58 Matching Results

Results open in a new window/tab.

The Slice Balance Approach (SBA): A Characteristic-Based, Multiple Balance Sn Approach on Unstructured Polyhedral Meshes (open access)
2004 Structural, Function and Evolutionary Genomics (open access)

2004 Structural, Function and Evolutionary Genomics

This Gordon conference will cover the areas of structural, functional and evolutionary genomics. It will take a systematic approach to genomics, examining the evolution of proteins, protein functional sites, protein-protein interactions, regulatory networks, and metabolic networks. Emphasis will be placed on what we can learn from comparative genomics and entire genomes and proteomes.
Date: March 23, 2005
Creator: Gray, Douglas L. Brutlag Nancy Ryan
System: The UNT Digital Library
2004 Reversible Associations in Structure & Molecular Biology (open access)

2004 Reversible Associations in Structure & Molecular Biology

The Gordon Research Conference (GRC) on 2004 Gordon Research Conference on Reversible Associations in Structure & Molecular Biology was held at Four Points Sheraton, CA, 1/25-30/2004. The Conference was well attended with 82 participants (attendees list attached). The attendees represented the spectrum of endeavor in this field coming from academia, industry, and government laboratories, both U.S. and foreign scientists, senior researchers, young investigators, and students.
Date: March 23, 2005
Creator: Gray, Edward Eisenstein Nancy Ryan
System: The UNT Digital Library
Aging and weathering of cool roofing membranes (open access)

Aging and weathering of cool roofing membranes

Aging and weathering can reduce the solar reflectance of cool roofing materials. This paper summarizes laboratory measurements of the solar spectral reflectance of unweathered, weathered, and cleaned samples collected from single-ply roofing membranes at various sites across the United States. Fifteen samples were examined in each of the following six conditions: unweathered; weathered; weathered and brushed; weathered, brushed and then rinsed with water; weathered, brushed, rinsed with water, and then washed with soap and water; and weathered, brushed, rinsed with water, washed with soap and water, and then washed with an algaecide. Another 25 samples from 25 roofs across the United States and Canada were measured in their unweathered state, weathered, and weathered and wiped. We document reduction in reflectivity resulted from various soiling mechanisms and provide data on the effectiveness of various cleaning approaches. Results indicate that although the majority of samples after being washed with detergent could be brought to within 90% of their unweathered reflectivity, in some instances an algaecide was required to restore this level of reflectivity.
Date: August 23, 2005
Creator: Akbari, Hashem; Berhe, Asmeret A.; Levinson, Ronnen; Graveline,Stanley; Foley, Kevin; Delgado, Ana H. et al.
System: The UNT Digital Library
Pore Fluid Effects on Shear Modulus in a Model of Heterogeneous Rocks, Reservoirs, and Granular Media (open access)

Pore Fluid Effects on Shear Modulus in a Model of Heterogeneous Rocks, Reservoirs, and Granular Media

To provide quantitative measures of the importance of fluid effects on shear waves in heterogeneous reservoirs, a model material called a ''random polycrystal of porous laminates'' is introduced. This model poroelastic material has constituent grains that are layered (or laminated), and each layer is an isotropic, microhomogeneous porous medium. All grains are composed of exactly the same porous constituents, and have the same relative volume fractions. The order of lamination is not important because the up-scaling method used to determine the transversely isotropic (hexagonal) properties of the grains is Backus averaging, which--for quasi-static or long-wavelength behavior--depends only on the volume fractions and layer properties. Grains are then jumbled together totally at random, filling all space, and producing an overall isotropic poroelastic medium. The poroelastic behavior of this medium is then analyzed using the Peselnick-Meister-Watt bounds (of Hashin-Shtrikman type). We study the dependence of the shear modulus on pore fluid properties and determine the range of behavior to be expected. In particular we compare and contrast these results to those anticipated from Gassmann's fluid substitution formulas, and to the predictions of Mavko and Jizba for very low porosity rocks with flat cracks. This approach also permits the study of arbitrary numbers …
Date: March 23, 2005
Creator: Berger, E. L.
System: The UNT Digital Library
CP: AN INVESTIGATION OF COEFFICIENT OF THERMAL EXPANSION, DECOMPOSITION KINETICS, AND REACTION TO VARIOUS STIMULI (open access)

CP: AN INVESTIGATION OF COEFFICIENT OF THERMAL EXPANSION, DECOMPOSITION KINETICS, AND REACTION TO VARIOUS STIMULI

The properties of pentaamine (5-cyano-2H-tetrazolato-N2) cobalt (III) perchlorate (CP), which was first synthesized in 1968, continues to be of interest for predicting behavior in handling, shipping, aging, and thermal cook-off situations. We report coefficient of thermal expansion (CTE) values over four specific temperature ranges, decomposition kinetics using linear heating rates, and the reaction to three different types of stimuli: impact, spark, and friction. The CTE was measured using a Thermal Mechanical Analyzer (TMA) for samples that were uniaxially compressed at 10,000 psi and analyzed over a dynamic temperature range of -20 C to 70 C. Using differential scanning calorimetry, DSC, CP was decomposed at linear heating rates of 1, 3, and 7 C/min and the kinetic triplet calculated using the LLNL code Kinetics05. Values are also reported for spark, friction, and impact sensitivity.
Date: March 23, 2005
Creator: Weese, R. K.; Burnham, A. K. & Fontes, A. T.
System: The UNT Digital Library
Picosecond X-Ray Diffraction From Laser-Shocked Copper and Iron (open access)

Picosecond X-Ray Diffraction From Laser-Shocked Copper and Iron

In situ X-ray diffraction allows the determination of the structure of transient states of matter. We have used laser-plasma generated X-rays to study how single crystals of metals (copper and iron) react to uniaxial shock compression. We find that copper, as a face-centered-cubic material, allows rapid generation and motion of dislocations, allowing close to hydrostatic conditions to be achieved on sub-nanosecond timescales. Detailed molecular dynamics calculations provide novel information about the process, and point towards methods whereby the dislocation density might be measured during the passage of the shock wave itself. We also report on recent experiments where we have obtained diffraction images from shock-compressed single-crystal iron. The single crystal sample transforms to the hcp phase above a critical pressure, below which it appears to be uniaxially compressed bcc, with no evidence of plasticity. Above the transition threshold, clear evidence for the hcp phase can be seen in the diffraction images, and via a mechanism that is also consistent with recent multi-million atom molecular dynamics simulations that use the Voter-Chen potential. We believe these data to be of import, in that they constitute the first conclusive in situ evidence of the transformed structure of iron during the passage of a …
Date: August 23, 2005
Creator: Wark, J. S.; Belak, J. F.; Collins, G. W.; Colvin, J. D.; Davies, H. M.; Duchaineau, M. et al.
System: The UNT Digital Library
An Overview of the Target Fabrication Operations at Lawrence Livermore National Laboratory (open access)

An Overview of the Target Fabrication Operations at Lawrence Livermore National Laboratory

The Target Engineering team at Lawrence Livermore National Laboratory (LLNL) builds precision laser targets for the National Ignition Facility (NIF) and the Omega Laser in Rochester, NY, and other experimental facilities. The physics requirements demand precision in these targets, which creates a constant need for innovative manufacturing processes. As experimental diagnostics improve, there is greater demand for precision in fabrication, assembly, metrology, and documentation of as-built targets. The team specializes in meso-scale fabrication with core competencies in diamond turning, assembly, and metrology. Figure 1 shows a typical diamond turning center. The team builds over 200 laser targets per year in batches of five to fifteen targets. Thus, all are small-lot custom builds, and most are novel designs requiring engineering and process development. Component materials are metals, polymers and low density aerogel foams. Custom fixturing is used to locate parts on the Diamond Turning Machines (DTM) and assembly stations. This ensures parts can be repeatably located during manufacturing operations. Most target builds involve a series of fabricating one surface with features and then relocating the components on another fixture to finish the opposite side of the component. These components are then assembled to complete multiple-component targets. These targets are typically built …
Date: March 23, 2005
Creator: Hibbard, R L & Bono, M J
System: The UNT Digital Library
Oxidation Resistance of Ru-Capped EUV Multilayers (open access)

Oxidation Resistance of Ru-Capped EUV Multilayers

Differently prepared Ru-capping layers, deposited on Mo/Si EUV multilayers, have been characterized using a suite of metrologies to establish their baseline structural, optical, and surface properties in as-deposited state. Same capping layer structures were tested for their thermal stability and oxidation resistance. Post-mortem characterization identified changes due to accelerated tests. The best performing Ru-capping layer structure was studied in detail with transmission electron microscopy to identify the grain microstructure and texture. This information is essential for modeling and performance optimization of EUVL multilayers.
Date: February 23, 2005
Creator: Bajt, S.; Dai, Z.; Nelson, E. J.; Wall, M. A.; Alameda, J.; Nguyen, N. et al.
System: The UNT Digital Library
The Spin Structure of the Nucleon. (open access)

The Spin Structure of the Nucleon.

For many years now, spin has played a very prominent role in QCD. The field of QCD spin physics has been carried by the hugely successful experimental program of polarized deeply-inelastic lepton-nucleon scattering (DIS), and by a simultaneous tremendous progress in theory. A new milestone has now been reached with the advent of RHIC, the world's first polarized proton-proton collider. RHIC is poised to help answer many of the important question pertaining to the spin structure of the nucleon. Recently, it has also been proposed to study spin phenomena in transversely polarized {bar p}p collisions at the planned GSI-FAIR facility. This talk describes some of the opportunities provided by RHIC and the proposed GSI experiments.
Date: May 23, 2005
Creator: Vogelsang, W.
System: The UNT Digital Library
Measurement of Time-Dependent CP-Violating Asymmetries in B^0 Meson Decays to eta' K^0_L (open access)

Measurement of Time-Dependent CP-Violating Asymmetries in B^0 Meson Decays to eta' K^0_L

The authors present a preliminary measurement of CP-violating parameters S and C from fits of the time-dependence of B{sup 0} meson decays to {eta}'K{sub L}{sup 0}. The data were recorded with the BABAR detector at PEP-II and correspond to 232 x 10{sup 6} B{bar B} pairs produced in e{sup +}e{sup -} annihilation through the {Upsilon}(4S) resonance. By fitting the time-dependent CP asymmetry of the reconstructed B{sup 0} {yields} {eta}'K{sub L}{sup 0} events, they find S = 0.60 {+-} 0.31 {+-} 0.04 and C = 0.10 {+-} 0.21 {+-} 0.03, where the first error quoted is statistical and the second is systematic. They also perform a combined fit using both {eta}'K{sub S}{sup 0} and {eta}'K{sub L}{sup 0} data, and find S = 0.36 {+-} 0.13 {+-} 0.03 and C = -0.16 {+-} 0.09 {+-} 0.02.
Date: August 23, 2005
Creator: Aubert, B.; Barate, R.; Boutigny, D.; Couderc, F.; Karyotakis, Y.; Lees, J. P. et al.
System: The UNT Digital Library
Multi-Gev Energy Gain in a Plasma-Wakefield Accelerator (open access)

Multi-Gev Energy Gain in a Plasma-Wakefield Accelerator

None
Date: September 23, 2005
Creator: Hogan, M. J.; Barnes, C. D.; Clayton, C. E.; Decker, F. J.; Deng, S.; Emma, P. et al.
System: The UNT Digital Library
3D Arcing for Offset Measurements with a Hamar Laser (Presentation material) (open access)

3D Arcing for Offset Measurements with a Hamar Laser (Presentation material)

This report is about 3D Arcing for Offset Measurements with a Hamar Laser on 7th International workshop on accelerator alignment.
Date: August 23, 2005
Creator: Fuss, B.
System: The UNT Digital Library
FERRITE-FREE STACKED BLUMLEIN PULSE GENERATOR FOR COMPACT INDUCTION LINACS (open access)

FERRITE-FREE STACKED BLUMLEIN PULSE GENERATOR FOR COMPACT INDUCTION LINACS

Stacked Blumlein Pulse Generators comprised of parallel-plate transmission lines are potentially a useful pulse-power architecture for high-gradient, compact, electron-beam induction accelerators. However, like induction accelerators driven by other pulse-power architectures, it is generally a system requirement that the multi-stage accelerator structure be enclosed in a grounded metal enclosure so that the full beam voltage is not developed on the exterior of the machine. In the past, this has been accomplished by using magnetic cores to prevent the external metal case from shorting the accelerating field. However, magnetic cores are heavy, bulky, expensive, lossy, nonlinear, and therefore generally undesirable. Various core-free pulse architectures have been reported in the past. One class uses pairs of lines with widely different dielectric constants while another class uses combinations of open-circuit lines combined with short-circuit lines. These designs are encased in metal and support stackable output pulses without the need for magnetic isolation cores. These configurations are also known as bi-polar or zero-integral configurations because they produce a positive and negative voltage pulse with a net time integral of zero. Some of these designs are inefficient leaving substantial stored energy in the lines while others have never been realized as practical accelerating structures. We present …
Date: May 23, 2005
Creator: Rhodes, M. A.
System: The UNT Digital Library
Selective Immobilization of Proteins onto Solid Supports Through Split-Intein Mediated Protein Trans-Splicing (open access)

Selective Immobilization of Proteins onto Solid Supports Through Split-Intein Mediated Protein Trans-Splicing

Protein microarrays have emerged as important tools for screening protein-protein interactions and hold great potential for various applications including proteomics research, drug discovery, and diagnostics. This work describes a novel method for the traceless immobilization of proteins to a solid support through split-intein mediated protein trans-splicing. This method has been successfully used for the immobilization of biologically active proteins from very diluted samples ({approx}1{micro}M) and it does not require the purification of the protein to be attached. This makes possible the direct immobilization of proteins from complex mixtures such as cellular lysates and it can also be easily interfaced with cell-free expression systems for high-throughput production of protein microarrays.
Date: August 23, 2005
Creator: Kwon, Y; Coleman, M A & Camarero, J A
System: The UNT Digital Library
WinGEONET: What's New? (Presentation material) (open access)

WinGEONET: What's New? (Presentation material)

The name GEONET means data reduction software for the accelerator alignment community. It was developed in the early 1980's but the only thing left from the original version is the hierarchical directory structure to hold the observations and results. This poster presents the three components of WinGEONET: the Windows interface, the computational engine and the visualization tool. It also presents further developments towards a more versatile toolbox architecture.
Date: August 23, 2005
Creator: Gaydosh, M.; Langer, L. & LeCocq, C.
System: The UNT Digital Library
Missing and Spurious Level Corrections for Nuclear Resonances (open access)

Missing and Spurious Level Corrections for Nuclear Resonances

Neutron and proton resonances provide detailed level density information. However, due to experimental limitations, some levels are missed and some are assigned incorrect quantum numbers. The standard method to correct for missing levels uses the experimental widths and the Porter-Thomas distribution. Analysis of the spacing distribution provides an independent determination of the fraction of missing levels. We have derived a general expression for such an imperfect spacing distribution using the maximum entropy principle and applied it to a variety of nuclear resonance data. The problem of spurious levels has not been extensively addressed.
Date: June 23, 2005
Creator: Mitchell, G. E.; Agvaanluvsan, U.; Pato, M. P. & Shriner, J. F.
System: The UNT Digital Library
An Accelerator Control Middle Layer Using Matlab (open access)

An Accelerator Control Middle Layer Using Matlab

None
Date: August 23, 2005
Creator: Portmann, G.; /LBL, Berkeley; Corbett, J.; Terebilo, A. & /SLAC, SSRL /SLAC
System: The UNT Digital Library
NARAC: An Emergency Response Resource for Predicting the Atmospheric Dispersion and Assessing the Consequences of Airborne Radionuclides (open access)

NARAC: An Emergency Response Resource for Predicting the Atmospheric Dispersion and Assessing the Consequences of Airborne Radionuclides

Hazardous radioactive materials can be released into the atmosphere by accidents at nuclear power plants, fuel processing facilities, and other facilities, and by transportation accidents involving nuclear materials. In addition, the post-cold-war proliferation of nuclear material has increased the potential for terrorism scenarios involving radiological dispersal devices, improvised nuclear devices, and inadequately secured military nuclear weapons. To mitigate these risks, the National Atmospheric Release Advisory Center (NARAC) serves as a national resource for the United States, providing tools and services to quickly predict the environmental contamination and health effects caused by airborne radionuclides, and to provide scientifically based guidance to emergency managers for the protection of human life. NARAC's expert staff uses computer models, supporting databases, software systems, and communications systems to predict the plume paths and consequences of radiological, chemical, and biological atmospheric releases.
Date: August 23, 2005
Creator: Bradley, M M
System: The UNT Digital Library
Development of the Hybrid Sulfur Thermochemical Cycle (open access)

Development of the Hybrid Sulfur Thermochemical Cycle

The production of hydrogen via the thermochemical splitting of water is being considered as a primary means for utilizing the heat from advanced nuclear reactors to provide fuel for a hydrogen economy. The Hybrid Sulfur (HyS) Process is one of the baseline candidates identified by the U.S. Department of Energy [1] for this purpose. The HyS Process is a two-step hybrid thermochemical cycle that only involves sulfur, oxygen and hydrogen compounds. Recent work has resulted in an improved process design with a calculated overall thermal efficiency (nuclear heat to hydrogen, higher heating value basis) approaching 50%. Economic analyses indicate that a nuclear hydrogen plant employing the HyS Process in conjunction with an advanced gas-cooled nuclear reactor system can produce hydrogen at competitive prices. Experimental work has begun on the sulfur dioxide depolarized electrolyzer, the major developmental component in the cycle. Proof-of-concept tests have established proton-exchange-membrane cells (a state-of-the-art technology) as a viable approach for conducting this reaction. This is expected to lead to more efficient and economical cell designs than were previously available. Considerable development and scale-up issues remain to be resolved, but the development of a viable commercial-scale HyS Process should be feasible in time to meet the commercialization …
Date: September 23, 2005
Creator: Summers, William A. & Steimke, John L
System: The UNT Digital Library
Measurement of the Branching Ratios Gamma(D*+s -> D+s pi0)/Gamma(D*+s ->D+s gamma) and Gamma(D*0 ->D0 pi0)/Gamma(D*0 -> D0gamma) (open access)

Measurement of the Branching Ratios Gamma(D*+s -> D+s pi0)/Gamma(D*+s ->D+s gamma) and Gamma(D*0 ->D0 pi0)/Gamma(D*0 -> D0gamma)

Data samples corresponding to the isospin-violating decay D*{sub s}{sup +} {yields} D{sub s}{sup +}{pi}{sup 0} and the decays D*{sub s}{sup +} {yields} D{sub s}{sup +}, D*{sup 0} {yields} D{sup 0}{pi}{sup 0} and D*{sup 0} {yields} D{sup 0}{gamma} are reconstructed using 90.4 fb{sup -1} of data recorded by the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collider. The following branching ratios are extracted: {Lambda}(D*{sub s}{sup +} {yields} D{sub s}{sup +}{pi}{sup 0})/{Lambda}(D*{sub s}{sup +} {yields} D{sub s}{sup +}{gamma}) = 0.062 {+-} 0.005(stat.) {+-} 0.006(syst.) and {Lambda}(D*{sup 0} {yields} D{sup 0}{pi}{sup 0})/{Lambda}(D*{sup 0} {yields} D{sup 0}{gamma}) = 1.74 {+-} 0.02(stat.) {+-} 0.13(syst.). Both measurements represent significant improvements over present world averages.
Date: August 23, 2005
Creator: Aubert, B.; Barate, R.; Boutigny, D.; Couderc, F.; Karyotakis, Y.; Lees, J. P. et al.
System: The UNT Digital Library
Status of the E166-Experiment (open access)

Status of the E166-Experiment

The E166 experiment is a proof-of-principle experiment to demonstrate the production of polarized positrons with a helical undulator. The experiment has taken first data in June 2005 at SLAC. This article gives a short overview of the performance of various components of the experiment.
Date: August 23, 2005
Creator: Poeschl, R.
System: The UNT Digital Library
How Small Can a Launch Vehicle Be? (open access)

How Small Can a Launch Vehicle Be?

Trajectory simulations from Earth to orbit indicate comparative velocity requirements depending on vehicle size, for several propellant options. Smaller vehicles are more affected by drag, resulting in steeper trajectories that require more total velocity. Although they are technically challenging, launch vehicles smaller than 1 ton are not ruled out by the nature of ascent trajectories.
Date: June 23, 2005
Creator: Whitehead, J C
System: The UNT Digital Library
Surrogate Nuclear Reactions - An Indirect Method for Determining Reaction Cross Sections (open access)

Surrogate Nuclear Reactions - An Indirect Method for Determining Reaction Cross Sections

An indirect method for determining cross sections of reactions proceeding through a compound nucleus is presented. Some applications of the Surrogate nuclear reaction approach are considered and challenges that need to be addressed are outlined.
Date: March 23, 2005
Creator: Escher, J; Ahle, L; Bernstein, L; Burke, J; Church, J A; Dietrich, F et al.
System: The UNT Digital Library