A chemical signature from fast-rotating low-metallicity massive stars: ROA 276 in ω Centauri

© 2017. The American Astronomical Society. All rights reserved. We present a chemical abundance analysis of a metal-poor star, ROA 276, in the stellar system ω Centauri. We confirm that this star has an unusually high [Sr/Ba] abundance ratio. Additionally, ROA 276 exhibits remarkably high abundance ratios, [X/Fe] , for all elements from Cu to Mo along with normal abundance ratios for the elements from Ba to Pb. The chemical abundance pattern of ROA 276, relative to a primordial ω Cen star ROA 46, is best fit by a fast-rotating low-metallicity massive stellar model of 20 , [Fe/H] = -1.8, and an initial rotation 0.4 times the critical value; no other nucleosynthetic source can match the neutron-capture element distribution. ROA 276 arguably offers the most definitive proof to date that fast-rotating massive stars contributed to the production of heavy elements in the early universe

Multi-Scale Simulation Modeling for Prevention and Public Health Management of Diabetes in Pregnancy and Sequelae

Diabetes in pregnancy (DIP) is an increasing public health priority in the Australian Capital Territory, particularly due to its impact on risk for developing Type 2 diabetes. While earlier diagnostic screening results in greater capacity for early detection and treatment, such benefits must be balanced with the greater demands this imposes on public health services. To address such planning challenges, a multi-scale hybrid simulation model of DIP was built to explore the interaction of risk factors and capture the dynamics underlying the development of DIP. The impact of interventions on health outcomes at the physiological, health service and population level is measured. Of particular central significance in the model is a compartmental model representing the underlying physiological regulation of glycemic status based on beta-cell dynamics and insulin resistance. The model also simulated the dynamics of continuous BMI evolution, glycemic status change during pregnancy and diabetes classification driven by the individual-level physiological model. We further modeled public health service pathways providing diagnosis and care for DIP to explore the optimization of resource use during service delivery. The model was extensively calibrated against empirical data.Comment: 10 pages, SBP-BRiMS 201

The s-process enrichment of the globular clusters M4 and M22

We investigate the enrichment in elements produced by the slow neutron-capture process (s-process) in the globular clusters M4 (NGC 6121) and M22 (NGC 6656). Stars in M4 have homogeneous abundances of Fe and neutron-capture elements, but the entire cluster is enhanced in s-process elements (Sr, Y, Ba, Pb) relative to other clusters with a similar metallicity. In M22, two stellar groups exhibit different abundances of Fe and s-process elements. By subtracting the mean abundances of s-poor from s-rich stars, we derive s-process residuals or empirical s-process distributions for M4 and M22. We find that the s-process distribution in M22 is more weighted toward the heavy s-peak (Ba, La, Ce) and Pb than M4, which has been enriched mostly with light s-peak elements (Sr, Y, Zr). We construct simple chemical evolution models using yields from massive star models that include rotation, which dramatically increases s-process production at low metallicity. We show that our massive star models with rotation rates of up to 50% of the critical (break-up) velocity and changes to the preferred 17O(α, γ)21Ne rate produce insufficient heavy s-elements and Pb to match the empirical distributions. For models that incorporate asymptotic giant branch yields, we find that intermediate-mass yields (with a 22Ne neutron source) alone do not reproduce the light-to-heavy s-element ratios for M4 and M22, and that a small contribution from models with a 13C pocket is required. With our assumption that 13C pockets form for initial masses below a transition range between 3.0 and 3.5 M ⊙, we match the light-to-heavy s-element ratio in the s-process residual of M22 and predict a minimum enrichment timescale of between 240 and 360 Myr. Our predicted value is consistent with the 300 Myr upper limit age difference between the two groups derived from isochrone fitting

Chiral Perturbation Theory in Few-Nucleon Systems

The low-energy effective theory of nuclear physics based on chiral symmetry is reviewed. Topics discussed include the nucleon-nucleon force, few-body potentials, isospin violation, pion-deuteron scattering, proton-neutron radiative capture, pion photoproduction on the deuteron, and pion production in proton-proton collisions.Comment: 15 pages, 2 figures, Latex, aipproc.sty and epsfig, invited talk at the 6th Conference on the Intersections of Particle and Nuclear Physics, Big Sky, May 199

Comparison of GFED3, QFED2 and FEER1 Biomass Burning Emissions Datasets in a Global Model

Biomass burning contributes about 40% of the global loading of carbonaceous aerosols, significantly affecting air quality and the climate system by modulating solar radiation and cloud properties. However, fire emissions are poorly constrained in models on global and regional levels. In this study, we investigate 3 global biomass burning emission datasets in NASA GEOS5, namely: (1) GFEDv3.1 (Global Fire Emissions Database version 3.1); (2) QFEDv2.4 (Quick Fire Emissions Dataset version 2.4); (3) FEERv1 (Fire Energetics and Emissions Research version 1.0). The simulated aerosol optical depth (AOD), absorption AOD (AAOD), angstrom exponent and surface concentrations of aerosol plumes dominated by fire emissions are evaluated and compared to MODIS, OMI, AERONET, and IMPROVE data over different regions. In general, the spatial patterns of biomass burning emissions from these inventories are similar, although the strength of the emissions can be noticeably different. The emissions estimates from QFED are generally larger than those of FEER, which are in turn larger than those of GFED. AOD simulated with all these 3 databases are lower than the corresponding observations in Southern Africa and South America, two of the major biomass burning regions in the world