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https://en.wikipedia.org/wiki/Johann%20Deisenhofer
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Johann Deisenhofer (; born September 30, 1943) is a German biochemist who, along with Hartmut Michel and Robert Huber, received the Nobel Prize for Chemistry in 1988 for their determination of the first crystal structure of an integral membrane protein, a membrane-bound complex of proteins and co-factors that is essential to photosynthesis.
Early life and education
Born in Bavaria, Deisenhofer earned his doctorate from the Technical University of Munich for research work done at the Max Planck Institute of Biochemistry in Martinsried, West Germany, in 1974. He conducted research there until 1988, when he joined the scientific staff of the Howard Hughes Medical Institute and the faculty of the Department of Biochemistry at The University of Texas Southwestern Medical Center at Dallas.
Career
Together with Michel and Huber, Deisenhofer determined the three-dimensional structure of a protein complex found in certain photosynthetic bacteria. This membrane protein complex, called a photosynthetic reaction center, was known to play a crucial role in initiating a simple type of photosynthesis. Between 1982 and 1985, the three scientists used X-ray crystallography to determine the exact arrangement of the more than 10,000 atoms that make up the protein complex. Their research increased the general understanding of the mechanisms of photosynthesis and revealed similarities between the photosynthetic processes of plants and bacteria.
Deisenhofer currently serves on the board of adv
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https://en.wikipedia.org/wiki/Receptor%20%28biochemistry%29
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In biochemistry and pharmacology, receptors are chemical structures, composed of protein, that receive and transduce signals that may be integrated into biological systems. These signals are typically chemical messengers which bind to a receptor and produce physiological responses such as change in the electrical activity of a cell. For example, GABA, an inhibitory neurotransmitter inhibits electrical activity of neurons by binding to GABA receptors. There are three main ways the action of the receptor can be classified: relay of signal, amplification, or integration. Relaying sends the signal onward, amplification increases the effect of a single ligand, and integration allows the signal to be incorporated into another biochemical pathway.
Receptor proteins can be classified by their location. Cell surface receptors also known as transmembrane receptors, include ligand-gated ion channels, G protein-coupled receptors, and enzyme-linked hormone receptors. Intracellular receptors are those found inside the cell, and include cytoplasmic receptors and nuclear receptors. A molecule that binds to a receptor is called a ligand and can be a protein, peptide (short protein), or another small molecule, such as a neurotransmitter, hormone, pharmaceutical drug, toxin, calcium ion or parts of the outside of a virus or microbe. An endogenously produced substance that binds to a particular receptor is referred to as its endogenous ligand. E.g. the endogenous ligand for the nicotinic acetyl
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https://en.wikipedia.org/wiki/Coulomb%20%28disambiguation%29
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The coulomb (symbol: C) is a unit of electric charge, named after French physicist Charles-Augustin de Coulomb.
Coulomb may also refer to:
People
Charles-Augustin de Coulomb (1736–1806), French physicist and namesake of the term coulomb
Coulomb's law, a law of physics first published by Coulomb in 1785
List of things named after Charles-Augustin de Coulomb
A family of French naval architects
François Coulomb the Elder (1654–1717)
François Coulomb the Younger (1691–1751)
Joseph-Marie-Blaise Coulomb, (1728–1803)
Adrien Coulomb (born 1990), French professional footballer
Jean Coulomb (1904–1999), French mathematician, geophysicist and scientific administrator
Places
Coulomb (crater), a lunar crater named after the French physicist
Saint-Coulomb, a French commune
Other
Coulomb (submarine), a Brumaire-class submarine of the French Navy
COULOMB, a high-energy physics experiment at CERN that ran from 1979 to 1995
Coulomb Affair, a theosophical conflict in the 1870s
Coulomb Technologies, former name of electric vehicle infrastructure company ChargePoint
Coulomb stress transfer, a concept used to study how earthquakes influence hazard on other faults.
See also
Coulombs (disambiguation)
Coulombe, a surname
Colombo (surname)
French-language surnames
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https://en.wikipedia.org/wiki/Joseph%20B.%20McCormick
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Joseph B. McCormick (Birth October 16, 1942) is an American epidemiologist, physician, and academic.
Early life and education
Joseph B. McCormick was born in Knoxville, Tennessee. His early years were spent on a farm in Indiana.
He attended Florida Southern College, graduating with degrees in chemistry and mathematics in 1964. He had a summer fellowship with the Institute of Nutrition of Central America and Panama, Guatemala. in 1969.
McCormick received a Master of Science from the Harvard School of Public Health in 1970. He had a summer followship in Haiti at the Rural Health Clinc in 1971. He attended Duke University School of Medicine, graduating in 1971. His residency and internship was at the Children's Hospital of Philadelphia under Dr. C. Everett Koop, from 1971 to 1973. He was a fellow in the Preventive Medicine Residency Program at the Centers for Disease Control and Prevention from 1975 and 1976.
Following graduation from college, McCormick went to Brussels, Belgium and attended the Alliance Francaise and the Free University for a year. He learned the French language to enable him to teach sciences and mathematics in a secondary school in Kinshasa, Congo.
Career
While living in the Congo, McCormick worked in a local hospital and developed an interest in medicine,specifically tropical diseases. In 1974, following his residency training, he was appointed an Epidemic Intelligence Service Officer at the Centers for Disease Control and Prevention (CDC). He was the
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https://en.wikipedia.org/wiki/Timothy%20Sprigge
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Timothy Lauro Squire Sprigge (14 January 1932 – 11 July 2007), usually cited as T. L. S. Sprigge, was a British idealist philosopher who spent the latter portion of his career at the University of Edinburgh, where he was Professor of Logic and Metaphysics, and latterly an Emeritus Fellow.
Biography
Sprigge was educated at the Dragon School, Oxford, and Bryanston School in Dorset. He studied English at Gonville and Caius College, Cambridge (1952–1955), then switched to philosophy, completing his PhD under A. J. Ayer. He taught philosophy at University College, London and Sussex University before becoming Regius Professor of Logic and Metaphysics at the University of Edinburgh.
Long concerned with the nature of experience and the relationship between mind and reality, Sprigge was the philosopher who first posed the question made famous by Thomas Nagel: "What is it like to be a bat?" Throughout his career he argued that physicalism or materialism is not only false, but has contributed to a distortion of our moral sense. The failure to respect the rights of human beings and non-human animals is therefore largely a metaphysical error of failing to grasp the true reality of the first person, subjective perspective of consciousness, or sentience. The practice of vivisection, which gained wide acceptance with Descartes's view of animals as machines, would be an example of this failure. He was an advocate of animal rights and defended an environmental ethic.
The author of The V
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https://en.wikipedia.org/wiki/Action%20at%20a%20distance
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In physics, action at a distance is the concept that an object's motion can be affected by another object without being physically contact (as in mechanical contact) by the other object. That is, it is the non-local interaction of objects that are separated in space. Coulomb's law and Newton's law of universal gravitation are based on action at a distance.
Historically, action at a distance was the earliest scientific model for gravity and electricity and it continues to be useful in many practical cases. In the 19th and 20th centuries, field models arose to explain these phenomena with more precision. The discovery of electrons and of special relativity lead to new action at a distance models providing alternative to field theories.
Categories of action
In the study of mechanics, action at a distance is one of three fundamental actions on matter that cause motion. The other two are direct impact (elastic or inelastic collisions) and actions in a continuous medium as in fluid mechanics or solid mechanics.
Historically, physical explanations for particular phenomena have moved between these three categories over time as new models were developed.
Action at a distance and actions in a continuous medium may be easily distinguished when the medium dynamics are visible, like waves in water or in an elastic solid. In the case of electricity or gravity, there is no medium required. In the nineteenth century, criteria like the effect of actions on intervening matter, the observa
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https://en.wikipedia.org/wiki/BGM
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BGM can refer to:
Locations
Boddington Gold Mine, a gold mine in Western Australia.
Mathematics
Bayesian Graphical Model, a form of probability model.
Brace Gatarek Musiela LIBOR market model: a finance model, also called BGM in reference to some of its inventors
Medicine
Blood glucose monitoring, or the device used to monitor blood glucose levels
Music
Background music
BGM (album), 1981 album by Yellow Magic Orchestra
Bonnier Gazell Music
BGM (song), track on 2019 Wale album Wow... That's Crazy
Blackpool Grime Media, a controversial grime channel
Transport
Bellingham railway station serving London, England (National Rail station code: BGM)
Greater Binghamton Airport serving Binghamton, New York (IATA Code: BGM)
Other
Black Guns Matter
an abbreviation for the former Bell Globemedia, now Bell Media
The US Military designation for a surface attack guided missile with multiple launch environments
BGM-71 TOW missile
BGM-109 Tomahawk missile
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https://en.wikipedia.org/wiki/1945%20in%20science
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The year 1945 in science and technology involved some significant events, listed below.
Biology
Salvador Edward Luria and Alfred Day Hershey independently recognize that viruses undergo mutations.
Chemistry
A team at Oak Ridge National Laboratory led by Charles Coryell discovers chemical element 61, the only one still missing between 1 and 96 on the periodic table, which they will name promethium. Found by analysis of fission products of irradiated uranium fuel, its discovery is not made public until 1947.
Dorothy Hodgkin and C. H. (Harry) Carlisle publish the first three-dimensional molecular structure of a steroid, cholesteryl iodide. In January, Hodgkin also discovers the structure of penicillin, not published until 1949.
A team at American Cyanamid's Lederle Laboratories, Pearl River, New York, led by Yellapragada Subbarow, obtain folic acid in a pure crystalline form.
Computer science
June 30 – Distribution of John von Neumann's First Draft of a Report on the EDVAC, containing the first published description of the logical design of a computer with stored-program and instruction data stored in the same address space within the memory (von Neumann architecture).
July – Publication of Vannevar Bush's article "As We May Think" proposing a proto-hypertext collective memory machine which he calls 'memex'.
November – Assembly of the world's first general purpose electronic computer, the Electronic Numerical Integrator Analyzer and Computer (ENIAC), is completed in th
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https://en.wikipedia.org/wiki/1946%20in%20science
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The year 1946 in science and technology involved some significant events, listed below.
Astronomy
January 10 – The United States Army Signal Corps' Project Diana bounces radar waves off the Moon.
Reginald Aldworth Daly of Harvard University first proposes a giant impact hypothesis to account for formation of the Moon.
Biology
November 10 – Peter Scott opens the Slimbridge Wetland Reserve in England.
December 2 – The International Convention for the Regulation of Whaling is signed in Washington, D.C. to "provide for the proper conservation of whale stocks and thus make possible the orderly development of the whaling industry" through establishment of the International Whaling Commission.
Karl von Frisch publishes "Die Tänze der Bienen" ("The dances of the bees").
Edmund Jaeger discovers and later documents, in The Condor, a state of extended torpor, approaching hibernation, in a bird, the common poorwill.
Cartography
The Chamberlin trimetric projection is developed by Wellman Chamberlin for the National Geographic Society.
Computer science
February 14–15 – ENIAC, the first non-classified all-electronic Turing complete computer, built under the direction of J. Presper Eckert and John Mauchly, is announced and dedicated at the University of Pennsylvania's Moore School of Electrical Engineering. It is programmable by plugboard and uses conditional branching.
December 11 – Frederic Calland Williams receives a patent for a random-access memory device.
Earth sciences
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https://en.wikipedia.org/wiki/Dirichlet%20problem
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In mathematics, a Dirichlet problem is the problem of finding a function which solves a specified partial differential equation (PDE) in the interior of a given region that takes prescribed values on the boundary of the region.
The Dirichlet problem can be solved for many PDEs, although originally it was posed for Laplace's equation. In that case the problem can be stated as follows:
Given a function f that has values everywhere on the boundary of a region in Rn, is there a unique continuous function u twice continuously differentiable in the interior and continuous on the boundary, such that u is harmonic in the interior and u = f on the boundary?
This requirement is called the Dirichlet boundary condition. The main issue is to prove the existence of a solution; uniqueness can be proven using the maximum principle.
History
The Dirichlet problem goes back to George Green, who studied the problem on general domains with general boundary conditions in his Essay on the Application of Mathematical Analysis to the Theories of Electricity and Magnetism, published in 1828. He reduced the problem into a problem of constructing what we now call Green's functions, and argued that Green's function exists for any domain. His methods were not rigorous by today's standards, but the ideas were highly influential in the subsequent developments. The next steps in the study of the Dirichlet's problem were taken by Karl Friedrich Gauss, William Thomson (Lord Kelvin) and Peter Gustav Leje
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https://en.wikipedia.org/wiki/Stratification%20%28mathematics%29
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Stratification has several usages in mathematics.
In mathematical logic
In mathematical logic, stratification is any consistent assignment of numbers to predicate symbols guaranteeing that a unique formal interpretation of a logical theory exists. Specifically, we say that a set of clauses of the form is stratified if and only if
there is a stratification assignment S that fulfills the following conditions:
If a predicate P is positively derived from a predicate Q (i.e., P is the head of a rule, and Q occurs positively in the body of the same rule), then the stratification number of P must be greater than or equal to the stratification number of Q, in short .
If a predicate P is derived from a negated predicate Q (i.e., P is the head of a rule, and Q occurs negatively in the body of the same rule), then the stratification number of P must be greater than the stratification number of Q, in short .
The notion of stratified negation leads to a very effective operational semantics for stratified programs in terms of the stratified least fixpoint, that is obtained by iteratively applying the fixpoint operator to each stratum of the program, from the lowest one up.
Stratification is not only useful for guaranteeing unique interpretation of Horn clause
theories.
In a specific set theory
In New Foundations (NF) and related set theories, a formula in the language of first-order logic with equality and membership is said to be
stratified if and only if there is a function
wh
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https://en.wikipedia.org/wiki/Better%20Living%20Through%20Chemistry%20%28album%29
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Better Living Through Chemistry is the debut studio album by English electronic music producer Fatboy Slim. It was released on 23 September 1996 in the United Kingdom by Skint Records and in the United States by Astralwerks. It was Fatboy Slim's first work to chart outside of the UK, with the single "Going Out of My Head" notably charting in the US, and was certified gold by the BPI.
Background
Skint Records founder Damian Harris has described the album as having been "more of a compilation than an album", as some of the tracks had been recorded some time before its release, due to Norman Cook's other musical projects. Three songs from the album were previously released in Skint's first volume of their Brassic Beats compilation album series, which is advertised in the album's booklet.
The album's cover features an image of a 3.5-inch floppy disk, paying homage to the cover of New Order's "Blue Monday" single, which featured a 5.25-inch disk. The album's title is a variation of a DuPont advertising slogan, "Better Things for Better Living...Through Chemistry".
Critical reception
The album received generally positive reviews from critics. A 1997 review from Rolling Stone claimed the album to be "of the most fun, shamelessly genre-hopping dance albums of the year". AllMusic rated it four stars out of five, recommending the album to "those who can't get enough of the popular technoid-sampled alternative dance style of the late '90s".
Legacy
The album was included in the boo
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https://en.wikipedia.org/wiki/Dragline%20excavator
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A dragline excavator is a piece of heavy equipment used in civil engineering and surface mining.
Draglines fall into two broad categories: those that are based on standard, lifting cranes, and the heavy units which have to be built on-site. Most crawler cranes, with an added winch drum on the front, can act as a dragline. These units (like other cranes) are designed to be dismantled and transported over the road on flatbed trailers. Draglines used in civil engineering are almost always of this smaller, crane type. These are used for road, port construction, pond and canal dredging, and as pile driving rigs. These types are built by crane manufacturers such as Link-Belt and Hyster.
The much larger type which is built on site is commonly used in strip-mining operations to remove overburden above coal and more recently for oil sands mining. The largest heavy draglines are among the largest mobile land machines ever built. The smallest and most common of the heavy type weigh around 8,000 tons while the largest built weighed around 13,000 tons.
A dragline bucket system consists of a large bucket which is suspended from a boom (a large truss-like structure) with wire ropes. The bucket is maneuvered by means of a number of ropes and chains. The hoist rope, powered by large diesel or electric motors, supports the bucket and hoist-coupler assembly from the boom. The dragrope is used to draw the bucket assembly horizontally. By skillful maneuver of the hoist and the dragropes the b
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https://en.wikipedia.org/wiki/Ferranti%20Mark%201
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The Ferranti Mark 1, also known as the Manchester Electronic Computer in its sales literature, and thus sometimes called the Manchester Ferranti, was produced by British electrical engineering firm Ferranti Ltd. It was the world's first commercially available electronic general-purpose stored program digital computer.
Although preceded as a commercial digital computer by the BINAC and the Z4, the Z4 was electromechanical and lacked software programmability, while BINAC never operated successfully after delivery
The Ferranti Mark 1 was "the tidied up and commercialised version of the Manchester Mark I". The first machine was delivered to the Victoria University of Manchester in February 1951 (publicly demonstrated in July) ahead of the UNIVAC I which was delivered to the United States Census Bureau in late December 1952, having been sold on 31 March 1951.
History and specifications
Based on the Manchester Mark 1, which was designed at the University of Manchester by Freddie Williams and Tom Kilburn, the machine was built by Ferranti of the United Kingdom. The main improvements over it were in the size of the primary and secondary storage, a faster multiplier, and additional instructions.
The Mark 1 used a 20-bit word stored as a single line of dots of electric charges settled on the surface of a Williams tube display, each cathodic tube storing 64 lines of dots. Instructions were stored in a single word, while numbers were stored in two words. The main memory consisted o
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https://en.wikipedia.org/wiki/Lynn%20Abbey
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Marilyn Lorraine "Lynn" Abbey (born September 18, 1948) is an American fantasy author.
Background
Born in Peekskill, New York, Abbey was daughter of Ronald Lionel (an insurance manager) and Doris Lorraine (a homemaker; maiden name, De Wees). She attended the University of Rochester, where she began as an astrophysics major. She earned a A.B. (1969) and an M.A. (1971) in European history, but shifted to computer programming as a profession "when my advisor pointed out that, given the natural rise and fall of demographic curves, tenured university faculty positions were going to be as scarce as hen's teeth for the next twenty-five years and my education was turning into an expensive hobby. (He was right, too.)" She had married Ralph Dressler July 14, 1969; they were divorced October 31, 1972. During this period she also became a member of science fiction fandom.
Move to Michigan; accident and aftermath
In 1976, after a stint as a programmer for insurance companies, and work on the state task force involved in documenting the New York City bankruptcy crisis, she moved to Ann Arbor, Michigan. In January 1977, she was injured in an automobile accident while going to pick up Gordon R. Dickson, who was to be a Guest of Honor at that year's ConFusion. The guilt-ridden Dickson volunteered to assist her by reading and critiquing her work (she'd been writing since childhood). The manuscript he helped her with became Daughter of the Bright Moon.
Publication and marriage
Abbey began pu
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https://en.wikipedia.org/wiki/Complete%20partial%20order
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In mathematics, the phrase complete partial order is variously used to refer to at least three similar, but distinct, classes of partially ordered sets, characterized by particular completeness properties. Complete partial orders play a central role in theoretical computer science: in denotational semantics and domain theory.
Definitions
A complete partial order, abbreviated cpo, can refer to any of the following concepts depending on context.
A partially ordered set is a directed-complete partial order (dcpo) if each of its directed subsets has a supremum. A subset of a partial order is directed if it is non-empty and every pair of elements has an upper bound in the subset. In the literature, dcpos sometimes also appear under the label up-complete poset.
A partially ordered set is a pointed directed-complete partial order if it is a dcpo with a least element. They are sometimes abbreviated cppos.
A partially ordered set is a ω-complete partial order (ω-cpo) if it is a poset in which every ω-chain (x1 ≤ x2 ≤ x3 ≤ x4 ≤ ...) has a supremum that belongs to the poset. Every dcpo is an ω-cpo, since every ω-chain is a directed set, but the converse is not true. However, every ω-cpo with a basis is also a dcpo (with the same basis). An ω-cpo (dcpo) with a basis is also called a continuous ω-cpo (continuous dcpo).
Note that complete partial order is never used to mean a poset in which all subsets have suprema; the terminology complete lattice is used for this concept.
Re
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https://en.wikipedia.org/wiki/DCPO
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DCPO or Dcpo may refer to:
Dame Commander of the Pontifical Order of Pius IX, female variant of a class in one of the orders of knighthood of the Holy See
Directed complete partial order, in mathematics a special class of partially ordered sets, characterized by particular completeness properties
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https://en.wikipedia.org/wiki/Bell%20polynomials
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In combinatorial mathematics, the Bell polynomials, named in honor of Eric Temple Bell, are used in the study of set partitions. They are related to Stirling and Bell numbers. They also occur in many applications, such as in the Faà di Bruno's formula.
Definitions
Exponential Bell polynomials
The partial or incomplete exponential Bell polynomials are a triangular array of polynomials given by
where the sum is taken over all sequences j1, j2, j3, ..., jn−k+1 of non-negative integers such that these two conditions are satisfied:
The sum
is called the nth complete exponential Bell polynomial.
Ordinary Bell polynomials
Likewise, the partial ordinary Bell polynomial is defined by
where the sum runs over all sequences j1, j2, j3, ..., jn−k+1 of non-negative integers such that
The ordinary Bell polynomials can be expressed in the terms of exponential Bell polynomials:
In general, Bell polynomial refers to the exponential Bell polynomial, unless otherwise explicitly stated.
Combinatorial meaning
The exponential Bell polynomial encodes the information related to the ways a set can be partitioned. For example, if we consider a set {A, B, C}, it can be partitioned into two non-empty, non-overlapping subsets, which are also referred to as parts or blocks, in 3 different ways:
{{A}, {B, C}}
{{B}, {A, C}}
{{C}, {B, A}}
Thus, we can encode the information regarding these partitions as
Here, the subscripts of B3,2 tell us that we are considering the partitioning of a set wit
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https://en.wikipedia.org/wiki/Michel%20Mayor
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Michel Gustave Édouard Mayor (; born 12 January 1942) is a Swiss astrophysicist and professor emeritus at the University of Geneva's Department of Astronomy. He formally retired in 2007, but remains active as a researcher at the Observatory of Geneva. He is co-laureate of the 2019 Nobel Prize in Physics along with Jim Peebles and Didier Queloz, and the winner of the 2010 Viktor Ambartsumian International Prize and the 2015 Kyoto Prize.
Together with Didier Queloz in 1995, he discovered , the first extrasolar planet orbiting a sun-like star, 51 Pegasi. For this achievement, they were awarded the 2019 Nobel Prize in Physics "for the discovery of an exoplanet orbiting a solar-type star" resulting in "contributions to our understanding of the evolution of the universe and Earth’s place in the cosmos".
Related to the discovery, Mayor noted that humans will never migrate to such exoplanets since they are "much, much too far away ... [and would take] hundreds of millions of days using the means we have available today". However, due to discoveries by Mayor, searching for extraterrestrial communications from exoplanets may now be a more practical consideration than thought earlier.
Mayor holds MS in Physics from the University of Lausanne (1966) and PhD in Astronomy from the Geneva Observatory (1971). He was a researcher at the Institute of Astronomy at the University of Cambridge in 1971. Subsequently, he spent sabbatical semesters at the European Southern Observatory (ESO) in nor
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https://en.wikipedia.org/wiki/Generator%20%28computer%20programming%29
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In computer science, a generator is a routine that can be used to control the iteration behaviour of a loop. All generators are also iterators. A generator is very similar to a function that returns an array, in that a generator has parameters, can be called, and generates a sequence of values. However, instead of building an array containing all the values and returning them all at once, a generator yields the values one at a time, which requires less memory and allows the caller to get started processing the first few values immediately. In short, a generator looks like a function but behaves like an iterator.
Generators can be implemented in terms of more expressive control flow constructs, such as coroutines or first-class continuations. Generators, also known as semicoroutines, are a special case of (and weaker than) coroutines, in that they always yield control back to the caller (when passing a value back), rather than specifying a coroutine to jump to; see comparison of coroutines with generators.
Uses
Generators are usually invoked inside loops. The first time that a generator invocation is reached in a loop, an iterator object is created that encapsulates the state of the generator routine at its beginning, with arguments bound to the corresponding parameters. The generator's body is then executed in the context of that iterator until a special yield action is encountered; at that time, the value provided with the yield action is used as the value of the invoc
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https://en.wikipedia.org/wiki/Refractory%20metals
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Refractory metals are a class of metals that are extraordinarily resistant to heat and wear. The expression is mostly used in the context of materials science, metallurgy and engineering. The definition of which elements belong to this group differs. The most common definition includes five elements: two of the fifth period (niobium and molybdenum) and three of the sixth period (tantalum, tungsten, and rhenium). They all share some properties, including a melting point above 2000 °C and high hardness at room temperature. They are chemically inert and have a relatively high density. Their high melting points make powder metallurgy the method of choice for fabricating components from these metals. Some of their applications include tools to work metals at high temperatures, wire filaments, casting molds, and chemical reaction vessels in corrosive environments. Partly due to the high melting point, refractory metals are stable against creep deformation to very high temperatures.
Definition
Most definitions of the term 'refractory metals' list the extraordinarily high melting point as a key requirement for inclusion. By one definition, a melting point above is necessary to qualify. The five elements niobium, molybdenum, tantalum, tungsten and rhenium are included in all definitions, while the wider definition, including all elements with a melting point above , includes nine additional elements: vanadium, chromium, zirconium, hafnium, ruthenium, rhodium, osmium and iridium.
Th
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https://en.wikipedia.org/wiki/Charles%20%C3%89douard%20Guillaume
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Charles Édouard Guillaume (15 February 1861, in Fleurier, Switzerland – 13 May 1938, in Sèvres, France) was a Swiss physicist who received the Nobel Prize in Physics in 1920 in recognition of the service he had rendered to precision measurements in physics by his discovery of anomalies in nickel steel alloys. In 1919, he gave the fifth Guthrie Lecture at the Institute of Physics in London with the title "The Anomaly of the Nickel-Steels".
Personal life
Charles-Edouard Guillaume was born in Fleurier, Switzerland, on 15 February 1861. Guillaume received his early education in Neuchâtel, and obtained a doctoral degree in Physics at ETH Zurich in 1883.
Guillaume was married in 1888 to A. M. Taufflieb, with whom he had three children.
He died on 13 May 1938 at Sèvres, aged 77.
Scientific career
Guillaume was head of the International Bureau of Weights and Measures. He also worked with Kristian Birkeland, serving at the Observatoire de Paris – Section de Meudon. He conducted several experiments with thermostatic measurements at the observatory.
Nickel–steel alloy
Guillaume is known for his discovery of nickel–steel alloys he named invar, elinvar and , also known as red platinum. Invar has a near-zero coefficient of thermal expansion, making it useful in constructing precision instruments whose dimensions need to remain constant in spite of varying temperature. Elinvar has a near-zero thermal coefficient of the modulus of elasticity, making it useful in constructing instr
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https://en.wikipedia.org/wiki/Manne%20Siegbahn
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Karl Manne Georg Siegbahn FRS(For) HFRSE (3 December 1886 – 26 September 1978) was a Swedish physicist who was awarded the Nobel Prize in Physics in 1924 "for his discoveries and research in the field of X-ray spectroscopy".
Biography
Siegbahn was born in Örebro, Sweden, the son of Georg Siegbahn and his wife, Emma Zetterberg.
He graduated in Stockholm 1906 and began his studies at Lund University in the same year. During his education he was secretarial assistant to Johannes Rydberg. In 1908 he studied at the University of Göttingen. He obtained his doctorate (PhD) at the Lund University in 1911, his thesis was titled Magnetische Feldmessungen (magnetic field measurements). He became acting professor for Rydberg when his (Rydberg's) health was failing, and succeeded him as full professor in 1920. However, in 1922 he left Lund for a professorship at Uppsala University.
In 1937, Siegbahn was appointed Director of the Physics Department of the Nobel Institute of the Royal Swedish Academy of Sciences. In 1988 this was renamed the Manne Siegbahn Institute (MSI). The institute research groups have been reorganized since, but the name lives on in the Manne Siegbahn Laboratory hosted by Stockholm University.
X-ray spectroscopy
Manne Siegbahn began his studies of X-ray spectroscopy in 1914. Initially he used the same type of spectrometer as Henry Moseley had done for finding the relationship between the wavelength of some elements and their place at the periodic system. Shortly
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https://en.wikipedia.org/wiki/LBB
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LBB may stand for:
Lactobacillus delbrueckii subsp. bulgaricus, a bacterium used in the production of yogurt
Ladyzhenskaya–Babuška–Brezzi condition, in mathematics
Laura Bell Bundy, an actress and singer
Little brown bird or little brown bats, name given to an unidentified species
Little Black Book (disambiguation)
Lubbock Preston Smith International Airport, by IATA code
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https://en.wikipedia.org/wiki/Measurement%20in%20quantum%20mechanics
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In quantum physics, a measurement is the testing or manipulation of a physical system to yield a numerical result. A fundamental feature of quantum theory is that the predictions it makes are probabilistic. The procedure for finding a probability involves combining a quantum state, which mathematically describes a quantum system, with a mathematical representation of the measurement to be performed on that system. The formula for this calculation is known as the Born rule. For example, a quantum particle like an electron can be described by a quantum state that associates to each point in space a complex number called a probability amplitude. Applying the Born rule to these amplitudes gives the probabilities that the electron will be found in one region or another when an experiment is performed to locate it. This is the best the theory can do; it cannot say for certain where the electron will be found. The same quantum state can also be used to make a prediction of how the electron will be moving, if an experiment is performed to measure its momentum instead of its position. The uncertainty principle implies that, whatever the quantum state, the range of predictions for the electron's position and the range of predictions for its momentum cannot both be narrow. Some quantum states imply a near-certain prediction of the result of a position measurement, but the result of a momentum measurement will be highly unpredictable, and vice versa. Furthermore, the fact that nature vio
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https://en.wikipedia.org/wiki/Corps%20des%20mines
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The Corps des mines is the foremost technical Grand Corps of the French State (grands corps de l'Etat). It is composed of the state industrial engineers. The Corps is attached to the French Ministry of Economy and Finance. Its purpose is to entice French students in mathematics and physics to serve the government and train them for executive careers in France.
Members are educated at the École nationale supérieure des mines de Paris, also known as Mines ParisTech. Each year, the Corps recruits between 10 and 20 members. Most of them are alumni from École polytechnique, who are usually among the top ranked students, others come from École normale supérieure (ENS), Télécom Paris or regular graduates of the Mines ParisTech. Upon graduation, Corps des mines engineers hold executive positions in the French administration.
Corps des mines engineers tend to hold top executive positions in France's major industrial companies in the course of their career.
Being admitted to the Corps des mines program is considered a significant fast-track for executive careers in France.
Missions
Corps des Mines engineers contribute to the conception, implementation and evaluation of public policies in the fields of:
industry and economy
energy and natural resources
information and communication technologies
environment sustainability, industrial safety and public health
research, innovation and new technologies
land use planning and transportation
standardization and metrology
banking, insuran
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https://en.wikipedia.org/wiki/Hilbert%20transform
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In mathematics and signal processing, the Hilbert transform is a specific singular integral that takes a function, of a real variable and produces another function of a real variable . The Hilbert transform is given by the Cauchy principal value of the convolution with the function (see ). The Hilbert transform has a particularly simple representation in the frequency domain: It imparts a phase shift of ±90° (/2 radians) to every frequency component of a function, the sign of the shift depending on the sign of the frequency (see ). The Hilbert transform is important in signal processing, where it is a component of the analytic representation of a real-valued signal . The Hilbert transform was first introduced by David Hilbert in this setting, to solve a special case of the Riemann–Hilbert problem for analytic functions.
Definition
The Hilbert transform of can be thought of as the convolution of with the function , known as the Cauchy kernel. Because 1/ is not integrable across , the integral defining the convolution does not always converge. Instead, the Hilbert transform is defined using the Cauchy principal value (denoted here by ). Explicitly, the Hilbert transform of a function (or signal) is given by
provided this integral exists as a principal value. This is precisely the convolution of with the tempered distribution . Alternatively, by changing variables, the principal-value integral can be written explicitly as
When the Hilbert transform is applied twic
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https://en.wikipedia.org/wiki/Circular%20motion
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In physics, circular motion is a movement of an object along the circumference of a circle or rotation along a circular arc. It can be uniform, with a constant rate of rotation and constant tangential speed, or non-uniform with a changing rate of rotation. The rotation around a fixed axis of a three-dimensional body involves the circular motion of its parts. The equations of motion describe the movement of the center of mass of a body, which remains at a constant distance from the axis of rotation. In circular motion, the distance between the body and a fixed point on its surface remains the same, i.e., the body is assumed rigid.
Examples of circular motion include: special satellite orbits around the Earth (circular orbits), a ceiling fan's blades rotating around a hub, a stone that is tied to a rope and is being swung in circles, a car turning through a curve in a race track, an electron moving perpendicular to a uniform magnetic field, and a gear turning inside a mechanism.
Since the object's velocity vector is constantly changing direction, the moving object is undergoing acceleration by a centripetal force in the direction of the center of rotation. Without this acceleration, the object would move in a straight line, according to Newton's laws of motion.
Uniform circular motion
In physics, uniform circular motion describes the motion of a body traversing a circular path at a constant speed. Since the body describes circular motion, its distance from the axis of rota
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https://en.wikipedia.org/wiki/Feed%20forward%20%28control%29
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A feed forward (sometimes written feedforward) is an element or pathway within a control system that passes a controlling signal from a source in its external environment to a load elsewhere in its external environment. This is often a command signal from an external operator.
In mechanical engineering, a feedforward control system is a control system that uses sensors to detect disturbances affecting the machine and then applies an additional input to minimize the effect of the disturbance. This requires a mathematical model of the machine so that the effect of disturbances can be properly predicted.
A control system which has only feed-forward behavior responds to its control signal in a pre-defined way without responding to the way the load reacts; it is in contrast with a system that also has feedback, which adjusts the input to take account of how it affects the load, and how the load itself may vary unpredictably; the load is considered to belong to the external environment of the system.
In a feed-forward system, the control variable adjustment is not error-based. Instead it is based on knowledge about the process in the form of a mathematical model of the process and knowledge about, or measurements of, the process disturbances.
Some prerequisites are needed for control scheme to be reliable by pure feed-forward without feedback: the external command or controlling signal must be available, and the effect of the output of the system on the load should be known (th
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https://en.wikipedia.org/wiki/Half-Life%202
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Half-Life 2 is a 2004 first-person shooter (FPS) game developed and published by Valve Corporation. It was initially published for Microsoft Windows through Valve’s digital distribution service Steam. Like the original Half-Life (1998), Half-Life 2 combines shooting, puzzles, and storytelling, and adds features such as vehicles and physics-based gameplay. The player controls Gordon Freeman as he joins a resistance movement to liberate Earth from the control of the Combine, a multidimensional alien empire.
Half-Life 2 was created using Valve's Source game engine, which was developed simultaneously. Development lasted five years and cost US$40million. Valve's president, Gabe Newell, set his team the goal of redefining the FPS genre. They integrated Havok physics into the game engine, which simulates real-world physics, to reinforce the player's sense of presence and create new gameplay, and developed the characterization, with more detailed character models and animations.
Valve announced Half-Life 2 at E3 2003, with a release date for September of that year. A delay of fourteen months caused Valve to be criticized. A year before its release, an unfinished version was stolen by a hacker and published online, which damaged the development team’s morale and slowed their work.
Half-Life 2 was released on Steam on November 16, 2004, and received universal acclaim. It won 39 Game of the Year awards and has been cited as one of the best games ever made. It was ported to Xbox, X
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https://en.wikipedia.org/wiki/Cheminformatics
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Cheminformatics (also known as chemoinformatics) refers to the use of physical chemistry theory with computer and information science techniques—so called "in silico" techniques—in application to a range of descriptive and prescriptive problems in the field of chemistry, including in its applications to biology and related molecular fields. Such in silico techniques are used, for example, by pharmaceutical companies and in academic settings to aid and inform the process of drug discovery, for instance in the design of well-defined combinatorial libraries of synthetic compounds, or to assist in structure-based drug design. The methods can also be used in chemical and allied industries, and such fields as environmental science and pharmacology, where chemical processes are involved or studied.
History
Cheminformatics has been an active field in various guises since the 1970s and earlier, with activity in academic departments and commercial pharmaceutical research and development departments. The term chemoinformatics was defined in its application to drug discovery by F.K. Brown in 1998:Chemoinformatics is the mixing of those information resources to transform data into information and information into knowledge for the intended purpose of making better decisions faster in the area of drug lead identification and optimization. Since then, both terms, cheminformatics and chemoinformatics, have been used, although, lexicographically, cheminformatics appears to be more frequentl
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https://en.wikipedia.org/wiki/Pierre-Gilles%20de%20Gennes
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Pierre-Gilles de Gennes (; 24 October 1932 – 18 May 2007) was a French physicist and the Nobel Prize laureate in physics in 1991.
Education and early life
He was born in Paris, France, and was home-schooled to the age of 12. By the age of 13, he had adopted adult reading habits and was visiting museums.
Later, de Gennes studied at the École Normale Supérieure. After leaving the École in 1955, he became a research engineer at the Saclay center of the Commissariat à l'Énergie Atomique, working mainly on neutron scattering and magnetism, with advice from Anatole Abragam and Jacques Friedel. He defended his Ph.D. in 1957 at the University of Paris.
Career and research
In 1959, he was a postdoctoral research visitor with Charles Kittel at the University of California, Berkeley, and then spent 27 months in the French Navy. In 1961, he was assistant professor in Orsay and soon started the Orsay group on superconductors. In 1968, he switched to studying liquid crystals.
In 1971, he became professor at the Collège de France, and participated in STRASACOL (a joint action of Strasbourg, Saclay and Collège de France) on polymer physics. From 1980 on, he became interested in interfacial problems: the dynamics of wetting and adhesion.
He worked on granular materials and on the nature of memory objects in the brain.
Awards and honours
Awarded the Fernand Holweck Medal and Prize in 1968.
He was awarded the Harvey Prize, Lorentz Medal and Wolf Prize in 1988 and 1990. In 1991, he receive
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https://en.wikipedia.org/wiki/Scientific%20visualization
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Scientific visualization (also spelled scientific visualisation) is an interdisciplinary branch of science concerned with the visualization of scientific phenomena. It is also considered a subset of computer graphics, a branch of computer science. The purpose of scientific visualization is to graphically illustrate scientific data to enable scientists to understand, illustrate, and glean insight from their data. Research into how people read and misread various types of visualizations is helping to determine what types and features of visualizations are most understandable and effective in conveying information.
History
One of the earliest examples of three-dimensional scientific visualisation was Maxwell's thermodynamic surface, sculpted in clay in 1874 by James Clerk Maxwell. This prefigured modern scientific visualization techniques that use computer graphics.
Notable early two-dimensional examples include the flow map of Napoleon's March on Moscow produced by Charles Joseph Minard in 1869; the "coxcombs" used by Florence Nightingale in 1857 as part of a campaign to improve sanitary conditions in the British army; and the dot map used by John Snow in 1855 to visualise the Broad Street cholera outbreak.
Data visualization methods
Criteria for classifications:
dimension of the data
method
textura based methods
geometry-based approaches such as arrow plots, streamlines, pathlines, timelines, streaklines, particle tracing, surface particles, stream arrows, stream tub
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https://en.wikipedia.org/wiki/Parametric%20equation
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In mathematics, a parametric equation defines a group of quantities as functions of one or more independent variables called parameters. Parametric equations are commonly used to express the coordinates of the points that make up a geometric object such as a curve or surface, called a parametric curve and parametric surface, respectively. In such cases, the equations are collectively called a parametric representation, or parametric system, or parameterization (alternatively spelled as parametrisation) of the object.
For example, the equations
form a parametric representation of the unit circle, where is the parameter: A point is on the unit circle if and only if there is a value of such that these two equations generate that point. Sometimes the parametric equations for the individual scalar output variables are combined into a single parametric equation in vectors:
Parametric representations are generally nonunique (see the "Examples in two dimensions" section below), so the same quantities may be expressed by a number of different parameterizations.
In addition to curves and surfaces, parametric equations can describe manifolds and algebraic varieties of higher dimension, with the number of parameters being equal to the dimension of the manifold or variety, and the number of equations being equal to the dimension of the space in which the manifold or variety is considered (for curves the dimension is one and one parameter is used, for surfaces dimension two and
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https://en.wikipedia.org/wiki/Discriminated%20union
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The term discriminated union may refer to:
Disjoint union in set theory.
Tagged union in computer science.
Mathematics disambiguation pages
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https://en.wikipedia.org/wiki/Tropism
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In biology, a tropism is a phenomenon indicating the growth or turning movement of an organism, usually a plant, in response to an environmental stimulus. In tropisms, this response is dependent on the direction of the stimulus (as opposed to nastic movements which are non-directional responses). Tropisms are usually named for the stimulus involved; for example, a phototropism is a movement to the light source, and an anemotropism is the response and adaptation of plants to the wind.
Tropisms occur in three sequential steps. First, there is a sensation to a stimulus. Next, signal transduction occurs. And finally, the directional growth response occurs.
Tropisms can be regarded by behaviorists as taxis (directional response) or kinesis (non-directional response).
The Cholodny–Went model, proposed in 1927, is an early model describing tropism in emerging shoots of monocotyledons, including the tendencies for the stalk to grow towards light (phototropism) and the roots to grow downward (gravitropism).
In both cases, the directional growth is considered to be due to asymmetrical distribution of auxin, a plant growth hormone.
The term "tropism" () is also used in unrelated contexts. Viruses and other pathogens affect what is called "host tropism", "tissue tropism", or "cell tropism"; in which case tropism refers to the way in which different viruses/pathogens have evolved to preferentially target specific host species, specific tissue, or specific cell types within those spe
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https://en.wikipedia.org/wiki/Finite%20field%20arithmetic
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In mathematics, finite field arithmetic is arithmetic in a finite field (a field containing a finite number of elements) contrary to arithmetic in a field with an infinite number of elements, like the field of rational numbers.
There are infinitely many different finite fields. Their number of elements is necessarily of the form pn where p is a prime number and n is a positive integer, and two finite fields of the same size are isomorphic. The prime p is called the characteristic of the field, and the positive integer n is called the dimension of the field over its prime field.
Finite fields are used in a variety of applications, including in classical coding theory in linear block codes such as BCH codes and Reed–Solomon error correction, in cryptography algorithms such as the Rijndael (AES) encryption algorithm, in tournament scheduling, and in the design of experiments.
Effective polynomial representation
The finite field with pn elements is denoted GF(pn) and is also called the Galois field of order pn, in honor of the founder of finite field theory, Évariste Galois. GF(p), where p is a prime number, is simply the ring of integers modulo p. That is, one can perform operations (addition, subtraction, multiplication) using the usual operation on integers, followed by reduction modulo p. For instance, in GF(5), is reduced to 2 modulo 5. Division is multiplication by the inverse modulo p, which may be computed using the extended Euclidean algorithm.
A particular case is
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https://en.wikipedia.org/wiki/Environmental%20Audio%20Extensions
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The Environmental Audio Extensions (or EAX) are a number of digital signal processing presets for audio, present in Creative Technology Sound Blaster sound cards starting with the Sound Blaster Live and the Creative NOMAD/Creative ZEN product lines. Due to the release of Windows Vista in 2007, which deprecated the DirectSound3D API that EAX was based on, Creative discouraged EAX implementation in favour of its OpenAL-based EFX equivalent – though at that point relatively few games used the API.
Technology
EAX is a library of extensions to Microsoft's DirectSound3D, itself an extension to DirectSound introduced with DirectX 3 in 1996 with the intention to standardize 3D audio for Microsoft Windows, adding environmental audio presets to DS3D's audio positioning. Ergo, the aim of EAX has nothing to do with 3D audio positioning, this is usually done by a sound library like DirectSound3D or OpenAL. Rather, EAX can be seen as a library of sound effects written and compiled to be executed on a DSP instead of the CPU, often called "hardware-accelerated".
The aim of EAX was to create more ambiance within video games by more accurately simulating a real-world audio environment. Up to EAX 2.0, the technology was based around the effects engine aboard the E-mu 10K1 on Creative Technology's and the Maestro2 on ESS1968 chipset driven sound cards. The hardware accelerated effects engine is an E-mu FX8010 DSP integrated into the Creative Technology's audio chip and was historically used t
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https://en.wikipedia.org/wiki/Time%20%28disambiguation%29
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Time is the continued sequence of existence and events, and a fundamental quantity of measuring systems.
Time or times may also refer to:
Temporal measurement
Time in physics, defined by its measurement
Time standard, civil time specification
Horology, study of the measurement of time
Chronometry, science of the measurement of time
Metre (music), the grouping of basic temporal units, called beats, into regular measures
Time signature, notational convention for the metre
Businesses
Time (bicycle company), a French bicycle manufacturer
Time Inc., an American publisher of periodicals
Time Computer Systems, a British brand of Granville Technology Group
TIME Hotels Management, a UAE hotel management company
Mathematics and its typography
Times, the operation used for multiplication in mathematics
Times symbol ×
Computing
Time (metadata), a representation term
time (Unix), a shell command on Unix and Unix-like operating systems
TIME (command), a shell command on DOS, OS/2 and Microsoft Windows operating systems
System time, a computer's reckoning of real-world time
Time Protocol, an Internet protocol
Film and television
Time (1999 film), a Tamil film
Time (2006 film), a South Korean film
Time (2007 film), a Malayalam film
Time (2020 film), an American film
Time (American TV series) or Timeless, a 2016–2018 NBC series
Time (2021 TV series), a 2021 BBC drama series
Time (British TV programme), a 2006 documentary programme
Vremya or Time, a Russian TV
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https://en.wikipedia.org/wiki/Durham%20tube
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Durham tubes are used in microbiology to detect production of gas by microorganisms. They are simply smaller test tubes inserted upside down in another test tube so they are freely movable. The culture media to be tested is then added to the larger tube and sterilized, which also eliminates the initial air gap produced when the tube is inserted upside down. The culture media typically contains a single substance to be tested with the organism, such as to determine whether an organism can ferment a particular carbohydrate. After inoculation and incubation, any gas that is produced will form a visible gas bubble inside the small tube. Litmus solution can also be added to the culture media to give a visual representation of pH changes that occur during the production of gas. The method was first reported in 1898 by British microbiologist Herbert Durham.
One limitation of the Durham tube is that it does not allow for precise determination of the type of gas that is produced within the inner tube, or measurements of the quantity of gas produced. However, Durham argued that quantitive measurements are of limited value because of the culture solution will absorb some of the gas in unknown, variable proportions. Additionally, using Durham tubes to provide evidence of fermentation may not be able to detect slow- or weakly-fermenting organisms when the resultant carbon dioxide diffuses back into the solution as quickly as it is formed, so a negative test using Durham tubes do
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https://en.wikipedia.org/wiki/Binary%20decision%20diagram
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In computer science, a binary decision diagram (BDD) or branching program is a data structure that is used to represent a Boolean function. On a more abstract level, BDDs can be considered as a compressed representation of sets or relations. Unlike other compressed representations, operations are performed directly on the compressed representation, i.e. without decompression.
Similar data structures include negation normal form (NNF), Zhegalkin polynomials, and propositional directed acyclic graphs (PDAG).
Definition
A Boolean function can be represented as a rooted, directed, acyclic graph, which consists of several (decision) nodes and two terminal nodes. The two terminal nodes are labeled 0 (FALSE) and 1 (TRUE). Each (decision) node is labeled by a Boolean variable and has two child nodes called low child and high child. The edge from node to a low (or high) child represents an assignment of the value FALSE (or TRUE, respectively) to variable . Such a BDD is called 'ordered' if different variables appear in the same order on all paths from the root. A BDD is said to be 'reduced' if the following two rules have been applied to its graph:
Merge any isomorphic subgraphs.
Eliminate any node whose two children are isomorphic.
In popular usage, the term BDD almost always refers to Reduced Ordered Binary Decision Diagram (ROBDD in the literature, used when the ordering and reduction aspects need to be emphasized). The advantage of an ROBDD is that it is canonical (unique
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https://en.wikipedia.org/wiki/PMSA
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PMSA may stand for:
Pakistan Maritime Security Agency (PMSA)
Port Said Medical Students' Association
Presbyterian and Methodist Schools Association
Primary Metropolitan Statistical Area (see: United States metropolitan area)
Project Management South Africa (PMSA)
Proviso Mathematics and Science Academy
Public Monuments and Sculpture Association
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https://en.wikipedia.org/wiki/CMSA
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CMSA may refer to:
Chain Makers' and Strikers' Association, a former British trade union
Chicago Math and Science Academy
China Manned Space Agency, the human spaceflight agency of China
China Maritime Safety Administration
Classical Mandolin Society of America
Colleges of Medicine of South Africa
Combinatorial Mathematics Society of Australasia
Commercial Mortgage Securities Association
Congressional Muslim Staffer Association
Consolidated Metropolitan Statistical Area
See also
Case management (disambiguation)
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https://en.wikipedia.org/wiki/Decision%20tree%20learning
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Decision tree learning is a supervised learning approach used in statistics, data mining and machine learning. In this formalism, a classification or regression decision tree is used as a predictive model to draw conclusions about a set of observations.
Tree models where the target variable can take a discrete set of values are called classification trees; in these tree structures, leaves represent class labels and branches represent conjunctions of features that lead to those class labels. Decision trees where the target variable can take continuous values (typically real numbers) are called regression trees. More generally, the concept of regression tree can be extended to any kind of object equipped with pairwise dissimilarities such as categorical sequences.
Decision trees are among the most popular machine learning algorithms given their intelligibility and simplicity.
In decision analysis, a decision tree can be used to visually and explicitly represent decisions and decision making. In data mining, a decision tree describes data (but the resulting classification tree can be an input for decision making).
General
Decision tree learning is a method commonly used in data mining. The goal is to create a model that predicts the value of a target variable based on several input variables.
A decision tree is a simple representation for classifying examples. For this section, assume that all of the input features have finite discrete domains, and there is a single target
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https://en.wikipedia.org/wiki/Association%20rule%20learning
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Association rule learning is a rule-based machine learning method for discovering interesting relations between variables in large databases. It is intended to identify strong rules discovered in databases using some measures of interestingness. In any given transaction with a variety of items, association rules are meant to discover the rules that determine how or why certain items are connected.
Based on the concept of strong rules, Rakesh Agrawal, Tomasz Imieliński and Arun Swami introduced association rules for discovering regularities between products in large-scale transaction data recorded by point-of-sale (POS) systems in supermarkets. For example, the rule found in the sales data of a supermarket would indicate that if a customer buys onions and potatoes together, they are likely to also buy hamburger meat. Such information can be used as the basis for decisions about marketing activities such as, e.g., promotional pricing or product placements.
In addition to the above example from market basket analysis, association rules are employed today in many application areas including Web usage mining, intrusion detection, continuous production, and bioinformatics. In contrast with sequence mining, association rule learning typically does not consider the order of items either within a transaction or across transactions.
The association rule algorithm itself consists of various parameters that can make it difficult for those without some expertise in data mining to exec
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https://en.wikipedia.org/wiki/Otu
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Otu or OTU may refer to:
Otu:
Otu, Iran, a village in Mazandaran Province, Iran
Otu, Siga, Japan
Otú Airport, an airport in the village of Otú and serving the town of Remedios, Colombia
OTU:
Ontario Tech University, a postsecondary institution in Ontario, Canada
Operational taxonomic unit, in biology
Operational Training Unit (Royal Air Force)
Optical channel Transport Unit, a layer of the Optical Transport Network
Oxygen toxicity unit, a measure of exposure to a toxic concentration of oxygen in breathing gas.
People with the name
Michael Otu (1925–2006), senior commander in the Ghana Air Force
See also
Otu Jeremi, a town in Ughelli South LGA of Delta State, Nigeria
Otu barrage, a masonry weir on the Ghaggar-Hakra river in Haryana state of India
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https://en.wikipedia.org/wiki/Relativistic%20wave%20equations
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In physics, specifically relativistic quantum mechanics (RQM) and its applications to particle physics, relativistic wave equations predict the behavior of particles at high energies and velocities comparable to the speed of light. In the context of quantum field theory (QFT), the equations determine the dynamics of quantum fields.
The solutions to the equations, universally denoted as or (Greek psi), are referred to as "wave functions" in the context of RQM, and "fields" in the context of QFT. The equations themselves are called "wave equations" or "field equations", because they have the mathematical form of a wave equation or are generated from a Lagrangian density and the field-theoretic Euler–Lagrange equations (see classical field theory for background).
In the Schrödinger picture, the wave function or field is the solution to the Schrödinger equation;
one of the postulates of quantum mechanics. All relativistic wave equations can be constructed by specifying various forms of the Hamiltonian operator Ĥ describing the quantum system. Alternatively, Feynman's path integral formulation uses a Lagrangian rather than a Hamiltonian operator.
More generally – the modern formalism behind relativistic wave equations is Lorentz group theory, wherein the spin of the particle has a correspondence with the representations of the Lorentz group.
History
Early 1920s: Classical and quantum mechanics
The failure of classical mechanics applied to molecular, atomic, and nuclear sys
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https://en.wikipedia.org/wiki/Frithjof%20Schuon
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Frithjof Schuon (, , ; 18 June 1907 – 5 May 1998) was a Swiss metaphysician of German descent, belonging to the Perennialist or Traditionalist School of thought. He was the author of more than twenty works in French on metaphysics, spirituality, religion, anthropology and art, which have been translated into English and many other languages. He was also a painter and a poet.
With René Guénon and Ananda Coomaraswamy, Schuon is recognized as one of the major 20th-century representatives of the philosophia perennis. Like them, he affirmed the reality of an absolute Principle – God – from which the universe emanates, and maintained that all divine revelations, despite their differences, possess a common essence: one and the same Truth. He also shared with them the certitude that man is potentially capable of supra-rational knowledge, and undertook a sustained critique of the modern mentality severed, according to him, from its traditional roots. Following Plato, Plotinus, Adi Shankara, Meister Eckhart, Ibn Arabī and other metaphysicians, Schuon sought to affirm the metaphysical unity between the Principle and its manifestation.
Initiated by Sheikh Ahmad al-Alawī into the Sufi Shādhilī order, he founded the Tarīqa Maryamiyya. His writings strongly emphasize the universality of metaphysical doctrine, along with the necessity of practising a religion; he also insists on the importance of the virtues and of beauty.
Schuon cultivated close relationships with a large number of pers
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https://en.wikipedia.org/wiki/Mass%20concentration%20%28astronomy%29
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In astronomy, astrophysics and geophysics, a mass concentration (or mascon) is a region of a planet's or moon's crust that contains a large positive gravity anomaly. In general, the word "mascon" can be used as a noun to refer to an excess distribution of mass on or beneath the surface of an astronomical body (compared to some suitable average), such as is found around Hawaii on Earth. However, this term is most often used to describe a geologic structure that has a positive gravitational anomaly associated with a feature (e.g. depressed basin) that might otherwise have been expected to have a negative anomaly, such as the "mascon basins" on the Moon.
Lunar and Martian mascons
The Moon is the most gravitationally "lumpy" major body known in the Solar System. Its largest mascons can cause a plumb bob to hang about a third of a degree off vertical, pointing toward the mascon, and increase the force of gravity by one-half percent.
Typical examples of mascon basins on the Moon are the Imbrium, Serenitatis, Crisium and Orientale impact basins, all of which exhibit significant topographic depressions and positive gravitational anomalies. Examples of mascon basins on Mars are the Argyre, Isidis, and Utopia basins. Theoretical considerations imply that a topographic low in isostatic equilibrium would exhibit a slight negative gravitational anomaly. Thus, the positive gravitational anomalies associated with these impact basins indicate that some form of positive density anomaly must
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https://en.wikipedia.org/wiki/Magnitude%20%28mathematics%29
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In mathematics, the magnitude or size of a mathematical object is a property which determines whether the object is larger or smaller than other objects of the same kind. More formally, an object's magnitude is the displayed result of an ordering (or ranking) of the class of objects to which it belongs.
In physics, magnitude can be defined as quantity or distance.
History
The Greeks distinguished between several types of magnitude, including:
Positive fractions
Line segments (ordered by length)
Plane figures (ordered by area)
Solids (ordered by volume)
Angles (ordered by angular magnitude)
They proved that the first two could not be the same, or even isomorphic systems of magnitude. They did not consider negative magnitudes to be meaningful, and magnitude is still primarily used in contexts in which zero is either the smallest size or less than all possible sizes.
Numbers
The magnitude of any number is usually called its absolute value or modulus, denoted by .
Real numbers
The absolute value of a real number r is defined by:
Absolute value may also be thought of as the number's distance from zero on the real number line. For example, the absolute value of both 70 and −70 is 70.
Complex numbers
A complex number z may be viewed as the position of a point P in a 2-dimensional space, called the complex plane. The absolute value (or modulus) of z may be thought of as the distance of P from the origin of that space. The formula for the absolute value of is si
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https://en.wikipedia.org/wiki/Banach%E2%80%93Alaoglu%20theorem
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In functional analysis and related branches of mathematics, the Banach–Alaoglu theorem (also known as Alaoglu's theorem) states that the closed unit ball of the dual space of a normed vector space is compact in the weak* topology.
A common proof identifies the unit ball with the weak-* topology as a closed subset of a product of compact sets with the product topology.
As a consequence of Tychonoff's theorem, this product, and hence the unit ball within, is compact.
This theorem has applications in physics when one describes the set of states of an algebra of observables, namely that any state can be written as a convex linear combination of so-called pure states.
History
According to Lawrence Narici and Edward Beckenstein, the Alaoglu theorem is a “very important result—maybe most important fact about the weak-* topology—[that] echos throughout functional analysis.”
In 1912, Helly proved that the unit ball of the continuous dual space of is countably weak-* compact.
In 1932, Stefan Banach proved that the closed unit ball in the continuous dual space of any separable normed space is sequentially weak-* compact (Banach only considered sequential compactness).
The proof for the general case was published in 1940 by the mathematician Leonidas Alaoglu.
According to Pietsch [2007], there are at least twelve mathematicians who can lay claim to this theorem or an important predecessor to it.
The Bourbaki–Alaoglu theorem is a generalization of the original theorem by Bour
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https://en.wikipedia.org/wiki/Compact%20operator
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In functional analysis, a branch of mathematics, a compact operator is a linear operator , where are normed vector spaces, with the property that maps bounded subsets of to relatively compact subsets of (subsets with compact closure in ). Such an operator is necessarily a bounded operator, and so continuous. Some authors require that are Banach, but the definition can be extended to more general spaces.
Any bounded operator that has finite rank is a compact operator; indeed, the class of compact operators is a natural generalization of the class of finite-rank operators in an infinite-dimensional setting. When is a Hilbert space, it is true that any compact operator is a limit of finite-rank operators, so that the class of compact operators can be defined alternatively as the closure of the set of finite-rank operators in the norm topology. Whether this was true in general for Banach spaces (the approximation property) was an unsolved question for many years; in 1973 Per Enflo gave a counter-example, building on work by Grothendieck and Banach.
The origin of the theory of compact operators is in the theory of integral equations, where integral operators supply concrete examples of such operators. A typical Fredholm integral equation gives rise to a compact operator K on function spaces; the compactness property is shown by equicontinuity. The method of approximation by finite-rank operators is basic in the numerical solution of such equations. The abstract idea of Fr
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https://en.wikipedia.org/wiki/Center%20frequency
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In electrical engineering and telecommunications, the center frequency of a filter or channel is a measure of a central frequency between the upper and lower cutoff frequencies. It is usually defined as either the arithmetic mean or the geometric mean of the lower cutoff frequency and the upper cutoff frequency of a band-pass system or a band-stop system.
Typically, the geometric mean is used in systems based on certain transformations of lowpass filter designs, where the frequency response is constructed to be symmetric on a logarithmic frequency scale. The geometric center frequency corresponds to a mapping of the DC response of the prototype lowpass filter, which is a resonant frequency sometimes equal to the peak frequency of such systems, for example as in a Butterworth filter.
The arithmetic definition is used in more general situations, such as in describing passband telecommunication systems, where filters are not necessarily symmetric but are treated on a linear frequency scale for applications such as frequency-division multiplexing.
References
External links
Calculations and comparisons between the geometric mean and the arithmetic mean
Electrical engineering
Telecommunication theory
Frequency-domain analysis
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https://en.wikipedia.org/wiki/Charles%20Thomson%20Rees%20Wilson
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Charles Thomson Rees Wilson, (14 February 1869 – 15 November 1959) was a Scottish physicist and meteorologist who won the Nobel Prize in Physics for his invention of the cloud chamber.
Education and early life
Wilson was born in the parish of Glencorse, Midlothian to Annie Clark Harper and John Wilson, a sheep farmer. After his father died in 1873, he moved with his family to Manchester. With financial support from his step-brother he studied biology at Owens College, now the University of Manchester, with the intent of becoming a doctor. In 1887, he graduated from the College with a BSc. He won a scholarship to attend Sidney Sussex College, Cambridge, where he became interested in physics and chemistry. In 1892 he received 1st class honours in both parts of the Natural Science Tripos.
Career
He became particularly interested in meteorology, and in 1893 he began to study clouds and their properties. Beginning in 1894, he worked for some time at the observatory on Ben Nevis, where he made observations of cloud formation. He was particularly fascinated by the appearance of glories. He then tried to reproduce this effect on a smaller scale at the Cavendish Laboratory in Cambridge, expanding humid air within a sealed container. He later experimented with the creation of cloud trails in his chamber by condensation onto ions generated by radioactivity. Several of his cloud chambers survive.
Wilson was made Fellow of Sidney Sussex College, and University Lecturer and Demonstrato
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https://en.wikipedia.org/wiki/William%20Alfred%20Fowler
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William Alfred Fowler ( ) was an American nuclear physicist, later astrophysicist, who, with Subrahmanyan Chandrasekhar, was awarded the 1983 Nobel Prize in Physics. He is known for his theoretical and experimental research into nuclear reactions within stars and the energy elements produced in the process and was one of the authors of the influential BFH paper.
Early life
On , Fowler was born in Pittsburgh. Fowler's parents were John MacLeod Fowler and Jennie Summers Watson. Fowler was the eldest of his siblings, Arthur and Nelda.
The family moved to Lima, Ohio, a steam railroad town, when Fowler was two years old. Growing up near the Pennsylvania Railroad yard influenced Fowler's interest in locomotives. In 1973, he travelled to the Soviet Union just to observe the steam engine that powered the Trans-Siberian Railway plying the nearly route that connects Khabarovsk and Moscow.
Education
In 1933, Fowler graduated from the Ohio State University, where he was a member of the Tau Kappa Epsilon fraternity. In 1936, Fowler received a Ph.D. in nuclear physics from the California Institute of Technology in Pasadena, California.
Career
In 1936, Fowler became a research fellow at Caltech. He was elected to the United States National Academy of Sciences in 1938. In 1939, Fowler became an assistant professor at Caltech.
Although an experimental nuclear physicist, Fowler's most famous paper was "Synthesis of the Elements in Stars", coauthored with Cambridge cosmologist Fred Hoyle
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https://en.wikipedia.org/wiki/James%20Alan%20Gardner
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James Alan Gardner (born January 10, 1955) is a Canadian science fiction author.
Raised in Simcoe and Bradford, Ontario, he earned bachelor's and master's degrees in applied mathematics from the University of Waterloo.
Gardner has published science fiction short stories in a range of periodicals, including The Magazine of Fantasy and Science Fiction and Amazing Stories. In 1989, his short story "The Children of Creche" was awarded the Grand Prize in the Writers of the Future contest. Two years later his story "Muffin Explains Teleology to the World at Large" won a Prix Aurora Award; another story, "Three Hearings on the Existence of Snakes in the Human Bloodstream," won an Aurora and was nominated for both the Nebula and Hugo Awards.
He has written a number of novels in a "League of Peoples" universe in which murderers are defined as "dangerous non-sentients" and are killed if they try to leave their solar system by aliens who are so advanced that they think of humans like humans think of bacteria. This precludes the possibility of interstellar wars.
He has also explored themes of gender in his novels, including Commitment Hour in which people change sex every year, and Vigilant in which group marriages are traditional.
Gardner is also an educator and technical writer. His book Learning UNIX is used as a textbook in some Canadian universities.
He lives in Waterloo, Ontario.
Bibliography
Lara Croft, Tomb Raider series
No. 3 Lara Croft and the Man of Bronze
League of
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https://en.wikipedia.org/wiki/Department%20of%20Plant%20Sciences%2C%20University%20of%20Cambridge
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The Department of Plant Sciences is a department of the University of Cambridge that conducts research and teaching in plant sciences. It was established in 1904, although the university has had a professor of botany since 1724.
Research
, the department pursues three strategic targets of research
Global food security
Synthetic biology and biotechnology
Climate science and ecosystem conservation
See also the Sainsbury Laboratory Cambridge University
Notable academic staff
Sir David Baulcombe, FRS, Regius Professor of Botany
Beverley Glover, Professor of Plant systematics and evolution, director of the Cambridge University Botanic Garden
Howard Griffiths, Professor of Plant Ecology
Julian Hibberd, Professor of Photosynthesis
Alison Smith, Professor of Plant Biochemistry and Head of Department
, the department also has 66 members of faculty and postdoctoral researchers, 100 graduate students, 19 Biotechnology and Biological Sciences Research Council (BBSRC) Doctoral Training Program (DTP) PhD students, 20 part II Tripos undergraduate students and 44 support staff.
History
The University of Cambridge has a long and distinguished history in Botany including work by John Ray and Stephen Hales in the 17th century and 18th century, Charles Darwin’s mentor John Stevens Henslow in the 19th century, and Frederick Blackman, Arthur Tansley and Harry Godwin in the 20th century.
Emeritus and alumni
More recently, the department has been home to:
John C. Gray, Emeritus Profe
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https://en.wikipedia.org/wiki/Half-cell
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In electrochemistry, a half-cell is a structure that contains a conductive electrode and a surrounding conductive electrolyte separated by a naturally occurring Helmholtz double layer. Chemical reactions within this layer momentarily pump electric charges between the electrode and the electrolyte, resulting in a potential difference between the electrode and the electrolyte. The typical anode reaction involves a metal atom in the electrode being dissolved and transported as a positive ion across the double layer, causing the electrolyte to acquire a net positive charge while the electrode acquires a net negative charge. The growing potential difference creates an intense electric field within the double layer, and the potential rises in value until the field halts the net charge-pumping reactions. This self-limiting action occurs almost instantly in an isolated half-cell; in applications two dissimilar half-cells are appropriately connected to constitute a Galvanic cell.
A standard half-cell consists of a metal electrode in a 1 molar (1 mol/L) aqueous solution of the metal's salt, at 298 kelvins (25 °C). The electrochemical series, which consists of standard electrode potentials and is closely related to the reactivity series, was generated by measuring the difference in potential between the metal half-cell in a circuit with a standard hydrogen half-cell, connected by a salt bridge.
The standard hydrogen half-cell:
2H+(aq) + 2e− → H2(g)
The half-cells of a Daniell cell:
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https://en.wikipedia.org/wiki/Arthur%20Scherbius
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Arthur Scherbius (30 October 1878 – 13 May 1929) was a German electrical engineer who invented the mechanical cipher Enigma machine. He patented the invention and later sold the machine under the brand name Enigma.
Scherbius offered unequalled opportunities and showed the importance of cryptography to both military and civil intelligence.
Biography
Early life and work
Scherbius was born in Frankfurt am Main, Germany. His father was a businessman.
He studied electrical engineering at the Technical University Munich and then went on to study at the Leibniz University Hannover, finishing in March 1903. The next year he completed a dissertation entitled "Proposal for the Construction of an Indirect Water Turbine Governor" and was awarded a doctorate in engineering (Dr.-Eng.).
Career
Scherbius subsequently worked for a number of electrical firms in Germany and Switzerland. In 1918 he founded the firm of Scherbius & Ritter. He made a number of inventions including asynchronous motors, electric pillows and ceramic heating parts. His research contributions led to his name being associated with the Scherbius principle for asynchronous motors.
Scherbius applied for a patent (filed 23 February 1918) for a cipher machine based on rotating wired wheels that is now known as a rotor machine.
The Enigma machine
His first design of the Enigma was called Model A and was about the size and shape of a cash register (50 kg). Then followed Model B and Model C, which was a portable device
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https://en.wikipedia.org/wiki/Boris%20Hagelin
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Boris Caesar Wilhelm Hagelin (2 July 1892 – 7 September 1983) was a Swedish businessman and inventor of encryption machines.
Biography
Born of Swedish parents in Adshikent, Russian Empire (now Azerbaijan), Hagelin attended Lundsberg boarding school and later studied mechanical engineering at the Royal Institute of Technology in Stockholm, graduating in 1914. He gained experience in engineering through work in Sweden and the United States.
His father Karl Wilhelm Hagelin worked for Nobel in Baku (part of the Russian Empire at the time), but the family returned to Sweden after the Russian revolution. Karl Wilhelm was an investor in Arvid Gerhard Damm's company Aktiebolaget Cryptograph, established to sell rotor machines built using Damm's 1919 patent. Boris Hagelin was placed in the firm to represent the family investment. In 1925, Hagelin took over the firm, later reorganising it as Aktiebolaget Cryptoteknik in 1932. His machines competed with Scherbius' Enigma machines, but sold rather better.
At the beginning of World War II, Hagelin moved from Sweden to Switzerland, all the way across Germany and through Berlin to Genoa, carrying the design documents for the company's latest machine, and re-established his company there. That design was small, cheap and moderately secure, and he convinced the US military to adopt it. Many tens of thousands of them were made, and Hagelin became quite wealthy as a result. After his company, Crypto AG, was secretly sold to foreign intellige
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https://en.wikipedia.org/wiki/Clifford%20Cocks
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Clifford Christopher Cocks (born 28 December 1950) is a British mathematician and cryptographer.
In 1973, while working at the United Kingdom Government Communications Headquarters (GCHQ), he invented a public-key cryptography algorithm equivalent to what would become (in 1977) the RSA algorithm.
The idea was classified information and his insight remained hidden for 24 years, although it was independently invented by Ronald Rivest, Adi Shamir, and Leonard Adleman in 1977. Public-key cryptography using prime factorisation is now part of nearly every Internet transaction.
Education
Cocks was educated at Manchester Grammar School and went on to study the Mathematical Tripos as an undergraduate at King's College, Cambridge. He continued as a PhD student at the University of Oxford, where he specialised in number theory under Bryan Birch, but left academia without finishing his doctorate.
Career
Non-secret encryption
Cocks left Oxford to join Communications-Electronics Security Group (CESG), an arm of GCHQ, in September 1973. Soon after, Nick Patterson told Cocks about James H. Ellis' non-secret encryption, an idea which had been published in 1969 but never successfully implemented. Several people had attempted creating the required one-way functions, but Cocks, with his background in number theory, decided to use prime factorization, and did not even write it down at the time. With this insight, he quickly developed what later became known as the RSA encryption algorithm.
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https://en.wikipedia.org/wiki/Scott%20Vanstone
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Scott A. Vanstone was a mathematician and cryptographer in the University of Waterloo Faculty of Mathematics. He was a member of the school's Centre for Applied Cryptographic Research, and was also a founder of the cybersecurity company Certicom. He received his PhD in 1974 at the University of Waterloo, and for about a decade worked principally in combinatorial design theory, finite geometry, and finite fields. In the 1980s he started working in cryptography. An early result of Vanstone (joint with Ian Blake, R. Fuji-Hara, and Ron Mullin) was an improved algorithm for computing discrete logarithms in binary fields, which inspired Don Coppersmith to develop his famous exp(n^{1/3+ε}) algorithm (where n is the degree of the field).
Vanstone was one of the first to see the commercial potential of Elliptic Curve Cryptography (ECC), and much of his subsequent work was devoted to developing ECC algorithms, protocols, and standards. In 1985 he co-founded Certicom, which later became the chief developer and promoter of ECC.
Vanstone authored or coauthored five widely used books and almost two hundred research articles, and he held several patents.
He was a Fellow of the Royal Society of Canada and a Fellow of the International Association for Cryptologic Research. In 2001 he won the RSA Award for Excellence in Mathematics, and in 2009 he received the Ontario Premier's Catalyst Award for Lifetime Achievement in Innovation.
He died on March 2, 2014, shortly after a cancer diagn
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https://en.wikipedia.org/wiki/David%20Kahn%20%28writer%29
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David Kahn (b. February 7, 1930) is an American historian, journalist, and writer. He has written extensively on the history of cryptography and military intelligence.
Kahn's first published book, The Codebreakers - The Story of Secret Writing (1967), has been widely considered to be a definitive account of the history of cryptography.
Biography
David Kahn was born in New York City to Florence Abraham Kahn, a glass manufacturer, and Jesse Kahn, a lawyer.
Kahn has said he traces his interest in cryptography to reading Fletcher Pratt's Secret and Urgent as a boy. Kahn is a founding editor of the Cryptologia journal. In 1969, Kahn married Susanne Fiedler; they are now divorced. They have two sons, Oliver and Michael.
He attended Bucknell University. After graduation, he worked as a reporter at Newsday. He also served as an editor at the International Herald Tribune in Paris in the 1960s.
It was during this period that he wrote an article for the New York Times Magazine about two defectors from the National Security Agency. It was the origin of his monumental book, The Codebreakers.
The Codebreakers
The Codebreakers comprehensively chronicles the history of cryptography from ancient Egypt to the time of its writing. It is widely regarded as the best account of the history of cryptography up to its publication. Most of the editing, German translating, and insider contributions were from American World War II cryptographer Bradford Hardie III. William Crowell, the former
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https://en.wikipedia.org/wiki/Key%20exchange
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Key exchange (also key establishment) is a method in cryptography by which cryptographic keys are exchanged between two parties, allowing use of a cryptographic algorithm.
If the sender and receiver wish to exchange encrypted messages, each must be equipped to encrypt messages to be sent and decrypt messages received. The nature of the equipping they require depends on the encryption technique they might use. If they use a code, both will require a copy of the same codebook. If they use a cipher, they will need appropriate keys. If the cipher is a symmetric key cipher, both will need a copy of the same key. If it is an asymmetric key cipher with the public/private key property, both will need the other's public key.
Channel of exchange
Key exchange is done either in-band or out-of-band.
The key exchange problem
The key exchange problem describes ways to exchange whatever keys or other information are needed for establishing a secure communication channel so that no one else can obtain a copy. Historically, before the invention of public-key cryptography (asymmetrical cryptography), symmetric-key cryptography utilized a single key to encrypt and decrypt messages. For two parties to communicate confidentially, they must first exchange the secret key so that each party is able to encrypt messages before sending, and decrypt received ones. This process is known as the key exchange.
The overarching problem with symmetrical cryptography, or single-key cryptography, is that it r
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https://en.wikipedia.org/wiki/Standard%20hydrogen%20electrode
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In electrochemistry, the standard hydrogen electrode (abbreviated SHE), is a redox electrode which forms the basis of the thermodynamic scale of oxidation-reduction potentials. Its absolute electrode potential is estimated to be at 25 °C, but to form a basis for comparison with all other electrochemical reactions, hydrogen's standard electrode potential () is declared to be zero volts at any temperature. Potentials of all other electrodes are compared with that of the standard hydrogen electrode at the same temperature.
Nernst equation for SHE
The hydrogen electrode is based on the redox half cell corresponding to the reduction of two hydrated protons, into one gaseous hydrogen molecule,
General equation for a reduction reaction:
The reaction quotient () of the half-reaction is the ratio between the chemical activities () of the reduced form (the reductant, ) and the oxidized form (the oxidant, ).
Considering the redox couple:
2H_{(aq)}+ + 2e- <=> H2_{(g)}
at chemical equilibrium, the ratio of the reaction products by the reagents is equal to the equilibrium constant of the half-reaction:
where
and correspond to the chemical activities of the reduced and oxidized species involved in the redox reaction
represents the activity of .
denotes the chemical activity of gaseous hydrogen (), which is approximated here by its fugacity
denotes the partial pressure of gaseous hydrogen, expressed without unit; where
is the mole fraction
is the total
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https://en.wikipedia.org/wiki/Additive
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Additive may refer to:
Mathematics
Additive function, a function in number theory
Additive map, a function that preserves the addition operation
Additive set-function see Sigma additivity
Additive category, a preadditive category with finite biproducts
Additive inverse, an arithmetic concept
Science
Additive color, as opposed to subtractive color
Additive model, a statistical regression model
Additive synthesis, an audio synthesis technique
Additive genetic effects
Additive quantity, a physical quantity that is additive for subsystems; see Intensive and extensive properties
Engineering
Feed additive
Gasoline additive, a substance used to improve the performance of a fuel, lower emissions or clean the engine
Oil additive, a substance used to improve the performance of a lubricant
Weakly additive, the quality of preferences in some logistics problems
Polymer additive
Pit additive, a material aiming to reduce fecal sludge build-up and control odor in pit latrines, septic tanks and wastewater treatment plants
Biodegradable additives
Other uses
, one of the grammatical cases in Estonian
Food additive, any substance added to food to improve flavor, appearance, shelf life, etc.
Additive rhythm, a larger period of time constructed from smaller ones
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https://en.wikipedia.org/wiki/VBI
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VBI may refer to:
Biocomplexity Institute of Virginia Tech (formerly the Virginia Bioinformatics Institute), a research organization specializing in bioinformatics, computational biology, and systems biology in Virginia, United States
Value-based investing, also known as value investing, an investment paradigm that involves buying securities that appear underpriced by some form of fundamental analysis
VBI Vaccines Inc. and Variation Biotechnologies, related manufacturers of vaccines
Vertebrobasilar insufficiency, a temporary set of symptoms due to decreased blood flow (ischemia) in the posterior circulation of the brain
Vertical blank interrupt, a hardware feature found in some computer systems that generate a video display
vertical blanking interval, a portion of a television signal
Visible Broadband Imager, part of the Daniel K. Inouye Solar Telescope
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https://en.wikipedia.org/wiki/Loop%20invariant
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In computer science, a loop invariant is a property of a program loop that is true before (and after) each iteration. It is a logical assertion, sometimes checked with a code assertion. Knowing its invariant(s) is essential in understanding the effect of a loop.
In formal program verification, particularly the Floyd-Hoare approach, loop invariants are expressed by formal predicate logic and used to prove properties of loops and by extension algorithms that employ loops (usually correctness properties).
The loop invariants will be true on entry into a loop and following each iteration, so that on exit from the loop both the loop invariants and the loop termination condition can be guaranteed.
From a programming methodology viewpoint, the loop invariant can be viewed as a more abstract specification of the loop, which characterizes the deeper purpose of the loop beyond the details of this implementation. A survey article covers fundamental algorithms from many areas of computer science (searching, sorting, optimization, arithmetic etc.), characterizing each of them from the viewpoint of its invariant.
Because of the similarity of loops and recursive programs, proving partial correctness of loops with invariants is very similar to proving the correctness of recursive programs via induction. In fact, the loop invariant is often the same as the inductive hypothesis to be proved for a recursive program equivalent to a given loop.
Informal example
The following C subroutine ma
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https://en.wikipedia.org/wiki/Roll
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Roll or Rolls may refer to:
Physics and engineering
Rolling, a motion of two objects with respect to each-other such that the two stay in contact without sliding
Roll angle (or roll rotation), one of the 3 angular degrees of freedom of any stiff body (for example a vehicle), describing motion about the longitudinal axis
Roll (aviation), one of the aircraft principal axes of rotation of an aircraft (angle of tilt to the left or right measured from the longitudinal axis)
Roll (ship motion), one of the ship motions' principal axes of rotation of a ship (angle of tilt to the port or starboard measured from the longitudinal axis)
Rolling manoeuvre, a manoeuvre of any stiff body (for example a vehicle) around its roll axis:
Roll, an aerobatic maneuver with an airplane, usually referring to an aileron roll, but sometimes instead a barrel roll, rudder roll or slow roll
Kayak roll, a maneuver used to right a capsized kayak
Roll program, an aerodynamic maneuver performed in a rocket launch
Roll rate (or roll velocity), the angular speed at which an aircraft can change its roll attitude, typically expressed in degrees per second
Food
Bread roll, a small individual loaf of bread
Roll (food), a type of food that is either rolled in its preparation, rolled in something, served in a bread roll, or otherwise called a "roll"
Arts, entertainment and media
Roll (Anne McCue album), 2004
Roll (Emerson Drive album), 2012
"Roll", a song by Flo Rida from the 2008 album Mail on Sun
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https://en.wikipedia.org/wiki/Claim
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Claim may refer to:
Claim (legal)
Claim of Right Act 1689
Claims-based identity
Claim (philosophy)
Land claim
A main contention, see conclusion of law
Patent claim
The assertion of a proposition; see Douglas N. Walton
A right
Sequent, in mathematics
Another term for an advertising slogan
Health claim
A term in contract bridge
king of claim (Indonesia)
Entertainment
The Claim, a 2000 British-Canadian Western romance film
The Claim (band), a British band
See also
"Claimed", an episode of the television series The Walking Dead
Reclaim (disambiguation)
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https://en.wikipedia.org/wiki/Scholz%20conjecture
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In mathematics, the Scholz conjecture is a conjecture on the length of certain addition chains.
It is sometimes also called the Scholz–Brauer conjecture or the Brauer–Scholz conjecture, after Arnold Scholz who formulated it in 1937 and Alfred Brauer who studied it soon afterward and proved a weaker bound.
Statement
The conjecture states that
,
where is the length of the shortest addition chain producing n.
Here, an addition chain is defined as a sequence of numbers, starting with 1, such that every number after the first can be expressed as a sum of two earlier numbers (which are allowed to both be equal). Its length is the number of sums needed to express all its numbers, which is one less than the length of the sequence of numbers (since there is no sum of previous numbers for the first number in the sequence, 1). Computing the length of the shortest addition chain that contains a given number can be done by dynamic programming for small numbers, but it is not known whether it can be done in polynomial time measured as a function of the length of the binary representation of . Scholz's conjecture, if true, would provide short addition chains for numbers of a special form, the Mersenne numbers.
Example
As an example, : it has a shortest addition chain
1, 2, 4, 5
of length three, determined by the three sums
1 + 1 = 2,
2 + 2 = 4,
4 + 1 = 5.
Also, : it has a shortest addition chain
1, 2, 3, 6, 12, 24, 30, 31
of length seven, determined by the seven sums
1 + 1 = 2,
2 + 1
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https://en.wikipedia.org/wiki/Addition%20chain
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In mathematics, an addition chain for computing a positive integer can be given by a sequence of natural numbers starting with 1 and ending with , such that each number in the sequence is the sum of two previous numbers. The length of an addition chain is the number of sums needed to express all its numbers, which is one less than the cardinality of the sequence of numbers.
Examples
As an example: (1,2,3,6,12,24,30,31) is an addition chain for 31 of length 7, since
2 = 1 + 1
3 = 2 + 1
6 = 3 + 3
12 = 6 + 6
24 = 12 + 12
30 = 24 + 6
31 = 30 + 1
Addition chains can be used for addition-chain exponentiation. This method allows exponentiation with integer exponents to be performed using a number of multiplications equal to the length of an addition chain for the exponent. For instance, the addition chain for 31 leads to a method for computing the 31st power of any number using only seven multiplications, instead of the 30 multiplications that one would get from repeated multiplication, and eight multiplications with exponentiation by squaring:
2 = ×
3 = 2 ×
6 = 3 × 3
12 = 6 × 6
24 = 12 × 12
30 = 24 × 6
31 = 30 ×
Methods for computing addition chains
Calculating an addition chain of minimal length is not easy; a generalized version of the problem, in which one must find a chain that simultaneously forms each of a sequence of values, is NP-complete. There is no known algorithm which can calculate a minimal addition chain for a given number with any guarantees of reasonable ti
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https://en.wikipedia.org/wiki/Photobiology
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Photobiology is the scientific study of the beneficial and harmful interactions of light (technically, non-ionizing radiation) in living organisms. The field includes the study of photophysics, photochemistry, photosynthesis, photomorphogenesis, visual processing, circadian rhythms, photomovement, bioluminescence, and ultraviolet radiation effects.
The division between ionizing radiation and non-ionizing radiation is typically considered to be a photon energy greater than 10 eV, which approximately corresponds to both the first ionization energy of oxygen, and the ionization energy of hydrogen at about 14 eV.
When photons come into contact with molecules, these molecules can absorb the energy in photons and become excited. Then they can react with molecules around them and stimulate "photochemical" and "photophysical" changes of molecular structures.
Photophysics
This area of Photobiology focuses on the physical interactions of light and matter. When molecules absorb photons that matches their energy requirements they promote a valence electron from a ground state to an excited state and they become a lot more reactive. This is an extremely fast process, but very important for different processes.
Photochemistry
This area of Photobiology studies the reactivity of a molecule when it absorbs energy that comes from light. It also studies what happens with this energy, it could be given off as heat or fluorescence so the molecule goes back to ground state.
There are 3 basi
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https://en.wikipedia.org/wiki/Magnetomotive%20force
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In physics, the magnetomotive force (abbreviated mmf or MMF, symbol ) is a quantity appearing in the equation for the magnetic flux in a magnetic circuit, Hopkinson's law. It is the property of certain substances or phenomena that give rise to magnetic fields:
where is the magnetic flux and is the reluctance of the circuit. It can be seen that the magnetomotive force plays a role in this equation analogous to the voltage in Ohm's law, , since it is the cause of magnetic flux in a magnetic circuit:
where is the number of turns in the coil and is the electric current through the circuit.
where is the magnetic flux and is the magnetic reluctance
where is the magnetizing force (the strength of the magnetizing field) and is the mean length of a solenoid or the circumference of a toroid.
Units
The SI unit of mmf is the ampere, the same as the unit of current (analogously the units of emf and voltage are both the volt). Informally, and frequently, this unit is stated as the ampere-turn to avoid confusion with current. This was the unit name in the MKS system. Occasionally, the cgs system unit of the gilbert may also be encountered.
History
The term magnetomotive force was coined by Henry Augustus Rowland in 1880. Rowland intended this to indicate a direct analogy with electromotive force. The idea of a magnetic analogy to electromotive force can be found much earlier in the work of Michael Faraday (1791–1867) and it is hinted at by James Clerk Maxwell (183
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https://en.wikipedia.org/wiki/Image%20%28mathematics%29
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In mathematics, the image of a function is the set of all output values it may produce.
More generally, evaluating a given function at each element of a given subset of its domain produces a set, called the "image of under (or through) ". Similarly, the inverse image (or preimage) of a given subset of the codomain of is the set of all elements of the domain that map to the members of
Image and inverse image may also be defined for general binary relations, not just functions.
Definition
The word "image" is used in three related ways. In these definitions, is a function from the set to the set
Image of an element
If is a member of then the image of under denoted is the value of when applied to is alternatively known as the output of for argument
Given the function is said to "" or "" if there exists some in the function's domain such that
Similarly, given a set is said to "" if there exists in the function's domain such that
However, "" and "" means that for point in 's domain.
Image of a subset
Throughout, let be a function.
The under of a subset of is the set of all for It is denoted by or by when there is no risk of confusion. Using set-builder notation, this definition can be written as
This induces a function where denotes the power set of a set that is the set of all subsets of See below for more.
Image of a function
The image of a function is the image of its entire domain, also known as the range of the functi
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https://en.wikipedia.org/wiki/Anton%20Kutter
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Anton Kutter (13 June 1903, in Biberach an der Riß – 1 February 1985, in Biberach) was a German film director and screenwriter. He studied mechanical engineering at Stuttgart Technical University.
In 1926 Kutter went to Cologne and joined the Phototechnical Laboratory, and created his first films the same year. From 1931 to 1947 he worked for the Bavaria Film in Munich. In 1937 he made the science fiction movie, Weltraumschiff I startet [Space Ship I Launches], a story about a first Moon flight which he dated on 13 June 1963, his 60th birthday. Kutter was awarded two golden medals at the Venice Biennale.
Already at age 12, Kutter manufactured his first refracting telescope from lenses taken from a toy cinematograph. Later he became known to Anton Staus (1872-1955) who introduced him to the theory of 's "Brachy" telescopes. He invented the Schiefspiegler telescope which is a modified Cassegrain reflector featuring superb optical definition due to an off-axis secondary mirror. An obituary was published by Roger W. Sinnott in Sky & Telescope.<ref>"Optical Innovator Dies – Kutter, Anton by Roger W. Sinnott in Sky & Telescope, May 1985, p. 461.</ref>
Selected filmography
Frau Sixta (1938)
Dark Clouds Over the Dachstein (1953)
Open Your Window (1953)
The Song of Kaprun'' (1955)
References
External links
Biography
1903 births
1985 deaths
People from Biberach an der Riss
People from the Kingdom of Württemberg
Film people from Baden-Württemberg
20th-century German inventors
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https://en.wikipedia.org/wiki/Gene%20prediction
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In computational biology, gene prediction or gene finding refers to the process of identifying the regions of genomic DNA that encode genes. This includes protein-coding genes as well as RNA genes, but may also include prediction of other functional elements such as regulatory regions. Gene finding is one of the first and most important steps in understanding the genome of a species once it has been sequenced.
In its earliest days, "gene finding" was based on painstaking experimentation on living cells and organisms. Statistical analysis of the rates of homologous recombination of several different genes could determine their order on a certain chromosome, and information from many such experiments could be combined to create a genetic map specifying the rough location of known genes relative to each other. Today, with comprehensive genome sequence and powerful computational resources at the disposal of the research community, gene finding has been redefined as a largely computational problem.
Determining that a sequence is functional should be distinguished from determining the function of the gene or its product. Predicting the function of a gene and confirming that the gene prediction is accurate still demands in vivo experimentation through gene knockout and other assays, although frontiers of bioinformatics research are making it increasingly possible to predict the function of a gene based on its sequence alone.
Gene prediction is one of the key steps in genome anno
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https://en.wikipedia.org/wiki/Ecoinformatics
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Ecoinformatics, or ecological informatics, is the science of information in ecology and environmental science. It integrates environmental and information sciences to define entities and natural processes with language common to both humans and computers. However, this is a rapidly developing area in ecology and there are alternative perspectives on what constitutes ecoinformatics.
A few definitions have been circulating, mostly centered on the creation of tools to access and analyze natural system data. However, the scope and aims of ecoinformatics are certainly broader than the development of metadata standards to be used in documenting datasets. Ecoinformatics aims to facilitate environmental research and management by developing ways to access, integrate databases of environmental information, and develop new algorithms enabling different environmental datasets to be combined to test ecological hypotheses. Ecoinformatics is related to the concept of ecosystem services.
Ecoinformatics characterize the semantics of natural system knowledge. For this reason, much of today's ecoinformatics research relates to the branch of computer science known as knowledge representation, and active ecoinformatics projects are developing links to activities such as the Semantic Web.
Current initiatives to effectively manage, share, and reuse ecological data are indicative of the increasing importance of fields like ecoinformatics to develop the foundations for effectively managing ecolog
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https://en.wikipedia.org/wiki/Tubulin
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Tubulin in molecular biology can refer either to the tubulin protein superfamily of globular proteins, or one of the member proteins of that superfamily. α- and β-tubulins polymerize into microtubules, a major component of the eukaryotic cytoskeleton. Microtubules function in many essential cellular processes, including mitosis. Tubulin-binding drugs kill cancerous cells by inhibiting microtubule dynamics, which are required for DNA segregation and therefore cell division.
In eukaryotes, there are six members of the tubulin superfamily, although not all are present in all species. Both α and β tubulins have a mass of around 50 kDa and are thus in a similar range compared to actin (with a mass of ~42 kDa). In contrast, tubulin polymers (microtubules) tend to be much bigger than actin filaments due to their cylindrical nature.
Tubulin was long thought to be specific to eukaryotes. More recently, however, several prokaryotic proteins have been shown to be related to tubulin.
Characterization
Tubulin is characterized by the evolutionarily conserved Tubulin/FtsZ family, GTPase protein domain.
This GTPase protein domain is found in all eukaryotic tubulin chains, as well as the bacterial protein TubZ, the archaeal protein CetZ, and the FtsZ protein family widespread in bacteria and archaea.
Function
Microtubules
α- and β-tubulin polymerize into dynamic microtubules. In eukaryotes, microtubules are one of the major components of the cytoskeleton, and function in many proces
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https://en.wikipedia.org/wiki/International%20Union%20of%20Pure%20and%20Applied%20Physics
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The International Union of Pure and Applied Physics (IUPAP; ) is an international non-governmental organization whose mission is to assist in the worldwide development of physics, to foster international cooperation in physics, and to help in the application of physics toward solving problems of concern to humanity. It was established in 1922 and the first General Assembly was held in 1923 in Paris. The Union is domiciled in Geneva, Switzerland.
IUPAP carries out this mission by: sponsoring international meetings; fostering communications and publications; encouraging research and education; fostering the free circulation of scientists; promoting international agreements on the use of symbols, units, nomenclature and standards; and cooperating with other organizations on disciplinary and interdisciplinary problems.
IUPAP is a member of the International Science Council.
IUPAP is the lead organization promoting the adoption of the International Year of Basic Sciences for Sustainable Development, a proposal to be considered by the 76th session of the UN General Assembly.
History
In 1919 was formed the International Research Council “largely through the representatives of the National Academy of Sciences, Washington, and of the Royal Society, London, to coordinate international efforts in the different branches of sciences, under whose aegis international associations or unions in different branches of science could be formed".
In accordance with this principle, the 1922 Ge
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https://en.wikipedia.org/wiki/World%20Year%20of%20Physics%202005
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The year 2005 was named the World Year of Physics, also known as Einstein Year, in recognition of the 100th anniversary of Albert Einstein's "Miracle Year", in which he published four landmark papers, and the subsequent advances in the field of physics.
History
Physics has been the basis for understanding the physical world and nature as a whole. The applications of physics are the basis for much of today's technology. In order to both raise worldwide awareness of physics and celebrate the major advances made in the field, the World Congress of Physical Societies proposed and the International Union of Pure and Applied Physics resolved that 2005 should be commemorated as the World Year of Physics. This was subsequently endorsed by UNESCO.
Selected celebrations
The World Year of Physics officially began with a conference held in mid-January in Paris, titled Physics for Tomorrow.
In the United States, the University of Maryland sponsored several activities in cooperation with the Smithsonian Institution and NASA's Goddard Space Flight Center, including various lecture series and resident programs.
In Berlin, sixteen large, red E's have been erected along a section of the famous Unter den Linden boulevard. Called the "Einstein Mile", the E's were in place from April to September 2005 and displayed information on the theories and life of Albert Einstein.
In Egypt, the Library of Alexandria organized the Einstein Symposium.
San Marino issued a €2 commemorative coin.
The
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https://en.wikipedia.org/wiki/Plus%20construction
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In mathematics, the plus construction is a method for simplifying the fundamental group of a space without changing its homology and cohomology groups.
Explicitly, if is a based connected CW complex and is a perfect normal subgroup of then a map is called a +-construction relative to if induces an isomorphism on homology, and is the kernel of .
The plus construction was introduced by , and was used by Daniel Quillen to define algebraic K-theory. Given a perfect normal subgroup of the fundamental group of a connected CW complex , attach two-cells along loops in whose images in the fundamental group generate the subgroup. This operation generally changes the homology of the space, but these changes can be reversed by the addition of three-cells.
The most common application of the plus construction is in algebraic K-theory. If is a unital ring, we denote by the group of invertible -by- matrices with elements in . embeds in by attaching a along the diagonal and s elsewhere. The direct limit of these groups via these maps is denoted and its classifying space is denoted . The plus construction may then be applied to the perfect normal subgroup of , generated by matrices which only differ from the identity matrix in one off-diagonal entry. For , the -th homotopy group of the resulting space, , is isomorphic to the -th -group of , that is,
See also
Semi-s-cobordism
References
.
.
.
External links
Algebraic topology
Homotopy theory
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https://en.wikipedia.org/wiki/Hexapod
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Hexapod may refer to:
Things with six limbs, e.g. a hexapod chair would have six not the traditional four limbs
Biology
Hexapoda, a subphylum of arthropods including the insects
Hexapodidae, a family of crabs
Technology
Hexapod (robotics), a mechanical vehicle that walks on six legs
Stewart platform, a machine platform supported by six struts, used in robotics
Hexapod-Telescope, a telescope in Chile mounted on a Stewart platform chassis frame
See also
Tetrapod
Octopod
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https://en.wikipedia.org/wiki/Acyl%20chloride
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In organic chemistry, an acyl chloride (or acid chloride) is an organic compound with the functional group . Their formula is usually written , where R is a side chain. They are reactive derivatives of carboxylic acids (). A specific example of an acyl chloride is acetyl chloride, . Acyl chlorides are the most important subset of acyl halides.
Nomenclature
Where the acyl chloride moiety takes priority, acyl chlorides are named by taking the name of the parent carboxylic acid, and substituting -yl chloride for -ic acid. Thus:
When other functional groups take priority, acyl chlorides are considered prefixes — chlorocarbonyl-:
Properties
Lacking the ability to form hydrogen bonds, acyl chlorides have lower boiling and melting points than similar carboxylic acids. For example, acetic acid boils at 118 °C, whereas acetyl chloride boils at 51 °C. Like most carbonyl compounds, infrared spectroscopy reveals a band near 1750 cm−1.
The simplest stable acyl chloride is acetyl chloride; formyl chloride is not stable at room temperature, although it can be prepared at –60 °C or below.
Acyl chlorides hydrolyze (react with water) to form the corresponding carboxylic acid and hydrochloric acid:
RCOCl + H2O -> RCOOH + HCl
Synthesis
Industrial routes
The industrial route to acetyl chloride involves the reaction of acetic anhydride with hydrogen chloride:
(CH3CO)2O + HCl -> CH3COCl + CH3CO2H
Propionyl chloride is produced by chlorination of propionic acid with phosgene:
CH3CH2CO2H
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https://en.wikipedia.org/wiki/Table%20of%20standard%20reduction%20potentials%20for%20half-reactions%20important%20in%20biochemistry
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The values below are standard apparent reduction potentials for electro-biochemical half-reactions measured at 25 °C, 1 atmosphere and a pH of 7 in aqueous solution.
The actual physiological potential depends on the ratio of the reduced () and oxidized () forms according to the Nernst equation and the thermal voltage.
When an oxidizer () accepts a number z of electrons () to be converted in its reduced form (), the half-reaction is expressed as:
+ z →
The reaction quotient (r) is the ratio of the chemical activity (ai) of the reduced form (the reductant, aRed) to the activity of the oxidized form (the oxidant, aox). It is equal to the ratio of their concentrations (Ci) only if the system is sufficiently diluted and the activity coefficients (γi) are close to unity (ai = γi Ci):
The Nernst equation is a function of and can be written as follows:
At chemical equilibrium, the reaction quotient of the product activity (aRed) by the reagent activity (aOx) is equal to the equilibrium constant () of the half-reaction and in the absence of driving force () the potential () also becomes nul.
The numerically simplified form of the Nernst equation is expressed as:
Where is the standard reduction potential of the half-reaction expressed versus the standard reduction potential of hydrogen. For standard conditions in electrochemistry (T = 25 °C, P = 1 atm and all concentrations being fixed at 1 mol/L, or 1 M) the standard reduction potential of hydrogen is fixed at zer
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https://en.wikipedia.org/wiki/Singularity%20theory
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In mathematics, singularity theory studies spaces that are almost manifolds, but not quite. A string can serve as an example of a one-dimensional manifold, if one neglects its thickness. A singularity can be made by balling it up, dropping it on the floor, and flattening it. In some places the flat string will cross itself in an approximate "X" shape. The points on the floor where it does this are one kind of singularity, the double point: one bit of the floor corresponds to more than one bit of string. Perhaps the string will also touch itself without crossing, like an underlined "U". This is another kind of singularity. Unlike the double point, it is not stable, in the sense that a small push will lift the bottom of the "U" away from the "underline".
Vladimir Arnold defines the main goal of singularity theory as describing how objects depend on parameters, particularly in cases where the properties undergo sudden change under a small variation of the parameters. These situations are called perestroika (), bifurcations or catastrophes. Classifying the types of changes and characterizing sets of parameters which give rise to these changes are some of the main mathematical goals. Singularities can occur in a wide range of mathematical objects, from matrices depending on parameters to wavefronts.
How singularities may arise
In singularity theory the general phenomenon of points and sets of singularities is studied, as part of the concept that manifolds (spaces without singula
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https://en.wikipedia.org/wiki/MDH
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MDH may refer to:
Chemistry
Malate dehydrogenase
(S)-mandelate dehydrogenase
Methanol dehydrogenase (cytochrome c)
Methylenedioxyhydroxyamphetamine
Health and medicine
Manila Doctors Hospital, in Ermita, Manila, Philippines
Mater Dei Hospital, in Msida, Malta
Milton District Hospital, in Milton, Ontario, Canada
Minnesota Department of Health
Other uses
MDH (spice company), an Indian spice producer and seller
Maguindanao language (ISO 639-3: mdh)
Mälardalen University College (Mälardalens högskola; MdH), in Sweden
Minimum descent height, for aircraft landing; see List of aviation, avionics, aerospace and aeronautical abbreviations
Miss Die Hard, a Rick and Morty character
Multidimensional hierarchical toolkit
Southern Illinois Airport (IATA: MDH)
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https://en.wikipedia.org/wiki/Invertible%20sheaf
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In mathematics, an invertible sheaf is a sheaf on a ringed space which has an inverse with respect to tensor product of sheaves of modules. It is the equivalent in algebraic geometry of the topological notion of a line bundle. Due to their interactions with Cartier divisors, they play a central role in the study of algebraic varieties.
Definition
Let (X, OX) be a ringed space. Isomorphism classes of sheaves of OX-modules form a monoid under the operation of tensor product of OX-modules. The identity element for this operation is OX itself. Invertible sheaves are the invertible elements of this monoid. Specifically, if L is a sheaf of OX-modules, then L is called invertible if it satisfies any of the following equivalent conditions:
There exists a sheaf M such that .
The natural homomorphism is an isomorphism, where denotes the dual sheaf .
The functor from OX-modules to OX-modules defined by is an equivalence of categories.
Every locally free sheaf of rank one is invertible. If X is a locally ringed space, then L is invertible if and only if it is locally free of rank one. Because of this fact, invertible sheaves are closely related to line bundles, to the point where the two are sometimes conflated.
Examples
Let X be an affine scheme . Then an invertible sheaf on X is the sheaf associated to a rank one projective module over R. For example, this includes fractional ideals of algebraic number fields, since these are rank one projective modules over the rings
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https://en.wikipedia.org/wiki/Concurrent%20user
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In computer science, the number of concurrent users (sometimes abbreviated CCU) for a resource in a location, with the location being a computing network or a single computer, refers to the total number of people simultaneously accessing or using the resource. The resource can, for example, be a computer program, a file, or the computer as a whole.
Keeping track of concurrent users is important in several cases. First, some operating system models such as time-sharing operating systems allow several users to access a resource on the computer at the same time. As system performance may degrade due to the complexity of processing multiple jobs from multiple users at the same time, the capacity of such a system may be measured in terms of maximum concurrent users.
Second, commercial software vendors often license a software product by means of a concurrent users restriction. This allows a fixed number of users access to the product at a given time and contrasts with an unlimited user license. For example: Company X buys software and pays for 20 concurrent users. However, there are 100 logins created at implementation. Only 20 of those 100 can be in the system at the same time, this is known as floating licensing.
Concurrent user licensing allows firms to purchase computer systems and software at a lower cost because the maximum number of concurrent users expected to use the system or software at any given time (those users all logged in together) is only a portion of the tota
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https://en.wikipedia.org/wiki/Directional%20selection
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In population genetics, directional selection is a mode of negative natural selection in which an extreme phenotype is favored over other phenotypes, causing the allele frequency to shift over time in the direction of that phenotype. Under directional selection, the advantageous allele increases as a consequence of differences in survival and reproduction among different phenotypes. The increases are independent of the dominance of the allele, and even if the allele is recessive, it will eventually become fixed.
Directional selection was first described by Charles Darwin in the book On the Origin of Species as a form of natural selection. Other types of natural selection include stabilizing and disruptive selection. Each type of selection contains the same principles, but is slightly different. Disruptive selection favors both extreme phenotypes, different from one extreme in directional selection. Stabilizing selection favors the middle phenotype, causing the decline in variation in a population over time.
Evidence
Directional selection occurs most often under environmental changes and when populations migrate to new areas with different environmental pressures. Directional selection allows for fast changes in allele frequency, and plays a major role in speciation. Analysis on QTL effects has been used to examine the impact of directional selection in phenotypic diversification. This analysis showed that the genetic loci correlating to directional selection was higher t
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https://en.wikipedia.org/wiki/Pushout%20%28category%20theory%29
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In category theory, a branch of mathematics, a pushout (also called a fibered coproduct or fibered sum or cocartesian square or amalgamated sum) is the colimit of a diagram consisting of two morphisms f : Z → X and g : Z → Y with a common domain. The pushout consists of an object P along with two morphisms X → P and Y → P that complete a commutative square with the two given morphisms f and g. In fact, the defining universal property of the pushout (given below) essentially says that the pushout is the "most general" way to complete this commutative square. Common notations for the pushout are and .
The pushout is the categorical dual of the pullback.
Universal property
Explicitly, the pushout of the morphisms f and g consists of an object P and two morphisms i1 : X → P and i2 : Y → P such that the diagram
commutes and such that (P, i1, i2) is universal with respect to this diagram. That is, for any other such triple (Q, j1, j2) for which the following diagram commutes, there must exist a unique u : P → Q also making the diagram commute:
As with all universal constructions, the pushout, if it exists, is unique up to a unique isomorphism.
Examples of pushouts
Here are some examples of pushouts in familiar categories. Note that in each case, we are only providing a construction of an object in the isomorphism class of pushouts; as mentioned above, though there may be other ways to construct it, they are all equivalent.
Suppose that X, Y, and Z as above are sets, and tha
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https://en.wikipedia.org/wiki/P5
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P5 may refer to:
In science and technology
311P/PANSTARRS, also known as P/2013 P5 (PANSTARRS), an asteroid discovered by the Pan-STARRS telescope on 27 August 2013
P5 Truss Segment, an element of the International Space Station
Period 5 of the periodic table of elements
Styx (moon), the fifth moon of the dwarf planet Pluto
Particle Physics Project Prioritization Panel, a scientific funding advisory group in the United States
Pregnenolone, a steroid hormone
Vehicles
P-5 Hawk, a 1923 aircraft
Martin P5M Marlin, a flying boat
Rover P5 (commonly called 3-Litre and 3½ Litre), a group of automobiles produced from 1958–1973
Palatine P 5, a 1908 locomotive
PRR P5, mixed-traffic electric locomotives constructed 1931–1935
Protegé5, a 5-door sport-wagon produced by Mazda from 2002–2003
Polikarpov P-5, Soviet passenger aircraft, modification of the R-5
In computing
P5 Glove, an input device for human-computer interaction
P5 (microarchitecture), a fifth-generation central processing unit introduced in 1993
System p5, a family of servers and workstations created by IBM in 2005
p5.js is the JavaScript port of Processing
Perl, version 5
Weapons
P-5 Pyatyorka, a 1959 anti-shipping missile of the Soviet Union
Walther P5, a pistol made by German arms maker Walther in the 1970s
In arts and entertainment
P5 (comics), a comic strip also known as Class Act, in the UK comic The Dandy
Persona 5, a 2016 video game from Atlus
In music
Perfect fifth, a music interv
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https://en.wikipedia.org/wiki/Lev%20Pontryagin
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Lev Semenovich Pontryagin (, also written Pontriagin or Pontrjagin) (3 September 1908 – 3 May 1988) was a Soviet mathematician. Completely blind from the age of 14, he made major discoveries in a number of fields of mathematics, including algebraic topology, differential topology and optimal control.
Early life and career
He was born in Moscow and lost his eyesight completely due to an unsuccessful eye surgery after a primus stove explosion when he was 14. His mother Tatyana Andreevna, who did not know mathematical symbols, read mathematical books and papers (notably those of Heinz Hopf, J. H. C. Whitehead, and Hassler Whitney) to him, and later worked as his secretary. His mother used alternative names for math symbols, such as "tails up" for the set-union symbol .
In 1925 he entered Moscow State University, where he was strongly influenced by the lectures of Pavel Aleksandrov who would become his doctoral thesis advisor. After graduating in 1929, he obtained a position at Moscow State University. In 1934 he joined the Steklov Institute in Moscow. In 1970 he became vice president of the International Mathematical Union.
Work
Pontryagin worked on duality theory for homology while still a student. He went on to lay foundations for the abstract theory of the Fourier transform, now called Pontryagin duality. Using these tools, he was able to solve the case of Hilbert's fifth problem for abelian groups in 1934.
In 1935, he was able to compute the homology groups of the classi
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https://en.wikipedia.org/wiki/Hyper
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Hyper may refer to:
Arts and entertainment
Hyper (2016 film), 2016 Indian Telugu film
Hyper (2018 film), 2018 Indian Kannada film
Hyper (magazine), an Australian video game magazine
Hyper (TV channel), a Filipino sports channel
Hyper+, a former Polish programming block on Teletoon+
Mathematics
Hypercube, the n-dimensional analogue of a square and a cube
Hyperoperation, an arithmetic operation beyond exponentiation
Hyperplane, a subspace whose dimension is one less than that of its ambient space
Hypersphere, the set of points at a constant distance from a given point called its centre
Hypersurface, a generalization of the concepts of hyperplane, plane curve, and surface
Hyperstructure, an algebraic structure equipped with at least one multivalued operation
Hyperbolic functions, analogues of trigonometric functions defined using the hyperbola rather than the circle
Other uses
DJ Hyper (born 1977), a British electronic musician
Hyper key, a modifier key on the space-cadet keyboard
Hyper engine, a hypothetical aircraft engine design
Hyper Island, a Swedish educational company
Europe Sails Hyper, an Austrian hang glider
See also
Hyperspace (disambiguation)
Hyperactivity, a state in which a person is abnormally excitable and exuberant
Super (disambiguation)
Meta (disambiguation)
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https://en.wikipedia.org/wiki/George%20Christopher%20Williams
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George Christopher Williams (May 12, 1926 – September 8, 2010) was an American evolutionary biologist.
Williams was a professor of biology at the State University of New York at Stony Brook who was best known for his vigorous critique of group selection. The work of Williams in this area, along with W. D. Hamilton, John Maynard Smith, Richard Dawkins, and others led to the development of the gene-centered view of evolution in the 1960s.
Academic work
Williams' 1957 paper Pleiotropy, Natural Selection, and the Evolution of Senescence is one of the most influential in 20th century evolutionary biology, and contains at least 3 foundational ideas. The central hypothesis of antagonistic pleiotropy remains the prevailing evolutionary explanation of senescence. In this paper Williams was also the first to propose that senescence should be generally synchronized by natural selection. According to this original formulation
... if the adverse genic effects appeared earlier in one system than any other, they would be removed by selection from that system more readily than from any other. In other words, natural selection will always be in greatest opposition to the decline of the most senescence-prone system.
This important concept of synchrony of senescence was taken up a short time later by John Maynard Smith, and the origin of the idea is often misattributed to him, including in his obituary in the journal Nature. Finally, Williams' 1957 paper was the first to outline the "gran
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https://en.wikipedia.org/wiki/Rabi%20cycle
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In physics, the Rabi cycle (or Rabi flop) is the cyclic behaviour of a two-level quantum system in the presence of an oscillatory driving field. A great variety of physical processes belonging to the areas of quantum computing, condensed matter, atomic and molecular physics, and nuclear and particle physics can be conveniently studied in terms of two-level quantum mechanical systems, and exhibit Rabi flopping when coupled to an optical driving field. The effect is important in quantum optics, magnetic resonance and quantum computing, and is named after Isidor Isaac Rabi.
A two-level system is one that has two possible energy levels. These two levels are a ground state with lower energy and an excited state with higher energy. If the energy levels are not degenerate (i.e. not having equal energies), the system can absorb a quantum of energy and transition from the ground state to the "excited" state. When an atom (or some other two-level system) is illuminated by a coherent beam of photons, it will cyclically absorb photons and re-emit them by stimulated emission. One such cycle is called a Rabi cycle, and the inverse of its duration is the Rabi frequency of the system. The effect can be modeled using the Jaynes–Cummings model and the Bloch vector formalism.
Mathematical description
A detailed mathematical description of the effect can be found on the page for the Rabi problem. For example, for a two-state atom (an atom in which an electron can either be in the excited or gr
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https://en.wikipedia.org/wiki/Lefschetz%20fixed-point%20theorem
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In mathematics, the Lefschetz fixed-point theorem is a formula that counts the fixed points of a continuous mapping from a compact topological space to itself by means of traces of the induced mappings on the homology groups of . It is named after Solomon Lefschetz, who first stated it in 1926.
The counting is subject to an imputed multiplicity at a fixed point called the fixed-point index. A weak version of the theorem is enough to show that a mapping without any fixed point must have rather special topological properties (like a rotation of a circle).
Formal statement
For a formal statement of the theorem, let
be a continuous map from a compact triangulable space to itself. Define the Lefschetz number of by
the alternating (finite) sum of the matrix traces of the linear maps induced by on , the singular homology groups of with rational coefficients.
A simple version of the Lefschetz fixed-point theorem states: if
then has at least one fixed point, i.e., there exists at least one in such that . In fact, since the Lefschetz number has been defined at the homology level, the conclusion can be extended to say that any map homotopic to has a fixed point as well.
Note however that the converse is not true in general: may be zero even if has fixed points, as is the case for the identity map on odd-dimensional spheres.
Sketch of a proof
First, by applying the simplicial approximation theorem, one shows that if has no fixed points, then (possibly after subdivi
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https://en.wikipedia.org/wiki/ISE
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ISE may refer to:
Organizations
International Society of Electrochemistry, a global scientific society founded in 1949
Islamic Society of Engineers, principlist political organization of engineers in Iran
Education
Iceland School of Energy, a school jointly owned by Reykjavik Energy, Reykjavik University, and Iceland GeoSurvey
Institute for Shipboard Education, administrator of the Semester at Sea study-abroad program
Institute for Social Ecology, an educational institution in Plainfield, Vermont
International School Eindhoven, an international school in the northern part of Eindhoven, Netherlands
International Student Exchange, Ontario, a non-profit organization allowing students to participate in reciprocal student exchange programs
Stock exchanges
International Securities Exchange, a United States stock exchange
Irish Stock Exchange, Ireland's main stock exchange
Islamabad Stock Exchange, now Pakistan Stock Exchange
Istanbul Stock Exchange, a former Turkish stock exchange that merged and became Borsa Istanbul
Other
Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE), an institute of the Fraunhofer Society
Information Sharing Environment, a United States government program
Initiative for Science in Europe, an independent platform of European learned societies and scientific organisations
ISE Corporation, a company that developed hybrid electric drivetrains for heavy-duty transportation
Ion selective electrode, a transducer that converts the ac
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https://en.wikipedia.org/wiki/Karl%20Ludwig%20Harding
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Karl Ludwig Harding (29 September 1765 – 31 August 1834) was a German astronomer, who discovered Juno, the third asteroid of the main-belt in 1804.
Life and career
Harding was born in Lauenburg. From 1786–89, he was educated at the University of Göttingen, where he studied theology, mathematics, and physics. In 1796 Johann Hieronymus Schröter hired Harding as a tutor for his son. Schröter was an enthusiastic astronomer and owner of a well-equipped observatory in Lilienthal near Bremen, where Harding was soon appointed observer and inspector.
In 1800, he was among the 24 astronomers invited to participate in the celestial police, a group dedicated to finding additional planets in the solar system. As part of the group, in 1804, Harding discovered Juno at Schröter's observatory. In the next year he left Lilienthal, where his successor became Friedrich Wilhelm Bessel, as he was appointed extraordinary professor of astronomy at the University of Göttingen, since 1812 as ordinary professor. He worked at Göttingen Observatory, since 1807 as colleague of Carl Friedrich Gauss, until his sudden death in 1834.
In addition to Juno, he discovered three comets and the variable stars R Virginis, R Aquarii, R Serpentis and S Serpentis. Furthermore, he found some new nebulae, among them NGC 7293, today popularly known as "helix nebula" or "the Eye of God".
Honours and Awards
Harding was corresponding member of the Royal Academy of Sciences in Göttingen since 1803 and full member sin
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https://en.wikipedia.org/wiki/Drosophila%20embryogenesis
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Drosophila embryogenesis, the process by which Drosophila (fruit fly) embryos form, is a favorite model system for genetics and developmental biology. The study of its embryogenesis unlocked the century-long puzzle of how development was controlled, creating the field of evolutionary developmental biology. The small size, short generation time, and large brood size make it ideal for genetic studies. Transparent embryos facilitate developmental studies. Drosophila melanogaster was introduced into the field of genetic experiments by Thomas Hunt Morgan in 1909.
Life cycle
Drosophila display a holometabolous method of development, meaning that they have three distinct stages of their post-embryonic life cycle, each with a radically different body plan: larva, pupa and finally, adult. The machinery necessary for the function and smooth transition between these three phases develops during embryogenesis. During embryogenesis, the larval stage fly will develop and hatch at a stage of its life known as the first larval instar. Cells that will produce adult structures are put aside in imaginal discs. During the pupal stage, the larval body breaks down as the imaginal disks grow and produce the adult body. This process is called complete metamorphosis. About 24 hours after fertilization, an egg hatches into a larva, which undergoes three molts taking about 5.5 to 6 days, after which it is called a pupa. The pupa metamorphoses into an adult fly, which takes about 3.5 to 4.5 days. The
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