6,843 research outputs found

    Evidence for anisotropic motion of the clouds in broad-line regions of BL Lacertae objects

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    The masses of central massive black holes in BL Lac objects are estimated from their host galaxy absolute magnitude at R-band by using the empirical relation between absolute magnitude of host galaxy and black hole mass. Only a small fraction of BL Lac objects exhibit weak broad-line emission, and we derive the sizes of the broad-line regions (BLRs) in these BL Lac objects from the widths of their broad emission lines on the assumption of the clouds being virilized in BLRs. It is found that the sizes of the BLRs in these sources are usually 2-3 orders of magnitude larger than that expected by the empirical correlation between BLR size and optical luminosity defined by a sample of Seyfert galaxies and quasars. We discuss a variety of possibilities and suggest it may probably be attributed to anisotropic motion of the BLR clouds in these BL Lac objects. If the BLR geometry of these sources is disk-like, the viewing angles between the axis and the line of sight are in the range of 2-12 degrees, which is consistent with the unification schemes.Comment: 5 pages, accepted for publication in Ap

    An evaluation of the Islington community education provider network super hub.

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    ‘Super Hubs’ are novel initiatives which have arisen in order to aid various workforce developments and service improvements for promoting creative thinking and practice. The Islington Super Hub is a workstream of the Islington Community Education Provider Network (CEPN) which aids the learning and development of community nursing and new apprenticeships (Health Education North Central and East London 2015). In this paper we report on the findings from a realist evaluation of the Islington Super Hub (Pawson and Tilley 1997) using data from a range of provider organisations. The following areas of direct relevance to the Super Hub’s activity will be analysed: i) the factors enabling nursing staff to transfer between sectors; ii) the variety of current preceptorship and induction programmes supporting newly registered nurses moving into community roles; iii) the current links between primary/secondary care for strengthening inter-sectoral working and the core training needed for hospital-based nurses to support patient journeys; iv) the practice learning experiences of specialist practice community nurses, such as General Practice Nurses, District Nurses and Health Visitors as well as non-specialist practitioners and health care assistants; v) the current approaches for sustaining practice-based learning for enhanced learning/development; vi) the current approaches to multi-professional education across localities which contribute to establishing robust community focussed multi-professional collaborative educational approaches; vii) the availability of student nurse placements in community settings and the associated mentorship capacity. Our analysis concludes with critical reflection on the relative merits of the Super Hub’s programme of learning and development which aims to promote creative thought/practice and the contextual factors surrounding the newly emerging apprenticeship roles. References Health Education North Central and East London (2015) Nursing and Midwifery Education Strategy. London: Health Education North Central and East London. Pawson R, Tilley N (1997) Realistic Evaluation. London: Sag

    A Spectropolarimetric Atlas of Seyfert 1 Galaxies

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    We present optical spectropolarimetry of the nuclei of 36 Seyfert 1 galaxies, obtained with the William Herschel and the Anglo-Australian Telescopes from 1996 to 1999. In 20 of these, the optical emission from the active nucleus is intrinsically polarized. We have measured a significant level of polarization in a further 7 objects but these may be heavily contaminated by Galactic interstellar polarization. The intrinsically polarized Seyfert 1s exhibit a variety of characteristics, with the average polarization ranging from < 0.5 to 5 per cent and many showing variations in both the degree and position angle of polarization across the broad H alpha emission line. We identify a small group of Seyfert 1s that exhibit polarization properties similar to those of Seyfert 2 galaxies in which polarized broad-lines have been discovered. These objects represent direct observational evidence that a Seyfert 2-like far-field polar scattering region is also present in Seyfert 1s. Several other objects have features that can be explained in terms of equatorial scattering of line emission from a rotating disk. We propose that much of the diversity in the polarization properties of Seyfert galaxies can be understood in terms of a model involving both equatorial and polar scattering, the relative importance of the two geometries as sources of polarized light being determined principally by the inclination of the system axis to the line-of-sight.Comment: Accepted for publication in MNRAS (28 pages, 25 figures

    Distal humeral plating of an intramedullary nail periprosthetic fracture using a miss-a-nail technique: a case report

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    The treatment of distal humeral periprosthetic fractures is not widely described in the literature. We present a difficult clinical scenario of a 72-year-old man who sustained a displaced distal humeral periprosthetic fracture about a Polarus Plus intramedullary nail. In this case, stable fixation was achieved using bicondylar Acumed Mayo congruent Plates using a miss-a-nail technique. Four months following the post operative period, the patient regained satisfactory range of movement with full function and no further complications up to 18 months post fixation. Treatment of such complex periprosthetic fractures is technically achievable and with potentially good results

    Does Every Quasar Harbor A Blazar?

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    Assuming there is a blazar type continuum in every radio-loud quasar, we find that the free-free heating due to the beamed infrared continuum can greatly enhance collisionally excited lines, and thus explain the stronger CIV λ\lambda1549 line emission observed in radio loud quasars. We further predict that the CIV line should show variability {\it not} associated with observed continuum or Lyα\alpha variability.Comment: 15 pages, 3 figures; to appear in Astrophys. J. Let

    Analyzing the Multiwavelength Spectrum and Variability of BL Lacertae During the July 1997 Outburst

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    The multiwavelength spectrum of BL Lacertae during its July 1997 outburst is analyzed in terms of different variations of the homogeneous leptonic jet model for the production of high-energy radiation from blazars. We find that a two-component gamma-ray spectrum, consisting of a synchrotron self-Compton and an external Compton component, is required in order to yield an acceptable fit to the broadband spectrum. Our analysis indicates that in BL Lac, unlike other BL Lac objects, the broad emission line region plays an important role for the high-energy emission. Several alternative blazar jet models are briefly discussed. In the appendix, we describe the formalism in which the process of Comptonization of reprocessed accretion disk photons is treated in the previously developed blazar jet simulation code which we use.Comment: Now accepted for publication in The Astronomical Journal. Significantly extended discussion w.r.t. original version. 3 Figures included using epsf.sty, rotate.st

    mGlu5 Inhibition in the Basolateral Amygdala Prevents Estrous Cycle-Dependent Changes in Cue-Induced Cocaine Seeking

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    Drug associated cues are a common relapse trigger for individuals recovering from cocaine use disorder. Sex and ovarian hormones influence patterns of cocaine use and relapse vulnerability, with studies indicating that females show increased cue-induced craving and relapse vulnerability compared to males. In a rodent model of cocaine craving and relapse vulnerability, cue-induced cocaine seeking behavior following weeks of withdrawal from extended-access cocaine self-administration is higher in females in the estrus stage of the reproductive (estrous) cycle (Estrus Females) compared to both Males and females in all other stages (Non-Estrus Females). However, the neuronal substrates and cellular mechanisms underlying these sex differences is not fully understood. One region that contributes to both sex differences in behavioral responding and cue-induced cocaine seeking is the basolateral amygdala (BLA), while one receptor known to play a critical role in mediating cocaine seeking behavior is metabotropic glutamate receptor 5 (mGlu5). Here we assessed the effects of BLA mGlu5 inhibition following prolonged withdrawal from cocaine self-administration on observed estrous cycle-dependent changes in cue-induced cocaine seeking behavior. We found that BLA microinjections of the mGlu5 antagonist MTEP selectively reduced the enhanced cue-induced cocaine seeking normally observed in Estrus Females while having no effect on cocaine seeking in Males and Non-Estrus Females. These findings identify a unique interaction between cocaine-exposure, estrous cycle fluctuations and BLA mGlu5-dependent transmission on cue-induced cocaine seeking behavior
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