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Tetrad
Tetrad ('group of 4') or tetrade may refer to: * Tetrad (area), an area 2 km x 2 km square * Tetrad (astronomy), four total lunar eclipses within two years * Tetrad (chromosomal formation) * Tetrad (general relativity), or frame field ** Tetrad formalism, an approach to general relativity * Tetrad (geometry puzzle), a set of four simply connected disjoint planar regions in the plane * Tetrad (meiosis), the four cells produced by meiotic cell division * Tetrad (music), a set of four notes ** Tetrad (chord), a series of four notes * Tetrad (symbol), or tetractys, a triangular figure of ten points arranged in four rows, and mystical symbol * Medical tetrad, a group of four signs or symptoms which characterise a specific medical condition * Nibble, or tetrade, a 4-bit group * a tuple of length 4 * Tetrad Islands, in the Antarctic See also * * 4 * Triad (other) ('group of 3') * Pentad (other) ('group of 5') * Dark tetrad, group of four undesirable personality tr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetrad Formalism
The tetrad formalism is an approach to general relativity that generalizes the choice of basis for the tangent bundle from a coordinate basis to the less restrictive choice of a local basis, i.e. a locally defined set of four linearly independent vector fields called a ''tetrad'' or ''vierbein''. It is a special case of the more general idea of a ''vielbein formalism'', which is set in (pseudo-)Riemannian geometry. This article as currently written makes frequent mention of general relativity; however, almost everything it says is equally applicable to (pseudo-)Riemannian manifolds in general, and even to spin manifolds. Most statements hold simply by substituting arbitrary n for n=4. In German, "vier" translates to "four", and "viel" to "many". The general idea is to write the metric tensor as the product of two ''vielbeins'', one on the left, and one on the right. The effect of the vielbeins is to change the coordinate system used on the tangent manifold to one that is simple ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetrad (meiosis)
The tetrad is the four spores produced after meiosis of a yeast or other Ascomycota, ''Chlamydomonas'' or other alga, or a plant. After parent haploids mate, they produce diploids. Under appropriate environmental conditions, diploids sporulate and undergo meiosis. The meiotic products, spores, remain packaged in the parental cell body to produce the tetrad. Genetic typification If the two parents have a mutation in two different genes, the tetrad can segregate these genes as the parental ditype ( PD), the non-parental ditype (NPD) or as the tetratype (TT). Parental ditype is a tetrad type containing two different genotypes, both of which are parental. A spore arrangement in ascomycetes that contains only the two non-recombinant-type ascospores. Non-parental ditype (NPD) is a spore that contains only the two recombinant-type ascospores (assuming two segregating loci). A tetrad type containing two different genotypes, both of which are recombinant. Tetratype is a tetrad containin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetrad Of Media Effects
Marshall McLuhan's tetrad of media effects uses a tetrad to examine the effects on society of any technology/medium (put another way: a means of explaining the social processes underlying the adoption of a technology/medium) by dividing its effects into four categories and displaying them simultaneously. The tetrad first appeared in print in McLuhan's posthumously-published works ''Laws of Media'' (1988) and ''The Global Village'' (1989). The tetrad The tetrad consists of four questions. #What does the medium enhance? #What does the medium make obsolete? #What does the medium retrieve that had been obsolesced earlier? #What does the medium reverse or flip into when pushed to extremes? The laws of the tetrad exist simultaneously, not successively or chronologically, and allow the questioner to explore the "grammar and syntax" of the "language" of media. McLuhan departs from the media theory of Harold Innis in suggesting that a medium "overheats", or reverses into an opposing form, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetrad (geometry Puzzle)
In geometry, a tetrad is a set of four simply connected disjoint planar regions in the plane, each pair sharing a finite portion of common boundary. It was named by Michael R. W. Buckley in 1975 in the Journal of Recreational Mathematics. A further question was proposed that became a puzzle, whether the 4 regions could be congruent, with or without ''holes'', other enclosed regions.Martin Gardner, ''Penrose Tiles to Trapdoor ciphers'', 1989, p.121-12/ref> Fewest sides and vertices The solutions with four congruent tiles include some with five sides.Further Questions about Tetrads by Walter Trump However, their placement surrounds an uncovered hole in the plane. Among solutions without holes, the ones with the fewest possible sides are given by a hexagon identified by Scott Kim as a student at Stanford University. I ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetrad (chromosomal Formation)
Tetrad ('group of 4') or tetrade may refer to: * Tetrad (area), an area 2 km x 2 km square * Tetrad (astronomy), four total lunar eclipses within two years * Tetrad (chromosomal formation) * Tetrad (general relativity), or frame field ** Tetrad formalism, an approach to general relativity * Tetrad (geometry puzzle), a set of four simply connected disjoint planar regions in the plane * Tetrad (meiosis), the four cells produced by meiotic cell division * Tetrad (music), a set of four notes ** Tetrad (chord), a series of four notes * Tetrad (symbol), or tetractys, a triangular figure of ten points arranged in four rows, and mystical symbol * Medical tetrad, a group of four signs or symptoms which characterise a specific medical condition * Nibble, or tetrade, a 4-bit group * a tuple of length 4 * Tetrad Islands, in the Antarctic See also * * 4 * Triad (other) ('group of 3') * Pentad (other) ('group of 5') * Dark tetrad, group of four undesirable personality tr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetrad (general Relativity)
A frame field in general relativity (also called a tetrad or vierbein) is a set of four pointwise-orthonormal vector fields, one timelike and three spacelike, defined on a Lorentzian manifold that is physically interpreted as a model of spacetime. The timelike unit vector field is often denoted by \vec_0 and the three spacelike unit vector fields by \vec_1, \vec_2, \, \vec_3. All tensorial quantities defined on the manifold can be expressed using the frame field and its dual coframe field. Frame were introduced into general relativity by Albert Einstein in 1928 and by Hermann Weyl in 1929.Hermann Weyl "Elektron und Gravitation I", ''Zeitschrift Physik'', 56, p330–352, 1929. The index notation for tetrads is explained in tetrad (index notation). Physical interpretation Frame fields of a Lorentzian manifold always correspond to a family of ideal observers immersed in the given spacetime; the integral curves of the timelike unit vector field are the worldlines of these observe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetrad (astronomy)
In astronomy, a tetrad is a set of four total lunar eclipses within two consecutive years. List of tetrad events 1949–2000 2001–51 See also * for statistics by century * Grouping of dark personality traits. * Apocalyptic preaching of |
Tetrad (music)
A tetrad is a set of four notes in music theory. When these four notes form a tertian chord they are more specifically called a ''seventh chord'', after the diatonic interval from the root of the chord to its fourth note (in root position close voicing). Four-note chords are often formed of intervals other than thirds in 20th- and 21st-century music, however, where they are more generally referred to as ''tetrads'' (see, for example, , , and ). Allen Forte in his ''The Structure of Atonal Music'' never uses the term "tetrad", but occasionally employs the word ''tetrachord'' to mean any collection of four pitch class In music, a pitch class (p.c. or pc) is a set of all pitches that are a whole number of octaves apart; for example, the pitch class C consists of the Cs in all octaves. "The pitch class C stands for all possible Cs, in whatever octave positio ...es . In 20th-century music theory, such sets of four pitch classes are usually called "tetrachords" (; ). Reference ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nibble
In computing, a nibble (occasionally nybble, nyble, or nybl to match the spelling of byte) is a four-bit aggregation, or half an octet. It is also known as half-byte or tetrade. In a networking or telecommunication context, the nibble is often called a semi-octet, quadbit, or quartet. A nibble has sixteen () possible values. A nibble can be represented by a single hexadecimal digit (–) and called a hex digit. A full byte (octet) is represented by two hexadecimal digits (–); therefore, it is common to display a byte of information as two nibbles. Sometimes the set of all 256-byte values is represented as a table, which gives easily readable hexadecimal codes for each value. Four-bit computer architectures use groups of four bits as their fundamental unit. Such architectures were used in early microprocessors, pocket calculators and pocket computers. They continue to be used in some microcontrollers. In this context, 4-bit groups were sometimes also called ''characters' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dark Tetrad
The dark triad is a psychological theory of personality, first published by Delroy L. Paulhus and Kevin M. Williams in 2002, that describes three notably offensive, but non-pathological personality types: Machiavellianism, sub-clinical narcissism, and sub-clinical psychopathy. Each of these personality types are called ''dark'' because each is considered to contain malevolent qualities. All three dark triad traits are conceptually distinct although empirical evidence shows them to be overlapping. They are associated with a callous–manipulative interpersonal style. * Narcissism is characterized by grandiosity, pride, egotism, and a lack of empathy. * Machiavellianism is characterized by manipulation and exploitation of others, an absence of morality, unemotional callousness, and a higher level of self-interest. * Psychopathy is characterized by continuous antisocial behavior, impulsivity, selfishness, callous and unemotional traits (CU), and remorselessness. High scores in these ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetrad (area)
A tetrad is an area 2 km x 2 km square. The term refers to any of the 25 such squares which make up a standard hectad A hectad is an area 10 km x 10 km square. The term has a particular use in connection with the British Ordnance Survey national grid, and then refers to any of the 100 such squares which make up a standard 100 km x 100 km myr .... Tetrads are sometimes used by biologists for reporting the distribution of species to maintain a degree of confidentiality about their data, though the system is not in universal use. The tetrads are labelled from ''A'' to ''Z'' (omitting ''O'') according to the "DINTY" system as shown in the grid below, which takes its name from the letters of the second line. References Units of area {{measurement-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Medical Triad
A medical triad is a group of three signs or symptoms, the result of injury to three organs, which characterise a specific medical condition. The appearance of all three signs conjoined together in another patient, points to that the patient has the same medical condition, or diagnosis. A medical tetrad is a group of four, while a pentad is a group of five. Triads Tetrads Pentads See also * Medical eponyms * Pathognomonic * List of eponymously named medical signs References {{reflist Medical lists, Medical triads and pentads Medical triads Medical pentads ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
