Kazutoyo Endo

Chemical characteristics of metal phases of the Richardton H5 chondrite

Abstract The magnetic fraction was separated from the Richardton H5 chondrite with a hand magnet and was leached with concentrated HF at high temperature for different periods. The resulting metallic fractions and the untreated magnetic fraction were analyzed using Mossbauer spectroscopy and instrumental neutron activation analysis (INAA). Leaching in concentrated HF for 1.5–5 min was effective in removing silicates from the magnetic fraction while leaving the metal grains intact. Leaching with increasing time selectively dissolved kamacite, with only little attack of the taenite grains. The Mossbauer spectroscopy shows that martensite (α-phase iron) is present in the Richardton metals and is dissolved in HF less easily than kamacite, but more easily than taenite. The distributions of trace siderophile elements among the different metal phases of Richardton were obtained based on the INAA data. Siderophile elements, except for Co, are enriched in the taenite fraction but with different concentration ratios between taenite and kamacite, suggesting that kamacite and taenite were not formed by either oxidation/reduction of Fe of the Fe Ni metal, or by condensation from the nebula, or by metal-solid differentiation. A more likely explanation is that kamacite and taenite have equilibrated by low-temperature diffusion. It seems that most trace siderophile elements were once dissolved in the Fe Ni metal and later distributed among the metal phases by diffusion. However, Ir, Os and Ru may still partly exist as tiny separate grains in the FeNi metal and their distributions among the metal phases are not completely equilibrated.

Determination of lanthanoids in Japanese standard rocks by radiochemical neutron activation method

Samples of two older geochemical reference rocks GSJ JG-1 (granodiorite) and JB-1 (basalt) and three new ones GSJ JA-1 (andesite), JR-1 (rhyolite) and JB-2 (basalt) were subjected to determination of lanthanoid elements by radiochemical neutron activation analysis. The contents of 9 lanthanoid elements could be re-determined for the older reference rocks and those of 11 elements were determined for the new rocks. The results were compared with the previously published data.

Positron annihilation in high molecular weight compounds

Positron lifetime measurement has been applied to high molecular weight compounds—epoxy resin, polyvinylidene fluoride, and polyethylene—which are commonly used in the field of electrical engineering. The effect of radicals produced in these samples by γ-ray irradiation on ortho-positronium formation is discussed. It has been shown that the composition of epoxy resin affects positronium formation. Some electric characteristics are compared with the results of positron annihilation.

Biochemical reactions of various trace elements with blood components and transport proteins

The multitracer technique was applied to the simultaneous evaluation of the behavior of a large number of radioactive nuclides. The binding affinity of various trace elements with blood components and the pH-dependence of binding affinity of the elements with serum proteins were examined using the multitracer technique. Each element showed characteristic binding to each blood component and serum protein. The results are discussed in terms of chelating ability of metal ions and the nature of the serum proteins.

Calibration of the isomer shift of125Te from internal conversion and mössbauer measurement

Radioactive125I was ion-implanted into 7 different metal matrices. Al, Au, In, Pt, Sn, Te and Zn, and internal conversion and Mössbauer spectra associated with the 35.46 keV M1 transition of125Te were measured for the same samples. A value ΔR/R=(0.853±0.115)×10−4 was derived for the relative difference of the nuclear charge radius for the 35.46 keV M1 transition of125Te.

Studies of γ-ray irradiation effects on tris(β-diketonato)iron(III) and cobalt(III) coordination compounds by means of mössbauer spectroscopy and magnetic susceptibility measurements

Both absorption Mossbauer spectroscopy and magnetic susceptibility measurements on tris( β -diketonato)iron(III) and cobalt(III) compounds indicate that ligands which have phenyl group as a substituent are more stable to γ -ray radiolysis, in accordance with previous results of emission Mossbauer spectroscopic studies of 57 Co-labelled tris( β -diketonato)cobalt(III) compounds.

Time dependence of distribution of radioactive trace elements in Se-deficient rats: Application of the multitracer technique

The uptake and the distribution of radioactive trace elements in Se-deficient rats were examined by the multitracer technique, which can be used to evaluate the behavior of many elements under the same experimental conditions. The uptake of Se was larger in the brain, spleen, and testicles of the Se-deficient rats than in those of the normal ones. The uptake of As, Fe, and Sc was larger in the liver of Se-deficient rats than in that of normal ones. In the bone, the uptake of Zr of Se-deficient rats was larger than that of normal ones. Selenium is known to be in a competitive or synergetic relationship with several metals. From the present results on Sc and Zr, it was newly cleared up that there is also some interaction between those elements and Se.

Positron annihilation and polymerization of epoxy

Abstract Positron lifetime measurement has been applied to the investigation of solidification from the liquid state to the solid state in epoxy with different mixing ratios of resin and hardener. It has been shown that the mixing ratios and the physical states of liquid, gel, and solid affect positronium formation. In samples with an excess of hardener, long-lived components were observed in the liquid and gel states, while they disappeared after solidification. Positronium formation in epoxy is strongly affected by the heating process of epoxy samples.

Preconcentration of trace elements for neutron activation analysis using activable tracers

Use of an enriched isotope as an activable tracer is proposed for the preconcentration of trace elements in neutron activation analysis. As a test of this method, contents of cadmium in various biological standard samples were determined by addition of an enriched116Cd tracer in the preconcentration step followed by neutron irradiation and γ-ray spectrometry. The principle, advantage, and limitations of the method are also discussed.

Emission Mössbauer spectroscopic studies on mixed-valence states of57Fe atoms produced in57Co-labeled trinuclear cobalt-iron carboxylates

Mixed-valence states of57Fe-atoms produced after EC-decay of57Co in oxo-centered trinuclear cobalt-iron carboxylates have been studied by means of emission Mössbauer spectroscopy. The emission Mössbauer spectra show nearly the same temperature dependence of the mixed-valence state as found in the absorption Mössbauer spectra of the corresponding trinuclear iron carboxylates. The results indicate that most of the decayed atoms keep their position at the sites of original57Co atoms.