二种淡水微囊藻rDNA16S-235基因间隔区的序列测定与分析

本研究采用ＰＣＲ及序列测定的方法，对我国淡水铜绿微囊藻有毒株（Ｍ８６４１）和另一低毒的种类惠氏微囊藻（Ｍ５７４）ｒＤＮＡ１６Ｓ－２３Ｓ基因间隔区进行了序列的测定和分析，结果表明：ｒＤＮＡ１６Ｓ－２３Ｓ基因间隔区可以作为一个精细且稳定的指标，用于微囊藻的分类和鉴定。并从分子水平提出了铜绿微囊藻与惠氏微囊藻在种系发生上有较近缘的关系。本文首次对微囊藻属Ｍｉｃｒｏｃｙｓｔｉｓ　ｒＤＮＡ基因间隔区全序列作了报道，为微囊藻属的鉴定及系统学研究提供了分子基础。

超铀区缺中子新核素~235 Am的合成与鉴别

本实验利用中国科学院高能物理研究所质子直线加速器提供的35MeV质子束流，轰击稀有放射性同位素靶238Pu，通过（p，4n）反应合成了超铀缺中子新核素235Am。反应产物是由氦喷嘴长毛细管传输系统传输和收集的，用快速化学分离方法分离出Am的同位素，使用两台高纯锗探测器对分离样品进行了X射线，γ射线和γ-γ（X）符合关系的测量，通过235Pu的衰变γ射线的生长——衰变趋势指定了235Am的生成，并通过Np的Kx射线的生长——衰变曲线确定了235Am的半衰期为（15±5）分钟。这是我国首次在超铀区合成缺中子新核素。

Robust Nanoadhesion Under Torque

In this article, optimization of shear adhesion strength between an elastic cylindrical fiber and a rigid substrate under torque is studied. We find that when the radius of the fiber is less than a critical value, the bonding-breaking along the contact interface occurs uniformly, rather than by mode III crack propagation. Comparison between adhesion models under torque and tension shows that nanometer scale of fibers may have evolved to achieve optimization of not only the normal adhesive strength but also the shear adhesive strength in tolerance of possible contact flaws.

条形装药土中爆炸空腔发展过程的实验研究

本文通过X光摄影观察无限介质(土)中条形装药爆炸空腔发展的高速现象。得到了实验条件下的空腔发展规律,分析了空腔发展过程中一些重要现象。实验表明:空腔发展符合幂函数规律:空腔运动过程受装药的传爆特征、空腔长径比和裂缝出现时间的影响、空腔最终形状与起爆端位置无关。

分子法激光分离同位素中的物理化学气体动力学研究

<正> 尽管激光分离同位素(LIS)才出现十几年,但由于其突出优点,受到世界各国的重视,发展极快。其中有大量课题与力学紧密相关,但迄未见到从这两个乍看起来关系不大的学术领域的结合上作出的总结和评述。本文希望填补这一空白。 1.激光同位素分离 从天然矿物或人工产物中将对人类用处较大的同位素分离出来,对于国民经济和军事应用十分重要。例如,天然矿物中铀235的含量只有约0.7％;而世界

一类平板组合结构的杂交有限元解法

<正> 1.引言由几块平板组成的空间结构在工程上得到广泛应用.其动力、静力问题是很难用经典材料力学和弹性力学方法解决的.有限元方法是解决这类问题的强有力手段.各国力学工作者已经发展了很多解决板壳问题的有限元素法,Zienkiewicz 等提出的位移法有限元公式是最常用的,这个元素的位移函数在边界上一阶法向导数不连续是它的最大缺点,另外一些人提出的位移法边界协调元素公式太复杂,而不为人们所

塑性大变形问题的唯一性、稳定性和极值原理

本文从考虑几何非线性的塑性大变形基本方程出发,讨论了塑性大变形问题的唯一性、稳定性与极值原理。提出了确定边值问题的解的唯一性判别准则;分析了平衡状态稳定性的充分条件。最后讨论了边值问题与变分问题等价的充分条件。

Orthotropy rescaling and implications for fracture in composites

For most practically important plane elasticity problems of orthotropic materials, stresses depend on elastic constants through two nondimensional combinations. A spatial rescaling has been found to reduce the orthotropic problems to equivalent problems in materials with cubic symmetry. The latter, under favorable conditions, may be approximated by isotropic materials. Consequently, solutions for orthotropic materials can be constructed approximately from isotropic material solutions or rigorously from cubic ones. The concept is developed to gain insight into the interplay between anisotropy and finite geometry. The inherent simplicity of the solutions allows a variety of technical problems to be addressed efficiently. Included are stress concentration related cracking, effective contraction of orthotropic material specimens, crack deflection onto easy fracture planes, and surface flaw induced delamination.

关于气液两相流流型及其判别的若干问题

气液两相流体系是一个复杂的多变量随机过程体系，流型的定义、流型过渡准则和判别方法等方面的研究是多相流学科目前研究的重点内容。本文就与气液两相流流型及其判别有关的研究状况进行了回顾和评述，力图反映近年来气液两相流流型及其判别问题研究的状态和趋势。

30K单级高频同轴脉冲管制冷机

介绍了一套实用型单级高频同轴脉冲制冷机工作在深低温区的性能特性。输入功率为200 W时,冷头无负荷最低温度可达到29.35 K,输入功率为235 W时,冷头无负荷温度可稳定在28.55 K。这是目前国内无多路旁通的单级高频脉冲管制冷机获得的最低温度,国际上位于先进行列。200 W输入条件下,35.6 K可提供0.5W制冷量,为30 40 K温区相关的小冷量应用提供了一种简单有效的方法。

一种同时测量温度和应变的光纤光栅传感器

报道了一种新型实用的用单根光纤布拉格光栅(FBG)实现温度和应变分离传感的技术。当光纤光栅一部分包层直径变小时，整个光栅可以看成由两个周期相同但直径不同的子光栅连接而成。理沦分析和实验都证实了这两个子光栅具有相同的温度敏感性和不同的应变敏感性．由此实现光纤光栅传感器中温度和应变两参数的分离测量，而且这两个子光栅的中心波长间距可以直接测量应变大小．温度变化不影响所测量的应变值。实验中光栅的一部分包层直径被HF酸腐蚀到82μm．获得了两子光栅应变响应系数分别为0．00201nm/με．0．000858nm/μ

High-density holographic recording parameters under different wavelength of a two dyes-sensitized photopolymer

The high-density holographic recording parameters of a novel two dyes-sensitized photopolymer under different exposure wavelengths are studied. The results show that the maximum diffraction efficiency, exposure sensitivity, maximum refraction index modulation, dynamic range, and the exposure time constant increases with the increase of the exposure wavelength. The analysis indicates that the scattering has an important role in the forming of the holographic grating. (c) 2005 Elsevier GmbH. All rights reserved.

Excimer laser plasma to control laser pulse duration

An injection-locking excimer laser beam with a pulse duration of 25 ns is focused on the surface of a polymide film. The laser beam that passes through the etching film is shorter than the original one. By optimizing the thickness of the film and the beam power density, a pulse with a 3-ns pulse duration can be obtained using this switch technology.

新型氧氟化物玻璃的化学稳定性

对新型含碲氧氟化物玻璃在中性、碱性、酸性条件下的化学稳定性进行了研究。实验表明：水的侵蚀使玻璃表面形成碱性沉淀物．阻碍了侵蚀反应进一步发生，使在抗水实验中，质量损失并不随碲含量的增加而增加。对碱侵蚀后的样品用盐酸漂洗的实验显示，随氧化碲含量增加，玻璃化学稳定性变差；经碱腐蚀后，玻璃表面雾化，可见透过率明显减低。碱中浸泡后未用酸漂洗的样品在3100nm附近出现明显的水吸收峰；盐酸处理后，羟基吸收峰消失，但整体的中红外透过率下降。玻璃在酸性条件下侵蚀相同时间的质量损失是碱中的7倍．但由于是均匀腐蚀，侵蚀前后玻

Effect of air annealing on the spectral properties of Ce : Y3Al5O12 single crystals grown by the temperature gradient technique

Five absorption hands, at 227, 300 340, 370 and 457nm, were observed in the optical absorption spectrum of Ce:Y3Al5O12 (Ce:YAG) crystals grown by the temperature gradient technique (TGT). The absorption bands at 227, 340, and 457 nm were identified Lis belonging to the Ce3+ -ion in the YAG crystal. A near UV optical emission band at 398nm was observed. with an excitation spectrum containing two bands, at 235 and 370nm. No fluorescence was detected under 300 nm excitation. The pair of absorption bands at 235 and 370 nm and the absorption band at 300 nm were attributed to the F- and F+-type color centers, respectively. The color centers model was also applied to explain the spectral changes in the Ce:YAG (TGT) crystal, including the reduction in the Ce 31 -ion absorption intensity, after annealing in an oxidizing atmosphere (air). (C) 2004 Elsevier B.V. All rights reserved.