青海湖裸鲤生长特征的研究

对2002年5月—2003年7月采自青海湖的1174尾青海湖裸鲤样本年龄进行了耳石鉴定,并依据年龄推算了生长率。青海湖裸鲤体长与体重的关系为:W=0.000174×L2.4990(♀)、W=0.0000402×L2.7538(♂),雌、雄个体生长差异显著。其体长Von Bertalanffy生长方程为:Lt=551.9301(1-e-0.0711(t+0.3044))(♀),Lt=682.8688(1-e-0.0530(t+0.4240))(♂);体重Von Bertalanffy生长方程为:Wt=123

似鮈(Pseudogobio vaillanti)的分子生物地理学分析

似鮈(Pseudogobiovaillanti)是广布于中国淡水水体中的一种小型鲤科鱼类.通过分析线粒体细胞色素b(cytb)基因序列变异,探讨似鮈不同地理种群的相互关系,研究似鮈的生物地理学过程,并讨论其物种分化的现状.收集了来自辽河、长江(赣江、信江等)、富春江、珠江、万泉河等水系的样品.在获得的似鮈61个样本的线粒体cytb基因全序列(1140bp)中,共检测出了45个单倍型.线粒体单倍型的网络分析发现45个单倍型不形成一个网络图,而是分成9个单元群.邻接树的结果显示,这些单倍型形成5个大的分支,基

Occlusive Components Analysis

We study unsupervised learning in a probabilistic generative model for occlusion. The model uses two types of latent variables: one indicates which objects are present in the image, and the other how they are ordered in depth. This depth order then determines how the positions and appearances of the objects present, specified in the model parameters, combine to form the image. We show that the object parameters can be learnt from an unlabelled set of images in which objects occlude one another. Exact maximum-likelihood learning is intractable. However, we show that tractable approximations to Expectation Maximization (EM) can be found if the training images each contain only a small number of objects on average. In numerical experiments it is shown that these approximations recover the correct set of object parameters. Experiments on a novel version of the bars test using colored bars, and experiments on more realistic data, show that the algorithm performs well in extracting the generating causes. Experiments based on the standard bars benchmark test for object learning show that the algorithm performs well in comparison to other recent component extraction approaches. The model and the learning algorithm thus connect research on occlusion with the research field of multiple-causes component extraction methods.

副沙鳅属系统发育分析

以沙鳅属Botia为外类群 ,共发现了副沙鳅属Parabotia 35个有系统发育意义的外部与骨骼形态特征 ,并由此重建副沙鳅属系统发育关系为 :漓江副沙鳅 +(双斑副沙鳅 +(花斑副沙鳅 +(武昌副沙鳅 +点面副沙鳅 ) ) )或漓江副沙鳅 +(双斑副沙鳅 +(武昌副沙鳅 +(点面副沙鳅 +花斑副沙鳅 ) ) )。具有囟门 ;后翼骨外侧面为不规则的梯形 ;吻骨侧面观呈一长方形 ;无下舌软骨 ;具有 3对咽鳃骨 ;中喙骨弯曲较大 ,近直角 ;上吻皮中间有切刻状缺口 ,左右不连续 ;以及颐部无纽状突起等构成

草鱼呼肠孤病毒RNA聚合酶基因的表达与产物纯化

草鱼呼肠孤病毒是引起草鱼出血病的主要病原,隶属于呼肠孤病毒科水生呼肠孤病毒属。序列分析表明,GCRV S2 片段长为3 877核苷酸,编码一个分子量为138kDa 的蛋白VP2,具有RNA聚合酶性质。为进一步了解该病毒 RNA聚合酶特性,本研究在对GCRV RNA聚合酶基因(GCRV-RdRp)保守区(约1.5kb)重组质粒pR/RRp高效表达的基础上,分别构建了编码GCRV RNA聚合酶保守区N端与C端部分基因的 pR/RRpN及pR/RRpC重组表达载体,并在原核细胞中获得成功表达。筛选的重组表达菌株

彩鲫Ran基因全长cDNA的克隆及其组织表达特异性分析

根据Ran的保守区序列设计简并引物 ,结合SMARTcDNA合成及RACE PCR技术 ,克隆到彩鲫(Carassiusauratuscolorvariety)的Ran基因的cDNA全长 ,其编码区全长为 6 4 8bp ,编码 2 15个氨基酸。采用BLAST程序在NCBI数据库中对其进行同源基因搜索 ,结果表明 ,其推测的编码氨基酸序列与斑马鱼和鲑鱼的Ran基因编码的氨基酸序列的同源性分别高达 98%和 97%。还对其编码区全长序列进行了原核表达 ,以经纯化的表达蛋白免疫家兔 ,制备出了具有较高特异性

长湖水生植物多样性及其变化

研究了湖北省第三大湖泊长湖水生植物多样性的现状及其长期变化 ,并探讨了多样性丧失的机理及多样性恢复与保护的有效途径。主要结论 :(1)长湖现有水生植物 98种 ,多度最大的是微齿眼子菜 (Potamogetonmaackianus)、密齿苦草 (Vallisneriadenseserrulata)、野菱(Trapaincisa)、双角菱 (T bispinosa)、菹草 (Potamogetoncrispus)、紫萍 (Spirodelapolyrhiza)、穗花狐尾藻 (Myriophyllumspic

高体鳑鲏(Rhodeus ocellatus(kner))的形态变异及地理分化研究

采用鱼类形态度量学和框架度量学相结合的方法 ,对不同地区的高体的形态进行了测量 ,并对其 19个比例性状进行了主成分分析 .结果表明 :分布于各区域的高体不具有地理分隔特征 ,可视为一个种 .其形态差异主要表现在与游泳、摄食有关的眼径、吻和尾柄长度上 .这些形态差异的产生主要是其对环境的长期适应的结果 .

Anchors, scales and the relative coding of value in the brain.

People are alarmingly susceptible to manipulations that change both their expectations and experience of the value of goods. Recent studies in behavioral economics suggest such variability reflects more than mere caprice. People commonly judge options and prices in relative terms, rather than absolutely, and display strong sensitivity to exemplar and price anchors. We propose that these findings elucidate important principles about reward processing in the brain. In particular, relative valuation may be a natural consequence of adaptive coding of neuronal firing to optimise sensitivity across large ranges of value. Furthermore, the initial apparent arbitrariness of value may reflect the brains' attempts to optimally integrate diverse sources of value-relevant information in the face of perceived uncertainty. Recent findings in neuroscience support both accounts, and implicate regions in the orbitofrontal cortex, striatum, and ventromedial prefrontal cortex in the construction of value.