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  • Author or Editor: Y. Sakamoto x
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Abstract  

Thirty samples from a limestone stratum across the Pemian-Triassic (P-Tr) boundary layer in China were analyzed for 30 elements by instrumental neutron activation analysis, wavelength dispersive X-ray fluorescence and ICP-MS, and also for mineral compositions with a powder X-ray diffractometer. The depth profile was found to indicate a sudden change of elemental and mineral compositions across the P-Tr boundary. Also the profile showed severa peaks in elemental concentrations in the lower Permian layered samples as well as in the overlying Triassic strata, which are associated with the change of mineral compositions. Elemental profiles were found to be classified into 4 groups and to give some insights in the geochemical records. Ir is far less abundant (0.1 ppt) compared with that of the K-T boundaries (10 ppb), and the Ir/Co ratio is outside the K-T and Cl chondrite trends. This change of elementary profile is suggestive of the internal causes rather than the external ones such as an asteroid impact for the mass extinction at the P-Tr boundary.

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Abstract  

Reversed-phase extraction chromatography employing a Daiflon-supported HDEHP column and HCl as eluent was examined for carrier-free separation of167Tm from a photo-irradiated Yb target and also from particle-bombarded Er and Ho targets. The examination was performed with radioassays of radioactive Tm and Yb tracers and57Co--induced X-ray analysis of Er and Ho. An example of the separation of about 1 mCi of167Tm from a 100 mg irradiated Yb target enriched in168Yb and a procedure for the final preparation for medical use are described. The YbSO4 precipitation could be combined with this chromatographic separation of167Tm from a more massive Yb target of natural abundance, weighing several tens of grams. A procedure for YbSO4 precipitation is also presented in the Appendix.

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Abstract  

The synthesis of [γ-32P]ATP with high specific radioactivity was investigated by the enzymatic method. We utilized a part of the glycolytic pathway which consists of three reaction steps. First, we examined the maximum radioactivity of H3 32PO4 without the decrease of labeling yield. Next, we examined the minimum amount of reagent without the decrease of labeling yield, because some reagents contain the phosphorus species as impurity. In this paper, we propose the optimum condition for synthesis of [γ-32P]ATP with high specific radioactivity. As our calculation, we will be able to obtain about 220 TBq/mmol specific radioactivity using 1.5 GBq of H3 32PO4.

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Abstract  

Terrestrial zircon and apatite, as examples of uranium rich refractory minerals, and chromite, also highly refractory but uranium poor, were neutron-irradiated for their133Xe release studies. Uranium determination by133Xe was found not to be successful in these refractory samples, due to incomplete fissiogenic-xenon release at 1600°C as revealed by stepwise heating experiment. The high temperature release peaks appeared at ≾1500°C in these terrestrial minerals studied, but at 1000∼1200°C in reported meteoritic whitlockite and chromite.

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Abstract  

Samples of an andesite (Asama-yama, Japan) and a basalt (Kilauea, Hawaii) were finely fractioned by density and the U distributions among the separates were determined by homogenized fission track method. Groundmass was found to be enriched with U; one half of the andesite U and almost all of the basalt U are accounted for by the groundmass U. Cerium and other REE are correlated with U. In the andesite separates Na is accompanied by these elements, but Fe and Co are rather anticorrelated. Uranium concentrations in the bulk samples and some of the separates were then compared with those determined by133Xe extracted by heating at 1600°C. Fissiogenic133Xe seems to become labile in groundmass, especially of the andesite, during reactor irradiations for 5 h or more. Stepwise heating experiments suggested that133Xe in U-rich groundmass tends to escape at low temperatures and the remaining133Xe is mostly retained in highly refractory sites in phenocryst rather poor in U.

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Abstract  

Thomsonite with ideal chemical composition and with an ordered framework structure was synthesised hydrothermally from zeolite Na−A, which was ground to X-ray amorphous, with 0.05 mol dm−3 CaCl2 solution at 200°C. The dehydration behaviour of the prepared thomsonite was examined by TG-DTA. It was revealed that thomsonite lost most of zeolitic water below 450°C in three steps at about 180°, 340° and 390°C. The peak profiles of, the two higher-temperature endotherms were sharp and similar, and the weight loss at each step was approximately equal.

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Abstract  

The association properties of Pu with aquatic humic substances in a 0.01M NaClO4 solution at pH 6–8 were studied on the basis of molecular size distribution. Seven humic substances were isolated from river water and groundwaters using XAD extraction technique. They were used for comparing their effects on the association of Pu. In the presence of humic acid, the dominant molecular size of Pu was 100–30 kDa. In the presence of fulvic acid, Pu exhibited three dominant molecular sizes: 30–10 kDa, 30–5 kDa, and less than 5 kDa. The association of Pu-humus complexes might be controlled by the molecular size distribution of humic substances and characteristics of their respective size fractions.

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Abstract  

INAA, RNAA and IPAA were employed to determine upto 26 trace elements in 32 spices of 18 species and 16 pulses of 8 species originating from different localities. The results are compared with each other and the reported values. The concentration levels, their variations and the correlations of the analysed elements in these samples were also investigated. The variability of concentrations among the samples of different origin are small. The levels and ranges of the concentration are highly variable which are found to be characteristic to each element. High elemental correlations exist in some sets of elements, reflecting characteristics of chemical nature of elements and/or of their physiological functions.

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Abstract  

Fifteen GSJ (Geological Survey of Japan) and six KIER (Korean Institute of Energy and Resources; now Korean Institute of Geology, Mining and Materials, KIGAM) igneous rock series and nine GSJ sedimentary rock series reference samples were analysed for 21–29 elements by neutron and/or photon activation analysis (NAA and PAA); 14 MeV-NAA for Si and Al, fission track method for U, radiochemical and instrumental NAA for rare earth elements, with reactor neutrons for the latter two. Instrumental neutron and photon AA for the remaining elements were performed with reactor neutrons and bremsstrahlung of end-point energy of 30 MeV, respectively. The reactor irradiations were performed at core sites and also a thermal column of the Kyoto University Research Reactor. All of the radioassays were performed by -ray spectrometry with HPGe-detectors. The present results from the different types of irradiation are compared and discussed in terms of elemental abundances and rock types.

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