Radiation, chemical changes ionization

Changes in the properties of polymer materials caused by absorption of high-energy radiation result from a variety of chemical reactions subsequent to the initial ionization and excitation. A number of experimental procedures may be used to measure, directly or indirectly, the radiation chemical yields for these reactions. The chemical structure of the polymer molecule is the main determinant of the nature and extent of the radiation degradation, but there are many other parameters which influence the behaviour of any polymer material when subjected to high-energy radiation. 

The primary target of biological effects appears to be the DNA (see Chap. 15), although effect on the cytoplasmic membrane may also play a role [8]. Ionizing radiation affects DNA in a number of ways. It causes chemical changes in specific nucleotide bases it causes single-strand breaks and it causes double-strand breaks in a dose-dependent manner. 

When polypropylene is exposed to ionizing radiation, free radicals are formed and these cause chemical changes. Since PP is highly crystalline, these radicals are relatively immobile, and consequently may not be available for reaction for long periods of time. ... 

It appears that the chemical change produced by a given amount of energy degradation is far less sensitive to the rate of energy loss of the radiation in hydrocarbons than in water. While pure water behaves very differently when irradiated with radiations of differing ionization densities, the chemical effects in hydrocarbons appear to be quite insensitive... 

In this chapter we will consider the techniques developed to detect and quantitatively measure how much ionization and/or excitation is caused by different nuclear radiations. As all radiation creates ionization and/or excitation, we will separate the discussion of detection methods according to the general techniques used to collect and amplify the results of the interaction of the primary radiation with matter rather than by the type of radiation. These detection methods can be classified as (a) collection of the ionization produced in a gas or solid, (b) detection of secondary electronic excitation in a solid or liquid scintillator, or (c) detection of specific chemical changes induced in sensitive emulsions. 

Hutchinson F (1985) Chemical changes induced in DNA by ionizing radiation. Progr Nucleic Acid Res Mol Biol 32 115-154... 

In the future the nature of chemical exposure has been predicted to change. The level of exposures will decrease, but at the same time simultaneous exposure to many chemicals with low concentration will become more general as the usage of chemicals in the society is growing continuously. In western countries, approximately 200-1000 new chemicals (in quantities of 500 kg or more) are developed and introduced into the marketplace every year. A potential reproductive hazard, in addition to chemicals, is ionizing and nonionizing radiation, the use of which will also grow in future work environment. It has been estimated that internationally the number of workers exposed to radiation will increase over 100 % by the year 2000. 

Quantitative description of the chemical changes Initiated by radiation requires an understanding of the processes by which the rays transfer energy to a system and knowledge of how much enejrgy is transferred. For particulate radiations (a, 3 > e and e ) the important interaction is inelastic collisions between the particles and the molecules of the medium resulting in their ionization and excitation. 

When ions and excited molecules have been formed in this manner, a variety of secondary processes may occur before the final chemical change takes place. To illustrate the nature of such primary and secondary processes, the behavior of water on exposure to ionizing radiations will be considered this is a matter of fundamental importance in the present review, because the majority of carbohydrate investigations in this field have been undertaken in aqueous solution. 

For quantitative studies in radiation chemistry, it is essential that the energy input into the irradiated volume should be accurately determined. For this purpose, the most versatile and reliable method is the ferrous sulfate dosimeter, proposed by Fricke and Morse. The method involves the use of an air-saturated solution of 10 M ferrous sulfate and 10 M sodium chloride in 0.8 N sulfuric acid. On exposure of the solution to ionizing radiations, the ferrous ion is oxidized to ferric ion, which may conveniently be determined accurately by spectrophotometry. The amount of chemical change is proportional to the total energy-input, independent of dose rate, and (within wide limits) independent of the concentration of ferrous ion, ferric ion, and oxygen. The main reactions involved are as follows. 

A stressor is a substance, circumstance, or energy field that causes impacts, either positive or negative, upon a biological system. Stressors could be as wide ranging as chemical effects, ionizing radiation, or rapid changes in temperature. 

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