518 research outputs found

    Electroweak Effective Operators and Higgs Physics

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    We derive bounds from oblique parameters on the dimension-6 operators of an effective field theory of electroweak gauge bosons and the Higgs doublet. The loop- induced contributions to the S, T, and U oblique parameters are sensitive to these contributions and we pay particular attention to the role of renormalization when computing loop corrections in the effective theory. Limits on the coefficients of the effective theory from loop contributions to oblique parameters yield complementary information to direct Higgs production measurements.Comment: 33 pages, 6 figures; additional scalar operator included and references adde

    Assessment of the behavior of vertical ties in RC structures under progressive collapse

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    Despite the recent amount of theoretical and technological developements, structural robustness is still an issue of controversy being underlined by serveral progressive collapses in te past. Current design codes point out different strategies, among which strategies to limit progressive structual damage by applying prescriptive design and detailing rules. For example, for consequence class 2 structures, EN1991-1-7 defines a risk class CC2b for which also vertical ties are required. However, te background of the design values of vertical ties in current code is not clear and their adequacy should be validated. Moreover, effects such as membrane action and Vierendeel action are important to consider when assessing structural robustness and are difficult to incorporate when applying only traditional design methodologies. To this extent, a set of numerical simulations have been executed in this contribution in order to verify and investigate the progressive collapse behavior of RC frames including the redistribution of internal forces and the response of the vertical ties in columns

    A tunable plasmonic refractive index sensor with nanoring-strip graphene arrays

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    In this paper, a tunable plasmonic refractive index sensor with nanoring-strip graphene arrays is numerically investigated by the finite difference time domain (FDTD) method. The simulation results exhibit that by changing the sensing medium refractive index nmed of the structure, the sensing range of the system is large. By changing the doping level ng, we noticed that the transmission characteristics can be adjusted flexibly. The resonance wavelength remains entirely the same and the transmission dip enhancement over a big range of incidence angles [0,45] for both TM and TE polarizations, which indicates that the resonance of the graphene nanoring-strip arrays is insensitive to angle polarization. The above results are undoubtedly a new way to realize various tunable plasmon devices, and may have a great application prospect in biosensing, detection and imaging

    FORMATION OF GLOBULAR CLUSTERS IN ATOMIC-COOLING HALOS VIA RAPID GAS CONDENSATION AND FRAGMENTATION DURING THE EPOCH OF REIONIZATION

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    We investigate the formation of metal-poor globular clusters (GCs) at the center of two dark matter halos with Mhalo\textit{M}_{halo} ~ 4 ×\times 107^7 M\textit{M}_\odot at z\textit{z} > 10 using cosmological radiation-hydrodynamics simulations. We find that very compact (\lesssim1 pc) and massive (~ 6 ×\times 105^5 M\textit{M}_\odot) clusters form rapidly when pristine gas collapses isothermally with the aid of efficient Lyα\alpha emission during the transition from molecular-cooling halos to atomic-cooling halos. Because the local free-fall time of dense star-forming gas is very short (\ll1 Myr), a large fraction of the collapsed gas is turned into stars before stellar feedback processes blow out the gas and shut down star formation. Although the early stage of star formation is limited to a small region of the central star-forming disk, we find that the disk quickly fragments due to metal enrichment from supernovae. Sub-clusters formed in the fragmented clouds eventually merge with the main cluster at the center. The simulated clusters closely resemble the local GCs in mass and size but show a metallicity spread that is much wider than found in the local GCs. We discuss a role of pre-enrichment by Pop III and II stars as a potential solution to the latter issue. Although not without shortcomings, it is encouraging that a naive blind (not tuned) cosmological simulation presents a possible channel for the formation of at least some massive GCs.The research is supported in part by NSF grant AST-1108700 and NASA grant NNX12AF91G and in part by the ERC Advanced Grant 320596 “The Emergence of Structure during the epoch of Reionization.” JR was funded by the European Research Council under the European Unions Seventh Framework Programme (FP7/2007- 2013)/ERC Grant agreement 278594-GasAroundGalaxies, and the Marie Curie Training Network CosmoComp (PITN-GA- 2009-238356). SKY acknowledges support from the Korean National Research Foundation (Doyak 2014003730).This is the final version of the article. It first appeared from the Institute of Physics via http://dx.doi.org/10.3847/0004-637X/823/1/5

    Estimating ecological indicators of karst rocky desertification by linear spectral unmixing method

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    AbstractCoverage rates of vegetation and exposed bedrock are two key indicators of karst rocky desertification. In this study, the abundances of vegetation and exposed rock were retrieved from a hyperspectral Hyperion image using linear spectral unmixing method. The results were verified using the spectral indices of karst rocky desertification (KRDSI) and an integrated LAI spectral index: modified chlorophyll absorption ratio index (MCARI2). The abundances showed significant linear correlations with KRDSI and MCARI2. The coefficients of determination (R2) were 0.93, 0.66, and 0.84 for vegetation, soil, and rock, respectively, indicating that the abundances of vegetation and bedrock can characterize their coverage rates to a certain extent. Finally, the abundances of vegetation and bedrock were graded and integrated to evaluate rocky desertification in a typical karst region. This study suggests that spectral unmixing algorithm and hyperspectral remote sensing imagery can be used to monitor and evaluate karst rocky desertification

    Characterization of severe fever with thrombocytopenia syndrome in rural regions of Zhejiang, China.

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    Severe fever with thrombocytopenia syndrome virus (SFTSV) infections have recently been found in rural regions of Zhejiang. A severe fever with thrombocytopenia syndrome (SFTS) surveillance and sero-epidemiological investigation was conducted in the districts with outbreaks. During the study period of 2011-2014, a total of 51 SFTSV infection cases were identified and the case fatality rate was 12% (6/51). Ninety two percent of the patients (47/51) were over 50 years of age, and 63% (32/51) of laboratory confirmed cases occurred from May to July. Nine percent (11/120) of the serum samples from local healthy people without symptoms were found to be positive for antibodies to the SFTS virus. SFTSV strains were isolated by culture using Vero, and the whole genomic sequences of two SFTSV strains (01 and Zhao) were sequenced and submitted to the GenBank. Homology analysis showed that the similarity of the target nucleocapsid gene from the SFTSV strains from different geographic areas was 94.2-100%. From the constructed phylogenetic tree, it was found that all the SFTSV strains diverged into two main clusters. Only the SFTSV strains from the Zhejiang (Daishan) region of China and the Yamaguchi, Miyazakj regions of Japan, were clustered into lineage II, consistent with both of these regions being isolated areas with similar geographic features. Two out of eight predicted linear B cell epitopes from the nucleocapsid protein showed mutations between the SFTSV strains of different clusters, but did not contribute to the binding ability of the specific SFTSV antibodies. This study confirmed that SFTSV has been circulating naturally and can cause a seasonal prevalence in Daishan, China. The results also suggest that the molecular characteristics of SFTSV are associated with the geographic region and all SFTSV strains can be divided into two genotypes

    Numerical Simulation and Experimental Study of the Tube Receiver's Performance of Solar Thermal Power Tower

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    AbstractA water-vapor tube receiver is a significant component in the solar thermal power tower plant. However, the tube flow performance is much different from others. Because semi-circumference of the tube is heated with an uneven heat flux, which is into a Gaussian distribution in this paper, and the other semi-circumference is insulated. A 5kW- Xe-arc lamp was used to simulate a solar light source. In this study, the effect of different entrance velocity on the flow performance and thermal efficiency of the tube receiver are investigated with numerical and experimental methods. The results of experiment and simulation agree well. The results show that the temperature distribution of water and tube wall are very uneven both in the axial and radial directions. The thermal efficiency of the tube receiver increases with the increase of entrance velocity
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