2,847 research outputs found

    Massive Science with VO and Grids

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    There is a growing need for massive computational resources for the analysis of new astronomical datasets. To tackle this problem, we present here our first steps towards marrying two new and emerging technologies; the Virtual Observatory (e.g, AstroGrid) and the computational grid (e.g. TeraGrid, COSMOS etc.). We discuss the construction of VOTechBroker, which is a modular software tool designed to abstract the tasks of submission and management of a large number of computational jobs to a distributed computer system. The broker will also interact with the AstroGrid workflow and MySpace environments. We discuss our planned usages of the VOTechBroker in computing a huge number of n-point correlation functions from the SDSS data and massive model-fitting of millions of CMBfast models to WMAP data. We also discuss other applications including the determination of the XMM Cluster Survey selection function and the construction of new WMAP maps.Comment: Invited talk at ADASSXV conference published as ASP Conference Series, Vol. XXX, 2005 C. Gabriel, C. Arviset, D. Ponz and E. Solano, eds. 9 page

    Statistical Computations with AstroGrid and the Grid

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    We outline our first steps towards marrying two new and emerging technologies; the Virtual Observatory (e.g, AstroGrid) and the computational grid. We discuss the construction of VOTechBroker, which is a modular software tool designed to abstract the tasks of submission and management of a large number of computational jobs to a distributed computer system. The broker will also interact with the AstroGrid workflow and MySpace environments. We present our planned usage of the VOTechBroker in computing a huge number of n-point correlation functions from the SDSS, as well as fitting over a million CMBfast models to the WMAP data.Comment: Invited talk to appear in "Proceedings of PHYSTAT05: Statistical Problems in Particle Physics, Astrophysics and Cosmology

    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

    Finding Minimum-Power Broadcast Trees for Wireless Networks

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    Some algorithms have been devised for use in a method of constructing tree graphs that represent connections among the nodes of a wireless communication network. These algorithms provide for determining the viability of any given candidate connection tree and for generating an initial set of viable trees that can be used in any of a variety of search algorithms (e.g., a genetic algorithm) to find a tree that enables the network to broadcast from a source node to all other nodes while consuming the minimum amount of total power. The method yields solutions better than those of a prior algorithm known as the broadcast incremental power algorithm, albeit at a slightly greater computational cost

    Distance dependence of photoinduced long-range electron transfer in zinc/ruthenium-modified myoglobins

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    An experimental investigation of the distance dependence of long-range electron transfer in zinc/ruthenium-modified myoglobins has been performed. The modified proteins were prepared by substitution of zinc mesoporphyrin IX diacid (ZnP) for the heme in each of four previously characterized pentaammineruthenium(III) (a_5Ru;a = NH_3) derivatives of sperm whale myoglobin (Mb): a_5Ru(His-48)Mb, a_5Ru(His-12)Mb, a_5Ru(His-116)Mb, a_5Ru(His-81)Mb. Electron transfer from the ZnP triplet excited state (^3ZnP*) to Ru^3+, ^3ZnP*-Ru^3+ → ZnP^+-Ru^2+ (ΔE° ~ 0.8V) was measured by time-resolved transient absorption spectroscopy: rate constants (k_f) are 7.0 × 10^4 (His-48), 1.0 × 10^2 (His-12), 8.9 × 10^1 (His-116), and 8.5 × 10^1 (His-81) s^-1 at 25 °C. Activation enthalpies calculated from the temperature dependences of the electron-transfer rates over the range 5-40 °C are 1.7 ± 1.6 (His-48), 4.7 ± 0.9 (His-12), 5.4 ± 0.4 (His-116), and 5.6 ± 2.5 (His-81) kcal mol^-1. Electron-transfer distances (d = closest ZnP edge to a_5Ru(His) edge; angstroms) were calculated to fall in the following ranges: His-48, 11.8-16.6; His-12, 21.5-22.3; His-116, 19.8-20.4; His-81, 18.8-19.3. The rate-distance equation is k_f = 7.8 × 10^8 exp[-0.9l(d - 3)] s^-1 . The data indicate that the ^3ZnP*-Ru(His-12)^3+ electronic coupling may be enhanced by an intervening tryptophan (Trp-14)
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