1,317 research outputs found

    Recovering piecewise smooth functions from nonuniform Fourier measurements

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    In this paper, we consider the problem of reconstructing piecewise smooth functions to high accuracy from nonuniform samples of their Fourier transform. We use the framework of nonuniform generalized sampling (NUGS) to do this, and to ensure high accuracy we employ reconstruction spaces consisting of splines or (piecewise) polynomials. We analyze the relation between the dimension of the reconstruction space and the bandwidth of the nonuniform samples, and show that it is linear for splines and piecewise polynomials of fixed degree, and quadratic for piecewise polynomials of varying degree

    A temperature-controlled device for volumetric measurements of Helium adsorption in porous media

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    We describe a set-up for studying adsorption of helium in silica aerogels, where the adsorbed amount is easily and precisely controlled by varying the temperature of a gas reservoir between 80 K and 180 K. We present validation experiments and a first application to aerogels. This device is well adapted to study hysteresis, relaxation, and metastable states in the adsorption and desorption of fluids in porous media

    On the New Conditions for a Total Neutrino Conversion in a Medium

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    We show that the arguments forming the basis for the claim that the conditions for total neutrino conversion derived and studied in detail in [1,2] ``are just the conditions of the parametric resonance of neutrino oscillations supplemented by the requirement that the parametric enhancement be complete'', given in [4] have flaws which make the claim physically questionable. We show also that in the case of the transitions in the Earth of the Earth-core-crossing solar and atmospheric neutrinos the peaks in the relevant transitions probabilities PabP_{a b}, associated with the new conditions, maxPab=1max P_{a b} = 1, are of physical relevance - in contrast to what is suggested in [4]. Actually, the enhancement of PabP_{a b} in any region of the corresponding parameter space are essentially determined by these absolute maxima of PabP_{a b}. We comment on few other aspects of the results derived in [1,2,3] which have been misunderstood and/or misinterpreted in [4].Comment: 8 pages, late

    Evidence for a disorder driven phase transition in the condensation of 4He in aerogels

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    We report on thermodynamic and optical measurements of the condensation process of 4^4He in three silica aerogels of different microstructures. For the two base-catalysed aerogels, the temperature dependence of the shape of adsorption isotherms and of the morphology of the condensation process show evidence of a disorder driven transition, in agreement with recent theoretical predictions. This transition is not observed for a neutral-catalysed aerogel, which we interpret as due to a larger disorder in this case.Comment: 11 page

    Back reaction of a long range force on a Friedmann-Robertson-Walker background

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    It is possible that there may exist long-range forces in addition to gravity. In this paper we construct a simple model for such a force based on exchange of a massless scalar field and analyze its effect on the evolution of a homogeneous Friedmann-Robertson-Walker cosmology. The presence of such an interaction leads to an equation of state characterized by positive pressure and to resonant particle production similar to that observed in preheating scenarios.Comment: 14 pages, 6 color Postscript figures, LaTe

    Measurement of the solar neutrino capture rate with gallium metal

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    The solar neutrino capture rate measured by the Russian-American Gallium Experiment (SAGE) on metallic gallium during the period January 1990 through December 1997 is 67.2 (+7.2-7.0) (+3.5-3.0) SNU, where the uncertainties are statistical and systematic, respectively. This represents only about half of the predicted Standard Solar Model rate of 129 SNU. All the experimental procedures, including extraction of germanium from gallium, counting of 71Ge, and data analysis are discussed in detail.Comment: 34 pages including 14 figures, Revtex, slightly shortene

    Seasonal Variations of the 7Be Solar Neutrino Flux

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    Measuring the 7Be solar neutrino flux is crucial towards solving the solar neutrino puzzle. The Borexino experiment, and possibly the KamLAND experiment, will be capable of studying the 7Be neutrinos in the near future. We discuss (1) how the seasonal variation of the Borexino and KamLAND data can be used to measure the 7Be solar neutrino flux in a background independent way and (2) how anomalous seasonal variations might be used to discover vacuum neutrino oscillations, independent of the solar model and the measurement of the background. In particular, we find that, after three years of Borexino or KamLAND running, vacuum neutrino oscillations can be either established or excluded for almost all values of (sin^2 2 theta, Delta m^2) preferred by the Homestake, GALLEX, SAGE, and Super-Kamiokande data. We also discuss how well seasonal variations of the data can be used to measure (sin^2 2 theta, Delta m^2) in the case of vacuum oscillations.Comment: 39 pages, 13 figures, uses psfig. Now the impact of the MSW effect on vacuum oscillations taken into account. Conclusions unchanged. References adde

    Averages of bb-hadron, cc-hadron, and τ\tau-lepton properties as of summer 2014

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    This article reports world averages of measurements of bb-hadron, cc-hadron, and τ\tau-lepton properties obtained by the Heavy Flavor Averaging Group (HFAG) using results available through summer 2014. For the averaging, common input parameters used in the various analyses are adjusted (rescaled) to common values, and known correlations are taken into account. The averages include branching fractions, lifetimes, neutral meson mixing parameters, CPCP violation parameters, parameters of semileptonic decays and CKM matrix elements.Comment: 436 pages, many figures and tables. Online updates available at http://www.slac.stanford.edu/xorg/hfag

    The General Practice Assessment Questionnaire (GPAQ) – Development and psychometric characteristics

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    <p>Abstract</p> <p>Background</p> <p>Continual quality improvement in primary care is an international priority. In the United Kingdom, the major initiative for improving quality of care is the Quality and Outcomes Framework (QoF) of the 2004 GP contract. Although the primary focus of the QoF is on clinical care, it is acknowledged that a comprehensive assessment of quality also requires valid and reliable measurement of the patient perspective, so financial incentives are included in the contract for general practices to survey patients' views. One questionnaire specified for use in the QoF is the General Practice Assessment Questionnaire (GPAQ). This paper describes the development of the GPAQ (with post-consultation and postal versions) and presents a preliminary examination of the psychometric properties of the questionnaire.</p> <p>Methods</p> <p>Description of scale development and preliminary analysis of psychometric characteristics (internal reliability, factor structure), based on a large dataset of routinely collected GPAQ surveys (n = 190,038 responses to the consultation version of GPAQ and 20,309 responses to the postal version) from practices in the United Kingdom during the 2005–6 contract year.</p> <p>Results</p> <p>Respondents tend to report generally favourable ratings. Responses were particularly skewed on the GP communication scale, though no more so than for other questionnaires in current use in the UK for which data were available. Factor analysis identified 2 factors that clearly relate to core concepts in primary care quality ('access' and 'interpersonal care') that were common to both version of the GPAQ. The other factors related to 'enablement' in the post-consultation version and 'nursing care' in the postal version.</p> <p>Conclusion</p> <p>This preliminary evaluation indicates that the scales of the GPAQ are internally reliable and that the items demonstrate an interpretable factor structure. Issues concerning the distributions of GPAQ responses are discussed. Potential further developments of the item content for the GPAQ are also outlined.</p

    Search for Bhννˉ\boldsymbol{B\to h\nu\bar{\nu}} decays with semileptonic tagging at Belle

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    We present the results of a search for the rare decays BhννB\to h\nu\overline{\nu}, where hh stands for K+,KS0,K+,K0,π+,π0,ρ+K^+,\:K^0_{\mathrm{S}},\:K^{\ast +},\:K^{\ast 0},\:\pi^+,\:\pi^0,\:\rho^+ and ρ0\rho^{0}. The results are obtained with 772×106772\times10^{6} BBB\overline{B} pairs collected with the Belle detector at the KEKB e+ee^+ e^- collider. We reconstruct one BB meson in a semileptonic decay and require a single hh meson but nothing else on the signal side. We observe no significant signal and set upper limits on the branching fractions. The limits set on the BKS0ννB\to K^0_{\mathrm{S}}\nu\overline{\nu}, B0K0ννB^0\to K^{*0}\nu\overline{\nu}, Bπ+ννB\to \pi^+\nu\overline{\nu}, B0π0ννB^0\to\pi^0\nu\overline{\nu}, B+ρ+ννB^+\to\rho^+\nu\overline{\nu}, and B0ρ0ννB^0\to\rho^0\nu\overline{\nu} channels are the world's most stringent.Comment: Submitted to PR
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