Alpha mechanism

Gendelman HE, Baca LM, Turpin J, Kalter DC, Hansen B, Orenstein JM, Dieffenbach CW, Friedman RM, Meltzer MS (1990) Regulation of HIV rephcation in infected monocytes by IFN-alpha. Mechanisms for viral restriction. J Immunol 145 2669-26676 Giovannini M, Zuccotti GV, Biasucci G, Locatelh V, Riva E (1992) Combined zidovudine and interferon-alpha 2a therapy in children with acquired immune deficiency syndrome. J Int Med Res 20 295-301... 

Tomkhis WA (1999) hnmuiiomoduladon and therapeudc effects of die oral use of hr terferoii-alpha mechanism of acdon. J Interferon CytokhieRes 19 817-828. 

Tomkins WA (1999) Immunomodulation and therapeutic effects of the oral use of interferon-alpha mechanism of action. J Interferon Cytokine Res 19 817-828. 

Guilhot E, Lacotte-Thierry L. Interferon-alpha Mechanisms of action in chronic myelogenous leukemia in chronic phase. Hematol Cell Ther 1998 40 237-239. 

This impasse was partly surmounted in 1952 by Edwin Saltpeter at Cornell University. His suggestion was that a triple alpha mechanism could provide a means of building nuclei beyond mass number 4, as summarized in the following equation ... 

The mechanical movements and the data aequisition is controlled by a DEC Alpha-Workstation which is also able to perform the tomographic reconstruction and parts of the visualization of the results. 

Graphite exists in two forms alpha and beta. These have identical physical properties, except for their crystal structure. Naturally occurring graphites are reported to contain as much as 30% of the rhombohedral (beta) form, whereas synthetic materials contain only the alpha form. The hexagonal alpha type can be converted to the beta by mechanical treatment, and the beta form reverts to the alpha on heating it above lOOOoC. 

HyperChem quantum mechanics calculations must start with the number of electrons (N) and how many of them have alpha spins (the remaining electrons have beta spins). HyperChem obtains this information from the charge and spin multiplicity that you specify in the Semi-empirical Options dialog box or Ab Initio Options dialog box. N is then computed by counting the electrons (valence electrons in semi-empirical methods and all electrons in fll) mitio method) associated with each (assumed neutral) atom and... 

As a class of compounds, the two main toxicity concerns for nitriles are acute lethality and osteolathyrsm. A comprehensive review of the toxicity of nitriles, including detailed discussion of biochemical mechanisms of toxicity and stmcture-activity relationships, is available (12). Nitriles vary broadly in their abiUty to cause acute lethaUty and subde differences in stmcture can greatly affect toxic potency. The biochemical basis of their acute toxicity is related to their metaboHsm in the body. Following exposure and absorption, nitriles are metabolized by cytochrome p450 enzymes in the Hver. The metaboHsm involves initial hydrogen abstraction resulting in the formation of a carbon radical, followed by hydroxylation of the carbon radical. MetaboHsm at the carbon atom adjacent (alpha) to the cyano group would yield a cyanohydrin metaboHte, which decomposes readily in the body to produce cyanide. Hydroxylation at other carbon positions in the nitrile does not result in cyanide release. 

Bulk Polymerization. The bulk polymerization of acryUc monomers is characterized by a rapid acceleration in the rate and the formation of a cross-linked insoluble network polymer at low conversion (90,91). Such network polymers are thought to form by a chain-transfer mechanism involving abstraction of the hydrogen alpha to the ester carbonyl in a polymer chain followed by growth of a branch radical. Ultimately, two of these branch radicals combine (91). Commercially, the bulk polymerization of acryUc monomers is of limited importance. 

An alternative chain-terminating decomposition of the tetroxide, known as the Russell mechanism (29), can occur when there is at least one hydrogen atom in an alpha position the products are a ketone, an alcohol and oxygen (eq. 15). This mechanism is troubling on theoretical grounds (1). Questions about its vaUdity remain (30), but it has received some recent support (31). 

Proliferous Polymerization. Eady attempts to polymerize VP anionicaHy resulted in proliferous or "popcorn" polymerization (48). This was found to be a special form of free-radical addition polymerization, and not an example of anionic polymerization, as originally thought. VP contains a relatively acidic proton alpha to the pyrroHdinone carbonyl. In the presence of strong base such as sodium hydroxide, VP forms cross-linkers in situ probably by the following mechanism ... 

The Zn—A1 system permits manipulation of the mechanical properties by suitable heat treatment. The aluminum-rich alpha phase is especially suitable for solution hardening since it can be supersaturated by as much as 30 wt % zinc. Furthermore, both alpha and beta phases can be strengthened by precipitation because of decreasing solute solubiUty with decreasing temperature. 

Resistivity measurements of doped, alpha-siUcon carbide single crystals from —195 to 725°C showed a negative coefficient of resistivity below room temperature, which gradually changed to positive above room temperature (45). The temperature at which the changeover occurred increased as the ionization of the donor impurity increased. This is beUeved to be caused by a change in conduction mechanism. 

Alpha—beta aluminum alloys respond to heat treatment with a general improvement of mechanical properties. Heat treatment is accompHshed by heating to 815—870°C, quenching in water, and reannealing at 370—535°C, depending on the size and section of the casting. Different combinations of strength, hardness, and ductility can be obtained. Some nickel in aluminum bronze is in soHd solution with the matrix and helps refine the precipitate, and a smaller amount is in the K-intermetaUic compound. 

Polyimides, both photodefinable and nonphotodefinable, are coming iato iacreased use. AppHcatioas iaclude planarizing iatedayer dielectrics oa iategrated circuits and for interconnects, passivation layers, thermal and mechanical stress buffers ia packagiag, alpha particle barriers oa memory devices, and ion implantation (qv) and dry etching masks. 

W. J. Evans. Optimising mechanical properties in alpha + beta titanium alloys. Mater Sci Eng A 243 %%, 1998. 

Radioactive transformations are accomplished by several different mechanisms, most importantly alpha ptirticle, beta particle, tuid gamma ray emissions, Each of tliese mechanisms are sponuuieous nuclear transformations. The result of these transformations is tlie formation of different tuid more stable elements. 

Oligomerization of ethylene using a Ziegler catalyst produces unbranched alpha olefins in the C12-C16 range by an insertion mechanism. A similar reaction using triethylaluminum produces linear alcohols for the production of biodegradable detergents. 

Both in the laboratory and in living organisms, the reactions of carbonyl compounds take place by one of four general mechanisms nucleophilic addition, nucleophilic acyl substitution, alpha substitution, and carbonyl condensation. These... 

Reactivity of Ends The Mechanism of Alpha-Substitution Reactions 84... 

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