Chromosome-wide SNPs reveal an ancient origin for Plasmodium falciparum

The Malaria's Eve hypothesis, proposing a severe recent population bottleneck (about 3,000-5,000 years ago) of the human malaria parasite Plasmodium falciparum, has prompted a debate about the origin and evolution of the parasite. The hypothesis implies that the parasite population is relatively homogeneous, favouring malaria control measures. Other studies, however, suggested an ancient origin and large effective population size. To test the hypothesis, we analysed single nucleotide polymorphisms (SNPs) from 204 genes on chromosome 3 of P. falciparum. We have identified 403 polymorphic sites, including 238 SNPs and 165 microsatellites, from five parasite clones, establishing chromosome-wide haplotypes and a dense map with one polymorphic marker per approximately 2.3 kilobases. On the basis of synonymous SNPs and non-coding SNPs, we estimate the time to the most recent common ancestor to be approximately 100,000-180,000 years, significantly older than the proposed bottleneck. Our estimated divergence time coincides approximately with the start of human population expansion, and is consistent with a genetically complex organism able to evade host immunity and other antimalarial efforts.     

Helly第二定理及其在极限计算中的应用

在极限计算中应用概率论中的HelIy第二定理推导出了一些熟如的数学分析结果,使一些极限的计算得到了一定的简化。     

基于信息共享的上海铁路集装箱多式联运中心

提出了组建上海铁路集装箱多式联运中心 ,建成铁路国际集装箱运输信息交换系统 .以运输信息为资源 ,提高运输效率 ,促进集装箱多式联运 ,最终达到运输经济增长的效果 .     

汉语广告英译中修辞手法的应用

广告讲究修辞技巧，广告英译时适当使用修辞手段能够体现广告的特点。从重复、头尾韵、隐喻、拟人、对比、排比、对偶、双关、套用或更改惯用句式等方面探讨了如何使用修辞手段翻译汉语广告。     

地层条件下砂岩储层的AVO响应模板

在实验室对WXS凹陷的W3地层岩芯样品进行了地层压力和温度条件下的密度、孔隙度和声波速度测试,基于岩石物理模型提出一种集成目标储层孔隙度、厚度和饱和流体信息的AVO响应模板制作方法。该方法以砂岩孔隙度与干燥状态下的密度和纵、横波阻抗的线性关系为核心,利用Gassmann流体替换技术构建岩石物理模型,通过正演模拟获得不同...     

Apolipoprotein-mediated pathways of lipid antigen presentation

Peptide antigens are presented to T cells by major histocompatibility complex (MHC) molecules, with endogenous peptides presented by MHC class I and exogenous peptides presented by MHC class II. In contrast to the MHC system, CD1 molecules bind lipid antigens that are presented at the antigen-presenting cell (APC) surface to lipid antigen-reactive T cells. Because CD1 molecules survey endocytic compartments, it is self-evident that they encounter antigens from extracellular sources. However, the mechanisms of exogenous lipid antigen delivery to CD1-antigen-loading compartments are not known. Serum apolipoproteins are mediators of extracellular lipid transport for metabolic needs. Here we define the pathways mediating markedly efficient exogenous lipid antigen delivery by apolipoproteins to achieve T-cell activation. Apolipoprotein E binds lipid antigens and delivers them by receptor-mediated uptake into endosomal compartments containing CD1 in APCs. Apolipoprotein E mediates the presentation of serum-borne lipid antigens and can be secreted by APCs as a mechanism to survey the local environment to capture antigens or to transfer microbial lipids from infected cells to bystander APCs. Thus, the immune system has co-opted a component of lipid metabolism to develop immunological responses to lipid antigens.     

抗日战争时期华北根据地农民的政治参与

抗日战争时期,华北根据地农民在中国共产党领导下进行了大规模的政治参与.根据地农村政权结构、社会组织及政治文化等方面的变化,为农民政治参与提供了有利的客观环境.农民的内容广泛形式多样的政治参与对农民自身和中共的革命目标而言,均产生了深远影响.     

磨床爬行的原因分析及排除

从动静摩擦阻力、传动件刚性、运动部件质量等5个方面分析了磨床产生爬行的原因，绘制出了磨床产生爬行因果图，针对磨床产生爬行的原因，提出了相应的防治措施。