Convergent dental adaptations in pseudo-tribosphenic and tribosphenic mammals

Tribosphenic molars of basal marsupials and placentals are a major adaptation, with the protocone (pestle) of the upper molar crushing and grinding in the talonid basin (mortar) on the lower molar. The extinct pseudo-tribosphenic mammals have a reversed tribosphenic molar in which a pseudo-talonid is anterior to the trigonid, to receive the pseudo-protocone of the upper molar. The pseudo-protocone is analogous to the protocone, but the anteriorly placed pseudo-talonid is opposite to the posterior talonid basin of true tribosphenic mammals. Here we describe a mammal of the Middle Jurassic period with highly derived pseudo-tribosphenic molars but predominantly primitive mandibular and skeletal features, and place it in a basal position in mammal phylogeny. Its shoulder girdle and limbs show fossorial features similar to those of mammaliaforms and monotremes, but different compared with those of the earliest-known Laurasian tribosphenic (boreosphenid) mammals. The find reveals a much greater range of dental evolution in Mesozoic mammals than in their extant descendants, and strengthens the hypothesis of homoplasy of 'tribosphenic-like' molars among mammals.     

A second generation human haplotype map of over 3.1 million SNPs

We describe the Phase II HapMap, which characterizes over 3.1 million human single nucleotide polymorphisms (SNPs) genotyped in 270 individuals from four geographically diverse populations and includes 25-35% of common SNP variation in the populations surveyed. The map is estimated to capture untyped common variation with an average maximum r2 of between 0.9 and 0.96 depending on population. We demonstrate that the current generation of commercial genome-wide genotyping products captures common Phase II SNPs with an average maximum r2 of up to 0.8 in African and up to 0.95 in non-African populations, and that potential gains in power in association studies can be obtained through imputation. These data also reveal novel aspects of the structure of linkage disequilibrium. We show that 10-30% of pairs of individuals within a population share at least one region of extended genetic identity arising from recent ancestry and that up to 1% of all common variants are untaggable, primarily because they lie within recombination hotspots. We show that recombination rates vary systematically around genes and between genes of different function. Finally, we demonstrate increased differentiation at non-synonymous, compared to synonymous, SNPs, resulting from systematic differences in the strength or efficacy of natural selection between populations.     

Genome-wide detection and characterization of positive selection in human populations

With the advent of dense maps of human genetic variation, it is now possible to detect positive natural selection across the human genome. Here we report an analysis of over 3 million polymorphisms from the International HapMap Project Phase 2 (HapMap2). We used 'long-range haplotype' methods, which were developed to identify alleles segregating in a population that have undergone recent selection, and we also developed new methods that are based on cross-population comparisons to discover alleles that have swept to near-fixation within a population. The analysis reveals more than 300 strong candidate regions. Focusing on the strongest 22 regions, we develop a heuristic for scrutinizing these regions to identify candidate targets of selection. In a complementary analysis, we identify 26 non-synonymous, coding, single nucleotide polymorphisms showing regional evidence of positive selection. Examination of these candidates highlights three cases in which two genes in a common biological process have apparently undergone positive selection in the same population:LARGE and DMD, both related to infection by the Lassa virus, in West Africa;SLC24A5 and SLC45A2, both involved in skin pigmentation, in Europe; and EDAR and EDA2R, both involved in development of hair follicles, in Asia.     

大型二维装箱问题及其禁忌算法研究

对大型二维装箱问题进行描述,提出求解该问题的禁忌算法.算法基于自然数编码,设计了货物的摆放规则和序列生成方式,采用二种邻域,根据邻域的不同,构造了两种禁忌表.算法采用惩罚函‘数处理空间利用率约束.介绍算法的原理,给出了具有代表性算例试验结果并且进行了分析.试验结果表明了提出的禁忌算法对优化大型二维装箱问题的有效性.     

水溶液中相转化制备六方相三氧化钼及其电化学嵌锂性质

三氧化钼(MoO3)以三种常见的物相存在:正交相、六方相和单斜相,前者为热力学稳定相,后两者为热力学介稳相.相对于稳定的正交相MoO3,介稳的六方相MoO3较难制备.笔者采用对已商品化的正交相MoO3再次结晶的方法制得了纯六方相MoO3.通过透射电镜(TEM)观察可知产物为均匀的纳米棒.实验结果表明合成的六方相MoO3的首次放电容量比商品化的正交相MoO3高.六方相MoO3有望成为理想的锂离子电池阴极材料.     

Hydroxyl radical electrochemically generated with water as the complete atom source and its environmental application

The most reactive hydroxyl radical （OH） was generated by electrochemical approach with safe water as the complete atom source. The direct evidence for OH formation was obtained by electron spin resonance method. The powerful OH electrochemically generated could effectively degrade organic pollutants and reduce the toxicity of wastewater. Electrochemical disinfection by OH was considerably efficient even without the aid of active chlorine. Bacteria inactivation of 99.99% was achieved for contact time of 30 min and current density of 5 mA·cm^-2, In comparison with active chlorine, OH is rather attractive as a promising environmentally benign disinfectant and opens a new route for microbial inactivation.     

祁门县非物质文化遗产旅游资源开发研究

在阐述了非物质文化遗产与旅游发展关系的基础上,分析评价了祁门县非物质文化遗产旅游资源类型及开发现状,构筑了该县非物质文化遗产旅游产品体系,并针对目前开发过程中的困境提出了相应的开发、保障措施.     

从价格的演变历程浅析国内民航运输价格改革

从价格的演变历程入手,对目前民航客运价格存在的问题及成因进行初步分析,提出价格改革的思路,进而促进相关垄断行业的改革与发展.     

An improved traitor tracing scheme based on bilinear map

T6 et al presented a bilinear-map-based traitor tracing scheme（TSZ scheme） with revocation, but it is a symmetric scheme because it does not provide non-repudiation. In this paper, an improved TSZ scheme was proposed by using oblivious polynomial evaluation （OPE） protocol and service parameters. Under the recondition of general sameness capabilities of both TSZ and improved TSZ scheme, the new scheme adds some advantages such as providing multi-service capability, user＇s non-repudiation and data provider＇s no-framing innocent users. Furthermore, it is also proved to be semantically secure under the decisional bilinear Diffie-Hellman （DBDH problem） assumption.     

New crystal structure of molecular complex 1-piperidine carboxylate-piperidinium-H<Subscript>2</Subscript>O studied by X-ray single crystal diffraction

Piperidine absorbs CO2 and H2O in air to form a molecular complex： piperidium-l-piperidinecarboxylate-H2O. The structure of the complex was characterized by X-ray single crystal diffraction. The crystal structure was determined to be triclinic, space group P1^-with a=0.648 6（8） nm, b=0.809 200） nm, c= 1.357 1（16） nm, a=96.96706）°, β =102.506（15）°,γ=104.202 05）°, Z=2. The complex is stabilized via five hydrogen bonds between the three components, N-O electrostatic interaction and O-O interaction （electron transfer） betweenl-piperidinecarboxylate and H2O. Due to electron transference of carbamate ion, the oxygen atom in water molecule is strongly negatively charged and the O-H bond is considerably shorter than that of the free molecule of water. The formation of the molecular complex is a reversible process and will decompose upon heating. The mechanism of formation and stabilization is further investigated herein.