5,971 research outputs found

    First record of Poecilochirus mrciaki Mašán, 1999 (Acari, Parasitidae) and its phoretic carriers in the Iberian peninsula

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    We report for the first time the presence of Poecilochirus mrciaki Mašán, 1999 in the South of Europe, in the Iberian peninsula and on new carrier insects. Mites were collected from carrion insects, during a decomposition experiment carried out in the natural park “Aiako Harria” (Errenteria, Gipuzkoa). Most deutonymphs were found on the body of the necrophagous beetle Necrodes littoralis (Coleoptera, Silphidae). Other species of insects in families Geotrupidae, Staphylinidae (Coleoptera) and Calliphoridae (Diptera) were also transporting mites. All carriers were colonising or visiting the pig carcasses. Sampling lasted 3 months in the summers 2009 and 2010. Most mites were sampled from bloat to advanced decay. This is also the first record of P. mrciaki phoretic on flies (Diptera)

    A new locking-free polygonal plate element for thin and thick plates based on Reissner-Mindlin plate theory and assumed shear strain fields

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    A new nn- noded polygonal plate element is proposed for the analysis of plate structures comprising of thin and thick members. The formulation is based on the discrete Kirchhoff Mindlin theory. On each side of the polygonal element, discrete shear constraints are considered to relate the kinematical and the independent shear strains. The proposed element: (a) has proper rank; (b) passes patch test for both thin and thick plates; (c) is free from shear locking and (d) yields optimal convergence rates in L2L^2-norm and H1H^1-semi-norm. The accuracy and the convergence properties are demonstrated with a few benchmark examples

    Stabilized lowest order finite element approximation for linear three-field poroelasticity

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    A stabilized conforming mixed finite element method for the three-field (displacement, fluid flux and pressure) poroelasticity problem is developed and analyzed. We use the lowest possible approximation order, namely piecewise constant approximation for the pressure and piecewise linear continuous elements for the displacements and fluid flux. By applying a local pressure jump stabilization term to the mass conservation equation we ensure stability and avoid pressure oscillations. Importantly, the discretization leads to a symmetric linear system. For the fully discretized problem we prove existence and uniqueness, an energy estimate and an optimal a-priori error estimate, including an error estimate for the divergence of the fluid flux. Numerical experiments in 2D and 3D illustrate the convergence of the method, show the effectiveness of the method to overcome spurious pressure oscillations, and evaluate the added mass effect of the stabilization term.Comment: 25 page

    An extended finite element model for modelling localised fracture of reinforced concrete beams in fire

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    Open Access funded by Engineering and Physical Sciences Research Council under a Creative Commons license.A robust finite element procedure for modelling the localised fracture of reinforced concrete beams at elevated temperatures is developed. In this model a reinforced concrete beam is represented as an assembly of 4-node quadrilateral plain concrete, 3-node main reinforcing steel bar, and 2-node bond-link elements. The concrete element is subdivided into layers for considering the temperature distribution over the cross-section of a beam. An extended finite element method (XFEM) has been incorporated into the concrete elements in order to capture the localised cracks within the concrete. The model has been validated against previous fire test results on the concrete beams.The Engineering and Physical Sciences Research Council of Great Britain under Grant No. EP/I031553/1

    Detection of persistent gamma-ray emission toward SS433/W50

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    The microquasar SS433 features the most energetic jets known in our Galaxy. A large fraction of the jet kinetic power is delivered to the surrounding W50 nebula at the jet termination shock, from which high-energy emission and cosmic-ray production have been anticipated. Here we report on the detection of a persistent gamma-ray signal from the direction of SS433/W50 with the Fermi Large Area Telescope. The steady flux and a narrow spectral energy distribution with a maximum around 250 MeV suggest that gamma-rays are rendered by the bulk jet kinetic power through proton-proton collisions at the SS433/W50 interaction regions. If the same mechanism is operating in other baryon-loaded microquasar jets, their collective contribution may represent a significant fraction of the total galactic cosmic-ray flux at GeV energies.Comment: Accepted for publication in ApJ