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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)
This paper examines the economics of cloud computing charging from the perspective of a supercomputing resource provider offering its own resources. To evaluate the competitiveness of our computing center with cloud computing resources, we develop a comprehensive system utilization charging model similar to that used by Amazon EC2 and apply the model to our(More)
We first demonstrate the parallel performance of the dynam-ical core of a spectral element atmospheric model. The model uses continuous Galerkin spectral elements to dis-cretize the surface of the Earth, coupled with finite differences in the radial direction. Results are presented from two distributed memory, mesh interconnect supercomput-ers (ASCI Red and(More)
Infrastructure-as-a-service (IaaS) clouds, such as Amazon EC2, offer pay-for-use virtual resources on-demand. This allows users to outsource computation and storage when needed and create elastic computing environments that adapt to changing demand. However, existing services, such as cluster resource managers (e.g. Torque), do not include support for(More)