6,524 research outputs found

    The VLT-FLAMES Tarantula Survey X: Evidence for a bimodal distribution of rotational velocities for the single early B-type stars

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    Aims: Projected rotational velocities (\vsini) have been estimated for 334 targets in the VLT-FLAMES Tarantula survey that do not manifest significant radial velocity variations and are not supergiants. They have spectral types from approximately O9.5 to B3. The estimates have been analysed to infer the underlying rotational velocity distribution, which is critical for understanding the evolution of massive stars. Methods: Projected rotational velocities were deduced from the Fourier transforms of spectral lines, with upper limits also being obtained from profile fitting. For the narrower lined stars, metal and non-diffuse helium lines were adopted, and for the broader lined stars, both non-diffuse and diffuse helium lines; the estimates obtained using the different sets of lines are in good agreement. The uncertainty in the mean estimates is typically 4% for most targets. The iterative deconvolution procedure of Lucy has been used to deduce the probability density distribution of the rotational velocities. Results: Projected rotational velocities range up to approximately 450 \kms and show a bi-modal structure. This is also present in the inferred rotational velocity distribution with 25% of the sample having 00\leq\ve\leq100\,\kms and the high velocity component having \ve250\sim 250\,\kms. There is no evidence from the spatial and radial velocity distributions of the two components that they represent either field and cluster populations or different episodes of star formation. Be-type stars have also been identified. Conclusions: The bi-modal rotational velocity distribution in our sample resembles that found for late-B and early-A type stars. While magnetic braking appears to be a possible mechanism for producing the low-velocity component, we can not rule out alternative explanations.Comment: to be publisged in A&

    Integrin beta 1 inhibition alleviates the chronic hyperproliferative dermatitis phenotype of SHARPIN-deficient mice

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    SHARPIN (Shank-Associated RH Domain-Interacting Protein) is a component of the linear ubiquitin chain assembly complex (LUBAC), which enhances TNF-induced NF-kappa B activity. SHARPIN-deficient (Sharpin(cpdm/cpdm)) mice display multi-organ inflammation and chronic proliferative dermatitis (cpdm) due to TNF-induced keratinocyte apoptosis. In cells, SHARPIN also inhibits integrins independently of LUBAC, but it has remained enigmatic whether elevated integrin activity levels in the dermis of Sharpin(cpdm/cpdm) mice is due to increased integrin activity or is secondary to inflammation. In addition, the functional contribution of increased integrin activation to the Sharpin(cpdm/cpdm) phenotype has not been investigated. Here, we find increased integrin activity in keratinocytes from Tnfr1(-/-) Sharpin(cpdm/cpdm) double knockout mice, which do not display chronic inflammation or proliferative dermatitis, thus suggesting that SHARPIN indeed acts as an integrin inhibitor in vivo. In addition, we present evidence for a functional contribution of integrin activity to the Sharpin(cpdm/cpdm) skin phenotype. Treatment with an integrin beta 1 function blocking antibody reduced epidermal hyperproliferation and epidermal thickness in Sharpin(cpdm/cpdm) mice. Our data indicate that, while TNF-induced cell death triggers the chronic inflammation and proliferative dermatitis, absence of SHARPIN-dependent integrin inhibition exacerbates the epidermal hyperproliferation in Sharpin(cpdm/cpdm) mice.Peer reviewe

    Continuous in-home walking speed monitoring in older people with a low-cost ambient sensor: Results of a feasibility study

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    BACKGROUND: Walking speed predicts important clinical outcomes in older adults and is one of the most significant indicators of frailty. OBJECTIVE: To test whether it is feasible to measure walking speed frequently and unobtrusively in the home. METHODS: A longitudinal feasibility study was conducted comprising the installation and monitoring of continuous measurement walking speed sensors in twenty frail older adults’ homes for a period of twelve weeks (eighteen participants completed the study). Manual walking speed, frailty level and health status were measured at four-weekly intervals. Qualitative interviews were conducted at the end of the study to assess participants’ attitudes to the sensors and to the concept of continuous in-home walking speed measurement. RESULTS: There was a high degree of variance to the number of walking speed measurements recorded by each participant’s sensor (median 1942.39, range 2-3617). Participants indicated acceptability of both the sensor within the home and the concept of in-home walking speed measurement. CONCLUSIONS: Where regular measurement was achieved, the results indicate that walking speed might be better viewed as a distribution rather than a single figure, taking into account the natural variation to walking speed in daily life. This study demonstrates the feasibility of continuous ambient in-home walking speed monitoring of older adults with a low-cost, easily deployed device

    Unravelling social constructionism

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    Social constructionist research is an area of rapidly expanding influence that has brought together theorists from a range of different disciplines. At the same time, however, it has fuelled the development of a new set of divisions. There would appear to be an increasing uneasiness about the implications of a thoroughgoing constructionism, with some regarding it as both theoretically parasitic and politically paralysing. In this paper I review these debates and clarify some of the issues involved. My main argument is that social constructionism is not best understood as a unitary paradigm and that one very important difference is between what Edwards (1997) calls its ontological and epistemic forms. I argue that an appreciation of this distinction not only exhausts many of the disputes that currently divide the constructionist community, but also takes away from the apparent radicalism of much of this work

    Evidence of Planetesimal infall on to the very young Herbig Be star LkHα_\alpha234

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    We report here the first evidence for planetesimal infall onto the very young Herbig Be star LkHα_\alpha234. These results are based on observations acquired over 31 days using spectroscopy of the sodium D lines, the He I 5876\AA, and hydrogen Hα_\alpha lines. We find Redshifted Absorption Components (RAC) with velocities up to 200 km/s and very mild Blueshifted Absorption Components (BEC) up to 100 km/s in the Na I lines. No correlation is observed between the appearance of the Na I RAC & BEC and the Hα_\alpha and He I line variability, which suggests that these (Na I RAC & BEC) are formed in a process unrelated to the circumstellar gas accretion. We interpret the Na I RAC as evidence for an infalling evaporating body, greater than 100 km in diameter, which is able to survive at distances between 2.0 to 0.1 AU from the star. The dramatic appearance of the sodium RAC and mild BEC is readily explained by the dynamics of this infalling body making LkHα_\alpha234 the youngest (age \sim 0.1 Myr) system with evidence for the presence of planetesimals.Comment: Accepted for publications in ApJLetter
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