Osaka University

About: Osaka University is a education organization based out in Osaka, Japan. It is known for research contribution in the topics: Laser & Catalysis. The organization has 83778 authors who have published 185669 publications receiving 5158122 citations. The organization is also known as: Ōsaka daigaku.

Large bulk resistivity and surface quantum oscillations in the topological insulator Bi 2 Te 2 Se

Abstract: Topological insulators are predicted to present interesting surface transport phenomena but their experimental studies have been hindered by a metallic bulk conduction that overwhelms the surface transport. We show that the topological insulator ${\text{Bi}}_{2}{\text{Te}}_{2}\text{Se}$ presents a high resistivity exceeding $1\text{ }\ensuremath{\Omega}\text{ }\text{cm}$ and a variable-range hopping behavior, and yet presents Shubnikov-de Haas oscillations coming from the topological surface state. Furthermore, we have been able to clarify both the bulk and surface transport channels, establishing a comprehensive understanding of the transport in this material. Our results demonstrate that ${\text{Bi}}_{2}{\text{Te}}_{2}\text{Se}$ is, to our knowledge, the best material to date for studying the surface quantum transport in a topological insulator.

Photocatalytic Conversion of Nitrogen to Ammonia with Water on Surface Oxygen Vacancies of Titanium Dioxide

Abstract: Ammonia (NH3) is an essential chemical in modern society. It is currently manufactured by the Haber–Bosch process using H2 and N2 under extremely high-pressure (>200 bar) and high-temperature (>673 K) conditions. Photocatalytic NH3 production from water and N2 at atmospheric pressure and room temperature is ideal. Several semiconductor photocatalysts have been proposed, but all suffer from low efficiency. Here we report that a commercially available TiO2 with a large number of surface oxygen vacancies, when photoirradiated by UV light in pure water with N2, successfully produces NH3. The active sites for N2 reduction are the Ti3+ species on the oxygen vacancies. These species act as adsorption sites for N2 and trapping sites for the photoformed conduction band electrons. These properties therefore promote efficient reduction of N2 to NH3. The solar-to-chemical energy conversion efficiency is 0.02%, which is the highest efficiency among the early reported photocatalytic systems. This noble-metal-free TiO2 ...

Making microgrids work

Abstract: Distributed energy resources including distributed generation and distributed storage are sources of energy located near local loads and can provide a variety of benefits including improved reliability if they are properly operated in the electrical distribution system. Microgrids are systems that have at least one distributed energy resource and associated loads and can form intentional islands in the electrical distribution systems. This paper gives an overview of the microgrid operation. Microgrid testing experiences from different counties was also provided.

Prevention of hypoxia-induced cell death by Bcl-2 and Bcl-xL

Abstract: The proto-oncogene bcl-2, isolated from the t(14;18) chromosomal breakpoint in follicular B-lymphoma, and a bcl-2-related gene bcl-x (ref. 4) prevent apoptotic cell death induced by various treatments. Although a mechanism has been proposed that involves Bcl-2 activity on reactive oxygen species (ROS), expression of Bcl-2 or Bcl-xL prevents cell death induced by withdrawal of oxygen (hypoxia), which drastically decreases the net formation of oxygen free radicals and does not increase oxidized lipid, protein or DNA. Furthermore, neither ROS scavenger nor inhibitor of ROS scavenger affects cell death, regardless of the expression of Bcl-2 or Bcl-xL. Thus our data suggest that Bcl-2 and Bcl-xL exert an anti-cell death function by a mechanism other than regulation of ROS activity.