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Sensor Development for the Large Synoptic Survey Telescope. (open access)

Sensor Development for the Large Synoptic Survey Telescope.

The Large Synoptic Survey project proposes to build an 8m-class ground-based telescope with a dedicated wide field camera. The camera consists of a large focal plane mosaic composed of multi-output CCDs with extended red response. Design considerations and preliminary characterization results for the sensors are presented in this contribution to the Workshop.
Date: June 7, 2007
Creator: O'Connor, P.; Radeka, V. & Takacs, P.
System: The UNT Digital Library
Effect of High Temperature Aging on the Corrosion Resistance of Iron Based Amorphous Alloys (open access)

Effect of High Temperature Aging on the Corrosion Resistance of Iron Based Amorphous Alloys

None
Date: June 7, 2007
Creator: Day, S D; Haslam, J J; Farmer, J C & Rebak, R B
System: The UNT Digital Library
Interlayer Interaction and Electronic Screening in MultilayerGraphene (open access)

Interlayer Interaction and Electronic Screening in MultilayerGraphene

The unusual transport properties of graphene are the direct consequence of a peculiar bandstructure near the Dirac point. We determine the shape of the {pi} bands and their characteristic splitting, and find the transition from two-dimensional to bulk character for 1 to 4 layers of graphene by angle-resolved photoemission. By detailed measurements of the {pi} bands we derive the stacking order, layer-dependent electron potential, screening length and strength of interlayer interaction by comparison with tight binding calculations, yielding a comprehensive description of multilayer graphene's electronic structure.
Date: June 7, 2007
Creator: Ohta, Taisuke; Bostwick, Aaron; McChesney, J.L.; Seyller, Thomas; Horn, Karsten & Rotenberg, Eli
System: The UNT Digital Library
HIGH TEMPERATURE PRESSURE PROCESSING OF MIXED ALANATE COMPOUNDS (open access)

HIGH TEMPERATURE PRESSURE PROCESSING OF MIXED ALANATE COMPOUNDS

Mixtures of light-weight elements and hydrides were investigated to increase the understanding of the chemical reactions that take place between various materials. This report details investigations we have made into mixtures that include NaAlH{sub 4}, LiAlH{sub 4}, MgH{sub 2}, Mg{sub 2}NiH{sub 4}, alkali(ne) hydrides, and early third row transition metals (V, Cr, Mn). Experimental parameters such as stoichiometry, heat from ball milling versus hand milling, and varying the temperature of high pressure molten state processing were studied to examine the effects of these parameters on the reactions of the complex metal hydrides.
Date: June 7, 2007
Creator: Berseth, P; Ragaiy Zidan, R; Donald Anton, D; Kirk Shanahan, K & Ashley Stowe, A
System: The UNT Digital Library
Monolithic Active Pixel Matrix with Binary Counters in an SOI Process (open access)

Monolithic Active Pixel Matrix with Binary Counters in an SOI Process

The design of a Prototype monolithic active pixel matrix, designed in a 0.15 {micro}m CMOS SOI Process, is presented. The process allowed connection between the electronics and the silicon volume under the layer of buried oxide (BOX). The small size vias traversing through the BOX and implantation of small p-type islands in the n-type bulk result in a monolithic imager. During the acquisition time, all pixels register individual radiation events incrementing the counters. The counting rate is up to 1 MHz per pixel. The contents of counters are shifted out during the readout phase. The designed prototype is an array of 64 x 64 pixels and the pixel size is 26 x 26 {micro}m{sup 2}.
Date: June 7, 2007
Creator: Duptuch, G. & Yarema, R.
System: The UNT Digital Library
Optimal Design of a Tunable Thomson-Scattering Based Gamma-Ray Source (open access)

Optimal Design of a Tunable Thomson-Scattering Based Gamma-Ray Source

Thomson-Scattering based systems offer a path to high-brightness high-energy (> 1 MeV) x-ray and {gamma}-ray sources due to their favorable scaling with electron energy. LLNL is currently engaged in an effort to optimize such a device, dubbed the ''Thomson-Radiated Extreme X-Ray'' (T-REX) source, targeting up to 680 keV photon energy. Such a system requires precise design of the interaction between a high-intensity laser pulse and a high-brightness electron beam. Presented here are the optimal design parameters for such an interaction, including factors such as the collision angle, focal spot size, optimal bunch charge, and laser energy. These parameters were chosen based on extensive modeling using PARMELA and in-house, well-benchmarked scattering simulation codes.
Date: June 7, 2007
Creator: Gibson, D J; Anderson, S G; Betts, S M; Hartemann, F V; Jovanovic, I; McNabb, D P et al.
System: The UNT Digital Library
A GRADED APPROACH TO FLOW AND TRANSPORT MODELING TO SUPPORT DECOMMISSIONING ACTIVITIES AT THE SAVANNAH RIVER SITE, AIKEN SC (open access)

A GRADED APPROACH TO FLOW AND TRANSPORT MODELING TO SUPPORT DECOMMISSIONING ACTIVITIES AT THE SAVANNAH RIVER SITE, AIKEN SC

A graded approach to flow and transport modeling has been used as a cost effective solution to evaluating potential groundwater risk in support of Deactivation and Decommissioning activities at the United States Department of Energy's Savannah River Site. This approach incorporates both simple spreadsheet calculations and complex numerical modeling to evaluate the threat to human health posed by contaminants leaching from decommissioned concrete building slabs. Simple spread sheet calculations were used to produce generic slab concentration limits for a suite of radiological and non-radiological contaminants for a chemical separations area at Savannah River Site. These limits, which are based upon the United States Environmental Protection Agency Soil Screening guidance, were used to eliminate most building slabs from further risk assessment. Of the more than 58 facilities located in the area, to date only one slab has been found to have a contaminant concentration in excess of the area specific slab limit. For this slab, a more rigorous numerical modeling effort was undertaken reducing the conservatisms inherent in the spreadsheet calculations. Using the more sophisticated numerical model, it was possible to show that the remaining contaminant of concern would not likely impact groundwater above drinking water standards.
Date: June 7, 2007
Creator: Dixon, Kenneth L.; Lee, Patricia L. & Flach, Gregory P.
System: The UNT Digital Library
Characterization and Reconstruction of Nanolipoprotein Particles (Nlps) by Cryo-EM and Image Reconstruction (open access)

Characterization and Reconstruction of Nanolipoprotein Particles (Nlps) by Cryo-EM and Image Reconstruction

Nanolipoprotein particles (NLPs) are small 10-20 nm diameter assemblies of apolipoproteins and lipids. At Lawrence Livermore National Laboratory (LLNL), they have constructed multiple variants of these assemblies. NLPs have been generated from a variety of lipoproteins, including apolipoprotein Al, apolipophorin III, apolipoprotein E4 22K, and MSP1T2 (nanodisc, Inc.). Lipids used included DMPC (bulk of the bilayer material), DMPE (in various amounts), and DPPC. NLPs were made in either the absence or presence of the detergent cholate. They have collected electron microscopy data as a part of the characterization component of this research. Although purified by size exclusion chromatography (SEC), samples are somewhat heterogeneous when analyzed at the nanoscale by negative stained cryo-EM. Images reveal a broad range of shape heterogeneity, suggesting variability in conformational flexibility, in fact, modeling studies point to dynamics of inter-helical loop regions within apolipoproteins as being a possible source for observed variation in NLP size. Initial attempts at three-dimensional reconstructions have proven to be challenging due to this size and shape disparity. They are pursuing a strategy of computational size exclusion to group particles into subpopulations based on average particle diameter. They show here results from their ongoing efforts at statistically and computationally subdividing NLP populations …
Date: June 7, 2007
Creator: Pesavento, Joseph B.; Morgan, David; Bermingham, Rachelle; Zamora, Deborah; Chromy, Brett; Segelke, Brent et al.
System: The UNT Digital Library