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Brilliant Bash (open access)

Brilliant Bash

Article about Alice Carrington Foulz's and Linda Pace's appearances in Brilliant Magazine and their Portrait Show to be held on November 3, 2005.
Date: October 23, 2005
Creator: Yerkes, Susan
System: The UNT Digital Library
FROM THE ISR TO RHIC - MEASUREMENTS OF HARD-SCATTERING AND JETS USING INCLUSIVE SINGLE PARTICLE PRODUCTION AND 2-PARTICLE CORRELATIONS. (open access)

FROM THE ISR TO RHIC - MEASUREMENTS OF HARD-SCATTERING AND JETS USING INCLUSIVE SINGLE PARTICLE PRODUCTION AND 2-PARTICLE CORRELATIONS.

Hard scattering in p-p collisions, discovered at the CERN ISR in 1972 by the method of leading particles, proved that the partons of Deeply Inelastic Scattering strongly interacted with each other. Further ISR measurements utilizing inclusive single or pairs of hadrons established that high p{sub T} particles are produced from states with two roughly back-to-back jets which are the result of scattering of constituents of the nucleons as described by Quantum Chromodynamics (QCD), which was developed during the course of these measurements. These techniques, which are the only practical method to study hard-scattering and jet phenomena in Au+Au central collisions at RHIC energies, are reviewed, as an introduction to present RHIC measurements.
Date: April 23, 2005
Creator: Tannenbaum, M. J.
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
Nanometer-scale imaging and pore-scale fluid flow modeling inchalk (open access)

Nanometer-scale imaging and pore-scale fluid flow modeling inchalk

For many rocks of high economic interest such as chalk,diatomite, tight gas sands or coal, nanometer scale resolution is neededto resolve the 3D-pore structure, which controls the flow and trapping offluids in the rocks. Such resolutions cannot be achieved with existingtomographic technologies. A new 3D imaging method, based on serialsectioning and using the Focused Ion Beam (FIB) technology has beendeveloped. FIB allows for the milling of layers as thin as 10 nanometersby using accelerated Ga+ ions to sputter atoms from the sample surface.After each milling step, as a new surface is exposed, a 2D image of thissurface is generated. Next, the 2D images are stacked to reconstruct the3D pore or grain structure. Resolutions as high as 10 nm are achievableusing this technique. A new image processing method uses directmorphological analysis of the pore space to characterize thepetrophysical properties of diverse formations. In addition to estimationof the petrophysical properties (porosity, permeability, relativepermeability and capillary pressures), the method is used for simulationof fluid displacement processes, such as those encountered in variousimproved oil recovery (IOR) approaches. Computed with the new methodcapillary pressure curves are in good agreement with laboratory data. Themethod has also been applied for visualization of the fluid distributionat various saturations …
Date: August 23, 2005
Creator: Tomutsa, Liviu; Silin, Dmitriy & Radmilovich, Velimir
System: The UNT Digital Library
Effect of Shock Compression Method on the Defect Substructure in Monocrystalline Copper (open access)

Effect of Shock Compression Method on the Defect Substructure in Monocrystalline Copper

Monocrystalline copper samples with orientations of [001] and [221] were shocked at pressures ranging from 20 GPa to 60 GPa using two techniques: direct drive lasers and explosively driven flyer plates. The pulse duration for these techniques differed substantially: 40 ns for the laser experiments at 0.5 mm into the sample and 1.1 {approx} 1.4 {micro}s for the flyer-plate experiments at 5 mm into the sample. The residual microstructures were dependent on orientation, pressure, and shocking method. The much shorter pulse duration in the laser driven shock yielded microstructures closer to the ones generated at the shock front. For the flyer-plate experiments, the longer pulse duration allows shock-generated defects to reorganize into lower energy configurations. Calculations show that the post-shock cooling for the laser driven shock is 10{sup 3} {approx} 10{sup 4} faster than that for plate-impact shock, propitiating recovery and recrystallization conditions for the latter. At the higher pressure level, extensive recrystallization was observed in the plate-impact samples, while it was absent in the laser driven shock. An effect that is proposed to contribute significantly to the formation of recrystallized regions is the existence of micro-shear-bands, which increase the local temperature beyond the prediction from adiabatic compression.
Date: September 23, 2005
Creator: Cao, B. Y.; Lassila, D. H.; Schneider, M. S.; Kad, B. K.; Huang, C. X.; Xu, Y. B. et al.
System: The UNT Digital Library
PIMC Simulation of Ps Annihilation: From Micro to Mesopores (open access)

PIMC Simulation of Ps Annihilation: From Micro to Mesopores

Path Integral Monte Carlo (PIMC) can reproduce the results of simple analytical calculations in which a single quantum particle is used to represent positronium within an idealized, spherical pore. Our calculations improve on this approach by explicitly treating the positronium as a two-particle e{sup -}, e{sup +} system interacting via the Coulomb interaction. We study the lifetime and the internal contact density, {kappa}, which controls the self-annihilation behavior, for positronium in model spherical pores, as a function of temperature and pore size. We compare the results with both PIMC and analytical calculations for a single-particle model.
Date: August 23, 2005
Creator: Bug, A. R. & Sterne, P. A.
System: The UNT Digital Library
A QSAR for the Mutagenic Potencies of Twelve 2-Amino-trimethylimidazopyridine Isomers: Structural, Quantum Chemical,and Hydropathic Factors (open access)

A QSAR for the Mutagenic Potencies of Twelve 2-Amino-trimethylimidazopyridine Isomers: Structural, Quantum Chemical,and Hydropathic Factors

An isomeric series of heterocyclic amines related to one found in heated muscle meats was investigated for properties that predict their measured mutagenic potency. Eleven of the 12 possible 2-amino-trimethylimidazopyridine (TMIP) isomers were tested for mutagenic potency in the Ames/Salmonella test with bacterial strain TA98, and resulted in a 600-fold range in potency. Structural, quantum chemical and hydropathic data were calculated on the parent molecules and the corresponding nitrenium ions of all of the tested isomers to establish models for predicting the potency of the unknown isomer. The regression model accounting for the largest fraction of the total variance in mutagenic potency contains four predictor variables: dipole moment, a measure of the gap between amine LUMO and HOMO energies, percent hydrophilic surface, and energy of amine LUMO. The most important determinants of high mutagenic potency in these amines are: (1) a small dipole moment, (2) the combination of b-face ring fusion and N3-methyl group, and (3) a lower calculated energy of the {pi} electron system. Based on predicted potency from the average of five models, the isomer not yet synthesized and tested is expected to have a mutagenic potency of 0.84 revertants/{micro}g in test strain TA98.
Date: April 23, 2005
Creator: Knize, M G; Hatch, F T; Tanga, M J; Lau, E V & Colvin, M E
System: The UNT Digital Library
DIRECT OBSERVATION OF THE ALPHA-EPSILON TRANSITION IN SHOCKED SINGLE CRYSTAL IRON (open access)

DIRECT OBSERVATION OF THE ALPHA-EPSILON TRANSITION IN SHOCKED SINGLE CRYSTAL IRON

In-situ x-ray diffraction was used to study the response of single crystal iron under shock conditions. Measurements of the response of [001] iron showed a uniaxial compression of the initially bcc lattice along the shock direction by up to 6% at 13 GPa. Above this pressure, the lattice responded with a further collapse of the lattice by 15-18% and a transformation to a hcp structure. The in-situ measurements are discussed and results summarized.
Date: August 23, 2005
Creator: Kalantar, D H; Collins, G W; Colvin, J D; Davies, H M; Eggert, J H; Hawreliak, J et al.
System: The UNT Digital Library
Muon G-2 and Electric Dipole Moments in Storage Rings: Powerful Probes of Physics Beyond the Standard Model. (open access)

Muon G-2 and Electric Dipole Moments in Storage Rings: Powerful Probes of Physics Beyond the Standard Model.

We have shown that the study of dipole moments, both magnetic and electric, in storage rings offer unique opportunities in probing physics beyond the Standard Model (SM). Both methods use similar techniques (particle and spin precession in magnetic storage rings). We are currently investigating the systematic errors associated with the resonance electric dipole moment (EDM) method. So far it looks very promising.
Date: May 23, 2005
Creator: Semertzidis, Y. K.
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
Evidence for the Spectroscopic Signature of Aging in (delta)-Pu(Ga) (open access)

Evidence for the Spectroscopic Signature of Aging in (delta)-Pu(Ga)

Plutonium, because of its radioactive nature, ages from the 'inside out' by means of self-irradiation damage and thus produces nanoscale internal defects. The self-irradiation induced defects come in the form of Frenkel-type defects (vacancies and self-interstitial atoms), helium in-growth, and defect clusters. At present there are neither experimental nor theoretical models describing the changes in the electronic structure caused by the aging in Pu. This fact appears to be associated primarily with the absence of reasonably convincing spectroscopic evidence of the changes. This paper demonstrates that Resonant Photoemission, a variant of Photoelectron Spectroscopy, has strong sensitivity to aging of Pu samples. The spectroscopic results are correlated with an extra-atomic screening model [1], and are shown to be the fingerprint of mesoscopic or nanoscale internal damage in the Pu physical structure. This means that a spectroscopic signature of internal damage due to aging in Pu has been established.
Date: November 23, 2005
Creator: Chung, B. W.; Schwartz, A. J.; Ebbinghaus, B. B.; Fluss, M. J.; Haslam, J. J.; Blobaum, K. M. et al.
System: The UNT Digital Library
Reference Material for Radionuclides in Sediment, IAEA-384 (Fangataufa Lagoon Sediment) (open access)

Reference Material for Radionuclides in Sediment, IAEA-384 (Fangataufa Lagoon Sediment)

The IAEA Marine Environment Laboratory (IAEA-MEL) in Monaco has conducted intercomparison exercises on radionuclides in marine samples for many years as part of its contribution to the IAEA's program of Analytical Quality Control Services (AQCS). An important part of the AQCS program has been a production of Reference Materials (RMs) and their provision to radioanalytical laboratories. The RMs have been developed for different marine matrices (sediment, water, biota), with accuracy and precision required for the present state of the art of radiometrics and mass spectrometry methods. The RMs have been produced as the final products of world-wide intercomparison exercises organized during last 30 years. A total of 44 intercomparison exercises were undertaken and 39 RMs were produced for radionuclides in the marine environment. All required matrices (seawater, biota, sediment) have been covered with radionuclide concentrations ranging from typical environmental levels to elevated levels affected by discharges from nuclear reprocessing plants. The long-term availability of RMs (over 10 years) requires the use of very specific techniques to collect and pretreat large quantities of material (e.g., in excess of 100 kg) in order to ensure sample stability and homogenization of any analytes of interest. The production of a RM is therefore a …
Date: September 23, 2005
Creator: Povinec, P. P.; Pham, M. K.; Barci-Funel, G.; Bojanawski, R.; Boshkova, T.; Burnett, W. et al.
System: The UNT Digital Library
Last Annotation of Fugu rubripes at JGI (open access)

Last Annotation of Fugu rubripes at JGI

None
Date: November 23, 2005
Creator: Salamov, A.; Putnam, N.; Terry, A.; Grigoriev, I.; Rokhsar, D.; Loh, E. et al.
System: The UNT Digital Library
Development of an Explosive Bonding Process for Producing High Strength Bonds between Niobium and 6061-T651 Aluminum (open access)

Development of an Explosive Bonding Process for Producing High Strength Bonds between Niobium and 6061-T651 Aluminum

An explosive bonding procedure for joining 9.5 mm thick niobium plate to 203 mm thick 6061-T651 Al plate has been developed in order to maximize the bond tensile and impact strengths and the amount of bonded material across the surface of the plate. This procedure improves upon previous efforts, in which the 9.5 mm thick niobium plate is bonded directly to 6061-T4 Al plate. In this improved procedure, thin Nb and Al interlayers are explosively clad between the thicker niobium and aluminum plates. Bonds produced using these optimized parameters display a tensile strength of approximately 255 MPa and an impact strength per unit area of approximately 0.148 J/mm{sup 2}. Specialized mechanical testing geometries and procedures are required to measure these bond properties because of the unique bond geometry. In order to ensure that differences in the thermal expansion coefficients of aluminum and niobium do not adversely affect the bond strength, the effects of thermal cycling at temperatures between -22 C and 45 C on the mechanical properties of these bonds have also been investigated by testing samples in both the as-received and thermal cycled conditions. Based on the results obtained from this series of mechanical tests, thermal cycling is shown …
Date: September 23, 2005
Creator: Palmer, T A; Elmer, J W; Brasher, D; Butler, D & Riddle, R
System: The UNT Digital Library
A High-Order Accurate Parallel Solver for Maxwell's Equations on Overlapping Grids (open access)

A High-Order Accurate Parallel Solver for Maxwell's Equations on Overlapping Grids

A scheme for the solution of the time dependent Maxwell's equations on composite overlapping grids is described. The method uses high-order accurate approximations in space and time for Maxwell's equations written as a second-order vector wave equation. High-order accurate symmetric difference approximations to the generalized Laplace operator are constructed for curvilinear component grids. The modified equation approach is used to develop high-order accurate approximations that only use three time levels and have the same time-stepping restriction as the second-order scheme. Discrete boundary conditions for perfect electrical conductors and for material interfaces are developed and analyzed. The implementation is optimized for component grids that are Cartesian, resulting in a fast and efficient method. The solver runs on parallel machines with each component grid distributed across one or more processors. Numerical results in two- and three-dimensions are presented for the fourth-order accurate version of the method. These results demonstrate the accuracy and efficiency of the approach.
Date: September 23, 2005
Creator: Henshaw, W D
System: The UNT Digital Library
Towards Understanding the Mechanism of PETN Coarsening (open access)

Towards Understanding the Mechanism of PETN Coarsening

The long-term goal is to determine the mechanism of PETN crystallization and coarsening at the solid-vapor interface and to quantify the thermodynamic and kinetic parameters that control those processes. We achieve this goal by investigating the surface evolution of synthetic PETN single crystals using in situ atomic force microscopy (AFM) at various temperatures.
Date: March 23, 2005
Creator: Qiu, R.; Overturf, G.; Gee, R.; Burnham, A.; Weeks, B. & De Yoreo, J.
System: The UNT Digital Library
An assumed partition algorithm for determining processor inter-communication (open access)

An assumed partition algorithm for determining processor inter-communication

The recent advent of parallel machines with tens of thousands of processors is presenting new challenges for obtaining scalability. A particular challenge for large-scale scientific software is determining the inter-processor communications required by the computation when a global description of the data is unavailable or too costly to store. We present a type of rendezvous algorithm that determines communication partners in a scalable manner by assuming the global distribution of the data. We demonstrate the scaling properties of the algorithm on up to 32,000 processors in the context of determining communication patterns for a matrix-vector multiply in the hypre software library. Our algorithm is very general and is applicable to a variety of situations in parallel computing.
Date: September 23, 2005
Creator: Baker, A H; Falgout, R D & Yang, U M
System: The UNT Digital Library
Review of U.S. Neutrino Factory Studies (open access)

Review of U.S. Neutrino Factory Studies

We summarize the status of the two U.S. feasibility studies carried out by the Neutrino Factory and Muon Collider Collaboration (NFMCC) along with recent improvements to Neutrino Factory design developed during the American Physical Society (APS) Neutrino Physics Study. Suggested accelerator topics for the International Scoping Study (ISS) are also indicated.
Date: August 23, 2005
Creator: Zisman, Michael S.
System: The UNT Digital Library
Young organic matter as a source of carbon dioxide outgassing from Amazonian rivers (open access)

Young organic matter as a source of carbon dioxide outgassing from Amazonian rivers

Rivers are generally supersaturated with respect to carbon dioxide, resulting in large gas evasion fluxes that can be a significant component of regional net carbon budgets. Amazonian rivers were recently shown to outgas more than ten times the amount of carbon exported to the ocean in the form of total organic carbon or dissolved inorganic carbon. High carbon dioxide concentrations in rivers originate largely from in situ respiration of organic carbon, but little agreement exists about the sources or turnover times of this carbon. Here we present results of an extensive survey of the carbon isotope composition ({sup 13}C and {sup 14}C) of dissolved inorganic carbon and three size-fractions of organic carbon across the Amazonian river system. We find that respiration of contemporary organic matter (less than 5 years old) originating on land and near rivers is the dominant source of excess carbon dioxide that drives outgassing in mid-size to large rivers, although we find that bulk organic carbon fractions transported by these rivers range from tens to thousands of years in age. We therefore suggest that a small, rapidly cycling pool of organic carbon is responsible for the large carbon fluxes from land to water to atmosphere in the …
Date: June 23, 2005
Creator: Mayorga, E; Aufdenkampe, A K; Masiello, C A; Krusche, A V; Hedges, J I; Quay, P D et al.
System: The UNT Digital Library
Neutrino Factory Accelerator R&D: Status and Priorities (open access)

Neutrino Factory Accelerator R&D: Status and Priorities

This paper summarizes the status of worldwide Neutrino Factory R&D efforts. Activities are categorized as simulations, component development, and system tests. An indication of R&D tasks that remain to be accomplished is also given.
Date: August 23, 2005
Creator: Zisman, Michael S.
System: The UNT Digital Library
OpWise: Operons aid the identification of differentially expressedgenes in bacterial microarray experiments (open access)

OpWise: Operons aid the identification of differentially expressedgenes in bacterial microarray experiments

Differentially expressed genes are typically identified by analyzing the variation between replicate measurements. These procedures implicitly assume that there are no systematic errors in the data even though several sources of systematic error are known. Results-OpWise estimates the amount of systematic error in bacterial microarray data by assuming that genes in the same operon have matching expression patterns. OpWise then performs a Bayesian analysis of a linear model to estimate significance. In simulations, OpWise corrects for systematic error and is robust to deviations from its assumptions. In several bacterial data sets, significant amounts of systematic error are present, and replicate-based approaches overstate the confidence of the changers dramatically, while OpWise does not. Finally, OpWise can identify additional changers by assigning genes higher confidence if they are consistent with other genes in the same operon. Although microarray data can contain large amounts of systematic error, operons provide an external standard and allow for reasonable estimates of significance. OpWise is available at http://microbesonline.org/OpWise.
Date: November 23, 2005
Creator: Price, Morgan N.; Arkin, Adam P. & Alm, Eric J.
System: The UNT Digital Library
Monitored Energy Performance of Electrochromic Windows Controlledfor Daylight and Visual Comfort (open access)

Monitored Energy Performance of Electrochromic Windows Controlledfor Daylight and Visual Comfort

A 20-month field study was conducted to measure the energy performance of south-facing large-area tungsten-oxide absorptive electrochromic (EC) windows with a broad switching range in a private office setting. The EC windows were controlled by a variety of means to bring in daylight while minimizing window glare. For some cases, a Venetian blind was coupled with the EC window to block direct sun. Some tests also involved dividing the EC window wall into zones where the upper EC zone was controlled to admit daylight while the lower zone was controlled to prevent glare yet permit view. If visual comfort requirements are addressed by EC control and Venetian blinds, a 2-zone EC window configuration provided average daily lighting energy savings of 10 {+-} 15% compared to the reference case with fully lowered Venetian blinds. Cooling load reductions were 0 {+-} 3%. If the reference case assumes no daylighting controls, lighting energy savings would be 44 {+-} 11%. Peak demand reductions due to window cooling load, given a critical demand-response mode, were 19-26% maximum on clear sunny days. Peak demand reductions in lighting energy use were 0% or 72-100% compared to a reference case with and without daylighting controls, respectively. Lighting energy …
Date: September 23, 2005
Creator: Lee, Eleanor S.; DiBartolomeo, Dennis L.; Klems, Joseph; Yazdanian, Mehry & Selkowitz, Stephen E.
System: The UNT Digital Library