Ohm's Law for a Relativistic Pair Plasma

We derive the fully relativistic Ohm's law for an electron-positron plasma. The absence of non-resistive terms in Ohm's law and the natural substitution of the 4-velocity for the velocity flux in the relativistic bulk plasma equations do not require the field gradient length scale to be much larger than the lepton inertial lengths, or the existence of a frame in which the distribution functions are isotropic.Comment: 12 pages, plain TeX, Phys. Rev. Lett. 71 3481 (1993

The iron KαK_\alpha lines as a tool for magnetic field estimations in non-flat accretion flows

Observations of AGNs and microquasars by ASCA, RXTE, Chandra and XMM-Newton indicate the existence of broad X-ray emission lines of ionized heavy elements in their spectra. Such spectral lines were discovered also in X-ray spectra of neutron stars and X-ray afterglows of GRBs. Recently, Zakharov et al. (MNRAS, 2003, 342, 1325) described a procedure to estimate an upper limit of the magnetic fields in regions from which X-ray photons are emitted. The authors simulated typical profiles of the iron $K_\alpha$ line in the presence of magnetic field and compared them with observational data in the framework of the widely accepted accretion disk model. Here we further consider typical Zeeman splitting in the framework of a model of non-flat accretion flows, which is a generalization of previous consideration into non-equatorial plane motion of particles emitting X-ray photons. Using perspective facilities of space borne instruments (e.g. Constellation-X mission) a better resolution of the blue peak structure of iron $K_\alpha$ line will allow to evaluate the magnetic fields with higher accuracy.Comment: 22 pages, 6 figure

On the linear stability of magnetized jets without current sheets - non-relativistic case

In this paper we consider stability of magnetized jets that carry no net electric current and do not have current sheets. The non-relativistic magnetohydrodynamics equations are linearized around the background velocity and the magnetic field structure of the jet. The resulting linear equations are solved numerically inside the jet. We find that introduction of current-sheet-free magnetic field significantly improves jet stability relative to unmagnetized jets or magnetized jets with current sheets at their surface. This particularly applies to the fundamental pinch and kink modes – they become completely suppressed in a wide range of long wavelengths that are known to become most pernicious to jet stability when the evolution enters the non-linear regime. The reflection modes, both for the pinch and kink instability, also become progressively more stable with increased magnetization

Error-analysis and comparison to analytical models of numerical waveforms produced by the NRAR Collaboration

The Numerical-Relativity-Analytical-Relativity (NRAR) collaboration is a joint effort between members of the numerical relativity, analytical relativity and gravitational-wave data analysis communities. The goal of the NRAR collaboration is to produce numerical-relativity simulations of compact binaries and use them to develop accurate analytical templates for the LIGO/Virgo Collaboration to use in detecting gravitational-wave signals and extracting astrophysical information from them. We describe the results of the first stage of the NRAR project, which focused on producing an initial set of numerical waveforms from binary black holes with moderate mass ratios and spins, as well as one non-spinning binary configuration which has a mass ratio of 10. All of the numerical waveforms are analysed in a uniform and consistent manner, with numerical errors evaluated using an analysis code created by members of the NRAR collaboration. We compare previously-calibrated, non-precessing analytical waveforms, notably the effective-one-body (EOB) and phenomenological template families, to the newly-produced numerical waveforms. We find that when the binary's total mass is ~100-200 solar masses, current EOB and phenomenological models of spinning, non-precessing binary waveforms have overlaps above 99% (for advanced LIGO) with all of the non-precessing-binary numerical waveforms with mass ratios <= 4, when maximizing over binary parameters. This implies that the loss of event rate due to modelling error is below 3%. Moreover, the non-spinning EOB waveforms previously calibrated to five non-spinning waveforms with mass ratio smaller than 6 have overlaps above 99.7% with the numerical waveform with a mass ratio of 10, without even maximizing on the binary parameters.Comment: 51 pages, 10 figures; published versio

Improved Outcomes Associated With the Use of Intravenous Acetaminophen for Management of Acute Post-Surgical Pain in Cesarean Sections and Hysterectomies

Background: Post-surgical pain impacts many patient outcomes. Effective pain management increasingly relies on multimodal analgesia regimens in which acetaminophen (APAP) is a key component. The aim of our study was to examine the impact of oral APAP versus intravenous (IV) APAP as a component of post-surgical pain management after Cesarean sections and hysterectomies. Methods: A retrospective analysis of the Cerner HealthFacts® database (from January, 2011 to December, 2015) was conducted to compare outcomes of Cesarean section and hysterectomy surgery patients who received oral APAP to those who received IV APAP post-surgically. Length of stay (LOS), daily morphine milligram equivalent (MME) consumption, the presence of potential opioid-related adverse events (ORADEs), and total pharmacy costs were assessed. Adjusted results were derived using inverse probability weighted regression adjustment (IPW-RA) estimators based on covariates that included demographics, comorbidities, patient clinical characteristics, and hospital characteristics. Results: The study identified 29,124 Cesarean section patients (24,612 oral APAP; 4,512 IV APAP) and 9,767 hysterectomy surgery patients (5,586 oral APAP; 4,181 IV APAP). Compared to the oral APAP group, the IV APAP group had reductions in adjusted LOS (Cesarean section: -11.7% days (P < 0.001), hysterectomy: -11.8% days (P = 0.005)), lowered adjusted daily MME consumption from day 0 to day 3 (Cesarean section: -1.6 mg (P < 0.001), hysterectomy: -1.7 mg (P = 0.014)), and reduced risk of ORADEs for Cesarean sections (relative risk of 0.45, P < 0.001). Total pharmacy costs were not significantly different between the two APAP groups. Conclusions: Post-surgical pain managed with IV APAP in patients undergoing Cesarean section or hysterectomy was associated with shorter LOS, reduced risk of ORADEs, and lower opioid consumption compared to patients managed with oral APAP, without adversely impacting total pharmacy costs

Matter Outflows from AGN: A Unifying Model

We discuss a self-consistent unified model of the matter outflows from AGNs based on a theoretical approach and involving data on AGN evolution and structure. The model includes a unified geometry, two-phase gas dynamics, radiation transfer, and absorption spectrum calculations in the UV and X-ray bands. We briefly discuss several questions about the mass sources of the flows, the covering factors, and the stability of the narrow absorption details.Comment: 6 figures, accepted for publication in Astrophysics and Space Scienc

First narrow-band search for continuous gravitational waves from known pulsars in advanced detector data

Spinning neutron stars asymmetric with respect to their rotation axis are potential sources of continuous gravitational waves for ground-based interferometric detectors. In the case of known pulsars a fully coherent search, based on matched filtering, which uses the position and rotational parameters obtained from electromagnetic observations, can be carried out. Matched filtering maximizes the signalto- noise (SNR) ratio, but a large sensitivity loss is expected in case of even a very small mismatch between the assumed and the true signal parameters. For this reason, narrow-band analysis methods have been developed, allowing a fully coherent search for gravitational waves from known pulsars over a fraction of a hertz and several spin-down values. In this paper we describe a narrow-band search of 11 pulsars using data from Advanced LIGO’s first observing run. Although we have found several initial outliers, further studies show no significant evidence for the presence of a gravitational wave signal. Finally, we have placed upper limits on the signal strain amplitude lower than the spin-down limit for 5 of the 11 targets over the bands searched; in the case of J1813-1749 the spin-down limit has been beaten for the first time. For an additional 3 targets, the median upper limit across the search bands is below the spin-down limit. This is the most sensitive narrow-band search for continuous gravitational waves carried out so far

Trust, Connectivity, and Thriving: Implications for Innovative Behaviors at Work

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/89545/1/j.2162-6057.2009.tb01313.x.pd

Binary black holes and tori in AGN II. Can stellar winds constitute a dusty torus?

We determine the properties of the stellar torus that we showed in a previous paper to result as a product of two merging black holes. If the surrounding stellar cluster is as massive as the binary black hole, the torque acting on the stars ejects a fraction which extracts all the binary's angular momentum on scales of ~10^7 yr, and a geometrically thick torus remains. In the present article we show that a certain fraction of the stars has winds, shaped into elongated tails by the central radiation pressure, which are optically thick for line of sights aligned with them. These stars are sufficiently numerous to achieve a covering factor of 1, so that the complete torus is optically thick. We find the parameters of such a patchy torus to be in the right range to explain the observed large column densities in AGN and their temporal variations on time scales of about a decade. Within this model the BAL quasars can be interpreted as quasars seen at intermediate inclination angles, with the line of sight grazing the edge of the torus. The opening angle of the torus is wider for major mergers and thus correlates with the central luminosity. In this picture the spin of the merged black hole is possibly dominated by the orbital angular momentum of the binary. Thus the spin of the merged black hole points into a new direction, and consequently the jet experiences a spin-flip according to the spin-paradigm. This re-orientation could be an explanation for the X-shaped radio galaxies, and the advancing of a new jet through the ambient medium for Compact Symmetric Objects.Comment: 20 pages, 10 figures, final version, A&A accepte