43,581 research outputs found

    Is there a role for thoracic aortic calcium to fine-tune cardiovascular risk prediction?

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    Screening asymptomatic subjects to streamline measures for the prevention of cardiovascular events remains a major challenge. The established primary prevention risk-scoring methods use equations derived from large prospective cohort studies, but further fine-tuning of cardiovascular risk assessment remains important as 25 % of individuals with low estimated risk may experience cardiac events. Independent studies provided evidence that extended risk assessment using coronary artery calcium quantification may improve risk stratification as it can lead to reclassification of persons at increased risk. Particularly in intermediate-risk subjects, coronary artery calcium scoring can help to correctly identify individuals at highest risk. Data on the extent of calcification of the ascending and descending thoracic aorta might be useful for additional cardiovascular risk stratification. Future analyses and studies will be required to answer the question of whether the implementation of such data may allow further fine-tuning of cardiovascular risk prediction in specific subpopulations—for instance in women or men with an increased risk of stroke and/or symptomatic peripheral vascular diseas

    Large scale Gd-beta-diketonate based organic liquid scintillator production for antineutrino detection

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    Over the course of several decades, organic liquid scintillators have formed the basis for successful neutrino detectors. Gadolinium-loaded liquid scintillators provide efficient background suppression for electron antineutrino detection at nuclear reactor plants. In the Double Chooz reactor antineutrino experiment, a newly developed beta-diketonate gadolinium-loaded scintillator is utilized for the first time. Its large scale production and characterization are described. A new, light yield matched metal-free companion scintillator is presented. Both organic liquids comprise the target and "Gamma Catcher" of the Double Chooz detectors.Comment: 16 pages, 4 figures, 5 table

    Welfarism and the Assessments of Social Decision Rules

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    Symmetries and Triplet Dispersion in a Modified Shastry-Sutherland Model for SrCu_2(BO_3)_2

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    We investigate the one-triplet dispersion in a modified Shastry-Sutherland Model for SrCu_2(BO_3)_2 by means of a series expansion about the limit of strong dimerization. Our perturbative method is based on a continuous unitary transformation that maps the original Hamiltonian to an effective, energy quanta conserving block diagonal Hamiltonian H_{eff}. The dispersion splits into two branches which are nearly degenerated. We analyse the symmetries of the model and show that space group operations are necessary to explain the degeneracy of the dispersion at k=0 and at the border of the magnetic Brillouin zone. Moreover, we investigate the behaviour of the dispersion for small |k| and compare our results to INS data.Comment: 9 pages, 8 figures accepted by J. Phys.: Condens. Matte

    Effective dynamics using conditional expectations

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    The question of coarse-graining is ubiquitous in molecular dynamics. In this article, we are interested in deriving effective properties for the dynamics of a coarse-grained variable ξ(x)\xi(x), where xx describes the configuration of the system in a high-dimensional space Rn\R^n, and ξ\xi is a smooth function with value in R\R (typically a reaction coordinate). It is well known that, given a Boltzmann-Gibbs distribution on xRnx \in \R^n, the equilibrium properties on ξ(x)\xi(x) are completely determined by the free energy. On the other hand, the question of the effective dynamics on ξ(x)\xi(x) is much more difficult to address. Starting from an overdamped Langevin equation on xRnx \in \R^n, we propose an effective dynamics for ξ(x)R\xi(x) \in \R using conditional expectations. Using entropy methods, we give sufficient conditions for the time marginals of the effective dynamics to be close to the original ones. We check numerically on some toy examples that these sufficient conditions yield an effective dynamics which accurately reproduces the residence times in the potential energy wells. We also discuss the accuracy of the effective dynamics in a pathwise sense, and the relevance of the free energy to build a coarse-grained dynamics

    Photospheric Emission in the Joint GBM and Konus Prompt Spectra of GRB 120323A

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    GRB 120323A is a very intense short Gamma Ray Burst (GRB) detected simultaneously during its prompt gamma-ray emission phase with the Gamma-ray Burst Monitor (GBM) on board the Fermi Gamma-ray Space Telescope and the Konus experiment on board the Wind satellite. GBM and Konus operate in the keV--MeV regime, however, the GBM range is broader both toward the low and the high parts of the gamma-ray spectrum. Analysis of such bright events provide a unique opportunity to check the consistency of the data analysis as well as cross-calibrate the two instruments. We performed time-integrated and coarse time-resolved spectral analysis of GRB 120323A prompt emission. We conclude that the analyses of GBM and Konus data are only consistent when using a double-hump spectral shape for both data sets; in contrast, the single-hump of the empirical Band function, traditionally used to fit GRB prompt emission spectra, leads to significant discrepancies between GBM and Konus analysis results. Our two-hump model is a combination of a thermal-like and a non-thermal component. We interpret the first component as a natural manifestation of the jet photospheric emission.Comment: 7 pages of article (3 figures and 1 table) + 3 pages of Appendix (3 figures). Submitted to ApJ on 2017 March 2

    A generalization of bounds for cyclic codes, including the HT and BS bounds

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    We use the algebraic structure of cyclic codes and some properties of the discrete Fourier transform to give a reformulation of several classical bounds for the distance of cyclic codes, by extending techniques of linear algebra. We propose a bound, whose computational complexity is polynomial bounded, which is a generalization of the Hartmann-Tzeng bound and the Betti-Sala bound. In the majority of computed cases, our bound is the tightest among all known polynomial-time bounds, including the Roos bound

    Minimizing the Pervasiveness of Women’s Personal Experiences of Gender Discrimination

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    Given the Rejection-Identification Model (Branscombe, et al., 1999) which shows that perceiving discrimination to be pervasive is a negative experience, it was suggested that there would be conditions under which women would instead minimize the pervasiveness of discrimination. Study 1 (N = 91) showed that when women envisioned themselves in a situation of academic discrimination, they defined it as pervasive but when they experienced a similar laboratory simulation of academic discrimination, its pervasiveness was minimized. Study 2 (N = 159) showed that women who envisioned themselves experiencing discrimination minimized its pervasiveness more so than women reading about discrimination happening to someone else. Further, mediation analysis showed that minimizing the pervasiveness enhanced positive affect about personal discrimination. Implications for minimizing on both an individual and social level are discussed

    Is negative-weight percolation compatible with SLE?

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    We study numerically the geometrical properties of minimally weighted paths that appear in the negative-weight percolation (NWP) model on two-dimensional lattices assuming a combination of periodic and free boundary conditions (BCs). Each realization of the disorder consists of a random fraction 1-rho of bonds with unit strength and a fraction rho of bond strengths drawn from a Gaussian distribution with zero mean and unit width. For each such sample, the path is forced to span the lattice along the direction with the free BCs. The path and a set of negatively weighted loops form a ground state (GS). A ground state on such a lattice can be determined performing a non-trivial transformation of the original graph and applying sophisticated matching algorithms. Here we examine whether the geometrical properties of the paths are in accordance with predictions of Schramm-Loewner evolution (SLE). Measuring the fractal dimension and reviewing Schramm's left passage formula indicates that the paths cannot be described in terms of SLE.Comment: 9 pages, 8 figures, paper summary available at http://papercore.org/Norrenbrock201

    Pioneer Mars 1979 mission options

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    A preliminary investigation of lower cost Mars missions which perform useful exploration objectives after the Viking/75 mission was conducted. As a study guideline, it was assumed that significant cost savings would be realized by utilizing Pioneer hardware currently being developed for a pair of 1978 Venus missions. This in turn led to the additional constraint of a 1979 launch with the Atlas/Centaur launch vehicle which has been designated for the Pioneer Venus missions. Two concepts, using an orbiter bus platform, were identified which have both good science potential and mission simplicity indicative of lower cost. These are: (1) an aeronomy/geology orbiter, and (2) a remote sensing orbiter with a number of deployable surface penetrometers
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