7,051 research outputs found
A recalibration of IUE NEWSIPS low dispersion data
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
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
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 O2âO3 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 O2âO3. 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.
Occupational science is of importance to multiple disciplines due to its potential to contribute to understandings of complex social issues. âOccupationâ, 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 studentsâ 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
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 1032
region, the O VI 1038 wind varies only in 30% 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 Âpostgraduate medical training: A mixed methods Âexploratory study
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
âWhat can you do then?â Integrating new roles into healthcare teams: Regional experience with physician associates
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
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
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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