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this scaffold and cells were placed in a bioreactor, where it matured to become a partially or fully transplantable organ. the work was called a " landmark ". the lab first stripped the cells away from a rat heart ( a process called " decellularization " ) and then injected rat stem cells into the decellularized rat heart. tissue - engineered blood vessels : blood vessels that have been grown in a lab and can be used to repair damaged blood vessels without eliciting an immune response. tissue engineered blood vessels have been developed by many different approaches. they could be implanted as pre - seeded cellularized blood vessels, as acellular vascular grafts made with decellularized vessels or synthetic vascular grafts. artificial skin constructed from human skin cells embedded in a hydrogel, such as in the case of bio - printed constructs for battlefield burn repairs. artificial bone marrow : bone marrow cultured in vitro to be transplanted serves as a " just cells " approach to tissue engineering. tissue engineered bone : a structural matrix can be composed of metals such as titanium, polymers of varying degradation rates, or certain types of ceramics. materials are often chosen to recruit osteoblasts to aid in reforming the bone and returning biological function. various types of cells can be added directly into the matrix to expedite the process. laboratory - grown penis : decellularized scaffolds of rabbit penises were recellularised with smooth muscle and endothelial cells. the organ was then transplanted to live rabbits and functioned comparably to the native organ, suggesting potential as treatment for genital trauma. oral mucosa tissue engineering uses a cells and scaffold approach to replicate the 3 dimensional structure and function of oral mucosa. = = cells as building blocks = = cells are one of the main components for the success of tissue engineering approaches. tissue engineering uses cells as strategies for creation / replacement of new tissue. examples include fibroblasts used for skin repair or renewal, chondrocytes used for cartilage repair ( maci β fda approved product ), and hepatocytes used in liver support systems cells can be used alone or with support matrices for tissue engineering applications. an adequate environment for promoting cell growth, differentiation, and integration with the existing tissue is a critical factor for cell - based building blocks. manipulation of any of these cell processes create alternative avenues for the development of new tissue ( e. g., cell reprogramming - somatic
cells into the decellularized rat heart. tissue - engineered blood vessels : blood vessels that have been grown in a lab and can be used to repair damaged blood vessels without eliciting an immune response. tissue engineered blood vessels have been developed by many different approaches. they could be implanted as pre - seeded cellularized blood vessels, as acellular vascular grafts made with decellularized vessels or synthetic vascular grafts. artificial skin constructed from human skin cells embedded in a hydrogel, such as in the case of bio - printed constructs for battlefield burn repairs. artificial bone marrow : bone marrow cultured in vitro to be transplanted serves as a " just cells " approach to tissue engineering. tissue engineered bone : a structural matrix can be composed of metals such as titanium, polymers of varying degradation rates, or certain types of ceramics. materials are often chosen to recruit osteoblasts to aid in reforming the bone and returning biological function. various types of cells can be added directly into the matrix to expedite the process. laboratory - grown penis : decellularized scaffolds of rabbit penises were recellularised with smooth muscle and endothelial cells. the organ was then transplanted to live rabbits and functioned comparably to the native organ, suggesting potential as treatment for genital trauma. oral mucosa tissue engineering uses a cells and scaffold approach to replicate the 3 dimensional structure and function of oral mucosa. = = cells as building blocks = = cells are one of the main components for the success of tissue engineering approaches. tissue engineering uses cells as strategies for creation / replacement of new tissue. examples include fibroblasts used for skin repair or renewal, chondrocytes used for cartilage repair ( maci β fda approved product ), and hepatocytes used in liver support systems cells can be used alone or with support matrices for tissue engineering applications. an adequate environment for promoting cell growth, differentiation, and integration with the existing tissue is a critical factor for cell - based building blocks. manipulation of any of these cell processes create alternative avenues for the development of new tissue ( e. g., cell reprogramming - somatic cells, vascularization ). = = = isolation = = = techniques for cell isolation depend on the cell source. centrifugation and apheresis are techniques used for extracting cells from biofluids ( e. g., blood ). whereas digestion processes, typically using enzymes to remove the extra
into seven out of approximately 20 human test subjects as part of a long - term experiment. cartilage : lab - grown cartilage, cultured in vitro on a scaffold, was successfully used as an autologous transplant to repair patients ' knees. scaffold - free cartilage : cartilage generated without the use of exogenous scaffold material. in this methodology, all material in the construct is cellular produced directly by the cells. bioartificial heart : doris taylor ' s lab constructed a biocompatible rat heart by re - cellularising a de - cellularised rat heart. this scaffold and cells were placed in a bioreactor, where it matured to become a partially or fully transplantable organ. the work was called a " landmark ". the lab first stripped the cells away from a rat heart ( a process called " decellularization " ) and then injected rat stem cells into the decellularized rat heart. tissue - engineered blood vessels : blood vessels that have been grown in a lab and can be used to repair damaged blood vessels without eliciting an immune response. tissue engineered blood vessels have been developed by many different approaches. they could be implanted as pre - seeded cellularized blood vessels, as acellular vascular grafts made with decellularized vessels or synthetic vascular grafts. artificial skin constructed from human skin cells embedded in a hydrogel, such as in the case of bio - printed constructs for battlefield burn repairs. artificial bone marrow : bone marrow cultured in vitro to 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
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
the following purposes : allowing cell attachment and migration, delivering and retaining cells and biochemical factors, enabling diffusion of vital cell nutrients and expressed products, and exerting certain mechanical and biological influences to modify the behaviour of the cell phase. in 2009, an interdisciplinary team led by the thoracic surgeon thorsten walles implanted the first bioartificial transplant that provides an innate vascular network for post - transplant graft supply successfully into a patient awaiting tracheal reconstruction. to achieve the goal of tissue reconstruction, scaffolds must meet some specific requirements. high porosity and adequate pore size are necessary to facilitate cell seeding and diffusion throughout the whole structure of both cells and nutrients. biodegradability is often an essential factor since scaffolds should preferably be absorbed by the surrounding tissues without the necessity of surgical removal. the rate at which degradation occurs has to coincide as much as possible with the rate of tissue formation : this means that while cells are fabricating their own natural matrix structure around themselves, the scaffold is able to provide structural integrity within the body and eventually it will break down leaving the newly formed tissue which will take over the mechanical load. injectability is also important for clinical uses. recent research on organ printing is showing how crucial a good control of the 3d environment is to ensure reproducibility of experiments and offer better results. = = = materials = = = material selection is an essential aspect of producing a scaffold. the materials utilized can be natural or synthetic and can be biodegradable or non - biodegradable. additionally, they must be biocompatible, meaning that they do not cause any adverse effects to cells. silicone, for example, is a synthetic, non - biodegradable material commonly used as a drug delivery material, while gelatin is a biodegradable, natural material commonly used in cell - culture scaffolds the material needed for each application is different, and dependent on the desired mechanical properties of the material. tissue engineering of long bone defects for example, will require a rigid scaffold with a compressive strength similar to that of cortical bone ( 100 - 150 mpa ), which is much higher compared to a scaffold for skin regeneration. there are a few versatile synthetic materials used for many different scaffold applications. one of these commonly used materials is polylactic acid ( pla ), a synthetic polymer. pla β polylactic acid. this is a polyester which
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
##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
fluid dynamics video demonstrating the evolution of dynamic stall on a wind turbine blade.
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
medical purposes. cells are often ' seeded ' into these structures capable of supporting three - dimensional tissue formation. scaffolds mimic the extracellular matrix of the native tissue, recapitulating the in vivo milieu and allowing cells to influence their own microenvironments. they usually serve at least one of the following purposes : allowing cell attachment and migration, delivering and retaining cells and biochemical factors, enabling diffusion of vital cell nutrients and expressed products, and exerting certain mechanical and biological influences to modify the behaviour of the cell phase. in 2009, an interdisciplinary team led by the thoracic surgeon thorsten walles implanted the first bioartificial transplant that provides an innate vascular network for post - transplant graft supply successfully into a patient awaiting tracheal reconstruction. to achieve the goal of tissue reconstruction, scaffolds must meet some specific requirements. high porosity and adequate pore size are necessary to facilitate cell seeding and diffusion throughout the whole structure of both cells and nutrients. biodegradability is often an essential factor since scaffolds should preferably be absorbed by the surrounding tissues without the necessity of surgical removal. the rate at which degradation occurs has to coincide as much as possible with the rate of tissue formation : this means that while cells are fabricating their own natural matrix structure around themselves, the scaffold is able to provide structural integrity within the body and eventually it will break down leaving the newly formed tissue which will take over the mechanical load. injectability is also important for clinical uses. recent research on organ printing is showing how crucial a good control of the 3d environment is to ensure reproducibility of experiments and offer better results. = = = materials = = = material selection is an essential aspect of producing a scaffold. the materials utilized can be natural or synthetic and can be biodegradable or non - biodegradable. additionally, they must be biocompatible, meaning that they do not cause any adverse effects to cells. silicone, for example, is a synthetic, non - biodegradable material commonly used as a drug delivery material, while gelatin is a biodegradable, natural material commonly used in cell - culture scaffolds the material needed for each application is different, and dependent on the desired mechanical properties of the material. tissue engineering of long bone defects for example, will require a rigid scaffold with a compressive strength similar to that of cortical bone ( 100 - 150 mpa ),
Question: What is only effective if ventilation is matched to blood flow through alveolar capillaries?
A) blood pressur control
B) breathing control
C) iron lung
D) assisted breathing
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B) breathing control
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Context:
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
diploid embryo sporophyte within its tissues for at least part of its life, even in the seed plants, where the gametophyte itself is nurtured by its parent sporophyte. other groups of organisms that were previously studied by botanists include bacteria ( now studied in bacteriology ), fungi ( mycology ) β including lichen - forming fungi ( lichenology ), non - chlorophyte algae ( phycology ), and viruses ( virology ). however, attention is still given to these groups by botanists, and fungi ( including lichens ) and photosynthetic protists are usually covered in introductory botany courses. palaeobotanists study ancient plants in the fossil record to provide information about the evolutionary history of plants. cyanobacteria, the first oxygen - releasing photosynthetic organisms on earth, are thought to have given rise to the ancestor of plants by entering into an endosymbiotic relationship with an early eukaryote, ultimately becoming the chloroplasts in plant cells. the new photosynthetic plants ( along with their algal relatives ) accelerated the rise in atmospheric oxygen started by the cyanobacteria, changing the ancient oxygen - free, reducing, atmosphere to one in which free oxygen has been abundant for more than 2 billion years. among the important botanical questions of the 21st century are the role of plants as primary producers in the global cycling of life ' s basic ingredients : energy, carbon, oxygen, nitrogen and water, and ways that our plant stewardship can help address the global environmental issues of resource management, conservation, human food security, biologically invasive organisms, carbon sequestration, climate change, and sustainability. = = = human nutrition = = = virtually all staple foods come either directly from primary production by plants, or indirectly from animals that eat them. plants and other photosynthetic organisms are at the base of most food chains because they use the energy from the sun and nutrients from the soil and atmosphere, converting them into a form that can be used by animals. this is what ecologists call the first trophic level. the modern forms of the major staple foods, such as hemp, teff, maize, rice, wheat and other cereal grasses, pulses, bananas and plantains, as well as hemp, flax and cotton grown for their fibres, are the outcome of prehistoric selection over thousands of years from among wild ancestral plants with the most
plants, the liverworts, hornworts and mosses do not produce ground - penetrating vascular roots and most of the plant participates in photosynthesis. the sporophyte generation is nonphotosynthetic in liverworts but may be able to contribute part of its energy needs by photosynthesis in mosses and hornworts. the root system and the shoot system are interdependent β the usually nonphotosynthetic root system depends on the shoot system for food, and the usually photosynthetic shoot system depends on water and minerals from the root system. cells in each system are capable of creating cells of the other and producing adventitious shoots or roots. stolons and tubers are examples of shoots that can grow roots. roots that spread out close to the surface, such as those of willows, can produce shoots and ultimately new plants. in the event that one of the systems is lost, the other can often regrow it. in fact it is possible to grow an entire plant from a single leaf, as is the case with plants in streptocarpus sect. saintpaulia, or even a single cell β which can dedifferentiate into a callus ( a mass of unspecialised cells ) that can grow into a new plant. in vascular plants, the xylem and phloem are the conductive tissues that transport resources between shoots and roots. roots are often adapted to store food such as sugars or starch, as in sugar beets and carrots. stems mainly provide support to the leaves and reproductive structures, but can store water in succulent plants such as cacti, food as in potato tubers, or reproduce vegetatively as in the stolons of strawberry plants or in the process of layering. leaves gather sunlight and carry out 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,
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
pectin and xyloglucan from which the land plant cell wall is constructed. vascular land plants make lignin, a polymer used to strengthen the secondary cell walls of xylem tracheids and vessels to keep them from collapsing when a plant sucks water through them under water stress. lignin is also used in other cell types like sclerenchyma fibres that provide structural support for a plant and is a major constituent of wood. sporopollenin is a chemically resistant polymer found in the outer cell walls of spores and pollen of land plants responsible for the survival of early land plant spores and the pollen of seed plants in the fossil record. it is widely regarded as a marker for the start of land plant evolution during the ordovician period. the concentration of carbon dioxide in the atmosphere today is much lower than it was when plants emerged onto land during the ordovician and silurian periods. many monocots like maize and the pineapple and some dicots like the asteraceae have since independently evolved pathways like crassulacean acid metabolism and the c4 carbon fixation pathway for photosynthesis which avoid the losses resulting from photorespiration in the more common c3 carbon fixation pathway. these biochemical strategies are unique to land plants. = = = medicine and materials = = = phytochemistry is a branch of plant biochemistry primarily concerned with the chemical substances produced by plants during secondary metabolism. some of these compounds are toxins such as the alkaloid coniine from hemlock. others, such as the essential oils peppermint oil and lemon oil are useful for their aroma, as flavourings and spices ( e. g., capsaicin ), and in medicine as pharmaceuticals as in opium from opium poppies. many medicinal and recreational drugs, such as tetrahydrocannabinol ( active ingredient in cannabis ), caffeine, morphine and nicotine come directly from plants. others are simple derivatives of botanical natural products. for example, the pain killer aspirin is the acetyl ester of salicylic acid, originally isolated from the bark of willow trees, and a wide range of opiate painkillers like heroin are obtained by chemical modification of morphine obtained from the opium poppy. popular stimulants come from plants, such as caffeine from coffee, tea and chocolate, and nicotine from tobacco. most alcoholic beverages come from fermentation of carbohy
or lipids ( elaioplasts ). uniquely, streptophyte cells and those of the green algal order trentepohliales divide by construction of a phragmoplast as a template for building a cell plate late in cell division. the bodies of vascular plants including clubmosses, ferns and seed plants ( gymnosperms and angiosperms ) generally have aerial and subterranean subsystems. the shoots consist of stems bearing green photosynthesising leaves and reproductive structures. the underground vascularised roots bear root hairs at their tips and generally lack chlorophyll. non - vascular plants, the liverworts, hornworts and mosses do not produce ground - penetrating vascular roots and most of the plant participates in photosynthesis. the sporophyte generation is nonphotosynthetic in liverworts but may be able to contribute part of its energy needs by photosynthesis in mosses and hornworts. the root system and the shoot system are interdependent β the usually nonphotosynthetic root system depends on the shoot system for food, and the usually photosynthetic shoot system depends on water and minerals from the root system. cells in each system are capable of creating cells of the other and producing adventitious shoots or roots. stolons and tubers are examples of shoots that can grow roots. roots that spread out close to the surface, such as those of willows, can produce shoots and ultimately new plants. in the event that one of the systems is lost, the other can often regrow it. in fact it is possible to grow an entire plant from a single leaf, as is the case with plants in streptocarpus sect. saintpaulia, or even a single cell β which can dedifferentiate into a callus ( a mass of unspecialised cells ) that can grow into a new plant. in vascular plants, the xylem and phloem are the conductive tissues that transport resources between shoots and roots. roots are often adapted to store food such as sugars or starch, as in sugar beets and carrots. stems mainly provide support to the leaves and reproductive structures, but can store water in succulent plants such as cacti, food as in potato tubers, or reproduce vegetatively as in the stolons of strawberry plants or in the process of layering. leaves gather sunlight and carry out photosyn
pigmentation, chloroplast structure and nutrient reserves. the algal division charophyta, sister to the green algal division chlorophyta, is considered to contain the ancestor of true plants. the charophyte class charophyceae and the land plant sub - kingdom embryophyta together form the monophyletic group or clade streptophytina. nonvascular land plants are embryophytes that lack the vascular tissues xylem and phloem. they include mosses, liverworts and hornworts. pteridophytic vascular plants with true xylem and phloem that reproduced by spores germinating into free - living gametophytes evolved during the silurian period and diversified into several lineages during the late silurian and early devonian. representatives of the lycopods have survived to the present day. by the end of the devonian period, several groups, including the lycopods, sphenophylls and progymnosperms, had independently evolved " megaspory " β their spores were of two distinct sizes, larger megaspores and smaller microspores. their reduced gametophytes developed from megaspores retained within the spore - producing organs ( megasporangia ) of the sporophyte, a condition known as endospory. seeds consist of an endosporic megasporangium surrounded by one or two sheathing layers ( integuments ). the young sporophyte develops within the seed, which on germination splits to release it. the earliest known seed plants date from the latest devonian famennian stage. following the evolution of the seed habit, seed plants diversified, giving rise to a number of now - extinct groups, including seed ferns, as well as the modern gymnosperms and angiosperms. gymnosperms produce " naked seeds " not fully enclosed in an ovary ; modern representatives include conifers, cycads, ginkgo, and gnetales. angiosperms produce seeds enclosed in a structure such as a carpel or an ovary. ongoing research on the molecular phylogenetics of living plants appears to show that the angiosperms are a sister clade to the gymnosperms. = = plant physiology = = plant physiology encompasses all the internal chemical and physical activities of plants associated with life. chemicals obtained from the air, soil and water form
##es. embryophytes are multicellular eukaryotes descended from an ancestor that obtained its energy from sunlight by photosynthesis. they have life cycles with alternating haploid and diploid phases. the sexual haploid phase of embryophytes, known as the gametophyte, nurtures the developing diploid embryo sporophyte within its tissues for at least part of its life, even in the seed plants, where the gametophyte itself is nurtured by its parent sporophyte. other groups of organisms that were previously studied by botanists include bacteria ( now studied in bacteriology ), fungi ( mycology ) β including lichen - forming fungi ( lichenology ), non - chlorophyte algae ( phycology ), and viruses ( virology ). however, attention is still given to these groups by botanists, and fungi ( including lichens ) and photosynthetic protists are usually covered in introductory botany courses. palaeobotanists study ancient plants in the fossil record to provide information about the evolutionary history of plants. cyanobacteria, the first oxygen - releasing photosynthetic organisms on earth, are thought to have given rise to the ancestor of plants by entering into an endosymbiotic relationship with an early eukaryote, ultimately becoming the chloroplasts in plant cells. the new photosynthetic plants ( along with their algal relatives ) accelerated the rise in atmospheric oxygen started by the cyanobacteria, changing the ancient oxygen - free, reducing, atmosphere to one in which free oxygen has been abundant for more than 2 billion years. among the important botanical questions of the 21st century are the role of plants as primary producers in the global cycling of life ' s basic ingredients : energy, carbon, oxygen, nitrogen and water, and ways that our plant stewardship can help address the global environmental issues of resource management, conservation, human food security, biologically invasive organisms, carbon sequestration, climate change, and sustainability. = = = human nutrition = = = virtually all staple foods come either directly from primary production by plants, or indirectly from animals that eat them. plants and other photosynthetic organisms are at the base of most food chains because they use the energy from the sun and nutrients from the soil and atmosphere, converting them into a form that can be used by animals. this is what ecologists call the first trophic level. the modern forms of
##ses, ferns and seed plants ( gymnosperms and angiosperms ) generally have aerial and subterranean subsystems. the shoots consist of stems bearing green photosynthesising leaves and reproductive structures. the underground vascularised roots bear root hairs at their tips and generally lack chlorophyll. non - vascular plants, the liverworts, hornworts and mosses do not produce ground - penetrating vascular roots and most of the plant participates in photosynthesis. the sporophyte generation is nonphotosynthetic in liverworts but may be able to contribute part of its energy needs by photosynthesis in mosses and hornworts. the root system and the shoot system are interdependent β the usually nonphotosynthetic root system depends on the shoot system for food, and the usually photosynthetic shoot system depends on water and minerals from the root system. cells in each system are capable of creating cells of the other and producing adventitious shoots or roots. stolons and tubers are examples of shoots that can grow roots. roots that spread out close to the surface, such as those of willows, can produce shoots and ultimately new plants. in the event that one of the systems is lost, the other can often regrow it. in fact it is possible to grow an entire plant from a single leaf, as is the case with plants in streptocarpus sect. saintpaulia, or even a single cell β which can dedifferentiate into a callus ( a mass of unspecialised cells ) that can grow into a new plant. in vascular plants, the xylem and phloem are the conductive tissues that transport resources between shoots and roots. roots are often adapted to store food such as sugars or starch, as in sugar beets and carrots. stems mainly provide support to the leaves and reproductive structures, but can store water in succulent plants such as cacti, food as in potato tubers, or reproduce vegetatively as in the stolons of strawberry plants or in the process of layering. leaves gather sunlight and carry out 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
##ta together form the monophyletic group or clade streptophytina. nonvascular land plants are embryophytes that lack the vascular tissues xylem and phloem. they include mosses, liverworts and hornworts. pteridophytic vascular plants with true xylem and phloem that reproduced by spores germinating into free - living gametophytes evolved during the silurian period and diversified into several lineages during the late silurian and early devonian. representatives of the lycopods have survived to the present day. by the end of the devonian period, several groups, including the lycopods, sphenophylls and progymnosperms, had independently evolved " megaspory " β their spores were of two distinct sizes, larger megaspores and smaller microspores. their reduced gametophytes developed from megaspores retained within the spore - producing organs ( megasporangia ) of the sporophyte, a condition known as endospory. seeds consist of an endosporic megasporangium surrounded by one or two sheathing layers ( integuments ). the young sporophyte develops within the seed, which on germination splits to release it. the earliest known seed plants date from the latest devonian famennian stage. following the evolution of the seed habit, seed plants diversified, giving rise to a number of now - extinct groups, including seed ferns, as well as the modern gymnosperms and angiosperms. gymnosperms produce " naked seeds " not fully enclosed in an ovary ; modern representatives include conifers, cycads, ginkgo, and gnetales. angiosperms produce seeds enclosed in a structure such as a carpel or an ovary. ongoing research on the molecular phylogenetics of living plants appears to show that the angiosperms are a sister clade to the gymnosperms. = = plant physiology = = plant physiology encompasses all the internal chemical and physical activities of plants associated with life. chemicals obtained from the air, soil and water form the basis of all plant metabolism. the energy of sunlight, captured by oxygenic photosynthesis and released by cellular respiration, is the basis of almost all life. photoautotrophs, including all green plants, algae and cyanobacteria gather energy directly from sunlight by photosynthesis. hetero
Question: What sprouts up on stalks from the bed of moss gametophytes?
A) fibroblasts
B) stomata
C) sporophytes
D) monocots
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C) sporophytes
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Context:
they may have been present earlier, their diversification accelerated when they started using oxygen in their metabolism. later, around 1. 7 billion years ago, multicellular organisms began to appear, with differentiated cells performing specialised functions. algae - like multicellular land plants are dated back to about 1 billion years ago, although evidence suggests that microorganisms formed the earliest terrestrial ecosystems, at least 2. 7 billion years ago. microorganisms are thought to have paved the way for the inception of land plants in the ordovician period. land plants were so successful that they are thought to have contributed to the late devonian extinction event. ediacara biota appear during the ediacaran period, while vertebrates, along with most other modern phyla originated about 525 million years ago during the cambrian explosion. during the permian period, synapsids, including the ancestors of mammals, dominated the land, but most of this group became extinct in the permian β triassic extinction event 252 million years ago. during the recovery from this catastrophe, archosaurs became the most abundant land vertebrates ; one archosaur group, the dinosaurs, dominated the jurassic and cretaceous periods. after the cretaceous β paleogene extinction event 66 million years ago killed off the non - avian dinosaurs, mammals increased rapidly in size and diversity. such mass extinctions may have accelerated evolution by providing opportunities for new groups of organisms to diversify. = = diversity = = = = = bacteria and archaea = = = bacteria are a type of cell that constitute a large domain of prokaryotic microorganisms. typically a few micrometers in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. bacteria were among the first life forms to appear on earth, and are present in most of its habitats. bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep biosphere of the earth ' s crust. bacteria also live in symbiotic and parasitic relationships with plants and animals. most bacteria have not been characterised, and only about 27 percent of the bacterial phyla have species that can be grown in the laboratory. archaea constitute the other domain of prokaryotic cells and were initially classified as bacteria, receiving the name archaebacteria ( in the archaebacteria kingdom ), a term that has fallen out of use. archaeal cells have unique properties separating them from the other two domains, bacteria and eukaryota. archaea
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 '
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
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 ' 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
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
can be activated by inducers are called inducible genes, in contrast to constitutive genes that are almost constantly active. in contrast to both, structural genes encode proteins that are not involved in gene regulation. in addition to regulatory events involving the promoter, gene expression can also be regulated by epigenetic changes to chromatin, which is a complex of dna and protein found in eukaryotic cells. = = = genes, development, and evolution = = = development is the process by which a multicellular organism ( plant or animal ) goes through a series of changes, starting from a single cell, and taking on various forms that are characteristic of its life cycle. there are four key processes that underlie development : determination, differentiation, morphogenesis, and growth. determination sets the developmental fate of a cell, which becomes more restrictive during development. differentiation is the process by which specialized cells arise from less specialized cells such as stem cells. stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. cellular differentiation dramatically changes a cell ' s size, shape, membrane potential, metabolic activity, and responsiveness to signals, which are largely due to highly controlled modifications in gene expression and epigenetics. with a few exceptions, cellular differentiation almost never involves a change in the dna sequence itself. thus, different cells can have very different physical characteristics despite having the same genome. morphogenesis, or the development of body form, is the result of spatial differences in gene expression. a small fraction of the genes in an organism ' s genome called the developmental - genetic toolkit control the development of that organism. these toolkit genes are highly conserved among phyla, meaning that they are ancient and very similar in widely separated groups of animals. differences in deployment of toolkit genes affect the body plan and the number, identity, and pattern of body parts. among the most important toolkit genes are the hox genes. hox genes determine where repeating parts, such as the many vertebrae of snakes, will grow in a developing embryo or larva. = = evolution = = = = = evolutionary processes = = = evolution is a central organizing concept in biology. it is the change in heritable characteristics of populations over successive generations. in artificial selection, animals were selectively bred for specific traits. given that traits are inherited, populations contain a varied mix of traits, and reproduction is able to increase any population,
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
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
( 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
a brief description of some salient aspects of four - dimensional supersymmetry : early history, supermanifolds, the mssm, cold dark matter, the cosmological constant and the string landscape.
Question: Like all chordates, vertebrates are animals with four defining traits, at least during which stage?
A) adult
B) embryonic
C) larval
D) pupal
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B) embryonic
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Context:
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,
schr \ " odinger ' s cat puzzle is resolved. the reason why we do not see a macroscopic superposition of states is cleared in the light of everett ' s formulation of quantum mechanics.
produces. the mastering engineer makes any final adjustments to the overall sound of the record in the final step before commercial duplication. mastering engineers use principles of equalization, compression and limiting to fine - tune the sound timbre and dynamics and to achieve a louder recording. sound designer β broadly an artist who produces soundtracks or sound effects content for media. live sound engineer front of house ( foh ) engineer, or a1. β a person dealing with live sound reinforcement. this usually includes planning and installation of loudspeakers, cabling and equipment and mixing sound during the show. this may or may not include running the foldback sound. a live / sound reinforcement engineer hears source material and tries to correlate that sonic experience with system performance. wireless microphone engineer, or a2. this position is responsible for wireless microphones during a theatre production, a sports event or a corporate event. foldback or monitor engineer β a person running foldback sound during a live event. the term foldback comes from the old practice of folding back audio signals from the front of house ( foh ) mixing console to the stage so musicians can hear themselves while performing. monitor engineers usually have a separate audio system from the foh engineer and manipulate audio signals independently from what the audience hears so they can satisfy the requirements of each performer on stage. in - ear systems, digital and analog mixing consoles, and a variety of speaker enclosures are typically used by monitor engineers. in addition, most monitor engineers must be familiar with wireless or rf ( radio - frequency ) equipment and often must communicate personally with the artist ( s ) during each performance. systems engineer β responsible for the design setup of modern pa systems, which are often very complex. a systems engineer is usually also referred to as a crew chief on tour and is responsible for the performance and day - to - day job requirements of the audio crew as a whole along with the foh audio system. this is a sound - only position concerned with implementation, not to be confused with the interdisciplinary field of system engineering, which typically requires a college degree. re - recording mixer β a person in post - production who mixes audio tracks for feature films or television programs. = = equipment = = an audio engineer is proficient with different types of recording media, such as analog tape, digital multi - track recorders and workstations, plug - ins and computer knowledge. with the advent of the digital age, it is increasingly important for the audio engineer to understand software and hardware integration, from synchronization to analog to digital transfers
as negation and trigonometric functions. binary operations, on the other hand, take two values, and include addition, subtraction, multiplication, division, and exponentiation. operations can involve mathematical objects other than numbers. the logical values true and false can be combined using logic operations, such as and, or, and not. vectors can be added and subtracted. rotations can be combined using the function composition operation, performing the first rotation and then the second. operations on sets include the binary operations union and intersection and the unary operation of complementation. operations on functions include composition and convolution. operations may not be defined for every possible value of its domain. for example, in the real numbers one cannot divide by zero or take square roots of negative numbers. the values for which an operation is defined form a set called its domain of definition or active domain. the set which contains the values produced is called the codomain, but the set of actual values attained by the operation is its codomain of definition, active codomain, image or range. for example, in the real numbers, the squaring operation only produces non - negative numbers ; the codomain is the set of real numbers, but the range is the non - negative numbers. operations can involve dissimilar objects : a vector can be multiplied by a scalar to form another vector ( an operation known as scalar multiplication ), and the inner product operation on two vectors produces a quantity that is scalar. an operation may or may not have certain properties, for example it may be associative, commutative, anticommutative, idempotent, and so on. the values combined are called operands, arguments, or inputs, and the value produced is called the value, result, or output. operations can have fewer or more than two inputs ( including the case of zero input and infinitely many inputs ). an operator is similar to an operation in that it refers to the symbol or the process used to denote the operation. hence, their point of view is different. for instance, one often speaks of " the operation of addition " or " the addition operation, " when focusing on the operands and result, but one switch to " addition operator " ( rarely " operator of addition " ), when focusing on the process, or from the more symbolic viewpoint, the function + : x Γ x β x ( where x is a set such as the set of real numbers ).
mixes of multi - track recordings. it is common to record a commercial record at one studio and have it mixed by different engineers in other studios. mastering engineer β the person who masters the final mixed stereo tracks ( or sometimes a series of audio stems, which consists in a mix of the main sections ) that the mix engineer produces. the mastering engineer makes any final adjustments to the overall sound of the record in the final step before commercial duplication. mastering engineers use principles of equalization, compression and limiting to fine - tune the sound timbre and dynamics and to achieve a louder recording. sound designer β broadly an artist who produces soundtracks or sound effects content for media. live sound engineer front of house ( foh ) engineer, or a1. β a person dealing with live sound reinforcement. this usually includes planning and installation of loudspeakers, cabling and equipment and mixing sound during the show. this may or may not include running the foldback sound. a live / sound reinforcement engineer hears source material and tries to correlate that sonic experience with system performance. wireless microphone engineer, or a2. this position is responsible for wireless microphones during a theatre production, a sports event or a corporate event. foldback or monitor engineer β a person running foldback sound during a live event. the term foldback comes from the old practice of folding back audio signals from the front of house ( foh ) mixing console to the stage so musicians can hear themselves while performing. monitor engineers usually have a separate audio system from the foh engineer and manipulate audio signals independently from what the audience hears so they can satisfy the requirements of each performer on stage. in - ear systems, digital and analog mixing consoles, and a variety of speaker enclosures are typically used by monitor engineers. in addition, most monitor engineers must be familiar with wireless or rf ( radio - frequency ) equipment and often must communicate personally with the artist ( s ) during each performance. systems engineer β responsible for the design setup of modern pa systems, which are often very complex. a systems engineer is usually also referred to as a crew chief on tour and is responsible for the performance and day - to - day job requirements of the audio crew as a whole along with the foh audio system. this is a sound - only position concerned with implementation, not to be confused with the interdisciplinary field of system engineering, which typically requires a college degree. re - recording mixer β a person in post - production who mixes audio tracks for feature films or television programs. = = equipment = = an audio engineer is
more resistance to fading than am or fm. in ofdm, multiple radio carrier waves closely spaced in frequency are transmitted within the radio channel, with each carrier modulated with bits from the incoming bitstream so multiple bits are being sent simultaneously, in parallel. at the receiver, the carriers are demodulated and the bits 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
a producer or independently. recording engineer β the engineer who records sound. assistant engineer β often employed in larger studios, allowing them to train to become full - time engineers. they often assist full - time engineers with microphone setups, session breakdowns and in some cases, rough mixes. mixing engineer β a person who creates mixes of multi - track recordings. it is common to record a commercial record at one studio and have it mixed by different engineers in other studios. mastering engineer β the person who masters the final mixed stereo tracks ( or sometimes a series of audio stems, which consists in a mix of the main sections ) that the mix engineer produces. the mastering engineer makes any final adjustments to the overall sound of the record in the final step before commercial duplication. mastering engineers use principles of equalization, compression and limiting to fine - tune the sound timbre and dynamics and to achieve a louder recording. sound designer β broadly an artist who produces soundtracks or sound effects content for media. live sound engineer front of house ( foh ) engineer, or a1. β a person dealing with live sound reinforcement. this usually includes planning and installation of loudspeakers, cabling and equipment and mixing sound during the show. this may or may not include running the foldback sound. a live / sound reinforcement engineer hears source material and tries to correlate that sonic experience with system performance. wireless microphone engineer, or a2. this position is responsible for wireless microphones during a theatre production, a sports event or a corporate event. foldback or monitor engineer β a person running foldback sound during a live event. the term foldback comes from the old practice of folding back audio signals from the front of house ( foh ) mixing console to the stage so musicians can hear themselves while performing. monitor engineers usually have a separate audio system from the foh engineer and manipulate audio signals independently from what the audience hears so they can satisfy the requirements of each performer on stage. in - ear systems, digital and analog mixing consoles, and a variety of speaker enclosures are typically used by monitor engineers. in addition, most monitor engineers must be familiar with wireless or rf ( radio - frequency ) equipment and often must communicate personally with the artist ( s ) during each performance. systems engineer β responsible for the design setup of modern pa systems, which are often very complex. a systems engineer is usually also referred to as a crew chief on tour and is responsible for the performance and day - to - day job requirements of the audio crew as a whole along with the foh
it is stronger, then demodulates it, extracting the original modulation signal from the modulated carrier wave. the modulation signal is converted by a transducer back to a human - usable form : an audio signal is converted to sound waves by a loudspeaker or earphones, a video signal is converted to images by a display, while a digital signal is applied to a computer or microprocessor, which interacts with human users. the radio waves from many transmitters pass through the air simultaneously without interfering with each other because each transmitter ' s radio waves oscillate at a different frequency, measured in hertz ( hz ), kilohertz ( khz ), megahertz ( mhz ) or gigahertz ( ghz ). the receiving antenna typically picks up the radio signals of many transmitters. the receiver uses tuned circuits to select the radio signal desired out of all the signals picked up by the antenna and reject the others. a tuned circuit acts like a resonator, similar to a tuning fork. it has a natural resonant frequency at which it oscillates. the resonant frequency of the receiver ' s tuned circuit is adjusted by the user to the frequency of the desired radio station ; this is called tuning. the oscillating radio signal from the desired station causes the tuned circuit to oscillate in sympathy, and it passes the signal on to the rest of the receiver. radio signals at other frequencies are blocked by the tuned circuit and not passed on. = = = bandwidth = = = a modulated radio wave, carrying an information signal, occupies a range of frequencies. the information in a radio signal is usually concentrated in narrow frequency bands called sidebands ( sb ) just above and below the carrier frequency. the width in hertz of the frequency range that the radio signal occupies, the highest frequency minus the lowest frequency, is called its bandwidth ( bw ). for any given signal - to - noise ratio, a given bandwidth can carry the same amount of information regardless of where in the radio frequency spectrum it is located ; bandwidth is a measure of information - carrying capacity. the bandwidth required by a radio transmission depends on the data rate of the information being sent, and the spectral efficiency of the modulation method used ; how much data it can transmit in each unit of bandwidth. different types of information signals carried by radio have different data rates. for example, a television signal has a greater data rate than an audio signal. the radio spectrum, the total range of
or, and not. vectors can be added and subtracted. rotations can be combined using the function composition operation, performing the first rotation and then the second. operations on sets include the binary operations union and intersection and the unary operation of complementation. operations on functions include composition and convolution. operations may not be defined for every possible value of its domain. for example, in the real numbers one cannot divide by zero or take square roots of negative numbers. the values for which an operation is defined form a set called its domain of definition or active domain. the set which contains the values produced is called the codomain, but the set of actual values attained by the operation is its codomain of definition, active codomain, image or range. for example, in the real numbers, the squaring operation only produces non - negative numbers ; the codomain is the set of real numbers, but the range is the non - negative numbers. operations can involve dissimilar objects : a vector can be multiplied by a scalar to form another vector ( an operation known as scalar multiplication ), and the inner product operation on two vectors produces a quantity that is scalar. an operation may or may not have certain properties, for example it may be associative, commutative, anticommutative, idempotent, and so on. the values combined are called operands, arguments, or inputs, and the value produced is called the value, result, or output. operations can have fewer or more than two inputs ( including the case of zero input and infinitely many inputs ). an operator is similar to an operation in that it refers to the symbol or the process used to denote the operation. hence, their point of view is different. for instance, one often speaks of " the operation of addition " or " the addition operation, " when focusing on the operands and result, but one switch to " addition operator " ( rarely " operator of addition " ), when focusing on the process, or from the more symbolic viewpoint, the function + : x Γ x β x ( where x is a set such as the set of real numbers ). = = definition = = an n - ary operation Ο on a set x is a function Ο : xn β x. the set xn is called the domain of the operation, the output set is called the codomain of the operation, and the fixed non - negative integer n ( the number of opera
generation of direct current in zigzag carbon nanotubes due to harmonic mixing of two coherent electromagnetic waves is being considered. the electromagnetic waves have commensurate frequencies of omega and two omega. the rectification of the waves at high frequencies is quite smooth whiles at low frequencies there are some fluctuations. the nonohmicity observed in the i - vcharacteristics is attributed to the nonparabolicity of the electron energy band which is very strong in carbon nanotubes because of high stark component. it is observed that the current falls off faster at lower electric field than the case in superlattice. for omega tau equal to two? the external electric field strength emax for the observation of negative differential conductivity occurs around 1. 03x10e6 v / m which is quite weak. it is interesting to note that the peak of the curve shifts to the left with increasing value of omega tau?
Question: What occurs when two waves combine and cancel each other out?
A) terrible interference
B) destructive interference
C) molecular interference
D) primitive interference
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B) destructive interference
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Context:
current in passing over from one concave bank to the next on the opposite side. the lowering of such a shoal by dredging merely effects a temporary deepening, for it soon forms again from the causes which produced it. the removal, moreover, of the rocky obstructions at rapids, though increasing the depth and equalizing the flow at these places, produces a lowering of the river above the rapids by facilitating the efflux, which may result in the appearance of fresh shoals at the low stage of the river. where, however, narrow rocky reefs or other hard shoals stretch across the bottom of a river and present obstacles to the erosion by the current of the soft materials forming the bed of the river above and below, their removal may result in permanent improvement by enabling the river to deepen its bed by natural scour. the capability of a river to provide a waterway for navigation during the summer or throughout the dry season depends on the depth that can be secured in the channel at the lowest stage. the problem in the dry season is the small discharge and deficiency in scour during this period. a typical solution is to restrict the width of the low - water channel, concentrate all of the flow in it, and also to fix its position so that it is scoured out every year by the floods which follow the deepest part of the bed along the line of the strongest current. this can be effected by closing subsidiary low - water channels with dikes across them, and narrowing the channel at the low stage by low - dipping cross dikes extending from the river banks down the slope and pointing slightly up - stream so as to direct the water flowing over them into a central channel. = = estuarine works = = the needs of navigation may also require that a stable, continuous, navigable channel is prolonged from the navigable river to deep water at the mouth of the estuary. the interaction of river flow and tide needs to be modeled by computer or using scale models, moulded to the configuration of the estuary under consideration and reproducing in miniature the tidal ebb and flow and fresh - water discharge over a bed of fine sand, in which various lines of training walls can be successively inserted. the models should be capable of furnishing valuable indications of the respective effects and comparative merits of the different schemes proposed for works. = = see also = = bridge scour flood control = = references = = = = external links = = u. s. army corps of engineers β civil works program river morphology and stream restoration references
. 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
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 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
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
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 )
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 structure of the boundary hilbert - space and the condition that amplitudes behave appropriately under compositions determine the face amplitude of a spinfoam theory. in quantum gravity the face amplitude turns out to be simpler than originally thought.
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 '
##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
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.
Question: What occurs when the crests of one wave overlap the troughs, or lowest points, of another wave?
A) random interference
B) destructive interference
C) constructive interference
D) harmful interference
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B) destructive interference
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Context:
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
an attempt had been made to get algebraic structure of 2d complex harmonic oscillator.
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
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
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 / practical decision. also, unlike the egyptians, greeks, and romans, the babylonians had a place - value system, where digits written in the left column represented larger values, much as in the decimal system. the power of the babylonian notational system lay in that it could be used to represent fractions as easily as whole numbers ; thus multiplying two numbers that contained fractions was no different from multiplying integers, similar to modern notation. the notational system of the babylonians was the best of any civilization until the renaissance, and its power allowed it to achieve remarkable computational accuracy ; for example, the babylonian tablet ybc 7289 gives an approximation of β2 accurate to five decimal places. the babylonians lacked, however, an equivalent of the decimal point, and so the place value of a symbol often had to be inferred from the context. by the seleucid period, the babylonians had developed a zero symbol as a placeholder for empty positions ; however it was only used for intermediate positions. this zero sign does not appear in terminal positions, thus the babylonians came close but did not develop a true place value system. other topics covered by babylonian mathematics include fractions, algebra, quadratic and cubic equations, and the calculation of regular numbers, and their reciprocal pairs. the tablets also include multiplication tables and methods for solving linear, quadratic equations and cubic equations, a remarkable achievement for the time. tablets from the old babylonian period also contain the earliest known statement of the pythagorean theorem. however, as with egyptian mathematics,
##nosperms and angiosperms. gymnosperms produce " naked seeds " not fully enclosed in an ovary ; modern representatives include conifers, cycads, ginkgo, and gnetales. angiosperms produce seeds enclosed in a structure such as a carpel or an ovary. ongoing research on the molecular phylogenetics of living plants appears to show that the angiosperms are a sister clade to the gymnosperms. = = plant physiology = = plant physiology encompasses all the internal chemical and physical activities of plants associated with life. chemicals obtained from the air, soil and water form the basis of all plant metabolism. the energy of sunlight, captured by oxygenic photosynthesis and released by cellular respiration, is the basis of almost all life. photoautotrophs, including all green plants, algae and cyanobacteria gather energy directly from sunlight by photosynthesis. heterotrophs including all animals, all fungi, all completely parasitic plants, and non - photosynthetic bacteria take in organic molecules produced by photoautotrophs and respire them or use them in the construction of cells and tissues. respiration is the oxidation of carbon compounds by breaking them down into simpler structures to release the energy they contain, essentially the opposite of photosynthesis. molecules are moved within plants by transport processes that operate at a variety of spatial scales. subcellular transport of ions, electrons and molecules such as water and enzymes occurs across cell membranes. minerals and water are transported from roots to other parts of the plant in the transpiration stream. diffusion, osmosis, and active transport and mass flow are all different ways transport can occur. examples of elements that plants need to transport are nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. in vascular plants, these elements are extracted from the soil as soluble ions by the roots and transported throughout the plant in the xylem. most of the elements required for plant nutrition come from the chemical breakdown of soil minerals. sucrose produced by photosynthesis is transported from the leaves to other parts of the plant in the phloem and plant hormones are transported by a variety of processes. = = = plant hormones = = = plants are not passive, but respond to external signals such as light, touch, and injury by moving or growing towards or away from the stimulus, as appropriate. tangible evidence of touch sensitivity is the almost instantaneous collapse of leaflets of mimosa pudica, the insect traps of
, 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. 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
an article for the springer encyclopedia of complexity and system science
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
. 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
Question: What system in both males and females consists of structures that produce reproductive cells, or gametes, and secrete sex hormone?
A) circulatory system
B) digestion
C) immune system
D) reproductive
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D) reproductive
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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 no adverse effect on pilot vision. = = = = ships = = = = ships have also adopted similar methods. though the earlier american arleigh burke - class destroyers incorporated some signature - reduction features. the norwegian skjold - class corvettes was the first coastal defence and the french la fayette - class frigates the
##ta together form the monophyletic group or clade streptophytina. nonvascular land plants are embryophytes that lack the vascular tissues xylem and phloem. they include mosses, liverworts and hornworts. pteridophytic vascular plants with true xylem and phloem that reproduced by spores germinating into free - living gametophytes evolved during the silurian period and diversified into several lineages during the late silurian and early devonian. representatives of the lycopods have survived to the present day. by the end of the devonian period, several groups, including the lycopods, sphenophylls and progymnosperms, had independently evolved " megaspory " β their spores were of two distinct sizes, larger megaspores and smaller microspores. their reduced gametophytes developed from megaspores retained within the spore - producing organs ( megasporangia ) of the sporophyte, a condition known as endospory. seeds consist of an endosporic megasporangium surrounded by one or two sheathing layers ( integuments ). the young sporophyte develops within the seed, which on germination splits to release it. the earliest known seed plants date from the latest devonian famennian stage. following the evolution of the seed habit, seed plants diversified, giving rise to a number of now - extinct groups, including seed ferns, as well as the modern gymnosperms and angiosperms. gymnosperms produce " naked seeds " not fully enclosed in an ovary ; modern representatives include conifers, cycads, ginkgo, and gnetales. angiosperms produce seeds enclosed in a structure such as a carpel or an ovary. ongoing research on the molecular phylogenetics of living plants appears to show that the angiosperms are a sister clade to the gymnosperms. = = plant physiology = = plant physiology encompasses all the internal chemical and physical activities of plants associated with life. chemicals obtained from the air, soil and water form the basis of all plant metabolism. the energy of sunlight, captured by oxygenic photosynthesis and released by cellular respiration, is the basis of almost all life. photoautotrophs, including all green plants, algae and cyanobacteria gather energy directly from sunlight by photosynthesis. hetero
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 ' 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
##d product that is the focus of a tooling drawing. lines can also be classified by a letter classification in which each line is given a letter. type a lines show the outline of the feature of an object. they are the thickest lines on a drawing and done with a pencil softer than hb. type b lines are dimension lines and are used for dimensioning, projecting, extending, or leaders. a harder pencil should be used, such as a 2h pencil. type c lines are used for breaks when the whole object is not shown. these are freehand drawn and only for short breaks. 2h pencil type d lines are similar to type c, except these are zigzagged and only for longer breaks. 2h pencil type e lines indicate hidden outlines of internal features of an object. these are dotted lines. 2h pencil type f lines are type e lines, except these are used for drawings in electrotechnology. 2h pencil type g lines are used for centre lines. these are dotted lines, but a long line of 10 β 20 mm, then a 1 mm gap, then a small line of 2 mm. 2h pencil type h lines are the same as type g, except that every second long line is thicker. these indicate the cutting plane of an object. 2h pencil type k lines indicate the alternate positions of an object and the line taken by that object. these are drawn with a long line of 10 β 20 mm, then a small gap, then a small line of 2 mm, then a gap, then another small line. 2h pencil. = = = multiple views and projections = = = in most cases, a single view is not sufficient to show all necessary features, and several views are used. types of views include the following : = = = = multiview projection = = = = a multiview projection is a type of orthographic projection that shows the object as it looks from the front, right, left, top, bottom, or back ( e. g. the primary views ), and is typically positioned relative to each other according to the rules of either first - angle or third - angle projection. the origin and vector direction of the projectors ( 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
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
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.
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
the film is developed and it shows any internal defects of the material. gauges - gauges use the exponential absorption law of gamma rays level indicators : source and detector are placed at opposite sides of a container, indicating the presence or absence of material in the horizontal radiation path. beta or gamma sources are used, depending on the thickness and the density of the material to be measured. the method is used for containers of liquids or of grainy substances thickness gauges : if the material is of constant density, the signal measured by the radiation detector depends on the thickness of the material. this is useful for continuous production, like of paper, rubber, etc. electrostatic control - to avoid the build - up of static electricity in production of paper, plastics, synthetic textiles, etc., a ribbon - shaped source of the alpha emitter 241am can be placed close to the material at the end of the production line. the source ionizes the air to remove electric charges on the material. radioactive tracers - since radioactive isotopes behave, chemically, mostly like the inactive element, the behavior of a certain chemical substance can be followed by tracing the radioactivity. examples : adding a gamma tracer to a gas or liquid in a closed system makes it possible to find a hole in a tube. adding a tracer to the surface of the component of a motor makes it possible to measure wear by measuring the activity of the lubricating oil. oil and gas exploration - nuclear well logging is used to help predict the commercial viability of new or existing wells. the technology involves the use of a neutron or gamma - ray source and a radiation detector which are lowered into boreholes to determine the properties of the surrounding rock such as porosity and lithography. [ 1 ] road construction - nuclear moisture / density gauges are used to determine the density of soils, asphalt, and concrete. typically a cesium - 137 source is used. = = = commercial applications = = = radioluminescence tritium illumination : tritium is used with phosphor in rifle sights to increase nighttime firing accuracy. some runway markers and building exit signs use the same technology, to remain illuminated during blackouts. betavoltaics. smoke detector : an ionization smoke detector includes a tiny mass of radioactive americium - 241, which is a source of alpha radiation. two ionisation chambers are placed next to each other. both contain a small source of 241am that gives rise to a small constant current. one is closed and serves for comparison
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
the structure of the boundary hilbert - space and the condition that amplitudes behave appropriately under compositions determine the face amplitude of a spinfoam theory. in quantum gravity the face amplitude turns out to be simpler than originally thought.
Question: What type of creature is noted for having its eyes at the tips of stalks or tentacles that emerge from its head?
A) arthropods
B) gastropods
C) arachnids
D) corals
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B) gastropods
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Context:
they may have been present earlier, their diversification accelerated when they started using oxygen in their metabolism. later, around 1. 7 billion years ago, multicellular organisms began to appear, with differentiated cells performing specialised functions. algae - like multicellular land plants are dated back to about 1 billion years ago, although evidence suggests that microorganisms formed the earliest terrestrial ecosystems, at least 2. 7 billion years ago. microorganisms are thought to have paved the way for the inception of land plants in the ordovician period. land plants were so successful that they are thought to have contributed to the late devonian extinction event. ediacara biota appear during the ediacaran period, while vertebrates, along with most other modern phyla originated about 525 million years ago during the cambrian explosion. during the permian period, synapsids, including the ancestors of mammals, dominated the land, but most of this group became extinct in the permian β triassic extinction event 252 million years ago. during the recovery from this catastrophe, archosaurs became the most abundant land vertebrates ; one archosaur group, the dinosaurs, dominated the jurassic and cretaceous periods. after the cretaceous β paleogene extinction event 66 million years ago killed off the non - avian dinosaurs, mammals increased rapidly in size and diversity. such mass extinctions may have accelerated evolution by providing opportunities for new groups of organisms to diversify. = = diversity = = = = = bacteria and archaea = = = bacteria are a type of cell that constitute a large domain of prokaryotic microorganisms. typically a few micrometers in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. bacteria were among the first life forms to appear on earth, and are present in most of its habitats. bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep biosphere of the earth ' s crust. bacteria also live in symbiotic and parasitic relationships with plants and animals. most bacteria have not been characterised, and only about 27 percent of the bacterial phyla have species that can be grown in the laboratory. archaea constitute the other domain of prokaryotic cells and were initially classified as bacteria, receiving the name archaebacteria ( in the archaebacteria kingdom ), a term that has fallen out of use. archaeal cells have unique properties separating them from the other two domains, bacteria and eukaryota. archaea
##ta together form the monophyletic group or clade streptophytina. nonvascular land plants are embryophytes that lack the vascular tissues xylem and phloem. they include mosses, liverworts and hornworts. pteridophytic vascular plants with true xylem and phloem that reproduced by spores germinating into free - living gametophytes evolved during the silurian period and diversified into several lineages during the late silurian and early devonian. representatives of the lycopods have survived to the present day. by the end of the devonian period, several groups, including the lycopods, sphenophylls and progymnosperms, had independently evolved " megaspory " β their spores were of two distinct sizes, larger megaspores and smaller microspores. their reduced gametophytes developed from megaspores retained within the spore - producing organs ( megasporangia ) of the sporophyte, a condition known as endospory. seeds consist of an endosporic megasporangium surrounded by one or two sheathing layers ( integuments ). the young sporophyte develops within the seed, which on germination splits to release it. the earliest known seed plants date from the latest devonian famennian stage. following the evolution of the seed habit, seed plants diversified, giving rise to a number of now - extinct groups, including seed ferns, as well as the modern gymnosperms and angiosperms. gymnosperms produce " naked seeds " not fully enclosed in an ovary ; modern representatives include conifers, cycads, ginkgo, and gnetales. angiosperms produce seeds enclosed in a structure such as a carpel or an ovary. ongoing research on the molecular phylogenetics of living plants appears to show that the angiosperms are a sister clade to the gymnosperms. = = plant physiology = = plant physiology encompasses all the internal chemical and physical activities of plants associated with life. chemicals obtained from the air, soil and water form the basis of all plant metabolism. the energy of sunlight, captured by oxygenic photosynthesis and released by cellular respiration, is the basis of almost all life. photoautotrophs, including all green plants, algae and cyanobacteria gather energy directly from sunlight by photosynthesis. hetero
pectin and xyloglucan from which the land plant cell wall is constructed. vascular land plants make lignin, a polymer used to strengthen the secondary cell walls of xylem tracheids and vessels to keep them from collapsing when a plant sucks water through them under water stress. lignin is also used in other cell types like sclerenchyma fibres that provide structural support for a plant and is a major constituent of wood. sporopollenin is a chemically resistant polymer found in the outer cell walls of spores and pollen of land plants responsible for the survival of early land plant spores and the pollen of seed plants in the fossil record. it is widely regarded as a marker for the start of land plant evolution during the ordovician period. the concentration of carbon dioxide in the atmosphere today is much lower than it was when plants emerged onto land during the ordovician and silurian periods. many monocots like maize and the pineapple and some dicots like the asteraceae have since independently evolved pathways like crassulacean acid metabolism and the c4 carbon fixation pathway for photosynthesis which avoid the losses resulting from photorespiration in the more common c3 carbon fixation pathway. these biochemical strategies are unique to land plants. = = = medicine and materials = = = phytochemistry is a branch of plant biochemistry primarily concerned with the chemical substances produced by plants during secondary metabolism. some of these compounds are toxins such as the alkaloid coniine from hemlock. others, such as the essential oils peppermint oil and lemon oil are useful for their aroma, as flavourings and spices ( e. g., capsaicin ), and in medicine as pharmaceuticals as in opium from opium poppies. many medicinal and recreational drugs, such as tetrahydrocannabinol ( active ingredient in cannabis ), caffeine, morphine and nicotine come directly from plants. others are simple derivatives of botanical natural products. for example, the pain killer aspirin is the acetyl ester of salicylic acid, originally isolated from the bark of willow trees, and a wide range of opiate painkillers like heroin are obtained by chemical modification of morphine obtained from the opium poppy. popular stimulants come from plants, such as caffeine from coffee, tea and chocolate, and nicotine from tobacco. most alcoholic beverages come from fermentation of carbohy
, characterizing organs as predominantly yin or yang, and understood the relationship between the pulse, the heart, and the flow of blood in the body centuries before it became accepted in the west. little evidence survives of how ancient indian cultures around the indus river understood nature, but some of their perspectives may be reflected in the vedas, a set of sacred hindu texts. they reveal a conception of the universe as ever - expanding and constantly being recycled and reformed. surgeons in the ayurvedic tradition saw health and illness as a combination of three humors : wind, bile and phlegm. a healthy life resulted from a balance among these humors. in ayurvedic thought, the body consisted of five elements : earth, water, fire, wind, and space. ayurvedic surgeons performed complex surgeries and developed a detailed understanding of human anatomy. pre - socratic philosophers in ancient greek culture brought natural philosophy a step closer to direct inquiry about cause and effect in nature between 600 and 400 bc. however, an element of magic and mythology remained. natural phenomena such as earthquakes and eclipses were explained increasingly in the context of nature itself instead of being attributed to angry gods. thales of miletus, an early philosopher who lived from 625 to 546 bc, explained earthquakes by theorizing that the world floated on water and that water was the fundamental element in nature. in the 5th century bc, leucippus was an early exponent of atomism, the idea that the world is made up of fundamental indivisible particles. pythagoras applied greek innovations in mathematics to astronomy and suggested that the earth was spherical. = = = aristotelian natural philosophy ( 400 bc β 1100 ad ) = = = later socratic and platonic thought focused on ethics, morals, and art and did not attempt an investigation of the physical world ; plato criticized pre - socratic thinkers as materialists and anti - religionists. aristotle, however, a student of plato who lived from 384 to 322 bc, paid closer attention to the natural world in his philosophy. in his history of animals, he described the inner workings of 110 species, including the stingray, catfish and bee. he investigated chick embryos by breaking open eggs and observing them at various stages of development. aristotle ' s works were influential through the 16th century, and he is considered to be the father of biology for his pioneering work in that science. he also presented philosophies about physics, nature, and astronomy using
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
##das, a set of sacred hindu texts. they reveal a conception of the universe as ever - expanding and constantly being recycled and reformed. surgeons in the ayurvedic tradition saw health and illness as a combination of three humors : wind, bile and phlegm. a healthy life resulted from a balance among these humors. in ayurvedic thought, the body consisted of five elements : earth, water, fire, wind, and space. ayurvedic surgeons performed complex surgeries and developed a detailed understanding of human anatomy. pre - socratic philosophers in ancient greek culture brought natural philosophy a step closer to direct inquiry about cause and effect in nature between 600 and 400 bc. however, an element of magic and mythology remained. natural phenomena such as earthquakes and eclipses were explained increasingly in the context of nature itself instead of being attributed to angry gods. thales of miletus, an early philosopher who lived from 625 to 546 bc, explained earthquakes by theorizing that the world floated on water and that water was the fundamental element in nature. in the 5th century bc, leucippus was an early exponent of atomism, the idea that the world is made up of fundamental indivisible particles. pythagoras applied greek innovations in mathematics to astronomy and suggested that the earth was spherical. = = = aristotelian natural philosophy ( 400 bc β 1100 ad ) = = = later socratic and platonic thought focused on ethics, morals, and art and did not attempt an investigation of the physical world ; plato criticized pre - socratic thinkers as materialists and anti - religionists. aristotle, however, a student of plato who lived from 384 to 322 bc, paid closer attention to the natural world in his philosophy. in his history of animals, he described the inner workings of 110 species, including the stingray, catfish and bee. he investigated chick embryos by breaking open eggs and observing them at various stages of development. aristotle ' s works were influential through the 16th century, and he is considered to be the father of biology for his pioneering work in that science. he also presented philosophies about physics, nature, and astronomy using inductive reasoning in his works physics and meteorology. while aristotle considered natural philosophy more seriously than his predecessors, he approached it as a theoretical branch of science. still, inspired by his work, ancient roman philosophers of the early 1st century ad, including lucretius, seneca and pliny the elder, wrote treatise
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.
pigmentation, chloroplast structure and nutrient reserves. the algal division charophyta, sister to the green algal division chlorophyta, is considered to contain the ancestor of true plants. the charophyte class charophyceae and the land plant sub - kingdom embryophyta together form the monophyletic group or clade streptophytina. nonvascular land plants are embryophytes that lack the vascular tissues xylem and phloem. they include mosses, liverworts and hornworts. pteridophytic vascular plants with true xylem and phloem that reproduced by spores germinating into free - living gametophytes evolved during the silurian period and diversified into several lineages during the late silurian and early devonian. representatives of the lycopods have survived to the present day. by the end of the devonian period, several groups, including the lycopods, sphenophylls and progymnosperms, had independently evolved " megaspory " β their spores were of two distinct sizes, larger megaspores and smaller microspores. their reduced gametophytes developed from megaspores retained within the spore - producing organs ( megasporangia ) of the sporophyte, a condition known as endospory. seeds consist of an endosporic megasporangium surrounded by one or two sheathing layers ( integuments ). the young sporophyte develops within the seed, which on germination splits to release it. the earliest known seed plants date from the latest devonian famennian stage. following the evolution of the seed habit, seed plants diversified, giving rise to a number of now - extinct groups, including seed ferns, as well as the modern gymnosperms and angiosperms. gymnosperms produce " naked seeds " not fully enclosed in an ovary ; modern representatives include conifers, cycads, ginkgo, and gnetales. angiosperms produce seeds enclosed in a structure such as a carpel or an ovary. ongoing research on the molecular phylogenetics of living plants appears to show that the angiosperms are a sister clade to the gymnosperms. = = plant physiology = = plant physiology encompasses all the internal chemical and physical activities of plants associated with life. chemicals obtained from the air, soil and water form
required. for example, certain cells respond to changes in oxygen tension as part of their normal development, such as chondrocytes, which must adapt to low oxygen conditions or hypoxia during skeletal development. others, such as endothelial cells, respond to shear stress from fluid flow, which is encountered in blood vessels. mechanical stimuli, such as pressure pulses seem to be beneficial to all kind of cardiovascular tissue such as heart valves, blood vessels or pericardium. = = = bioreactors = = = in tissue engineering, a bioreactor is a device that attempts to simulate a physiological environment in order to promote cell or tissue growth in vitro. a physiological environment can consist of many different parameters such as temperature, pressure, oxygen or carbon dioxide concentration, or osmolality of fluid environment, and it can extend to all kinds of biological, chemical or mechanical stimuli. therefore, there are systems that may include the application of forces such as electromagnetic forces, mechanical pressures, or fluid pressures to the tissue. these systems can be two - or three - dimensional setups. bioreactors can be used in both academic and industry applications. general - use and application - specific bioreactors are also commercially available, which may provide static chemical stimulation or a combination of chemical and mechanical stimulation. cell proliferation and differentiation are largely influenced by mechanical and biochemical cues in the surrounding extracellular matrix environment. bioreactors are typically developed to replicate the specific physiological environment of the tissue being grown ( e. g., flex and fluid shearing for heart tissue growth ). this can allow specialized cell lines to thrive in cultures replicating their native environments, but it also makes bioreactors attractive tools for culturing stem cells. a successful stem - cell - based bioreactor is effective at expanding stem cells with uniform properties and / or promoting controlled, reproducible differentiation into selected mature cell types. there are a variety of bioreactors designed for 3d cell cultures. there are small plastic cylindrical chambers, as well as glass chambers, with regulated internal humidity and moisture specifically engineered for the purpose of growing cells in three dimensions. the bioreactor uses bioactive synthetic materials such as polyethylene terephthalate membranes to surround the spheroid cells in an environment that maintains high levels of nutrients. they are easy to open and close, so that cell spheroids can be removed for testing, yet the chamber is able to maintain 100 % humidity throughout. this humidity is important to achieve maximum cell growth and function. the
the 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
Question: What were the first animals to have true lungs and limbs for life on land?
A) reptiles
B) birds
C) amphibians
D) mammals
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C) amphibians
|
Context:
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
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,
. these biochemical strategies are unique to land plants. = = = medicine and materials = = = phytochemistry is a branch of plant biochemistry primarily concerned with the chemical substances produced by plants during secondary metabolism. some of these compounds are toxins such as the alkaloid coniine from hemlock. others, such as the essential oils peppermint oil and lemon oil are useful for their aroma, as flavourings and spices ( e. g., capsaicin ), and in medicine as pharmaceuticals as in opium from opium poppies. many medicinal and recreational drugs, such as tetrahydrocannabinol ( active ingredient in cannabis ), caffeine, morphine and nicotine come directly from plants. others are simple derivatives of botanical natural products. for example, the pain killer aspirin is the acetyl ester of salicylic acid, originally isolated from the bark of willow trees, and a wide range of opiate painkillers like heroin are obtained by chemical modification of morphine obtained from the opium poppy. popular stimulants come from plants, such as caffeine from coffee, tea and chocolate, and nicotine from tobacco. most alcoholic beverages come from fermentation of carbohydrate - rich plant products such as barley ( beer ), rice ( sake ) and grapes ( wine ). native americans have used various plants as ways of treating illness or disease for thousands of years. this knowledge native americans have on plants has been recorded by enthnobotanists and then in turn has been used by pharmaceutical companies as a way of drug discovery. plants can synthesise coloured dyes and pigments such as the anthocyanins responsible for the red colour of red wine, yellow weld and blue woad used together to produce lincoln green, indoxyl, source of the blue dye indigo traditionally used to dye denim and the artist ' s pigments gamboge and rose madder. sugar, starch, cotton, linen, hemp, some types of rope, wood and particle boards, papyrus and paper, vegetable oils, wax, and natural rubber are examples of commercially important materials made from plant tissues or their secondary products. charcoal, a pure form of carbon made by pyrolysis of wood, has a long history as a metal - smelting fuel, as a filter material and adsorbent and as an artist ' s material and is one of the three ingredients of gunpowder. cellulose, the world
##l ( active ingredient in cannabis ), caffeine, morphine and nicotine come directly from plants. others are simple derivatives of botanical natural products. for example, the pain killer aspirin is the acetyl ester of salicylic acid, originally isolated from the bark of willow trees, and a wide range of opiate painkillers like heroin are obtained by chemical modification of morphine obtained from the opium poppy. popular stimulants come from plants, such as caffeine from coffee, tea and chocolate, and nicotine from tobacco. most alcoholic beverages come from fermentation of carbohydrate - rich plant products such as barley ( beer ), rice ( sake ) and grapes ( wine ). native americans have used various plants as ways of treating illness or disease for thousands of years. this knowledge native americans have on plants has been recorded by enthnobotanists and then in turn has been used by pharmaceutical companies as a way of drug discovery. plants can synthesise coloured dyes and pigments such as the anthocyanins responsible for the red colour of red wine, yellow weld and blue woad used together to produce lincoln green, indoxyl, source of the blue dye indigo traditionally used to dye denim and the artist ' s pigments gamboge and rose madder. sugar, starch, cotton, linen, hemp, some types of rope, wood and particle boards, papyrus and paper, vegetable oils, wax, and natural rubber are examples of commercially important materials made from plant tissues or their secondary products. charcoal, a pure form of carbon made by pyrolysis of wood, has a long history as a metal - smelting fuel, as a filter material and adsorbent and as an artist ' s material and is one of the three ingredients of gunpowder. cellulose, the world ' s most abundant organic polymer, can be converted into energy, fuels, materials and chemical feedstock. products made from cellulose include rayon and cellophane, wallpaper paste, biobutanol and gun cotton. sugarcane, rapeseed and soy are some of the plants with a highly fermentable sugar or oil content that are used as sources of biofuels, important alternatives to fossil fuels, such as biodiesel. sweetgrass was used by native americans to ward off bugs like mosquitoes. these bug repelling properties of sweetgrass were later found by the american chemical society in the molecules phytol
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
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
many monocots like maize and the pineapple and some dicots like the asteraceae have since independently evolved pathways like crassulacean acid metabolism and the c4 carbon fixation pathway for photosynthesis which avoid the losses resulting from photorespiration in the more common c3 carbon fixation pathway. these biochemical strategies are unique to land plants. = = = medicine and materials = = = phytochemistry is a branch of plant biochemistry primarily concerned with the chemical substances produced by plants during secondary metabolism. some of these compounds are toxins such as the alkaloid coniine from hemlock. others, such as the essential oils peppermint oil and lemon oil are useful for their aroma, as flavourings and spices ( e. g., capsaicin ), and in medicine as pharmaceuticals as in opium from opium poppies. many medicinal and recreational drugs, such as tetrahydrocannabinol ( active ingredient in cannabis ), caffeine, morphine and nicotine come directly from plants. others are simple derivatives of botanical natural products. for example, the pain killer aspirin is the acetyl ester of salicylic acid, originally isolated from the bark of willow trees, and a wide range of opiate painkillers like heroin are obtained by chemical modification of morphine obtained from the opium poppy. popular stimulants come from plants, such as caffeine from coffee, tea and chocolate, and nicotine from tobacco. most alcoholic beverages come from fermentation of 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
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
the work is a study of the geometry of the molecules via molecular mechanics of the main alkaloids found in the seeds of argemone mexicana linn, a prickly poppy, which is considered one of the most important species of plants in traditional mexican and indian medicine system. the seeds have toxic properties as well as bactericide, hallucinogenic, fungicide, insecticide, in isoquinolines and sanguinarine alkaloids such as berberine. a computational study of the molecular geometry of the molecules through molecular mechanics of the main alkaloids compounds present in plant seeds is described in a computer simulation. the plant has active ingredients compounds : allocryptopine, berberine, chelerythrine, copsitine, dihydrosanguinarine, protopine and sanguinarine. the studied alkaloids form two groups having similar charge distribution among themselves, which have dipole moments of these two times higher than in the other group.
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
Question: What do they call 2,2,4-trimethylpentane in the gasoline industry?
A) xerophyte
B) spirogyra
C) isooctane
D) methane
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C) isooctane
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Context:
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 no adverse effect on pilot vision. = = = = ships = = = = ships have also adopted similar methods. though the earlier american arleigh burke - class destroyers incorporated some signature - reduction features. the norwegian skjold - class corvettes was the first coastal defence and the french la fayette - class frigates the
soft interactions are not easily disentangled from hard ones. in an operational definition of soft and hard processes one finds that at presently analyzed scales there is an interplay of soft and hard processes. as the scale increases, so does the amount of hard processes. so far, nothing is as soft nor as hard as we would like.
other electrons either in bonds or in lone pairs. thus, molecules exist as electrically neutral units, unlike ions. when this rule is broken, giving the " molecule " a charge, the result is sometimes named a molecular ion or a polyatomic ion. however, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature. = = = = substance and mixture = = = = a chemical substance is a kind of matter with a definite composition and set of properties. a collection of substances is called a mixture. examples of mixtures are air and alloys. = = = = mole and amount of substance = = = = the mole is a unit
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
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 no adverse effect on pilot vision. = = = = ships = = = = ships have also adopted similar methods. though the earlier american arleigh burke - class destroyers incorporated some signature - reduction features. the norwegian skjold - class corvettes was the first coastal defence and the french la fayette - class frigates the first ocean - going stealth ships to enter service. other examples are the dutch de zeven provincien - class frigates, the taiwanese tuo chiang - class corvettes, german sachsen - class frigates, the swedish visby - class corvette, the american san antonio - class amphibious transport docks, and most modern
. 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
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
such as rigid motions. dual to the notion of invariants are coinvariants, also known as orbits, which formalizes the notion of congruence : objects which can be taken to each other by a group action. for example, under the group of rigid motions of the plane, the perimeter of a triangle is an invariant, while the set of triangles congruent to a given triangle is a coinvariant. these are connected as follows : invariants are constant on coinvariants ( for example, congruent triangles have the same perimeter ), while two objects which agree in the value of one invariant may or may not be congruent ( for example, two triangles with the same perimeter need not be congruent ). in classification problems, one might seek to find a complete set of invariants, such that if two objects have the same values for this set of invariants, then they are congruent. for example, triangles such that all three sides are equal are congruent under rigid motions, via sss congruence, and thus the lengths of all three sides form a complete set of invariants for triangles. the three angle measures of a triangle are also invariant under rigid motions, but do not form a complete set as incongruent triangles can share the same angle measures. however, if one allows scaling in addition to rigid motions, then the aaa similarity criterion shows that this is a complete set of invariants. = = = independent of presentation = = = secondly, a function may be defined in terms of some presentation or decomposition of a mathematical object ; for instance, the euler characteristic of a cell complex is defined as the alternating sum of the number of cells in each dimension. one may forget the cell complex structure and look only at the underlying topological space ( the manifold ) β as different cell complexes give the same underlying manifold, one may ask if the function is independent of choice of presentation, in which case it is an intrinsically defined invariant. this is the case for the euler characteristic, and a general method for defining and computing invariants is to define them for a given presentation, and then show that they are independent of the choice of presentation. note that there is no notion of a group action in this sense. the most common examples are : the presentation of a manifold in terms of coordinate charts β invariants must be unchanged under change of coordinates. various manifold decompositions, as discussed for euler characteristic. invariants of a presentation of a group. = =
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
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
Question: What do we call any way that animals act, either alone or with other animals.
A) animal behavior
B) animal habits
C) typical behavior
D) animal communication
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A) animal behavior
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Context:
generation of direct current in zigzag carbon nanotubes due to harmonic mixing of two coherent electromagnetic waves is being considered. the electromagnetic waves have commensurate frequencies of omega and two omega. the rectification of the waves at high frequencies is quite smooth whiles at low frequencies there are some fluctuations. the nonohmicity observed in the i - vcharacteristics is attributed to the nonparabolicity of the electron energy band which is very strong in carbon nanotubes because of high stark component. it is observed that the current falls off faster at lower electric field than the case in superlattice. for omega tau equal to two? the external electric field strength emax for the observation of negative differential conductivity occurs around 1. 03x10e6 v / m which is quite weak. it is interesting to note that the peak of the curve shifts to the left with increasing value of omega tau?
wave, carrying an information signal, occupies a range of frequencies. the information in a radio signal is usually concentrated in narrow frequency bands called sidebands ( sb ) just above and below the carrier frequency. the width in hertz of the frequency range that the radio signal occupies, the highest frequency minus the lowest frequency, is called its bandwidth ( bw ). for any given signal - to - noise ratio, a given bandwidth can carry the same amount of information regardless of where in the radio frequency spectrum it is located ; bandwidth is a measure of information - carrying capacity. the bandwidth required by a radio transmission depends on the data rate of the information being sent, and the spectral efficiency of the modulation method used ; how much data it can transmit in each unit of bandwidth. different types of information signals carried by radio have different data rates. for example, a television signal has a greater data rate than an audio signal. the radio spectrum, the total range of radio frequencies that can be used for communication in a given area, is a limited resource. each radio transmission occupies a portion of the total bandwidth available. radio bandwidth is regarded as an economic good which has a monetary cost and is in increasing demand. in some parts of the radio spectrum, the right to use a frequency band or even a single radio channel is bought and sold for millions of dollars. so there is an incentive to employ technology to minimize the bandwidth used by radio services. a slow transition from analog to digital radio transmission technologies began in the late 1990s. part of the reason for this is that digital modulation can often transmit more information ( a greater data rate ) in a given bandwidth than analog modulation, by using data compression algorithms, which reduce redundancy in the data to be sent, and more efficient modulation. other reasons for the transition is that digital modulation has greater noise immunity than analog, digital signal processing chips have more power and flexibility than analog circuits, and a wide variety of types of information can be transmitted using the same digital modulation. because it is a fixed resource which is in demand by an increasing number of users, the radio spectrum has become increasingly congested in recent decades, and the need to use it more effectively is driving many additional radio innovations such as trunked radio systems, spread spectrum ( ultra - wideband ) transmission, frequency reuse, dynamic spectrum management, frequency pooling, and cognitive radio. = = = itu frequency bands = = = the itu arbitrarily divides the radio spectrum into 12 bands, each beginning at a wavelength which is a power
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,
the only group of three non - overlapping channels in north america. however, whether the overlap is significant depends on physical spacing. channels that are four apart interfere a negligible amount β much less than reusing channels ( which causes co - channel interference ) β if transmitters are at least a few metres apart. in europe and japan where channel 13 is available, using channels 1, 5, 9, and 13 for 802. 11g and 802. 11n is viable and recommended. however, multiple 2. 4 ghz 802. 11b and 802. 11g access - points default to the same channel on initial startup, contributing to congestion on certain channels. wi - fi pollution, or an excessive number of access points in the area, can prevent access and interfere with other devices ' use of other access points as well as with decreased signal - to - noise ratio ( snr ) between access points. these issues can become a problem in high - density areas, such as large apartment complexes or office buildings with multiple wi - fi access points. other devices use the 2. 4 ghz band : microwave ovens, ism band devices, security cameras, zigbee devices, bluetooth devices, video senders, cordless phones, baby monitors, and, in some countries, amateur radio, all of which can cause significant additional interference. it is also an issue when municipalities or other large entities ( such as universities ) seek to provide large area coverage. on some 5 ghz bands interference from radar systems can occur in some places. for base stations that support those bands they employ dynamic frequency selection which listens for radar, and if it is found, it will not permit a network on that band. these bands can be used by low power transmitters without a licence, and with few restrictions. however, while unintended interference is common, users that have been found to cause deliberate interference ( particularly for attempting to locally monopolize these bands for commercial purposes ) have been issued large fines. = = = throughput = = = various layer - 2 variants of ieee 802. 11 have different characteristics. across all flavours of 802. 11, maximum achievable throughputs are either given based on measurements under ideal conditions or in the layer - 2 data rates. this, however, does not apply to typical deployments in which data are transferred between two endpoints of which at least one is typically connected to a wired infrastructure, and the other is connected to an infrastructure via a wireless link. this means that typically data frames pass an 802
it is stronger, then demodulates it, extracting the original modulation signal from the modulated carrier wave. the modulation signal is converted by a transducer back to a human - usable form : an audio signal is converted to sound waves by a loudspeaker or earphones, a video signal is converted to images by a display, while a digital signal is applied to a computer or microprocessor, which interacts with human users. the radio waves from many transmitters pass through the air simultaneously without interfering with each other because each transmitter ' s radio waves oscillate at a different frequency, measured in hertz ( hz ), kilohertz ( khz ), megahertz ( mhz ) or gigahertz ( ghz ). the receiving antenna typically picks up the radio signals of many transmitters. the receiver uses tuned circuits to select the radio signal desired out of all the signals picked up by the antenna and reject the others. a tuned circuit acts like a resonator, similar to a tuning fork. it has a natural resonant frequency at which it oscillates. the resonant frequency of the receiver ' s tuned circuit is adjusted by the user to the frequency of the desired radio station ; this is called tuning. the oscillating radio signal from the desired station causes the tuned circuit to oscillate in sympathy, and it passes the signal on to the rest of the receiver. radio signals at other frequencies are blocked by the tuned circuit and not passed on. = = = bandwidth = = = a modulated radio wave, carrying an information signal, occupies a range of frequencies. the information in a radio signal is usually concentrated in narrow frequency bands called sidebands ( sb ) just above and below the carrier frequency. the width in hertz of the frequency range that the radio signal occupies, the highest frequency minus the lowest frequency, is called its bandwidth ( bw ). for any given signal - to - noise ratio, a given bandwidth can carry the same amount of information regardless of where in the radio frequency spectrum it is located ; bandwidth is a measure of information - carrying capacity. the bandwidth required by a radio transmission depends on the data rate of the information being sent, and the spectral efficiency of the modulation method used ; how much data it can transmit in each unit of bandwidth. different types of information signals carried by radio have different data rates. for example, a television signal has a greater data rate than an audio signal. the radio spectrum, the total range of
, and this often works with little to no disruption. to minimize collisions with wi - fi and non - wi - fi devices, wi - fi employs carrier - sense multiple access with collision avoidance ( csma / ca ), where transmitters listen before transmitting and delay transmission of packets if they detect that other devices are active on the channel, or if noise is detected from adjacent channels or non - wi - fi sources. nevertheless, wi - fi networks are still susceptible to the hidden node and exposed node problem. a standard speed wi - fi signal occupies five channels in the 2. 4 ghz band. interference can be caused by overlapping channels. any two channel numbers that differ by five or more, such as 2 and 7, do not overlap ( no adjacent - channel interference ). the oft - repeated adage that channels 1, 6, and 11 are the only non - overlapping channels is, therefore, not accurate. channels 1, 6, and 11 are the only group of three non - overlapping channels in north america. however, whether the overlap is significant depends on physical spacing. channels that are four apart interfere a negligible amount β much less than reusing channels ( which causes co - channel interference ) β if transmitters are at least a few metres apart. in europe and japan where channel 13 is available, using channels 1, 5, 9, and 13 for 802. 11g and 802. 11n is viable and recommended. however, multiple 2. 4 ghz 802. 11b and 802. 11g access - points default to the same channel on initial startup, contributing to congestion on certain channels. wi - fi pollution, or an excessive number of access points in the area, can prevent access and interfere with other devices ' use of other access points as well as with decreased signal - to - noise ratio ( snr ) between access points. these issues can become a problem in high - density areas, such as large apartment complexes or office buildings with multiple wi - fi access points. other devices use the 2. 4 ghz band : microwave ovens, ism band devices, security cameras, zigbee devices, bluetooth devices, video senders, cordless phones, baby monitors, and, in some countries, amateur radio, all of which can cause significant additional interference. it is also an issue when municipalities or other large entities ( such as universities ) seek to provide large area coverage. on some 5 ghz bands interference from radar systems can occur in some places. for base stations that support those bands they employ dynamic frequency selection
the channel, or if noise is detected from adjacent channels or non - wi - fi sources. nevertheless, wi - fi networks are still susceptible to the hidden node and exposed node problem. a standard speed wi - fi signal occupies five channels in the 2. 4 ghz band. interference can be caused by overlapping channels. any two channel numbers that differ by five or more, such as 2 and 7, do not overlap ( no adjacent - channel interference ). the oft - repeated adage that channels 1, 6, and 11 are the only non - overlapping channels is, therefore, not accurate. channels 1, 6, and 11 are the only group of three non - overlapping channels in north america. however, whether the overlap is significant depends on physical spacing. channels that are four apart interfere a negligible amount β much less than reusing channels ( which causes co - channel interference ) β if transmitters are at least a few metres apart. in europe and japan where channel 13 is available, using channels 1, 5, 9, and 13 for 802. 11g and 802. 11n is viable and recommended. however, multiple 2. 4 ghz 802. 11b and 802. 11g access - points default to the same channel on initial startup, contributing to congestion on certain channels. wi - fi pollution, or an excessive number of access points in the area, can prevent access and interfere with other devices ' use of other access points as well as with decreased signal - to - noise ratio ( snr ) between access points. these issues can become a problem in high - density areas, such as large apartment complexes or office buildings with multiple wi - fi access points. other devices use the 2. 4 ghz band : microwave ovens, ism band devices, security cameras, zigbee devices, bluetooth devices, video senders, cordless phones, baby monitors, and, in some countries, amateur radio, all of which can cause significant additional interference. it is also an issue when municipalities or other large entities ( such as universities ) seek to provide large area coverage. on some 5 ghz bands interference from radar systems can occur in some places. for base stations that support those bands they employ dynamic frequency selection which listens for radar, and if it is found, it will not permit a network on that band. these bands can be used by low power transmitters without a licence, and with few restrictions. however, while unintended interference is common, users that have been found to cause deliberate interference ( particularly for attempting to
congestion on certain channels. wi - fi pollution, or an excessive number of access points in the area, can prevent access and interfere with other devices ' use of other access points as well as with decreased signal - to - noise ratio ( snr ) between access points. these issues can become a problem in high - density areas, such as large apartment complexes or office buildings with multiple wi - fi access points. other devices use the 2. 4 ghz band : microwave ovens, ism band devices, security cameras, zigbee devices, bluetooth devices, video senders, cordless phones, baby monitors, and, in some countries, amateur radio, all of which can cause significant additional interference. it is also an issue when municipalities or other large entities ( such as universities ) seek to provide large area coverage. on some 5 ghz bands interference from radar systems can occur in some places. for base stations that support those bands they employ dynamic frequency selection which listens for radar, and if it is found, it will not permit a network on that band. these bands can be used by low power transmitters without a licence, and with few restrictions. however, while unintended interference is common, users that have been found to cause deliberate interference ( particularly for attempting to locally monopolize these bands for commercial purposes ) have been issued large fines. = = = throughput = = = various layer - 2 variants of ieee 802. 11 have different characteristics. across all flavours of 802. 11, maximum achievable throughputs are either given based on measurements under ideal conditions or in the layer - 2 data rates. this, however, does not apply to typical deployments in which data are transferred between two endpoints of which at least one is typically connected to a wired infrastructure, and the other is connected to an infrastructure via a wireless link. this means that typically data frames pass an 802. 11 ( wlan ) medium and are being converted to 802. 3 ( ethernet ) or vice versa. due to the difference in the frame ( header ) lengths of these two media, the packet size of an application determines the speed of the data transfer. this means that an application that uses small packets ( e. g. voip ) creates a data flow with high overhead traffic ( low goodput ). other factors that contribute to the overall application data rate are the speed with which the application transmits the packets ( i. e. the data rate ) and the energy with which the wireless signal is received. the latter is determined
an extended josephson junction consists of two superconducting electrodes that are separated by an insulator and it is therefore also a microwave cavity. the superconducting phase difference across the junction determines the supercurrent as well as its spatial distribution. both, an external magnetic field and a resonant cavity intrafield produce a spatial modification of the superconducting phase along the junction. the interplay between these two effects leads to interference in the critical current of the junction and allows us to continuously tune the coupling strength between the first cavity mode and the josephson phase from 1 to - 0. 5. this enables static and dynamic control over the junction in the ultra - strong coupling regime.
standards allow for neighbouring channels to be bonded together to form a wider channel for higher throughput. countries apply their own regulations to the allowable channels, allowed users and maximum power levels within these frequency ranges. 802. 11b / g / n can use the 2. 4 ghz band, operating in the united states under fcc part 15 rules and regulations. in this frequency band, equipment may occasionally suffer interference from microwave ovens, cordless telephones, usb 3. 0 hubs, bluetooth and other devices. spectrum assignments and operational limitations are not consistent worldwide : australia and europe allow for an additional two channels ( 12, 13 ) beyond the 11 permitted in the united states for the 2. 4 ghz band, while japan has three more ( 12 β 14 ). 802. 11a / h / j / n / ac / ax can use the 5 ghz u - nii band, which, for much of the world, offers at least 23 non - overlapping 20 mhz channels. this is in contrast to the 2. 4 ghz frequency band where the channels are only 5 mhz wide. in general, lower frequencies have longer range but have less capacity. the 5 ghz bands are absorbed to a greater degree by common building materials than the 2. 4 ghz bands and usually give a shorter range. as 802. 11 specifications evolved to support higher throughput, the protocols have become much more efficient in their bandwidth use. additionally, they have gained the ability to aggregate channels together to gain still more throughput where the bandwidth for additional channels is available. 802. 11n allows for double radio spectrum bandwidth ( 40 mhz ) per channel compared to 802. 11a or 802. 11g ( 20 mhz ). 802. 11n can be set to limit itself to 20 mhz bandwidth to prevent interference in dense communities. in the 5 ghz band, 20 mhz, 40 mhz, 80 mhz, and 160 mhz channels are permitted with some restrictions, giving much faster connections. = = = communication stack = = = wi - fi is part of the ieee 802 protocol family. the data is organized into 802. 11 frames that are very similar to ethernet frames at the data link layer, but with extra address fields. mac addresses are used as network addresses for routing over the lan. wi - fi ' s mac and physical layer ( phy ) specifications are defined by ieee 802. 11 for modulating and receiving one or more carrier waves to transmit the data in the infrared, and 2. 4, 3. 6, 5, 6, or 60 ghz frequency bands
Question: When waves of two different frequencies interfere, what phenomenon occurs?
A) making
B) opening
C) beating
D) soaking
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C) beating
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Context:
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 accumulation of favorable traits over successive generations, thereby increasing the match between the organisms and their environment. = = = speciation = = = a species is a group of organisms that mate with one another and speciation is the process by which one lineage splits into two lineages as a result of having evolved independently from each other
of a point on the object, including whole - body translations and rotations ( rigid transformations ). deformation are changes in the relative position between internals points on the object, excluding rigid transformations, causing the body to change shape or size. strain is the relative internal deformation, the dimensionless change in shape of an infinitesimal cube of material relative to a reference configuration. mechanical strains are caused by mechanical stress, see stress - strain curve. the relationship between stress and strain is generally linear and reversible up until the yield point and the deformation is elastic. elasticity in materials occurs when applied stress does not surpass the energy required to break molecular bonds, allowing the material to deform reversibly and return to its original shape once the stress is removed. the linear relationship for a material is known as young ' s modulus. above the yield point, some degree of permanent distortion remains after unloading and is termed plastic deformation. the determination of the stress and strain throughout a solid object is given by the field of strength of materials and for a structure by structural analysis. in the above figure, it can be seen that the compressive loading ( indicated by the arrow ) has caused deformation in the cylinder so that the original shape ( dashed lines ) has changed ( deformed ) into one with bulging sides. the sides bulge because the material, although strong enough to not crack or otherwise fail, is not strong enough to support the load without change. as a result, the material is forced out laterally. internal forces ( in this case at right angles to the deformation ) resist the applied load. = = types of deformation = = depending on the type of material, size and geometry of the object, and the forces applied, various types of deformation may result. the image to the right shows the engineering stress vs. strain diagram for a typical ductile material such as steel. different deformation modes may occur under different conditions, as can be depicted using a deformation mechanism map. permanent deformation is irreversible ; the deformation stays even after removal of the applied forces, while the temporary deformation is recoverable as it disappears after the removal of applied forces. temporary deformation is also called elastic deformation, while the permanent deformation is called plastic deformation. = = = elastic deformation = = = the study of temporary or elastic deformation in the case of engineering strain is applied to materials used in mechanical and structural engineering, such as concrete and steel, which are subjected to very small deformations. engineering strain is modeled by infinitesimal strain theory, also called
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
( 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
of the desired gene has been altered to make it non - functional. embryonic stem cells incorporate the altered gene, which replaces the already present functional copy. these stem cells are injected into blastocysts, which are implanted into surrogate mothers. this allows the experimenter to analyse the defects caused by this mutation and thereby determine the role of particular genes. it is used especially frequently in developmental biology. when this is done by creating a library of genes with point mutations at every position in the area of interest, or even every position in the whole gene, this is called " scanning mutagenesis ". the simplest method, and the first to be used, is " alanine scanning ", where every position in turn is mutated to the unreactive amino acid alanine. gain of function experiments, the logical counterpart of knockouts. these are sometimes performed in conjunction with knockout experiments to more finely establish the function of the desired gene. the process is much the same as that in knockout engineering, except that the construct is designed to increase the function of the gene, usually by providing extra copies of the gene or inducing synthesis of the protein more frequently. gain of function is used to tell whether or not a protein is sufficient for a function, but does not always mean it is required, especially when dealing with genetic or functional redundancy. tracking experiments, which seek to gain information about the localisation and interaction of the desired protein. one way to do this is to replace the wild - type gene with a ' fusion ' gene, which is a juxtaposition of the wild - type gene with a reporting element such as green fluorescent protein ( gfp ) that will allow easy visualisation of the products of the genetic modification. while this is a useful technique, the manipulation can destroy the function of the gene, creating secondary effects and possibly calling into question the results of the experiment. more sophisticated techniques are now in development that can track protein products without mitigating their function, such as the addition of small sequences that will serve as binding motifs to monoclonal antibodies. expression studies aim to discover where and when specific proteins are produced. in these experiments, the dna sequence before the dna that codes for a protein, known as a gene ' s promoter, is reintroduced into an organism with the protein coding region replaced by a reporter gene such as gfp or an enzyme that catalyses the production of a dye. thus the time and place where a particular protein is produced can be observed. expression studies can be taken a
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
, 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
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,
in plants the dna is often inserted using agrobacterium - mediated transformation, taking advantage of the agrobacteriums t - dna sequence that allows natural insertion of genetic material into plant cells. other methods include biolistics, where particles of gold or tungsten are coated with dna and then shot into young plant cells, and electroporation, which involves using an electric shock to make the cell membrane permeable to plasmid dna. as only a single cell is transformed with genetic material, the organism must be regenerated from that single cell. in plants this is accomplished through the use of tissue culture. in animals it is necessary to ensure that the inserted dna is present in the embryonic stem cells. bacteria consist of a single cell and reproduce clonally so regeneration is not necessary. selectable markers are used to easily differentiate transformed from untransformed cells. these markers are usually present in the transgenic organism, although a number of strategies have been developed that can remove the selectable marker from the mature transgenic plant. further testing using pcr, southern hybridization, and dna sequencing is conducted to confirm that an organism contains the new gene. these tests can also confirm the chromosomal location and copy number of the inserted gene. the presence of the gene does not guarantee it will be expressed at appropriate levels in the target tissue so methods that look for and measure the gene products ( rna and protein ) are also used. these include northern hybridisation, quantitative rt - pcr, western blot, immunofluorescence, elisa and phenotypic analysis. the new genetic material can be inserted randomly within the host genome or targeted to a specific location. the technique of gene targeting uses homologous recombination to make desired changes to a specific endogenous gene. this tends to occur at a relatively low frequency in plants and animals and generally requires the use of selectable markers. the frequency of gene targeting can be greatly enhanced through genome editing. genome editing uses artificially engineered nucleases that create specific double - stranded breaks at desired locations in the genome, and use the cell ' s endogenous mechanisms to repair the induced break by the natural processes of homologous recombination and nonhomologous end - joining. there are four families of engineered nucleases : meganucleases, zinc finger nucleases, transcription activator - like effector nucleases ( talens ), and the cas9 - guide
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
Question: Further transformation occurs during organogenesis, the formation of what?
A) arteries
B) muscles
C) bones
D) organs
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D) organs
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Context:
an antibody is to be generated. usually this is done by a series of injections of the antigen in question, over the course of several weeks. these injections are typically followed by the use of in vivo electroporation, which significantly enhances the immune response. once splenocytes are isolated from the mammal ' s spleen, the b cells are fused with immortalised myeloma cells. the fusion of the b cells with myeloma cells can be done using electrofusion. electrofusion causes the b cells and myeloma cells to align and fuse with the application of an electric field. alternatively, the b - cells and myelomas can be made to fuse by chemical protocols, most often using polyethylene glycol. the myeloma cells are selected beforehand to ensure they are not secreting antibody themselves and that they lack the hypoxanthine - guanine phosphoribosyltransferase ( hgprt ) gene, making them sensitive ( or vulnerable ) to the hat medium ( see below ). fused cells are incubated in hat medium ( hypoxanthine - aminopterin - thymidine medium ) for roughly 10 to 14 days. aminopterin blocks the pathway that allows for nucleotide synthesis. hence, unfused myeloma cells die, as they cannot produce nucleotides by the de novo or salvage pathways because they lack hgprt. removal of the unfused myeloma cells is necessary because they have the potential to outgrow other cells, especially weakly established hybridomas. unfused b cells die as they have a short life span. in this way, only the b cell - myeloma hybrids survive, since the hgprt gene coming from the b cells is functional. these cells produce antibodies ( a property of b cells ) and are immortal ( a property of myeloma cells ). the incubated medium is then diluted into multi - well plates to such an extent that each well contains only one cell. since the antibodies in a well are produced by the same b cell, they will be directed towards the same epitope, and are thus monoclonal antibodies. the next stage is a rapid primary screening process, which identifies and selects only those hybridomas that produce antibodies of appropriate specificity. the first screening technique used is called elisa. the hybridoma culture supernatant, secondary enzyme labeled conjugate, and chromogenic substrate, are then inc
, 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. 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
weakly established hybridomas. unfused b cells die as they have a short life span. in this way, only the b cell - myeloma hybrids survive, since the hgprt gene coming from the b cells is functional. these cells produce antibodies ( a property of b cells ) and are immortal ( a property of myeloma cells ). the incubated medium is then diluted into multi - well plates to such an extent that each well contains only one cell. since the antibodies in a well are produced by the same b cell, they will be directed towards the same epitope, and are thus monoclonal antibodies. the next stage is a rapid primary screening process, which identifies and selects only those hybridomas that produce antibodies of appropriate specificity. the first screening technique used is called elisa. the hybridoma culture supernatant, secondary enzyme labeled conjugate, and chromogenic substrate, are then incubated, and the formation of a colored product indicates a positive hybridoma. alternatively, immunocytochemical, western blot, and immunoprecipitation - mass spectrometry. unlike western blot assays, immunoprecipitation - mass spectrometry facilitates screening and ranking of clones which bind to the native ( non - denaturated ) forms of antigen proteins. flow cytometry screening has been used for primary screening of a large number ( ~ 1000 ) of hybridoma clones recognizing the native form of the antigen on the cell surface. in the flow cytometry - based screening, a mixture of antigen - negative cells and antigen - positive cells is used as the antigen to be tested for each hybridoma supernatant sample. the b cell that produces the desired antibodies can be cloned to produce many identical daughter clones. supplemental media containing interleukin - 6 ( such as briclone ) are essential for this step. once a hybridoma colony is established, it will continually grow in culture medium like rpmi - 1640 ( with antibiotics and fetal bovine serum ) and produce antibodies. multiwell plates are used initially to grow the hybridomas, and after selection, are changed to larger tissue culture flasks. this maintains the well - being of the hybridomas and provides enough cells for cryopreservation and supernatant for subsequent investigations. the culture supernatant can yield 1 to 60 ΞΌg / ml of monoclonal antibody, which is maintained at -
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,
a property of myeloma cells ). the incubated medium is then diluted into multi - well plates to such an extent that each well contains only one cell. since the antibodies in a well are produced by the same b cell, they will be directed towards the same epitope, and are thus monoclonal antibodies. the next stage is a rapid primary screening process, which identifies and selects only those hybridomas that produce antibodies of appropriate specificity. the first screening technique used is called elisa. the hybridoma culture supernatant, secondary enzyme labeled conjugate, and chromogenic substrate, are then incubated, and the formation of a colored product indicates a positive hybridoma. alternatively, immunocytochemical, western blot, and immunoprecipitation - mass spectrometry. unlike western blot assays, immunoprecipitation - mass spectrometry facilitates screening and ranking of clones which bind to the native ( non - denaturated ) forms of antigen proteins. flow cytometry screening has been used for primary screening of a large number ( ~ 1000 ) of hybridoma clones recognizing the native form of the antigen on the cell surface. in the flow cytometry - based screening, a mixture of antigen - negative cells and antigen - positive cells is used as the antigen to be tested for each hybridoma supernatant sample. the b cell that produces the desired antibodies can be cloned to produce many identical daughter clones. supplemental media containing interleukin - 6 ( such as briclone ) are essential for this step. once a hybridoma colony is established, it will continually grow in culture medium like rpmi - 1640 ( with antibiotics and fetal bovine serum ) and produce antibodies. multiwell plates are used initially to grow the hybridomas, and after selection, are changed to larger tissue culture flasks. this maintains the well - being of the hybridomas and provides enough cells for cryopreservation and supernatant for subsequent investigations. the culture supernatant can yield 1 to 60 ΞΌg / ml of monoclonal antibody, which is maintained at - 20 Β°c or lower until required. by using culture supernatant or a purified immunoglobulin preparation, further analysis of a potential monoclonal antibody producing hybridoma can be made in terms of reactivity, specificity, and cross - reactivity. = = applications = = the use of mono
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
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, 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
and myelomas can be made to fuse by chemical protocols, most often using polyethylene glycol. the myeloma cells are selected beforehand to ensure they are not secreting antibody themselves and that they lack the hypoxanthine - guanine phosphoribosyltransferase ( hgprt ) gene, making them sensitive ( or vulnerable ) to the hat medium ( see below ). fused cells are incubated in hat medium ( hypoxanthine - aminopterin - thymidine medium ) for roughly 10 to 14 days. aminopterin blocks the pathway that allows for nucleotide synthesis. hence, unfused myeloma cells die, as they cannot produce nucleotides by the de novo or salvage pathways because they lack hgprt. removal of the unfused myeloma cells is necessary because they have the potential to outgrow other cells, especially weakly established hybridomas. unfused b cells die as they have a short life span. in this way, only the b cell - myeloma hybrids survive, since the hgprt gene coming from the b cells is functional. these cells produce antibodies ( a property of b cells ) and are immortal ( a property of myeloma cells ). the incubated medium is then diluted into multi - well plates to such an extent that each well contains only one cell. since the antibodies in a well are produced by the same b cell, they will be directed towards the same epitope, and are thus monoclonal antibodies. the next stage is a rapid primary screening process, which identifies and selects only those hybridomas that produce antibodies of appropriate specificity. the first screening technique used is called elisa. the hybridoma culture supernatant, secondary enzyme labeled conjugate, and chromogenic substrate, are then incubated, and the formation of a colored product indicates a positive hybridoma. alternatively, immunocytochemical, western blot, and immunoprecipitation - mass spectrometry. unlike western blot assays, immunoprecipitation - mass spectrometry facilitates screening and ranking of clones which bind to the native ( non - denaturated ) forms of antigen proteins. flow cytometry screening has been used for primary screening of a large number ( ~ 1000 ) of hybridoma clones recognizing the native form of the antigen on the cell surface. in the flow
##clonal antibodies. the next stage is a rapid primary screening process, which identifies and selects only those hybridomas that produce antibodies of appropriate specificity. the first screening technique used is called elisa. the hybridoma culture supernatant, secondary enzyme labeled conjugate, and chromogenic substrate, are then incubated, and the formation of a colored product indicates a positive hybridoma. alternatively, immunocytochemical, western blot, and immunoprecipitation - mass spectrometry. unlike western blot assays, immunoprecipitation - mass spectrometry facilitates screening and ranking of clones which bind to the native ( non - denaturated ) forms of antigen proteins. flow cytometry screening has been used for primary screening of a large number ( ~ 1000 ) of hybridoma clones recognizing the native form of the antigen on the cell surface. in the flow cytometry - based screening, a mixture of antigen - negative cells and antigen - positive cells is used as the antigen to be tested for each hybridoma supernatant sample. the b cell that produces the desired antibodies can be cloned to produce many identical daughter clones. supplemental media containing interleukin - 6 ( such as briclone ) are essential for this step. once a hybridoma colony is established, it will continually grow in culture medium like rpmi - 1640 ( with antibiotics and fetal bovine serum ) and produce antibodies. multiwell plates are used initially to grow the hybridomas, and after selection, are changed to larger tissue culture flasks. this maintains the well - being of the hybridomas and provides enough cells for cryopreservation and supernatant for subsequent investigations. the culture supernatant can yield 1 to 60 ΞΌg / ml of monoclonal antibody, which is maintained at - 20 Β°c or lower until required. by using culture supernatant or a purified immunoglobulin preparation, further analysis of a potential monoclonal antibody producing hybridoma can be made in terms of reactivity, specificity, and cross - reactivity. = = applications = = the use of monoclonal antibodies is numerous and includes the prevention, diagnosis, and treatment of disease. for example, monoclonal antibodies can distinguish subsets of b cells and t cells, which is helpful in identifying different types of leukaemias. in addition, specific monoclonal antibodies have been used to define cell surface markers
water - repelling ) substances. proteins are the most diverse of the macromolecules. they include enzymes, transport proteins, large signaling molecules, antibodies, and structural proteins. the basic unit ( or monomer ) of a protein is an amino acid. twenty amino acids are used in proteins. nucleic acids are polymers of nucleotides. their function is to store, transmit, and express hereditary information. = = cells = = cell theory states that cells are the fundamental units of life, that all living things are composed of one or more cells, and that all cells arise from preexisting cells through cell division. most cells are very small, with diameters ranging from 1 to 100 micrometers and are therefore only visible under a light or electron microscope. there are generally two types of cells : eukaryotic cells, which contain a nucleus, and prokaryotic cells, which do not. prokaryotes are single - celled organisms such as bacteria, whereas eukaryotes can be single - celled or multicellular. in multicellular organisms, every cell in the organism ' s body is derived ultimately from a single cell in a fertilized egg. = = = cell structure = = = every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions. cell membranes also contain membrane proteins, including integral membrane proteins that go across the membrane serving as membrane transporters, and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes shaping the cell. cell membranes are involved in various cellular processes such as cell adhesion, storing electrical energy, and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall, glycocalyx, and cytoskeleton. within the cytoplasm of a cell, there are many biomolecules such as proteins and nucleic acids. in addition to biomolecules, eukaryotic cells have specialized structures called organelles that have their own lipid bilayers or are spatially units. these organelles include the cell nucleus, which contains most of
Question: Each antibody can bind with just one specific type of what, resulting in a signal for a phagocyte to destroy them?
A) pathogen
B) adhesion
C) immunogen
D) antigen
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D) antigen
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Context:
light and cold extrasolar planets such as ogle 2005 - blg - 390lb, a 5. 5 earth - mass planet detected via microlensing, could be frequent in the galaxy according to some preliminary results from microlensing experiments. these planets can be frozen rocky - or ocean - planets, situated beyond the snow line and, therefore, beyond the habitable zone of their system. they can nonetheless host a layer of liquid water, heated by radiogenic energy, underneath an ice shell surface for billions of years, before freezing completely. these results suggest that oceans under ice, like those suspected to be present on icy moons in the solar system, could be a common feature of cold low - mass extrasolar planets.
three major planets, venus, earth, and mercury formed out of the solar nebula. a fourth planetesimal, theia, also formed near earth where it collided in a giant impact, rebounding as the planet mars. during this impact earth lost $ { \ approx } 4 $ \ % of its crust and mantle that is now is found on mars and the moon. at the antipode of the giant impact, $ \ approx $ 60 \ % of earth ' s crust, atmosphere, and a large amount of mantle were ejected into space forming the moon. the lost crust never reformed and became the earth ' s ocean basins. the theia impact site corresponds to indian ocean gravitational anomaly on earth and the hellas basin on mars. the dynamics of the giant impact are consistent with the rotational rates and axial tilts of both earth and mars. the giant impact removed sufficient co $ _ 2 $ from earth ' s atmosphere to avoid a runaway greenhouse effect, initiated plate tectonics, and gave life time to form near geothermal vents at the continental margins. mercury formed near venus where on a close approach it was slingshot into the sun ' s convective zone losing 94 \ % of its mass, much of which remains there today. black carbon, from co $ _ 2 $ decomposed by the intense heat, is still found on the surface of mercury. arriving at 616 km / s, mercury dramatically altered the sun ' s rotational energy, explaining both its anomalously slow rotation rate and axial tilt. these results are quantitatively supported by mass balances, the current locations of the terrestrial planets, and the orientations of their major orbital axes.
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.
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.
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.
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 }
or solid as is the case with water ( h2o ) ; a liquid at room temperature because its molecules are bound by hydrogen bonds. whereas hydrogen sulfide ( h2s ) is a gas at room temperature and standard pressure, as its molecules are bound by weaker dipole β dipole interactions. the transfer of energy from one chemical substance to another depends on the size of energy quanta emitted from one substance. however, heat energy is often transferred more easily from almost any substance to another because the phonons responsible for vibrational and rotational energy levels in a substance have much less energy than photons invoked for the electronic energy transfer. thus, because vibrational and rotational energy levels are more closely spaced than electronic energy levels, heat is more easily transferred between substances relative to light or other forms of electronic energy. for example, ultraviolet electromagnetic radiation is not transferred with as much efficacy from one substance to another as thermal or electrical energy. the existence of characteristic energy levels for different chemical substances is useful for their identification by the analysis of spectral lines. different kinds of spectra are often used in chemical spectroscopy, e. g. ir, microwave, nmr, esr, etc. spectroscopy is also used to identify the composition of remote objects β like stars and distant galaxies β by analyzing their radiation spectra. the term chemical energy is often used to indicate the potential of a chemical substance to undergo a transformation through a chemical reaction or to transform other chemical substances. = = = reaction = = = when a chemical substance is transformed as a result of its interaction with another substance or with energy, a chemical reaction is said to have occurred. a chemical reaction is therefore a concept related to the " reaction " of a substance when it comes in close contact with another, whether as a mixture or a solution ; exposure to some form of energy, or both. it results in some energy exchange between the constituents of the reaction as well as with the system environment, which may be designed vessels β often laboratory glassware. chemical reactions can result in the formation or dissociation of molecules, that is, molecules breaking apart to form two or more molecules or rearrangement of atoms within or across molecules. chemical reactions usually involve the making or breaking of chemical bonds. oxidation, reduction, dissociation, acid β base neutralization and molecular rearrangement are some examples of common chemical reactions. a chemical reaction can be symbolically depicted through a chemical equation. while in a non - nuclear chemical reaction the number and kind of atoms on both sides of the equation are equal, for
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
planets less massive than about 10 mearth are expected to have no massive h - he atmosphere and a cometary composition ( 50 % rocks, 50 % water, by mass ) provided they formed beyond the snowline of protoplanetary disks. due to inward migration, such planets could be found at any distance between their formation site and the star. if migration stops within the habitable zone, this will produce a new kind of planets, called ocean - planets. ocean - planets typically consist in a silicate core, surrounded by a thick ice mantle, itself covered by a 100 km deep ocean. the existence of ocean - planets raises important astrobiological questions : can life originate on such body, in the absence of continent and ocean - silicate interfaces? what would be the nature of the atmosphere and the geochemical cycles? in this work, we address the fate of hot ocean - planets produced when migration ends at a closer distance. in this case the liquid / gas interface can disappear, and the hot h2o envelope is made of a supercritical fluid. although we do not expect these bodies to harbor life, their detection and identification as water - rich planets would give us insight as to the abundance of hot and, by extrapolation, cool ocean - planets.
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
Question: What kind of surface temperature is found on venus?
A) a little hot
B) cool
C) cold
D) extremely high
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D) extremely high
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Context:
the world is changing at an ever - increasing pace. and it has changed in a much more fundamental way than one would think, primarily because it has become more connected and interdependent than in our entire history. every new product, every new invention can be combined with those that existed before, thereby creating an explosion of complexity : structural complexity, dynamic complexity, functional complexity, and algorithmic complexity. how to respond to this challenge? and what are the costs?
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
this third part of the lecture series deals with the question : who will pay for your retirement? for western europe the answer may be ` ` nobody ' ', but for algeria the demography looks more promising.
##hthalmology and dermatology, but are not considered surgical sub - specialties per se. surgical training in the u. s. requires a minimum of five years of residency after medical school. sub - specialties of surgery often require seven or more years. in addition, fellowships can last an additional one to three years. because post - residency fellowships can be competitive, many trainees devote two additional years to research. thus in some cases surgical training will not finish until more than a decade after medical school. furthermore, surgical training can be very difficult and time - consuming. surgical subspecialties include those a physician may specialize in after undergoing general surgery residency training as well as several surgical fields with separate residency training. surgical subspecialties that one may pursue following general surgery residency training : bariatric surgery cardiovascular surgery β may also be pursued through a separate cardiovascular surgery residency track colorectal surgery endocrine surgery general surgery hand surgery hepatico - pancreatico - biliary surgery minimally invasive surgery pediatric surgery plastic surgery β may also be pursued through a separate plastic surgery residency track surgical critical care surgical oncology transplant surgery trauma surgery vascular surgery β may also be pursued through a separate vascular surgery residency track other surgical specialties within medicine with their own individual residency training : dermatology neurosurgery ophthalmology oral and maxillofacial surgery orthopedic surgery otorhinolaryngology podiatric surgery β do not undergo medical school training, but rather separate training in podiatry school urology = = = = internal medicine specialty = = = = internal medicine is the medical specialty dealing with the prevention, diagnosis, and treatment of adult diseases. according to some sources, an emphasis on internal structures is implied. in north america, specialists in internal medicine are commonly called " internists ". elsewhere, especially in commonwealth nations, such specialists are often called physicians. these terms, internist or physician ( in the narrow sense, common outside north america ), generally exclude practitioners of gynecology and obstetrics, pathology, psychiatry, and especially surgery and its subspecialities. because their patients are often seriously ill or require complex investigations, internists do much of their work in hospitals. formerly, many internists were not subspecialized ; such general physicians would see any complex nonsurgical problem ; this style of practice has become much less common. in modern urban practice, most internists are subspecialists : that is, they generally limit their medical practice
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.
with a synthetic, but naturally occurring, bone mineral. ultimately these ceramic materials may be used as bone replacements or with the incorporation of protein collagens, synthetic bones. durable actinide - containing ceramic materials have many applications such as in nuclear fuels for burning excess pu and in chemically - inert sources of alpha irradiation for power supply of unmanned space vehicles or to produce electricity for microelectronic devices. both use and disposal of radioactive actinides require their immobilization in a durable host material. nuclear waste long - lived radionuclides such as actinides are immobilized using chemically - durable crystalline materials based on polycrystalline ceramics and large single crystals. alumina ceramics are widely utilized in the chemical industry due to their excellent chemical stability and high resistance to corrosion. it is used as acid - resistant pump impellers and pump bodies, ensuring long - lasting performance in transferring aggressive fluids. they are also used in acid - carrying pipe linings to prevent contamination and maintain fluid purity, which is crucial in industries like pharmaceuticals and food processing. valves made from alumina ceramics demonstrate exceptional durability and resistance to chemical attack, making them reliable for controlling the flow of corrosive liquids. = = glass - ceramics = = glass - ceramic materials share many properties with both glasses and ceramics. glass - ceramics have an amorphous phase and one or more crystalline phases and are produced by a so - called " controlled crystallization ", which is typically avoided in glass manufacturing. glass - ceramics often contain a crystalline phase which constitutes anywhere from 30 % [ m / m ] to 90 % [ m / m ] of its composition by volume, yielding an array of materials with interesting thermomechanical properties. in the processing of glass - ceramics, molten glass is cooled down gradually before reheating and annealing. in this heat 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
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
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
received within a limited distance of its transmitter. systems that broadcast from satellites can generally be received over an entire country or continent. older terrestrial radio and television are paid for by commercial advertising or governments. in subscription systems like satellite television and satellite radio the customer pays a monthly fee. in these systems, the radio signal is encrypted and can only be decrypted by the receiver, which is controlled by the company and can be deactivated if the customer does not pay. broadcasting uses several parts of the radio spectrum, depending on the type of signals transmitted and the desired target audience. longwave and medium wave signals can give reliable coverage of areas several hundred kilometers across, but have a more limited information - carrying capacity and so work best with audio signals ( speech and music ), and the sound quality can be degraded by radio noise from natural and artificial sources. the shortwave bands have a greater potential range but are more subject to interference by distant stations and varying atmospheric conditions that affect reception. in the very high frequency band, greater than 30 megahertz, the earth ' s atmosphere has less of an effect on the range of signals, and line - of - sight propagation becomes the principal mode. these higher frequencies permit the great bandwidth required for television broadcasting. since natural and artificial noise sources are less present at these frequencies, high - quality audio transmission is possible, using frequency modulation. = = = = audio : radio broadcasting = = = = radio broadcasting means transmission of audio ( sound ) to radio receivers belonging to a public audience. analog audio is the earliest form of radio broadcast. am broadcasting began around 1920. fm broadcasting was introduced in the late 1930s with improved fidelity. a broadcast radio receiver is called a radio. most radios can receive both am and fm. am ( amplitude modulation ) β in am, the amplitude ( strength ) of the radio carrier wave is varied by the audio signal. am broadcasting, the oldest broadcasting technology, is allowed in the am broadcast bands, between 148 and 283 khz in the low frequency ( lf ) band for longwave broadcasts and between 526 and 1706 khz in the medium frequency ( mf ) band for medium - wave broadcasts. because waves in these bands travel as ground waves following the terrain, am radio stations can be received beyond the horizon at hundreds of miles distance, but am has lower fidelity than fm. radiated power ( erp ) of am stations in the us is usually limited to a maximum of 10 kw, although a few ( clear - channel stations ) are allowed to transmit at 50
; 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
Question: What type of resource is limited in supply and cannot be replaced except over millions of years?
A) capital resources
B) natural resource
C) human resources
D) renewable energy
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B) natural resource
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Context:
ion or cation. when an atom gains an electron and thus has more electrons than protons, the atom is a negatively charged ion or anion. cations and anions can form a crystalline lattice of neutral salts, such as the na + and clβ ions forming sodium chloride, or nacl. examples of polyatomic ions that do not split up during acid β base reactions are hydroxide ( ohβ ) and phosphate ( po43β ). plasma is composed of gaseous matter that has been completely ionized, usually through high temperature. = = = acidity and basicity = = = a substance can often be classified as an acid or a base. there are several different theories which explain acid β base behavior. the simplest is arrhenius theory, which states that an acid is a substance that produces hydronium ions when it is dissolved in water, and a base is one that produces hydroxide ions when dissolved in water. according to brΓΈnsted β lowry acid β base theory, acids are substances that donate a positive hydrogen ion to another substance in a chemical reaction ; by extension, a base is the substance which receives that hydrogen ion. a third common theory is lewis acid β base theory, which is based on the formation of new chemical bonds. lewis theory explains that an acid is a substance which is capable of accepting a pair of electrons from another substance during the process of bond formation, while a base is a substance which can provide a pair of electrons to form a new bond. there are several other ways in which a substance may be classified as an acid or a base, as is evident in the history of this concept. acid strength is commonly measured by two methods. one measurement, based on the arrhenius definition of acidity, is ph, which is a measurement of the hydronium ion concentration in a solution, as expressed on a negative logarithmic scale. thus, solutions that have a low ph have a high hydronium ion concentration and can be said to be more acidic. the other measurement, based on the brΓΈnsted β lowry definition, is the acid dissociation constant ( ka ), which measures the relative ability of a substance to act as an acid under the brΓΈnsted β lowry definition of an acid. that is, substances with a higher ka are more likely to donate hydrogen ions in chemical reactions than those with lower ka values. = = = redox = = = redox ( reduction - oxidation ) reactions include all chemical reactions in which atoms have their
to explain molecular structure and composition. an ionic bond is formed when a metal loses one or more of its electrons, becoming a positively charged cation, and the electrons are then gained by the non - metal atom, becoming a negatively charged anion. the two oppositely charged ions attract one another, and the ionic bond is the electrostatic force of attraction between them. for example, sodium ( na ), a metal, loses one electron to become an na + cation while chlorine ( cl ), a non - metal, gains this electron to become clβ. the ions are held together due to electrostatic attraction, and that compound sodium chloride ( nacl ), or common table salt, is formed. in a covalent bond, one or more pairs of valence electrons are shared by two atoms : the resulting electrically neutral group of bonded atoms is termed a molecule. atoms will share valence electrons in such a way as to create a noble gas electron configuration ( eight electrons in their outermost shell ) for each atom. atoms that tend to combine in such a way that they each have eight electrons in their valence shell are said to follow the octet rule. however, some elements like hydrogen and lithium need only two electrons in their outermost shell to attain this stable configuration ; these atoms are said to follow the duet rule, and in this way they are reaching the electron configuration of the noble gas helium, which has two electrons in its outer shell. similarly, theories from classical physics can be used to predict many ionic structures. with more complicated compounds, such as metal complexes, valence bond theory is less applicable and alternative approaches, such as the molecular orbital theory, are generally used. = = = energy = = = in the context of chemistry, energy is an attribute of a substance as a consequence of its atomic, molecular or aggregate structure. since a chemical transformation is accompanied by a change in one or more of these kinds of structures, it is invariably accompanied by an increase or decrease of energy of the substances involved. some energy is transferred between the surroundings and the reactants of the reaction in the form of heat or light ; thus the products of a reaction may have more or less energy than the reactants. a reaction is said to be exergonic if the final state is lower on the energy scale than the initial state ; in the case of endergonic reactions the situation is the reverse. a reaction is said to be exothermic if the reaction releases heat to the surroundings ; in the case of
##als force. each of these kinds of bonds is ascribed to some potential. these potentials create the interactions which hold atoms together in molecules or crystals. in many simple compounds, valence bond theory, the valence shell electron pair repulsion model ( vsepr ), and the concept of oxidation number can be used to explain molecular structure and composition. an ionic bond is formed when a metal loses one or more of its electrons, becoming a positively charged cation, and the electrons are then gained by the non - metal atom, becoming a negatively charged anion. the two oppositely charged ions attract one another, and the ionic bond is the electrostatic force of attraction between them. for example, sodium ( na ), a metal, loses one electron to become an na + cation while chlorine ( cl ), a non - metal, gains this electron to become clβ. the ions are held together due to electrostatic attraction, and that compound sodium chloride ( nacl ), or common table salt, is formed. in a covalent bond, one or more pairs of valence electrons are shared by two atoms : the resulting electrically neutral group of bonded atoms is termed a molecule. atoms will share valence electrons in such a way as to create a noble gas electron configuration ( eight electrons in their outermost shell ) for each atom. atoms that tend to combine in such a way that they each have eight electrons in their valence shell are said to follow the octet rule. however, some elements like hydrogen and lithium need only two electrons in their outermost shell to attain this stable configuration ; these atoms are said to follow the duet rule, and in this way they are reaching the electron configuration of the noble gas helium, which has two electrons in its outer shell. similarly, theories from classical physics can be used to predict many ionic structures. with more complicated compounds, such as metal complexes, valence bond theory is less applicable and alternative approaches, such as the molecular orbital theory, are generally used. = = = energy = = = in the context of chemistry, energy is an attribute of a substance as a consequence of its atomic, molecular or aggregate structure. since a chemical transformation is accompanied by a change in one or more of these kinds of structures, it is invariably accompanied by an increase or decrease of energy of the substances involved. some energy is transferred between the surroundings and the reactants of the reaction in the form of heat or light ; thus the products of a reaction may have more or less energy than the reactants
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
. these biochemical strategies are unique to land plants. = = = medicine and materials = = = phytochemistry is a branch of plant biochemistry primarily concerned with the chemical substances produced by plants during secondary metabolism. some of these compounds are toxins such as the alkaloid coniine from hemlock. others, such as the essential oils peppermint oil and lemon oil are useful for their aroma, as flavourings and spices ( e. g., capsaicin ), and in medicine as pharmaceuticals as in opium from opium poppies. many medicinal and recreational drugs, such as tetrahydrocannabinol ( active ingredient in cannabis ), caffeine, morphine and nicotine come directly from plants. others are simple derivatives of botanical natural products. for example, the pain killer aspirin is the acetyl ester of salicylic acid, originally isolated from the bark of willow trees, and a wide range of opiate painkillers like heroin are obtained by chemical modification of morphine obtained from the opium poppy. popular stimulants come from plants, such as caffeine from coffee, tea and chocolate, and nicotine from tobacco. most alcoholic beverages come from fermentation of carbohydrate - rich plant products such as barley ( beer ), rice ( sake ) and grapes ( wine ). native americans have used various plants as ways of treating illness or disease for thousands of years. this knowledge native americans have on plants has been recorded by enthnobotanists and then in turn has been used by pharmaceutical companies as a way of drug discovery. plants can synthesise coloured dyes and pigments such as the anthocyanins responsible for the red colour of red wine, yellow weld and blue woad used together to produce lincoln green, indoxyl, source of the blue dye indigo traditionally used to dye denim and the artist ' s pigments gamboge and rose madder. sugar, starch, cotton, linen, hemp, some types of rope, wood and particle boards, papyrus and paper, vegetable oils, wax, and natural rubber are examples of commercially important materials made from plant tissues or their secondary products. charcoal, a pure form of carbon made by pyrolysis of wood, has a long history as a metal - smelting fuel, as a filter material and adsorbent and as an artist ' s material and is one of the three ingredients of gunpowder. cellulose, the world
##l ( active ingredient in cannabis ), caffeine, morphine and nicotine come directly from plants. others are simple derivatives of botanical natural products. for example, the pain killer aspirin is the acetyl ester of salicylic acid, originally isolated from the bark of willow trees, and a wide range of opiate painkillers like heroin are obtained by chemical modification of morphine obtained from the opium poppy. popular stimulants come from plants, such as caffeine from coffee, tea and chocolate, and nicotine from tobacco. most alcoholic beverages come from fermentation of carbohydrate - rich plant products such as barley ( beer ), rice ( sake ) and grapes ( wine ). native americans have used various plants as ways of treating illness or disease for thousands of years. this knowledge native americans have on plants has been recorded by enthnobotanists and then in turn has been used by pharmaceutical companies as a way of drug discovery. plants can synthesise coloured dyes and pigments such as the anthocyanins responsible for the red colour of red wine, yellow weld and blue woad used together to produce lincoln green, indoxyl, source of the blue dye indigo traditionally used to dye denim and the artist ' s pigments gamboge and rose madder. sugar, starch, cotton, linen, hemp, some types of rope, wood and particle boards, papyrus and paper, vegetable oils, wax, and natural rubber are examples of commercially important materials made from plant tissues or their secondary products. charcoal, a pure form of carbon made by pyrolysis of wood, has a long history as a metal - smelting fuel, as a filter material and adsorbent and as an artist ' s material and is one of the three ingredients of gunpowder. cellulose, the world ' s most abundant organic polymer, can be converted into energy, fuels, materials and chemical feedstock. products made from cellulose include rayon and cellophane, wallpaper paste, biobutanol and gun cotton. sugarcane, rapeseed and soy are some of the plants with a highly fermentable sugar or oil content that are used as sources of biofuels, important alternatives to fossil fuels, such as biodiesel. sweetgrass was used by native americans to ward off bugs like mosquitoes. these bug repelling properties of sweetgrass were later found by the american chemical society in the molecules phytol
index chemical substances. in this scheme each chemical substance is identifiable by a number known as its cas registry number. = = = = molecule = = = = a molecule is the smallest indivisible portion of a pure chemical substance that has its unique set of chemical properties, that is, its potential to undergo a certain set of chemical reactions with other substances. however, this definition only works well for substances that are composed of molecules, which is not true of many substances ( see below ). molecules are typically a set of atoms bound together by covalent bonds, such that the structure is electrically neutral and all valence electrons are paired with other electrons either in bonds or in lone pairs. thus, molecules exist as electrically neutral units, unlike ions. when this rule is broken, giving the " molecule " a charge, the result is sometimes named a molecular ion or a polyatomic ion. however, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry
technology developed, medicine became more reliant upon medications. throughout history and in europe right until the late 18th century, not only plant products were used as medicine, but also animal ( including human ) body parts and fluids. pharmacology developed in part from herbalism and some drugs are still derived from plants ( atropine, ephedrine, warfarin, aspirin, digoxin, vinca alkaloids, taxol, hyoscine, etc. ). vaccines were discovered by edward jenner and louis pasteur. the first antibiotic was arsphenamine ( salvarsan ) discovered by paul ehrlich in 1908 after he observed that bacteria took up toxic dyes that human cells did not. the first major class of antibiotics was the sulfa drugs, derived by german chemists originally from azo dyes. pharmacology has become increasingly sophisticated ; modern biotechnology allows drugs targeted towards specific physiological processes to be developed, sometimes designed for compatibility with the body to reduce side - effects. genomics and knowledge of human genetics and human evolution is having increasingly significant influence on medicine, as the causative genes of most monogenic genetic disorders have now been identified, and the development of techniques in molecular biology, evolution, and genetics are influencing medical technology, practice and decision - making. evidence - based medicine is a contemporary movement to establish the most effective algorithms of practice ( ways of doing things ) through the use of systematic reviews and meta - analysis. the movement is facilitated by modern global information science, which allows as much of the available evidence as possible to be collected and analyzed according to standard protocols that are then disseminated to healthcare providers. the cochrane collaboration leads this movement. a 2001 review of 160 cochrane systematic reviews revealed that, according to two readers, 21. 3 % of the reviews concluded insufficient evidence, 20 % concluded evidence of no effect, and 22. 5 % concluded positive effect. = = quality, efficiency, and access = = evidence - based medicine, prevention of medical error ( and other " iatrogenesis " ), and avoidance of unnecessary health care are a priority in modern medical systems. these topics generate significant political and public policy attention, particularly in the united states where healthcare is regarded as excessively costly but population health metrics lag similar nations. globally, many developing countries lack access to care and access to medicines. as of 2015, most wealthy developed countries provide health care to all citizens, with a few exceptions such as the united states where lack of health insurance
charges in the nuclei and the negative charges oscillating about them. more than simple attraction and repulsion, the energies and distributions characterize the availability of an electron to bond to another atom. the chemical bond can be a covalent bond, an ionic bond, a hydrogen bond or just because of van der waals force. each of these kinds of bonds is ascribed to some potential. these potentials create the interactions which hold atoms together in molecules or crystals. in many simple compounds, valence bond theory, the valence shell electron pair repulsion model ( vsepr ), and the concept of oxidation number can be used to explain molecular structure and composition. an ionic bond is formed when a metal loses one or more of its electrons, becoming a positively charged cation, and the electrons are then gained by the non - metal atom, becoming a negatively charged anion. the two oppositely charged ions attract one another, and the ionic bond is the electrostatic force of attraction between them. for example, sodium ( na ), a metal, loses one electron to become an na + cation while chlorine ( cl ), a non - metal, gains this electron to become clβ. the ions are held together due to electrostatic attraction, and that compound sodium chloride ( nacl ), or common table salt, is formed. in a covalent bond, one or more pairs of valence electrons are shared by two atoms : the resulting electrically neutral group of bonded atoms is termed a molecule. atoms will share valence electrons in such a way as to create a noble gas electron configuration ( eight electrons in their outermost shell ) for each atom. atoms that tend to combine in such a way that they each have eight electrons in their valence shell are said to follow the octet rule. however, some elements like hydrogen and lithium need only two electrons in their outermost shell to attain this stable configuration ; these atoms are said to follow the duet rule, and in this way they are reaching the electron configuration of the noble gas helium, which has two electrons in its outer shell. similarly, theories from classical physics can be used to predict many ionic structures. with more complicated compounds, such as metal complexes, valence bond theory is less applicable and alternative approaches, such as the molecular orbital theory, are generally used. = = = energy = = = in the context of chemistry, energy is an attribute of a substance as a consequence of its atomic, molecular or aggregate structure. since a chemical transformation is accompanied by a change
; kitasato shibasaburo ( japan ) ; jean - martin charcot, claude bernard, paul broca ( france ) ; adolfo lutz ( brazil ) ; nikolai korotkov ( russia ) ; sir william osler ( canada ) ; and harvey cushing ( united states ). as science and technology developed, medicine became more reliant upon medications. throughout history and in europe right until the late 18th century, not only plant products were used as medicine, but also animal ( including human ) body parts and fluids. pharmacology developed in part from herbalism and some drugs are still derived from plants ( atropine, ephedrine, warfarin, aspirin, digoxin, vinca alkaloids, taxol, hyoscine, etc. ). vaccines were discovered by edward jenner and louis pasteur. the first antibiotic was arsphenamine ( salvarsan ) discovered by paul ehrlich in 1908 after he observed that bacteria took up toxic dyes that human cells did not. the first major class of antibiotics was the sulfa drugs, derived by german chemists originally from azo dyes. pharmacology has become increasingly sophisticated ; modern biotechnology allows drugs targeted towards specific physiological processes to be developed, sometimes designed for compatibility with the body to reduce side - effects. genomics and knowledge of human genetics and human evolution is having increasingly significant influence on medicine, as the causative genes of most monogenic genetic disorders have now been identified, and the development of techniques in molecular biology, evolution, and genetics are influencing medical technology, practice and decision - making. evidence - based medicine is a contemporary movement to establish the most effective algorithms of practice ( ways of doing things ) through the use of systematic reviews and meta - analysis. the movement is facilitated by modern global information science, which allows as much of the available evidence as possible to be collected and analyzed according to standard protocols that are then disseminated to healthcare providers. the cochrane collaboration leads this movement. a 2001 review of 160 cochrane systematic reviews revealed that, according to two readers, 21. 3 % of the reviews concluded insufficient evidence, 20 % concluded evidence of no effect, and 22. 5 % concluded positive effect. = = quality, efficiency, and access = = evidence - based medicine, prevention of medical error ( and other " iatrogenesis " ), and avoidance of unnecessary health care are a priority in modern medical systems. these topics generate significant political and public policy attention, particularly in
Question: The name of the cation comes first, followed by the name of the anion, in what kind of compound?
A) covalent bonds
B) localized compound
C) ionic compound
D) magnetic compound
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C) ionic compound
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Context:
, natural phenomena on earth only involve gravity and electromagnetism, and not nuclear reactions. this is because atomic nuclei are generally kept apart because they contain positive electrical charges and therefore repel each other. in 1896, henri becquerel was investigating phosphorescence in uranium salts when he discovered a new phenomenon which came to be called radioactivity. he, pierre curie and marie curie began investigating the phenomenon. in the process, they isolated the element radium, which is highly radioactive. they discovered that radioactive materials produce intense, penetrating rays of three distinct sorts, which they labeled alpha, beta, and gamma after the first three greek letters. some of these kinds of radiation could pass through ordinary matter, and all of them could be harmful in large amounts. all of the early researchers received various radiation burns, much like sunburn, and thought little of it. the new phenomenon of radioactivity was seized upon by the manufacturers of quack medicine ( as had the discoveries of electricity and magnetism, earlier ), and a number of patent medicines and treatments involving radioactivity were put forward. gradually it was realized that the radiation produced by radioactive decay was ionizing radiation, and that even quantities too small to burn could pose a severe long - term hazard. many of the scientists working on radioactivity died of cancer as a result of their exposure. radioactive patent medicines mostly disappeared, but other applications of radioactive materials persisted, such as the use of radium salts to produce glowing dials on meters. as the atom came to be better understood, the nature of radioactivity became clearer. some larger atomic nuclei are unstable, and so decay ( release matter or energy ) after a random interval. the three forms of radiation that becquerel and the curies discovered are also more fully understood. alpha decay is when a nucleus releases an alpha particle, which is two protons and two neutrons, equivalent to a helium nucleus. beta decay is the release of a beta particle, a high - energy electron. gamma decay releases gamma rays, which unlike alpha and beta radiation are not matter but electromagnetic radiation of very high frequency, and therefore energy. this type of radiation is the most dangerous and most difficult to block. all three types of radiation occur naturally in certain elements. it has also become clear that the ultimate source of most terrestrial energy is nuclear, either through radiation from the sun caused by stellar thermonuclear reactions or by radioactive decay of uranium within the earth, the principal source of geothermal energy.
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
which came to be called radioactivity. he, pierre curie and marie curie began investigating the phenomenon. in the process, they isolated the element radium, which is highly radioactive. they discovered that radioactive materials produce intense, penetrating rays of three distinct sorts, which they labeled alpha, beta, and gamma after the first three greek letters. some of these kinds of radiation could pass through ordinary matter, and all of them could be harmful in large amounts. all of the early researchers received various radiation burns, much like sunburn, and thought little of it. the new phenomenon of radioactivity was seized upon by the manufacturers of quack medicine ( as had the discoveries of electricity and magnetism, earlier ), and a number of patent medicines and treatments involving radioactivity were put forward. gradually it was realized that the radiation produced by radioactive decay was ionizing radiation, and that even quantities too small to burn could pose a severe long - term hazard. many of the scientists working on radioactivity died of cancer as a result of their exposure. radioactive patent medicines mostly disappeared, but other applications of radioactive materials persisted, such as the use of radium salts to produce glowing dials on meters. as the atom came to be better understood, the nature of radioactivity became clearer. some larger atomic nuclei are unstable, and so decay ( release matter or energy ) after a random interval. the three forms of radiation that becquerel and the curies discovered are also more fully understood. alpha decay is when a nucleus releases an alpha particle, which is two protons and two neutrons, equivalent to a helium nucleus. beta decay is the release of a beta particle, a high - energy electron. gamma decay releases gamma rays, which unlike alpha and beta radiation are not matter but electromagnetic radiation of very high frequency, and therefore energy. this type of radiation is the most dangerous and most difficult to block. all three types of radiation occur naturally in certain elements. it has also become clear that the ultimate source of most terrestrial energy is nuclear, either through radiation from the sun caused by stellar thermonuclear reactions or by radioactive decay of uranium within the earth, the principal source of geothermal energy. = = = nuclear fission = = = in natural nuclear radiation, the byproducts are very small compared to the nuclei from which they originate. nuclear fission is the process of splitting a nucleus into roughly equal parts, and releasing energy and neutrons in the process. if these neutrons are captured by another unstable nucleus
##iation is the process of exposing food to ionizing radiation in order to destroy microorganisms, bacteria, viruses, or insects that might be present in the food. the radiation sources used include radioisotope gamma ray sources, x - ray generators and electron accelerators. further applications include sprout inhibition, delay of ripening, increase of juice yield, and improvement of re - hydration. irradiation is a more general term of deliberate exposure of materials to radiation to achieve a technical goal ( in this context ' ionizing radiation ' is implied ). as such it is also used on non - food items, such as medical hardware, plastics, tubes for gas - pipelines, hoses for floor - heating, shrink - foils for food packaging, automobile parts, wires and cables ( isolation ), tires, and even gemstones. compared to the amount of food irradiated, the volume of those every - day applications is huge but not noticed by the consumer. the genuine effect of processing food by ionizing radiation relates to damages to the dna, the basic genetic information for life. microorganisms can no longer proliferate and continue their malignant or pathogenic activities. spoilage causing micro - organisms cannot continue their activities. insects do not survive or become incapable of procreation. plants cannot continue the natural ripening or aging process. all these effects are beneficial to the consumer and the food industry, likewise. the amount of energy imparted for effective food irradiation is low compared to cooking the same ; even at a typical dose of 10 kgy most food, which is ( with regard to warming ) physically equivalent to water, would warm by only about 2. 5 Β°c ( 4. 5 Β°f ). the specialty of processing food by ionizing radiation is the fact, that the energy density per atomic transition is very high, it can cleave molecules and induce ionization ( hence the name ) which cannot be achieved by mere heating. this is the reason for new beneficial effects, however at the same time, for new concerns. the treatment of solid food by ionizing radiation can provide an effect similar to heat pasteurization of liquids, such as milk. however, the use of the term, cold pasteurization, to describe irradiated foods is controversial, because pasteurization and irradiation are fundamentally different processes, although the intended end results can in some cases be similar. detractors of food irradiation have concerns about the health hazards of induced radioact
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 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
##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
the first three greek letters. some of these kinds of radiation could pass through ordinary matter, and all of them could be harmful in large amounts. all of the early researchers received various radiation burns, much like sunburn, and thought little of it. the new phenomenon of radioactivity was seized upon by the manufacturers of quack medicine ( as had the discoveries of electricity and magnetism, earlier ), and a number of patent medicines and treatments involving radioactivity were put forward. gradually it was realized that the radiation produced by radioactive decay was ionizing radiation, and that even quantities too small to burn could pose a severe long - term hazard. many of the scientists working on radioactivity died of cancer as a result of their exposure. radioactive patent medicines mostly disappeared, but other applications of radioactive materials persisted, such as the use of radium salts to produce glowing dials on meters. as the atom came to be better understood, the nature of radioactivity became clearer. some larger atomic nuclei are unstable, and so decay ( release matter or energy ) after a random interval. the three forms of radiation that becquerel and the curies discovered are also more fully understood. alpha decay is when a nucleus releases an alpha particle, which is two protons and two neutrons, equivalent to a helium nucleus. beta decay is the release of a beta particle, a high - energy electron. gamma decay releases gamma rays, which unlike alpha and beta radiation are not matter but electromagnetic radiation of very high frequency, and therefore energy. this type of radiation is the most dangerous and most difficult to block. all three types of radiation occur naturally in certain elements. it has also become clear that the ultimate source of most terrestrial energy is nuclear, either through radiation from the sun caused by stellar thermonuclear reactions or by radioactive decay of uranium within the earth, the principal source of geothermal energy. = = = nuclear fission = = = in natural nuclear radiation, the byproducts are very small compared to the nuclei from which they originate. nuclear fission is the process of splitting a nucleus into roughly equal parts, and releasing energy and neutrons in the process. if these neutrons are captured by another unstable nucleus, they can fission as well, leading to a chain reaction. the average number of neutrons released per nucleus that go on to fission another nucleus is referred to as k. values of k larger than 1 mean that the fission reaction is releasing more neutrons than it absorbs, and therefore is referred to as a self
nuclear jets containing relativistic ` ` hot ' ' particles close to the central engine cool dramatically by producing high energy radiation. the radiative dissipation is similar to the famous compton drag acting upon ` ` cold ' ' thermal particles in a relativistic bulk flow. highly relativistic protons induce anisotropic showers raining electromagnetic power down onto the putative accretion disk. thus, the radiative signature of hot hadronic jets is x - ray irradiation of cold thermal matter. the synchrotron radio emission of the accelerated electrons is self - absorbed due to the strong magnetic fields close to the magnetic nozzle.
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.
the film is developed and it shows any internal defects of the material. gauges - gauges use the exponential absorption law of gamma rays level indicators : source and detector are placed at opposite sides of a container, indicating the presence or absence of material in the horizontal radiation path. beta or gamma sources are used, depending on the thickness and the density of the material to be measured. the method is used for containers of liquids or of grainy substances thickness gauges : if the material is of constant density, the signal measured by the radiation detector depends on the thickness of the material. this is useful for continuous production, like of paper, rubber, etc. electrostatic control - to avoid the build - up of static electricity in production of paper, plastics, synthetic textiles, etc., a ribbon - shaped source of the alpha emitter 241am can be placed close to the material at the end of the production line. the source ionizes the air to remove electric charges on the material. radioactive tracers - since radioactive isotopes behave, chemically, mostly like the inactive element, the behavior of a certain chemical substance can be followed by tracing the radioactivity. examples : adding a gamma tracer to a gas or liquid in a closed system makes it possible to find a hole in a tube. adding a tracer to the surface of the component of a motor makes it possible to measure wear by measuring the activity of the lubricating oil. oil and gas exploration - nuclear well logging is used to help predict the commercial viability of new or existing wells. the technology involves the use of a neutron or gamma - ray source and a radiation detector which are lowered into boreholes to determine the properties of the surrounding rock such as porosity and lithography. [ 1 ] road construction - nuclear moisture / density gauges are used to determine the density of soils, asphalt, and concrete. typically a cesium - 137 source is used. = = = commercial applications = = = radioluminescence tritium illumination : tritium is used with phosphor in rifle sights to increase nighttime firing accuracy. some runway markers and building exit signs use the same technology, to remain illuminated during blackouts. betavoltaics. smoke detector : an ionization smoke detector includes a tiny mass of radioactive americium - 241, which is a source of alpha radiation. two ionisation chambers are placed next to each other. both contain a small source of 241am that gives rise to a small constant current. one is closed and serves for comparison
Question: Electromagnetic radiation is a form of what?
A) energy
B) wave
C) fusion
D) fuel
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A) energy
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Context:
sight, hearing, touch, and sometimes smell ( e. g., in infection, uremia, diabetic ketoacidosis ). four actions are the basis of physical examination : inspection, palpation ( feel ), percussion ( tap to determine resonance characteristics ), and auscultation ( listen ), generally in that order, although auscultation occurs prior to percussion and palpation for abdominal assessments. the clinical examination involves the study of : abdomen and rectum cardiovascular ( heart and blood vessels ) general appearance of the patient and specific indicators of disease ( nutritional status, presence of jaundice, pallor or clubbing ) genitalia ( and pregnancy if the patient is or could be pregnant ) head, eye, ear, nose, and throat ( heent ) musculoskeletal ( including spine and extremities ) neurological ( consciousness, awareness, brain, vision, cranial nerves, spinal cord and peripheral nerves ) psychiatric ( orientation, mental state, mood, evidence of abnormal perception or thought ). respiratory ( large airways and lungs ) skin vital signs including height, weight, body temperature, blood pressure, pulse, respiration rate, and hemoglobin oxygen saturation it is to likely focus on areas of interest highlighted in the medical history and may not include everything listed above. the treatment plan may include ordering additional medical laboratory tests and medical imaging studies, starting therapy, referral to a specialist, or watchful observation. a follow - up may be advised. depending upon the health insurance plan and the managed care system, various forms of " utilization review ", such as prior authorization of tests, may place barriers on accessing expensive services. the medical decision - making ( mdm ) process includes the analysis and synthesis of all the above data to come up with a list of possible diagnoses ( the differential diagnoses ), along with an idea of what needs to be done to obtain a definitive diagnosis that would explain the patient ' s problem. on subsequent visits, the process may be repeated in an abbreviated manner to obtain any new history, symptoms, physical findings, lab or imaging results, or specialist consultations. = = institutions = = contemporary medicine is, in general, conducted within health care systems. legal, credentialing, and financing frameworks are established by individual governments, augmented on occasion by international organizations, such as churches. the characteristics of any given health care system have a significant impact on the way medical care is provided. from ancient times,
ability of cells to receive, process, and transmit signals with its environment and with itself. signals can be non - chemical such as light, electrical impulses, and heat, or chemical signals ( or ligands ) that interact with receptors, which can be found embedded in the cell membrane of another cell or located deep inside a cell. there are generally four types of chemical signals : autocrine, paracrine, juxtacrine, and hormones. in autocrine signaling, the ligand affects the same cell that releases it. tumor cells, for example, can reproduce uncontrollably because they release signals that initiate their own self - division. in paracrine signaling, the ligand diffuses to nearby cells and affects them. for example, brain cells called neurons release ligands called neurotransmitters that diffuse across a synaptic cleft to bind with a receptor on an adjacent cell such as another neuron or muscle cell. in juxtacrine signaling, there is direct contact between the signaling and responding cells. finally, hormones are ligands that travel through the circulatory systems of animals or vascular systems of plants to reach their target cells. once a ligand binds with a receptor, it can influence the behavior of another cell, depending on the type of receptor. for instance, neurotransmitters that bind with an inotropic receptor can alter the excitability of a target cell. other types of receptors include protein kinase receptors ( e. g., receptor for the hormone insulin ) and g protein - coupled receptors. activation of g protein - coupled receptors can initiate second messenger cascades. the process by which a chemical or physical signal is transmitted through a cell as a series of molecular events is called signal transduction. = = = cell cycle = = = the cell cycle is a series of events that take place in a cell that cause it to divide into two daughter cells. these events include the duplication of its dna and some of its organelles, and the subsequent partitioning of its cytoplasm into two daughter cells in a process called cell division. in eukaryotes ( i. e., animal, plant, fungal, and protist cells ), there are two distinct types of cell division : mitosis and meiosis. mitosis is part of the cell cycle, in which replicated chromosomes are separated into two new nuclei. cell division gives rise to genetically identical cells in which the total number of chromosomes is maintained. in general, mitosis
, 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. 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
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.
, 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
the action potential is widely considered a purely electrical phenomenon. however, one also finds mechanical and thermal changes that can be observed experimentally. in particular, nerve membranes become thicker and axons contract. the spatial length of the action potential can be quite large, ranging from millimeters to many centimeters. this suggests to employ macroscopic thermodynamics methods to understand its properties. the pulse length is several orders of magnitude larger than the synaptic gap, larger than the distance of the nodes of ranvier, and even larger than the size of many neurons such as pyramidal cells or brain stem motor neurons. here, we review the mechanical changes in nerves, theoretical possibilities to explain them, and implications of a mechanical nerve pulse for the neuron and for the brain. in particular, the contraction of nerves gives rise to the possibility of fast mechanical synapses.
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
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
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 ),
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
Question: What are the cells or structures that detect sensations?
A) membranes
B) receptors
C) proteins
D) hormones
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B) receptors
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Context:
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
##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.
genetic engineering takes the gene directly from one organism and delivers it to the other. this is much faster, can be used to insert any genes from any organism ( even ones from different domains ) and prevents other undesirable genes from also being added. genetic engineering could potentially fix severe genetic disorders in humans by replacing the defective gene with a functioning one. it is an important tool in research that allows the function of specific genes to be studied. drugs, vaccines and other products have been harvested from organisms engineered to produce them. crops have been developed that aid food security by increasing yield, nutritional value and tolerance to environmental stresses. the dna can be introduced directly into the host organism or into a cell that is then fused or hybridised with the host. this relies on recombinant nucleic acid techniques to form new combinations of heritable genetic material followed by the incorporation of that material either indirectly through a vector system or directly through micro - injection, macro - injection or micro - encapsulation. genetic engineering does not normally include traditional breeding, in vitro fertilisation, induction of polyploidy, mutagenesis and cell fusion techniques that do not use recombinant nucleic acids or a genetically modified organism in the process. however, some broad definitions of genetic engineering include selective breeding. cloning and stem cell research, although not considered genetic engineering, are closely related and genetic engineering can be used within them. synthetic biology is an emerging discipline that takes genetic engineering a step further by introducing artificially synthesised material into an organism. plants, animals or microorganisms that have been changed through genetic engineering are termed genetically modified organisms or gmos. if genetic material from another species is added to the host, the resulting organism is called transgenic. if genetic material from the same species or a species that can naturally breed with the host is used the resulting organism is called cisgenic. if genetic engineering is used to remove genetic material from the target organism the resulting organism is termed a knockout organism. in europe genetic modification is synonymous with genetic engineering while within the united states of america and canada genetic modification can also be used to refer to more conventional breeding methods. = = history = = humans have altered the genomes of species for thousands of years through selective breeding, or artificial selection : 1 : 1 as contrasted with natural selection. more recently, mutation breeding has used exposure to chemicals or radiation to produce a high frequency of random mutations, for selective breeding purposes. genetic engineering as the direct manipulation of dna by humans outside breeding and
be introduced directly into the host organism or into a cell that is then fused or hybridised with the host. this relies on recombinant nucleic acid techniques to form new combinations of heritable genetic material followed by the incorporation of that material either indirectly through a vector system or directly through micro - injection, macro - injection or micro - encapsulation. genetic engineering does not normally include traditional breeding, in vitro fertilisation, induction of polyploidy, mutagenesis and cell fusion techniques that do not use recombinant nucleic acids or a genetically modified organism in the process. however, some broad definitions of genetic engineering include selective breeding. cloning and stem cell research, although not considered genetic engineering, are closely related and genetic engineering can be used within them. synthetic biology is an emerging discipline that takes genetic engineering a step further by introducing artificially synthesised material into an organism. plants, animals or microorganisms that have been changed through genetic engineering are termed genetically modified organisms or gmos. if genetic material from another species is added to the host, the resulting organism is called transgenic. if genetic material from the same species or a species that can naturally breed with the host is used the resulting organism is called cisgenic. if genetic engineering is used to remove genetic material from the target organism the resulting organism is termed a knockout organism. in europe genetic modification is synonymous with genetic engineering while within the united states of america and canada genetic modification can also be used to refer to more conventional breeding methods. = = history = = humans have altered the genomes of species for thousands of years through selective breeding, or artificial selection : 1 : 1 as contrasted with natural selection. more recently, mutation breeding has used exposure to chemicals or radiation to produce a high frequency of random mutations, for selective breeding purposes. genetic engineering as the direct manipulation of dna by humans outside breeding and mutations has only existed since the 1970s. the term " genetic engineering " was coined by the russian - born geneticist nikolay timofeev - ressovsky in his 1934 paper " the experimental production of mutations ", published in the british journal biological reviews. jack williamson used the term in his science fiction novel dragon ' s island, published in 1951 β one year before dna ' s role in heredity was confirmed by alfred hershey and martha chase, and two years before james watson and francis crick showed that the dna molecule has a double - helix structure β though the general concept of direct genetic manipulation was explored in rudimentary form
genetic engineering, also called genetic modification or genetic manipulation, is the modification and manipulation of an organism ' s genes using technology. it is a set of technologies used to change the genetic makeup of cells, including the transfer of genes within and across species boundaries to produce improved or novel organisms. new dna is obtained by either isolating and copying the genetic material of interest using recombinant dna methods or by artificially synthesising the dna. a construct is usually created and used to insert this dna into the host organism. the first recombinant dna molecule was made by paul berg in 1972 by combining dna from the monkey virus sv40 with the lambda virus. as well as inserting genes, the process can be used to remove, or " knock out ", genes. the new dna can be inserted randomly, or targeted to a specific part of the genome. an organism that is generated through genetic engineering is considered to be genetically modified ( gm ) and the resulting entity is a genetically modified organism ( gmo ). the first gmo was a bacterium generated by herbert boyer and stanley cohen in 1973. rudolf jaenisch created the first gm animal when he inserted foreign dna into a mouse in 1974. the first company to focus on genetic engineering, genentech, was founded in 1976 and started the production of human proteins. genetically engineered human insulin was produced in 1978 and insulin - producing bacteria were commercialised in 1982. genetically modified food has been sold since 1994, with the release of the flavr savr tomato. the flavr savr was engineered to have a longer shelf life, but most current gm crops are modified to increase resistance to insects and herbicides. glofish, the first gmo designed as a pet, was sold in the united states in december 2003. in 2016 salmon modified with a growth hormone were sold. genetic engineering has been applied in numerous fields including research, medicine, industrial biotechnology and agriculture. in research, gmos are used to study gene function and expression through loss of function, gain of function, tracking and expression experiments. by knocking out genes responsible for certain conditions it is possible to create animal model organisms of human diseases. as well as producing hormones, vaccines and other drugs, genetic engineering has the potential to cure genetic diseases through gene therapy. chinese hamster ovary ( cho ) cells are used in industrial genetic engineering. additionally mrna vaccines are made through genetic engineering to prevent infections by viruses such as covid - 19. the same techniques that are used to produce drugs can also have industrial applications such
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
animal cells using microinjection, where it can be injected through the cell ' s nuclear envelope directly into the nucleus, or through the use of viral vectors. plant genomes can be engineered by physical methods or by use of agrobacterium for the delivery of sequences hosted in t - dna binary vectors. in plants the dna is often inserted using agrobacterium - mediated transformation, taking advantage of the agrobacteriums t - dna sequence that allows natural insertion of genetic material into plant cells. other methods include biolistics, where particles of gold or tungsten are coated with dna and then shot into young plant cells, and electroporation, which involves using an electric shock to make the cell membrane permeable to plasmid dna. as only a single cell is transformed with genetic material, the organism must be regenerated from that single cell. in plants this is accomplished through the use of tissue culture. in animals it is necessary to ensure that the inserted dna is present in the embryonic stem cells. bacteria consist of a single cell and reproduce clonally so regeneration is not necessary. selectable markers are used to easily differentiate transformed from untransformed cells. these markers are usually present in the transgenic organism, although a number of strategies have been developed that can remove the selectable marker from the mature transgenic plant. further testing using pcr, southern hybridization, and dna sequencing is conducted to confirm that an organism contains the new gene. these tests can also confirm the chromosomal location and copy number of the inserted gene. the presence of the gene does not guarantee it will be expressed at appropriate levels in the target tissue so methods that look for and measure the gene products ( rna and protein ) are also used. these include northern hybridisation, quantitative rt - pcr, western blot, immunofluorescence, elisa and phenotypic analysis. the new genetic material can be inserted randomly within the host genome or targeted to a specific location. the technique of gene targeting uses homologous recombination to make desired changes to a specific endogenous gene. this tends to occur at a relatively low frequency in plants and animals and generally requires the use of selectable markers. the frequency of gene targeting can be greatly enhanced through genome editing. genome editing uses artificially engineered nucleases that create specific double - stranded breaks at desired locations in the genome, and use the cell ' s endogenous mechanisms to repair the induced break by the natural processes
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,
in plants the dna is often inserted using agrobacterium - mediated transformation, taking advantage of the agrobacteriums t - dna sequence that allows natural insertion of genetic material into plant cells. other methods include biolistics, where particles of gold or tungsten are coated with dna and then shot into young plant cells, and electroporation, which involves using an electric shock to make the cell membrane permeable to plasmid dna. as only a single cell is transformed with genetic material, the organism must be regenerated from that single cell. in plants this is accomplished through the use of tissue culture. in animals it is necessary to ensure that the inserted dna is present in the embryonic stem cells. bacteria consist of a single cell and reproduce clonally so regeneration is not necessary. selectable markers are used to easily differentiate transformed from untransformed cells. these markers are usually present in the transgenic organism, although a number of strategies have been developed that can remove the selectable marker from the mature transgenic plant. further testing using pcr, southern hybridization, and dna sequencing is conducted to confirm that an organism contains the new gene. these tests can also confirm the chromosomal location and copy number of the inserted gene. the presence of the gene does not guarantee it will be expressed at appropriate levels in the target tissue so methods that look for and measure the gene products ( rna and protein ) are also used. these include northern hybridisation, quantitative rt - pcr, western blot, immunofluorescence, elisa and phenotypic analysis. the new genetic material can be inserted randomly within the host genome or targeted to a specific location. the technique of gene targeting uses homologous recombination to make desired changes to a specific endogenous gene. this tends to occur at a relatively low frequency in plants and animals and generally requires the use of selectable markers. the frequency of gene targeting can be greatly enhanced through genome editing. genome editing uses artificially engineered nucleases that create specific double - stranded breaks at desired locations in the genome, and use the cell ' s endogenous mechanisms to repair the induced break by the natural processes of homologous recombination and nonhomologous end - joining. there are four families of engineered nucleases : meganucleases, zinc finger nucleases, transcription activator - like effector nucleases ( talens ), and the cas9 - guide
young plant cells, and electroporation, which involves using an electric shock to make the cell membrane permeable to plasmid dna. as only a single cell is transformed with genetic material, the organism must be regenerated from that single cell. in plants this is accomplished through the use of tissue culture. in animals it is necessary to ensure that the inserted dna is present in the embryonic stem cells. bacteria consist of a single cell and reproduce clonally so regeneration is not necessary. selectable markers are used to easily differentiate transformed from untransformed cells. these markers are usually present in the transgenic organism, although a number of strategies have been developed that can remove the selectable marker from the mature transgenic plant. further testing using pcr, southern hybridization, and dna sequencing is conducted to confirm that an organism contains the new gene. these tests can also confirm the chromosomal location and copy number of the inserted gene. the presence of the gene does not guarantee it will be expressed at appropriate levels in the target tissue so methods that look for and measure the gene products ( rna and protein ) are also used. these include northern hybridisation, quantitative rt - pcr, western blot, immunofluorescence, elisa and phenotypic analysis. the new genetic material can be inserted randomly within the host genome or targeted to a specific location. the technique of gene targeting uses homologous recombination to make desired changes to a specific endogenous gene. this tends to occur at a relatively low frequency in plants and animals and generally requires the use of selectable markers. the frequency of gene targeting can be greatly enhanced through genome editing. genome editing uses artificially engineered nucleases that create specific double - stranded breaks at desired locations in the genome, and use the cell ' s endogenous mechanisms to repair the induced break by the natural processes of homologous recombination and nonhomologous end - joining. there are four families of engineered nucleases : meganucleases, zinc finger nucleases, transcription activator - like effector nucleases ( talens ), and the cas9 - guiderna system ( adapted from crispr ). talen and crispr are the two most commonly used and each has its own advantages. talens have greater target specificity, while crispr is easier to design and more efficient. in addition to enhancing gene targeting, engineered nucleases can be used to introduce mutations
Question: What artificial process involves making an exact copy of a gene?
A) gene cloning
B) ribosome cloning
C) candidate cloning
D) material cloning
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A) gene cloning
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Context:
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, 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
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
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
##s can be tested against these mouse models. gene therapy is the genetic engineering of humans, generally by replacing defective genes with effective ones. clinical research using somatic gene therapy has been conducted with several diseases, including x - linked scid, chronic lymphocytic leukemia ( cll ), and parkinson ' s disease. in 2012, alipogene tiparvovec became the first gene therapy treatment to be approved for clinical use. in 2015 a virus was used to insert a healthy gene into the skin cells of a boy suffering from a rare skin disease, epidermolysis bullosa, in order to grow, and then graft healthy skin onto 80 percent of the boy ' s body which was affected by the illness. germline gene therapy would result in any change being inheritable, which has raised concerns within the scientific community. in 2015, crispr was used to edit the dna of non - viable human embryos, leading scientists of major world academies to call for a moratorium on inheritable human genome edits. there are also concerns that the technology could be used not just for treatment, but for enhancement, modification or alteration of a human beings ' appearance, adaptability, intelligence, character or behavior. the distinction between cure and enhancement can also be difficult to establish. in november 2018, he jiankui announced that he had edited the genomes of two human embryos, to attempt to disable the ccr5 gene, which codes for a receptor that hiv uses to enter cells. the work was widely condemned as unethical, dangerous, and premature. currently, germline modification is banned in 40 countries. scientists that do this type of research will often let embryos grow for a few days without allowing it to develop into a baby. researchers are altering the genome of pigs to induce the growth of human organs, with the aim of increasing the success of pig to human organ transplantation. scientists are creating " gene drives ", changing the genomes of mosquitoes to make them immune to malaria, and then looking to spread the genetically altered mosquitoes throughout the mosquito population in the hopes of eliminating the disease. = = = research = = = genetic engineering is an important tool for natural scientists, with the creation of transgenic organisms one of the most important tools for analysis of gene function. genes and other genetic information from a wide range of organisms can be inserted into bacteria for storage and modification, creating genetically modified bacteria in the process. bacteria are cheap, easy to grow, clonal, multi
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,
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 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
##angulation from bearings taken by two rdf stations separated geographically, as the point where the two bearing lines cross, this is called a " fix ". military forces use rdf to locate enemy forces by their tactical radio transmissions, counterintelligence services use it to locate clandestine transmitters used by espionage agents, and governments use it to locate unlicensed transmitters or interference sources. older rdf receivers used rotatable loop antennas, the antenna is rotated until the radio signal strength is weakest, indicating the transmitter is in one of the antenna ' s two nulls. the nulls are used since they are sharper than the antenna ' s lobes ( maxima ). more modern receivers use phased array antennas which have a much greater angular resolution. animal migration tracking β a widely used technique in wildlife biology, conservation biology, and wildlife management in which small battery - powered radio transmitters are attached to wild animals so their movements can be tracked with a directional rdf receiver. sometimes the transmitter is implanted in the animal. the vhf band is typically used since antennas in this band are fairly compact. the receiver has a directional antenna ( typically a small yagi ) which is rotated until the received signal is strongest ; at this point the antenna is pointing in the direction of the animal. sophisticated systems used in recent years use satellites to track the animal, or geolocation tags with gps receivers which record and transmit a log of the animal ' s location. = = = = remote control = = = = radio remote control is the use of electronic control signals sent by radio waves from a transmitter to control the 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
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
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
##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
Question: Deer ticks are the vectors for what disease that affects humans?
A) malaria
B) dengue fever
C) ringworm
D) lyme disease
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D) lyme disease
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Context:
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
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
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
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
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
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 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
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
##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
river - beds ), but not for where there may be large obstructions in the ground. an open caisson that is used in soft grounds or high water tables, where open trench excavations are impractical, can also be used to install deep manholes, pump stations and reception / launch pits for microtunnelling, pipe jacking and other operations. a caisson is sunk by self - weight, concrete or water ballast placed on top, or by hydraulic jacks. the leading edge ( or cutting shoe ) of the caisson is sloped out at a sharp angle to aid sinking in a vertical manner ; it is usually made of steel. the shoe is generally wider than the caisson to reduce friction, and the leading edge may be supplied with pressurised bentonite slurry, which swells in water, stabilizing settlement by filling depressions and voids. an open caisson may fill with water during sinking. the material is excavated by clamshell excavator bucket on crane. the formation level subsoil may still not be suitable for excavation or bearing capacity. the water in the caisson ( due to a high water table ) balances the upthrust forces of the soft soils underneath. if dewatered, the base may " pipe " or " boil ", causing the caisson to sink. to combat this problem, piles may be driven from the surface to act as : load - bearing walls, in that they transmit loads to deeper soils. anchors, in that they resist flotation because of the friction at the interface between their surfaces and the surrounding earth into which they have been driven. h - beam sections ( typical column sections, due to resistance to bending in all axis ) may be driven at angles " raked " to rock or other firmer soils ; the h - beams are left extended above the base. a reinforced concrete plug may be placed under the water, a process known as tremie concrete placement. when the caisson is dewatered, this plug acts as a pile cap, resisting the upward forces of the subsoil. = = = monolithic = = = a monolithic caisson ( or simply a monolith ) is larger than the other types of caisson, but similar to open caissons. such caissons are often found in quay walls, where resistance to impact from ships is required. = = = pneumatic = = = shallow caissons may be open to the air, whereas pneumatic caisson
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
Question: A highway that switches back and forth as it climbs up a steep hillside, yeilding a much gentler slope, is an example of what simple machine?
A) lever
B) pulley
C) wheel
D) inclined plane
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D) inclined plane
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Context:
, lightning strikes, tornadoes, building fires, wildfires, and mass shootings disabling most of the system if not the entirety of it. geographic redundancy locations can be more than 621 miles ( 999 km ) continental, more than 62 miles apart and less than 93 miles ( 150 km ) apart, less than 62 miles apart, but not on the same campus, or different buildings that are more than 300 feet ( 91 m ) apart on the same campus. the following methods can reduce the risks of damage by a fire conflagration : large buildings at least 80 feet ( 24 m ) to 110 feet ( 34 m ) apart, but sometimes a minimum of 210 feet ( 64 m ) apart. : 9 high - rise buildings at least 82 feet ( 25 m ) apart : 12 open spaces clear of flammable vegetation within 200 feet ( 61 m ) on each side of objects different wings on the same building, in rooms that are separated by more than 300 feet ( 91 m ) different floors on the same wing of a building in rooms that are horizontally offset by a minimum of 70 feet ( 21 m ) with fire walls between the rooms that are on different floors two rooms separated by another room, leaving at least a 70 - foot gap between the two rooms there should be a minimum of two separated fire walls and on opposite sides of a corridor geographic redundancy is used by amazon web services ( aws ), google cloud platform ( gcp ), microsoft azure, netflix, dropbox, salesforce, linkedin, paypal, twitter, facebook, apple icloud, cisco meraki, and many others to provide geographic redundancy, high availability, fault tolerance and to ensure availability and reliability for their cloud services. as another example, to minimize risk of damage from severe windstorms or water damage, buildings can be located at least 2 miles ( 3. 2 km ) away from the shore, with an elevation of at least 5 feet ( 1. 5 m ) above sea level. for additional protection, they can be located at least 100 feet ( 30 m ) away from flood plain areas. = = functions of redundancy = = the two functions of redundancy are passive redundancy and active redundancy. both functions prevent performance decline from exceeding specification limits without human intervention using extra capacity. passive redundancy uses excess capacity to reduce the impact of component failures. one common form of passive redundancy is the extra strength of cabling and struts used in bridges.
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
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 :
so mars below means blood and war ", is a false cause fallacy. : 26 many astrologers claim that astrology is scientific. if one were to attempt to try to explain it scientifically, there are only four fundamental forces ( conventionally ), limiting the choice of possible natural mechanisms. : 65 some astrologers have proposed conventional causal agents such as electromagnetism and gravity. the strength of these forces drops off with distance. : 65 scientists reject these proposed mechanisms as implausible since, for example, the magnetic field, when measured from earth, of a large but distant planet such as jupiter is far smaller than that produced by ordinary household appliances. astronomer phil plait noted that in terms of magnitude, the sun is the only object with an electromagnetic field of note, but astrology isn ' t based just off the sun alone. : 65 while astrologers could try to suggest a fifth force, this is inconsistent with the trends in physics with the unification of electromagnetism and the weak force into the electroweak force. if the astrologer insisted on being inconsistent with the current understanding and evidential basis of physics, that would be an extraordinary claim. : 65 it would also be inconsistent with the other forces which drop off with distance. : 65 if distance is irrelevant, then, logically, all objects in space should be taken into account. : 66 carl jung sought to invoke synchronicity, the claim that two events have some sort of acausal connection, to explain the lack of statistically significant results on astrology from a single study he conducted. however, synchronicity itself is considered neither testable nor falsifiable. the study was subsequently heavily criticised for its non - random sample and its use of statistics and also its lack of consistency with astrology. = = psychology = = psychological studies have not found any robust relationship between astrological signs and life outcomes. for example, a study showed that zodiac signs are no more effective than random numbers in predicting subjective well - being and quality of life. it has also been shown that confirmation bias is a psychological factor that contributes to belief in astrology. : 344 : 180 β 181 : 42 β 48 confirmation bias is a form of cognitive bias. : 553 from the literature, astrology believers often tend to selectively remember those predictions that turned out to be true and do not remember those that turned out false. another, separate, form of confirmation bias also plays a role, where believers often fail to
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
. this, he argued, would have been more persuasive and would have produced less controversy. the use of poetic imagery based on the concepts of the macrocosm and microcosm, " as above so below " to decide meaning such as edward w. james ' example of " mars above is red, so mars below means blood and war ", is a false cause fallacy. : 26 many astrologers claim that astrology is scientific. if one were to attempt to try to explain it scientifically, there are only four fundamental forces ( conventionally ), limiting the choice of possible natural mechanisms. : 65 some astrologers have proposed conventional causal agents such as electromagnetism and gravity. the strength of these forces drops off with distance. : 65 scientists reject these proposed mechanisms as implausible since, for example, the magnetic field, when measured from earth, of a large but distant planet such as jupiter is far smaller than that produced by ordinary household appliances. astronomer phil plait noted that in terms of magnitude, the sun is the only object with an electromagnetic field of note, but astrology isn ' t based just off the sun alone. : 65 while astrologers could try to suggest a fifth force, this is inconsistent with the trends in physics with the unification of electromagnetism and the weak force into the electroweak force. if the astrologer insisted on being inconsistent with the current understanding and evidential basis of physics, that would be an extraordinary claim. : 65 it would also be inconsistent with the other forces which drop off with distance. : 65 if distance is irrelevant, then, logically, all objects in space should be taken into account. : 66 carl jung sought to invoke synchronicity, the claim that two events have some sort of acausal connection, to explain the lack of statistically significant results on astrology from a single study he conducted. however, synchronicity itself is considered neither testable nor falsifiable. the study was subsequently heavily criticised for its non - random sample and its use of statistics and also its lack of consistency with astrology. = = psychology = = psychological studies have not found any robust relationship between astrological signs and life outcomes. for example, a study showed that zodiac signs are no more effective than random numbers in predicting subjective well - being and quality of life. it has also been shown that confirmation bias is a psychological factor that contributes to belief in astrology. : 344 : 180 β 181 :
and by processing power using accelerators. food irradiation is only a niche application compared to medical supplies, plastic materials, raw materials, gemstones, cables and wires, etc. = = accidents = = nuclear accidents, because of the powerful forces involved, are often very dangerous. historically, the first incidents involved fatal radiation exposure. marie curie died from aplastic anemia which resulted from her high levels of exposure. two scientists, an american and canadian respectively, harry daghlian and louis slotin, died after mishandling the same plutonium mass. unlike conventional weapons, the intense light, heat, and explosive force is not the only deadly component to a nuclear weapon. approximately half of the deaths from hiroshima and nagasaki died two to five years afterward from radiation exposure. civilian nuclear and radiological accidents primarily involve nuclear power plants. most common are nuclear leaks that expose workers to hazardous material. a nuclear meltdown refers to the more serious hazard of 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
anemia is a major health burden worldwide. examining the hemoglobin level of blood is an important way to achieve the diagnosis of anemia, but it requires blood drawing and a blood test. in this work we propose a non - invasive, fast, and cost - effective screening test for iron - deficiency anemia in peruvian young children. our initial results show promising evidence for detecting conjunctival pallor anemia and artificial intelligence techniques with photos taken with a popular smartphone.
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
Question: The loss of too much blood may lead to shock of what system?
A) circulatory
B) nervous
C) heart
D) Circular
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A) circulatory
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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.
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 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
Question: What is the tectonic zone called where two plates come together?
A) paralleled boundary
B) lateral boundary
C) precursors boundary
D) convergent boundary
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D) convergent boundary
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Context:
. these biochemical strategies are unique to land plants. = = = medicine and materials = = = phytochemistry is a branch of plant biochemistry primarily concerned with the chemical substances produced by plants during secondary metabolism. some of these compounds are toxins such as the alkaloid coniine from hemlock. others, such as the essential oils peppermint oil and lemon oil are useful for their aroma, as flavourings and spices ( e. g., capsaicin ), and in medicine as pharmaceuticals as in opium from opium poppies. many medicinal and recreational drugs, such as tetrahydrocannabinol ( active ingredient in cannabis ), caffeine, morphine and nicotine come directly from plants. others are simple derivatives of botanical natural products. for example, the pain killer aspirin is the acetyl ester of salicylic acid, originally isolated from the bark of willow trees, and a wide range of opiate painkillers like heroin are obtained by chemical modification of morphine obtained from the opium poppy. popular stimulants come from plants, such as caffeine from coffee, tea and chocolate, and nicotine from tobacco. most alcoholic beverages come from fermentation of carbohydrate - rich plant products such as barley ( beer ), rice ( sake ) and grapes ( wine ). native americans have used various plants as ways of treating illness or disease for thousands of years. this knowledge native americans have on plants has been recorded by enthnobotanists and then in turn has been used by pharmaceutical companies as a way of drug discovery. plants can synthesise coloured dyes and pigments such as the anthocyanins responsible for the red colour of red wine, yellow weld and blue woad used together to produce lincoln green, indoxyl, source of the blue dye indigo traditionally used to dye denim and the artist ' s pigments gamboge and rose madder. sugar, starch, cotton, linen, hemp, some types of rope, wood and particle boards, papyrus and paper, vegetable oils, wax, and natural rubber are examples of commercially important materials made from plant tissues or their secondary products. charcoal, a pure form of carbon made by pyrolysis of wood, has a long history as a metal - smelting fuel, as a filter material and adsorbent and as an artist ' s material and is one of the three ingredients of gunpowder. cellulose, the world
##l ( active ingredient in cannabis ), caffeine, morphine and nicotine come directly from plants. others are simple derivatives of botanical natural products. for example, the pain killer aspirin is the acetyl ester of salicylic acid, originally isolated from the bark of willow trees, and a wide range of opiate painkillers like heroin are obtained by chemical modification of morphine obtained from the opium poppy. popular stimulants come from plants, such as caffeine from coffee, tea and chocolate, and nicotine from tobacco. most alcoholic beverages come from fermentation of carbohydrate - rich plant products such as barley ( beer ), rice ( sake ) and grapes ( wine ). native americans have used various plants as ways of treating illness or disease for thousands of years. this knowledge native americans have on plants has been recorded by enthnobotanists and then in turn has been used by pharmaceutical companies as a way of drug discovery. plants can synthesise coloured dyes and pigments such as the anthocyanins responsible for the red colour of red wine, yellow weld and blue woad used together to produce lincoln green, indoxyl, source of the blue dye indigo traditionally used to dye denim and the artist ' s pigments gamboge and rose madder. sugar, starch, cotton, linen, hemp, some types of rope, wood and particle boards, papyrus and paper, vegetable oils, wax, and natural rubber are examples of commercially important materials made from plant tissues or their secondary products. charcoal, a pure form of carbon made by pyrolysis of wood, has a long history as a metal - smelting fuel, as a filter material and adsorbent and as an artist ' s material and is one of the three ingredients of gunpowder. cellulose, the world ' s most abundant organic polymer, can be converted into energy, fuels, materials and chemical feedstock. products made from cellulose include rayon and cellophane, wallpaper paste, biobutanol and gun cotton. sugarcane, rapeseed and soy are some of the plants with a highly fermentable sugar or oil content that are used as sources of biofuels, important alternatives to fossil fuels, such as biodiesel. sweetgrass was used by native americans to ward off bugs like mosquitoes. these bug repelling properties of sweetgrass were later found by the american chemical society in the molecules phytol
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
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,
##trophs including all animals, all fungi, all completely parasitic plants, and non - photosynthetic bacteria take in organic molecules produced by photoautotrophs and respire them or use them in the construction of cells and tissues. respiration is the oxidation of carbon compounds by breaking them down into simpler structures to release the energy they contain, essentially the opposite of photosynthesis. molecules are moved within plants by transport processes that operate at a variety of spatial scales. subcellular transport of ions, electrons and molecules such as water and enzymes occurs across cell membranes. minerals and water are transported from roots to other parts of the plant in the transpiration stream. diffusion, osmosis, and active transport and mass flow are all different ways transport can occur. examples of elements that plants need to transport are nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. in vascular plants, these elements are extracted from the soil as soluble ions by the roots and transported throughout the plant in the xylem. most of the elements required for plant nutrition come from the chemical breakdown of soil minerals. sucrose produced by photosynthesis is transported from the leaves to other parts of the plant in the phloem and plant hormones are transported by a variety of processes. = = = plant hormones = = = plants are not passive, but respond to external signals such as light, touch, and injury by moving or growing towards or away from the stimulus, as appropriate. tangible evidence of touch sensitivity is the almost instantaneous collapse of leaflets of mimosa pudica, the insect traps of venus flytrap and bladderworts, and the pollinia of orchids. the hypothesis that plant growth and development is coordinated by plant hormones or plant growth regulators first emerged in the late 19th century. darwin experimented on the movements of plant shoots and roots towards light and gravity, and concluded " it is hardly an exaggeration to say that the tip of the radicle.. acts like the brain of one of the lower animals.. directing the several movements ". about the same time, the role of auxins ( from the greek auxein, to grow ) in control of plant growth was first outlined by the dutch scientist 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
the work is a study of the geometry of the molecules via molecular mechanics of the main alkaloids found in the seeds of argemone mexicana linn, a prickly poppy, which is considered one of the most important species of plants in traditional mexican and indian medicine system. the seeds have toxic properties as well as bactericide, hallucinogenic, fungicide, insecticide, in isoquinolines and sanguinarine alkaloids such as berberine. a computational study of the molecular geometry of the molecules through molecular mechanics of the main alkaloids compounds present in plant seeds is described in a computer simulation. the plant has active ingredients compounds : allocryptopine, berberine, chelerythrine, copsitine, dihydrosanguinarine, protopine and sanguinarine. the studied alkaloids form two groups having similar charge distribution among themselves, which have dipole moments of these two times higher than in the other group.
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
many monocots like maize and the pineapple and some dicots like the asteraceae have since independently evolved pathways like crassulacean acid metabolism and the c4 carbon fixation pathway for photosynthesis which avoid the losses resulting from photorespiration in the more common c3 carbon fixation pathway. these biochemical strategies are unique to land plants. = = = medicine and materials = = = phytochemistry is a branch of plant biochemistry primarily concerned with the chemical substances produced by plants during secondary metabolism. some of these compounds are toxins such as the alkaloid coniine from hemlock. others, such as the essential oils peppermint oil and lemon oil are useful for their aroma, as flavourings and spices ( e. g., capsaicin ), and in medicine as pharmaceuticals as in opium from opium poppies. many medicinal and recreational drugs, such as tetrahydrocannabinol ( active ingredient in cannabis ), caffeine, morphine and nicotine come directly from plants. others are simple derivatives of botanical natural products. for example, the pain killer aspirin is the acetyl ester of salicylic acid, originally isolated from the bark of willow trees, and a wide range of opiate painkillers like heroin are obtained by chemical modification of morphine obtained from the opium poppy. popular stimulants come from plants, such as caffeine from coffee, tea and chocolate, and nicotine from tobacco. most alcoholic beverages come from fermentation of 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
scale. thus, solutions that have a low ph have a high hydronium ion concentration and can be said to be more acidic. the other measurement, based on the brΓΈnsted β lowry definition, is the acid dissociation constant ( ka ), which measures the relative ability of a substance to act as an acid under the brΓΈnsted β lowry definition of an acid. that is, substances with a higher ka are more likely to donate hydrogen ions in chemical reactions than those with lower ka values. = = = redox = = = redox ( reduction - oxidation ) reactions include all chemical reactions in which atoms have their oxidation state changed by either gaining electrons ( reduction ) or losing electrons ( oxidation ). substances that have the ability to oxidize other substances are said to be oxidative and are known as oxidizing agents, oxidants or oxidizers. an oxidant removes electrons from another substance. similarly, substances that have the ability to reduce other substances are said to be reductive and are known as reducing agents, reductants, or reducers. a reductant transfers electrons to another substance and is thus oxidized itself. and because it " donates " electrons it is also called an electron donor. oxidation and reduction properly refer to a change in oxidation number β the actual transfer of electrons may never occur. thus, oxidation is better defined as an increase in oxidation number, and reduction as a decrease in oxidation number. = = = equilibrium = = = although the concept of equilibrium is widely used across sciences, in the context of chemistry, it arises whenever a number of different states of the chemical composition are possible, as for example, in a mixture of several chemical compounds that can react with one another, or when a substance can be present in more than one kind of phase. a system of chemical substances at equilibrium, even though having an unchanging composition, is most often not static ; molecules of the substances continue to react with one another thus giving rise to a dynamic equilibrium. thus the concept describes the state in which the parameters such as chemical composition remain unchanged over time. = = = chemical laws = = = chemical reactions are governed by certain laws, which have become fundamental concepts in chemistry. some of them are : = = history = = the history of chemistry spans a period from the ancient past to the present. since several millennia bc, civilizations were using technologies that would eventually form the basis of the various branches of chemistry. examples include extracting metals from ores
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,
Question: The mild oxidation of thiols gives compounds called what?
A) dioxides
B) carbonates
C) halides
D) disulfides
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D) disulfides
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Context:
##es. embryophytes are multicellular eukaryotes descended from an ancestor that obtained its energy from sunlight by photosynthesis. they have life cycles with alternating haploid and diploid phases. the sexual haploid phase of embryophytes, known as the gametophyte, nurtures the developing diploid embryo sporophyte within its tissues for at least part of its life, even in the seed plants, where the gametophyte itself is nurtured by its parent sporophyte. other groups of organisms that were previously studied by botanists include bacteria ( now studied in bacteriology ), fungi ( mycology ) β including lichen - forming fungi ( lichenology ), non - chlorophyte algae ( phycology ), and viruses ( virology ). however, attention is still given to these groups by botanists, and fungi ( including lichens ) and photosynthetic protists are usually covered in introductory botany courses. palaeobotanists study ancient plants in the fossil record to provide information about the evolutionary history of plants. cyanobacteria, the first oxygen - releasing photosynthetic organisms on earth, are thought to have given rise to the ancestor of plants by entering into an endosymbiotic relationship with an early eukaryote, ultimately becoming the chloroplasts in plant cells. the new photosynthetic plants ( along with their algal relatives ) accelerated the rise in atmospheric oxygen started by the cyanobacteria, changing the ancient oxygen - free, reducing, atmosphere to one in which free oxygen has been abundant for more than 2 billion years. among the important botanical questions of the 21st century are the role of plants as primary producers in the global cycling of life ' s basic ingredients : energy, carbon, oxygen, nitrogen and water, and ways that our plant stewardship can help address the global environmental issues of resource management, conservation, human food security, biologically invasive organisms, carbon sequestration, climate change, and sustainability. = = = human nutrition = = = virtually all staple foods come either directly from primary production by plants, or indirectly from animals that eat them. plants and other photosynthetic organisms are at the base of most food chains because they use the energy from the sun and nutrients from the soil and atmosphere, converting them into a form that can be used by animals. this is what ecologists call the first trophic level. the modern forms of
the strictest definition of " plant " includes only the " land plants " or embryophytes, which include seed plants ( gymnosperms, including the pines, and flowering plants ) and the free - sporing cryptogams including ferns, clubmosses, liverworts, hornworts and mosses. embryophytes are multicellular eukaryotes descended from an ancestor that obtained its energy from sunlight by photosynthesis. they have life cycles with alternating haploid and diploid phases. the sexual haploid phase of embryophytes, known as the gametophyte, nurtures the developing diploid embryo sporophyte within its tissues for at least part of its life, even in the seed plants, where the gametophyte itself is nurtured by its parent sporophyte. other groups of organisms that were previously studied by botanists include bacteria ( now studied in bacteriology ), fungi ( mycology ) β including lichen - forming fungi ( lichenology ), non - chlorophyte algae ( phycology ), and viruses ( virology ). however, attention is still given to these groups by botanists, and fungi ( including lichens ) and photosynthetic protists are usually covered in introductory botany courses. palaeobotanists study ancient plants in the fossil record to provide information about the evolutionary history of plants. cyanobacteria, the first oxygen - releasing photosynthetic organisms on earth, are thought to have given rise to the ancestor of plants by entering into an endosymbiotic relationship with an early eukaryote, ultimately becoming the chloroplasts in plant cells. the new photosynthetic plants ( along with their algal relatives ) accelerated the rise in atmospheric oxygen started by the cyanobacteria, changing the ancient oxygen - free, reducing, atmosphere to one in which free oxygen has been abundant for more than 2 billion years. among the important botanical questions of the 21st century are the role of plants as primary producers in the global cycling of life ' s basic ingredients : energy, carbon, oxygen, nitrogen and water, and ways that our plant stewardship can help address the global environmental issues of resource management, conservation, human food security, biologically invasive organisms, carbon sequestration, climate change, and sustainability. = = = human nutrition = = = virtually all staple foods come either directly from primary production by plants, or indirectly from animals that
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,
diploid embryo sporophyte within its tissues for at least part of its life, even in the seed plants, where the gametophyte itself is nurtured by its parent sporophyte. other groups of organisms that were previously studied by botanists include bacteria ( now studied in bacteriology ), fungi ( mycology ) β including lichen - forming fungi ( lichenology ), non - chlorophyte algae ( phycology ), and viruses ( virology ). however, attention is still given to these groups by botanists, and fungi ( including lichens ) and photosynthetic protists are usually covered in introductory botany courses. palaeobotanists study ancient plants in the fossil record to provide information about the evolutionary history of plants. cyanobacteria, the first oxygen - releasing photosynthetic organisms on earth, are thought to have given rise to the ancestor of plants by entering into an endosymbiotic relationship with an early eukaryote, ultimately becoming the chloroplasts in plant cells. the new photosynthetic plants ( along with their algal relatives ) accelerated the rise in atmospheric oxygen started by the cyanobacteria, changing the ancient oxygen - free, reducing, atmosphere to one in which free oxygen has been abundant for more than 2 billion years. among the important botanical questions of the 21st century are the role of plants as primary producers in the global cycling of life ' s basic ingredients : energy, carbon, oxygen, nitrogen and water, and ways that our plant stewardship can help address the global environmental issues of resource management, conservation, human food security, biologically invasive organisms, carbon sequestration, climate change, and sustainability. = = = human nutrition = = = virtually all staple foods come either directly from primary production by plants, or indirectly from animals that eat them. plants and other photosynthetic organisms are at the base of most food chains because they use the energy from the sun and nutrients from the soil and atmosphere, converting them into a form that can be used by animals. this is what ecologists call the first trophic level. the modern forms of the major staple foods, such as hemp, teff, maize, rice, wheat and other cereal grasses, pulses, bananas and plantains, as well as hemp, flax and cotton grown for their fibres, are the outcome of prehistoric selection over thousands of years from among wild ancestral plants with the most
, 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
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
##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
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
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
##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
Question: What is the structure in a diploid sporophyte that undergoes meiosis to form haploid spores?
A) hymenium
B) sporangium
C) dikaryotic
D) hyphae
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B) sporangium
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Context:
to rna to protein. there are two gene expression processes : transcription ( dna to rna ) and translation ( rna to protein ). = = = gene regulation = = = the regulation of gene expression by environmental factors and during different stages of development can occur at each step of the process such as transcription, rna splicing, translation, and post - translational modification of a protein. gene expression can be influenced by positive or negative regulation, depending on which of the two types of regulatory proteins called transcription factors bind to the dna sequence close to or at a promoter. a cluster of genes that share the same promoter is called an operon, found mainly in prokaryotes and some lower eukaryotes ( e. g., caenorhabditis elegans ). in positive regulation of gene expression, the activator is the transcription factor that stimulates transcription when it binds to the sequence near or at the promoter. negative regulation occurs when another transcription factor called a repressor binds to a dna sequence called an operator, which is part of an operon, to prevent transcription. repressors can be inhibited by compounds called inducers ( e. g., allolactose ), thereby allowing transcription to occur. specific genes that can be activated by inducers are called inducible genes, in contrast to constitutive genes that are almost constantly active. in contrast to both, structural genes encode proteins that are not involved in gene regulation. in addition to regulatory events involving the promoter, gene expression can also be regulated by epigenetic changes to chromatin, which is a complex of dna and protein found in eukaryotic cells. = = = genes, development, and evolution = = = development is the process by which a multicellular organism ( plant or animal ) goes through a series of changes, starting from a single cell, and taking on various forms that are characteristic of its life cycle. there are four key processes that underlie development : determination, differentiation, morphogenesis, and growth. determination sets the developmental fate of a cell, which becomes more restrictive during development. differentiation is the process by which specialized cells arise from less specialized cells such as stem cells. stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. cellular differentiation dramatically changes a cell ' s size, shape, membrane potential, metabolic activity, and responsiveness to signals, which are largely due
, translation, and post - translational modification of a protein. gene expression can be influenced by positive or negative regulation, depending on which of the two types of regulatory proteins called transcription factors bind to the dna sequence close to or at a promoter. a cluster of genes that share the same promoter is called an operon, found mainly in prokaryotes and some lower eukaryotes ( e. g., caenorhabditis elegans ). in positive regulation of gene expression, the activator is the transcription factor that stimulates transcription when it binds to the sequence near or at the promoter. negative regulation occurs when another transcription factor called a repressor binds to a dna sequence called an operator, which is part of an operon, to prevent transcription. repressors can be inhibited by compounds called inducers ( e. g., allolactose ), thereby allowing transcription to occur. specific genes that can be activated by inducers are called inducible genes, in contrast to constitutive genes that are almost constantly active. in contrast to both, structural genes encode proteins that are not involved in gene regulation. in addition to regulatory events involving the promoter, gene expression can also be regulated by epigenetic changes to chromatin, which is a complex of dna and protein found in eukaryotic cells. = = = genes, development, and evolution = = = development is the process by which a multicellular organism ( plant or animal ) goes through a series of changes, starting from a single cell, and taking on various forms that are characteristic of its life cycle. there are four key processes that underlie development : determination, differentiation, morphogenesis, and growth. determination sets the developmental fate of a cell, which becomes more restrictive during development. differentiation is the process by which specialized cells arise from less specialized cells such as stem cells. stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. cellular differentiation dramatically changes a cell ' s size, shape, membrane potential, metabolic activity, and responsiveness to signals, which are largely due to highly controlled modifications in gene expression and epigenetics. with a few exceptions, cellular differentiation almost never involves a change in the dna sequence itself. thus, different cells can have very different physical characteristics despite having the same genome. morphogenesis, or the development of body form, is the result of spatial
process by which a genotype encoded in dna gives rise to an observable phenotype in the proteins of an organism ' s body. this process is summarized by the central dogma of molecular biology, which was formulated by francis crick in 1958. according to the central dogma, genetic information flows from dna to rna to protein. there are two gene expression processes : transcription ( dna to rna ) and translation ( rna to protein ). = = = gene regulation = = = the regulation of gene expression by environmental factors and during different stages of development can occur at each step of the process such as transcription, rna splicing, translation, and post - translational modification of a protein. gene expression can be influenced by positive or negative regulation, depending on which of the two types of regulatory proteins called transcription factors bind to the dna sequence close to or at a promoter. a cluster of genes that share the same promoter is called an operon, found mainly in prokaryotes and some lower eukaryotes ( e. g., caenorhabditis elegans ). in positive regulation of gene expression, the activator is the transcription factor that stimulates transcription when it binds to the sequence near or at the promoter. negative regulation occurs when another transcription factor called a repressor binds to a dna sequence called an operator, which is part of an operon, to prevent transcription. repressors can be inhibited by compounds called inducers ( e. g., allolactose ), thereby allowing transcription to occur. specific genes that can be activated by inducers are called inducible genes, in contrast to constitutive genes that are almost constantly active. in contrast to both, structural genes encode proteins that are not involved in gene regulation. in addition to regulatory events involving the promoter, gene expression can also be regulated by epigenetic changes to chromatin, which is a complex of dna and protein found in eukaryotic cells. = = = genes, development, and evolution = = = development is the process by which a multicellular organism ( plant or animal ) goes through a series of changes, starting from a single cell, and taking on various forms that are characteristic of its life cycle. there are four key processes that underlie development : determination, differentiation, morphogenesis, and growth. determination sets the developmental fate of a cell, which becomes more restrictive during development. differentiation is the process by which specialized cells arise from less specialized cells such as stem
can be activated by inducers are called inducible genes, in contrast to constitutive genes that are almost constantly active. in contrast to both, structural genes encode proteins that are not involved in gene regulation. in addition to regulatory events involving the promoter, gene expression can also be regulated by epigenetic changes to chromatin, which is a complex of dna and protein found in eukaryotic cells. = = = genes, development, and evolution = = = development is the process by which a multicellular organism ( plant or animal ) goes through a series of changes, starting from a single cell, and taking on various forms that are characteristic of its life cycle. there are four key processes that underlie development : determination, differentiation, morphogenesis, and growth. determination sets the developmental fate of a cell, which becomes more restrictive during development. differentiation is the process by which specialized cells arise from less specialized cells such as stem cells. stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. cellular differentiation dramatically changes a cell ' s size, shape, membrane potential, metabolic activity, and responsiveness to signals, which are largely due to highly controlled modifications in gene expression and epigenetics. with a few exceptions, cellular differentiation almost never involves a change in the dna sequence itself. thus, different cells can have very different physical characteristics despite having the same genome. morphogenesis, or the development of body form, is the result of spatial differences in gene expression. a small fraction of the genes in an organism ' s genome called the developmental - genetic toolkit control the development of that organism. these toolkit genes are highly conserved among phyla, meaning that they are ancient and very similar in widely separated groups of animals. differences in deployment of toolkit genes affect the body plan and the number, identity, and pattern of body parts. among the most important toolkit genes are the hox genes. hox genes determine where repeating parts, such as the many vertebrae of snakes, will grow in a developing embryo or larva. = = evolution = = = = = evolutionary processes = = = evolution is a central organizing concept in biology. it is the change in heritable characteristics of populations over successive generations. in artificial selection, animals were selectively bred for specific traits. given that traits are inherited, populations contain a varied mix of traits, and reproduction is able to increase any population,
is opened and the dna is purified. the gene is separated by using restriction enzymes to cut the dna into fragments or polymerase chain reaction ( pcr ) to amplify up the gene segment. these segments can then be extracted through gel electrophoresis. if the chosen gene or the donor organism ' s genome has been well studied it may already be accessible from a genetic library. if the dna sequence is known, but no copies of the gene are available, it can also be artificially synthesised. once isolated the gene is ligated into a plasmid that is then inserted into a bacterium. the plasmid is replicated when the bacteria divide, ensuring unlimited copies of the gene are available. the rk2 plasmid is notable for its ability to replicate in a wide variety of single - celled organisms, which makes it suitable as a genetic engineering tool. before the gene is inserted into the target organism it must be combined with other genetic elements. these include a promoter and terminator region, which initiate and end transcription. a selectable marker gene is added, which in most cases confers antibiotic resistance, so researchers can easily determine which cells have been successfully transformed. the gene can also be modified at this stage for better expression or effectiveness. these manipulations are carried out using recombinant dna techniques, such as restriction digests, ligations and molecular cloning. = = = inserting dna into the host genome = = = there are a number of techniques used to insert genetic material into the host genome. some bacteria can naturally take up foreign dna. this ability can be induced in other bacteria via stress ( e. g. thermal or electric shock ), which increases the cell membrane ' s permeability to dna ; up - taken dna can either integrate with the genome or exist as extrachromosomal dna. dna is generally inserted into animal cells using microinjection, where it can be injected through the cell ' s nuclear envelope directly into the nucleus, or through the use of viral vectors. plant genomes can be engineered by physical methods or by use of agrobacterium for the delivery of sequences hosted in t - dna binary vectors. in plants the dna is often inserted using agrobacterium - mediated transformation, taking advantage of the agrobacteriums t - dna sequence that allows natural insertion of genetic material into plant cells. other methods include biolistics, where particles of gold or tungsten are coated with dna and then shot into
not always mean it is required, especially when dealing with genetic or functional redundancy. tracking experiments, which seek to gain information about the localisation and interaction of the desired protein. one way to do this is to replace the wild - type gene with a ' fusion ' gene, which is a juxtaposition of the wild - type gene with a reporting element such as green fluorescent protein ( gfp ) that will allow easy visualisation of the products of the genetic modification. while this is a useful technique, the manipulation can destroy the function of the gene, creating secondary effects and possibly calling into question the results of the experiment. more sophisticated techniques are now in development that can track protein products without mitigating their function, such as the addition of small sequences that will serve as binding motifs to monoclonal antibodies. expression studies aim to discover where and when specific proteins are produced. in these experiments, the dna sequence before the dna that codes for a protein, known as a gene ' s promoter, is reintroduced into an organism with the protein coding region replaced by a reporter gene such as gfp or an enzyme that catalyses the production of a dye. thus the time and place where a particular protein is produced can be observed. expression studies can be taken a step further by altering the promoter to find which pieces are crucial for the proper expression of the gene and are actually bound by transcription factor proteins ; this process is known as promoter bashing. = = = industrial = = = organisms can have their cells transformed with a gene coding for a useful protein, such as an enzyme, so that they will overexpress the desired protein. mass quantities of the protein can then be manufactured by growing the transformed organism in bioreactor equipment using industrial fermentation, and then purifying the protein. some genes do not work well in bacteria, so yeast, insect cells or mammalian cells can also be used. these techniques are used to produce medicines such as insulin, human growth hormone, and vaccines, supplements such as tryptophan, aid in the production of food ( chymosin in cheese making ) and fuels. other applications with genetically engineered bacteria could involve making them perform tasks outside their natural cycle, such as making biofuels, cleaning up oil spills, carbon and other toxic waste and detecting arsenic in drinking water. certain genetically modified microbes can also be used in biomining and bioremediation, due to their ability to extract heavy metals from their environment and incorporate them into compounds that are more easily recover
##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.
of epigenetic change is the marking of the genes by dna methylation which determines whether they will be expressed or not. gene expression can also be controlled by repressor proteins that attach to silencer regions of the dna and prevent that region of the dna code from being expressed. epigenetic marks may be added or removed from the dna during programmed stages of development of the plant, and are responsible, for example, for the differences between anthers, petals and normal leaves, despite the fact that they all have the same underlying genetic code. epigenetic changes may be temporary or may remain through successive cell divisions for the remainder of the cell ' s life. some epigenetic changes have been shown to be heritable, while others are reset in the germ cells. epigenetic changes in eukaryotic biology serve to regulate the process of cellular differentiation. during morphogenesis, totipotent stem cells become the various pluripotent cell lines of the embryo, which in turn become fully differentiated cells. a single fertilised egg cell, the zygote, gives rise to the many different plant cell types including parenchyma, xylem vessel elements, phloem sieve tubes, guard cells of the epidermis, etc. as it continues to divide. the process results from the epigenetic activation of some genes and inhibition of others. unlike animals, many plant cells, particularly those of the parenchyma, do not terminally differentiate, remaining totipotent with the ability to give rise to a new individual plant. exceptions include highly lignified cells, the sclerenchyma and xylem which are dead at maturity, and the phloem sieve tubes which lack nuclei. while plants use many of the same epigenetic mechanisms as animals, such as chromatin remodelling, an alternative hypothesis is that plants set their gene expression patterns using positional information from the environment and surrounding cells to determine their developmental fate. epigenetic changes can lead to paramutations, which do not follow the mendelian heritage rules. these epigenetic marks are carried from one generation to the next, with one allele inducing a change on the other. = = plant evolution = = the chloroplasts of plants have a number of biochemical, structural and genetic similarities to cyanobacteria, ( commonly but incorrectly known as " blue - green algae " ) and are thought to be derived from an
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 accumulation of favorable traits over successive generations, thereby increasing the match between the organisms and their environment. = = = speciation = = = a species is a group of organisms that mate with one another and speciation is the process by which one lineage splits into two lineages as a result of having evolved independently from each other
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
Question: Gene expression and what else are usually considered the same molecular process?
A) protein synthesis
B) organism synthesis
C) subtractive synthesis
D) photosynthesis
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A) protein synthesis
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Context:
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
, 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 '
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
##ization. the fouling is usually induced faster at higher driving forces. membrane fouling and particle retention in a feed solution also builds up a concentration gradients and particle backflow ( concentration polarization ). the tangential flow devices are more cost and labor - intensive, but they are less susceptible to fouling due to the sweeping effects and high shear rates of the passing flow. the most commonly used synthetic membrane devices ( modules ) are flat sheets / plates, spiral wounds, and hollow fibers. flat membranes used in filtration and separation processes can be enhanced with surface patterning, where microscopic structures are introduced to improve performance. these patterns increase surface area, optimize water flow, and reduce fouling, leading to higher permeability and longer membrane lifespan. research has shown that such modifications can significantly enhance efficiency in water purification, energy applications, and industrial separations. flat plates are usually constructed as circular thin flat membrane surfaces to be used in dead - end geometry modules. spiral wounds are constructed from similar flat membranes but in the form of a " pocket " containing two membrane sheets separated by a highly porous support plate. several such pockets are then wound around a tube to create a tangential flow geometry and to reduce membrane fouling. hollow fiber modules consist of an assembly of self - supporting fibers with dense skin separation layers, and a more open matrix helping to withstand pressure gradients and maintain structural integrity. the hollow fiber modules can contain up to 10, 000 fibers ranging from 200 to 2500 ΞΌm in diameter ; the main advantage of hollow fiber modules is the very large surface area within an enclosed volume, increasing the efficiency of the separation process. the disc tube module uses a cross - flow geometry and consists of a pressure tube and hydraulic discs, which are held by a central tension rod, and membrane cushions that lie between two discs. = = membrane performance and governing equations = = the selection of synthetic membranes for a targeted separation process is usually based on few requirements. membranes have to provide enough mass transfer area to process large amounts of feed stream. the selected membrane has to have high selectivity ( rejection ) properties for certain particles ; it has to resist fouling and to have high mechanical stability. it also needs to be reproducible and to have low manufacturing costs. the main modeling equation for the dead - end filtration at constant pressure drop is represented by darcy ' s law : d v p d t = q = Ξ΄ p ΞΌ a ( 1 r m + r ) { \ displaystyle { \ frac { dv _
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.
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 no adverse effect on pilot vision. = = = = ships = = = = ships have also adopted similar methods. though the earlier american arleigh burke - class destroyers incorporated some signature - reduction features. the norwegian skjold - class corvettes was the first coastal defence and the french la fayette - class frigates the
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 ' 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
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
side aspect rcs ), compared with three or more on most other types. while writing about radar systems, authors simon kingsley and shaun quegan singled out the vulcan ' s shape as acting to reduce the rcs. in contrast, the tupolev tu - 95 russian long - range bomber ( nato reporting name ' 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 - 22
Question: Centipedes have what on their foremost trunk segment, used to paralyze prey and aid in defense?
A) diploid claws
B) animal claws
C) poison claws
D) board claws
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C) poison claws
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Context:
kidneys and the majority of those currently in use are extracorporeal, such as with hemodialysis, which filters blood directly, or peritoneal dialysis, which filters via a fluid in the abdomen. in order to contribute to the biological functions of a kidney such as producing metabolic factors or hormones, some artificial kidneys incorporate renal cells. there has been progress in the way of making these devices smaller and more transportable, or even implantable. one challenge still to be faced in these smaller devices is countering the limited volume and therefore limited filtering capabilities. bioscaffolds have also been introduced to provide a framework upon which normal kidney tissue can be regenerated. these scaffolds encompass natural scaffolds ( e. g., decellularized kidneys, collagen hydrogel, or silk fibroin ), synthetic scaffolds ( e. g., poly [ lactic - co - glycolic acid ] or other polymers ), or a combination of two or more natural and synthetic scaffolds. these scaffolds can be implanted into the body either without cell treatment or after a period of stem cell seeding and incubation. in vitro and in vivo studies are being conducted to compare and optimize the type of scaffold and to assess whether cell seeding prior to implantation adds to the viability, regeneration and effective function of the kidneys. a recent systematic review and meta - analysis compared the results of published animal studies and identified that improved outcomes are reported with the use of hybrid ( mixed ) scaffolds and cell seeding ; however, the meta - analysis of these results were not in agreement with the evaluation of descriptive results from the review. therefore, further studies involving larger animals and novel scaffolds, and more transparent reproduction of previous studies are advisable. = = = biomimetics = = = biomimetics is a field that aims to produce materials and systems that replicate those present in nature. in the context of tissue engineering, this is a common approach used by engineers to create materials for these applications that are comparable to native tissues in terms of their structure, properties, and biocompatibility. material properties are largely dependent on physical, structural, and chemical characteristics of that material. subsequently, a biomimetic approach to system design will become significant in material integration, and a sufficient understanding of biological processes and interactions will be necessary. replication of biological systems and
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
equivalent of us $ 790 million in state subsidies. the same year, catl introduced its m3p battery, offering a 15 % increase in energy density, reaching 210 wh / kg. the battery replaces the iron in the lithium iron phosphate battery with a combination of magnesium, zinc, and aluminum. later that year, the company announced its shenxing lfp battery. the cathode of shenxing lfp is fully nano - crystallized, which accelerates ion movement and the response to charging signals. the anode ' s second - generation fast ion ring technology increases intercalation channels and shortens intercalation distance. its superconducting electrolyte formula reduces viscosity and improves conductivity. a new separator film reduces resistance. at room temperature, shenxing can charge from 0 to 80 % in 10 minutes and in just 30 minutes at - 10 Β°c, maintains 0 - 100 kph performance at low temperatures. safety is enhanced by using a safe coating for the electrolyte and the separator. a real - time fault testing system allows safe and fast refueling. ford announced a 2, 500 worker battery plant in marshall, michigan using catl technology. the facility would be a ford subsidiary. making the batteries domestically would enable ford customers to access federal subsidies. the project was paused after lawmakers questioned the tax subsidies. in november 2023, catl and stellantis announced that they are considering the possibility of a joint investment in the form of a joint venture with equivalent contributions. on 7 december 2023, catl and hong kong science and technology parks corporation ( hkstp ) signed a memorandum of understanding to establish a catl research center at the hkstp with investment of over hkd 1. 2 billion. in 2023, the world intellectual property organization ( wipo ) β s annual pct review ranked catl ' s number of patent applications published under the pct system as 8th in the world, with 1, 799 patent applications being published during 2023. in april 2024, catl announced tener, a large scale stationary energy storage system. it is claimed to feature all - round safety, zero degradation over five - years and 6. 25 mwh capacity per unit. it incorporates biomimetic sei ( solid electrolyte interphase ) and self - assembled electrolyte technologies. in august 2024, american legislators marco rubio and john moolenaar asked defense secretary lloyd austin to add catl to a list of companies prohibited
##ate flux which is the volumetric flow rate per unit of membrane area. the solute sieving coefficient and hydraulic permeability allow the quick assessment of the synthetic membrane performance. = = membrane separation processes = = membrane separation processes have a very important role in the separation industry. nevertheless, they were not considered technically important until the mid - 1970s. membrane separation processes differ based on separation mechanisms and size of the separated particles. the widely used membrane processes include microfiltration, ultrafiltration, nanofiltration, reverse osmosis, electrolysis, dialysis, electrodialysis, gas separation, vapor permeation, pervaporation, membrane distillation, and membrane contactors. all processes except for pervaporation involve no phase change. all processes except electrodialysis are pressure driven. microfiltration and ultrafiltration is widely used in food and beverage processing ( beer microfiltration, apple juice ultrafiltration ), biotechnological applications and pharmaceutical industry ( antibiotic production, protein purification ), water purification and wastewater treatment, the microelectronics industry, and others. nanofiltration and reverse osmosis membranes are mainly used for water purification purposes. dense membranes are utilized for gas separations ( removal of co2 from natural gas, separating n2 from air, organic vapor removal from air or a nitrogen stream ) and sometimes in membrane distillation. the later process helps in the separation of azeotropic compositions reducing the costs of distillation processes. = = pore size and selectivity = = the pore sizes of technical membranes are specified differently depending on the manufacturer. one common distinction is by nominal pore size. it describes the maximum pore size distribution and gives only vague information about the retention capacity of a membrane. the exclusion limit or " cut - off " of the membrane is usually specified in the form of nmwc ( nominal molecular weight cut - off, or mwco, molecular weight cut off, with units in dalton ). it is defined as the minimum molecular weight of a globular molecule that is retained to 90 % by the membrane. the cut - off, depending on the method, can by converted to so - called d90, which is then expressed in a metric unit. in practice the mwco of the membrane should be at least 20 % lower than the molecular weight of the molecule that is to be separated. using track etched mica membranes beck and schultz demonstrated that hindered diffusion of molecules in pores can be described by the rankin equation. filter membranes are divided into four
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 ),
tissue engineering. it is the first bioreactor in the world to have a spherical glass chamber with biaxial rotation ; specifically to mimic the rotation of the fetus in the womb ; which provides a conducive environment for the growth of tissues. multiple forms of mechanical stimulation have also been combined into a single bioreactor. using gene expression analysis, one academic study found that applying a combination of cyclic strain and ultrasound stimulation to pre - osteoblast cells in a bioreactor accelerated matrix maturation and differentiation. the technology of this combined stimulation bioreactor could be used to grow bone cells more quickly and effectively in future clinical stem cell therapies. mc2 biotek has also developed a bioreactor known as prototissue that uses gas exchange to maintain high oxygen levels within the cell chamber ; improving upon previous bioreactors, since the higher oxygen levels help the cell grow and undergo normal cell respiration. active areas of research on bioreactors includes increasing production scale and refining the physiological environment, both of which could improve the efficiency and efficacy of bioreactors in research or clinical use. bioreactors are currently used to study, among other things, cell and tissue level therapies, cell and tissue response to specific physiological environment changes, and development of disease and injury. = = = long fiber generation = = = in 2013, a group from the university of tokyo developed cell laden fibers up to a meter in length and on the order of 100 ΞΌm in size. these fibers were created using a microfluidic device that forms a double coaxial laminar flow. each ' layer ' of the microfluidic device ( cells seeded in ecm, a hydrogel sheath, and finally a calcium chloride solution ). the seeded cells culture within the hydrogel sheath for several days, and then the sheath is removed with viable cell fibers. various cell types were inserted into the ecm core, including myocytes, endothelial cells, nerve cell fibers, and epithelial cell fibers. this group then showed that these fibers can be woven together to fabricate tissues or organs in a mechanism similar to textile weaving. fibrous morphologies are advantageous in that they provide an alternative to traditional scaffold design, and many organs ( such as muscle ) are composed of fibrous cells. = = = bioartificial organs = = = an artificial organ is an engineered device that can be extra corporeal or implanted to support impaired or failing organ
when the hydration shell of a protein is filled with at least 0. 6 gram of water per gram of protein, a significant anti - correlation between the vibrational free energy and the potential energy of energy - minimized conformers is observed. this means that low potential energy, well - hydrated, protein conformers tend to be more rigid than high - energy ones. on the other hand, in the case of casp target 624, when its hydration shell is filled, a significant average energy gap is observed between the crystal structure and the best conformers proposed during the prediction experiment, strongly suggesting that including explicit water molecules may help identifying unlikely conformers among good - looking ones.
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 channel, or if noise is detected from adjacent channels or non - wi - fi sources. nevertheless, wi - fi networks are still susceptible to the hidden node and exposed node problem. a standard speed wi - fi signal occupies five channels in the 2. 4 ghz band. interference can be caused by overlapping channels. any two channel numbers that differ by five or more, such as 2 and 7, do not overlap ( no adjacent - channel interference ). the oft - repeated adage that channels 1, 6, and 11 are the only non - overlapping channels is, therefore, not accurate. channels 1, 6, and 11 are the only group of three non - overlapping channels in north america. however, whether the overlap is significant depends on physical spacing. channels that are four apart interfere a negligible amount β much less than reusing channels ( which causes co - channel interference ) β if transmitters are at least a few metres apart. in europe and japan where channel 13 is available, using channels 1, 5, 9, and 13 for 802. 11g and 802. 11n is viable and recommended. however, multiple 2. 4 ghz 802. 11b and 802. 11g access - points default to the same channel on initial startup, contributing to congestion on certain channels. wi - fi pollution, or an excessive number of access points in the area, can prevent access and interfere with other devices ' use of other access points as well as with decreased signal - to - noise ratio ( snr ) between access points. these issues can become a problem in high - density areas, such as large apartment complexes or office buildings with multiple wi - fi access points. other devices use the 2. 4 ghz band : microwave ovens, ism band devices, security cameras, zigbee devices, bluetooth devices, video senders, cordless phones, baby monitors, and, in some countries, amateur radio, all of which can cause significant additional interference. it is also an issue when municipalities or other large entities ( such as universities ) seek to provide large area coverage. on some 5 ghz bands interference from radar systems can occur in some places. for base stations that support those bands they employ dynamic frequency selection which listens for radar, and if it is found, it will not permit a network on that band. these bands can be used by low power transmitters without a licence, and with few restrictions. however, while unintended interference is common, users that have been found to cause deliberate interference ( particularly for attempting to
the following purposes : allowing cell attachment and migration, delivering and retaining cells and biochemical factors, enabling diffusion of vital cell nutrients and expressed products, and exerting certain mechanical and biological influences to modify the behaviour of the cell phase. in 2009, an interdisciplinary team led by the thoracic surgeon thorsten walles implanted the first bioartificial transplant that provides an innate vascular network for post - transplant graft supply successfully into a patient awaiting tracheal reconstruction. to achieve the goal of tissue reconstruction, scaffolds must meet some specific requirements. high porosity and adequate pore size are necessary to facilitate cell seeding and diffusion throughout the whole structure of both cells and nutrients. biodegradability is often an essential factor since scaffolds should preferably be absorbed by the surrounding tissues without the necessity of surgical removal. the rate at which degradation occurs has to coincide as much as possible with the rate of tissue formation : this means that while cells are fabricating their own natural matrix structure around themselves, the scaffold is able to provide structural integrity within the body and eventually it will break down leaving the newly formed tissue which will take over the mechanical load. injectability is also important for clinical uses. recent research on organ printing is showing how crucial a good control of the 3d environment is to ensure reproducibility of experiments and offer better results. = = = materials = = = material selection is an essential aspect of producing a scaffold. the materials utilized can be natural or synthetic and can be biodegradable or non - biodegradable. additionally, they must be biocompatible, meaning that they do not cause any adverse effects to cells. silicone, for example, is a synthetic, non - biodegradable material commonly used as a drug delivery material, while gelatin is a biodegradable, natural material commonly used in cell - culture scaffolds the material needed for each application is different, and dependent on the desired mechanical properties of the material. tissue engineering of long bone defects for example, will require a rigid scaffold with a compressive strength similar to that of cortical bone ( 100 - 150 mpa ), which is much higher compared to a scaffold for skin regeneration. there are a few versatile synthetic materials used for many different scaffold applications. one of these commonly used materials is polylactic acid ( pla ), a synthetic polymer. pla β polylactic acid. this is a polyester which
Question: What paired organs together receive about 25 percent of cardiac output and are protected in the retroperitoneal space by the renal fat pad and overlying ribs and muscle?
A) brain
B) kidneys
C) lungs
D) hands
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B) kidneys
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Context:
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
. 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
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.
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
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
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 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,
, 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
the richness of the universe teaches us modesty and guides us to search for both primitive and intelligent forms of life elsewhere without prejudice.
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
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
Question: The diversity of life on earth today is the result of what?
A) evolution
B) spontaneous mutation
C) generation
D) mass extinction
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A) evolution
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Context:
and is invariant under the process of counting. an identity is an equation that remains true for all values of its variables. there are also inequalities that remain true when the values of their variables change. the distance between two points on a number line is not changed by adding the same quantity to both numbers. on the other hand, multiplication does not have this same property, as distance is not invariant under multiplication. angles and ratios of distances are invariant under scalings, rotations, translations and reflections. these transformations produce similar shapes, which is the basis of trigonometry. in contrast, angles and ratios are not invariant under non - uniform scaling ( such as stretching ). the sum of a triangle ' s interior angles ( 180Β° ) is invariant under all the above operations. as another example, all circles are similar : they can be transformed into each other and the ratio of the circumference to the diameter is invariant ( denoted by the greek letter Ο ( pi ) ). some more complicated examples : the real part and the absolute value of a complex number are invariant under complex conjugation. the tricolorability of knots. the degree of a polynomial is invariant under a linear change of variables. the dimension and homology groups of a topological object are invariant under homeomorphism. the number of fixed points of a dynamical system is invariant under many mathematical operations. euclidean distance is invariant under orthogonal transformations. area is invariant under linear maps which have determinant Β±1 ( see equiareal map Β§ linear transformations ). some invariants of projective transformations include collinearity of three or more points, concurrency of three or more lines, conic sections, and the cross - ratio. the determinant, trace, eigenvectors, and eigenvalues of a linear endomorphism are invariant under a change of basis. in other words, the spectrum of a matrix is invariant under a change of basis. the principal invariants of tensors do not change with rotation of the coordinate system ( see invariants of tensors ). the singular values of a matrix are invariant under orthogonal transformations. lebesgue measure is invariant under translations. the variance of a probability distribution is invariant under translations of the real line. hence the variance of a random variable is unchanged after the addition of a constant. the fixed points of a transformation are the elements in the domain that are invariant under the transformation. they may, depending on the application, be called symmetric with respect to that transformation. for example,
the value of excess charge in the kernel of massive body ( and the opposite in sign excess charge at the surface ) caused by the influence of gravitational forces is determined.
the 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.
= = a simple example of invariance is expressed in our ability to count. for a finite set of objects of any kind, there is a number to which we always arrive, regardless of the order in which we count the objects in the set. the quantity β a cardinal number β is associated with the set, and is invariant under the process of counting. an identity is an equation that remains true for all values of its variables. there are also inequalities that remain true when the values of their variables change. the distance between two points on a number line is not changed by adding the same quantity to both numbers. on the other hand, multiplication does not have this same property, as distance is not invariant under multiplication. angles and ratios of distances are invariant under scalings, rotations, translations and reflections. these transformations produce similar shapes, which is the basis of trigonometry. in contrast, angles and ratios are not invariant under non - uniform scaling ( such as stretching ). the sum of a triangle ' s interior angles ( 180Β° ) is invariant under all the above operations. as another example, all circles are similar : they can be transformed into each other and the ratio of the circumference to the diameter is invariant ( denoted by the greek letter Ο ( pi ) ). some more complicated examples : the real part and the absolute value of a complex number are invariant under complex conjugation. the tricolorability of knots. the degree of a polynomial is invariant under a linear change of variables. the dimension and homology groups of a topological object are invariant under homeomorphism. the number of fixed points of a dynamical system is invariant under many mathematical operations. euclidean distance is invariant under orthogonal transformations. area is invariant under linear maps which have determinant Β±1 ( see equiareal map Β§ linear transformations ). some invariants of projective transformations include collinearity of three or more points, concurrency of three or more lines, conic sections, and the cross - ratio. the determinant, trace, eigenvectors, and eigenvalues of a linear endomorphism are invariant under a change of basis. in other words, the spectrum of a matrix is invariant under a change of basis. the principal invariants of tensors do not change with rotation of the coordinate system ( see invariants of tensors ). the singular values of a matrix are invariant under orthogonal transformations. lebesgue measure is invariant under translations. the variance of a probability distribution
the work studies some difference equations, which are connected with mejer ' s function.
calculus and its application to physics and other sciences, it is rather common to consider a variable, say y, whose possible values depend on the value of another variable, say x. in mathematical terms, the dependent variable y represents the value of a function of x. to simplify formulas, it is often useful to use the same symbol for the dependent variable y and the function mapping x onto y. for example, the state of a physical system depends on measurable quantities such as the pressure, the temperature, the spatial position,..., and all these quantities vary when the system evolves, that is, they are function of the time. in the formulas describing the system, these quantities are represented by variables which are dependent on the time, and thus considered implicitly as functions of the time. therefore, in a formula, a dependent variable is a variable that is implicitly a function of another ( or several other ) variables. an independent variable is a variable that is not dependent. the property of a variable to be dependent or independent depends often of the point of view and is not intrinsic. for example, in the notation f ( x, y, z ), the three variables may be all independent and the notation represents a function of three variables. on the other hand, if y and z depend on x ( are dependent variables ) then the notation represents a function of the single independent variable x. = = = examples = = = if one defines a function f from the real numbers to the real numbers by f ( x ) = x 2 + sin ( x + 4 ) { \ displaystyle f ( x ) = x ^ { 2 } + \ sin ( x + 4 ) } then x is a variable standing for the argument of the function being defined, which can be any real number. in the identity [UNK] i = 1 n i = n 2 + n 2 { \ displaystyle \ sum _ { i = 1 } ^ { n } i = { \ frac { n ^ { 2 } + n } { 2 } } } the variable i is a summation variable which designates in turn each of the integers 1, 2,..., n ( it is also called index because its variation is over a discrete set of values ) while n is a parameter ( it does not vary within the formula ). in the theory of polynomials, a polynomial of degree 2 is generally denoted as ax2 + bx + c, where a, b and c are called coefficients ( they are assumed to be
, 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
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
are independent of x define constant functions and are therefore called constant. for example, a constant of integration is an arbitrary constant function that is added to a particular antiderivative to obtain the other antiderivatives. because of the strong relationship between polynomials and polynomial functions, the term " constant " is often used to denote the coefficients of a polynomial, which are constant functions of the indeterminates. other specific names for variables are : an unknown is a variable in an equation which has to be solved for. an indeterminate is a symbol, commonly called variable, that appears in a polynomial or a formal power series. formally speaking, an indeterminate is not a variable, but a constant in the polynomial ring or the ring of formal power series. however, because of the strong relationship between polynomials or power series and the functions that they define, many authors consider indeterminates as a special kind of variables. a parameter is a quantity ( usually a number ) which is a part of the input of a problem, and remains constant during the whole solution of this problem. for example, in mechanics the mass and the size of a solid body are parameters for the study of its movement. in computer science, parameter has a different meaning and denotes an argument of a function. free variables and bound variables a random variable is a kind of variable that is used in probability theory and its applications. all these denominations of variables are of semantic nature, and the way of computing with them ( syntax ) is the same for all. = = = dependent and independent variables = = = in calculus and its application to physics and other sciences, it is rather common to consider a variable, say y, whose possible values depend on the value of another variable, say x. in mathematical terms, the dependent variable y represents the value of a function of x. to simplify formulas, it is often useful to use the same symbol for the dependent variable y and the function mapping x onto y. for example, the state of a physical system depends on measurable quantities such as the pressure, the temperature, the spatial position,..., and all these quantities vary when the system evolves, that is, they are function of the time. in the formulas describing the system, these quantities are represented by variables which are dependent on the time, and thus considered implicitly as functions of the time. therefore, in a formula, a dependent variable is a variable that is implicitly a function of another ( or several other ) variables. an independent variable
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
Question: In science, coefficients are used to balance what kind of equations?
A) mineral
B) liquid
C) chemical
D) isolated
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C) chemical
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Context:
as you read these words you are using a complex biological neural network. you have a highly interconnected set of some neurons to facilitate your reading, breathing, motion and thinking. each of your biological neurons, a rich assembly of tissue and chemistry, has the complexity, if not the speed, of a microprocessor. some of your neural structure was with you at birth. other parts have been established by experience.
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.
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
baby while they are in other parts of the house. the wavebands used vary by region, but analog baby monitors generally transmit with low power in the 16, 9. 3 β 49. 9 or 900 mhz wavebands, and digital systems in the 2. 4 ghz waveband. many baby monitors have duplex channels so the parent can talk to the baby, and cameras to show video of the baby. wireless microphone β a battery - powered microphone with a short - range transmitter that is handheld or worn on a person ' s body which transmits its sound by radio to a nearby receiver unit connected to a sound system. wireless microphones are used by public speakers, performers, and television personalities so they can move freely without trailing a microphone cord. traditionally, analog models transmit in fm on unused portions of the television broadcast frequencies in the vhf and uhf bands. some models transmit on two frequency channels for diversity reception to prevent nulls from interrupting transmission as the performer moves around. some models use digital modulation to prevent unauthorized reception by scanner radio receivers ; these operate in the 900 mhz, 2. 4 ghz or 6 ghz ism bands. european standards also support wireless multichannel audio systems ( wmas ) that can better support the use of large numbers of wireless microphones at a single event or venue. as of 2021, u. s. regulators were considering adopting rules for wmas. = = = data communication = = = wireless networking β automated radio links which transmit digital data between computers and other wireless devices using radio waves, linking the devices together transparently in a computer network. computer networks can transmit any form of data : in addition to email and web pages, they also carry phone calls ( voip ), audio, and video content ( called streaming media ). security is more of an issue for wireless networks than for wired networks since anyone nearby with a wireless modem can access the signal and attempt to log in. the radio signals of wireless networks are encrypted using wpa. wireless lan ( wireless local area network or wi - fi ) β based on the ieee 802. 11 standards, these are the most widely used computer networks, used to implement local area networks without cables, linking computers, laptops, cell phones, video game consoles, smart tvs and printers in a home or office together, and to a wireless router connecting them to the internet with a wire or cable connection. wireless routers in public places like libraries, hotels and coffee shops create wireless access points ( hotspots ) to allow the public to
listen ), generally in that order, although auscultation occurs prior to percussion and palpation for abdominal assessments. the clinical examination involves the study of : abdomen and rectum cardiovascular ( heart and blood vessels ) general appearance of the patient and specific indicators of disease ( nutritional status, presence of jaundice, pallor or clubbing ) genitalia ( and pregnancy if the patient is or could be pregnant ) head, eye, ear, nose, and throat ( heent ) musculoskeletal ( including spine and extremities ) neurological ( consciousness, awareness, brain, vision, cranial nerves, spinal cord and peripheral nerves ) psychiatric ( orientation, mental state, mood, evidence of abnormal perception or thought ). respiratory ( large airways and lungs ) skin vital signs including height, weight, body temperature, blood pressure, pulse, respiration rate, and hemoglobin oxygen saturation it is to likely focus on areas of interest highlighted in the medical history and may not include everything listed above. the treatment plan may include ordering additional medical laboratory tests and medical imaging studies, starting therapy, referral to a specialist, or watchful observation. a follow - up may be advised. depending upon the health insurance plan and the managed care system, various forms of " utilization review ", such as prior authorization of tests, may place barriers on accessing expensive services. the medical decision - making ( mdm ) process includes the analysis and synthesis of all the above data to come up with a list of possible diagnoses ( the differential diagnoses ), along with an idea of what needs to be done to obtain a definitive diagnosis that would explain the patient ' s problem. on subsequent visits, the process may be repeated in an abbreviated manner to obtain any new history, symptoms, physical findings, lab or imaging results, or specialist consultations. = = institutions = = contemporary medicine is, in general, conducted within health care systems. legal, credentialing, and financing frameworks are established by individual governments, augmented on occasion by international organizations, such as churches. the characteristics of any given health care system have a significant impact on the way medical care is provided. from ancient times, christian emphasis on practical charity gave rise to the development of systematic nursing and hospitals, and the catholic church today remains the largest non - government provider of medical services in the world. advanced industrial countries ( with the exception of the united states ) and many developing countries provide medical services through a system of universal health care that aims to
to maintain the culture, such as the creation of capillary networks within the tissue. another issue with tissue culture is introducing the proper factors or stimuli required to induce functionality. in many cases, simple maintenance culture is not sufficient. growth factors, hormones, specific metabolites or nutrients, chemical and physical stimuli are sometimes required. for example, certain cells respond to changes in oxygen tension as part of their normal development, such as chondrocytes, which must adapt to low oxygen conditions or hypoxia during skeletal development. others, such as endothelial cells, respond to shear stress from fluid flow, which is encountered in blood vessels. mechanical stimuli, such as pressure pulses seem to be beneficial to all kind of cardiovascular tissue such as heart valves, blood vessels or pericardium. = = = bioreactors = = = in tissue engineering, a bioreactor is a device that attempts to simulate a physiological environment in order to promote cell or tissue growth in vitro. a physiological environment can consist of many different parameters such as temperature, pressure, oxygen or carbon dioxide concentration, or osmolality of fluid environment, and it can extend to all kinds of biological, chemical or mechanical stimuli. therefore, there are systems that may include the application of forces such as electromagnetic forces, mechanical pressures, or fluid pressures to the tissue. these systems can be two - or three - dimensional setups. bioreactors can be used in both academic and industry applications. general - use and application - specific bioreactors are also commercially available, which may provide static chemical stimulation or a combination of chemical and mechanical stimulation. cell proliferation and differentiation are largely influenced by mechanical and biochemical cues in the surrounding extracellular matrix environment. bioreactors are typically developed to replicate the specific physiological environment of the tissue being grown ( e. g., flex and fluid shearing for heart tissue growth ). this can allow specialized cell lines to thrive in cultures replicating their native environments, but it also makes bioreactors attractive tools for culturing stem cells. a successful stem - cell - based bioreactor is effective at expanding stem cells with uniform properties and / or promoting controlled, reproducible differentiation into selected mature cell types. there are a variety of bioreactors designed for 3d cell cultures. there are small plastic cylindrical chambers, as well as glass chambers, with regulated internal humidity and moisture specifically engineered for the purpose of growing cells in three dimensions. the bioreactor uses bioactive synthetic materials such as polyethylene terephthala
the structure of the boundary hilbert - space and the condition that amplitudes behave appropriately under compositions determine the face amplitude of a spinfoam theory. in quantum gravity the face amplitude turns out to be simpler than originally thought.
required. for example, certain cells respond to changes in oxygen tension as part of their normal development, such as chondrocytes, which must adapt to low oxygen conditions or hypoxia during skeletal development. others, such as endothelial cells, respond to shear stress from fluid flow, which is encountered in blood vessels. mechanical stimuli, such as pressure pulses seem to be beneficial to all kind of cardiovascular tissue such as heart valves, blood vessels or pericardium. = = = bioreactors = = = in tissue engineering, a bioreactor is a device that attempts to simulate a physiological environment in order to promote cell or tissue growth in vitro. a physiological environment can consist of many different parameters such as temperature, pressure, oxygen or carbon dioxide concentration, or osmolality of fluid environment, and it can extend to all kinds of biological, chemical or mechanical stimuli. therefore, there are systems that may include the application of forces such as electromagnetic forces, mechanical pressures, or fluid pressures to the tissue. these systems can be two - or three - dimensional setups. bioreactors can be used in both academic and industry applications. general - use and application - specific bioreactors are also commercially available, which may provide static chemical stimulation or a combination of chemical and mechanical stimulation. cell proliferation and differentiation are largely influenced by mechanical and biochemical cues in the surrounding extracellular matrix environment. bioreactors are typically developed to replicate the specific physiological environment of the tissue being grown ( e. g., flex and fluid shearing for heart tissue growth ). this can allow specialized cell lines to thrive in cultures replicating their native environments, but it also makes bioreactors attractive tools for culturing stem cells. a successful stem - cell - based bioreactor is effective at expanding stem cells with uniform properties and / or promoting controlled, reproducible differentiation into selected mature cell types. there are a variety of bioreactors designed for 3d cell cultures. there are small plastic cylindrical chambers, as well as glass chambers, with regulated internal humidity and moisture specifically engineered for the purpose of growing cells in three dimensions. the bioreactor uses bioactive synthetic materials such as polyethylene terephthalate membranes to surround the spheroid cells in an environment that maintains high levels of nutrients. they are easy to open and close, so that cell spheroids can be removed for testing, yet the chamber is able to maintain 100 % humidity throughout. this humidity is important to achieve maximum cell growth and function. the
the 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
fluid dynamics video demonstrating the evolution of dynamic stall on a wind turbine blade.
Question: What connection is required for a newborn baby to begin breathing?
A) connection to a ventilator
B) connection to a heat source
C) connection to the father
D) connection to the placenta
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D) connection to the placenta
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Context:
the thickness and the density of the material to be measured. the method is used for containers of liquids or of grainy substances thickness gauges : if the material is of constant density, the signal measured by the radiation detector depends on the thickness of the material. this is useful for continuous production, like of paper, rubber, etc. electrostatic control - to avoid the build - up of static electricity in production of paper, plastics, synthetic textiles, etc., a ribbon - shaped source of the alpha emitter 241am can be placed close to the material at the end of the production line. the source ionizes the air to remove electric charges on the material. radioactive tracers - since radioactive isotopes behave, chemically, mostly like the inactive element, the behavior of a certain chemical substance can be followed by tracing the radioactivity. examples : adding a gamma tracer to a gas or liquid in a closed system makes it possible to find a hole in a tube. adding a tracer to the surface of the component of a motor makes it possible to measure wear by measuring the activity of the lubricating oil. oil and gas exploration - nuclear well logging is used to help predict the commercial viability of new or existing wells. the technology involves the use of a neutron or gamma - ray source and a radiation detector which are lowered into boreholes to determine the properties of the surrounding rock such as porosity and lithography. [ 1 ] road construction - nuclear moisture / density gauges are used to determine the density of soils, asphalt, and concrete. typically a cesium - 137 source is used. = = = commercial applications = = = radioluminescence tritium illumination : tritium is used with phosphor in rifle sights to increase nighttime firing accuracy. some runway markers and building exit signs use the same technology, to remain illuminated during blackouts. betavoltaics. smoke detector : an ionization smoke detector includes a tiny mass of radioactive americium - 241, which is a source of alpha radiation. two ionisation chambers are placed next to each other. both contain a small source of 241am that gives rise to a small constant current. one is closed and serves for comparison, the other is open to ambient air ; it has a gridded electrode. when smoke enters the open chamber, the current is disrupted as the smoke particles attach to the charged ions and restore them to a neutral electrical state. this reduces the current in the open chamber. when the current drops below a certain threshold, the
has rest mass and volume ( it takes up space ) and is made up of particles. the particles that make up matter have rest mass as well β not all particles have rest mass, such as the photon. matter can be a pure chemical substance or a mixture of substances. = = = = atom = = = = the atom is the basic unit of chemistry. it consists of a dense core called the atomic nucleus surrounded by a space occupied by an electron cloud. the nucleus is made up of positively charged protons and uncharged neutrons ( together called nucleons ), while the electron cloud consists of negatively charged electrons which orbit the nucleus. in a neutral atom, the negatively charged electrons balance out the positive charge of the protons. the nucleus is dense ; the mass of a nucleon is approximately 1, 836 times that of an electron, yet the radius of an atom is about 10, 000 times that of its nucleus. the atom is also the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state ( s ), coordination number, and preferred types of bonds to form ( e. g., metallic, ionic, covalent ). = = = = element = = = = a chemical element is a pure substance which is composed of a single type of atom, characterized by its particular number of protons in the nuclei of its atoms, known as the atomic number and represented by the symbol z. the mass number is the sum of the number of protons and neutrons in a nucleus. although all the nuclei of all atoms belonging to one element will have the same atomic number, they may not necessarily have the same mass number ; atoms of an element which have different mass numbers are known as isotopes. for example, all atoms with 6 protons in their nuclei are atoms of the chemical element carbon, but atoms of carbon may have mass numbers of 12 or 13. the standard presentation of the chemical elements is in the periodic table, which orders elements by atomic number. the periodic table is arranged in groups, or columns, and periods, or rows. the periodic table is useful in identifying periodic trends. = = = = compound = = = = a compound is a pure chemical substance composed of more than one element. the properties of a compound bear little similarity to those of its elements. the standard nomenclature of compounds is set by the international union of pure and applied chemistry ( iupac ). organic compounds are named
final version. to appear in discrete and continuous dynamical systems - a.
please refer to the abstract part in the paper.
process by which a genotype encoded in dna gives rise to an observable phenotype in the proteins of an organism ' s body. this process is summarized by the central dogma of molecular biology, which was formulated by francis crick in 1958. according to the central dogma, genetic information flows from dna to rna to protein. there are two gene expression processes : transcription ( dna to rna ) and translation ( rna to protein ). = = = gene regulation = = = the regulation of gene expression by environmental factors and during different stages of development can occur at each step of the process such as transcription, rna splicing, translation, and post - translational modification of a protein. gene expression can be influenced by positive or negative regulation, depending on which of the two types of regulatory proteins called transcription factors bind to the dna sequence close to or at a promoter. a cluster of genes that share the same promoter is called an operon, found mainly in prokaryotes and some lower eukaryotes ( e. g., caenorhabditis elegans ). in positive regulation of gene expression, the activator is the transcription factor that stimulates transcription when it binds to the sequence near or at the promoter. negative regulation occurs when another transcription factor called a repressor binds to a dna sequence called an operator, which is part of an operon, to prevent transcription. repressors can be inhibited by compounds called inducers ( e. g., allolactose ), thereby allowing transcription to occur. specific genes that can be activated by inducers are called inducible genes, in contrast to constitutive genes that are almost constantly active. in contrast to both, structural genes encode proteins that are not involved in gene regulation. in addition to regulatory events involving the promoter, gene expression can also be regulated by epigenetic changes to chromatin, which is a complex of dna and protein found in eukaryotic cells. = = = genes, development, and evolution = = = development is the process by which a multicellular organism ( plant or animal ) goes through a series of changes, starting from a single cell, and taking on various forms that are characteristic of its life cycle. there are four key processes that underlie development : determination, differentiation, morphogenesis, and growth. determination sets the developmental fate of a cell, which becomes more restrictive during development. differentiation is the process by which specialized cells arise from less specialized cells such as stem
is called its bandwidth ( bw ). for any given signal - to - noise ratio, a given bandwidth can carry the same amount of information regardless of where in the radio frequency spectrum it is located ; bandwidth is a measure of information - carrying capacity. the bandwidth required by a radio transmission depends on the data rate of the information being sent, and the spectral efficiency of the modulation method used ; how much data it can transmit in each unit of bandwidth. different types of information signals carried by radio have different data rates. for example, a television signal has a greater data rate than an audio signal. the radio spectrum, the total range of radio frequencies that can be used for communication in a given area, is a limited resource. each radio transmission occupies a portion of the total bandwidth available. radio bandwidth is regarded as an economic good which has a monetary cost and is in increasing demand. in some parts of the radio spectrum, the right to use a frequency band or even a single radio channel is bought and sold for millions of dollars. so there is an incentive to employ technology to minimize the bandwidth used by radio services. a slow transition from analog to digital radio transmission technologies began in the late 1990s. part of the reason for this is that digital modulation can often transmit more information ( a greater data rate ) in a given bandwidth than analog modulation, by using data compression algorithms, which reduce redundancy in the data to be sent, and more efficient modulation. other reasons for the transition is that digital modulation has greater noise immunity than analog, digital signal processing chips have more power and flexibility than analog circuits, and a wide variety of types of information can be transmitted using the same digital modulation. because it is a fixed resource which is in demand by an increasing number of users, the radio spectrum has become increasingly congested in recent decades, and the need to use it more effectively is driving many additional radio innovations such as trunked radio systems, spread spectrum ( ultra - wideband ) transmission, frequency reuse, dynamic spectrum management, frequency pooling, and cognitive radio. = = = itu frequency bands = = = the itu arbitrarily divides the radio spectrum into 12 bands, each beginning at a wavelength which is a power of ten ( 10n ) metres, with corresponding frequency of 3 times a power of ten, and each covering a decade of frequency or wavelength. each of these bands has a traditional name : it can be seen that the bandwidth, the range of frequencies, contained in each band is not equal but increases exponentially as the
this third part of the lecture series deals with the question : who will pay for your retirement? for western europe the answer may be ` ` nobody ' ', but for algeria the demography looks more promising.
an oscillation with a period of around 500 kb in guanine and cytosine content ( gc % ) is observed in the dna sequence of human chromosome 21. this oscillation is localized in the rightmost one - eighth region of the chromosome, from 43. 5 mb to 46. 5 mb. five cycles of oscillation are observed in this region with six gc - rich peaks and five gc - poor valleys. the gc - poor valleys comprise regions with low density of cpg islands and, alternating between the two dna strands, low gene density regions. consequently, the long - range oscillation of gc % result in spacing patterns of both cpg island density, and to a lesser extent, gene densities.
the prevalence of sexual reproduction ( " sex " ) in eukaryotes is an enigma of evolutionary biology. sex increases genetic variation only tells its long - term superiority in essence. the accumulation of harmful mutations causes an immediate and ubiquitous pressure for organisms. contrary to the common sense, our theoretical model suggests that reproductive rate can influence initiatively the accumulation of harmful mutations. the interaction of reproductive rate and the integrated harm of mutations causes a critical reproductive rate r *. a population will become irreversibly extinct once the reproductive rate reduces to lower than r *. a sexual population has a r * lower than 1 and an asexual population has a r * higher than 1. the mean reproductive rate of a population reached to the carrying capacity has to reduce to 1. that explains the widespread sex as well as the persistence of facultative and asexual organisms. computer simulations support significantly our conclusion.
, high ( near theoretical ) density and microstructural uniformity. the increasing use and diversity of specialty forms of ceramics adds to the diversity of process technologies to be used. thus, reinforcing fibers and filaments are mainly made by polymer, sol - gel, or cvd processes, but melt processing also has applicability. the most widely used specialty form is layered structures, with tape casting for electronic substrates and packages being pre - eminent. photo - lithography is of increasing interest for precise patterning of conductors and other components for such packaging. tape casting or forming processes are also of increasing interest for other applications, ranging from open structures such as fuel cells to ceramic composites. the other major layer structure is coating, where thermal spraying is very important, but chemical and physical vapor deposition and chemical ( e. g., sol - gel and polymer pyrolysis ) methods are all seeing increased use. besides open structures from formed tape, extruded structures, such as honeycomb catalyst supports, and highly porous structures, including various foams, for example, reticulated foam, are of increasing use. densification of consolidated powder bodies continues to be achieved predominantly by ( pressureless ) sintering. however, the use of pressure sintering by hot pressing is increasing, especially for non - oxides and parts of simple shapes where higher quality ( mainly microstructural homogeneity ) is needed, and larger size or multiple parts per pressing can be an advantage. = = the sintering process = = the principles of sintering - based methods are simple ( " sinter " has roots in the english " cinder " ). the firing is done at a temperature below the melting point of the ceramic. once a roughly - held - together object called a " green body " is made, it is fired in a kiln, where atomic and molecular diffusion processes give rise to significant changes in the primary microstructural features. this includes the gradual elimination of porosity, which is typically accompanied by a net shrinkage and overall densification of the component. thus, the pores in the object may close up, resulting in a denser product of significantly greater strength and fracture toughness. another major change in the body during the firing or sintering process will be the establishment of the polycrystalline nature of the solid. significant grain growth tends to occur during sintering, with this growth depending on temperature and duration of the sintering process. the growth of
Question: How is population density expressed?
A) arable land per capita
B) number per area
C) number per household
D) per arable land
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B) number per area
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Context:
for the treatment of diabetes, was previously extracted from the pancreas of abattoir animals ( cattle or pigs ). the genetically engineered bacteria are able to produce large quantities of synthetic human insulin at relatively low cost. biotechnology has also enabled emerging therapeutics like gene therapy. the application of biotechnology to basic science ( for example through the human genome project ) has also dramatically improved our understanding of biology and as our scientific knowledge of normal and disease biology has increased, our ability to develop new medicines to treat previously untreatable diseases has increased as well. genetic testing allows the genetic diagnosis of vulnerabilities to inherited diseases, and can also be used to determine a child ' s parentage ( genetic mother and father ) or in general a person ' s ancestry. in addition to studying chromosomes to the level of individual genes, genetic testing in a broader sense includes biochemical tests for the possible presence of genetic diseases, or mutant forms of genes associated with increased risk of developing genetic disorders. genetic testing identifies changes in chromosomes, genes, or proteins. most of the time, testing is used to find changes that are associated with inherited disorders. the results of a genetic test can confirm or rule out a suspected genetic condition or help determine a person ' s chance of developing or passing on a genetic disorder. as of 2011 several hundred genetic tests were in use. since genetic testing may open up ethical or psychological problems, genetic testing is often accompanied by genetic counseling. = = = agriculture = = = genetically modified crops ( " gm crops ", or " biotech crops " ) are plants used in agriculture, the dna of which has been modified with genetic engineering techniques. in most cases, the main aim is to introduce a new trait that does not occur naturally in the species. biotechnology firms can contribute to future food security by improving the nutrition and viability of urban agriculture. furthermore, the protection of intellectual property rights encourages private sector investment in agrobiotechnology. examples in food crops include resistance to certain pests, diseases, stressful environmental conditions, resistance to chemical treatments ( e. g. resistance to a herbicide ), reduction of spoilage, or improving the nutrient profile of the crop. examples in non - food crops include production of pharmaceutical agents, biofuels, and other industrially useful goods, as well as for bioremediation. farmers have widely adopted gm technology. between 1996 and 2011, the total surface area of land cultivated with gm crops had increased by a factor of 94, from 17, 000 to 1, 600, 000 square
used to manufacture existing medicines relatively easily and cheaply. the first genetically engineered products were medicines designed to treat human diseases. to cite one example, in 1978 genentech developed synthetic humanized insulin by joining its gene with a plasmid vector inserted into the bacterium escherichia coli. insulin, widely used for the treatment of diabetes, was previously extracted from the pancreas of abattoir animals ( cattle or pigs ). the genetically engineered bacteria are able to produce large quantities of synthetic human insulin at relatively low cost. biotechnology has also enabled emerging therapeutics like gene therapy. the application of biotechnology to basic science ( for example through the human genome project ) has also dramatically improved our understanding of biology and as our scientific knowledge of normal and disease biology has increased, our ability to develop new medicines to treat previously untreatable diseases has increased as well. genetic testing allows the genetic diagnosis of vulnerabilities to inherited diseases, and can also be used to determine a child ' s parentage ( genetic mother and father ) or in general a person ' s ancestry. in addition to studying chromosomes to the level of individual genes, genetic testing in a broader sense includes biochemical tests for the possible presence of genetic diseases, or mutant forms of genes associated with increased risk of developing genetic disorders. genetic testing identifies changes in chromosomes, genes, or proteins. most of the time, testing is used to find changes that are associated with inherited disorders. the results of a genetic test can confirm or rule out a suspected genetic condition or help determine a person ' s chance of developing or passing on a genetic disorder. as of 2011 several hundred genetic tests were in use. since genetic testing may open up ethical or psychological problems, genetic testing is often accompanied by genetic counseling. = = = agriculture = = = genetically modified crops ( " gm crops ", or " biotech crops " ) are plants used in agriculture, the dna of which has been modified with genetic engineering techniques. in most cases, the main aim is to introduce a new trait that does not occur naturally in the species. biotechnology firms can contribute to future food security by improving the nutrition and viability of urban agriculture. furthermore, the protection of intellectual property rights encourages private sector investment in agrobiotechnology. examples in food crops include resistance to certain pests, diseases, stressful environmental conditions, resistance to chemical treatments ( e. g. resistance to a herbicide ), reduction of spoilage, or improving the nutrient profile of the crop. examples in non - food crops include production of
##artificial liver device, " temporary liver ", extracorporeal liver assist device ( elad ) : the human hepatocyte cell line ( c3a line ) in a hollow fiber bioreactor can mimic the hepatic function of the liver for acute instances of liver failure. a fully capable elad would temporarily function as an individual ' s liver, thus avoiding transplantation and allowing regeneration of their own liver. artificial pancreas : research involves using islet cells to regulate the body ' s blood sugar, particularly in cases of diabetes. biochemical factors may be used to cause human pluripotent stem cells to differentiate ( turn into ) cells that function similarly to beta cells, which are in an islet cell in charge of producing insulin. artificial bladders : anthony atala ( wake forest university ) has successfully implanted artificial bladders, constructed of cultured cells seeded onto a bladder - shaped scaffold, into seven out of approximately 20 human test subjects as part of a long - term experiment. cartilage : lab - grown cartilage, cultured in vitro on a scaffold, was successfully used as an autologous transplant to repair patients ' knees. scaffold - free cartilage : cartilage generated without the use of exogenous scaffold material. in this methodology, all material in the construct is cellular produced directly by the cells. bioartificial heart : doris taylor ' s lab constructed a biocompatible rat heart by re - cellularising a de - cellularised rat heart. this scaffold and cells were placed in a bioreactor, where it matured to become a partially or fully transplantable organ. the work was called a " landmark ". the lab first stripped the cells away from a rat heart ( a process called " decellularization " ) and then injected rat stem cells into the decellularized rat heart. tissue - engineered blood vessels : blood vessels that have been grown in a lab and can be used to repair damaged blood vessels without eliciting an immune response. tissue engineered blood vessels have been developed by many different approaches. they could be implanted as pre - seeded cellularized blood vessels, as acellular vascular grafts made with decellularized vessels or synthetic vascular grafts. artificial skin constructed from human skin cells embedded in a hydrogel, such as in the case of bio - printed constructs for battlefield burn repairs. artificial bone marrow : bone marrow cultured in vitro to
capable elad would temporarily function as an individual ' s liver, thus avoiding transplantation and allowing regeneration of their own liver. artificial pancreas : research involves using islet cells to regulate the body ' s blood sugar, particularly in cases of diabetes. biochemical factors may be used to cause human pluripotent stem cells to differentiate ( turn into ) cells that function similarly to beta cells, which are in an islet cell in charge of producing insulin. artificial bladders : anthony atala ( wake forest university ) has successfully implanted artificial bladders, constructed of cultured cells seeded onto a bladder - shaped scaffold, into seven out of approximately 20 human test subjects as part of a long - term experiment. cartilage : lab - grown cartilage, cultured in vitro on a scaffold, was successfully used as an autologous transplant to repair patients ' knees. scaffold - free cartilage : cartilage generated without the use of exogenous scaffold material. in this methodology, all material in the construct is cellular produced directly by the cells. bioartificial heart : doris taylor ' s lab constructed a biocompatible rat heart by re - cellularising a de - cellularised rat heart. this scaffold and cells were placed in a bioreactor, where it matured to become a partially or fully transplantable organ. the work was called a " landmark ". the lab first stripped the cells away from a rat heart ( a process called " decellularization " ) and then injected rat stem cells into the decellularized rat heart. tissue - engineered blood vessels : blood vessels that have been grown in a lab and can be used to repair damaged blood vessels without eliciting an immune response. tissue engineered blood vessels have been developed by many different approaches. they could be implanted as pre - seeded cellularized blood vessels, as acellular vascular grafts made with decellularized vessels or synthetic vascular grafts. artificial skin constructed from human skin cells embedded in a hydrogel, such as in the case of bio - printed constructs for battlefield burn repairs. artificial bone marrow : bone marrow cultured in vitro to 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
founded in 1976 and started the production of human proteins. genetically engineered human insulin was produced in 1978 and insulin - producing bacteria were commercialised in 1982. genetically modified food has been sold since 1994, with the release of the flavr savr tomato. the flavr savr was engineered to have a longer shelf life, but most current gm crops are modified to increase resistance to insects and herbicides. glofish, the first gmo designed as a pet, was sold in the united states in december 2003. in 2016 salmon modified with a growth hormone were sold. genetic engineering has been applied in numerous fields including research, medicine, industrial biotechnology and agriculture. in research, gmos are used to study gene function and expression through loss of function, gain of function, tracking and expression experiments. by knocking out genes responsible for certain conditions it is possible to create animal model organisms of human diseases. as well as producing hormones, vaccines and other drugs, genetic engineering has the potential to cure genetic diseases through gene therapy. chinese hamster ovary ( cho ) cells are used in industrial genetic engineering. additionally mrna vaccines are made through genetic engineering to prevent infections by viruses such as covid - 19. the same techniques that are used to produce drugs can also have industrial applications such as producing enzymes for laundry detergent, cheeses and other products. the rise of commercialised genetically modified crops has provided economic benefit to farmers in many different countries, but has also been the source of most of the controversy surrounding the technology. this has been present since its early use ; the first field trials were destroyed by anti - gm activists. although there is a scientific consensus that currently available food derived from gm crops poses no greater risk to human health than conventional food, critics consider gm food safety a leading concern. gene flow, impact on non - target organisms, control of the food supply and intellectual property rights have also been raised as potential issues. these concerns have led to the development of a regulatory framework, which started in 1975. it has led to an international treaty, the cartagena protocol on biosafety, that was adopted in 2000. individual countries have developed their own regulatory systems regarding gmos, with the most marked differences occurring between the united states and europe. = = overview = = genetic engineering is a process that alters the genetic structure of an organism by either removing or introducing dna, or modifying existing genetic material in situ. unlike traditional animal and plant breeding, which involves doing multiple crosses and then selecting for the organism with the desired phenotype,
in 2013, using a 3 - d scaffolding of matrigel in various configurations, substantial pancreatic organoids was produced in vitro. clusters of small numbers of cells proliferated into 40, 000 cells within one week. the clusters transform into cells that make either digestive enzymes or hormones like insulin, self - organizing into branched pancreatic organoids that resemble the pancreas. the cells are sensitive to the environment, such as gel stiffness and contact with other cells. individual cells do not thrive ; a minimum of four proximate cells was required for subsequent organoid development. modifications to the medium composition produced either hollow spheres mainly composed of pancreatic progenitors, or complex organoids that spontaneously undergo pancreatic morphogenesis and differentiation. maintenance and expansion of pancreatic progenitors require active notch and fgf signaling, recapitulating in vivo niche signaling interactions. the organoids were seen as potentially offering mini - organs for drug testing and for spare insulin - producing cells. aside from matrigel 3 - d scaffolds, other collagen gel systems have been developed. collagen / hyaluronic acid scaffolds have been used for modeling the mammary gland in vitro while co - coculturing epithelial and adipocyte cells. the hystem kit is another 3 - d platform containing ecm components and hyaluronic acid that has been used for cancer research. additionally, hydrogel constituents can be chemically modified to assist in crosslinking and enhance their mechanical properties. = = tissue culture = = in many cases, creation of functional tissues and biological structures in vitro requires extensive culturing to promote survival, growth and inducement of functionality. in general, the basic requirements of cells must be maintained in culture, which include oxygen, ph, humidity, temperature, nutrients and osmotic pressure maintenance. tissue engineered cultures also present additional problems in maintaining culture conditions. in standard cell culture, diffusion is often the sole means of nutrient and metabolite transport. however, as a culture becomes larger and more complex, such as the case with engineered organs and whole tissues, other mechanisms must be employed to maintain the culture, such as the creation of capillary networks within the tissue. another issue with tissue culture is introducing the proper factors or stimuli required to induce functionality. in many cases, simple maintenance culture is not sufficient. growth factors, hormones, specific metabolites or nutrients, chemical and physical stimuli are sometimes
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
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
self - organizing into branched pancreatic organoids that resemble the pancreas. the cells are sensitive to the environment, such as gel stiffness and contact with other cells. individual cells do not thrive ; a minimum of four proximate cells was required for subsequent organoid development. modifications to the medium composition produced either hollow spheres mainly composed of pancreatic progenitors, or complex organoids that spontaneously undergo pancreatic morphogenesis and differentiation. maintenance and expansion of pancreatic progenitors require active notch and fgf signaling, recapitulating in vivo niche signaling interactions. the organoids were seen as potentially offering mini - organs for drug testing and for spare insulin - producing cells. aside from matrigel 3 - d scaffolds, other collagen gel systems have been developed. collagen / hyaluronic acid scaffolds have been used for modeling the mammary gland in vitro while co - coculturing epithelial and adipocyte cells. the hystem kit is another 3 - d platform containing ecm components and hyaluronic acid that has been used for cancer research. additionally, hydrogel constituents can be chemically modified to assist in crosslinking and enhance their mechanical properties. = = tissue culture = = in many cases, creation of functional tissues and biological structures in vitro requires extensive culturing to promote survival, growth and inducement of functionality. in general, the basic requirements of cells must be maintained in culture, which include oxygen, ph, humidity, temperature, nutrients and osmotic pressure maintenance. tissue engineered cultures also present additional problems in maintaining culture conditions. in standard cell culture, diffusion is often the sole means of nutrient and metabolite transport. however, as a culture becomes larger and more complex, such as the case with engineered organs and whole tissues, other mechanisms must be employed to maintain the culture, such as the creation of capillary networks within the tissue. another issue with tissue culture is introducing the proper factors or stimuli required to induce functionality. in many cases, simple maintenance culture is not sufficient. growth factors, hormones, specific metabolites or nutrients, chemical and physical stimuli are sometimes required. for example, certain cells respond to changes in oxygen tension as part of their normal development, such as chondrocytes, which must adapt to low oxygen conditions or hypoxia during skeletal development. others, such as endothelial cells, respond to shear stress from fluid flow, which is encountered in
with the lambda virus. as well as inserting genes, the process can be used to remove, or " knock out ", genes. the new dna can be inserted randomly, or targeted to a specific part of the genome. an organism that is generated through genetic engineering is considered to be genetically modified ( gm ) and the resulting entity is a genetically modified organism ( gmo ). the first gmo was a bacterium generated by herbert boyer and stanley cohen in 1973. rudolf jaenisch created the first gm animal when he inserted foreign dna into a mouse in 1974. the first company to focus on genetic engineering, genentech, was founded in 1976 and started the production of human proteins. genetically engineered human insulin was produced in 1978 and insulin - producing bacteria were commercialised in 1982. genetically modified food has been sold since 1994, with the release of the flavr savr tomato. the flavr savr was engineered to have a longer shelf life, but most current gm crops are modified to increase resistance to insects and herbicides. glofish, the first gmo designed as a pet, was sold in the united states in december 2003. in 2016 salmon modified with a growth hormone were sold. genetic engineering has been applied in numerous fields including research, medicine, industrial biotechnology and agriculture. in research, gmos are used to study gene function and expression through loss of function, gain of function, tracking and expression experiments. by knocking out genes responsible for certain conditions it is possible to create animal model organisms of human diseases. as well as producing hormones, vaccines and other drugs, genetic engineering has the potential to cure genetic diseases through gene therapy. chinese hamster ovary ( cho ) cells are used in industrial genetic engineering. additionally mrna vaccines are made through genetic engineering to prevent infections by viruses such as covid - 19. the same techniques that are used to produce drugs can also have industrial applications such 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
Question: Type 1 diabetes results in the pancreas not being able to make what ?
A) glucose
B) hemoglobin
C) insulin
D) sugar
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C) insulin
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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
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
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
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
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 )
##vary. ongoing research on the molecular phylogenetics of living plants appears to show that the angiosperms are a sister clade to the gymnosperms. = = plant physiology = = plant physiology encompasses all the internal chemical and physical activities of plants associated with life. chemicals obtained from the air, soil and water form the basis of all plant metabolism. the energy of sunlight, captured by oxygenic photosynthesis and released by cellular respiration, is the basis of almost all life. photoautotrophs, including all green plants, algae and cyanobacteria gather energy directly from sunlight by photosynthesis. heterotrophs including all animals, all fungi, all completely parasitic plants, and non - photosynthetic bacteria take in organic molecules produced by photoautotrophs and respire them or use them in the construction of cells and tissues. respiration is the oxidation of carbon compounds by breaking them down into simpler structures to release the energy they contain, essentially the opposite of photosynthesis. molecules are moved within plants by transport processes that operate at a variety of spatial scales. subcellular transport of ions, electrons and molecules such as water and enzymes occurs across cell membranes. minerals and water are transported from roots to other parts of the plant in the transpiration stream. diffusion, osmosis, and active transport and mass flow are all different ways transport can occur. examples of elements that plants need to transport are nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. in vascular plants, these elements are extracted from the soil as soluble ions by the roots and transported throughout the plant in the xylem. most of the elements required for plant nutrition come from the chemical breakdown of soil minerals. sucrose produced by photosynthesis is transported from the leaves to other parts of the plant in the phloem and plant hormones are transported by a variety of processes. = = = plant hormones = = = plants are not passive, but respond to external signals such as light, touch, and injury by moving or growing towards or away from the stimulus, as appropriate. tangible evidence of touch sensitivity is the almost instantaneous collapse of leaflets of mimosa pudica, the insect traps of venus flytrap and bladderworts, and the pollinia of orchids. the hypothesis that plant growth and development is coordinated by plant hormones or plant growth regulators first emerged in the late 19th century. darwin experimented on the movements of plant shoots and roots towards light and gravity, and concluded " it is hardly an ex
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
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
##nosperms and angiosperms. gymnosperms produce " naked seeds " not fully enclosed in an ovary ; modern representatives include conifers, cycads, ginkgo, and gnetales. angiosperms produce seeds enclosed in a structure such as a carpel or an ovary. ongoing research on the molecular phylogenetics of living plants appears to show that the angiosperms are a sister clade to the gymnosperms. = = plant physiology = = plant physiology encompasses all the internal chemical and physical activities of plants associated with life. chemicals obtained from the air, soil and water form the basis of all plant metabolism. the energy of sunlight, captured by oxygenic photosynthesis and released by cellular respiration, is the basis of almost all life. photoautotrophs, including all green plants, algae and cyanobacteria gather energy directly from sunlight by photosynthesis. heterotrophs including all animals, all fungi, all completely parasitic plants, and non - photosynthetic bacteria take in organic molecules produced by photoautotrophs and respire them or use them in the construction of cells and tissues. respiration is the oxidation of carbon compounds by breaking them down into simpler structures to release the energy they contain, essentially the opposite of photosynthesis. molecules are moved within plants by transport processes that operate at a variety of spatial scales. subcellular transport of ions, electrons and molecules such as water and enzymes occurs across cell membranes. minerals and water are transported from roots to other parts of the plant in the transpiration stream. diffusion, osmosis, and active transport and mass flow are all different ways transport can occur. examples of elements that plants need to transport are nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. in vascular plants, these elements are extracted from the soil as soluble ions by the roots and transported throughout the plant in the xylem. most of the elements required for plant nutrition come from the chemical breakdown of soil minerals. sucrose produced by photosynthesis is transported from the leaves to other parts of the plant in the phloem and plant hormones are transported by a variety of processes. = = = plant hormones = = = plants are not passive, but respond to external signals such as light, touch, and injury by moving or growing towards or away from the stimulus, as appropriate. tangible evidence of touch sensitivity is the almost instantaneous collapse of leaflets of mimosa pudica, the insect traps of
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
Question: Photosynthesis produces oxygen as a byproduct, and respiration produces what as a byproduct?
A) carbon dioxide
B) carbon monoxide
C) nitrogen
D) ozone
|
A) carbon dioxide
|
Context:
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 :
with a synthetic, but naturally occurring, bone mineral. ultimately these ceramic materials may be used as bone replacements or with the incorporation of protein collagens, synthetic bones. durable actinide - containing ceramic materials have many applications such as in nuclear fuels for burning excess pu and in chemically - inert sources of alpha irradiation for power supply of unmanned space vehicles or to produce electricity for microelectronic devices. both use and disposal of radioactive actinides require their immobilization in a durable host material. nuclear waste long - lived radionuclides such as actinides are immobilized using chemically - durable crystalline materials based on polycrystalline ceramics and large single crystals. alumina ceramics are widely utilized in the chemical industry due to their excellent chemical stability and high resistance to corrosion. it is used as acid - resistant pump impellers and pump bodies, ensuring long - lasting performance in transferring aggressive fluids. they are also used in acid - carrying pipe linings to prevent contamination and maintain fluid purity, which is crucial in industries like pharmaceuticals and food processing. valves made from alumina ceramics demonstrate exceptional durability and resistance to chemical attack, making them reliable for controlling the flow of corrosive liquids. = = glass - ceramics = = glass - ceramic materials share many properties with both glasses and ceramics. glass - ceramics have an amorphous phase and one or more crystalline phases and are produced by a so - called " controlled crystallization ", which is typically avoided in glass manufacturing. glass - ceramics often contain a crystalline phase which constitutes anywhere from 30 % [ m / m ] to 90 % [ m / m ] of its composition by volume, yielding an array of materials with interesting thermomechanical properties. in the processing of glass - ceramics, molten glass is cooled down gradually before reheating and annealing. in this heat 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
the luminescence of 3 speleothem samples from the acquafredda karst system and 1 from the novella cave ( gessi bolognesi natural park, italy ) has been recorded using excitation by impulse xe - lamp. all these carbonate speleothems are believed to be formed only from active co2 from the air, because the bedrock of the cave consist of gypsum and does not contain carbonates. the obtained photos of luminescence record the climate changes during the speleothem growth. u / th and 14c dating proved that studied speleothems started to grow since about 5, 000 years ago. the detailed analyses of the luminescence records is still in progress.
##nosperms and angiosperms. gymnosperms produce " naked seeds " not fully enclosed in an ovary ; modern representatives include conifers, cycads, ginkgo, and gnetales. angiosperms produce seeds enclosed in a structure such as a carpel or an ovary. ongoing research on the molecular phylogenetics of living plants appears to show that the angiosperms are a sister clade to the gymnosperms. = = plant physiology = = plant physiology encompasses all the internal chemical and physical activities of plants associated with life. chemicals obtained from the air, soil and water form the basis of all plant metabolism. the energy of sunlight, captured by oxygenic photosynthesis and released by cellular respiration, is the basis of almost all life. photoautotrophs, including all green plants, algae and cyanobacteria gather energy directly from sunlight by photosynthesis. heterotrophs including all animals, all fungi, all completely parasitic plants, and non - photosynthetic bacteria take in organic molecules produced by photoautotrophs and respire them or use them in the construction of cells and tissues. respiration is the oxidation of carbon compounds by breaking them down into simpler structures to release the energy they contain, essentially the opposite of photosynthesis. molecules are moved within plants by transport processes that operate at a variety of spatial scales. subcellular transport of ions, electrons and molecules such as water and enzymes occurs across cell membranes. minerals and water are transported from roots to other parts of the plant in the transpiration stream. diffusion, osmosis, and active transport and mass flow are all different ways transport can occur. examples of elements that plants need to transport are nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. in vascular plants, these elements are extracted from the soil as soluble ions by the roots and transported throughout the plant in the xylem. most of the elements required for plant nutrition come from the chemical breakdown of soil minerals. sucrose produced by photosynthesis is transported from the leaves to other parts of the plant in the phloem and plant hormones are transported by a variety of processes. = = = plant hormones = = = plants are not passive, but respond to external signals such as light, touch, and injury by moving or growing towards or away from the stimulus, as appropriate. tangible evidence of touch sensitivity is the almost instantaneous collapse of leaflets of mimosa pudica, the insect traps of
##ta together form the monophyletic group or clade streptophytina. nonvascular land plants are embryophytes that lack the vascular tissues xylem and phloem. they include mosses, liverworts and hornworts. pteridophytic vascular plants with true xylem and phloem that reproduced by spores germinating into free - living gametophytes evolved during the silurian period and diversified into several lineages during the late silurian and early devonian. representatives of the lycopods have survived to the present day. by the end of the devonian period, several groups, including the lycopods, sphenophylls and progymnosperms, had independently evolved " megaspory " β their spores were of two distinct sizes, larger megaspores and smaller microspores. their reduced gametophytes developed from megaspores retained within the spore - producing organs ( megasporangia ) of the sporophyte, a condition known as endospory. seeds consist of an endosporic megasporangium surrounded by one or two sheathing layers ( integuments ). the young sporophyte develops within the seed, which on germination splits to release it. the earliest known seed plants date from the latest devonian famennian stage. following the evolution of the seed habit, seed plants diversified, giving rise to a number of now - extinct groups, including seed ferns, as well as the modern gymnosperms and angiosperms. gymnosperms produce " naked seeds " not fully enclosed in an ovary ; modern representatives include conifers, cycads, ginkgo, and gnetales. angiosperms produce seeds enclosed in a structure such as a carpel or an ovary. ongoing research on the molecular phylogenetics of living plants appears to show that the angiosperms are a sister clade to the gymnosperms. = = plant physiology = = plant physiology encompasses all the internal chemical and physical activities of plants associated with life. chemicals obtained from the air, soil and water form the basis of all plant metabolism. the energy of sunlight, captured by oxygenic photosynthesis and released by cellular respiration, is the basis of almost all life. photoautotrophs, including all green plants, algae and cyanobacteria gather energy directly from sunlight by photosynthesis. hetero
as for precipitation - toughened, partially stabilized zirconia. similarly, it is known that one can directionally solidify ceramic eutectic mixtures and hence obtain uniaxially aligned fiber composites. such composite processing has typically been limited to very simple shapes and thus suffers from serious economic problems due to high machining costs. there is a possibility for melt casting to be used for many of these approaches. potentially even more desirable is using melt - derived particles. in this method, quenching is done in a solid solution or in a fine eutectic structure, in which the particles are then processed by more typical ceramic powder processing methods into a useful body. there have also been preliminary attempts to use melt spraying as a means of forming composites by introducing the dispersed particulate, whisker, or fiber phase in conjunction with the melt spraying process. other methods besides melt infiltration to manufacture ceramic composites with long fiber reinforcement are chemical vapor infiltration and the infiltration of fiber preforms with organic precursor, which after pyrolysis yield an amorphous ceramic matrix, initially with a low density. with repeated cycles of infiltration and pyrolysis one of those types of ceramic matrix composites is produced. chemical vapor infiltration is used to manufacture carbon / carbon and silicon carbide reinforced with carbon or silicon carbide fibers. besides many process improvements, the first of two major needs for fiber composites is lower fiber costs. the second major need is fiber compositions or coatings, or composite processing, to reduce degradation that results from high - temperature composite exposure under oxidizing conditions. = = applications = = the products of technical ceramics include tiles used in the space shuttle program, gas burner nozzles, ballistic protection, nuclear fuel uranium oxide pellets, bio - medical implants, jet engine turbine blades, and missile nose cones. its products are often made from materials other than clay, chosen for their particular physical properties. these may be classified as follows : oxides : silica, alumina, zirconia non - oxides : carbides, borides, nitrides, silicides composites : particulate or whisker reinforced matrices, combinations of oxides and non - oxides ( e. g. polymers ). ceramics can be used in many technological industries. one application is the ceramic tiles on nasa ' s space shuttle, used to protect it and the future supersonic space planes from the searing heat of re - entry into
passive redundancy and active redundancy. both functions prevent performance decline from exceeding specification limits without human intervention using extra capacity. passive redundancy uses excess capacity to reduce the impact of component failures. one common form of passive redundancy is the extra strength of cabling and struts used in bridges. this extra strength allows some structural components to fail without bridge collapse. the extra strength used in the design is called the margin of safety. eyes and ears provide working examples of passive redundancy. vision loss in one eye does not cause blindness but depth perception is impaired. hearing loss in one ear does not cause deafness but directionality is lost. performance decline is commonly associated with passive redundancy when a limited number of failures occur. active redundancy eliminates performance declines by monitoring the performance of individual devices, and this monitoring is used in voting logic. the voting logic is linked to switching that automatically reconfigures the components. error detection and correction and the global positioning system ( gps ) are two examples of active redundancy. electrical power distribution provides an example of active redundancy. several power lines connect each generation facility with customers. each power line includes monitors that detect overload. each power line also includes circuit breakers. the combination of power lines provides excess capacity. circuit breakers disconnect a power line when monitors detect an overload. power is redistributed across the remaining lines. at the toronto airport, there are 4 redundant electrical lines. each of the 4 lines supply enough power for the entire airport. a spot network substation uses reverse current relays to open breakers to lines that fail, but lets power continue to flow the airport. electrical power systems use power scheduling to reconfigure active redundancy. computing systems adjust the production output of each generating facility when other generating facilities are suddenly lost. this prevents blackout conditions during major events such as an earthquake. = = disadvantages = = charles perrow, author of normal accidents, has said that sometimes redundancies backfire and produce less, not more reliability. this may happen in three ways : first, redundant safety devices result in a more complex system, more prone to errors and accidents. second, redundancy may lead to shirking of responsibility among workers. third, redundancy may lead to increased production pressures, resulting in a system that operates at higher speeds, but less safely. = = voting logic = = voting logic uses performance monitoring to determine how to reconfigure individual components
, 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
, 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
##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
Question: Volcanoes are termed active, dormant, or extinct depending on the possibility of the presence of what in chamber structures?
A) coal
B) sulpher
C) water
D) magma
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D) magma
|
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.
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.
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.
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 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.
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
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
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 )
of a point on the object, including whole - body translations and rotations ( rigid transformations ). deformation are changes in the relative position between internals points on the object, excluding rigid transformations, causing the body to change shape or size. strain is the relative internal deformation, the dimensionless change in shape of an infinitesimal cube of material relative to a reference configuration. mechanical strains are caused by mechanical stress, see stress - strain curve. the relationship between stress and strain is generally linear and reversible up until the yield point and the deformation is elastic. elasticity in materials occurs when applied stress does not surpass the energy required to break molecular bonds, allowing the material to deform reversibly and return to its original shape once the stress is removed. the linear relationship for a material is known as young ' s modulus. above the yield point, some degree of permanent distortion remains after unloading and is termed plastic deformation. the determination of the stress and strain throughout a solid object is given by the field of strength of materials and for a structure by structural analysis. in the above figure, it can be seen that the compressive loading ( indicated by the arrow ) has caused deformation in the cylinder so that the original shape ( dashed lines ) has changed ( deformed ) into one with bulging sides. the sides bulge because the material, although strong enough to not crack or otherwise fail, is not strong enough to support the load without change. as a result, the material is forced out laterally. internal forces ( in this case at right angles to the deformation ) resist the applied load. = = types of deformation = = depending on the type of material, size and geometry of the object, and the forces applied, various types of deformation may result. the image to the right shows the engineering stress vs. strain diagram for a typical ductile material such as steel. different deformation modes may occur under different conditions, as can be depicted using a deformation mechanism map. permanent deformation is irreversible ; the deformation stays even after removal of the applied forces, while the temporary deformation is recoverable as it disappears after the removal of applied forces. temporary deformation is also called elastic deformation, while the permanent deformation is called plastic deformation. = = = elastic deformation = = = the study of temporary or elastic deformation in the case of engineering strain is applied to materials used in mechanical and structural engineering, such as concrete and steel, which are subjected to very small deformations. engineering strain is modeled by infinitesimal strain theory, also called
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: Ciliary muscles control the shape of the lens, which bends light and focuses it on what?
A) the retina
B) the cornea
C) the vitreous fluid
D) the pupil
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A) the retina
|
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
##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
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
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
##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
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 = = = = =
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
Question: Convection in which part of the earth drives the movement of the plates of lithosphere over the earthβs surface?
A) atmosphere
B) ocean
C) mantle
D) upper crust
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C) mantle
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Context:
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.
can the apparent complexity we observe in the real world be generated from simple initial conditions via simple, deterministic rules?
and measuring radiation levels. the surveyor program conducted uncrewed lunar landings and takeoffs, as well as taking surface and regolith observations. despite the setback caused by the apollo 1 fire, which killed three astronauts, the program proceeded. apollo 8 was the first crewed spacecraft to leave low earth orbit and the first human spaceflight to reach the moon. the crew orbited the moon ten times on december 24 and 25, 1968, and then traveled safely back to earth. the three apollo 8 astronauts β frank borman, james lovell, and william anders β were the first humans to see the earth as a globe in space, the first to witness an earthrise, and the first to see and manually photograph the far side of the moon. the first lunar landing was conducted by apollo 11. commanded by neil armstrong with astronauts buzz aldrin and michael collins, apollo 11 was one of the most significant missions in nasa ' s history, marking the end of the space race when the soviet union gave up its lunar ambitions. as the first human to step on the surface of the moon, neil armstrong uttered the now famous words : that ' s one small step for man, one giant leap for mankind. nasa would conduct six total lunar landings as part of the apollo program, with apollo 17 concluding the program in 1972. = = = = end of apollo = = = = wernher von braun had advocated for nasa to develop a space station since the agency was created. in 1973, following the end of the apollo lunar missions, nasa launched its first space station, skylab, on the final launch of the saturn v. skylab reused a significant amount of apollo and saturn hardware, with a repurposed saturn v third stage serving as the primary module for the space station. damage to skylab during its launch required spacewalks to be performed by the first crew to make it habitable and operational. skylab hosted nine missions and was decommissioned in 1974 and deorbited in 1979, two years prior to the first launch of the space shuttle and any possibility of boosting its orbit. in 1975, the apollo β soyuz mission was the first ever international spaceflight and a major diplomatic accomplishment between the cold war rivals, which also marked the last flight of the apollo capsule. flown in 1975, a us apollo spacecraft docked with a soviet soyuz capsule. = = = interplanetary exploration and space science = = = during the 1960s, nasa started its space science and interplanetary probe program. the mariner program was its flagship
##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
fuel cells instead of batteries, and conducted the first american spacewalks and rendezvous operations. the ranger program was started in the 1950s as a response to soviet lunar exploration, however most missions ended in failure. the lunar orbiter program had greater success, mapping the surface in preparation for apollo landings, conducting meteoroid detection, and measuring radiation levels. the surveyor program conducted uncrewed lunar landings and takeoffs, as well as taking surface and regolith observations. despite the setback caused by the apollo 1 fire, which killed three astronauts, the program proceeded. apollo 8 was the first crewed spacecraft to leave low earth orbit and the first human spaceflight to reach the moon. the crew orbited the moon ten times on december 24 and 25, 1968, and then traveled safely back to earth. the three apollo 8 astronauts β frank borman, james lovell, and william anders β were the first humans to see the earth as a globe in space, the first to witness an earthrise, and the first to see and manually photograph the far side of the moon. the first lunar landing was conducted by apollo 11. commanded by neil armstrong with astronauts buzz aldrin and michael collins, apollo 11 was one of the most significant missions in nasa ' s history, marking the end of the space race when the soviet union gave up its lunar ambitions. as the first human to step on the surface of the moon, neil armstrong uttered the now famous words : that ' s one small step for man, one giant leap for mankind. nasa would conduct six total lunar landings as part of the apollo program, with apollo 17 concluding the program in 1972. = = = = end of apollo = = = = wernher von braun had advocated for nasa to develop a space station since the agency was created. in 1973, following the end of the apollo lunar missions, nasa launched its first space station, skylab, on the final launch of the saturn v. skylab reused a significant amount of apollo and saturn hardware, with a repurposed saturn v third stage serving as the primary module for the space station. damage to skylab during its launch required spacewalks to be performed by the first crew to make it habitable and operational. skylab hosted nine missions and was decommissioned in 1974 and deorbited in 1979, two years prior to the first launch of the space shuttle and any possibility of boosting its orbit. in 1975, the apollo β soyuz mission was the first ever international spaceflight and a major diplomatic accomplishment between the cold war
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
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.
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.
also launched missions to mercury in 2004, with the messenger probe demonstrating as the first use of a solar sail. nasa also launched probes to the outer solar system starting in the 1960s. pioneer 10 was the first probe to the outer planets, flying by jupiter, while pioneer 11 provided the first close up view of the planet. both probes became the first objects to leave the solar system. the voyager program launched in 1977, conducting flybys of jupiter and saturn, neptune, and uranus on a trajectory to leave the solar system. the galileo spacecraft, deployed from the space shuttle flight sts - 34, was the first spacecraft to orbit jupiter, discovering evidence of subsurface oceans on the europa and observed that the moon may hold ice or liquid water. a joint nasa - european space agency - italian space agency mission, cassini β huygens, was sent to saturn ' s moon titan, which, along with mars and europa, are the only celestial bodies in the solar system suspected of being capable of harboring life. cassini discovered three new moons of saturn and the huygens probe entered titan ' s atmosphere. the mission discovered evidence of liquid hydrocarbon lakes on titan and subsurface water oceans on the moon of enceladus, which could harbor life. finally launched in 2006, the new horizons mission was the first spacecraft to visit pluto and the kuiper belt. beyond interplanetary probes, nasa has launched many space telescopes. launched in the 1960s, the orbiting astronomical observatory were nasa ' s first orbital telescopes, providing ultraviolet, gamma - ray, x - ray, and infrared observations. nasa launched the orbiting geophysical observatory in the 1960s and 1970s to look down at earth and observe its interactions with the sun. the uhuru satellite was the first dedicated x - ray telescope, mapping 85 % of the sky and discovering a large number of black holes. launched in the 1990s and early 2000s, the great observatories program are among nasa ' s most powerful telescopes. the hubble space telescope was launched in 1990 on sts - 31 from the discovery and could view galaxies 15 billion light years away. a major defect in the telescope ' s mirror could have crippled the program, had nasa not used computer enhancement to compensate for the imperfection and launched five space shuttle servicing flights to replace the damaged components. the compton gamma ray observatory was launched from the atlantis on sts - 37 in 1991, discovering a possible source of antimatter at the center of the milky way and observing that the majority of gamma - ray bursts
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
Question: Simple eyes, like the human eye, have how many lenses?
A) one
B) none
C) two
D) four
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A) one
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Context:
##ta together form the monophyletic group or clade streptophytina. nonvascular land plants are embryophytes that lack the vascular tissues xylem and phloem. they include mosses, liverworts and hornworts. pteridophytic vascular plants with true xylem and phloem that reproduced by spores germinating into free - living gametophytes evolved during the silurian period and diversified into several lineages during the late silurian and early devonian. representatives of the lycopods have survived to the present day. by the end of the devonian period, several groups, including the lycopods, sphenophylls and progymnosperms, had independently evolved " megaspory " β their spores were of two distinct sizes, larger megaspores and smaller microspores. their reduced gametophytes developed from megaspores retained within the spore - producing organs ( megasporangia ) of the sporophyte, a condition known as endospory. seeds consist of an endosporic megasporangium surrounded by one or two sheathing layers ( integuments ). the young sporophyte develops within the seed, which on germination splits to release it. the earliest known seed plants date from the latest devonian famennian stage. following the evolution of the seed habit, seed plants diversified, giving rise to a number of now - extinct groups, including seed ferns, as well as the modern gymnosperms and angiosperms. gymnosperms produce " naked seeds " not fully enclosed in an ovary ; modern representatives include conifers, cycads, ginkgo, and gnetales. angiosperms produce seeds enclosed in a structure such as a carpel or an ovary. ongoing research on the molecular phylogenetics of living plants appears to show that the angiosperms are a sister clade to the gymnosperms. = = plant physiology = = plant physiology encompasses all the internal chemical and physical activities of plants associated with life. chemicals obtained from the air, soil and water form the basis of all plant metabolism. the energy of sunlight, captured by oxygenic photosynthesis and released by cellular respiration, is the basis of almost all life. photoautotrophs, including all green plants, algae and cyanobacteria gather energy directly from sunlight by photosynthesis. hetero
or lipids ( elaioplasts ). uniquely, streptophyte cells and those of the green algal order trentepohliales divide by construction of a phragmoplast as a template for building a cell plate late in cell division. the bodies of vascular plants including clubmosses, ferns and seed plants ( gymnosperms and angiosperms ) generally have aerial and subterranean subsystems. the shoots consist of stems bearing green photosynthesising leaves and reproductive structures. the underground vascularised roots bear root hairs at their tips and generally lack chlorophyll. non - vascular plants, the liverworts, hornworts and mosses do not produce ground - penetrating vascular roots and most of the plant participates in photosynthesis. the sporophyte generation is nonphotosynthetic in liverworts but may be able to contribute part of its energy needs by photosynthesis in mosses and hornworts. the root system and the shoot system are interdependent β the usually nonphotosynthetic root system depends on the shoot system for food, and the usually photosynthetic shoot system depends on water and minerals from the root system. cells in each system are capable of creating cells of the other and producing adventitious shoots or roots. stolons and tubers are examples of shoots that can grow roots. roots that spread out close to the surface, such as those of willows, can produce shoots and ultimately new plants. in the event that one of the systems is lost, the other can often regrow it. in fact it is possible to grow an entire plant from a single leaf, as is the case with plants in streptocarpus sect. saintpaulia, or even a single cell β which can dedifferentiate into a callus ( a mass of unspecialised cells ) that can grow into a new plant. in vascular plants, the xylem and phloem are the conductive tissues that transport resources between shoots and roots. roots are often adapted to store food such as sugars or starch, as in sugar beets and carrots. stems mainly provide support to the leaves and reproductive structures, but can store water in succulent plants such as cacti, food as in potato tubers, or reproduce vegetatively as in the stolons of strawberry plants or in the process of layering. leaves gather sunlight and carry out photosyn
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 :
unspecialised cells ) that can grow into a new plant. in vascular plants, the xylem and phloem are the conductive tissues that transport resources between shoots and roots. roots are often adapted to store food such as sugars or starch, as in sugar beets and carrots. stems mainly provide support to the leaves and reproductive structures, but can store water in succulent plants such as cacti, food as in potato tubers, or reproduce vegetatively as in the stolons of strawberry plants or in the process of layering. leaves gather sunlight and carry out photosynthesis. large, flat, flexible, green leaves are called foliage leaves. gymnosperms, such as conifers, cycads, ginkgo, and gnetophytes are seed - producing plants with open seeds. angiosperms are seed - producing plants that produce flowers and have enclosed seeds. woody plants, such as azaleas and oaks, undergo a secondary growth phase resulting in two additional types of tissues : wood ( secondary xylem ) and bark ( secondary phloem and cork ). all gymnosperms and many angiosperms are woody plants. some plants reproduce sexually, some asexually, and some via both means. although reference to major morphological categories such as root, stem, leaf, and trichome are useful, one has to keep in mind that these categories are linked through intermediate forms so that a continuum between the categories results. furthermore, structures can be seen as processes, that is, process combinations. = = systematic botany = = systematic botany is part of systematic biology, which is concerned with the range and diversity of organisms and their relationships, particularly as determined by their evolutionary history. it involves, or is related to, biological classification, scientific taxonomy and phylogenetics. biological classification is the method by which botanists group organisms into categories such as genera or species. biological classification is a form of scientific taxonomy. modern taxonomy is rooted in the work of carl linnaeus, who grouped species according to shared physical characteristics. these groupings have since been revised to align better with the darwinian principle of common descent β grouping organisms by ancestry rather than superficial characteristics. while scientists do not always agree on how to classify organisms, molecular phylogenetics, which uses dna sequences as data, has driven many recent revisions along evolutionary lines and is likely to continue to do so. the dominant classification system is called linnaean taxonomy. it includes ranks and binomi
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
pigmentation, chloroplast structure and nutrient reserves. the algal division charophyta, sister to the green algal division chlorophyta, is considered to contain the ancestor of true plants. the charophyte class charophyceae and the land plant sub - kingdom embryophyta together form the monophyletic group or clade streptophytina. nonvascular land plants are embryophytes that lack the vascular tissues xylem and phloem. they include mosses, liverworts and hornworts. pteridophytic vascular plants with true xylem and phloem that reproduced by spores germinating into free - living gametophytes evolved during the silurian period and diversified into several lineages during the late silurian and early devonian. representatives of the lycopods have survived to the present day. by the end of the devonian period, several groups, including the lycopods, sphenophylls and progymnosperms, had independently evolved " megaspory " β their spores were of two distinct sizes, larger megaspores and smaller microspores. their reduced gametophytes developed from megaspores retained within the spore - producing organs ( megasporangia ) of the sporophyte, a condition known as endospory. seeds consist of an endosporic megasporangium surrounded by one or two sheathing layers ( integuments ). the young sporophyte develops within the seed, which on germination splits to release it. the earliest known seed plants date from the latest devonian famennian stage. following the evolution of the seed habit, seed plants diversified, giving rise to a number of now - extinct groups, including seed ferns, as well as the modern gymnosperms and angiosperms. gymnosperms produce " naked seeds " not fully enclosed in an ovary ; modern representatives include conifers, cycads, ginkgo, and gnetales. angiosperms produce seeds enclosed in a structure such as a carpel or an ovary. ongoing research on the molecular phylogenetics of living plants appears to show that the angiosperms are a sister clade to the gymnosperms. = = plant physiology = = plant physiology encompasses all the internal chemical and physical activities of plants associated with life. chemicals obtained from the air, soil and water form
##ses, ferns and seed plants ( gymnosperms and angiosperms ) generally have aerial and subterranean subsystems. the shoots consist of stems bearing green photosynthesising leaves and reproductive structures. the underground vascularised roots bear root hairs at their tips and generally lack chlorophyll. non - vascular plants, the liverworts, hornworts and mosses do not produce ground - penetrating vascular roots and most of the plant participates in photosynthesis. the sporophyte generation is nonphotosynthetic in liverworts but may be able to contribute part of its energy needs by photosynthesis in mosses and hornworts. the root system and the shoot system are interdependent β the usually nonphotosynthetic root system depends on the shoot system for food, and the usually photosynthetic shoot system depends on water and minerals from the root system. cells in each system are capable of creating cells of the other and producing adventitious shoots or roots. stolons and tubers are examples of shoots that can grow roots. roots that spread out close to the surface, such as those of willows, can produce shoots and ultimately new plants. in the event that one of the systems is lost, the other can often regrow it. in fact it is possible to grow an entire plant from a single leaf, as is the case with plants in streptocarpus sect. saintpaulia, or even a single cell β which can dedifferentiate into a callus ( a mass of unspecialised cells ) that can grow into a new plant. in vascular plants, the xylem and phloem are the conductive tissues that transport resources between shoots and roots. roots are often adapted to store food such as sugars or starch, as in sugar beets and carrots. stems mainly provide support to the leaves and reproductive structures, but can store water in succulent plants such as cacti, food as in potato tubers, or reproduce vegetatively as in the stolons of strawberry plants or in the process of layering. leaves gather sunlight and carry out 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
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
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
pectin and xyloglucan from which the land plant cell wall is constructed. vascular land plants make lignin, a polymer used to strengthen the secondary cell walls of xylem tracheids and vessels to keep them from collapsing when a plant sucks water through them under water stress. lignin is also used in other cell types like sclerenchyma fibres that provide structural support for a plant and is a major constituent of wood. sporopollenin is a chemically resistant polymer found in the outer cell walls of spores and pollen of land plants responsible for the survival of early land plant spores and the pollen of seed plants in the fossil record. it is widely regarded as a marker for the start of land plant evolution during the ordovician period. the concentration of carbon dioxide in the atmosphere today is much lower than it was when plants emerged onto land during the ordovician and silurian periods. many monocots like maize and the pineapple and some dicots like the asteraceae have since independently evolved pathways like crassulacean acid metabolism and the c4 carbon fixation pathway for photosynthesis which avoid the losses resulting from photorespiration in the more common c3 carbon fixation pathway. these biochemical strategies are unique to land plants. = = = medicine and materials = = = phytochemistry is a branch of plant biochemistry primarily concerned with the chemical substances produced by plants during secondary metabolism. some of these compounds are toxins such as the alkaloid coniine from hemlock. others, such as the essential oils peppermint oil and lemon oil are useful for their aroma, as flavourings and spices ( e. g., capsaicin ), and in medicine as pharmaceuticals as in opium from opium poppies. many medicinal and recreational drugs, such as tetrahydrocannabinol ( active ingredient in cannabis ), caffeine, morphine and nicotine come directly from plants. others are simple derivatives of botanical natural products. for example, the pain killer aspirin is the acetyl ester of salicylic acid, originally isolated from the bark of willow trees, and a wide range of opiate painkillers like heroin are obtained by chemical modification of morphine obtained from the opium poppy. popular stimulants come from plants, such as caffeine from coffee, tea and chocolate, and nicotine from tobacco. most alcoholic beverages come from fermentation of carbohy
Question: What are the most advanced group of seedless vascular plants called?
A) shrubs
B) conifers
C) grasses
D) ferns
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D) ferns
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Context:
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
within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions. cell membranes also contain membrane proteins, including integral membrane proteins that go across the membrane serving as membrane transporters, and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes shaping the cell. cell membranes are involved in various cellular processes such as cell adhesion, storing electrical energy, and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall, glycocalyx, and cytoskeleton. within the cytoplasm of a cell, there are many biomolecules such as proteins and nucleic acids. in addition to biomolecules, eukaryotic cells have specialized structures called organelles that have their own lipid bilayers or are spatially units. these organelles include the cell nucleus, which contains most of the cell ' s dna, or mitochondria, which generate adenosine triphosphate ( atp ) to power cellular processes. other organelles such as endoplasmic reticulum and golgi apparatus play a role in the synthesis and packaging of proteins, respectively. biomolecules such as proteins can be engulfed by lysosomes, another specialized organelle. plant cells have additional organelles that distinguish them from animal cells such as a cell wall that provides support for the plant cell, chloroplasts that harvest sunlight energy to produce sugar, and vacuoles that provide storage and structural support as well as being involved in reproduction and breakdown of plant seeds. eukaryotic cells also have cytoskeleton that is made up of microtubules, intermediate filaments, and microfilaments, all of which provide support for the cell and are involved in the movement of the cell and its organelles. in terms of their structural composition, the microtubules are made up of tubulin ( e. g., Ξ± - tubulin and Ξ² - tubulin ) whereas intermediate filaments are made up of fibrous proteins. microfilaments are made up of actin molecules that interact with
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
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
, there are many biomolecules such as proteins and nucleic acids. in addition to biomolecules, eukaryotic cells have specialized structures called organelles that have their own lipid bilayers or are spatially units. these organelles include the cell nucleus, which contains most of the cell ' s dna, or mitochondria, which generate adenosine triphosphate ( atp ) to power cellular processes. other organelles such as endoplasmic reticulum and golgi apparatus play a role in the synthesis and packaging of proteins, respectively. biomolecules such as proteins can be engulfed by lysosomes, another specialized organelle. plant cells have additional organelles that distinguish them from animal cells such as a cell wall that provides support for the plant cell, chloroplasts that harvest sunlight energy to produce sugar, and vacuoles that provide storage and structural support as well as being involved in reproduction and breakdown of plant seeds. eukaryotic cells also have cytoskeleton that is made up of microtubules, intermediate filaments, and microfilaments, all of which provide support for the cell and are involved in the movement of the cell and its organelles. in terms of their structural composition, the microtubules are made up of tubulin ( e. g., Ξ± - tubulin and Ξ² - tubulin ) whereas intermediate filaments are made up of fibrous proteins. microfilaments are made up of actin molecules that interact with other strands of proteins. = = = metabolism = = = all cells require energy to sustain cellular processes. metabolism is the set of chemical reactions in an organism. the three main purposes of metabolism are : the conversion of food to energy to run cellular processes ; the conversion of food / fuel to monomer building blocks ; and the elimination of metabolic wastes. these enzyme - catalyzed reactions allow organisms to grow and reproduce, maintain their structures, and respond to their environments. metabolic reactions may be categorized as catabolic β the breaking down of compounds ( for example, the breaking down of glucose to pyruvate by cellular respiration ) ; or anabolic β the building up ( synthesis ) of compounds ( such as proteins, carbohydrates, lipids, and nucleic acids ). usually, catabolism releases energy, and anabolism consumes energy. the chemical reactions of metabolism are organized into metabolic pathways, in which
chloroplasts make are used for many things, such as providing material to build cell membranes out of and making the polymer cutin which is found in the plant cuticle that protects land plants from drying out. plants synthesise a number of unique polymers like the polysaccharide molecules cellulose, pectin and xyloglucan from which the land plant cell wall is constructed. vascular land plants make lignin, a polymer used to strengthen the secondary cell walls of xylem tracheids and vessels to keep them from collapsing when a plant sucks water through them under water stress. lignin is also used in other cell types like sclerenchyma fibres that provide structural support for a plant and is a major constituent of wood. sporopollenin is a chemically resistant polymer found in the outer cell walls of spores and pollen of land plants responsible for the survival of early land plant spores and the pollen of seed plants in the fossil record. it is widely regarded as a marker for the start of land plant evolution during the ordovician period. the concentration of carbon dioxide in the atmosphere today is much lower than it was when plants emerged onto land during the ordovician and silurian periods. many monocots like maize and the pineapple and some dicots like the asteraceae have since independently evolved pathways like crassulacean acid metabolism and the c4 carbon fixation pathway for photosynthesis which avoid the losses resulting from photorespiration in the more common c3 carbon fixation pathway. these biochemical strategies are unique to land plants. = = = medicine and materials = = = phytochemistry is a branch of plant biochemistry primarily concerned with the chemical substances produced by plants during secondary metabolism. some of these compounds are toxins such as the alkaloid coniine from hemlock. others, such as the essential oils peppermint oil and lemon oil are useful for their aroma, as flavourings and spices ( e. g., capsaicin ), and in medicine as pharmaceuticals as in opium from opium poppies. many medicinal and recreational drugs, such as tetrahydrocannabinol ( active ingredient in cannabis ), caffeine, morphine and nicotine come directly from plants. others are simple derivatives of botanical natural products. for example, the pain killer aspirin is the acetyl ester of salicylic acid, originally isolated from the bark of willow trees, and
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
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
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
Question: What is a rigid layer that surrounds the plasma membrane of a plant cell?
A) mitochondria
B) the cell wall
C) the nucleic wall
D) the cell center
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B) the cell wall
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Context:
pigment chlorophyll a. chlorophyll a ( as well as its plant and green algal - specific cousin chlorophyll b ) absorbs light in the blue - violet and orange / red parts of the spectrum while reflecting and transmitting the green light that we see as the characteristic colour of these organisms. the energy in the red and blue light that these pigments absorb is used by chloroplasts to make energy - rich carbon compounds from carbon dioxide and water by oxygenic photosynthesis, a process that generates molecular oxygen ( o2 ) as a by - product. the light energy captured by chlorophyll a is initially in the form of electrons ( and later a proton gradient ) that is used to make molecules of atp and nadph which temporarily store and transport energy. their energy is used in the light - independent reactions of the calvin cycle by the enzyme rubisco to produce molecules of the 3 - carbon sugar glyceraldehyde 3 - phosphate ( g3p ). glyceraldehyde 3 - phosphate is the first product of photosynthesis and the raw material from which glucose and almost all other organic molecules of biological origin are synthesised. some of the glucose is converted to starch which is stored in the chloroplast. starch is the characteristic energy store of most land plants and algae, while inulin, a polymer of fructose is used for the same purpose in the sunflower family asteraceae. some of the glucose is converted to sucrose ( common table sugar ) for export to the rest of the plant. unlike in animals ( which lack chloroplasts ), plants and their eukaryote relatives have delegated many biochemical roles to their chloroplasts, including synthesising all their fatty acids, and most amino acids. the fatty acids that chloroplasts make are used for many things, such as providing material to build cell membranes out of and making the polymer cutin which is found in the plant cuticle that protects land plants from drying out. plants synthesise a number of unique polymers like the polysaccharide molecules cellulose, pectin and xyloglucan from which the land plant cell wall is constructed. vascular land plants make lignin, a polymer used to strengthen the secondary cell walls of xylem tracheids and vessels to keep them from collapsing when a plant sucks water through them under water stress. lignin
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
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
sight, hearing, touch, and sometimes smell ( e. g., in infection, uremia, diabetic ketoacidosis ). four actions are the basis of physical examination : inspection, palpation ( feel ), percussion ( tap to determine resonance characteristics ), and auscultation ( listen ), generally in that order, although auscultation occurs prior to percussion and palpation for abdominal assessments. the clinical examination involves the study of : abdomen and rectum cardiovascular ( heart and blood vessels ) general appearance of the patient and specific indicators of disease ( nutritional status, presence of jaundice, pallor or clubbing ) genitalia ( and pregnancy if the patient is or could be pregnant ) head, eye, ear, nose, and throat ( heent ) musculoskeletal ( including spine and extremities ) neurological ( consciousness, awareness, brain, vision, cranial nerves, spinal cord and peripheral nerves ) psychiatric ( orientation, mental state, mood, evidence of abnormal perception or thought ). respiratory ( large airways and lungs ) skin vital signs including height, weight, body temperature, blood pressure, pulse, respiration rate, and hemoglobin oxygen saturation it is to likely focus on areas of interest highlighted in the medical history and may not include everything listed above. the treatment plan may include ordering additional medical laboratory tests and medical imaging studies, starting therapy, referral to a specialist, or watchful observation. a follow - up may be advised. depending upon the health insurance plan and the managed care system, various forms of " utilization review ", such as prior authorization of tests, may place barriers on accessing expensive services. the medical decision - making ( mdm ) process includes the analysis and synthesis of all the above data to come up with a list of possible diagnoses ( the differential diagnoses ), along with an idea of what needs to be done to obtain a definitive diagnosis that would explain the patient ' s problem. on subsequent visits, the process may be repeated in an abbreviated manner to obtain any new history, symptoms, physical findings, lab or imaging results, or specialist consultations. = = institutions = = contemporary medicine is, in general, conducted within health care systems. legal, credentialing, and financing frameworks are established by individual governments, augmented on occasion by international organizations, such as churches. the characteristics of any given health care system have a significant impact on the way medical care is provided. from ancient times,
a graviton laser works, in principle, by the stimulated emission of coherent gravitons from a lasing medium. for significant amplification, we must have a very long path length and / or very high densities. black holes and the existence of weakly interacting sub - ev dark matter particles ( wisps ) solve both of these obstacles. orbiting trajectories for massless particles around black holes are well understood \ cite { mtw } and allow for arbitrarily long graviton path lengths. superradiance from kerr black holes of wisps can provide the sufficiently high density \ cite { abh }. this suggests that black holes can act as efficient graviton lasers. thus directed graviton laser beams have been emitted since the beginning of the universe and give rise to new sources of gravitational wave signals. to be in the path of particularly harmfully amplified graviton death rays will not be pleasant.
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
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
pigmentation, chloroplast structure and nutrient reserves. the algal division charophyta, sister to the green algal division chlorophyta, is considered to contain the ancestor of true plants. the charophyte class charophyceae and the land plant sub - kingdom embryophyta together form the monophyletic group or clade streptophytina. nonvascular land plants are embryophytes that lack the vascular tissues xylem and phloem. they include mosses, liverworts and hornworts. pteridophytic vascular plants with true xylem and phloem that reproduced by spores germinating into free - living gametophytes evolved during the silurian period and diversified into several lineages during the late silurian and early devonian. representatives of the lycopods have survived to the present day. by the end of the devonian period, several groups, including the lycopods, sphenophylls and progymnosperms, had independently evolved " megaspory " β their spores were of two distinct sizes, larger megaspores and smaller microspores. their reduced gametophytes developed from megaspores retained within the spore - producing organs ( megasporangia ) of the sporophyte, a condition known as endospory. seeds consist of an endosporic megasporangium surrounded by one or two sheathing layers ( integuments ). the young sporophyte develops within the seed, which on germination splits to release it. the earliest known seed plants date from the latest devonian famennian stage. following the evolution of the seed habit, seed plants diversified, giving rise to a number of now - extinct groups, including seed ferns, as well as the modern gymnosperms and angiosperms. gymnosperms produce " naked seeds " not fully enclosed in an ovary ; modern representatives include conifers, cycads, ginkgo, and gnetales. angiosperms produce seeds enclosed in a structure such as a carpel or an ovary. ongoing research on the molecular phylogenetics of living plants appears to show that the angiosperms are a sister clade to the gymnosperms. = = plant physiology = = plant physiology encompasses all the internal chemical and physical activities of plants associated with life. chemicals obtained from the air, soil and water form
, 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
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
Question: A tropism where light is the stimulus is known as what?
A) Atropism
B) Geotropism
C) phototropism
D) Thermotropism
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C) phototropism
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Context:
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,
wave, carrying an information signal, occupies a range of frequencies. the information in a radio signal is usually concentrated in narrow frequency bands called sidebands ( sb ) just above and below the carrier frequency. the width in hertz of the frequency range that the radio signal occupies, the highest frequency minus the lowest frequency, is called its bandwidth ( bw ). for any given signal - to - noise ratio, a given bandwidth can carry the same amount of information regardless of where in the radio frequency spectrum it is located ; bandwidth is a measure of information - carrying capacity. the bandwidth required by a radio transmission depends on the data rate of the information being sent, and the spectral efficiency of the modulation method used ; how much data it can transmit in each unit of bandwidth. different types of information signals carried by radio have different data rates. for example, a television signal has a greater data rate than an audio signal. the radio spectrum, the total range of radio frequencies that can be used for communication in a given area, is a limited resource. each radio transmission occupies a portion of the total bandwidth available. radio bandwidth is regarded as an economic good which has a monetary cost and is in increasing demand. in some parts of the radio spectrum, the right to use a frequency band or even a single radio channel is bought and sold for millions of dollars. so there is an incentive to employ technology to minimize the bandwidth used by radio services. a slow transition from analog to digital radio transmission technologies began in the late 1990s. part of the reason for this is that digital modulation can often transmit more information ( a greater data rate ) in a given bandwidth than analog modulation, by using data compression algorithms, which reduce redundancy in the data to be sent, and more efficient modulation. other reasons for the transition is that digital modulation has greater noise immunity than analog, digital signal processing chips have more power and flexibility than analog circuits, and a wide variety of types of information can be transmitted using the same digital modulation. because it is a fixed resource which is in demand by an increasing number of users, the radio spectrum has become increasingly congested in recent decades, and the need to use it more effectively is driving many additional radio innovations such as trunked radio systems, spread spectrum ( ultra - wideband ) transmission, frequency reuse, dynamic spectrum management, frequency pooling, and cognitive radio. = = = itu frequency bands = = = the itu arbitrarily divides the radio spectrum into 12 bands, each beginning at a wavelength which is a power
more resistance to fading than am or fm. in ofdm, multiple radio carrier waves closely spaced in frequency are transmitted within the radio channel, with each carrier modulated with bits from the incoming bitstream so multiple bits are being sent simultaneously, in parallel. at the receiver, the carriers are demodulated and the bits 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
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 digital cellular. wireless lans use spread spectrum technology to enable communication between multiple devices in a limited area. ieee 802. 11 defines a common flavor of open - standards wireless radio - wave technology known as wi - fi. free - space optical communication uses visible or invisible light for communications. in most cases, line - of
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
is called its bandwidth ( bw ). for any given signal - to - noise ratio, a given bandwidth can carry the same amount of information regardless of where in the radio frequency spectrum it is located ; bandwidth is a measure of information - carrying capacity. the bandwidth required by a radio transmission depends on the data rate of the information being sent, and the spectral efficiency of the modulation method used ; how much data it can transmit in each unit of bandwidth. different types of information signals carried by radio have different data rates. for example, a television signal has a greater data rate than an audio signal. the radio spectrum, the total range of radio frequencies that can be used for communication in a given area, is a limited resource. each radio transmission occupies a portion of the total bandwidth available. radio bandwidth is regarded as an economic good which has a monetary cost and is in increasing demand. in some parts of the radio spectrum, the right to use a frequency band or even a single radio channel is bought and sold for millions of dollars. so there is an incentive to employ technology to minimize the bandwidth used by radio services. a slow transition from analog to digital radio transmission technologies began in the late 1990s. part of the reason for this is that digital modulation can often transmit more information ( a greater data rate ) in a given bandwidth than analog modulation, by using data compression algorithms, which reduce redundancy in the data to be sent, and more efficient modulation. other reasons for the transition is that digital modulation has greater noise immunity than analog, digital signal processing chips have more power and flexibility than analog circuits, and a wide variety of types of information can be transmitted using the same digital modulation. because it is a fixed resource which is in demand by an increasing number of users, the radio spectrum has become increasingly congested in recent decades, and the need to use it more effectively is driving many additional radio innovations such as trunked radio systems, spread spectrum ( ultra - wideband ) transmission, frequency reuse, dynamic spectrum management, frequency pooling, and cognitive radio. = = = itu frequency bands = = = the itu arbitrarily divides the radio spectrum into 12 bands, each beginning at a wavelength which is a power of ten ( 10n ) metres, with corresponding frequency of 3 times a power of ten, and each covering a decade of frequency or wavelength. each of these bands has a traditional name : it can be seen that the bandwidth, the range of frequencies, contained in each band is not equal but increases exponentially as the
it is stronger, then demodulates it, extracting the original modulation signal from the modulated carrier wave. the modulation signal is converted by a transducer back to a human - usable form : an audio signal is converted to sound waves by a loudspeaker or earphones, a video signal is converted to images by a display, while a digital signal is applied to a computer or microprocessor, which interacts with human users. the radio waves from many transmitters pass through the air simultaneously without interfering with each other because each transmitter ' s radio waves oscillate at a different frequency, measured in hertz ( hz ), kilohertz ( khz ), megahertz ( mhz ) or gigahertz ( ghz ). the receiving antenna typically picks up the radio signals of many transmitters. the receiver uses tuned circuits to select the radio signal desired out of all the signals picked up by the antenna and reject the others. a tuned circuit acts like a resonator, similar to a tuning fork. it has a natural resonant frequency at which it oscillates. the resonant frequency of the receiver ' s tuned circuit is adjusted by the user to the frequency of the desired radio station ; this is called tuning. the oscillating radio signal from the desired station causes the tuned circuit to oscillate in sympathy, and it passes the signal on to the rest of the receiver. radio signals at other frequencies are blocked by the tuned circuit and not passed on. = = = bandwidth = = = a modulated radio wave, carrying an information signal, occupies a range of frequencies. the information in a radio signal is usually concentrated in narrow frequency bands called sidebands ( sb ) just above and below the carrier frequency. the width in hertz of the frequency range that the radio signal occupies, the highest frequency minus the lowest frequency, is called its bandwidth ( bw ). for any given signal - to - noise ratio, a given bandwidth can carry the same amount of information regardless of where in the radio frequency spectrum it is located ; bandwidth is a measure of information - carrying capacity. the bandwidth required by a radio transmission depends on the data rate of the information being sent, and the spectral efficiency of the modulation method used ; how much data it can transmit in each unit of bandwidth. different types of information signals carried by radio have different data rates. for example, a television signal has a greater data rate than an audio signal. the radio spectrum, the total range of
dish " antennas up to 25 metres ( 82 ft ) in diameter and extremely sensitive receivers. high frequencies in the microwave band are used, since microwaves pass through the ionosphere without refraction, and at microwave frequencies the high - gain antennas needed to focus the radio energy into a narrow beam pointed at the receiver are small and take up a minimum of space in a satellite. portions of the uhf, l, c, s, ku and ka band are allocated for space communication. a radio link that transmits data from the earth ' s surface to a spacecraft is called an uplink, while a link that transmits data from the spacecraft to the ground is called a downlink. communication satellite β an artificial satellite used as a telecommunications relay to transmit data between widely separated points on earth. these are used because the microwaves used for telecommunications travel by line of sight and so cannot propagate around the curve of the earth. as of 1 january 2021, there were 2, 224 communications satellites in earth orbit. most are in geostationary orbit 22, 200 miles ( 35, 700 km ) above the equator, so that the satellite appears stationary at the same point in the sky, so the satellite dish antennas of ground stations can be aimed permanently at that spot and do not have to move to track it. in a satellite ground station a microwave transmitter and large satellite dish antenna transmit a microwave uplink beam to the satellite. the uplink signal carries many channels of telecommunications traffic, such as long - distance telephone calls, television programs, and internet signals, using a technique called frequency - division multiplexing ( fdm ). on the satellite, a transponder receives the signal, translates it to a different downlink frequency to avoid interfering with the uplink signal, and retransmits it down to another ground station, which may be widely separated from the first. there the downlink signal is demodulated and the telecommunications traffic it carries is sent to its local destinations through landlines. communication satellites typically have several dozen transponders on different frequencies, which are leased by different users. direct broadcast satellite β a geostationary communication satellite that transmits retail programming directly to receivers in subscriber ' s homes and vehicles on earth, in satellite radio and tv systems. it uses a higher transmitter power than other communication satellites, to allow the signal to be received by consumers with a small unobtrusive antenna. for example, satellite television uses downlink frequencies from 12. 2 to 12. 7 ghz in the ku band transmitted at
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 fan - shaped beam of microwaves around the water surface surrounding the craft out to the horizon. weather radar β a doppler radar which maps weather precipitation intensities and wind speeds with the echoes returned from raindrops and their radial velocity by their doppler shift. phased - array radar β a radar set that uses a phased array, a computer - controlled antenna that can steer the radar beam quickly to point in different directions without moving the antenna. phased - array radars were developed by the military to track fast - moving missiles and aircraft. they are widely used in military equipment and are now spreading to civilian applications. synthetic aperture
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
Question: What is transmitted that makes up the electromagnetic spectrum?
A) gamma rays
B) light waves of different wavelengths
C) sound waves of different frequencies
D) electromagnetic radiation in different wavelengths
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D) electromagnetic radiation in different wavelengths
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Context:
. 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.
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
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
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
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 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
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
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
##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
Question: Rust is an example of the reaction of oxygen with what?
A) iron
B) coal
C) fuel
D) carbon
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A) iron
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Context:
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.
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.
the mean apparent magnitude of starlink mini direct - to - cell ( dtc ) satellites is 4. 62 while the mean of magnitudes adjusted to a uniform distance of 1000 km is 5. 50. dtcs average 4. 9 times brighter than other starlink mini spacecraft at a common distance. we cannot currently separate the effects of the dtc antenna itself, the different attitude modes that may be required for dtc operations and to what extent brightness mitigation procedures were in place at the times of our observations. in a best case scenario, where dtc brightness mitigation is as successful as that for other minis and the dtc antenna does not add significantly to brightness, we estimate that dtcs will be about 2. 6 times as bright as the others based upon their lower altitudes. the dtcs spend a greater fraction of their time in the earth ' s shadow than satellites at higher altitudes. that will offset some of their impact on astronomical observing.
so mars below means blood and war ", is a false cause fallacy. : 26 many astrologers claim that astrology is scientific. if one were to attempt to try to explain it scientifically, there are only four fundamental forces ( conventionally ), limiting the choice of possible natural mechanisms. : 65 some astrologers have proposed conventional causal agents such as electromagnetism and gravity. the strength of these forces drops off with distance. : 65 scientists reject these proposed mechanisms as implausible since, for example, the magnetic field, when measured from earth, of a large but distant planet such as jupiter is far smaller than that produced by ordinary household appliances. astronomer phil plait noted that in terms of magnitude, the sun is the only object with an electromagnetic field of note, but astrology isn ' t based just off the sun alone. : 65 while astrologers could try to suggest a fifth force, this is inconsistent with the trends in physics with the unification of electromagnetism and the weak force into the electroweak force. if the astrologer insisted on being inconsistent with the current understanding and evidential basis of physics, that would be an extraordinary claim. : 65 it would also be inconsistent with the other forces which drop off with distance. : 65 if distance is irrelevant, then, logically, all objects in space should be taken into account. : 66 carl jung sought to invoke synchronicity, the claim that two events have some sort of acausal connection, to explain the lack of statistically significant results on astrology from a single study he conducted. however, synchronicity itself is considered neither testable nor falsifiable. the study was subsequently heavily criticised for its non - random sample and its use of statistics and also its lack of consistency with astrology. = = psychology = = psychological studies have not found any robust relationship between astrological signs and life outcomes. for example, a study showed that zodiac signs are no more effective than random numbers in predicting subjective well - being and quality of life. it has also been shown that confirmation bias is a psychological factor that contributes to belief in astrology. : 344 : 180 β 181 : 42 β 48 confirmation bias is a form of cognitive bias. : 553 from the literature, astrology believers often tend to selectively remember those predictions that turned out to be true and do not remember those that turned out false. another, separate, form of confirmation bias also plays a role, where believers often fail to
are continuous lines used to depict edges directly visible from a particular angle. hidden β are short - dashed lines that may be used to represent edges that are not directly visible. center β are alternately long - and short - dashed lines that may be used to represent the axes of circular features. cutting plane β are thin, medium - dashed lines, or thick alternately long - and double short - dashed that may be used to define sections for section views. section β are thin lines in a pattern ( pattern determined by the material being " cut " or " sectioned " ) used to indicate surfaces in section views resulting from " cutting ". section lines are commonly referred to as " cross - hatching ". phantom β ( not shown ) are alternately long - and double short - dashed thin lines used to represent a feature or component that is not part of the specified part or assembly. e. g. billet ends that may be used for testing, or the machined product that is the focus of a tooling drawing. lines can also be classified by a letter classification in which each line is given a letter. type a lines show the outline of the feature of an object. they are the thickest lines on a drawing and done with a pencil softer than hb. type b lines are dimension lines and are used for dimensioning, projecting, extending, or leaders. a harder pencil should be used, such as a 2h pencil. type c lines are used for breaks when the whole object is not shown. these are freehand drawn and only for short breaks. 2h pencil type d lines are similar to type c, except these are zigzagged and only for longer breaks. 2h pencil type e lines indicate hidden outlines of internal features of an object. these are dotted lines. 2h pencil type f lines are type e lines, except these are used for drawings in electrotechnology. 2h pencil type g lines are used for centre lines. these are dotted lines, but a long line of 10 β 20 mm, then a 1 mm gap, then a small line of 2 mm. 2h pencil type h lines are the same as type g, except that every second long line is thicker. these indicate the cutting plane of an object. 2h pencil type k lines indicate the alternate positions of an object and the line taken by that object. these are drawn with a long line of 10 β 20 mm, then a small gap, then a small line of 2 mm, then a gap, then another small line. 2h
emitter rather than returning a diffuse signal detectable at many angles. the effect is sometimes called " glitter " after the very brief signal seen when the reflected beam passes across a detector. it can be difficult for the radar operator to distinguish between a glitter event and a digital glitch in the processing system. stealth airframes sometimes display distinctive serrations on some exposed edges, such as the engine ports. the yf - 23 has such serrations on the exhaust ports. this is another example in the parallel alignment of features, this time on the external airframe. the shaping requirements detracted greatly from the f - 117 ' s aerodynamic properties. it is inherently unstable, and cannot be flown without a fly - by - wire control system. similarly, coating the cockpit canopy with a thin film transparent conductor ( vapor - deposited gold or indium tin oxide ) helps to reduce the aircraft ' s radar profile, because radar waves would normally enter the cockpit, reflect off objects ( the inside of a cockpit has a complex shape, with a pilot helmet alone forming a sizeable return ), and possibly return to the radar, but the conductive coating creates a controlled shape that deflects the incoming radar waves away from the radar. the coating is thin enough that it has no adverse effect on pilot vision. = = = = ships = = = = ships have also adopted similar methods. though the earlier american arleigh burke - class destroyers incorporated some signature - reduction features. the norwegian skjold - class corvettes was the first coastal defence and the french la fayette - class frigates the first ocean - going stealth ships to enter service. other examples are the dutch de zeven provincien - class frigates, the taiwanese tuo chiang - class corvettes, german sachsen - class frigates, the swedish visby - class corvette, the american san antonio - class amphibious transport docks, and most modern warship designs. = = = materials = = = = = = = non - metallic airframe = = = = dielectric composite materials are more transparent to radar, whereas electrically conductive materials such as metals and carbon fibers reflect electromagnetic energy incident on the material ' s surface. composites may also contain ferrites to optimize the dielectric and magnetic properties of a material for its application. = = = = radar - absorbent material = = = = radiation - absorbent material ( ram ), often as paints, are used especially on the edges of metal surfaces. while the material and thickness of ram coatings can
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.
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 '
, 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
the first observations of saturn ' s visible - wavelength aurora were made by the cassini camera. the aurora was observed between 2006 and 2013 in the northern and southern hemispheres. the color of the aurora changes from pink at a few hundred km above the horizon to purple at 1000 - 1500 km above the horizon. the spectrum observed in 9 filters spanning wavelengths from 250 nm to 1000 nm has a prominent h - alpha line and roughly agrees with laboratory simulated auroras. auroras in both hemispheres vary dramatically with longitude. auroras form bright arcs between 70 and 80 degree latitude north and between 65 and 80 degree latitude south, which sometimes spiral around the pole, and sometimes form double arcs. a large 10, 000 - km - scale longitudinal brightness structure persists for more than 100 hours. this structure rotates approximately together with saturn. on top of the large steady structure, the auroras brighten suddenly on the timescales of a few minutes. these brightenings repeat with a period of about 1 hour. smaller, 1000 - km - scale structures may move faster or lag behind saturn ' s rotation on timescales of tens of minutes. the persistence of nearly - corotating large bright longitudinal structure in the auroral oval seen in two movies spanning 8 and 11 rotations gives an estimate on the period of 10. 65 $ \ pm $ 0. 15 h for 2009 in the northern oval and 10. 8 $ \ pm $ 0. 1 h for 2012 in the southern oval. the 2009 north aurora period is close to the north branch of saturn kilometric radiation ( skr ) detected at that time.
Question: When the sun is below the horizon and thus not visible on a direct line, the light path will bend slightly and thus make the sun visible by what?
A) reflection
B) refraction
C) thermal
D) infrared
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B) refraction
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Context:
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
##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
diagnosis and management of hereditary disorders. neurology is concerned with diseases of the nervous system. in the uk, neurology is a subspecialty of general medicine. obstetrics and gynecology ( often abbreviated as ob / gyn ( american english ) or obs & gynae ( british english ) ) are concerned respectively with childbirth and the female reproductive and associated organs. reproductive medicine and fertility medicine are generally practiced by gynecological specialists. pediatrics ( ae ) or paediatrics ( be ) is devoted to the care of infants, children, and adolescents. like internal medicine, there are many pediatric subspecialties for specific age ranges, organ systems, disease classes, and sites of care delivery. pharmaceutical medicine is the medical scientific discipline concerned with the discovery, development, evaluation, registration, monitoring and medical aspects of marketing of medicines for the benefit of patients and public health. physical medicine and rehabilitation ( or physiatry ) is concerned with functional improvement after injury, illness, or congenital disorders. podiatric medicine is the study of, diagnosis, and medical and surgical treatment of disorders of the foot, ankle, lower limb, hip and lower back. preventive medicine is the branch of medicine concerned with preventing disease. community health or public health is an aspect of health services concerned with threats to the overall health of a community based on population health analysis. psychiatry is the branch of medicine concerned with the bio - psycho - social study of the etiology, diagnosis, treatment and prevention of cognitive, perceptual, emotional and behavioral disorders. related fields include psychotherapy and clinical psychology. = = = interdisciplinary fields = = = some interdisciplinary sub - specialties of medicine include : addiction medicine deals with the treatment of addiction. aerospace medicine deals with medical problems related to flying and space travel. biomedical engineering is a field dealing with the application of engineering principles to medical practice. clinical pharmacology is concerned with how systems of therapeutics interact with patients. conservation medicine studies the relationship between human and non - human animal health, and environmental conditions. also known as ecological medicine, environmental medicine, or medical geology. disaster medicine deals with medical aspects of emergency preparedness, disaster mitigation and management. diving medicine ( or hyperbaric medicine ) is the prevention and treatment of diving - related problems. evolutionary medicine is a perspective on medicine derived through applying evolutionary theory. forensic medicine deals with medical questions in legal context, such as determination of the time and cause of death, type of weapon used to inflict
a cell. there are generally four types of chemical signals : autocrine, paracrine, juxtacrine, and hormones. in autocrine signaling, the ligand affects the same cell that releases it. tumor cells, for example, can reproduce uncontrollably because they release signals that initiate their own self - division. in paracrine signaling, the ligand diffuses to nearby cells and affects them. for example, brain cells called neurons release ligands called neurotransmitters that diffuse across a synaptic cleft to bind with a receptor on an adjacent cell such as another neuron or muscle cell. in juxtacrine signaling, there is direct contact between the signaling and responding cells. finally, hormones are ligands that travel through the circulatory systems of animals or vascular systems of plants to reach their target cells. once a ligand binds with a receptor, it can influence the behavior of another cell, depending on the type of receptor. for instance, neurotransmitters that bind with an inotropic receptor can alter the excitability of a target cell. other types of receptors include protein kinase receptors ( e. g., receptor for the hormone insulin ) and g protein - coupled receptors. activation of g protein - coupled receptors can initiate second messenger cascades. the process by which a chemical or physical signal is transmitted through a cell as a series of molecular events is called signal transduction. = = = cell cycle = = = the cell cycle is a series of events that take place in a cell that cause it to divide into two daughter cells. these events include the duplication of its dna and some of its organelles, and the subsequent partitioning of its cytoplasm into two daughter cells in a process called cell division. in eukaryotes ( i. e., animal, plant, fungal, and protist cells ), there are two distinct types of cell division : mitosis and meiosis. mitosis is part of the cell cycle, in which replicated chromosomes are separated into two new nuclei. cell division gives rise to genetically identical cells in which the total number of chromosomes is maintained. in general, mitosis ( division of the nucleus ) is preceded by the s stage of interphase ( during which the dna is replicated ) and is often followed by telophase and cytokinesis ; which divides the cytoplasm, organelles and cell membrane of one cell into two new cells containing roughly equal shares
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,
judgments to the practice of medicine. medical humanities includes the humanities ( literature, philosophy, ethics, history and religion ), social science ( anthropology, cultural studies, psychology, sociology ), and the arts ( literature, theater, film, and visual arts ) and their application to medical education and practice. nosokinetics is the science / subject of measuring and modelling the process of care in health and social care systems. nosology is the classification of diseases for various purposes. occupational medicine is the provision of health advice to organizations and individuals to ensure that the highest standards of health and safety at work can be achieved and maintained. pain management ( also called pain medicine, or algiatry ) is the medical discipline concerned with the relief of pain. pharmacogenomics is a form of individualized medicine. podiatric medicine is the study of, diagnosis, and medical treatment of disorders of the foot, ankle, lower limb, hip and lower back. sexual medicine is concerned with diagnosing, assessing and treating all disorders related to sexuality. sports medicine deals with the treatment and prevention and rehabilitation of sports / exercise injuries such as muscle spasms, muscle tears, injuries to ligaments ( ligament tears or ruptures ) and their repair in athletes, amateur and professional. therapeutics is the field, more commonly referenced in earlier periods of history, of the various remedies that can be used to treat disease and promote health. travel medicine or emporiatrics deals with health problems of international travelers or travelers across highly different environments. tropical medicine deals with the prevention and treatment of tropical diseases. it is studied separately in temperate climates where those diseases are quite unfamiliar to medical practitioners and their local clinical needs. urgent care focuses on delivery of unscheduled, walk - in care outside of the hospital emergency department for injuries and illnesses that are not severe enough to require care in an emergency department. in some jurisdictions this function is combined with the emergency department. veterinary medicine ; veterinarians apply similar techniques as physicians to the care of non - human animals. wilderness medicine entails the practice of medicine in the wild, where conventional medical facilities may not be available. = = education and legal controls = = medical education and training varies around the world. it typically involves entry level education at a university medical school, followed by a period of supervised practice or internship, or residency. this can be followed by postgraduate vocational training. a variety of teaching methods have been employed in medical education, still itself a focus of active research. in canada and the united states of
considered the father of modern neuroscience. from new zealand and australia came maurice wilkins, howard florey, and frank macfarlane burnet. others that did significant work include william williams keen, william coley, james d. watson ( united states ) ; salvador luria ( italy ) ; alexandre yersin ( switzerland ) ; kitasato shibasaburo ( japan ) ; jean - martin charcot, claude bernard, paul broca ( france ) ; adolfo lutz ( brazil ) ; nikolai korotkov ( russia ) ; sir william osler ( canada ) ; and harvey cushing ( united states ). as science and technology developed, medicine became more reliant upon medications. throughout history and in europe right until the late 18th century, not only plant products were used as medicine, but also animal ( including human ) body parts and fluids. pharmacology developed in part from herbalism and some drugs are still derived from plants ( atropine, ephedrine, warfarin, aspirin, digoxin, vinca alkaloids, taxol, hyoscine, etc. ). vaccines were discovered by edward jenner and louis pasteur. the first antibiotic was arsphenamine ( salvarsan ) discovered by paul ehrlich in 1908 after he observed that bacteria took up toxic dyes that human cells did not. the first major class of antibiotics was the sulfa drugs, derived by german chemists originally from azo dyes. pharmacology has become increasingly sophisticated ; modern biotechnology allows drugs targeted towards specific physiological processes to be developed, sometimes designed for compatibility with the body to reduce side - effects. genomics and knowledge of human genetics and human evolution is having increasingly significant influence on medicine, as the causative genes of most monogenic genetic disorders have now been identified, and the development of techniques in molecular biology, evolution, and genetics are influencing medical technology, practice and decision - making. evidence - based medicine is a contemporary movement to establish the most effective algorithms of practice ( ways of doing things ) through the use of systematic reviews and meta - analysis. the movement is facilitated by modern global information science, which allows as much of the available evidence as possible to be collected and analyzed according to standard protocols that are then disseminated to healthcare providers. the cochrane collaboration leads this movement. a 2001 review of 160 cochrane systematic reviews revealed that, according to two readers, 21. 3 % of the reviews concluded insufficient evidence, 20 % concluded evidence of no effect,
and cell phones are a particular challenge because the stream of data can interfere with focusing and learning. although these technologies affect adults too, young people may be more influenced by it as their developing brains can easily become habituated to switching tasks and become unaccustomed to sustaining attention. too much information, coming too rapidly, can overwhelm thinking. technology is " rapidly and profoundly altering our brains. " high exposure levels stimulate brain cell alteration and release neurotransmitters, which causes the strengthening of some neural pathways and the weakening of others. this leads to heightened stress levels on the brain that, at first, boost energy levels, but, over time, actually augment memory, impair cognition, lead to depression, and alter the neural circuitry of the hippocampus, amygdala and prefrontal cortex. these are the brain regions that control mood and thought. if unchecked, the underlying structure of the brain could be altered. overstimulation due to technology may begin too young. when children are exposed before the age of seven, important developmental tasks may be delayed, and bad learning habits might develop, which " deprives children of the exploration and play that they need to develop. " media psychology is an emerging specialty field that embraces electronic devices and the sensory behaviors occurring from the use of educational technology in learning. = = = sociocultural criticism = = = according to lai, " the learning environment is a complex system where the interplay and interactions of many things impact the outcome of learning. " when technology is brought into an educational setting, the pedagogical setting changes in that technology - driven teaching can change the entire meaning of an activity without adequate research validation. if technology monopolizes an activity, students can begin to develop the sense that " life would scarcely be thinkable without technology. " leo marx considered the word " technology " itself as problematic, susceptible to reification and " phantom objectivity ", which conceals its fundamental nature as something that is only valuable insofar as it benefits the human condition. technology ultimately comes down to affecting the relations between people, but this notion is obfuscated when technology is treated as an abstract notion devoid of good and evil. langdon winner makes a similar point by arguing that the underdevelopment of the philosophy of technology leaves us with an overly simplistic reduction in our discourse to the supposedly dichotomous notions of the " making " versus the " uses " of new technologies and that a narrow focus on " use
the operating room, the anesthesiology physician also serves the same function in the labor and delivery ward, and some are specialized in critical medicine. emergency medicine is concerned with the diagnosis and treatment of acute or life - threatening conditions, including trauma, surgical, medical, pediatric, and psychiatric emergencies. family medicine, family practice, general practice or primary care is, in many countries, the first port - of - call for patients with non - emergency medical problems. family physicians often provide services across a broad range of settings including office based practices, emergency department coverage, inpatient care, and nursing home care. medical genetics is concerned with the diagnosis and management of hereditary disorders. neurology is concerned with diseases of the nervous system. in the uk, neurology is a subspecialty of general medicine. obstetrics and gynecology ( often abbreviated as ob / gyn ( american english ) or obs & gynae ( british english ) ) are concerned respectively with childbirth and the female reproductive and associated organs. reproductive medicine and fertility medicine are generally practiced by gynecological specialists. pediatrics ( ae ) or paediatrics ( be ) is devoted to the care of infants, children, and adolescents. like internal medicine, there are many pediatric subspecialties for specific age ranges, organ systems, disease classes, and sites of care delivery. pharmaceutical medicine is the medical scientific discipline concerned with the discovery, development, evaluation, registration, monitoring and medical aspects of marketing of medicines for the benefit of patients and public health. physical medicine and rehabilitation ( or physiatry ) is concerned with functional improvement after injury, illness, or congenital disorders. podiatric medicine is the study of, diagnosis, and medical and surgical treatment of disorders of the foot, ankle, lower limb, hip and lower back. preventive medicine is the branch of medicine concerned with preventing disease. community health or public health is an aspect of health services concerned with threats to the overall health of a community based on population health analysis. psychiatry is the branch of medicine concerned with the bio - psycho - social study of the etiology, diagnosis, treatment and prevention of cognitive, perceptual, emotional and behavioral disorders. related fields include psychotherapy and clinical psychology. = = = interdisciplinary fields = = = some interdisciplinary sub - specialties of medicine include : addiction medicine deals with the treatment of addiction. aerospace medicine deals with medical problems related to flying and space travel. biomedical engineering is a field dealing with the application of engineering principles to medical practice
. 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
Question: What term describes a drug that has an effect on the central nervous system?
A) nonaddictive drug
B) psychoactive drug
C) elemental drug
D) steroidal drug
|
B) psychoactive drug
|
Context:
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
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.
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 ). "
there cannot exist a single parametrization that covers the whole surface. therefore, one often considers surfaces which are parametrized by several parametric equations, whose images cover the surface. this is formalized by the concept of manifold : in the context of manifolds, typically in topology and differential geometry, a surface is a manifold of dimension two ; this means that a surface is a topological space such that every point has a neighborhood which is homeomorphic to an open subset of the euclidean plane ( see surface ( topology ) and surface ( differential geometry ) ). this allows defining surfaces in spaces of dimension higher than three, and even abstract surfaces, which are not contained in any other space. on the other hand, this excludes surfaces that have singularities, such as the vertex of a conical surface or points where a surface crosses itself. in classical geometry, a surface is generally defined as a locus of a point or a line. for example, a sphere is the locus of a point which is at a given distance of a fixed point, called the center ; a conical surface is the locus of a line passing through a fixed point and crossing a curve ; a surface of revolution is the locus of a curve rotating around a line. a ruled surface is the locus of a moving line satisfying some constraints ; in modern terminology, a ruled surface is a surface, which is a union of lines. = = terminology = = there are several kinds of surfaces that are considered in mathematics. an unambiguous terminology is thus necessary to distinguish them when needed. a topological surface is a surface that is a 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
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
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
of a light source can be measured with a spectroradiometer, which works by optically collecting the light, then passing it through a monochromator before reading it in narrow bands of wavelength. reflected color can be measured using a spectrophotometer ( also called spectroreflectometer or reflectometer ), which takes measurements in the visible region ( and a little beyond ) of a given color sample. if the custom of taking readings at 10 nanometer increments is followed, the visible light range of 400 β 700 nm will yield 31 readings. these readings are typically used to draw the sample ' s spectral reflectance curve ( how much it reflects, as a function of wavelength ) β the most accurate data that can be provided regarding its characteristics. the readings by themselves are typically not as useful as their tristimulus values, which can be converted into chromaticity co - ordinates and manipulated through color space transformations. for this purpose, a spectrocolorimeter may be used. a spectrocolorimeter is simply a spectrophotometer that can estimate tristimulus values by numerical integration ( of the color matching functions ' inner product with the illuminant ' s spectral power distribution ). one benefit of spectrocolorimeters over tristimulus colorimeters is that they do not have optical filters, which are subject to manufacturing variance, and have a fixed spectral transmittance curve β until they age. on the other hand, tristimulus colorimeters are purpose - built, cheaper, and easier to use. the cie ( international commission on illumination ) recommends using measurement intervals under 5 nm, even for smooth spectra. sparser measurements fail to accurately characterize spiky emission spectra, such as that of the red phosphor of a crt display, depicted aside. = = = color temperature meter = = = photographers and cinematographers use information provided by these meters to decide what color balancing should be done to make different light sources appear to have the same color temperature. if the user enters the reference color temperature, the meter can calculate the mired difference between the measurement and the reference, enabling the user to choose a corrective color gel or photographic filter with the closest mired factor. internally the meter is typically a silicon photodiode tristimulus colorimeter. the correlated color temperature can be calculated from the tristimulus values by first calculating the chromaticity co - ordinates in the cie 1960 color space, then finding the closest
##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
are continuous lines used to depict edges directly visible from a particular angle. hidden β are short - dashed lines that may be used to represent edges that are not directly visible. center β are alternately long - and short - dashed lines that may be used to represent the axes of circular features. cutting plane β are thin, medium - dashed lines, or thick alternately long - and double short - dashed that may be used to define sections for section views. section β are thin lines in a pattern ( pattern determined by the material being " cut " or " sectioned " ) used to indicate surfaces in section views resulting from " cutting ". section lines are commonly referred to as " cross - hatching ". phantom β ( not shown ) are alternately long - and double short - dashed thin lines used to represent a feature or component that is not part of the specified part or assembly. e. g. billet ends that may be used for testing, or the machined product that is the focus of a tooling drawing. lines can also be classified by a letter classification in which each line is given a letter. type a lines show the outline of the feature of an object. they are the thickest lines on a drawing and done with a pencil softer than hb. type b lines are dimension lines and are used for dimensioning, projecting, extending, or leaders. a harder pencil should be used, such as a 2h pencil. type c lines are used for breaks when the whole object is not shown. these are freehand drawn and only for short breaks. 2h pencil type d lines are similar to type c, except these are zigzagged and only for longer breaks. 2h pencil type e lines indicate hidden outlines of internal features of an object. these are dotted lines. 2h pencil type f lines are type e lines, except these are used for drawings in electrotechnology. 2h pencil type g lines are used for centre lines. these are dotted lines, but a long line of 10 β 20 mm, then a 1 mm gap, then a small line of 2 mm. 2h pencil type h lines are the same as type g, except that every second long line is thicker. these indicate the cutting plane of an object. 2h pencil type k lines indicate the alternate positions of an object and the line taken by that object. these are drawn with a long line of 10 β 20 mm, then a small gap, then a small line of 2 mm, then a gap, then another small line. 2h
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 = = = = =
Question: What is the physical area where a specie lives?
A) habitat
B) farmland
C) marine biome
D) ecosystem
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A) habitat
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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
##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
##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
, 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
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
##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
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 ). "
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 = = = = =
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
, glaciology. geophysics and geodesy investigate the shape of the earth, its reaction to forces and its magnetic and gravity fields. geophysicists explore the earth ' s core and mantle as well as the tectonic and seismic activity of the lithosphere. geophysics is commonly used to supplement the work of geologists in developing a comprehensive understanding of crustal geology, particularly in mineral and petroleum exploration. seismologists use geophysics to understand plate tectonic movement, as well as predict seismic activity. geochemistry studies the processes that control the abundance, composition, and distribution of chemical compounds and isotopes in geologic environments. geochemists use the tools and principles of chemistry to study the earth ' s composition, structure, processes, and other physical aspects. major subdisciplines are aqueous geochemistry, cosmochemistry, isotope geochemistry and biogeochemistry. soil science covers the outermost layer of the earth ' s crust that is subject to soil formation processes ( or pedosphere ). major subdivisions in this field of study include edaphology and pedology. ecology covers the interactions between organisms and their environment. this field of study differentiates the study of earth from other planets in the solar system, earth being the only planet teeming with life. hydrology, oceanography and limnology are studies which focus on the movement, distribution, and quality of the water and involve all the components of the hydrologic cycle on the earth and its atmosphere ( or hydrosphere ). " sub - disciplines of hydrology include hydrometeorology, surface water hydrology, hydrogeology, watershed science, forest hydrology, and water chemistry. " glaciology covers the icy parts of the earth ( or cryosphere ). atmospheric sciences cover the gaseous parts of the earth ( or atmosphere ) between the surface and the exosphere ( about 1000 km ). major subdisciplines include meteorology, climatology, atmospheric chemistry, and atmospheric physics. = = = earth science breakup = = = = = see also = = = = references = = = = = sources = = = = = further reading = = = = external links = = earth science picture of the day, a service of universities space research association, sponsored by nasa goddard space flight center. geoethics in planetary and space exploration. geology buzz : earth science archived 2021 - 11 - 04 at the wayback machine
Question: Where does most geologic activity take place?
A) asthenosphere
B) outer core
C) inner core
D) plate boundaries
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D) plate boundaries
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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.
winds from agn and quasars will form large amounts of dust, as the cool gas in these winds passes through the ( pressure, temperature ) region where dust is formed in agb stars. conditions in the gas are benign to dust at these radii. as a result quasar winds may be a major source of dust at high redshifts, obviating a difficulty with current observations, and requiring far less dust to exist at early epochs.
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
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
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
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
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
i suggest that the main process that amplifies magnetic fields in cooling flows in clusters and group of galaxies is a jet - driven dynamo ( jedd ). the main processes that are behind the jedd is the turbulence that is formed by the many vortices formed in the inflation processes of bubbles, and the large scale shear formed by the propagating jet. it is sufficient that a strong turbulence exits in the vicinity of the jets and bubbles, just where the shear is large. the typical amplification time of magnetic fields by the jedd near the jets and bubbles is approximately hundred million years. the amplification time in the entire cooling flow region is somewhat longer. the vortices that create the turbulence are those that also transfer energy from the jets to the intra - cluster medium, by mixing shocked jet gas with the intra - cluster medium gas, and by exciting sound waves. the jedd model adds magnetic fields to the cyclical behavior of energy and mass in the jet - feedback mechanism ( jfm ) in cooling flows.
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
Question: What type of winds move the same way as mountain and valley breezes?
A) prevailing winds
B) katabatic winds
C) pyroclastic winds
D) planetary winds
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B) katabatic winds
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Context:
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
lines are dimension lines and are used for dimensioning, projecting, extending, or leaders. a harder pencil should be used, such as a 2h pencil. type c lines are used for breaks when the whole object is not shown. these are freehand drawn and only for short breaks. 2h pencil type d lines are similar to type c, except these are zigzagged and only for longer breaks. 2h pencil type e lines indicate hidden outlines of internal features of an object. these are dotted lines. 2h pencil type f lines are type e lines, except these are used for drawings in electrotechnology. 2h pencil type g lines are used for centre lines. these are dotted lines, but a long line of 10 β 20 mm, then a 1 mm gap, then a small line of 2 mm. 2h pencil type h lines are the same as type g, except that every second long line is thicker. these indicate the cutting plane of an object. 2h pencil type k lines indicate the alternate positions of an object and the line taken by that object. these are drawn with a long line of 10 β 20 mm, then a small gap, then a small line of 2 mm, then a gap, then another small line. 2h pencil. = = = multiple views and projections = = = in most cases, a single view is not sufficient to show all necessary features, and several views are used. types of views include the following : = = = = multiview projection = = = = a multiview projection is a type of orthographic projection that shows the object as it looks from the front, right, left, top, bottom, or back ( e. g. the primary views ), and is typically positioned relative to each other according to the rules of either first - angle or third - angle projection. the origin and vector direction of the projectors ( 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
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
are commonly referred to as " cross - hatching ". phantom β ( not shown ) are alternately long - and double short - dashed thin lines used to represent a feature or component that is not part of the specified part or assembly. e. g. billet ends that may be used for testing, or the machined product that is the focus of a tooling drawing. lines can also be classified by a letter classification in which each line is given a letter. type a lines show the outline of the feature of an object. they are the thickest lines on a drawing and done with a pencil softer than hb. type b lines are dimension lines and are used for dimensioning, projecting, extending, or leaders. a harder pencil should be used, such as a 2h pencil. type c lines are used for breaks when the whole object is not shown. these are freehand drawn and only for short breaks. 2h pencil type d lines are similar to type c, except these are zigzagged and only for longer breaks. 2h pencil type e lines indicate hidden outlines of internal features of an object. these are dotted lines. 2h pencil type f lines are type e lines, except these are used for drawings in electrotechnology. 2h pencil type g lines are used for centre lines. these are dotted lines, but a long line of 10 β 20 mm, then a 1 mm gap, then a small line of 2 mm. 2h pencil type h lines are the same as type g, except that every second long line is thicker. these indicate the cutting plane of an object. 2h pencil type k lines indicate the alternate positions of an object and the line taken by that object. these are drawn with a long line of 10 β 20 mm, then a small gap, then a small line of 2 mm, then a gap, then another small line. 2h pencil. = = = multiple views and projections = = = in most cases, a single view is not sufficient to show all necessary features, and several views are used. types of views include the following : = = = = multiview projection = = = = a multiview projection is a type of orthographic projection that shows the object as it looks from the front, right, left, top, bottom, or back ( e. g. the primary views ), and is typically positioned relative to each other according to the rules of either first - angle or third - angle projection. the origin and vector direction of the projectors (
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 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
- and right - bounded ; and is said to be unbounded otherwise. intervals that are bounded at only one end are said to be half - bounded. the empty set is bounded, and the set of all reals is the only interval that is unbounded at both ends. bounded intervals are also commonly known as finite intervals. bounded intervals are bounded sets, in the sense that their diameter ( which is equal to the absolute difference between the endpoints ) is finite. the diameter may be called the length, width, measure, range, or size of the interval. the size of unbounded intervals is usually defined as + β, and the size of the empty interval may be defined as 0 ( or left undefined ). the centre ( midpoint ) of a bounded interval with endpoints a and b is ( a + b ) / 2, and its radius is the half - length | a β b | / 2. these concepts are undefined for empty or unbounded intervals. an interval is said to be left - open if and only if it contains no minimum ( an element that is smaller than all other elements ) ; right - open if it contains no maximum ; and open if it contains neither. the interval [ 0, 1 ) = { x | 0 β€ x < 1 }, for example, is left - closed and right - open. the empty set and the set of all reals are both open and closed intervals, while the set of non - negative reals, is a closed interval that is right - open but not left - open. the open intervals are open sets of the real line in its standard topology, and form a base of the open sets. an interval is said to be left - closed if it has a minimum element or is left - unbounded, right - closed if it has a maximum or is right unbounded ; it is simply closed if it is both left - closed and right closed. so, the closed intervals coincide with the closed sets in that topology. the interior of an interval i is the largest open interval that is contained in i ; it is also the set of points in i which are not endpoints of i. the closure of i is the smallest closed interval that contains i ; which is also the set i augmented with its finite endpoints. for any set x of real numbers, the interval enclosure or interval span of x is the unique interval that contains x, and does not properly contain any other interval that also contains x. an interval i is
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.
are continuous lines used to depict edges directly visible from a particular angle. hidden β are short - dashed lines that may be used to represent edges that are not directly visible. center β are alternately long - and short - dashed lines that may be used to represent the axes of circular features. cutting plane β are thin, medium - dashed lines, or thick alternately long - and double short - dashed that may be used to define sections for section views. section β are thin lines in a pattern ( pattern determined by the material being " cut " or " sectioned " ) used to indicate surfaces in section views resulting from " cutting ". section lines are commonly referred to as " cross - hatching ". phantom β ( not shown ) are alternately long - and double short - dashed thin lines used to represent a feature or component that is not part of the specified part or assembly. e. g. billet ends that may be used for testing, or the machined product that is the focus of a tooling drawing. lines can also be classified by a letter classification in which each line is given a letter. type a lines show the outline of the feature of an object. they are the thickest lines on a drawing and done with a pencil softer than hb. type b lines are dimension lines and are used for dimensioning, projecting, extending, or leaders. a harder pencil should be used, such as a 2h pencil. type c lines are used for breaks when the whole object is not shown. these are freehand drawn and only for short breaks. 2h pencil type d lines are similar to type c, except these are zigzagged and only for longer breaks. 2h pencil type e lines indicate hidden outlines of internal features of an object. these are dotted lines. 2h pencil type f lines are type e lines, except these are used for drawings in electrotechnology. 2h pencil type g lines are used for centre lines. these are dotted lines, but a long line of 10 β 20 mm, then a 1 mm gap, then a small line of 2 mm. 2h pencil type h lines are the same as type g, except that every second long line is thicker. these indicate the cutting plane of an object. 2h pencil type k lines indicate the alternate positions of an object and the line taken by that object. these are drawn with a long line of 10 β 20 mm, then a small gap, then a small line of 2 mm, then a gap, then another small line. 2h
empty nor degenerate is said to be proper, and has infinitely many elements. an interval is said to be left - bounded or right - bounded, if there is some real number that is, respectively, smaller than or larger than all its elements. an interval is said to be bounded, if it is both left - and right - bounded ; and is said to be unbounded otherwise. intervals that are bounded at only one end are said to be half - bounded. the empty set is bounded, and the set of all reals is the only interval that is unbounded at both ends. bounded intervals are also commonly known as finite intervals. bounded intervals are bounded sets, in the sense that their diameter ( which is equal to the absolute difference between the endpoints ) is finite. the diameter may be called the length, width, measure, range, or size of the interval. the size of unbounded intervals is usually defined as + β, and the size of the empty interval may be defined as 0 ( or left undefined ). the centre ( midpoint ) of a bounded interval with endpoints a and b is ( a + b ) / 2, and its radius is the half - length | a β b | / 2. these concepts are undefined for empty or unbounded intervals. an interval is said to be left - open if and only if it contains no minimum ( an element that is smaller than all other elements ) ; right - open if it contains no maximum ; and open if it contains neither. the interval [ 0, 1 ) = { x | 0 β€ x < 1 }, for example, is left - closed and right - open. the empty set and the set of all reals are both open and closed intervals, while the set of non - negative reals, is a closed interval that is right - open but not left - open. the open intervals are open sets of the real line in its standard topology, and form a base of the open sets. an interval is said to be left - closed if it has a minimum element or is left - unbounded, right - closed if it has a maximum or is right unbounded ; it is simply closed if it is both left - closed and right closed. so, the closed intervals coincide with the closed sets in that topology. the interior of an interval i is the largest open interval that is contained in i ; it is also the set of points in i which are not endpoints of i. the closure of
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
Question: What is the term for the length of the route between two points?
A) length
B) area
C) distance
D) trajectory
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C) distance
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Context:
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.
##ry facilitates screening and ranking of clones which bind to the native ( non - denaturated ) forms of antigen proteins. flow cytometry screening has been used for primary screening of a large number ( ~ 1000 ) of hybridoma clones recognizing the native form of the antigen on the cell surface. in the flow cytometry - based screening, a mixture of antigen - negative cells and antigen - positive cells is used as the antigen to be tested for each hybridoma supernatant sample. the b cell that produces the desired antibodies can be cloned to produce many identical daughter clones. supplemental media containing interleukin - 6 ( such as briclone ) are essential for this step. once a hybridoma colony is established, it will continually grow in culture medium like rpmi - 1640 ( with antibiotics and fetal bovine serum ) and produce antibodies. multiwell plates are used initially to grow the hybridomas, and after selection, are changed to larger tissue culture flasks. this maintains the well - being of the hybridomas and provides enough cells for cryopreservation and supernatant for subsequent investigations. the culture supernatant can yield 1 to 60 ΞΌg / ml of monoclonal antibody, which is maintained at - 20 Β°c or lower until required. by using culture supernatant or a purified immunoglobulin preparation, further analysis of a potential monoclonal antibody producing hybridoma can be made in terms of reactivity, specificity, and cross - reactivity. = = applications = = the use of monoclonal antibodies is numerous and includes the prevention, diagnosis, and treatment of disease. for example, monoclonal antibodies can distinguish subsets of b cells and t cells, which is helpful in identifying different types of leukaemias. in addition, specific monoclonal antibodies have been used to define cell surface markers on white blood cells and other cell types. this led to the cluster of differentiation series of markers. these are often referred to as cd markers and define several hundred different cell surface components of cells, each specified by binding of a particular monoclonal antibody. such antibodies are extremely useful for fluorescence - activated cell sorting, the specific isolation of particular types of cells. = = = in diagnostic histopathology = = = with the help of monoclonal antibodies, tissues and organs can be classified based on their expression of certain defined markers, which reflect tissue or cellular genesis. prostate specific antigen, placental alkaline phospha
- 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 band that can be used without a license. they are often installed in vehicles, with the mobile units communicating with a dispatcher at a fixed base station. special systems with reserved frequencies are used by first responder services ; police, fire, ambulance, and emergency services, and other government services. other systems are made for use by commercial firms such as taxi and delivery services. vhf systems use channels in the range 30 β 50 mhz and 150 β 172 mhz. uhf systems use the 450 β 470 mhz band and in some areas the 470 β 512 mhz range. in general, vhf systems have a longer range than uhf but require longer antennas. am or fm modulation is mainly used, but digital systems such as dmr are being introduced. the radiated power is typically limited to 4 watts. these systems have a fairly limited range, usually 3 to 20 miles ( 4. 8 to 32 km ) depending on terrain. repeaters installed on tall buildings, hills, or mountain peaks are often used to increase the range when it is desired to cover a larger area than line - of - sight. examples of land mobile systems are cb, frs, gmrs, and murs. modern digital systems, called trunked radio systems, have a digital channel management system using a control channel that automatically assigns frequency channels to user groups. walkie - talkie β a battery - powered portable handheld half - duplex two - way radio, used in land mobile radio systems. airband β half - duplex radio system used by aircraft pilots to talk to other aircraft and ground - based air traffic controllers. this vital system is the main communication channel for air traffic control. for most communication in overland flights in air corridors a vhf - am system using channels between 108 and 137 mhz in the vhf band is used. this system has a typical transmission range of 200 miles ( 320 km ) for aircraft flying at cruising altitude. for flights in more remote areas, such as transoceanic airline flights, aircraft use the hf band or channels on the inmarsat or iridium satphone satellites. military aircraft also use a dedicated uhf - am band from 225. 0 to 399. 95 mhz. marine radio β medium - range transceivers on
a minus sign is inserted, for good reason, into the formula for the energy - momentum tensor for tachyons. this leads to remarkable theoretical consequences and a plausible explanation for the phenomenon called dark energy in the cosmos.
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
an oscillation with a period of around 500 kb in guanine and cytosine content ( gc % ) is observed in the dna sequence of human chromosome 21. this oscillation is localized in the rightmost one - eighth region of the chromosome, from 43. 5 mb to 46. 5 mb. five cycles of oscillation are observed in this region with six gc - rich peaks and five gc - poor valleys. the gc - poor valleys comprise regions with low density of cpg islands and, alternating between the two dna strands, low gene density regions. consequently, the long - range oscillation of gc % result in spacing patterns of both cpg island density, and to a lesser extent, gene densities.
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 band that can be used without a license. they are often installed in vehicles, with the mobile units communicating with a dispatcher at a fixed base station. special systems with reserved frequencies are used by first responder services ; police, fire, ambulance, and emergency services, and other government services. other systems are made for use by commercial firms such as taxi and delivery services. vhf systems use channels in the range 30 β 50 mhz and 150 β 172 mhz. uhf systems use the 450 β 470 mhz band and in some areas the 470 β 512 mhz range. in general, vhf systems have a longer range than uhf but require longer antennas. am or fm modulation is mainly used, but digital systems such as dmr are being introduced. the radiated power is typically limited to 4 watts. these systems have a fairly limited range, usually 3 to 20 miles ( 4. 8 to 32 km ) depending on terrain. repeaters installed on tall buildings, hills, or mountain peaks are often used to increase the range when it is desired to cover a larger area than line - of - sight. examples of land mobile systems are cb, frs, gmrs, and murs. modern digital systems, called trunked radio systems, have a digital channel management system using a control channel that automatically assigns frequency channels to user groups. walkie - talkie β a battery - powered portable handheld half - duplex two - way radio, used in land mobile radio systems. airband β half - duplex radio system used by aircraft pilots to talk to other aircraft and ground - based air traffic controllers. this vital
have to move to track it. in a satellite ground station a microwave transmitter and large satellite dish antenna transmit a microwave uplink beam to the satellite. the uplink signal carries many channels of telecommunications traffic, such as long - distance telephone calls, television programs, and internet signals, using a technique called frequency - division multiplexing ( fdm ). on the satellite, a transponder receives the signal, translates it to a different downlink frequency to avoid interfering with the uplink signal, and retransmits it down to another ground station, which may be widely separated from the first. there the downlink signal is demodulated and the telecommunications traffic it carries is sent to its local destinations through landlines. communication satellites typically have several dozen transponders on different frequencies, which are leased by different users. direct broadcast satellite β a geostationary communication satellite that transmits retail programming directly to receivers in subscriber ' s homes and vehicles on earth, in satellite radio and tv systems. it uses a higher transmitter power than other communication satellites, to allow the signal to be received by consumers with a small unobtrusive antenna. for example, satellite television uses downlink frequencies from 12. 2 to 12. 7 ghz in the ku band transmitted at 100 to 250 watts, which can be received by relatively small 43 β 80 cm ( 17 β 31 in ) satellite dishes mounted on the outside of buildings. = = = other applications = = = = = = = radar = = = = radar is a radiolocation method used to locate and track aircraft, spacecraft, missiles, ships, vehicles, and also to map weather patterns and terrain. a radar set consists of a transmitter and receiver. the transmitter emits a narrow beam of radio waves which is swept around the surrounding space. when the beam strikes a target object, radio waves are reflected back to the receiver. the direction of the beam reveals the object ' s location. since radio waves travel at a constant speed close to the speed of light, by measuring the brief time delay between the outgoing pulse and the received " echo ", the range to the target can be calculated. the targets are often displayed graphically on a map display called a radar screen. doppler radar can measure a moving object ' s velocity, by measuring the change in frequency of the return radio waves due to the doppler effect. radar sets mainly use high frequencies in the microwave bands, because these frequencies create strong reflections from objects the size of vehicles and can be focused into narrow beams with
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.
band that can be used without a license. they are often installed in vehicles, with the mobile units communicating with a dispatcher at a fixed base station. special systems with reserved frequencies are used by first responder services ; police, fire, ambulance, and emergency services, and other government services. other systems are made for use by commercial firms such as taxi and delivery services. vhf systems use channels in the range 30 β 50 mhz and 150 β 172 mhz. uhf systems use the 450 β 470 mhz band and in some areas the 470 β 512 mhz range. in general, vhf systems have a longer range than uhf but require longer antennas. am or fm modulation is mainly used, but digital systems such as dmr are being introduced. the radiated power is typically limited to 4 watts. these systems have a fairly limited range, usually 3 to 20 miles ( 4. 8 to 32 km ) depending on terrain. repeaters installed on tall buildings, hills, or mountain peaks are often used to increase the range when it is desired to cover a larger area than line - of - sight. examples of land mobile systems are cb, frs, gmrs, and murs. modern digital systems, called trunked radio systems, have a digital channel management system using a control channel that automatically assigns frequency channels to user groups. walkie - talkie β a battery - powered portable handheld half - duplex two - way radio, used in land mobile radio systems. airband β half - duplex radio system used by aircraft pilots to talk to other aircraft and ground - based air traffic controllers. this vital system is the main communication channel for air traffic control. for most communication in overland flights in air corridors a vhf - am system using channels between 108 and 137 mhz in the vhf band is used. this system has a typical transmission range of 200 miles ( 320 km ) for aircraft flying at cruising altitude. for flights in more remote areas, such as transoceanic airline flights, aircraft use the hf band or channels on the inmarsat or iridium satphone satellites. military aircraft also use a dedicated uhf - am band from 225. 0 to 399. 95 mhz. marine radio β medium - range transceivers on ships, used for ship - to - ship, ship - to - air, and ship - to - shore communication with harbormasters they use fm channels between 156 and 174 mhz in the vhf band with up to 25 watts power, giving them a range of about 60 miles ( 97 km ). some channels are half -
Question: An individual with down's syndrome has 47 of what instead of the normal 46?
A) prokaryotes
B) chromosomes
C) ribosomes
D) mitochondria
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B) chromosomes
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Context:
##tion, and pasteurization in order to become products that can be sold. there are three levels of food processing : primary, secondary, and tertiary. primary food processing involves turning agricultural products into other products that can be turned into food, secondary food processing is the making of food from readily available ingredients, and tertiary food processing is commercial production of ready - to eat or heat - and - serve foods. drying, pickling, salting, and fermenting foods were some of the oldest food processing techniques used to preserve food by preventing yeasts, molds, and bacteria to cause spoiling. methods for preserving food have evolved to meet current standards of food safety but still use the same processes as the past. biochemical engineers also work to improve the nutritional value of food products, such as in golden rice, which was developed to prevent vitamin a deficiency in certain areas where this was an issue. efforts to advance preserving technologies can also ensure lasting retention of nutrients as foods are stored. packaging plays a key role in preserving as well as ensuring the safety of the food by protecting the product from contamination, physical damage, and tampering. packaging can also make it easier to transport and serve food. a common job for biochemical engineers working in the food industry is to design ways to perform all these processes on a large scale in order to meet the demands of the population. responsibilities for this career path include designing and performing experiments, optimizing processes, consulting with groups to develop new technologies, and preparing project plans for equipment and facilities. = = = pharmaceuticals = = = in the pharmaceutical industry, bioprocess engineering plays a crucial role in the large - scale production of biopharmaceuticals, such as monoclonal antibodies, vaccines, and therapeutic proteins. the development and optimization of bioreactors and fermentation systems are essential for the mass production of these products, ensuring consistent quality and high yields. for example, recombinant proteins like insulin and erythropoietin are produced through cell culture systems using genetically modified cells. the bioprocess engineer β s role is to optimize variables like temperature, ph, nutrient availability, and oxygen levels to maximize the efficiency of these systems. the growing field of gene therapy also relies on bioprocessing techniques to produce viral vectors, which are used to deliver therapeutic genes to patients. this involves scaling up processes from laboratory to industrial scale while maintaining safety and regulatory compliance. as the demand for biopharmaceutical products increases, advancements
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
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
process of lactic acid fermentation, which produced other preserved foods, such as soy sauce. fermentation was also used in this time period to produce leavened bread. although the process of fermentation was not fully understood until louis pasteur ' s work in 1857, it is still the first use of biotechnology to convert a food source into another form. before the time of charles darwin ' s work and life, animal and plant scientists had already used selective breeding. darwin added to that body of work with his scientific observations about the ability of science to change species. these accounts contributed to darwin ' s theory of natural selection. for thousands of years, humans have used selective breeding to improve the production of crops and livestock to use them for food. in selective breeding, organisms with desirable characteristics are mated to produce offspring with the same characteristics. for example, this technique was used with corn to produce the largest and sweetest crops. in the early twentieth century scientists gained a greater understanding of microbiology and explored ways of manufacturing specific products. in 1917, chaim weizmann first used a pure microbiological culture in an industrial process, that of manufacturing corn starch using clostridium acetobutylicum, to produce acetone, which the united kingdom desperately needed to manufacture explosives during world war i. biotechnology has also led to the development of antibiotics. in 1928, alexander fleming discovered the mold penicillium. his work led to the purification of the antibiotic formed by the mold by howard florey, ernst boris chain and norman heatley β to form what we today know as penicillin. in 1940, penicillin became available for medicinal use to treat bacterial infections in humans. the field of modern biotechnology is generally thought of as having been born in 1971 when paul berg ' s ( stanford ) experiments in gene splicing had early success. herbert w. boyer ( univ. calif. at san francisco ) and stanley n. cohen ( stanford ) significantly advanced the new technology in 1972 by transferring genetic material into a bacterium, such that the imported material would be reproduced. the commercial viability of a biotechnology industry was significantly expanded on june 16, 1980, when the united states supreme court ruled that a genetically modified microorganism could be patented in the case of diamond v. chakrabarty. indian - born ananda chakrabarty, working for general electric, had modified a bacterium ( of the genus pseudomonas ) capable of breaking down crude oil, which he proposed to
. 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
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
and still use the same basic biological methods. in brewing, malted grains ( containing enzymes ) convert starch from grains into sugar and then adding specific yeasts to produce beer. in this process, carbohydrates in the grains broke down into alcohols, such as ethanol. later, other cultures produced the process of lactic acid fermentation, which produced other preserved foods, such as soy sauce. fermentation was also used in this time period to produce leavened bread. although the process of fermentation was not fully understood until louis pasteur ' s work in 1857, it is still the first use of biotechnology to convert a food source into another form. before the time of charles darwin ' s work and life, animal and plant scientists had already used selective breeding. darwin added to that body of work with his scientific observations about the ability of science to change species. these accounts contributed to darwin ' s theory of natural selection. for thousands of years, humans have used selective breeding to improve the production of crops and livestock to use them for food. in selective breeding, organisms with desirable characteristics are mated to produce offspring with the same characteristics. for example, this technique was used with corn to produce the largest and sweetest crops. in the early twentieth century scientists gained a greater understanding of microbiology and explored ways of manufacturing specific products. in 1917, chaim weizmann first used a pure microbiological culture in an industrial process, that of manufacturing corn starch using clostridium acetobutylicum, to produce acetone, which the united kingdom desperately needed to manufacture explosives during world war i. biotechnology has also led to the development of antibiotics. in 1928, alexander fleming discovered the mold penicillium. his work led to the purification of the antibiotic formed by the mold by howard florey, ernst boris chain and norman heatley β to form what we today know as penicillin. in 1940, penicillin became available for medicinal use to treat bacterial infections in humans. the field of modern biotechnology is generally thought of as having been born in 1971 when paul berg ' s ( stanford ) experiments in gene splicing had early success. herbert w. boyer ( univ. calif. at san francisco ) and stanley n. cohen ( stanford ) significantly advanced the new technology in 1972 by transferring genetic material into a bacterium, such that the imported material would be reproduced. the commercial viability of a biotechnology industry was significantly expanded on june 16, 1980, when the united states
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
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
best - known and controversial applications of genetic engineering is the creation and use of genetically modified crops or genetically modified livestock to produce genetically modified food. crops have been developed to increase production, increase tolerance to abiotic stresses, alter the composition of the food, or to produce novel products. the first crops to be released commercially 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
Question: Where is the fruiting body normally produced in relation to the food source?
A) in the soil
B) underneath the surface
C) at the root
D) at the surface
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D) at the surface
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Context:
the manufacturer. one common distinction is by nominal pore size. it describes the maximum pore size distribution and gives only vague information about the retention capacity of a membrane. the exclusion limit or " cut - off " of the membrane is usually specified in the form of nmwc ( nominal molecular weight cut - off, or mwco, molecular weight cut off, with units in dalton ). it is defined as the minimum molecular weight of a globular molecule that is retained to 90 % by the membrane. the cut - off, depending on the method, can by converted to so - called d90, which is then expressed in a metric unit. in practice the mwco of the membrane should be at least 20 % lower than the molecular weight of the molecule that is to be separated. using track etched mica membranes beck and schultz demonstrated that hindered diffusion of molecules in pores can be described by the rankin equation. filter membranes are divided into four classes according to pore size : the form and shape of the membrane pores are highly dependent on the manufacturing process and are often difficult to specify. therefore, for characterization, test filtrations are carried out and the pore diameter refers to the diameter of the smallest particles which could not pass through the membrane. the rejection can be determined in various ways and provides an indirect measurement of the pore size. one possibility is the filtration of macromolecules ( often dextran, polyethylene glycol or albumin ), another is measurement of the cut - off by gel permeation chromatography. these methods are used mainly to measure membranes for ultrafiltration applications. another testing method is the filtration of particles with defined size and their measurement with a particle sizer or by laser induced breakdown spectroscopy ( libs ). a vivid characterization is to measure the rejection of dextran blue or other colored molecules. the retention of bacteriophage and bacteria, the so - called " bacteria challenge test ", can also provide information about the pore size. to determine the pore diameter, physical methods such as porosimeter ( mercury, liquid - liquid porosimeter and bubble point test ) are also used, but a certain form of the pores ( such as cylindrical or concatenated spherical holes ) is assumed. such methods are used for membranes whose pore geometry does not match the ideal, and we get " nominal " pore diameter, which characterizes the membrane, but does not necessarily reflect its actual filt
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.
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
called the natural logarithm. a real function f is monotonic in an interval if the sign of f ( x ) β f ( y ) x β y { \ displaystyle { \ frac { f ( x ) - f ( y ) } { x - y } } } does not depend of the choice of x and y in the interval. if the function is differentiable in the interval, it is monotonic if the sign of the derivative is constant in the interval. if a real function f is monotonic in an interval i, it has an inverse function, which is a real function with domain f ( i ) and image i. this is how inverse trigonometric functions are defined in terms of trigonometric functions, where the trigonometric functions are monotonic. another example : the natural logarithm is monotonic on the positive real numbers, and its image is the whole real line ; therefore it has an inverse function that is a bijection between the real numbers and the positive real numbers. this inverse is the exponential function. many other real functions are defined either by the implicit function theorem ( the inverse function is a particular instance ) or as solutions of differential equations. for example, the sine and the cosine functions are the solutions of the linear differential equation y β³ + y = 0 { \ displaystyle y ' ' + y = 0 } such that sin 0 = 0, cos 0 = 1, β sin x β x ( 0 ) = 1, β cos x β x ( 0 ) = 0. { \ displaystyle \ sin 0 = 0, \ quad \ cos 0 = 1, \ quad { \ frac { \ partial \ sin x } { \ partial x } } ( 0 ) = 1, \ quad { \ frac { \ partial \ cos x } { \ partial x } } ( 0 ) = 0. } = = = vector - valued function = = = when the elements of the codomain of a function are vectors, the function is said to be a vector - valued function. these functions are particularly useful in applications, for example modeling physical properties. for example, the function that associates to each point of a fluid its velocity vector is a vector - valued function. some vector - valued functions are defined on a subset of r n { \ displaystyle \ mathbb { r } ^ { n } } or other spaces that share geometric or topological properties of r n { \ displaystyle \ mathbb {
significantly greater strength and fracture toughness. another major change in the body during the firing or sintering process will be the establishment of the polycrystalline nature of the solid. significant grain growth tends to occur during sintering, with this growth depending on temperature and duration of the sintering process. the growth of grains will result in some form of grain size distribution, which will have a significant impact on the ultimate physical properties of the material. in particular, abnormal grain growth in which certain grains grow very large in a matrix of finer grains will significantly alter the physical and mechanical properties of the obtained ceramic. in the sintered body, grain sizes are a product of the thermal processing parameters as well as the initial particle size, or possibly the sizes of aggregates or particle clusters which arise during the initial stages of processing. the ultimate microstructure ( and thus the physical properties ) of the final product will be limited by and subject to the form of the structural template or precursor which is created in the initial stages of chemical synthesis and physical forming. hence the importance of chemical powder and polymer processing as it pertains to the synthesis of industrial ceramics, glasses and glass - ceramics. there are numerous possible refinements of the sintering process. some of the most common involve pressing the green body to give the densification a head start and reduce the sintering time needed. sometimes organic binders such as polyvinyl alcohol are added to hold the green body together ; these burn out during the firing ( at 200 β 350 Β°c ). sometimes organic lubricants are added during pressing to increase densification. it is common to combine these, and add binders and lubricants to a powder, then press. ( the formulation of these organic chemical additives is an art in itself. this is particularly important in the manufacture of high performance ceramics such as those used by the billions for electronics, in capacitors, inductors, sensors, etc. ) a slurry can be used in place of a powder, and then cast into a desired shape, dried and then sintered. indeed, traditional pottery is done with this type of method, using a plastic mixture worked with the hands. if a mixture of different materials is used together in a ceramic, the sintering temperature is sometimes above the melting point of one minor component β a liquid phase sintering. this results in shorter sintering times compared to solid state sintering. such liquid phase sintering involves in faster diffusion processes and may result in abnormal grain
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.
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 you talk through them and hit the coil, it makes this natural reverb, like talking in another dimension. " " summer romance ( anti - gravity love song ) " was the first love ballad the band wrote, but was written in a less serious manner than later songs touching on similar subjects, such as " stellar
? if the latter, an important question is how the internal experiences of others can be measured. self - reports of feelings and beliefs may not be reliable because, even in cases in which there is no apparent incentive for subjects to intentionally deceive in their answers, self - deception or selective memory may affect their responses. then even in the case of accurate self - reports, how can responses be compared across individuals? even if two individuals respond with the same answer on a likert scale, they may be experiencing very different things. other issues in philosophy of psychology are philosophical questions about the nature of mind, brain, and cognition, and are perhaps more commonly thought of as part of cognitive science, or philosophy of mind. for example, are humans rational creatures? is there any sense in which they have free will, and how does that relate to the experience of making choices? philosophy of psychology also closely monitors contemporary work conducted in cognitive neuroscience, psycholinguistics, and artificial intelligence, questioning what they can and cannot explain in psychology. philosophy of psychology is a relatively young field, because psychology only became a discipline of its own in the late 1800s. in particular, neurophilosophy has just recently become its own field with the works of paul churchland and patricia churchland. philosophy of mind, by contrast, has been a well - established discipline since before psychology was a field of study at all. it is concerned with questions about the very nature of mind, the qualities of experience, and particular issues like the debate between dualism and monism. = = = philosophy of social science = = = the philosophy of social science is the study of the logic and method of the social sciences, such as sociology and cultural anthropology. philosophers of social science are concerned with the differences and similarities between the social and the natural sciences, causal relationships between social phenomena, the possible existence of social laws, and the ontological significance of structure and agency. the french philosopher, auguste comte ( 1798 β 1857 ), established the epistemological perspective of positivism in the course in positivist philosophy, a series of texts published between 1830 and 1842. the first three volumes of the course dealt chiefly with the natural sciences already in existence ( geoscience, astronomy, physics, chemistry, biology ), whereas the latter two emphasised the inevitable coming of social science : " sociologie ". for comte, the natural sciences had to necessarily arrive first, before humanity could adequately channel its efforts into the most challenging and complex " queen science " of human society
discussion of ` ` the dantzig selector : statistical estimation when $ p $ is much larger than $ n $ ' ' [ math / 0506081 ]
. 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 fan - shaped beam of microwaves around the water surface surrounding the craft out to the horizon. weather radar β a doppler radar which maps weather precipitation intensities and wind speeds with the echoes returned from raindrops and their radial velocity by their doppler shift. phased - array radar β a radar set that uses a phased array, a computer - controlled antenna that can steer the radar beam quickly to point in different directions without moving the antenna. phased - array radars were developed by the military to track fast - moving missiles and aircraft. they are widely used in military equipment and are now spreading to civilian applications. synthetic aperture radar ( sar ) β a specialized airborne radar set that produces a high - resolution map of ground terrain. the radar is mounted on an aircraft or spacecraft and the radar antenna radiates a beam of radio waves sideways at right angles to the direction of motion, toward the ground. in processing the return radar signal, the motion of the vehicle is used to simulate a large antenna, giving the radar a higher resolution. ground - penetrating radar β a specialized radar instrument that is rolled along the ground surface in a cart and transmits a beam of radio waves into the ground, producing an image of subsurface objects. frequencies from 100 mhz to
Question: What is the largest of the sinuses?
A) Maxillary sinus
B) superior sagittal sinus
C) Sphenoid sinus
D) Frontal sinus
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B) superior sagittal sinus
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Context:
##ulating the liquid below from the cold air above. water has the capacity to absorb energy, giving it a higher specific heat capacity than other solvents such as ethanol. thus, a large amount of energy is needed to break the hydrogen bonds between water molecules to convert liquid water into water vapor. as a molecule, water is not completely stable as each water molecule continuously dissociates into hydrogen and hydroxyl ions before reforming into a water molecule again. in pure water, the number of hydrogen ions balances ( or equals ) the number of hydroxyl ions, resulting in a ph that is neutral. = = = organic compounds = = = organic compounds are molecules that contain carbon bonded to another element such as hydrogen. with the exception of water, nearly all the molecules that make up each organism contain carbon. carbon can form covalent bonds with up to four other atoms, enabling it to form diverse, large, and complex molecules. for example, a single carbon atom can form four single covalent bonds such as in methane, two double covalent bonds such as in carbon dioxide ( co2 ), or a triple covalent bond such as in carbon monoxide ( co ). moreover, carbon can form very long chains of interconnecting carbon β carbon bonds such as octane or ring - like structures such as glucose. the simplest form of an organic molecule is the hydrocarbon, which is a large family of organic compounds that are composed of hydrogen atoms bonded to a chain of carbon atoms. a hydrocarbon backbone can be substituted by other elements such as oxygen ( o ), hydrogen ( h ), phosphorus ( p ), and sulfur ( s ), which can change the chemical behavior of that compound. groups of atoms that contain these elements ( o -, h -, p -, and s - ) and are bonded to a central carbon atom or skeleton are called functional groups. there are six prominent functional groups that can be found in organisms : amino group, carboxyl group, carbonyl group, hydroxyl group, phosphate group, and sulfhydryl group. in 1953, the miller β urey experiment showed that organic compounds could be synthesized abiotically within a closed system mimicking the conditions of early earth, thus suggesting that complex organic molecules could have arisen spontaneously in early earth ( see abiogenesis ). = = = macromolecules = = = macromolecules are large molecules made up of smaller subunits or monomers. monomers include sugars, amino acids,
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.
or solid as is the case with water ( h2o ) ; a liquid at room temperature because its molecules are bound by hydrogen bonds. whereas hydrogen sulfide ( h2s ) is a gas at room temperature and standard pressure, as its molecules are bound by weaker dipole β dipole interactions. the transfer of energy from one chemical substance to another depends on the size of energy quanta emitted from one substance. however, heat energy is often transferred more easily from almost any substance to another because the phonons responsible for vibrational and rotational energy levels in a substance have much less energy than photons invoked for the electronic energy transfer. thus, because vibrational and rotational energy levels are more closely spaced than electronic energy levels, heat is more easily transferred between substances relative to light or other forms of electronic energy. for example, ultraviolet electromagnetic radiation is not transferred with as much efficacy from one substance to another as thermal or electrical energy. the existence of characteristic energy levels for different chemical substances is useful for their identification by the analysis of spectral lines. different kinds of spectra are often used in chemical spectroscopy, e. g. ir, microwave, nmr, esr, etc. spectroscopy is also used to identify the composition of remote objects β like stars and distant galaxies β by analyzing their radiation spectra. the term chemical energy is often used to indicate the potential of a chemical substance to undergo a transformation through a chemical reaction or to transform other chemical substances. = = = reaction = = = when a chemical substance is transformed as a result of its interaction with another substance or with energy, a chemical reaction is said to have occurred. a chemical reaction is therefore a concept related to the " reaction " of a substance when it comes in close contact with another, whether as a mixture or a solution ; exposure to some form of energy, or both. it results in some energy exchange between the constituents of the reaction as well as with the system environment, which may be designed vessels β often laboratory glassware. chemical reactions can result in the formation or dissociation of molecules, that is, molecules breaking apart to form two or more molecules or rearrangement of atoms within or across molecules. chemical reactions usually involve the making or breaking of chemical bonds. oxidation, reduction, dissociation, acid β base neutralization and molecular rearrangement are some examples of common chemical reactions. a chemical reaction can be symbolically depicted through a chemical equation. while in a non - nuclear chemical reaction the number and kind of atoms on both sides of the equation are equal, for
the branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including molecular synthesis, modification, mechanisms, and interactions. = = = water = = = life arose from the earth ' s first ocean, which formed some 3. 8 billion years ago. since then, water continues to be the most abundant molecule in every organism. water is important to life because it is an effective solvent, capable of dissolving solutes such as sodium and chloride ions or other small molecules to form an aqueous solution. once dissolved in water, these solutes are more likely to come in contact with one another and therefore take part in chemical reactions that sustain life. in terms of its molecular structure, water is a small polar molecule with a bent shape formed by the polar covalent bonds of two hydrogen ( h ) atoms to one oxygen ( o ) atom ( h2o ). because the o β h bonds are polar, the oxygen atom has a slight negative charge and the two hydrogen atoms have a slight positive charge. this polar property of water allows it to attract other water molecules via hydrogen bonds, which makes water cohesive. surface tension results from the cohesive force due to the attraction between molecules at the surface of the liquid. water is also adhesive as it is able to adhere to the surface of any polar or charged non - water molecules. water is denser as a liquid than it is as a solid ( or ice ). this unique property of water allows ice to float above liquid water such as ponds, lakes, and oceans, thereby insulating the liquid below from the cold air above. water has the capacity to absorb energy, giving it a higher specific heat capacity than other solvents such as ethanol. thus, a large amount of energy is needed to break the hydrogen bonds between water molecules to convert liquid water into water vapor. as a molecule, water is not completely stable as each water molecule continuously dissociates into hydrogen and hydroxyl ions before reforming into a water molecule again. in pure water, the number of hydrogen ions balances ( or equals ) the number of hydroxyl ions, resulting in a ph that is neutral. = = = organic compounds = = = 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
the recent report on laser cooling of liquid may contradict the law of energy conservation.
temperature changes up to 1000 Β°c. = = processing steps = = the traditional ceramic process generally follows this sequence : milling β batching β mixing β forming β drying β firing β assembly. milling is the process by which materials are reduced from a large size to a smaller size. milling may involve breaking up cemented material ( in which case individual particles retain their shape ) or pulverization ( which involves grinding the particles themselves to a smaller size ). milling is generally done by mechanical means, including attrition ( which is particle - to - particle collision that results in agglomerate break up or particle shearing ), compression ( which applies a forces that results in fracturing ), and impact ( which employs a milling medium or the particles themselves to cause fracturing ). attrition milling equipment includes the wet scrubber ( also called the planetary mill or wet attrition mill ), which has paddles in water creating vortexes in which the material collides and break up. compression mills include the jaw crusher, roller crusher and cone crusher. impact mills include the ball mill, which has media that tumble and fracture the material, or the resonantacoustic mixer. shaft impactors cause particle - to particle attrition and compression. batching is the process of weighing the oxides according to recipes, and preparing them for mixing and drying. mixing occurs after batching and is performed with various machines, such as dry mixing ribbon mixers ( a type of cement mixer ), resonantacoustic mixers, mueller mixers, and pug mills. wet mixing generally involves the same equipment. forming is making the mixed material into shapes, ranging from toilet bowls to spark plug insulators. forming can involve : ( 1 ) extrusion, such as extruding " slugs " to make bricks, ( 2 ) pressing to make shaped parts, ( 3 ) slip casting, as in making toilet bowls, wash basins and ornamentals like ceramic statues. forming produces a " green " part, ready for drying. green parts are soft, pliable, and over time will lose shape. handling the green product will change its shape. for example, a green brick can be " squeezed ", and after squeezing it will stay that way. drying is removing the water or binder from the formed material. spray drying is widely used to prepare powder for pressing operations. other dryers are tunnel dryers and periodic dryers. controlled heat is applied in this two - stage process. first,
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
not only is the bekenstein expression for the entropy of a black hole a convex function of the energy, rather than being a concave function as it must be, it predicts a final equilibrium temperature given by the harmonic mean. this violates the third law, and the principle of maximum work. the property that means are monotonically increasing functions of their argument underscores the error of transferring from temperature means to means in the internal energy when the energy is not a monotonically increasing function of temperature. whereas the former leads to an increase in entropy, the latter lead to a decrease in entropy thereby violating the second law. the internal energy cannot increase at a slower rate than the temperature itself.
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
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
Question: As the temperature of water decreases what happens to the speed of the water molecules?
A) begin to boil
B) move faster
C) evaporate
D) slow down
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D) slow down
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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 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,
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.
other electrons either in bonds or in lone pairs. thus, molecules exist as electrically neutral units, unlike ions. when this rule is broken, giving the " molecule " a charge, the result is sometimes named a molecular ion or a polyatomic ion. however, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature. = = = = substance and mixture = = = = a chemical substance is a kind of matter with a definite composition and set of properties. a collection of substances is called a mixture. examples of mixtures are air and alloys. = = = = mole and amount of substance = = = = the mole is a unit
molecular nitrogen is the most commonly assumed background gas that supports habitability on rocky planets. despite its chemical inertness, nitrogen molecule is broken by lightning, hot volcanic vents, and bolide impacts, and can be converted into soluble nitrogen compounds and then sequestered in the ocean. the very stability of nitrogen, and that of nitrogen - based habitability, is thus called into question. here we determine the lifetime of molecular nitrogen vis - a - vis aqueous sequestration, by developing a novel model that couples atmospheric photochemistry and oceanic chemistry. we find that hno, the dominant nitrogen compounds produced in anoxic atmospheres, is converted to n2o in the ocean, rather than oxidized to nitrites or nitrates as previously assumed. this n2o is then released back into the atmosphere and quickly converted to n2. we also find that the deposition rate of no is severely limited by the kinetics of the aqueous - phase reaction that converts no to nitrites in the ocean. putting these insights together, we conclude that the atmosphere must produce nitrogen species at least as oxidized as no2 and hno2 to enable aqueous sequestration. the lifetime of molecular nitrogen in anoxic atmospheres is determined to be > 1 billion years on temperate planets of both sun - like and m dwarf stars. this result upholds the validity of molecular nitrogen as a universal background gas on rocky planets.
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
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 :
and myelomas can be made to fuse by chemical protocols, most often using polyethylene glycol. the myeloma cells are selected beforehand to ensure they are not secreting antibody themselves and that they lack the hypoxanthine - guanine phosphoribosyltransferase ( hgprt ) gene, making them sensitive ( or vulnerable ) to the hat medium ( see below ). fused cells are incubated in hat medium ( hypoxanthine - aminopterin - thymidine medium ) for roughly 10 to 14 days. aminopterin blocks the pathway that allows for nucleotide synthesis. hence, unfused myeloma cells die, as they cannot produce nucleotides by the de novo or salvage pathways because they lack hgprt. removal of the unfused myeloma cells is necessary because they have the potential to outgrow other cells, especially weakly established hybridomas. unfused b cells die as they have a short life span. in this way, only the b cell - myeloma hybrids survive, since the hgprt gene coming from the b cells is functional. these cells produce antibodies ( a property of b cells ) and are immortal ( a property of myeloma cells ). the incubated medium is then diluted into multi - well plates to such an extent that each well contains only one cell. since the antibodies in a well are produced by the same b cell, they will be directed towards the same epitope, and are thus monoclonal antibodies. the next stage is a rapid primary screening process, which identifies and selects only those hybridomas that produce antibodies of appropriate specificity. the first screening technique used is called elisa. the hybridoma culture supernatant, secondary enzyme labeled conjugate, and chromogenic substrate, are then incubated, and the formation of a colored product indicates a positive hybridoma. alternatively, immunocytochemical, western blot, and immunoprecipitation - mass spectrometry. unlike western blot assays, immunoprecipitation - mass spectrometry facilitates screening and ranking of clones which bind to the native ( non - denaturated ) forms of antigen proteins. flow cytometry screening has been used for primary screening of a large number ( ~ 1000 ) of hybridoma clones recognizing the native form of the antigen on the cell surface. in the flow
that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature. = = = = substance and mixture = = = = a chemical substance is a kind of matter with a definite composition and set of properties. a collection of substances is called a mixture. examples of mixtures are air and alloys. = = = = mole and amount of substance = = = = the mole is a unit of measurement that denotes an amount of substance ( also called chemical amount ). one mole is defined to contain exactly 6. 02214076Γ1023 particles ( atoms, molecules, ions, or electrons ), where the number of particles per mole is known as the avogadro constant. molar concentration is
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 ' 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
on earth in suitable amounts. one isotope of uranium, namely uranium - 235, is naturally occurring and sufficiently unstable, but it is always found mixed with the more stable isotope uranium - 238. the latter accounts for more than 99 % of the weight of natural uranium. therefore, some method of isotope separation based on the weight of three neutrons must be performed to enrich ( isolate ) uranium - 235. alternatively, the element plutonium possesses an isotope that is sufficiently unstable for this process to be usable. terrestrial plutonium does not currently occur naturally in sufficient quantities for such use, so it must be manufactured in a nuclear reactor. ultimately, the manhattan project manufactured nuclear weapons based on each of these elements. they detonated the first nuclear weapon in a test code - named " trinity ", near alamogordo, new mexico, on july 16, 1945. the test was conducted to ensure that the implosion method of detonation would work, which it did. a uranium bomb, little boy, was dropped on the japanese city hiroshima on august 6, 1945, followed three days later by the plutonium - based fat man on nagasaki. in the wake of unprecedented devastation and casualties from a single weapon, the japanese government soon surrendered, ending world war ii. since these bombings, no nuclear weapons have been deployed offensively. nevertheless, they prompted an arms race to develop increasingly destructive bombs to provide a nuclear deterrent. just over four years later, on august 29, 1949, the soviet union detonated its first fission weapon. the united kingdom followed on october 2, 1952 ; france, on february 13, 1960 ; and china component to a nuclear weapon. approximately half of the deaths from hiroshima and nagasaki died two to five years afterward from radiation exposure. a radiological weapon is a type of nuclear weapon designed to distribute hazardous nuclear material in enemy areas. such a weapon would not have the explosive capability of a fission or fusion bomb, but would kill many people and contaminate a large area. a radiological weapon has never been deployed. while considered useless by a conventional military, such a weapon raises concerns over nuclear terrorism. there have been over 2, 000 nuclear tests conducted since 1945. in 1963, all nuclear and many non - nuclear states signed the limited test ban treaty, pledging to refrain from testing nuclear weapons in the atmosphere, underwater, or in outer space. the treaty permitted underground nuclear testing. france continued atmospheric testing until 1974, while china continued up until 1980. the last underground test by the united states was in 1992, the soviet union
Question: Amines are weak bases due to the presence of a lone pair of what on the nitrogen atom?
A) nuclei
B) electrons
C) atoms
D) protons
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B) electrons
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Context:
prominent functional groups that can be found in organisms : amino group, carboxyl group, carbonyl group, hydroxyl group, phosphate group, and sulfhydryl group. in 1953, the miller β urey experiment showed that organic compounds could be synthesized abiotically within a closed system mimicking the conditions of early earth, thus suggesting that complex organic molecules could have arisen spontaneously in early earth ( see abiogenesis ). = = = macromolecules = = = macromolecules are large molecules made up of smaller subunits or monomers. monomers include sugars, amino acids, and nucleotides. carbohydrates include monomers and polymers of sugars. lipids are the only class of macromolecules that are not made up of polymers. they include steroids, phospholipids, and fats, largely nonpolar and hydrophobic ( water - repelling ) substances. proteins are the most diverse of the macromolecules. they include enzymes, transport proteins, large signaling molecules, antibodies, and structural proteins. the basic unit ( or monomer ) of a protein is an amino acid. twenty amino acids are used in proteins. nucleic acids are polymers of nucleotides. their function is to store, transmit, and express hereditary information. = = cells = = cell theory states that cells are the fundamental units of life, that all living things are composed of one or more cells, and that all cells arise from preexisting cells through cell division. most cells are very small, with diameters ranging from 1 to 100 micrometers and are therefore only visible under a light or electron microscope. there are generally two types of cells : eukaryotic cells, which contain a nucleus, and prokaryotic cells, which do not. prokaryotes are single - celled organisms such as bacteria, whereas eukaryotes can be single - celled or multicellular. in multicellular organisms, every cell in the organism ' s body is derived ultimately from a single cell in a fertilized egg. = = = cell structure = = = every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as
if a fintie group g acts topologically and faithfully on r ^ 3, then g is a subgroup of o ( 3 )
a suitable choice of the four components of the metric tensor which are at our discretion allows to represent geodesically also the non - gravitational motions.
##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
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
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.
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
( 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
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
of a point on the object, including whole - body translations and rotations ( rigid transformations ). deformation are changes in the relative position between internals points on the object, excluding rigid transformations, causing the body to change shape or size. strain is the relative internal deformation, the dimensionless change in shape of an infinitesimal cube of material relative to a reference configuration. mechanical strains are caused by mechanical stress, see stress - strain curve. the relationship between stress and strain is generally linear and reversible up until the yield point and the deformation is elastic. elasticity in materials occurs when applied stress does not surpass the energy required to break molecular bonds, allowing the material to deform reversibly and return to its original shape once the stress is removed. the linear relationship for a material is known as young ' s modulus. above the yield point, some degree of permanent distortion remains after unloading and is termed plastic deformation. the determination of the stress and strain throughout a solid object is given by the field of strength of materials and for a structure by structural analysis. in the above figure, it can be seen that the compressive loading ( indicated by the arrow ) has caused deformation in the cylinder so that the original shape ( dashed lines ) has changed ( deformed ) into one with bulging sides. the sides bulge because the material, although strong enough to not crack or otherwise fail, is not strong enough to support the load without change. as a result, the material is forced out laterally. internal forces ( in this case at right angles to the deformation ) resist the applied load. = = types of deformation = = depending on the type of material, size and geometry of the object, and the forces applied, various types of deformation may result. the image to the right shows the engineering stress vs. strain diagram for a typical ductile material such as steel. different deformation modes may occur under different conditions, as can be depicted using a deformation mechanism map. permanent deformation is irreversible ; the deformation stays even after removal of the applied forces, while the temporary deformation is recoverable as it disappears after the removal of applied forces. temporary deformation is also called elastic deformation, while the permanent deformation is called plastic deformation. = = = elastic deformation = = = the study of temporary or elastic deformation in the case of engineering strain is applied to materials used in mechanical and structural engineering, such as concrete and steel, which are subjected to very small deformations. engineering strain is modeled by infinitesimal strain theory, also called
Question: Muscle groups are controlled by what mechanism?
A) cerebral cortex
B) motor cortex
C) growth hormones
D) activation energy
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B) motor cortex
|
Context:
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
of ceramic parts in the requisite precision and durability is difficult. imperfection in the ceramic leads to cracks, which can lead to potentially dangerous equipment failure. such engines are possible in laboratory settings, but mass - production is not feasible with current technology. work is being done in developing ceramic parts for gas turbine engines. currently, even blades made of advanced metal alloys used in the engines ' hot section require cooling and careful limiting of operating temperatures. turbine engines made with ceramics could operate more efficiently, giving aircraft greater range and payload for a set amount of fuel. recently, there have been advances in ceramics which include bio - ceramics, such as dental implants and synthetic bones. hydroxyapatite, the natural mineral component of bone, has been made synthetically from a number of biological and chemical sources and can be formed into ceramic materials. orthopedic implants made from these materials bond readily to bone and other tissues in the body without rejection or inflammatory reactions. because of this, they are of great interest for gene delivery and tissue engineering scaffolds. most hydroxyapatite ceramics are very porous and lack mechanical strength and are used to coat metal orthopedic devices to aid in forming a bond to bone or as bone fillers. they are also used as fillers for orthopedic plastic screws to aid in reducing the inflammation and increase absorption of these plastic materials. work is being done to make strong, fully dense nano crystalline hydroxyapatite ceramic materials for orthopedic weight bearing devices, replacing foreign metal and plastic orthopedic materials with a synthetic, but naturally occurring, bone mineral. ultimately these ceramic materials may be used as bone replacements or with the incorporation of protein collagens, synthetic bones. durable actinide - containing ceramic materials have many applications such as in nuclear fuels for burning excess pu and in chemically - inert sources of alpha irradiation for power supply of unmanned space vehicles or to produce electricity for microelectronic devices. both use and disposal of radioactive actinides require their immobilization in a durable host material. nuclear waste long - lived radionuclides such as actinides are immobilized using chemically - durable crystalline materials based on polycrystalline ceramics and large single crystals. alumina ceramics are widely utilized in the chemical industry due to their excellent chemical stability and high resistance to corrosion. it is used as acid - resistant pump impellers and pump bodies, ensuring long - lasting performance in transferring aggressive
inflammatory reactions. because of this, they are of great interest for gene delivery and tissue engineering scaffolds. most hydroxyapatite ceramics are very porous and lack mechanical strength and are used to coat metal orthopedic devices to aid in forming a bond to bone or as bone fillers. they are also used as fillers for orthopedic plastic screws to aid in reducing the inflammation and increase absorption of these plastic materials. work is being done to make strong, fully dense nano crystalline hydroxyapatite ceramic materials for orthopedic weight bearing devices, replacing foreign metal and plastic orthopedic materials with a synthetic, but naturally occurring, bone mineral. ultimately these ceramic materials may be used as bone replacements or with the incorporation of protein collagens, synthetic bones. durable actinide - containing ceramic materials have many applications such as in nuclear fuels for burning excess pu and in chemically - inert sources of alpha irradiation for power supply of unmanned space vehicles or to produce electricity for microelectronic devices. both use and disposal of radioactive actinides require their immobilization in a durable host material. nuclear waste long - lived radionuclides such as actinides are immobilized using chemically - durable crystalline materials based on polycrystalline ceramics and large single crystals. alumina ceramics are widely utilized in the chemical industry due to their excellent chemical stability and high resistance to corrosion. it is used as acid - resistant pump impellers and pump bodies, ensuring long - lasting performance in transferring aggressive fluids. they are also used in acid - carrying pipe linings to prevent contamination and maintain fluid purity, which is crucial in industries like pharmaceuticals and food processing. valves made from alumina ceramics demonstrate exceptional durability and resistance to chemical attack, making them reliable for controlling the flow of corrosive liquids. = = glass - ceramics = = glass - ceramic materials share many properties with both glasses and ceramics. glass - ceramics have an amorphous phase and one or more crystalline phases and are produced by a so - called " controlled crystallization ", which is typically avoided in glass manufacturing. glass - ceramics often contain a crystalline phase which constitutes anywhere from 30 % [ m / m ] to 90 % [ m / m ] of its composition by volume, yielding an array of materials with interesting thermomechanical properties. in the processing of glass - ceramics, molten glass is cooled down gradually before reheating and annealing. in this heat
. 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. =
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 third millennium bc in palmela, portugal, los millares, spain, and stonehenge, united kingdom. the precise beginnings, however, have not be clearly ascertained and new discoveries are both continuous and ongoing. in approximately 1900 bc, ancient iron smelting sites existed in tamil nadu. in the near east, about 3, 500 bc, it was discovered that by combining copper and tin, a superior metal could be made, an alloy called bronze. this represented a major technological shift known as the bronze age. the extraction of iron from its ore into a workable metal is much more difficult than for copper or tin. the process appears to have been invented by the hittites in about 1200 bc, beginning the iron age. the secret of extracting and working iron was a key factor in the success of the philistines. historical developments in ferrous metallurgy can be found in a wide variety of past cultures and civilizations. this includes the ancient and medieval kingdoms and empires of the middle east and near east, ancient iran, ancient egypt, ancient nubia, and anatolia in present - day turkey, ancient nok, carthage, the celts, greeks and romans of ancient europe, medieval europe, ancient and medieval china, ancient and medieval india, ancient and medieval japan, amongst others. a 16th century book by georg agricola, de re metallica, describes the highly developed and complex processes of mining metal ores, metal extraction, and metallurgy of the time. agricola has been described as the " father of metallurgy ". = = extraction = = extractive metallurgy is the practice of removing valuable metals from an ore and refining the extracted raw metals into a purer form. in order to convert a metal oxide or sulphide to a purer metal, the ore must be reduced physically, chemically, or electrolytically. extractive metallurgists are interested in three primary streams : feed, concentrate ( metal oxide / sulphide ) and tailings ( waste ). after mining, large pieces of the ore feed are broken through crushing or grinding in order to obtain particles small enough, where each particle is either mostly valuable or mostly waste. concentrating the particles of value in a form supporting separation enables the desired metal to be removed from waste products. mining may not be necessary, if the ore body and physical environment are conducive to leaching. leaching dissolves minerals in an ore body and results in an enriched solution. the solution
was used before copper smelting was known. copper smelting is believed to have originated when the technology of pottery kilns allowed sufficiently high temperatures. the concentration of various elements such as arsenic increase with depth in copper ore deposits and smelting of these ores yields arsenical bronze, which can be sufficiently work hardened to be suitable for making tools. bronze is an alloy of copper with tin ; the latter being found in relatively few deposits globally caused a long time to elapse before true tin bronze became widespread. ( see : tin sources and trade in ancient times ) bronze was a major advancement over stone as a material for making tools, both because of its mechanical properties like strength and ductility and because it could be cast in molds to make intricately shaped objects. bronze significantly advanced shipbuilding technology with better tools and bronze nails. bronze nails replaced the old method of attaching boards of the hull with cord woven through drilled holes. better ships enabled long - distance trade and the advance of civilization. this technological trend apparently began in the fertile crescent and spread outward over time. these developments were not, and still are not, universal. the three - age system does not accurately describe the technology history of groups outside of eurasia, and does not apply at all in the case of some isolated populations, such as the spinifex people, the sentinelese, and various amazonian tribes, which still make use of stone age technology, and have not developed agricultural or metal technology. these villages preserve traditional customs in the face of global modernity, exhibiting a remarkable resistance to the rapid advancement of technology. = = = = iron age = = = = before iron smelting was developed the only iron was obtained from meteorites and is usually identified by having nickel content. meteoric iron was rare and valuable, but was sometimes used to make tools and other implements, such as fish hooks. the iron age involved the adoption of iron smelting technology. it generally replaced bronze and made it possible to produce tools which were stronger, lighter and cheaper to make than bronze equivalents. the raw materials to make iron, such as ore and limestone, are far more abundant than copper and especially tin ores. consequently, iron was produced in many areas. it was not possible to mass manufacture steel or pure iron because of the high temperatures required. furnaces could reach melting temperature but the crucibles and molds needed for melting and casting had not been developed. steel could be produced by forging bloomery iron to reduce the carbon content in a
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
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
##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
Question: Deficiency of what mineral causes bones to become porous and weak?
A) calcium
B) potassium
C) zinc
D) magnesium
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A) calcium
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Context:
scale. thus, solutions that have a low ph have a high hydronium ion concentration and can be said to be more acidic. the other measurement, based on the brΓΈnsted β lowry definition, is the acid dissociation constant ( ka ), which measures the relative ability of a substance to act as an acid under the brΓΈnsted β lowry definition of an acid. that is, substances with a higher ka are more likely to donate hydrogen ions in chemical reactions than those with lower ka values. = = = redox = = = redox ( reduction - oxidation ) reactions include all chemical reactions in which atoms have their oxidation state changed by either gaining electrons ( reduction ) or losing electrons ( oxidation ). substances that have the ability to oxidize other substances are said to be oxidative and are known as oxidizing agents, oxidants or oxidizers. an oxidant removes electrons from another substance. similarly, substances that have the ability to reduce other substances are said to be reductive and are known as reducing agents, reductants, or reducers. a reductant transfers electrons to another substance and is thus oxidized itself. and because it " donates " electrons it is also called an electron donor. oxidation and reduction properly refer to a change in oxidation number β the actual transfer of electrons may never occur. thus, oxidation is better defined as an increase in oxidation number, and reduction as a decrease in oxidation number. = = = equilibrium = = = although the concept of equilibrium is widely used across sciences, in the context of chemistry, it arises whenever a number of different states of the chemical composition are possible, as for example, in a mixture of several chemical compounds that can react with one another, or when a substance can be present in more than one kind of phase. a system of chemical substances at equilibrium, even though having an unchanging composition, is most often not static ; molecules of the substances continue to react with one another thus giving rise to a dynamic equilibrium. thus the concept describes the state in which the parameters such as chemical composition remain unchanged over time. = = = chemical laws = = = chemical reactions are governed by certain laws, which have become fundamental concepts in chemistry. some of them are : = = history = = the history of chemistry spans a period from the ancient past to the present. since several millennia bc, civilizations were using technologies that would eventually form the basis of the various branches of chemistry. examples include extracting metals from ores
". = = 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
, etc. electrostatic control - to avoid the build - up of static electricity in production of paper, plastics, synthetic textiles, etc., a ribbon - shaped source of the alpha emitter 241am can be placed close to the material at the end of the production line. the source ionizes the air to remove electric charges on the material. radioactive tracers - since radioactive isotopes behave, chemically, mostly like the inactive element, the behavior of a certain chemical substance can be followed by tracing the radioactivity. examples : adding a gamma tracer to a gas or liquid in a closed system makes it possible to find a hole in a tube. adding a tracer to the surface of the component of a motor makes it possible to measure wear by measuring the activity of the lubricating oil. oil and gas exploration - nuclear well logging is used to help predict the commercial viability of new or existing wells. the technology involves the use of a neutron or gamma - ray source and a radiation detector which are lowered into boreholes to determine the properties of the surrounding rock such as porosity and lithography. [ 1 ] road construction - nuclear moisture / density gauges are used to determine the density of soils, asphalt, and concrete. typically a cesium - 137 source is used. = = = commercial applications = = = radioluminescence tritium illumination : tritium is used with phosphor in rifle sights to increase nighttime firing accuracy. some runway markers and building exit signs use the same technology, to remain illuminated during blackouts. betavoltaics. smoke detector : an ionization smoke detector includes a tiny mass of radioactive americium - 241, which is a source of alpha radiation. two ionisation chambers are placed next to each other. both contain a small source of 241am that gives rise to a small constant current. one is closed and serves for comparison, the other is open to ambient air ; it has a gridded electrode. when smoke enters the open chamber, the current is disrupted as the smoke particles attach to the charged ions and restore them to a neutral electrical state. this reduces the current in the open chamber. when the current drops below a certain threshold, the 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
eremets and troyan ( nature mater. 10, 927 - 931 ( 2011 ) ) claim that they produced the conducting liquid hydrogen state at 270 gpa and 295 k. their evidence consists of disappearance of raman signals, visual observations, and measurements of electrical conductivity in diamond anvil cells ( dac ). however, there is no proof that the reported observations are due to transformations in hydrogen.
. 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
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
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
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
the electric dipole strength in 120sn has been extracted from proton inelastic scattering experiments at e _ p = 295 mev and at forward angles including 0 degree. below neutron threshoild it differs from the results of a 120sn ( gamma, gamma ' ) experiment and peaks at an excitation energy of 8. 3 mev. the total strength corresponds to 2. 3 ( 2 ) % of the energy - weighted sum rule and is more than three times larger than what is observed with the ( gamma, gamma ' ) reaction. this implies a strong fragmentation of the e1 strength and / or small ground state branching ratios of the excited 1 - states.
with curved sidewalls as with isotropic etching. hydrofluoric acid is commonly used as an aqueous etchant for silicon dioxide ( sio2, also known as box for soi ), usually in 49 % concentrated form, 5 : 1, 10 : 1 or 20 : 1 boe ( buffered oxide etchant ) or bhf ( buffered hf ). they were first used in medieval times for glass etching. it was used in ic fabrication for patterning the gate oxide until the process step was replaced by rie. hydrofluoric acid is considered one of the more dangerous acids in the cleanroom. electrochemical etching ( ece ) for dopant - selective removal of silicon is a common method to automate and to selectively control etching. an active p β n diode junction is required, and either type of dopant can be the etch - resistant ( " etch - stop " ) material. boron is the most common etch - stop dopant. in combination with wet anisotropic etching as described above, ece has been used successfully for controlling silicon diaphragm thickness in commercial piezoresistive silicon pressure sensors. selectively doped regions can be created either by implantation, diffusion, or epitaxial deposition of silicon. = = = = dry etching = = = = xenon difluoride ( xef2 ) is a dry vapor phase isotropic etch for silicon originally applied for mems in 1995 at university of california, los angeles. primarily used for releasing metal and dielectric structures by undercutting silicon, xef2 has the advantage of a stiction - free release unlike wet etchants. its etch selectivity to silicon is very high, allowing it to work with photoresist, sio2, silicon nitride, and various metals for masking. its reaction to silicon is " plasmaless ", is purely chemical and spontaneous and is often operated in pulsed mode. models of the etching action are available, and university laboratories and various commercial tools offer solutions using this approach. modern vlsi processes avoid wet etching, and use plasma etching instead. plasma etchers can operate in several modes by adjusting the parameters of the plasma. ordinary plasma etching operates between 0. 1 and 5 torr. ( this unit of pressure, commonly used in vacuum engineering, equals approximately 133. 3 pascal
Question: What is the apparatus used for carrying out an electrolysis reaction called?
A) biochemical cell
B) fluorescent cell
C) electrolytic cell
D) reversible cell
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C) electrolytic cell
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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.
this process may release or absorb energy. when the resulting nucleus is lighter than that of iron, energy is normally released ; when the nucleus is heavier than that of iron, energy is generally absorbed. this process of fusion occurs in stars, which derive their energy from hydrogen and helium. they form, through stellar nucleosynthesis, the light elements ( lithium to calcium ) as well as some of the heavy elements ( beyond iron and nickel, via the s - process ). the remaining abundance of heavy elements, from nickel to uranium and beyond, is due to supernova nucleosynthesis, the r - process. of course, these natural processes of astrophysics are not examples of nuclear " technology ". because of the very strong repulsion of nuclei, fusion is difficult to achieve in a controlled fashion. hydrogen bombs, formally known as thermonuclear weapons, obtain their enormous destructive power from fusion, but their energy cannot be controlled. controlled fusion is achieved in particle accelerators ; this is how many synthetic elements are produced. a fusor can also produce controlled fusion and is a useful neutron source. however, both of these devices operate at a net energy loss. controlled, viable fusion power has proven elusive, despite the occasional hoax. technical and theoretical difficulties have hindered the development of working civilian fusion technology, though research continues to this day around the world. nuclear fusion was initially pursued only in theoretical stages during world war ii, when scientists on the manhattan project ( led by edward teller ) investigated it as a method to build a bomb. the project abandoned fusion after concluding that it would require a fission reaction to detonate. it took until 1952 for the first full hydrogen bomb to be detonated, so - called because it used reactions between deuterium and tritium. fusion reactions are much more energetic per unit mass of fuel than fission reactions, but starting the fusion chain reaction is much more difficult. = = nuclear weapons = = a nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or a combination of fission and fusion. both reactions release vast quantities of energy from relatively small amounts of matter. even small nuclear devices can devastate a city by blast, fire and radiation. nuclear weapons are considered weapons of mass destruction, and their use and control has been a major aspect of international policy since their debut. the design of a nuclear weapon is more complicated than it might seem. such a weapon must hold one or more subcritical fissile masses stable for deployment, then induce criticality
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.
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.
oscillations of the sun have been used to understand its interior structure. the extension of similar studies to more distant stars has raised many difficulties despite the strong efforts of the international community over the past decades. the corot ( convection rotation and planetary transits ) satellite, launched in december 2006, has now measured oscillations and the stellar granulation signature in three main sequence stars that are noticeably hotter than the sun. the oscillation amplitudes are about 1. 5 times as large as those in the sun ; the stellar granulation is up to three times as high. the stellar amplitudes are about 25 % below the theoretic values, providing a measurement of the nonadiabaticity of the process ruling the oscillations in the outer layers of the stars.
the mechanism of stabilization of neutron - excess nuclei in stars is considered. this mechanism must produce the neutronisation process in hot stars in the same way as it occurs in the dwarfs.
stars of ~ 8 - 100 solar masses end their lives as core - collapse supernovae ( sne ). in the process they emit a powerful burst of neutrinos, produce a variety of elements, and leave behind either a neutron star or a black hole. the wide mass range for sn progenitors results in diverse neutrino signals, explosion energies, and nucleosynthesis products. a major mechanism to produce nuclei heavier than iron is rapid neutron capture, or the r process. this process may be connected to sne in several ways. a brief review is presented on current understanding of neutrino emission, explosion, and nucleosynthesis of sne.
in the present - day universe, it appears that most, and perhaps all, massive stars are born in star clusters. it also appears that all star clusters contain stars drawn from an approximately universal initial mass function, so that almost all rich young star clusters contain massive stars. in this review i discuss the physical processes associated with both massive star formation and with star cluster formation. first i summarize the observed properties of star - forming gas clumps, then address the following questions. how do these clumps emerge from giant molecular clouds? in these clustered environments, how do individual stars form and gain mass? can a forming star cluster be treated as an equilibrium system or is this process too rapid for equilibrium to be established? how does feedback affect the formation process?
in steady state, the fuel cycle of a fusion plasma requires inward particle fluxes of fuel ions. these particle flows are also accompanied by heating. in the case of classical transport in a rotating cylindrical plasma, this heating can proceed through several distinct channels depending on the physical mechanisms involved. some channels directly heat the fuel ions themselves, whereas others heat electrons. which channel dominates depends, in general, on the details of the temperature, density, and rotation profiles of the plasma constituents. however, remarkably, under relatively few assumptions concerning these profiles, if the alpha particles, the byproducts of the fusion reaction, can be removed directly by other means, a hot - ion mode tends to emerge naturally.
i suggest that the main process that amplifies magnetic fields in cooling flows in clusters and group of galaxies is a jet - driven dynamo ( jedd ). the main processes that are behind the jedd is the turbulence that is formed by the many vortices formed in the inflation processes of bubbles, and the large scale shear formed by the propagating jet. it is sufficient that a strong turbulence exits in the vicinity of the jets and bubbles, just where the shear is large. the typical amplification time of magnetic fields by the jedd near the jets and bubbles is approximately hundred million years. the amplification time in the entire cooling flow region is somewhat longer. the vortices that create the turbulence are those that also transfer energy from the jets to the intra - cluster medium, by mixing shocked jet gas with the intra - cluster medium gas, and by exciting sound waves. the jedd model adds magnetic fields to the cyclical behavior of energy and mass in the jet - feedback mechanism ( jfm ) in cooling flows.
Question: After what life stage does the fusion inside a star end?
A) red giant
B) white dwarf
C) yellow dwarf
D) blue giant
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A) red giant
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Context:
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.
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.
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.
also launched missions to mercury in 2004, with the messenger probe demonstrating as the first use of a solar sail. nasa also launched probes to the outer solar system starting in the 1960s. pioneer 10 was the first probe to the outer planets, flying by jupiter, while pioneer 11 provided the first close up view of the planet. both probes became the first objects to leave the solar system. the voyager program launched in 1977, conducting flybys of jupiter and saturn, neptune, and uranus on a trajectory to leave the solar system. the galileo spacecraft, deployed from the space shuttle flight sts - 34, was the first spacecraft to orbit jupiter, discovering evidence of subsurface oceans on the europa and observed that the moon may hold ice or liquid water. a joint nasa - european space agency - italian space agency mission, cassini β huygens, was sent to saturn ' s moon titan, which, along with mars and europa, are the only celestial bodies in the solar system suspected of being capable of harboring life. cassini discovered three new moons of saturn and the huygens probe entered titan ' s atmosphere. the mission discovered evidence of liquid hydrocarbon lakes on titan and subsurface water oceans on the moon of enceladus, which could harbor life. finally launched in 2006, the new horizons mission was the first spacecraft to visit pluto and the kuiper belt. beyond interplanetary probes, nasa has launched many space telescopes. launched in the 1960s, the orbiting astronomical observatory were nasa ' s first orbital telescopes, providing ultraviolet, gamma - ray, x - ray, and infrared observations. nasa launched the orbiting geophysical observatory in the 1960s and 1970s to look down at earth and observe its interactions with the sun. the uhuru satellite was the first dedicated x - ray telescope, mapping 85 % of the sky and discovering a large number of black holes. launched in the 1990s and early 2000s, the great observatories program are among nasa ' s most powerful telescopes. the hubble space telescope was launched in 1990 on sts - 31 from the discovery and could view galaxies 15 billion light years away. a major defect in the telescope ' s mirror could have crippled the program, had nasa not used computer enhancement to compensate for the imperfection and launched five space shuttle servicing flights to replace the damaged components. the compton gamma ray observatory was launched from the atlantis on sts - 37 in 1991, discovering a possible source of antimatter at the center of the milky way and observing that the majority of gamma - ray bursts
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.
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 minimum atmospheric temperature, or tropopause, occurs at a pressure of around 0. 1 bar in the atmospheres of earth, titan, jupiter, saturn, uranus and neptune, despite great differences in atmospheric composition, gravity, internal heat and sunlight. in all these bodies, the tropopause separates a stratosphere with a temperature profile that is controlled by the absorption of shortwave solar radiation, from a region below characterised by convection, weather, and clouds. however, it is not obvious why the tropopause occurs at the specific pressure near 0. 1 bar. here we use a physically - based model to demonstrate that, at atmospheric pressures lower than 0. 1 bar, transparency to thermal radiation allows shortwave heating to dominate, creating a stratosphere. at higher pressures, atmospheres become opaque to thermal radiation, causing temperatures to increase with depth and convection to ensue. a common dependence of infrared opacity on pressure, arising from the shared physics of molecular absorption, sets the 0. 1 bar tropopause. we hypothesize that a tropopause at a pressure of approximately 0. 1 bar is characteristic of many thick atmospheres, including exoplanets and exomoons in our galaxy and beyond. judicious use of this rule could help constrain the atmospheric structure, and thus the surface environments and habitability, of exoplanets.
the 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.
three planets with minimum masses less than 10 earth masses orbit the star hd 40307, suggesting these planets may be rocky. however, with only radial velocity data, it is impossible to determine if these planets are rocky or gaseous. here we exploit various dynamical features of the system in order to assess the physical properties of the planets. observations allow for circular orbits, but a numerical integration shows that the eccentricities must be at least 0. 0001. also, planets b and c are so close to the star that tidal effects are significant. if planet b has tidal parameters similar to the terrestrial planets in the solar system and a remnant eccentricity larger than 0. 001, then, going back in time, the system would have been unstable within the lifetime of the star ( which we estimate to be 6. 1 + / - 1. 6 gyr ). moreover, if the eccentricities are that large and the inner planet is rocky, then its tidal heating may be an order of magnitude greater than extremely volcanic io, on a per unit surface area basis. if planet b is not terrestrial, e. g. neptune - like, these physical constraints would not apply. this analysis suggests the planets are not terrestrial - like, and are more like our giant planets. in either case, we find that the planets probably formed at larger radii and migrated early - on ( via disk interactions ) into their current orbits. this study demonstrates how the orbital and dynamical properties of exoplanet systems may be used to constrain the planets ' physical properties.
the first observations of saturn ' s visible - wavelength aurora were made by the cassini camera. the aurora was observed between 2006 and 2013 in the northern and southern hemispheres. the color of the aurora changes from pink at a few hundred km above the horizon to purple at 1000 - 1500 km above the horizon. the spectrum observed in 9 filters spanning wavelengths from 250 nm to 1000 nm has a prominent h - alpha line and roughly agrees with laboratory simulated auroras. auroras in both hemispheres vary dramatically with longitude. auroras form bright arcs between 70 and 80 degree latitude north and between 65 and 80 degree latitude south, which sometimes spiral around the pole, and sometimes form double arcs. a large 10, 000 - km - scale longitudinal brightness structure persists for more than 100 hours. this structure rotates approximately together with saturn. on top of the large steady structure, the auroras brighten suddenly on the timescales of a few minutes. these brightenings repeat with a period of about 1 hour. smaller, 1000 - km - scale structures may move faster or lag behind saturn ' s rotation on timescales of tens of minutes. the persistence of nearly - corotating large bright longitudinal structure in the auroral oval seen in two movies spanning 8 and 11 rotations gives an estimate on the period of 10. 65 $ \ pm $ 0. 15 h for 2009 in the northern oval and 10. 8 $ \ pm $ 0. 1 h for 2012 in the southern oval. the 2009 north aurora period is close to the north branch of saturn kilometric radiation ( skr ) detected at that time.
Question: What color is neptune?
A) white
B) yellow
C) blue
D) pink
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C) blue
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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
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
significantly greater strength and fracture toughness. another major change in the body during the firing or sintering process will be the establishment of the polycrystalline nature of the solid. significant grain growth tends to occur during sintering, with this growth depending on temperature and duration of the sintering process. the growth of grains will result in some form of grain size distribution, which will have a significant impact on the ultimate physical properties of the material. in particular, abnormal grain growth in which certain grains grow very large in a matrix of finer grains will significantly alter the physical and mechanical properties of the obtained ceramic. in the sintered body, grain sizes are a product of the thermal processing parameters as well as the initial particle size, or possibly the sizes of aggregates or particle clusters which arise during the initial stages of processing. the ultimate microstructure ( and thus the physical properties ) of the final product will be limited by and subject to the form of the structural template or precursor which is created in the initial stages of chemical synthesis and physical forming. hence the importance of chemical powder and polymer processing as it pertains to the synthesis of industrial ceramics, glasses and glass - ceramics. there are numerous possible refinements of the sintering process. some of the most common involve pressing the green body to give the densification a head start and reduce the sintering time needed. sometimes organic binders such as polyvinyl alcohol are added to hold the green body together ; these burn out during the firing ( at 200 β 350 Β°c ). sometimes organic lubricants are added during pressing to increase densification. it is common to combine these, and add binders and lubricants to a powder, then press. ( the formulation of these organic chemical additives is an art in itself. this is particularly important in the manufacture of high performance ceramics such as those used by the billions for electronics, in capacitors, inductors, sensors, etc. ) a slurry can be used in place of a powder, and then cast into a desired shape, dried and then sintered. indeed, traditional pottery is done with this type of method, using a plastic mixture worked with the hands. if a mixture of different materials is used together in a ceramic, the sintering temperature is sometimes above the melting point of one minor component β a liquid phase sintering. this results in shorter sintering times compared to solid state sintering. such liquid phase sintering involves in faster diffusion processes and may result in abnormal grain
intense research in the materials science community due to the unique properties that they exhibit. nanostructure deals with objects and structures that are in the 1 β 100 nm range. in many materials, atoms or molecules agglomerate to form objects at the nanoscale. this causes many interesting electrical, magnetic, optical, and mechanical properties. in describing nanostructures, it is necessary to differentiate between the number of dimensions on the nanoscale. nanotextured surfaces have one dimension on the nanoscale, i. e., only the thickness of the surface of an object is between 0. 1 and 100 nm. nanotubes have two dimensions on the nanoscale, i. e., the diameter of the tube is between 0. 1 and 100 nm ; its length could be much greater. finally, spherical nanoparticles have three dimensions on the nanoscale, i. e., the particle is between 0. 1 and 100 nm in each spatial dimension. the terms nanoparticles and ultrafine particles ( ufp ) often are used synonymously although ufp can reach into the micrometre range. the term ' nanostructure ' is often used, when referring to magnetic technology. nanoscale structure in biology is often called ultrastructure. = = = = microstructure = = = = microstructure is defined as the structure of a prepared surface or thin foil of material as revealed by a microscope above 25Γ magnification. it deals with objects from 100 nm to a few cm. the microstructure of a material ( which can be broadly classified into metallic, polymeric, ceramic and composite ) can strongly influence physical properties such as strength, toughness, ductility, hardness, corrosion resistance, high / low temperature behavior, wear resistance, and so on. most of the traditional materials ( such as metals and ceramics ) are microstructured. the manufacture of a perfect crystal of a material is physically impossible. for example, any crystalline material will contain defects such as precipitates, grain boundaries ( hall β petch relationship ), vacancies, interstitial atoms or substitutional atoms. the microstructure of materials reveals these larger defects and advances in simulation have allowed an increased understanding of how defects can be used to enhance material properties. = = = = macrostructure = = = = macrostructure is the appearance of a material in the scale millimeters to meters, it is the structure of
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,
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,
be at most one morphism between any two objects. the existence of identity morphisms and the composability of the morphisms are guaranteed by the reflexivity and the transitivity of the preorder. by the same argument, any partially ordered set and any equivalence relation can be seen as a small category. any ordinal number can be seen as a category when viewed as an ordered set. any monoid ( any algebraic structure with a single associative binary operation and an identity element ) forms a small category with a single object x. ( here, x is any fixed set. ) the morphisms from x to x are precisely the elements of the monoid, the identity morphism of x is the identity of the monoid, and the categorical composition of morphisms is given by the monoid operation. several definitions and theorems about monoids may be generalized for categories. similarly any group can be seen as a category with a single object in which every morphism is invertible, that is, for every morphism f there is a morphism g that is both left and right inverse to f under composition. a morphism that is invertible in this sense is called an isomorphism. a groupoid is a category in which every morphism is an isomorphism. groupoids are generalizations of groups, group actions and equivalence relations. actually, in the view of category the only difference between groupoid and group is that a groupoid may have more than one object but the group must have only one. consider a topological space x and fix a base point x 0 { \ displaystyle x _ { 0 } } of x, then Ο 1 ( x, x 0 ) { \ displaystyle \ pi _ { 1 } ( x, x _ { 0 } ) } is the fundamental group of the topological space x and the base point x 0 { \ displaystyle x _ { 0 } }, and as a set it has the structure of group ; if then let the base point x 0 { \ displaystyle x _ { 0 } } runs over all points of x, and take the union of all Ο 1 ( x, x 0 ) { \ displaystyle \ pi _ { 1 } ( x, x _ { 0 } ) }, then the set we get has only the structure of groupoid ( which is called as the fundamental groupoid of x ) : two loops ( under equivalence relation of homotopy ) may
there are four puzzling questions about by the magnitudes of neutrino mixings and mass splittings. a brief sketch is given of the various kinds of models of neutrino masses and how they answer these questions. special attention is given to so - called " lopsided " models.
molecular diffusion processes give rise to significant changes in the primary microstructural features. this includes the gradual elimination of porosity, which is typically accompanied by a net shrinkage and overall densification of the component. thus, the pores in the object may close up, resulting in a denser product of significantly greater strength and fracture toughness. another major change in the body during the firing or sintering process will be the establishment of the polycrystalline nature of the solid. significant grain growth tends to occur during sintering, with this growth depending on temperature and duration of the sintering process. the growth of grains will result in some form of grain size distribution, which will have a significant impact on the ultimate physical properties of the material. in particular, abnormal grain growth in which certain grains grow very large in a matrix of finer grains will significantly alter the physical and mechanical properties of the obtained ceramic. in the sintered body, grain sizes are a product of the thermal processing parameters as well as the initial particle size, or possibly the sizes of aggregates or particle clusters which arise during the initial stages of processing. the ultimate microstructure ( and thus the physical properties ) of the final product will be limited by and subject to the form of the structural template or precursor which is created in the initial stages of chemical synthesis and physical forming. hence the importance of chemical powder and polymer processing as it pertains to the synthesis of industrial ceramics, glasses and glass - ceramics. there are numerous possible refinements of the sintering process. some of the most common involve pressing the green body to give the densification a head start and reduce the sintering time needed. sometimes organic binders such as polyvinyl alcohol are added to hold the green body together ; these burn out during the firing ( at 200 β 350 Β°c ). sometimes organic lubricants are added during pressing to increase densification. it is common to combine these, and add binders and lubricants to a powder, then press. ( the formulation of these organic chemical additives is an art in itself. this is particularly important in the manufacture of high performance ceramics such as those used by the billions for electronics, in capacitors, inductors, sensors, etc. ) a slurry can be used in place of a powder, and then cast into a desired shape, dried and then sintered. indeed, traditional pottery is done with this type of method, using a plastic mixture worked with the hands.
small category. any ordinal number can be seen as a category when viewed as an ordered set. any monoid ( any algebraic structure with a single associative binary operation and an identity element ) forms a small category with a single object x. ( here, x is any fixed set. ) the morphisms from x to x are precisely the elements of the monoid, the identity morphism of x is the identity of the monoid, and the categorical composition of morphisms is given by the monoid operation. several definitions and theorems about monoids may be generalized for categories. similarly any group can be seen as a category with a single object in which every morphism is invertible, that is, for every morphism f there is a morphism g that is both left and right inverse to f under composition. a morphism that is invertible in this sense is called an isomorphism. a groupoid is a category in which every morphism is an isomorphism. groupoids are generalizations of groups, group actions and equivalence relations. actually, in the view of category the only difference between groupoid and group is that a groupoid may have more than one object but the group must have only one. consider a topological space x and fix a base point x 0 { \ displaystyle x _ { 0 } } of x, then Ο 1 ( x, x 0 ) { \ displaystyle \ pi _ { 1 } ( x, x _ { 0 } ) } is the fundamental group of the topological space x and the base point x 0 { \ displaystyle x _ { 0 } }, and as a set it has the structure of group ; if then let the base point x 0 { \ displaystyle x _ { 0 } } runs over all points of x, and take the union of all Ο 1 ( x, x 0 ) { \ displaystyle \ pi _ { 1 } ( x, x _ { 0 } ) }, then the set we get has only the structure of groupoid ( which is called as the fundamental groupoid of x ) : two loops ( under equivalence relation of homotopy ) may not have the same base point so they cannot multiply with each other. in the language of category, this means here two morphisms may not have the same source object ( or target object, because in this case for any morphism the source object and the target object are same : the base point ) so
Question: What is it called when large objects are broken down into smaller pieces?
A) weathering
B) metamorphosis
C) evolution
D) decay
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A) weathering
|
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
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 ( 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
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
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
( 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
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
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
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
the usual modelling of the syllogisms of the organon by a calculus of classes does not include relations. aristotle may however have envisioned them in the first two books as the category of relatives, where he allowed them to compose with themselves. composition is the main operation in combinatory logic, which therefore offers itself for a new kind of modelling. the resulting calculus includes also composition of predicates by logical connectives.
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,
Question: What is the term for species in symbiotic relationships evolving together?
A) interconnection
B) autogeneration
C) coevolution
D) innervation
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C) coevolution
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Context:
prominent functional groups that can be found in organisms : amino group, carboxyl group, carbonyl group, hydroxyl group, phosphate group, and sulfhydryl group. in 1953, the miller β urey experiment showed that organic compounds could be synthesized abiotically within a closed system mimicking the conditions of early earth, thus suggesting that complex organic molecules could have arisen spontaneously in early earth ( see abiogenesis ). = = = macromolecules = = = macromolecules are large molecules made up of smaller subunits or monomers. monomers include sugars, amino acids, and nucleotides. carbohydrates include monomers and polymers of sugars. lipids are the only class of macromolecules that are not made up of polymers. they include steroids, phospholipids, and fats, largely nonpolar and hydrophobic ( water - repelling ) substances. proteins are the most diverse of the macromolecules. they include enzymes, transport proteins, large signaling molecules, antibodies, and structural proteins. the basic unit ( or monomer ) of a protein is an amino acid. twenty amino acids are used in proteins. nucleic acids are polymers of nucleotides. their function is to store, transmit, and express hereditary information. = = cells = = cell theory states that cells are the fundamental units of life, that all living things are composed of one or more cells, and that all cells arise from preexisting cells through cell division. most cells are very small, with diameters ranging from 1 to 100 micrometers and are therefore only visible under a light or electron microscope. there are generally two types of cells : eukaryotic cells, which contain a nucleus, and prokaryotic cells, which do not. prokaryotes are single - celled organisms such as bacteria, whereas eukaryotes can be single - celled or multicellular. in multicellular organisms, every cell in the organism ' s body is derived ultimately from a single cell in a fertilized egg. = = = cell structure = = = every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as
and nucleotides. carbohydrates include monomers and polymers of sugars. lipids are the only class of macromolecules that are not made up of polymers. they include steroids, phospholipids, and fats, largely nonpolar and hydrophobic ( water - repelling ) substances. proteins are the most diverse of the macromolecules. they include enzymes, transport proteins, large signaling molecules, antibodies, and structural proteins. the basic unit ( or monomer ) of a protein is an amino acid. twenty amino acids are used in proteins. nucleic acids are polymers of nucleotides. their function is to store, transmit, and express hereditary information. = = cells = = cell theory states that cells are the fundamental units of life, that all living things are composed of one or more cells, and that all cells arise from preexisting cells through cell division. most cells are very small, with diameters ranging from 1 to 100 micrometers and are therefore only visible under a light or electron microscope. there are generally two types of cells : eukaryotic cells, which contain a nucleus, and prokaryotic cells, which do not. prokaryotes are single - celled organisms such as bacteria, whereas eukaryotes can be single - celled or multicellular. in multicellular organisms, every cell in the organism ' s body is derived ultimately from a single cell in a fertilized egg. = = = cell structure = = = every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions. cell membranes also contain membrane proteins, including integral membrane proteins that go across the membrane serving as membrane transporters, and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes shaping the cell. cell membranes are involved in various cellular processes such as cell adhesion, storing electrical energy, and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall, glycocalyx, and cytoskeleton. within the cytoplasm of a cell
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
conditions of early earth, thus suggesting that complex organic molecules could have arisen spontaneously in early earth ( see abiogenesis ). = = = macromolecules = = = macromolecules are large molecules made up of smaller subunits or monomers. monomers include sugars, amino acids, and nucleotides. carbohydrates include monomers and polymers of sugars. lipids are the only class of macromolecules that are not made up of polymers. they include steroids, phospholipids, and fats, largely nonpolar and hydrophobic ( water - repelling ) substances. proteins are the most diverse of the macromolecules. they include enzymes, transport proteins, large signaling molecules, antibodies, and structural proteins. the basic unit ( or monomer ) of a protein is an amino acid. twenty amino acids are used in proteins. nucleic acids are polymers of nucleotides. their function is to store, transmit, and express hereditary information. = = cells = = cell theory states that cells are the fundamental units of life, that all living things are composed of one or more cells, and that all cells arise from preexisting cells through cell division. most cells are very small, with diameters ranging from 1 to 100 micrometers and are therefore only visible under a light or electron microscope. there are generally two types of cells : eukaryotic cells, which contain a nucleus, and prokaryotic cells, which do not. prokaryotes are single - celled organisms such as bacteria, whereas eukaryotes can be single - celled or multicellular. in multicellular organisms, every cell in the organism ' s body is derived ultimately from a single cell in a fertilized egg. = = = cell structure = = = every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions. cell membranes also contain membrane proteins, including integral membrane proteins that go across the membrane serving as membrane transporters, and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes
water - repelling ) substances. proteins are the most diverse of the macromolecules. they include enzymes, transport proteins, large signaling molecules, antibodies, and structural proteins. the basic unit ( or monomer ) of a protein is an amino acid. twenty amino acids are used in proteins. nucleic acids are polymers of nucleotides. their function is to store, transmit, and express hereditary information. = = cells = = cell theory states that cells are the fundamental units of life, that all living things are composed of one or more cells, and that all cells arise from preexisting cells through cell division. most cells are very small, with diameters ranging from 1 to 100 micrometers and are therefore only visible under a light or electron microscope. there are generally two types of cells : eukaryotic cells, which contain a nucleus, and prokaryotic cells, which do not. prokaryotes are single - celled organisms such as bacteria, whereas eukaryotes can be single - celled or multicellular. in multicellular organisms, every cell in the organism ' s body is derived ultimately from a single cell in a fertilized egg. = = = cell structure = = = every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions. cell membranes also contain membrane proteins, including integral membrane proteins that go across the membrane serving as membrane transporters, and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes shaping the cell. cell membranes are involved in various cellular processes such as cell adhesion, storing electrical energy, and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall, glycocalyx, and cytoskeleton. within the cytoplasm of a cell, there are many biomolecules such as proteins and nucleic acids. in addition to biomolecules, eukaryotic cells have specialized structures called organelles that have their own lipid bilayers or are spatially units. these organelles include the cell nucleus, which contains most of
when the hydration shell of a protein is filled with at least 0. 6 gram of water per gram of protein, a significant anti - correlation between the vibrational free energy and the potential energy of energy - minimized conformers is observed. this means that low potential energy, well - hydrated, protein conformers tend to be more rigid than high - energy ones. on the other hand, in the case of casp target 624, when its hydration shell is filled, a significant average energy gap is observed between the crystal structure and the best conformers proposed during the prediction experiment, strongly suggesting that including explicit water molecules may help identifying unlikely conformers among good - looking ones.
small ubiquitin - related modifier ( sumo ) proteins are widely expressed in eukaryotic cells, which are reversibly coupled to their substrates by motif recognition, called sumoylation. two interesting questions are 1 ) how many potential sumo substrates may be included in mammalian proteomes, such as human and mouse, 2 ) and given a sumo substrate, can we recognize its sumoylation sites? to answer these two questions, previous prediction systems of sumo substrates mainly adopted the pattern recognition methods, which could get high sensitivity with relatively too many potential false positives. so we use phylogenetic conservation between mouse and human to reduce the number of potential false positives.
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,
( 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
##ubated, and the formation of a colored product indicates a positive hybridoma. alternatively, immunocytochemical, western blot, and immunoprecipitation - mass spectrometry. unlike western blot assays, immunoprecipitation - mass spectrometry facilitates screening and ranking of clones which bind to the native ( non - denaturated ) forms of antigen proteins. flow cytometry screening has been used for primary screening of a large number ( ~ 1000 ) of hybridoma clones recognizing the native form of the antigen on the cell surface. in the flow cytometry - based screening, a mixture of antigen - negative cells and antigen - positive cells is used as the antigen to be tested for each hybridoma supernatant sample. the b cell that produces the desired antibodies can be cloned to produce many identical daughter clones. supplemental media containing interleukin - 6 ( such as briclone ) are essential for this step. once a hybridoma colony is established, it will continually grow in culture medium like rpmi - 1640 ( with antibiotics and fetal bovine serum ) and produce antibodies. multiwell plates are used initially to grow the hybridomas, and after selection, are changed to larger tissue culture flasks. this maintains the well - being of the hybridomas and provides enough cells for cryopreservation and supernatant for subsequent investigations. the culture supernatant can yield 1 to 60 ΞΌg / ml of monoclonal antibody, which is maintained at - 20 Β°c or lower until required. by using culture supernatant or a purified immunoglobulin preparation, further analysis of a potential monoclonal antibody producing hybridoma can be made in terms of reactivity, specificity, and cross - reactivity. = = applications = = the use of monoclonal antibodies is numerous and includes the prevention, diagnosis, and treatment of disease. for example, monoclonal antibodies can distinguish subsets of b cells and t cells, which is helpful in identifying different types of leukaemias. in addition, specific monoclonal antibodies have been used to define cell surface markers on white blood cells and other cell types. this led to the cluster of differentiation series of markers. these are often referred to as cd markers and define several hundred different cell surface components of cells, each specified by binding of a particular monoclonal antibody. such antibodies are extremely useful for fluorescence - activated cell sorting,
Question: Hemoglobin, with four polypeptide chains or subunits, is the most frequently cited example of a protein having what kind of structure?
A) quaternary
B) ternary
C) binary
D) unary
|
A) quaternary
|
Context:
and peripheral blood. they concluded from the results that immuno - cytochemical staining of bone marrow and peripheral blood is a sensitive and simple way to detect and quantify breast cancer cells. one of the main reasons for metastatic relapse in patients with solid tumours is the early dissemination of malignant cells. the use of monoclonal antibodies ( mabs ) specific for cytokeratins can identify disseminated individual epithelial tumor cells in the bone marrow. one study reports on having developed an immuno - cytochemical procedure for simultaneous labeling of cytokeratin component no. 18 ( ck18 ) and prostate specific antigen ( psa ). this would help in the further characterization of disseminated individual epithelial tumor cells in patients with prostate cancer. the twelve control aspirates from patients with benign prostatic hyperplasia showed negative staining, which further supports the specificity of ck18 in detecting epithelial tumour cells in bone marrow. in most cases of malignant disease complicated by effusion, neoplastic cells can be easily recognized. however, in some cases, malignant cells are not so easily seen or their presence is too doubtful to call it a positive report. the use of immuno - cytochemical techniques increases diagnostic accuracy in these cases. ghosh, mason and spriggs analysed 53 samples of pleural or peritoneal fluid from 41 patients with malignant disease. conventional cytological examination had not revealed any neoplastic cells. three monoclonal antibodies ( anti - cea, ca 1 and hmfg - 2 ) were used to search for malignant cells. immunocytochemical labelling was performed on unstained smears, which had been stored at - 20 Β°c up to 18 months. twelve of the forty - one cases in which immuno - cytochemical staining was performed, revealed malignant cells. the result represented an increase in diagnostic accuracy of approximately 20 %. the study concluded that in patients with suspected malignant disease, immuno - cytochemical labeling should be used routinely in the examination of cytologically negative samples and has important implications with respect to patient management. another application of immuno - cytochemical staining is for the detection of two antigens in the same smear. double staining with light chain antibodies and with t and b cell markers can indicate the neoplastic origin of a lymph
cells into the decellularized rat heart. tissue - engineered blood vessels : blood vessels that have been grown in a lab and can be used to repair damaged blood vessels without eliciting an immune response. tissue engineered blood vessels have been developed by many different approaches. they could be implanted as pre - seeded cellularized blood vessels, as acellular vascular grafts made with decellularized vessels or synthetic vascular grafts. artificial skin constructed from human skin cells embedded in a hydrogel, such as in the case of bio - printed constructs for battlefield burn repairs. artificial bone marrow : bone marrow cultured in vitro to be transplanted serves as a " just cells " approach to tissue engineering. tissue engineered bone : a structural matrix can be composed of metals such as titanium, polymers of varying degradation rates, or certain types of ceramics. materials are often chosen to recruit osteoblasts to aid in reforming the bone and returning biological function. various types of cells can be added directly into the matrix to expedite the process. laboratory - grown penis : decellularized scaffolds of rabbit penises were recellularised with smooth muscle and endothelial cells. the organ was then transplanted to live rabbits and functioned comparably to the native organ, suggesting potential as treatment for genital trauma. oral mucosa tissue engineering uses a cells and scaffold approach to replicate the 3 dimensional structure and function of oral mucosa. = = cells as building blocks = = cells are one of the main components for the success of tissue engineering approaches. tissue engineering uses cells as strategies for creation / replacement of new tissue. examples include fibroblasts used for skin repair or renewal, chondrocytes used for cartilage repair ( maci β fda approved product ), and hepatocytes used in liver support systems cells can be used alone or with support matrices for tissue engineering applications. an adequate environment for promoting cell growth, differentiation, and integration with the existing tissue is a critical factor for cell - based building blocks. manipulation of any of these cell processes create alternative avenues for the development of new tissue ( e. g., cell reprogramming - somatic cells, vascularization ). = = = isolation = = = techniques for cell isolation depend on the cell source. centrifugation and apheresis are techniques used for extracting cells from biofluids ( e. g., blood ). whereas digestion processes, typically using enzymes to remove the extra
this scaffold and cells were placed in a bioreactor, where it matured to become a partially or fully transplantable organ. the work was called a " landmark ". the lab first stripped the cells away from a rat heart ( a process called " decellularization " ) and then injected rat stem cells into the decellularized rat heart. tissue - engineered blood vessels : blood vessels that have been grown in a lab and can be used to repair damaged blood vessels without eliciting an immune response. tissue engineered blood vessels have been developed by many different approaches. they could be implanted as pre - seeded cellularized blood vessels, as acellular vascular grafts made with decellularized vessels or synthetic vascular grafts. artificial skin constructed from human skin cells embedded in a hydrogel, such as in the case of bio - printed constructs for battlefield burn repairs. artificial bone marrow : bone marrow cultured in vitro to be transplanted serves as a " just cells " approach to tissue engineering. tissue engineered bone : a structural matrix can be composed of metals such as titanium, polymers of varying degradation rates, or certain types of ceramics. materials are often chosen to recruit osteoblasts to aid in reforming the bone and returning biological function. various types of cells can be added directly into the matrix to expedite the process. laboratory - grown penis : decellularized scaffolds of rabbit penises were recellularised with smooth muscle and endothelial cells. the organ was then transplanted to live rabbits and functioned comparably to the native organ, suggesting potential as treatment for genital trauma. oral mucosa tissue engineering uses a cells and scaffold approach to replicate the 3 dimensional structure and function of oral mucosa. = = cells as building blocks = = cells are one of the main components for the success of tissue engineering approaches. tissue engineering uses cells as strategies for creation / replacement of new tissue. examples include fibroblasts used for skin repair or renewal, chondrocytes used for cartilage repair ( maci β fda approved product ), and hepatocytes used in liver support systems cells can be used alone or with support matrices for tissue engineering applications. an adequate environment for promoting cell growth, differentiation, and integration with the existing tissue is a critical factor for cell - based building blocks. manipulation of any of these cell processes create alternative avenues for the development of new tissue ( e. g., cell reprogramming - somatic
##rates and peripheral blood, further development of this method is necessary before it can be used routinely. one major drawback of immuno - cytochemistry is that only tumor - associated and not tumor - specific monoclonal antibodies are used, and as a result, some cross - reaction with normal cells can occur. in order to effectively stage breast cancer and assess the efficacy of purging regimens prior to autologous stem cell infusion, it is important to detect even small quantities of breast cancer cells. immuno - histochemical methods are ideal for this purpose because they are simple, sensitive, and quite specific. franklin et al. performed a sensitive immuno - cytochemical assay by using a combination of four monoclonal antibodies ( 260f9, 520c9, 317g5 and bre - 3 ) against tumor cell surface glycoproteins to identify breast tumour cells in bone marrow and peripheral blood. they concluded from the results that immuno - cytochemical staining of bone marrow and peripheral blood is a sensitive and simple way to detect and quantify breast cancer cells. one of the main reasons for metastatic relapse in patients with solid tumours is the early dissemination of malignant cells. the use of monoclonal antibodies ( mabs ) specific for cytokeratins can identify disseminated individual epithelial tumor cells in the bone marrow. one study reports on having developed an immuno - cytochemical procedure for simultaneous labeling of cytokeratin component no. 18 ( ck18 ) and prostate specific antigen ( psa ). this would help in the further characterization of disseminated individual epithelial tumor cells in patients with prostate cancer. the twelve control aspirates from patients with benign prostatic hyperplasia showed negative staining, which further supports the specificity of ck18 in detecting epithelial tumour cells in bone marrow. in most cases of malignant disease complicated by effusion, neoplastic cells can be easily recognized. however, in some cases, malignant cells are not so easily seen or their presence is too doubtful to call it a positive report. the use of immuno - cytochemical techniques increases diagnostic accuracy in these cases. ghosh, mason and spriggs analysed 53 samples of pleural or peritoneal fluid from 41 patients with malignant disease. conventional cytological examination had not revealed any neoplastic cells. three monocl
combination of chemical and mechanical stimulation. cell proliferation and differentiation are largely influenced by mechanical and biochemical cues in the surrounding extracellular matrix environment. bioreactors are typically developed to replicate the specific physiological environment of the tissue being grown ( e. g., flex and fluid shearing for heart tissue growth ). this can allow specialized cell lines to thrive in cultures replicating their native environments, but it also makes bioreactors attractive tools for culturing stem cells. a successful stem - cell - based bioreactor is effective at expanding stem cells with uniform properties and / or promoting controlled, reproducible differentiation into selected mature cell types. there are a variety of bioreactors designed for 3d cell cultures. there are small plastic cylindrical chambers, as well as glass chambers, with regulated internal humidity and moisture specifically engineered for the purpose of growing cells in three dimensions. the bioreactor uses bioactive synthetic materials such as polyethylene terephthalate membranes to surround the spheroid cells in an environment that maintains high levels of nutrients. they are easy to open and close, so that cell spheroids can be removed for testing, yet the chamber is able to maintain 100 % humidity throughout. this humidity is important to achieve maximum cell growth and function. the bioreactor chamber is part of a larger device that rotates to ensure equal cell growth in each direction across three dimensions. quinxell technologies now under quintech life sciences from singapore has developed a bioreactor known as the tisxell biaxial bioreactor which is specially designed for the purpose of tissue engineering. it is the first bioreactor in the world to have a spherical glass chamber with biaxial rotation ; specifically to mimic the rotation of the fetus in the womb ; which provides a conducive environment for the growth of tissues. multiple forms of mechanical stimulation have also been combined into a single bioreactor. using gene expression analysis, one academic study found that applying a combination of cyclic strain and ultrasound stimulation to pre - osteoblast cells in a bioreactor accelerated matrix maturation and differentiation. the technology of this combined stimulation bioreactor could be used to grow bone cells more quickly and effectively in future clinical stem cell therapies. mc2 biotek has also developed a bioreactor known as prototissue that uses gas exchange to maintain high oxygen levels within the cell chamber ; improving upon previous bioreactors, since the higher oxygen levels help the cell grow and undergo normal cell respiration. active
cell or tissue growth in vitro. a physiological environment can consist of many different parameters such as temperature, pressure, oxygen or carbon dioxide concentration, or osmolality of fluid environment, and it can extend to all kinds of biological, chemical or mechanical stimuli. therefore, there are systems that may include the application of forces such as electromagnetic forces, mechanical pressures, or fluid pressures to the tissue. these systems can be two - or three - dimensional setups. bioreactors can be used in both academic and industry applications. general - use and application - specific bioreactors are also commercially available, which may provide static chemical stimulation or a combination of chemical and mechanical stimulation. cell proliferation and differentiation are largely influenced by mechanical and biochemical cues in the surrounding extracellular matrix environment. bioreactors are typically developed to replicate the specific physiological environment of the tissue being grown ( e. g., flex and fluid shearing for heart tissue growth ). this can allow specialized cell lines to thrive in cultures replicating their native environments, but it also makes bioreactors attractive tools for culturing stem cells. a successful stem - cell - based bioreactor is effective at expanding stem cells with uniform properties and / or promoting controlled, reproducible differentiation into selected mature cell types. there are a variety of bioreactors designed for 3d cell cultures. there are small plastic cylindrical chambers, as well as glass chambers, with regulated internal humidity and moisture specifically engineered for the purpose of growing cells in three dimensions. the bioreactor uses bioactive synthetic materials such as polyethylene terephthalate membranes to surround the spheroid cells in an environment that maintains high levels of nutrients. they are easy to open and close, so that cell spheroids can be removed for testing, yet the chamber is able to maintain 100 % humidity throughout. this humidity is important to achieve maximum cell growth and function. the bioreactor chamber is part of a larger device that rotates to ensure equal cell growth in each direction across three dimensions. quinxell technologies now under quintech life sciences from singapore has developed a bioreactor known as the tisxell biaxial bioreactor which is specially designed for the purpose of tissue engineering. it is the first bioreactor in the world to have a spherical glass chamber with biaxial rotation ; specifically to mimic the rotation of the fetus in the womb ; which provides a conducive environment for the growth of tissues. multiple forms of mechanical stimulation have also been combined into a single
##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
. in order to effectively stage breast cancer and assess the efficacy of purging regimens prior to autologous stem cell infusion, it is important to detect even small quantities of breast cancer cells. immuno - histochemical methods are ideal for this purpose because they are simple, sensitive, and quite specific. franklin et al. performed a sensitive immuno - cytochemical assay by using a combination of four monoclonal antibodies ( 260f9, 520c9, 317g5 and bre - 3 ) against tumor cell surface glycoproteins to identify breast tumour cells in bone marrow and peripheral blood. they concluded from the results that immuno - cytochemical staining of bone marrow and peripheral blood is a sensitive and simple way to detect and quantify breast cancer cells. one of the main reasons for metastatic relapse in patients with solid tumours is the early dissemination of malignant cells. the use of monoclonal antibodies ( mabs ) specific for cytokeratins can identify disseminated individual epithelial tumor cells in the bone marrow. one study reports on having developed an immuno - cytochemical procedure for simultaneous labeling of cytokeratin component no. 18 ( ck18 ) and prostate specific antigen ( psa ). this would help in the further characterization of disseminated individual epithelial tumor cells in patients with prostate cancer. the twelve control aspirates from patients with benign prostatic hyperplasia showed negative staining, which further supports the specificity of ck18 in detecting epithelial tumour cells in bone marrow. in most cases of malignant disease complicated by effusion, neoplastic cells can be easily recognized. however, in some cases, malignant cells are not so easily seen or their presence is too doubtful to call it a positive report. the use of immuno - cytochemical techniques increases diagnostic accuracy in these cases. ghosh, mason and spriggs analysed 53 samples of pleural or peritoneal fluid from 41 patients with malignant disease. conventional cytological examination had not revealed any neoplastic cells. three monoclonal antibodies ( anti - cea, ca 1 and hmfg - 2 ) were used to search for malignant cells. immunocytochemical labelling was performed on unstained smears, which had been stored at - 20 Β°c up to 18 months. twelve of the forty - one cases
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
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
Question: What causes blood vessels to grow toward the tumour in cancer cells?
A) signaling molecules
B) communicating molecules
C) addressing molecules
D) harnessing molecules
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A) signaling molecules
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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
, 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
was used before copper smelting was known. copper smelting is believed to have originated when the technology of pottery kilns allowed sufficiently high temperatures. the concentration of various elements such as arsenic increase with depth in copper ore deposits and smelting of these ores yields arsenical bronze, which can be sufficiently work hardened to be suitable for making tools. bronze is an alloy of copper with tin ; the latter being found in relatively few deposits globally caused a long time to elapse before true tin bronze became widespread. ( see : tin sources and trade in ancient times ) bronze was a major advancement over stone as a material for making tools, both because of its mechanical properties like strength and ductility and because it could be cast in molds to make intricately shaped objects. bronze significantly advanced shipbuilding technology with better tools and bronze nails. bronze nails replaced the old method of attaching boards of the hull with cord woven through drilled holes. better ships enabled long - distance trade and the advance of civilization. this technological trend apparently began in the fertile crescent and spread outward over time. these developments were not, and still are not, universal. the three - age system does not accurately describe the technology history of groups outside of eurasia, and does not apply at all in the case of some isolated populations, such as the spinifex people, the sentinelese, and various amazonian tribes, which still make use of stone age technology, and have not developed agricultural or metal technology. these villages preserve traditional customs in the face of global modernity, exhibiting a remarkable resistance to the rapid advancement of technology. = = = = iron age = = = = before iron smelting was developed the only iron was obtained from meteorites and is usually identified by having nickel content. meteoric iron was rare and valuable, but was sometimes used to make tools and other implements, such as fish hooks. the iron age involved the adoption of iron smelting technology. it generally replaced bronze and made it possible to produce tools which were stronger, lighter and cheaper to make than bronze equivalents. the raw materials to make iron, such as ore and limestone, are far more abundant than copper and especially tin ores. consequently, iron was produced in many areas. it was not possible to mass manufacture steel or pure iron because of the high temperatures required. furnaces could reach melting temperature but the crucibles and molds needed for melting and casting had not been developed. steel could be produced by forging bloomery iron to reduce the carbon content in a
##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
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
snake called jormungandr. the norse creation account preserved in gylfaginning ( viii ) states that during the creation of the earth, an impassable sea was placed around it : and jafnharr said : " of the blood, which ran and welled forth freely out of his wounds, they made the sea, when they had formed and made firm the earth together, and laid the sea in a ring round. about her ; and it may well seem a hard thing to most men to cross over it. " the late norse konungs skuggsja, on the other hand, explains earth ' s shape as a sphere : if you take a lighted candle and set it in a room, you may expect it to light up the entire interior, unless something should hinder, though the room be quite large. but if you take an apple and hang it close to the flame, so near that it is heated, the apple will darken nearly half the room or even more. however, if you hang the apple near the wall, it will not get hot ; the candle will light up the whole house ; and the shadow on the wall where the apple hangs will be scarcely half as large as the apple itself. from this you may infer that the earth - circle is round like a ball and not equally near the sun at every point. but where the curved surface lies nearest the sun ' s path, there will the greatest heat be ; and some of the lands that lie continuously under the unbroken rays cannot be inhabited. = = = = east asia = = = = in ancient china, the prevailing belief was that the earth was flat and square, while the heavens were round, an assumption virtually unquestioned until the introduction of european astronomy in the 17th century. the english sinologist cullen emphasizes the point that there was no concept of a round earth in ancient chinese astronomy : chinese thought on the form of the earth remained almost unchanged from early times until the first contacts with modern science through the medium of jesuit missionaries in the seventeenth century. while the heavens were variously described as being like an umbrella covering the earth ( the kai tian theory ), or like a sphere surrounding it ( 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
##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
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
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
near east, about 3, 500 bc, it was discovered that by combining copper and tin, a superior metal could be made, an alloy called bronze. this represented a major technological shift known as the bronze age. the extraction of iron from its ore into a workable metal is much more difficult than for copper or tin. the process appears to have been invented by the hittites in about 1200 bc, beginning the iron age. the secret of extracting and working iron was a key factor in the success of the philistines. historical developments in ferrous metallurgy can be found in a wide variety of past cultures and civilizations. this includes the ancient and medieval kingdoms and empires of the middle east and near east, ancient iran, ancient egypt, ancient nubia, and anatolia in present - day turkey, ancient nok, carthage, the celts, greeks and romans of ancient europe, medieval europe, ancient and medieval china, ancient and medieval india, ancient and medieval japan, amongst others. a 16th century book by georg agricola, de re metallica, describes the highly developed and complex processes of mining metal ores, metal extraction, and metallurgy of the time. agricola has been described as the " father of metallurgy ". = = extraction = = extractive metallurgy is the practice of removing valuable metals from an ore and refining the extracted raw metals into a purer form. in order to convert a metal oxide or sulphide to a purer metal, the ore must be reduced physically, chemically, or electrolytically. extractive metallurgists are interested in three primary streams : feed, concentrate ( metal oxide / sulphide ) and tailings ( waste ). after mining, large pieces of the ore feed are broken through crushing or grinding in order to obtain particles small enough, where each particle is either mostly valuable or mostly waste. concentrating the particles of value in a form supporting separation enables the desired metal to be removed from waste products. mining may not be necessary, if the ore body and physical environment are conducive to leaching. leaching dissolves minerals in an ore body and results in an enriched solution. the solution is collected and processed to extract valuable metals. ore bodies often contain more than one valuable metal. tailings of a previous process may be used as a feed in another process to extract a secondary product from the original ore. additionally, a concentrate may contain more than one valuable metal. that concentrate would then be processed to separate
Question: What is igneous rock created from?
A) carbon dioxide
B) magma aging
C) magma cooling
D) volcanic ash
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C) magma cooling
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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
the standard theory of ideal gases ignores the interaction of the gas particles with the thermal radiation ( photon gas ) that fills the otherwise vacuum space between them. this is an unphysical feature since every material absorbs and radiates thermal energy. this interaction may be important in gases since the latter, unlike solids and liquids are capable of undergoing conspicuous volume changes. taking it into account makes the behaviour of the ideal gases more realistic and removes gibbs ' paradox.
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
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.
quantum mechanics is interpreted by the adjacent vacuum that behaves as a virtual particle to be absorbed and emitted by its matter. as described in the vacuum universe model, the adjacent vacuum is derived from the pre - inflationary universe in which the pre - adjacent vacuum is absorbed by the pre - matter. this absorbed pre - adjacent vacuum is emitted to become the added space for the inflation in the inflationary universe whose space - time is separated from the pre - inflationary universe. this added space is the adjacent vacuum. the absorption of the adjacent vacuum as the added space results in the adjacent zero space ( no space ), quantum mechanics is the interaction between matter and the three different types of vacuum : the adjacent vacuum, the adjacent zero space, and the empty space. the absorption of the adjacent vacuum results in the empty space superimposed with the adjacent zero space, confining the matter in the form of particle. when the absorbed vacuum is emitted, the adjacent vacuum can be anywhere instantly in the empty space superimposed with the adjacent zero space where any point can be the starting point ( zero point ) of space - time. consequently, the matter that expands into the adjacent vacuum has the probability to be anywhere instantly in the form of wavefunction. in the vacuum universe model, the universe not only gains its existence from the vacuum but also fattens itself with the vacuum. during the inflation, the adjacent vacuum also generates the periodic table of elementary particles to account for all elementary particles and their masses in a good agreement with the observed values.
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
oxygen ion migration in li2mno3 was systematically studied by first - principles calculations. hole polaron is found effective to lower the migration barrier of oxygen ion.
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.
gas load and pumping determine the quality of vacuum systems. in particle accelerators, once leaks are excluded, outgassing of materials is an important source of gas together with degassing induced by particle beams. understanding, predicting, and measuring gas release from materials in vacuum are among the fundamental tasks of ultrahigh - vacuum experts. the knowledge of outgassing phenomena is essential for the choice of materials and their treatments so that the required gas density is achieved in such demanding and expensive scientific instruments. this note provides the background to understand outgassing in vacuum and gives references for further study.
functions of the human body, if necessary, through the use of technology. modern medicine can replace several of the body ' s functions through the use of artificial organs and can significantly alter the function of the human body through artificial devices such as, for example, brain implants and pacemakers. the fields of bionics and medical bionics are dedicated to the study of synthetic implants pertaining to natural systems. conversely, some engineering disciplines view the human body as a biological machine worth studying and are dedicated to emulating many of its functions by replacing biology with technology. this has led to fields such as artificial intelligence, neural networks, fuzzy logic, and robotics. there are also substantial interdisciplinary interactions between engineering and medicine. both fields provide solutions to real world problems. this often requires moving forward before phenomena are completely understood in a more rigorous scientific sense and therefore experimentation and empirical knowledge is an integral part of both. medicine, in part, studies the function of the human body. the human body, as a biological machine, has many functions that can be modeled using engineering methods. the heart for example functions much like a pump, the skeleton is like a linked structure with levers, the brain produces electrical signals etc. these similarities as well as the increasing importance and application of engineering principles in medicine, led to the development of the field of biomedical engineering that uses concepts developed in both disciplines. newly emerging branches of science, such as systems biology, are adapting analytical tools traditionally used for engineering, such as systems modeling and computational analysis, to the description of biological systems. = = = art = = = there are connections between engineering and art, for example, architecture, landscape architecture and industrial design ( even to the extent that these disciplines may sometimes be included in a university ' s faculty of engineering ). the art institute of chicago, for instance, held an exhibition about the art of nasa ' s aerospace design. robert maillart ' s bridge design is perceived by some to have been deliberately artistic. at the university of south florida, an engineering professor, through a grant with the national science foundation, has developed a course that connects art and engineering. among famous historical figures, leonardo da vinci is a well - known renaissance artist and engineer, and a prime example of the nexus between art and engineering. = = = business = = = business engineering deals with the relationship between professional engineering, it systems, business administration and change management. engineering management or " management engineering " is a specialized field of management concerned with engineering practice or the engineering industry sector. the demand for management
Question: What is the exchange of gases between the body and outside air?
A) metabolism
B) respiration
C) expulsion
D) secretion
|
B) respiration
|
Context:
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
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
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
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
. 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
still a complex and relatively expensive material to produce. polymers on the other hand can be produced in huge volumes, with a great variety of material characteristics. mems devices can be made from polymers by processes such as injection molding, embossing or stereolithography and are especially well suited to microfluidic applications such as disposable blood testing cartridges. metals metals can also be used to create mems elements. while metals do not have some of the advantages displayed by silicon in terms of mechanical properties, when used within their limitations, metals can exhibit very high degrees of reliability. metals can be deposited by electroplating, evaporation, and sputtering processes. commonly used metals include gold, nickel, aluminium, copper, chromium, titanium, tungsten, platinum, and silver. ceramics the nitrides of silicon, aluminium and titanium as well as silicon carbide and other ceramics are increasingly applied in mems fabrication due to advantageous combinations of material properties. aln crystallizes in the wurtzite structure and thus shows pyroelectric and piezoelectric properties enabling sensors, for instance, with sensitivity to normal and shear forces. tin, on the other hand, exhibits a high electrical conductivity and large elastic modulus, making it possible to implement electrostatic mems actuation schemes with ultrathin beams. moreover, the high resistance of tin against biocorrosion qualifies the material for applications in biogenic environments. the figure shows an electron - microscopic picture of a mems biosensor with a 50 nm thin bendable tin beam above a tin ground plate. both can be driven as opposite electrodes of a capacitor, since the beam is fixed in electrically isolating side walls. when a fluid is suspended in the cavity its viscosity may be derived from bending the beam by electrical attraction to the ground plate and measuring the bending velocity. = = basic processes = = = = = deposition processes = = = one of the basic building blocks in mems processing is the ability to deposit thin films of material with a thickness anywhere from one micrometre to about 100 micrometres. the nems process is the same, although the measurement of film deposition ranges from a few nanometres to one micrometre. there are two types of deposition processes, as follows. = = = = physical deposition = = = = physical vapor deposition ( " pvd " ) consists of a process in which a material is removed from a target, and
##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
". = = 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
was used before copper smelting was known. copper smelting is believed to have originated when the technology of pottery kilns allowed sufficiently high temperatures. the concentration of various elements such as arsenic increase with depth in copper ore deposits and smelting of these ores yields arsenical bronze, which can be sufficiently work hardened to be suitable for making tools. bronze is an alloy of copper with tin ; the latter being found in relatively few deposits globally caused a long time to elapse before true tin bronze became widespread. ( see : tin sources and trade in ancient times ) bronze was a major advancement over stone as a material for making tools, both because of its mechanical properties like strength and ductility and because it could be cast in molds to make intricately shaped objects. bronze significantly advanced shipbuilding technology with better tools and bronze nails. bronze nails replaced the old method of attaching boards of the hull with cord woven through drilled holes. better ships enabled long - distance trade and the advance of civilization. this technological trend apparently began in the fertile crescent and spread outward over time. these developments were not, and still are not, universal. the three - age system does not accurately describe the technology history of groups outside of eurasia, and does not apply at all in the case of some isolated populations, such as the spinifex people, the sentinelese, and various amazonian tribes, which still make use of stone age technology, and have not developed agricultural or metal technology. these villages preserve traditional customs in the face of global modernity, exhibiting a remarkable resistance to the rapid advancement of technology. = = = = iron age = = = = before iron smelting was developed the only iron was obtained from meteorites and is usually identified by having nickel content. meteoric iron was rare and valuable, but was sometimes used to make tools and other implements, such as fish hooks. the iron age involved the adoption of iron smelting technology. it generally replaced bronze and made it possible to produce tools which were stronger, lighter and cheaper to make than bronze equivalents. the raw materials to make iron, such as ore and limestone, are far more abundant than copper and especially tin ores. consequently, iron was produced in many areas. it was not possible to mass manufacture steel or pure iron because of the high temperatures required. furnaces could reach melting temperature but the crucibles and molds needed for melting and casting had not been developed. steel could be produced by forging bloomery iron to reduce the carbon content in a
Question: What type of metal is a good conductor of electricity?
A) Aluminium
B) zinc
C) Tin
D) copper
|
D) copper
|
Context:
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 (
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
ranks varying from family to subgenus have terms for their study, including agrostology ( or graminology ) for the study of grasses, synantherology for the study of composites, and batology for the study of brambles. study can also be divided by guild rather than clade or grade. for example, dendrology is the study of woody plants. many divisions of biology have botanical subfields. these are commonly denoted by prefixing the word plant ( e. g. plant taxonomy, plant ecology, plant anatomy, plant morphology, plant systematics ), or prefixing or substituting the prefix phyto - ( e. g. phytochemistry, phytogeography ). the study of fossil plants is called palaeobotany. other fields are denoted by adding or substituting the word botany ( e. g. systematic botany ). phytosociology is a subfield of plant ecology that classifies and studies communities of plants. the intersection of fields from the above pair of categories gives rise to fields such as bryogeography, the study of the distribution of mosses. different parts of plants also give rise to their own subfields, including xylology, carpology ( or fructology ), and palynology, these being the study of wood, fruit and pollen / spores respectively. botany also overlaps on the one hand with agriculture, horticulture and silviculture, and on the other hand with medicine and pharmacology, giving rise to fields such as agronomy, horticultural botany, phytopathology, and phytopharmacology. = = scope and importance = = the study of plants is vital because they underpin almost all animal life on earth by generating a large proportion of the oxygen and food that provide humans and other organisms with aerobic respiration with the chemical energy they need to exist. plants, algae and cyanobacteria are the major groups of organisms that carry out photosynthesis, a process that uses the energy of sunlight to convert water and carbon dioxide into sugars that can be used both as a source of chemical energy and of organic molecules that are used in the structural components of cells. as a by - product of photosynthesis, plants release oxygen into the atmosphere, a gas that is required by nearly all living things to carry out cellular respiration. in addition, they are influential in the global carbon and water cycles and plant roots bind and stabilise soils, preventing
, 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
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
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
contrast to macroscopic or gross anatomy, cytology and histology are concerned with microscopic structures. biochemistry is the study of the chemistry taking place in living organisms, especially the structure and function of their chemical components. biomechanics is the study of the structure and function of biological systems by means of the methods of mechanics. biophysics is an interdisciplinary science that uses the methods of physics and physical chemistry to study biological systems. biostatistics is the application of statistics to biological fields in the broadest sense. a knowledge of biostatistics is essential in the planning, evaluation, and interpretation of medical research. it is also fundamental to epidemiology and evidence - based medicine. cytology is the microscopic study of individual cells. embryology is the study of the early development of organisms. endocrinology is the study of hormones and their effect throughout the body of animals. epidemiology is the study of the demographics of disease processes, and includes, but is not limited to, the study of epidemics. genetics is the study of genes, and their role in biological inheritance. gynecology is the study of female reproductive system. histology is the study of the structures of biological tissues by light microscopy, electron microscopy and immunohistochemistry. immunology is the study of the immune system, which includes the innate and adaptive immune system in humans, for example. lifestyle medicine is the study of the chronic conditions, and how to prevent, treat and reverse them. medical physics is the study of the applications of physics principles in medicine. microbiology is the study of microorganisms, including protozoa, bacteria, fungi, and viruses. molecular biology is the study of molecular underpinnings of the process of replication, transcription and translation of the genetic material. neuroscience includes those disciplines of science that are related to the study of the nervous system. a main focus of neuroscience is the biology and physiology of the human brain and spinal cord. some related clinical specialties include neurology, neurosurgery and psychiatry. nutrition science ( theoretical focus ) and dietetics ( practical focus ) is the study of the relationship of food and drink to health and disease, especially in determining an optimal diet. medical nutrition therapy is done by dietitians and is prescribed for diabetes, cardiovascular diseases, weight and eating disorders, allergies, malnutrition, and neoplastic diseases. pathology as a science is the study of disease β the causes, course, progression and resolution thereof.
. biophysics is an interdisciplinary science that uses the methods of physics and physical chemistry to study biological systems. biostatistics is the application of statistics to biological fields in the broadest sense. a knowledge of biostatistics is essential in the planning, evaluation, and interpretation of medical research. it is also fundamental to epidemiology and evidence - based medicine. cytology is the microscopic study of individual cells. embryology is the study of the early development of organisms. endocrinology is the study of hormones and their effect throughout the body of animals. epidemiology is the study of the demographics of disease processes, and includes, but is not limited to, the study of epidemics. genetics is the study of genes, and their role in biological inheritance. gynecology is the study of female reproductive system. histology is the study of the structures of biological tissues by light microscopy, electron microscopy and immunohistochemistry. immunology is the study of the immune system, which includes the innate and adaptive immune system in humans, for example. lifestyle medicine is the study of the chronic conditions, and how to prevent, treat and reverse them. medical physics is the study of the applications of physics principles in medicine. microbiology is the study of microorganisms, including protozoa, bacteria, fungi, and viruses. molecular biology is the study of molecular underpinnings of the process of replication, transcription and translation of the genetic material. neuroscience includes those disciplines of science that are related to the study of the nervous system. a main focus of neuroscience is the biology and physiology of the human brain and spinal cord. some related clinical specialties include neurology, neurosurgery and psychiatry. nutrition science ( theoretical focus ) and dietetics ( practical focus ) is the study of the relationship of food and drink to health and disease, especially in determining an optimal diet. medical nutrition therapy is done by dietitians and is prescribed for diabetes, cardiovascular diseases, weight and eating disorders, allergies, malnutrition, and neoplastic diseases. pathology as a science is the study of disease β the causes, course, progression and resolution thereof. pharmacology is the study of drugs and their actions. photobiology is the study of the interactions between non - ionizing radiation and living organisms. physiology is the study of the normal functioning of the body and the underlying regulatory mechanisms. radiobiology is the study of the interactions between ionizing radiation and living organisms.
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
eat them. plants and other photosynthetic organisms are at the base of most food chains because they use the energy from the sun and nutrients from the soil and atmosphere, converting them into a form that can be used by animals. this is what ecologists call the first trophic level. the modern forms of the major staple foods, such as hemp, teff, maize, rice, wheat and other cereal grasses, pulses, bananas and plantains, as well as hemp, flax and cotton grown for their fibres, are the outcome of prehistoric selection over thousands of years from among wild ancestral plants with the most desirable characteristics. botanists study how plants produce food and how to increase yields, for example through plant breeding, making their work important to humanity ' s ability to feed the world and provide food security for future generations. botanists also study weeds, which are a considerable problem in agriculture, and the biology and control of plant pathogens in agriculture and natural ecosystems. ethnobotany is the study of the relationships between plants and people. when applied to the investigation of historical plant β people relationships ethnobotany may be referred to as archaeobotany or palaeoethnobotany. some of the earliest plant - people relationships arose between the indigenous people of canada in identifying edible plants from inedible plants. this relationship the indigenous people had with plants was recorded by ethnobotanists. = = plant biochemistry = = plant biochemistry is the study of the chemical processes used by plants. some of these processes are used in their primary metabolism like the photosynthetic calvin cycle and crassulacean acid metabolism. others make specialised materials like the cellulose and lignin used to build their bodies, and secondary products like resins and aroma compounds. plants and various other groups of photosynthetic eukaryotes collectively known as " algae " have unique organelles known as chloroplasts. chloroplasts are thought to be descended from cyanobacteria that formed endosymbiotic relationships with ancient plant and algal ancestors. chloroplasts and cyanobacteria contain the blue - green pigment chlorophyll a. chlorophyll a ( as well as its plant and green algal - specific cousin chlorophyll b ) absorbs light in the blue - violet and orange / red parts of the spectrum while reflecting and transmitting the green light that we see as the characteristic colour
Question: What is the study of ecosystems?
A) botany
B) physics
C) ecology
D) geology
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C) ecology
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Context:
of the device. examples of radio remote control : unmanned aerial vehicle ( uav, drone ) β a drone is an aircraft without an onboard pilot, flown by remote control by a pilot in another location, usually in a piloting station on the ground. they are used by the military for reconnaissance and ground attack, and more recently by the civilian world for news reporting and aerial photography. the pilot uses aircraft controls like a joystick or steering wheel, which create control signals which are transmitted to the drone by radio to control the flight surfaces and engine. a telemetry system transmits back a video image from a camera in the drone to allow the pilot to see where the aircraft is going, and data from a gps receiver giving the real - time position of the aircraft. uavs have sophisticated onboard automatic pilot systems that maintain stable flight and only require manual control to change directions. keyless entry system β a short - range handheld battery powered key fob transmitter, included with most modern cars, which can lock and unlock the doors of a vehicle from outside, eliminating the need to use a key. when a button is pressed, the transmitter sends a coded radio signal to a receiver in the vehicle, operating the locks. the fob must be close to the vehicle, typically within 5 to 20 meters. north america and japan use a frequency of 315 mhz, while europe uses 433. 92 and 868 mhz. some models can also remotely start the engine, to warm up the car. a security concern with all keyless entry systems is a replay attack, in which a thief uses a special receiver ( " code grabber " ) to record the radio signal during opening, which can later be replayed to open the door. to prevent this, keyless systems use a rolling code system in which a pseudorandom number generator in the remote control generates a different random key each time it is used. to prevent thieves from simulating the pseudorandom generator to calculate the next key, the radio signal is also encrypted. garage door opener β a short - range handheld transmitter which can open or close a building ' s electrically operated garage door from outside, so the owner can open the door upon arrival, and close it after departure. when a button is pressed the control transmits a coded fsk radio signal to a receiver in the opener, raising or lowering the door. modern openers use 310, 315 or 390 mhz. to prevent a thief using a replay attack, modern openers use a rolling code system. radio - controlled models
quantum mechanics is interpreted by the adjacent vacuum that behaves as a virtual particle to be absorbed and emitted by its matter. as described in the vacuum universe model, the adjacent vacuum is derived from the pre - inflationary universe in which the pre - adjacent vacuum is absorbed by the pre - matter. this absorbed pre - adjacent vacuum is emitted to become the added space for the inflation in the inflationary universe whose space - time is separated from the pre - inflationary universe. this added space is the adjacent vacuum. the absorption of the adjacent vacuum as the added space results in the adjacent zero space ( no space ), quantum mechanics is the interaction between matter and the three different types of vacuum : the adjacent vacuum, the adjacent zero space, and the empty space. the absorption of the adjacent vacuum results in the empty space superimposed with the adjacent zero space, confining the matter in the form of particle. when the absorbed vacuum is emitted, the adjacent vacuum can be anywhere instantly in the empty space superimposed with the adjacent zero space where any point can be the starting point ( zero point ) of space - time. consequently, the matter that expands into the adjacent vacuum has the probability to be anywhere instantly in the form of wavefunction. in the vacuum universe model, the universe not only gains its existence from the vacuum but also fattens itself with the vacuum. during the inflation, the adjacent vacuum also generates the periodic table of elementary particles to account for all elementary particles and their masses in a good agreement with the observed values.
development and interaction of starting vortices initiated by dielectric barrier discharge ( dbd ) plasma actuators in quiescent air are illustrated in the attached fluid dynamics videos. these include a series of smoke flow visualisations, showing the starting vortices moving parallel or normal to the wall at several different actuator configurations.
##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
the realization of karl popper ' s epr - like experiment by shih and kim ( published 1999 ) produced the result that popper hoped for : no ` ` action at a distance ' ' on one photon of an entangled pair when a measurement is made on the other photon. this experimental result is interpretable in local realistic terms : each photon has a definite position and transverse momentum most of the time ; the position measurement on one photon ( localization within a slit ) disturbs the transverse momentum of that photon in a non - predictable way in accordance with the uncertainty principle ; however, there is no effect on the other photon ( the photon that is not in a slit ) no action at a distance. the position measurement ( localization within a slit ) of the one photon destroys the entanglement between the photons ; i. e. decoherence occurs.
this is a comment on phys. rev. lett. 98, 180403 ( 2007 ) [ arxiv : 0704. 2162 ].
. 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
this is an experimentalist ' s list of questions concerning the physics of the charmed baryon sector which have no satisfactory answer.
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
fuel cells instead of batteries, and conducted the first american spacewalks and rendezvous operations. the ranger program was started in the 1950s as a response to soviet lunar exploration, however most missions ended in failure. the lunar orbiter program had greater success, mapping the surface in preparation for apollo landings, conducting meteoroid detection, and measuring radiation levels. the surveyor program conducted uncrewed lunar landings and takeoffs, as well as taking surface and regolith observations. despite the setback caused by the apollo 1 fire, which killed three astronauts, the program proceeded. apollo 8 was the first crewed spacecraft to leave low earth orbit and the first human spaceflight to reach the moon. the crew orbited the moon ten times on december 24 and 25, 1968, and then traveled safely back to earth. the three apollo 8 astronauts β frank borman, james lovell, and william anders β were the first humans to see the earth as a globe in space, the first to witness an earthrise, and the first to see and manually photograph the far side of the moon. the first lunar landing was conducted by apollo 11. commanded by neil armstrong with astronauts buzz aldrin and michael collins, apollo 11 was one of the most significant missions in nasa ' s history, marking the end of the space race when the soviet union gave up its lunar ambitions. as the first human to step on the surface of the moon, neil armstrong uttered the now famous words : that ' s one small step for man, one giant leap for mankind. nasa would conduct six total lunar landings as part of the apollo program, with apollo 17 concluding the program in 1972. = = = = end of apollo = = = = wernher von braun had advocated for nasa to develop a space station since the agency was created. in 1973, following the end of the apollo lunar missions, nasa launched its first space station, skylab, on the final launch of the saturn v. skylab reused a significant amount of apollo and saturn hardware, with a repurposed saturn v third stage serving as the primary module for the space station. damage to skylab during its launch required spacewalks to be performed by the first crew to make it habitable and operational. skylab hosted nine missions and was decommissioned in 1974 and deorbited in 1979, two years prior to the first launch of the space shuttle and any possibility of boosting its orbit. in 1975, the apollo β soyuz mission was the first ever international spaceflight and a major diplomatic accomplishment between the cold war
Question: Where do sperm go after leaving the testicles and before entering the vas deferens?
A) clitoris
B) skin
C) epididymis
D) anus
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C) epididymis
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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
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
, 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
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
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
##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
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
##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
Question: What theory brings together continental drift and seafloor spreading?
A) theory of water tectonics
B) theory of front tectonics
C) theory of order tectonics
D) theory of plate tectonics
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D) theory of plate tectonics
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Context:
= = 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
the motion of celestial bodies through a higher power such as god. aristotle did not have the technological advancements that would have explained the motion of celestial bodies. in addition, aristotle had many views on the elements. he believed that everything was derived of the elements earth, water, air, fire, and lastly the aether. the aether was a celestial element, and therefore made up the matter of the celestial bodies. the elements of earth, water, air and fire were derived of a combination of two of the characteristics of hot, wet, cold, and dry, and all had their inevitable place and motion. the motion of these elements begins with earth being the closest to " the earth, " then water, air, fire, and finally aether. in addition to the makeup of all things, aristotle came up with theories as to why things did not return to their natural motion. he understood that water sits above earth, air above water, and fire above air in their natural state. he explained that although all elements must return to their natural state, the human body and other living things have a constraint on the elements β thus not allowing the elements making one who they are to return to their natural state. the important legacy of this period included substantial advances in factual knowledge, especially in anatomy, zoology, botany, mineralogy, geography, mathematics and astronomy ; an awareness of the importance of certain scientific problems, especially those related to the problem of change and its causes ; and a recognition of the methodological importance of applying mathematics to natural phenomena and of undertaking empirical research. in the hellenistic age scholars frequently employed the principles developed in earlier greek thought : the application of mathematics and deliberate empirical research, in their scientific investigations. thus, clear unbroken lines of influence lead from ancient greek and hellenistic philosophers, to medieval muslim philosophers and scientists, to the european renaissance and enlightenment, to the secular sciences of the modern day. neither reason nor inquiry began with the ancient greeks, but the socratic method did, along with the idea of forms, give great advances in geometry, logic, and the natural sciences. according to benjamin farrington, former professor of classics at swansea university : " men were weighing for thousands of years before archimedes worked out the laws of equilibrium ; they must have had practical and intuitional knowledge of the principals involved. what archimedes did was to sort out the theoretical implications of this practical knowledge and present the resulting body of knowledge as a logically coherent system. " and again : " with astonishment we find ourselves on the threshold of modern science
##ting the principle of conservation of mass and developing a new system of chemical nomenclature used to this day. english scientist john dalton proposed the modern theory of atoms ; that all substances are composed of indivisible ' atoms ' of matter and that different atoms have varying atomic weights. the development of the electrochemical theory of chemical combinations occurred in the early 19th century as the result of the work of two scientists in particular, jons jacob berzelius and humphry davy, made possible by the prior invention of the voltaic pile by alessandro volta. davy discovered nine new elements including the alkali metals by extracting them from their oxides with electric current. british william prout first proposed ordering all the elements by their atomic weight as all atoms had a weight that was an exact multiple of the atomic weight of hydrogen. j. a. r. newlands devised an early table of elements, which was then developed into the modern periodic table of elements in the 1860s by dmitri mendeleev and independently by several other scientists including julius lothar meyer. the inert gases, later called the noble gases were discovered by william ramsay in collaboration with lord rayleigh at the end of the century, thereby filling in the basic structure of the table. organic chemistry was developed by justus von liebig and others, following friedrich wohler ' s synthesis of urea. other crucial 19th century advances were ; an understanding of valence bonding ( edward frankland in 1852 ) and the application of thermodynamics to chemistry ( j. w. gibbs and svante arrhenius in the 1870s ). at the turn of the twentieth century the theoretical underpinnings of chemistry were finally understood due to a series of remarkable discoveries that succeeded in probing and discovering the very nature of the internal structure of atoms. in 1897, j. j. thomson of the university of cambridge discovered the electron and soon after the french scientist becquerel as well as the couple pierre and marie curie investigated the phenomenon of radioactivity. in a series of pioneering scattering experiments ernest rutherford at the university of manchester discovered the internal structure of the atom and the existence of the proton, classified and explained the different types of radioactivity and successfully transmuted the first element by bombarding nitrogen with alpha particles. his work on atomic structure was improved on by his students, the danish physicist niels bohr, the englishman henry moseley and the german otto hahn, who went on to father the emerging nuclear chemistry and discovered nuclear fission. the electronic theory
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
, 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
has rest mass and volume ( it takes up space ) and is made up of particles. the particles that make up matter have rest mass as well β not all particles have rest mass, such as the photon. matter can be a pure chemical substance or a mixture of substances. = = = = atom = = = = the atom is the basic unit of chemistry. it consists of a dense core called the atomic nucleus surrounded by a space occupied by an electron cloud. the nucleus is made up of positively charged protons and uncharged neutrons ( together called nucleons ), while the electron cloud consists of negatively charged electrons which orbit the nucleus. in a neutral atom, the negatively charged electrons balance out the positive charge of the protons. the nucleus is dense ; the mass of a nucleon is approximately 1, 836 times that of an electron, yet the radius of an atom is about 10, 000 times that of its nucleus. the atom is also the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state ( s ), coordination number, and preferred types of bonds to form ( e. g., metallic, ionic, covalent ). = = = = element = = = = a chemical element is a pure substance which is composed of a single type of atom, characterized by its particular number of protons in the nuclei of its atoms, known as the atomic number and represented by the symbol z. the mass number is the sum of the number of protons and neutrons in a nucleus. although all the nuclei of all atoms belonging to one element will have the same atomic number, they may not necessarily have the same mass number ; atoms of an element which have different mass numbers are known as isotopes. for example, all atoms with 6 protons in their nuclei are atoms of the chemical element carbon, but atoms of carbon may have mass numbers of 12 or 13. the standard presentation of the chemical elements is in the periodic table, which orders elements by atomic number. the periodic table is arranged in groups, or columns, and periods, or rows. the periodic table is useful in identifying periodic trends. = = = = compound = = = = a compound is a pure chemical substance composed of more than one element. the properties of a compound bear little similarity to those of its elements. the standard nomenclature of compounds is set by the international union of pure and applied chemistry ( iupac ). organic compounds are named
is also the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state ( s ), coordination number, and preferred types of bonds to form ( e. g., metallic, ionic, covalent ). = = = = element = = = = a chemical element is a pure substance which is composed of a single type of atom, characterized by its particular number of protons in the nuclei of its atoms, known as the atomic number and represented by the symbol z. the mass number is the sum of the number of protons and neutrons in a nucleus. although all the nuclei of all atoms belonging to one element will have the same atomic number, they may not necessarily have the same mass number ; atoms of an element which have different mass numbers are known as isotopes. for example, all atoms with 6 protons in their nuclei are atoms of the chemical element carbon, but atoms of carbon may have mass numbers of 12 or 13. the standard presentation of the chemical elements is in the periodic table, which orders elements by atomic number. the periodic table is arranged in groups, or columns, and periods, or rows. the periodic table is useful in identifying periodic trends. = = = = compound = = = = a compound is a pure chemical substance composed of more than one element. the properties of a compound bear little similarity to those of its elements. the standard nomenclature of compounds is set by the international union of pure and applied chemistry ( iupac ). organic compounds are named according to the organic nomenclature system. the names for inorganic compounds are created according to the inorganic nomenclature system. when a compound has more than one component, then they are divided into two classes, the electropositive and the electronegative components. in addition the chemical abstracts service ( cas ) has devised a method to index chemical substances. in this scheme each chemical substance is identifiable by a number known as its cas registry number. = = = = molecule = = = = a molecule is the smallest indivisible portion of a pure chemical substance that has its unique set of chemical properties, that is, its potential to undergo a certain set of chemical reactions with other substances. however, this definition only works well for substances that are composed of molecules, which is not true of many substances ( see below ). molecules are typically a set of atoms bound together by covalent bonds, such that the structure is electrically neutral and all valence electrons are paired with
approximatively equal ", or it means " has the same order of magnitude as ". 2. denotes the asymptotic equivalence of two functions or sequences. 3. often used for denoting other types of similarity, for example, matrix similarity or similarity of geometric shapes. 4. standard notation for an equivalence relation. 5. in probability and statistics, may specify the probability distribution of a random variable. for example, x [UNK] n ( 0, 1 ) { \ displaystyle x \ sim n ( 0, 1 ) } means that the distribution of the random variable x is standard normal. 6. notation for proportionality. see also [UNK] for a less ambiguous symbol. β‘ ( triple bar ) 1. denotes an identity ; that is, an equality that is true whichever values are given to the variables occurring in it. 2. in number theory, and more specifically in modular arithmetic, denotes the congruence modulo an integer. 3. may denote a logical equivalence. [UNK] { \ displaystyle \ cong } 1. may denote an isomorphism between two mathematical structures, and is read as " is isomorphic to ". 2. in geometry, may denote the congruence of two geometric shapes ( that is the equality up to a displacement ), and is read " is congruent to ". = = comparison = = < ( less - than sign ) 1. strict inequality between two numbers ; means and is read as " less than ". 2. commonly used for denoting any strict order. 3. between two groups, may mean that the first one is a proper subgroup of the second one. > ( greater - than sign ) 1. strict inequality between two numbers ; means and is read as " greater than ". 2. commonly used for denoting any strict order. 3. between two groups, may mean that the second one is a proper subgroup of the first one. β€ 1. means " less than or equal to ". that is, whatever a and b are, a β€ b is equivalent to a < b or a = b. 2. between two groups, may mean that the first one is a subgroup of the second one. β₯ 1. means " greater than or equal to ". that is, whatever a and b are, a β₯ b is equivalent to a > b or a = b. 2. between two groups, may mean that the second one is a subgroup of the first one. [UNK] and [UNK] { \ displaystyle \ ll { \ text { and } } \
fi is not short - form for ' wireless fidelity ', although the wi - fi alliance did use the advertising slogan " the standard for wireless fidelity " for a short time after the brand name was created, and the wi - fi alliance was also called the " wireless fidelity alliance inc. " in some publications. ieee is a separate, but related, organization and their website has stated " wifi is a short name for wireless fidelity ". the name wi - fi was partly chosen because it sounds similar to hi - fi, which consumers take to mean high fidelity or high quality. interbrand hoped consumers would find the name catchy, and that they would assume this wireless protocol has high fidelity because of its name. other technologies intended for fixed points, including motorola canopy, are usually called fixed wireless. alternative wireless technologies include zigbee, z - wave, bluetooth and mobile phone standards. to connect to a wi - fi lan, a computer must be equipped with a wireless network interface controller. the combination of a computer and an interface controller is called a station. stations are identified by one or more mac addresses. wi - fi nodes often operate in infrastructure mode in which all communications go through a base station. ad hoc mode refers to devices communicating directly with each other, without communicating with an access point. a service set is the set of all the devices associated with a particular wi - fi network. devices in a service set need not be on the same wavebands or channels. a service set can be local, independent, extended, mesh, or a combination. each service set has an associated identifier, a 32 - byte service set identifier ( ssid ), which identifies the network. the ssid is configured within the devices that are part of the network. a basic service set ( bss ) is a group of stations that share the same wireless channel, ssid, and other settings that have wirelessly connected, usually to the same access point. : 3. 6 each bss is identified by a mac address called the bssid. = = certification = = the ieee does not test equipment for compliance with their standards. the wi - fi alliance was formed in 1999 to establish and enforce standards for interoperability and backward compatibility, and to promote wireless local - area - network technology. the wi - fi alliance enforces the use of the wi - fi brand to technologies based on the ieee 802. 11 standards from the ieee. manufacturers with membership in the wi - fi alliance, whose products pass the certification process
the purpose of this research is to apply technical analysis of sutte indicator in stock trading which will assist in the investment decision making process i. e. buying or selling shares. this research takes data of " a " on the indonesia stock exchange ( idx or bei ) 29 november 2006 until 20 september 2016 period. to see the performance of sutte indicator, other technical analysis are used as a comparison, simple moving average ( sma ) and moving average convergence / divergence ( macd ). to see a comparison of the level of reliability prediction, the stock data were compared using the mean absolute deviation ( mad ), mean of square error ( mse ), and mean absolute percentage error ( mape ). the result of this research is that sutte indicator can be used as a reference in predicting stock movements, and if it is compared to other indicator methods ( sma and macd ) via mad, mse, and mape, the sutte indicator has a better level of reliability.
Question: Different forms of the same element are called what?
A) subclasses
B) allotropes
C) amines
D) polymorphs
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B) allotropes
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Context:
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.
in supersymmetric theories, the presence of axions usually implies the existence of a non - compact, ( pseudo ) moduli space. in gauge mediated models, the axion would seem a particularly promising dark matter candidate. the cosmology of the moduli then constrains the gravitino mass and the axion decay constant ; the former can ' t be much below 10 mev ; the latter can ' t be much larger than 10 ^ { 13 } gev. axinos, when identifiable, are typically heavy and do not play an important role in cosmology.
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.
so mars below means blood and war ", is a false cause fallacy. : 26 many astrologers claim that astrology is scientific. if one were to attempt to try to explain it scientifically, there are only four fundamental forces ( conventionally ), limiting the choice of possible natural mechanisms. : 65 some astrologers have proposed conventional causal agents such as electromagnetism and gravity. the strength of these forces drops off with distance. : 65 scientists reject these proposed mechanisms as implausible since, for example, the magnetic field, when measured from earth, of a large but distant planet such as jupiter is far smaller than that produced by ordinary household appliances. astronomer phil plait noted that in terms of magnitude, the sun is the only object with an electromagnetic field of note, but astrology isn ' t based just off the sun alone. : 65 while astrologers could try to suggest a fifth force, this is inconsistent with the trends in physics with the unification of electromagnetism and the weak force into the electroweak force. if the astrologer insisted on being inconsistent with the current understanding and evidential basis of physics, that would be an extraordinary claim. : 65 it would also be inconsistent with the other forces which drop off with distance. : 65 if distance is irrelevant, then, logically, all objects in space should be taken into account. : 66 carl jung sought to invoke synchronicity, the claim that two events have some sort of acausal connection, to explain the lack of statistically significant results on astrology from a single study he conducted. however, synchronicity itself is considered neither testable nor falsifiable. the study was subsequently heavily criticised for its non - random sample and its use of statistics and also its lack of consistency with astrology. = = psychology = = psychological studies have not found any robust relationship between astrological signs and life outcomes. for example, a study showed that zodiac signs are no more effective than random numbers in predicting subjective well - being and quality of life. it has also been shown that confirmation bias is a psychological factor that contributes to belief in astrology. : 344 : 180 β 181 : 42 β 48 confirmation bias is a form of cognitive bias. : 553 from the literature, astrology believers often tend to selectively remember those predictions that turned out to be true and do not remember those that turned out false. another, separate, form of confirmation bias also plays a role, where believers often fail to
the 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.
. this, he argued, would have been more persuasive and would have produced less controversy. the use of poetic imagery based on the concepts of the macrocosm and microcosm, " as above so below " to decide meaning such as edward w. james ' example of " mars above is red, so mars below means blood and war ", is a false cause fallacy. : 26 many astrologers claim that astrology is scientific. if one were to attempt to try to explain it scientifically, there are only four fundamental forces ( conventionally ), limiting the choice of possible natural mechanisms. : 65 some astrologers have proposed conventional causal agents such as electromagnetism and gravity. the strength of these forces drops off with distance. : 65 scientists reject these proposed mechanisms as implausible since, for example, the magnetic field, when measured from earth, of a large but distant planet such as jupiter is far smaller than that produced by ordinary household appliances. astronomer phil plait noted that in terms of magnitude, the sun is the only object with an electromagnetic field of note, but astrology isn ' t based just off the sun alone. : 65 while astrologers could try to suggest a fifth force, this is inconsistent with the trends in physics with the unification of electromagnetism and the weak force into the electroweak force. if the astrologer insisted on being inconsistent with the current understanding and evidential basis of physics, that would be an extraordinary claim. : 65 it would also be inconsistent with the other forces which drop off with distance. : 65 if distance is irrelevant, then, logically, all objects in space should be taken into account. : 66 carl jung sought to invoke synchronicity, the claim that two events have some sort of acausal connection, to explain the lack of statistically significant results on astrology from a single study he conducted. however, synchronicity itself is considered neither testable nor falsifiable. the study was subsequently heavily criticised for its non - random sample and its use of statistics and also its lack of consistency with astrology. = = psychology = = psychological studies have not found any robust relationship between astrological signs and life outcomes. for example, a study showed that zodiac signs are no more effective than random numbers in predicting subjective well - being and quality of life. it has also been shown that confirmation bias is a psychological factor that contributes to belief in astrology. : 344 : 180 β 181 :
the atmospheric terraforming of mars, for example, would require " significant quantities of gas " to be added to the martian atmosphere. this gas has been thought to be stored in solid and liquid form within mars ' polar ice caps and underground reservoirs. it is unlikely, however, that enough co2 for sufficient atmospheric change is present within mars ' polar deposits, and liquid co2 could only be present at warmer temperatures " deep within the crust ". furthermore, sublimating the entire volume of mars ' polar caps would increase its current atmospheric pressure to 15 millibar, where an increase to around 1000 millibar would be required for habitability. for reference, earth ' s average sea - level pressure is 1013. 25 mbar. first formally proposed by astrophysicist carl sagan, the terraforming of venus has since been discussed through methods such as organic molecule - induced carbon conversion, sun reflection, increasing planetary spin, and various chemical means. due to the high presence of sulfuric acid and solar wind on venus, which are harmful to organic environments, organic methods of carbon conversion have been found unfeasible. other methods, such as solar shading, hydrogen bombardment, and magnesium - calcium bombardment are theoretically sound but would require large - scale resources and space technologies not yet available to humans. = = = ethical considerations = = = while successful terraforming would allow life to prosper on other planets, philosophers have debated whether this practice is morally sound. certain ethics experts suggest that planets like mars hold an intrinsic value independent of their utility to humanity and should therefore be free from human interference. also, some argue that through the steps that are necessary to make mars habitable - such as fusion reactors, space - based solar - powered lasers, or spreading a thin layer of soot on mars ' polar ice caps - would deteriorate the current aesthetic value that mars possesses. this calls into question humanity ' s intrinsic ethical and moral values, as it raises the question of whether humanity is willing to eradicate the current ecosystem of another planet for their benefit. through this ethical framework, terraforming attempts on these planets could be seen to threaten their intrinsically valuable environments, rendering these efforts unethical. = = seeding = = = = = environmental considerations = = = mars is the primary subject of discussion for seeding. locations for seeding are chosen based on atmospheric temperature, air pressure, existence of harmful radiation, and availability of natural resources, such as water and other compounds essential to terrestrial life. = = = developing
a hot and inhospitable planet. follow - on missions included the pioneer venus project in the 1970s and magellan, which performed radar mapping of venus ' surface in the 1980s and 1990s. future missions were flybys of venus, on their way to other destinations in the solar system. mars has long been a planet of intense fascination for nasa, being suspected of potentially having harbored life. mariner 5 was the first nasa spacecraft to flyby mars, followed by mariner 6 and mariner 7. mariner 9 was the first orbital mission to mars. launched in 1975, viking program consisted of two landings on mars in 1976. follow - on missions would not be launched until 1996, with the mars global surveyor orbiter and mars pathfinder, deploying the first mars rover, sojourner. during the early 2000s, the 2001 mars odyssey orbiter reached the planet and in 2004 the sprit and opportunity rovers landed on the red planet. this was followed in 2005 by the mars reconnaissance orbiter and 2007 phoenix mars lander. the 2012 landing of curiosity discovered that the radiation levels on mars were equal to those on the international space station, greatly increasing the possibility of human exploration, and observed the key chemical ingredients for life to occur. in 2013, the mars atmosphere and volatile evolution ( maven ) mission observed the martian upper atmosphere and space environment and in 2018, the interior exploration using seismic investigations geodesy, and heat transport ( insight ) studied the martian interior. the 2021 perseverance rover carried the first extraplanetary aircraft, a helicopter named ingenuity. nasa also launched missions to mercury in 2004, with the messenger probe demonstrating as the first use of a solar sail. nasa also launched probes to the outer solar system starting in the 1960s. pioneer 10 was the first probe to the outer planets, flying by jupiter, while pioneer 11 provided the first close up view of the planet. both probes became the first objects to leave the solar system. the voyager program launched in 1977, conducting flybys of jupiter and saturn, neptune, and uranus on a trajectory to leave the solar system. the galileo spacecraft, deployed from the space shuttle flight sts - 34, was the first spacecraft to orbit jupiter, discovering evidence of subsurface oceans on the europa and observed that the moon may hold ice or liquid water. a joint nasa - european space agency - italian space agency mission, cassini β huygens, was sent to saturn ' s moon titan, which, along with mars and europa, are the only
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
##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
Question: What is the only marsupial in north america?
A) oppossum
B) Marmosa
C) Raccoon
D) Didelphinae
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A) oppossum
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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
this preprint was split in two and became the first two parts of a four - part series ( arxiv : 1405. 1956, arxiv : 1405 : 1955, and two in preparation ). the remaining relevance of this preprint is due to the series of videotaped lectures ( wclips ) that are linked within.
##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
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
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 that helped design the gear trains of the industrial revolution, and are widely used in fields such as robotics and automotive engineering. ancient chinese, greek, roman and hunnic armies employed military machines and inventions such as artillery which was developed by the greeks around the 4th century bc, the trireme, the ballista and the catapult, the trebuchet by chinese circa 6th - 5th century bce. = = = middle ages = = = the earliest practical wind - powered machines, the windmill and wind pump, first appeared in the muslim world during the islamic golden age, in what are now iran, afghanistan, and pakistan, by the 9th century ad. the earliest practical steam - powered machine was a steam jack driven by a steam turbine, described in 1551 by taqi al - din muhammad ibn ma ' ruf in ottoman egypt. the cotton gin was invented in india by the 6th century ad, and the spinning wheel was invented in the islamic
are stem cells which can divide into further stem cells or differentiate into any cell type in the body, including extra - embryonic tissue. pluripotent cells are stem cells which can differentiate into any cell type in the body except extra - embryonic tissue. induced pluripotent stem cells ( ipscs ) are subclass of pluripotent stem cells resembling embryonic stem cells ( escs ) that have been derived from adult differentiated cells. ipscs are created by altering the expression of transcriptional factors in adult cells until they become like embryonic stem cells. multipotent stem cells can be differentiated into any cell within the same class, such as blood or bone. a common example of multipotent cells is mesenchymal stem cells ( mscs ). = = scaffolds = = scaffolds are materials that have been engineered to cause desirable cellular interactions to contribute to the formation of new functional tissues for medical purposes. cells are often ' seeded ' into these structures capable of supporting three - dimensional tissue formation. scaffolds mimic the extracellular matrix of the native tissue, recapitulating the in vivo milieu and allowing cells to influence their own microenvironments. they usually serve at least one of the following purposes : allowing cell attachment and migration, delivering and retaining cells and biochemical factors, enabling diffusion of vital cell nutrients and expressed products, and exerting certain mechanical and biological influences to modify the behaviour of the cell phase. in 2009, an interdisciplinary team led by the thoracic surgeon thorsten walles implanted the first bioartificial transplant that provides an innate vascular network for post - transplant graft supply successfully into a patient awaiting tracheal reconstruction. to achieve the goal of tissue reconstruction, scaffolds must meet some specific requirements. high porosity and adequate pore size are necessary to facilitate cell seeding and diffusion throughout the whole structure of both cells and nutrients. biodegradability is often an essential factor since scaffolds should preferably be absorbed by the surrounding tissues without the necessity of surgical removal. the rate at which degradation occurs has to coincide as much as possible with the rate of tissue formation : this means that while cells are fabricating their own natural matrix structure around themselves, the scaffold is able to provide structural integrity within the body and eventually it will break down leaving the newly formed tissue which will take over the mechanical load. injectability is also important for clinical uses. recent research on organ printing is showing
herbicides. the people ' s republic of china was the first country to commercialise transgenic plants, introducing a virus - resistant tobacco in 1992. in 1994 calgene attained approval to commercially release the first genetically modified food, the flavr savr, a tomato engineered to have a longer shelf life. in 1994, the european union approved tobacco engineered to be resistant to the herbicide bromoxynil, making it the first genetically engineered crop commercialised in europe. in 1995, bt potato was approved safe by the environmental protection agency, after having been approved by the fda, making it the first pesticide producing crop to be approved in the us. in 2009 11 transgenic crops were grown commercially in 25 countries, the largest of which by area grown were the us, brazil, argentina, india, canada, china, paraguay and south africa. in 2010, scientists at the j. craig venter institute created the first synthetic genome and inserted it into an empty bacterial cell. the resulting bacterium, named mycoplasma laboratorium, could replicate and produce proteins. four years later this was taken a step further when a bacterium was developed that replicated a plasmid containing a unique base pair, creating the first organism engineered to use an expanded genetic alphabet. in 2012, jennifer doudna and emmanuelle charpentier collaborated to develop the crispr / cas9 system, a technique which can be used to easily and specifically alter the genome of almost any organism. = = process = = creating a gmo is a multi - step process. genetic engineers must first choose what gene they wish to insert into the organism. this is driven by what the aim is for the resultant organism and is built on earlier research. genetic screens can be carried out to determine potential genes and further tests then used to identify the best candidates. the development of microarrays, transcriptomics and genome sequencing has made it much easier to find suitable genes. luck also plays its part ; the roundup ready gene was discovered after scientists noticed a bacterium thriving in the presence of the herbicide. = = = gene isolation and cloning = = = the next step is to isolate the candidate gene. the cell containing the gene 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
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
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
two people meet in a coffeehouse and decide to share one dessert from a menu of several possible choices. how should they choose which one? a method is presented that is intended to be practical, avoiding the need for long negotiations or complete menu rankings, while offering a high likelihood of satisfaction and fairness to both participants. the method is also extended to parties of 3 or more people sharing one item from a menu of several choices.
Question: What is the generation of electricity using photovoltaic cells to split water molecules called?
A) aqua-electricity
B) photovoltaic cells
C) photoelectrolysis
D) hybrid electricity
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C) photoelectrolysis
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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
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
and nine classes, depending on its color, texture and hydrology. contemporaries friedrich albert fallou ( the german founder of modern soil science ) and vasily dokuchaev ( the russian founder of modern soil science ) are both credited with being among the first to identify soil as a resource whose distinctness and complexity deserved 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
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
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 status of the theory of color confinemnt is discussed.
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
, 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 been without its share of controversy and criticism, including critiques by nobel laureate norman borlaug and world food prize winner pedro sanchez. a more traditional role for soil scientists has been to map soils. almost every area in the united states now has a published soil survey, including interpretive tables on how soil properties support or limit activities and uses. an internationally accepted soil taxonomy allows uniform communication of soil characteristics and soil functions. national and international soil survey efforts have given the profession unique insights into landscape - scale functions. the landscape functions that soil scientists are called upon to address in the field seem to fall roughly into six areas : land - based treatment of wastes septic system manure municipal biosolids food and fiber processing waste identification and protection of environmentally critical areas sensitive and unstable soils wetlands unique soil situations that support valuable habitat, and ecosystem diversity management for optimum land productivity silviculture agronomy nutrient management water management native vegetation grazing management for optimum water quality stormwater management sediment and erosion control remediation and restoration of damaged lands mine reclamation flood and storm damage contamination sustainability of desired uses soil conservation there are also practical applications of soil science that might not be apparent from looking at a published soil survey. radiometric dating : specifically a knowledge of local pedology is used to date prior activity at the site stratification ( archeology ) where soil formation processes and preservative qualities can inform the study of archaeological sites geological phenomena landslides active faults altering soils to achieve new uses vitrification to contain radioactive wastes enhancing soil microbial capabilities in degrading
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
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
Question: What does the color of soil indicate?
A) chemical makeup
B) fertility
C) density
D) temperature
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B) fertility
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Context:
strangelets ( stable lumps of quark matter ) can have masses and charges much higher than those of nuclei, but have very low charge - to - mass ratios. this is confirmed in a relativistic thomas - fermi model. the high charge allows astrophysical strangelet acceleration to energies orders of magnitude higher than for protons. in addition, strangelets are much less susceptible to the interactions with the cosmic microwave background that suppress the flux of cosmic ray protons and nuclei above energies of $ 10 ^ { 19 } $ - - $ 10 ^ { 20 } $ ev ( the gzk - cutoff ). this makes strangelets an interesting possibility for explaining ultra - high energy cosmic rays.
it is believed that there may have been a large number of black holes formed in the very early universe. these would have quantised masses. a charged ` ` elementary black hole ' ' ( with the minimum possible mass ) can capture electrons, protons and other charged particles to form a ` ` black hole atom ' '. we find the spectrum of such an object with a view to laboratory and astronomical observation of them, and estimate the lifetime of the bound states. there is no limit to the charge of the black hole, which gives us the possibility of observing z > 137 bound states and transitions at the lower continuum. negatively charged black holes can capture protons. for z > 1, the orbiting protons will coalesce to form a nucleus ( after beta - decay of some protons to neutrons ), with a stability curve different to that of free nuclei. in this system there is also the distinct possibility of single quark capture. this leads to the formation of a coloured black hole that plays the role of an extremely heavy quark interacting strongly with the other two quarks. finally we consider atoms formed with much larger black holes.
it is well known and well established by scientific observation that a free neutron radioactively decays into a proton plus an electron plus an anti - neutrino with a mean life time before decay of about 900 seconds. that established fact conflicts sharply with the hypothesis that the neutron is composed of two down plus one up quark and that the proton is composed of one down plus two up quarks. that conflict throws doubt on the entire quark hypothesis.
has rest mass and volume ( it takes up space ) and is made up of particles. the particles that make up matter have rest mass as well β not all particles have rest mass, such as the photon. matter can be a pure chemical substance or a mixture of substances. = = = = atom = = = = the atom is the basic unit of chemistry. it consists of a dense core called the atomic nucleus surrounded by a space occupied by an electron cloud. the nucleus is made up of positively charged protons and uncharged neutrons ( together called nucleons ), while the electron cloud consists of negatively charged electrons which orbit the nucleus. in a neutral atom, the negatively charged electrons balance out the positive charge of the protons. the nucleus is dense ; the mass of a nucleon is approximately 1, 836 times that of an electron, yet the radius of an atom is about 10, 000 times that of its nucleus. the atom is also the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state ( s ), coordination number, and preferred types of bonds to form ( e. g., metallic, ionic, covalent ). = = = = element = = = = a chemical element is a pure substance which is composed of a single type of atom, characterized by its particular number of protons in the nuclei of its atoms, known as the atomic number and represented by the symbol z. the mass number is the sum of the number of protons and neutrons in a nucleus. although all the nuclei of all atoms belonging to one element will have the same atomic number, they may not necessarily have the same mass number ; atoms of an element which have different mass numbers are known as isotopes. for example, all atoms with 6 protons in their nuclei are atoms of the chemical element carbon, but atoms of carbon may have mass numbers of 12 or 13. the standard presentation of the chemical elements is in the periodic table, which orders elements by atomic number. the periodic table is arranged in groups, or columns, and periods, or rows. the periodic table is useful in identifying periodic trends. = = = = compound = = = = a compound is a pure chemical substance composed of more than one element. the properties of a compound bear little similarity to those of its elements. the standard nomenclature of compounds is set by the international union of pure and applied chemistry ( iupac ). organic compounds are named
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.
, natural phenomena on earth only involve gravity and electromagnetism, and not nuclear reactions. this is because atomic nuclei are generally kept apart because they contain positive electrical charges and therefore repel each other. in 1896, henri becquerel was investigating phosphorescence in uranium salts when he discovered a new phenomenon which came to be called radioactivity. he, pierre curie and marie curie began investigating the phenomenon. in the process, they isolated the element radium, which is highly radioactive. they discovered that radioactive materials produce intense, penetrating rays of three distinct sorts, which they labeled alpha, beta, and gamma after the first three greek letters. some of these kinds of radiation could pass through ordinary matter, and all of them could be harmful in large amounts. all of the early researchers received various radiation burns, much like sunburn, and thought little of it. the new phenomenon of radioactivity was seized upon by the manufacturers of quack medicine ( as had the discoveries of electricity and magnetism, earlier ), and a number of patent medicines and treatments involving radioactivity were put forward. gradually it was realized that the radiation produced by radioactive decay was ionizing radiation, and that even quantities too small to burn could pose a severe long - term hazard. many of the scientists working on radioactivity died of cancer as a result of their exposure. radioactive patent medicines mostly disappeared, but other applications of radioactive materials persisted, such as the use of radium salts to produce glowing dials on meters. as the atom came to be better understood, the nature of radioactivity became clearer. some larger atomic nuclei are unstable, and so decay ( release matter or energy ) after a random interval. the three forms of radiation that becquerel and the curies discovered are also more fully understood. alpha decay is when a nucleus releases an alpha particle, which is two protons and two neutrons, equivalent to a helium nucleus. beta decay is the release of a beta particle, a high - energy electron. gamma decay releases gamma rays, which unlike alpha and beta radiation are not matter but electromagnetic radiation of very high frequency, and therefore energy. this type of radiation is the most dangerous and most difficult to block. all three types of radiation occur naturally in certain elements. it has also become clear that the ultimate source of most terrestrial energy is nuclear, either through radiation from the sun caused by stellar thermonuclear reactions or by radioactive decay of uranium within the earth, the principal source of geothermal energy.
, they can fission as well, leading to a chain reaction. the average number of neutrons released per nucleus that go on to fission another nucleus is referred to as k. values of k larger than 1 mean that the fission reaction is releasing more neutrons than it absorbs, and therefore is referred to as a self - sustaining chain reaction. a mass of fissile material large enough ( and in a suitable configuration ) to induce a self - sustaining chain reaction is called a critical mass. when a neutron is captured by a suitable nucleus, fission may occur immediately, or the nucleus may persist in an unstable state for a short time. if there are enough immediate decays to carry on the chain reaction, the mass is said to be prompt critical, and the energy release will grow rapidly and uncontrollably, usually leading to an explosion. when discovered on the eve of world war ii, this insight led multiple countries to begin programs investigating the possibility of constructing an atomic bomb β a weapon which utilized fission reactions to generate far more energy than could be created with chemical explosives. the manhattan project, run by the united states with the help of the united kingdom and canada, developed multiple fission weapons which were used against japan in 1945 at hiroshima and nagasaki. during the project, the first fission reactors were developed as well, though they were primarily for weapons manufacture and did not generate electricity. in 1951, the first nuclear fission power plant was the first to produce electricity at the experimental breeder reactor no. 1 ( ebr - 1 ), in arco, idaho, ushering in the " atomic age " of more intensive human energy use. however, if the mass is critical only when the delayed neutrons are included, then the reaction can be controlled, for example by the introduction or removal of neutron absorbers. this is what allows nuclear reactors to be built. fast neutrons are not easily captured by nuclei ; they must be slowed ( slow neutrons ), generally by collision with the nuclei of a neutron moderator, before they can be easily captured. today, this type of fission is commonly used to generate electricity. = = = nuclear fusion = = = if nuclei are forced to collide, they can undergo nuclear fusion. this process may release or absorb energy. when the resulting nucleus is lighter than that of iron, energy is normally released ; when the nucleus is heavier than that of iron, energy is generally absorbed. this process of fusion occurs in stars, which derive their energy from hydrogen and helium. they form, through stellar nucleos
the value of excess charge in the kernel of massive body ( and the opposite in sign excess charge at the surface ) caused by the influence of gravitational forces is determined.
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
lower limits are found for the disorder resistivity of solid neutron - star matter in the neutron - drip region which is amorphous and heterogeneous in nuclear charge. this temperature - independent resistivity, large compared with that produced by phonon scattering, has direct consequences for theories of neutron - star magnetic field generation and evolution.
Question: What kind of charge does a neutron have?
A) static
B) neutral
C) positive
D) negative
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B) neutral
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Context:
of the desired gene has been altered to make it non - functional. embryonic stem cells incorporate the altered gene, which replaces the already present functional copy. these stem cells are injected into blastocysts, which are implanted into surrogate mothers. this allows the experimenter to analyse the defects caused by this mutation and thereby determine the role of particular genes. it is used especially frequently in developmental biology. when this is done by creating a library of genes with point mutations at every position in the area of interest, or even every position in the whole gene, this is called " scanning mutagenesis ". the simplest method, and the first to be used, is " alanine scanning ", where every position in turn is mutated to the unreactive amino acid alanine. gain of function experiments, the logical counterpart of knockouts. these are sometimes performed in conjunction with knockout experiments to more finely establish the function of the desired gene. the process is much the same as that in knockout engineering, except that the construct is designed to increase the function of the gene, usually by providing extra copies of the gene or inducing synthesis of the protein more frequently. gain of function is used to tell whether or not a protein is sufficient for a function, but does not always mean it is required, especially when dealing with genetic or functional redundancy. tracking experiments, which seek to gain information about the localisation and interaction of the desired protein. one way to do this is to replace the wild - type gene with a ' fusion ' gene, which is a juxtaposition of the wild - type gene with a reporting element such as green fluorescent protein ( gfp ) that will allow easy visualisation of the products of the genetic modification. while this is a useful technique, the manipulation can destroy the function of the gene, creating secondary effects and possibly calling into question the results of the experiment. more sophisticated techniques are now in development that can track protein products without mitigating their function, such as the addition of small sequences that will serve as binding motifs to monoclonal antibodies. expression studies aim to discover where and when specific proteins are produced. in these experiments, the dna sequence before the dna that codes for a protein, known as a gene ' s promoter, is reintroduced into an organism with the protein coding region replaced by a reporter gene such as gfp or an enzyme that catalyses the production of a dye. thus the time and place where a particular protein is produced can be observed. expression studies can be taken a
##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.
the gene is expressed or what other genes it interacts with. these experiments generally involve loss of function, gain of function, tracking and expression. loss of function experiments, such as in a gene knockout experiment, in which an organism is engineered to lack the activity of one or more genes. in a simple knockout a copy of the desired gene has been altered to make it non - functional. embryonic stem cells incorporate the altered gene, which replaces the already present functional copy. these stem cells are injected into blastocysts, which are implanted into surrogate mothers. this allows the experimenter to analyse the defects caused by this mutation and thereby determine the role of particular genes. it is used especially frequently in developmental biology. when this is done by creating a library of genes with point mutations at every position in the area of interest, or even every position in the whole gene, this is called " scanning mutagenesis ". the simplest method, and the first to be used, is " alanine scanning ", where every position in turn is mutated to the unreactive amino acid alanine. gain of function experiments, the logical counterpart of knockouts. these are sometimes performed in conjunction with knockout experiments to more finely establish the function of the desired gene. the process is much the same as that in knockout engineering, except that the construct is designed to increase the function of the gene, usually by providing extra copies of the gene or inducing synthesis of the protein more frequently. gain of function is used to tell whether or not a protein is sufficient for a function, but does not always mean it is required, especially when dealing with genetic or functional redundancy. tracking experiments, which seek to gain information about the localisation and interaction of the desired protein. one way to do this is to replace the wild - type gene with a ' fusion ' gene, which is a juxtaposition of the wild - type gene with a reporting element such as green fluorescent protein ( gfp ) that will allow easy visualisation of the products of the genetic modification. while this is a useful technique, the manipulation can destroy the function of the gene, creating secondary effects and possibly calling into question the results of the experiment. more sophisticated techniques are now in development that can track protein products without mitigating their function, such as the addition of small sequences that will serve as binding motifs to monoclonal antibodies. expression studies aim to discover where and when specific proteins are produced. in these experiments, the dna sequence before the dna that codes for
mutation and thereby determine the role of particular genes. it is used especially frequently in developmental biology. when this is done by creating a library of genes with point mutations at every position in the area of interest, or even every position in the whole gene, this is called " scanning mutagenesis ". the simplest method, and the first to be used, is " alanine scanning ", where every position in turn is mutated to the unreactive amino acid alanine. gain of function experiments, the logical counterpart of knockouts. these are sometimes performed in conjunction with knockout experiments to more finely establish the function of the desired gene. the process is much the same as that in knockout engineering, except that the construct is designed to increase the function of the gene, usually by providing extra copies of the gene or inducing synthesis of the protein more frequently. gain of function is used to tell whether or not a protein is sufficient for a function, but does not always mean it is required, especially when dealing with genetic or functional redundancy. tracking experiments, which seek to gain information about the localisation and interaction of the desired protein. one way to do this is to replace the wild - type gene with a ' fusion ' gene, which is a juxtaposition of the wild - type gene with a reporting element such as green fluorescent protein ( gfp ) that will allow easy visualisation of the products of the genetic modification. while this is a useful technique, the manipulation can destroy the function of the gene, creating secondary effects and possibly calling into question the results of the experiment. more sophisticated techniques are now in development that can track protein products without mitigating their function, such as the addition of small sequences that will serve as binding motifs to monoclonal antibodies. expression studies aim to discover where and when specific proteins are produced. in these experiments, the dna sequence before the dna that codes for a protein, known as a gene ' s promoter, is reintroduced into an organism with the protein coding region replaced by a reporter gene such as gfp or an enzyme that catalyses the production of a dye. thus the time and place where a particular protein is produced can be observed. expression studies can be taken a 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,
genetic engineering, also called genetic modification or genetic manipulation, is the modification and manipulation of an organism ' s genes using technology. it is a set of technologies used to change the genetic makeup of cells, including the transfer of genes within and across species boundaries to produce improved or novel organisms. new dna is obtained by either isolating and copying the genetic material of interest using recombinant dna methods or by artificially synthesising the dna. a construct is usually created and used to insert this dna into the host organism. the first recombinant dna molecule was made by paul berg in 1972 by combining dna from the monkey virus sv40 with the lambda virus. as well as inserting genes, the process can be used to remove, or " knock out ", genes. the new dna can be inserted randomly, or targeted to a specific part of the genome. an organism that is generated through genetic engineering is considered to be genetically modified ( gm ) and the resulting entity is a genetically modified organism ( gmo ). the first gmo was a bacterium generated by herbert boyer and stanley cohen in 1973. rudolf jaenisch created the first gm animal when he inserted foreign dna into a mouse in 1974. the first company to focus on genetic engineering, genentech, was founded in 1976 and started the production of human proteins. genetically engineered human insulin was produced in 1978 and insulin - producing bacteria were commercialised in 1982. genetically modified food has been sold since 1994, with the release of the flavr savr tomato. the flavr savr was engineered to have a longer shelf life, but most current gm crops are modified to increase resistance to insects and herbicides. glofish, the first gmo designed as a pet, was sold in the united states in december 2003. in 2016 salmon modified with a growth hormone were sold. genetic engineering has been applied in numerous fields including research, medicine, industrial biotechnology and agriculture. in research, gmos are used to study gene function and expression through loss of function, gain of function, tracking and expression experiments. by knocking out genes responsible for certain conditions it is possible to create animal model organisms of human diseases. as well as producing hormones, vaccines and other drugs, genetic engineering has the potential to cure genetic diseases through gene therapy. chinese hamster ovary ( cho ) cells are used in industrial genetic engineering. additionally mrna vaccines are made through genetic engineering to prevent infections by viruses such as covid - 19. the same techniques that are used to produce drugs can also have industrial applications such
for the treatment of diabetes, was previously extracted from the pancreas of abattoir animals ( cattle or pigs ). the genetically engineered bacteria are able to produce large quantities of synthetic human insulin at relatively low cost. biotechnology has also enabled emerging therapeutics like gene therapy. the application of biotechnology to basic science ( for example through the human genome project ) has also dramatically improved our understanding of biology and as our scientific knowledge of normal and disease biology has increased, our ability to develop new medicines to treat previously untreatable diseases has increased as well. genetic testing allows the genetic diagnosis of vulnerabilities to inherited diseases, and can also be used to determine a child ' s parentage ( genetic mother and father ) or in general a person ' s ancestry. in addition to studying chromosomes to the level of individual genes, genetic testing in a broader sense includes biochemical tests for the possible presence of genetic diseases, or mutant forms of genes associated with increased risk of developing genetic disorders. genetic testing identifies changes in chromosomes, genes, or proteins. most of the time, testing is used to find changes that are associated with inherited disorders. the results of a genetic test can confirm or rule out a suspected genetic condition or help determine a person ' s chance of developing or passing on a genetic disorder. as of 2011 several hundred genetic tests were in use. since genetic testing may open up ethical or psychological problems, genetic testing is often accompanied by genetic counseling. = = = agriculture = = = genetically modified crops ( " gm crops ", or " biotech crops " ) are plants used in agriculture, the dna of which has been modified with genetic engineering techniques. in most cases, the main aim is to introduce a new trait that does not occur naturally in the species. biotechnology firms can contribute to future food security by improving the nutrition and viability of urban agriculture. furthermore, the protection of intellectual property rights encourages private sector investment in agrobiotechnology. examples in food crops include resistance to certain pests, diseases, stressful environmental conditions, resistance to chemical treatments ( e. g. resistance to a herbicide ), reduction of spoilage, or improving the nutrient profile of the crop. examples in non - food crops include production of pharmaceutical agents, biofuels, and other industrially useful goods, as well as for bioremediation. farmers have widely adopted gm technology. between 1996 and 2011, the total surface area of land cultivated with gm crops had increased by a factor of 94, from 17, 000 to 1, 600, 000 square
##s can be tested against these mouse models. gene therapy is the genetic engineering of humans, generally by replacing defective genes with effective ones. clinical research using somatic gene therapy has been conducted with several diseases, including x - linked scid, chronic lymphocytic leukemia ( cll ), and parkinson ' s disease. in 2012, alipogene tiparvovec became the first gene therapy treatment to be approved for clinical use. in 2015 a virus was used to insert a healthy gene into the skin cells of a boy suffering from a rare skin disease, epidermolysis bullosa, in order to grow, and then graft healthy skin onto 80 percent of the boy ' s body which was affected by the illness. germline gene therapy would result in any change being inheritable, which has raised concerns within the scientific community. in 2015, crispr was used to edit the dna of non - viable human embryos, leading scientists of major world academies to call for a moratorium on inheritable human genome edits. there are also concerns that the technology could be used not just for treatment, but for enhancement, modification or alteration of a human beings ' appearance, adaptability, intelligence, character or behavior. the distinction between cure and enhancement can also be difficult to establish. in november 2018, he jiankui announced that he had edited the genomes of two human embryos, to attempt to disable the ccr5 gene, which codes for a receptor that hiv uses to enter cells. the work was widely condemned as unethical, dangerous, and premature. currently, germline modification is banned in 40 countries. scientists that do this type of research will often let embryos grow for a few days without allowing it to develop into a baby. researchers are altering the genome of pigs to induce the growth of human organs, with the aim of increasing the success of pig to human organ transplantation. scientists are creating " gene drives ", changing the genomes of mosquitoes to make them immune to malaria, and then looking to spread the genetically altered mosquitoes throughout the mosquito population in the hopes of eliminating the disease. = = = research = = = genetic engineering is an important tool for natural scientists, with the creation of transgenic organisms one of the most important tools for analysis of gene function. genes and other genetic information from a wide range of organisms can be inserted into bacteria for storage and modification, creating genetically modified bacteria in the process. bacteria are cheap, easy to grow, clonal, multi
genetic engineering takes the gene directly from one organism and delivers it to the other. this is much faster, can be used to insert any genes from any organism ( even ones from different domains ) and prevents other undesirable genes from also being added. genetic engineering could potentially fix severe genetic disorders in humans by replacing the defective gene with a functioning one. it is an important tool in research that allows the function of specific genes to be studied. drugs, vaccines and other products have been harvested from organisms engineered to produce them. crops have been developed that aid food security by increasing yield, nutritional value and tolerance to environmental stresses. the dna can be introduced directly into the host organism or into a cell that is then fused or hybridised with the host. this relies on recombinant nucleic acid techniques to form new combinations of heritable genetic material followed by the incorporation of that material either indirectly through a vector system or directly through micro - injection, macro - injection or micro - encapsulation. genetic engineering does not normally include traditional breeding, in vitro fertilisation, induction of polyploidy, mutagenesis and cell fusion techniques that do not use recombinant nucleic acids or a genetically modified organism in the process. however, some broad definitions of genetic engineering include selective breeding. cloning and stem cell research, although not considered genetic engineering, are closely related and genetic engineering can be used within them. synthetic biology is an emerging discipline that takes genetic engineering a step further by introducing artificially synthesised material into an organism. plants, animals or microorganisms that have been changed through genetic engineering are termed genetically modified organisms or gmos. if genetic material from another species is added to the host, the resulting organism is called transgenic. if genetic material from the same species or a species that can naturally breed with the host is used the resulting organism is called cisgenic. if genetic engineering is used to remove genetic material from the target organism the resulting organism is termed a knockout organism. in europe genetic modification is synonymous with genetic engineering while within the united states of america and canada genetic modification can also be used to refer to more conventional breeding methods. = = history = = humans have altered the genomes of species for thousands of years through selective breeding, or artificial selection : 1 : 1 as contrasted with natural selection. more recently, mutation breeding has used exposure to chemicals or radiation to produce a high frequency of random mutations, for selective breeding purposes. genetic engineering as the direct manipulation of dna by humans outside breeding and
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,
of a point on the object, including whole - body translations and rotations ( rigid transformations ). deformation are changes in the relative position between internals points on the object, excluding rigid transformations, causing the body to change shape or size. strain is the relative internal deformation, the dimensionless change in shape of an infinitesimal cube of material relative to a reference configuration. mechanical strains are caused by mechanical stress, see stress - strain curve. the relationship between stress and strain is generally linear and reversible up until the yield point and the deformation is elastic. elasticity in materials occurs when applied stress does not surpass the energy required to break molecular bonds, allowing the material to deform reversibly and return to its original shape once the stress is removed. the linear relationship for a material is known as young ' s modulus. above the yield point, some degree of permanent distortion remains after unloading and is termed plastic deformation. the determination of the stress and strain throughout a solid object is given by the field of strength of materials and for a structure by structural analysis. in the above figure, it can be seen that the compressive loading ( indicated by the arrow ) has caused deformation in the cylinder so that the original shape ( dashed lines ) has changed ( deformed ) into one with bulging sides. the sides bulge because the material, although strong enough to not crack or otherwise fail, is not strong enough to support the load without change. as a result, the material is forced out laterally. internal forces ( in this case at right angles to the deformation ) resist the applied load. = = types of deformation = = depending on the type of material, size and geometry of the object, and the forces applied, various types of deformation may result. the image to the right shows the engineering stress vs. strain diagram for a typical ductile material such as steel. different deformation modes may occur under different conditions, as can be depicted using a deformation mechanism map. permanent deformation is irreversible ; the deformation stays even after removal of the applied forces, while the temporary deformation is recoverable as it disappears after the removal of applied forces. temporary deformation is also called elastic deformation, while the permanent deformation is called plastic deformation. = = = elastic deformation = = = the study of temporary or elastic deformation in the case of engineering strain is applied to materials used in mechanical and structural engineering, such as concrete and steel, which are subjected to very small deformations. engineering strain is modeled by infinitesimal strain theory, also called
Question: But a point mutation can also change a codon for an amino acid into a what?
A) exon
B) stop codon
C) stop mutation
D) axon
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B) stop codon
|
Context:
earth. each satellite has an onboard atomic clock and transmits a continuous radio signal containing a precise time signal as well as its current position. two frequencies are used, 1. 2276 and 1. 57542 ghz. since the velocity of radio waves is virtually constant, the delay of the radio signal from a satellite is proportional to the distance of the receiver from the satellite. by receiving the signals from at least four satellites a gps receiver can calculate its position on earth by comparing the arrival time of the radio signals. since each satellite ' s position is known precisely at any given time, from the delay the position of the receiver can be calculated by a microprocessor in the receiver. the position can be displayed as latitude and longitude, or as a marker on an electronic map. gps receivers are incorporated in almost all cellphones and in vehicles such as automobiles, aircraft, and ships, and are used to guide drones, missiles, cruise missiles, and even artillery shells to their target, and handheld gps receivers are produced for hikers and the military. radio beacon β a fixed location terrestrial radio transmitter which transmits a continuous radio signal used by aircraft and ships for navigation. the locations of beacons are plotted on navigational maps used by aircraft and ships. vhf omnidirectional range ( vor ) β a worldwide aircraft radio navigation system consisting of fixed ground radio beacons transmitting between 108. 00 and 117. 95 mhz in the very high frequency ( vhf ) band. an automated navigational instrument on the aircraft displays a bearing to a nearby vor transmitter. a vor beacon transmits two signals simultaneously on different frequencies. a directional antenna transmits a beam of radio waves that rotates like a lighthouse at a fixed rate, 30 times per second. when the directional beam is facing north, an omnidirectional antenna transmits a pulse. by measuring the difference in phase of these two signals, an aircraft can determine its bearing ( or " radial " ) from the station accurately. by taking a bearing on two vor beacons an aircraft can determine its position ( called a " fix " ) to an accuracy of about 90 metres ( 300 ft ). most vor beacons also have a distance measuring capability, called distance measuring equipment ( dme ) ; these are called vor / dme ' s. the aircraft transmits a radio signal to the vor / dme beacon and a transponder transmits a return signal. from the propagation delay between the transmitted and received signal the aircraft can calculate
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
that shows the object as it looks from the front, right, left, top, bottom, or back ( e. g. the primary views ), and is typically positioned relative to each other according to the rules of either first - angle or third - angle projection. the origin and vector direction of the projectors ( 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 ),
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
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 european union ' s galileo. global positioning system ( gps ) β the most widely used satellite navigation system, maintained by the us air force, which uses a constellation of 31 satellites in low earth orbit. the orbits of the satellites are distributed so at any time at least four satellites are above the horizon over each point on earth. each satellite has an onboard atomic clock and transmits a continuous radio signal containing a precise time signal as well as its current position. two frequencies are used, 1. 2276 and 1. 57542 ghz. since the velocity of radio waves is virtually constant, the delay of the radio signal from a satellite is proportional to the distance of the receiver from the satellite. by receiving the signals from at least four satellites a gps receiver can calculate its position on earth by comparing the arrival time of the radio signals. since each satellite ' s position is known precisely at any given time, from the delay the position of the receiver can be calculated by a microprocessor in the receiver. the position can be displayed as latitude and longitude, or as a marker on an electronic map. gps receivers are incorporated in almost all cellphones and in vehicles such as automobiles, aircraft, and ships, and are used to guide drones, missiles, cruise missiles, and even artillery shells to their target, and handheld gps receivers are produced for hikers and the military. radio beacon β a fixed location terrestrial radio transmitter which transmits a continuous radio signal used by aircraft and ships for navigation. the locations of beacons are plotted on navigational maps used by aircraft and ships. vhf omnidirectional range ( vor ) β a worldwide aircraft radio navigation system consisting of fixed ground radio beacons transmitting between 108. 00 and 117. 95 mhz in the very high frequency ( vhf ) band. an automated navigational instrument on the aircraft displays a bearing to a nearby vor transmitter. a vor beacon transmits two signals simultaneously on different frequencies. a directional antenna transmits a beam of radio waves that rotates like a lighthouse at a fixed rate, 30 times per second. when the directional beam is facing north, an omnidirectional antenna transmits a pulse. by measuring the difference in phase of these two signals, an aircraft can determine its bearing ( or " radial " ) from the station accurately. by taking a bearing on two vor beacons an aircraft can determine its position ( called a " fix " ) to an accuracy of about 90 metres ( 300 ft ). most vor beacons also have a
of a point on the object, including whole - body translations and rotations ( rigid transformations ). deformation are changes in the relative position between internals points on the object, excluding rigid transformations, causing the body to change shape or size. strain is the relative internal deformation, the dimensionless change in shape of an infinitesimal cube of material relative to a reference configuration. mechanical strains are caused by mechanical stress, see stress - strain curve. the relationship between stress and strain is generally linear and reversible up until the yield point and the deformation is elastic. elasticity in materials occurs when applied stress does not surpass the energy required to break molecular bonds, allowing the material to deform reversibly and return to its original shape once the stress is removed. the linear relationship for a material is known as young ' s modulus. above the yield point, some degree of permanent distortion remains after unloading and is termed plastic deformation. the determination of the stress and strain throughout a solid object is given by the field of strength of materials and for a structure by structural analysis. in the above figure, it can be seen that the compressive loading ( indicated by the arrow ) has caused deformation in the cylinder so that the original shape ( dashed lines ) has changed ( deformed ) into one with bulging sides. the sides bulge because the material, although strong enough to not crack or otherwise fail, is not strong enough to support the load without change. as a result, the material is forced out laterally. internal forces ( in this case at right angles to the deformation ) resist the applied load. = = types of deformation = = depending on the type of material, size and geometry of the object, and the forces applied, various types of deformation may result. the image to the right shows the engineering stress vs. strain diagram for a typical ductile material such as steel. different deformation modes may occur under different conditions, as can be depicted using a deformation mechanism map. permanent deformation is irreversible ; the deformation stays even after removal of the applied forces, while the temporary deformation is recoverable as it disappears after the removal of applied forces. temporary deformation is also called elastic deformation, while the permanent deformation is called plastic deformation. = = = elastic deformation = = = the study of temporary or elastic deformation in the case of engineering strain is applied to materials used in mechanical and structural engineering, such as concrete and steel, which are subjected to very small deformations. engineering strain is modeled by infinitesimal strain theory, also called
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
##elting. 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 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
##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
Question: The location of an object in a frame of reference is called what?
A) fact
B) position
C) marker
D) change
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B) position
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Context:
this paper has been withdrawn by the authors until some changes are made.
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,
genetic engineering, also called genetic modification or genetic manipulation, is the modification and manipulation of an organism ' s genes using technology. it is a set of technologies used to change the genetic makeup of cells, including the transfer of genes within and across species boundaries to produce improved or novel organisms. new dna is obtained by either isolating and copying the genetic material of interest using recombinant dna methods or by artificially synthesising the dna. a construct is usually created and used to insert this dna into the host organism. the first recombinant dna molecule was made by paul berg in 1972 by combining dna from the monkey virus sv40 with the lambda virus. as well as inserting genes, the process can be used to remove, or " knock out ", genes. the new dna can be inserted randomly, or targeted to a specific part of the genome. an organism that is generated through genetic engineering is considered to be genetically modified ( gm ) and the resulting entity is a genetically modified organism ( gmo ). the first gmo was a bacterium generated by herbert boyer and stanley cohen in 1973. rudolf jaenisch created the first gm animal when he inserted foreign dna into a mouse in 1974. the first company to focus on genetic engineering, genentech, was founded in 1976 and started the production of human proteins. genetically engineered human insulin was produced in 1978 and insulin - producing bacteria were commercialised in 1982. genetically modified food has been sold since 1994, with the release of the flavr savr tomato. the flavr savr was engineered to have a longer shelf life, but most current gm crops are modified to increase resistance to insects and herbicides. glofish, the first gmo designed as a pet, was sold in the united states in december 2003. in 2016 salmon modified with a growth hormone were sold. genetic engineering has been applied in numerous fields including research, medicine, industrial biotechnology and agriculture. in research, gmos are used to study gene function and expression through loss of function, gain of function, tracking and expression experiments. by knocking out genes responsible for certain conditions it is possible to create animal model organisms of human diseases. as well as producing hormones, vaccines and other drugs, genetic engineering has the potential to cure genetic diseases through gene therapy. chinese hamster ovary ( cho ) cells are used in industrial genetic engineering. additionally mrna vaccines are made through genetic engineering to prevent infections by viruses such as covid - 19. the same techniques that are used to produce drugs can also have industrial applications such
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?
this paper is withdrawn by the authors, a better version is available as hep - ph / 0505139.
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.
, 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
this paper has been withdrawn by the author for further investigation.
this paper has been withdrawn by the authors due to an unlikely results.
process by which a genotype encoded in dna gives rise to an observable phenotype in the proteins of an organism ' s body. this process is summarized by the central dogma of molecular biology, which was formulated by francis crick in 1958. according to the central dogma, genetic information flows from dna to rna to protein. there are two gene expression processes : transcription ( dna to rna ) and translation ( rna to protein ). = = = gene regulation = = = the regulation of gene expression by environmental factors and during different stages of development can occur at each step of the process such as transcription, rna splicing, translation, and post - translational modification of a protein. gene expression can be influenced by positive or negative regulation, depending on which of the two types of regulatory proteins called transcription factors bind to the dna sequence close to or at a promoter. a cluster of genes that share the same promoter is called an operon, found mainly in prokaryotes and some lower eukaryotes ( e. g., caenorhabditis elegans ). in positive regulation of gene expression, the activator is the transcription factor that stimulates transcription when it binds to the sequence near or at the promoter. negative regulation occurs when another transcription factor called a repressor binds to a dna sequence called an operator, which is part of an operon, to prevent transcription. repressors can be inhibited by compounds called inducers ( e. g., allolactose ), thereby allowing transcription to occur. specific genes that can be activated by inducers are called inducible genes, in contrast to constitutive genes that are almost constantly active. in contrast to both, structural genes encode proteins that are not involved in gene regulation. in addition to regulatory events involving the promoter, gene expression can also be regulated by epigenetic changes to chromatin, which is a complex of dna and protein found in eukaryotic cells. = = = genes, development, and evolution = = = development is the process by which a multicellular organism ( plant or animal ) goes through a series of changes, starting from a single cell, and taking on various forms that are characteristic of its life cycle. there are four key processes that underlie development : determination, differentiation, morphogenesis, and growth. determination sets the developmental fate of a cell, which becomes more restrictive during development. differentiation is the process by which specialized cells arise from less specialized cells such as stem
Question: What kind of change causes evolution in population?
A) allele frequency changes
B) paragenic frequency changes
C) morphogenesis frequency changes
D) transgenic frequency changes
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A) allele frequency changes
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Context:
= = 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
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
( 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
prominent functional groups that can be found in organisms : amino group, carboxyl group, carbonyl group, hydroxyl group, phosphate group, and sulfhydryl group. in 1953, the miller β urey experiment showed that organic compounds could be synthesized abiotically within a closed system mimicking the conditions of early earth, thus suggesting that complex organic molecules could have arisen spontaneously in early earth ( see abiogenesis ). = = = macromolecules = = = macromolecules are large molecules made up of smaller subunits or monomers. monomers include sugars, amino acids, and nucleotides. carbohydrates include monomers and polymers of sugars. lipids are the only class of macromolecules that are not made up of polymers. they include steroids, phospholipids, and fats, largely nonpolar and hydrophobic ( water - repelling ) substances. proteins are the most diverse of the macromolecules. they include enzymes, transport proteins, large signaling molecules, antibodies, and structural proteins. the basic unit ( or monomer ) of a protein is an amino acid. twenty amino acids are used in proteins. nucleic acids are polymers of nucleotides. their function is to store, transmit, and express hereditary information. = = cells = = cell theory states that cells are the fundamental units of life, that all living things are composed of one or more cells, and that all cells arise from preexisting cells through cell division. most cells are very small, with diameters ranging from 1 to 100 micrometers and are therefore only visible under a light or electron microscope. there are generally two types of cells : eukaryotic cells, which contain a nucleus, and prokaryotic cells, which do not. prokaryotes are single - celled organisms such as bacteria, whereas eukaryotes can be single - celled or multicellular. in multicellular organisms, every cell in the organism ' s body is derived ultimately from a single cell in a fertilized egg. = = = cell structure = = = every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as
and nucleotides. carbohydrates include monomers and polymers of sugars. lipids are the only class of macromolecules that are not made up of polymers. they include steroids, phospholipids, and fats, largely nonpolar and hydrophobic ( water - repelling ) substances. proteins are the most diverse of the macromolecules. they include enzymes, transport proteins, large signaling molecules, antibodies, and structural proteins. the basic unit ( or monomer ) of a protein is an amino acid. twenty amino acids are used in proteins. nucleic acids are polymers of nucleotides. their function is to store, transmit, and express hereditary information. = = cells = = cell theory states that cells are the fundamental units of life, that all living things are composed of one or more cells, and that all cells arise from preexisting cells through cell division. most cells are very small, with diameters ranging from 1 to 100 micrometers and are therefore only visible under a light or electron microscope. there are generally two types of cells : eukaryotic cells, which contain a nucleus, and prokaryotic cells, which do not. prokaryotes are single - celled organisms such as bacteria, whereas eukaryotes can be single - celled or multicellular. in multicellular organisms, every cell in the organism ' s body is derived ultimately from a single cell in a fertilized egg. = = = cell structure = = = every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions. cell membranes also contain membrane proteins, including integral membrane proteins that go across the membrane serving as membrane transporters, and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes shaping the cell. cell membranes are involved in various cellular processes such as cell adhesion, storing electrical energy, and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall, glycocalyx, and cytoskeleton. within the cytoplasm of a cell
has rest mass and volume ( it takes up space ) and is made up of particles. the particles that make up matter have rest mass as well β not all particles have rest mass, such as the photon. matter can be a pure chemical substance or a mixture of substances. = = = = atom = = = = the atom is the basic unit of chemistry. it consists of a dense core called the atomic nucleus surrounded by a space occupied by an electron cloud. the nucleus is made up of positively charged protons and uncharged neutrons ( together called nucleons ), while the electron cloud consists of negatively charged electrons which orbit the nucleus. in a neutral atom, the negatively charged electrons balance out the positive charge of the protons. the nucleus is dense ; the mass of a nucleon is approximately 1, 836 times that of an electron, yet the radius of an atom is about 10, 000 times that of its nucleus. the atom is also the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state ( s ), coordination number, and preferred types of bonds to form ( e. g., metallic, ionic, covalent ). = = = = element = = = = a chemical element is a pure substance which is composed of a single type of atom, characterized by its particular number of protons in the nuclei of its atoms, known as the atomic number and represented by the symbol z. the mass number is the sum of the number of protons and neutrons in a nucleus. although all the nuclei of all atoms belonging to one element will have the same atomic number, they may not necessarily have the same mass number ; atoms of an element which have different mass numbers are known as isotopes. for example, all atoms with 6 protons in their nuclei are atoms of the chemical element carbon, but atoms of carbon may have mass numbers of 12 or 13. the standard presentation of the chemical elements is in the periodic table, which orders elements by atomic number. the periodic table is arranged in groups, or columns, and periods, or rows. the periodic table is useful in identifying periodic trends. = = = = compound = = = = a compound is a pure chemical substance composed of more than one element. the properties of a compound bear little similarity to those of its elements. the standard nomenclature of compounds is set by the international union of pure and applied chemistry ( iupac ). organic compounds are named
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
modern electronics rely on devices whose functionality can be adjusted by the end - user with an external ' knob '. a new tuning knob to modify the band gap of black phosphorus has been experimentally demonstrated.
managing blood lipid levels is important for the treatment and prevention of diabetes, cardiovascular disease, and obesity. an easy - to - use, portable lipid blood test will accelerate more frequent testing by patients and at - risk populations. we used smartphone systems that are already familiar to many people. because smartphone systems can be carried around everywhere, blood can be measured easily and frequently. we compared the results of lipid tests with those of existing clinical diagnostic laboratory methods. we found that smartphone - based point - of - care lipid blood tests are as accurate as hospital - grade laboratory tests. our system will be useful for those who need to manage blood lipid levels to motivate them to track and control their behavior.
that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature. = = = = substance and mixture = = = = a chemical substance is a kind of matter with a definite composition and set of properties. a collection of substances is called a mixture. examples of mixtures are air and alloys. = = = = mole and amount of substance = = = = the mole is a unit of measurement that denotes an amount of substance ( also called chemical amount ). one mole is defined to contain exactly 6. 02214076Γ1023 particles ( atoms, molecules, ions, or electrons ), where the number of particles per mole is known as the avogadro constant. molar concentration is
Question: What type of lipids contain the element phosphorus, carbon, hydrogen and oxygen?
A) filaments
B) eukaryotes
C) phospholipids
D) alleles
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C) phospholipids
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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
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
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
is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. in most cases, oxygen is released as a waste product. most plants, algae, and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of the earth ' s atmosphere, and supplies most of the energy necessary for life on earth. photosynthesis has four stages : light absorption, electron transport, atp synthesis, and carbon fixation. light absorption is the initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to proteins in the thylakoid membranes. the absorbed light energy is used to remove electrons from a donor ( water ) to a primary electron acceptor, a quinone designated as q. in the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach a final electron acceptor, which is usually the oxidized form of nadp +, which is reduced to nadph, a process that takes place in a protein complex called photosystem i ( psi ). the transport of electrons is coupled to the movement of protons ( or hydrogen ) from the stroma to the thylakoid membrane, which forms a ph gradient across the membrane as hydrogen becomes more concentrated in the lumen than in the stroma. this is analogous to the proton - motive force generated across the inner mitochondrial membrane in aerobic respiration. during the third stage of photosynthesis, the movement of protons down their concentration gradients from the thylakoid lumen to the stroma through the atp synthase is coupled to the synthesis of atp by that same atp synthase. the nadph and atps generated by the light - dependent reactions in the second and third stages, respectively, provide the energy and electrons to drive the synthesis of glucose by fixing atmospheric carbon dioxide into existing organic carbon compounds, such as ribulose bisphosphate ( rubp ) in a sequence of light - independent ( or dark ) reactions called the calvin cycle. = = = cell signaling = = = cell signaling ( or communication ) is the ability of cells to receive, process, and transmit signals with its environment and with itself. signals can be non - chemical such as light, electrical impulses, and heat, or chemical signals ( or ligands ) that interact with receptors, which can be found embedded in the cell membrane of another cell or located deep inside
pigment chlorophyll a. chlorophyll a ( as well as its plant and green algal - specific cousin chlorophyll b ) absorbs light in the blue - violet and orange / red parts of the spectrum while reflecting and transmitting the green light that we see as the characteristic colour of these organisms. the energy in the red and blue light that these pigments absorb is used by chloroplasts to make energy - rich carbon compounds from carbon dioxide and water by oxygenic photosynthesis, a process that generates molecular oxygen ( o2 ) as a by - product. the light energy captured by chlorophyll a is initially in the form of electrons ( and later a proton gradient ) that is used to make molecules of atp and nadph which temporarily store and transport energy. their energy is used in the light - independent reactions of the calvin cycle by the enzyme rubisco to produce molecules of the 3 - carbon sugar glyceraldehyde 3 - phosphate ( g3p ). glyceraldehyde 3 - phosphate is the first product of photosynthesis and the raw material from which glucose and almost all other organic molecules of biological origin are synthesised. some of the glucose is converted to starch which is stored in the chloroplast. starch is the characteristic energy store of most land plants and algae, while inulin, a polymer of fructose is used for the same purpose in the sunflower family asteraceae. some of the glucose is converted to sucrose ( common table sugar ) for export to the rest of the plant. unlike in animals ( which lack chloroplasts ), plants and their eukaryote relatives have delegated many biochemical roles to their chloroplasts, including synthesising all their fatty acids, and most amino acids. the fatty acids that chloroplasts make are used for many things, such as providing material to build cell membranes out of and making the polymer cutin which is found in the plant cuticle that protects land plants from drying out. plants synthesise a number of unique polymers like the polysaccharide molecules cellulose, pectin and xyloglucan from which the land plant cell wall is constructed. vascular land plants make lignin, a polymer used to strengthen the secondary cell walls of xylem tracheids and vessels to keep them from collapsing when a plant sucks water through them under water stress. lignin
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 basis of all plant metabolism. the energy of sunlight, captured by oxygenic photosynthesis and released by cellular respiration, is the basis of almost all life. photoautotrophs, including all green plants, algae and cyanobacteria gather energy directly from sunlight by photosynthesis. heterotrophs including all animals, all fungi, all completely parasitic plants, and non - photosynthetic bacteria take in organic molecules produced by photoautotrophs and respire them or use them in the construction of cells and tissues. respiration is the oxidation of carbon compounds by breaking them down into simpler structures to release the energy they contain, essentially the opposite of photosynthesis. molecules are moved within plants by transport processes that operate at a variety of spatial scales. subcellular transport of ions, electrons and molecules such as water and enzymes occurs across cell membranes. minerals and water are transported from roots to other parts of the plant in the transpiration stream. diffusion, osmosis, and active transport and mass flow are all different ways transport can occur. examples of elements that plants need to transport are nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. in vascular plants, these elements are extracted from the soil as soluble ions by the roots and transported throughout the plant in the xylem. most of the elements required for plant nutrition come from the chemical breakdown of soil minerals. sucrose produced by photosynthesis is transported from the leaves to other parts of the plant in the phloem and plant hormones are transported by a variety of processes. = = = plant hormones = = = plants are not passive, but respond to external signals such as light, touch, and injury by moving or growing towards or away from the stimulus, as appropriate. tangible evidence of touch sensitivity is the almost instantaneous collapse of leaflets of mimosa pudica, the insect traps of venus flytrap and bladderworts, and the pollinia of orchids. the hypothesis that plant growth and development is coordinated by plant hormones or plant growth regulators first emerged in the late 19th century. darwin experimented on the movements of plant shoots and roots towards light and gravity, and concluded " it is hardly an exaggeration to say that the tip of the radicle.. acts like the brain of one of the lower animals.. directing the several movements ". about the same time, the role of auxins ( from the greek auxein, to grow ) in control of plant growth was first outlined by the dutch scientist
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
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
proteins in the thylakoid membranes. the absorbed light energy is used to remove electrons from a donor ( water ) to a primary electron acceptor, a quinone designated as q. in the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach a final electron acceptor, which is usually the oxidized form of nadp +, which is reduced to nadph, a process that takes place in a protein complex called photosystem i ( psi ). the transport of electrons is coupled to the movement of protons ( or hydrogen ) from the stroma to the thylakoid membrane, which forms a ph gradient across the membrane as hydrogen becomes more concentrated in the lumen than in the stroma. this is analogous to the proton - motive force generated across the inner mitochondrial membrane in aerobic respiration. during the third stage of photosynthesis, the movement of protons down their concentration gradients from the thylakoid lumen to the stroma through the atp synthase is coupled to the synthesis of atp by that same atp synthase. the nadph and atps generated by the light - dependent reactions in the second and third stages, respectively, provide the energy and electrons to drive the synthesis of glucose by fixing atmospheric carbon dioxide into existing organic carbon compounds, such as ribulose bisphosphate ( rubp ) in a sequence of light - independent ( or dark ) reactions called the calvin cycle. = = = cell signaling = = = cell signaling ( or communication ) is the ability of cells to receive, process, and transmit signals with its environment and with itself. signals can be non - chemical such as light, electrical impulses, and heat, or chemical signals ( or ligands ) that interact with receptors, which can be found embedded in the cell membrane of another cell or located deep inside a cell. there are generally four types of chemical signals : autocrine, paracrine, juxtacrine, and hormones. in autocrine signaling, the ligand affects the same cell that releases it. tumor cells, for example, can reproduce uncontrollably because they release signals that initiate their own self - division. in paracrine signaling, the ligand diffuses to nearby cells and affects them. for example, brain cells called neurons release ligands called neurotransmitters that diffuse across a synaptic cleft to bind with a receptor on an adjacent cell such as another neuron or muscle
Question: Photosynthesis requires light, water and what else?
A) carbon dioxide
B) seasons
C) soil
D) nitrogen
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A) carbon dioxide
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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
ranks varying from family to subgenus have terms for their study, including agrostology ( or graminology ) for the study of grasses, synantherology for the study of composites, and batology for the study of brambles. study can also be divided by guild rather than clade or grade. for example, dendrology is the study of woody plants. many divisions of biology have botanical subfields. these are commonly denoted by prefixing the word plant ( e. g. plant taxonomy, plant ecology, plant anatomy, plant morphology, plant systematics ), or prefixing or substituting the prefix phyto - ( e. g. phytochemistry, phytogeography ). the study of fossil plants is called palaeobotany. other fields are denoted by adding or substituting the word botany ( e. g. systematic botany ). phytosociology is a subfield of plant ecology that classifies and studies communities of plants. the intersection of fields from the above pair of categories gives rise to fields such as bryogeography, the study of the distribution of mosses. different parts of plants also give rise to their own subfields, including xylology, carpology ( or fructology ), and palynology, these being the study of wood, fruit and pollen / spores respectively. botany also overlaps on the one hand with agriculture, horticulture and silviculture, and on the other hand with medicine and pharmacology, giving rise to fields such as agronomy, horticultural botany, phytopathology, and phytopharmacology. = = scope and importance = = the study of plants is vital because they underpin almost all animal life on earth by generating a large proportion of the oxygen and food that provide humans and other organisms with aerobic respiration with the chemical energy they need to exist. plants, algae and cyanobacteria are the major groups of organisms that carry out photosynthesis, a process that uses the energy of sunlight to convert water and carbon dioxide into sugars that can be used both as a source of chemical energy and of organic molecules that are used in the structural components of cells. as a by - product of photosynthesis, plants release oxygen into the atmosphere, a gas that is required by nearly all living things to carry out cellular respiration. in addition, they are influential in the global carbon and water cycles and plant roots bind and stabilise soils, preventing
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
, 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
pathogens in agriculture and natural ecosystems. ethnobotany is the study of the relationships between plants and people. when applied to the investigation of historical plant β people relationships ethnobotany may be referred to as archaeobotany or palaeoethnobotany. some of the earliest plant - people relationships arose between the indigenous people of canada in identifying edible plants from inedible plants. this relationship the indigenous people had with plants was recorded by ethnobotanists. = = plant biochemistry = = plant biochemistry is the study of the chemical processes used by plants. some of these processes are used in their primary metabolism like the photosynthetic calvin cycle and crassulacean acid metabolism. others make specialised materials like the cellulose and lignin used to build their bodies, and secondary products like resins and aroma compounds. plants and various other groups of photosynthetic eukaryotes collectively known as " algae " have unique organelles known as chloroplasts. chloroplasts are thought to be descended from cyanobacteria that formed endosymbiotic relationships with ancient plant and algal ancestors. chloroplasts and cyanobacteria contain the blue - green pigment chlorophyll a. chlorophyll a ( as well as its plant and green algal - specific cousin chlorophyll b ) absorbs light in the blue - violet and orange / red parts of the spectrum while reflecting and transmitting the green light that we see as the characteristic colour of these organisms. the energy in the red and blue light that these pigments absorb is used by chloroplasts to make energy - rich carbon compounds from carbon dioxide and water by oxygenic photosynthesis, a process that generates molecular oxygen ( o2 ) as a by - product. the light energy captured by chlorophyll a is initially in the form of electrons ( and later a proton gradient ) that is used to make molecules of atp and nadph which temporarily store and transport energy. their energy is used in the light - independent reactions of the calvin cycle by the enzyme rubisco to produce molecules of the 3 - carbon sugar glyceraldehyde 3 - phosphate ( g3p ). glyceraldehyde 3 - phosphate is the first product of photosynthesis and the raw material from which glucose and almost all other organic molecules of biological origin are synthesised. some of the glucose is converted to star
navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with a rapid fall near the sources of rivers can carry down rocks, boulders and large stones, which are by degrees ground by attrition in their onward course into slate, gravel, sand and silt, simultaneously with the gradual reduction in fall, and, consequently, in the transporting force of the current. accordingly, under ordinary conditions, most of the materials brought down from the high lands by torrential water courses are carried forward by the main river to the sea, or partially strewn over flat alluvial plains during floods ; the size of the materials forming the bed of the river or borne along by the stream is gradually reduced on proceeding sea
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 )
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
of the questions about relationships among angiosperm families and species. the theoretical possibility of a practical method for identification of plant species and commercial varieties by dna barcoding is the subject of active current research. = = branches of botany = = botany is divided along several axes. some subfields of botany relate to particular 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,
by which botanists group organisms into categories such as genera or species. biological classification is a form of scientific taxonomy. modern taxonomy is rooted in the work of carl linnaeus, who grouped species according to shared physical characteristics. these groupings have since been revised to align better with the darwinian principle of common descent β grouping organisms by ancestry rather than superficial characteristics. while scientists do not always agree on how to classify organisms, molecular phylogenetics, which uses dna sequences as data, has driven many recent revisions along evolutionary lines and is likely to continue to do so. the dominant classification system is called linnaean taxonomy. it includes ranks and binomial nomenclature. the nomenclature of botanical organisms is codified in the international code of nomenclature for algae, fungi, and plants ( icn ) and administered by the international botanical congress. kingdom plantae belongs to domain eukaryota and is broken down recursively until each species is separately classified. the order is : kingdom ; phylum ( or division ) ; class ; order ; family ; genus ( plural genera ) ; species. the scientific name of a plant represents its genus and its species within the genus, resulting in a single worldwide name for each organism. for example, the tiger lily is lilium columbianum. lilium is the genus, and columbianum the specific epithet. the combination is the name of the species. when writing the scientific name of an organism, it is proper to capitalise the first letter in the genus and put all of the specific epithet in lowercase. additionally, the entire term is ordinarily italicised ( or underlined when italics are not available ). the evolutionary relationships and heredity of a group of organisms is called its phylogeny. phylogenetic studies attempt to discover phylogenies. the basic approach is to use similarities based on shared inheritance to determine relationships. as an example, species of pereskia are trees or bushes with prominent leaves. they do not obviously resemble a typical leafless cactus such as an echinocactus. however, both pereskia and echinocactus have spines produced from areoles ( highly specialised pad - like structures ) suggesting that the two genera are indeed related. judging relationships based on shared characters requires care, since plants may resemble one another through convergent evolution in which characters have arisen independently. some euphorbias have leafless, rounded bodies adapted to water conservation similar to those of globular cacti, but characters such as the structure of their flowers make it clear that the
Question: Tropical rainforest, temperate grassland, and tundra are examples of what type of biomes?
A) atmospheric
B) oceanic
C) terrestrial
D) horizontal
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C) terrestrial
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Context:
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
scale. thus, solutions that have a low ph have a high hydronium ion concentration and can be said to be more acidic. the other measurement, based on the brΓΈnsted β lowry definition, is the acid dissociation constant ( ka ), which measures the relative ability of a substance to act as an acid under the brΓΈnsted β lowry definition of an acid. that is, substances with a higher ka are more likely to donate hydrogen ions in chemical reactions than those with lower ka values. = = = redox = = = redox ( reduction - oxidation ) reactions include all chemical reactions in which atoms have their oxidation state changed by either gaining electrons ( reduction ) or losing electrons ( oxidation ). substances that have the ability to oxidize other substances are said to be oxidative and are known as oxidizing agents, oxidants or oxidizers. an oxidant removes electrons from another substance. similarly, substances that have the ability to reduce other substances are said to be reductive and are known as reducing agents, reductants, or reducers. a reductant transfers electrons to another substance and is thus oxidized itself. and because it " donates " electrons it is also called an electron donor. oxidation and reduction properly refer to a change in oxidation number β the actual transfer of electrons may never occur. thus, oxidation is better defined as an increase in oxidation number, and reduction as a decrease in oxidation number. = = = equilibrium = = = although the concept of equilibrium is widely used across sciences, in the context of chemistry, it arises whenever a number of different states of the chemical composition are possible, as for example, in a mixture of several chemical compounds that can react with one another, or when a substance can be present in more than one kind of phase. a system of chemical substances at equilibrium, even though having an unchanging composition, is most often not static ; molecules of the substances continue to react with one another thus giving rise to a dynamic equilibrium. thus the concept describes the state in which the parameters such as chemical composition remain unchanged over time. = = = chemical laws = = = chemical reactions are governed by certain laws, which have become fundamental concepts in chemistry. some of them are : = = history = = the history of chemistry spans a period from the ancient past to the present. since several millennia bc, civilizations were using technologies that would eventually form the basis of the various branches of chemistry. examples include extracting metals from ores
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
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.
a letter to the editor shortly summing up ten or so years of research into the h - index.
the most abundant molecule in every organism. water is important to life because it is an effective solvent, capable of dissolving solutes such as sodium and chloride ions or other small molecules to form an aqueous solution. once dissolved in water, these solutes are more likely to come in contact with one another and therefore take part in chemical reactions that sustain life. in terms of its molecular structure, water is a small polar molecule with a bent shape formed by the polar covalent bonds of two hydrogen ( h ) atoms to one oxygen ( o ) atom ( h2o ). because the o β h bonds are polar, the oxygen atom has a slight negative charge and the two hydrogen atoms have a slight positive charge. this polar property of water allows it to attract other water molecules via hydrogen bonds, which makes water cohesive. surface tension results from the cohesive force due to the attraction between molecules at the surface of the liquid. water is also adhesive as it is able to adhere to the surface of any polar or charged non - water molecules. water is denser as a liquid than it is as a solid ( or ice ). this unique property of water allows ice to float above liquid water such as ponds, lakes, and oceans, thereby insulating the liquid below from the cold air above. water has the capacity to absorb energy, giving it a higher specific heat capacity than other solvents such as ethanol. thus, a large amount of energy is needed to break the hydrogen bonds between water molecules to convert liquid water into water vapor. as a molecule, water is not completely stable as each water molecule continuously dissociates into hydrogen and hydroxyl ions before reforming into a water molecule again. in pure water, the number of hydrogen ions balances ( or equals ) the number of hydroxyl ions, resulting in a ph that is neutral. = = = organic compounds = = = organic compounds are molecules that contain carbon bonded to another element such as hydrogen. with the exception of water, nearly all the molecules that make up each organism contain carbon. carbon can form covalent bonds with up to four other atoms, enabling it to form diverse, large, and complex molecules. for example, a single carbon atom can form four single covalent bonds such as in methane, two double covalent bonds such as in carbon dioxide ( co2 ), or a triple covalent bond such as in carbon monoxide ( co ). moreover, carbon can form very long chains of interconnecting carbon β carbon bonds such
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,
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.
eremets and troyan ( nature mater. 10, 927 - 931 ( 2011 ) ) claim that they produced the conducting liquid hydrogen state at 270 gpa and 295 k. their evidence consists of disappearance of raman signals, visual observations, and measurements of electrical conductivity in diamond anvil cells ( dac ). however, there is no proof that the reported observations are due to transformations in hydrogen.
with curved sidewalls as with isotropic etching. hydrofluoric acid is commonly used as an aqueous etchant for silicon dioxide ( sio2, also known as box for soi ), usually in 49 % concentrated form, 5 : 1, 10 : 1 or 20 : 1 boe ( buffered oxide etchant ) or bhf ( buffered hf ). they were first used in medieval times for glass etching. it was used in ic fabrication for patterning the gate oxide until the process step was replaced by rie. hydrofluoric acid is considered one of the more dangerous acids in the cleanroom. electrochemical etching ( ece ) for dopant - selective removal of silicon is a common method to automate and to selectively control etching. an active p β n diode junction is required, and either type of dopant can be the etch - resistant ( " etch - stop " ) material. boron is the most common etch - stop dopant. in combination with wet anisotropic etching as described above, ece has been used successfully for controlling silicon diaphragm thickness in commercial piezoresistive silicon pressure sensors. selectively doped regions can be created either by implantation, diffusion, or epitaxial deposition of silicon. = = = = dry etching = = = = xenon difluoride ( xef2 ) is a dry vapor phase isotropic etch for silicon originally applied for mems in 1995 at university of california, los angeles. primarily used for releasing metal and dielectric structures by undercutting silicon, xef2 has the advantage of a stiction - free release unlike wet etchants. its etch selectivity to silicon is very high, allowing it to work with photoresist, sio2, silicon nitride, and various metals for masking. its reaction to silicon is " plasmaless ", is purely chemical and spontaneous and is often operated in pulsed mode. models of the etching action are available, and university laboratories and various commercial tools offer solutions using this approach. modern vlsi processes avoid wet etching, and use plasma etching instead. plasma etchers can operate in several modes by adjusting the parameters of the plasma. ordinary plasma etching operates between 0. 1 and 5 torr. ( this unit of pressure, commonly used in vacuum engineering, equals approximately 133. 3 pascal
Question: What is described by the concentration of hydrogen ions in a solution?
A) oxidation
B) hydrogeny
C) neutrality
D) ph
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D) ph
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Context:
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
. 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 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
, 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
and nucleotides. carbohydrates include monomers and polymers of sugars. lipids are the only class of macromolecules that are not made up of polymers. they include steroids, phospholipids, and fats, largely nonpolar and hydrophobic ( water - repelling ) substances. proteins are the most diverse of the macromolecules. they include enzymes, transport proteins, large signaling molecules, antibodies, and structural proteins. the basic unit ( or monomer ) of a protein is an amino acid. twenty amino acids are used in proteins. nucleic acids are polymers of nucleotides. their function is to store, transmit, and express hereditary information. = = cells = = cell theory states that cells are the fundamental units of life, that all living things are composed of one or more cells, and that all cells arise from preexisting cells through cell division. most cells are very small, with diameters ranging from 1 to 100 micrometers and are therefore only visible under a light or electron microscope. there are generally two types of cells : eukaryotic cells, which contain a nucleus, and prokaryotic cells, which do not. prokaryotes are single - celled organisms such as bacteria, whereas eukaryotes can be single - celled or multicellular. in multicellular organisms, every cell in the organism ' s body is derived ultimately from a single cell in a fertilized egg. = = = cell structure = = = every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions. cell membranes also contain membrane proteins, including integral membrane proteins that go across the membrane serving as membrane transporters, and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes shaping the cell. cell membranes are involved in various cellular processes such as cell adhesion, storing electrical energy, and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall, glycocalyx, and cytoskeleton. within the cytoplasm of a cell
it seems natural to ask why the universe exists at all. modern physics suggests that the universe can exist all by itself as a self - contained system, without anything external to create or sustain it. but there might not be an absolute answer to why it exists. i argue that any attempt to account for the existence of something rather than nothing must ultimately bottom out in a set of brute facts ; the universe simply is, without ultimate cause or explanation.
the formulas discussed in the previous version are not new.
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
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
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
Question: Which theory states that all organisms are composed of one or more cells, the cell is the basic unit of life, and new cells arise from existing cells?
A) microcellular theory
B) unified cell theory
C) theory of evolution
D) natural selection
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B) unified cell theory
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Context:
pigment chlorophyll a. chlorophyll a ( as well as its plant and green algal - specific cousin chlorophyll b ) absorbs light in the blue - violet and orange / red parts of the spectrum while reflecting and transmitting the green light that we see as the characteristic colour of these organisms. the energy in the red and blue light that these pigments absorb is used by chloroplasts to make energy - rich carbon compounds from carbon dioxide and water by oxygenic photosynthesis, a process that generates molecular oxygen ( o2 ) as a by - product. the light energy captured by chlorophyll a is initially in the form of electrons ( and later a proton gradient ) that is used to make molecules of atp and nadph which temporarily store and transport energy. their energy is used in the light - independent reactions of the calvin cycle by the enzyme rubisco to produce molecules of the 3 - carbon sugar glyceraldehyde 3 - phosphate ( g3p ). glyceraldehyde 3 - phosphate is the first product of photosynthesis and the raw material from which glucose and almost all other organic molecules of biological origin are synthesised. some of the glucose is converted to starch which is stored in the chloroplast. starch is the characteristic energy store of most land plants and algae, while inulin, a polymer of fructose is used for the same purpose in the sunflower family asteraceae. some of the glucose is converted to sucrose ( common table sugar ) for export to the rest of the plant. unlike in animals ( which lack chloroplasts ), plants and their eukaryote relatives have delegated many biochemical roles to their chloroplasts, including synthesising all their fatty acids, and most amino acids. the fatty acids that chloroplasts make are used for many things, such as providing material to build cell membranes out of and making the polymer cutin which is found in the plant cuticle that protects land plants from drying out. plants synthesise a number of unique polymers like the polysaccharide molecules cellulose, pectin and xyloglucan from which the land plant cell wall is constructed. vascular land plants make lignin, a polymer used to strengthen the secondary cell walls of xylem tracheids and vessels to keep them from collapsing when a plant sucks water through them under water stress. lignin
the recent report on laser cooling of liquid may contradict the law of energy conservation.
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,
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.
the celebrated franck - hertz experiment is reinterpreted by analogy with the glimmentladung experiment, formerly performed by heinrich hertz.
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
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
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
##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
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
Question: Light retains its original color under water because what remains the same when light is refracted?
A) frequency
B) sound
C) density
D) wave length
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A) frequency
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Context:
as you read these words you are using a complex biological neural network. you have a highly interconnected set of some neurons to facilitate your reading, breathing, motion and thinking. each of your biological neurons, a rich assembly of tissue and chemistry, has the complexity, if not the speed, of a microprocessor. some of your neural structure was with you at birth. other parts have been established by experience.
the union of space telescopes and interstellar spaceships guarantees that if extraterrestrial civilizations were common, someone would have come here long ago.
an extended josephson junction consists of two superconducting electrodes that are separated by an insulator and it is therefore also a microwave cavity. the superconducting phase difference across the junction determines the supercurrent as well as its spatial distribution. both, an external magnetic field and a resonant cavity intrafield produce a spatial modification of the superconducting phase along the junction. the interplay between these two effects leads to interference in the critical current of the junction and allows us to continuously tune the coupling strength between the first cavity mode and the josephson phase from 1 to - 0. 5. this enables static and dynamic control over the junction in the ultra - strong coupling regime.
the antiproton flux measured by pamela experiment might have originated from galactic sources of cosmic rays. these antiprotons are expected to be produced in the interactions of cosmic ray protons and nuclei with cold protons. gamma rays are also produced in similar interactions inside some of the cosmic acceleratos. we consider a few nearby supernova remnants observed by fermi lat. many of them are associated with molecular clouds. gamma rays have been detected from these sources which most likely originate in decay of neutral pions produced in hadronic interactions. the observed gamma ray fluxes from these snrs are used to find out their contributions to the observed diffuse cosmic ray antiproton flux near the earth.
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
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
. 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
the gravitational acceleration of antimatter, $ \ bar g $, has yet to be directly measured but could change our understanding of gravity, the universe, and the possibility of a fifth force. three avenues are apparent for such a measurement : antihydrogen, positronium, and muonium, the last requiring a precision atom interferometer and benefiting from a novel muonium beam under development. the interferometer and its few - picometer alignment and calibration systems appear to be feasible. with 100 nm grating pitch, measurements of $ \ bar g $ to 10 %, 1 %, or better can be envisioned. this could constitute the first gravitational measurement of leptonic matter, of second - generation matter and, possibly, the first measurement of the gravitational acceleration of antimatter.
one often wishes to quickly add a few overlined characters such as anti - b0 or anti - neutrino to a microsoft word document. underlined characters are straightforward but overlined characters require equation editor which makes small picture files. the font here allows one to directly add overlined english and the most used overlined greek characters to microsoft word documents on apple macintosh computers.
Question: What are interferons?
A) oncogenes
B) T cells
C) pathogens
D) cytokines
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D) cytokines
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Context:
i have submitted a new version to arxiv : 1910. 13806. i forget to choose to replace the old version, but submitted a new one. it ' s my mistake.
pectin and xyloglucan from which the land plant cell wall is constructed. vascular land plants make lignin, a polymer used to strengthen the secondary cell walls of xylem tracheids and vessels to keep them from collapsing when a plant sucks water through them under water stress. lignin is also used in other cell types like sclerenchyma fibres that provide structural support for a plant and is a major constituent of wood. sporopollenin is a chemically resistant polymer found in the outer cell walls of spores and pollen of land plants responsible for the survival of early land plant spores and the pollen of seed plants in the fossil record. it is widely regarded as a marker for the start of land plant evolution during the ordovician period. the concentration of carbon dioxide in the atmosphere today is much lower than it was when plants emerged onto land during the ordovician and silurian periods. many monocots like maize and the pineapple and some dicots like the asteraceae have since independently evolved pathways like crassulacean acid metabolism and the c4 carbon fixation pathway for photosynthesis which avoid the losses resulting from photorespiration in the more common c3 carbon fixation pathway. these biochemical strategies are unique to land plants. = = = medicine and materials = = = phytochemistry is a branch of plant biochemistry primarily concerned with the chemical substances produced by plants during secondary metabolism. some of these compounds are toxins such as the alkaloid coniine from hemlock. others, such as the essential oils peppermint oil and lemon oil are useful for their aroma, as flavourings and spices ( e. g., capsaicin ), and in medicine as pharmaceuticals as in opium from opium poppies. many medicinal and recreational drugs, such as tetrahydrocannabinol ( active ingredient in cannabis ), caffeine, morphine and nicotine come directly from plants. others are simple derivatives of botanical natural products. for example, the pain killer aspirin is the acetyl ester of salicylic acid, originally isolated from the bark of willow trees, and a wide range of opiate painkillers like heroin are obtained by chemical modification of morphine obtained from the opium poppy. popular stimulants come from plants, such as caffeine from coffee, tea and chocolate, and nicotine from tobacco. most alcoholic beverages come from fermentation of carbohy
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
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
##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
we reply to the comment arxiv : quant - ph / 0702060 on our letter arxiv : quant - ph / 0603120 [ phys. rev. lett. 96, 100402 ( 2006 ) ]
##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
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
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
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.
Question: What is the air that remains after a forced exhalation called?
A) abundant volume
B) residual volume
C) remaining volume
D) kinetic volume
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B) residual volume
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the standard theory of ideal gases ignores the interaction of the gas particles with the thermal radiation ( photon gas ) that fills the otherwise vacuum space between them. this is an unphysical feature since every material absorbs and radiates thermal energy. this interaction may be important in gases since the latter, unlike solids and liquids are capable of undergoing conspicuous volume changes. taking it into account makes the behaviour of the ideal gases more realistic and removes gibbs ' paradox.
or molecules that show characteristic chemical properties in a compound. physical chemistry is the study of the physical and fundamental basis of chemical systems and processes. in particular, the energetics and dynamics of such systems and processes are of interest to physical chemists. important areas of study include chemical thermodynamics, chemical kinetics, electrochemistry, statistical mechanics, spectroscopy, and more recently, astrochemistry. physical chemistry has large overlap with molecular physics. physical chemistry involves the use of infinitesimal calculus in deriving equations. it is usually associated with quantum chemistry and theoretical chemistry. physical chemistry is a distinct discipline from chemical physics, but again, there is very strong overlap. theoretical chemistry is the study of chemistry via fundamental theoretical reasoning ( usually within mathematics or physics ). in particular the application of quantum mechanics to chemistry is called quantum chemistry. since the end of the second world war, the development of computers has allowed a systematic development of computational chemistry, which is the art of developing and applying computer programs for solving chemical problems. theoretical chemistry has large overlap with ( theoretical and experimental ) condensed matter physics and molecular physics. other subdivisions include electrochemistry, femtochemistry, flavor chemistry, flow chemistry, immunohistochemistry, hydrogenation chemistry, mathematical chemistry, molecular mechanics, natural product chemistry, organometallic chemistry, petrochemistry, photochemistry, physical organic chemistry, polymer chemistry, radiochemistry, sonochemistry, supramolecular chemistry, synthetic chemistry, and many others. = = = interdisciplinary = = = interdisciplinary fields include agrochemistry, astrochemistry ( and cosmochemistry ), atmospheric chemistry, chemical engineering, chemical biology, chemo - informatics, environmental chemistry, geochemistry, green chemistry, immunochemistry, marine chemistry, materials science, mechanochemistry, medicinal chemistry, molecular biology, nanotechnology, oenology, pharmacology, phytochemistry, solid - state chemistry, surface science, thermochemistry, and many others. = = = industry = = = the chemical industry represents an important economic activity worldwide. the global top 50 chemical producers in 2013 had sales of us $ 980. 5 billion with a profit margin of 10. 3 %. = = = professional societies = = = = = see also = = = = references = = = = bibliography = = = = further reading = = popular reading atkins, p. w. galileo ' s finger ( oxford university press )
endothermic reactions, the reaction absorbs heat from the surroundings. chemical reactions are invariably not possible unless the reactants surmount an energy barrier known as the activation energy. the speed of a chemical reaction ( at given temperature t ) is related to the activation energy e, by the boltzmann ' s population factor e β e / k t { \ displaystyle e ^ { - e / kt } } β that is the probability of a molecule to have energy greater than or equal to e at the given temperature t. this exponential dependence of a reaction rate on temperature is known as the arrhenius equation. the activation energy necessary for a chemical reaction to occur can be in the form of heat, light, electricity or mechanical force in the form of ultrasound. a related concept free energy, which also incorporates entropy considerations, is a very useful means for predicting the feasibility of a reaction and determining the state of equilibrium of a chemical reaction, in chemical thermodynamics. a reaction is feasible only if the total change in the gibbs free energy is negative, Ξ΄ g β€ 0 { \ displaystyle \ delta g \ leq 0 \, } ; if it is equal to zero the chemical reaction is said to be at equilibrium. there exist only limited possible states of energy for electrons, atoms and molecules. these are determined by the rules of quantum mechanics, which require quantization of energy of a bound system. the atoms / molecules in a higher energy state are said to be excited. the molecules / atoms of substance in an excited energy state are often much more reactive ; that is, more amenable to chemical reactions. the phase of a substance is invariably determined by its energy and the energy of its surroundings. when the intermolecular forces of a substance are such that the energy of the surroundings is not sufficient to overcome them, it occurs in a more ordered phase like liquid or solid as is the case with water ( h2o ) ; a liquid at room temperature because its molecules are bound by hydrogen bonds. whereas hydrogen sulfide ( h2s ) is a gas at room temperature and standard pressure, as its molecules are bound by weaker dipole β dipole interactions. the transfer of energy from one chemical substance to another depends on the size of energy quanta emitted from one substance. however, heat energy is often transferred more easily from almost any substance to another because the phonons responsible for vibrational and rotational energy levels in a substance have much less energy than photons invoked for the electronic energy transfer
, 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
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 (
logical and mathematical aspects of the basic concepts of thermodynamics are considered.
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
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 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
. 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
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 = = = =
Question: What is the term for a gas that completely abides by the kinetic-molecular theory?
A) heat gas
B) cold gas
C) fast gas
D) ideal gas
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D) ideal gas
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Context:
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
; that is, more amenable to chemical reactions. the phase of a substance is invariably determined by its energy and the energy of its surroundings. when the intermolecular forces of a substance are such that the energy of the surroundings is not sufficient to overcome them, it occurs in a more ordered phase like liquid or solid as is the case with water ( h2o ) ; a liquid at room temperature because its molecules are bound by hydrogen bonds. whereas hydrogen sulfide ( h2s ) is a gas at room temperature and standard pressure, as its molecules are bound by weaker dipole β dipole interactions. the transfer of energy from one chemical substance to another depends on the size of energy quanta emitted from one substance. however, heat energy is often transferred more easily from almost any substance to another because the phonons responsible for vibrational and rotational energy levels in a substance have much less energy than photons invoked for the electronic energy transfer. thus, because vibrational and rotational energy levels are more closely spaced than electronic energy levels, heat is more easily transferred between substances relative to light or other forms of electronic energy. for example, ultraviolet electromagnetic radiation is not transferred with as much efficacy from one substance to another as thermal or electrical energy. the existence of characteristic energy levels for different chemical substances is useful for their identification by the analysis of spectral lines. different kinds of spectra are often used in chemical spectroscopy, e. g. ir, microwave, nmr, esr, etc. spectroscopy is also used to identify the composition of remote objects β like stars and distant galaxies β by analyzing their radiation spectra. the term chemical energy is often used to indicate the potential of a chemical substance to undergo a transformation through a chemical reaction or to transform other chemical substances. = = = reaction = = = when a chemical substance is transformed as a result of its interaction with another substance or with energy, a chemical reaction is said to have occurred. a chemical reaction is therefore a concept related to the " reaction " of a substance when it comes in close contact with another, whether as a mixture or a solution ; exposure to some form of energy, or both. it results in some energy exchange between the constituents of the reaction as well as with the system environment, which may be designed vessels β often laboratory glassware. chemical reactions can result in the formation or dissociation of molecules, that is, molecules breaking apart to form two or more molecules or rearrangement of atoms within or across molecules. chemical reactions usually involve the making or breaking of chemical bonds
or solid as is the case with water ( h2o ) ; a liquid at room temperature because its molecules are bound by hydrogen bonds. whereas hydrogen sulfide ( h2s ) is a gas at room temperature and standard pressure, as its molecules are bound by weaker dipole β dipole interactions. the transfer of energy from one chemical substance to another depends on the size of energy quanta emitted from one substance. however, heat energy is often transferred more easily from almost any substance to another because the phonons responsible for vibrational and rotational energy levels in a substance have much less energy than photons invoked for the electronic energy transfer. thus, because vibrational and rotational energy levels are more closely spaced than electronic energy levels, heat is more easily transferred between substances relative to light or other forms of electronic energy. for example, ultraviolet electromagnetic radiation is not transferred with as much efficacy from one substance to another as thermal or electrical energy. the existence of characteristic energy levels for different chemical substances is useful for their identification by the analysis of spectral lines. different kinds of spectra are often used in chemical spectroscopy, e. g. ir, microwave, nmr, esr, etc. spectroscopy is also used to identify the composition of remote objects β like stars and distant galaxies β by analyzing their radiation spectra. the term chemical energy is often used to indicate the potential of a chemical substance to undergo a transformation through a chemical reaction or to transform other chemical substances. = = = reaction = = = when a chemical substance is transformed as a result of its interaction with another substance or with energy, a chemical reaction is said to have occurred. a chemical reaction is therefore a concept related to the " reaction " of a substance when it comes in close contact with another, whether as a mixture or a solution ; exposure to some form of energy, or both. it results in some energy exchange between the constituents of the reaction as well as with the system environment, which may be designed vessels β often laboratory glassware. chemical reactions can result in the formation or dissociation of molecules, that is, molecules breaking apart to form two or more molecules or rearrangement of atoms within or across molecules. chemical reactions usually involve the making or breaking of chemical bonds. oxidation, reduction, dissociation, acid β base neutralization and molecular rearrangement are some examples of common chemical reactions. a chemical reaction can be symbolically depicted through a chemical equation. while in a non - nuclear chemical reaction the number and kind of atoms on both sides of the equation are equal, for
##ulating the liquid below from the cold air above. water has the capacity to absorb energy, giving it a higher specific heat capacity than other solvents such as ethanol. thus, a large amount of energy is needed to break the hydrogen bonds between water molecules to convert liquid water into water vapor. as a molecule, water is not completely stable as each water molecule continuously dissociates into hydrogen and hydroxyl ions before reforming into a water molecule again. in pure water, the number of hydrogen ions balances ( or equals ) the number of hydroxyl ions, resulting in a ph that is neutral. = = = organic compounds = = = organic compounds are molecules that contain carbon bonded to another element such as hydrogen. with the exception of water, nearly all the molecules that make up each organism contain carbon. carbon can form covalent bonds with up to four other atoms, enabling it to form diverse, large, and complex molecules. for example, a single carbon atom can form four single covalent bonds such as in methane, two double covalent bonds such as in carbon dioxide ( co2 ), or a triple covalent bond such as in carbon monoxide ( co ). moreover, carbon can form very long chains of interconnecting carbon β carbon bonds such as octane or ring - like structures such as glucose. the simplest form of an organic molecule is the hydrocarbon, which is a large family of organic compounds that are composed of hydrogen atoms bonded to a chain of carbon atoms. a hydrocarbon backbone can be substituted by other elements such as oxygen ( o ), hydrogen ( h ), phosphorus ( p ), and sulfur ( s ), which can change the chemical behavior of that compound. groups of atoms that contain these elements ( o -, h -, p -, and s - ) and are bonded to a central carbon atom or skeleton are called functional groups. there are six prominent functional groups that can be found in organisms : amino group, carboxyl group, carbonyl group, hydroxyl group, phosphate group, and sulfhydryl group. in 1953, the miller β urey experiment showed that organic compounds could be synthesized abiotically within a closed system mimicking the conditions of early earth, thus suggesting that complex organic molecules could have arisen spontaneously in early earth ( see abiogenesis ). = = = macromolecules = = = macromolecules are large molecules made up of smaller subunits or monomers. monomers include sugars, amino acids,
possible states of energy for electrons, atoms and molecules. these are determined by the rules of quantum mechanics, which require quantization of energy of a bound system. the atoms / molecules in a higher energy state are said to be excited. the molecules / atoms of substance in an excited energy state are often much more reactive ; that is, more amenable to chemical reactions. the phase of a substance is invariably determined by its energy and the energy of its surroundings. when the intermolecular forces of a substance are such that the energy of the surroundings is not sufficient to overcome them, it occurs in a more ordered phase like liquid or solid as is the case with water ( h2o ) ; a liquid at room temperature because its molecules are bound by hydrogen bonds. whereas hydrogen sulfide ( h2s ) is a gas at room temperature and standard pressure, as its molecules are bound by weaker dipole β dipole interactions. the transfer of energy from one chemical substance to another depends on the size of energy quanta emitted from one substance. however, heat energy is often transferred more easily from almost any substance to another because the phonons responsible for vibrational and rotational energy levels in a substance have much less energy than photons invoked for the electronic energy transfer. thus, because vibrational and rotational energy levels are more closely spaced than electronic energy levels, heat is more easily transferred between substances relative to light or other forms of electronic energy. for example, ultraviolet electromagnetic radiation is not transferred with as much efficacy from one substance to another as thermal or electrical energy. the existence of characteristic energy levels for different chemical substances is useful for their identification by the analysis of spectral lines. different kinds of spectra are often used in chemical spectroscopy, e. g. ir, microwave, nmr, esr, etc. spectroscopy is also used to identify the composition of remote objects β like stars and distant galaxies β by analyzing their radiation spectra. the term chemical energy is often used to indicate the potential of a chemical substance to undergo a transformation through a chemical reaction or to transform other chemical substances. = = = reaction = = = when a chemical substance is transformed as a result of its interaction with another substance or with energy, a chemical reaction is said to have occurred. a chemical reaction is therefore a concept related to the " reaction " of a substance when it comes in close contact with another, whether as a mixture or a solution ; exposure to some form of energy, or both. it results in some energy exchange between the constituents of the reaction as well as
the most abundant molecule in every organism. water is important to life because it is an effective solvent, capable of dissolving solutes such as sodium and chloride ions or other small molecules to form an aqueous solution. once dissolved in water, these solutes are more likely to come in contact with one another and therefore take part in chemical reactions that sustain life. in terms of its molecular structure, water is a small polar molecule with a bent shape formed by the polar covalent bonds of two hydrogen ( h ) atoms to one oxygen ( o ) atom ( h2o ). because the o β h bonds are polar, the oxygen atom has a slight negative charge and the two hydrogen atoms have a slight positive charge. this polar property of water allows it to attract other water molecules via hydrogen bonds, which makes water cohesive. surface tension results from the cohesive force due to the attraction between molecules at the surface of the liquid. water is also adhesive as it is able to adhere to the surface of any polar or charged non - water molecules. water is denser as a liquid than it is as a solid ( or ice ). this unique property of water allows ice to float above liquid water such as ponds, lakes, and oceans, thereby insulating the liquid below from the cold air above. water has the capacity to absorb energy, giving it a higher specific heat capacity than other solvents such as ethanol. thus, a large amount of energy is needed to break the hydrogen bonds between water molecules to convert liquid water into water vapor. as a molecule, water is not completely stable as each water molecule continuously dissociates into hydrogen and hydroxyl ions before reforming into a water molecule again. in pure water, the number of hydrogen ions balances ( or equals ) the number of hydroxyl ions, resulting in a ph that is neutral. = = = organic compounds = = = organic compounds are molecules that contain carbon bonded to another element such as hydrogen. with the exception of water, nearly all the molecules that make up each organism contain carbon. carbon can form covalent bonds with up to four other atoms, enabling it to form diverse, large, and complex molecules. for example, a single carbon atom can form four single covalent bonds such as in methane, two double covalent bonds such as in carbon dioxide ( co2 ), or a triple covalent bond such as in carbon monoxide ( co ). moreover, carbon can form very long chains of interconnecting carbon β carbon bonds such
the branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including molecular synthesis, modification, mechanisms, and interactions. = = = water = = = life arose from the earth ' s first ocean, which formed some 3. 8 billion years ago. since then, water continues to be the most abundant molecule in every organism. water is important to life because it is an effective solvent, capable of dissolving solutes such as sodium and chloride ions or other small molecules to form an aqueous solution. once dissolved in water, these solutes are more likely to come in contact with one another and therefore take part in chemical reactions that sustain life. in terms of its molecular structure, water is a small polar molecule with a bent shape formed by the polar covalent bonds of two hydrogen ( h ) atoms to one oxygen ( o ) atom ( h2o ). because the o β h bonds are polar, the oxygen atom has a slight negative charge and the two hydrogen atoms have a slight positive charge. this polar property of water allows it to attract other water molecules via hydrogen bonds, which makes water cohesive. surface tension results from the cohesive force due to the attraction between molecules at the surface of the liquid. water is also adhesive as it is able to adhere to the surface of any polar or charged non - water molecules. water is denser as a liquid than it is as a solid ( or ice ). this unique property of water allows ice to float above liquid water such as ponds, lakes, and oceans, thereby insulating the liquid below from the cold air above. water has the capacity to absorb energy, giving it a higher specific heat capacity than other solvents such as ethanol. thus, a large amount of energy is needed to break the hydrogen bonds between water molecules to convert liquid water into water vapor. as a molecule, water is not completely stable as each water molecule continuously dissociates into hydrogen and hydroxyl ions before reforming into a water molecule again. in pure water, the number of hydrogen ions balances ( or equals ) the number of hydroxyl ions, resulting in a ph that is neutral. = = = organic compounds = = = 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
, 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
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
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 { \ sqrt { d } } } } where ky is the strengthening coefficient ( a constant unique to each material ), Οo is a materials constant for the starting stress for dislocation movement ( or the resistance of the lattice to dislocation motion ), d is the grain diameter, and Οy is the
Question: What is required to partially overcome the attractive forces between molecules in a solid to form a liquid?
A) fuel
B) energy
C) oxygen
D) hydrogen
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B) energy
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Context:
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
( 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
the exceptional log del pezzo surfaces with delta = 1 are classified.
this article has been withdrown by the author.
sciences are the clinical diagnostic services that apply laboratory techniques to diagnosis and management of patients. in the united states, these services are supervised by a pathologist. the personnel that work in these medical laboratory departments are technically trained staff who do not hold medical degrees, but who usually hold an undergraduate medical technology degree, who actually perform the tests, assays, and procedures needed for providing the specific services. subspecialties include transfusion medicine, cellular pathology, clinical chemistry, hematology, clinical microbiology and clinical immunology. clinical neurophysiology is concerned with testing the physiology or function of the central and peripheral aspects of the nervous system. these kinds of tests can be divided into recordings of : ( 1 ) spontaneous or continuously running electrical activity, or ( 2 ) stimulus evoked responses. subspecialties include electroencephalography, electromyography, evoked potential, nerve conduction study and polysomnography. sometimes these tests are performed by techs without a medical degree, but the interpretation of these tests is done by a medical professional. diagnostic radiology is concerned with imaging of the body, e. g. by x - rays, x - ray computed tomography, ultrasonography, and nuclear magnetic resonance tomography. interventional radiologists can access areas in the body under imaging for an intervention or diagnostic sampling. nuclear medicine is concerned with studying human organ systems by administering radiolabelled substances ( radiopharmaceuticals ) to the body, which can then be imaged outside the body by a gamma camera or a pet scanner. each radiopharmaceutical consists of two parts : a tracer that is specific for the function under study ( e. g., neurotransmitter pathway, metabolic pathway, blood flow, or other ), and a radionuclide ( usually either a gamma - emitter or a positron emitter ). there is a degree of overlap between nuclear medicine and radiology, as evidenced by the emergence of combined devices such as the pet / ct scanner. pathology as a medical specialty is the branch of medicine that deals with the study of diseases and the morphologic, physiologic changes produced by them. as a diagnostic specialty, pathology can be considered the basis of modern scientific medical knowledge and plays a large role in evidence - based medicine. many modern molecular tests such as flow cytometry, polymerase chain reaction ( pcr ), immunohistochemistry, cytogenetic
by ancestry rather than superficial characteristics. while scientists do not always agree on how to classify organisms, molecular phylogenetics, which uses dna sequences as data, has driven many recent revisions along evolutionary lines and is likely to continue to do so. the dominant classification system is called linnaean taxonomy. it includes ranks and binomial nomenclature. the nomenclature of botanical organisms is codified in the international code of nomenclature for algae, fungi, and plants ( icn ) and administered by the international botanical congress. kingdom plantae belongs to domain eukaryota and is broken down recursively until each species is separately classified. the order is : kingdom ; phylum ( or division ) ; class ; order ; family ; genus ( plural genera ) ; species. the scientific name of a plant represents its genus and its species within the genus, resulting in a single worldwide name for each organism. for example, the tiger lily is lilium columbianum. lilium is the genus, and columbianum the specific epithet. the combination is the name of the species. when writing the scientific name of an organism, it is proper to capitalise the first letter in the genus and put all of the specific epithet in lowercase. additionally, the entire term is ordinarily italicised ( or underlined when italics are not available ). the evolutionary relationships and heredity of a group of organisms is called its phylogeny. phylogenetic studies attempt to discover phylogenies. the basic approach is to use similarities based on shared inheritance to determine relationships. as an example, species of pereskia are trees or bushes with prominent leaves. they do not obviously resemble a typical leafless cactus such as an echinocactus. however, both pereskia and echinocactus have spines produced from areoles ( highly specialised pad - like structures ) suggesting that the two genera are indeed related. judging relationships based on shared characters requires care, since plants may resemble one another through convergent evolution in which characters have arisen independently. some euphorbias have leafless, rounded bodies adapted to water conservation similar to those of globular cacti, but characters such as the structure of their flowers make it clear that the two groups are not closely related. the cladistic method takes a systematic approach to characters, distinguishing between those that carry no information about shared evolutionary history β such as those evolved separately in different groups ( homoplasies ) or those left over from ancestors ( plesiomorphies ) β and derived characters, which
##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
these lectures describe how to study the geometry of some black holes without the use of coordinates.
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
subject. electronics engineers typically possess an academic degree with a major in electronics engineering. the length of study for such a degree is usually three or four years and the completed degree may be designated as a bachelor of engineering, bachelor of science, bachelor of applied science, or bachelor of technology depending upon the university. many uk universities also offer master of engineering ( meng ) degrees at the graduate level. some electronics engineers also choose to pursue a postgraduate degree such as a master of science, doctor of philosophy in engineering, or an engineering doctorate. the master ' s degree is being introduced in some european and american universities as a first degree and the differentiation of an engineer with graduate and postgraduate studies is often difficult. in these cases, experience is taken into account. the master ' s degree may consist of either research, coursework or a mixture of the two. the doctor of philosophy consists of a significant research component and is often viewed as the entry point to academia. in most countries, a bachelor ' s degree in engineering represents the first step towards certification and the degree program itself is certified by a professional body. certification allows engineers to legally sign off on plans for projects affecting public safety. after completing a certified degree program, the engineer must satisfy a range of requirements, including work experience requirements, before being certified. once certified the engineer is designated the title of professional engineer ( in the united states, canada, and south africa ), chartered engineer or incorporated engineer ( in the united kingdom, ireland, india, and zimbabwe ), chartered professional engineer ( in australia and new zealand ) or european engineer ( in much of the european union ). a degree in electronics generally includes units covering physics, chemistry, mathematics, project management and specific topics in electrical engineering. initially, such topics cover most, if not all, of the subfields of electronics engineering. students then choose to specialize in one or more subfields towards the end of the degree. fundamental to the discipline are the sciences of physics and mathematics as these help to obtain both a qualitative and quantitative description of how such systems will work. today, most engineering work involves the use of computers and it is commonplace to use computer - aided design and simulation software programs when designing electronic systems. although most electronic engineers will understand basic circuit theory, the theories employed by engineers generally depend upon the work they do. for example, quantum mechanics and solid - state physics might be relevant to an engineer working on vlsi but are largely irrelevant to engineers working with embedded systems. apart from electromagnetics and network theory, other items in the
Question: Cephalochordates have a notochord and nerve cord but not a?
A) backbone
B) nervous system
C) brain
D) digestive system
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A) backbone
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Context:
which came to be called radioactivity. he, pierre curie and marie curie began investigating the phenomenon. in the process, they isolated the element radium, which is highly radioactive. they discovered that radioactive materials produce intense, penetrating rays of three distinct sorts, which they labeled alpha, beta, and gamma after the first three greek letters. some of these kinds of radiation could pass through ordinary matter, and all of them could be harmful in large amounts. all of the early researchers received various radiation burns, much like sunburn, and thought little of it. the new phenomenon of radioactivity was seized upon by the manufacturers of quack medicine ( as had the discoveries of electricity and magnetism, earlier ), and a number of patent medicines and treatments involving radioactivity were put forward. gradually it was realized that the radiation produced by radioactive decay was ionizing radiation, and that even quantities too small to burn could pose a severe long - term hazard. many of the scientists working on radioactivity died of cancer as a result of their exposure. radioactive patent medicines mostly disappeared, but other applications of radioactive materials persisted, such as the use of radium salts to produce glowing dials on meters. as the atom came to be better understood, the nature of radioactivity became clearer. some larger atomic nuclei are unstable, and so decay ( release matter or energy ) after a random interval. the three forms of radiation that becquerel and the curies discovered are also more fully understood. alpha decay is when a nucleus releases an alpha particle, which is two protons and two neutrons, equivalent to a helium nucleus. beta decay is the release of a beta particle, a high - energy electron. gamma decay releases gamma rays, which unlike alpha and beta radiation are not matter but electromagnetic radiation of very high frequency, and therefore energy. this type of radiation is the most dangerous and most difficult to block. all three types of radiation occur naturally in certain elements. it has also become clear that the ultimate source of most terrestrial energy is nuclear, either through radiation from the sun caused by stellar thermonuclear reactions or by radioactive decay of uranium within the earth, the principal source of geothermal energy. = = = nuclear fission = = = in natural nuclear radiation, the byproducts are very small compared to the nuclei from which they originate. nuclear fission is the process of splitting a nucleus into roughly equal parts, and releasing energy and neutrons in the process. if these neutrons are captured by another unstable nucleus
, natural phenomena on earth only involve gravity and electromagnetism, and not nuclear reactions. this is because atomic nuclei are generally kept apart because they contain positive electrical charges and therefore repel each other. in 1896, henri becquerel was investigating phosphorescence in uranium salts when he discovered a new phenomenon which came to be called radioactivity. he, pierre curie and marie curie began investigating the phenomenon. in the process, they isolated the element radium, which is highly radioactive. they discovered that radioactive materials produce intense, penetrating rays of three distinct sorts, which they labeled alpha, beta, and gamma after the first three greek letters. some of these kinds of radiation could pass through ordinary matter, and all of them could be harmful in large amounts. all of the early researchers received various radiation burns, much like sunburn, and thought little of it. the new phenomenon of radioactivity was seized upon by the manufacturers of quack medicine ( as had the discoveries of electricity and magnetism, earlier ), and a number of patent medicines and treatments involving radioactivity were put forward. gradually it was realized that the radiation produced by radioactive decay was ionizing radiation, and that even quantities too small to burn could pose a severe long - term hazard. many of the scientists working on radioactivity died of cancer as a result of their exposure. radioactive patent medicines mostly disappeared, but other applications of radioactive materials persisted, such as the use of radium salts to produce glowing dials on meters. as the atom came to be better understood, the nature of radioactivity became clearer. some larger atomic nuclei are unstable, and so decay ( release matter or energy ) after a random interval. the three forms of radiation that becquerel and the curies discovered are also more fully understood. alpha decay is when a nucleus releases an alpha particle, which is two protons and two neutrons, equivalent to a helium nucleus. beta decay is the release of a beta particle, a high - energy electron. gamma decay releases gamma rays, which unlike alpha and beta radiation are not matter but electromagnetic radiation of very high frequency, and therefore energy. this type of radiation is the most dangerous and most difficult to block. all three types of radiation occur naturally in certain elements. it has also become clear that the ultimate source of most terrestrial energy is nuclear, either through radiation from the sun caused by stellar thermonuclear reactions or by radioactive decay of uranium within the earth, the principal source of geothermal energy.
the first three greek letters. some of these kinds of radiation could pass through ordinary matter, and all of them could be harmful in large amounts. all of the early researchers received various radiation burns, much like sunburn, and thought little of it. the new phenomenon of radioactivity was seized upon by the manufacturers of quack medicine ( as had the discoveries of electricity and magnetism, earlier ), and a number of patent medicines and treatments involving radioactivity were put forward. gradually it was realized that the radiation produced by radioactive decay was ionizing radiation, and that even quantities too small to burn could pose a severe long - term hazard. many of the scientists working on radioactivity died of cancer as a result of their exposure. radioactive patent medicines mostly disappeared, but other applications of radioactive materials persisted, such as the use of radium salts to produce glowing dials on meters. as the atom came to be better understood, the nature of radioactivity became clearer. some larger atomic nuclei are unstable, and so decay ( release matter or energy ) after a random interval. the three forms of radiation that becquerel and the curies discovered are also more fully understood. alpha decay is when a nucleus releases an alpha particle, which is two protons and two neutrons, equivalent to a helium nucleus. beta decay is the release of a beta particle, a high - energy electron. gamma decay releases gamma rays, which unlike alpha and beta radiation are not matter but electromagnetic radiation of very high frequency, and therefore energy. this type of radiation is the most dangerous and most difficult to block. all three types of radiation occur naturally in certain elements. it has also become clear that the ultimate source of most terrestrial energy is nuclear, either through radiation from the sun caused by stellar thermonuclear reactions or by radioactive decay of uranium within the earth, the principal source of geothermal energy. = = = nuclear fission = = = in natural nuclear radiation, the byproducts are very small compared to the nuclei from which they originate. nuclear fission is the process of splitting a nucleus into roughly equal parts, and releasing energy and neutrons in the process. if these neutrons are captured by another unstable nucleus, they can fission as well, leading to a chain reaction. the average number of neutrons released per nucleus that go on to fission another nucleus is referred to as k. values of k larger than 1 mean that the fission reaction is releasing more neutrons than it absorbs, and therefore is referred to as a self
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.
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
what kind of new physics, if any, we expect to discover at the lhc? i will try to address this formidable question by re - formulating it as follows : is the breaking of the electroweak symmetry strong or weak?
g. spectroscopy and chromatography. scientists engaged in chemical research are known as chemists. most chemists specialize in one or more sub - disciplines. several concepts are essential for the study of chemistry ; some of them are : = = = matter = = = in chemistry, matter is defined as anything that has rest mass and volume ( it takes up space ) and is made up of particles. the particles that make up matter have rest mass as well β not all particles have rest mass, such as the photon. matter can be a pure chemical substance or a mixture of substances. = = = = atom = = = = the atom is the basic unit of chemistry. it consists of a dense core called the atomic nucleus surrounded by a space occupied by an electron cloud. the nucleus is made up of positively charged protons and uncharged neutrons ( together called nucleons ), while the electron cloud consists of negatively charged electrons which orbit the nucleus. in a neutral atom, the negatively charged electrons balance out the positive charge of the protons. the nucleus is dense ; the mass of a nucleon is approximately 1, 836 times that of an electron, yet the radius of an atom is about 10, 000 times that of its nucleus. the atom is also the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state ( s ), coordination number, and preferred types of bonds to form ( e. g., metallic, ionic, covalent ). = = = = element = = = = a chemical element is a pure substance which is composed of a single type of atom, characterized by its particular number of protons in the nuclei of its atoms, known as the atomic number and represented by the symbol z. the mass number is the sum of the number of protons and neutrons in a nucleus. although all the nuclei of all atoms belonging to one element will have the same atomic number, they may not necessarily have the same mass number ; atoms of an element which have different mass numbers are known as isotopes. for example, all atoms with 6 protons in their nuclei are atoms of the chemical element carbon, but atoms of carbon may have mass numbers of 12 or 13. the standard presentation of the chemical elements is in the periodic table, which orders elements by atomic number. the periodic table is arranged in groups, or columns, and periods, or rows. the periodic table is useful in identifying periodic trends
##al radiologists can access areas in the body under imaging for an intervention or diagnostic sampling. nuclear medicine is concerned with studying human organ systems by administering radiolabelled substances ( radiopharmaceuticals ) to the body, which can then be imaged outside the body by a gamma camera or a pet scanner. each radiopharmaceutical consists of two parts : a tracer that is specific for the function under study ( e. g., neurotransmitter pathway, metabolic pathway, blood flow, or other ), and a radionuclide ( usually either a gamma - emitter or a positron emitter ). there is a degree of overlap between nuclear medicine and radiology, as evidenced by the emergence of combined devices such as the pet / ct scanner. pathology as a medical specialty is the branch of medicine that deals with the study of diseases and the morphologic, physiologic changes produced by them. as a diagnostic specialty, pathology can be considered the basis of modern scientific medical knowledge and plays a large role in evidence - based medicine. many modern molecular tests such as flow cytometry, polymerase chain reaction ( pcr ), immunohistochemistry, cytogenetics, gene rearrangements studies and fluorescent in situ hybridization ( fish ) fall within the territory of pathology. = = = = other major specialties = = = = the following are some major medical specialties that do not directly fit into any of the above - mentioned groups : anesthesiology ( also known as anaesthetics ) : concerned with the perioperative management of the surgical patient. the anesthesiologist ' s role during surgery is to prevent derangement in the vital organs ' ( i. e. brain, heart, kidneys ) functions and postoperative pain. outside of the operating room, the anesthesiology physician also serves the same function in the labor and delivery ward, and some are specialized in critical medicine. emergency medicine is concerned with the diagnosis and treatment of acute or life - threatening conditions, including trauma, surgical, medical, pediatric, and psychiatric emergencies. family medicine, family practice, general practice or primary care is, in many countries, the first port - of - call for patients with non - emergency medical problems. family physicians often provide services across a broad range of settings including office based practices, emergency department coverage, inpatient care, and nursing home care. medical genetics is concerned with the
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
the thickness and the density of the material to be measured. the method is used for containers of liquids or of grainy substances thickness gauges : if the material is of constant density, the signal measured by the radiation detector depends on the thickness of the material. this is useful for continuous production, like of paper, rubber, etc. electrostatic control - to avoid the build - up of static electricity in production of paper, plastics, synthetic textiles, etc., a ribbon - shaped source of the alpha emitter 241am can be placed close to the material at the end of the production line. the source ionizes the air to remove electric charges on the material. radioactive tracers - since radioactive isotopes behave, chemically, mostly like the inactive element, the behavior of a certain chemical substance can be followed by tracing the radioactivity. examples : adding a gamma tracer to a gas or liquid in a closed system makes it possible to find a hole in a tube. adding a tracer to the surface of the component of a motor makes it possible to measure wear by measuring the activity of the lubricating oil. oil and gas exploration - nuclear well logging is used to help predict the commercial viability of new or existing wells. the technology involves the use of a neutron or gamma - ray source and a radiation detector which are lowered into boreholes to determine the properties of the surrounding rock such as porosity and lithography. [ 1 ] road construction - nuclear moisture / density gauges are used to determine the density of soils, asphalt, and concrete. typically a cesium - 137 source is used. = = = commercial applications = = = radioluminescence tritium illumination : tritium is used with phosphor in rifle sights to increase nighttime firing accuracy. some runway markers and building exit signs use the same technology, to remain illuminated during blackouts. betavoltaics. smoke detector : an ionization smoke detector includes a tiny mass of radioactive americium - 241, which is a source of alpha radiation. two ionisation chambers are placed next to each other. both contain a small source of 241am that gives rise to a small constant current. one is closed and serves for comparison, the other is open to ambient air ; it has a gridded electrode. when smoke enters the open chamber, the current is disrupted as the smoke particles attach to the charged ions and restore them to a neutral electrical state. this reduces the current in the open chamber. when the current drops below a certain threshold, the
Question: Name the physicist who discovered radioactivity?
A) antoine henri becquerel
B) louis pasteur
C) albert einstein
D) neal degrasse tyson
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A) antoine henri becquerel
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Context:
, 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. 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
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
and nucleotides. carbohydrates include monomers and polymers of sugars. lipids are the only class of macromolecules that are not made up of polymers. they include steroids, phospholipids, and fats, largely nonpolar and hydrophobic ( water - repelling ) substances. proteins are the most diverse of the macromolecules. they include enzymes, transport proteins, large signaling molecules, antibodies, and structural proteins. the basic unit ( or monomer ) of a protein is an amino acid. twenty amino acids are used in proteins. nucleic acids are polymers of nucleotides. their function is to store, transmit, and express hereditary information. = = cells = = cell theory states that cells are the fundamental units of life, that all living things are composed of one or more cells, and that all cells arise from preexisting cells through cell division. most cells are very small, with diameters ranging from 1 to 100 micrometers and are therefore only visible under a light or electron microscope. there are generally two types of cells : eukaryotic cells, which contain a nucleus, and prokaryotic cells, which do not. prokaryotes are single - celled organisms such as bacteria, whereas eukaryotes can be single - celled or multicellular. in multicellular organisms, every cell in the organism ' s body is derived ultimately from a single cell in a fertilized egg. = = = cell structure = = = every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions. cell membranes also contain membrane proteins, including integral membrane proteins that go across the membrane serving as membrane transporters, and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes shaping the cell. cell membranes are involved in various cellular processes such as cell adhesion, storing electrical energy, and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall, glycocalyx, and cytoskeleton. within the cytoplasm of a cell
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
- 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
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
prominent functional groups that can be found in organisms : amino group, carboxyl group, carbonyl group, hydroxyl group, phosphate group, and sulfhydryl group. in 1953, the miller β urey experiment showed that organic compounds could be synthesized abiotically within a closed system mimicking the conditions of early earth, thus suggesting that complex organic molecules could have arisen spontaneously in early earth ( see abiogenesis ). = = = macromolecules = = = macromolecules are large molecules made up of smaller subunits or monomers. monomers include sugars, amino acids, and nucleotides. carbohydrates include monomers and polymers of sugars. lipids are the only class of macromolecules that are not made up of polymers. they include steroids, phospholipids, and fats, largely nonpolar and hydrophobic ( water - repelling ) substances. proteins are the most diverse of the macromolecules. they include enzymes, transport proteins, large signaling molecules, antibodies, and structural proteins. the basic unit ( or monomer ) of a protein is an amino acid. twenty amino acids are used in proteins. nucleic acids are polymers of nucleotides. their function is to store, transmit, and express hereditary information. = = cells = = cell theory states that cells are the fundamental units of life, that all living things are composed of one or more cells, and that all cells arise from preexisting cells through cell division. most cells are very small, with diameters ranging from 1 to 100 micrometers and are therefore only visible under a light or electron microscope. there are generally two types of cells : eukaryotic cells, which contain a nucleus, and prokaryotic cells, which do not. prokaryotes are single - celled organisms such as bacteria, whereas eukaryotes can be single - celled or multicellular. in multicellular organisms, every cell in the organism ' s body is derived ultimately from a single cell in a fertilized egg. = = = cell structure = = = every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as
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
when the hydration shell of a protein is filled with at least 0. 6 gram of water per gram of protein, a significant anti - correlation between the vibrational free energy and the potential energy of energy - minimized conformers is observed. this means that low potential energy, well - hydrated, protein conformers tend to be more rigid than high - energy ones. on the other hand, in the case of casp target 624, when its hydration shell is filled, a significant average energy gap is observed between the crystal structure and the best conformers proposed during the prediction experiment, strongly suggesting that including explicit water molecules may help identifying unlikely conformers among good - looking ones.
founded in 1976 and started the production of human proteins. genetically engineered human insulin was produced in 1978 and insulin - producing bacteria were commercialised in 1982. genetically modified food has been sold since 1994, with the release of the flavr savr tomato. the flavr savr was engineered to have a longer shelf life, but most current gm crops are modified to increase resistance to insects and herbicides. glofish, the first gmo designed as a pet, was sold in the united states in december 2003. in 2016 salmon modified with a growth hormone were sold. genetic engineering has been applied in numerous fields including research, medicine, industrial biotechnology and agriculture. in research, gmos are used to study gene function and expression through loss of function, gain of function, tracking and expression experiments. by knocking out genes responsible for certain conditions it is possible to create animal model organisms of human diseases. as well as producing hormones, vaccines and other drugs, genetic engineering has the potential to cure genetic diseases through gene therapy. chinese hamster ovary ( cho ) cells are used in industrial genetic engineering. additionally mrna vaccines are made through genetic engineering to prevent infections by viruses such as covid - 19. the same techniques that are used to produce drugs can also have industrial applications such as producing enzymes for laundry detergent, cheeses and other products. the rise of commercialised genetically modified crops has provided economic benefit to farmers in many different countries, but has also been the source of most of the controversy surrounding the technology. this has been present since its early use ; the first field trials were destroyed by anti - gm activists. although there is a scientific consensus that currently available food derived from gm crops poses no greater risk to human health than conventional food, critics consider gm food safety a leading concern. gene flow, impact on non - target organisms, control of the food supply and intellectual property rights have also been raised as potential issues. these concerns have led to the development of a regulatory framework, which started in 1975. it has led to an international treaty, the cartagena protocol on biosafety, that was adopted in 2000. individual countries have developed their own regulatory systems regarding gmos, with the most marked differences occurring between the united states and europe. = = overview = = genetic engineering is a process that alters the genetic structure of an organism by either removing or introducing dna, or modifying existing genetic material in situ. unlike traditional animal and plant breeding, which involves doing multiple crosses and then selecting for the organism with the desired phenotype,
Question: Researchers have identified the receptor proteins for all of the tastes except which?
A) salty
B) sweet
C) acid
D) bitter
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A) salty
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Context:
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
the most abundant molecule in every organism. water is important to life because it is an effective solvent, capable of dissolving solutes such as sodium and chloride ions or other small molecules to form an aqueous solution. once dissolved in water, these solutes are more likely to come in contact with one another and therefore take part in chemical reactions that sustain life. in terms of its molecular structure, water is a small polar molecule with a bent shape formed by the polar covalent bonds of two hydrogen ( h ) atoms to one oxygen ( o ) atom ( h2o ). because the o β h bonds are polar, the oxygen atom has a slight negative charge and the two hydrogen atoms have a slight positive charge. this polar property of water allows it to attract other water molecules via hydrogen bonds, which makes water cohesive. surface tension results from the cohesive force due to the attraction between molecules at the surface of the liquid. water is also adhesive as it is able to adhere to the surface of any polar or charged non - water molecules. water is denser as a liquid than it is as a solid ( or ice ). this unique property of water allows ice to float above liquid water such as ponds, lakes, and oceans, thereby insulating the liquid below from the cold air above. water has the capacity to absorb energy, giving it a higher specific heat capacity than other solvents such as ethanol. thus, a large amount of energy is needed to break the hydrogen bonds between water molecules to convert liquid water into water vapor. as a molecule, water is not completely stable as each water molecule continuously dissociates into hydrogen and hydroxyl ions before reforming into a water molecule again. in pure water, the number of hydrogen ions balances ( or equals ) the number of hydroxyl ions, resulting in a ph that is neutral. = = = organic compounds = = = organic compounds are molecules that contain carbon bonded to another element such as hydrogen. with the exception of water, nearly all the molecules that make up each organism contain carbon. carbon can form covalent bonds with up to four other atoms, enabling it to form diverse, large, and complex molecules. for example, a single carbon atom can form four single covalent bonds such as in methane, two double covalent bonds such as in carbon dioxide ( co2 ), or a triple covalent bond such as in carbon monoxide ( co ). moreover, carbon can form very long chains of interconnecting carbon β carbon bonds such
or solid as is the case with water ( h2o ) ; a liquid at room temperature because its molecules are bound by hydrogen bonds. whereas hydrogen sulfide ( h2s ) is a gas at room temperature and standard pressure, as its molecules are bound by weaker dipole β dipole interactions. the transfer of energy from one chemical substance to another depends on the size of energy quanta emitted from one substance. however, heat energy is often transferred more easily from almost any substance to another because the phonons responsible for vibrational and rotational energy levels in a substance have much less energy than photons invoked for the electronic energy transfer. thus, because vibrational and rotational energy levels are more closely spaced than electronic energy levels, heat is more easily transferred between substances relative to light or other forms of electronic energy. for example, ultraviolet electromagnetic radiation is not transferred with as much efficacy from one substance to another as thermal or electrical energy. the existence of characteristic energy levels for different chemical substances is useful for their identification by the analysis of spectral lines. different kinds of spectra are often used in chemical spectroscopy, e. g. ir, microwave, nmr, esr, etc. spectroscopy is also used to identify the composition of remote objects β like stars and distant galaxies β by analyzing their radiation spectra. the term chemical energy is often used to indicate the potential of a chemical substance to undergo a transformation through a chemical reaction or to transform other chemical substances. = = = reaction = = = when a chemical substance is transformed as a result of its interaction with another substance or with energy, a chemical reaction is said to have occurred. a chemical reaction is therefore a concept related to the " reaction " of a substance when it comes in close contact with another, whether as a mixture or a solution ; exposure to some form of energy, or both. it results in some energy exchange between the constituents of the reaction as well as with the system environment, which may be designed vessels β often laboratory glassware. chemical reactions can result in the formation or dissociation of molecules, that is, molecules breaking apart to form two or more molecules or rearrangement of atoms within or across molecules. chemical reactions usually involve the making or breaking of chemical bonds. oxidation, reduction, dissociation, acid β base neutralization and molecular rearrangement are some examples of common chemical reactions. a chemical reaction can be symbolically depicted through a chemical equation. while in a non - nuclear chemical reaction the number and kind of atoms on both sides of the equation are equal, for
; and the wafer surfaces are sufficiently clean. the most stringent criteria for wafer bonding is usually the direct fusion wafer bonding since even one or more small particulates can render the bonding unsuccessful. in comparison, wafer bonding methods that use intermediary layers are often far more forgiving. both bulk and surface silicon micromachining are used in the industrial production of sensors, ink - jet nozzles, and other devices. but in many cases the distinction between these two has diminished. a new etching technology, deep reactive - ion etching, has made it possible to combine good performance typical of bulk micromachining with comb structures and in - plane operation typical of surface micromachining. while it is common in surface micromachining to have structural layer thickness in the range of 2 ΞΌm, in har silicon micromachining the thickness can be from 10 to 100 ΞΌm. the materials commonly used in har silicon micromachining are thick polycrystalline silicon, known as epi - poly, and bonded silicon - on - insulator ( soi ) wafers although processes for bulk silicon wafer also have been created ( scream ). bonding a second wafer by glass frit bonding, anodic bonding or alloy bonding is used to protect the mems structures. integrated circuits are typically not combined with har silicon micromachining. = = applications = = some common commercial applications of mems include : inkjet printers, which use piezoelectrics or thermal bubble ejection to deposit ink on paper. accelerometers in modern cars for a large number of purposes including airbag deployment and electronic stability control. inertial measurement units ( imus ) : mems accelerometers. mems gyroscopes in remote controlled, or autonomous, helicopters, planes and multirotors ( also known as drones ), used for automatically sensing and balancing flying characteristics of roll, pitch and yaw. mems magnetic field sensor ( magnetometer ) may also be incorporated in such devices to provide directional heading. mems inertial navigation systems ( inss ) of modern cars, airplanes, submarines and other vehicles to detect yaw, pitch, and roll ; for example, the autopilot of an airplane. accelerometers in consumer electronics devices such as game controllers ( nintendo wii ), personal media players / cell phones ( virtually all smartphones, various htc pda models ), augmented
the branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including molecular synthesis, modification, mechanisms, and interactions. = = = water = = = life arose from the earth ' s first ocean, which formed some 3. 8 billion years ago. since then, water continues to be the most abundant molecule in every organism. water is important to life because it is an effective solvent, capable of dissolving solutes such as sodium and chloride ions or other small molecules to form an aqueous solution. once dissolved in water, these solutes are more likely to come in contact with one another and therefore take part in chemical reactions that sustain life. in terms of its molecular structure, water is a small polar molecule with a bent shape formed by the polar covalent bonds of two hydrogen ( h ) atoms to one oxygen ( o ) atom ( h2o ). because the o β h bonds are polar, the oxygen atom has a slight negative charge and the two hydrogen atoms have a slight positive charge. this polar property of water allows it to attract other water molecules via hydrogen bonds, which makes water cohesive. surface tension results from the cohesive force due to the attraction between molecules at the surface of the liquid. water is also adhesive as it is able to adhere to the surface of any polar or charged non - water molecules. water is denser as a liquid than it is as a solid ( or ice ). this unique property of water allows ice to float above liquid water such as ponds, lakes, and oceans, thereby insulating the liquid below from the cold air above. water has the capacity to absorb energy, giving it a higher specific heat capacity than other solvents such as ethanol. thus, a large amount of energy is needed to break the hydrogen bonds between water molecules to convert liquid water into water vapor. as a molecule, water is not completely stable as each water molecule continuously dissociates into hydrogen and hydroxyl ions before reforming into a water molecule again. in pure water, the number of hydrogen ions balances ( or equals ) the number of hydroxyl ions, resulting in a ph that is neutral. = = = organic compounds = = = 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
##ulating the liquid below from the cold air above. water has the capacity to absorb energy, giving it a higher specific heat capacity than other solvents such as ethanol. thus, a large amount of energy is needed to break the hydrogen bonds between water molecules to convert liquid water into water vapor. as a molecule, water is not completely stable as each water molecule continuously dissociates into hydrogen and hydroxyl ions before reforming into a water molecule again. in pure water, the number of hydrogen ions balances ( or equals ) the number of hydroxyl ions, resulting in a ph that is neutral. = = = organic compounds = = = organic compounds are molecules that contain carbon bonded to another element such as hydrogen. with the exception of water, nearly all the molecules that make up each organism contain carbon. carbon can form covalent bonds with up to four other atoms, enabling it to form diverse, large, and complex molecules. for example, a single carbon atom can form four single covalent bonds such as in methane, two double covalent bonds such as in carbon dioxide ( co2 ), or a triple covalent bond such as in carbon monoxide ( co ). moreover, carbon can form very long chains of interconnecting carbon β carbon bonds such as octane or ring - like structures such as glucose. the simplest form of an organic molecule is the hydrocarbon, which is a large family of organic compounds that are composed of hydrogen atoms bonded to a chain of carbon atoms. a hydrocarbon backbone can be substituted by other elements such as oxygen ( o ), hydrogen ( h ), phosphorus ( p ), and sulfur ( s ), which can change the chemical behavior of that compound. groups of atoms that contain these elements ( o -, h -, p -, and s - ) and are bonded to a central carbon atom or skeleton are called functional groups. there are six prominent functional groups that can be found in organisms : amino group, carboxyl group, carbonyl group, hydroxyl group, phosphate group, and sulfhydryl group. in 1953, the miller β urey experiment showed that organic compounds could be synthesized abiotically within a closed system mimicking the conditions of early earth, thus suggesting that complex organic molecules could have arisen spontaneously in early earth ( see abiogenesis ). = = = macromolecules = = = macromolecules are large molecules made up of smaller subunits or monomers. monomers include sugars, amino acids,
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.
, 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
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 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.
Question: What has high surface tension because of extensive hydrogen bonding?
A) hydrocarbons
B) air
C) water
D) gases
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C) water
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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
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 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,
pectin and xyloglucan from which the land plant cell wall is constructed. vascular land plants make lignin, a polymer used to strengthen the secondary cell walls of xylem tracheids and vessels to keep them from collapsing when a plant sucks water through them under water stress. lignin is also used in other cell types like sclerenchyma fibres that provide structural support for a plant and is a major constituent of wood. sporopollenin is a chemically resistant polymer found in the outer cell walls of spores and pollen of land plants responsible for the survival of early land plant spores and the pollen of seed plants in the fossil record. it is widely regarded as a marker for the start of land plant evolution during the ordovician period. the concentration of carbon dioxide in the atmosphere today is much lower than it was when plants emerged onto land during the ordovician and silurian periods. many monocots like maize and the pineapple and some dicots like the asteraceae have since independently evolved pathways like crassulacean acid metabolism and the c4 carbon fixation pathway for photosynthesis which avoid the losses resulting from photorespiration in the more common c3 carbon fixation pathway. these biochemical strategies are unique to land plants. = = = medicine and materials = = = phytochemistry is a branch of plant biochemistry primarily concerned with the chemical substances produced by plants during secondary metabolism. some of these compounds are toxins such as the alkaloid coniine from hemlock. others, such as the essential oils peppermint oil and lemon oil are useful for their aroma, as flavourings and spices ( e. g., capsaicin ), and in medicine as pharmaceuticals as in opium from opium poppies. many medicinal and recreational drugs, such as tetrahydrocannabinol ( active ingredient in cannabis ), caffeine, morphine and nicotine come directly from plants. others are simple derivatives of botanical natural products. for example, the pain killer aspirin is the acetyl ester of salicylic acid, originally isolated from the bark of willow trees, and a wide range of opiate painkillers like heroin are obtained by chemical modification of morphine obtained from the opium poppy. popular stimulants come from plants, such as caffeine from coffee, tea and chocolate, and nicotine from tobacco. most alcoholic beverages come from fermentation of carbohy
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.
##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
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
river - beds ), but not for where there may be large obstructions in the ground. an open caisson that is used in soft grounds or high water tables, where open trench excavations are impractical, can also be used to install deep manholes, pump stations and reception / launch pits for microtunnelling, pipe jacking and other operations. a caisson is sunk by self - weight, concrete or water ballast placed on top, or by hydraulic jacks. the leading edge ( or cutting shoe ) of the caisson is sloped out at a sharp angle to aid sinking in a vertical manner ; it is usually made of steel. the shoe is generally wider than the caisson to reduce friction, and the leading edge may be supplied with pressurised bentonite slurry, which swells in water, stabilizing settlement by filling depressions and voids. an open caisson may fill with water during sinking. the material is excavated by clamshell excavator bucket on crane. the formation level subsoil may still not be suitable for excavation or bearing capacity. the water in the caisson ( due to a high water table ) balances the upthrust forces of the soft soils underneath. if dewatered, the base may " pipe " or " boil ", causing the caisson to sink. to combat this problem, piles may be driven from the surface to act as : load - bearing walls, in that they transmit loads to deeper soils. anchors, in that they resist flotation because of the friction at the interface between their surfaces and the surrounding earth into which they have been driven. h - beam sections ( typical column sections, due to resistance to bending in all axis ) may be driven at angles " raked " to rock or other firmer soils ; the h - beams are left extended above the base. a reinforced concrete plug may be placed under the water, a process known as tremie concrete placement. when the caisson is dewatered, this plug acts as a pile cap, resisting the upward forces of the subsoil. = = = monolithic = = = a monolithic caisson ( or simply a monolith ) is larger than the other types of caisson, but similar to open caissons. such caissons are often found in quay walls, where resistance to impact from ships is required. = = = pneumatic = = = shallow caissons may be open to the air, whereas pneumatic caisson
##ta together form the monophyletic group or clade streptophytina. nonvascular land plants are embryophytes that lack the vascular tissues xylem and phloem. they include mosses, liverworts and hornworts. pteridophytic vascular plants with true xylem and phloem that reproduced by spores germinating into free - living gametophytes evolved during the silurian period and diversified into several lineages during the late silurian and early devonian. representatives of the lycopods have survived to the present day. by the end of the devonian period, several groups, including the lycopods, sphenophylls and progymnosperms, had independently evolved " megaspory " β their spores were of two distinct sizes, larger megaspores and smaller microspores. their reduced gametophytes developed from megaspores retained within the spore - producing organs ( megasporangia ) of the sporophyte, a condition known as endospory. seeds consist of an endosporic megasporangium surrounded by one or two sheathing layers ( integuments ). the young sporophyte develops within the seed, which on germination splits to release it. the earliest known seed plants date from the latest devonian famennian stage. following the evolution of the seed habit, seed plants diversified, giving rise to a number of now - extinct groups, including seed ferns, as well as the modern gymnosperms and angiosperms. gymnosperms produce " naked seeds " not fully enclosed in an ovary ; modern representatives include conifers, cycads, ginkgo, and gnetales. angiosperms produce seeds enclosed in a structure such as a carpel or an ovary. ongoing research on the molecular phylogenetics of living plants appears to show that the angiosperms are a sister clade to the gymnosperms. = = plant physiology = = plant physiology encompasses all the internal chemical and physical activities of plants associated with life. chemicals obtained from the air, soil and water form the basis of all plant metabolism. the energy of sunlight, captured by oxygenic photosynthesis and released by cellular respiration, is the basis of almost all life. photoautotrophs, including all green plants, algae and cyanobacteria gather energy directly from sunlight by photosynthesis. hetero
, 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
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
Question: Where are sponges most likely anchored to?
A) beaches
B) reef or rock
C) sea floor
D) sand
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B) reef or rock
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Context:
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 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.
final version. to appear in discrete and continuous dynamical systems - a.
onset of electro - chemical corrosion. similar problems are encountered in coastal and offshore structures. = = = anti - fouling = = = anti - fouling is the process of eliminating obstructive organisms from essential components of seawater systems. depending on the nature and location of marine growth, this process is performed in a number of different ways : marine organisms may grow and attach to the surfaces of the outboard suction inlets used to obtain water for cooling systems. electro - chlorination involves running high electrical current through sea water, altering the water ' s chemical composition to create sodium hypochlorite, purging any bio - matter. an electrolytic method of anti - fouling involves running electrical current through two anodes ( scardino, 2009 ). these anodes typically consist of copper and aluminum ( or alternatively, iron ). the first metal, copper anode, releases its ion into the water, creating an environment that is too toxic for bio - matter. the second metal, aluminum, coats the inside of the pipes to prevent corrosion. other forms of marine growth such as mussels and algae may attach themselves to the bottom of a ship ' s hull. this growth interferes with the smoothness and uniformity of the ship ' s hull, causing the ship to have a less hydrodynamic shape that causes it to be slower and less fuel - efficient. marine growth on the hull can be remedied by using special paint that prevents the growth of such organisms. = = = pollution control = = = = = = = sulfur emission = = = = the burning of marine fuels releases harmful pollutants into the atmosphere. ships burn marine diesel in addition to heavy fuel oil. heavy fuel oil, being the heaviest of refined oils, releases sulfur dioxide when burned. sulfur dioxide emissions have the potential to raise atmospheric and ocean acidity causing harm to marine life. however, heavy fuel oil may only be burned in international waters due to the pollution created. it is commercially advantageous due to the cost effectiveness compared to other marine fuels. it is prospected that heavy fuel oil will be phased out of commercial use by the year 2020 ( smith, 2018 ). = = = = oil and water discharge = = = = water, oil, and other substances collect at the bottom of the ship in what is known as the bilge. bilge water is pumped overboard, but must pass a pollution threshold test of 15 ppm ( parts per million ) of oil to be discharged. water is tested
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
unitary recordings in freely - moving pulse weakly electric fish suggest spike timing encoding of electrosensory signals
i transform the trapdoor problem of hfe into a linear algebra problem.
anticommutative engel algebras of the first five degeneration levels are classified. all algebras appearing in this classification are nilpotent malcev algebras.
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
ultramagnetized neutron stars or magnetars are magnetically powered neutron stars. their strong magnetic fields dominate the physical processes in their crusts and their surroundings. the past few years have seen several advances in our theoretical and observational understanding of these objects. in spite of a surfeit of observations, their spectra are still poorly understood. i will discuss the emission from strongly magnetized condensed matter surfaces of neutron stars, recent advances in our expectations of the surface composition of magnetars and a model for the non - thermal emission from these objects.
Question: What do jellyfish use to startle predators?
A) black light
B) bicellular light
C) visible light
D) harsh light
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C) visible light
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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 ",
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.
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
subsea engineering and the ability to detect, track and destroy submarines ( anti - submarine warfare ) required the parallel development of a host of marine scientific instrumentation and sensors. visible light is not transferred far underwater, so the medium for transmission of data is primarily acoustic. high - frequency sound is used to measure the depth of the ocean, determine the nature of the seafloor, and detect submerged objects. the higher the frequency, the higher the definition of the data that is returned. sound navigation and ranging or sonar was developed during the first world war to detect submarines, and has been greatly refined through to the present day. submarines similarly use sonar equipment to detect and target other submarines and surface ships, and to detect submerged obstacles such as seamounts that pose a navigational obstacle. simple echo - sounders point straight down and can give an accurate reading of ocean depth ( or look up at the underside of sea - ice ). more advanced echo sounders use a fan - shaped beam or sound, or multiple beams to derive highly detailed images of the ocean floor. high power systems can penetrate the soil and seabed rocks to give information about the geology of the seafloor, and are widely used in geophysics for the discovery of hydrocarbons, or for engineering survey. for close - range underwater communications, optical transmission is possible, mainly using blue lasers. these have a high bandwidth compared with acoustic systems, but the range is usually only a few tens of metres, and ideally at night. as well as acoustic communications and navigation, sensors have been developed to measure ocean parameters such as temperature, salinity, oxygen levels and other properties including nitrate levels, levels of trace chemicals and environmental dna. the industry trend has been towards smaller, more accurate and more affordable systems so that they can be purchased and used by university departments and small companies as well as large corporations, research organisations and governments. the sensors and instruments are fitted to autonomous and remotely - operated systems as well as ships, and are enabling these systems to take on tasks that hitherto required an expensive human - crewed platform. manufacture of marine sensors and instruments mainly takes place in asia, europe and north america. products are advertised in specialist journals, and through trade shows such as oceanology international and ocean business which help raise awareness of the products. = = = environmental engineering = = = in every coastal and offshore project, environmental sustainability is an important consideration for the preservation of ocean ecosystems and natural resources. instances in which marine engineers benefit from knowledge of environmental engineering include creation of fisheries, clean
onset of electro - chemical corrosion. similar problems are encountered in coastal and offshore structures. = = = anti - fouling = = = anti - fouling is the process of eliminating obstructive organisms from essential components of seawater systems. depending on the nature and location of marine growth, this process is performed in a number of different ways : marine organisms may grow and attach to the surfaces of the outboard suction inlets used to obtain water for cooling systems. electro - chlorination involves running high electrical current through sea water, altering the water ' s chemical composition to create sodium hypochlorite, purging any bio - matter. an electrolytic method of anti - fouling involves running electrical current through two anodes ( scardino, 2009 ). these anodes typically consist of copper and aluminum ( or alternatively, iron ). the first metal, copper anode, releases its ion into the water, creating an environment that is too toxic for bio - matter. the second metal, aluminum, coats the inside of the pipes to prevent corrosion. other forms of marine growth such as mussels and algae may attach themselves to the bottom of a ship ' s hull. this growth interferes with the smoothness and uniformity of the ship ' s hull, causing the ship to have a less hydrodynamic shape that causes it to be slower and less fuel - efficient. marine growth on the hull can be remedied by using special paint that prevents the growth of such organisms. = = = pollution control = = = = = = = sulfur emission = = = = the burning of marine fuels releases harmful pollutants into the atmosphere. ships burn marine diesel in addition to heavy fuel oil. heavy fuel oil, being the heaviest of refined oils, releases sulfur dioxide when burned. sulfur dioxide emissions have the potential to raise atmospheric and ocean acidity causing harm to marine life. however, heavy fuel oil may only be burned in international waters due to the pollution created. it is commercially advantageous due to the cost effectiveness compared to other marine fuels. it is prospected that heavy fuel oil will be phased out of commercial use by the year 2020 ( smith, 2018 ). = = = = oil and water discharge = = = = water, oil, and other substances collect at the bottom of the ship in what is known as the bilge. bilge water is pumped overboard, but must pass a pollution threshold test of 15 ppm ( parts per million ) of oil to be discharged. water is tested
river - beds ), but not for where there may be large obstructions in the ground. an open caisson that is used in soft grounds or high water tables, where open trench excavations are impractical, can also be used to install deep manholes, pump stations and reception / launch pits for microtunnelling, pipe jacking and other operations. a caisson is sunk by self - weight, concrete or water ballast placed on top, or by hydraulic jacks. the leading edge ( or cutting shoe ) of the caisson is sloped out at a sharp angle to aid sinking in a vertical manner ; it is usually made of steel. the shoe is generally wider than the caisson to reduce friction, and the leading edge may be supplied with pressurised bentonite slurry, which swells in water, stabilizing settlement by filling depressions and voids. an open caisson may fill with water during sinking. the material is excavated by clamshell excavator bucket on crane. the formation level subsoil may still not be suitable for excavation or bearing capacity. the water in the caisson ( due to a high water table ) balances the upthrust forces of the soft soils underneath. if dewatered, the base may " pipe " or " boil ", causing the caisson to sink. to combat this problem, piles may be driven from the surface to act as : load - bearing walls, in that they transmit loads to deeper soils. anchors, in that they resist flotation because of the friction at the interface between their surfaces and the surrounding earth into which they have been driven. h - beam sections ( typical column sections, due to resistance to bending in all axis ) may be driven at angles " raked " to rock or other firmer soils ; the h - beams are left extended above the base. a reinforced concrete plug may be placed under the water, a process known as tremie concrete placement. when the caisson is dewatered, this plug acts as a pile cap, resisting the upward forces of the subsoil. = = = monolithic = = = a monolithic caisson ( or simply a monolith ) is larger than the other types of caisson, but similar to open caissons. such caissons are often found in quay walls, where resistance to impact from ships is required. = = = pneumatic = = = shallow caissons may be open to the air, whereas pneumatic caisson
material is demonstrated by northwestern university, consisting of 100 trillion bonds per square centimetre, which its creators describe as having exceptional flexibility and strength. adding just 2. 5 % of the new material to ultem boosted the latter ' s tensile modulus by 45 %. the air monitoring station at mauna loa observatory in hawaii reports that co2 jumped by 3. 58 parts per million ( ppm ) in 2024, exceeding the previous record of 3. 36 ppm set in 2023. the global atmospheric concentration of co2 is now at 427 ppm, more than 50 % higher than the pre - industrial level. 21 january coral bleaching on the southern great barrier reef in early 2024 is reported to have struck 80 % of colonies, with some coral genera, such as acropora, experiencing a 95 % mortality rate. more than a third ( 34 % ) of the arctic - boreal zone is now reported to be a source of carbon emissions, rather than a carbon sink, a figure that rises to 40 % when including emissions from fires. the exoplanet wasp - 127b is discovered to have wind speeds of up to 33, 000 km / h, the fastest jetstream of its kind ever measured. 22 january β the second trump administration imposes an immediate freeze on scientific grants, communications, hiring, and meetings at the national institutes of health ( nih ) β by far the biggest supporter of biomedical research worldwide β impacting $ 47. 4 billion worth of activities. 23 january machine learning and 3d printing are used at the university of toronto to design nano - architected materials exhibiting the strength of carbon steel but the lightness of styrofoam. a study of adults with attention deficit hyperactivity disorder ( adhd ) finds that the condition may reduce life expectancy by 4. 5 to 9 years for men, and 6. 5 to 11 years for women. 24 january β a study by the university of birmingham finds that electric vehicles now have an average lifespan of 18. 4 years, outlasting the average diesel vehicle at 16. 8 years and almost matching the average petrol vehicle at 18. 7 years. 29 january β the european space agency ( esa ) announces that it has begun monitoring the asteroid 2024 yr4, which at the time had a 1 in 77 ( 1. 3 % ) chance of impacting earth on 22 december 2032. = = = february = = = 3 february β researchers in berkeley and cambridge attach copper nanoflower catalysts on per
ocean, determine the nature of the seafloor, and detect submerged objects. the higher the frequency, the higher the definition of the data that is returned. sound navigation and ranging or sonar was developed during the first world war to detect submarines, and has been greatly refined through to the present day. submarines similarly use sonar equipment to detect and target other submarines and surface ships, and to detect submerged obstacles such as seamounts that pose a navigational obstacle. simple echo - sounders point straight down and can give an accurate reading of ocean depth ( or look up at the underside of sea - ice ). more advanced echo sounders use a fan - shaped beam or sound, or multiple beams to derive highly detailed images of the ocean floor. high power systems can penetrate the soil and seabed rocks to give information about the geology of the seafloor, and are widely used in geophysics for the discovery of hydrocarbons, or for engineering survey. for close - range underwater communications, optical transmission is possible, mainly using blue lasers. these have a high bandwidth compared with acoustic systems, but the range is usually only a few tens of metres, and ideally at night. as well as acoustic communications and navigation, sensors have been developed to measure ocean parameters such as temperature, salinity, oxygen levels and other properties including nitrate levels, levels of trace chemicals and environmental dna. the industry trend has been towards smaller, more accurate and more affordable systems so that they can be purchased and used by university departments and small companies as well as large corporations, research organisations and governments. the sensors and instruments are fitted to autonomous and remotely - operated systems as well as ships, and are enabling these systems to take on tasks that hitherto required an expensive human - crewed platform. manufacture of marine sensors and instruments mainly takes place in asia, europe and north america. products are advertised in specialist journals, and through trade shows such as oceanology international and ocean business which help raise awareness of the products. = = = environmental engineering = = = in every coastal and offshore project, environmental sustainability is an important consideration for the preservation of ocean ecosystems and natural resources. instances in which marine engineers benefit from knowledge of environmental engineering include creation of fisheries, clean - up of oil spills, and creation of coastal solutions. = = = offshore systems = = = a number of systems designed fully or in part by marine engineers are used offshore - far away from coastlines. = = = = offshore oil platforms = = = = the design of offshore oil platforms involves a number of
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
this is a personal history of the hastings - michalakis proof of quantum hall conductance quantization.
Question: What do corals secrete that builds up to become a coral reef?
A) exoskeleton
B) scales
C) mucous
D) membrane
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A) exoskeleton
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Context:
. currently, even blades made of advanced metal alloys used in the engines ' hot section require cooling and careful limiting of operating temperatures. turbine engines made with ceramics could operate more efficiently, giving aircraft greater range and payload for a set amount of fuel. recently, there have been advances in ceramics which include bio - ceramics, such as dental implants and synthetic bones. hydroxyapatite, the natural mineral component of bone, has been made synthetically from a number of biological and chemical sources and can be formed into ceramic materials. orthopedic implants made from these materials bond readily to bone and other tissues in the body without rejection or inflammatory reactions. because of this, they are of great interest for gene delivery and tissue engineering scaffolds. most hydroxyapatite ceramics are very porous and lack mechanical strength and are used to coat metal orthopedic devices to aid in forming a bond to bone or as bone fillers. they are also used as fillers for orthopedic plastic screws to aid in reducing the inflammation and increase absorption of these plastic materials. work is being done to make strong, fully dense nano crystalline hydroxyapatite ceramic materials for orthopedic weight bearing devices, replacing foreign metal and plastic orthopedic materials with a synthetic, but naturally occurring, bone mineral. ultimately these ceramic materials may be used as bone replacements or with the incorporation of protein collagens, synthetic bones. durable actinide - containing ceramic materials have many applications such as in nuclear fuels for burning excess pu and in chemically - inert sources of alpha irradiation for power supply of unmanned space vehicles or to produce electricity for microelectronic devices. both use and disposal of radioactive actinides require their immobilization in a durable host material. nuclear waste long - lived radionuclides such as actinides are immobilized using chemically - durable crystalline materials based on polycrystalline ceramics and large single crystals. alumina ceramics are widely utilized in the chemical industry due to their excellent chemical stability and high resistance to corrosion. it is used as acid - resistant pump impellers and pump bodies, ensuring long - lasting performance in transferring aggressive fluids. they are also used in acid - carrying pipe linings to prevent contamination and maintain fluid purity, which is crucial in industries like pharmaceuticals and food processing. valves made from alumina ceramics demonstrate exceptional durability and resistance to chemical attack, making them reliable for controlling the flow of corrosive liquids. =
as dental implants and synthetic bones. hydroxyapatite, the natural mineral component of bone, has been made synthetically from a number of biological and chemical sources and can be formed into ceramic materials. orthopedic implants made from these materials bond readily to bone and other tissues in the body without rejection or inflammatory reactions. because of this, they are of great interest for gene delivery and tissue engineering scaffolds. most hydroxyapatite ceramics are very porous and lack mechanical strength and are used to coat metal orthopedic devices to aid in forming a bond to bone or as bone fillers. they are also used as fillers for orthopedic plastic screws to aid in reducing the inflammation and increase absorption of these plastic materials. work is being done to make strong, fully dense nano crystalline hydroxyapatite ceramic materials for orthopedic weight bearing devices, replacing foreign metal and plastic orthopedic materials with a synthetic, but naturally occurring, bone mineral. ultimately these ceramic materials may be used as bone replacements or with the incorporation of protein collagens, synthetic bones. durable actinide - containing ceramic materials have many applications such as in nuclear fuels for burning excess pu and in chemically - inert sources of alpha irradiation for power supply of unmanned space vehicles or to produce electricity for microelectronic devices. both use and disposal of radioactive actinides require their immobilization in a durable host material. nuclear waste long - lived radionuclides such as actinides are immobilized using chemically - durable crystalline materials based on polycrystalline ceramics and large single crystals. alumina ceramics are widely utilized in the chemical industry due to their excellent chemical stability and high resistance to corrosion. it is used as acid - resistant pump impellers and pump bodies, ensuring long - lasting performance in transferring aggressive fluids. they are also used in acid - carrying pipe linings to prevent contamination and maintain fluid purity, which is crucial in industries like pharmaceuticals and food processing. valves made from alumina ceramics demonstrate exceptional durability and resistance to chemical attack, making them reliable for controlling the flow of corrosive liquids. = = glass - ceramics = = glass - ceramic materials share many properties with both glasses and ceramics. glass - ceramics have an amorphous phase and one or more crystalline phases and are produced by a so - called " controlled crystallization ", which is typically avoided in glass manufacturing. glass - ceramics often contain a crystalline phase
inflammatory reactions. because of this, they are of great interest for gene delivery and tissue engineering scaffolds. most hydroxyapatite ceramics are very porous and lack mechanical strength and are used to coat metal orthopedic devices to aid in forming a bond to bone or as bone fillers. they are also used as fillers for orthopedic plastic screws to aid in reducing the inflammation and increase absorption of these plastic materials. work is being done to make strong, fully dense nano crystalline hydroxyapatite ceramic materials for orthopedic weight bearing devices, replacing foreign metal and plastic orthopedic materials with a synthetic, but naturally occurring, bone mineral. ultimately these ceramic materials may be used as bone replacements or with the incorporation of protein collagens, synthetic bones. durable actinide - containing ceramic materials have many applications such as in nuclear fuels for burning excess pu and in chemically - inert sources of alpha irradiation for power supply of unmanned space vehicles or to produce electricity for microelectronic devices. both use and disposal of radioactive actinides require their immobilization in a durable host material. nuclear waste long - lived radionuclides such as actinides are immobilized using chemically - durable crystalline materials based on polycrystalline ceramics and large single crystals. alumina ceramics are widely utilized in the chemical industry due to their excellent chemical stability and high resistance to corrosion. it is used as acid - resistant pump impellers and pump bodies, ensuring long - lasting performance in transferring aggressive fluids. they are also used in acid - carrying pipe linings to prevent contamination and maintain fluid purity, which is crucial in industries like pharmaceuticals and food processing. valves made from alumina ceramics demonstrate exceptional durability and resistance to chemical attack, making them reliable for controlling the flow of corrosive liquids. = = glass - ceramics = = glass - ceramic materials share many properties with both glasses and ceramics. glass - ceramics have an amorphous phase and one or more crystalline phases and are produced by a so - called " controlled crystallization ", which is typically avoided in glass manufacturing. glass - ceramics often contain a crystalline phase which constitutes anywhere from 30 % [ m / m ] to 90 % [ m / m ] of its composition by volume, yielding an array of materials with interesting thermomechanical properties. in the processing of glass - ceramics, molten glass is cooled down gradually before reheating and annealing. in this heat
of ceramic parts in the requisite precision and durability is difficult. imperfection in the ceramic leads to cracks, which can lead to potentially dangerous equipment failure. such engines are possible in laboratory settings, but mass - production is not feasible with current technology. work is being done in developing ceramic parts for gas turbine engines. currently, even blades made of advanced metal alloys used in the engines ' hot section require cooling and careful limiting of operating temperatures. turbine engines made with ceramics could operate more efficiently, giving aircraft greater range and payload for a set amount of fuel. recently, there have been advances in ceramics which include bio - ceramics, such as dental implants and synthetic bones. hydroxyapatite, the natural mineral component of bone, has been made synthetically from a number of biological and chemical sources and can be formed into ceramic materials. orthopedic implants made from these materials bond readily to bone and other tissues in the body without rejection or inflammatory reactions. because of this, they are of great interest for gene delivery and tissue engineering scaffolds. most hydroxyapatite ceramics are very porous and lack mechanical strength and are used to coat metal orthopedic devices to aid in forming a bond to bone or as bone fillers. they are also used as fillers for orthopedic plastic screws to aid in reducing the inflammation and increase absorption of these plastic materials. work is being done to make strong, fully dense nano crystalline hydroxyapatite ceramic materials for orthopedic weight bearing devices, replacing foreign metal and plastic orthopedic materials with a synthetic, but naturally occurring, bone mineral. ultimately these ceramic materials may be used as bone replacements or with the incorporation of protein collagens, synthetic bones. durable actinide - containing ceramic materials have many applications such as in nuclear fuels for burning excess pu and in chemically - inert sources of alpha irradiation for power supply of unmanned space vehicles or to produce electricity for microelectronic devices. both use and disposal of radioactive actinides require their immobilization in a durable host material. nuclear waste long - lived radionuclides such as actinides are immobilized using chemically - durable crystalline materials based on polycrystalline ceramics and large single crystals. alumina ceramics are widely utilized in the chemical industry due to their excellent chemical stability and high resistance to corrosion. it is used as acid - resistant pump impellers and pump bodies, ensuring long - lasting performance in transferring aggressive
this is an expository paper about the topics listed in the title.
##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
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 formation. the use of thiolated polymers ( thiomers ) as scaffold material for tissue engineering was initially introduced at the 4th central european symposium on pharmaceutical technology in vienna 2001. as thiomers are biocompatible, exhibit cellular mimicking properties and efficiently support proliferation and differentiation of various cell types,
##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
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: What layer covers the bones that make them look tough, shiny, and white?
A) cuticle
B) epithelium
C) epidermis
D) periosteum
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D) periosteum
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Context:
has rest mass and volume ( it takes up space ) and is made up of particles. the particles that make up matter have rest mass as well β not all particles have rest mass, such as the photon. matter can be a pure chemical substance or a mixture of substances. = = = = atom = = = = the atom is the basic unit of chemistry. it consists of a dense core called the atomic nucleus surrounded by a space occupied by an electron cloud. the nucleus is made up of positively charged protons and uncharged neutrons ( together called nucleons ), while the electron cloud consists of negatively charged electrons which orbit the nucleus. in a neutral atom, the negatively charged electrons balance out the positive charge of the protons. the nucleus is dense ; the mass of a nucleon is approximately 1, 836 times that of an electron, yet the radius of an atom is about 10, 000 times that of its nucleus. the atom is also the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state ( s ), coordination number, and preferred types of bonds to form ( e. g., metallic, ionic, covalent ). = = = = element = = = = a chemical element is a pure substance which is composed of a single type of atom, characterized by its particular number of protons in the nuclei of its atoms, known as the atomic number and represented by the symbol z. the mass number is the sum of the number of protons and neutrons in a nucleus. although all the nuclei of all atoms belonging to one element will have the same atomic number, they may not necessarily have the same mass number ; atoms of an element which have different mass numbers are known as isotopes. for example, all atoms with 6 protons in their nuclei are atoms of the chemical element carbon, but atoms of carbon may have mass numbers of 12 or 13. the standard presentation of the chemical elements is in the periodic table, which orders elements by atomic number. the periodic table is arranged in groups, or columns, and periods, or rows. the periodic table is useful in identifying periodic trends. = = = = compound = = = = a compound is a pure chemical substance composed of more than one element. the properties of a compound bear little similarity to those of its elements. the standard nomenclature of compounds is set by the international union of pure and applied chemistry ( iupac ). organic compounds are named
other electrons either in bonds or in lone pairs. thus, molecules exist as electrically neutral units, unlike ions. when this rule is broken, giving the " molecule " a charge, the result is sometimes named a molecular ion or a polyatomic ion. however, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature. = = = = substance and mixture = = = = a chemical substance is a kind of matter with a definite composition and set of properties. a collection of substances is called a mixture. examples of mixtures are air and alloys. = = = = mole and amount of substance = = = = the mole is a unit
##ting the principle of conservation of mass and developing a new system of chemical nomenclature used to this day. english scientist john dalton proposed the modern theory of atoms ; that all substances are composed of indivisible ' atoms ' of matter and that different atoms have varying atomic weights. the development of the electrochemical theory of chemical combinations occurred in the early 19th century as the result of the work of two scientists in particular, jons jacob berzelius and humphry davy, made possible by the prior invention of the voltaic pile by alessandro volta. davy discovered nine new elements including the alkali metals by extracting them from their oxides with electric current. british william prout first proposed ordering all the elements by their atomic weight as all atoms had a weight that was an exact multiple of the atomic weight of hydrogen. j. a. r. newlands devised an early table of elements, which was then developed into the modern periodic table of elements in the 1860s by dmitri mendeleev and independently by several other scientists including julius lothar meyer. the inert gases, later called the noble gases were discovered by william ramsay in collaboration with lord rayleigh at the end of the century, thereby filling in the basic structure of the table. organic chemistry was developed by justus von liebig and others, following friedrich wohler ' s synthesis of urea. other crucial 19th century advances were ; an understanding of valence bonding ( edward frankland in 1852 ) and the application of thermodynamics to chemistry ( j. w. gibbs and svante arrhenius in the 1870s ). at the turn of the twentieth century the theoretical underpinnings of chemistry were finally understood due to a series of remarkable discoveries that succeeded in probing and discovering the very nature of the internal structure of atoms. in 1897, j. j. thomson of the university of cambridge discovered the electron and soon after the french scientist becquerel as well as the couple pierre and marie curie investigated the phenomenon of radioactivity. in a series of pioneering scattering experiments ernest rutherford at the university of manchester discovered the internal structure of the atom and the existence of the proton, classified and explained the different types of radioactivity and successfully transmuted the first element by bombarding nitrogen with alpha particles. his work on atomic structure was improved on by his students, the danish physicist niels bohr, the englishman henry moseley and the german otto hahn, who went on to father the emerging nuclear chemistry and discovered nuclear fission. the electronic theory
g. spectroscopy and chromatography. scientists engaged in chemical research are known as chemists. most chemists specialize in one or more sub - disciplines. several concepts are essential for the study of chemistry ; some of them are : = = = matter = = = in chemistry, matter is defined as anything that has rest mass and volume ( it takes up space ) and is made up of particles. the particles that make up matter have rest mass as well β not all particles have rest mass, such as the photon. matter can be a pure chemical substance or a mixture of substances. = = = = atom = = = = the atom is the basic unit of chemistry. it consists of a dense core called the atomic nucleus surrounded by a space occupied by an electron cloud. the nucleus is made up of positively charged protons and uncharged neutrons ( together called nucleons ), while the electron cloud consists of negatively charged electrons which orbit the nucleus. in a neutral atom, the negatively charged electrons balance out the positive charge of the protons. the nucleus is dense ; the mass of a nucleon is approximately 1, 836 times that of an electron, yet the radius of an atom is about 10, 000 times that of its nucleus. the atom is also the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state ( s ), coordination number, and preferred types of bonds to form ( e. g., metallic, ionic, covalent ). = = = = element = = = = a chemical element is a pure substance which is composed of a single type of atom, characterized by its particular number of protons in the nuclei of its atoms, known as the atomic number and represented by the symbol z. the mass number is the sum of the number of protons and neutrons in a nucleus. although all the nuclei of all atoms belonging to one element will have the same atomic number, they may not necessarily have the same mass number ; atoms of an element which have different mass numbers are known as isotopes. for example, all atoms with 6 protons in their nuclei are atoms of the chemical element carbon, but atoms of carbon may have mass numbers of 12 or 13. the standard presentation of the chemical elements is in the periodic table, which orders elements by atomic number. the periodic table is arranged in groups, or columns, and periods, or rows. the periodic table is useful in identifying periodic trends
mwco, molecular weight cut off, with units in dalton ). it is defined as the minimum molecular weight of a globular molecule that is retained to 90 % by the membrane. the cut - off, depending on the method, can by converted to so - called d90, which is then expressed in a metric unit. in practice the mwco of the membrane should be at least 20 % lower than the molecular weight of the molecule that is to be separated. using track etched mica membranes beck and schultz demonstrated that hindered diffusion of molecules in pores can be described by the rankin equation. filter membranes are divided into four classes according to pore size : the form and shape of the membrane pores are highly dependent on the manufacturing process and are often difficult to specify. therefore, for characterization, test filtrations are carried out and the pore diameter refers to the diameter of the smallest particles which could not pass through the membrane. the rejection can be determined in various ways and provides an indirect measurement of the pore size. one possibility is the filtration of macromolecules ( often dextran, polyethylene glycol or albumin ), another is measurement of the cut - off by gel permeation chromatography. these methods are used mainly to measure membranes for ultrafiltration applications. another testing method is the filtration of particles with defined size and their measurement with a particle sizer or by laser induced breakdown spectroscopy ( libs ). a vivid characterization is to measure the rejection of dextran blue or other colored molecules. the retention of bacteriophage and bacteria, the so - called " bacteria challenge test ", can also provide information about the pore size. to determine the pore diameter, physical methods such as porosimeter ( mercury, liquid - liquid porosimeter and bubble point test ) are also used, but a certain form of the pores ( such as cylindrical or concatenated spherical holes ) is assumed. such methods are used for membranes whose pore geometry does not match the ideal, and we get " nominal " pore diameter, which characterizes the membrane, but does not necessarily reflect its actual 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 )
set of chemical reactions with other substances. however, this definition only works well for substances that are composed of molecules, which is not true of many substances ( see below ). molecules are typically a set of atoms bound together by covalent bonds, such that the structure is electrically neutral and all valence electrons are paired with other electrons either in bonds or in lone pairs. thus, molecules exist as electrically neutral units, unlike ions. when this rule is broken, giving the " molecule " a charge, the result is sometimes named a molecular ion or a polyatomic ion. however, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature.
the manufacturer. one common distinction is by nominal pore size. it describes the maximum pore size distribution and gives only vague information about the retention capacity of a membrane. the exclusion limit or " cut - off " of the membrane is usually specified in the form of nmwc ( nominal molecular weight cut - off, or mwco, molecular weight cut off, with units in dalton ). it is defined as the minimum molecular weight of a globular molecule that is retained to 90 % by the membrane. the cut - off, depending on the method, can by converted to so - called d90, which is then expressed in a metric unit. in practice the mwco of the membrane should be at least 20 % lower than the molecular weight of the molecule that is to be separated. using track etched mica membranes beck and schultz demonstrated that hindered diffusion of molecules in pores can be described by the rankin equation. filter membranes are divided into four classes according to pore size : the form and shape of the membrane pores are highly dependent on the manufacturing process and are often difficult to specify. therefore, for characterization, test filtrations are carried out and the pore diameter refers to the diameter of the smallest particles which could not pass through the membrane. the rejection can be determined in various ways and provides an indirect measurement of the pore size. one possibility is the filtration of macromolecules ( often dextran, polyethylene glycol or albumin ), another is measurement of the cut - off by gel permeation chromatography. these methods are used mainly to measure membranes for ultrafiltration applications. another testing method is the filtration of particles with defined size and their measurement with a particle sizer or by laser induced breakdown spectroscopy ( libs ). a vivid characterization is to measure the rejection of dextran blue or other colored molecules. the retention of bacteriophage and bacteria, the so - called " bacteria challenge test ", can also provide information about the pore size. to determine the pore diameter, physical methods such as porosimeter ( mercury, liquid - liquid porosimeter and bubble point test ) are also used, but a certain form of the pores ( such as cylindrical or concatenated spherical holes ) is assumed. such methods are used for membranes whose pore geometry does not match the ideal, and we get " nominal " pore diameter, which characterizes the membrane, but does not necessarily reflect its actual filt
classes according to pore size : the form and shape of the membrane pores are highly dependent on the manufacturing process and are often difficult to specify. therefore, for characterization, test filtrations are carried out and the pore diameter refers to the diameter of the smallest particles which could not pass through the membrane. the rejection can be determined in various ways and provides an indirect measurement of the pore size. one possibility is the filtration of macromolecules ( often dextran, polyethylene glycol or albumin ), another is measurement of the cut - off by gel permeation chromatography. these methods are used mainly to measure membranes for ultrafiltration applications. another testing method is the filtration of particles with defined size and their measurement with a particle sizer or by laser induced breakdown spectroscopy ( libs ). a vivid characterization is to measure the rejection of dextran blue or other colored molecules. the retention of bacteriophage and bacteria, the so - called " bacteria challenge test ", can also provide information about the pore size. to determine the pore diameter, physical methods such as porosimeter ( mercury, liquid - liquid porosimeter and bubble point test ) are also used, but a certain form of the pores ( such as cylindrical or concatenated spherical holes ) is assumed. such methods are used for membranes whose pore geometry does not match the ideal, and we get " nominal " pore diameter, which characterizes the membrane, but does not necessarily reflect its actual filtration behavior and selectivity. the selectivity is highly dependent on the separation process, the composition of the membrane and its electrochemical properties in addition to the pore size. with high selectivity, isotopes can be enriched ( uranium enrichment ) in nuclear engineering or industrial gases like nitrogen can be recovered ( gas separation ). ideally, even racemics can be enriched with a suitable membrane. when choosing membranes selectivity has priority over a high permeability, as low flows can easily be offset by increasing the filter surface with a modular structure. in gas phase filtration different deposition mechanisms are operative, so that particles having sizes below the pore size of the membrane can be retained as well. = = membrane classification = = bio - membrane is classified in two categories, synthetic membrane and natural membrane. synthetic membranes further classified in organic and inorganic membranes. organic membrane sub classified polymeric membranes and inorganic membrane sub classified ceramic polymers. = = synthesis of biomass membrane
intense research in the materials science community due to the unique properties that they exhibit. nanostructure deals with objects and structures that are in the 1 β 100 nm range. in many materials, atoms or molecules agglomerate to form objects at the nanoscale. this causes many interesting electrical, magnetic, optical, and mechanical properties. in describing nanostructures, it is necessary to differentiate between the number of dimensions on the nanoscale. nanotextured surfaces have one dimension on the nanoscale, i. e., only the thickness of the surface of an object is between 0. 1 and 100 nm. nanotubes have two dimensions on the nanoscale, i. e., the diameter of the tube is between 0. 1 and 100 nm ; its length could be much greater. finally, spherical nanoparticles have three dimensions on the nanoscale, i. e., the particle is between 0. 1 and 100 nm in each spatial dimension. the terms nanoparticles and ultrafine particles ( ufp ) often are used synonymously although ufp can reach into the micrometre range. the term ' nanostructure ' is often used, when referring to magnetic technology. nanoscale structure in biology is often called ultrastructure. = = = = microstructure = = = = microstructure is defined as the structure of a prepared surface or thin foil of material as revealed by a microscope above 25Γ magnification. it deals with objects from 100 nm to a few cm. the microstructure of a material ( which can be broadly classified into metallic, polymeric, ceramic and composite ) can strongly influence physical properties such as strength, toughness, ductility, hardness, corrosion resistance, high / low temperature behavior, wear resistance, and so on. most of the traditional materials ( such as metals and ceramics ) are microstructured. the manufacture of a perfect crystal of a material is physically impossible. for example, any crystalline material will contain defects such as precipitates, grain boundaries ( hall β petch relationship ), vacancies, interstitial atoms or substitutional atoms. the microstructure of materials reveals these larger defects and advances in simulation have allowed an increased understanding of how defects can be used to enhance material properties. = = = = macrostructure = = = = macrostructure is the appearance of a material in the scale millimeters to meters, it is the structure of
the r - process of nucleosynthesis requires a large neutron - to - seed nucleus ratio. this does not, however, that there be an excess of neutrons over protons. if the expansion of the material is sufficiently rapid and the entropy per nucleon is sufficiently high, the nucleosynthesis enters a heavy - element synthesis regime heretofore unexplored. in this extreme regime, characterized by a persistent disequilibrium between free nucleons and the abundant alpha particles, heavy r - process nuclei can form even in matter with more protons than neutrons. this observation bears on the issue of the site of the r - process, on the variability of abundance yields from r - process events, and on cnstraints on neutrino physics derived from nucleosynthesis. it also clarifies the difference between nucleosynthesis in the early universe and that in less extreme stellar explosive environments.
Question: John dalton thought that what unit, which means "indivisible", could not be divided into smaller, simpler particles?
A) electron
B) nucleus
C) atom
D) neutron
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C) atom
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Context:
snake called jormungandr. the norse creation account preserved in gylfaginning ( viii ) states that during the creation of the earth, an impassable sea was placed around it : and jafnharr said : " of the blood, which ran and welled forth freely out of his wounds, they made the sea, when they had formed and made firm the earth together, and laid the sea in a ring round. about her ; and it may well seem a hard thing to most men to cross over it. " the late norse konungs skuggsja, on the other hand, explains earth ' s shape as a sphere : if you take a lighted candle and set it in a room, you may expect it to light up the entire interior, unless something should hinder, though the room be quite large. but if you take an apple and hang it close to the flame, so near that it is heated, the apple will darken nearly half the room or even more. however, if you hang the apple near the wall, it will not get hot ; the candle will light up the whole house ; and the shadow on the wall where the apple hangs will be scarcely half as large as the apple itself. from this you may infer that the earth - circle is round like a ball and not equally near the sun at every point. but where the curved surface lies nearest the sun ' s path, there will the greatest heat be ; and some of the lands that lie continuously under the unbroken rays cannot be inhabited. = = = = east asia = = = = in ancient china, the prevailing belief was that the earth was flat and square, while the heavens were round, an assumption virtually unquestioned until the introduction of european astronomy in the 17th century. the english sinologist cullen emphasizes the point that there was no concept of a round earth in ancient chinese astronomy : chinese thought on the form of the earth remained almost unchanged from early times until the first contacts with modern science through the medium of jesuit missionaries in the seventeenth century. while the heavens were variously described as being like an umbrella covering the earth ( the kai tian theory ), or like a sphere surrounding it ( 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
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
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
still a complex and relatively expensive material to produce. polymers on the other hand can be produced in huge volumes, with a great variety of material characteristics. mems devices can be made from polymers by processes such as injection molding, embossing or stereolithography and are especially well suited to microfluidic applications such as disposable blood testing cartridges. metals metals can also be used to create mems elements. while metals do not have some of the advantages displayed by silicon in terms of mechanical properties, when used within their limitations, metals can exhibit very high degrees of reliability. metals can be deposited by electroplating, evaporation, and sputtering processes. commonly used metals include gold, nickel, aluminium, copper, chromium, titanium, tungsten, platinum, and silver. ceramics the nitrides of silicon, aluminium and titanium as well as silicon carbide and other ceramics are increasingly applied in mems fabrication due to advantageous combinations of material properties. aln crystallizes in the wurtzite structure and thus shows pyroelectric and piezoelectric properties enabling sensors, for instance, with sensitivity to normal and shear forces. tin, on the other hand, exhibits a high electrical conductivity and large elastic modulus, making it possible to implement electrostatic mems actuation schemes with ultrathin beams. moreover, the high resistance of tin against biocorrosion qualifies the material for applications in biogenic environments. the figure shows an electron - microscopic picture of a mems biosensor with a 50 nm thin bendable tin beam above a tin ground plate. both can be driven as opposite electrodes of a capacitor, since the beam is fixed in electrically isolating side walls. when a fluid is suspended in the cavity its viscosity may be derived from bending the beam by electrical attraction to the ground plate and measuring the bending velocity. = = basic processes = = = = = deposition processes = = = one of the basic building blocks in mems processing is the ability to deposit thin films of material with a thickness anywhere from one micrometre to about 100 micrometres. the nems process is the same, although the measurement of film deposition ranges from a few nanometres to one micrometre. there are two types of deposition processes, as follows. = = = = physical deposition = = = = physical vapor deposition ( " pvd " ) consists of a process in which a material is removed from a target, and
. 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,
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.
billet is passed through successively narrower rollers to create a sheet. extrusion β a hot and malleable metal is forced under pressure through a die, which shapes it before it cools. machining β lathes, milling machines and drills cut the cold metal to shape. sintering β a powdered metal is heated in a non - oxidizing environment after being compressed into a die. fabrication β sheets of metal are cut with guillotines or gas cutters and bent and welded into structural shape. laser cladding β metallic powder is blown through a movable laser beam ( e. g. mounted on a nc 5 - axis machine ). the resulting melted metal reaches a substrate to form a melt pool. by moving the laser head, it is possible to stack the tracks and build up a three - dimensional piece. 3d printing β sintering or melting amorphous powder metal in a 3d space to make any object to shape. cold - working processes, in which the product ' s shape is altered by rolling, fabrication or other processes, while the product is cold, can increase the strength of the product by a process called work hardening. work hardening creates microscopic defects in the metal, which resist further changes of shape. = = = heat treatment = = = metals can be heat - treated to alter the properties of strength, ductility, toughness, hardness and resistance to corrosion. common heat treatment processes include annealing, precipitation strengthening, quenching, and tempering : annealing process softens the metal by heating it and then allowing it to cool very slowly, which gets rid of stresses in the metal and makes the grain structure large and soft - edged so that, when the metal is hit or stressed it dents or perhaps bends, rather than breaking ; it is also easier to sand, grind, or cut annealed metal. quenching is the process of cooling metal very quickly after heating, thus " freezing " the metal ' s molecules in the very hard martensite form, which makes the metal harder. tempering relieves stresses in the metal that were caused by the hardening process ; tempering makes the metal less hard while making it better able to sustain impacts without breaking. often, mechanical and thermal treatments are combined in what are known as thermo - mechanical treatments for better properties and more efficient processing of materials. these processes are common to high - alloy special steels, superalloys and titanium alloys. = = = plating = = = electroplating is
##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
torsion oscillations of the neutron star crust are landau damped by the alfven continuum in the bulk. for strong magnetic fields ( in magnetars ), undamped alfven eigenmodes appear.
Question: What gems are created by mollusks, such as oysters?
A) crystals
B) pearls
C) turquoise
D) diamonds
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B) pearls
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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
, 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
was used before copper smelting was known. copper smelting is believed to have originated when the technology of pottery kilns allowed sufficiently high temperatures. the concentration of various elements such as arsenic increase with depth in copper ore deposits and smelting of these ores yields arsenical bronze, which can be sufficiently work hardened to be suitable for making tools. bronze is an alloy of copper with tin ; the latter being found in relatively few deposits globally caused a long time to elapse before true tin bronze became widespread. ( see : tin sources and trade in ancient times ) bronze was a major advancement over stone as a material for making tools, both because of its mechanical properties like strength and ductility and because it could be cast in molds to make intricately shaped objects. bronze significantly advanced shipbuilding technology with better tools and bronze nails. bronze nails replaced the old method of attaching boards of the hull with cord woven through drilled holes. better ships enabled long - distance trade and the advance of civilization. this technological trend apparently began in the fertile crescent and spread outward over time. these developments were not, and still are not, universal. the three - age system does not accurately describe the technology history of groups outside of eurasia, and does not apply at all in the case of some isolated populations, such as the spinifex people, the sentinelese, and various amazonian tribes, which still make use of stone age technology, and have not developed agricultural or metal technology. these villages preserve traditional customs in the face of global modernity, exhibiting a remarkable resistance to the rapid advancement of technology. = = = = iron age = = = = before iron smelting was developed the only iron was obtained from meteorites and is usually identified by having nickel content. meteoric iron was rare and valuable, but was sometimes used to make tools and other implements, such as fish hooks. the iron age involved the adoption of iron smelting technology. it generally replaced bronze and made it possible to produce tools which were stronger, lighter and cheaper to make than bronze equivalents. the raw materials to make iron, such as ore and limestone, are far more abundant than copper and especially tin ores. consequently, iron was produced in many areas. it was not possible to mass manufacture steel or pure iron because of the high temperatures required. furnaces could reach melting temperature but the crucibles and molds needed for melting and casting had not been developed. steel could be produced by forging bloomery iron to reduce the carbon content in a
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
this is erratum of the paper [ phys. rev. lett. { \ bf 84 }, 4260 ( 2000 ) ]
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 ). "
. a reaction is said to be exergonic if the final state is lower on the energy scale than the initial state ; in the case of endergonic reactions the situation is the reverse. a reaction is said to be exothermic if the reaction releases heat to the surroundings ; in the case of endothermic reactions, the reaction absorbs heat from the surroundings. chemical reactions are invariably not possible unless the reactants surmount an energy barrier known as the activation energy. the speed of a chemical reaction ( at given temperature t ) is related to the activation energy e, by the boltzmann ' s population factor e β e / k t { \ displaystyle e ^ { - e / kt } } β that is the probability of a molecule to have energy greater than or equal to e at the given temperature t. this exponential dependence of a reaction rate on temperature is known as the arrhenius equation. the activation energy necessary for a chemical reaction to occur can be in the form of heat, light, electricity or mechanical force in the form of ultrasound. a related concept free energy, which also incorporates entropy considerations, is a very useful means for predicting the feasibility of a reaction and determining the state of equilibrium of a chemical reaction, in chemical thermodynamics. a reaction is feasible only if the total change in the gibbs free energy is negative, Ξ΄ g β€ 0 { \ displaystyle \ delta g \ leq 0 \, } ; if it is equal to zero the chemical reaction is said to be at equilibrium. there exist only limited possible states of energy for electrons, atoms and molecules. these are determined by the rules of quantum mechanics, which require quantization of energy of a bound system. the atoms / molecules in a higher energy state are said to be excited. the molecules / atoms of substance in an excited energy state are often much more reactive ; that is, more amenable to chemical reactions. the phase of a substance is invariably determined by its energy and the energy of its surroundings. when the intermolecular forces of a substance are such that the energy of the surroundings is not sufficient to overcome them, it occurs in a more ordered phase like liquid or solid as is the case with water ( h2o ) ; a liquid at room temperature because its molecules are bound by hydrogen bonds. whereas hydrogen sulfide ( h2s ) is a gas at room temperature and standard pressure, as its molecules are bound by weaker dipole β dipole interactions. the transfer of
in this brief note we point out that in the case of two dimensional crystals like graaphene, there is an interesting anomalous behaviour of fermions. this could potentially be useful.
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
Question: Extrusive igneous rocks are also called what?
A) metamorphic
B) volcanic rocks
C) agates
D) magma minerals
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B) volcanic rocks
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Context:
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
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
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 (
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.
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
. 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
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 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
endothermic reactions, the reaction absorbs heat from the surroundings. chemical reactions are invariably not possible unless the reactants surmount an energy barrier known as the activation energy. the speed of a chemical reaction ( at given temperature t ) is related to the activation energy e, by the boltzmann ' s population factor e β e / k t { \ displaystyle e ^ { - e / kt } } β that is the probability of a molecule to have energy greater than or equal to e at the given temperature t. this exponential dependence of a reaction rate on temperature is known as the arrhenius equation. the activation energy necessary for a chemical reaction to occur can be in the form of heat, light, electricity or mechanical force in the form of ultrasound. a related concept free energy, which also incorporates entropy considerations, is a very useful means for predicting the feasibility of a reaction and determining the state of equilibrium of a chemical reaction, in chemical thermodynamics. a reaction is feasible only if the total change in the gibbs free energy is negative, Ξ΄ g β€ 0 { \ displaystyle \ delta g \ leq 0 \, } ; if it is equal to zero the chemical reaction is said to be at equilibrium. there exist only limited possible states of energy for electrons, atoms and molecules. these are determined by the rules of quantum mechanics, which require quantization of energy of a bound system. the atoms / molecules in a higher energy state are said to be excited. the molecules / atoms of substance in an excited energy state are often much more reactive ; that is, more amenable to chemical reactions. the phase of a substance is invariably determined by its energy and the energy of its surroundings. when the intermolecular forces of a substance are such that the energy of the surroundings is not sufficient to overcome them, it occurs in a more ordered phase like liquid or solid as is the case with water ( h2o ) ; a liquid at room temperature because its molecules are bound by hydrogen bonds. whereas hydrogen sulfide ( h2s ) is a gas at room temperature and standard pressure, as its molecules are bound by weaker dipole β dipole interactions. the transfer of energy from one chemical substance to another depends on the size of energy quanta emitted from one substance. however, heat energy is often transferred more easily from almost any substance to another because the phonons responsible for vibrational and rotational energy levels in a substance have much less energy than photons invoked for the electronic energy transfer
, 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
Question: What happened to chemical reactions when temperature increases?
A) it became faster
B) it becomes slower
C) it slows down for a short time then speeds up
D) it stays the same
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A) it became faster
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Context:
energy they need to exist. plants, algae and cyanobacteria are the major groups of organisms that carry out photosynthesis, a process that uses the energy of sunlight to convert water and carbon dioxide into sugars that can be used both as a source of chemical energy and of organic molecules that are used in the structural components of cells. as a by - product of photosynthesis, plants release oxygen into the atmosphere, a gas that is required by nearly all living things to carry out cellular respiration. in addition, they are influential in the global carbon and water cycles and plant roots bind and stabilise soils, preventing soil erosion. plants are crucial to the future of human society as they provide food, oxygen, biochemicals, and products for people, as well as creating and preserving soil. historically, all living things were classified as either animals or plants and botany covered the study of all organisms not considered animals. botanists examine both the internal functions and processes within plant organelles, cells, tissues, whole plants, plant populations and plant communities. at each of these levels, a botanist may be concerned with the classification ( taxonomy ), phylogeny and evolution, structure ( anatomy and morphology ), or function ( physiology ) of plant life. the strictest definition of " plant " includes only the " land plants " or embryophytes, which include seed plants ( gymnosperms, including the pines, and flowering plants ) and the free - sporing cryptogams including ferns, clubmosses, liverworts, hornworts and mosses. embryophytes are multicellular eukaryotes descended from an ancestor that obtained its energy from sunlight by photosynthesis. they have life cycles with alternating haploid and diploid phases. the sexual haploid phase of embryophytes, known as the gametophyte, nurtures the developing diploid embryo sporophyte within its tissues for at least part of its life, even in the seed plants, where the gametophyte itself is nurtured by its parent sporophyte. other groups of organisms that were previously studied by botanists include bacteria ( now studied in bacteriology ), fungi ( mycology ) β including lichen - forming fungi ( lichenology ), non - chlorophyte algae ( phycology ), and viruses ( virology ). however, attention is still given to these groups by botanists, and fungi ( including lichens ) and photos
substrate - level phosphorylation, which does not require oxygen. = = = photosynthesis = = = photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organism ' s metabolic activities via cellular respiration. this chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. in most cases, oxygen is released as a waste product. most plants, algae, and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of the earth ' s atmosphere, and supplies most of the energy necessary for life on earth. photosynthesis has four stages : light absorption, electron transport, atp synthesis, and carbon fixation. light absorption is the initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to proteins in the thylakoid membranes. the absorbed light energy is used to remove electrons from a donor ( water ) to a primary electron acceptor, a quinone designated as q. in the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach a final electron acceptor, which is usually the oxidized form of nadp +, which is reduced to nadph, a process that takes place in a protein complex called photosystem i ( psi ). the transport of electrons is coupled to the movement of protons ( or hydrogen ) from the stroma to the thylakoid membrane, which forms a ph gradient across the membrane as hydrogen becomes more concentrated in the lumen than in the stroma. this is analogous to the proton - motive force generated across the inner mitochondrial membrane in aerobic respiration. during the third stage of photosynthesis, the movement of protons down their concentration gradients from the thylakoid lumen to the stroma through the atp synthase is coupled to the synthesis of atp by that same atp synthase. the nadph and atps generated by the light - dependent reactions in the second and third stages, respectively, provide the energy and electrons to drive the synthesis of glucose by fixing atmospheric carbon dioxide into existing organic carbon compounds, such as ribulose bisphosphate ( rubp ) in a sequence of light - independent ( or dark ) reactions called the calvin cycle. = = = cell signaling = = = cell signaling ( or communication ) is the
##vary. ongoing research on the molecular phylogenetics of living plants appears to show that the angiosperms are a sister clade to the gymnosperms. = = plant physiology = = plant physiology encompasses all the internal chemical and physical activities of plants associated with life. chemicals obtained from the air, soil and water form the basis of all plant metabolism. the energy of sunlight, captured by oxygenic photosynthesis and released by cellular respiration, is the basis of almost all life. photoautotrophs, including all green plants, algae and cyanobacteria gather energy directly from sunlight by photosynthesis. heterotrophs including all animals, all fungi, all completely parasitic plants, and non - photosynthetic bacteria take in organic molecules produced by photoautotrophs and respire them or use them in the construction of cells and tissues. respiration is the oxidation of carbon compounds by breaking them down into simpler structures to release the energy they contain, essentially the opposite of photosynthesis. molecules are moved within plants by transport processes that operate at a variety of spatial scales. subcellular transport of ions, electrons and molecules such as water and enzymes occurs across cell membranes. minerals and water are transported from roots to other parts of the plant in the transpiration stream. diffusion, osmosis, and active transport and mass flow are all different ways transport can occur. examples of elements that plants need to transport are nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. in vascular plants, these elements are extracted from the soil as soluble ions by the roots and transported throughout the plant in the xylem. most of the elements required for plant nutrition come from the chemical breakdown of soil minerals. sucrose produced by photosynthesis is transported from the leaves to other parts of the plant in the phloem and plant hormones are transported by a variety of processes. = = = plant hormones = = = plants are not passive, but respond to external signals such as light, touch, and injury by moving or growing towards or away from the stimulus, as appropriate. tangible evidence of touch sensitivity is the almost instantaneous collapse of leaflets of mimosa pudica, the insect traps of venus flytrap and bladderworts, and the pollinia of orchids. the hypothesis that plant growth and development is coordinated by plant hormones or plant growth regulators first emerged in the late 19th century. darwin experimented on the movements of plant shoots and roots towards light and gravity, and concluded " it is hardly an ex
the basis of all plant metabolism. the energy of sunlight, captured by oxygenic photosynthesis and released by cellular respiration, is the basis of almost all life. photoautotrophs, including all green plants, algae and cyanobacteria gather energy directly from sunlight by photosynthesis. heterotrophs including all animals, all fungi, all completely parasitic plants, and non - photosynthetic bacteria take in organic molecules produced by photoautotrophs and respire them or use them in the construction of cells and tissues. respiration is the oxidation of carbon compounds by breaking them down into simpler structures to release the energy they contain, essentially the opposite of photosynthesis. molecules are moved within plants by transport processes that operate at a variety of spatial scales. subcellular transport of ions, electrons and molecules such as water and enzymes occurs across cell membranes. minerals and water are transported from roots to other parts of the plant in the transpiration stream. diffusion, osmosis, and active transport and mass flow are all different ways transport can occur. examples of elements that plants need to transport are nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. in vascular plants, these elements are extracted from the soil as soluble ions by the roots and transported throughout the plant in the xylem. most of the elements required for plant nutrition come from the chemical breakdown of soil minerals. sucrose produced by photosynthesis is transported from the leaves to other parts of the plant in the phloem and plant hormones are transported by a variety of processes. = = = plant hormones = = = plants are not passive, but respond to external signals such as light, touch, and injury by moving or growing towards or away from the stimulus, as appropriate. tangible evidence of touch sensitivity is the almost instantaneous collapse of leaflets of mimosa pudica, the insect traps of venus flytrap and bladderworts, and the pollinia of orchids. the hypothesis that plant growth and development is coordinated by plant hormones or plant growth regulators first emerged in the late 19th century. darwin experimented on the movements of plant shoots and roots towards light and gravity, and concluded " it is hardly an exaggeration to say that the tip of the radicle.. acts like the brain of one of the lower animals.. directing the several movements ". about the same time, the role of auxins ( from the greek auxein, to grow ) in control of plant growth was first outlined by the dutch scientist
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 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
##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
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
##nosperms and angiosperms. gymnosperms produce " naked seeds " not fully enclosed in an ovary ; modern representatives include conifers, cycads, ginkgo, and gnetales. angiosperms produce seeds enclosed in a structure such as a carpel or an ovary. ongoing research on the molecular phylogenetics of living plants appears to show that the angiosperms are a sister clade to the gymnosperms. = = plant physiology = = plant physiology encompasses all the internal chemical and physical activities of plants associated with life. chemicals obtained from the air, soil and water form the basis of all plant metabolism. the energy of sunlight, captured by oxygenic photosynthesis and released by cellular respiration, is the basis of almost all life. photoautotrophs, including all green plants, algae and cyanobacteria gather energy directly from sunlight by photosynthesis. heterotrophs including all animals, all fungi, all completely parasitic plants, and non - photosynthetic bacteria take in organic molecules produced by photoautotrophs and respire them or use them in the construction of cells and tissues. respiration is the oxidation of carbon compounds by breaking them down into simpler structures to release the energy they contain, essentially the opposite of photosynthesis. molecules are moved within plants by transport processes that operate at a variety of spatial scales. subcellular transport of ions, electrons and molecules such as water and enzymes occurs across cell membranes. minerals and water are transported from roots to other parts of the plant in the transpiration stream. diffusion, osmosis, and active transport and mass flow are all different ways transport can occur. examples of elements that plants need to transport are nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. in vascular plants, these elements are extracted from the soil as soluble ions by the roots and transported throughout the plant in the xylem. most of the elements required for plant nutrition come from the chemical breakdown of soil minerals. sucrose produced by photosynthesis is transported from the leaves to other parts of the plant in the phloem and plant hormones are transported by a variety of processes. = = = plant hormones = = = plants are not passive, but respond to external signals such as light, touch, and injury by moving or growing towards or away from the stimulus, as appropriate. tangible evidence of touch sensitivity is the almost instantaneous collapse of leaflets of mimosa pudica, the insect traps of
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: Where do living things obtain the energy to carry out all life processes?
A) fuel
B) food
C) oxygen
D) waste
|
B) food
|
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