Radiation reactions

Am(V), Am02, undergoes disproportionation and redox reactions in aqueous acidic media, which can be followed by spectrophotometry at wavelengths of 812 m/ii for Am(III), 715 m t for Am(V) and 992 mpt for Am(VI). The earlier work " on solutions of Am(V) in hydrochloric, nitric , sulphuric , and perchloric acid media, which were hindered by a-radiation reactions ( Am), led to the conclusion that the rate law... 

In a recent study, classical heating, microwave radiation and gamma radiation have been compared as energy sources to perform 1,3-dipolar reactions between unsaturated oximes and conventional dipolarophiles. On using gamma radiation the reactions were clean and yields obtained were similar to those for the thermal reactions. However, microwave radiation reactions were extremely clean, occurred more rapidly and gave higher yields [102],... 

Pulse Radiolysis. Surprisingly few studies have been carried out using the powerful technique of pulse radiolysis to study radiation reactions in polymers although an increasing number of studies on organic systems (67) and on monomers (68,69) are appearing. 

Note 1 Radiation reactions involving polymers often lead to chain scission and cross-linking. 

Note 2 A photochemical reaction is sometimes regarded as a type of radiation reaction. 

Interfacial tension, defmition, 233 Ionic taste, groups, 138 Ionizing radiation, reactions with protein, saturated fatty acids, and water, 295-296... 

Trifluoronitrosomethane (b.p. 86.0°C, 767 mm Hg) is of considerable interest as a component of high temperature-resistant elastomers. This compound has been prepared by treatment of trifluoroiodomethane, in the presence of mercury, with nitric oxide in a photochemical reactor whose mercury lamp emitted radiation at 253.7 mp.. The preparation is particularly sensitive to the initial pressure of the gases, reactant ratio, irradiation time, intensity of the ultraviolet radiation, reaction temperature, and method of removal of nitric oxide from the product [60]. 

Phillips (P2) has studied the radiation reactions of sugars in dilute solution and reported a preferential oxidation occurring at the C 6 position, which results in conversion of the glucose to glucuronic acid. Other oxidizing reactions resulting in the formation of aldehyde offer alternative pathways. 

Radionuclide Half-life Radiation Reaction Parent of Parent... 

Because many solvents, including water, are largely transparent to UV-vis radiation, reactions in the liquid phase can be investigated, as well as reactions on surfaces in the presence of liquids. 

Whilst thermolyses have aspects in common with photolyses, redox reactions are closely related to radiation reactions, in that they involve electron-transfer reactions. Electron-transfers, like proton transfers, can be extremely fast processes, and are therefore often key steps in biochemical systems. Probably the best understood example is that of photosynthesis, but there are many others not involving initial light absorption. The basic process is [2.19], but this... 

Fig. 6-3. Magnetic field effects observed in the radiation reaction of a squalane (S) solution of fluorene (M) for pulse radiolysis with a 4-MeV electron accelerator. The reaction temperature is not described in the present papers, but may be room temperature, (a) Time profile of fluorine fluorescence during and after pulse radiolysis of a squalane solution (1) at the minimum field less than 0.05 mT, where the residual field of an electromagnet is cancelled by passing a small reverse current through the magnet s coils (2) at 0.3 T. (b) The time dependence of the magnetic field enhancement of the fluorescence intensity (A) 15-ns pulse ( ) 50-ns pulse, (c) The MFE on the increase in fluorescence intensity at 200 ns after the pulse. (Reproduced from Ref. [18b] by permission from The American Chemical Society)...

In the interaction of ionizing radiation with cellular DNA, two effects contribute the direct effect [reactions (I) and (2)], where the energy of the ionizing radiation is absorbed by DNA itself and the indirect effect, where the water that surrounds the DNA absorbs the energy of the ionizing radiation [reactions (3) and (4)]. 

Comparison of the two elementary processes (2) and (3) shows the latter to be the most endothermic one. Indeed, decomposition of N2O yielding NO and N entails the rupture of the N=N bond, which requires 85 kcal. mole (3.6 e.v. molecule ) whereas for N2O decomposition into Na and 0, the breaking of the NO bond requires only 38 kcal. mole (1.6 e.v. molecule 0-This explains that thermally, in the absence of radiation, reaction (2) is always considerably favored, compared to reaction (3). Under irradiation, however, a great number of excess free carriers are produced in the conduction and valency bands these carriers tend to recombine. In this respect the adsorbed N2O molecule may behave like a recombination center. This phenomenon can be accounted for by considering the adsorbed N2O molecule to be an acceptor level. Under this hypothesis, the N2O chemisorption results from the capture, by the weakly adsorbed molecule, of an electron from the conduction band. At the moment of recombination with a positive hole from the valency band, a variable amount of energy can be recovered, depending on the position of the level constituted by the adsorbed N2O molecule. For the silica and alumina we have utilized, the width of the forbidden region is about 10 e.v. process (3) which only requires 3.6 e.v. may thus become possible. 

Usually four types of curing system are used for silicone elastomers. One is condensation reaction type using the hydrolyzable radical, second is addition reaction type, which uses hydrosilation reaction. The third type is organic peroxide curing and the last is radiation reaction using EB cure... 

The photodecomposition of ozone may form electronically excited oxygen atoms, 0( D), and excited molecular oxygen with absorption of the 193-nm radiation (Reaction [13.35]). The 0( D) species formed in Reaction [13.35] is much more reactive than the ground-state oxygen atoms [0( P)] ... 

Nausea, vomiting, diarrhea, hypersensitivity, bone marrow depression, ulcers, acne, increased radiation reactions, injection site necrosis. 

Aanderud, L. et al.. Hyperbaric oxygen treatment for radiation reactions, Tidsskr. Nor Laegeforen, 120(9), 1020-1022,2000. 

Some primordial radionuclides are still with us because their half-lives are near or exceed 1 billion years or because they are shorter-lived progeny of these long-lived radionuclides. All other radionuclides are formed by reaction of a nucleus with atomic or subatomic particles or radiation. Reactions with high-energy cosmic rays form some radionuclides in nature. Others are man-made, mostly in accelerators, nuclear reactors, and nuclear explosions. The hundreds of such radionuclides are shown in the Chart of Nuclides (Farrington et al. 1996) on both sides of the stable elements and at masses heavier than the stable elements. 

It is often the case that the aggregate state changes occur in (not only) radiation reactions, which is another big obstacle to many experimental methods as well as measuring the changes in thick samples. In both cases electrical conductivity can provide adequate information. Additionally, great sensitivity of electrical measurements to phase transitions makes it easy to study the effects of such... 

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