双高斯空心光束的传输特性分析

对双高斯空心光束经非线性介质后传输和直接经自由空间传输的两种方式分别进行了数值模拟,研究了双高斯空心光束在两种介质中的传输特性.研究结果表明,双高斯空心光束具有稳定的近场传输特性,而在远场光束中心暗斑将消失,此时轴上的光强变为最大,且在中心边缘出现衍射环;同时在远场,经非线性介质后传输比直接在自由空间中传输的轴上光强增加更快.     

薄膜-基底式管材中脉冲激光产生的温度场

基于材料的热物理参数随温度的变化,用有限元方法对脉冲激光作用于薄膜-基底式双层管状材料时产生的温升进行了数值计算.采用铝薄膜和有机玻璃为基底的慢基底快涂层式组合,分别得到了不同时刻薄膜铝和基底有机玻璃中的温度场随径向和周向的分布曲线.计算结果表明:如果薄膜的热扩散系数远大于基底的,则基底中的温升远小于薄膜中的温升,可忽略不计;薄膜中沿周向除了激光辐照范围外,有意义的温升范围很小.     

Fabrication of MgB2 superconducting films by different methods

MgB₂ superconducting films have been successfully fabricated on single crystal MgO(111) and c-AL₂O₃ substrates by different methods. The film deposited by pulsed laser deposition is c-axis oriented with zero resistance transition temperature of 38.4 K, while the other two films fabricated by chemical vapor deposition and electrophoresis are c-axis textured with the zero resistance transition temperature of 38 K and 39 K, respectively. Magnetization hysteresis measurements yield critical current density J_c of 10⁷ A/cm² at 15 K in zero field for the thin film and of 10⁵ A/cm² for the thick film. For the thin film deposited by chemical vapor deposition, the microwave surface resistance at 10 K is found to be as low as 100 μΩ, which is comparable with that of a high-quality high-temperature superconducting thin film of YBCO.     

4气门汽油机缸内空气运动的试验研究

使用激光多普勒测速仪(LDA)在发动机倒拖工况下测量了一台4气门Fox350汽油机缸内的空气运动．试验结果显示，在靠近缸盖底平面附近，单气门独立工作与双气门同时工作有不同的流场形态．缸内的空气运动增加了涡流分量，总体表现为滚流和涡流合成的斜铀涡流．     

Experimental Set-up of Laser Ultrasonic Techniques and Applications

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1.3μm InGaAsP激光器电光采样技术测量超快速电信号

研究超高速器件和微波集成电路瞬态特性需要在时间畴测量非常快的电信号,这对测量手段的时间分辨率提出了更高的要求。以实用的高速采样示波器(Tck7104,带S4采样头,上升时间为25ps)已经不能完全满足测量的需要。我们建造了1.3 μm InGaAsP激光器超高速电光采样测试装置,采样光源是1.3 μm增益开关InGaAsP/IaP激光器。如果用以Ⅲ-V族材料为衬底的高速集成电路芯片代替微带采样器,则可以实现对集成电路动态特性进行无触点检     

激光光斑面积对多光子电离离子产量的影响

研究了在激光脉冲能量和激光脉冲宽度一定时激光光斑面积对多光子电离离子产量的影响。得到了离子产量最高的条件即最佳探测条件 ,同时还讨论了激光光斑面积对探测中常用的多光子电离的离子产量影响的程度。结果表明 ,激光光斑面积对离子产量的影响与光强指数在 1附近变化快慢有关 ,光强指数变化越快 ,激光光斑面积对离子产量的影响越大     

Laser photolysis of indolinospirobenzopyran bearing crown ether moity

The photochromic reaction of the indolinospirobenzopyran possessing a monoaza-benzo-15-C-5 at the 1′-position with or without alkali-metal cation as studied using nanosecond laser photolysis technique. Supported by the National Natural Science Foundation of China and the Special Funds of the State Education Committee for Doctorate Scientific Research Wu Xinyan: born in March, 1971, Ph. D. graduate student     

An anti-Bcl-2 antibody prevents 2-deoxy-D-ribose-induced apoptosis in the IPLB-LdFB insect cell line

Confocal microscopy reveals that the anti-Bcl-2 antibody (pAb) is able to diffuse across the plasma membrane of the fat body cell line IPLB-LdFB from the insect Lymantria dispar, demonstrating the presence of Bcl-2-like molecules in the cytoplasm. Immunoperoxidase procedure confirms the cellular localization. Furthermore, an immunoprecipitation corresponding to a molecular weight of 29 KDa is observed with western blot analysis using the anti-Bcl-2 pAb. Cytofluorimetric experiments show that anti-Bcl-2 pAb counteracts 2-deoxy-d-ribose-induced apoptosis and provokes morphological changes in the insect cell line, i.e. a reduction in cell size, the disappearance of the vacuola and changes in shape. At the same time, the antibody provokes mitochondrial membrane depolarization, and N-acetyl-l-cysteine is unable to reconstitute the physiological conditions. The present findings suggest that Bcl-2-like proteins play a main role in maintaining of the integrity of cellular components, e.g. mitochondria, rather than in controlling programmed cell death. Received 23 January 2001; received after revision 1 March 2001; accepted 1 March 2001