Multidimensional replica-exchange method for free-energy calculations

We have developed a new simulation algorithm for free-energy calculations. The method is a multidimensional extension of the replica-exchange method. While pairs of replicas with different temperatures are exchanged during the simulation in the original replica-exchange method, pairs of replicas with different temperatures and/or different parameters of the potential energy are exchanged in the new algorithm. This greatly enhances the sampling of the conformational space and allows accurate calculations of free energy in a wide temperature range from a single simulation run, using the weighted histogram analysis method.Comment: 13 pages, (ReVTeX), 9 figures. J. Chem. Phys. 113 (2000), in pres

Simplified expression of shielded MR head response for double-layerperpendicular medium

科研費報告書収録論文(課題番号:09355012・基盤研究(A)(2)・H9～H11/研究代表者:中村, 慶久/垂直ハード磁気ディスク装置を用いる超大容量ストレージシステムの研究

Intergranular exchange pinning effects in perpendicular recordingmedia

科研費報告書収録論文(課題番号:09355012・基盤研究(A)(2)・H9～H11/研究代表者:中村, 慶久/垂直ハード磁気ディスク装置を用いる超大容量ストレージシステムの研究

Dietary Deoxynivalenol Exposure Assessment in University Students from Japan

This study was conducted to give a preliminary estimation of deoxynivalenol (DON) dietary exposure in Japanese university students (n = 30, aged 22–25 years) using a biomarker approach and to examine the correlation between wheat food intake and DON exposure levels. Spot urine samples were collected from 30 students of Azabu University, Tokyo. Urine samples were treated with enzyme digestion (for total DON measurement) and without (for unconjugated DON analysis) before clean-up using an immuno-affinity column and analysis using an LC-MS method, with a 13C15- DON internal standard used for accurate quantification. The limit of detection for this method is 0.5 ng/mL urine. The geometric mean (95% CI) of DON concentration was 2.03 (1.64 – 6.87) ng per mL urine. Ninety of the urine samples had detectable levels of urinary DON. The DON dietary intake exposure estimation suggested that one out of the 30 subjects had an intake of DON that exceeded Joint FAO/WHO Expert Committee on Food Additives (JECFA) provisional maximum tolerable daily intake (PMTDI) level. Mean ratio of free DON to total DON was determined to be 19%. Wheat intake assessed using a basic food frequent questionnaire method did not show a significant correlation with the urinary DON level

Thermal fluctuation of magnetization in nanocrystalline FePt thin films with high coercivity

科研費報告書収録論文(課題番号:11305027・基盤研究(A)(2)・H11～H12/研究代表者:中村, 慶久/柔軟なスピンクラスター配列からなる超高密度磁気記録メディアの研究

Effective Sampling in the Configurational Space by the Multicanonical-Multioverlap Algorithm

We propose a new generalized-ensemble algorithm, which we refer to as the multicanonical-multioverlap algorithm. By utilizing a non-Boltzmann weight factor, this method realizes a random walk in the multi-dimensional, energy-overlap space and explores widely in the configurational space including specific configurations, where the overlap of a configuration with respect to a reference state is a measure for structural similarity. We apply the multicanonical-multioverlap molecular dynamics method to a penta peptide, Met-enkephalin, in vacuum as a test system. We also apply the multicanonical and multioverlap molecular dynamics methods to this system for the purpose of comparisons. We see that the multicanonical-multioverlap molecular dynamics method realizes effective sampling in the configurational space including specific configurations more than the other two methods. From the results of the multicanonical-multioverlap molecular dynamics simulation, furthermore, we obtain a new local-minimum state of the Met-enkephalin system.Comment: 15 pages, (Revtex4), 9 figure

Thermal relaxation in perpendicular double-layered media

科研費報告書収録論文(課題番号:09355012・基盤研究(A)(2)・H9～H11/研究代表者:中村, 慶久/垂直ハード磁気ディスク装置を用いる超大容量ストレージシステムの研究

Thermal bit writing simulations in magneto-optic recording media

科研費報告書収録論文(課題番号:11305027・基盤研究(A)(2)・H11～H12/研究代表者:中村, 慶久/柔軟なスピンクラスター配列からなる超高密度磁気記録メディアの研究