Effects Ionizing Radiations

Table 9 Ionizing Radiation—Effects on Polymeric Materials...

When it was recognized that the clastogenic effect of this phorbol diester involved the release of superoxide, clastogenicity was suppressed and cell survival increased by concomitant incubation with Cu-Zn SOD [497-499]. Pretreatment with Cu-Zn SOD also reduced X-ray and phorbol diester promoted transformations and increased survival of culture hamster embryo cells [493, 500]. In still another study it was found that Cu-Zn SOD reduced transformation of lOTl/2 cells produced by concomitant X-ray irradiation and exposure to misonidazole, a hypoxic cell radiosensitizer [501]. These observations were most pronounced when Cu-Zn SOD was present during fixation and expression periods [502], consistent with the observation that Cu-Zn SOD protects DNA [503] and proteins [474] against ionizing radiation. Effective radiation protection as a result of superoxide removal does offer anticlastogenic activity as well. 

Ma, T. P. 1989. Ionizing Radiation Effects in MOS Devices and Circuits. New York Wiley. 

Collins A. Cellular responses to ionizing radiation Effects of interrupting DNA repair with chemical agents. Int J Radiat Biol Relat Stud Phys Chem Med 1987 51 971-83. 

Copolymerization is effected by suspension or emulsion techniques under such conditions that tetrafluoroethylene, but not ethylene, may homopolymerize. Bulk polymerization is not commercially feasible, because of heat-transfer limitations and explosion hazard of the comonomer mixture. Polymerizations typically take place below 100°C and 5 MPa (50 atm). Initiators include peroxides, redox systems (10), free-radical sources (11), and ionizing radiation (12). 

Microwaves may be used to ionize gases when sufficient power is apphed, but only through the intermediate process of classical acceleration of plasma electrons. The electrons must have energy values exceeding the ioniza tion potential of molecules in the gas (see Plasma technology). Ionizing radiation exhibits more biological-effect potential whatever the power flux levels (2). 

U.S. radiation protection guidelines are estabHshed by the National CouncH on Radiation Protection and Measurement (NCRP) and are based on the recommendations of the International Commission on Radiological Protection (ICRP). The National Research CouncH also sponsors a report from its advisory committee on the biological effects of ionizing radiations (20). 

The stabilizing of halogen resins against the adverse effects of ionizing radiation has been obtained by using an ester of glycerol and thioglycolic acid... 

N.uional Research Council, 1972, The Biological Effects of Ionizing Radiations, National Academy of Sciences. 

Toxic Effects on the Blood-Forming Tissues Reduced formation of erythrocytes and other elements of blood is an indication of damage to the bone marrow. Chemical compounds toxic to the bone marrow may cause pancytopenia, in which the levels of all elements of blood are reduced. Ionizing radiation, benzene, lindane, chlordane, arsenic, chloramphenicol, trinitrotoluene, gold salts, and phenylbutazone all induce pancytopenia. If the damage to the bone marrow is so severe that the production of blood elements is totally inhibited, the disease state is termed aplastic anemia. In the occupational environment, high concentrations of benzene can cause aplastic anemia. 

The theory of radiation-induced grafting has received extensive treatment. The direct effect of ionizing radiation in material is to produce active radical sites. A material s sensitivity to radiation ionization is reflected in its G value, which represents the number of radicals in a specific type (e.g., peroxy or allyl) produced in the material per 100 eV of energy absorbed. For example, the G value of poly(vinyl chloride) is 10-15, of PE is 6-8, and of polystyrene is 1.5-3. Regarding monomers, the G value of methyl methacrylate is 11.5, of acrylonitrile is 5.6, and of styrene is >0.69. 

Ionizing radiation is unselective and has its effect on the monomer, the polymer, the solvent, and any other substances present in the system. The radiation sensitivity of a substrate is measured in terms of its G value or free radical yield G(R). Since radiation-induced grafting proceeds by generation of free radicals on the polymer as well as on the monomer, the highest graft yield is obtained when the free radical yield for the polymer is much greater than that for the monomer. Hence, the free radical yield plays an important role in grafting process [85]. 

This section will deal briefly with some aspects of expls safety peculiar to neutron activation analysis expts. We are concerned here with a) the possible effect of the ionizing radiation dose on the energetic material which will cause it to be more sensitive or hazardous to normal handling as an expl, and b) the potential direct expl hazards involved in the physical and mechanical transportation of samples to and horn the irradiation source and in a nuclear counting system... 

The effects of ionizing radiation on expls and related energetic materials have been well investigated over the years (see Radiation Effects on Explosives in Vol 9) and are quite predictable. 

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