Radiation preirradiation treatment

MetaHoelement complexes may be useful for the post-irradiation treatment of radiation injury, based on the observation that several of these compounds accelerate recovery of, among other things, lympho/hemopoiesis. Preirradiation Mn2(0)(DIPS)g increases the survival of y-irradiated mice (103). Treatment of mice that have been exposed to an LD q q dose of y-rays plus Mn2(0)(DIPS)g either 1 or 3 h after irradiation also increases survival, which supports the hypothesis that this compound is an effective radiorecovery agent (105). Again, this increase in survival may result from the resynthesis of radiation-depleted Mn-dependent enzymes that facHitate the recovery of immunocompetence and tissue repair, as reported for Cu(II)2(DIPS)4. 

Color." The most obvious effect produced in silica gel by radiation is a grayish-purple color (64), which can be almost surely attributed to the same type of center as that responsible for the similar color in irradiated quartz, namely, a positive hole trapped at an oxygen ion adjacent to a substitutional Al + impurity ion (65-67). The attribution rests on the similarity in optical absorption between irradiated gel and irradiated quartz (66), on the dependence of the intensity of the color on the aluminum content (69), and on the observation of a hyperfine interaction characteristic of the spin of the 2 a1 nucleus (I = 5/2) in the ESR spectrum of the irradiated gel (70). Furthermore, the ESR sextet and the color are annealed at comparable rates above 200° (70) and are both destroyed by adsorption of H2 at room temperature (64, 70). Their intensities increase in parallel as the aluminum content, the severity of preirradiation heat treatment, or the length of irradiation is increased (70). The concentration of the center does not increase indefinitely. After some lO i ev/gm, it approaches a limiting value which depends on the impurity content, for typical gels around lO H2/gm (69). 

Although considerable work has been reported using preirradiation grafting, the present treatment will be confined to the mutual or simultaneous procedure since by this latter technique, much lower doses are needed to accomplish a particular percentage graft The simultaneous method is also amenable to the use of additives to accelerate copolymerization. The additives to be discussed in this paper include solvent, mineral acid and polyfunctional monomers for the grafting of styrene monomer to polyethylene and polypropylene films in the presence of gamma radiation ... 

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