Radiation in the Environment and Living Systems

We are continuously bombarded by radiation from both natural and artificial sources. We are exposed to infrared, ultraviolet, and visible radiation from the Sun radio waves from radio and television stations microwaves from microwave ovens X rays from medical procedures and radioactivity from natural materials (T Table 21.8). Understanding the different energies of these various kinds of radiation is necessary in order to understand their difierent effects on matter. 

A star is born from a cloud of gas and dust called a nebula. When conditions are right, gravitational forces collapse the cloud, and its core density and temperature rise until nuclear fusion com- 

Some of the sC nuclei go on to react with alpha particles to form oxygen-16  

This stage of nuclear fusion is called helium burning. Notice that carbon, element 6, is formed without prior formation of elements 3, 4, and 5, etqjlaining in part their unusually low abundance. Nitrogen is relatively abundant because it can be produced from carbon through a series of reactions involving proton capture and positron emission. 

Most stars gradually cool and dim as the hehum is converted to carbon and oxygen, ending their hves as white dwarfs, a phase in which stars become incredibly dense—generally about one milhon times denser than the Sun. The extreme density of white dwarfs is accompanied by much higher temperatures and pressures at the core, where a variety of fusion processes lead to synthesis of the elements from neon to sulfur. These fusion reactions are collectively called advanced burning. 

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RADIATION IN THE ENVIRONMENT AND LIVING SYSTEMS We discover that naturally occurring radioisotopes bathe our planet—and us—with low levels of radiation. The radiation emitted in nuclear reactions can damage living cells but also has diagnostic and therapeutic applications. 

The last three chapters consider special aspects of radioanalytical chemistry that have become increasingly important and visible. Chapter 15 describes the automated systems that are used to measure radionuclides in the counting room and in the environment. Chapter 16 is devoted to identification and measurement of the radionuclides beyond the actinides. These are research projects at the cutting edge of radiochemistry that apply novel rapid separations in order to measure a few radioactive atoms before they decay. Much must be inferred from limited observations. In Chapter 17, several versions of mass spectrometers combined with sample preparation devices are described. The mass spectrometer, applied in the past as a research tool to detect a small number of radioactive atoms per sample, is now so improved that it serves as a reliable alternative to radiation detection for radionuclides with half-lives as short as a few thousand years. 

Some new trends can be recognized in the points such as the interaction of short-lived active species in some spatial distributions measured by spin echo and pulse radiolysis methods. The application of polymers for drug-delivery systems is here discussed with reference to low temperature radiation polymerization techniques. Ion beam irradiation of polymers is also reviewed for which further research is becoming important and attractive for so-called LET effects and high density excitation problems. In the applied fields the durable polymers used in strong and dense irradiation environments at extremely low temperature are here surveyed in connection with their use in nuclear fusion facilities. 

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