This report gives information about the Adaptation of subsurface microbial communities to mercury.

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Over the past two decades, numerous studies have produced high quality information on the rates at which bacteria can reduce metal oxides. The prototypical study--such as the one depicted to the right--focuses on only a few of the myriad variables affecting the rate. This approach allows for effective dissection of the mechanisms underlying DMRB activity, but, it also produces disjoint information that must be synthesized if we hope to predict the behavior of bacteria at the systems level.

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Cross-comparison of the results of two computer codes for the same problem provides a mutual validation of their computational methods. This cross-validation exercise was performed for LLNL's ALE3D code and AKTS's Thermal Safety code, using the thermal ignition of HMX in two standard LLNL cookoff experiments: the One-Dimensional Time to Explosion (ODTX) test and the Scaled Thermal Explosion (STEX) test. The chemical kinetics model used in both codes was the extended Prout-Tompkins model, a relatively new addition to ALE3D. This model was applied using ALE3D's new pseudospecies feature. In addition, an advanced isoconversional kinetic approach was used in the AKTS code. The mathematical constants in the Prout-Tompkins code were calibrated using DSC data from hermetically sealed vessels and the LLNL optimization code Kinetics05. The isoconversional kinetic parameters were optimized using the AKTS Thermokinetics code. We found that the Prout-Tompkins model calculations agree fairly well between the two codes, and the isoconversional kinetic model gives very similar results as the Prout-Tompkins model. We also found that an autocatalytic approach in the beta-delta phase transition model does affect the times to explosion for some conditions, especially STEX-like simulations at ramp rates above 100 C/hr, and further exploration of that effect is warranted.

Aperiodic multilayers have been designed for various applications, using numeric algorithms and analytical solutions, for many years with varying levels of success. This work developed a more realistic model for simulating aperiodic Mo/Si multilayers to be used in these algorithms by including the formation of MoSi{sub 2}. Using a genetic computer code we were able to optimize a 45{sup o} multilayer for a large bandpass reflection multilayer that gave good agreement with the model.

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The GLAST Large Area Telescope (LAT) is the next generation satellite experiment for high-energy gamma-ray astronomy. It is a pair conversion telescope built with a plastic anticoincidence shield, a segmented CsI electromagnetic calorimeter, and the largest silicon strip tracker ever built. It will cover the energy range from 30 MeV to 300 GeV, shedding light on many issues left open by its predecessor EGRET. One of the most exciting science topics is the detection and observation of gamma-ray bursts (GRBs). In this paper we present the work done so far by the GRB LAT science group in studying the performance of the LAT detector to observe GRBs.We report on the simulation framework developed by the group as well as on the science tools dedicated to GRBs data analysis. We present the LAT sensitivity to GRBs obtained with such simulations, and, finally, the general scheme of GRBs detection that will be adopted on orbit.

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Soft x-ray microscopy has now achieved 15 nm spatial resolution with new zone plates and bending magnet radiation. Combined with elemental sensitivity and flexible sample environment (applied magnetic or electric fields, wet samples, windows, overcoatings) this emerges as a valuable tool for nanoscience and nanotechnology, complimenting common electron and scanning tip microscopies. In this presentation we describe recent advances in spatial resolution, expectations for the near future, and applications to magnetic materials, bio-tomography, etc.

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For the in situ reductive immobilization of U to be an acceptable strategy for the removal of that element from groundwater, the long-term stability of U(IV) must be determined. Rates of biotransformation of Fe species influence the mineralogy of the resulting products (Fredrickson et al., 2003; Senko et al., 2005), and we hypothesize that the rate of U(VI) reduction influences the mineralogy of resultant U(IV) precipitates. We hypothesize that slower rates of U(VI) reduction will yield U(IV) phases that are more resistant to reoxidation, and will therefore be more stable upon cessation of electron donor addition. U(IV) phases formed by relatively slow reduction may be more crystalline or larger in comparison to their relatively rapidly-formed counterparts (Figure 1), thus limiting the reactivity of slowly-formed U(IV) phases toward various oxidants. The physical location of U(IV) precipitates relative to bacterial cells may also limit the reactivity of biogenic U(IV) phases. In this situation, we expect that precipitation of U(IV) within the bacterial cell may protect U(IV) from reoxidation by limiting physical contact between U(IV) and oxidants (Figure 1). We assessed the effect of U(VI) reduction rate on the subsequent reoxidation of biogenic U(IV) and are currently conducting column scale studies to determine …

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A simple method to estimate the atomic degree Hessian matrixof a nanosystem is presented. The estimated Hessian matrix, based on themotif decomposition of the nanosystem, can be used to accelerate abinitio atomic relaxations with speedups of 2 to 4 depending on the sizeof the system. In addition, the programing implementation for using thismethod in a standard ab initio package is trivial.

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The objective of the analysis was to determine the failure of the Vent and Purge (V&P) Machine due to potential explosion in the Transuranic (TRU) drum during its venting and/or subsequent explosion in the V&P machine from the flammable gases (e.g., hydrogen and Volatile Organic Compounds [VOCs]) vented into the V&P machine from the TRU drum. The analysis considers: (a) increase in the pressure in the V&P cabinet from the original deflagration in the TRU drum including lid ejection, (b) pressure wave impact from TRU drum failure, and (c) secondary burns or deflagrations resulting from excess, unburned gases in the cabinet area. A variety of cases were considered that maximized the pressure produced in the V&P cabinet. Also, cases were analyzed that maximized the shock wave pressure in the cabinet from TRU drum failure. The calculations were performed for various initial drum pressures (e.g., 1.5 and 6 psig) for 55 gallon TRU drum. The calculated peak cabinet pressures ranged from 16 psig to 50 psig for various flammable gas compositions. The blast on top of cabinet and in outlet duct ranged from 50 psig to 63 psig and 12 psig to 16 psig, respectively, for various flammable gas compositions. The …