1,494 research outputs found

    An analysis of life expectancy and economic production using expectile frontier zones

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    The wealth of a country is assumed to have a strong non-linear influence on the life expectancy of its inhabitants. We follow up on research by Preston and study the relationship with gross domestic product. Smooth curves for the average but also for (upper) frontiers are constructed by a combination of least asymmetrically weighted squares and P-splines. Guidelines are given for optimizing the amount of smoothing and the definition of frontiers. The model is applied to a large set of countries in different years. It is also used to estimate life expectancy performance for individual countries and to show how it changed over time.frontier estimation, gross domestic product, least asymmetrically weighted squares, life expectancy, production frontier, smoothing

    Periods of second kind differentials of (n,s)-curves

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    For elliptic curves, expressions for the periods of elliptic integrals of the second kind in terms of theta-constants, have been known since the middle of the 19th century. In this paper we consider the problem of generalizing these results to curves of higher genera, in particular to a special class of algebraic curves, the so-called (n,s)(n,s)-curves. It is shown that the representations required can be obtained by the comparison of two equivalent expressions for the projective connection, one due to Fay-Wirtinger and the other from Klein-Weierstrass. As a principle example, we consider the case of the genus two hyperelliptic curve, and a number of new Thomae and Rosenhain-type formulae are obtained. We anticipate that our analysis for the genus two curve can be extended to higher genera hyperelliptic curves, as well as to other classes of (n,s)(n,s) non-hyperelliptic curves.Comment: 21 page

    Fermi Surface of KFe2_2As2_2 from Quantum Oscillations in Magnetostriction

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    We present a study of the Fermi surface of KFe2_2As2_2 single crystals. Quantum oscillations were observed in magnetostriction measured down to 50 mK and in magnetic fields HH up to 14 T. For H∥cH \parallel c, the calculated effective masses are in agreement with recent de Haas-van Alphen and ARPES experiments, showing enhanced values with respect to the ones obtained from previous band calculations. For H∥aH \parallel a, we observed a small orbit at a cyclotron frequency of 64 T, characterized by an effective mass of ∼0.8me\sim 0.8 m_e, supporting the presence of a three-dimensional pocket at the Z-point.Comment: SCES Conference, Tokyo 201

    Morphisms of Extensions of C*-Algebras: Pushing Forward the Busby Invariant

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    AbstractWe study completions of diagrams of extensions of C*-algebras in which all three C*-algebras in one of the rows and either the ideal or the quotient in the other are given, along with the three morphisms between them. We find universal solutions to all four of these problems under restrictions of varying severity, on the given vertical maps and describe the solutions in terms of push-outs and pull-backs of certain diagrams. Our characterization of the universal solution to one of the diagrams yields a concrete description of various amalgamated free products. This leads to new results about the K-theory of amalgamated free products, verifying the Cuntz conjecture in certain cases. We also obtain new results about extensions of matricial fieldC*-algebras, verifying partially a conjecture of Blackadar and Kirchberg. Finally, we show that almost commuting unitary matrices can be uniformly approximated by commuting unitaries when an index obstruction vanishes

    Copepod (Crustacea) distribution in the freshwater and hyposaline lakes of the Pantanal of Nhecolandia (Mato Grosso do Sul, Brazil).

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    Eighteen freshwater and hyposaline lakes of the Nhecolândia floodplain were sampled in two periods, April/03 (beginning of dry period) and March/04 (end of wet period). Dezoito lagoas de água doce e de água hiposalina do Pantanal da Nhecolândia foram amostrados em dois períodos, abril/03 (início da seca) e março/04(fim da cheia)

    Gray and white matter astrocytes differ in basal metabolism but respond similarly to neuronal activity

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    Astrocytes are a heterogeneous population of glial cells in the brain, which adapt their properties to the requirements of the local environment. Two major groups of astrocytes are protoplasmic astrocytes residing in gray matter as well as fibrous astrocytes of white matter. Here, we compared the energy metabolism of astrocytes in the cortex and corpus callosum as representative gray matter and white matter regions, in acute brain slices taking advantage of genetically encoded fluorescent nanosensors for the NADH/NAD+ redox ratio and for ATP. Astrocytes of the corpus callosum presented a more reduced basal NADH/NAD+ redox ratio, and a lower cytosolic concentration of ATP compared to cortical astrocytes. In cortical astrocytes, the neurotransmitter glutamate and increased extracellular concentrations of K+, typical correlates of neuronal activity, induced a more reduced NADH/NAD+ redox ratio. While application of glutamate decreased [ATP], K+ as well as the combination of glutamate and K+ resulted in an increase of ATP levels. Strikingly, a very similar regulation of metabolism by K+ and glutamate was observed in astrocytes in the corpus callosum. Finally, strong intrinsic neuronal activity provoked by application of bicuculline and withdrawal of Mg2+ caused a shift of the NADH/NAD+ redox ratio to a more reduced state as well as a slight reduction of [ATP] in gray and white matter astrocytes. In summary, the metabolism of astrocytes in cortex and corpus callosum shows distinct basal properties, but qualitatively similar responses to neuronal activity, probably reflecting the different environment and requirements of these brain regions

    Extensions of operator algebras I

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    We transcribe a portion of the theory of extensions of C*-algebras to general operator algebras. We also include several new general facts about approximately unital ideals in operator algebras and the C*-algebras which they generate
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