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Flint, occasionally flintstone, is a sedimentary cryptocrystalline form of the mineral quartz, categorized as the variety of chert that occurs in chalk or marly limestone. Historically, flint was widely used to make stone tools and start fires.
Flint occurs chiefly as nodules and masses in sedimentary rocks, such as c... | Flint | Wikipedia | 394 | 43701 | https://en.wikipedia.org/wiki/Flint | Physical sciences | Sedimentary rocks | Earth science |
The exact mode of formation of flint is not yet clear, but it is thought that it occurs as a result of chemical changes in compressed sedimentary rock formations during the process of diagenesis. One hypothesis is that a gelatinous material fills cavities in the sediment, such as holes bored by crustaceans or molluscs ... | Flint | Wikipedia | 416 | 43701 | https://en.wikipedia.org/wiki/Flint | Physical sciences | Sedimentary rocks | Earth science |
Flint mining is attested since the Paleolithic, but became more common since the Neolithic (Michelsberg culture, Funnelbeaker culture). In Europe, some of the best toolmaking flint has come from Belgium (Obourg, flint mines of Spiennes), the coastal chalks of the English Channel, the Paris Basin, Thy in Jutland (flint ... | Flint | Wikipedia | 461 | 43701 | https://en.wikipedia.org/wiki/Flint | Physical sciences | Sedimentary rocks | Earth science |
A later, major use of flint and steel was in the flintlock mechanism, used primarily in flintlock firearms, but also used on dedicated fire-starting tools. A piece of flint held in the jaws of a spring-loaded hammer, when released by a trigger, strikes a hinged piece of steel ("frizzen") at an angle, creating a shower ... | Flint | Wikipedia | 397 | 43701 | https://en.wikipedia.org/wiki/Flint | Physical sciences | Sedimentary rocks | Earth science |
Flint, knapped or unknapped, has been used from antiquity (for example at the Late Roman fort of Burgh Castle in Norfolk) up to the present day as a material for building stone walls, using lime mortar, and often combined with other available stone or brick rubble. It was most common in those parts of southern England ... | Flint | Wikipedia | 333 | 43701 | https://en.wikipedia.org/wiki/Flint | Physical sciences | Sedimentary rocks | Earth science |
Until recently calcined flint was also an important raw material in clay-based ceramic bodies produced in the UK. In clay bodies, calcined flint attenuates the shrinkage whilst drying, and modifies the fired thermal expansion. Flint can also be used in glazes as a network former. In preparation for use flint pebbles, f... | Flint | Wikipedia | 211 | 43701 | https://en.wikipedia.org/wiki/Flint | Physical sciences | Sedimentary rocks | Earth science |
Radiation pressure (also known as light pressure) is mechanical pressure exerted upon a surface due to the exchange of momentum between the object and the electromagnetic field. This includes the momentum of light or electromagnetic radiation of any wavelength that is absorbed, reflected, or otherwise emitted (e.g. bl... | Radiation pressure | Wikipedia | 436 | 43709 | https://en.wikipedia.org/wiki/Radiation%20pressure | Physical sciences | Classical mechanics | Physics |
Radiation pressure can equally well be accounted for by considering the momentum of a classical electromagnetic field or in terms of the momenta of photons, particles of light. The interaction of electromagnetic waves or photons with matter may involve an exchange of momentum. Due to the law of conservation of momentum... | Radiation pressure | Wikipedia | 388 | 43709 | https://en.wikipedia.org/wiki/Radiation%20pressure | Physical sciences | Classical mechanics | Physics |
Consider the momentum transferred to a perfectly absorbing (black) surface. The energy flux (irradiance) of a plane wave is calculated using the Poynting vector , which is the cross product of the electric field vector E and the magnetic field's auxiliary field vector (or magnetizing field) H. The magnitude, denoted b... | Radiation pressure | Wikipedia | 485 | 43709 | https://en.wikipedia.org/wiki/Radiation%20pressure | Physical sciences | Classical mechanics | Physics |
The emission can be from black-body radiation or any other radiative mechanism. Since all materials emit black-body radiation (unless they are totally reflective or at absolute zero), this source for radiation pressure is ubiquitous but usually tiny. However, because black-body radiation increases rapidly with temperat... | Radiation pressure | Wikipedia | 510 | 43709 | https://en.wikipedia.org/wiki/Radiation%20pressure | Physical sciences | Classical mechanics | Physics |
Solar radiation pressure
Solar radiation pressure is due to the Sun's radiation at closer distances, thus especially within the Solar System. While it acts on all objects, its net effect is generally greater on smaller bodies, since they have a larger ratio of surface area to mass. All spacecraft experience such a pr... | Radiation pressure | Wikipedia | 500 | 43709 | https://en.wikipedia.org/wiki/Radiation%20pressure | Physical sciences | Classical mechanics | Physics |
Finally, considering not an absorbing but a perfectly reflecting surface, the pressure is doubled due to the reflected wave, resulting in:
Note that unlike the case of an absorbing material, the resulting force on a reflecting body is given exactly by this pressure acting normal to the surface, with the tangential for... | Radiation pressure | Wikipedia | 469 | 43709 | https://en.wikipedia.org/wiki/Radiation%20pressure | Physical sciences | Classical mechanics | Physics |
The Poynting–Robertson effect applies to grain-size particles. From the perspective of a grain of dust circling the Sun, the Sun's radiation appears to be coming from a slightly forward direction (aberration of light). Therefore, the absorption of this radiation leads to a force with a component against the direction o... | Radiation pressure | Wikipedia | 482 | 43709 | https://en.wikipedia.org/wiki/Radiation%20pressure | Physical sciences | Classical mechanics | Physics |
A sail reflects about 90% of the incident radiation. The 10% that is absorbed is radiated away from both surfaces, with the proportion emitted from the unlit surface depending on the thermal conductivity of the sail. A sail has curvature, surface irregularities, and other minor factors that affect its performance.
The... | Radiation pressure | Wikipedia | 454 | 43709 | https://en.wikipedia.org/wiki/Radiation%20pressure | Physical sciences | Classical mechanics | Physics |
Star formation is the process by which dense regions within molecular clouds in interstellar space collapse to form stars. As a branch of astronomy, star formation includes the study of the interstellar medium and giant molecular clouds (GMC) as precursors to the star formation process, and the study of protostars and ... | Radiation pressure | Wikipedia | 474 | 43709 | https://en.wikipedia.org/wiki/Radiation%20pressure | Physical sciences | Classical mechanics | Physics |
The reflection of a laser pulse from the surface of an elastic solid can give rise to various types of elastic waves that propagate inside the solid or liquid. In other words, the light can excite and/or amplify motion of, and in, materials. This is the subject of study in the field of optomechanics. The weakest waves ... | Radiation pressure | Wikipedia | 437 | 43709 | https://en.wikipedia.org/wiki/Radiation%20pressure | Physical sciences | Classical mechanics | Physics |
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant families of materials, existing as a compound of several minerals and as a syn... | Silicon dioxide | Wikipedia | 454 | 43710 | https://en.wikipedia.org/wiki/Silicon%20dioxide | Physical sciences | Ceramic compounds | Chemistry |
Polymorphism
Alpha quartz is the most stable form of solid SiO2 at room temperature. The high-temperature minerals, cristobalite and tridymite, have both lower densities and indices of refraction than quartz. The transformation from α-quartz to beta-quartz takes place abruptly at 573 °C. Since the transformation is acc... | Silicon dioxide | Wikipedia | 447 | 43710 | https://en.wikipedia.org/wiki/Silicon%20dioxide | Physical sciences | Ceramic compounds | Chemistry |
Molecular SiO2
The molecular SiO2 has a linear structure like . It has been produced by combining silicon monoxide (SiO) with oxygen in an argon matrix.
The dimeric silicon dioxide, (SiO2)2 has been obtained by reacting O2 with matrix isolated dimeric silicon monoxide, (Si2O2). In dimeric silicon dioxide there are two... | Silicon dioxide | Wikipedia | 443 | 43710 | https://en.wikipedia.org/wiki/Silicon%20dioxide | Physical sciences | Ceramic compounds | Chemistry |
Prominent examples include:
Tests or frustules (i.e. shells) of diatoms, Radiolaria, and testate amoebae.
Silica phytoliths in the cells of many plants including Equisetaceae, many grasses, and a wide range of dicotyledons.
The spicules forming the skeleton of many sponges.
Uses
Structural use
About 95% of the commer... | Silicon dioxide | Wikipedia | 470 | 43710 | https://en.wikipedia.org/wiki/Silicon%20dioxide | Physical sciences | Ceramic compounds | Chemistry |
Fumed silica
Fumed silica, also known as pyrogenic silica, is prepared by burning SiCl4 in an oxygen-rich hydrogen flame to produce a "smoke" of SiO2.
SiCl4 + 2 H2 + O2 -> SiO2 + 4 HCl
It can also be produced by vaporizing quartz sand in a 3000 °C electric arc. Both processes result in microscopic droplets of amorphou... | Silicon dioxide | Wikipedia | 494 | 43710 | https://en.wikipedia.org/wiki/Silicon%20dioxide | Physical sciences | Ceramic compounds | Chemistry |
for the primary passivation (directly on the semiconductor surface),
as an original gate dielectric in MOS technology. Today when scaling (dimension of the gate length of the MOS transistor) has progressed below 10 nm, silicon dioxide has been replaced by other dielectric materials like hafnium oxide or similar with h... | Silicon dioxide | Wikipedia | 500 | 43710 | https://en.wikipedia.org/wiki/Silicon%20dioxide | Physical sciences | Ceramic compounds | Chemistry |
Silica aerogel was used in the Stardust spacecraft to collect extraterrestrial particles.
Pure silica (silicon dioxide), when cooled as fused quartz into a glass with no true melting point, can be used as a glass fibre for fibreglass.
Production
Silicon dioxide is mostly obtained by mining, including sand mining and ... | Silicon dioxide | Wikipedia | 504 | 43710 | https://en.wikipedia.org/wiki/Silicon%20dioxide | Physical sciences | Ceramic compounds | Chemistry |
Si(OC2H5)4 + 12 O2 -> SiO2 + 10 H2O + 8 CO2
TEOS undergoes hydrolysis via the so-called sol-gel process. The course of the reaction and nature of the product are affected by catalysts, but the idealized equation is:
Si(OC2H5)4 + 2 H2O -> SiO2 + 4 HOCH2CH3
Other methods
Being highly stable, silicon dioxide arises fr... | Silicon dioxide | Wikipedia | 505 | 43710 | https://en.wikipedia.org/wiki/Silicon%20dioxide | Physical sciences | Ceramic compounds | Chemistry |
Silicon dioxide will neutralise basic metal oxides (e.g. sodium oxide, potassium oxide, lead(II) oxide, zinc oxide, or mixtures of oxides, forming silicates and glasses as the Si-O-Si bonds in silica are broken successively). As an example the reaction of sodium oxide and SiO2 can produce sodium orthosilicate, sodium s... | Silicon dioxide | Wikipedia | 448 | 43710 | https://en.wikipedia.org/wiki/Silicon%20dioxide | Physical sciences | Ceramic compounds | Chemistry |
Silica ingested orally is essentially nontoxic, with an of 5000 mg/kg (5 g/kg). A 2008 study following subjects for 15 years found that higher levels of silica in water appeared to decrease the risk of dementia. An increase of 10 mg/day of silica in drinking water was associated with a reduced risk of dementia of 11%.... | Silicon dioxide | Wikipedia | 497 | 43710 | https://en.wikipedia.org/wiki/Silicon%20dioxide | Physical sciences | Ceramic compounds | Chemistry |
Crystalline forms
SiO2, more so than almost any material, exists in many crystalline forms. These forms are called polymorphs.
Safety
Inhaling finely divided crystalline silica can lead to severe inflammation of the lung tissue, silicosis, bronchitis, lung cancer, and systemic autoimmune diseases, such as lupus and rh... | Silicon dioxide | Wikipedia | 139 | 43710 | https://en.wikipedia.org/wiki/Silicon%20dioxide | Physical sciences | Ceramic compounds | Chemistry |
The prisoner's dilemma is a game theory thought experiment involving two rational agents, each of whom can either cooperate for mutual benefit or betray their partner ("defect") for individual gain. The dilemma arises from the fact that while defecting is rational for each agent, cooperation yields a higher payoff for ... | Prisoner's dilemma | Wikipedia | 492 | 43717 | https://en.wikipedia.org/wiki/Prisoner%27s%20dilemma | Mathematics | Game theory | null |
This leads to three different possible outcomes for prisoners A and B:
If A and B both remain silent, they will each serve one year in prison.
If one testifies against the other but the other doesn’t, the one testifying will be set free while the other serves three years in prison.
If A and B testify against each ot... | Prisoner's dilemma | Wikipedia | 512 | 43717 | https://en.wikipedia.org/wiki/Prisoner%27s%20dilemma | Mathematics | Game theory | null |
The iterated prisoner's dilemma
If two players play the prisoner's dilemma more than once in succession, remember their opponent's previous actions, and are allowed to change their strategy accordingly, the game is called the iterated prisoner's dilemma.
In addition to the general form above, the iterative version al... | Prisoner's dilemma | Wikipedia | 501 | 43717 | https://en.wikipedia.org/wiki/Prisoner%27s%20dilemma | Mathematics | Game theory | null |
Axelrod's tournament and successful strategy conditions
Interest in the iterated prisoner's dilemma was kindled by Robert Axelrod in his 1984 book The Evolution of Cooperation, in which he reports on a tournament that he organized of the N-step prisoner's dilemma (with N fixed) in which participants have to choose thei... | Prisoner's dilemma | Wikipedia | 373 | 43717 | https://en.wikipedia.org/wiki/Prisoner%27s%20dilemma | Mathematics | Game theory | null |
Nice: The strategy will not be the first to defect (this is sometimes referred to as an "optimistic" algorithm), i.e., it will not "cheat" on its opponent for purely self-interested reasons first. Almost all the top-scoring strategies were nice.
Retaliating: The strategy must sometimes retaliate. An example of a non-r... | Prisoner's dilemma | Wikipedia | 496 | 43717 | https://en.wikipedia.org/wiki/Prisoner%27s%20dilemma | Mathematics | Game theory | null |
Although tit-for-tat is considered the most robust basic strategy, a team from Southampton University in England introduced a more successful strategy at the 20th-anniversary iterated prisoner's dilemma competition. It relied on collusion between programs to achieve the highest number of points for a single program. Th... | Prisoner's dilemma | Wikipedia | 495 | 43717 | https://en.wikipedia.org/wiki/Prisoner%27s%20dilemma | Mathematics | Game theory | null |
This can also be illustrated using the Darwinian ESS simulation. In such a simulation, tit-for-tat will almost always come to dominate, though nasty strategies will drift in and out of the population because a tit-for-tat population is penetrable by non-retaliating nice strategies, which in turn are easy prey for the n... | Prisoner's dilemma | Wikipedia | 360 | 43717 | https://en.wikipedia.org/wiki/Prisoner%27s%20dilemma | Mathematics | Game theory | null |
If is defined as the above 4-element strategy vector of X and as the 4-element strategy vector of Y (where the indices are from Y's point of view), a transition matrix M may be defined for X whose ij-th entry is the probability that the outcome of a particular encounter between X and Y will be j given that the previo... | Prisoner's dilemma | Wikipedia | 441 | 43717 | https://en.wikipedia.org/wiki/Prisoner%27s%20dilemma | Mathematics | Game theory | null |
In 2012, William H. Press and Freeman Dyson published a new class of strategies for the stochastic iterated prisoner's dilemma called "zero-determinant" (ZD) strategies. The long term payoffs for encounters between X and Y can be expressed as the determinant of a matrix which is a function of the two strategies and the... | Prisoner's dilemma | Wikipedia | 497 | 43717 | https://en.wikipedia.org/wiki/Prisoner%27s%20dilemma | Mathematics | Game theory | null |
Theory and simulations confirm that beyond a critical population size, ZD extortion loses out in evolutionary competition against more cooperative strategies, and as a result, the average payoff in the population increases when the population is larger. In addition, there are some cases in which extortioners may even c... | Prisoner's dilemma | Wikipedia | 302 | 43717 | https://en.wikipedia.org/wiki/Prisoner%27s%20dilemma | Mathematics | Game theory | null |
Continuous iterated prisoner's dilemma
Most work on the iterated prisoner's dilemma has focused on the discrete case, in which players either cooperate or defect, because this model is relatively simple to analyze. However, some researchers have looked at models of the continuous iterated prisoner's dilemma, in which p... | Prisoner's dilemma | Wikipedia | 427 | 43717 | https://en.wikipedia.org/wiki/Prisoner%27s%20dilemma | Mathematics | Game theory | null |
An important difference between climate-change politics and the prisoner's dilemma is uncertainty; the extent and pace at which pollution can change climate is not known. The dilemma faced by governments is therefore different from the prisoner's dilemma in that the payoffs of cooperation are unknown. This difference s... | Prisoner's dilemma | Wikipedia | 489 | 43717 | https://en.wikipedia.org/wiki/Prisoner%27s%20dilemma | Mathematics | Game theory | null |
In The Science of Trust, John Gottman defines good relationships as those where partners know not to enter into mutual defection behavior, or at least not to get dynamically stuck there in a loop. In cognitive neuroscience, fast brain signaling associated with processing different rounds may indicate choices at the nex... | Prisoner's dilemma | Wikipedia | 496 | 43717 | https://en.wikipedia.org/wiki/Prisoner%27s%20dilemma | Mathematics | Game theory | null |
Sport
Doping in sport has been cited as an example of a prisoner's dilemma. Two competing athletes have the option to use an illegal and/or dangerous drug to boost their performance. If neither athlete takes the drug, then neither gains an advantage. If only one does, then that athlete gains a significant advantage ove... | Prisoner's dilemma | Wikipedia | 435 | 43717 | https://en.wikipedia.org/wiki/Prisoner%27s%20dilemma | Mathematics | Game theory | null |
The commons are not always exploited: William Poundstone, in a book about the prisoner's dilemma, describes a situation in New Zealand where newspaper boxes are left unlocked. It is possible for people to take a paper without paying (defecting), but very few do, feeling that if they do not pay then neither will others,... | Prisoner's dilemma | Wikipedia | 474 | 43717 | https://en.wikipedia.org/wiki/Prisoner%27s%20dilemma | Mathematics | Game theory | null |
Friend or Foe?
Friend or Foe? is a game show that aired from 2002 to 2003 on the Game Show Network in the US. On the game show, three pairs of people compete. When a pair is eliminated, they play a game similar to the prisoner's dilemma to determine how the winnings are split. If they both cooperate (Friend), they shar... | Prisoner's dilemma | Wikipedia | 490 | 43717 | https://en.wikipedia.org/wiki/Prisoner%27s%20dilemma | Mathematics | Game theory | null |
This may better reflect real-world scenarios, the researchers giving the example of two scientists collaborating on a report, both of whom would benefit if the other worked harder. "But when your collaborator doesn't do any work, it's probably better for you to do all the work yourself. You'll still end up with a compl... | Prisoner's dilemma | Wikipedia | 424 | 43717 | https://en.wikipedia.org/wiki/Prisoner%27s%20dilemma | Mathematics | Game theory | null |
In fiction
Hannu Rajaniemi set the opening scene of his The Quantum Thief trilogy in a "dilemma prison". The main theme of the series has been described as the "inadequacy of a binary universe" and the ultimate antagonist is a character called the All-Defector. The first book in the series was published in 2010, with t... | Prisoner's dilemma | Wikipedia | 474 | 43717 | https://en.wikipedia.org/wiki/Prisoner%27s%20dilemma | Mathematics | Game theory | null |
Some game theorists have criticized the use of the prisoner's dilemma as a thinking tool in moral philosophy. Kenneth Binmore argued that the prisoner's dilemma does not accurately describe the game played by humanity, which he argues is closer to a coordination game. Brian Skyrms shares this perspective.
Steven Kuhn ... | Prisoner's dilemma | Wikipedia | 187 | 43717 | https://en.wikipedia.org/wiki/Prisoner%27s%20dilemma | Mathematics | Game theory | null |
Linear programming (LP), also called linear optimization, is a method to achieve the best outcome (such as maximum profit or lowest cost) in a mathematical model whose requirements and objective are represented by linear relationships. Linear programming is a special case of mathematical programming (also known as math... | Linear programming | Wikipedia | 456 | 43730 | https://en.wikipedia.org/wiki/Linear%20programming | Mathematics | Other | null |
The turning point came during World War II when linear programming emerged as a vital tool. It found extensive use in addressing complex wartime challenges, including transportation logistics, scheduling, and resource allocation. Linear programming proved invaluable in optimizing these processes while considering criti... | Linear programming | Wikipedia | 496 | 43730 | https://en.wikipedia.org/wiki/Linear%20programming | Mathematics | Other | null |
The linear programming problem was first shown to be solvable in polynomial time by Leonid Khachiyan in 1979, but a larger theoretical and practical breakthrough in the field came in 1984 when Narendra Karmarkar introduced a new interior-point method for solving linear-programming problems.
Uses
Linear programming is... | Linear programming | Wikipedia | 352 | 43730 | https://en.wikipedia.org/wiki/Linear%20programming | Mathematics | Other | null |
Suppose that a farmer has a piece of farm land, say L hectares, to be planted with either wheat or barley or some combination of the two. The farmer has F kilograms of fertilizer and P kilograms of pesticide. Every hectare of wheat requires F1 kilograms of fertilizer and P1 kilograms of pesticide, while every hectare o... | Linear programming | Wikipedia | 487 | 43730 | https://en.wikipedia.org/wiki/Linear%20programming | Mathematics | Other | null |
There are two ideas fundamental to duality theory. One is the fact that (for the symmetric dual) the dual of a dual linear program is the original primal linear program. Additionally, every feasible solution for a linear program gives a bound on the optimal value of the objective function of its dual. The weak duality... | Linear programming | Wikipedia | 486 | 43730 | https://en.wikipedia.org/wiki/Linear%20programming | Mathematics | Other | null |
Suppose that x = (x1, x2, ... , xn) is primal feasible and that y = (y1, y2, ... , ym) is dual feasible. Let (w1, w2, ..., wm) denote the corresponding primal slack variables, and let (z1, z2, ... , zn) denote the corresponding dual slack variables. Then x and y are optimal for their respective problems if and only if
... | Linear programming | Wikipedia | 489 | 43730 | https://en.wikipedia.org/wiki/Linear%20programming | Mathematics | Other | null |
Optimal vertices (and rays) of polyhedra
Otherwise, if a feasible solution exists and if the constraint set is bounded, then the optimum value is always attained on the boundary of the constraint set, by the maximum principle for convex functions (alternatively, by the minimum principle for concave functions) since li... | Linear programming | Wikipedia | 500 | 43730 | https://en.wikipedia.org/wiki/Linear%20programming | Mathematics | Other | null |
However, the simplex algorithm has poor worst-case behavior: Klee and Minty constructed a family of linear programming problems for which the simplex method takes a number of steps exponential in the problem size. In fact, for some time it was not known whether the linear programming problem was solvable in polynomial ... | Linear programming | Wikipedia | 508 | 43730 | https://en.wikipedia.org/wiki/Linear%20programming | Mathematics | Other | null |
Vaidya's 87 algorithm
In 1987, Vaidya proposed an algorithm that runs in time.
Vaidya's 89 algorithm
In 1989, Vaidya developed an algorithm that runs in time. Formally speaking, the algorithm takes arithmetic operations in the worst case, where is the number of constraints, is the number of variables, and is ... | Linear programming | Wikipedia | 424 | 43730 | https://en.wikipedia.org/wiki/Linear%20programming | Mathematics | Other | null |
This closely related set of problems has been cited by Stephen Smale as among the 18 greatest unsolved problems of the 21st century. In Smale's words, the third version of the problem "is the main unsolved problem of linear programming theory." While algorithms exist to solve linear programming in weakly polynomial t... | Linear programming | Wikipedia | 424 | 43730 | https://en.wikipedia.org/wiki/Linear%20programming | Mathematics | Other | null |
Simplex pivot methods preserve primal (or dual) feasibility. On the other hand, criss-cross pivot methods do not preserve (primal or dual) feasibilitythey may visit primal feasible, dual feasible or primal-and-dual infeasible bases in any order. Pivot methods of this type have been studied since the 1970s. Essential... | Linear programming | Wikipedia | 452 | 43730 | https://en.wikipedia.org/wiki/Linear%20programming | Mathematics | Other | null |
A linear program in real variables is said to be integral if it has at least one optimal solution which is integral, i.e., made of only integer values. Likewise, a polyhedron is said to be integral if for all bounded feasible objective functions c, the linear program has an optimum with integer coordinates. As obser... | Linear programming | Wikipedia | 471 | 43730 | https://en.wikipedia.org/wiki/Linear%20programming | Mathematics | Other | null |
In telecommunications and computer networking, a network packet is a formatted unit of data carried by a packet-switched network. A packet consists of control information and user data; the latter is also known as the payload. Control information provides data for delivering the payload (e.g., source and destination ne... | Network packet | Wikipedia | 470 | 43734 | https://en.wikipedia.org/wiki/Network%20packet | Technology | Networks | null |
At the transmitter, the calculation is performed before the packet is sent. When received at the destination, the checksum is recalculated, and compared with the one in the packet. If discrepancies are found, the packet may be corrected or discarded. Any packet loss due to these discards is dealt with by the network pr... | Network packet | Wikipedia | 505 | 43734 | https://en.wikipedia.org/wiki/Network%20packet | Technology | Networks | null |
NASA Deep Space Network
The Consultative Committee for Space Data Systems (CCSDS) packet telemetry standard defines the protocol used for the transmission of spacecraft instrument data over the deep-space channel. Under this standard, an image or other data sent from a spacecraft instrument is transmitted using one or... | Network packet | Wikipedia | 299 | 43734 | https://en.wikipedia.org/wiki/Network%20packet | Technology | Networks | null |
Clostridium botulinum is a gram-positive, rod-shaped, anaerobic, spore-forming, motile bacterium with the ability to produce botulinum toxin, which is a neurotoxin.
C. botulinum is a diverse group of pathogenic bacteria. Initially, they were grouped together by their ability to produce botulinum toxin and are now know... | Clostridium botulinum | Wikipedia | 418 | 43922 | https://en.wikipedia.org/wiki/Clostridium%20botulinum | Biology and health sciences | Gram-positive bacteria | Plants |
C. botulinum is divided into four distinct phenotypic groups (I-IV) and is also classified into seven serotypes (A–G) based on the antigenicity of the botulinum toxin produced. On the level visible to DNA sequences, the phenotypic grouping matches the results of whole-genome and rRNA analyses, and setotype grouping app... | Clostridium botulinum | Wikipedia | 443 | 43922 | https://en.wikipedia.org/wiki/Clostridium%20botulinum | Biology and health sciences | Gram-positive bacteria | Plants |
Toxin types in disease
Only botulinum toxin types A, B, E, F and H (FA) cause disease in humans. Types A, B, and E are associated with food-borne illness, while type E is specifically associated with fish products. Type C produces limber-neck in birds and type D causes botulism in other mammals. No disease is asso... | Clostridium botulinum | Wikipedia | 496 | 43922 | https://en.wikipedia.org/wiki/Clostridium%20botulinum | Biology and health sciences | Gram-positive bacteria | Plants |
Laboratory isolation
In the laboratory, C. botulinum is usually isolated in tryptose sulfite cycloserine (TSC) growth medium in an anaerobic environment with less than 2% oxygen. This can be achieved by several commercial kits that use a chemical reaction to replace O2 with CO2. C. botulinum (groups I through III) is a... | Clostridium botulinum | Wikipedia | 349 | 43922 | https://en.wikipedia.org/wiki/Clostridium%20botulinum | Biology and health sciences | Gram-positive bacteria | Plants |
C. botulinum is a soil bacterium. The spores can survive in most environments and are very hard to kill. They can survive the temperature of boiling water at sea level, thus many foods are canned with a pressurized boil that achieves even higher temperatures, sufficient to kill the spores. This bacteria is widely distr... | Clostridium botulinum | Wikipedia | 412 | 43922 | https://en.wikipedia.org/wiki/Clostridium%20botulinum | Biology and health sciences | Gram-positive bacteria | Plants |
The control of food-borne botulism caused by C. botulinum is based almost entirely on thermal destruction (heating) of the spores or inhibiting spore germination into bacteria and allowing cells to grow and produce toxins in foods. Conditions conducive of growth are dependent on various environmental factors.
Growth of... | Clostridium botulinum | Wikipedia | 453 | 43922 | https://en.wikipedia.org/wiki/Clostridium%20botulinum | Biology and health sciences | Gram-positive bacteria | Plants |
Smith et al. (2018) argues that group I should be called C. parabotulinum and group III be called C. novyi sensu lato, leaving only group II in C. botulinum. This argument is not accepted by the LPSN and would cause an unjustified change of the type strain under the Prokaryotic Code. (The current type strain ATCC 25763... | Clostridium botulinum | Wikipedia | 506 | 43922 | https://en.wikipedia.org/wiki/Clostridium%20botulinum | Biology and health sciences | Gram-positive bacteria | Plants |
Foodborne botulism
Signs and symptoms of foodborne botulism typically begin between 18 and 36 hours after the toxin gets into your body, but can range from a few hours to several days, depending on the amount of toxin ingested. Symptoms include:
Double vision
Blurred vision
Ptosis
Nausea, vomiting, and abdominal c... | Clostridium botulinum | Wikipedia | 483 | 43922 | https://en.wikipedia.org/wiki/Clostridium%20botulinum | Biology and health sciences | Gram-positive bacteria | Plants |
In North America, an equine-derived heptavalent botulinum antitoxin is used to treat all serotypes of non-infant naturally occurring botulism. For infants less than one year of age, botulism immune globulin is used to treat type A or type B.
Outcomes vary between one and three months, but with prompt interventions, mo... | Clostridium botulinum | Wikipedia | 424 | 43922 | https://en.wikipedia.org/wiki/Clostridium%20botulinum | Biology and health sciences | Gram-positive bacteria | Plants |
Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson characterised parasites as "predators that eat prey in units of less than one". Parasi... | Parasitism | Wikipedia | 475 | 43937 | https://en.wikipedia.org/wiki/Parasitism | Biology and health sciences | Ecology | null |
Human knowledge of parasites such as roundworms and tapeworms dates back to ancient Egypt, Greece, and Rome. In early modern times, Antonie van Leeuwenhoek observed Giardia lamblia with his microscope in 1681, while Francesco Redi described internal and external parasites including sheep liver fluke and ticks. Modern p... | Parasitism | Wikipedia | 373 | 43937 | https://en.wikipedia.org/wiki/Parasitism | Biology and health sciences | Ecology | null |
Within that scope are many possible strategies. Taxonomists classify parasites in a variety of overlapping schemes, based on their interactions with their hosts and on their life cycles, which can be complex. An obligate parasite depends completely on the host to complete its life cycle, while a facultative parasite do... | Parasitism | Wikipedia | 452 | 43937 | https://en.wikipedia.org/wiki/Parasitism | Biology and health sciences | Ecology | null |
The sensory inputs that a parasite employs to identify and approach a potential host are known as "host cues". Such cues can include, for example, vibration, exhaled carbon dioxide, skin odours, visual and heat signatures, and moisture. Parasitic plants can use, for example, light, host physiochemistry, and volatiles t... | Parasitism | Wikipedia | 502 | 43937 | https://en.wikipedia.org/wiki/Parasitism | Biology and health sciences | Ecology | null |
Directly transmitted parasites, not requiring a vector to reach their hosts, include such parasites of terrestrial vertebrates as lice and mites; marine parasites such as copepods and cyamid amphipods; monogeneans; and many species of nematodes, fungi, protozoans, bacteria, and viruses. Whether endoparasites or ectopar... | Parasitism | Wikipedia | 360 | 43937 | https://en.wikipedia.org/wiki/Parasitism | Biology and health sciences | Ecology | null |
Vector-transmitted parasites rely on a third party, an intermediate host, where the parasite does not reproduce sexually, to carry them from one definitive host to another. These parasites are microorganisms, namely protozoa, bacteria, or viruses, often intracellular pathogens (disease-causers). Their vectors are mostl... | Parasitism | Wikipedia | 499 | 43937 | https://en.wikipedia.org/wiki/Parasitism | Biology and health sciences | Ecology | null |
A micropredator attacks more than one host, reducing each host's fitness by at least a small amount, and is only in contact with any one host intermittently. This behavior makes micropredators suitable as vectors, as they can pass smaller parasites from one host to another. Most micropredators are hematophagic, feeding... | Parasitism | Wikipedia | 453 | 43937 | https://en.wikipedia.org/wiki/Parasitism | Biology and health sciences | Ecology | null |
Social parasites take advantage of interspecific interactions between members of eusocial animals such as ants, termites, and bumblebees. Examples include the large blue butterfly, Phengaris arion, its larvae employing ant mimicry to parasitise certain ants, Bombus bohemicus, a bumblebee which invades the hives of othe... | Parasitism | Wikipedia | 263 | 43937 | https://en.wikipedia.org/wiki/Parasitism | Biology and health sciences | Ecology | null |
In brood parasitism, the hosts suffer increased parental investment and energy expenditure to feed parasitic young, which are commonly larger than host young. The growth rate of host nestlings is slowed, reducing the host's fitness. Brood parasites include birds in different families such as cowbirds, whydahs, cuckoos,... | Parasitism | Wikipedia | 500 | 43937 | https://en.wikipedia.org/wiki/Parasitism | Biology and health sciences | Ecology | null |
Adelphoparasitism, (from Greek ἀδελφός (adelphós), brother), also known as sibling-parasitism, occurs where the host species is closely related to the parasite, often in the same family or genus. In the citrus blackfly parasitoid, Encarsia perplexa, unmated females may lay haploid eggs in the fully developed larvae of ... | Parasitism | Wikipedia | 281 | 43937 | https://en.wikipedia.org/wiki/Parasitism | Biology and health sciences | Ecology | null |
A hemiparasite or partial parasite such as mistletoe derives some of its nutrients from another living plant, whereas a holoparasite such as Cuscuta derives all of its nutrients from another plant. Parasitic plants make up about one per cent of angiosperms and are in almost every biome in the world. All these plants ha... | Parasitism | Wikipedia | 512 | 43937 | https://en.wikipedia.org/wiki/Parasitism | Biology and health sciences | Ecology | null |
Fungi
Parasitic fungi derive some or all of their nutritional requirements from plants, other fungi, or animals.
Plant pathogenic fungi are classified into three categories depending on their mode of nutrition: biotrophs, hemibiotrophs and necrotrophs. Biotrophic fungi derive nutrients from living plant cells, and d... | Parasitism | Wikipedia | 354 | 43937 | https://en.wikipedia.org/wiki/Parasitism | Biology and health sciences | Ecology | null |
Many bacteria are parasitic, though they are more generally thought of as pathogens causing disease. Parasitic bacteria are extremely diverse, and infect their hosts by a variety of routes. To give a few examples, Bacillus anthracis, the cause of anthrax, is spread by contact with infected domestic animals; its spores,... | Parasitism | Wikipedia | 369 | 43937 | https://en.wikipedia.org/wiki/Parasitism | Biology and health sciences | Ecology | null |
Parasitism is a major aspect of evolutionary ecology; for example, almost all free-living animals are host to at least one species of parasite. Vertebrates, the best-studied group, are hosts to between 75,000 and 300,000 species of helminths and an uncounted number of parasitic microorganisms. On average, a mammal spec... | Parasitism | Wikipedia | 386 | 43937 | https://en.wikipedia.org/wiki/Parasitism | Biology and health sciences | Ecology | null |
Long-term partnerships can lead to a relatively stable relationship tending to commensalism or mutualism, as, all else being equal, it is in the evolutionary interest of the parasite that its host thrives. A parasite may evolve to become less harmful for its host or a host may evolve to cope with the unavoidable presen... | Parasitism | Wikipedia | 428 | 43937 | https://en.wikipedia.org/wiki/Parasitism | Biology and health sciences | Ecology | null |
An example is between the simian foamy virus (SFV) and its primate hosts. The phylogenies of SFV polymerase and the mitochondrial cytochrome c oxidase subunit II from African and Asian primates were found to be closely congruent in branching order and divergence times, implying that the simian foamy viruses cospeciated... | Parasitism | Wikipedia | 372 | 43937 | https://en.wikipedia.org/wiki/Parasitism | Biology and health sciences | Ecology | null |
Some parasites modify host behaviour in order to increase their transmission between hosts, often in relation to predator and prey (parasite increased trophic transmission). For example, in the California coastal salt marsh, the fluke Euhaplorchis californiensis reduces the ability of its killifish host to avoid predat... | Parasitism | Wikipedia | 445 | 43937 | https://en.wikipedia.org/wiki/Parasitism | Biology and health sciences | Ecology | null |
The evolutionary biologist W. D. Hamilton suggested that sexual reproduction could have evolved to help to defeat multiple parasites by enabling genetic recombination, the shuffling of genes to create varied combinations. Hamilton showed by mathematical modelling that sexual reproduction would be evolutionarily stable ... | Parasitism | Wikipedia | 386 | 43937 | https://en.wikipedia.org/wiki/Parasitism | Biology and health sciences | Ecology | null |
Insects often adapt their nests to reduce parasitism. For example, one of the key reasons why the wasp Polistes canadensis nests across multiple combs, rather than building a single comb like much of the rest of its genus, is to avoid infestation by tineid moths. The tineid moth lays its eggs within the wasps' nests an... | Parasitism | Wikipedia | 386 | 43937 | https://en.wikipedia.org/wiki/Parasitism | Biology and health sciences | Ecology | null |
Parasitism and parasite evolution were until the twenty-first century studied by parasitologists, in a science dominated by medicine, rather than by ecologists or evolutionary biologists. Even though parasite-host interactions were plainly ecological and important in evolution, the history of parasitology caused what t... | Parasitism | Wikipedia | 408 | 43937 | https://en.wikipedia.org/wiki/Parasitism | Biology and health sciences | Ecology | null |
Although parasites are widely considered to be harmful, the eradication of all parasites would not be beneficial. Parasites account for at least half of life's diversity; they perform important ecological roles; and without parasites, organisms might tend to asexual reproduction, diminishing the diversity of traits bro... | Parasitism | Wikipedia | 501 | 43937 | https://en.wikipedia.org/wiki/Parasitism | Biology and health sciences | Ecology | null |
In his Canon of Medicine, completed in 1025, the Persian physician Avicenna recorded human and animal parasites including roundworms, threadworms, the Guinea worm and tapeworms.
In his 1397 book Traité de l'état, science et pratique de l'art de la Bergerie (Account of the state, science and practice of the art of shep... | Parasitism | Wikipedia | 427 | 43937 | https://en.wikipedia.org/wiki/Parasitism | Biology and health sciences | Ecology | null |
Modern parasitology developed in the 19th century with accurate observations and experiments by many researchers and clinicians; the term was first used in 1870. In 1828, James Annersley described amoebiasis, protozoal infections of the intestines and the liver, though the pathogen, Entamoeba histolytica, was not disco... | Parasitism | Wikipedia | 463 | 43937 | https://en.wikipedia.org/wiki/Parasitism | Biology and health sciences | Ecology | null |
Poulin observes that the widespread prophylactic use of anthelmintic drugs in domestic sheep and cattle constitutes a worldwide uncontrolled experiment in the life-history evolution of their parasites. The outcomes depend on whether the drugs decrease the chance of a helminth larva reaching adulthood. If so, natural se... | Parasitism | Wikipedia | 508 | 43937 | https://en.wikipedia.org/wiki/Parasitism | Biology and health sciences | Ecology | null |
The entomopathogenic fungus Cordyceps is represented culturally as a deadly threat to the human race. The video game series The Last of Us (2013–present) and its television adaptation present Cordyceps as a parasite of humans, causing a zombie apocalypse. Its human hosts initially become violent "infected" beings, befo... | Parasitism | Wikipedia | 86 | 43937 | https://en.wikipedia.org/wiki/Parasitism | Biology and health sciences | Ecology | null |
Massage is the rubbing or kneading of the body's soft tissues. Massage techniques are commonly applied with hands, fingers, elbows, knees, forearms, feet, or a device. The purpose of massage is generally for the treatment of body stress or pain. In English-speaking European countries, a person professionally trained to... | Massage | Wikipedia | 408 | 43945 | https://en.wikipedia.org/wiki/Massage | Biology and health sciences | Treatments | Health |
722–481 BC: Huangdi Neijing is composed during the Chinese Spring and Autumn period. The Nei-jing is a compilation of medical knowledge known up to that date, and is the foundation of traditional Chinese medicine. Massage is referred to in 30 different chapters of the Nei Jing. It specifies the use of different massage... | Massage | Wikipedia | 459 | 43945 | https://en.wikipedia.org/wiki/Massage | Biology and health sciences | Treatments | Health |
Middle Ages
Many of Galen's manuscripts, for instance, were collected and translated by Hunayn ibn Ishaq in the 9th century. Later in the 11th-century copies were translated into Latin and again in the 15th and 16th centuries, when they helped enlighten European scholars as to the achievements of the Ancient Greeks. T... | Massage | Wikipedia | 459 | 43945 | https://en.wikipedia.org/wiki/Massage | Biology and health sciences | Treatments | Health |
AD 1776: Pehr Henrik Ling, a Swedish physical therapist and teacher of medical-gymnastics, is born. Ling has often been erroneously credited for having invented "Classic Massage", also known as "Swedish Massage", and has been called the "Father of Massage".
AD 1779: Frenchman Pierre-Martial Cibot publishes "Notice du ... | Massage | Wikipedia | 424 | 43945 | https://en.wikipedia.org/wiki/Massage | Biology and health sciences | Treatments | Health |
As of 2005, with the city of Shanghai alone there were an estimated 1,300–2,000 foot massage centers, with more than 3,000 in Shenzhen. It was also estimated that there were nearly 30,000 massage workers in Shanghai and over 40,000 in Shenzhen. The average rate of pay for a worker in the massage industry in China is ov... | Massage | Wikipedia | 440 | 43945 | https://en.wikipedia.org/wiki/Massage | Biology and health sciences | Treatments | Health |
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