Some characteristics of low-speed streaks under sheared air-water interfaces

The characteristics of low-speed fluid streaks occurring under sheared air-water interfaces were examined by means of hydrogen bubble visualization technique. A critical shear condition under which the streaky structure first appears was determined to be u(tau) approximate to 0.19 cm/s. The mean spanwise streak spacing increases with distance from the water surface owing to merging and bursting processes, and a linear relationship describing variation of non-dimensional spacing <(+)over bar> versus y(+) was found essentially independent of shear stress on the interface. Values of <(+)over bar>, however, are remarkably smaller than their counterparts in the near-wall region of turbulent boundary layers. Though low-speed streaks occur randomly in time and space, the streak spacing exhibits a lognormal probability distribution behavior. A tentative explanation concerning the formation of streaky structure is suggested, and the fact that <(+)over bar> takes rather smaller values than that in wall turbulence is briefly discussed.

微分方程公式的机器推导(Ⅰ)

本文阐述了微分方程公式推导程序系统的算法,这个系统已经实现,并成功地用于极限环的研究工作.作为一个具体例子和验证,文中给出了右方为二次多项式方程的机器结果,并指出了Н.Н.Баутин所发表结果中的符号错误. 本文是微分方程公式推导研究成果的第一部分.

菠菜甜菜碱醛脱氢酶的研究

本实验以菠菜叶片为材料，分离并纯化了甜菜碱醛脱氢酶（BADH，EC 1.2.1.8），并对其某些性质进行了研究。此外，还提取并纯化了poly (A)+RNA，并对其完整性进行了分析，主要结果如下： 1.菠菜甜菜碱醛脱氢酶存在于60％硫酸铵沉淀部分，70％硫酸铵沉淀部分未检出其活性。用层析法纯化该酶，使纯化倍数达到405.3倍。菠菜甜菜碱醛脱氢酶有两个同工酶。 2.菠菜甜菜碱醛脱氢酶主要定位于胞液中。其中，在过氧化物酶体及微粒体中有一定量活性存在，但在叶绿体中未检出其活性。 3.菠菜甜菜碱醛脱氢酶活性有较广的pH值范围，其最适pH范围为9.5左右。该酶以NAD作为特异性辅酶，其Km值为8.0×10-6M, Vmax为0.143nmol/min。该酶以甜菜碱醛作为特异性底物，其Km值为1.82×10-4M，Vmax为0.182nmol/min。该酶活性为0.125～1M的NaCl、KCl和脯氨酸所抑制，但0.125～1M的蔗糖及甜菜碱对其活性没有影响。 4.PCMB和Mersalyl抑制该酶的活性，DTT可逐步恢复被抑制的活性。稀土元素LaCl3对该酶活性没有影响，但CeCl则使其完全失活。另外，Mn2+和Mo6+离子对其活性没有影响，Mg2+离子可增加其活性。 5.菠菜叶片中有菠菜甜菜碱醛脱氢酶的抑制因子存在，该因子可能是一种小分子化合物。 6.应用酚-氯仿方法分离了菠菜叶片的poly (A)+RNA，并在-80℃低温下长期贮存。

谐振线圈的制造工艺

本发明涉及一种谐振线圈的制造工艺，包括下述工艺步骤：（１）选用０．３５－１ｍｍ的漆包线绕制线圈，在线圈绕制时，线圈匝间绝缘除常规漆包外还添加匝间环氧树脂：同时在线圈层间绝缘采用青稞纸，并刷层间环氧树脂；然后在绕制的线圈外包扎绝缘材料并再刷环氧树脂；（２）将包扎后的线圈与绕制模具一起置于真空浇铸模具中，然后按常规线圈真空浇铸工艺用环氧树脂浇铸线圈即可完成；本发明制造的谐振线圈的绝缘性能好，线圈的分布电容和线圈电感都能较好地满足谐振变压器型直流高压加速器的要求，且其制造工艺简单，可降低制造和运行成本。

云南纳帕海越冬黑颈鹤日间行为模式与年龄和集群的关系

2006年10月2007年5月,在云南省西北部纳帕海,采用路线调查结合瞬时扫描行为取样法,对越冬黑颈鹤(Grus nigricollis)种群的时间分配及其与年龄、集群和时间的关系进行了观察.结果说明,黑颈鹤越冬活动主要足以觅食为主,占日间时间的(76.81±9.1)%.越冬期间黑颈鹤日间行为的节律性较为明显,具有适应高寒气候的特点.集群形式对成鹤的行为有着显著影响,集群和家庭中活动的成鹤红觅食、警戒和争斗中存在显著差异(F1.76=0.27、0.77,U=2779,P=0.001-0.000).年龄是影响鹤群行为的因素之一.幼鹤相比成鹤有较多的觅食时间和休息时间,警戒行为比例较低(F1.76=0.04-2.59,U=188-2779,P=0.006-0.000),且小受集群形式的影响.随着越冬期间的早、中、晚3个时期的环境变化,黑颁鹤的时间分配有显著变化(F2.36=4.63-26.54,x22=5.29-13.68,P=0.0016-0.000).不同越冬地的黑颈鹤行为存在差异.气候、食物资源和人为影响可能是造成这些差异的主要因素.

Improving effects of huperzine A on spatial working memory in aged monkeys and young adult monkeys with experimental cognitive impairment

Our previous studies demonstrated that huperzine A, a reversible and selective acetylcholinesterase inhibitor, exerts beneficial effects on memory deficits in various rodent models of amnesia. To extend the antiamnesic action of huperzine A to nonhuman primates, huperzine A was evaluated for its ability to reverse the deficits in spatial memory produced by scopolamine in young adult monkeys or those that are naturally occurring in aged monkeys using a delayed-response task. Scopolamine, a muscarinic receptor antagonist, dose dependently impaired performance with the highest dose (0.03 mg/kg, i.m.) producing a significant reduction in choice accuracy in young adult monkeys. The delayed performance changed from an average of 26.8/30 trials correct on saline control to an average of 20.2/30 trials correct after scopolamine administration. Huperzine A (0.01-0.1 mg/kg, i.m.) significantly reversed deficits induced by scopolamine in young adult monkeys on a delayed-response task; performance after an optimal dose (0.1 mg/kg) averaged 25.0/30 correct. In four aged monkeys, huperzine A (0.001-0.01 mg/kg, i.m.) significantly increased choice accuracy from 20.5/30 on saline control to 25.2/30 at the optimal dose (0.001 mg/kg for two monkeys and 0.01 mg/kg for the other two monkeys). The beneficial effects of huperzine A on delayed-response performance were long lasting; monkeys remained improved for about 24 h after a single injection of huperzine A. This study extended the findings that huperzine A improves the mnemonic performance requiring working memory in monkeys, and suggests that huperzine A may be a promising agent for clinical therapy of cognitive impairments in patients with Alzheimer's disease.

秀丽隐杆线虫抗性基因研究进展

从3个方面总结了秀丽隐杆线虫在抗性基因方面的研究进展。秀丽隐杆线虫的先天性免疫系统在抗病原菌、抗氧化应激等方面至关重要,它主要是通过MAPK、DAF-2、TGF-β三条信号途径发挥作用;另外,含TIR区蛋白和抗菌多肽也是秀丽隐杆线虫抗微生物感染机制的重要组成部分。在秀丽隐杆线虫的抗药性基因研究方面,发现了许多抗药性相关蛋白,如P-糖蛋白和多药耐药性相关蛋白MRP在抵抗多种药物的过程中发挥重要作用;而抗驱虫剂相关蛋白也在专门针对各种驱虫剂作用机制的研究中被发现;转录因子SKN-1、信息沉默调节蛋白SIR2、

城市污水处理厂进出水中类雌激素暴露影响评价

以稀有鮈鲫(Gobiocypris rarus)为模型动物,利用卵黄蛋白原(VTG)和生长发育指标作为类雌激素污染的生物标志物,评价了沙湖污水处理厂进出水中类雌激素暴露对稀有鮈鲫仔鱼的影响.结果表明:暴露21d后,未稀释进水和一级处理出水对稀有鮈鲫仔鱼VTG有显著诱导,各级处理水对稀有鮈鲫的生长发育也造成了一定的影响,在进水和一级处理出水暴露组中有死亡现象发生.以17β-雌二醇(E2)为阳性对照,对稀有鮈鲫VTG的诱导作标准曲线,计算进水以及各级出水的类雌激素E2的活性当量,发现污水处理厂一级和二级处理工

蓝藻高CO_2需求突变株的研究进展

“海洋863”项目(819-03-03-4); 曾呈奎海洋科学基金; 武汉市“晨光计划”的资助

Homoepitaxial growth and device characteristics of SiC on Si-face (0001) 6H-SiC

Homoepitaxial growth of SiC on a Si-face (0 0 0 1) GH-SIC substrate has been performed in a modified gas-source molecular beam epitaxy system with Si2H6 and C2H4 at temperatures ranging 1000 1450 degreesC while keeping a constant SiC ratio (0.7) in the gas phase. X-ray diffraction patterns, Raman scattering measurements. and low-temperature photoluminescence spectra showed single-crystalline SiC. Mesa-type SiC p-n junctions were obtained on these epitaxial layers, and their I-V characteristics are presented. (C) 2001 Elsevier Science B.V. All rights reserved.