222 research outputs found

    The merger that led to the formation of the Milky Way's inner stellar halo and thick disk

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    The assembly process of our Galaxy can be retrieved using the motions and chemistry of individual stars. Chemo-dynamical studies of the nearby halo have long hinted at the presence of multiple components such as streams, clumps, duality and correlations between the stars' chemical abundances and orbital parameters. More recently, the analysis of two large stellar surveys have revealed the presence of a well-populated chemical elemental abundance sequence, of two distinct sequences in the colour-magnitude diagram, and of a prominent slightly retrograde kinematic structure all in the nearby halo, which may trace an important accretion event experienced by the Galaxy. Here report an analysis of the kinematics, chemistry, age and spatial distribution of stars in a relatively large volume around the Sun that are mainly linked to two major Galactic components, the thick disk and the stellar halo. We demonstrate that the inner halo is dominated by debris from an object which at infall was slightly more massive than the Small Magellanic Cloud, and which we refer to as Gaia-Enceladus. The stars originating in Gaia-Enceladus cover nearly the full sky, their motions reveal the presence of streams and slightly retrograde and elongated trajectories. Hundreds of RR Lyrae stars and thirteen globular clusters following a consistent age-metallicity relation can be associated to Gaia-Enceladus on the basis of their orbits. With an estimated 4:1 mass-ratio, the merger with Gaia-Enceladus must have led to the dynamical heating of the precursor of the Galactic thick disk and therefore contributed to the formation of this component approximately 10 Gyr ago. These findings are in line with simulations of galaxy formation, which predict that the inner stellar halo should be dominated by debris from just a few massive progenitors.Comment: 19 pages, 8 figures. Published in Nature in the issue of Nov. 1st, 2018. This is the authors' version before final edit

    The Economic Value of Environmental Services on Indigenous-Held Lands in Australia

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    Australians could be willing to pay from 878mto878m to 2b per year for Indigenous people to provide environmental services. This is up to 50 times the amount currently invested by government. This result was derived from a nationwide survey that included a choice experiment in which 70% of the 927 respondents were willing to contribute to a conservation fund that directly pays Indigenous people to carry out conservation activities. Of these the highest values were found for benefits that are likely to improve biodiversity outcomes, carbon emission reductions and improved recreational values. Of the activities that could be undertaken to provide the services, feral animal control attracted the highest level of support followed by coastal surveillance, weed control and fire management. Respondents' decisions to pay were not greatly influenced by the additional social benefits that can arise for Indigenous people spending time on country and providing the services, although there was approval for reduced welfare payments that might arise

    Viral Decay Kinetics in the Highly Active Antiretroviral Therapy-Treated Rhesus Macaque Model of AIDS

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    To prevent progression to AIDS, persons infected with human immunodeficiency virus type 1 (HIV-1) must remain on highly active antiretroviral therapy (HAART) indefinitely since this modality does not eradicate the virus. The mechanisms involved in viral persistence during HAART are poorly understood, but an animal model of HAART could help elucidate these mechanisms and enable studies of HIV-1 eradication strategies. Due to the specificity of non-nucleoside reverse transcriptase (RT) inhibitors (NNRTIs) for HIV-1, we have used RT-SHIV, a chimeric virus of simian immunodeficiency virus with RT from HIV-1. This virus is susceptible to NNRTIs and causes an AIDS-like disease in rhesus macaques. In this study, two groups of HAART-treated, RT-SHIV-infected macaques were analyzed to determine viral decay kinetics. In the first group, viral loads were monitored with a standard TaqMan RT-PCR assay with a limit of detection of 50 viral RNA copies per mL. Upon initiation of HAART, viremia decayed in a bi-phasic manner with half-lives of 1.7 and 8.5 days, respectively. A third phase was observed with little further decay. In the second group, the macaques were followed longitudinally with a more sensitive assay utilizing ultracentrifugation to concentrate virus from plasma. Bi-phasic decay of viral RNA was also observed in these animals with half-lives of 1.8 and 5.8 days. Viral loads in these animals during a third phase ranged from 2–58 RNA copies/mL, with little decay over time. The viral decay kinetics observed in these macaques are similar to those reported for HIV-1 infected humans. These results demonstrate that low-level viremia persists in RT-SHIV-infected macaques despite a HAART regimen commonly used in humans

    Breakfast habits and differences regarding abdominal obesity in a cross-sectional study in Spanish adults: The ANIBES study

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    Background: Previous studies have indicated that breakfast has a protective effect against obesity. The aim of this study was to describe the breakfast habits of the Spanish adult population and to assess the possible association between breakfast frequency and the presence of abdominal obesity, in a cross-sectional analysis of the ANIBES Study. Methods: A representative sample of 1655 Spanish adults (aged 39±12 y; (mean±sd)) from the ANIBES Study was investigated. The final field work was carried out from mid-September to November (three months) 2013. Collected data included a dietary data collected by a 3-days food record, and health, socioeconomic, physical activity and anthropometric (weight, height and waist circumference) data. Abdominal obesity was defined as having a waist-to-height ratio ≄0.5. The adults were also classified into three groups based on the number of days they ate breakfast (never (0/3 days), sometimes (1-2/3 days) and always (3/3 days)). Logistic regression analyses were used to evaluate the association between breakfast and abdominal obesity. Results: In total, 3.6% of adults skipped breakfast and 14.1% ate breakfast sometimes. Having always breakfast was negatively associated with abdominal obesity [OR = 0.738 (0.558–0.975) p = 0.033]. The odds of abdominal obesity after full adjustment (age, gender, and educational and activity level) were 1.5 times higher for those who skipped breakfast when compared to those who always have breakfast. By correcting the model considered for other variables, the odds among smokers decreased when they have breakfast sometimes [OR = 0.032 (0.003–0.387) p = 0.007] and always [OR = 0.023 (0.002–0.270) p = 0.003] comparing with smokers who skip breakfast. Conclusion: Breakfast frequency could be negatively associated with abdominal obesity, especially among smokers.ANIBES Study was financially supported by Coca Cola Iberia through an agreement with the Spanish Nutrition Foundation (FEN)

    Characterization of Geographical and Meteorological Parameters

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    [EN]This chapter is devoted to the introduction of some geographical and meteorological information involved in the numerical modeling of wind fields and solar radiation. First, a brief description of the topographical data given by a Digital Elevation Model and Land Cover databases is provided. In particular, the Information System of Land Cover of Spain (SIOSE) is considered. The study is focused on the roughness length and the displacement height parameters that appear in the logarithmic wind profile, as well as in the albedo related to solar radiation computation. An extended literature review and characterization of both parameters are reported. Next, the concept of atmospheric stability is introduced from the Monin–Obukhov similarity theory to the recent revision of Zilitinkevich of the Neutral and Stable Boundary Layers (SBL). The latter considers the effect of the free-flow static stability and baroclinicity on the turbulent transport of momentum and of the Convective Boundary Layers (CBL), more precisely, the scalars in the boundary layer, as well as the model of turbulent entrainment
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