5,232 research outputs found

    Finding high-order analytic post-Newtonian parameters from a high-precision numerical self-force calculation

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    We present a novel analytic extraction of high-order post-Newtonian (pN) parameters that govern quasi-circular binary systems. Coefficients in the pN expansion of the energy of a binary system can be found from corresponding coefficients in an extreme-mass-ratio inspiral (EMRI) computation of the change ΔU\Delta U in the redshift factor of a circular orbit at fixed angular velocity. Remarkably, by computing this essentially gauge-invariant quantity to accuracy greater than one part in 1022510^{225}, and by assuming that a subset of pN coefficients are rational numbers or products of π\pi and a rational, we obtain the exact analytic coefficients. We find the previously unexpected result that the post-Newtonian expansion of ΔU\Delta U (and of the change ΔΩ\Delta\Omega in the angular velocity at fixed redshift factor) have conservative terms at half-integral pN order beginning with a 5.5 pN term. This implies the existence of a corresponding 5.5 pN term in the expansion of the energy of a binary system. Coefficients in the pN series that do not belong to the subset just described are obtained to accuracy better than 1 part in 10265−23n10^{265-23n} at nnth pN order. We work in a radiation gauge, finding the radiative part of the metric perturbation from the gauge-invariant Weyl scalar ψ0\psi_0 via a Hertz potential. We use mode-sum renormalization, and find high-order renormalization coefficients by matching a series in L=ℓ+1/2L=\ell+1/2 to the large-LL behavior of the expression for ΔU\Delta U. The non-radiative parts of the perturbed metric associated with changes in mass and angular momentum are calculated in the Schwarzschild gauge

    Multi-object spectroscopy of the field surrounding PKS 2126-158: Discovery of a z=0.66 galaxy group

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    The high-redshift radio-loud quasar PKS 2126-158 is found to have a large number of red galaxies in close apparent proximity. We use the Gemini Multi-Object Spectrograph (GMOS) on Gemini South to obtain optical spectra for a large fraction of these sources. We show that there is a group of galaxies at z∌0.66z\sim0.66, coincident with a metal-line absorption system seen in the quasar's optical spectrum. The multiplexing capabilities of GMOS also allow us to measure redshifts of many foreground galaxies in the field surrounding the quasar. The galaxy group has five confirmed members, and a further four fainter galaxies are possibly associated. All confirmed members exhibit early-type galaxy spectra, a rare situation for a Mg II absorbing system. We discuss the relationship of this group to the absorbing gas, and the possibility of gravitational lensing of the quasar due to the intervening galaxies.Comment: Monthly Notices of the Royal Astronomical Society, in press. 10 pages, 8 figure

    LAW ENFORCEMENT RISK MODEL TO COMBAT OPIOID RECIDIVISM

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    Bergen County, New Jersey, has seen opioid-related overdoses and deaths spike in the last few years. One of the challenges in addressing this epidemic is that “at-risk” individuals may encounter multiple segmented domains such as law enforcement, recovery services, and healthcare institutions, but no one agency has oversight of all the contacts. Each encounter with at-risk populations, including those who suffer from opioid addiction or who may recidivate, becomes a data record in a system. This thesis asks how can law enforcement leverage such data sets to address the opioid epidemic and battle recidivism? This research examined law enforcement arrest data and overdose reporting in Bergen County, analyzing which risk factors in recidivism could be discerned using statistical information, cross-tabulations, Pearson’s chi-squared tests, and data modeling from the Cox proportional hazards model. The results showed that no demographic profile was more likely to have another overdose or death, and theft arrests coincided with a decreased chance of overdose, despite law enforcement’s presumption of the contrary. The strongest predictor of an overdose was a prior overdose, with the risk increasing for each additional overdose. Additionally, having any contact with law enforcement was an indicator of a significantly higher chance of overdose or death. Thus, each interaction between law enforcement and an observed opioid abuser is a critical point for intervention.Civilian, Bergen County Prosecutor's Office New JerseyApproved for public release. Distribution is unlimited

    Approximate Killing Vectors on S^2

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    We present a new method for computing the best approximation to a Killing vector on closed 2-surfaces that are topologically S^2. When solutions of Killing's equation do not exist, this method is shown to yield results superior to those produced by existing methods. In addition, this method appears to provide a new tool for studying the horizon geometry of distorted black holes.Comment: 4 pages, 3 figures, submitted to Physical Review D, revtex

    Res Ipsa Loquitur

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    Acceptance and commitment therapy delivered in a dyad after a severe traumatic brain injury: a feasibility study

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    Objective: There is a high prevalence of complex psychological distress after a traumatic brain injury but limited evidence of effective interventions. We examined the feasibility of Acceptance and Commitment Therapy after a severe traumatic brain injury using the criteria, investigating a therapeutic effect, and reviewing the acceptability of measures, treatment protocol, and delivery method (in a dyad of two clients and a therapist). Method: Two male outpatients with severe traumatic brain injury and associated psychological distress jointly engaged in a seven session treatment program based on Acceptance and Commitment Therapy principles. Pre- and post-treatment measures of mood, psychological flexibility, and participation were taken in addition to weekly measures. Results: The intervention showed a therapeutic effect with one participant, and appeared to be acceptable for both participants with regard to program content, measures, and delivery mode by in a dyad. One participant showed both significant clinical and reliable change across several outcome measures including measures of mood and psychological flexibility. The second participant did not show a reduction in psychological inflexibility, but did show a significant drop in negative affect. Significant changes pre- to post-treatment for measures of participation were not indicated. Qualitatively, both participants engaged in committed action set in accordance with their values. Conclusions: This study suggests that Acceptance and Commitment Therapy may be feasible to be delivered in a dyad with individuals who have a severe traumatic brain injury. A further test of its potential efficacy in a phase II clinical trial is recommended

    Letter from the Firm J. L. Whiting and Adams to A. C. Van Raalte

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    A letter from the firm of J. L. Whiting and Adams to A.C.V.R., stating that they had received by Mr. Post a package of deeds and certificates. The firm is to research the titles for A.C.V.R. See Hyma, page 164.https://digitalcommons.hope.edu/vrp_1850s/1170/thumbnail.jp

    The Optical Emission from Gamma-ray Quasars

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    We present photometric observations of six radio-loud quasars that were detected by the COMPTEL gamma-ray telescope. The data encompasses seven wavebands in the optical and near-infrared. After correction for Galactic extinction, we find a wide range in optical slopes. Two sources are as blue as optically-selected quasars, and are likely to be dominated by the accretion disc emission, while three others show colours consistent with a red synchrotron component. We discuss the properties of the COMPTEL sample of quasars, as well as the implications our observations have for multi-wavelength modelling of gamma-ray quasars.Comment: 12 pages, 3 figures, accepted for publication in P.A.S.A; minor typos correcte
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