30,780 research outputs found

    From Microscales to Macroscales in 3D: Selfconsistent Equation of State for Supernova and Neutron Star Models

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    First results from a fully self-consistent, temperature-dependent equation of state that spans the whole density range of neutron stars and supernova cores are presented. The equation of state (EoS) is calculated using a mean-field Hartree-Fock method in three dimensions (3D). The nuclear interaction is represented by the phenomenological Skyrme model in this work, but the EoS can be obtained in our framework for any suitable form of the nucleon-nucleon effective interaction. The scheme we employ naturally allows effects such as (i) neutron drip, which results in an external neutron gas, (ii) the variety of exotic nuclear shapes expected for extremely neutron heavy nuclei, and (iii) the subsequent dissolution of these nuclei into nuclear matter. In this way, the equation of state is calculated across phase transitions without recourse to interpolation techniques between density regimes described by different physical models. EoS tables are calculated in the wide range of densities, temperature and proton/neutron ratios on the ORNL NCCS XT3, using up to 2000 processors simultaneously.Comment: 6 pages, 11 figures. Published in conference proceedings Journal of Physics: Conference Series 46 (2006) 408. Extended version to be submitted to Phys. Rev.

    High energy electron spikes at high latitudes

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    Over 750 spikes of precipitating electrons with E or = 425 KeV were observed aboard the low altitude polar orbiter OGO-D between 30 July 1967 and 31 December 1967. The spikes may be divided into three distinct populations, depending on whether they occur at latitudes below, at, or above the local limit of trapping

    Introducing a Practitioner-focused Publication in Exercise Science and Kinesiology

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    The purpose is to introduce Topics in Exercise and Science Kinesiology (TESK) as an outlet for practical information. We searched available journals in the field to determine practitioner-focused options, we also determined the percentage of presented abstracts at a popular meeting compared to the number of published papers in a leading peer-reviewed scientific journal. Point of application 1: Only 2% of publication options in kinesiology or exercise science have a practitioner focus. Point of application 2: A relatively small number of peer-reviewed conference abstracts (less than 10%) are deemed publication-worthy following journal peer-review. Point of application 3: To be more inclusive, we announce the International Community of Scholars in Kinesiology (ICSK); and to provide students with important information on professional development and trending research, we will host a virtual Student Research Week each year

    Classical limit of transport in quantum kicked maps

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    We investigate the behavior of weak localization, conductance fluctuations, and shot noise of a chaotic scatterer in the semiclassical limit. Time resolved numerical results, obtained by truncating the time-evolution of a kicked quantum map after a certain number of iterations, are compared to semiclassical theory. Considering how the appearance of quantum effects is delayed as a function of the Ehrenfest time gives a new method to compare theory and numerical simulations. We find that both weak localization and shot noise agree with semiclassical theory, which predicts exponential suppression with increasing Ehrenfest time. However, conductance fluctuations exhibit different behavior, with only a slight dependence on the Ehrenfest time.Comment: 17 pages, 13 figures. Final versio

    Neutron Star Properties with Hyperons

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    In the light of the recent discovery of a neutron star with a mass accurately determined to be almost two solar masses, it has been suggested that hyperons cannot play a role in the equation of state of dense matter in β\beta-equilibrium. We re-examine this issue in the most recent development of the quark-meson coupling model. Within a relativistic Hartree-Fock approach and including the full tensor structure at the vector-meson-baryon vertices, we find that not only must hyperons appear in matter at the densities relevant to such a massive star but that the maximum mass predicted is completely consistent with the observation.Comment: Minor correction

    Finite Nuclei in the Quark-Meson Coupling (QMC) Model

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    We report the first use of the effective QMC energy density functional (EDF), derived from a quark model of hadron structure, to study a broad range of ground state properties of even-even nuclei across the periodic table in the non-relativistic Hartree-Fock+BCS framework. The novelty of the QMC model is that the nuclear medium effects are treated through modification of the internal structure of the nucleon. The density dependence is microscopically derived and the spin-orbit term arises naturally. The QMC EDF depends on a single set of four adjustable parameters having clear physical basis. When applied to diverse ground state data the QMC EDF already produces, in its present simple form, overall agreement with experiment of a quality comparable to a representative Skyrme EDF. There exist however multiple Skyrme paramater sets, frequently tailored to describe selected nuclear phenomena. The QMC EDF set of fewer parameters, as derived in this work, is not open to such variation, chosen set being applied, without adjustment, to both the properties of finite nuclei and nuclear matter.Comment: 9 pages, 1 table, 4 figures; in print in Phys. Rev. Letters. A minor change in the abstract, a few typos corrected and some small technical adjustments made to comply with the journal regulation

    Flight test evaluation of a separate surface attitude command control system on a Beech 99 airplane

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    A joint NASA/university/industry program was conducted to flight evaluate a potentially low cost separate surface implementation of attitude command in a Beech 99 airplane. Saturation of the separate surfaces was the primary cause of many problems during development. Six experienced professional pilots who made simulated instrument flight evaluations experienced improvements in airplane handling qualities in the presence of turbulence and a reduction in pilot workload. For ride quality, quantitative data show that the attitude command control system results in all cases of airplane motion being removed from the uncomfortable ride region
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