Kiyotaka Shibata

Genetic Structures of Laguncula pulchella Metapopulations Along the Northeast Coast of Japan After the Tsunamis Caused by the Great East Japan Earthquake

The carnivorous snail (Laguncula pulchella) was once considered an endangered species in Japan because its habitat was limited to western Japan. However, alien L. pulchella populations were transported from China and the Korean Peninsula to the Pacific coast of northeast Japan, presumably via anthropogenic activities. This study examined the genetic structures of the invasive L. pulchella populations in various coastal estuaries of Sendai Bay and Sanriku Ria areas to determine how the metapopulations were affected by the tsunamis caused by the Great East Japan Earthquake. The genetic compositions of these carnivorous snails significantly varied between the Sendai Bay and Sanriku areas. The result suggests that local L. pulchella populations were relatively isolated, and their genetic structure was minimally affected by the tsunamis. In addition, their genetic compositions were locally fixed. These results suggest that difference in the genetic composition among L. pulchella populations reflects that of artificial transport source.

Photoconduction of Black Phosphorus in the Infrared Region

Photoconduction of elemental black phosphorus has been investigated for the first time in the spectral range from 1.5 µm to 5.5 µm, including its fundamental absorption edge. It has been found that black phosphorus shows a broad spectral response from the absorption edge to the visible region and a linear response to the light intensity, which has a fairly response even at room temperature. These results suggest that black phosphorus can be applicable to IR detecting devices. In addition, the direct allowed transition at the absorption edge was confirmed and its temperature dependence was measured.

E1 mice epilepsy shows genetic polymorphism for s-Adenosyl-l-homocysteine hydrolase

E1 mice are an animal model of human epilepsy (idiopathic complex partial seizures). We have previously demonstrated abrupt poly(A)(+) RNA expression in liver from 1-day-old E1 mouse [Mita et al., 1991. Devl. Brain Res. 64, 27-35]. In the present study, we constructed a cDNA library of the poly(A)(+) RNA. By analyzing cDNA clones and nucleotide sequences, we found a clone that was homologous to a rat gene of S-adenosyl-L-homocysteine hydrolase (EC 3.3.1.1.) (SAHH) (a key enzyme in the active methyl transfer pathway) and showed the gene polymorphism/RFLP(PstI) between the epileptic strain, E1, and the non-epileptic mother strain, ddY, as indicated in a gel electrophoresis by cleaving 2.6 kb with PstI into 1.9 kb and 0.7 kb fragment bands. F1(E1xddY) showed the heterozygosity. An attempt to determine the mutation on the genomic SAHH gene in the E1 disclosed a single nucleotide polymorphism indicated by a C-->T transition in the 8th intron, by which the PstI site was created. SAHH enzymatic activity in the liver in 1-day-old E1 mice was slight (approximately 10%), and in fact was significantly lower than that of the control ddY. Results suggested that the abrupt primary mRNA transcribed on the SAHH gene in the liver of 1-day-old E1 mice was processed partially or incompletely because of the presence of the point mutation in the intron. Accordingly, poor energy supply by the insufficient SAHH enzymatic activity in the brain postnatally may be responsible for epileptogenesis in this animal model. It is concluded that a single nucleotide SAHH gene polymorphism may be associated with epilepsy in E1 mice.

Two-Dimensional Anderson Localization in Black Phosphorus Crystals Prepared by Bismuth-Flux Method

The temperature and magnetic field dependence of the electrical resistivity of black phosphorus single crystals prepared by the bismuth-flux method was measured down to 0.5 K in temperature and up to 6 T in magnetic field. While a typical semiconducting behavior of p-type conduction has been observed above about 10 K, the log T -like dependence of the conductivity and the log B dependence of the negative magnetoresistance have been found below 10 K. Results of the field dependence of the magnetoresistance are in good agreement with the theory of the two-dimensional Anderson localization. The whole results are understood by a model that the 3D hole conduction process in the high temperature region is replaced at about 10 K by a 2D electron gas confined near the surface.

The Energy Band Structure of Black Phosphorus and Angle-Resolved Ultraviolet Photoelectron Spectra

The energy band structure of black phosphorus is recalculated using the ab initio norm-conserving pseudopotential calculation. The results show better agreement with the experiment of angle-resolved ultraviolet photoelectron spectroscopy than a previous band structure calculation, based on the pseudopotential of the Appelbaum-Hamann type.

Novel and simple two-step purification of a full-length rat glucocorticoid-receptor expressed in a baculovirus system

We purified the activated recombinant glucicorticoid receptor (GR) overexpressed in insect cells by sequential chromatographies using Mono Q and Mono S columns. This procedure was based upon a new finding that the activated GR binds both to a Mono Q column and to a Mono S column at the same pH (pH 8.4). The entire chromatographies took about 3 h and GR represented 97% of the purified protein sample. The purified GR was able to bind specifically to a DNA fragment containing the glucocorticoid response element. This purification protocol will be applicable to the purification of native GR, point-mutated recombinant GR and other nuclear receptors.

A Pressure-Induced Isostructural Transition in Black Phosphorus

The crystal structure of orthorhombic black phosphorus under pressure is calculated as a function of volume using the pseudopotential total-energy method. As a result, it is shown that the anomaly of the lattice constants observed experimentally at the density of 17.5A 3 /atom is due to an unusual isostructural second order phase transition and its physical origin is attributed the repulsive force effect due to overlap between valence electron charge clouds of neighboring puckered layers

Photoconductive Decay Measurements on Semiconducting Black Phosphorus Crystals

Photoconductive decay measurements on black phosphorus crystals have been carried out in the temperature range 80-330 K. It was found that the measured lifetime is nearly constant below about 260 K, while it decreases with increasing temperature. From such temperature dependence, it was suggested that the indirect Shockley-Read recombination is dominant below 260 K, while the direct recombination such as the intrinsic Auger process is dominant above 260 K. It was also found that the measurement lifetime depends strongly on applied voltage. The fast response of the order of 10-6-10-7 s indicates that black phosphorus can be used as a photoconductive detector of high-frequency operation for infrared radiation below 4.4 µm.

Optical Properties of Black Phosphorus and Its Application to the Infrared Detector

Electrical and optical properties, especially the photoconductive ones, of an elemental black phosphorus semiconductor have been investigated. It has been found that the black phosphorus crystal shows photoconductive properties in the near-IR region. It shows a linear response for light intensity, a fast response with a decay time of about 0.5 µs and a selective response for polarized light. These results indicate that black phosphorus is applicable to IR detecting devices.

Thermoluminescence and Optical Absorption of NaBr:S- Crystals

Thermoluminescence and optical absorption in NaBr:S- crystals have been studied in the temperature range between 80 and 300 K. The kinetics of formation and decomposition of the so-called FH center, which consists of an F center associated with a neighboring sulfur ion, has been investigated in relation to thermoluminescence. It has been found that the thermoluminescence glow peak, which has an emission band with a peak at 815 nm (1.52 eV), appears at 230±3 K and is strongly concerned with recombination of the electron of the FH center. Such a model has been supported by observing the change in the optical absorption due to the S- centers and the FH centers.