1,954 research outputs found

    A radio jet drives a molecular and atomic gas outflow in multiple regions within one square kiloparsec of the nucleus of the nearby galaxy IC5063

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    We analyzed near-infrared data of the nearby galaxy IC5063 taken with the Very Large Telescope SINFONI instrument. IC5063 is an elliptical galaxy that has a radio jet nearly aligned with the major axis of a gas disk in its center. The data reveal multiple signatures of molecular and atomic gas that has been kinematically distorted by the passage of the jet plasma or cocoon within an area of ~1 kpc^2. Concrete evidence that the interaction of the jet with the gas causes the gas to accelerate comes from the detection of outflows in four different regions along the jet trail: near the two radio lobes, between the radio emission tip and the optical narrow-line-region cone, and at a region with diffuse 17.8 GHz emission midway between the nucleus and the north radio lobe. The outflow in the latter region is biconical, centered 240 pc away from the nucleus, and oriented perpendicularly to the jet trail. The diffuse emission that is observed as a result of the gas entrainment or scattering unfolds around the trail and away from the nucleus with increasing velocity. It overall extends for >700 pc parallel and perpendicular to the trail. Near the outflow starting points, the gas has a velocity excess of 600 km/s to 1200 km/s with respect to ordered motions, as seen in [FeII], Pa alpha, or H2 lines. High H2 (1-0) S(3)/S(1) flux ratios indicate non-thermal excitation of gas in the diffuse outflow.Comment: Accepted for publication in Ap

    Relativistic Disk Reflection in the Neutron Star X-ray Binary XTE J1709-267 with NuSTAR

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    We perform the first reflection study of the soft X-ray transient and Type 1 burst source XTE J1709-267 using NuSTAR observations during its 2016 June outburst. There was an increase in flux near the end of the observations, which corresponds to an increase from \sim0.04 LEdd_{\mathrm{Edd}} to \sim0.06 LEdd_{\mathrm{Edd}} assuming a distance of 8.5 kpc. We have separately examined spectra from the low and high flux intervals, which were soft and show evidence of a broad Fe K line. Fits to these intervals with relativistic disk reflection models have revealed an inner disk radius of 13.81.8+3.0 Rg13.8_{-1.8}^{+3.0}\ R_{g} (where Rg=GM/c2R_{g} = GM/c^{2}) for the low flux spectrum and 23.45.4+15.6 Rg23.4_{-5.4}^{+15.6}\ R_{g} for the high flux spectrum at the 90\% confidence level. The disk is likely truncated by a boundary layer surrounding the neutron star or the magnetosphere. Based on the measured luminosity and using the accretion efficiency for a disk around a neutron star, we estimate that the theoretically expected size for the boundary layer would be 0.91.1 Rg\sim0.9-1.1 \ R_{g} from the neutron star's surface, which can be increased by spin or viscosity effects. Another plausible scenario is that the disk could be truncated by the magnetosphere. We place a conservative upper limit on the strength of the magnetic field at the poles, assuming a=0a_{*}=0 and MNS=1.4 MM_{NS}=1.4\ M_{\odot}, of B0.753.70×109B\leq0.75-3.70\times10^{9} G, though X-ray pulsations have not been detected from this source.Comment: Accepted for publication in ApJ, 5 pages, 4 figures, 1 table. arXiv admin note: text overlap with arXiv:1701.0177

    Prediction and explanation in the multiverse

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    Probabilities in the multiverse can be calculated by assuming that we are typical representatives in a given reference class. But is this class well defined? What should be included in the ensemble in which we are supposed to be typical? There is a widespread belief that this question is inherently vague, and that there are various possible choices for the types of reference objects which should be counted in. Here we argue that the ``ideal'' reference class (for the purpose of making predictions) can be defined unambiguously in a rather precise way, as the set of all observers with identical information content. When the observers in a given class perform an experiment, the class branches into subclasses who learn different information from the outcome of that experiment. The probabilities for the different outcomes are defined as the relative numbers of observers in each subclass. For practical purposes, wider reference classes can be used, where we trace over all information which is uncorrelated to the outcome of the experiment, or whose correlation with it is beyond our current understanding. We argue that, once we have gathered all practically available evidence, the optimal strategy for making predictions is to consider ourselves typical in any reference class we belong to, unless we have evidence to the contrary. In the latter case, the class must be correspondingly narrowed.Comment: Minor clarifications adde

    Anthropic reasoning in multiverse cosmology and string theory

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    Anthropic arguments in multiverse cosmology and string theory rely on the weak anthropic principle (WAP). We show that the principle, though ultimately a tautology, is nevertheless ambiguous. It can be reformulated in one of two unambiguous ways, which we refer to as WAP_1 and WAP_2. We show that WAP_2, the version most commonly used in anthropic reasoning, makes no physical predictions unless supplemented by a further assumption of "typicality", and we argue that this assumption is both misguided and unjustified. WAP_1, however, requires no such supplementation; it directly implies that any theory that assigns a non-zero probability to our universe predicts that we will observe our universe with probability one. We argue, therefore, that WAP_1 is preferable, and note that it has the benefit of avoiding the inductive overreach characteristic of much anthropic reasoning.Comment: 7 pages. Expanded discussion of selection effects and some minor clarifications, as publishe

    Parathyroid hormone 1-34 and skeletal anabolic action: The use of parathyroid hormone in bone formation

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    Intermittently administered parathyroid hormone (PTH 1-34) has been shown to promote bone formation in both human and animal studies. The hormone and its analogues stimulate both bone formation and resorption, and as such at low doses are now in clinical use for the treatment of severe osteoporosis. By varying the duration of exposure, parathyroid hormone can modulate genes leading to increased bone formation within a so-called ‘anabolic window’. The osteogenic mechanisms involved are multiple, affecting the stimulation of osteoprogenitor cells, osteoblasts, osteocytes and the stem cell niche, and ultimately leading to increased osteoblast activation, reduced osteoblast apoptosis, upregulation of Wnt/β-catenin signalling, increased stem cell mobilisation, and mediation of the RANKL/OPG pathway. Ongoing investigation into their effect on bone formation through ‘coupled’ and ‘uncoupled’ mechanisms further underlines the impact of intermittent PTH on both cortical and cancellous bone. Given the principally catabolic actions of continuous PTH, this article reviews the skeletal actions of intermittent PTH 1-34 and the mechanisms underlying its effect

    The influence of ion binding and ion specific potentials on the double layer pressure between charged bilayers at low salt concentrations

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    Measurements of surface forces between double-chained cationic bilayers adsorbed onto molecularly smooth mica surfaces across different millimolar salt solutions have revealed a large degree of ion specificity [Pashley et al., J. Phys. Chem. 90, 1637 (1986)]. This has been interpreted in terms of highly specific anion binding to the adsorbed bilayers. We show here that inclusion in the double layer theory of nonspecific ion binding and ion specific nonelectrostatic potentials acting between ions and the two surfaces can account for the phenomenon. It also gives the right Hofmeister series for the double layer pressure.M.B. thanks the Swedish Research Council and the German Arbeitsgemeinschaft industrieller Forschungvereinigungen Otto von Guericke e.V. AiF for financial support. E.R.A.L. and F.W.T. thank FAPERJ and CNPq the Brazilian Agencies for financial support

    The spherical probe electric field and wave experiment

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    The experiment is designed to measure the electric field and density fluctuations with sampling rates up to 40,000 samples/sec. The description includes Langmuir sweeps that can be made to determine the electron density and temperature, the study of nonlinear processes that result in acceleration of plasma, and the analysis of large scale phenomena where all four spacecraft are needed

    Dalbavancin is thermally stable at clinically relevant temperatures against methicillin-sensitive <i>Staphylococcus Aureus</i>

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    Introduction: While the rate of orthopaedic infections has remained constant over the years, the burden on healthcare systems continues to rise with an aging population. Local antibiotic delivery via polymethyl methacrylate bone cement is a common adjunct in treating bone and joint infections. Dalbavancin is a novel lipoglycopeptide antibiotic in the same class as vancomycin that has shown efficacy against Gram-positive organisms when used systemically but has not been investigated as a local antibiotic. This study aims to identify whether dalbavancin is thermally stable at the temperatures expected during the polymerization of polymethyl methacrylate cement. Methods: Stock solutions of dalbavancin were prepared and heated using a polymerase chain reaction machine based upon previously defined models of curing temperatures in two clinically relevant models: a 10 mm polymethyl methacrylate bead and a polymethyl methacrylate articulating knee spacer model. Aliquots of heated dalbavancin were then transferred to be incubated at core body temperature (37 ∘C) and analyzed at various time points up to 28 d. The minimum inhibitory concentration at which 90 % of colonies were inhibited (MIC90) for each heated sample was determined against methicillin-sensitive Staphylococcus aureus (American Type Culture Collection, ATCC, 0173K) using a standard microbroth dilution assay. Results: The average MIC90 of dalbavancin was 1.63 µg mL−1 ±0.49 against 0173K S. aureus. There were no significant differences in the relative MIC90 values after heating dalbavancin in either model compared to unheated control dalbavancin. Conclusions: Dalbavancin is thermally stable at the curing temperatures of polymethyl methacrylate cement and at human core body temperature over 28 d. Future in vitro and in vivo studies are warranted to further investigate the role of dalbavancin as a local antibiotic prior to its clinical use.</p
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