18,982 research outputs found

    Radio Continuum Study of Supernova Remnants in the Large Magellanic Cloud - SNR J0519-6926

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    We present the results of new high resolution ATCA observations of SNR J0519-6926. We found that this SNR exhibits a typical "horseshoe" appearance with alpha = -0.55 +- 0.08 and D=28+-1 pc. No polarization (or magnetic fields) are detected to a level of 1%. This is probably due to a relatively poor sampling of the uv plane caused be observing in "snap-shot" mode.Comment: 6 pages 4 figures, to be published in Serbian Astronomical Journa

    Quadrupole moment of a magnetically confined mountain on an accreting neutron star: effect of the equation of state

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    Magnetically confined mountains on accreting neutron stars are promising sources of continuous-wave gravitational radiation and are currently the targets of directed searches with long-baseline detectors like the Laser Interferometer Gravitational Wave Observatory (LIGO). In this paper, previous ideal-magnetohydrodynamic models of isothermal mountains are generalized to a range of physically motivated, adiabatic equations of state. It is found that the mass ellipticity drops substantially, from \epsilon ~ 3e-4 (isothermal) to \epsilon ~ 9e-7 (non-relativistic degenerate neutrons), 6e-8 (relativistic degenerate electrons) and 1e-8 (non-relativistic degenerate electrons) (assuming a magnetic field of 3e12 G at birth). The characteristic mass M_{c} at which the magnetic dipole moment halves from its initial value is also modified, from M_{c}/M_{\sun} ~ 5e-4 (isothermal) to M_{c}/M_{\sun} ~ 2e-6, 1e-7, and 3e-8 for the above three equations of state, respectively. Similar results are obtained for a realistic, piecewise-polytropic nuclear equation of state. The adiabatic models are consistent with current LIGO upper limits, unlike the isothermal models. Updated estimates of gravitational-wave detectability are made. Monte Carlo simulations of the spin distribution of accreting millisecond pulsars including gravitational-wave stalling agree better with observations for certain adiabatic equations of state, implying that X-ray spin measurements can probe the equation of state when coupled with magnetic mountain models.Comment: 20 pages, 15 figures, to be published in MNRA

    Empirical Traffic Data and Their Implications for Traffic Modeling

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    From single vehicle data a number of new empirical results about the temporal evolution, correlation, and density-dependence of macroscopic traffic quantities have been determined. These have relevant implications for traffic modeling and allow to test existing traffic models.Comment: For related work see http://www.theo2.physik.uni-stuttgart.de/helbing.htm

    Ligand Discrimination in Myoglobin from Linear-Scaling DFT+U

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    Myoglobin modulates the binding of diatomic molecules to its heme group via hydrogen-bonding and steric interactions with neighboring residues, and is an important benchmark for computational studies of biomolecules. We have performed calculations on the heme binding site and a significant proportion of the protein environment (more than 1000 atoms) using linear-scaling density functional theory and the DFT+U method to correct for self-interaction errors associated with localized 3d states. We confirm both the hydrogen-bonding nature of the discrimination effect (3.6 kcal/mol) and assumptions that the relative strain energy stored in the protein is low (less than 1 kcal/mol). Our calculations significantly widen the scope for tackling problems in drug design and enzymology, especially in cases where electron localization, allostery or long-ranged polarization influence ligand binding and reaction.Comment: 15 pages, 3 figures. Supplementary material 8 pages, 3 figures. This version matches that accepted for J. Phys. Chem. Lett. on 10th May 201

    Illumination waveform optimization for time-of-flight range imaging cameras

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    Time-of-flight range imaging sensors acquire an image of a scene, where in addition to standard intensity information, the range (or distance) is also measured concurrently by each pixel. Range is measured using a correlation technique, where an amplitude modulated light source illuminates the scene and the reflected light is sampled by a gain modulated image sensor. Typically the illumination source and image sensor are amplitude modulated with square waves, leading to a range measurement linearity error caused by aliased harmonic components within the correlation waveform. A simple method to improve measurement linearity by reducing the duty cycle of the illumination waveform to suppress problematic aliased harmonic components is demonstrated. If the total optical power is kept constant, the measured correlation waveform amplitude also increases at these reduced illumination duty cycles. Measurement performance is evaluated over a range of illumination duty cycles, both for a standard range imaging camera configuration, and also using a more complicated phase encoding method that is designed to cancel aliased harmonics during the sampling process. The standard configuration benefits from improved measurement linearity for illumination duty cycles around 30%, while the measured amplitude, hence range precision, is increased for both methods as the duty cycle is reduced below 50% (while maintaining constant optical power)

    Gravitational waves from an accreting neutron star with a magnetic mountain

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    We calculate the amplitude of gravitational waves from a neutron star accreting symmetrically at its magnetic poles. The magnetic field, which is compressed into an equatorial belt during accretion, confines accreted matter in a mountain at the magnetic pole, producing gravitational waves. We compute hydromagnetic equilibria and the corresponding quadrupole moment as a function of the accreted mass, Ma, finding the polarization- and orientation- averaged wave strain at Earth to be h_c = 6.3 × 10^(–25)(M_a/10^(–5)M_☉)(ƒ/0.6kHz)^2(d/1kpc)^(–1) for a range of conditions, where ƒ is the wave frequency and d is the distance to the source. This is ~ 10^2 times greater than previous estimates, which failed to treat the mass-flux distribution self-consistently with respect to flux-freezin

    From 35,000 to 15,000 Feet: Evangelical Statistics in the U.S. and Canada: A State/Province, Metro and County Glimpse

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    Identifying the areas of the greatest evangelical need in the U.S. and Canada, this paper is designed to help churches and denominations take seriously the realities presented and to make any necessary adjustments in their church multiplication strategies to better extend the Kingdom into areas where few are laboring. This article is to be used in conjunction with an extensive corresponding PowerPoint presentation (10MB) showing evangelical statistics in selected places of the United States and Canada. The presentation may be downloaded for free from the Articles section at www.NorthAmericanMissions.org under the title “From 35,000 to 15,000 Feet: Evangelical Statistics in the U.S. and Canada.

    Suggested Shifts in Preparation for the Spontaneous Expansion of the North American Church

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    In this major article, Payne notes three paradigm shifts—theological, strategical, methodological—that need to be rethought in increase effectiveness in church planting
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