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Curvature invariant In Riemannian geometry and pseudo-Riemannian geometry, curvature invariants are scalar quantities constructed from tensors that represent curvature. These tensors are usually the Riemann tensor, the Weyl tensor, the Ricci tensor and tensors formed from these by the operations of taking dual contractions and covariant differentiations. The invariants most often considered are "polynomial invariants". These are polynomials constructed from contractions such as traces. Second degree examples are called "quadratic invariants", and so forth. Invariants constructed using covariant derivatives up to order n are called n-th order "differential invariants". The Riemann tensor is a multilinear operator of fourth rank acting on tangent vectors. However, it can also be considered a linear operator acting on bivectors, and as such it has a characteristic polynomial, whose coefficients and roots (eigenvalues) are polynomial scalar invariants. In metric theories of gravitation such as general relativity, curvature scalars play an important role in telling distinct spacetimes apart. Two of the most basic curvature invariants in general relativity are the Kretschmann scalar and the "Chern–Pontryagin scalar",
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Photon diffusion is a situation where photons travel through a material without being absorbed, but rather undergoing repeated scattering events which change the direction of their path. The path of any given photon is then effectively a random walk. A large ensemble of such photons can be said to exhibit diffusion in the material, and can be described with a diffusion equation. In astrophysics, photon diffusion occurs inside a stellar atmosphere. To describe this phenomenon, one should develop the transfer equation in moments and use the Eddington approximation to radiative transfer (i.e. the diffusion approximation). In 3D the results are two equations for the photon energy flux: where formula_3 is the opacity. By substituting the first equation into the second, one obtains the diffusion equation for the photon energy density: In medicine, the diffusion of photons can be used to create images of the body (mainly brain and breast) and has contributed much to the advance of certain fields of research, such as neuroscience. This technique is known as diffuse optical imaging.
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Reverse diffusion refers to a situation where the transport of particles (atoms or molecules) in a medium occurs towards regions of higher concentration gradients, opposite to that observed during diffusion. This phenomenon occurs during phase separation and is described by the Cahn–Hilliard equation. also refers to when water is forced from a region of lower concentration to high. It can occur in osmosis.
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Drag count A drag count is a dimensionless unit used by aerospace engineers where 1 drag count is equal to a formula_1 of 0.0001. A drag count formula_2 is defined as: where: The drag coefficient is used to compare the solutions of different geometries by means of a dimensionless number. A drag count is used as a more user-friendly measurement as the coefficient of drag is usually much less than 1. A drag count of 200 to 400 is typical for an airplane at cruise. A reduction of one drag count on a subsonic civil transport airplane means about more in payload.
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Level-spacing distribution In mathematical physics, level spacing is the difference between consecutive elements in some set of real numbers. In particular, it is the difference between consecutive energy levels or eigenvalues of a matrix or linear operator.
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Polyphenism A polyphenic trait is a trait for which multiple, discrete phenotypes can arise from a single genotype as a result of differing environmental conditions. It is therefore a special case of phenotypic plasticity. There are several types of polyphenism in animals, from having sex determined by the environment to the castes of honey bees and other social insects. Some polyphenisms are seasonal, as in some butterflies which have different patterns during the year, and some Arctic animals like the snowshoe hare and Arctic fox, which are white in winter. Other animals have predator-induced or resource polyphenisms, allowing them to exploit variations in their environment. Some nematode worms can develop either into adults or into resting dauer larvae according to resource availability. A polyphenism is a biological mechanism that causes a trait to be polyphenic. For example, crocodiles possess a temperature-dependent sex determining polyphenism, where sex is the trait influenced by variations in nest temperature. When polyphenic forms exist at the same time in the same panmictic (interbreeding) population they can be compared to genetic polymorphism. With polyphenism, the switch between morphs is environmental, but with genetic polymorphism the determination of morph is genetic. These two cases have in common that more than one morph is part of the population at any one time. This is rather different from cases where one morph predictably follows another during, for instance, the course of a year
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Polyphenism In essence the latter is normal ontogeny where young forms can and do have different forms, colours and habits to adults. The discrete nature of polyphenic traits differentiates them from traits like weight and height, which are also dependent on environmental conditions but vary continuously across a spectrum. When a polyphenism is present, an environmental cue causes the organism to develop along a separate pathway, resulting in distinct morphologies; thus, the response to the environmental cue is “all or nothing.” The nature of these environmental conditions varies greatly, and includes seasonal cues like temperature and moisture, pheromonal cues, kairomonal cues (signals released from one species that can be recognized by another), and nutritional cues. Sex-determining polyphenisms allow a species to benefit from sexual reproduction while permitting an unequal gender ratio. This can be beneficial to a species because a large female-to-male ratio maximizes reproductive capacity. However, temperature-dependent sex determination (as seen in crocodiles) limits the range in which a species can exist, and makes the species susceptible to endangerment by changes in weather pattern. Temperature-dependent sex determination has been proposed as an explanation for the extinction of the dinosaurs. Population-dependent and reversible sex determination, found in animals such as the blue wrasse fish, have less potential for failure
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Polyphenism In the blue wrasse, only one male is found in a given territory: larvae within the territory develop into females, and adult males will not enter the same territory. If a male dies, one of the females in his territory becomes male, replacing him. While this system ensures that there will always be a mating couple when two animals of the same species are present, it could potentially decrease genetic variance in a population, for example if the females remain in a single male's territory. The caste system of insects enables eusociality, the division of labor between non-breeding and breeding individuals. A series of polyphenisms determines whether larvae develop into queens, workers, and, in some cases soldiers. In the case of the ant, "P. morrisi", an embryo must develop under certain temperature and photoperiod conditions in order to become a reproductively-active queen. This allows for control of the mating season but, like sex determination, limits the spread of the species into certain climates. In bees, royal jelly provided by worker bees causes a developing larva to become a queen. Royal jelly is only produced when the queen is aging or has died. This system is less subject to influence by environmental conditions, yet prevents unnecessary production of queens. Polyphenic pigmentation is adaptive for insect species that undergo multiple mating seasons each year. Different pigmentation patterns provide appropriate camouflage throughout the seasons, as well as alter heat retention as temperatures change
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Polyphenism Because insects cease growth and development after eclosion, their pigment pattern is invariable in adulthood: thus, a polyphenic pigment adaptation would be less valuable for species whose adult form survives longer than one year. Birds and mammals are capable of continued physiological changes in adulthood, and some display reversible seasonal polyphenisms, such as in the Arctic fox, which becomes all white in winter as snow camouflage. Predator-induced polyphenisms allow the species to develop in a more reproductively-successful way in a predator's absence, but to otherwise assume a more defensible morphology. However, this can fail if the predator evolves to stop producing the kairomone to which the prey responds. For example, the fly larvae that feed on "Daphnia cucullata" (a water flea) release a kairomone that "Daphnia" can detect. When the fly larvae are present, "Daphnia" grow large helmets that protect them from being eaten. However, when the predator is absent, "Daphnia" have smaller heads and are therefore more agile swimmers. Organisms with resource polyphenisms show alternative phenotypes that allow differential use of food or other resources. One example is the western spadefoot toad, which maximizes its reproductive capacity in temporary desert ponds. While the water is at a safe level, the tadpoles develop slowly on a diet of other opportunistic pond inhabitants
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Polyphenism However, when the water level is low and desiccation is imminent, the tadpoles develop a morphology (wide mouth, strong jaw) that permits them to cannibalize. Cannibalistic tadpoles receive better nutrition and thus metamorphose more quickly, avoiding death as the pond dries up. Among invertebrates, the nematode "Pristionchus pacificus" has one morph that primarily feeds on bacteria and a second morph that produces large teeth, enabling it to feed on other nematodes, including competitors for bacterial food. In this species, cues of starvation and crowding by other nematodes, as sensed by pheromones, trigger a hormonal signal that ultimately activates a developmental switch gene that specifies formation of the predatory morph. Density-dependent polyphenism allows species to show a different phenotype based on the population density in which it was reared. In Lepidoptera, African armyworm larvae exhibit one of two appearances: the gregarious or solitary phase. Under crowded or "gregarious" conditions, the larvae have black bodies and yellow stripes along their bodies. However, under solitary conditions, they have green bodies with a brown stripe down their backs. The different phenotypes emerge during the third instar and remain until the last instar. Under conditions of stress such as crowding and high temperature, L2 larvae of some free living nematodes such as "Caenorhabditis elegans" can switch development to the so-called dauer larva state, instead of going the normal molts into a reproductive adult
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Polyphenism These dauer larvae are a stress-resistant, non-feeding, long-lived stage, enabling the animals to survive harsh conditions. On return to favorable conditions, the animal resumes reproductive development from L3 stage onwards. A mechanism has been proposed for the evolutionary development of polyphenisms: Evolution of novel polyphenisms through this mechanism has been demonstrated in the laboratory. Suzuki and Nijhout used an existing mutation ("black") in a monophenic green hornworm ("Manduca sexta") that causes a black phenotype. They found that if larvae from an existing population of "black" mutants were raised at 20˚C, then all the final instar larvae were black; but if the larvae were instead raised at 28˚C, the final instar larvae ranged in color from black to green. By selecting for larvae that were black if raised at 20˚C but green if raised at 28˚C, they produced a polyphenic strain after thirteen generations. This fits the model described above because a new mutation (black) was required to reveal pre-existing genetic variation and to permit selection. Furthermore, the production of a polyphenic strain was only possible because of background variation within the species: two alleles, one temperature-sensitive and one stable, were present for a single gene upstream of "black" (in the pigment production pathway) before selection occurred. The temperature-sensitive allele was not observable because at high temperatures, it caused an increase in green pigment in hornworms that were already bright green
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Polyphenism However, introduction of the black mutant caused the temperature-dependent changes in pigment production to become obvious. The researchers could then select for larvae with the temperature-sensitive allele, resulting in a polyphenism.
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SHEEP (symbolic computation system) SHEEP is one of the earliest interactive symbolic computation systems. It is specialized for computations with tensors, and was designed for the needs of researchers working with general relativity and other theories involving extensive tensor calculus computations. SHEEP is a freeware package (copyrighted, but free for educational and research use). The name "SHEEP" is pun on the Lisp Algebraic Manipulator or "LAM" on which SHEEP is based. The package was written by Inge Frick, using earlier work by Ian Cohen and Ray d'Inverno, who had written ALAM - Atlas LISP Algebraic Manipulation in earlier (designed in 1970). SHEEP was an interactive computer package whereas LAM and ALAM were batch processing languages. Jan E. Åman wrote an important package in SHEEP to carry out the Cartan-Karlhede algorithm. A more recent version of SHEEP, written by Jim Skea, runs under Cambridge Lisp, which is also used for REDUCE.
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Eos Chasma is a chasma in the southern part of the Valles Marineris canyon system of the Coprates quadrangle and the Margaritifer Sinus quadrangles of the planet Mars. Eos Chasma’s western floor is mainly composed of an etched massive material composed of either volcanic or eolian deposits later eroded by the Martian wind. The eastern end of the Eos chasma has a large area of streamlined bars and longitudinal striations. This is interpreted to be stream-carved plateau deposits and material transported and deposited by flowing fluid. Ganges Chasma is an offshoot of Eos Chasma. MRO discovered sulfate, hydrated sulfate, and iron oxides in Eos Chasma. According to an analysis by Vicky Hamilton of the University of Hawaii, may be the source of the ALH84001 meteorite, which some believe to be evidence of past life on Mars. However, the analysis was not conclusive, in part because it was limited to parts of Mars not obscured by dust.
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János Irinyi (; sometimes also spelled "János Irínyi"; Romanian: Ioan Irinyi; 18 May 1817, in Albis [Romanian: Buduslau] – 17 December 1895, in Vértes (today Létavértes - Hungary) was a Hungarian chemist and inventor of the noiseless and non-explosive match. He achieved this by mixing the phosphorus with lead dioxide instead of the potassium chlorate used previously. Irinyi also took part in the Hungarian Revolution of 1848. Asteroid 106869 Irinyi, discovered by Hungarian astronomer Krisztián Sárneczky and László L. Kiss at Piszkéstető Station in 2000, was named in his memory. The official was published by the Minor Planet Center on 22 January 2008 ().
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Fluid pipe Fluid pipes are a phenomenon driven by surface tension. When a pure water jet impinges on a reservoir, capillary waves are excited and propagate up the jet at the same speed that the jet falls. phenomenon may be observed with a kitchen faucet. When the diameter of the stream is 2–3 mm, placing an obstacle in the stream will give the desired effect. Contamination of the reservoir with a surfactant will eliminate the effect of capillary waves up a fluid pipe and results in the jet entering the reservoir as a rigid pipe.
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Anthelion An anthelion (plural anthelia, from late Greek ανθηλιος, "opposite the sun") is a rare optical phenomenon of the halo family. It appears on the parhelic circle opposite to the sun as a faint white spot, not unlike a sundog, and may be crossed by an X-shaped pair of diffuse arcs. How anthelia are formed is disputed. Walter Tape, among others, has argued they are not separate haloes, but simply where various haloes caused by horizontally oriented column-shaped ice crystals coincide on the parhelic circle to create a bright spot. If this theory is correct, anthelia should only appear together with these other haloes. However, anthelia occur unaccompanied by other plate crystal haloes, thus scientists have produced alternative explanations. The Dutch professor S.W. Visser proposed they form by two exterior light reflections in quadrangular prisms, while Robert Greenler has suggested two interior reflections in column-shaped crystals produces the phenomenon. While the anthelion area is usually sparse on haloes, in a complex display it features various rare optic phenomena: Flanking the anthelion on the parhelic circle are two 120° parhelia (and two Liljequist parhelia) caused by plate crystals. The Tricker and diffuse arcs are produced in singly oriented column crystals and form an Ankh-like shape passing through the anthelion. Wegener arcs occasionally cross the sky to converge in the anthelion.
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Eberhard Köllner (born 29 September 1939 in Stassfurt, Germany) was selected for Soyuz 31 as the backup for Sigmund Jähn. He later became the Director of the Airforce Academy of the German Democratic Republic in the rank of an "Oberst" ("Colonel"), following the reunion of Germany he refused to be transferred to the (West) German "Bundeswehr". He is currently working in private industries.
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Ravish Malhotra (born 25 December 1943 in Lahore, British India) is a retired Air Commodore of the Indian Air Force. He was an Air Force test pilot stationed at the test center in Bangalore. He was also the Air Officer Commanding of Hindon Air Force Station near Delhi. In 1982, he was chosen to train for spaceflight in the Soviet Union's Intercosmos program. Malhotra served as backup for Rakesh Sharma on the Soyuz T-11 mission which launched the first Indian into space, but never went to space himself. Malhotra was awarded the Kirti Chakra and Soviet order of Friendship of Peoples in 1984. qualified as a test pilot and the highly experienced Wing Commander Malhotra was chosen to undergo training in Russia for the Indo-Soviet Space mission planned in 1984. He successfully completed the extremely demanding training schedule with credit and distinction. Service No 7678 Branch : F(P) Rank : Wing Commander Unit : Indo Soviet Space Reference : Gazette of India, 19 May 1984 - No.58 - Pres/85 dated 7 May 1985
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Awn (botany) In botany, an awn is either a hair- or bristle-like appendage on a larger structure, or in the case of the Asteraceae, a stiff needle-like element of the pappus. Awns are characteristic of various plant families, including Geraniaceae and many grasses (Poaceae). In grasses awns typically extend from the lemmas of the florets. This often makes the hairy appearance of the grass synfloresce. Awns may be long (several centimeters) or short, straight or curved, single or multiple per floret. Some genera are named after their awns, such as the three-awns ("Aristida"). In some species, the awns can contribute significantly to photosynthesis, as, for example, in barley. The awns of wild emmer wheat spikelets effectively self-cultivate by propelling themselves mechanically into soils. During a period of increased humidity during the night, the awns of the spikelet become erect and draw together, and in the process push the grain into the soil. During the daytime the humidity drops and the awns slacken back again; however, fine silica hairs on the awns act as ratchet hooks in the soil and prevent the spikelets from reversing back out again. During the course of alternating stages of daytime and nighttime humidity, the awns' pumping movements, which resemble a swimming frog kick, drill the spikelet as much as an inch into the soil. When awns occur in the Geraniaceae, they form the distal (rostral) points of the five carpels, lying parallel in the style above the ovary
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Awn (botany) Depending on the species, such awns have various seed dispersal functions, either dispersing the seed by flinging it out (seed ejection); flinging away the entire carpel so that it snaps off (carpel projection); entangling the awn or bristles on passing animals (zoochory); or possibly burying the seed by twisting as it lies on soft soil.
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Emil Godlewski (junior) Emil Godlewski (1875–1944) was a Polish embryologist, professor of the Jagiellonian University in Kraków. After early research on the development and histogenesis of muscles, professor Godlewski's scientific interests focused on regeneration and mechanisms regulating the process of fertilization, as well as early embryo development, blastulation and gastrulation. He was also interested in the origin of the primary differentiating cells in regenerates. He postulated the importance of epithelial tissue in this process and was the first to point out the change in the function, organization and role of the cells under the influence of external stimuli. Investigating fertilization and early development, he focused on the cooperation between the nucleus and the cytoplasm in the regulation of the early stages of development. Godlewski was also the author of the theory of migration of the inherited substances from the nucleus to the cytoplasm and, after their processing, from the cytoplasm to the nucleus. His works were never fragmentary, but always synthetic attempts at explaining important issues relating to the mechanisms of development. In 1936 Professor Godlewski was awarded the title of Member of the Pontifical Academy of Sciences. Apart from doing research and teaching, Emil Godlewski devoted a lot of time to social issues, especially those connected to medicine. When Poland regained independence after World War I, he actively participated in the reopening of the Jagiellonian University.
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August Dehnel s. Michała (June 25, 1903, Warsaw – November 22, 1962, Warsaw) was a Polish zoologist, Ph.D. (1926), professor. Until 1949 he signed his popular science and embryology works with the name Gustaw Dehnel. Denhel is credited with discovering that the braincase of shrews shrinks significantly over the winter and expands again in the spring. This fact has come to be known as the Dehnel phenomenon. It affects not only the brain, but also other major organs such as the liver and kidneys. This factor explains why such small animals can survive harsh winters with associated reduction in food availability. The phenomenon may be responsible for the preservation of certain rare populations such as the Suisun Shrew. For this discovery, reported in his habilitation thesis (1949) at the University of Warsaw, he received the State Award.
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Plant Patent Act of 1930 The (enacted on 1930-06-17 as Title III of the Smoot–Hawley Tariff, ch. 497, , codified as 35 U.S.C. Ch. 15) is a United States federal law spurred by the work of Luther Burbank. This piece of legislation made it possible to patent new varieties of plants, excluding sexual and tuber-propagated plants ("see" Plant Variety Protection Act of 1970). In supporting the legislation, Thomas Edison testified before Congress in support of the legislation and said, Plant patents PP12, PP13, PP14, PP15, PP16, PP18, PP41, PP65, PP66, PP235, PP266, PP267, PP269, PP290, PP291 and PP1041 were issued to Burbank posthumously.
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Volborthite is a mineral containing copper and vanadium, with the formula CuVO(OH)·2HO. Found originally in 1838 in the Urals, it was first named knaufite but was later changed to volborthite for Alexander von Volborth (1800–1876), a Russian paleontologist. Tangeite (synonym: calciovolborthite), CaCuVO(OH), is closely related. was first described in 1837 for an occurrence in the Sofronovskii Mine, Yugovskii Zavod, Perm, Permskaya Oblast, Middle Urals, Russia. It occurs as an uncommon oxidation mineral in vanadium bearing hydrothermal copper ores. It is associated with brochantite, malachite, atacamite, tangeite, chrysocolla, baryte and gypsum.
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Warwickite is an iron magnesium titanium borate mineral with formula: (MgFe)Ti(O, BO) "or" Mg(Ti,Fe, Al)(BO)O. It occurs as brown to black prismatic orthorhombic crystals which are vitreous and transparent. It has a Mohs hardness of 3 to 4 and a specific gravity of 3.36. It occurs metasomatized limestone skarns and in lamproite and carbonatite veinlets. It was first described in 1838 near Warwick, Orange County, New York. It has also been reported from Bancroft, Ontario; in Murcia Province, Spain; in Siberia and near Pyongyang, North Korea.
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Industrial fermentation is the intentional use of fermentation by microorganisms such as bacteria and fungi as well as eukaryotic cells like CHO cells and insect cells, to make products useful to humans. Fermented products have applications as food as well as in general industry. Some commodity chemicals, such as acetic acid, citric acid, and ethanol are made by fermentation. The rate of fermentation depends on the concentration of microorganisms, cells, cellular components, and enzymes as well as temperature, pH and for aerobic fermentation oxygen. Product recovery frequently involves the concentration of the dilute solution. Nearly all commercially produced enzymes, such as lipase, invertase and rennet, are made by fermentation with genetically modified microbes. In some cases, production of biomass itself is the objective, as in the case of baker's yeast and lactic acid bacteria starter cultures for cheesemaking. In general, fermentations can be divided into four types: These types are not necessarily disjoint from each other, but provide a framework for understanding the differences in approach. The organisms used may be bacteria, yeasts, molds, algae, animal cells, or plant cells. Special considerations are required for the specific organisms used in the fermentation, such as the dissolved oxygen level, nutrient levels, and temperature
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Industrial fermentation In most industrial fermentations, the organisms or eukaryotic cells are submerged in a liquid medium; in others, such as the fermentation of cocoa beans, coffee cherries, and miso, fermentation takes place on the moist surface of the medium. There are also industrial considerations related to the fermentation process. For instance, to avoid biological process contamination, the fermentation medium, air, and equipment are sterilized. Foam control can be achieved by either mechanical foam destruction or chemical anti-foaming agents. Several other factors must be measured and controlled such as pressure, temperature, agitator shaft power, and viscosity. An important element for industrial fermentations is scale up. This is the conversion of a laboratory procedure to an industrial process. It is well established in the field of industrial microbiology that what works well at the laboratory scale may work poorly or not at all when first attempted at large scale. It is generally not possible to take fermentation conditions that have worked in the laboratory and blindly apply them to industrial-scale equipment. Although many parameters have been tested for use as scale up criteria, there is no general formula because of the variation in fermentation processes. The most important methods are the maintenance of constant power consumption per unit of broth and the maintenance of constant volumetric transfer rate. Fermentation begins once the growth medium is inoculated with the organism of interest
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Industrial fermentation Growth of the inoculum does not occur immediately. This is the period of adaptation, called the lag phase. Following the lag phase, the rate of growth of the organism steadily increases, for a certain period—this period is the log or exponential phase. After a phase of exponential growth, the rate of growth slows down, due to the continuously falling concentrations of nutrients and/or a continuously increasing (accumulating) concentrations of toxic substances. This phase, where the increase of the rate of growth is checked, is the deceleration phase. After the deceleration phase, growth ceases and the culture enters a stationary phase or a steady state. The biomass remains constant, except when certain accumulated chemicals in the culture lyse the cells (chemolysis). Unless other micro-organisms contaminate the culture, the chemical constitution remains unchanged. If all of the nutrients in the medium are consumed, or if the concentration of toxins is too great, the cells may become scenescent and begin to die off. The total amount of biomass may not decrease, but the number of viable organisms will decrease. The microbes or eukaryotic cells used for fermentation grow in (or on) specially designed growth medium which supplies the nutrients required by the organisms or cells. A variety of media exist, but invariably contain a carbon source, a nitrogen source, water, salts, and micronutrients. In the production of wine, the medium is grape must
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Industrial fermentation In the production of bio-ethanol, the medium may consist mostly of whatever inexpensive carbon source is available. Carbon sources are typically sugars or other carbohydrates, although in the case of substrate transformations (such as the production of vinegar) the carbon source may be an alcohol or something else altogether. For large scale fermentations, such as those used for the production of ethanol, inexpensive sources of carbohydrates, such as molasses, corn steep liquor, sugar cane juice, or sugar beet juice are used to minimize costs. More sensitive fermentations may instead use purified glucose, sucrose, glycerol or other sugars, which reduces variation and helps ensure the purity of the final product. Organisms meant to produce enzymes such as beta galactosidase, invertase or other amylases may be fed starch to select for organisms that express the enzymes in large quantity. Fixed nitrogen sources are required for most organisms to synthesize proteins, nucleic acids and other cellular components. Depending on the enzyme capabilities of the organism, nitrogen may be provided as bulk protein, such as soy meal; as pre-digested polypeptides, such as peptone or tryptone; or as ammonia or nitrate salts. Cost is also an important factor in the choice of a nitrogen source. Phosphorus is needed for production of phospholipids in cellular membranes and for the production of nucleic acids
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Industrial fermentation The amount of phosphate which must be added depends upon the composition of the broth and the needs of the organism, as well as the objective of the fermentation. For instance, some cultures will not produce secondary metabolites in the presence of phosphate. Growth factors and trace nutrients are included in the fermentation broth for organisms incapable of producing all of the vitamins they require. Yeast extract is a common source of micronutrients and vitamins for fermentation media. Inorganic nutrients, including trace elements such as iron, zinc, copper, manganese, molybdenum and cobalt are typically present in unrefined carbon and nitrogen sources, but may have to be added when purified carbon and nitrogen sources are used. Fermentations which produce large amounts of gas (or which require the addition of gas) will tend to form a layer of foam, since fermentation broth typically contains a variety of foam-reinforcing proteins, peptides or starches. To prevent this foam from occurring or accumulating, antifoaming agents may be added. Mineral buffering salts, such as carbonates and phosphates, may be used to stabilize pH near optimum. When metal ions are present in high concentrations, use of a chelating agent may be necessary. Developing an optimal medium for fermentation is a key concept to efficient optimization. One-factor-at-a-time (OFAT) is the preferential choice that researchers use for designing a medium composition
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Industrial fermentation This method involves changing only one factor at a time while keeping the other concentrations constant. This method can be separated into some sub groups. One is Removal Experiments. In this experiment all the components of the medium are removed one at a time and their effects on the medium are observed. Supplementation experiments involve evaluating the effects of nitrogen and carbon supplements on production. The final experiment is a replacement experiment. This involves replacing the nitrogen and carbon sources that show an enhancement effect on the intended production. Overall OFAT is a major advantage over other optimization methods because of its simplicity. Microbial cells or biomass is sometimes the intended product of fermentation. Examples include single cell protein, bakers yeast, lactobacillus, E. coli, and others. In the case of single-cell protein, algae is grown in large open ponds which allow photosynthesis to occur. If the biomass is to be used for inoculation of other fermentations, care must be taken to prevent mutations from occurring. Metabolites can be divided into two groups: those produced during the growth phase of the organism, called primary metabolites and those produced during the stationary phase, called secondary metabolites. Some examples of primary metabolites are ethanol, citric acid, glutamic acid, lysine, vitamins and polysaccharides. Some examples of secondary metabolites are penicillin, cyclosporin A, gibberellin, and lovastatin
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Industrial fermentation Primary metabolites are compounds made during the ordinary metabolism of the organism during the growth phase. A common example is ethanol or lactic acid, produced during glycolysis. Citric acid is produced by some strains of "Aspergillus niger" as part of the citric acid cycle to acidify their environment and prevent competitors from taking over. Glutamate is produced by some " Micrococcus " species, and some " Corynebacterium " species produce lysine, threonine, tryptophan and other amino acids. All of these compounds are produced during the normal "business" of the cell and released into the environment. There is therefore no need to rupture the cells for product recovery. Secondary metabolites are compounds made in the stationary phase; penicillin, for instance, prevents the growth of bacteria which could compete with "Penicillium" molds for resources. Some bacteria, such as "Lactobacillus" species, are able to produce bacteriocins which prevent the growth of bacterial competitors as well. These compounds are of obvious value to humans wishing to prevent the growth of bacteria, either as antibiotics or as antiseptics (such as gramicidin S). Fungicides, such as griseofulvin are also produced as secondary metabolites. Typically secondary metabolites are not produced in the presence of glucose or other carbon sources which would encourage growth, and like primary metabolites are released into the surrounding medium without rupture of the cell membrane
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Industrial fermentation In the early days of the biotechnology industry, most biopharmaceutical products were made in "E. coli"; by 2004 more biopharmaceuticals were manufactured in eukaryotic cells, like CHO cells, than in microbes, but used similar bioreactor systems. Insect cell culture systems came into use in the 2000s as well. Of primary interest among the intracellular components are microbial enzymes: catalase, amylase, protease, pectinase, cellulase, hemicellulase, lipase, lactase, streptokinase and many others. Recombinant proteins, such as insulin, hepatitis B vaccine, interferon, granulocyte colony-stimulating factor, streptokinase and others are also made this way. The largest difference between this process and the others is that the cells must be ruptured (lysed) at the end of fermentation, and the environment must be manipulated to maximize the amount of the product. Furthermore, the product (typically a protein) must be separated from all of the other cellular proteins in the lysate to be purified. Substrate transformation involves the transformation of a specific compound into another, such as in the case of phenylacetylcarbinol, and steroid biotransformation, or the transformation of a raw material into a finished product, in the case of food fermentations and sewage treatment. Ancient fermented food processes, such as making bread, wine, cheese, curds, idli, dosa, etc., can be dated to more than seven thousand years ago
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Industrial fermentation They were developed long before man had any knowledge of the existence of the microorganisms involved. Some foods such as Marmite are the byproduct of the fermentation process, in this case in the production of beer. Fermentation is the main source of ethanol in the production of ethanol fuel. Common crops such as sugar cane, potato, cassava and corn are fermented by yeast to produce ethanol which is further processed to become fuel. In the process of sewage treatment, sewage is digested by enzymes secreted by bacteria. Solid organic matters are broken down into harmless, soluble substances and carbon dioxide. Liquids that result are disinfected to remove pathogens before being discharged into rivers or the sea or can be used as liquid fertilizers. Digested solids, known also as sludge, is dried and used as fertilizer. Gaseous byproducts such as methane can be utilized as biogas to fuel electrical generators. One advantage of bacterial digestion is that it reduces the bulk and odor of sewage, thus reducing space needed for dumping. The main disadvantage of bacterial digestion in sewage disposal is that it is a very slow process. A wide variety of agroindustrial waste products can be fermented to use as food for animals, especially ruminants. Fungi have been employed to break down cellulosic wastes to increase protein content and improve "in vitro" digestibility.
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Van Slyke determination The is a chemical test for the determination of amino acids containing a primary amine group. It is named after the biochemist Donald Dexter Van Slyke (1883-1971). One of Van Slyke's first professional achievements was the quantification of amino acids by the reaction. To quantify aliphatic amino acids, the sample is diluted in glycerol and then treated with a solution of sodium nitrite, water and acetic acid. The resulting diazotisation reaction produces nitrogen gas which can be observed qualitatively or measured quantitatively. Van Slyke Reaction: R-NH + HONO → ROH + N + HO In addition, Van Slyke developed the so-called Van Slyke apparatus, which can be used to determine the concentration of respiratory gases in the blood, especially the concentration of sodium bicarbonate. This was of high importance to be able to recognize a beginning acidosis in diabetic patients as early as possible, in order to start alkali treatment. The Van Slyke apparatus became a standard equipment in clinical laboratories around the world and the results of Van Slyke's research are still used today to determine abnormalities in the acid-base homeostasis. Later on, Van Slyke further improved his apparatus, increasing its accuracy and sensitivity. Using the new method, he was able to further investigate the role of gas and electrolyte equilibria in the blood and how they change in response to respiration.
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Trapp mixture The is a specific mixture of organic solvents that allows chemical reactions to take place at very low temperatures. It is made up of THF:diethyl ether:pentane in a 4:4:1 ratio which remains liquid down to −110 °C and the same solvents in a 4:1:1 ratio remain a liquid down to −120 °C. This solvent system retains a low viscosity until just before freezing and it allows a lower temperature reaction than pure THF, which melts at −108.4 °C. An illustrative application of Trapp solvent is the preparation of vinyllithium by lithium halogen exchange from vinyl bromide and "tert"-butyllithium. The low temperatures suppress the reaction of the strongly basic organolithium reagent with the THF.
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Whewellite is a mineral, hydrated calcium oxalate, formula Ca CO·HO. Because of its organic content it is thought to have an indirect biological origin; this hypothesis is supported by its presence in coal and sedimentary nodules. However, it has also been found in hydrothermal deposits where a biological source appears improbable. For this reason, it may be classed as a true mineral. Whewellite, or at least crystalline calcium oxalate, does also arise from biological sources. Small crystals or flakes of it are sometimes found on the surfaces of some cacti, and kidney stones frequently have the same composition. was named after William Whewell (1794–1866), an English polymath, naturalist and scientist, professor of moral philosophy at Cambridge and inventor of the system of crystallographic indexing. is used as a thermogravimetric analysis standard due to its well-known decomposition temperatures and products.
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Fenestra A fenestra (fenestration; plural fenestrae or fenestrations) is any small opening or pore, commonly used as a term in the biological sciences. It is Latin for the word "window", and is used in various fields to describe a pore in an anatomical structure. In morphology, fenestrae are found in cancellous bones, particularly in the skull. In anatomy, the round window and oval window are also known as the "fenestra rotunda" and the "fenestra ovalis". In microanatomy, fenestrae are found in endothelium of fenestrated capillaries, enabling the rapid exchange of molecules between the blood and surrounding tissue. The elastic layer of the tunica intima is a fenestrated membrane. In surgery, a fenestration is a new opening made in a part of the body to enable drainage or access. In plant biology, the perforations in a perforate leaf are also described as fenestrae, and the leaf is called a fenestrate leaf. The leaf window is also known as a fenestra, and is a translucent structure that transmits light, as in "Fenestraria". In zoology, the trilobite "Fenestraspis" possessed extensive fenestrae in the posterior part of the body. In the paleognathae, there is an ilio–ischiatic fenestra.
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Entomoplasmatales is a small order of mollicute bacteria. The genus "Spiroplasma" is part of this order.
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Anaeroplasmatales is an order of mollicute bacteria which are generally found in the rumens of cattle and sheep. The only family in the order is the family Anaeroplasmataceae. Members of the order can appear as different shapes at different times in their lifecycles. Cells which are 16–18 hours old tend to be spherical. When the cells are older, they can take on various shapes. are not motile. cannot grow in the presence of oxygen. They do grow at a temperature of 37 °C on microbiological media, where they form irregular-shaped colonies with a "fried-egg" appearance, similar to other mycoplasmas. are negative by Gram stain. The order was created in 1987 to encompass the family Anaeroplasmataceae which itself was created to hold the anaerobic mycoplasmas "Anaeroplasma" and "Asteroleplasma".
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https://en.wikipedia.org/wiki?curid=2731947
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Judith Lapierre is a professor in Nursing at the Université Laval. She studied at the International Space University in France. In 1999, Lapierre accused two Russian cosmonauts of sexual harassment after a 110-day simulation of space station living. Among the claims were an unwarranted kiss during a New Year's Celebration; project coordinator Valery Gushin later claimed that her "refusing to be kissed" had been a leading cause for the experiment's failure.
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Wood opal is a form of petrified wood which has developed an opalescent sheen or, more rarely, where the wood has been completely replaced by opal. Other names for this opalized sheen-like wood are opalized wood and opalized petrified wood. It is often used as a gemstone.
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https://en.wikipedia.org/wiki?curid=2736688
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Nanoelectrochemistry is a branch of electrochemistry that investigates the electrical and electrochemical properties of materials at the nanometer size regime. plays significant role in the fabrication of various sensors, and devices for detecting molecules at very low concentrations. Two transport mechanisms are fundamental for nanoelectrochemistry: electron transfer and mass transport. The formulation of theoretical models allows to understand the role of the different species involved in the electrochemical reactions. The electron transfer between the reactant and the nanoelectrode can be explained by the combination of various theories based on the Marcus theory. Mass transport, that is the diffusion of the reactant molecules from the electrolyte bulk to the nanoelectrode, is influenced by the formation of a double electric layer at the electrode/electrolyte interface. At the nanoscale it is necessary to theorize a dynamic double electric layer which takes into account an overlap of the Stern layer and the diffuse layer. Knowledge of the mechanisms involved allows to build computational models that combine the density functional theory with electron transfer theories and the dynamic double electric layer. In the field of molecular modelling, accurate models could predict the behaviour of the system as reactants, electrolyte or electrode change. The role of the surface is strongly reaction-specific: in fact, one site can catalyze certain reactions and inhibit other ones
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Nanoelectrochemistry <br> According to TSK model, surface atoms in nanocrystals can occupy terrace, step or kink positions: each site has a different tendency to adsorb reactants and to let them move along the surface. Generally, sites having lower coordination number (steps and kinks) are more reactive due to their high free energy. High energy sites, however, are less thermodynamically stable and nanocrystals have a tendency to transform to their equilibrium shape. Thanks to the progress in nanoparticles synthesis it is now possible to have a single-crystal approach to surface science, allowing more precise research on the effect of a given surface. Studies have been conducted on nanoelectrodes exposing a (100), (110) or (111) plane to a solution containing the reactants, in order to define the surface effect on reaction rate and selectivity of the most common electrochemical reactions.<ref name="10.1039/c0nr00857e"></ref> Nanoelectrodes are tiny electrodes made of metals or semiconducting materials having typical dimensions of 1-100 nm. Various forms of nanoelectrodes have been developed taking advantage of the different possible fabrication techniques: among the most studied are the nanoband, disk, hemispherical, nanopore geometries as well as the different forms of carbon nanostructures. It is necessary to characterize each produced electrode: size and shape determine its behaviour
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Nanoelectrochemistry The most used characterization techniques are: There are mainly two properties that distinguish nanoelectrodes from electrodes: smaller RC constant and faster mass transfer. The former allows measurements to be made in high-resistance solutions because they offer less resistance, the latter, due to radial diffusion, allows much faster voltammetry responses. Due to these and other properties, nanoelectrodes are used in various applications:
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Algodonite is a copper arsenide mineral with formula: CuAs. It is a gray white metallic mineral crystallizing in the hexagonal system. It has a Mohs hardness of 4 and a specific gravity of 8.38 - 8.72. It was first described in 1857 from the Algodones silver mine, Coquimbo, Chile.
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Biological thermodynamics is the quantitative study of the energy transductions that occur in or between living organisms, structures, and cells and of the nature and function of the chemical processes underlying these transductions. may address the question of whether the benefit associated with any particular phenotypic trait is worth the energy investment it requires. German-British medical doctor and biochemist Hans Krebs' 1957 book "Energy Transformations in Living Matter" (written with Hans Kornberg) was the first major publication on the thermodynamics of biochemical reactions. In addition, the appendix contained the first-ever published thermodynamic tables, written by Kenneth Burton, to contain equilibrium constants and Gibbs free energy of formations for chemical species, able to calculate biochemical reactions that had not yet occurred. Non-equilibrium thermodynamics has been applied for explaining how biological organisms can develop from disorder. Ilya Prigogine developed methods for the thermodynamic treatment of such systems. He called these systems dissipative systems, because they are formed and maintained by the dissipative processes that exchange energy between the system and its environment, and because they disappear if that exchange ceases. It may be said that they live in symbiosis with their environment. Energy transformations in biology are dependent primarily on photosynthesis. The total energy captured by photosynthesis in green plants from the solar radiation is about 2 x 10 joules of energy per year
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Biological thermodynamics Annual energy captured by photosynthesis in green plants is about 4% of the total sunlight energy that reaches Earth. The energy transformations in biological communities surrounding hydrothermal vents are exceptions; they oxidize sulfur, obtaining their energy via chemosynthesis rather than photosynthesis. The field of biological thermodynamics is focused on principles of chemical thermodynamics in biology and biochemistry. Principles covered include the first law of thermodynamics, the second law of thermodynamics, Gibbs free energy, statistical thermodynamics, reaction kinetics, and on hypotheses of the origin of life. Presently, biological thermodynamics concerns itself with the study of internal biochemical dynamics as: ATP hydrolysis, protein stability, DNA binding, membrane diffusion, enzyme kinetics, and other such essential energy controlled pathways. In terms of thermodynamics, the amount of energy capable of doing work during a chemical reaction is measured quantitatively by the change in the Gibbs free energy. The physical biologist Alfred Lotka attempted to unify the change in the Gibbs free energy with evolutionary theory. The sun is the primary source of energy for living organisms. Some living organisms like plants need sunlight directly while other organisms like humans can acquire energy from the sun indirectly. There is however evidence that some bacteria can thrive in harsh environments like Antarctica as evidence by the blue-green algae beneath thick layers of ice in the lakes
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Biological thermodynamics No matter what the type of living species, all living organisms must capture, transduce, store, and use energy to live. The relationship between the energy of the incoming sunlight and its wavelength or frequency is given by where "h" is the Planck constant (6.63x10Js) and "c" is the speed of light (2.998x10 m/s). Plants trap this energy from the sunlight and undergo photosynthesis, effectively converting solar energy into chemical energy. To transfer the energy once again, animals will feed on plants and use the energy of digested plant materials to create biological macromolecules. The biological evolution may be explained through a thermodynamic theory. The four laws of thermodynamics are used to frame the biological theory behind evolution. The first law of thermodynamics states that states that energy can not be created or destroyed. No life can create energy but must obtain it through its environment. The second law of thermodynamics states that energy can be transformed and that occurs everyday in lifeforms. As organisms take energy from their environment they can transform it into useful energy. This is the foundation of tropic dynamics. The general example is that the open system can be defined as any ecosystem that moves toward maximizing the dispersal of energy. All things strive towards maximum entropy production, which in terms of evolution, occurs in changes in DNA to increase biodiversity. Thus, diversity can be linked to the second law of thermodynamics
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Biological thermodynamics Diversity can also be argued to be a diffusion process that diffuses toward a dynamic equilibrium to maximize entropy. Therefore, thermodynamics can explain the direction and rate of evolution along with the direction and rate of succession. The First Law of Thermodynamics is a statement of the conservation of energy; though it can be changed from one form to another, energy can be neither created nor destroyed. From the first law, a principle called Hess's Law arises. Hess’s Law states that the heat absorbed or evolved in a given reaction must always be constant and independent of the manner in which the reaction takes place. Although some intermediate reactions may be endothermic and others may be exothermic, the total heat exchange is equal to the heat exchange had the process occurred directly. This principle is the basis for the calorimeter, a device used to determine the amount of heat in a chemical reaction. Since all incoming energy enters the body as food and is ultimately oxidized, the total heat production may be estimated by measuring the heat produced by the oxidation of food in a calorimeter. This heat is expressed in kilocalories, which are the common unit of food energy found on nutrition labels. The Second Law of Thermodynamics is concerned primarily with whether or not a given process is possible. The Second Law states that no natural process can occur unless it is accompanied by an increase in the entropy of the universe. Stated differently, an isolated system will always tend to disorder
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Biological thermodynamics Living organisms are often mistakenly believed to defy the Second Law because they are able to increase their level of organization. To correct this misinterpretation, one must refer simply to the definition of systems and boundaries. A living organism is an open system, able to exchange both matter and energy with its environment. For example, a human being takes in food, breaks it down into its components, and then uses those to build up cells, tissues, ligaments, etc. This process increases order in the body, and thus decreases entropy. However, humans also 1) conduct heat to clothing and other objects they are in contact with, 2) generate convection due to differences in body temperature and the environment, 3) radiate heat into space, 4) consume energy-containing substances (i.e., food), and 5) eliminate waste (e.g., carbon dioxide, water, and other components of breath, urine, feces, sweat, etc.). When taking all these processes into account, the total entropy of the greater system (i.e., the human and her/his environment) increases. When the human ceases to live, none of these processes (1-5) take place, and any interruption in the processes (esp. 4 or 5) will quickly lead to morbidity and/or mortality. In biological systems, in general energy and entropy change together. Therefore, it is necessary to be able to define a state function that accounts for these changes simultaneously. This state function is the Gibbs Free Energy, "G"
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Biological thermodynamics where: The change in Gibbs Free Energy can be used to determine whether a given chemical reaction can occur spontaneously. If ∆"G" is negative, the reaction can occur spontaneously. Likewise, if ∆"G" is positive, the reaction is nonspontaneous. Chemical reactions can be “coupled” together if they share intermediates. In this case, the overall Gibbs Free Energy change is simply the sum of the ∆"G" values for each reaction. Therefore, an unfavorable reaction (positive ∆"G") can be driven by a second, highly favorable reaction (negative ∆"G" where the magnitude of ∆"G" > magnitude of ∆"G"). For example, the reaction of glucose with fructose to form sucrose has a ∆"G" value of +5.5 kcal/mole. Therefore, this reaction will not occur spontaneously. The breakdown of ATP to form ADP and inorganic phosphate has a ∆"G" value of -7.3 kcal/mole. These two reactions can be coupled together, so that glucose binds with ATP to form glucose-1-phosphate and ADP. The glucose-1-phosphate is then able to bond with fructose yielding sucrose and inorganic phosphate. The ∆"G" value of the coupled reaction is -1.8 kcal/mole, indicating that the reaction will occur spontaneously. This principle of coupling reactions to alter the change in Gibbs Free Energy is the basic principle behind all enzymatic action in biological organisms.
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Anchialine pool An anchialine pool or pond (pronounced "AN-key-ah-line", from Greek "ankhialos", "near the sea") is a landlocked body of water with a subterranean connection to the ocean. Anchialine pools are a feature of coastal aquifers which are density stratified, with the water near the surface being fresh or brackish, and saline water intruding from the coast below at some depth. Depending on the site, it is sometimes possible to access the deeper saline water directly in the anchialine pool, or sometimes it may be accessible by cave diving. Water levels in anchialine pools often fluctuate with tidal changes due to the coastal location and the connection with the ocean. The range in water levels fluctuations will be decreased (damped) and delayed compared to the range and time observed for the adjacent tide. The primary controls on the damping and lag are the distance from the coast, and the hydraulic conductivity of the geological materials. Anchialine pools are extremely common worldwide especially along Neotropical coastlines where the geology and aquifer system are relatively young, and there is minimal soil development. Such conditions occur notably where the bedrock is limestone or recently formed volcanic lava. Many anchialine pools are found on the coastlines of the island of Hawaii, and on the Yucatán Peninsula, where they are locally called cenotes, as well as Christmas Island. The Sailor's Hat crater created by an explosives test in 1965 is an anchialine pool
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Anchialine pool Ecological studies of anchialine pools frequently identify regionally rare and sometimes endemic species. In Hawaii, the pools are home to the ʻōpaeʻula (Hawaiian shrimp, "Halocaridina rubra"). In karst anchialine pools and the caves that these may be connected to, the fauna are diverse and include crustaceans, including remipedia and copepods. Vertebrates are also found, including several species of blind cave fish.
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Sulfur-reducing bacteria (SRB) get their energy by reducing elemental sulfur to hydrogen sulfide. They couple this reaction with the oxidation of acetate, succinate or other organic compounds. Several types of bacteria and many non-methanogenic archaea can reduce sulfur. Some bacteriasuch as "Proteus", "Campylobacter", "Pseudomonas" and "Salmonella"have the ability to reduce sulfur, but can also use oxygen and other terminal electron acceptors. Others, such as "Desulfuromonas", use only sulfur. These bacteria can be used in industrial processes to generate hydrogen sulfide for the precipitation of metals. Some bacteria can use both elemental sulfur and sulfate as electron acceptors. See sulfate-reducing bacteria.
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List of Penrose Medal winners The Penrose Medal was created in 1925 by R.A.F. Penrose, Jr., as the top prize awarded by the Geological Society of America. Originally created as the Geological Society of America Medal it was soon renamed the Penrose Medal by popular assent of the society's membership, and was first awarded in 1927. It is awarded only at the discretion of the GSA council, "in recognition of eminent research in pure geology, for outstanding original contributions or achievements that mark a major advance in the science of geology." Source: GSA
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Acotyledon is used to refer to seed plants or spermatophytes that lack cotyledons, such as orchids and dodder. Orchid seeds are tiny with underdeveloped embryos. They depend on mycorrhizal fungi for their early nutrition so are myco-heterotrophs at that stage. Although some authors, especially in the 19th century and earlier, use the word acotyledon to include plants which have no cotyledons because they lack seeds entirely (such as ferns and mosses), others restrict the term to plants which have seeds but no cotyledons. Flowering plants or angiosperms are divided into two large groups. Monocotyledons or monocots have one seed lobe, which is often modified to absorb stored nutrients from the seed so never emerges from the seed or becomes photosynthetic. Dicotyledons or dicots have two cotyledons and often germinate to produce two leaf-like cotyledons. Conifers and other gymnosperms lack flowers but may have two or more cotyledons in the seedling.
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Pantropical A pantropical ("all tropics") distribution is one which covers tropical regions of both hemispheres. Examples include caecilians, modern sirenians and the plant genera "Acacia" and "Bacopa". Neotropical is a zoogeographic term that covers a large part of the Americas, roughly from Mexico and the Caribbean southwards (including cold regions in southernmost South America). Palaeotropical refers to geographical occurrence. For a distribution to be palaeotropical a taxon must occur in tropical regions in the Old World. According to Takhtajan (1978), the following families have a pantropical distribution: Annonaceae, Hernandiaceae, Lauraceae, Piperaceae, Urticaceae, Dilleniaceae, Tetrameristaceae, Passifloraceae, Bombacaceae, Euphorbiaceae, Rhizophoraceae, Myrtaceae, Anacardiaceae, Sapindaceae, Malpighiaceae, Proteaceae, Bignoniaceae, Orchidaceae and Arecaceae.
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Abeona Mons is a mountain on Venus named after the goddess Abeona.
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Critical distance is, in acoustics, the distance at which the sound pressure level of the direct sound D and the reverberant sound R are equal when dealing with a directional source. As the source is directional, the sound pressure as a function of distance between source and sampling point (listener) varies with their relative position, so that for a particular room and source the set of points where direct and reverberant sound pressure are equal constitutes a surface rather than a distinguished location in the room. In other words, it is the point in space at which the combined amplitude of all the reflected echoes are the same as the amplitude of the sound coming directly from the source (D = R). This distance, called the critical distance formula_1, is dependent on the geometry and absorption of the space in which the sound waves propagate, as well as the dimensions and shape of the sound source. A reverberant room generates a short critical distance and an acoustically dead (anechoic) room generates a longer critical distance. The calculation of the critical distance for a diffuse approximation of the reverberant field: where formula_3 is the degree of directivity of the source (formula_4 for an omnidirectional source), formula_5 the equivalent absorption surface, formula_6 the room volume in m and formula_7 the reverberation time of room in seconds. The latter approximation is using Sabine's reverberation formula formula_8.
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NGC 6745 (also known as UGC 11391) is an irregular galaxy about 206 million light-years (63.5 mega-parsecs) away in the constellation Lyra. It is actually a trio of galaxies in the process of colliding. The three galaxies have been colliding for hundreds of millions of years. After passing through the larger galaxy (NGC 6745A), the smaller one (NGC 6745B) is now moving away. The larger galaxy was probably a spiral galaxy before the collision, but was damaged and now appears peculiar. It is unlikely that any stars in the two galaxies collided directly because of the vast distances between them. The gas, dust, and ambient magnetic fields of the galaxies, however, do interact directly in a collision. As a result of this interaction, the smaller galaxy has probably lost most of its interstellar medium to the larger one.
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Mycoremediation (from ancient Greek "μύκης (mukēs)", meaning "fungus" and the suffix "-remedium", in Latin meaning 'restoring balance') is a form of bioremediation in which fungi-based technology is used to decontaminate the environment. Fungi have been proven to be a very cheap, effective and environmentally sound way for helping to remove a wide array of toxins from damaged environments or wastewater. The toxins include heavy metals, persistent organic pollutants, textile dyes, leather tanning industry chemicals and wastewater, petroleum fuels, polycyclic aromatic hydrocarbon, pharmaceuticals and personal care products, pesticides and herbicide, in land, fresh water and marine environments. The byproducts of the remediation can be valuable materials themselves, such as enzymes (like laccase), edible or medicinal mushrooms, making the remediation process even more profitable. Fungi, thanks to their non-specific enzymes, are able to break down many kinds of substances. They are used for pharmaceuticals and fragrances that normally are recalcitrant to bacteria degradation, such as paracetamol, the breakdown products of which are toxic in traditional water treatment, using "Mucor hiemalis", but also the phenols and pigments of wine distillery wastewater, X-ray contrast agents and ingredients of personal care products. is one of the cheaper solutions to remediation, and it doesn't usually require expensive equipment
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Mycoremediation For this reasons it is often used also in small scale applications, such as mycofiltration of domestic wastewater, and to help with the decomposition process of a compost toilet. Pollution from metals is very common, as they are used in many industrial processes such as electroplating, textiles, paint and leather. The wastewater from these industries is often used for agricultural purposes, so besides the immediate damage to the ecosystem it is spilled into, the metals can enter far away creatures and humans through the food chain. is one of the cheapest, most effective and environmental-friendly solutions to this problem. Many fungi are hyperaccumulators, that means they are able to concentrate toxins in their fruiting bodies for later removal. This is usually true for populations that have been exposed to contaminants for long time, and have developed a high tolerance, and happens via biosorption on the cellular surface, which means that the metals enter the mycelium in a passive way with very little intracellular uptake. A variety of fungi, such as "Pleurotus", "Aspergillus", "Trichoderma" has proven to be effective in the removal of lead, cadmium, nickel, chromium, mercury, arsenic, copper, boron, iron and zinc in marine environment, wastewater and on land. Not all the individuals of a species are effective in the same way in the accumulation of toxins
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Mycoremediation The single individuals are usually selected from an old-time polluted environment, such as sludge or wastewater, where they had time to adapt to the circumstances, and the selection is carried on in the laboratory. A dilution of the water can drastically improve the ability of biosorption of the fungi. The capacity of certain fungi to extract metals from the ground also can be useful for bioindicator purposes, and can be a problem when the mushroom is an edible one. For example, the shaggy ink cap ("Coprinus comatus"), a common edible north-hemisphere mushroom, can be a very good bioindicator of mercury, and accumulate it in its body, which can also be toxic to the consumer. The capacity of metals uptake of mushroom has also been used to recover precious metals from medium. VTT Technical Research Centre of Finland reported an 80% recovery of gold from electronic waste using mycofiltration techniques. Fungi are amongst the primary saprotrophic organisms in an ecosystem, as they are efficient in the decomposition of matter. Wood-decay fungi, especially white rot, secretes extracellular enzymes and acids that break down lignin and cellulose, the two main building blocks of plant fiber. These are long-chain organic (carbon-based) compounds, structurally similar to many organic pollutants. They do so using a wide array of enzymes
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Mycoremediation In the case of polycyclic aromatic hydrocarbons (PAHs), complex organic compounds with fused, highly stable, polycyclic aromatic rings, fungi are very effective also in marine environments. The enzymes involved in this degradation are ligninolytic and include lignin peroxidase, versatile peroxidase, manganese peroxidase, general lipase, laccase and sometimes intracellular enzymes, especially the cytochrome P450. Other toxins fungi are able to degrade into harmless compounds include petroleum fuels, phenols in wastewater, polychlorinated biphenyl (PCB) in contaminated soils using "Pleurotus ostreatus", polyurethane in aerobic and anaerobic conditions such as found at the bottom of landfills using two species of the Ecuadorian fungus "Pestalotiopsis", and more. The mechanisms of degradation are not always clear, as the mushroom may be a precursor to subsequent microbial activity rather than individually effective in the removal of pollutants. Pesticide contamination can be long-term and have a significant impact on decomposition processes and thus nutrient cycling and their degradation can be expensive and difficult. The most used fungi for helping in the degradation of such substances are white rot ones which, thanks to their extracellular ligninolytic enzymes like laccase and manganese peroxidase, are able to degrade high quantity of such components
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Mycoremediation Examples includes the insecticide endosulfan, imazalil, thiophanate methyl, ortho-phenylphenol, diphenylamine, chlorpyrifos in wastewater, and atrazine in clay-loamy soils. Dyes are used in many industries, like paper printing or textile. They are often recalcitrant to degradation and in some cases, like some azo dyes, cancerogenic or otherwise toxic. The mechanism the fungi degrade this dyes is their lignolytic enzymes, especially laccase, so white rot mushrooms are the most commonly used. has proven to be a cheap and effective remediation technology for dyes such as malachite green, nigrosin and basic fuchsin with "Aspergillus niger" and "Phanerochaete chrysosporium" and Congo red, a carcinogenic dye recalcitrant to biodegradative processes, direct blue 14 (using "Pleurotus"). Phytoremediation is the use of plant-based technologies to decontaminate an area. Most of the plants can form a symbiosis with fungi, from which both the organisms get an advantage. This relationship is called mycorrhiza. Mycorrhizal fungi, especially arbuscular mycorrhizal fungi (AMF), can greatly improve the phytoremediation capacity of some plants. This is mostly because the stress the plants suffer because of the pollutants is greatly reduced in presence of AMF, so they can grow more and produce more biomass. The fungi also provide more nutrition, especially phosphorus, and promotes the overall health of the plant
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Mycoremediation The mycelium quick expansion also can greatly extend the rhizosphere influenze zone (hyphosphere), providing the plant with access to more nutrients and contaminants. Increasing the rhizosphere overall health also means a rise in the bacteria population, which can also contribute to the bioremediation process. This relationship has been proven useful with many pollutants, such as "Rhizophagus intraradices" and "Robinia pseudoacacia" in lead contaminated soil, "Rhizophagus intraradices "with "Glomus versiforme "incoulated into vetiver grass for lead removal, AMF and "Calendula officinalis" in cadmium and lead contaminated soil, and in general was effective in increasing the plant bioremediation capacity for metals, petroleum fuels, and PAHs. In wetlands AMF greatly promote the biodegradation of organic pollutants like benzene-, methyl tert-butyl ether- and ammonia from groundwater when inoculated into "Phragmites australis".
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Spectral imaging is imaging that uses multiple bands across the electromagnetic spectrum. While an ordinary camera captures light across three wavelength bands in the visible spectrum, red, green, and blue (RGB), spectral imaging encompasses a wide variety of techniques that go beyond RGB. may use the infrared, the visible spectrum, the ultraviolet, x-rays, or some combination of the above. It may include the acquisition of image data in visible and non-visible bands simultaneously, illumination from outside the visible range, or the use of optical filters to capture a specific spectral range. It is also possible to capture hundreds of wavelength bands for each pixel in an image. Multispectral imaging captures a small number of spectral bands, typically three to fifteen, through the use of varying filters and illumination. Many off-the-shelf RGB cameras will detect a small amount of Near-Infrared (NIR) light. A scene may be illuminated with NIR light, and, simultaneously, an infrared-passing filter may be used on the camera to ensure that visible light is blocked and only NIR is captured in the image. Industrial, military, and scientific work, however, uses sensors built for the purpose. Hyperspectral imaging is another subcategory of spectral imaging, which combines spectroscopy and digital photography. In hyperspectral imaging, a complete spectrum or some spectral information (such as the Doppler shift or Zeeman splitting of a spectral line) is collected at every pixel in an image plane
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Spectral imaging A hyperspectral camera uses special hardware to capture hundreds of wavelength bands for each pixel, which can be interpreted as a complete spectrum. In other words, the camera has a high spectral resolution. The phrase "spectral imaging" is sometimes used as a shorthand way of referring to this technique, but it is preferable to use the term "hyperspectral imaging" in places when ambiguity may arise. Hyperspectral images are often represented as an image cube, which is type of data cube. Applications of spectral imaging include art conservation, astronomy, solar physics, planetology, and Earth remote sensing.
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Adult stem cell Adult stem cells are undifferentiated cells, found throughout the body after development, that multiply by cell division to replenish dying cells and regenerate damaged tissues. Also known as somatic stem cells (from Greek Σωματικóς, meaning "of the body"), they can be found in juvenile as well as adult animals and humans, unlike embryonic stem cells. Scientific interest in adult stem cells is centered on their ability to divide or "self-renew" indefinitely, and generate all the cell types of the organ from which they originate, potentially regenerating the entire organ from a few cells. Unlike for embryonic stem cells, the use of human adult stem cells in research and therapy is not considered to be controversial, as they are derived from adult tissue samples rather than human embryos designated for scientific research. They have mainly been studied in humans and model organisms such as mice and rats. A stem cell possesses two properties: To ensure self-renewal, stem cells undergo two types of cell division (see "Stem cell division and differentiation" diagram). Symmetric division gives rise to two identical daughter stem cells, whereas asymmetric division produces one stem cell and one progenitor cell with limited self-renewal potential. Progenitors can go through several rounds of cell division before finally differentiating into a mature cell
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Adult stem cell It is believed that the molecular distinction between symmetric and asymmetric divisions lies in differential segregation of cell membrane proteins (such as receptors) and their associated proteins between the daughter cells. Under normal conditions, tissue stem cells divide slowly and infrequently. They exhibit signs of quiescence, or reversible growth arrest. The niche the stem cell is found in plays a large role in maintaining quiescence. Perturbed niches cause the stem cell to begin actively dividing again to replace lost or damaged cells until the niche is restored. In hematopoietic stem cells, the MAPK/ERK pathway and PI3K/AKT/mTOR pathway regulate this transition. The ability to regulate the cell cycle in response to external cues helps prevent stem cell exhaustion, or the gradual loss of stem cells following an altered balance between dormant and active states. Infrequent cell divisions also help reduce the risk of acquiring DNA mutations that would be passed on to daughter cells. Discoveries in recent years have suggested that adult stem cells might have the ability to differentiate into cell types from different germ layers. For instance, neural stem cells from the brain, which are derived from ectoderm, can differentiate into ectoderm, mesoderm, and endoderm. Stem cells from the bone marrow, which is derived from mesoderm, can differentiate into liver, lung, GI tract and skin, which are derived from endoderm and mesoderm. This phenomenon is referred to as stem cell transdifferentiation or plasticity
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Adult stem cell It can be induced by modifying the growth medium when stem cells are cultured "in vitro" or transplanting them to an organ of the body different from the one they were originally isolated from. There is yet no consensus among biologists on the prevalence and physiological and therapeutic relevance of stem cell plasticity. More recent findings suggest that pluripotent stem cells may reside in blood and adult tissues in a dormant state. These cells are referred to as "Blastomere Like Stem Cells" (BLSCs) and "very small embryonic like" (VSEL) stem cells, and display pluripotency in vitro. As BLSCs and VSEL cells are present in virtually all adult tissues, including lung, brain, kidneys, muscles, and pancreas Co-purification of BLSCs and VSEL cells with other populations of adult stem cells may explain the apparent pluripotency of adult stem cell populations. However, recent studies have shown that both human and murine VSEL cells lack stem cell characteristics and are not pluripotent. Stem cell function becomes impaired with age, and this contributes to progressive deterioration of tissue maintenance and repair. A likely important cause of increasing stem cell dysfunction is age-dependent accumulation of DNA damage in both stem cells and the cells that comprise the stem cell environment. (See also DNA damage theory of aging.) Adult stem cells can, however, be artificially reverted to a state where they behave like embryonic stem cells (including the associated DNA repair mechanisms)
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Adult stem cell This was done with mice as early as 2006 with future prospects to slow down human aging substantially. Such cells are one of the various classes of induced stem cells. research has been focused on uncovering the general molecular mechanisms that control their self-renewal and differentiation. Hematopoietic stem cells (HSCs) are stem cells that can differentiate into all blood cells. This process is called haematopoiesis. Hematopoietic stem cells are found in the bone marrow and umbilical cord blood. Mammary stem cells provide the source of cells for growth of the mammary gland during puberty and gestation and play an important role in carcinogenesis of the breast. Mammary stem cells have been isolated from human and mouse tissue as well as from cell lines derived from the mammary gland. Single such cells can give rise to both the luminal and myoepithelial cell types of the gland and have been shown to have the ability to regenerate the entire organ in mice. Intestinal stem cells divide continuously throughout life and use a complex genetic program to produce the cells lining the surface of the small and large intestines. Intestinal stem cells reside near the base of the stem cell niche, called the crypts of Lieberkuhn. Intestinal stem cells are probably the source of most cancers of the small intestine and colon. Mesenchymal stem cells (MSCs) are of stromal origin and may differentiate into a variety of tissues
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Adult stem cell MSCs have been isolated from placenta, adipose tissue, lung, bone marrow and blood, Wharton's jelly from the umbilical cord, and teeth (perivascular niche of dental pulp and periodontal ligament). MSCs are attractive for clinical therapy due to their ability to differentiate, provide trophic support, and modulate innate immune response. These cells have the ability to differentiate into various cell types such as osteoblasts, chondroblasts, adipocytes, neuroectodermal cells, and hepatocytes. Bioactive mediators that favor local cell growth are also secreted by MSCs. Anti-inflammatory effects on the local microenvironment, which promote tissue healing, are also observed. The inflammatory response can be modulated by adipose-derived regenerative cells (ADRC) including mesenchymal stem cells and regulatory T-lymphocytes. The mesenchymal stem cells thus alter the outcome of the immune response by changing the cytokine secretion of dendritic and T-cell subsets. This results in a shift from a pro-inflammatory environment to an anti-inflammatory or tolerant cell environment. Endothelial stem cells are one of the three types of multipotent stem cells found in the bone marrow. They are a rare and controversial group with the ability to differentiate into endothelial cells, the cells that line blood vessels. The existence of stem cells in the adult brain has been postulated following the discovery that the process of neurogenesis, the birth of new neurons, continues into adulthood in rats
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Adult stem cell The presence of stem cells in the mature primate brain was first reported in 1967. It has since been shown that new neurons are generated in adult mice, songbirds and primates, including humans. Normally, adult neurogenesis is restricted to two areas of the brain – the subventricular zone, which lines the lateral ventricles, and the dentate gyrus of the hippocampal formation. Although the generation of new neurons in the hippocampus is well established, the presence of true self-renewing stem cells there has been debated. Under certain circumstances, such as following tissue damage in ischemia, neurogenesis can be induced in other brain regions, including the neocortex. Neural stem cells are commonly cultured "in vitro" as so called neurospheres – floating heterogeneous aggregates of cells, containing a large proportion of stem cells. They can be propagated for extended periods of time and differentiated into both neuronal and glia cells, and therefore behave as stem cells. However, some recent studies suggest that this behaviour is induced by the culture conditions in progenitor cells, the progeny of stem cell division that normally undergo a strictly limited number of replication cycles "in vivo". Furthermore, neurosphere-derived cells do not behave as stem cells when transplanted back into the brain. Neural stem cells share many properties with haematopoietic stem cells (HSCs). Remarkably, when injected into the blood, neurosphere-derived cells differentiate into various cell types of the immune system
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Adult stem cell Olfactory adult stem cells have been successfully harvested from the human olfactory mucosa cells, which are found in the lining of the nose and are involved in the sense of smell. If they are given the right chemical environment, these cells have the same ability as embryonic stem cells to develop into many different cell types. Olfactory stem cells hold the potential for therapeutic applications and, in contrast to neural stem cells, can be harvested with ease without harm to the patient. This means they can be easily obtained from all individuals, including older patients who might be most in need of stem cell therapies. Hair follicles contain two types of stem cells, one of which appears to represent a remnant of the stem cells of the embryonic neural crest. Similar cells have been found in the gastrointestinal tract, sciatic nerve, cardiac outflow tract and spinal and sympathetic ganglia. These cells can generate neurons, Schwann cells, myofibroblast, chondrocytes and melanocytes. Multipotent stem cells with a claimed equivalency to embryonic stem cells have been derived from spermatogonial progenitor cells found in the testicles of laboratory mice by scientists in Germany and the United States, and, a year later, researchers from Germany and the United Kingdom confirmed the same capability using cells from the testicles of humans. The extracted stem cells are known as human adult germline stem cells (GSCs) Multipotent stem cells have also been derived from germ cells found in human testicles
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Adult stem cell treatments have been used for many years to successfully treat leukemia and related bone/blood cancers utilizing bone marrow transplants. The use of adult stem cells in research and therapy is not considered as controversial as the use of embryonic stem cells, because the production of adult stem cells does not require the destruction of an embryo. Early regenerative applications of adult stem cells has focused on intravenous delivery of blood progenitors known as Hematopetic Stem Cells (HSC's). CD34+ hematopoietic Stem Cells have been clinically applied to treat various diseases including spinal cord injury, liver cirrhosis and Peripheral Vascular disease. Research has shown that CD34+ hematopoietic Stem Cells are relatively more numerous in men than in women of reproductive age group among spinal cord Injury victims. Other early commercial applications have focused on Mesenchymal Stem Cells (MSCs). For both cell lines, direct injection or placement of cells into a site in need of repair may be the preferred method of treatment, as vascular delivery suffers from a "pulmonary first pass effect" where intravenous injected cells are sequestered in the lungs. Clinical case reports in orthopedic applications have been published. Wakitani has published a small case series of nine defects in five knees involving surgical transplantation of mesenchymal stem cells with coverage of the treated chondral defects. Centeno et al
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Adult stem cell have reported high field MRI evidence of increased cartilage and meniscus volume in individual human clinical subjects as well as a large n=227 safety study. Many other stem cell based treatments are operating outside the US, with much controversy being reported regarding these treatments as some feel more regulation is needed as clinics tend to exaggerate claims of success and minimize or omit risks. The therapeutic potential of adult stem cells is the focus of much scientific research, due to their ability to be harvested from the parent body that is females during the delivery. In common with embryonic stem cells, adult stem cells have the ability to differentiate into more than one cell type, but unlike the former they are often restricted to certain types or "lineages". The ability of a differentiated stem cell of one lineage to produce cells of a different lineage is called transdifferentiation. Some types of adult stem cells are more capable of transdifferentiation than others, but for many there is no evidence that such a transformation is possible. Consequently, adult stem therapies require a stem cell source of the specific lineage needed, and harvesting and/or culturing them up to the numbers required is a challenge. Additionally, cues from the immediate environment (including how stiff or porous the surrounding structure/extracellular matrix is) can alter or enhance the fate and differentiation of the stem cells. Pluripotent stem cells, i.e
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Adult stem cell cells that can give rise to any fetal or adult cell type, can be found in a number of tissues, including umbilical cord blood. Using genetic reprogramming, pluripotent stem cells equivalent to embryonic stem cells have been derived from human adult skin tissue. Other adult stem cells are multipotent, meaning they are restricted in the types of cell they can become, and are generally referred to by their tissue origin (such as mesenchymal stem cell, adipose-derived stem cell, endothelial stem cell, etc.). A great deal of adult stem cell research has focused on investigating their capacity to divide or self-renew indefinitely, and their potential for differentiation. In mice, pluripotent stem cells can be directly generated from adult fibroblast cultures. In recent years, acceptance of the concept of adult stem cells has increased. There is now a hypothesis that stem cells reside in many adult tissues and that these unique reservoirs of cells not only are responsible for the normal reparative and regenerative processes but are also considered to be a prime target for genetic and epigenetic changes, culminating in many abnormal conditions including cancer. (See cancer stem cell for more details.) Adult stem cells express transporters of the ATP-binding cassette family that actively pump a diversity of organic molecules out of the cell. Many pharmaceuticals are exported by these transporters conferring multidrug resistance onto the cell
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Adult stem cell This complicates the design of drugs, for instance neural stem cell targeted therapies for the treatment of clinical depression.
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Mario Garavaglia (born 1937) is an Argentine physicist. He was born in Junín (Buenos Aires Province, Argentina) in 1937. In 1999 the International Commission for Optics awarded him the "Galileo Galilei Award" by unanimous vote for his work on lasers and their applications in industry, medicine and biology and for promoting optics in Latin America. In 2004 he received the Houssay Career Award.
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HEPnet or the High-Energy Physics Network is a telecommunications network for researchers in high-energy physics. It originated in the United States, but that has spread to most places involved in such research. Well-known sites include Argonne National Laboratory, Brookhaven National Laboratory and Lawrence Berkeley.
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Neutron economy is defined as the ratio of an adjoint weighted average of the excess neutron production divided by an adjoint weighted average of the fission production. The distribution of neutron energies in a nuclear reactor differs from the fission neutron spectrum due to the slowing down of neutrons in elastic and inelastic collisions with fuel, coolant and construction material. Neutrons slow down in elastic and inelastic collisions, until they are absorbed via Neutron capture or lost by leakage. is the balanced account, in a reactor, of the neutrons created and the neutrons lost through absorption by non-fuel elements, resonance absorption by fuel, and leakage while fast and thermal energy ranges. Heavy water is an extremely efficient moderator. As a result, reactors using heavy water, such as the CANDU, also have a high neutron economy. The quantity that indicates how much the neutron economy is out of balance is given the term reactivity. If a reactor is exactly critical—that is, the neutron production is exactly equal to neutron destruction—the reactivity is zero. If the reactivity is positive, the reactor is supercritical. If the reactivity is negative, the reactor is subcritical. The term "neutron economy" is used not just for the instantaneous reactivity of a reactor, but also to describe the overall efficiency of a nuclear reactor design.
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National Collegiate Weather Forecasting Contest The National Collegiate Weather Forecasting Contest, or NCWFC, was a yearly competition among colleges and Universities in the US run by Penn State. There were over 1000 participants from about 45 institutions. In 2006, the competition was transferred to the University of Oklahoma and run as the WxChallenge. Entrants in the contest must be affiliated with a college or university, but they range in age and knowledge from undergraduates to professors. Each year, 13 cities are picked for forecasting; the current city changes every 2 weeks. Contestants forecast 4 days per week for the following day's high temperature (in Fahrenheit), low temperature, and precipitation (forecast by category). The precipitation categories are: One "error" point is given for each degree of error on temperature, and 4 error points are given for each error in precipitation category.
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Selenite (ion) The selenite anion is a selenium oxoanion with the chemical formula . A selenite (compound) is a compound that contains this ion. In slightly acid conditions, the hydrogenselenite ion, , is formed; in more acidic conditions selenous acid, HSeO, exists. Most selenite salts can be formed by heating the relevant metal oxide with selenium dioxide, e.g.: See for a list.
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Subtelomere Subtelomeres are segments of DNA between telomeric caps and chromatin. Telomeres are specialized protein–DNA constructs present at the ends of eukaryotic chromosomes, which prevent them from degradation and end-to-end chromosomal fusion. Introductory biology courses often describe telomeres as a type of chromosomal aglet. Most vertebrate telomeric DNA consists of long (TTAGGG)n repeats of variable length, often around 3-20kb. "Subtelomeres" are segments of DNA between telomeric caps and chromatin. Each chromosome has two subtelomeres immediately adjacent to the long (TTAGGG)n repeats. Subtelomeres are considered to be the most distal (farthest from the centromere) region of unique DNA on a chromosome and they are unusually dynamic and variable mosaics of multichromosomal blocks of sequence. The subtelomeres of such diverse species as Humans, Plasmodium falciparum, Drosophila melanogaster or Saccharomyces cerevisiae, are structurally similar in that they are composed of various repeated elements, but the extent of the subtelomeres and the sequence of the elements vary greatly among organisms. In yeast ("S. cerevisiae"), subtelomeres are composed of two domains : the proximal and distal (telomeric) domains
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Subtelomere The two domains differ in sequence content and extent of homology to other chromosome ends and they are often separated by a stretch of degenerate telomere repeats (TTAGGG) and an element called 'core X', which is found at all chromosome ends and contains an autonomously replicating sequence (ARS) and an ABF1 binding site. The proximal domain is composed of variable interchromosomal duplications (<1-30 kb), this region can contain genes such "Pho", "Mel", "Mal" and open reading frames (ORFs). The distal domain is composed of 0-4 tandem copies of the highly conserved Y' element which contains other ORFs, the number and chromosomal distribution of Y′ elements varies among yeast strains. Between the core X and the Y' element or the core X and TTAGGG sequence there is often a set of 4 'subtelomeric repeats elements' (STR) : STR-A, STR-B, STR-C and STR-D which consists of multiple copies of the vertebrate telomeric motif TTAGGG. This two-domain structure is remarkably similar to the subtelomere structure in human chromosomes 20p, 4q and 18p in which proximal and distal subtelomeric domains are separated by a stretch of degenerate TTAGGG repeats, but, the picture that emerges from studies of the subtelomeres of other human chromosomes indicates that the two-domain model does not apply universally. This structure with repeated sequences is responsible for frequent duplication events (which create new genes) and recombination events, at the origin of combination diversity
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Subtelomere These peculiar properties are mechanisms that generate diversity at an individual scale and therefore contribute to adaptation of organisms to their environments. For example, in "Plasmodium falciparum" during interphase of erythrocytic stage, the chromosomic extremities are gathered at the cell nucleus periphery, where they undergo frequent deletion and telomere position effect (TPE). This event in addition to expansion and deletion of subtelomeric repeats, give rise to chromosome size polymorphisms and so, subtelomeres undergo epigenetic and genetic controls. Thanks to the properties of subtelomeres, "Plasmodium falciparum" evades host immunity by varying the antigenic and adhesive character of infected erythrocytes (see Subtelomeric transcripts). Variation of subtelomeric regions are mostly variation on STRs, due to recombination of large-scale stretches delimited by (TTAGGG)n-like repeated sequences, which play an important role in recombination and transcription. Haplotype (DNA sequence variants) and length differences are therefore observed between individuals. Subtelomeric transcripts are pseudogenes (transcribed genes producing RNA sequences not translated into protein) and gene families. In humans, they code for olfactory receptors, immunoglobulin heavy chains, and zinc-finger proteins
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Subtelomere In other species, several parasites such as Plasmodium and Trypanosoma brucei have developed sophisticated evasion mechanisms to adapt to the hostile environment posed by the host, such as exposing variable surface antigens to escape the immune system. Genes coding for surface antigens in these organisms are located at subtelomeric regions, and it has been speculated that this preferred location facilitates gene switching and expression, and the generation of new variants. For example, the genes belonging to the "var" family in Plasmodium falciparum (agent of malaria) code for the PfEMP1 ("Plasmodium falciparum" erythrocyte membrane protein 1), a major virulence factor of erythrocytic stages, "var" genes are mostly localized in subtelomeric regions. Antigenic variation is orchestrated by epigenetic factors including monoallelic var transcription at separate spatial domains at the nuclear periphery (nuclear pore), differential histone marks on otherwise identical var genes, and var silencing mediated by telomeric heterochromatin. Other factors such as non-coding RNA produced in subtelomeric regions adjacent or within "var" genes may contribute as well to antigenic variation. In "Trypanosoma brucei" (agent of sleeping sickness), variable surface glycoprotein (VSG) antigenic variation is a relevant mechanism used by the parasite to evade the host immune system
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Subtelomere VSG expression is exclusively subtelomeric and occurs either by in situ activation of a silent VSG gene or by DNA rearrangement that inserts an internal silent copy of a VSG gene into an active telomeric expression site. To contrast with "Plasmodium falciparum", in "Trypanosoma brucei", antigenic variation is orchestrated by epigenetic and genetic factors. In Pneumocystis jirovecii major surface glycoprotein (MSG) gene family cause antigenic variation. MSG genes are like boxes at chromosome ends and only the MSG gene at the unique locus UCS (upstream conserved sequence) is transcribed. Different MSG genes can occupy the expression site (UCS), suggesting that recombination can take a gene from a pool of silent donors and install it at the expression site, possibly via crossovers, activating transcription of a new MSG gene, and changing the surface antigen of "Pneumocystis jirovecii". Switching at the expression site is probably facilitated by the subtelomeric locations of expressed and silent MSG genes. A second subtelomeric gene family, MSR, is not strictly regulated at the transcriptional level, but may contribute to phenotypic diversity. Antigenic variation in "P. jirovecii" is dominated by genetic regulation. Loss of telomeric DNA through repeated cycles of cell division is associated with senescence or somatic cell aging
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Subtelomere In contrast, germ line and cancer cells possess an enzyme, telomerase, which prevents telomere degradation and maintains telomere integrity, causing these types of cells to be very long-lived. In humans, the role of subtelomere disorders is demonstrated in facioscapulohumeral muscular dystrophy (FSHD), Alzheimer's disease, and peculiar syndromic diseases (malformation and mental retardation). For example, FSHD is associated with a deletion in the subtelomeric region of chromosome 4q. A series of 10 to >100 kb repeats is located in the normal 4q subtelomere, but FSHD patients have only 1–10 repeat units. This deletion is thought to cause disease owing to a position effect that influences the transcription of nearby genes, rather than through the loss of the repeat array itself. Subtelomeres are DNA segments located before telomeres and after chromatin. Subtelomeres are homologous to other subtelomeres that are located at different chromosomes and are a type of transposable element; DNA segments that can move around the genome. Although subtelomeres are pseudogenes and do not code for protein, they provide an evolutionary advantage by diversifying genes. The duplication, recombination, and deletion of subtelomeres allows for the creation of new genes and new chromosomal properties
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Subtelomere The advantages of subtelomeres have been studied in different species such as Plasmodium_falciparum, Drosophila melanogaster, Saccharomyces cerevisiae, since they have similar genetic elements to humans, not accounting for length and sequence. Subtelomeres might have the same role in plants since the same advantage have been found in a common bean plant known as Phaseolus vulgaris. Different varieties of subtelomeres are frequently rearranging during meiotic and mitotic recombination, indicating that subtelomeres are frequently shuffling, which causes new and rapid genetic changes in chromosomes. In Saccharomyces cerevisiae, 15kb region of chromosome 7L in subtelomeres maintained cell viability in the removal of telomerase, while the removal of the last 15kb increased chromosome senescence. The knockout of subtelomeres in fission yeast, Schizosaccharomyces pombe cells does not impede mitosis and meiosis from occurring, indicating that subtelomeres are not necessary for cell division. They are not needed for the procession of mitosis and meiosis yet, subtelomeres take advantage of cellular DNA recombination. The knockout of subtelomeres in Schizosaccharomyces pombe cells does not affect the regulation of multiple stress responses, when treated with high doses of hydroxyurea, camptothecin, ultraviolet radiation, and thiabendazole. Knockout of Subtelomeres in Schizosaccharomyces pombe cells did not affect the length of telomeres, indicating that they play no role it the regulation of length
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Subtelomere However, subtelomeres strongly influences the replication timing of telomeres. Knockout of subtelomeres in Schizosaccharomyces pombe cells after the loss of telomerase does not affect cell survival, indicating that subtelomeres are not necessary for cell survival. An explanation as to why subtelomeres are not necessary after the loss of telomerase is because the chromosomes can use intra or inter-chromosomal circularization or HAATI to maintain chromosomal stabilization. However, the use of inter-chromosomal circularization engenders chromosome instability by creating two centromeres in a single chromosome, causing chromosomal breakage during mitosis. In response to this, the chromosome could induce centromere inactivation to impede the formation of two centromeres but, this would induce heterochromatin formation in centromeres. Heterochromatin can be deleterious if it gets into a location that it is not supposed to be in. Subtelomeres are responsible to block heterochromatin from getting into the euchromatin region. Subtelomeres can mitigate the effects of heterochromatin invasion, by distributing heterochromatin around the ends of the subtelomeres. Without subtelomeres, heterochromatin would spread around the region of subtelomeres, getting too close to important genes. At this distance, heterochromatin can silence genes that are nearby, resulting in a higher sensitivity to osmotic stress. Subtelomeres carry out essential functions with Shugonshi protein
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Subtelomere Shugonshi is a centromere protein for chromosome segregation during meiosis and mitosis. There are two types of Shugonshi protein: SGOL1 and SGOL2. Sgo1 is only expressed in meiosis 1 for centromeric cohesion of the sister chromosomes, while Sgo2 is expressed in both cell cycles and is responsible for the segregation of chromosomes in the M phase. Not only is Sgo2 expressed in centromeres, but it is also expressed in subtelomeres. Sgo2 interacts with subtelomeres during interphase; middle of the G2 phase. Sgo2 remains in subtelomeres, whose cells lack telomere DNA and plays a major role in creating knobs, which is a highly concentrated chromatin body. Sog2 increases the gene expression of subtelomeres, but it does not increase gene expression in other Sog2 cells. Sog2 increases gene expressions that have to do with transcription and histone configurations by Sgo2 forms a new chromatin repressor for telomere gene expression that is different from the H3K9me3- Swi6-mediated heterochromatin. Sgo2 represses subtelomeres replication by suppressing Sld3, a replication factor, at the start of the replication. analysis, especially sequencing and profiling of patient subtelomeres, is difficult because of the repeated sequences, length of stretches, and lack of databases on the topic.
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Logan Sapphire The is a flawless specimen from Sri Lanka, a cushion-cut stone which possesses a rich deep blue color and is the second largest (blue) sapphire known, weighing 422.99 carats (84.6 g). The stone, roughly the size of an egg, is one of the world's largest and most famous sapphires. The is named after Polly Logan, who donated the gemstone to the Smithsonian Institution in 1960. The is set in a brooch surrounded by 20 round brilliant cut diamonds weighing, in total, 16 carats (3.2 g). It is currently on display at the National Museum of Natural History in Washington, D.C., alongside the Bismarck Sapphire Necklace and the Hall Sapphire and Diamond Necklace.
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https://en.wikipedia.org/wiki?curid=2794892
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Malcolm MacLeod (British Army officer) Major-General Malcolm Neynoe MacLeod (23 May 1882–1 August 1969) was Director General of the Ordnance Survey from 1935 to 1943. In 1935 he started the retriangulation of Great Britain, an immense task which involved erecting concrete triangulation pillars (trig points) on prominent (often inaccessible) hilltops throughout Britain. As well as being an immense physical task, it was also an extremely complex mathematical undertaking. MacLeod can fairly be said to be the creator of the Ordnance Survey in its modern form. MacLeod was commissioned in the Royal Engineers in 1900, serving in India from 1902 until 1914. During World War I he commanded the 4th Field Survey Battalion and was awarded the MC in the 1917 New Year Honours. He became Chief Instructor at the School of Artillery, Larkhill in 1920, serving until 1923 when he moved to the Ordnance Survey. He was Director-General of the Ordnance Survey in 1935, retiring in 1943.
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https://en.wikipedia.org/wiki?curid=2796159
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Sarepta Therapeutics Sarepta Therapeutics, Inc. () is a medical research and drug development company with corporate offices and research facilities in Cambridge, Massachusetts, United States. Incorporated in 1980 as AntiVirals, shortly before going public the company changed its name from AntiVirals to AVI BioPharma soon with stock symbol AVII and in July 2012 changed name from AVI BioPharma to and SRPT respectively. As of the end of 2019, the company has two approved drugs (see the Products section below). Sarepta started in Corvallis, Oregon on January 1, 1980 and was originally named Antivirals Inc.. After occupying several research laboratory spaces in Corvallis the company opened a production laboratory in Corvallis in February 2002 and was renamed AVI BioPharma Inc. The company made headlines in 2003 when it announced work on treatments for severe acute respiratory syndrome (SARS) and the West Nile virus. In July 2009, the company announced they would move their headquarters from Portland, Oregon, north to Bothell, Washington, near Seattle. At that time the company led by president and CEO Leslie Hudson had 83 employees and quarterly revenues of $3.2 million. AVI had yet to turn a profit and had not yet developed any commercial products as of July 2009. The company lost $19.7 million in the second quarter of 2009, and then won an $11.5 million contract with the U.S. Department of Defense's Defense Threat Reduction Agency in October 2009. By this time the company had completed its headquarters move to Bothell
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https://en.wikipedia.org/wiki?curid=2796300
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Sarepta Therapeutics In 2012 the company moved a second time, to Cambridge, Massachusetts. At the time, CEO Chris Garabedian indicated the move was motivated by the need to recruit expertise in rare diseases. The Corvallis laboratory facility was closed in 2016. In February, Sarepta acquired five gene therapy candidates for $165 million after one of them, MYO-101, produced results with a new gene therapy candidate for patients with Limb-Girdle muscular dystrophy; two months after receiving a single treatment, muscles from all three patients were producing the protein they couldn't make on their own. Its primary products are Morpholino oligomers (PMOs), synthetic nucleic acid analogs that were conceived of by James Summerton and invented by Summerton with Dwight Weller, originally developed under the name NeuGene Antisense. Since morpholino oligomers can form sequence-specific double-stranded complexes with RNA they are suitable use in antisense therapy. In one application, translation blocking, a morpholino oligomer binds to messenger RNA produced by a known disease-causing gene to prevent it from being translated into protein. Morpholinos can also work as splice-switching oligos, targeting pre-mRNA to alter splicing and so causing changes in the structure of the mature mRNA (the mechanism of the approved drug eteplirsen)
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https://en.wikipedia.org/wiki?curid=2796300
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Sarepta Therapeutics Morpholinos have been tested for a wide range of applications including prevention of cardiac restenosis after angioplasty, treatment of coronary artery bypass grafts, treatment of polycystic kidney disease, redirection of drug metabolism, treatment of some mutations causing Duchenne muscular dystrophy (DMD), and inhibition of infectious diseases. Their greatest clinical & commercial success thus far has been in treatment of DMD. A new class of Morpholino oligos, the peptide-linked Morpholinos or PPMO, are linked to an arginine-rich cell-penetrating peptide to enhance their delivery into cells and have entered clinical trials The Morpholino drug eteplirsen, targeting exon 51 of the dystrophin mRNA, has been approved as a human therapeutic by the FDA in 2016 and clinical trials for Morpholinos targeting other exons are ongoing. Morpholinos have been used in preclinical studies to inhibit replication of a broad range of viruses, including influenza, West Nile virus, SARS, hepatitis C, dengue fever, Ebola and Calicivirus, all of which are single stranded RNA viruses. They are in advanced development for prevention and treatment of Ebola and Marburg viruses. In March 2013, the Company announced positive results from a non-human primate study of AVI-7288, the drug candidate for treatment of Marburg virus infection. The results showed that intramuscular administration of AVI-7288 resulted in survival rates up to 100 percent in monkeys exposed to this fatal virus
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https://en.wikipedia.org/wiki?curid=2796300
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