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2005 Chemical Reactions at Surfaces (open access)

2005 Chemical Reactions at Surfaces

The Gordon Research Conference (GRC) on 2005 Chemical Reactions at Surfaces was held at Ventura Beach Marriott, Ventura California from February 13, 2005 through February 18, 2005. The Conference was well-attended with 124 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. In designing the formal speakers program, emphasis was placed on current unpublished research and discussion of the future target areas in this field. There was a conscious effort to stimulate lively discussion about the key issues in the field today. Time for formal presentations was limited in the interest of group discussions. In order that more scientists could communicate their most recent results, poster presentation time was scheduled. Attached is a copy of the formal schedule and speaker program and the poster program. In addition to these formal interactions, 'free time' was scheduled to allow informal discussions. Such discussions are fostering new collaborations and joint efforts in the field.
Date: March 14, 2006
Creator: Friend, Cynthia M.
System: The UNT Digital Library
2005 Radiation Oncology Gordon Research Conference (open access)

2005 Radiation Oncology Gordon Research Conference

This Report is about the Gordon Research Conference on Radiation Oncology Which was held at Crowne Plazza
Date: March 10, 2006
Creator: Gray, Elizabeth L. Travis Nancy Ryan
System: The UNT Digital Library
Adaptive Optics Imaging Survey of Luminous Infrared Galaxies (open access)

Adaptive Optics Imaging Survey of Luminous Infrared Galaxies

We present high resolution imaging observations of a sample of previously unidentified far-infrared galaxies at z < 0.3. The objects were selected by cross-correlating the IRAS Faint Source Catalog with the VLA FIRST catalog and the HST Guide Star Catalog to allow for adaptive optics observations. We found two new ULIGs (with L{sub FIR} {ge} 10{sup 12} L{sub {circle_dot}}) and 19 new LIGs (with L{sub FIR} {ge} 10{sup 11} L{sub {circle_dot}}). Twenty of the galaxies in the sample were imaged with either the Lick or Keck adaptive optics systems in H or K{prime}. Galaxy morphologies were determined using the two dimensional fitting program GALFIT and the residuals examined to look for interesting structure. The morphologies reveal that at least 30% are involved in tidal interactions, with 20% being clear mergers. An additional 50% show signs of possible interaction. Line ratios were used to determine powering mechanism; of the 17 objects in the sample showing clear emission lines--four are active galactic nuclei and seven are starburst galaxies. The rest exhibit a combination of both phenomena.
Date: March 13, 2006
Creator: Laag, E. A.; Canalizo, G.; van Breugel, W.; Gates, E. L.; de Vries, W. & Stanford, S. A.
System: The UNT Digital Library
Advances in HFE Methods and Their Implications for Regulatory Reviews. (open access)

Advances in HFE Methods and Their Implications for Regulatory Reviews.

There is renewed interest in the United States (U.S.) to construct new Generation III and III+ reactors within the next decade and Generation IV reactors in the future. Licensing by the U.S. Nuclear Regulatory Commission (NRC) is a significant consideration and these new plants may pose new challenges. One such challenge is the advances in human factors engineering (HFE) methods that are used. These methods are used to design and evaluate the HFE aspects of a plant, such as the human-system interface (HSI). These methods are important because NRC HFE reviews are design process oriented, thus, the criteria are mostly technology neutral with regard to reactor design.[1] However, the HFE review criteria are not neutral with respect to the HFE methods that are used as part of the design process This will be important for new reactor reviews because the diversity of reactor types, HSIs, and operational concepts will increase, especially for Generation III+ and IV plants. Thus the NRC is conducting research to identify advances in HFE methods and to develop additional guidance to address their review.
Date: March 21, 2006
Creator: O'hara, J.; Persensky, J. & Szabo, A.
System: The UNT Digital Library
Alternate Tunings for the Linac Coherent Light Source Photoinjector (open access)

Alternate Tunings for the Linac Coherent Light Source Photoinjector

The Linac Coherent Light Source (LCLS) is an x-ray free-electron laser (FEL) project based on the SLAC linac. The LCLS Photoinjector beamline has been designed to deliver 10-ps long electron bunches of 1 nC with a normalized projected transverse emittance smaller than 1.2 mm-mrad at 135 MeV. Tolerances and regulation requirements are tight for this tuning. Half of the total emittance at the end of the injector comes from the ''cathode emittance'' which is 0.7 mm-mrad for our nominal 1nC tuning. As the ''cathode emittance'' scales linearly with laser spot radius, the emittance will be dramatically reduced for smaller radius, but this is only possible at lower charge. In particular, for a 0.2 nC charge, we believe we can achieve an emittance closer to 0.4 mm-mrad. This working point will be easier to tune and the beam quality should be much easier to maintain than for the 1 nC case. In the second half of this paper, we discuss optimum laser pulse shapes. We demonstrate that the benefits of the ellipsoidal shapes seem to be important enough so that serious investigations should be carried out in the production of such pulses.
Date: March 17, 2006
Creator: Limborg-Deprey, C. & Emma, P.
System: The UNT Digital Library
Aluminosilicate Precipitation Impact on Uranium (open access)

Aluminosilicate Precipitation Impact on Uranium

Experiments have been conducted to examine the fate of uranium during the formation of sodium aluminosilicate (NAS) when wastes containing high aluminate concentrations are mixed with wastes of high silicate concentration. Testing was conducted at varying degrees of uranium saturation. Testing examined typical tank conditions, e.g., stagnant, slightly elevated temperature (50 C). The results showed that under sub-saturated conditions uranium is not removed from solution to any large extent in both simulant testing and actual tank waste testing. This aspect was not thoroughly understood prior to this work and was necessary to avoid criticality issues when actual tank wastes were aggregated. There are data supporting a small removal due to sorption of uranium on sites in the NAS. Above the solubility limit the data are clear that a reduction in uranium concentration occurs concomitant with the formation of aluminosilicate. This uranium precipitation is fairly rapid and ceases when uranium reaches its solubility limit. At the solubility limit, it appears that uranium is not affected, but further testing might be warranted.
Date: March 10, 2006
Creator: WILMARTH, WILLIAM
System: The UNT Digital Library
Analyses of Wind Energy Impact on WFEC System Operations: Preprint (open access)

Analyses of Wind Energy Impact on WFEC System Operations: Preprint

The National Renewable Energy Laboratory worked with the Western Farmers Electric Cooperative to analyze the impact of wind power from the Blue Canyon Wind Power Project on WFEC system operations.
Date: March 1, 2006
Creator: Wan, Y. & Liao, J. R.
System: The UNT Digital Library
Analysis of the causes of failure in high chrome oxide refractory materials from slagging gasifiers (open access)

Analysis of the causes of failure in high chrome oxide refractory materials from slagging gasifiers

High Cr2O3 refractory materials are used to line the hot face of slagging gasifiers. Gasifiers are reaction chambers that convert water, oxygen, and a carbon feedstock into CO, H2, and methane at temperatures as high as 1575oC and pressures up to 1000 psi. Ash in the carbon feedstock liquefies, erodes and corrodes the gasifier’s refractory liner, contributing to liner failure within a few months to two years. The failure of a refractory liner decreases a gasifier’s on-line availability and causes costly system downtime and repairs. Many factors contribute to refractory lining failure, including slag penetration and corrosion, thermal cycling, gasifier environment, and mechanical loads. The results of refractory post-mortem failure analysis and how observations relate to gasifier service life will be discussed.
Date: March 1, 2006
Creator: Bennett, J. P.; Kwong, K. -S.; Powell, C. A.; Thomas, H. & Krabbe, R. A.
System: The UNT Digital Library
Anodic Behavior of Alloy 22 in High Nitrate Brines at Temperatures Higher than 100(degree)C (open access)

Anodic Behavior of Alloy 22 in High Nitrate Brines at Temperatures Higher than 100(degree)C

Alloy 22 (N06022) may be susceptible to crevice corrosion in chloride solutions. Nitrate acts as an inhibitor to crevice corrosion. Several papers have been published regarding the effect of nitrate on the corrosion resistance of Alloy 22 at temperatures 100 C and lower. However, very little is known about the behavior of this alloy in highly concentrated brines at temperatures above 100 C. In the current work, electrochemical tests have been carried out to explore the anodic behavior of Alloy 22 in high chloride high nitrate electrolytes at temperatures as high as 160 C at ambient atmospheres. Even though Alloy 22 may adopt corrosion potentials in the order of +0.5 V (in the saturated silver chloride scale), it does not suffer crevice corrosion if there is high nitrate in the solution. That is, the inhibitive effect of nitrate on crevice corrosion is active for temperatures higher than 100 C.
Date: March 28, 2006
Creator: Ilevbare, G. O.; Etien, R. A.; Estill, J. C.; Hust, G. A.; Yilmaz, A.; Stuart, M. L. et al.
System: The UNT Digital Library
Application of a Dynamic Stress Theory to Pike Leaks (open access)

Application of a Dynamic Stress Theory to Pike Leaks

This report talks about Application of a Dynamic Stress Theory to Pike Leaks
Date: March 13, 2006
Creator: Leishear, Robert A.
System: The UNT Digital Library
The application of Tiny Triplet Finder (TTF) in BTeV pixel trigger (open access)

The application of Tiny Triplet Finder (TTF) in BTeV pixel trigger

We describe a track segment recognition scheme called the Tiny Triplet Finder (TTF) that involves grouping of three hits satisfying a constraint such as forming of a straight line. The TTF performs this O(n{sup 3}) function in O(n) time, where n is number of hits in each detector plane. The word ''tiny'' reflects the fact that the FPGA resource usage is small. The number of logic elements needed for the TTF is O(Nlog(N)), where N is the number of bins in the coordinate considered, which for large N, is significantly smaller than O(N{sup 2}) needed for typical implementations of similar functions. The TTF is also suitable for software implementations as well as many other pattern recognition problems.
Date: March 1, 2006
Creator: Wu, Jin-Yuan; Wang, M.; Gottschalk, E. & Shi, Z.
System: The UNT Digital Library
Applications of barrier bucket RF systems at Fermilab (open access)

Applications of barrier bucket RF systems at Fermilab

In recent years, the barrier rf systems have become important tools in a variety of beam manipulation applications at synchrotrons. Four out of six proton synchrotrons at Fermilab are equipped with broad-band barrier rf systems. All of the beam manipulations pertaining to the longitudinal phase space in the Fermilab Recycler (synchrotron used for antiproton storage) are carried out using a barrier system. Recently, a number of new applications of barrier rf systems have been developed- the longitudinal momentum mining, longitudinal phase-space coating, antiproton stacking, fast bunch compression and more. Some of these techniques have been critical for the recent spectacular success of the collider performance at the Fermilab Tevatron. Barrier bunch coalescing to produce bright proton bunches has a high potential to increase proton antiproton luminosity significantly. In this paper, I will describe some of these techniques in detail. Finally, I make a few general remarks on issues related to barrier systems.
Date: March 1, 2006
Creator: Bhat, C.M.
System: The UNT Digital Library
Autonomous UAV-Based Mapping of Large-Scale Urban Firefights (open access)

Autonomous UAV-Based Mapping of Large-Scale Urban Firefights

This paper describes experimental results from a live-fire data collect designed to demonstrate the ability of IR and acoustic sensing systems to detect and map high-volume gunfire events from tactical UAVs. The data collect supports an exploratory study of the FightSight concept in which an autonomous UAV-based sensor exploitation and decision support capability is being proposed to provide dynamic situational awareness for large-scale battalion-level firefights in cluttered urban environments. FightSight integrates IR imagery, acoustic data, and 3D scene context data with prior time information in a multi-level, multi-step probabilistic-based fusion process to reliably locate and map the array of urban firing events and firepower movements and trends associated with the evolving urban battlefield situation. Described here are sensor results from live-fire experiments involving simultaneous firing of multiple sub/super-sonic weapons (2-AK47, 2-M16, 1 Beretta, 1 Mortar, 1 rocket) with high optical and acoustic clutter at ranges up to 400m. Sensor-shooter-target configurations and clutter were designed to simulate UAV sensing conditions for a high-intensity firefight in an urban environment. Sensor systems evaluated were an IR bullet tracking system by Lawrence Livermore National Laboratory (LLNL) and an acoustic gunshot detection system by Planning Systems, Inc. (PSI). The results demonstrate convincingly the ability for …
Date: March 9, 2006
Creator: Snarski, S.; Scheibner, K. F.; Shaw, S.; Roberts, R. S.; LaRow, A.; Oakley, D. et al.
System: The UNT Digital Library
Beam Characterizations at Femtosecond Electron Beam Facility (open access)

Beam Characterizations at Femtosecond Electron Beam Facility

The SURIYA project at the Fast Neutron Research Facility (FNRF) has been established and is being commissioning to generate femtosecond (fs) electron bunches. Theses short bunches are produced by a system consisting of an S-band thermionic cathode RF-gun, an alpha magnet (a-magnet) serving as a magnetic bunch compressor, and a SLAC-type linear accelerator (linac). The characteristics of its major components and the beam characterizations as well as the preliminary experimental results will be presented and discussed in this paper.
Date: March 17, 2006
Creator: Rimjaem, S.; Jinamoon, V.; Kangrang, M.; Kusoljariyakul, K.; Saisut, J.; Thongbai, C. et al.
System: The UNT Digital Library
Beam Energy Scaling of Ion-Induced Electron Yield from K+ Impact on Stainless Steel (open access)

Beam Energy Scaling of Ion-Induced Electron Yield from K+ Impact on Stainless Steel

Electron clouds limit the performance of many major accelerators and storage rings. Significant quantities of electrons result when halo ions are lost to beam tubes, generating gas which can be ionized and ion-induced electrons that can multiply and accumulate, causing degradation or loss of the ion beam. In order to understand the physical mechanisms of ion-induced electron production, experiments studied the impact of 50 to 400 keV K{sup +} ions on stainless steel surfaces near grazing incidence, using the 500 kV Ion Source Test Stand (STS-500) at LLNL. The experimental electron yield scales with the electronic component (dE{sub e}/dx) of the stopping power and its angular dependence does not follow l/cos({theta}). A theoretical model is developed, using TRIM code to evaluate dE{sub e}/dx at several depths in the target, to estimate the electron yield, which is compared with the experimental results. The experiment extends the range of energy from previous works and the model reproduces the angular dependence and magnitude of the electron yield.
Date: March 6, 2006
Creator: Covo, M K; Molvik, A; Friedman, A; Westenskow, G; Barnard, J J; Cohen, R et al.
System: The UNT Digital Library
Beam interaction measurements with a Retarding Field Analyzer (open access)

Beam interaction measurements with a Retarding Field Analyzer

A Retarding Field Analyzer (RFA) was designed and inserted in a drift region of a magnetic transport section of the High Current Experiment (HCX). It measures ions or electrons resulting from the beam interaction with the background gas and walls. The ions are expelled during the beam by the space-charge beam potential, and the electrons are expelled mainly at the end of the beam, when the beam potential decays. The measured electrons have a Maxwellian energy distribution and the measured ions have an energy distribution that gives the information of the beam profile, details will be presented and discussed.
Date: March 28, 2006
Creator: Covo, M K; Molvik, A W; Friedman, A; Barnard, J J; Seidl, P; Logan, B G et al.
System: The UNT Digital Library
Beam Test Proposal of An ODR Beam Size Monitor at the SLAC FFTB (open access)

Beam Test Proposal of An ODR Beam Size Monitor at the SLAC FFTB

ODR (Optical Diffraction Radiation) transverse beam size measurement at the SLAC FFTB at 28.5 GeV is a challenge and it requires special target and optics system, which is much difficult than the conventional ODR beam size measurement. We propose to use a curved disphased conductive slit target to recover the sensitivity in the measurement of the single bunch transverse beam size by using ODR photons from a conductive slit. In order to cancel the effect of the beam divergence, the conductive slit target surface must be curved. Also, we can obtain the focused interference pattern of the ODR photons at the detector at the shorter distance from the target than the {gamma}{sup 2}{lambda}, by using lens optics system.
Date: March 14, 2006
Creator: Fukui, Y.; Cline, D.; Zhou, F.; /UCLA; Aryshev, A.; Karataev, P. et al.
System: The UNT Digital Library
Benefits of IEEE-754 features in modern symmetric tridiagonaleigensolvers (open access)

Benefits of IEEE-754 features in modern symmetric tridiagonaleigensolvers

Bisection is one of the most common methods used to compute the eigenvalues of symmetric tridiagonal matrices. Bisection relies on the Sturm count: For a given shift a, the number of negative pivots in the factorization T - {sigma}I = LDL{sup T} equals the number of eigenvalues of T that are smaller than a. In IEEE-754 arithmetic, the value oo permits the computation to continue past a zero pivot, producing a correct Sturm count when T is unreduced. Demmel and Li showed that using oo rather than testing for zero pivots within the loop could significantly improve performance on certain architectures. When eigenvalues are to be computed to high relative accuracy, it is often preferable to work with LDL{sup T} factorizations instead of the original tridiagonal T. One important example is the MRRR algorithm. When bisection is applied to the factored matrix, the Sturm count is computed from LDL{sup T} which makes differential stationary and progressive qds algorithms the methods of choice. While it seems trivial to replace T by LDL{sup T}, in reality these algorithms are more complicated: In IEEE-754 arithmetic, a zero pivot produces an overflow followed by an invalid exception (NaN, or 'Not a Number') that renders …
Date: March 12, 2006
Creator: Marques, Osni; Riedy, Jason E. & Vomel, Christof
System: The UNT Digital Library
A broadband high-resolution elliptical crystal x-ray spectrometer for high energy density physics experiments (open access)

A broadband high-resolution elliptical crystal x-ray spectrometer for high energy density physics experiments

Spectroscopic investigation of high temperature laser produced plasmas in general, and x-ray opacity experiments in particular, often requires instruments with both a broad coverage of x-ray energies and high spectral, spatial, and temporal resolution. We analyze the design, model the response, and report the commissioning of a spectrometer using elliptical crystals in conjunction with a large format, gated microchannel plate detector. Measurements taken with this instrument at the JANUS laser facilities demonstrate the designed spectral range of 0.24 to 5.8 keV, and spectral resolution E/{Delta}E > 500, resulting in 2 to 3 times more spectral data than achieved by previous spectrometer designs. The observed 100 picosecond temporal resolution and 35 {micro}m spatial resolution are consistent with the requirements of high energy density opacity experiments.
Date: March 31, 2006
Creator: Anderson, S G; Heeter, R F; Booth, R; Emig, J; Fulkerson, S; McCarville, T et al.
System: The UNT Digital Library
Capital night for movies and shakers (open access)

Capital night for movies and shakers

Article about the Texas Film Hall of Fame Awards dinner and other celebrations in the Houston, Texas area in March of 2006.
Date: March 13, 2006
Creator: Hodge, Shelby
System: The UNT Digital Library
Challenges in Detecting Gamma-Rays From Dark Matter Annihilations in the Galactic Center (open access)

Challenges in Detecting Gamma-Rays From Dark Matter Annihilations in the Galactic Center

None
Date: March 1, 2006
Creator: Zaharijas, Gabrijela & Hooper, Dan
System: The UNT Digital Library
Characterization of ambient aerosols at the San Francisco International Airport using BioAerosol Mass Spectrometry (open access)

Characterization of ambient aerosols at the San Francisco International Airport using BioAerosol Mass Spectrometry

The BioAerosol Mass Spectrometry (BAMS) system is a rapidly fieldable, fully autonomous instrument that can perform correlated measurements of multiple orthogonal properties of individual aerosol particles. The BAMS front end uses optical techniques to nondestructively measure a particle's aerodynamic diameter and fluorescence properties. Fluorescence can be excited at 266nm or 355nm and is detected in two broad wavelength bands. Individual particles with appropriate size and fluorescence properties can then be analyzed more thoroughly in a dual-polarity time-of-flight mass spectrometer. Over the course of two deployments to the San Francisco International Airport, more than 6.5 million individual aerosol particles were fully analyzed by the system. Analysis of the resulting data has provided a number of important insights relevant to rapid bioaerosol detection, which are described here.
Date: March 16, 2006
Creator: Steele, P T; McJimpsey, E L; Coffee, K R; Fergenson, D P; Riot, V J; Tobias, H J et al.
System: The UNT Digital Library
Charge-State-Resolved Ion Energy Distribution Functions ofCathodic Vacuum Arcs: A Study Involving the Plasma Potential and BiasedPlasmas (open access)

Charge-State-Resolved Ion Energy Distribution Functions ofCathodic Vacuum Arcs: A Study Involving the Plasma Potential and BiasedPlasmas

There are divergent results in the literature on the(in)dependence of the ion velocity distribution functions on the ioncharge states. Apparently, most time-of-flight methods of measurementsindicate independence whereas most measurements with electrostaticanalyzers state the opposite. It is shown here that this grouping iscoincidental with investigations of pulsed and continuous arcs. Allresults can be consolidated by taking ion-neutral interaction intoaccount, especially charge exchange collisions with the metal neutralsproduced by the arc itself. The velocity distribution functions areindependent of charge state when produced at cathode spots but becomecharge-state dependent when the plasma interacts withneutrals.
Date: March 9, 2006
Creator: Anders, Andre & Oks, Efim
System: The UNT Digital Library
Charm quark contribution to K+ ---> pi+ nu anti-nu at next-to-next-to-leading order (open access)

Charm quark contribution to K+ ---> pi+ nu anti-nu at next-to-next-to-leading order

The authors calculate the complete next-to-next-to-leading order QCD corrections to the charm contribution of the rare decay K{sup +} {yields} {pi}{sup +}{nu}{bar {nu}}. They encounter several new features, which were absent in lower orders. They discuss them in detail and present the results for the two-loop matching conditions of the Wilson coefficients, the three-loop anomalous dimensions, and the two-loop matrix elements of the relevant operators that enter the next-to-next-to-leading order renormalization group analysis of the Z-penguin and the electroweak box contribution. The inclusion of the next-to-next-to-leading order QCD corrections leads to a significant reduction of the theoretical uncertainty from {+-} 9.8% down to {+-} 2.4% in the relevant parameter P{sub c}(X), implying the leftover scale uncertainties in {Beta}(K{sup +} {yields} {pi}{sup +}{nu}{bar {nu}}) and in the determination of |V{sub td}|, sin 2{beta}, and {gamma} from the K {yields} {pi}{nu}{bar {nu}} system to be {+-} 1.3%, {+-} 1.0%, {+-} 0.006, and {+-} 1.2{sup o}, respectively. For the charm quark {ovr MS} mass m{sub c}(m{sub c}) = (1.30 {+-} 0.05) GeV and |V{sub us}| = 0.2248 the next-to-leading order value P{sub c}(X) = 0.37 {+-} 0.06 is modified to P{sub c}(X) = 0.38 {+-} 0.04 at the next-to-next-to-leading order level with the …
Date: March 1, 2006
Creator: Buras, Andrzej J.; Gorbahn, Martin; Haisch, Ulrich & Nierste, Ulrich
System: The UNT Digital Library