盐度对大獭蛤胚胎发育的影响

在广西海洋研究所古城海水养殖实验基地进行人工养殖大獭蛤(Lutraria maxima Jonas)的实验。实验把大獭蛤精、卵置于盐度为21．3‰、24．0‰、26．6‰、29．3‰、31．9‰、34．6‰、37．3‰的海水中静水受精及孵化，从人工受精开始到D型幼虫期连续观察盐度对胚胎发育情况。每个海水盐度设3个重复，海水温度保持恒温(28．7℃)。实验结果表明，大獭蛤的受精过程和受精卵发育过程都受到海水盐度的影响，大獭蛤能正常受精的适宜盐度为29．3‰～31．9‰，大獭蛤受精卵正常发育的适宜盐度为26．6‰～31．9‰。     

大獭蛤苗种池塘中间培育试验

2002年9月至2003年4月，在广西海洋研究所古城基地进行大獭蛤（LutmriamaximaJonas）苗种池塘中间培育试验。试验在铺沙的池塘里进行，放养的大獭蛤苗种规格为壳长0．2～0．8mm，大獭蛤稚贝饵料为施肥繁殖的浮游藻类，以大部分大獭蛤稚贝壳长达到2cm为出苗标准。结果表明，在水温为20～30℃、盐度为zo％。以上，放苗量为375万粒／公顷的条件下，大獭蛤稚贝经过45～60d即可以培育成壳长为2cm左右的大规格苗种。     

团头鲂的胚胎发育与观察方法优化

通过人工繁殖获得团头鲂受精卵,在体视显微镜下对其胚胎和早期仔鱼发育过程进行了连续观察、拍照与测量.结果显示,团头鲂受精卵呈圆球形,具黏性,卵径(1.18±0.09)mm;在水温(21±1)℃条件下,团头鲂胚胎发育从受精到孵化历时39h10min,经历了胚盘形成、卵裂期、囊胚期、原肠胚期、神经胚期、器官形成期和出膜期7个发育阶段;初孵仔鱼体长(3.44±0.29)mm,出膜后第4d仔鱼鳔完全充气,卵黄囊消失;观察时,受精卵至尾鳍出现期胚胎置0.7%生理盐水中,肌肉效应期和后面各时期的胚胎经4%多聚甲醛固定后置3%甲基纤维素中拍照可获得良好效果.该工作为研究团头鲂胚胎早期发育过程提供了实时和动态的图像资料,并为鱼类胚胎发育观察提供了基本技术参考.     

淡水驯化后大鳞鲃胚胎发育观察

通过人工授精获得大鳞鲃(Barbus capito)受精卵,并在23℃~26℃的孵化条件下,详细观察了大鳞鲃胚胎发育及未受精卵的特征.结果显示,大鳞鲃受精卵为漂流性卵(半浮性卵),卵径为(1.55±0.1)mm,吸水后卵膜膨大,卵径达到(4.3±0.2)mm.在水温23℃~26℃的条件下,胚胎发育总历时为47 h 29 min,胚胎发育过程所需总积温为1 081℃~1 222℃.大鳞鲃受精卵卵裂方式与其他鲤科鱼类一样,属于盘状卵裂.根据胚胎发育各阶段的形态特征,将其划分为胚盘隆起、卵裂、囊胚、原肠胚、神经胚期至尾芽期和胚动期至孵化期等6个连续发育阶段,22个时期.未受精卵入水后吸水膨胀,由原生质集中形成"胚盘",但无如两细胞卵裂的现象;未受精卵的突起或分裂球陆续脱离胚盘会形成类似受精卵囊胚末期时的"假囊胚".研究结果有助于提高大鳞鲃人工繁育效率及对孵化条件及时调控处理,有助于大鳞鲃亲鱼受精率计算方法的掌握.     

澳洲宝石斑鱼的胚胎发育

采用体视解剖镜、显微镜对澳洲宝石斑鱼的胚胎发育进行观察,描述了各个发育时期的主要形态特征.结果显示:(1)宝石斑鱼的卵和受精卵较小,受精卵径平均1.5mm;(2)受精卵吸水后呈圆形,为浮性卵;(3)胚胎卵黄囊表面有一个大的圆形脂肪球;(4)在水温23-29℃条件下,受精卵历时24 h脱膜孵出仔鱼,再经3.5 d开口摄食,转入混合营养时期;(5)胚胎发育主要经历卵裂期、囊胚至原肠期、神经胚期、器官形成期和孵出期5个主要时期.     

大獭蛤工厂化育苗技术研究

于2002年秋季在广西海洋研究所古城育苗基地和海滨公园育苗场进行大獭蛤（Lutraria（Psammophila）mascima Jonas）工厂化育苗研究。在育苗过程中采用成串的塑料片作为稚贝附着基立体附苗，使单位水体出苗量得到极大的提高。大獭蛤壳顶后期浮游苗至稚贝平均变态率为23．5％，小苗（大于8×10^4粒／500g）的平均单位面积出苗量为5．16×10^4粒／米^2，大苗（小于或等于8×10^4粒／500g）的平均单位面积出苗量为1．42×10^4粒／米^2，平均单位面积出苗量为3．29×10^4粒／米^2。     

鮸状黄姑鱼与大黄鱼人工杂交子代的胚胎发育

以Mian状黄姑鱼为母本、大黄鱼为父本的人工杂交试验表明：在温度17－20℃、盐度29．9－30．8的条件下，杂交卵经39.9h孵出，受精率为58．9％，孵化率为1．4％，仔鱼存活18d。对照组Mian状黄姑鱼受精率95％，受精卵孵化率56％。杂交组受精卵的胚胎发育与母本Mian状黄姑鱼的胚胎发育主要差别为：杂交卵在进入原肠期时，多数胚胎发育速度明显变慢，囊胚不能正常下包，胚胎畸形率较高。     

日本沼虾受精卵的离体培养及其胚胎发育的初步观察

本文报道了日本沼虾的受精卵离体培养实验，并初步描述了其胚胎发育的特征。结果表明：日本沼虾受精卵以及各期胚胎（即卵裂期、囊胚期、原肠期、无节幼体期、后无节幼体期、前蚤状幼体期的胚胎）分别离体培养，均可孵化出蚤状Ｉ期幼体；并且离体受精卵及各发育时期胚胎与亲虾所抱受精卵和相同时期胚胎发育同步。日本沼虾的卵裂方式属于完全卵裂和表面卵裂之间的过渡类型     

耳萝卜螺胚胎发育的初步观察

采用定时取样 ,间断观察的方法 ,对耳萝卜螺胚胎发育的形态特征进行了观察。发现耳萝卜螺的胚胎发育过程分 7个时期 :卵裂期、囊胚期、原肠期、担轮幼虫期、面盘幼虫期、幼螺形成期和孵化期。对各期的外部形态特征进行了描述 ,并绘制了各期形态图 ,记录了各期发育所经历的时间     

豫北地区大鳞副泥鳅胚胎发育的观察

目前泥鳅和大鳞副泥鳅的养殖热潮正在全国范围内兴起,优良新品种的培育早已经为养殖者所期待.胚胎发育过程特征的研究是进行新品种培育的基础工作.对产自豫北地区的大鳞副泥鳅的胚胎发育过程进行了连续观察,对其各个胚胎时期的发育特征和持续时间进行了记录.结果表明从受精卵到出膜共划分为6个阶段和卵裂期、囊胚期、原肠期、神经胚期、肌节期、尾芽期、胚动期、出膜前期、孵出期、眼黑色素期等10个连续的典型时期,在23℃时胚胎发育历时共24 h 20 min.     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Wuhan University Journal of Natural Sciences TOTAL CONTENTS

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Advances in broadband wireless communications under high-mobility scenarios

Future mobile communication systems aim at providing very high data transmission rates, even in high-mobility scenarios such as high-speed wheel-track trains, maglev trains, highway vehicles, airplanes, guided missiles or spacecraft. A particularly important commercial application is the strong and increasing worldwide demand for high- speed broadband wireless communications （up to 574.8 km/ h test speeds or 380 km/h commercial speeds） in railways, providing data, voice and video services for applications such as onboard entertainment services to passengers, train control, train dispatch, train sensor status handling and sur- veillance. In such high-mobility scenarios, there are a number of communication challenges, including fast hand- over, location updating, high-speed channel modeling, estimation and equalization, anti-Doppler spreading tech- niques, fast power control, and dedicated network architec- ture. Because signal transmission in very high-speed scenarios will inevitably experience serious deterioration, it is imperative to develop key broadband mobile communi- cation techniques for such high-speed vehicles.     

Perspherical Approaches for Electrons in Atoms and Charged Excitons in Quantum Wells

Instead of following Fock’s expansion,we solve the Schrodinger equation for some quantum mechanical manybody systems such as electrons in atoms and charged excitons in quantum wells in a similar way in hyperspherical coordinates by expanding the wave functions into orthonormal complete basis sets of the hyperspherical hannonics(HHs)of hyperangles and generalized Laguerre polynomials(GLPs)of the hyperradius.This leads the equation to     

Scale-based spatial data model for GIS

Being the primary media of geographical information and the elementary objects manipulated, almost all of maps adopt the layer-based model to represent geographic information in the existent GIS. However, it is difficult to extend the map represented in layer-based model. Furthermore, in Web-Based GIS, It is slow to transmit the spatial data for map viewing. In this paper, for solving the questions above, we have proposed a new method for representing the spatial data. That is scale-based model. In this model we represent maps in three levels: scale-view, block, and spatial object, and organize the maps in a set of map layers, named Scale-View, which associates some given scales.Lastly, a prototype Web-Based GIS using the proposed spatial data representation is described briefly.     

英文诗歌中的喻类修辞

为了有助于提高英文爱好者的个人情操、文化素养和学习兴趣,以及专业人员对英语学习和研究进行多途径的探索,本文通过一些精选诗歌的引证和分析,着重论述了喻类修辞法在英文诗歌中的运用其及效果。     

Man Is Unable to Change the Miserable Life——Analysis of the Arrangement of Four Characters in The Glass Menagerie

Tennessee Williams is considered as one of the most important American playwrights since World War II.The Glass Menagerie is his first successful drama,which describes a tragic situation of family and means to say that Man is unable to change the miserable life,no matter whatever means he try,This essay focuses on the analysis of the arrangement of the four main characters:Laura.Amanda,Jim and Tom to reveal the theme.Laura is fragile.Amanda is brave.Jim is vital.Tom is sensible.And all of them develop and try the different means to struggle against life,but fail tragically.With the evidence,the paper comes to conclusion naturally that Man is unable to change the miserable life,and he dooms to fail.     

Characterization of root-nodulating bacteria on Retama raetam in arid Tunisian soils

The aim of this study is to investigate the diversity of Retama raetam root-nodule bacteria isolated from arid regions of Tunisia. Twelve isolates, chosen as representative for different 16S rRNA gene patterns, were characterized by 16S rRNA gene sequencing and phenotypic analysis. Isolates were assigned to Sinorhizobium, Rhizobium and Agrobacterium. Symbiotic properties of Sinorhizobium and Rhizobium isolates showed a large diversity in their capacity to infect their host plant and fix atmospheric nitrogen. Strain RK 22 identified as Rhizobium was the most effective isolate.     

An Affordable Accurate Evaluation of the Binding Conformations Predicted by Molecular Docking Studies in Bio-System

正Recently,docking has been widely used to predict the binding-modes of protein-inhibitors,when the crystal complexes structure was absent.Most docking algorithms are able to generate a large number of probable conformations,it,however,is difficult to effectively evaluate these docking poses and identify the most reasonable bindingmode.In the present study,on the basis of the crystallographic data of human 3-hydroxy-3-methylglutaryl coenzyme     

WIMAX与WI-FI技术分析及联合组网

介绍了WiMAX与Wi-Fi两种无线宽带接入技术,并对两者之间的关系及相互之间的影响做了对比及分析,并对WiMAX的关键技术进行了详细说明,最后对两者的联合组网方式做了简单的探讨。