HE 0557-4840 - Ultra-Metal-Poor and Carbon-Rich

We report the discovery and high-resolution, high S/N, spectroscopic analysis of the ultra-metal-poor red giant HE 0557-4840, which is the third most heavy-element deficient star currently known. Its atmospheric parameters are T_eff = 4900 K, log g = 2.2, and [Fe/H]= -4.75. This brings the number of stars with [Fe/H] < -4.0 to three, and the discovery of HE 0557-4840 suggests that the metallicity distribution function of the Galactic halo does not have a "gap" between [Fe/H] = -4.0, where several stars are known, and the two most metal-poor stars, at [Fe/H] ~ -5.3. HE 0557-4840 is carbon rich - [C/Fe] = +1.6 - a property shared by all three objects with [Fe/H] < -4.0, suggesting that the well-known increase of carbon relative to iron with decreasing [Fe/H] reaches its logical conclusion - ubiquitous carbon richness - at lowest abundance. We also present abundances (nine) and limits (nine) for a further 18 elements. For species having well-measured abundances or strong upper limits, HE 0557-4840 is "normal" in comparison with the bulk of the stellar population at [Fe/H] ~ -4.0 - with the possible exception of Co. We discuss the implications of these results for chemical enrichment at the earliest times, in the context of single ("mixing and fallback") and two-component enrichment models. While neither offers a clear solution, the latter appears closer to the mark. Further data are required to determine the oxygen abundance and improve that of Co, and hence more strongly constrain the origin of this object.Comment: Submitted to Astrophysical Journal. 52 pages (41 text, 11 figures

The Tip of the Red Giant Branch Distance to the Large Magellanic Cloud

We present the I-band luminosity function of the red giant branch stars in the Large Magellanic Cloud (LMC) using the data from the Magellanic Clouds Photometric Survey (Zaritsky, Harris & Thompson, 1997). Selecting stars in uncrowded, low-extinction regions, a discontinuity in the luminosity function is observed at I_0 = 14.54 mag. Identifying this feature with the tip of the red giant branch (TRGB), and adopting an absolute TRGB magnitude of -4.05 +- 0.04 mag based on the calibration of Lee, Freedman & Madore (1993), we obtain a distance modulus of 18.59 +- 0.09 (random) +- 0.16 (systematic) mag. If the theoretical TRGB calibration provided by Cassisi & Salaris (1997) is adopted instead, the derived distance would be 4% greater. The LMC distance modulus reported here, 18.59 +- 0.09, is larger by 0.09 mag (1-sigma) than the value that is most commonly used in the extragalactic distance scale calibrated by the period-luminosity relation of the Cepheid variable stars. Our TRGB distance modulus agrees with several RR Lyrae distances to the LMC based on HIPPARCOS parallaxes. Finally, we note that using the same MCPS data, we obtain a distance modulus of 18.29 +- 0.03 mag using the red clump method, which is shorter by 0.3 mag compared to the TRGB estimate.Comment: 19 pages, 5 figure

The Temperature Scale of Metal-Rich M Giants Based on TiO Bands: Population Synthesis in the Near Infrared

We have computed a grid of high resolution synthetic spectra for cool stars (2500<Teff<6000 K) in the wavelength range 6000 -- 10200A, by employing an updated line list of atomic and molecular lines, together with state-of-the-art model atmospheres. As a by-product, by fitting TiO bandheads in spectra of well-known M giants, we have derived the electronic oscillator strengths of the TiO gamma prime, delta, epsilon and phi systems. The derived oscillator strenghts for the gamma prime, epsilon and phi systems differ from the laboratory and ab initio values found in the literature, but are consistent with the model atmospheres and line lists employed, resulting in a good match to the observed spectra of M giants of known parameters. The behavior of TiO bands as a function of the stellar parameters Teff, log g and [Fe/H] is presented and the use of TiO spectral indices in stellar population studies is discussed.Comment: ApJ accepted, 27 pages + 11 figures, AASLatex v4.

The UV Upturn in Elliptical Galaxies as an Age Indicator

We show that the UV flux of old stellar systems can tell us about their ages. Two independent populations synthesis groups that have had wildly different views have here worked together and generated two solutions that can be easily tested using space telescopes. Proposed tests will constrain the ages of giant Es, that are often considered the oldest populations in the universe, and thus cosmology.Comment: LaTeX and 11 eps figures Accepted for publication in Ap

Early Galactic Evolution of Carbon, Nitrogen and Oxygen

We present results on carbon, nitrogen, and oxygen abundances for a sample of unevolved metal-poor stars with metallicities in the range -0.3< [Fe/H]< -3. Oxygen abundances derived from different indicators are compared showing consistently that in the range 0.3 >[Fe/H]>-3.0, the [O/Fe] ratio increases from approximately 0 to 1. We find a good agreement between abundances based on the forbidden line, the OH and IR triplet lines when gravities based on Hipparcos} parallaxes are considered for the sample stars. Gravities derived from LTE ionization balance in metal-poor stars with [Fe/H]< -1 are likely too low, and could be responsible for an underestimation of the oxygen abundances derived using the [OI] line. [C/Fe] and [N/Fe] ratios appear to be constant, independently of metallicity, in the same range. However, they show larger scatter than oxygen at a given metallicity, which could reflect the larger variety of stellar production sites for these other elements.Comment: 10 pages, 3 figures, To appear in the proceedings of the conference "The Chemical Evolution of The Milky Way: Stars versus Clusters", eds. F. Matteucci and F. Giovannelli, Vulcano, Italy, September 20-24 199

The Initial Conditions to Star Formation: Low Mass Stars at Low Metallicity

We have measured the present accretion rate of roughly 800 low-mass (~1-1.4 Mo) pre-Main Sequence stars in the field of SN 1987A in the Large Magellanic Cloud. The stars with statistically significant Balmer continuum and Halpha excesses are measured to have accretion rates larger than about 1.5x10^{-8} Mo/yr at an age of 12-16 Myrs. For comparison, the time scale for disk dissipation observed in the Galaxy is of the order of 6 Myrs.Comment: 4 pages, 1 figure, to appear in IMF@50, ed. by E. Corbelli, F. Palla, H. Zinnecker (Dordrecht: Kluwer

Using combined diagnostic test results to hindcast trends of infection from cross-sectional data

Infectious disease surveillance is key to limiting the consequences from infectious pathogens and maintaining animal and public health. Following the detection of a disease outbreak, a response in proportion to the severity of the outbreak is required. It is thus critical to obtain accurate information concerning the origin of the outbreak and its forward trajectory. However, there is often a lack of situational awareness that may lead to over- or under-reaction. There is a widening range of tests available for detecting pathogens, with typically different temporal characteristics, e.g. in terms of when peak test response occurs relative to time of exposure. We have developed a statistical framework that combines response level data from multiple diagnostic tests and is able to ‘hindcast’ (infer the historical trend of) an infectious disease epidemic. Assuming diagnostic test data from a cross-sectional sample of individuals infected with a pathogen during an outbreak, we use a Bayesian Markov Chain Monte Carlo (MCMC) approach to estimate time of exposure, and the overall epidemic trend in the population prior to the time of sampling. We evaluate the performance of this statistical framework on simulated data from epidemic trend curves and show that we can recover the parameter values of those trends. We also apply the framework to epidemic trend curves taken from two historical outbreaks: a bluetongue outbreak in cattle, and a whooping cough outbreak in humans. Together, these results show that hindcasting can estimate the time since infection for individuals and provide accurate estimates of epidemic trends, and can be used to distinguish whether an outbreak is increasing or past its peak. We conclude that if temporal characteristics of diagnostics are known, it is possible to recover epidemic trends of both human and animal pathogens from cross-sectional data collected at a single point in time

Comparison of total parathyroidectomy without autotransplantation and without thymectomy versus total parathyroidectomy with autotransplantation and with thymectomy for secondary hyperparathyroidism: TOPAR PILOT-Trial

<p>Abstract</p> <p>Background</p> <p>Secondary hyperparathyroidism (sHPT) is common in patients with chronic renal failure. Despite the initiation of new therapeutic agents, several patients will require parathyroidectomy (PTX). Total PTX with autotransplantation of parathyroid tissue (TPTX+AT) and subtotal parathyroidectomy (SPTX) are currently considered as standard surgical procedures in the treatment of sHPT. Recurrencerates after TPTX+AT or SPTX are between 10% and 12% (median follow up: 36 months).</p> <p>Recent retrospective studies demonstrated a lower rate of recurrent sHPT of 0–4% after PTX without autotransplantation and thymectomy (TPTX) with no higher morbidity when compared to the standard procedures. The observed superiority of TPTX is flawed due to different definitions of outcomes, varying follow up periods and different surgical treatment strategies (with and without thymectomy).</p> <p>Methods/Design</p> <p>Patients with sHPT (intact parathyroid hormone > 10 times above the upper limit of normal) on long term dialysis (>12 months) will be randomized either to TPTX or TPTX+AT and followed for 36 months. Outcome parameters are recurrence rates of sHPT, frequencies of reoperations due to refractory hypoparathyroidism or recurrent/persistent hyperparathyroidism, postoperative morbidity and mortality and quality of life. 50 patients per group will be randomized in order to obtain relevant frequencies of outcome parameters that will form the basis for a large scale confirmatory multicentred randomized controlled trial.</p> <p>Discussion</p> <p>sHPT is a disease with a high incidence in patients with chronic renal failure. Even a small difference in outcomes will be of clinical relevance. To assess sufficient data about the rate of recurrent sHPT after both methods, a multicentred, randomized controlled trial (MRCT) under standardized conditions is mandatory.</p> <p>Due to the existing uncertainties the calculated number of patients necessary in each treatment arm (n > 4000) makes it impossible to perform this study as a confirmatory trial. Therefore estimates of different outcomes are performed using a pilot MRCT comparing 50 versus 50 randomized patients in order to establish a hypothesis that can be tested thereafter.</p> <p>If TPTX proves to have a lower rate of recurrent sHPT, no relevant disadvantages and no higher morbidity than TPTX+AT, current surgical practice may be changed.</p> <p>Trial registration</p> <p>International Standard Randomized Controlled Trial Number Registration (ISRCTN86202793)</p

Antireflux Transoral Incisionless Fundoplication Using EsophyX: 12-Month Results of a Prospective Multicenter Study

BACKGROUND: A novel transoral incisionless fundoplication (TIF) procedure using the EsophyX system with SerosaFuse fasteners was designed to reconstruct a full-thickness valve at the gastroesophageal junction through tailored delivery of multiple fasteners during a single-device insertion. The safety and efficacy of TIF for treating gastroesophageal reflux disease (GERD) were evaluated in a prospective multicenter trial. METHODS: Patients (n = 86) with chronic GERD treated with proton pump inhibitors (PPIs) were enrolled. Exclusion criteria included an irreducible hiatal hernia > 2 cm. RESULTS: The TIF procedure (n = 84) reduced all hiatal hernias (n = 49) and constructed valves measuring 4 cm (2-6 cm) and 230 degrees (160 degrees -300 degrees ). Serious adverse events consisted of two esophageal perforations upon device insertion and one case of postoperative intraluminal bleeding. Other adverse events were mild and transient. At 12 months, aggregate (n = 79) and stratified Hill grade I tight (n = 21) results showed 73% and 86% of patients with >or=50% improvement in GERD health-related quality of life (HRQL) scores, 85% discontinuation of daily PPI use, and 81% complete cessation of PPIs; 37% and 48% normalization of esophageal acid exposure; 60% and 89% hiatal hernia reduction; and 62% and 80% esophagitis reduction, respectively. More than 50% of patients with Hill grade I tight valves had a normalized cardia circumference. Resting pressure of the lower esophageal sphincter (LES) was improved significantly (p < 0.001), by 53%. EsophyX-TIF cured GERD in 56% of patients based on their symptom reduction and PPI discontinuation. CONCLUSION: The 12-month results showed that EsophyX-TIF was safe and effective in improving quality of life and for reducing symptoms, PPI use, hiatal hernia, and esophagitis, as well as increasing the LES resting pressure and normalizing esophageal pH and cardia circumference in chronic GERD patients.Journal ArticleMulticenter StudyResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe