Parasite adaptation to locally common host genotypes

According to the Red Queen hypothesis--which states that interactions among species (such as hosts and parasites) lead to constant natural selection for adaptation and counter-adaptation--the disproportionate evolutionary success of parasites on common host genotypes leads to correlated selection for sexual reproduction and local adaptation by the parasite population. Here we determined whether local adaptation is due to disproportionate infection of common host genotypes, and, if so, whether infection of common host genotypes is due to commonness per se, or some other aspect of these genotypes. In a reciprocal cross-inoculation experiment parasites occupying the same geographical area (sympatric) infected locally common host genotypes significantly more often than rare host genotypes, whereas parasites occupying separate geographical areas (allopatric) showed no such significant difference. A mixed source of parasites (containing F1 hybrids) also showed no difference in infection between rare and common host genotypes. These results show that local adaptation results from parasite tracking of locally common host genotypes, and, as such, a necessary condition of the Red Queen hypothesis is met.     

下临界多物种分支过程后代总人口数生成函数

讨论下临界多物种分支过程后代总人口数的生成函数.通过推导出的下临界多物种分支过程前n代总人口数生成函数Rn(s)的递归公式,利用其单调性得到Rn(s)的极限生成函数ρ(s)为方程t=s*f(t)的解.又ρ(s)即为下临界多物种分支过程后代总人口数的概率生成函数,故有下临界多物种分支过程后代总人口数的概率生成函数为方程t=s*f(t)的解.     

Dispersal and the sex ratio at birth in primates

The females of many species of primates settle for life within the home ranges of their mothers, whereas males disperse as immatures. According to the theory of sex allocation, the costs incurred by mothers through local competition for resources with their philopatric daughters should favour the evolution of male-biased sex ratios at birth. I report here two tests of this hypothesis based on data from 15 genera of primates. First, I show that the intensity of competition for resources within kin groups is strongly and positively correlated with sex ratios at birth. Second, I show that sex ratios at birth are higher in genera with female-biased philopatry than in genera in which philopatry is not female-biased. These analyses suggest that local resource competition among kin powerfully influences the evolution of sex ratios in primates.     

合成博弈与竞争博弈性质及应用

在合成博弈的基础上,提出了竞争博弈及竞争博弈转移量的概念,给出了竞争博弈转移量及稳定集的判定定理.通过例子说明了竞争博弈与合成博弈的区别:竞争博弈使两个不同的博弈变成一个博弈,合成博弈使两个不同的博弈保持各自的独立性;竞争博弈的转移量从联盟外部获得,合成博弈的转移量从联盟内部获得.从理论上,竞争博弈丰富了博弈论的内容;从应用上,竞争博弈与合成博弈基本上涵盖了战略联盟之间兼并与重组的各种类型,使得博弈论关于联盟之间再联盟的模型更趋完善.     

The ecological cost of sex

Why sex prevails in nature remains one of the great puzzles of evolution. Sexual reproduction has an immediate cost relative to asexual reproduction, as males only express their contribution to population growth through females. With no males to sustain, an asexual mutant can double its relative representation in the population in successive generations. This is the widely accepted 'twofold cost of males'. Many studies have attempted to explain how sex can recoup this cost from fitness benefits associated with the recombination of parental genotypes, but these require complex biological environments that cycle over evolutionary timescales. In contrast, we have considered the ecological dynamics that govern asexual invasion. Here we show the existence of a threshold growth rate for the sexual population, above which the invasion is halted by intraspecific competition. The asexual population then exerts a weaker inhibitory effect on the carrying capacity of the sexual population than on its own carrying capacity. The stable outcome of this is coexistence on a depleted resource base. Under these ecological circumstances, longer-term benefits of sex may eventually drive out the asexual competitor.     

等级考试题库系统的开发研究

从理论和具体实现两个方面对用Visual Foxpro开发的计算机等级考试辅助教学中的试题库系统进行分析和论述.该系统可以实现试题的统一管理、试卷的自动生成以及试题和试卷的简单测试和分析.     

Sex increases the efficacy of natural selection in experimental yeast populations

Why sex evolved and persists is a problem for evolutionary biology, because sex disrupts favourable gene combinations and requires an expenditure of time and energy. Further, in organisms with unequal-sized gametes, the female transmits her genes at only half the rate of an asexual equivalent (the twofold cost of sex). Many modern theories that provide an explanation for the advantage of sex incorporate an idea originally proposed by Weismann more than 100 years ago: sex allows natural selection to proceed more effectively because it increases genetic variation. Here we test this hypothesis, which still lacks robust empirical support, with the use of experiments on yeast populations. Capitalizing on recent advances in the molecular biology of recombination in yeast, we produced by genetic manipulation strains that differed only in their capacity for sexual reproduction. We show that, as predicted by the theory, sex increases the rate of adaptation to a new harsh environment but has no measurable effect on fitness in a new benign environment where there is little selection.     

基于客户满意的4R营销策略研究——以重庆建行转型网点为例

在激烈的市场竞争中,"以市场为导向,以客户为中心"的变革时代慢慢的渗透我国金融业营销环境.相应的营销理念,也从4P、4C模式进入了4R的模式.本文从现有营销组合策略出发,对重庆建行转型网点调研数据进行分析,为重庆建行转型网点营销策略的制定寻找理论依据.     

Generation of optical 'Schrödinger cats' from photon number states

Schr?dinger's cat is a Gedankenexperiment in quantum physics, in which an atomic decay triggers the death of the cat. Because quantum physics allow atoms to remain in superpositions of states, the classical cat would then be simultaneously dead and alive. By analogy, a 'cat' state of freely propagating light can be defined as a quantum superposition of well separated quasi-classical states-it is a classical light wave that simultaneously possesses two opposite phases. Such states play an important role in fundamental tests of quantum theory and in many quantum information processing tasks, including quantum computation, quantum teleportation and precision measurements. Recently, optical Schr?dinger 'kittens' were prepared; however, they are too small for most of the aforementioned applications and increasing their size is experimentally challenging. Here we demonstrate, theoretically and experimentally, a protocol that allows the generation of arbitrarily large squeezed Schr?dinger cat states, using homodyne detection and photon number states as resources. We implemented this protocol with light pulses containing two photons, producing a squeezed Schr?dinger cat state with a negative Wigner function. This state clearly exhibits several quantum phase-space interference fringes between the 'dead' and 'alive' components, and is large enough to become useful for quantum information processing and experimental tests of quantum theory.     

对我国部分武术运动员职业意识指向的研究

本文运用“运动员职业意识指向问卷表”对我国部分武术运动员进行调查,以了解我国武术运动员的职业意识,探索我国武术运动员的职业意识与职业成就的关系以及不同性别、不同运动年限的武术运动员在职业意识指向上的差异或特点。研究表明,武术运动员职业意识主要指向于竞争型、竞争事业型、事业竞争型、竞争娱乐型、竞争求职型。男女武术运动员在职业意识指向上无较大差异。武术运动员职业意识指向随运动年限的变化呈现一定的特点。竞争型运动员最适合武术运动的要求。     

基于重复博弈的集群网络供应链竞合关系分析

在对集群网络供应链特征进行分析的基础上,运用动态重复博弈理论,分析了集群网络供应链中单链供应链上下游节点间企业,及并行供应链相同价值链环节点企业间的竞争与合作状态,并给出合作均衡的条件,得出集群内单链供应链节点间存在着较大的合作空间,而并行供应链相同价值链环节点间竞争性空间较大、合作较难的结论.     

发展红色旅游传承中华民族伟大精神

红色旅游是个具有明显政治与文化意义的主题性旅游形式,是发挥旅游教育功能有益而可行的尝试,尤其对全民族优秀思想与精神的进一步凝聚将产生不可估量的作用。在对红色旅游的涵义极其产生背景的介绍下,着重分析其强大的政治功能与文化意义,为广大旅游者更好地理解红色旅游、吸收先进文化提供帮助。     

The Srs2 helicase prevents recombination by disrupting Rad51 nucleoprotein filaments

Homologous recombination is a ubiquitous process with key functions in meiotic and vegetative cells for the repair of DNA breaks. It is initiated by the formation of single-stranded DNA on which recombination proteins bind to form a nucleoprotein filament that is active in searching for homology, in the formation of joint molecules and in the exchange of DNA strands. This process contributes to genome stability but it is also potentially dangerous to cells if intermediates are formed that cannot be processed normally and thus are toxic or generate genomic rearrangements. Cells must therefore have developed strategies to survey recombination and to prevent the occurrence of such deleterious events. In Saccharomyces cerevisiae, genetic data have shown that the Srs2 helicase negatively modulates recombination, and later experiments suggested that it reverses intermediate recombination structures. Here we show that DNA strand exchange mediated in vitro by Rad51 is inhibited by Srs2, and that Srs2 disrupts Rad51 filaments formed on single-stranded DNA. These data provide an explanation for the anti-recombinogenic role of Srs2 in vivo and highlight a previously unknown mechanism for recombination control.     

“钦州红荔”新株系形态及同工酶分析

在广西钦州市钦北区新棠镇进行田间试验,观测“钦州红荔”株系和“黑叶”、“香荔”等品种单株的植株形态和果实性状表现,采集营养梢老熟叶片进行过氧化物酶（ＰＯＤ）同工酶分析。结果表明：“钦州红荔”植株形态和果实性状保留有“黑叶”和“香荔”品种单株的一些特性,该株系早结丰产,果形特大,果皮鲜红色、品质优。叶片ＰＯＤ同工酶分析,它们具有相似遗传基础、迁移率为０．３３和０．５４的２条特征酶带,初步鉴定认为“钦     

偏好分布和利润对品牌竞争差异化的影响

要从经济学市场理论出发，提出品牌竞争是不完全竞争，品牌竞争的差异化是市场竞争的必然结果，是企业获利大小的一个决定因素。运用概率论随面变量分布理论，对消费者偏好的概率分布与消费者效用函数、品牌需求关系进行了定量分析，推导出消费者偏好差异化通过价格的作用而影响市场对品牌的需求，因而厂商为获得较高的市场份额需要进行品牌的差异化竞争。运用Shaked and Sutton模型，对厂商的利润大小与品牌差异化程度的关系进行分析，得出厂商为获取更多的利润，也需要进行品牌差异化竞争的结论。     

Fine-scale recombination rate differences between sexes, populations and individuals

Meiotic recombinations contribute to genetic diversity by yielding new combinations of alleles. Recently, high-resolution recombination maps were inferred from high-density single-nucleotide polymorphism (SNP) data using linkage disequilibrium (LD) patterns that capture historical recombination events. The use of these maps has been demonstrated by the identification of recombination hotspots and associated motifs, and the discovery that the PRDM9 gene affects the proportion of recombinations occurring at hotspots. However, these maps provide no information about individual or sex differences. Moreover, locus-specific demographic factors like natural selection can bias LD-based estimates of recombination rate. Existing genetic maps based on family data avoid these shortcomings, but their resolution is limited by relatively few meioses and a low density of markers. Here we used genome-wide SNP data from 15,257 parent-offspring pairs to construct the first recombination maps based on directly observed recombinations with a resolution that is effective down to 10 kilobases (kb). Comparing male and female maps reveals that about 15% of hotspots in one sex are specific to that sex. Although male recombinations result in more shuffling of exons within genes, female recombinations generate more new combinations of nearby genes. We discover novel associations between recombination characteristics of individuals and variants in the PRDM9 gene and we identify new recombination hotspots. Comparisons of our maps with two LD-based maps inferred from data of HapMap populations of Utah residents with ancestry from northern and western Europe (CEU) and Yoruba in Ibadan, Nigeria (YRI) reveal population differences previously masked by noise and map differences at regions previously described as targets of natural selection.     

Interference among deleterious mutations favours sex and recombination in finite populations

Sex and recombination are widespread, but explaining these phenomena has been one of the most difficult problems in evolutionary biology. Recombination is advantageous when different individuals in a population carry different advantageous alleles. By bringing together advantageous alleles onto the same chromosome, recombination speeds up the process of adaptation and opposes the fixation of harmful mutations by means of Muller's ratchet. Nevertheless, adaptive substitutions favour sex and recombination only if the rate of adaptive mutation is high, and Muller's ratchet operates only in small or asexual populations. Here, by tracking the fate of modifier alleles that alter the frequency of sex and recombination, we show that background selection against deleterious mutant alleles provides a stochastic advantage to sex and recombination that increases with population size. The advantage arises because, with low levels of recombination, selection at other loci severely reduces the effective population size and genetic variance in fitness at a focal locus (the Hill-Robertson effect), making a population less able to respond to selection and to rid itself of deleterious mutations. Sex and recombination reveal the hidden genetic variance in fitness by combining chromosomes of intermediate fitness to create chromosomes that are relatively free of (or are loaded with) deleterious mutations. This increase in genetic variance within finite populations improves the response to selection and generates a substantial advantage to sex and recombination that is fairly insensitive to the form of epistatic interactions between deleterious alleles. The mechanism supported by our results offers a robust and broadly applicable explanation for the evolutionary advantage of recombination and can explain the spread of costly sex.     

竞争的法经济学解读及其启示

竞争法律制度的构建,是法律对现实社会经济生活的回应.竞争法律制度的完善,又需要经济学理论的支撑.因此,从法经济学的视角解析竞争本身,有利于从法律制度上不断完善对竞争的规制,保障和促进竞争,从而构建与维护合理高效的竞争秩序,推动市场经济和谐繁荣发展.采取经济分析、比较分析等研究方法,对各种类型的竞争及其效用、竞争的性质、竞争的豁免等问题进行了深入探讨,认为我国竞争法律制度的完善必须首先明确竞争法的调整对象是存在垄断因素的"有效竞争";竞争的豁免虽然不可避免,但仍呈现出不断缩小的趋势,竞争法律制度必将在社会主义市场经济的发展中发挥更加重要的作用.     

商业银行个人业务顾客满意度研究——以宁波银行为例

商业银行实施顾客满意度战略是维系顾客争取顾客忠诚的必备条件。文章通过问卷调查的形式,对宁波银行个人客户展开银行顾客满意度抽样调查,对影响顾客选购银行产品和服务的各因素的重要程度和满意程度进行分析。结果发现诸如服务质量、ATM位置分布、金融创新速度等因素会显著影响宁波银行的客户满意度。因此宁波银行可以通过差异化服务获得竞争优势。     

电力产业激励性管制机制

电力产业过去一直处于垂直一体化的垄断经营状态，从20世纪80年代以来，电力改革在世界范围广泛进行。将发输配供四个环节分析，在发电和供电环节引入竞争，对仍然需要垄断经营的输电和配电环节进行管制改革，用激励性管制理论取代了传统的服务成本管制。对电力产业管制改革中广泛应用的激励管制理论-价格上限管制进行了介绍和分析。并在对价格上限管制在实践应用中经验和教训的基础上，提出了结合绩效标杆方法和标尺竞争理论的价格上限管制的综合激励性管制机制。