鱼类病原菌中R~+质粒的检出及其特性

本文研究了5个属的15株鱼类病原菌对17种抗菌药物的耐药性。其中，对β-内酰胺类和红霉素的耐药率最高，对妥布霉素最敏感。以E．coliK-12RC85为受体菌，鱼类病原菌为供体菌，采用细菌接合试验，从耐氨苄青霉素、四环素和磺胺的嗜水气单胞菌CJ26株中检测到一株耐四环素和磺胺的可自身传递的R质粒pWH9601。它对四环素的抗性可被四环素类药物所诱导。pWH9601上的耐药基因在供体菌和受体菌中的表达水平有所不同。该质粒可在37℃下，15min内通过接合方式，转移到E．coliK－12RC85中，而且这种转

三峡库区地表水和鱼体中甲基汞含量的分布特征

首次报道了三峡库区鲤鱼（Ｃｙｐｒｉｎｕｓｃａｒｐｉｏ）、铜鱼（Ｃｏｒｅｉｕｓｈｅｔｅｒｏｄｏｎ）、长吻鱼危（Ｌｅｉｏｃａｓｉｓｌｏｎｇｉｒｓｔｒｉｓ）和翘嘴鱼白（Ｃｕｌｔｅｒａｌｂｕｅｎｕｓ）各组织器官中甲基汞的含量水平，以及地表水甲基汞的浓度。证明鱼体肌肉中甲基含量最高，其次为肝脏、肾脏、脾脏。各组织器官中甲基汞含量与有机汞、无机汞和总贡含量呈显著线性关系；水库鲤鱼甲基汞含量高于河流鲤鱼；三峡库区江段江水甲基汞浓度与加拿大未被污染湖泊湖水相当。

江苏串珠藻属一新种

<正>植物体丛生（图版2:4）,睢雄同株，高10～18cm.分板稠密且不规则，它不仅发生在轮处，也出自节间（图版2：1），轮

温度对草鱼能量收支的影响

于1992年4月-1992年5月在22，26及3℃下，以莴苣叶为食物，不限量摄食，测定草鱼的能量收支。结果表明，草鱼摄食率及生长率均随温度上升而增加；最大摄食率（Cw：％　W／d）与水温（T：℃）的关系为：CW=0．0405T2.324；温度对食物能分配于能量收支各组分的比例没有显著影响，在3个温度下测定的平均能量收支式为：100C=29.89F＋3．30U＋52．48R十14．34G，式中C为食物能，F为排粪能，U为排泄能，R为代谢能，G为生长能。

武汉东湖浮游动物群落结构的研究

对１９９１年武汉东湖不同湖区浮游动物群落结构的研究表明，Ⅰ、Ⅱ、Ⅲ站浮游动物的数量为１２２７８２、７０４１５和１８１８４个·Ｌ（－１），并随水体富营养化程度增加而增加．生物量分别为８．６３９、５．８７２和２．０８２ｍｇ·Ｌ（－１）。大于１ｍｍ的甲壳动物个体频度为０．１５、０．３０、０．４１．其体长随鱼产量的增加而缩小．最后，对影响东湖浮游动物群落结构的主要生态因子进行了讨论．

柱孢鱼腥藻固氮酶防氧的呼吸保护

柱孢鱼腥藻生长在缺氮情况下,发现其固氮活性增加的同时也减少了对氧的敏感性。缺氮生长细胞的乙炔还原活性给氧抑制一半时的氧分压(pO_2)是0.5atm.,而有氮生长细胞的半抑制浓度为0.35atm.。这表明蓝藻有可能通过增加呼吸耗氧而提高了它的固氮酶活性。呼吸作用与固氮酶活性之间存在着密切的关系。无论在有氮、缺氮还是光诱导固氮酶形成的情况下,其固氮活性均随着呼吸速率的变化而变化。本研究结果,支持了柱孢鱼腥藻固氮酶的主要防氧手段是呼吸保护的观点。

长江中游(武汉—岳阳江段)豚类的分布、生态、行为和保护

<正> 白暨豚Lipotes vexillifer Miller和江豚Neophocaena asiaeorientalis(Pilleri and Gihr)这两种动物,中国人民早就对它们有所认识,并作了记述(图1,2)。已发现的最早记述这两种豚类的文献,是在公元前200年左右的西汉时代写成的《尔雅》一书,记载了“暨,是鲢”。晋代的郭璞(公元276—324年),为《尔雅》作注释时,进一步对白暨豚的形态特征和生活习性作了科学的描述,并将白暨豚和江豚区别开来。他是这样记述的:“鱀(鱼昔)属

太湖所产银鱼的初步研究

<正> 银鱼是太湖的名产,以夏季的产量为最高,除一部分在附近市场鲜售外,大部分就在船上晒制成为银角干,再销售各地。到了冬季,渔民以价值较银鱼为高的鱼类为捕捞对象,所以专捕银鱼的船大大地减少,捕捞所得的大部分供市场鲜售。作者从1951年1月起至1952年3月止,对于银鱼作了周年的采集与观察。采集的地点,有时在五里湖,有时在太湖(界于苏州与无锡之间的一段区域)。五里湖是太

Response of Microcystis to copper stress - Do phenotypes of Microcystis make a difference in stress tolerance?

To elucidate the role of phenotype in stress-tolerant bloom-forming cyanobacterium Microcystis, two phenotypes of M. aeruginosa-unicellular and colonial strains were selected to investigate how they responded to copper stress. Flow cytometry (FCM) examination indicated that the percents of viable cells in unicellular and colonial Microcystis were 1.92-2.83% and 72.3-97.51%, respectively, under 0.25 mg l(-1) copper sulfate treatment for 24 h. Upon exposure to 0.25 mg l(-1) copper sulfate, the activities of antioxidative enzyme, such as superoxide dismutase (SOD) and catalase (CAT), were significantly increased in colonial Microcystis compared to unicellular Microcystis. Meanwhile, the values of the photosynthetic parameters (F-v/F-m, ETRmax and oxygen evolution rate) decreased more rapidly in unicellular Microcystis than in colonial Microcystis. The results indicate that colonial Microcystis has a higher endurance to copper than unicellular Microcystis. This suggests that the efficient treatment concentration of copper sulfate as algaecides will be dependent on the phenotypes of Microcystis. (C) 2006 Elsevier Ltd. All rights reserved.

Distribution and morphology of two endemic gomphonemoid species, Gohphonema kaznakowi Mereschkowsky and G-yangtzensis Li nov sp in China

The morphology of Gomphonema kaznakowi Mereschkowsky was investigated using light microscopy. This species has two morphologically distinct areas near the headpole; an unornamented and an ornamented area. The two areas are distinguished from each other by the combination of size and striae number. A new species, Gomphonema yangtzensis Li nov. sp. is identified based on an ornamented area near the headpole. G. kaznakowi is reported from the upper and middle part of the Yangtze River, and was also found in the upper section of the Yellow River. G. yangtzensis was found in the upper area of the Yellow River and the middle of the Yangtze River. Their limited distribution may be due to certain environmental conditions or a different dispersal rate. Both species are illustrated.

Analysis of lateral current spreading in solar cell devices by spatially-resolved electroluminescence

Spatially-resolved electroluminescence (EL) images from solar cells contain information of local current distribution. By theoretical analysis of the EL intensity distribution, the current density distribution under a certain current bias and the sheet resistance can be obtained quantitatively. Two-dimensional numerical simulation of the current density distribution is employed to a GaInP cell, which agrees very well with the experimental results. A reciprocity theorem for current spreading is found and used to interpret the EL images from the viewpoint of current extraction. The optimization of front electrodes is discussed based on the results. (C) 2010 American Institute of Physics. [doi:10.1063/1.3431390]

1.3 mu m InAs/GaAs self-assembled quantum dots grown on In0.2Ga0.8As-GaAs combined strain-buffer layer

Optical properties and surface structures of InAs/CaAs self-assembled quantum dots (QDs) grown on 2 nm In-0.2 Ga0.8As and x ML GaAs combined strain-buffer layer were investigated systematically by photoluminescence ( PL) and atomic force microscopy (AFM). The QD density increased from similar to 1.7 x 10(9) cm(-2) to similar to 3.8 x 10(9) cm(-1) due to the decreasing of the lattice mismatch. The combined layer was of benefit to increasing In incorporated into dots and the average height-to-width ratios, which resulted in the red-shift of the emission peaks. For the sample of x = 10 ML, the ground state transition is shifted to 1350 nm at room temperature.

Effect of interaction between periodic delta-doping in both well and barrier layers on modulation of superlattice band structure

The modulation of superlattice band structure via periodic delta-doping in both well and barrier layers have been theoretically investigated, and the importance of interaction between the delta-function potentials in the well layers and those in the barrier layers on SL band structure have been revealed. It is pointed out that the energy dispersion relation Eq. (3) given in [G. Ihm, S.K. Noh, J.I. Lee, J.-S. Hwang, T.W. Kim, Phys. Rev. B 44 (1991) 6266] is an incomplete one, as the interaction between periodic delta-doping in both well and barrier layers had been overlooked. Finally, we have shown numerically that the electron states of a GaAs/Ga0.7Al0.3As superlattice can be altered more efficiently by intelligent tuning the two delta-doping's positions and heights. (c) 2007 Elsevier B.V. All rights reserved.

简评AES工作模式

工作模式是一个算法，它刻画了如何利用分组密码提供信息安全服务.在给AES征集工作模式标准的过程中，NIST收到了15个候选工作模式.简要介绍15个候选工作模式及它们的设计思想。