Ionizing radiation defined

Dose equivalent or rem is a special radiation protection quantity that is used, for administrative and radiation safety purposes only, to express the absorbed dose in a manner which considers the difference in biological effectiveness of various kinds of ionizing radiation. The ICRU has defined the dose equivalent, H, as the product of the absorbed dose, D, and the quality factor, Q, at the point of interest in biological tissue. This relationship is expressed as H = D x Q. The dose equivalent concept is applicable only to doses that are not great enough to produce biomedical effects. 

Lind (1961) defines radiation chemistry as the science of the chemical effects brought about by the absorption of ionizing radiation in matter. It can be said that in 1895, along with X-rays, Roentgen also discovered the chemical action of ionizing radiation. He drew attention to the similarity of the chemical effects induced by visible light and X-rays on the silver salt of the photographic plate. This was quickly followed by the discovery of radioactivity of uranium by Becquerel in 1896. In 1898, the Curies discovered two more radioactive elements—polonium and radium. 

About 1910, M. Curie suggested that ions were responsible for the chemical effects of radioactive radiations. Soon thereafter, mainly due to the pioneering work of Lind on gases, the notation M/N was introduced for a quantitative measure of the radiation effect, where N is the number of ion pairs formed and M is the number of molecules transformed—either created or destroyed. This notation, referred to as the ion pair yield, was most conveniently employed in gases where N is a measurable quantity. However, for some time the same usage was extended to condensed systems assuming that ionization did not depend on the phase. This, however, is not necessarily correct. The notation G was introduced by Burton (1947) and others to denote the number of species produced or destroyed per 100 eV absorption of ionizing radiation. In this sense, it is defined... 

According to my view, the polymerizations by ionizing radiations at the lowest m are bimolecular reactions, propagated by the species P+ Sv. For these reactions there are no ambiguities, and [P+ Sv] = c, so that k+p is defined by (4.1) and (4.15). The available values, including those calculated in this Section and in Section 5, are collected in Table 5. 

Elastin-mimetic protein polymers have been fabricated into elastic networks primarily via y-radiation-induced, radical crosslinking of the material in the coacervate state [10]. Although effective, this method cannot produce polymers gels of defined molecular architecture, i.e., specific crosslink position and density, due to the lack of chemoselectivity in radical reactions. In addition, the ionizing radiation employed in this technique can cause material damage, and the reproducibility of specimen preparations may vary between different batches of material. In contrast, the e-amino groups of the lysine residues in polymers based on Lys-25 can be chemically crosslinked under controllable conditions into synthetic protein networks (vide infra). Elastic networks based on Lys-25 should contain crosslinks at well-defined position and density, determined by the sequence of the repeat, in the limit of complete substitution of the amino groups. 

Lind [2] has defined radiation chemistry as the science of the chemical effects brought about by the absorption of ionizing radiation in matter. It should be distinguished from radiation damage which refers to structural transformation induced by irradiation, particularly in the solid state. The distinction is not always maintained, perhaps unconsciously, and sometimes both effects may be present simultaneously. Following a suggestion of M. Curie around 1910, that ions were responsible for the chemical effects of radioactive radiations, the symbol MjN was introduced to quantify the radiation chemical effect, where M is the number of molecules transformed (created or destroyed) and N is the number of ion pairs formed. Later, Burton [3] and others advocated the notation G for the number of species produced or destroyed per 100 eV (= 1.602 x 10 J) absorption of ionizing radiation. It was purposely defined as a purely experimental quantity independent of implied mechanism or assumed theory. 

Ionizing radiation, as the term implies, defines those radiations that interact with matter by the production of charged particles, namely electrons and residual positive ions. 

Absorbed dose is a scientifically rigorously defined quantity which is used to quantify the exposure of humans, biological systems, and any type of material to ionizing radiation. 

The acronym kerma for kinetic energy released in absorbing material has been used to conceptually connect the energy deposited by ionizing radiation with the radiation field. It is defined to include the kinetic energy, which is locally absorbed from products of interaction with the particular medium such as Compton electrons, photoelectrons, and pah production while excluding the energy, which is not locally absorbed, from Compton-scattered photons, characteristic fluorescence radiation, and annihilation photons. The kerma is defined as ... 

Oscillator strength or transition probability is the individual characteristic of a separate atom or ion. However, in reality we usually have to deal with a large number of them, where, depending on the specific physical situation, various elementary processes of excitation, ionization, recombination, etc. may take place. Real spectral lines are characterized by the intensity of radiation, defined in the conditions of natural isotropic excitation as... 

From studies of human populations exposed to certain chemicals, available data are sufficient to characterize the dose-incidence relationships for some types of cancer at high dose levels. However, as in the case of ionizing radiation, the data are not sufficient to define the dose-incidence relationships precisely for any form of cancer over a wide range of doses and dose rates. Therefore, the probability of cancer induction that may be associated with low doses of chemicals that would be of primary concern in protection of public health can be estimated only by interpolation and extrapolation of data at higher doses and dose rates, based on assumptions about the dose-incidence relationships and mechanisms of toxicity. For the few chemicals for which incidence data are available over a range of doses, the dose-incidence relationship is not inconsistent with linearity, but this result does not constitute proof of linearity. 

Few chemicals identified as carcinogens in laboratory animals are known to cause cancer in humans, and the dose to affected tissues for these chemicals usually is not known well enough to define the dose-response relationship except in a general way. In this respect, the carcinogenic effects of most chemicals in humans are far less well known than are those of ionizing radiation. 

Recently, Ramamurthy and colleagues demonstrated that certain zeolites, including Na-ZSM-5, spontaneously oxidize a variety of olefmic or aromatic substrates (Fig. 1) [34, 35], Zeolites have been utilized frequently as supporting matrix materials [36-38], These materials contain host cavities of well defined geometries and allow molecules of appropriate shapes to be incorporated. Typically, the host contained in the zeolite is oxidized by exposure to ionizing radiation (vide infra), and the resulting radical cation is protected against ion... 

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