2,823 research outputs found

    The Detailed Chemical Abundance Patterns of M31 Globular Clusters

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    We present detailed chemical abundances for >>20 elements in \sim30 globular clusters in M31. These results have been obtained using high resolution (λ/Δλ\lambda/\Delta\lambda\sim24,000) spectra of their integrated light and analyzed using our original method. The globular clusters have galactocentric radii between 2.5 kpc and 117 kpc, and therefore provide abundance patterns for different phases of galaxy formation recorded in the inner and outer halo of M31. We find that the clusters in our survey have a range in metallicity of 2.2<-2.2<[Fe/H]<0.11<-0.11. The inner halo clusters cover this full range, while the outer halo globular clusters at R>>20 kpc have a small range in abundance of [Fe/H]=1.6±0.10=-1.6 \pm 0.10. We also measure abundances of alpha, r- and s-process elements. These results constitute the first abundance pattern constraints for old populations in M31 that are comparable to those known for the Milky Way halo.Comment: XII International Symposium on Nuclei in the Cosmos August 5-12, 2012 Cairns, Australia. To appear in Proceedings of Scienc

    Globular Cluster Abundances from High-Resolution, Integrated-Light Spectroscopy. II. Expanding the Metallicity Range for Old Clusters and Updated Analysis Techniques

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    We present abundances of globular clusters in the Milky Way and Fornax from integrated light spectra. Our goal is to evaluate the consistency of the integrated light analysis relative to standard abundance analysis for individual stars in those same clusters. This sample includes an updated analysis of 7 clusters from our previous publications and results for 5 new clusters that expand the metallicity range over which our technique has been tested. We find that the [Fe/H] measured from integrated light spectra agrees to \sim0.1 dex for globular clusters with metallicities as high as [Fe/H]=0.3-0.3, but the abundances measured for more metal rich clusters may be underestimated. In addition we systematically evaluate the accuracy of abundance ratios, [X/Fe], for Na I, Mg I, Al I, Si I, Ca I, Ti I, Ti II, Sc II, V I, Cr I, Mn I, Co I, Ni I, Cu I, Y II, Zr I, Ba II, La II, Nd II, and Eu II. The elements for which the integrated light analysis gives results that are most similar to analysis of individual stellar spectra are Fe I, Ca I, Si I, Ni I, and Ba II. The elements that show the greatest differences include Mg I and Zr I. Some elements show good agreement only over a limited range in metallicity. More stellar abundance data in these clusters would enable more complete evaluation of the integrated light results for other important elements.Comment: Accepted for publication in ApJ, 37 pages, 13 tables, 29 figure

    Influence of the façades convective heat transfer coefficients on the thermal energy demand for an urban street canyon building

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    In an urban micro-climate environment, the convective heat transfer coefficient (CHTC) on the façades influences simulated building's energy demand and exterior wall surfaces temperatures. In this paper, it is analyzed how the CHTC values on the façades of a building located in an urban canyon influence the façades temperatures and how important is the choice of an accurate CHTC correlation on the space cooling and heating energy demand. CHTC correlations found in literature are based on some specific micro-climate parameters such as local wind speed, district construction density, temperature differences between façades and canyon air and wind direction. An accurate choice of the right correlation for the simulated urban environment is important to better represent the exterior walls heat removal due to outside wind climate. The effects of the use of different CHTC correlations have been evaluated by means of TRNSYS 17.0 simulation program. The study is performed for a building sited an urban street canyon with the aspect ratio H/W=1 and located in a Mediterranean climate, in Rome. The comparison performed between the results of the numerical simulations shows that some correlations lead to an underestimation of the space heating demand around 9.7% and to an overestimation of the space cooling demand around 17.5%

    A bayesian meta-analysis of multiple treatment comparisons of systemic regimens for advanced pancreatic cancer

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    © 2014 Chan et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Background: For advanced pancreatic cancer, many regimens have been compared with gemcitabine (G) as the standard arm in randomized controlled trials. Few regimens have been directly compared with each other in randomized controlled trials and the relative efficacy and safety among them remains unclear

    R-mode oscillations and rocket effect in rotating superfluid neutron stars. I. Formalism

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    We derive the hydrodynamical equations of r-mode oscillations in neutron stars in presence of a novel damping mechanism related to particle number changing processes. The change in the number densities of the various species leads to new dissipative terms in the equations which are responsible of the {\it rocket effect}. We employ a two-fluid model, with one fluid consisting of the charged components, while the second fluid consists of superfluid neutrons. We consider two different kind of r-mode oscillations, one associated with comoving displacements, and the second one associated with countermoving, out of phase, displacements.Comment: 10 page

    Patterns of genomic instability in gastric cancer: clinical implications and perspectives.

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    In gastric cancer (GC) the loss of genomic stability represents a key molecular step that occurs early in the carcinogenesis process and creates a permissive environment for the accumulation of genetic and epigenetic alterations in tumor suppressor genes and oncogenes. It is widely accepted that GC can follow at least two major genomic instability pathways, microsatellite instability (MSI) and chromosome instability (CIN). MSI is responsible for a well-defined subset of GCs. CIN represents a more common pathway comprising heterogeneous subsets of GC. In addition to MSI and CIN, the CpG islands methylator phenotype (CIMP) plays an important role in gastric carcinogenesis. CIMP may lead to the transcriptional silencing of various genes in gastric carcinogenesis. Intriguingly, more recently in addition to CpG island hypermethylation, a global DNA demethylation, that precedes genomic damage, has been observed in GC. Thus, epigenetic alterations may play a relevant role in gastric carcinogenesis as alternative mechanisms. Evidence suggests that although MSI, CIN and CIMP phenotypes can be distinguished from one another, there might be some degree of overlap. This review describes our current knowledge of the instability pathways in gastric carcinogenesis and the potential clinical applications for different forms of genomic instability in GC
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