Optimal Integrated Abundances for Chemical Tagging of Extragalactic Globular Clusters

High resolution integrated light (IL) spectroscopy provides detailed abundances of distant globular clusters whose stars cannot be resolved. Abundance comparisons with other systems (e.g. for chemical tagging) require understanding the systematic offsets that can occur between clusters, such as those due to uncertainties in the underlying stellar population. This paper analyses high resolution IL spectra of the Galactic globular clusters 47 Tuc, M3, M13, NGC 7006, and M15 to (1) quantify potential systematic uncertainties in Fe, Ca, Ti, Ni, Ba, and Eu and (2) identify the most stable abundance ratios that will be useful in future analyses of unresolved targets. When stellar populations are well-modelled, uncertainties are ~0.1-0.2 dex based on sensitivities to the atmospheric parameters alone; in the worst case scenarios, uncertainties can rise to 0.2-0.4 dex. The [Ca I/Fe I] ratio is identified as the optimal integrated [alpha/Fe] indicator (with offsets <0.1 dex), while [Ni I/Fe I] is also extremely stable to within <0.1 dex. The [Ba II/Eu II] ratios are also stable when the underlying populations are well modelled and may also be useful for chemical tagging.Comment: 28 pages, 4 figures, accepted for publication in the Monthly Notices of the Royal Astronomical Societ

The abundance of boron in evolved A- and B-type stars

Boron abundances in A- and B-type stars may be a successful way to track evolutionary effects in these hot stars. The light elements -- Li, Be, and B -- are tracers of exposure to temperatures more moderate than those in which the H-burning CN-cycle operates. Thus, any exposure of surface stellar layers to deeper layers will affect these light element abundances. Li and Be are used in this role in investigations of evolutionary processes in cool stars, but are not observable in hotter stars. An investigation of boron, however, is possible through the B II 1362=C5 resonance line. We have gathered high resolution spectra from the IUE database of A- and B-type stars near 10~M_\odot for which nitrogen abundances have been determined (by Gies & Lambert, 1992, and Venn 1995). The B II 1362=C5 line is blended throughout the temperature range of this program, requiring spectrum syntheses to recover the boron abundances. For no star could we synthesize the 1362=C5 region using the meteoritic/solar boron abundance of log(B) =3D 2.88 (Anders & Grevesse 1989); a lower boron abundance was necessary which may reflect evolutionary effects (e.g., mass loss or mixing near the main-sequence), the natal composition of the star forming regions, or a systematic error in the analyses (e.g., non-LTE effects). Regardless of the initial boron abundance, and despite the possibility of non-LTE effects, it seems clear that boron is severely depleted in some stars. It may be that the nitrogen and boron abundances are anticorrelated, as would be expected from mixing between the H-burning and outer stellar layers. If, as we suspect, a residue of boron is present in the A-type supergiants, we may exclude a scenario in which mixing occurs continuously between the surface and the dee

Socio - demographic characteristics of HIV patients diagnosed at immunization centres in Calabar, South – south, Calabar, Nigeria

Introduction: The World Health Organization (WHO) estimated that 3.2 million children were living with Human Immunodeficiency Virus (HIV) at the end of 2013, mostly in sub- Saharan Africa. Socio- economic and demographic factors do not only affect viral transmission but also the success of preventive strategies and treatment.Objective: To determine the socio -demographic characteristics of mothers, and the relationship between maternal and HIV status of their infants attending immunization clinics in Calabar.Methods: Using multistage sampling method, 330 subjects were enrolled and screened from 63 immunization centres. The sociodemographic characteristic ofeach infant’s mother was documented. The results of Rapid test for mothers and Dried Blood Spots (DBS) results for infants were compared.Results: Of the 330 subjects recruited, 173 (52.4%) were males while 157(47.6%) were females. Mean age of the infants was 9.20 ± 3.1 weeks. Twenty four mothers and infants tested positive for HIV antibodies. After confirmatory tests using HIV Deoxyribosenucleic acid (DNA PCR), 14(58.3%) out of 24 antibody seropositive infants were infected. The transmission rate after confirmation was 58.3%.Conclusion: Parental education, social class and low maternal Antiretroviral drug (ARV) use were responsible for transmission. It is therefore recommended that health education on ARV use during antenatal period and HIV status of mother baby pair be done at immunization centres. HIV positive mothers and babies should be promptly referred for therapy.Keywords: Immunization, HIV, Infants, DNA PCR, PMTCT, AR

Investigation and modeling of direct toppling using a three-dimensional distinct element approach with incorporation of point cloud geometry

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this recordBlock toppling instability can be a common problem in natural rock masses, especially in mining environments where excavation activity may trigger discontinuity-controlled instability by modifying the natural slope geometry. Traditional investigations of block toppling failure consider classic kinematic analyses and simplified two-dimensional limit equilibrium methods. This approach is still the most commonly adopted, but the simple two-dimensional conceptual model may often oversimplify the instability mechanisms, ignoring potential critical factors specifically related to the three-dimensional geometry. This paper uses a three-dimensional distinct element method approach applied to an example case study, identifying the critical parameters that influence direct toppling instability in an open pit environment. Terrestrial laser scanning was used to obtain detailed three-dimensional geometrical information of the slope face geometry for subsequent stability analyses. A series of sensitivity analyses on critical parameters such as friction angle, discontinuity shear and normal stiffness, discontinuity spacing, and orientation was performed, using simple conceptual three-dimensional numerical modeling. Results of the analyses revealed the importance of undertaking three-dimensional analyses for direct toppling investigations that allow identification of critical parameters. A three-dimensional distinct element analysis was then performed using a more realistic complex volumetric mesh model of the case study slope which confirmed the previous modeling results but also identified unstable blocks in high slope angle areas, providing useful information for life of mine design. The paper highlights the importance of slope geometry and fracture network orientation on potential slope instability mechanisms.European CommissionEuropean Commissio