26,427 research outputs found

    Multiple-channel generalization of Lellouch-Luscher formula

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    We generalize the Lellouch-Luscher formula, relating weak matrix elements in finite and infinite volumes, to the case of multiple strongly-coupled decay channels into two scalar particles. This is a necessary first step on the way to a lattice QCD calculation of weak decay rates for processes such as D -> pi pi and D -> KK. We also present a field theoretic derivation of the generalization of Luscher's finite volume quantization condition to multiple two-particle channels. We give fully explicit results for the case of two channels, including a form of the generalized Lellouch-Luscher formula expressed in terms of derivatives of the energies of finite volume states with respect to the box size. Our results hold for arbitrary total momentum and for degenerate or non-degenerate particles.Comment: 16 pages, 2 figures. v3: Added references, clarified relation to and corrected comments about previous work, and minor stylistic improvements. v4: Minor clarifications added, typos fixed, references updated---matches published versio

    Geometrical characterization of textures consisting of two or three discrete colorings

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    Geometrical characterization for discretized contrast textures is realized by computing the Gaussian and mean curvatures relative to the central pixel of a clique and four neighboring pixels, these four neighbors either being first or second order neighbors. Practical formulae for computing these curvatures are presented. Curvatures based on the central pixel depend upon the brightness configuration of the clique pixels. Therefore the cliques are classified into classes by configuration of pixel contrast or coloring. To look at the textures formed by geometrically classified cliques, we create several textures using overlapping tiling of cliques belonging to a single curvature class. Several examples of hyperbolic textures, consisting of repeated hyperbolic cliques surrounded by non-hyperbolic cliques, are presented with the nonhyperbolic textures. We also introduce a system of 81 rotationally and brightness shift invariant geo-cliques that have shared curvatures and show that histograms of these 81 geo-cliques seem to be able to distinguish isotrigon textures

    E-cigarette use among women of reproductive age: Impulsivity, cigarette smoking status, and other risk factors.

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    INTRODUCTION: The study aim was to examine impulsivity and other risk factors for e-cigarette use among women of reproductive age comparing current daily cigarette smokers to never cigarette smokers. Women of reproductive age are of special interest because of the additional risk that tobacco and nicotine use represents should they become pregnant. METHOD: Survey data were collected anonymously online using Amazon Mechanical Turk in 2014. Participants were 800 women ages 24-44years from the US. Half (n=400) reported current, daily smoking and half (n=400) reported smokingsociodemographics, tobacco/nicotine use, and impulsivity (i.e., delay discounting & Barratt Impulsiveness Scale). Predictors of smoking and e-cigarette use were examined using logistic regression. RESULTS: Daily cigarette smoking was associated with greater impulsivity, lower education, past illegal drug use, and White race/ethnicity. E-cigarette use in the overall sample was associated with being a cigarette smoker and greater education. E-cigarette use among current smokers was associated with increased nicotine dependence and quitting smoking; among never smokers it was associated with greater impulsivity and illegal drug use. E-cigarette use was associated with hookah use, and for never smokers only with use of cigars and other nicotine products. CONCLUSIONS: E-cigarette use among women of reproductive age varies by smoking status, with use among current smokers reflecting attempts to quit smoking whereas among non-smokers use may be a marker of a more impulsive repertoire that includes greater use of alternative tobacco products and illegal drugs

    High-efficiency receptor-mediated delivery of small and large (48 kilobase gene constructs using the endosome-disruption activity of defective or chemically inactivated adenovirus particles.

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    One limit to successful receptor-mediated gene delivery is the exit of the endocytosed material from the endosome. We demonstrate here the delivery of marker genes to tissue culture cells using a modification of the receptor-mediated gene delivery technique that exploits the endosomolytic activity of defective adenovirus particles. In particular, greater than 90% of the transfected-cell population is found to express a beta-galactosidase gene, and, most importantly, this high level of expression can be obtained with psoralen-inactivated virus particles. Furthermore, because the delivered gene is not carried within the genome of the adenovirus particle, the size constraints are relieved, and we can, therefore, show the delivery of a 48-kilobase cosmid DNA molecule

    Comment on ZZ''s and the H1 and ZEUS High Q2Q^2 Anomalies

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    We investigate the effects of extra neutral gauge bosons on the high Q2Q^2 region of the e+pe+Xe^+p \to e^+ X cross section at s=300\sqrt{s}=300 GeV. We found that the only models with electroweak strength coupling, typical of extended gauge theories, that give a better fit to the H1 and ZEUS high Q2Q^2 data than the standard model, are ruled out by existing data from the Tevatron. From general scaling arguments, using the allowed contact interactions, the only allowed models with ZZ''s would be those with strong couplings although even in this case the statistical evidence is not compelling.Comment: Latex file uses revtex version 3, epsfig, 1 postscript figure is attache

    \u3cem\u3eDe Novo\u3c/em\u3e [PSI\u3csup\u3e+\u3c/sup\u3e] Prion Formation Involves Multiple Pathways to Form Infectious Oligomers

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    Prion and other neurodegenerative diseases are associated with misfolded protein assemblies called amyloid. Research has begun to uncover common mechanisms underlying transmission of amyloids, yet how amyloids form in vivo is still unclear. Here, we take advantage of the yeast prion, [PSI +], to uncover the early steps of amyloid formation in vivo. [PSI +] is the prion form of the Sup35 protein. While [PSI +] formation is quite rare, the prion can be greatly induced by overexpression of the prion domain of the Sup35 protein. This de novo induction of [PSI +] shows the appearance of fluorescent cytoplasmic rings when the prion domain is fused with GFP. Our current work shows that de novoinduction is more complex than previously thought. Using 4D live cell imaging, we observed that fluorescent structures are formed by four different pathways to yield [PSI +] cells. Biochemical analysis of de novo induced cultures indicates that newly formed SDS resistant oligomers change in size over time and lysates made from de novo induced cultures are able to convert [psi −] cells to [PSI +] cells. Taken together, our findings suggest that newly formed prion oligomers are infectious

    Experimental investigation of the mechanical stiffness of periodic framework-patterned elastomers

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    Recent advances in the cataloguing of three-dimensional nets mean a systematic search for framework structures with specific properties is now feasible. Theoretical arguments about the elastic deformation of frameworks suggest characteristics of mechanically isotropic networks. We explore these concepts on both isotropic and anisotropic networks by manufacturing porous elastomers with three different periodic net geometries. The blocks of patterned elastomers are subjected to a range of mechanical tests to determine the dependence of elastic moduli on geometric and topological parameters. We report results from axial compression experiments, three-dimensional X-ray computed tomography imaging and image-based finite-element simulations of elastic properties of framework-patterned elastomers

    The influence of tropospheric biennial oscillation on mid-tropospheric CO_2

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    Mid-tropospheric CO_2 retrieved from the Atmospheric Infrared Sounder (AIRS) was used to investigate CO_2 interannual variability over the Indo-Pacific region. A signal with periodicity around two years was found for the AIRS mid-tropospheric CO_2 for the first time, which is related to the Tropospheric Biennial Oscillation (TBO) associated with the strength of the monsoon. During a strong (weak) monsoon year, the Western Walker Circulation is strong (weak), resulting in enhanced (diminished) CO_2 transport from the surface to the mid-troposphere. As a result, there are positive (negative) CO2 anomalies at mid-troposphere over the Indo-Pacific region. We simulated the influence of the TBO on the mid-tropospheric CO_2 over the Indo-Pacific region using the MOZART-2 model, and results were consistent with observations, although we found the TBO signal in the model CO_2 is to be smaller than that in the AIRS observations
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