6,732 research outputs found

    Constraints on the Growth and Spin of the Supermassive Black Hole in M32 From High Cadence Visible Light Observations

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    We present 1-second cadence observations of M32 (NGC221) with the CHIMERA instrument at the Hale 200-inch telescope of the Palomar Observatory. Using field stars as a baseline for relative photometry, we are able to construct a light curve of the nucleus in the g-prime and r-prime band with 1sigma=36 milli-mag photometric stability. We derive a temporal power spectrum for the nucleus and find no evidence for a time-variable signal above the noise as would be expected if the nuclear black hole were accreting gas. Thus, we are unable to constrain the spin of the black hole although future work will use this powerful instrument to target more actively accreting black holes. Given the black hole mass of (2.5+/-0.5)*10^6 Msun inferred from stellar kinematics, the absence of a contribution from a nuclear time-variable signal places an upper limit on the accretion rate which is 4.6*10^{-8} of the Eddington rate, a factor of two more stringent than past upper limits from HST. The low mass of the black hole despite the high stellar density suggests that the gas liberated by stellar interactions was primarily at early cosmic times when the low-mass black hole had a small Eddington luminosity. This is at least partly driven by a top-heavy stellar initial mass function at early cosmic times which is an efficient producer of stellar mass black holes. The implication is that supermassive black holes likely arise from seeds formed through the coalescence of 3-100 Msun mass black holes that then accrete gas produced through stellar interaction processes.Comment: 8 pages, 3 figures, submitted to the Astrophysical Journal, comments welcom

    Key dating features for timber-framed dwellings in Surrey

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    This article is made available through the Brunel Open Access Publishing Fund. Copyright @ The Vernacular Architecture Group 2013. MORE OpenChoice articles are open access and distributed under the terms of the Creative Commons Attribution License 3.0.The main component of the Surrey Dendrochronology Project is the accurate dating of 177 ‘dwellings’, nearly all by tree-ring analysis. The dates are used to establish date ranges for 52 ‘key features’, which cover many aspects of timber-framing from building type to details of carpentry. It is shown that changes of method and fashion were in many cases surprisingly rapid, almost abrupt in historical terms. Previous dating criteria for timber-framed dwellings in the county have been refined and new criteria introduced. Clusters of change from the 1440s and the 1540s are shown and some possible historical links suggested.The Heritage Lottery Fund, the Domestic Buildings Research Group (Surrey), the Surrey Archaeological Society and the historical societies of Charlwood, Farnham and Nutfield

    Using psychological and physiological measures in arts-based activities in a community sample of people with a dementia and their caregivers: a feasibility and pilot study

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    Introduction: Nearly all community-based dementia care studies employ either qualitative methods or use a combination of self-report questionnaire within mixed-methods research designs. Physiological measures, however, are rarely used in community-based studies with this population yet could provide valuable biological information for specific activities across the course of the dementias. Method: The study employed a within-subjects design to assess the feasibility of obtaining physiological measures (salivary cortisol and Heart Rate Variability (HRV)) alongside subjective measures of wellbeing and stress using Visual Analogue Scales (VAS) during two community-based activiti of choral singing and art viewing, respectively, for People With Dementia (PWD) in the early to middle stages of impairment and their caregivers. Results: As anticipated, pre-post subjective wellbeing measures were relatively easy to complete by PWD and caregivers with no substantive difficulties observed or reported; significant increases in composite wellbeing, happiness and optimism were found. Continuous measurement of physiological data of HRV through a sensor-based device (Empatica® E4) was also found to be neither non-intrusive to participants nor disruptive to the interventions. Preliminary indications showed, for example, HRV significantly increased for PWD during choral singing, which may be associated with an increase in wellbeing. Measuring stress hormones through pre-post saliva samples, however, encountered several difficulties. Conclusions: The findings provide support for the feasibility of using non-intrusive sensor-based physiological measures alongside subjective measures for this population. Subjective measures may also give more confidence in interpreting directionality of physiological measures. A full pilot study is warranted to further investigate interactions of physiological and psychological variables in choral singing and viewing art activities but it is uncertain whether measuring stress hormones through saliva collection is feasible for this population and raised doubts about their use in a large scale trial. Holding particular promise is the use of sensor-based technology across different stages of dementia as well as across different activities

    Full polar cap cascade scenario: γ\gamma-ray and X-ray luminosities from spin-powered pulsars

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    We modify polar cap cascade picture to include the ICS of the higher generation pairs. In such a ``full-cascade'' scenario, not only the perpendicular portion of the energy of the pairs goes to high energy radiation via SR, but the parallel portion of the energy of the pairs can also contribute to high energy emission via ICS with the soft thermal photons from either the full neutron star surface or the hot polar cap. An important output of such a scenario is that the soft tail of the ICS spectrum can naturally result in a non-thermal X-ray component which can contribute to the luminosities observed by ROSAT and ASCA. Here we present an analytic description of such a full polar cap cascade scenario within the framework of Harding & Muslimov acceleration model. We present the theoretical predictions of the γ\gamma-ray luminosities, the thermal and non-thermal X-ray luminosities for the known spin-powered X-ray pulsars. Our results show that the observed different dependences of the high energy luminosities on the pulsar spin-down luminosities, i.e., Lγ(Lsd)1/2L_\gamma \propto (L_{\rm sd})^{1/2} and Lx103LsdL_x \sim 10^{-3} L_{\rm sd}, are well reproduced. Our model predicts that the {\em pulsed} soft X-rays in the ROSAT band from most of the millisecond pulsars might be of thermal origin if there is no strong multipole field components near the surfaces of these pulsars.Comment: 23 pages, emulateapj style, final version to appear in the Astrophysical Journa

    EPHA2 Segregates with Microphthalmia and Congenital Cataracts in Two Unrelated Families

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    EPHA2 is a transmembrane tyrosine kinase receptor that, when disrupted, causes congenital and age-related cataracts. Cat-Map reports 22 pathogenic EPHA2 variants associated with congenital cataracts, variable microcornea, and lenticonus, but no previous association with microphthalmia (small, underdeveloped eye, ≥2 standard deviations below normal axial length). Microphthalmia arises from ocular maldevelopment with >90 monogenic causes, and can include a complex ocular phenotype. In this paper, we report two pathogenic EPHA2 variants in unrelated families presenting with bilateral microphthalmia and congenital cataracts. Whole genome sequencing through the 100,000 Genomes Project and cataract-related targeted gene panel testing identified autosomal dominant heterozygous mutations segregating with the disease: (i) missense c.1751C>T, p.(Pro584Leu) and (ii) splice site c.2826-9G>A. To functionally validate pathogenicity, morpholino knockdown of epha2a/epha2b in zebrafish resulted in significantly reduced eye size ± cataract formation. Misexpression of N-cadherin and retained fibre cell nuclei were observed in the developing lens of the epha2b knockdown morphant fish by 3 days post-fertilisation, which indicated a putative mechanism for microphthalmia pathogenesis through disruption of cadherin-mediated adherens junctions, preventing lens maturation and the critical signals stimulating eye growth. This study demonstrates a novel association of EPHA2 with microphthalmia, suggesting further analysis of pathogenic variants in unsolved microphthalmia cohorts may increase molecular diagnostic rates
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