Free radical gamma radiation-induced

Gamma Radiation-Induced Free Radical Chain Reactions... 

The free radical mechanism of the gamma radiation induced decomposition of alkanesulfonyl chlorides (RSO2CI) in cyclohexane was studied C35-37) to obtain kinetic and thermochemical information on the reactions of alkylsulfonyl radicals CRSO2). Previously discussed systems are relatively simple and their kinetic analysis is almost straightforward. The radiolysis of alkanesulfonyl chlorides presents a more complex situation. The problems encountered in the radiolysis of alkanesulfonyl chlorides will be illustrated in the C-C6H12 MeS02Cl system (36,37). 

Polymerization of monomer-impregnated concrete was initially carried out with 60Co gamma radiation. A principal advantage of using radiation is that free radical chain reactions can be induced at ambient temperature. This limits vaporization loss and may produce a better concrete-polymer bond. The disadvantages are the dose requirements and the relatively high initial investment required for the radiation source and facility. 

Manevich Y, Held KD, Biaglow JE (1997) Coumarin-3-carboxylic acid as a detector for hydroxyl radicals generated chemically and by gamma radiation. Radiat Res 148 580-591 Maples KR, Johnson NF (1992) Fiber-induced hydroxyl radical formation correlation with mesothelioma induction on rats and humans. Carcinogenesis 13 2035-2039 MarkG, Korth H-G, Schuchmann H-P, von Sonntag C (1996) The photochemistry of aqueous nitrate revisited. J Photochem Photobiol A Chem 101 89-103 Maskos Z, Rush JD, Koppenol WH (1990) The hydroxylation of the salicylate anion by a Fenton reaction and v-radiolysis a consideration of the respective mechanisms. Free Rad Biol Med 8 153-162... 

Glogard et have devised a novel contrast agent which is responsive to the concentration of free radicals. They used a Gd-chelate conjugated to a liposome by a disulfide linkage. Radical-induced cleavage of the disulfide bond frees the Gd-chelate from the liposome, reducing its relaxivity (due to faster reorientation). They report in vitro tests in which gamma radiation and dithiothreitol were both used to cleave the disulfide bond. 

Radiation processing of polymers can be operated with several types of ionizing radiations e-beam (accelerated electrons generated by an accelerator), gamma rays (photons emitted by a cobalt 60 source), and X-rays (since recently). It acts by a spontaneous ionizing process, in two steps formation of ions that decomposes into free radicals. There is no need to add an initiator like peroxides or photoinitiators. Then, the free radicals can induce some chemical reactions, depending on different parameters that will be considered hereafter. 

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