The results of the experiment were previously reported in which the moisture-content of a thin slab could be detected by using the geometrical arrangement with a neutron source (Ra+Be) placed in a moderator. In this paper it is described that some investigations have been made to pursue the effects of energy-dependent neutrons on the moisture-detection in the same arrangement as previous. In the first place, the present experiment is performed with the arrangement that the surface of the moderator is covered with the cadmic plate, and its result shows that the epicadmium neutrons contribute little to moisture-detection. Therefore, an object of this analysis is limited to those neutrons with less energies than them, which are assumptively divided into two groups of thermal neutrons (0.025-0.07 eV) and slow neutrons (0.07-0.5 eV) . Then, two-group diffusion equations apply to calculate the rate of the thermalization of slow neutrons in the slab, and on the assumption that thermal neutrons reciprocate repeatedly through the air gap where detectors are placed between the moderator and the slab, the total number of neutron corresponding to the counting rate is calculated with the aid of the rate of the thermalization obtained above, the albedo of thermal neutrons and the decrement-rate of neutron current density in the air gap. The results of these calculations are in good agreement with the experimental results at various moisture-contents, and it is quantitatively shown that the thermalization of slow neutrons and the thermal neutrons repeatedly reflected in both the moderator and the slab contribute remarkably to moisture-detection. This approximate analysis will lead to the means by which the position of the source and the quantity of the moderator to make the efficiency of detection the highest can be decided.
Efficiencies with which trace quantities of 60Co, 106Ru and 65Zn in sea-water are carried down were examined for scavengers such as manganese dioxide and hydroxides of iron (III), iron (III) -magnesium and iron (III) -manganese (II) . These scavengers were previously made and dried at 90-100°C and then put into sea-water. Efficiencies were found low in iron hydroxide for60Co carrying. Iron-magnesium and iron-manganese hydroxides showed high efficiencies for all of these tracers, but were found dificultly filterable. The highest practicability was found in commercial granular α-manganese dioxide. As the removal of these tracers from manganese dioxide was found most difficult at pH 7-8, no pretreatment is required in dealing with sea-water of normal pH. Only 0.2 g of this scavenger (50-100 mesh) can carry these tracers almost completely from 50 ml of sea-water in about an hour of agitation.
Fourier analysis has not yet been applied to the analysis of radioisotope image transmission systems. Using 131I-paper Siemens star, the authors measured the optical transfer function (OTF) of its system, and confirmed the justification of theoretical calculation. The assessment of various types of collimators were examined quantitatively, and the effective length were obtained in the case of focusing and defocusing. When calculated taking account of tissue absorption, the average cut-off frequeneies (OTF-O) through tissue thickness correspond to the clinical perceptible limits of hole deft tct size. Thus, it is concluded that the treatment of OTF is very useful for the quantitative diagnosing of radioisotope image as well as comprehension and improvement of radioisotope image transmission systems.
The whole-body retention of86Rb was investigated by mice of 7, 21 and 98 days old. The effect of age on the86Rb retention in mice was observed clearly. The authors found that the suckling mice of 7 days old had a very different and unusual retention pattern, and had a longer biological half-time of 11 days. However, the young mice of 21 days old had more rapid decreasing patterns than those of the adult mice, and the biological half-times of 21 and 98 day-old mice were 2.5 and 3.5 days, respectively. There were no significant differences in the retention values between oral and intraperitoneal administration, so that86Rb was absorbed almost completely from the gastrointestinal tract.