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Annealing, lattice disorder and non-Fermi liquid behavior in UCu4Pd

Description: The magnetic and electronic properties of non-Fermi liquid UCu{sub 4Pd} depend on annealing conditions. Local structural changes due to this annealing are reported from UL{sub III}- and Pd K-edge x-ray absorption fine-structure measurements. In particular, annealing decreases the fraction of Pd atoms on nominally Cu 16e sites and the U-Cu pair-distance distribution width. This study provides quantitative information on the amount of disorder in UCu{sub 4Pd} and allows an assessment of its possible importance to the observed non-Fermi liquid behavior.
Date: July 30, 2002
Creator: Booth, C.H.; Scheidt, E.-W.; Killer, U.; Weber, A. & Kehrein, S.
Partner: UNT Libraries Government Documents Department

Annotating animal mitochondrial tRNAs: A new scoring scheme and an empirical evaluation of four methods

Description: Identification of transfer RNAs in animal mitochondrial genomes is important for many areas of genome analysis including phylogenetic reconstruction, understanding inheritance of disease, and identifying forensic materials. Animal mitochondrial tRNAs differ from the canonical tRNAs in both their secondary structure and level of conservation of nucleotide sequence and therefore, conventional tRNA or general RNA searching software cannot be used for identification and custom methods are required. Here we present the results of an experimental analysis of four different methods tested on a large dataset consisting of 5,720 tRNAs extracted from the entire set of complete animal mitochondrial genomes in GenBank. Methods were evaluated based on number of false negatives and false positives. Additionally, we present a new scoring scheme customized for animal mitochondrial tRNAs.
Date: December 31, 2003
Creator: Wyman, Stacia K. & Boore, Jeffrey L.
Partner: UNT Libraries Government Documents Department

Anodic polymerization of vinyl ethylene carbonate in Li-Ion battery electrolyte

Description: A study of the anodic oxidation of vinyl ethylene carbonate (VEC) was conducted with post-mortem analysis of reaction products by ATR-FTIR and gel permeation chromatography (GPC). The half-wave potential (E1/2) for oxidation of VEC is ca. 3.6 V producing a resistive film on the electrode surface. GPC analysis of the film on a gold electrode produced by anodization of a commercial Li-ion battery electrolyte containing 2 percent VEC at 4.1 V showed the presence of a high molecular weight polymer. IR analysis indicated polycarbonate with alkyl carbonate rings linked by aliphatic methylene and methyl branches.
Date: February 28, 2005
Creator: Chen, Guoying; Zhuang, Guorong V.; Richardson, Thomas J.; Gao, Liu & Ross Jr., Philip N.
Partner: UNT Libraries Government Documents Department

Antenna-coupled arrays of voltage-biased superconducting bolometers

Description: We report on the development of antenna-coupled Voltage-biased Superconducting Bolometers (VSBs) which use Transition-edge Sensors (TES). Antenna coupling can greatly simplify the fabrication of large multi-frequency bolometer arrays compared to horn-coupled techniques. This simplification can make it practical to implement 1000+ element arrays that fill the focal plane of mm/sub-mm wave telescopes. We have designed a prototype device with a double-slot dipole antenna, integrated band-defining filters, and a membrane-suspended bolometer. A test chip has been constructed and will be tested shortly.
Date: July 23, 2001
Creator: Myers, Michael J.; Lee, Adrian T.; Richards, P.L.; Schwan, D.; Skidmore, J.T.; Smith, A.D. et al.
Partner: UNT Libraries Government Documents Department

Antinucleus productions at RHIC

Description: Light antinuclei may be formed in relativistic heavy ion collisions via final state coalescence of antinucleons. The yields of antinuclei are sensitive to primordial antinucleon production, the volume of the system at kinetic freeze-out, and space-momentum correlations among antinucleons at freeze-out. We report here preliminary STAR results on {bar d} and {bar {sup 3}He} production in 130A GeV Au+Au collisions. These results are examined in a coalescence framework to elucidate the space-time structure of the antinucleon source.
Date: May 1, 2001
Creator: Hardtke, D. & Collaboration, STAR
Partner: UNT Libraries Government Documents Department

Apacheta, a new geothermal prospect in Northern Chile

Description: The discovery of two high-temperature fumaroles, with gas geochemistry compatible with an economic geothermal system, established Apacheta as one of the most attractive geothermal exploration prospects in northern Chile. These remote fumaroles at 5,150 m elevation were first sampled in 1999 by ENAP and its partners, following up on the reports of a CODELCO water exploration well that flowed small amounts of dry steam at 4,540 m elevation in the valley 4.5 km east of the fumaroles. The prospect is associated with a Plio-Pleistocene volcanic complex located within a NW-trending graben along the axis of the high Andes. The regional water table is 4,200 masl. There are no hot springs, just the 88 degrees C steam well and the 109 degrees and 118 degrees C fumaroles with gas compositions that indicate reservoir temperatures of greater than or equal to 250 degrees C, using a variety of gas geothermometers. An MT-TDEM survey was completed in 2001-2002 by Geotermica del Norte (SDN), an ENAP-C ODELCO partnership, to explore the Apacheta geothermal concession. The survey results indicated that base of the low resistivity clay cap has a structural apex just west of the fumaroles, a pattern typically associated with shallow permeability within a high temperature geothermal resource. SGN plans to drill at least one exploration well in 2002-03 to characterize a possible economic resource at Apacheta.
Date: May 24, 2002
Creator: Urzua, Luis; Powell, Tom; Cumming, William B. & Dobson, Patrick
Partner: UNT Libraries Government Documents Department

Aperture studies for the AP2 anti-proton Line at Fermilab

Description: The AP2 beamline transports anti-protons from the production target to the Debuncher ring. For many years the observed aperture has been smaller than that estimated from linear, on-energy optics. We have investigated possible reasons for the aperture restriction and have identified several possible sources, including residual vertical dispersion from alignment errors and chromatic effects due to very large chromatic lattice functions. We discuss the possible sources, suggest some remedies, and propose specific studies, where needed, to evaluate suspected problems.
Date: December 5, 2003
Creator: Reichel, Ina; Zisman, Michael & Placidi, Massimo
Partner: UNT Libraries Government Documents Department

Apolipoprotein AIF gene variant S347 is associated with increased risk of coronary heart disease and lower apolipoprotein AIV plasma concentrations

Description: The impact of common variants in the apolipoprotein gene cluster (APOC3-A4-A5) on prospective CHD risk was examined in healthy UK men. Of the 2808 men followed over nine years, 187 had a clinically defined CHD event. Examination of 9 single nucleotide polymorphisms (SNPs) in this group revealed that homozygotes for APOA4 S347 had significantly increased risk of CHD [Hazard ratio (HR) of 2.07 (95%CI 1.04-4.12)] while men homozygous for APOC3 1100T were protected (HR 0.28 (95%CI 0.09-0.87)). In stepwise multiple regression analysis, after entering all the variants and adjusting for established risk factors APOA4 T347S alone remained in the model. Using nine-SNP haplotype analysis, highest risk-estimate haplotypes carried APOA4 S347 and rare alleles of the two flanking intergenic markers. The protective effect of APOC31100T could be explained by negative linkage disequilibrium with these alleles. To determine the association of APOA4 T347S with apoAIVlevels, the relationship was examined in over 1600 healthy young European men and women. S347 homozygotes had significantly lower apoAIV plasma levels (13.48 + 0.6mg/dl) compared to carriers of the T347 allele (14.85 + 0.12 mg/dl) (p=0.025). These results demonstrate that genetic variation in and around APOA4, independent of effects of TG, is associated with risk of CHD and apoAIV levels, supporting an anti-atherogenic role for apoAIV.
Date: January 30, 2003
Creator: Wong, Wai-man R.; Hawe, Emma; Li, Lai K.; Miller, George J.; Nicaud, Viviane; Pennacchio, Len A. et al.
Partner: UNT Libraries Government Documents Department

Application of adaptive mesh refinement to particle-in-cell simulations of plasmas and beams

Description: Plasma simulations are often rendered challenging by the disparity of scales in time and in space which must be resolved. When these disparities are in distinctive zones of the simulation domain, a method which has proven to be effective in other areas (e.g. fluid dynamics simulations) is the mesh refinement technique. We briefly discuss the challenges posed by coupling this technique with plasma Particle-In-Cell simulations, and present examples of application in Heavy Ion Fusion and related fields which illustrate the effectiveness of the approach. We also report on the status of a collaboration under way at Lawrence Berkeley National Laboratory between the Applied Numerical Algorithms Group (ANAG) and the Heavy Ion Fusion group to upgrade ANAG's mesh refinement library Chombo to include the tools needed by Particle-In-Cell simulation codes.
Date: November 4, 2003
Creator: Vay, J.-L.; Colella, P.; Kwan, J.W.; McCorquodale, P.; Serafini, D.B.; Friedman, A. et al.
Partner: UNT Libraries Government Documents Department

Application of automatic differentiation for the simulation of nonisothermal, multiphase flow in geothermal reservoirs

Description: Simulation of nonisothermal, multiphase flow through fractured geothermal reservoirs involves the solution of a system of strongly nonlinear algebraic equations. The Newton-Raphson method used to solve such a nonlinear system of equations requires the evaluation of a Jacobian matrix. In this paper we discuss automatic differentiation (AD) as a method for analytically computing the Jacobian matrix of derivatives. Robustness and efficiency of the AD-generated derivative codes are compared with a conventional derivative computation approach based on first-order finite differences.
Date: January 8, 2002
Creator: Kim, Jong G. & Finsterle, Stefan
Partner: UNT Libraries Government Documents Department

Application of automatic differentiation in TOUGH2

Description: Automatic differentiation (AD) is a way to accurately and efficiently compute derivatives of a function written in computer codes. We describe the procedures necessary to apply the AD method to the multiphase, multicomponent, nonisothermal flow simulator TOUGH2. In particular, we apply the AD method to the ECO2 module of the TOUGH2 code to explore a scheme for efficiently calculating the Jacobian matrix, which is required by the Newton-Raphson method for handling the nonlinearities arising at each iteration. The ECO2 module allows TOUGH2 to accurately simulate CO2 sequestration in aquifers. The robustness and efficiency of the AD-generated derivative codes are compared to the conventional derivative computation approach based on first-order finite differences (FD). Our result with the test problem set indicates that the AD-generated derivative code could improve the convergence behavior in the linear solution step, taking less computational time to compute one linear matrix system.
Date: May 12, 2003
Creator: Kim, Jong G. & Finsterle, Stefan
Partner: UNT Libraries Government Documents Department

Adaptive dimension reduction for clustering high dimensional data

Description: It is well-known that for high dimensional data clustering, standard algorithms such as EM and the K-means are often trapped in local minimum. many initialization methods were proposed to tackle this problem, but with only limited success. In this paper they propose a new approach to resolve this problem by repeated dimension reductions such that K-means or EM are performed only in very low dimensions. Cluster membership is utilized as a bridge between the reduced dimensional sub-space and the original space, providing flexibility and ease of implementation. Clustering analysis performed on highly overlapped Gaussians, DNA gene expression profiles and internet newsgroups demonstrate the effectiveness of the proposed algorithm.
Date: October 1, 2002
Creator: Ding, Chris; He, Xiaofeng; Zha, Hongyuan & Simon, Horst
Partner: UNT Libraries Government Documents Department

Adaptive low mach number simulations of a premixed turbulent laboratory burner

Description: A parallel adaptive low Mach number model is used to study an experimental lean premixed turbulent methane V-flame that is stabilized on a rod spanning the exit plane of a circular nozzle. The fuel is turbulent due to an upstream perforated-plate, and the resulting flame extends downstream of the rod. We present three-dimensional time-dependent simulations of this configuration. The computations incorporate detailed reaction chemistry and transport using a dynamically adaptive block-structured grid algorithm and a time-split integration procedure. Flow field and flame surface statistics are gathered from the experiment and are compared to the computed results.
Date: October 20, 2003
Creator: Day, M.S.; Bell, J.B.; Lijewski, M.J.; Johnson, M.; Cheng, R.K. & Shepherd, I.G.
Partner: UNT Libraries Government Documents Department

Adaptive low Mach number simulations of nuclear flame microphysics

Description: We introduce a numerical model for the simulation of nuclear flames in Type Ia supernovae. This model is based on a low Mach number formulation that analytically removes acoustic wave propagation while retaining the compressibility effects resulting from nuclear burning. The formulation presented here generalizes low Mach number models used in combustion that are based on an ideal gas approximation to the arbitrary equations of state such as those describing the degenerate matter found in stellar material. The low Mach number formulation permits time steps that are controlled by the advective time scales resulting in a substantial improvement in computational efficiency compared to a compressible formulation. We briefly discuss the basic discretization methodology for the low Mach number equations and their implementation in an adaptive projection framework. We present validation computations in which the computational results from the low Mach number model are compared to a compressible code and present an application of the methodology to the Landau-Darrieus instability of a carbon flame.
Date: March 20, 2003
Creator: Bell, J.B.; Day, M.S.; Rendleman, C.A.; Woosley, S.E. & Zingale, M.A.
Partner: UNT Libraries Government Documents Department

Adaptive mesh refinement in titanium

Description: In this paper, we evaluate Titanium's usability as a high-level parallel programming language through a case study, where we implement a subset of Chombo's functionality in Titanium. Chombo is a software package applying the Adaptive Mesh Refinement methodology to numerical Partial Differential Equations at the production level. In Chombo, the library approach is used to parallel programming (C++ and Fortran, with MPI), whereas Titanium is a Java dialect designed for high-performance scientific computing. The performance of our implementation is studied and compared with that of Chombo in solving Poisson's equation based on two grid configurations from a real application. Also provided are the counts of lines of code from both sides.
Date: January 21, 2005
Creator: Colella, Phillip & Wen, Tong
Partner: UNT Libraries Government Documents Department

Adding static printing capabilities to the EUV phase-shifting point diffraction interferometer

Description: While interferometry is routinely used for the characterization and alignment of lithographic optics, the ultimate performance metric for these optics is printing in photoresist. Direct comparison of imaging and wavefront performance is also useful for verifying and improving the predictive power of wavefront metrology under actual printing conditions. To address these issues, static, small-field printing capabilities are being added to the extreme ultraviolet (EUV) phase-shifting point diffraction interferometer (PS/PDI) implemented at the Advanced Light Source at Lawrence Berkeley National Laboratory. This Sub-field Exposure Station (SES) will enable the earliest possible imaging characterization of the upcoming Engineering Test Stand (ETS) Set-2 projection optics. Relevant printing studies with the ETS projection optics require illumination partial coherence with {sigma} of approximately 0.7. This {sigma} value is very different from the coherent illumination requirements of the EUV PS/PDI and the coherence properties naturally provided by synchrotron undulator beamline illumination. Adding printing capabilities to the PS/PDI experimental system thus necessitates the development of an alternative illumination system capable of destroying the inherent coherence of the beamline. The SES is being implemented with two independent illuminators: the first is based on a novel EUV diffuser currently under development and the second is based on a scanning mirror design. Here we describe the design and implementation of the new SES, including a discussion of the illuminators and the fabrication of the EUV diffuser.
Date: March 1, 2001
Creator: Naulleau, Patrick; Goldberg, Kenneth A.; Anderson, Erik H.; Batson, Phillip; Denham, Paul; Jackson, Keith et al.
Partner: UNT Libraries Government Documents Department

The advanced computational testing and simulation toolkit (ACTS)

Description: During the past decades there has been a continuous growth in the number of physical and societal problems that have been successfully studied and solved by means of computational modeling and simulation. Distinctively, a number of these are important scientific problems ranging in scale from the atomic to the cosmic. For example, ionization is a phenomenon as ubiquitous in modern society as the glow of fluorescent lights and the etching on silicon computer chips; but it was not until 1999 that researchers finally achieved a complete numerical solution to the simplest example of ionization, the collision of a hydrogen atom with an electron. On the opposite scale, cosmologists have long wondered whether the expansion of the Universe, which began with the Big Bang, would ever reverse itself, ending the Universe in a Big Crunch. In 2000, analysis of new measurements of the cosmic microwave background radiation showed that the geometry of the Universe is flat, and thus the Universe will continue expanding forever. Both of these discoveries depended on high performance computer simulations that utilized computational tools included in the Advanced Computational Testing and Simulation (ACTS) Toolkit. The ACTS Toolkit is an umbrella project that brought together a number of general purpose computational tool development projects funded and supported by the U.S. Department of Energy (DOE). These tools, which have been developed independently, mainly at DOE laboratories, make it easier for scientific code developers to write high performance applications for parallel computers. They tackle a number of computational issues that are common to a large number of scientific applications, mainly implementation of numerical algorithms, and support for code development, execution and optimization. The ACTS Toolkit Project enables the use of these tools by a much wider community of computational scientists, and promotes code portability, reusability, reduction of duplicate efforts, and ...
Date: May 21, 2002
Creator: Drummond, L.A. & Marques, O.
Partner: UNT Libraries Government Documents Department

Advanced Duct Sealing Testing

Description: Duct leakage has been identified as a major source of energy loss in residential buildings. Most duct leakage occurs at the connections to registers, plenums or branches in the duct system. At each of these connections a method of sealing the duct system is required. Typical sealing methods include tapes or mastics applied around the joints in the system. Field examinations of duct systems have typically shown that these seals tend to fail over extended periods of time. The Lawrence Berkeley National Laboratory has been testing sealant durability for several years. Typical duct tape (i.e. fabric backed tapes with natural rubber adhesives) was found to fail more rapidly than all other duct sealants. This report summarizes the results of duct sealant durability testing of five UL 181B-FX listed duct tapes (three cloth tapes, a foil tape and an Oriented Polypropylene (OPP) tape). One of the cloth tapes was specifically developed in collaboration with a tape manufacturer to perform better in our durability testing. The first test involved the aging of common ''core-to-collar joints'' of flexible duct to sheet metal collars, and sheet metal ''collar-to-plenum joints'' pressurized with 200 F (93 C) air. The second test consisted of baking duct tape specimens in a constant 212 F (100 C) oven following the UL 181B-FX ''Temperature Test'' requirements. Additional tests were also performed on only two tapes using sheet metal collar-to-plenum joints. Since an unsealed flexible duct joint can have a variable leakage depending on the positioning of the flexible duct core, the durability of the flexible duct joints could not be based on the 10% of unsealed leakage criteria. Nevertheless, the leakage of the sealed specimens prior to testing could be considered as a basis for a failure criteria. Visual inspection was also documented throughout the tests. The flexible duct core-to-collar ...
Date: August 1, 2003
Creator: Sherman, Max H. & Walker, Iain S.
Partner: UNT Libraries Government Documents Department

Advanced Light Source Activity Report 2002

Description: This annual report of the Advanced Light Source details science highlights and facility improvements during the year. It also offers information on events sponsored by the facility, technical specifications, and staff and publication information.
Date: June 12, 2003
Creator: Duque, Theresa; Greiner, Annette; Moxon, Elizabeth; Robinson, Arthur & Tamura, Lori (Editors)
Partner: UNT Libraries Government Documents Department

Surface electrochemistry of CO on Pt(111): Anion Effects

Description: In-situ studies of CO adsorption by surface x-ray scattering (SXS) and Fourier transform infrared (FTIR) spectroscopy techniques are used to create the link between the macroscopic kinetic rates of CO oxidation and the microscopic level of understanding the structure/site occupancy of CO on Pt(111). A remarkable difference in activity was observed between alkaline and acid solutions. In alkaline solution the oxidation of CO proceeds at low overpotential (<0.2 V) by the surface reaction between the adsorbed CO and OH, the latter forming selectively in the hydrogen underpotential potential region at defect sites. In acid solution these sites are blocked by specific adsorption of anions, and consequently in a solution containing Br{sup -} the ignition potential is shifted positively by 0.6 V. Anions of supporting electrolytes also have dramatic effects on both the potential range of stability and the domain size of the p(2x2)-3CO structure which is formed at 0.05 V. The stability/domain size of this structure increases from KOH (ca. 30 {angstrom} between 0.05 < E < 0.3V), to HClO{sub 4} (ca. 140 {angstrom} between 0.05 < E < 0.6V) to HClO{sub 4} + Br{sup -} (ca 350 {angstrom} between 0.05 < E < 0.8V). The larger the ordered domains of the p(2x2)-CO{sub ad} structure are, the less active the surface is towards CO oxidation.
Date: July 30, 2001
Creator: Markovic, N.M.; Lucas, C.A.; Rodes, A.; Stamenkovic, V. & Ross, P.N.
Partner: UNT Libraries Government Documents Department

Synchrotron-based investigations of the nature and impact of ironcontamination in multicrystalline silicon solar cell materials

Description: Synchrotron-based microprobe techniques were used to obtain precise and systematic information about the size distribution, spatial distribution, shape, electrical activity, and chemical states of iron-rich impurity clusters in multicrystalline silicon materials used for cost-effective solar cells. These experimentally observed properties of iron-rich clusters allow one to derive conclusions about the origins of iron contamination, the mechanisms for incorporating large amounts of Fe into mc-Si, quantitative information about the distribution of Fe in mc-Si and the impacts of such contamination on solar cell performance. Two distinct groups of iron-rich clusters have been identified in both materials: (a) the occasional large (diameter greater than or equal to 1 mu-m) particles, either oxidized and/or present with multiple other metal species reminiscent of stainless steels or ceramics, which are believed to originate from a foreign source such as the growth surfaces, production equipment, or feedstock, and (b) the more numerous, homogeneously distributed, and smaller iron silicide precipitates (dia. less than or equal to 800 nm, often < 100 nm), originating from a variety of possible formation mechanisms involving atomically dissolved iron in the melt or in the crystal. It was found that iron silicide nanoprecipitates account for bulk Fe concentrations as high as 1014-15cm-3 and can have a large negative impact on device performance because of their homogeneous distribution along structural defects. The large (dia. greater than or equal to 1 mu-m) particles, while containing elevated amounts of metals, are low in spatial density and thus deemed to have a low direct impact on device performance, although they may have a large indirect impact via the dissolution of Fe, thus assisting the formation of iron silicide nanoprecipitates. These results demonstrate that it is not necessarily the total Fe content that limits mc-Si device performance, but the distribution of Fe within the material.
Date: November 8, 2004
Creator: Buonassisi, Tonio; Istratov, Andrei A.; Heuer, Matthias; Marcus,Matthew A.; Jonczyk, Ralf; Lai, Barry et al.
Partner: UNT Libraries Government Documents Department

Synthesis ofN-(2-chloro-5-methylthiophenyl)-N'-(3-methyl-thiophenyl)-N'-[3H3]methylguanidine, l brace [3H3]CNS-5161 r brace

Description: The preparation of the title compound, [{sup 3}H{sub 3}]CNS-5161, was accomplished in three steps starting with the production of [{sup 3}H{sub 3}]iodomethane (CT{sub 3}I). The intermediate N-[{sup 3}H{sub 3}]methyl-3-(thiomethylphenyl)cyanamide was prepared in 77% yield by the addition of CT{sub 3}I to 3-(thiomethylphenyl)cyanamide, previously treated with sodium hydride. Reaction of this tritiated intermediate with 2-chloro-5-thiomethylaniline hydrochloride formed the guanidine compound [{sup 3}H{sub 3}]CNS-5161. Purification by HPLC gave the desired labeled product in an overall yield of 9% with greater than 96% radiochemical purity and a final specific activity of 66 Ci mmol{sup -1}.
Date: September 28, 2001
Creator: Gibbs, Andrew R.; Morimoto, Hiromi; VanBrocklin, Henry F.; Williams, Philip G. & Biegon, Anat
Partner: UNT Libraries Government Documents Department