517 research outputs found

    Technical product risk assessment: Standards, integration in the erm model and uncertainty modeling

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    European Union has accomplished, through introducing New Approach to technical harmonization and standardization, a breakthrough in the field of technical products safety and in assessing their conformity, in such a manner that it integrated products safety requirements into the process of products development. This is achieved by quantifying risk levels with the aim of determining the scope of the required safety measures and systems. The theory of probability is used as a tool for modeling uncertainties in the assessment of that risk. In the last forty years are developed new mathematical theories have proven to be better at modeling uncertainty when we have not enough data about uncertainty events which is usually the case in product development. Bayesian networks based on modeling of subjective probability and Evidence networks based on Dempster-Shafer theory of belief functions proved to be an excellent tool for modeling uncertainty when we do not have enough information about all events aspect

    Pointwise consistency of the kriging predictor with known mean and covariance functions

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    This paper deals with several issues related to the pointwise consistency of the kriging predictor when the mean and the covariance functions are known. These questions are of general importance in the context of computer experiments. The analysis is based on the properties of approximations in reproducing kernel Hilbert spaces. We fix an erroneous claim of Yakowitz and Szidarovszky (J. Multivariate Analysis, 1985) that the kriging predictor is pointwise consistent for all continuous sample paths under some assumptions.Comment: Submitted to mODa9 (the Model-Oriented Data Analysis and Optimum Design Conference), 14th-19th June 2010, Bertinoro, Ital

    The nature of the different zero-temperature phases in discrete two-dimensional spin glasses: Entropy, universality, chaos and cascades in the renormalization group flow

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    The properties of discrete two-dimensional spin glasses depend strongly on the way the zero-temperature limit is taken. We discuss this phenomenon in the context of the Migdal-Kadanoff renormalization group. We see, in particular, how these properties are connected with the presence of a cascade of fixed points in the renormalization group flow. Of particular interest are two unstable fixed points that correspond to two different spin-glass phases at zero temperature. We discuss how these phenomena are related with the presence of entropy fluctuations and temperature chaos, and universality in this model.Comment: 14 pages, 5 figures, 2 table

    Sorption of rhenium on alumina under dynamic conditions

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    The sorption of perrhenate anion on alumina from aqueous solutions of sodium chloride was investigated under dynamic conditions. The initial concentrations of rhenium were in the range of 2.7 x 10(-2)-2.7 mmol/dM(3). The breakthrough curves as the function of Re and NaCl concentrations (0. 12-0.20 mol/dm(3)), pH 2-6 and flow rate 3-10 ml/min were determined. According to the experimental results, it was concluded that the breakthrough capacities, the capacities at c/c(0) = 0.5, the total column capacities and the utilization degrees (column efficiency) increase with increasing Re and NaCl concentrations and decreasing pH. The optimal flow rate was found to be 3 ml/min. At pH 2 and c(0) = 2.7 mmol Re/dm(3), the total capacity was found to be Q(0.9) (max) = 2.1 x 10(-2) mmol Re/g Al2O3. The data for perrhenate anions fit with a Henry-type isotherm. It was found that, under the above mentioned conditions, the value of the Henry constant K-H was 7.8 x 10(-3) dm(3)/g and the Gibbs energy change, Delta G was -0.5 kJ/mol

    Large random correlations in individual mean field spin glass samples

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    We argue that complex systems must possess long range correlations and illustrate this idea on the example of the mean field spin glass model. Defined on the complete graph, this model has no genuine concept of distance, but the long range character of correlations is translated into a broad distribution of the spin-spin correlation coefficients for almost all realizations of the random couplings. When we sample the whole phase space we find that this distribution is so broad indeed that at low temperatures it essentially becomes uniform, with all possible correlation values appearing with the same probability. The distribution of correlations inside a single phase space valley is also studied and found to be much narrower.Comment: Added a few references and a comment phras

    TRIM5α associates with proteasomal subunits in cells while in complex with HIV-1 virions

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    <p>Abstract</p> <p>Background</p> <p>The TRIM5 proteins are cellular restriction factors that prevent retroviral infection in a species-specific manner. Multiple experiments indicate that restriction activity requires accessory host factors, including E2-enzymes. To better understand the mechanism of restriction, we conducted yeast-two hybrid screens to identify proteins that bind to two TRIM5 orthologues.</p> <p>Results</p> <p>The only cDNAs that scored on repeat testing with both TRIM5 orthologues were the proteasome subunit PSMC2 and ubiquitin. Using co-immunoprecipitation assays, we demonstrated an interaction between TRIM5α and PSMC2, as well as numerous other proteasome subunits. Fluorescence microscopy revealed co-localization of proteasomes and TRIM5α cytoplasmic bodies. Forster resonance energy transfer (FRET) analysis indicated that the interaction between TRIM5 and PSMC2 was direct. Previous imaging experiments demonstrated that, when cells are challenged with fluorescently-labeled HIV-1 virions, restrictive TRIM5α orthologues assemble cytoplasmic bodies around incoming virion particles. Following virus challenge, we observed localization of proteasome subunits to rhTRIM5α cytoplasmic bodies that contained fluorescently labeled HIV-1 virions.</p> <p>Conclusions</p> <p>Taken together, the results presented here suggest that localization of the proteasome to TRIM5α cytoplasmic bodies makes an important contribution to TRIM5α-mediated restriction.</p

    A class of Schrodinger operators with decaying oscillatory potentials

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    We discuss Schr\"odinger operators on a half-line with decaying oscillatory potentials, such as products of an almost periodic function and a decaying function. We provide sufficient conditions for preservation of absolutely continuous spectrum and give bounds on the Hausdorff dimension of the singular part of the spectral measure. We also discuss the analogs for orthogonal polynomials on the real line and unit circle.Comment: 18 page

    Numerical solution to the hermitian Yang-Mills equation on the Fermat quintic

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    We develop an iterative method for finding solutions to the hermitian Yang-Mills equation on stable holomorphic vector bundles, following ideas recently developed by Donaldson. As illustrations, we construct numerically the hermitian Einstein metrics on the tangent bundle and a rank three vector bundle on P^2. In addition, we find a hermitian Yang-Mills connection on a stable rank three vector bundle on the Fermat quintic.Comment: 25 pages, 2 figure
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