建筑室外风环境数值模拟的湍流模型比较

对日本建筑学会提供的室外无污染物扩散和有污染物扩散的建筑风洞实验模型,采用15种湍流模型分别求解其室外流场,通过模拟结果与风洞实验结果的对比分析,确定建筑室外风环境数值模拟所用的最优湍流模型.结果表明,Suga三次式高Re k-ε模型对风场和浓度场的求解具有很高的精度,是最优的模拟室外风环境的湍流模型,不足之处是该模型...     

Polymerization within a molecular-scale stereoregular template

Enzymes efficiently synthesize biopolymers by organizing monomer units within regularly structured molecular-scale spaces and exploiting weak non-covalent interactions, such as hydrogen bonds, to control the polymerization process. This 'template' approach is both attractive and challenging for synthetic polymer synthesis, where structurally regulated molecular-scale spaces could in principle provide solid-phase reaction sites for precision polymerization. Previously, free-radical polymerization of methyl methacrylate in solutions containing stereoregular isotactic (it) or syndiotactic (st) poly(methyl methacrylate) (PMMA) has been shown to result in template synthesis of the opposite PMMA based on stereocomplex formation with van der Waals interactions. However, using the structure of a solid to determine the stereochemical structure of a polymer has not been satisfactorily achieved. Here we show that macromolecularly porous ultrathin films, fabricated by a single assembly step, can be used for the highly efficient stereoregular template polymerization of methacrylates through stereocomplex formation. This reaction mould accurately transfers its structural properties of stereoregularity, molecular weight and organization within the template to the new polymer.     

A clonogenic common myeloid progenitor that gives rise to all myeloid lineages

Haematopoietic stem cells give rise to progeny that progressively lose self-renewal capacity and become restricted to one lineage. The points at which haematopoietic stem cell-derived progenitors commit to each of the various lineages remain mostly unknown. We have identified a clonogenic common lymphoid progenitor that can differentiate into T, B and natural killer cells but not myeloid cells. Here we report the prospective identification, purification and characterization, using cell-surface markers and flow cytometry, of a complementary clonogenic common myeloid progenitor that gives rise to all myeloid lineages. Common myeloid progenitors give rise to either megakaryocyte/erythrocyte or granulocyte/macrophage progenitors. Purified progenitors were used to provide a first-pass expression profile of various haematopoiesis-related genes. We propose that the common lymphoid progenitor and common myeloid progenitor populations reflect the earliest branch points between the lymphoid and myeloid lineages, and that the commitment of common myeloid progenitors to either the megakaryocyte/erythrocyte or the granulocyte/macrophage lineages are mutually exclusive events.     

A new species of Proctophyllodes Robin, 1868 (Acari: Proctophyllodidae) from two tanagers of the genus Piranga Vieillot (Passeriformes: Cardinalidae) from North America

A new feather mite species, Proctophyllodes pirangae sp. n. (Acari: Proctophyllodidae) is described from two tanagers of the genus Piranga Vieillot, 1808 (Passeriformes: Cardinalidae) in North America: the Scarlet Tanager, Piranga olivacea (Gmelin) and the Western Tanager, Piranga ludoviciana (Wilson) (Passeriformes: Cardinalidae) from North America. The new species belongs to the anthi species group and differs from the most similar species, Proctophyllodes polyxenus Atyeo and Braasch, by having in males, the aedeagus and genital sheath extending to or slightly beyond the level of setae g, the anterior margin of the opisthogastric shield shallowly concave, and its posterior margin nearly square-shaped, and the lamellae smaller; in females, both the lobar cleft and the transverse band of soft tegument at level of setae h1 are considerably narrower.

www.zoobank.org/urn:lsid:zoobank.org:pub:29B3D157-8114-48EC-AF31-61A99F6D0C3B     

铕-钆-聚N-乙烯基乙酰胺共发光体系的光学性能

在乙醇溶液中合成了掺杂Gd^2 的铕-聚N-乙烯基乙酰胺(PNVA)的配合物．测定并研究了配合物的红外光谱、紫外光谱和荧光光谱．结果表明：配合物的最佳激发波长为262nm；在此波长激发下配合物发出较强的荧光，不发光的Gd^3 离子对Eu^3 离子的发光有一定的增强作用，而不发光稀土Gd件离子对Eu^3 离子的发射峰位影响不大.     

聚N-异丙基丙烯酰胺-丙烯酸共聚微凝胶与Eu(Ⅲ)的相互作用

利用分散聚合法合成了聚N-异丙基丙烯酰胺-丙烯酸共聚微凝胶及其与Eu（Ⅲ）离子的配合物.用激光光散射、Zeta电位、紫外光谱、红外光谱及荧光光谱进行了表征.结果表明,加入Eu（Ⅲ）后,微凝胶粒子半径减小了约40 nm;Eu（Ⅲ）与微凝胶之间同时存在配位作用和静电作用;微凝胶和Eu（Ⅲ）之间可发生一定的能量传递,配合物的最佳激发波长为 293 nm,在此激发波长下Eu（Ⅲ）有较强的荧光特征发射,且Eu（Ⅲ）的质量分数为0.7%时强度最大.     

Evolution of genes and genomes on the Drosophila phylogeny

Comparative analysis of multiple genomes in a phylogenetic framework dramatically improves the precision and sensitivity of evolutionary inference, producing more robust results than single-genome analyses can provide. The genomes of 12 Drosophila species, ten of which are presented here for the first time (sechellia, simulans, yakuba, erecta, ananassae, persimilis, willistoni, mojavensis, virilis and grimshawi), illustrate how rates and patterns of sequence divergence across taxa can illuminate evolutionary processes on a genomic scale. These genome sequences augment the formidable genetic tools that have made Drosophila melanogaster a pre-eminent model for animal genetics, and will further catalyse fundamental research on mechanisms of development, cell biology, genetics, disease, neurobiology, behaviour, physiology and evolution. Despite remarkable similarities among these Drosophila species, we identified many putatively non-neutral changes in protein-coding genes, non-coding RNA genes, and cis-regulatory regions. These may prove to underlie differences in the ecology and behaviour of these diverse species.     

Tying a molecular knot with optical tweezers.

Filamentous structures are abundant in cells. Relatively rigid filaments, such as microtubules and actin, serve as intracellular scaffolds that support movement and force, and their mechanical properties are crucial to their function in the cell. Some aspects of the behaviour of DNA, meanwhile, depend critically on its flexibility-for example, DNA-binding proteins can induce sharp bends in the helix. The mechanical characterization of such filaments has generally been conducted without controlling the filament shape, by the observation of thermal motions or of the response to external forces or flows. Controlled buckling of a microtubule has been reported, but the analysis of the buckled shape was complicated. Here we report the continuous control of the radius of curvature of a molecular strand by tying a knot in it, using optical tweezers to manipulate the strand's ends. We find that actin filaments break at the knot when the knot diameter falls below 0.4 microm. The pulling force at breakage is around 1 pN, two orders of magnitude smaller than the tensile stress of a straight filament. The flexural rigidity of the filament remained unchanged down to this diameter. We have also knotted a single DNA molecule, opening up the possibility of studying curvature-dependent interactions with associated proteins. We find that the knotted DNA is stronger than actin.