386 research outputs found

    WISE J064336.71-022315.4: A Thick Disk L8 Gaia DR2-Discovered Brown Dwarf at 13.9 Parsecs

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    While spectroscopically characterizing nearby ultracool dwarfs discovered in the Gaia Second Data Release with the TripleSpec spectrograph on the Palomar 200'' telescope, we encountered a particularly cool, nearby, new member of the solar neighborhood: Gaia DR2 3106548406384807680 = WISE J064336.71-022315.4 = 2MASS J06433670-0223130. The Gaia\it{Gaia} parallax corresponds to a distance of 13.9 ±\pm 0.3 pc. Using our TripleSpec spectrum we classify W0643 as spectral type L8, and measured a heliocentric radial velocity of 142 ±\pm 12 km s1^{-1}. When combined with Gaia\it{Gaia} astrometry, we determine a Galactic velocity (heliocentric; UU towards Galactic center) of U,V,WU, V, W = -109, -91, -12 (±\pm10, 5, 3) km s1^{-1}. We estimate that W0643 passed within \sim1.4 pc away from the Sun \sim100,000 years ago

    Pre-main-sequence isochrones - III: The Cluster Collaboration isochrone server

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    We present an isochrone server for semi-empirical pre-main-sequence model isochrones in the following systems: Johnson–Cousins, Sloan Digital Sky Survey, Two-Micron All-Sky Survey, Isaac Newton Telescope (INT) Wide-Field Camera and INT Photometric Hα Survey (IPHAS)/UV-Excess Survey (UVEX). The server can be accessed via the Cluster Collaboration webpage http://www.astro.ex.ac.uk/people/timn/isochrones/. To achieve this, we have used the observed colours of member stars in young clusters with well-established age, distance and reddening to create fiducial loci in the colour–magnitude diagram. These empirical sequences have been used to quantify the discrepancy between the models and data arising from uncertainties in both the interior and atmospheric models, resulting in tables of semi-empirical bolometric corrections (BCs) in the various photometric systems. The model isochrones made available through the server are based on existing stellar interior models coupled with our newly derived semi-empirical BCs. As part of this analysis, we also present new cluster parameters for both the Pleiades and Praesepe, yielding ages of 135+20−11 and 665+14−7Myr as well as distances of 132 ± 2 and 184 ± 2 pc, respectively (statistical uncertainty only)

    Pre-main-sequence isochrones - III. The cluster collaboration isochrone server

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    We present an isochrone server for semi-empirical pre-main-sequence model isochrones in the following systems: Johnson-Cousins, Sloan Digital Sky Survey, Two-Micron All-Sky Survey, Isaac Newton Telescope (INT) Wide-Field Camera and INT Photometric Ha Survey (IPHAS)/UV-Excess Survey (UVEX). The server can be accessed via the Cluster Collaboration webpage http://www.astro.ex.ac.uk/people/timn/isochrones/. To achieve this, we have used the observed colours ofmember stars in young clusters with well-established age, distance and reddening to create fiducial loci in the colour-magnitude diagram. These empirical sequences have been used to quantify the discrepancy between the models and data arising from uncertainties in both the interior and atmospheric models, resulting in tables of semi-empirical bolometric corrections (BCs) in the various photometric systems. The model isochrones made available through the server are based on existing stellar interior models coupled with our newly derived semi-empirical BCs. As part of this analysis, we also present new cluster parameters for both the Pleiades and Praesepe, yielding ages of 135+20 -11 and 665+14 -7 Myr as well as distances of 132 ± 2 and 184 ± 2 pc, respectively (statistical uncertainty only).JMR is funded by a UK Science and Technology Facilities Council (STFC) studentship. EEM acknowledges support from the National Science Foundation (NSF) Award AST-1008908. The authors would like to thank Emanuele Tognelli for the updated set of Pisa models and John Stauffer for sharing his catalogue of Kron photometric measurements of Pleiades members. The authors would also like to thank the referee for comments which have vastly improved the clarity of the manuscript. This research has made use of data obtained at the Isaac Newton Telescope, which is operated on the island of La Palma by the Isaac Newton Group (ING) in the Spanish Observatorio del Roque de los Muchachos of the Institutio de Astrofisica de Canarias. This research has made use of archival data products from the Two-Micron All-Sky Survey (2MASS), which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center, funded by the National Aeronautics and Space Administration (NASA) and the National Science Foundation. This research has made use of public data from the SDSS. Funding for the SDSS was provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the US Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society and the Higher Education Funding Council for England. The SDSS was managed by the Astrophysical Research Consortium for the Participating Institutions

    Black Hole Models of Quasars

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    Observations of active galactic nuclei are interpreted in terms of a theoretical model involving accretion onto a massive black hole. Optical quasars and Seyfert galaxies are associated with holes accreting near the Eddington rate and radio galaxies with sub-critical accretion. It is argued that magnetic fields are largely responsible for extracting energy and angular momentum from black holes and disks. Recent studies of electron-positron pair plasmas and their possible role in establishing the emergent X-ray spectrum are reviewed. The main evolutionary properties of active galactic nuclei can be interpreted in terms of a simple model in which black holes accrete gas at a rate dictated by the rate of gas supply which decreases with cosmic time. It may be worth searching for eclipsing binary black holes in lower power Seyferts

    The Formation and Evolution of the First Massive Black Holes

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    The first massive astrophysical black holes likely formed at high redshifts (z>10) at the centers of low mass (~10^6 Msun) dark matter concentrations. These black holes grow by mergers and gas accretion, evolve into the population of bright quasars observed at lower redshifts, and eventually leave the supermassive black hole remnants that are ubiquitous at the centers of galaxies in the nearby universe. The astrophysical processes responsible for the formation of the earliest seed black holes are poorly understood. The purpose of this review is threefold: (1) to describe theoretical expectations for the formation and growth of the earliest black holes within the general paradigm of hierarchical cold dark matter cosmologies, (2) to summarize several relevant recent observations that have implications for the formation of the earliest black holes, and (3) to look into the future and assess the power of forthcoming observations to probe the physics of the first active galactic nuclei.Comment: 39 pages, review for "Supermassive Black Holes in the Distant Universe", Ed. A. J. Barger, Kluwer Academic Publisher

    Gravitational Waves from Gravitational Collapse

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    Gravitational wave emission from the gravitational collapse of massive stars has been studied for more than three decades. Current state of the art numerical investigations of collapse include those that use progenitors with realistic angular momentum profiles, properly treat microphysics issues, account for general relativity, and examine non--axisymmetric effects in three dimensions. Such simulations predict that gravitational waves from various phenomena associated with gravitational collapse could be detectable with advanced ground--based and future space--based interferometric observatories.Comment: 68 pages including 13 figures; revised version accepted for publication in Living Reviews in Relativity (http://www.livingreviews.org

    Manifestations of Post-COVID Syndrome in Healthcare Workers in Northeast England

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    \ua9 2025 by the authors.Post-COVID-19 syndrome (PCS) is a common outcome of severe COVID-19 infection; however, less is known about PCS following mild COVID-19. Healthcare workers (HCWs) are more susceptible to acquiring COVID-19 and potentially suffering physical and psychological morbidity secondary to their role. We surveyed HCWs at four hospitals in northeast England at two timepoints during the pandemic, assessing physical and psychophysiological symptoms of PCS, alongside associated factors, whilst also testing for COVID-19 status by SARS-CoV-2 serology and reviewing evidence of infection from previous PCR nasopharyngeal swabs. Of the 379 participants at baseline and 250 HCWs recruited 18 months later, 46% and 64% (respectively) had evidence of previous COVID-19, with no significant associations between COVID-19 status or demographics and symptom scores or self-described PCS. Depression and fatigue were more common later in the pandemic. Furthermore, 20% self-described having PCS, 34% of whom had no evidence of previous COVID-19. Scores for fatigue, pain, mobility, anxiety, and depression were significantly worse in the PCS group compared to those without ongoing symptoms. Significant proportions of HCWs continued to suffer debilitating symptoms during the later pandemic period, although a significant minority had no evidence of previous COVID-19 infection, suggesting that other factors may be involved in their symptomatology

    Medical Therapies for Uterine Fibroids - A Systematic Review and Network Meta-Analysis of Randomised Controlled Trials

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    BACKGROUND: Uterine fibroids are common, often symptomatic and a third of women need repeated time off work. Consequently 25% to 50% of women with fibroids receive surgical treatment, namely myomectomy or hysterectomy. Hysterectomy is the definitive treatment as fibroids are hormone dependent and frequently recurrent. Medical treatment aims to control symptoms in order to replace or delay surgery. This may improve the outcome of surgery and prevent recurrence. PURPOSE: To determine whether any medical treatment can be recommended in the treatment of women with fibroids about to undergo surgery and in those for whom surgery is not planned based on currently available evidence. STUDY SELECTION: Two authors independently identified randomised controlled trials (RCT) of all pharmacological treatments aimed at the treatment of fibroids from a list of references obtained by formal search of MEDLINE, EMBASE, Cochrane library, Science Citation Index, and ClinicalTrials.gov until December 2013. DATA EXTRACTION: Two authors independently extracted data from identified studies. DATA SYNTHESIS: A Bayesian network meta-analysis was performed following the National Institute for Health and Care Excellence-Decision Support Unit guidelines. Odds ratios, rate ratios, or mean differences with 95% credible intervals (CrI) were calculated. RESULTS AND LIMITATIONS: A total of 75 RCT met the inclusion criteria, 47 of which were included in the network meta-analysis. The overall quality of evidence was very low. The network meta-analysis showed differing results for different outcomes. CONCLUSIONS: There is currently insufficient evidence to recommend any medical treatment in the management of fibroids. Certain treatments have future promise however further, well designed RCTs are needed

    A922 Sequential measurement of 1 hour creatinine clearance (1-CRCL) in critically ill patients at risk of acute kidney injury (AKI)

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    Worldwide comparison of survival from childhood leukaemia for 1995–2009, by subtype, age, and sex (CONCORD-2): a population-based study of individual data for 89 828 children from 198 registries in 53 countries

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    Background Global inequalities in access to health care are reflected in differences in cancer survival. The CONCORD programme was designed to assess worldwide differences and trends in population-based cancer survival. In this population-based study, we aimed to estimate survival inequalities globally for several subtypes of childhood leukaemia. Methods Cancer registries participating in CONCORD were asked to submit tumour registrations for all children aged 0-14 years who were diagnosed with leukaemia between Jan 1, 1995, and Dec 31, 2009, and followed up until Dec 31, 2009. Haematological malignancies were defined by morphology codes in the International Classification of Diseases for Oncology, third revision. We excluded data from registries from which the data were judged to be less reliable, or included only lymphomas, and data from countries in which data for fewer than ten children were available for analysis. We also excluded records because of a missing date of birth, diagnosis, or last known vital status. We estimated 5-year net survival (ie, the probability of surviving at least 5 years after diagnosis, after controlling for deaths from other causes [background mortality]) for children by calendar period of diagnosis (1995-99, 2000-04, and 2005-09), sex, and age at diagnosis (< 1, 1-4, 5-9, and 10-14 years, inclusive) using appropriate life tables. We estimated age-standardised net survival for international comparison of survival trends for precursor-cell acute lymphoblastic leukaemia (ALL) and acute myeloid leukaemia (AML). Findings We analysed data from 89 828 children from 198 registries in 53 countries. During 1995-99, 5-year agestandardised net survival for all lymphoid leukaemias combined ranged from 10.6% (95% CI 3.1-18.2) in the Chinese registries to 86.8% (81.6-92.0) in Austria. International differences in 5-year survival for childhood leukaemia were still large as recently as 2005-09, when age-standardised survival for lymphoid leukaemias ranged from 52.4% (95% CI 42.8-61.9) in Cali, Colombia, to 91.6% (89.5-93.6) in the German registries, and for AML ranged from 33.3% (18.9-47.7) in Bulgaria to 78.2% (72.0-84.3) in German registries. Survival from precursor-cell ALL was very close to that of all lymphoid leukaemias combined, with similar variation. In most countries, survival from AML improved more than survival from ALL between 2000-04 and 2005-09. Survival for each type of leukaemia varied markedly with age: survival was highest for children aged 1-4 and 5-9 years, and lowest for infants (younger than 1 year). There was no systematic difference in survival between boys and girls. Interpretation Global inequalities in survival from childhood leukaemia have narrowed with time but remain very wide for both ALL and AML. These results provide useful information for health policy makers on the effectiveness of health-care systems and for cancer policy makers to reduce inequalities in childhood survival
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