186 research outputs found
The Wolf-Rayet binaries of the nitrogen sequence in the Large Magellanic Cloud: spectroscopy, orbital analysis, formation, and evolution
Massive Wolf-Rayet (WR) stars dominate the radiative and mechanical energy
budget of galaxies and probe a critical phase in the evolution of massive stars
prior to core-collapse. It is not known whether core He-burning WR stars
(classical WR, cWR) form predominantly through wind-stripping (w-WR) or binary
stripping (b-WR). With spectroscopy of WR binaries so-far largely avoided due
to its complexity, our study focuses on the 44 WR binaries / binary candidates
of the Large Magellanic Cloud (LMC, metallicity Z~0.5 Zsun), identified on the
basis of radial velocity variations, composite spectra, or high X-ray
luminosities. Relying on a diverse spectroscopic database, we aim to derive the
physical and orbital parameters of our targets, confronting evolution models of
evolved massive stars at sub-solar metallicity, and constraining the impact of
binary interaction in forming them. Spectroscopy is performed using the Potsdam
Wolf-Rayet (PoWR) code and cross-correlation techniques. Disentanglement is
performed using the code Spectangular or the shift-and-add algorithm.
Evolutionary status is interpreted using the Binary Population and Spectral
Synthesis (BPASS) code, exploring binary interaction and chemically-homogeneous
evolution.
No obvious dichotomy in the locations of apparently-single and binary WN
stars on the Hertzsprung-Russell diagram is apparent. According to commonly
used stellar evolution models (BPASS, Geneva), most apparently-single WN stars
could not have formed as single stars, implying that they were stripped by an
undetected companion. Otherwise, it must follow that pre-WR mass-loss/mixing
(e.g., during the red supergiant phase) are strongly underestimated in standard
stellar evolution models.Comment: accepted to A&A on 10.05.2019; 69 pages (25 main paper + 44
appendix); Corrigendum: Shenar et al. 2020, A&A, 641, 2: An unfortunate typo
in the implementation of the "transformed radius" caused errors of up to
~0.5dex in the derived mass-loss rates. This has now been correcte
Mental Health Diagnoses and Utilization of VA Non-Mental Health Medical Services Among Returning Iraq and Afghanistan Veterans
Over 35% of returned Iraq and Afghanistan veterans in VA care have received mental health diagnoses; the most prevalent is post-traumatic stress disorder (PTSD). Little is known about these patients’ use of non-mental health medical services and the impact of mental disorders on utilization.
To compare utilization across three groups of Iraq and Afghanistan veterans: those without mental disorders, those with mental disorders other than PTSD, and those with PTSD.
National, descriptive study of 249,440 veterans newly utilizing VA healthcare between October 7, 2001 and March 31, 2007, followed until March 31, 2008.
We used ICD9-CM diagnostic codes to classify mental health status. We compared utilization of outpatient non-mental health services, primary care, medical subspecialty, ancillary services, laboratory tests/diagnostic procedures, emergency services, and hospitalizations during veterans’ first year in VA care. Results were adjusted for demographics and military service and VA facility characteristics.
Veterans with mental disorders had 42–146% greater utilization than those without mental disorders, depending on the service category (all P < 0.001). Those with PTSD had the highest utilization in all categories: 71–170% greater utilization than those without mental disorders (all P < 0.001). In adjusted analyses, compared with veterans without mental disorders, those with mental disorders other than PTSD had 55% higher utilization of all non-mental health outpatient services; those with PTSD had 91% higher utilization. Female sex and lower rank were also independently associated with greater utilization.
Veterans with mental health diagnoses, particularly PTSD, utilize significantly more VA non-mental health medical services. As more veterans return home, we must ensure resources are allocated to meet their outpatient, inpatient, and emergency needs
A RAVE investigation on Galactic open clusters: II. Open cluster pairs, groups and complexes
© ESO, 2017. Context. It is generally agreed upon that stars form in open clusters (OCs) and stellar associations, but little is known about structures in the Galactic OC population; whether OCs and stellar associations are born isolated or if they prefer to form in groups, for example. Answering this question provides new insight into star and cluster formation, along with a better understanding of Galactic structures. Aims. In the past decade, studies of OC groupings have either been based solely on spatial criteria or have also included tangential velocities for identifications. In contrast to previous approaches, we assumed that real OC groupings occupy a well defined area in the sky and show similar velocity vectors. For the first time, we have used 6D phase-space information, including radial velocities from the RAdial Velocity Experiment (RAVE) and other catalogues, for the detection of OC groupings. We also checked the age spread of potential candidates to distinguish between genuine groupings and chance alignments. Methods. We explored the Catalogue of Open Cluster Data (COCD) and determined 6D phase-space information for 432 out of 650 listed OCs and compact associations. The group identification was performed using an adapted version of the Friends-of-Friends algorithm, as used in cosmology, with linking lengths of 100 pc and 10-20 km s-1. For the verification of the identified structures, we applied Monte Carlo simulations with randomised samples. Results. For the linking lengths 100 pc and 10 km s-1, we detected 19 groupings, including 14 pairs, 4 groups with 3-5 members, and 1 complex with 15 members. The Monte Carlo simulations revealed that, in particular, the complex is most likely genuine, whereas pairs are more likely chance alignments. A closer look at the age spread of the complex and the comparison between spatial distributions of young and old cluster populations suggested that OC groupings likely originated from a common molecular cloud
The VLT-FLAMES Tarantula Survey I: Introduction and observational overview
The VLT-FLAMES Tarantula Survey (VFTS) is an ESO Large Programme that has
obtained multi-epoch optical spectroscopy of over 800 massive stars in the 30
Doradus region of the Large Magellanic Cloud (LMC). Here we introduce our
scientific motivations and give an overview of the survey targets, including
optical and near-infrared photometry and comprehensive details of the data
reduction. One of the principal objectives was to detect massive binary systems
via variations in their radial velocities, thus shaping the multi-epoch
observing strategy. Spectral classifications are given for the massive
emission-line stars observed by the survey, including the discovery of a new
Wolf-Rayet star (VFTS 682, classified as WN5h), 2' to the northeast of R136. To
illustrate the diversity of objects encompassed by the survey, we investigate
the spectral properties of sixteen targets identified by Gruendl & Chu from
Spitzer photometry as candidate young stellar objects or stars with notable
mid-infrared excesses. Detailed spectral classification and quantitative
analysis of the O- and B-type stars in the VFTS sample, paying particular
attention to the effects of rotational mixing and binarity, will be presented
in a series of future articles to address fundamental questions in both stellar
and cluster evolution.Comment: Accepted by A&A, 52 pages (main body: 19 pages, supplementary tables:
33 pages), v3: two classifications updated to match a parallel pape
Incidence and survival of childhood bone cancer in northern England and the West Midlands, 1981–2002
There is a paucity of population-based studies examining incidence and survival trends in childhood bone tumours. We used high quality data from four population-based registries in England. Incidence patterns and trends were described using Poisson regression. Survival trends were analysed using Cox regression. There were 374 cases of childhood (ages 0–14 years) bone tumours (206 osteosarcomas, 144 Ewing sarcomas, 16 chondrosarcomas, 8 other bone tumours) registered in the period 1981–2002. Overall incidence (per million person years) rates were 2.63 (95% confidence interval (CI) 2.27–2.99) for osteosarcoma, 1.90 (1.58–2.21) for Ewing sarcoma and 0.21 (0.11–0.31) for chondrosarcoma. Incidence of Ewing sarcoma declined at an average rate of 3.1% (95% CI 0.6–5.6) per annum (P=0.04), which may be due to tumour reclassification, but there was no change in osteosarcoma incidence. Survival showed marked improvement over the 20 years (1981–2000) for Ewing sarcoma (hazard ratio (HR) per annum=0.95 95% CI 0.91–0.99; P=0.02). However, no improvement was seen for osteosarcoma patients (HR per annum=1.02 95% CI 0.98–1.05; P=0.35) over this time period. Reasons for failure to improve survival including potential delays in diagnosis, accrual to trials, adherence to therapy and lack of improvement in treatment strategies all need to be considered
4MOST Scientific Operations
The 4MOST instrument is a multi-object spectrograph that will address
Galactic and extragalactic science cases simultaneously by observing targets
from a large number of different surveys within each science exposure. This
parallel mode of operation and the survey nature of 4MOST require some distinct
4MOST-specific operational features within the overall operations model of ESO.
The main feature is that the 4MOST Consortium will deliver, not only the
instrument, but also contractual services to the user community, which is why
4MOST is also described as a facility. This white paper concentrates on
information particularly useful to answering the forthcoming Call for Letters
of Intent.Comment: Part of the 4MOST issue of The Messenger, published in preparation of
4MOST Community Workshop, see http://www.eso.org/sci/meetings/2019/4MOST.htm
The Evolution of Compact Binary Star Systems
We review the formation and evolution of compact binary stars consisting of
white dwarfs (WDs), neutron stars (NSs), and black holes (BHs). Binary NSs and
BHs are thought to be the primary astrophysical sources of gravitational waves
(GWs) within the frequency band of ground-based detectors, while compact
binaries of WDs are important sources of GWs at lower frequencies to be covered
by space interferometers (LISA). Major uncertainties in the current
understanding of properties of NSs and BHs most relevant to the GW studies are
discussed, including the treatment of the natal kicks which compact stellar
remnants acquire during the core collapse of massive stars and the common
envelope phase of binary evolution. We discuss the coalescence rates of binary
NSs and BHs and prospects for their detections, the formation and evolution of
binary WDs and their observational manifestations. Special attention is given
to AM CVn-stars -- compact binaries in which the Roche lobe is filled by
another WD or a low-mass partially degenerate helium-star, as these stars are
thought to be the best LISA verification binary GW sources.Comment: 105 pages, 18 figure
Factors contributing to posttraumatic growth and its buffering effect in adult chidren of cancer patients undergoing treatment
This study examined relationships among demographic, clinical,
and psychosocial variables in adult children of cancer patients.
Two hundred and fourteen participants completed measures of
posttraumatic growth (PTG), distress, posttraumatic stress disorder
(PTSD) symptoms, social support, and family functioning. Significant
gender differences in all PTG dimensions were found, as well
as associations among PTG, gender, parental dependency, distress,
PTSD, and family functioning. Social support was not a mediator
in the relationship between gender and PTG. Gender, education,
disease duration, dependency, distress, and family flexibility predicted
PTG. Finally, PTG had amoderating effect in the relationship
between distress and PTSD/social support. These results may guide
psychosocial interventions in this population.Fundação para a Ciência e Tecnologia (FCT
Income Splitting and Gender Equality: The Case for Incentivizing Intra-Household Wealth Transfers
Purinergic mechanism in the immune system: A signal of danger for dendritic cells
There is increasing appreciation that injured or stressed cells release molecules endowed with the ability to modulate dendritic cell maturation. The role of these molecules is thought to be that of alerting the body of an impending danger, and initiate and shape the subsequent immune response. Nucleotides are perfectly suited for this task as they are easily released upon damage of the cell membrane, rapidly diffuse in the extracellular environment and ligate specific plasma membrane receptors expressed by dendritic cells and other mononuclear phagocytes. A better knowledge of the modulation of dendritic cell responses by extracellular nucleotides may provide novel routes to enhance the immune response and increase the efficacy of vaccination
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