Lecture 19: Biological Effects of Radiation I. Radiation Chemistry Interaction of Radiation with Matter: Emphasis on effect of medium on incident radiation Biological Effects of Radiation: Emphasis on effect of radiation on medium A. Chemical Species Formed in Medium 1. Cation-Electron Pairs a. Gases and Liquids mobile ions – facilitates detection e.g., CH4CH4++ ebiological systems: alters electrolyte balance b. Solids trapped electrons and lattice defects modified conduction bands: impurities, Si bit upsets 2. Free Radicals Bond cleavage CH4CH3+ Ha. Radioalysis: Decomposition of compounds; esp. H2O, by radiation H2O H + OH H + H H2(reducing agent) Body mostly H2O OH + OH H2O (oxidizing agent) TMI b. Compounds CxHyOzCO2, H2O, H2,etc. recombinants may alter properties – negative or positive Negative: biological alterations (DNA) Positive: cross-linking of polymers (Cook, Inc.)dE/dx AZ2/E for charged particles dE/dx Efor photons hvhvhvcan improve qualities of polymers
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