7,051 research outputs found

    A recalibration of IUE NEWSIPS low dispersion data

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    While the low dispersion IUE NEWSIPS data products represent a significant improvement over original IUE SIPS data, they still contain serious systematic effects which compromise their utility for certain applications. We show that NEWSIPS low resolution data are internally consistent to only 10-15% at best, with the majority of the problem due to time dependent systematic effects. In addition, the NEWSIPS flux calibration is shown to be inconsistent by nearly 10%. We examine the origin of these problems and proceed to formulate and apply algorithms to correct them to ~ 3% level -- a factor of 5 improvement in accuracy. Because of the temporal systematics, transforming the corrected data to the IUE flux calibration becomes ambiguous. Therefore, we elect to transform the corrected data onto the HST FOS system. This system is far more self-consistent, and transforming the IUE data to it places data from both telescopes on a single system. Finally, we argue that much of the remaining 3% systematic effects in the corrected data is traceable to problems with the NEWSIPS intensity transformation function (ITF). The accuracy could probably be doubled by rederiving the ITF.Comment: Submitted to ApJ Supplement, 35 pages, 13 figures, LaTeX - AASTEX aas2pp4.st

    A Search for Intrinsic Polarization in O Stars with Variable Winds

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    New observations of 9 of the brightest northern O stars have been made with the Breger polarimeter on the 0.9~m telescope at McDonald Observatory and the AnyPol polarimeter on the 0.4~m telescope at Limber Observatory, using the Johnson-Cousins UBVRI broadband filter system. Comparison with earlier measurements shows no clearly defined long-term polarization variability. For all 9 stars the wavelength dependence of the degree of polarization in the optical range can be fit by a normal interstellar polarization law. The polarization position angles are practically constant with wavelength and are consistent with those of neighboring stars. Thus the simplest conclusion is that the polarization of all the program stars is primarily interstellar. The O stars chosen for this study are generally known from ultraviolet and optical spectroscopy to have substantial mass loss rates and variable winds, as well as occasional circumstellar emission. Their lack of intrinsic polarization in comparison with the similar Be stars may be explained by the dominance of radiation as a wind driving force due to higher luminosity, which results in lower density and less rotational flattening in the electron scattering inner envelopes where the polarization is produced. However, time series of polarization measurements taken simultaneously with H-alpha and UV spectroscopy during several coordinated multiwavelength campaigns suggest two cases of possible small-amplitude, periodic short-term polarization variability, and therefore intrinsic polarization, which may be correlated with the more widely recognized spectroscopic variations.Comment: LaTeX2e, 22 pages including 11 tables; 12 separate gif figures; uses aastex.cls preprint package; accepted by The Astronomical Journa

    A new spectral classification system for the earliest O stars: definition of type O2

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    High-quality, blue-violet spectroscopic data are collected for 24 stars that have been classified as type O3 and that display the hallmark N IV and N V lines. A new member of the class is presented; it is the second known in the Cyg OB2 association, and only the second in the northern hemisphere. New digital data are also presented for several of the other stars. Although the data are inhomogeneous, the uniform plots by subcategory reveal some interesting new relationships. Several issues concerning the classification of the hottest O-type spectra are discussed, and new digital data are presented for the five original O3 dwarfs in the Carina Nebula, in which the N IV, N V features are very weak or absent. New spectral types O2 and O3.5 are introduced here as steps toward resolving these issues. The relationship between the derived absolute visual magnitudes and the spectroscopic luminosity classes of the O2–O3 stars shows more scatter than at later O types, at least partly because some overluminous dwarfs are unresolved multiple systems, and some close binary systems of relatively low luminosity and mass emulate O3 supergiant spectra. However, it also appears that the behavior of He II λ4686, the primary luminosity criterion at later O types, responds to other phenomena in addition to luminosity at spectral types O2–O3. There is evidence that these spectral types may correspond to an immediate pre-WN phase, with a correspondingly large range of luminosities and masses. A complete census of spectra classified into the original O3 subcategories considered here (not including intermediate O3/WN types or O3 dwarfs without N IV, N V features) totals 45 stars; 34 of them belong to the Large Magellanic Cloud and 20 of the latter to 30 Doradus

    Challenges of teaching occupation: Introduction of an occupation focused teaching tool.

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    Occupational science is of importance to multiple disciplines due to its potential to contribute to understandings of complex social issues. “Occupation”, as a key concept of occupational science, is recognised as being highly complex, making it challenging for students to develop a comprehensive understanding of the concept. Terminology of occupational science literature has been noted at times as using the terms occupation, purposeful activity and activity interchangeably, which further adds to the challenge of teaching the concept. This paper explores evolving definitions of occupation, challenges this evolution has created within education, and the potential use of occupation as a threshold concept. Consideration of a selection of pedagogic methods used in teaching the concept of occupation is briefly explored. The paper concludes with identification of a newly developed occupation-focused teaching tool as a proposed alternative approach to teaching the concept of occupation. The teaching tool was originally developed to teach occupation as a discrete concept, rather than the therapeutic use of occupation as taught in occupational therapy education. The tool is an analogy for occupation, and has utility in supporting the transformation of students’ understanding of the concept of occupation, commensurate to understandings of occupational science.N/

    The Influence of Stellar Wind Variability on Measurements of Interstellar O VI Along Sightlines to Early-Type Stars

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    A primary goal of the FUSE mission is to understand the origin of the O VI ion in the interstellar medium of the Galaxy and the Magellanic Clouds. Along sightlines to OB-type stars, these interstellar components are usually blended with O VI stellar wind profiles, which frequently vary in shape. In order to assess the effects of this time-dependent blending on measurements of the interstellar O VI lines, we have undertaken a mini-survey of repeated observations toward OB-type stars in the Galaxy and the Large Magellanic Cloud. These sparse time series, which consist of 2-3 observations separated by intervals ranging from a few days to several months, show that wind variability occurs commonly in O VI (about 60% of a sample of 50 stars), as indeed it does in other resonance lines. However, in the interstellar O VI λ\lambda1032 region, the O VI λ\lambda1038 wind varies only in ∌\sim30% of the cases. By examining cases exhibiting large amplitude variations, we conclude that stellar-wind variability {\em generally} introduces negligible uncertainty for single interstellar O VI components along Galactic lines of sight, but can result in substantial errors in measurements of broader components or blends of components like those typically observed toward stars in the Large Magellanic Cloud. Due to possible contamination by discrete absorption components in the stellar O VI line, stars with terminal velocities greater than or equal to the doublet separation (1654 km/s) should be treated with care.Comment: Accepted for publication in the Astrophysical Journal Lette

    Experience of the impact of physician associates on ­postgraduate medical training: A mixed methods ­exploratory study

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    The introduction of new professional roles to the multidisciplinary team has been heralded as a way to facilitate medical education in the face of increasing service pressures. However, concerns have been raised that the training of new healthcare professionals will dilute the availability of learning opportunities, thereby detracting from postgraduate medical education. As part of a mixed methods exploratory study, the experienced impact of newly qualified physician associates on medical training was explored. Within 6 months of newly qualified physician associates being introduced, half of junior doctors reported no overall impact on their training and a third felt that their training was enhanced by the presence of physician associates. A minority of trainees experienced dilution of training opportunities. The findings support the notion that new healthcare professionals do not detract from medical training and suggest that roles such as the physician associate have potential to enhance postgraduate medical education

    ‘What can you do then?’ Integrating new roles into healthcare teams: Regional experience with physician associates

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    In the context of NHS workforce shortages, providers are increasingly looking to new models of care, diversifying the workforce and introducing new roles such as physician associates (PAs) into clinical teams. The current study used qualitative methods to investigate how PAs are integrated into a workforce in a region largely unfamiliar with the profession. We conducted an observational study examining factors that facilitated and challenged PA integration. Findings suggest that the factors influencing PA integration relate to attributes of the individual, interpersonal relationships and organisational elements. From these, five key considerations have been derived which may aid organisations when planning to integrate new roles into the clinical workforce: prior to introducing PAs organisations should consider how to fully inform current staff about the PA profession; how to define the role of the PA within teams including clinical supervision arrangements; investment in educational and career development support for PAs; communication of remuneration to existing staff and conveying an organisational vision of PAs within the future workforce. Through consideration of these areas, organisations can facilitate role integration, maximising the potential of the workforce to contribute to sustainable healthcare provision

    Of?p stars: a class of slowly rotating magnetic massive stars

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    Only 5 Of?p stars have been identified in the Galaxy. Of these, 3 have been studied in detail, and within the past 5 years magnetic fields have been detected in each of them. The observed magnetic and spectral characteristics are indicative of organised magnetic fields, likely of fossil origin, confining their supersonic stellar winds into dense, structured magnetospheres. The systematic detection of magnetic fields in these stars strongly suggests that the Of?p stars represent a general class of magnetic O-type stars.Comment: Proceedings of IAUS 272: Active OB star

    Effects of Brief Mindfulness-Based Interventions on Health-Related Outcomes: a Systematic Review

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    Objectives Traditional mindfulness-based interventions (MBIs) have been applied successfully across many populations. The time commitment for these programs is often a barrier, and while brief MBIs have become popular, the impact of these on health-related outcomes is unclear as they have not yet been reviewed. Methods A search of databases, including Medline, Embase, and PsycINFO, was conducted with qualitative and case studies being excluded. Findings were summarized using a narrative approach for all studies that met the inclusion criteria. Results With one exception, all 85 studies that were included were randomized controlled trials and were relatively robust methodologically. Seventy-nine reported significant positive effects on at least one health-related outcome and over a quarter targeted a clinical population. The majority of studies focused on psychological outcomes, such as anxiety and depression, as well as emotion regulation, stress, and cognitive outcomes. Conclusions Despite heterogeneity of outcomes across studies, there is evidence that brief MBIs can impact numerous health-related outcomes, after only one session and with interventions as brief as 5 min. These interventions have the potential to be the initial steps leading to sustainable and positive health outcomes
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