Shock Tube Studies on the Nonequlibrium Electron Affinity Kinetics of Fluorine Atom at High Temperatures

To study electron affinity kinetics, a shock tube method was applied, in which the test gas was ionized by a reflected shock wave and subsequently quenched by a strong rarefaction wave. As the quenching speed of 106 K/s was reached, a nonequilibrium ionization-recombination process occurred, which was dominated by ion recombination with electrons. A Langmuir electrostatic probe was used to monitor variation in the ion number density at the reflection shock region. The working state of the probe was analyzed...

激光光子压力

<正> 光是由无静止质量的基本粒子组成,而这些粒子能对物质施加压力的认识,从理论预测到实验证实经历了漫长的时间.早在1873���,苏格兰物理学家麦克斯韦在研究光的本质时,根据他的电磁波理论,断言了光对物质能施加压力,并且予言,这种力的大小取决于

Preparation of Y1.84La0.16O3 nanopowders by oxalate co-precipitation method

Nanopowder of Y(1.84)mLa(0.16)O(3) was prepared by oxalate co-precipitation method. The powder was characterized by TG-DTA, XRD and TEM. The results show that the precursor is Re-2 (NO3)(2) (C2O4)(2)center dot 2H(2)O (Re=Y, La), and the Y1.84La0.16O3 nanopowders produced by calcining the precursor at 1000 degrees C for 4 h are 20 similar to 40 nm spherical particles and well dispersed. The powders were with high sintering activity and could be fabricated to transparent ceramic without additive at 1450 similar to 1550 degrees C in H-2 atmosphere for 3 hours. The total transmission of the transparent ceramic could reach 80%.

旌节花科的分类和系统学研究

旌节花科是东亚特有科，仅有旌节花属1属。本文研究了该科植物的生活习性、外部形态、花粉形态和外壁超微结构以及花器官发生，并根据多个DNA区段的序列探讨了科的系统位置和属下关系。在此基础上，综合各方面的证据，对旌节花科进行了全面的分类学修订，完善了该科的分类系统。主要内容包括： 　　1、习性和外部形态学 　　结合室内标本和野外考察，对旌节花科植物的生活习性、叶、花序、花和果实各个性状的变异式样、变异幅度、变异规律及其相关性进行了深入研究，并讨论了它们的分类学价值。结果表明：叶片形状、叶缘齿、花序下的叶片是否宿存以及花序是否具花序梗等性状在种间变异非常大，单个性状对旌节花属属下分类意义不大;而叶片毛被、脉序和结构，花序长度，花的大小和颜色以及果实大小等性状通常较稳定，可作为旌节花属划分种和变种的重要依据。 　　2、花粉形态学和外壁超微结构 　　在透射电镜下研究了旌节花属5个代表种和1个外类群（Crossosoma californicum）的花粉外壁超微结构，并在扫描电镜下研究了外类群Crossosomataceae 1个代表种（Crossosoma californicum）的花粉形态学特征，结合前人的研究，探讨了上述性状的分类学意义。结果表明：旌节花属植物花粉形态的共同特征是：花粉粒球形或近球形，三孔沟;外壁具穴状纹饰，穴较细小;外壁内壁分层明显，容易区分（柳叶旌节花除外），覆盖层光滑，几无附属物，柱状层明显，穿孔较少，不形成半覆盖层。各种植物花粉外壁超微结构的特征在旌节花属两个组中较一致，但其差异可作为探讨属下种的分类和系统学关系的依据。此外，对旌节花科和Crossosomataceae花粉表面纹饰和外壁超微结构的研究结果提示：这两个科与省沽油科和山茶科厚皮香亚科有较近缘的关系，而不支持这两个科的姐妹群关系。 　　3、花器官发生 　　首次对旌节花属常绿组和落叶组共2个代表种的花器官发生进行了研究，结果表明：该科植物花为功能性单性花，雌雄异株，花发育过程长达10个月，其中2-3个月是冬季休眠期。在花发育早期，雄花和雌花的发育没有差异，花性别的分化发生在花发育后期，即每年春天花开前后的2-3天，雌花中雌蕊的子房开始膨大，柱头伸长，胚珠多数，能育，而雄蕊逐渐干瘪收缩直至最后花粉不育;此时雄花的雄蕊发育良好，花丝粗壮发达，花药饱满，花粉能育，而雌蕊发育逐渐停滞直至败育。花器官发生方式为向心式，发生顺序为：苞片—外轮萼片—内轮萼片—花瓣—外轮雄蕊—内轮雄蕊—雌蕊。花萼4枚，两轮，交互对生，花瓣和雄蕊均4枚一轮几乎同时发生，花瓣覆瓦状排列。旌节花属常绿组和落叶组植物的花器官发生发育过程没有差别。 　　4、基于多个DNA区段序列的系统发育分析 　　首次选取进化速率较快的5个DNA区段：核核糖体ITS区和叶绿体rps16, ndhF，trnL-F及trnS-G-G区段，对旌节花属分别代表常绿组和落叶组的10种2变种及外类群Crossosomataceae和省沽油科3种植物的相关序列进行测定，并将上述序列合并构建系统树。研究结果表明：旌节花科作为一个单系群得到很好的支持。旌节花属落叶组和常绿组的划分在基于ITS、叶绿体4个区段单独分析及联合分析得到的系统树中没有得到支持，表现在该联合分析得到的树的两个分支与该属植物的习性和外部形态特征无关，而与它们的地理分布密切相关：其中一支主要分布在东亚的偏北部，另一支主要分布在东亚的南部地区，常绿和落叶的种类则混合在这两支中。此外，分子序列分析的结果对该属植物的分类、系统关系、起源和该科的系统位置均有重要意义。系统树显示出分布于台湾的S. sigeyosii与分布于日本的早春旌节花聚成稳定的一支，说明前者与后者，而不是与西域旌节花关系密切。叶绿体基因树与核基因树存在冲突，表明该属经历过网状进化。推测变种披针叶旌节花与云南旌节花可能是杂交起源。根据叶绿体rbcL序列得出的系统树显示旌节花科与产北美的Crossosomataceae的姊妹群关系支持率低于50%。基于最大似然树，运用罚分似然法推算出这两个科分化时间为68.25 ± 10.36 MYA，这两者共同与省沽油科近缘。 　　5、分类学研究 　　综合上述研究结果，对旌节花属进行了分类学修订。属下不设立组;确认该属植物有6种6变种，其中中国特有种3个，变种3个。5种5变种被作为新异名，新组合3个，其中2个改级新组合。对西域旌节花、云南旌节花和滇缅旌节花等进行了模式指定。本文还给出了分种和变种检索表、各类群的形态学描述、地理分布图、标本引证和讨论等。 　　

无指盘臭蛙臭蛙肽及其基因和在制药中的应用

本发明涉及一种无指盘臭蛙臭蛙肽及其基因和在制药中的应用，属于生物医学领域。无指盘臭蛙臭蛙肽是无指盘臭蛙臭蛙肽基因编码的一种单链多肽，分子量1814.11道尔顿，等电点8.08，多肽全序列一级结构为： Gly Cys Ser Arg Trp Ile Ile Gly Ile His Gly Gln Ile Cys Arg Asp。(GCSRWIIGIHGQICRD)。编码无指盘臭蛙臭蛙肽的基因由312个核苷酸组成，其中编码成熟无指盘臭蛙臭蛙肽为第141-189位核苷酸。人工合成的无指盘臭蛙臭蛙肽具有很强的抑制细菌和真菌生长的作用，可以作为制备病原微生物感染疾病的治疗药物被应用。本发明的无指盘臭蛙臭蛙肽具有结构简单、人工合成方便、抗菌谱系广、抗菌活性强的特点。

A Plant Needs Ants like a Dog Needs Fleas: Myrmelachista schumanni Ants Gall Many Tree Species to Create Housing

Hundreds of tropical plant species house ant colonies in specialized chambers called domatia. When, in 1873, Richard Spruce likened plant-ants to fleas and asserted that domatia are ant-created galls, he incited a debate that lasted almost a century. Alth

Human immunodeficiency virus-1 genotypic drug resistance among volunteer blood donors in Yunnan, China

BACKGROUND: Drug resistance profiles of human immunodeficiency virus-1 (HIV-1) in treatment-naive infections have been reported in developed countries. However, little is known in developing countries, including China, especially in treatment-naive volunt

Molecular evidence for diphyly of the Asian catfish family Amblycipitidae (Teleostei: Siluriformes) and exclusion of the South American Aspredinidae from Sisoroidea

Amblycipitidae Day, 1873 is an Asian family of catfishes (Siluriformes) usually considered to contain 28 species placed in three genera: Amblyceps (14 spp.), Liobagrus (12 spp.) and Xiurenbagrus (2 spp.). Morphology-based systematics has supported the monophyly of this family, with some authors placing Amblycipitidae within a larger group including Akysidae, Sisoridae and Aspredinidae, termed the Sisoroidea. Here we investigate the phylogenetic relationships among four species of Amblyceps, six species of Liobagrus and the two species of Xiurenbagrus with respect to other sisoroid taxa as well as other catfish groups using 6100 aligned base pairs of DNA sequence data from the rag1 and rag2 genes of the nuclear genome and from three regions (cyt b, COL ND4 plus tRNA-His and tRNA-Ser) of the mitochondrial genome. Parsimony and Bayesian analyses of the data indicate strong support for a diphyletic Amblycipitidae in which the genus Amblyceps is the sister group to the Sisoridae and a clade formed by genera Liobagrus and Xiurenbagrus is the sister group to Akysidae. These taxa together form a well supported monophyletic group that assembles all Asian sisoroid taxa, but excludes the South American Aspredinidae. Results for aspredinids are consistent with previous molecular studies that indicate these catfishes are not sisoroids, but the sister group to the South American doradoid catfishes (Auchenipteridae + Doradidae). The redefined sisoroid clade plus Bagridae, Horabagridae and (Ailia + Laides) make up a larger monophyletic group informally termed "Big Asia." Likelihood-based SH tests and Bayes Factor comparisons of the rag and the mitochondrial data partitions considered separately and combined reject both the hypothesis of amblycipitid monophyly and the hypothesis of aspredinid inclusion within Sisoroidea. This result for amblycipitids conflicts with a number of well documented morphological synapomorphies that we briefly review. Possible nomenclatural changes for amblycipitid taxa are noted.

A new species of Allocreadium (Trematoda : Allocreadiidae) from freshwater fishes in the Danjiangkou Reservoir in China

A new species of Allocreadium, Allocreadium danjiangensis n. sp., is described from the intestine of several species of freshwater fish, including Abbottina rivularis (Basilewsky, 1855), Sarcocheilichthys nigripinnis nigripinns (Gunther, 1873), Gnathopogon argentatus (Sauvage et Dabry 1874), Opsariichthys uncirostris bidens (Gunther, 1873), and Erythroculter mongolicus mongolicus (Basilewsky, 1855) (Cyprinidae) from the Danjiangkou Reservoir in central China. The main morphological characters of the new species are as follows: vitelline follicles numerous, extending from the level of acetabulum to posterior extremity, distributed over both sides around the ceca; cirrus sac relatively large, developed, lying obliquely anterior to the acetabulum, extending from the level of the intestinal bifurcation to the central level of acetabulum, and overlapping left or right cecal; and ovary much smaller than testes, generally close to or even overlapping the anterior border of anterior testis. Observation by scanning electron microscopy shows only 2 kinds of tegumental formations, i.e., papillae and tubercles, instead of 3 types of tegumental formations, i.e., papillae, bosses, and minute sensor receptors observed on other species of the Allocreadiidae. The tegumental striations of the present species vary on the different parts of the body. In addition, a new structure, identified as the "groove" with a tonguelike tubercle, was observed on the inner wall of acetabulum.

基于3×3耦合器的迈克尔逊干涉仪相位特性分析

国家８６３计划（２００７ＡＡ０３Ｚ４１５）

基于LDA模型的文本分割

文本分割在信息提取、文摘自动生成、语言建模、首语消解等诸多领域都有极为重要的应用.基于LDA模型的文本分割以LDA为语料库及文本建模,利用MCMC中的Gibbs抽样进行推理,间接计算模型参数,获取词汇的概率分布,使隐藏于片段内的不同主题与文本表面的字词建立联系.实验以汉语的整句作为基本块,尝试多种相似性度量手段及边界估计策略,其最佳结果表明二者的恰当结合可以使片段边界的识别错误率远远低于其它同类算法.

多室流化床内固体颗粒的流动行为研究——褐煤有效利用项目的冷态实验

基于褐煤热分解时既除去煤中的氮、又可回收焦油这一特点,该文针对褐煤的水分、灰分含量高及热解时释放的挥发份多但燃烧热值低而导致褐煤总的热值低、热利用效率不高的问题,提出了一种有效利用褐煤的方案:利用多室流化床技术,褐煤首先于缺氧条件下在热分解室内热解,释放出挥发份、水分、从挥发份中冷凝出焦油;然后热解得到的高热值的褐煤焦炭通过多室流化床的室与室之间分隔板上的开孔流入燃烧室内燃烧.这样处理既克服了褐煤热值低的缺点,又利用了其挥发份多的特点,收集到焦油.该文的研究工作作为该方案的冷态实验部分,在小型多室流化床冷态实验装置上,对固体颗粒(如由褐煤得到的焦炭等)通过多室流化床的室与室之间的分隔板上之开孔流通的行为及规律进行了研究. 

基于3×3耦合器的迈克耳孙干涉仪相位特性分析

研究了基于3×3耦合器的非平衡迈克耳孙干涉仪的相位特性。由光纤耦合器的散射矩阵理论,推导出了当3×3耦合器分光比不均匀时,干涉仪三路输出信号相位差的表达式。根据实际使用的3×3耦合器各通道的插入损耗,经计算与修正得到其散射矩阵,并求出干涉仪三路输出信号的相位差分别为120.21°、120.77°和119.02°,与理想值120°的偏差在1°以内。实验测得的干涉仪三路输出信号的相位差随时间随机变化,经分析是由光偏振态随机变化引起的。相位差与理想值120°的偏离均在1°以内,符合理论分析得到的结论。