224 research outputs found
The Hamburg/ESO R-process Enhanced Star survey (HERES) II. Spectroscopic analysis of the survey sample
We present the results of analysis of ``snapshot'' spectra of 253 metal-poor
halo stars -3.8 < [Fe/H] < -1.5 obtained in the HERES survey. The spectra are
analysed using an automated line profile analysis method based on the
Spectroscopy Made Easy codes of Valenti & Piskunov. Elemental abundances of
moderate precision have been obtained for 22 elements, C, Mg, Al, Ca, Sc, Ti,
V, Cr, Mn, Fe, Co, Ni, Zn, Sr, Y, Zr, Ba, La, Ce, Nd, Sm, and Eu, where
detectable. Among the sample of 253 stars, we find 8 r-II stars and 35 r-I
stars. We also find three stars with strong enhancements of Eu which are
s-process rich. A significant number of new very metal-poor stars are
confirmed: 49 stars with [Fe/H] < -3 and 181 stars with -3 < [Fe/H] < -2. We
find one star with [Fe/H] < -3.5. We find the scatter in the abundance ratios
of Mg, Ca, Sc, Ti, Cr, Fe, Co, and Ni, with respect to Fe and Mg, to be similar
to the estimated relative errors and thus the cosmic scatter to be small,
perhaps even non-existent. The elements C, Sr, Y, Ba and Eu, and perhaps Zr,
show scatter at [Fe/H] < -2.5 significantly larger than can be explained from
the errors in the analysis, implying scatter which is cosmic in origin.
Significant scatter is observed in abundance ratios between light and heavy
neutron-capture elements at low metallicity and low levels of r-process
enrichment. (*** abridged ***)Comment: Accepted for A&A; 31 pages, 2 electronic tables presently available
at http://www.astro.uu.se/~barklem/papers/heres_tables.tar.gz ; Minor
corrections adde
The Frequency of Carbon-Enhanced Metal-Poor Stars in the Galaxy from the HERES sample
We estimate the frequency of Carbon-Enhanced Metal-Poor (CEMP) stars among very metal-poor stars, based on an analysis of 349 stars with available high-resolution spectra observed as part of the Hamburg/ESO R-process Enhanced Star (HERES) survey. We obtain that {\it a lower limit of} 21 2% of stars with [Fe/H] exhibit [C/Fe] . These fractions are higher than have been reported by recent examinations of this question, based on substantially smaller samples of stars. We discuss the source of this difference and suggest that in order to take into account effects that result in a decrease of surface carbon abundance with advancing evolution, a definition of CEMP stars based on a [C/Fe] cutoff that varies as a function of luminosity is more appropriate. We discuss the likely occurrence of dilution and mixing for many CEMP stars, which, if properly accounted for, would increase this fraction still further
Multilevel Interventions To Address Health Disparities Show Promise In Improving Population Health
Multilevel interventions are those that affect at least two levels of influenceâfor example, the patient and the health care provider. They can be experimental designs or natural experiments caused by changes in policy, such as the implementation of the Affordable Care Act or local policies. Measuring the effects of multilevel interventions is challenging, because they allow for interaction among levels, and the impact of each intervention must be assessed and translated into practice. We discuss how two projects from the National Institutes of Healthâs Centers for Population Health and Health Disparities used multilevel interventions to reduce health disparities. The interventions, which focused on the uptake of the human papillomavirus vaccine and community-level dietary change, had mixed results. The design and implementation of multilevel interventions are facilitated by input from the community, and more advanced methods and measures are needed to evaluate the impact of the various levels and components of such interventions
Near-Infrared Spectroscopy of Carbon-Enhanced Metal-Poor Stars. I. A SOAR/OSIRIS Pilot Study
We report on an abundance analysis for a pilot study of seven Carbon-Enhanced
Metal-Poor (CEMP) stars, based on medium-resolution optical and near-infrared
spectroscopy. The optical spectra are used to estimate [Fe/H], [C/Fe], [N/Fe],
and [Ba/Fe] for our program stars. The near-infrared spectra, obtained during a
limited early science run with the new SOAR 4.1m telescope and the Ohio State
Infrared Imager and Spectrograph (OSIRIS), are used to obtain estimates of
[O/Fe] and 12C/13C. The chemical abundances of CEMP stars are of importance for
understanding the origin of CNO in the early Galaxy, as well as for placing
constraints on the operation of the astrophysical s-process in very
low-metallicity Asymptotic Giant Branch (AGB) stars.
This pilot study includes a few stars with previously measured [Fe/H],
[C/Fe], [N/Fe],[O/Fe], 12C/13C, and [Ba/Fe], based on high-resolution optical
spectra obtained with large-aperture telescopes. Our analysis demonstrates that
we are able to achieve reasonably accurate determinations of these quantities
for CEMP stars from moderate-resolution optical and near-infrared spectra. This
opens the pathway for the study of significantly larger samples of CEMP stars
in the near future. Furthermore, the ability to measure [Ba/Fe] for (at least
the cooler) CEMP stars should enable one to separate stars that are likely to
be associated with s-process enhancements (the CEMP-s stars) from those that do
not exhibit neutron-capture enhancements (the CEMP-no stars).Comment: 27 pages, including 5 tables, 6 figures, accepted for publication in
The Astronomical Journa
Carbon-Enhanced Metal-Poor Stars in the Early Galaxy
Very metal-deficient stars that exhibit enhancements of their carbon
abundances are of crucial importance for understanding a number of issues --
the nature of stellar evolution among the first generations of stars, the shape
of the Initial Mass Function, and the relationship between carbon enhancement
and neutron-capture processes, in particular the astrophysical s-process. One
recent discovery from objective-prism surveys dedicated to the discovery of
metal-deficient stars is that the frequency of Carbon-Enhanced Metal-Poor
(CEMP) stars increases with declining metallicity, reaching roughly 25% for
[Fe/H] < -2.5. In order to explore this phenomenon in greater detail we have
obtained medium-resolution (2 A) spectroscopy for about 350 of the 413 objects
in the Christlieb et al. catalog of carbon-rich stars, selected from the
Hamburg/ESO objective prism survey on the basis of their carbon-enhancement,
rather than metal deficiency. Based on these spectra, and near-IR JHK
photometry from the 2MASS Point Source Catalog, we obtain estimates of [Fe/H]
and [C/Fe] for most of the stars in this sample, along with reasonably accurate
determinations of their radial velocities. Of particular importance, we find
that the upper envelope of carbon enhancement observed for these stars is
nearly constant, at [C/H] ~ -1.0, over the metallicity range -4.0 < [Fe/H] <
-2.0; this same level of [C/H] applies to the most iron-deficent star yet
discovered, HE 0107-5240, at [Fe/H] = -5.3.Comment: Contributed paper to The Eigth Nuclei in the Cosmos conference, to
appear (in refereed form) in Nuclear Physics
Interactive effects between payleanâą (Ractopamine HCl) and dietary lysine on finishing pig growth performance, carcass characteristics and tissue accretion
A total of 432 pigs were used to evaluate
the effects of Paylean and dietary lysine on
finishing pig growth performance, carcass
characteristics and tissue accretion. The 12
dietary treatments included Paylean (0, 4.5,
and 9.0 g/ton) and 4 levels of lysine. For
pigs fed no Paylean, lysine levels were 0.60,
0.80, 1.00, and 1.20%. For pigs fed 4.5 or
9.0 g/ton of Paylean, lysine levels were 0.80, 1.00, 1.20, and 1.40%. The results indicate that pigs fed Paylean need at least 1.0% dietary lysine to optimize growth, carcass parameters, and tissue accretion
Validity and usefulness of members reports of implementation progress in a quality improvement initiative: findings from the Team Check-up Tool (TCT)
<p>Abstract</p> <p>Background</p> <p>Team-based interventions are effective for improving safety and quality of healthcare. However, contextual factors, such as team functioning, leadership, and organizational support, can vary significantly across teams and affect the level of implementation success. Yet, the science for measuring context is immature. The goal of this study is to validate measures from a short instrument tailored to track dynamic context and progress for a team-based quality improvement (QI) intervention.</p> <p>Methods</p> <p>Design: Secondary cross-sectional and longitudinal analysis of data from a clustered randomized controlled trial (RCT) of a team-based quality improvement intervention to reduce central line-associated bloodstream infection (CLABSI) rates in intensive care units (ICUs).</p> <p>Setting: Forty-six ICUs located within 35 faith-based, not-for-profit community hospitals across 12 states in the U.S.</p> <p>Population: Team members participating in an ICU-based QI intervention.</p> <p>Measures: The primary measure is the Team Check-up Tool (TCT), an original instrument that assesses context and progress of a team-based QI intervention. The TCT is administered monthly. Validation measures include CLABSI rate, Team Functioning Survey (TFS) and Practice Environment Scale (PES) from the Nursing Work Index.</p> <p>Analysis: Temporal stability, responsiveness and validity of the TCT.</p> <p>Results</p> <p>We found evidence supporting the temporal stability, construct validity, and responsiveness of TCT measures of intervention activities, perceived group-level behaviors, and barriers to team progress.</p> <p>Conclusions</p> <p>The TCT demonstrates good measurement reliability, validity, and responsiveness. By having more validated measures on implementation context, researchers can more readily conduct rigorous studies to identify contextual variables linked to key intervention and patient outcomes and strengthen the evidence base on successful spread of efficacious team-based interventions. QI teams participating in an intervention should also find data from a validated tool useful for identifying opportunities to improve their own implementation.</p
Neutral tritium gas reduction in the KATRIN differential pumping sections
The KArlsruhe TRItium Neutrino experiment (KATRIN) aims to measure the
effective electron anti-neutrino mass with an unprecedented sensitivity of
, using -electrons from tritium decay.
The electrons are guided magnetically by a system of superconducting magnets
through a vacuum beamline from the windowless gaseous tritium source through
differential and cryogenic pumping sections to a high resolution spectrometer
and a segmented silicon pin detector. At the same time tritium gas has to be
prevented from entering the spectrometer. Therefore, the pumping sections have
to reduce the tritium flow by more than 14 orders of magnitude. This paper
describes the measurement of the reduction factor of the differential pumping
section performed with high purity tritium gas during the first measurement
campaigns of the KATRIN experiment. The reduction factor results are compared
with previously performed simulations, as well as the stringent requirements of
the KATRIN experiment.Comment: 19 pages, 4 figures, submitted to Vacuu
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