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Initiator
An initiator can refer to: * A person who instigates something. * Modulated neutron initiator, a neutron source used in some nuclear weapons ** Initiator, an Explosive booster ** Initiator, the first Nuclear chain reaction * Pyrotechnic initiator, a device containing a pyrotechnic composition used primarily to ignite other, more difficult to ignite materials * Radical initiator, chemical substances that can produce radical species under mild conditions ** Photoinitiator, chemical substances that produce radical specials upon exposure to light * SCSI initiator, the host-side endpoint of a SCSI session * Monomeric polyols, such as glycerin, pentaerythritol, ethylene glycol and sucrose, serving as the starting point for polymeric polyols Biology * Initiator element * Initiator protein * Initiation factor See also * Initiation (other) Initiation is a rite of passage marking entrance or acceptance into a group or society. Anthropology * Bora (Australian), both an initiat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyrotechnic Initiator
In pyrotechnics, a pyrotechnic initiator (also initiator or igniter) is a device containing a pyrotechnic composition used primarily to ignite other, more difficult-to-ignite materials, such as thermites, gas generators, and solid-fuel rockets. The name is often used also for the compositions themselves. Pyrotechnic initiators are often controlled electrically (called electro-pyrotechnic initiators), e.g. using a heated bridgewire or a ''bridge resistor''. They are somewhat similar to blasting caps or other detonators, but they differ in that there is no intention to produce a shock wave. An example of such pyrotechnic initiator is an electric match. Composition The energetic material used, often called pyrogen, is usually a pyrotechnic composition made of a fuel and oxidizer, where the fuel produces a significant amount of hot particles that cause/promote the ignition of the desired material. Initiator compositions are similar to flash powders, but they differ in burning speed, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Modulated Neutron Initiator
A modulated neutron initiator is a neutron source capable of producing a burst of neutrons on activation. It is a crucial part of some nuclear weapons, as its role is to "kick-start" the chain reaction at the optimal moment when the configuration is prompt critical. It is also known as an internal neutron initiator. The initiator is typically placed in the center of the plutonium pit, and is activated by impact of the converging shock wave. One of the key elements in the proper operation of a nuclear weapon is initiation of the fission chain reaction at the proper time. To obtain a significant nuclear yield, sufficient neutrons must be present within the supercritical core at the right time. If the chain reaction starts too soon (" predetonation"), the result will be only a ' fizzle yield', well below the design specification. If it occurs too late, the core will have begun to expand and disassemble into a less-dense state, leading to a lowered yield (less of the core material unde ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SCSI Initiator
In computer data storage, a SCSI initiator is the endpoint that initiates a SCSI session, that is, sends a SCSI command. The initiator usually does not provide any Logical Unit Numbers (LUNs). On the other hand, a SCSI target is the endpoint that does ''not'' initiate sessions, but instead waits for initiators' commands and provides required input/output data transfers. The target usually provides to the initiators one or more LUNs, because otherwise no read or write command would be possible. Detailed information Typically, a computer is an initiator and a data storage device is a target. As in a client–server architecture, an initiator is analogous to the client, and a target is analogous to the server. Each SCSI address (each identifier on a SCSI bus) displays behavior of initiator, target, or (rarely) both at the same time. There is nothing in the SCSI protocol that prevents an initiator from acting as a target or vice versa. SCSI initiators are sometimes wrongly called ' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radical Initiator
In chemistry, radical initiators are substances that can produce radical species under mild conditions and promote radical reactions. These substances generally possess weak bonds—bonds that have small bond dissociation energies. Radical initiators are utilized in industrial processes such as polymer synthesis. Typical examples are molecules with a nitrogen-halogen bond, azo compounds, and organic and inorganic peroxides. Main types of initiation reaction *Halogens undergo homolytic fission relatively easily. Chlorine, for example, gives two chlorine radicals (Cl•) by irradiation with ultraviolet light. This process is used for chlorination of alkanes. *Azo compounds (R- N=N-R') can be the precursor of two carbon-centered radicals (R• and R'•) and nitrogen gas upon heating and/or by irradiation. For example, AIBN and ABCN yield isobutyronitrile and cyclohexanecarbonitrile radicals, respectively. : *Organic peroxides each have a peroxide bond (- O-O-), which is readi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Initiator Element
The initiator element (''Inr''), sometimes referred to as initiator motif, is a core promoter that is similar in function to the Pribnow box (in prokaryotes) or the TATA box (in eukaryotes). The ''Inr'' is the simplest functional promoter that is able to direct transcription initiation without a functional TATA box. It has the consensus sequence YYANWYY in humans. Similarly to the TATA box, the Inr element facilitates the binding of transcription Factor II D (TFIID). The Inr works by enhancing binding affinity and strengthening the promoter. Overview The initiator element (Inr) is the most common sequence found at the transcription start site of eukaryotic genes. It is a 17 bp element. Inr in humans was first explained and sequenced by two MIT biologists, Stephen T. Smale and David Baltimore in 1989. Their research showed that Inr promoter is able to initiate basal transcription in absence of the TATA box. In the presence of a TATA box or other promoters, the Inr increases the ef ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Initiation (other)
Initiation is a rite of passage marking entrance or acceptance into a group or society. Anthropology * Bora (Australian), both an initiation ceremony of Indigenous Australians, and the site on which the initiation is performed * Buddhist initiation ritual, the public ordination ceremony wherein a lay student of Buddhism receives certain Buddhist precepts * Hazing, refers to the practice of rituals, challenges, and other activities involving harassment, abuse or humiliation used as a way of initiating a person into a group including a new fraternity, sorority, team, or club * Initiation (guru), a diksha, or giving of a mantra or an initiation by the guru in Indian religions * Initiation (Theosophy), a concept about the levels of spiritual development * Initiation ritual (mafia), a ceremony involving significant ritual, oaths, blood, and an agreement * Masonic initiation rituals, part of the Masonic ritual and symbolism * Ndut initiation rite, a rite of passage as well as a religio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Weapons
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission bomb) or a combination of fission and fusion reactions (thermonuclear bomb), producing a nuclear explosion. Both bomb types release large quantities of energy from relatively small amounts of matter. The first test of a fission ("atomic") bomb released an amount of energy approximately equal to . The first thermonuclear ("hydrogen") bomb test released energy approximately equal to . Nuclear bombs have had yields between 10 tons TNT (the W54) and 50 megatons for the Tsar Bomba (see TNT equivalent). A thermonuclear weapon weighing as little as can release energy equal to more than . A nuclear device no larger than a conventional bomb can devastate an entire city by blast, fire, and radiation. Since they are weapons of mass destruction, the proliferation of nuclear weapons is a focus of international relations policy. Nuclear weapons have been deployed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Explosive Booster
{{unreferenced, date=August 2011 An explosive booster is a sensitive explosive charge that acts as a bridge between a (relatively weak) conventional detonator and a low-sensitivity (but typically high-energy) explosive such as TNT. By itself, the initiating detonator would not deliver sufficient energy to set off the low-sensitivity charge. However, it detonates the primary charge (the booster), which then delivers an explosive shockwave that is sufficient to detonate the secondary, main, high-energy charge. Unlike C4 plastic explosive, not all explosives can be detonated simply by inserting a detonator and firing it. An initiator such as a shock tube, cannon fuse, or even a conventional detonator does not deliver sufficient shock to detonate charges comprising TNT, Composition B, ANFO and many other high explosives. Therefore, some form of "booster" is required to amplify the energy released by the detonator so that the main charge will detonate. At first, picric acid was use ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Chain Reaction
In nuclear physics, a nuclear chain reaction occurs when one single nuclear reaction causes an average of one or more subsequent nuclear reactions, thus leading to the possibility of a self-propagating series of these reactions. The specific nuclear reaction may be the fission of heavy isotopes (e.g., uranium-235, 235U). A nuclear chain reaction releases several million times more energy per reaction than any chemical reaction. History Chemical chain reactions were first proposed by German chemist Max Bodenstein in 1913, and were reasonably well understood before nuclear chain reactions were proposed. It was understood that chemical chain reactions were responsible for exponentially increasing rates in reactions, such as produced in chemical explosions. The concept of a nuclear chain reaction was reportedly first hypothesized by Hungarian scientist Leó Szilárd on September 12, 1933. Szilárd that morning had been reading in a London paper of an experiment in which protons f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photoinitiator
A photoinitiator is a molecule that creates reactive species (free radicals, cations or anions) when exposed to radiation (UV or visible). Synthetic photoinitiators are key components in photopolymers (for example, photo-curable coatings, adhesives and dental restoratives). Some small molecules in the atmosphere can also act as photoinitiators by decomposing to give free radicals (in photochemical smog). For instance, nitrogen dioxide (NO2) is produced in large quantities by gasoline-burning internal combustion engines. NO2 in the troposphere gives smog its brown coloration and catalyzes production of toxic ground-level ozone (O3). Molecular oxygen (O2) also serves as a photoinitiator in the stratosphere, breaking down into atomic oxygen and combining with O2 in order to form the ozone in the ozone layer. Reactions Photoinitators can create reactive species by different pathways including photodissociation and electron transfer. As an example of dissociation, hydrogen peroxide c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Initiator Protein
The initiator proteins are the proteins that recognize a specific DNA sequence within the origin of replication. The origin of replication is the site where the helicase attaches to the template strand Transcription is the process of copying a segment of DNA into RNA. The segments of DNA transcribed into RNA molecules that can encode proteins are said to produce messenger RNA (mRNA). Other segments of DNA are copied into RNA molecules called ... and starts to unwind the DNA into two strands.''Life :The Science of Biology'' by David Sadava, Craig Heller, May Berenbaum and, David Hillis References Proteins by function {{protein-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Initiation Factor
Initiation factors are proteins that bind to the small subunit of the ribosome during the initiation of translation, a part of protein biosynthesis. Initiation factors can interact with repressors to slow down or prevent translation. They have the ability to interact with activators to help them start or increase the rate of translation. In bacteria, they are simply called IFs (i.e.., IF1, IF2, & IF3) and in eukaryotes they are known as eIFs (i.e.., eIF1, eIF2, eIF3). Translation initiation is sometimes described as three step process by which initiation factors help to carry out. First, the tRNA carrying a methionine amino acid binds to the small ribosome, then binds to the mRNA, and finally joining together with the large ribosome. The initiation factors that help with this process each have different roles and structures. Types The initiation factors are divided into three major groups by taxonomic domains. There are some homologies shared (click the domain names to see the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
