Rational Homotopy Theory and Nonnegative Curvature

in this note, we answer positively a question by Belegradek and Kapovitch about the relation between rational homotopy theory and a problem in Riemannian geometry which asks that total spaces of which vector bundles over compact non-negative curved manifolds admit （complete） metrics with non-negative curvature.     

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HT-7中性束诊断电源系统的计算机控制系统由PLC、工控机、逻辑控制和定时单元等组成。对起弧、束流引出等实验进行了研究。在多种参数下,通过调节弧压、进气量等观察了其对弧流的影响。初步实验结果表明,在高压35kV、弧流80A的情况下,束电流可以达到3.6A,引出的中性束流功率可以稳定地达到50kW以上。     

Enhanced transmission of electromagnetic waves through metamaterials

This paper reviews our recent experimental and simulation results regarding the electromagnetic wave transmission through three configurations of sandwiching structures of metamaterials: a metallic mesh sandwiched between two identical layers composed of split rings, metallic fractals, and fractal slits, respectively. We observed the enhanced transmission of the waves through these three types of sandwiching composites with respect to the opaque metallic mesh. The locations of the transmission peaks in the spectrum are associated closely with the band characteristics of the sandwiching layer by appearing either on the left- or the right-hand side of its band. PACS 41.20.Jb; 42.70.Qs; 78.20.-e; 42.25.Bs; 47.53.+n     

醌蛋白——猪肾二胺氧化酶的提取和性质

新鲜猪肾匀浆后，经热处理、盐析、羟基磷灰石和ＤＥＡＥ－纤维素柱层析等纯化步骤，二胺氧化酶的收得率为２３．９％，纯化倍数为４２５．该酶进行凝胶电泳后，经氨基黑、酶活性和ＮＢＴ溶液染色分别得到相对应的蛋白质、酶活性及醌辅基谱带．该酶可与腐胺、尸胺、己二胺、组胺等底物作用，释放出Ｈ２Ｏ２，当底物为腐胺时，最适浓度为５ｍｍｏｌＬ－１，Ｋｍ值为０．５ｍｍｏｌＬ－１，最适ｐＨ为７．０，最适温度为４０°Ｃ．在非酶系统中，该酶可与ＮＢＴ溶液反应，呈现紫色，并随时间延长而加深．经ＳＤＳ板状不连续聚丙烯酰胺凝胶电泳，得该酶亚基分子量为８．３×１０４．     

Chemoselective Catalytic Hydrogenation of α,β-Unsaturated Ketones and α,β-Unsaturated Carboxylic Esters

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准直小孔法自动调焦在激光直写入系统中的应用

本文介绍了一种新的自动调焦方法准直小孔法.对自动调焦的原理和后继电路处理方法作了详细的分析.它具有响应时间短、灵敏度高,能够很好的在激光直接写入系统中克服物镜工作台运动中导轨的不平和轴向窜动所造成的离焦。     

The practice for eight-year operation of the cobalt-60 irradiation facility at Beijing Radiation Application Research Center

The radiation facility was made by Sulzer Company in Switzerland. The designed capacity is 3.7 × 10¹⁶Bq( 1MCi) and 12.21 × 10¹⁵Bq(330kCi)of Cobalt -60 source was loaded at the first phase. Current cobalt -60 source-loading is 2.4 × 10¹⁶Bq(650kCi). The equipment assembling and installation regulating and testing were completed at the end of 1988. The facility was put into commissioning in 1989. It operates 7000–8000 hours per year. The facility has been utilized to carry out many research work and irradiate many kinds of items. Lots of economical benefits have been gained since then. Now it is becoming a radiation processing model base in China. This paper summarized the strong and weak points of the design of the facility through in eight years' practice and analysed the economical benefits.     

Amperometric flow-injection analysis of hydrazine by electrocatalytic oxidation at cobalt tetraphenylporphyrin modified electrode with heat treatment

Chemically modified electrodes prepared by treating the cobalt tetraphenylporphyrin modified glassy-carbon electrode at 750 degrees (HCME) are shown to catalyze the electrooxidation of hydrazine. The oxidation occurred at +0.63 V vs. Ag/AgCl (saturated potassium chloride) in pH 2.5 media. The catalytic response is evaluated with respect to solution pH, potential scan-rate, concentration dependence and flow-rate. The catalytic stability of the HCME is compared with that of the cobalt tetraphenylporphyrin adsorbed glassy-carbon electrode. The stability of the HCME was excellent in acidic solution and even in solutions containing organic solvent (50% CH(3)OH). When used as the sensing electrode in amperometric detection in flow-injection analysis, the HCME permitted sensitive detection of hydrazine at 0.5 V. The limit of detection was 0.1 ng. The linear range was from 50 ng to 2.4 mug. The method is very sensitive and selective.     

Two New Acetylenic Compounds from Asparagus gobicus

Two new acetylenic compounds were isolated from the roots of Asparagus gobicus. Their structures were elucidated by spectroscopic methods including 2D NMR techniques.