ナンセイ ショトウ ニ オケル メヒルギ オヨビ オヒルギ シュウダンカン ノ イデンテキ ブンカ

南西諸島におけるメヒルギ,オヒルギ集団間の遺伝的分化を調査した。南西諸島はこの2種の分布域の周縁部に位置し,集団は比較的小さい。メヒルギでは3遺伝子座,オヒルギでは6遺伝子座のマイクロサテライトマーカーを用いた遺伝分析から2種ともに高い遺伝的変異が示された。メヒルギの対立遺伝子の有効数は2.152,ヘテロ接合度は0.409であった。一方,オヒルギの対立遺伝子の有効数は1.593,ヘテロ接合度は0.318であった。集団間の遺伝子分化係数は高く,メヒルギで0.316,オヒルギで0.380であった。メヒルギの遺伝的多様性は,沖縄本島,奄美大島が西表島よりも大きかった。また,オヒルギの遺伝的多様性は,西表島が沖縄本島,奄美大島よりも大きかった。2種の遺伝的多様性の水準は,集団の規模と地域性に関連すると考えられる。The genetic differentitation of the mangrove tree species Kandelia cadel and Bruguiera gymnorrhiza in the Southwest Islands of Japan was investigated. These island are located at the periphery of the distribution area of the two species, and their populations are relatively small. Genetic analyses using microsatelite marker of 3 markers in Kandelia cadel and 6 markers in Bruguiera gymnorrhiza revealed very high genetic variation in both species. At the species level, the average effective number of alleles per locus was 2.152, and the average expected heterozygosity was 0.409 in Kandelia cadel. The corresponding figures for B. gymnorrhiza were 1.593 and 0.318, respectively. The coefficients of genetic differentiation among the populations were high (G_=0.316 for K. cadel and 0.380 for B. gymnorrhiza). The genetic variationn and habitat area of K. cadel on the lslands Amami and Okinawa are greater than on Iriomote island. The genetic variation and habitat area B. gymnorrhiza is greater on Iriomote island than the islands Okinawa and Amami. The level of genetic variation in both of the species might be related to their population size and locality

The Observation of “Conduction Spot” on NiO Resistance Random Access Memory

We succeeded in observing the “conduction spot” (CS) in the capacitor structure resistance random access memory (ReRAM), which includes a conductive filament. In this study, we used NiO prepared by thermal oxidation at a high temperature as 800 °C. It requires a forming process using an extra high voltage, which partly removes the top electrode from the resistance switched area. These experiments enabled us to observe the conductive filament directly in CS on NiO ReRAM by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). From SEM images, CSs seem to be produced by some kind of breakdown, but we confirmed the reproducible resistance switching at least 50 cycles after the CS generation. By energy dispersive X-ray spectroscopy (EDX) with TEM observations, drastic oxygen reduction was observed in a local area within CS of NiO films. Moreover, the CS area depended on the injection power for forming. These experimental data suggest that the miniaturization of ReRAM will be achieved by reducing the injection power for forming

I-V measurement of NiO nanoregion during observation by transmission electron microscopy

Conduction measurements with simultaneous observations by transmission electron microscopy (TEM) were performed on a thin NiO film, which is a candidate material for resistance random access memories (ReRAMs). To conduct nanoscale experiments, a piezo-controlled TEM holder was used, where a fixed NiO sample and a movable Pt-Ir counter electrode were placed. After the counter electrode was moved to make contact with NiO, I-V measurements were carried out from any selected nanoregions. By applying a voltage of 2 V, the insulating NiO film was converted to a low resistance film. This phenomenon may be the "forming process" required to initialize ReRAMs. The corresponding TEM image indicated a structural change in the NiO layer generating a conductive bridge with a width of 30-40 nm. This finding supports the "breakdown" type forming in the so-called "filament model" of operation by ReRAMs. The inhomogeneity of resistance in the NiO film was also investigated