International Journal of Radiation Applications and Instrumentation. Part C. Radiation Physics and Chemistry最新文献

The experimental thermalization lengths, l_th, for hot electrons e^-_hot produced by photoionization of solvated electrons in 3-methylpentane glass are discussed. For electron energies ranging from the initial value E₀>1 eV down to 0.1–0.2 eV, the electron e^-_hot is assumed to loss energy mainly due to excitation of intramolecular vibrations with energy losses σE>k_BT. It is concluded that this model is in agreement with experimental data on l_th. The spatial distribution of subvibrational electrons is obtained.

CuO-Al₂O₃ catalyst containing 16.2 wt% CuO, precalcined at 300°C was subjected to different doses of γ-rays ranging between 20 and 160 Mrad. The magnetic properties were measured by the Gouy method and the catalytic activity and selectivity towards isopropanol conversion were investigated using a microcatalytic pulse technique at temperatures between 260–300°C.

The CuO-Al₂O₃ system exhibited a lower paramagnetic moment compared to that of unloaded CuO. γ-Irradiation induced changes in the magnetic properties of the system. The presence of diamagnetic alumina as a support and its dehydroxylation with γ-rays contributed to the observed changes in the magnetic properties.

Loading of CuO on alumina decreased the dehydration activity which disappeared completely at 16.2 wt% CuO. γ-Irradiation resulted in a progressive decrease in the dehydrogenation activity falling to a minimum at a dose of 40 Mrad. At greater doses the activity increased with the increase of the irradiation dose. Unirradiated and 160 Mrad-irradiated samples measured more or less the same dehydrogenation activity.

By using WAXD, DSC and gel fraction determination techniques, the mechanism of radiation crosslinking of polyethylene oxide (PEO) was explored, and the dependence of aggregated state on the chemical reaction and physical structure was also discussed. It was found that just like other semi-crystalline polymers, the state of aggregation of the specimen has a profound influence on the radiation effects on PEO. On the contrary, the crystalline structure of the specimen is severely affected with the increase in radiation dose and eventually amorphortized when subjected to an extremely high radiation dose.

A modular instrumental system for processing transient signals in laser flash photolysis and pulse radiolysis experiments is described. Modules with fast time-response and terminated interconnections allow signal capturing over a large time range, from nanoseconds to infinity, through the use of various kinds of detectors. A standard data bus is used to connect this system to the computer.

A new method of obtaining thermal electron mobilities from experimental dependencies observed in the electron swarm is described; the method is suitable for both electron accepting and non-accepting systems. The electron mobilities for CO₂, CH₄, C₂H₆ as well as for N₂, Ar, Xe, Kr and their mixtures with carbon dioxide are obtained.

This paper describes the effect of an antioxidant, a monomer and fillers (silica or carbon black), alone or in certain combinations with each other, on the mechanical and chemical response of a low density polyethylene (and, more briefly, that of other polyethylenes), to exposure to ionizing radiation. It is shown that, if chain scission is a significant factor in the radiolysis of a polymer, then the inter-relations between sol fraction, elastic modulus and ultimate elongation (both at 160°C) should change depending on whether an additive inhibits or enhances crosslinking. It was found that such additives do not significantly or consistently alter the inter-relations between these properties in polyethylene, indicating that chain scission is not an important feature of the radiolysis of this polymer.

The study of the radio degradation of DNA is one of a number of phenomena being investigated to develop methods for identifying irradiated foods. The specific behaviour under radiation of the mitochondrial DNA from beef liver gives the possibility of detecting if the product has been irradiated or not. An identification method could finally be developed. The appraisal of the mitochondrial supercoiled DNA fraction constitutes an unambiguous detection test for beef liver irradiation. A total of 120 different samples were irradiated at 5 different doses. The dose limit of detection is lower than 2 kGy. No effects due to storage conditions were observed.

Electron impact cross sections for various electronic excited states and for ionization of water vapor are represented by analytic forms that cover non-relativistic as well as relativistic energy region. This inelastic cross section set may serve as a convenient input for electron transport calculations relevant in several fields. With this cross section input an electron energy deposition study has been carried out using a Monte Carlo simulation giving excitation and ionization yields, the Fano factor and the subexcitation spectra for initial energies up to 1 MeV.