Three-body decay of a rubidium Bose–Einstein condensate

We have measured the three-body decay of a Bose–Einstein condensate of rubidium (⁸⁷Rb) atoms prepared in the doubly polarized ground state F=m _F =2. Our data are taken for a peak atomic density in the condensate varying between 2×10¹⁴ cm^-3 at initial time and 7×10¹³ cm^-3, 16 s later. Taking into account the influence of the uncondensed atoms on the decay of the condensate, we deduce a rate constant for condensed atoms L=1.8 (±0.5) ×10^-29 cm⁶ s^-1. For these densities we did not find a significant contribution of two-body processes such as spin dipole relaxation. Received: 24 November 1998 / Revised version: 26 June 1999 / Published online: 8 September 1999     

非均质材料力学研究进展: 热点、焦点和生长点 ————- ICHMM2008的观察和启迪

本文结合第二届国际非均质材料力学会议 (ICHMM2008,黄山)专题讨论会和部分特邀报告的情况, 以及2011年5月22$\sim$26日在上海崇明岛举行的ICHMM2011国际会议的内容, 对该领域的研究进展及其热点、焦点和生长点进行了综合性的评述. 重点讨论了多物理场与多尺度模拟、材料结构与力学行为从原子到连续介质的分析、随机微结构演化与退化、真实材料微结构的模拟、生物材料力学与仿生设计、在位实验和模型验证、功能梯度材料结构力学、微纳米功能器件开发等前沿性课题. 其中特别用较多的篇幅讨论了多物理场与多尺度模拟的背景、目标、必要性、现有方法的优缺点、障碍、应用例子与其他前沿研究领域的联系及其发展态势, 并阐述其研究焦点与值得注意的进展.      

Beam deceleration for block-face scanning electron microscopy of embedded biological tissue

The beam deceleration (BD) method for scanning electron microscopes (SEM) also referred to as "retarding" was applied to back-scattered electron (BSE) imaging of the flat block face of a resin embedded biological specimen under low accelerating voltage and low beam current conditions. BSE imaging was performed with 0-4 kV of BD on en bloc stained rat hepatocyte. BD drastically enhanced the compositional contrast of the specimen and also improved the resolution at low landing energy levels (1.5-3 keV) and a low beam current (10 pA). These effects also functioned in long working distance observation, however, stage tilting caused uncorrectable astigmatism in BD observation. Stage tilting is mechanically required for a FIB/SEM, so we designed a novel specimen holder to minimize the unfavorable tilting effect. The FIB/SEM 3D reconstruction using the new holder showed a reasonable contrast and resolution high enough to analyze individual cell organelles and also the mitochondrial cristae structures (~5 nm) of the hepatocyte. These results indicate the advantages of BD for block face imaging of biological materials such as cells and tissues under low-voltage and low beam current conditions.     

Ruthenium catalyzed transformation of alcohols to esters and lactones

Homogeneous catalytic oxidative condensation of alcohols and diols to their corresponding esters and lactones has been accomplished using RuH₂(PPh₃)₄.     

Generation in singularity categories of hypersurfaces of countable representation type

The Orlov spectrum and Rouquier dimension are invariants of a triangulated category to measure how big the category is, and they have been studied actively. In this paper, we investigate the singularity category $$\textsf {D} _{\textsf {sg} }(R)$$ of a hypersurface R of countable representation type. For a thick subcategory $${\mathcal {T}}$$ of $$\textsf {D} _{\textsf {sg} }(R)$$ and a full subcategory $$\mathcal {X}$$ of $${\mathcal {T}}$$, we calculate the Rouquier dimension of $${\mathcal {T}}$$ with respect to $$\mathcal {X}$$. Furthermore, we prove that the level in $$\textsf {D} _{\textsf {sg} }(R)$$ of the residue field of R with respect to each nonzero object is at most one.     

Novel hypotensive peptides from the body of Elaphe climacophora

Four hypotensive peptides called elapherine-A, -B, -C and -D were isolated from the body of Elaphe climacophora after removal of the internal organs. Elapherine-A, which had the lowest molecular weight, exhibited a prolonged fall for 5 min in the blood pressure of spontaneously hypertensive rats, whereas elapherin-B, -C and -D displayed a transient fall in the blood pressure. The molecular weights of elapherine-A---D estimated from sodium dodecyl sulfate (SDS) gel disk electrophoresis were 6600, 6900, 7000 and 7200, respectively. The isoelectric points of these peptides were 10.4, 10.6, 10.7 and 10.5, respectively. They possessed a single polypeptide chain of 34-35 (elapherine-A), 56-58 (elapherine-B), 56-57 (elapherine-C) and 52-53 (elapherine-D) amino acid residues.     

Gröbner Bases for the Polynomial Ring with Infinite Variables and Their Applications

We develop the theory of Gröbner bases for ideals in a polynomial ring with countably infinite variables over a field. As an application we reconstruct some of the one-to-one correspondences among various sets of partitions by using the division algorithm.