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Long-Lived Radioiodine in Japanese Environment
Authors: R. Seki, M. Watanabe and K. Kurihara

Abstract  

The amount of long-lived radioiodine, 129I (half-life 1.57·107 y) in the Japanese environment has been studied by measuring thyroids of humans and animals. The collected samples were thyroids of (1) humans in Ibaraki Prefecture, in Kanto district, the central part of Japan, (2) cattle in Aomori Prefecture, north part of Japan, and (3) wild deer in Chiba Prefecture, in Kanto district. The measured mean isotopic ratio 129I/127I for thyroids of cattle in Aomori Prefecture is 3.5±1.8·10-9. A higher value of 14±5·10-9 has been obtained for thyroids of wild deer in Kanto district. On the other hand, the measured ratio for human thyroids in Kanto district is 1±0.2·10-9. This value is significantly lower than that of cattle thyroids in Aomori and also those reported for human thyroids in Europe and USA. The higher mean ratio for cattle thyroid in Kanto district is possibly explained by the influence of nuclear reprocessing plant. Lower mean ratio for human thyroid might be due to higher dietary intake of algae.

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Isotope effect in retention value between55Cr and51Cr in recoll chemistry of Cr/acac/3
Authors: T. Matsuura, H. Kurihara, T. Nagahara and K. Sasaki

Abstract  

Recoiling behaviour of55Cr produced by54Cr/n, /55Cr reaction was studied by choosing solid Cr/acac/3 or its benzene solution as target material and by using rapid separation technique. The approximate retention value /R-value/ of55Cr, defined as the percentage of the activity retained in the benzene phase which was not extracted with an oxalic acid solution, was found to be higher than that of55Cr for practically all experimental runs tested /15 runs/. The ratio (55Cr/51Cr) was 1.115±0.027.

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With continuing proliferation of human influences on landscapes, there is mounting incentive to undertake quantification of relationships between spatial patterns of human populations and vegetation. In considering such quantification, it is apparent that investigations must be conducted at different scales and in a comparative manner across regions. At the broader scales it becomes necessary to utilize remote sensing of vegetation for comparative studies against map referenced census data. This paper explores such an approach for the urbanized area in the Tokyo vicinity. Vegetation is represented by the normalized difference vegetation index (NDVI) as determined from data acquired by the thematic mapper (TM) sensor of the Landsat satellite. Sparseness of vegetation is analyzed in relation to density of human residence, first by regression analysis involving stratified distance zones and then by the recent echelon approach for characterization of surfaces. Echelons reveal structural organization of surfaces in an objective and explicit manner. The virtual surface determined by census data collected on a grid is shown to have structural correspondence with the surface representing vegetation greenness as reflected in magnitude of NDVI values computed from red and infrared bands of image data.

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