1,558 research outputs found

    A precessing jet model for the PN K 3-35: simulated radio-continuum emission

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    The bipolar morphology of the planetary nebula (PN) K 3-35 observed in radio-continuum images was modelled with 3D hydrodynamic simulations with the adaptive grid code yguazu-a. We find that the observed morphology of this PN can be reproduced considering a precessing jet evolving in a dense AGB circumstellar medium, given by a mass loss rate \dot{M}_{csm}=5x10^{-5}M_{\odot}/yr and a terminal velocity v_{w}=10 km/s. Synthetic thermal radio-continuum maps were generated from numerical results for several frequencies. Comparing the maps and the total fluxes obtained from the simulations with the observational results, we find that a model of precessing dense jets, where each jet injects material into the surrounding CSM at a rate \dot{M}_j=2.8x10^{-4} {M_{\odot}/yr (equivalent to a density of 8x10^{4} {cm}^{-3}, a velocity of 1500 km/s, a precession period of 100 yr, and a semi-aperture precession angle of 20 degrees agrees well with the observations.Comment: 6 pages, 4 figures, accepted to MNRA

    X/X/Ka-band prime focus feed antenna for the Mars Observer beacon spacecraft

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    The results of an X/X/Ka-band feed design concept demonstration are presented. The purpose is to show the feasibility of adding a Ka-band beacon to the Mars Observer spacecraft. Scale model radiation patterns were made and analyzed

    Modeling Compressible Non-Newtonian Chicken Flow

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    This paper addresses a few modeling issues relevant for the basic theoretical understanding of the meat flow behavior in simple geometries. We model the meat mixture as a non-Newtonian compressible fluid. Focusing on conceptually easy-to-follow cases like flow in thin molds, or steady incompressible or compressible flow in straight pipes we derive explicit expressions for the velocity and pressure profiles. For the thin moldcase, we formulate a one-dimensional free-boundary problem able to capture the a priori unknown position of the moving meat-air interface. Special attention is payed on the derivation of the free boundary conditions

    3D MHD simulation of polarized emission in SN 1006

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    We use three dimensional magnetohydrodynamic (MHD) simulations to model the supernova remnant SN 1006. From our numerical results, we have carried out a polarization study, obtaining synthetic maps of the polarized intensity, the Stokes parameter QQ, and the polar-referenced angle, which can be compared with observational results. Synthetic maps were computed considering two possible particle acceleration mechanisms: quasi-parallel and quasi-perpendicular. The comparison of synthetic maps of the Stokes parameter QQ maps with observations proves to be a valuable tool to discern unambiguously which mechanism is taking place in the remnant of SN 1006, giving strong support to the quasi-parallel model.Comment: 6 pages, 4 figures, accepted by MNRA

    Lymphoma and hypercalcemia in a pediatric orthotopic liver transplant patient

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    We present a case report of a pediatric orthotopic liver transplant recipient who developed lymphoma with hypercalcemia on cyclosporine and prednisone immunosuppression. This is the first reported posttransplant lymphoproliferative disorder complicated by hypercalcemia, with a finding of an elevated 1,25 dihydroxyl vitamin D state, suggesting that it has a role in the pathophysiology of this B cell lymphoma hypercalcemia. The clinical course and management of this disorder with a 31-month follow-up are described. © 1989 by Williams & Wilkins

    On the sensitivity of extrasolar mass-loss rate ranges: HD 209458b a case study

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    We present a 3D hydrodynamic study of the effects that different stellar wind conditions and planetary wind structures have on the calculated Ly-α\alpha absorptions produced during the transit of HD 209458b. Considering a range of stellar wind speeds ∼\sim[350-800] km s−1^{-1}, coronal temperature ∼\sim[3-7] ×106\times10^{6} K and two values of the polytropic index Γ\Gamma ∼\sim[1.01-1.13], while keeping fixed the stellar mass loss rate, we found a that a M˙p\dot M_p range between ∼\sim[3-5] ×1010\times 10^{10}g s−1^{-1} give account for the observational absorption in Ly-α\alpha measured for the planetary system. Also, several models with anisotropic evaporation profiles for the planetary escaping atmosphere were carried out, showing that both, the escape through polar regions and through the night side yields larger absorptions than an isotropic planetary wind
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