10,473 research outputs found

    Low-lying magnetic excitations of doubly-closed-shell nuclei and nucleon-nucleon effective interactions

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    We have studied the low lying magnetic spectra of 12C, 16O, 40Ca, 48Ca and 208Pb nuclei within the Random Phase Approximation (RPA) theory, finding that the description of low-lying magnetic states of doubly-closed-shell nuclei imposes severe constraints on the spin and tensor terms of the nucleon-nucleon effective interaction. We have first made an investigation by using four phenomenological effective interactions and we have obtained good agreement with the experimental magnetic spectra, and, to a lesser extent, with the electron scattering responses. Then we have made self-consistent RPA calculations to test the validity of the finite-range D1 Gogny interaction. For all the nuclei under study we have found that this interaction inverts the energies of all the magnetic states forming isospin doublets.Comment: 19 pages, 13 figures, 7 tables, accepted for publication in Phys. Rev.

    Effects of state dependent correlations on nucleon density and momentum distributions

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    The proton momentum and density distributions of closed shell nuclei are calculated within a model treating short--range correlations up to first order in the cluster expansion. The validity of the model is verified by comparing the results obtained with purely scalar correlations with those produced by finite nuclei Fermi Hypernetted Chain calculations. State dependent correlations are used to calculate momentum and density distributions of 12C, 16O, 40Ca, and 48Ca, and the effects of their tensor components are studied.Comment: 16 pages, latex, 8 figures, accepted for publication in Phys. Rev.

    Orthotopic liver transplantation for massive hepatic lymphangiomatosis

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    Lymphangiomatosis is a rare malformation of the lymphatic system that causes severe symptoms secondary to progressive growth into or close to vital structures. A case report of liver failure related to this space-occupying intrahepatic mechanism is taken as a starting point for a discussion of the problems of liver transplantation related to large hepatomegalies. © 1988

    Mean-field calculations of exotic nuclei ground states

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    We study the predictions of three mean-field theoretical approaches in the description of the ground state properties of some spherical nuclei far from the stability line. We compare binding energies, single particle spectra, density distributions, charge and neutron radii obtained with non-relativistic Hartree-Fock calculations carried out with both zero and finite-range interactions, and with a relativistic Hartree approach which uses a finite-range interaction. The agreement between the results obtained with the three different approaches indicates that these results are more related to the basic hypotheses of the mean-field approach rather than to its implementation in actual calculations.Comment: 16 pages, 12 figures, 2 tables, accepted for publication in Physical Review

    Effects of nuclear re-interactions in quasi-elastic neutrino-nucleus scattering

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    The effects of nuclear re-interactions in the quasi-elastic neutrino-nucleus scattering are investigated with a phenomenological model. We found that the nuclear responses are lowered and their maxima are shifted towards higher excitation energies. This is reflected on the total neutrino-nucleus cross section in a general reduction of about 15% for neutrino energies above 300 MeV.Comment: 15 pages, 5 figures. Submitted to AstroParticle Physic

    A model for two-proton emission induced by electron scattering

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    A model to study two-proton emission processes induced by electron scattering is developed. The process is induced by one-body electromagnetic operators acting together with short-range correlations, and by two-body Δ\Delta currents. The model includes all the diagrams containing a single correlation function. A test of the sensitivity of the model to the various theoretical inputs is done. An investigation of the relevance of the Δ\Delta currents is done by changing the final state angular momentum, excitation energy and momentum transfer. The sensitivity of the cross section to the details of the correlation function is studied by using realistic and schematic correlations. Results for 12^{12}C, 16^{16}O and 40^{40}Ca nuclei are presented.Comment: 30 pages, 18 figures, 3 table

    Water and cosmology in the prehistoric Maltese world: Fault control on the hydrogeology of Ä gantija, Gozo (Maltese Islands)

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    The dry limestone geology of the Maltese islands presented a challenging environment to prehistoric communities, who required reliable water sources to support agricultural subsistence. Ġgantija, one of the iconic Maltese Late Neolithic Temples on Gozo, and now a World Heritage Site, was surveyed using Ground Penetrating Radar to reveal a significant line of geological faulting running beneath the megalithic structure. The seepage of water from this fault had major implications for the siting of the monument. This seems to reflect a pattern of situating many of these key sites adjacent to ancient sources of water, as is shown by the close association of two thirds of these sites with toponym evidence for the presence of springs in the medieval period. It is possible that the prehistoric Maltese embraced this natural resource as part of the cosmology of their ritual sites. © 201

    Is self-assessment in religious education unique?

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    This paper addresses the question: is self-assessment in religious education unique? It first presents an overview of some challenges for assessment from subject differences, and then reviews the generic literature on self-assessment. It builds on earlier empirical research on self-assessment in religious education, carried out in an English state secondary school (Fancourt 2010); this was used to propose a variant of self-assessment which is tailored to the demands of religious education – reflexive self-assessment. Its implications for more general understandings of the relationship between subject pedagogy and self-assessment are discussed, especially the recognition of values not only in religious education but in other subjects too, reinforcing the need to develop subject-specific variants of self-assessment that reflect the breadth of learning outcomes

    The Role of Final State Interactions in Quasielastic 56^{56}Fe(e,e′)(e,e') Reactions at large ∣q⃗∣|\vec q|

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    A relativistic finite nucleus calculation using a Dirac optical potential is used to investigate the importance of final state interactions [FSI] at large momentum transfers in inclusive quasielastic electronuclear reactions. The optical potential is derived from first-order multiple scattering theory and then is used to calculate the FSI in a nonspectral Green's function doorway approach. At intermediate momentum transfers excellent predictions of the quasielastic 56^{56}Fe(e,e′)(e,e') experimental data for the longitudinal response function are obtained. In comparisons with recent measurements at ∣q⃗∣=1.14|{\vec q|}=1.14~GeV/c the theoretical calculations of RLR_L give good agreement for the quasielastic peak shape and amplitude, but place the position of the peak at an energy transfer of about 4040~MeV higher than the data.Comment: 13 pages typeset using revtex 3.0 with 6 postscript figures in accompanying uuencoded file; submitted to Phys. Rev.
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