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  • Author or Editor: Y. Yamamoto x
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Abstract  

Mixed-valence μ-phenolate-bis(μ-carboxylate) diiron(II, III) complex [Fe2(bpmp)(ppa)2](BF4)2 (1) is prepared. The temperature dependence of the Mössbauer spectra of the complex 1 is measured. The Mössbauer parameters of the complex 1 show the unusual increase of isomer shift and quadrupole splitting with an increase in temperature. The spectra are explained by the dynamic electronic states in which the valence states of two iron atoms in a molecule are 2.2 and 2.8 on the Mössbauer time scale at 293 K. The single crystal X-ray structure of the complex 1 is determined at 133 K. The complex 1 crystallizes in the triclinic space group
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1. Two iron atoms in the complex 1 are crystallographycally inequivalent.
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Abstract  

An analytical method was developed for the measurement of low-level 54Mn in soil sample by ultra low-background g-ray spectrometry after radiochemical separation. The method consists of decomposition of sample by a mixture of HNO3 and HF, dissolution by HNO3, precipitation as hydroxide, solvent extraction with diisopropyl ether and anion exchange. Finally, for purification of Mn it was precipitated as MnO2 by adding KClO3. 54Mn in the precipitate was measured by ultra low-background well-type Ge detector at Ogoya Underground Laboratory. Measurements of 54Mn using 30-200 g of soil samples from the JCO grounds were successfully performed by the present method. The minimum detectable activity of 54Mn was about 0.01 dpm (0.2 mBq) for a 7-day counting period.

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Abstract  

The interactions of benzalkonium chloride (BC)with components of stratum corneum, a model system of intercellular lipids in human stratum corneum and homogenized rat stratum corneum were characterized in terms of thermodynamics at pH 7.5 and 37C. BC was strongly bound to cholesterol and cholesterol sulfate with higher affinities (105~106 M-1) than to any other components of the stratum corneum by hydrophobic interaction and ionic interaction, respectively. BC binding to the model system of intercellular lipids significantly decreased only in the absence of cholesterol. It is indicated that cholesterol and its derivatives play an important role in the penetration and/or accumulation of BC in stratum corneum.

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Abstract  

Two different types (structures) of inclusion complexes with a 1:1 stoichiometry between barbiturates and 2-hydroxypropyl-β-cyclodextrin (HPCyD) were realized in aqueous solution using isothermal titration calorimetry and molecular dynamics simulation. The first type of complex with a higher association constant was entropy driven and the substituent R 2 was inserted into the HPCyD cavity by hydrophobic interaction. The barbituric acid ring contributed to the second type of complex, which was characterized by large negative values of ΔH and small positive ΔS reflecting van der Waals interaction and/or hydrogen bonding formation between the hetero atoms in the barbituric acid ring and the secondary hydroxyl groups of HPCyD.

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Abstract  

Atmospheric concentration and total (wet plus dry) and dry deposition of210Pb and7Be have been measured at our laboratory in Ishikawa Prefecture in Japan which faced the Sea of Japan during 1993–1994. At the same time inventories of excess210Pb in soil samples were measured from a mixed pine forest. On the basis of the data obtained, an attempt was made to evaluate the dry deposition velocity as a result of the interception by the canopies of airborne210Pb in a pine stand The dry deposition velocity of210Pb in the pine stand was roughly estimated to be 0.9–0.8 cm/s, higher by a factor of about 10 than the value (mean: 0.12±0.09 cm/s; range: 0.06–0.28 cm/s) in the open area measured on the roof of our laboratory.

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Abstract  

This paper decribes syntheses for the11C-labelled chemotherapeutic drug, CCNU,11C-labelled BFNU and CFNU (analogs of BCNU) as well as an improved synthesis for11C-BCNU. Also discussed are procedures for the separation of dual isomers in the case of11C-labelled CCNU and CFNU. The specific activity of these no-carrier-added radiopharmaceuticals was approximately 104 lower than expected for a carrier-free product. The syntheses were normally finished 20–25 min after the end of the collection of11C-COCl2. Chemical and radiochemical purity of the final product, as determined by HPLC and TLRC respectively, was at least 98%. The syntheses yielded 10–25 mCi of nitrosourea ready for use in PET studies.

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Abstract  

Since 1962, we have been investigating the levels of239,240Pu in human tissues. In the 1960s, the quantities of239,240Pu found in the gonad and spleen were higher than those in liver and lung, as reported in our previous papers. This work was done to provide a reassessment of239,240Pu distribution among several tissue samples from the 1960s and early 1970s, using current analytical techniques for plutonium. The autopsy tissues were collected from the Hospital of Niigata Prefectural Institute for Cancer Research in Northern Japan from 1968 to 1975. The subjects were at least 50 years old at the time of death. The accuracy and precision of239,240Pu determinations were examined using NBS-SRM 4352 human liver samples. Our results are consistent with certified values.

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Summary  

A rapid method was developed using ultrafilters with a tangential flow filtering system for molecular size separation of naturally occurring 210Pb and 210Po in a freshwater sample. Generally, ultrafiltering of a large volume water sample for measuring the nuclides was too time consuming and not practical. The tangential flow filtering system made the filtering time short enough to adapt for in-situ ultrafiltering the large volume sample. In this method, a 20 liter water sample was at first passed through the 0.45mm pore size membrane filter immediately after sample collection to obtain suspended particle matter [>0.45mm particulate fraction (PRT)]. Two ultrafilters (Millipore Pellicon 2Ò) were used sequentially. The nuclides in the filtrate were separated into three fractions: high molecular mass (100 kDa-0.45mm; HMM), low molecular mass (10 k-100 kDa; LMM) and ionic (<10 kDa; INC) fractions. It took 80 minutes to process the sample after collection. The cut-off molecular size of each ultrafilter was confirmed by size exclusion chromatographs (SEC) of the LMN and the HMM fractions. Adsorption of the nuclides and organic compounds in the sample onto the ultrafilters was negligibly small. Good reproducibility of the nuclide concentrations in each fraction was confirmed by repeated experiments. The method was successfully applied to obtaine the molecular size distributions of 210Pb and 210Po in an oligotrophic lake, Lake Towada located in the northern area of Japan.

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Abstract  

A delayed coincidence method has been developed for the selective extraction of radionuclides with half-lives of millisecond order using a personal computer. The time interval analysis is fundamentally based on the distinction of the time interval distribution between the correlated and random events, which arise from radioactive disintegration and/or background events within a certain fixed time. Theoretical functions of a time spectrum or a time distribution curve were dealt with from aspects of statistical treatments consisting of a single time interval analysis and a multiple one (STA and MTA). The theoretical equations obtained were used to simulate time spectra on the assumption of some ideal data and compared with the experimental results. Conclusively, the MTA method has been verified to be more suitable for the selective extraction of the objective correlated events from random or background events for the search of radioactive nuclides with millisecond life-times.

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Abstract  

The free-volume, of size ranging from 0.2 to 0.4 nm in radius, in an ethylene-vinyl alcohol copolymer was estimated using positronium lifetime measurement to elucidate the dependence of oxygen permeability on the free-volume size and fraction, on the ethylene content and on the crystallinity. The permeability and the free-volume fraction with varying the ethylene content were well related and the relation was interpreted based on the free-volume theory near below and above the glass transition temperature. On the other hand, the crystallinity significantly influenced the fraction of the amorphous region, where the free-volume hole exists, along with a slight change of the free-volume size. The variation of the permeability with the crystalline degree cannot be explained from the averaged free-volume fraction estimated by the whole volume of the polymer, but the permeability correlated with the free-volume size apparently.

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