Tsuchimoto M.,Hokkaido University of Science
IEEE Transactions on Magnetics | Year: 2013
In magnetization process by field cooling of a bulk high-Tc superconductor (HTS), stresses are induced by the Lorentz force between shielding currents and magnetic fields. Evaluation of the maximum stress during the magnetization is important from the viewpoint of the destruction of the bulk HTS. Stresses in a hollow cylindrical bulk HTS are numerically evaluated in the axisymmetric three-dimensional analysis. Shielding current distributions are obtained through a macroscopic numerical simulation with the Maxwell equations and the critical state model. Uniform trapped fields are discussed for piled bulk magnets. The stress distributions are obtained through numerical analysis with the finite-difference method. Maximum hoop stress is discussed for different boundary conditions of the bulk HTS. © 1965-2012 IEEE.
Tsuchimoto M.,Hokkaido University of Science
Physics Procedia | Year: 2013
In magnetization process by field cooling of a bulk high-Tc superconductor (HTS), stresses are induced by the Lorentz force between shielding currents and magnetic fields. Stresses in a cylindrical bulk HTS are numerically evaluated in the axisymmetric three-dimensional analysis. Shielding current distributions are obtained through a macroscopic numerical simulation with the Maxwell equations and the critical state model. The stress distributions are obtained through numerical analysis with the finite-difference method. Maximum stresses are discussed for the case with anisotropic Poisson's ratio of the bulk HTS. © 2013 The Authors.
Ichikawa S.,Hokkaido University of Science
Chemical Record | Year: 2016
It is important to pursue function-oriented synthesis (FOS), a strategy for the design of less structurally complex targets with comparable or superior activity that can be made in a practical manner, because compared to synthetic drugs, many biologically relevant natural products possess large and complex chemical structures that may restrict chemical modifications in a structure–activity relationship study. In this account, we describe recent efforts to simplify complex nucleoside natural products including caprazamycins. Considering the structure–activity relationship study with several truncated analogues, three types of simplified derivatives, namely, oxazolidine, isoxazolidine, and lactam-fused isoxazolidine-containing uridine derivatives, were designed and efficiently synthesized. These simplified derivatives have exhibited promising antibacterial activities. A significant feature of our studies is the rational and drastic simplification of the molecular architecture of caprazamycins. This study provides a novel strategy for the development of a new type of antibacterial agent effective against drug-resistant bacteria. © 2016 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Nihashi S.,Hokkaido University of Science |
Ohshima K.I.,Hokkaido University
Journal of Climate | Year: 2015
Sinking of dense water from Antarctic coastal polynyas produces Antarctic Bottom Water (AABW), which is the densest water in the global overturning circulation and is a key player in climate change as a significant sink for heat and carbon dioxide. Very recent studies have suggested that landfast sea ice (fast ice) plays an important role in the formation and variability of the polynyas and possibly AABW. However, they have been limited to regional and case investigations only. This study provides the first coincident circumpolar mapping of Antarctic coastal polynyas and fast ice. The map reveals that most of the polynyas are formed on the western side of fast ice, indicating an important role of fast ice in the polynya formation. Winds diverging from a boundary comprising both coastline and fast ice are the primary determinant of polynya formation. The blocking effect of fast ice on westward sea ice advection by the coastal current would be another key factor. These effects on the variability in sea ice production for 13 major polynyas are evaluated quantitatively. Furthermore, it is demonstrated that a drastic change in fast ice extent, which is particularly vulnerable to climate change, causes dramatic changes in the polynyas and possibly AABW formation that can potentially contribute to further climate change. These results suggest that fast ice and precise polynya processes should be addressed by next-generation models to produce more accurate climate projections. This study provides the boundary and validation data of fast ice and sea ice production for such models. © 2015 American Meteorological Society.
Ogawa N.,Hokkaido University of Science
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2013
The diffusion of particles in confining walls forming a tube is discussed. Such a transport phenomenon is observed in biological cells and porous media. We consider the case in which the tube is winding with curvature and torsion, and the thickness of the tube is sufficiently small compared with its curvature radius. We discuss how geometrical quantities appear in a quasi-one-dimensional diffusion equation. © 2013 Elsevier B.V.