2,883 research outputs found

    Fast Algorithms and Efficient Statistics: N-point Correlation Functions

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    We present here a new algorithm for the fast computation of N-point correlation functions in large astronomical data sets. The algorithm is based on kdtrees which are decorated with cached sufficient statistics thus allowing for orders of magnitude speed-ups over the naive non-tree-based implementation of correlation functions. We further discuss the use of controlled approximations within the computation which allows for further acceleration. In summary, our algorithm now makes it possible to compute exact, all-pairs, measurements of the 2, 3 and 4-point correlation functions for cosmological data sets like the Sloan Digital Sky Survey (SDSS; York et al. 2000) and the next generation of Cosmic Microwave Background experiments (see Szapudi et al. 2000).Comment: To appear in Proceedings of MPA/MPE/ESO Conference "Mining the Sky", July 31 - August 4, 2000, Garching, German

    Microfluidic Chip for High Efficiency Microinjection of Caenorhabditis elegans

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    The terrestrial nematode, Caenorhabditis elegans, is an invaluable model organism for the study of molecular and cellular processes due to their small size, rapid generation time, easy cultivation, and invariant cell number. Additionally, 40% of genes known to be associated with human disease have clear orthologs in the C. elegans genome. In C. elegans genetics research, microinjection of genetic material into the worms is critical. Although an established technique, manual microinjection is tedious, low-throughput, and requires an expert researcher. This thesis details a novel microfluidic device designed to perform high-throughput microinjection. This two-layer, PDMS-based chip integrates microfluidic elements to control worm sorting, reduction of immobilization time and stress, and novel on-chip microinjection using only a positive pressure source. Our project aim is to increase microinjection efficiency, consistency, and accessibility to researchers of all experience levels in order to advance genetics research and genetic engineering technology in C. elegans. Preliminary results are promising, as our on-chip microinjection device has been able to successfully inject dye into C. elegans animals

    Data Mining the SDSS SkyServer Database

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    An earlier paper (Szalay et. al. "Designing and Mining MultiTerabyte Astronomy Archives: The Sloan Digital Sky Survey," ACM SIGMOD 2000) described the Sloan Digital Sky Survey's (SDSS) data management needs by defining twenty database queries and twelve data visualization tasks that a good data management system should support. We built a database and interfaces to support both the query load and also a website for ad-hoc access. This paper reports on the database design, describes the data loading pipeline, and reports on the query implementation and performance. The queries typically translated to a single SQL statement. Most queries run in less than 20 seconds, allowing scientists to interactively explore the database. This paper is an in-depth tour of those queries. Readers should first have studied the companion overview paper Szalay et. al. "The SDSS SkyServer, Public Access to the Sloan Digital Sky Server Data" ACM SIGMOND 2002.Comment: 40 pages, Original source is at http://research.microsoft.com/~gray/Papers/MSR_TR_O2_01_20_queries.do
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