172 research outputs found

    The QUEST RR Lyrae Survey II: The Halo Overdensities in the First Catalog

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    The first catalog of the RR Lyrae stars (RRLS) in the Galactic halo by the QUEST Survey has been searched for significant overdensities that may be debris from disrupted dwarf galaxies or globular clusters. Away from the major overdensities, the distribution of these stars is adequately fit by a smooth halo model, in which the flattening of the halo decreases with increasing galactocentric distance (Preston et al 1991). This model was used to estimate the ``background'' of RRLS on which the halo overdensities are overlaid. A procedure was developed for recognizing groups of stars that constitute significant overdensities with respect to this background. To test this procedure, a Monte Carlo routine was used to make artificial RRLS surveys that follow the smooth halo model, but with Poisson distributed noise in the numbers of RRLS and, within limits, random variations in the positions and magnitudes of the artificial stars. The artificial surveys created by this routine were examined for significant groups in exactly the same way as the QUEST survey. These calculations provided estimates of the frequencies with which random fluctuations produce significant groups. In the QUEST survey, there are six significant overdensities that contain six or more stars and several smaller ones. The small ones and possibly one or two of the larger ones may be artifacts of statistical fluctuations, and they need to be confirmed by measurements of radial velocity and/or proper motion. The most prominent groups are the northern stream from the Sagittarius dwarf spheroidal galaxy and a large group in Virgo. Two other groups lie in the direction of the Monoceros stream and at approximately the right distance for membership. Another group is related to the globular cluster Palomar 5.Comment: Accepted for publication in the Astronomical Journa

    Of monkeys and men:Impatience in perceptual decision-making

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    For decades sequential sampling models have successfully accounted for human and monkey decision-making, relying on the standard assumption that decision makers maintain a pre-set decision standard throughout the decision process. Based on the theoretical argument of reward rate maximization, some authors have recently suggested that decision makers become increasingly impatient as time passes and therefore lower their decision standard. Indeed, a number of studies show that computational models with an impatience component provide a good fit to human and monkey decision behavior. However, many of these studies lack quantitative model comparisons and systematic manipulations of rewards. Moreover, the often-cited evidence from single-cell recordings is not unequivocal and complimentary data from human subjects is largely missing. We conclude that, despite some enthusiastic calls for the abandonment of the standard model, the idea of an impatience component has yet to be fully established; we suggest a number of recently developed tools that will help bring the debate to a conclusive settlement

    Charting the course for a Blue Economy in Peru: A Research Agenda

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    Ocean- and coastal-based economic activities are increasingly recognised as key drivers for supporting global economies. This move towards the “blue economy” is becoming globally widespread, with the recognition that if ocean-based activities are to be sustainable, they will need to move beyond solely extractive and exploitative endeavours, aligning more closely with marine conservation and effective marine spatial planning. In this paper we define the “blue economy” as a “platform for strategic, integrated and participatory coastal and ocean development and protection that incorporates a low carbon economy, the ecosystem approach and human well-being through advancing regional industries, services and activities”. In Peru, while the seas contribute greatly to the national economy, the full potential of the blue economy has yet to be realised. This paper presents the findings of an early career scientist workshop in Lima, Peru, in March 2016. The workshop “Advancing Green Growth in Peru” brought together researchers to identify challenges and opportunities for green growth across three Peruvian economic sectors—tourism, transport and the blue economy with this paper exploring in detail the priorities generated from the “blue economy” stream. These priorities include themes such as marine spatial planning, detailed evaluations of existing maritime industries (e.g. guano collection and fisheries), development of an effective MPA network, support for sustainable coastal tourism, and better inclusion of social science disciplines in understanding societal and political support for a Peruvian blue economy. In addition, the paper discusses the research requirements associated with these priorities. While not a comprehensive list, these priorities provide a starting point for future dialogue on a co-ordinated scientific platform supporting the blue growth agenda in Peru, and in other regions working towards a successful “blue economy”

    Discovery and Development of Toll-Like Receptor 4 (TLR4) Antagonists: A New Paradigm for Treating Sepsis and Other Diseases

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    Abstract. Sepsis remains the most common cause of death in intensive care units in the USA, with a current estimate of at least 750,000 cases per year, and 215,000 deaths annually. Despite extensive research still we do not quite understand the cellular and molecular mechanisms that are involved in triggering and propagation of septic injury. Endotoxin (lipopolysaccharide from Gram-negative bacteria, or LPS) has been implicated as a major cause of this syndrome. Inflammatory shock as a consequence of LPS release remains a serious clinical concern. In humans, inflammatory responses to LPS result in the release of cytokines and other cell mediators from monocytes and macrophages, which can cause fever, shock, organ failure and death. A number of different approaches have been investigated to try to treat and/or prevent the septic shock associated with infections caused by Gram-negative bacteria, including blockage of one or more of the cytokines induced by LPS. Recently several novel amphipathic compounds have been developed as direct LPS antagonists at the LPS receptor, TLR4. This review article will outline the current knowledge on the TLR4-LPS synthesis and discuss the signaling, in vitro pre-clinical and in vivo clinical evaluation of TLR4 antagonists and their potential use in sepsis and a variety of diseases such as atherosclerosis as well as hepatic and renal malfunction. KEY WORDS: drug discovery; LPS; sepsis; toll-like receptor antagonists

    Specific antenatal interventions for Black, Asian and Minority Ethnic (BAME) pregnant women at high risk of poor birth outcomes in the United Kingdom: a scoping review

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    Background: Disparity exists in maternal and infant birth outcomes of Black and Minority Ethnic (BAME) women giving birth in the United Kingdom (UK) compared to the majority. There is therefore a need to reconsider existing maternity service provision to ensure culturally competent services. The purpose of this scoping review was to ascertain what specific maternity interventions have been implemented in the UK for BAME women (2004–2014) so that increased awareness of the need and scope of specific maternity interventions for BAME women can be identified. Methods: A scoping review was conducted in order to determine the evidence base. It was determined that no prior systematic reviews had been conducted and it was apparent that literature in this field was sparse. Scoping review is an ideal method when literature is likely to be heterogeneous and the research field relatively unexplored. A keyword strategy was used implementing population (P), intervention (I), comparison (C) and outcomes (O). Results: An initial 2188 papers were identified. Following screening and review, only 5 heterogeneous papers remained suitable and were included. The included interventions employed sample sizes of N = 160-1441, examined a range of different outcome measures and were delivered across different parts of the UK with high numbers of BAME residents. Conclusions: There is a lack of rigorous research interventions and practice interventions which are currently documented, of specific maternity interventions which are aimed to address culturally competent maternity services and the sharing of best practice addressing the increased risks of BAME women delivering in the UK

    New H-mode regimes with small ELMs and high thermal confinement in the Joint European Torus

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    New H-mode regimes with high confinement, low core impurity accumulation, and small edge-localized mode perturbations have been obtained in magnetically confined plasmas at the Joint European Torus tokamak. Such regimes are achieved by means of optimized particle fueling conditions at high input power, current, and magnetic field, which lead to a self-organized state with a strong increase in rotation and ion temperature and a decrease in the edge density. An interplay between core and edge plasma regions leads to reduced turbulence levels and outward impurity convection. These results pave the way to an attractive alternative to the standard plasmas considered for fusion energy generation in a tokamak with a metallic wall environment such as the ones expected in ITER.& nbsp;Published under an exclusive license by AIP Publishing
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