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NEW CORRECTION PROCEDURE FOR X-RAY SPECTROSCOPIC FLUORESCENCE DATA: SIMULATIONS AND EXPERIMENT.

Description: X-ray fluorescence spectroscopy is a widely used method for determining the electronic configuration and local structure of dilute species with high sensitivity. In the dilute limit, and for thin films, the X-ray fluorescence signal is directly proportional to the atomic sub-shell absorption coefficient. However, for concentrated samples, the well-documented self-absorption effect often leads to the severe suppression of XANES (X-ray Absorption Near-Edge Structure) and EXAFS (Extended X-ray Absorption Fine-Structure) amplitudes. Thus to recover the real value of the sub-shell absorption coefficient, it is important to apply correction procedures to the measured fluorescence spectra. In this paper, we describe a new straightforward method to correct for self-absorption effects (the difference in the measured fluorescence signal compared to that of the true sub-shell photoabsorption coefficient) in XANES and EXAFS fluorescence measurements. Using a variety of sample and detector configurations, this method is used to extract the sub-shell absorption coefficient on elemental nickel and thick single-crystals of Gd{sub 3}Ga{sub 5}O{sub 12} and LaAlO{sub 3}.
Date: August 2, 2004
Creator: ABLETT, J.M.; WOICIK, J.C. & KAO, C.C.
Partner: UNT Libraries Government Documents Department

Characterization of Environmental Stability of Pulsed Laser Deposited Oxide Ceramic Coatings

Description: A systematic investigation of candidate hydrogen permeation materials applied to a substrate using Pulsed Laser Deposition has been performed. The investigation focused on application of leading permeation-resistant materials types (oxide, carbides, and metals) on a stainless steel substrate. and evaluation of the stability of the applied coatings. Type 304L stainless steel substrates were coated with aluminum oxide, chromium oxide, and aluminum. Characterization of the coating-substrate system adhesion was performed using scratch adhesion testing and microindentation. Coating stability and environmental susceptibility were evaluated for two conditions-air at 350 degrees Celsius and Ar-H2 at 350 degrees Celsius for up to 100 hours. Results from this study have shown the pulsed laser deposition process to be an extremely versatile technology that is capable of producing a sound coating/substrate system for a wide variety of coating materials.
Date: March 2, 2004
Creator: ADAMS, THADM
Partner: UNT Libraries Government Documents Department

Measurements of Transverse Energy Distributions in Au+Au Collisions at {radical}s{sub NN} = 200 GeV

Description: Transverse energy (E{sub T}) distributions have been measured for Au+Au collisions at {radical}s{sub NN} = 200 GeV by the STAR collaboration at RHIC. E{sub T} is constructed from its hadronic and electromagnetic components, which have been measured separately. E{sub T} production for the most central collisions is well described by several theoretical models whose common feature is large energy density achieved early in the fireball evolution. The magnitude and centrality dependence of E{sub T} per charged particle agrees well with measurements at lower collision energy, indicating that the growth in E{sub T} for larger collision energy results from the growth in particle production. The electromagnetic fraction of the total E{sub T} is consistent with a final state dominated by mesons and independent of centrality.
Date: July 2, 2004
Creator: Adams, J.; Aggarwal, M.M.; Ahammed, Z.; Amonett, J.; Anderson, B.D.; Arkhipkin, D. et al.
Partner: UNT Libraries Government Documents Department

Efficient traffic grooming in SONET/WDM BLSR Networks

Description: In this paper, we study traffic grooming in SONET/WDM BLSR networks under the uniform all-to-all traffic model with an objective to reduce total network costs (wavelength and electronic multiplexing costs), in particular, to minimize the number of ADMs while using the optimal number of wavelengths. We derive a new tighter lower bound for the number of wavelengths when the number of nodes is a multiple of 4. We show that this lower bound is achievable. All previous ADM lower bounds except perhaps that in were derived under the assumption that the magnitude of the traffic streams (r) is one unit (r = 1) with respect to the wavelength capacity granularity g. We then derive new, more general and tighter lower bounds for the number of ADMs subject to that the optimal number of wavelengths is used, and propose heuristic algorithms (circle construction algorithm and circle grooming algorithm) that try to minimize the number of ADMs while using the optimal number of wavelengths in BLSR networks. Both the bounds and algorithms are applicable to any value of r and for different wavelength granularity g. Performance evaluation shows that wherever applicable, our lower bounds are at least as good as existing bounds and are much tighter than existing ones in many cases. Our proposed heuristic grooming algorithms perform very well with traffic streams of larger magnitude. The resulting number of ADMs required is very close to the corresponding lower bounds derived in this paper.
Date: April 2, 2004
Creator: Awwal, Abdul S.; Billah, Abdur R. B. & Wang, Bin
Partner: UNT Libraries Government Documents Department

Exploring little Higgs models with ATLAS at the LHC

Description: We discuss possible searches for the new particles predicted by Little Higgs Models at the LHC. By using a simulation of the ATLAS detector, we demonstrate how the predicted quark, gauge bosons and additional Higgs bosons can be found and estimate the mass range over which their properties can be constrained.
Date: February 2, 2004
Creator: Azuelos, G.; Benslama, K.; Costanzo, D.; Couture, G.; Garcia, J.E.; Hinchliffe, I.G. et al.
Partner: UNT Libraries Government Documents Department

ELECTRON INJECTORS FOR NEXT GENERATION X-RAY SOURCES.

Description: Next generation x-ray sources require very high-brightness electron beams that are typically at or beyond the present state-of-the-art, and thus place stringent and demanding requirements upon the electron injector parameters. No one electron source concept is suitable for all the diverse applications envisaged, which have operating characteristics ranging from high-average-current, quasi-CW, to high-peak-current, single-pulse electron beams. Advanced Energy Systems, in collaboration with various partners, is developing several electron injector concepts for these x-ray source applications. The performance and design characteristics of five specific RF injectors, spanning ''L'' to ''X''-band, normal-conducting to superconducting, and low repetition rate to CW, which are presently in various stages of design, construction or testing, is described. We also discuss the status and schedule of each with respect to testing.
Date: August 2, 2004
Creator: BLUEM,H.; BEN-ZVI,I.; SRINIVASAN-RAO,T. & AL., ET
Partner: UNT Libraries Government Documents Department

Group Representations and Multinomial Combinatorics of the Icosahedral Symmetry

Description: The icosahedral symmetry is one of the most intriguing symmetries, as it not only presents challenge but it appears in many fullerenes and high energetic materials such as the dodecahedral N{sub 20}. We have considered the combinatorics of all irreducible representations of the icosahedral symmetry for a number of multinomial partitions for vertex, face and edge colorings in this work. We have constructed the combinatorial tables for all irreducible representations for various multinomial partitions of colorings for the vertices, edge and faces of the icosahedron. These techniques should have important applications to enumerations and spectroscopy of fullerenes and high-energy materials such as N{sub 20}.
Date: February 2, 2004
Creator: Balasubramanian, K
Partner: UNT Libraries Government Documents Department

Non-rigid Group Theory, Tunneling Splittings and Nuclear Spin Statistics of Water Pentamer: (H2O5)

Description: The character table of the fully non-rigid water pentamer, (H{sub 2}O){sub 5} is derived for the first time. The group of all feasible permutations is the wreath product group S{sub 5}[S{sub 2}] and it consists of 3840 operations divided into 36 conjugacy classes and irreducible representations. We have shown that the full character table can be constructed using elegant matrix type generator algebra. The character table has been applied to the water pentamer by obtaining the nuclear spin statistical weights of the rovibronic levels and tunneling splittings of the fully non-rigid pentamer. We have also obtained the statistical weights and tunneling splittings of a semi-rigid deuterated pentamer that exhibits pseudo rotation with an averaged C{sub 5h}(G{sub 10}) symmetry used in the assignment of vibration-rotation-tunneling spectra . The correlation tables have been constructed for the semirigid (G{sub 10}) to non-rigid (G{sub 3840}) groups for the rotational levels and tunneling levels. The nuclear spin statistical weights have also been derived for both the limits.
Date: February 2, 2004
Creator: Balasubramanian, K
Partner: UNT Libraries Government Documents Department

The CKM matrix and the unitarity triangle. Proceedings, workshop, Geneva, Switzerland, February 13-16, 2002

Description: This report contains the results of the Workshop on the CKM Unitarity Triangle that was held at CERN on 13-16 February 2002. There had been several Workshops on B physics that concentrated on studies at e{sup +}e{sup -} machines, at the Tevatron, or at LHC separately. Here we brought together experts of different fields, both theorists and experimentalists, to study the determination of the CKM matrix from all the available data of K, D, and B physics. The analysis of LEP data for B physics is reaching its end, and one of the goals of the Workshop was to underline the results that have been achieved at LEP, SLC, and CESR. Another goal was to prepare for the transfer of responsibility for averaging B physics properties, that has developed within the LEP community, to the present main actors of these studies, from the B factory and the Tevatron experiments. The optimal way to combine the various experimental and theoretical inputs and to fit for the apex of the Unitarity Triangle has been a contentious issue. A further goal of the Workshop was to bring together the proponents of different fitting strategies, and to compare their approaches when applied to the same inputs. Since lattice QCD plays a very important role in the determination of the non-perturbative parameters needed to constrain the CKM unitarity triangle, the first Workshop was seen as an excellent opportunity to bring together lattice theorists with the aim of establishing a working group to compile averages for phenomenologically relevant quantities. Representatives from lattice collaborations around the world were invited to attend a meeting during the Workshop. A consensus was reached to set up three test working groups, collectively known as the ''CKM Lattice Working Group'', to review a number of well-studied quantities: quark masses, the kaon B-parameter, ...
Date: April 2, 2004
Creator: Battaglia, M.; Buras, A. J.; Gambino, P. & Stocchi, A.
Partner: UNT Libraries Government Documents Department

PKI-based security for peer-to-peer information sharing

Description: The free flow of information is the feature that has made peer-to-peer information sharing applications popular. However, this very feature holds back the acceptance of these applications by the corporate and scientific communities. In these communities it is important to provide confidentiality and integrity of communication and to enforce access control to shared resources. We present a number of security mechanisms that can be used to satisfy these security requirements. Our solutions are based on established and proven security techniques and we utilize existing technologies when possible. As a proof of concept, we have developed an information sharing system, called scishare, which integrates a number of these security mechanisms to provide a secure environment for information sharing. This system will allow a broader set of user communities to benefit from peer-to-peer information sharing.
Date: May 2, 2004
Creator: Berket, Karlo; Essiari, Abdelilah & Muratas, Artur
Partner: UNT Libraries Government Documents Department

Enhanced transient reactivity of an O-sputtered Au(111) surface

Description: The interaction of SO{sub 2} with oxygen-sputtered Au(111) surfaces ({theta}{sub oxygen} {le} 0.35 ML) was studied by monitoring the oxygen and sulfur coverages as a function of SO{sub 2} exposure. Two reaction regimes were observed: oxygen depletion followed by sulfur deposition. An enhanced, transient sulfur deposition rate is observed at the oxygen depletion point. This effect is specifically pronounced if the Au surface is continuously exposed to SO{sub 2}. The enhanced reactivity towards S deposition seems to be linked to the presence of highly reactive, under-coordinated Au atoms. Adsorbed oxygen appears to stabilize, but also to block these sites. In absence of the stabilization effect of adsorbed oxygen, i.e. at the oxygen depletion point, the enhanced reactivity decays on a timescale of a few minutes. These observations shed a new light on the catalytic reactivity of highly dispersed gold nanoparticles.
Date: December 2, 2004
Creator: Biener, M M; Biener, J & Friend, C M
Partner: UNT Libraries Government Documents Department

Sulfur-induced corrosion of Au(111) studied by real-time STM

Description: The interaction of sulfur with gold surfaces has attracted considerable interest due to numerous technological applications such as the formation of self-assembled monolayers (SAMs), use as a corrosion inhibitor, and as a chemical sensor. In this work, the interaction of sulfur with Au(111) at two different temperatures (300 K and 420 K) was studied by real-time scanning tunneling microscopy (STM), low energy electron diffraction (LEED) and Auger electron spectroscopy (AES). In the low coverage regime (< 0.1 monolayer), S modifies the surface stress leading to a lateral expansion of the Au surface layer. An ordered ({radical}3 x {radical}3)R30{sup o} sulfur adlayer develops as the coverage reaches {approx}0.3 ML. With further increasing S coverage the Au(111) surface undergoes a dynamic rearrangement while forming a two-dimensional AuS phase: gold surface atoms are removed from regular terrace sites and incorporated into the growing gold sulfide phase resulting in the appearance of pits and irregularly shaped AuS islands. Gold sulfide prepared at room temperature exhibits short-range order; an incommensurate, long-range ordered AuS phase develops upon annealing at 450-525 K. Higher temperatures lead to decomposition of the AuS corrosion film. Formation of an ordered AuS phase via rapid step retraction rather than etch pit formation is observed during S-interaction with Au(111) surfaces at 420 K. Our results shed new light on the S-Au(111) interaction.
Date: November 2, 2004
Creator: Biener, M; Biener, J & Friend, C
Partner: UNT Libraries Government Documents Department

Fabrication and Metrology of Micro-Scale Sinusoidal Surfaces in Polymer Workpiece Materials

Description: This study investigates the fabrication of precision, micro-scale sinusoidal surfaces in polymer workpiece materials and discusses methods to quantitatively characterize these surfaces. These precision sinusoidal surfaces are an important feature in a mesoscale assembly that will be used as part of a physics experiment. The experiment will study the formation of Rayleigh Taylor instabilities and requires a sinusoidal surface with an amplitude of 2.5 {micro}m and a wavelength of 70.7 {micro}m in both the x- and y-directions. The sinusoids must have sub-{micro}m form accuracy with a surface finish on the order of 100 nm, and they must be produced in a workpiece consisting of adjacent pieces of polyimide and iodine-doped polystyrene, a portion of which is illustrated in Figure 1.
Date: August 2, 2004
Creator: Bono, M J & Hibbard, R L
Partner: UNT Libraries Government Documents Department

Cesium Ion Exchange Program at the Hanford River Protection Project Waste Treatment Plant

Description: The River Protection Project - Hanford Tank Waste Treatment and Immobilization Plant will use cesium ion exchange to remove 137Cs from Low Activity Waste down to 0.3 Ci/m3 in the Immobilized LAW, ILAW product. The project baseline for cesium ion exchange is the elutable SuperLig, R, 644, SL-644, resin registered trademark of IBC Advanced Technologies, Inc., American Fork, UT or the Department of Energy approved equivalent. SL-644 is solely available through IBC Advanced Technologies. To provide an alternative to this sole-source resin supply, the RPP-WTP initiated a three-stage process for selection and qualification of an alternative ion exchange resin for cesium removal in the RPPWTP. It was recommended that resorcinol formaldehyde RF be pursued as a potential alternative to SL-644.
Date: December 2, 2004
Creator: CHARLES, NASH
Partner: UNT Libraries Government Documents Department

Continuous Material Balance Reconciliation for a Modern Plutonium Processing Facility

Description: This paper describes a safeguards approach that can be deployed at any modern plutonium processing facility to increase the level of safeguards assurance and significantly reduce the impact of safeguards on process operations. One of the most perplexing problems facing the designers of plutonium processing facilities is the constraint placed upon the limit of error of the inventory difference (LEID). The current DOE manual constrains the LEID for Category I and II material balance areas to 2 per cent of active inventory up to a Category II quantity of the material being processed. For 239Pu a Category II quantity is two kilograms. Due to the large material throughput anticipated for some of the modern plutonium facilities, the required LEID cannot be achieved reliably during a nominal two month inventory period, even by using state-of-the-science non-destructive assay (NDA) methods. The most cost-effective and least disruptive solution appears to be increasing the frequency of material balance closure and thus reducing the throughput being measured during each inventory period. Current inventory accounting practices and systems can already provide the book inventory values at any point in time. However, closing the material balance with measured values has typically required the process to be cleaned out, and in-process materials packaged and measured. This process requires one to two weeks of facility down time every two months for each inventory, thus significantly reducing productivity. To provide a solution to this problem, a non-traditional approach is proposed that will include using in-line instruments to provide measurement of the process materials on a near real-time basis. A new software component will be developed that will operate with the standard LANMAS application to provide the running material balance reconciliation, including the calculation of the inventory difference and variance propagation. The combined measurement system and software implementation will make it ...
Date: July 2, 2004
Creator: CLARK, THOMAS G.
Partner: UNT Libraries Government Documents Department

Characterization of an Effective Cleaning Procedure for Aluminum Alloys: Surface Enhanced Raman Spectroscopy and Zeta Potential Analysis

Description: We have developed a cleaning procedure for aluminum alloys for effective minimization of surface-adsorbed sub-micron particles and non-volatile residue. The procedure consists of a phosphoric acid etch followed by an alkaline detergent wash. To better understand the mechanism whereby this procedure reduces surface contaminants, we characterized the aluminum surface as a function of cleaning step using Surface Enhanced Raman Spectroscopy (SERS). SERS indicates that phosphoric acid etching re-establishes a surface oxide of different characteristics, including deposition of phosphate and increased hydration, while the subsequent alkaline detergent wash appears to remove the phosphate and modify the new surface oxide, possibly leading to a more compact surface oxide. We also studied the zeta potential of <5 micron pure aluminum and aluminum alloy 6061-T6 particles to determine how surface electrostatics may be affected during the cleaning process. The particles show a decrease in the magnitude of their zeta potential in the presence of detergent, and this effect is most pronounced for particles that have been etched with phosphoric acid. This reduction in magnitude of the surface attractive potential is in agreement with our observation that the phosphoric acid etch followed by detergent wash results in a decrease in surface-adsorbed sub-micron particulates.
Date: June 2, 2004
Creator: Cherepy, N J; Shen, T H; Esposito, A P & Tillotson, T M
Partner: UNT Libraries Government Documents Department

Interpretation of long-offset transient electromagnetic data fromMount Merapi, Indonesia, using a three-dimensional optimizationapproach

Description: In the years 1998, 2000, and 2001, long-offset transientelectromagnetic (LOTEM) surveys were carried out at the active volcanoMerapi in Central Java. The measurements investigated the conductivitystructure of the volcanic edifice. Our area of interest, which is belowthe summit and the upper flanks, was investigated using horizontal andvertical magnetic field time derivative data from seventransmitter-receiver setups. Because of topography and athree-dimensional (3-D) underground structure, a 3-D interpretation isused. The method optimizes few parameters of a 3-D model by a stableleast squares joint inversion of the data, providing sufficientresolution capability. Reasonable data fits are achieved with anonhorizontally layered model featuring a very conductive basement belowdepths of 1.5 km. While hydrothermal alteration is also considered, wetentatively explain the high conductivities by aqueous solutions withrelatively high salt contents. A large magma body or a small superficialreservoir below Merapi's central volcanic complex, as discussed by otherauthors, cannot be resolved by the LOTEM data.
Date: June 2, 2004
Creator: Commer, Michael; Helwig, Stefan L.; Hordt, Andreas & Tezkan, Bulent
Partner: UNT Libraries Government Documents Department

Construction and Changes in the Sludge Receipt and Adjustment Tank(Glass Apparatus Development Laboratory)

Description: The Defense Waste Processing Facility (DWPF), at the Savannah River Site is processing and immobilizing the radioactive high level waste sludge slurry at SRS into a durable borosilicate glass for final geological disposal. Each time a new batch of radioactive sludge is to be processed by the DWPF, the process flow sheet is to be tested and demonstrated to ensure an acceptable melter feed and glass can be made. These demonstrations are completed in the Shielded Cells Facility in the Savannah River National Laboratory at SRS.
Date: June 2, 2004
Creator: DOBOS, JAMES
Partner: UNT Libraries Government Documents Department

Gravitational Baryogenesis

Description: We show that a gravitational interaction between the derivative of the Ricci scalar curvature and the baryon-number current dynamically breaks CPT in an expanding universe and, combined with baryon-number-violating interactions, can drive the universe towards an equilibrium baryon asymmetry that is observationally acceptable.
Date: March 2, 2004
Creator: Davoudias, Hooman; Kitano, Ryuichiro; Kribs, Graham D.; Murayama, Hitoshi & Steinhardt, Paul J.
Partner: UNT Libraries Government Documents Department

Containerized Wetland Bioreactor Evaluated for Perchlorate and Nitrate Degradation

Description: The U.S. Department of Energy (DOE) and Lawrence Livermore Laboratory (LLNL) designed and constructed an innovative containerized wetlands (bioreactor) system that began operation in November 2000 to biologically degrade perchlorate and nitrate under relatively low-flow conditions at a remote location at Site 300 known as Building 854. Since initial start-up, the system has processed over 3,463,000 liters of ground water and treated over 38 grams of perchlorate and 148 kilograms of nitrate. Site 300 is operated by the University of California as a high-explosives and materials testing facility supporting nuclear weapons research. The 11-square mile site located in northern California was added to the NPL in 1990 primarily due to the presence of elevated concentrations of volatile organic compounds (VOCs) in ground water. At the urging of the regulatory agencies, perchlorate was looked for and detected in the ground water in 1999. VOCs, nitrate and perchlorate were released into the soil and ground water in the Building 854 area as the result of accidental leaks during stability testing of weapons or from waste discharge practices that are no longer permitted at Site 300. Design of the wetland bioreactors was based on earlier studies showing that indigenous chlorate-respiring bacteria could effectively degrade perchlorate into nontoxic concentrations of chlorate, chlorite, oxygen, and chloride. Studies also showed that the addition of organic carbon would enhance microbial denitrification. Early onsite testing showed acetic acid to be a more effective carbon source than dried leaf matter, dried algae, or milk replacement starter; a nutrient and carbon source used in a Department of Defense phytoremediation demonstration. No inocula were added to the system. Groundwater was allowed to circulate through the bioreactor for three weeks to acclimate the wetland plants and to build a biofilm from indigenous flora. Using solar energy, ground water is pumped into granular ...
Date: December 2, 2004
Creator: Dibley, V R & Krauter, P W
Partner: UNT Libraries Government Documents Department

Heterodyning Time Resolution Boosting for Velocimetry and Reflectivity Measurements

Description: A theoretical technique is described for boosting the temporal resolving power by several times, of detectors such as streak cameras in experiments that measure light reflected from or transmitted through a target, including velocity interferometer (VISAR) measurements. This is a means of effectively increasing the number of resolvable time bins in a streak camera record past the limit imposed by input slit width and blur on the output phosphor screen. The illumination intensity is modulated sinusoidally at a frequency similar to the limiting time response of the detector. A heterodyning effect beats the high frequency science signal down a lower frequency beat signal, which is recorded together with the conventional science signal. Using 3 separate illuminating channels having different phases, the beat term is separated algebraically from the conventional signal. By numerically reversing the heterodyning, and combining with the ordinary signal, the science signal can be reconstructed to better effective time resolution than the detector used alone. The effective time resolution can be approximately halved for a single modulation frequency, and further decreased inversely proportional to the number of independent modulation frequencies employed.
Date: August 2, 2004
Creator: Erskine, D J
Partner: UNT Libraries Government Documents Department

DISTINGUISHING SPONTANEOUS FISSION NEUTRONS FROM COSMIC-RAY BACKGROUND.

Description: We have measured the neutron spectra of cosmic-rays and a spontaneous fission emitting source (Cf-252) using a neutron double scatter spectrometer. The energy range of measurements was 0.1-10 MeV where the spectrometer efficiency is determined to be up to 8.7% depending on the separation between detection planes. Our cosmic-ray neutron spectrum measurement is in good agreement with the sea-level data reported by Goldhagen and his co-workers. In the energy range 0.1-1.0 MeV, the cosmic-ray and Cf-252 spectra are different and separable. This difference is expected from the applicable models that describe the phenomena, ''equilibrium slowing down'' (cosmic-rays) and ''Maxwellian kinetic temperature'' emission (spontaneous fission). We show that >80% of Cf-252 neutrons and <25% of cosmic-ray related neutrons are emitted in this energy range of measurement, and conclude that neutron spectroscopy provides effective ways to distinguish a fission source from the cosmic-ray background.
Date: August 2, 2004
Creator: FORMAN,L.
Partner: UNT Libraries Government Documents Department