Current-driven resonant excitation of magnetic vortex

A magnetic vortex core in a ferromagnetic circular nanodot has a resonance frequency originating from the confinement of the vortex core. By the micromagnetic simulation including the spin-transfer torque, we show that the vortex core can be resonantly excited by an AC (spin-polarized) current through the dot and that the resonance frequency can be tuned by the dot shape. The resistance measurement under the AC current successfully detects the resonance at the frequency consistent with the simulation.Comment: 16 pages, 4 figure

Current-induced Vortex Motion by Spin-Transfer Torque

We investigate the dynamics of a magnetic vortex driven by spin-transfer torque due to spin current in the adiabatic case. The vortex core represented by collective coordinate experiences a transverse force proportional to the product of spin current and gyrovector, which can be interpreted as the geometric force determined by topological charges. We show that this force is just a reaction force of Lorentz-type force from the spin current of conduction electrons. Based on our analyses, we propose analytically and numerically a possible experiment to check the vortex displacement by spin current in the case of single magnetic nanodot

The development of US extended nuclear deterrence over Japan: a study of invisible deterrence between 1945 and 1970

This thesis seeks to offer a novel theoretical and empirical insight into the unique form of the United States (US) extended nuclear deterrence (END) - also known as a nuclear umbrella - provided to Japan. In contrast to the main trend of nuclear weapons deployment in America‘s close allies during the Cold War, Japan was only the key allied state that never hosted US nuclear weapons on its soil throughout the Cold War. Japan, instead, relied on US END backed by strategic forces mainly at sea. US END over Japan was thus "invisible" in that US nuclear weapons were not forward-deployed. This situation has not changed since it was developed in the 1960s. The thesis is an essentially historical project but its main aim is to understand US END over Japan today. Its approach is to use history as a tool to understand the present. The thesis unravels the complex developments of such deterrence between 1945 and 1970. More specifically it seeks to understand under what circumstances Japan came under the US nuclear umbrella and what factors have shaped "Invisible" END. The primary argument of this thesis is that public anti-military and nuclear sentiment in Japan shaped by its historical experience in the devastating World War Two significantly influenced the strategic calculations of Japanese leaders as well as American leaders. Key events in the foregoing period set social and political conditions on strategy making of Japan even today. The thesis will specifically examine the formation process of Japan‘s non-nuclear path chosen. In order to understand the non-nuclear path taken, the thesis will also examine the meaning of the Japan‘s alternative nuclear path. In fact there were some Japanese leaders such as Prime Minister Eisaku Sato, who clearly saw strategic value in nuclear deterrence. "Invisible" END was arguably a product of political compromise for Japan

Adenylate Cyclase Mediates Olfactory Transduction of Amino Acid Responses in the Newt

It has been reported that amphibians can smell not only airborne odorants but also aminoacids. It is not clear, however, whether the signal transduction pathway of the amino acid responses is sameas that of volatile odorant responses. In this study, we use patch-clamp recordings of newt olfactory receptorneurons to show that amino acid (200 μM glutamic acid, acidic; 200 μM arginine, basic; 200 μM alanine orcysteine, neutral) responses are accompanied by inducing depolarizing currents. Moreover, responses toboth amino acids and forskolin, a stimulator of adenylate cyclase, were observed in the same cells, whichindicates that the cells responding to amino acids possess the cAMP-system. In addition, our EOG (electroolfactogram)studies show that forskolin attenuates not only responses to volatile odorants, but also those toamino acids. These data provide evidence that the cyclic AMP system might underlie the signal transductionpathway of amino acid responses in addition to volatile odorant responses