[en] The leukemogenic effect of internal irradiation with radiostrontium (⁹⁰Sr) was compared with that of external irradiation with x rays in ICR/JCL mice. Immunological, hematological, and cytogenetical changes were also studied during the preleukemic period in mice treated with ⁹⁰Sr or with x rays. A single intraperitoneal injection of 1.0 μCi of ⁹⁰Sr per gram of body weight resulted in leukemia in 62 percent of the mice. Only one of the ⁹⁰Sr-induced leukemias was of thymic origin. The occurrence of the leukemia was not affected by thymectomy. A fractionated whole-body x-irradiation of 680 R induced leukemia in 77 percent of the mice; the majority of the leukemias were of thymic origin. Although x-irradiation over the thymic region was ineffective in eliciting leukemia, a combined treatment of ⁹⁰Sr and local x-irradiation of the thymus was effective in inducing thymic lymphomas. The single intraperitoneal administration of ⁹⁰Sr caused an enhancement of both direct and indirect splenic plaque-forming cell (PFC) responses to sheep red blood cells, lasting for 35 days after treatment. No changes were observed in delayed-type hypersensitivity to picryl chloride. Thymectomy caused no appreciable effect in these immune responses. The fractionated whole-body x-irradiation rapidly depressed both PFC and delayed-type hypersensitivity responses, which persisted for a long period, especially in thymectomized mice. An abrupt increase of chromosomally aberrant cells in the thymus 60 days after the last x-irradiation was preceded by an increase of aberrant population in the bone marrow. On the other hand, a long-lasting appearance of aberrant population in the bone marrow and lymph nodes was observed in ⁹⁰Sr-injected mice

[en] The unequilibrated hypersthene chondrite Yamato-74191 was studied mass spectrometrically for rare gases released at various temperatures. Cosmogenic gases dominate in He and Ne. The meteorite contains large amounts of trapped Ar, Kr and Xe, and radiogenic ⁴⁰Ar and ¹²⁹Xe. Cosmic-ray irradiation and K-Ar ages were determined. In addition to spallogenic components of Kr and Xe, isotopic excesses of ⁸sup(O)Kr, ⁸²Kr, ¹²⁸Xe and ¹²⁶Xe relative to AVCC-Kr and -Xe were found. The ratio of ⁸⁰Kr-excess to ⁸²Kr-excess is 2.66 after correction for spallogenic Kr. A correlation between ¹²⁸Xe/¹³²Xe and ¹²⁹Xe/¹³²Xe was found. The ¹²⁹Xe/¹³²Xe ratio for trapped Xe in Yamato-74191 was determined as 1.12 +- 0.29 with the correlation plot. The excesses found in Yamato-74191 are best explained by epithermal neutron capture on Br and I, and by the ¹²⁷I(n,2nβ) ¹²⁶Xe reaction. Using neutron-produced ⁸⁰Kr, the neutron slowing-down density was estimated to be 0.14 +- 0.03 cm^-3 sec^-1. A minimum mass and a preatmospheric radius was estimated to be 470 kg and 32 cm, respectively. (orig.)

No abstract available

[en] The origins of baryons and dark matter have been considered to be unrelated. We discuss the probability that both of the baryon number and dark matter arise from the same origin in the supersymmetric anomalous U(1) grand unified theory. We derive some conditions to make this scenario successful, and show they can be satisfied with appropriate model parameters.

[en] Results on temperature, moisture migration, strain variation during the heating of simulated mass concrete mock-up specimens, strength and elastic modulus after heating are summarized, so as to correctly estimate the characteristics of concrete structures subjected to a high temperature. (orig./HP)

[en] Experiments on electron cyclotron wave excitation are carried out. Mode conversion of a left-hand polarized wave into an electron cyclotron wave is examined in detail. When small inhomogeneity exists in the magnetic field, the trapped electrons chaotically accelerated to a few tens of KeV range. The experimental results on the onset of chaos are presented. (author) 5 refs., 5 figs

[en] Noble gas isotopic compositions and concentrations were measured for two monomict eucrites Yamato-791186 and -792510 and for three polymict eucrites Yamato-791960, -791962 and -792769. Terrestrial ages calculated on the concentrations of cosmogenic radionuclide ⁸¹Kr are in the range of 0.23-0.35 Ma, which are older than those reported for Yamato meteorites including eucrites. The noble gas result suggests that the monomict eucrites, Y-791186 and Y-792510, and the polymict eucrites, Y-791960 and Y-791962, are paired. If shielding effect on the cosmogenic ⁷⁸Kr/⁸³Kr ratio was considered, the preatmospheric radius of Y-791186 and Y-792510 was estimated to be small (about 10 cm in diameter). It was also calculated that Y-791960 was near the surface and Y-791962 was at the center of a preatmospheric body of about 1m in diameter. At least five pairs are identified for eucrites in the Yamato ice field referred to the published data. (author)

[en] Isotopic and elemental compositions of rare gases were determined for gas samples enriched in CO₂ collected in The Nigorikawa geothermal area, Hokkaido, Japan. A high isotopic ratio of ³He/⁴He=(9.95+-0.25)x10⁶ was obtained for a sample collected from bubbles naturally seeping out. This sample has a rare gas elemental abundance pattern attributable to low-temperature solubility of atmospheric rare gases into water. Soil gas samples yield evidence for mass fractionation of atmospheric rare gases, in addition to the originally high ³He/⁴He ratio. The higher ²⁰Ne/²²Ne ratio found, 10.33+-0.10, was accompanied by the highest ³⁶Ar/³⁸Ar ratio, 5.60+-0.08, and a systematic enrichment of the light isotopes of Kr and Xe. The enrichment of the light isotopes in each gas in the soil gas samples were also accompanied by a systematic elemental enrichment of the light gases. Migration of rare gas in the crust is responsible for this isotopic and elemental fractionation. Primordial He from the mantle is extensively present in CO₂-rich gases in this area. (Auth.)

[en] Isotopic and elemental compositions of rare gases in various types of gas samples collected in the Japanese Islands were investigated. Excess ³He was found in most samples. Many samples showed a regionally uniform high ³He/⁴He ratio of about 7 times the atmospheric ratio. (orig./ME)

[en] Physical property tests of concrete subjected to high temperature were performed to obtain basic data to be reflected in design of nuclear reactor buildings for 'Monju'. Based on the result of tests on mechanical properties, thermal deformation properties, and thermal constants of concrete in a temperature range of 20 to 175degC, studies were made of the influences of various factors on the physical properties of concrete subjected to high temperature. (author)