摘要:

Experimental and theoretical studies as well as computer simulations of particle and energy reflection coefficients which are of interest to fusion research are reviewed.

ISSN:0033-7579    

DOI:10.1080/00337578108207123

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

An important source of information on the question of whether or not toxic or other deleterious substances are formed in the radiation sterilization of foods is the chemical study of reaction products and reaction mechanisms in the radiolysis of individual food components. The present evaluation of the radiation chemistry of amino acids, peptides and proteins outlines the various radiation-induced processes which lead to amino acid degradation and to the synthesis of amino acid derivatives of higher molecular weight. Among the latter are the α,α'-diamino dicarboxylic acids which are formed as major products in the radiolysis of peptides both in aqueous solution and in the solid state. The α,α'-diamino acids are of particular interest as irradiation products because they represent a class of compounds not normally encountered in plant and animal protein sources. Such compounds have, however, been isolated from certain types of bacteria and bacterial products. All of the available data strongly suggest that the α,α'-diamino acids are produced in significant yield in the radiation sterilization of high protein foods. The importance of initiating extensive chemical and biological studies of these and of other high molecular weight products in irradiated food is emphasizéd.

ISSN:0033-7579    

DOI:10.1080/00337578108207124

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The report concerns the modern state of a theory of radiation by particles channeled in crystals.

ISSN:0033-7579    

DOI:10.1080/00337578108207125

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

A novel extension for the trap model of electron mobilities in liquid hydrocarbons is described. The new model assumes: (a) two main types of electron trap exist in liquid hydrocarbons, one is deep and the second is shallow; (b) these traps are the same in all liquid alkanes. The difference in electron mobilities in different alkanes is accounted for by the difference in the frequency of electron trapping in each state.

ISSN:0033-7579    

DOI:10.1080/00337578108207126

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Several silicates, including α-quartz, zirconium silicate, thorium silicate, LiAlSiO4, a silicate glass and several nitrides, α and β Si3N4, AlN, ZrN as well as Si2N2O and ThO2, have been irradiated by 1019-1021Krypton(3MeV)ions/m−2The damaged powders of original particle size less than 5 μm, have been examined by x-ray diffraction and electron microscope methods. The silicates and Si2N2O become non-crystalline by 10 × 19 ions/m2. The particles change shape, extending and bloating under prolonged irradiations of the order of 100 × 1019ions/m2. Silicate glass also undergoes this irradiation creep process. The nitrides and ThO2behave quite differently and even at fluences of 200 × 1019ions/m−2the powders remain crystalline, retaining relatively sharp edges to the particles without exhibiting irradiation creep. This difference in behavior can be related to the nature of the framework crystal structures, flexible for the silicates with variable bond angles, rigid for the nitrides with fixed bond angles. This may explain the behavior of radioactive minerals not found in a metamict condition.

ISSN:0033-7579    

DOI:10.1080/00337578108207127

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The response of positron annihilation parameters to the defect structures produced by neutron irradiation in copper, and their annealing behaviour, have been studied on specimens irradiated at two different temperatures, 50°C and 250°C. Both lifetime and angular correlation measurements were made while some aspects of the irradiation damage substructure were also covered by transmission electron microscopy. Marked changes in the positron parameters were found after the two irradiations. After the 50°C irradiation the dominant TEM defect was a high concentration of small loops, after the 250°C irradiation it was a population of voids. The voids gave rise to a long-lived component (420 ± 75 psec) that disappeared during isochronal annealing to between 450T and 550T in agreement with TEM observations. Another trapped positron component (180 ± 7 psec) appearing after both irradiations annealed out between 275 ± 25°C and 475 ± 25°C. Although we could not entirely exclude that the defects giving rise to this trapping were the dislocation loops, the results suggested that the traps were a population of small submicroscopic vacancy clusters (microvoids), probably gas stabilised. This appears to be important since such clusters are usually not considered, although there are good physical arguments to support their existence. The question of positron trapping at dislocations and loops still appears to be an open one.

ISSN:0033-7579    

DOI:10.1080/00337578108207128

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The growth of dislocation loops in Fe-15wt% Cr ferritic stainless steel was examined in the temperature range 200° ∼ 600°C using a high voltage electron microscope. At about 200°C black dots occurred in close proximity with one another and formed clusters. In the temperature range 300° ∼ 400°C small dislocation loops were formed and gathered into clusters of peculiar crystal orientations. Most of those loops lay on the {100} plane and were of the interstitial nature. Between 450° and 550°C, star-like dislocation loops grew, some of which formed the “pair.” Most of the loops existed on the {111} plane.

ISSN:0033-7579    

DOI:10.1080/00337578108207129

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

It is shown that inelastic losses included in calculations ofenergy spectra of ions reflected from the crystal surface result in worse resolution of the peaks related to quasisingle and multiple scattering. The great inelastic losses, for small sliding angles could explain the nonmonotonic appearance of two peaks when the ion beam is parallel to the crystallographic planes.

ISSN:0033-7579    

DOI:10.1080/00337578108207130

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The properties of carbon materials treated at various temperatures (1300–3000°C) have been investigated both in initial state and after irradiation.

ISSN:0033-7579    

DOI:10.1080/00337578108207131

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The glow curves of most thermoluminescent (TL) materials generally exhibit several peaks even in the range of room temperature (RT) to 400°C. Do the traps corresponding to the various peaks compete with each other during filling for the free charge carriers that are produced upon irradiation. Radiation induced sensitization in TL has generally been ascribed to the elimination of a competing deep trap though there is evidence to the contrary and alternate models have been proposed. In this paper competition for charge carriers during trap filling has been examined in natural yellow fluorite by post-irradiation annealing and irradiation at elevated temperatures. The results obtained indicate that there is no significant competition during trap filling in yellow fluorite.

ISSN:0033-7579    

DOI:10.1080/00337578108207132

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor