The Frequency of Carbon Stars Among Extremely Metal-Poor Stars

We demonstrate that there are systematic scale errors in the [Fe/H] values determined by the Hamburg/ESO Survey (and by inference by the HK Survey in the past) for certain extremely metal poor highly C-enhanced giants. The consequences of these scale errors are that a) the fraction of carbon stars at extremely low metallicities has been overestimated in several papers in the recent literature b) the number of extremely metal poor stars known is somewhat lower than has been quoted in the recent literature c) the yield for extremely metal poor stars by the HES Survey is somewhat lower than is stated in the recent literature. A preliminary estimate for the frequency of Carbon stars among the giants in the HES sample with -4 < [Fe/H] < -2.0 dex is 7.4 +-2.9%; adding an estimate for the C-enhanced giants with [C/Fe] > 1.0 dex without detectable C2 bands raises the fraction to 14 +-4$%. We rely on the results of an extensive set of homogeneous detailed abundance analyses of stars expected to have [Fe/H] < -3.0 dex selected from the HES to establish these claims. We have found that the Fe-metallicity of the cooler (Teff < 5200K) C-stars as derived from spectra taken with HIRES at Keck are a factor of ~10 higher than those obtained via the algorithm used by the HES project to analyze the moderate resolution follow-up spectra, which is identical to that used until very recently by the HK Survey. This error in Fe-abundance estimate for C-stars arises from a lowering of the emitted flux in the continuum bandpasses of the KP (3933 A line of CaII) and particularly the HP2 (Hdelta) indices used to estimate [Fe/H] due to absorption from strong molecular bands.Comment: Accepted to the ApJL after a very lengthly duel with the 3 simultaneous referee

The Frequency of Carbon Rich Stars Among Extremely Metal Poor Stars

We demonstrate that there are systematic scale errors in the [Fe/H] values determined by the Hamburg/ESO Survey (and by the HK Survey by inference) for certain extremely metal poor (EMP) highly C-enhanced giants. The consequences of these scale errors are that a) the fraction of carbon stars at extremely low metallicities has been substantially overestimated in several papers in the recent literature b) the number of EMP stars known is somewhat lower than has been quoted in the recent literature c) the yield for EMP stars by the HK and the HES Survey is somewhat lower than is stated in the recent literature. A preliminary estimate for the frequency of Carbon stars among the giants in the HES sample with -4 < [Fe/H] < -2.0 dex is 7.4 \pm 2.9%, and for C-rich giants with [C/Fe] > +1.0 dex is 14.4 \pm 4%. Here we present the key results of detailed abundance analyses of 14 C-stars selected from the HES as candidate EMP stars, of ~50 such stars analyzed. About 80% of such C-stars show highly enhanced Ba as well, with C enhanced by a factor of about 100, and [Ba/C] roughly Solar. These stars often show prominent lead lines, The remaining 20% of the C-stars do not show an enhancemement of the s-process neutron capture elements around the Ba peak. They tend to be the most metal-poor stars studied. We suggest that all these EMP C-stars are the remnants of the secondary in a mass transfer binary system where the former primary was an AGB star, which transferred substantial mass at that evolutionary stage. (published abstract will be shorter due to space limitations)Comment: Submitted to the proceedings of the IAU Symposium 228, From Lithium to Uranium: Elemental Tracers of Early Cosmic Evolution (Paris, 23--27 May 2005), Cambridge University Press, ed: Vanessa Hill, Patrick Francois & Francesca Prima

A high resolution record of Greenland mass balance

We map recent Greenland Ice Sheet elevation change at high spatial (5-km) and temporal (monthly) resolution using CryoSat-2 altimetry. After correcting for the impact of changing snowpack properties associated with unprecedented surface melting in 2012, we find good agreement (3 cm/yr bias) with airborne measurements. With the aid of regional climate and firn modelling, we compute high spatial and temporal resolution records of Greenland mass evolution, which correlate (R=0.96) with monthly satellite gravimetry, and reveal glacier dynamic imbalance. During 2011-2014, Greenland mass loss averaged 269±51 Gt/yr. Atmospherically-driven losses were widespread, with surface melt variability driving large fluctuations in the annual mass deficit. Terminus regions of five dynamically-thinning glaciers, which constitute less than 1% of Greenland's area, contributed more than 12% of the net ice loss. This high-resolution record demonstrates that mass deficits extending over small spatial and temporal scales have made a relatively large contribution to recent ice sheet imbalance

Factors Associated with Revision Surgery after Internal Fixation of Hip Fractures

Background: Femoral neck fractures are associated with high rates of revision surgery after management with internal fixation. Using data from the Fixation using Alternative Implants for the Treatment of Hip fractures (FAITH) trial evaluating methods of internal fixation in patients with femoral neck fractures, we investigated associations between baseline and surgical factors and the need for revision surgery to promote healing, relieve pain, treat infection or improve function over 24 months postsurgery. Additionally, we investigated factors associated with (1) hardware removal and (2) implant exchange from cancellous screws (CS) or sliding hip screw (SHS) to total hip arthroplasty, hemiarthroplasty, or another internal fixation device. Methods: We identified 15 potential factors a priori that may be associated with revision surgery, 7 with hardware removal, and 14 with implant exchange. We used multivariable Cox proportional hazards analyses in our investigation. Results: Factors associated with increased risk of revision surgery included: female sex, [hazard ratio (HR) 1.79, 95% confidence interval (CI) 1.25-2.50; P = 0.001], higher body mass index (fo

Substrate Utilization and Competitive Interactions Among Soil Bacteria Vary With Life-History Strategies.

Microorganisms have evolved various life-history strategies to survive fluctuating resource conditions in soils. However, it remains elusive how the life-history strategies of microorganisms influence their processing of organic carbon, which may affect microbial interactions and carbon cycling in soils. Here, we characterized the genomic traits, exometabolite profiles, and interactions of soil bacteria representing copiotrophic and oligotrophic strategists. Isolates were selected based on differences in ribosomal RNA operon (rrn) copy number, as a proxy for life-history strategies, with pairs of "high" and "low" rrn copy number isolates represented within the Micrococcales, Corynebacteriales, and Bacillales. We found that high rrn isolates consumed a greater diversity and amount of substrates than low rrn isolates in a defined growth medium containing common soil metabolites. We estimated overlap in substrate utilization profiles to predict the potential for resource competition and found that high rrn isolates tended to have a greater potential for competitive interactions. The predicted interactions positively correlated with the measured interactions that were dominated by negative interactions as determined through sequential growth experiments. This suggests that resource competition was a major force governing interactions among isolates, while cross-feeding of metabolic secretion likely contributed to the relatively rare positive interactions observed. By connecting bacterial life-history strategies, genomic features, and metabolism, our study advances the understanding of the links between bacterial community composition and the transformation of carbon in soils