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dust grains absorb half of the radiation emitted by stars throughout the history of the universe, re - emitting this energy at infrared wavelengths. polycyclic aromatic hydrocarbons ( pahs ) are large organic molecules that trace millimeter - size dust grains and regulate the cooling of the interstellar gas within galaxies. observations of pah features in very distant galaxies have been difficult due to the limited sensitivity and wavelength coverage of previous infrared telescopes. here we present jwst observations that detect the 3. 3um pah feature in a galaxy observed less than 1. 5 billion years after the big bang. the high equivalent width of the pah feature indicates that star formation, rather than black hole accretion, dominates the infrared emission throughout the galaxy. the light from pah molecules, large dust grains, and stars and hot dust are spatially distinct from one another, leading to order - of - magnitude variations in the pah equivalent width and the ratio of pah to total infrared luminosity across the galaxy. the spatial variations we observe suggest either a physical offset between the pahs and large dust grains or wide variations in the local ultraviolet radiation field. our observations demonstrate that differences in the emission from pah molecules and large dust grains are a complex result of localized processes within early galaxies.
##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
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
using only lidar or radar an accurate cloud boundary height estimate is often not possible. the combination of lidar and radar can give a reliable cloud boundary estimate in a much broader range of cases. however, also this combination with standard methods still can not measure the cloud boundaries in all cases. this will be illustrated with data from the clouds and radiation measurement campaigns, clara. rain is a problem : the radar has problems to measure the small cloud droplets in the presence of raindrops. similarly, few large particles below cloud base can obscure the cloud base in radar measurements. and the radar reflectivity can be very low at the cloud base of water clouds or in large regions of ice clouds, due to small particles. multiple cloud layers and clouds with specular reflections can pose problems for lidar. more advanced measurement techniques are suggested to solve these problems. an angle scanning lidar can, for example, detect specular reflections, while using information from the radars doppler velocity spectrum may help to detect clouds during rain.
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.
the transiting dust clouds that orbit the white dwarf j0328 - 1219 are devoid of small particles ( < 0. 1 micron ). observations show that fade amount doesn ' t depend on wavelength. this finding resembles a similar observation for white dwarf wd 1145 + 017, but the explanations for an absence of small particles in the two white dwarf systems may differ due to their different distances from the star.
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
a bose star passing through cold molecular clouds may capture atoms, molecules and dust particles. the observational signature of such an event would be a relatively small amount of matter that is gravitationally bound. this binding may actually be provided by invisible dark matter forming the bose star. we may expect a relative excess of heavier atoms, molecules, and solid dust compared to the content of giant cold molecular clouds since the velocity of heavy particles at a given temperature is lower and it may be small compared to the escape velocity, $ v _ \ mathrm { rms } = \ sqrt { 3k _ \ mathrm { b } t / m _ \ mathrm { gas } } \ ll v _ \ mathrm { esc } = \ sqrt { 2gm / r } $. finally, the velocity of this captured matter cloud may correlate with the expected velocity of free dark matter particles ( e. g. expected axion wind velocity relative to earth ).
haptic technology ( also kinaesthetic communication or 3d touch ) is technology that can create an experience of touch by applying forces, vibrations, or motions to the user. these technologies can be used to create virtual objects in a computer simulation, to control virtual objects, and to enhance remote control of machines and devices ( telerobotics ). haptic devices may incorporate tactile sensors that measure forces exerted by the user on the interface. the word haptic, from the ancient greek : απτικος ( haptikos ), means " tactile, pertaining to the sense of touch ". simple haptic devices are common in the form of game controllers, joysticks, and steering wheels. haptic technology facilitates investigation of how the human sense of touch works by allowing the creation of controlled haptic virtual objects. vibrations and other tactile cues have also become an integral part of mobile user experience and interface design. most researchers distinguish three sensory systems related to sense of touch in humans : cutaneous, kinaesthetic and haptic. all perceptions mediated by cutaneous and kinaesthetic sensibility are referred to as tactual perception. the sense of touch may be classified as passive and active, and the term " haptic " is often associated with active touch to communicate or recognize objects. = = history = = one of the earliest applications of haptic technology was in large aircraft that use servomechanism systems to operate control surfaces. in lighter aircraft without servo systems, as the aircraft approached a stall, the aerodynamic buffeting ( vibrations ) was felt in the pilot ' s controls. this was a useful warning of a dangerous flight condition. servo systems tend to be " one - way ", meaning external forces applied aerodynamically to the control surfaces are not perceived at the controls, resulting in the lack of this important sensory cue. to address this, the missing normal forces are simulated with springs and weights. the angle of attack is measured, and as the critical stall point approaches a stick shaker is engaged which simulates the response of a simpler control system. alternatively, the servo force may be measured and the signal directed to a servo system on the control, also known as force feedback. force feedback has been implemented experimentally in some excavators and is useful when excavating mixed material such as large rocks embedded in silt or clay. it allows the operator to " feel " and work around unseen obstacles. in the 1960s, paul bach -
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 drilling at grade, although this can be problematic with deep caissons, as unsupported excavations can collapse before the caisson form can be inserted. in this manner, the earth placed around the empty caisson form provides stability and strength, allowing concrete to be poured with fewer complications and with less risk of a
Question: What is the cloud of brown dust-like power that escapes when a puffball fungus is touched?
A) seeds
B) ions
C) spores
D) pollon
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C) spores
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Context:
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 ) – 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
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
##ian period, several groups, including the lycopods, sphenophylls and progymnosperms, had independently evolved " megaspory " – 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
##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 " – 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
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 – 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 – 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.
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
##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 " – 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
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 – 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 – 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
sugar ) for export to the rest of the plant. unlike in animals ( which lack chloroplasts ), plants and their eukaryote relatives have delegated many biochemical roles to their chloroplasts, including synthesising all their fatty acids, and most amino acids. the fatty acids that chloroplasts make are used for many things, such as providing material to build cell membranes out of and making the polymer cutin which is found in the plant cuticle that protects land plants from drying out. plants synthesise a number of unique polymers like the polysaccharide molecules cellulose, pectin and xyloglucan from which the land plant cell wall is constructed. vascular land plants make lignin, a polymer used to strengthen the secondary cell walls of xylem tracheids and vessels to keep them from collapsing when a plant sucks water through them under water stress. lignin is also used in other cell types like sclerenchyma fibres that provide structural support for a plant and is a major constituent of wood. sporopollenin is a chemically resistant polymer found in the outer cell walls of spores and pollen of land plants responsible for the survival of early land plant spores and the pollen of seed plants in the fossil record. it is widely regarded as a marker for the start of land plant evolution during the ordovician period. the concentration of carbon dioxide in the atmosphere today is much lower than it was when plants emerged onto land during the ordovician and silurian periods. many monocots like maize and the pineapple and some dicots like the asteraceae have since independently evolved pathways like crassulacean acid metabolism and the c4 carbon fixation pathway for photosynthesis which avoid the losses resulting from photorespiration in the more common c3 carbon fixation pathway. these biochemical strategies are unique to land plants. = = = medicine and materials = = = phytochemistry is a branch of plant biochemistry primarily concerned with the chemical substances produced by plants during secondary metabolism. some of these compounds are toxins such as the alkaloid coniine from hemlock. others, such as the essential oils peppermint oil and lemon oil are useful for their aroma, as flavourings and spices ( e. g., capsaicin ), and in medicine as pharmaceuticals as in opium from opium poppies. many medicinal and recreational drugs, such as tetrahydrocannabino
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.
Question: What are the cone-like structures that contain sporangia called?
A) strobili
B) gametes
C) medulla
D) contrail
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A) strobili
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Context:
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. 02214076×1023 particles ( atoms, molecules, ions, or electrons ), where the number of particles per mole is known as the avogadro constant. molar concentration is
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
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 – 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. 02214076×1023 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
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
it is believed that there may have been a large number of black holes formed in the very early universe. these would have quantised masses. a charged ` ` elementary black hole ' ' ( with the minimum possible mass ) can capture electrons, protons and other charged particles to form a ` ` black hole atom ' '. we find the spectrum of such an object with a view to laboratory and astronomical observation of them, and estimate the lifetime of the bound states. there is no limit to the charge of the black hole, which gives us the possibility of observing z > 137 bound states and transitions at the lower continuum. negatively charged black holes can capture protons. for z > 1, the orbiting protons will coalesce to form a nucleus ( after beta - decay of some protons to neutrons ), with a stability curve different to that of free nuclei. in this system there is also the distinct possibility of single quark capture. this leads to the formation of a coloured black hole that plays the role of an extremely heavy quark interacting strongly with the other two quarks. finally we consider atoms formed with much larger black holes.
set of chemical reactions with other substances. however, this definition only works well for substances that are composed of molecules, which is not true of many substances ( see below ). molecules are typically a set of atoms bound together by covalent bonds, such that the structure is electrically neutral and all valence electrons are paired with other electrons either in bonds or in lone pairs. thus, molecules exist as electrically neutral units, unlike ions. when this rule is broken, giving the " molecule " a charge, the result is sometimes named a molecular ion or a polyatomic ion. however, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well - separated form, such as a directed beam in a vacuum in a mass spectrometer. charged polyatomic collections residing in solids ( for example, common sulfate or nitrate ions ) are generally not considered " molecules " in chemistry. some molecules contain one or more unpaired electrons, creating radicals. most radicals are comparatively reactive, but some, such as nitric oxide ( no ) can be stable. the " inert " or noble gas elements ( helium, neon, argon, krypton, xenon and radon ) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals. however, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the earth are chemical compounds without molecules. these other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. examples of such substances are mineral salts ( such as table salt ), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite. one of the main characteristics of a molecule is its geometry often called its structure. while the structure of diatomic, triatomic or tetra - atomic molecules may be trivial, ( linear, angular pyramidal etc. ) the structure of polyatomic molecules, that are constituted of more than six atoms ( of several elements ) can be crucial for its chemical nature.
an important question of theoretical physics is whether sound is able to propagate in vacuums at all and if this is the case, then it must lead to the reinterpretation of one zero - restmass particle which corresponds to vacuum - sound waves. taking the electron - neutrino as the corresponding particle, its observed non - vanishing rest - energy may only appear for neutrino - propagation inside material media. the idea may also influence the physics of dense matter, restricting the maximum speed of sound, both in vacuums and in matter to the speed of light.
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 – 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
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
Question: What are considered to be the smallest particles of matter?
A) atoms
B) cells
C) ions
D) molecules
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A) atoms
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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 – civil works program river morphology and stream restoration references
##ediment to up - stream navigation, and there are generally variations in water level, and when the discharge becomes small in the dry season. it is impossible to maintain a sufficient depth of water in the low - water channel. the possibility to secure uniformity of depth in a river by lowering the shoals obstructing the channel depends on the nature of the shoals. a soft shoal in the bed of a river is due to deposit from a diminution in velocity of flow, produced by a reduction in fall and by a widening of the channel, or to a loss in concentration of the scour of the main current in passing over from one concave bank to the next on the opposite side. the lowering of such a shoal by dredging merely effects a temporary deepening, for it soon forms again from the causes which produced it. the removal, moreover, of the rocky obstructions at rapids, though increasing the depth and equalizing the flow at these places, produces a lowering of the river above the rapids by facilitating the efflux, which may result in the appearance of fresh shoals at the low stage of the river. where, however, narrow rocky reefs or other hard shoals stretch across the bottom of a river and present obstacles to the erosion by the current of the soft materials forming the bed of the river above and below, their removal may result in permanent improvement by enabling the river to deepen its bed by natural scour. the capability of a river to provide a waterway for navigation during the summer or throughout the dry season depends on the depth that can be secured in the channel at the lowest stage. the problem in the dry season is the small discharge and deficiency in scour during this period. a typical solution is to restrict the width of the low - water channel, concentrate all of the flow in it, and also to fix its position so that it is scoured out every year by the floods which follow the deepest part of the bed along the line of the strongest current. this can be effected by closing subsidiary low - water channels with dikes across them, and narrowing the channel at the low stage by low - dipping cross dikes extending from the river banks down the slope and pointing slightly up - stream so as to direct the water flowing over them into a central channel. = = estuarine works = = the needs of navigation may also require that a stable, continuous, navigable channel is prolonged from the navigable river to deep water at the mouth of the estuary. the interaction of river
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 – civil works program river morphology and stream restoration references - wildland hydrology at the library of congress web archives ( archived 2002 - 08 - 13 )
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
forming another gaseous material. this is known as the chemical part of reactive ion etching. there is also a physical part, which is similar to the sputtering deposition process. if the ions have high enough energy, they can knock atoms out of the material to be etched without a chemical reaction. it is a very complex task to develop dry etch processes that balance chemical and physical etching, since there are many parameters to adjust. by changing the balance it is possible to influence the anisotropy of the etching, since the chemical part is isotropic and the physical part highly anisotropic the combination can form sidewalls that have shapes from rounded to vertical. deep reactive ion etching ( drie ) is a special subclass of rie that is growing in popularity. in this process, etch depths of hundreds of micrometers are achieved with almost vertical sidewalls. the primary technology is based on the so - called " bosch process ", named after the german company robert bosch, which filed the original patent, where two different gas compositions alternate in the reactor. currently, there are two variations of the drie. the first variation consists of three distinct steps ( the original bosch process ) while the second variation only consists of two steps. in the first variation, the etch cycle is as follows : ( i ) sf6 isotropic etch ; ( ii ) c4f8 passivation ; ( iii ) sf6 anisotropic etch for floor cleaning. in the 2nd variation, steps ( i ) and ( iii ) are combined. both variations operate similarly. the c4f8 creates a polymer on the surface of the substrate, and the second gas composition ( sf6 and o2 ) etches the substrate. the polymer is immediately sputtered away by the physical part of the etching, but only on the horizontal surfaces and not the sidewalls. since the polymer only dissolves very slowly in the chemical part of the etching, it builds up on the sidewalls and protects them from etching. as a result, etching aspect ratios of 50 to 1 can be achieved. the process can easily be used to etch completely through a silicon substrate, and etch rates are 3 – 6 times higher than wet etching. after preparing a large number of mems devices on a silicon wafer, individual dies have to be separated, which is called die preparation in semiconductor technology. for some applications, the separation is preceded by wafer backgrin
to that of a flat crack through the plain matrix. the magnitude of the toughening is determined by the mismatch strain caused by thermal contraction incompatibility and the microfracture resistance of the particle / matrix interface. the toughening becomes noticeable with a narrow size distribution of appropriately sized particles, and researchers typically accept that deflection effects in materials with roughly equiaxial grains may increase the fracture toughness by about twice the grain boundary value. the model reveals that the increase in toughness is dependent on particle shape and the volume fraction of the second phase, with the most effective morphology being the rod of high aspect ratio, which can account for a fourfold increase in fracture toughness. the toughening arises primarily from the twist of the crack front between particles, as indicated by deflection profiles. disc - shaped particles and spheres are less effective in toughening. fracture toughness, regardless of morphology, is determined by the twist of the crack front at its most severe configuration, rather than the initial tilt of the crack front. only for disc - shaped particles does the initial tilting of the crack front provide significant toughening ; however, the twist component still overrides the tilt - derived toughening. additional important features of the deflection analysis include the appearance of asymptotic toughening for the three morphologies at volume fractions in excess of 0. 2. it is also noted that a significant influence on the toughening by spherical particles is exerted by the interparticle spacing distribution ; greater toughening is afforded when spheres are nearly contacting such that twist angles approach π / 2. these predictions provide the basis for the design of high - toughness two - phase ceramic materials. the ideal second phase, in addition to maintaining chemical compatibility, should be present in amounts of 10 to 20 volume percent. greater amounts may diminish the toughness increase due to overlapping particles. particles with high aspect ratios, especially those with rod - shaped morphologies, are most suitable for maximum toughening. this model is often used to determine the factors that contribute to the increase in fracture toughness in ceramics which is ultimately useful in the development of advanced ceramic materials with improved performance. = = theory of chemical processing = = = = = microstructural uniformity = = = in the processing of fine ceramics, the irregular particle sizes and shapes in a typical powder often lead to non - uniform packing morphologies that result in packing density variations in the powder compact. uncontrolled aggl
the utility of jet spectroscopy at the lhc is compromised by the existence of multiple interactions within a bunch crossing. the energy deposits from these interactions at the design luminosity of the lhc may degrade the dijet mass resolution unless great care is taken. energy clusters making up the jet can be required to have an energy flow with respect to the jet axis which resembles qcd. in addition, subsidiary information such as the jet mass or the out of jet cone mass or transverse momentum can be deployed so as to alleviate the adverse effects of pileup.
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
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
Question: The mechanics of dynein-based bending involve a process that resembles what?
A) jumping
B) standing
C) running
D) walking
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D) walking
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Context:
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.
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 – 139 ad ) to
##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 " – 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
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 – such as those evolved separately in different groups ( homoplasies ) or those left over from ancestors ( plesiomorphies ) – 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
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.
quantum mechanics is nonlocal. classical mechanics is local. consequently classical mechanics can not explain all quantum phenomena. conversely, it is cumbersome to use quantum mechanics to describe classical phenomena. not only are the computations more complex, but - and this is the main point - it is conceptually more difficult : one has to argue that nonlocality, entanglement and the principle of superposition can be set aside when crossing the " quantum $ \ rightarrow $ classical " border. clearly, nonlocality, entanglement and the principle of superposition should become irrelevant in the classical limit. but why should one argue? shouldn ' t it just come out of the equations? does it come out of the equations? this contribution is about the last question. and the answer is : " it depends on which equation ".
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 – 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
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 – such as those evolved separately in different groups ( homoplasies ) or those left over from ancestors ( plesiomorphies ) – 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
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 π 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 π 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
two planetary nebulae are shown to belong to the sagittarius dwarf galaxy, on the basis of their radial velocities. this is only the second dwarf spheroidal galaxy, after fornax, found to contain planetary nebulae. their existence confirms that this galaxy is at least as massive as the fornax dwarf spheroidal which has a single planetary nebula, and suggests a mass of a few times 10 * * 7 solar masses. the two planetary nebulae are located along the major axis of the galaxy, near the base of the tidal tail. there is a further candidate, situated at a very large distance along the direction of the tidal tail, for which no velocity measurement is available. the location of the planetary nebulae and globular clusters of the sagittarius dwarf galaxy suggests that a significant fraction of its mass is contained within the tidal tail.
Question: What type of creature is a scallop?
A) insect
B) mollusk
C) vertabrate
D) algae
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B) mollusk
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Context:
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 – beneficial uses
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.
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.
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.
astronomically, there are viable mechanisms for distributing organic material throughout the milky way. biologically, the destructive effects of ultraviolet light and cosmic rays means that the majority of organisms arrive broken and dead on a new world. the likelihood of conventional forms of panspermia must therefore be considered low. however, the information content of dam - aged biological molecules might serve to seed new life ( necropanspermia ).
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
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
observed solar neutrino fluxes are employed to constrain the interior composition of the sun. including the effects of neutrino flavor mixing, the results from homestake, sudbury, and gallium experiments constrain the mg, si, and fe abundances in the solar interior to be within a factor 0. 89 to 1. 34 of the surface values with 68 % confidence. if the o and / or ne abundances are increased in the interior to resolve helioseismic discrepancies with recent standard solar models, then the nominal interior mg, si, and fe abundances are constrained to a range of 0. 83 to 1. 24 relative to the surface. additional research is needed to determine whether the sun ' s interior is metal poor relative to its surface.
the value of excess charge in the kernel of massive body ( and the opposite in sign excess charge at the surface ) caused by the influence of gravitational forces is determined.
Question: The risk of what is raised by overexposure to the sun?
A) flux cancer
B) brain cancer
C) particle cancer
D) skin cancer
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D) skin cancer
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Context:
##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
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
i transform the trapdoor problem of hfe into a linear algebra problem.
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 – 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
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
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 – 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
unitary recordings in freely - moving pulse weakly electric fish suggest spike timing encoding of electrosensory signals
teeth. forensic optometry is the study of glasses and other eyewear relating to crime scenes and criminal investigations. forensic pathology is a field in which the principles of medicine and pathology are applied to determine a cause of death or injury in the context of a legal inquiry. forensic podiatry is an application of the study of feet footprint or footwear and their traces to analyze scene of crime and to establish personal identity in forensic examinations. forensic psychiatry is a specialized branch of psychiatry as applied to and based on scientific criminology. forensic psychology is the study of the mind of an individual, using forensic methods. usually it determines the circumstances behind a criminal ' s behavior. forensic seismology is the study of techniques to distinguish the seismic signals generated by underground nuclear explosions from those generated by earthquakes. forensic serology is the study of the body fluids. forensic social work is the specialist study of social work theories and their applications to a clinical, criminal justice or psychiatric setting. practitioners of forensic social work connected with the criminal justice system are often termed social supervisors, whilst the remaining use the interchangeable titles forensic social worker, approved mental health professional or forensic practitioner and they conduct specialist assessments of risk, care planning and act as an officer of the court. forensic toxicology is the study of the effect of drugs and poisons on / in the human body. forensic video analysis is the scientific examination, comparison and evaluation of video in legal matters. mobile device forensics is the scientific examination and evaluation of evidence found in mobile phones, e. g. call history and deleted sms, and includes sim card forensics. trace evidence analysis is the analysis and comparison of trace evidence including glass, paint, fibres and hair ( e. g., using micro - spectrophotometry ). wildlife forensic science applies a range of scientific disciplines to legal cases involving non - human biological evidence, to solve crimes such as poaching, animal abuse, and trade in endangered species. = = questionable techniques = = some forensic techniques, believed to be scientifically sound at the time they were used, have turned out later to have much less scientific merit or none. some such techniques include : comparative bullet - lead analysis was used by the fbi for over four decades, starting with the john f. kennedy assassination in 1963. the theory was that each batch of ammunition possessed a chemical makeup so distinct that a bullet could be traced back to a particular batch or even a specific box. internal studies and an outside study by the national academy of sciences found that the technique was unreliable due to
holomorphic manifolds over cayley - dickson algebras are defined and their embeddings and immersions are studied.
##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 – 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 – 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: Which artery enters the cranium through the carotid canal in the temporal bone?
A) internal carotid artery
B) external carotid
C) venal artery
D) atrial artery
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A) internal carotid artery
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Context:
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 — of which around 1 million are insects — 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 — pieces of dna that can move between cells — 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.
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 (
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 – 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
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 — of which around 1 million are insects — 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 — pieces of dna
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 – such as those evolved separately in different groups ( homoplasies ) or those left over from ancestors ( plesiomorphies ) – and derived characters, which
##yotic microorganisms. typically a few micrometers in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. bacteria were among the first life forms to appear on earth, and are present in most of its habitats. bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep biosphere of the earth ' s crust. bacteria also live in symbiotic and parasitic relationships with plants and animals. most bacteria have not been characterised, and only about 27 percent of the bacterial phyla have species that can be grown in the laboratory. archaea constitute the other domain of prokaryotic cells and were initially classified as bacteria, receiving the name archaebacteria ( in the archaebacteria kingdom ), a term that has fallen out of use. archaeal cells have unique properties separating them from the other two domains, bacteria and eukaryota. archaea are further divided into multiple recognized phyla. archaea and bacteria are generally similar in size and shape, although a few archaea have very different shapes, such as the flat and square cells of haloquadratum walsbyi. despite this morphological similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes, notably for the enzymes involved in transcription and translation. other aspects of archaeal biochemistry are unique, such as their reliance on ether lipids in their cell membranes, including archaeols. archaea use more energy sources than eukaryotes : these range from organic compounds, such as sugars, to ammonia, metal ions or even hydrogen gas. salt - tolerant archaea ( the haloarchaea ) use sunlight as an energy source, and other species of archaea fix carbon, but unlike plants and cyanobacteria, no known species of archaea does both. archaea reproduce asexually by binary fission, fragmentation, or budding ; unlike bacteria, no known species of archaea form endospores. the first observed archaea were extremophiles, living in extreme environments, such as hot springs and salt lakes with no other organisms. improved molecular detection tools led to the discovery of archaea in almost every habitat, including soil, oceans, and marshlands. archaea are particularly numerous in the oceans, and the archaea in plankton may be one of the most abundant groups of organisms on the planet. archaea are a major part of earth ' s life.
, which would exclude fungi and some algae. plant cells were derived by endosymbiosis of a cyanobacterium into an early eukaryote about one billion years ago, which gave rise to chloroplasts. the first several clades that emerged following primary endosymbiosis were aquatic and most of the aquatic photosynthetic eukaryotic organisms are collectively described as algae, which is a term of convenience as not all algae are closely related. algae comprise several distinct clades such as glaucophytes, which are microscopic freshwater algae that may have resembled in form to the early unicellular ancestor of plantae. unlike glaucophytes, the other algal clades such as red and green algae are multicellular. green algae comprise three major clades : chlorophytes, coleochaetophytes, and stoneworts. fungi are eukaryotes that digest foods outside their bodies, secreting digestive enzymes that break down large food molecules before absorbing them through their cell membranes. many fungi are also saprobes, feeding on dead organic matter, making them important decomposers in ecological systems. animals are multicellular eukaryotes. with few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and grow from a hollow sphere of cells, the blastula, during embryonic development. over 1. 5 million living animal species have been described — of which around 1 million are insects — 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 — pieces of dna that can move between cells — 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 ",
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
##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 – such as those evolved separately in different groups ( homoplasies ) or those left over from ancestors ( plesiomorphies ) – 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
groups of organisms. divisions related to the broader historical sense of botany include bacteriology, mycology ( or fungology ), and phycology – respectively, the study of bacteria, fungi, and algae – 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
Question: How are aquatic biomes often classified?
A) amount of life
B) amount of light
C) amount of salt
D) depth
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C) amount of salt
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Context:
the carbon - based biosphere has generated a system ( humans ) capable of creating technology that will result in a comparable evolutionary transition. the digital information created by humans has reached a similar magnitude to biological information in the biosphere. since the 1980s, the quantity of digital information stored has doubled about every 2. 5 years, reaching about 5 zettabytes in 2014 ( 5×1021 bytes ). in biological terms, there are 7. 2 billion humans on the planet, each having a genome of 6. 2 billion nucleotides. since one byte can encode four nucleotide pairs, the individual genomes of every human on the planet could be encoded by approximately 1×1019 bytes. the digital realm stored 500 times more information than this in 2014 ( see figure ). the total amount of dna contained in all of the cells on earth is estimated to be about 5. 3×1037 base pairs, equivalent to 1. 325×1037 bytes of information. if growth in digital storage continues at its current rate of 30 – 38 % compound annual growth per year, it will rival the total information content contained in all of the dna in all of the cells on earth in about 110 years. this would represent a doubling of the amount of information stored in the biosphere across a total time period of just 150 years ". = = = implications for human society = = = in february 2009, under the auspices of the association for the advancement of artificial intelligence ( aaai ), eric horvitz chaired a meeting of leading computer scientists, artificial intelligence researchers and roboticists at the asilomar conference center in pacific grove, california. the goal was to discuss the potential impact of the hypothetical possibility that robots could become self - sufficient and able to make their own decisions. they discussed the extent to which computers and robots might be able to acquire autonomy, and to what degree they could use such abilities to pose threats or hazards. some machines are programmed with various forms of semi - autonomy, including the ability to locate their own power sources and choose targets to attack with weapons. also, some computer viruses can evade elimination and, according to scientists in attendance, could therefore be said to have reached a " cockroach " stage of machine intelligence. the conference attendees noted that self - awareness as depicted in science - fiction is probably unlikely, but that other potential hazards and pitfalls exist. frank s. robinson predicts that once humans achieve a machine with the intelligence of a human, scientific and technological problems will be tackled and solved with
) of the mass of all organisms, with calcium, phosphorus, sulfur, sodium, chlorine, and magnesium constituting essentially all the remainder. different elements can combine to form compounds such as water, which is fundamental to life. biochemistry is the study of chemical processes within and relating to living organisms. molecular biology is the branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including molecular synthesis, modification, mechanisms, and interactions. = = = water = = = life arose from the earth ' s first ocean, which formed some 3. 8 billion years ago. since then, water continues to be the most abundant molecule in every organism. water is important to life because it is an effective solvent, capable of dissolving solutes such as sodium and chloride ions or other small molecules to form an aqueous solution. once dissolved in water, these solutes are more likely to come in contact with one another and therefore take part in chemical reactions that sustain life. in terms of its molecular structure, water is a small polar molecule with a bent shape formed by the polar covalent bonds of two hydrogen ( h ) atoms to one oxygen ( o ) atom ( h2o ). because the o – 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 =
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 – 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
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 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 – 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 – carbon bonds such
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
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,
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 – 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
ultra high energy particles arrive at earth constantly. they provide a beam at energies higher than any man - made accelerator, but at a very low rate. two large experiments, the pierre auger observatory and the telescope array experiment, have been taking data for several years now covering together the whole sky. i summarize the most recent measurements from both experiments, i compare their results and, for a change, i highlight their agreements.
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 – the environments where they complete their life cycles. plant ecologists study the composition of local and regional floras, their biodiversity, genetic diversity and fitness, the adaptation of plants to their environment, and their competitive or mutualistic interactions with other species. some ecologists even rely on empirical data from indigenous people that is gathered by ethnobotanists. this information can relay a great deal of information on how the land once was thousands of years ago and how it has changed over that time. the goals of plant ecology are to understand the causes of their distribution patterns, productivity, environmental impact, evolution, and responses to environmental change. plants depend on certain edaphic ( soil ) and climatic factors in their environment but can modify these factors too. for example, they can change their environment ' s albedo, increase runoff interception, stabilise mineral soils and develop their organic content, and affect local temperature. plants compete with other organisms in their ecosystem for resources. they interact with their neighbours at a variety of spatial scales in groups, populations and communities that collectively constitute vegetation. regions with characteristic vegetation types and dominant plants as well as similar abiot
Question: What is the most abundant type of biological entity on the earth?
A) reptiles
B) insects
C) bacteria
D) viruses
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D) viruses
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Context:
invertebrates, or protozoans, the protist grouping is not a formal taxonomic group but is used for convenience. most protists are unicellular ; these are called microbial eukaryotes. plants are mainly multicellular organisms, predominantly photosynthetic eukaryotes of the kingdom plantae, which would exclude fungi and some algae. plant cells were derived by endosymbiosis of a cyanobacterium into an early eukaryote about one billion years ago, which gave rise to chloroplasts. the first several clades that emerged following primary endosymbiosis were aquatic and most of the aquatic photosynthetic eukaryotic organisms are collectively described as algae, which is a term of convenience as not all algae are closely related. algae comprise several distinct clades such as glaucophytes, which are microscopic freshwater algae that may have resembled in form to the early unicellular ancestor of plantae. unlike glaucophytes, the other algal clades such as red and green algae are multicellular. green algae comprise three major clades : chlorophytes, coleochaetophytes, and stoneworts. fungi are eukaryotes that digest foods outside their bodies, secreting digestive enzymes that break down large food molecules before absorbing them through their cell membranes. many fungi are also saprobes, feeding on dead organic matter, making them important decomposers in ecological systems. animals are multicellular eukaryotes. with few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and grow from a hollow sphere of cells, the blastula, during embryonic development. over 1. 5 million living animal species have been described — of which around 1 million are insects — 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 — pieces of dna
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 – 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
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 – 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
, 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 – 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 – 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
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 – such as those evolved separately in different groups ( homoplasies ) or those left over from ancestors ( plesiomorphies ) – and derived characters, which
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 — of which around 1 million are insects — 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,
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
excavates, stramenopiles, plants, rhizarians, amoebozoans, fungi, and animals. five of these clades are collectively known as protists, which are mostly microscopic eukaryotic organisms that are not plants, fungi, or animals. while it is likely that protists share a common ancestor ( the last eukaryotic common ancestor ), protists by themselves do not constitute a separate clade as some protists may be more closely related to plants, fungi, or animals than they are to other protists. like groupings such as algae, invertebrates, or protozoans, the protist grouping is not a formal taxonomic group but is used for convenience. most protists are unicellular ; these are called microbial eukaryotes. plants are mainly multicellular organisms, predominantly photosynthetic eukaryotes of the kingdom plantae, which would exclude fungi and some algae. plant cells were derived by endosymbiosis of a cyanobacterium into an early eukaryote about one billion years ago, which gave rise to chloroplasts. the first several clades that emerged following primary endosymbiosis were aquatic and most of the aquatic photosynthetic eukaryotic organisms are collectively described as algae, which is a term of convenience as not all algae are closely related. algae comprise several distinct clades such as glaucophytes, which are microscopic freshwater algae that may have resembled in form to the early unicellular ancestor of plantae. unlike glaucophytes, the other algal clades such as red and green algae are multicellular. green algae comprise three major clades : chlorophytes, coleochaetophytes, and stoneworts. fungi are eukaryotes that digest foods outside their bodies, secreting digestive enzymes that break down large food molecules before absorbing them through their cell membranes. many fungi are also saprobes, feeding on dead organic matter, making them important decomposers in ecological systems. animals are multicellular eukaryotes. with few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and grow from a hollow sphere of cells, the blastula, during embryonic development. over 1. 5 million living animal species have been described — of which around 1 million are insects — but it has been estimated there are over 7 million
the carbon - based biosphere has generated a system ( humans ) capable of creating technology that will result in a comparable evolutionary transition. the digital information created by humans has reached a similar magnitude to biological information in the biosphere. since the 1980s, the quantity of digital information stored has doubled about every 2. 5 years, reaching about 5 zettabytes in 2014 ( 5×1021 bytes ). in biological terms, there are 7. 2 billion humans on the planet, each having a genome of 6. 2 billion nucleotides. since one byte can encode four nucleotide pairs, the individual genomes of every human on the planet could be encoded by approximately 1×1019 bytes. the digital realm stored 500 times more information than this in 2014 ( see figure ). the total amount of dna contained in all of the cells on earth is estimated to be about 5. 3×1037 base pairs, equivalent to 1. 325×1037 bytes of information. if growth in digital storage continues at its current rate of 30 – 38 % compound annual growth per year, it will rival the total information content contained in all of the dna in all of the cells on earth in about 110 years. this would represent a doubling of the amount of information stored in the biosphere across a total time period of just 150 years ". = = = implications for human society = = = in february 2009, under the auspices of the association for the advancement of artificial intelligence ( aaai ), eric horvitz chaired a meeting of leading computer scientists, artificial intelligence researchers and roboticists at the asilomar conference center in pacific grove, california. the goal was to discuss the potential impact of the hypothetical possibility that robots could become self - sufficient and able to make their own decisions. they discussed the extent to which computers and robots might be able to acquire autonomy, and to what degree they could use such abilities to pose threats or hazards. some machines are programmed with various forms of semi - autonomy, including the ability to locate their own power sources and choose targets to attack with weapons. also, some computer viruses can evade elimination and, according to scientists in attendance, could therefore be said to have reached a " cockroach " stage of machine intelligence. the conference attendees noted that self - awareness as depicted in science - fiction is probably unlikely, but that other potential hazards and pitfalls exist. frank s. robinson predicts that once humans achieve a machine with the intelligence of a human, scientific and technological problems will be tackled and solved with
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 – 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 – paleogene extinction event 66 million years ago killed off
Question: What is the most diverse and abundant group of organisms on earth, numbering in the millions of trillions?
A) bacteria
B) pests
C) viruses
D) pathogens
|
A) bacteria
|
Context:
practice, general practice or primary care is, in many countries, the first port - of - call for patients with non - emergency medical problems. family physicians often provide services across a broad range of settings including office based practices, emergency department coverage, inpatient care, and nursing home care. medical genetics is concerned with the diagnosis and management of hereditary disorders. neurology is concerned with diseases of the nervous system. in the uk, neurology is a subspecialty of general medicine. obstetrics and gynecology ( often abbreviated as ob / gyn ( american english ) or obs & gynae ( british english ) ) are concerned respectively with childbirth and the female reproductive and associated organs. reproductive medicine and fertility medicine are generally practiced by gynecological specialists. pediatrics ( ae ) or paediatrics ( be ) is devoted to the care of infants, children, and adolescents. like internal medicine, there are many pediatric subspecialties for specific age ranges, organ systems, disease classes, and sites of care delivery. pharmaceutical medicine is the medical scientific discipline concerned with the discovery, development, evaluation, registration, monitoring and medical aspects of marketing of medicines for the benefit of patients and public health. physical medicine and rehabilitation ( or physiatry ) is concerned with functional improvement after injury, illness, or congenital disorders. podiatric medicine is the study of, diagnosis, and medical and surgical treatment of disorders of the foot, ankle, lower limb, hip and lower back. preventive medicine is the branch of medicine concerned with preventing disease. community health or public health is an aspect of health services concerned with threats to the overall health of a community based on population health analysis. psychiatry is the branch of medicine concerned with the bio - psycho - social study of the etiology, diagnosis, treatment and prevention of cognitive, perceptual, emotional and behavioral disorders. related fields include psychotherapy and clinical psychology. = = = interdisciplinary fields = = = some interdisciplinary sub - specialties of medicine include : addiction medicine deals with the treatment of addiction. aerospace medicine deals with medical problems related to flying and space travel. biomedical engineering is a field dealing with the application of engineering principles to medical practice. clinical pharmacology is concerned with how systems of therapeutics interact with patients. conservation medicine studies the relationship between human and non - human animal health, and environmental conditions. also known as ecological medicine, environmental medicine, or medical geology. disaster medicine deals with medical aspects of emergency preparedness, disaster mitigation
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
english ) ) are concerned respectively with childbirth and the female reproductive and associated organs. reproductive medicine and fertility medicine are generally practiced by gynecological specialists. pediatrics ( ae ) or paediatrics ( be ) is devoted to the care of infants, children, and adolescents. like internal medicine, there are many pediatric subspecialties for specific age ranges, organ systems, disease classes, and sites of care delivery. pharmaceutical medicine is the medical scientific discipline concerned with the discovery, development, evaluation, registration, monitoring and medical aspects of marketing of medicines for the benefit of patients and public health. physical medicine and rehabilitation ( or physiatry ) is concerned with functional improvement after injury, illness, or congenital disorders. podiatric medicine is the study of, diagnosis, and medical and surgical treatment of disorders of the foot, ankle, lower limb, hip and lower back. preventive medicine is the branch of medicine concerned with preventing disease. community health or public health is an aspect of health services concerned with threats to the overall health of a community based on population health analysis. psychiatry is the branch of medicine concerned with the bio - psycho - social study of the etiology, diagnosis, treatment and prevention of cognitive, perceptual, emotional and behavioral disorders. related fields include psychotherapy and clinical psychology. = = = interdisciplinary fields = = = some interdisciplinary sub - specialties of medicine include : addiction medicine deals with the treatment of addiction. aerospace medicine deals with medical problems related to flying and space travel. biomedical engineering is a field dealing with the application of engineering principles to medical practice. clinical pharmacology is concerned with how systems of therapeutics interact with patients. conservation medicine studies the relationship between human and non - human animal health, and environmental conditions. also known as ecological medicine, environmental medicine, or medical geology. disaster medicine deals with medical aspects of emergency preparedness, disaster mitigation and management. diving medicine ( or hyperbaric medicine ) is the prevention and treatment of diving - related problems. evolutionary medicine is a perspective on medicine derived through applying evolutionary theory. forensic medicine deals with medical questions in legal context, such as determination of the time and cause of death, type of weapon used to inflict trauma, reconstruction of the facial features using remains of deceased ( skull ) thus aiding identification. gender - based medicine studies the biological and physiological differences between the human sexes and how that affects differences in disease. health informatics is a relatively recent field that deal with the application of computers and information technology to medicine. hospice and pal
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,
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
medicine, babylonian medicine, ayurvedic medicine ( in the indian subcontinent ), classical chinese medicine ( alternative medicine ) predecessor to the modern traditional chinese medicine ), and ancient greek medicine and roman medicine. in egypt, imhotep ( 3rd millennium bce ) is the first physician in history known by name. the oldest egyptian medical text is the kahun gynaecological papyrus from around 2000 bce, which describes gynaecological diseases. the edwin smith papyrus dating back to 1600 bce is an early work on surgery, while the ebers papyrus dating back to 1500 bce is akin to a textbook on medicine. in china, archaeological evidence of medicine in chinese dates back to the bronze age shang dynasty, based on seeds for herbalism and tools presumed to have been used for surgery. the huangdi neijing, the progenitor of chinese medicine, is a medical text written beginning in the 2nd century bce and compiled in the 3rd century. in india, the surgeon sushruta described numerous surgical operations, including the earliest forms of plastic surgery. earliest records of dedicated hospitals come from mihintale in sri lanka where evidence of dedicated medicinal treatment facilities for patients are found. in greece, the ancient greek physician hippocrates, the " father of modern medicine ", laid the foundation for a rational approach to medicine. hippocrates introduced the hippocratic oath for physicians, which is still relevant and in use today, and was the first to categorize illnesses as acute, chronic, endemic and epidemic, and use terms such as, " exacerbation, relapse, resolution, crisis, paroxysm, peak, and convalescence ". the greek physician galen was also one of the greatest surgeons of the ancient world and performed many audacious operations, including brain and eye surgeries. after the fall of the western roman empire and the onset of the early middle ages, the greek tradition of medicine went into decline in western europe, although it continued uninterrupted in the eastern roman ( byzantine ) empire. most of our knowledge of ancient hebrew medicine during the 1st millennium bc comes from the torah, i. e. the five books of moses, which contain various health related laws and rituals. the hebrew contribution to the development of modern medicine started in the byzantine era, with the physician asaph the jew. = = = middle ages = = = the concept of hospital as institution to offer medical care and possibility of a cure for the patients due to the ideals of christian charity,
cortisol, corticosterone and aldosterone activate full - length glucocorticoid receptor ( gr ) from elephant shark, a cartilaginous fish belonging to the oldest group of jawed vertebrates. activation by aldosterone a mineralocorticoid, indicates partial divergence of elephant shark gr from the mr. progesterone activates elephant shark mr, but not elephant shark gr. progesterone inhibits steroid binding to elephant shark gr, but not to human gr. deletion of the n - terminal domain ( ntd ) from elephant shark gr ( truncated gr ) reduced the response to corticosteroids, while truncated and full - length elephant shark mr had similar responses to corticosteroids. chimeras of elephant shark gr ntd fused to mr dbd + lbd had increased activation by corticosteroids and progesterone compared to full - length elephant shark mr. elephant shark mr ntd fused to gr dbd + lbd had similar activation as full - length elephant shark mr, indicating that activation of human gr by the ntd evolved early in gr divergence from the mr.
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
due to a computational mistake this paper has been withdrawn.
##ian period, several groups, including the lycopods, sphenophylls and progymnosperms, had independently evolved " megaspory " – 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
Question: What kind of hormones are secreted by organs classified as gonads?
A) growth hormones
B) sex hormones
C) cortisol hormones
D) anterior hormones
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B) sex hormones
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Context:
patterned surface approximately the same as its downward etch rate, or can be anisotropic, i. e., exhibiting a smaller lateral undercut rate than its downward etch rate. such anisotropy is maximized in deep reactive ion etching. the use of the term anisotropy for plasma etching should not be conflated with the use of the same term when referring to orientation - dependent etching. the source gas for the plasma usually contains small molecules rich in chlorine or fluorine. for instance, carbon tetrachloride ( ccl4 ) etches silicon and aluminium, and trifluoromethane etches silicon dioxide and silicon nitride. a plasma containing oxygen is used to oxidize ( " ash " ) photoresist and facilitate its removal. ion milling, or sputter etching, uses lower pressures, often as low as 10−4 torr ( 10 mpa ). it bombards the wafer with energetic ions of noble gases, often ar +, which knock atoms from the substrate by transferring momentum. because the etching is performed by ions, which approach the wafer approximately from one direction, this process is highly anisotropic. on the other hand, it tends to display poor selectivity. reactive - ion etching ( rie ) operates under conditions intermediate between sputter and plasma etching ( between 10−3 and 10−1 torr ). deep reactive - ion etching ( drie ) modifies the rie technique to produce deep, narrow features. in reactive - ion etching ( rie ), the substrate is placed inside a reactor, and several gases are introduced. a plasma is struck in the gas mixture using an rf power source, which breaks the gas molecules into ions. the ions accelerate towards, and react with, the surface of the material being etched, forming another gaseous material. this is known as the chemical part of reactive ion etching. there is also a physical part, which is similar to the sputtering deposition process. if the ions have high enough energy, they can knock atoms out of the material to be etched without a chemical reaction. it is a very complex task to develop dry etch processes that balance chemical and physical etching, since there are many parameters to adjust. by changing the balance it is possible to influence the anisotropy of the etching, since the chemical part is isotropic and the physical part highly anisotropic the combination can
, and trifluoromethane etches silicon dioxide and silicon nitride. a plasma containing oxygen is used to oxidize ( " ash " ) photoresist and facilitate its removal. ion milling, or sputter etching, uses lower pressures, often as low as 10−4 torr ( 10 mpa ). it bombards the wafer with energetic ions of noble gases, often ar +, which knock atoms from the substrate by transferring momentum. because the etching is performed by ions, which approach the wafer approximately from one direction, this process is highly anisotropic. on the other hand, it tends to display poor selectivity. reactive - ion etching ( rie ) operates under conditions intermediate between sputter and plasma etching ( between 10−3 and 10−1 torr ). deep reactive - ion etching ( drie ) modifies the rie technique to produce deep, narrow features. in reactive - ion etching ( rie ), the substrate is placed inside a reactor, and several gases are introduced. a plasma is struck in the gas mixture using an rf power source, which breaks the gas molecules into ions. the ions accelerate towards, and react with, the surface of the material being etched, forming another gaseous material. this is known as the chemical part of reactive ion etching. there is also a physical part, which is similar to the sputtering deposition process. if the ions have high enough energy, they can knock atoms out of the material to be etched without a chemical reaction. it is a very complex task to develop dry etch processes that balance chemical and physical etching, since there are many parameters to adjust. by changing the balance it is possible to influence the anisotropy of the etching, since the chemical part is isotropic and the physical part highly anisotropic the combination can form sidewalls that have shapes from rounded to vertical. deep reactive ion etching ( drie ) is a special subclass of rie that is growing in popularity. in this process, etch depths of hundreds of micrometers are achieved with almost vertical sidewalls. the primary technology is based on the so - called " bosch process ", named after the german company robert bosch, which filed the original patent, where two different gas compositions alternate in the reactor. currently, there are two variations of the drie. the first variation consists of three distinct steps ( the original bosch process ) while the second variation only consists of
cobalt nanowires with a diameter in the range between 50 to 100nm can be prepared as single - crystal wires with the easy axis ( the c - axis ) perpendicular to the wire axis. the competition between the crystal anisotropy and demagnetization energy frustrates the magnetization direction. a periodic modulation of the angle between m and the wire axis yields a lower energy.
##thic, or " old stone age ", and spans all of human history up to the development of agriculture approximately 12, 000 years ago. to make a stone tool, a " core " of hard stone with specific flaking properties ( such as flint ) was struck with a hammerstone. this flaking produced sharp edges which could be used as tools, primarily in the form of choppers or scrapers. these tools greatly aided the early humans in their hunter - gatherer lifestyle to perform a variety of tasks including butchering carcasses ( and breaking bones to get at the marrow ) ; chopping wood ; cracking open nuts ; skinning an animal for its hide, and even forming other tools out of softer materials such as bone and wood. the earliest stone tools were irrelevant, being little more than a fractured rock. in the acheulian era, beginning approximately 1. 65 million years ago, methods of working these stones into specific shapes, such as hand axes emerged. this early stone age is described as the lower paleolithic. the middle paleolithic, approximately 300, 000 years ago, saw the introduction of the prepared - core technique, where multiple blades could be rapidly formed from a single core stone. the upper paleolithic, beginning approximately 40, 000 years ago, saw the introduction of pressure flaking, where a wood, bone, or antler punch could be used to shape a stone very finely. the end of the last ice age about 10, 000 years ago is taken as the end point of the upper paleolithic and the beginning of the epipaleolithic / mesolithic. the mesolithic technology included the use of microliths as composite stone tools, along with wood, bone, and antler tools. the later stone age, during which the rudiments of agricultural technology were developed, is called the neolithic period. during this period, polished stone tools were made from a variety of hard rocks such as flint, jade, jadeite, and greenstone, largely by working exposures as quarries, but later the valuable rocks were pursued by tunneling underground, the first steps in mining technology. the polished axes were used for forest clearance and the establishment of crop farming and were so effective as to remain in use when bronze and iron appeared. these stone axes were used alongside a continued use of stone tools such as a range of projectiles, knives, and scrapers, as well as tools, made from organic materials such as wood, bone, and antler. stone age cultures
of tool usage was found in ethiopia within the great rift valley, dating back to 2. 5 million years ago. the earliest methods of stone tool making, known as the oldowan " industry ", date back to at least 2. 3 million years ago. this era of stone tool use is called the paleolithic, or " old stone age ", and spans all of human history up to the development of agriculture approximately 12, 000 years ago. to make a stone tool, a " core " of hard stone with specific flaking properties ( such as flint ) was struck with a hammerstone. this flaking produced sharp edges which could be used as tools, primarily in the form of choppers or scrapers. these tools greatly aided the early humans in their hunter - gatherer lifestyle to perform a variety of tasks including butchering carcasses ( and breaking bones to get at the marrow ) ; chopping wood ; cracking open nuts ; skinning an animal for its hide, and even forming other tools out of softer materials such as bone and wood. the earliest stone tools were irrelevant, being little more than a fractured rock. in the acheulian era, beginning approximately 1. 65 million years ago, methods of working these stones into specific shapes, such as hand axes emerged. this early stone age is described as the lower paleolithic. the middle paleolithic, approximately 300, 000 years ago, saw the introduction of the prepared - core technique, where multiple blades could be rapidly formed from a single core stone. the upper paleolithic, beginning approximately 40, 000 years ago, saw the introduction of pressure flaking, where a wood, bone, or antler punch could be used to shape a stone very finely. the end of the last ice age about 10, 000 years ago is taken as the end point of the upper paleolithic and the beginning of the epipaleolithic / mesolithic. the mesolithic technology included the use of microliths as composite stone tools, along with wood, bone, and antler tools. the later stone age, during which the rudiments of agricultural technology were developed, is called the neolithic period. during this period, polished stone tools were made from a variety of hard rocks such as flint, jade, jadeite, and greenstone, largely by working exposures as quarries, but later the valuable rocks were pursued by tunneling underground, the first steps in mining technology. the polished axes were used for forest clearance and the establishment of crop
plasma etching should not be conflated with the use of the same term when referring to orientation - dependent etching. the source gas for the plasma usually contains small molecules rich in chlorine or fluorine. for instance, carbon tetrachloride ( ccl4 ) etches silicon and aluminium, and trifluoromethane etches silicon dioxide and silicon nitride. a plasma containing oxygen is used to oxidize ( " ash " ) photoresist and facilitate its removal. ion milling, or sputter etching, uses lower pressures, often as low as 10−4 torr ( 10 mpa ). it bombards the wafer with energetic ions of noble gases, often ar +, which knock atoms from the substrate by transferring momentum. because the etching is performed by ions, which approach the wafer approximately from one direction, this process is highly anisotropic. on the other hand, it tends to display poor selectivity. reactive - ion etching ( rie ) operates under conditions intermediate between sputter and plasma etching ( between 10−3 and 10−1 torr ). deep reactive - ion etching ( drie ) modifies the rie technique to produce deep, narrow features. in reactive - ion etching ( rie ), the substrate is placed inside a reactor, and several gases are introduced. a plasma is struck in the gas mixture using an rf power source, which breaks the gas molecules into ions. the ions accelerate towards, and react with, the surface of the material being etched, forming another gaseous material. this is known as the chemical part of reactive ion etching. there is also a physical part, which is similar to the sputtering deposition process. if the ions have high enough energy, they can knock atoms out of the material to be etched without a chemical reaction. it is a very complex task to develop dry etch processes that balance chemical and physical etching, since there are many parameters to adjust. by changing the balance it is possible to influence the anisotropy of the etching, since the chemical part is isotropic and the physical part highly anisotropic the combination can form sidewalls that have shapes from rounded to vertical. deep reactive ion etching ( drie ) is a special subclass of rie that is growing in popularity. in this process, etch depths of hundreds of micrometers are achieved with almost vertical sidewalls. the primary technology is based on the
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
##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
##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
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.
Question: An oxy-acetylene torch is an effective way to cut what?
A) wood
B) plastic
C) metal
D) coal
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C) metal
|
Context:
within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions. cell membranes also contain membrane proteins, including integral membrane proteins that go across the membrane serving as membrane transporters, and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes shaping the cell. cell membranes are involved in various cellular processes such as cell adhesion, storing electrical energy, and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall, glycocalyx, and cytoskeleton. within the cytoplasm of a cell, there are many biomolecules such as proteins and nucleic acids. in addition to biomolecules, eukaryotic cells have specialized structures called organelles that have their own lipid bilayers or are spatially units. these organelles include the cell nucleus, which contains most of the cell ' s dna, or mitochondria, which generate adenosine triphosphate ( atp ) to power cellular processes. other organelles such as endoplasmic reticulum and golgi apparatus play a role in the synthesis and packaging of proteins, respectively. biomolecules such as proteins can be engulfed by lysosomes, another specialized organelle. plant cells have additional organelles that distinguish them from animal cells such as a cell wall that provides support for the plant cell, chloroplasts that harvest sunlight energy to produce sugar, and vacuoles that provide storage and structural support as well as being involved in reproduction and breakdown of plant seeds. eukaryotic cells also have cytoskeleton that is made up of microtubules, intermediate filaments, and microfilaments, all of which provide support for the cell and are involved in the movement of the cell and its organelles. in terms of their structural composition, the microtubules are made up of tubulin ( e. g., α - tubulin and β - tubulin ) whereas intermediate filaments are made up of fibrous proteins. microfilaments are made up of actin molecules that interact with
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., α - tubulin and β - 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 — the breaking down of compounds ( for example, the breaking down of glucose to pyruvate by cellular respiration
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., α - tubulin and β - 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
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 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
. 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 a variety of bioreactors designed for 3d cell cultures. there are small plastic cylindrical chambers, as well as glass chambers, with regulated internal humidity and moisture specifically engineered for the purpose of growing cells in three dimensions. the bioreactor uses bioactive synthetic materials such as polyethylene terephthalate membranes to surround the spheroid cells in an environment that maintains high levels of nutrients. they are easy to open and close, so that cell spheroids can be removed for testing, yet the chamber is able to maintain 100 % humidity throughout. this humidity is important to achieve maximum cell growth and function. the bioreactor chamber is part of a larger device that rotates to ensure equal cell growth in each direction across three dimensions. quinxell technologies now under quintech life sciences from singapore has developed a bioreactor known as the tisxell biaxial bioreactor which is specially designed for the purpose of tissue engineering. it is the first bioreactor in the world to have a spherical glass chamber with biaxial rotation ; specifically to mimic the rotation of the fetus in the womb ; which provides a conducive environment for the growth of tissues. multiple forms of mechanical stimulation have also been combined into a single bioreactor. using gene expression analysis, one academic study found that applying a combination of cyclic strain and ultrasound stimulation to pre - osteoblast cells in a bioreactor accelerated matrix maturation and differentiation. the technology of this combined stimulation bioreactor could be used to grow bone cells more quickly and effectively in future clinical stem cell therapies. mc2 biotek has also developed a bioreactor known as prototissue that uses gas exchange to maintain high oxygen levels within the cell chamber ; improving upon previous bioreactors, since the higher oxygen levels help the cell grow and undergo normal cell respiration. active areas of research on bioreactors includes increasing production scale and refining the physiological environment, both of which could improve the efficiency and efficacy of bioreactors in research or clinical use. bioreactors are currently used to study, among other things, cell and tissue level therapies, cell and tissue response to specific physiological environment changes, and development of disease and injury. = = = long fiber generation = = = in 2013, a group from the university of tokyo developed cell laden fibers up to a meter in length and on the order of 100 μm in size. these fibers were created using a microfluidic device that forms a
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
the surface of the membrane, retentate is removed from the same side further downstream, whereas the permeate flow is tracked on the other side. in dead - end filtration, the direction of the fluid flow is normal to the membrane surface. both flow geometries offer some advantages and disadvantages. generally, dead - end filtration is used for feasibility studies on a laboratory scale. the dead - end membranes are relatively easy to fabricate which reduces the cost of the separation process. the dead - end membrane separation process is easy to implement and the process is usually cheaper than cross - flow membrane filtration. the dead - end filtration process is usually a batch - type process, where the filtering solution is loaded ( or slowly fed ) into the membrane device, which then allows passage of some particles subject to the driving force. the main disadvantage of dead - end filtration is the extensive membrane fouling and concentration polarization. the fouling is usually induced faster at higher driving forces. membrane fouling and particle retention in a feed solution also builds up a concentration gradients and particle backflow ( concentration polarization ). the tangential flow devices are more cost and labor - intensive, but they are less susceptible to fouling due to the sweeping effects and high shear rates of the passing flow. the most commonly used synthetic membrane devices ( modules ) are flat sheets / plates, spiral wounds, and hollow fibers. flat membranes used in filtration and separation processes can be enhanced with surface patterning, where microscopic structures are introduced to improve performance. these patterns increase surface area, optimize water flow, and reduce fouling, leading to higher permeability and longer membrane lifespan. research has shown that such modifications can significantly enhance efficiency in water purification, energy applications, and industrial separations. flat plates are usually constructed as circular thin flat membrane surfaces to be used in dead - end geometry modules. spiral wounds are constructed from similar flat membranes but in the form of a " pocket " containing two membrane sheets separated by a highly porous support plate. several such pockets are then wound around a tube to create a tangential flow geometry and to reduce membrane fouling. hollow fiber modules consist of an assembly of self - supporting fibers with dense skin separation layers, and a more open matrix helping to withstand pressure gradients and maintain structural integrity. the hollow fiber modules can contain up to 10, 000 fibers ranging from 200 to 2500 μm in diameter ; the main advantage of hollow fiber modules is the very large surface area within
##ration fuel cell operations in a temperature gradient membrane distillation = = membrane shapes and flow geometries = = there are two main flow configurations of membrane processes : cross - flow ( or tangential flow ) and dead - end filtrations. in cross - flow filtration the feed flow is tangential to the surface of the membrane, retentate is removed from the same side further downstream, whereas the permeate flow is tracked on the other side. in dead - end filtration, the direction of the fluid flow is normal to the membrane surface. both flow geometries offer some advantages and disadvantages. generally, dead - end filtration is used for feasibility studies on a laboratory scale. the dead - end membranes are relatively easy to fabricate which reduces the cost of the separation process. the dead - end membrane separation process is easy to implement and the process is usually cheaper than cross - flow membrane filtration. the dead - end filtration process is usually a batch - type process, where the filtering solution is loaded ( or slowly fed ) into the membrane device, which then allows passage of some particles subject to the driving force. the main disadvantage of dead - end filtration is the extensive membrane fouling and concentration polarization. the fouling is usually induced faster at higher driving forces. membrane fouling and particle retention in a feed solution also builds up a concentration gradients and particle backflow ( concentration polarization ). the tangential flow devices are more cost and labor - intensive, but they are less susceptible to fouling due to the sweeping effects and high shear rates of the passing flow. the most commonly used synthetic membrane devices ( modules ) are flat sheets / plates, spiral wounds, and hollow fibers. flat membranes used in filtration and separation processes can be enhanced with surface patterning, where microscopic structures are introduced to improve performance. these patterns increase surface area, optimize water flow, and reduce fouling, leading to higher permeability and longer membrane lifespan. research has shown that such modifications can significantly enhance efficiency in water purification, energy applications, and industrial separations. flat plates are usually constructed as circular thin flat membrane surfaces to be used in dead - end geometry modules. spiral wounds are constructed from similar flat membranes but in the form of a " pocket " containing two membrane sheets separated by a highly porous support plate. several such pockets are then wound around a tube to create a tangential flow geometry and to reduce membrane fouling. hollow fiber modules consist of an
Question: What are the infoldings of the inner membrane called?
A) brickle
B) ceranae
C) lineage
D) cristae
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D) cristae
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Context:
and nucleotides. carbohydrates include monomers and polymers of sugars. lipids are the only class of macromolecules that are not made up of polymers. they include steroids, phospholipids, and fats, largely nonpolar and hydrophobic ( water - repelling ) substances. proteins are the most diverse of the macromolecules. they include enzymes, transport proteins, large signaling molecules, antibodies, and structural proteins. the basic unit ( or monomer ) of a protein is an amino acid. twenty amino acids are used in proteins. nucleic acids are polymers of nucleotides. their function is to store, transmit, and express hereditary information. = = cells = = cell theory states that cells are the fundamental units of life, that all living things are composed of one or more cells, and that all cells arise from preexisting cells through cell division. most cells are very small, with diameters ranging from 1 to 100 micrometers and are therefore only visible under a light or electron microscope. there are generally two types of cells : eukaryotic cells, which contain a nucleus, and prokaryotic cells, which do not. prokaryotes are single - celled organisms such as bacteria, whereas eukaryotes can be single - celled or multicellular. in multicellular organisms, every cell in the organism ' s body is derived ultimately from a single cell in a fertilized egg. = = = cell structure = = = every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions. cell membranes also contain membrane proteins, including integral membrane proteins that go across the membrane serving as membrane transporters, and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes shaping the cell. cell membranes are involved in various cellular processes such as cell adhesion, storing electrical energy, and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall, glycocalyx, and cytoskeleton. within the cytoplasm of a cell
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
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.
the injuries of the inundations they have been designed to prevent, as the escape of floods from the raised river must occur sooner or later. inadequate planning controls which have permitted development on floodplains have been blamed for the flooding of domestic properties. channelization was done under the auspices or overall direction of engineers employed by the local authority or the national government. one of the most heavily channelized areas in the united states is west tennessee, where every major stream with one exception ( the hatchie river ) has been partially or completely channelized. channelization of a stream may be undertaken for several reasons. one is to make a stream more suitable for navigation or for navigation by larger vessels with deep draughts. another is to restrict water to a certain area of a stream ' s natural bottom lands so that the bulk of such lands can be made available for agriculture. a third reason is flood control, with the idea of giving a stream a sufficiently large and deep channel so that flooding beyond those limits will be minimal or nonexistent, at least on a routine basis. one major reason is to reduce natural erosion ; as a natural waterway curves back and forth, it usually deposits sand and gravel on the inside of the corners where the water flows slowly, and cuts sand, gravel, subsoil, and precious topsoil from the outside corners where it flows rapidly due to a change in direction. unlike sand and gravel, the topsoil that is eroded does not get deposited on the inside of the next corner of the river. it simply washes away. = = loss of wetlands = = channelization has several predictable and negative effects. one of them is loss of wetlands. wetlands are an excellent habitat for multiple forms of wildlife, and additionally serve as a " filter " for much of the world ' s surface fresh water. another is the fact that channelized streams are almost invariably straightened. for example, the channelization of florida ' s kissimmee river has been cited as a cause contributing to the loss of wetlands. this straightening causes the streams to flow more rapidly, which can, in some instances, vastly increase soil erosion. it can also increase flooding downstream from the channelized area, as larger volumes of water traveling more rapidly than normal can reach choke points over a shorter period of time than they otherwise would, with a net effect of flood control in one area coming at the expense of aggravated flooding in another. in addition, studies have shown that stream channelization results in declines of river fish populations. : 3 - 1ff a
are commonly referred to as " cross - hatching ". phantom – ( 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 – 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 – 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 (
##ructing the channel depends on the nature of the shoals. a soft shoal in the bed of a river is due to deposit from a diminution in velocity of flow, produced by a reduction in fall and by a widening of the channel, or to a loss in concentration of the scour of the main current in passing over from one concave bank to the next on the opposite side. the lowering of such a shoal by dredging merely effects a temporary deepening, for it soon forms again from the causes which produced it. the removal, moreover, of the rocky obstructions at rapids, though increasing the depth and equalizing the flow at these places, produces a lowering of the river above the rapids by facilitating the efflux, which may result in the appearance of fresh shoals at the low stage of the river. where, however, narrow rocky reefs or other hard shoals stretch across the bottom of a river and present obstacles to the erosion by the current of the soft materials forming the bed of the river above and below, their removal may result in permanent improvement by enabling the river to deepen its bed by natural scour. the capability of a river to provide a waterway for navigation during the summer or throughout the dry season depends on the depth that can be secured in the channel at the lowest stage. the problem in the dry season is the small discharge and deficiency in scour during this period. a typical solution is to restrict the width of the low - water channel, concentrate all of the flow in it, and also to fix its position so that it is scoured out every year by the floods which follow the deepest part of the bed along the line of the strongest current. this can be effected by closing subsidiary low - water channels with dikes across them, and narrowing the channel at the low stage by low - dipping cross dikes extending from the river banks down the slope and pointing slightly up - stream so as to direct the water flowing over them into a central channel. = = estuarine works = = the needs of navigation may also require that a stable, continuous, navigable channel is prolonged from the navigable river to deep water at the mouth of the estuary. the interaction of river flow and tide needs to be modeled by computer or using scale models, moulded to the configuration of the estuary under consideration and reproducing in miniature the tidal ebb and flow and fresh - water discharge over a bed of fine sand, in which various lines of training walls can be successively inserted. the models
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 – much less than reusing channels ( which causes co - channel interference ) – 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
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
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 – 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,
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: A channel protein is an example of what type of protein?
A) choice proteins
B) component proteins
C) transport proteins
D) hemoglobin protein
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C) transport proteins
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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 – 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 – paleogene extinction event 66 million years ago killed off the non - avian dinosaurs, mammals increased rapidly in size and diversity. such mass extinctions may have accelerated evolution by providing opportunities for new groups of organisms to diversify. = = diversity = = = = = bacteria and archaea = = = bacteria are a type of cell that constitute a large domain of prokaryotic microorganisms. typically a few micrometers in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. bacteria were among the first life forms to appear on earth, and are present in most of its habitats. bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep biosphere of the earth ' s crust. bacteria also live in symbiotic and parasitic relationships with plants and animals. most bacteria have not been characterised, and only about 27 percent of the bacterial phyla have species that can be grown in the laboratory. archaea constitute the other domain of prokaryotic cells and were initially classified as bacteria, receiving the name archaebacteria ( in the archaebacteria kingdom ), a term that has fallen out of use. archaeal cells have unique properties separating them from the other two domains, bacteria and eukaryota. archaea
have evolved from the earliest emergence of life to present day. earth formed about 4. 5 billion years ago and all life on earth, both living and extinct, descended from a last universal common ancestor that lived about 3. 5 billion years ago. geologists have developed a geologic time scale that divides the history of the earth into major divisions, starting with four eons ( hadean, archean, proterozoic, and phanerozoic ), the first three of which are collectively known as the precambrian, which lasted approximately 4 billion years. each eon can be divided into eras, with the phanerozoic eon that began 539 million years ago being subdivided into paleozoic, mesozoic, and cenozoic eras. these three eras together comprise eleven periods ( cambrian, ordovician, silurian, devonian, carboniferous, permian, triassic, jurassic, cretaceous, tertiary, and quaternary ). the similarities among all known present - day species indicate that they have diverged through the process of evolution from their common ancestor. biologists regard the ubiquity of the genetic code as evidence of universal common descent for all bacteria, archaea, and eukaryotes. microbial mats of coexisting bacteria and archaea were the dominant form of life in the early archean eon and many of the major steps in early evolution are thought to have taken place in this environment. the earliest evidence of eukaryotes dates from 1. 85 billion years ago, and while they may have been present earlier, their diversification accelerated when they started using oxygen in their metabolism. later, around 1. 7 billion years ago, multicellular organisms began to appear, with differentiated cells performing specialised functions. algae - like multicellular land plants are dated back to about 1 billion years ago, although evidence suggests that microorganisms formed the earliest terrestrial ecosystems, at least 2. 7 billion years ago. microorganisms are thought to have paved the way for the inception of land plants in the ordovician period. land plants were so successful that they are thought to have contributed to the late devonian extinction event. ediacara biota appear during the ediacaran period, while vertebrates, along with most other modern phyla originated about 525 million years ago during the cambrian explosion. during the permian period, synapsids, including the ancestors of mammals, dominated the land, but most of this group became
the origins of the series of european cosmic - ray symposia are briefly described. the first meeting in the series, on hadronic interactions and extensive air showers, held in lodz, poland in 1968, was attended by the author : some memories are recounted.
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.
in 2023, 639, 300 people died in france, 35, 900 fewer than in 2022, a year of high mortality. over the last twenty years, from 2004 to 2023, january 3rd was the deadliest day, while august 15th was the least deadly one. elderly people die significantly less often in the summer. deaths are also less frequent on public holidays and sundays. finally, the risk of dying is higher on one ' s birthday, especially for young people.
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.
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.
we throw a brief glance at galois ' life, on the occasion of his 200th anniversary ( written in german ).
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.
##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 – 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 – may also be pursued through a separate plastic surgery residency track surgical critical care surgical oncology transplant surgery trauma surgery vascular surgery – 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 – 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
Question: Eight of the hottest years on record have occurred since what year?
A) 1991
B) 2002
C) 1998
D) 1997
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C) 1998
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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 – 60 mph, etc. ), its top speed, how short and quickly a car can come to a complete stop from a set speed ( e. g. 70 - 0 mph ), how much g - force a car can generate without losing grip, recorded lap - times, cornering speed, brake fade, etc. performance can also reflect the amount of control in inclement weather ( snow, ice, rain ). shift quality : shift quality is the driver ' s perception of the vehicle to an automatic transmission shift event. this is influenced by the powertrain ( internal combustion engine, transmission ), and the vehicle ( driveline, suspension, engine and powertrain mounts, etc. ) shift feel is both a tactile ( felt ) and audible ( heard ) response of the vehicle. shift quality is experienced as various events : transmission shifts are felt as an upshift at acceleration ( 1 – 2 ), or a downshift maneuver in passing ( 4 – 2 ). shift engagements of the vehicle are also evaluated, as in park to reverse, etc. durability / corrosion engineering : durability and corrosion engineering is the evaluation testing of a vehicle for its useful life. tests include mileage accumulation, severe driving conditions, and corrosive salt baths. drivability : drivability is the vehicle ' s response to general driving conditions. cold starts and stalls, rpm dips, idle response, launch hesitations and stumbles, and performance levels all contribute to the overall drivability of any given vehicle. cost : the cost of a vehicle program is typically split into the effect on the variable cost of the vehicle, and the up - front tooling and fixed costs associated with developing the vehicle. there are also costs associated with warranty reductions and marketing. program timing : to some extent programs are timed with respect to the market, and also to the production - schedules of assembly plants. any new part in the design must support the development and manufacturing schedule of the model. design for manufacturability ( dfm ) : dfm refers to designing vehicular components in such a way that they are not only feasible to manufacture, but also such that they are cost - efficient to produce while resulting in acceptable
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?
variation in total solar irradiance is thought to have little effect on the earth ' s surface temperature because of the thermal time constant - - the characteristic response time of the earth ' s global surface temperature to changes in forcing. this time constant is large enough to smooth annual variations but not necessarily variations having a longer period such as those due to solar inertial motion ; the magnitude of these surface temperature variations is estimated.
the dynamic impedance of a sphere oscillating in an elastic medium is considered. oestreicher ' s formula for the impedance of a sphere bonded to the surrounding medium can be expressed simply in terms of three lumped impedances associated with the displaced mass and the longitudinal and transverse waves. if the surface of the sphere slips while the normal velocity remains continuous, the impedance formula is modified by adjusting the definition of the transverse impedance to include the interfacial impedance.
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.
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
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 – 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 – 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 – 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
at the end of the 19th century light was regarded as an electromagnetic wave propagating in a material medium called ether. the speed c appearing in maxwell ' s wave equations was the speed of light with respect to the ether. therefore, according to the galilean addition of velocities, the speed of light in the laboratory would differ from c. the measure of such difference would reveal the motion of the laboratory ( the earth ) relative to the ether ( a sort of absolute motion ). however the earth ' s absolute motion was never evidenced. galileo addition of velocities is based on the assumption that lengths and time intervals are invariant ( independent of the state of motion ). this way of thinking the spacetime emanates from our daily experience and lies at the heart of newton ' s classical mechanics. nevertheless, in 1905 einstein defied galileo addition of velocities by postulating that light travels at the same speed c in any inertial frame. in doing so, einstein extended the principle of relativity to the electromagnetic phenomena described by maxwell ' s laws. in einstein ' s special relativity the ether does not exist and the absolute motion is devoid of meaning. the invariance of the speed of light forced the replacement of galileo transformations with lorentz transformations. thus, relativistic length contractions and time dilations entered our understanding of the spacetime. newtonian mechanics had to be reformulated, which led to the discovery of the mass - energy equivalence.
corrections are brought to an article of friesen on continued fractions of a given period.
algorithms differs from an increase in raw computation speed in two ways. first, it does not require external influence : machines designing faster hardware would still require humans to create the improved hardware, or to program factories appropriately. an ai rewriting its own source code could do so while contained in an ai box. second, as with vernor vinge ' s conception of the singularity, it is much harder to predict the outcome. while speed increases seem to be only a quantitative difference from human intelligence, actual algorithm improvements would be qualitatively different. eliezer yudkowsky compares it to the changes that human intelligence brought : humans changed the world thousands of times quicker than evolution had done, and in totally different ways. similarly, the evolution of life was a massive departure and acceleration from the previous geological rates of change, and improved intelligence could cause change to be as different again. there are substantial dangers associated with an intelligence explosion singularity originating from a recursively self - improving set of algorithms. first, the goal structure of the ai might self - modify, potentially causing the ai to optimise for something other than what was originally intended. secondly, ais could compete for the same scarce resources humankind uses to survive. while not actively malicious, ais would promote the goals of their programming, not necessarily broader human goals, and thus might crowd out humans. carl shulman and anders sandberg suggest that algorithm improvements may be the limiting factor for a singularity ; while hardware efficiency tends to improve at a steady pace, software innovations are more unpredictable and may be bottlenecked by serial, cumulative research. they suggest that in the case of a software - limited singularity, intelligence explosion would actually become more likely than with a hardware - limited singularity, because in the software - limited case, once human - level ai is developed, it could run serially on very fast hardware, and the abundance of cheap hardware would make ai research less constrained. an abundance of accumulated hardware that can be unleashed once the software figures out how to use it has been called " computing overhang ". = = criticism = = some critics, like philosophers hubert dreyfus and john searle, assert that computers or machines cannot achieve human intelligence. others, like physicist stephen hawking, object that whether machines can achieve a true intelligence or merely something similar to intelligence is irrelevant if the net result is the same. psychologist steven pinker stated in 2008 : " there is not the slightest reason to believe in a coming singularity. the fact that you can
Question: Average acceleration is the rate of change of what?
A) speed
B) velocity
C) displacement
D) direction
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B) velocity
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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
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,
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
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
##ply quickly, relatively easy to transform and can be stored at - 80 °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.
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
and the creation of genetically modified crops. = = = epigenetics = = = epigenetics is the study of heritable changes in gene function that cannot be explained by changes in the underlying dna sequence but cause the organism ' s genes to behave ( or " express themselves " ) differently. one example of epigenetic change is the marking of the genes by dna methylation which determines whether they will be expressed or not. gene expression can also be controlled by repressor proteins that attach to silencer regions of the dna and prevent that region of the dna code from being expressed. epigenetic marks may be added or removed from the dna during programmed stages of development of the plant, and are responsible, for example, for the differences between anthers, petals and normal leaves, despite the fact that they all have the same underlying genetic code. epigenetic changes may be temporary or may remain through successive cell divisions for the remainder of the cell ' s life. some epigenetic changes have been shown to be heritable, while others are reset in the germ cells. epigenetic changes in eukaryotic biology serve to regulate the process of cellular differentiation. during morphogenesis, totipotent stem cells become the various pluripotent cell lines of the embryo, which in turn become fully differentiated cells. a single fertilised egg cell, the zygote, gives rise to the many different plant cell types including parenchyma, xylem vessel elements, phloem sieve tubes, guard cells of the epidermis, etc. as it continues to divide. the process results from the epigenetic activation of some genes and inhibition of others. unlike animals, many plant cells, particularly those of the parenchyma, do not terminally differentiate, remaining totipotent with the ability to give rise to a new individual plant. exceptions include highly lignified cells, the sclerenchyma and xylem which are dead at maturity, and the phloem sieve tubes which lack nuclei. while plants use many of the same epigenetic mechanisms as animals, such as chromatin remodelling, an alternative hypothesis is that plants set their gene expression patterns using positional information from the environment and surrounding cells to determine their developmental fate. epigenetic changes can lead to paramutations, which do not follow the mendelian heritage rules. these epigenetic marks are carried from one generation to the next,
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
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
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 °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
Question: What is studied to understand gene expression patterns in cells?
A) mutations
B) protein
C) dna
D) rna
|
D) rna
|
Context:
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.
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
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. 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
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., α - tubulin and β - 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 — the breaking down of compounds ( for example, the breaking down of glucose to pyruvate by cellular respiration ) ; or anabolic — 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 — they allow a
the origins of the series of european cosmic - ray symposia are briefly described. the first meeting in the series, on hadronic interactions and extensive air showers, held in lodz, poland in 1968, was attended by the author : some memories are recounted.
; 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. 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
the rise with energy of the neutrino - - nucleon cross section implies that at energies above few tev the earth is becoming opaque to cosmic neutrinos. the neutrinos interact with the nucleons through the weak charged current, resulting into absorption, and the weak neutral current, which provides a redistribution of the neutrino energy. we mellin transform the neutrino transport equation and find its exact solution in the moment space. a simple analytical formula is provided, which describes accurately the neutrino spectrum, after the neutrinos have traversed the earth. the effect of the weak neutral current is most prominent for an initial flat neutrino spectrum and we find that at low energies ( around 1 tev ) the neutrino intensity is even enhanced.
organelles. in terms of their structural composition, the microtubules are made up of tubulin ( e. g., α - tubulin and β - 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 — the breaking down of compounds ( for example, the breaking down of glucose to pyruvate by cellular respiration ) ; or anabolic — 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 — they allow a reaction to proceed more rapidly without being consumed by it — 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
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 — a weapon which utilized fission reactions to generate far more energy than could be created with chemical explosives. the manhattan project, run by the united states with the help of the united kingdom and canada, developed multiple fission weapons which were used against japan in 1945 at hiroshima and nagasaki. during the project, the first fission reactors were developed as well, though they were primarily for weapons manufacture and did not generate electricity. in 1951, the first nuclear fission power plant was the first to produce electricity at the experimental breeder reactor no. 1 ( ebr - 1 ), in arco, idaho, ushering in the " atomic age " of more intensive human energy use. however, if the mass is critical only when the delayed neutrons are included, then the reaction can be controlled, for example by the introduction or removal of neutron absorbers. this is what allows nuclear reactors to be built. fast neutrons are not easily captured by nuclei
two neutrons, equivalent to a helium nucleus. beta decay is the release of a beta particle, a high - energy electron. gamma decay releases gamma rays, which unlike alpha and beta radiation are not matter but electromagnetic radiation of very high frequency, and therefore energy. this type of radiation is the most dangerous and most difficult to block. all three types of radiation occur naturally in certain elements. it has also become clear that the ultimate source of most terrestrial energy is nuclear, either through radiation from the sun caused by stellar thermonuclear reactions or by radioactive decay of uranium within the earth, the principal source of geothermal energy. = = = nuclear fission = = = in natural nuclear radiation, the byproducts are very small compared to the nuclei from which they originate. nuclear fission is the process of splitting a nucleus into roughly equal parts, and releasing energy and neutrons in the process. if these neutrons are captured by another unstable nucleus, they can fission as well, leading to a chain reaction. the average number of neutrons released per nucleus that go on to fission another nucleus is referred to as k. values of k larger than 1 mean that the fission reaction is releasing more neutrons than it absorbs, and therefore is referred to as a self - sustaining chain reaction. a mass of fissile material large enough ( and in a suitable configuration ) to induce a self - sustaining chain reaction is called a critical mass. when a neutron is captured by a suitable nucleus, fission may occur immediately, or the nucleus may persist in an unstable state for a short time. if there are enough immediate decays to carry on the chain reaction, the mass is said to be prompt critical, and the energy release will grow rapidly and uncontrollably, usually leading to an explosion. when discovered on the eve of world war ii, this insight led multiple countries to begin programs investigating the possibility of constructing an atomic bomb — a weapon which utilized fission reactions to generate far more energy than could be created with chemical explosives. the manhattan project, run by the united states with the help of the united kingdom and canada, developed multiple fission weapons which were used against japan in 1945 at hiroshima and nagasaki. during the project, the first fission reactors were developed as well, though they were primarily for weapons manufacture and did not generate electricity. in 1951, the first nuclear fission power plant was the first to produce electricity at the experimental breeder reactor no. 1 ( ebr - 1 ), in arco, idaho, ushering in the "
Question: Ribosomes are produced in the nucleolus, and then transported to the what?
A) cerebellum
B) nucleus
C) cytoskeleton
D) cytoplasm
|
D) cytoplasm
|
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
##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 — 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
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
= = = = = = environmental remediation = = = environmental remediation is the process through which contaminants or pollutants in soil, water and other media are removed to improve environmental quality. the main focus is the reduction of hazardous substances within the environment. some of the areas involved in environmental remediation include ; soil contamination, hazardous waste, groundwater contamination, oil, gas and chemical spills. there are three most common types of environmental remediation. these include soil, water, and sediment remediation. soil remediation consists of removing contaminants in soil, as these pose great risks to humans and the ecosystem. some examples of this are heavy metals, pesticides, and radioactive materials. depending on the contaminant the remedial processes can be physical, chemical, thermal, or biological. water remediation is one of the most important considering water is an essential natural resource. depending on the source of water there will be different contaminants. surface water contamination mainly consists of agricultural, animal, and industrial waste, as well as acid mine drainage. there has been a rise in the need for water remediation due to the increased discharge of industrial waste, leading to a demand for sustainable water solutions. the market for water remediation is expected to consistently increase to $ 19. 6 billion by 2030. sediment remediation consists of removing contaminated sediments. is it almost similar to soil remediation except it is often more sophisticated as it involves additional contaminants. to reduce the contaminants it is likely to use physical, chemical, and biological processes that help with source control, but if these processes are executed correctly, there ' s a risk of contamination resurfacing. = = = solid waste management = = = solid waste management is the purification, consumption, reuse, disposal, and treatment of solid waste that is undertaken by the government or the ruling bodies of a city / town. it refers to the collection, treatment, and disposal of non - soluble, solid waste material. solid waste is associated with both industrial, institutional, commercial and residential activities. hazardous solid waste, when improperly disposed can encourage the infestation of insects and rodents, contributing to the spread of diseases. some of the most common types of solid waste management include ; landfills, vermicomposting, composting, recycling, and incineration. however, a major barrier for solid waste management practices is the high costs associated with recycling
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
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 )
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
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 – 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
fluid dynamics video demonstrating the evolution of dynamic stall on a wind turbine blade.
##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
Question: Ecosystem dynamics include more than the flow of energy and recycling of matter. ecosystems are also dynamic because they?
A) stay the same
B) recreate exactly alike
C) change through time
D) never move
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C) change through time
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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 — 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
occurs when another transcription factor called a repressor binds to a dna sequence called an operator, which is part of an operon, to prevent transcription. repressors can be inhibited by compounds called inducers ( e. g., allolactose ), thereby allowing transcription to occur. specific genes that can be activated by inducers are called inducible genes, in contrast to constitutive genes that are almost constantly active. in contrast to both, structural genes encode proteins that are not involved in gene regulation. in addition to regulatory events involving the promoter, gene expression can also be regulated by epigenetic changes to chromatin, which is a complex of dna and protein found in eukaryotic cells. = = = genes, development, and evolution = = = development is the process by which a multicellular organism ( plant or animal ) goes through a series of changes, starting from a single cell, and taking on various forms that are characteristic of its life cycle. there are four key processes that underlie development : determination, differentiation, morphogenesis, and growth. determination sets the developmental fate of a cell, which becomes more restrictive during development. differentiation is the process by which specialized cells arise from less specialized cells such as stem cells. stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. cellular differentiation dramatically changes a cell ' s size, shape, membrane potential, metabolic activity, and responsiveness to signals, which are largely due to highly controlled modifications in gene expression and epigenetics. with a few exceptions, cellular differentiation almost never involves a change in the dna sequence itself. thus, different cells can have very different physical characteristics despite having the same genome. morphogenesis, or the development of body form, is the result of spatial differences in gene expression. a small fraction of the genes in an organism ' s genome called the developmental - genetic toolkit control the development of that organism. these toolkit genes are highly conserved among phyla, meaning that they are ancient and very similar in widely separated groups of animals. differences in deployment of toolkit genes affect the body plan and the number, identity, and pattern of body parts. among the most important toolkit genes are the hox genes. hox genes determine where repeating parts, such as the many vertebrae of snakes, will grow in a developing embryo or larva. = = evolution = = = = = evolutionary
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
their mechanical properties. = = tissue culture = = in many cases, creation of functional tissues and biological structures in vitro requires extensive culturing to promote survival, growth and inducement of functionality. in general, the basic requirements of cells must be maintained in culture, which include oxygen, ph, humidity, temperature, nutrients and osmotic pressure maintenance. tissue engineered cultures also present additional problems in maintaining culture conditions. in standard cell culture, diffusion is often the sole means of nutrient and metabolite transport. however, as a culture becomes larger and more complex, such as the case with engineered organs and whole tissues, other mechanisms must be employed to maintain the culture, such as the creation of capillary networks within the tissue. another issue with tissue culture is introducing the proper factors or stimuli required to induce functionality. in many cases, simple maintenance culture is not sufficient. growth factors, hormones, specific metabolites or nutrients, chemical and physical stimuli are sometimes required. for example, certain cells respond to changes in oxygen tension as part of their normal development, such as chondrocytes, which must adapt to low oxygen conditions or hypoxia during skeletal development. others, such as endothelial cells, respond to shear stress from fluid flow, which is encountered in blood vessels. mechanical stimuli, such as pressure pulses seem to be beneficial to all kind of cardiovascular tissue such as heart valves, blood vessels or pericardium. = = = bioreactors = = = in tissue engineering, a bioreactor is a device that attempts to simulate a physiological environment in order to promote cell or tissue growth in vitro. a physiological environment can consist of many different parameters such as temperature, pressure, oxygen or carbon dioxide concentration, or osmolality of fluid environment, and it can extend to all kinds of biological, chemical or mechanical stimuli. therefore, there are systems that may include the application of forces such as electromagnetic forces, mechanical pressures, or fluid pressures to the tissue. these systems can be two - or three - dimensional setups. bioreactors can be used in both academic and industry applications. general - use and application - specific bioreactors are also commercially available, which may provide static chemical stimulation or a combination of chemical and mechanical stimulation. cell proliferation and differentiation are largely influenced by mechanical and biochemical cues in the surrounding extracellular matrix environment. bioreactors are typically developed to replicate the specific physiological environment of the tissue being grown ( e. g., flex and fluid shearing for heart tissue growth ). this can
, 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
the universe is found to have undergone several phases in which the gravitational constant had different behaviors. during some epochs the energy density of the universe remained constant and the universe remained static. in the radiation dominated epoch the radiation field satisfies stefan ' s formula while the scale factor varies linearly with time. the model enhances the formation of the structure in the universe as observed today.
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 — 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
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
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.
##simal 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 small strain theory, small deformation theory, small displacement theory, or small displacement - gradient theory where strains and rotations are both small. for some materials, e. g. elastomers and polymers, subjected to large deformations, the engineering definition of strain is not applicable, e. g. typical engineering strains
Question: Muscle contraction requires repeated cycles of binding and what?
A) release
B) lunging
C) twisting
D) push
|
A) release
|
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 – 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 – 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
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 ) – 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
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. 02214076×1023 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
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 – 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 – 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
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. 02214076×1023 particles ( atoms, molecules, ions, or electrons ), where the number of particles per mole is known as the avogadro constant. molar concentration is
the topic of using nuclear power sources for generating energy. organic chemistry is the study of the structure, properties, composition, mechanisms, and reactions of organic compounds. an organic compound is defined as any compound based on a carbon skeleton. organic compounds can be classified, organized and understood in reactions by their functional groups, unit atoms or molecules that show characteristic chemical properties in a compound. physical chemistry is the study of the physical and fundamental basis of chemical systems and processes. in particular, the energetics and dynamics of such systems and processes are of interest to physical chemists. important areas of study include chemical thermodynamics, chemical kinetics, electrochemistry, statistical mechanics, spectroscopy, and more recently, astrochemistry. physical chemistry has large overlap with molecular physics. physical chemistry involves the use of infinitesimal calculus in deriving equations. it is usually associated with quantum chemistry and theoretical chemistry. physical chemistry is a distinct discipline from chemical physics, but again, there is very strong overlap. theoretical chemistry is the study of chemistry via fundamental theoretical reasoning ( usually within mathematics or physics ). in particular the application of quantum mechanics to chemistry is called quantum chemistry. since the end of the second world war, the development of computers has allowed a systematic development of computational chemistry, which is the art of developing and applying computer programs for solving chemical problems. theoretical chemistry has large overlap with ( theoretical and experimental ) condensed matter physics and molecular physics. other subdivisions include electrochemistry, femtochemistry, flavor chemistry, flow chemistry, immunohistochemistry, hydrogenation chemistry, mathematical chemistry, molecular mechanics, natural product chemistry, organometallic chemistry, petrochemistry, photochemistry, physical organic chemistry, polymer chemistry, radiochemistry, sonochemistry, supramolecular chemistry, synthetic chemistry, and many others. = = = interdisciplinary = = = interdisciplinary fields include agrochemistry, astrochemistry ( and cosmochemistry ), atmospheric chemistry, chemical engineering, chemical biology, chemo - informatics, environmental chemistry, geochemistry, green chemistry, immunochemistry, marine chemistry, materials science, mechanochemistry, medicinal chemistry, molecular biology, nanotechnology, oenology, pharmacology, phytochemistry, solid - state chemistry, surface science, thermochemistry, and many others. = = = industry = = = the chemical industry represents an important economic activity worldwide. the global top 50 chemical producers in 2013 had sales
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.
##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 – 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 – 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,
) of the mass of all organisms, with calcium, phosphorus, sulfur, sodium, chlorine, and magnesium constituting essentially all the remainder. different elements can combine to form compounds such as water, which is fundamental to life. biochemistry is the study of chemical processes within and relating to living organisms. molecular biology is the branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including molecular synthesis, modification, mechanisms, and interactions. = = = water = = = life arose from the earth ' s first ocean, which formed some 3. 8 billion years ago. since then, water continues to be the most abundant molecule in every organism. water is important to life because it is an effective solvent, capable of dissolving solutes such as sodium and chloride ions or other small molecules to form an aqueous solution. once dissolved in water, these solutes are more likely to come in contact with one another and therefore take part in chemical reactions that sustain life. in terms of its molecular structure, water is a small polar molecule with a bent shape formed by the polar covalent bonds of two hydrogen ( h ) atoms to one oxygen ( o ) atom ( h2o ). because the o – 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 =
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 ) – 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
Question: An important chemical compound, which supplies living things with the energy they need to survive, is composed of carbon, oxygen and atoms of what other element?
A) hydrogen
B) nitrogen
C) calcium
D) magnesium
|
A) hydrogen
|
Context:
. 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 °c up to 18 months. twelve of the forty - one cases
minimum market transparency requirements impose hedge fund ( hf ) managers to use the statement declared strategy in practice. however each declared strategy may actually origin a multiplicity of implemented management decisions. is then the " actual " strategy the same as the " announced " strategy? can the actual strategy be monitored or compared to the actual strategy of hf belonging to the same " announced " class? can the announced or actual strategy be used as a quantitative argument in the fund of funds policy? with the appropriate metric, it is possible to draw a minimum spanning tree ( mst ) to emphasize the similarity structure that could be hidden in raw correlation matrix of hf returns.
an electron inside liquid helium forms a bubble of 17 \ aa in radius. in an external magnetic field, the two - level system of a spin 1 / 2 electron is ideal for the implementation of a qubit for quantum computing. the electron spin is well isolated from other thermal reservoirs so that the qubit should have very long coherence time. by confining a chain of single electron bubbles in a linear rf quadrupole trap, a multi - bit quantum register can be implemented. all spins in the register can be initialized to the ground state either by establishing thermal equilibrium at a temperature around 0. 1 k and at a magnetic field of 1 t or by sorting the bubbles to be loaded into the trap with magnetic separation. schemes are designed to address individual spins and to do two - qubit cnot operations between the neighboring spins. the final readout can be carried out through a measurement similar to the stern - gerlach experiment.
interaction between tannin and bovine serum albumin ( bsa ) was examined by the fluorescent quenching. the process of elimination between bsa and tannin was the one of a stationary state, and the coupling coefficient was one. the working strength between the tannin and the beef serum was hydrophobic one.
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 – 139 ad ) to describe the heavens as spherical : the heavens are like a hen ' s egg and as round as a crossbow bullet ; the earth is like the yolk of the egg, and lies in the centre. this analogy with a curved egg led some modern historians, notably joseph needham, to conjecture that chinese astronomers were, after all, aware of the earth ' s sphericity. the egg reference, however, was rather meant to clarify the relative position of the flat earth to the heavens : in a passage of zhang heng ' s cosmogony not translated by needham, zhang himself says : " heaven takes its body from the yang, so it is round and in motion. earth takes its body from the yin, so it is flat and quiescent ". the point of the egg analogy is simply to stress that the earth is completely enclosed by heaven, rather than merely covered from above as the kai tian describes. chinese astronomers, many of them brilliant men by any standards, continued to think in flat - earth terms until the seventeenth century ; this surprising fact might be the starting - point for a re - examination of the apparent facility with which the idea of a spherical earth found acceptance in fifth - century bc greece. further examples cited by needham supposed to demonstrate dissenting voices from the ancient chinese consensus actually refer without exception to the earth being square, not to it being flat. accordingly, the 13th - century scholar li ye, who argued that the movements of the round heaven would be hindered by a square earth, did not advocate a spherical earth, but rather that its edge should be rounded off so as to be circular. however, needham disagrees, affirming that li ye believed the earth to be spherical, similar in shape to the heavens but much smaller. this was preconceived by the 4th - century scholar yu xi, who argued for the infinity of outer space surrounding the earth and that the latter could be either square or round, in accordance to the shape of the heavens. when chinese geographers of the 17th century, influenced by european cartography and astronomy, showed the earth as a sphere that could be circumnavigated by sailing around the globe, they
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.
##ian period, several groups, including the lycopods, sphenophylls and progymnosperms, had independently evolved " megaspory " – 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
histochemical staining of bone marrow aspirates are very useful to detect occult bone marrow metastases in patients with apparently localized prostate cancer. although immuno - cytochemistry using tumor - associated monoclonal antibodies has led to an improved ability to detect occult breast cancer cells in bone marrow aspirates and peripheral blood, further development of this method is necessary before it can be used routinely. one major drawback of immuno - cytochemistry is that only tumor - associated and not tumor - specific monoclonal antibodies are used, and as a result, some cross - reaction with normal cells can occur. in order to effectively stage breast cancer and assess the efficacy of purging regimens prior to autologous stem cell infusion, it is important to detect even small quantities of breast cancer cells. immuno - histochemical methods are ideal for this purpose because they are simple, sensitive, and quite specific. franklin et al. performed a sensitive immuno - cytochemical assay by using a combination of four monoclonal antibodies ( 260f9, 520c9, 317g5 and bre - 3 ) against tumor cell surface glycoproteins to identify breast tumour cells in bone marrow and peripheral blood. they concluded from the results that immuno - cytochemical staining of bone marrow and peripheral blood is a sensitive and simple way to detect and quantify breast cancer cells. one of the main reasons for metastatic relapse in patients with solid tumours is the early dissemination of malignant cells. the use of monoclonal antibodies ( mabs ) specific for cytokeratins can identify disseminated individual epithelial tumor cells in the bone marrow. one study reports on having developed an immuno - cytochemical procedure for simultaneous labeling of cytokeratin component no. 18 ( ck18 ) and prostate specific antigen ( psa ). this would help in the further characterization of disseminated individual epithelial tumor cells in patients with prostate cancer. the twelve control aspirates from patients with benign prostatic hyperplasia showed negative staining, which further supports the specificity of ck18 in detecting epithelial tumour cells in bone marrow. in most cases of malignant disease complicated by effusion, neoplastic cells can be easily recognized. however, in some cases, malignant cells are not so easily seen or their presence is too doubtful to call it a positive report. the use
a prediction and observational evidence for the mass of a dark matter particle are presented..
safety security assurance framework applied to two standards iec 61508 and common criteria - iso 15408
Question: What are the glands that secrete milk in a woman's breasts?
A) mammary glands
B) lactic acids
C) pituitary glands
D) primordial glands
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A) mammary glands
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Context:
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 – 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 – slower degradation, more pga – 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 – 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,
material. silicon nitride parts are used in ceramic ball bearings. their higher hardness means that they are much less susceptible to wear and can offer more than triple lifetimes. they also deform less under load meaning they have less contact with the bearing retainer walls and can roll faster. in very high speed applications, heat from friction during rolling can cause problems for metal bearings ; problems which are reduced by the use of ceramics. ceramics are also more chemically resistant and can be used in wet environments where steel bearings would rust. the major drawback to using ceramics is a significantly higher cost. in many cases their electrically insulating properties may also be valuable in bearings. in the early 1980s, toyota researched production of an adiabatic ceramic engine which can run at a temperature of over 6000 °f ( 3300 °c ). ceramic engines do not require a cooling system and hence allow a major weight reduction and therefore greater fuel efficiency. fuel efficiency of the engine is also higher at high temperature, as shown by carnot ' s theorem. in a conventional metallic engine, much of the energy released from the fuel must be dissipated as waste heat in order to prevent a meltdown of the metallic parts. despite all of these desirable properties, such engines are not in production because the manufacturing of ceramic parts in the requisite precision and durability is difficult. imperfection in the ceramic leads to cracks, which can lead to potentially dangerous equipment failure. such engines are possible in laboratory settings, but mass - production is not feasible with current technology. work is being done in developing ceramic parts for gas turbine engines. currently, even blades made of advanced metal alloys used in the engines ' hot section require cooling and careful limiting of operating temperatures. turbine engines made with ceramics could operate more efficiently, giving aircraft greater range and payload for a set amount of fuel. recently, there have been advances in ceramics which include bio - ceramics, such as dental implants and synthetic bones. hydroxyapatite, the natural mineral component of bone, has been made synthetically from a number of biological and chemical sources and can be formed into ceramic materials. orthopedic implants made from these materials bond readily to bone and other tissues in the body without rejection or inflammatory reactions. because of this, they are of great interest for gene delivery and tissue engineering scaffolds. most hydroxyapatite ceramics are very porous and lack mechanical strength and are used to coat metal orthopedic devices to aid in forming a bond to bone or as bone fillers. they are
surface. ceramics such as alumina, boron carbide and silicon carbide have been used in bulletproof vests to repel small arms rifle fire. such plates are known commonly as ballistic plates. similar material is used to protect cockpits of some military aircraft, because of the low weight of the material. silicon nitride parts are used in ceramic ball bearings. their higher hardness means that they are much less susceptible to wear and can offer more than triple lifetimes. they also deform less under load meaning they have less contact with the bearing retainer walls and can roll faster. in very high speed applications, heat from friction during rolling can cause problems for metal bearings ; problems which are reduced by the use of ceramics. ceramics are also more chemically resistant and can be used in wet environments where steel bearings would rust. the major drawback to using ceramics is a significantly higher cost. in many cases their electrically insulating properties may also be valuable in bearings. in the early 1980s, toyota researched production of an adiabatic ceramic engine which can run at a temperature of over 6000 °f ( 3300 °c ). ceramic engines do not require a cooling system and hence allow a major weight reduction and therefore greater fuel efficiency. fuel efficiency of the engine is also higher at high temperature, as shown by carnot ' s theorem. in a conventional metallic engine, much of the energy released from the fuel must be dissipated as waste heat in order to prevent a meltdown of the metallic parts. despite all of these desirable properties, such engines are not in production because the manufacturing of ceramic parts in the requisite precision and durability is difficult. imperfection in the ceramic leads to cracks, which can lead to potentially dangerous equipment failure. such engines are possible in laboratory settings, but mass - production is not feasible with current technology. work is being done in developing ceramic parts for gas turbine engines. currently, even blades made of advanced metal alloys used in the engines ' hot section require cooling and careful limiting of operating temperatures. turbine engines made with ceramics could operate more efficiently, giving aircraft greater range and payload for a set amount of fuel. recently, there have been advances in ceramics which include bio - ceramics, such as dental implants and synthetic bones. hydroxyapatite, the natural mineral component of bone, has been made synthetically from a number of biological and chemical sources and can be formed into ceramic materials. orthopedic implants made from these materials bond readily to bone and other tissues in the body without rejection or
##logous in nature, and can be used in a myriad of ways, from helping repair skeletal tissue to replenishing beta cells in diabetic patients. allogenic : cells are obtained from the body of a donor of the same species as the recipient. while there are some ethical constraints to the use of human cells for in vitro studies ( i. e. human brain tissue chimera development ), the employment of dermal fibroblasts from human foreskin demonstrates an immunologically safe and thus a viable choice for allogenic tissue engineering of the skin. xenogenic : these cells are derived isolated cells from alternate species from the recipient. a notable example of xenogeneic tissue utilization is cardiovascular implant construction via animal cells. chimeric human - animal farming raises ethical concerns around the potential for improved consciousness from implanting human organs in animals. syngeneic or isogenic : these cells describe those borne from identical genetic code. this imparts an immunologic benefit similar to autologous cell lines ( see above ). autologous cells can be considered syngenic, but the classification also extends to non - autologously derived cells such as those from an identical twin, from genetically identical ( cloned ) research models, or induced stem cells ( isc ) as related to the donor. = = = stem cells = = = stem cells are undifferentiated cells with the ability to divide in culture and give rise to different forms of specialized cells. stem cells are divided into " adult " and " embryonic " stem cells according to their source. while there is still a large ethical debate related to the use of embryonic stem cells, it is thought that another alternative source – induced pluripotent stem cells – may be useful for the repair of diseased or damaged tissues, or may be used to grow new organs. totipotent cells are stem cells which can divide into further stem cells or differentiate into any cell type in the body, including extra - embryonic tissue. pluripotent cells are stem cells which can differentiate into any cell type in the body except extra - embryonic tissue. induced pluripotent stem cells ( ipscs ) are subclass of pluripotent stem cells resembling embryonic stem cells ( escs ) that have been derived from adult differentiated cells. ipscs are created by altering the expression of transcriptional factors in adult cells until they become like embryonic stem cells. multipotent stem cells can be differentiated into any cell
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.
##able. additionally, they must be biocompatible, meaning that they do not cause any adverse effects to cells. silicone, for example, is a synthetic, non - biodegradable material commonly used as a drug delivery material, while gelatin is a biodegradable, natural material commonly used in cell - culture scaffolds the material needed for each application is different, and dependent on the desired mechanical properties of the material. tissue engineering of long bone defects for example, will require a rigid scaffold with a compressive strength similar to that of cortical bone ( 100 - 150 mpa ), which is much higher compared to a scaffold for skin regeneration. there are a few versatile synthetic materials used for many different scaffold applications. one of these commonly used materials is polylactic acid ( pla ), a synthetic polymer. pla – 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 – slower degradation, more pga – 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 – 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
the decomposition theorem is deduced from local purity.
decision making during a task, and they provide us with some insight into the ways in which those decisions may be processed. = = = brain imaging = = = brain imaging involves analyzing activity within the brain while performing various tasks. this allows us to link behavior and brain function to help understand how information is processed. different types of imaging techniques vary in their temporal ( time - based ) and spatial ( location - based ) resolution. brain imaging is often used in cognitive neuroscience. single - photon emission computed tomography and positron emission tomography. spect and pet use radioactive isotopes, which are injected into the subject ' s bloodstream and taken up by the brain. by observing which areas of the brain take up the radioactive isotope, we can see which areas of the brain are more active than other areas. pet has similar spatial resolution to fmri, but it has extremely poor temporal resolution. electroencephalography. eeg measures the electrical fields generated by large populations of neurons in the cortex by placing a series of electrodes on the scalp of the subject. this technique has an extremely high temporal resolution, but a relatively poor spatial resolution. functional magnetic resonance imaging. fmri measures the relative amount of oxygenated blood flowing to different parts of the brain. more oxygenated blood in a particular region is assumed to correlate with an increase in neural activity in that part of the brain. this allows us to localize particular functions within different brain regions. fmri has moderate spatial and temporal resolution. optical imaging. this technique uses infrared transmitters and receivers to measure the amount of light reflectance by blood near different areas of the brain. since oxygenated and deoxygenated blood reflects light by different amounts, we can study which areas are more active ( i. e., those that have more oxygenated blood ). optical imaging has moderate temporal resolution, but poor spatial resolution. it also has the advantage that it is extremely safe and can be used to study infants ' brains. magnetoencephalography. meg measures magnetic fields resulting from cortical activity. it is similar to eeg, except that it has improved spatial resolution since the magnetic fields it measures are not as blurred or attenuated by the scalp, meninges and so forth as the electrical activity measured in eeg is. meg uses squid sensors to detect tiny magnetic fields. = = = computational modeling = = = computational models require a mathematically and logically formal representation of a problem. computer models are used in the simulation and experimental verification of different
are commonly referred to as " cross - hatching ". phantom – ( 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 – 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 – 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 (
. currently, even blades made of advanced metal alloys used in the engines ' hot section require cooling and careful limiting of operating temperatures. turbine engines made with ceramics could operate more efficiently, giving aircraft greater range and payload for a set amount of fuel. recently, there have been advances in ceramics which include bio - ceramics, such as dental implants and synthetic bones. hydroxyapatite, the natural mineral component of bone, has been made synthetically from a number of biological and chemical sources and can be formed into ceramic materials. orthopedic implants made from these materials bond readily to bone and other tissues in the body without rejection or inflammatory reactions. because of this, they are of great interest for gene delivery and tissue engineering scaffolds. most hydroxyapatite ceramics are very porous and lack mechanical strength and are used to coat metal orthopedic devices to aid in forming a bond to bone or as bone fillers. they are also used as fillers for orthopedic plastic screws to aid in reducing the inflammation and increase absorption of these plastic materials. work is being done to make strong, fully dense nano crystalline hydroxyapatite ceramic materials for orthopedic weight bearing devices, replacing foreign metal and plastic orthopedic materials with a synthetic, but naturally occurring, bone mineral. ultimately these ceramic materials may be used as bone replacements or with the incorporation of protein collagens, synthetic bones. durable actinide - containing ceramic materials have many applications such as in nuclear fuels for burning excess pu and in chemically - inert sources of alpha irradiation for power supply of unmanned space vehicles or to produce electricity for microelectronic devices. both use and disposal of radioactive actinides require their immobilization in a durable host material. nuclear waste long - lived radionuclides such as actinides are immobilized using chemically - durable crystalline materials based on polycrystalline ceramics and large single crystals. alumina ceramics are widely utilized in the chemical industry due to their excellent chemical stability and high resistance to corrosion. it is used as acid - resistant pump impellers and pump bodies, ensuring long - lasting performance in transferring aggressive fluids. they are also used in acid - carrying pipe linings to prevent contamination and maintain fluid purity, which is crucial in industries like pharmaceuticals and food processing. valves made from alumina ceramics demonstrate exceptional durability and resistance to chemical attack, making them reliable for controlling the flow of corrosive liquids. =
Question: Like a thick cap covering the brain, the dura mater is a tough outer covering. the name comes from the latin for?
A) protecting mother
B) back mother
C) difficult mother
D) tough mother
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D) tough mother
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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 ) – 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
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,
= = 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 – 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 – 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 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
participates as a consumer, resource, or both in consumer – resource interactions, which form the core of food chains or food webs. there are different trophic levels within any food web, with the lowest level being the primary producers ( or autotrophs ) such as plants and algae that convert energy and inorganic material into organic compounds, which can then be used by the rest of the community. at the next level are the heterotrophs, which are the species that obtain energy by breaking apart organic compounds from other organisms. heterotrophs that consume plants are primary consumers ( or herbivores ) whereas heterotrophs that consume herbivores are secondary consumers ( or carnivores ). and those that eat secondary consumers are tertiary consumers and so on. omnivorous heterotrophs are able to consume at multiple levels. finally, there are decomposers that feed on the waste products or dead bodies of organisms. on average, the total amount of energy incorporated into the biomass of a trophic level per unit of time is about one - tenth of the energy of the trophic level that it consumes. waste and dead material used by decomposers as well as heat lost from metabolism make up the other ninety percent of energy that is not consumed by the next trophic level. = = = biosphere = = = in the global ecosystem or biosphere, matter exists as different interacting compartments, which can be biotic or abiotic as well as accessible or inaccessible, depending on their forms and locations. for example, matter from terrestrial autotrophs are both biotic and accessible to other organisms whereas the matter in rocks and minerals are abiotic and inaccessible. a biogeochemical cycle is a pathway by which specific elements of matter are turned over or moved through the biotic ( biosphere ) and the abiotic ( lithosphere, atmosphere, and hydrosphere ) compartments of earth. there are biogeochemical cycles for nitrogen, carbon, and water. = = = conservation = = = conservation biology is the study of the conservation of earth ' s biodiversity with the aim of protecting species, their habitats, and ecosystems from excessive rates of extinction and the erosion of biotic interactions. it is concerned with factors that influence the maintenance, loss, and restoration of biodiversity and the science of sustaining evolutionary processes that engender genetic, population, species, and ecosystem diversity. the concern stems from estimates suggesting that up to 50 % of all species on the planet
##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
liver glycogen. during recovery, when oxygen becomes available, nad + attaches to hydrogen from lactate to form atp. in yeast, the waste products are ethanol and carbon dioxide. this type of fermentation is known as alcoholic or ethanol fermentation. the atp generated in this process is made by substrate - level phosphorylation, which does not require oxygen. = = = photosynthesis = = = photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organism ' s metabolic activities via cellular respiration. this chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. in most cases, oxygen is released as a waste product. most plants, algae, and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of the earth ' s atmosphere, and supplies most of the energy necessary for life on earth. photosynthesis has four stages : light absorption, electron transport, atp synthesis, and carbon fixation. light absorption is the initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to proteins in the thylakoid membranes. the absorbed light energy is used to remove electrons from a donor ( water ) to a primary electron acceptor, a quinone designated as q. in the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach a final electron acceptor, which is usually the oxidized form of nadp +, which is reduced to nadph, a process that takes place in a protein complex called photosystem i ( psi ). the transport of electrons is coupled to the movement of protons ( or hydrogen ) from the stroma to the thylakoid membrane, which forms a ph gradient across the membrane as hydrogen becomes more concentrated in the lumen than in the stroma. this is analogous to the proton - motive force generated across the inner mitochondrial membrane in aerobic respiration. during the third stage of photosynthesis, the movement of protons down their concentration gradients from the thylakoid lumen to the stroma through the atp synthase is coupled to the synthesis of atp by that same atp synthase. the nadph and atps generated by the light - dependent reactions in the second and third stages, respectively, provide the energy and
of 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
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 topic of using nuclear power sources for generating energy. organic chemistry is the study of the structure, properties, composition, mechanisms, and reactions of organic compounds. an organic compound is defined as any compound based on a carbon skeleton. organic compounds can be classified, organized and understood in reactions by their functional groups, unit atoms or molecules that show characteristic chemical properties in a compound. physical chemistry is the study of the physical and fundamental basis of chemical systems and processes. in particular, the energetics and dynamics of such systems and processes are of interest to physical chemists. important areas of study include chemical thermodynamics, chemical kinetics, electrochemistry, statistical mechanics, spectroscopy, and more recently, astrochemistry. physical chemistry has large overlap with molecular physics. physical chemistry involves the use of infinitesimal calculus in deriving equations. it is usually associated with quantum chemistry and theoretical chemistry. physical chemistry is a distinct discipline from chemical physics, but again, there is very strong overlap. theoretical chemistry is the study of chemistry via fundamental theoretical reasoning ( usually within mathematics or physics ). in particular the application of quantum mechanics to chemistry is called quantum chemistry. since the end of the second world war, the development of computers has allowed a systematic development of computational chemistry, which is the art of developing and applying computer programs for solving chemical problems. theoretical chemistry has large overlap with ( theoretical and experimental ) condensed matter physics and molecular physics. other subdivisions include electrochemistry, femtochemistry, flavor chemistry, flow chemistry, immunohistochemistry, hydrogenation chemistry, mathematical chemistry, molecular mechanics, natural product chemistry, organometallic chemistry, petrochemistry, photochemistry, physical organic chemistry, polymer chemistry, radiochemistry, sonochemistry, supramolecular chemistry, synthetic chemistry, and many others. = = = interdisciplinary = = = interdisciplinary fields include agrochemistry, astrochemistry ( and cosmochemistry ), atmospheric chemistry, chemical engineering, chemical biology, chemo - informatics, environmental chemistry, geochemistry, green chemistry, immunochemistry, marine chemistry, materials science, mechanochemistry, medicinal chemistry, molecular biology, nanotechnology, oenology, pharmacology, phytochemistry, solid - state chemistry, surface science, thermochemistry, and many others. = = = industry = = = the chemical industry represents an important economic activity worldwide. the global top 50 chemical producers in 2013 had sales
Question: Which organisms get their energy source and carbon source from organic sources?
A) sporozoans
B) ectomorphs
C) herbivores
D) chemoheterotrophs
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D) chemoheterotrophs
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Context:
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 – beneficial uses
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
= = = = = = environmental remediation = = = environmental remediation is the process through which contaminants or pollutants in soil, water and other media are removed to improve environmental quality. the main focus is the reduction of hazardous substances within the environment. some of the areas involved in environmental remediation include ; soil contamination, hazardous waste, groundwater contamination, oil, gas and chemical spills. there are three most common types of environmental remediation. these include soil, water, and sediment remediation. soil remediation consists of removing contaminants in soil, as these pose great risks to humans and the ecosystem. some examples of this are heavy metals, pesticides, and radioactive materials. depending on the contaminant the remedial processes can be physical, chemical, thermal, or biological. water remediation is one of the most important considering water is an essential natural resource. depending on the source of water there will be different contaminants. surface water contamination mainly consists of agricultural, animal, and industrial waste, as well as acid mine drainage. there has been a rise in the need for water remediation due to the increased discharge of industrial waste, leading to a demand for sustainable water solutions. the market for water remediation is expected to consistently increase to $ 19. 6 billion by 2030. sediment remediation consists of removing contaminated sediments. is it almost similar to soil remediation except it is often more sophisticated as it involves additional contaminants. to reduce the contaminants it is likely to use physical, chemical, and biological processes that help with source control, but if these processes are executed correctly, there ' s a risk of contamination resurfacing. = = = solid waste management = = = solid waste management is the purification, consumption, reuse, disposal, and treatment of solid waste that is undertaken by the government or the ruling bodies of a city / town. it refers to the collection, treatment, and disposal of non - soluble, solid waste material. solid waste is associated with both industrial, institutional, commercial and residential activities. hazardous solid waste, when improperly disposed can encourage the infestation of insects and rodents, contributing to the spread of diseases. some of the most common types of solid waste management include ; landfills, vermicomposting, composting, recycling, and incineration. however, a major barrier for solid waste management practices is the high costs associated with recycling
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
, lightning strikes, tornadoes, building fires, wildfires, and mass shootings disabling most of the system if not the entirety of it. geographic redundancy locations can be more than 621 miles ( 999 km ) continental, more than 62 miles apart and less than 93 miles ( 150 km ) apart, less than 62 miles apart, but not on the same campus, or different buildings that are more than 300 feet ( 91 m ) apart on the same campus. the following methods can reduce the risks of damage by a fire conflagration : large buildings at least 80 feet ( 24 m ) to 110 feet ( 34 m ) apart, but sometimes a minimum of 210 feet ( 64 m ) apart. : 9 high - rise buildings at least 82 feet ( 25 m ) apart : 12 open spaces clear of flammable vegetation within 200 feet ( 61 m ) on each side of objects different wings on the same building, in rooms that are separated by more than 300 feet ( 91 m ) different floors on the same wing of a building in rooms that are horizontally offset by a minimum of 70 feet ( 21 m ) with fire walls between the rooms that are on different floors two rooms separated by another room, leaving at least a 70 - foot gap between the two rooms there should be a minimum of two separated fire walls and on opposite sides of a corridor geographic redundancy is used by amazon web services ( aws ), google cloud platform ( gcp ), microsoft azure, netflix, dropbox, salesforce, linkedin, paypal, twitter, facebook, apple icloud, cisco meraki, and many others to provide geographic redundancy, high availability, fault tolerance and to ensure availability and reliability for their cloud services. as another example, to minimize risk of damage from severe windstorms or water damage, buildings can be located at least 2 miles ( 3. 2 km ) away from the shore, with an elevation of at least 5 feet ( 1. 5 m ) above sea level. for additional protection, they can be located at least 100 feet ( 30 m ) away from flood plain areas. = = functions of redundancy = = the two functions of redundancy are passive redundancy and active redundancy. both functions prevent performance decline from exceeding specification limits without human intervention using extra capacity. passive redundancy uses excess capacity to reduce the impact of component failures. one common form of passive redundancy is the extra strength of cabling and struts used in bridges.
the injuries of the inundations they have been designed to prevent, as the escape of floods from the raised river must occur sooner or later. inadequate planning controls which have permitted development on floodplains have been blamed for the flooding of domestic properties. channelization was done under the auspices or overall direction of engineers employed by the local authority or the national government. one of the most heavily channelized areas in the united states is west tennessee, where every major stream with one exception ( the hatchie river ) has been partially or completely channelized. channelization of a stream may be undertaken for several reasons. one is to make a stream more suitable for navigation or for navigation by larger vessels with deep draughts. another is to restrict water to a certain area of a stream ' s natural bottom lands so that the bulk of such lands can be made available for agriculture. a third reason is flood control, with the idea of giving a stream a sufficiently large and deep channel so that flooding beyond those limits will be minimal or nonexistent, at least on a routine basis. one major reason is to reduce natural erosion ; as a natural waterway curves back and forth, it usually deposits sand and gravel on the inside of the corners where the water flows slowly, and cuts sand, gravel, subsoil, and precious topsoil from the outside corners where it flows rapidly due to a change in direction. unlike sand and gravel, the topsoil that is eroded does not get deposited on the inside of the next corner of the river. it simply washes away. = = loss of wetlands = = channelization has several predictable and negative effects. one of them is loss of wetlands. wetlands are an excellent habitat for multiple forms of wildlife, and additionally serve as a " filter " for much of the world ' s surface fresh water. another is the fact that channelized streams are almost invariably straightened. for example, the channelization of florida ' s kissimmee river has been cited as a cause contributing to the loss of wetlands. this straightening causes the streams to flow more rapidly, which can, in some instances, vastly increase soil erosion. it can also increase flooding downstream from the channelized area, as larger volumes of water traveling more rapidly than normal can reach choke points over a shorter period of time than they otherwise would, with a net effect of flood control in one area coming at the expense of aggravated flooding in another. in addition, studies have shown that stream channelization results in declines of river fish populations. : 3 - 1ff a
navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with a rapid fall near the sources of rivers can carry down rocks, boulders and large stones, which are by degrees ground by attrition in their onward course into slate, gravel, sand and silt, simultaneously with the gradual reduction in fall, and, consequently, in the transporting force of the current. accordingly, under ordinary conditions, most of the materials brought down from the high lands by torrential water courses are carried forward by the main river to the sea, or partially strewn over flat alluvial plains during floods ; the size of the materials forming the bed of the river or borne along by the stream is gradually reduced on proceeding sea
approximately corresponds to the slope of the country it traverses ; as rivers rise close to the highest part of their basins, generally in hilly regions, their fall is rapid near their source and gradually diminishes, with occasional irregularities, until, in traversing plains along the latter part of their course, their fall usually becomes quite gentle. accordingly, in large basins, rivers in most cases begin as torrents with a variable flow, and end as gently flowing rivers with a comparatively regular discharge. the irregular flow of rivers throughout their course forms one of the main difficulties in devising works for mitigating inundations or for increasing the navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with
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 — 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
##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 — 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: What natural disaster is california most linked with?
A) hurricanes
B) earthquakes
C) fires
D) volcanoes
|
B) earthquakes
|
Context:
a lattice l is " meet - distributive " if for each element of l, the meets of the elements directly below it form a boolean lattice. these objects are in bijection with " convex geometries ", which are an abstract model of convexity. do they give rise to an incidence hopf algebra of convex geometries?
my main results are simple formulas for the surface area of d - dimensional lattice polytopes using ehrhart theory.
this note fixes a small gap in kerckhoff ' s proof that the limit set of the handlebody set has measure zero.
we reveal the hydrogen isotope effect of three chemical reactions, i. e, the reflection, the absorption and the penetration ratios, by classical molecular dynamics simulation with a modified brenner ' s reactive empirical bond order ( rebo ) potential potential. we find that the reflection by pi - electron does not depend on the mass of the incident isotope, but the peak of the reflection by nuclear moves to higher side of incident energy. in addition to the reflection, we also find that the absorption ratio in the positive z side of the graphene becomes larger, as the mass of the incident isotope becomes larger. on the other hand, the absorption ratio in the negative z side of the graphene becomes smaller. last, it is found that the penetration ratio does not depend on the mass of the incident isotope because the graphene potential is not affected by the mass.
recent surveys have revealed a lack of close - in planets around evolved stars more massive than 1. 2 msun. such planets are common around solar - mass stars. we have calculated the orbital evolution of planets around stars with a range of initial masses, and have shown how planetary orbits are affected by the evolution of the stars all the way to the tip of the red giant branch ( rgb ). we find that tidal interaction can lead to the engulfment of close - in planets by evolved stars. the engulfment is more efficient for more - massive planets and less - massive stars. these results may explain the observed semi - major axis distribution of planets around evolved stars with masses larger than 1. 5 msun. our results also suggest that massive planets may form more efficiently around intermediate - mass stars.
the smallness and hierarchy of the fermion parameters could be explained in theories with extra dimensions where doublets and singlets are localized at slightly separated points. scattering cross sections for collisions of such fermions vanish exponentially at energies high enough to probe the separation distance. this is because the separation puts a lower bound on the attainable impact parameter in the collision. the nlc, and in particular the combination of the e ^ + e ^ - and e ^ - e ^ - modes, can probe this scenario, even if the inverse fermion separation is of order tens of tevs.
abstraction, from which information and then knowledge are derived. = = = basic two - dimensional geometry = = = two - dimensional geometry is a branch of mathematics concerned with questions of shape, size, and relative position of two - dimensional figures. basic topics in elementary mathematics include polygons, circles, perimeter and areas. 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
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 – 350 °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.
we cut the volume of surface code s gates by 25 % by omitting a hadamard gate.
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.
Question: Small crustaceans exchange gases across thin areas of the cuticle; larger species have what to accomplish this?
A) lungs
B) gills
C) pores
D) noses
|
B) gills
|
Context:
, characterizing organs as predominantly yin or yang, and understood the relationship between the pulse, the heart, and the flow of blood in the body centuries before it became accepted in the west. little evidence survives of how ancient indian cultures around the indus river understood nature, but some of their perspectives may be reflected in the vedas, a set of sacred hindu texts. they reveal a conception of the universe as ever - expanding and constantly being recycled and reformed. surgeons in the ayurvedic tradition saw health and illness as a combination of three humors : wind, bile and phlegm. a healthy life resulted from a balance among these humors. in ayurvedic thought, the body consisted of five elements : earth, water, fire, wind, and space. ayurvedic surgeons performed complex surgeries and developed a detailed understanding of human anatomy. pre - socratic philosophers in ancient greek culture brought natural philosophy a step closer to direct inquiry about cause and effect in nature between 600 and 400 bc. however, an element of magic and mythology remained. natural phenomena such as earthquakes and eclipses were explained increasingly in the context of nature itself instead of being attributed to angry gods. thales of miletus, an early philosopher who lived from 625 to 546 bc, explained earthquakes by theorizing that the world floated on water and that water was the fundamental element in nature. in the 5th century bc, leucippus was an early exponent of atomism, the idea that the world is made up of fundamental indivisible particles. pythagoras applied greek innovations in mathematics to astronomy and suggested that the earth was spherical. = = = aristotelian natural philosophy ( 400 bc – 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
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 – fda approved product ), and hepatocytes used in liver support systems cells can be used alone or with
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 – 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
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
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 – 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
the clinical symptoms of pulmonary embolism ( pe ) are very diverse and non - specific, which makes it difficult to diagnose. in addition, pulmonary embolism has multiple triggers and is one of the major causes of vascular death. therefore, if it can be detected and treated quickly, it can significantly reduce the risk of death in hospitalized patients. in the detection process, the cost of computed tomography pulmonary angiography ( ctpa ) is high, and angiography requires the injection of contrast agents, which increase the risk of damage to the patient. therefore, this study will use a deep learning approach to detect pulmonary embolism in all patients who take a ct image of the chest using a convolutional neural network. with the proposed pulmonary embolism detection system, we can detect the possibility of pulmonary embolism at the same time as the patient ' s first ct image, and schedule the ctpa test immediately, saving more than a week of ct image screening time and providing timely diagnosis and treatment to the patient.
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
a tradition of scientific inquiry also emerged in ancient china, where taoist alchemists and philosophers experimented with elixirs to extend life and cure ailments. they focused on the yin and yang, or contrasting elements in nature ; the yin was associated with femininity and coldness, while yang was associated with masculinity and warmth. the five phases – fire, earth, metal, wood, and water – described a cycle of transformations in nature. the water turned into wood, which turned into the fire when it burned. the ashes left by fire were earth. using these principles, chinese philosophers and doctors explored human anatomy, characterizing organs as predominantly yin or yang, and understood the relationship between the pulse, the heart, and the flow of blood in the body centuries before it became accepted in the west. little evidence survives of how ancient indian cultures around the indus river understood nature, but some of their perspectives may be reflected in the vedas, a set of sacred hindu texts. they reveal a conception of the universe as ever - expanding and constantly being recycled and reformed. surgeons in the ayurvedic tradition saw health and illness as a combination of three humors : wind, bile and phlegm. a healthy life resulted from a balance among these humors. in ayurvedic thought, the body consisted of five elements : earth, water, fire, wind, and space. ayurvedic surgeons performed complex surgeries and developed a detailed understanding of human anatomy. pre - socratic philosophers in ancient greek culture brought natural philosophy a step closer to direct inquiry about cause and effect in nature between 600 and 400 bc. however, an element of magic and mythology remained. natural phenomena such as earthquakes and eclipses were explained increasingly in the context of nature itself instead of being attributed to angry gods. thales of miletus, an early philosopher who lived from 625 to 546 bc, explained earthquakes by theorizing that the world floated on water and that water was the fundamental element in nature. in the 5th century bc, leucippus was an early exponent of atomism, the idea that the world is made up of fundamental indivisible particles. pythagoras applied greek innovations in mathematics to astronomy and suggested that the earth was spherical. = = = aristotelian natural philosophy ( 400 bc – 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
, 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
Question: The superior vena cava and the inferior vena cava are veins that return blood lacking what to the heart?
A) hemoglobin
B) nitrogen
C) carbon dioxide
D) oxygen
|
D) oxygen
|
Context:
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.
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 – 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 – 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
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 – 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 – 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 (
penner coordinates are extended to the teichm \ " uller spaces of oriented closed surfaces.
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
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
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 ≤ 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 a subinterval of interval j if i is a subset of j. an interval i is a proper subinterval of j if i is a proper subset of j. however, there is conflicting terminology for the terms segment and interval, which have been employed in the literature in two essentially opposite ways, resulting in ambiguity when these terms are used. the encyclopedia of mathematics defines interval ( without a qualifier ) to exclude both endpoints ( i. e., open interval ) and segment to include both endpoints ( i. e., closed interval ), while rudin ' s principles of mathematical analysis calls sets of the form [ a, b ] intervals and sets of the form ( a, b ) segments throughout. these terms tend to appear in older works ; modern texts increasingly favor the term interval ( qualified by open, closed, or half - open ), regardless of whether endpoints are included. = = notations for intervals = =
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
some properties of the nuclear matter as revealed by cherenkov gluons are discussed.
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 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
Question: There are only four possible bases that make up each dna nucleotide: adenine, guanine, thymine, and?
A) cytosine
B) taurine
C) phenylalanine
D) guarine
|
A) cytosine
|
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 – 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 – 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,
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 °c ( 4. 5 °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
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 – 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 – like stars and distant galaxies – 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 — 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 – 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
10 kgy most food, which is ( with regard to warming ) physically equivalent to water, would warm by only about 2. 5 °c ( 4. 5 °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
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 – 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 – 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
an electron inside liquid helium forms a bubble of 17 \ aa in radius. in an external magnetic field, the two - level system of a spin 1 / 2 electron is ideal for the implementation of a qubit for quantum computing. the electron spin is well isolated from other thermal reservoirs so that the qubit should have very long coherence time. by confining a chain of single electron bubbles in a linear rf quadrupole trap, a multi - bit quantum register can be implemented. all spins in the register can be initialized to the ground state either by establishing thermal equilibrium at a temperature around 0. 1 k and at a magnetic field of 1 t or by sorting the bubbles to be loaded into the trap with magnetic separation. schemes are designed to address individual spins and to do two - qubit cnot operations between the neighboring spins. the final readout can be carried out through a measurement similar to the stern - gerlach experiment.
, 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 – 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
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
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 °c ( 4. 5 °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
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
Question: What affects the boiling point of water?
A) latter pressure
B) external pressure
C) internal pressure
D) heat source
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B) external pressure
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Context:
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.
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
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.
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
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, 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
the purpose of this article is to view the penrose kite from the perspective of symplectic geometry.
the periods of the harmonic oscillations of the ion core of charged sodium clusters around the equilibrium shapes are considered. it is found that these periods are of the order of magnitude of the experimentally measured relaxation times of the plasmons, which suggests the importance of the electron - ion coupling and stresses the role played by the electron - phonon interaction in the dissipation of the plasmon energy. the relation of the process to fission is briefly discussed.
the attenuation length and refractive index of liquid xenon for intrinsic scintillation light ( 178nm ) have been measured in a single experiment. the value obtained for attenuation length is 364 + - 18 mm. the refractive index is found to be 1. 69 + - 0. 02. both values were measured at a temperature of 170 + - 1 k.
at the end of the 19th century light was regarded as an electromagnetic wave propagating in a material medium called ether. the speed c appearing in maxwell ' s wave equations was the speed of light with respect to the ether. therefore, according to the galilean addition of velocities, the speed of light in the laboratory would differ from c. the measure of such difference would reveal the motion of the laboratory ( the earth ) relative to the ether ( a sort of absolute motion ). however the earth ' s absolute motion was never evidenced. galileo addition of velocities is based on the assumption that lengths and time intervals are invariant ( independent of the state of motion ). this way of thinking the spacetime emanates from our daily experience and lies at the heart of newton ' s classical mechanics. nevertheless, in 1905 einstein defied galileo addition of velocities by postulating that light travels at the same speed c in any inertial frame. in doing so, einstein extended the principle of relativity to the electromagnetic phenomena described by maxwell ' s laws. in einstein ' s special relativity the ether does not exist and the absolute motion is devoid of meaning. the invariance of the speed of light forced the replacement of galileo transformations with lorentz transformations. thus, relativistic length contractions and time dilations entered our understanding of the spacetime. newtonian mechanics had to be reformulated, which led to the discovery of the mass - energy equivalence.
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 × 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 √2 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,
Question: The average length of a woman’s menstrual cycle is what?
A) 28 days
B) 19 days
C) 16 days
D) 5 days
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A) 28 days
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Context:
becomes quite gentle. accordingly, in large basins, rivers in most cases begin as torrents with a variable flow, and end as gently flowing rivers with a comparatively regular discharge. the irregular flow of rivers throughout their course forms one of the main difficulties in devising works for mitigating inundations or for increasing the navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with a rapid fall near the sources of rivers can carry down rocks, boulders and large stones, which are by degrees ground by attrition in their onward course into slate, gravel, sand and silt, simultaneously with the gradual reduction in fall, and, consequently, in the transporting force of the current. accordingly, under
navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with a rapid fall near the sources of rivers can carry down rocks, boulders and large stones, which are by degrees ground by attrition in their onward course into slate, gravel, sand and silt, simultaneously with the gradual reduction in fall, and, consequently, in the transporting force of the current. accordingly, under ordinary conditions, most of the materials brought down from the high lands by torrential water courses are carried forward by the main river to the sea, or partially strewn over flat alluvial plains during floods ; the size of the materials forming the bed of the river or borne along by the stream is gradually reduced on proceeding sea
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 (
approximately corresponds to the slope of the country it traverses ; as rivers rise close to the highest part of their basins, generally in hilly regions, their fall is rapid near their source and gradually diminishes, with occasional irregularities, until, in traversing plains along the latter part of their course, their fall usually becomes quite gentle. accordingly, in large basins, rivers in most cases begin as torrents with a variable flow, and end as gently flowing rivers with a comparatively regular discharge. the irregular flow of rivers throughout their course forms one of the main difficulties in devising works for mitigating inundations or for increasing the navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with
weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with a rapid fall near the sources of rivers can carry down rocks, boulders and large stones, which are by degrees ground by attrition in their onward course into slate, gravel, sand and silt, simultaneously with the gradual reduction in fall, and, consequently, in the transporting force of the current. accordingly, under ordinary conditions, most of the materials brought down from the high lands by torrential water courses are carried forward by the main river to the sea, or partially strewn over flat alluvial plains during floods ; the size of the materials forming the bed of the river or borne along by the stream is gradually reduced on proceeding seawards, so that in the po river in italy, for instance, pebbles and gravel are found for about 140 miles below turin, sand along the next 100 miles, and silt and mud in the last 110 miles ( 176 km ). = = channelization = = the removal of obstructions, natural or artificial
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.
earliest record of a ship under sail is that of a nile boat dating to around 7, 000 bce. from prehistoric times, egyptians likely used the power of the annual flooding of the nile to irrigate their lands, gradually learning to regulate much of it through purposely built irrigation channels and " catch " basins. the ancient sumerians in mesopotamia used a complex system of canals and levees to divert water from the tigris and euphrates rivers for irrigation. archaeologists estimate that the wheel was invented independently and concurrently in mesopotamia ( in present - day iraq ), the northern caucasus ( maykop culture ), and central europe. time estimates range from 5, 500 to 3, 000 bce with most experts putting it closer to 4, 000 bce. the oldest artifacts with drawings depicting wheeled carts date from about 3, 500 bce. more recently, the oldest - known wooden wheel in the world as of 2024 was found in the ljubljana marsh of slovenia ; austrian experts have established that the wheel is between 5, 100 and 5, 350 years old. the invention of the wheel revolutionized trade and war. it did not take long to discover that wheeled wagons could be used to carry heavy loads. the ancient sumerians used a potter ' s wheel and may have invented it. a stone pottery wheel found in the city - state of ur dates to around 3, 429 bce, and even older fragments of wheel - thrown pottery have been found in the same area. fast ( rotary ) potters ' wheels enabled early mass production of pottery, but it was the use of the wheel as a transformer of energy ( through water wheels, windmills, and even treadmills ) that revolutionized the application of nonhuman power sources. the first two - wheeled carts were derived from travois and were first used in mesopotamia and iran in around 3, 000 bce. the oldest known constructed roadways are the stone - paved streets of the city - state of ur, dating to c. 4, 000 bce, and timber roads leading through the swamps of glastonbury, england, dating to around the same period. the first long - distance road, which came into use around 3, 500 bce, spanned 2, 400 km from the persian gulf to the mediterranean sea, but was not paved and was only partially maintained. in around 2, 000 bce, the minoans on the greek island of crete built a 50 km road leading from the palace of gortyn on the south side of the island, through the mountains,
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 – civil works program river morphology and stream restoration references - wildland hydrology at the library of congress web archives ( archived 2002 - 08 - 13 )
the injuries of the inundations they have been designed to prevent, as the escape of floods from the raised river must occur sooner or later. inadequate planning controls which have permitted development on floodplains have been blamed for the flooding of domestic properties. channelization was done under the auspices or overall direction of engineers employed by the local authority or the national government. one of the most heavily channelized areas in the united states is west tennessee, where every major stream with one exception ( the hatchie river ) has been partially or completely channelized. channelization of a stream may be undertaken for several reasons. one is to make a stream more suitable for navigation or for navigation by larger vessels with deep draughts. another is to restrict water to a certain area of a stream ' s natural bottom lands so that the bulk of such lands can be made available for agriculture. a third reason is flood control, with the idea of giving a stream a sufficiently large and deep channel so that flooding beyond those limits will be minimal or nonexistent, at least on a routine basis. one major reason is to reduce natural erosion ; as a natural waterway curves back and forth, it usually deposits sand and gravel on the inside of the corners where the water flows slowly, and cuts sand, gravel, subsoil, and precious topsoil from the outside corners where it flows rapidly due to a change in direction. unlike sand and gravel, the topsoil that is eroded does not get deposited on the inside of the next corner of the river. it simply washes away. = = loss of wetlands = = channelization has several predictable and negative effects. one of them is loss of wetlands. wetlands are an excellent habitat for multiple forms of wildlife, and additionally serve as a " filter " for much of the world ' s surface fresh water. another is the fact that channelized streams are almost invariably straightened. for example, the channelization of florida ' s kissimmee river has been cited as a cause contributing to the loss of wetlands. this straightening causes the streams to flow more rapidly, which can, in some instances, vastly increase soil erosion. it can also increase flooding downstream from the channelized area, as larger volumes of water traveling more rapidly than normal can reach choke points over a shorter period of time than they otherwise would, with a net effect of flood control in one area coming at the expense of aggravated flooding in another. in addition, studies have shown that stream channelization results in declines of river fish populations. : 3 - 1ff a
also known as the gradient or slope. when two rivers of different sizes have the same fall, the larger river has the quicker flow, as its retardation by friction against its bed and banks is less in proportion to its volume than is the case with the smaller river. the fall available in a section of a river approximately corresponds to the slope of the country it traverses ; as rivers rise close to the highest part of their basins, generally in hilly regions, their fall is rapid near their source and gradually diminishes, with occasional irregularities, until, in traversing plains along the latter part of their course, their fall usually becomes quite gentle. accordingly, in large basins, rivers in most cases begin as torrents with a variable flow, and end as gently flowing rivers with a comparatively regular discharge. the irregular flow of rivers throughout their course forms one of the main difficulties in devising works for mitigating inundations or for increasing the navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in
Question: Water leaves ponds and lakes through evaporation and also as what?
A) inflow
B) influx
C) outflow
D) mid flow
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C) outflow
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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 – 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
. 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
the chemistry of condensed phases ( solids, liquids, polymers ) and interfaces between different phases. neurochemistry is the study of neurochemicals ; including transmitters, peptides, proteins, lipids, sugars, and nucleic acids ; their interactions, and the roles they play in forming, maintaining, and modifying the nervous system. nuclear chemistry is the study of how subatomic particles come together and make nuclei. modern transmutation is a large component of nuclear chemistry, and the table of nuclides is an important result and tool for this field. in addition to medical applications, nuclear chemistry encompasses nuclear engineering which explores the topic of using nuclear power sources for generating energy. organic chemistry is the study of the structure, properties, composition, mechanisms, and reactions of organic compounds. an organic compound is defined as any compound based on a carbon skeleton. organic compounds can be classified, organized and understood in reactions by their functional groups, unit atoms or molecules that show characteristic chemical properties in a compound. physical chemistry is the study of the physical and fundamental basis of chemical systems and processes. in particular, the energetics and dynamics of such systems and processes are of interest to physical chemists. important areas of study include chemical thermodynamics, chemical kinetics, electrochemistry, statistical mechanics, spectroscopy, and more recently, astrochemistry. physical chemistry has large overlap with molecular physics. physical chemistry involves the use of infinitesimal calculus in deriving equations. it is usually associated with quantum chemistry and theoretical chemistry. physical chemistry is a distinct discipline from chemical physics, but again, there is very strong overlap. theoretical chemistry is the study of chemistry via fundamental theoretical reasoning ( usually within mathematics or physics ). in particular the application of quantum mechanics to chemistry is called quantum chemistry. since the end of the second world war, the development of computers has allowed a systematic development of computational chemistry, which is the art of developing and applying computer programs for solving chemical problems. theoretical chemistry has large overlap with ( theoretical and experimental ) condensed matter physics and molecular physics. other subdivisions include electrochemistry, femtochemistry, flavor chemistry, flow chemistry, immunohistochemistry, hydrogenation chemistry, mathematical chemistry, molecular mechanics, natural product chemistry, organometallic chemistry, petrochemistry, photochemistry, physical organic chemistry, polymer chemistry, radiochemistry, sonochemistry, supramolecular chemistry, synthetic chemistry, and many others. = = = interdisciplinary = = = interdisciplinary fields include ag
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
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 — the breaking down of compounds ( for example, the breaking down of glucose to pyruvate by cellular respiration ) ; or anabolic — 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 — they allow a reaction to proceed more rapidly without being consumed by it — 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
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 – 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 – 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
organelles. in terms of their structural composition, the microtubules are made up of tubulin ( e. g., α - tubulin and β - 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 — the breaking down of compounds ( for example, the breaking down of glucose to pyruvate by cellular respiration ) ; or anabolic — 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 — they allow a reaction to proceed more rapidly without being consumed by it — 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
##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 – such as those evolved separately in different groups ( homoplasies ) or those left over from ancestors ( plesiomorphies ) – 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
= = 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 – 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 – 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
methods may be used in all subdisciplines of chemistry, excluding purely theoretical chemistry. biochemistry is the study of the chemicals, chemical reactions and interactions that take place at a molecular level in living organisms. biochemistry is highly interdisciplinary, covering medicinal chemistry, neurochemistry, molecular biology, forensics, plant science and genetics. inorganic chemistry is the study of the properties and reactions of inorganic compounds, such as metals and minerals. the distinction between organic and inorganic disciplines is not absolute and there is much overlap, most importantly in the sub - discipline of organometallic chemistry. materials chemistry is the preparation, characterization, and understanding of solid state components or devices with a useful current or future function. the field is a new breadth of study in graduate programs, and it integrates elements from all classical areas of chemistry like organic chemistry, inorganic chemistry, and crystallography with a focus on fundamental issues that are unique to materials. primary systems of study include the chemistry of condensed phases ( solids, liquids, polymers ) and interfaces between different phases. neurochemistry is the study of neurochemicals ; including transmitters, peptides, proteins, lipids, sugars, and nucleic acids ; their interactions, and the roles they play in forming, maintaining, and modifying the nervous system. nuclear chemistry is the study of how subatomic particles come together and make nuclei. modern transmutation is a large component of nuclear chemistry, and the table of nuclides is an important result and tool for this field. in addition to medical applications, nuclear chemistry encompasses nuclear engineering which explores the topic of using nuclear power sources for generating energy. organic chemistry is the study of the structure, properties, composition, mechanisms, and reactions of organic compounds. an organic compound is defined as any compound based on a carbon skeleton. organic compounds can be classified, organized and understood in reactions by their functional groups, unit atoms or molecules that show characteristic chemical properties in a compound. physical chemistry is the study of the physical and fundamental basis of chemical systems and processes. in particular, the energetics and dynamics of such systems and processes are of interest to physical chemists. important areas of study include chemical thermodynamics, chemical kinetics, electrochemistry, statistical mechanics, spectroscopy, and more recently, astrochemistry. physical chemistry has large overlap with molecular physics. physical chemistry involves the use of infinitesimal calculus in deriving equations. it is usually associated with quantum chemistry and theoretical chemistry. physical chemistry is a distinct discipline from chemical physics, but
Question: What is a biochemical compound that is a chain of amino acids called?
A) lipids
B) DNA
C) hormones
D) proteins
|
D) proteins
|
Context:
of these cellular components. the different stages of mitosis all together define the mitotic phase of an animal cell cycle — 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
- 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
studies of the molecular genetics of model plants such as the thale cress, arabidopsis thaliana, a weedy species in the mustard family ( brassicaceae ). the genome or hereditary information contained in the genes of this species is encoded by about 135 million base pairs of dna, forming one of the smallest genomes among flowering plants. arabidopsis was the first plant to have its genome sequenced, in 2000. the sequencing of some other relatively small genomes, of rice ( oryza sativa ) and brachypodium distachyon, has made them important model species for understanding the genetics, cellular and molecular biology of cereals, grasses and monocots generally. model plants such as arabidopsis thaliana are used for studying the molecular biology of plant cells and the chloroplast. ideally, these organisms have small genomes that are well known or completely sequenced, small stature and short generation times. corn has been used to study mechanisms of photosynthesis and phloem loading of sugar in c4 plants. the single celled green alga chlamydomonas reinhardtii, while not an embryophyte itself, contains a green - pigmented chloroplast related to that of land plants, making it useful for study. a red alga cyanidioschyzon merolae has also been used to study some basic chloroplast functions. spinach, peas, soybeans and a moss physcomitrella patens are commonly used to study plant cell biology. agrobacterium tumefaciens, a soil rhizosphere bacterium, can attach to plant cells and infect them with a callus - inducing ti plasmid by horizontal gene transfer, causing a callus infection called crown gall disease. schell and van montagu ( 1977 ) hypothesised that the ti plasmid could be a natural vector for introducing the nif gene responsible for nitrogen fixation in the root nodules of legumes and other plant species. today, genetic modification of the ti plasmid is one of the main techniques for introduction of transgenes to plants and the creation of genetically modified crops. = = = epigenetics = = = epigenetics is the study of heritable changes in gene function that cannot be explained by changes in the underlying dna sequence but cause the organism ' s genes to behave ( or " express themselves " ) differently. one example
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 " – 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
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
cross. the chromosome theory of inheritance, which states that genes are found on chromosomes, was supported by thomas morgans ' s experiments with fruit flies, which established the sex linkage between eye color and sex in these insects. = = = genes and dna = = = a gene is a unit of heredity that corresponds to a region of deoxyribonucleic acid ( dna ) that carries genetic information that controls form or function of an organism. dna is composed of two polynucleotide chains that coil around each other to form a double helix. it is found as linear chromosomes in eukaryotes, and circular chromosomes in prokaryotes. the set of chromosomes in a cell is collectively known as its genome. in eukaryotes, dna is mainly in the cell nucleus. in prokaryotes, the dna is held within the nucleoid. the genetic information is held within genes, and the complete assemblage in an organism is called its genotype. dna replication is a semiconservative process whereby each strand serves as a template for a new strand of dna. mutations are heritable changes in dna. they can arise spontaneously as a result of replication errors that were not corrected by proofreading or can be induced by an environmental mutagen such as a chemical ( e. g., nitrous acid, benzopyrene ) or radiation ( e. g., x - ray, gamma ray, ultraviolet radiation, particles emitted by unstable isotopes ). mutations can lead to phenotypic effects such as loss - of - function, gain - of - function, and conditional mutations. some mutations are beneficial, as they are a source of genetic variation for evolution. others are harmful if they were to result in a loss of function of genes needed for survival. = = = gene expression = = = gene expression is the molecular process by which a genotype encoded in dna gives rise to an observable phenotype in the proteins of an organism ' s body. this process is summarized by the central dogma of molecular biology, which was formulated by francis crick in 1958. according to the central dogma, genetic information flows from dna to rna to protein. there are two gene expression processes : transcription ( dna to rna ) and translation ( rna to protein ). = = = gene regulation = = = the regulation of gene expression by environmental factors and during different stages of development can occur at each step of the process such as transcription, rna splicing
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 " – 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
( 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 – such as those evolved separately in different groups ( homoplasies ) or those left over from ancestors ( plesiomorphies ) – 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 – 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
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,
mitochondria and chloroplasts in plants is non - mendelian. chloroplasts are inherited through the male parent in gymnosperms but often through the female parent in flowering plants. = = = molecular genetics = = = a considerable amount of new knowledge about plant function comes from studies of the molecular genetics of model plants such as the thale cress, arabidopsis thaliana, a weedy species in the mustard family ( brassicaceae ). the genome or hereditary information contained in the genes of this species is encoded by about 135 million base pairs of dna, forming one of the smallest genomes among flowering plants. arabidopsis was the first plant to have its genome sequenced, in 2000. the sequencing of some other relatively small genomes, of rice ( oryza sativa ) and brachypodium distachyon, has made them important model species for understanding the genetics, cellular and molecular biology of cereals, grasses and monocots generally. model plants such as arabidopsis thaliana are used for studying the molecular biology of plant cells and the chloroplast. ideally, these organisms have small genomes that are well known or completely sequenced, small stature and short generation times. corn has been used to study mechanisms of photosynthesis and phloem loading of sugar in c4 plants. the single celled green alga chlamydomonas reinhardtii, while not an embryophyte itself, contains a green - pigmented chloroplast related to that of land plants, making it useful for study. a red alga cyanidioschyzon merolae has also been used to study some basic chloroplast functions. spinach, peas, soybeans and a moss physcomitrella patens are commonly used to study plant cell biology. agrobacterium tumefaciens, a soil rhizosphere bacterium, can attach to plant cells and infect them with a callus - inducing ti plasmid by horizontal gene transfer, causing a callus infection called crown gall disease. schell and van montagu ( 1977 ) hypothesised that the ti plasmid could be a natural vector for introducing the nif gene responsible for nitrogen fixation in the root nodules of legumes and other plant species. today, genetic modification of the ti plasmid is one of the main techniques for introduction of transgenes to plants
Question: Each what is made of two identical sister chromatids?
A) gene
B) chromosome
C) helix
D) genome
|
B) chromosome
|
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 – 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
prokaryotic cells and were initially classified as bacteria, receiving the name archaebacteria ( in the archaebacteria kingdom ), a term that has fallen out of use. archaeal cells have unique properties separating them from the other two domains, bacteria and eukaryota. archaea are further divided into multiple recognized phyla. archaea and bacteria are generally similar in size and shape, although a few archaea have very different shapes, such as the flat and square cells of haloquadratum walsbyi. despite this morphological similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes, notably for the enzymes involved in transcription and translation. other aspects of archaeal biochemistry are unique, such as their reliance on ether lipids in their cell membranes, including archaeols. archaea use more energy sources than eukaryotes : these range from organic compounds, such as sugars, to ammonia, metal ions or even hydrogen gas. salt - tolerant archaea ( the haloarchaea ) use sunlight as an energy source, and other species of archaea fix carbon, but unlike plants and cyanobacteria, no known species of archaea does both. archaea reproduce asexually by binary fission, fragmentation, or budding ; unlike bacteria, no known species of archaea form endospores. the first observed archaea were extremophiles, living in extreme environments, such as hot springs and salt lakes with no other organisms. improved molecular detection tools led to the discovery of archaea in almost every habitat, including soil, oceans, and marshlands. archaea are particularly numerous in the oceans, and the archaea in plankton may be one of the most abundant groups of organisms on the planet. archaea are a major part of earth ' s life. they are part of the microbiota of all organisms. in the human microbiome, they are important in the gut, mouth, and on the skin. their morphological, metabolic, and geographical diversity permits them to play multiple ecological roles : carbon fixation ; nitrogen cycling ; organic compound turnover ; and maintaining microbial 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 mit
are further divided into multiple recognized phyla. archaea and bacteria are generally similar in size and shape, although a few archaea have very different shapes, such as the flat and square cells of haloquadratum walsbyi. despite this morphological similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes, notably for the enzymes involved in transcription and translation. other aspects of archaeal biochemistry are unique, such as their reliance on ether lipids in their cell membranes, including archaeols. archaea use more energy sources than eukaryotes : these range from organic compounds, such as sugars, to ammonia, metal ions or even hydrogen gas. salt - tolerant archaea ( the haloarchaea ) use sunlight as an energy source, and other species of archaea fix carbon, but unlike plants and cyanobacteria, no known species of archaea does both. archaea reproduce asexually by binary fission, fragmentation, or budding ; unlike bacteria, no known species of archaea form endospores. the first observed archaea were extremophiles, living in extreme environments, such as hot springs and salt lakes with no other organisms. improved molecular detection tools led to the discovery of archaea in almost every habitat, including soil, oceans, and marshlands. archaea are particularly numerous in the oceans, and the archaea in plankton may be one of the most abundant groups of organisms on the planet. archaea are a major part of earth ' s life. they are part of the microbiota of all organisms. in the human microbiome, they are important in the gut, mouth, and on the skin. their morphological, metabolic, and geographical diversity permits them to play multiple ecological roles : carbon fixation ; nitrogen cycling ; organic compound turnover ; and maintaining microbial symbiotic and syntrophic communities, for example. = = = eukaryotes = = = eukaryotes are hypothesized to have split from archaea, which was followed by their endosymbioses with bacteria ( or symbiogenesis ) that gave rise to mitochondria and chloroplasts, both of which are now part of modern - day eukaryotic cells. the major lineages of eukaryotes diversified in the precambrian about 1. 5 billion years ago and can be classified into eight major clades : alveolates,
( 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 – 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
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
##yotic microorganisms. typically a few micrometers in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. bacteria were among the first life forms to appear on earth, and are present in most of its habitats. bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep biosphere of the earth ' s crust. bacteria also live in symbiotic and parasitic relationships with plants and animals. most bacteria have not been characterised, and only about 27 percent of the bacterial phyla have species that can be grown in the laboratory. archaea constitute the other domain of prokaryotic cells and were initially classified as bacteria, receiving the name archaebacteria ( in the archaebacteria kingdom ), a term that has fallen out of use. archaeal cells have unique properties separating them from the other two domains, bacteria and eukaryota. archaea are further divided into multiple recognized phyla. archaea and bacteria are generally similar in size and shape, although a few archaea have very different shapes, such as the flat and square cells of haloquadratum walsbyi. despite this morphological similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes, notably for the enzymes involved in transcription and translation. other aspects of archaeal biochemistry are unique, such as their reliance on ether lipids in their cell membranes, including archaeols. archaea use more energy sources than eukaryotes : these range from organic compounds, such as sugars, to ammonia, metal ions or even hydrogen gas. salt - tolerant archaea ( the haloarchaea ) use sunlight as an energy source, and other species of archaea fix carbon, but unlike plants and cyanobacteria, no known species of archaea does both. archaea reproduce asexually by binary fission, fragmentation, or budding ; unlike bacteria, no known species of archaea form endospores. the first observed archaea were extremophiles, living in extreme environments, such as hot springs and salt lakes with no other organisms. improved molecular detection tools led to the discovery of archaea in almost every habitat, including soil, oceans, and marshlands. archaea are particularly numerous in the oceans, and the archaea in plankton may be one of the most abundant groups of organisms on the planet. archaea are a major part of earth ' s life.
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
waste, and the deep biosphere of the earth ' s crust. bacteria also live in symbiotic and parasitic relationships with plants and animals. most bacteria have not been characterised, and only about 27 percent of the bacterial phyla have species that can be grown in the laboratory. archaea constitute the other domain of prokaryotic cells and were initially classified as bacteria, receiving the name archaebacteria ( in the archaebacteria kingdom ), a term that has fallen out of use. archaeal cells have unique properties separating them from the other two domains, bacteria and eukaryota. archaea are further divided into multiple recognized phyla. archaea and bacteria are generally similar in size and shape, although a few archaea have very different shapes, such as the flat and square cells of haloquadratum walsbyi. despite this morphological similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes, notably for the enzymes involved in transcription and translation. other aspects of archaeal biochemistry are unique, such as their reliance on ether lipids in their cell membranes, including archaeols. archaea use more energy sources than eukaryotes : these range from organic compounds, such as sugars, to ammonia, metal ions or even hydrogen gas. salt - tolerant archaea ( the haloarchaea ) use sunlight as an energy source, and other species of archaea fix carbon, but unlike plants and cyanobacteria, no known species of archaea does both. archaea reproduce asexually by binary fission, fragmentation, or budding ; unlike bacteria, no known species of archaea form endospores. the first observed archaea were extremophiles, living in extreme environments, such as hot springs and salt lakes with no other organisms. improved molecular detection tools led to the discovery of archaea in almost every habitat, including soil, oceans, and marshlands. archaea are particularly numerous in the oceans, and the archaea in plankton may be one of the most abundant groups of organisms on the planet. archaea are a major part of earth ' s life. they are part of the microbiota of all organisms. in the human microbiome, they are important in the gut, mouth, and on the skin. their morphological, metabolic, and geographical diversity permits them to play multiple ecological roles : carbon fixation ; nitrogen cycling ; organic compound turnover ; and maintaining microbial
conditions of early earth, thus suggesting that complex organic molecules could have arisen spontaneously in early earth ( see abiogenesis ). = = = macromolecules = = = macromolecules are large molecules made up of smaller subunits or monomers. monomers include sugars, amino acids, and nucleotides. carbohydrates include monomers and polymers of sugars. lipids are the only class of macromolecules that are not made up of polymers. they include steroids, phospholipids, and fats, largely nonpolar and hydrophobic ( water - repelling ) substances. proteins are the most diverse of the macromolecules. they include enzymes, transport proteins, large signaling molecules, antibodies, and structural proteins. the basic unit ( or monomer ) of a protein is an amino acid. twenty amino acids are used in proteins. nucleic acids are polymers of nucleotides. their function is to store, transmit, and express hereditary information. = = cells = = cell theory states that cells are the fundamental units of life, that all living things are composed of one or more cells, and that all cells arise from preexisting cells through cell division. most cells are very small, with diameters ranging from 1 to 100 micrometers and are therefore only visible under a light or electron microscope. there are generally two types of cells : eukaryotic cells, which contain a nucleus, and prokaryotic cells, which do not. prokaryotes are single - celled organisms such as bacteria, whereas eukaryotes can be single - celled or multicellular. in multicellular organisms, every cell in the organism ' s body is derived ultimately from a single cell in a fertilized egg. = = = cell structure = = = every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions. cell membranes also contain membrane proteins, including integral membrane proteins that go across the membrane serving as membrane transporters, and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes
Question: Amino groups are found within amino acids, nicknamed the building blocks of what?
A) carbohydrates
B) lipids
C) protons
D) proteins
|
D) proteins
|
Context:
outer satellites of the planets have distant, eccentric orbits that can be highly inclined or even retrograde relative to the equatorial planes of their planets. these irregular orbits cannot have formed by circumplanetary accretion and are likely products of early capture from heliocentric orbit. the irregular satellites may be the only small bodies remaining which are still relatively near their formation locations within the giant planet region. the study of the irregular satellites provides a unique window on processes operating in the young solar system and allows us to probe possible planet formation mechanisms and the composition of the solar nebula between the rocky objects in the main asteroid belt and the very volatile rich objects in the kuiper belt. the gas and ice giant planets all appear to have very similar irregular satellite systems irrespective of their mass or formation timescales and mechanisms. water ice has been detected on some of the outer satellites of saturn and neptune whereas none has been observed on jupiter ' s outer satellites.
to the ground is called a downlink. communication satellite – 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 – 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 – 80 cm ( 17 – 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
are more expensive than cell phones ; but their advantage is that, unlike a cell phone which is limited to areas covered by cell towers, satphones can be used over most or all of the geographical area of the earth. in order for the phone to communicate with a satellite using a small omnidirectional antenna, first - generation systems use satellites in low earth orbit, about 400 – 700 miles ( 640 – 1, 100 km ) above the surface. with an orbital period of about 100 minutes, a satellite can only be in view of a phone for about 4 – 15 minutes, so the call is " handed off " to another satellite when one passes beyond the local horizon. therefore, large numbers of satellites, about 40 to 70, are required to ensure that at least one satellite is in view continuously from each point on earth. other satphone systems use satellites in geostationary orbit in which only a few satellites are needed, but these cannot be used at high latitudes because of terrestrial interference. cordless phone – 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 – 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 – 50 mhz and 150 – 172 mhz. uhf systems use the 450 – 470 mhz band and in some areas the 470 – 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,
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 – 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 – 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 – 80 cm ( 17 – 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,
the european union ' s galileo. global positioning system ( gps ) – 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 – 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 ) – 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
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 — frank borman, james lovell, and william anders — 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 – 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
metres ) by small portable navigation instruments, by timing the arrival of radio signals from the satellites. these are the most widely used navigation systems today. the main satellite navigation systems are the us global positioning system ( gps ), russia ' s glonass, china ' s beidou navigation satellite system ( bds ) and the european union ' s galileo. global positioning system ( gps ) – 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 – 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 ) – 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
long, and instead of a cell base station and antenna tower, they will have many small antennas attached to utility poles and buildings. satellite phone ( satphone ) – a portable wireless telephone similar to a cell phone, connected to the telephone network through a radio link to an orbiting communications satellite instead of through cell towers. they are more expensive than cell phones ; but their advantage is that, unlike a cell phone which is limited to areas covered by cell towers, satphones can be used over most or all of the geographical area of the earth. in order for the phone to communicate with a satellite using a small omnidirectional antenna, first - generation systems use satellites in low earth orbit, about 400 – 700 miles ( 640 – 1, 100 km ) above the surface. with an orbital period of about 100 minutes, a satellite can only be in view of a phone for about 4 – 15 minutes, so the call is " handed off " to another satellite when one passes beyond the local horizon. therefore, large numbers of satellites, about 40 to 70, are required to ensure that at least one satellite is in view continuously from each point on earth. other satphone systems use satellites in geostationary orbit in which only a few satellites are needed, but these cannot be used at high latitudes because of terrestrial interference. cordless phone – 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 – 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 – 50 mhz and 150 – 172 mhz. uhf systems use the 450 – 470 mhz band and in some areas the 470 – 512 mhz range. in general, vhf systems have a longer range than uhf but require longer antennas.
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 – 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 – 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 – 50 mhz and 150 – 172 mhz. uhf systems use the 450 – 470 mhz band and in some areas the 470 – 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 – a battery - powered portable handheld half - duplex two - way radio, used in land mobile radio systems. airband – half - duplex radio system used by aircraft pilots to talk to other aircraft and ground - based air traffic controllers. this vital
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 – 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 – 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
Question: What is the name of earth’s only natural satellite?
A) titan
B) venus
C) sun
D) moon
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D) moon
|
Context:
the valuable metals into individual constituents. = = metal and its alloys = = much effort has been placed on understanding iron – 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 – molten metal is poured into a shaped mold. variants of casting include sand casting, investment
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 – 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
based on 1 / 10 and 1 / 100 weight percentages of the carbon and other alloying elements they contain. thus, the extracting and purifying methods used to extract iron in a blast furnace can affect the quality of steel that is produced. solid materials are generally grouped into three basic classifications : ceramics, metals, and polymers. this broad classification is based on the empirical makeup and atomic structure of the solid materials, and most solids fall into one of these broad categories. an item that is often made from each of these materials types is the beverage container. the material types used for beverage containers accordingly provide different advantages and disadvantages, depending on the material used. ceramic ( glass ) containers are optically transparent, impervious to the passage of carbon dioxide, relatively inexpensive, and are easily recycled, but are also heavy and fracture easily. metal ( aluminum alloy ) is relatively strong, is a good barrier to the diffusion of carbon dioxide, and is easily recycled. however, the cans are opaque, expensive to produce, and are easily dented and punctured. polymers ( polyethylene plastic ) are relatively strong, can be optically transparent, are inexpensive and lightweight, and can be recyclable, but are not as impervious to the passage of carbon dioxide as aluminum and glass. = = = ceramics and glasses = = = another application of materials science is the study of ceramics and glasses, typically the most brittle materials with industrial relevance. many ceramics and glasses exhibit covalent or ionic - covalent bonding with sio2 ( silica ) as a fundamental building block. ceramics – not to be confused with raw, unfired clay – are usually seen in crystalline form. the vast majority of commercial glasses contain a metal oxide fused with silica. at the high temperatures used to prepare glass, the material is a viscous liquid which solidifies into a disordered state upon cooling. windowpanes and eyeglasses are important examples. fibers of glass are also used for long - range telecommunication and optical transmission. scratch resistant corning gorilla glass is a well - known example of the application of materials science to drastically improve the properties of common components. engineering ceramics are known for their stiffness and stability under high temperatures, compression and electrical stress. alumina, silicon carbide, and tungsten carbide are made from a fine powder of their constituents in a process of sintering with a binder. hot pressing provides higher density material. chemical vapor deposition can place a film of a ceramic on another
prehistory. the oldest gold treasure in the world, dating from 4, 600 bc to 4, 200 bc, was discovered at the site. the gold piece dating from 4, 500 bc, found in 2019 in durankulak, near varna is another important example. other signs of early metals are found from the third millennium bc in palmela, portugal, los millares, spain, and stonehenge, united kingdom. the precise beginnings, however, have not be clearly ascertained and new discoveries are both continuous and ongoing. in approximately 1900 bc, ancient iron smelting sites existed in tamil nadu. in the near east, about 3, 500 bc, it was discovered that by combining copper and tin, a superior metal could be made, an alloy called bronze. this represented a major technological shift known as the bronze age. the extraction of iron from its ore into a workable metal is much more difficult than for copper or tin. the process appears to have been invented by the hittites in about 1200 bc, beginning the iron age. the secret of extracting and working iron was a key factor in the success of the philistines. historical developments in ferrous metallurgy can be found in a wide variety of past cultures and civilizations. this includes the ancient and medieval kingdoms and empires of the middle east and near east, ancient iran, ancient egypt, ancient nubia, and anatolia in present - day turkey, ancient nok, carthage, the celts, greeks and romans of ancient europe, medieval europe, ancient and medieval china, ancient and medieval india, ancient and medieval japan, amongst others. a 16th century book by georg agricola, de re metallica, describes the highly developed and complex processes of mining metal ores, metal extraction, and metallurgy of the time. agricola has been described as the " father of metallurgy ". = = extraction = = extractive metallurgy is the practice of removing valuable metals from an ore and refining the extracted raw metals into a purer form. in order to convert a metal oxide or sulphide to a purer metal, the ore must be reduced physically, chemically, or electrolytically. extractive metallurgists are interested in three primary streams : feed, concentrate ( metal oxide / sulphide ) and tailings ( waste ). after mining, large pieces of the ore feed are broken through crushing or grinding in order to obtain particles small enough, where each particle is either mostly valuable or
casting, foundry methods, blast furnace extraction, and electrolytic extraction are all part of the required knowledge of a materials engineer. often the presence, absence, or variation of minute quantities of secondary elements and compounds in a bulk material will greatly affect the final properties of the materials produced. for example, steels are classified based on 1 / 10 and 1 / 100 weight percentages of the carbon and other alloying elements they contain. thus, the extracting and purifying methods used to extract iron in a blast furnace can affect the quality of steel that is produced. solid materials are generally grouped into three basic classifications : ceramics, metals, and polymers. this broad classification is based on the empirical makeup and atomic structure of the solid materials, and most solids fall into one of these broad categories. an item that is often made from each of these materials types is the beverage container. the material types used for beverage containers accordingly provide different advantages and disadvantages, depending on the material used. ceramic ( glass ) containers are optically transparent, impervious to the passage of carbon dioxide, relatively inexpensive, and are easily recycled, but are also heavy and fracture easily. metal ( aluminum alloy ) is relatively strong, is a good barrier to the diffusion of carbon dioxide, and is easily recycled. however, the cans are opaque, expensive to produce, and are easily dented and punctured. polymers ( polyethylene plastic ) are relatively strong, can be optically transparent, are inexpensive and lightweight, and can be recyclable, but are not as impervious to the passage of carbon dioxide as aluminum and glass. = = = ceramics and glasses = = = another application of materials science is the study of ceramics and glasses, typically the most brittle materials with industrial relevance. many ceramics and glasses exhibit covalent or ionic - covalent bonding with sio2 ( silica ) as a fundamental building block. ceramics – not to be confused with raw, unfired clay – 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
the monocrystalline silicon neutron beam window is one of the key components of neutron spectrometers and thin circular plate. monocrystalline silicon is a brittle material and its strength is not constant but is consistent with the weibull distribution. the window is designed not simply through the average strength, but according to the survival rate. bending deformation is the main form of the window, so dangerous parts of the neutron beam window is stress - linearized to the combination of membrane stress and bending stress. according to the weibull distribution of bending strength of monocrystalline silicon based on a large number of experimental data, finally the optimized neutron beam window is 1. 5mm thick. its survival rate is 0. 9994 and its transmittance is 0. 98447 ; it meets both physical requirements and the mechanical strength.
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
##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
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 μεταλλουργος, metallourgos, " worker in metal ", from μεταλλον, metallon, " mine, metal " + εργον, ergon
Question: Which is the lightest of the widely used structural metals?
A) calcium
B) Metal
C) magnesium
D) potassium
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C) magnesium
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Context:
##ctonics, mountain ranges, volcanoes, and earthquakes are geological phenomena that can be explained in terms of physical and chemical processes in the earth ' s crust. beneath the earth ' s crust lies the mantle which is heated by the radioactive decay of heavy elements. the mantle is not quite solid and consists of magma which is in a state of semi - perpetual convection. this convection process causes the lithospheric plates to move, albeit slowly. the resulting process is known as plate tectonics. areas of the crust where new crust is created are called divergent boundaries, those where it is brought back into the earth are convergent boundaries and those where plates slide past each other, but no new lithospheric material is created or destroyed, are referred to as transform ( or conservative ) boundaries. earthquakes result from the movement of the lithospheric plates, and they often occur near convergent boundaries where parts of the crust are forced into the earth as part of subduction. plate tectonics might be thought of as the process by which the earth is resurfaced. as the result of seafloor spreading, new crust and lithosphere is created by the flow of magma from the mantle to the near surface, through fissures, where it cools and solidifies. through subduction, oceanic crust and lithosphere vehemently returns to the convecting mantle. volcanoes result primarily from the melting of subducted crust material. crust material that is forced into the asthenosphere melts, and some portion of the melted material becomes light enough to rise to the surface — 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 — 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 — 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
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 — 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 — created by the internal motions of the core — produces the magnetosphere which protects earth '
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 °c. = = processing steps = = the traditional ceramic process generally follows this sequence : milling → batching → mixing → forming → drying → firing → 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
##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
casting, also called the lost wax process, die casting, centrifugal casting, both vertical and horizontal, and continuous castings. each of these forms has advantages for certain metals and applications considering factors like magnetism and corrosion. forging – a red - hot billet is hammered into shape. rolling – a billet is passed through successively narrower rollers to create a sheet. extrusion – a hot and malleable metal is forced under pressure through a die, which shapes it before it cools. machining – lathes, milling machines and drills cut the cold metal to shape. sintering – a powdered metal is heated in a non - oxidizing environment after being compressed into a die. fabrication – sheets of metal are cut with guillotines or gas cutters and bent and welded into structural shape. laser cladding – 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 – 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
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
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
billet is passed through successively narrower rollers to create a sheet. extrusion – a hot and malleable metal is forced under pressure through a die, which shapes it before it cools. machining – lathes, milling machines and drills cut the cold metal to shape. sintering – a powdered metal is heated in a non - oxidizing environment after being compressed into a die. fabrication – sheets of metal are cut with guillotines or gas cutters and bent and welded into structural shape. laser cladding – 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 – 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
Question: When lava flows over a large area and cools, it creates a large, flat surface of what type of rock?
A) tidal
B) igneous
C) sedimentary
D) metamorphic
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B) igneous
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Context:
. most cells are very small, with diameters ranging from 1 to 100 micrometers and are therefore only visible under a light or electron microscope. there are generally two types of cells : eukaryotic cells, which contain a nucleus, and prokaryotic cells, which do not. prokaryotes are single - celled organisms such as bacteria, whereas eukaryotes can be single - celled or multicellular. in multicellular organisms, every cell in the organism ' s body is derived ultimately from a single cell in a fertilized egg. = = = cell structure = = = every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions. cell membranes also contain membrane proteins, including integral membrane proteins that go across the membrane serving as membrane transporters, and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes shaping the cell. cell membranes are involved in various cellular processes such as cell adhesion, storing electrical energy, and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall, glycocalyx, and cytoskeleton. within the cytoplasm of a cell, there are many biomolecules such as proteins and nucleic acids. in addition to biomolecules, eukaryotic cells have specialized structures called organelles that have their own lipid bilayers or are spatially units. these organelles include the cell nucleus, which contains most of the cell ' s dna, or mitochondria, which generate adenosine triphosphate ( atp ) to power cellular processes. other organelles such as endoplasmic reticulum and golgi apparatus play a role in the synthesis and packaging of proteins, respectively. biomolecules such as proteins can be engulfed by lysosomes, another specialized organelle. plant cells have additional organelles that distinguish them from animal cells such as a cell wall that provides support for the plant cell, chloroplasts that harvest sunlight energy to produce sugar, and vacuoles that provide storage and structural support
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
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., α - tubulin and β - tubulin ) whereas intermediate filaments are made up of fibrous proteins. microfilaments are made up of actin molecules that interact with
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., α - tubulin and β - 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 — the breaking down of compounds ( for example, the breaking down of glucose to pyruvate by cellular respiration
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
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., α - tubulin and β - 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
generally, dead - end filtration is used for feasibility studies on a laboratory scale. the dead - end membranes are relatively easy to fabricate which reduces the cost of the separation process. the dead - end membrane separation process is easy to implement and the process is usually cheaper than cross - flow membrane filtration. the dead - end filtration process is usually a batch - type process, where the filtering solution is loaded ( or slowly fed ) into the membrane device, which then allows passage of some particles subject to the driving force. the main disadvantage of dead - end filtration is the extensive membrane fouling and concentration polarization. the fouling is usually induced faster at higher driving forces. membrane fouling and particle retention in a feed solution also builds up a concentration gradients and particle backflow ( concentration polarization ). the tangential flow devices are more cost and labor - intensive, but they are less susceptible to fouling due to the sweeping effects and high shear rates of the passing flow. the most commonly used synthetic membrane devices ( modules ) are flat sheets / plates, spiral wounds, and hollow fibers. flat membranes used in filtration and separation processes can be enhanced with surface patterning, where microscopic structures are introduced to improve performance. these patterns increase surface area, optimize water flow, and reduce fouling, leading to higher permeability and longer membrane lifespan. research has shown that such modifications can significantly enhance efficiency in water purification, energy applications, and industrial separations. flat plates are usually constructed as circular thin flat membrane surfaces to be used in dead - end geometry modules. spiral wounds are constructed from similar flat membranes but in the form of a " pocket " containing two membrane sheets separated by a highly porous support plate. several such pockets are then wound around a tube to create a tangential flow geometry and to reduce membrane fouling. hollow fiber modules consist of an assembly of self - supporting fibers with dense skin separation layers, and a more open matrix helping to withstand pressure gradients and maintain structural integrity. the hollow fiber modules can contain up to 10, 000 fibers ranging from 200 to 2500 μm 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
the surface of the membrane, retentate is removed from the same side further downstream, whereas the permeate flow is tracked on the other side. in dead - end filtration, the direction of the fluid flow is normal to the membrane surface. both flow geometries offer some advantages and disadvantages. generally, dead - end filtration is used for feasibility studies on a laboratory scale. the dead - end membranes are relatively easy to fabricate which reduces the cost of the separation process. the dead - end membrane separation process is easy to implement and the process is usually cheaper than cross - flow membrane filtration. the dead - end filtration process is usually a batch - type process, where the filtering solution is loaded ( or slowly fed ) into the membrane device, which then allows passage of some particles subject to the driving force. the main disadvantage of dead - end filtration is the extensive membrane fouling and concentration polarization. the fouling is usually induced faster at higher driving forces. membrane fouling and particle retention in a feed solution also builds up a concentration gradients and particle backflow ( concentration polarization ). the tangential flow devices are more cost and labor - intensive, but they are less susceptible to fouling due to the sweeping effects and high shear rates of the passing flow. the most commonly used synthetic membrane devices ( modules ) are flat sheets / plates, spiral wounds, and hollow fibers. flat membranes used in filtration and separation processes can be enhanced with surface patterning, where microscopic structures are introduced to improve performance. these patterns increase surface area, optimize water flow, and reduce fouling, leading to higher permeability and longer membrane lifespan. research has shown that such modifications can significantly enhance efficiency in water purification, energy applications, and industrial separations. flat plates are usually constructed as circular thin flat membrane surfaces to be used in dead - end geometry modules. spiral wounds are constructed from similar flat membranes but in the form of a " pocket " containing two membrane sheets separated by a highly porous support plate. several such pockets are then wound around a tube to create a tangential flow geometry and to reduce membrane fouling. hollow fiber modules consist of an assembly of self - supporting fibers with dense skin separation layers, and a more open matrix helping to withstand pressure gradients and maintain structural integrity. the hollow fiber modules can contain up to 10, 000 fibers ranging from 200 to 2500 μm in diameter ; the main advantage of hollow fiber modules is the very large surface area within
##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 μm 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 = δ p μ a ( 1 r m + r ) { \ displaystyle { \ frac { dv _
classes according to pore size : the form and shape of the membrane pores are highly dependent on the manufacturing process and are often difficult to specify. therefore, for characterization, test filtrations are carried out and the pore diameter refers to the diameter of the smallest particles which could not pass through the membrane. the rejection can be determined in various ways and provides an indirect measurement of the pore size. one possibility is the filtration of macromolecules ( often dextran, polyethylene glycol or albumin ), another is measurement of the cut - off by gel permeation chromatography. these methods are used mainly to measure membranes for ultrafiltration applications. another testing method is the filtration of particles with defined size and their measurement with a particle sizer or by laser induced breakdown spectroscopy ( libs ). a vivid characterization is to measure the rejection of dextran blue or other colored molecules. the retention of bacteriophage and bacteria, the so - called " bacteria challenge test ", can also provide information about the pore size. to determine the pore diameter, physical methods such as porosimeter ( mercury, liquid - liquid porosimeter and bubble point test ) are also used, but a certain form of the pores ( such as cylindrical or concatenated spherical holes ) is assumed. such methods are used for membranes whose pore geometry does not match the ideal, and we get " nominal " pore diameter, which characterizes the membrane, but does not necessarily reflect its actual filtration behavior and selectivity. the selectivity is highly dependent on the separation process, the composition of the membrane and its electrochemical properties in addition to the pore size. with high selectivity, isotopes can be enriched ( uranium enrichment ) in nuclear engineering or industrial gases like nitrogen can be recovered ( gas separation ). ideally, even racemics can be enriched with a suitable membrane. when choosing membranes selectivity has priority over a high permeability, as low flows can easily be offset by increasing the filter surface with a modular structure. in gas phase filtration different deposition mechanisms are operative, so that particles having sizes below the pore size of the membrane can be retained as well. = = membrane classification = = bio - membrane is classified in two categories, synthetic membrane and natural membrane. synthetic membranes further classified in organic and inorganic membranes. organic membrane sub classified polymeric membranes and inorganic membrane sub classified ceramic polymers. = = synthesis of biomass membrane
Question: Examples of what process are evident in many biological systems because cells are surrounded by semipermeable membranes?
A) osmosis
B) photosynthesis
C) apoptosis
D) reproduction
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A) osmosis
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Context:
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
. 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. =
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
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 – 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 – slower degradation, more pga – 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 – 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,
material. silicon nitride parts are used in ceramic ball bearings. their higher hardness means that they are much less susceptible to wear and can offer more than triple lifetimes. they also deform less under load meaning they have less contact with the bearing retainer walls and can roll faster. in very high speed applications, heat from friction during rolling can cause problems for metal bearings ; problems which are reduced by the use of ceramics. ceramics are also more chemically resistant and can be used in wet environments where steel bearings would rust. the major drawback to using ceramics is a significantly higher cost. in many cases their electrically insulating properties may also be valuable in bearings. in the early 1980s, toyota researched production of an adiabatic ceramic engine which can run at a temperature of over 6000 °f ( 3300 °c ). ceramic engines do not require a cooling system and hence allow a major weight reduction and therefore greater fuel efficiency. fuel efficiency of the engine is also higher at high temperature, as shown by carnot ' s theorem. in a conventional metallic engine, much of the energy released from the fuel must be dissipated as waste heat in order to prevent a meltdown of the metallic parts. despite all of these desirable properties, such engines are not in production because the manufacturing of ceramic parts in the requisite precision and durability is difficult. imperfection in the ceramic leads to cracks, which can lead to potentially dangerous equipment failure. such engines are possible in laboratory settings, but mass - production is not feasible with current technology. work is being done in developing ceramic parts for gas turbine engines. currently, even blades made of advanced metal alloys used in the engines ' hot section require cooling and careful limiting of operating temperatures. turbine engines made with ceramics could operate more efficiently, giving aircraft greater range and payload for a set amount of fuel. recently, there have been advances in ceramics which include bio - ceramics, such as dental implants and synthetic bones. hydroxyapatite, the natural mineral component of bone, has been made synthetically from a number of biological and chemical sources and can be formed into ceramic materials. orthopedic implants made from these materials bond readily to bone and other tissues in the body without rejection or inflammatory reactions. because of this, they are of great interest for gene delivery and tissue engineering scaffolds. most hydroxyapatite ceramics are very porous and lack mechanical strength and are used to coat metal orthopedic devices to aid in forming a bond to bone or as bone fillers. they are
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
under this elastic region is known as resilience. note that not all elastic materials undergo linear elastic deformation ; some, such as concrete, gray cast iron, and many polymers, respond in a nonlinear fashion. for these materials hooke ' s law is inapplicable. = = = plastic deformation = = = this type of deformation is not undone simply by removing the applied force. an object in the plastic deformation range, however, will first have undergone elastic deformation, which is undone simply by removing the applied force, so the object will return part way to its original shape. soft thermoplastics have a rather large plastic deformation range as do ductile metals such as copper, silver, and gold. steel does, too, but not cast iron. hard thermosetting plastics, rubber, crystals, and ceramics have minimal plastic deformation ranges. an example of a material with a large plastic deformation range is wet chewing gum, which can be stretched to dozens of times its original length. under tensile stress, plastic deformation is characterized by a strain hardening region and a necking region and finally, fracture ( also called rupture ). during strain hardening the material becomes stronger through the movement of atomic dislocations. the necking phase is indicated by a reduction in cross - sectional area of the specimen. necking begins after the ultimate strength is reached. during necking, the material can no longer withstand the maximum stress and the strain in the specimen rapidly increases. plastic deformation ends with the fracture of the material. = = failure = = = = = compressive failure = = = usually, compressive stress applied to bars, columns, etc. leads to shortening. loading a structural element or specimen will increase the compressive stress until it reaches its compressive strength. according to the properties of the material, failure modes are yielding for materials with ductile behavior ( most metals, some soils and plastics ) or rupturing for brittle behavior ( geomaterials, cast iron, glass, etc. ). in long, slender structural elements — such as columns or truss bars — an increase of compressive force f leads to structural failure due to buckling at lower stress than the compressive strength. = = = fracture = = = a break occurs after the material has reached the end of the elastic, and then plastic, deformation ranges. at this point forces accumulate until they are sufficient to cause a fracture. all materials will eventually fracture, if sufficient forces are applied. = = types of stress and strain =
; 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
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
Question: What does cartilage lack compared to bones, making it softer and less rigid?
A) potassium
B) calcium
C) magnesium
D) protein
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B) calcium
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Context:
becomes quite gentle. accordingly, in large basins, rivers in most cases begin as torrents with a variable flow, and end as gently flowing rivers with a comparatively regular discharge. the irregular flow of rivers throughout their course forms one of the main difficulties in devising works for mitigating inundations or for increasing the navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with a rapid fall near the sources of rivers can carry down rocks, boulders and large stones, which are by degrees ground by attrition in their onward course into slate, gravel, sand and silt, simultaneously with the gradual reduction in fall, and, consequently, in the transporting force of the current. accordingly, under
navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with a rapid fall near the sources of rivers can carry down rocks, boulders and large stones, which are by degrees ground by attrition in their onward course into slate, gravel, sand and silt, simultaneously with the gradual reduction in fall, and, consequently, in the transporting force of the current. accordingly, under ordinary conditions, most of the materials brought down from the high lands by torrential water courses are carried forward by the main river to the sea, or partially strewn over flat alluvial plains during floods ; the size of the materials forming the bed of the river or borne along by the stream is gradually reduced on proceeding sea
weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with a rapid fall near the sources of rivers can carry down rocks, boulders and large stones, which are by degrees ground by attrition in their onward course into slate, gravel, sand and silt, simultaneously with the gradual reduction in fall, and, consequently, in the transporting force of the current. accordingly, under ordinary conditions, most of the materials brought down from the high lands by torrential water courses are carried forward by the main river to the sea, or partially strewn over flat alluvial plains during floods ; the size of the materials forming the bed of the river or borne along by the stream is gradually reduced on proceeding seawards, so that in the po river in italy, for instance, pebbles and gravel are found for about 140 miles below turin, sand along the next 100 miles, and silt and mud in the last 110 miles ( 176 km ). = = channelization = = the removal of obstructions, natural or artificial
approximately corresponds to the slope of the country it traverses ; as rivers rise close to the highest part of their basins, generally in hilly regions, their fall is rapid near their source and gradually diminishes, with occasional irregularities, until, in traversing plains along the latter part of their course, their fall usually becomes quite gentle. accordingly, in large basins, rivers in most cases begin as torrents with a variable flow, and end as gently flowing rivers with a comparatively regular discharge. the irregular flow of rivers throughout their course forms one of the main difficulties in devising works for mitigating inundations or for increasing the navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with
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
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 drilling at grade, although this can be problematic with deep caissons, as unsupported excavations can collapse before the caisson form can be inserted. in this manner, the earth placed around the empty caisson form provides stability and strength, allowing concrete to be poured with fewer complications and with less risk of a form blowout. while, technically, only the form itself is actually a caisson, it is not uncommon for any below - grade cast concrete pillar to be referred to as, simply, a caisson. ventilation filtration systems : the word caisson is also used as a name for an airtight housing for ventilation filters in facilities that handle hazardous materials. the housing usually has an upstream compartment for a pre - filter element and a downstream compartment for a high - efficiency filter element. it may have multiple sets of compartments. the housing has gasketed access doors to allow for the change out of the filter elements. the housing is usually equipped with connection points used to test the efficiency of the filters and monitor changes in the differential pressure across the filter media. = = see also = = suction caisson – open bottomed tube anchor embedded and released by pressure differential air lock diving - bell plant – underwater work support barge used at gibraltar, a mobile barge - mounted engineering caisson used in the port of gibraltar cofferdam – barrier allowing liquid to be pumped out of an enclosed area, a temporary water - excluding structure built in place, sometimes surrounding a working area as does an open caisson. offshore geotechnical engineering – sub - field of engineering concerned with human - made structures in the sea, for information on geotechnical considerations. = = patents = = u. s. patent 123, 002 – improvement in construction of sub - aqueous foundations = = references = = = = external links = = works related to caisson at wikisource
; however, a successful large - scale industrial application of the process was the development of continuous freeze drying of coffee. high - temperature short time processing – these processes, for the most part, are characterized by rapid heating and cooling, holding for a short time at a relatively high temperature and filling aseptically into sterile containers. decaffeination of coffee and tea – decaffeinated coffee and tea was first developed on a commercial basis in europe around 1900. the process is described in u. s. patent 897, 763. green coffee beans are treated with water, heat and solvents to remove the caffeine from the beans. process optimization – food technology now allows production of foods to be more efficient, oil saving technologies are now available on different forms. production methods and methodology have also become increasingly sophisticated. aseptic packaging – the process of filling a commercially sterile product into a sterile container and hermetically sealing the containers so that re - infection is prevented. thus, this results into a shelf stable product at ambient conditions. food irradiation – the process of exposing food and food packaging to ionizing radiation can effectively destroy organisms responsible for spoilage and foodborne illness and inhibit sprouting, extending shelf life. commercial fruit ripening rooms using ethylene as a plant hormone. food delivery – an order is typically made either through a restaurant or grocer ' s website or mobile app, or through a food ordering company. the ordered food is typically delivered in boxes or bags to the customer ' s doorsteps. = = categories = = technology has innovated these categories from the food industry : agricultural technology – or agtech, it is the use of technology in agriculture, horticulture, and aquaculture with the aim of improving yield, efficiency, and profitability. agricultural technology can be products, services or applications derived from agriculture that improve various input / output processes. food science – technology in this sector focuses on the development of new functional ingredients and alternative proteins. foodservice – technology innovated the way establishments prepare, supply, and serve food outside the home. there ' s a tendency to create the conditions for the restaurant of the future with robotics and cloudkitchens. consumer tech – technology allows what we call consumer electronics, which is the equipment of consumers with devices that facilitates the cooking process. food delivery – as the food delivery market is growing, companies and startups are rapidly revolutionizing the communication process between consumers and food establishments, with platform - to - consumer delivery as the
high machining costs. there is a possibility for melt casting to be used for many of these approaches. potentially even more desirable is using melt - derived particles. in this method, quenching is done in a solid solution or in a fine eutectic structure, in which the particles are then processed by more typical ceramic powder processing methods into a useful body. there have also been preliminary attempts to use melt spraying as a means of forming composites by introducing the dispersed particulate, whisker, or fiber phase in conjunction with the melt spraying process. other methods besides melt infiltration to manufacture ceramic composites with long fiber reinforcement are chemical vapor infiltration and the infiltration of fiber preforms with organic precursor, which after pyrolysis yield an amorphous ceramic matrix, initially with a low density. with repeated cycles of infiltration and pyrolysis one of those types of ceramic matrix composites is produced. chemical vapor infiltration is used to manufacture carbon / carbon and silicon carbide reinforced with carbon or silicon carbide fibers. besides many process improvements, the first of two major needs for fiber composites is lower fiber costs. the second major need is fiber compositions or coatings, or composite processing, to reduce degradation that results from high - temperature composite exposure under oxidizing conditions. = = applications = = the products of technical ceramics include tiles used in the space shuttle program, gas burner nozzles, ballistic protection, nuclear fuel uranium oxide pellets, bio - medical implants, jet engine turbine blades, and missile nose cones. its products are often made from materials other than clay, chosen for their particular physical properties. these may be classified as follows : oxides : silica, alumina, zirconia non - oxides : carbides, borides, nitrides, silicides composites : particulate or whisker reinforced matrices, combinations of oxides and non - oxides ( e. g. polymers ). ceramics can be used in many technological industries. one application is the ceramic tiles on nasa ' s space shuttle, used to protect it and the future supersonic space planes from the searing heat of re - entry into the earth ' s atmosphere. they are also used widely in electronics and optics. in addition to the applications listed here, ceramics are also used as a coating in various engineering cases. an example would be a ceramic bearing coating over a titanium frame used for an aircraft. recently the field has come to include the studies of single
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
temperature changes up to 1000 °c. = = processing steps = = the traditional ceramic process generally follows this sequence : milling → batching → mixing → forming → drying → firing → 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,
Question: What three forms does frozen precipitation take?
A) snow, sleet, freezing rain
B) vapor, fog, ice
C) blizzard, frost, fog
D) hail, wind, typhoon
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A) snow, sleet, freezing rain
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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
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
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
##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
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 (
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
approximately corresponds to the slope of the country it traverses ; as rivers rise close to the highest part of their basins, generally in hilly regions, their fall is rapid near their source and gradually diminishes, with occasional irregularities, until, in traversing plains along the latter part of their course, their fall usually becomes quite gentle. accordingly, in large basins, rivers in most cases begin as torrents with a variable flow, and end as gently flowing rivers with a comparatively regular discharge. the irregular flow of rivers throughout their course forms one of the main difficulties in devising works for mitigating inundations or for increasing the navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with
equalizing the flow at these places, produces a lowering of the river above the rapids by facilitating the efflux, which may result in the appearance of fresh shoals at the low stage of the river. where, however, narrow rocky reefs or other hard shoals stretch across the bottom of a river and present obstacles to the erosion by the current of the soft materials forming the bed of the river above and below, their removal may result in permanent improvement by enabling the river to deepen its bed by natural scour. the capability of a river to provide a waterway for navigation during the summer or throughout the dry season depends on the depth that can be secured in the channel at the lowest stage. the problem in the dry season is the small discharge and deficiency in scour during this period. a typical solution is to restrict the width of the low - water channel, concentrate all of the flow in it, and also to fix its position so that it is scoured out every year by the floods which follow the deepest part of the bed along the line of the strongest current. this can be effected by closing subsidiary low - water channels with dikes across them, and narrowing the channel at the low stage by low - dipping cross dikes extending from the river banks down the slope and pointing slightly up - stream so as to direct the water flowing over them into a central channel. = = estuarine works = = the needs of navigation may also require that a stable, continuous, navigable channel is prolonged from the navigable river to deep water at the mouth of the estuary. the interaction of river flow and tide needs to be modeled by computer or using scale models, moulded to the configuration of the estuary under consideration and reproducing in miniature the tidal ebb and flow and fresh - water discharge over a bed of fine sand, in which various lines of training walls can be successively inserted. the models should be capable of furnishing valuable indications of the respective effects and comparative merits of the different schemes proposed for works. = = see also = = bridge scour flood control = = references = = = = external links = = u. s. army corps of engineers – civil works program river morphology and stream restoration references - wildland hydrology at the library of congress web archives ( archived 2002 - 08 - 13 )
for inland navigation in the lower portion of their course, as, for instance, the rhine, the danube and the mississippi. river engineering works are only required to prevent changes in the course of the stream, to regulate its depth, and especially to fix the low - water channel and concentrate the flow in it, so as to increase as far as practicable the navigable depth at the lowest stage of the water level. engineering works to increase the navigability of rivers can only be advantageously undertaken in large rivers with a moderate fall and a fair discharge at their lowest stage, for with a large fall the current presents a great impediment to up - stream navigation, and there are generally variations in water level, and when the discharge becomes small in the dry season. it is impossible to maintain a sufficient depth of water in the low - water channel. the possibility to secure uniformity of depth in a river by lowering the shoals obstructing the channel depends on the nature of the shoals. a soft shoal in the bed of a river is due to deposit from a diminution in velocity of flow, produced by a reduction in fall and by a widening of the channel, or to a loss in concentration of the scour of the main current in passing over from one concave bank to the next on the opposite side. the lowering of such a shoal by dredging merely effects a temporary deepening, for it soon forms again from the causes which produced it. the removal, moreover, of the rocky obstructions at rapids, though increasing the depth and equalizing the flow at these places, produces a lowering of the river above the rapids by facilitating the efflux, which may result in the appearance of fresh shoals at the low stage of the river. where, however, narrow rocky reefs or other hard shoals stretch across the bottom of a river and present obstacles to the erosion by the current of the soft materials forming the bed of the river above and below, their removal may result in permanent improvement by enabling the river to deepen its bed by natural scour. the capability of a river to provide a waterway for navigation during the summer or throughout the dry season depends on the depth that can be secured in the channel at the lowest stage. the problem in the dry season is the small discharge and deficiency in scour during this period. a typical solution is to restrict the width of the low - water channel, concentrate all of the flow in it, and also to fix its position so that it is
Question: What is a stream of moving water that flows through the ocean?
A) waterfall
B) creek
C) current
D) tidal wave
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C) current
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Context:
28 size spectra of extensive air showers from 7 different experiments are analysed consistently. they are fitted by adjusting either 4 or 5 parameters : knee position, power law exponents above and below the knee, overall intensity and, in addition, a parameter describing the smoothness of the bend. the residuals are then normalized to the same knee position and averaged. when 5 parameters are employed no systematic deviation from a single smooth knee is apparent at the 1 % level up to a factor of 4 above the knee. at larger shower sizes a moderately significant deviation can be seen whose shape and position are compatible with a second knee caused by iron group nuclei.
i state some open problems coming from joint work with paul erd \ h { o } s
as a traditional tool of external assistance, crutches play an important role in society. they have a wide range of applications to help either the elderly and disabled to walk or to treat certain illnesses or for post - operative rehabilitation. but there are many different types of crutches, including shoulder crutches and elbow crutches. how to choose has become an issue that deserves to be debated. because while crutches help people walk, they also have an impact on the body. inappropriate choice of crutches or long - term misuse can lead to problems such as scoliosis. previous studies were mainly experimental measurements or the construction of dynamic models to calculate the load on joints with crutches. these studies focus only on the level of the joints, ignoring the role that muscles play in this process. although some also take into account the degree of muscle activation, there is still a lack of quantitative analysis. the traditional dynamic model can be used to calculate the load on each joint. however, due to the activation of the muscle, this situation only causes part of the load transmitted to the joint, and the work of the chair will compensate the other part of the load. analysis at the muscle level allows a better understanding of the impact of crutches on the body. by comparing the levels of activation of the trunk muscles, it was found that the use of crutches for walking, especially a single crutch, can cause a large difference in the activation of the back muscles on the left and right sides, and this difference will cause muscle degeneration for a long time, leading to scoliosis. in this article taking scoliosis as an example, by analyzing the muscles around the spine, we can better understand the pathology and can better prevent diseases. the objective of this article is to analyze normal walking compared to walking with one or two crutches using opensim software to obtain the degree of activation of different muscles in order to analyze the impact of crutches on the body.
ring mass density and the corresponding circular velocity in thin disk model are known to be integral transforms of one another. but it may be less familiar that the transforms can be reduced to one - fold integrals with identical weight functions. it may be of practical value that the integral for the surface density does not involve the velocity derivative, unlike the equivalent and widely known toomre ' s formula.
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 – 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 — from a
dimension 3, typically r3. a surface that is contained in a projective space is called a projective surface ( see § 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 }
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
defective body parts. inside the body, artificial heart valves are in common use with artificial hearts and lungs seeing less common use but under active technology development. other medical devices and aids that can be considered prosthetics include hearing aids, artificial eyes, palatal obturator, gastric bands, and dentures. prostheses are specifically not orthoses, although given certain circumstances a prosthesis might end up performing some or all of the same functionary benefits as an orthosis. prostheses are technically the complete finished item. for instance, a c - leg knee alone is not a prosthesis, but only a prosthetic component. the complete prosthesis would consist of the attachment system to the residual limb – usually a " socket ", and all the attachment hardware components all the way down to and including the terminal device. despite the technical difference, the terms are often used interchangeably. the terms " prosthetic " and " orthotic " are adjectives used to describe devices such as a prosthetic knee. the terms " prosthetics " and " orthotics " are used to describe the respective allied health fields. an occupational therapist ' s role in prosthetics include therapy, training and evaluations. prosthetic training includes orientation to prosthetics components and terminology, donning and doffing, wearing schedule, and how to care for residual limb and the prosthesis. = = = exoskeletons = = = a powered exoskeleton is a wearable mobile machine that is powered by a system of electric motors, pneumatics, levers, hydraulics, or a combination of technologies that allow for limb movement with increased strength and endurance. its design aims to provide back support, sense the user ' s motion, and send a signal to motors which manage the gears. the exoskeleton supports the shoulder, waist and thigh, and assists movement for lifting and holding heavy items, while lowering back stress. = = = adaptive seating and positioning = = = people with balance and motor function challenges often need specialized equipment to sit or stand safely and securely. this equipment is frequently specialized for specific settings such as in a classroom or nursing home. positioning is often important in seating arrangements to ensure that user ' s body pressure is distributed equally without inhibiting movement in a desired way. positioning devices have been developed to aid in allowing people to stand and bear weight on their legs without risk of a fall.
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.
used for tools, weapons and monumental statuary. by 1200 bc they could cast objects 5 m long in a single piece. several of the six classic simple machines were invented in mesopotamia. mesopotamians have been credited with the invention of the wheel. the wheel and axle mechanism first appeared with the potter ' s wheel, invented in mesopotamia ( modern iraq ) during the 5th millennium bc. this led to the invention of the wheeled vehicle in mesopotamia during the early 4th millennium bc. depictions of wheeled wagons found on clay tablet pictographs at the eanna district of uruk are dated between 3700 and 3500 bc. the lever was used in the shadoof water - lifting device, the first crane machine, which appeared in mesopotamia circa 3000 bc, and then in ancient egyptian technology circa 2000 bc. the earliest evidence of pulleys date back to mesopotamia in the early 2nd millennium bc. the screw, the last of the simple machines to be invented, first appeared in mesopotamia during the neo - assyrian period ( 911 – 609 ) bc. the assyrian king sennacherib ( 704 – 681 bc ) claims to have invented automatic sluices and to have been the first to use water screw pumps, of up to 30 tons weight, which were cast using two - part clay molds rather than by the ' lost wax ' process. the jerwan aqueduct ( c. 688 bc ) is made with stone arches and lined with waterproof concrete. the babylonian astronomical diaries spanned 800 years. they enabled meticulous astronomers to plot the motions of the planets and to predict eclipses. the earliest evidence of water wheels and watermills date back to the ancient near east in the 4th century bc, specifically in the persian empire before 350 bc, in the regions of mesopotamia ( iraq ) and persia ( iran ). this pioneering use of water power constituted the first human - devised motive force not to rely on muscle power ( besides the sail ). = = = = egypt = = = = the egyptians, known for building pyramids centuries before the creation of modern tools, invented and used many simple machines, such as the ramp to aid construction processes. historians and archaeologists have found evidence that the pyramids were built using three of what is called the six simple machines, from which all machines are based. these machines are the inclined plane, the wedge, and the lever, which allowed the ancient egyptians to move millions of limestone blocks which weighed approximately 3. 5 tons ( 7, 000 lbs. ) each into place to create structures like the
Question: The elbow is an example of a what type of joint?
A) frame joint
B) pipe joint
C) toe joint
D) hinge joint
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D) hinge joint
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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 " – 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
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 ) – 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
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
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 " – 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
, fungi ( mycology ) – including lichen - forming fungi ( lichenology ), non - chlorophyte algae ( phycology ), and viruses ( virology ). however, attention is still given to these groups by botanists, and fungi ( including lichens ) and photosynthetic protists are usually covered in introductory botany courses. palaeobotanists study ancient plants in the fossil record to provide information about the evolutionary history of plants. cyanobacteria, the first oxygen - releasing photosynthetic organisms on earth, are thought to have given rise to the ancestor of plants by entering into an endosymbiotic relationship with an early eukaryote, ultimately becoming the chloroplasts in plant cells. the new photosynthetic plants ( along with their algal relatives ) accelerated the rise in atmospheric oxygen started by the cyanobacteria, changing the ancient oxygen - free, reducing, atmosphere to one in which free oxygen has been abundant for more than 2 billion years. among the important botanical questions of the 21st century are the role of plants as primary producers in the global cycling of life ' s basic ingredients : energy, carbon, oxygen, nitrogen and water, and ways that our plant stewardship can help address the global environmental issues of resource management, conservation, human food security, biologically invasive organisms, carbon sequestration, climate change, and sustainability. = = = human nutrition = = = virtually all staple foods come either directly from primary production by plants, or indirectly from animals that eat them. plants and other photosynthetic organisms are at the base of most food chains because they use the energy from the sun and nutrients from the soil and atmosphere, converting them into a form that can be used by animals. this is what ecologists call the first trophic level. the modern forms of the major staple foods, such as hemp, teff, maize, rice, wheat and other cereal grasses, pulses, bananas and plantains, as well as hemp, flax and cotton grown for their fibres, are the outcome of prehistoric selection over thousands of years from among wild ancestral plants with the most desirable characteristics. botanists study how plants produce food and how to increase yields, for example through plant breeding, making their work important to humanity ' s ability to feed the world and provide food security for future generations. botanists also study weeds, which are a considerable problem in agriculture, and the biology and control of plant
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 ) – 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
##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 – 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 – 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
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 – 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 :
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 – 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 – 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
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 " – their spores were of two distinct sizes, larger megaspores and smaller microspores. their reduced gametophytes developed from megaspores retained within the spore - producing organs ( megasporangia ) of the sporophyte, a condition known as endospory. seeds consist of an endosporic megasporangium surrounded by one or two sheathing layers ( integuments ). the young sporophyte develops within the seed, which on germination splits to release it. the earliest known seed plants date from the latest devonian famennian stage. following the evolution of the seed habit, seed plants diversified, giving rise to a number of now - extinct groups, including seed ferns, as well as the modern gym
Question: The first leaves of most ferns appear curled up into what?
A) petals
B) nanotubes
C) volatiles
D) fiddleheads
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D) fiddleheads
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Context:
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
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?
##idermal electronics mirror those of skin to allow them to perform in this same way. like skin, epidermal electronics are ultrathin ( h < 100 μm ), low - modulus ( e ≈70 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
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 cl−. 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
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.
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.
in a voltaic cell, positive ( negative ) ions flow from the low ( high ) potential electrode to the high ( low ) potential electrode, driven by an ` electromotive force ' which points in opposite direction and overcomes the electric force. similarly in a superconductor charge flows in direction opposite to that dictated by the faraday electric field as the magnetic field is expelled in the meissner effect. the puzzle is the same in both cases : what drives electric charges against electromagnetic forces? i propose that the answer is also the same in both cases : kinetic energy lowering, or ` quantum pressure '.
two types of stars are known to have strong, large scale magnetic fields : the main sequence ap stars and the magnetic white dwarfs. this suggest that the former might be the progenitors of the latter. in order to test this idea, i have carried out a search for large scale magnetic fields in stars with evolutionary states which are intermediate, i. e. in horizontal branch stars and in hot subdwarfs.
directly on the skin is currently available as a sole study source. the significance of epidermal electronics involves their mechanical properties, which resemble those of skin. the skin can be modeled as bilayer, composed of an epidermis having young ' s modulus ( e ) of 2 - 80 kpa and thickness of 0. 3 – 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 ≥ 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 μm ), low - modulus ( e ≈70 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
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,
Question: Electrophiles have a strong tendency to react with what?
A) acids
B) resistors
C) nucleophiles
D) neutrons
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C) nucleophiles
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Context:
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 – the environments where they complete their life cycles. plant ecologists study the composition of local and regional floras, their biodiversity, genetic diversity and fitness, the adaptation of plants to their environment, and their competitive or mutualistic interactions with other species. some ecologists even rely on empirical data from indigenous people that is gathered by ethnobotanists. this information can relay a great deal of information on how the land once was thousands of years ago and how it has changed over that time. the goals of plant ecology are to understand the causes of their distribution patterns, productivity, environmental impact, evolution, and responses to environmental change. plants depend on certain edaphic ( soil ) and climatic factors in their environment but can modify these factors too. for example, they can change their environment ' s albedo, increase runoff interception, stabilise mineral soils and develop their organic content, and affect local temperature. plants compete with other organisms in their ecosystem for resources. they interact with their neighbours at a variety of spatial scales in groups, populations and communities that collectively constitute vegetation. regions with characteristic vegetation types and dominant plants as well as similar abiot
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 – 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
##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 – 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 – 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
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 – 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 – 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
high machining costs. there is a possibility for melt casting to be used for many of these approaches. potentially even more desirable is using melt - derived particles. in this method, quenching is done in a solid solution or in a fine eutectic structure, in which the particles are then processed by more typical ceramic powder processing methods into a useful body. there have also been preliminary attempts to use melt spraying as a means of forming composites by introducing the dispersed particulate, whisker, or fiber phase in conjunction with the melt spraying process. other methods besides melt infiltration to manufacture ceramic composites with long fiber reinforcement are chemical vapor infiltration and the infiltration of fiber preforms with organic precursor, which after pyrolysis yield an amorphous ceramic matrix, initially with a low density. with repeated cycles of infiltration and pyrolysis one of those types of ceramic matrix composites is produced. chemical vapor infiltration is used to manufacture carbon / carbon and silicon carbide reinforced with carbon or silicon carbide fibers. besides many process improvements, the first of two major needs for fiber composites is lower fiber costs. the second major need is fiber compositions or coatings, or composite processing, to reduce degradation that results from high - temperature composite exposure under oxidizing conditions. = = applications = = the products of technical ceramics include tiles used in the space shuttle program, gas burner nozzles, ballistic protection, nuclear fuel uranium oxide pellets, bio - medical implants, jet engine turbine blades, and missile nose cones. its products are often made from materials other than clay, chosen for their particular physical properties. these may be classified as follows : oxides : silica, alumina, zirconia non - oxides : carbides, borides, nitrides, silicides composites : particulate or whisker reinforced matrices, combinations of oxides and non - oxides ( e. g. polymers ). ceramics can be used in many technological industries. one application is the ceramic tiles on nasa ' s space shuttle, used to protect it and the future supersonic space planes from the searing heat of re - entry into the earth ' s atmosphere. they are also used widely in electronics and optics. in addition to the applications listed here, ceramics are also used as a coating in various engineering cases. an example would be a ceramic bearing coating over a titanium frame used for an aircraft. recently the field has come to include the studies of single
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
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 – 350 °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 – 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 σ y = σ 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 ), σo 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 σy is the
are commonly referred to as " cross - hatching ". phantom – ( 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 – 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 – 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 (
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 °c ( 2, 750 °f ) and protects the space shuttle ' s wing leading edges and nose cap. rcc is a laminated composite material made from graphite rayon cloth and impregnated with a phenolic resin. after curing at high temperature in an autoclave, the laminate is pyrolized to convert the resin to carbon, impregnated with furfuryl alcohol in a vacuum chamber, and cured - pyrolized to convert the furfuryl alcohol to carbon. to provide oxidation resistance for reusability, the outer layers of the rcc are converted to silicon carbide. other examples can be seen in the " plastic " casings of television sets, cell - phones and so on. these plastic casings are usually a composite material made up of a thermoplastic matrix such as acrylonitrile butadiene styrene ( abs ) in which calcium carbonate chalk, talc, glass fibers or carbon fibers have been added for added strength, bulk, or electrostatic dispersion. these additions may be termed reinforcing fibers, or dispersants, depending on their purpose. = = = polymers = = = polymers are chemical compounds made up of a large number of identical components linked together like chains. polymers are the raw materials ( the resins ) used to make what are commonly called plastics and rubber. plastics and rubber are the final product, created after one or more polymers or additives have been added to a resin during processing, which is then shaped into a final form. plastics in former and in current widespread use include polyethylene, polypropylene, polyvinyl chloride ( pvc ), polystyrene, nylons, polyesters, acrylics, polyurethanes, and polycarbonates. rubbers include natural rubber, styrene - butadiene rubber, chloroprene, and butadiene rubber. plastics are generally classified as commodity, specialty and engineering plastics. polyvinyl chloride ( pvc ) is widely used, inexpensive, and annual production quantities are large. it lends itself to a vast array of applications, from artificial leather to electrical insulation and cabling, packaging, and containers. its fabrication and processing are simple and well - established.
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 °c ( 2, 750 °f ) and protects the space shuttle ' s wing leading edges and nose cap. rcc is a laminated composite material made from graphite rayon cloth and impregnated with a phenolic resin. after curing at high temperature in an autoclave, the laminate is pyrolized to convert the resin to carbon, impregnated with furfuryl alcohol in a vacuum chamber, and cured - pyrolized to convert the furfuryl alcohol to carbon. to provide oxidation resistance for reusability, the outer layers of the rcc are converted to silicon carbide. other examples can be seen in the " plastic " casings of television sets, cell - phones and so on. these plastic casings are usually a composite material made up of a thermoplastic matrix such as acrylonitrile butadiene styrene ( abs ) in which calcium carbonate chalk, talc, glass fibers or carbon fibers have been added for added strength, bulk, or electrostatic dispersion. these additions may be termed reinforcing fibers, or dispersants, depending on their purpose. = = = polymers = = = polymers are chemical compounds made up of a large number of identical components linked together like chains. polymers are the raw materials ( the resins ) used to make what are commonly called plastics and rubber. plastics and rubber are the final product, created after one or more polymers or additives have been added to a resin during processing, which is then shaped into a final form. plastics in former and in current widespread use include polyethylene, polypropylene, polyvinyl chloride ( pvc ), polystyrene, nylons, polyesters, acrylics, polyurethanes, and polycarbonates. rubbers include natural rubber, styrene - butadiene rubber, chloroprene, and butadiene rubber. plastics are generally classified as commodity
Question: What layered form of carbon is used as a lubricant and in pencils?
A) lead
B) graphite
C) carbonite
D) copper
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B) graphite
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Context:
material includes the unit cell, which is the smallest unit of a crystal lattice ( space lattice ) that repeats to make up the macroscopic crystal structure. most common structural materials include parallelpiped and hexagonal lattice types. in single crystals, the effects of the crystalline arrangement of atoms is often easy to see macroscopically, because the natural shapes of crystals reflect the atomic structure. further, physical properties are often controlled by crystalline defects. the understanding of crystal structures is an important prerequisite for understanding crystallographic defects. examples of crystal defects consist of dislocations including edges, screws, vacancies, self inter - stitials, and more that are linear, planar, and three dimensional types of defects. new and advanced materials that are being developed include nanomaterials, biomaterials. mostly, materials do not occur as a single crystal, but in polycrystalline form, as an aggregate of small crystals or grains with different orientations. because of this, the powder diffraction method, which uses diffraction patterns of polycrystalline samples with a large number of crystals, plays an important role in structural determination. most materials have a crystalline structure, but some important materials do not exhibit regular crystal structure. polymers display varying degrees of crystallinity, and many are completely non - crystalline. glass, some ceramics, and many natural materials are amorphous, not possessing any long - range order in their atomic arrangements. the study of polymers combines elements of chemical and statistical thermodynamics to give thermodynamic and mechanical descriptions of physical properties. = = = = nanostructure = = = = materials, which atoms and molecules form constituents in the nanoscale ( i. e., they form nanostructures ) are called nanomaterials. nanomaterials are the subject of intense research in the materials science community due to the unique properties that they exhibit. nanostructure deals with objects and structures that are in the 1 – 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
##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
##ally, because the natural shapes of crystals reflect the atomic structure. further, physical properties are often controlled by crystalline defects. the understanding of crystal structures is an important prerequisite for understanding crystallographic defects. examples of crystal defects consist of dislocations including edges, screws, vacancies, self inter - stitials, and more that are linear, planar, and three dimensional types of defects. new and advanced materials that are being developed include nanomaterials, biomaterials. mostly, materials do not occur as a single crystal, but in polycrystalline form, as an aggregate of small crystals or grains with different orientations. because of this, the powder diffraction method, which uses diffraction patterns of polycrystalline samples with a large number of crystals, plays an important role in structural determination. most materials have a crystalline structure, but some important materials do not exhibit regular crystal structure. polymers display varying degrees of crystallinity, and many are completely non - crystalline. glass, some ceramics, and many natural materials are amorphous, not possessing any long - range order in their atomic arrangements. the study of polymers combines elements of chemical and statistical thermodynamics to give thermodynamic and mechanical descriptions of physical properties. = = = = nanostructure = = = = materials, which atoms and molecules form constituents in the nanoscale ( i. e., they form nanostructures ) are called nanomaterials. nanomaterials are the subject of intense research in the materials science community due to the unique properties that they exhibit. nanostructure deals with objects and structures that are in the 1 – 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
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
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
building block. ceramics – not to be confused with raw, unfired clay – 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 °c ( 2, 750 °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
patterned surface approximately the same as its downward etch rate, or can be anisotropic, i. e., exhibiting a smaller lateral undercut rate than its downward etch rate. such anisotropy is maximized in deep reactive ion etching. the use of the term anisotropy for plasma etching should not be conflated with the use of the same term when referring to orientation - dependent etching. the source gas for the plasma usually contains small molecules rich in chlorine or fluorine. for instance, carbon tetrachloride ( ccl4 ) etches silicon and aluminium, and trifluoromethane etches silicon dioxide and silicon nitride. a plasma containing oxygen is used to oxidize ( " ash " ) photoresist and facilitate its removal. ion milling, or sputter etching, uses lower pressures, often as low as 10−4 torr ( 10 mpa ). it bombards the wafer with energetic ions of noble gases, often ar +, which knock atoms from the substrate by transferring momentum. because the etching is performed by ions, which approach the wafer approximately from one direction, this process is highly anisotropic. on the other hand, it tends to display poor selectivity. reactive - ion etching ( rie ) operates under conditions intermediate between sputter and plasma etching ( between 10−3 and 10−1 torr ). deep reactive - ion etching ( drie ) modifies the rie technique to produce deep, narrow features. in reactive - ion etching ( rie ), the substrate is placed inside a reactor, and several gases are introduced. a plasma is struck in the gas mixture using an rf power source, which breaks the gas molecules into ions. the ions accelerate towards, and react with, the surface of the material being etched, forming another gaseous material. this is known as the chemical part of reactive ion etching. there is also a physical part, which is similar to the sputtering deposition process. if the ions have high enough energy, they can knock atoms out of the material to be etched without a chemical reaction. it is a very complex task to develop dry etch processes that balance chemical and physical etching, since there are many parameters to adjust. by changing the balance it is possible to influence the anisotropy of the etching, since the chemical part is isotropic and the physical part highly anisotropic the combination can
resistant to the wet etchants. this has been used in mews pressure sensor manufacturing for example. etching progresses at the same speed in all directions. long and narrow holes in a mask will produce v - shaped grooves in the silicon. the surface of these grooves can be atomically smooth if the etch is carried out correctly, with dimensions and angles being extremely accurate. some single crystal materials, such as silicon, will have different etching rates depending on the crystallographic orientation of the substrate. this is known as anisotropic etching and one of the most common examples is the etching of silicon in koh ( potassium hydroxide ), where si < 111 > planes etch approximately 100 times slower than other planes ( crystallographic orientations ). therefore, etching a rectangular hole in a ( 100 ) - si wafer results in a pyramid shaped etch pit with 54. 7° walls, instead of a hole 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 – 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 me
an important question of theoretical physics is whether sound is able to propagate in vacuums at all and if this is the case, then it must lead to the reinterpretation of one zero - restmass particle which corresponds to vacuum - sound waves. taking the electron - neutrino as the corresponding particle, its observed non - vanishing rest - energy may only appear for neutrino - propagation inside material media. the idea may also influence the physics of dense matter, restricting the maximum speed of sound, both in vacuums and in matter to the speed of light.
Question: What kind of solids have particles that are arranged in a regular repeating pattern?
A) crystalline solids
B) carbon-based solids
C) salts
D) metabolic solids
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A) crystalline solids
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Context:
28 size spectra of extensive air showers from 7 different experiments are analysed consistently. they are fitted by adjusting either 4 or 5 parameters : knee position, power law exponents above and below the knee, overall intensity and, in addition, a parameter describing the smoothness of the bend. the residuals are then normalized to the same knee position and averaged. when 5 parameters are employed no systematic deviation from a single smooth knee is apparent at the 1 % level up to a factor of 4 above the knee. at larger shower sizes a moderately significant deviation can be seen whose shape and position are compatible with a second knee caused by iron group nuclei.
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.
##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
coherent motion of electrons in a twisted quantum ring is considered to explore the effect of torsion inherent to the ring. internal torsion of the ring composed of helical atomic configuration yields a non - trivial quantum phase shift in the electrons ' eigenstates. this torsion - induced phase shift causes novel kinds of persistent current flow and an aharonov - bohm like conductance oscillation. the two phenomena can occur even when no magnetic flux penetrates inside the twisted ring, thus being in complete contrast with the counterparts observed in untwisted rings.
a statistical study of the environment around polar ring galaxies is presented. two kinds of search are performed : 1 ) a study of the concentration and diameters of all the objects surrounding the polar rings, within a search field 5 times the ring diameter. new magnitudes for polar ring galaxies are presented. 2 ) a search, in a wider field, for galaxies of similar size that may have encountered the polar ring host galaxy in a time of the order of 1 gyr. differently from the results of similar searches in the fields of active galaxies, the environment of the polar ring galaxies seems to be similar to that of normal galaxies. this result may give support to the models suggesting long times for formation and evolution of the rings. if the rings are old ( and stable or in equilibrium ), no traces of the past interaction are expected in their surroundings. in addition, the formation of massive polar rings, too big to derive from the ingestion of a present - day dwarf galaxy, may be easily placed in epochs with a higher number of gas - rich galaxies.
in the muon storage rings the muons are subject to a very large radial acceleration. the equivalence principle implies a large gravity force. it has no effect on the muon lifetime.
there is an odd tension in electroweak physics. perturbation theory is extremely successful. at the same time, fundamental field theory gives manifold reasons why this should not be the case. this tension is resolved by the fr \ " ohlich - morchio - strocchi mechanism. however, the legacy of this work goes far beyond the resolution of this tension, and may usher in a fundamentally and ontologically different perspective on elementary particles, and even quantum gravity.
cosmic strings in the brane universe have recently gained a great interest. i think the most interesting story is that future cosmological observations distinguish them from the conventional cosmic strings. if the strings are the higher - dimensional objects that can ( at least initially ) move along the compactified space, and finally settle down to ( quasi - ) degenerated vacua in the compactified space, then kinks should appear on the strings, which interpolate between the degenerated vacua. these kinks look like ` ` beads ' ' on the strings, which means that the strings turn into necklaces. moreover, in the case that the compact manifold is not simply connected, the string loop that winds around a non - trivial circle is stable due to the topological reason. since the existence of degenerated vacua and a non - trivial circle is the common feature of the brane models, it is important to study cosmological constraints on the cosmic necklaces and their stable winding states in the brane universe.
we have found an oscillating instability of fast - running cracks in thin rubber sheets. a well - defined transition from straight to oscillating cracks occurs as the amount of biaxial strain increases. measurements of the amplitude and wavelength of the oscillation near the onset of this instability indicate that the instability is a hopf bifurcation.
as a traditional tool of external assistance, crutches play an important role in society. they have a wide range of applications to help either the elderly and disabled to walk or to treat certain illnesses or for post - operative rehabilitation. but there are many different types of crutches, including shoulder crutches and elbow crutches. how to choose has become an issue that deserves to be debated. because while crutches help people walk, they also have an impact on the body. inappropriate choice of crutches or long - term misuse can lead to problems such as scoliosis. previous studies were mainly experimental measurements or the construction of dynamic models to calculate the load on joints with crutches. these studies focus only on the level of the joints, ignoring the role that muscles play in this process. although some also take into account the degree of muscle activation, there is still a lack of quantitative analysis. the traditional dynamic model can be used to calculate the load on each joint. however, due to the activation of the muscle, this situation only causes part of the load transmitted to the joint, and the work of the chair will compensate the other part of the load. analysis at the muscle level allows a better understanding of the impact of crutches on the body. by comparing the levels of activation of the trunk muscles, it was found that the use of crutches for walking, especially a single crutch, can cause a large difference in the activation of the back muscles on the left and right sides, and this difference will cause muscle degeneration for a long time, leading to scoliosis. in this article taking scoliosis as an example, by analyzing the muscles around the spine, we can better understand the pathology and can better prevent diseases. the objective of this article is to analyze normal walking compared to walking with one or two crutches using opensim software to obtain the degree of activation of different muscles in order to analyze the impact of crutches on the body.
Question: During what in the small intestine do rings of smooth muscle repeatedly contract and then relax?
A) mitosis
B) segmentation
C) compression
D) contraction
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B) segmentation
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Context:
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 )
##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
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
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 – 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
to investigate the affinity of acetylated wood for organic liquids, yezo spruce wood specimens were acetylated with acetic anhydride, and their swelling in various liquids were compared to those of untreated specimens. the acetylated wood was rapidly and remarkably swollen in aprotic organic liquids such as benzene and toluene in which the untreated wood was swollen only slightly and / or very slowly. on the other hand, the swelling of wood in water, ethylene glycol and alcohols remained unchanged or decreased by the acetylation. consequently the maximum volume of wood swollen in organic liquids was always larger than that in water. the effect of acetylation on the maximum swollen volume of wood was greater in liquids having smaller solubility parameters. the easier penetration of aprotic organic liquids into the acetylated wood was considered to be due to the scission of hydrogen bonds among the amorphous wood constituents by the substitution of hydroxyl groups with hydrophobic acetyl groups.
elongation and the control of flowering. abscisic acid ( aba ) occurs in all land plants except liverworts, and is synthesised from carotenoids in the chloroplasts and other plastids. it inhibits cell division, promotes seed maturation, and dormancy, and promotes stomatal closure. it was so named because it was originally thought to control abscission. ethylene is a gaseous hormone that is produced in all higher plant tissues from methionine. it is now known to be the hormone that stimulates or regulates fruit ripening and abscission, and it, or the synthetic growth regulator ethephon which is rapidly metabolised to produce ethylene, are used on industrial scale to promote ripening of cotton, pineapples and other climacteric crops. another class of phytohormones is the jasmonates, first isolated from the oil of jasminum grandiflorum which regulates wound responses in plants by unblocking the expression of genes required in the systemic acquired resistance response to pathogen attack. in addition to being the primary energy source for plants, light functions as a signalling device, providing information to the plant, such as how much sunlight the plant receives each day. this can result in adaptive changes in a process known as photomorphogenesis. phytochromes are the photoreceptors in a plant that are sensitive to light. = = plant anatomy and morphology = = plant anatomy is the study of the structure of plant cells and tissues, whereas plant morphology is the study of their external form. all plants are multicellular eukaryotes, their dna stored in nuclei. the characteristic features of plant cells that distinguish them from those of animals and fungi include a primary cell wall composed of the polysaccharides cellulose, hemicellulose and pectin, larger vacuoles than in animal cells and the presence of plastids with unique photosynthetic and biosynthetic functions as in the chloroplasts. other plastids contain storage products such as starch ( amyloplasts ) or lipids ( elaioplasts ). uniquely, streptophyte cells and those of the green algal order trentepohliales divide by construction of a phragmoplast as a template for building a cell plate late in cell division. the bodies of vascular plants including clubmos
are continuous lines used to depict edges directly visible from a particular angle. hidden – are short - dashed lines that may be used to represent edges that are not directly visible. center – are alternately long - and short - dashed lines that may be used to represent the axes of circular features. cutting plane – are thin, medium - dashed lines, or thick alternately long - and double short - dashed that may be used to define sections for section views. section – 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 – ( 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 – 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 – 20 mm, then a small gap, then a small line of 2 mm, then a gap, then another small line. 2h
the mechanism leading to an auger transition is based on the residual coulomb interaction between the valence electron and the core electrons. on the assumption that the wave field is switched on adiabatically, the probability of the auger effect of the inner electrons of the atom is determined.
generic axion models give rise to axion domain walls in the early universe and they have to disappear not to overclose the universe, thus limiting the nature of discrete symmetry allowed in these type of models. through qcd sphalerons, net chiral charge can be created by these collapsing walls which in turn can result the observed baryon assymmetry.
##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 – 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 – 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
Question: Acetyl-coa is formed from the breakdown of carbohydrates, lipids, and what else?
A) hydrocarbons
B) acids
C) hormones
D) proteins
|
D) proteins
|
Context:
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
and child health in boston, said of the digital generation, " their brains are rewarded not for staying on task, but for jumping to the next thing. the worry is we ' re raising a generation of kids in front of screens whose brains are going to be wired differently. " students have always faced distractions ; computers and cell phones are a particular challenge because the stream of data can interfere with focusing and learning. although these technologies affect adults too, young people may be more influenced by it as their developing brains can easily become habituated to switching tasks and become unaccustomed to sustaining attention. too much information, coming too rapidly, can overwhelm thinking. technology is " rapidly and profoundly altering our brains. " high exposure levels stimulate brain cell alteration and release neurotransmitters, which causes the strengthening of some neural pathways and the weakening of others. this leads to heightened stress levels on the brain that, at first, boost energy levels, but, over time, actually augment memory, impair cognition, lead to depression, and alter the neural circuitry of the hippocampus, amygdala and prefrontal cortex. these are the brain regions that control mood and thought. if unchecked, the underlying structure of the brain could be altered. overstimulation due to technology may begin too young. when children are exposed before the age of seven, important developmental tasks may be delayed, and bad learning habits might develop, which " deprives children of the exploration and play that they need to develop. " media psychology is an emerging specialty field that embraces electronic devices and the sensory behaviors occurring from the use of educational technology in learning. = = = sociocultural criticism = = = according to lai, " the learning environment is a complex system where the interplay and interactions of many things impact the outcome of learning. " when technology is brought into an educational setting, the pedagogical setting changes in that technology - driven teaching can change the entire meaning of an activity without adequate research validation. if technology monopolizes an activity, students can begin to develop the sense that " life would scarcely be thinkable without technology. " leo marx considered the word " technology " itself as problematic, susceptible to reification and " phantom objectivity ", which conceals its fundamental nature as something that is only valuable insofar as it benefits the human condition. technology ultimately comes down to affecting the relations between people, but this notion is obfuscated when technology is treated as an abstract notion devoid of
elongation and the control of flowering. abscisic acid ( aba ) occurs in all land plants except liverworts, and is synthesised from carotenoids in the chloroplasts and other plastids. it inhibits cell division, promotes seed maturation, and dormancy, and promotes stomatal closure. it was so named because it was originally thought to control abscission. ethylene is a gaseous hormone that is produced in all higher plant tissues from methionine. it is now known to be the hormone that stimulates or regulates fruit ripening and abscission, and it, or the synthetic growth regulator ethephon which is rapidly metabolised to produce ethylene, are used on industrial scale to promote ripening of cotton, pineapples and other climacteric crops. another class of phytohormones is the jasmonates, first isolated from the oil of jasminum grandiflorum which regulates wound responses in plants by unblocking the expression of genes required in the systemic acquired resistance response to pathogen attack. in addition to being the primary energy source for plants, light functions as a signalling device, providing information to the plant, such as how much sunlight the plant receives each day. this can result in adaptive changes in a process known as photomorphogenesis. phytochromes are the photoreceptors in a plant that are sensitive to light. = = plant anatomy and morphology = = plant anatomy is the study of the structure of plant cells and tissues, whereas plant morphology is the study of their external form. all plants are multicellular eukaryotes, their dna stored in nuclei. the characteristic features of plant cells that distinguish them from those of animals and fungi include a primary cell wall composed of the polysaccharides cellulose, hemicellulose and pectin, larger vacuoles than in animal cells and the presence of plastids with unique photosynthetic and biosynthetic functions as in the chloroplasts. other plastids contain storage products such as starch ( amyloplasts ) or lipids ( elaioplasts ). uniquely, streptophyte cells and those of the green algal order trentepohliales divide by construction of a phragmoplast as a template for building a cell plate late in cell division. the bodies of vascular plants including clubmos
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,
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 — 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
occurs when another transcription factor called a repressor binds to a dna sequence called an operator, which is part of an operon, to prevent transcription. repressors can be inhibited by compounds called inducers ( e. g., allolactose ), thereby allowing transcription to occur. specific genes that can be activated by inducers are called inducible genes, in contrast to constitutive genes that are almost constantly active. in contrast to both, structural genes encode proteins that are not involved in gene regulation. in addition to regulatory events involving the promoter, gene expression can also be regulated by epigenetic changes to chromatin, which is a complex of dna and protein found in eukaryotic cells. = = = genes, development, and evolution = = = development is the process by which a multicellular organism ( plant or animal ) goes through a series of changes, starting from a single cell, and taking on various forms that are characteristic of its life cycle. there are four key processes that underlie development : determination, differentiation, morphogenesis, and growth. determination sets the developmental fate of a cell, which becomes more restrictive during development. differentiation is the process by which specialized cells arise from less specialized cells such as stem cells. stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. cellular differentiation dramatically changes a cell ' s size, shape, membrane potential, metabolic activity, and responsiveness to signals, which are largely due to highly controlled modifications in gene expression and epigenetics. with a few exceptions, cellular differentiation almost never involves a change in the dna sequence itself. thus, different cells can have very different physical characteristics despite having the same genome. morphogenesis, or the development of body form, is the result of spatial differences in gene expression. a small fraction of the genes in an organism ' s genome called the developmental - genetic toolkit control the development of that organism. these toolkit genes are highly conserved among phyla, meaning that they are ancient and very similar in widely separated groups of animals. differences in deployment of toolkit genes affect the body plan and the number, identity, and pattern of body parts. among the most important toolkit genes are the hox genes. hox genes determine where repeating parts, such as the many vertebrae of snakes, will grow in a developing embryo or larva. = = evolution = = = = = evolutionary
venus flytrap and bladderworts, and the pollinia of orchids. the hypothesis that plant growth and development is coordinated by plant hormones or plant growth regulators first emerged in the late 19th century. darwin experimented on the movements of plant shoots and roots towards light and gravity, and concluded " it is hardly an exaggeration to say that the tip of the radicle.. acts like the brain of one of the lower animals.. directing the several movements ". about the same time, the role of auxins ( from the greek auxein, to grow ) in control of plant growth was first outlined by the dutch scientist frits went. the first known auxin, indole - 3 - acetic acid ( iaa ), which promotes cell growth, was only isolated from plants about 50 years later. this compound mediates the tropic responses of shoots and roots towards light and gravity. the finding in 1939 that plant callus could be maintained in culture containing iaa, followed by the observation in 1947 that it could be induced to form roots and shoots by controlling the concentration of growth hormones were key steps in the development of plant biotechnology and genetic modification. cytokinins are a class of plant hormones named for their control of cell division ( especially cytokinesis ). the natural cytokinin zeatin was discovered in corn, zea mays, and is a derivative of the purine adenine. zeatin is produced in roots and transported to shoots in the xylem where it promotes cell division, bud development, and the greening of chloroplasts. the gibberelins, such as gibberelic acid are diterpenes synthesised from acetyl coa via the mevalonate pathway. they are involved in the promotion of germination and dormancy - breaking in seeds, in regulation of plant height by controlling stem elongation and the control of flowering. abscisic acid ( aba ) occurs in all land plants except liverworts, and is synthesised from carotenoids in the chloroplasts and other plastids. it inhibits cell division, promotes seed maturation, and dormancy, and promotes stomatal closure. it was so named because it was originally thought to control abscission. ethylene is a gaseous hormone that is produced in all higher plant tissues from methionine. it is now known to be the hormone that stimulates or regulates fruit ripening and abscission,
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
could be maintained in culture containing iaa, followed by the observation in 1947 that it could be induced to form roots and shoots by controlling the concentration of growth hormones were key steps in the development of plant biotechnology and genetic modification. cytokinins are a class of plant hormones named for their control of cell division ( especially cytokinesis ). the natural cytokinin zeatin was discovered in corn, zea mays, and is a derivative of the purine adenine. zeatin is produced in roots and transported to shoots in the xylem where it promotes cell division, bud development, and the greening of chloroplasts. the gibberelins, such as gibberelic acid are diterpenes synthesised from acetyl coa via the mevalonate pathway. they are involved in the promotion of germination and dormancy - breaking in seeds, in regulation of plant height by controlling stem elongation and the control of flowering. abscisic acid ( aba ) occurs in all land plants except liverworts, and is synthesised from carotenoids in the chloroplasts and other plastids. it inhibits cell division, promotes seed maturation, and dormancy, and promotes stomatal closure. it was so named because it was originally thought to control abscission. ethylene is a gaseous hormone that is produced in all higher plant tissues from methionine. it is now known to be the hormone that stimulates or regulates fruit ripening and abscission, and it, or the synthetic growth regulator ethephon which is rapidly metabolised to produce ethylene, are used on industrial scale to promote ripening of cotton, pineapples and other climacteric crops. another class of phytohormones is the jasmonates, first isolated from the oil of jasminum grandiflorum which regulates wound responses in plants by unblocking the expression of genes required in the systemic acquired resistance response to pathogen attack. in addition to being the primary energy source for plants, light functions as a signalling device, providing information to the plant, such as how much sunlight the plant receives each day. this can result in adaptive changes in a process known as photomorphogenesis. phytochromes are the photoreceptors in a plant that are sensitive to light. = = plant anatomy and morphology = = plant anatomy is the study of the structure of
##aggeration to say that the tip of the radicle.. acts like the brain of one of the lower animals.. directing the several movements ". about the same time, the role of auxins ( from the greek auxein, to grow ) in control of plant growth was first outlined by the dutch scientist frits went. the first known auxin, indole - 3 - acetic acid ( iaa ), which promotes cell growth, was only isolated from plants about 50 years later. this compound mediates the tropic responses of shoots and roots towards light and gravity. the finding in 1939 that plant callus could be maintained in culture containing iaa, followed by the observation in 1947 that it could be induced to form roots and shoots by controlling the concentration of growth hormones were key steps in the development of plant biotechnology and genetic modification. cytokinins are a class of plant hormones named for their control of cell division ( especially cytokinesis ). the natural cytokinin zeatin was discovered in corn, zea mays, and is a derivative of the purine adenine. zeatin is produced in roots and transported to shoots in the xylem where it promotes cell division, bud development, and the greening of chloroplasts. the gibberelins, such as gibberelic acid are diterpenes synthesised from acetyl coa via the mevalonate pathway. they are involved in the promotion of germination and dormancy - breaking in seeds, in regulation of plant height by controlling stem elongation and the control of flowering. abscisic acid ( aba ) occurs in all land plants except liverworts, and is synthesised from carotenoids in the chloroplasts and other plastids. it inhibits cell division, promotes seed maturation, and dormancy, and promotes stomatal closure. it was so named because it was originally thought to control abscission. ethylene is a gaseous hormone that is produced in all higher plant tissues from methionine. it is now known to be the hormone that stimulates or regulates fruit ripening and abscission, and it, or the synthetic growth regulator ethephon which is rapidly metabolised to produce ethylene, are used on industrial scale to promote ripening of cotton, pineapples and other climacteric crops. another class of phytohormones is the jasmonates, first isolated
Question: Juvenile hormone modulates the activity of what?
A) growth
B) ecdysteroid
C) estrogen
D) reproduction
|
B) ecdysteroid
|
Context:
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 – 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
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
##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 – 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
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
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
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
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
prehistory. the oldest gold treasure in the world, dating from 4, 600 bc to 4, 200 bc, was discovered at the site. the gold piece dating from 4, 500 bc, found in 2019 in durankulak, near varna is another important example. other signs of early metals are found from the third millennium bc in palmela, portugal, los millares, spain, and stonehenge, united kingdom. the precise beginnings, however, have not be clearly ascertained and new discoveries are both continuous and ongoing. in approximately 1900 bc, ancient iron smelting sites existed in tamil nadu. in the near east, about 3, 500 bc, it was discovered that by combining copper and tin, a superior metal could be made, an alloy called bronze. this represented a major technological shift known as the bronze age. the extraction of iron from its ore into a workable metal is much more difficult than for copper or tin. the process appears to have been invented by the hittites in about 1200 bc, beginning the iron age. the secret of extracting and working iron was a key factor in the success of the philistines. historical developments in ferrous metallurgy can be found in a wide variety of past cultures and civilizations. this includes the ancient and medieval kingdoms and empires of the middle east and near east, ancient iran, ancient egypt, ancient nubia, and anatolia in present - day turkey, ancient nok, carthage, the celts, greeks and romans of ancient europe, medieval europe, ancient and medieval china, ancient and medieval india, ancient and medieval japan, amongst others. a 16th century book by georg agricola, de re metallica, describes the highly developed and complex processes of mining metal ores, metal extraction, and metallurgy of the time. agricola has been described as the " father of metallurgy ". = = extraction = = extractive metallurgy is the practice of removing valuable metals from an ore and refining the extracted raw metals into a purer form. in order to convert a metal oxide or sulphide to a purer metal, the ore must be reduced physically, chemically, or electrolytically. extractive metallurgists are interested in three primary streams : feed, concentrate ( metal oxide / sulphide ) and tailings ( waste ). after mining, large pieces of the ore feed are broken through crushing or grinding in order to obtain particles small enough, where each particle is either mostly valuable or
##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
the status of the theory of color confinemnt is discussed.
Question: What causes the red color of laterite soils?
A) iron oxides
B) toxins
C) oxygen
D) erosion
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A) iron oxides
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Context:
doing research is fighting, what any other thing the human being could do? fight against powers or to get powers, that depends on us. science can be a revolution or deadlocked idleness. still waters, without hitting the stones along their history, trend to form bogs.
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
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 (
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
effects content for media. live sound engineer front of house ( foh ) engineer, or a1. – 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 – 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 – 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 – 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. in their daily work, audio engineers use many tools, including : tape machines analog - to - digital converters digital - to - analog converters digital audio workstations ( daws ) audio plug - ins dynamic range compressors audio data compressors equalization ( audio ) music sequencers signal processors headphones microphone
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 – 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
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 – 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
is not present ( e. g., litter in a parking lot or readings on an electric meter ). behavioral observations involve the direct witnessing of the actor engaging in the behavior ( e. g., watching how close a person sits next to another person ). behavioral choices are when a person selects between two or more options ( e. g., voting behavior, choice of a punishment for another participant ). reaction time. the time between the presentation of a stimulus and an appropriate response can indicate differences between two cognitive processes, and can indicate some things about their nature. for example, if in a search task the reaction times vary proportionally with the number of elements, then it is evident that this cognitive process of searching involves serial instead of parallel processing. psychophysical responses. psychophysical experiments are an old psychological technique, which has been adopted by cognitive psychology. they typically involve making judgments of some physical property, e. g. the loudness of a sound. correlation of subjective scales between individuals can show cognitive or sensory biases as compared to actual physical measurements. some examples include : sameness judgments for colors, tones, textures, etc. threshold differences for colors, tones, textures, etc. eye tracking. this methodology is used to study a variety of cognitive processes, most notably visual perception and language processing. the fixation point of the eyes is linked to an individual ' s focus of attention. thus, by monitoring eye movements, we can study what information is being processed at a given time. eye tracking allows us to study cognitive processes on extremely short time scales. eye movements reflect online decision making during a task, and they provide us with some insight into the ways in which those decisions may be processed. = = = brain imaging = = = brain imaging involves analyzing activity within the brain while performing various tasks. this allows us to link behavior and brain function to help understand how information is processed. different types of imaging techniques vary in their temporal ( time - based ) and spatial ( location - based ) resolution. brain imaging is often used in cognitive neuroscience. single - photon emission computed tomography and positron emission tomography. spect and pet use radioactive isotopes, which are injected into the subject ' s bloodstream and taken up by the brain. by observing which areas of the brain take up the radioactive isotope, we can see which areas of the brain are more active than other areas. pet has similar spatial resolution to fmri, but it has extremely poor temporal resolution. electroencephalography. eeg measures the electrical fields
. 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 – 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.
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
Question: The scientific process of collecting data outside the lab (in the "wild") is known as what kind of work?
A) track work
B) scientific investigation
C) field work
D) experimentation
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C) field work
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Context:
human blood primarily comprises plasma, red blood cells, white blood cells, and platelets. it plays a vital role in transporting nutrients to different organs, where it stores essential health - related data about the human body. blood cells are utilized to defend the body against diverse infections, including fungi, viruses, and bacteria. hence, blood analysis can help physicians assess an individual ' s physiological condition. blood cells have been sub - classified into eight groups : neutrophils, eosinophils, basophils, lymphocytes, monocytes, immature granulocytes ( promyelocytes, myelocytes, and metamyelocytes ), erythroblasts, and platelets or thrombocytes on the basis of their nucleus, shape, and cytoplasm. traditionally, pathologists and hematologists in laboratories have examined these blood cells using a microscope before manually classifying them. the manual approach is slower and more prone to human error. therefore, it is essential to automate this process. in our paper, transfer learning with cnn pre - trained models. vgg16, vgg19, resnet - 50, resnet - 101, resnet - 152, inceptionv3, mobilenetv2, and densenet - 20 applied to the pbc dataset ' s normal dib. the overall accuracy achieved with these models lies between 91. 375 and 94. 72 %. hence, inspired by these pre - trained architectures, a model has been proposed to automatically classify the ten types of blood cells with increased accuracy. a novel cnn - based framework has been presented to improve accuracy. the proposed cnn model has been tested on the pbc dataset normal dib. the outcomes of the experiments demonstrate that our cnn - based framework designed for blood cell classification attains an accuracy of 99. 91 % on the pbc dataset. our proposed convolutional neural network model performs competitively when compared to earlier results reported in the literature.
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.
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.
drag ( up to 15 % less during use ), and inertia ( for faster, stronger control response to change vehicle orientation to reduce detection ). two promising approaches are flexible wings, and fluidics. in flexible wings, much or all of a wing surface can change shape in flight to deflect air flow. adaptive compliant wings are a military and commercial effort. the x - 53 active aeroelastic wing was a us air force, boeing, and nasa effort. in fluidics, fluid injection into airflows is being researched for use in aircraft to control direction, in two ways : circulation control and thrust vectoring. in both, larger more complex mechanical parts are replaced by smaller, simpler, lower mass fluidic systems, in which larger forces in fluids are diverted by smaller jets or flows of fluid intermittently, to change the direction of vehicles. mechanical control surfaces that must move cause an important part of aircraft radar cross - section. omitting mechanical control surfaces can reduce radar returns. as of 2023, at least two countries are known to be researching fluidic control. in britain, bae systems has tested two fluidically controlled unmanned aircraft, one starting in 2010 named demon, and another starting in 2017 named magma, with the university of manchester. in the united states, the defense advanced research projects agency ( darpa ) program named control of revolutionary aircraft with novel effectors ( crane ) seeks "... to design, build, and flight test a novel x - plane that incorporates active flow control ( afc ) as a primary design consideration.... in 2023, the aircraft received its official designation as x - 65. " in january 2024, construction began, at boeing subsidiary aurora flight sciences. according to darpa, the aurora x - 65 could be completed and unveiled as soon as early 2025, with the first flight occurring in summer 2025. in circulation control, near the trailing edges of wings, aircraft flight control systems are replaced by slots which emit fluid flows. = = list of stealth aircraft = = f - 117 nighthawk b - 2 spirit f - 22 raptor f - 35 lightning ii j - 20 su - 57 b - 21 raider fc - 31 su - 75 checkmate = = list of stealth helicopters = = boeing – sikorsky rah - 66 comanche hughes 500p = = list of reduced - signature ships = = navy ships worldwide have incorporated signature - reduction features, mostly for the purpose of reducing anti - ship missile detection range and enhancing countermeasure effectiveness
the flow of fluids at branching junctions plays important kinematic and dynamic roles in most biological and industrial flow systems. the present paper highlights some key issues related to the flow of fluids at these junctions with special emphasis on the biological flow networks particularly blood transportation vasculature.
knowledge about the flow field of the plasma around the red blood cells in capillary flow is important for a physical understanding of blood flow and the transport of micro - and nanoparticles and molecules in the flowing plasma. we conduct an experimental study on the flow field around red blood cells in capillary flow that are complemented by simulations of vortical flow between red blood cells. red blood cells were injected in a 10x12 micrometer rectangular microchannel at a low hematocrit and the flow field around a single or two cells have been characterized thanks to a highspeed camera and by tracking 250 nm nanoparticles in flow behaving as tracers. while the flow field around a steady croissant shape is found to be relatively similar to that of a rigid sphere, the flow field around a slipper shape exhibits a small vortex at the rear of the red blood cell. even more pronounced are vortex - like structures observed in the central region between two neighboring croissants. conclusions : the rotation frequency of the vortices is to a good approximation, inversely proportional to the distance between the cells. our experimental data are confirmed and complemented by numerical simulations.
##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 μg / ml of monoclonal antibody, which is maintained at - 20 °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,
. adaptive compliant wings are a military and commercial effort. the x - 53 active aeroelastic wing was a us air force, boeing, and nasa effort. in fluidics, fluid injection into airflows is being researched for use in aircraft to control direction, in two ways : circulation control and thrust vectoring. in both, larger more complex mechanical parts are replaced by smaller, simpler, lower mass fluidic systems, in which larger forces in fluids are diverted by smaller jets or flows of fluid intermittently, to change the direction of vehicles. mechanical control surfaces that must move cause an important part of aircraft radar cross - section. omitting mechanical control surfaces can reduce radar returns. as of 2023, at least two countries are known to be researching fluidic control. in britain, bae systems has tested two fluidically controlled unmanned aircraft, one starting in 2010 named demon, and another starting in 2017 named magma, with the university of manchester. in the united states, the defense advanced research projects agency ( darpa ) program named control of revolutionary aircraft with novel effectors ( crane ) seeks "... to design, build, and flight test a novel x - plane that incorporates active flow control ( afc ) as a primary design consideration.... in 2023, the aircraft received its official designation as x - 65. " in january 2024, construction began, at boeing subsidiary aurora flight sciences. according to darpa, the aurora x - 65 could be completed and unveiled as soon as early 2025, with the first flight occurring in summer 2025. in circulation control, near the trailing edges of wings, aircraft flight control systems are replaced by slots which emit fluid flows. = = list of stealth aircraft = = f - 117 nighthawk b - 2 spirit f - 22 raptor f - 35 lightning ii j - 20 su - 57 b - 21 raider fc - 31 su - 75 checkmate = = list of stealth helicopters = = boeing – sikorsky rah - 66 comanche hughes 500p = = list of reduced - signature ships = = navy ships worldwide have incorporated signature - reduction features, mostly for the purpose of reducing anti - ship missile detection range and enhancing countermeasure effectiveness rather than actual detection avoidance. such ships include : bhumibol adulyadej - class frigate independence - class littoral combat ship kamorta - class corvette klewang - class fast attack craft kolkata - class destroyer la fayette - class frigate nilgiri - class frigate sachsen - class frigate
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,
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.
Question: Red blood cells, white blood cells, platelets, and plasma are all components of what fluid?
A) heart
B) blood
C) brain
D) Vessals
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B) blood
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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 – such as those evolved separately in different groups ( homoplasies ) or those left over from ancestors ( plesiomorphies ) – 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 – such as those evolved separately in different groups ( homoplasies ) or those left over from ancestors ( plesiomorphies ) – 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 – 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
- 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
, 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 – 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 – 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
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 – such as those evolved separately in different groups ( homoplasies ) or those left over from ancestors ( plesiomorphies ) – 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
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 – such as those evolved separately in different groups ( homoplasies ) or those left over from ancestors ( plesiomorphies ) – and derived characters, which
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 – 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
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 – 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
studies of the molecular genetics of model plants such as the thale cress, arabidopsis thaliana, a weedy species in the mustard family ( brassicaceae ). the genome or hereditary information contained in the genes of this species is encoded by about 135 million base pairs of dna, forming one of the smallest genomes among flowering plants. arabidopsis was the first plant to have its genome sequenced, in 2000. the sequencing of some other relatively small genomes, of rice ( oryza sativa ) and brachypodium distachyon, has made them important model species for understanding the genetics, cellular and molecular biology of cereals, grasses and monocots generally. model plants such as arabidopsis thaliana are used for studying the molecular biology of plant cells and the chloroplast. ideally, these organisms have small genomes that are well known or completely sequenced, small stature and short generation times. corn has been used to study mechanisms of photosynthesis and phloem loading of sugar in c4 plants. the single celled green alga chlamydomonas reinhardtii, while not an embryophyte itself, contains a green - pigmented chloroplast related to that of land plants, making it useful for study. a red alga cyanidioschyzon merolae has also been used to study some basic chloroplast functions. spinach, peas, soybeans and a moss physcomitrella patens are commonly used to study plant cell biology. agrobacterium tumefaciens, a soil rhizosphere bacterium, can attach to plant cells and infect them with a callus - inducing ti plasmid by horizontal gene transfer, causing a callus infection called crown gall disease. schell and van montagu ( 1977 ) hypothesised that the ti plasmid could be a natural vector for introducing the nif gene responsible for nitrogen fixation in the root nodules of legumes and other plant species. today, genetic modification of the ti plasmid is one of the main techniques for introduction of transgenes to plants and the creation of genetically modified crops. = = = epigenetics = = = epigenetics is the study of heritable changes in gene function that cannot be explained by changes in the underlying dna sequence but cause the organism ' s genes to behave ( or " express themselves " ) differently. one example
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 " – 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
Question: Who created the idea of an evolutionary tree to represent the relationships between different species and their common ancestors?
A) Scopes
B) Carl Sagan
C) charles darwin
D) Isaac Newton
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C) charles darwin
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Context:
= = = = = = environmental remediation = = = environmental remediation is the process through which contaminants or pollutants in soil, water and other media are removed to improve environmental quality. the main focus is the reduction of hazardous substances within the environment. some of the areas involved in environmental remediation include ; soil contamination, hazardous waste, groundwater contamination, oil, gas and chemical spills. there are three most common types of environmental remediation. these include soil, water, and sediment remediation. soil remediation consists of removing contaminants in soil, as these pose great risks to humans and the ecosystem. some examples of this are heavy metals, pesticides, and radioactive materials. depending on the contaminant the remedial processes can be physical, chemical, thermal, or biological. water remediation is one of the most important considering water is an essential natural resource. depending on the source of water there will be different contaminants. surface water contamination mainly consists of agricultural, animal, and industrial waste, as well as acid mine drainage. there has been a rise in the need for water remediation due to the increased discharge of industrial waste, leading to a demand for sustainable water solutions. the market for water remediation is expected to consistently increase to $ 19. 6 billion by 2030. sediment remediation consists of removing contaminated sediments. is it almost similar to soil remediation except it is often more sophisticated as it involves additional contaminants. to reduce the contaminants it is likely to use physical, chemical, and biological processes that help with source control, but if these processes are executed correctly, there ' s a risk of contamination resurfacing. = = = solid waste management = = = solid waste management is the purification, consumption, reuse, disposal, and treatment of solid waste that is undertaken by the government or the ruling bodies of a city / town. it refers to the collection, treatment, and disposal of non - soluble, solid waste material. solid waste is associated with both industrial, institutional, commercial and residential activities. hazardous solid waste, when improperly disposed can encourage the infestation of insects and rodents, contributing to the spread of diseases. some of the most common types of solid waste management include ; landfills, vermicomposting, composting, recycling, and incineration. however, a major barrier for solid waste management practices is the high costs associated with recycling
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
release the energy they contain, essentially the opposite of photosynthesis. molecules are moved within plants by transport processes that operate at a variety of spatial scales. subcellular transport of ions, electrons and molecules such as water and enzymes occurs across cell membranes. minerals and water are transported from roots to other parts of the plant in the transpiration stream. diffusion, osmosis, and active transport and mass flow are all different ways transport can occur. examples of elements that plants need to transport are nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. in vascular plants, these elements are extracted from the soil as soluble ions by the roots and transported throughout the plant in the xylem. most of the elements required for plant nutrition come from the chemical breakdown of soil minerals. sucrose produced by photosynthesis is transported from the leaves to other parts of the plant in the phloem and plant hormones are transported by a variety of processes. = = = plant hormones = = = plants are not passive, but respond to external signals such as light, touch, and injury by moving or growing towards or away from the stimulus, as appropriate. tangible evidence of touch sensitivity is the almost instantaneous collapse of leaflets of mimosa pudica, the insect traps of venus flytrap and bladderworts, and the pollinia of orchids. the hypothesis that plant growth and development is coordinated by plant hormones or plant growth regulators first emerged in the late 19th century. darwin experimented on the movements of plant shoots and roots towards light and gravity, and concluded " it is hardly an exaggeration to say that the tip of the radicle.. acts like the brain of one of the lower animals.. directing the several movements ". about the same time, the role of auxins ( from the greek auxein, to grow ) in control of plant growth was first outlined by the dutch scientist frits went. the first known auxin, indole - 3 - acetic acid ( iaa ), which promotes cell growth, was only isolated from plants about 50 years later. this compound mediates the tropic responses of shoots and roots towards light and gravity. the finding in 1939 that plant callus could be maintained in culture containing iaa, followed by the observation in 1947 that it could be induced to form roots and shoots by controlling the concentration of growth hormones were key steps in the development of plant biotechnology and genetic modification. cytokinins are a class of plant hormones named for their control of cell division ( especially
, 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 – 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
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
remediation include ; soil contamination, hazardous waste, groundwater contamination, oil, gas and chemical spills. there are three most common types of environmental remediation. these include soil, water, and sediment remediation. soil remediation consists of removing contaminants in soil, as these pose great risks to humans and the ecosystem. some examples of this are heavy metals, pesticides, and radioactive materials. depending on the contaminant the remedial processes can be physical, chemical, thermal, or biological. water remediation is one of the most important considering water is an essential natural resource. depending on the source of water there will be different contaminants. surface water contamination mainly consists of agricultural, animal, and industrial waste, as well as acid mine drainage. there has been a rise in the need for water remediation due to the increased discharge of industrial waste, leading to a demand for sustainable water solutions. the market for water remediation is expected to consistently increase to $ 19. 6 billion by 2030. sediment remediation consists of removing contaminated sediments. is it almost similar to soil remediation except it is often more sophisticated as it involves additional contaminants. to reduce the contaminants it is likely to use physical, chemical, and biological processes that help with source control, but if these processes are executed correctly, there ' s a risk of contamination resurfacing. = = = solid waste management = = = solid waste management is the purification, consumption, reuse, disposal, and treatment of solid waste that is undertaken by the government or the ruling bodies of a city / town. it refers to the collection, treatment, and disposal of non - soluble, solid waste material. solid waste is associated with both industrial, institutional, commercial and residential activities. hazardous solid waste, when improperly disposed can encourage the infestation of insects and rodents, contributing to the spread of diseases. some of the most common types of solid waste management include ; landfills, vermicomposting, composting, recycling, and incineration. however, a major barrier for solid waste management practices is the high costs associated with recycling and the risks of creating more pollution. = = = e - waste recycling = = = the recycling of electronic waste ( e - waste ) has seen significant technological advancements due to increasing environmental concerns and the growing volume of electronic product disposals. traditional e - waste recycling methods, which often involve manual disassemb
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
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 ) – 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
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
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 — of which around 1 million are insects — 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 — pieces of dna that can move between cells — while others may have evolved from bacteria. in evolution, viruses are an important means of horizontal gene transfer, which increases genetic diversity in a way analogous to sexual reproduction. because viruses possess some but not all characteristics of life, they have been described as " organisms at the edge of life ", and as self - replicators. = = ecology = = ecology is the study of the distribution and abundance of life, the interaction between organisms and their environment. = = = ecosystems = = = the community of living ( biotic ) organisms in conjunction with the nonliving ( abiotic ) components ( e. g., water, light, radiation, temperature, humidity, atmosphere, acidity, and soil ) of their environment is called an ecosystem. these biotic and abiotic components are linked together through nutrient cycles and energy flows. energy from the sun enters the system through photosynthesis and is incorporated into plant tissue. by feeding on plants and on one another, animals move matter and energy through the system. they also influence the quantity of plant and microbial biomass present. by breaking down dead organic matter, decomposers release carbon back to the atmosphere and facilitate nutrient cycling by converting nutrients stored in dead biomass back to a form
Question: What organs absorb water and nutrients from the soil?
A) leaves
B) flowers
C) roots
D) buds
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C) roots
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Context:
, crystal structure, hazards associated with minerals, and the physical and chemical properties of minerals. petrology is the study of rocks, including the formation and composition of rocks. petrography is a branch of petrology that studies the typology and classification of rocks. = = earth ' s interior = = plate tectonics, mountain ranges, volcanoes, and earthquakes are geological phenomena that can be explained in terms of physical and chemical processes in the earth ' s crust. beneath the earth ' s crust lies the mantle which is heated by the radioactive decay of heavy elements. the mantle is not quite solid and consists of magma which is in a state of semi - perpetual convection. this convection process causes the lithospheric plates to move, albeit slowly. the resulting process is known as plate tectonics. areas of the crust where new crust is created are called divergent boundaries, those where it is brought back into the earth are convergent boundaries and those where plates slide past each other, but no new lithospheric material is created or destroyed, are referred to as transform ( or conservative ) boundaries. earthquakes result from the movement of the lithospheric plates, and they often occur near convergent boundaries where parts of the crust are forced into the earth as part of subduction. plate tectonics might be thought of as the process by which the earth is resurfaced. as the result of seafloor spreading, new crust and lithosphere is created by the flow of magma from the mantle to the near surface, through fissures, where it cools and solidifies. through subduction, oceanic crust and lithosphere vehemently returns to the convecting mantle. volcanoes result primarily from the melting of subducted crust material. crust material that is forced into the asthenosphere melts, and some portion of the melted material becomes light enough to rise to the surface — 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 — 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
##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 — 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
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.
##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
building block. ceramics – not to be confused with raw, unfired clay – 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 °c ( 2, 750 °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
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 — 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 — created by the internal motions of the core — 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
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
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 °c. = = processing steps = = the traditional ceramic process generally follows this sequence : milling → batching → mixing → forming → drying → firing → 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
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 ". = = 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 electroly
Question: What does magma that cools underground form?
A) chambers
B) fluctuations
C) instrusions
D) new crust
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C) instrusions
|
Context:
becomes quite gentle. accordingly, in large basins, rivers in most cases begin as torrents with a variable flow, and end as gently flowing rivers with a comparatively regular discharge. the irregular flow of rivers throughout their course forms one of the main difficulties in devising works for mitigating inundations or for increasing the navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with a rapid fall near the sources of rivers can carry down rocks, boulders and large stones, which are by degrees ground by attrition in their onward course into slate, gravel, sand and silt, simultaneously with the gradual reduction in fall, and, consequently, in the transporting force of the current. accordingly, under
navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with a rapid fall near the sources of rivers can carry down rocks, boulders and large stones, which are by degrees ground by attrition in their onward course into slate, gravel, sand and silt, simultaneously with the gradual reduction in fall, and, consequently, in the transporting force of the current. accordingly, under ordinary conditions, most of the materials brought down from the high lands by torrential water courses are carried forward by the main river to the sea, or partially strewn over flat alluvial plains during floods ; the size of the materials forming the bed of the river or borne along by the stream is gradually reduced on proceeding sea
weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with a rapid fall near the sources of rivers can carry down rocks, boulders and large stones, which are by degrees ground by attrition in their onward course into slate, gravel, sand and silt, simultaneously with the gradual reduction in fall, and, consequently, in the transporting force of the current. accordingly, under ordinary conditions, most of the materials brought down from the high lands by torrential water courses are carried forward by the main river to the sea, or partially strewn over flat alluvial plains during floods ; the size of the materials forming the bed of the river or borne along by the stream is gradually reduced on proceeding seawards, so that in the po river in italy, for instance, pebbles and gravel are found for about 140 miles below turin, sand along the next 100 miles, and silt and mud in the last 110 miles ( 176 km ). = = channelization = = the removal of obstructions, natural or artificial
approximately corresponds to the slope of the country it traverses ; as rivers rise close to the highest part of their basins, generally in hilly regions, their fall is rapid near their source and gradually diminishes, with occasional irregularities, until, in traversing plains along the latter part of their course, their fall usually becomes quite gentle. accordingly, in large basins, rivers in most cases begin as torrents with a variable flow, and end as gently flowing rivers with a comparatively regular discharge. the irregular flow of rivers throughout their course forms one of the main difficulties in devising works for mitigating inundations or for increasing the navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with
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.
enough to rise to the surface — 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 — created by the internal motions of the core — 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
, 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.
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 ( e. g., trunks of trees, boulders and accumulations of gravel ) from a river bed furnishes a simple and efficient means of increasing the discharging capacity of its channel. such removals will consequently lower the height of floods upstream. every impediment to the flow, in proportion to
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 – civil works program river morphology and stream restoration references - wildland hydrology at the library of congress web archives ( archived 2002 - 08 - 13 )
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.
Question: Which season is moist, causing the most thunderstorms?
A) spring
B) summer
C) winter
D) autumn
|
B) summer
|
Context:
occurs when another transcription factor called a repressor binds to a dna sequence called an operator, which is part of an operon, to prevent transcription. repressors can be inhibited by compounds called inducers ( e. g., allolactose ), thereby allowing transcription to occur. specific genes that can be activated by inducers are called inducible genes, in contrast to constitutive genes that are almost constantly active. in contrast to both, structural genes encode proteins that are not involved in gene regulation. in addition to regulatory events involving the promoter, gene expression can also be regulated by epigenetic changes to chromatin, which is a complex of dna and protein found in eukaryotic cells. = = = genes, development, and evolution = = = development is the process by which a multicellular organism ( plant or animal ) goes through a series of changes, starting from a single cell, and taking on various forms that are characteristic of its life cycle. there are four key processes that underlie development : determination, differentiation, morphogenesis, and growth. determination sets the developmental fate of a cell, which becomes more restrictive during development. differentiation is the process by which specialized cells arise from less specialized cells such as stem cells. stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. cellular differentiation dramatically changes a cell ' s size, shape, membrane potential, metabolic activity, and responsiveness to signals, which are largely due to highly controlled modifications in gene expression and epigenetics. with a few exceptions, cellular differentiation almost never involves a change in the dna sequence itself. thus, different cells can have very different physical characteristics despite having the same genome. morphogenesis, or the development of body form, is the result of spatial differences in gene expression. a small fraction of the genes in an organism ' s genome called the developmental - genetic toolkit control the development of that organism. these toolkit genes are highly conserved among phyla, meaning that they are ancient and very similar in widely separated groups of animals. differences in deployment of toolkit genes affect the body plan and the number, identity, and pattern of body parts. among the most important toolkit genes are the hox genes. hox genes determine where repeating parts, such as the many vertebrae of snakes, will grow in a developing embryo or larva. = = evolution = = = = = evolutionary
##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
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,
practice, general practice or primary care is, in many countries, the first port - of - call for patients with non - emergency medical problems. family physicians often provide services across a broad range of settings including office based practices, emergency department coverage, inpatient care, and nursing home care. medical genetics is concerned with the diagnosis and management of hereditary disorders. neurology is concerned with diseases of the nervous system. in the uk, neurology is a subspecialty of general medicine. obstetrics and gynecology ( often abbreviated as ob / gyn ( american english ) or obs & gynae ( british english ) ) are concerned respectively with childbirth and the female reproductive and associated organs. reproductive medicine and fertility medicine are generally practiced by gynecological specialists. pediatrics ( ae ) or paediatrics ( be ) is devoted to the care of infants, children, and adolescents. like internal medicine, there are many pediatric subspecialties for specific age ranges, organ systems, disease classes, and sites of care delivery. pharmaceutical medicine is the medical scientific discipline concerned with the discovery, development, evaluation, registration, monitoring and medical aspects of marketing of medicines for the benefit of patients and public health. physical medicine and rehabilitation ( or physiatry ) is concerned with functional improvement after injury, illness, or congenital disorders. podiatric medicine is the study of, diagnosis, and medical and surgical treatment of disorders of the foot, ankle, lower limb, hip and lower back. preventive medicine is the branch of medicine concerned with preventing disease. community health or public health is an aspect of health services concerned with threats to the overall health of a community based on population health analysis. psychiatry is the branch of medicine concerned with the bio - psycho - social study of the etiology, diagnosis, treatment and prevention of cognitive, perceptual, emotional and behavioral disorders. related fields include psychotherapy and clinical psychology. = = = interdisciplinary fields = = = some interdisciplinary sub - specialties of medicine include : addiction medicine deals with the treatment of addiction. aerospace medicine deals with medical problems related to flying and space travel. biomedical engineering is a field dealing with the application of engineering principles to medical practice. clinical pharmacology is concerned with how systems of therapeutics interact with patients. conservation medicine studies the relationship between human and non - human animal health, and environmental conditions. also known as ecological medicine, environmental medicine, or medical geology. disaster medicine deals with medical aspects of emergency preparedness, disaster mitigation
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 – the causes, course, progression and resolution thereof. pharmacology is the study of drugs and their actions. photobiology is the study of the interactions between non - ionizing radiation and living organisms. physiology is the study of the normal functioning of the body and the underlying regulatory mechanisms. radiobiology is the study of the interactions between ionizing radiation and living organisms. toxicology is the study of hazardous effects of drugs and poisons. = = = specialties = = = in the broadest meaning of " medicine ", there are many different specialties. in the uk, most specialities have their own body or college, which has its own entrance examination. these are collectively known
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 — 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
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
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
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
medical history comprises hpi and pmh. medications ( rx ) : what drugs the patient takes including prescribed, over - the - counter, and home remedies, as well as alternative and herbal medicines or remedies. allergies are also recorded. past medical history ( pmh / pmhx ) : concurrent medical problems, past hospitalizations and operations, injuries, past infectious diseases or vaccinations, history of known allergies. review of systems ( ros ) or systems inquiry : a set of additional questions to ask, which may be missed on hpi : a general enquiry ( have you noticed any weight loss, change in sleep quality, fevers, lumps and bumps? etc. ), followed by questions on the body ' s main organ systems ( heart, lungs, digestive tract, urinary tract, etc. ). social history ( sh ) : birthplace, residences, marital history, social and economic status, habits ( including diet, medications, tobacco, alcohol ). the physical examination is the examination of the patient for medical signs of disease that are objective and observable, in contrast to symptoms that are volunteered by the patient and are not necessarily objectively observable. the healthcare provider uses sight, hearing, touch, and sometimes smell ( e. g., in infection, uremia, diabetic ketoacidosis ). four actions are the basis of physical examination : inspection, palpation ( feel ), percussion ( tap to determine resonance characteristics ), and auscultation ( listen ), generally in that order, although auscultation occurs prior to percussion and palpation for abdominal assessments. the clinical examination involves the study of : abdomen and rectum cardiovascular ( heart and blood vessels ) general appearance of the patient and specific indicators of disease ( nutritional status, presence of jaundice, pallor or clubbing ) genitalia ( and pregnancy if the patient is or could be pregnant ) head, eye, ear, nose, and throat ( heent ) musculoskeletal ( including spine and extremities ) neurological ( consciousness, awareness, brain, vision, cranial nerves, spinal cord and peripheral nerves ) psychiatric ( orientation, mental state, mood, evidence of abnormal perception or thought ). respiratory ( large airways and lungs ) skin vital signs including height, weight, body temperature, blood pressure, pulse, respiration rate, and hemoglobin oxygen saturation it is to likely focus on
Question: What are the two hormones primarily responsible for maintaining homeostasis of blood glucose levels?
A) anabolic and metabolic
B) insulin and glucagon
C) dopamine and melanin
D) insulin and estrogen
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B) insulin and glucagon
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Context:
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 – 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
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 – 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 – which can dedifferentiate into a callus ( a mass of
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 – grouping organisms by ancestry rather than superficial characteristics. while scientists do not always agree on how to classify organisms, molecular phylogenetics, which uses dna sequences as data, has driven many recent revisions along evolutionary lines and is likely to continue to do so. the dominant classification system is called linnaean taxonomy. it includes ranks and binomial nomenclature. the nomenclature of botanical organisms is codified in the international code of nomenclature for algae, fungi, and plants ( icn ) and administered by the international botanical congress. kingdom plantae belongs to domain eukaryota and is broken down recursively until each species is separately classified. the order is :
the 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 ) – 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
, 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 – which can dedifferentiate into a callus ( a mass of unspecialised cells ) that can grow into a new plant. in vascular plants, the xylem and phloem are the conductive tissues that transport resources between shoots and roots. roots are often adapted to store food such as sugars or starch, as in sugar beets and carrots. stems mainly provide support to the leaves and reproductive structures, but can store water in succulent plants such as cacti, food as in potato tubers, or reproduce vegetatively as in the stolons of strawberry plants or in the process of layering. leaves gather sunlight and carry out photosynthesis. large, flat, flexible, green leaves are called foliage leaves. gymnosperms, such as conifers, cycads, ginkgo, and gnetophytes are seed - producing plants with open seeds. angiosperms are seed - producing plants that produce flowers and have enclosed seeds. woody plants, such as azaleas and oaks, undergo a secondary growth phase resulting in two additional types of tissues : wood ( secondary xylem ) and bark ( secondary phloem and cork ). all gymnosperms and many angiosperms are woody plants. some plants reproduce sexually, some asexually, and some via both means. although reference to major morphological categories such as root, stem, leaf, and trichome are useful, one has to keep in mind that these categories are linked through intermediate forms so that a continuum between the categories results. furthermore, structures can be seen as processes, that is, process combinations. = = systematic botany = = systematic botany is part of systematic biology, which is concerned with the range and diversity of organisms and their relationships, particularly as determined by their evolutionary history. it involves, or is related to, biological classification, scientific taxonomy and phylogenetics. biological classification is the method by which botanists group organisms into categories such as genera or species. biological classification is a form of scientific taxonomy. modern taxonomy is rooted in the work of carl linnaeus, who grouped species according to shared physical characteristics. these groupings have since been revised to align better with the darwinian principle of common descent – grouping organisms
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 ) – 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
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 – which can dedifferentiate into a callus ( a mass of unspecialised cells ) that can grow into a new plant. in vascular plants, the xylem and phloem are the conductive tissues that transport resources between shoots and roots. roots are often adapted to store food such as sugars or starch, as in sugar beets and carrots. stems mainly provide support to the leaves and reproductive structures, but can store water in succulent plants such as cacti, food as in potato tubers, or reproduce vegetatively as in the stolons of strawberry plants or in the process of layering. leaves gather sunlight and carry out photosynthesis. large, flat, flexible, green leaves are called foliage leaves. gymnosperms, such as conifers, cycads, ginkgo, and gnetophytes are seed - producing plants with open seeds. angiosperms are seed - producing plants that produce flowers and have enclosed seeds. woody plants, such as azaleas and oaks, undergo a secondary growth phase resulting in two additional types of tissues : wood ( secondary xylem ) and bark ( secondary phloem and cork ). all gymnosperms and many angiosperms are woody plants. some plants reproduce sexually, some asexually, and some via both means. although reference to major morphological categories such as root, stem, leaf, and trichome are useful, one has to keep in mind that these categories are linked through intermediate forms so that a continuum between the categories results. furthermore, structures can be seen as processes, that is, process combinations. = = systematic botany = = systematic botany is part of systematic biology, which is concerned with the range and diversity of organisms and their relationships, particularly as determined by their evolutionary history. it involves, or is related to, biological classification, scientific taxonomy and phylogenetics. biological classification is the method
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 – 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
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
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 important process takes place in specialized tissue inside plant leaves?
A) mitosis
B) pollination
C) reproduction
D) photosynthesis
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D) photosynthesis
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Context:
smallest genomes among flowering plants. arabidopsis was the first plant to have its genome sequenced, in 2000. the sequencing of some other relatively small genomes, of rice ( oryza sativa ) and brachypodium distachyon, has made them important model species for understanding the genetics, cellular and molecular biology of cereals, grasses and monocots generally. model plants such as arabidopsis thaliana are used for studying the molecular biology of plant cells and the chloroplast. ideally, these organisms have small genomes that are well known or completely sequenced, small stature and short generation times. corn has been used to study mechanisms of photosynthesis and phloem loading of sugar in c4 plants. the single celled green alga chlamydomonas reinhardtii, while not an embryophyte itself, contains a green - pigmented chloroplast related to that of land plants, making it useful for study. a red alga cyanidioschyzon merolae has also been used to study some basic chloroplast functions. spinach, peas, soybeans and a moss physcomitrella patens are commonly used to study plant cell biology. agrobacterium tumefaciens, a soil rhizosphere bacterium, can attach to plant cells and infect them with a callus - inducing ti plasmid by horizontal gene transfer, causing a callus infection called crown gall disease. schell and van montagu ( 1977 ) hypothesised that the ti plasmid could be a natural vector for introducing the nif gene responsible for nitrogen fixation in the root nodules of legumes and other plant species. today, genetic modification of the ti plasmid is one of the main techniques for introduction of transgenes to plants and the creation of genetically modified crops. = = = epigenetics = = = epigenetics is the study of heritable changes in gene function that cannot be explained by changes in the underlying dna sequence but cause the organism ' s genes to behave ( or " express themselves " ) differently. one example of epigenetic change is the marking of the genes by dna methylation which determines whether they will be expressed or not. gene expression can also be controlled by repressor proteins that attach to silencer regions of the dna and prevent that region of the dna code from being expressed. epigenetic marks may be added
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 – 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
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
venus flytrap and bladderworts, and the pollinia of orchids. the hypothesis that plant growth and development is coordinated by plant hormones or plant growth regulators first emerged in the late 19th century. darwin experimented on the movements of plant shoots and roots towards light and gravity, and concluded " it is hardly an exaggeration to say that the tip of the radicle.. acts like the brain of one of the lower animals.. directing the several movements ". about the same time, the role of auxins ( from the greek auxein, to grow ) in control of plant growth was first outlined by the dutch scientist frits went. the first known auxin, indole - 3 - acetic acid ( iaa ), which promotes cell growth, was only isolated from plants about 50 years later. this compound mediates the tropic responses of shoots and roots towards light and gravity. the finding in 1939 that plant callus could be maintained in culture containing iaa, followed by the observation in 1947 that it could be induced to form roots and shoots by controlling the concentration of growth hormones were key steps in the development of plant biotechnology and genetic modification. cytokinins are a class of plant hormones named for their control of cell division ( especially cytokinesis ). the natural cytokinin zeatin was discovered in corn, zea mays, and is a derivative of the purine adenine. zeatin is produced in roots and transported to shoots in the xylem where it promotes cell division, bud development, and the greening of chloroplasts. the gibberelins, such as gibberelic acid are diterpenes synthesised from acetyl coa via the mevalonate pathway. they are involved in the promotion of germination and dormancy - breaking in seeds, in regulation of plant height by controlling stem elongation and the control of flowering. abscisic acid ( aba ) occurs in all land plants except liverworts, and is synthesised from carotenoids in the chloroplasts and other plastids. it inhibits cell division, promotes seed maturation, and dormancy, and promotes stomatal closure. it was so named because it was originally thought to control abscission. ethylene is a gaseous hormone that is produced in all higher plant tissues from methionine. it is now known to be the hormone that stimulates or regulates fruit ripening and abscission,
studies of the molecular genetics of model plants such as the thale cress, arabidopsis thaliana, a weedy species in the mustard family ( brassicaceae ). the genome or hereditary information contained in the genes of this species is encoded by about 135 million base pairs of dna, forming one of the smallest genomes among flowering plants. arabidopsis was the first plant to have its genome sequenced, in 2000. the sequencing of some other relatively small genomes, of rice ( oryza sativa ) and brachypodium distachyon, has made them important model species for understanding the genetics, cellular and molecular biology of cereals, grasses and monocots generally. model plants such as arabidopsis thaliana are used for studying the molecular biology of plant cells and the chloroplast. ideally, these organisms have small genomes that are well known or completely sequenced, small stature and short generation times. corn has been used to study mechanisms of photosynthesis and phloem loading of sugar in c4 plants. the single celled green alga chlamydomonas reinhardtii, while not an embryophyte itself, contains a green - pigmented chloroplast related to that of land plants, making it useful for study. a red alga cyanidioschyzon merolae has also been used to study some basic chloroplast functions. spinach, peas, soybeans and a moss physcomitrella patens are commonly used to study plant cell biology. agrobacterium tumefaciens, a soil rhizosphere bacterium, can attach to plant cells and infect them with a callus - inducing ti plasmid by horizontal gene transfer, causing a callus infection called crown gall disease. schell and van montagu ( 1977 ) hypothesised that the ti plasmid could be a natural vector for introducing the nif gene responsible for nitrogen fixation in the root nodules of legumes and other plant species. today, genetic modification of the ti plasmid is one of the main techniques for introduction of transgenes to plants and the creation of genetically modified crops. = = = epigenetics = = = epigenetics is the study of heritable changes in gene function that cannot be explained by changes in the underlying dna sequence but cause the organism ' s genes to behave ( or " express themselves " ) differently. one example
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 " – 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
##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
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 " – 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
- 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
Question: What type of plants were the first to evolve?
A) vascular
B) cocklebur
C) nonvascular
D) kilocalorie
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C) nonvascular
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Context:
are single - celled organisms such as bacteria, whereas eukaryotes can be single - celled or multicellular. in multicellular organisms, every cell in the organism ' s body is derived ultimately from a single cell in a fertilized egg. = = = cell structure = = = every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions. cell membranes also contain membrane proteins, including integral membrane proteins that go across the membrane serving as membrane transporters, and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes shaping the cell. cell membranes are involved in various cellular processes such as cell adhesion, storing electrical energy, and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall, glycocalyx, and cytoskeleton. within the cytoplasm of a cell, there are many biomolecules such as proteins and nucleic acids. in addition to biomolecules, eukaryotic cells have specialized structures called organelles that have their own lipid bilayers or are spatially units. these organelles include the cell nucleus, which contains most of the cell ' s dna, or mitochondria, which generate adenosine triphosphate ( atp ) to power cellular processes. other organelles such as endoplasmic reticulum and golgi apparatus play a role in the synthesis and packaging of proteins, respectively. biomolecules such as proteins can be engulfed by lysosomes, another specialized organelle. plant cells have additional organelles that distinguish them from animal cells such as a cell wall that provides support for the plant cell, chloroplasts that harvest sunlight energy to produce sugar, and vacuoles that provide storage and structural support as well as being involved in reproduction and breakdown of plant seeds. eukaryotic cells also have cytoskeleton that is made up of microtubules, intermediate filaments, and microfilaments, all of which provide support for the cell and are involved in the movement of the cell and its
. most cells are very small, with diameters ranging from 1 to 100 micrometers and are therefore only visible under a light or electron microscope. there are generally two types of cells : eukaryotic cells, which contain a nucleus, and prokaryotic cells, which do not. prokaryotes are single - celled organisms such as bacteria, whereas eukaryotes can be single - celled or multicellular. in multicellular organisms, every cell in the organism ' s body is derived ultimately from a single cell in a fertilized egg. = = = cell structure = = = every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions. cell membranes also contain membrane proteins, including integral membrane proteins that go across the membrane serving as membrane transporters, and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes shaping the cell. cell membranes are involved in various cellular processes such as cell adhesion, storing electrical energy, and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall, glycocalyx, and cytoskeleton. within the cytoplasm of a cell, there are many biomolecules such as proteins and nucleic acids. in addition to biomolecules, eukaryotic cells have specialized structures called organelles that have their own lipid bilayers or are spatially units. these organelles include the cell nucleus, which contains most of the cell ' s dna, or mitochondria, which generate adenosine triphosphate ( atp ) to power cellular processes. other organelles such as endoplasmic reticulum and golgi apparatus play a role in the synthesis and packaging of proteins, respectively. biomolecules such as proteins can be engulfed by lysosomes, another specialized organelle. plant cells have additional organelles that distinguish them from animal cells such as a cell wall that provides support for the plant cell, chloroplasts that harvest sunlight energy to produce sugar, and vacuoles that provide storage and structural support
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 — of which around 1 million are insects — 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 — pieces of dna
there are a variety of bioreactors designed for 3d cell cultures. there are small plastic cylindrical chambers, as well as glass chambers, with regulated internal humidity and moisture specifically engineered for the purpose of growing cells in three dimensions. the bioreactor uses bioactive synthetic materials such as polyethylene terephthalate membranes to surround the spheroid cells in an environment that maintains high levels of nutrients. they are easy to open and close, so that cell spheroids can be removed for testing, yet the chamber is able to maintain 100 % humidity throughout. this humidity is important to achieve maximum cell growth and function. the bioreactor chamber is part of a larger device that rotates to ensure equal cell growth in each direction across three dimensions. quinxell technologies now under quintech life sciences from singapore has developed a bioreactor known as the tisxell biaxial bioreactor which is specially designed for the purpose of tissue engineering. it is the first bioreactor in the world to have a spherical glass chamber with biaxial rotation ; specifically to mimic the rotation of the fetus in the womb ; which provides a conducive environment for the growth of tissues. multiple forms of mechanical stimulation have also been combined into a single bioreactor. using gene expression analysis, one academic study found that applying a combination of cyclic strain and ultrasound stimulation to pre - osteoblast cells in a bioreactor accelerated matrix maturation and differentiation. the technology of this combined stimulation bioreactor could be used to grow bone cells more quickly and effectively in future clinical stem cell therapies. mc2 biotek has also developed a bioreactor known as prototissue that uses gas exchange to maintain high oxygen levels within the cell chamber ; improving upon previous bioreactors, since the higher oxygen levels help the cell grow and undergo normal cell respiration. active areas of research on bioreactors includes increasing production scale and refining the physiological environment, both of which could improve the efficiency and efficacy of bioreactors in research or clinical use. bioreactors are currently used to study, among other things, cell and tissue level therapies, cell and tissue response to specific physiological environment changes, and development of disease and injury. = = = long fiber generation = = = in 2013, a group from the university of tokyo developed cell laden fibers up to a meter in length and on the order of 100 μm in size. these fibers were created using a microfluidic device that forms a
excavates, stramenopiles, plants, rhizarians, amoebozoans, fungi, and animals. five of these clades are collectively known as protists, which are mostly microscopic eukaryotic organisms that are not plants, fungi, or animals. while it is likely that protists share a common ancestor ( the last eukaryotic common ancestor ), protists by themselves do not constitute a separate clade as some protists may be more closely related to plants, fungi, or animals than they are to other protists. like groupings such as algae, invertebrates, or protozoans, the protist grouping is not a formal taxonomic group but is used for convenience. most protists are unicellular ; these are called microbial eukaryotes. plants are mainly multicellular organisms, predominantly photosynthetic eukaryotes of the kingdom plantae, which would exclude fungi and some algae. plant cells were derived by endosymbiosis of a cyanobacterium into an early eukaryote about one billion years ago, which gave rise to chloroplasts. the first several clades that emerged following primary endosymbiosis were aquatic and most of the aquatic photosynthetic eukaryotic organisms are collectively described as algae, which is a term of convenience as not all algae are closely related. algae comprise several distinct clades such as glaucophytes, which are microscopic freshwater algae that may have resembled in form to the early unicellular ancestor of plantae. unlike glaucophytes, the other algal clades such as red and green algae are multicellular. green algae comprise three major clades : chlorophytes, coleochaetophytes, and stoneworts. fungi are eukaryotes that digest foods outside their bodies, secreting digestive enzymes that break down large food molecules before absorbing them through their cell membranes. many fungi are also saprobes, feeding on dead organic matter, making them important decomposers in ecological systems. animals are multicellular eukaryotes. with few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and grow from a hollow sphere of cells, the blastula, during embryonic development. over 1. 5 million living animal species have been described — of which around 1 million are insects — but it has been estimated there are over 7 million
, 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 – 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 – 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
tissue engineering is a biomedical engineering discipline that uses a combination of cells, engineering, materials methods, and suitable biochemical and physicochemical factors to restore, maintain, improve, or replace different types of biological tissues. tissue engineering often involves the use of cells placed on tissue scaffolds in the formation of new viable tissue for a medical purpose, but is not limited to applications involving cells and tissue scaffolds. while it was once categorized as a sub - field of biomaterials, having grown in scope and importance, it can be considered as a field of its own. while most definitions of tissue engineering cover a broad range of applications, in practice, the term is closely associated with applications that repair or replace portions of or whole tissues ( i. e. organs, bone, cartilage, blood vessels, bladder, skin, muscle etc. ). often, the tissues involved require certain mechanical and structural properties for proper functioning. the term has also been applied to efforts to perform specific biochemical functions using cells within an artificially - created support system ( e. g. an artificial pancreas, or a bio artificial liver ). the term regenerative medicine is often used synonymously with tissue engineering, although those involved in regenerative medicine place more emphasis on the use of stem cells or progenitor cells to produce tissues. = = overview = = a commonly applied definition of tissue engineering, as stated by langer and vacanti, is " an interdisciplinary field that applies the principles of engineering and life sciences toward the development of biological substitutes that restore, maintain, or improve [ biological tissue ] function or a whole organ ". in addition, langer and vacanti also state that there are three main types of tissue engineering : cells, tissue - inducing substances, and a cells + matrix approach ( often referred to as a scaffold ). tissue engineering has also been defined as " understanding the principles of tissue growth, and applying this to produce functional replacement tissue for clinical use ". a further description goes on to say that an " underlying supposition of tissue engineering is that the employment of natural biology of the system will allow for greater success in developing therapeutic strategies aimed at the replacement, repair, maintenance, or enhancement of tissue function ". developments in the multidisciplinary field of tissue engineering have yielded a novel set of tissue replacement parts and implementation strategies. scientific advances in biomaterials, stem cells, growth and differentiation factors, and biomimetic environments have created unique opportunities to fabric
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 — of which around 1 million are insects — 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,
##ochondria and chloroplasts, both of which are now part of modern - day eukaryotic cells. the major lineages of eukaryotes diversified in the precambrian about 1. 5 billion years ago and can be classified into eight major clades : alveolates, excavates, stramenopiles, plants, rhizarians, amoebozoans, fungi, and animals. five of these clades are collectively known as protists, which are mostly microscopic eukaryotic organisms that are not plants, fungi, or animals. while it is likely that protists share a common ancestor ( the last eukaryotic common ancestor ), protists by themselves do not constitute a separate clade as some protists may be more closely related to plants, fungi, or animals than they are to other protists. like groupings such as algae, invertebrates, or protozoans, the protist grouping is not a formal taxonomic group but is used for convenience. most protists are unicellular ; these are called microbial eukaryotes. plants are mainly multicellular organisms, predominantly photosynthetic eukaryotes of the kingdom plantae, which would exclude fungi and some algae. plant cells were derived by endosymbiosis of a cyanobacterium into an early eukaryote about one billion years ago, which gave rise to chloroplasts. the first several clades that emerged following primary endosymbiosis were aquatic and most of the aquatic photosynthetic eukaryotic organisms are collectively described as algae, which is a term of convenience as not all algae are closely related. algae comprise several distinct clades such as glaucophytes, which are microscopic freshwater algae that may have resembled in form to the early unicellular ancestor of plantae. unlike glaucophytes, the other algal clades such as red and green algae are multicellular. green algae comprise three major clades : chlorophytes, coleochaetophytes, and stoneworts. fungi are eukaryotes that digest foods outside their bodies, secreting digestive enzymes that break down large food molecules before absorbing them through their cell membranes. many fungi are also saprobes, feeding on dead organic matter, making them important decomposers in ecological systems. animals are multicellular eukaryotes. with few exceptions, animals
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
Question: In multicellular organisms, specialized cells may be organized into what, which in turn may be organized into organs?
A) tissues
B) blood cells
C) nutrients
D) muscles
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A) tissues
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Context:
some references for the breaking strength of fused silica fibers compiled in 1999.
wounds or dead bodies should be examined, not avoided. the book became the first form of literature to help determine the cause of death. in one of song ci ' s accounts ( washing away of wrongs ), the case of a person murdered with a sickle was solved by an investigator who instructed each suspect to bring his sickle to one location. ( he realized it was a sickle by testing various blades on an animal carcass and comparing the wounds. ) flies, attracted by the smell of blood, eventually gathered on a single sickle. in light of this, the owner of that sickle confessed to the murder. the book also described how to distinguish between a drowning ( water in the lungs ) and strangulation ( broken neck cartilage ), and described evidence from examining corpses to determine if a death was caused by murder, suicide or accident. methods from around the world involved saliva and examination of the mouth and tongue to determine innocence or guilt, as a precursor to the polygraph test. in ancient india, some suspects were made to fill their mouths with dried rice and spit it back out. similarly, in ancient china, those accused of a crime would have rice powder placed in their mouths. in ancient middle - eastern cultures, the accused were made to lick hot metal rods briefly. it is thought that these tests had some validity since a guilty person would produce less saliva and thus have a drier mouth ; the accused would be considered guilty if rice was sticking to their mouths in abundance or if their tongues were severely burned due to lack of shielding from saliva. = = education and training = = initial glance, forensic intelligence may appear as a nascent facet of forensic science facilitated by advancements in information technologies such as computers, databases, and data - flow management software. however, a more profound examination reveals that forensic intelligence represents a genuine and emerging inclination among forensic practitioners to actively participate in investigative and policing strategies. in doing so, it elucidates existing practices within scientific literature, advocating for a paradigm shift from the prevailing conception of forensic science as a conglomerate of disciplines merely aiding the criminal justice system. instead, it urges a perspective that views forensic science as a discipline studying the informative potential of traces — remnants of criminal activity. embracing this transformative shift poses a significant challenge for education, necessitating a shift in learners ' mindset to accept concepts and methodologies in forensic intelligence. recent calls advocating for the integration of forensic scientists into the criminal justice system, as well as policing and intelligence missions, undersco
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 — 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.
the walls of a victim ' s stomach. toxicology, a subfield of forensic chemistry, focuses on detecting and identifying drugs, poisons, and other toxic substances in biological samples. forensic toxicologists work on cases involving drug overdoses, poisoning, and substance abuse. their work is critical in determining whether harmful substances play a role in a person ’ s death or impairment. read more james marsh was the first to apply this new science to the art of forensics. he was called by the prosecution in a murder trial to give evidence as a chemist in 1832. the defendant, john bodle, was accused of poisoning his grandfather with arsenic - laced coffee. marsh performed the standard test by mixing a suspected sample with hydrogen sulfide and hydrochloric acid. while he was able to detect arsenic as yellow arsenic trisulfide, when it was shown to the jury it had deteriorated, allowing the suspect to be acquitted due to reasonable doubt. annoyed by that, marsh developed a much better test. he combined a sample containing arsenic with sulfuric acid and arsenic - free zinc, resulting in arsine gas. the gas was ignited, and it decomposed to pure metallic arsenic, which, when passed to a cold surface, would appear as a silvery - black deposit. so sensitive was the test, known formally as the marsh test, that it could detect as little as one - fiftieth of a milligram of arsenic. he first described this test in the edinburgh philosophical journal in 1836. = = = ballistics and firearms = = = ballistics is " the science of the motion of projectiles in flight ". in forensic science, analysts examine the patterns left on bullets and cartridge casings after being ejected from a weapon. when fired, a bullet is left with indentations and markings that are unique to the barrel and firing pin of the firearm that ejected the bullet. this examination can help scientists identify possible makes and models of weapons connected to a crime. henry goddard at scotland yard pioneered the use of bullet comparison in 1835. he noticed a flaw in the bullet that killed the victim and was able to trace this back to the mold that was used in the manufacturing process. = = = anthropometry = = = the french police officer alphonse bertillon was the first to apply the anthropological technique of anthropometry to law enforcement, thereby creating an identification system based on physical measurements. before that time, criminals could be identified only by name or photograph. dissatisfied with the ad hoc methods used to identify captured
oil umbrella ) ; for calculating the time of death ( allowing for weather and insect activity ) ; described how to wash and examine the dead body to ascertain the reason for death. at that time the book had described methods for distinguishing between suicide and faked suicide. he wrote the book on forensics stating that all wounds or dead bodies should be examined, not avoided. the book became the first form of literature to help determine the cause of death. in one of song ci ' s accounts ( washing away of wrongs ), the case of a person murdered with a sickle was solved by an investigator who instructed each suspect to bring his sickle to one location. ( he realized it was a sickle by testing various blades on an animal carcass and comparing the wounds. ) flies, attracted by the smell of blood, eventually gathered on a single sickle. in light of this, the owner of that sickle confessed to the murder. the book also described how to distinguish between a drowning ( water in the lungs ) and strangulation ( broken neck cartilage ), and described evidence from examining corpses to determine if a death was caused by murder, suicide or accident. methods from around the world involved saliva and examination of the mouth and tongue to determine innocence or guilt, as a precursor to the polygraph test. in ancient india, some suspects were made to fill their mouths with dried rice and spit it back out. similarly, in ancient china, those accused of a crime would have rice powder placed in their mouths. in ancient middle - eastern cultures, the accused were made to lick hot metal rods briefly. it is thought that these tests had some validity since a guilty person would produce less saliva and thus have a drier mouth ; the accused would be considered guilty if rice was sticking to their mouths in abundance or if their tongues were severely burned due to lack of shielding from saliva. = = education and training = = initial glance, forensic intelligence may appear as a nascent facet of forensic science facilitated by advancements in information technologies such as computers, databases, and data - flow management software. however, a more profound examination reveals that forensic intelligence represents a genuine and emerging inclination among forensic practitioners to actively participate in investigative and policing strategies. in doing so, it elucidates existing practices within scientific literature, advocating for a paradigm shift from the prevailing conception of forensic science as a conglomerate of disciplines merely aiding the criminal justice system. instead, it urges a perspective that views forensic science as a discipline studying the informative potential of
defective body parts. inside the body, artificial heart valves are in common use with artificial hearts and lungs seeing less common use but under active technology development. other medical devices and aids that can be considered prosthetics include hearing aids, artificial eyes, palatal obturator, gastric bands, and dentures. prostheses are specifically not orthoses, although given certain circumstances a prosthesis might end up performing some or all of the same functionary benefits as an orthosis. prostheses are technically the complete finished item. for instance, a c - leg knee alone is not a prosthesis, but only a prosthetic component. the complete prosthesis would consist of the attachment system to the residual limb – usually a " socket ", and all the attachment hardware components all the way down to and including the terminal device. despite the technical difference, the terms are often used interchangeably. the terms " prosthetic " and " orthotic " are adjectives used to describe devices such as a prosthetic knee. the terms " prosthetics " and " orthotics " are used to describe the respective allied health fields. an occupational therapist ' s role in prosthetics include therapy, training and evaluations. prosthetic training includes orientation to prosthetics components and terminology, donning and doffing, wearing schedule, and how to care for residual limb and the prosthesis. = = = exoskeletons = = = a powered exoskeleton is a wearable mobile machine that is powered by a system of electric motors, pneumatics, levers, hydraulics, or a combination of technologies that allow for limb movement with increased strength and endurance. its design aims to provide back support, sense the user ' s motion, and send a signal to motors which manage the gears. the exoskeleton supports the shoulder, waist and thigh, and assists movement for lifting and holding heavy items, while lowering back stress. = = = adaptive seating and positioning = = = people with balance and motor function challenges often need specialized equipment to sit or stand safely and securely. this equipment is frequently specialized for specific settings such as in a classroom or nursing home. positioning is often important in seating arrangements to ensure that user ' s body pressure is distributed equally without inhibiting movement in a desired way. positioning devices have been developed to aid in allowing people to stand and bear weight on their legs without risk of a fall.
##tronics, the science of using mechanical devices with human muscular, musculoskeletal, and nervous systems to assist or enhance motor control lost by trauma, disease, or defect. prostheses are typically used to replace parts lost by injury ( traumatic ) or missing from birth ( congenital ) or to supplement defective body parts. inside the body, artificial heart valves are in common use with artificial hearts and lungs seeing less common use but under active technology development. other medical devices and aids that can be considered prosthetics include hearing aids, artificial eyes, palatal obturator, gastric bands, and dentures. prostheses are specifically not orthoses, although given certain circumstances a prosthesis might end up performing some or all of the same functionary benefits as an orthosis. prostheses are technically the complete finished item. for instance, a c - leg knee alone is not a prosthesis, but only a prosthetic component. the complete prosthesis would consist of the attachment system to the residual limb – usually a " socket ", and all the attachment hardware components all the way down to and including the terminal device. despite the technical difference, the terms are often used interchangeably. the terms " prosthetic " and " orthotic " are adjectives used to describe devices such as a prosthetic knee. the terms " prosthetics " and " orthotics " are used to describe the respective allied health fields. an occupational therapist ' s role in prosthetics include therapy, training and evaluations. prosthetic training includes orientation to prosthetics components and terminology, donning and doffing, wearing schedule, and how to care for residual limb and the prosthesis. = = = exoskeletons = = = a powered exoskeleton is a wearable mobile machine that is powered by a system of electric motors, pneumatics, levers, hydraulics, or a combination of technologies that allow for limb movement with increased strength and endurance. its design aims to provide back support, sense the user ' s motion, and send a signal to motors which manage the gears. the exoskeleton supports the shoulder, waist and thigh, and assists movement for lifting and holding heavy items, while lowering back stress. = = = adaptive seating and positioning = = = people with balance and motor function challenges often need specialized equipment to sit or stand safely and securely. this equipment is frequently
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
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 ),
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?
Question: What are accessory digestive organs critical for breaking down?
A) pathogens
B) food
C) enzymes
D) hormones
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B) food
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Context:
depends on the extent of the continent in which it is situated, its position in relation to the hilly regions in which rivers generally arise and the sea into which they flow, and the distance between the source and the outlet into the sea of the river draining it. the rate of flow of rivers depends mainly upon their fall, also known as the gradient or slope. when two rivers of different sizes have the same fall, the larger river has the quicker flow, as its retardation by friction against its bed and banks is less in proportion to its volume than is the case with the smaller river. the fall available in a section of a river approximately corresponds to the slope of the country it traverses ; as rivers rise close to the highest part of their basins, generally in hilly regions, their fall is rapid near their source and gradually diminishes, with occasional irregularities, until, in traversing plains along the latter part of their course, their fall usually becomes quite gentle. accordingly, in large basins, rivers in most cases begin as torrents with a variable flow, and end as gently flowing rivers with a comparatively regular discharge. the irregular flow of rivers throughout their course forms one of the main difficulties in devising works for mitigating inundations or for increasing the navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform
approximately corresponds to the slope of the country it traverses ; as rivers rise close to the highest part of their basins, generally in hilly regions, their fall is rapid near their source and gradually diminishes, with occasional irregularities, until, in traversing plains along the latter part of their course, their fall usually becomes quite gentle. accordingly, in large basins, rivers in most cases begin as torrents with a variable flow, and end as gently flowing rivers with a comparatively regular discharge. the irregular flow of rivers throughout their course forms one of the main difficulties in devising works for mitigating inundations or for increasing the navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with
also known as the gradient or slope. when two rivers of different sizes have the same fall, the larger river has the quicker flow, as its retardation by friction against its bed and banks is less in proportion to its volume than is the case with the smaller river. the fall available in a section of a river approximately corresponds to the slope of the country it traverses ; as rivers rise close to the highest part of their basins, generally in hilly regions, their fall is rapid near their source and gradually diminishes, with occasional irregularities, until, in traversing plains along the latter part of their course, their fall usually becomes quite gentle. accordingly, in large basins, rivers in most cases begin as torrents with a variable flow, and end as gently flowing rivers with a comparatively regular discharge. the irregular flow of rivers throughout their course forms one of the main difficulties in devising works for mitigating inundations or for increasing the navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in
the large scale pattern in the arrival directions of extragalactic cosmic rays that reach the earth is different from that of the flux arriving to the halo of the galaxy as a result of the propagation through the galactic magnetic field. two different effects are relevant in this process : deflections of trajectories and ( de ) acceleration by the electric field component due to the galactic rotation. the deflection of the cosmic ray trajectories makes the flux intensity arriving to the halo from some direction to appear reaching the earth from another direction. this applies to any intrinsic anisotropy in the extragalactic distribution or, even in the absence of intrinsic anisotropies, to the dipolar compton - getting anisotropy induced when the observer is moving with respect to the cosmic rays rest frame. for an observer moving with the solar system, cosmic rays traveling through far away regions of the galaxy also experience an electric force coming from the relative motion ( due to the rotation of the galaxy ) of the local system in which the field can be considered as being purely magnetic. this produces small changes in the particles momentum that can originate large scale anisotropies even for an isotropic extragalactic flux.
becomes quite gentle. accordingly, in large basins, rivers in most cases begin as torrents with a variable flow, and end as gently flowing rivers with a comparatively regular discharge. the irregular flow of rivers throughout their course forms one of the main difficulties in devising works for mitigating inundations or for increasing the navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with a rapid fall near the sources of rivers can carry down rocks, boulders and large stones, which are by degrees ground by attrition in their onward course into slate, gravel, sand and silt, simultaneously with the gradual reduction in fall, and, consequently, in the transporting force of the current. accordingly, under
from the 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
fluid dynamics video demonstrating the evolution of dynamic stall on a wind turbine blade.
the injuries of the inundations they have been designed to prevent, as the escape of floods from the raised river must occur sooner or later. inadequate planning controls which have permitted development on floodplains have been blamed for the flooding of domestic properties. channelization was done under the auspices or overall direction of engineers employed by the local authority or the national government. one of the most heavily channelized areas in the united states is west tennessee, where every major stream with one exception ( the hatchie river ) has been partially or completely channelized. channelization of a stream may be undertaken for several reasons. one is to make a stream more suitable for navigation or for navigation by larger vessels with deep draughts. another is to restrict water to a certain area of a stream ' s natural bottom lands so that the bulk of such lands can be made available for agriculture. a third reason is flood control, with the idea of giving a stream a sufficiently large and deep channel so that flooding beyond those limits will be minimal or nonexistent, at least on a routine basis. one major reason is to reduce natural erosion ; as a natural waterway curves back and forth, it usually deposits sand and gravel on the inside of the corners where the water flows slowly, and cuts sand, gravel, subsoil, and precious topsoil from the outside corners where it flows rapidly due to a change in direction. unlike sand and gravel, the topsoil that is eroded does not get deposited on the inside of the next corner of the river. it simply washes away. = = loss of wetlands = = channelization has several predictable and negative effects. one of them is loss of wetlands. wetlands are an excellent habitat for multiple forms of wildlife, and additionally serve as a " filter " for much of the world ' s surface fresh water. another is the fact that channelized streams are almost invariably straightened. for example, the channelization of florida ' s kissimmee river has been cited as a cause contributing to the loss of wetlands. this straightening causes the streams to flow more rapidly, which can, in some instances, vastly increase soil erosion. it can also increase flooding downstream from the channelized area, as larger volumes of water traveling more rapidly than normal can reach choke points over a shorter period of time than they otherwise would, with a net effect of flood control in one area coming at the expense of aggravated flooding in another. in addition, studies have shown that stream channelization results in declines of river fish populations. : 3 - 1ff a
oriented strontium ferrite films with the c axis orientation were deposited with varying oxygen partial pressure on al2o3 ( 0001 ) substrate using pld technique. the angle dependent magnetic hysteresis, remanent coercivity and temperature dependent coercivity had been employed to understand the magnetization reversal of these films. it was found that the strontium ferrite thin film grown at lower ( higher ) oxygen partial pressure shows stoner - wohlfarth type ( kondorsky like ) reversal. the relative importance of pinning and nucleation processes during magnetization reversal is used to explain the type of the magnetization reversal with different oxygen partial pressure during growth.
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
Question: The direction of prevailing winds determines the type of what that usually moves over an area?
A) air mass
B) water mass
C) storm
D) weather
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A) air mass
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Context:
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 – induced pluripotent stem cells – may be useful for the repair of diseased or damaged tissues, or may be used to grow new organs. totipotent cells
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
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
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
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,
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 – induced pluripotent stem cells – may be useful for the repair of diseased or damaged tissues, or may be used to grow new organs. totipotent cells are stem cells which can divide into further stem cells or differentiate into any cell type in the body, including extra - embryonic tissue. pluripotent cells are stem cells which can differentiate into any cell type in the body except extra - embryonic tissue. induced pluripotent stem cells ( ipscs )
##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
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
##logous in nature, and can be used in a myriad of ways, from helping repair skeletal tissue to replenishing beta cells in diabetic patients. allogenic : cells are obtained from the body of a donor of the same species as the recipient. while there are some ethical constraints to the use of human cells for in vitro studies ( i. e. human brain tissue chimera development ), the employment of dermal fibroblasts from human foreskin demonstrates an immunologically safe and thus a viable choice for allogenic tissue engineering of the skin. xenogenic : these cells are derived isolated cells from alternate species from the recipient. a notable example of xenogeneic tissue utilization is cardiovascular implant construction via animal cells. chimeric human - animal farming raises ethical concerns around the potential for improved consciousness from implanting human organs in animals. syngeneic or isogenic : these cells describe those borne from identical genetic code. this imparts an immunologic benefit similar to autologous cell lines ( see above ). autologous cells can be considered syngenic, but the classification also extends to non - autologously derived cells such as those from an identical twin, from genetically identical ( cloned ) research models, or induced stem cells ( isc ) as related to the donor. = = = stem cells = = = stem cells are undifferentiated cells with the ability to divide in culture and give rise to different forms of specialized cells. stem cells are divided into " adult " and " embryonic " stem cells according to their source. while there is still a large ethical debate related to the use of embryonic stem cells, it is thought that another alternative source – induced pluripotent stem cells – may be useful for the repair of diseased or damaged tissues, or may be used to grow new organs. totipotent cells are stem cells which can divide into further stem cells or differentiate into any cell type in the body, including extra - embryonic tissue. pluripotent cells are stem cells which can differentiate into any cell type in the body except extra - embryonic tissue. induced pluripotent stem cells ( ipscs ) are subclass of pluripotent stem cells resembling embryonic stem cells ( escs ) that have been derived from adult differentiated cells. ipscs are created by altering the expression of transcriptional factors in adult cells until they become like embryonic stem cells. multipotent stem cells can be differentiated into any cell
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
Question: As blood glucose levels rise what is released from the pancreas?
A) insulin
B) estrogen
C) adrenaline
D) hemoglobin
|
A) insulin
|
Context:
liver glycogen. during recovery, when oxygen becomes available, nad + attaches to hydrogen from lactate to form atp. in yeast, the waste products are ethanol and carbon dioxide. this type of fermentation is known as alcoholic or ethanol fermentation. the atp generated in this process is made by substrate - level phosphorylation, which does not require oxygen. = = = photosynthesis = = = photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organism ' s metabolic activities via cellular respiration. this chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. in most cases, oxygen is released as a waste product. most plants, algae, and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of the earth ' s atmosphere, and supplies most of the energy necessary for life on earth. photosynthesis has four stages : light absorption, electron transport, atp synthesis, and carbon fixation. light absorption is the initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to proteins in the thylakoid membranes. the absorbed light energy is used to remove electrons from a donor ( water ) to a primary electron acceptor, a quinone designated as q. in the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach a final electron acceptor, which is usually the oxidized form of nadp +, which is reduced to nadph, a process that takes place in a protein complex called photosystem i ( psi ). the transport of electrons is coupled to the movement of protons ( or hydrogen ) from the stroma to the thylakoid membrane, which forms a ph gradient across the membrane as hydrogen becomes more concentrated in the lumen than in the stroma. this is analogous to the proton - motive force generated across the inner mitochondrial membrane in aerobic respiration. during the third stage of photosynthesis, the movement of protons down their concentration gradients from the thylakoid lumen to the stroma through the atp synthase is coupled to the synthesis of atp by that same atp synthase. the nadph and atps generated by the light - dependent reactions in the second and third stages, respectively, provide the energy and
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 – 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 – 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
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 – 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 – 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 (
##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
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
nadh. during anaerobic glycolysis, nad + regenerates when pairs of hydrogen combine with pyruvate to form lactate. lactate formation is catalyzed by lactate dehydrogenase in a reversible reaction. lactate can also be used as an indirect precursor for liver glycogen. during recovery, when oxygen becomes available, nad + attaches to hydrogen from lactate to form atp. in yeast, the waste products are ethanol and carbon dioxide. this type of fermentation is known as alcoholic or ethanol fermentation. the atp generated in this process is made by substrate - level phosphorylation, which does not require oxygen. = = = photosynthesis = = = photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organism ' s metabolic activities via cellular respiration. this chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. in most cases, oxygen is released as a waste product. most plants, algae, and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of the earth ' s atmosphere, and supplies most of the energy necessary for life on earth. photosynthesis has four stages : light absorption, electron transport, atp synthesis, and carbon fixation. light absorption is the initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to proteins in the thylakoid membranes. the absorbed light energy is used to remove electrons from a donor ( water ) to a primary electron acceptor, a quinone designated as q. in the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach a final electron acceptor, which is usually the oxidized form of nadp +, which is reduced to nadph, a process that takes place in a protein complex called photosystem i ( psi ). the transport of electrons is coupled to the movement of protons ( or hydrogen ) from the stroma to the thylakoid membrane, which forms a ph gradient across the membrane as hydrogen becomes more concentrated in the lumen than in the stroma. this is analogous to the proton - motive force generated across the inner mitochondrial membrane in aerobic respiration. during the third stage of photosynthesis, the movement of
##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
##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 – 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 – 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,
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
##colysis. 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 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
Question: Hydrocarbons are combined with oxygen in a series of enzymatic steps to product water, carbon dioxide, and energy, which is stored in the form of what?
A) reactive molecules
B) dormant molecules
C) light
D) energy
|
A) reactive molecules
|
Context:
is not present ( e. g., litter in a parking lot or readings on an electric meter ). behavioral observations involve the direct witnessing of the actor engaging in the behavior ( e. g., watching how close a person sits next to another person ). behavioral choices are when a person selects between two or more options ( e. g., voting behavior, choice of a punishment for another participant ). reaction time. the time between the presentation of a stimulus and an appropriate response can indicate differences between two cognitive processes, and can indicate some things about their nature. for example, if in a search task the reaction times vary proportionally with the number of elements, then it is evident that this cognitive process of searching involves serial instead of parallel processing. psychophysical responses. psychophysical experiments are an old psychological technique, which has been adopted by cognitive psychology. they typically involve making judgments of some physical property, e. g. the loudness of a sound. correlation of subjective scales between individuals can show cognitive or sensory biases as compared to actual physical measurements. some examples include : sameness judgments for colors, tones, textures, etc. threshold differences for colors, tones, textures, etc. eye tracking. this methodology is used to study a variety of cognitive processes, most notably visual perception and language processing. the fixation point of the eyes is linked to an individual ' s focus of attention. thus, by monitoring eye movements, we can study what information is being processed at a given time. eye tracking allows us to study cognitive processes on extremely short time scales. eye movements reflect online decision making during a task, and they provide us with some insight into the ways in which those decisions may be processed. = = = brain imaging = = = brain imaging involves analyzing activity within the brain while performing various tasks. this allows us to link behavior and brain function to help understand how information is processed. different types of imaging techniques vary in their temporal ( time - based ) and spatial ( location - based ) resolution. brain imaging is often used in cognitive neuroscience. single - photon emission computed tomography and positron emission tomography. spect and pet use radioactive isotopes, which are injected into the subject ' s bloodstream and taken up by the brain. by observing which areas of the brain take up the radioactive isotope, we can see which areas of the brain are more active than other areas. pet has similar spatial resolution to fmri, but it has extremely poor temporal resolution. electroencephalography. eeg measures the electrical fields
behavioral responses to different stimuli, one can understand something about how those stimuli are processed. lewandowski & strohmetz ( 2009 ) reviewed a collection of innovative uses of behavioral measurement in psychology including behavioral traces, behavioral observations, and behavioral choice. behavioral traces are pieces of evidence that indicate behavior occurred, but the actor is not present ( e. g., litter in a parking lot or readings on an electric meter ). behavioral observations involve the direct witnessing of the actor engaging in the behavior ( e. g., watching how close a person sits next to another person ). behavioral choices are when a person selects between two or more options ( e. g., voting behavior, choice of a punishment for another participant ). reaction time. the time between the presentation of a stimulus and an appropriate response can indicate differences between two cognitive processes, and can indicate some things about their nature. for example, if in a search task the reaction times vary proportionally with the number of elements, then it is evident that this cognitive process of searching involves serial instead of parallel processing. psychophysical responses. psychophysical experiments are an old psychological technique, which has been adopted by cognitive psychology. they typically involve making judgments of some physical property, e. g. the loudness of a sound. correlation of subjective scales between individuals can show cognitive or sensory biases as compared to actual physical measurements. some examples include : sameness judgments for colors, tones, textures, etc. threshold differences for colors, tones, textures, etc. eye tracking. this methodology is used to study a variety of cognitive processes, most notably visual perception and language processing. the fixation point of the eyes is linked to an individual ' s focus of attention. thus, by monitoring eye movements, we can study what information is being processed at a given time. eye tracking allows us to study cognitive processes on extremely short time scales. eye movements reflect online decision making during a task, and they provide us with some insight into the ways in which those decisions may be processed. = = = brain imaging = = = brain imaging involves analyzing activity within the brain while performing various tasks. this allows us to link behavior and brain function to help understand how information is processed. different types of imaging techniques vary in their temporal ( time - based ) and spatial ( location - based ) resolution. brain imaging is often used in cognitive neuroscience. single - photon emission computed tomography and positron emission tomography. spect and pet use radioactive isotopes, which are injected into the subject ' s bloodstream
options ( e. g., voting behavior, choice of a punishment for another participant ). reaction time. the time between the presentation of a stimulus and an appropriate response can indicate differences between two cognitive processes, and can indicate some things about their nature. for example, if in a search task the reaction times vary proportionally with the number of elements, then it is evident that this cognitive process of searching involves serial instead of parallel processing. psychophysical responses. psychophysical experiments are an old psychological technique, which has been adopted by cognitive psychology. they typically involve making judgments of some physical property, e. g. the loudness of a sound. correlation of subjective scales between individuals can show cognitive or sensory biases as compared to actual physical measurements. some examples include : sameness judgments for colors, tones, textures, etc. threshold differences for colors, tones, textures, etc. eye tracking. this methodology is used to study a variety of cognitive processes, most notably visual perception and language processing. the fixation point of the eyes is linked to an individual ' s focus of attention. thus, by monitoring eye movements, we can study what information is being processed at a given time. eye tracking allows us to study cognitive processes on extremely short time scales. eye movements reflect online decision making during a task, and they provide us with some insight into the ways in which those decisions may be processed. = = = brain imaging = = = brain imaging involves analyzing activity within the brain while performing various tasks. this allows us to link behavior and brain function to help understand how information is processed. different types of imaging techniques vary in their temporal ( time - based ) and spatial ( location - based ) resolution. brain imaging is often used in cognitive neuroscience. single - photon emission computed tomography and positron emission tomography. spect and pet use radioactive isotopes, which are injected into the subject ' s bloodstream and taken up by the brain. by observing which areas of the brain take up the radioactive isotope, we can see which areas of the brain are more active than other areas. pet has similar spatial resolution to fmri, but it has extremely poor temporal resolution. electroencephalography. eeg measures the electrical fields generated by large populations of neurons in the cortex by placing a series of electrodes on the scalp of the subject. this technique has an extremely high temporal resolution, but a relatively poor spatial resolution. functional magnetic resonance imaging. fmri measures the relative amount of oxygenated blood flowing to different parts of the brain. more oxygen
##ent governmental regulations. some of these requirements include : seat belt and air bag functionality testing, front and side - impact testing, and tests of rollover resistance. assessments are done with various methods and tools, including computer crash simulation ( typically finite element analysis ), crash - test dummy, and partial system sled and full vehicle crashes. fuel economy / emissions : fuel economy is the measured fuel efficiency of the vehicle in miles per gallon or kilometers per liter. emissions - testing covers the measurement of vehicle emissions, including hydrocarbons, nitrogen oxides ( nox ), carbon monoxide ( co ), carbon dioxide ( co2 ), and evaporative emissions. nvh engineering ( noise, vibration, and harshness ) : nvh involves customer feedback ( both tactile [ felt ] and audible [ heard ] ) concerning a vehicle. while sound can be interpreted as a rattle, squeal, or hot, a tactile response can be seat vibration or a buzz in the steering wheel. this feedback is generated by components either rubbing, vibrating, or rotating. nvh response can be classified in various ways : powertrain nvh, road noise, wind noise, component noise, and squeak and rattle. note, there are both good and bad nvh qualities. the nvh engineer works to either eliminate bad nvh or change the " bad nvh " to good ( i. e., exhaust tones ). vehicle electronics : automotive electronics is an increasingly important aspect of automotive engineering. modern vehicles employ dozens of electronic systems. these systems are responsible for operational controls such as the throttle, brake and steering controls ; as well as many comfort - and - convenience systems such as the hvac, infotainment, and lighting systems. it would not be possible for automobiles to meet modern safety and fuel - economy requirements without electronic controls. performance : performance is a measurable and testable value of a vehicle ' s ability to perform in various conditions. performance can be considered in a wide variety of tasks, but it generally considers how quickly a car can accelerate ( e. g. standing start 1 / 4 mile elapsed time, 0 – 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
here are a few random thoughts on the interpretations of the quantum double slit experiment, the mach zehnder experiment, the delayed - choice experiment and the measurement problem.
scientists look through telescopes, study images on electronic screens, record meter readings, and so on. generally, on a basic level, they can agree on what they see, e. g., the thermometer shows 37. 9 degrees c. but, if these scientists have different ideas about the theories that have been developed to explain these basic observations, they may disagree about what they are observing. for example, before albert einstein ' s general theory of relativity, observers would have likely interpreted an image of the einstein cross as five different objects in space. in light of that theory, however, astronomers will tell you that there are actually only two objects, one in the center and four different images of a second object around the sides. alternatively, if other scientists suspect that something is wrong with the telescope and only one object is actually being observed, they are operating under yet another theory. observations that cannot be separated from theoretical interpretation are said to be theory - laden. all observation involves both perception and cognition. that is, one does not make an observation passively, but rather is actively engaged in distinguishing the phenomenon being observed from surrounding sensory data. therefore, observations are affected by one ' s underlying understanding of the way in which the world functions, and that understanding may influence what is perceived, noticed, or deemed worthy of consideration. in this sense, it can be argued that all observation is theory - laden. = = = the purpose of science = = = should science aim to determine ultimate truth, or are there questions that science cannot answer? scientific realists claim that science aims at truth and that one ought to regard scientific theories as true, approximately true, or likely true. conversely, scientific anti - realists argue that science does not aim ( or at least does not succeed ) at truth, especially truth about unobservables like electrons or other universes. instrumentalists argue that scientific theories should only be evaluated on whether they are useful. in their view, whether theories are true or not is beside the point, because the purpose of science is to make predictions and enable effective technology. realists often point to the success of recent scientific theories as evidence for the truth ( or near truth ) of current theories. antirealists point to either the many false theories in the history of science, epistemic morals, the success of false modeling assumptions, or widely termed postmodern criticisms of objectivity as evidence against scientific realism. antirealists attempt to explain the success of scientific theories without reference to truth. some antirealists claim that scientific
a comparison of the sensitivities of methods which allow us to determine the coordinates of a moving hot body is made.
the celebrated franck - hertz experiment is reinterpreted by analogy with the glimmentladung experiment, formerly performed by heinrich hertz.
i reject the following null hypothesis : { h0 : your data are normal }. such drastic decision is motivated by theoretical reasons, and applies to your current data, the past ones, and the future ones. while this situation may appear embarrassing, it does not invalidate any of your results. moreover, it allows to save time and energy that are currently spent in vain by performing the following unnecessary tasks : ( i ) carrying out normality tests ; ( ii ) pretending to do something if normality is rejected ; and ( iii ) arguing about normality with referee # 2.
the walls of a victim ' s stomach. toxicology, a subfield of forensic chemistry, focuses on detecting and identifying drugs, poisons, and other toxic substances in biological samples. forensic toxicologists work on cases involving drug overdoses, poisoning, and substance abuse. their work is critical in determining whether harmful substances play a role in a person ’ s death or impairment. read more james marsh was the first to apply this new science to the art of forensics. he was called by the prosecution in a murder trial to give evidence as a chemist in 1832. the defendant, john bodle, was accused of poisoning his grandfather with arsenic - laced coffee. marsh performed the standard test by mixing a suspected sample with hydrogen sulfide and hydrochloric acid. while he was able to detect arsenic as yellow arsenic trisulfide, when it was shown to the jury it had deteriorated, allowing the suspect to be acquitted due to reasonable doubt. annoyed by that, marsh developed a much better test. he combined a sample containing arsenic with sulfuric acid and arsenic - free zinc, resulting in arsine gas. the gas was ignited, and it decomposed to pure metallic arsenic, which, when passed to a cold surface, would appear as a silvery - black deposit. so sensitive was the test, known formally as the marsh test, that it could detect as little as one - fiftieth of a milligram of arsenic. he first described this test in the edinburgh philosophical journal in 1836. = = = ballistics and firearms = = = ballistics is " the science of the motion of projectiles in flight ". in forensic science, analysts examine the patterns left on bullets and cartridge casings after being ejected from a weapon. when fired, a bullet is left with indentations and markings that are unique to the barrel and firing pin of the firearm that ejected the bullet. this examination can help scientists identify possible makes and models of weapons connected to a crime. henry goddard at scotland yard pioneered the use of bullet comparison in 1835. he noticed a flaw in the bullet that killed the victim and was able to trace this back to the mold that was used in the manufacturing process. = = = anthropometry = = = the french police officer alphonse bertillon was the first to apply the anthropological technique of anthropometry to law enforcement, thereby creating an identification system based on physical measurements. before that time, criminals could be identified only by name or photograph. dissatisfied with the ad hoc methods used to identify captured
Question: The validity of thought experiments, of course, is determined by this?
A) actual observation
B) theoretical observation
C) hypothetical observation
D) predictive observation
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A) actual observation
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Context:
species occupying the same geographical area at the same time. a biological interaction is the effect that a pair of organisms living together in a community have on each other. they can be either of the same species ( intraspecific interactions ), or of different species ( interspecific interactions ). these effects may be short - term, like pollination and predation, or long - term ; both often strongly influence the evolution of the species involved. a long - term interaction is called a symbiosis. symbioses range from mutualism, beneficial to both partners, to competition, harmful to both partners. every species participates as a consumer, resource, or both in consumer – 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
( 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 – such as those evolved separately in different groups ( homoplasies ) or those left over from ancestors ( plesiomorphies ) – 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 – 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
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 – such as those evolved separately in different groups ( homoplasies ) or those left over from ancestors ( plesiomorphies ) – 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
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 – 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
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 " – 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
. species boundaries in plants may be weaker than in animals, and cross species hybrids are often possible. a familiar example is peppermint, mentha × 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
- 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
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 – 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
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
cortisol, corticosterone and aldosterone activate full - length glucocorticoid receptor ( gr ) from elephant shark, a cartilaginous fish belonging to the oldest group of jawed vertebrates. activation by aldosterone a mineralocorticoid, indicates partial divergence of elephant shark gr from the mr. progesterone activates elephant shark mr, but not elephant shark gr. progesterone inhibits steroid binding to elephant shark gr, but not to human gr. deletion of the n - terminal domain ( ntd ) from elephant shark gr ( truncated gr ) reduced the response to corticosteroids, while truncated and full - length elephant shark mr had similar responses to corticosteroids. chimeras of elephant shark gr ntd fused to mr dbd + lbd had increased activation by corticosteroids and progesterone compared to full - length elephant shark mr. elephant shark mr ntd fused to gr dbd + lbd had similar activation as full - length elephant shark mr, indicating that activation of human gr by the ntd evolved early in gr divergence from the mr.
Question: What do you call a close relationship between two species that benefits both?
A) commensalism
B) symbiotic relationship
C) primordial relationship
D) parasitic relationship
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B) symbiotic relationship
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Context:
any two generating systems of the fundamental group of a closed surface are nielsen equivalent.
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 – 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
; 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
is also higher at high temperature, as shown by carnot ' s theorem. in a conventional metallic engine, much of the energy released from the fuel must be dissipated as waste heat in order to prevent a meltdown of the metallic parts. despite all of these desirable properties, such engines are not in production because the manufacturing of ceramic parts in the requisite precision and durability is difficult. imperfection in the ceramic leads to cracks, which can lead to potentially dangerous equipment failure. such engines are possible in laboratory settings, but mass - production is not feasible with current technology. work is being done in developing ceramic parts for gas turbine engines. currently, even blades made of advanced metal alloys used in the engines ' hot section require cooling and careful limiting of operating temperatures. turbine engines made with ceramics could operate more efficiently, giving aircraft greater range and payload for a set amount of fuel. recently, there have been advances in ceramics which include bio - ceramics, such as dental implants and synthetic bones. hydroxyapatite, the natural mineral component of bone, has been made synthetically from a number of biological and chemical sources and can be formed into ceramic materials. orthopedic implants made from these materials bond readily to bone and other tissues in the body without rejection or inflammatory reactions. because of this, they are of great interest for gene delivery and tissue engineering scaffolds. most hydroxyapatite ceramics are very porous and lack mechanical strength and are used to coat metal orthopedic devices to aid in forming a bond to bone or as bone fillers. they are also used as fillers for orthopedic plastic screws to aid in reducing the inflammation and increase absorption of these plastic materials. work is being done to make strong, fully dense nano crystalline hydroxyapatite ceramic materials for orthopedic weight bearing devices, replacing foreign metal and plastic orthopedic materials with a synthetic, but naturally occurring, bone mineral. ultimately these ceramic materials may be used as bone replacements or with the incorporation of protein collagens, synthetic bones. durable actinide - containing ceramic materials have many applications such as in nuclear fuels for burning excess pu and in chemically - inert sources of alpha irradiation for power supply of unmanned space vehicles or to produce electricity for microelectronic devices. both use and disposal of radioactive actinides require their immobilization in a durable host material. nuclear waste long - lived radionuclides such as actinides are immobilized using chemical
and irrigation in the alluvial south, and catchment systems stretching for tens of kilometers in the hilly north. their palaces had sophisticated drainage systems. writing was invented in mesopotamia, using the cuneiform script. many records on clay tablets and stone inscriptions have survived. these civilizations were early adopters of bronze technologies which they used for tools, weapons and monumental statuary. by 1200 bc they could cast objects 5 m long in a single piece. several of the six classic simple machines were invented in mesopotamia. mesopotamians have been credited with the invention of the wheel. the wheel and axle mechanism first appeared with the potter ' s wheel, invented in mesopotamia ( modern iraq ) during the 5th millennium bc. this led to the invention of the wheeled vehicle in mesopotamia during the early 4th millennium bc. depictions of wheeled wagons found on clay tablet pictographs at the eanna district of uruk are dated between 3700 and 3500 bc. the lever was used in the shadoof water - lifting device, the first crane machine, which appeared in mesopotamia circa 3000 bc, and then in ancient egyptian technology circa 2000 bc. the earliest evidence of pulleys date back to mesopotamia in the early 2nd millennium bc. the screw, the last of the simple machines to be invented, first appeared in mesopotamia during the neo - assyrian period ( 911 – 609 ) bc. the assyrian king sennacherib ( 704 – 681 bc ) claims to have invented automatic sluices and to have been the first to use water screw pumps, of up to 30 tons weight, which were cast using two - part clay molds rather than by the ' lost wax ' process. the jerwan aqueduct ( c. 688 bc ) is made with stone arches and lined with waterproof concrete. the babylonian astronomical diaries spanned 800 years. they enabled meticulous astronomers to plot the motions of the planets and to predict eclipses. the earliest evidence of water wheels and watermills date back to the ancient near east in the 4th century bc, specifically in the persian empire before 350 bc, in the regions of mesopotamia ( iraq ) and persia ( iran ). this pioneering use of water power constituted the first human - devised motive force not to rely on muscle power ( besides the sail ). = = = = egypt = = = = the egyptians, known for building pyramids centuries before the creation of modern tools, invented and used many simple machines, such as the ramp to aid construction processes. historians and archaeologists have found evidence that the pyramids were built using
. 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. =
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
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
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 – 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
- 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 – 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 – though the general concept of direct genetic manipulation was explored in rudimentary form in stanley g. weinbaum ' s 1936 science fiction story proteus island. in 1972, paul berg created the first recombinant dna molecules by combining dna from the monkey virus sv40 with that of the lambda virus. in 1973 herbert boyer and stanley cohen created the first transgenic organism by insert
Question: Generators convert mechanical energy to which kind?
A) electrical
B) kinetic
C) radiation
D) static
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A) electrical
|
Context:
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 — of which around 1 million are insects — 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,
##ochondria and chloroplasts, both of which are now part of modern - day eukaryotic cells. the major lineages of eukaryotes diversified in the precambrian about 1. 5 billion years ago and can be classified into eight major clades : alveolates, excavates, stramenopiles, plants, rhizarians, amoebozoans, fungi, and animals. five of these clades are collectively known as protists, which are mostly microscopic eukaryotic organisms that are not plants, fungi, or animals. while it is likely that protists share a common ancestor ( the last eukaryotic common ancestor ), protists by themselves do not constitute a separate clade as some protists may be more closely related to plants, fungi, or animals than they are to other protists. like groupings such as algae, invertebrates, or protozoans, the protist grouping is not a formal taxonomic group but is used for convenience. most protists are unicellular ; these are called microbial eukaryotes. plants are mainly multicellular organisms, predominantly photosynthetic eukaryotes of the kingdom plantae, which would exclude fungi and some algae. plant cells were derived by endosymbiosis of a cyanobacterium into an early eukaryote about one billion years ago, which gave rise to chloroplasts. the first several clades that emerged following primary endosymbiosis were aquatic and most of the aquatic photosynthetic eukaryotic organisms are collectively described as algae, which is a term of convenience as not all algae are closely related. algae comprise several distinct clades such as glaucophytes, which are microscopic freshwater algae that may have resembled in form to the early unicellular ancestor of plantae. unlike glaucophytes, the other algal clades such as red and green algae are multicellular. green algae comprise three major clades : chlorophytes, coleochaetophytes, and stoneworts. fungi are eukaryotes that digest foods outside their bodies, secreting digestive enzymes that break down large food molecules before absorbing them through their cell membranes. many fungi are also saprobes, feeding on dead organic matter, making them important decomposers in ecological systems. animals are multicellular eukaryotes. with few exceptions, animals
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
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
, 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., α - tubulin and β - 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 — the breaking down of compounds ( for example, the breaking down of glucose to pyruvate by cellular respiration ) ; or anabolic — 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
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
prokaryotic cells and were initially classified as bacteria, receiving the name archaebacteria ( in the archaebacteria kingdom ), a term that has fallen out of use. archaeal cells have unique properties separating them from the other two domains, bacteria and eukaryota. archaea are further divided into multiple recognized phyla. archaea and bacteria are generally similar in size and shape, although a few archaea have very different shapes, such as the flat and square cells of haloquadratum walsbyi. despite this morphological similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes, notably for the enzymes involved in transcription and translation. other aspects of archaeal biochemistry are unique, such as their reliance on ether lipids in their cell membranes, including archaeols. archaea use more energy sources than eukaryotes : these range from organic compounds, such as sugars, to ammonia, metal ions or even hydrogen gas. salt - tolerant archaea ( the haloarchaea ) use sunlight as an energy source, and other species of archaea fix carbon, but unlike plants and cyanobacteria, no known species of archaea does both. archaea reproduce asexually by binary fission, fragmentation, or budding ; unlike bacteria, no known species of archaea form endospores. the first observed archaea were extremophiles, living in extreme environments, such as hot springs and salt lakes with no other organisms. improved molecular detection tools led to the discovery of archaea in almost every habitat, including soil, oceans, and marshlands. archaea are particularly numerous in the oceans, and the archaea in plankton may be one of the most abundant groups of organisms on the planet. archaea are a major part of earth ' s life. they are part of the microbiota of all organisms. in the human microbiome, they are important in the gut, mouth, and on the skin. their morphological, metabolic, and geographical diversity permits them to play multiple ecological roles : carbon fixation ; nitrogen cycling ; organic compound turnover ; and maintaining microbial 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 mit
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 — 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
, 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 — 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
Question: What is common in two eukaryotic proteins?
A) translation
B) cells
C) DNA
D) one domain
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D) one domain
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Context:
i will discuss the presence of massive star clusters in starburst galaxies with an emphasis on low mass galaxies outside the local group. i will show that such galaxies, with respect to their mass and luminosity, may be very rich in young luminous clusters.
two 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.
star clusters can be found in galaxy mergers, not only in central regions, but also in the tidal debris. in both the eastern and western tidal tails of ngc 3256 there are dozens of young star clusters, confirmed by their blue colors and larger concentration index as compared to sources off of the tail. tidal tails of other galaxy pairs do not have such widespread cluster formation, indicating environmental influences on the process of star formation or the packaging of the stars.
we bring you, as usual, the sun and moon and stars, plus some galaxies and a new section on astrobiology. some highlights are short ( the newly identified class of gamma - ray bursts, and the deep impact on comet 9p / tempel 1 ), some long ( the age of the universe, which will be found to have the earth at its center ), and a few metonymic, for instance the term " down - sizing " to describe the evolution of star formation rates with redshift.
v735 sgr was known as an enigmatic star with rapid brightness variations. long - term ogle photometry, brightness measurements in infrared bands, and recently obtained moderate resolution spectrum from the 6. 5 - m magellan telescope show that this star is an active young stellar object of herbig ae / be type.
in a diagram of metallicity ( \ ~ z ) vs. luminosity ( m $ _ b $ ), the different types of nearby ( z $ < 0. 05 $ ) starburst galaxies seem to follow the same linear relationship as the normal spiral and irregular galaxies. however, for comparable luminosities the more massive starburst nucleus galaxies ( sbngs ) show a slight metallic defficiency as compared to the giant spiral galaxies. furthermore, the sbngs do not seem to follow the same relationship between \ ~ z and hubble type ( t ) than the normal galaxies. the early - type sbngs are metal poor as compared to normal galaxies. it may suggests that the chemical evolution of a majority of the nearby starbursts galaxies is not completely over and that the present burst represent an important phase of this process.
occur outside of the milky way galaxy. the chandra x - ray observatory was launched from the columbia on sts - 93 in 1999, observing black holes, quasars, supernova, and dark matter. it provided critical observations on the sagittarius a * black hole at the center of the milky way galaxy and the separation of dark and regular matter during galactic collisions. finally, the spitzer space telescope is an infrared telescope launched in 2003 from a delta ii rocket. it is in a trailing orbit around the sun, following the earth and discovered the existence of brown dwarf stars. other telescopes, such as the cosmic background explorer and the wilkinson microwave anisotropy probe, provided evidence to support the big bang. the james webb space telescope, named after the nasa administrator who lead the apollo program, is an infrared observatory launched in 2021. the james webb space telescope is a direct successor to the hubble space telescope, intended to observe the formation of the first galaxies. other space telescopes include the kepler space telescope, launched in 2009 to identify planets orbiting extrasolar stars that may be terran and possibly harbor life. the first exoplanet that the kepler space telescope confirmed was kepler - 22b, orbiting within the habitable zone of its star. nasa also launched a number of different satellites to study earth, such as television infrared observation satellite ( tiros ) in 1960, which was the first weather satellite. nasa and the united states weather bureau cooperated on future tiros and the second generation nimbus program of weather satellites. it also worked with the environmental science services administration on a series of weather satellites and the agency launched its experimental applications technology satellites into geosynchronous orbit. nasa ' s first dedicated earth observation satellite, landsat, was launched in 1972. this led to nasa and the national oceanic and atmospheric administration jointly developing the geostationary operational environmental satellite and discovering ozone depletion. = = = space shuttle = = = nasa had been pursuing spaceplane development since the 1960s, blending the administration ' s dual aeronautics and space missions. nasa viewed a spaceplane as part of a larger program, providing routine and economical logistical support to a space station in earth orbit that would be used as a hub for lunar and mars missions. a reusable launch vehicle would then have ended the need for expensive and expendable boosters like the saturn v. in 1969, nasa designated the johnson space center as the lead center for the design, development, and manufacturing of the space shuttle orbiter, while the marshall space flight center
the dark matter in the halos of galaxies may well be baryonic, and much of the mass within them could be in the form of clusters of substellar objects within which are embedded cold gas globules. such halos might play an active role in galaxy formation and evolution.
a statistical study of the environment around polar ring galaxies is presented. two kinds of search are performed : 1 ) a study of the concentration and diameters of all the objects surrounding the polar rings, within a search field 5 times the ring diameter. new magnitudes for polar ring galaxies are presented. 2 ) a search, in a wider field, for galaxies of similar size that may have encountered the polar ring host galaxy in a time of the order of 1 gyr. differently from the results of similar searches in the fields of active galaxies, the environment of the polar ring galaxies seems to be similar to that of normal galaxies. this result may give support to the models suggesting long times for formation and evolution of the rings. if the rings are old ( and stable or in equilibrium ), no traces of the past interaction are expected in their surroundings. in addition, the formation of massive polar rings, too big to derive from the ingestion of a present - day dwarf galaxy, may be easily placed in epochs with a higher number of gas - rich galaxies.
the 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 – 139 ad ) to describe the heavens as spherical : the heavens are like a hen ' s egg and as round as a crossbow bullet ; the earth is like the yolk of the egg, and lies in the centre. this analogy with a curved egg led some modern historians, notably joseph needham, to conjecture that chinese astronomers were, after all, aware of the earth ' s sphericity. the egg reference, however, was rather meant to clarify the relative position of the flat earth to the heavens : in a passage of zhang heng ' s cosmogony not translated by needham, zhang himself says : " heaven takes its body from the yang, so it is round and in motion. earth takes its body from the yin, so it is flat and quiescent ". the point of the egg analogy is simply to stress that the earth is completely enclosed by heaven, rather than merely covered from above as the kai tian describes. chinese astronomers, many of them brilliant men by any standards, continued to think in flat - earth terms until the seventeenth century ; this surprising fact might be the starting - point for a re - examination of the apparent facility with which the idea of a spherical earth found acceptance in fifth - century bc greece. further examples cited by needham supposed to demonstrate dissenting voices from the ancient chinese consensus actually refer without exception to the earth being square, not to it being flat. accordingly, the 13th - century scholar li ye, who argued that the movements of the round heaven would be hindered by a square earth, did not advocate a spherical earth, but rather that its edge should be rounded off so as to be circular. however, needham disagrees, affirming that li ye believed the earth to be spherical, similar in shape to the heavens but much smaller. this was preconceived by the 4th - century scholar yu xi, who argued for the infinity of outer space surrounding the earth and that the latter could be either square or round, in accordance to the shape of the heavens. when chinese geographers of the 17th century, influenced by european cartography and astronomy, showed the earth as a sphere that could be circumnavigated by sailing around the globe, they
Question: What do you call egg-shaped galaxies, which are reddish to yellowish in color because they contain mostly old stars?
A) conical galaxies
B) irregular galaxies
C) spiral galaxies
D) elliptical galaxies
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D) elliptical galaxies
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Context:
einstein, when he began working on the general theory of relativity, believed that energy of any kind is the source of the gravitational field. therefore, the energy of gravity, like any energy, must be the source of the field. it was previously discovered that the energy - momentum tensor of the gravitational field is already contained in the ricci tensor. this hypothesis is used to construct a new equation of the gravitational field.
also called pain medicine, or algiatry ) is the medical discipline concerned with the relief of pain. pharmacogenomics is a form of individualized medicine. podiatric medicine is the study of, diagnosis, and medical treatment of disorders of the foot, ankle, lower limb, hip and lower back. sexual medicine is concerned with diagnosing, assessing and treating all disorders related to sexuality. sports medicine deals with the treatment and prevention and rehabilitation of sports / exercise injuries such as muscle spasms, muscle tears, injuries to ligaments ( ligament tears or ruptures ) and their repair in athletes, amateur and professional. therapeutics is the field, more commonly referenced in earlier periods of history, of the various remedies that can be used to treat disease and promote health. travel medicine or emporiatrics deals with health problems of international travelers or travelers across highly different environments. tropical medicine deals with the prevention and treatment of tropical diseases. it is studied separately in temperate climates where those diseases are quite unfamiliar to medical practitioners and their local clinical needs. urgent care focuses on delivery of unscheduled, walk - in care outside of the hospital emergency department for injuries and illnesses that are not severe enough to require care in an emergency department. in some jurisdictions this function is combined with the emergency department. veterinary medicine ; veterinarians apply similar techniques as physicians to the care of non - human animals. wilderness medicine entails the practice of medicine in the wild, where conventional medical facilities may not be available. = = education and legal controls = = medical education and training varies around the world. it typically involves entry level education at a university medical school, followed by a period of supervised practice or internship, or residency. this can be followed by postgraduate vocational training. a variety of teaching methods have been employed in medical education, still itself a focus of active research. in canada and the united states of america, a doctor of medicine degree, often abbreviated m. d., or a doctor of osteopathic medicine degree, often abbreviated as d. o. and unique to the united states, must be completed in and delivered from a recognized university. since knowledge, techniques, and medical technology continue to evolve at a rapid rate, many regulatory authorities require continuing medical education. medical practitioners upgrade their knowledge in various ways, including medical journals, seminars, conferences, and online programs. a database of objectives covering medical knowledge, as suggested by national societies across the united states, can be searched at http : / / data. medobjectives
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.
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 – 181 : 42 – 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
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
an essay on horndeski gravity, how it was formulated in the early 1970s and how it was ' re - discovered ' and widely adopted by cosmologists more than thirty years later.
astronomical observations have shown that the expansion of the universe is at present accelerating, consistently with a constant negative pressure or tension. this is a major puzzle because we do not understand why this tension is so small compared to the planck density ; why, being so small, it is not exactly zero ; and why it has precisely the required value to make the expansion start accelerating just at the epoch when we are observing the universe. the recently proposed conjecture by afshordi that black holes create a gravitational aether owing to quantum gravity effects, which may be identified with this invisible tension, can solve this coincidence problem. the fact that the expansion of the universe is starting to accelerate at the epoch when we observe it is a necessity that is implied by our origin in a planet orbiting a star that formed when the age of the universe was of the same order as the lifetime of the star. this argument is unrelated to any anthropic reasoning.
. 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 – 181 :
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 — frank borman, james lovell, and william anders — 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 – 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
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 america, a doctor of medicine degree, often abbreviated m. d., or a doctor of osteopathic medicine degree, often abbreviated as d. o. and unique to the united states, must be completed in and delivered from a recognized university. since knowledge, techniques, and medical technology continue to evolve at a
Question: When it was found that, without the force of gravity exerting pressure on the bones, bone mass was lost in astronauts, what kind of exercise provided an antidote?
A) resistive
B) sedentary
C) aerobic
D) anaerobic
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A) resistive
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Context:
becomes quite gentle. accordingly, in large basins, rivers in most cases begin as torrents with a variable flow, and end as gently flowing rivers with a comparatively regular discharge. the irregular flow of rivers throughout their course forms one of the main difficulties in devising works for mitigating inundations or for increasing the navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with a rapid fall near the sources of rivers can carry down rocks, boulders and large stones, which are by degrees ground by attrition in their onward course into slate, gravel, sand and silt, simultaneously with the gradual reduction in fall, and, consequently, in the transporting force of the current. accordingly, under
navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with a rapid fall near the sources of rivers can carry down rocks, boulders and large stones, which are by degrees ground by attrition in their onward course into slate, gravel, sand and silt, simultaneously with the gradual reduction in fall, and, consequently, in the transporting force of the current. accordingly, under ordinary conditions, most of the materials brought down from the high lands by torrential water courses are carried forward by the main river to the sea, or partially strewn over flat alluvial plains during floods ; the size of the materials forming the bed of the river or borne along by the stream is gradually reduced on proceeding sea
approximately corresponds to the slope of the country it traverses ; as rivers rise close to the highest part of their basins, generally in hilly regions, their fall is rapid near their source and gradually diminishes, with occasional irregularities, until, in traversing plains along the latter part of their course, their fall usually becomes quite gentle. accordingly, in large basins, rivers in most cases begin as torrents with a variable flow, and end as gently flowing rivers with a comparatively regular discharge. the irregular flow of rivers throughout their course forms one of the main difficulties in devising works for mitigating inundations or for increasing the navigable capabilities of rivers. in tropical countries subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year, while in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with
weather than in the winter months, so that the rivers fall to their low stage in the summer and are liable to be in flood in the winter. in fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from may to october and from november to april in the northern hemisphere respectively ; the rivers are low and moderate floods are of rare occurrence during the warm period, and the rivers are high and subject to occasional heavy floods after a considerable rainfall during the cold period in most years. the only exceptions are rivers which have their sources amongst mountains clad with perpetual snow and are fed by glaciers ; their floods occur in the summer from the melting of snow and ice, as exemplified by the rhone above the lake of geneva, and the arve which joins it below. but even these rivers are liable to have their flow modified by the influx of tributaries subject to different conditions, so that the rhone below lyon has a more uniform discharge than most rivers, as the summer floods of the arve are counteracted to a great extent by the low stage of the saone flowing into the rhone at lyon, which has its floods in the winter when the arve, on the contrary, is low. another serious obstacle encountered in river engineering consists in the large quantity of detritus they bring down in flood - time, derived mainly from the disintegration of the surface layers of the hills and slopes in the upper parts of the valleys by glaciers, frost and rain. the power of a current to transport materials varies with its velocity, so that torrents with a rapid fall near the sources of rivers can carry down rocks, boulders and large stones, which are by degrees ground by attrition in their onward course into slate, gravel, sand and silt, simultaneously with the gradual reduction in fall, and, consequently, in the transporting force of the current. accordingly, under ordinary conditions, most of the materials brought down from the high lands by torrential water courses are carried forward by the main river to the sea, or partially strewn over flat alluvial plains during floods ; the size of the materials forming the bed of the river or borne along by the stream is gradually reduced on proceeding seawards, so that in the po river in italy, for instance, pebbles and gravel are found for about 140 miles below turin, sand along the next 100 miles, and silt and mud in the last 110 miles ( 176 km ). = = channelization = = the removal of obstructions, natural or artificial
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
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 ( e. g., trunks of trees, boulders and accumulations of gravel ) from a river bed furnishes a simple and efficient means of increasing the discharging capacity of its channel. such removals will consequently lower the height of floods upstream. every impediment to the flow, in proportion to
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
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
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 – civil works program river morphology and stream restoration references - wildland hydrology at the library of congress web archives ( archived 2002 - 08 - 13 )
##ediment to up - stream navigation, and there are generally variations in water level, and when the discharge becomes small in the dry season. it is impossible to maintain a sufficient depth of water in the low - water channel. the possibility to secure uniformity of depth in a river by lowering the shoals obstructing the channel depends on the nature of the shoals. a soft shoal in the bed of a river is due to deposit from a diminution in velocity of flow, produced by a reduction in fall and by a widening of the channel, or to a loss in concentration of the scour of the main current in passing over from one concave bank to the next on the opposite side. the lowering of such a shoal by dredging merely effects a temporary deepening, for it soon forms again from the causes which produced it. the removal, moreover, of the rocky obstructions at rapids, though increasing the depth and equalizing the flow at these places, produces a lowering of the river above the rapids by facilitating the efflux, which may result in the appearance of fresh shoals at the low stage of the river. where, however, narrow rocky reefs or other hard shoals stretch across the bottom of a river and present obstacles to the erosion by the current of the soft materials forming the bed of the river above and below, their removal may result in permanent improvement by enabling the river to deepen its bed by natural scour. the capability of a river to provide a waterway for navigation during the summer or throughout the dry season depends on the depth that can be secured in the channel at the lowest stage. the problem in the dry season is the small discharge and deficiency in scour during this period. a typical solution is to restrict the width of the low - water channel, concentrate all of the flow in it, and also to fix its position so that it is scoured out every year by the floods which follow the deepest part of the bed along the line of the strongest current. this can be effected by closing subsidiary low - water channels with dikes across them, and narrowing the channel at the low stage by low - dipping cross dikes extending from the river banks down the slope and pointing slightly up - stream so as to direct the water flowing over them into a central channel. = = estuarine works = = the needs of navigation may also require that a stable, continuous, navigable channel is prolonged from the navigable river to deep water at the mouth of the estuary. the interaction of river
Question: What can occur during periods of heavy rain?
A) volcanoes
B) floods
C) glaciers
D) earthquakes
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B) floods
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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
energy is no doubt an intuitive concept. following a previous analysis on the nature of elementary particles and associated elementary quantum fields, the peculiar status and role of energy is scrutinised further at elementary and larger scales. energy physical characterisation shows that it is a primordial component of reality highlighting the quantum fields natural tendencies to interact, the elementary particles natural tendency to constitute complex bodies and every material thing natural tendency to actualise and be active. energy therefore is a primordial notion in need of a proper assessment.
education, science, in fact the whole society, extensively use images. between us and the world are the visual displays. screens, small and large, individual or not, are everywhere. images are increasingly the 2d substrate of our virtual interaction with reality. however images will never support a complete representation of the reality. three - dimensional representations will not change that. images are primarily a spatial representation of our world dedicated to our sight. key aspects such as energy and the associated forces are not spatially materialized. in classical physics, interaction description is based on newton equations with trajectory and force as the dual central concepts. images can in real time show all aspects of trajectories but not the associated dynamical aspects described by forces and energies. contrary to the real world, the world of images opposes no constrain, nor resistance to our actions. only the physical quantities, that do not contain mass in their dimension can be satisfactory represented by images. often symbols such as arrows are introduced to visualize the force vectors.
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.
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.
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 — 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 – 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 – 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 (
the rapidly developing research field of organic analogue sensors aims to replace traditional semiconductors with naturally occurring materials. photosensors, or photodetectors, change their electrical properties in response to the light levels they are exposed to. organic photosensors can be functionalised to respond to specific wavelengths, from ultra - violet to red light. performing cyclic voltammetry on fungal mycelium and fruiting bodies under different lighting conditions shows no appreciable response to changes in lighting condition. however, functionalising the specimen using pedot : pss yields in a photosensor that produces large, instantaneous current spikes when the light conditions change. future works would look at interfacing this organic photosensor with an appropriate digital back - end for interpreting and processing the response.
, 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 − e / k t { \ displaystyle e ^ { - e / kt } } – 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, δ g ≤ 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
a rail gun launching at 9 mj of energy would need roughly 32 mj worth of energy from capacitors. current advances in energy storage allow for energy densities as high as 2. 5 mj / dm3, which means that a battery delivering 32 mj of energy would require a volume of 12. 8 dm3 per shot ; this is not a viable volume for use in a modern main battle tank, especially one designed to be lighter than existing models. there has even been discussion about eliminating the necessity for an outside electrical source in etc ignition by initiating the plasma cartridge through a small explosive force. furthermore, etc technology is not only applicable to solid propellants. to increase muzzle velocity even further electrothermal - chemical ignition can work with liquid propellants, although this would require further research into plasma ignition. etc technology is also compatible with existing projects to reduce the amount of recoil delivered to the vehicle while firing. understandably, recoil of a gun firing a projectile at 17 mj or more will increase directly with the increase in muzzle energy in accordance to newton ' s third law of motion and successful implementation of recoil reduction mechanisms will be vital to the installation of an etc powered gun in an existing vehicle design. for example, oto melara ' s new lightweight 120 mm l / 45 gun has achieved a recoil force of 25 t by using a longer recoil mechanism ( 550 mm ) and a pepperpot muzzle brake. reduction in recoil can also be achieved through mass attenuation of the thermal sleeve. the ability of etc technology to be applied to existing gun designs means that for future gun upgrades there ' s no longer the necessity to redesign the turret to include a larger breech or caliber gun barrel. several countries have already determined that etc technology is viable for the future and have funded indigenous projects considerably. these include the united states, germany and the united kingdom, amongst others. the united states ' xm360, which was planned to equip the future combat systems mounted combat system light tank and may be the m1 abrams ' next gun upgrade, is reportedly based on the xm291 and may include etc technology, or portions of etc technology. tests of this gun have been performed using " precision ignition " technology, which may refer to etc ignition. = = notes = = = = bibliography = = = = external links = = electromagnetic launch symposium http : / / www. powerlabs. org / electrothermal. htm
classical mechanics is based upon a mechanical picture of nature that is fundamentally incorrect. it has been replaced at the basic level by a radically different theory : quantum mechanics. this change entails an enormous shift in our basic conception of nature, one that can profoundly alter the scientific image of man himself. self - image is the foundation of values, and the replacement of the mechanistic self - image derived from classical mechanics by one concordant with quantum mechanics may provide the foundation of a moral order better suited to our times, a self - image that endows human life with meaning, responsibility, and a deeper linkage to nature as a whole.
Question: What type of energy can be used to change the position or shape of an object, thus giving it potential energy?
A) static energy
B) binary energy
C) kinetic energy
D) harmonic energy
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C) kinetic energy
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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 – induced pluripotent stem cells – may be useful for the repair of diseased or damaged tissues, or may be used to grow new organs. totipotent cells are stem cells which can divide into further stem cells or differentiate into any cell type in the body, including extra - embryonic tissue. pluripotent cells are stem cells which can differentiate into any cell type in the body except extra - embryonic tissue. induced pluripotent stem cells ( ipscs ) are subclass of pluripotent stem cells resembling embryonic stem cells ( escs ) that have been derived from adult differentiated cells. ipscs are created by altering the expression of transcriptional factors in adult cells until they become like embryonic stem cells. multipotent stem cells can be differentiated into any cell within the same class, such as blood or bone. a common example of multipotent cells is mesenchymal stem cells ( mscs ). = = scaffolds = = scaffolds are materials that have been engineered to cause desirable cellular interactions to contribute to the formation of new functional tissues for medical purposes. cells are often ' seeded ' into these structures capable of supporting three - dimensional tissue formation. scaffolds mimic the extracellular matrix of the native tissue, recapitulating the in vivo milieu and allowing cells to influence their own microenvironments. they usually serve at least one of the following purposes : allowing cell attachment and migration, delivering and retaining cells and biochemical factors, enabling diffusion of vital cell nutrients and expressed products, and exerting certain mechanical and biological influences to modify the behaviour of the cell phase. in 2009, an interdisciplinary team led by the thoracic surgeon thorsten walles implanted the first bioartificial transplant that provides an innate vascular network for post - transplant graft supply successfully into a patient awaiting tracheal reconstruction. to achieve the goal of tissue reconstruction, scaffolds must meet some specific requirements. high porosity and adequate pore size are necessary to facilitate cell seed
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
represent 6. 28 = = = the meaning of the symbol π { \ displaystyle \ pi } was not originally defined as the ratio of circumference to diameter, and at times was used in representations of the 6. 28... constant. early works in circle geometry used the letter π to designate the perimeter ( i. e., circumference ) in different fractional representations of circle constants and in 1697 david gregory used π / ρ ( pi over rho ) to denote the perimeter divided by the radius ( 6. 28... ). subsequently π came to be used as a single symbol to represent the ratios in whole. leonhard euler initially used the single letter π was to denote the constant 6. 28... in his 1727 essay explaining the properties of air. euler would later use the letter π for 3. 14... in his 1736 mechanica and 1748 introductio in analysin infinitorum, though defined as half the circumference of a circle of radius 1 rather than the ratio of circumference to diameter. elsewhere in mechanica, euler instead used the letter π for one - fourth of the circumference of a unit circle, or 1. 57.... usage of the letter π, sometimes for 3. 14... and other times for 6. 28..., became widespread, with the definition varying as late as 1761 ; afterward, π was standardized as being equal to 3. 14.... = = notion using [UNK] = = proponents argue that while use of [UNK] in place of 2π does not change any of the underlying mathematics, it does lead to simpler and more intuitive notation in many areas. michael hartl ' s tau manifesto gives many examples of formulas that are asserted to be clearer where τ is used instead of π. = = = units of angle = = = hartl and robert palais have argued that [UNK] allows radian angles to be expressed more directly and in a way that makes clear the link between the radian measure and rotation around the unit circle. for instance, 3τ / 4 rad can be easily interpreted as 3 / 4 of a turn around the unit circle in contrast with the numerically equal 3π / 2 rad, where the meaning could be obscured, particularly for children and students of mathematics. critics have responded that a full rotation is not necessarily the correct or fundamental reference measure for angles and two other possibilities, the right angle and straight angle
currently we produce 10 to power 21 digital bits of information annually on earth. assuming 20 percent annual growth rate, we estimate that 350 years from now, the number of bits produced will exceed the number of all atoms on earth, or 10 to power 50. after 250 years, the power required to sustain this digital production will exceed 18. 5 tw, or the total planetary power consumption today, and 500 years from now the digital content will account for more than half of the earths mass, according to the mass energy information equivalence principle. besides the existing global challenges such as climate, environment, population, food, health, energy and security, our estimates here point to another singularity event for our planet, called the information catastrophe.
= = 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 — a cardinal number — 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 ( 180° ) 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 π ( 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 ±1 ( see equiareal map § 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
denoted as | |. ± ( plus – minus sign ) 1. denotes either a plus sign or a minus sign. 2. denotes the range of values that a measured quantity may have ; for example, 10 ± 2 denotes an unknown value that lies between 8 and 12. [UNK] ( minus - plus sign ) used paired with ±, denotes the opposite sign ; that is, + if ± is −, and − if ± is +. ÷ ( division sign ) widely used for denoting division in anglophone countries, it is no longer in common use in mathematics and its use is " not recommended ". in some countries, it can indicate subtraction. : ( colon ) 1. denotes the ratio of two quantities. 2. in some countries, may denote division. 3. in set - builder notation, it is used as a separator meaning " such that " ; see { [UNK] : [UNK] }. / ( slash ) 1. denotes division and is read as divided by or over. often replaced by a horizontal bar. for example, 3 / 2 or 3 2 { \ displaystyle { \ frac { 3 } { 2 } } }. 2. denotes a quotient structure. for example, quotient set, quotient group, quotient category, etc. 3. in number theory and field theory, f / e { \ displaystyle f / e } denotes a field extension, where f is an extension field of the field e. 4. in probability theory, denotes a conditional probability. for example, p ( a / b ) { \ displaystyle p ( a / b ) } denotes the probability of a, given that b occurs. usually denoted p ( a [UNK] b ) { \ displaystyle p ( a \ mid b ) } : see " | ". √ ( square - root symbol ) denotes square root and is read as the square root of. rarely used in modern mathematics without a horizontal bar delimiting the width of its argument ( see the next item ). for example, √2. √ ( radical symbol ) 1. denotes square root and is read as the square root of. for example, 3 + 2 { \ displaystyle { \ sqrt { 3 + 2 } } }. 2. with an integer greater than 2 as a left superscript, denotes an nth root. for example, 3 7 { \ displaystyle { \ sqrt [ { 7 } ] { 3 } } } denotes the 7th root of 3. ^ ( caret
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
arithmetic, denotes multiplication, and is read as times ; for example, 3 × 2. 2. in geometry and linear algebra, denotes the cross product. 3. in set theory and category theory, denotes the cartesian product and the direct product. see also × in § set theory. · ( dot ) 1. denotes multiplication and is read as times ; for example, 3 ⋅ 2. 2. in geometry and linear algebra, denotes the dot product. 3. placeholder used for replacing an indeterminate element. for example, saying " the absolute value is denoted by | · | " is perhaps clearer than saying that it is denoted as | |. ± ( plus – minus sign ) 1. denotes either a plus sign or a minus sign. 2. denotes the range of values that a measured quantity may have ; for example, 10 ± 2 denotes an unknown value that lies between 8 and 12. [UNK] ( minus - plus sign ) used paired with ±, denotes the opposite sign ; that is, + if ± is −, and − if ± is +. ÷ ( division sign ) widely used for denoting division in anglophone countries, it is no longer in common use in mathematics and its use is " not recommended ". in some countries, it can indicate subtraction. : ( colon ) 1. denotes the ratio of two quantities. 2. in some countries, may denote division. 3. in set - builder notation, it is used as a separator meaning " such that " ; see { [UNK] : [UNK] }. / ( slash ) 1. denotes division and is read as divided by or over. often replaced by a horizontal bar. for example, 3 / 2 or 3 2 { \ displaystyle { \ frac { 3 } { 2 } } }. 2. denotes a quotient structure. for example, quotient set, quotient group, quotient category, etc. 3. in number theory and field theory, f / e { \ displaystyle f / e } denotes a field extension, where f is an extension field of the field e. 4. in probability theory, denotes a conditional probability. for example, p ( a / b ) { \ displaystyle p ( a / b ) } denotes the probability of a, given that b occurs. usually denoted p ( a [UNK] b ) { \ displaystyle p ( a \ mid b ) } : see " | ". √ ( square - root symbol ) denotes square root and is read as the square
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 × x → x ( where x is a set such as the set of real numbers ). = = definition = = an n - ary operation ω on a set x is a function ω : xn → 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 operands ) is called the arity of the operation. thus a unary operation has arity one, and a binary operation has arity two. an operation of arity zero, called a nullary operation, is simply an element of the codomain y. an n - ary operation can also be viewed
the aforesaid quantities is said to be equal or unequal. for instance, one solid is said to be equal or unequal to another ; number, too, and time can have these terms applied to them, indeed can all those kinds of quantity that have been mentioned. that which is not a quantity can by no means, it would seem, be termed equal or unequal to anything else. one particular disposition or one particular quality, such as whiteness, is by no means compared with another in terms of equality and inequality but rather in terms of similarity. thus it is the distinctive mark of quantity that it can be called equal and unequal. ― ( translated by e. m. edghill ) aristotle had separate categories for quantities ( number, length, volume ) and qualities ( temperature, density, pressure ), now called intensive and extensive properties. the scholastics, particularly richard swineshead and other oxford calculators in the 14th century, began seriously thinking about kinematics and quantitative treatment of qualities. for example, two flames have the same heat - intensity if they produce the same effect on water ( e. g, warming vs boiling ). since two intensities could be shown to be equal, and equality was considered the defining feature of quantities, it meant those intensities were quantifiable. around the 19th century, with the growth of modern logic, it became necessary to have a more concrete description of equality. with the rise of predicate logic due to the work of gottlob frege, logic shifted from being focused on classes of objects to being property - based. this was followed by a movement for describing mathematics in logical foundations, called logicism. this trend lead to the axiomatization of equality through the law of identity and the substitution property especially in mathematical logic and analytic philosophy. the precursor to the substitution property of equality was first formulated by gottfried leibniz in his discourse on metaphysics ( 1686 ), stating, roughly, that " no two distinct things can have all properties in common. " this has since broken into two principles, the substitution property ( if x = y, { \ displaystyle x = y, } then any property of x { \ displaystyle x } is a property of y { \ displaystyle y } ), and its converse, the identity of indiscernibles ( if x { \ displaystyle x } and y { \ displaystyle y } have all properties in common, then x = y { \ displaystyle x =
Question: What equals the output power divided by the input power?
A) output
B) potential
C) efficiency
D) inertia
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C) efficiency
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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 non - avian dinosaurs, mammals increased rapidly in size and diversity. such mass extinctions may have accelerated evolution by providing opportunities for new groups of organisms to diversify. = = diversity = = = = = bacteria and archaea = = = bacteria are a type of cell that constitute a large domain of prokaryotic microorganisms. typically a few micrometers in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. bacteria were among the first life forms to appear on earth, and are present in most of its habitats. bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep biosphere of the earth ' s crust. bacteria also live in symbiotic and parasitic relationships with plants and animals. most bacteria have not been characterised, and only about 27 percent of the bacterial phyla have species that can be grown in the laboratory. archaea constitute the other domain of prokaryotic cells and were initially classified as bacteria, receiving the name archaebacteria ( in the archaebacteria kingdom ), a term that has fallen out of use. archaeal cells have unique properties separating them from the other two domains, bacteria and eukaryota. archaea are further divided into multiple recognized phyla. archaea and bacteria are generally similar in size and shape, although a few archaea have very different shapes, such as the flat and square cells of haloquadratum walsbyi. despite this morphological similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes, notably for the enzymes involved in transcription and translation. other aspects of archaeal biochemistry are unique, such as their reliance on ether lipids in their cell membranes, including archaeols. archaea use more energy sources than eukaryotes : these range from organic compounds, such as sugars, to ammonia, metal ions or even hydrogen gas. salt - tolerant archaea ( the haloarchaea ) use sunlight as an energy source, and other species of archaea fix carbon, but unlike plants and cyanobacteria, no known species of archaea does both. archaea reproduce asexually by binary fission, fragmentation, or budding ; unlike bacteria, no known species of archaea form endospores. the first observed archaea were extremophiles, living in extreme environments, such as hot springs and salt lakes with no other organisms. improved molecular detection
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.
kilometers ( 4, 200, 000 to 395, 400, 000 acres ). 10 % of the world ' s crop lands were planted with gm crops in 2010. as of 2011, 11 different transgenic crops were grown commercially on 395 million acres ( 160 million hectares ) in 29 countries such as the us, brazil, argentina, india, canada, china, paraguay, pakistan, south africa, uruguay, bolivia, australia, philippines, myanmar, burkina faso, mexico and spain. genetically modified foods are foods produced from organisms that have had specific changes introduced into their dna with the methods of genetic engineering. these techniques have allowed for the introduction of new crop traits as well as a far greater control over a food ' s genetic structure than previously afforded by methods such as selective breeding and mutation breeding. commercial sale of genetically modified foods began in 1994, when calgene first marketed its flavr savr delayed ripening tomato. to date most genetic modification of foods have primarily focused on cash crops in high demand by farmers such as soybean, corn, canola, and cotton seed oil. these have been engineered for resistance to pathogens and herbicides and better nutrient profiles. gm livestock have also been experimentally developed ; in november 2013 none were available on the market, but in 2015 the fda approved the first gm salmon for commercial production and consumption. there is a scientific consensus that currently available food derived from gm crops poses no greater risk to human health than conventional food, but that each gm food needs to be tested on a case - by - case basis before introduction. nonetheless, members of the public are much less likely than scientists to perceive gm foods as safe. the legal and regulatory status of gm foods varies by country, with some nations banning or restricting them, and others permitting them with widely differing degrees of regulation. gm crops also provide a number of ecological benefits, if not used in excess. insect - resistant crops have proven to lower pesticide usage, therefore reducing the environmental impact of pesticides as a whole. however, opponents have objected to gm crops per se on several grounds, including environmental concerns, whether food produced from gm crops is safe, whether gm crops are needed to address the world ' s food needs, and economic concerns raised by the fact these organisms are subject to intellectual property law. biotechnology has several applications in the realm of food security. crops like golden rice are engineered to have higher nutritional content, and there is potential for food products with longer shelf lives. though not a form of agricultural biotechnology, vaccines can help prevent diseases found in
" thrashing ". this frequently leads to high, runaway cpu utilization that can grind the system to a halt. in modern computers, thrashing may occur in the paging system ( if there is not sufficient physical memory or the disk access time is overly long ), or in the i / o communications subsystem ( especially in conflicts over internal bus access ), etc. depending on the configuration and algorithms involved, the throughput and latency of a system may degrade by multiple orders of magnitude. thrashing is when the cpu performs ' productive ' work less and ' swapping ' work more. the overall memory access time may increase since the higher level memory is only as fast as the next lower level in the memory hierarchy. the cpu is busy swapping pages so much that it cannot respond to users ' programs and interrupts as much as required. thrashing occurs when there are too many pages in memory, and each page refers to another page. real memory reduces its capacity to contain all the pages, so it uses ' virtual memory '. when each page in execution demands that page that is not currently in real memory ( ram ) it places some pages on virtual memory and adjusts the required page on ram. if the cpu is too busy doing this task, thrashing occurs. = = = causes = = = in virtual memory systems, thrashing may be caused by programs or workloads that present insufficient locality of reference : if the working set of a program or a workload cannot be effectively held within physical memory, then constant data swapping, i. e., thrashing, may occur. the term was first used during the tape operating system days to describe the sound the tapes made when data was being rapidly written to and read. a worst case might occur on vax processors. a single movl crossing a page boundary could have a source operand using a displacement deferred addressing mode, where the longword containing the operand address crosses a page boundary, and a destination operand using a displacement deferred addressing mode, where the longword containing the operand address crosses a page boundary, and the source and destination could both cross page boundaries. this single instruction references ten pages ; if not all are in ram, each will cause a page fault. the total number of pages thus involved in this particular instruction is ten, and all ten pages must be simultaneously present in memory. if any one of the ten pages cannot be swapped in ( for example to make room for any of the other pages )
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 — of which around 1 million are insects — 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 — pieces of dna that can move between cells — while others may have evolved from bacteria. in evolution, viruses are an important means of horizontal gene transfer, which increases genetic diversity in a way analogous to sexual reproduction. because viruses possess some but not all characteristics of life, they have been described as " organisms at the edge of life ", and as self - replicators. = = ecology = = ecology is the study of the distribution and abundance of life, the interaction between organisms and their environment. = = = ecosystems = = = the community of living ( biotic ) organisms in conjunction with the nonliving ( abiotic ) components ( e. g., water, light, radiation, temperature, humidity, atmosphere, acidity, and soil ) of their environment is called an ecosystem. these biotic and abiotic components are linked together through nutrient cycles and energy flows. energy from the sun enters the system through photosynthesis and is incorporated into plant tissue. by feeding on plants and on one another, animals move matter and energy through the system. they also influence the quantity of plant and microbial biomass present. by breaking down dead organic matter, decomposers release carbon back to the atmosphere and facilitate nutrient cycling by converting nutrients stored in dead biomass back to a form that can be readily used by plants and other microbes. = = = populations = = = a population is the group of organisms of the same species that occupies an area and reproduce from generation to generation. population size can be estimated by multiplying population density by the area or volume. the carrying capacity of an environment
mathematical analysis for one - sided limits ( right - sided limit and left - sided limit, respectively ). this notation refers to the behaviour of a function as its real input variable approaches 0 along positive ( resp., negative ) values ; the two limits need not exist or agree. = = = terminology for signs = = = when 0 is said to be neither positive nor negative, the following phrases may refer to the sign of a number : a number is positive if it is greater than zero. a number is negative if it is less than zero. a number is non - negative if it is greater than or equal to zero. a number is non - positive if it is less than or equal to zero. when 0 is said to be both positive and negative, modified phrases are used to refer to the sign of a number : a number is strictly positive if it is greater than zero. a number is strictly negative if it is less than zero. a number is positive if it is greater than or equal to zero. a number is negative if it is less than or equal to zero. for example, the absolute value of a real number is always " non - negative ", but is not necessarily " positive " in the first interpretation, whereas in the second interpretation, it is called " positive " — though not necessarily " strictly positive ". the same terminology is sometimes used for functions that yield real or other signed values. for example, a function would be called a positive function if its values are positive for all arguments of its domain, or a non - negative function if all of its values are non - negative. = = = complex numbers = = = complex numbers are impossible to order, so they cannot carry the structure of an ordered ring, and, accordingly, cannot be partitioned into positive and negative complex numbers. they do, however, share an attribute with the reals, which is called absolute value or magnitude. magnitudes are always non - negative real numbers, and to any non - zero number there belongs a positive real number, its absolute value. for example, the absolute value of −3 and the absolute value of 3 are both equal to 3. this is written in symbols as | −3 | = 3 and | 3 | = 3. in general, any arbitrary real value can be specified by its magnitude and its sign. using the standard encoding, any real value is given by the product of the magnitude and the sign in standard encoding. this relation can be generalized to define a sign for complex numbers. since the real and
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.
in mathematics, a degenerate case is a limiting case of a class of objects which appears to be qualitatively different from ( and usually simpler than ) the rest of the class ; " degeneracy " is the condition of being a degenerate case. the definitions of many classes of composite or structured objects often implicitly include inequalities. for example, the angles and the side lengths of a triangle are supposed to be positive. the limiting cases, where one or several of these inequalities become equalities, are degeneracies. in the case of triangles, one has a degenerate triangle if at least one side length or angle is zero. equivalently, it becomes a " line segment ". often, the degenerate cases are the exceptional cases where changes to the usual dimension or the cardinality of the object ( or of some part of it ) occur. for example, a triangle is an object of dimension two, and a degenerate triangle is contained in a line, which makes its dimension one. this is similar to the case of a circle, whose dimension shrinks from two to zero as it degenerates into a point. as another example, the solution set of a system of equations that depends on parameters generally has a fixed cardinality and dimension, but cardinality and / or dimension may be different for some exceptional values, called degenerate cases. in such a degenerate case, the solution set is said to be degenerate. for some classes of composite objects, the degenerate cases depend on the properties that are specifically studied. in particular, the class of objects may often be defined or characterized by systems of equations. in most scenarios, a given class of objects may be defined by several different systems of equations, and these different systems of equations may lead to different degenerate cases, while characterizing the same non - degenerate cases. this may be the reason for which there is no general definition of degeneracy, despite the fact that the concept is widely used and defined ( if needed ) in each specific situation. a degenerate case thus has special features which makes it non - generic, or a special case. however, not all non - generic or special cases are degenerate. for example, right triangles, isosceles triangles and equilateral triangles are non - generic and non - degenerate. in fact, degenerate cases often correspond to singularities, either in the object
pharmaceutical agents, biofuels, and other industrially useful goods, as well as for bioremediation. farmers have widely adopted gm technology. between 1996 and 2011, the total surface area of land cultivated with gm crops had increased by a factor of 94, from 17, 000 to 1, 600, 000 square kilometers ( 4, 200, 000 to 395, 400, 000 acres ). 10 % of the world ' s crop lands were planted with gm crops in 2010. as of 2011, 11 different transgenic crops were grown commercially on 395 million acres ( 160 million hectares ) in 29 countries such as the us, brazil, argentina, india, canada, china, paraguay, pakistan, south africa, uruguay, bolivia, australia, philippines, myanmar, burkina faso, mexico and spain. genetically modified foods are foods produced from organisms that have had specific changes introduced into their dna with the methods of genetic engineering. these techniques have allowed for the introduction of new crop traits as well as a far greater control over a food ' s genetic structure than previously afforded by methods such as selective breeding and mutation breeding. commercial sale of genetically modified foods began in 1994, when calgene first marketed its flavr savr delayed ripening tomato. to date most genetic modification of foods have primarily focused on cash crops in high demand by farmers such as soybean, corn, canola, and cotton seed oil. these have been engineered for resistance to pathogens and herbicides and better nutrient profiles. gm livestock have also been experimentally developed ; in november 2013 none were available on the market, but in 2015 the fda approved the first gm salmon for commercial production and consumption. there is a scientific consensus that currently available food derived from gm crops poses no greater risk to human health than conventional food, but that each gm food needs to be tested on a case - by - case basis before introduction. nonetheless, members of the public are much less likely than scientists to perceive gm foods as safe. the legal and regulatory status of gm foods varies by country, with some nations banning or restricting them, and others permitting them with widely differing degrees of regulation. gm crops also provide a number of ecological benefits, if not used in excess. insect - resistant 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
Question: Overpopulation takes place when the number of organisms in an area exceeds what?
A) consumers
B) biome size
C) carrying capacity
D) predators
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C) carrying capacity
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Context:
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
, 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 — 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
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.
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 — 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
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
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 – beneficial uses
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
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 ( create a critical mass ) for detonation. it also is quite difficult to ensure that such a chain reaction consumes a significant fraction of the fuel before the device flies apart. the procurement of a nuclear fuel is also more difficult than it might seem, since sufficiently unstable substances for this process do not currently occur naturally on earth in suitable amounts. one isotope of uranium, namely uranium - 235, is naturally occurring and sufficiently unstable, but it is always found mixed with the more stable isotope uranium - 238. the latter accounts for more than 99 % of the weight of natural uranium. therefore, some method of isotope separation based on the weight of three neutrons must be performed to enrich ( isolate ) uranium - 235. alternatively, the element plutonium possesses an isotope that is sufficiently unstable for this process to be usable. terrestrial plutonium does not currently occur naturally in sufficient quantities for such use, so it must be manufactured in a nuclear reactor. ultimately, the manhattan project manufactured nuclear weapons based on each of these elements. they detonated the first nuclear weapon in a test code - named " trinity ", near alamogordo, new mexico, on july 16, 1945. the test was conducted to ensure that the implosion method of detonation would work, which it did. a uranium bomb, little boy, was dropped on the japanese city hiroshima on august 6, 1945, followed three days later by the plutonium - based fat man on nagasaki. in the wake of unprecedented devastation and casualties from a single weapon, the japanese government soon surrendered, ending world war ii. since these bombings, no nuclear weapons have been deployed offensively. nevertheless, they prompted an arms race to develop increasingly destructive bombs to provide a nuclear deterrent. just over four years later, on august 29, 1949, the soviet union detonated its first fission weapon. the united kingdom followed on october 2, 1952 ; france, on february
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 in 1990, the united kingdom in 1991, and both france and china continued testing until 1996. after signing the comprehensive test ban treaty in 1996 ( which had as of 2011 not entered into force ), all of these states have pledged to discontinue all nuclear testing. non - signatories india and pakistan last tested nuclear weapons in 1998. nuclear weapons are the most destructive weapons known - the archetypal weapons of mass destruction. throughout the cold war, the opposing powers had huge nuclear arsenals, sufficient to kill hundreds of millions of people. generations of people grew up under the shadow of nuclear devastation, portrayed in films such as dr. strangelove and the atomic cafe. however, the tremendous energy release in the detonation of a nuclear weapon also suggested the possibility of a new energy source. = = civilian uses = = = = = nuclear power = = = nuclear power is a type of nuclear technology involving the controlled use of nuclear fission
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 – 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 cl− ions forming sodium chloride, or nacl. examples of polyatomic ions that do not split up during acid – base reactions are hydroxide ( oh− ) and phosphate ( po43− ). 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 – 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.
Question: There are six fundamentally different kinds of nuclear decay reactions, and each releases a different kind of particle or what?
A) energy
B) protein
C) mineral
D) mass
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A) energy
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Context:
; 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 – 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 – like stars and distant galaxies – 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 — 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 – 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 – like stars and distant galaxies – 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 — 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 – 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 valuable metals into individual constituents. = = metal and its alloys = = much effort has been placed on understanding iron – 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
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 – 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 — from a few to millions — of devices manufactured and interconnected on a single semiconductor substrate. of all the semiconductors in use today, silicon makes up the largest portion both by quantity and commercial value. monocrystalline silicon is used to produce wafers used in the semiconductor and electronics industry. gallium arsenide (
based on 1 / 10 and 1 / 100 weight percentages of the carbon and other alloying elements they contain. thus, the extracting and purifying methods used to extract iron in a blast furnace can affect the quality of steel that is produced. solid materials are generally grouped into three basic classifications : ceramics, metals, and polymers. this broad classification is based on the empirical makeup and atomic structure of the solid materials, and most solids fall into one of these broad categories. an item that is often made from each of these materials types is the beverage container. the material types used for beverage containers accordingly provide different advantages and disadvantages, depending on the material used. ceramic ( glass ) containers are optically transparent, impervious to the passage of carbon dioxide, relatively inexpensive, and are easily recycled, but are also heavy and fracture easily. metal ( aluminum alloy ) is relatively strong, is a good barrier to the diffusion of carbon dioxide, and is easily recycled. however, the cans are opaque, expensive to produce, and are easily dented and punctured. polymers ( polyethylene plastic ) are relatively strong, can be optically transparent, are inexpensive and lightweight, and can be recyclable, but are not as impervious to the passage of carbon dioxide as aluminum and glass. = = = ceramics and glasses = = = another application of materials science is the study of ceramics and glasses, typically the most brittle materials with industrial relevance. many ceramics and glasses exhibit covalent or ionic - covalent bonding with sio2 ( silica ) as a fundamental building block. ceramics – not to be confused with raw, unfired clay – 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
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 – molten metal is poured into a shaped mold. variants of casting include sand casting, investment
building block. ceramics – not to be confused with raw, unfired clay – 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 °c ( 2, 750 °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
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
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 – 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 — from a
classifications ; however, some more exotic phases are incompatible with certain chemical properties. a phase is a set of states of a chemical system that have similar bulk structural properties, over a range of conditions, such as pressure or temperature. physical properties, such as density and refractive index tend to fall within values characteristic of the phase. the phase of matter is defined by the phase transition, which is when energy put into or taken out of the system goes into rearranging the structure of the system, instead of changing the bulk conditions. sometimes the distinction between phases can be continuous instead of having a discrete boundary ; in this case the matter is considered to be in a supercritical state. when three states meet based on the conditions, it is known as a triple point and since this is invariant, it is a convenient way to define a set of conditions. the most familiar examples of phases are solids, liquids, and gases. many substances exhibit multiple solid phases. for example, there are three phases of solid iron ( alpha, gamma, and delta ) that vary based on temperature and pressure. a principal difference between solid phases is the crystal structure, or arrangement, of the atoms. another phase commonly encountered in the study of chemistry is the aqueous phase, which is the state of substances dissolved in aqueous solution ( that is, in water ). less familiar phases include plasmas, bose – einstein condensates and fermionic condensates and the paramagnetic and ferromagnetic phases of magnetic materials. while most familiar phases deal with three - dimensional systems, it is also possible to define analogs in two - dimensional systems, which has received attention for its relevance to systems in biology. = = = bonding = = = atoms sticking together in molecules or crystals are said to be bonded with one another. a chemical bond may be visualized as the multipole balance between the positive charges in the nuclei and the negative charges oscillating about them. more than simple attraction and repulsion, the energies and distributions characterize the availability of an electron to bond to another atom. the chemical bond can be a covalent bond, an ionic bond, a hydrogen bond or just because of van der waals force. each of these kinds of bonds is ascribed to some potential. these potentials create the interactions which hold atoms together in molecules or crystals. in many simple compounds, valence bond theory, the valence shell electron pair repulsion model ( vsepr ), and the concept of oxidation number can be used
Question: What is the only metal that is a liquid at room temperature?
A) copper
B) tin
C) aluminum
D) mercury
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D) mercury
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Context:
blood vessels. mechanical stimuli, such as pressure pulses seem to be beneficial to all kind of cardiovascular tissue such as heart valves, blood vessels or pericardium. = = = bioreactors = = = in tissue engineering, a bioreactor is a device that attempts to simulate a physiological environment in order to promote cell or tissue growth in vitro. a physiological environment can consist of many different parameters such as temperature, pressure, oxygen or carbon dioxide concentration, or osmolality of fluid environment, and it can extend to all kinds of biological, chemical or mechanical stimuli. therefore, there are systems that may include the application of forces such as electromagnetic forces, mechanical pressures, or fluid pressures to the tissue. these systems can be two - or three - dimensional setups. bioreactors can be used in both academic and industry applications. general - use and application - specific bioreactors are also commercially available, which may provide static chemical stimulation or a combination of chemical and mechanical stimulation. cell proliferation and differentiation are largely influenced by mechanical and biochemical cues in the surrounding extracellular matrix environment. bioreactors are typically developed to replicate the specific physiological environment of the tissue being grown ( e. g., flex and fluid shearing for heart tissue growth ). this can allow specialized cell lines to thrive in cultures replicating their native environments, but it also makes bioreactors attractive tools for culturing stem cells. a successful stem - cell - based bioreactor is effective at expanding stem cells with uniform properties and / or promoting controlled, reproducible differentiation into selected mature cell types. there are a variety of bioreactors designed for 3d cell cultures. there are small plastic cylindrical chambers, as well as glass chambers, with regulated internal humidity and moisture specifically engineered for the purpose of growing cells in three dimensions. the bioreactor uses bioactive synthetic materials such as polyethylene terephthalate membranes to surround the spheroid cells in an environment that maintains high levels of nutrients. they are easy to open and close, so that cell spheroids can be removed for testing, yet the chamber is able to maintain 100 % humidity throughout. this humidity is important to achieve maximum cell growth and function. the bioreactor chamber is part of a larger device that rotates to ensure equal cell growth in each direction across three dimensions. quinxell technologies now under quintech life sciences from singapore has developed a bioreactor known as the tisxell biaxial bioreactor which is specially designed for the purpose of
, 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 – 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
defective body parts. inside the body, artificial heart valves are in common use with artificial hearts and lungs seeing less common use but under active technology development. other medical devices and aids that can be considered prosthetics include hearing aids, artificial eyes, palatal obturator, gastric bands, and dentures. prostheses are specifically not orthoses, although given certain circumstances a prosthesis might end up performing some or all of the same functionary benefits as an orthosis. prostheses are technically the complete finished item. for instance, a c - leg knee alone is not a prosthesis, but only a prosthetic component. the complete prosthesis would consist of the attachment system to the residual limb – usually a " socket ", and all the attachment hardware components all the way down to and including the terminal device. despite the technical difference, the terms are often used interchangeably. the terms " prosthetic " and " orthotic " are adjectives used to describe devices such as a prosthetic knee. the terms " prosthetics " and " orthotics " are used to describe the respective allied health fields. an occupational therapist ' s role in prosthetics include therapy, training and evaluations. prosthetic training includes orientation to prosthetics components and terminology, donning and doffing, wearing schedule, and how to care for residual limb and the prosthesis. = = = exoskeletons = = = a powered exoskeleton is a wearable mobile machine that is powered by a system of electric motors, pneumatics, levers, hydraulics, or a combination of technologies that allow for limb movement with increased strength and endurance. its design aims to provide back support, sense the user ' s motion, and send a signal to motors which manage the gears. the exoskeleton supports the shoulder, waist and thigh, and assists movement for lifting and holding heavy items, while lowering back stress. = = = adaptive seating and positioning = = = people with balance and motor function challenges often need specialized equipment to sit or stand safely and securely. this equipment is frequently specialized for specific settings such as in a classroom or nursing home. positioning is often important in seating arrangements to ensure that user ' s body pressure is distributed equally without inhibiting movement in a desired way. positioning devices have been developed to aid in allowing people to stand and bear weight on their legs without risk of a fall.
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
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 heart beat data recorded from samples before and during meditation are analyzed using two different scaling analysis methods. these analyses revealed that mediation severely affects the long range correlation of heart beat of a normal heart. moreover, it is found that meditation induces periodic behavior in the heart beat. the complexity of the heart rate variability is quantified using multiscale entropy analysis and recurrence analysis. the complexity of the heart beat during mediation is found to be more.
numerical model of the peripheral circulation and dynamical model of the large vessels and the heart are discussed in this paper. they combined together into the global model of blood circulation. some results of numerical simulations concerning matter transport through the human organism and heart diseases are represented in the end.
this paper has been withdrawn by the authors until some changes are made.
the flow of fluids at branching junctions plays important kinematic and dynamic roles in most biological and industrial flow systems. the present paper highlights some key issues related to the flow of fluids at these junctions with special emphasis on the biological flow networks particularly blood transportation vasculature.
paper has been withdrawn due to non - compliance with ijcsi terms and conditions.
Question: Heart valves prevent what kind of blood flow from happening in the heart?
A) backflow
B) irregular flow
C) quick flow
D) slow flow
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A) backflow
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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
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 ) – 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
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
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 basis of all plant metabolism. the energy of sunlight, captured by oxygenic photosynthesis and released by cellular respiration, is the basis of almost all life. photoautotrophs, including all green plants, algae and cyanobacteria gather energy directly from sunlight by photosynthesis. heterotrophs including all animals, all fungi, all completely parasitic plants, and non - photosynthetic bacteria take in organic molecules produced by photoautotrophs and respire them or use them in the construction of cells and tissues. respiration is the oxidation of carbon compounds by breaking them down into simpler structures to release the energy they contain, essentially the opposite of photosynthesis. molecules are moved within plants by transport processes that operate at a variety of spatial scales. subcellular transport of ions, electrons and molecules such as water and enzymes occurs across cell membranes. minerals and water are transported from roots to other parts of the plant in the transpiration stream. diffusion, osmosis, and active transport and mass flow are all different ways transport can occur. examples of elements that plants need to transport are nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. in vascular plants, these elements are extracted from the soil as soluble ions by the roots and transported throughout the plant in the xylem. most of the elements required for plant nutrition come from the chemical breakdown of soil minerals. sucrose produced by photosynthesis is transported from the leaves to other parts of the plant in the phloem and plant hormones are transported by a variety of processes. = = = plant hormones = = = plants are not passive, but respond to external signals such as light, touch, and injury by moving or growing towards or away from the stimulus, as appropriate. tangible evidence of touch sensitivity is the almost instantaneous collapse of leaflets of mimosa pudica, the insect traps of venus flytrap and bladderworts, and the pollinia of orchids. the hypothesis that plant growth and development is coordinated by plant hormones or plant growth regulators first emerged in the late 19th century. darwin experimented on the movements of plant shoots and roots towards light and gravity, and concluded " it is hardly an exaggeration to say that the tip of the radicle.. acts like the brain of one of the lower animals.. directing the several movements ". about the same time, the role of auxins ( from the greek auxein, to grow ) in control of plant growth was first outlined by the dutch scientist
the 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
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
##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
by chlorophyll a is initially in the form of electrons ( and later a proton gradient ) that is used to make molecules of atp and nadph which temporarily store and transport energy. their energy is used in the light - independent reactions of the calvin cycle by the enzyme rubisco to produce molecules of the 3 - carbon sugar glyceraldehyde 3 - phosphate ( g3p ). glyceraldehyde 3 - phosphate is the first product of photosynthesis and the raw material from which glucose and almost all other organic molecules of biological origin are synthesised. some of the glucose is converted to starch which is stored in the chloroplast. starch is the characteristic energy store of most land plants and algae, while inulin, a polymer of fructose is used for the same purpose in the sunflower family asteraceae. some of the glucose is converted to sucrose ( common table sugar ) for export to the rest of the plant. unlike in animals ( which lack chloroplasts ), plants and their eukaryote relatives have delegated many biochemical roles to their chloroplasts, including synthesising all their fatty acids, and most amino acids. the fatty acids that chloroplasts make are used for many things, such as providing material to build cell membranes out of and making the polymer cutin which is found in the plant cuticle that protects land plants from drying out. plants synthesise a number of unique polymers like the polysaccharide molecules cellulose, pectin and xyloglucan from which the land plant cell wall is constructed. vascular land plants make lignin, a polymer used to strengthen the secondary cell walls of xylem tracheids and vessels to keep them from collapsing when a plant sucks water through them under water stress. lignin is also used in other cell types like sclerenchyma fibres that provide structural support for a plant and is a major constituent of wood. sporopollenin is a chemically resistant polymer found in the outer cell walls of spores and pollen of land plants responsible for the survival of early land plant spores and the pollen of seed plants in the fossil record. it is widely regarded as a marker for the start of land plant evolution during the ordovician period. the concentration of carbon dioxide in the atmosphere today is much lower than it was when plants emerged onto land during the ordovician and silurian periods.
Question: What is the source of energy for photosynthesis?
A) air
B) light
C) carbon
D) gravity
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B) light
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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 – 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,
, 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.
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 – much less than reusing channels ( which causes co - channel interference ) – 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
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 – 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
rolling out 5g services across the us. 5g started being deployed at the beginning of 2020 and has been growing ever since. according to the gsm association, by 2025, approximately 1. 7 billion subscribers will have a subscription with 5g service. 5g wireless signals are transmitted through large numbers of small cell stations located in places like light poles or building roofs. in the past, 4g networking had to rely on large cell towers in order to transmit signals over large distances. with the introduction of 5g networking, it is imperative that small cell stations are used because the mm wave spectrum, which is the specific type of band used in 5g services, strictly travels over short distances. if the distances between cell stations were longer, signals may suffer from interference from inclimate weather, or other objects such as houses, buildings, trees, and much more. in 5g networking, there are 3 main kinds of 5g : low - band, mid - band, and high - band. low - band frequencies operate below 2 ghz, mid - band frequencies operate between 2 – 10 ghz, and high - band frequencies operate between 20 and 100 ghz. verizon have seen outrageous numbers on their high - band 5g service, which they deem " ultraband ", which hit speeds of over 3 gbit / s. the main advantage of 5g networks is that the data transmission rate is much higher than the previous cellular network, up to 10 gbit / s, which is faster than the current wired internet and 100 times faster than the previous 4g lte cellular network. another advantage is lower network latency ( faster response time ), less than 1 millisecond, and 4g is 30 - 70 milliseconds. the peak rate needs to reach the gbit / s standard to meet the high data volume of high - definition video, virtual reality and so on. the air interface delay level needs to be around 1ms, which meets real - time applications such as autonomous driving and telemedicine. large network capacity, providing the connection capacity of 100 billion devices to meet iot communication. the spectrum efficiency is 10 times higher than lte. with continuous wide area coverage and high mobility, the user experience rate reaches 100 mbit / s. the flow density and the number of connections are greatly increased. since 5g is a relatively new type of service, only phones which are newly released or are upcoming can support 5g service. some of these phones include the iphone 12 / 13 ; select
device connectivity. 5g is still a fairly new type of networking and is still being spread across nations. moving forward, 5g is going to set the standard of cellular service around the whole globe. corporations such as at & t, verizon, and t - mobile are some of the notorious cellular companies that are rolling out 5g services across the us. 5g started being deployed at the beginning of 2020 and has been growing ever since. according to the gsm association, by 2025, approximately 1. 7 billion subscribers will have a subscription with 5g service. 5g wireless signals are transmitted through large numbers of small cell stations located in places like light poles or building roofs. in the past, 4g networking had to rely on large cell towers in order to transmit signals over large distances. with the introduction of 5g networking, it is imperative that small cell stations are used because the mm wave spectrum, which is the specific type of band used in 5g services, strictly travels over short distances. if the distances between cell stations were longer, signals may suffer from interference from inclimate weather, or other objects such as houses, buildings, trees, and much more. in 5g networking, there are 3 main kinds of 5g : low - band, mid - band, and high - band. low - band frequencies operate below 2 ghz, mid - band frequencies operate between 2 – 10 ghz, and high - band frequencies operate between 20 and 100 ghz. verizon have seen outrageous numbers on their high - band 5g service, which they deem " ultraband ", which hit speeds of over 3 gbit / s. the main advantage of 5g networks is that the data transmission rate is much higher than the previous cellular network, up to 10 gbit / s, which is faster than the current wired internet and 100 times faster than the previous 4g lte cellular network. another advantage is lower network latency ( faster response time ), less than 1 millisecond, and 4g is 30 - 70 milliseconds. the peak rate needs to reach the gbit / s standard to meet the high data volume of high - definition video, virtual reality and so on. the air interface delay level needs to be around 1ms, which meets real - time applications such as autonomous driving and telemedicine. large network capacity, providing the connection capacity of 100 billion devices to meet iot communication. the spectrum efficiency is 10 times higher than lte. with continuous wide area coverage and
, 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 in 1990, the united kingdom in 1991, and both france and china continued testing until 1996. after signing the comprehensive test ban treaty in 1996 ( which had as of 2011 not entered into force ), all of these states have pledged to discontinue all nuclear testing. non - signatories india and pakistan last tested nuclear weapons in 1998. nuclear weapons are the most destructive weapons known - the archetypal weapons of mass destruction. throughout the cold war, the opposing powers had huge nuclear arsenals, sufficient to kill hundreds of millions of people. generations of people grew up under the shadow of nuclear devastation, portrayed in films such as dr. strangelove and the atomic cafe. however, the tremendous energy release in the detonation of a nuclear weapon also suggested the possibility of a new energy source. = = civilian uses = = = = = nuclear power = = = nuclear power is a type of nuclear technology involving the controlled use of nuclear fission to release energy for work including propulsion, heat, and the generation of electricity. nuclear energy is produced by a controlled nuclear chain reaction which creates heat — and which is used to boil water, produce steam, and drive a steam turbine. the turbine is used to generate electricity and / or to do mechanical work. currently nuclear
effects content for media. live sound engineer front of house ( foh ) engineer, or a1. – 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 – 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 – 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 – 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. in their daily work, audio engineers use many tools, including : tape machines analog - to - digital converters digital - to - analog converters digital audio workstations ( daws ) audio plug - ins dynamic range compressors audio data compressors equalization ( audio ) music sequencers signal processors headphones microphone
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 – much less than reusing channels ( which causes co - channel interference ) – 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
Question: Different types of interference include destructive and what else?
A) consistent
B) constructive
C) active
D) helpful
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B) constructive
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Context:
development of a tumor is known to be a result of accumulation of dna changes in somatic cells. however, the processes of how dna changes are produced and how they accumulate in somatic cells are not clear. dna changes include two types : point dna mutations and chromosome changes. however, point dna mutations ( dna mutations ) are the main type of dna changes that can remain and accumulate in cells. severe dna injuries are the causes for dna mutations. however, misrepair of dna is an essential process for transforming a dna injury into a survivable and inheritable dna mutation. in somatic cells, misrepair of dna is the main source of dna mutations. since the surviving chance of a cell by misrepair of dna is low, accumulation of dna mutations can take place only possibly in the cells that can proliferate. tumors can only develop in the tissues that are regenerable. the accumulation of misrepairs of dna needs to proceed in many generations of cells, and cell transformation from a normal cell into a tumor cell is a slow and long process. however, once a cell is transformed especially when it is malignantly transformed, the deficiency of dna repair and the rapid cell proliferation will accelerate the accumulation of dna mutations. the process of accumulation of dna mutations is actually the process of aging of a genome dna. repeated cell injuries and repeated cell regenerations are the two preconditions for tumor - development. for cancer prevention, a moderate and flexible living style is advised.
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 °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
apoptosis is a complex pathway regulated by the concerted action of multiple pro - and anti - apoptotic molecules. the intrinsic ( mitochondrial ) pathway of apoptosis is governed up - stream of mitochondria, by the family of bcl - 2 proteins, and down - stream of mitochondria, by low - probability events, such as apoptosome formation, and by feedback circuits involving caspases and inhibitor of apoptosis proteins ( iaps ), such as xiap. all these regulatory mechanisms ensure that cells only commit to death once a threshold of damage has been reached and the anti - apoptotic reserve of the cell is overcome. as cancer cells are invariably exposed to strong intracellular and extracellular stress stimuli, they are particularly reliant on the expression of anti - apoptotic proteins. hence, many cancer cells undergo apoptosis when exposed to agents that inhibit anti - apoptotic bcl - 2 molecules, such as bh3 mimetics, while normal cells remain relatively insensitive to single agent treatments with the same class of molecules. targeting different proteins within the apoptotic network with combinatorial treatment approaches often achieves even greater specificity. this led us to investigate the sensitivity of leukemia and lymphoma cells to a pro - apoptotic action of a bh3 mimetic combined with a small molecule inhibitor of xiap. using computational probabilistic model of apoptotic pathway, verified by experimental results from human leukemia and lymphoma cell lines, we show that inhibition of xiap has a non - linear effect on sensitization towards apoptosis induced by the bh3 mimetic ha14 - 1. this study justifies further ex vivo and animal studies on the potential of the treatment of leukemia and lymphoma with a combination of bh3 mimetics and xiap inhibitors.
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 – 181 : 42 – 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
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 – beneficial uses
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
the term most responsible physician ( mrp ) or attending physician is also used interchangeably to describe this role. laser medicine involves the use of lasers in the diagnostics or treatment of various conditions. many other health science fields, e. g. dietetics medical ethics deals with ethical and moral principles that apply values and judgments to the practice of medicine. medical humanities includes the humanities ( literature, philosophy, ethics, history and religion ), social science ( anthropology, cultural studies, psychology, sociology ), and the arts ( literature, theater, film, and visual arts ) and their application to medical education and practice. nosokinetics is the science / subject of measuring and modelling the process of care in health and social care systems. nosology is the classification of diseases for various purposes. occupational medicine is the provision of health advice to organizations and individuals to ensure that the highest standards of health and safety at work can be achieved and maintained. pain management ( also called pain medicine, or algiatry ) is the medical discipline concerned with the relief of pain. pharmacogenomics is a form of individualized medicine. podiatric medicine is the study of, diagnosis, and medical treatment of disorders of the foot, ankle, lower limb, hip and lower back. sexual medicine is concerned with diagnosing, assessing and treating all disorders related to sexuality. sports medicine deals with the treatment and prevention and rehabilitation of sports / exercise injuries such as muscle spasms, muscle tears, injuries to ligaments ( ligament tears or ruptures ) and their repair in athletes, amateur and professional. therapeutics is the field, more commonly referenced in earlier periods of history, of the various remedies that can be used to treat disease and promote health. travel medicine or emporiatrics deals with health problems of international travelers or travelers across highly different environments. tropical medicine deals with the prevention and treatment of tropical diseases. 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
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
as possible in order to avoid frustration or injury. there are two main types of human errors which are categorized as slips and mistakes. slips are a very common kind of error involving automatic behaviors ( i. e. typos, hitting the wrong menu item ). when we experience slips, we have the correct goal in mind, but execute the wrong action. mistakes on the other hand involve conscious deliberation that result in the incorrect conclusion. when we experience mistakes, we have the wrong goal in mind and thereby execute the wrong action. even though slips are the more common type of error, they are no less dangerous. a certain type of slip error, a mode error, can be especially dangerous if a user is executing a high - risk task. for instance, if a user is operating a vehicle and does not realize they are in the wrong mode ( i. e. reverse ), they might step on the gas intending to drive, but instead accelerate into a garage wall or another car. in order to avoid modal errors, designers often employ modeless states in which users do not have to choose a mode at all, or they must execute a continuous action while intending to execute a certain mode ( i. e. pressing a key continuously in order to activate " lasso " mode in photoshop ). = = evaluation methods = = usability engineers conduct usability evaluations of existing or proposed interfaces and their findings are fed back to the designer for use in design or redesign. common usability evaluation methods include : card sorting cognitive task analysis cognitive walkthroughs contextual inquiry focus groups heuristic evaluations interviews questionnaires rite method surveys think aloud protocol usability testing = = software applications and development tools = = there are a variety of online resources that make the job of a usability engineer a little easier. online tools are only a useful tool, and do not substitute for a complete usability engineering analysis. some examples of these include : = = = the web metrics tool suite = = = this is a product of the national institute of standards and technology. this toolkit is focused on evaluating the html of a website versus a wide range of usability guidelines and includes : web static analyzer tool ( websat ) – checks web page html against typical usability guidelines web category analysis tool ( webcat ) – lets the usability engineer construct and conduct a web category analysis web variable instrumenter program ( webvip ) – instruments a website to capture a log of user interaction framework for logging usability data ( flu
in space, can adversely affect the earth ' s environment. some hypergolic rocket propellants, such as hydrazine, are highly toxic prior to combustion, but decompose into less toxic compounds after burning. rockets using hydrocarbon fuels, such as kerosene, release carbon dioxide and soot in their exhaust. carbon dioxide emissions are insignificant compared to those from other sources ; on average, the united states consumed 803 million us gal ( 3. 0 million m3 ) of liquid fuels per day in 2014, while a single falcon 9 rocket first stage burns around 25, 000 us gallons ( 95 m3 ) of kerosene fuel per launch. even if a falcon 9 were launched every single day, it would only represent 0. 006 % of liquid fuel consumption ( and carbon dioxide emissions ) for that day. additionally, the exhaust from lox - and lh2 - fueled engines, like the ssme, is almost entirely water vapor. nasa addressed environmental concerns with its canceled constellation program in accordance with the national environmental policy act in 2011. in contrast, ion engines use harmless noble gases like xenon for propulsion. an example of nasa ' s environmental efforts is the nasa sustainability base. additionally, the exploration sciences building was awarded the leed gold rating in 2010. on may 8, 2003, the environmental protection agency recognized nasa as the first federal agency to directly use landfill gas to produce energy at one of its facilities — the goddard space flight center, greenbelt, maryland. in 2018, nasa along with other companies including sensor coating systems, pratt & whitney, monitor coating and utrc launched the project caution ( coatings for ultra high temperature detection ). this project aims to enhance the temperature range of the thermal history coating up to 1, 500 °c ( 2, 730 °f ) and beyond. the final goal of this project is improving the safety of jet engines as well as increasing efficiency and reducing co2 emissions. = = = climate change = = = nasa also researches and publishes on climate change. its statements concur with the global scientific consensus that the climate is warming. bob walker, who has advised former us president donald trump on space issues, has advocated that nasa should focus on space exploration and that its climate study operations should be transferred to other agencies such as noaa. former nasa atmospheric scientist j. marshall shepherd countered that earth science study was built into nasa ' s mission at its creation in the 1958 national aeronautics and space act. nasa won the 2020 webby people ' s voice award for green in the category
Question: What is anything that causes cancer called?
A) pesticide
B) chemical
C) carcinogen
D) bacteria
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C) carcinogen
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Context:
= = when 0 is said to be neither positive nor negative, the following phrases may refer to the sign of a number : a number is positive if it is greater than zero. a number is negative if it is less than zero. a number is non - negative if it is greater than or equal to zero. a number is non - positive if it is less than or equal to zero. when 0 is said to be both positive and negative, modified phrases are used to refer to the sign of a number : a number is strictly positive if it is greater than zero. a number is strictly negative if it is less than zero. a number is positive if it is greater than or equal to zero. a number is negative if it is less than or equal to zero. for example, the absolute value of a real number is always " non - negative ", but is not necessarily " positive " in the first interpretation, whereas in the second interpretation, it is called " positive " — though not necessarily " strictly positive ". the same terminology is sometimes used for functions that yield real or other signed values. for example, a function would be called a positive function if its values are positive for all arguments of its domain, or a non - negative function if all of its values are non - negative. = = = complex numbers = = = complex numbers are impossible to order, so they cannot carry the structure of an ordered ring, and, accordingly, cannot be partitioned into positive and negative complex numbers. they do, however, share an attribute with the reals, which is called absolute value or magnitude. magnitudes are always non - negative real numbers, and to any non - zero number there belongs a positive real number, its absolute value. for example, the absolute value of −3 and the absolute value of 3 are both equal to 3. this is written in symbols as | −3 | = 3 and | 3 | = 3. in general, any arbitrary real value can be specified by its magnitude and its sign. using the standard encoding, any real value is given by the product of the magnitude and the sign in standard encoding. this relation can be generalized to define a sign for complex numbers. since the real and complex numbers both form a field and contain the positive reals, they also contain the reciprocals of the magnitudes of all non - zero numbers. this means that any non - zero number may be multiplied with the reciprocal of its magnitude, that is, divided by its magnitude. it is immediate that the quotient
other thing ". this tradition can be traced back to at least 350 bc by aristotle : in his categories, he defines the notion of quantity in terms of a more primitive equality ( distinct from identity or similarity ), stating : the most distinctive mark of quantity is that equality and inequality are predicated of it. each of the aforesaid quantities is said to be equal or unequal. for instance, one solid is said to be equal or unequal to another ; number, too, and time can have these terms applied to them, indeed can all those kinds of quantity that have been mentioned. that which is not a quantity can by no means, it would seem, be termed equal or unequal to anything else. one particular disposition or one particular quality, such as whiteness, is by no means compared with another in terms of equality and inequality but rather in terms of similarity. thus it is the distinctive mark of quantity that it can be called equal and unequal. ― ( translated by e. m. edghill ) aristotle had separate categories for quantities ( number, length, volume ) and qualities ( temperature, density, pressure ), now called intensive and extensive properties. the scholastics, particularly richard swineshead and other oxford calculators in the 14th century, began seriously thinking about kinematics and quantitative treatment of qualities. for example, two flames have the same heat - intensity if they produce the same effect on water ( e. g, warming vs boiling ). since two intensities could be shown to be equal, and equality was considered the defining feature of quantities, it meant those intensities were quantifiable. around the 19th century, with the growth of modern logic, it became necessary to have a more concrete description of equality. with the rise of predicate logic due to the work of gottlob frege, logic shifted from being focused on classes of objects to being property - based. this was followed by a movement for describing mathematics in logical foundations, called logicism. this trend lead to the axiomatization of equality through the law of identity and the substitution property especially in mathematical logic and analytic philosophy. the precursor to the substitution property of equality was first formulated by gottfried leibniz in his discourse on metaphysics ( 1686 ), stating, roughly, that " no two distinct things can have all properties in common. " this has since broken into two principles, the substitution property ( if x = y, { \ displaystyle x = y, } then any property of x
the aforesaid quantities is said to be equal or unequal. for instance, one solid is said to be equal or unequal to another ; number, too, and time can have these terms applied to them, indeed can all those kinds of quantity that have been mentioned. that which is not a quantity can by no means, it would seem, be termed equal or unequal to anything else. one particular disposition or one particular quality, such as whiteness, is by no means compared with another in terms of equality and inequality but rather in terms of similarity. thus it is the distinctive mark of quantity that it can be called equal and unequal. ― ( translated by e. m. edghill ) aristotle had separate categories for quantities ( number, length, volume ) and qualities ( temperature, density, pressure ), now called intensive and extensive properties. the scholastics, particularly richard swineshead and other oxford calculators in the 14th century, began seriously thinking about kinematics and quantitative treatment of qualities. for example, two flames have the same heat - intensity if they produce the same effect on water ( e. g, warming vs boiling ). since two intensities could be shown to be equal, and equality was considered the defining feature of quantities, it meant those intensities were quantifiable. around the 19th century, with the growth of modern logic, it became necessary to have a more concrete description of equality. with the rise of predicate logic due to the work of gottlob frege, logic shifted from being focused on classes of objects to being property - based. this was followed by a movement for describing mathematics in logical foundations, called logicism. this trend lead to the axiomatization of equality through the law of identity and the substitution property especially in mathematical logic and analytic philosophy. the precursor to the substitution property of equality was first formulated by gottfried leibniz in his discourse on metaphysics ( 1686 ), stating, roughly, that " no two distinct things can have all properties in common. " this has since broken into two principles, the substitution property ( if x = y, { \ displaystyle x = y, } then any property of x { \ displaystyle x } is a property of y { \ displaystyle y } ), and its converse, the identity of indiscernibles ( if x { \ displaystyle x } and y { \ displaystyle y } have all properties in common, then x = y { \ displaystyle x =
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. ≤ 1. means " less than or equal to ". that is, whatever a and b are, a ≤ 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. ≥ 1. means " greater than or equal to ". that is, whatever a and b are, a ≥ 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 } } \ gg } 1. means " much less than " and " much greater than ". generally, much is not formally defined, but means that the lesser quantity can be neglected with respect to the other. this is generally the case when the lesser quantity is smaller than the other by one or several orders of magnitude. 2. in measure theory, μ [UNK] ν { \ displaystyle \ mu \ ll \ nu } means that the measure μ { \ displaystyle \ mu } is absolutely continuous with respect to the measure ν { \ displaystyle \ nu }. [UNK] { \ displaystyle \ leqq } a rarely used symbol, generally a synonym of ≤. [UNK] and [UNK] { \ displaystyle \ prec { \ text { and } } \ succ } 1. often used for denoting an order or, more generally, a preorder, when it would be confusing or not convenient to use < and >. 2. sequention in asynchronous logic. = = set theory = = ∅ denotes the empty set, and is more often written ∅ { \ displaystyle \ emptyset }. using set - builder notation, it may also be denoted { } { \ displaystyle \ { \ } }. # ( number sign ) 1. number of elements : # s { \ displaystyle \ # { } s } may denote the cardinality of the set s. an alternative notation is | s | { \ displaystyle | s | } ; see | [UNK] | { \ displaystyle | \ square | }. 2. primorial : n
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 brønsted – lowry definition, is the acid dissociation constant ( ka ), which measures the relative ability of a substance to act as an acid under the brønsted – 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 — 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
displaystyle \ mathbb { r } } that are both open and closed. a degenerate interval is any set consisting of a single real number ( i. e., an interval of the form [ a, a ] ). some authors include the empty set in this definition. a real interval that is neither 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 + ∞, 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 − 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 ≤ 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
end { aligned } } } in summary, a set of the real numbers is an interval, if and only if it is an open interval, a closed interval, or a half - open interval. the only intervals that appear twice in the above classification are ∅ { \ displaystyle \ emptyset } and r { \ displaystyle \ mathbb { r } } that are both open and closed. a degenerate interval is any set consisting of a single real number ( i. e., an interval of the form [ a, a ] ). some authors include the empty set in this definition. a real interval that is neither 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 + ∞, 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 − 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 ≤ 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.
mathematical analysis for one - sided limits ( right - sided limit and left - sided limit, respectively ). this notation refers to the behaviour of a function as its real input variable approaches 0 along positive ( resp., negative ) values ; the two limits need not exist or agree. = = = terminology for signs = = = when 0 is said to be neither positive nor negative, the following phrases may refer to the sign of a number : a number is positive if it is greater than zero. a number is negative if it is less than zero. a number is non - negative if it is greater than or equal to zero. a number is non - positive if it is less than or equal to zero. when 0 is said to be both positive and negative, modified phrases are used to refer to the sign of a number : a number is strictly positive if it is greater than zero. a number is strictly negative if it is less than zero. a number is positive if it is greater than or equal to zero. a number is negative if it is less than or equal to zero. for example, the absolute value of a real number is always " non - negative ", but is not necessarily " positive " in the first interpretation, whereas in the second interpretation, it is called " positive " — though not necessarily " strictly positive ". the same terminology is sometimes used for functions that yield real or other signed values. for example, a function would be called a positive function if its values are positive for all arguments of its domain, or a non - negative function if all of its values are non - negative. = = = complex numbers = = = complex numbers are impossible to order, so they cannot carry the structure of an ordered ring, and, accordingly, cannot be partitioned into positive and negative complex numbers. they do, however, share an attribute with the reals, which is called absolute value or magnitude. magnitudes are always non - negative real numbers, and to any non - zero number there belongs a positive real number, its absolute value. for example, the absolute value of −3 and the absolute value of 3 are both equal to 3. this is written in symbols as | −3 | = 3 and | 3 | = 3. in general, any arbitrary real value can be specified by its magnitude and its sign. using the standard encoding, any real value is given by the product of the magnitude and the sign in standard encoding. this relation can be generalized to define a sign for complex numbers. since the real and
in mathematics, an inequality is a relation which makes a non - equal comparison between two numbers or other mathematical expressions. it is used most often to compare two numbers on the number line by their size. the main types of inequality are less than and greater than ( denoted by < and >, respectively the less - than and greater - than signs ). = = notation = = there are several different notations used to represent different kinds of inequalities : the notation a < b means that a is less than b. the notation a > b means that a is greater than b. in either case, a is not equal to b. these relations are known as strict inequalities, meaning that a is strictly less than or strictly greater than b. equality is excluded. in contrast to strict inequalities, there are two types of inequality relations that are not strict : the notation a ≤ b or a [UNK] b or a [UNK] b means that a is less than or equal to b ( or, equivalently, at most b, or not greater than b ). the notation a ≥ b or a [UNK] b or a [UNK] b means that a is greater than or equal to b ( or, equivalently, at least b, or not less than b ). in the 17th and 18th centuries, personal notations or typewriting signs were used to signal inequalities. for example, in 1670, john wallis used a single horizontal bar above rather than below the < and >. later in 1734, [UNK] and [UNK], known as " less than ( greater - than ) over equal to " or " less than ( greater than ) or equal to with double horizontal bars ", first appeared in pierre bouguer ' s work. after that, mathematicians simplified bouguer ' s symbol to " less than ( greater than ) or equal to with one horizontal bar " ( ≤ ), or " less than ( greater than ) or slanted equal to " ( [UNK] ). the relation not greater than can also be represented by a > b, { \ displaystyle a \ ngtr b, } the symbol for " greater than " bisected by a slash, " not ". the same is true for not less than, a < b. { \ displaystyle a \ nless b. } the notation a = b means that a is not equal to b ; this inequation sometimes is considered a form of strict inequality. it does not say that one is greater than the other ; it does not
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 + ∞, 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 − 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 ≤ 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
Question: In comparing two solutions of unequal solute concentration, the solution with the higher solute concentration is called what?
A) hypothermic
B) hydrophilic
C) acetic
D) hypertonic
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D) hypertonic
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Context:
of imaging techniques vary in their temporal ( time - based ) and spatial ( location - based ) resolution. brain imaging is often used in cognitive neuroscience. single - photon emission computed tomography and positron emission tomography. spect and pet use radioactive isotopes, which are injected into the subject ' s bloodstream and taken up by the brain. by observing which areas of the brain take up the radioactive isotope, we can see which areas of the brain are more active than other areas. pet has similar spatial resolution to fmri, but it has extremely poor temporal resolution. electroencephalography. eeg measures the electrical fields generated by large populations of neurons in the cortex by placing a series of electrodes on the scalp of the subject. this technique has an extremely high temporal resolution, but a relatively poor spatial resolution. functional magnetic resonance imaging. fmri measures the relative amount of oxygenated blood flowing to different parts of the brain. more oxygenated blood in a particular region is assumed to correlate with an increase in neural activity in that part of the brain. this allows us to localize particular functions within different brain regions. fmri has moderate spatial and temporal resolution. optical imaging. this technique uses infrared transmitters and receivers to measure the amount of light reflectance by blood near different areas of the brain. since oxygenated and deoxygenated blood reflects light by different amounts, we can study which areas are more active ( i. e., those that have more oxygenated blood ). optical imaging has moderate temporal resolution, but poor spatial resolution. it also has the advantage that it is extremely safe and can be used to study infants ' brains. magnetoencephalography. meg measures magnetic fields resulting from cortical activity. it is similar to eeg, except that it has improved spatial resolution since the magnetic fields it measures are not as blurred or attenuated by the scalp, meninges and so forth as the electrical activity measured in eeg is. meg uses squid sensors to detect tiny magnetic fields. = = = computational modeling = = = computational models require a mathematically and logically formal representation of a problem. computer models are used in the simulation and experimental verification of different specific and general properties of intelligence. computational modeling can help us understand the functional organization of a particular cognitive phenomenon. approaches to cognitive modeling can be categorized as : ( 1 ) symbolic, on abstract mental functions of an intelligent mind by means of symbols ; ( 2 ) subsymbolic, on the neural and associa
##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 – 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 – 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
and taken up by the brain. by observing which areas of the brain take up the radioactive isotope, we can see which areas of the brain are more active than other areas. pet has similar spatial resolution to fmri, but it has extremely poor temporal resolution. electroencephalography. eeg measures the electrical fields generated by large populations of neurons in the cortex by placing a series of electrodes on the scalp of the subject. this technique has an extremely high temporal resolution, but a relatively poor spatial resolution. functional magnetic resonance imaging. fmri measures the relative amount of oxygenated blood flowing to different parts of the brain. more oxygenated blood in a particular region is assumed to correlate with an increase in neural activity in that part of the brain. this allows us to localize particular functions within different brain regions. fmri has moderate spatial and temporal resolution. optical imaging. this technique uses infrared transmitters and receivers to measure the amount of light reflectance by blood near different areas of the brain. since oxygenated and deoxygenated blood reflects light by different amounts, we can study which areas are more active ( i. e., those that have more oxygenated blood ). optical imaging has moderate temporal resolution, but poor spatial resolution. it also has the advantage that it is extremely safe and can be used to study infants ' brains. magnetoencephalography. meg measures magnetic fields resulting from cortical activity. it is similar to eeg, except that it has improved spatial resolution since the magnetic fields it measures are not as blurred or attenuated by the scalp, meninges and so forth as the electrical activity measured in eeg is. meg uses squid sensors to detect tiny magnetic fields. = = = computational modeling = = = computational models require a mathematically and logically formal representation of a problem. computer models are used in the simulation and experimental verification of different specific and general properties of intelligence. computational modeling can help us understand the functional organization of a particular cognitive phenomenon. approaches to cognitive modeling can be categorized as : ( 1 ) symbolic, on abstract mental functions of an intelligent mind by means of symbols ; ( 2 ) subsymbolic, on the neural and associative properties of the human brain ; and ( 3 ) across the symbolic – subsymbolic border, including hybrid. symbolic modeling evolved from the computer science paradigms using the technologies of knowledge - based systems, as well as a philosophical perspective ( e. g. " good old - fashioned artificial intelligence " ( gofa
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
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 – 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
generated by large populations of neurons in the cortex by placing a series of electrodes on the scalp of the subject. this technique has an extremely high temporal resolution, but a relatively poor spatial resolution. functional magnetic resonance imaging. fmri measures the relative amount of oxygenated blood flowing to different parts of the brain. more oxygenated blood in a particular region is assumed to correlate with an increase in neural activity in that part of the brain. this allows us to localize particular functions within different brain regions. fmri has moderate spatial and temporal resolution. optical imaging. this technique uses infrared transmitters and receivers to measure the amount of light reflectance by blood near different areas of the brain. since oxygenated and deoxygenated blood reflects light by different amounts, we can study which areas are more active ( i. e., those that have more oxygenated blood ). optical imaging has moderate temporal resolution, but poor spatial resolution. it also has the advantage that it is extremely safe and can be used to study infants ' brains. magnetoencephalography. meg measures magnetic fields resulting from cortical activity. it is similar to eeg, except that it has improved spatial resolution since the magnetic fields it measures are not as blurred or attenuated by the scalp, meninges and so forth as the electrical activity measured in eeg is. meg uses squid sensors to detect tiny magnetic fields. = = = computational modeling = = = computational models require a mathematically and logically formal representation of a problem. computer models are used in the simulation and experimental verification of different specific and general properties of intelligence. computational modeling can help us understand the functional organization of a particular cognitive phenomenon. approaches to cognitive modeling can be categorized as : ( 1 ) symbolic, on abstract mental functions of an intelligent mind by means of symbols ; ( 2 ) subsymbolic, on the neural and associative properties of the human brain ; and ( 3 ) across the symbolic – subsymbolic border, including hybrid. symbolic modeling evolved from the computer science paradigms using the technologies of knowledge - based systems, as well as a philosophical perspective ( e. g. " good old - fashioned artificial intelligence " ( gofai ) ). they were developed by the first cognitive researchers and later used in information engineering for expert systems. since the early 1990s it was generalized in systemics for the investigation of functional human - like intelligence models, such as personoids, and, in parallel, developed as the soar environment. recently, especially in
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
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,
##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 – fda approved product ), and hepatocytes used in liver support systems cells can be used alone or with
cortisol, corticosterone and aldosterone activate full - length glucocorticoid receptor ( gr ) from elephant shark, a cartilaginous fish belonging to the oldest group of jawed vertebrates. activation by aldosterone a mineralocorticoid, indicates partial divergence of elephant shark gr from the mr. progesterone activates elephant shark mr, but not elephant shark gr. progesterone inhibits steroid binding to elephant shark gr, but not to human gr. deletion of the n - terminal domain ( ntd ) from elephant shark gr ( truncated gr ) reduced the response to corticosteroids, while truncated and full - length elephant shark mr had similar responses to corticosteroids. chimeras of elephant shark gr ntd fused to mr dbd + lbd had increased activation by corticosteroids and progesterone compared to full - length elephant shark mr. elephant shark mr ntd fused to gr dbd + lbd had similar activation as full - length elephant shark mr, indicating that activation of human gr by the ntd evolved early in gr divergence from the mr.
Question: What broad group of animals - which includes rats, dogs and camels - have highly developed brains and often perform work for humans?
A) arachnids
B) amphibians
C) reptiles
D) mammals
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D) mammals
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Context:
oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions. cell membranes also contain membrane proteins, including integral membrane proteins that go across the membrane serving as membrane transporters, and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes shaping the cell. cell membranes are involved in various cellular processes such as cell adhesion, storing electrical energy, and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall, glycocalyx, and cytoskeleton. within the cytoplasm of a cell, there are many biomolecules such as proteins and nucleic acids. in addition to biomolecules, eukaryotic cells have specialized structures called organelles that have their own lipid bilayers or are spatially units. these organelles include the cell nucleus, which contains most of the cell ' s dna, or mitochondria, which generate adenosine triphosphate ( atp ) to power cellular processes. other organelles such as endoplasmic reticulum and golgi apparatus play a role in the synthesis and packaging of proteins, respectively. biomolecules such as proteins can be engulfed by lysosomes, another specialized organelle. plant cells have additional organelles that distinguish them from animal cells such as a cell wall that provides support for the plant cell, chloroplasts that harvest sunlight energy to produce sugar, and vacuoles that provide storage and structural support as well as being involved in reproduction and breakdown of plant seeds. eukaryotic cells also have cytoskeleton that is made up of microtubules, intermediate filaments, and microfilaments, all of which provide support for the cell and are involved in the movement of the cell and its organelles. in terms of their structural composition, the microtubules are made up of tubulin ( e. g., α - tubulin and β - 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
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., α - tubulin and β - tubulin ) whereas intermediate filaments are made up of fibrous proteins. microfilaments are made up of actin molecules that interact with
. most cells are very small, with diameters ranging from 1 to 100 micrometers and are therefore only visible under a light or electron microscope. there are generally two types of cells : eukaryotic cells, which contain a nucleus, and prokaryotic cells, which do not. prokaryotes are single - celled organisms such as bacteria, whereas eukaryotes can be single - celled or multicellular. in multicellular organisms, every cell in the organism ' s body is derived ultimately from a single cell in a fertilized egg. = = = cell structure = = = every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space. a cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. cell membranes are semipermeable, allowing small molecules such as oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions. cell membranes also contain membrane proteins, including integral membrane proteins that go across the membrane serving as membrane transporters, and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes shaping the cell. cell membranes are involved in various cellular processes such as cell adhesion, storing electrical energy, and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall, glycocalyx, and cytoskeleton. within the cytoplasm of a cell, there are many biomolecules such as proteins and nucleic acids. in addition to biomolecules, eukaryotic cells have specialized structures called organelles that have their own lipid bilayers or are spatially units. these organelles include the cell nucleus, which contains most of the cell ' s dna, or mitochondria, which generate adenosine triphosphate ( atp ) to power cellular processes. other organelles such as endoplasmic reticulum and golgi apparatus play a role in the synthesis and packaging of proteins, respectively. biomolecules such as proteins can be engulfed by lysosomes, another specialized organelle. plant cells have additional organelles that distinguish them from animal cells such as a cell wall that provides support for the plant cell, chloroplasts that harvest sunlight energy to produce sugar, and vacuoles that provide storage and structural support
shaping the cell. cell membranes are involved in various cellular processes such as cell adhesion, storing electrical energy, and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall, glycocalyx, and cytoskeleton. within the cytoplasm of a cell, there are many biomolecules such as proteins and nucleic acids. in addition to biomolecules, eukaryotic cells have specialized structures called organelles that have their own lipid bilayers or are spatially units. these organelles include the cell nucleus, which contains most of the cell ' s dna, or mitochondria, which generate adenosine triphosphate ( atp ) to power cellular processes. other organelles such as endoplasmic reticulum and golgi apparatus play a role in the synthesis and packaging of proteins, respectively. biomolecules such as proteins can be engulfed by lysosomes, another specialized organelle. plant cells have additional organelles that distinguish them from animal cells such as a cell wall that provides support for the plant cell, chloroplasts that harvest sunlight energy to produce sugar, and vacuoles that provide storage and structural support as well as being involved in reproduction and breakdown of plant seeds. eukaryotic cells also have cytoskeleton that is made up of microtubules, intermediate filaments, and microfilaments, all of which provide support for the cell and are involved in the movement of the cell and its organelles. in terms of their structural composition, the microtubules are made up of tubulin ( e. g., α - tubulin and β - 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 — the breaking down of compounds ( for example, the breaking down of glucose to pyruvate by cellular respiration
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
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 )
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
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 — 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
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 ). 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
Question: What term describes a way that small molecules or ions move across the cell membrane without input of energy by the cell?
A) impassive transport
B) passive transport
C) immune transport
D) physical transport
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B) passive transport
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Context:
participates as a consumer, resource, or both in consumer – resource interactions, which form the core of food chains or food webs. there are different trophic levels within any food web, with the lowest level being the primary producers ( or autotrophs ) such as plants and algae that convert energy and inorganic material into organic compounds, which can then be used by the rest of the community. at the next level are the heterotrophs, which are the species that obtain energy by breaking apart organic compounds from other organisms. heterotrophs that consume plants are primary consumers ( or herbivores ) whereas heterotrophs that consume herbivores are secondary consumers ( or carnivores ). and those that eat secondary consumers are tertiary consumers and so on. omnivorous heterotrophs are able to consume at multiple levels. finally, there are decomposers that feed on the waste products or dead bodies of organisms. on average, the total amount of energy incorporated into the biomass of a trophic level per unit of time is about one - tenth of the energy of the trophic level that it consumes. waste and dead material used by decomposers as well as heat lost from metabolism make up the other ninety percent of energy that is not consumed by the next trophic level. = = = biosphere = = = in the global ecosystem or biosphere, matter exists as different interacting compartments, which can be biotic or abiotic as well as accessible or inaccessible, depending on their forms and locations. for example, matter from terrestrial autotrophs are both biotic and accessible to other organisms whereas the matter in rocks and minerals are abiotic and inaccessible. a biogeochemical cycle is a pathway by which specific elements of matter are turned over or moved through the biotic ( biosphere ) and the abiotic ( lithosphere, atmosphere, and hydrosphere ) compartments of earth. there are biogeochemical cycles for nitrogen, carbon, and water. = = = conservation = = = conservation biology is the study of the conservation of earth ' s biodiversity with the aim of protecting species, their habitats, and ecosystems from excessive rates of extinction and the erosion of biotic interactions. it is concerned with factors that influence the maintenance, loss, and restoration of biodiversity and the science of sustaining evolutionary processes that engender genetic, population, species, and ecosystem diversity. the concern stems from estimates suggesting that up to 50 % of all species on the planet
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 – 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
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 – 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 – 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
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 — of which around 1 million are insects — 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 — pieces of dna that can move between cells — 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.
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
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.
##icellular 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 — of which around 1 million are insects — 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 — pieces of dna that can move between cells — while others may have evolved from bacteria. in evolution, viruses are an important means of horizontal gene transfer, which increases genetic diversity in a way analogous to sexual reproduction. because viruses possess some but not all characteristics of life, they have been described as " organisms at the edge of life ", and as self - replicators. = = ecology = = ecology is the study of the distribution and abundance of life, the interaction between organisms and their environment. = = = ecosystems = = = the community of living ( biotic ) organisms in conjunction with the nonliving ( abiotic ) components ( e. g., water, light, radiation, temperature, humidity, atmosphere, acidity, and soil ) of their environment is called an ecosystem. these biotic and abiotic components are linked together through nutrient cycles and energy flows. energy from the sun enters the system through photosynthesis and is incorporated into plant tissue
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
into organic compounds, which can then be used by the rest of the community. at the next level are the heterotrophs, which are the species that obtain energy by breaking apart organic compounds from other organisms. heterotrophs that consume plants are primary consumers ( or herbivores ) whereas heterotrophs that consume herbivores are secondary consumers ( or carnivores ). and those that eat secondary consumers are tertiary consumers and so on. omnivorous heterotrophs are able to consume at multiple levels. finally, there are decomposers that feed on the waste products or dead bodies of organisms. on average, the total amount of energy incorporated into the biomass of a trophic level per unit of time is about one - tenth of the energy of the trophic level that it consumes. waste and dead material used by decomposers as well as heat lost from metabolism make up the other ninety percent of energy that is not consumed by the next trophic level. = = = biosphere = = = in the global ecosystem or biosphere, matter exists as different interacting compartments, which can be biotic or abiotic as well as accessible or inaccessible, depending on their forms and locations. for example, matter from terrestrial autotrophs are both biotic and accessible to other organisms whereas the matter in rocks and minerals are abiotic and inaccessible. a biogeochemical cycle is a pathway by which specific elements of matter are turned over or moved through the biotic ( biosphere ) and the abiotic ( lithosphere, atmosphere, and hydrosphere ) compartments of earth. there are biogeochemical cycles for nitrogen, carbon, and water. = = = conservation = = = conservation biology is the study of the conservation of earth ' s biodiversity with the aim of protecting species, their habitats, and ecosystems from excessive rates of extinction and the erosion of biotic interactions. it is concerned with factors that influence the maintenance, loss, and restoration of biodiversity and the science of sustaining evolutionary processes that engender genetic, population, species, and ecosystem diversity. the concern stems from estimates suggesting that up to 50 % of all species on the planet will disappear within the next 50 years, which has contributed to poverty, starvation, and will reset the course of evolution on this planet. biodiversity affects the functioning of ecosystems, which provide a variety of services upon which people depend. conservation biologists research and educate on the trends of biodiversity loss, species extinctions, and the
Question: Do most humans feed at one trophic level, or more than one?
A) more than one
B) none
C) less than one
D) one
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A) more than one
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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 – 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,
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.
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 – broadly an artist who produces soundtracks or sound effects content for media. live sound engineer front of house ( foh ) engineer, or a1. – 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 – 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 – 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 – 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
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 – 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 – broadly an artist who produces soundtracks or sound effects content for media. live sound engineer front of house ( foh ) engineer, or a1. – 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 – 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 – 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 – a person in post - production who mixes audio tracks for feature films or television programs. = = equipment = = an audio engineer is
one of the greatest discoveries of modern times is that of the expanding universe, almost invariably attributed to hubble ( 1929 ). what is not widely known is that the original treatise by lemaitre ( 1927 ) contained a rich fusion of both theory and of observation. stiglers law of eponymy is yet again affirmed : no scientific discovery is named after its original discoverer ( merton, 1957 ). an appeal is made for a lemaitre telescope, to honour the discoverer of the expanding universe.
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?
a producer or independently. recording engineer – the engineer who records sound. assistant engineer – 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 – 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 – 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 – broadly an artist who produces soundtracks or sound effects content for media. live sound engineer front of house ( foh ) engineer, or a1. – 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 – 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 – 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
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 × x → x ( where x is a set such as the set of real numbers ).
when fast radio burst ( frb ) waves propagate through the local ( < 1 pc ) environment of the frb source, electrons in the plasma undergo large - amplitude oscillations. the finite - amplitude effects cause the effective plasma frequency and cyclotron frequency to be dependent on the wave strength. the dispersion measure and rotation measure should therefore vary slightly from burst to burst for a repeating source, depending on the luminosity and frequency of the individual burst. furthermore, free - free absorption of strong waves is suppressed due to the accelerated electrons ' reduced energy exchange in coulomb collisions. this allows bright low - frequency bursts to propagate through an environment that would be optically thick to low - amplitude waves. given a large sample of bursts from a repeating source, it would be possible to use the deficit of low - frequency and low - luminosity bursts to infer the emission measure of the local intervening plasma and its distance from the source. information about the local environment will shed light on the nature of frb sources.
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.
Question: What is it called when two waves combine to create a larger wave?
A) constructive interference
B) wave propagation
C) Destructive Interference
D) consistent interference
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A) constructive interference
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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 – 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
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 ( الكیمیاء ). this may have egyptian origins since al - kimia is derived from the ancient greek χημια, 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 χημεια ' 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
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 — 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 – 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 – 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
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 — 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 – 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 – 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 (
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 )
. oxidation, reduction, dissociation, acid – 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 – 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 cl− ions forming sodium chloride, or nacl. examples of polyatomic ions that do not split up during acid – base reactions are hydroxide ( oh− ) and phosphate ( po43− ). plasma is composed of gaseous matter that has been completely ionized, usually through high temperature. = = = acidity and basicity = = = a substance can often be
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 – 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 cl− ions forming sodium chloride, or nacl. examples of polyatomic ions that do not split up during acid – base reactions are hydroxide ( oh− ) and phosphate ( po43− ). 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 – 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.
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 – 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
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 − e / k t { \ displaystyle e ^ { - e / kt } } – 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, δ g ≤ 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 – 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
methods may be used in all subdisciplines of chemistry, excluding purely theoretical chemistry. biochemistry is the study of the chemicals, chemical reactions and interactions that take place at a molecular level in living organisms. biochemistry is highly interdisciplinary, covering medicinal chemistry, neurochemistry, molecular biology, forensics, plant science and genetics. inorganic chemistry is the study of the properties and reactions of inorganic compounds, such as metals and minerals. the distinction between organic and inorganic disciplines is not absolute and there is much overlap, most importantly in the sub - discipline of organometallic chemistry. materials chemistry is the preparation, characterization, and understanding of solid state components or devices with a useful current or future function. the field is a new breadth of study in graduate programs, and it integrates elements from all classical areas of chemistry like organic chemistry, inorganic chemistry, and crystallography with a focus on fundamental issues that are unique to materials. primary systems of study include the chemistry of condensed phases ( solids, liquids, polymers ) and interfaces between different phases. neurochemistry is the study of neurochemicals ; including transmitters, peptides, proteins, lipids, sugars, and nucleic acids ; their interactions, and the roles they play in forming, maintaining, and modifying the nervous system. nuclear chemistry is the study of how subatomic particles come together and make nuclei. modern transmutation is a large component of nuclear chemistry, and the table of nuclides is an important result and tool for this field. in addition to medical applications, nuclear chemistry encompasses nuclear engineering which explores the topic of using nuclear power sources for generating energy. organic chemistry is the study of the structure, properties, composition, mechanisms, and reactions of organic compounds. an organic compound is defined as any compound based on a carbon skeleton. organic compounds can be classified, organized and understood in reactions by their functional groups, unit atoms or molecules that show characteristic chemical properties in a compound. physical chemistry is the study of the physical and fundamental basis of chemical systems and processes. in particular, the energetics and dynamics of such systems and processes are of interest to physical chemists. important areas of study include chemical thermodynamics, chemical kinetics, electrochemistry, statistical mechanics, spectroscopy, and more recently, astrochemistry. physical chemistry has large overlap with molecular physics. physical chemistry involves the use of infinitesimal calculus in deriving equations. it is usually associated with quantum chemistry and theoretical chemistry. physical chemistry is a distinct discipline from chemical physics, but
Question: What is the study of the relationship between electricity and chemical reactions called?
A) inorganic chemistry
B) physical chemistry
C) analytical chemistry
D) electrochemistry
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D) electrochemistry
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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 — 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.
wounds or dead bodies should be examined, not avoided. the book became the first form of literature to help determine the cause of death. in one of song ci ' s accounts ( washing away of wrongs ), the case of a person murdered with a sickle was solved by an investigator who instructed each suspect to bring his sickle to one location. ( he realized it was a sickle by testing various blades on an animal carcass and comparing the wounds. ) flies, attracted by the smell of blood, eventually gathered on a single sickle. in light of this, the owner of that sickle confessed to the murder. the book also described how to distinguish between a drowning ( water in the lungs ) and strangulation ( broken neck cartilage ), and described evidence from examining corpses to determine if a death was caused by murder, suicide or accident. methods from around the world involved saliva and examination of the mouth and tongue to determine innocence or guilt, as a precursor to the polygraph test. in ancient india, some suspects were made to fill their mouths with dried rice and spit it back out. similarly, in ancient china, those accused of a crime would have rice powder placed in their mouths. in ancient middle - eastern cultures, the accused were made to lick hot metal rods briefly. it is thought that these tests had some validity since a guilty person would produce less saliva and thus have a drier mouth ; the accused would be considered guilty if rice was sticking to their mouths in abundance or if their tongues were severely burned due to lack of shielding from saliva. = = education and training = = initial glance, forensic intelligence may appear as a nascent facet of forensic science facilitated by advancements in information technologies such as computers, databases, and data - flow management software. however, a more profound examination reveals that forensic intelligence represents a genuine and emerging inclination among forensic practitioners to actively participate in investigative and policing strategies. in doing so, it elucidates existing practices within scientific literature, advocating for a paradigm shift from the prevailing conception of forensic science as a conglomerate of disciplines merely aiding the criminal justice system. instead, it urges a perspective that views forensic science as a discipline studying the informative potential of traces — remnants of criminal activity. embracing this transformative shift poses a significant challenge for education, necessitating a shift in learners ' mindset to accept concepts and methodologies in forensic intelligence. recent calls advocating for the integration of forensic scientists into the criminal justice system, as well as policing and intelligence missions, undersco
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 – 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 σ 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 σ = 4π a2 / λ2 ( where a = area, λ = wavelength ), or 13, 982 m2 at 10 ghz if the radar is perpendicular to the flat
the surface of the membrane, retentate is removed from the same side further downstream, whereas the permeate flow is tracked on the other side. in dead - end filtration, the direction of the fluid flow is normal to the membrane surface. both flow geometries offer some advantages and disadvantages. generally, dead - end filtration is used for feasibility studies on a laboratory scale. the dead - end membranes are relatively easy to fabricate which reduces the cost of the separation process. the dead - end membrane separation process is easy to implement and the process is usually cheaper than cross - flow membrane filtration. the dead - end filtration process is usually a batch - type process, where the filtering solution is loaded ( or slowly fed ) into the membrane device, which then allows passage of some particles subject to the driving force. the main disadvantage of dead - end filtration is the extensive membrane fouling and concentration polarization. the fouling is usually induced faster at higher driving forces. membrane fouling and particle retention in a feed solution also builds up a concentration gradients and particle backflow ( concentration polarization ). the tangential flow devices are more cost and labor - intensive, but they are less susceptible to fouling due to the sweeping effects and high shear rates of the passing flow. the most commonly used synthetic membrane devices ( modules ) are flat sheets / plates, spiral wounds, and hollow fibers. flat membranes used in filtration and separation processes can be enhanced with surface patterning, where microscopic structures are introduced to improve performance. these patterns increase surface area, optimize water flow, and reduce fouling, leading to higher permeability and longer membrane lifespan. research has shown that such modifications can significantly enhance efficiency in water purification, energy applications, and industrial separations. flat plates are usually constructed as circular thin flat membrane surfaces to be used in dead - end geometry modules. spiral wounds are constructed from similar flat membranes but in the form of a " pocket " containing two membrane sheets separated by a highly porous support plate. several such pockets are then wound around a tube to create a tangential flow geometry and to reduce membrane fouling. hollow fiber modules consist of an assembly of self - supporting fibers with dense skin separation layers, and a more open matrix helping to withstand pressure gradients and maintain structural integrity. the hollow fiber modules can contain up to 10, 000 fibers ranging from 200 to 2500 μm in diameter ; the main advantage of hollow fiber modules is the very large surface area within
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
oil umbrella ) ; for calculating the time of death ( allowing for weather and insect activity ) ; described how to wash and examine the dead body to ascertain the reason for death. at that time the book had described methods for distinguishing between suicide and faked suicide. he wrote the book on forensics stating that all wounds or dead bodies should be examined, not avoided. the book became the first form of literature to help determine the cause of death. in one of song ci ' s accounts ( washing away of wrongs ), the case of a person murdered with a sickle was solved by an investigator who instructed each suspect to bring his sickle to one location. ( he realized it was a sickle by testing various blades on an animal carcass and comparing the wounds. ) flies, attracted by the smell of blood, eventually gathered on a single sickle. in light of this, the owner of that sickle confessed to the murder. the book also described how to distinguish between a drowning ( water in the lungs ) and strangulation ( broken neck cartilage ), and described evidence from examining corpses to determine if a death was caused by murder, suicide or accident. methods from around the world involved saliva and examination of the mouth and tongue to determine innocence or guilt, as a precursor to the polygraph test. in ancient india, some suspects were made to fill their mouths with dried rice and spit it back out. similarly, in ancient china, those accused of a crime would have rice powder placed in their mouths. in ancient middle - eastern cultures, the accused were made to lick hot metal rods briefly. it is thought that these tests had some validity since a guilty person would produce less saliva and thus have a drier mouth ; the accused would be considered guilty if rice was sticking to their mouths in abundance or if their tongues were severely burned due to lack of shielding from saliva. = = education and training = = initial glance, forensic intelligence may appear as a nascent facet of forensic science facilitated by advancements in information technologies such as computers, databases, and data - flow management software. however, a more profound examination reveals that forensic intelligence represents a genuine and emerging inclination among forensic practitioners to actively participate in investigative and policing strategies. in doing so, it elucidates existing practices within scientific literature, advocating for a paradigm shift from the prevailing conception of forensic science as a conglomerate of disciplines merely aiding the criminal justice system. instead, it urges a perspective that views forensic science as a discipline studying the informative potential of
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,
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 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
, 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
generally, dead - end filtration is used for feasibility studies on a laboratory scale. the dead - end membranes are relatively easy to fabricate which reduces the cost of the separation process. the dead - end membrane separation process is easy to implement and the process is usually cheaper than cross - flow membrane filtration. the dead - end filtration process is usually a batch - type process, where the filtering solution is loaded ( or slowly fed ) into the membrane device, which then allows passage of some particles subject to the driving force. the main disadvantage of dead - end filtration is the extensive membrane fouling and concentration polarization. the fouling is usually induced faster at higher driving forces. membrane fouling and particle retention in a feed solution also builds up a concentration gradients and particle backflow ( concentration polarization ). the tangential flow devices are more cost and labor - intensive, but they are less susceptible to fouling due to the sweeping effects and high shear rates of the passing flow. the most commonly used synthetic membrane devices ( modules ) are flat sheets / plates, spiral wounds, and hollow fibers. flat membranes used in filtration and separation processes can be enhanced with surface patterning, where microscopic structures are introduced to improve performance. these patterns increase surface area, optimize water flow, and reduce fouling, leading to higher permeability and longer membrane lifespan. research has shown that such modifications can significantly enhance efficiency in water purification, energy applications, and industrial separations. flat plates are usually constructed as circular thin flat membrane surfaces to be used in dead - end geometry modules. spiral wounds are constructed from similar flat membranes but in the form of a " pocket " containing two membrane sheets separated by a highly porous support plate. several such pockets are then wound around a tube to create a tangential flow geometry and to reduce membrane fouling. hollow fiber modules consist of an assembly of self - supporting fibers with dense skin separation layers, and a more open matrix helping to withstand pressure gradients and maintain structural integrity. the hollow fiber modules can contain up to 10, 000 fibers ranging from 200 to 2500 μm 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
Question: What is the term for expelling air out of the body through the nose or mouth?
A) exhalation
B) inhalation
C) perspiration
D) induction
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A) exhalation
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Context:
the extremely small probability of tunneling through an almost classical potential barrier may become not small under the action of the specially adapted non - stationary signal which selects the certain particle energy e _ r. for particle energies close to this value, the tunneling rate is not small during a finite interval of time and has a very sharp peak at the energy e _ r. after entering inside the barrier, the particle emits electromagnetic quanta and exits the barrier with a lower energy. the signal amplitude can be much less compared to the field of the static barrier. this phenomenon can be called the euclidean resonance since the under - barrier motion occurs in imaginary time. the resonance may stimulate chemical and biochemical reactions in a selective way by adapting the signal to a certain particular chemical bond. the resonance may be used in search of the soft alpha - decay for which a conventional observation is impossible due to an extremely small decay rate.
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?
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 brønsted – lowry definition, is the acid dissociation constant ( ka ), which measures the relative ability of a substance to act as an acid under the brønsted – 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 — the actual transfer of electrons may never occur. thus, oxidation is better defined as an increase in oxidation number, and reduction as a decrease in oxidation number. = = = equilibrium = = = although the concept of equilibrium is widely used across sciences, in the context of chemistry, it arises whenever a number of different states of the chemical composition are possible, as for example, in a mixture of several chemical compounds that can react with one another, or when a substance can be present in more than one kind of phase. a system of chemical substances at equilibrium, even though having an unchanging composition, is most often not static ; molecules of the substances continue to react with one another thus giving rise to a dynamic equilibrium. thus the concept describes the state in which the parameters such as chemical composition remain unchanged over time. = = = chemical laws = = = chemical reactions are governed by certain laws, which have become fundamental concepts in chemistry. some of them are : = = history = = the history of chemistry spans a period from the ancient past to the present. since several millennia bc, civilizations were using technologies that would eventually form the basis of the various branches of chemistry. examples include extracting metals from ores
the higher microwave band 3 – 6 ghz, and millimeter wave band, around 28 and 39 ghz. since these frequencies have a shorter range than previous cellphone bands, the cells will be smaller than the cells in previous cellular networks which could be many miles across. millimeter - wave cells will only be a few blocks long, and instead of a cell base station and antenna tower, they will have many small antennas attached to utility poles and buildings. satellite phone ( satphone ) – a portable wireless telephone similar to a cell phone, connected to the telephone network through a radio link to an orbiting communications satellite instead of through cell towers. they are more expensive than cell phones ; but their advantage is that, unlike a cell phone which is limited to areas covered by cell towers, satphones can be used over most or all of the geographical area of the earth. in order for the phone to communicate with a satellite using a small omnidirectional antenna, first - generation systems use satellites in low earth orbit, about 400 – 700 miles ( 640 – 1, 100 km ) above the surface. with an orbital period of about 100 minutes, a satellite can only be in view of a phone for about 4 – 15 minutes, so the call is " handed off " to another satellite when one passes beyond the local horizon. therefore, large numbers of satellites, about 40 to 70, are required to ensure that at least one satellite is in view continuously from each point on earth. other satphone systems use satellites in geostationary orbit in which only a few satellites are needed, but these cannot be used at high latitudes because of terrestrial interference. cordless phone – 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 – 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
cobalt nanowires with a diameter in the range between 50 to 100nm can be prepared as single - crystal wires with the easy axis ( the c - axis ) perpendicular to the wire axis. the competition between the crystal anisotropy and demagnetization energy frustrates the magnetization direction. a periodic modulation of the angle between m and the wire axis yields a lower energy.
the connection between the quantum frequency of radiation by the transition of the electron from orbit n to orbit k and frequencies of circling of electron in these orbits for the atom of hydrogen is determined.
an alternative explanation of 1 / f - noise in manganites is suggested and discussed
parametric excitation of rotons by oscillating electric field exhibits a narrow resonance at the roton minimum frequency. the resonance width is in good agreement with experimental results on the microwave absorption in superfluid helium.
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
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
Question: The lowest resonant frequency is called the what?
A) simplest
B) lowest
C) basic
D) fundamental
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D) fundamental
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Context:
, crystal structure, hazards associated with minerals, and the physical and chemical properties of minerals. petrology is the study of rocks, including the formation and composition of rocks. petrography is a branch of petrology that studies the typology and classification of rocks. = = earth ' s interior = = plate tectonics, mountain ranges, volcanoes, and earthquakes are geological phenomena that can be explained in terms of physical and chemical processes in the earth ' s crust. beneath the earth ' s crust lies the mantle which is heated by the radioactive decay of heavy elements. the mantle is not quite solid and consists of magma which is in a state of semi - perpetual convection. this convection process causes the lithospheric plates to move, albeit slowly. the resulting process is known as plate tectonics. areas of the crust where new crust is created are called divergent boundaries, those where it is brought back into the earth are convergent boundaries and those where plates slide past each other, but no new lithospheric material is created or destroyed, are referred to as transform ( or conservative ) boundaries. earthquakes result from the movement of the lithospheric plates, and they often occur near convergent boundaries where parts of the crust are forced into the earth as part of subduction. plate tectonics might be thought of as the process by which the earth is resurfaced. as the result of seafloor spreading, new crust and lithosphere is created by the flow of magma from the mantle to the near surface, through fissures, where it cools and solidifies. through subduction, oceanic crust and lithosphere vehemently returns to the convecting mantle. volcanoes result primarily from the melting of subducted crust material. crust material that is forced into the asthenosphere melts, and some portion of the melted material becomes light enough to rise to the surface — 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 — 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
##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 — 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
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
electromagnetic soliton - particle with both quasi - static and quick - oscillating wave parts is considered. its mass, spin, charge, and magnetic moment appear naturally when the interaction with distant solitons is considered. the substantiation of dirac equation for the wave part of the interacting soliton - particle is given.
stations located in places like light poles or building roofs. in the past, 4g networking had to rely on large cell towers in order to transmit signals over large distances. with the introduction of 5g networking, it is imperative that small cell stations are used because the mm wave spectrum, which is the specific type of band used in 5g services, strictly travels over short distances. if the distances between cell stations were longer, signals may suffer from interference from inclimate weather, or other objects such as houses, buildings, trees, and much more. in 5g networking, there are 3 main kinds of 5g : low - band, mid - band, and high - band. low - band frequencies operate below 2 ghz, mid - band frequencies operate between 2 – 10 ghz, and high - band frequencies operate between 20 and 100 ghz. verizon have seen outrageous numbers on their high - band 5g service, which they deem " ultraband ", which hit speeds of over 3 gbit / s. the main advantage of 5g networks is that the data transmission rate is much higher than the previous cellular network, up to 10 gbit / s, which is faster than the current wired internet and 100 times faster than the previous 4g lte cellular network. another advantage is lower network latency ( faster response time ), less than 1 millisecond, and 4g is 30 - 70 milliseconds. the peak rate needs to reach the gbit / s standard to meet the high data volume of high - definition video, virtual reality and so on. the air interface delay level needs to be around 1ms, which meets real - time applications such as autonomous driving and telemedicine. large network capacity, providing the connection capacity of 100 billion devices to meet iot communication. the spectrum efficiency is 10 times higher than lte. with continuous wide area coverage and high mobility, the user experience rate reaches 100 mbit / s. the flow density and the number of connections are greatly increased. since 5g is a relatively new type of service, only phones which are newly released or are upcoming can support 5g service. some of these phones include the iphone 12 / 13 ; select samsung devices such as the s21 series, note series, flip / fold series, a series ; google pixel 4a / 5 ; and a few more devices from other manufacturers. the first ever 5g smartphone, the samsung galaxy s20, was released by samsung in march 2020. following the release of samsung ' s s
the most puzzling issue in the foundations of quantum mechanics is perhaps that of the status of the wave function of a system in a quantum universe. is the wave function objective or subjective? does it represent the physical state of the system or merely our information about the system? and if the former, does it provide a complete description of the system or only a partial description? we shall address these questions here mainly from a bohmian perspective, and shall argue that part of the difficulty in ascertaining the status of the wave function in quantum mechanics arises from the fact that there are two different sorts of wave functions involved. the most fundamental wave function is that of the universe. from it, together with the configuration of the universe, one can define the wave function of a subsystem. we argue that the fundamental wave function, the wave function of the universe, has a law - like character.
radio is the technology of communicating using radio waves. radio waves are electromagnetic waves of frequency between 3 hertz ( hz ) and 300 gigahertz ( ghz ). they are generated by an electronic device called a transmitter connected to an antenna which radiates the waves. they can be received by other antennas connected to a radio receiver ; this is the fundamental principle of radio communication. in addition to communication, radio is used for radar, radio navigation, remote control, remote sensing, and other applications. in radio communication, used in radio and television broadcasting, cell phones, two - way radios, wireless networking, and satellite communication, among numerous other uses, radio waves are used to carry information across space from a transmitter to a receiver, by modulating the radio signal ( impressing an information signal on the radio wave by varying some aspect of the wave ) in the transmitter. in radar, used to locate and track objects like aircraft, ships, spacecraft and missiles, a beam of radio waves emitted by a radar transmitter reflects off the target object, and the reflected waves reveal the object ' s location to a receiver that is typically colocated with the transmitter. in radio navigation systems such as gps and vor, a mobile navigation instrument receives radio signals from multiple navigational radio beacons whose position is known, and by precisely measuring the arrival time of the radio waves the receiver can calculate its position on earth. in wireless radio remote control devices like drones, garage door openers, and keyless entry systems, radio signals transmitted from a controller device control the actions of a remote device. the existence of radio waves was first proven by german physicist heinrich hertz on 11 november 1886. in the mid - 1890s, building on techniques physicists were using to study electromagnetic waves, italian physicist guglielmo marconi developed the first apparatus for long - distance radio communication, sending a wireless morse code message to a recipient over a kilometer away in 1895, and the first transatlantic signal on 12 december 1901. the first commercial radio broadcast was transmitted on 2 november 1920, when the live returns of the harding - cox presidential election were broadcast by westinghouse electric and manufacturing company in pittsburgh, under the call sign kdka. the emission of radio waves is regulated by law, coordinated by the international telecommunication union ( itu ), which allocates frequency bands in the radio spectrum for various uses. = = etymology = = the word radio is derived from the latin word radius, meaning " spoke of a wheel, beam of light, ray. " it was first
##hosphere ) and its historic development. major subdisciplines are mineralogy and petrology, geomorphology, paleontology, stratigraphy, structural geology, engineering geology, and sedimentology. physical geography focuses on geography as an earth science. physical geography is the study of earth ' s seasons, climate, atmosphere, soil, streams, landforms, and oceans. physical geography can be divided into several branches or related fields, as follows : geomorphology, biogeography, environmental geography, palaeogeography, climatology, meteorology, coastal geography, hydrology, ecology, glaciology. geophysics and geodesy investigate the shape of the earth, its reaction to forces and its magnetic and gravity fields. geophysicists explore the earth ' s core and mantle as well as the tectonic and seismic activity of the lithosphere. geophysics is commonly used to supplement the work of geologists in developing a comprehensive understanding of crustal geology, particularly in mineral and petroleum exploration. seismologists use geophysics to understand plate tectonic movement, as well as predict seismic activity. geochemistry studies the processes that control the abundance, composition, and distribution of chemical compounds and isotopes in geologic environments. geochemists use the tools and principles of chemistry to study the earth ' s composition, structure, processes, and other physical aspects. major subdisciplines are aqueous geochemistry, cosmochemistry, isotope geochemistry and biogeochemistry. soil science covers the outermost layer of the earth ' s crust that is subject to soil formation processes ( or pedosphere ). major subdivisions in this field of study include edaphology and pedology. ecology covers the interactions between organisms and their environment. this field of study differentiates the study of earth from other planets in the solar system, earth being the only planet teeming with life. hydrology, oceanography and limnology are studies which focus on the movement, distribution, and quality of the water and involve all the components of the hydrologic cycle on the earth and its atmosphere ( or hydrosphere ). " sub - disciplines of hydrology include hydrometeorology, surface water hydrology, hydrogeology, watershed science, forest hydrology, and water chemistry. " glaciology covers the icy parts of the earth ( or cryosphere ). atmospheric sciences cover the gaseous parts of the earth ( or atmosphere
##sphere ( or lithosphere ). earth science can be considered to be a branch of planetary science but with a much older history. = = geology = = geology is broadly the study of earth ' s structure, substance, and processes. geology is largely the study of the lithosphere, or earth ' s surface, including the crust and rocks. it includes the physical characteristics and processes that occur in the lithosphere as well as how they are affected by geothermal energy. it incorporates aspects of chemistry, physics, and biology as elements of geology interact. historical geology is the application of geology to interpret earth history and how it has changed over time. geochemistry studies the chemical components and processes of the earth. geophysics studies the physical properties of the earth. paleontology studies fossilized biological material in the lithosphere. planetary geology studies geoscience as it pertains to extraterrestrial bodies. geomorphology studies the origin of landscapes. structural geology studies the deformation of rocks to produce mountains and lowlands. resource geology studies how energy resources can be obtained from minerals. environmental geology studies how pollution and contaminants affect soil and rock. mineralogy is the study of minerals and includes the study of mineral formation, crystal structure, hazards associated with minerals, and the physical and chemical properties of minerals. petrology is the study of rocks, including the formation and composition of rocks. petrography is a branch of petrology that studies the typology and classification of rocks. = = earth ' s interior = = plate tectonics, mountain ranges, volcanoes, and earthquakes are geological phenomena that can be explained in terms of physical and chemical processes in the earth ' s crust. beneath the earth ' s crust lies the mantle which is heated by the radioactive decay of heavy elements. the mantle is not quite solid and consists of magma which is in a state of semi - perpetual convection. this convection process causes the lithospheric plates to move, albeit slowly. the resulting process is known as plate tectonics. areas of the crust where new crust is created are called divergent boundaries, those where it is brought back into the earth are convergent boundaries and those where plates slide past each other, but no new lithospheric material is created or destroyed, are referred to as transform ( or conservative ) boundaries. earthquakes result from the movement of the lithospheric plates, and they often occur near convergent boundaries where parts of the crust are forced into the earth as
Question: Body waves and surface waves are the two major types of what, which occur during earthquakes?
A) seismic waves
B) current waves
C) sound waves
D) tidal waves
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A) seismic waves
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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 – civil works program river morphology and stream restoration references
the reply to g. w. bruhn is added.
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
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 – civil works program river morphology and stream restoration references - wildland hydrology at the library of congress web archives ( archived 2002 - 08 - 13 )
was done using the spinning wheel and weaving was done on a hand - and - foot - operated loom. it took from three to five spinners to supply one weaver. the invention of the flying shuttle in 1733 doubled the output of a weaver, creating a shortage of spinners. the spinning frame for wool was invented 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,
##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
##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
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
( e. g., trunks of trees, boulders and accumulations of gravel ) from a river bed furnishes a simple and efficient means of increasing the discharging capacity of its channel. such removals will consequently lower the height of floods upstream. every impediment to the flow, in proportion to its extent, raises the level of the river above it so as to produce the additional artificial fall necessary to convey the flow through the restricted channel, thereby reducing the total available fall. reducing the length of the channel by substituting straight cuts for a winding course is the only way in which the effective fall can be increased. this involves some loss of capacity in the channel as a whole, and in the case of a large river with a considerable flow it is difficult to maintain a straight cut owing to the tendency of the current to erode the banks and form again a sinuous channel. even if the cut is preserved by protecting the banks, it is liable to produce changes shoals and raise the flood - level in the channel just below its termination. nevertheless, where the available fall is exceptionally small, as in land originally reclaimed from the sea, such as the english fenlands, and where, in consequence, the drainage is in a great measure artificial, straight channels have been formed for the rivers. because of the perceived value in protecting these fertile, low - lying lands from inundation, additional straight channels have also been provided for the discharge of rainfall, known as drains in the fens. even extensive modification of the course of a river combined with an enlargement of its channel often produces only a limited reduction in flood damage. consequently, such floodworks are only commensurate with the expenditure involved where significant assets ( such as a town ) are under threat. additionally, even when successful, such floodworks may simply move the problem further downstream and threaten some other town. recent floodworks in europe have included restoration of natural floodplains and winding courses, so that floodwater is held back and released more slowly. human intervention sometimes inadvertently modifies the course or characteristics of a river, for example by introducing obstructions such as mining refuse, sluice gates for mills, fish - traps, unduly wide piers for bridges and solid weirs. by impeding flow these measures can raise the flood - level upstream. regulations for the management of rivers may include stringent prohibitions with regard to pollution, requirements for enlarging sluice - ways and the compulsory raising of their gates for the passage of floods
driven by cheap energy in the form of coal, produced in ever - increasing amounts from the abundant resources of britain. the british industrial revolution is characterized by developments in the areas of textile machinery, mining, metallurgy, transport and the invention of machine tools. before invention of machinery to spin yarn and weave cloth, spinning was done using the spinning wheel and weaving was done on a hand - and - foot - operated loom. it took from three to five spinners to supply one weaver. the invention of the flying shuttle in 1733 doubled the output of a weaver, creating a shortage of spinners. the spinning frame for wool was invented 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
Question: Inferior rotation occurs during limb adduction and involves the downward motion of what?
A) glenoid cavity
B) choroidal cavity
C) pelvic cavity
D) dialysate cavity
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A) glenoid cavity
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Context:
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 – 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 – 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 – 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
the sn explosion in the closed binary can give the magnetospheric flare possessing the properties of grb. the sn shock, flowing around the magnetosphere of a magnetized neutron star or a white dwarf, produces a narrow magnetic tail 10 ^ 9 cm long, 10 ^ 8 cm wide and a magnetic field of 10 ^ 6 gauss. fast particles ( lorentz factor of 10 ^ 4 ), generated in the tail by reconnection processes, radaite gamma rays of the 100 kev - 1 mev energies. the duration of radiation t < 1 sec corresponds to a short grb. apart, the powerful shock can tear and accelerate part of the tail. that is the relativistic, strongly magnetized jet, producing gamma radiation and also x - rays and optic afterglow. that is long ( t > 10 sec ) grb. the duration of the afterglow is inversly proportional to the photon energy and is several months for optic.
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 – 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 – 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 – 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 ) – 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 – an s or x band radar on ships used to detect nearby ships and obstructions like bridges. a rotating antenna sweeps a vertical
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?
, phone lines and power lines ) to create a high - speed local area network. twisted pair cabling is used for wired ethernet and other standards. it typically consists of 4 pairs of copper cabling that can be utilized for both voice and data transmission. the use of two wires twisted together helps to reduce crosstalk and electromagnetic induction. the transmission speed ranges from 2 mbit / s to 10 gbit / s. twisted pair cabling comes in two forms : unshielded twisted pair ( utp ) and shielded twisted - pair ( stp ). each form comes in several category ratings, designed for use in various scenarios. an optical fiber is a glass fiber. it carries pulses of light that represent data via lasers and optical amplifiers. some advantages of optical fibers over metal wires are very low transmission loss and immunity to electrical interference. using dense wave division multiplexing, optical fibers can simultaneously carry multiple streams of data on different wavelengths of light, which greatly increases the rate that data can be sent to up to trillions of bits per second. optic fibers can be used for long runs of cable carrying very high data rates, and are used for undersea communications cables to interconnect continents. there are two basic types of fiber optics, single - mode optical fiber ( smf ) and multi - mode optical fiber ( mmf ). single - mode fiber has the advantage of being able to sustain a coherent signal for dozens or even a hundred kilometers. multimode fiber is cheaper to terminate but is limited to a few hundred or even only a few dozens of meters, depending on the data rate and cable grade. = = = wireless = = = network connections can be established wirelessly using radio or other electromagnetic means of communication. terrestrial microwave – 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 – 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 – wireless lans use a high - frequency radio technology similar to
electromagnetic soliton - particle with both quasi - static and quick - oscillating wave parts is considered. its mass, spin, charge, and magnetic moment appear naturally when the interaction with distant solitons is considered. the substantiation of dirac equation for the wave part of the interacting soliton - particle is given.
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.
there are no limits for the speeds of light and particles in general relativity ( gr ). four examples illustrate this basic result, which is too often neglected.
the relations among the components of the exit momenta of ultrarelativistic electrons scattered on a strong electromagnetic wave of a low ( optical ) frequency and linear polarization are established using the exact solutions to the equations of motion with radiation reaction included ( the landau - lifshitz equation ). it is found that the momentum components of the electrons traversed the electromagnetic wave depend weakly on the initial values of the momenta. these electrons are mostly scattered at the small angles to the direction of propagation of the electromagnetic wave. the maximum lorentz factor of the electrons crossed the electromagnetic wave is proportional to the work done by the electromagnetic field and is independent of the initial momenta. the momentum component parallel to the electric field strength vector of the electromagnetic wave is determined only by the diameter of the laser beam measured in the units of the classical electron radius. as for the reflected electrons, they for the most part lose the energy, but remain relativistic. there is a reflection law for these electrons that relates the incident and the reflection angles and is independent of any parameters.
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
Question: The speed of an electromagnetic wave is the product of its wavelength and what else?
A) density
B) height
C) resonance
D) frequency
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D) frequency
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Context:
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 cl−. 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
defective body parts. inside the body, artificial heart valves are in common use with artificial hearts and lungs seeing less common use but under active technology development. other medical devices and aids that can be considered prosthetics include hearing aids, artificial eyes, palatal obturator, gastric bands, and dentures. prostheses are specifically not orthoses, although given certain circumstances a prosthesis might end up performing some or all of the same functionary benefits as an orthosis. prostheses are technically the complete finished item. for instance, a c - leg knee alone is not a prosthesis, but only a prosthetic component. the complete prosthesis would consist of the attachment system to the residual limb – usually a " socket ", and all the attachment hardware components all the way down to and including the terminal device. despite the technical difference, the terms are often used interchangeably. the terms " prosthetic " and " orthotic " are adjectives used to describe devices such as a prosthetic knee. the terms " prosthetics " and " orthotics " are used to describe the respective allied health fields. an occupational therapist ' s role in prosthetics include therapy, training and evaluations. prosthetic training includes orientation to prosthetics components and terminology, donning and doffing, wearing schedule, and how to care for residual limb and the prosthesis. = = = exoskeletons = = = a powered exoskeleton is a wearable mobile machine that is powered by a system of electric motors, pneumatics, levers, hydraulics, or a combination of technologies that allow for limb movement with increased strength and endurance. its design aims to provide back support, sense the user ' s motion, and send a signal to motors which manage the gears. the exoskeleton supports the shoulder, waist and thigh, and assists movement for lifting and holding heavy items, while lowering back stress. = = = adaptive seating and positioning = = = people with balance and motor function challenges often need specialized equipment to sit or stand safely and securely. this equipment is frequently specialized for specific settings such as in a classroom or nursing home. positioning is often important in seating arrangements to ensure that user ' s body pressure is distributed equally without inhibiting movement in a desired way. positioning devices have been developed to aid in allowing people to stand and bear weight on their legs without risk of a fall.
the mechanism leading to an auger transition is based on the residual coulomb interaction between the valence electron and the core electrons. on the assumption that the wave field is switched on adiabatically, the probability of the auger effect of the inner electrons of the atom is determined.
the boron buckyball avoids the high symmetry icosahedral cage structure. the previously reported ih symmetric structure is not an energy minimum in the potential energy surface and exhibits a spontaneous symmetry breaking to yield a puckered cage with a rare th symmetry. the homo - lumo gap is twice as large as the reported value and amounts to 1. 94 ev at b3lyp / 6 - 31g ( d ) level. the valence orbital structure of boron buckyball is identical to the one in the carbon analogue.
various charge pairings in strongly correlated electron systems are interpreted as quantum entanglement of a composite system. particles in the intermediate phase have a tendency to form the coherent superposition state of the localized state and the itinerant state, which induces the entanglement of both particles in the bipartite subsystems for increasing the entropy of the system. the correction to the entropic coulomb force becomes an immediate cause of charge pairing.
an electron inside liquid helium forms a bubble of 17 \ aa in radius. in an external magnetic field, the two - level system of a spin 1 / 2 electron is ideal for the implementation of a qubit for quantum computing. the electron spin is well isolated from other thermal reservoirs so that the qubit should have very long coherence time. by confining a chain of single electron bubbles in a linear rf quadrupole trap, a multi - bit quantum register can be implemented. all spins in the register can be initialized to the ground state either by establishing thermal equilibrium at a temperature around 0. 1 k and at a magnetic field of 1 t or by sorting the bubbles to be loaded into the trap with magnetic separation. schemes are designed to address individual spins and to do two - qubit cnot operations between the neighboring spins. the final readout can be carried out through a measurement similar to the stern - gerlach experiment.
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
the connection between the quantum frequency of radiation by the transition of the electron from orbit n to orbit k and frequencies of circling of electron in these orbits for the atom of hydrogen is determined.
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 '
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 cl−. 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: Electrons in inner shells are called what?
A) inner electrons
B) surface electrons
C) core electrons
D) valence electrons
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C) core electrons
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Context:
to a region of deoxyribonucleic acid ( dna ) that carries genetic information that controls form or function of an organism. dna is composed of two polynucleotide chains that coil around each other to form a double helix. it is found as linear chromosomes in eukaryotes, and circular chromosomes in prokaryotes. the set of chromosomes in a cell is collectively known as its genome. in eukaryotes, dna is mainly in the cell nucleus. in prokaryotes, the dna is held within the nucleoid. the genetic information is held within genes, and the complete assemblage in an organism is called its genotype. dna replication is a semiconservative process whereby each strand serves as a template for a new strand of dna. mutations are heritable changes in dna. they can arise spontaneously as a result of replication errors that were not corrected by proofreading or can be induced by an environmental mutagen such as a chemical ( e. g., nitrous acid, benzopyrene ) or radiation ( e. g., x - ray, gamma ray, ultraviolet radiation, particles emitted by unstable isotopes ). mutations can lead to phenotypic effects such as loss - of - function, gain - of - function, and conditional mutations. some mutations are beneficial, as they are a source of genetic variation for evolution. others are harmful if they were to result in a loss of function of genes needed for survival. = = = gene expression = = = gene expression is the molecular process by which a genotype encoded in dna gives rise to an observable phenotype in the proteins of an organism ' s body. this process is summarized by the central dogma of molecular biology, which was formulated by francis crick in 1958. according to the central dogma, genetic information flows from dna to rna to protein. there are two gene expression processes : transcription ( dna to rna ) and translation ( rna to protein ). = = = gene regulation = = = the regulation of gene expression by environmental factors and during different stages of development can occur at each step of the process such as transcription, rna splicing, translation, and post - translational modification of a protein. gene expression can be influenced by positive or negative regulation, depending on which of the two types of regulatory proteins called transcription factors bind to the dna sequence close to or at a promoter. a cluster of genes that share the same promoter is called an operon,
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 cl−. 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
cross. the chromosome theory of inheritance, which states that genes are found on chromosomes, was supported by thomas morgans ' s experiments with fruit flies, which established the sex linkage between eye color and sex in these insects. = = = genes and dna = = = a gene is a unit of heredity that corresponds to a region of deoxyribonucleic acid ( dna ) that carries genetic information that controls form or function of an organism. dna is composed of two polynucleotide chains that coil around each other to form a double helix. it is found as linear chromosomes in eukaryotes, and circular chromosomes in prokaryotes. the set of chromosomes in a cell is collectively known as its genome. in eukaryotes, dna is mainly in the cell nucleus. in prokaryotes, the dna is held within the nucleoid. the genetic information is held within genes, and the complete assemblage in an organism is called its genotype. dna replication is a semiconservative process whereby each strand serves as a template for a new strand of dna. mutations are heritable changes in dna. they can arise spontaneously as a result of replication errors that were not corrected by proofreading or can be induced by an environmental mutagen such as a chemical ( e. g., nitrous acid, benzopyrene ) or radiation ( e. g., x - ray, gamma ray, ultraviolet radiation, particles emitted by unstable isotopes ). mutations can lead to phenotypic effects such as loss - of - function, gain - of - function, and conditional mutations. some mutations are beneficial, as they are a source of genetic variation for evolution. others are harmful if they were to result in a loss of function of genes needed for survival. = = = gene expression = = = gene expression is the molecular process by which a genotype encoded in dna gives rise to an observable phenotype in the proteins of an organism ' s body. this process is summarized by the central dogma of molecular biology, which was formulated by francis crick in 1958. according to the central dogma, genetic information flows from dna to rna to protein. there are two gene expression processes : transcription ( dna to rna ) and translation ( rna to protein ). = = = gene regulation = = = the regulation of gene expression by environmental factors and during different stages of development can occur at each step of the process such as transcription, rna splicing
and then graft healthy skin onto 80 percent of the boy ' s body which was affected by the illness. germline gene therapy would result in any change being inheritable, which has raised concerns within the scientific community. in 2015, crispr was used to edit the dna of non - viable human embryos, leading scientists of major world academies to call for a moratorium on inheritable human genome edits. there are also concerns that the technology could be used not just for treatment, but for enhancement, modification or alteration of a human beings ' appearance, adaptability, intelligence, character or behavior. the distinction between cure and enhancement can also be difficult to establish. in november 2018, he jiankui announced that he had edited the genomes of two human embryos, to attempt to disable the ccr5 gene, which codes for a receptor that hiv uses to enter cells. the work was widely condemned as unethical, dangerous, and premature. currently, germline modification is banned in 40 countries. scientists that do this type of research will often let embryos grow for a few days without allowing it to develop into a baby. researchers are altering the genome of pigs to induce the growth of human organs, with the aim of increasing the success of pig to human organ transplantation. scientists are creating " gene drives ", changing the genomes of mosquitoes to make them immune to malaria, and then looking to spread the genetically altered mosquitoes throughout the mosquito population in the hopes of eliminating the disease. = = = research = = = genetic engineering is an important tool for natural scientists, with the creation of transgenic organisms one of the most important tools for analysis of gene function. genes and other genetic information from a wide range of organisms can be inserted into bacteria for storage and modification, creating genetically modified bacteria in the process. bacteria are cheap, easy to grow, clonal, multiply quickly, relatively easy to transform and can be stored at - 80 °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
##tes, i. e., genes are unlinked. an exception to this rule would include traits that are sex - linked. test crosses can be performed to experimentally determine the underlying genotype of an organism with a dominant phenotype. a punnett square can be used to predict the results of a test cross. the chromosome theory of inheritance, which states that genes are found on chromosomes, was supported by thomas morgans ' s experiments with fruit flies, which established the sex linkage between eye color and sex in these insects. = = = genes and dna = = = a gene is a unit of heredity that corresponds to a region of deoxyribonucleic acid ( dna ) that carries genetic information that controls form or function of an organism. dna is composed of two polynucleotide chains that coil around each other to form a double helix. it is found as linear chromosomes in eukaryotes, and circular chromosomes in prokaryotes. the set of chromosomes in a cell is collectively known as its genome. in eukaryotes, dna is mainly in the cell nucleus. in prokaryotes, the dna is held within the nucleoid. the genetic information is held within genes, and the complete assemblage in an organism is called its genotype. dna replication is a semiconservative process whereby each strand serves as a template for a new strand of dna. mutations are heritable changes in dna. they can arise spontaneously as a result of replication errors that were not corrected by proofreading or can be induced by an environmental mutagen such as a chemical ( e. g., nitrous acid, benzopyrene ) or radiation ( e. g., x - ray, gamma ray, ultraviolet radiation, particles emitted by unstable isotopes ). mutations can lead to phenotypic effects such as loss - of - function, gain - of - function, and conditional mutations. some mutations are beneficial, as they are a source of genetic variation for evolution. others are harmful if they were to result in a loss of function of genes needed for survival. = = = gene expression = = = gene expression is the molecular process by which a genotype encoded in dna gives rise to an observable phenotype in the proteins of an organism ' s body. this process is summarized by the central dogma of molecular biology, which was formulated by francis crick in 1958. according to the central dogma, genetic information flows from dna
of 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
occurs when another transcription factor called a repressor binds to a dna sequence called an operator, which is part of an operon, to prevent transcription. repressors can be inhibited by compounds called inducers ( e. g., allolactose ), thereby allowing transcription to occur. specific genes that can be activated by inducers are called inducible genes, in contrast to constitutive genes that are almost constantly active. in contrast to both, structural genes encode proteins that are not involved in gene regulation. in addition to regulatory events involving the promoter, gene expression can also be regulated by epigenetic changes to chromatin, which is a complex of dna and protein found in eukaryotic cells. = = = genes, development, and evolution = = = development is the process by which a multicellular organism ( plant or animal ) goes through a series of changes, starting from a single cell, and taking on various forms that are characteristic of its life cycle. there are four key processes that underlie development : determination, differentiation, morphogenesis, and growth. determination sets the developmental fate of a cell, which becomes more restrictive during development. differentiation is the process by which specialized cells arise from less specialized cells such as stem cells. stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. cellular differentiation dramatically changes a cell ' s size, shape, membrane potential, metabolic activity, and responsiveness to signals, which are largely due to highly controlled modifications in gene expression and epigenetics. with a few exceptions, cellular differentiation almost never involves a change in the dna sequence itself. thus, different cells can have very different physical characteristics despite having the same genome. morphogenesis, or the development of body form, is the result of spatial differences in gene expression. a small fraction of the genes in an organism ' s genome called the developmental - genetic toolkit control the development of that organism. these toolkit genes are highly conserved among phyla, meaning that they are ancient and very similar in widely separated groups of animals. differences in deployment of toolkit genes affect the body plan and the number, identity, and pattern of body parts. among the most important toolkit genes are the hox genes. hox genes determine where repeating parts, such as the many vertebrae of snakes, will grow in a developing embryo or larva. = = evolution = = = = = evolutionary
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 '
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, multiply quickly, relatively easy to transform and can be stored at - 80 °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
##s can be tested against these mouse models. gene therapy is the genetic engineering of humans, generally by replacing defective genes with effective ones. clinical research using somatic gene therapy has been conducted with several diseases, including x - linked scid, chronic lymphocytic leukemia ( cll ), and parkinson ' s disease. in 2012, alipogene tiparvovec became the first gene therapy treatment to be approved for clinical use. in 2015 a virus was used to insert a healthy gene into the skin cells of a boy suffering from a rare skin disease, epidermolysis bullosa, in order to grow, and then graft healthy skin onto 80 percent of the boy ' s body which was affected by the illness. germline gene therapy would result in any change being inheritable, which has raised concerns within the scientific community. in 2015, crispr was used to edit the dna of non - viable human embryos, leading scientists of major world academies to call for a moratorium on inheritable human genome edits. there are also concerns that the technology could be used not just for treatment, but for enhancement, modification or alteration of a human beings ' appearance, adaptability, intelligence, character or behavior. the distinction between cure and enhancement can also be difficult to establish. in november 2018, he jiankui announced that he had edited the genomes of two human embryos, to attempt to disable the ccr5 gene, which codes for a receptor that hiv uses to enter cells. the work was widely condemned as unethical, dangerous, and premature. currently, germline modification is banned in 40 countries. scientists that do this type of research will often let embryos grow for a few days without allowing it to develop into a baby. researchers are altering the genome of pigs to induce the growth of human organs, with the aim of increasing the success of pig to human organ transplantation. scientists are creating " gene drives ", changing the genomes of mosquitoes to make them immune to malaria, and then looking to spread the genetically altered mosquitoes throughout the mosquito population in the hopes of eliminating the disease. = = = research = = = genetic engineering is an important tool for natural scientists, with the creation of transgenic organisms one of the most important tools for analysis of gene function. genes and other genetic information from a wide range of organisms can be inserted into bacteria for storage and modification, creating genetically modified bacteria in the process. bacteria are cheap, easy to grow, clonal, multi
Question: The binding of complementary bases allows dna molecules to take their well-known shape, called a what?
A) simple helix
B) triple helix
C) double helix
D) single helix
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C) double helix
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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 " – 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
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 " – 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
unitary recordings in freely - moving pulse weakly electric fish suggest spike timing encoding of electrosensory signals
##nosperms and angiosperms. gymnosperms produce " naked seeds " not fully enclosed in an ovary ; modern representatives include conifers, cycads, ginkgo, and gnetales. angiosperms produce seeds enclosed in a structure such as a carpel or an ovary. ongoing research on the molecular phylogenetics of living plants appears to show that the angiosperms are a sister clade to the gymnosperms. = = plant physiology = = plant physiology encompasses all the internal chemical and physical activities of plants associated with life. chemicals obtained from the air, soil and water form the basis of all plant metabolism. the energy of sunlight, captured by oxygenic photosynthesis and released by cellular respiration, is the basis of almost all life. photoautotrophs, including all green plants, algae and cyanobacteria gather energy directly from sunlight by photosynthesis. heterotrophs including all animals, all fungi, all completely parasitic plants, and non - photosynthetic bacteria take in organic molecules produced by photoautotrophs and respire them or use them in the construction of cells and tissues. respiration is the oxidation of carbon compounds by breaking them down into simpler structures to release the energy they contain, essentially the opposite of photosynthesis. molecules are moved within plants by transport processes that operate at a variety of spatial scales. subcellular transport of ions, electrons and molecules such as water and enzymes occurs across cell membranes. minerals and water are transported from roots to other parts of the plant in the transpiration stream. diffusion, osmosis, and active transport and mass flow are all different ways transport can occur. examples of elements that plants need to transport are nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. in vascular plants, these elements are extracted from the soil as soluble ions by the roots and transported throughout the plant in the xylem. most of the elements required for plant nutrition come from the chemical breakdown of soil minerals. sucrose produced by photosynthesis is transported from the leaves to other parts of the plant in the phloem and plant hormones are transported by a variety of processes. = = = plant hormones = = = plants are not passive, but respond to external signals such as light, touch, and injury by moving or growing towards or away from the stimulus, as appropriate. tangible evidence of touch sensitivity is the almost instantaneous collapse of leaflets of mimosa pudica, the insect traps of
the 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.
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.
an alternative explanation of 1 / f - noise in manganites is suggested and discussed
##idermal electronics mirror those of skin to allow them to perform in this same way. like skin, epidermal electronics are ultrathin ( h < 100 μm ), low - modulus ( e ≈70 kpa ), and lightweight ( < 10 mg / cm2 ), enabling them to conform to the skin without applying strain. conformal contact and proper adhesion enable the device to bend and stretch without delaminating, deforming or failing, thereby eliminating the challenges with conventional, bulky wearables, including measurement artifacts, hysteresis, and motion - induced irritation to the skin. with this inherent ability to take the shape of skin, epidermal electronics can accurately acquire data without altering the natural motion or behavior of skin. the thin, soft, flexible design of epidermal electronics resembles that of temporary tattoos laminated on the skin. essentially, these devices are " mechanically invisible " to the wearer. epidermal electronics devices may adhere to the skin via van der waals forces or elastomeric substrates. with only van der waals forces, an epidermal device has the same thermal mass per unit area ( 150 mj / cm2k ) as skin, when the skin ' s thickness is < 500 nm. along with van der waals forces, the low values of e and thickness are effective in maximizing adhesion because they prevent deformation - induced detachment due to tension or compression. introducing an elastomeric substrate can improve adhesion but will raise the thermal mass per unit area slightly. several materials have been studied to produce these skin - like properties, including photolithography patterned serpentine gold nanofilm and patterned doping of silicon nanomembranes. = = = foot - worn = = = smart shoes are an example of wearable technology that incorporate smart features into shoes. smart shoes often work with smartphone applications to support tasks cannot be done with standard footwear. the uses include vibrating of the smart phone to tell users when and where to turn to reach their destination via google maps or self - lacing. self - lacing sneaker technology, similar to the nike mag in back to the future part ii, is another use of the smart shoe. in 2019 german footwear company puma was recognized as one of the " 100 best inventions of 2019 " by time for its fi laceless shoe that uses micro - motors to adjust the fit from an iphone. nike also introduced a smart shoe in 2019 known as adapt bb. the shoe featured buttons on the
the motion and photon emission of electrons in a superlattice may be described as in an undulator. therefore, there is a close analogy between ballistic electrons in a superlattice and electrons in a free electron laser ( fel ). touching upon this analogy the intensity of photon emission in the ir region and the gain are calculated. it is shown that the amplification can be significant, reaching tens of percent.
an extended polya urn model with two colors, black and white, is studied with some slln and clt on the proportion of white balls.
Question: What are the only amphibians without legs?
A) crustaceans
B) newts
C) caecilians
D) porifera
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C) caecilians
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Context:
waste, and the deep biosphere of the earth ' s crust. bacteria also live in symbiotic and parasitic relationships with plants and animals. most bacteria have not been characterised, and only about 27 percent of the bacterial phyla have species that can be grown in the laboratory. archaea constitute the other domain of prokaryotic cells and were initially classified as bacteria, receiving the name archaebacteria ( in the archaebacteria kingdom ), a term that has fallen out of use. archaeal cells have unique properties separating them from the other two domains, bacteria and eukaryota. archaea are further divided into multiple recognized phyla. archaea and bacteria are generally similar in size and shape, although a few archaea have very different shapes, such as the flat and square cells of haloquadratum walsbyi. despite this morphological similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes, notably for the enzymes involved in transcription and translation. other aspects of archaeal biochemistry are unique, such as their reliance on ether lipids in their cell membranes, including archaeols. archaea use more energy sources than eukaryotes : these range from organic compounds, such as sugars, to ammonia, metal ions or even hydrogen gas. salt - tolerant archaea ( the haloarchaea ) use sunlight as an energy source, and other species of archaea fix carbon, but unlike plants and cyanobacteria, no known species of archaea does both. archaea reproduce asexually by binary fission, fragmentation, or budding ; unlike bacteria, no known species of archaea form endospores. the first observed archaea were extremophiles, living in extreme environments, such as hot springs and salt lakes with no other organisms. improved molecular detection tools led to the discovery of archaea in almost every habitat, including soil, oceans, and marshlands. archaea are particularly numerous in the oceans, and the archaea in plankton may be one of the most abundant groups of organisms on the planet. archaea are a major part of earth ' s life. they are part of the microbiota of all organisms. in the human microbiome, they are important in the gut, mouth, and on the skin. their morphological, metabolic, and geographical diversity permits them to play multiple ecological roles : carbon fixation ; nitrogen cycling ; organic compound turnover ; and maintaining microbial
##yotic microorganisms. typically a few micrometers in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. bacteria were among the first life forms to appear on earth, and are present in most of its habitats. bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep biosphere of the earth ' s crust. bacteria also live in symbiotic and parasitic relationships with plants and animals. most bacteria have not been characterised, and only about 27 percent of the bacterial phyla have species that can be grown in the laboratory. archaea constitute the other domain of prokaryotic cells and were initially classified as bacteria, receiving the name archaebacteria ( in the archaebacteria kingdom ), a term that has fallen out of use. archaeal cells have unique properties separating them from the other two domains, bacteria and eukaryota. archaea are further divided into multiple recognized phyla. archaea and bacteria are generally similar in size and shape, although a few archaea have very different shapes, such as the flat and square cells of haloquadratum walsbyi. despite this morphological similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes, notably for the enzymes involved in transcription and translation. other aspects of archaeal biochemistry are unique, such as their reliance on ether lipids in their cell membranes, including archaeols. archaea use more energy sources than eukaryotes : these range from organic compounds, such as sugars, to ammonia, metal ions or even hydrogen gas. salt - tolerant archaea ( the haloarchaea ) use sunlight as an energy source, and other species of archaea fix carbon, but unlike plants and cyanobacteria, no known species of archaea does both. archaea reproduce asexually by binary fission, fragmentation, or budding ; unlike bacteria, no known species of archaea form endospores. the first observed archaea were extremophiles, living in extreme environments, such as hot springs and salt lakes with no other organisms. improved molecular detection tools led to the discovery of archaea in almost every habitat, including soil, oceans, and marshlands. archaea are particularly numerous in the oceans, and the archaea in plankton may be one of the most abundant groups of organisms on the planet. archaea are a major part of earth ' s life.
prokaryotic cells and were initially classified as bacteria, receiving the name archaebacteria ( in the archaebacteria kingdom ), a term that has fallen out of use. archaeal cells have unique properties separating them from the other two domains, bacteria and eukaryota. archaea are further divided into multiple recognized phyla. archaea and bacteria are generally similar in size and shape, although a few archaea have very different shapes, such as the flat and square cells of haloquadratum walsbyi. despite this morphological similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes, notably for the enzymes involved in transcription and translation. other aspects of archaeal biochemistry are unique, such as their reliance on ether lipids in their cell membranes, including archaeols. archaea use more energy sources than eukaryotes : these range from organic compounds, such as sugars, to ammonia, metal ions or even hydrogen gas. salt - tolerant archaea ( the haloarchaea ) use sunlight as an energy source, and other species of archaea fix carbon, but unlike plants and cyanobacteria, no known species of archaea does both. archaea reproduce asexually by binary fission, fragmentation, or budding ; unlike bacteria, no known species of archaea form endospores. the first observed archaea were extremophiles, living in extreme environments, such as hot springs and salt lakes with no other organisms. improved molecular detection tools led to the discovery of archaea in almost every habitat, including soil, oceans, and marshlands. archaea are particularly numerous in the oceans, and the archaea in plankton may be one of the most abundant groups of organisms on the planet. archaea are a major part of earth ' s life. they are part of the microbiota of all organisms. in the human microbiome, they are important in the gut, mouth, and on the skin. their morphological, metabolic, and geographical diversity permits them to play multiple ecological roles : carbon fixation ; nitrogen cycling ; organic compound turnover ; and maintaining microbial 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 mit
are further divided into multiple recognized phyla. archaea and bacteria are generally similar in size and shape, although a few archaea have very different shapes, such as the flat and square cells of haloquadratum walsbyi. despite this morphological similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes, notably for the enzymes involved in transcription and translation. other aspects of archaeal biochemistry are unique, such as their reliance on ether lipids in their cell membranes, including archaeols. archaea use more energy sources than eukaryotes : these range from organic compounds, such as sugars, to ammonia, metal ions or even hydrogen gas. salt - tolerant archaea ( the haloarchaea ) use sunlight as an energy source, and other species of archaea fix carbon, but unlike plants and cyanobacteria, no known species of archaea does both. archaea reproduce asexually by binary fission, fragmentation, or budding ; unlike bacteria, no known species of archaea form endospores. the first observed archaea were extremophiles, living in extreme environments, such as hot springs and salt lakes with no other organisms. improved molecular detection tools led to the discovery of archaea in almost every habitat, including soil, oceans, and marshlands. archaea are particularly numerous in the oceans, and the archaea in plankton may be one of the most abundant groups of organisms on the planet. archaea are a major part of earth ' s life. they are part of the microbiota of all organisms. in the human microbiome, they are important in the gut, mouth, and on the skin. their morphological, metabolic, and geographical diversity permits them to play multiple ecological roles : carbon fixation ; nitrogen cycling ; organic compound turnover ; and maintaining microbial symbiotic and syntrophic communities, for example. = = = eukaryotes = = = eukaryotes are hypothesized to have split from archaea, which was followed by their endosymbioses with bacteria ( or symbiogenesis ) that gave rise to mitochondria and chloroplasts, both of which are now part of modern - day eukaryotic cells. the major lineages of eukaryotes diversified in the precambrian about 1. 5 billion years ago and can be classified into eight major clades : alveolates,
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
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,
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 – 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
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
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 – 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 – which can dedifferentiate into a callus ( a mass of
. 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 – 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 – 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
Question: Plants, fungi, bacteria and archaea cells all have what feature that keeps them rigid that animal cells do not have?
A) cell membrane
B) plastids
C) cytoplasm
D) cell walls
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D) cell walls
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Context:
species occupying the same geographical area at the same time. a biological interaction is the effect that a pair of organisms living together in a community have on each other. they can be either of the same species ( intraspecific interactions ), or of different species ( interspecific interactions ). these effects may be short - term, like pollination and predation, or long - term ; both often strongly influence the evolution of the species involved. a long - term interaction is called a symbiosis. symbioses range from mutualism, beneficial to both partners, to competition, harmful to both partners. every species participates as a consumer, resource, or both in consumer – 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
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 — 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
, 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.
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 – 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
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 — 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
own self - division. in paracrine signaling, the ligand diffuses to nearby cells and affects them. for example, brain cells called neurons release ligands called neurotransmitters that diffuse across a synaptic cleft to bind with a receptor on an adjacent cell such as another neuron or muscle cell. in juxtacrine signaling, there is direct contact between the signaling and responding cells. finally, hormones are ligands that travel through the circulatory systems of animals or vascular systems of plants to reach their target cells. once a ligand binds with a receptor, it can influence the behavior of another cell, depending on the type of receptor. for instance, neurotransmitters that bind with an inotropic receptor can alter the excitability of a target cell. other types of receptors include protein kinase receptors ( e. g., receptor for the hormone insulin ) and g protein - coupled receptors. activation of g protein - coupled receptors can initiate second messenger cascades. the process by which a chemical or physical signal is transmitted through a cell as a series of molecular events is called signal transduction. = = = cell cycle = = = the cell cycle is a series of events that take place in a cell that cause it to divide into two daughter cells. these events include the duplication of its dna and some of its organelles, and the subsequent partitioning of its cytoplasm into two daughter cells in a process called cell division. in eukaryotes ( i. e., animal, plant, fungal, and protist cells ), there are two distinct types of cell division : mitosis and meiosis. mitosis is part of the cell cycle, in which replicated chromosomes are separated into two new nuclei. cell division gives rise to genetically identical cells in which the total number of chromosomes is maintained. in general, mitosis ( division of the nucleus ) is preceded by the s stage of interphase ( during which the dna is replicated ) and is often followed by telophase and cytokinesis ; which divides the cytoplasm, organelles and cell membrane of one cell into two new cells containing roughly equal shares of these cellular components. the different stages of mitosis all together define the mitotic phase of an animal cell cycle — 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
various charge pairings in strongly correlated electron systems are interpreted as quantum entanglement of a composite system. particles in the intermediate phase have a tendency to form the coherent superposition state of the localized state and the itinerant state, which induces the entanglement of both particles in the bipartite subsystems for increasing the entropy of the system. the correction to the entropic coulomb force becomes an immediate cause of charge pairing.
. species boundaries in plants may be weaker than in animals, and cross species hybrids are often possible. a familiar example is peppermint, mentha × 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
, 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 — 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
interventions lacked sufficient evidence to support either benefit or harm. in modern clinical practice, physicians and physician assistants personally assess patients to diagnose, prognose, treat, and prevent disease using clinical judgment. the doctor - patient relationship typically begins with an interaction with an examination of the patient ' s medical history and medical record, followed by a medical interview and a physical examination. basic diagnostic medical devices ( e. g., stethoscope, tongue depressor ) are typically used. after examining for signs and interviewing for symptoms, the doctor may order medical tests ( e. g., blood tests ), take a biopsy, or prescribe pharmaceutical drugs or other therapies. differential diagnosis methods help to rule out conditions based on the information provided. during the encounter, properly informing the patient of all relevant facts is an important part of the relationship and the development of trust. the medical encounter is then documented in the medical record, which is a legal document in many jurisdictions. follow - ups may be shorter but follow the same general procedure, and specialists follow a similar process. the diagnosis and treatment may take only a few minutes or a few weeks, depending on the complexity of the issue. the components of the medical interview and encounter are : chief complaint ( cc ) : the reason for the current medical visit. these are the symptoms. they are in the patient ' s own words and are recorded along with the duration of each one. also called chief concern or presenting complaint. current activity : occupation, hobbies, what the patient actually does. family history ( fh ) : listing of diseases in the family that may impact the patient. a family tree is sometimes used. history of present illness ( hpi ) : the chronological order of events of symptoms and further clarification of each symptom. distinguishable from history of previous illness, often called past medical history ( pmh ). medical history comprises hpi and pmh. medications ( rx ) : what drugs the patient takes including prescribed, over - the - counter, and home remedies, as well as alternative and herbal medicines or remedies. allergies are also recorded. past medical history ( pmh / pmhx ) : concurrent medical problems, past hospitalizations and operations, injuries, past infectious diseases or vaccinations, history of known allergies. review of systems ( ros ) or systems inquiry : a set of additional questions to ask, which may be missed on hpi : a general enquiry ( have
Question: What type of interspecies relationship involves one party being actively harmed?
A) mosaicism
B) parasitism
C) symbiosis
D) mutualism
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B) parasitism
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Context:
the tests, assays, and procedures needed for providing the specific services. subspecialties include transfusion medicine, cellular pathology, clinical chemistry, hematology, clinical microbiology and clinical immunology. clinical neurophysiology is concerned with testing the physiology or function of the central and peripheral aspects of the nervous system. these kinds of tests can be divided into recordings of : ( 1 ) spontaneous or continuously running electrical activity, or ( 2 ) stimulus evoked responses. subspecialties include electroencephalography, electromyography, evoked potential, nerve conduction study and polysomnography. sometimes these tests are performed by techs without a medical degree, but the interpretation of these tests is done by a medical professional. diagnostic radiology is concerned with imaging of the body, e. g. by x - rays, x - ray computed tomography, ultrasonography, and nuclear magnetic resonance tomography. interventional radiologists can access areas in the body under imaging for an intervention or diagnostic sampling. nuclear medicine is concerned with studying human organ systems by administering radiolabelled substances ( radiopharmaceuticals ) to the body, which can then be imaged outside the body by a gamma camera or a pet scanner. each radiopharmaceutical consists of two parts : a tracer that is specific for the function under study ( e. g., neurotransmitter pathway, metabolic pathway, blood flow, or other ), and a radionuclide ( usually either a gamma - emitter or a positron emitter ). there is a degree of overlap between nuclear medicine and radiology, as evidenced by the emergence of combined devices such as the pet / ct scanner. pathology as a medical specialty is the branch of medicine that deals with the study of diseases and the morphologic, physiologic changes produced by them. as a diagnostic specialty, pathology can be considered the basis of modern scientific medical knowledge and plays a large role in evidence - based medicine. many modern molecular tests such as flow cytometry, polymerase chain reaction ( pcr ), immunohistochemistry, cytogenetics, gene rearrangements studies and fluorescent in situ hybridization ( fish ) fall within the territory of pathology. = = = = other major specialties = = = = the following are some major medical specialties that do not directly fit into any of the above - mentioned groups : anesthesiology ( also
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
the nervous system. these kinds of tests can be divided into recordings of : ( 1 ) spontaneous or continuously running electrical activity, or ( 2 ) stimulus evoked responses. subspecialties include electroencephalography, electromyography, evoked potential, nerve conduction study and polysomnography. sometimes these tests are performed by techs without a medical degree, but the interpretation of these tests is done by a medical professional. diagnostic radiology is concerned with imaging of the body, e. g. by x - rays, x - ray computed tomography, ultrasonography, and nuclear magnetic resonance tomography. interventional radiologists can access areas in the body under imaging for an intervention or diagnostic sampling. nuclear medicine is concerned with studying human organ systems by administering radiolabelled substances ( radiopharmaceuticals ) to the body, which can then be imaged outside the body by a gamma camera or a pet scanner. each radiopharmaceutical consists of two parts : a tracer that is specific for the function under study ( e. g., neurotransmitter pathway, metabolic pathway, blood flow, or other ), and a radionuclide ( usually either a gamma - emitter or a positron emitter ). there is a degree of overlap between nuclear medicine and radiology, as evidenced by the emergence of combined devices such as the pet / ct scanner. pathology as a medical specialty is the branch of medicine that deals with the study of diseases and the morphologic, physiologic changes produced by them. as a diagnostic specialty, pathology can be considered the basis of modern scientific medical knowledge and plays a large role in evidence - based medicine. many modern molecular tests such as flow cytometry, polymerase chain reaction ( pcr ), immunohistochemistry, cytogenetics, gene rearrangements studies and fluorescent in situ hybridization ( fish ) fall within the territory of pathology. = = = = other major specialties = = = = the following are some major medical specialties that do not directly fit into any of the above - mentioned groups : anesthesiology ( also known as anaesthetics ) : concerned with the perioperative management of the surgical patient. the anesthesiologist ' s role during surgery is to prevent derangement in the vital organs ' ( i. e. brain, heart, kidneys ) functions and postoperative pain. outside of
cross - fertilization that takes place among the various fields. psychology differs from biology and neuroscience in that it is primarily concerned with the interaction of mental processes and behaviour, and of the overall processes of a system, and not simply the biological or neural processes themselves, though the subfield of neuropsychology combines the study of the actual neural processes with the study of the mental effects they have subjectively produced. many people associate psychology with clinical psychology, which focuses on assessment and treatment of problems in living and psychopathology. in reality, psychology has myriad specialties including social psychology, developmental psychology, cognitive psychology, educational psychology, industrial - organizational psychology, mathematical psychology, neuropsychology, and quantitative analysis of behaviour. psychology is a very broad science that is rarely tackled as a whole, major block. although some subfields encompass a natural science base and a social science application, others can be clearly distinguished as having little to do with the social sciences or having a lot to do with the social sciences. for example, biological psychology is considered a natural science with a social scientific application ( as is clinical medicine ), social and occupational psychology are, generally speaking, purely social sciences, whereas neuropsychology is a natural science that lacks application out of the scientific tradition entirely. in british universities, emphasis on what tenet of psychology a student has studied and / or concentrated is communicated through the degree conferred : bpsy indicates a balance between natural and social sciences, bsc indicates a strong ( or entire ) scientific concentration, whereas a ba underlines a majority of social science credits. this is not always necessarily the case however, and in many uk institutions students studying the bpsy, bsc, and ba follow the same curriculum as outlined by the british psychological society and have the same options of specialism open to them regardless of whether they choose a balance, a heavy science basis, or heavy social science basis to their degree. if they applied to read the ba. for example, but specialized in heavily science - based modules, then they will still generally be awarded the ba. = = = sociology = = = sociology is the systematic study of society, individuals ' relationship to their societies, the consequences of difference, and other aspects of human social action. the meaning of the word comes from the suffix - logy, which means " study of ", derived from ancient greek, and the stem soci -, which is from the latin word socius, meaning " companion ", or society in general. auguste comte ( 1798 – 1857 ) coined
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
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
practice, general practice or primary care is, in many countries, the first port - of - call for patients with non - emergency medical problems. family physicians often provide services across a broad range of settings including office based practices, emergency department coverage, inpatient care, and nursing home care. medical genetics is concerned with the diagnosis and management of hereditary disorders. neurology is concerned with diseases of the nervous system. in the uk, neurology is a subspecialty of general medicine. obstetrics and gynecology ( often abbreviated as ob / gyn ( american english ) or obs & gynae ( british english ) ) are concerned respectively with childbirth and the female reproductive and associated organs. reproductive medicine and fertility medicine are generally practiced by gynecological specialists. pediatrics ( ae ) or paediatrics ( be ) is devoted to the care of infants, children, and adolescents. like internal medicine, there are many pediatric subspecialties for specific age ranges, organ systems, disease classes, and sites of care delivery. pharmaceutical medicine is the medical scientific discipline concerned with the discovery, development, evaluation, registration, monitoring and medical aspects of marketing of medicines for the benefit of patients and public health. physical medicine and rehabilitation ( or physiatry ) is concerned with functional improvement after injury, illness, or congenital disorders. podiatric medicine is the study of, diagnosis, and medical and surgical treatment of disorders of the foot, ankle, lower limb, hip and lower back. preventive medicine is the branch of medicine concerned with preventing disease. community health or public health is an aspect of health services concerned with threats to the overall health of a community based on population health analysis. psychiatry is the branch of medicine concerned with the bio - psycho - social study of the etiology, diagnosis, treatment and prevention of cognitive, perceptual, emotional and behavioral disorders. related fields include psychotherapy and clinical psychology. = = = interdisciplinary fields = = = some interdisciplinary sub - specialties of medicine include : addiction medicine deals with the treatment of addiction. aerospace medicine deals with medical problems related to flying and space travel. biomedical engineering is a field dealing with the application of engineering principles to medical practice. clinical pharmacology is concerned with how systems of therapeutics interact with patients. conservation medicine studies the relationship between human and non - human animal health, and environmental conditions. also known as ecological medicine, environmental medicine, or medical geology. disaster medicine deals with medical aspects of emergency preparedness, disaster mitigation
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
decision making during a task, and they provide us with some insight into the ways in which those decisions may be processed. = = = brain imaging = = = brain imaging involves analyzing activity within the brain while performing various tasks. this allows us to link behavior and brain function to help understand how information is processed. different types of imaging techniques vary in their temporal ( time - based ) and spatial ( location - based ) resolution. brain imaging is often used in cognitive neuroscience. single - photon emission computed tomography and positron emission tomography. spect and pet use radioactive isotopes, which are injected into the subject ' s bloodstream and taken up by the brain. by observing which areas of the brain take up the radioactive isotope, we can see which areas of the brain are more active than other areas. pet has similar spatial resolution to fmri, but it has extremely poor temporal resolution. electroencephalography. eeg measures the electrical fields generated by large populations of neurons in the cortex by placing a series of electrodes on the scalp of the subject. this technique has an extremely high temporal resolution, but a relatively poor spatial resolution. functional magnetic resonance imaging. fmri measures the relative amount of oxygenated blood flowing to different parts of the brain. more oxygenated blood in a particular region is assumed to correlate with an increase in neural activity in that part of the brain. this allows us to localize particular functions within different brain regions. fmri has moderate spatial and temporal resolution. optical imaging. this technique uses infrared transmitters and receivers to measure the amount of light reflectance by blood near different areas of the brain. since oxygenated and deoxygenated blood reflects light by different amounts, we can study which areas are more active ( i. e., those that have more oxygenated blood ). optical imaging has moderate temporal resolution, but poor spatial resolution. it also has the advantage that it is extremely safe and can be used to study infants ' brains. magnetoencephalography. meg measures magnetic fields resulting from cortical activity. it is similar to eeg, except that it has improved spatial resolution since the magnetic fields it measures are not as blurred or attenuated by the scalp, meninges and so forth as the electrical activity measured in eeg is. meg uses squid sensors to detect tiny magnetic fields. = = = computational modeling = = = computational models require a mathematically and logically formal representation of a problem. computer models are used in the simulation and experimental verification of different
industrial - organizational psychology, mathematical psychology, neuropsychology, and quantitative analysis of behaviour. psychology is a very broad science that is rarely tackled as a whole, major block. although some subfields encompass a natural science base and a social science application, others can be clearly distinguished as having little to do with the social sciences or having a lot to do with the social sciences. for example, biological psychology is considered a natural science with a social scientific application ( as is clinical medicine ), social and occupational psychology are, generally speaking, purely social sciences, whereas neuropsychology is a natural science that lacks application out of the scientific tradition entirely. in british universities, emphasis on what tenet of psychology a student has studied and / or concentrated is communicated through the degree conferred : bpsy indicates a balance between natural and social sciences, bsc indicates a strong ( or entire ) scientific concentration, whereas a ba underlines a majority of social science credits. this is not always necessarily the case however, and in many uk institutions students studying the bpsy, bsc, and ba follow the same curriculum as outlined by the british psychological society and have the same options of specialism open to them regardless of whether they choose a balance, a heavy science basis, or heavy social science basis to their degree. if they applied to read the ba. for example, but specialized in heavily science - based modules, then they will still generally be awarded the ba. = = = sociology = = = sociology is the systematic study of society, individuals ' relationship to their societies, the consequences of difference, and other aspects of human social action. the meaning of the word comes from the suffix - logy, which means " study of ", derived from ancient greek, and the stem soci -, which is from the latin word socius, meaning " companion ", or society in general. auguste comte ( 1798 – 1857 ) coined the term sociology to describe a way to apply natural science principles and techniques to the social world in 1838. comte endeavoured to unify history, psychology and economics through the descriptive understanding of the social realm. he proposed that social ills could be remedied through sociological positivism, an epistemological approach outlined in the course in positive philosophy [ 1830 – 1842 ] and a general view of positivism ( 1844 ). though comte is generally regarded as the " father of sociology ", the discipline was formally established by another french thinker, emile durkheim ( 1858 – 1917 ), who developed positivism as
Question: Which nervous system consists of all the nervous tissue that lies outside the central nervous system?
A) auxiliary nervous system
B) significant nervous system
C) function nervous system
D) peripheral nervous system
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D) peripheral nervous system
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Context:
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 °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
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 — 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 – to form
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
##ply quickly, relatively easy to transform and can be stored at - 80 °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.
in star wars episode v, we see luke skywalker being repaired by a surgical robot. in the context of the movie, this doesn ' t seem surprising or disturbing. after all, it is a long, long time ago, in a galaxy far, far away. it would never happen here. or could it? would we accept a robot as our doctor, our surgeon, or our in - home care specialist? imagine walking into an operating room and no one was there. you are instructed to lie down on the operating table, and the or system takes over. would you feel comfortable with this possible future world?
their mechanical properties. = = tissue culture = = in many cases, creation of functional tissues and biological structures in vitro requires extensive culturing to promote survival, growth and inducement of functionality. in general, the basic requirements of cells must be maintained in culture, which include oxygen, ph, humidity, temperature, nutrients and osmotic pressure maintenance. tissue engineered cultures also present additional problems in maintaining culture conditions. in standard cell culture, diffusion is often the sole means of nutrient and metabolite transport. however, as a culture becomes larger and more complex, such as the case with engineered organs and whole tissues, other mechanisms must be employed to maintain the culture, such as the creation of capillary networks within the tissue. another issue with tissue culture is introducing the proper factors or stimuli required to induce functionality. in many cases, simple maintenance culture is not sufficient. growth factors, hormones, specific metabolites or nutrients, chemical and physical stimuli are sometimes required. for example, certain cells respond to changes in oxygen tension as part of their normal development, such as chondrocytes, which must adapt to low oxygen conditions or hypoxia during skeletal development. others, such as endothelial cells, respond to shear stress from fluid flow, which is encountered in blood vessels. mechanical stimuli, such as pressure pulses seem to be beneficial to all kind of cardiovascular tissue such as heart valves, blood vessels or pericardium. = = = bioreactors = = = in tissue engineering, a bioreactor is a device that attempts to simulate a physiological environment in order to promote cell or tissue growth in vitro. a physiological environment can consist of many different parameters such as temperature, pressure, oxygen or carbon dioxide concentration, or osmolality of fluid environment, and it can extend to all kinds of biological, chemical or mechanical stimuli. therefore, there are systems that may include the application of forces such as electromagnetic forces, mechanical pressures, or fluid pressures to the tissue. these systems can be two - or three - dimensional setups. bioreactors can be used in both academic and industry applications. general - use and application - specific bioreactors are also commercially available, which may provide static chemical stimulation or a combination of chemical and mechanical stimulation. cell proliferation and differentiation are largely influenced by mechanical and biochemical cues in the surrounding extracellular matrix environment. bioreactors are typically developed to replicate the specific physiological environment of the tissue being grown ( e. g., flex and fluid shearing for heart tissue growth ). this can
the 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 — 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
techniques that provide heart and lung support. it is used primarily to support the lungs for a prolonged but still temporary timeframe ( 1 – 30 days ) and allow for recovery from reversible diseases. robert bartlett is known as the father of ecmo and performed the first treatment of a newborn using an ecmo machine in 1975. skin tissue - engineered skin is a type of bioartificial organ that is often used to treat burns, diabetic foot ulcers, or other large wounds that cannot heal well on their own. artificial skin can be made from autografts, allografts, and xenografts. autografted skin comes from a patient ' s own skin, which allows the dermis to have a faster healing rate, and the donor site can be re - harvested a few times. allograft skin often comes from cadaver skin and is mostly used to treat burn victims. lastly, xenografted skin comes from animals and provides a temporary healing structure for the skin. they assist in dermal regeneration, but cannot become part of the host skin. tissue - engineered skin is now available in commercial products. integra, originally used to only treat burns, consists of a collagen matrix and chondroitin sulfate that can be used as a skin replacement. the chondroitin sulfate functions as a component of proteoglycans, which helps to form the extracellular matrix. integra can be repopulated and revascularized while maintaining its dermal collagen architecture, making it a bioartificial organ dermagraft, another commercial - made tissue - engineered skin product, is made out of living fibroblasts. these fibroblasts proliferate and produce growth factors, collagen, and ecm proteins, that help build granulation tissue. = = = = heart = = = = since the number of patients awaiting a heart transplant is continuously increasing over time, and the number of patients on the waiting list surpasses the organ availability, artificial organs used as replacement therapy for terminal heart failure would help alleviate this difficulty. artificial hearts are usually used to bridge the heart transplantation or can be applied as replacement therapy for terminal heart malfunction. the total artificial heart ( tah ), first introduced by dr. vladimir p. demikhov in 1937, emerged as an ideal alternative. since then it has been developed and improved as a mechanical pump that provides long - term circulatory support and
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 °c ( 4. 5 °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
tissue engineering is a biomedical engineering discipline that uses a combination of cells, engineering, materials methods, and suitable biochemical and physicochemical factors to restore, maintain, improve, or replace different types of biological tissues. tissue engineering often involves the use of cells placed on tissue scaffolds in the formation of new viable tissue for a medical purpose, but is not limited to applications involving cells and tissue scaffolds. while it was once categorized as a sub - field of biomaterials, having grown in scope and importance, it can be considered as a field of its own. while most definitions of tissue engineering cover a broad range of applications, in practice, the term is closely associated with applications that repair or replace portions of or whole tissues ( i. e. organs, bone, cartilage, blood vessels, bladder, skin, muscle etc. ). often, the tissues involved require certain mechanical and structural properties for proper functioning. the term has also been applied to efforts to perform specific biochemical functions using cells within an artificially - created support system ( e. g. an artificial pancreas, or a bio artificial liver ). the term regenerative medicine is often used synonymously with tissue engineering, although those involved in regenerative medicine place more emphasis on the use of stem cells or progenitor cells to produce tissues. = = overview = = a commonly applied definition of tissue engineering, as stated by langer and vacanti, is " an interdisciplinary field that applies the principles of engineering and life sciences toward the development of biological substitutes that restore, maintain, or improve [ biological tissue ] function or a whole organ ". in addition, langer and vacanti also state that there are three main types of tissue engineering : cells, tissue - inducing substances, and a cells + matrix approach ( often referred to as a scaffold ). tissue engineering has also been defined as " understanding the principles of tissue growth, and applying this to produce functional replacement tissue for clinical use ". a further description goes on to say that an " underlying supposition of tissue engineering is that the employment of natural biology of the system will allow for greater success in developing therapeutic strategies aimed at the replacement, repair, maintenance, or enhancement of tissue function ". developments in the multidisciplinary field of tissue engineering have yielded a novel set of tissue replacement parts and implementation strategies. scientific advances in biomaterials, stem cells, growth and differentiation factors, and biomimetic environments have created unique opportunities to fabric
Question: What do organisms use to grow and repair themselves?
A) mutation
B) diffusion
C) cell solution
D) cell division
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D) cell division
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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
also called pain medicine, or algiatry ) is the medical discipline concerned with the relief of pain. pharmacogenomics is a form of individualized medicine. podiatric medicine is the study of, diagnosis, and medical treatment of disorders of the foot, ankle, lower limb, hip and lower back. sexual medicine is concerned with diagnosing, assessing and treating all disorders related to sexuality. sports medicine deals with the treatment and prevention and rehabilitation of sports / exercise injuries such as muscle spasms, muscle tears, injuries to ligaments ( ligament tears or ruptures ) and their repair in athletes, amateur and professional. therapeutics is the field, more commonly referenced in earlier periods of history, of the various remedies that can be used to treat disease and promote health. travel medicine or emporiatrics deals with health problems of international travelers or travelers across highly different environments. tropical medicine deals with the prevention and treatment of tropical diseases. it is studied separately in temperate climates where those diseases are quite unfamiliar to medical practitioners and their local clinical needs. urgent care focuses on delivery of unscheduled, walk - in care outside of the hospital emergency department for injuries and illnesses that are not severe enough to require care in an emergency department. in some jurisdictions this function is combined with the emergency department. veterinary medicine ; veterinarians apply similar techniques as physicians to the care of non - human animals. wilderness medicine entails the practice of medicine in the wild, where conventional medical facilities may not be available. = = education and legal controls = = medical education and training varies around the world. it typically involves entry level education at a university medical school, followed by a period of supervised practice or internship, or residency. this can be followed by postgraduate vocational training. a variety of teaching methods have been employed in medical education, still itself a focus of active research. in canada and the united states of america, a doctor of medicine degree, often abbreviated m. d., or a doctor of osteopathic medicine degree, often abbreviated as d. o. and unique to the united states, must be completed in and delivered from a recognized university. since knowledge, techniques, and medical technology continue to evolve at a rapid rate, many regulatory authorities require continuing medical education. medical practitioners upgrade their knowledge in various ways, including medical journals, seminars, conferences, and online programs. a database of objectives covering medical knowledge, as suggested by national societies across the united states, can be searched at http : / / data. medobjectives
, 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
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,
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
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 america, a doctor of medicine degree, often abbreviated m. d., or a doctor of osteopathic medicine degree, often abbreviated as d. o. and unique to the united states, must be completed in and delivered from a recognized university. since knowledge, techniques, and medical technology continue to evolve at a
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 – 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
, 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 – 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
the clinical symptoms of pulmonary embolism ( pe ) are very diverse and non - specific, which makes it difficult to diagnose. in addition, pulmonary embolism has multiple triggers and is one of the major causes of vascular death. therefore, if it can be detected and treated quickly, it can significantly reduce the risk of death in hospitalized patients. in the detection process, the cost of computed tomography pulmonary angiography ( ctpa ) is high, and angiography requires the injection of contrast agents, which increase the risk of damage to the patient. therefore, this study will use a deep learning approach to detect pulmonary embolism in all patients who take a ct image of the chest using a convolutional neural network. with the proposed pulmonary embolism detection system, we can detect the possibility of pulmonary embolism at the same time as the patient ' s first ct image, and schedule the ctpa test immediately, saving more than a week of ct image screening time and providing timely diagnosis and treatment to the patient.
Question: The afferent arterioles service about 1.3 million of what in each kidney?
A) neurons
B) dendrites
C) axons
D) nephrons
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D) nephrons
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Context:
the thickness of freshly made soap films is usually in the micron range, and interference colors make thickness fluctuations easily visible. circular patterns of constant thickness are commonly observed, either a thin film disc in a thicker film or the reverse. in this letter, we evidence the line tension at the origin of these circular patterns. using a well controlled soap film preparation, we produce a piece of thin film surrounded by a thicker film. the thickness profile, measured with a spectral camera, leads to a line tension of the order of 0. 1 nn which drives the relaxation of the thin film shape, initially very elongated, toward a circular shape. a balance between line tension and air friction leads to a quantitative prediction of the relaxation process. such a line tension is expected to play a role in the production of marginal regeneration patches, involved in soap film drainage and stability.
also called pain medicine, or algiatry ) is the medical discipline concerned with the relief of pain. pharmacogenomics is a form of individualized medicine. podiatric medicine is the study of, diagnosis, and medical treatment of disorders of the foot, ankle, lower limb, hip and lower back. sexual medicine is concerned with diagnosing, assessing and treating all disorders related to sexuality. sports medicine deals with the treatment and prevention and rehabilitation of sports / exercise injuries such as muscle spasms, muscle tears, injuries to ligaments ( ligament tears or ruptures ) and their repair in athletes, amateur and professional. therapeutics is the field, more commonly referenced in earlier periods of history, of the various remedies that can be used to treat disease and promote health. travel medicine or emporiatrics deals with health problems of international travelers or travelers across highly different environments. tropical medicine deals with the prevention and treatment of tropical diseases. it is studied separately in temperate climates where those diseases are quite unfamiliar to medical practitioners and their local clinical needs. urgent care focuses on delivery of unscheduled, walk - in care outside of the hospital emergency department for injuries and illnesses that are not severe enough to require care in an emergency department. in some jurisdictions this function is combined with the emergency department. veterinary medicine ; veterinarians apply similar techniques as physicians to the care of non - human animals. wilderness medicine entails the practice of medicine in the wild, where conventional medical facilities may not be available. = = education and legal controls = = medical education and training varies around the world. it typically involves entry level education at a university medical school, followed by a period of supervised practice or internship, or residency. this can be followed by postgraduate vocational training. a variety of teaching methods have been employed in medical education, still itself a focus of active research. in canada and the united states of america, a doctor of medicine degree, often abbreviated m. d., or a doctor of osteopathic medicine degree, often abbreviated as d. o. and unique to the united states, must be completed in and delivered from a recognized university. since knowledge, techniques, and medical technology continue to evolve at a rapid rate, many regulatory authorities require continuing medical education. medical practitioners upgrade their knowledge in various ways, including medical journals, seminars, conferences, and online programs. a database of objectives covering medical knowledge, as suggested by national societies across the united states, can be searched at http : / / data. medobjectives
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.
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 ),
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,
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 – civil works program river morphology and stream restoration references
static black holes in two - dimensional string theory can carry tachyon hair. configurations which are non - singular at the event horizon have non - vanishing asymptotic energy density. such solutions can be smoothly extended through the event horizon and have non - vanishing energy flux emerging from the past singularity. dynamical processes will not change the amount of tachyon hair on a black hole. in particular, there will be no tachyon hair on a black hole formed in gravitational collapse if the initial geometry is the linear dilaton vacuum. there also exist static solutions with finite total energy, which have singular event horizons. simple dynamical arguments suggest that black holes formed in gravitational collapse will not have tachyon hair of this type.
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
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 america, a doctor of medicine degree, often abbreviated m. d., or a doctor of osteopathic medicine degree, often abbreviated as d. o. and unique to the united states, must be completed in and delivered from a recognized university. since knowledge, techniques, and medical technology continue to evolve at a
manifold of dimension two ( see § topological surface ). a differentiable surface is a surfaces that is a differentiable manifold ( see § 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 § 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
Question: Kyphosis, lordosis, and scoliosis are all diseases involving improper curvature of which bodily structure (which is supposed to be curved in a certain way anyway)?
A) spine
B) aorta
C) lungs
D) femur
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A) spine
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