823 research outputs found
Renormalization of Fermion-Flavour Mixing
We report on an explicit on-shell framework to renormalize the
fermion-flavour mixing matrices in the Standard Model and its extensions, at
one-loop level. It is based on a novel procedure to separate the external-leg
mixing corrections into gauge-independent self-mass and gauge-dependent
wave-function renormalization contributions.Comment: to appear in Proceedings of Lepton-Photon 2009, Hamburg, German
Leading large-x logarithms of the quark-gluon contributions to inclusive Higgs-boson and lepton-pair production
We present all-order expressions for the leading double-logarithmic threshold
contributions to the quark-gluon coefficient functions for inclusive
Higgs-boson production in the heavy top-quark limit and for Drell-Yan
lepton-pair production. These results have been derived using the structure of
the unfactorized cross sections in dimensional regularization and the large-x
resummation of the gluon-quark and quark-gluon splitting functions. The
resummed coefficient functions, which are identical up to colour factor
replacements, are similar to their counterparts in deep-inelastic scattering
but slightly more complicated.Comment: 8 pages, LaTeX, 1 figure (.eps). DESY address until 31 August 201
Quark mixing renormalization effects in the determination of |V_{tq}|
We study the numerical effects of several renormalization schemes of the
Cabibbo-Kobayashi-Maskawa (CKM) quark mixing matrix on the top-quark decay
widths. We then employ these results to infer the relative shifts in the CKM
parameters |V_{tq}|^2 due to the quark mixing renormalization corrections,
assuming that they are determined directly from the top-quark partial decay
widths, without imposing unitarity constraints. We also discuss the
implications of these effects on the ratio R = Gamma(t -> Wb) / Gamma_t and the
determination of |V_{tb}|^2.Comment: 10 pages, 3 table
Confidence set of putative quantitative trait loci in whole genome scans with application to the Genetic Analysis Workshop 17 simulated data
As genetic maps become more highly dense, the ability to sufficiently localize putative disease loci becomes an achievable goal. This has prompted an increased interest in methods for constructing confidence intervals for the location of variants that contribute to a trait. Such intervals are important because, by reducing the number of candidate loci, they can help in the design of cost-effective and time-efficient follow-up studies. We introduce a new approach that can be used in whole-genome scans to obtain a confidence set of loci that contribute at least a predetermined percentage h to the overall genetic variation of a quantitative phenotype. The method is developed in the framework of generalized linear mixed models and can accommodate families of arbitrary size and structure. We apply our method to the Genetic Analysis Workshop 17 simulated data where we scan chromosomes 6, 15, 20, 21, and 22 to uncover loci regulating the simulated phenotype Q2. For the analyses we had prior knowledge of the simulation model used to generate the phenotype
TEMPO-oxidized cellulose nanofibril/polyvalent cations hydrogels: a multifaceted view of network interactions and inner structure
In the last years, hydrogels from renewable biopolymers and low-cost row materials are a hot topic for biomedical applications. In this context, cellulose nanofibrils are considered suitable building blocks for the synthesis of many biocompatible products, with a variety of chemical-physical properties. Herein we report a multi-technique and multi-scale study, from the molecular to the nanometric length scale, of the sol-gel transition observed in aqueous solutions of TEMPO-oxidized nano-sized cellulose fibrils (TOCNFs), when in the presence of polyvalent cations (Mg2+ and Ca2+). We combine the data from Small Angle Neutron Scattering (SANS), which provide information about the inner structure of the nanofibril, with those from UV Resonant Raman (UVRR) spectroscopy, which is a sensitive probe of the intra- and inter-molecular interactions in the gel and the liquid state. The transition between the gel and the liquid phases is investigated as a function of the concentration of both TOCNFs and cations, the nature of the latter, and the pH at which the phenomenon is observed. SANS analysis reveals that ion concentration induces an anisotropic swelling in the nanofibrils which, at the same time, become more and more flexible. The nanofibrils flexibility is also dependent on TOCNF concentration and pH value. UVRR allows us to elucidate the structural organization and hydrogen-bonding properties of water in aqueous TOCNF dispersions and gels, showing how water molecules partially lose their typical bulk-like tetrahedral organization when ions are added, and the gel phase is formed
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