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Fixation Indices
Fixation may refer to: * Carbon fixation, a biochemical process, usually driven by photosynthesis, whereby carbon dioxide is converted into organic compounds * Fixation (alchemy), a process in the alchemical magnum opus * Fixation (histology) in biochemistry, histology, cell biology and pathology, the technique of preserving a specimen for microscopic study * Fixation (population genetics), the state when every individual in a population has the same allele at a particular locus * Fixation (psychology), the state in which an individual becomes obsessed with an attachment to another human, an animal, or an inanimate object * Fixation (surgical), an operative technique in orthopedics * Fixation (visual) maintaining the gaze in a constant direction * Fixation agent, a process chemical * Fixation in Canadian copyright law, a concept in Canadian copyright law * Nitrogen fixation, a process by which nitrogen is converted from its inert molecular form to a compound more readily available ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbon Fixation
Biological carbon fixation or сarbon assimilation is the process by which inorganic carbon (particularly in the form of carbon dioxide) is converted to organic compounds by living organisms. The compounds are then used to store energy and as structure for other biomolecules. Carbon is primarily fixed through photosynthesis, but some organisms use a process called chemosynthesis in the absence of sunlight. Organisms that grow by fixing carbon are called autotrophs, which include photoautotrophs (which use sunlight), and lithoautotrophs (which use inorganic oxidation). Heterotrophs are not themselves capable of carbon fixation but are able to grow by consuming the carbon fixed by autotrophs or other heterotrophs. "Fixed carbon", "reduced carbon", and "organic carbon" may all be used interchangeably to refer to various organic compounds. Chemosynthesis is carbon fixation driven by chemical energy, rather than from sunlight. Sulfur- and hydrogen-oxidizing bacteria often use the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fixation (alchemy)
In alchemy, fixation is a process by which a previously volatile substance is "transformed" into a form (often solid) that is not affected by fire. It separates the substance or object and puts it back in the same or different shape at a subatomic level. Fixation is sometimes listed as one of the processes required for transformation of a substance, or completion of the alchemical magnum opus. See also * Atomic layer deposition * Mond process * Thermal decomposition Thermal decomposition, or thermolysis, is a chemical decomposition caused by heat. The decomposition temperature of a substance is the temperature at which the substance chemically decomposes. The reaction is usually endothermic as heat is re ... Alchemical processes {{Occult-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fixation (histology)
In the fields of histology, pathology, and cell biology, fixation is the preservation of biological tissues from decay due to autolysis or putrefaction. It terminates any ongoing biochemical reactions and may also increase the treated tissues' mechanical strength or stability. Tissue fixation is a critical step in the preparation of histological sections, its broad objective being to preserve cells and tissue components and to do this in such a way as to allow for the preparation of thin, stained sections. This allows the investigation of the tissues' structure, which is determined by the shapes and sizes of such macromolecules (in and around cells) as proteins and nucleic acids. Purposes In performing their protective role, fixatives denature proteins by coagulation, by forming additive compounds, or by a combination of coagulation and additive processes. A compound that adds chemically to macromolecules stabilizes structure most effectively if it is able to combine with part ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fixation (population Genetics)
In population genetics, fixation is the change in a gene pool from a situation where there exists at least two variants of a particular gene (allele) in a given population to a situation where only one of the alleles remains. In the absence of mutation or heterozygote advantage, any allele must eventually be lost completely from the population or fixed (permanently established at 100% frequency in the population). Whether a gene will ultimately be lost or fixed is dependent on selection coefficients and chance fluctuations in allelic proportions. Fixation can refer to a gene in general or particular nucleotide position in the DNA chain (locus). In the process of substitution, a previously non-existent allele arises by mutation and undergoes fixation by spreading through the population by random genetic drift or positive selection. Once the frequency of the allele is at 100%, i.e. being the only gene variant present in any member, it is said to be "fixed" in the population. Simil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fixation (psychology)
Fixation (german: Fixierung) is a concept (in human psychology) that was originated by Sigmund Freud (1905) to denote the persistence of anachronistic sexual traits. The term subsequently came to denote object relationships with attachments to people or things in general persisting from childhood into adult life. Freud In ''Three Essays on the Theory of Sexuality'' (1905), Freud distinguished the fixations of the libido on an incestuous object from a fixation upon a specific, partial ''aim'', such as voyeurism. Freud theorized that some humans may develop psychological fixation due to one or more of the following: #A lack of proper gratification during one of the psychosexual stages of development. #Receiving a strong impression from one of these stages, in which case the person's personality would reflect that stage throughout adult life. #"An excessively strong manifestation of these instincts at a very early age hichleads to a kind of partial ''fixation'', which then constit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fixation (surgical)
Fixation in orthopedics is the process by which an injury is rendered immobile. This may be accomplished by internal fixation, using intramedullary rod, Kirschner wire or dynamic compression plate; or by external fixation, using a spanning external fixator, Taylor Spatial Frame or Ilizarov apparatus In medicine, the Ilizarov apparatus is a type of external fixation apparatus used in orthopedic surgery to lengthen or to reshape the damaged bones of an arm or a leg; used as a limb-sparing technique for treating complex fractures and open bone .... References Orthopedic surgical procedures {{Orthopedics-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fixation (visual)
Fixation or visual fixation is the maintaining of the gaze on a single location. An animal can exhibit visual fixation if it possess a fovea in the anatomy of their eye. The fovea is typically located at the center of the retina and is the point of clearest vision. The species in which fixational eye movement has been verified thus far include humans, primates, cats, rabbits, turtles, salamanders, and owls. Regular eye movement alternates between saccades and visual fixations, the notable exception being in smooth pursuit, controlled by a different neural substrate that appears to have developed for hunting prey. The term "fixation" can either be used to refer to the point in time and space of focus or the act of fixating. Fixation, in the act of fixating, is the point between any two saccades, during which the eyes are relatively stationary and virtually all visual input occurs. In the absence of retinal jitter, a laboratory condition known as retinal stabilization, perceptions ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fixation Agent
A fixation agent is a chemical that is capable to fixate one substance to another substance that the first substance have little affinity to. Applications Pulp and paper production In pulp and paper production fixation agents are used to fixate pitch or stickies to the paper fibers to transport the problems out of the production process and have a cleaner production plant. As fixation agents used in pulp and paper production are minerals like talc and bentonite or different cationic polymers like polyDADMAC Polydiallyldimethylammonium chloride (shortened polyDADMAC or polyDDA), also commonly polyquaternium-6, is a homopolymer of diallyldimethylammonium chloride (DADMAC). The molecular weight of polyDADMAC is typically in the range of hundreds of tho .... The polymer based fixation agents are often called detackifiers as they reduce the tackiness of the pitch and stickies. Process chemicals {{chem-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fixation In Canadian Copyright Law
Fixation in Canadian copyright law is a threshold consideration that must be used in copyright infringement cases by courts to determine if copyright actually exists. In Canada, a work "must be expressed to some extent at least in some material form, capable of identification and having a more or less permanent endurance"Canadian Admiral Corp v Rediffusion Inc., 95420 C.P.R. 75, para 28. to be subject to copyright protection. Fixation is not a statutory requirement in Canada and the rationale for its use in court has been the subject of much scrutiny. Case law In Canadian Admiral Corp. v. Rediffusion Inc., 95420 C.P.R. 75, the plaintiffs had purchased the exclusive right to live telecasts of football matches played by the Montreal Alouettes. Rediffusion Inc., the defendant, had taken those live telecasts and re-transmitted them to its own subscribers without license or permission. Canadian Admiral alleged copyright over the live telecasts and this was the central issue in the ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitrogen Fixation
Nitrogen fixation is a chemical process by which molecular nitrogen (), with a strong triple covalent bond, in the air is converted into ammonia () or related nitrogenous compounds, typically in soil or aquatic systems but also in industry. Atmospheric nitrogen is molecular dinitrogen, a relatively nonreactive molecule that is metabolically useless to all but a few microorganisms. Biological nitrogen fixation or ''diazotrophy'' is an important microbials mediated process that converts dinitrogen (N2) gas to ammonia (NH3) using the nitrogenase protein complex (Nif). Nitrogen fixation is essential to life because fixed inorganic nitrogen compounds are required for the biosynthesis of all nitrogen-containing organic compounds, such as amino acids and proteins, nucleoside triphosphates and nucleic acids. As part of the nitrogen cycle, it is essential for agriculture and the manufacture of fertilizer. It is also, indirectly, relevant to the manufacture of all nitrogen chemical c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Session Fixation
In computer network security, session fixation attacks attempt to exploit the vulnerability of a system that allows one person to fixate (find or set) another person's session identifier. Most session fixation attacks are web based, and most rely on session identifiers being accepted from URLs (query string) or POST data. Attack scenarios Alice has an account at the bank http://unsafe.example.com/ Mallory intends to target Alice's money from her bank. Alice has a reasonable level of trust in Mallory, and will visit links Mallory sends her. A simple attack scenario Straightforward scenario: # Mallory has determined that http://unsafe.example.com/ accepts any session identifier, accepts session identifiers from query strings and has no security validation. http://unsafe.example.com/ is thus not secure. # Mallory sends Alice an e-mail: "Hey, check this out, there is a cool new account summary feature on our bank, http://unsafe.example.com/?SID=I_WILL_KNOW_THE_SID". Mallory i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Target Fixation
Target fixation is an attentional phenomenon observed in humans in which an individual becomes so focused on an observed object (be it a target or hazard) that they inadvertently increase their risk of colliding with the object. It is associated with scenarios in which the operator is in control of a high-speed vehicle or other mode of transportation, such as fighter pilots, race-car drivers, paragliders, and motorcyclists. In such cases, the observer may fixate so intently on the target that they steer in the direction of their gaze, which is often the ultimate cause of a collision. The term target fixation was originally used in World War II fighter-bomber pilot training to describe pilots flying into targets during a strafing or bombing run. Cause and effect Target fixation is caused by becoming focused on one thing that is usually distracting, dangerous, or rewarding. Focus can be caused by "anticipated success", such as when trying to arrive at a destination in a certain am ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
