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The microbial mats of Guerrero Negro (GN), Baja California Sur, Mexico historically were considered a simple environment, dominated by cyanobacteria and sulfate-reducing bacteria. Culture-independent rRNA community profiling instead revealed these microbial mats as among the most phylogenetically diverse environments known. A preliminary molecular survey of(More)
33 T he Center for Astrophysical Thermonuclear Flashes at the University of Chicago—a collaboration between scientists primarily at Chicago and Argonne National Laboratory—studies the long-standing problem of thermonuclear flashes on the surfaces of compact stars (such as neutron stars and white dwarfs) and in the interior of white dwarfs (such as Type Ia(More)
We develop a fast direct solver for parallel solution of \coarse grid" problems, Ax = b, such as arise when domain decomposition or multigrid methods are applied to elliptic partial diierential equations in d space dimensions. The approach is based upon a (quasi-) sparse factorization of the inverse of A. If the dimension of the system is n and the number(More)
We present simulations and performance results of nuclear burning fronts in supernovae on the largest domain and at the finest spatial resolution studied to date. These simulations were performed on the Intel ASCI-Red machine at Sandia National Laboratories using FLASH, a code developed at the Center for Astrophysical Thermonuclear Flashes at the University(More)
In this paper, we examine parallel filesystems for shared deployment across multiple Linux clusters running with different hardware architectures and operating systems. Specifically, we deploy PVFS2, GPFS, Lustre, and TerraFS in our test environment containing Intel Xeon, Intel x86-64, and IBM PPC970 systems. We comment on the feature sets of each(More)
This paper examines a class of low density parity check (LDPC) erasure codes called Tornado codes for applications in archival storage systems. The fault tolerance of Tornado code graphs is analyzed and it is shown that it is possible to identify and mitigate worst-case failure scenarios in small (96 node) graphs through use of simulations to find and(More)
The design and procurement of supercomputers may require months, but the construction of a facility to house a supercomputer can extend to years. This paper describes the design and construction of a Top-50 supercomputer system and a fully-customized pre-fabricated facility to house it. The use of a co-design process reduced the time from conception to(More)