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  • Author or Editor: K. Endo x
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Abstract  

Time resolved Mössbauer spectra were measured for57Co-labelled Co/IO3/2 using a delayed coincidence technique. A life-time for unstable57Fe(II)-species formed through EC-decay was estimated to be 43±5 ns at room temperature and the initial distribution of57Fe(II)/57Fe(III) at 14.4 keV nuclear level to be 0.47±0.13. The results are discussed in terms of electron transfer from the decayed57Fe(II) atoms to iodate ions.

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Abstract  

Polyoxyethylene nonyl phenyl ether with 2 oxyethylene units (PONPE-2) is immiscible with water and is suspended on the surface of aqueous layer as a droplet. Its unique property is applied to the solvent extraction of uranium(VI) with 5-Br-PADAP. Uranium(VI) chelates are quantitatively enriched into a small volume of PONPE-2 and the absorbance was measured in the mixed ethanol solution. The apparent molar absorptivity of uranium(VI)-5-Br-PADAP complex at 578 nm is 6.46×104 l mol–1 cm–1 and the calibration curve is linear over the range of 0.7–7 g of uranium(VI) per 1.5 ml of the final solution.

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Abstract  

The dynamics of redox related elements (Fe, Co, Zn, and Se) were studied using instrumental neutron activation analysis as a function of rat age in the range of 4 to 16 weeks. Activity levels of glutathione peroxidase (GSH-Px), thiobarbituric acid reactive substance (TBARS) were assayed, and hydrogen peroxide (H2O2) concentrations were measured for the same liver homogenates using an X-band ESR spectrometer. The oxidative stress, the aging effect, and the mineral valance are discussed.

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Abstract  

Time series of the distribution of bio-trace elements in the upper abdomen of living rats were examined using the in vivo multitracer analysis technique. The in vivo dynamics of the elements were estimated by comparison with the distribution of 74As. Vanadium, Mn, Fe, Co, Zn, Se, and Rb were distributed in tissues of the upper abdomen, i.e., mainly in the liver. Be, Sr, and Y might be in the blood or bone at a low level and in the excretion stage already. Dynamics of bio-trace elements were noninvasively obtained in a living rat within one hour after administration.

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Abstract  

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.

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Abstract  

The crystal structures of oxo-centered trineclear cobalt-iron chloroacetate complex [CoIIFe 2 III O(CH2ClCO2)6(H2O)3]·3H2O (1) was compared with that of previously reported trinuclear iron complex [FeIIFe 2 III O(CH2ClCO2)6(H2O)3]·3H2O (2) which has an isomorphous structure to 1. Compound 1 crystallizes in space group P21/n with Z=4 in a unit cell of a=14.826 (4) Å, b=4.536 (8) Å, c=14.000 (4) Å, =100.32 (2)0 and V=2968 (11) Å3. The structure was refined to R=0.75 and Rw=0.82. The coordination geometries of the three iron atoms are observed equivalent in 1 indicating a static disorder of the position among cobalt and iron atoms. Two distinct FeIII doublets observed in Mössbauer spectra of 1 become an indistinguishable broad doublet by dehydration of crystal water. On the other hand, no significant line-broadening is observed after the dehydration in complex 2. The results indicate that the dehydration in 2 induces a local environmental change reordering of an electronic configuration around iron atoms, whereas the remaining disordering is reflected in Mössbauer spectrum after the dehydration in 1.

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Abstract  

Coincidence Mössbauer spectra of57Co-labelled [CoFe2O(CH3CO2)6(H2O)3] were determined at 78 K and 298 K with three timewindows of 0–50, 50–150 and 150–300 ns. Temperature dependence in the spectral shape ascribed to an intramolecular electron transfer was observed in all the time-window spectra, while little time dependence was observed. The results indicate that57Fe atoms produced by EC-decay are incorporated in a chemical environment similar to that of the parent57Co atoms, forming a trinuclear FeIIFe2 III structure at an early stage after the EC-decay.

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Abstract  

Use of an enriched156Dy isotope as an activable yield tracer for the determination of lanthanoid contents in various biological reference materials has been proposed. The method consists of preconcentration of the lanthanoid in the156Dy doped samples followed by neutron irradiation and further chemical purification steps. The chemical behaviour of lanthanoid elements in the whole procedure was found, in separate runs, similar to that of the added156Dy within experimental errors. Simple purification steps after irradiation allow the measurement of relatively short-lived nuclides and diminish the radiation dose received during the chemical treatment. The present results for orchard leaves (NBS SRM 1571) are generally in good agreement with the previously reported data. Some new data are obtained for other biological reference materials.

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Abstract  

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.

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Abstract  

The irradiation of atmospheric air with high-energy protons has been performed at the 12 GeV proton synchrotron. The specific activity of 13N, one of the principal airborne radioactivities, was measured as a function of the irradiation time at a dose rate of about 6·1016 eV/g/s, and compared with the calculated values. The predominant chemical species of 13N produced were found to be 13N2and 13NO2. Their proportions were approximately 55% for 13N2 and 45% for13NO2, being almost independent of the irradiation time. Smaller quantities of 13NO and H13NO2 were also observed. Measurements of radiolytic products showed that ozone is a main product and that NO2predominates among the products of nitrogen compounds, including HNO2 and HNO3. The G-value for ozone formation in air was estimated from the experimental data as 6.4 molecules/100 eV.

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