Forms Of Radiation Damage Research Articles

Radiation pathology is a part of Military field therapy

A great contribution to the study of problems of radiation pathology, the study of the body’s response to radiation, in the development of treatment and prevention of radiation injuries belong to the staff of the Department of military field therapy. In the period of over 60 years, the Military Field Therapy Department was consistently involved in rectification and study of the medical consequences of the radiological accidents, accompanied by radiation exposure. Problems of radiation pathology took a leading place in scholastic, scientific and clinical research of Department staff. Scientific research was based on established at Department experimental toxic-radiological laboratory where different types of radiation injury were simulated. Obtained results were penetrated into the educational process and have found practical application in the treatment of victims of the accident at the nuclear submarine. Patients with other forms of radiation damage were treated in the clinic of military field therapy in the following years. There are 2 cases of radiation disease due to intestinal irradiation caused by radium poisoning, the intestinal case of radiation disease, which was treated using extracorporal haemadsorption. After Chernobyl disaster Department research is concentrated on biological outcomes of «low dose radiation». The research aimed at solving problems relevant to military radiology is continuing. Organizational forms of specialized assistance to victims of radiation accidents and peacetime disasters within the framework of the disaster medicine service of the Ministry of defense of the Russian Federation are being improved.

The Effect of Electron Beam Irradiation in Environmental Scanning Transmission Electron Microscopy of Whole Cells in Liquid

Whole cells can be studied in their native liquid environment using electron microscopy, and unique information about the locations and stoichiometry of individual membrane proteins can be obtained from many cells thus taking cell heterogeneity into account. Of key importance for the further development of this microscopy technology is knowledge about the effect of electron beam radiation on the samples under investigation. We used environmental scanning electron microscopy (ESEM) with scanning transmission electron microscopy (STEM) detection to examine the effect of radiation for whole fixed COS7 fibroblasts in liquid. The main observation was the localization of nanoparticle labels attached to epidermal growth factor receptors (EGFRs). It was found that the relative distances between the labels remained mostly unchanged (<1.5%) for electron doses ranging from the undamaged native state at 10 e-/Å2 toward 103 e-/Å2. This dose range was sufficient to determine the EGFR locations with nanometer resolution and to distinguish between monomers and dimers. Various different forms of radiation damage became visible at higher doses, including severe dislocation, and the dissolution of labels.

Choice of operating voltage for a transmission electron microscope

An accelerating voltage of 100-300kV remains a good choice for the majority of TEM or STEM specimens, avoiding the expense of high-voltage microscopy but providing the possibility of atomic resolution even in the absence of lens-aberration correction. For specimens thicker than a few tens of nm, the image intensity and scattering contrast are likely to be higher than at lower voltage, as is the visibility of ionization edges below 1000eV (as required for EELS elemental analysis). In thick (>100nm) specimens, higher voltage ensures less beam broadening and better spatial resolution for STEM imaging and EDX spectroscopy. Low-voltage (e.g. 30kV) TEM or STEM is attractive for a very thin (e.g. 10nm) specimen, as it provides higher scattering contrast and fewer problems for valence-excitation EELS. Specimens that are immune to radiolysis suffer knock-on damage at high current densities, and this form of radiation damage can be reduced or avoided by choosing a low accelerating voltage. Low-voltage STEM with an aberration-corrected objective lens (together with a high-angle dark-field detector and/or EELS) offers atomic resolution and elemental identification from very thin specimens. Conventional TEM can provide atomic resolution in low-voltage phase-contrast images but requires correction of chromatic aberration and preferably an electron-beam monochromator. Many non-conducting (e.g. organic) specimens damage easily by radiolysis and radiation damage then determines the TEM image resolution. For bright-field scattering contrast, low kV can provide slightly better dose-limited resolution if the specimen is very thin (a few nm) but considerably better resolution is possible from a thicker specimen, for which higher kV is required. Use of a phase plate in a conventional TEM offers the most dose-efficient way of achieving atomic resolution from beam-sensitive specimens.

Laser desorption study of deuterium implanted in silicon carbide

Laser desorption of deuterium implanted in hot‐pressed silicon carbide samples was performed. The samples had been implanted at ion energies ranging from 1 keV/D to 3 keV/D and at fluences from 0.6×1020 m−2 to 1.8×1021 m−2. For the high fluence samples (≥3×1020 m−2), comparison of the experimental data of desorption rate versus laser energy with the results of computer simulations reveals that second order detrapping is the limiting re‐emission process. The effective trap activation energy decreases from 0.9±0.1 eV/molecule at 1 keV/D to 0.5±0.1 eV/molecule at 3 keV/D. Blister formation and exfoliation or other forms of radiation damage could explain the energy dependence in the high fluence samples. At low fluence (<3×1020 m−2), most of the D2 re‐emission takes place above the melting threshold (12 kJ/m2). Computer simulations, using the thermal properties of the solid phase of SiC extrapolated above the melting point, give information about the nature of the detrapping process. A first order detrapping mechanism with an activation energy of 2.0±0.2 eV was found under those conditions. A comparaison is made with the deuterium laser desorption behaviour in Be, C and Si.

Irradiation of the embryo and fetus.

The human evidence on radiation damage to the individual developing in utero is confined to mental impairment and carcinogenesis. New evidence is becoming available about levels of mental impairment of direct interest to radiological protection, but as yet no framework of understanding exists to allow quantitative predictions for the purposes of radiological protection. There is general agreement that malignant disease has been increased following antenatal radiography but no unanimity yet in concluding that irradiation was the main causal factor: reasons are given for accepting that radiography was the cause. Recent increases in biological understanding suggest why maldevelopment is not to be expected after irradiation of the conceptus. A clonal hypothesis for organogenesis provides a reasonable explanation for quantitative aspects of experimental observations on teratogenesis by ionising radiation, including the commonly found highly curvilinear dose-response relationship, the occurrence of so-called critical stages of sensitivity after exposures of a few hundred roentgens, and the reduction in frequency of induced abnormality with protraction of exposure. Clonal hypotheses predict that there will be a virtual threshold for polycystic (non-stochastic) forms of radiation damage. It may be misguided to adopt a linear dose-response relationship for deriving risk estimates for the practical purposes of radiological protection unless some mechanism for production of clinically evident harm can be advanced which provides a plausible reason for expecting linearity.

An overview of ion sputtering physics and practical implications

The first part of this review surveys the forms of energy exchange between incident ions and target atoms, going on to an examination of the distribution in depth of deposited energy. This analysis is then used to interpret the sputtering yield under various circumstances. The last part of the paper is devoted to a survey of different forms of radiation damage in sputtered targets, with special reference to the many factors that modify the original composition profile: such modification is related to the bombardment conditions used in analytical techniques such as AES, ESCA or SIMS which may be used,inter alia, to determine composition profiles.

Ion implantation phenomena related to hard bubble suppression in magnetic bubble YIG

Some aspects of the hard bubble suppression mechanism have been investigated in LPE grown magnetic bubble garnets, (Y1.65Sm0.18Lu0.21Ca0.96) (Fe0.96Ge4.04) O12. Following implantation of neon ions at a standard suppression dose of 5*1014 cm-2 collapse field measurements indicate effective hard bubble suppression. For this dose however, 57Fe Mossbauer spectra indicate the pressure of a non-magnetic surface layer while X-ray diffraction traces and alpha particle backscattering measurements indicate that the layer is structurally disordered. These observations are inconsistent with the capping layer model of hard bubble suppression. Implantation of nitrogen ions resulted in similar hard bubble suppression but produced a totally different form of radiation damage. Axial channelling of 800 keV nitrogen ions along the (111) direction is observed.

The relationship between early and late radiation damage in rodents' skin.

A study is made of the relationship between early and late damage after irradiation of the feet or ears of rats. In one type of experiment in which large groups of animals were given the same dose, there was a good correlation between the early and late forms of damage. In another experiment, the relationship between these two forms of radiation damage was found to be unaltered by a single dose of X-rays given 8 months earlier. Thus, both types of experiment point to the early and late forms of reaction in the skin of rodents resulting from a common cause. Other relevant experimental data and their relationship to clinical observations are discussed.

Actinomycin D inhibition of repair of a DNA complex from Chinese hamster cells.

SummaryUsing the technique of velocity sedimentation in alkaline sucrose gradients, the effect of actinomycin D, acting separately and in conjunction with x-radiation, has been examined in respect of the damage to and repair of DNA from Chinese hamster cells. Similarly to x-irradiation, high survival doses of this antibiotic resolve the DNA complex, which is initially released during alkaline lysis, giving rise to a 2 × 108 dalton species. Relative to damage which leads to resolution of the DNA complex and single-break formation by radiation, actinomycin D impedes the repair of former but not of the latter. However, in cells treated with actinomycin D alone, repair of the complex is also suppressed, probably because of the ability of this drug to bind to DNA. The results suggest: (1) a direct action of actinomycin on DNA; (2) different forms of radiation damage, which lead to complex resolution as opposed to single-break formation; and (3) an equivalence in the action of actinomycin D and x-radiation rela...

Comparison of gamma and ultra-violet radiation effects in polymethyl methacrylate at higher temperatures

Measurements of G (scission) values for γ-irradiation of PMMA at temperatures up to 180°C show a limiting value of 10 ± 1, with an activation energy of 0·98 kcal/mole, and no significant intensity dependence. Depolymerization at the higher temperatures is far smaller than with u.v. radiation and this is interpreted as showing a difference between the two forms of radiation damage. Ultra-violet radiation is selectively absorbed at chain ends which initiate depolymerization. The main chain scissions produced by γ-radiation (and to a lesser extent by u.v.) are far less effective in the initiation of depolymerization.