6,057 research outputs found

    The Optical Velocity of the Antlia Dwarf Galaxy

    Full text link
    We present the results of a VLT observing program carried out in service mode using FORS1 on ANTU in Long Slit mode to determine the optical velocities of nearby low surface brightness galaxies. Outlying Local Group galaxies are of paramount importance in placing constraints the dynamics and thus on both the age and the total mass of the Local Group. Optical velocities are also necessary to determine if the observations of HI gas in and around these systems are the result of gas associated with these galaxies or a chance superposition with high velocity HI clouds or the Magellanic Stream. The data were of sufficient signal-to-noise to obtain a reliable result in one of the galaxies we observed - Antlia - for which we have found an optical helio-centric radial velocity of 351 ±\pm 15 km/s.Comment: 11 pages, 4 figures, 5 tables MNRAS, in pres

    Sleep and inflammation in resilient aging.

    Get PDF
    Sleep quality is important to health, and increasingly viewed as critical in promoting successful, resilient aging. In this review, the interplay between sleep and mental and physical health is considered with a focus on the role of inflammation as a biological pathway that translates the effects of sleep on risk of depression, pain and chronic disease risk in aging. Given that sleep regulates inflammatory biologic mechanisms with effects on mental and physical health outcomes, the potential of interventions that target sleep to reduce inflammation and promote health in aging is also discussed

    Learning to Rank Using Localized Geometric Mean Metrics

    Full text link
    Many learning-to-rank (LtR) algorithms focus on query-independent model, in which query and document do not lie in the same feature space, and the rankers rely on the feature ensemble about query-document pair instead of the similarity between query instance and documents. However, existing algorithms do not consider local structures in query-document feature space, and are fragile to irrelevant noise features. In this paper, we propose a novel Riemannian metric learning algorithm to capture the local structures and develop a robust LtR algorithm. First, we design a concept called \textit{ideal candidate document} to introduce metric learning algorithm to query-independent model. Previous metric learning algorithms aiming to find an optimal metric space are only suitable for query-dependent model, in which query instance and documents belong to the same feature space and the similarity is directly computed from the metric space. Then we extend the new and extremely fast global Geometric Mean Metric Learning (GMML) algorithm to develop a localized GMML, namely L-GMML. Based on the combination of local learned metrics, we employ the popular Normalized Discounted Cumulative Gain~(NDCG) scorer and Weighted Approximate Rank Pairwise (WARP) loss to optimize the \textit{ideal candidate document} for each query candidate set. Finally, we can quickly evaluate all candidates via the similarity between the \textit{ideal candidate document} and other candidates. By leveraging the ability of metric learning algorithms to describe the complex structural information, our approach gives us a principled and efficient way to perform LtR tasks. The experiments on real-world datasets demonstrate that our proposed L-GMML algorithm outperforms the state-of-the-art metric learning to rank methods and the stylish query-independent LtR algorithms regarding accuracy and computational efficiency.Comment: To appear in SIGIR'1

    OVCS Newsletter April 2010

    Get PDF
    corecore