超声速气流中含灰气体点源流动特性

采用Lagrange方法，研究了超声速气流中含灰气体点源的流动特性，求得了对称辆附近激波层内的流动参数。计算数值模拟结果揭示了大惯性颗粒在激波层内沿着相互交叉的振荡轨迹运动，颗粒分布形成了高、低密度层交错出现的“多层结构”，而且粒子子在轨迹包络线附近急剧聚集。

高温下CF_4在H_2中解离的反应动力学研究

用单脉冲激波管研究了有少量ＣＦ３Ｃｌ参予下的ＣＦ４与Ｈ２的混合物在高温下的反应动力学，发现主要产物为Ｃ２Ｆ４和ＣＦ３Ｈ．对实验结果的分析表明，反应过程为一个双中心链反应。始发反应为ＣＦ３Ｃｌ的Ｃ—Ｃｌ键的断裂，继之以由Ｈ２和ＣＦ４为媒介的双中心链传递，最后测得温度由１０００至１０８０Ｋ，压力为０．１ＭＰａ下的ＣＦ４表观分解速率常数为Ｋｅｆｆ＝１０１３．７ｅｘｐ（－５５０００／ＲＴ）１１／２ｍｏｌ－１ｓ－１对这一结果进行分析，得到以下相关的反应速度常数ｋ（ＣＦ３Ｃｌ→ＣＦ３＋Ｃｌ?）＝１０１５ｅｘｐ（－８１０００／ＲＴ）ｓ－１ｋ（ＣＦ３＋Ｈ２→ＣＦ３Ｈ＋Ｈ?）＝１０８．６ｅｘｐ（－８８００／ＲＴ）１?ｍｏｌ－１?ｓ－１ｋ（ＣＦ４＋Ｈ?→ＣＦ３?＋ＨＦ）＝１０１１．４ｅｘｐ（Ｇ２００００／ＲＴ）１?ｍｏｌ－１?ｓ－１ｋ（ＣＦ３?＋Ｈ?→ＣＦ３Ｈ）＝１０８．０１?ｍｏｌ－１?ｓ－１

IP Simulation of Micro Gas Flows under 3-D Head Sliders

Gas film lubrication of a three-dimensional flat read-write head slider is calculated using the information preservation (IP) method and the direct simulation Monte Carlo (DSMC) method, respectively. The pressure distributions on the head slider surface at different velocities and flying heights obtained by the two methods are in excellent agreement. IP method is also employed to deal with head slider with three-dimensional complex configuration. The pressure distribution on the head slider surface and the net lifting force obtained by the IP method also agree well with those of DSMC method. Much less (of the order about 10(2) less) computational time (the sum of the time used to reach a steady stage and the time used in sampling process) is needed by the IP method than the DSMC method and such an advantage is more remarkable as the gas velocity decreases.

Electron injection by a nanowire in the bubble regime

The triggering of wave-breaking in a three-dimensional laser plasma wake (bubble) is investigated. The Coulomb potential from a nanowire is used to disturb the wake field to initialize the wave-breaking. The electron acceleration becomes more stable and the laser power needed for self-trapping is lowered. Three-dimensional particle-in-cell simulations were performed. Electrons with a charge of about 100 pC can be accelerated stably to energy about 170 MeV with a laser energy of 460 mJ. The first step towards tailoring the electron beam properties such as the energy, energy spread, and charge is discussed. (C) 2007 American Institute of Physics.

激光稳频的共焦法布里-珀罗干涉仪

针对多普勒激光雷达激光源短期频率漂移低于1 MHz的要求,设计了一种共焦干涉仪作为频率标准进行稳频。通过对三种不同材料制成的共焦法布里-珀罗(Fabry-Perot)干涉仪中心频率随温度漂移情况进行分析对比,选用零膨胀微晶玻璃材料制作共焦法布里-珀罗干涉仪,腔镜和隔离器通过光胶的方式进行组合,并且置于温控精度优于0.01 K的双层密封温控箱中。经过实验测量,共焦法布里-珀罗干涉仪的自由光谱范围为370 MHz,透射谱半峰全宽(FWHM)为1.7 MHz,精细度为220。采用该共焦干涉仪进行稳频,理论稳频精度可达0.15 MHz,满足激光多普勒雷达单频激光源的稳频要求。

中国澜沧江(鱼芒)科鱼类种群现状及洄游原因分析

我国曾经记录有(鱼芒)科鱼类4种.国际上近年来对(鱼芒)科鱼类的分类进行了许多重要的修订,物种数量已达3属22种.我国的(鱼芒)科鱼类也因长时间没有进行及时的分类修订而存在许多疑问.基于国内自1960年以来所收集的珍贵标本和记录,确认我国记录有(鱼芒)科鱼类1属3种.它们是:长丝(鱼芒)(Pangasius sanitwongsei Smith)、贾巴(鱼芒)(Pangasius djambal Bleeker)、短须(鱼芒)(Pangasius micronemus Bleeker).在此基础上,根据掌握的资料对我国(鱼芒)科鱼类的种群现状和濒危原因、洄游的性质及洄游群体数量下降原因以及水电站建设对大型洄游鱼类的影响进行了分析.以往记录显示,捕获时间都集中于4-5月份,无冬季捕获记录.捕获季节与(鱼芒)科鱼类产卵繁殖季节高度吻合,提示其上溯到我国澜沧江下游应属生殖洄游,而不是索饵洄游.被捕获记录主要出现于20世纪60-70年代,之后则数量锐减.导致这种情况发生的主要原因可能有三方面:1)下游湄公河对(鱼芒)科鱼类的捕捞压力过大;2)湄公河-澜沧江航运船只对(鱼芒)科鱼类有损害作用;3)由于西南季风变化的影响,澜沧江径流量发生变化,可能间接导致(鱼芒)科鱼类洄游行为发生改变.分析显示,(鱼芒)科鱼类的洄游与3-4月份澜沧江流量呈密切相关规律,提示适合鱼类产卵的雨季及西南夏季风比往年较早到达该地区,从而激发它们较往年提前启动生殖洄游,并且溯河的高度较高.以往的捕获记录还表明,(鱼芒)科鱼类主要洄游至景洪下方的澜沧江河段及支流补远江,上述水域是其喜好的产卵场之一.景洪大桥以下的干支流不适合建设水电站,因为电站大坝必然会阻断(鱼芒)科鱼类的繁殖洄游,影响其繁殖活动.而景洪大桥上方的干流电站不在(鱼芒)科鱼类正常繁殖洄游通道中,大坝阻隔作用对(鱼芒)科鱼类的影响相对较小.建议把补远江建设成为鱼类和水生生物保护区.

卵黄萤荧光素再生酶基因的克隆与序列分析

目的 克隆和分析荧光素再生酶基因(LRE).方法 通过GeneBank中已知的荧光素再生酶基因保守区段设计引物,利用5'RACE(rapid-amplification of cDNA ends)和3'RACE技术克隆了来自云南省两双版纳州的卵黄萤(Luciola ovalis)荧光素再生酶基因cDNA和全基因序列.通过GeneBank、National Center for Bioteclmology Information和ProDom at the ExPASy Server软件和数据库进行序列分析.结果 卵黄萤荧光素再牛酶的cDNA序列和基因序列存在2个不同碱基位点,但是它们编码的荧光素再生酶是相同的.卵黄萤荧光素再生酶基因全长(从起始密码子到终止密码子)为1131 bp,包含5个外显子4个内含子,其cDNA 序列为1008 bp,包含924bp的荧光素酶基因开放阅读框和84 bp的3'UTR序列.卵黄萤荧光素酶基因的开放阅读框编码1个307个氨基酸的蛋白质.它与北美萤火虫(Photinus pyralis)荧光素再生酶在碱基序列和氨基酸序列上分别有61.8%和53.3%的相似性.结论 成功地克隆了荧光素再生酶的cDNA和基因序列,为其在基因工程中的应用奠定了基础.

湖北省若干浅水湖泊沉积物有机质与富营养化的关系

分析了湖北省月湖、龙阳湖、后官湖、梁子湖、牛山湖、保安湖、鲁湖等7个湖泊表层沉积物有机质、总氮与总磷的含量,并考察了其在月湖、龙阳湖沉积物中的垂直分布及月湖、龙阳湖与保安湖表层沉积物的颗粒组成,结果表明:位于城市与城郊的月湖与龙阳湖表层沉积物有机质含量较高,且表现出沿岸带较丰富的空间分布特征。在垂直及水平方向上,有机质与总氮和总磷含量均显著相关,颗粒组成与有机质和总氮含量亦显著相关。有机质富集应是促进城市湖泊富营养化的重要因素。

Androgen receptor targets NFKB and TSPI to suppress prostate tumor growth in vivo

The androgen role in the maintenance of prostate epithelium is subject to conflicting opinions. While androgen ablation drives the regression of normal and cancerous prostate, testosterone may cause both proliferation and apoptosis. Several investigators note decreased proliferation and stronger response to chemotherapy of the prostate cancer cells stably expressing androgen receptor (AR), however no mechanistic explanation was offered. In this paper we demonstrate in vivo anti-tumor effect of the AR on prostate cancer growth and identify its molecular mediators. We analyzed the effect of AR on the tumorigenicity of prostate cancer cells. Unexpectedly, the AR-expressing cells formed tumors in male mice at a much lower rate than the AR-negative controls. Moreover, the AR-expressing tumors showed decreased vascularity and massive apoptosis. AR expression lowered the angiogenic potential of cancer cells, by increasing secretion of an anti-angiogenic protein, thrombospondin-1. AR activation caused a decrease in RelA, a subunit of the pro-survival transcription factor NF kappa B, reduced its nuclear localization and transcriptional activity. This, in turn, diminished the expression of its anti-apoptotic targets, Bcl-2 and IL-6. Increased apoptosis within AR-expressing tumors was likely due to the NF kappa B suppression, since it was restricted to the cells lacking nuclear (active) NF kappa B. Thus we for the first time identified combined decrease of NF kappa B and increased TSP1 as molecular events underlying the AR anti-tumor activity in vivo. Our data indicate that intermittent androgen ablation is preferable to continuous withdrawal, a standard treatment for early-stage prostate cancer. (C) 2007 Wiley-Liss, Inc.

Influence of growth parameters of frequency-radio plasma nitrogen source on extending emission wavelengths from 1.31 mu m to 1.55 mu m GaInNAs/GaAs quantum wells grown by molecular-beam epitaxy

High (42.5%) indium content GaInNAs/GaAs quantum wells with room temperature emission wavelength from 1.3 mu m to 1.5 mu m range were successfully grown by Radio Frequency Plasma Nitrogen source assisted Molecular Beam Epitaxy. The growth parameters of plasma power and N-2 How rate were optimized systematically to improve the material quality. Photoluminescence and transmission electron microscopy measurements showed that the optical and crystal quality of the 1.54 mu m GaInNAs/GaAs QWs was kept as comparable as that in 1.31 mu m.

Microstructure and photoluminescence of a-SiOx : H

Two strong photoluminescence (PL) bands in the spectral range of 550-900 nm have been observed at room temperature from a series of a-SiOx:H films fabricated by plasma-enhanced chemical vapor deposition (PECVD) technique. One is composed of a main band in the red-light region and a shoulder; the other is located at about 850 nm, only found after 1170 degrees C annealing in N-2 atmosphere. In conjunction with infrared (IR) and micro-Raman spectra, it is thought that the two PL bands are associated with a-Si clusters in the SiOx network and nanocrystalline silicon in SiO2, respectively.

Pool boiling heat transfer of ultra-light copper foam with open cells

High speed visualizations and thermal performance studies of pool boiling heat transfer on copper foam covers were performed at atmospheric pressure, with the heating surface area of 12.0 mm by 12.0 mm, using acetone as the working fluid. The foam covers have ppi (pores per inch) from 30 to 90, cover thickness from 2.0 to 5.0 mm, and porosity of 0.88 and 0.95. The surface superheats are from -20 to 190 K, and the heat fluxes reach 140 W/cm(2). The 30 and 60 ppi foam covers show the periodic single bubble generation and departure pattern at low surface superheats. With continuous increases in surface superheats, they show the periodic bubble coalescence and/or re-coalescence pattern. Cage bubbles were observed to be those with liquid filled inside and vented to the pool liquid. For the 90 ppi foam covers, the bubble coalescence takes place at low surface superheats. At moderate or large surface superheats, vapor fragments continuously escape to the pool liquid. Boiling curves of copper foams show three distinct regions. Region I and II are those of natural convection heat transfer, and nucleate boiling heat transfer for all the foam covers. Region III is that of either a resistance to vapor release for the 30 and 60 ppi foam covers, or a capillary-assist liquid flow towards foam cells for the 90 ppi foam covers. The value of ppi has an important effect on the thermal performance. Boiling curves are crossed between the high and low ppi foam covers. Low ppi foams have better thermal performance at low surface superheats, but high ppi foams have better one at moderate or large surface superheats and extend the operation range of surface superheats. The effects of other factors such as pool liquid temperature, foam cover thickness on the thermal performance are also discussed.