We studied the solvent extraction behavior of astatine and found the anomalous behavior of this element similar to radioiodine. Astatine was extracted into CS2 from acidic solution over a wide range of carrier iodine concentration. The distribution ratios of astatine were determined by measuring the -ray from 210 At with a Nal(TI) detector. A drastic change was observed around at 10–4 mol/l as in the case of 131 I. This tendency is well explained by the kinematics of the chemical reactions concemed.
Authors:Xianglian, T. Sakuma, K. Basar, and H. Takahashi
Diffuse X-ray scattering from lead chalcogenides (PbS, PbSe, and PbTe) was measured at 15 and 294 K. The increase of the diffuse
scattering intensities with the temperature was explained by the thermal correlation effects among thermal displacements of
second nearest neighboring Pb–Pb atoms. The contribution from the second nearest neighboring atoms to the diffuse scattering
was clearly confirmed.
Seven representative wood species constituting caatinger forest were chosen to analyze Sc, V, Cr, Mn, Fe and Co, as well as Na, Mg and Al, by instrumental neutron activation analysis. In most cases of the soil, the concentration of the element tended to be higher with the increase of depth. Generally, the element partition from soil to root was higher in Mg and Co, whereas V showed higher partition rate from root to bark. The correlation within the elements was higher in the order of soil, root and bark.
Authors:I. Yamaguchi, H. Terada, M. Takahashi, and H. Sugiyama
Radioactive nuclides with relatively long half-lives in the target assemblies of medical accelerators were investigated. The
samples were the target assembly of a 10 MV linear accelerator, a 20 MV microtron and screws of a cyclotron. Gamma-spectroscopy
was performed with a high-purity germanium (HPGe) detector. Detected nuclides were 51Cr, 54Mn, 59Fe, 57Co, 58Co, 60Co, 65Zn, 108mAg, and 110mAg. As the half-lives of some generated nuclides are relatively long, it is difficult to adapt to decay-in-storage.
Authors:T. Ishikawa, Y. Yasuoka, S. Tokonami, H. Takahashi, and H. Suda
Water originated from groundwater systems can have relatively high concentration of radon. In many situations, radon is released
from the water and mixes with the indoor air. In the present study, laboratory experiments were conducted to characterize
the airborne radon released by showering and the use of a washing machine. The followings were discussed: (1) a comparison
between the loss of waterborne radon and the increase of airborne radon, (2) time-related changes in airborne radon after
the water use, (3) changes in the equilibrium factor, and (4) the relationship between radon concentration and the distance
from the source of radon release.
Authors:T. Shibasaki, T. Furuya, J. Kuwahara, Y. Takahashi, H. Takahashi, and T. Hashimoto
Summary Structural phase transitions upon the application of high pressure in LaGaO3 and LaCrO3, which were prospected from diffraction and thermal analyses of phase transition under ambient pressure, were discovered by using high-pressure X-ray diffraction. It was revealed that the crystal structures of LaCrO3 and LaGaO3 changed completely from that of orthorhombic distorted perovskite to that of a rhombohedral distorted one upon the application of pressure higher than 5.4 and 3.0 GPa, respectively, at room temperature. The variation of lattice constants with pressure was investigated for the high-pressure rhombohedral phases of LaCrO3 and LaGaO3 and isothermal compressibility was estimated. The variation of lattice constants with pressure at room temperature in the high-pressure rhombohedral phase was compared with that with temperature at ambient pressure in high-temperature rhombohedral phase. It was found that the application of pressure decreased the crystal symmetry, which was opposite to the result in the case of increasing the temperature.
Authors:H. Baba, N. Takahashi, A. Yokoyama, and T. Saito
The reaction of238U with12C was studied radiochemically with the purpose of elucidating fast fission characteristics. Fast fission component was extracted
in far-asymmetric mass region and interpreted as the mass diffusion following the Fokker-Planck equation. Anomalous charge
dispersion widths in the corresponding mass region and a sudden increase of the whole mass distribution width at the critical
energy were also observed to support the above interpretation. The reaction time of fast fission was determined to be 5·10−21 s from the width and position of the mass distribution.
Authors:R. Ozao, M. Ochiai, Y. Ichimura, H. Takahashi, and T. Takano
The previously described method involving the use of transient DSC was applied to pharmaceutical powder compacts and to ceramic
powder compacts. The samples were prepared by compressing powders of pentaerythritol tetraacetate and two kinds of alumina
powder (differing in particle size distribution) up to a pressure of 20 MPa by using a jig. For pentaerythritol tetraacetate,
a linear relationship was obtained between the parameter obtained by DSC and the compaction pressure.
Authors:R. Williams, A. Hirsh, H. Meryman, and T. Takahashi
The rate of cytolysis in osmotically stressed unfertilized sea urchin eggs was analysed using a version of the Johnson-Mehl-Avrami
equation, and fit with high precision (r2>0.90) if the data sets were divided into two sectors. The slow process was first-order but the Avrami coefficient,n, for the initial fast reaction was 7. Suspecting that this might be a peculiarity of cells which are primed for climactic
behaviour, we examined the process in red cells, whose decay is known to be of first or lower order at low temperatures if
protected from excessive osmotic stress. Human red cells subjected to ‘thermal shock’, in which osmotically stressed cells
are cooled below +12°C, show a pattern almost identical to the stressed sea urchin eggs except thatn of the rapid process exceeded 10. Based on the geometrical implications of such a highn, we believe that this phenomenon reflects a stress failure in the cytoskeleton and has important ramifications in cryopreservation.
Authors:T. Omori, H. Takahashi, K. Yoshihara, and M. Yagi
An effective coprecipitation method of carrier-free96TcO4– with tetraphenylarsonium perchlorate has been developed. The precipitation yield is independent of pH. However, it depends on the concentrations of tetraphanylarsonium and perchlorate ions. A possible coprecipitation mechanism is discussed.