and surface treatment of product. the task of the metallurgist is to achieve balance between material properties, such as cost, weight, strength, toughness, hardness, corrosion, fatigue resistance and performance in temperature extremes. to achieve this goal, the operating environment must be carefully considered. determining the hardness of the metal using the rockwell, vickers, and brinell hardness scales is a commonly used practice that helps better understand the metal ' s elasticity and plasticity for different applications and production processes. in a saltwater environment, most ferrous metals and some non - ferrous alloys corrode quickly. metals exposed to cold or cryogenic conditions may undergo a ductile to brittle transition and lose their toughness, becoming more brittle and prone to cracking. metals under continual cyclic loading can suffer from metal fatigue. metals under constant stress at elevated temperatures can creep. = = = metalworking processes = = = casting β molten metal is poured into a shaped mold. variants of casting include sand casting, investment
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. nickel - based superalloys like inconel are used in high - temperature applications such as gas turbines, turbochargers, pressure vessels, and heat exchangers. for extremely high temperatures, single crystal alloys are used to minimize creep. in modern electronics, high purity single crystal silicon is essential for metal - oxide - silicon transistors ( mos ) and integrated circuits. = = production = = in production engineering, metallurgy is concerned with the production of metallic components for use in consumer or engineering products. this involves production of alloys, shaping, heat treatment and surface treatment of product. the task of the metallurgist is to achieve balance between material properties, such as cost, weight, strength, toughness, hardness, corrosion, fatigue resistance and performance in temperature extremes. to achieve this goal, the operating environment must be carefully considered. determining the hardness of the metal using the rockwell, vickers, and brinell hardness scales is a commonly used practice that helps better understand the metal ' s elasticity and plasticity for different applications and production processes. in a saltwater environment, most ferrous metals and some non - ferrous alloys corrode quickly. metals exposed to cold or cryogenic conditions may undergo a ductile to brittle
##chemistry, and chemical degradation ( corrosion ). in contrast, physical metallurgy focuses on the mechanical properties of metals, the physical properties of metals, and the physical performance of metals. topics studied in physical metallurgy include crystallography, material characterization, mechanical metallurgy, phase transformations, and failure mechanisms. historically, metallurgy has predominately focused on the production of metals. metal production begins with the processing of ores to extract the metal, and includes the mixture of metals to make alloys. metal alloys are often a blend of at least two different metallic elements. however, non - metallic elements are often added to alloys in order to achieve properties suitable for an application. the study of metal production is subdivided into ferrous metallurgy ( also known as black metallurgy ) and non - ferrous metallurgy, also known as colored metallurgy. ferrous metallurgy involves processes and alloys based on iron, while non - ferrous metallurgy involves processes and alloys based on other metals. the production of ferrous metals accounts for 95 % of world metal production. modern metallurgists work in both emerging and traditional areas as part of an interdisciplinary team alongside material scientists and other engineers. some traditional areas include mineral processing, metal production, heat treatment, failure analysis, and the joining of metals ( including welding, brazing, and soldering ). emerging areas for metallurgists include nanotechnology, superconductors, composites, biomedical materials, electronic materials ( semiconductors ) and surface engineering. = = etymology and pronunciation = = metallurgy derives from the ancient greek ΞΌΞ΅ΟαλλοΟ
ΟΞ³ΞΏΟ, metallourgos, " worker in metal ", from ΞΌΞ΅Οαλλον, metallon, " mine, metal " + Ξ΅ΟΞ³ΞΏΞ½, ergon, " work " the word was originally an alchemist ' s term for the extraction of metals from minerals, the ending - urgy signifying a process, especially manufacturing : it was discussed in this sense in the 1797 encyclopΓ¦dia britannica. in the late 19th century, metallurgy ' s definition was extended to the more general scientific study of metals, alloys, and related processes. in english, the pronunciation is the more common one in the united kingdom. the pronunciation is the more common one in the us and is the first - listed variant in various american dictionaries, including merriam - webster collegiate
metallurgy is a domain of materials science and engineering that studies the physical and chemical behavior of metallic elements, their inter - metallic compounds, and their mixtures, which are known as alloys. metallurgy encompasses both the science and the technology of metals, including the production of metals and the engineering of metal components used in products for both consumers and manufacturers. metallurgy is distinct from the craft of metalworking. metalworking relies on metallurgy in a similar manner to how medicine relies on medical science for technical advancement. a specialist practitioner of metallurgy is known as a metallurgist. the science of metallurgy is further subdivided into two broad categories : chemical metallurgy and physical metallurgy. chemical metallurgy is chiefly concerned with the reduction and oxidation of metals, and the chemical performance of metals. subjects of study in chemical metallurgy include mineral processing, the extraction of metals, thermodynamics, electrochemistry, and chemical degradation ( corrosion ). in contrast, physical metallurgy focuses on the mechanical properties of metals, the physical properties of metals, and the physical performance of metals. topics studied in physical metallurgy include crystallography, material characterization, mechanical metallurgy, phase transformations, and failure mechanisms. historically, metallurgy has predominately focused on the production of metals. metal production begins with the processing of ores to extract the metal, and includes the mixture of metals to make alloys. metal alloys are often a blend of at least two different metallic elements. however, non - metallic elements are often added to alloys in order to achieve properties suitable for an application. the study of metal production is subdivided into ferrous metallurgy ( also known as black metallurgy ) and non - ferrous metallurgy, also known as colored metallurgy. ferrous metallurgy involves processes and alloys based on iron, while non - ferrous metallurgy involves processes and alloys based on other metals. the production of ferrous metals accounts for 95 % of world metal production. modern metallurgists work in both emerging and traditional areas as part of an interdisciplinary team alongside material scientists and other engineers. some traditional areas include mineral processing, metal production, heat treatment, failure analysis, and the joining of metals ( including welding, brazing, and soldering ). emerging areas for metallurgists include nanotechnology, superconductors, composites, biomedical materials, electronic materials ( semiconductors ) and surface engineering
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.
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 are studied in chemistry are usually the result of interactions between atoms, leading to rearrangements of the chemical bonds which hold atoms together. such behaviors are studied in a chemistry laboratory. the chemistry laboratory stereotypically uses various forms of laboratory glassware. however glassware is not central to chemistry, and a great deal of experimental ( as well as applied / industrial ) chemistry is done without it. a chemical reaction is a transformation of some substances into one or more different substances. the basis of such a chemical transformation is the rearrangement of electrons in the chemical bonds between atoms. it can be symbolically depicted through a chemical equation, which usually involves atoms as subjects. the number of atoms on the left and the right in the equation for a chemical transformation is equal. ( when the number of atoms on either side is unequal, the transformation is referred to as a nuclear reaction or radioactive decay. ) the type of chemical reactions a substance may undergo and the energy changes that may accompany it are constrained by certain basic rules, known as chemical laws. energy and entropy considerations are invariably important in almost all chemical studies. chemical substances are classified in terms of their structure, phase, as well as their chemical compositions. they can be analyzed using the tools of chemical analysis, e. 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 = = = =
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. nickel - based superalloys like inconel are used in high - temperature applications such as gas turbines, turbochargers, pressure vessels, and heat exchangers. for extremely high temperatures, single crystal alloys are used to minimize creep. in modern electronics, high purity single crystal silicon is essential for metal - oxide - silicon transistors ( mos ) and integrated circuits. = = production = = in production engineering, metallurgy is concerned with the production of metallic components for use in consumer or engineering products. this involves production of alloys, shaping, heat treatment and surface treatment of product. the task of the metallurgist is to achieve balance between material properties, such as cost, weight, strength, toughness, hardness, corrosion, fatigue resistance and performance in temperature extremes. to achieve this goal, the operating environment must be carefully considered. determining the hardness of the metal using the rockwell, vickers, and brinell hardness scales
". = = 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
Question: Which of these is the chemical symbol for magnesium?
A) Ma
B) Mg
C) Mn
D) Mu
|
B) Mg
|
Context:
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
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
i reject the following null hypothesis : { h0 : your data are normal }. such drastic decision is motivated by theoretical reasons, and applies to your current data, the past ones, and the future ones. while this situation may appear embarrassing, it does not invalidate any of your results. moreover, it allows to save time and energy that are currently spent in vain by performing the following unnecessary tasks : ( i ) carrying out normality tests ; ( ii ) pretending to do something if normality is rejected ; and ( iii ) arguing about normality with referee # 2.
a binary 1 - error - correcting code can always be embedded in a 1 - perfect code of some larger length
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
the theoretical reasons at the root of ligo ' s experimental failure in searching gravitational waves ( gw ' s ) from binary black hole ( bbh ) inspirals.
this article is withdrawn because of a mistake in the main result of the paper.
reference to recent papers and experimental feasibility are added. the paper will not be published in a hard - copy journal.
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
expected to seek consilience β fitting with other accepted facts related to an observation or scientific question. this tentative explanation is used to make falsifiable predictions, which are typically posted before being tested by experimentation. disproof of a prediction is evidence of progress. : 4 β 5 experimentation is especially important in science to help establish causal relationships to avoid the correlation fallacy, though in some sciences such as astronomy or geology, a predicted observation might be more appropriate. when a hypothesis proves unsatisfactory it is modified or discarded. if the hypothesis survives testing, it may become adopted into the framework of a scientific theory, a validly reasoned, self - consistent model or framework for describing the behaviour of certain natural events. a theory typically describes the behaviour of much broader sets of observations than a hypothesis ; commonly, a large number of hypotheses can be logically bound together by a single theory. thus, a theory is a hypothesis explaining various other hypotheses. in that vein, theories are formulated according to most of the same scientific principles as hypotheses. scientists may generate a model, an attempt to describe or depict an observation in terms of a logical, physical or mathematical representation, and to generate new hypotheses that can be tested by experimentation. while performing experiments to test hypotheses, scientists may have a preference for one outcome over another. eliminating the bias can be achieved through transparency, careful experimental design, and a thorough peer review process of the experimental results and conclusions. after the results of an experiment are announced or published, it is normal practice for independent researchers to double - check how the research was performed, and to follow up by performing similar experiments to determine how dependable the results might be. taken in its entirety, the scientific method allows for highly creative problem solving while minimising the effects of subjective and confirmation bias. intersubjective verifiability, the ability to reach a consensus and reproduce results, is fundamental to the creation of all scientific knowledge. = = = scientific literature = = = scientific research is published in a range of literature. scientific journals communicate and document the results of research carried out in universities and various other research institutions, serving as an archival record of science. the first scientific journals, journal des scavans followed by philosophical transactions, began publication in 1665. since that time the total number of active periodicals has steadily increased. in 1981, one estimate for the number of scientific and technical journals in publication was 11, 500. most scientific journals cover a
Question: Which of the following is most likely to lead to error in an experiment?
A) bias
B) repeated trials
C) peer review
D) use of a control
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A) bias
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Context:
; 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 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
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
vehicle crashes. fuel economy / emissions : fuel economy is the measured fuel efficiency of the vehicle in miles per gallon or kilometers per liter. emissions - testing covers the measurement of vehicle emissions, including hydrocarbons, nitrogen oxides ( nox ), carbon monoxide ( co ), carbon dioxide ( co2 ), and evaporative emissions. nvh engineering ( noise, vibration, and harshness ) : nvh involves customer feedback ( both tactile [ felt ] and audible [ heard ] ) concerning a vehicle. while sound can be interpreted as a rattle, squeal, or hot, a tactile response can be seat vibration or a buzz in the steering wheel. this feedback is generated by components either rubbing, vibrating, or rotating. nvh response can be classified in various ways : powertrain nvh, road noise, wind noise, component noise, and squeak and rattle. note, there are both good and bad nvh qualities. the nvh engineer works to either eliminate bad nvh or change the " bad nvh " to good ( i. e., exhaust tones ). vehicle electronics : automotive electronics is an increasingly important aspect of automotive engineering. modern vehicles employ dozens of electronic systems. these systems are responsible for operational controls such as the throttle, brake and steering controls ; as well as many comfort - and - convenience systems such as the hvac, infotainment, and lighting systems. it would not be possible for automobiles to meet modern safety and fuel - economy requirements without electronic controls. performance : performance is a measurable and testable value of a vehicle ' s ability to perform in various conditions. performance can be considered in a wide variety of tasks, but it generally considers how quickly a car can accelerate ( e. g. standing start 1 / 4 mile elapsed time, 0 β 60 mph, etc. ), its top speed, how short and quickly a car can come to a complete stop from a set speed ( e. g. 70 - 0 mph ), how much g - force a car can generate without losing grip, recorded lap - times, cornering speed, brake fade, etc. performance can also reflect the amount of control in inclement weather ( snow, ice, rain ). shift quality : shift quality is the driver ' s perception of the vehicle to an automatic transmission shift event. this is influenced by the powertrain ( internal combustion engine, transmission ), and the vehicle ( driveline, suspension, engine and power
a measurable and testable value of a vehicle ' s ability to perform in various conditions. performance can be considered in a wide variety of tasks, but it generally considers how quickly a car can accelerate ( e. g. standing start 1 / 4 mile elapsed time, 0 β 60 mph, etc. ), its top speed, how short and quickly a car can come to a complete stop from a set speed ( e. g. 70 - 0 mph ), how much g - force a car can generate without losing grip, recorded lap - times, cornering speed, brake fade, etc. performance can also reflect the amount of control in inclement weather ( snow, ice, rain ). shift quality : shift quality is the driver ' s perception of the vehicle to an automatic transmission shift event. this is influenced by the powertrain ( internal combustion engine, transmission ), and the vehicle ( driveline, suspension, engine and powertrain mounts, etc. ) shift feel is both a tactile ( felt ) and audible ( heard ) response of the vehicle. shift quality is experienced as various events : transmission shifts are felt as an upshift at acceleration ( 1 β 2 ), or a downshift maneuver in passing ( 4 β 2 ). shift engagements of the vehicle are also evaluated, as in park to reverse, etc. durability / corrosion engineering : durability and corrosion engineering is the evaluation testing of a vehicle for its useful life. tests include mileage accumulation, severe driving conditions, and corrosive salt baths. drivability : drivability is the vehicle ' s response to general driving conditions. cold starts and stalls, rpm dips, idle response, launch hesitations and stumbles, and performance levels all contribute to the overall drivability of any given vehicle. cost : the cost of a vehicle program is typically split into the effect on the variable cost of the vehicle, and the up - front tooling and fixed costs associated with developing the vehicle. there are also costs associated with warranty reductions and marketing. program timing : to some extent programs are timed with respect to the market, and also to the production - schedules of assembly plants. any new part in the design must support the development and manufacturing schedule of the model. design for manufacturability ( dfm ) : dfm refers to designing vehicular components in such a way that they are not only feasible to manufacture, but also such that they are cost - efficient to produce while resulting in acceptable
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 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
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 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
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
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
, buses, trucks, etc. it includes branch study of mechanical, electronic, software and safety elements. some of the engineering attributes and disciplines that are of importance to the automotive engineer include : safety engineering : safety engineering is the assessment of various crash scenarios and their impact on the vehicle occupants. these are tested against very stringent governmental regulations. some of these requirements include : seat belt and air bag functionality testing, front and side - impact testing, and tests of rollover resistance. assessments are done with various methods and tools, including computer crash simulation ( typically finite element analysis ), crash - test dummy, and partial system sled and full vehicle crashes. fuel economy / emissions : fuel economy is the measured fuel efficiency of the vehicle in miles per gallon or kilometers per liter. emissions - testing covers the measurement of vehicle emissions, including hydrocarbons, nitrogen oxides ( nox ), carbon monoxide ( co ), carbon dioxide ( co2 ), and evaporative emissions. nvh engineering ( noise, vibration, and harshness ) : nvh involves customer feedback ( both tactile [ felt ] and audible [ heard ] ) concerning a vehicle. while sound can be interpreted as a rattle, squeal, or hot, a tactile response can be seat vibration or a buzz in the steering wheel. this feedback is generated by components either rubbing, vibrating, or rotating. nvh response can be classified in various ways : powertrain nvh, road noise, wind noise, component noise, and squeak and rattle. note, there are both good and bad nvh qualities. the nvh engineer works to either eliminate bad nvh or change the " bad nvh " to good ( i. e., exhaust tones ). vehicle electronics : automotive electronics is an increasingly important aspect of automotive engineering. modern vehicles employ dozens of electronic systems. these systems are responsible for operational controls such as the throttle, brake and steering controls ; as well as many comfort - and - convenience systems such as the hvac, infotainment, and lighting systems. it would not be possible for automobiles to meet modern safety and fuel - economy requirements without electronic controls. performance : performance is a measurable and testable value of a vehicle ' s ability to perform in various conditions. performance can be considered in a wide variety of tasks, but it generally considers how quickly a car can accelerate ( e. g. standing start 1 / 4 mile elapsed time, 0 β 60 mph, etc. )
5g cellular network β next - generation cellular networks which began deployment in 2019. their major advantage is much higher data rates than previous cellular networks, up to 10 gbps ; 100 times faster than the previous cellular technology, 4g lte. the higher data rates are achieved partly by using higher frequency radio waves, in the higher microwave band 3 β 6 ghz, and millimeter wave band, around 28 and 39 ghz. since these frequencies have a shorter range than previous cellphone bands, the cells will be smaller than the cells in previous cellular networks which could be many miles across. millimeter - wave cells will only be a few blocks long, and instead of a cell base station and antenna tower, they will have many small antennas attached to utility poles and buildings. satellite phone ( satphone ) β a portable wireless telephone similar to a cell phone, connected to the telephone network through a radio link to an orbiting communications satellite instead of through cell towers. they are more expensive than cell phones ; but their advantage is that, unlike a cell phone which is limited to areas covered by cell towers, satphones can be used over most or all of the geographical area of the earth. in order for the phone to communicate with a satellite using a small omnidirectional antenna, first - generation systems use satellites in low earth orbit, about 400 β 700 miles ( 640 β 1, 100 km ) above the surface. with an orbital period of about 100 minutes, a satellite can only be in view of a phone for about 4 β 15 minutes, so the call is " handed off " to another satellite when one passes beyond the local horizon. therefore, large numbers of satellites, about 40 to 70, are required to ensure that at least one satellite is in view continuously from each point on earth. other satphone systems use satellites in geostationary orbit in which only a few satellites are needed, but these cannot be used at high latitudes because of terrestrial interference. cordless phone β a landline telephone in which the handset is portable and communicates with the rest of the phone by a short - range full duplex radio link, instead of being attached by a cord. both the handset and the base station have low - power radio transceivers that handle the short - range bidirectional radio link. as of 2022, cordless phones in most nations use the dect transmission standard. land mobile radio system β short - range mobile or portable half - duplex radio transceivers operating in the vhf or uhf
Question: Which best describes transportation technology?
A) a system that is used to move people and products
B) an enterprise that changes raw materials into goods
C) the building and finishing of structures
D) the conversion of mechanical energy into heat energy
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A) a system that is used to move people and products
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Context:
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 (
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
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
. 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 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
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 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.
are studied in chemistry are usually the result of interactions between atoms, leading to rearrangements of the chemical bonds which hold atoms together. such behaviors are studied in a chemistry laboratory. the chemistry laboratory stereotypically uses various forms of laboratory glassware. however glassware is not central to chemistry, and a great deal of experimental ( as well as applied / industrial ) chemistry is done without it. a chemical reaction is a transformation of some substances into one or more different substances. the basis of such a chemical transformation is the rearrangement of electrons in the chemical bonds between atoms. it can be symbolically depicted through a chemical equation, which usually involves atoms as subjects. the number of atoms on the left and the right in the equation for a chemical transformation is equal. ( when the number of atoms on either side is unequal, the transformation is referred to as a nuclear reaction or radioactive decay. ) the type of chemical reactions a substance may undergo and the energy changes that may accompany it are constrained by certain basic rules, known as chemical laws. energy and entropy considerations are invariably important in almost all chemical studies. chemical substances are classified in terms of their structure, phase, as well as their chemical compositions. they can be analyzed using the tools of chemical analysis, e. 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
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
, 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 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
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
vehicle crashes. fuel economy / emissions : fuel economy is the measured fuel efficiency of the vehicle in miles per gallon or kilometers per liter. emissions - testing covers the measurement of vehicle emissions, including hydrocarbons, nitrogen oxides ( nox ), carbon monoxide ( co ), carbon dioxide ( co2 ), and evaporative emissions. nvh engineering ( noise, vibration, and harshness ) : nvh involves customer feedback ( both tactile [ felt ] and audible [ heard ] ) concerning a vehicle. while sound can be interpreted as a rattle, squeal, or hot, a tactile response can be seat vibration or a buzz in the steering wheel. this feedback is generated by components either rubbing, vibrating, or rotating. nvh response can be classified in various ways : powertrain nvh, road noise, wind noise, component noise, and squeak and rattle. note, there are both good and bad nvh qualities. the nvh engineer works to either eliminate bad nvh or change the " bad nvh " to good ( i. e., exhaust tones ). vehicle electronics : automotive electronics is an increasingly important aspect of automotive engineering. modern vehicles employ dozens of electronic systems. these systems are responsible for operational controls such as the throttle, brake and steering controls ; as well as many comfort - and - convenience systems such as the hvac, infotainment, and lighting systems. it would not be possible for automobiles to meet modern safety and fuel - economy requirements without electronic controls. performance : performance is a measurable and testable value of a vehicle ' s ability to perform in various conditions. performance can be considered in a wide variety of tasks, but it generally considers how quickly a car can accelerate ( e. g. standing start 1 / 4 mile elapsed time, 0 β 60 mph, etc. ), its top speed, how short and quickly a car can come to a complete stop from a set speed ( e. g. 70 - 0 mph ), how much g - force a car can generate without losing grip, recorded lap - times, cornering speed, brake fade, etc. performance can also reflect the amount of control in inclement weather ( snow, ice, rain ). shift quality : shift quality is the driver ' s perception of the vehicle to an automatic transmission shift event. this is influenced by the powertrain ( internal combustion engine, transmission ), and the vehicle ( driveline, suspension, engine and power
Question: In a gasoline-powered car, chemical energy from gasoline is transformed to make the car move. The motion of the car is what form of energy?
A) radiant energy
B) nuclear energy
C) electrical energy
D) mechanical energy
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D) mechanical energy
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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
= = = = = = 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
##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
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 weak value of a variable o is a description of an effective interaction with that variable in the limit of weak coupling. it is particularly important for a pre - and post - selected quantum system.
have you ever typed particularly powerful on your keyboard, maybe even harsh, to write and send a message with some emphasis of your emotional state or message? did it work? probably not. it didn ' t affect how you typed or interacted with your mouse. but what if you had other, connected devices, with other modalities for inputs and outputs? which would you have chosen, and how would you characterize your interactions with them? we researched with our multisensory and multimodal tool, the loaded dice, in co - design workshops the design space of iot usage scenarios : what interaction qualities users want, characterized using an interaction vocabulary, and how they might map them to a selection of sensors and actuators. we discuss based on our experience some thoughts of such a mapping.
examples are given of the usefulness of electrons in interaction with nuclei for probing fundamental interactions and structure
it is perceived as a threat or manageable obstacle ) ; finally, the ' x ' indicates the crisis ( the overall experience and response to the stressor that either strengthens or weakens families / couples ). see figure 1. in 1977, 1979, and 1986, urie bronfenbrenner published a model that integrated the multiple different levels or domains of an individual ' s environment. it was first developed to apply to child development, but has been widely applied in relationship science. the first level is the microsystem, which contains the single, immediate context people or dyads ( e. g., couple, parent - child, friends ) directly find themselves in β such as a home, school, or work. the second level is the mesosystem, which considers the combined effects of two or more contexts / settings. the third level is the exosystem, which also considers the effects of two or more contexts, but specifically contains at least one context that the individual or dyad is not directly in ( e. g., government, social services ) but affects an environment they are directly in ( e. g., home, work ). the fourth level is the macrosystem, which is the broader cultural and social attitudes that affect an individual. finally, the chronosystem is the broadest level that is specifically the dimension of time as it relates to an individual ' s context changes and life events. see figure 2. researchers in relationship science have used social ecological models to study changes and stressors in relationships over time, and how couples, families, or even friends manage them given the contexts they evolve in. application of social ecological models in relationship research have been seen in influential works such as benjamin karney and thomas bradbury ' s vulnerability - stress - adaptation ( vsa ) model. the vsa model is a theoretical approach that enables researchers to study the impact of stressful events on relationship quality and stability over time ( e. g., determine risk of divorce / relationship dissolution ), given a couple ' s capacity to manage and adapt to such events. see figure 3. = = = = relational mobility = = = = in the early 2000s, a japan - based research team defined relational mobility as a measure of how much choice individuals have in terms of whom to form relationships with, including friendships, romantic partnerships, and work relations. relational mobility is low in cultures with a subsistence economy that requires tight cooperation and coordination, such as farming, while it is
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 (
Question: Which characteristic is affected by interactions with the environment?
A) weight
B) eye color
C) blood type
D) handedness
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A) weight
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Context:
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
the effect of the energy deposition inside the human body made by radioactive substances is discussed. for the first time, we stress the importance of the recoiling nucleus in such reactions, particularly concerning the damage caused on the dna structure.
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.
monovalent impurities on graphene can be divided into ionically and covalently bond impurities. the covalent impurities cause universal midgap states as the carbon atom next to the impurity is effectively decoupled from the graphene pi - bands. the electronic structure of graphene suppresses migration of these impurities and making the universal midgap very stable. this effect is strongest for neutral covalently bond impurities. the ionically bond impurities have migration barriers of typically less than 0. 1ev. an asymmetry between anions and cations regarding their adsorption sites and topology of their potential energy landscape is predicted.
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 vacuum chamber, and cured - pyrolized to convert the furfuryl alcohol to carbon. to provide oxidation resistance for reusability, the outer layers of the rcc are converted to silicon carbide. other examples can be seen in the " plastic " casings of television sets, cell - phones and 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 decay rate for isotopes subject to extreme pressures, those differences were too small to significantly impact date estimates. the constancy of the decay rates is also governed by first principles in quantum mechanics, wherein any deviation in the rate would require a change in the fundamental constants. according to these principles, a change in the fundamental constants could not influence different elements uniformly, and a comparison between each of the elements ' resulting unique chronological timescales would then give inconsistent time estimates. in refutation of young earth claims of inconstant decay rates affecting the reliability of radiometric dating, roger c. wiens, a physicist specializing in isotope dating states : there are only three quite technical instances where a half - life changes, and these do not affect the dating methods : " only one technical exception occurs under terrestrial conditions, and this is not for an isotope used for dating.... the artificially - produced isotope, beryllium - 7 has been shown to change by up to 1. 5 %, depending on its chemical environment.... heavier atoms are even less subject to these minute changes, so the dates of rocks made by electron - capture decays would only be off by at most a few hundredths of a percent. " "... another case is material inside of stars, which is in a plasma state where electrons are not bound to atoms. in the extremely hot stellar environment, a completely different kind of decay can occur. ' bound - state beta decay ' occurs when the nucleus emits an electron into a bound electronic state close to the nucleus.... all normal matter, such as everything on earth, the moon, meteorites, etc. has electrons in normal positions, so these instances never apply to rocks, or anything colder than several hundred thousand degrees. " " the last case also involves very fast - moving matter. it has been demonstrated by atomic clocks in very fast spacecraft. these atomic clocks slow down very slightly ( only a second or so per year ) as predicted by einstein ' s theory of relativity. no rocks in our solar system are going fast enough to make a noticeable change in their dates. " = = = = radiohaloes = = = = in the 1970s, young earth creationist robert v. gentry proposed that radiohaloes in certain granites represented evidence for the earth being created instantaneously rather than gradually. this idea has been criticized by physicists and geologists on many grounds including that the rocks gentry studied were not primordial and that the radionucl
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, 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
. 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,
##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
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
Question: Which is the greatest impact humans have had on the carbon cycle?
A) clear-cutting forests
B) manufacturing plastics
C) burning fossil fuels
D) growing agricultural crops
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C) burning fossil fuels
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Context:
##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
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 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
##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
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
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 of any non - zero real number by its magnitude yields exactly its sign. by analogy, the sign of a complex number z can be defined as the quotient of z and its magnitude | z |. the sign of a complex number is the exponential of the product of its argument with the imaginary unit. represents in some sense its complex argument. this is to be compared to the sign of real numbers, except with e i Ο = β 1. { \ displaystyle e ^ { i \ pi } = - 1. } for the definition of a complex sign - function. see Β§ complex sign function below. = = = sign functions = = = when dealing with numbers, it is often convenient to have their sign available as a number. this is accomplished by functions that extract the sign of any number, and map it to a predefined value before making it available for further calculations. for example, it might be advantageous to formulate an intricate algorithm for positive values only, and take care of the sign only afterwards. = = = = real sign function = = = = the sign function or signum function extracts the sign of a real number, by mapping the set of real numbers to the set of the three reals { β 1, 0, 1 }. { \ displaystyle \ { - 1, \ ; 0, \ ; 1 \ }. } it can be defined as follows : sgn : r β { β 1, 0, 1 } x β¦ sgn ( x ) = { β 1 if x < 0, 0 if x = 0
from the insignificant drainage areas of streams rising on high ground near the coast and flowing straight down into the sea, up to immense tracts of continents, where rivers rising on the slopes of mountain ranges far inland have to traverse vast stretches of valleys and plains before reaching the ocean. the size of the largest river basin of any country 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
in the understanding of the fundamental interactions, the origin of an arrow of time is viewed as problematic. however, quantum field theory has an arrow of causality, which tells us which time direction is the past lightcone and which is the future. this direction is tied to the conventions used in the quantization procedures. the different possible causal directions have related physics - in this sense they are covariant under time - reversal. however, only one causal direction emerges for a given set of conventions. this causal arrow tells us the direction that scattering reactions proceed. the time direction of scattering in turn tells us the time direction for which entropy increases - the so - called arrow of thermodynamics. this connection is overlooked in most discussions of the arrow of time.
.... 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, on the ground that the earth is suspended within the concavity of the sky, and that it has as much room on the one side of it as on the other : hence they say that the part that is beneath must also be inhabited. but they do not remark that, although it be supposed or scientifically demonstrated that the world is of a round and spherical form, yet it does not follow that the other side of the earth is bare of water ; nor even, though it be bare, does it immediately follow that it is peopled. for scripture, which proves the truth of its historical statements by the accomplishment of its prophecies, gives no false information ; and it is too absurd to say, that some men might have taken ship and traversed the whole wide ocean, and crossed from this side of the world to the other, and that thus even the inhabitants of that distant region are descended from that one first man. some historians do not view augustine ' s scriptural commentaries as endorsing any particular cosmological model, endorsing instead the view that augustine shared the common view of his contemporaries that the earth is spherical, in line with his endorsement of science in de genesi ad litteram. c. p. e. nothaft, responding to writers like leo ferrari who described augustine as endorsing a flat earth, says that "... other recent writers on the subject treat augustine ' s acceptance of the earth ' s spherical shape as a well - established fact ". while it always remained a minority view, from the mid - fourth to the seventh centuries ad, the flat - earth view experienced a revival, around the time when diodorus of tarsus founded the exegetical school known as the school of antioch, which sought to counter what he saw as the pagan cosmology of the greeks with a return to the traditional cosmology. the writings
= = 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
the location of a repeat plume detected at europa is found to be coincident with the strongest ionosphere detection made by galileo radio occultation in 1997.
Question: The floating arrow on a compass always points towards the
A) west.
B) east.
C) south.
D) north.
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D) north.
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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.
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
##itive material by selective exposure to a radiation source such as light. a photosensitive material is a material that experiences a change in its physical properties when exposed to a radiation source. if a photosensitive material is selectively exposed to radiation ( e. g. by masking some of the radiation ) the pattern of the radiation on the material is transferred to the material exposed, as the properties of the exposed and unexposed regions differs. this exposed region can then be removed or treated providing a mask for the underlying substrate. photolithography is typically used with metal or other thin film deposition, wet and dry etching. sometimes, photolithography is used to create structure without any kind of post etching. one example is su8 based lens where su8 based square blocks are generated. then the photoresist is melted to form a semi - sphere which acts as a lens. electron beam lithography ( often abbreviated as e - beam lithography ) is the practice of scanning a beam of electrons in a patterned fashion across a surface covered with a film ( called the resist ), ( " exposing " the resist ) and of selectively removing either exposed or non - exposed regions of the resist ( " developing " ). the purpose, as with photolithography, is to create very small structures in the resist that can subsequently be transferred to the substrate material, often by etching. it was developed for manufacturing integrated circuits, and is also used for creating nanotechnology architectures. the primary advantage of electron beam lithography is that it is one of 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 lit
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
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
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,
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
dust grains absorb half of the radiation emitted by stars throughout the history of the universe, re - emitting this energy at infrared wavelengths. polycyclic aromatic hydrocarbons ( pahs ) are large organic molecules that trace millimeter - size dust grains and regulate the cooling of the interstellar gas within galaxies. observations of pah features in very distant galaxies have been difficult due to the limited sensitivity and wavelength coverage of previous infrared telescopes. here we present jwst observations that detect the 3. 3um pah feature in a galaxy observed less than 1. 5 billion years after the big bang. the high equivalent width of the pah feature indicates that star formation, rather than black hole accretion, dominates the infrared emission throughout the galaxy. the light from pah molecules, large dust grains, and stars and hot dust are spatially distinct from one another, leading to order - of - magnitude variations in the pah equivalent width and the ratio of pah to total infrared luminosity across the galaxy. the spatial variations we observe suggest either a physical offset between the pahs and large dust grains or wide variations in the local ultraviolet radiation field. our observations demonstrate that differences in the emission from pah molecules and large dust grains are a complex result of localized processes within early galaxies.
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.
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
Question: Which color shirt will reflect the most light on a hot, sunny day?
A) black
B) blue
C) red
D) white
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D) white
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Context:
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 % carbon. stainless steel is defined as a regular steel alloy with greater than 10 % by weight alloying content of chromium. nickel and molybdenum are typically also added in stainless steels. other significant metallic alloys are those of aluminium, titanium, copper and magnesium. copper alloys have been known for a long time ( since the bronze age ), while the alloys of the other three metals have been relatively recently developed. due to the chemical reactivity of these metals, the electrolytic extraction processes required were only developed relatively recently. the alloys of aluminium, titanium and magnesium are also known and valued for their high strength to weight ratios and, in the case of magnesium, their ability to provide electromagnetic shielding. these materials are ideal for situations where high strength to weight ratios are more important than bulk cost, such as in the aerospace industry and certain automotive engineering applications. = = = semiconductors = = = a semiconductor is a material that has a resistivity between a conductor and insulator. modern day electronics run on semiconductors, and the industry had an estimated us $ 530 billion market in 2021. its electronic properties can be greatly altered through intentionally introducing impurities in a process referred to as doping. semiconductor materials are used to build diodes, transistors, light - emitting diodes ( leds ), and analog and digital electric circuits, among their many uses. semiconductor devices have replaced thermionic devices like vacuum tubes in most applications. semiconductor devices are manufactured both as single discrete devices and as integrated circuits ( ics ), which consist of a number β from a
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
high quality thread. the power loom was invented by edmund cartwright in 1787. in the mid - 1750s, the steam engine was applied to the water power - constrained iron, copper and lead industries for powering blast bellows. these industries were located near the mines, some of which were using steam engines for mine pumping. steam engines were too powerful for leather bellows, so cast iron blowing cylinders were developed in 1768. steam powered blast furnaces achieved higher temperatures, allowing the use of more lime in iron blast furnace feed. ( lime rich slag was not free - flowing at the previously used temperatures. ) with a sufficient lime ratio, sulfur from coal or coke fuel reacts with the slag so that the sulfur does not contaminate the iron. coal and coke were cheaper and more abundant fuel. as a result, iron production rose significantly during the last decades of the 18th century. coal converted to coke fueled higher temperature blast furnaces and produced cast iron in much larger amounts than before, allowing the creation of a range of structures such as the iron bridge. cheap coal meant that industry was no longer constrained by water resources driving the mills, although it continued as a valuable source of power. the steam engine helped drain the mines, so more coal reserves could be accessed, and the output of coal increased. the development of the high - pressure steam engine made locomotives possible, and a transport revolution followed. the steam engine which had existed since the early 18th century, was practically applied to both steamboat and railway transportation. the liverpool and manchester railway, the first purpose - built railway line, opened in 1830, the rocket locomotive of robert stephenson being one of its first working locomotives used. manufacture of ships ' pulley blocks by all - metal machines at the portsmouth block mills in 1803 instigated the age of sustained mass production. machine tools used by engineers to manufacture parts began in the first decade of the century, notably by richard roberts and joseph whitworth. the development of interchangeable parts through what is now called the american system of manufacturing began in the firearms industry at the u. s. federal arsenals in the early 19th century, and became widely used by the end of the century. until the enlightenment era, little progress was made in water supply and sanitation and the engineering skills of the romans were largely neglected throughout europe. the first documented use of sand filters to purify the water supply dates to 1804, when the owner of a bleachery in paisley, scotland, john gibb, installed an experimental filter, selling his unwanted
in 1738. the spinning jenny, invented in 1764, was a machine that used multiple spinning wheels ; however, it produced low quality thread. the water frame patented by richard arkwright in 1767, produced a better quality thread than the spinning jenny. the spinning mule, patented in 1779 by samuel crompton, produced a high quality thread. the power loom was invented by edmund cartwright in 1787. in the mid - 1750s, the steam engine was applied to the water power - constrained iron, copper and lead industries for powering blast bellows. these industries were located near the mines, some of which were using steam engines for mine pumping. steam engines were too powerful for leather bellows, so cast iron blowing cylinders were developed in 1768. steam powered blast furnaces achieved higher temperatures, allowing the use of more lime in iron blast furnace feed. ( lime rich slag was not free - flowing at the previously used temperatures. ) with a sufficient lime ratio, sulfur from coal or coke fuel reacts with the slag so that the sulfur does not contaminate the iron. coal and coke were cheaper and more abundant fuel. as a result, iron production rose significantly during the last decades of the 18th century. coal converted to coke fueled higher temperature blast furnaces and produced cast iron in much larger amounts than before, allowing the creation of a range of structures such as the iron bridge. cheap coal meant that industry was no longer constrained by water resources driving the mills, although it continued as a valuable source of power. the steam engine helped drain the mines, so more coal reserves could be accessed, and the output of coal increased. the development of the high - pressure steam engine made locomotives possible, and a transport revolution followed. the steam engine which had existed since the early 18th century, was practically applied to both steamboat and railway transportation. the liverpool and manchester railway, the first purpose - built railway line, opened in 1830, the rocket locomotive of robert stephenson being one of its first working locomotives used. manufacture of ships ' pulley blocks by all - metal machines at the portsmouth block mills in 1803 instigated the age of sustained mass production. machine tools used by engineers to manufacture parts began in the first decade of the century, notably by richard roberts and joseph whitworth. the development of interchangeable parts through what is now called the american system of manufacturing began in the firearms industry at the u. s. federal arsenals in the early 19th century, and became widely used by the end of the century. until the enlightenment era, little progress
pumping. steam engines were too powerful for leather bellows, so cast iron blowing cylinders were developed in 1768. steam powered blast furnaces achieved higher temperatures, allowing the use of more lime in iron blast furnace feed. ( lime rich slag was not free - flowing at the previously used temperatures. ) with a sufficient lime ratio, sulfur from coal or coke fuel reacts with the slag so that the sulfur does not contaminate the iron. coal and coke were cheaper and more abundant fuel. as a result, iron production rose significantly during the last decades of the 18th century. coal converted to coke fueled higher temperature blast furnaces and produced cast iron in much larger amounts than before, allowing the creation of a range of structures such as the iron bridge. cheap coal meant that industry was no longer constrained by water resources driving the mills, although it continued as a valuable source of power. the steam engine helped drain the mines, so more coal reserves could be accessed, and the output of coal increased. the development of the high - pressure steam engine made locomotives possible, and a transport revolution followed. the steam engine which had existed since the early 18th century, was practically applied to both steamboat and railway transportation. the liverpool and manchester railway, the first purpose - built railway line, opened in 1830, the rocket locomotive of robert stephenson being one of its first working locomotives used. manufacture of ships ' pulley blocks by all - metal machines at the portsmouth block mills in 1803 instigated the age of sustained mass production. machine tools used by engineers to manufacture parts began in the first decade of the century, notably by richard roberts and joseph whitworth. the development of interchangeable parts through what is now called the american system of manufacturing began in the firearms industry at the u. s. federal arsenals in the early 19th century, and became widely used by the end of the century. until the enlightenment era, little progress was made in water supply and sanitation and the engineering skills of the romans were largely neglected throughout europe. the first documented use of sand filters to purify the water supply dates to 1804, when the owner of a bleachery in paisley, scotland, john gibb, installed an experimental filter, selling his unwanted surplus to the public. the first treated public water supply in the world was installed by engineer james simpson for the chelsea waterworks company in london in 1829. the first screw - down water tap was patented in 1845 by guest and chrimes, a brass foundry in rotherham. the practice of water treatment soon became mainstream,
, 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
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.
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 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
high temperature superconducting ( hts ) tape can be cut and stacked to generate large magnetic fields at cryogenic temperatures after inducing persistent currents in the superconducting layers. a field of 17. 7 t was trapped between two stacks of hts tape at 8 k with no external mechanical reinforcement. 17. 6 t could be sustained when warming the stack up to 14 k. a new type of hybrid stack was used consisting of a 12 mm square insert stack embedded inside a larger 34. 4 mm diameter stack made from different tape. the magnetic field generated is the largest for any trapped field magnet reported and 30 % greater than previously achieved in a stack of hts tapes. such stacks are being considered for superconducting motors as rotor field poles where the cryogenic penalty is justified by the increased power to weight ratio. the sample reported can be considered the strongest permanent magnet ever created.
Question: A 10 g sample of aluminum and a 10 g sample of iron were each heated by 100 joules of energy. The temperature of the aluminum sample rose 11Β°C, while the temperature of the iron sample increased 23Β°C. Which statement best accounts for these results?
A) Iron is twice as dense as aluminum.
B) Atoms of aluminum are smaller than atoms of iron.
C) Using equal masses results in similar heat capacities.
D) The specific heat of iron is less than that of aluminum.
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D) The specific heat of iron is less than that of aluminum.
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Context:
the less of it people would be prepared to buy ( other things unchanged ). as the price of a commodity falls, consumers move toward it from relatively more expensive goods ( the substitution effect ). in addition, purchasing power from the price decline increases ability to buy ( the income effect ). other factors can change demand ; for example an increase in income will shift the demand curve for a normal good outward relative to the origin, as in the figure. all determinants are predominantly taken as constant factors of demand and supply. supply is the relation between the price of a good and the quantity available for sale at that price. it may be represented as a table or graph relating price and quantity supplied. producers, for example business firms, are hypothesised to be profit maximisers, meaning that they attempt to produce and supply the amount of goods that will bring them the highest profit. supply is typically represented as a function relating price and quantity, if other factors are unchanged. that is, the higher the price at which the good can be sold, the more of it producers will supply, as in the figure. the higher price makes it profitable to increase production. just as on the demand side, the position of the supply can shift, say from a change in the price of a productive input or a technical improvement. the " law of supply " states that, in general, a rise in price leads to an expansion in supply and a fall in price leads to a contraction in supply. here as well, the determinants of supply, such as price of substitutes, cost of production, technology applied and various factors inputs of production are all taken to be constant for a specific time period of evaluation of supply. market equilibrium occurs where quantity supplied equals quantity demanded, the intersection of the supply and demand curves in the figure above. at a price below equilibrium, there is a shortage of quantity supplied compared to quantity demanded. this is posited to bid the price up. at a price above equilibrium, there is a surplus of quantity supplied compared to quantity demanded. this pushes the price down. the model of supply and demand predicts that for given supply and demand curves, price and quantity will stabilise at the price that makes quantity supplied equal to quantity demanded. similarly, demand - and - supply theory predicts a new price - quantity combination from a shift in demand ( as to the figure ), or in supply. = = = firms = = = people frequently do not trade directly on markets. instead, on the supply side, they may work
the magnetization of superconducting samples is influenced by their porosity. in addition to structural modifications and improved cooling, the presence of pores also plays a role in trapping magnetic flux. pores have an impact on the irreversibility field, the full penetration field, and the remnant magnetization. generally, as porosity increases, these parameters tend to decrease. however, in the case of mesoscopic samples or samples with low critical current densities, increased porosity can actually enhance the trapping of magnetic flux.
sequences. genetic engineering is also used to create animal models of human diseases. genetically modified mice are the most common genetically engineered animal model. they have been used to study and model cancer ( the oncomouse ), obesity, heart disease, diabetes, arthritis, substance abuse, anxiety, aging and parkinson disease. potential cures 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
##ilage 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 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
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
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
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, 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
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
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 and pulp, textiles and biofuels. in the current decades, significant progress has been done in creating genetically modified organisms ( gmos ) that enhance the diversity of applications and economical viability of industrial biotechnology. by using renewable raw materials to produce a variety of chemicals and fuels, industrial biotechnology is actively advancing towards lowering greenhouse gas emissions and moving away from a petrochemical - based economy. synthetic biology is considered one of the essential cornerstones in industrial biotechnology due to its financial and sustainable contribution to the manufacturing sector. jointly biotechnology and synthetic biology play a crucial role in generating cost - effective products with nature - friendly features by using bio - based
include the manufacturing of drugs, creation of model animals that mimic human conditions and gene therapy. one of the earliest uses of genetic engineering was to mass - produce human insulin in bacteria. this application has now been applied to human growth hormones, follicle stimulating hormones ( for treating infertility ), human albumin, monoclonal antibodies, antihemophilic factors, vaccines and many other drugs. mouse hybridomas, cells fused together to create monoclonal antibodies, have been adapted through genetic engineering to create human monoclonal antibodies. genetically engineered viruses are being developed that can still confer immunity, but lack the infectious sequences. genetic engineering is also used to create animal models of human diseases. genetically modified mice are the most common genetically engineered animal model. they have been used to study and model cancer ( the oncomouse ), obesity, heart disease, diabetes, arthritis, substance abuse, anxiety, aging and parkinson disease. potential cures 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,
Question: If its food supply in a field decreases, the mouse population in that field will probably
A) increase.
B) decrease.
C) remain the same.
D) become extinct.
|
B) decrease.
|
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
= = = = = = 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
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
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
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
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 :
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
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
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
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 that gives us long - term ( decade - to - decade ) feedback on our performance as stewards of the planet. the effort includes understanding the functions of soil microbiotic crusts and exploring the potential to sequester atmospheric carbon in soil organic matter. relating the concept of agriculture to soil quality, however, has not
Question: Overuse of soil for farming causes local disruptions of several Earth subsystems. Which of these is a part of the biogeochemical cycle that experiences the most severe local disruption?
A) release of carbon into the atmosphere
B) release of oxygen into the atmosphere
C) cycling phosphorus into the soil
D) cycling hydrogen into the soil
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C) cycling phosphorus into the soil
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Context:
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 (
are studied in chemistry are usually the result of interactions between atoms, leading to rearrangements of the chemical bonds which hold atoms together. such behaviors are studied in a chemistry laboratory. the chemistry laboratory stereotypically uses various forms of laboratory glassware. however glassware is not central to chemistry, and a great deal of experimental ( as well as applied / industrial ) chemistry is done without it. a chemical reaction is a transformation of some substances into one or more different substances. the basis of such a chemical transformation is the rearrangement of electrons in the chemical bonds between atoms. it can be symbolically depicted through a chemical equation, which usually involves atoms as subjects. the number of atoms on the left and the right in the equation for a chemical transformation is equal. ( when the number of atoms on either side is unequal, the transformation is referred to as a nuclear reaction or radioactive decay. ) the type of chemical reactions a substance may undergo and the energy changes that may accompany it are constrained by certain basic rules, known as chemical laws. energy and entropy considerations are invariably important in almost all chemical studies. chemical substances are classified in terms of their structure, phase, as well as their chemical compositions. they can be analyzed using the tools of chemical analysis, e. 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
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 are studied in chemistry are usually the result of interactions between atoms, leading to rearrangements of the chemical bonds which hold atoms together. such behaviors are studied in a chemistry laboratory. the chemistry laboratory stereotypically uses various forms of laboratory glassware. however glassware is not central to chemistry, and a great deal of experimental ( as well as applied / industrial ) chemistry is done without it. a chemical reaction is a transformation of some substances into one or more different substances. the basis of such a chemical transformation is the rearrangement of electrons in the chemical bonds between atoms. it can be symbolically depicted through a chemical equation, which usually involves atoms as subjects. the number of atoms on the left and the right in the equation for a chemical transformation is equal. ( when the number of atoms on either side is unequal, the transformation is referred to as a nuclear reaction or radioactive decay. ) the type of chemical reactions a substance may undergo and the energy changes that may accompany it are constrained by certain basic rules, known as chemical laws. energy and entropy considerations are invariably important in almost all chemical studies. chemical substances are classified in terms of their structure, phase, as well as their chemical compositions. they can be analyzed using the tools of chemical analysis, e. 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
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 ( 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
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
. 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 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
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
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 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 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.
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 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.
Question: Which of the following is an example of a physical change but not a chemical change?
A) A log gives off heat and light as it burns.
B) A tree stores energy from the Sun in its fruit.
C) A penny lost in the grass slowly changes color.
D) A water pipe freezes and cracks on a cold night.
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D) A water pipe freezes and cracks on a cold night.
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Context:
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.
the luminosity variation of a stellar source due to the gravitational microlensing effect can be considered also if the light rays are defocused ( instead of focused ) toward the observer. in this case, we should detect a gap instead of a peak in the light curve of the source. actually, we describe how the phenomenon depends on the relative position of source and lens with respect to the observer : if the lens is between, we have focusing, if the lens is behind, we have defocusing. it is shown that the number of events with predicted gaps is equal to the number of events with peaks in the light curves.
during their exposure, nuclear emulsion sheets detect both tracks from experiment - related particles, as well as a considerable amount of background tracks, mainly due to cosmic rays. unless the exposure has been fairly short, it is therefore fairly likely that a fraction of the tracks that have been identified as belonging to the particles the experiment is interested in, are really due to background. a method, which allows to measure this fraction reliably directly from the data, is described.
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
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
the curvature radiation is applied to the explain the circular polarization of frbs. significant circular polarization is reported in both apparently non - repeating and repeating frbs. curvature radiation can produce significant circular polarization at the wing of the radiation beam. in the curvature radiation scenario, in order to see significant circular polarization in frbs ( 1 ) more energetic bursts, ( 2 ) burst with electrons having higher lorentz factor, ( 3 ) a slowly rotating neutron star at the centre are required. different rotational period of the central neutron star may explain why some frbs have high circular polarization, while others don ' t. considering possible difference in refractive index for the parallel and perpendicular component of electric field, the position angle may change rapidly over the narrow pulse window of the radiation beam. the position angle swing in frbs may also be explained by this non - geometric origin, besides that of the rotating vector model.
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
due to its location and climate, antarctica offers unique conditions for long - period observations across a broad wavelength regime, where important diagnostic lines for molecules and ions can be found, that are essential to understand the chemical properties of the interstellar medium. in addition to the natural benefits of the site, new technologies, resulting from astrophotonics, may allow miniaturised instruments, that are easier to winterise and advanced filters to further reduce the background in the infrared.
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
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 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
Question: While conducting an investigation on refraction, a teacher uses a red laser pointer to show how a beam of light is affected as it passes through several glass objects. The teacher should make sure that the
A) room is totally dark.
B) light source is ultraviolet.
C) beam of light does not travel toward the students.
D) room walls are shielded with insulating material.
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C) beam of light does not travel toward the students.
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Context:
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
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 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
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
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 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
astronomy uses methods from astronomy to determine past celestial constellations for forensic purposes. forensic botany is the study of plant life in order to gain information regarding possible crimes. forensic chemistry is the study of detection and identification of illicit drugs, accelerants used in arson cases, explosive and gunshot residue. forensic dactyloscopy is the study of fingerprints. forensic document examination or questioned document examination answers questions about a disputed document using a variety of scientific processes and methods. many examinations involve a comparison of the questioned document, or components of the document, with a set of known standards. the most common type of examination involves handwriting, whereby the examiner tries to address concerns about potential authorship. forensic dna analysis takes advantage of the uniqueness of an individual ' s dna to answer forensic questions such as paternity / maternity testing and placing a suspect at a crime scene, e. g. in a rape investigation. forensic engineering is the scientific examination and analysis of structures and products relating to their failure or cause of damage. forensic entomology deals with the examination of insects in, on and around human remains to assist in determination of time or location of death. it is also possible to determine if the body was moved after death using entomology. forensic geology deals with trace evidence in the form of soils, minerals and petroleum. forensic geomorphology is the study of the ground surface to look for potential location ( s ) of buried object ( s ). forensic geophysics is the application of geophysical techniques such as radar for detecting objects hidden underground or underwater. forensic intelligence process starts with the collection of data and ends with the integration of results within into the analysis of crimes under investigation. forensic interviews are conducted using the science of professionally using expertise to conduct a variety of investigative interviews with victims, witnesses, suspects or other sources to determine the facts regarding suspicions, allegations or specific incidents in either public or private sector settings. 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
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
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
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
designates the relationship between two or more variables. conceptual definition : description of a concept by relating it to other concepts. operational definition : details in regards to defining the variables and how they will be measured / assessed in the study. gathering of data : consists of identifying a population and selecting samples, gathering information from or about 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
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 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 )
Question: One student wrote a report about an investigation in which fertilizer was added to tomato plants. Which information from that student's report would most help a second student repeat the investigation?
A) the amount of fertilizer added
B) the height of the fertilized plants
C) the size of each tomato produced
D) the number of tomatoes produced
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A) the amount of fertilizer added
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Context:
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, 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
##thic, 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, 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
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, 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
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
##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
and were considered among the seven wonders of the ancient world. the six classic simple machines were known in the ancient near east. the wedge and the inclined plane ( ramp ) were known since prehistoric times. the wheel, along with the wheel and axle mechanism, was invented in mesopotamia ( modern iraq ) during the 5th millennium bc. the lever mechanism first appeared around 5, 000 years ago in the near east, where it was used in a simple balance scale, and to move large objects in ancient egyptian technology. the lever was also used in the shadoof water - lifting device, the first crane machine, which appeared in mesopotamia c. 3000 bc, and then in ancient egyptian technology c. 2000 bc. the earliest evidence of pulleys date back to mesopotamia in the early 2nd millennium bc, and ancient egypt during the twelfth dynasty ( 1991 β 1802 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 egyptian pyramids were built using three of the six simple machines, the inclined plane, the wedge, and the lever, to create structures like the great pyramid of giza. the earliest civil engineer known by name is imhotep. as one of the officials of the pharaoh, djoser, he probably designed and supervised the construction of the pyramid of djoser ( the step pyramid ) at saqqara in egypt around 2630 β 2611 bc. the earliest practical water - powered machines, the water wheel and watermill, first appeared in the persian empire, in what are now iraq and iran, by the early 4th century bc. kush developed the sakia during the 4th century bc, which relied on animal power instead of human energy. hafirs were developed as a type of reservoir in kush to store and contain water as well as boost irrigation. sappers were employed to build causeways during military campaigns. kushite ancestors built speos during the bronze age between 3700 and 3250 bc. bloomeries and blast furnaces were also created during the 7th centuries bc in kush. ancient greece developed machines in both civilian and military domains. the antikythera mechanism, an early known mechanical analog computer, and the mechanical inventions of archimedes, are examples of greek mechanical engineering. some of archimedes ' inventions, as well as the antikythera mechanism, required sophisticated knowledge of differential gearing or epicyclic gearing, two key principles in machine theory
some topics which can be easily explained to undergraduate students are presented, with elementary derivations. for a more systematic treatment of heavy - quark physics, see the textbook by manohar and wise.
##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
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
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
Question: A student wants to look under a heavy rock. Which simple machine would be BEST to use to lift the rock?
A) Wheel and axle
B) Lever
C) Inclined plane
D) Screw
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B) Lever
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Context:
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. nickel - based superalloys like inconel are used in high - temperature applications such as gas turbines, turbochargers, pressure vessels, and heat exchangers. for extremely high temperatures, single crystal alloys are used to minimize creep. in modern electronics, high purity single crystal silicon is essential for metal - oxide - silicon transistors ( mos ) and integrated circuits. = = production = = in production engineering, metallurgy is concerned with the production of metallic components for use in consumer or engineering products. this involves production of alloys, shaping, heat treatment and surface treatment of product. the task of the metallurgist is to achieve balance between material properties, such as cost, weight, strength, toughness, hardness, corrosion, fatigue resistance and performance in temperature extremes. to achieve this goal, the operating environment must be carefully considered. determining the hardness of the metal using the rockwell, vickers, and brinell hardness scales
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 % carbon. stainless steel is defined as a regular steel alloy with greater than 10 % by weight alloying content of chromium. nickel and molybdenum are typically also added in stainless steels. other significant metallic alloys are those of aluminium, titanium, copper and magnesium. copper alloys have been known for a long time ( since the bronze age ), while the alloys of the other three metals have been relatively recently developed. due to the chemical reactivity of these metals, the electrolytic extraction processes required were only developed relatively recently. the alloys of aluminium, titanium and magnesium are also known and valued for their high strength to weight ratios and, in the case of magnesium, their ability to provide electromagnetic shielding. these materials are ideal for situations where high strength to weight ratios are more important than bulk cost, such as in the aerospace industry and certain automotive engineering applications. = = = semiconductors = = = a semiconductor is a material that has a resistivity between a conductor and insulator. modern day electronics run on semiconductors, and the industry had an estimated us $ 530 billion market in 2021. its electronic properties can be greatly altered through intentionally introducing impurities in a process referred to as doping. semiconductor materials are used to build diodes, transistors, light - emitting diodes ( leds ), and analog and digital electric circuits, among their many uses. semiconductor devices have replaced thermionic devices like vacuum tubes in most applications. semiconductor devices are manufactured both as single discrete devices and as integrated circuits ( ics ), which consist of a number β from a
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. nickel - based superalloys like inconel are used in high - temperature applications such as gas turbines, turbochargers, pressure vessels, and heat exchangers. for extremely high temperatures, single crystal alloys are used to minimize creep. in modern electronics, high purity single crystal silicon is essential for metal - oxide - silicon transistors ( mos ) and integrated circuits. = = production = = in production engineering, metallurgy is concerned with the production of metallic components for use in consumer or engineering products. this involves production of alloys, shaping, heat treatment and surface treatment of product. the task of the metallurgist is to achieve balance between material properties, such as cost, weight, strength, toughness, hardness, corrosion, fatigue resistance and performance in temperature extremes. to achieve this goal, the operating environment must be carefully considered. determining the hardness of the metal using the rockwell, vickers, and brinell hardness scales is a commonly used practice that helps better understand the metal ' s elasticity and plasticity for different applications and production processes. in a saltwater environment, most ferrous metals and some non - ferrous alloys corrode quickly. metals exposed to cold or cryogenic conditions may undergo a ductile to brittle
. historically, metallurgy has predominately focused on the production of metals. metal production begins with the processing of ores to extract the metal, and includes the mixture of metals to make alloys. metal alloys are often a blend of at least two different metallic elements. however, non - metallic elements are often added to alloys in order to achieve properties suitable for an application. the study of metal production is subdivided into ferrous metallurgy ( also known as black metallurgy ) and non - ferrous metallurgy, also known as colored metallurgy. ferrous metallurgy involves processes and alloys based on iron, while non - ferrous metallurgy involves processes and alloys based on other metals. the production of ferrous metals accounts for 95 % of world metal production. modern metallurgists work in both emerging and traditional areas as part of an interdisciplinary team alongside material scientists and other engineers. some traditional areas include mineral processing, metal production, heat treatment, failure analysis, and the joining of metals ( including welding, brazing, and soldering ). emerging areas for metallurgists include nanotechnology, superconductors, composites, biomedical materials, electronic materials ( semiconductors ) and surface engineering. = = etymology and pronunciation = = metallurgy derives from the ancient greek ΞΌΞ΅ΟαλλοΟ
ΟΞ³ΞΏΟ, metallourgos, " worker in metal ", from ΞΌΞ΅Οαλλον, metallon, " mine, metal " + Ξ΅ΟΞ³ΞΏΞ½, ergon, " work " the word was originally an alchemist ' s term for the extraction of metals from minerals, the ending - urgy signifying a process, especially manufacturing : it was discussed in this sense in the 1797 encyclopΓ¦dia britannica. in the late 19th century, metallurgy ' s definition was extended to the more general scientific study of metals, alloys, and related processes. in english, the pronunciation is the more common one in the united kingdom. the pronunciation is the more common one in the us and is the first - listed variant in various american dictionaries, including merriam - webster collegiate and american heritage. = = history = = the earliest metal employed by humans appears to be gold, which can be found " native ". small amounts of natural gold, dating to the late paleolithic period, 40, 000 bc, have been found in spanish caves. silver, copper, tin and meteoric iron
iron - peroxide intermediates are central in the reaction cycle of many iron - containing biomolecules. we trapped iron ( iii ) - ( hydro ) peroxo species in crystals of superoxide reductase ( sor ), a nonheme mononuclear iron enzyme that scavenges superoxide radicals. x - ray diffraction data at 1. 95 angstrom resolution and raman spectra recorded in crystallo revealed iron - ( hydro ) peroxo intermediates with the ( hydro ) peroxo group bound end - on. the dynamic sor active site promotes the formation of transient hydrogen bond networks, which presumably assist the cleavage of the iron - oxygen bond in order to release the reaction product, hydrogen peroxide.
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
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
in 1738. the spinning jenny, invented in 1764, was a machine that used multiple spinning wheels ; however, it produced low quality thread. the water frame patented by richard arkwright in 1767, produced a better quality thread than the spinning jenny. the spinning mule, patented in 1779 by samuel crompton, produced a high quality thread. the power loom was invented by edmund cartwright in 1787. in the mid - 1750s, the steam engine was applied to the water power - constrained iron, copper and lead industries for powering blast bellows. these industries were located near the mines, some of which were using steam engines for mine pumping. steam engines were too powerful for leather bellows, so cast iron blowing cylinders were developed in 1768. steam powered blast furnaces achieved higher temperatures, allowing the use of more lime in iron blast furnace feed. ( lime rich slag was not free - flowing at the previously used temperatures. ) with a sufficient lime ratio, sulfur from coal or coke fuel reacts with the slag so that the sulfur does not contaminate the iron. coal and coke were cheaper and more abundant fuel. as a result, iron production rose significantly during the last decades of the 18th century. coal converted to coke fueled higher temperature blast furnaces and produced cast iron in much larger amounts than before, allowing the creation of a range of structures such as the iron bridge. cheap coal meant that industry was no longer constrained by water resources driving the mills, although it continued as a valuable source of power. the steam engine helped drain the mines, so more coal reserves could be accessed, and the output of coal increased. the development of the high - pressure steam engine made locomotives possible, and a transport revolution followed. the steam engine which had existed since the early 18th century, was practically applied to both steamboat and railway transportation. the liverpool and manchester railway, the first purpose - built railway line, opened in 1830, the rocket locomotive of robert stephenson being one of its first working locomotives used. manufacture of ships ' pulley blocks by all - metal machines at the portsmouth block mills in 1803 instigated the age of sustained mass production. machine tools used by engineers to manufacture parts began in the first decade of the century, notably by richard roberts and joseph whitworth. the development of interchangeable parts through what is now called the american system of manufacturing began in the firearms industry at the u. s. federal arsenals in the early 19th century, and became widely used by the end of the century. until the enlightenment era, little progress
##chemistry, and chemical degradation ( corrosion ). in contrast, physical metallurgy focuses on the mechanical properties of metals, the physical properties of metals, and the physical performance of metals. topics studied in physical metallurgy include crystallography, material characterization, mechanical metallurgy, phase transformations, and failure mechanisms. historically, metallurgy has predominately focused on the production of metals. metal production begins with the processing of ores to extract the metal, and includes the mixture of metals to make alloys. metal alloys are often a blend of at least two different metallic elements. however, non - metallic elements are often added to alloys in order to achieve properties suitable for an application. the study of metal production is subdivided into ferrous metallurgy ( also known as black metallurgy ) and non - ferrous metallurgy, also known as colored metallurgy. ferrous metallurgy involves processes and alloys based on iron, while non - ferrous metallurgy involves processes and alloys based on other metals. the production of ferrous metals accounts for 95 % of world metal production. modern metallurgists work in both emerging and traditional areas as part of an interdisciplinary team alongside material scientists and other engineers. some traditional areas include mineral processing, metal production, heat treatment, failure analysis, and the joining of metals ( including welding, brazing, and soldering ). emerging areas for metallurgists include nanotechnology, superconductors, composites, biomedical materials, electronic materials ( semiconductors ) and surface engineering. = = etymology and pronunciation = = metallurgy derives from the ancient greek ΞΌΞ΅ΟαλλοΟ
ΟΞ³ΞΏΟ, metallourgos, " worker in metal ", from ΞΌΞ΅Οαλλον, metallon, " mine, metal " + Ξ΅ΟΞ³ΞΏΞ½, ergon, " work " the word was originally an alchemist ' s term for the extraction of metals from minerals, the ending - urgy signifying a process, especially manufacturing : it was discussed in this sense in the 1797 encyclopΓ¦dia britannica. in the late 19th century, metallurgy ' s definition was extended to the more general scientific study of metals, alloys, and related processes. in english, the pronunciation is the more common one in the united kingdom. the pronunciation is the more common one in the us and is the first - listed variant in various american dictionaries, including merriam - webster collegiate
high quality thread. the power loom was invented by edmund cartwright in 1787. in the mid - 1750s, the steam engine was applied to the water power - constrained iron, copper and lead industries for powering blast bellows. these industries were located near the mines, some of which were using steam engines for mine pumping. steam engines were too powerful for leather bellows, so cast iron blowing cylinders were developed in 1768. steam powered blast furnaces achieved higher temperatures, allowing the use of more lime in iron blast furnace feed. ( lime rich slag was not free - flowing at the previously used temperatures. ) with a sufficient lime ratio, sulfur from coal or coke fuel reacts with the slag so that the sulfur does not contaminate the iron. coal and coke were cheaper and more abundant fuel. as a result, iron production rose significantly during the last decades of the 18th century. coal converted to coke fueled higher temperature blast furnaces and produced cast iron in much larger amounts than before, allowing the creation of a range of structures such as the iron bridge. cheap coal meant that industry was no longer constrained by water resources driving the mills, although it continued as a valuable source of power. the steam engine helped drain the mines, so more coal reserves could be accessed, and the output of coal increased. the development of the high - pressure steam engine made locomotives possible, and a transport revolution followed. the steam engine which had existed since the early 18th century, was practically applied to both steamboat and railway transportation. the liverpool and manchester railway, the first purpose - built railway line, opened in 1830, the rocket locomotive of robert stephenson being one of its first working locomotives used. manufacture of ships ' pulley blocks by all - metal machines at the portsmouth block mills in 1803 instigated the age of sustained mass production. machine tools used by engineers to manufacture parts began in the first decade of the century, notably by richard roberts and joseph whitworth. the development of interchangeable parts through what is now called the american system of manufacturing began in the firearms industry at the u. s. federal arsenals in the early 19th century, and became widely used by the end of the century. until the enlightenment era, little progress was made in water supply and sanitation and the engineering skills of the romans were largely neglected throughout europe. the first documented use of sand filters to purify the water supply dates to 1804, when the owner of a bleachery in paisley, scotland, john gibb, installed an experimental filter, selling his unwanted
Question: Rust is a compound with the formula Fe_{2}O_{3}. Which elements combine to form rust?
A) iron and water
B) iron and oxygen
C) iron and air
D) iron and acid
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B) iron and oxygen
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Context:
##resistibly funky. and at their heaviest β notably on the frantic ' favorite things ' β they ' re reminiscent of faith no more at their wildest. " elliot added that people who were upset about the split of faith no more " [ should go along ] to an incubus gig. " the daily nebraskan referred to them as a " funk - heavy foursome " in 1998, while billboard labelled them a funk rock band in december 1997. according to rolling stone writer rob kemp, s. c. i. e. n. c. e. " links funk metal to the rap - metal ". though sometimes retrospectively associated with it, the term nu metal was not yet in usage when s. c. i. e. n. c. e. was released, but rather terms such as alternative metal, funk metal and rap metal. in 1997, boyd said " people are real quick to put labels on music, so i ' m sure they ' re going to do that with us. but we think we ' re doing something cool, and judging from the responses that we ' ve gotten from all over the world, others do too. " einziger has since stated that incubus were not part of the same southern californian scene as bands like korn and system of a down during their independent years, despite having similar influences. in interviews from the late 2010s and 2020s, boyd has said that he dislikes the nu metal label and doesn ' t consider the band ' s early work to be part of the movement. in a 2022 metal hammer interview, he remarked, " we weren β t trying to fit into a particular niche at a particular time. we were just kids being influenced by a small handful of bands that we grew up with. " revolver describe brandon boyd as vocally " drawing on the eccentric funk - rap " of faith no more, primus and red hot chili peppers. they consider him to have a " goofy yet also badass presence " on s. c. i. e. n. c. e. boyd has cited faith no more ' s vocalist mike patton as being an influence from since he was an early teenager, as well as patton ' s side project mr. bungle, who were similarly known for mixing a wide array of genres. through mr. bungle, boyd also went on to become a fan of avant - garde musician john zorn, who produced their 1991 debut album. in a 2003 interview with the philippine daily inquirer, boyd said
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 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
can also be found in native form, allowing a limited amount of metalworking in early cultures. early cold metallurgy, using native copper not melted from mineral has been documented at sites in anatolia and at the site of tell maghzaliyah in iraq, dating from the 7th / 6th millennia bc. the earliest archaeological support of smelting ( hot metallurgy ) in eurasia is found in the balkans and carpathian mountains, as evidenced by findings of objects made by metal casting and smelting dated to around 6200 β 5000 bc, with the invention of copper metallurgy. certain metals, such as tin, lead, and copper can be recovered from their ores by simply heating the rocks in a fire or blast furnace in a process known as smelting. the first evidence of copper smelting, dating from the 6th millennium bc, has been found at archaeological sites in majdanpek, jarmovac and plocnik, 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
##n referred to them as a " funk - heavy foursome " in 1998, while billboard labelled them a funk rock band in december 1997. according to rolling stone writer rob kemp, s. c. i. e. n. c. e. " links funk metal to the rap - metal ". though sometimes retrospectively associated with it, the term nu metal was not yet in usage when s. c. i. e. n. c. e. was released, but rather terms such as alternative metal, funk metal and rap metal. in 1997, boyd said " people are real quick to put labels on music, so i ' m sure they ' re going to do that with us. but we think we ' re doing something cool, and judging from the responses that we ' ve gotten from all over the world, others do too. " einziger has since stated that incubus were not part of the same southern californian scene as bands like korn and system of a down during their independent years, despite having similar influences. in interviews from the late 2010s and 2020s, boyd has said that he dislikes the nu metal label and doesn ' t consider the band ' s early work to be part of the movement. in a 2022 metal hammer interview, he remarked, " we weren β t trying to fit into a particular niche at a particular time. we were just kids being influenced by a small handful of bands that we grew up with. " revolver describe brandon boyd as vocally " drawing on the eccentric funk - rap " of faith no more, primus and red hot chili peppers. they consider him to have a " goofy yet also badass presence " on s. c. i. e. n. c. e. boyd has cited faith no more ' s vocalist mike patton as being an influence from since he was an early teenager, as well as patton ' s side project mr. bungle, who were similarly known for mixing a wide array of genres. through mr. bungle, boyd also went on to become a fan of avant - garde musician john zorn, who produced their 1991 debut album. in a 2003 interview with the philippine daily inquirer, boyd said that around this period, both he and einziger gravitated towards more experimental artists that " you ' ll never hear on the radio ". alex katunich uses a slap bass playing style on the album, and has said he was influenced by funk music since he was a young child, and got an album
more readily than they could participate in hunter - gatherer activities. with this increase in population and availability of labor came an increase in labor specialization. what triggered the progression from early neolithic villages to the first cities, such as uruk, and the first civilizations, such as sumer, is not specifically known ; however, the emergence of increasingly hierarchical social structures and specialized labor, of trade and war among adjacent cultures, and the need for collective action to overcome environmental challenges such as irrigation, are all thought to have played a role. the invention of writing led to the spread of cultural knowledge and became the basis for history, libraries, schools, and scientific research. continuing improvements led to the furnace and bellows and provided, for the first time, the ability to smelt and forge gold, copper, silver, and lead β native metals found in relatively pure form in nature. the advantages of copper tools over stone, bone and wooden tools were quickly apparent to early humans, and native copper was probably used from near the beginning of neolithic times ( about 10 kya ). native copper does not naturally occur in large amounts, but copper ores are quite common and some of them produce metal easily when burned in wood or charcoal fires. eventually, the working of metals led to the discovery of alloys such as bronze and brass ( about 4, 000 bce ). the first use of iron alloys such as steel dates to around 1, 800 bce. = = = ancient = = = after harnessing fire, humans discovered other forms of energy. the earliest known use of wind power is the sailing ship ; the 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
and american heritage. = = history = = the earliest metal employed by humans appears to be gold, which can be found " native ". small amounts of natural gold, dating to the late paleolithic period, 40, 000 bc, have been found in spanish caves. silver, copper, tin and meteoric iron can also be found in native form, allowing a limited amount of metalworking in early cultures. early cold metallurgy, using native copper not melted from mineral has been documented at sites in anatolia and at the site of tell maghzaliyah in iraq, dating from the 7th / 6th millennia bc. the earliest archaeological support of smelting ( hot metallurgy ) in eurasia is found in the balkans and carpathian mountains, as evidenced by findings of objects made by metal casting and smelting dated to around 6200 β 5000 bc, with the invention of copper metallurgy. certain metals, such as tin, lead, and copper can be recovered from their ores by simply heating the rocks in a fire or blast furnace in a process known as smelting. the first evidence of copper smelting, dating from the 6th millennium bc, has been found at archaeological sites in majdanpek, jarmovac and plocnik, 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
, and copper can be recovered from their ores by simply heating the rocks in a fire or blast furnace in a process known as smelting. the first evidence of copper smelting, dating from the 6th millennium bc, has been found at archaeological sites in majdanpek, jarmovac and plocnik, 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
find the value of the expression when the variable is assigned a given number. expressions can be evaluated or simplified by replacing operations that appear in them with their result, or by combining like - terms. for example, take the expression 4 x 2 + 8 { \ displaystyle 4x ^ { 2 } + 8 } ; it can be evaluated at x = 3 in the following steps : 4 ( 3 ) 2 + 3 { \ textstyle 4 ( 3 ) ^ { 2 } + 3 }, ( replace x with 3 ) 4 β
( 3 β
3 ) + 8 { \ displaystyle 4 \ cdot ( 3 \ cdot 3 ) + 8 } ( use definition of exponent ) 4 β
9 + 8 { \ displaystyle 4 \ cdot 9 + 8 } ( simplify ) 36 + 8 { \ displaystyle 36 + 8 } 44 { \ displaystyle 44 } a term is a constant or the product of a constant and one or more variables. some examples include 7, 5 x, 13 x 2 y, 4 b { \ displaystyle 7, \ ; 5x, \ ; 13x ^ { 2 } y, \ ; 4b } the constant of the product is called the coefficient. terms that are either constants or have the same variables raised to the same powers are called like terms. if there are like terms in an expression, one can simplify the expression by combining the like terms. one adds the coefficients and keeps the same variable. 4 x + 7 x + 2 x = 15 x { \ displaystyle 4x + 7x + 2x = 15x } any variable can be classified as being either a free variable or a bound variable. for a given combination of values for the free variables, an expression may be evaluated, although for some combinations of values of the free variables, the value of the expression may be undefined. thus an expression represents an operation over constants and free variables and whose output is the resulting value of the expression. for a non - formalized language, that is, in most mathematical texts outside of mathematical logic, for an individual expression it is not always possible to identify which variables are free and bound. for example, in [UNK] i < k a i k { \ textstyle \ sum _ { i < k } a _ { ik } }, depending on the context, the variable i { \ textstyle i } can be free and k { \ textstyle k } bound, or vice - versa, but they cannot both be free. determining which
the mineralogy and physical properties of chelyabinsk meteorites ( fall, february 15, 2013 ) are presented. three types of meteorite material are present, described as the light - colored, dark - colored, and impact - melt lithologies. all are of ll5 composition with the impact - melt lithology being close to whole - rock melt and the dark - colored lithology being shock - darkened due to partial melting of iron metal and sulfides. this enables us to study the effect of increasing shock on material with identical composition and origin. based on the magnetic susceptibility, the chelyabinsk meteorites are richer in metallic iron as compared to other ll chondrites. the measured bulk and grain densities and the porosity closely resemble other ll chondrites. shock darkening does not have a significant effect on the material physical properties, but causes a decrease of reflectance and decrease in silicate absorption bands in the reflectance spectra. this is similar to the space weathering effects observed on asteroids. however, compared to space weathered materials, there is a negligible to minor slope change observed in impact - melt and shock - darkened meteorite spectra. thus, it is possible that some dark asteroids with invisible silicate absorption bands may be composed of relatively fresh shock - darkened chondritic material.
archaeological support of smelting ( hot metallurgy ) in eurasia is found in the balkans and carpathian mountains, as evidenced by findings of objects made by metal casting and smelting dated to around 6200 β 5000 bc, with the invention of copper metallurgy. certain metals, such as tin, lead, and copper can be recovered from their ores by simply heating the rocks in a fire or blast furnace in a process known as smelting. the first evidence of copper smelting, dating from the 6th millennium bc, has been found at archaeological sites in majdanpek, jarmovac and plocnik, 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
Question: The chemical equation below shows a reaction of copper (Cu) with silver nitrate (AgNO_{3}) yielding silver (Ag) and copper(II) nitrate (Cu(NO_{3})_{2}) Cu + 2AgNO_{3} -> 2Ag + Cu(NO_{3})_{2} Silver and copper(II) nitrate are called the
A) reactants.
B) products.
C) catalysts.
D) inhibitors.
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B) products.
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Context:
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
( 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
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 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 = = = mei
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 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 xyle
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
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,
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
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,
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
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
Question: What role does the centromere play in cellular reproduction?
A) It is the area where microtubules are formed.
B) It is the area where the nucleus is during cell division.
C) It is the area of alignment for the chromosomes.
D) It is the area of attachment for chromatids.
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D) It is the area of attachment for chromatids.
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Context:
the word " ceramic " is derived from the greek word ΞΊΞ΅ΟΞ±ΞΌΞΉΞΊΞΏΟ ( keramikos ) meaning pottery. it is related to the older indo - european language root " to burn ". " ceramic " may be used as a noun in the singular to refer to a ceramic material or the 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,
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.
##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
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
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 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
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.
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
##ynastic egyptian sources. = = babylonian = = babylonian mathematics refers to any mathematics of the peoples of mesopotamia ( modern iraq ) from the days of the early sumerians through the hellenistic period almost to the dawn of christianity. the majority of babylonian mathematical work comes from two widely separated periods : the first few hundred years of the second millennium bc ( old babylonian period ), and the last few centuries of the first millennium bc ( seleucid period ). it is named babylonian mathematics due to the central role of babylon as a place of study. later under the arab empire, mesopotamia, especially baghdad, once again became an important center of study for islamic mathematics. in contrast to the sparsity of sources in egyptian mathematics, knowledge of babylonian mathematics is derived from more than 400 clay tablets unearthed since the 1850s. written in cuneiform script, tablets were inscribed whilst the clay was moist, and baked hard in an oven or by the heat of the sun. some of these appear to be graded homework. the earliest evidence of written mathematics dates back to the ancient sumerians, who built the earliest civilization in mesopotamia. they developed a complex system of metrology from 3000 bc that was chiefly concerned with administrative / financial counting, such as grain allotments, workers, weights of silver, or even liquids, among other things. from around 2500 bc onward, the sumerians wrote multiplication tables on clay tablets and dealt with geometrical exercises and division problems. the earliest traces of the babylonian numerals also date back to this period. babylonian mathematics were written using a sexagesimal ( base - 60 ) numeral system. from this derives the modern - day usage of 60 seconds in a minute, 60 minutes in an hour, and 360 ( 60 Γ 6 ) degrees in a circle, as well as the use of seconds and minutes of arc to denote fractions of a degree. it is thought the sexagesimal system was initially used by sumerian scribes because 60 can be evenly divided by 2, 3, 4, 5, 6, 10, 12, 15, 20 and 30, and for scribes ( doling out the aforementioned grain allotments, recording weights of silver, etc. ) being able to easily calculate by hand was essential, and so a sexagesimal system is pragmatically easier to calculate by hand with ; however, there is the possibility that using a sexagesimal system was an ethno - linguistic phenomenon ( that might not ever be known ), and not a mathematical
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
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
Question: If 1 kg of the compound toluene melts at -95Β°C, then 500 g of toluene will
A) melt at -47.5Β°C.
B) melt at -95Β°C.
C) boil at 95Β°C.
D) boil at 47.5Β°C.
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B) melt at -95Β°C.
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Context:
vehicle crashes. fuel economy / emissions : fuel economy is the measured fuel efficiency of the vehicle in miles per gallon or kilometers per liter. emissions - testing covers the measurement of vehicle emissions, including hydrocarbons, nitrogen oxides ( nox ), carbon monoxide ( co ), carbon dioxide ( co2 ), and evaporative emissions. nvh engineering ( noise, vibration, and harshness ) : nvh involves customer feedback ( both tactile [ felt ] and audible [ heard ] ) concerning a vehicle. while sound can be interpreted as a rattle, squeal, or hot, a tactile response can be seat vibration or a buzz in the steering wheel. this feedback is generated by components either rubbing, vibrating, or rotating. nvh response can be classified in various ways : powertrain nvh, road noise, wind noise, component noise, and squeak and rattle. note, there are both good and bad nvh qualities. the nvh engineer works to either eliminate bad nvh or change the " bad nvh " to good ( i. e., exhaust tones ). vehicle electronics : automotive electronics is an increasingly important aspect of automotive engineering. modern vehicles employ dozens of electronic systems. these systems are responsible for operational controls such as the throttle, brake and steering controls ; as well as many comfort - and - convenience systems such as the hvac, infotainment, and lighting systems. it would not be possible for automobiles to meet modern safety and fuel - economy requirements without electronic controls. performance : performance is a measurable and testable value of a vehicle ' s ability to perform in various conditions. performance can be considered in a wide variety of tasks, but it generally considers how quickly a car can accelerate ( e. g. standing start 1 / 4 mile elapsed time, 0 β 60 mph, etc. ), its top speed, how short and quickly a car can come to a complete stop from a set speed ( e. g. 70 - 0 mph ), how much g - force a car can generate without losing grip, recorded lap - times, cornering speed, brake fade, etc. performance can also reflect the amount of control in inclement weather ( snow, ice, rain ). shift quality : shift quality is the driver ' s perception of the vehicle to an automatic transmission shift event. this is influenced by the powertrain ( internal combustion engine, transmission ), and the vehicle ( driveline, suspension, engine and power
##ent governmental regulations. some of these requirements include : seat belt and air bag functionality testing, front and side - impact testing, and tests of rollover resistance. assessments are done with various methods and tools, including computer crash simulation ( typically finite element analysis ), crash - test dummy, and partial system sled and full vehicle crashes. fuel economy / emissions : fuel economy is the measured fuel efficiency of the vehicle in miles per gallon or kilometers per liter. emissions - testing covers the measurement of vehicle emissions, including hydrocarbons, nitrogen oxides ( nox ), carbon monoxide ( co ), carbon dioxide ( co2 ), and evaporative emissions. nvh engineering ( noise, vibration, and harshness ) : nvh involves customer feedback ( both tactile [ felt ] and audible [ heard ] ) concerning a vehicle. while sound can be interpreted as a rattle, squeal, or hot, a tactile response can be seat vibration or a buzz in the steering wheel. this feedback is generated by components either rubbing, vibrating, or rotating. nvh response can be classified in various ways : powertrain nvh, road noise, wind noise, component noise, and squeak and rattle. note, there are both good and bad nvh qualities. the nvh engineer works to either eliminate bad nvh or change the " bad nvh " to good ( i. e., exhaust tones ). vehicle electronics : automotive electronics is an increasingly important aspect of automotive engineering. modern vehicles employ dozens of electronic systems. these systems are responsible for operational controls such as the throttle, brake and steering controls ; as well as many comfort - and - convenience systems such as the hvac, infotainment, and lighting systems. it would not be possible for automobiles to meet modern safety and fuel - economy requirements without electronic controls. performance : performance is a measurable and testable value of a vehicle ' s ability to perform in various conditions. performance can be considered in a wide variety of tasks, but it generally considers how quickly a car can accelerate ( e. g. standing start 1 / 4 mile elapsed time, 0 β 60 mph, etc. ), its top speed, how short and quickly a car can come to a complete stop from a set speed ( e. g. 70 - 0 mph ), how much g - force a car can generate without losing grip, recorded lap - times, cornering speed, brake fade, etc. performance can also reflect the
, buses, trucks, etc. it includes branch study of mechanical, electronic, software and safety elements. some of the engineering attributes and disciplines that are of importance to the automotive engineer include : safety engineering : safety engineering is the assessment of various crash scenarios and their impact on the vehicle occupants. these are tested against very stringent governmental regulations. some of these requirements include : seat belt and air bag functionality testing, front and side - impact testing, and tests of rollover resistance. assessments are done with various methods and tools, including computer crash simulation ( typically finite element analysis ), crash - test dummy, and partial system sled and full vehicle crashes. fuel economy / emissions : fuel economy is the measured fuel efficiency of the vehicle in miles per gallon or kilometers per liter. emissions - testing covers the measurement of vehicle emissions, including hydrocarbons, nitrogen oxides ( nox ), carbon monoxide ( co ), carbon dioxide ( co2 ), and evaporative emissions. nvh engineering ( noise, vibration, and harshness ) : nvh involves customer feedback ( both tactile [ felt ] and audible [ heard ] ) concerning a vehicle. while sound can be interpreted as a rattle, squeal, or hot, a tactile response can be seat vibration or a buzz in the steering wheel. this feedback is generated by components either rubbing, vibrating, or rotating. nvh response can be classified in various ways : powertrain nvh, road noise, wind noise, component noise, and squeak and rattle. note, there are both good and bad nvh qualities. the nvh engineer works to either eliminate bad nvh or change the " bad nvh " to good ( i. e., exhaust tones ). vehicle electronics : automotive electronics is an increasingly important aspect of automotive engineering. modern vehicles employ dozens of electronic systems. these systems are responsible for operational controls such as the throttle, brake and steering controls ; as well as many comfort - and - convenience systems such as the hvac, infotainment, and lighting systems. it would not be possible for automobiles to meet modern safety and fuel - economy requirements without electronic controls. performance : performance is a measurable and testable value of a vehicle ' s ability to perform in various conditions. performance can be considered in a wide variety of tasks, but it generally considers how quickly a car can accelerate ( e. g. standing start 1 / 4 mile elapsed time, 0 β 60 mph, etc. )
, 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
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.
in space, can adversely affect the earth ' s environment. some hypergolic rocket propellants, such as hydrazine, are highly toxic prior to combustion, but decompose into less toxic compounds after burning. rockets using hydrocarbon fuels, such as kerosene, release carbon dioxide and soot in their exhaust. carbon dioxide emissions are insignificant compared to those from other sources ; on average, the united states consumed 803 million us gal ( 3. 0 million m3 ) of liquid fuels per day in 2014, while a single falcon 9 rocket first stage burns around 25, 000 us gallons ( 95 m3 ) of kerosene fuel per launch. even if a falcon 9 were launched every single day, it would only represent 0. 006 % of liquid fuel consumption ( and carbon dioxide emissions ) for that day. additionally, the exhaust from lox - and lh2 - fueled engines, like the ssme, is almost entirely water vapor. nasa addressed environmental concerns with its canceled constellation program in accordance with the national environmental policy act in 2011. in contrast, ion engines use harmless noble gases like xenon for propulsion. an example of nasa ' s environmental efforts is the nasa sustainability base. additionally, the exploration sciences building was awarded the leed gold rating in 2010. on may 8, 2003, the environmental protection agency recognized nasa as the first federal agency to directly use landfill gas to produce energy at one of its facilities β the goddard space flight center, greenbelt, maryland. in 2018, nasa along with other companies including sensor coating systems, pratt & whitney, monitor coating and utrc launched the project caution ( coatings for ultra high temperature detection ). this project aims to enhance the temperature range of the thermal history coating up to 1, 500 Β°c ( 2, 730 Β°f ) and beyond. the final goal of this project is improving the safety of jet engines as well as increasing efficiency and reducing co2 emissions. = = = climate change = = = nasa also researches and publishes on climate change. its statements concur with the global scientific consensus that the climate is warming. bob walker, who has advised former us president donald trump on space issues, has advocated that nasa should focus on space exploration and that its climate study operations should be transferred to other agencies such as noaa. former nasa atmospheric scientist j. marshall shepherd countered that earth science study was built into nasa ' s mission at its creation in the 1958 national aeronautics and space act. nasa won the 2020 webby people ' s voice award for green in the category
a rail gun launching at 9 mj of energy would need roughly 32 mj worth of energy from capacitors. current advances in energy storage allow for energy densities as high as 2. 5 mj / dm3, which means that a battery delivering 32 mj of energy would require a volume of 12. 8 dm3 per shot ; this is not a viable volume for use in a modern main battle tank, especially one designed to be lighter than existing models. there has even been discussion about eliminating the necessity for an outside electrical source in etc ignition by initiating the plasma cartridge through a small explosive force. furthermore, etc technology is not only applicable to solid propellants. to increase muzzle velocity even further electrothermal - chemical ignition can work with liquid propellants, although this would require further research into plasma ignition. etc technology is also compatible with existing projects to reduce the amount of recoil delivered to the vehicle while firing. understandably, recoil of a gun firing a projectile at 17 mj or more will increase directly with the increase in muzzle energy in accordance to newton ' s third law of motion and successful implementation of recoil reduction mechanisms will be vital to the installation of an etc powered gun in an existing vehicle design. for example, oto melara ' s new lightweight 120 mm l / 45 gun has achieved a recoil force of 25 t by using a longer recoil mechanism ( 550 mm ) and a pepperpot muzzle brake. reduction in recoil can also be achieved through mass attenuation of the thermal sleeve. the ability of etc technology to be applied to existing gun designs means that for future gun upgrades there ' s no longer the necessity to redesign the turret to include a larger breech or caliber gun barrel. several countries have already determined that etc technology is viable for the future and have funded indigenous projects considerably. these include the united states, germany and the united kingdom, amongst others. the united states ' xm360, which was planned to equip the future combat systems mounted combat system light tank and may be the m1 abrams ' next gun upgrade, is reportedly based on the xm291 and may include etc technology, or portions of etc technology. tests of this gun have been performed using " precision ignition " technology, which may refer to etc ignition. = = notes = = = = bibliography = = = = external links = = electromagnetic launch symposium http : / / www. powerlabs. org / electrothermal. htm
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 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.
ratio, sulfur from coal or coke fuel reacts with the slag so that the sulfur does not contaminate the iron. coal and coke were cheaper and more abundant fuel. as a result, iron production rose significantly during the last decades of the 18th century. coal converted to coke fueled higher temperature blast furnaces and produced cast iron in much larger amounts than before, allowing the creation of a range of structures such as the iron bridge. cheap coal meant that industry was no longer constrained by water resources driving the mills, although it continued as a valuable source of power. the steam engine helped drain the mines, so more coal reserves could be accessed, and the output of coal increased. the development of the high - pressure steam engine made locomotives possible, and a transport revolution followed. the steam engine which had existed since the early 18th century, was practically applied to both steamboat and railway transportation. the liverpool and manchester railway, the first purpose - built railway line, opened in 1830, the rocket locomotive of robert stephenson being one of its first working locomotives used. manufacture of ships ' pulley blocks by all - metal machines at the portsmouth block mills in 1803 instigated the age of sustained mass production. machine tools used by engineers to manufacture parts began in the first decade of the century, notably by richard roberts and joseph whitworth. the development of interchangeable parts through what is now called the american system of manufacturing began in the firearms industry at the u. s. federal arsenals in the early 19th century, and became widely used by the end of the century. until the enlightenment era, little progress was made in water supply and sanitation and the engineering skills of the romans were largely neglected throughout europe. the first documented use of sand filters to purify the water supply dates to 1804, when the owner of a bleachery in paisley, scotland, john gibb, installed an experimental filter, selling his unwanted surplus to the public. the first treated public water supply in the world was installed by engineer james simpson for the chelsea waterworks company in london in 1829. the first screw - down water tap was patented in 1845 by guest and chrimes, a brass foundry in rotherham. the practice of water treatment soon became mainstream, and the virtues of the system were made starkly apparent after the investigations of the physician john snow during the 1854 broad street cholera outbreak demonstrated the role of the water supply in spreading the cholera epidemic. = = = second industrial revolution ( 1860s β 1914 ) = = = the 19th century saw astonishing developments in transportation, construction,
railgun currently cannot achieve a higher muzzle velocity than the amount of energy input. even at 50 % efficiency a rail gun launching a projectile with a kinetic energy of 20 mj would require an energy input into the rails of 40 mj, and 50 % efficiency has not yet been achieved. to put this into perspective, a rail gun launching at 9 mj of energy would need roughly 32 mj worth of energy from capacitors. current advances in energy storage allow for energy densities as high as 2. 5 mj / dm3, which means that a battery delivering 32 mj of energy would require a volume of 12. 8 dm3 per shot ; this is not a viable volume for use in a modern main battle tank, especially one designed to be lighter than existing models. there has even been discussion about eliminating the necessity for an outside electrical source in etc ignition by initiating the plasma cartridge through a small explosive force. furthermore, etc technology is not only applicable to solid propellants. to increase muzzle velocity even further electrothermal - chemical ignition can work with liquid propellants, although this would require further research into plasma ignition. etc technology is also compatible with existing projects to reduce the amount of recoil delivered to the vehicle while firing. understandably, recoil of a gun firing a projectile at 17 mj or more will increase directly with the increase in muzzle energy in accordance to newton ' s third law of motion and successful implementation of recoil reduction mechanisms will be vital to the installation of an etc powered gun in an existing vehicle design. for example, oto melara ' s new lightweight 120 mm l / 45 gun has achieved a recoil force of 25 t by using a longer recoil mechanism ( 550 mm ) and a pepperpot muzzle brake. reduction in recoil can also be achieved through mass attenuation of the thermal sleeve. the ability of etc technology to be applied to existing gun designs means that for future gun upgrades there ' s no longer the necessity to redesign the turret to include a larger breech or caliber gun barrel. several countries have already determined that etc technology is viable for the future and have funded indigenous projects considerably. these include the united states, germany and the united kingdom, amongst others. the united states ' xm360, which was planned to equip the future combat systems mounted combat system light tank and may be the m1 abrams ' next gun upgrade, is reportedly based on the xm291 and may include etc technology, or portions of etc technology. tests of this gun have been performed using "
Question: A calculation based on the chemical energy of gasoline shows that a car should be able to go 100 miles on a gallon of fuel. When the car was driven on a test track, the car only went 25 miles on a gallon of fuel. What accounts for most of the difference?
A) the mass of the driver and the fuel carried by the car
B) the wind resistance between the car and the air nearby
C) the waste heat from the combustion of fuel in the engine
D) the friction between the tires and the surface of the track
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C) the waste heat from the combustion of fuel in the engine
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Context:
the thickness of freshly made soap films is usually in the micron range, and interference colors make thickness fluctuations easily visible. circular patterns of constant thickness are commonly observed, either a thin film disc in a thicker film or the reverse. in this letter, we evidence the line tension at the origin of these circular patterns. using a well controlled soap film preparation, we produce a piece of thin film surrounded by a thicker film. the thickness profile, measured with a spectral camera, leads to a line tension of the order of 0. 1 nn which drives the relaxation of the thin film shape, initially very elongated, toward a circular shape. a balance between line tension and air friction leads to a quantitative prediction of the relaxation process. such a line tension is expected to play a role in the production of marginal regeneration patches, involved in soap film drainage and stability.
a polygon is a shape that is bounded by a finite chain of straight line segments closing in a loop to form a closed chain or circuit. these segments are called its edges or sides, and the points where two edges meet are the polygon ' s vertices ( singular : vertex ) or corners. the interior of the polygon is sometimes called its body. an n - gon is a polygon with n sides. a polygon is a 2 - dimensional example of the more general polytope in any number of dimensions. a circle is a simple shape of two - dimensional geometry that is the set of all points in a plane that are at a given distance from a given point, the center. the distance between any of the points and the center is called the radius. it can also be defined as the locus of a point equidistant from a fixed point. a perimeter is a path that surrounds a two - dimensional shape. the term may be used either for the path or its length - it can be thought of as the length of the outline of a shape. the perimeter of a circle or ellipse is called its circumference. area is the quantity that expresses the extent of a two - dimensional figure or shape. there are several well - known formulas for the areas of simple shapes such as triangles, rectangles, and circles. = = = proportions = = = two quantities are proportional if a change in one is always accompanied by a change in the other, and if the changes are always related by use of a constant multiplier. the constant is called the coefficient of proportionality or proportionality constant. if one quantity is always the product of the other and a constant, the two are said to be directly proportional. x and y are directly proportional if the ratio y x { \ displaystyle { \ tfrac { y } { x } } } is constant. if the product of the two quantities is always equal to a constant, the two are said to be inversely proportional. x and y are inversely proportional if the product x y { \ displaystyle xy } is constant. = = = analytic geometry = = = analytic geometry is the study of geometry using a coordinate system. this contrasts with synthetic geometry. usually the cartesian coordinate system is applied to manipulate equations for planes, straight lines, and squares, often in two and sometimes in three dimensions. geometrically, one studies the euclidean plane ( 2 dimensions ) and euclidean space ( 3 dimensions ). as taught in school
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
dimension 3, typically r3. a surface that is contained in a projective space is called a projective surface ( see Β§ projective surface ). a surface that is not supposed to be included in another space is called an abstract surface. = = examples = = the graph of a continuous function of two variables, defined over a connected open subset of r2 is a topological surface. if the function is differentiable, the graph is a differentiable surface. a plane is both an algebraic surface and a differentiable surface. it is also a ruled surface and a surface of revolution. a circular cylinder ( that is, the locus of a line crossing a circle and parallel to a given direction ) is an algebraic surface and a differentiable surface. a circular cone ( locus of a line crossing a circle, and passing through a fixed point, the apex, which is outside the plane of the circle ) is an algebraic surface which is not a differentiable surface. if one removes the apex, the remainder of the cone is the union of two differentiable surfaces. the surface of a polyhedron is a topological surface, which is neither a differentiable surface nor an algebraic surface. a hyperbolic paraboloid ( the graph of the function z = xy ) is a differentiable surface and an algebraic surface. it is also a ruled surface, and, for this reason, is often used in architecture. a two - sheet hyperboloid is an algebraic surface and the union of two non - intersecting differentiable surfaces. = = parametric surface = = a parametric surface is the image of an open subset of the euclidean plane ( typically r 2 { \ displaystyle \ mathbb { r } ^ { 2 } } ) by a continuous function, in a topological space, generally a euclidean space of dimension at least three. usually the function is supposed to be continuously differentiable, and this will be always the case in this article. specifically, a parametric surface in r 3 { \ displaystyle \ mathbb { r } ^ { 3 } } is given by three functions of two variables u and v, called parameters x = f 1 ( u, v ), y = f 2 ( u, v ), z = f 3 ( u, v ). { \ displaystyle { \ begin { aligned } x & = f _ { 1 } ( u, v ), \ \ [ 4pt ] y & = f _ { 2 } ( u, v ), \ \ [ 4pt ] z & = f _ { 3 }
that are at a given distance from a given point, the center. the distance between any of the points and the center is called the radius. it can also be defined as the locus of a point equidistant from a fixed point. a perimeter is a path that surrounds a two - dimensional shape. the term may be used either for the path or its length - it can be thought of as the length of the outline of a shape. the perimeter of a circle or ellipse is called its circumference. area is the quantity that expresses the extent of a two - dimensional figure or shape. there are several well - known formulas for the areas of simple shapes such as triangles, rectangles, and circles. = = = proportions = = = two quantities are proportional if a change in one is always accompanied by a change in the other, and if the changes are always related by use of a constant multiplier. the constant is called the coefficient of proportionality or proportionality constant. if one quantity is always the product of the other and a constant, the two are said to be directly proportional. x and y are directly proportional if the ratio y x { \ displaystyle { \ tfrac { y } { x } } } is constant. if the product of the two quantities is always equal to a constant, the two are said to be inversely proportional. x and y are inversely proportional if the product x y { \ displaystyle xy } is constant. = = = analytic geometry = = = analytic geometry is the study of geometry using a coordinate system. this contrasts with synthetic geometry. usually the cartesian coordinate system is applied to manipulate equations for planes, straight lines, and squares, often in two and sometimes in three dimensions. geometrically, one studies the euclidean plane ( 2 dimensions ) and euclidean space ( 3 dimensions ). as taught in school books, analytic geometry can be explained more simply : it is concerned with defining and representing geometrical shapes in a numerical way and extracting numerical information from shapes ' numerical definitions and representations. transformations are ways of shifting and scaling functions using different algebraic formulas. = = = negative numbers = = = a negative number is a real number that is less than zero. such numbers are often used to represent the amount of a loss or absence. for example, a debt that is owed may be thought of as a negative asset, or a decrease in some quantity may be thought of as a negative increase. negative numbers are used to describe values on a scale
a statistical study of the environment around polar ring galaxies is presented. two kinds of search are performed : 1 ) a study of the concentration and diameters of all the objects surrounding the polar rings, within a search field 5 times the ring diameter. new magnitudes for polar ring galaxies are presented. 2 ) a search, in a wider field, for galaxies of similar size that may have encountered the polar ring host galaxy in a time of the order of 1 gyr. differently from the results of similar searches in the fields of active galaxies, the environment of the polar ring galaxies seems to be similar to that of normal galaxies. this result may give support to the models suggesting long times for formation and evolution of the rings. if the rings are old ( and stable or in equilibrium ), no traces of the past interaction are expected in their surroundings. in addition, the formation of massive polar rings, too big to derive from the ingestion of a present - day dwarf galaxy, may be easily placed in epochs with a higher number of gas - rich galaxies.
the infrared excess around the white dwarf g29 - 38 can be explained by emission from an opaque flat ring of dust with an inner radius 0. 14 of the radius of the sun and an outer radius approximately equal to the sun ' s. this ring lies within the roche region of the white dwarf where an asteroid could have been tidally destroyed, producing a system reminiscent of saturn ' s rings. accretion onto the white dwarf from this circumstellar dust can explain the observed calcium abundance in the atmosphere of g29 - 38. either as a bombardment by a series of asteroids or because of one large disruption, the total amount of matter accreted onto the white dwarf may have been comparable to the total mass of asteroids in the solar system, or, equivalently, about 1 % of the mass in the asteroid belt around the main sequence star zeta lep.
, 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 %
##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
( 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 than animals. genetic evidence suggests that the true evolutionary relationship of multicelled organisms is as shown in the cladogram below β fungi are more closely related to animals than to plants. in 1998, the angiosperm phylogeny group published a phylogeny for flowering plants based on an analysis of
Question: A student wants to find the relationship between the diameter of several plastic disks and the circumference of each disk. Which of these types of graphs should be constructed to determine this relationship?
A) pie graph
B) line graph
C) scatterplot
D) box-and-whisker plot
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B) line graph
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Context:
in mathematics, a reflection ( also spelled reflexion ) is a mapping from a euclidean space to itself that is an isometry with a hyperplane as the set of fixed points ; this set is called the axis ( in dimension 2 ) or plane ( in dimension 3 ) of reflection. the image of a figure by a reflection is its mirror image in the axis or plane of reflection. for example the mirror image of the small latin letter p for a reflection with respect to a vertical axis ( a vertical reflection ) would look like q. its image by reflection in a horizontal axis ( a horizontal reflection ) would look like b. a reflection is an involution : when applied twice in succession, every point returns to its original location, and every geometrical object is restored to its original state. the term reflection is sometimes used for a larger class of mappings from a euclidean space to itself, namely the non - identity isometries that are involutions. the set of fixed points ( the " mirror " ) of such an isometry is an affine subspace, but is possibly smaller than a hyperplane. for instance a reflection through a point is an involutive isometry with just one fixed point ; the image of the letter p under it would look like a d. this operation is also known as a central inversion ( coxeter 1969, Β§ 7. 2 ), and exhibits euclidean space as a symmetric space. in a euclidean vector space, the reflection in the point situated at the origin is the same as vector negation. other examples include reflections in a line in three - dimensional space. typically, however, unqualified use of the term " reflection " means reflection in a hyperplane. some mathematicians use " flip " as a synonym for " reflection ". = = construction = = in a plane ( or, respectively, 3 - dimensional ) geometry, to find the reflection of a point drop a perpendicular from the point to the line ( plane ) used for reflection, and extend it the same distance on the other side. to find the reflection of a figure, reflect each point in the figure. to reflect point p through the line ab using compass and straightedge, proceed as follows ( see figure ) : step 1 ( red ) : construct a circle with center at p and some fixed radius r to create points a β² and b β² on the line ab, which will be equidistant from p. step 2 ( green ) : construct circles centered at a β² and b β² having radius r
reflection is its mirror image in the axis or plane of reflection. for example the mirror image of the small latin letter p for a reflection with respect to a vertical axis ( a vertical reflection ) would look like q. its image by reflection in a horizontal axis ( a horizontal reflection ) would look like b. a reflection is an involution : when applied twice in succession, every point returns to its original location, and every geometrical object is restored to its original state. the term reflection is sometimes used for a larger class of mappings from a euclidean space to itself, namely the non - identity isometries that are involutions. the set of fixed points ( the " mirror " ) of such an isometry is an affine subspace, but is possibly smaller than a hyperplane. for instance a reflection through a point is an involutive isometry with just one fixed point ; the image of the letter p under it would look like a d. this operation is also known as a central inversion ( coxeter 1969, Β§ 7. 2 ), and exhibits euclidean space as a symmetric space. in a euclidean vector space, the reflection in the point situated at the origin is the same as vector negation. other examples include reflections in a line in three - dimensional space. typically, however, unqualified use of the term " reflection " means reflection in a hyperplane. some mathematicians use " flip " as a synonym for " reflection ". = = construction = = in a plane ( or, respectively, 3 - dimensional ) geometry, to find the reflection of a point drop a perpendicular from the point to the line ( plane ) used for reflection, and extend it the same distance on the other side. to find the reflection of a figure, reflect each point in the figure. to reflect point p through the line ab using compass and straightedge, proceed as follows ( see figure ) : step 1 ( red ) : construct a circle with center at p and some fixed radius r to create points a β² and b β² on the line ab, which will be equidistant from p. step 2 ( green ) : construct circles centered at a β² and b β² having radius r. p and q will be the points of intersection of these two circles. point q is then the reflection of point p through line ab. = = properties = = the matrix for a reflection is orthogonal with determinant β1 and eigenvalues β1, 1, 1,..., 1.
, 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 '
what if someone built a " box " that applies quantum superposition not just to quantum bits in the microscopic but also to macroscopic everyday " objects ", such as schr \ " odinger ' s cat or a human being? if that were possible, and if the different " copies " of a man could exploit quantum interference to synchronize and collapse into their preferred state, then one ( or they? ) could in a sense choose their future, win the lottery, break codes and other security devices, and become king of the world, or actually of the many - worlds. we set up the plot - line of a new episode of black mirror to reflect on what might await us if one were able to build such a technology.
if stimulated emission could be turned off then only uncorrelated photons would be emitted from black bodies and the photon counting statistics would be poissonian. through the process of stimulated emission, some fraction of the photons emitted from a black body are correlated and thus emitted in clusters. this photon clustering can be calculated by semi - classical means. the corresponding results are in agreement with quantum theory.
time interval between the incident and scattered photon in raman effect and absorption of photon and emission of electron in photoelectric effect has not been determined till now. this is because there is no such high level instrument discovered till now to detect time interval to such a small level. but this can be calculated theoretically by applying a basic principle of physics like impulse is equal to the change in momentum. considering the collision between electron and photon as perfect inelastic collision in photoelectric effect, elastic and inelastic collision in raman effect and elastic collision in plane mirror reflection and the interaction between electron and photon as strong gravitational interaction we calculate the required time interval. during these phenomena there is lattice vibration which can be quantized as phonon particles.
we throw a brief glance at galois ' life, on the occasion of his 200th anniversary ( written in german ).
the luminosity variation of a stellar source due to the gravitational microlensing effect can be considered also if the light rays are defocused ( instead of focused ) toward the observer. in this case, we should detect a gap instead of a peak in the light curve of the source. actually, we describe how the phenomenon depends on the relative position of source and lens with respect to the observer : if the lens is between, we have focusing, if the lens is behind, we have defocusing. it is shown that the number of events with predicted gaps is equal to the number of events with peaks in the light curves.
pairs of planck - mass - scale drops of superfluid helium coated by electrons ( i. e., " millikan oil drops " ), when levitated in the presence of strong magnetic fields and at low temperatures, can be efficient quantum transducers between electromagnetic ( em ) and gravitational ( gr ) radiation. a hertz - like experiment, in which em waves are converted at the source into gr waves, and then back - converted at the receiver from gr waves back into em waves, should be practical to perform. this would open up observations of the gravity - wave analog of the cosmic microwave background from the extremely early big bang, and also communications directly through the interior of the earth.
Question: When light is bounced off a mirror, the light is
A) reflected.
B) refracted.
C) absorbed.
D) diffracted.
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A) reflected.
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Context:
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
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
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
basic properties of black holes are explained in terms of trapping horizons. it is shown that matter and information will escape from an evaporating black hole. a general scenario is outlined whereby a black hole evaporates completely without singularity, event horizon or loss of energy or information.
this is an exposition of gauss ' s proof of descartes ' s rule of signs.
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.
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.
the recent report on laser cooling of liquid may contradict the law of energy conservation.
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
Question: Which of the following sentences best explains what happens when puddles evaporate?
A) The water absorbs into the ground.
B) The particles of matter move more slowly.
C) The water changes from one form to another.
D) The particles of matter move closer together.
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C) The water changes from one form to another.
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Context:
fluid dynamics video demonstrating the evolution of dynamic stall on a wind turbine blade.
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
##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
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 :
##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
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
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 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
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
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
Question: Plants on hills keep dirt in place during a rain storm. Plant roots grow into the dirt and keep the dirt from moving. Why do roots grow into the dirt?
A) to release gases
B) to release water
C) to absorb energy
D) to absorb nutrients
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D) to absorb nutrients
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Context:
( 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
##fts. autografted skin comes from a patient ' s own skin, which allows the dermis to have a faster healing rate, and the donor site can be re - harvested a few times. allograft skin often comes from cadaver skin and is mostly used to treat burn victims. lastly, xenografted skin comes from animals and provides a temporary healing structure for the skin. they assist in dermal regeneration, but cannot become part of the host skin. tissue - engineered skin is now available in commercial products. integra, originally used to only treat burns, consists of a collagen matrix and chondroitin sulfate that can be used as a skin replacement. the chondroitin sulfate functions as a component of proteoglycans, which helps to form the extracellular matrix. integra can be repopulated and revascularized while maintaining its dermal collagen architecture, making it a bioartificial organ dermagraft, another commercial - made tissue - engineered skin product, is made out of living fibroblasts. these fibroblasts proliferate and produce growth factors, collagen, and ecm proteins, that help build granulation tissue. = = = = heart = = = = since the number of patients awaiting a heart transplant is continuously increasing over time, and the number of patients on the waiting list surpasses the organ availability, artificial organs used as replacement therapy for terminal heart failure would help alleviate this difficulty. artificial hearts are usually used to bridge the heart transplantation or can be applied as replacement therapy for terminal heart malfunction. the total artificial heart ( tah ), first introduced by dr. vladimir p. demikhov in 1937, emerged as an ideal alternative. since then it has been developed and improved as a mechanical pump that provides long - term circulatory support and replaces diseased or damaged heart ventricles that cannot properly pump the blood, restoring thus the pulmonary and systemic flow. some of the current tahs include abiocor, an fda - approved device that comprises two artificial ventricles and their valves, and does not require subcutaneous connections, and is indicated for patients with biventricular heart failure. in 2010 syncardia released the portable freedom driver that allows patients to have a portable device without being confined to the hospital. = = = = kidney = = = = while kidney transplants are possible, renal failure is more often treated using an artificial kidney. the first artificial
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
1975. skin tissue - engineered skin is a type of bioartificial organ that is often used to treat burns, diabetic foot ulcers, or other large wounds that cannot heal well on their own. artificial skin can be made from autografts, allografts, and xenografts. autografted skin comes from a patient ' s own skin, which allows the dermis to have a faster healing rate, and the donor site can be re - harvested a few times. allograft skin often comes from cadaver skin and is mostly used to treat burn victims. lastly, xenografted skin comes from animals and provides a temporary healing structure for the skin. they assist in dermal regeneration, but cannot become part of the host skin. tissue - engineered skin is now available in commercial products. integra, originally used to only treat burns, consists of a collagen matrix and chondroitin sulfate that can be used as a skin replacement. the chondroitin sulfate functions as a component of proteoglycans, which helps to form the extracellular matrix. integra can be repopulated and revascularized while maintaining its dermal collagen architecture, making it a bioartificial organ dermagraft, another commercial - made tissue - engineered skin product, is made out of living fibroblasts. these fibroblasts proliferate and produce growth factors, collagen, and ecm proteins, that help build granulation tissue. = = = = heart = = = = since the number of patients awaiting a heart transplant is continuously increasing over time, and the number of patients on the waiting list surpasses the organ availability, artificial organs used as replacement therapy for terminal heart failure would help alleviate this difficulty. artificial hearts are usually used to bridge the heart transplantation or can be applied as replacement therapy for terminal heart malfunction. the total artificial heart ( tah ), first introduced by dr. vladimir p. demikhov in 1937, emerged as an ideal alternative. since then it has been developed and improved as a mechanical pump that provides long - term circulatory support and replaces diseased or damaged heart ventricles that cannot properly pump the blood, restoring thus the pulmonary and systemic flow. some of the current tahs include abiocor, an fda - approved device that comprises two artificial ventricles and their valves, and does not require subcutaneous connections, and is indicated for
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 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 = = = mei
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
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
techniques that provide heart and lung support. it is used primarily to support the lungs for a prolonged but still temporary timeframe ( 1 β 30 days ) and allow for recovery from reversible diseases. robert bartlett is known as the father of ecmo and performed the first treatment of a newborn using an ecmo machine in 1975. skin tissue - engineered skin is a type of bioartificial organ that is often used to treat burns, diabetic foot ulcers, or other large wounds that cannot heal well on their own. artificial skin can be made from autografts, allografts, and xenografts. autografted skin comes from a patient ' s own skin, which allows the dermis to have a faster healing rate, and the donor site can be re - harvested a few times. allograft skin often comes from cadaver skin and is mostly used to treat burn victims. lastly, xenografted skin comes from animals and provides a temporary healing structure for the skin. they assist in dermal regeneration, but cannot become part of the host skin. tissue - engineered skin is now available in commercial products. integra, originally used to only treat burns, consists of a collagen matrix and chondroitin sulfate that can be used as a skin replacement. the chondroitin sulfate functions as a component of proteoglycans, which helps to form the extracellular matrix. integra can be repopulated and revascularized while maintaining its dermal collagen architecture, making it a bioartificial organ dermagraft, another commercial - made tissue - engineered skin product, is made out of living fibroblasts. these fibroblasts proliferate and produce growth factors, collagen, and ecm proteins, that help build granulation tissue. = = = = heart = = = = since the number of patients awaiting a heart transplant is continuously increasing over time, and the number of patients on the waiting list surpasses the organ availability, artificial organs used as replacement therapy for terminal heart failure would help alleviate this difficulty. artificial hearts are usually used to bridge the heart transplantation or can be applied as replacement therapy for terminal heart malfunction. the total artificial heart ( tah ), first introduced by dr. vladimir p. demikhov in 1937, emerged as an ideal alternative. since then it has been developed and improved as a mechanical pump that provides long - term circulatory support and
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
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. 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
Question: In animal skin tissue, cell division is responsible for
A) growth and repair
B) sexual reproduction
C) obtaining energy
D) production of sex cells
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A) growth and repair
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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
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.
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
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
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
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,
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
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
Question: Which process drives most of the ATP synthesis in a chloroplast?
A) flow of protons across an electrochemical gradient
B) flow of tRNA across an electrochemical gradient
C) exposure of ADP to electromagnetic waves
D) exposure of carbohydrates to electromagnetic waves
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A) flow of protons across an electrochemical gradient
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, 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
living things, computers, societies, and even books are part of a grand evolutionary struggle to survive. that struggle shapes nature, nations, religions, art, science, and you. what you think, feel, and do is determined by it. darwinian evolution does not apply solely to the genes that are stored in dna. using the insights of alan turing and richard dawkins, we will see that it also applies to the memes we store in our brains and the information we store in our computers. the next time you run for president, fight a war, or just deal with the ordinary problems humans are heir to, perhaps this book will be of use. if you want to understand why and when you will die, or if you want to achieve greatness this book may help. if you are concerned about where the computer revolution is headed, this book may provide some answers.
the theory outright... lakatos sought to reconcile the rationalism of popperian falsificationism with what seemed to be its own refutation by history ". many philosophers have tried to solve the problem of demarcation in the following terms : a statement constitutes knowledge if sufficiently many people believe it sufficiently strongly. but the history of thought shows us that many people were totally committed to absurd beliefs. if the strengths of beliefs were a hallmark of knowledge, we should have to rank some tales about demons, angels, devils, and of heaven and hell as knowledge. scientists, on the other hand, are very sceptical even of their best theories. newton ' s is the most powerful theory science has yet produced, but newton himself never believed that bodies attract each other at a distance. so no degree of commitment to beliefs makes them knowledge. indeed, the hallmark of scientific behaviour is a certain scepticism even towards one ' s most cherished theories. blind commitment to a theory is not an intellectual virtue : it is an intellectual crime. thus a statement may be pseudoscientific even if it is eminently ' plausible ' and everybody believes in it, and it may be scientifically valuable even if it is unbelievable and nobody believes in it. a theory may even be of supreme scientific value even if no one understands it, let alone believes in it. the boundary between science and pseudoscience is disputed and difficult to determine analytically, even after more than a century of study by philosophers of science and scientists, and despite some basic agreements on the fundamentals of the scientific method. the concept of pseudoscience rests on an understanding that the scientific method has been misrepresented or misapplied with respect to a given theory, but many philosophers of science maintain that different kinds of methods are held as appropriate across different fields and different eras of human history. according to lakatos, the typical descriptive unit of great scientific achievements is not an isolated hypothesis but " a powerful problem - solving machinery, which, with the help of sophisticated mathematical techniques, digests anomalies and even turns them into positive evidence ". to popper, pseudoscience uses induction to generate theories, and only performs experiments to seek to verify them. to popper, falsifiability is what determines the scientific status of a theory. taking a historical approach, kuhn observed that scientists did not follow popper ' s rule, and might ignore falsifying data, unless overwhelming. to kuhn, puzzle - solving within
##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
the universe is found to have undergone several phases in which the gravitational constant had different behaviors. during some epochs the energy density of the universe remained constant and the universe remained static. in the radiation dominated epoch the radiation field satisfies stefan ' s formula while the scale factor varies linearly with time. the model enhances the formation of the structure in the universe as observed today.
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
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
a detailed analysis of primordial nucleosynthesis predictions for light element abundances is performed. contents : 1. the standard cosmology : an overview. 2. primordial nucleosynthesis. 3. the born rates for n < - > p reactions. 4. finite nucleon mass corrections. 5. qed thermal radiative corrections. 6. calculations of big bang nucleosynthesis. results.
one of the greatest discoveries of modern times is that of the expanding universe, almost invariably attributed to hubble ( 1929 ). what is not widely known is that the original treatise by lemaitre ( 1927 ) contained a rich fusion of both theory and of observation. stiglers law of eponymy is yet again affirmed : no scientific discovery is named after its original discoverer ( merton, 1957 ). an appeal is made for a lemaitre telescope, to honour the discoverer of the expanding universe.
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
Question: Which of the following is most consistent with the modern theory of evolution?
A) Parents pass their physical traits to their offspring; those offspring with traits that help them survive in the environment are able to reproduce.
B) Parents change their physical traits in order to survive in the environment, then those parental traits are passed to their offspring.
C) Life on this planet came from another planet far out in space.
D) Living organisms have not changed for hundreds of millions of years.
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A) Parents pass their physical traits to their offspring; those offspring with traits that help them survive in the environment are able to reproduce.
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Context:
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
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
oil umbrella ) ; for calculating the time of death ( allowing for weather and insect activity ) ; described how to wash and examine the dead body to ascertain the reason for death. at that time the book had described methods for distinguishing between suicide and faked suicide. he wrote the book on forensics stating that all wounds or dead bodies should be examined, not avoided. the book became the first form of literature to help determine the cause of death. in one of song ci ' s accounts ( washing away of wrongs ), the case of a person murdered with a sickle was solved by an investigator who instructed each suspect to bring his sickle to one location. ( he realized it was a sickle by testing various blades on an animal carcass and comparing the wounds. ) flies, attracted by the smell of blood, eventually gathered on a single sickle. in light of this, the owner of that sickle confessed to the murder. the book also described how to distinguish between a drowning ( water in the lungs ) and strangulation ( broken neck cartilage ), and described evidence from examining corpses to determine if a death was caused by murder, suicide or accident. methods from around the world involved saliva and examination of the mouth and tongue to determine innocence or guilt, as a precursor to the polygraph test. in ancient india, some suspects were made to fill their mouths with dried rice and spit it back out. similarly, in ancient china, those accused of a crime would have rice powder placed in their mouths. in ancient middle - eastern cultures, the accused were made to lick hot metal rods briefly. it is thought that these tests had some validity since a guilty person would produce less saliva and thus have a drier mouth ; the accused would be considered guilty if rice was sticking to their mouths in abundance or if their tongues were severely burned due to lack of shielding from saliva. = = education and training = = initial glance, forensic intelligence may appear as a nascent facet of forensic science facilitated by advancements in information technologies such as computers, databases, and data - flow management software. however, a more profound examination reveals that forensic intelligence represents a genuine and emerging inclination among forensic practitioners to actively participate in investigative and policing strategies. in doing so, it elucidates existing practices within scientific literature, advocating for a paradigm shift from the prevailing conception of forensic science as a conglomerate of disciplines merely aiding the criminal justice system. instead, it urges a perspective that views forensic science as a discipline studying the informative potential of
masculinity and warmth. the five phases β fire, earth, metal, wood, and water β described a cycle of transformations in nature. the water turned into wood, which turned into the fire when it burned. the ashes left by fire were earth. using these principles, chinese philosophers and doctors explored human anatomy, 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
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
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
the group velocity of light has been measured at eight different wavelengths between 385 nm and 532 nm in the mediterranean sea at a depth of about 2. 2 km with the antares optical beacon systems. a parametrisation of the dependence of the refractive index on wavelength based on the salinity, pressure and temperature of the sea water at the antares site is in good agreement with these measurements.
a tradition of scientific inquiry also emerged in ancient china, where taoist alchemists and philosophers experimented with elixirs to extend life and cure ailments. they focused on the yin and yang, or contrasting elements in nature ; the yin was associated with femininity and coldness, while yang was associated with masculinity and warmth. the five phases β fire, earth, metal, wood, and water β described a cycle of transformations in nature. the water turned into wood, which turned into the fire when it burned. the ashes left by fire were earth. using these principles, chinese philosophers and doctors explored human anatomy, 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
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
high quality thread. the power loom was invented by edmund cartwright in 1787. in the mid - 1750s, the steam engine was applied to the water power - constrained iron, copper and lead industries for powering blast bellows. these industries were located near the mines, some of which were using steam engines for mine pumping. steam engines were too powerful for leather bellows, so cast iron blowing cylinders were developed in 1768. steam powered blast furnaces achieved higher temperatures, allowing the use of more lime in iron blast furnace feed. ( lime rich slag was not free - flowing at the previously used temperatures. ) with a sufficient lime ratio, sulfur from coal or coke fuel reacts with the slag so that the sulfur does not contaminate the iron. coal and coke were cheaper and more abundant fuel. as a result, iron production rose significantly during the last decades of the 18th century. coal converted to coke fueled higher temperature blast furnaces and produced cast iron in much larger amounts than before, allowing the creation of a range of structures such as the iron bridge. cheap coal meant that industry was no longer constrained by water resources driving the mills, although it continued as a valuable source of power. the steam engine helped drain the mines, so more coal reserves could be accessed, and the output of coal increased. the development of the high - pressure steam engine made locomotives possible, and a transport revolution followed. the steam engine which had existed since the early 18th century, was practically applied to both steamboat and railway transportation. the liverpool and manchester railway, the first purpose - built railway line, opened in 1830, the rocket locomotive of robert stephenson being one of its first working locomotives used. manufacture of ships ' pulley blocks by all - metal machines at the portsmouth block mills in 1803 instigated the age of sustained mass production. machine tools used by engineers to manufacture parts began in the first decade of the century, notably by richard roberts and joseph whitworth. the development of interchangeable parts through what is now called the american system of manufacturing began in the firearms industry at the u. s. federal arsenals in the early 19th century, and became widely used by the end of the century. until the enlightenment era, little progress was made in water supply and sanitation and the engineering skills of the romans were largely neglected throughout europe. the first documented use of sand filters to purify the water supply dates to 1804, when the owner of a bleachery in paisley, scotland, john gibb, installed an experimental filter, selling his unwanted
Question: Felicia investigated whether water color affected how fast the water heated in sunlight. She poured tap water into five beakers and placed food coloring in four out of the five beakers. Felicia then used a thermometer to measure the temperature of the water in each of the beakers. Which of these was used as control in her investigation?
A) mixing the food coloring in water
B) testing the beaker of uncolored tap water
C) using the same amount of water in each trial
D) testing the colored water samples at different times
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B) testing the beaker of uncolored tap water
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Context:
##morphology 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 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
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, 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
, 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
##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
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, 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
##thic, 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, 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
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 {
##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
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
##sphere ( 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 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
Question: One process in the formation of sedimentary rocks is when rocks are
A) compressed by moving plates.
B) heated and subjected to high pressure.
C) broken up and deposited in layers.
D) moved up along fault planes.
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C) broken up and deposited in layers.
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Context:
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
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
his sickle to one location. ( he realized it was a sickle by testing various blades on an animal carcass and comparing the wounds. ) flies, attracted by the smell of blood, eventually gathered on a single sickle. in light of this, the owner of that sickle confessed to the murder. the book also described how to distinguish between a drowning ( water in the lungs ) and strangulation ( broken neck cartilage ), and described evidence from examining corpses to determine if a death was caused by murder, suicide or accident. methods from around the world involved saliva and examination of the mouth and tongue to determine innocence or guilt, as a precursor to the polygraph test. in ancient india, some suspects were made to fill their mouths with dried rice and spit it back out. similarly, in ancient china, those accused of a crime would have rice powder placed in their mouths. in ancient middle - eastern cultures, the accused were made to lick hot metal rods briefly. it is thought that these tests had some validity since a guilty person would produce less saliva and thus have a drier mouth ; the accused would be considered guilty if rice was sticking to their mouths in abundance or if their tongues were severely burned due to lack of shielding from saliva. = = education and training = = initial glance, forensic intelligence may appear as a nascent facet of forensic science facilitated by advancements in information technologies such as computers, databases, and data - flow management software. however, a more profound examination reveals that forensic intelligence represents a genuine and emerging inclination among forensic practitioners to actively participate in investigative and policing strategies. in doing so, it elucidates existing practices within scientific literature, advocating for a paradigm shift from the prevailing conception of forensic science as a conglomerate of disciplines merely aiding the criminal justice system. instead, it urges a perspective that views forensic science as a discipline studying the informative potential of traces β remnants of criminal activity. embracing this transformative shift poses a significant challenge for education, necessitating a shift in learners ' mindset to accept concepts and methodologies in forensic intelligence. recent calls advocating for the integration of forensic scientists into the criminal justice system, as well as policing and intelligence missions, underscore the necessity for the establishment of educational and training initiatives in the field of forensic intelligence. this article contends that a discernible gap exists between the perceived and actual comprehension of forensic intelligence among law enforcement and forensic science managers, positing that this asymmetry can be rectified only through educational interventions.
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.
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
wounds or dead bodies should be examined, not avoided. the book became the first form of literature to help determine the cause of death. in one of song ci ' s accounts ( washing away of wrongs ), the case of a person murdered with a sickle was solved by an investigator who instructed each suspect to bring his sickle to one location. ( he realized it was a sickle by testing various blades on an animal carcass and comparing the wounds. ) flies, attracted by the smell of blood, eventually gathered on a single sickle. in light of this, the owner of that sickle confessed to the murder. the book also described how to distinguish between a drowning ( water in the lungs ) and strangulation ( broken neck cartilage ), and described evidence from examining corpses to determine if a death was caused by murder, suicide or accident. methods from around the world involved saliva and examination of the mouth and tongue to determine innocence or guilt, as a precursor to the polygraph test. in ancient india, some suspects were made to fill their mouths with dried rice and spit it back out. similarly, in ancient china, those accused of a crime would have rice powder placed in their mouths. in ancient middle - eastern cultures, the accused were made to lick hot metal rods briefly. it is thought that these tests had some validity since a guilty person would produce less saliva and thus have a drier mouth ; the accused would be considered guilty if rice was sticking to their mouths in abundance or if their tongues were severely burned due to lack of shielding from saliva. = = education and training = = initial glance, forensic intelligence may appear as a nascent facet of forensic science facilitated by advancements in information technologies such as computers, databases, and data - flow management software. however, a more profound examination reveals that forensic intelligence represents a genuine and emerging inclination among forensic practitioners to actively participate in investigative and policing strategies. in doing so, it elucidates existing practices within scientific literature, advocating for a paradigm shift from the prevailing conception of forensic science as a conglomerate of disciplines merely aiding the criminal justice system. instead, it urges a perspective that views forensic science as a discipline studying the informative potential of traces β remnants of criminal activity. embracing this transformative shift poses a significant challenge for education, necessitating a shift in learners ' mindset to accept concepts and methodologies in forensic intelligence. recent calls advocating for the integration of forensic scientists into the criminal justice system, as well as policing and intelligence missions, undersco
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,
groups of organisms. divisions related to the broader historical sense of botany include bacteriology, mycology ( or fungology ), and phycology β respectively, the study of bacteria, fungi, and algae β with lichenology as a subfield of mycology. the narrower sense of botany as the study 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
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
##morphology 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 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
Question: Western coral snakes have a striped color pattern and are poisonous. Arizona mountain king snakes look like western coral snakes but are not poisonous. The color pattern of the Arizona mountain king snake is an example of
A) camouflage.
B) mimicry.
C) mutualism.
D) parasitism.
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B) mimicry.
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Context:
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
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
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 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 o
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
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
##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
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
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
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
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 )
Question: Which plant trait is inherited?
A) the shape of its leaves
B) the amount of water it receives
C) the number of minerals it absorbs from soil
D) the level of sunlight to which it is exposed
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A) the shape of its leaves
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Context:
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
masculinity and warmth. the five phases β fire, earth, metal, wood, and water β described a cycle of transformations in nature. the water turned into wood, which turned into the fire when it burned. the ashes left by fire were earth. using these principles, chinese philosophers and doctors explored human anatomy, 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
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
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,
a tradition of scientific inquiry also emerged in ancient china, where taoist alchemists and philosophers experimented with elixirs to extend life and cure ailments. they focused on the yin and yang, or contrasting elements in nature ; the yin was associated with femininity and coldness, while yang was associated with masculinity and warmth. the five phases β fire, earth, metal, wood, and water β described a cycle of transformations in nature. the water turned into wood, which turned into the fire when it burned. the ashes left by fire were earth. using these principles, chinese philosophers and doctors explored human anatomy, 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
the recent report on laser cooling of liquid may contradict the law of energy conservation.
every riordan array has what we call a horizontal half and a vertical half. these halves of a riordan array have been studied separately before. here, we place them in a common context, showing that one may be obtained from the other. we also ask and answer the question : given a riordan array, when is it the half ( either horizontal of vertical ) of a riordan array?
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,
and ancient egyptian cultures, which produced the first known written evidence of natural philosophy, the precursor of natural science. while the writings show an interest in astronomy, mathematics, and other aspects of the physical world, the ultimate aim of inquiry about nature ' s workings was, in all cases, religious or mythological, not scientific. a tradition of scientific inquiry also emerged in ancient china, where taoist alchemists and philosophers experimented with elixirs to extend life and cure ailments. they focused on the yin and yang, or contrasting elements in nature ; the yin was associated with femininity and coldness, while yang was associated with masculinity and warmth. the five phases β fire, earth, metal, wood, and water β described a cycle of transformations in nature. the water turned into wood, which turned into the fire when it burned. the ashes left by fire were earth. using these principles, chinese philosophers and doctors explored human anatomy, 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. pytha
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
Question: A student put 200 milliliters (mL) of water into a pot, sets the pot on a burner, and heats the water to boil. When the pot is taken off the burner, it contains only 180 milliliters (mL) of water. What happened to the rest of the water?
A) It was used up.
B) It condensed.
C) It was absorbed by the heat.
D) It turned into water vapor.
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D) It turned into water vapor.
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Context:
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
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
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
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,
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
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
##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
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
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
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
Question: Howie put his plants under a plant light. What was he helping his plants do by providing light?
A) make food
B) attract insects
C) release pollen
D) grow roots
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A) make food
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Context:
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.
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.
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.
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.
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.
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
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.
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.
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.
Question: Which lists the diameter of the planets in order from smallest to largest?
A) Venus, Earth, Mercury, Mars
B) Earth, Mars, Venus, Mercury
C) Mars, Mercury, Earth, Venus
D) Mercury, Mars, Venus, Earth
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D) Mercury, Mars, Venus, Earth
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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 :
, 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
the reply to g. w. bruhn is added.
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
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
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.
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
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.
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
##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
Question: The aloe plant can absorb a lot of water during a rain shower. The extra water is stored in its leaves. The ability to store water in its leaves is most likely an adaptation to which type of environment?
A) one near the ocean
B) one with dry conditions
C) one with a variety of organisms
D) one that receives a lot of sunlight
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B) one with dry conditions
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Context:
major stellar - wind emission features in the spectrum of eta car have recently decreased by factors of order 2 relative to the continuum. this is unprecedented in the modern observational record. the simplest, but unproven, explanation is a rapid decrease in the wind density.
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
astronomically, there are viable mechanisms for distributing organic material throughout the milky way. biologically, the destructive effects of ultraviolet light and cosmic rays means that the majority of organisms arrive broken and dead on a new world. the likelihood of conventional forms of panspermia must therefore be considered low. however, the information content of dam - aged biological molecules might serve to seed new life ( necropanspermia ).
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?
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
the infrared excess around the white dwarf g29 - 38 can be explained by emission from an opaque flat ring of dust with an inner radius 0. 14 of the radius of the sun and an outer radius approximately equal to the sun ' s. this ring lies within the roche region of the white dwarf where an asteroid could have been tidally destroyed, producing a system reminiscent of saturn ' s rings. accretion onto the white dwarf from this circumstellar dust can explain the observed calcium abundance in the atmosphere of g29 - 38. either as a bombardment by a series of asteroids or because of one large disruption, the total amount of matter accreted onto the white dwarf may have been comparable to the total mass of asteroids in the solar system, or, equivalently, about 1 % of the mass in the asteroid belt around the main sequence star zeta lep.
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 - 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
, 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 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
Question: When stratospheric ozone levels are reduced, the amount of ultraviolet radiation hitting Earth increases. Ozone depletion is most often caused
A) by the reversal of the magnetic field of Earth.
B) when fluorocarbons are released into the atmosphere.
C) when electromagnetic waves from the Sun increase.
D) by abrupt changes in weather and climate patterns.
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B) when fluorocarbons are released into the atmosphere.
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Context:
one may identify the general properties of the neutrino mass matrix by generating many random mass matrices and testing them against the results of the neutrino experiments.
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
, 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
##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
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.
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
the model of neutrino mass matrix with minimal texture is now tightly constrained by experiment so that it can yield a prediction for the phase of cp violation. this phase is predicted to lie in the range $ \ delta _ { cp } = 0. 77 \ pi - 1. 24 \ pi $. if neutrino oscillation experiment would find the cp violation phase outside this range, this means that the minimal - texture neutrino mass matrix, the element of which is all real, fails and the neutrino mass matrix must be complex, i. e., the phase must be present that is responsible for leptogenesis.
##copy is the study of fingerprints. forensic document examination or questioned document examination answers questions about a disputed document using a variety of scientific processes and methods. many examinations involve a comparison of the questioned document, or components of the document, with a set of known standards. the most common type of examination involves handwriting, whereby the examiner tries to address concerns about potential authorship. forensic dna analysis takes advantage of the uniqueness of an individual ' s dna to answer forensic questions such as paternity / maternity testing and placing a suspect at a crime scene, e. g. in a rape investigation. forensic engineering is the scientific examination and analysis of structures and products relating to their failure or cause of damage. forensic entomology deals with the examination of insects in, on and around human remains to assist in determination of time or location of death. it is also possible to determine if the body was moved after death using entomology. forensic geology deals with trace evidence in the form of soils, minerals and petroleum. forensic geomorphology is the study of the ground surface to look for potential location ( s ) of buried object ( s ). forensic geophysics is the application of geophysical techniques such as radar for detecting objects hidden underground or underwater. forensic intelligence process starts with the collection of data and ends with the integration of results within into the analysis of crimes under investigation. forensic interviews are conducted using the science of professionally using expertise to conduct a variety of investigative interviews with victims, witnesses, suspects or other sources to determine the facts regarding suspicions, allegations or specific incidents in either public or private sector settings. 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
28 size spectra of extensive air showers from 7 different experiments are analysed consistently. they are fitted by adjusting either 4 or 5 parameters : knee position, power law exponents above and below the knee, overall intensity and, in addition, a parameter describing the smoothness of the bend. the residuals are then normalized to the same knee position and averaged. when 5 parameters are employed no systematic deviation from a single smooth knee is apparent at the 1 % level up to a factor of 4 above the knee. at larger shower sizes a moderately significant deviation can be seen whose shape and position are compatible with a second knee caused by iron group nuclei.
Question: Owen tested a physical property of a mineral. He rubbed a mineral sample on a piece of white tile. The mineral left a red mark on the tile. Which of the following physical properties of the mineral was Owen most likely testing?
A) cleavage
B) hardness
C) luster
D) streak
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D) streak
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Context:
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
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
humanoid robots are a form of embodied artificial intelligence ( ai ) that looks and acts more and more like humans. powered by generative ai and advances in robotics, humanoid robots can speak and interact with humans rather naturally but are still easily recognizable as robots. but how will we treat humanoids when they seem indistinguishable from humans in appearance and mind? we find a tendency ( called " anti - robot " speciesism ) to deny such robots humanlike capabilities, driven by motivations to accord members of the human species preferential treatment. six experiments show that robots are denied humanlike attributes, simply because they are not biological beings and because humans want to avoid feelings of cognitive dissonance when utilizing such robots for unsavory tasks. thus, people do not rationally attribute capabilities to perfectly humanlike robots but deny them capabilities as it suits them.
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. 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
the sloan digital sky survey has discovered a population of broad absorption line quasars with various extreme properties. many show absorption from metastable states of feii with varying excitations ; several objects are almost completely absorbed bluewards of mgii ; at least one shows stronger absorption from feiii than feii, indicating temperatures t > 35000 k in the absorbing region ; and one object even seems to have broad h - beta absorption. many of these extreme bals are also heavily reddened, though ` normal ' bals ( particularly lobals ) from sdss also show evidence for internal reddening.
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 guarantee care for all through a single - payer health care system or compulsory private or cooperative health insurance. this is intended to ensure that the entire population has access to medical care on the basis of need rather than ability to pay. delivery may be via private medical practices, state - owned hospitals and clinics, or charities,
a massless dirac particle is considered, moving along the x - axis while pauli - coupled by its anomalous magnetic moment to a piecewise constant magnetic field along the same axis, with stochastically varying sign. the motion is approximated as a quantum walk with unitary noise, for which the evolution can be found exactly. initially ballistic, the motion approaches a classical diffusion on a time - scale determined by the speed of light, the size of the magnetic moment, the strength of the field and the time interval between changes in its direction. it is suggested that a process of this type could occur in the sun ' s corona, significantly affecting the solar fluxes of one or more neutrino types.
, 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
the magnetic fields of the ice giant planets uranus and neptune ( u / n ) are unique in the solar system. based on a substantial database measured on earth for representative planetary fluids at representative dynamic pressures up to 200 gpa ( 2 mbar ) and a few 1000 k, the complex magnetic fields of u / n are ( i ) probably made primarily by degenerate metallic fluid h ( mfh ) at or near the crossover from the h - he envelopes to ice cores at ~ 100 gpa ( mbar ) pressures and normalized radii of ~ 90 % of the radii of u / n ; ( ii ) because those magnetic fields are made relatively close to the surfaces of u / n, non - dipolar fields can be expected ; ( iii ) the ice cores are most probably a heterogeneous fluid mixture of h, n, o, c, fe / ni and silicate - oxides and their mutual reaction products at high pressures and temperatures, as discussed elsewhere. ironically, there is probably little nebular ice in the ice giant planets.
in a diagram of metallicity ( \ ~ z ) vs. luminosity ( m $ _ b $ ), the different types of nearby ( z $ < 0. 05 $ ) starburst galaxies seem to follow the same linear relationship as the normal spiral and irregular galaxies. however, for comparable luminosities the more massive starburst nucleus galaxies ( sbngs ) show a slight metallic defficiency as compared to the giant spiral galaxies. furthermore, the sbngs do not seem to follow the same relationship between \ ~ z and hubble type ( t ) than the normal galaxies. the early - type sbngs are metal poor as compared to normal galaxies. it may suggests that the chemical evolution of a majority of the nearby starbursts galaxies is not completely over and that the present burst represent an important phase of this process.
Question: Which of these animals has a young form that looks the most like the adult form?
A) moth
B) human
C) frog
D) butterfly
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B) human
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Context:
##ctonics, 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 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
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 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 '
, 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
##morphology 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 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
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
, 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
##hosphere ) 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 ). " 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
##sphere ( 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 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
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
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 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
Question: Two tectonic plates pushing toward each other cause intense heat and pressure in Earth's crust. Into which will crust material be changed by heat and pressure?
A) fossils
B) sediments
C) igneous rock
D) metamorphic rock
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D) metamorphic rock
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Context:
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,
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
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 :
##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
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
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
in gravitational lensing, the concept of optical depth assumes the lens is dark. several microlensing detections have now been made where the lens may be bright. relations are developed between apparent and absolute optical depth in the regime of the apparent and absolute brightness of the lens. an apparent optical depth through bright lenses is always less than the true, absolute optical depth. the greater the intrinsic brightness of the lens, the more likely it will be found nearer the source.
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
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.
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: A student states that plants grow taller when grown in natural light than they do in artificial light. Which method is the best way to determine if the statement is fact or opinion?
A) conduct a controlled experiment
B) discuss the statement with other students
C) ask several teachers their thoughts
D) propose a scientific conclusion
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A) conduct a controlled experiment
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Context:
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 '.
engineering. a wide range of instrumentation is used by electrical engineers. for simple control circuits and alarms, a basic multimeter measuring voltage, current, and resistance may suffice. where time - varying signals need to be studied, the oscilloscope is also an ubiquitous instrument. in rf engineering and high - frequency telecommunications, spectrum analyzers and network analyzers are used. in some disciplines, safety can be a particular concern with instrumentation. for instance, medical electronics designers must take into account that much lower voltages than normal can be dangerous when electrodes are directly in contact with internal body fluids. power transmission engineering also has great safety concerns due to the high voltages used ; although voltmeters may in principle be similar to their low voltage equivalents, safety and calibration issues make them very different. many disciplines of electrical engineering use tests specific to their discipline. audio electronics engineers use audio test sets consisting of a signal generator and a meter, principally to measure level but also other parameters such as harmonic distortion and noise. likewise, information technology have their own test sets, often specific to a particular data format, and the same is true of television broadcasting. for many engineers, technical work accounts for only a fraction of the work they do. a lot of time may also be spent on tasks such as discussing proposals with clients, preparing budgets and determining project schedules. many senior engineers manage a team of technicians or other engineers and for this reason project management skills are important. most engineering projects involve some form of documentation and strong written communication skills are therefore very important. the workplaces of engineers are just as varied as the types of work they do. electrical engineers may be found in the pristine lab environment of a fabrication plant, on board a naval ship, the offices of a consulting firm or on site at a mine. during their working life, electrical engineers may find themselves supervising a wide range of individuals including scientists, electricians, computer programmers, and other engineers. electrical engineering has an intimate relationship with the physical sciences. for instance, the physicist lord kelvin played a major role in the engineering of the first transatlantic telegraph cable. conversely, the engineer oliver heaviside produced major work on the mathematics of transmission on telegraph cables. electrical engineers are often required on major science projects. for instance, large particle accelerators such as cern need electrical engineers to deal with many aspects of the project including the power distribution, the instrumentation, and the manufacture and installation of the superconducting electromagnets. = = see also = = = = notes
that moved gold leaf through electrical conduction. in 1795, francisco salva campillo proposed an electrostatic telegraph system. between 1803 and 1804, he worked on electrical telegraphy, and in 1804, he presented his report at the royal academy of natural sciences and arts of barcelona. salva ' s electrolyte telegraph system was very innovative though it was greatly influenced by and based upon two discoveries made in europe in 1800 β alessandro volta ' s electric battery for generating an electric current and william nicholson and anthony carlyle ' s electrolysis of water. electrical telegraphy may be considered the first example of electrical engineering. electrical engineering became a profession in the later 19th century. practitioners had created a global electric telegraph network, and the first professional electrical engineering institutions were founded in the uk and the us to support the new discipline. francis ronalds created an electric telegraph system in 1816 and documented his vision of how the world could be transformed by electricity. over 50 years later, he joined the new society of telegraph engineers ( soon to be renamed the institution of electrical engineers ) where he was regarded by other members as the first of their cohort. by the end of the 19th century, the world had been forever changed by the rapid communication made possible by the engineering development of land - lines, submarine cables, and, from about 1890, wireless telegraphy. practical applications and advances in such fields created an increasing need for standardized units of measure. they led to the international standardization of the units volt, ampere, coulomb, ohm, farad, and henry. this was achieved at an international conference in chicago in 1893. the publication of these standards formed the basis of future advances in standardization in various industries, and in many countries, the definitions were immediately recognized in relevant legislation. during these years, the study of electricity was largely considered to be a subfield of physics since early electrical technology was considered electromechanical in nature. the technische universitat darmstadt founded the world ' s first department of electrical engineering in 1882 and introduced the first - degree course in electrical engineering in 1883. the first electrical engineering degree program in the united states was started at massachusetts institute of technology ( mit ) in the physics department under professor charles cross, though it was cornell university to produce the world ' s first electrical engineering graduates in 1885. the first course in electrical engineering was taught in 1883 in cornell ' s sibley college of mechanical engineering and mechanic arts. in about 1885, cornell president andrew dickson white established the first department of electrical engineering in the united
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
. 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
##rs in their design. from that time on transistors were almost exclusively used for computer logic circuits and peripheral devices. however, early junction transistors were relatively bulky devices that were difficult to manufacture on a mass - production basis, which limited them to a number of specialised applications. the mosfet was invented at bell labs between 1955 and 1960. it was the first truly compact transistor that could be miniaturised and mass - produced for a wide range of uses. its advantages include high scalability, affordability, low power consumption, and high density. it revolutionized the electronics industry, becoming the most widely used electronic device in the world. the mosfet is the basic element in most modern electronic equipment. as the complexity of circuits grew, problems arose. one problem was the size of the circuit. a complex circuit like a computer was dependent on speed. if the components were large, the wires interconnecting them must be long. the electric signals took time to go through the circuit, thus slowing the computer. the invention of the integrated circuit by jack kilby and robert noyce solved this problem by making all the components and the chip out of the same block ( monolith ) of semiconductor material. the circuits could be made smaller, and the manufacturing process could be automated. this led to the idea of integrating all components on a single - crystal silicon wafer, which led to small - scale integration ( ssi ) in the early 1960s, and then medium - scale integration ( msi ) in the late 1960s, followed by vlsi. in 2008, billion - transistor processors became commercially available. = = subfields = = = = devices and components = = an electronic component is any component in an electronic system either active or passive. components are connected together, usually by being soldered to a printed circuit board ( pcb ), to create an electronic circuit with a particular function. components may be packaged singly, or in more complex groups as integrated circuits. passive electronic components are capacitors, inductors, resistors, whilst active components are such as semiconductor devices ; transistors and thyristors, which control current flow at electron level. = = types of circuits = = electronic circuit functions can be divided into two function groups : analog and digital. a particular device may consist of circuitry that has either or a mix of the two types. analog circuits are becoming less common, as many of their functions are being digitized. = = = analog circuits = =
joseph henry and edward davy, who invented the electrical relay in 1835 ; of georg ohm, who in 1827 quantified the relationship between the electric current and potential difference in a conductor ; of michael faraday, the discoverer of electromagnetic induction in 1831 ; and of james clerk maxwell, who in 1873 published a unified theory of electricity and magnetism in his treatise electricity and magnetism. in 1782, georges - louis le sage developed and presented in berlin probably the world ' s first form of electric telegraphy, using 24 different wires, one for each letter of the alphabet. this telegraph connected two rooms. it was an electrostatic telegraph that moved gold leaf through electrical conduction. in 1795, francisco salva campillo proposed an electrostatic telegraph system. between 1803 and 1804, he worked on electrical telegraphy, and in 1804, he presented his report at the royal academy of natural sciences and arts of barcelona. salva ' s electrolyte telegraph system was very innovative though it was greatly influenced by and based upon two discoveries made in europe in 1800 β alessandro volta ' s electric battery for generating an electric current and william nicholson and anthony carlyle ' s electrolysis of water. electrical telegraphy may be considered the first example of electrical engineering. electrical engineering became a profession in the later 19th century. practitioners had created a global electric telegraph network, and the first professional electrical engineering institutions were founded in the uk and the us to support the new discipline. francis ronalds created an electric telegraph system in 1816 and documented his vision of how the world could be transformed by electricity. over 50 years later, he joined the new society of telegraph engineers ( soon to be renamed the institution of electrical engineers ) where he was regarded by other members as the first of their cohort. by the end of the 19th century, the world had been forever changed by the rapid communication made possible by the engineering development of land - lines, submarine cables, and, from about 1890, wireless telegraphy. practical applications and advances in such fields created an increasing need for standardized units of measure. they led to the international standardization of the units volt, ampere, coulomb, ohm, farad, and henry. this was achieved at an international conference in chicago in 1893. the publication of these standards formed the basis of future advances in standardization in various industries, and in many countries, the definitions were immediately recognized in relevant legislation. during these years, the study of electricity was largely considered to be a subfield of physics since early electrical technology was considered electromechan
major in electrical engineering, electronics engineering, electrical engineering technology, or electrical and electronic engineering. the same fundamental principles are taught in all programs, though emphasis may vary according to title. the length of study for such a degree is usually four or five years and the completed degree may be designated as a bachelor of science in electrical / electronics engineering technology, bachelor of engineering, bachelor of science, bachelor of technology, or bachelor of applied science, depending on the university. the bachelor ' s degree generally includes units covering physics, mathematics, computer science, project management, and a variety of topics in electrical engineering. initially such topics cover most, if not all, of the subdisciplines of electrical engineering. at many schools, electronic engineering is included as part of an electrical award, sometimes explicitly, such as a bachelor of engineering ( electrical and electronic ), but in others, electrical and electronic engineering are both considered to be sufficiently broad and complex that separate degrees are offered. some electrical engineers choose to study for a postgraduate degree such as a master of engineering / master of science ( meng / msc ), a master of engineering management, a doctor of philosophy ( phd ) in engineering, an engineering doctorate ( eng. d. ), or an engineer ' s degree. the master ' s and engineer ' s degrees may consist of either research, coursework or a mixture of the two. the doctor of philosophy and engineering doctorate degrees consist of a significant research component and are often viewed as the entry point to academia. in the united kingdom and some other european countries, master of engineering is often considered to be an undergraduate degree of slightly longer duration than the bachelor of engineering rather than a standalone postgraduate degree. = = professional practice = = in most countries, a bachelor ' s degree in engineering represents the first step towards professional certification and the degree program itself is certified by a professional body. 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 india, pakistan, the united kingdom, ireland and zimbabwe ), chartered professional engineer ( in australia and new zealand ) or european engineer ( in much of the european union ). the advantages of licensure vary depending upon location. for example, in the united states and canada " only a licensed engineer may seal engineering work for public and private clients ". this requirement is enforced by state and provincial legislation such as quebec
##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
theory of electricity and magnetism in his treatise electricity and magnetism. in 1782, georges - louis le sage developed and presented in berlin probably the world ' s first form of electric telegraphy, using 24 different wires, one for each letter of the alphabet. this telegraph connected two rooms. it was an electrostatic telegraph that moved gold leaf through electrical conduction. in 1795, francisco salva campillo proposed an electrostatic telegraph system. between 1803 and 1804, he worked on electrical telegraphy, and in 1804, he presented his report at the royal academy of natural sciences and arts of barcelona. salva ' s electrolyte telegraph system was very innovative though it was greatly influenced by and based upon two discoveries made in europe in 1800 β alessandro volta ' s electric battery for generating an electric current and william nicholson and anthony carlyle ' s electrolysis of water. electrical telegraphy may be considered the first example of electrical engineering. electrical engineering became a profession in the later 19th century. practitioners had created a global electric telegraph network, and the first professional electrical engineering institutions were founded in the uk and the us to support the new discipline. francis ronalds created an electric telegraph system in 1816 and documented his vision of how the world could be transformed by electricity. over 50 years later, he joined the new society of telegraph engineers ( soon to be renamed the institution of electrical engineers ) where he was regarded by other members as the first of their cohort. by the end of the 19th century, the world had been forever changed by the rapid communication made possible by the engineering development of land - lines, submarine cables, and, from about 1890, wireless telegraphy. practical applications and advances in such fields created an increasing need for standardized units of measure. they led to the international standardization of the units volt, ampere, coulomb, ohm, farad, and henry. this was achieved at an international conference in chicago in 1893. the publication of these standards formed the basis of future advances in standardization in various industries, and in many countries, the definitions were immediately recognized in relevant legislation. during these years, the study of electricity was largely considered to be a subfield of physics since early electrical technology was considered electromechanical in nature. the technische universitat darmstadt founded the world ' s first department of electrical engineering in 1882 and introduced the first - degree course in electrical engineering in 1883. the first electrical engineering degree program in the united states was started at massachusetts institute of technology ( mit ) in the physics department under professor
Question: Which object is powered by an electrical circuit?
A) a drum
B) a flashlight
C) a matchstick
D) a wind-up toy
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B) a flashlight
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Context:
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
. 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
, 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 ",
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 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
, 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
##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
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 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,
. 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
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
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 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
Question: Which concept supports the endosymbiotic origin of complex, eukaryotic double-membrane structures?
A) Mitochondria and chloroplasts arise from preexisting mitochondria and chloroplasts.
B) Mitochondria and chloroplasts arise from preexisting endomembrane systems.
C) Mitochondria and chloroplasts are synthesized in the nucleus.
D) Mitochondria and chloroplasts are synthesized in ribosomes.
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A) Mitochondria and chloroplasts arise from preexisting mitochondria and chloroplasts.
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Context:
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
= = = = = = 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
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
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
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
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
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
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
##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
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: Which of these human activities most relies on high-quality soil?
A) Hiking
B) Hunting
C) Coal mining
D) Growing crops
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D) Growing crops
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Context:
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
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
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
any two generating systems of the fundamental group of a closed surface are nielsen equivalent.
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, pcm or fsk. wireless doorbell β a residential doorbell that uses wireless technology to eliminate the need to run wires through the building walls. it consists of a doorbell button beside the door containing a small battery powered transmitter. when the doorbell is pressed it sends a signal to a receiver inside the house with a speaker that sounds chimes to indicate someone is at the door. they usually use the 2. 4 ghz ism band. the frequency channel used can usually be changed by the owner in case another nearby doorbell is using the same channel. = = = = scientific research = = = = radio astronomy is the scientific study of radio waves emitted by astronomical objects. radio astronomers use radio telescopes, large radio antennas and receivers, to receive and study the radio waves from astronomical radio sources. since astronomical radio sources are so far away, the radio waves from them are extremely weak, requiring extremely sensitive receivers, and radio telescopes are the most sensitive radio receivers in existence. they use
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
some examples and basic properties of ultrametric spaces are briefly discussed.
, 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
possible value. the most common representation of a positive integer is a string of bits, using the binary numeral system. the order of the memory bytes storing the bits varies ; see endianness. the width, precision, or bitness of an integral type is the number of bits in its representation. an integral type with n bits can encode 2n numbers ; for example an unsigned type typically represents the non - negative values 0 through 2n β 1. other encodings of integer values to bit patterns are sometimes used, for example binary - coded decimal or gray code, or as printed character codes such as ascii. there are four well - known ways to represent signed numbers in a binary computing system. the most common is two ' s complement, which allows a signed integral type with n bits to represent numbers from β2 ( nβ1 ) through 2 ( nβ1 ) β 1. two ' s complement arithmetic is convenient because there is a perfect one - to - one correspondence between representations and values ( in particular, no separate + 0 and β0 ), and because addition, subtraction and multiplication do not need to distinguish between signed and unsigned types. other possibilities include offset binary, sign - magnitude, and ones ' complement. some computer languages define integer sizes in a machine - independent way ; others have varying definitions depending on the underlying processor word size. not all language implementations define variables of all integer sizes, and defined sizes may not even be distinct in a particular implementation. an integer in one programming language may be a different size in a different language, on a different processor, or in an execution context of different bitness ; see Β§ words. some older computer architectures used decimal representations of integers, stored in binary - coded decimal ( bcd ) or other format. these values generally require data sizes of 4 bits per decimal digit ( sometimes called a nibble ), usually with additional bits for a sign. many modern cpus provide limited support for decimal integers as an extended datatype, providing instructions for converting such values to and from binary values. depending on the architecture, decimal integers may have fixed sizes ( e. g., 7 decimal digits plus a sign fit into a 32 - bit word ), or may be variable - length ( up to some maximum digit size ), typically occupying two digits per byte ( octet ). = = common integral data types = = different cpus support different integral data types. typically, hardware will support both signed and unsigned types, but only a small, fixed set of widths
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: What is an example of a shelter in an ecosystem?
A) a gray squirrel eating an acorn
B) a raccoon in a hollow log
C) a blue whale migrating
D) a tick feeding on a coyote
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B) a raccoon in a hollow log
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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
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
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.
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
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 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
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
##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
the creation of your own reality and your own world. the metaphor i used was humans being like magic markers. for so long, they painted black and white pictures in their life because that ' s all they thought they could do. but they can paint with a different color and make a very vibrant and beautiful picture if they take control. on the single " new skin ", he further elaborated : in " new skin ", i attribute a scab to the present state of society. the way the scab looks in its worst state is gross and chaotic and horrible, that ' s now, but when it breaks away, there ' s a brand new piece of skin that ' s stronger than before. it ' s like creation out of chaos. the song " favorite things ", according to boyd, related to the topic of religion : " my favorite things " is my personal beliefs about religion and how it oppresses the things i enjoy the most. unfortunately, the simplest things, such as thinking for myself, creating my own reality and being whatever the hell i want to be each day of my life, are a sin. to be a good christian basically means to give up the reigns of your life and let some unseen force do it for you. " favorite things " also includes a sample of the 1959 track " flamenco fantasy ", by easy listening group the 101 strings orchestra. the song has a similar title to " my favorite things ", from the mary poppins musical and film, with both songs repeatedly mentioning their titles in the lyrics. however, it does not musically reference " my favorite things ". the single " a certain shade of green " has been described as being a song about procrastination. the line " are you gonna stand around till 2012 a. d.? " is a reference to an interpretation of the mayan calendar which dictated that the world would end on december 21, 2012. boyd did not believe this to be true, but it was on his mind as his mother was researching it for a book called maya memory : the glory that was palenque. while recording " nebula ", boyd said in 1997, " we found out what it ' s like to actually plug a phaser pedal into the wall while it ' s on. it sounds like a laser gun, and that ' s the first sound you hear in ' nebula '. " he added that for the song, " we used these walkie - talkies for children that have this slinky - like coil between them. when
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 that gives us long - term ( decade - to - decade ) feedback on our performance as stewards of the planet. the effort includes understanding the functions of soil microbiotic crusts and exploring the potential to sequester atmospheric carbon in soil organic matter. relating the concept of agriculture to soil quality, however, has not
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.
Question: Some areas of the world are experiencing more desert-like conditions. This change most favors survival of species with the ability to do which of the following?
A) consume large amounts of food
B) become dormant for long periods
C) sense infrared and ultraviolet light
D) transpire water through the skin to the atmosphere
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B) become dormant for long periods
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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
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
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
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
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 shastra ', suggests a thorough understanding of materials engineering, hydrology, and sanitation. = = = = china = = = = the chinese made many first - known discoveries and developments. major technological contributions from china include the earliest known form of the binary code and epigenetic sequencing, early seismological detectors, matches, paper, helicopter rotor, raised - relief map, the double - action piston pump, cast iron, water powered blast furnace bellows, the iron plough, the multi - tube seed drill, the wheelbarrow, the parachute, the compass, the rudder, the crossbow, the south pointing chariot and gunpowder
, 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
##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
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
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, according to the respective operating principle. structural caissons : caisson is also sometimes used as a colloquial term for a reinforced concrete structure formed by pouring into a hollow cylindrical form, typically by placing a caisson form below grade in an open excavation and pouring once backfill is complete, or by
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,
Question: Roger poured water over a pile of sand. Some of the sand washed away. This process is similar to which of the following?
A) The eruption of a volcano
B) The erosion of the walls of a canyon
C) The uplifting of mountain ranges
D) The forming of dunes or mounds in a desert
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B) The erosion of the walls of a canyon
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Context:
##ctonics, 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 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
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 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 '
, 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
##morphology 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 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
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
the group velocity of light has been measured at eight different wavelengths between 385 nm and 532 nm in the mediterranean sea at a depth of about 2. 2 km with the antares optical beacon systems. a parametrisation of the dependence of the refractive index on wavelength based on the salinity, pressure and temperature of the sea water at the antares site is in good agreement with these measurements.
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
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
the brilliant idea of jean betrema and jean - guy penaud that proved the celebrated " three to the power n " theorem of dominique gouyou - beauchamps and xavier viennot, counting towers of domino pieces is extended and used to enumerate much more general towers, where the pieces can be many i - mers.
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 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
Question: When an earthquake wave passes from the crust to the mantle, the wave
A) reverses direction.
B) changes speed.
C) increases energy.
D) stops moving.
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B) changes speed.
|
Context:
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
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 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
cobalt nanowires with a diameter in the range between 50 to 100nm can be prepared as single - crystal wires with the easy axis ( the c - axis ) perpendicular to the wire axis. the competition between the crystal anisotropy and demagnetization energy frustrates the magnetization direction. a periodic modulation of the angle between m and the wire axis yields a lower energy.
using first principles density functional calculations, gold monatomic wires are found to exhibit a zigzag shape which remains under tension, becoming linear just before breaking. at room temperature they are found to spin, what explains the extremely long apparent interatomic distances shown by electron microscopy. the zigzag structure is stable if the tension is relieved, the wire holding its chainlike shape even as a free - standing cluster. this unexpected metallic - wire stiffness stems from the transverse quantization in the wire, as shown in a simple free electron model.
higher education and advanced scientific research lead to social, economic, and political development of any country. all developed societies like the current 2022 g7 countries : canada, france, germany, italy, japan, the uk, and the us have all not only heavily invested in higher education but also in advanced scientific research in their respective countries. similarly, for african countries to develop socially, economically, and politically, they must follow suit by massively investing in higher education and local scientific research.
learning to use math in physics involves combining ( blending ) our everyday experiences and the conceptual ideas of physics with symbolic mathematical representations. graphs are one of the best ways to learn to build the blend. they are a mathematical representation that builds on visual recognition to create a bridge between words and equations. but students in introductory physics classes often see a graph as an endpoint, a task the teacher asks them to complete, rather than as a tool to help them make sense of a physical system. and most of the graph problems in traditional introductory physics texts simply ask students to extract a number from a graph. but if graphs are used appropriately, they can be a powerful tool in helping students learn to build the blend and develop their physical intuition and ability to think with math.
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 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
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 '.
insights from stripe incommensurabilities and antiferromagnetic stability indicate that the magnetic moments of both host cu ^ 2 + ions and cu atoms from electron doping support the thermal hall effect in cuprates, whereas those of o atoms from hole doping oppose it.
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.
Question: A student wraps a wire around an iron nail. The student then connects the wire to a battery. The nail attracts another nail and they stick together. What force holds the two nails together?
A) gravitational force
B) magnetic force
C) electric force
D) friction force
|
B) magnetic force
|
Context:
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.
##sphere ( 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 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
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
##ctonics, 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 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
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
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 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 '
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
manifold of dimension two ( see Β§ topological surface ). a differentiable surface is a surfaces that is a differentiable manifold ( see Β§ differentiable surface ). every differentiable surface is a topological surface, but the converse is false. a " surface " is often implicitly supposed to be contained in a euclidean space of dimension 3, typically r3. a surface that is contained in a projective space is called a projective surface ( see Β§ projective surface ). a surface that is not supposed to be included in another space is called an abstract surface. = = examples = = the graph of a continuous function of two variables, defined over a connected open subset of r2 is a topological surface. if the function is differentiable, the graph is a differentiable surface. a plane is both an algebraic surface and a differentiable surface. it is also a ruled surface and a surface of revolution. a circular cylinder ( that is, the locus of a line crossing a circle and parallel to a given direction ) is an algebraic surface and a differentiable surface. a circular cone ( locus of a line crossing a circle, and passing through a fixed point, the apex, which is outside the plane of the circle ) is an algebraic surface which is not a differentiable surface. if one removes the apex, the remainder of the cone is the union of two differentiable surfaces. the surface of a polyhedron is a topological surface, which is neither a differentiable surface nor an algebraic surface. a hyperbolic paraboloid ( the graph of the function z = xy ) is a differentiable surface and an algebraic surface. it is also a ruled surface, and, for this reason, is often used in architecture. a two - sheet hyperboloid is an algebraic surface and the union of two non - intersecting differentiable surfaces. = = parametric surface = = a parametric surface is the image of an open subset of the euclidean plane ( typically r 2 { \ displaystyle \ mathbb { r } ^ { 2 } } ) by a continuous function, in a topological space, generally a euclidean space of dimension at least three. usually the function is supposed to be continuously differentiable, and this will be always the case in this article. specifically, a parametric surface in r 3 { \ displaystyle \ mathbb { r } ^ { 3 } } is given by three functions of two variables u and v, called parameters x = f 1 ( u, v ), y = f 2 ( u, v ), z = f 3
, 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
##morphology 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 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
Question: Natural processes cause rapid and slow changes to Earth's surface. Which event causes changes to Earth's surface most rapidly?
A) an earthquake shaking the ground
B) sediment washing into a bay
C) a rainstorm weathering rock
D) water flowing in stream
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A) an earthquake shaking the ground
|
Context:
##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
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 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
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
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
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. 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
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
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
##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
##nita 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. 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
also called projection lines ) differs, as explained below. in first - angle projection, the parallel projectors originate as if radiated from behind the viewer and pass through the 3d object to project a 2d image onto the orthogonal plane behind it. the 3d object is projected into 2d " paper " space as if you were looking at a radiograph of the object : the top view is under the front view, the right view is at the left of the front view. first - angle projection is the iso standard and is primarily used in europe. in third - angle projection, the parallel projectors originate as if radiated from the far side of the object and pass through the 3d object to project a 2d image onto the orthogonal plane in front of it. the views of the 3d object are like the panels of a box that envelopes the object, and the panels pivot as they open up flat into the plane of the drawing. thus the left view is placed on the left and the top view on the top ; and the features closest to the front of the 3d object will appear closest to the front view in the drawing. third - angle projection is primarily used in the united states and canada, where it is the default projection system according to asme standard asme y14. 3m. until the late 19th century, first - angle projection was the norm in north america as well as europe ; but circa the 1890s, third - angle projection spread throughout the north american engineering and manufacturing communities to the point of becoming a widely followed convention, and it was an asa standard by the 1950s. circa world war i, british practice was frequently mixing the use of both projection methods. as shown above, the determination of what surface constitutes the front, back, top, and bottom varies depending on the projection method used. not all views are necessarily used. generally only as many views are used as are necessary to convey all needed information clearly and economically. the front, top, and right - side views are commonly considered the core group of views included by default, but any combination of views may be used depending on the needs of the particular design. in addition to the six principal views ( front, back, top, bottom, right side, left side ), any auxiliary views or sections may be included as serve the purposes of part definition and its communication. view lines or section lines ( lines with arrows marked " a - a ", " b - b ", etc. ) define the direction and location of viewing or sectioning. sometimes a note tells the reader in which zone
Question: Since 1961, Nevada has led the United States in production of which resource?
A) gold
B) uranium
C) lumber
D) iron
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A) gold
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Context:
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.
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
within the military ranges from educational purposes, training exercises and sustainability technology. the technology used for educational purposes within the military are mainly wearables that tracks a soldier ' s vitals. by tracking a soldier ' s heart rate, blood pressure, emotional status, etc. helps the research and development team best help the soldiers. according to chemist, matt coppock, he has started to enhance a soldier ' s lethality by collecting different biorecognition receptors. by doing so it will eliminate emerging environmental threats to the soldiers. with the emergence of virtual reality it is only natural to start creating simulations using vr. this will better prepare the user for whatever situation they are training for. in the military there are combat simulations that soldiers will train on. the reason the military will use vr to train its soldiers is because it is the most interactive / immersive experience the user will feels without being put in a real situation. recent simulations include a soldier wearing a shock belt during a combat simulation. each time they are shot the belt will release a certain amount of electricity directly to the user ' s skin. this is to simulate a shot wound in the most humane way possible. there are many sustainability technologies that military personnel wear in the field. one of which is a boot insert. this insert gauges how soldiers are carrying the weight of their equipment and how daily terrain factors impact their mission panning optimization. these sensors will not only help the military plan the best timeline but will help keep the soldiers at best physical / mental health. = = fashion = = fashionable wearables are " designed garments and accessories that combines aesthetics and style with functional technology. " garments are the interface to the exterior mediated through digital technology. it allows endless possibilities for the dynamic customization of apparel. all clothes have social, psychological and physical functions. however, with the use of technology these functions can be amplified. there are some wearables that are called e - textiles. these are the combination of textiles ( fabric ) and electronic components to create wearable technology within clothing. they are also known as smart textile and digital textile. wearables are made from a functionality perspective or from an aesthetic perspective. when made from a functionality perspective, designers and engineers create wearables to provide convenience to the user. clothing and accessories are used as a tool to provide assistance to the user. designers and engineers are working together to incorporate technology in the manufacturing of garments in order to provide functionalities that can simplify the lives of the user. for example, through smartwatches
pushes more individuals to take part. wearable technology also helps with chronic disease development and monitoring physical activity in terms of context. for example, according to the american journal of preventive medicine, " wearables can be used across different chronic disease trajectory phases ( e. g., pre - versus post - surgery ) and linked to medical record data to obtain granular data on how activity frequency, intensity, and duration changes over the disease course and with different treatments. " wearable technology can be beneficial in tracking and helping analyze data in terms of how one is performing as time goes on, and how they may be performing with different changes in their diet, workout routine, or sleep patterns. also, not only can wearable technology be helpful in measuring results pre and post surgery, but it can also help measure results as someone may be rehabbing from a chronic disease such as cancer, or heart disease, etc. wearable technology has the potential to create new and improved ways of how we look at health and how we actually interpret that science behind our health. it can propel us into higher levels of medicine and has already made a significant impact on how patients are diagnosed, treated, and rehabbed over time. however, extensive research still needs to be continued on how to properly integrate wearable technology into health care and how to best utilize it. in addition, despite the reaping benefits of wearable technology, a lot of research still also has to be completed in order to start transitioning wearable technology towards very sick high risk patients. = = = sense - making of the data = = = while wearables can collect data in aggregate form, most of them are limited in their ability to analyze or make conclusions based on this data β thus, most are used primarily for general health information. end user perception of how their data is used plays a big role in how such datasets can be fully optimized. exception include seizure - alerting wearables, which continuously analyze the wearer ' s data and make a decision about calling for help β the data collected can then provide doctors with objective evidence that they may find useful in diagnoses. wearables can account for individual differences, although most just collect data and apply one - size - fits - all algorithms. software on the wearables may analyze the data directly or send the data to a nearby device ( s ), such as a smartphone, which processes, displays or uses the data for analysis. for analysis and real - term sense - making, machine
this is a very short review of neutrino - nucleus interactions and their influence on the analysis of long - baseline experiments.
results of an experiment are presented whose aim is to explore the relationship between respiration and cerebral oxygenation. measurements of end tidal co2 ( etco2 ) were taken simultaneously with cerebral oxygen saturation ( rso2 ) using the invos cerebral oximeter of somanetics. due to the device limitations we could explore only subjects who could perform with a breathing rate of around 2 / min or less. six subjects were used who were experienced in yoga breathing techniques. they performed an identical periodic breathing exercise including periodicity of about 2 / min. the results of all six subjects clearly show a periodic change of cerebral oxygenation with the same period as the breathing exercises. similar periodic changes in blood volume index were observed as well.
modification of three ideas underlying newton ' s original world view, with only minor changes in context, might offer two advantages to introductory physics students. first, the students will experience less cognitive dissonance when they encounter relativistic effects. secondly, the map - based newtonian tools that they spend so much time learning about can be extended to high speeds, non - inertial frames, and even ( locally, of course ) to curved - spacetime.
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
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 ),
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
Question: A class is testing the effect of exercise on heart rate. The heart rate of two students before exercise is compared to their heart rate after running around a track. Which procedure will most likely help the class correctly compare the results of the two students?
A) test students who are the same height
B) have the students run on the same day
C) measure the distance each student runs
D) have the students run for the same amount of time
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D) have the students run for the same amount of time
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