Study on bioactivity of extracts from marine sponges in Chinese Sea

The bioactivity screening of fractions from two inter-tidal sponges collected from the north of China Yellow Sea and one sponge collected from the South Chinese Sea was reported in this study. In sponge Hymeniacidon perleve there were 9 fractions out of 15 from CHCl3 extract with anti Staphylococcus aureus activity, 9 fractions out of 19 from BuOH extract with anti Escherichia coli activity, and three fractions from CHCl3 extract which had moderate to strong activity in inhibiting Bacillus subtilis, Candida albicans, and Aspergilus niger. The fractions of Reniochalina sp. showed bioactivity against bacteria and fungi. The fractions of Acanthella acuta Schmidt showed bioactivity against S. aureus and fungi. One compound from H. perleve obtained by the bioactively directing isolation was tested for bioactivity against the human hepatoma cell line Qgy7701 (IC50 10.1 mug/ml), Burkitt's lymphoma cell line Raji (IC50 9.76 mug/ml) and chronic myelogenous leukemia K562 (IC50 1.90 mug/ml). (C) 2003 Elsevier B.V. All rights reserved.

Direct Numerical Simulation of Passive Scalar in Decaying Compressible Turbulence

The passive scalars in the decaying compressible turbulence with the initial Reynolds number (defined by Taylor scale and RMS velocity) Re=72, the initial turbulent Mach numbers (defined by RMS velocity and mean sound speed) Mt=0.2-0.9, and the Schmidt numbers of passive scalar Sc=2-10 are numerically simulated by using a 7th order upwind difference scheme and 8th order group velocity control scheme. The computed results are validated with different numerical methods and different mesh sizes. The Batchelor scaling with k(-1) range is found in scalar spectra. The passive scalar spectra decay faster with the increasing turbulent Mach number. The extended self-similarity (ESS) is found in the passive scalar of compressible turbulence.

可压衰减湍流中被动标量场的直接数值模拟及谱分析

运用高精度迎风差分方法及8阶精度群速度控制型差分格式(GVC8)对初始 Reynolds数为72，初始湍流Mach数0．2-43．9的可压衰减湍流的流场及被动标量场进行了直接数值模拟，被动标量场的Schmidt数为2~10．通过不同计算网格及不同方法的数值计算对本文结果进行了验证．指出了可压衰减湍流中被动标量能谱存在的一1律，压缩性效应使得高波数成分衰减加快．对被动标量场进行了标度律分析，发现可压湍流中被动标量场具有扩展自相似性，而压缩性效应对被动标量标度指数的影响较小．发现随着被动标量Schmidt数增加，其标度指数的奇异性增强．

蝰科(Viperidae)蝮亚科(Crotalinae)线粒体12S rRNA基因序列分析及其系统发育

对蝮亚科(蛇岛蝮Gloydius shedaoensis Zhao、黑眉蝮Gloydius saxatilis Emelianov、乌苏里蝮Gloydius ussurriensis Emelianov、竹叶青Trimeresurus stejnegeri Schmidt和分别来自不同地区的尖吻蝮Deinagkistrodon acutus Guenther、短尾蝮Gloydius brevicaudus Stejneger各两条)6种蛇共8个个体测定、分析了约370bp线粒体12S rRNA基因序列,以游蛇科链蛇属半棱鳞链蛇Dinodon semicarinatus序列为外群构建分子系统树。

中国树鼩的寄生虫调查研究

树鼩是一种新开发的小型实验动物. 研究树鼩的寄生虫对保护树鼩群体, 保证准确的实验结果, 以及寻找人类疾病的动物模型等方面都有着重要的实用意义和理论意义. 关于缅甸、越南、婆罗洲、马来西亚、马来亚、印度、和印度尼西亚树鼩的体内外寄生虫研究, 国外学者已作过许多研究(Dunn, 1963, 1964; Van Peenen等, 1967;Durette-Desset等, 1975, 1981; File, 1974; Quentin等, 1975, 1977; Chabaud等, 1975;Ohbayashi等, 1983; Betteron等, 1977; Betterton, 1979, 1980; Myers, 1960; Orihel, 1966; Nandi, 1982; Manning等, 1972; Mallin等, 1972; Schmidt等, 1977; Houdemer, 1938; Heyneman 等, 1965; Jordan,1926; Durden 等, 1984)。

大兴安岭达尔滨湖桥弯藻科(硅藻门)中国新记录植物

报道了采自大兴安岭达尔滨湖及其周围沼泽水体的硅藻门桥弯藻科中国新记录植物9种1变种,分别为新箱形桥弯藻新月变种Cymbella neocistulavar.lunataKrammer、近箱形桥弯藻Cymbella subcistulaKrammer、疏纹内丝藻Encyonema paucistriatum(Cleve-Euler)Mann、普通内丝藻Encyonema vulgareKrammer、尖锐弯肋藻Cymbopleuraacuta(Schmidt)Krammer、英吉利弯肋藻Cymbopleur

西德环境保护的出发点和环保科研的重点

<正> 我们在西德考察时,专门对位于西柏林的西德联邦环境保护局进行了访问。由四位博士(Uppenbrik,Kanowski,Schmidt-Bleek及Gregor)分别向我们介绍了情况。联邦环保局共有员工约400人。其中一半以上的雇员是大学毕业生。这些毕业生中有三分之一是科学研究人员,有三分之一是

青海湖的理化性質和生物学特性

<正> 青海省青海湖是我国最大的內陆湖,湖水的化学性貭,过去仅有俄国科学院的Schmidt以在1872年和1880年先后在青海湖南部采得的水样进行过分析,測定湖水中总盐量为11.1463—13.5937％,其中含氯量为4.2889—5.4029％。作者等于1956年8月間在青海湖調查时,曾进行了湖的东、南、西三部分湖水的理化性貭观察和分析,其結果如表所列。青海湖面积将近4,000平方公里,湖床平坦,湖水平均深度在25米以上,最深处有31.4米。湖水在

Distribution of phytoplankton in the Three-Gorge Reservoir during rainy and dry seasons

After damming of the Yangtze River, in order to explore the impacts of the Three-Gorge Dam (TGD) on the aquatic ecosystem, phytoplankton composition, abundance and biomass spatial distribution were studied in the Three-Gorge Reservoir (TGR), and the closest upstream anabranch Xiangxi River, which is 38 kin away from the Three-Gorge Dam (TGD) during August (rainy season) 2004 and April (dry season) 2005. In surveys, 6 transects (2 downstream and 4 cross-stream) and 25 stations have been investigated and 314 samples were collected from the surface to the river bed with water samplers. In TGR, 63 taxa and 60 taxa were identified in the rainy and dry seasons, respectively. In the Xiangxi River, 39 taxa were observed in the rainy and dry seasons. Algal blooms occurred in the Xiangxi River and at the influx region of the Yangtze and Xiangxi in both seasons, but had not occurred prior to damming. In the rainy season, the dominant species was Chroomonas acuta with 1.84 x 10(7) cells l(-1), and in the dry season the dominant species were Asterionella formosa and Cryptomonas ovata with 1.34 x 10(7) cells l(-1) and 1.79 x 10(6) cells(.)l(-1), respectively. In the main channel of TGR, there were no significant correlations between phytoplankton abundance and the concentrations of the main soluble nutrients. In the Xiangxi River, significant negative correlations were observed between phytoplankton abundance and nitrate (Spearman, p < 0.01, n=21), phosphate (Spearman, p < 0.05, n=21) and silicate (Spearman, p < 0.01, n=21) in the rainy season, and similar correlations were also observed with nitrate (Spearman, p < 0.05, n=28) and silicate (Speannan, p < 0.01, n=28), but not with phosphate in the dry season. Since the damming of the Yangtze River, eutrophication in the anabranch within the backwater has occurred and become severe, and the frequency of algal bloom within TGR and anabranches is expected to increase. (c) 2006 Elsevier B.V. All rights reserved.

Unveiling the morphology of buried In(Ga)As nanostructures by selective wet chemical etching: From quantum dots to quantum rings

The three-dimensional morphology of In(Ga)As nanostructures embedded in a GaAs matrix is investigated by combining atomic force microscopy and removal of the GaAs cap layer by selective wet etching. This method is used to investigate how the morphology of In(Ga)As quantum dots changes upon GaAs capping and subsequent in situ etching with AsBr3. A wave function calculation based on the experimentally determined morphologies suggests that quantum dots transform into quantum rings during in situ etching. (c) 2007 American Institute of Physics.

Tunneling magnetoresistance in devices based on epitaxial NiMnSb with uniaxial anisotropy

We demonstrate tunnel magnetoresistance junctions based on a trilayer system consisting of an epitaxial NiMnSb, an aluminum oxide, and a CoFe trilayer. The junctions show a tunneling magnetoresistance of Delta R/R of 8.7% at room temperature which increases to 14.7% at 4.2 K. The layers show a clear separate switching and a small ferromagnetic coupling. A uniaxial in-plane anisotropy in the NiMnSb layer leads to different switching characteristics depending on the direction in which the magnetic field is applied, an effect which can be used for sensor applications. (c) 2006 American Institute of Physics.

A new frequency offset estimation for OFDM-Based systems

A-new-carrier-frequency offset estimation scheme in orthogonal frequency division multiplexing (OFDM) is proposed. The scheme includes coarse frequency offset estimation and fine frequency offset estimation. The coarse frequency offset estimation method we present is a improvement of Zhang's method. The estimation range of the new method is as large as the overall signal-band width. A new fine frequency offset estimation algorithm is also discussed in this paper. The new algorithm has a better performance than the Schmidt's algorithm. The system we use to calculate and simulate is based on the high rate WLAN standard adopted by the IEEE 802.11 standardization group. Numerical results are presented to demonstrate the performance of the proposed algorithm.