Statistical analysis on protein-protein interface in crystals： Specific and non-specific interfaces are differentially distributed

The distribution of contact areas, or fractions of contacting, of protein-protein interfaces in crystals of pure polypeptides contains two components: a major exponential distribution and a minor flatter distribution. Suppose the two components belong to specific and non-specific contacts,respectively, then the probability of a contact with a givena rea, or fraction of contacting, can be estimated. By dividing the whole database into two sub-databases, one of them is known to contain more specific contacts than the other, this hypothesis is confirmed and it is also proved that the fraction of contacting is more effective than the contact area on discriminating specific and non-specific contacts in protein crystals.     

基于渠道竞争与品牌竞争的供应链定价策略和协调研究

构建了由两个制造商同时拥有线上和线下销售渠道组成的竞争供应链系统;分析了供应链系统中渠道竞争与品牌竞争共存时,两个制造商的Nash博弈决策和合作博弈决策的定价问题,探讨了不同的渠道竞争对价格决策和系统利润的影响,并通过数值算例验证了模型的有效性。研究发现:渠道的利润与渠道竞争与品牌竞争程度成反比,两个制造商通过联合调价的方式能实现双赢。     

Cooperation and competition in pathogenic bacteria

Explaining altruistic cooperation is one of the greatest challenges for evolutionary biology. One solution to this problem is if costly cooperative behaviours are directed towards relatives. This idea of kin selection has been hugely influential and applied widely from microorganisms to vertebrates. However, a problem arises if there is local competition for resources, because this leads to competition between relatives, reducing selection for cooperation. Here we use an experimental evolution approach to test the effect of the scale of competition, and how it interacts with relatedness. The cooperative trait that we examine is the production of siderophores, iron-scavenging agents, in the pathogenic bacterium Pseudomonas aeruginosa. As expected, our results show that higher levels of cooperative siderophore production evolve in the higher relatedness treatments. However, our results also show that more local competition selects for lower levels of siderophore production and that there is a significant interaction between relatedness and the scale of competition, with relatedness having less effect when the scale of competition is more local. More generally, the scale of competition is likely to be of particular importance for the evolution of cooperation in microorganisms, and also the virulence of pathogenic microorganisms, because cooperative traits such as siderophore production have an important role in determining virulence.     

不同搭接率时主方支圆钢管节点的承载力分析

K形搭接节点是空间结构中经常使用的一种连接方式.为深入了解K形搭接节点的特性,使用ANSYS软件,对一系列不同搭接率下的主方支圆K形钢管节点进行数值模拟,并将有限元分析结果绘制成曲线.分析支主管径宽比β,支主管厚度比τ,主管宽厚比γ支主管夹角θ等几何参数对此类节点极限承载力的影响.分析结果显示,当τ较小时,搭接率Ov对...     

战略创新改变企业竞争模式

在21世纪,重大的新产品可能会来源于生物技术,生物制药、医学治疗护理的手段已经开始出现重大的革新。但是,不管是哪个行业,要实现产品的重大革新都不是件容易的事。对于大多数企业来说,往往由于资源的限制,更难以在产品创新上取得突破。所以说,在21世纪,战略创新将是企业生存与成长的关键,而它仅受限于企业的创新能力和勇气。在过去20年内,涌现了一类新的商界明星——他们不是新产品的创造者,而是新战略的刨造者。迈克·戴尔(戴尔电脑)、     

Intrasexual competition and sexual selection in cooperative mammals

In most animals, the sex that invests least in its offspring competes more intensely for access to the opposite sex and shows greater development of secondary sexual characters than the sex that invests most. However, in some mammals where females are the primary care-givers, females compete more frequently or intensely with each other than males. A possible explanation is that, in these species, the resources necessary for successful female reproduction are heavily concentrated and intrasexual competition for breeding opportunities is more intense among females than among males. Intrasexual competition between females is likely to be particularly intense in cooperative breeders where a single female monopolizes reproduction in each group. Here, we use data from a twelve-year study of wild meerkats (Suricata suricatta), where females show high levels of reproductive skew, to show that females gain greater benefits from acquiring dominant status than males and traits that increase competitive ability exert a stronger influence on their breeding success. Females that acquire dominant status also develop a suite of morphological, physiological and behavioural characteristics that help them to control other group members. Our results show that sex differences in parental investment are not the only mechanism capable of generating sex differences in reproductive competition and emphasize the extent to which competition for breeding opportunities between females can affect the evolution of sex differences and the operation of sexual selection.     

特异性抗体和特异性免疫复合物的检测对结核病的诊断意义

以ＥＬＩＳＡ检测１０８例活动性肺结核、３９例稳定期肺结核、３０例肿瘤、１０１例非结核性肺部疾病患者及２０２例正常人血清的抗结核菌纯蛋白衍生物（ＰＰＤ）ＩｇＧ抗体（简称抗－ＰＰＤ）和循环免疫复合物（ＣＩＣ）中的抗－ＰＰＤＩｇＧ抗体（简称ＣＩＣ－ＰＰＤ）。结果表明，活动性肺结核患者的抗－ＰＰＤ和ＣＩＣ－ＰＰＤ水平明显高于正常人和各疾病组患者的水平（Ｐ＜０．００１），但与其病变范围无关。单一测定活动性肺结核患者的抗－ＰＰＤ，敏感性为８５．２％，特异性为９８．５％；测定ＣＩＣ－ＰＰＤ，敏感性为８６．１％．特异性９６．９％。以两者任一项阳性作为诊断活动性肺结核的标准，则敏感性为９３．５％。此外，对１１例活动性肺结核患者的动态观察表明，随着治疗天数的增加和临床症状的改善，患者的抗－ＰＰＤ和ＣＩＣ－ＰＰＤ水平会逐渐降低，前者于治疗后第２０～２４周降至正常水平，后者则于治疗后第１２～１６周降至正常值。研究结果提示测定患者的抗－ＰＰＤ和ＣＩＣ－ＰＰＤ的水平，可用于结核病诊断，对结核病的疗效判定亦有帮助。     

物理竞赛与素质教育

第二课堂是开展素质教育、打造精品课程的重要环节,本文就第二课堂中的物理竞赛活动所反映出的问题,结合当前教学现状,对竞赛的组织、题目的选择以及答题结果进行了分析,并提出了相应的看法与思考.     

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.     

4腿机器人足球比赛的通信机制及协作控制

针对4腿机器人足球比赛中机器人的通信机制及协作控制等问题,提出了一种新的完整的分布式多主体系统控制方法,包括通信控制、路径规划以及动态角色分配.该方法通过启发式投标函数进行任务分配,通过电场法表示抽象的环境信息.协作控制中不必进行大量的计算,主体之间不必频繁地进行数据交换.该方法能够满足比赛动态性和不确定性的需要,并在实际比赛中得到了很好的验证.     

Extra-pair copulation and sperm competition in the zebra finch

Most birds are monogamous, but recent studies have shown that extra-pair copulations (EPCs) occur frequently despite a range of paternity guards, including mate-guarding and frequent copulation. Although EPCs are known to result in extra-pair paternity, there are no previous quantitative estimates of the success of EPCs in fertilizing eggs. We present here estimates of the likelihood of success of extra-pair copulations in a monogamous passerine, the zebra finch Poephila guttata. We show that (1) EPCs occurring under semi-natural conditions in captivity result in extra-pair paternity, (2) sperm from the last male to mate has precedence over previous matings: a single EPC occurring last is disproportionately successful in fertilizing eggs, but EPCs followed by further pair copulations have a low probability of success. These results have important implications for sexual selection theory.