污染环境中单种群生存分析

本文研究了污染环境中种群的动力学模型,基于已有结果,考虑了内禀增长率为非线性函数的情形.利用微分方程定性理论中的比较定理,对于种群的持续生存与绝灭给出了判别条件.     

判别水体污染的一个线性模式

本文应用判别分析的原理,根据Fisher判别准则,采用检测资料比较全面的金沙江(渡口市段)枯水期的水质资料,建立了“污染值”F与水体指标之间的数学模式,并进行了回代检验,取得了理想的效果。一、数学原理假设选用三个判别污染等级的指标X_1,X_2,X_3,并且确定判别函数为线性函数。     

基于大型底栖动物群落的上海市河道水质生物学评价

2011年夏秋季,在上海市全境83个河道断面开展了河道底栖动物采样,共获取底栖动物20个分类单位（种）。9个极严重污染断面未采集到活体生物,生境基本丧失。其余74个有活体生物断面,采用三种常用生物指数：Shannon-Wiener多样性指数、Hilsenhoff耐污指数、Goodnight修正指数分别进行计算及评价。Shannon-Wiener多样性指数判别为25个严重污染和49个重污染断面;Hilsenhoff耐污指数划分38个重污染、5个中污染和31个轻污染断面;Goodnight修正指数划分33个重污染、2个中污染和39个轻污染断面。与典型河道断面的水质理化指标监测值进行对照,Shannon-Weiner多样性指数对河道水质评价的准确度较低,Hilsenhoff生物指数和Goodnight修正指数的水质评价效率及准确度均较高,断面污染等级与水质理化指标基本对应。     

基于大型底栖无脊椎动物群落的上海市河道水质生物学评价

2011年夏秋季,在上海市全境83个河道断面开展了大型底栖无脊椎动物采样,共获取底栖动物20个分类单位(种).9个极严重污染断面未采集到活体大型底栖生物,生境基本丧失.其余74个有活体生物断面,采用三种常用生物指数:Shannon-Wiener多样性指数、Hilsenhoff耐污指数、Goodnight修正指数分别进行计算及评价.Shannon-Wiener多样性指数判别为25个严重污染和49个重污染断面;Hilsenhoff耐污指数划分38个重污染、5个中污染和31个轻污染断面;Goodnight修正指数划分33个重污染、2个中污染和39个轻污染断面.与典型河道断面的水质理化指标监测值进行对照,Shannon-Weiner多样性指数对河道水质评价的准确度较低,Hilsenhoff生物指数和Goodnight修正指数的水质评价效率及准确度均较高,断面污染等级与水质理化指标基本对应.     

一类Hopfield型时滞神经网络模型的全局渐近稳定性

用拓扑度和Lyapunov泛函方法，讨论了一类具有时滞的Hopfield神经网络平衡点的存在性及其全局渐近稳定性．所获得的若干判别条件，都去掉了有关文献中关于激活函数的可微性和有界性限制，增强了模型的适用性．     

全退化型小参数问题周期解的存在性

运用拓扑度方法给出高维非自治系统全爱化型小参数问题周期解存在性的一些简明的判别方法,即在非线性项满足强制性条件时,无需计算便能判别周期解的存在。     

典型平原河网地区底栖动物生物指数筛选及评价基准研究

2011年夏、秋季在上海市全境主要河流的83个断面进行大型底栖动物的采样, 共获取底栖动物20个分类单位(种), 其中软体动物、环节动物和节肢动物分别占50%、30% 和20%。选取常见的28个生物指数分别进行计算, 并采用非参数统计检验方法筛选出8个敏感生物指数。通过记分法对8种敏感生物指数统一量纲后, 获得数值范围为8-40的综合生物指数, 运用四分法划分了判别河道水环境质量的生物基准: 32-40, 较好(Good); 24-31, 一般(Fair); 16-23, 污染(Poor); 8-15, 严重污染(Very poor)。9个断面未发现活体生物, 定为超严重污染(Super poor)。依照生物基准比较上海市41个代表性断面近5年主要水质理化指标, 基本反映出水质理化指标的空间差异性, 该综合生物指数及判别基准也可适用于评价平原河网地区的河道水质状况。       

一类中立型Hopfield神经网络的全局吸引集

讨论了中立型Hopfield神经网络模型,利用矩阵谱的性质和微分不等式分析等技巧,给出了其不变集和全局吸引集的判别准则．特别地,当系统有平衡点时,我们也得到了平衡点全局稳定的判别条件．     

两类非耗散系统的弱持久性

利用Perron-Frobenuis定理及定性理论,讨论了环状捕食－被捕食模型及文[1]中提出的一类食物链模型为非耗散系统的条件及模型为非耗散系统时的弱持久性问题,得到其弱持久的判别准则,解决了文[1]提出的问题。     

水体中氮稳定同位素的研究进展

随着工农业生产的发展,水体氮污染已日益严重.利用氮稳定同位素来判别水体氮污染的源和汇、研究氮循环等显得尤为重要.本文就以下几方面进行综述:1)氮稳定同位素的基本概念、氮在水体中的循环及相应的同位素分馏情况;2)系统比较了水中氮同位素测定过程中氮同位素的分离、富集和不同形态氮的转化方法;3)讨论了氮稳定同位素在研究地表水、地下水及海水中的氮循环、判断氮污染的源和汇、氮在生态系统中转化以及水体富营养化等方面的应用;4)总结了水体中反硝化作用的判断方法和水体中硝酸盐的两种自然衰减机制——反硝化作用和稀释作用;5)指出了该研究领域的不足之处.     

Distribution of fishes on the Cretan shelf

Information on the abundance of demersal fishes on the shelf of Crete has been collected through a 3-year bottom trawl survey carried out at fixed sampling stations. Cluster analysis identified three major station-groups delimited by the nature of the substrate. Two of the identified substrate zones were situated on the continental shelf while the beginning of the third zone coincided with the start of the continental slope. Discriminant analysis applied to the abiotic variables defined that depth was the most important variable in discriminating between the identified groups. Discriminant analysis also identified that the most important species in discriminating among station-groups were Capros aper (Linnaeus, 1758), Gadicuh argenieus argenteus Guichenot, 1850, Merluccius merluccius (Linnaeus, 1758), Mullus surmuletus Linnaeus, 1758 and Spicara flexuosa Rafinesque, 18 10. Association analysis revealed few species pairs having significant associations which in most cases seem to be related to the reproductive migration of these species. The results demonstrate that there is a pronounced change with the substrate and by extension with depth in the ichthyofaunal composition of the shelf of Crete. It has also been suggested that there may be a particular relationship between the fish communities of the two zones of the continental shelf.     

Classification of transporters using efficient radial basis function networks with position‐specific scoring matrices and biochemical properties

Transporters are proteins that are involved in the movement of ions or molecules across biological membranes. Transporters are generally classified into channels/pores, electrochemical transporters, and active transporters. Discriminating the specific class of transporters and their subfamilies are essential tasks in computational biology for the advancement of structural and functional genomics. We have systematically analyzed the amino acid composition, residue pair preference and amino acid properties in six different families of transporters. Utilizing the information, we have developed a radial basis function (RBF) network method based on profiles obtained with position specific scoring matrices for discriminating transporters belonging to three different classes and six families. Our method showed a fivefold cross validation accuracy of 76%, 73%, and 69% for discriminating transporters and nontransporters, three different classes and six different families of transporters, respectively. Further, the method was tested with independent datasets, which showed similar level of accuracy. A web server has been developed for discriminating transporters based on three classes and six families, and it is available at http://rbf.bioinfo.tw/～sachen/tcrbf.html . We suggest that our method could be effectively used to identify transporters and discriminating them into different classes and families. Proteins 2010;. © 2010 Wiley‐Liss, Inc.     

中国20个民族中PGM_1及其亚型EsD、GLO1、AK、ADA和6-PGD酶型分布调查

调查了汉族、鄂伦春、赫哲、朝鲜、蒙古、羌、土家、苗、侗、畲、壮、纳西、傈僳、白、彝、景颇、哈尼、傣、维吾尔和塔吉克等20个民族的PGM_1及其亚型,EsD、GLO_1、AK、ADA和6-PGD等酶型的分布及基因频率。PGM_1及其亚型、EsD和GLO_1在中国各民族中是分布较好的,个人识别能力较高的酶。有12个民族查出有PQM_1~6基因,壮族的频率最高,PGM_1 6-1表型达4.15％。对在4174份血样中所检出的带有PGM_1~6基因的68份血样做亚型分析,在凝胶上PGM_1~6谱带均在同一位置上。EsD_1基因频率的总趋向是北方各民族高于南方。哈尼、傈僳、傣、纳西、畲、壮、侗和苗等民族EsD2-2表型达15％以上,哈尼族高达32.4％。GLO1~1基因频率塔吉克和维吾尔族为0.2927和0.2112,羌族为0.0583,其它各族在0.0714—0.1527。各民族AK~1、ADA和6-PGD~(?)基因频率均甚高。     

作物品种区域试验试点区辨力评价方法的比较(英文)

试点区辨力是作物品种区域试验试点选择的重要依据,可以用不同的方法进行评价。本研究分别对西南玉米区域试验2003和2004两年的产量数据进行联合方差分析,然后用变异系数(CV)、遗传变异系数(GCV)、环境区分指数(DI)、B型生态价(WE)、回归系数(RC)、基于AM MI分析结果的试点互作主成分点到原点的距离(DA)、AMMI稳定性值(ASV)和基于GGE双标图分析的试点到原点的距离(DG)对西南玉米区域试验试点的区辨力进行评价,进而用秩次相关分析和主成分分析揭示试点区辨力评价方法间的内在关系。结果表明,两年试验品种间、试点间均存在极显著差异,且品种和试点间互作也极显著;8个统计数也许可以用来度量试点的区辨力,但是不同统计数对同一年度内试点的区辨力评价结果不完全一致;统计数CV、GCV、WE、DA和DG间都存在极显著的秩次相关,但是统计数DG也许更有利于评价试点的区辨力。     

Behaviour and fecundity of female rats mated with preferred or non-preferred males

Sexually experienced female rats were allowed to choose between two inaccessible males. Approximately half of the females developed a consistent preference, and the most ‘discriminating’ females were mated with either their preferred or their non-preferred male. Females without a decided preference were mated with one of the two males randomly selected by the experimenter. The pairs of discriminating females and preferred males had higher levels of non-sexual contacts, solicitations and sexual activity than the pairs of discriminating females and non-preferred males. Specifically, the former pairings were characterized by higher levels of non-sexual contact and affiliative behaviour (crawl over and under responses) and solicitation responses (ear-wiggling and darting) by the female and shorter latencies for intromissions and ejaculations than the pairings with a non-preferred male. The pairs that included non-discriminating females behaved more like the pairs with a discriminating female and a preferred male than those with a discriminating female and a non-preferred male. Even so, the number of females delivering litters and the size of the litters did not differ between the different experimental pairings. These data suggest that discriminating famale rat is not conferred and obvious reproductive advantage over a less discriminating female.     

Two-point discrimination distances in the normal hand and forearm: application to various methods of fingertip reconstruction.

Two-point discrimination in the hand and forearm is best during the third decade of life. In the fingertips, the ulnar digits are more discriminating than the radial digits. Males and females have equal two-point discrimination during each age decade. Fingertips are twice as discriminating as the thenar and hypothenar areas, and the thenar and hypothenar areas are twice as discriminating as the volar side of the wrist; the wrist is twice as discriminating as the forearm. The Kleinert and Kutler flaps demonstrated the best two-point discrimination among the repaired fingertips.     

Evolution of habitat selection: stochastic acquisition of cognitive clues?

Different habitat preferences in animals have been interpreted mostly as a result of different adaptive design of the species and/or as a result of interspecific competition. We propose an alternative view of evolution of habitat preferences. Our model is based on progressive stochastic acquisition of cognitive clues discriminating habitat features which correlate with expected fitness. We assume that acquisition of each cognitive clue allowing discrimination of ‘better’ and ‘worse’ habitats (according to the average fitness in each habitat) will constrain further evolution, because each further clue will discriminate habitats only within previously acquired preferences. Simple simulation model shows that if it is the case, even the species with equal habitat-related fitness differences will rapidly diversify in their habitat preferences. Therefore, similarly as in the evolution of other species-specific traits, the evolution of animal–habitat relationship may be strongly affected by stochastic events and historical contingency. This revised version was published online in July 2006 with corrections to the Cover Date.     

A diagnostic assay discriminating between two major Ovis aries mitochondrial DNA haplogroups

Two major Ovis aries mitochondrial DNA (mtDNA) haplogroups have been described in independent studies. HinfI RFLP data of mitochondrial genomes from a large sample set (n = 239) indicated an ancient mutation which differentiates between the two mtDNA types. A completely determined sheep mtDNA sequence was used to assign this mutation to the COI gene and to develop a PCR based assay discriminating between the two phylogenetic branches. The haplogroup specificity of the mutation was further investigated in 26 randomly selected individuals. The animals were unequivocally assigned to their respective groups on the basis of the developed test and their complete control region sequences. The assay provides a rapid and economic means of discriminating between both major domestic sheep mtDNAs.     

Without quality presence–absence data,discrimination metrics such as TSS can be misleading measures of model performance

The discriminating capacity (i.e. ability to correctly classify presences and absences) of species distribution models (SDMs) is commonly evaluated with metrics such as the area under the receiving operating characteristic curve (AUC), the Kappa statistic and the true skill statistic (TSS). AUC and Kappa have been repeatedly criticized, but TSS has fared relatively well since its introduction, mainly because it has been considered as independent of prevalence. In addition, discrimination metrics have been contested because they should be calculated on presence–absence data, but are often used on presence‐only or presence‐background data. Here, we investigate TSS and an alternative set of metrics—similarity indices, also known as F‐measures. We first show that even in ideal conditions (i.e. perfectly random presence–absence sampling), TSS can be misleading because of its dependence on prevalence, whereas similarity/F‐measures provide adequate estimations of model discrimination capacity. Second, we show that in real‐world situations where sample prevalence is different from true species prevalence (i.e. biased sampling or presence‐pseudoabsence), no discrimination capacity metric provides adequate estimation of model discrimination capacity, including metrics specifically designed for modelling with presence‐pseudoabsence data. Our conclusions are twofold. First, they unequivocally impel SDM users to understand the potential shortcomings of discrimination metrics when quality presence–absence data are lacking, and we recommend obtaining such data. Second, in the specific case of virtual species, which are increasingly used to develop and test SDM methodologies, we strongly recommend the use of similarity/F‐measures, which were not biased by prevalence, contrary to TSS.     

To be at the right place at the right time

Diagnosing Alzheimer's disease through MRI neuroimaging biomarkers has been used as a complementary marker for traditional clinical markers to improve diagnostic accuracy and also help in developing new pharmacotherapeutic trials. It has been revealed that longitudinal analysis of the whole brain atrophy has the power of discriminating Alzheimer's disease and elderly normal controls. In this work, effect of involving intermediate atrophy rates and impact of using uncorrelated principal components of these features instead of original ones on discriminating normal controls and Alzheimer's disease subjects, is inspected. In fact, linear discriminative analysis of atrophy rates is used to classify subjects into Alzheimer's disease and controls. Leave-one-out cross-validation has been adopted to evaluate the generalization rate of the classifier along with its memorization. Results show that incorporating uncorrelated version of intermediate features leads to the same memorization performance as the original ones but higher generalization rate. As a conclusion, it is revealed that in a longitudinal study, using intermediate MRI scans and transferring them to an uncorrelated feature space can improve diagnostic accuracy.