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https://en.wikipedia.org/wiki/Nonnegative%20matrix
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In mathematics, a nonnegative matrix, written
is a matrix in which all the elements are equal to or greater than zero, that is,
A positive matrix is a matrix in which all the elements are strictly greater than zero. The set of positive matrices is a subset of all non-negative matrices. While such matrices are commonly found, the term is only occasionally used due to the possible confusion with positive-definite matrices, which are different. A matrix which is both non-negative and is positive semidefinite is called a doubly non-negative matrix.
A rectangular non-negative matrix can be approximated by a decomposition with two other non-negative matrices via non-negative matrix factorization.
Eigenvalues and eigenvectors of square positive matrices are described by the Perron–Frobenius theorem.
Properties
The trace and every row and column sum/product of a nonnegative matrix is nonnegative.
Inversion
The inverse of any non-singular M-matrix is a non-negative matrix. If the non-singular M-matrix is also symmetric then it is called a Stieltjes matrix.
The inverse of a non-negative matrix is usually not non-negative. The exception is the non-negative monomial matrices: a non-negative matrix has non-negative inverse if and only if it is a (non-negative) monomial matrix. Note that thus the inverse of a positive matrix is not positive or even non-negative, as positive matrices are not monomial, for dimension .
Specializations
There are a number of groups of matrices that form specializations of non-negative matrices, e.g. stochastic matrix; doubly stochastic matrix; symmetric non-negative matrix.
See also
Metzler matrix
Bibliography
Abraham Berman, Robert J. Plemmons, Nonnegative Matrices in the Mathematical Sciences, 1994, SIAM. .
A. Berman and R. J. Plemmons, Nonnegative Matrices in the Mathematical Sciences, Academic Press, 1979 (chapter 2),
R.A. Horn and C.R. Johnson, Matrix Analysis, Cambridge University Press, 1990 (chapter 8).
Henryk Minc, N
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https://en.wikipedia.org/wiki/Urobilin
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Urobilin or urochrome is the chemical primarily responsible for the yellow color of urine. It is a linear tetrapyrrole compound that, along with the related colorless compound urobilinogen, are degradation products of the cyclic tetrapyrrole heme.
Metabolism
Urobilin is generated from the degradation of heme, which is first degraded through biliverdin to bilirubin. Bilirubin is then excreted as bile, which is further degraded by microbes present in the large intestine to urobilinogen. Some of this remains in the large intestine, and its conversion to stercobilin gives feces their brown color. Some is reabsorbed into the bloodstream and then delivered to kidney. When urobilinogen is exposed to air, it is oxidized to urobilin, giving urine its yellow color.
Importance
Many urine tests (urinalysis) monitor the amount of urobilin in urine, as its levels can give insight on the effectiveness of urinary tract function. Normally, urine would appear as either light yellow or colorless. A lack of water intake, for example following sleep or dehydration, reduces the water content of urine, thereby concentrating urobilin and producing a darker color of urine. Obstructive jaundice reduces biliary bilirubin excretion, which is then excreted directly from the blood stream into the urine, giving a dark-colored urine but with a paradoxically low urobilin concentration, no urobilinogen, and usually with correspondingly pale faeces. Darker urine can also be due to other chemicals, such as various ingested dietary components or drugs, porphyrins in patients with porphyria, and homogentisate in patients with alkaptonuria.
See also
Bile pigment
Bilirubin
Biliverdin
Heme
Stercobilin
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https://en.wikipedia.org/wiki/Fundamental%20vector%20field
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In the study of mathematics and especially differential geometry, fundamental vector fields are an instrument that describes the infinitesimal behaviour of a smooth Lie group action on a smooth manifold. Such vector fields find important applications in the study of Lie theory, symplectic geometry, and the study of Hamiltonian group actions.
Motivation
Important to applications in mathematics and physics is the notion of a flow on a manifold. In particular, if is a smooth manifold and is a smooth vector field, one is interested in finding integral curves to . More precisely, given one is interested in curves such that:
for which local solutions are guaranteed by the Existence and Uniqueness Theorem of Ordinary Differential Equations. If is furthermore a complete vector field, then the flow of , defined as the collection of all integral curves for , is a diffeomorphism of . The flow given by is in fact an action of the additive Lie group on .
Conversely, every smooth action defines a complete vector field via the equation:
It is then a simple result that there is a bijective correspondence between actions on and complete vector fields on .
In the language of flow theory, the vector field is called the infinitesimal generator. Intuitively, the behaviour of the flow at each point corresponds to the "direction" indicated by the vector field. It is a natural question to ask whether one may establish a similar correspondence between vector fields and more arbitrary Lie group actions on .
Definition
Let be a Lie group with corresponding Lie algebra . Furthermore, let be a smooth manifold endowed with a smooth action . Denote the map such that , called the orbit map of corresponding to . For , the fundamental vector field corresponding to is any of the following equivalent definitions:
where is the differential of a smooth map and is the zero vector in the vector space .
The map can then be shown to be a Lie algebra homomorphism.
Application
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https://en.wikipedia.org/wiki/Wine%20lake
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Wine lake is a cultural phrase referring to the phenomenon of perceived overproduction of wine in the European Union. The phenomenon first came in perception & persistence around 2005 to 2007. The EU's Common Agricultural Policy contained a number of subsidies for wine producers, leading to a supply glut. This surplus forced an overhaul of EU farm policies.
In 2007 it was reported that for the previous several vintages, Europe had been producing 1.7 Billion more bottles of wine than they sold. Hundreds of millions of bottles of wine had been turned into industrial alcohol every year, a practice that had sometimes been described as 'emergency distillation' at a cost to taxpayers of €500 million per year. A major contributor was reported to be Languedoc-Roussillon wine production, which used one third of the grapes grown in France.
One of the proposed remedies to wine lake was Plan Bordeaux, an initiative introduced in 2005 by the French vintners association ONIVINS to reduce France's production and raise prices. Part of the plan was to uproot of the of vineyards in Bordeaux. The proposed plan was met with some resistance.
In 2020, wine growers warned that the EU risked another massive surplus due to the effects of the COVID-19 pandemic, particularly the restaurant closures. The growers called for additional subsidies to distill surplus wine.
In 2023, €200 million was again earmarked for conversion of surplus wine into industrial products.
See also
Butter mountain
Crop destruction
Artificial scarcity
Deer Terrace Pavilion, site of a historical 'Lake of Wine' in China
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https://en.wikipedia.org/wiki/Generalized%20quadrangle
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In geometry, a generalized quadrangle is an incidence structure whose main feature is the lack of any triangles (yet containing many quadrangles). A generalized quadrangle is by definition a polar space of rank two. They are the with n = 4 and near 2n-gons with n = 2. They are also precisely the partial geometries pg(s,t,α) with α = 1.
Definition
A generalized quadrangle is an incidence structure (P,B,I), with I ⊆ P × B an incidence relation, satisfying certain axioms. Elements of P are by definition the points of the generalized quadrangle, elements of B the lines. The axioms are the following:
There is an s (s ≥ 1) such that on every line there are exactly s + 1 points. There is at most one point on two distinct lines.
There is a t (t ≥ 1) such that through every point there are exactly t + 1 lines. There is at most one line through two distinct points.
For every point p not on a line L, there is a unique line M and a unique point q, such that p is on M, and q on M and L.
(s,t) are the parameters of the generalized quadrangle. The parameters are allowed to be infinite. If either s or t is one, the generalized quadrangle is called trivial. For example, the 3x3 grid with P = {1,2,3,4,5,6,7,8,9} and B = {123, 456, 789, 147, 258, 369} is a trivial GQ with s = 2 and t = 1. A generalized quadrangle with parameters (s,t) is often denoted by GQ(s,t).
The smallest non-trivial generalized quadrangle is GQ(2,2), whose representation was dubbed "the doily" by Stan Payne in 1973.
Properties
Graphs
There are two interesting graphs that can be obtained from a generalized quadrangle.
The collinearity graph having as vertices the points of a generalized quadrangle, with the collinear points connected. This graph is a strongly regular graph with parameters ((s+1)(st+1), s(t+1), s-1, t+1) where (s,t) is the order of the GQ.
The incidence graph whose vertices are the points and lines of the generalized quadrangle and two vertices are adjacent if one is a point, t
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https://en.wikipedia.org/wiki/General%20knowledge
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General knowledge is information that has been accumulated over time through various media and sources. It excludes specialized learning that can only be obtained with extensive training and information confined to a single medium. General knowledge is an essential component of crystallized intelligence. It is strongly associated with general intelligence and with openness to experience.
Studies have found that people who are highly knowledgeable in a particular domain tend to be knowledgeable in many. General knowledge is thought to be supported by long-term semantic memory ability. General knowledge also supports schemata for textual understanding.
Individual differences
Intelligence
High scorers on tests of general knowledge tend to also score highly on intelligence tests. IQ has been found to robustly predict general knowledge scores even after accounting for differences in age, and five-factor model personality traits. However, many general knowledge tests are designed to create a normal distribution of answers, creating a bell-shaped curve.
General knowledge is also moderately associated with verbal ability, though only weakly or not at all with numerical and spatial ability. As with crystallized intelligence, general knowledge has been found to increase with age.
Long-term semantic memory
General knowledge is stored as semantic memory. Most semantic memory is preserved through old age, though there are deficits in retrieval of certain specific words correlated with aging. In addition, stress or various emotional levels can negatively affect semantic memory retrieval.
Personality
People high in general knowledge tend to be highly open to new experiences and in typical intellectual engagement. The relationship between openness to experience and general knowledge remains robust even when IQ is taken into account. People high in openness may be more motivated to engage in intellectual pursuits that increase their knowledge. Relationships between general kno
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https://en.wikipedia.org/wiki/Cockade%20of%20Uruguay
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The National Cockade of Uruguay was first adopted by law on December 22, 1828. It features the colours of the national flag, blue and white.
Civilian and military usage
Civilian
The National cockade is used mainly by civilians. The period of civilian-military administration in Uruguay from 1973 to 1985 made a strict distinction between civilian and military usage somewhat fluid at times.
Military
The Military of Uruguay uses the Artigas's Cockade. This design is blue-white-blue with a red diagonal stripe.
Police usage
Meanwhile, the police uses a red-white-blue cockade design which is based on the Flag of the Treinta y Tres.
See also
Flag of Uruguay
Flag of Artigas
Flag of the Treinta y Tres
National symbols of Uruguay
Uruguay
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https://en.wikipedia.org/wiki/Non-stoichiometric%20compound
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Non-stoichiometric compounds are chemical compounds, almost always solid inorganic compounds, having elemental composition whose proportions cannot be represented by a ratio of small natural numbers (i.e. an empirical formula); most often, in such materials, some small percentage of atoms are missing or too many atoms are packed into an otherwise perfect lattice work.
Contrary to earlier definitions, modern understanding of non-stoichiometric compounds view them as homogeneous, and not mixtures of stoichiometric chemical compounds. Since the solids are overall electrically neutral, the defect is compensated by a change in the charge of other atoms in the solid, either by changing their oxidation state, or by replacing them with atoms of different elements with a different charge. Many metal oxides and sulfides have non-stoichiometric examples; for example, stoichiometric iron(II) oxide, which is rare, has the formula , whereas the more common material is nonstoichiometric, with the formula . The type of equilibrium defects in non-stoichiometric compounds can vary with attendant variation in bulk properties of the material. Non-stoichiometric compounds also exhibit special electrical or chemical properties because of the defects; for example, when atoms are missing, electrons can move through the solid more rapidly. Non-stoichiometric compounds have applications in ceramic and superconductive material and in electrochemical (i.e., battery) system designs.
Occurrence
Iron oxides
Nonstoichiometry is pervasive for metal oxides, especially when the metal is not in its highest oxidation state. For example, although wüstite (ferrous oxide) has an ideal (stoichiometric) formula , the actual stoichiometry is closer to . The non-stoichiometry reflect the ease of oxidation of to effectively replacing a small portion of with two thirds their number of . Thus for every three "missing" ions, the crystal contains two ions to balance the charge. The composition of a non-
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https://en.wikipedia.org/wiki/Cyclopamine
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Cyclopamine (11-deoxojervine) is a naturally occurring steroidal alkaloid. It is a teratogenic component of corn lily (Veratrum californicum), which when consumed during gestation has been demonstrated to induce birth defects, including the development of a single eye (cyclopia) in offspring. The molecule was named after this effect, which was originally observed by Idaho lamb farmers in 1957 after their herds gave birth to cycloptic lambs. It then took more than a decade to identify corn lily as the culprit. Later work suggested that differing rain patterns had changed grazing behaviours, which led to a greater quantity of corn lily to be ingested by pregnant sheep. Cyclopamine interrupts the sonic hedgehog signalling pathway, instrumental in early development, ultimately causing birth defects.
Discovery and naming
In 1957, Idaho sheep ranchers contacted the US Department of Agriculture (USDA) after their sheep gave birth to lambs with a fatal singular eye deformity. After collecting local flora and feeding them to mice, USDA scientists struggled to recreate the cyclopia. After a decade of trial and error, they came across wild corn lilies and advised the ranchers to avoid the corn lilies. Cyclopamine was discovered as one of three steroidal alkaloids isolated from Veratrum californicum and was named after its effects on sheep embryos. Four decades later, a team led by Professor Phillip Beachy linked the effect of cyclopamine to the sonic hedgehog gene. Cyclopia was induced through silencing the sonic hedgehog gene, suggesting Cyclopamine acted through a similar mechanism.
Source and structure
Cyclopamine consists of six rings, including a C-nor-D-homosteroid backbone linked to a octahydrofuro[3,2-b]pyridine system through a spirocentre. The molecule contains ten chiral centres, six of which at ring junctions.
The Veratrum species were found to contain five related families of alkaloid: (1) solanidine alkaloids, (2) verazine alkaloids, (3) veratramine alkaloid
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https://en.wikipedia.org/wiki/HomoloGene
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HomoloGene, a tool of the United States National Center for Biotechnology Information (NCBI), is a system for automated detection of homologs (similarity attributable to descent from a common ancestor) among the annotated genes of several completely sequenced eukaryotic genomes.
The HomoloGene processing consists of the protein analysis from the input organisms. Sequences are compared using blastp, then matched up and put into groups, using a taxonomic tree built from sequence similarity, where closer related organisms are matched up first, and then further organisms are added to the tree. The protein alignments are mapped back to their corresponding DNA sequences, and then distance metrics as molecular distances Jukes and Cantor (1969), Ka/Ks ratio can be calculated.
The sequences are matched up by using a heuristic algorithm for maximizing the score globally, rather than locally, in a bipartite matching (see complete bipartite graph). And then it calculates the statistical significance of each match. Cutoffs are made per position and Ks values are set to prevent false "orthologs" from being grouped together. “Paralogs” are identified by finding sequences that are closer within species than other species.
This resource ceased making updates in 2014.
Input organisms
Metazoa
Vertebrates
Homo sapiens, Pan troglodytes, Mus musculus, Rattus norvegicus, Canis lupus familiaris, Bos taurus, Gallus gallus, Xenopus tropicalis, Danio rerio"
Invertebrates
"Drosophila melanogaster, Anopheles gambiae, Caenorhabditis elegans"
Fungi
"Saccharomyces cerevisiae, Schizosaccharomyces pombe, Kluyveromyces lactis, Eremothecium gossypii, Magnaporthe grisea, Neurospora crassa"
Plants
Dicots
"Arabidopsis thaliana"
Monocots
"Oryza sativa"
Protista
"Plasmodium falciparum.
Interface
The HomoloGene is linked to all Entrez databases and based on homology and phenotype information of these links:
Mouse Genome Informatics (MGI),
Zebrafish Information Network (ZFIN),
Saccharomyce
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https://en.wikipedia.org/wiki/Leccinum%20scabrum
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Leccinum scabrum, commonly known as the rough-stemmed bolete, scaber stalk, and birch bolete, is an edible mushroom in the family Boletaceae, and was formerly classified as Boletus scaber. The birch bolete is widespread in Europe, in the Himalayas in Asia, and elsewhere in the Northern Hemisphere, occurring only in mycorrhizal association with birch trees. It fruits from June to October. This mushroom is also becoming increasingly common in Australia and New Zealand where it is likely introduced.
Description
The cap is wide. At first, it is hemispherical, and later becomes flatter. The skin of the cap is tan or brownish, usually with a lighter edge; it is smooth, bald, and dry to viscid.
The pores are whitish at a young age, later gray. In older specimens, the pores on the pileus can bulge out, while around the stipe they dent in strongly. The pore covering is easy to remove from the skin of the pileus.
The stipe is long and wide, slim, with white and dark to black flakes, and tapers upward. The basic mycelium is white.
The flesh is whitish, sometimes darkening following exposure. In young specimens, the meat is relatively firm, but it very soon becomes spongy and holds water, especially in rainy weather. When cooked, the meat of the birch bolete turns black.
Leccinum scabrum has been found in association with ornamental birch trees planted outside of its native range, such as in California.
Habitat and distribution
Leccinum scabrum is a European species that has been introduced to various areas of the world, mostly appearing in urban areas. In New Zealand, it associates solely with Betula pendula.
Uses
The birch bolete is edible but considered not to be worthwhile by some guides. It can be pickled in brine or vinegar. It is used also in mixed mushroom dishes, fried or steamed.
It is commonly harvested for food in Finland and Russia.
A few reports in North America (New England and the Rocky Mountains) after 2009 suggest that Leccinums (birch boletes) sho
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https://en.wikipedia.org/wiki/Grid%20dip%20oscillator
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"Dip meter" can also refer to an influential early commercial expert system called Dipmeter Advisor; or may refer to an instrument that measures the magnetic dip angle of Earth's magnetic field, the field line angle in a vertical plane.
Grid dip oscillator (GDO), also called grid dip meter, gate dip meter, dip meter, or just dipper, is a type of electronic instrument that measures the resonant frequency of nearby unconnected radio frequency tuned circuits. It is a variable-frequency oscillator that circulates a small-amplitude signal through an exposed coil, whose electromagnetic field can interact with adjacent circuitry. The oscillator loses power when its coil is near a circuit that resonates at the same frequency. A meter on the GDO registers the amplitude drop, or "dip", hence the name.
Dip oscillators have been widely used by amateur radio operators for measuring the properties of resonant circuits, filters, and antennas. They can also be used for transmission line testing, as signal generators, and for measuring inductance and capacitance of components. Measurement with a GDO is called "dipping" a circuit.
Principle of operation
Central to the dip meter is a high-frequency variable-frequency oscillator with a calibrated tuning capacitor and matching interchangeable coils, as shown in the circuit diagram on the right. Resonance is indicated by a dip in amplitude of the signal within the GDO, by a meter on the device.
When the oscillator's exposed coil is in the vicinity of another resonant circuit, the coupled pair behaves as a low-Q transformer whose coupling is most effective when their respective resonant frequencies match. The degree of coupling affects the frequency and amplitude of oscillation in the dip meter, which is sensed in any of several ways, the simplest and most usual of which is a built-in microammeter. The distance between the coil and the tested circuit needs to be adjusted carefully so that the GDO amplitude is significantly affected
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https://en.wikipedia.org/wiki/Design%20marker
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In software engineering, a design marker is a technique of documenting design choices in source code using the Marker Interface pattern. Marker interfaces have traditionally been limited to those interfaces intended for explicit, runtime verification (normally via instanceof). A design marker is a marker interface used to document a design choice. In Java programs the design choice is documented in the marker interface's Javadoc documentation.
Many choices made at software design time cannot be directly expressed in today's implementation languages like C# and Java. These design choices (known by names like Design Pattern, Design Contract, Refactoring, Effective Programming Idioms, Blueprints, etc.) must be implemented via programming and naming conventions, because they go beyond the built-in functionality of production programming languages. The consequences of this limitation conspire over time to erode design investments as well as to promote a false segregation between the designer and implementer mindsets.
Two independent proposals recognize these problems and give the same basic strategies for tackling them. Until now, the budding explicit programming movement has been linked to the use of an experimental Java research tool called ELIDE. The Design Markers technique requires only standard Javadoc-like tools to garner many of the benefits of Explicit Programming.
See also
Design Patterns
Marker interface pattern
External links
Design Markers: Explicit Programming for the rest of us
Design Markers home page
Explicit Programming manifesto
Software design
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https://en.wikipedia.org/wiki/Polar%20space
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In mathematics, in the field of geometry, a polar space of rank n (), or projective index , consists of a set P, conventionally called the set of points, together with certain subsets of P, called subspaces, that satisfy these axioms:
Every subspace is isomorphic to a projective space with and K a division ring. (That is, it is a Desarguesian projective geometry.) For each subspace the corresponding d is called its dimension.
The intersection of two subspaces is always a subspace.
For each subspace A of dimension and each point p not in A, there is a unique subspace B of dimension containing p and such that is -dimensional. The points in are exactly the points of A that are in a common subspace of dimension 1 with p.
There are at least two disjoint subspaces of dimension .
It is possible to define and study a slightly bigger class of objects using only relationship between points and lines: a polar space is a partial linear space (P,L), so that for each point p ∈ P and
each line l ∈ L, the set of points of l collinear to p, is either a singleton or the whole l.
Finite polar spaces (where P is a finite set) are also studied as combinatorial objects.
Generalized quadrangles
A polar space of rank two is a generalized quadrangle; in this case, in the latter definition, the set of points of a line collinear with a point p is the whole of only if p ∈ . One recovers the former definition from the latter under the assumptions that lines have more than 2 points, points lie on more than 2 lines, and there exist a line and a point p not on so that p is collinear to all points of .
Finite classical polar spaces
Let be the projective space of dimension over the finite field and let be a reflexive sesquilinear form or a quadratic form on the underlying vector space. The elements of the finite classical polar space associated with this form are the elements of the totally isotropic subspaces (when is a sesquilinear form) or the totally singular subspa
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https://en.wikipedia.org/wiki/Hyperbolic%20equilibrium%20point
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In the study of dynamical systems, a hyperbolic equilibrium point or hyperbolic fixed point is a fixed point that does not have any center manifolds. Near a hyperbolic point the orbits of a two-dimensional, non-dissipative system resemble hyperbolas. This fails to hold in general. Strogatz notes that "hyperbolic is an unfortunate name—it sounds like it should mean 'saddle point'—but it has become standard." Several properties hold about a neighborhood of a hyperbolic point, notably
A stable manifold and an unstable manifold exist,
Shadowing occurs,
The dynamics on the invariant set can be represented via symbolic dynamics,
A natural measure can be defined,
The system is structurally stable.
Maps
If is a C1 map and p is a fixed point then p is said to be a hyperbolic fixed point when the Jacobian matrix has no eigenvalues on the unit circle.
One example of a map whose only fixed point is hyperbolic is Arnold's cat map:
Since the eigenvalues are given by
We know that the Lyapunov exponents are:
Therefore it is a saddle point.
Flows
Let be a C1 vector field with a critical point p, i.e., F(p) = 0, and let J denote the Jacobian matrix of F at p. If the matrix J has no eigenvalues with zero real parts then p is called hyperbolic. Hyperbolic fixed points may also be called hyperbolic critical points or elementary critical points.
The Hartman–Grobman theorem states that the orbit structure of a dynamical system in a neighbourhood of a hyperbolic equilibrium point is topologically equivalent to the orbit structure of the linearized dynamical system.
Example
Consider the nonlinear system
(0, 0) is the only equilibrium point. The Jacobian matrix of the linearization at the equilibrium point is
The eigenvalues of this matrix are . For all values of α ≠ 0, the eigenvalues have non-zero real part. Thus, this equilibrium point is a hyperbolic equilibrium point. The linearized system will behave similar to the non-linear system near (0, 0). When α
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https://en.wikipedia.org/wiki/Center%20manifold
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In the mathematics of evolving systems, the concept of a center manifold was originally developed to determine stability of degenerate equilibria. Subsequently, the concept of center manifolds was realised to be fundamental to mathematical modelling.
Center manifolds play an important role in bifurcation theory because interesting behavior takes place on the center manifold and in multiscale mathematics because the long time dynamics of the micro-scale often are attracted to a relatively simple center manifold involving the coarse scale variables.
Informal description
Saturn's rings capture much center-manifold geometry. Dust particles in the rings are subject to tidal forces, which act characteristically to "compress and stretch". The forces compress particle orbits into the rings, stretch particles along the rings, and ignore small shifts in ring radius. The compressing direction defines the stable manifold, the stretching direction defining the unstable manifold, and the neutral direction is the center manifold.
While geometrically accurate, one major difference distinguishes Saturn's rings from a physical center manifold. Like most dynamical systems, particles in the rings are governed by second-order laws. Understanding trajectories requires modeling position and a velocity/momentum variable, to give a tangent manifold structure called phase space. Physically speaking, the stable, unstable and neutral manifolds of Saturn's ring system do not divide up the coordinate space for a particle's position; they analogously divide up phase space instead.
The center manifold typically behaves as an extended collection of saddle points. Some position-velocity pairs are driven towards the center manifold, while others are flung away from it. Small perturbations that generally push them about randomly, and often push them out of the center manifold. There are, however, dramatic counterexamples to instability at the center manifold, called Lagrangian coheren
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https://en.wikipedia.org/wiki/Homoclinic%20orbit
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In the study of dynamical systems, a homoclinic orbit is a path through phase space which joins a saddle equilibrium point to itself. More precisely, a homoclinic orbit lies in the intersection of the stable manifold and the unstable manifold of an equilibrium. It is a heteroclinic orbit–a path between any two equilibrium points–in which the endpoints are one and the same.
Consider the continuous dynamical system described by the ordinary differential equation
Suppose there is an equilibrium at , then a solution is a homoclinic orbit if
If the phase space has three or more dimensions, then it is important to consider the topology of the unstable manifold of the saddle point. The figures show two cases. First, when the stable manifold is topologically a cylinder, and secondly, when the unstable manifold is topologically a Möbius strip; in this case the homoclinic orbit is called twisted.
Discrete dynamical system
Homoclinic orbits and homoclinic points are defined in the same way for iterated functions, as the intersection of the stable set and unstable set of some fixed point or periodic point of the system.
We also have the notion of homoclinic orbit when considering discrete dynamical systems. In such a case, if is a diffeomorphism of a manifold , we say that is a homoclinic point if it has the same past and future - more specifically, if there exists a fixed (or periodic) point
such that
Properties
The existence of one homoclinic point implies the existence of an infinite number of them.
This comes from its definition: the intersection of a stable and unstable set. Both sets are invariant by definition, which means that the forward iteration of the homoclinic point is both on the stable and unstable set. By iterating N times, the map approaches the equilibrium point by the stable set, but in every iteration it is on the unstable manifold too, which shows this property.
This property suggests that complicated dynamics arise by the existence of a hom
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https://en.wikipedia.org/wiki/Heteroclinic%20orbit
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[[Image:Heteroclinic orbit in pendulum phaseportrait.png|thumb|right|The phase portrait of the pendulum equation {{math|1=''x + sin x = 0}}. The highlighted curve shows the heteroclinic orbit from to . This orbit corresponds with the (rigid) pendulum starting upright, making one revolution through its lowest position, and ending upright again.]]
In mathematics, in the phase portrait of a dynamical system, a heteroclinic orbit (sometimes called a heteroclinic connection) is a path in phase space which joins two different equilibrium points. If the equilibrium points at the start and end of the orbit are the same, the orbit is a homoclinic orbit.
Consider the continuous dynamical system described by the ordinary differential equation
Suppose there are equilibria at Then a solution is a heteroclinic orbit from to if both limits are satisfied:
This implies that the orbit is contained in the stable manifold of and the unstable manifold of .
Symbolic dynamics
By using the Markov partition, the long-time behaviour of hyperbolic system can be studied using the techniques of symbolic dynamics. In this case, a heteroclinic orbit has a particularly simple and clear representation. Suppose that is a finite set of M symbols. The dynamics of a point x is then represented by a bi-infinite string of symbols
A periodic point of the system is simply a recurring sequence of letters. A heteroclinic orbit is then the joining of two distinct periodic orbits. It may be written as
where is a sequence of symbols of length k, (of course, ), and is another sequence of symbols, of length m (likewise, ). The notation simply denotes the repetition of p an infinite number of times. Thus, a heteroclinic orbit can be understood as the transition from one periodic orbit to another. By contrast, a homoclinic orbit can be written as
with the intermediate sequence being non-empty, and, of course, not being p, as otherwise, the orbit would simply be .
See also
Heteroclinic co
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https://en.wikipedia.org/wiki/Sucker%20bet
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A sucker bet is a gambling wager in which the expected return does not reflect the odds of winning, and is significantly lower. For example, the chances of correctly guessing the order of the final three cards in a game of Faro is usually 1 in 6, yet the bet only pays 4:1 or 5:1. The complexity of the game can disguise the nature of the odds, so that the player does not realise that they are taking a sucker bet.
The name originates in that sucker bets are often created to lure inexperienced players into betting against large odds, blinded by the offer of "fast money".
Variants include:
Parlay: One bet ticket written with at least two wagers (all must win for the ticket to cash).
Teaser: A sucker wager that allows bettors to add and subtract points from posted odds.
Exotic: Any wager other than a straight bet or parlay (also referred to as a proposition or prop).
Taking insurance in blackjack is also often considered a sucker bet.
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https://en.wikipedia.org/wiki/Intelligence%20amplification
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Intelligence amplification (IA) (also referred to as cognitive augmentation, machine augmented intelligence and enhanced intelligence) refers to the effective use of information technology in augmenting human intelligence. The idea was first proposed in the 1950s and 1960s by cybernetics and early computer pioneers.
IA is sometimes contrasted with AI (artificial intelligence), that is, the project of building a human-like intelligence in the form of an autonomous technological system such as a computer or robot. AI has encountered many fundamental obstacles, practical as well as theoretical, which for IA seem moot, as it needs technology merely as an extra support for an autonomous intelligence that has already proven to function. Moreover, IA has a long history of success, since all forms of information technology, from the abacus to writing to the Internet, have been developed basically to extend the information processing capabilities of the human mind (see extended mind and distributed cognition).
Major contributions
William Ross Ashby: Intelligence Amplification
The term intelligence amplification (IA) has enjoyed a wide currency since William Ross Ashby wrote of "amplifying intelligence" in his Introduction to Cybernetics (1956). Related ideas were explicitly proposed as an alternative to Artificial Intelligence by Hao Wang from the early days of automatic theorem provers.
J. C. R. Licklider: Man-Computer Symbiosis
"Man-Computer Symbiosis" is a key speculative paper published in 1960 by psychologist/computer scientist J.C.R. Licklider, which envisions that mutually-interdependent, "living together", tightly-coupled human brains and computing machines would prove to complement each other's strengths to a high degree:
In Licklider's vision, many of the pure artificial intelligence systems envisioned at the time by over-optimistic researchers would prove unnecessary. (This paper is also seen by some historians as marking the genesis of ideas about computer
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https://en.wikipedia.org/wiki/Cyclic%20compound
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A cyclic compound (or ring compound) is a term for a compound in the field of chemistry in which one or more series of atoms in the compound is connected to form a ring. Rings may vary in size from three to many atoms, and include examples where all the atoms are carbon (i.e., are carbocycles), none of the atoms are carbon (inorganic cyclic compounds), or where both carbon and non-carbon atoms are present (heterocyclic compounds with rings containing both carbon and non-carbon). Depending on the ring size, the bond order of the individual links between ring atoms, and their arrangements within the rings, carbocyclic and heterocyclic compounds may be aromatic or non-aromatic; in the latter case, they may vary from being fully saturated to having varying numbers of multiple bonds between the ring atoms. Because of the tremendous diversity allowed, in combination, by the valences of common atoms and their ability to form rings, the number of possible cyclic structures, even of small size (e.g., < 17 total atoms) numbers in the many billions.
Adding to their complexity and number, closing of atoms into rings may lock particular atoms with distinct substitution (by functional groups) such that stereochemistry and chirality of the compound results, including some manifestations that are unique to rings (e.g., configurational isomers). As well, depending on ring size, the three-dimensional shapes of particular cyclic structures – typically rings of five atoms and larger – can vary and interconvert such that conformational isomerism is displayed. Indeed, the development of this important chemical concept arose historically in reference to cyclic compounds. Finally, cyclic compounds, because of the unique shapes, reactivities, properties, and bioactivities that they engender, are the majority of all molecules involved in the biochemistry, structure, and function of living organisms, and in man-made molecules such as drugs, pesticides, etc.
Structure and classification
A cy
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https://en.wikipedia.org/wiki/Balanced%20prime
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In number theory, a balanced prime is a prime number with equal-sized prime gaps above and below it, so that it is equal to the arithmetic mean of the nearest primes above and below. Or to put it algebraically, given a prime number , where is its index in the ordered set of prime numbers,
For example, 53 is the sixteenth prime; the fifteenth and seventeenth primes, 47 and 59, add up to 106, and half of that is 53; thus 53 is a balanced prime.
Examples
The first few balanced primes are
5, 53, 157, 173, 211, 257, 263, 373, 563, 593, 607, 653, 733, 947, 977, 1103, 1123, 1187, 1223, 1367, 1511, 1747, 1753, 1907, 2287, 2417, 2677, 2903 .
Infinitude
It is conjectured that there are infinitely many balanced primes.
Three consecutive primes in arithmetic progression is sometimes called a CPAP-3. A balanced prime is by definition the second prime in a CPAP-3. the largest known CPAP-3 has 15004 digits and was found by Serge Batalov. It is:
The value of n (its rank in the sequence of all primes) is not known.
Generalization
The balanced primes may be generalized to the balanced primes of order n. A balanced prime of order n is a prime number that is equal to the arithmetic mean of the nearest n primes above and below. Algebraically, given a prime number , where k is its index in the ordered set of prime numbers,
Thus, an ordinary balanced prime is a balanced prime of order 1. The sequences of balanced primes of orders 2, 3, and 4 are given as sequences , , and in the OEIS respectively.
See also
Strong prime, a prime that is greater than the arithmetic mean of its two neighboring primes
Interprime, a composite number balanced between two prime neighbours
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https://en.wikipedia.org/wiki/Tone%20hole
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A tone hole is an opening in the body of a wind instrument which, when alternately closed and opened, changes the pitch of the sound produced. Tone holes may serve specific purposes, such as a trill hole or register hole. A tone hole is, "in wind instruments[,] a hole that may be stopped by the finger, or a key, to change the pitch of the tone produced."
The resonant frequencies of the air column in a pipe are inversely proportional to the pipe's effective length. In other words, a shorter pipe produces higher notes. For a pipe with no tone holes but open at both ends, the effective length is the physical length of the pipe plus a little more for the small volumes of air just beyond the ends of the pipe that are also involved in the resonance. An open hole anywhere along the middle of the pipe shortens the pipe's effective length and therefore raises the pitch of the notes it produces. The closer an open hole is to the blowing end, the shorter the remaining effective length is and the more it raises the pitch. Generally, a hole in a given position doesn't reduce the effective length quite as much as cutting the pipe at that position would, and the smaller the hole, the less it reduces the effective length when open. Closing the hole increases the effective length and lowers the pitch again. However, a pipe with a closed tone hole is not acoustically identical to a pipe with no hole; the shape of the fingertip or pad that closes the hole modifies the pipe's internal volume and effective length.
When there are multiple tone holes, the first (closest to the blowing end) open tone hole usually has the largest influence on the pipe's effective length. However, closing holes below the first open hole without closing the first hole can also lower the pitch significantly; such cross fingerings may often be useful. Generally, the pitch and timbre of the notes produced will depend on the positions, sizes, heights, and shapes of all the tone holes, both open and closed. Theo
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https://en.wikipedia.org/wiki/Peixoto%27s%20theorem
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In the theory of dynamical systems, Peixoto's theorem, proved by Maurício Peixoto, states that among all smooth flows on surfaces, i.e. compact two-dimensional manifolds, structurally stable systems may be characterized by the following properties:
The set of non-wandering points consists only of periodic orbits and fixed points.
The set of fixed points is finite and consists only of hyperbolic equilibrium points.
Finiteness of attracting or repelling periodic orbits.
Absence of saddle-to-saddle connections.
Moreover, they form an open set in the space of all flows endowed with C1 topology.
See also
Andronov–Pontryagin criterion
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https://en.wikipedia.org/wiki/Phytofluene
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Phytofluene is a colorless carotenoid found naturally in tomatoes and other vegetables. It is the second product of carotenoid biosynthesis. It is formed from phytoene in a desaturation reaction leading to the formation of five conjugated double bonds. In the following step, addition of carbon-carbon conjugated double bonds leads to the formation of z-carotene and appearance of visible color.
Phytofluene has an absorption spectra in the UVA range, with maximal absorption at 348 nm and with ε1% of 1557.
Analysis of several fruits and vegetables showed that phytoene and phytofluene are found in majority of fruits and vegetables. In contrast to all other carotenoids, phytoene and phytofluene, the first carotenoid precursors in the biosynthetic pathway of other carotenoids absorb light in the UV range.
Dietary phytoene and phytofluene are accumulated in human skin. The accumulation of these carotenoids may protect the skin by several mechanisms: acting as UV absorbers, as antioxidants, as anti-inflammatory agents.
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https://en.wikipedia.org/wiki/Vicine
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Vicine is an alkaloid glycoside found mainly in fava beans, which are also called broad beans (Vicia faba). Vicine is toxic in individuals who have a hereditary loss of the enzyme glucose-6-phosphate dehydrogenase. It causes haemolytic anaemia, called favism. The formation of vicine in Vicia faba has been studied, but this natural formation has not yet been found.
History
Vicine was initially isolated in 1870 from the seeds of Vicia sativa by a method of extraction with sulfuric acid and subsequent precipitation with mercury sulfate (HgSO4). Later vicine was also found in other Vicia species, namely Vicia faba, beet juice and peas. The chemical structure of the compound was built gradually. First the glycosidic nature of the compound was recognized in 1896. The same year the aglycone of vicine, divicine, was isolated. In the beginning of the 20th century the pyrimidine structure was recognized. Despite these initial successes, the correct formula of vicine was determined only in 1953 and it is 2,4-diamino-6-oxypyrimidine-5-(ß-d-glucopyranoside).
Metabolism
Vicine is an inactive compound in the body. When vicine enters the body through food, it is hydrolysed by the intestinal microflora to a highly reactive free radical generating compound, the aglycone divicine. Upon hydrolysis, the glucose part of the molecule is split off and that results in the reduced divicine. Divicine is then taken up in the blood through the intestinal epithelium.
Adverse effects
Adverse effects almost solely occur in humans that suffer from glucose-6-phosphate dehydrogenase deficiency. This deficiency causes a shortage of glutathione in erythrocytes and glutathione is needed for the neutralization of ROS (reactive oxygen species) created by the strongly oxidizing agent divicine.
Indications
Persons with G6PD deficiency are asymptomatic. An attack of acute haemolytic anaemia can appear out of nowhere and can be very severe and life-threatening. Indications of such a sudden attack of f
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https://en.wikipedia.org/wiki/Diode%20modelling
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In electronics, diode modelling refers to the mathematical models used to approximate the actual behaviour of real diodes to enable calculations and circuit analysis. A diode's I-V curve is nonlinear.
A very accurate, but complicated, physical model composes the I-V curve from three exponentials with a slightly different steepness (i.e. ideality factor), which correspond to different recombination mechanisms in the device; at very large and very tiny currents the curve can be continued by linear segments (i.e. resistive behaviour).
In a relatively good approximation a diode is modelled by the single-exponential Shockley diode law. This nonlinearity still complicates calculations in circuits involving diodes
so even simpler models are often used.
This article discusses the modelling of p-n junction diodes, but the techniques may be generalized to other solid state diodes.
Large-signal modelling
Shockley diode model
The Shockley diode equation relates the diode current of a p-n junction diode to the diode voltage . This relationship is the diode I-V characteristic:
,
where is the saturation current or scale current of the diode (the magnitude of the current that flows for negative in excess of a few , typically 10−12A). The scale current is proportional to the cross-sectional area of the diode. Continuing with the symbols: is the thermal voltage (, about 26 mV at normal temperatures), and is known as the diode ideality factor (for silicon diodes is approximately 1 to 2).
When the formula can be simplified to:
.
This expression is, however, only an approximation of a more complex I-V characteristic. Its applicability is particularly limited in case of ultrashallow junctions, for which better analytical models exist.
Diode-resistor circuit example
To illustrate the complications in using this law, consider the problem of finding the voltage across the diode in Figure 1.
Because the current flowing through the diode is the same as the current thro
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https://en.wikipedia.org/wiki/El%20Nombre
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El Nombre is a children's educational programme about an anthropomorphic Mexican gerbil character, originally from a series of educational sketches on Numbertime, the BBC schools programme about mathematics. He was also the only character to appear in all Numbertime episodes. His voice was provided by Steve Steen, while the other characters' voices were provided by Sophie Aldred, Kate Robbins, and (from 1999) former Blue Peter host Janet Ellis. For the ninth (and final) series of Numbertime in 2001, Michael Fenton-Stevens also provided voices of certain other characters in the El Nombre sketches.
The character's name means "The Name" in Spanish, not "The Number", which would be "El Número", but does mean "The Number" in Catalan.
Setting
El Nombre is set in the fictional town of Santa Flamingo (originally known as Santo Flamingo), home of Little Juan, his Mama, Pedro Gonzales, Juanita Conchita, Maria Consuela Tequila Chiquita, Little Pepita Consuela Tequila Chiquita, Tanto the tarantula, Señor Gelato the ice-cream seller, Leonardo de Sombrero the pizza delivery boy, Señor Calculo the bank manager, Señor Manuel the greengrocer, Miss Constanza Bonanza the school teacher, Señora Fedora the balloon seller and mayor, Señor Loco the steam engine driver, Señor Chipito the carpenter and the local bandit Don Fandango (although it was not actually given a name until the fifth series of Numbertime premiered in January 1998); whenever he was needed, El Nombre swung into action to solve the townspeople's simple mathematical problems, usually talking in rhyme. His character was a parody of the fictional hero Zorro, wearing a similar black cowl mask and huge sombrero, appearing unexpectedly to save the townsfolk from injustice, and generally swinging around on his bullwhip – however, unlike Zorro, he was often quite inept (in fact, on one occasion, Tanto tipped a bucket of water onto him after he made him reenact the Incy Wincy Spider rhyme).
When El Nombre first appeared on Nu
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https://en.wikipedia.org/wiki/Gain%20compression
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Gain compression is a reduction in differential or slope gain caused by nonlinearity of the transfer function of the amplifying device. This nonlinearity may be caused by heat due to power dissipation or by overdriving the active device beyond its linear region. It is a large-signal phenomenon of circuits.
Relevance
Gain compression is relevant in any system with a wide dynamic range, such as audio or RF. It is more common in tube circuits than transistor circuits, due to topology differences, possibly causing the differences in audio performance called "valve sound". The front-end RF amps of radio receivers are particularly susceptible to this phenomenon when overloaded by a strong unwanted signal.
Audio effects
A tube radio or tube amplifier will increase in volume to a point, and then as the input signal extends beyond the linear range of the device, the effective gain is reduced, altering the shape of the waveform. The effect is also present in transistor circuits. The extent of the effect depends on the topology of the amplifier.
Differences between clipping and compression
Clipping, as a form of signal compression, differs from the operation of the typical studio audio level compressor, in which gain compression is not instantaneous (delayed in time via attack and release settings).
Clipping destroys any audio information which is over a certain threshold. Compression and limiting, change the shape of the entire waveform, not just the shape of the waveform above the threshold. This is why it is possible to limit and compress with very high ratios without causing distortion.
Limiting or clipping
Gain is a linear operation. Gain compression is not linear and, as such, its effect is one of distortion, due to the nonlinearity of the transfer characteristic which also causes a loss of 'slope' or 'differential' gain. So the output is less than expected using the small signal gain of the amplifier.
In clipping, the signal is abruptly limited to a cert
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https://en.wikipedia.org/wiki/Dilator%20naris%20muscle
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The dilator naris muscle (or alae nasi muscle) is a part of the nasalis muscle. It has an anterior and a posterior part. It has origins from the nasal notch of the maxilla and the major alar cartilage, and a single insertion near the margin of the nostril. It controls nostril width, including changes during breathing. Its function can be tested as an analogue for the function of the facial nerve (VII), which supplies it.
Structure
The dilator naris muscle is divided into posterior and anterior parts.
The dilator naris posterior is placed partly beneath the levator labii superioris muscle. It arises from the margin of the nasal notch of the maxilla, and from the minor alar cartilages. It is inserted into the skin near the margin of the nostril.
The dilator naris anterior is a delicate fasciculus. It originates from the lateral crus of the major alar cartilage, more laterally. It inserts into the margin of the nostril, the alar groove. It is situated in front of the dilatator naris posterior muscle.
Nerve supply
The dilator naris muscle is supplied by the facial nerve (VII).
Function
The dilator naris muscle has a role in widening and narrowing the nostril, along with other muscles. It may prevent the collapse of the nostril during inhalation, particularly in people with narrower nostrils. The respiratory centre of the brainstem can use the muscle to control nostril width in relation to breathing. It also moves the tip of the nose slightly.
Clinical significance
The function of the dilator naris muscle can be used as an analogue for the activity of the facial nerve (VII).
History
The dilator naris muscle may also be known as the alae nasi muscle.
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https://en.wikipedia.org/wiki/Arytenoid%20muscle
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The arytenoid muscle or interarytenoid muscle is a composite intrinsic muscle of the larynx, consisting of a transverse part and an oblique part - the two parts may be considered as separate muscles: an unpaired transverse arytenoid muscle, and a bilaterally paired oblique arytenoid muscle.
The two constituent parts differ in their attachments, structure and actions. Both receive motor innervation from the recurrent laryngeal nerve(s) (each nerve being a branch of one vagus nerve (CN X)).
Clinical significance
Electromyography
Function of the arytenoid muscle is a good method to determine function of the recurrent laryngeal nerve. Continuous electromyography of the arytenoid muscle can provide confidence to surgeons that the recurrent laryngeal nerve is not damaged during neck surgeries, such as thyroidectomy.
Other animals
The arytenoid muscle is found in many animals, including dogs.
Additional images
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https://en.wikipedia.org/wiki/Thyroarytenoid%20muscle
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The thyroarytenoid muscle is a broad, thin muscle that forms the body of the vocal fold and that supports the wall of the ventricle and its appendix. It functions to shorten the vocal folds.
Structure
It arises in front from the lower half of the angle of the thyroid cartilage, and from the middle cricothyroid ligament.
Its fibers pass backward and laterally, to be inserted into the base and anterior surface of the arytenoid cartilage.
Parts
The lower and deeper fibers of the muscle can be differentiated as a triangular band which is inserted into the vocal process of the arytenoid cartilage, and into the adjacent portion of its anterior surface; it is termed the Vocalis, and lies parallel with the vocal ligament, to which it is adherent.
The vocal muscle is the upper portion of the thyroarytenoid muscle which is primarily involved in producing speech.
A considerable number of the fibers of the thyroarytenoid muscle are prolonged into the aryepiglottic fold, where some of them become lost, while others are continued to the margin of the epiglottis. They have received a distinctive name, thyroepiglottic muscle, thyreoepiglotticus or thyroepiglottic, and are sometimes described as a separate muscle.
A few fibers extend along the wall of the ventricle from the lateral wall of the arytenoid cartilage to the side of the epiglottis and constitute the ventricularis muscle.
Function
The thyroarytenoid muscle, consisting of two parts having different attachments and different directions, is rather complicated regarding its action.
Its main use is to draw the arytenoid cartilages forward toward the thyroid, thus relaxing and shortening the vocal folds.
But, owing to the connection of the deeper portion with the vocal fold, this part, if acting separately, is supposed to modify its elasticity and tension, while the lateral portion rotates the arytenoid cartilage inward, and thus narrows the rima glottidis by bringing the two vocal folds together.
Additional images
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https://en.wikipedia.org/wiki/Chondroglossus
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The chondroglossus muscle is a muscle of the tongue. It arises from the medial side of the lesser horn of the hyoid bone, before blending with intrinsic muscles of the tongue. It is supplied by the hypoglossal nerve.
Structure
The chondroglossus muscle is about 2 cm long. It arises from the medial side and base of the lesser horn of the hyoid bone. It passes directly upward. It then inserts by blending with the intrinsic muscles of the tongue, between the hyoglossus and genioglossus.
The chondroglossus muscle is sometimes described as a part of the hyoglossus. However, is separated from it by fibers of the genioglossus, which pass to the side of the pharynx.
Nerve supply
The chondroglossus muscle is supplied by the first lateral branch of the hypoglossal nerve. Some studies have found that it does not contain proprioceptive spindles to determine stretch.
Clinical significance
The chondroglossus muscle may be cut in the suprahyoid release surgery, which can be used during resection of the trachea.
Additional images
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https://en.wikipedia.org/wiki/Pair%20bond
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In biology, a pair bond is the strong affinity that develops in some species between a mating pair, often leading to the production and rearing of offspring and potentially a lifelong bond. Pair-bonding is a term coined in the 1940s that is frequently used in sociobiology and evolutionary biology circles. The term often implies either a lifelong socially monogamous relationship or a stage of mating interaction in socially monogamous species. It is sometimes used in reference to human relationships.
Varieties
According to evolutionary psychologists David P. Barash and Judith Lipton, from their 2001 book The Myth of Monogamy, there are several varieties of pair bonds:
Short-term pair-bond: a transient mating or associations
Long-term pair-bond: bonded for a significant portion of the life cycle of that pair
Lifelong pair-bond: mated for life
Social pair-bond: attachments for territorial or social reasons
Clandestine pair-bond: quick extra-pair copulations
Dynamic pair-bond: e.g. gibbon mating systems being analogous to "divorce"
Human pair bonding
Humans can experience all of the above-mentioned varieties of pair bonds. These bonds can be temporary or last a lifetime. Pair bonding is a behavioral and physiological bond between two mated individuals, and is rare among non-human primates. Humans also engage in social pair bonding, where two individuals will form a close relationship that does not involve sex. In humans and other vertebrates, pair bonds are created by a combination of social interaction and biological factors including neurotransmitters like oxytocin, vasopressin, and dopamine.
Pair bonds are a biological phenomenon and are not equivalent to the human social institution of marriage. Married couples are not necessarily pair bonded. Marriage may be a consequence of pair bonding and vice versa. One of the functions of romantic love is pair bonding.
Examples
Birds
Close to ninety percent of known avian species are monogamous, compared to five percent
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https://en.wikipedia.org/wiki/Extinction%20vortex
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Extinction vortices are a class of models through which conservation biologists, geneticists and ecologists can understand the dynamics of and categorize extinctions in the context of their causes. This model shows the events that ultimately lead small populations to become increasingly vulnerable as they spiral toward extinction. Developed by M. E. Gilpin and M. E. Soulé in 1986, there are currently four classes of extinction vortices. The first two (R and D) deal with environmental factors that have an effect on the ecosystem or community level, such as disturbance, pollution, habitat loss etc. Whereas the second two (F and A) deal with genetic factors such as inbreeding depression and outbreeding depression, genetic drift etc.
Types of vortices
R Vortex: The R vortex is initiated when there is a disturbance which facilitates a lowering of population size (N) and a corresponding increase in variability (Var(r)). This event can make populations vulnerable to additional disturbances which will lead to further decreases in population size (N) and further increases in variability (Var(r)). A prime example of this would be the disruption of sex ratios in a population away from the species optimum.
D Vortex: The D vortex is initiated when population size (N) decreases and variability (Var(r)) increases such that the spatial distribution (D) of the population is increased and the population becomes "patchy" or fragmented. Within these fragments, local extinction rates increase which, through positive feedback, further increases D.
F Vortex: The F vortex is initiated by a decrease in population size (N) which leads to a decrease in heterozygosity, and therefore a decrease in genetic diversity. Decreased population size makes the effects of genetic drift more prominent, resulting in increased risk of inbreeding depression and an increase in population genetic load, which over time will result in extinction.
A Vortex: The A vortex is a result of an increase in the impact
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https://en.wikipedia.org/wiki/Juxtacrine%20signalling
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In biology, juxtacrine signalling (or contact-dependent signalling) is a type of cell–cell or cell–extracellular matrix signalling in multicellular organisms that requires close contact. In this type of signalling, a ligand on one surface binds to a receptor on another adjacent surface. Hence, this stands in contrast to releasing a signaling molecule by diffusion into extracellular space, the use of long-range conduits like membrane nanotubes and cytonemes (akin to 'bridges') or the use of extracellular vesicles like exosomes or microvesicles (akin to 'boats'). There are three types of juxtacrine signaling:
A membrane-bound ligand (protein, oligosaccharide, lipid) and a membrane protein of two adjacent cells interact.
A communicating junction links the intracellular compartments of two adjacent cells, allowing transit of relatively small molecules.
An extracellular matrix glycoprotein and a membrane protein interact.
Additionally, in unicellular organisms such as bacteria, juxtacrine signaling refers to interactions by membrane contact.
Juxtacrine signaling has been observed for some growth factors, cytokine and chemokine cellular signals, playing an important role in the immune response. It has a critical role in development, particularly of cardiac and neural function. Other types of cell signaling include paracrine signalling and autocrine signalling. Paracrine signaling occurs over short distances, while autocrine signaling involves a cell responding to its own paracrine factors.
The term "juxtacrine" was originally introduced by Anklesaria et al. (1990) to describe a possible way of signal transduction between TGF alpha and EGFR.
Cell–cell signaling
In this type of signaling, specific membrane-bound ligands bind to a cell’s membrane. A cell with the appropriate cell surface receptor or cell adhesion molecule can bind to it. An important example is the Notch signaling pathway, notably involved in neural development. In the Notch signaling pathway for verte
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https://en.wikipedia.org/wiki/FLAG-tag
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FLAG-tag, or FLAG octapeptide, or FLAG epitope, is a peptide protein tag that can be added to a protein using recombinant DNA technology, having the sequence DYKDDDDK (where D=aspartic acid, Y=tyrosine, and K=lysine). It is one of the most specific tags and it is an artificial antigen to which specific, high affinity monoclonal antibodies have been developed and hence can be used for protein purification by affinity chromatography and also can be used for locating proteins within living cells. FLAG-tag has been used to separate recombinant, overexpressed protein from wild-type protein expressed by the host organism. FLAG-tag can also be used in the isolation of protein complexes with multiple subunits, because FLAG-tag's mild purification procedure tends not to disrupt such complexes. FLAG-tag-based purification has been used to obtain proteins of sufficient purity and quality to carry out 3D structure determination by x-ray crystallography.
A FLAG-tag can be used in many different assays that require recognition by an antibody. If there is no antibody against a given protein, adding a FLAG-tag to a protein allows the protein to be studied with an antibody against the FLAG-tag sequence. Examples are cellular localization studies by immunofluorescence, immunoprecipitation or detection by SDS PAGE protein electrophoresis and Western blotting.
The peptide sequence of the FLAG-tag from the N-terminus to the C-terminus is: DYKDDDDK (1012 Da). Additionally, FLAG-tags may be used in tandem, commonly the 3xFLAG peptide: DYKDHD-G-DYKDHD-I-DYKDDDDK (with the final tag encoding an enterokinase cleavage site). FLAG-tag can be fused to the C-terminus or the N-terminus of a protein, or inserted within a protein. Some commercially available antibodies (e.g., M1/4E11) recognize the epitope only when FLAG-tag is present at the N-terminus. However, other available antibodies (e.g., M2) are position-insensitive. The tyrosine residue in the FLAG-tag can be sulfated when expressed on
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https://en.wikipedia.org/wiki/Iddq%20testing
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Iddq testing is a method for testing CMOS integrated circuits for the presence of manufacturing faults. It relies on measuring the supply current (Idd) in the quiescent state (when the circuit is not switching and inputs are held at static values). The current consumed in the state is commonly called Iddq for Idd (quiescent) and hence the name.
Iddq testing uses the principle that in a correctly operating quiescent CMOS digital circuit, there is no static current path between the power supply and ground, except for a small amount of leakage. Many common semiconductor manufacturing faults will cause the current to increase by orders of magnitude, which can be easily detected. This has the advantage of checking the chip for many possible faults with one measurement. Another advantage is that it may catch faults that are not found by conventional stuck-at fault test vectors.
Iddq testing is somewhat more complex than just measuring the supply current. If a line is shorted to Vdd, for example, it will still draw no extra current if the gate driving the signal is attempting to set it to '1'. However, a different input that attempts to set the signal to 0 will show a large increase in quiescent current, signalling a bad part. Typical Iddq tests may use 20 or so inputs. Note that Iddq test inputs require only controllability, and not observability. This is because the observability is through the shared power supply connection.
Advantages and disadvantages
Iddq testing has many advantages:
It is a simple and direct test that can identify physical defects.
The area and design time overhead are very low.
Test generation is fast.
Test application time is fast since the vector sets are small.
It catches some defects that other tests, particularly stuck-at logic tests, do not.
Drawback:
Compared to scan chain testing, Iddq testing is time consuming, and thus more expensive, as is achieved by current measurements that take much more time than reading digital pins i
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https://en.wikipedia.org/wiki/Boolean%20domain
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In mathematics and abstract algebra, a Boolean domain is a set consisting of exactly two elements whose interpretations include false and true. In logic, mathematics and theoretical computer science, a Boolean domain is usually written as {0, 1}, or
The algebraic structure that naturally builds on a Boolean domain is the Boolean algebra with two elements. The initial object in the category of bounded lattices is a Boolean domain.
In computer science, a Boolean variable is a variable that takes values in some Boolean domain. Some programming languages feature reserved words or symbols for the elements of the Boolean domain, for example false and true. However, many programming languages do not have a Boolean datatype in the strict sense. In C or BASIC, for example, falsity is represented by the number 0 and truth is represented by the number 1 or −1, and all variables that can take these values can also take any other numerical values.
Generalizations
The Boolean domain {0, 1} can be replaced by the unit interval , in which case rather than only taking values 0 or 1, any value between and including 0 and 1 can be assumed. Algebraically, negation (NOT) is replaced with conjunction (AND) is replaced with multiplication (), and disjunction (OR) is defined via De Morgan's law to be .
Interpreting these values as logical truth values yields a multi-valued logic, which forms the basis for fuzzy logic and probabilistic logic. In these interpretations, a value is interpreted as the "degree" of truth – to what extent a proposition is true, or the probability that the proposition is true.
See also
Boolean-valued function
GF(2)
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https://en.wikipedia.org/wiki/Portable%20object%20%28computing%29
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In distributed programming, a portable object is an object which can be accessed through a normal method call while possibly residing in memory on another computer. It is portable in the sense that it moves from machine to machine, irrespective of operating system or computer architecture. This mobility is the end goal of many remote procedure call systems.
The advantage of portable objects is that they are easy to use and very expressive, allowing programmers to be completely unaware that objects reside in other locations. Detractors cite this as a fault, as naïve programmers will not expect network-related errors or the unbounded nondeterminism associated with large networks.
See also
CORBA Common Object Request Broker Architecture, cross-language cross-platform object model
Portable Object Adapter part of the CORBA standard
D-Bus current open cross-language cross-platform Freedesktop.org Object Model
Bonobo deprecated GNOME cross-language Object Model
DCOP deprecated KDE interprocess and software componentry communication system
KParts KDE component framework
XPCOM Mozilla applications cross-platform Component Object Model
COM Microsoft Windows only cross-language Object Model
DCOM Distributed COM, extension making COM able to work in networks
Common Language Infrastructure current .NET cross-language cross-platform Object Model
IBM System Object Model SOM, a component system from IBM used in OS/2
Java Beans
Java Remote Method Invocation (Java RMI)
Internet Communications Engine
Language binding
Foreign function interface
Calling convention
Name mangling
Application programming interface - API
Application Binary Interface - ABI
Comparison of application virtual machines
SWIG open source automatic interfaces bindings generator from many languages to many languages
Distributed computing architecture
Object (computer science)
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https://en.wikipedia.org/wiki/Static%20cast
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In the C++ programming language, static_cast is an operator that performs an explicit type conversion.
Syntax
static_cast<type> (object);
The type parameter must be a data type to which object can be converted via a known method, whether it be a builtin or a cast. The type can be a reference or an enumerator.
All types of conversions that are well-defined and allowed by the compiler are performed using static_cast.
The static_cast<> operator can be used for operations such as:
converting a pointer of a base class to a pointer of a non-virtual derived class (downcasting);
converting numeric data types such as enums to ints or floats.
Although static_cast conversions are checked at compile time to prevent obvious incompatibilities, no run-time type checking is performed that would prevent a cast between incompatible data types, such as pointers. A static_cast from a pointer to a class B to a pointer to a derived class D is ill-formed if B is an inaccessible or ambiguous base of D. A static_cast from a pointer of a virtual base class (or a base class of a virtual base class) to a pointer of a derived class is ill-formed.
See also
dynamic cast
reinterpret_cast
const_cast
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https://en.wikipedia.org/wiki/Iliohypogastric%20nerve
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The iliohypogastric nerve is a nerve that originates from the lumbar plexus that supplies sensation to skin over the lateral gluteal and hypogastric regions and motor to the internal oblique muscles and transverse abdominal muscles.
Structure
Origin
The iliohypogastric nerve originates from the superior branch of the anterior ramus of spinal nerve L1. It also receives fibers from T12 via the subcostal nerve. The branch below it is the ilioinguinal nerve.
Course
It emerges from the upper lateral border of the psoas major. It then crosses in front of the quadratus lumborum muscle to an area superior to the iliac crest. It runs behind the kidneys. Just superior to the iliac crest, it pierces the posterior part of the transversus abdominis muscle and continues anteriorly in the abdominal wall between the transversus abdominis and internal oblique muscles.
It divides into a lateral cutaneous branch and an anterior cutaneous branch between the transversus abdominis muscle and the internal oblique muscle.
Branches
Lateral cutaneous branch
The lateral cutaneous branch ("iliac branch") pierces the internal oblique muscles and the external oblique muscles immediately above the iliac crest. It is distributed to the skin of the gluteal region, behind the lateral cutaneous branch of the subcostal nerve; the size of this branch bears an inverse proportion to that of the lateral cutaneous branch of the subcostal nerve.
When harvesting bone from the anterior iliac crest (AICBG), the lateral cutaneous branch of the Iliohypogastric nerve (L1) is most likely to be injured.
Anterior cutaneous branch
The anterior cutaneous branch ("hypogastric branch") continues onward between the abdominal internal oblique and transverse muscles.
It then pierces the internal oblique, becomes cutaneous by perforating the aponeurosis of the external oblique about 2.5 cm above the subcutaneous inguinal ring, and is distributed to the skin of the hypogastric region.
Communications
The iliohy
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https://en.wikipedia.org/wiki/Ilioinguinal%20nerve
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The ilioinguinal nerve is a branch of the first lumbar nerve (L1). It separates from the first lumbar nerve along with the larger iliohypogastric nerve. It emerges from the lateral border of the psoas major just inferior to the iliohypogastric, and passes obliquely across the quadratus lumborum and iliacus. The ilioinguinal nerve then perforates the transversus abdominis near the anterior part of the iliac crest, and communicates with the iliohypogastric nerve between the transversus and the internal oblique muscle.
It then pierces the internal oblique muscle, distributing filaments to it, and then accompanies the spermatic cord (in males) or the round ligament of uterus (in females) through the superficial inguinal ring. Its fibres are then distributed to the skin of the upper and medial part of the thigh, and to the following locations in the male and female:
In the male ("anterior scrotal nerve"): to the skin over the root of the penis and upper part of the scrotum.
In the female ("anterior labial nerve"): to the skin covering the mons pubis and labia majora.
The ilioinguinal nerve does not pass through the deep inguinal ring, and thus only travels through part of the inguinal canal. It mediates the cremasteric reflex.
Variations
The size of this nerve is in inverse proportion to that of the iliohypogastric. Occasionally it is very small, and ends by joining the iliohypogastric; in such cases, a branch from the iliohypogastric takes the place of the ilioinguinal, or the latter nerve may be altogether absent.
Ilioinguinal nerve block
The ilioinguinal nerve is clinically important when considering an ilioinguinal or iliohypogastric nerve block.
The indications for nerve block include anaesthesia for procedures involving the abdominal region such as inguinal herniorrhaphy or pain relief for procedures such as a c-section. Ropivacaine is an example of the anaesthetic which may be used for the block.
Additional images
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https://en.wikipedia.org/wiki/Lumbar%20nerves
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The lumbar nerves are the five pairs of spinal nerves emerging from the lumbar vertebrae. They are divided into posterior and anterior divisions.
Structure
The lumbar nerves are five spinal nerves which arise from either side of the spinal cord below the thoracic spinal cord and above the sacral spinal cord. They arise from the spinal cord between each pair of lumbar spinal vertebrae and travel through the intervertebral foramina. The nerves then split into an anterior branch, which travels forward, and a posterior branch, which travels backwards and supplies the area of the back.
Posterior divisions
The middle divisions of the posterior branches run close to the articular processes of the vertebrae and end in the multifidus muscle. The outer branches supply the erector spinae muscles.
The nerves give off branches to the skin. These pierce the aponeurosis of the greater trochanter.
Anterior divisions
The anterior divisions of the lumbar nerves () increase in size from above downward.
The anterior divisions communicate with the sympathetic trunk. Near the origin of the divisions, they are joined by gray rami communicantes from the lumbar ganglia of the sympathetic trunk. These rami consist of long, slender branches which accompany the lumbar arteries around the sides of the vertebral bodies, beneath the Psoas major. Their arrangement is somewhat irregular: one ganglion may give rami to two lumbar nerves, or one lumbar nerve may receive rami (branches) from two ganglia. The first and second, and sometimes the third and fourth lumbar nerves are each connected with the lumbar part of the sympathetic trunk by a white ramus communicans.
The nerves pass obliquely outward behind the Psoas major, or between its fasciculi, distributing filaments to it and the Quadratus lumborum.
As the nerves travel forward, they create nervous plexuses. The first three lumbar nerves, and the greater part of the fourth together form the lumbar plexus. The smaller part of the fourth
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https://en.wikipedia.org/wiki/Obturator%20nerve
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The obturator nerve in human anatomy arises from the ventral divisions of the second, third, and fourth lumbar nerves in the lumbar plexus; the branch from the third is the largest, while that from the second is often very small.
Structure
The obturator nerve originates from the anterior divisions of the L2, L3, and L4 spinal nerve roots. It descends through the fibers of the psoas major, and emerges from its medial border near the brim of the pelvis. It then passes behind the common iliac arteries, and on the lateral side of the internal iliac artery and vein, and runs along the lateral wall of the lesser pelvis, above and in front of the obturator vessels, to the upper part of the obturator foramen.
Here it enters the thigh, through the obturator canal, and divides into an anterior and a posterior branch, which are separated at first by some of the fibers of the obturator externus, and lower down by the adductor brevis.
An accessory obturator nerve may be present in approximately 8% to 29% of the general population.
Branches
Anterior branch of obturator nerve
Posterior branch of obturator nerve
Cutaneous branch of the obturator nerve
Function
The obturator nerve is responsible for the sensory innervation of the skin of the medial aspect of the thigh.
The nerve is also responsible for the motor innervation of the adductor muscles of the lower limb (external obturator, adductor longus, adductor brevis, adductor magnus, gracilis) and the pectineus (inconstant). It is, notably, not responsible for the innervation of the obturator internus, despite the similarity in name.
Clinical significance
An obturator nerve block may be used during knee surgery and urethral surgery in combination with other anaesthetics.
Additional images
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https://en.wikipedia.org/wiki/Lateral%20cutaneous%20nerve%20of%20thigh
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The lateral cutaneous nerve of the thigh (also called the lateral femoral cutaneous nerve) is a cutaneous nerve of the thigh. It originates from the dorsal divisions of the second and third lumbar nerves from of lumbar plexus. It passes under the inguinal ligament to reach the thigh. It supplies sensation to the skin on the lateral part of the thigh by an anterior branch and a posterior branch.
The lateral cutaneous nerve of the thigh can be investigated using ultrasound. Local anaesthetic can be injected around the nerve for skin grafts and surgery around the outer thigh. Nerve compression (usually around the inguinal ligament) can cause meralgia paraesthetica.
Structure
The nerve is usually 1-2 mm thick.
Origin
The lateral cutaneous nerve of the thigh is a nerve of the lumbar plexus. It arises from the posterior rami of the second and third lumbar nerves (L2-L3).
Course and relations
It passes through psoas major muscle, and emerges from its lateral border. It crosses the iliacus muscle obliquely, toward the anterior superior iliac spine (ASIS). It is crossed by the deep circumflex iliac artery and the deep circumflex iliac vein. It enters the thigh by passing beneath (the lateral part of) the inguinal ligament in the muscular lacuna, or through (the lateral part of) the inguinal ligament itself. It then passes over the sartorius muscle, travelling from medial to lateral.
Branches
The lateral cutaneous nerve of the thigh usually divides into an anterior (or anterolateral) branch and a posterior branch.
Anterior branch
The anterior branch becomes superficial about 10 cm below the inguinal ligament. It divides into branches which are distributed to the skin of the anterior and lateral parts of the thigh, as far down as the knee. The terminal filaments of this nerve frequently communicate with the anterior cutaneous branches of the femoral nerve, and with the infrapatellar branch of the saphenous nerve, forming with them the peripatellar plexus.
Posterior
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https://en.wikipedia.org/wiki/Illegal%20opcode
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An illegal opcode, also called an unimplemented operation, unintended opcode or undocumented instruction, is an instruction to a CPU that is not mentioned in any official documentation released by the CPU's designer or manufacturer, which nevertheless has an effect. Illegal opcodes were common on older CPUs designed during the 1970s, such as the MOS Technology 6502, Intel 8086, and the Zilog Z80. On these older processors, many exist as a side effect of the wiring of transistors in the CPU, and usually combine functions of the CPU that were not intended to be combined. On old and modern processors, there are also instructions intentionally included in the processor by the manufacturer, but that are not documented in any official specification.
The effect of many illegal opcodes, on many processors, is just a trap to an error handler. However, some processors that trap for most illegal opcodes do not do so for some illegal opcodes, and some other processors do not check for illegal opcodes, and, instead, perform an undocumented operation.
Overview
While most accidental illegal instructions have useless or even highly undesirable effects (such as crashing the computer), some can have useful functions in certain situations. Such instructions were sometimes exploited in computer games of the 1970s and 1980s to speed up certain time-critical sections. Another common use was in the ongoing battle between copy protection implementations and cracking. Here, they were a form of security through obscurity, and their secrecy usually did not last very long.
A danger associated with the use of illegal instructions was that, given the fact that the manufacturer does not guarantee their existence and function, they might disappear or behave differently with any change of the CPU internals or any new revision of the CPU, rendering programs that use them incompatible with the newer revisions. For example, a number of older Apple II games did not work correctly on the newer Apple
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https://en.wikipedia.org/wiki/Join%20and%20meet
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In mathematics, specifically order theory, the join of a subset of a partially ordered set is the supremum (least upper bound) of denoted and similarly, the meet of is the infimum (greatest lower bound), denoted In general, the join and meet of a subset of a partially ordered set need not exist. Join and meet are dual to one another with respect to order inversion.
A partially ordered set in which all pairs have a join is a join-semilattice. Dually, a partially ordered set in which all pairs have a meet is a meet-semilattice. A partially ordered set that is both a join-semilattice and a meet-semilattice is a lattice. A lattice in which every subset, not just every pair, possesses a meet and a join is a complete lattice. It is also possible to define a partial lattice, in which not all pairs have a meet or join but the operations (when defined) satisfy certain axioms.
The join/meet of a subset of a totally ordered set is simply the maximal/minimal element of that subset, if such an element exists.
If a subset of a partially ordered set is also an (upward) directed set, then its join (if it exists) is called a directed join or directed supremum. Dually, if is a downward directed set, then its meet (if it exists) is a directed meet or directed infimum.
Definitions
Partial order approach
Let be a set with a partial order and let An element of is called the (or or ) of and is denoted by if the following two conditions are satisfied:
(that is, is a lower bound of ).
For any if then (that is, is greater than or equal to any other lower bound of ).
The meet need not exist, either since the pair has no lower bound at all, or since none of the lower bounds is greater than all the others. However, if there is a meet of then it is unique, since if both are greatest lower bounds of then and thus If not all pairs of elements from have a meet, then the meet can still be seen as a partial binary operation on
If the meet does exist the
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https://en.wikipedia.org/wiki/Keith%20O%27Brien
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Keith Michael Patrick Cardinal O'Brien (17 March 1938 – 19 March 2018) was a senior-ranking Catholic prelate in Scotland. He was the Archbishop of Saint Andrews and Edinburgh from 1985 to 2013.
Cardinal O'Brien was the leader of the Catholic Church in Scotland and had been the head of its conference of bishops until he stepped down as archbishop in February 2013. O'Brien's resignation followed publication of allegations that he had engaged in inappropriate and predatory sexual conduct with priests and seminarians under his jurisdiction and abused his power. O'Brien was opposed to homosexuality, which he described as "moral degradation", and a vehement opponent of same-sex marriage.
On 20 March 2015, the Vatican announced that though he remained a member of the College of Cardinals, O'Brien would not exercise his rights or duties as a cardinal, in particular voting in papal conclaves; he had excused himself from participating in the 2013 conclave. O'Brien died after a fall, aged 80, on 19 March 2018.
Early life and education
O’Brien was born at Ballycastle, in County Antrim, Northern Ireland, on St. Patrick's Day, 17 March 1938. After primary education in Ballycastle, his family moved to Scotland where his father was serving with the Royal Navy at Faslane. O'Brien initially attended St Stephen's Primary School, Dalmuir, before continuing to secondary school at St Patrick's High School, Dumbarton. His family then moved to Edinburgh, where he completed his secondary education at Holy Cross Academy.
O'Brien studied at the University of Edinburgh where he gained a Bachelor of Science degree in chemistry in 1959 (and a Diploma in Education in 1966). His studies for the priesthood were at St Andrew's College, Drygrange, Roxburghshire, and he was ordained priest on 3 April 1965 by his predecessor, Cardinal Gordon Gray. Initially serving as curate at Holy Cross, Edinburgh from 1965 until 1966, he completed his teacher training certificate at Moray House College of Educat
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https://en.wikipedia.org/wiki/Kleisli%20category
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In category theory, a Kleisli category is a category naturally associated to any monad T. It is equivalent to the category of free T-algebras. The Kleisli category is one of two extremal solutions to the question Does every monad arise from an adjunction? The other extremal solution is the Eilenberg–Moore category. Kleisli categories are named for the mathematician Heinrich Kleisli.
Formal definition
Let 〈T, η, μ〉 be a monad over a category C. The Kleisli category of C is the category CT whose objects and morphisms are given by
That is, every morphism f: X → T Y in C (with codomain TY) can also be regarded as a morphism in CT (but with codomain Y). Composition of morphisms in CT is given by
where f: X → T Y and g: Y → T Z. The identity morphism is given by the monad unit η:
.
An alternative way of writing this, which clarifies the category in which each object lives, is used by Mac Lane. We use very slightly different notation for this presentation. Given the same monad and category as above, we associate with each object in a new object , and for each morphism in a morphism . Together, these objects and morphisms form our category , where we define
Then the identity morphism in is
Extension operators and Kleisli triples
Composition of Kleisli arrows can be expressed succinctly by means of the extension operator (–)# : Hom(X, TY) → Hom(TX, TY). Given a monad 〈T, η, μ〉 over a category C and a morphism f : X → TY let
Composition in the Kleisli category CT can then be written
The extension operator satisfies the identities:
where f : X → TY and g : Y → TZ. It follows trivially from these properties that Kleisli composition is associative and that ηX is the identity.
In fact, to give a monad is to give a Kleisli triple 〈T, η, (–)#〉, i.e.
A function ;
For each object in , a morphism ;
For each morphism in , a morphism
such that the above three equations for extension operators are satisfied.
Kleisli adjunction
Kleisli categories were origina
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https://en.wikipedia.org/wiki/Solving%20the%20geodesic%20equations
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Solving the geodesic equations is a procedure used in mathematics, particularly Riemannian geometry, and in physics, particularly in general relativity, that results in obtaining geodesics. Physically, these represent the paths of (usually ideal) particles with no proper acceleration, their motion satisfying the geodesic equations. Because the particles are subject to no proper acceleration, the geodesics generally represent the straightest path between two points in a curved spacetime.
The differential geodesic equation
On an n-dimensional Riemannian manifold , the geodesic equation written in a coordinate chart with coordinates is:
where the coordinates xa(s) are regarded as the coordinates of a curve γ(s) in and are the Christoffel symbols. The Christoffel symbols are functions of the metric and are given by:
where the comma indicates a partial derivative with respect to the coordinates:
As the manifold has dimension , the geodesic equations are a system of ordinary differential equations for the coordinate variables. Thus, allied with initial conditions, the system can, according to the Picard–Lindelöf theorem, be solved. One can also use a Lagrangian approach to the problem: defining
and applying the Euler–Lagrange equation.
Heuristics
As the laws of physics can be written in any coordinate system, it is convenient to choose one that simplifies the geodesic equations. Mathematically, this means a coordinate chart is chosen in which the geodesic equations have a particularly tractable form.
Effective potentials
When the geodesic equations can be separated into terms containing only an undifferentiated variable and terms containing only its derivative, the former may be consolidated into an effective potential dependent only on position. In this case, many of the heuristic methods of analysing energy diagrams apply, in particular the location of turning points.
Solution techniques
Solving the geodesic equations means obtaining an exact solution,
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https://en.wikipedia.org/wiki/Mass-to-charge%20ratio
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The mass-to-charge ratio (m/Q) is a physical quantity relating the mass (quantity of matter) and the electric charge of a given particle, expressed in units of kilograms per coulomb (kg/C). It is most widely used in the electrodynamics of charged particles, e.g. in electron optics and ion optics.
It appears in the scientific fields of electron microscopy, cathode ray tubes, accelerator physics, nuclear physics, Auger electron spectroscopy, cosmology and mass spectrometry. The importance of the mass-to-charge ratio, according to classical electrodynamics, is that two particles with the same mass-to-charge ratio move in the same path in a vacuum, when subjected to the same electric and magnetic fields.
Some disciplines use the charge-to-mass ratio (Q/m) instead, which is the multiplicative inverse of the mass-to-charge ratio. The CODATA recommended value for an electron is
Origin
When charged particles move in electric and magnetic fields the following two laws apply:
Lorentz force law:
Newton's second law of motion:
where F is the force applied to the ion, m is the mass of the particle, a is the acceleration, Q is the electric charge, E is the electric field, and v × B is the cross product of the ion's velocity and the magnetic flux density.
This differential equation is the classic equation of motion for charged particles. Together with the particle's initial conditions, it completely determines the particle's motion in space and time in terms of m/Q. Thus mass spectrometers could be thought of as "mass-to-charge spectrometers". When presenting data in a mass spectrum, it is common to use the dimensionless m/z, which denotes the dimensionless quantity formed by dividing the mass number of the ion by its charge number.
Combining the two previous equations yields:
This differential equation is the classic equation of motion of a charged particle in a vacuum. Together with the particle's initial conditions, it determines the particle's motion in space and tim
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https://en.wikipedia.org/wiki/T.%20M.%20Scanlon
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Thomas Michael "Tim" Scanlon (; born 1940), usually cited as T. M. Scanlon, is an American philosopher. At the time of his retirement in 2016, he was the Alford Professor of Natural Religion, Moral Philosophy, and Civil Polity in Harvard University's Department of Philosophy, where he had taught since 1984. He was elected to the American Philosophical Society in 2018.
Life and career
Scanlon was born on June 28, 1940, and grew up in Indianapolis, Indiana. He obtained his undergraduate degree from Princeton University in 1962; earned his PhD in philosophy from Harvard under Burton Dreben in 1968; studied for a year at Oxford University on a Fulbright Scholarship; and returned to Princeton University, where he taught from 1966 until 1984. He was made a MacArthur Fellow in 1993.
His teaching in the department has included courses on theories of justice, equality, and recent ethical theory. His book, What We Owe to Each Other, was published by Harvard University Press in 1998; a collection of papers on political theory, The Difficulty of Tolerance, was published by Cambridge University Press in 2003.
Scanlon is the father-in-law of philosopher and African-American studies scholar Tommie Shelby.
Philosophical work
Scanlon's dissertation and some of his first papers were in mathematical logic, where his main concern was in proof theory, but he turned to ethics and political philosophy, where he developed a version of contractualism in the line of John Rawls, Immanuel Kant, and Jean-Jacques Rousseau. Scanlon has also published important work on freedom of speech, equality, tolerance, foundations of contract law, human rights, conceptions of welfare, and theories of justice, as well as on foundational questions in moral theory.
Contractualism
Contractualism is a constructivist attempt at providing a unified account of the subject matter of a central part of morality which Scanlon calls "what we owe to each other." The normative domain of what we owe to each other
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https://en.wikipedia.org/wiki/Pakicetus
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Pakicetus is an extinct genus of amphibious cetacean of the family Pakicetidae, which was endemic to Pakistan during the Ypresian (early Eocene) period, about 50 million years ago. It was a wolf-like animal, about to long, and lived in and around water where it ate fish and other small animals. The vast majority of paleontologists regard it as the most basal whale, representing a transitional stage between land mammals and whales. It belongs to the even-toed ungulates with the closest living non-cetacean relative being the hippopotamus.
Description
Based on the sizes of specimens, and to a lesser extent on composite skeletons, species of Pakicetus are thought to have been to in length.
Pakicetus looked very different from modern cetaceans, and its body shape more resembled those of land-dwelling hoofed mammals. Unlike all later cetaceans, it had four fully functional long legs. Pakicetus had a long snout; a typical complement of teeth that included incisors, canines, premolars, and molars; a distinct and flexible neck; and a very long and robust tail. As in most land mammals, the nose was at the tip of the snout.
Reconstructions of pakicetids that followed the discovery of composite skeletons often depicted them with fur; however, given their relatively close relationships with hippos, they may have had sparse body hair.
The first fossil found consisted of an incomplete skull with a skull cap and a broken mandible with some teeth. Based on the detail of the teeth, the molars suggest that the animal could rend and tear flesh. Wear, in the form of scrapes on the molars, indicated that Pakicetus ground its teeth as it chewed its food. Because of the tooth wear, Pakicetus is thought to have eaten fish and other small animals. The teeth also suggest that Pakicetus had herbivorous and omnivorous ancestors.
Palaeobiology
Possible semi-aquatic nature
It was illustrated on the cover of Science as a semiaquatic, vaguely crocodile-like mammal, diving after fish.
So
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https://en.wikipedia.org/wiki/Provider-independent%20address%20space
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A provider-independent address space (PI) is a block of IP addresses assigned by a regional Internet registry (RIR) directly to an end-user organization. The user must contract with a local Internet registry (LIR) through an Internet service provider to obtain routing of the address block within the Internet.
Provider-independent addresses offer end-users the opportunity to change service providers without renumbering of their networks and to use multiple access providers in a multi-homed configuration. However, provider-independent blocks may increase the burden on global routers, as the opportunity for efficient route aggregation through Classless Inter-Domain Routing (CIDR) may not exist.
IPv4 assignments
One of the RIRs is RIPE NCC. The RIPE NCC can no longer assign IPv4 Provider Independent (PI) address space as it is now using the last of IPv4 address space that it holds. IPv4 address space from this last is allocated according to section 5.1 of "IPv4 Address Allocation and Assignment Policies for the RIPE NCC Service Region". IPv4 Provider-aggregatable (PA) Address space
can only be allocated to RIPE NCC members.
IPv6 assignments
In April 2009 RIPE accepted a policy proposal of January 2006 to assign IPv6 provider-independent IPv6 prefixes. Assignments are taken from the address range and have a minimum size of a prefix.
See also
Multihoming
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https://en.wikipedia.org/wiki/The%20Lexicon%20of%20Comicana
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The Lexicon of Comicana is a 1980 book by the American cartoonist Mort Walker. It was intended as a tongue-in-cheek look at the devices used by comics cartoonists. In it, Walker invented an international set of symbols called symbolia after researching cartoons around the world (described by the term comicana). In 1964, Walker had written an article called "Let's Get Down to Grawlixes", a satirical piece for the National Cartoonists Society. He used terms such as grawlixes for his own amusement, but they soon began to catch on and acquired an unexpected validity. The Lexicon was written in response to this.
The names he invented for them sometimes appear in dictionaries, and serve as convenient terminology occasionally used by cartoonists and critics. A 2001 gallery showing of comic- and street-influenced art in San Francisco, for example, was called "Plewds! Squeans! and Spurls!"
Examples
Agitrons: wiggly lines around a shaking object or character.
Blurgits, swalloops: curved lines preceding or trailing after a character's moving limbs.
Briffits (💨): clouds of dust that hang in the wake of a swiftly departing character or object.
Dites, hites and vites: straight lines drawn across flat, clear and reflective surfaces, such as windows and mirrors. The first letter indicates direction: diagonal, horizontal and vertical respectively. Hites may also be used trailing after something moving with great speed.
Emanata: lines drawn around the head to indicate shock or surprise
Grawlixes (#, $, *, @): typographical symbols standing in for profanities, appearing in dialogue balloons in place of actual dialogue.
Indotherm (♨): wavy, rising lines used to represent steam or heat.
Lucaflect: a shiny spot on a surface of something, depicted as a four-paned window shape.
Plewds (💦): flying sweat droplets that appear around a character's head when working hard, stressed, etc.
Quimps (🪐): A special example of the grawlix, a symbol resembling the planet Saturn.
Solrads: radiating li
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https://en.wikipedia.org/wiki/Joichi%20Suetsuna
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Joichi Suetsuna (Japanese: 末綱 恕一 Suetsuna Joichi; alternative Romanziation: Zyoiti Suetuna; November 28, 1898 – August 6, 1970) was a Japanese mathematician who worked mainly on number theory. In addition to working in Japan, where he held a chair at Tokyo University and was eventually selected to the Japan Academy, Suetsuna also spent time studying in Europe and introduced to Japan research styles he witnessed there. Later in life, especially after World War II, he studied Buddhist philosophy.
He was a teacher of Hirofumi Uzawa.
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https://en.wikipedia.org/wiki/Biotin%20carboxyl%20carrier%20protein
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Biotin carboxyl carrier protein (BCCP) refers to proteins containing a biotin attachment domain that carry biotin and carboxybiotin throughout the ATP-dependent carboxylation by biotin-dependent carboxylases. The biotin carboxyl carrier protein is an Acetyl CoA subunit that allows for Acetyl CoA to be catalyzed and converted to malonyl-CoA. More specifically, BCCP catalyzes the carboxylation of the carrier protein to form an intermediate. Then the carboxyl group is transferred by the transcacrboxylase to form the malonyl-CoA. This conversion is an essential step in the biosynthesis of fatty acids. In the case of E. coli Acetyl-CoA carboxylase, the BCCP is a separate protein known as accB (). On the other hand, in Haloferax mediterranei, propionyl-CoA carboxylase, the BCCP pccA () is fused with biotin carboxylase.
The biosynthesis of fatty acids in plants, such as triacylglycerol, is vital to the plant's overall health because it allows for accumulation of seed oil. The biosynthesis that is catalyzed by BCCP usually takes place in the chloroplast of plant cells. The biosynthesis performed by the BCCP protein allows for the transfer of CO2 within active sites of the cell.
The biotin carboxyl carrier protein carries approximately 1 mol of biotin per 22,000 g of protein.
There is not much research on BCCPs at the moment. However, a recent studyon plant genomics found that Brassica BCCPs might play a key role in abiotic and biotic stress responses. Meaning that these proteins may be relaying messages to the rest of the plant body after it has been exposed to extreme conditions that disrupt the plant's homeostasis.
Synthesis of Malonyl-CoA
The synthesis of Malonyl-CoA consists of two half reactions. The first being the carboxylation of biotin with bicarbonate and the second being the transfer of the CO2 group to acetyl-CoA from carboxybiotin to allow for the formation of malonyl-CoA. Two different protein subassemblies, along with BCCP, are required for this two ste
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https://en.wikipedia.org/wiki/Comparison%20of%20parser%20generators
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This is a list of notable lexer generators and parser generators for various language classes.
Regular languages
Regular languages are a category of languages (sometimes termed Chomsky Type 3) which can be matched by a state machine (more specifically, by a deterministic finite automaton or a nondeterministic finite automaton) constructed from a regular expression. In particular, a regular language can match constructs like "A follows B", "Either A or B", "A, followed by zero or more instances of B", but cannot match constructs which require consistency between non-adjacent elements, such as "some instances of A followed by the same number of instances of B", and also cannot express the concept of recursive "nesting" ("every A is eventually followed by a matching B"). A classic example of a problem which a regular grammar cannot handle is the question of whether a given string contains correctly-nested parentheses. (This is typically handled by a Chomsky Type 2 grammar, also termed a context-free grammar.)
Deterministic context-free languages
Context-free languages are a category of languages (sometimes termed Chomsky Type 2) which can be matched by a sequence of replacement rules, each of which essentially maps each non-terminal element to a sequence of terminal elements and/or other nonterminal elements. Grammars of this type can match anything that can be matched by a regular grammar, and furthermore, can handle the concept of recursive "nesting" ("every A is eventually followed by a matching B"), such as the question of whether a given string contains correctly-nested parentheses. The rules of Context-free grammars are purely local, however, and therefore cannot handle questions that require non-local analysis such as "Does a declaration exist for every variable that is used in a function?". To do so technically would require a more sophisticated grammar, like a Chomsky Type 1 grammar, also termed a context-sensitive grammar. However, parser generators for c
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https://en.wikipedia.org/wiki/Enantiomer%20self-disproportionation
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Enantiomer self-disproportionation is a process in stereochemistry describing the separation of a non-racemic mixture of enantiomers in an enantioenriched fraction and a more racemic fraction as a result of the formation of heterochiral or homochiral aggregates. This process is known to occur in achiral column chromatography.
The phenomenon was first reported in 1983 in the separation of an excess of
carbon-14 labeled (S)-(−)-nicotine enantiomer and its isomer. Two fractions were recorded, one containing racemic nicotine and the other pure (S) enantiomer.
In 2006, Vadim A. Soloshonok introduced the term Enantiomer self-disproportionation or self-disproportionation of enantiomers. He investigated achiral separations of several trifluoromethyl compounds.
By column chromatography on regular silica gel with a hexane / ethyl acetate eluent (5:1), a 66.6% ee sample of a trifluoromethyl substrate is separated into several fractions ranging from 8.1% ee for the first fraction collected to > 99.9% ee for the last fraction collected. A presence of a strong electronegative group in the substrate such as the trifluoromethyl group is a prerequisite. The effect disappears when a more polar eluent is selected. A possible explanation is offered. Compounds with large electronegative groups such as trifluoromethyl can form supramolecular associations or aggregates or clusters in which these groups are separated from each other as much as possible with minimized electrostatic repulsions. When these associations are stacks of alternating (R) and (S) molecules (as in syndiotactic polymers) this can be accomplished very efficiently. This association will form a racemic fraction of relatively high molecular weight eluting more slowly than the non-associating enantiopure fraction.
See also
disproportionation
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https://en.wikipedia.org/wiki/Nebulin
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Nebulin is an actin-binding protein which is localized to the thin filament of the sarcomeres in skeletal muscle. Nebulin in humans is coded for by the gene NEB. It is a very large protein (600–900 kDa) and binds as many as 200 actin monomers. Because its length is proportional to thin filament length, it is believed that nebulin acts as a thin filament "ruler" and regulates thin filament length during sarcomere assembly and acts as the coats the actin filament. Other functions of nebulin, such as a role in cell signaling, remain uncertain.
Nebulin has also been shown to regulate actin-myosin interactions by inhibiting ATPase activity in a calcium-calmodulin sensitive manner.
Mutations in nebulin cause some cases of the autosomal recessive disorder nemaline myopathy.
A smaller member of the nebulin protein family, termed nebulette, is expressed in cardiac muscle.
Structure
The structure of the SH3 domain of nebulin was determined by protein nuclear magnetic resonance spectroscopy. The SH3 domain from nebulin is composed of 60 amino acid residues, of which 30 percent is in the beta sheet secondary structure (7 strands; 18 residues).
Knockout phenotype
As of 2007, two knockout mouse models for nebulin have been developed to better understand its in vivo function. Bang and colleagues demonstrated that nebulin-knockout mice die postnatally, have reduced thin filament length, and impaired contractile function. Postnatal sarcomere disorganization and degeneration occurred rapidly in these mice, indicating the nebulin is essential for maintaining the structural integrity of myofibrils. Witt and colleagues had similar results in their mice, which also died postnatally with reduced thin filament length and contractile function. These nebulin-knockout mice are being investigated as animal models of nemaline myopathy.
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https://en.wikipedia.org/wiki/GeneRIF
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A GeneRIF or Gene Reference Into Function is a short (255 characters or fewer) statement about the function of a gene. GeneRIFs provide a simple mechanism for allowing scientists to add to the functional annotation of genes described in the Entrez Gene database. In practice, function is constructed quite broadly. For example, there are GeneRIFs that discuss the role of a gene in a disease, GeneRIFs that point the viewer towards a review article about the gene, and GeneRIFs that discuss the structure of a gene. However, the stated intent is for GeneRIFs to be about gene function. Currently over half a million geneRIFs have been created for genes from almost 1000 different species.
GeneRIFs are always associated with specific entries in the Entrez Gene database. Each GeneRIF has a pointer to the PubMed ID (a type of document identifier) of a scientific publication that provides evidence for the statement made by the GeneRIF. GeneRIFs are often extracted directly from the document that is identified by the PubMed ID, very frequently from its title or from its final sentence.
GeneRIFs are usually produced by NCBI indexers, but anyone may submit a GeneRIF.
To be processed, a valid Gene ID must exist for the specific gene, or the Gene staff must have assigned an overall Gene ID to the species. The latter case is implemented via records in Gene with the symbol NEWENTRY. Once the Gene ID is identified, only three types of information are required to complete a submission:
a concise phrase describing a function or functions (less than 255 characters in length, preferably more than a restatement of the title of the paper);
a published paper describing that function, implemented by supplying the PubMed ID of a citation in PubMed;
a valid e-mail address (which will remain confidential).
Example
Here are some GeneRIFs taken from Entrez Gene for GeneID 7157, the human gene TP53.
The PubMed document identifiers have been omitted from the examples. Note the wide variab
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https://en.wikipedia.org/wiki/Hydnoroideae
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Hydnoroideae is a subfamily of parasitic flowering plants in the order Piperales. Traditionally, and as recently as the APG III system it given family rank under the name Hydnoraceae. It is now submerged in the Aristolochiaceae. It contains two genera, Hydnora and Prosopanche:
Prosopanche is native to Central and South America ;
Hydnora can be found in semi-arid to desert regions of Africa, the Arabian Peninsula, and Madagascar.
Members of this subfamily have been described as the strangest plants in the world.
Description
The most striking aspect of the Hydnoroideae is probably the complete absence of leaves (not even in modified forms such as scales). Some species are mildly thermogenic (capable of producing heat), presumably as a means of dispersing their scent.
Morphology in pictures
Ecology
The plants are pollinated by insects such as dermestid beetles or carrion flies, attracted by the fetid odor of the flowers. In Hydnora africana there are bait bodies with a strong smell, whereas in Hydnora johannis the scent comes from a region at the tip of the perianth called a cucullus. The flowers may be above ground or underground. The fruits have edible, fragrant pulp, which attracts animals such as porcupines, monkeys, jackals, rhinoceros, and armadillos, as well as humans. The host plants, in the case of Hydnora, generally are in the family Euphorbiaceae and the genus Acacia. Hosts for Prosopanche include various species of Prosopis and other legumes.
Biochemistry
The plants contain high levels of tannins.
Genomics
The complete plastid genome sequence of one species of Hydnoroideae, Hydnora visseri, has been determined. As compared to the chloroplast genome of its closest photosynthetic relatives, the plastome of Hydnora visseri shows extreme reduction in both size (27,233 bp) and gene content (24 genes appear to be functional). The plastome of Hydnora visseri is therefore one of the smallest among flowering plants.
Classification
Like many parasitic
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https://en.wikipedia.org/wiki/Wall%27s%20%28ice%20cream%29
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Wall's is an ice cream and frozen dessert brand in the United Kingdom owned by Unilever and is part of the Heartbrand global frozen dessert brand.
Wall's also owns the rights to the Mr. Whippy soft-serve ice cream mix.
History
Wall's was founded in 1786 by Richard Wall, when he opened a butcher's stall in St James's Market, London. In the 1900s the business was led by Richard's grandson Thomas Wall II. Every year the company had to lay off staff in the summer as demand for its sausages, pies and meat fell, so in 1913 Thomas Wall II conceived the idea of making ice cream in the summer to avoid those lay-offs; the First World War meant that his idea was not implemented until 1922. Following his retirement in 1920, Thomas Wall II created his Trust for the "encouragement and assistance of educational work and social service". Today, the Trust continues to assist in these areas by providing grants to individuals and organisations.
By 1922 the business had been jointly bought by Lever Brothers and Margarine Unie. Maxwell Holt was put in charge and he revived the idea of producing ice cream, with near instant success. Ice cream production commenced in 1922 at a factory in Acton, London. In 1959, Wall's doubled capacity by opening a purpose-built ice cream factory in Gloucester, England.
There is a garage on the corner of Aultone Way and Angel Hill in Benhilton, Sutton, London, built in about 1913 and still in use today, which was originally used for the storing of the 'Stop Me and Buy One' bicycles of Thomas Wall's business.
Ice cream
Unilever continues to use the brand for ice cream in the UK and it has become part of the company's international Heartbrand strategy, where it retains its local ice cream brand but shares one logo and most of the product's lineup with the various other Heartbrand brands across the world. Whilst remaining (2006) the market leader in the UK for individual hand-held products such as Cornetto and Magnum, and value-added multi-portion p
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https://en.wikipedia.org/wiki/Experience%20modifier
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In the insurance industry in the United States, an experience modifier or experience modification is an adjustment of an employer's premium for worker's compensation coverage based on the losses the insurer has experienced from that employer. An experience modifier of 1 would be applied for an employer that had demonstrated the actuarially expected performance. Poorer loss experience leads to a modifier greater than 1, and better experience to a modifier less than 1. The loss experience used in determining the modifier typically comprises three years but excluding the immediate past year. For instance, if a policy expired on January 1, 2018, the period reflected by the experience modifier would run from January 1, 2014 to January 1, 2017.
Methods of calculation
Experience modifiers are normally recalculated for an employer annually by using experience ratings. The rating is a method used by insurers to determine pricing of premiums for different groups or individuals based on the group or individual's history of claims. The experience rating approach uses an individual's or group’s historic data as a proxy for future risk, and insurers adjust and set insurance premiums and plans accordingly. Each year, a newer year's data is added to the three year window of experience used in the calculation, and the oldest year from the prior calculation is dropped off. The other two years worth of data in the rating window are also updated on an annual basis.
Experience modifiers are calculated by organizations known as "rating bureaus" and rely on information reported by insurance companies. The rating bureau used by most states is the NCCI, the National Council on Compensation Insurance. But a number of states have independent rating bureaus: California, Michigan, Delaware, and Pennsylvania have stand-alone rating bureaus that do not integrate data with NCCI. Other states such as Wisconsin, Texas, New York, New Jersey, Indiana, and North Carolina, maintain their own rati
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https://en.wikipedia.org/wiki/Salmonella%20virus%20Epsilon15
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Epsilon 15 (or ε15) is a virus, specifically a bacteriophage, known to infect species of Salmonella bacteria including Salmonella anatum. The virus is a short, tailed phage with a double-stranded DNA genome of 39,671 base pairs and 49 open reading frames.
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https://en.wikipedia.org/wiki/Knaster%E2%80%93Kuratowski%E2%80%93Mazurkiewicz%20lemma
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The Knaster–Kuratowski–Mazurkiewicz lemma is a basic result in mathematical fixed-point theory published in 1929 by Knaster, Kuratowski and Mazurkiewicz.
The KKM lemma can be proved from Sperner's lemma and can be used to prove the Brouwer fixed-point theorem.
Statement
Let be an -dimensional simplex with n vertices labeled as .
A KKM covering is defined as a set of closed sets such that for any , the convex hull of the vertices corresponding to is covered by .
The KKM lemma says that in every KKM covering, the common intersection of all n sets is nonempty, i.e:
Example
When , the KKM lemma considers the simplex which is a triangle, whose vertices can be labeled 1, 2 and 3. We are given three closed sets such that:
covers vertex 1, covers vertex 2, covers vertex 3.
The edge 12 (from vertex 1 to vertex 2) is covered by the sets and , the edge 23 is covered by the sets and , the edge 31 is covered by the sets and .
The union of all three sets covers the entire triangle
The KKM lemma states that the sets have at least one point in common.
The lemma is illustrated by the picture on the right, in which set #1 is blue, set #2 is red and set #3 is green. The KKM requirements are satisfied, since:
Each vertex is covered by a unique color.
Each edge is covered by the two colors of its two vertices.
The triangle is covered by all three colors.
The KKM lemma states that there is a point covered by all three colors simultaneously; such a point is clearly visible in the picture.
Note that it is important that all sets are closed, i.e., contain their boundary. If, for example, the red set is not closed, then it is possible that the central point is contained only in the blue and green sets, and then the intersection of all three sets may be empty.
Equivalent results
Generalizations
Rainbow KKM lemma (Gale)
David Gale proved the following generalization of the KKM lemma. Suppose that, instead of one KKM covering, we have n different KKM coverings: . T
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https://en.wikipedia.org/wiki/Ischium
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The ischium (; : ischia) forms the lower and back region of the hip bone (os coxae).
Situated below the ilium and behind the pubis, it is one of three regions whose fusion creates the coxal bone. The superior portion of this region forms approximately one-third of the acetabulum.
Structure
The ischium is made up of three parts–the body, the superior ramus and the inferior ramus. The body contains a prominent spine, which serves as the origin for the superior gemellus muscle. The indentation inferior to the spine is the lesser sciatic notch. Continuing down the posterior side, the ischial tuberosity is a thick, rough-surfaced prominence below the lesser sciatic notch. This is the portion that supports weight while sitting (especially noticeable on a hard surface) and can be felt simply by sitting on the fingers. It serves as the origin for the inferior gemellus muscle and the hamstrings. The superior ramus is a partial origin for the internal obturator and the external obturator muscles. The inferior ramus serves partially as origin for part of the adductor magnus muscle and the gracilis muscle. The inferior ischial ramus joins the inferior ramus of the pubis anteriorly and is the strongest of the hip (coxal) bones.
Body
The body enters into and constitutes a little more than two-fifths of the acetabulum. Its external surface forms part of the lunate surface of the acetabulum and a portion of the acetabular fossa. Its internal surface is part of the wall of the lesser pelvis; it gives origin to some fibers of the internal obturator. No muscles insert on the body.
Its anterior border projects as the posterior obturator tubercle. From its posterior border there extends backward a thin and pointed triangular eminence, more or less elongated in different subjects, the ischial spine, origin of the gemellus superior muscle.
Above the spine is a large notch, the greater sciatic notch; Below the spine is a smaller notch, the lesser sciatic notch.
Superior ramus
The sup
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https://en.wikipedia.org/wiki/Pubis%20%28bone%29
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In vertebrates, the pubis or pubic bone () forms the lower and anterior part of each side of the hip bone. The pubis is the most forward-facing (ventral and anterior) of the three bones that make up the hip bone. The left and right pubic bones are each made up of three sections, a superior ramus, inferior ramus, and a body.
Structure
The pubic bone is made up of a body, superior ramus, and inferior ramus (). The left and right coxal bones join at the pubic symphysis. It is covered by a layer of fat – the mons pubis. The pubis is the lower limit of the suprapubic region. In the female, the pubis is anterior to the urethral sponge.
Body
The body of pubis has:
a superior border or the pubic crest
a pubic tubercle at the lateral end of the pubic crest
three surfaces (anterior, posterior and medial).
The body forms the wide, strong, middle and flat part of the pubic bone. The bodies of the left and right pubic bones join at the pubic symphysis. The rough upper edge is the pubic crest, ending laterally in the pubic tubercle. This tubercle, found roughly 3 cm from the pubic symphysis, is a distinctive feature on the lower part of the abdominal wall; important when localizing the superficial inguinal ring and the femoral canal of the inguinal canal. The inner surface of the body forms part of the wall of the lesser pelvis and joints to the origin of a part of the obturator internus muscle.
Superior pubic ramus
The superior pubic ramus is the upper of the two rami. It forms the upper edge of the obturator foramen. It extends from the body to the median plane where it joins with the ramus of the opposite side. It consists of an inner flattened part and a narrow outer prismoid portion.
Medial surface
Surfaces
The anterior surface is rough, directed downward and outward, and serves for the origin of various muscles. The adductor longus arises from the upper and medial angle, immediately below the crest; lower down, the obturator externus, the adductor brevis and th
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https://en.wikipedia.org/wiki/Raphide
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Raphides ( ; singular raphide or raphis) are needle-shaped crystals of calcium oxalate monohydrate (prismatic monoclinic crystals) or calcium carbonate as aragonite (dipyramidal orthorhombic crystals), found in more than 200 families of plants.
Both ends are needle-like, but raphides tend to be blunt at one end and sharp at the other.
Calcium oxalate in plants
Many plants accumulate calcium oxalate crystals in response to surplus calcium, which is found throughout the natural environment. The crystals are produced in a variety of shapes. The crystal morphology depends on the taxonomic group of the plant. In one study of over 100 species, it was found that calcium oxalate accounted for 6.3% of plant dry weight. Crystal morphology and the distribution of raphides (in roots or leaves or tubers etc.) is similar in some taxa but different in others leaving possible opportunities for plant key characteristics and systematic identification; mucilage in raphide containing cells makes light microscopy difficult, though. Little is known about the mechanisms of sequestration or indeed the reason for accumulation of raphides but it is most likely as a defense mechanism against herbivory. It has also been suggested that in some cases raphides may help form plant skeletal structure. Raphides typically occur in parenchyma cells in aerial organs especially the leaves, and are generally confined to the mesophyll. As the leaf area increases, so does the number of raphides, the process starting in even young leaves. The first indications that the cell will contain crystals is shown when the cells enlarge with a larger nucleus.
Raphides are found in specialized plant cells or crystal chambers called idioblasts. Electron micrographs have shown that raphide needle crystals are normally four sided or H-shaped (with a groove down both sides) or with a hexagonal cross section and some are barbed. Wattendorf (1976) suggested that all circular sectioned raphides, as visible in a light m
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https://en.wikipedia.org/wiki/Lesser%20trochanter
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In human anatomy, the lesser trochanter is a conical, posteromedial, bony projection from the shaft of the femur. it serves as the principal insertion site of the iliopsoas muscle.
Structure
The lesser trochanter is a conical posteromedial projection of the shaft of the femur, projecting from the posteroinferior aspect of its junction with the femoral neck.
The summit and anterior surface of the lesser trochanter are rough, whereas its posterior surface is smooth.
From its apex three well-marked borders extend:
two of these are above
a medial continuous with the lower border of the femur neck
a lateral with the intertrochanteric crest
the inferior border is continuous with the middle division of the linea aspera
Attachments
The summit of the lesser trochanter gives insertion to the tendon of the psoas major muscle and the iliacus muscle; the lesser trochanter represents the principal attachment of the iliopsoas.
Anatomical relations
The intertrochanteric crest (which demarcates the junction of the femoral shaft and neck posteriorly) extends between the lesser trochanter and the greater trochanter on the posterior surface of the femur.
Clinical significance
The lesser trochanter can be involved in an avulsion fracture.
Other animals
Paleontology
The position of the lesser trochanter close to the head of the femur is one of the defining characteristics of the Prozostrodontia, which is the clade of cynodonts including mammals and their closest non-mammaliform relatives. It was erected as a node-based taxon as the least inclusive clade containing Prozostrodon brasiliensis, Tritylodon langaevus, Pachygenelus monus, and Mus musculus (the house mouse).
All living mammals have a lesser trochanter, whose size, shape, and position is distinctive to their species.
Additional images
See also
Greater trochanter
Third trochanter
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https://en.wikipedia.org/wiki/Sacrotuberous%20ligament
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The sacrotuberous ligament (great or posterior sacrosciatic ligament) is situated at the lower and back part of the pelvis. It is flat, and triangular in form; narrower in the middle than at the ends.
Structure
It runs from the sacrum (the lower transverse sacral tubercles, the inferior margins sacrum and the upper coccyx) to the tuberosity of the ischium.
It is a remnant of part of Biceps femoris muscle.
The sacrotuberous ligament is attached by its broad base to the posterior superior iliac spine, the posterior sacroiliac ligaments (with which it is partly blended), to the lower transverse sacral tubercles and the lateral margins of the lower sacrum and upper coccyx. Its oblique fibres descend laterally, converging to form a thick, narrow band that widens again below and is attached to the medial margin of the ischial tuberosity. It then spreads along the ischial ramus as the falciform process, whose concave edge blends with the fascial sheath of the internal pudendal vessels and pudendal nerve. The lowest fibres of gluteus maximus are attached to the posterior surface of the ligament; superficial fibres of the lower part of the ligament continue into the tendon of biceps femoris. The ligament is pierced by the coccygeal branches of the inferior gluteal artery, the perforating cutaneous nerve and filaments of the coccygeal plexus.
Variation
The membranous falciform process of the sacrotuberous ligament was found to be absent in 13% of cadavers. When present it extends towards the ischioanal fossa travelling along the ischial ramus and fusing with the obturator fascia.
The lower border of the ligament was found to be directly continuous with the tendon of origin of the long head of the Biceps femoris in approximately 50% of subjects. Biceps femoris could therefore act to stabilise the sacroiliac joint via the sacrotuberous ligament.
Function
The sacrotuberous ligament contains the coccygeal branch of the inferior gluteal artery.
Clinical significance
If the p
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https://en.wikipedia.org/wiki/Hong%20Kong%20Mathematics%20Olympiad
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Hong Kong Mathematics Olympiad (HKMO, ) is a Mathematics Competition held in Hong Kong every year, jointly organized by The Education University of Hong Kong and Education Bureau. At present, more than 250 secondary schools send teams of 4-6 students of or below Form 5 to enter the competition. It is made up of a Heat Event and a Final Event, which both forbid the usage of calculators and calculation assisting equipments (e.g. printed mathematical table). Though it bears the term Mathematics Olympiad, it has no relationship with the International Mathematical Olympiad.
History
The predecessor of HKMO is the Inter-school Mathematics Olympiad initiated by the Mathematics Society of Northcote College of Education in 1974, which had attracted 20 secondary schools to participate. Since 1983, the competition is jointly conducted by the Mathematics Department of Northcote College of Education and the Mathematics Section of the Advisory Inspectorate Division of the Education Department. Also in 1983, the competition is formally renamed as Hong Kong Mathematics Olympiad.
Format and Scoring in the Heat Event
The Heat Event is usually held in four venues, for contestants from schools on Hong Kong Island, and in Kowloon, New Territories East and New Territories West respectively. It comprises an individual event and a group event. Each team sends 4 contestants among 4-6 team members for each event.
For the individual event, 1 mark and 2 marks will be given to each correct answer in Part A and Part B respectively. The maximum score for a team should be 80.
For the group event, 2 marks will be given to each correct answer. The maximum score for a team should be 20.
For the geometric construction event, the maximum score for a team should be 20 (all working, including construction work, must be clearly shown).
In other words, a contesting school may earn 120 marks at most in the Heat Event. The top 50 may enter the Final Event.
Format and Scoring in the Final Event
The Fina
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https://en.wikipedia.org/wiki/Mesh%20Computers
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PC Peripherals Ltd, trading as MESH Computers, is a private computer company based in London, England. As well as being a manufacturer of personal computers, the company sells peripherals and components through their website.
History
MESH was founded in 1987. During its first 20 years of business, MESH Computers could only be purchased directly from the manufacturer; however, in November 2006, MESH began to sell through major retailers like Comet Group.
MESH Computers has recently opened up a number of new routes to market, including resellers in the UK like Ebuyer.
In 2009, Mesh announced the MESH Cute home theatre PC, in a variety of colours for the living room.
The BBC created a series of programmes to teach school children about computer technology and advanced production techniques in a modern factory setting and MESH was filmed as one of the examples, alongside Rolls-Royce and Coca-Cola.
MESH was the last of the major UK PC manufacturers that still create custom-built PCs for end users. At its peak, the mainstream market was full of local brands like Evesham Technology, Granville Technology (Tiny/Time), Elonex, Opus, Cube Enterprises, MJN and Dan; most of them shut down in the Great Recession.
Viglen and RM Plc continued to operate, but specialise in education systems.
MESH computers appeared on Watchdog having been accused of having inadequate customer support and services.
In the summer of 2010, MESH Computers was voted PC Manufacturer of the Year by both Computer Shopper magazine and the Expert Reviews web site.
MESH reviews have been mixed.
Administration
On 31 May 2011 it was announced that MESH Computers had gone into administration under the law firm MacIntyre Hudson, and that key assets had been bought by components firm PC Peripherals, owned by Reza Jafari.
In February 2012, the owner of MESH (and its largest creditor) at the time it went into administration, Mehdi ("Max") Sherafati, was appointed a director of PC Peripherals, effectively rega
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https://en.wikipedia.org/wiki/Fog%20bow
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A fog bow, sometimes called a white rainbow, is a similar phenomenon to a rainbow; however, as its name suggests, it appears as a bow in fog rather than rain. Because of the very small size of water droplets that cause fog—smaller than —the fog bow has only very weak colors, with a red outer edge and bluish inner edge. The colors fade due to being smeared out by the diffraction effect of the smaller droplets.
In many cases, when the droplets are very small, fog bows appear white, and are therefore sometimes called white rainbows. Along with its larger angular size, this lack of color is a feature of a fog bow that distinguishes it from a glory, which has multiple pale-colored rings caused by diffraction. When droplets forming it are almost all of the same size, the fog bow can have multiple inner rings, or supernumeraries, which are more strongly colored than the main bow.
A fog bow seen in clouds, typically from an aircraft looking downwards, is called a cloud bow. Mariners sometimes call fog bows sea-dogs.
Direction
A fog bow is seen in the same direction as a rainbow, thus the sun would be behind the head of the observer and the direction of view would be into a bank of fog (which may not be noticeable in directions away from the bow itself). Its outer radius is slightly less than that of a rainbow.
When a fog bow appears at night it is called a lunar fog bow.
See also
Circumhorizontal arc
Circumzenithal arc
Cloud iridescence
Dewbow
Halo
Moonbow
Sun dog
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https://en.wikipedia.org/wiki/Sacrospinous%20ligament
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The sacrospinous ligament (small or anterior sacrosciatic ligament) is a thin, triangular ligament in the human pelvis. The base of the ligament is attached to the outer edge of the sacrum and coccyx, and the tip of the ligament attaches to the spine of the ischium, a bony protuberance on the human pelvis. Its fibres are intermingled with the sacrotuberous ligament.
Structure
The sacrotuberous ligament passes behind the sacrospinous ligament. In its entire length, the sacrospinous ligament covers the equally triangular coccygeus muscle, to which its closely connected.
Function
The presence of the ligament in the greater sciatic notch creates an opening (foramen), the greater sciatic foramen, and also converts the lesser sciatic notch into the lesser sciatic foramen. The greater sciatic foramen lies above the ligament, and the lesser sciatic foramen lies below it.
The pudendal vessels and nerve pass behind the sacrospinous ligament directly medially and inferiorly to the ischial spine. The inferior gluteal artery, from a branch of the internal iliac artery, pass behind the sciatic nerve and the sacrospinous ligament and is left uncovered in a small opening above the top of the sacrospinous ligament. The coccygeal branch of the inferior gluteal artery passes behind the mid-portion of the sacrospinous ligament and pierces the sacrotuberous ligament at multiple locations. The main body of the inferior gluteal artery leaves the pelvis posteriorly to the upper border of the sacrospinous ligament, to follow the inferior portion of the sciatic nerve out of the greater sciatic foramen.
The main function of the ligament is to prevent rotation of the ilium past the sacrum. Laxity of this ligament and the sacrotuberous ligament allows this rotation to occur. Stresses to these ligaments occur most often when leaning forward or getting out of a chair.
Clinical significance
Vaginal prolapse or uterine prolapse may occur in women when other pelvic ligaments and supportive
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https://en.wikipedia.org/wiki/Ionic%20potential
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Ionic potential is the ratio of the electrical charge (z) to the radius (r) of an ion.
As such, this ratio is a measure of the charge density at the surface of the ion; usually the denser the charge, the stronger the bond formed by the ion with ions of opposite charge.
The ionic potential gives an indication of how strongly, or weakly, the ion will be electrostatically attracted by ions of opposite charge; and to what extent the ion will be repelled by ions of the same charge.
Victor Moritz Goldschmidt, the father of modern geochemistry found that the behavior of an element in its environment could be predicted from its ionic potential and illustrated this with a diagram (plot of the bare ionic radius as a function of the ionic charge). For instance, the solubility of dissolved iron is highly dependent on its redox state. with a lower ionic potential than is much more soluble because it exerts a weaker interaction force with ion present in water and exhibits a less pronounced trend to hydrolysis and precipitation. Under reducing conditions Fe(II) can be present at relatively high concentration in anoxic water, similar to these encountered for other divalent species such as and . However, once anoxic ground water is pumped from a deep well and is discharged to the surface, it enters in contact with atmospheric oxygen. Then is easily oxidized to and this latter rapidly hydrolyzes and precipitates because of its lower solubility due to a higher z/r ratio.
Millot (1970) also illustrated the importance of the ionic potential of cations to explain the high, or the low, solubility of minerals and the expansive behaviour (swelling/shrinking) of clay materials.
The ionic potential of the different cations (, , and ) present in the interlayer of clay minerals also contribute to explain their swelling/shrinking properties. The more hydrated cations such as and are responsible for the swelling of smectite while the less hydrated and cause the collapse of the
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https://en.wikipedia.org/wiki/Microsoft%20Speech%20API
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The Speech Application Programming Interface or SAPI is an API developed by Microsoft to allow the use of speech recognition and speech synthesis within Windows applications. To date, a number of versions of the API have been released, which have shipped either as part of a Speech SDK or as part of the Windows OS itself. Applications that use SAPI include Microsoft Office, Microsoft Agent and Microsoft Speech Server.
In general, all versions of the API have been designed such that a software developer can write an application to perform speech recognition and synthesis by using a standard set of interfaces, accessible from a variety of programming languages. In addition, it is possible for a 3rd-party company to produce their own Speech Recognition and Text-To-Speech engines or adapt existing engines to work with SAPI. In principle, as long as these engines conform to the defined interfaces they can be used instead of the Microsoft-supplied engines.
In general, the Speech API is a freely redistributable component which can be shipped with any Windows application that wishes to use speech technology. Many versions (although not all) of the speech recognition and synthesis engines are also freely redistributable.
There have been two main 'families' of the Microsoft Speech API. SAPI versions 1 through 4 are all similar to each other, with extra features in each newer version. SAPI 5, however, was a completely new interface, released in 2000. Since then several sub-versions of this API have been released.
Basic architecture
The Speech API can be viewed as an interface or piece of middleware which sits between applications and speech engines (recognition and synthesis). In SAPI versions 1 to 4, applications could directly communicate with engines. The API included an abstract interface definition which applications and engines conformed to. Applications could also use simplified higher-level objects rather than directly call methods on the engines.
In SAPI 5 howeve
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https://en.wikipedia.org/wiki/Microsoft%20Speech%20Server
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The Microsoft Speech Server is a product from Microsoft designed to allow the authoring and deployment of IVR applications incorporating Speech Recognition, Speech Synthesis and DTMF.
The first version of the server was released in 2004 as Microsoft Speech Server 2004 and supported applications developed for U.S. English-speaking users. A later release (Speech Server 2004 R2) was released in 2005 and added support for North American Spanish and Canadian French as well as additional features and fixes.
In August 2006, Microsoft announced that Speech Server 2007, originally slated to be released in May 2007, had been merged with the Microsoft Office Live Communications Server product line to create Microsoft Office Communications Server.
The Speech Server 2007 components of Office Communications Server are also available separately in the free Speech Server 2007 Developers Edition.
See also
Microsoft Office Communications Server
Speech Recognition
Speech Synthesis
Interactive voice response
External links
Free Speech Server 2007 Developers Edition
Microsoft Speech Server homepage
Speech Server
Voice technology
Speech processing software
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https://en.wikipedia.org/wiki/Ernst%20Steinitz
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Ernst Steinitz (13 June 1871 – 29 September 1928) was a German mathematician.
Biography
Steinitz was born in Laurahütte (Siemianowice Śląskie), Silesia, Germany (now in Poland), the son of Sigismund Steinitz, a Jewish coal merchant, and his wife Auguste Cohen; he had two brothers. He studied at the University of Breslau and the University of Berlin, receiving his Ph.D. from Breslau in 1894. Subsequently, he took positions at Charlottenburg (now the Technical University of Berlin), Breslau, and the University of Kiel, Germany, where he died in 1928. Steinitz married Martha Steinitz and had one son.
Mathematical works
Steinitz's 1894 thesis was on the subject of projective configurations; it contained the result that any abstract description of an incidence structure of three lines per point and three points per line could be realized as a configuration of straight lines in the Euclidean plane with the possible exception of one of the lines. His thesis also contains the proof of Kőnig's theorem for regular bipartite graphs, phrased in the language of configurations.
In 1910 Steinitz published the very influential paper Algebraische Theorie der Körper (German: Algebraic Theory of Fields, Crelle's Journal). In this paper he axiomatically studies the properties of fields and defines important concepts like prime field, perfect field and the transcendence degree of a field extension, and also normal and separable extensions (the latter he called algebraic extensions of the first kind). Besides numerous, today standard, results in field theory, he proved that every field has an (essentially unique) algebraic closure and a theorem, which characterizes the existence of primitive elements of a field extension in terms of its intermediate fields. Bourbaki called this article "a basic paper which may be considered as having given rise to the current conception of Algebra".
Steinitz also made fundamental contributions to the theory of polyhedra: Steinitz's theorem for poly
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https://en.wikipedia.org/wiki/Economic%20entomology
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Economic entomology is a field of entomology, which involves the study of insects that benefit or harm humans, domestic animals, and crops. Insects that pose disadvantages are considered pests. Some species can cause indirect damage by spreading diseases, and these are termed as disease vectors. Those that are beneficial include those that are reared for food such as honey, substances such as lac or pigments, and for their role in pollinating crops and controlling pests.
History
In the 18th century many works were published on agriculture. Many contained accounts of pest insects. In France Claude Sionnest (1749–1820) was a notable figure.
19th century
In Britain, John Curtis wrote the influential 1860 treatise Farm Insects, dealing with the insect pests of corn, roots, grass and stored grain. Fruit and pests were described by authors such as Saunders, Joseph Albert Lintner, Eleanor Anne Ormerod, Charles Valentine Riley, Mark Vernon Slingerland in America and Canada. The pioneers in Europe were Ernst Ludwig Taschenberg, Sven Lampa (1839–1914), Enzio Reuter (1867–1951) and Vincenze Kollar. Charles French (1842–1933), Walter Wilson Froggatt (1858–1937) and Henry Tryon (1856–1943) pioneered in Australia.
It was not until the last quarter of the 19th century that any real advance was made in the study of economic entomology. Among the early writings, apart from the book of Curtis, there was a publication by Pohl and Kollar, entitled Insects Injurious to Gardeners, Foresters and Farmers, published in 1837, and Taschenberg's Praktische Insecktenkunde. During the 19th century, Italian entomologists made significant progress in controlling diseases of the silkworm moth, in the control of agricultural pests and in stored product entomology. Significant figures were: Agostino Bassi ( 1773–1856), Camillo Rondani (1808–1879), Adolfo Targioni Tozzetti (1823–1902), Pietro Stefanelli (1835, 1919), Camillo Acqua (1863–1936) Antonio Berlese (1863–1927), Gustavo Leonardi(1869–191
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https://en.wikipedia.org/wiki/Frobenius%20theorem%20%28real%20division%20algebras%29
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In mathematics, more specifically in abstract algebra, the Frobenius theorem, proved by Ferdinand Georg Frobenius in 1877, characterizes the finite-dimensional associative division algebras over the real numbers. According to the theorem, every such algebra is isomorphic to one of the following:
(the real numbers)
(the complex numbers)
(the quaternions).
These algebras have real dimension , and , respectively. Of these three algebras, and are commutative, but is not.
Proof
The main ingredients for the following proof are the Cayley–Hamilton theorem and the fundamental theorem of algebra.
Introducing some notation
Let be the division algebra in question.
Let be the dimension of .
We identify the real multiples of with .
When we write for an element of , we imply that is contained in .
We can consider as a finite-dimensional -vector space. Any element of defines an endomorphism of by left-multiplication, we identify with that endomorphism. Therefore, we can speak about the trace of , and its characteristic and minimal polynomials.
For any in define the following real quadratic polynomial:
Note that if then is irreducible over .
The claim
The key to the argument is the following
Claim. The set of all elements of such that is a vector subspace of of dimension . Moreover as -vector spaces, which implies that generates as an algebra.
Proof of Claim: Let be the dimension of as an -vector space, and pick in with characteristic polynomial . By the fundamental theorem of algebra, we can write
We can rewrite in terms of the polynomials :
Since , the polynomials are all irreducible over . By the Cayley–Hamilton theorem, and because is a division algebra, it follows that either for some or that for some . The first case implies that is real. In the second case, it follows that is the minimal polynomial of . Because has the same complex roots as the minimal polynomial and because it is real it follows that
Since is t
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https://en.wikipedia.org/wiki/Noise%20%28electronics%29
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In electronics, noise is an unwanted disturbance in an electrical signal.
Noise generated by electronic devices varies greatly as it is produced by several different effects.
In particular, noise is inherent in physics and central to thermodynamics. Any conductor with electrical resistance will generate thermal noise inherently. The final elimination of thermal noise in electronics can only be achieved cryogenically, and even then quantum noise would remain inherent.
Electronic noise is a common component of noise in signal processing.
In communication systems, noise is an error or undesired random disturbance of a useful information signal in a communication channel. The noise is a summation of unwanted or disturbing energy from natural and sometimes man-made sources. Noise is, however, typically distinguished from interference, for example in the signal-to-noise ratio (SNR), signal-to-interference ratio (SIR) and signal-to-noise plus interference ratio (SNIR) measures. Noise is also typically distinguished from distortion, which is an unwanted systematic alteration of the signal waveform by the communication equipment, for example in signal-to-noise and distortion ratio (SINAD) and total harmonic distortion plus noise (THD+N) measures.
While noise is generally unwanted, it can serve a useful purpose in some applications, such as random number generation or dither.
Noise types
Different types of noise are generated by different devices and different processes. Thermal noise is unavoidable at non-zero temperature (see fluctuation-dissipation theorem), while other types depend mostly on device type (such as shot noise, which needs a steep potential barrier) or manufacturing quality and semiconductor defects, such as conductance fluctuations, including 1/f noise.
Thermal noise
Johnson–Nyquist noise (more often thermal noise) is unavoidable, and generated by the random thermal motion of charge carriers (usually electrons), inside an electrical conductor, which
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https://en.wikipedia.org/wiki/Photosynthetic%20reaction%20centre
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A photosynthetic reaction center is a complex of several proteins, pigments and other co-factors that together execute the primary energy conversion reactions of photosynthesis. Molecular excitations, either originating directly from sunlight or transferred as excitation energy via light-harvesting antenna systems, give rise to electron transfer reactions along the path of a series of protein-bound co-factors. These co-factors are light-absorbing molecules (also named chromophores or pigments) such as chlorophyll and pheophytin, as well as quinones. The energy of the photon is used to excite an electron of a pigment. The free energy created is then used, via a chain of nearby electron acceptors, for a transfer of hydrogen atoms (as protons and electrons) from H2O or hydrogen sulfide towards carbon dioxide, eventually producing glucose. These electron transfer steps ultimately result in the conversion of the energy of photons to chemical energy.
Transforming light energy into charge separation
Reaction centers are present in all green plants, algae, and many bacteria. A variety in light-harvesting complexes exist across the photosynthetic species. Green plants and algae have two different types of reaction centers that are part of larger supercomplexes known as P700 in Photosystem I and P680 in Photosystem II. The structures of these supercomplexes are large, involving multiple light-harvesting complexes. The reaction center found in Rhodopseudomonas bacteria is currently best understood, since it was the first reaction center of known structure and has fewer polypeptide chains than the examples in green plants.
A reaction center is laid out in such a way that it captures the energy of a photon using pigment molecules and turns it into a usable form. Once the light energy has been absorbed directly by the pigment molecules, or passed to them by resonance transfer from a surrounding light-harvesting complex, they release electrons into an electron transport chain an
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https://en.wikipedia.org/wiki/List%20of%20online%20music%20databases
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Below is a table of online music databases that are largely free of charge. Many of the sites provide a specialized service or focus on a particular music genre. Some of these operate as an online music store or purchase referral service in some capacity. Among the sites that have information on the largest number of entities are those sites that focus on discographies of composing and performing artists.
Performance rights organisations (PRO) typically have their own databases as per country they represent, in accordance with CISAC, to help domestic artists collect royalties. Information available on these portals include songwriting credits, publishing percentage splits, and alternate titles for different distribution channels. It is one of the most accurate and official types of databases because it involves direct communication between the artists, record labels, distributors, legal teams, publishers and a global governing body regulating PRO's. Many countries that observe copyright have an organisation established, currently there are 119 CISAC members, and they may be not-for-profit. The databases are typically known as 'repertory searches' or 'searching works' and may require an account while others are open to view for free as public including the USA's ASCAP Songview and Ace services, Canada's SOCAN, South Korea's KOMCA, France's SACEM, and Israel's ACUM.
General databases
Music genre specific
Specialized areas
Printed music (sheets) databases
Metadata providers and distributors
Non-functioning databases
See also
Automatic content recognition
Comparison of digital music stores
List of music sharing websites
Comparison of music streaming services
Comparison of online music lockers
List of music software
List of Internet radio stations
List of online digital musical document libraries
Streaming media
Virtual Library of Musicology
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https://en.wikipedia.org/wiki/Light-harvesting%20complex
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A light-harvesting complex consists of a number of chromophores which are complex subunit proteins that may be part of a larger super complex of a photosystem, the functional unit in photosynthesis. It is used by plants and photosynthetic bacteria to collect more of the incoming light than would be captured by the photosynthetic reaction center alone. The light which is captured by the chromophores is capable of exciting molecules from their ground state to a higher energy state, known as the excited state. This excited state does not last very long and is known to be short-lived.
Light-harvesting complexes are found in a wide variety among the different photosynthetic species, with no homology among the major groups. The complexes consist of proteins and photosynthetic pigments and surround a photosynthetic reaction center to focus energy, attained from photons absorbed by the pigment, toward the reaction center using Förster resonance energy transfer.
Function
Photosynthesis is a process where light is absorbed or harvested by pigment protein complexes which are able to turn sunlight into energy. Absorption of a photon by a molecule takes place when pigment protein complexes harvest sunlight leading to electronic excitation delivered to the reaction centre where the process of charge separation can take place. when the energy of the captured photon matches that of an electronic transition. The fate of such excitation can be a return to the ground state or another electronic state of the same molecule. When the excited molecule has a nearby neighbour molecule, the excitation energy may also be transferred, through electromagnetic interactions, from one molecule to another. This process is called resonance energy transfer, and the rate depends strongly on the distance between the energy donor and energy acceptor molecules. Before an excited photon can transition back to ground state, the energy needs to be harvested. This excitation is transferred among chromopho
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https://en.wikipedia.org/wiki/Reflective%20subcategory
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In mathematics, a full subcategory A of a category B is said to be reflective in B when the inclusion functor from A to B has a left adjoint. This adjoint is sometimes called a reflector, or localization. Dually, A is said to be coreflective in B when the inclusion functor has a right adjoint.
Informally, a reflector acts as a kind of completion operation. It adds in any "missing" pieces of the structure in such a way that reflecting it again has no further effect.
Definition
A full subcategory A of a category B is said to be reflective in B if for each B-object B there exists an A-object and a B-morphism such that for each B-morphism to an A-object there exists a unique A-morphism with .
The pair is called the A-reflection of B. The morphism is called the A-reflection arrow. (Although often, for the sake of brevity, we speak about only as being the A-reflection of B).
This is equivalent to saying that the embedding functor is a right adjoint. The left adjoint functor is called the reflector. The map is the unit of this adjunction.
The reflector assigns to the A-object and for a B-morphism is determined by the commuting diagram
If all A-reflection arrows are (extremal) epimorphisms, then the subcategory A is said to be (extremal) epireflective. Similarly, it is bireflective if all reflection arrows are bimorphisms.
All these notions are special case of the common generalization—-reflective subcategory, where is a class of morphisms.
The -reflective hull of a class A of objects is defined as the smallest -reflective subcategory containing A. Thus we can speak about reflective hull, epireflective hull, extremal epireflective hull, etc.
An anti-reflective subcategory is a full subcategory A such that the only objects of B that have an A-reflection arrow are those that are already in A.
Dual notions to the above-mentioned notions are coreflection, coreflection arrow, (mono)coreflective subcategory, coreflective hull, anti-coreflective subcatego
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https://en.wikipedia.org/wiki/List%20of%20sports%20team%20names%20and%20mascots%20derived%20from%20indigenous%20peoples
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The practice of deriving sports team names, imagery, and mascots from Indigenous peoples of North America is a significant phenomenon in the United States and Canada. The popularity of stereotypical representations of American Indians in global culture has led to a number of teams in Europe also adopting team names derived from Native Americans. While there are team names in North America derived from other ethnic groups, such as the Boston Celtics, the New York Yankees, the Montreal Canadiens, and the Notre Dame Fighting Irish, these are names selected by groups to represent themselves.
Globally, there are teams in Africa and Europe that use Native American images and logos, while in South America there are a number of teams that reference the Guaraní people. In Brazil, these teams may be referred to using the derogatory term bugre. However, the adoption of Indigenous names in Asia, Africa, Australia and South America may indicate that the team members are themselves Indigenous.
The rise of Indigenous rights movements has led to controversy regarding the continuation of practices rooted in colonialism. Such practices maintain the power relationship between the dominant culture and the Indigenous culture, and can be seen as a form of cultural imperialism. Such practices are seen as particularly harmful in schools and universities, which have the stated purpose of promoting ethnic diversity and inclusion. In recognition of the responsibility of higher education to eliminate behaviors that creates a hostile environment for education, in 2005 the NCAA initiated a policy against "hostile and abusive" names and mascots that led to the change of many derived from Native American culture, with the exception of those that established an agreement with particular tribes for the use of their specific names. Other schools retain their names because they were founded for the education of Native Americans, and continue to have a significant number of Indigenous students.
The
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https://en.wikipedia.org/wiki/Disturbance%20%28ecology%29
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In ecology, a disturbance is a temporary change in environmental conditions that causes a pronounced change in an ecosystem. Disturbances often act quickly and with great effect, to alter the physical structure or arrangement of biotic and abiotic elements. A disturbance can also occur over a long period of time and can impact the biodiversity within an ecosystem.
Major ecological disturbances may include fires, flooding, storms, insect outbreaks and trampling. Earthquakes, various types of volcanic eruptions, tsunami, firestorms, impact events, climate change, and the devastating effects of human impact on the environment (anthropogenic disturbances) such as clearcutting, forest clearing and the introduction of invasive species can be considered major disturbances.
Not only invasive species can have a profound effect on an ecosystem, but also naturally occurring species can cause disturbance by their behavior. Disturbance forces can have profound immediate effects on ecosystems and can, accordingly, greatly alter the natural community’s population size or species richness. Because of these and the impacts on populations, disturbance determines the future shifts in dominance, various species successively becoming dominant as their life history characteristics, and associated life-forms, are exhibited over time.
Definition and types
The scale of disturbance ranges from events as small as a single tree falling, to as large as a mass extinction. Many natural ecosystems experience periodic disturbance that may broadly fall into a cyclical pattern. Ecosystems that form under these conditions are often maintained by regular disturbance. Wetland ecosystems, for example, can be maintained by the movement of water through them and by periodic fires. Different types of disturbance events occur in different habitats and climates with different weather conditions. Natural fire disturbances for example occur more often in areas with a higher incidence of lightning and flam
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https://en.wikipedia.org/wiki/Extended%20boot%20record
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An extended boot record (EBR), or extended partition boot record (EPBR), is a descriptor for a logical partition under the common DOS disk drive partitioning system. In that system, when one (and only one) partition record entry in the master boot record (MBR) is designated an extended partition, then that partition can be subdivided into a number of logical partitions. The actual structure of that extended partition is described by one or more EBRs, which are located inside the extended partition. The first (and sometimes only) EBR will always be located on the very first sector of the extended partition.
Unlike primary partitions, which are all described by a single partition table within the MBR, and thus limited in number, each EBR precedes the logical partition it describes. If another logical partition follows, then the first EBR will contain an entry pointing to the next EBR; thus, multiple EBRs form a linked list. This means the number of logical drives that can be formed within an extended partition is limited only by the amount of available disk space in the given extended partition.
While in Windows versions up to XP logical partitions within the extended partition were aligned following conventions called "drive geometry" or "CHS", since Windows Vista they are aligned to a 1-MiB boundary. Due to this difference in alignment, the Logical Disk Manager of XP (Disk Management) may delete these extended partitions without warning.
EBR structure and values
EBRs have essentially the same structure as the MBR; except only the first two entries of the partition table are supposed to be used, besides having the mandatory boot record signature (or magic number) of at the end of the sector. This 2-byte signature appears in a disk editor as first and last, because IBM-compatible PCs store hexadecimal words in little-endian order (see table below).
Structures
The IBM Boot Manager (included with OS/2 operating systems and some early versions of Partition Mag
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https://en.wikipedia.org/wiki/Exner%20equation
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The Exner equation is a statement of conservation of mass that applies to sediment in a fluvial system such as a river. It was developed by the Austrian meteorologist and sedimentologist Felix Maria Exner, from whom it derives its name.
The equation
The Exner equation describes conservation of mass between sediment in the bed of a channel and sediment that is being transported. It states that bed elevation increases (the bed aggrades) proportionally to the amount of sediment that drops out of transport, and conversely decreases (the bed degrades) proportionally to the amount of sediment that becomes entrained by the flow.
Basic equation
The equation states that the change in bed elevation, , over time, , is equal to one over the grain packing density, , times the negative divergence of sediment flux, .
Note that can also be expressed as , where equals the bed porosity.
Good values of for natural systems range from 0.45 to 0.75. A typical good value for spherical grains is 0.64, as given by random close packing. An upper bound for close-packed spherical grains is 0.74048. (See sphere packing for more details); this degree of packing is extremely improbable in natural systems, making random close packing the more realistic upper bound on grain packing density.
Often, for reasons of computational convenience and/or lack of data, the Exner equation is used in its one-dimensional form. This is generally done with respect to the down-stream direction , as one is typically interested in the down-stream distribution of erosion and deposition though a river reach.
Including external changes in elevation
An additional form of the Exner equation adds a subsidence term, , to the mass-balance. This allows the absolute elevation of the bed to be tracked over time in a situation in which it is being changed by outside influences, such as tectonic or compression-related subsidence (isostatic compression or rebound). In the convention of the following equation, is pos
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https://en.wikipedia.org/wiki/The%20Neutral%20Theory%20of%20Molecular%20Evolution
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The Neutral Theory of Molecular Evolution is an influential monograph written in 1983 by Japanese evolutionary biologist Motoo Kimura. While the neutral theory of molecular evolution existed since his article in 1968, Kimura felt the need to write a monograph with up-to-date information and evidences showing the importance of his theory in evolution.
Evolution is a change in the frequency of alleles in a population over time. Mutations occur at random and in the Darwinian evolution model natural selection acts on the genetic variation in a population that has arisen through this mutation. These mutations can be beneficial or deleterious and are selected for or against based on that factor. In this theory, every evolutionary event, mutation, and gene polymorphism (neutral differences in phenotype or genotype) would have to be positively or negatively selected for and show some kind of change over many generations. If these genetic differences grow between different populations speciation events can occur. When this theory was first introduced to the scientific community, there was no understanding of genetic principles such as drift or synonymous mutation.
When molecular biologists, like Motoo Kimura (1979), began to examine the DNA evidence, they found that far more mutations occur in non-protein coding regions or are synonymous mutations in coding regions (which do not change the protein structure or function) and are, therefore, not involved in selection as they do not impact an organism’s fitness. These findings began to show that the positive or negative selection in Darwinian evolution was too simplistic to describe every evolutionary process. Through various experiments Kimura was able to determine that proteins in mammalian lineages were polymorphisms of each other, having only one or two point mutations that did not affect the actions of the protein in any way, whereas in Darwinian evolution a slow pattern of selection in genetic lineages with increasing f
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https://en.wikipedia.org/wiki/Liquefied%20gas
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Liquefied gas (sometimes referred to as liquid gas) is a gas that has been turned into a liquid by cooling or compressing it. Examples of liquefied gases include liquid air, liquefied natural gas, and liquefied petroleum gas.
Liquid air
At the Lister Institute of Preventive Medicine, liquid air has been brought into use as an agent in biological research. An inquiry into the intracellular constituents of the typhoid bacillus, initiated under the direction of Doctor Allan Macfadyen, necessitated the separation of the cell-plasma of the organism. The method at first adopted for the disintegration of the bacteria was to mix them with silver-sand and churn the whole up in a closed vessel in which a series of horizontal vanes revolved at a high speed. But certain disadvantages attached to this procedure, and accordingly some means was sought to do away with the sand and triturate the bacilli per se. This was found in liquid air, which, as had long before been shown at the Royal Institution, has the power of reducing materials like grass or the leaves of plants to such a state of brittleness that they can easily be powdered in a mortar. By its aid a complete trituration of the typhoid bacilli has been accomplished at the Jenner Institute, and the same process, already applied with success also to yeast cells and animal cells, is being extended in other directions.
When air is liquefied the oxygen and nitrogen are condensed simultaneously. However, owing to its greater volatility the latter boils off the more quickly of the two, so that the remaining liquid becomes gradually richer and richer in oxygen.
Liquefied natural gas
Liquefied natural gas is natural gas that has been liquefied for the purpose of storage or transport. Since transportation of natural gas requires a large network of pipeline that crosses through various terrains and oceans, a huge investment and long term planning are required. Before transport, natural gas is liquefied by pressurization. The li
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https://en.wikipedia.org/wiki/Sound%20level%20meter
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A sound level meter (also called sound pressure level meter (SPL)) is used for acoustic measurements. It is commonly a hand-held instrument with a microphone. The best type of microphone for sound level meters is the condenser microphone, which combines precision with stability and reliability. The diaphragm of the microphone responds to changes in air pressure caused by sound waves. That is why the instrument is sometimes referred to as a sound pressure level meter (SPL). This movement of the diaphragm, i.e. the sound pressure (unit pascal, Pa), is converted into an electrical signal (unit volt, V). While describing sound in terms of sound pressure, a logarithmic conversion is usually applied and the sound pressure level is stated instead, in decibels (dB), with 0 dB SPL equal to 20 micropascals.
A microphone is distinguishable by the voltage value produced when a known, constant root mean square sound pressure is applied. This is known as microphone sensitivity. The instrument needs to know the sensitivity of the particular microphone being used. Using this information, the instrument is able to accurately convert the electrical signal back to sound pressure, and display the resulting sound pressure level (unit decibel, dB).
Sound level meters are commonly used in noise pollution studies for the quantification of different kinds of noise, especially for industrial, environmental, mining and aircraft noise. The current international standard that specifies sound level meter functionality and performances is the IEC 61672-1:2013. However, the reading from a sound level meter does not correlate well to human-perceived loudness, which is better measured by a loudness meter. Specific loudness is a compressive nonlinearity and varies at certain levels and at certain frequencies. These metrics can also be calculated in a number of different ways.
The world's first hand-held and transistorized sound level meter, was released in 1960 and developed by the Danish company
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https://en.wikipedia.org/wiki/List%20of%20Argentine%20flags
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This is a list of flags used in or otherwise associated with Argentina.
National flags
Presidential standard
Military
Argentine Army
Argentine Navy
Argentine National Gendarmerie
Other
Scouts de Argentina
Sporting flags
Vexillology Association flags
First-level administrative divisions
Historical
City flags
Unofficial regional flags
Political flags
Ethnic groups flags
Historical National flags
Argentine shipping company
Burgees of Argentina
See also
Coat of arms of Argentina
Provinces of Argentina
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https://en.wikipedia.org/wiki/Chesty%20Bond
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Chesty Bond is a fictional cartoon character and trademark for the Australian clothing company Bonds. The character was created in 1940, a co-creation of the advertising account manager Ted Moloney and artist Syd Miller. Chesty Bond was conceived as a likeable and heroic character in a continuous newspaper comic-strip, intended as a marketing campaign to sell the Bonds Athletic singlet. The comic-strip format, with a constantly changing storyline, proved to be extremely popular and continued to be published until 1963. Chesty Bond was possibly the world’s first daily advertising comic-strip. By virtue of its popularity and longevity, Chesty Bond became absorbed into Australian popular culture as a national icon.
Origins
The nexus between cartooning and the advertising of Bonds Athletic vests began in October 1936 with a series of crudely-drawn cartoons used in advertisements for the singlet in Australian Women's Weekly.
The first Bonds advertising comic-strip, called Embarrassing Moments from History, commenced in March 1937. The advertising strip appeared in various eastern Australian newspapers, initially made up of comic-strips illustrated by the artists Syd Nicholls, Syd Miller, George C. Little and 'Wep' (Walter Pidgeon). The strips consisted of separate vignettes featuring historical, biblical and fictional characters, always somehow involving a "Bonds Athletic vest" (singlet). After the initial strips appeared and had been re-run, new comic-strips in the series began to be published from October 1937, all drawn by Miller. In the creation of the Bonds advertising content, Syd Miller collaborated with Ted Moloney, who worked for the J. Walter Thompson advertising agency. Moloney and Miller had known each other since the 1930s when they both worked for Smith's Weekly newspaper. The Embarrassing Moments from History advertising comic-strip continued to appear in newspapers until the end of 1939, though no new strips were drawn after October 1938.
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https://en.wikipedia.org/wiki/Wow%20and%20flutter%20measurement
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Measurement of wow and flutter is carried out on audio tape machines, cassette recorders and players, and other analog recording and reproduction devices with rotary components (e.g. movie projectors, turntables (vinyl recording), etc.) This measurement quantifies the amount of 'frequency wobble' (caused by speed fluctuations) present in subjectively valid terms. Turntables tend to suffer mainly slow wow. In digital systems, which are locked to crystal oscillators, variations in clock timing are referred to as wander or jitter, depending on speed.
While the terms wow and flutter used to be used separately (for wobbles at a rate below and above 4 Hz respectively), they tend to be combined now that universal standards exist for measurement which take both into account simultaneously. Listeners find flutter most objectionable when the actual frequency of wobble is 4 Hz, and less audible above and below this rate. This fact forms the basis for the weighting curve shown here. The weighting curve is misleading, inasmuch as it presumes inaudibility of flutters above 200 Hz, when actually faster flutters are quite damaging to the sound. A flutter of 200 Hz at a level of -50db will create 0.3% intermodulation distortion, which would be considered unacceptable in a preamp or amplifier.
Measurement techniques
Measuring instruments use a frequency discriminator to translate the pitch variations of a recorded tone into a flutter waveform, which is then passed through the weighting filter, before being full-wave rectified to produce a slowly varying signal which drives a meter or recording device. The maximum meter indication should be read as the flutter value.
The following standards all specify the weighting filter shown above, together with a special slow-quasi-peak full-wave rectifier designed to register any brief speed excursions. As with many audio standards, these are identical derivatives of a common specification.
IEC 386
DIN45507
BS4847
CCIR 409-3
AES6-2008
Mea
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https://en.wikipedia.org/wiki/Length%20constant
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In neurobiology, the length constant (λ) is a mathematical constant used to quantify the distance that a graded electric potential will travel along a neurite via passive electrical conduction. The greater the value of the length constant, the farther the potential will travel. A large length constant can contribute to spatial summation—the electrical addition of one potential with potentials from adjacent areas of the cell.
The length constant can be defined as:
where rm is the membrane resistance (the force that impedes the flow of electric current from the outside of the membrane to the inside, and vice versa), ri is the axial resistance (the force that impedes current flow through the axoplasm, parallel to the membrane), and ro is the extracellular resistance (the force that impedes current flow through the extracellular fluid, parallel to the membrane). In calculation, the effects of ro are negligible, so the equation is typically expressed as:
The membrane resistance is a function of the number of open ion channels, and the axial resistance is generally a function of the diameter of the axon. The greater the number of open channels, the lower the rm. The greater the diameter of the axon, the lower the ri.
The length constant is used to describe the rise of potential difference across the membrane
The fall of voltage can be expressed as:
Where voltage, V, is measured in millivolts, x is distance from the start of the potential (in millimeters), and λ is the length constant (in millimeters).
Vmax is defined as the maximum voltage attained in the action potential, where:
where rm is the resistance across the membrane and I is the current flow.
Setting for x = λ for the rise of voltage sets V(x) equal to .63 Vmax. This means that the length constant is the distance at which 63% of Vmax has been reached during the rise of voltage.
Setting for x = λ for the fall of voltage sets V(x) equal to .37 Vmax, meaning that the length constant is the
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https://en.wikipedia.org/wiki/Ruderal%20species
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A ruderal species is a plant species that is first to colonize disturbed lands. The disturbance may be natural for example, wildfires or avalanchesor the consequences of human activities, such as construction (of roads, of buildings, mining, etc.) or agriculture (abandoned fields, irrigation, etc.).
The term ruderal originates from the Latin word rudus, meaning "rubble".
Ruderal species typically dominate the disturbed area for a few years, gradually losing the competition to other native species. However, in extreme disturbance circumstances, such as when the natural topsoil is covered with a foreign substance, a single-species ruderal community may become permanently established. In addition, some ruderal invasive species may have such a competitive advantage over the native species that they, too, may permanently prevent a disturbed area from returning to its original state despite natural topsoil.
Features
Features contributing to a species' success as ruderal are:
Massive seed production
Seedlings whose nutritional requirements are modest
Fast-growing roots
Independence of mycorrhizae
Polyploidy
Quantification
Ecologists have proposed various scales for quantifying ruderality, which can be defined as the "ability to thrive where there is disturbance through partial or total destruction of plant biomass" (Grime, Hodgson & Hunt, 1988). The ruderality scale of Grime presents values that are readily available, and it takes into account disturbance factors as well as other indicators such as the annual or perennial character of the plants.
See also
Edge effect
Hemeroby
Pioneer species
Restoration ecology
Supertramp (ecology)
Examples of ruderal species:
Cannabis ruderalis (family Cannabaceae)
Conyza bonariensis (family Asteraceae)
Dittrichia viscosa (Asteraceae)
Nicotiana glauca (Solanaceae)
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https://en.wikipedia.org/wiki/Shaker%20%28gene%29
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The shaker (Sh) gene, when mutated, causes a variety of atypical behaviors in the fruit fly, Drosophila melanogaster. Under ether anesthesia, the fly’s legs will shake (hence the name); even when the fly is unanaesthetized, it will exhibit aberrant movements. Sh-mutant flies have a shorter lifespan than regular flies; in their larvae, the repetitive firing of action potentials as well as prolonged exposure to neurotransmitters at neuromuscular junctions occurs.
In Drosophila, the shaker gene is located on the X chromosome. The closest human homolog is KCNA3.
Function
The Sh gene plays a part in the operation of potassium ion channels, which are integral membrane proteins and are essential to the correct functioning of the cell. A working shaker channel is voltage-dependent and has four subunits, which form a pore through which ions flow, carrying type-A potassium current (IA). A mutation in the Sh gene reduces the conductance of charge across the neuron since the channels do not work, causing the severe phenotypical aberrations mentioned above. These types of ion channels are responsible for the repolarization of the cell.
The shaker K channel is a homo tetrameric protein complex. When confronted with a stimulus, the tetramers undergo conformational changes; some of these changes are cooperative. The final step involved in the opening of the channel is highly synchronized.
Recently, the shaker gene has also been identified as a gene that helps determine an organism's amount of sleep. The phenotype of the flies that need less sleep is called minisleep (mns).
Blockers
The shaker K channel is affected by various toxins, which effectively slow the opening of the channel, or reversibly block its functioning.
Toxins that affect the shaker K channel include:
Agitoxin
Charybdotoxin
Iberiotoxin
Pandinotoxin
6-bromo-2-mercaptotryptamine (BrMT)
BrMT can be seen working in the K channel to prevent the early activation of the channel – before the cooperation h
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