8,207 research outputs found

    Phase diagram and a possible unified description of intercalated iron selenide superconductors

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    We propose a theoretical description of the phase diagram and physical properties in A2Fe4Se5-type (A=K, Tl) compounds based on a coexistent local moment and itinerant electron picture. Using neutron scattering and ARPES measurements to fix the general structure of the local moment and itinerant Fermi pockets, we find a superconducting (SC) regime with s-wave pairing at the M pockets and an incipient sign-change s-wave near the Gamma point, which is adjacent to an insulating state at low doping and a charge-density-wave (CDW) state at high doping. The uniform susceptibility and resistivity are found to be consistent with the experiment. The main distinction with iron pnictide superconductors is also discussed.Comment: 4 pages, 5 figure

    Growth of Thin Oxidation-Resistive Crystalline Si Nanostructures on Graphene

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    We report the growth of Si nanostructures, either as thin films or nanoparticles, on graphene substrates. The Si nanostructures are shown to be single crystalline, air stable and oxidation resistive, as indicated by the observation of a single crystalline Si Raman mode at around 520 cm-1, a STM image of an ordered surface structure under ambient condition, and a Schottky junction with graphite. Ultra-thin silicon regions exhibit silicene-like behavior, including a Raman mode at around 550 cm-1, a triangular lattice structure in STM that has distinctly different lattice spacing from that of either graphene or thicker Si, and metallic conductivity of up to 500 times higher than that of graphite. This work suggests a bottom-up approach to forming a Si nanostructure array on a large scale patterned graphene substrate for fabricating nanoscale Si electronic devices

    Gene Transfer of Calcitonin Gene-Related Peptide Inhibits Macrophages and Inflammatory Mediators in Vein Graft Disease

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    Vein graft disease is a chronic inflammatory disease and limits the late results of coronary revascularization. Calcitonin gene-related peptide (CGRP) inhibits macrophages infiltrated and inflammatory mediators, we hypothesized that transfected CGRP gene inhibits macrophages infiltrated and inflammatory mediators in vein graft disease. Autologous rabbit jugular vein grafts were incubated ex vivo in a solution of mosaic adeno-associated virus vectors containing CGRP gene (AAV2/1.CGRP) 、escherichia coli lac Z gene (AAV2/1.LacZ) or saline and then interposed in the carotid artery. Intima/media ratio were evaluated at postoperative 4 weeks, Macrophages were marked with CD68 antibody by immunocytochemistry. Inflammatory mediators were mensurated with real-time PCR. Neointimal thickening was significantly suppressed in AAV2/1.CGRP group. Macrophages infiltrated and inflammatory mediators monocyte chemoattractant protein-1 (MCP-1)、tumor necrosis factorα(TNF-α)、inducible nitricoxide synthase (iNOS)、matrix metalloproteinase-9 (MMP-9) was significantly suppressed in AAV2/1.CGRP group.Gene transfected AAV2/1.CGRP suppressed neointimal hyperplasia in vein graft disease by suppressed macrophages infiltrated and inflammatory mediators

    QCD Approach to B->D \pi Decays and CP Violation

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    The branching ratios and CP violations of the BDπB\to D\pi decays, including both the color-allowed and the color-suppressed modes, are investigated in detail within QCD framework by considering all diagrams which lead to three effective currents of two quarks. An intrinsic mass scale as a dynamical gluon mass is introduced to treat the infrared divergence caused by the soft collinear approximation in the endpoint regions, and the Cutkosky rule is adopted to deal with a physical-region singularity of the on mass-shell quark propagators. When the dynamical gluon mass μg\mu_g is regarded as a universal scale, it is extracted to be around μg=440\mu_g = 440 MeV from one of the well-measured BDπB\to D\pi decay modes. The resulting predictions for all branching ratios are in agreement with the current experimental measurements. As these decays have no penguin contributions, there are no direct CPCP asymmetries. Due to interference between the Cabibbo-suppressed and the Cabibbo-favored amplitudes, mixing-induced CP violations are predicted in the BD±πB\to D^{\pm}\pi^{\mp} decays to be consistent with the experimental data at 1-σ\sigma level. More precise measurements will be helpful to extract weak angle 2β+γ2\beta+\gamma.Comment: 21pages,5 figures,3 tables, typos corrected and numerical result for one of decay channels is improve

    Recruitment of cyanobacteria from the sediments in the eutrophic Shanzi Reservoir

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    This study investigated the impact of four environmental factors on the recruitment of cyanobacteria from bottom sediments in the eutrophic Shanzi Reservoir. Temperature and light were identified as the key determinants for the recruitment of Microcystis and Oscillatoria. Cyanobacteria became dominant at higher temperature (20°C) and light intensity (2000 lx) and Microcystis and Oscillatoria were the major species. Detailed recruitment simulation undertaken with the respective gradients of temperature and light suggested that both Microcystis and Oscillatoria are temperature sensitive and that their critical temperature point was 10°C. However, distinct light impacts were observed only on Microcystis. The recruitment of Oscillatoria was light independent, whereas Microcystis had a positive relationship with light intensity. Physical disturbance promoted Microcystis recruitment and also affected the structure of the recruited cyanobacterial community at the water–sediment interface, based on quantitative polymerase chain reaction (qPCR) and phylogenetic analysis

    Continuous Acetone–Butanol–Ethanol (ABE) Fermentation with in Situ Solvent Recovery by Silicalite-1 Filled PDMS/PAN Composite Membrane

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    The pervaporation (PV) performance of a thin-film silicalite-1 filled PDMS/PAN composite membrane was investigated in the continuous acetone–butanol–ethanol (ABE) production by a fermentation–PV coupled process. Results showed that continuous removal of ABE from the broth at three different dilution rates greatly increased both the solvent productivity and the glucose utilization rate, in comparison to the control batch fermentation. The high solvent productivity reduced the acid accumulation in the broths because most acids were reassimilated by cells for ABE production. Therefore, a higher total solvent yield of 0.37 g/g was obtained in the fermentation–PV coupled process, with a highly concentrated condensate containing 89.11–160.00 g/L ABE. During 268 h of the fermentation–PV coupled process, the PV membrane showed a high ABE separation factor of more than 30 and a total flux of 486–710 g/m2h. Membrane fouling was negligible for the three different dilution rates. The solution-diffusion model, especially the mass transfer equation, was proved to be applicable to this coupled process.<br/

    Iron(III) Chloride-catalyzed Nucleophilic Substitution of Propargylic Alcohols: A General and Efficient Approach for the Synthesis of 1,4-Diynes

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    A wide variety of 1,4-diynes have been constructed via a novel FeCl(3)-catalyzed coupling reaction of propargylic alcohols with alkynylsilanes. This synthetic approach provides a general, efficient, and economical route to 1,4-cliynes.National Natural Science Foundation of China[20772098, 21072159

    Finite-size effect and the components of multifractality in financial volatility

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    Many financial variables are found to exhibit multifractal nature, which is usually attributed to the influence of temporal correlations and fat-tailedness in the probability distribution (PDF). Based on the partition function approach of multifractal analysis, we show that there is a marked finite-size effect in the detection of multifractality, and the effective multifractality is the apparent multifractality after removing the finite-size effect. We find that the effective multifractality can be further decomposed into two components, the PDF component and the nonlinearity component. Referring to the normal distribution, we can determine the PDF component by comparing the effective multifractality of the original time series and the surrogate data that have a normal distribution and keep the same linear and nonlinear correlations as the original data. We demonstrate our method by taking the daily volatility data of Dow Jones Industrial Average from 26 May 1896 to 27 April 2007 as an example. Extensive numerical experiments show that a time series exhibits effective multifractality only if it possesses nonlinearity and the PDF has impact on the effective multifractality only when the time series possesses nonlinearity. Our method can also be applied to judge the presence of multifractality and determine its components of multifractal time series in other complex systems.Comment: 9 RevTex pages including 9 eps figures. Comments and suggestions are warmly welcom
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