45,836 research outputs found

    Predicting Mercury's Precession using Simple Relativistic Newtonian Dynamics

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    We present a new simple relativistic model for planetary motion describing accurately the anomalous precession of the perihelion of Mercury and its origin. The model is based on transforming Newton's classical equation for planetary motion from absolute to real spacetime influenced by the gravitational potential and introducing the concept of influenced direction.Comment: 5 page

    Axial instability of rotating relativistic stars

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    Perturbations of rotating relativistic stars can be classified by their behavior under parity. For axial perturbations (r-modes), initial data with negative canonical energy is found with angular dependence eimϕe^{im\phi} for all values of m≥2m\geq 2 and for arbitrarily slow rotation. This implies instability (or marginal stability) of such perturbations for rotating perfect fluids. This low mm-instability is strikingly different from the instability to polar perturbations, which sets in first for large values of mm. The timescale for the axial instability appears, for small angular velocity Ω\Omega, to be proportional to a high power of Ω\Omega. As in the case of polar modes, viscosity will again presumably enforce stability except for hot, rapidly rotating neutron stars. This work complements Andersson's numerical investigation of axial modes in slowly rotating stars.Comment: Latex, 18 pages. Equations 84 and 85 are corrected. Discussion of timescales is corrected and update

    Predicting the relativistic periastron advance of a binary without curving spacetime

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    Relativistic Newtonian Dynamics, the simple model used previously for predicting accurately the anomalous precession of Mercury, is now applied to predict the periastron advance of a binary. The classical treatment of a binary as a two-body problem is modified to account for the influence of the gravitational potential on spacetime. Without curving spacetime, the model predicts the identical equation for the relativistic periastron advance as the post-Newtonian approximation of general relativity formalism thereby providing further substantiation of this model.Comment: 6 pages, 2 figure

    Calculation of compressible flow in and about three-dimensional inlets with and without auxiliary inlets by a higher-order panel method

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    A three dimensional higher order panel method was specialized to the case of inlets with auxiliary inlets. The resulting program has a number of graphical input-output features to make it highly useful to the designer. The various aspects of the program are described instructions for its use are presented

    Quasi-Adiabatic Continuation in Gapped Spin and Fermion Systems: Goldstone's Theorem and Flux Periodicity

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    We apply the technique of quasi-adiabatic continuation to study systems with continuous symmetries. We first derive a general form of Goldstone's theorem applicable to gapped nonrelativistic systems with continuous symmetries. We then show that for a fermionic system with a spin gap, it is possible to insert π\pi-flux into a cylinder with only exponentially small change in the energy of the system, a scenario which covers several physically interesting cases such as an s-wave superconductor or a resonating valence bond state.Comment: 19 pages, 2 figures, final version in press at JSTA

    Introduction: The Challenge of Risk Communication in a Democratic Society

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    The symposium editors review key issues concerning the relationship between risk communication and public participation

    Does Maternal Methadone Dose Correlate with Severity of Intrauterine Growth Restriction in Infants with Neonatal Abstinence Syndrome?

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    Introduction : Previous studies demonstrate a relationship between maternal opioid use during pregnancy and smaller head circumference of infants with neonatal abstinence syndrome (NAS). The goal of this study is to correlate maternal methadone dose and severity of growth restriction in infants with NAS admitted to the neonatal intensive care unit (NICU). Methods: This is a retrospective analysis of infants (≥35 weeks gestation) exposed to in utero methadone, born between August 2006 and May 2018, and admitted to a Philadelphia NICU for medical therapy for NAS. Growth parameters (birth weight, birth length, and birth head circumference) were compared between infants exposed various doses of methadone. The groups were compared using ANOVA, Post-Hoc Tukey, Chi-square and extended Fisher exact tests. Results: A total of 686 infants met the study criteria; 109 in the High dose group, 359 in the Intermediate dose group, and 218 in the Low dose group. There was no significant difference in the use of other drugs or smoking during the pregnancy. Infants exposed to higher doses of methadone displayed significantly smaller head circumferences and lengths at birth. The mean birth weight was similar between the three groups. Discussion: There may be a danger in prescribing high doses of methadone to pregnant mothers, as they may hinder the growth of the infant. We need to conduct more studies investigating how low head circumference and length affect long term developmental outcomes. These findings may help guide physicians toward the optimum dose of methadone for mothers

    Experience in feeding coal into a liquefaction process development unit

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    A system for preparing coal slurry and feeding it into a high pressure liquefaction plant is described. The system was developed to provide supporting research and development for the Bureau of Mines coal liquefaction pilot plant. Operating experiences are included
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