Search Results

You are looking at 1 - 10 of 14 items for

  • Author or Editor: T. Hayashi x
  • All content x
Clear All Modify Search

Abstract  

Several dead time correction methods were compared experimentally with the exact correction method and their limits were discussed. These correction methods were applied to neutron activation analysis of a biological sample. A special electronic circuit and an additional counting equipment were used to obtain the fractional dead time with a suficiently high frequency.

Restricted access

Understanding the relationship between the distribution of organisms and their environment is important for regional conservation planning. While most herpetofaunal community studies address environmental influence on species richness, few studies describe environmental influence on species composition at geographic scales. Field surveys of herpetofauna were conducted during 1994-2000 in Tochigi Prefecture, which covers ca. 6400 km_ of mainland Japan and includes a wide range of elevation, annual mean temperature, and human population densities. We evaluated whether (i) regional herpetofauna are distributed along a gradient of climate and elevation, as well as land cover and land use, and (ii) 'climate/elevation' and 'landcover' variables differ in their relative contribution. Ordination indicated a strong geographic gradient in species composition that was correlated with climate, elevation, land cover and land use. Reptiles were strongly influenced by land cover and land use (residential, agricultural, and forested area), while amphibians responded to all gradients (climate, elevation, and land cover and land use). All species with declining populations listed in the Prefectural Red Data Book were associated with mid-elevation regions, where anthropogenic modification is most intensive. All exotic species were strongly associated with anthropogenic gradients.

Restricted access

Abstract  

The results of research and development related to radiochemical characteristics of tritium to be considered in a fusion reactor facility design are summarized. Reactions induced by tritium beta-decay under presence of high purity tritium, which might give an impact to tritium inventory control and safety, have been identified and investigated. Results of researches of radiolysis of tritiated water implied necessity of some measures to prevent hydrogen explosion and avoid a corrosive condition. A calorimetric method to measure tritium decay heat has been applied successfully to accountancy of the ITER fuel storage system with satisfaction of the required specification.

Restricted access

Abstract  

The stability constants (β 1) of iodide ion-pairs of trivalent f-block element ions (lanthanoids Ce, Eu, Gd, Tb and Tm, and actinoid Am) were determined in the vicinity of pH 2.5 of mixed methanol/water solvent solutions of an ionic strength of 1.00 mol·dm−3 at 298±1 K. The values were less than 2. From the variation in distance between Eu3+ and I, which was calculated using a Born-type equation for Gibbs’ free energy derived from β 1(Eu), the Eu3+-I interaction was shown to be solvent-shared ion-pair formation when the mole fraction of methanol (X MeOH)≤0.40. In contrast, it was suggested that the interaction of Am3+-I changed from solvent-separated ion-pair to solvent-shared ion-pair with increasing X MeOH when X MeOH≤0.10, but remained as solvent-shared ion-pair in the range 0.16≤X MeOH≤0.40. Furthermore, β 2(Am) was measured in the range 0.31≤X MeOH≤0.40. It was also shown that the β 1 values of lanthanoids at X MeOH = 0.40, except for that of Gd(III), decreased with increasing atomic number.

Restricted access

Abstract  

The sensitivity in the determination of deuterium and15N by nuclear reactions was examined for the following reactions: (1)15N(d,n)16O (or p+)+(6.13, 7.11 MeV); (2) D(3He,)4He (13 MeV); and (3)15N(,n)18F. By these activations with suitable etching techniques, sub ppm regions of D and15N have proved to be measurable with their depth profiles. Some fundamental properties of hydrogen and nitrogen in silicon are under investigation using of these activable tracers.

Restricted access

Abstract  

We report the optical absorption characteristics of highly porous, polycrystalline TiO2electrodes and the influence of hydrolysis period for the preparation processes by photoacoustic (PA) spectroscopy together with photoelectrochemical (PEC) current ones. The PA spectra show peaks which are attributed to the lowest transition energy due to the quantum confinement effect. The peak intensity decreases with the increase of hydrolysis periods, indicating the possibilities of the changes in the thermal properties and the densities due to hydrolysis processes. The PEC spectra indicate that the photocurrent intensity also show peak and that of the longer hydrolysis periods is somewhat smaller than others, indicating the increase of interface states due to the formation of grain boundaries with the increase of hydrolysis processes.

Restricted access

Abstract  

A versatile system has been developed for the TL-reader of geological samples by using a personal computer system combined with a ceramic heater and a photon counting technique. A handy heater stack consisting of four ceramic heater plates was operated to ensure constant heating rate by applying phase-control circuit up to 400°C to a normal laboratory AC-power supply in order to obtain the TL-results as quantitatively as possible. From the results of the artificially irradiated quartz, a small amount of sample like 5 mg was verified to be applicable to obtain useful geochronological and geothermal information.

Restricted access

Abstract  

We developed a quantitative, real-time imaging system of labeled compounds in a living plant. The system was composed of CsI scintillator to convert β-rays to visible light and an image intensifier unit (composed of GaAsP semiconductor and MCP; micro channel plate) to detect extremely weak light. When the sensitivity and resolution of the image of our system was compared with that of an imaging plate (IP), the sensitivity of our system (with 20 minutes) was higher than that of an IP, with similar quality to that of an IP. Using this system, the translocation of 32P in a soybean plant tissue was shown in successive images.

Restricted access

Abstract  

We have analyzed 16 elements and the radioactivity of 210Pb in a wood disk, across the annual rings to find out a promising tool for dendrochronology (chronology of wood) both for a Japanese wood, Cryptomeria japonica, and for an Indonesian rain forest wood, Alstonia, which does not form annual rings because of the relatively constant climate of the rain forest. As a result, only Mg concentration showed similar, smooth decreasing tendency in both wood species. The smooth change of the Mg concentration across the annual rings along with the growth suggested the possibility of the Mg concentration determination as a promising dendrochronological tool.

Restricted access
Journal of Radioanalytical and Nuclear Chemistry
Authors: T. Suzuki, Y. Oki, M. Numajiri, T. Miura, K. Kondo, N. Oshima, T. Hayashi, H. Nakamura, and Y. Ito

Abstract  

The polymerization process of bisphenol-A dicyanate (BADCy) has been studied using a positron-annihilation lifetime technique (PAL). The polymerization was conducted at 150°C, and the process was followed by PAL. Seven kinds of samples with different curing times were also formed at 150°C, and the relation between the period of the curing time and the degree of polymerization was studied. It has been shown that theo-Ps lifetime increases in samples with a higher polymerization than 85%, which is consistent with measurements of the specific volume of BADCy.

Restricted access