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human-animal hybrids called the New Men who were created by the High Evolutionary by evolving the animals into humanoid forms. === Video games === Multiple video games have featured human-animal hybrids as enemies for the protagonist(s) to defeat, including powerful boss characters. For instance, the 2014 survival horror release The Evil Within includes grotesque hybrid beings, looking like the undead, attacking main character Detective Sebastian Castellanos. With partners Joseph Oda and Julie Kidman, the protagonist attempts investigate a multiple homicide at a mental hospital yet discovers a mysterious figure who turns the world around them into a living nightmare, Castellanos having to find the truth about the criminal psychopath. === Furry fandom === With general U.S. popular culture and its various subcultures, the furry fandom consists of individuals interested in a variety of artistic materials, this often featuring "furry art... [that] depicts a human-animal hybrid in everyday life". Specific people involved in creative media will frequently come up with a "fursona" depicting a version or versions of themselves as a hybrid creature. This practice functions as an outlet based on "personal ideas of self-expression" (self-realization). == See also == == References == == External links == "Chinese Human-animal Hybrid Embryo Experiments Have Been Interrupted" – Sina.com report (in Chinese) "The First Individual Animal-hybrid Embryos Are from China" – Xinhua News Agency report (in Chinese)
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{
"page_id": 47449480,
"source": null,
"title": "Human–animal hybrid"
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GCB Bioenergy: Bioproducts for a Sustainable Bioeconomy is a monthly peer-reviewed scientific journal covering research on the interface between biological systems and the production of bioenergy, biofuels and bioproducts directly from plants, algae and waste. The editor-in-chief is Stephen P. Long, environmental plant physiologist, Fellow of the Royal Society and member of the National Academy of Sciences (University of Illinois and Lancaster University). This journal is a sister journal to Global Change Biology. == External links == Official website == References ==
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{
"page_id": 68093322,
"source": null,
"title": "GCB Bioenergy"
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Claude Berger (January 20, 1679, Paris – May 22, 1712, Passy) was a French medical doctor and chemist. == Biography == He was a medical doctor from the Faculty of Paris and received his degree in medicine in 1669, after presenting a thesis under the presidency of Guy-Crescent Fagon, first physician to the king, against the use of tobacco. Claude Berger was related to Fagon, but the latter only knew him during this thesis. Fagon subsequently granted him his friendship and protection. He worked on the study of plants with Joseph Pitton de Tournefort, who appreciated him and recruited him as his pupil at the Royal Academy of Sciences. Berger joined the Academy on February 14, 1699. After various arrangements inside the academy, he became a pupil of Guillaume Homberg on January 27, 1700. Having been received as a doctor of medicine, he was obliged to give lessons at the Schools of Paris for two years, where he was quite successful. He visited the sick with his father and replaced him for the last two years of his father’s life, from 1703. He succeeded his father after his death and was appointed doctor regent, in 1705. In 1708 he obtained the position of medical adviser to the king for 22,000 pounds, which required him to be present at Versailles the first quarter of each year. == References ==
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"page_id": 71173518,
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"title": "Claude Berger"
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Multi-parametric surface plasmon resonance (MP-SPR) is based on surface plasmon resonance (SPR), an established real-time label-free method for biomolecular interaction analysis, but it uses a different optical setup, a goniometric SPR configuration. While MP-SPR provides same kinetic information as SPR (equilibrium constant, dissociation constant, association constant), it provides also structural information (refractive index, layer thickness). Hence, MP-SPR measures both surface interactions and nanolayer properties. == History == The goniometric SPR method was researched alongside focused beam SPR and Otto configurations at VTT Technical Research Centre of Finland since 1980s by Dr. Janusz Sadowski. The goniometric SPR optics was commercialized by Biofons Oy for use in point-of-care applications. Introduction of additional measurement laser wavelengths and first thin film analyses were performed in 2011 giving way to MP-SPR method. == Principle == The MP-SPR optical setup measures at multiple wavelengths simultaneously (similarly to spectroscopic SPR), but instead of measuring at a fixed angle, it rather scans across a wide range of θ angles (for instance 40 degrees). This results in measurements of full SPR curves at multiple wavelengths providing additional information about structure and dynamic conformation of the film. == Measured values == The measured full SPR curves (x-axis: angle, y-axis: reflected light intensity) can be transcribed into sensograms (x-axis: time, y-axis: selected parameter such as peak minimum, light intensity, peak width). The sensograms can be fitted using binding models to obtain kinetic parameters including on- and off-rates and affinity. The full SPR curves are used to fit Fresnel equations to obtain thickness and refractive index of the layers. Also due to the ability of scanning the whole SPR curve, MP-SPR is able to separate bulk effect and analyte binding from each other using parameters of the curve. While QCM-D measures wet mass, MP-SPR and other optical methods measure dry mass, which
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{
"page_id": 49808784,
"source": null,
"title": "Multi-parametric surface plasmon resonance"
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enables analysis of water content of nanocellulose films. == Applications == The method has been used in life sciences, material sciences and biosensor development. In life sciences, the main applications focus on pharmaceutical development including small-molecule, antibody or nanoparticle interactions with target with a biomembrane or with a living cell monolayer. As first in the world, MP-SPR is able to separate transcellular and paracellular drug uptake in real-time and label-free for targeted drug delivery. In biosensor development, MP-SPR is used for assay development for point-of-care applications. Typical developed biosensors include electrochemical printed biosensors, ELISA and SERS. In material sciences, MP-SPR is used for optimization of thin solid films from Ångströms to 100 nanometers (graphene, metals, oxides), soft materials up to microns (nanocellulose, polyelectrolyte) including nanoparticles. Applications including thin film solar cells, barrier coatings including anti-reflective coatings, antimicrobial surfaces, self-cleaning glass, plasmonic metamaterials, electro-switching surfaces, layer-by-layer assembly, and graphene. == References ==
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{
"page_id": 49808784,
"source": null,
"title": "Multi-parametric surface plasmon resonance"
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Artificial plants are imitations of natural plants used for commercial or residential decoration. They are sometimes made for scientific purposes (the collection of glass flowers at Harvard University, for example, illustrates the flora of the United States). Artificial plants vary widely from mass-produced varieties that are distinguishable from real plants by casual observation to highly detailed botanical or artistic specimens. Materials used in their manufacture have included painted linen and shavings of stained horn in ancient Egypt, gold and silver in ancient Rome, rice-paper in China, silkworm cocoons in Italy, colored feathers in South America, and wax and tinted shells. Modern techniques involve carved or formed soap, nylon netting stretched over wire frames, ground clay, and mass-produced injection plastic mouldings. Polyester has been the main material for manufacturing artificial flowers since the 1970s. Most artificial flowers in the market nowadays are made of polyester fabric and plastic. == Production == The industry is now highly specialized with several different manufacturing processes. Hundreds of artificial flower factories in the Pearl River delta area of Guangdong province in China have been built since the early 1980s. Thousands of 40-foot containers of polyester flowers and plants are exported to many countries every year. === Polyester and paper === Five main processes may be distinguished: The first step consists of putting the polyester fabric in gelatine in order to stiffen it. The second consists of cutting up the various polyester fabrics and materials employed into shapes suitable for forming the leaves, petals, etc.; this may be done with scissors, but is more often done with stamps that can cut through a dozen or more thicknesses at one blow. Next, the veins of the leaves are impressed by means of silk screen printing with a dye, and the petals are given their natural rounded forms
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{
"page_id": 2622866,
"source": null,
"title": "Artificial plants"
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by goffering irons of various shapes. The next step is to assemble the petals and other parts of the flower, which is built up from the center outwards. The fifth is to mount the flower on a stalk of brass or iron wire wrapped with suitably colored material, and to add the leaves to complete the spray. While the material most often used to make artificial flowers is polyester fabric, both paper and cloth flowers are also made with origami. === Nylon stocking flowers === The art of nylon flower making is an easy to learn craft which uses simple tools and inexpensive material to achieve stunning results. Nylon flower making enjoyed a brief popularity in the United States in the 1970s and soon became very popular in Japan. In recent years, the craft's popularity has spread Asia, Europe and Australia. With the advent of new colors and materials, the art has expanded to infinite new possibilities of nylon flower making. The basic materials needed to make nylon flowers include: wire, stem wire, nylon stocking, nylon threading, floral tape and stamen. Some flowers require cotton balls or sheets (or batting), white glue, acrylic paint and paint brushes. === Silk flowers === Silk flowers are crafted from a protein fibre spun by the silk worm, producing lifelike flowers. Flowers described as being made of silk with a "real touch technique" are not made of silk, but rather are made of polyester, polymers and plastics. Moreover, textile items made of polyester but marketed as "silk" violate the US federal law – specifically the 1959 Textile Fiber Products Identification Act. === Soap === There are two methods: Carved: A bar with layered coloured soap is mounted in a lathe, and circular grooves are chiseled into it. The finished flower is symmetric and regular,
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{
"page_id": 2622866,
"source": null,
"title": "Artificial plants"
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but the flowers are not identical and can be called handmade. Moulded: An oil-less soap milled to a powder is mixed with water, and the paste is used as a modelling material. Leaf and petal textures are stamped or rolled onto the soap. This is an expensive, labour-intensive process. === Clay === Clay flowers are made by hand from special air-dry polymer clay or cold porcelain, steel wire, paint, glue, tape and sometimes paper and foam as a filler. With the help of cutters, where each flower has its own cutter set, the parts are cut from the still soft clay and then formed with specially designed tools. After drying, these parts are, when needed, painted with precision and then very precisely assembled into a whole flower. When made by a skilful artisan, clay flowers can be very realistic. From Thailand, where this art is very popular, it has spread to Europe, Russia and the US. === Glass === Glass is melted and blown by hand into flower shapes. Working with glass at high temperatures to form a flower is very difficult, which is why glass flowers are much more expensive than typical artificial flowers. === Plastic === Injection moulding is used for mass manufacture of plastic flowers. Plastic is injected into a preformed metal die. == Simulacraceae == The journal Ethnobotany Research and Applications published a tongue-in-cheek paper that claims to be the culmination of a six-year project in the exhaustive taxonomy of artificial plants, and lumped the group into a single family called the Simulacraceae ("the family of simulated plants"). == History == Floral wreaths made by the ancient Egyptians were formed from thin plates of horn stained in different colors. They also sometimes consisted of leaves of copper, gilt or were silvered over. The ancient Romans excelled
|
{
"page_id": 2622866,
"source": null,
"title": "Artificial plants"
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in the art of imitating flowers in wax and in this branch of the art attained a degree of perfection which has not been approached in modern times. Crassus, renowned for his wealth, gave to the victors in the games he celebrated at Rome crowns of artificial leaves made of gold and silver. In more recent times, Italians were the first to acquire celebrity for the skill and taste they displayed in this manufacture. Later English, American, and especially French manufactures were celebrated. The Chinese and Japanese show great dexterity in this work. These early artificial flowers were made out of many-coloured ribbons which were twisted together and attached to small pieces of wire. But these first attempts were decidedly crude. In the first half of the 19th century, the Swedish artist Emma Fürstenhoff became internationally renowned in Europe for her artificial flower arrangements of wax in a technique regarded as a novelty in contemporary Europe. Wax flower sculptures were popular in the 1840s and 1850s in Britain, with noted sculptors including the London-based Emma Peachey and the Mintorn family. In the 1910s, Beat-Sofi Granqvist studied the manufacture of artificial flowers in Germany. After returning to Finland, she founded Finland's first artificial flower factory, next to her apartment at Pieni Roobertinkatu 4-6. In the course of time feathers were substituted for ribbons, a more delicate material, but one to which it was not so easy to give the requisite shades of color. The plumage of the birds of South America was adapted for artificial flowers on account of the brilliancy and permanence of the tints, and the natives of that continent long practised with success the making of feather flowers. The London Zoo contains a collection of artificial flowers made out of the feathers of hummingbirds. == Gallery == ==
|
{
"page_id": 2622866,
"source": null,
"title": "Artificial plants"
}
|
See also == Artificial Christmas tree == References ==
|
{
"page_id": 2622866,
"source": null,
"title": "Artificial plants"
}
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Cancer immunoprevention is the prevention of cancer onset with immunological means such as vaccines, immunostimulators or antibodies. Cancer immunoprevention is conceptually different from cancer immunotherapy, which aims at stimulating immunity in patients only after tumor onset, however the same immunological means can be used both in immunoprevention and in immunotherapy. == Immunoprevention of tumors caused by viruses == Immunoprevention of tumors caused by viruses or other infectious agents aims at preventing or curing infection before the onset of cancer. Effective vaccines are available for use in humans. Some tumor types in humans and in animals are the consequence of viral infections. In humans the most frequent viral tumors are liver cancer (also called hepatocellular carcinoma), arising in a small proportion of patients with chronic infection by hepatitis B virus (HBV) or hepatitis C virus (HCV), and carcinoma of the uterine cervix (also called cervical cancer), caused by human papilloma virus (HPV). Altogether these two tumors make 10% of all human cancers, affecting almost one million new patients each year worldwide. The HBV vaccine, now in worldwide use, was shown to reduce the incidence of liver carcinoma. Cancer immunoprevention by the HBV vaccine can be thought of as a beneficial side effect of vaccine developed and used to prevent hepatitis B. This is not the case with HPV vaccines, which were primarily developed for cancer prevention. Clinical trials showed that HPV vaccines can prevent HPV infection and carcinogenesis almost completely; these results led to vaccine approval by regulatory agencies in USA and Europe. == Immunoprevention of non-infectious tumors == Is it possible to devise immunopreventive strategies for tumors not caused by infectious agents? The challenge is to predict in each individual the risk of specific cancer types and to design immune strategies targeting these cancer types. This is not yet feasible
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{
"page_id": 15533459,
"source": null,
"title": "Cancer immunoprevention"
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in humans, thus immunoprevention of non-infectious tumors is at a preclinical stage of development. Effective immunoprevention of various types of cancer was obtained in murine models of cancer risk, in particular in transgenic mice harboring activated oncogenes, thus demonstrating that activation of the immune system in healthy hosts can indeed prevent carcinogenesis. Both non-specific immune stimuli, like cytokines and other immunostimulators, and vaccines containing a specific antigen were active in mouse models; combinations of both types of agents yielded the best results, up to an almost complete, long-term block of carcinogenesis in models of aggressive cancer development. === Clinical development and risks === The success of cancer immunoprevention in preclinical models suggests that it might have an impact also in humans. The main problems to be solved are the definition of appropriate human applications and of the risks for human health. Application to the general population, as is being done for vaccines against HBV and HPV, is currently unfeasible, because it would require a precise individual prediction of the risk of cancer. Subgroups at high risk of developing a defined type of tumor, for example families with hereditary cancer or individuals with preneoplastic lesions, are the natural candidates for immunoprevention of non-infectious tumors. It has also been suggested that immunopreventive strategies can have therapeutic effects against metastases, hence early human trials could aim at cancer therapy rather than prevention. The main risk of prolonged immune stimulation for cancer prevention is the development of autoimmune diseases. Most antitumor immune responses are autoimmune, because most tumor antigens are also expressed by normal cells, but it must be considered that autoimmune responses do not necessarily evolve into autoimmune diseases. The limited autoimmunity triggered by cancer immunoprevention did not cause overt autoimmune diseases in preclinical mouse studies, however this is an issue that will
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{
"page_id": 15533459,
"source": null,
"title": "Cancer immunoprevention"
}
|
require careful monitoring in early clinical trials. == References ==
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{
"page_id": 15533459,
"source": null,
"title": "Cancer immunoprevention"
}
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Biology appears in fiction, especially but not only in science fiction, both in the shape of real aspects of the science, used as themes or plot devices, and in the form of fictional elements, whether fictional extensions or applications of biological theory, or through the invention of fictional organisms. Major aspects of biology found in fiction include evolution, disease, genetics, physiology, parasitism and symbiosis (mutualism), ethology, and ecology. Speculative evolution enables authors with sufficient skill to create what the critic Helen N. Parker calls biological parables, illuminating the human condition from an alien viewpoint. Fictional alien animals and plants, especially humanoids, have frequently been created simply to provide entertaining monsters. Zoologists such as Sam Levin have argued that, driven by natural selection on other planets, aliens might indeed tend to resemble humans to some extent. Major themes of science fiction include messages of optimism or pessimism; Helen N. Parker has noted that in biological fiction, pessimism is by far the dominant outlook. Early works such as H. G. Wells's novels explored the grim consequences of Darwinian evolution, ruthless competition, and the dark side of human nature; Aldous Huxley's Brave New World was similarly gloomy about the effects of genetic engineering. Fictional biology, too, has enabled major science fiction authors like Stanley Weinbaum, Isaac Asimov, John Brunner, and Ursula Le Guin to create what Parker called biological parables, with convincing portrayals of alien worlds able to support deep analogies with Earth and humanity. == Aspects of biology == Aspects of biology found in fiction include evolution, disease, ecology, ethology, genetics, physiology, parasitism, and mutualism (symbiosis). === Evolution === Evolution, including speculative evolution, has been an important theme in fiction since the late 19th century. It began, however, before Charles Darwin's time, and reflects progressionist and Lamarckist views (as in Camille Flammarion's
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{
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"title": "Biology in fiction"
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1887 Lumen) as well as Darwin's. Darwinian evolution is pervasive in literature, whether taken optimistically in terms of how humanity may evolve towards perfection, or pessimistically in terms of the dire consequences of the interaction of human nature and the struggle for survival. Other themes include the replacement of humanity, either by other species or by intelligent machines. === Disease === Diseases, both real and fictional, play a significant role in both literary and science fiction, some like Huntington's disease and tuberculosis appearing in many books and films. Pandemic plagues threatening all human life, such as The Andromeda Strain, are among the many fictional diseases described in literature and film. Science fiction takes an interest, too, in imagined advances in medicine. The Economist suggests that the abundance of apocalyptic fiction describing the "near annihilation or total extinction of the human race" by threats including deadly viruses rises when general "fear and unease", as measured by the Doomsday Clock, increase. Tuberculosis was a common disease in the 19th century. In Russian literature, it appeared in several major works. Fyodor Dostoevsky used the theme of the consumptive nihilist repeatedly, with Katerina Ivanovna in Crime and Punishment; Kirillov in The Possessed, and both Ippolit and Marie in The Idiot. Turgenev did the same with Bazarov in Father and Sons. In English literature of the Victorian era, major tuberculosis novels include Charles Dickens's 1848 Dombey and Son, Elizabeth Gaskell's 1855 North and South, and Mrs. Humphry Ward's 1900 Eleanor. === Genetics === Aspects of genetics including mutation or hybridisation, cloning (as in Brave New World), genetic engineering, and eugenics have appeared in fiction since the 19th century. Genetics is a young science, having started in 1900 with the rediscovery of Gregor Mendel's study on the inheritance of traits in pea plants. During the 20th
|
{
"page_id": 58000788,
"source": null,
"title": "Biology in fiction"
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century it developed to create new sciences and technologies including molecular biology, DNA sequencing, cloning, and genetic engineering. The ethical implications of modifying humans (and all their descendants) were brought into focus with the eugenics movement. Since then, many science fiction novels and films have used aspects of genetics as plot devices, often taking one of two routes: a genetic accident with disastrous consequences; or, the feasibility and desirability of a planned genetic alteration. The treatment of science in these stories has been uneven and often unrealistic. The 1997 film Gattaca attempted to portray science accurately but was criticised by scientists. Michael Crichton's 1990 novel Jurassic Park portrayed the cloning of whole dinosaur genomes from fossil remains of species extinct for millions of years, and their use to recreate living animals, using what was then known of genetics and molecular biology to create an "entertaining" and "thought-provoking" story. The lack of scientific understanding of genetics in the 19th century did not prevent science fiction works such as Mary Shelley's 1818 novel Frankenstein; or, The Modern Prometheus and H. G. Wells's 1896 The Island of Dr Moreau from exploring themes of biological experiment, mutation, and hybridisation, with their disastrous consequences, asking serious questions about the nature of humanity and responsibility for science. === Physiology === The creation scene in James Whale's 1931 film Frankenstein makes use of electricity to bring the monster to life. Shelley's idea of reanimation through electric shock was based on the physiology experiments of Luigi Galvani, who noted that a shock made the leg of a dead frog twitch. Electric shock is now routinely used in pacemakers, maintaining heart rhythm, and defibrillators, restoring heart rhythm. The ability to produce electricity is central to Naomi Alderman's 2016 science fiction novel The Power. In the book, women develop the
|
{
"page_id": 58000788,
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"title": "Biology in fiction"
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ability to release electrical jolts from their fingers, powerful enough to stun or kill. Fish such as the electric eel, Electrophorus electricus, create powerful electric fields with modified muscles, stacked end-to-end as cells in a battery in their electric organs, and the novel indeed references such fish and the electricity generated in striated muscle. === Parasitism === Parasites appear frequently in fiction, from ancient times onwards as seen in mythical figures like the blood-drinking Lilith, with a flowering in the nineteenth century. These include intentionally disgusting alien monsters in science fiction films, though these are sometimes less "horrible" than real examples in nature. Authors and scriptwriters have to some extent exploited parasite biology: lifestyles including parasitoid, behaviour-altering parasite, brood parasite, parasitic castrator, and many forms of vampire are found in books and films. Some fictional parasites, like the deadly parasitoid Xenomorphs in Alien, have become well known in their own right. Terrifying monsters are clearly alluring: writer Matt Kaplan notes that they induce signs of stress including raised heart rate and sweating, but people continue indulging in such works. Kaplan compares this to the "masochism" of liking very hot spicy foods, which induce mouth burns, sweating, and tears. The psychologist Paul Rozin suggests that there is a pleasure in seeing one's own body react as if to stress while knowing that no real harm will result. Some parasitic organisms in fictional works often have a Hive mind that they associate with. An example of this would be The Flood, from the Halo franchise. === Symbiosis === Symbiosis (mutualism) appears in fiction, especially science fiction, as a plot device. It is distinguished from parasitism in fiction, a similar theme, by the mutual benefit to the organisms involved, whereas the parasite inflicts harm on its host. Fictional symbionts often confer special powers
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{
"page_id": 58000788,
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"title": "Biology in fiction"
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on their hosts. After the Second World War, science fiction moved towards more mutualistic relationships, as in Ted White's 1970 By Furies Possessed, which viewed aliens positively. In The Phantom Menace, Qui-Gon Jinn says microscopic lifeforms called midi-chlorians, inside all living cells, allow characters with enough of these symbionts in their cells to feel and use the Force. === Ethology === Ethology, the study of animal behaviour, appears in the wildlife scientist Delia Owens's 2018 novel Where the Crawdads Sing. The protagonist, Kya, is abandoned by her parents at age six, and grows up alone in a North Carolina swamp, learning camouflage and how to hunt from the animals there. The local townspeople call her "the marsh girl". She reads about ethology including an article entitled "Sneaky Fuckers", using her knowledge to navigate the tricks and dating rituals of the local boys; and she compares herself to a female firefly, who uses her coded flashing light signal to lure a male of another species to his death, or a female mantis, who starts eating her mate's head and thorax while his abdomen is still copulating with her. "Female insects, Kya thought, know how to deal with their lovers." === Ecology === Ecology, the study of the relationships between organisms and their environment, appears in fiction in novels such as Frank Herbert's 1965 Dune, Kim Stanley Robinson's 1992 Red Mars, and Margaret Atwood's 2013 MaddAddam. Dune brought ecology centre stage, with a whole planet struggling with its environment. Its lifeforms included giant sandworms for whom water is fatal and mouse-like animals able to survive in the planet's desert conditions. The book was influential on the environmental movement of the time. In the 1970s, the impact of human activity on the environment stimulated a new kind of writing, ecofiction. It has two
|
{
"page_id": 58000788,
"source": null,
"title": "Biology in fiction"
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branches: stories about human impact on nature; and stories about nature (rather than humans). It encompasses books written in styles from modernism to magical realism, and in genres from mainstream to romance and speculative fiction. A 1978 anthology of ecofiction includes 19th and 20th century works by authors as diverse as Ray Bradbury, John Steinbeck, Edgar Allan Poe, Daphne du Maurier, E. B. White, Kurt Vonnegut Jr., Frank Herbert, H. H. Munro, J. G. Ballard, and Isaac Asimov. === Fictional organisms === Fiction, especially science fiction, has created large numbers of fictional species, both alien and terrestrial. One branch of fiction, speculative evolution or speculative biology, consists specifically of the design of imaginary organisms in particular scenarios; this is sometimes informed by precise science. == Functions == Fictional biology serves a variety of function in film and literature, including the supply of suitably terrifying monsters, the communication of an author's worldview, and the creation of aliens for biological parables to illuminate what it is to be human. Real biology, such as of infectious diseases, equally provides a variety of contexts, from personal to highly dystopian, that can be exploited in fiction. === Monsters and aliens === A common use of fictional biology in science fiction is to provide plausible alien species, sometimes simply as terrifying subjects, but sometimes for more reflective purposes. Alien species include H. G. Wells's Martians in his 1898 novel The War of the Worlds, the bug-eyed monsters of early 20th century science fiction, fearsome parasitoids, and a variety of giant insects, especially in early 20th century big bug movies. Humanoid (roughly human-shaped) aliens are common in science fiction. One reason is that authors use the only example of intelligent life that they know: humans. The zoologist Sam Levin points out that aliens might indeed tend to
|
{
"page_id": 58000788,
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"title": "Biology in fiction"
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resemble humans, driven by natural selection. Luis Villazon points out that animals that move necessarily have a front and a back; as with bilaterian animals on Earth, sense organs tend to gather at the front as they encounter stimuli there, forming a head. Legs reduce friction, and with legs, bilateral symmetry makes coordination easier. Sentient organisms will, Villazon argues, likely use tools, in which case they need hands and at least two other limbs to stand on. In short, a generally humanoid shape is likely, though octopus- or starfish-like bodies are also possible. Many fictional plants were created in the 20th century, including John Wyndham's venomous, walking, carnivorous triffids. in his 1951 novel The Day of the Triffids, The idea of plants that could attack an incautious traveller began in the late 19th century; the potatoes in Samuel Butler's Erewhon had "low cunning". Early tales included Phil Robinson's 1881 The Man-Eating Tree with its gigantic flytraps, Frank Aubrey's 1897 The Devil Tree of El Dorado, and Fred White's 1899 Purple Terror. Algernon Blackwood's 1907 story "The Willows" powerfully tells of malevolent trees that manipulate people's minds. Types of monster in science fiction === Optimism and pessimism === A major theme of science fiction and of speculative biology is to convey a message of optimism or pessimism according to the author's worldview. Whereas optimistic visions of technological progress are common enough in hard science fiction, pessimistic views of the future of humanity are far more usual in fiction based on biology. A rare optimistic note is struck by the evolutionary biologist J. B. S. Haldane in his tale, The Last Judgement, in the 1927 collection Possible Worlds. Both Arthur C. Clarke's 1953 Childhood's End and Brian Aldiss's 1959 Galaxies Like Grains of Sand, too, optimistically imagine that humans will evolve godlike
|
{
"page_id": 58000788,
"source": null,
"title": "Biology in fiction"
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mental capacities. The grim possibilities of Darwinian evolution with its ruthless "survival of the fittest" has been explored repeatedly from the beginnings of science fiction, as in H. G. Wells's novels The Time Machine (1895), The Island of Dr Moreau (1896), and The War of the Worlds (1898); these all pessimistically explore the possible dire consequences of the darker sides of human nature in the struggle for survival. Aldous Huxley's 1931 novel Brave New World is similarly gloomy about the oppressive consequences of advances in genetic engineering applied to human reproduction. === Biological parables === The literary critic Helen N. Parker suggested in 1977 that speculative biology could serve as biological parables which throw light on the human condition. Such a parable brings aliens and humans into contact, allowing the author to view humanity from an alien perspective. She noted that the difficulty of doing this at length meant that only a few major authors had attempted it, naming Stanley Weinbaum, Isaac Asimov, John Brunner, and Ursula Le Guin. In her view, all four had impressively full characterizations of alien beings. Weinbaum had created a "bizarre assortment" of intelligent beings, unlike Brunner's crablike but extinct Draconians. What united all four writers, she argued, was that the novels centred on the interactions between aliens and humans, creating deep analogies between the two kinds of life and from there commenting on humanity now and in the future. Weinbaum's 1934 A Martian Odyssey explored the question of how aliens and humans could communicate, given that their thought processes were utterly different. Asimov's 1972 The Gods Themselves both makes the aliens major characters, and explores parallel universes. Brunner's 1974 Total Eclipse creates a whole alien world, extrapolated from terrestrial threats. In her 1969 The Left Hand of Darkness, Le Guin presents her vision of
|
{
"page_id": 58000788,
"source": null,
"title": "Biology in fiction"
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a universe of planets all inhabited by "men", descendants from the planet Hain. In the book, the ambassador Genly Ai from the civilised Ekumen worlds visits the "backward- and inward-looking" people of Gethen, only to end up in danger, from which he escapes by crossing the polar ice cap on a desperate but well-planned expedition with an exiled Gethenian Lord Chancellor, Estraven. They are ambisexual with no fixed gender, and go through periods of oestrus, called "kemmer", at which point an individual comes temporarily to function as either a male or a female, depending on whether they first encounter a male- or female-functioning partner during their period of kemmer. The invented biology reflects and exemplifies, according to Parker, the opposing but united dualities of Taoism such as light and darkness, maleness and femaleness, yin and yang. So too do the opposed characters of Genly Ai with his carefully objective reports, and of Estraven with his or her highly personal diary, as the story unfolds, illuminating humanity through adventure and science fiction strangeness. === Structure and themes === Modern novels sometimes make use of biology to provide structure and themes. Thomas Mann's 1912 Death in Venice relates the feelings of the protagonist to the progress of an epidemic of cholera, which eventually kills him. Richard Flanagan's 2001 novel Gould's Book of Fish makes use of the illustrations from artist and convict William Buelow Gould's book of 26 paintings of fish for chapter headings and as the inspiration for the various characters in the novel. == Realism == The geneticist Dan Koboldt observes that the science in science fiction is often oversimplified, reinforcing popular myths to the point of "pure fiction". In his own field, he gives as examples the idea that first-degree relatives have the same hair, eyes and nose as
|
{
"page_id": 58000788,
"source": null,
"title": "Biology in fiction"
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each other, and that a person's future is predicted by their genetic code, as (he states) in Gattaca. Koboldt points out that eye colour changes as children grow up: adults with green or brown eyes often had blue eyes as babies; that brown-eyed parents can have children with blue eyes, "and vice versa"; and that the brown pigment melanin is controlled by around 10 different genes, so inheritance is along a spectrum rather than being a blue/brown switch. Other authors in his edited collection Putting the Science in Fiction point out a wide variety of errors in the portrayal of other biological sciences. == References == == Sources == Koboldt, Dan, ed. (16 October 2018). Putting the Science in Fiction. Writer's Digest Books. ISBN 978-1-4403-5338-3. Parker, Helen N. (1977). Biological Themes in Modern Science Fiction. UMI Research Press. ISBN 978-0835715775.
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{
"page_id": 58000788,
"source": null,
"title": "Biology in fiction"
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Kirchhoff's circuit laws are two equalities that deal with the current and potential difference (commonly known as voltage) in the lumped element model of electrical circuits. They were first described in 1845 by German physicist Gustav Kirchhoff. This generalized the work of Georg Ohm and preceded the work of James Clerk Maxwell. Widely used in electrical engineering, they are also called Kirchhoff's rules or simply Kirchhoff's laws. These laws can be applied in time and frequency domains and form the basis for network analysis. Both of Kirchhoff's laws can be understood as corollaries of Maxwell's equations in the low-frequency limit. They are accurate for DC circuits, and for AC circuits at frequencies where the wavelengths of electromagnetic radiation are very large compared to the circuits. == Kirchhoff's current law == This law, also called Kirchhoff's first law, or Kirchhoff's junction rule, states that, for any node (junction) in an electrical circuit, the sum of currents flowing into that node is equal to the sum of currents flowing out of that node; or equivalently: The algebraic sum of currents in a network of conductors meeting at a point is zero. Recalling that current is a signed (positive or negative) quantity reflecting direction towards or away from a node, this principle can be succinctly stated as: ∑ i = 1 n I i = 0 {\displaystyle \sum _{i=1}^{n}I_{i}=0} where n is the total number of branches with currents flowing towards or away from the node. Kirchhoff's circuit laws were originally obtained from experimental results. However, the current law can be viewed as an extension of the conservation of charge, since charge is the product of current and the time the current has been flowing. If the net charge in a region is constant, the current law will hold on the boundaries of
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{
"page_id": 591253,
"source": null,
"title": "Kirchhoff's circuit laws"
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the region. This means that the current law relies on the fact that the net charge in the wires and components is constant. === Uses === A matrix version of Kirchhoff's current law is the basis of most circuit simulation software, such as SPICE. The current law is used with Ohm's law to perform nodal analysis. The current law is applicable to any lumped network irrespective of the nature of the network; whether unilateral or bilateral, active or passive, linear or non-linear. == Kirchhoff's voltage law == This law, also called Kirchhoff's second law, or Kirchhoff's loop rule, states the following: The directed sum of the potential differences (voltages) around any closed loop is zero. Similarly to Kirchhoff's current law, the voltage law can be stated as: ∑ i = 1 n V i = 0 {\displaystyle \sum _{i=1}^{n}V_{i}=0} Here, n is the total number of voltages measured. === Generalization === In the low-frequency limit, the voltage drop around any loop is zero. This includes imaginary loops arranged arbitrarily in space – not limited to the loops delineated by the circuit elements and conductors. In the low-frequency limit, this is a corollary of Faraday's law of induction (which is one of Maxwell's equations). This has practical application in situations involving "static electricity". == Limitations == Kirchhoff's circuit laws are the result of the lumped-element model and both depend on the model being applicable to the circuit in question. When the model is not applicable, the laws do not apply. The current law is dependent on the assumption that the net charge in any wire, junction or lumped component is constant. Whenever the electric field between parts of the circuit is non-negligible, such as when two wires are capacitively coupled, this may not be the case. This occurs in high-frequency AC
|
{
"page_id": 591253,
"source": null,
"title": "Kirchhoff's circuit laws"
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circuits, where the lumped element model is no longer applicable. For example, in a transmission line, the charge density in the conductor may be constantly changing. On the other hand, the voltage law relies on the fact that the actions of time-varying magnetic fields are confined to individual components, such as inductors. In reality, the induced electric field produced by an inductor is not confined, but the leaked fields are often negligible. === Modelling real circuits with lumped elements === The lumped element approximation for a circuit is accurate at low frequencies. At higher frequencies, leaked fluxes and varying charge densities in conductors become significant. To an extent, it is possible to still model such circuits using parasitic components. If frequencies are too high, it may be more appropriate to simulate the fields directly using finite element modelling or other techniques. To model circuits so that both laws can still be used, it is important to understand the distinction between physical circuit elements and the ideal lumped elements. For example, a wire is not an ideal conductor. Unlike an ideal conductor, wires can inductively and capacitively couple to each other (and to themselves), and have a finite propagation delay. Real conductors can be modeled in terms of lumped elements by considering parasitic capacitances distributed between the conductors to model capacitive coupling, or parasitic (mutual) inductances to model inductive coupling. Wires also have some self-inductance. == Example == Assume an electric network consisting of two voltage sources and three resistors. According to the first law: i 1 − i 2 − i 3 = 0 {\displaystyle i_{1}-i_{2}-i_{3}=0} Applying the second law to the closed circuit s1, and substituting for voltage using Ohm's law gives: − R 2 i 2 + E 1 − R 1 i 1 = 0 {\displaystyle -R_{2}i_{2}+{\mathcal
|
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"page_id": 591253,
"source": null,
"title": "Kirchhoff's circuit laws"
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{E}}_{1}-R_{1}i_{1}=0} The second law, again combined with Ohm's law, applied to the closed circuit s2 gives: − R 3 i 3 − E 2 − E 1 + R 2 i 2 = 0 {\displaystyle -R_{3}i_{3}-{\mathcal {E}}_{2}-{\mathcal {E}}_{1}+R_{2}i_{2}=0} This yields a system of linear equations in i1, i2, i3: { i 1 − i 2 − i 3 = 0 − R 2 i 2 + E 1 − R 1 i 1 = 0 − R 3 i 3 − E 2 − E 1 + R 2 i 2 = 0 {\displaystyle {\begin{cases}i_{1}-i_{2}-i_{3}&=0\\-R_{2}i_{2}+{\mathcal {E}}_{1}-R_{1}i_{1}&=0\\-R_{3}i_{3}-{\mathcal {E}}_{2}-{\mathcal {E}}_{1}+R_{2}i_{2}&=0\end{cases}}} which is equivalent to { i 1 + ( − i 2 ) + ( − i 3 ) = 0 R 1 i 1 + R 2 i 2 + 0 i 3 = E 1 0 i 1 + R 2 i 2 − R 3 i 3 = E 1 + E 2 {\displaystyle {\begin{cases}i_{1}+(-i_{2})+(-i_{3})&=0\\R_{1}i_{1}+R_{2}i_{2}+0i_{3}&={\mathcal {E}}_{1}\\0i_{1}+R_{2}i_{2}-R_{3}i_{3}&={\mathcal {E}}_{1}+{\mathcal {E}}_{2}\end{cases}}} Assuming R 1 = 100 Ω , R 2 = 200 Ω , R 3 = 300 Ω , E 1 = 3 V , E 2 = 4 V {\displaystyle {\begin{aligned}R_{1}&=100\Omega ,&R_{2}&=200\Omega ,&R_{3}&=300\Omega ,\\{\mathcal {E}}_{1}&=3{\text{V}},&{\mathcal {E}}_{2}&=4{\text{V}}\end{aligned}}} the solution is { i 1 = 1 1100 A i 2 = 4 275 A i 3 = − 3 220 A {\displaystyle {\begin{cases}i_{1}={\frac {1}{1100}}{\text{A}}\\[6pt]i_{2}={\frac {4}{275}}{\text{A}}\\[6pt]i_{3}=-{\frac {3}{220}}{\text{A}}\end{cases}}} The current i3 has a negative sign which means the assumed direction of i3 was incorrect and i3 is actually flowing in the direction opposite to the red arrow labeled i3. The current in R3 flows from left to right. == See also == Duality (electrical circuits) Faraday's law of induction Lumped matter discipline Tellegen's Theorem == References == == External links == Divider Circuits and Kirchhoff's Laws chapter from Lessons In Electric Circuits Vol 1
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"page_id": 591253,
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"title": "Kirchhoff's circuit laws"
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DC free ebook and Lessons In Electric Circuits series
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"page_id": 591253,
"source": null,
"title": "Kirchhoff's circuit laws"
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Vascular plants (from Latin vasculum 'duct'), also called tracheophytes (UK: , US: ) or collectively tracheophyta (; from Ancient Greek τραχεῖα ἀρτηρία (trakheîa artēría) 'windpipe' and φυτά (phutá) 'plants'), are plants that have lignified tissues (the xylem) for conducting water and minerals throughout the plant. They also have a specialized non-lignified tissue (the phloem) to conduct products of photosynthesis. The group includes most land plants (c. 300,000 accepted known species) excluding mosses. Vascular plants include the clubmosses, horsetails, ferns, gymnosperms (including conifers), and angiosperms (flowering plants). They are contrasted with nonvascular plants such as mosses and green algae. Scientific names for the vascular plants group include Tracheophyta,: 251 Tracheobionta and Equisetopsida sensu lato. Some early land plants (the rhyniophytes) had less developed vascular tissue; the term eutracheophyte has been used for all other vascular plants, including all living ones. Historically, vascular plants were known as "higher plants", as it was believed that they were further evolved than other plants due to being more complex organisms. However, this is an antiquated remnant of the obsolete scala naturae, and the term is generally considered to be unscientific. == Characteristics == Botanists define vascular plants by three primary characteristics: Vascular plants have vascular tissues which distribute resources through the plant. Two kinds of vascular tissue occur in plants: xylem and phloem. Phloem and xylem are closely associated with one another and are typically located immediately adjacent to each other in the plant. The combination of one xylem and one phloem strand adjacent to each other is known as a vascular bundle. The evolution of vascular tissue in plants allowed them to evolve to larger sizes than non-vascular plants, which lack these specialized conducting tissues and are thereby restricted to relatively small sizes. In vascular plants, the principal generation or phase is the sporophyte,
|
{
"page_id": 66966,
"source": null,
"title": "Vascular plant"
}
|
which produces spores and is diploid (having two sets of chromosomes per cell). (By contrast, the principal generation phase in non-vascular plants is the gametophyte, which produces gametes and is haploid, with one set of chromosomes per cell.) Vascular plants have true roots, leaves, and stems, even if some groups have secondarily lost one or more of these traits. Cavalier-Smith (1998) treated the Tracheophyta as a phylum or botanical division encompassing two of these characteristics defined by the Latin phrase "facies diploida xylem et phloem instructa" (diploid phase with xylem and phloem).: 251 One possible mechanism for the presumed evolution from emphasis on haploid generation to emphasis on diploid generation is the greater efficiency in spore dispersal with more complex diploid structures. Elaboration of the spore stalk enabled the production of more spores and the development of the ability to release them higher and to broadcast them further. Such developments may include more photosynthetic area for the spore-bearing structure, the ability to grow independent roots, woody structure for support, and more branching. Sexual reproduction in vascular land plants involves the process of meiosis. Meiosis provides a direct DNA repair capability for dealing with DNA damages, including oxidative DNA damages, in germline reproductive tissues. == Phylogeny == A proposed phylogeny of the vascular plants after Kenrick and Crane 1997 is as follows, with modification to the gymnosperms from Christenhusz et al. (2011a), Pteridophyta from Smith et al. and lycophytes and ferns by Christenhusz et al. (2011b) The cladogram distinguishes the rhyniophytes from the "true" tracheophytes, the eutracheophytes. This phylogeny is supported by several molecular studies. Other researchers state that taking fossils into account leads to different conclusions, for example that the ferns (Pteridophyta) are not monophyletic. Hao and Xue presented an alternative phylogeny in 2013 for pre-euphyllophyte plants. == Nutrient distribution
|
{
"page_id": 66966,
"source": null,
"title": "Vascular plant"
}
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== Water and nutrients in the form of inorganic solutes are drawn up from the soil by the roots and transported throughout the plant by the xylem. Organic compounds such as sucrose produced by photosynthesis in leaves are distributed by the phloem sieve-tube elements. The xylem consists of vessels in flowering plants and of tracheids in other vascular plants. Xylem cells are dead, hard-walled hollow cells arranged to form files of tubes that function in water transport. A tracheid cell wall usually contains the polymer lignin. The phloem, on the other hand, consists of living cells called sieve-tube members. Between the sieve-tube members are sieve plates, which have pores to allow molecules to pass through. Sieve-tube members lack such organs as nuclei or ribosomes, but cells next to them, the companion cells, function to keep the sieve-tube members alive. === Transpiration === The most abundant compound in all plants, as in all cellular organisms, is water, which has an important structural role and a vital role in plant metabolism. Transpiration is the main process of water movement within plant tissues. Plants constantly transpire water through their stomata to the atmosphere and replace that water with soil moisture taken up by their roots. When the stomata are closed at night, water pressure can build up in the plant. Excess water is excreted through pores known as hydathodes. The movement of water out of the leaf stomata sets up transpiration pull or tension in the water column in the xylem vessels or tracheids. The pull is the result of water surface tension within the cell walls of the mesophyll cells, from the surfaces of which evaporation takes place when the stomata are open. Hydrogen bonds exist between water molecules, causing them to line up; as the molecules at the top of the
|
{
"page_id": 66966,
"source": null,
"title": "Vascular plant"
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plant evaporate, each pulls the next one up to replace it, which in turn pulls on the next one in line. The draw of water upwards may be entirely passive and can be assisted by the movement of water into the roots via osmosis. Consequently, transpiration requires the plant to expend very little energy on water movement. Transpiration assists the plant in absorbing nutrients from the soil as soluble salts. Transpiration plays an important role in the absorption of nutrients from the soil as soluble salts are transported along with the water from the soil to the leaves. Plants can adjust their transpiration rate to optimize the balance between water loss and nutrient absorption. === Absorption === Living root cells passively absorb water. Pressure within the root increases when transpiration demand via osmosis is low and decreases when water demand is high. No water movement towards the shoots and leaves occurs when evapotranspiration is absent. This condition is associated with high temperature, high humidity, darkness, and drought. === Conduction === Xylem is the water-conducting tissue, and the secondary xylem provides the raw material for the forest products industry. Xylem and phloem tissues each play a part in the conduction processes within plants. Sugars are conveyed throughout the plant in the phloem; water and other nutrients pass through the xylem. Conduction occurs from a source to a sink for each separate nutrient. Sugars are produced in the leaves (a source) by photosynthesis and transported to the growing shoots and roots (sinks) for use in growth, cellular respiration or storage. Minerals are absorbed in the roots (a source) and transported to the shoots to allow cell division and growth. == See also == Fern allies Bryophytes Non-vascular plant Pteridophyte == References == == Bibliography == == External links == "Higher plants" or
|
{
"page_id": 66966,
"source": null,
"title": "Vascular plant"
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"vascular plants"?
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{
"page_id": 66966,
"source": null,
"title": "Vascular plant"
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|
Colostrum (from Latin, of unknown origin) is the first form of milk produced by the mammary glands of humans and other mammals immediately following delivery of the newborn. Animal colostrum may be called beestings, the traditional word from Old English dialects. Most species will begin to generate colostrum just prior to giving birth. Colostrum contains antibodies to protect the newborn against disease and infection, and immune and growth factors and other bioactives. The bioactives found in colostrum are beneficial for a newborn's health, growth and vitality. Colostrum strengthens a baby's immune system. At birth, the environment of the newborn mammal shifts from the sterile conditions of the mother's uterus, with a constant nutrient supply via the placenta, to the microbe-rich environment outside, with irregular oral intake of complex milk nutrients through the gastrointestinal tract. This transition puts high demands on the gastrointestinal tract of the neonate, as the gut plays an important part in both the digestive system and the immune system. Colostrum contributes significantly to initial immunological defense as well as to the growth, development, and maturation of the neonate's gastrointestinal tract by providing key nutrients and bioactive factors. Bovine colostrum powder is rich in protein and low in sugar and fat. Bovine colostrum can also be used for nonorganic failure to thrive in children and acute non-steroidal anti-inflammatory drug-induced increase in intestinal permeability in males and can boost a neonate's immunity. Colostrum also has a mild laxative effect, encouraging the passing of a baby's first stool, which is called meconium. This clears excess bilirubin, a waste-product of dead red blood cells which is produced in large quantities at birth due to blood volume reduction from the infant's body, and which is often responsible for jaundice. Research on possible health benefits and medical applications of bovine colostrum is ongoing.
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{
"page_id": 525722,
"source": null,
"title": "Colostrum"
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Currently, there is no accepted medical use of bovine colostrum to treat any condition. == Composition == Colostrum, like other forms of milk, is mostly water, and also contains lactose, fat, minerals and protein. It also contains bioactive components including antibodies to protect the newborn against disease and infection, and immune and growth factors. Colostrum contains white blood cells. Newborns have very immature and small digestive systems, and colostrum delivers its bioactives in a concentrated low-volume form. Colostrum is known to contain immune cells (as lymphocytes) and many antibodies such as IgA, IgG, and IgM. These are some of the components of the adaptive immune system. Other immune components of colostrum include the major components of the innate immune system, such as lactoferrin, lysozyme, lactoperoxidase, complement, and proline-rich polypeptides (PRP). A number of cytokines (small messenger peptides that control the functioning of the immune system) are found in colostrum as well, tumor necrosis factor, and others. Colostrum also contains a number of growth factors, such as insulin-like growth factor I (IGF-1), and II, transforming growth factor alpha, beta 1 and beta 2, fibroblast growth factors, epidermal growth factor, granulocyte-macrophage-stimulating growth factor, platelet-derived growth factor, vascular endothelial growth factor, and colony-stimulating factor 1. === Proline-rich polypeptides === Proline-rich polypeptides (PRPs) are small immune signaling peptides that were independently discovered in colostrum and other sources, such as blood plasma, in the United States, Czechoslovakia and Poland. Hence they appear under various names in the literature, including Colostrinin, CLN, transfer factor and PRP. They function as signal transducing molecules that accelerate the maturation of cells of the immune system. == Human colostrum == In humans, colostrum is produced for the first few days after childbirth. The antibodies in colostrum protect infants from infection and colostrum is hypothesized to have anti-inflammatory properties. It is
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{
"page_id": 525722,
"source": null,
"title": "Colostrum"
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suggested infants fed with human colostrum have lower incidence of gastrointestinal infections. Colostrum has a laxative effect, encouraging the baby's body to excrete stool, which helps eliminate excess bilirubin, although jaundice lasts longer in breastfed infants than in those who are formula-fed. == Bovine colostrum == Upon exposure to pathogens, dairy cattle produce antibodies against the pathogens. These antibodies are present in the cow's bloodstream and colostrum. Some of these antibodies are specific to human pathogens, including Escherichia coli, Cryptosporidium parvum, Shigella flexneri, Salmonella species, Staphylococcus species, and rotavirus (which causes diarrhea in infants). Albert Sabin, who developed the first oral vaccine against polio, used colostrum in an experiment to evaluate the protective effect of breastfeeding against the poliomyelitis virus. Sabin obtained blood serum and milk samples from 30 human nursing mothers at different times after delivery. He then mixed the serum and blood from each individual mother together, in systematically differing proportions, and added "a constant amount" of the Lansing strain of the poliomyelitis virus. The mixtures were then injected into the brains of mice. The results showed that 100% of the human colostrum samples had antipoliomyelitic activity whereas only "80 per cent of the milk specimens obtained between 101 and 340 days after delivery" had such activity. He also tested cow's milk (not specified as colostrum) and found that milk samples from 2 of 9 cows contained antipoliomyelitic activity. When antibiotics began to appear, interest in colostrum waned, but after antibiotic-resistant strains of pathogens developed, interest turned to colostrum as a natural alternative to antibiotics. === Health effects of consumption by humans === Bovine colostrum and human colostrum contain many of the same antibodies, immune and growth factors, and nutrients. There is also research suggesting that a large proportion of colostrum is not fit for human consumption "due
|
{
"page_id": 525722,
"source": null,
"title": "Colostrum"
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to tremendous bacterial loads". Salmonella was detected in 15% of unpasteurised samples. Pasteurisation reduces the bioactive proteins many of the benefits rely upon, however. ==== Respiratory system ==== Colostrum may support respiratory health in adults and children. One study of human subjects suggested that oral colostrum was effective in preventing influenza. Bovine colostrum was shown to reduce symptoms of allergic rhinitis in children. ==== Digestive system ==== Colostrum may help to maintain and support intestinal integrity and improve nutrient absorption, while its naturally occurring prebiotics feed beneficial gut bacteria in adults and children. ==== Older children ==== Colostrum may have continued benefits in children over the age of one: to support children's immune systems, soothe digestive upsets, and otherwise support digestive health. ==== Sports nutrition ==== Bovine colostrum may help maintain a healthy immune system during athletic training, while supporting cellular proliferation as well as protein synthesis and soft tissue repair. One study showed that one brand of concentrated bovine colostrum powder improved running performance in one test, on average, in thirty males but did not improve performance in another test. ==== Skin ==== Bovine colostrum (BC) affects skin. A study conducted in 2021 by Jogi Reena et al. found that Bovine Colostrum may help delay skin aging by reducing telomere shortening, which is a marker of cellular aging. The researchers attributed these benefits to the antioxidant properties of BC, which help maintain telomere length and boost fibroblast proliferation—a key element in collagen production and the maintenance of skin structure. Enhanced Healing and Regeneration: BC has been shown to stimulate fibroblast activity, aiding in the repair of damaged skin and the creation of new tissue, making it effective for wound healing and scar reduction. Anti-Aging Properties: BC is rich in antioxidants that combat free radicals, which are significant contributors to
|
{
"page_id": 525722,
"source": null,
"title": "Colostrum"
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skin aging. These antioxidants, combined with growth factors, improve skin elasticity and firmness, helping to diminish the appearance of wrinkles and fine lines. A clinical study published in the Journal of Cosmetic Dermatology found that topical application of antioxidants significantly improved skin texture and reduced signs of aging in participants over a 12-week period. Wound Healing: The immunoglobulins and lactoferrin in topically applied BC work together to improve the Bates-Jensen Wound Assessment score of chronic non-healing ulcers on day 21 of treatment. === Use in animal husbandry === Colostrum is beneficial for newborn farm animals. They receive no passive transfer of immunity via the placenta before birth, so any antibodies that they need have to be either ingested or supplied by injection or other artificial means. The ingested antibodies are absorbed from the intestine of the neonate. Maximum absorption of colostral antibodies by the newborn animal occurs within 4 hours or thirty minutes of birth. The role of colostrum for newborn animals is to provide nutrition, and protect against infection while the immune and digestive systems are developing and maturing. Bovine colostrum provides macro- and micro-nutrients, as well as growth factors, cytokines, nucleosides, oligosaccharides, natural antimicrobials, antioxidants; and a range of immunoglobulins such as IgG, IgA, IgD, IgM and IgE. Minimal levels of IgG are essential to prevent failure of passive transfer. The iron-binding glycoproteins lactoferrin and transferrin in bovine colostrum assist in attacking pathogens by impacting their cell membrane and making them more susceptible to the immune systems attack by neutrophils. Cytokines in bovine colostrum enhance B and T cell maturation and increase endogenous antibody production. They also help regulate epithelial cell growth and development, proliferation, and restitution. Transfer factors enhance the activity of T cells. Other growth and immune factors such as IGF-1, IGF-2, FGF, EGF, TGF, PDGF,
|
{
"page_id": 525722,
"source": null,
"title": "Colostrum"
}
|
etc. Bovine Colostrum contains bioactive components that support immunity and gut health in animals, and fight bacteria, viruses, and other pathogens. Early, high-quality colostrum is beneficial for survival and healthy development. It repairs intestinal damage and improves nutrient absorption. In calves, colostrum helps develop their gut and prevents death. It reduces infections, antibiotic use, and diarrhea, leading to faster growth and higher profits for farmers. === Use in companion animals === Much like in humans and production animals, companion animal survival in the newborn stage of life is largely dependent upon colostrum. Companion animal immune systems require several weeks to several months in order to fully develop. Maternal antibodies provide benefit for a relatively short period of time so a gap exists with immune sufficiency where an animal is at risk of infection. Like humans, companion animal immune response changes with age where early life and later in life have similarities. That is, an immune bias whereby the animal has less of an ability to fend off infections and greater prevalence of allergy at both ends of the age spectrum. Stress also affects a companion animal's immune system including changes in environment, diet, etc. Maintaining gut microbial balance is key to maintaining a healthy immune system as well as mucosal integrity, similar to humans, demonstrated to benefit companion animal immunity and digestive health. In humans, bovine colostrum plays a role in increasing Ig levels, increasing lymphocyte proliferation stimulating activity and increasing phagocytosis activity. These are supported by other components of colostrum which further enhance the activity of the immune response. The iron binding glycoproteins lactoferrin and transferrin in bovine colostrum assist in attacking pathogens by impacting their cell membrane and making them more susceptible to the immune systems attack by neutrophils. Cytokines present in bovine colostrum enhance B and T
|
{
"page_id": 525722,
"source": null,
"title": "Colostrum"
}
|
cell maturation and increase endogenous antibody production. They also play a major role in regulation of epithelial cell growth and development, proliferation, restitution. Transfer factors enhance the activity of T cells. Other growth and immune factors such as IGF-1, IGF-2, FGF, EGF, TGF, PDGF, etc. Colostrum contains glycomacropeptides which help to regulate appetite. Studies suggest that bovine colostrum may enhance animal immunity, improve gut health, and lower the risk of illness. === Hyperimmune === Hyperimmune colostrum is natural bovine colostrum collected from a population of cows immunized repeatedly with a specific pathogen. The colostrum is collected within 24 hours of the cow giving birth. Antibodies towards the specific pathogens or antigens that were used in the immunization are present in higher levels than in the population before treatment. Although some papers have been published stating that specific human pathogens were just as high as in hyperimmune colostrum, and natural colostrum nearly always had higher antibody titers than did the hyperimmune version. A clinical trial showed that if the immunization is by surface antigens of a strain of E. coli bacteria, the Bovine Colostrum Powder can be used to make tablets capable of binding to the bacteria so that they are excreted in stools, thus preventing diarrhea that is caused by this strain of E. coli. This prevents the successful colonization of the gut, which would otherwise lead to bacteria releasing enterotoxigenic materials which cause diarrhea. === Potential applications === Although bovine colostrum has been consumed by humans for centuries, only in recent decades have we seen randomized clinical trials to test for health benefits. It is probable that little absorption of intact growth factors and antibodies into the bloodstream occurs, due to digestion in the gastrointestinal tract. However, two experiments, one using human pancreatic fluid and one using rats, suggested
|
{
"page_id": 525722,
"source": null,
"title": "Colostrum"
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the presence of casein and other buffering proteins allows epidermal growth factor but not transforming growth factor α to survive degradation induced by human pancreatic fluid and allows epidermal growth factor to pass into the lumen of the small intestine in rats, where it can stimulate repair, working via local effects. This provides a probable mechanism explaining reductions in gut permeability after colostrum administration in some published studies, while another study found colostrum promising as treatment for distal colitis. The effect of colostrum on extra-gastrointestinal problems has been studied in a small number of randomised double-blind studies. The gut can be affected by ulcers, inflammation, and infectious diarrhea. There is currently much interest in the potential value of colostrum for the prevention and treatment of these conditions., As pointed out by Kelly, inconsistency between results in some published studies may be due in part to variation in dose given and to the timing of the colostrum collection being tested (first milking versus pooled colostrum collected up to day 5 following calving). Some athletes have used colostrum in an attempt to improve their performance, decrease recovery time, and prevent sickness during peak performance levels. Supplementation with bovine colostrum, 20 grams per day (g/d), in combination with exercise training for eight weeks may increase bone-free lean body mass in active men and women. Low IGF-1 levels may be associated with dementia in the very elderly, although causation has not been established. Malnutrition can cause low levels of IGF-1, as can obesity. Although IGF-1 is not absorbed intact by the body, some studies suggest it stimulates the production of IGF-1 when taken as a supplement whereas others do not. Colostrum also has antioxidant components, such as lactoferrin and hemopexin, which binds free heme in the body. The Isle of Man had a local
|
{
"page_id": 525722,
"source": null,
"title": "Colostrum"
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delicacy called "Groosniuys", a pudding made with colostrum. In Finland, a baked cheese called Leipäjuusto is traditionally made with either cow colostrum or reindeer milk. A sweet cheese-like delicacy called 'Junnu' or 'Ginna' is made with colostrum in the south Indian states of Karnataka, Andhra Pradesh and Telangana. It is made with both cow and buffalo milk; in both cases milk produced on the second day after birth is considered ideal for preparing this pudding-like delicacy. Colostrum is in very high demand in these states, resulting in product adulteration. Bovine colostrum has also found application in oral and dental care. Some formulations, such as protective tooth gels designed for children, utilize colostrum's natural immunoglobulins, lactoferrin, and growth factors to support gum tissue regeneration and strengthen mucosal immunity. One such example is a Turkish dental care brand that incorporates bovine colostrum into its pediatric protective dental gel formulations. These products are marketed as being free from synthetic preservatives and commonly used additives like SLS and parabens, focusing on biocompatible oral health support. == References == == External links == Maryland Cooperative Extension Usage of Bovine Colostrum
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{
"page_id": 525722,
"source": null,
"title": "Colostrum"
}
|
Fulgurites (from Latin fulgur 'lightning' and -ite), commonly called "fossilized lightning", are natural tubes, clumps, or masses of sintered, vitrified, or fused soil, sand, rock, organic debris and other sediments that sometimes form when lightning discharges into ground. When composed of silica, fulgurites are classified as a variety of the mineraloid lechatelierite. When ordinary negative polarity cloud-ground lightning discharges into a grounding substrate, greater than 100 million volts (100 MV) of potential difference may be bridged. Such current may propagate into silica-rich quartzose sand, mixed soil, clay, or other sediments, rapidly vaporizing and melting resistant materials within such a common dissipation regime. This results in the formation of generally hollow and/or vesicular, branching assemblages of glassy tubes, crusts, and clumped masses. Fulgurites have no fixed composition because their chemical composition is determined by the physical and chemical properties of whatever material is being struck by lightning. Fulgurites are structurally similar to Lichtenberg figures, which are the branching patterns produced on surfaces of insulators during dielectric breakdown by high-voltage discharges, such as lightning. == Description == Fulgurites are formed when lightning strikes the ground, fusing and vitrifying mineral grains. The primary SiO2 phase in common tube fulgurites is lechatelierite, an amorphous silica glass. Many fulgurites show some evidence of crystallization: in addition to glasses, many are partially protocrystalline or microcrystalline. Because fulgurites are generally amorphous in structure, fulgurites are classified as mineraloids. Peak temperatures within a lightning channel exceed 30,000 K, with sufficient pressure to produce planar deformation features in SiO2, a kind of polymorphism. This is also known colloquially as shocked quartz. Material properties (size, color, texture) of fulgurites vary widely, depending on the size of the lightning bolt and the composition and moisture content of the surface struck by lightning. Most natural fulgurites fall on a spectrum from white
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{
"page_id": 329115,
"source": null,
"title": "Fulgurite"
}
|
to black. Iron is a common impurity that can result in a deep brownish-green coloration. Lechatelierite similar to fulgurites can also be produced via controlled (or uncontrolled) arcing of artificial electricity into a medium. Downed high voltage power lines have produced brightly colored lechatelierites, due to the incorporation of copper or other materials from the power lines. Brightly colored lechatelierites resembling fulgurites are usually synthetic and reflect the incorporation of synthetic materials. However, lightning can strike man-made objects, resulting in colored fulgurites. The interior of Type I (sand) fulgurites normally is smooth or lined with fine bubbles, while their exteriors are coated with rough sedimentary particles or small rocks. Other types of fulgurites are usually vesicular, and may lack an open central tube; their exteriors can be porous or smooth. Branching fulgurites display fractal-like self-similarity and structural scale invariance as a macroscopic or microscopic network of root-like branches, and can display this texture without central channels or obvious divergence from morphology of context or target (e.g. sheet-like melt, rock fulgurites). Fulgurites are usually fragile, making the field collection of large specimens difficult. Fulgurites can exceed 20 centimeters in diameter and can penetrate deep into the subsoil, sometimes occurring as far as 15 m (49 ft) below the surface that was struck, although they may also form directly on a sedimentary surface. One of the longest fulgurites to have been found in modern times was a little over 4.9 m (16 ft) in length, found in northern Florida. The Yale University Peabody Museum of Natural History displays one of the longest known preserved fulgurites, approximately 4 m (13 ft) in length. Charles Darwin in The Voyage of the Beagle recorded that tubes such as these found in Drigg, Cumberland, UK reached a length of 9.1 m (30 ft). Fulgerites at Winans
|
{
"page_id": 329115,
"source": null,
"title": "Fulgurite"
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|
Lake, Livingston County, Michigan, extended discontinuously throughout a 30 m range and arguably include the largest reported fulgurite mass ever recovered and described: its largest section extending approximately 16 ft (4.88 m) in length by 1 ft in diameter (30 cm). === Classification === Fulgurites have been classified into five types related to the type of sediment in which the fulgurite formed, as follows: Type I – sand fulgurites with tubaceous structure; their central axial void may be collapsed Type II – soil fulgurites; these are glass-rich, and form in a wide range of sediment compositions, including clay-rich soils, silt-rich soils, gravel-rich soils, and loessoid; these may be tubaceous, branching, vesicular, irregular/slaggy, or may display a combination of these structures, and can produce exogenic fulgurites (droplet fulgurites) Type III – caliche or calcic sediment fulgurites, having thick, often surficially glazed granular walls with calcium-rich vitreous groundmass with little or no lechatelierite glass; their shapes are variable, with multiple narrow central channels common, and can span the entire range of morphological and structural variation for fulguritic objects Type IV – rock fulgurites, which are either crusts on minimally altered rocks, networks of tunneling within rocks, vesicular outgassed rocks (often glazed by a silicide-rich and/or metal oxide crust), or completely vitrified and dense rock material and masses of these forms with little sedimentary groundmass Type V – [droplet] fulgurites (exogenic fulgurites), which show evidence of ejection (e.g. spheroidal, filamentous, or aerodynamic), related by composition to Type II and Type IV fulgurites phytofulgurite – a proposed class of objects resulting from partial to total alteration of biomass (e.g. grasses, lichens, moss, wood) by lightning, described as "natural glasses formed by cloud-to-ground lightning." These were excluded from the classification scheme because they are not glasses, so classifying them as a subset of fulgurites is
|
{
"page_id": 329115,
"source": null,
"title": "Fulgurite"
}
|
debatable. == Significance == The presence of fulgurites in an area can be used to estimate the frequency of lightning over a period of time, which can help to understand past regional climates. Paleolightning is the study of various indicators of past lightning strikes, primarily in the form of fulgurites and lightning-induced remanent magnetization signatures. Many high-pressure, high-temperature materials have been observed in fulgurites. Many of these minerals and compounds are also known to be formed in extreme environments such as nuclear weapon tests, hypervelocity impacts, and interstellar space. Shocked quartz was first described in fulgurites in 1980. Other materials, including highly reduced silicon-metal alloys (silicides), the fullerene allotropes C60 (buckminsterfullerenes) and C70, as well as high-pressure polymorphs of SiO2, have since been identified in fulgurites. Reduced phosphides have been identified in fulgurites, in the form of schreibersite (Fe3P and (Fe,Ni)3P), and titanium(III) phosphide. These reduced compounds are otherwise rare on Earth due to the presence of oxygen in Earth's atmosphere, which creates oxidizing surface conditions. == History == Fulgurite tubes have been mentioned already by Persian polymaths Avicenna and Al-Biruni in the 11th century, without knowing their true origination. Over the following centuries fulgurites have been described but missinterpreted as a result of subterrestrial fires, falsely attributing curative powers to them, e.g. by Leonhard David Hermann 1711 in his Maslographia. Other famous natural scientists, among them Charles Darwin, Horace Bénédict de Saussure and Alexander von Humboldt gave attention to fulgurites, without discovering the relationship to lightning. In 1805 the true process of forming fulgurites by lightning strikes to the ground was identified by agriculturist Hentzen and mineralogist and mining engineer Johann Karl Wilhelm Voigt. In 1817 mineralogist and mining engineer Karl Gustav Fiedler published and comprehensively documented the phenomenon in the Annalen der Physik. == See also == Electromechanical
|
{
"page_id": 329115,
"source": null,
"title": "Fulgurite"
}
|
disintegration Impactite Tektite Trinitite == References == == External links == H. J. Melosh, "Impact geologists, beware!" (Archived 2020-08-06 at the Wayback Machine). Geophysical Research Letters, Volume 44, Issue 17, pp. 8873–8874, 2017 Petrified Lightning by Peter E. Viemeister (PDF) Interview with artist Allan McCollum along with an historical archive of 66 versions of booklets included in Allan McCollum's exhibition, The Event: Petrified Lightning from Central Florida Mindat with location data W. M. Myers and Albert B. Peck, "A Fulgurite from South Amboy, New Jersey", American Mineralogist, Volume 10, pages 152–155, 1925 Vladimir A. Rakov, "Lightning Makes Glass", 29th Annual Conference of the Glass Art Society, Tampa, Florida, 1999
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{
"page_id": 329115,
"source": null,
"title": "Fulgurite"
}
|
In physics, a renormalon (a term suggested by 't Hooft) is a particular source of divergence seen in perturbative approximations to quantum field theories (QFT). When a formally divergent series in a QFT is summed using Borel summation, the associated Borel transform of the series can have singularities as a function of the complex transform parameter. The renormalon is a possible type of singularity arising in this complex Borel plane, and is a counterpart of an instanton singularity. Associated with such singularities, renormalon contributions are discussed in the context of quantum chromodynamics (QCD) and usually have the power-like form ( Λ / Q ) p {\displaystyle \left(\Lambda /Q\right)^{p}} as functions of the momentum Q {\displaystyle Q} (here Λ {\displaystyle \Lambda } is the momentum cut-off). They are cited against the usual logarithmic effects like ln ( Λ / Q ) {\displaystyle \ln \left(\Lambda /Q\right)} . == Brief history == Perturbation series in quantum field theory are usually divergent as was firstly indicated by Freeman Dyson. According to the Lipatov method, N {\displaystyle N} -th order contribution of perturbation theory into any quantity can be evaluated at large N {\displaystyle N} in the saddle-point approximation for functional integrals and is determined by instanton configurations. This contribution behaves usually as N ! {\displaystyle N!} in dependence on N {\displaystyle N} and is frequently associated with approximately the same ( N ! {\displaystyle N!} ) number of Feynman diagrams. Lautrup has noted that there exist individual diagrams giving approximately the same contribution. In principle, it is possible that such diagrams are automatically taken into account in Lipatov's calculation, because its interpretation in terms of diagrammatic technique is problematic. However, 't Hooft put forward a conjecture that Lipatov's and Lautrup's contributions are associated with different types of singularities in the Borel plane, the
|
{
"page_id": 8324507,
"source": null,
"title": "Renormalon"
}
|
former with instanton ones and the latter with renormalon ones. Existence of instanton singularities is beyond any doubt, while existence of renormalon ones was never proved rigorously in spite of numerous efforts. Among the essential contributions one should mention the application of the operator product expansion, as was suggested by Parisi. Recently a proof was suggested for absence of renormalon singularities in ϕ 4 {\displaystyle \phi ^{4}} theory and a general criterion for their existence was formulated in terms of the asymptotic behavior of the Gell-Mann–Low function β ( g ) {\displaystyle \beta (g)} . Analytical results for asymptotics of β ( g ) {\displaystyle \beta (g)} in ϕ 4 {\displaystyle \phi ^{4}} theory and QED indicate the absence of renormalon singularities in these theories. == References ==
|
{
"page_id": 8324507,
"source": null,
"title": "Renormalon"
}
|
The hypothesis or paradigm of Mutualism Parasitism Continuum postulates that compatible host-symbiont associations can occupy a broad continuum of interactions with different fitness outcomes for each member. At one end of the continuum lies obligate mutualism where both host and symbiont benefit from the interaction and are dependent on it for survival. At the other end of the continuum highly parasitic interactions can occur, where one member gains a fitness benefit at the expense of the others survival. Between these extremes many different types of interaction are possible. The degree of change between mutualism or parasitism varies depending on the availability of resources, where there is environmental stress generated by few resources, symbiotic relationships are formed while in environments where there is an excess of resources, biological interactions turn to competition and parasitism. Classically the transmission mode of the symbiont can also be important in predicting where on the mutualism-parasitism-continuum an interaction will sit. Symbionts that are vertically transmitted (inherited symbionts) frequently occupy mutualism space on the continuum, this is due to the aligned reproductive interests between host and symbiont that are generated under vertical transmission. In some systems increases in the relative contribution of horizontal transmission can drive selection for parasitism. Studies of this hypothesis have focused on host-symbiont models of plants and fungi, and also of animals and microbes. == See also == Red King Hypothesis Red Queen Hypothesis Black Queen Hypothesis Biological interaction == References ==
|
{
"page_id": 68289950,
"source": null,
"title": "Mutualism Parasitism Continuum"
}
|
Pygsuia is a genus in the clade of Breviatea, which are basal eukaryotes. This genus contains only one species, Pygsuia biforma, which is known for its long flagella compared to other breviates. == Etymology == The genus name, Pygsuia, is derived from a part of the University of Arkansas Razorbacks sports cheer, which goes "Wooo Pig Sooie". This is because the species has a row of structures similar to those of actual razorbacks. "Pyg" in the genus name refers to pigs while also referencing the Latin term Pygmae, as a nod to the organisms' small size. "Sui" in the genus name refers to the sound made by hog callers. As a consequence, the full genus name means "little pig" in mock Latin. == References ==
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{
"page_id": 78513566,
"source": null,
"title": "Pygsuia"
}
|
In organic chemistry, the von Baeyer nomenclature is a system for describing polycyclic (i.e. multi-ringed) hydrocarbons. The system was originally developed in 1900 by German chemist Adolf von Baeyer for bicyclic systems and in 1913 expanded by Eduard Buchner and Wilhelm Weigand for tricyclic systems. The system has been adopted and extended by the IUPAC as part of its nomenclature for organic chemistry. The modern version has been extended to cover more cases of compounds including an arbitrary number of cycles, heterocyclic compounds and unsaturated compounds. == Extended Von Baeyer == == See also == Clar's rule == References ==
|
{
"page_id": 51119519,
"source": null,
"title": "Von Baeyer nomenclature"
}
|
Calculated value of a chemical in the environment on the basis of exposure models such as the European Union System for the Evaluation of Substances (EUSES). Used in the context of Chemical Safety Assessments (CSA) and referenced in Chemical Safety Reports (CSR). PECs may be compared with Measured Environmental Concentrations (MEC) if available.
|
{
"page_id": 25626017,
"source": null,
"title": "Predicted environmental concentration"
}
|
An epidemic (from Greek ἐπί epi "upon or above" and δῆμος demos "people") is the rapid spread of disease to a large number of hosts in a given population within a short period of time. For example, in meningococcal infections, an attack rate in excess of 15 cases per 100,000 people for two consecutive weeks is considered an epidemic. Epidemics of infectious disease are generally caused by several factors including a change in the ecology of the host population (e.g., increased stress or increase in the density of a vector species), a genetic change in the pathogen reservoir or the introduction of an emerging pathogen to a host population (by movement of pathogen or host). Generally, an epidemic occurs when host immunity to either an established pathogen or newly emerging novel pathogen is suddenly reduced below that found in the endemic equilibrium and the transmission threshold is exceeded. An epidemic may be restricted to one location; however, if it spreads to other countries or continents and affects a substantial number of people, it may be termed as a pandemic.: §1:72 The declaration of an epidemic usually requires a good understanding of a baseline rate of incidence; epidemics for certain diseases, such as influenza, are defined as reaching some defined increase in incidence above this baseline. A few cases of a very rare disease may be classified as an epidemic, while many cases of a common disease (such as the common cold) would not. An epidemic can cause enormous damage through financial and economic losses in addition to impaired health and loss of life. == Definition == The United States Centers for Disease Control and Prevention defines epidemic broadly: "Epidemic refers to an increase, often sudden, in the number of cases of a disease above what is normally expected in that
|
{
"page_id": 66981,
"source": null,
"title": "Epidemic"
}
|
population in that area." The term "outbreak" can also apply, but is usually restricted to smaller events.: §1:72 Any sudden increase in disease prevalence may generally be termed an epidemic. This may include contagious disease (i.e. easily spread between persons) such as influenza; vector-borne diseases such as malaria; water-borne diseases such as cholera; and sexually transmitted diseases such as HIV/AIDS. The term can also be used for non-communicable health issues such as obesity. The term epidemic derives from a word form attributed to Homer's Odyssey, which later took its medical meaning from the Epidemics, a treatise by Hippocrates. Before Hippocrates, epidemios, epidemeo, epidamos, and other variants had meanings similar to the current definitions of "indigenous" or "endemic". Thucydides' description of the Plague of Athens is considered one of the earliest accounts of a disease epidemic. By the early 17th century, the terms endemic and epidemic referred to contrasting conditions of population-level disease, with the endemic condition a "common sicknesse" and the epidemic "hapning in some region, or countrey, at a certaine time, ....... producing in all sorts of people, one and the same kind of sicknesse". The term "epidemic" is often applied to diseases in non-human animals, although "epizootic" is technically preferable. == Causes == There are several factors that may contribute (individually or in combination) to causing an epidemic. There may be changes in a pathogen, in the population that it can infect, in the environment, or in the interaction between all three. Factors include the following:: §1:72 === Antigenic Change === An antigen is a protein on the virus' surface that host antibodies can recognize and attack. Changes in the antigenic characteristics of the agent make it easier for the changed virus to spread throughout a previously immune population. There are two natural mechanisms for change - antigenic
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{
"page_id": 66981,
"source": null,
"title": "Epidemic"
}
|
drift and antigenic shift. Antigenic drift arises over a period of time as an accumulation of mutations in the virus genes, possibly through a series of hosts, and eventually gives rise to a new strain of virus which can evade existing immunity. Antigenic shift is abrupt - in this, two or more different strains of a virus, coinfecting a single host, combine to form a new subtype having a mixture of characteristics of the original strains. The best known and best documented example of both processes is influenza. SARS-CoV2 has demonstrated antigenic drift and possibly shift as well. === Drug resistance === Antibiotic resistance applies specifically to bacteria that become resistant to antibiotics. Resistance in bacteria can arise naturally by genetic mutation, or by one species acquiring resistance from another through horizontal gene transfer. Extended use of antibiotics appears to encourage selection for mutations which can render antibiotics ineffective. This is especially true of tuberculosis, with increasing occurrence of multiple drug-resistant tuberculosis (MDR-TB) worldwide. === Changes in transmission === Pathogen transmission is a term used to describe the mechanisms by which a disease-causing agent (virus, bacterium, or parasite) spreads from one host to another. Common modes of transmission include: - airborne (as with influenza and COVID-19), fecal-oral (as with cholera and typhoid), vector-borne (malaria, Zika) and sexual (syphilis, HIV) The first three of these require that pathogen must survive away from its host for a period of time; an evolutionary change which increases survival time will result in increased virulence. Another possibility, although rare, is that a pathogen may adapt to take advantage of a new mode of transmission === Seasonality === Seasonal diseases arise due to the change in the environmental conditions, especially such as humidity and temperature, during different seasons. Many diseases display seasonality, This may be due
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{
"page_id": 66981,
"source": null,
"title": "Epidemic"
}
|
to one or more of the following underlying factors: - The ability of the pathogen to survive outside the host - e.g. water-borne cholera which becomes prevalent in tropical wet seasons, or influenza which peaks in temperate regions during winter. The behaviour of people susceptible to the disease - such as spending more time in close contact indoors. Changes in immune function during winter - one possibility is a reduction in vitamin D, and another is the effect of cold on mucous membranes in the nose. Abundance of vectors such as mosquitoes. === Human behaviour === Changes in behaviour can affect the likelihood or severity of epidemics. The classic example is the 1854 Broad Street cholera outbreak, in which a cholera outbreak was mitigated by removing a supply of contaminated water - an event now regarded as the foundation of the science of epidemiology. Urbanisation and overcrowding (e.g. in refugee camps) increase the likelihood of disease outbreaks. A factor which contributed to the initial rapid increase in the 2014 Ebola virus epidemic was ritual bathing of (infective) corpses; one of the control measures was an education campaign to change behaviour around funeral rites. === Changes in the host population === The level of immunity to a disease in a population - herd immunity - is at its peak after a disease outbreak or a vaccination campaign. In the following years, immunity will decline, both within individuals and in the population as a whole as older individuals die and new individuals are born. Eventually, unless there is another vaccination campaign, an outbreak or epidemic will recur. It's also possible for disease which is endemic in one population to become epidemic if it is introduced into a novel setting where the host population is not immune. An example of this was the
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{
"page_id": 66981,
"source": null,
"title": "Epidemic"
}
|
introduction European diseases such as smallpox into indigenous populations during the 16th century. === Zoonosis === A zoonosis is an infectious disease of humans caused by a pathogen that can jump from a non-human host to a human. Major diseases such as Ebola virus disease and salmonellosis are zoonoses. HIV was a zoonotic disease transmitted to humans in the early part of the 20th century, though it has now evolved into a separate human-only disease. Some strains of bird flu and swine flu are zoonoses; these viruses occasionally recombine with human strains of the flu and can cause pandemics such as the 1918 Spanish flu or the 2009 swine flu. == Types == === Common source outbreak === In a common source outbreak epidemic, the affected individuals had an exposure to a common agent. If the exposure is singular and all of the affected individuals develop the disease over a single exposure and incubation course, it can be termed as a point source outbreak. If the exposure was continuous or variable, it can be termed as a continuous outbreak or intermittent outbreak, respectively.: 56 === Propagated outbreak === In a propagated outbreak, the disease spreads person-to-person. Affected individuals may become independent reservoirs leading to further exposures.: 56 Many epidemics will have characteristics of both common source and propagated outbreaks (sometimes referred to as mixed outbreak). For example, secondary person-to-person spread may occur after a common source exposure or an environmental vector may spread a zoonotic diseases agent.: 56–58 == Preparation == Preparations for an epidemic include having a disease surveillance system; the ability to quickly dispatch emergency workers, especially local-based emergency workers; and a legitimate way to guarantee the safety and health of health workers. Effective preparations for a response to a pandemic are multi-layered. The first layer is a
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{
"page_id": 66981,
"source": null,
"title": "Epidemic"
}
|
disease surveillance system. Tanzania, for example, runs a national lab that runs testing for 200 health sites and tracks the spread of infectious diseases. The next layer is the actual response to an emergency. According to U.S.-based columnist Michael Gerson in 2015, only the U.S. military and NATO have the global capability to respond to such an emergency. Still, despite the most extensive preparatory measures, a fast-spreading pandemic may easily exceed and overwhelm existing health-care resources. Consequently, early and aggressive mitigation efforts, aimed at the so-called "epidemic curve flattening" need to be taken. Such measures usually consist on non-pharmacological interventions such as social/physical distancing, aggressive contact tracing, "stay-at-home" orders, as well as appropriate personal protective equipment (i.e., masks, gloves, and other physical barriers to spread). Moreover, India has taken significant strides in its efforts to prepare for future respiratory pandemics through the development of the National Pandemic Preparedness Plan for Respiratory Viruses using a multisectoral approach. Preceding this national effort, a regional workshop on the Preparedness and Resilience for Emerging Threats (PRET) initiative was organized by WHO's South-East Asia Regional Office on October 12–13, 2023. Recognizing that the same capacities and capabilities can be leveraged and applied for groups of pathogens based on their mode of transmission, the workshop aimed to facilitate pandemic planning efficiency for countries in the region. The participating countries, in the aftermath of the workshop, outlined their immediate next steps and sought support from WHO and its partners to bolster regional preparedness against respiratory pathogen pandemics. == See also == == References == == Further reading == == External links ==
|
{
"page_id": 66981,
"source": null,
"title": "Epidemic"
}
|
Phytochemistry is the study of phytochemicals, which are chemicals derived from plants. Phytochemists strive to describe the structures of the large number of secondary metabolites found in plants, the functions of these compounds in human and plant biology, and the biosynthesis of these compounds. Plants synthesize phytochemicals for many reasons, including to protect themselves against insect attacks and plant diseases. The compounds found in plants are of many kinds, but most can be grouped into four major biosynthetic classes: alkaloids, phenylpropanoids, polyketides, and terpenoids. Phytochemistry can be considered a subfield of botany or chemistry. Activities can be led in botanical gardens or in the wild with the aid of ethnobotany. Phytochemical studies directed toward human (i.e. drug discovery) use may fall under the discipline of pharmacognosy, whereas phytochemical studies focused on the ecological functions and evolution of phytochemicals likely fall under the discipline of chemical ecology. Phytochemistry also has relevance to the field of plant physiology. == Techniques == Techniques commonly used in the field of phytochemistry are extraction, isolation, and structural elucidation (MS,1D and 2D NMR) of natural products, as well as various chromatography techniques (MPLC, HPLC, and LC-MS). == Phytochemicals == Many plants produce chemical compounds for defence against herbivores. The major classes of pharmacologically active phytochemicals are described below, with examples of medicinal plants that contain them. Human settlements are often surrounded by weeds containing phytochemicals, such as nettle, dandelion and chickweed. Many phytochemicals, including curcumin, epigallocatechin gallate, genistein, and resveratrol are pan-assay interference compounds and are not useful in drug discovery. === Alkaloids === Alkaloids are bitter-tasting chemicals, widespread in nature, and often toxic. There are several classes with different modes of action as drugs, both recreational and pharmaceutical. Medicines of different classes include atropine, scopolamine, and hyoscyamine (all from nightshade), the traditional medicine berberine (from
|
{
"page_id": 1246630,
"source": null,
"title": "Phytochemistry"
}
|
plants such as Berberis and Mahonia), caffeine (Coffea), cocaine (Coca), ephedrine (Ephedra), morphine (opium poppy), nicotine (tobacco), reserpine (Rauvolfia serpentina), quinidine and quinine (Cinchona), vincamine (Vinca minor), and vincristine (Catharanthus roseus). === Glycosides === Anthraquinone glycosides are found in senna, rhubarb, and Aloe. The cardiac glycosides are phytochemicals from plants including foxglove and lily of the valley. They include digoxin and digitoxin which act as diuretics. === Polyphenols === Polyphenols of several classes are widespread in plants, including anthocyanins, phytoestrogens, and tannins. Polyphenols are secondary metabolites produced by almost every part of plants, including fruits, flowers, leaves and bark. === Terpenes === Terpenes and terpenoids of many kinds are found in resinous plants such as the conifers. They are aromatic and serve to repel herbivores. Their scent makes them useful in essential oils, whether for perfumes such as rose and lavender, or for aromatherapy. Some have had medicinal uses: thymol is an antiseptic and was once used as a vermifuge (anti-worm medicine). == Genetics == Contrary to bacteria and fungi, most plant metabolic pathways are not grouped into biosynthetic gene clusters, but instead are scattered as individual genes. Some exceptions have been discovered: steroidal glycoalkaloids in Solanum, polyketides in Pooideae, benzoxazinoids in Zea mays, triterpenes in Avena sativa, Cucurbitaceae, Arabidopsis, and momilactone diterpenes in Oryza sativa. == References ==
|
{
"page_id": 1246630,
"source": null,
"title": "Phytochemistry"
}
|
The molecular formula C16H10N2Na2O7S2 (molar mass: 452.369 g/mol) may refer to: Orange G Orange GGN Sunset Yellow FCF
|
{
"page_id": 61539749,
"source": null,
"title": "C16H10N2Na2O7S2"
}
|
Electron-rich is jargon that is used in multiple related meanings with either or both kinetic and thermodynamic implications: with regards to electron-transfer, electron-rich species have low ionization energy and/or are reducing agents. Tetrakis(dimethylamino)ethylene is an electron-rich alkene because, unlike ethylene, it forms isolable radical cation. In contrast, electron-poor alkene tetracyanoethylene is an electron acceptor, forming isolable anions. with regards to acid-base reactions, electron-rich species have high pKa's and react with weak Lewis acids. with regards to nucleophilic substitution reactions, electron-rich species are relatively strong nucleophiles, as judged by rates of attack by electrophiles. For example, compared to benzene, pyrrole is more rapidly attacked by electrophiles. Pyrrole is therefore considered to be an electron-rich aromatic ring. Similarly, benzene derivatives with electron-donating groups (EDGs) are attacked by electrophiles faster than in benzene. The electron-donating vs electron-withdrawing influence of various functional groups have been extensively parameterized in linear free energy relationships. with regards to Lewis acidity, electron-rich species are strong Lewis bases. == See also == Electron-withdrawing group == References ==
|
{
"page_id": 40699303,
"source": null,
"title": "Electron-rich"
}
|
Damping torque is provided by indicating instrument. Damper is a generic term used to identify any mechanism used for vibration energy absorption, the shaft vibration suppression, soft start and overload protection device. In order to design an efficient damper, it is imperative that the damping torque is calculated first. Damping torque or damping forces is the speed deviation of an electromechanical torque deviations of a machine while the angle deviation is called synchronizing torque [1]. In a measuring instrument, the damping torque is necessary to bring the moving system to rest to indicate steady reflection in a reasonable short time. It exists only as long as the pointer is in motion. Under the absence of damping torque the pointer oscillates for a short period of time and comes to steady position and this situation is called under damping. If the damping force is too large, then the pointer will come to rest slowly and this is called as over damping. Damping torque is a physical process of controlling a system's movement through producing motion that opposes the natural oscillation of a system. Similar to friction, it only acts when a system is in motion, and is not present if the system is at rest. Its primary purpose is to enable fast and accurate readings for an oscillating system. Instead of allowing an object to oscillate at its fundamental frequency forever, damping torque applies a counteractive force that slows the oscillation enough for a reading to be made. Although damping torque is used in many measurement devices, it is not something that has a set value, but instead is adjusted based on a pointer that is graphed on a deflection torque vs. time graph. Damping torque is an integral part in the measurement of moving systems because of its ability to
|
{
"page_id": 23659948,
"source": null,
"title": "Damping torque"
}
|
control oscillation. == Production == There are four different ways of producing damping torque, these include air friction damping, fluid friction damping, eddy current damping, and electromagnetic damping. Air friction damping is created by a piston oscillating in and out of an air chamber. When the piston enters the chamber it causes compression, when it exits the chamber there is a force acting back against it. This method is often used in the presence of a relatively weak electrical field, as air friction damping does not involve the use of any electric components that could distort the electrical field. Fluid friction damping is created through the oscillation of a disk in and out of liquid, normally oil, thus causing it to always oppose motion. This method is very similar to air friction damping, except rather than having air in a chamber, it is replaced with fluid. This method is hindered by the fact that it can only be done vertically, as it requires the liquid to be in an upright position. Eddy current damping is the use of an Eddy current and an electric field to create an electromagnetic torque that opposes motion. In this method the damping torque produced is proportional to the strength of the current and magnetic field. This method is very efficient, but it has the downside of distorting a weak electrical field. Electromagnetic damping is created by sending an electric current through a magnetic coil, causing a torque that goes against the natural movement of the coil. It has the similar disadvantage to the Eddy current damping in that it can distort the electrical field. == Uses == Damping torque is used to enable fast and accurate reading of an object that undergoes oscillation. Due to inertia, an object in motion tends to stay in
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"page_id": 23659948,
"source": null,
"title": "Damping torque"
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motion, thus requiring a counteractive force to bring it to its final rate of oscillation in a short period of time. Damping torque does this by opposing the natural oscillation, enabling the user to get an accurate reading. It is used in most experiments that involve gathering data of a system that is in motion, as one of the only ways to obtain accurate data. It also has many different methods of production as outlined above, allowing it to be used in many models where a counteractive force is required. Although, as noted above there are certain methods of creating damping torque that are only applicable to a system if it meets the correct requirements. == Measurement == Damping torque is a motion that isn't assigned numbers while being used, but rather is tested and observed using a pointer in an experiment. A pointer of a device is the part that shows the damping torque based on a deflection torque vs time graph. This is done by taking into account both deflection and controlling torque in order to give the correct amount of damping torque. Deflection torque is what causes the pointer on the machine to oscillate, and the controlling torque is a counteractive force that stops the pointer from oscillating uncontrollably. Deflection torque and controlling torque work in a similar way to a scale, in that deflection torque is the weight that is pressed on the scale and the controlling torque is the counterweight that is used to balance out the initial weight. In order to get good results it is very important that these two forces equal one another. === Deflection and Controlling Torque Production === Deflection and controlling torque, like damping torque, are not explicitly measured, but can be created and thus controlled in different 2ways. By
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"title": "Damping torque"
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creating these two torques the pointer will move in a specific way that can be analyzed as shown below. Deflection torque can be any type of force that initially puts the system in motion. Controlling torque on the other hand is generated by a measuring device, and thus is not a naturally occurring motion. There are two ways of producing a controlling torque, spring control and gravity control: Spring control is created through the use of a control spring that is connected to the pointer of the system. When the system moves the spring is twisted in the opposite direction, thus creating a torque that directly counteracts the deflection torque. Gravity control is created by attaching small weights to a moving system, generating a torque based on the angle of deflection, which is the angle the back and forward tangents make with one another. This method is hindered by the fact that it requires the system to be vertical so that the weights can be acted on by gravity. When analyzing the deflection and controlling torque there are three main categories, under damped, over damped, and critically damped. If a system is under damped it will not reach its final rate of oscillation in a timely manner, and will oscillate slowly for a long period of time. If it is over damped, the system will oscillate at a rate that is too slow to give an accurate reading. Finally, if it is critically damped, it has an equal amount of deflection and controlling torque, thus allowing the pointer to quickly find the correct value, without the system oscillating past that value. Critically damped means the machine has the right amount of damping torque and is ready to be used for experiments. == References == Power Engineering Society General Meeting, 2006.
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"page_id": 23659948,
"source": null,
"title": "Damping torque"
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IEEE, 10.1109/PES.2006.1709001 == External links == Media related to Damping torque at Wikimedia Commons
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"source": null,
"title": "Damping torque"
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The Kochi reaction is an organic reaction for the decarboxylation of carboxylic acids to alkyl halides with lead(IV) acetate and a lithium halide. The reaction is a variation of the Hunsdiecker reaction. == References ==
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"page_id": 14091693,
"source": null,
"title": "Kochi reaction"
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In heat transfer, Kirchhoff's law of thermal radiation refers to wavelength-specific radiative emission and absorption by a material body in thermodynamic equilibrium, including radiative exchange equilibrium. It is a special case of Onsager reciprocal relations as a consequence of the time reversibility of microscopic dynamics, also known as microscopic reversibility. A body at temperature T radiates electromagnetic energy. A perfect black body in thermodynamic equilibrium absorbs all light that strikes it, and radiates energy according to a unique law of radiative emissive power for temperature T (Stefan–Boltzmann law), universal for all perfect black bodies. Kirchhoff's law states that: Here, the dimensionless coefficient of absorption (or the absorptivity) is the fraction of incident light (power) at each spectral frequency that is absorbed by the body when it is radiating and absorbing in thermodynamic equilibrium. In slightly different terms, the emissive power of an arbitrary opaque body of fixed size and shape at a definite temperature can be described by a dimensionless ratio, sometimes called the emissivity: the ratio of the emissive power of the body to the emissive power of a black body of the same size and shape at the same fixed temperature. With this definition, Kirchhoff's law states, in simpler language: In some cases, emissive power and absorptivity may be defined to depend on angle, as described below. The condition of thermodynamic equilibrium is necessary in the statement, because the equality of emissivity and absorptivity often does not hold when the material of the body is not in thermodynamic equilibrium. Kirchhoff's law has another corollary: the emissivity cannot exceed one (because the absorptivity cannot, by conservation of energy), so it is not possible to thermally radiate more energy than a black body, at equilibrium. In negative luminescence the angle and wavelength integrated absorption exceeds the material's emission; however, such
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systems are powered by an external source and are therefore not in thermodynamic equilibrium. == Principle of detailed balance == Kirchhoff's law of thermal radiation has a refinement in that not only is thermal emissivity equal to absorptivity, it is equal in detail. Consider a leaf. It is a poor absorber of green light (around 470 nm), which is why it looks green. By the principle of detailed balance, it is also a poor emitter of green light. In other words, if a material, illuminated by black-body radiation of temperature T {\displaystyle T} , is dark (well absorbing) at a certain frequency ν {\displaystyle \nu } , then its own thermal radiation will be strong (well emitting) at the same frequency ν {\displaystyle \nu } and the same temperature T {\displaystyle T} . More generally, all intensive properties are balanced in detail. So for example, the absorptivity at a certain incidence direction, for a certain frequency, of a certain polarization, is the same as the emissivity at the same direction, for the same frequency, of the same polarization. This is the principle of detailed balance. == History == Before Kirchhoff's law was recognized, it had been experimentally established that a good absorber is a good emitter, and a poor absorber is a poor emitter. Naturally, a good reflector must be a poor absorber. This is why, for example, lightweight emergency thermal blankets are based on reflective metallic coatings: they lose little heat by radiation. Kirchhoff's great insight was to recognize the universality and uniqueness of the function that describes the black body emissive power. But he did not know the precise form or character of that universal function. Attempts were made by Lord Rayleigh and Sir James Jeans 1900–1905 to describe it in classical terms, resulting in Rayleigh–Jeans law. This
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"page_id": 591280,
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law turned out to be inconsistent yielding the ultraviolet catastrophe. The correct form of the law was found by Max Planck in 1900, assuming quantized emission of radiation, and is termed Planck's law. This marks the advent of quantum mechanics. == Theory == In a blackbody enclosure that contains electromagnetic radiation with a certain amount of energy at thermodynamic equilibrium, this "photon gas" will have a Planck distribution of energies. One may suppose a second system, a cavity with walls that are opaque, rigid, and not perfectly reflective to any wavelength, to be brought into connection, through an optical filter, with the blackbody enclosure, both at the same temperature. Radiation can pass from one system to the other. For example, suppose in the second system, the density of photons at narrow frequency band around wavelength λ {\displaystyle \lambda } were higher than that of the first system. If the optical filter passed only that frequency band, then there would be a net transfer of photons, and their energy, from the second system to the first. This is in violation of the second law of thermodynamics, which requires that there can be no net transfer of heat between two bodies at the same temperature. In the second system, therefore, at each frequency, the walls must absorb and emit energy in such a way as to maintain the black body distribution. Hence absorptivity and emissivity must be equal. The absorptivity α λ {\displaystyle \alpha _{\lambda }} of the wall is the ratio of the energy absorbed by the wall to the energy incident on the wall, for a particular wavelength. Thus the absorbed energy is α λ E b λ ( λ , T ) {\displaystyle \alpha _{\lambda }E_{b\lambda }(\lambda ,T)} where E b λ ( λ , T ) {\displaystyle E_{b\lambda
|
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}(\lambda ,T)} is the intensity of black-body radiation at wavelength λ {\displaystyle \lambda } and temperature T {\displaystyle T} . Independent of the condition of thermal equilibrium, the emissivity of the wall is defined as the ratio of emitted energy to the amount that would be radiated if the wall were a perfect black body. The emitted energy is thus ε λ E b λ ( λ , T ) {\displaystyle \varepsilon _{\lambda }E_{b\lambda }(\lambda ,T)} where ε λ {\displaystyle \varepsilon _{\lambda }} is the emissivity at wavelength λ {\displaystyle \lambda } . For the maintenance of thermal equilibrium, these two quantities must be equal, or else the distribution of photon energies in the cavity will deviate from that of a black body. This yields Kirchhoff's law: α λ = ε λ {\displaystyle \alpha _{\lambda }=\varepsilon _{\lambda }} By a similar, but more complicated argument, it can be shown that, since black-body radiation is equal in every direction (isotropic), the emissivity and the absorptivity, if they happen to be dependent on direction, must again be equal for any given direction. Average and overall absorptivity and emissivity data are often given for materials with values which differ from each other. For example, white paint is quoted as having an absorptivity of 0.16, while having an emissivity of 0.93. This is because the absorptivity is averaged with weighting for the solar spectrum, while the emissivity is weighted for the emission of the paint itself at normal ambient temperatures. The absorptivity quoted in such cases is being calculated by: α s u n = ∫ 0 ∞ α λ ( λ ) I λ s u n ( λ ) d λ ∫ 0 ∞ I λ s u n ( λ ) d λ {\displaystyle \alpha _{\mathrm {sun} }=\displaystyle {\frac {\int _{0}^{\infty
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}\alpha _{\lambda }(\lambda )I_{\lambda \mathrm {sun} }(\lambda )\,d\lambda }{\int _{0}^{\infty }I_{\lambda \mathrm {sun} }(\lambda )\,d\lambda }}} while the average emissivity is given by: ε p a i n t = ∫ 0 ∞ ε λ ( λ , T ) E b λ ( λ , T ) d λ ∫ 0 ∞ E b λ ( λ , T ) d λ {\displaystyle \varepsilon _{\mathrm {paint} }={\frac {\int _{0}^{\infty }\varepsilon _{\lambda }(\lambda ,T)E_{b\lambda }(\lambda ,T)\,d\lambda }{\int _{0}^{\infty }E_{b\lambda }(\lambda ,T)\,d\lambda }}} where I λ s u n {\displaystyle I_{\lambda \mathrm {sun} }} is the emission spectrum of the sun, and ε λ E b λ ( λ , T ) {\displaystyle \varepsilon _{\lambda }E_{b\lambda }(\lambda ,T)} is the emission spectrum of the paint. Although, by Kirchhoff's law, ε λ = α λ {\displaystyle \varepsilon _{\lambda }=\alpha _{\lambda }} in the above equations, the above averages α s u n {\displaystyle \alpha _{\mathrm {sun} }} and ε p a i n t {\displaystyle \varepsilon _{\mathrm {paint} }} are not generally equal to each other. The white paint will serve as a very good insulator against solar radiation, because it is very reflective of the solar radiation, and although it therefore emits poorly in the solar band, its temperature will be around room temperature, and it will emit whatever radiation it has absorbed in the infrared, where its emission coefficient is high. === Planck's derivation === Historically, Planck derived the black body radiation law and detailed balance according to a classical thermodynamic argument, with a single heuristic step, which was later interpreted as a quantization hypothesis. In Planck's set up, he started with a large Hohlraum at a fixed temperature T {\displaystyle T} . At thermal equilibrium, the Hohlraum is filled with a distribution of EM waves at thermal equilibrium with
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the walls of the Hohlraum. Next, he considered connecting the Hohlraum to a single small resonator, such as Hertzian resonators. The resonator reaches a certain form of thermal equilibrium with the Hohlraum, when the spectral input into the resonator equals the spectral output at the resonance frequency. Next, suppose there are two Hohlraums at the same fixed temperature T {\displaystyle T} , then Planck argued that the thermal equilibrium of the small resonator is the same when connected to either Hohlraum. For, we can disconnect the resonator from one Hohlraum and connect it to another. If the thermal equilibrium were different, then we have just transported energy from one to another, violating the second law. Therefore, the spectrum of all black bodies are identical at the same temperature. Using a heuristic of quantization, which he gleaned from Boltzmann, Planck argued that a resonator tuned to frequency ν {\displaystyle \nu } , with average energy E {\displaystyle E} , would contain entropy S ν = k B [ ( 1 + E h ν ) ln ( 1 + E h ν ) − E h ν ln E h ν ] {\displaystyle S_{\nu }=k_{B}\left[\left(1+{\frac {E}{h\nu }}\right)\ln \left(1+{\frac {E}{h\nu }}\right)-{\frac {E}{h\nu }}\ln {\frac {E}{h\nu }}\right]} for some constant h {\displaystyle h} (later termed the Planck constant). Then applying k B T = ( ∂ E S ) − 1 {\displaystyle k_{B}T=(\partial _{E}S)^{-1}} , Planck obtained the black body radiation law. Another argument that does not depend on the precise form of the entropy function, can be given as follows. Next, suppose we have a material that violates Kirchhoff's law when integrated, such that the total coefficient of absorption is not equal to the coefficient of emission at a certain T {\displaystyle T} , then if the material at temperature
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T {\displaystyle T} is placed into a Hohlraum at temperature T {\displaystyle T} , it would spontaneously emit more than it absorbs, or conversely, thus spontaneously creating a temperature difference, violating the second law. Finally, suppose we have a material that violates Kirchhoff's law in detail, such that the total coefficient of absorption is not equal to the coefficient of emission at a certain T {\displaystyle T} and at a certain frequency ν {\displaystyle \nu } , then since it does not violate Kirchhoff's law when integrated, there must exist two frequencies ν 1 ≠ ν 2 {\displaystyle \nu _{1}\neq \nu _{2}} , such that the material absorbs more than it emits at ν 1 {\displaystyle \nu _{1}} , and conversely at ν 2 {\displaystyle \nu _{2}} . Now, place this material in one Hohlraum. It would spontaneously create a shift in the spectrum, making it higher at ν 2 {\displaystyle \nu _{2}} than at ν 1 {\displaystyle \nu _{1}} . However, this then allows us to tap from one Hohlraum with a resonator tuned at ν 2 {\displaystyle \nu _{2}} , then detach and attach to another Hohlraum at the same temperature, thus transporting energy from one to another, violating the second law. We may apply the same argument for polarization and direction of radiation, obtaining the full principle of detailed balance. == Black bodies == === Near-black materials === It has long been known that a lamp-black coating will make a body nearly black. Some other materials are nearly black in particular wavelength bands. Such materials do not survive all the very high temperatures that are of interest. An improvement on lamp-black is found in manufactured carbon nanotubes. Nano-porous materials can achieve refractive indices nearly that of vacuum, in one case obtaining average reflectance of 0.045%. === Opaque
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bodies === Bodies that are opaque to thermal radiation that falls on them are valuable in the study of heat radiation. Planck analyzed such bodies with the approximation that they be considered topologically to have an interior and to share an interface. They share the interface with their contiguous medium, which may be rarefied material such as air, or transparent material, through which observations can be made. The interface is not a material body and can neither emit nor absorb. It is a mathematical surface belonging jointly to the two media that touch it. It is the site of refraction of radiation that penetrates it and of reflection of radiation that does not. As such it obeys the Helmholtz reciprocity principle. The opaque body is considered to have a material interior that absorbs all and scatters or transmits none of the radiation that reaches it through refraction at the interface. In this sense the material of the opaque body is black to radiation that reaches it, while the whole phenomenon, including the interior and the interface, does not show perfect blackness. In Planck's model, perfectly black bodies, which he noted do not exist in nature, besides their opaque interior, have interfaces that are perfectly transmitting and non-reflective. === Cavity radiation === The walls of a cavity can be made of opaque materials that absorb significant amounts of radiation at all wavelengths. It is not necessary that every part of the interior walls be a good absorber at every wavelength. The effective range of absorbing wavelengths can be extended by the use of patches of several differently absorbing materials in parts of the interior walls of the cavity. In thermodynamic equilibrium the cavity radiation will precisely obey Planck's law. In this sense, thermodynamic equilibrium cavity radiation may be regarded as thermodynamic
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"page_id": 591280,
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equilibrium black-body radiation to which Kirchhoff's law applies exactly, though no perfectly black body in Kirchhoff's sense is present. A theoretical model considered by Planck consists of a cavity with perfectly reflecting walls, initially with no material contents, into which is then put a small piece of carbon. Without the small piece of carbon, there is no way for non-equilibrium radiation initially in the cavity to drift towards thermodynamic equilibrium. When the small piece of carbon is put in, it transduces amongst radiation frequencies so that the cavity radiation comes to thermodynamic equilibrium. === A hole in the wall of a cavity === For experimental purposes, a hole in a cavity can be devised to provide a good approximation to a black surface, but will not be perfectly Lambertian, and must be viewed from nearly right angles to get the best properties. The construction of such devices was an important step in the empirical measurements that led to the precise mathematical identification of Kirchhoff's universal function, now known as Planck's law. === Kirchhoff's perfect black bodies === Planck also noted that the perfect black bodies of Kirchhoff do not occur in physical reality. They are theoretical fictions. Kirchhoff's perfect black bodies absorb all the radiation that falls on them, right in an infinitely thin surface layer, with no reflection and no scattering. They emit radiation in perfect accord with Lambert's cosine law. == Original statements == Gustav Kirchhoff stated his law in several papers in 1859 and 1860, and then in 1862 in an appendix to his collected reprints of those and some related papers. Prior to Kirchhoff's studies, it was known that for total heat radiation, the ratio of emissive power to absorptive ratio was the same for all bodies emitting and absorbing thermal radiation in thermodynamic equilibrium. This
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"page_id": 591280,
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means that a good absorber is a good emitter. Naturally, a good reflector is a poor absorber. For wavelength specificity, prior to Kirchhoff, the ratio was shown experimentally by Balfour Stewart to be the same for all bodies, but the universal value of the ratio had not been explicitly considered in its own right as a function of wavelength and temperature. Kirchhoff's original contribution to the physics of thermal radiation was his postulate of a perfect black body radiating and absorbing thermal radiation in an enclosure opaque to thermal radiation and with walls that absorb at all wavelengths. Kirchhoff's perfect black body absorbs all the radiation that falls upon it. Every such black body emits from its surface with a spectral radiance that Kirchhoff labeled I (for specific intensity, the traditional name for spectral radiance). The precise mathematical expression for that universal function I was very much unknown to Kirchhoff, and it was just postulated to exist, until its precise mathematical expression was found in 1900 by Max Planck. It is nowadays referred to as Planck's law. Then, at each wavelength, for thermodynamic equilibrium in an enclosure, opaque to heat rays, with walls that absorb some radiation at every wavelength: == See also == Kirchhoff's laws (disambiguation) Sakuma–Hattori equation Wien's displacement law Stefan–Boltzmann law, which states that the power of emission is proportional to the fourth power of the black body's temperature == References == === Citations === === Bibliography === === General references === Evgeny Lifshitz and L. P. Pitaevskii, Statistical Physics: Part 2, 3rd edition (Elsevier, 1980). F. Reif, Fundamentals of Statistical and Thermal Physics (McGraw-Hill: Boston, 1965). Lemons, Don S.; Shanahan, William R.; Buchholtz, Louis (2022). On the trail of blackbody radiation: Max Planck and the physics of his era. Cambridge, Massachusetts: The MIT Press. ISBN 978-0-262-04704-3.
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Kuhn, Thomas S. (1993). Black-body theory and the quantum discontinuity: 1894 - 1912 (Nachdr. ed.). Chicago: Univ. of Chicago Press. ISBN 978-0-226-45800-7.
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Kin selection is a process whereby natural selection favours a trait due to its positive effects on the reproductive success of an organism's relatives, even when at a cost to the organism's own survival and reproduction. Kin selection can lead to the evolution of altruistic behaviour. It is related to inclusive fitness, which combines the number of offspring produced with the number an individual can ensure the production of by supporting others (weighted by the relatedness between individuals). A broader definition of kin selection includes selection acting on interactions between individuals who share a gene of interest even if the gene is not shared due to common ancestry. Charles Darwin discussed the concept of kin selection in his 1859 book, On the Origin of Species, where he reflected on the puzzle of sterile social insects, such as honey bees, which leave reproduction to their mothers, arguing that a selection benefit to related organisms (the same "stock") would allow the evolution of a trait that confers the benefit but destroys an individual at the same time. J.B.S. Haldane in 1955 briefly alluded to the principle in limited circumstances (Haldane famously joked that he would willingly die for two brothers or eight cousins), and R.A. Fisher mentioned a similar principle even more briefly in 1930. However, it was not until 1964 that W.D. Hamilton generalised the concept and developed it mathematically (resulting in Hamilton's rule) that it began to be widely accepted. The mathematical treatment was made more elegant in 1970 due to advances made by George R. Price. The term "kin selection" was first used by John Maynard Smith in 1964. According to Hamilton's rule, kin selection causes genes to increase in frequency when the genetic relatedness of a recipient to an actor multiplied by the benefit to the recipient is
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{
"page_id": 66996,
"source": null,
"title": "Kin selection"
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greater than the reproductive cost to the actor. Hamilton proposed two mechanisms for kin selection. First, kin recognition allows individuals to be able to identify their relatives. Second, in viscous populations, populations in which the movement of organisms from their place of birth is relatively slow, local interactions tend to be among relatives by default. The viscous population mechanism makes kin selection and social cooperation possible in the absence of kin recognition. In this case, nurture kinship, the interaction between related individuals, simply as a result of living in each other's proximity, is sufficient for kin selection, given reasonable assumptions about population dispersal rates. Kin selection is not the same thing as group selection, where natural selection is believed to act on the group as a whole. In humans, altruism is both more likely and on a larger scale with kin than with unrelated individuals; for example, humans give presents according to how closely related they are to the recipient. In other species, vervet monkeys use allomothering, where related females such as older sisters or grandmothers often care for young, according to their relatedness. The social shrimp Synalpheus regalis protects juveniles within highly related colonies. == Historical overview == Charles Darwin was the first to discuss the concept of kin selection (without using that term). In On the Origin of Species, he wrote about the conundrum represented by altruistic sterile social insects that: This difficulty, though appearing insuperable, is lessened, or, as I believe, disappears, when it is remembered that selection may be applied to the family, as well as to the individual, and may thus gain the desired end. Breeders of cattle wish the flesh and fat to be well marbled together. An animal thus characterised has been slaughtered, but the breeder has gone with confidence to the same
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{
"page_id": 66996,
"source": null,
"title": "Kin selection"
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stock and has succeeded. In this passage "the family" and "stock" stand for a kin group. These passages and others by Darwin about kin selection are highlighted in D.J. Futuyma's textbook of reference Evolutionary Biology and in E. O. Wilson's Sociobiology. Kin selection was briefly referred to by R.A. Fisher in 1930 and J.B.S. Haldane in 1932 and 1955. J.B.S. Haldane grasped the basic quantities in kin selection, famously writing "I would lay down my life for two brothers or eight cousins". Haldane's remark alluded to the fact that if an individual loses its life to save two siblings, four nephews, or eight cousins, it is a "fair deal" in evolutionary terms, as siblings are on average 50% identical by descent, nephews 25%, and cousins 12.5% (in a diploid population that is randomly mating and previously outbred). But Haldane also joked that he would truly die only to save more than a single identical twin of his or more than two full siblings. In 1955 he clarified: Let us suppose that you carry a rare gene that affects your behaviour so that you jump into a flooded river and save a child, but you have one chance in ten of being drowned, while I do not possess the gene, and stand on the bank and watch the child drown. If the child's your own child or your brother or sister, there is an even chance that this child will also have this gene, so five genes will be saved in children for one lost in an adult. If you save a grandchild or a nephew, the advantage is only two and a half to one. If you only save a first cousin, the effect is very slight. If you try to save your first cousin once removed the population is
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{
"page_id": 66996,
"source": null,
"title": "Kin selection"
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more likely to lose this valuable gene than to gain it. … It is clear that genes making for conduct of this kind would only have a chance of spreading in rather small populations when most of the children were fairly near relatives of the man who risked his life. W. D. Hamilton, in 1963 and especially in 1964 generalised the concept and developed it mathematically, showing that it holds for genes even when they are not rare, deriving Hamilton's rule and defining a new quantity known as an individual's inclusive fitness. He is widely credited as the founder of the field of social evolution. A more elegant mathematical treatment was made possible by George Price in 1970. John Maynard Smith may have coined the actual term "kin selection" in 1964: These processes I will call kin selection and group selection respectively. Kin selection has been discussed by Haldane and by Hamilton. … By kin selection I mean the evolution of characteristics which favour the survival of close relatives of the affected individual, by processes which do not require any discontinuities in the population breeding structure. Kin selection causes changes in gene frequency across generations, driven by interactions between related individuals. This dynamic forms the conceptual basis of the theory of sociobiology. Some cases of evolution by natural selection can only be understood by considering how biological relatives influence each other's fitness. Under natural selection, a gene encoding a trait that enhances the fitness of each individual carrying it should increase in frequency within the population; and conversely, a gene that lowers the individual fitness of its carriers should be eliminated. However, a hypothetical gene that prompts behaviour which enhances the fitness of relatives but lowers that of the individual displaying the behaviour, may nonetheless increase in frequency, because relatives
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{
"page_id": 66996,
"source": null,
"title": "Kin selection"
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often carry the same gene. According to this principle, the enhanced fitness of relatives can at times more than compensate for the fitness loss incurred by the individuals displaying the behaviour, making kin selection possible. This is a special case of a more general model, "inclusive fitness". This analysis has been challenged, Wilson writing that "the foundations of the general theory of inclusive fitness based on the theory of kin selection have crumbled" and that he now relies instead on the theory of eusociality and "gene-culture co-evolution" for the underlying mechanics of sociobiology. Inclusive fitness theory is still generally accepted however, as demonstrated by the publication of a rebuttal to Wilson's claims in Nature from over a hundred researchers. Kin selection is contrasted with group selection, according to which a genetic trait can become prevalent within a group because it benefits the group as a whole, regardless of any benefit to individual organisms. All known forms of group selection conform to the principle that an individual behaviour can be evolutionarily successful only if the genes responsible for this behaviour conform to Hamilton's Rule, and hence, on balance and in the aggregate, benefit from the behaviour. == Hamilton's rule == Formally, genes should increase in frequency when r B > C {\displaystyle rB>C} where r = the genetic relatedness of the recipient to the actor, often defined as the probability that a gene picked randomly from each at the same locus is identical by descent. B = the additional reproductive benefit gained by the recipient of the altruistic act, C = the reproductive cost to the individual performing the act. This inequality is known as Hamilton's rule after W. D. Hamilton who in 1964 published the first formal quantitative treatment of kin selection. The relatedness parameter (r) in Hamilton's rule was
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"page_id": 66996,
"source": null,
"title": "Kin selection"
}
|
introduced in 1922 by Sewall Wright as a coefficient of relationship that gives the probability that at a random locus, the alleles there will be identical by descent. Modern formulations of the rule use Alan Grafen's definition of relatedness based on the theory of linear regression. A 2014 review of many lines of evidence for Hamilton's rule found that its predictions were confirmed in a wide variety of social behaviours across a broad phylogenetic range of birds, mammals and insects, in each case comparing social and non-social taxa. Among the experimental findings, a 2010 study used a wild population of red squirrels in Yukon, Canada. Surrogate mothers adopted related orphaned squirrel pups but not unrelated orphans. The cost of adoption was calculated by measuring a decrease in the survival probability of the entire litter after increasing the litter by one pup, while benefit was measured as the increased chance of survival of the orphan. The degree of relatedness of the orphan and surrogate mother for adoption to occur depended on the number of pups the surrogate mother already had in her nest, as this affected the cost of adoption. Females always adopted orphans when rB was greater than C, but never adopted when rB was less than C, supporting Hamilton's rule. == Mechanisms == Altruism occurs where the instigating individual suffers a fitness loss while the receiving individual experiences a fitness gain. The sacrifice of one individual to help another is an example. Hamilton outlined two ways in which kin selection altruism could be favoured: The selective advantage which makes behaviour conditional in the right sense on the discrimination of factors which correlate with the relationship of the individual concerned is therefore obvious. It may be, for instance, that in respect of a certain social action performed towards neighbours indiscriminately,
|
{
"page_id": 66996,
"source": null,
"title": "Kin selection"
}
|
an individual is only just breaking even in terms of inclusive fitness. If he could learn to recognise those of his neighbours who really were close relatives and could devote his beneficial actions to them alone an advantage to inclusive fitness would at once appear. Thus a mutation causing such discriminatory behaviour itself benefits inclusive fitness and would be selected. In fact, the individual may not need to perform any discrimination so sophisticated as we suggest here; a difference in the generosity of his behaviour according to whether the situations evoking it were encountered near to, or far from, his own home might occasion an advantage of a similar kind. === Kin recognition and the green beard effect === First, if individuals have the capacity to recognise kin and to discriminate (positively) on the basis of kinship, then the average relatedness of the recipients of altruism could be high enough for kin selection. Because of the facultative nature of this mechanism, kin recognition and discrimination were expected to be unimportant except among 'higher' forms of life. However, as molecular recognition mechanisms have been shown to operate in organisms such as slime moulds kin recognition has much wider importance than previously recognised. Kin recognition may be selected for inbreeding avoidance, and little evidence indicates that 'innate' kin recognition plays a role in mediating altruism. A thought experiment on the kin recognition/discrimination distinction is the hypothetical 'green beard', where a gene for social behaviour is imagined also to cause a distinctive phenotype that can be recognised by other carriers of the gene. Due to conflicting genetic similarity in the rest of the genome, there should be selection pressure for green-beard altruistic sacrifices to be suppressed, making common ancestry the most likely form of inclusive fitness. This suppression is overcome if new phenotypes
|
{
"page_id": 66996,
"source": null,
"title": "Kin selection"
}
|
-other beard colours- are formed through mutation or introduced into the population from time to time. This proposed mechanism goes by the name of 'beard chromodynamics'. === Viscous populations === Secondly, indiscriminate altruism may be favoured in "viscous" populations, those with low rates or short ranges of dispersal. Here, social partners are typically related, and so altruism can be selective advantageous without the need for kin recognition and kin discrimination faculties—spatial proximity, together with limited dispersal, ensures that social interactions are more often with related individuals. This suggests a rather general explanation for altruism. Directional selection always favours those with higher rates of fecundity within a certain population. Social individuals can often enhance the survival of their own kin by participating in and following the rules of their own group. Hamilton later modified his thinking to suggest that an innate ability to recognise actual genetic relatedness was unlikely to be the dominant mediating mechanism for kin altruism: But once again, we do not expect anything describable as an innate kin recognition adaptation, used for social behaviour other than mating, for the reasons already given in the hypothetical case of the trees. Hamilton's later clarifications often go unnoticed. Stuart West and colleagues have countered the long-standing assumption that kin selection requires innate powers of kin recognition. Another doubtful assumption is that social cooperation must be based on limited dispersal and shared developmental context. Such ideas have obscured the progress made in applying kin selection to species including humans, on the basis of cue-based mediation of social bonding and social behaviours. == Special cases == === Eusociality === Eusociality (true sociality) occurs in social systems with three characteristics: an overlap in generations between parents and their offspring, cooperative brood care, and specialised castes of non-reproductive individuals. The social insects provide good examples
|
{
"page_id": 66996,
"source": null,
"title": "Kin selection"
}
|
of organisms with what appear to be kin selected traits. The workers of some species are sterile, a trait that would not occur if individual selection was the only process at work. The relatedness coefficient r is abnormally high between the worker sisters in a colony of Hymenoptera due to haplodiploidy. Hamilton's rule is presumed to be satisfied because the benefits in fitness for the workers are believed to exceed the costs in terms of lost reproductive opportunity, though this has never been demonstrated empirically. Competing hypotheses have been offered to explain the evolution of social behaviour in such organisms. The eusocial shrimp Synalpheus regalis protects juveniles in the colony. By defending the young, the large defender shrimp can increase its inclusive fitness. Allozyme data demonstrated high relatedness within colonies, averaging 0.50. This means that colonies represent close kin groups, supporting the hypothesis of kin selection. === Allomothering === Vervet monkeys utilise allomothering, parenting by group members other than the actual mother or father, where the allomother is typically an older female sibling or a grandmother. Individuals act aggressively toward other individuals that were aggressive toward their relatives. The behaviour implies kin selection between siblings, between mothers and offspring, and between grandparents and grandchildren. == In humans == Whether or not Hamilton's rule always applies, relatedness is often important for human altruism, in that humans are inclined to behave more altruistically toward kin than toward unrelated individuals. Many people choose to live near relatives, exchange sizeable gifts with relatives, and favour relatives in wills in proportion to their relatedness. === Experimental studies, interviews, and surveys === Interviews of several hundred women in Los Angeles showed that while non-kin friends were willing to help one another, their assistance was far more likely to be reciprocal. The largest amounts of non-reciprocal help,
|
{
"page_id": 66996,
"source": null,
"title": "Kin selection"
}
|
however, were reportedly provided by kin. Additionally, more closely related kin were considered more likely sources of assistance than distant kin. Similarly, several surveys of American college students found that individuals were more likely to incur the cost of assisting kin when a high probability that relatedness and benefit would be greater than cost existed. Participants' feelings of helpfulness were stronger toward family members than non-kin. Additionally, participants were found to be most willing to help those individuals most closely related to them. Interpersonal relationships between kin in general were more supportive and less Machiavellian than those between non-kin. In one experiment, the longer participants (from both the UK and the South African Zulus) held a painful skiing position, the more money or food was presented to a given relative. Participants repeated the experiment for individuals of different relatedness (parents and siblings at r=.5, grandparents, nieces, and nephews at r=.25, etc.). The results showed that participants held the position for longer intervals the greater the degree of relatedness between themselves and those receiving the reward. === Observational studies === A study of food-sharing practices on the West Caroline islets of Ifaluk determined that food-sharing was more common among people from the same islet, possibly because the degree of relatedness between inhabitants of the same islet would be higher than relatedness between inhabitants of different islets. When food was shared between islets, the distance the sharer was required to travel correlated with the relatedness of the recipient—a greater distance meant that the recipient needed to be a closer relative. The relatedness of the individual and the potential inclusive fitness benefit needed to outweigh the energy cost of transporting the food over distance. Humans may use the inheritance of material goods and wealth to maximise their inclusive fitness. By providing close kin
|
{
"page_id": 66996,
"source": null,
"title": "Kin selection"
}
|
with inherited wealth, an individual may improve his or her kin's reproductive opportunities and thus increase his or her own inclusive fitness even after death. A study of a thousand wills found that the beneficiaries who received the most inheritance were generally those most closely related to the will's writer. Distant kin received proportionally less inheritance, with the least amount of inheritance going to non-kin. A study of childcare practices among Canadian women found that respondents with children provide childcare reciprocally with non-kin. The cost of caring for non-kin was balanced by the benefit a woman received—having her own offspring cared for in return. However, respondents without children were significantly more likely to offer childcare to kin. For individuals without their own offspring, the inclusive fitness benefits of providing care to closely related children might outweigh the time and energy costs of childcare. Family investment in offspring among black South African households also appears consistent with an inclusive fitness model. A higher degree of relatedness between children and their caregivers was correlated with a higher degree of investment in the children, with more food, health care, and clothing. Relatedness was also associated with the regularity of a child's visits to local medical practitioners and with the highest grade the child had completed in school, and negatively associated with children being behind in school for their age. Observation of the Dolgan hunter-gatherers of northern Russia suggested that there are larger and more frequent asymmetrical transfers of food to kin. Kin are more likely to be welcomed to non-reciprocal meals, while non-kin are discouraged from attending. Finally, when reciprocal food-sharing occurs between families, these families are often closely related, and the primary beneficiaries are the offspring. Violence in families is more likely when step-parents are present, and that "genetic relationship is associated
|
{
"page_id": 66996,
"source": null,
"title": "Kin selection"
}
|
with a softening of conflict, and people's evident valuations of themselves and of others are systematically related to the parties' reproductive values". Numerous studies suggest how inclusive fitness may work amongst different peoples, such as the Ye'kwana of southern Venezuela, the Gypsies of Hungary, and the doomed Donner Party of the United States. === Human social patterns === Evolutionary psychologists, following early human sociobiologists' interpretation of kin selection theory initially attempted to explain human altruistic behaviour through kin selection by stating that "behaviors that help a genetic relative are favored by natural selection." However, many evolutionary psychologists recognise that this common shorthand formulation is inaccurate: Many misunderstandings persist. In many cases, they result from conflating "coefficient of relatedness" and "proportion of shared genes", which is a short step from the intuitively appealing—but incorrect—interpretation that "animals tend to be altruistic toward those with whom they share a lot of genes." These misunderstandings don't just crop up occasionally; they are repeated in many writings, including undergraduate psychology textbooks—most of them in the field of social psychology, within sections describing evolutionary approaches to altruism. As with the earlier sociobiological forays into the cross-cultural data, typical approaches are not able to find explanatory fit with the findings of ethnographers insofar that human kinship patterns are not necessarily built upon blood-ties. However, as Hamilton's later refinements of his theory make clear, it does not simply predict that genetically related individuals will inevitably recognise and engage in positive social behaviours with genetic relatives: rather, indirect context-based mechanisms may have evolved, which in historical environments have met the inclusive fitness criterion. Consideration of the demographics of the typical evolutionary environment of any species is crucial to understanding the evolution of social behaviours. As Hamilton himself put it, "Altruistic or selfish acts are only possible when a suitable
|
{
"page_id": 66996,
"source": null,
"title": "Kin selection"
}
|
social object is available. In this sense behaviours are conditional from the start". Under this perspective, and noting the necessity of a reliable context of interaction being available, the data on how altruism is mediated in social mammals is readily made sense of. In social mammals, primates and humans, altruistic acts that meet the kin selection criterion are typically mediated by circumstantial cues such as shared developmental environment, familiarity and social bonding. That is, it is the context that mediates the development of the bonding process and the expression of the altruistic behaviours, not genetic relatedness as such. This interpretation is compatible with the cross-cultural ethnographic data and has been called nurture kinship. == In plants == === Observations === Though originally thought unique to the animal kingdom, evidence of kin selection has been identified in the plant kingdom. Competition for resources between developing zygotes in plant ovaries increases when seeds had been pollinated with male gametes from different plants. How developing zygotes differentiate between full siblings and half-siblings in the ovary is undetermined, but genetic interactions are thought to play a role. Nonetheless, competition between zygotes in the ovary is detrimental to the reproductive success of the (female) plant, and fewer zygotes mature into seeds. As such, the reproductive traits and behaviors of plants suggests the evolution of behaviors and characteristics that increase the genetic relatedness of fertilized eggs in the plant ovary, thereby fostering kin selection and cooperation among the seeds as they develop. These traits differ among plant species. Some species have evolved to have fewer ovules per ovary, commonly one ovule per ovary, thereby decreasing the chance of developing multiple, differently fathered seeds within the same ovary. Multi-ovulated plants have developed mechanisms that increase the chances of all ovules within the ovary being fathered by the
|
{
"page_id": 66996,
"source": null,
"title": "Kin selection"
}
|
same parent. Such mechanisms include dispersal of pollen in aggregated packets and closure of the stigmatic lobes after pollen is introduced. The aggregated pollen packet releases pollen gametes in the ovary, thereby increasing likelihood that all ovules are fertilized by pollen from the same parent. Likewise, the closure of the ovary pore prevents entry of new pollen. Other multi-ovulated plants have evolved mechanisms that mimic the evolutionary adaption of single-ovulated ovaries; the ovules are fertilized by pollen from different individuals, but the mother ovary then selectively aborts fertilized ovules, either at the zygotic or embryonic stage. After seeds are dispersed, kin recognition and cooperation affects root formation in developing plants. Studies have found that the total root mass developed by Ipomoea hederacea (morning glory shrubs) grown next to kin is significantly smaller than those grown next to non-kin; shrubs grown next to kin thus allocate less energy and resources to growing the larger root systems needed for competitive growth. When seedlings were grown in individual pots placed next to kin or non-kin relatives, no difference in root growth was observed. This indicates that kin recognition occurs via signals received by the roots. Further, groups of I. hederacea plants are more varied in height when grown with kin than when grown with non-kin. The evolutionary benefit provided by this was further investigated by researchers at the Université de Montpellier. They found that the alternating heights seen in kin-grouped crops allowed for optimal light availability to all plants in the group; shorter plants next to taller plants had access to more light than those surrounded by plants of similar height. The above examples illustrate the effect of kin selection in the equitable allocation of light, nutrients, and water. The evolutionary emergence of single-ovulated ovaries in plants has eliminated the need for a
|
{
"page_id": 66996,
"source": null,
"title": "Kin selection"
}
|
developing seed to compete for nutrients, thus increasing its chance of survival and germination. Likewise, the fathering of all ovules in multi-ovulated ovaries by one father, decreases the likelihood of competition between developing seeds, thereby also increasing the seeds' chances of survival and germination. The decreased root growth in plants grown with kin increases the amount of energy available for reproduction; plants grown with kin produced more seeds than those grown with non-kin. Similarly, the increase in light made available by alternating heights in groups of related plants is associated with higher fecundity. Kin selection has also been observed in plant responses to herbivory. In an experiment done by Richard Karban et al., leaves of potted Artemisia tridentata (sagebrushes) were clipped with scissors to simulate herbivory. The gaseous volatiles emitted by the clipped leaves were captured in a plastic bag. When these volatiles were transferred to leaves of a closely related sagebrush, the recipient experienced lower levels of herbivory than those that had been exposed to volatiles released by non-kin plants. Sagebrushes do not uniformly emit the same volatiles in response to herbivory: the chemical ratios and composition of emitted volatiles vary from one sagebrush to another. Closely related sagebrushes emit similar volatiles, and the similarities decrease as relatedness decreases. This suggests that the composition of volatile gasses plays a role in kin selection among plants. Volatiles from a distantly related plant are less likely to induce a protective response against herbivory in a neighboring plant, than volatiles from a closely related plant. This fosters kin selection, as the volatiles emitted by a plant will activate the herbivorous defense response in related plants only, thus increasing their chance of survival and reproduction. Kin selection may play a role in plant-pollinator interactions, especially because pollinator attraction is influenced not only by
|
{
"page_id": 66996,
"source": null,
"title": "Kin selection"
}
|
floral displays, but by the spatial arrangement of plants in a group, which is referred to as the "magnet effect". For example, in an experiment performed on Moricandia moricandioides, Torices et al. demonstrated that focal plants in the presence of kin show increased advertising effort (defined as total petal mass of plants in a group divided by the plant biomass) compared to those in the presence of non-kin, and that this effect is greater in larger groups. M. moricandioides is a good model organism for the study of plant-pollinator interactions because it relies on pollinators for reproduction, as it is self-incompatible. The study design for this experiment included planting establishing pots of M. moricandioides with zero, three or six neighbors (either unrelated or half-sib progeny of the same mother) and advertising effort was calculated after 26 days of flowering. The exact mechanism of kin recognition in M. moricandioides is unknown, but possible mechanisms include above-ground communication with volatile compounds, or below-ground communication with root exudates. === Mechanisms in plants === The ability to differentiate between kin and non-kin is not necessary for kin selection in many animals. However, because plants do not reliably germinate in close proximity to kin, it is thought that, within the plant kingdom, kin recognition is especially important for kin selection there, but the mechanism remains unknown. One proposed mechanism for kin recognition involves communication through roots, with secretion and reception of root exudates. This would require exudates to be actively secreted by roots of one plant, and detected by roots of neighboring plants. The root exudate allantoin produced by rice plants, Oryza sativa, has been documented to be in greater production when growing next to cultivars that are largely unrelated. High production levels of Allantoin correlated to up regulation of auxin and auxin transporters, resulting
|
{
"page_id": 66996,
"source": null,
"title": "Kin selection"
}
|
in increased lateral root development and directional growth of their roots towards non kin, maximizing competition. This is mainly not observed in Oryza Sativa when surrounded by kin, invoking altruistic behaviors to promote inclusive fitness. However the root receptors responsible for recognition of kin exudates, and the pathway induced by receptor activation, remain unknown. The mycorrhiza associated with roots might facilitate reception of exudates, but again the mechanism is unknown. Another possibility is communication through green leaf volatiles. Karban et al. studied kin recognition in sagebrushes, Artemisia tridentata. The volatile-donating sagebrushes were kept in individual pots, separate from the plants that received the volatiles, finding that plants responded to herbivore damage to a neighbour's leaves. This suggests that root signalling is not necessary to induce a protective response against herbivory in neighbouring kin plants. Karban et al. suggest that plants may be able to differentiate between kin and non-kin based on the composition of volatiles. Because only the recipient sagebrush's leaves were exposed the volatiles presumably activated a receptor protein in the plant's leaves. The identity of this receptor, and the signalling pathway triggered by its activation, both remain to be discovered. == Objections == The theory of kin selection has been criticised by W. J. Alonso (in 1998) and by Alonso and C. Schuck-Paim (in 2002). They argue that the behaviours which kin selection attempts to explain are not altruistic (in pure Darwinian terms) because: (1) they may directly favour the performer as an individual aiming to maximise its progeny (so the behaviours can be explained as ordinary individual selection); (2) these behaviours benefit the group (so they can be explained as group selection); or (3) they are by-products of a developmental system of many "individuals" performing different tasks (like a colony of bees, or the cells of multicellular
|
{
"page_id": 66996,
"source": null,
"title": "Kin selection"
}
|
organisms, which are the focus of selection). They also argue that the genes involved in sex ratio conflicts could be treated as "parasites" of (already established) social colonies, not as their "promoters", and, therefore the sex ratio in colonies would be irrelevant to the transition to eusociality. Those ideas were mostly ignored until they were put forward again in a series of controversial papers by E. O. Wilson, Bert Hölldobler, Martin Nowak and Corina Tarnita. Nowak, Tarnita and Wilson argued that Inclusive fitness theory is not a simplification over the standard approach. It is an alternative accounting method, but one that works only in a very limited domain. Whenever inclusive fitness does work, the results are identical to those of the standard approach. Inclusive fitness theory is an unnecessary detour, which does not provide additional insight or information. They, like Alonso and Schuck-Paim, argue for a multi-level selection model instead. This aroused a strong response, including a rebuttal published in Nature from over a hundred researchers. == See also == Darwinian anthropology Group selection Price equation The Selfish Gene Genomic imprinting Hamiltonian spite == Notes == == References ==
|
{
"page_id": 66996,
"source": null,
"title": "Kin selection"
}
|
A skin bridge is a penile skin adhesion. It most commonly occurs as a consequence of an improperly healed circumcision, being formed when the inner lining of the remaining foreskin attaches to another part of the penis (normally the glans) as the cut heals. While less common, skin bridges can also occur in uncircumcised men due to difficulty of cleaning, resulting in buildups of smegma underneath wide skin bridges, but this is typically a minor inconvenience and does not lead to further issues. However, in more severe cases, this condition can result in painful erections, sometimes requiring surgical correction. == References == == External links == Pictures of skin bridges
|
{
"page_id": 18154936,
"source": null,
"title": "Skin bridge"
}
|
In nuclear physics, the internal conversion coefficient describes the rate of internal conversion. The internal conversion coefficient may be empirically determined by the following formula: α = number of de-excitations via electron emission number of de-excitations via gamma-ray emission {\displaystyle \alpha ={\frac {\text{number of de-excitations via electron emission}}{\text{number of de-excitations via gamma-ray emission}}}} There is no valid formulation for an equivalent concept for E0 (electric monopole) nuclear transitions. There are theoretical calculations that can be used to derive internal conversion coefficients. Their accuracy is not generally under dispute, but since the quantum mechanical models they depend on only take into account electromagnetic interactions between the nucleus and electrons, there may be unforeseen effects. Internal conversion coefficients can be looked up from tables, but this is time-consuming. Computer programs have been developed (see the BrIcc Program) which present internal conversion coefficients quickly and easily. Theoretical calculations of interest are the Rösel[1], Hager-Seltzer[2], and the Band[3], superseded by the Band-Raman[4] calculation called BrIcc. The Hager-Seltzer calculations omit the M and higher-energy shells on the grounds (usually valid) that those orbitals have little electron density at the nucleus and can be neglected. To first approximation this assumption is valid, upon comparing several internal conversion coefficients for different isotopes for transitions of about 100 keV. The Band and Band-Raman calculations assume that the M shell may contribute to internal conversion to a non-negligible extent, and incorporates a general term (called "N+") which takes into account the small effect of any higher shells there may be, while the Rösel calculation works like the Band, but does not assume that all shells contribute and so generally terminates at the N shell. Additionally, the Band-Raman calculation can now consider ("frozen orbitals") or neglect ("no hole") the effect of the electron vacancy; the frozen-orbitals approximation is considered generally
|
{
"page_id": 2098622,
"source": null,
"title": "Internal conversion coefficient"
}
|
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