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  • Author or Editor: S. Yokoyama x
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Abstract  

A rapid and precise method of determining radiocesium corresponding to 5 mrem/y, the Japan AEC's guideline, was proposed. The development and practical performance of cesium-selective resin and the determination method was described in this paper. The resin was prepared by the formation of ammonium molybdophosphate in the structure of Amberlite XAD-7 resin. It took only 3 hours to carry out all the procedures the authors proposed. This value represents 1/10∼1/2 of the time of conventional method. The concentration of137Cs and134Cs in sea water was determined to be 0.13∼0.16 pCi/1 and less than 7.1·10−2 pCi/1, respectively.

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Abstract  

Uranium concentrations in three types of inclusions of the Allende (C III), a bulk sample of the Plainview (H5), and a bulk and 5 to 15 density separates of the Huckitta pallasite were determined and discussed by comparing the results from homogenized fission track and/or239Np analyses with the133Xe results. Stepwise heating experiment revealed that the133Xe release from the Plainview is bimordal and incomplete by a simple heating at 1600 °C, and that the133Xe releases in the Huckitta bulk and metallic samples are multitudinous but can be extracted rather completely at 1600–1700 °C. In the Huckitta, uranium-rich phase (∼100 ppb) was in the lightest density fraction of d=2.9–3.3, but the bulk uranium was found to be mostly from the heavy metal-rich fraction of d>4.2.

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In Bombyx mori, pheromone-producing cells accumulate a number of lipid droplets in the cytoplasm preceding the production of the sex pheromone, bombykol. The process of lipid droplet formation in the pheromone-producing cells was investigated by using light and electron microscopy. Light microscopy revealed that the lipid droplets appeared from 2 days before adult eclosion and dramatic accumulation took place between 2 days and 1 day before eclosion. Electron microscopical studies revealed that smooth endoplasmic reticulum and numerous vesicles, their sizes being less than 1 µm, were detectable 2 days before eclosion, and some vesicles were fused with mitochondria at this stage. These characteristic changes in the pheromone-producing cells suggest that fatty acyl-CoA synthesis following de novo fatty acid synthesis takes place at this time. Involutions in the basal plasma membrane of the cells occurred throughout the observed period, which were extensive on the day before adult eclosion. Besides extensive basal involutions, immature lipid droplets appeared and then mature fully electron-dense lipid droplets were observed on the day of adult eclosion. These ultrastructural observations, combined with recent physiological studies suggest, that the basal involutions presumably reflect the uptake of lipidic components required for the construction of lipid droplets, the function of which is to store the bombykol precursor and to provide it for bombykol biosynthesis in response to pheromonotropic stimuli by pheromone biosynthesis activating neuropeptide (PBAN).

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Abstract  

We have focused on the poly(ethylene glycol) (PEG)-borate ester as a new type plasticizer for solid polymer electrolyte for lithium ion secondary battery. Adding the PEG-borate ester into the electrolyte shows the increase in the ionic conductivity of the polymer electrolyte. By measuring the glass-transition temperature of the polymer electrolytes with DSC, it is found that the increase in ionic conductivity of the polymer electrolyte is due to the increase in ionic mobility. By investigating the temperature dependence of the ionic conductivity of the polymer electrolytes using William-Landel-Ferry type equation, we considered that the PEG-borate ester does not have any influence for dissociation of Li-salt.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: A. Yokoyama, S. Morimoto, T. Inoue, J. Sanada, H. Araki, T. Saito, H. Baba, S. Shibata, A. Shinohara, T. Muroyama, and Y. Ohkubo

Abstract  

Target-like products, that is,191–200Au,185–200Pt, and183–195Ir, from197Au target bombarded with12C ions at the energies of 180, 230, and 400 MeV/u were measured by using off-line gamma-ray spectrometry combined with chemical separation procedures. Spallation systematics by Rudstam reproduces well the measured cross sections for formation of platinum and iridium isotopes. It was found that the cross sections of gold nuclides increase with increase of the incident energy in the range studied and they are enhanced if compared with the reported proton-induced reaction of gold at a similar incident energy. It is suggested that the electromagnetic dissociation process plays a role for production of such gold nuclides.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: T. Muroyama, A. Shinohara, T. Saito, A. Yokoyama, K. Takamiya, S. Morimoto, K. Nakanishi, H. Baba, T. Miura, Y. Hamajima, T. Kaneko, H. Muramatsu, S. Kojima, and M. Furukawa

Abstract  

Annihilation γ-rays of π0 and pionic X-rays were measured in the gas mixtures of H2+Z and CH4+Z systems (Z=He, Ne, Ar and Kr). Pion capture probability of hydrogen atom was obtained from the annihilation γ-ray counts and the capture probability of Z atom was obtained from the pionic X-ray intensities. Transfer rates were determined from the data based on a combined large mesomolecular model. The transfer rates obtained were smaller than the systematics of the Russian group. Difference in the transfer rate between the gas and the liquid phases was found by a comparison of the present results with our previous ones.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: N. Momoshima, H. Kakiuchi, T. Okai, S. Yokoyama, H. Noguchi, M. Atarashi, H. Amano, S. Hisamatsu, M. Ichimasa, Y. Ichimasa, and Y. Maeda

Abstract  

Potted plants were exposed to D2O vapor in a greenhouse and uptake of D2O by leaf and deposition of D2O to pot soil were examined. Atmospheric D2O concentration in the greenhouse increased rapidly after starting the release and reached constant level in a few hours. Although the variation of D2O concentration in leaf followed that in air with showing a time delay, D2O concentration in leaf did not become the same level as that in air and vein showed lower concentration that lamina. D2O concentration in the pot soil increased slowly with diffusing in deeper layer.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: A. Shinohara, T. Muroyama, T. Miura, A. Yokoyama, K. Takamiya, T. Kaneko, T. Saito, J. Sanada, H. Araki, S. Kojima, Y. Hamajima, H. Muramatsu, H. Baba, and M. Furukawa

Abstract  

Pionic X-rays and π0 decays were measured for gas mixtures of H2/D2/CH4+SF6/Ar and the individual pure gases. Chemical effects on the pion transfer process from pionic hydrogen to other atoms were revealed by the pionic X-ray spectrum. The changes of the intensity patterns of pionic X-rays were compared with the predictions by a cascade calculation taking the transfer process into account. The mechanism of pion transfer process was discussed based on the results for gas phase and the previous ones for liquid phase.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: R. Suzuki, T. Ohdaira, K. Yamada, T. Yamazaki, N. Sei, T. Mikado, T. Noguchi, H. Ohgaki, S. Sugiyama, M. Chiwaki, T. Shimizu, M. Kawai, M. Yokoyama, S. Hamada, K. Saeki, N. Nishimura, and T. Tomimasu

Abstract  

A positron lifetime study has been done on dielectric multilayer cavity mirrors for free-electron-laser experiments by the use of a variable-energy pulsed positron beam. A long-lived ortho-positronium component has been observed at low positron energy region, corresponding to the depth of the top amorphous SiO2 layer. The intensity of the positronium component correlates with the degradation and restoration of the mirrors. We discuss the relation between the positronium intensity and degradation mechanism of the mirrors. The present studies revealed that the slow positron lifetime technique is highly sensitive to the properties of the mirrors and is useful for the evaluation of the mirrors.

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