420 research outputs found

    Propagating functional dependencies with conditions

    Get PDF
    The dependency propagation problem is to determine, given a view defined on data sources and a set of dependencies on the sources, whether another dependency is guaranteed to hold on the view. This paper investigates dependency propagation for recently proposed conditional functional dependencies (CFDs). The need for this study is evident in data integration, exchange and cleaning since dependencies on data sources often only hold conditionally on the view. We investigate dependency propagation for views defined in various fragments of relational algebra, CFDs as view dependencies, and for source dependencies given as either CFDs or traditional functional dependencies (FDs). (a) We establish lower and upper bounds, all matching , ranging from PTIME to undecidable. These not only provide the first results for CFD propagation, but also extend the classical work of FD propagation by giving new complexity bounds in the presence of finite domains. (b) We provide the first algorithm for computing a minimal cover of all CFDs propagated via SPC views; the algorithm has the same complexity as one of the most efficient algorithms for computing a cover of FDs propagated via a projection view, despite the increased expressive power of CFDs and SPC views. (c) We experimentally verify that the algorithm is efficient. </jats:p

    Study on the Conceptual Model of E-Government standards Adoption Based on Institutional Theory

    Get PDF
    The purpose of this study is to investigate the forces that promote national e-government standards adoption and diffusion by government agencies. By using institutional theory as a theoretical basis, a conceptual model is set up and the hypotheses are proposed. Three forces of improving national e-government standards adoption are discussed. They are coercive forces, mimetic forces and normative forces. The survey questionnaire has been developed which will be used to test the theoretical model. All the data will be expectedly collected by the end of May, 2013 and then the structural equation model will be analyzed with PLS. From a theoretical perspective, the research model may be informative for researchers investigating the adoption of other technological standards. From the practical perspective, the research results may give some advice to government officials to promote the diffusion national e-government standards

    Quantum Hydrodynamic Model by Moment Closure of Wigner Equation

    Full text link
    In this paper, we derive the quantum hydrodynamics models based on the moment closure of the Wigner equation. The moment expansion adopted is of the Grad type firstly proposed in \cite{Grad}. The Grad's moment method was originally developed for the Boltzmann equation. In \cite{Fan_new}, a regularization method for the Grad's moment system of the Boltzmann equation was proposed to achieve the globally hyperbolicity so that the local well-posedness of the moment system is attained. With the moment expansion of the Wigner function, the drift term in the Wigner equation has exactly the same moment representation as in the Boltzmann equation, thus the regularization in \cite{Fan_new} applies. The moment expansion of the nonlocal Wigner potential term in the Wigner equation is turned to be a linear source term, which can only induce very mild growth of the solution. As the result, the local well-posedness of the regularized moment system for the Wigner equation remains as for the Boltzmann equation

    Exploratory chandra observation of the ultraluminous quasar SDSS J010013.02+280225.8 at redshift 6.30

    No full text
    We report exploratory Chandra observations of the ultraluminous quasar SDSS J010013.02+280225.8 at redshift 6.30. The quasar is clearly detected by Chandra with a possible component of extended emission.Y.-L.A. thanks the support from NSFC grant Nos. 11273060, 11333008, and State Key Development Program for Basic Research of China (Nos. 2013CB834900 and 2015CB857000). F.W. and X.-B.W. thank the support from the NSFC grants No.11373008 and 11533001, the Strategic Priority Research Program “The Emergence of Cosmological Structures” of the Chinese Academy of Sciences, grant No. XDB09000000, and the National Key Basic Research Program of China 2014CB845700

    The 3D Genome Browser: A web-based browser for visualizing 3D genome organization and long-range chromatin interactions

    Get PDF
    Abstract Here, we introduce the 3D Genome Browser, http://3dgenome.org, which allows users to conveniently explore both their own and over 300 publicly available chromatin interaction data of different types. We design a new binary data format for Hi-C data that reduces the file size by at least a magnitude and allows users to visualize chromatin interactions over millions of base pairs within seconds. Our browser provides multiple methods linking distal cis-regulatory elements with their potential target genes. Users can seamlessly integrate thousands of other omics data to gain a comprehensive view of both regulatory landscape and 3D genome structure

    The Role of Microbiome in Insomnia, Circadian Disturbance and Depression

    Get PDF
    Good sleep and mood are important for health and for keeping active. Numerous studies have suggested that the incidence of insomnia and depressive disorder are linked to biological rhythms, immune function, and nutrient metabolism, but the exact mechanism is not yet clear. There is considerable evidence showing that the gut microbiome not only affects the digestive, metabolic, and immune functions of the host but also regulates host sleep and mental states through the microbiome-gut-brain axis. Preliminary evidence indicates that microorganisms and circadian genes can interact with each other. The characteristics of the gastrointestinal microbiome and metabolism are related to the host's sleep and circadian rhythm. Moreover, emotion and physiological stress can also affect the composition of the gut microorganisms. The gut microbiome and inflammation may be linked to sleep loss, circadian misalignment, affective disorders, and metabolic disease. In this review article, we discuss various functions of the gut microbiome and how its activities interact with the circadian rhythms and emotions of the host. Exploring the effects of the gut microbiome on insomnia and depression will help further our understanding of the pathogenesis of mental disorders. It is therefore important to regulate and maintain a normal gastrointestinal micro-ecological environment in patients when treating mental disorders
    corecore