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1-4 of 4
Takashi Maruyama
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Journal Articles
Journal:
Radiation Research
Radiation Research (1988) 113 (1): 1–14.
Published: 01 January 1988
Abstract
Reassessment of γ doses from the atomic bombs in Hiroshima and Nagasaki has been carried out with thermoluminescent measurements of ceramic materials, such as bricks and decorative tiles, which were collected from buildings that remain as they were at the time of the explosions. The thermoluminescent measurements were performed using thermoluminescent dating techniques generally used in archaeology. Annual background dose rates from natural radionuclides in the ceramic materials and from environmental radiation including cosmic rays were determined with commercially available thermoluminescent detectors. A time-zero point at the original firing of the ceramic materials was estimated from the age of the buildings given in "the register book." Total background dose was evaluated by multiplying the period between the time-zero point and the time of measurement by the annual dose rate. The resultant γ doses in Hiroshima and Nagasaki are given as a function of distance from ground zero and are compared with the DS86 (Dosimetry System 1986) and the T65D (Tentative 1965 Dose) γ doses.
Journal Articles
Journal:
Radiation Research
Radiation Research (1977) 70 (2): 345–354.
Published: 01 May 1977
Abstract
The weight loss of the testes, the behavior of the primary spermatogonia Ia and Ib, and the inhibition of DNA synthesis in the testes of the fish, Oryzias latipes, which had been kept at low temperature, irradiated with 2 MeV of fast neutrons (100, 200, 400, and 600 rad), and transferred to 25°C, were investigated and compared with the effects of 200 kVp of X rays. A considerable weight loss of the testes was demonstrated at 15 days after irradiation with neutrons. The 50% effective dose ( ED 50 ) for weight loss of testes was less than 100 rad after fast neutrons and about 500 rad after 200 kVp of X rays. Although the primary spermatogonia Ia were not significantly reduced in number after neutron irradiation, the primary spermatogonia Ib were markedly damaged. At 3 days after irradiation, the pyknoses of the primary spermatogonia Ib and surviving fraction of the cells depended on the exposure dose. Fast neutrons had ED 50 values of 330 rad at 3 days and 130 rad at 5 days after irradiation in the surviving fraction of the primary spermatogonia Ib and after X irradiation; ED 50 values were 810 and 490 rad at 3 and 5 days, respectively. In all dose groups, the lowest number of the cells was observed at 15 days. Thereafter the number of the spermatogonia Ib increased, returning to the control level and 55% of the control in the fish irradiated with 100 and 200 rad of neutrons at 30 days.
Journal Articles
Journal:
Radiation Research
Radiation Research (1974) 59 (2): 513–520.
Published: 01 August 1974
Abstract
The mortality response of goldfish to whole-body irradiation with 2 MeV fast neutrons from a Van de Graaff accelerator was studied and compared with the effects of 200 kVp X-rays. Although the dose ranges leading to equivalent injury were different with the two types of radiation, the dose vs survival time relationship, and the distribution pattern of time of death after irradiation with fast neutrons were similar to those observed after X-irradiation. Mean lethal dose was used to determine the relative biological effectiveness of neutrons. The <tex-math>${\rm LD}_{50(30)}$</tex-math> was 375 rad for neutrons and 1238 rad for X-rays, from which the RBE of neutrons was calculated to be 3.4. The histological changes in hematopoietic tissue (body kidney) and intenstine to 400 or 1000 rad of neutrons were examined. In fish irradiated with 400 or 1000 rad of neutrons, the marked reduction in the number of hematopoietic cells occurred 5-10 postirradiation days. Severe lesions in the intestine were observed only in 1000 rad-irradiated fish at 10 days after irradiation. These results were compared with previous X-irradiation results in fish.
Journal Articles
Journal:
Radiation Research
Radiation Research (1971) 45 (2): 288–298.
Published: 01 February 1971
Abstract
The effects of a single exposure to 2-MeV fast neutrons were compared with the effects of exposure to 60 Co γ-ray irradiation on dry eggs of Artemia. Comparison of the survival data showed that neutrons were 2.1, 2.8, and 4.8 times as effective as γ-irradiation in producing mortality of nauplii at 1, 2, and 3 days after hatching. Irradiation with fast neutrons produces severe chromosomal abnormalities and leads to a depression in mitotic activity. On the basis of the cytological observations, the relative biological effectiveness of fast neutrons was about 2 with reference to γ-rays.