圆柱绕流局部冲刷机制的实验研究

采用粒子图像测速技术和粒子图像识别技术研究了冲刷坑的演化过程及局部冲刷的流体动力机制.首先研究了动床条件下圆柱周围的床面演化过程,给出垂直对称面输沙率随时间变化以及圆柱下游垂直对称面的沙颗粒浓度和泥沙分布规律;其次针对典型冲刷坑形状固定底床,测量了圆柱下游的瞬时流场,并给出平均流场.结果表明尾流区平均剪应力较低,但垂向涡量和湍流强度较高.分析指出平均剪应力较低的尾流区域,局部冲刷的主要动力机制是尾涡和湍流的综合作用.

卫星激光通信Ⅱ地面检测和验证技术

星间激光通信终端的主要技术指标和运行性能必须事先在地面实验室条件下进行模拟检验, 因此在研制卫星激光通信终端的同时必须发展相应的系统性检测和验证平台, 主要包括激光通信性能检验、光跟瞄性能检验和光束质量检验。本文综述了卫星激光通信终端检验技术的国外进展, 介绍了我们全物理模拟的地面检测验证思路和方法。

Influence of phosphate precursors on the structures of sodium aluminophosphate sols, gels and glasses

Transparent and homogeneous aluminophosphate gels and glasses have been widely synthesized through an aqueous sol-gel route, extending significantly the glass-forming range compared to that accessible via the melt-cooling route. Different phosphorus precursors, sodium polyphosphate (NaPO3) and orthophosphate species (NaH2PO4 and/or H3PO4) were compared with regard to the macroscopic properties and the microscopic structure of the resultant gels and glasses as characterized by extensive high-resolution liquid- and solid-state NMR. Sodium polyphosphate solution results in a substantially wider composition range of homogenous gel formation than orthophosphate solutions, and the two routes produce significant structural differences in the sol and xerogel states. Nevertheless, the structures of the glasses obtained upon gel annealing above 400 degrees C are independent of the P-precursors used. (c) 2007 Elsevier B.V. All rights reserved.

中国西南地区植物群落的可入侵性与紫茎泽兰的入侵

生物入侵作为全球变化的一部分，已经引起广泛的关注;而群落可入侵性是生物入侵研究的核心和热点问题之一。本文以原产墨西哥，广泛入侵我国西南地区的紫茎泽兰(Eupatorium adenophorum)为例：首先，对西南地区被紫茎泽兰入侵的群落和生境进行了分类;然后，就地形、本地植物物种多样性、环境梯度等对群落可入侵性的影响进行了探讨;最后，对紫茎泽兰的空间分布格局进行了模拟和预测。 在小尺度上，紫茎泽兰入侵与本地植物物种多样性呈负相关，表明资源的可利用性可能是调节群落可入侵性的主导因素;本地植物物种多样性在群落演替过程中和入侵的早期抑制紫茎泽兰入侵;在大的尺度上，物理环境的变异超过了内在生物因子的重要性，本地植物物种多样性与紫茎泽兰入侵成功呈正相关。 紫茎泽兰主要通过公路和河流在我国西南地区入侵和扩散;资源的可利用性是影响公路和河流两侧群落可入侵性的关键因子。 紫茎泽兰分布中心主要在沧源、元江和西昌;位于分布区边缘的乐业、重庆和泸定有可能成为新的分布中心，并对邻近地区，尤其北面和东面的区域形成繁殖体压力;紫茎泽兰整体上有向东和向北扩散的趋势。目前主要分布在云贵高原，将来的分布区还将以云贵高原为核心。

Purification and cloning of a novel C-type lectin-like protein with platelet aggregation activity from Trimeresurus mucrosquamatus venom

TMVA, a novel C-type lectin-like protein that induces platelet aggregation in a dose-dependent manner, was purified from the venom of Trimeresurus mucrosquamatus. It consists of two subunits, alpha (15,536 Da) and beta (14,873 Da). The mature amino acid sequences of the a (135 amino acids) and beta subunits (123 amino acids) were deduced from cloned cDNAs. Both of the sequences show great similarity to C-type lectin-like venom proteins, including a carbohydrate recognition domain. The cysteine residues of TMVA are conserved at positions corresponding to those of flavocetin-A and convulxin, including the additional Cys135 in the alpha subunit and Cys3 in the beta subunit. SDS-PAGE, mass spectrometry analysis and amino acid sequence showed that native TMVA exists as two convertible multimers Of (alphabeta)(2) and (alphabeta)(4) with molecular weights of 63,680 and 128,518 Da, respectively. The (alphabeta)(2) complex is stabilized by an interchain disulfide bridge between the two alphabeta-heterodimers, whereas the stabilization of the (alphabeta)(4) complex seems to involve non-covalent interactions between the (alphabeta)(2) complexes. (C) 2002 Elsevier Science Ltd. All rights reserved.

Purification, characterization and cytokine release function of a novel Arg-49 phospholipase A(2) from the venom of Protobothrops mucrosquamatus

Group IIA phospholipase A(2) (PLA(2)) are major components in Viperidae/Crotalidae venom. In the present study, a novel PLA(2) named promutoxin with Arg at the site 49 has been purified from the venom of Protobothrops muerosquamatus by chromatography. It

热休克蛋白HSP70和gp96在抗病毒感染中的作用

热休克蛋白(HSP)是一组在进化上高度保守、具有重要生理功能的蛋白质家族,是生物在应激条件下产生的一种非特异性防御产物,在调节免疫应答和抗病毒反应中起重要作用。现简要介绍HSP70、gp96(HSP96,GRP94)这两种HSP与病毒感染的关系及在抗病毒感染中的作用。

云南省澜沧江自然保护区鸟类资源调查

2005年3～4月,对云南省临沧地区澜沧江自然保护区的鸟类资源进行了调查.通过观察和网捕调查,共计采集记录105种鸟类.结合中国科学院昆明动物研究所鸟类标本室收藏的临沧地区的207种鸟类标本,以及该地区的有关文献资料记录的84种,保护区内共有396种鸟类,隶属55 科(另4亚科)19 目,占云南省所录鸟类种数848种的47%,全国鸟类种数1331种的30%.其中国家一级保护物种2种,二级保护物种39种.保护区内记录的鸟类有留鸟307种,占所录鸟类的78%.区系成分以东洋界物种为主,有292种,占繁殖鸟类总种数的83%.亚区级区系分析表明保护区内的鸟类以滇南山地亚区和西南山地亚区的种类为主,前者成分稍多于后者,说明该地区处于由滇南山地亚区向西南山地亚区过渡的地带.结合该区鸟类垂直分布的特点,提出应加强对原生及次生阔叶林的保护,尤其是对成熟次生林的保护,因为它们对保存该保护区的大多数物种具有重要的价值.