Radiation Physics and Chemistry (1977)最新文献

Investigations on the stratigraphic distribution of poly/methyl methacrylate/ in leather follow our earlier experiments on radiation grafting of vinyl monomers $\text{in situ}$.

Polymer distribution was determined for pigskins and cattlehides tanned with basic sulphates of chromium /III/. ¹⁴C-labelled methyl methacrylate was used in present experiments. Precision slicing technique was employed to cut consecutive slices parallel to the grain surface of the radiation modified leather. Quantitative analysis of polymer distribution in leather was based on radioactivity measurements. Each layer was burned in Oxymat apparatus and resulting ¹⁴CO₂ was analysed by liquid scintillation method.

On the basis of radioactivity measurements and visual observations with light microscope conclusion on desirable distribution of polymer was reached. In the midcorium part of leather polymer is evenly distributed and its content is much higher than for outer layers next to surface and flesh. Mechanism of relevant processes as well as formation and role played by peroxide compounds is discussed.

The relation between grafting conditions and antithrombogenicity has been examined from the purpose of clearing the necessity of controling grafting conditions to enhance blood compatibility. The grafting systems employed here were N, N-dimethylacrylamide (DMAA) — poly(tetrafluoroethylene) (PTFE) and DMAA- poly(ethylene-co-tetrafluoroethylene) (AFLON) and grafting parameters were dose rate, monomer concentration and total dose (irradiation time). Grafting DMAA onto the substrates was carried out by using simultaneous irradiation method of gamma rays from a ⁶⁰Co source. After evaluation of blood compatibility of the grafted films by using in vitro tests, it has been clear that control of grafting conditions is important. Especially, in both grafting systems, dose rate control has found to be very important for blood compatibility. When higher dose rate of 1.0 × 10⁵ to 3.0 × 10⁵ rad/hr was used for grafting DMAA onto PTFE or AFLON, blood compatibility of the substrates was not enhanced, whereas it was improved when the grafting was carried out at lower dose rate of 0.97 × 10⁴ rad/hr. The correlation between dose rate and antithrombogenicity has been interpretated in terms of surface-roughness of the grafted films. By scanning electron microscope (SEM) — observation, it has been observed that higher dose rate makes the surface rough, whereas lower dose rate does it smooth. In the grafting systems used here, therefore, dose rate is the most important factor to control the roughness of surface which gives a profound effect on antithrombogenicity.

The methods of technological dosimetry are discussed. The special attention is paid to the methods used in the U.S.S.R. The data on standard chemical and solid state dosimeters are presented. Some aspects on standardization of dosimeters in radiation processing are described. The information of high dose dosimeters which are lot produced in the U.S.S.R. is given. The examples of their application in radiation processing are presented.

A simple method utilizing a photochromic “intensity label” for monitoring electron-beam sources was evaluated. The labels exhibit a color change upon exposure to UV or e-beam radiation. A correlation was found between absorbed energy and Gardner Color Index at low electron-beam doses.

Modern physical ideas and technical possibilities of long-distance electrivity transmission to large distances by the intensive beams of relativistic electrons are considered. The basic scheme of line of electrical energy transmission by electron beam (LEETEE) is presented and the methods of technical realization of such line are discussed. The description of stands simulating LEETEB is given.

Casting process of optical plastic and its characteristics has been studied by radiation polymerization. The technique was applied to the production of various plastic lenses.

Radiation degradation of short-cotton linters has been studied by using X-rays diffraction,an infrared spectrometer and a viscosimeter. Average molecular weight and crystallinity of short-cotton linters and the change of reducing sugar in ɜ-radiation degradation were examined. It was found that cellulosic saccharification in hydrolysis was enhanced with preirradiation of linters. This probably resulted from the radiation induced change of cellulosic structure. Sensitizers to promote radiation degradation effect were investigated. Carbon tetrachloride has been found to be effective.

A dosimetry of mixed field, neutron and γ-ray, has been carried out by the activation method in a fast neutron source reactor “YAYOI,” which has been used for the study of fast neutron irradiation effects on organic materials and microorganisms. Neutron flux and energy distribution were obtained by an unfolding calculation based on the activation analysis. Absorbed dose was determined as a function of the distance from the center of the reactor core in a hole called “Glory Hole” used for irradiation of various materials. Contribution of absorbed dose from γ-rays coexisting with neutron was evaluated by measuring peroxide radicals formed in irradiated polytetrafluoroethylene, PTFE, which is insensitive to the neutron component. After evaluating the radiation field, relative sensitivities of popular dosimeters such as red acrylate, radiachromic, and alanine dosimeter for last neutron irradiation were determined by comparison with ⁶⁰Co γ-ray irradiation. Characteristics of the mixed field dosimetry and LET effect of recoil protons in samples at different neutron fields are discussed.

Problems in the studies of radiation effects in gases are discussed. By means of ionization-, excitation- and electron-capture yields various applications are characterized: ionization detectors, X-ray detectors, radionuclide battery, and radiation-induced chemical gas-phase reactions. Some new results of basic research in respect to the SO₂ oxidation are discussed.