Inspection of a chart of nuclides reveals a “sand bar”of actinoid and neighboring elements when a suitable half-life level is chosen. A bay of α-instability lying between the nuclides of neutron magic number 126 and the β-stability line in the actinoid group is a characteristic feature in this area. Calculation shows that fairly good agreement is obtained between the measured half-lives and those derived theoretically.
Since lead contains more or less210Pb, the selection for lead materials has to be done before construction of the low level radiation shield. In this paper, a method for determination of210Pb is based on radioanalytical separation such as DDTC (sodium diethyl dithio carbamate) extraction followed by β ray counting of210Bi. Fourteen commercial lead samples and three old lead samples were analysed for210Pb. The concentration for210Pb in commercial samples was found to range from 0.063 to 11 Bq/g (1.7 to 300 pCi/g) and in old samples was less than 0.01 Bq/g (0.3 pCi/g) . These results will be useful to the selection of shielding material. The detection limit and the time required for210Pb determination was 0.003 Bq/g (0.1 pCi/g) and 5.5 hours, respectively.
The acute radiation effects on the tongue and lip mucosa epithelium were cytokinetically investigated after the local irradiation at the head part of C3Hf/He mice with single dose of 516 mC/kg (2000R) of X rays. The microautoradiographic study was performed for these two kinds of oral epithelium at various times after the pulse-labeling with3H-thymidine, which followed immediately after the irradiation. The cell kinetics of irradiated as well as unirradiated basal cells were investigated by observing the changes in frequencies of the labeled cells and the labeled mitoses in the epithelium along the time course after irradiation. The results of the analysis of the percent frequencies of mitotic cells as a function of time after the labeling and the irradiation showed that the movement of the labeled cells were blocked at G2phase for about 6 hr and that the cell cycle time after the 1st post irradiation mitoses became shorter than that of the unirradiated cells. However, no change was found in the migration rate of the tongue epithelium, i.e., the time required for labeled cells to migrate from basal cell layer to prickle-granular cell layer. On the other hand, only 25% of labeled cells in the lip mucosa epithelium migrated into prickle-granular cell layer until 40 hr after irradiation, and it was hardly observed that the labeled cells moved into mitotic phase. These results suggest that basal cell of the lip mucosa is more radiosensitive than that of the tongue epithelium.
Most of the gastric diseases seat in the mucosa, and the present investigation was undertaken in order to see if amogastrin, a synthetic tetrapeptide, was capable of enhancing gastric accretion of intravenous99mTc Pertechnetate in man as well as in the rabbit. Improvement of gastric scintigraphy was achievable with a pretreatment of the agent by increasing the gastric accretion and reducing the background radioactivity in the liver and small intestinum.