Chemically Induced Processes

The longitudinal relaxation rate inversely decreases with the residence time of water molecules inside the agglomerate. This effect was demonstrated thanks to a controlled and chemically induced process of agglomeration amongst ferrite nanomagnets coated by polyelectrolyte polymers. The NMRD profile becomes flatter on increasing agglomeration (Pig. 10). 

The final fate of ions in many instances is the formation of electronically excited species. Therefore, similarities of radiation-chemically induced processes with those induced photochemically can be frequently expected. However, this point should be made with some reservatio mentalis only. 

TXN undergoes solid-state polymerization by chemical-induced processes as well as by radiation. That TXN may undergo polymerization in the solid state was observed as early as in 1930 U1), but for a long time this observation was not used. In 1954 Mesrobian et al. published the first paper on the radiation-induced polymerization in the solid state (acrylamide polymerization) 1121 and the solid-state polymerization of TXN was rediscovered a few years later 113). Radiation-induced solid-state polymerization of TXN gained importance and it was believed that it could lead... 

Radicals with undefined stoichiometry or structure refer to radicals which either result from radical-molecule reactions in which species with more than one radical site are formed, or the stoichiometry of which is essentially given by a distribution function as in polymer systems. Most of the former result from radiation-chemically induced processes, and the radicals generated in the reaction of OH radicals with substrates, for example, are listed as (substrate—OH ). A radical adduct is similarly indicated as substrate -R, e.g. toluene —CH3 denotes a CHj radical adduct to toluene. The other type of radicals is referred to by writing the parent compound in parentheses, e.g. (polyvinylacetate). ... 

Chemical precipitation Precipitation induced by addition of chemicals the process of softening water by the addition of lime and soda ash as the precipitants. Chloramines Compounds formed by the reaction of hypochlorous acid (or aqueous chlorine) with ammonia. 

Intermetallics also represent an ideal system for study of shock-induced solid state chemical synthesis processes. The materials are technologically important such that a large body of literature on their properties is available. Aluminides are a well known class of intermetallics, and nickel aluminides are of particular interest. Reactants of nickel and aluminum give a mixture with powders of significantly different shock impedances, which should lead to large differential particle velocities at constant pressure. Such localized motion should act to mix the reactants. The mixture also involves a low shock viscosity, deformable material, aluminum, with a harder, high shock viscosity material, nickel, which will not flow as well as the aluminum. 

Matsue et al. [43] attempted to study the molecular rocket reaction in a ruthenocene-/ -cyclodextrin inclusion compound using the I00Ru y, p) "raTc reaction. They noticed a parallel relationship between chemical processes and nuclear-recoil-induced processes in the non-included ruthenocene compound, as shown in Fig. 9. In the nuclear-recoil-induced processes no dimerization can be observed because of the extremely low concentration of the product, whereas in the chemical processes dimerization is possible, as demonstrated by Apostolidis et al. [48]. When ruthenocene included in /J-cyclodextrin is irradiated with y-rays, a part of the ruthenocene molecule is converted to [TcCp2-] which escapes from the jS-cyclodextrin cavity. The [TcCp2] rocket thus produced can attack neighboring inclusion compounds so as to extract the enclosed ruthenocene molecules and abstract H or Cp (Cp cyclopentadienyl radical). This process is shown schematically in Fig. 10. 

Chain processes, free radical, in aliphatic systems involving an electron transfer reaction, 23,271 Charge density-NMR chemical shift correlation in organic ions, 11,125 Chemically induced dynamic nuclear spin polarization and its applications, 10, 53 Chemiluminescence of organic compounds, 18,187... 

In order to measure molecular hyperpolarizabilities the now standard D-C induced SHG experiment is used (12). Although it would be more suitable to work in the gas phase to minimize molecular interactions, high molecular weights (low vapour pressure) and chemical decomposition processes make it hardly feasible for the molecules of interest. 

Development of models to assess chemical-induced allergic or autoimmune reactions is difficult in that both types of reactions are subject to complex processes, and are idiosyncratic in nature. Factors that must be considered include a large number of genetic as well as phenotypic, neuroendocrine, or environmental factors that are only in part related to the immune system. 

A number of new resist materials which provide very high sensitivities have been developed in recent years [1-3]. In general, these systems owe their high sensitivity to the achievement of chemical amplification, a process which ensures that each photoevent is used in a multiplicative fashion to generate a cascade of successive reactions. Examples of such systems include the electron-beam induced [4] ringopening polymerization of oxacyclobutanes, the acid-catalyzed thermolysis of polymer side-chains [5-6] or the acid-catalyzed thermolytic fragmentation of polymer main-chains [7], Other important examples of the chemical amplification process are found in resist systems based on the free-radical photocrosslinking of acrylated polyols [8]. 

The process in which energy is emitted as radiation after a chemically induced electronic transition is known as fluorescence BECAUSE... 

Both CIDNP and ESR techniques were used to study the mechanism for the photoreduction of 4-cyano-l-nitrobenzene in 2-propanol5. Evidence was obtained for hydrogen abstractions by triplet excited nitrobenzene moieties and for the existence of ArNHO, Ai N( )211 and hydroxyl amines. Time-resolved ESR experiments have also been carried out to elucidate the initial process in the photochemical reduction of aromatic nitro compounds6. CIDEP (chemically induced dynamic electron polarization) effects were observed for nitrobenzene anion radicals in the presence of triethylamine and the triplet mechanism was confirmed. 

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