8,606 research outputs found

    Analysis of light scattering off photonic crystal slabs in terms of Feshbach resonances

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    Techniques to deal with Feshbach resonances are applied to describe resonant light scattering off one dimensional photonic crystal slabs. Accurate expressions for scattering amplitudes, free of any fitting parameter, are obtained for isolated as well as overlapping resonances. They relate the resonance properties to the properties of the optical structure and of the incident light. For the most common case of a piecewise constant dielectric function, the calculations can be carried out essentially analytically. After establishing the accuracy of this approach we demonstrate its potential in the analysis of the reflection coefficients for the diverse shapes of overlapping, interacting resonances.Comment: 12 pages, 5 figure

    Bias of Maximum-Likelihood estimates in logistic and Cox regression models: A comparative simulation study

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    Parameter estimates of logistic and Cox regression models are biased for finite samples. In a simulation study we investigated for both models the behaviour of the bias in relation to sample size and further parameters. In the case of a dichotomous explanatory variable x the magnitude of the bias is strongly influenced by the baseline risk defined by the constants of the models and the risk resulting for the high risk group. To conduct a direct comparison of the bias of the two models analyses were based on the same simulated data. Overall, the bias of the two models appear to be similar, however, the Cox model has less bias in situations where the baseline risk is high

    Pulse shape simulation for segmented true-coaxial HPGe detectors

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    A new package to simulate the formation of electrical pulses in segmented true-coaxial high purity germanium detectors is presented. The computation of the electric field and weighting potentials inside the detector as well as of the trajectories of the charge carriers is described. In addition, the treatment of bandwidth limitations and noise are discussed. Comparison of simulated to measured pulses, obtained from an 18-fold segmented detector operated inside a cryogenic test facility, are presented.Comment: 20 pages, 16 figure

    The Prediction of Mass of Z'-Boson from bq0bq0barb_q^0-b_q^0 bar Mixing

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    B_q^0-B_^0 bar mixing offers a profound probe into the effects of new physics beyond the Standard Model. In this paper, Bs0Bs0barB_s^0-B_s^0 bar and Bd0Bd0barB_d^0-B_d^0 bar mass differences are considered taking the effect of both Z-and Z' -mediated flavour-changing neutral currents in the Bq0Bq0barB_q^0-B_q^0 bar mixing (q = d, s). Our estimated mass of Z' boson is accessible at the experiments LHC and B-factories in near future.Comment: 11 pages, 02 Figure

    The decay b -> s g at NLL in the Standard Model

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    I present the Standard Model calculation of the decay rate for b -> s g (g denotes a gluon) at next-to-leading logarithms (NLL). In order to get a meaningful physical result, the decay b -> s g g and certain contributions of b -> s \bar{f} f (where f are the light quark flavours u, d and s) have to be included as well. Numerically we get BR^(NLL) = (5.0 +/- 1.0) * 10^{-3} which is more than a factor 2 larger than the leading logarithmic result BR^(LL) = (2.2 +/- 0.8) * 10^{-3}. Further, I consider the impact of this contribution on the charmless hadronic branching ratio BRc, which could be used to extract the CKM-ratio |V_(ub)/V_(cb)| with more accuracy. Finally, I have a short look at BRc in scenarios where the Wilson coefficient C_8 is enhanced by new physics.Comment: 7 pages including 5 postscript figures; uses epsfi

    The colonial ascidian Diplosoma listerianum enhances the occurrence of the hydrozoan Obelia sp. during early phases of succession

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    Recruitment patterns of sessile species often do not reflect the composition of the local propagule pool. This is, among other processes, attributed to the stimulation or inhibition of settlement by resident species. In an experimental study, we evaluated the effects of different densities of the ascidian Diplosoma listerianum on the settlement of the hydrozoan Obelia sp. For this, we monitored the cover of the dominant fouler Obelia sp. on vertically orientated PVC tiles, which were either bare or pre-seeded with two different densities (sparse or dense) of Diplosoma colonies, over the course of 8 weeks. The settlement tiles were deployed at two study sites in La Herradura Bay, Chile. The presence of D. listerianum enhanced the settlement or the growth or both of the colonial hydrozoan, but this effect disappeared within 4–8 weeks. Furthermore, we tested whether the initial enhancement of Obelia sp. by Diplosoma colonies goes back to the fact that larvae, which reject the ascidian tunic as a settlement substratum after a first contact, colonize nearby surfaces because of their limited mobility. However, we found no support for this assumption. We rather suggest that D. listerianum facilitated colonization indirectly by the accumulation of organic material in its vicinity and/or by its pumping activity. Initial resident-mediated enhancement of the hydrozoan was overridden by processes such as competition between later colonizers within the course of weeks and we could not detect any lasting effects of D. listerianum on the structure of the developing communities

    Alimentación, ocio y cultura en el pazo de Goiáns en el siglo XVIII

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    Actas de la XII Reunión Científica de la Fundación Española de Historia Moderna, celebrada en la Universidad de León en 19-21 de junio de 2012. José Manuel Vázquez Lijó, Universidad de Coruña ([email protected])En esta comunicación se analizan algunos aspectos del micro cosmos cultural de un pazo gallego, el de Goiáns, cuya excepcional ubicación a orillas de la ría de Arousa dota de alto valor añadido a este solar con espacios singulares como pesquera y embarcadero. Los inventarios de bienes de la casa informan de varios indicadores culturales de las elites (libros, juegos, obras artísticas, instrumentos musicales) y otros, como la alimentación, pueden estudiarse gracias a la documentación contable. El breve esplendor material del pazo parece datarse a mediados del siglo XVIII coincidiendo con la exitosa promoción social de los señores de Goiáns y sus hijos consecuencia de un cúmulo de factores (relaciones familiares, poder económico, bodas ventajosas, educación privilegiada…). La carrera militar de los sucesivos dueños les obligó a residir allí donde ejercían estos empleos y Goiáns pasó a ser una segunda residencia, cada vez más vacía de vida y de muebles, convirtiéndose a partir de la década de 1820 en un simple centro de administración de rentas.Peer reviewe

    Transverse QCD Dynamics Near the Light Cone

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    Starting from the QCD Hamiltonian in near-light cone coordinates, we study the dynamics of the gluonic zero modes. Euclidean 2+1 dimensional lattice simulations show that the gap at strong coupling vanishes at intermediate coupling. This result opens the possibility to synchronize the continuum limit with the approach to the light cone.Comment: 15 pages, LaTeX, 3 figures (7 PS files
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