N-terminal of L protein of vesicular stomatitis virus contains a new signal sequence

The L protein (241kD) of vesicular stomatitis virus (VSV) is the most important snbnnit of the replication complex. The existence of specific localization signal in the L protein was investigated by making recombinant constructs expressing truncated mutants of the L protein fused to green fluorescent protein (GFP) in transient transfection assays. The chimeric genes encoding varied N-terminal of L and GFP gene were put under the control of T7 promoter or CMV promoter. The fusion proteins were transiently expressed in BHK-21, COS-7, CHO or Hep G2 cells. When more than 120 residues were deleted or only 96 residues were kept on the N-terminal, the fusion proteins were shown to be distributed throughout the cells, cytoplasm and nucleus under the confocal microscope. However, other chimeric proteins with 120 or more amino acids were dotted and distributed in the perinuclear regions. And the fusion protein with 96—120 aa has the similar distribution. A thirteen-residue peptide QGYSFLHEVDKEA (108—120) was identified as localization signal, whose function would be absolutely distributed with the deficiency of D or V. Our results show that there is an independent localizing signal in N-terminal domain of L protein of VSV and this functional signal is conserved in different cell lines.     

New geological evidence of crustal thickening in the Gangdese block prior to the Indo-Asian collision

Recent mapping in the Gangdese block has revealed many leucogranites that are similar to those in the High Himalaya. These leucogranites formed at ～140 Ma as indicated by monazite Th-Pb ion-microprobe dating and cooled at ～130 Ma as indicated by muscovite ^40Ar/^39Ar dating. In conjunction with previous structural and paleogeographic studies, the new data indicate that the Gangdese block underwent crustal thickening and associated exhumation during ～140—130 Ma. In this regard, the southern margin of Eurasia continent was comparable to the modern South American Altiplano-Puna plateau, the prime example of active ocean-continent subduction and associated thickened crust. Specifically, the early stages of crustal thickening and uplifting of the Gangdese block may result from subduction of the Neo-Tethyan Ocean. If the Tibetan Plateau would form by accretion of a series of blocks with thickened crust, an elevated topographic plateau similar to the Altiplano-Puna plateau had formed before collision between the Indian and Eurasian plates. Then the Tibetan Plateau would have quickly thickened, uplifted, and begun to extend soon after onset of the collision. Thus, the deformational mechanism of the Tibetan Plateau is not distributed shortening, but rather concentrating deformation within regions of thin crust between the accreted blocks.     

Contributions of different land cover types in Otindag Sandy Land and Bashang area of Hebei Province to the material source of sand stormy weather in Beijing

Different land cover types in Otindag Sandy Land and Bashang area of Hebei Province are linked to a material source of sand stormy weather in Beijing based on results of field vegetation and soil survey and laboratory works. Results of grain size analysis show that dust release potential in per unit area of moving sandy land is small,while lowland meadow and meadow steppe in stony hills have high potential of releasing dusts in per unit area during sand stormy weather occurrence. Further considering the effects of vegetation, it is inferred that the moving sandy land served as a material source of past dust storm and the possibility of dust release in per unit area is low in current time.Typical steppe in stony hills is undergoing desertification and its dust release possibility in per unit area is high. Farmland has strong potential of release dusts when they are ploughed in spring, but a large amount of therophytes grow and thus prevent dusts from release when cultivation was terminated.Potentials of dust release in per unit area in fixed sand dunes,stony mountain meadow steppe and low land meadow are lowdue to high cover of perennials. Sand dune reactivation and desiccation of lakes and lowlands under estimated future climatic change will make them serve as a future material source of sand stormy weather.     

皮革废渣渗漏液中铬的测定

对皮革废渣(蓝皮屑)渗漏液中铬的二苯碳酰二肼分光光度测定法进行了研究，结果表明此方法的线性范围0-0.400mg／L，吸光度A对浓度c(mg／L)关系回归方程为：A=0．779c-0．0005，线性相关系数为0．9993，检出限为0．007mg／L，相对标准偏差小于3％，加标回收率为100％～105％，用此法对废渣渗漏液中铬的测定表明铬的形态为三价铬，因此，测定总铬时需先加H2SO4-HNO3进行消解，再以KMnO4氧化，二苯碳酰二肼显色，分光光度法测定．     

电铲铲斗齿的修复工艺

通过分析铲斗齿的磨损原因，提出了采用堆焊的方法对铲斗齿进行修复。详细介绍了铲斗齿的修复工艺，堆焊材料的选择及堆焊时应注意的事项。实践表明，此修复工艺切实可行，取得了令人满意的效果。     

开关线性复合变换低阻输出特性对系统的优化

为了在现有电力电子技术基础上进一步提高功率变换器的综合性能，揭示了一种由电力电子开关电路与线性电路有机结合而派生的开关线性复合功率变换器(SLH)。简述了该类变换器的基本工作原理，列举了并联型和串联型两种电路拓扑及其特点，说明了SLH的低阻输出特性对提高功率变换器静动态性能的作用，并对SLH与典型的PWM LC滤波单元的变换器进行了比较分析，给出了用于电源和传动系统不同负载条件下的测试数据和典型波形。结果表明，SLH在高效与优波兼顾、多类负载适应性和抗负载扰动能力方面具有综合优化性能。     

梯度型聚合物光纤预制棒折射率分布的间接测试

利用紫外光对溴苯（BB）的吸收作用，采用紫外吸收光谱法对PMMA－BB梯度型聚合物光纤预制棒的折射率分布进行了间接测试，详细介绍了这种紫外有机光谱法的测试原理及方法，测试结果表明，所制备的预制棒的折射率分布是呈抛物线分布，但在最佳理论分布有着一定的偏差，与Lorentz-Lorenz模拟方程的结果相对接近。同其他复杂的测试方法相比，紫外光谱法所需仪器普通，测试简便，不失为实验室中较为简单易行的一种预制棒折射率分布测试方法。     

数字图像中照度不均匀校正技术研究

为了消除数字图像中的照度不均匀性，对现有数字图像的照度不均匀校正技术进行了归类和讨论．分析了这些方法在计算误差上的内在原因，并在此基础上提出了基于小波变换的数字图像照度不均匀校正技术．该技术兼顾了数字图像的频域和空域，使得采用本方法校正后的图像具有品质优，计算误差小和时间消耗较少等特点．     

试论如何开展图书馆的电子书服务

电子图书产业是伴随因特网发展而出现的一个新的产业，是数字化图书馆建设不可缺少的一个部分。文章从网络传播、电子图书内容、知识产权等方面对图书馆如何开展电子图书的服务进行了论述。     

硅压阻式传感器与AD7705芯片在压力测量中的应用

介绍一种新型测量压力的元件——硅半导体压阻式传感器，并以MPX2100压阻式传感器为例，配合AD7705芯片构成压力测量系统，阐述压力测量系统的工作原理，说明系统的软、硬件设计方法．