Context-dependent autonomous self-fertilization yields reproductive assurance and mixed mating

The evolution of self-fertilization in hermaphrodites is opposed by costs that decrease the value of self progeny relative to that of outcross progeny. However, self-fertilization is common in plants; 20% are highly selfing and 33% are intermediate between selfing and outcrossing. Darwin proposed an adaptive benefit of self-pollination in providing reproductive assurance when outcrossing is impossible. Moreover, if outcross pollen receipt is inconsistent within or between years, these conditions likewise favour self-pollination, and this can result in a mixture of self and outcross seed production (mixed mating). Despite wide acceptance, the reproductive assurance hypothesis has lacked the support of complete empirical evidence to show that variable pollination can create both the ecological and genetic conditions favouring self-pollination. We recently showed in Collinsia verna that during periods of infrequent pollinator visits, autonomous self-pollination boosted seed output per flower, the key ecological condition. Here we show low inbreeding depression and marker-based estimates of selfing, demonstrating that when the pollination environment in wild populations necessitates reproductive assurance, selfing rates increase. We provide a complete demonstration of reproductive assurance under variable pollination environments and mechanistically link reproductive assurance to intermediate selfing rates through mixed mating.     

Genetic selection for reproductive photoresponsiveness in deer mice

Seasonal breeding is common in mammals, particularly in habitats outside the tropics. Climate and availability of food are the ultimate factors that usually dictate the optimal time of year for a mammal to breed; however, day length (photoperiod) often serves as the proximal cue to signal the onset or cessation of seasonal reproduction. Some individuals in some populations of deer mice are reproductively responsive to photoperiod, while other individuals in the same population are not. As shown here, selection can dramatically alter the frequency of photoresponsiveness in a laboratory population in only two generations. To our knowledge this is the first demonstration of selection for reproductive photoresponsiveness in any mammal. By implication, some wild populations of deer mice must use multiple, genetic-based reproductive strategies, and the degree to which each such strategy is exhibited must be subject to rapid change in response to both seasonally and momentarily changing climatic and dietary conditions.     

Genetic recombination between RNA components of a multipartite plant virus

Genetic recombination of DNA is one of the fundamental mechanisms underlying the evolution of DNA-based organisms and results in their diversity and adaptability. The importance of the role of recombination is far less evident for the RNA-based genomes that occur in most plant viruses and in many animal viruses. RNA recombination has been shown to promote the evolutionary variation of picornaviruses, it is involved in the creation of defective interfering (DI) RNAs of positive- and negative-strand viruses and is implicated in the synthesis of the messenger RNAs of influenza virus and coronavirus. However, RNA recombination has not been found to date in viruses that infect plants. In fact, the lack of DI RNAs and the inability to demonstrate recombination in mixedly infected plants has been regarded as evidence that plants do not support recombination of viral RNAs. Here we provide the first molecular evidence for recombination of plant viral RNA. For brome mosaic virus (BMV), a plus-stranded, tripartite-genome virus of monocots, we show that a deletion in the 3' end region of a single BMV RNA genomic component can be repaired during the development of infection by recombination with the homologous region of either of the two remaining wild-type BMV RNA components. This result clearly shows that plant viruses have available powerful recombinatory mechanisms that previously were thought to exist only in animal hosts, thus they are able to adapt and diversify in a manner comparable to animal viruses. Moreover, our observation suggests an increased versatility of viruses for use as vectors in introducing new genes into plants.     

火电厂动态成本分析系统的研究

针对当前电力系统中企业竞价上网的需要,提出了火力发电厂动态成本分析系统系统框架,论述了如何获取动态成本的原始数据、如何分解和计算动态成本以及动态成本统计分析的方法及步骤。     

Genetic linkage of ecological specialization and reproductive isolation in pea aphids

The evolution of ecological specialization generates biological diversity and may lead to speciation. Genetic architecture can either speed or retard this process. If resource use and mate choice have a common genetic basis through pleiotropy or close linkage, the resulting genetic correlations can promote the joint evolution of specialization and reproductive isolation, facilitating speciation. Here we present a model of the role of genetic correlations in specialization and speciation, and test it by analysing the genetic architecture of key traits in two highly specialized host races of the pea aphid (Acyrthosiphon pisum pisum; Hemiptera : Aphididae). We found several complexes of pleiotropic or closely linked quantitative trait loci (QTL) that affect key traits in ways that would promote speciation: QTL with antagonistic effects on performance on the two hosts are linked to QTL that produce asortative mating (through habitat choice). This type of genetic architecture may be common in taxa that have speciated under divergent natural selection.     

狭边大叶藓(Rhodobryum ontariense)遗传多样性的ISSR分析

狭边大叶藓[Rhodobryum ontariense(Kindb.)Paris]为真藓科大叶藓属植物,具有治疗心血管疾病的功效。本研究选用ISSR分子标记对分布于河北、河南、四川和陕西四省的9个狭边大叶藓自然居群的遗传多样性进行研究,目的在于揭示狭边大叶藓居群的遗传结构和遗传多样性水平,为其保护和合理开发利用提供科学依据。用8个ISSR引物对9个居群共58个样品进行扩增,共获得47条清晰的扩增位点。POPGENE分析表明,狭边大叶藓居群遗传多样性水平较低(多态性位点比率为37.75%,Nei’s基因多样性为0.153 0,Shannon’信息指数为0.222 8,遗传分化指数Gst为0.299 7,居群间的基因流为1.168 2)。AMOVA分析表明,大多数遗传变异(84.07%)存在于居群内,15.93%的遗传变异存在于居群间(Φst=0.159 3)。UPGMA聚类分析表明,狭边大叶藓居群遗传距离和地理距离没有相关性(r=0.404 95,p=0.979 1)。     

植物病害生物防治菌的改良技术及产业化

介绍了植病生防菌的遗传改良技术,通过诱变育种、杂交育种及基因工程技术增强生防菌的抗菌活性和扩大防治对象,使改良后的生防菌较传统的生物杀菌剂具有更高的生防效率和更强的市场竞争力,这些改良技术的研究需要现代生物科学、分子生物学等多学科的结合。对生防菌的产业化研究作了综述,分析了生防菌产业化研究现状及实现产业化的关键技术指出了生防菌产业化的市场开发需要国家的支持,科研单位和企业等各方面的合作。     

南岭国家濒危植物长柄双花木遗传多样性研究

应用ISSR分子标记技术,对长柄双花木(Disanthus cercidifolius var.longipes)5个南岭野生种群的遗传多样性进行了初步研究.8条ISSR引物扩增出101条带,其中64条具多态性,多态位点百分率为63.37%.总的Nei's基因多样性指数为0.285 9,种群内基因多样性(Hs)为0.274 1,长柄双花木在物种水平上遗传多样性水平较低.在种群水平上,种群多态位点百分率在60%~75%之间,Nei's基因多样性指数为0.269 5~0.282 4,Shannon信息多态性指数为0.384 5~0.399 9.道县种群和莽山种群的遗传多样性水平较高.种群间的基因分化系数为0.041 4,表明长柄双花木绝大多数遗传变异发生在种群内的个体间(95.86%).UPGMA聚类分析结果表明:5个野生种群未按地理位置进行聚类,连州2个种群较为特殊,先与江西井冈山种群聚在一起,具体原因有待进一步研究.     

Flying in a flock comes at a cost in pigeons

Flying birds often form flocks, with social, navigational and anti-predator implications. Further, flying in a flock can result in aerodynamic benefits, thus reducing power requirements, as demonstrated by a reduction in heart rate and wingbeat frequency in pelicans flying in a V-formation. But how general is an aerodynamic power reduction due to group-flight? V-formation flocks are limited to moderately steady flight in relatively large birds, and may represent a special case. What are the aerodynamic consequences of flying in the more usual 'cluster' flock? Here we use data from innovative back-mounted Global Positioning System (GPS) and 6-degrees-of-freedom inertial sensors to show that pigeons (1) maintain powered, banked turns like aircraft, imposing dorsal accelerations of up to 2g, effectively doubling body weight and quadrupling induced power requirements; (2) increase flap frequency with increases in all conventional aerodynamic power requirements; and (3) increase flap frequency when flying near, particularly behind, other birds. Therefore, unlike V-formation pelicans, pigeons do not gain an aerodynamic advantage from flying in a flock. Indeed, the increased flap frequency, whether due to direct aerodynamic interactions or requirements for increased stability or control, suggests a considerable energetic cost to flight in a tight cluster flock.     

项目施工成本管理中的目标成本

通过对项目施工成本中目标成本的说明和现代企业成本管理理论中成本企画理论的阐述与比较分析,说明在我国的建筑施工过程中,目标成本的制定和执行,对施工项目成本控制的重要意义.指出广大施工企业要想在激烈的竞争中取胜,必须重视目标成本.     

青藏高原东缘克隆植物珠芽蓼的RAPD遗传多样性研究

以青藏高原分布广泛的克隆植物珠芽蓼(Polygonum viviparum)为研究材料,采用RAPD技术分析了珠芽蓼在不同海拔下7个自然种群的遗传多样性.通过贝叶斯法估测了种群的遗传分化程度,同时与其它算法(Nei遗传分化系数GST等)作以比较.13条随机引物共扩增出117条带,多态性位点PPL为84,多态位点比率PPL为71.79%,但种群水平平均多态位点比率仅为32.60%.求出θ B(Hickory)=0.602 3,同种群间基因分化系数GST=0.575 3较为接近,种群间基因分化大于种群内基因分化.AMOVA分析显示,在全部变异中,66.59%的遗传变异存在于种群间,33.41%的遗传变异存在于种群内.用POPGENE 32软件分析表明,珠芽蓼具有较高的遗传多样性,种群总的Nei's基因多样性为0.289 1,总的Shannon信息多样性指数为0.420 7,但各种群内遗传多样性水平则较低.种群内平均Nei's基因多样性为0.122 7,平均Shannon信息指数为0.180 4;基因流Nm=0.369 1,种群的基因交流很少.UPGMA聚类分析结果显示,7个种群中P1和P2先聚类,P5、P6, P4、P7分别聚在一起,最后与P3合为一支.相关性结果表明,遗传距离与海拔梯度、地理距离均相关不显著.     

目标成本管理在施工成本管理中的运用

通过对目标成本管理在施工企业成本管理中的运用说明 ,介绍了目标成本管理对施工企业所起的积极作用 ,以及实施这一制度和方法所带来的各种效应     

计数型截尾序贯保证试验的研究

针对高成本、破坏性试验特点的计数型产品,为减少产品的抽样验收试验成本,对截尾序贯型保证试验进行了研究。在产品已通过鉴定试验的条件下,采用贝叶斯分析方法对鉴定试验数据进行综合,给出了成败型产品成功率参数P的截尾序贯型保证试验T~A的相关理论及方案设计方法.研究结果表明,对高质量水平的产品,截尾序贯保证试验T~A与原试验方案T~(OA)相比具有相当的通过验收试验的概率水平,同时能大幅度减少产品的平均试验次数等优点。采用实例分析方式,对截尾序贯保证试验T~A的设计方法进行了详细说明,并通过与原试验方案T~(OA)的操作特征曲线(OC)及平均试验次数(ASN)曲线的比较,进一步对截尾序贯型保证试验方案的优良性进行了验证。     

分析测试中的质量保证和质量控制

文章详细介绍了分析测试中的质量、质量保证和质量控制技术。     

中国社会保障基金问题的国际比较

我国社会保障资金缺口巨大,各级财政,尤其中央财政承受着巨大压力和风险。文章从分析我国社会保障基金缺口原因入手,借鉴西方国家解决社会保障基金问题的经验,提出了解决我国社会保障基金缺口问题的对策。     

天然气联合循环电厂CO2捕获整体性能及成本敏感性分析

为研究天然气联合循环(NGCC)电厂引入燃烧后CO_2捕获系统后电厂整体性能及成本,利用整合环境控制模型(IECM)模拟了一乙醇胺(MEA)吸收剂的燃烧后CO_2捕获NGCC(NGCC+CC)电厂运行情景,其中以无CO_2捕获的NGCC电厂作为参考,同时和等发电量的燃烧后CO_2捕获燃煤电厂(PC+CC)进行对比.为研究NGCC+CC电厂的电力均化成本(LCOE)、CO_2捕获成本及吸收剂再生能耗等关键指标,对各指标的主要影响因子进行了敏感性分析,以优化CO_2捕获系统的运行参数.研究结果表明:MEA吸收剂的燃烧后CO_2捕获系统会降低NGCC电厂的整体效率,效率损失为6.92%,从而导致LCOE升高,从896元/MWh增长至1 020元/MWh,而PC+CC电厂的效率损失为4%.NGCC电厂容量因子和天然气价格是LCOE的主要敏感因素,尤其是天然气价格.NGCC+CC电厂的CO_2捕获成本主要受电厂容量因子、天然气价格及CO_2去除率等影响.吸收剂再生能耗则与吸收剂浓度、蒸汽热含量、贫液负荷、气液比及热电效率等相关.     

组织际信息系统运作成本： 结构成本与交易成本

全球企业都面临信息系统的运营收入与成本的最优化问题,为了更好解决组织际信息系统收益的有关问题,以运作成本为视角展开研究.设计组织际信息系统运作成本的结构,将其划分为结构成本与交易成本,构建成本的定量方法与模型并求解,最后进行仿真模拟来验证其合理性与作用,从而得到一系列扩展的结论.