Radiation-Induced Effects

Radiation-induced fatigue has received considerable attention. Polymers used in photoreceptors generally absorb only in the ultraviolet. Donor or acceptor molecules may absorb into the blue. Generation materials are designed to absorb throughout the visible and into the near infrared. Exposure to ultraviolet radiation can lead to irreversible changes due to transport-layer photochemistry. In fact, such chemistry has been used for many years in the production of 

Unfiltered cool-white fluorescent light has a significant ultraviolet component that can be absorbed by the transport materials and lead to photochemical 

Kanemitsu et al. (1989) observed decreased charge acceptance after prolonged irradiation of polymers doped with the hole transport molecule 2-(p-dipropylaminophenyl) -4- (p-dimethylaminophenyl) -5- (o-chlorophenyl) -1,3-oxazole. The effects depended on the polymer. A mechanism involving photo-induced charge transfer was proposed. Stolle et al. (1987) made a similar observation in studies of polymer photoconductors such as poly(N-vinyl- 

Mizuta et al. (1993) have reported that a single-layer photoreceptor containing 9-isopropylcarbazole-3-carbaldehyde-N,N-diphenylhydrazone is fatigued on exposure to ultraviolet radiation. The results were interpreted by a mechanism where radiation induces isomerization of the anti- to the -isomer. The latter has a lower ionization potential and is a hole trap. In the single-layer configuration, hole trapping near the free surface results in the creation of volume space charges, which cause decreased sensitivity. 

Enokida et al. (1991) reported that ultraviolet-induced fatigue of a photoreceptor using poly(methylphenylsilylene) (PMPS) as the transport layer could be explained by photodecomposition of the transport layer. The PMPS was both decomposed and cross-linked by the ultraviolet exposures. 

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This electric field-induced initiation concept is based on pulsed radiation. If a determination of a critical electric field is made in the absence of radiation it is probably not relevant to this area of radiation-induced effect since the critical field for an ionized material is likely to be very different from that for a non-ionized material... 

The experiments can be carried out in solution or in solid state (for example in KBr pellet) in order to study both direct and indirect effects of ionizing radiations. The experiments can also be carried out with samples in crystal, layer or gel. The experiments require only limited amounts of sample, a condition which is often restrictive to study the biological molecules for instance. The size of the studied molecules is not limited small molecules as well as macromolecules, such as the nucleic acids or polymers, can be studied, allowing the identification of radiation-induced effects. 

Fig. 1 illustrates the dissipative (i ) and Hall R cy) resistance characteristics of a high mobility device under microwave excitation at 103.5 GHz. Here, the new radiation-induced effect occurs at relatively low magnetic fields, in this instance B < 0.4 Tesla, and the effect includes giant magnetoresistance oscillations. Remarkably, it turns ont that, at the deepest minima, the resistance falls well below the R cx measnied withont photoexcitation, as it vanishes over broad 5-intervals around (4/5)Bf and 4/9)Bf Here, note that the small magnetic fields involved in this low B-field study can be easily realized with small solenoids or commercially available permanent magnets. 

Signoretti, E.C., Onori, S., Valvo, L., Fattibene, P, Savella, A.L., De Sena, C., and Alimonti, S. (1993) Ionizing radiation induced effects on cephradine. Influence on sample moisture content, irradiation dose and storage conditions, Drug. Dev. Ind. Pharm, 19,1693-1708. 

The selection on an empirical basis of collective-electron factors or active-site concepts or some combination thereof in order to account for the activity of surfaces in catalysing various processes has obvious disadvantages. Possibilities for a more systematic approach to the integration of collective-electron and localised-state aspects of surface structure have developed from theoretical treatments of intrinsic and extrinsic surface states, respectively. Models based on such developments, by reason of their relative novelty, have not yet been as widely applied as collective electron or active-site models to interpret catalytic activity of various surfaces and still less to considerations of sensitivity to irradiation. However, an abbreviated consideration of such surface state models is deemed essential here both as a basis for assessing their possible relevance in the explanation of radiation-induced effects and as an illustration of the integration of electronic and localised state aspects into a common framework. 

Agarwal, R., Katiyar, S.K., Khan, S.G., and Mukhtar, H., Protection against ultraviolet B radiation-induced effects in the skin of SKH-1 hairless mice by a polyphenohc fraction isolated from green tea, Photochem. PhotobioL, 58, 695-700,1993. 

FIGURE 8.1 Schematic representation of ionizing radiation-induced effects in MOS oxides. (From Gnana Prakash, A.P. et al., Radiat. Eff. Defects Solids, 157, 323, 2002. With permission.)... 

S. Hayashi, S. Takeda, K. Kaneto, K. Yoshino, and T. Matsuyama, Radiation- Induced Effect in Conducting Polymers, Synth. Met 18 591 (1987). 

Analysis of the Experimental Data on Life Shortening.—Our analysis proceeds from the hypothesis, induced by Lewis as a result of his study of the incidence of leukemia, that exposure of the bone marrow of an animal to radiation results in an increase in the probability per unit time that the animal will die at any time thereafter, the increase being proportional to the quantity of radiation absorbed. We shall suppose that this hypothesis applies to all of the radiation-induced effects in Dr. Finkel s experiments with mice. 

The toxic effects of the intake of uranium are based purely on its characteristics as a heavy element. There are no reports of radiation-induced effects in humans from the inhalation or ingestion of uranium. Inferential material on radiation effects has been gathered through animal experiments and comparison with human exposures to radium isotopes. Extensive reviews of the uranium literature concerning experimental studies in animals and humans are available [3,9,10]. 

As previously stated, the process of ionization changes atoms and molecules. If cellular damage does occur and is not adequately repaired, it may prevent the cell from surviving or reproducing, or it may result in a viable, but modified cell. Radiation-induced effects of concern in emergency response fall into two general categories deterministic and stochastic effects. 

Rodriguez F, Filimonov A, Henning A, Coughlin C, Greenberg. Radiation-induced effects in multiprogrammable pacemakers and implantable defibrillators. Pacing Clin Electrophysiol 1991 14 2143-2153. 

Radiation-induced effects in labeled molecules occur with compounds of high specific activity, labeled with weak P emitters or even a emitters. Since autoradiolysis lakes place mainly via secondary radical reactions of fragments formed from solvents or major components, radiolytic damage... 

The remainder tissues consist of a group of additional organs and tissues with a lower sensitivity for radiation-induced effects for which the average dose must be used ... 

Wedlake L, McGough C, Hackett C, Thomas K, Blakes P, Harrington K, Taits D, Khoo V, Deamaley D, Andreyev HJN (2008) Can biological markCTs act as noninvasive, sensitive indicators of radiation-induced effects in the gastrointestinal mucosa Aliment Pharmacol Ther 27 980-987... 

Ni/Cr multilayers. Factors known to limit the depth resolution include instrumental factors, sample characteristics and radiation-induced effects. 

Radiation-induced effects on the electrical characteristics are described extensively in Ref (69), which includes 40 references. Photoconductivity, along with other specialized characteristics including charge transfer and semiconductance, is described in Refs. (41) and (70). Electroluminescence and thermoelectric power (Siebeck effect) have been reported in pol3nners. 

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