Sperm competition between Drosophila males involves both displacement and incapacitation.

Females in almost all animal groups copulate with multiple males. This behaviour allows different males to compete for fertilization and gives females the opportunity to mediate this competition. In many animals and most insects, the second male to copulate with a female typically sires most of her offspring. In Drosophila melanogaster, this second-male sperm precedence has long been studied but, as in most species, its mechanism has remained unknown. Here we show, using labelled sperm in doubly mated females, that males can both physically displace and incapacitate stored sperm from earlier-mating males. Displacement occurs only if the second male transfers sperm to the female, and in only one of her three sperm-storage organs. Incapacitation can be caused by either fertile or spermless second males, but requires extended intervals between matings. Sperm from different males are not 'stratified' in the storage organs but mix freely. Many animal species may have multiple mechanisms of sperm competition like those observed here, and revealing these mechanisms is necessary to understand the genetic and evolutionary basis of second-male sperm precedence in animals.     

试论倾销与反倾销

随着全球经济与贸易的持续扩张，市场竞争不断激化，倾销与反倾销被越来越多地用于国际贸易中，随着中国进出口贸易总额的迅速增长，中国已成为“倾销与反倾销”下的最大受害国。本通过对西方国家对我国进行倾销与反倾销的现状、特点、原因及发展趋势的分析，提出面对西方国家的倾销、反倾销行为应采取的政策建议。     

WTO体制下的反倾销争端及我国的应对

在WTO多边贸易体制下,反倾销作为一种合法的贸易保护手段,已得到各国政府的普遍使用.随着中国加入WTO的日益临近,中国政府应对反倾销的形势也日趋严峻.国际社会反倾销立法与实践的演变,使我国应对反倾销工作更加困难.政府与企业对此应予高度重视,并积极采取措施,依法维护自身的利益,以促进国际贸易的正常发展.     

冻精顶体异常率与畸形率的测定结果分析

用普通生物显微镜对通辽市家畜繁育指导站10头西门塔尔种公牛的冷冻精液进行了顶体异常率与畸形率的测定。结果表明，精液经冷冻(-196℃)处理后，精子顶体异常率为56．22％，畸形率为10．93％，两项合计为67．15％。     

送料机凸轮的计算机仿真设计和虚拟制造

为了探讨虚拟制造在企业中的应用,运用机械CAD与计算机仿真技术设计送料机的凸轮,进而讨论如何在此基础上进行虚拟制造。结果表明虚拟制造可以动态模拟产品的设计、加工、检验,降低成本,提高质量,缩短开发周期,提高产量,增强企业市场竞争力,在氽业中有广泛的应用前景。     

Wolbachia在Drosophila auraria复合种和Drosophila simulans中的感染

用 Ｐ Ｃ Ｒ 方法检测了多种果蝇中共生菌 Ｗ ｏｌｂａｃｈｉａ 的感染,发现 Ｄｒｏｓｏｐｈｉｌａ ａｕｒａｒｉａ 复合种以及采集于北京地区的 Ｄｒｏｓｏｐｈｉｌａ ｓｉｍ ｕｌａｎｓ为 Ｗｏｌｂａｃｈｉａ 所感染, Ｒ Ｆ Ｌ Ｐ分析证实为单一感染．克隆了编码 Ｗ ｏｌｂａｃｈｉａ 外膜蛋白质的 ｗ ｓｐ 基因并进行了序列测定．同时比较了 Ｄｒｏｓｏｐｈｉｌａ ａｕｒａｒｉａ 复合种内 ４ 个种和采集于北京及美国加州的 Ｄｒｏｓｏｐｈｉｌａ ｓｉｍ ｕｌａｎｓ 的线粒体的细胞色素氧化酶 ２ 亚基基因的部分序列． 进而讨论了 Ｗｏｌｂａｃｈｉａ 对 Ｄｒｏｓｏｐｈｉｌａ ａｕｒａｒｉａ 复合种成员之间进化关系的影响．     

Sperm competition: motility and the midpiece in primates

In animals with multiple-partner mating systems, the gametes of two or more males must compete to fertilize a given set of ova. Here we show that the volume of the midpiece in individual sperm is significantly greater in primate species in which the females mate with multiple partners, and in which males have larger testes in relation to their body weight, than in those species that mate with only one partner and have relatively small testes. Our results indicate that sexual selection by sperm competition has influenced the evolution of a specific component of male-gamete morphology, the volume of the sperm midpiece.     

转炉倾动装置耳轴摆动故障原因

对某钢厂转炉倾动装置耳轴中心呈椭圆形轨迹运动进行了测量,分析其产生原因是由托圈耳轴轴线与转炉回转轴线不同轴引起耳轴挠曲变形.针对此现象,对倾动装置耳轴轴承的选择与扭力杆的设计提出建议.     

海洋倾倒实时监视系统设计

本文提出一种海洋倾倒自动监视系统的设计方法,采用高速单片机C8051F020,配合霍尼韦尔943系列超声波传感器,通过高性能滤波算法消除船只摇摆和波浪的影响,得到准确的船舶吃水线高度值。测量数据包含GPS信息、船舶状态等信息,经过特殊加密算法处理,通过DTU实时发送至岸站接收系统,作为倾倒管理和执法的依据。     

倾销与反倾销博弈分析

据关贸总协定中对倾销的定义，价格因素在判断有无倾销行为起重要作用，所以，选用以价格为变量的伯川德博弈模型来分析倾销与反倾销是合适的。本文用静态博弈得到伯川德价格均衡和伯川德贝叶斯价格均衡，并对两个均衡结果做了比较分析，表明信息不完全可导致两博弈方的价格差距扩大。这使得进口方便更容易错误地认为出口方有倾销行为。接下来，用不完全信息动态博弈分析了不存在倾销的低成本出口方便更容易被反倾销。     

新形势下反倾销与我国的应对措施

近年来 ,反倾销问题一直是我国对外贸易中的热门话题。我国政府应加强宏观调控 ,完善反倾销应诉机制 ,促进与国外的交流和合作 ;企业应规范内部管理 ,优化出口结构 ,建立灵活的经营策略 ,最大限度地维护我国企业的利益。     

试论中韩两国反倾销法的异同

论述了我国新出台的反倾销法与韩国反倾销法的产生背景,指出了同是发展中国家的这两个法律的共民点及在法律渊源、征收反倾销税、实施程序等方面的主要差异,并探讨了各自的利弊.这一比较对我国反倾销法的实施和完善将有积极的作用.     

倾销与损害因果关系模型中理论价格的方法研究

在建立倾销与损害因果关系模型中,作者引入“理论价格”的概念 ,并建立理论价格模型,利用该模型可以判定倾销与损害间是否存在逻辑关系。在建立理论价格模型时,假设了垄断竞争和寡头竞争的前提,结合反倾销的理论及实践,从各种寡头竞争理论价格模型中最终选用豪泰林模型作为基础,重新确定模型的假设前提,并对模型进行适用性的修正。经过推导和数学建模,确定出倾销造成的申请人理论损失的理论价格模型。利用该模型可将倾销造成的损失与所谓“排除因素”造成的损失区分开,因此可以用来直接判定因果关系,同时还可对产业损害进行计量描述。     

Charging for the waste dumping of open-pit metal mines

Based on the externality theory and the environmental value theory, the hypothesis of charging for waste dumping of open-pit metal mines was put forth. The charging methods were designed according to the characteristics of waste dumping of openpit metal mines, including charging based on the dumping amount of the total waste, multi-charging factors, exceeding standard punishment charging, and so on. The main charging parameter is based on the dumping area rather than the total amount of waste dumping.The charging model of waste dumping of open-pit mines was formulated, and the charging rate was divided into two parts, i.e., the standard charging rate and the differential charging rate. The standard charging rate was derived using the equilibrium dynamic model,whereas the differential one was obtained by establishing the fuzzy synthesized evaluation model.