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Homology Theory,
Homology may refer to: Sciences Biology *Homology (biology), any characteristic of biological organisms that is derived from a common ancestor *Sequence homology, biological homology between DNA, RNA, or protein sequences *Homologous chromosomes, chromosomes in a biological cell that pair up (synapse) during meiosis *Homologous recombination, genetic recombination in which nucleotide sequences are exchanged between molecules of DNA *Homologous desensitization, a receptor decreases its response to a signalling molecule when that agonist is in high concentration *Homology modeling, a method of protein structure prediction Chemistry *Homology (chemistry), the relationship between compounds in a homologous series *Homologous series, a series of organic compounds having different quantities of a repeated unit *Homologous temperature, the temperature of a material as a fraction of its absolute melting point *Homologation reaction, a chemical reaction which produces the next lo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homology (biology)
In biology, homology is similarity due to shared ancestry between a pair of structures or genes in different taxa. A common example of homologous structures is the forelimbs of vertebrates, where the wings of bats and birds, the arms of primates, the front flippers of whales and the forelegs of four-legged vertebrates like dogs and crocodiles are all derived from the same ancestral tetrapod structure. Evolutionary biology explains homologous structures adapted to different purposes as the result of descent with modification from a common ancestor. The term was first applied to biology in a non-evolutionary context by the anatomist Richard Owen in 1843. Homology was later explained by Charles Darwin's theory of evolution in 1859, but had been observed before this, from Aristotle onwards, and it was explicitly analysed by Pierre Belon in 1555. In developmental biology, organs that developed in the embryo in the same manner and from similar origins, such as from matching p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homology (anthropology)
In sociocultural anthropology and archaeology, homology is a type of analogy whereby two human beliefs, practices, or artifacts are separated by time and/or place but share similarities due to some underlying factor, whether genetics, historical connection, psychological archetype, or otherwise. This type of homology is the counterpart of biologic homology in physical anthropology, whereby an anatomic structure is shared through descent from a common ancestor. The concept was explored by the American archaeologist William Duncan Strong in his direct historical approach to archaeological theory. It is important in structural anthropology in particular but also in sociocultural anthropology Sociocultural anthropology is a portmanteau used to refer to social anthropology and cultural anthropology together. It is one of the four main branches of anthropology. Sociocultural anthropologists focus on the study of society and culture, while ... in general. See also * Jungian archety ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homologation (motorsport)
In motorsports, homologation is the type approval process through which a vehicle, a race track, or a standardised part is required to go for certification to race in a given league or series. The process of testing and certification for conformance to technical standards is usually known as type approval in English-language jurisdictions. The regulations and rules that must be met are generally set by the series's sanctioning body. The word is derived from Greek , . When a car loses the homologation form, that is, it becomes a historic vehicle, it can no longer be part of a competition and can only be used in historic competitions. Requirements In racing series that are "production-based", meaning that the vehicles entered in the series are based on production vehicles for sale to the public, homologation not only requires compliance with a racing series's technical guidelines (for example engine displacement, chassis construction, suspension design and such), but often i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homologation
Homologation (Greek ''homologeo'', ὁμολογέω, "to agree") is the granting of approval by an official authority. This may be a court of law, a government department, or an academic or professional body, any of which would normally work from a set of rules or standards to determine whether such approval should be given. The word may be considered very roughly synonymous with ''accreditation'', and in fact in French and Spanish may be used with regard to academic degrees (see apostille). ''Certification'' is another possible synonym, while ''to homologate'' is the infinitive verb form. In today's marketplace, for instance, products must often be homologated by some public agency to assure that they meet standards for such things as safety and environmental impact. A court action may also sometimes be homologated by a judicial authority before it can proceed, and the term has a precise legal meaning in the judicial codes of some countries. The equivalent process of testing ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homological Algebra
Homological algebra is the branch of mathematics that studies homology (mathematics), homology in a general algebraic setting. It is a relatively young discipline, whose origins can be traced to investigations in combinatorial topology (a precursor to algebraic topology) and abstract algebra (theory of module (mathematics), modules and Syzygy (mathematics), syzygies) at the end of the 19th century, chiefly by Henri Poincaré and David Hilbert. Homological algebra is the study of homological functors and the intricate algebraic structures that they entail; its development was closely intertwined with the emergence of category theory. A central concept is that of chain complexes, which can be studied through both their homology and cohomology. Homological algebra affords the means to extract information contained in these complexes and present it in the form of homological invariant (mathematics), invariants of ring (mathematics), rings, modules, topological spaces, and other 'tan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homology (mathematics)
In mathematics, homology is a general way of associating a sequence of algebraic objects, such as abelian groups or modules, with other mathematical objects such as topological spaces. Homology groups were originally defined in algebraic topology. Similar constructions are available in a wide variety of other contexts, such as abstract algebra, groups, Lie algebras, Galois theory, and algebraic geometry. The original motivation for defining homology groups was the observation that two shapes can be distinguished by examining their holes. For instance, a circle is not a disk because the circle has a hole through it while the disk is solid, and the ordinary sphere is not a circle because the sphere encloses a two-dimensional hole while the circle encloses a one-dimensional hole. However, because a hole is "not there", it is not immediately obvious how to define a hole or how to distinguish different kinds of holes. Homology was originally a rigorous mathematical method for defi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homology (sociology)
Homologies are "structural 'resonances'...between the different elements making up a socio-cultural whole." (Middleton 1990, p. 9) Examples include Alan Lomax's cantometrics, which: :Distinguishes ten musical styles, dealing most fully with Eurasian and Old European styles. These are correlated with sexual permissiveness, status of women, and treatment of children as the principal formative social influences. The musical styles are at the same time symbolic or expressive of such social influences, especially in the various musical communities of Spain and Italy, and are stable, persistent. Lomax states his expectation that further study and refinement of methods of measurement will increase our understanding of the relationships of musical style and culture in a way that Western European musical notation cannot adequately accomplish. Richard Middleton (1990, p. 9-10) argues that "such theories always end up in some kind of reductionism – 'upwards', into an idealist cultu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homologous Behaviors
Homology in psychology, as in biology, refers to a relationship between characteristics that reflects the characteristics' origins in either evolution or development. Homologous behaviors can theoretically be of at least two different varieties. As with homologous anatomical characteristics, behaviors present in different species can be considered homologous if they are likely present in those species because the behaviors were present in a common ancestor of the two species. Alternatively, in much the same way as reproductive structures (e.g., the penis and the clitoris) are considered homologous because they share a common origin in embryonic tissues, behaviors—or the neural substrates associated with those behaviors—can also be considered homologous if they share common origins in development. Behavioral homologies have been considered since at least 1958, when Konrad Lorenz studied the evolution of behavior. More recently, the question of behavioral homologies has been ad ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homology (psychology)
Homology in psychology, as in biology, refers to a relationship between characteristics that reflects the characteristics' origins in either evolution or development. Homologous behaviors can theoretically be of at least two different varieties. As with homologous anatomical characteristics, behaviors present in different species can be considered homologous if they are likely present in those species because the behaviors were present in a common ancestor of the two species. Alternatively, in much the same way as reproductive structures (e.g., the penis and the clitoris) are considered homologous because they share a common origin in embryonic tissues, behaviors—or the neural substrates associated with those behaviors—can also be considered homologous if they share common origins in development. Behavioral homologies have been considered since at least 1958, when Konrad Lorenz studied the evolution of behavior. More recently, the question of behavioral homologies has been ad ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homologation Reaction
In organic chemistry, a homologation reaction, also known as homologization, is any chemical reaction that converts the reactant into the next member of the homologous series. A homologous series is a group of compounds that differ by a constant unit, generally a methylene () group. The reactants undergo a homologation when the number of a repeated structural unit in the molecules is increased. The most common homologation reactions increase the number of methylene () units in saturated chain within the molecule. For example, the reaction of aldehydes or ketones with diazomethane or methoxymethylenetriphenylphosphine to give the next homologue in the series. Examples of homologation reactions include: * Kiliani-Fischer synthesis, where an aldose molecule is elongated through a three-step process consisting of: *# Nucleophillic addition of cyanide to the carbonyl to form a cyanohydrin *# Hydrolysis to form a lactone *# Reduction to form the homologous aldose * Wittig reacti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sequence Homology
Sequence homology is the biological homology between DNA, RNA, or protein sequences, defined in terms of shared ancestry in the evolutionary history of life. Two segments of DNA can have shared ancestry because of three phenomena: either a speciation event (orthologs), or a duplication event (paralogs), or else a horizontal (or lateral) gene transfer event (xenologs). Homology among DNA, RNA, or proteins is typically inferred from their nucleotide or amino acid sequence similarity. Significant similarity is strong evidence that two sequences are related by evolutionary changes from a common ancestral sequence. Alignments of multiple sequences are used to indicate which regions of each sequence are homologous. Identity, similarity, and conservation The term "percent homology" is often used to mean "sequence similarity”, that is the percentage of identical residues (''percent identity''), or the percentage of residues conserved with similar physicochemical properties (' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homologous Temperature
Homologous temperature expresses the thermodynamic temperature of a material as a fraction of the thermodynamic temperature of its melting point (i.e. using the Kelvin scale): T_H = \frac For example, the homologous temperature of lead at room temperature (25 °C) is approximately 0.50 (TH = T/Tmp = 298 K/601 K = 0.50). Significance of the homologous temperature The homologous temperature of a substance is useful for determining the rate of steady state creep (diffusion dependent deformation). A higher homologous temperature results in an exponentially higher rate of diffusion dependent deformation. Additionally, for a given fixed homologous temperature, two materials with different melting points would have similar diffusion-dependent deformation behaviour. For example, solder (Tmp = 456 K) at 115 °C would have comparable mechanical properties to copper (Tmp = 1358 K) at 881 °C, because they would both be at 0.85Tmp despite being at diff ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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