1,009 research outputs found
The Pristine survey II: a sample of bright stars observed with FEROS
Extremely metal-poor (EMP) stars are old objects formed in the first Gyr of
the Universe. They are rare and, to select them, the most successful strategy
has been to build on large and low-resolution spectroscopic surveys. The
combination of narrow- and broad band photometry provides a powerful and
cheaper alternative to select metal-poor stars. The on-going Pristine Survey is
adopting this strategy, conducting photometry with the CFHT MegaCam wide field
imager and a narrow-band filter centred at 395.2 nm on the CaII-H and -K lines.
In this paper we present the results of the spectroscopic follow-up conducted
on a sample of 26 stars at the bright end of the magnitude range of the Survey
(g<=15), using FEROS at the MPG/ESO 2.2 m telescope. From our chemical
investigation on the sample, we conclude that this magnitude range is too
bright to use the SDSS gri bands, which are typically saturated. Instead the
Pristine photometry can be usefully combined with the APASS gri photometry to
provide reliable metallicity estimates.Comment: AN accepte
Estimated Financial Performance of Exotic and Indigenous Tree Species in Smallholder Plantations in Leyte Province
This paper examines the need for estimates of financial performance of individual tree species for promoting smallholder forestry on Leyte Island in the Philippines, and presents some initial estimates of net present value and internal rate of return for smallholder plantings of indigenous and traditionally grown (exotic) tree species. Levels of profitability are found to be marginal for commercial production, particularly for native species. Data deficiencies are noted, and improved estimates of tree growth rates and rotation lengths in particular are needed to improve predictions of financial performance of smallholder forestry
Light elements in massive single and binary stars
We highlight the role of the light elements (Li, Be, B) in the evolution of
massive single and binary stars, which is largely restricted to a diagnostic
value, and foremost so for the element boron. However, we show that the boron
surface abundance in massive early type stars contains key information about
their foregoing evolution which is not obtainable otherwise. In particular, it
allows to constrain internal mixing processes and potential previous mass
transfer event for binary stars (even if the companion has disappeared). It may
also help solving the mystery of the slowly rotating nitrogen-rich massive main
sequence stars.Comment: 10 pages, 8 figures, to appear in proc. IAU-Symp. 268. C. Charbonnel
et al., eds
The i-process and CEMP-r/s stars
© Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. We investigate whether the anomalous elemental abundance patterns in some of the C-enhanced metal-poor-r/s (CEMP-r/s) stars are consistent with predictions of nucleosynthesis yields from the i-process, a neutron-capture regime at neutron densities intermediate between those typical for the slow (s) and rapid (r) processes. Conditions necessary for the i-process are expected to be met at multiple stellar sites, such as the He-core and He-shell flashes in low-metallicity low-mass stars, super-AGB and post-AGB stars, as well as low-metallicity massive stars. We have found that single-exposure one-zone simulations of the i-process reproduce the abundance patterns in some of the CEMP-r/s stars much better than the model that assumes a superposition of yields from s and r-process sources. Our previous study of nuclear data uncertainties relevant to the i-process revealed that they could have a significant impact on the i-process yields obtained in our idealized one-zone calculations, leading, for example, to ⌠0:7dex uncertainty in our predicted [Ba/La] ratio. Recent 3D hydrodynamic simulations of convection driven by a He-shell flash in post-AGB Sakurai's object have discovered a new mode of non-radial instabilities: the Global Oscillation of Shell H-ingestion. This has demonstrated that spherically symmetric stellar evolution simulations cannot be used to accurately model physical conditions for the i-process
The Spatial Homogeneity of Nebular and Stellar Oxygen Abundances in the Local Group Dwarf Irregular Galaxy NGC 6822
To test the existence of a possible radial gradient in oxygen abundances
within the Local Group dwarf irregular galaxy NGC 6822, we have obtained
optical spectra of 19 nebulae with the EFOSC2 spectrograph on the 3.6-m
telescope at ESO La Silla. The extent of the measured nebulae spans
galactocentric radii in the range between 0.05 kpc and 2 kpc (over four
exponential scale lengths). In five H II regions (Hubble I, Hubble V, Kalpha,
Kbeta, KD28e), the temperature-sensitive [O III] 4363 emission line was
detected, and direct oxygen abundances were derived. Oxygen abundances for the
remaining H II regions were derived using bright-line methods. The oxygen
abundances for three A-type supergiant stars are slightly higher than nebular
values at comparable radii. Linear least-square fits to various subsets of
abundance data were obtained. When all of the measured nebulae are included, no
clear signature is found for an abundance gradient. A fit to only newly
observed H II regions with [O III] 4363 detections yields an oxygen abundance
gradient of -0.14 +/- 0.07 dex/kpc. The gradient becomes slightly more
significant (-0.16 +/- 0.05 dex/kpc) when three additional H II regions with [O
III] 4363 measurements from the literature are added. Assuming no abundance
gradient, we derive a mean nebular oxygen abundance 12+log(O/H) = 8.11 +/- 0.10
from [O III] 4363 detections in the five H II regions from our present data;
this mean value corresponds to [O/H] = -0.55.Comment: Accepted, Ap.J.; 25 pages (AASTeX 5.2; emulateapj) with 14 figures.
Full paper with color figures may be retrieved from
http://www.astro.umn.edu/~hlee
Frequency and Types of Healthcare Encounters in the Week Preceding a Sepsis Hospitalization: A Systematic Review
OBJECTIVES: Early recognition and treatment are critical to improving sepsis outcomes. We sought to identify the frequency and types of encounters that patients have with the healthcare system in the week prior to a sepsis hospitalization.
DATA SOURCES: PubMed, Cumulative Index to Nursing and Allied Health Literature, Scopus, and the Cochrane Library.
STUDY SELECTION: Observational cohort studies of patients hospitalized with sepsis or septic shock that were assessed for an outpatient or emergency department encounter with the healthcare system in the week prior to hospital admission.
DATA EXTRACTION: The primary outcome was the proportion of patients with a healthcare encounter in the time period assessed (up to 1âweek) prior to a hospitalization with sepsis.
DATA SYNTHESIS: Six retrospective observational studies encompassing 6,785,728 sepsis admissions were included for evaluation, ranging from a 263-patient single-center cohort to a large database evaluating 6,731,827 sepsis admissions. The average (unweighted) proportion of patients having an encounter with the healthcare system in the week prior to a sepsis hospitalization was 32.7% and ranged from 10.3% to 52.9%. These encounters commonly involved presentation or potential symptoms of infectious diseases, antibiotic prescriptions, and appeared to increase in frequency closer to a sepsis hospitalization admission. No consistent factors were identified that distinguished a healthcare encounter as more or less likely to precede a sepsis hospitalization in the subsequent week.
CONCLUSIONS: Patients that present to the hospital with sepsis are frequently evaluated in the healthcare system in the week prior to admission. Further research is necessary to understand if these encounters offer earlier opportunities for intervention to prevent the transition from infection to sepsis, whether they merely reflect the comorbidities of sepsis patients with a high baseline rate of healthcare encounters, or the declining trajectory of a patient\u27s overall health in response to infection
Association of change in daily step count over five years with insulin sensitivity and adiposity: population based cohort study
addresses: Murdoch Children's Research Institute, Royal Children's Hospital, Parkville, Melbourne 3052, Australia. [email protected]: Journal Article; Research Support, Non-U.S. Gov'tCopyright © 2011 by the BMJ Publishing Group Ltd. This articles was first published in: BMJ, 2011, Vol. 342, pp. c7249 -To investigate the association between change in daily step count and both adiposity and insulin sensitivity and the extent to which the association between change in daily step count and insulin sensitivity may be mediated by adiposity
- âŠ