Radiation, basic concepts

Concluding this section, two interesting variants of the STM should be addressed. The spin-polarized STM (SPSTM), which works with a ferromagnetic tip, can be used to probe surface magnetism with high resolution [5.47, 5.48]. Other modifications of the STM involve electromagnetic radiation, whereby two basic concepts can... 

Accident scenarios leading to vapor cloud explosions, flash fires, and BLEVEs were described in the previous chapter. Blast effects are a characteristic feature of both vapor cloud explosions and BLEVEs. Fireballs and flash fires cause damage primarily from heat effects caused by thermal radiation. This chapter describes the basic concepts underlying these phenomena. 

Understanding the basic concepts in radiation physics, chemistry, and biology is important to the evaluation and interpretation of radiation-induced adverse health effects and to the derivation of radiation protection principles. This appendix presents a brief overview of the areas of radiation physics, chemistry, and biology and is based to a large extent on the reviews of Mcttler and Moseley (1985), Hobbs and McClellan (1986), Eichholz (1982), Hendee (1973), Cember (1996), and Early et al. (1979). 

Develop basic concepts about radiation quantities, units, and measurements, about the application of these concepts, and about radiation protection ... 

Using basic exponential radiation attenuation concepts, this reference shows the development of the expression for determining the hydrogen concn in a piece of mail ... 

Intra- and intermolecular hydrogen transfer processes are important in a wide variety of chemical processes, ranging from free radical reactions (which make up the foundation of radiation chemistry) and tautomeriza-tion in the ground and excited states (a fundamental photochemical process) to bulk and surface diffusion (critical for heterogeneous catalytic processes). The exchange reaction H2 + H has always been the preeminent model for testing basic concepts of chemical dynamics theory because it is amenable to carrying out exact three-dimensional fully quantum mechanical calculations. This reaction is now studied in low-temperature solids as well. 

Understanding the basic concepts in radiation physics, chemistry, and biology is important to the evaluation and interpretation of radiation-induced adverse health effects and to the derivation of... 

QM grew out of studies of blackbody radiation and of the photoelectric effect. Besides QM, radioactivity and relativity contributed to the transition from classical to modem physics. The classical Rutherford nuclear atom, the Bohr atom, and the Schrodinger wave-mechanical atom are discussed. Hybridization, wavefunctions, Slater determinants and other basic concepts are explained. For obtaining eigenvectors and eigenvalues from the secular equations the elegant and simple matrix diagonalization method is explained and used. All the necessary mathematics is explained. 

Abstract Photochemistry is concerned with the interaction between light and matter. The present chapter outlines the basic concepts of photochemistry in order to provide a foundation for the various aspects of environmental photochemistry explored later in the book. Electronically excited states are produced by the absorption of radiation in the visible and ultraviolet regions of the spectrum. The excited states that can be produced depend on the electronic structure of the absorbing species. Excited molecules can suffer a variety of fates together, these fates make up the various aspects of photochemistry. They include dissociation, ionization and isomerization emission of luminescent radiation as fluorescence or phosphorescence and transfer of energy by intramolecular processes to generate electronic states different from those first excited, or by intermo-lecular processes to produce electronically excited states of molecules chemically different from those in which the absorption first occurred. Each of these processes is described in the chapter, and the ideas of quantum yields and photonic efficiencies are introduced to provide a quantitative expression of their relative contributions. 

Radiative transfer models can be very complicated and their solution cumbersome, so it is always desirable to have simplified tools for this analysis. Very simple and intuitive models can be developed in some cases to study radiation transfer inside photocatalytic reactors. However, it must be pointed out that these models must be well grounded in radiative transfer theory, in order to provide results that are consistent and of lasting engineering interest. Here, we present the basic concepts and discuss some approximations and methods that have been used. 

The foundations for the edifice had been laid when I compiled my review on inorganic free radicals in solution ten years ago (23), in the sense that the basic concepts had been realized and kinetic studies based on sound energetics offered very great scope for further investigation in many fields polymerization and autoxidation reactions, photochemistry and radiation chemistry of aqueous systems, and even reactions in biological systems. 

The interferometer used in a non-dispersive instrument is a device that divides the beam of radiation into two paths and recombines the two beams after a path difference has or has not been introduced. The basic concept of the interferometer was introduced by Michelson almost a century ago (Fig. 2). It consists of a stationary mirror, a moving mirror, and a beam splitter. The radiation from the infrared source is divided at the beam splitter half the beam is passed to a fixed mirror and the other half is reflected to the moving mirror. The two beams are later recombined at the beam splitter and passed through the sample to the detector. For any particular wavelength, the... 

The course of chemical reactions in irradiated proteins is determined hy factors that influence the reactivity of the primary free radicals, the kind of protein radicals formed, and the decay of these protein radicals to stable products. To understand these reactions, basic radiation chemical concepts are considered, chemical changes in several representative proteins irradiated under different conditions are compared, and results from optical and electron spin resonance studies on model systems are presented. Among the reactions described are those involving cation, anion, and a-carbon radicals of amino acids and peptides. Analogous reactions common to proteins are then summarized. These mechanistic considerations have important implications for the irradiation of hydrated muscle proteins at — 40°C and for radiation sterilization of foods. 

Other review articles have been published on the radiation inactivation method (Pollard et al., 1955 Kempner and Schlegel, 1979), two of them recently (Jung, 1984 Harmon et al., 1985). Since we do not want to be repetitious, the theory and experimental procedure will only be described briefly, although enough details will be given to allow the reader to follow the discussion. We will focus our attention primarily on the basic concepts of target theory and protein inactivation. 

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