45,934 research outputs found

    DUET: A Generic Framework for Finding Special Quadratic Elements in Data Streams

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    Finding special items, like heavy hitters, top-k, and persistent items, has always been a hot issue in data stream processing for web analysis. While data streams nowadays are usually high-dimensional, most prior works focus on special items according to a certain primary dimension and yield little insight into the correlations between dimensions. Therefore, we propose to find special quadratic elements to reveal close correlations. Based on the items mentioned above, we extend our problem to three applications related to heavy hitters, top-k, and persistent items, and design a generic framework DUET to process them. Besides, we analyze the error bound of our algorithm and conduct extensive experiments on four data sets. Our experimental results show that DUET can achieve 3.5 times higher throughput and three orders of magnitude lower average relative error compared with cutting-edge algorithms

    Astro-WISE: Chaining to the Universe

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    The recent explosion of recorded digital data and its processed derivatives threatens to overwhelm researchers when analysing their experimental data or when looking up data items in archives and file systems. While current hardware developments allow to acquire, process and store 100s of terabytes of data at the cost of a modern sports car, the software systems to handle these data are lagging behind. This general problem is recognized and addressed by various scientific communities, e.g., DATAGRID/EGEE federates compute and storage power over the high-energy physical community, while the astronomical community is building an Internet geared Virtual Observatory, connecting archival data. These large projects either focus on a specific distribution aspect or aim to connect many sub-communities and have a relatively long trajectory for setting standards and a common layer. Here, we report "first light" of a very different solution to the problem initiated by a smaller astronomical IT community. It provides the abstract "scientific information layer" which integrates distributed scientific analysis with distributed processing and federated archiving and publishing. By designing new abstractions and mixing in old ones, a Science Information System with fully scalable cornerstones has been achieved, transforming data systems into knowledge systems. This break-through is facilitated by the full end-to-end linking of all dependent data items, which allows full backward chaining from the observer/researcher to the experiment. Key is the notion that information is intrinsic in nature and thus is the data acquired by a scientific experiment. The new abstraction is that software systems guide the user to that intrinsic information by forcing full backward and forward chaining in the data modelling.Comment: To be published in ADASS XVI ASP Conference Series, 2006, R. Shaw, F. Hill and D. Bell, ed

    Worrying and rumination are both associated with reduced cognitive control

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    Persistent negative thought is a hallmark feature of both major depressive disorder and generalized anxiety disorder. Despite its clinical significance, little is known about the underlying mechanisms of persistent negative thought. Recent studies suggest that reduced cognitive control might be an explanatory factor. We investigated the association between persistent negative thought and switching between internal representations in working memory, using the internal shift task (IST). The IST was administered to a group of undergraduates, classified as high-ruminators versus low-ruminators, or high-worriers versus low-worriers. Results showed that high-ruminators and high-worriers have more difficulties to switch between internal representations in working memory as opposed to low-ruminators and low-worriers. Importantly, results were only significant when the negative stimuli used in the IST reflected personally relevant worry themes for the participants. The results of this study indicate that rumination and worrying are both associated with reduced cognitive control for verbal information that is personally relevant
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