溪河大尾溞Leydigia fluminea Chen，1993（甲壳纲：双甲目）雄体的发现

溪河大尾溞ＬｅｙｄｉｇｉａｆｌｕｍｉｎｅａＣｈｅｎ，１９９３（甲壳纲：双甲目）雄体的发现陈受忠，唐文乔，刘焕章中国科学院水生生物研究所武汉４３００７２枝角类（Ｃｌａｄｏｃｅｒａ）的繁殖方式以孤雌生殖为主，雄性只在一定季节或特种条件下短期出现。而且还有...

黄淮海平原封丘试区水体营养状态的综合评价

选择封丘试区内有代表性的7类水体,对其营养状态进行综合评价和聚类分析,初步提出了用于水体营养状态评价的方法和标准。结果表明:各水体营养状态可依其植物组成而明显分成挺水植物、沉水植物和浮游植物型等,而且草型水体的营养指数均高于藻型水体。总的看来,该试区各类水体营养状态较为相似,营养指数均很高,属富营养—重富营养型,渔业发展潜力较大。

鲢鳙鱼流行性传染病的流行病学和细菌病因的初步研究

1990年3～10月,作者对湖北、湖南,河南三省部分地区的28个养殖场进行了鲢鳙鱼流行病学调查和致病菌的初步研究。结果显示:在调查范围内发病率达60%以上;受感染的除鲢、鳙外,还有鲫、鳊(鲂)、鲤、草鱼以及其它野杂鱼、河蚌;分离到138株细菌,经鉴定可归为三类,早期(3～4月)出现的鲁克氏耶尔森菌(Yersinia ruckeri)、中后期(5月下旬以后)出现的产气单胞菌(Aeromonas sp.)及弧菌(Vibrio sp.)。结合水质环境条件分析,致病细菌是继发侵入者,原发病因除水体的理化因子外,不

鱼类肠肾虫一新种

<正> 1986年6月,作者在四川涪陵的中华倒刺鲃(Barbodes sinensis Bleeker)后肠检获一种纤毛虫,根据虫体的特征及前人的分类方法,鉴定为斜口科(Plagiotomidae),肠肾虫属(Nyctotherus)一新种,定名为长江肠肾虫(Nyctotherus changjiangensis sp.nov.) 寄生虫的形态研究,除活体观察外,均采用纤毛虫常规涂片染色方法观察。测量了10个以上标本,测量单位为微米。模式标本保存于中国科学院水生生物研究所鱼病室。长江肠肾虫(新种)Nyct

茭草叶饲养草鱼效果

<正> 茭草又称野菰(Zizania latifolia),广泛分布于我国内陆水体,在湖北省洪湖中,茭草是沿岸呈环带状分布的优势挺水植物。由于该湖年平均水深仅1.35米,底泥肥沃,适于茭草生长繁殖,群落面积已达22.7万亩,占该湖总面积的42％。每年生产茎叶干物质达15万吨以上,但绝大部分废弃分解还湖,未被充分利用。根据洪湖大水面水体生物生产力综合开发利用研究计划,我们对茭草不同器官化学成分分析的结果证明,茭草乃优质饲料,茭草叶含粗蛋白16.8—18.7％,其必需氨基酸组成比例与草鱼肌

Serum concentrations of gonadotropins and steroid hormones of Neophocaena phocaenoides asiaeorientalis in middle and lower regions of the Yangtze River

As a relatively isolated and unique freshwater population, the Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientalis) is the most endangered subpopulation of this species. The objective of this study was to improve our understanding of their reproductive endocrinology by measuring (radioimmunoassay) serum concentrations of FSH, LH, estradiol (E-2), progesterone (P-4) and testosterone (T-2) in free-ranging animals. Blood samples were collected from 66 Yangtze finless porpoises (41 males and 25 females) captured in the middle and lower reaches of the Yangtze River. Based on significant variation of serum T-2 concentrations in males with body length (BL) > 138 cm, we inferred that they were mature; in these animals, there were significant seasonal variations in serum T-2 concentrations, with the highest concentrations in March and April (502.0 +/- 319.8 ng/dL, mean +/- S.D.) and the lowest in December (79.4 +/- 83.2 ng/dL). Serum T-2 concentrations positively correlated with serum concentrations of LH and weakly correlated with serum concentrations of E-2, whereas there was a significant negative correlation between serum LH and FSH concentrations in males > 138 cm. The smallest apparently pregnant female porpoise had a BL of 130 cm. Serum P-4 concentrations ranged from 13.2 to 112.4 ng/mL (43.9 +/- 28.3 ng/mL) in pregnant females, and fluctuated under 1.0 ng/mL in non-pregnant females with BL > 130 cm. Serum LH concentrations were significantly higher in non-pregnant females > 130 cm versus those females < 130 cm. To our knowledge, this is the first study of endocrine-related maturity and seasonal breeding characteristics of the Yangtze finless porpoise. (c) 2006 Elsevier Inc. All rights reserved.

Extracellular carbohydrate polymers from five desert soil algae with different cohesion in the stabilization of fine sand grain

Extracellular polymeric substances (EPS) from four filamentous cyanobacteria Microcoleus vaginatus, Scytonema javanicum, Phormidium tenue and Nostoc sp. and a coccoid single-cell green alga Desmococcus olivaceus that had been separated from desert algal crusts of Tegger desert of China, were investigated for their chemical composition, structure,and physical properties. The EPS contained 7.5-50.3% protein (in polymers ranging from 14 to more than 200 kD, SDS-PAGE) and 16.2-46.5% carbohydrate (110-460 kD, GFC). 6-12 kinds of monosaccharides, including 2-O-methyl rhamnose, 2-O-methyl glucose, and N-acetyl glucosamine were found. The main carbohydrate chains from M. vaginatus and S. javanicum consisted mainly of equal proportion of Man, Gal and Glc, that from P. tenue consisted mainly of arabinose, glucose and rhamnose. Arabinose was present in pyranose form, mainly alpha-L 1 --> 3 linked, with branches on C4 of almost half of the units. Glucose was responsible for the terminal units, in addition of having some units as beta1 --> 3 and some as beta1 --> 4 linked. Rhamnose was mainly 1 --> 3 linked with branches on C2 on half of the units. The carbohydrate polymer from D. olivaceus was composed mainly of beta1 --> 4 linked xylose, galactose and glucose. The galactose part was present both in beta-pyranose and -furanose forms. Arabinose in alpha-L-furanose form was mainly present as 1 --> 2 and 1 --> 2, 5 linked units, rhamnose only as alpha 1 --> 3 and xylose as beta 1 --> 4. The backbone of the polysaccharide from Nostoc sp. was composed of beta-1 --> 4 linked xylose, galactose and glucose. Most of the glucose was branched on position C6, terminal glucose and 2-O-methyl glucose units are also present. The relationship between structure, physical properties and potential biological function is discussed. (C) 2003 Elsevier Ltd. All rights reserved.

Circular photogalvanic effect of the two-dimensional electron gas in AlXGa1-XN/GaN heterostructures under uniaxial strain

The circular photogalvanic effect (CPGE) of the two-dimensional electron gas (2DEG) in Al0.25Ga0.75N/GaN heterostructures induced by infrared radiation has been investigated under uniaxial strain. The observed photocurrent consists of the superposition of the CPGE and the linear photogalvanic effect currents, both of which are up to 10(-2) nA. The amplitude of the CPGE current increases linearly with additional strain and is enhanced by 18.6% with a strain of 2.2x10(-3). Based on the experimental results, the contribution of bulk-inversion asymmetry (BIA) and structure-inversion asymmetry (SIA) spin splitting of the 2DEG to the CPGE current in the heterostructures is separated, and the ratio of SIA and BIA terms is estimated to be about 13.2, indicating that the SIA is the dominant mechanism to induce the k-linear spin splitting of the subbands in the triangular quantum well at AlxGa1-xN/GaN heterointerfaces. (C) 2007 American Institute of Physics.

Absolute measurement of detector quantum efficiency using optical parametric down-conversion pumped by femtosecond laser pulses

Absolute measurement of detector quantum efficiency using optical parametric down-conversion has been extensively studied for the case of a continuous wave pump. In this paper, we have used the temporally and spatially correlated properties of the down-converted photon pairs generated in a nonlinear crystal pumped by a femtosecond laser pulse to perform an absolute measurement of detector quantum efficiency. The measured detector quantum efficiency is in excellent agreement with the measured value in the conventional way. A lens with a long focal length was adopted for efficiently increasing the intensity of the down-conversion entangled photon source.

复制的移动数据库系统事务级同步处理策略

同步处理技术是保持复制的移动数据库系统一致性的一项关键技术,但现有的事务级同步处理算法存在着一定的局限性.为了克服这些缺陷,并增强其实用性,提出了一种新的移动数据库同步处理模型──基于双时间印的事务级同步(DTSTLS)模型.DTSTLS模型采用了一种三级复制体系结构,系统可以直接使用通用的数据库产品作为其数据库服务器,因此具有良好的可扩充性.作为一种异步的多主副本复制方法,DTSTLS模型允许移动计算机在断连的情况下存取本地副本,从而造成系统短暂的不一致,重新连接时进行冲突检测及同步处理,使系统重新收敛于一致性的状态.此外,通过一种独特的时间印处理策略,DTSTLS模型减少了通信代价,并降低了资源消耗.实验结果表明,DTSTLS模型提高了移动数据库系统的资源利用效率,保证了事务调度的可串行性和数据库的一致性.