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Function of Conserved Residues of Human Glutathione Synthetase: Implications for the ATP-grasp Enzymes (open access)

Function of Conserved Residues of Human Glutathione Synthetase: Implications for the ATP-grasp Enzymes

This article discusses human glutathione synthetase, an enzyme that belongs to the glutathione synthetase ATP-binding domain-like superfamily.
Date: February 27, 2004
Creator: Dinescu, Adriana; Cundari, Thomas R., 1964-; Bhansali, Vikas S.; Luo, Jia-Li & Anderson, Mary E.
System: The UNT Digital Library
Synthesis and Reactivity of a Coordinatively Unsaturated Ruthenium(II) Parent Amido Complex: Studies of X-H Activation (X = H or C) (open access)

Synthesis and Reactivity of a Coordinatively Unsaturated Ruthenium(II) Parent Amido Complex: Studies of X-H Activation (X = H or C)

Article discussing the synthesis and reactivity of a coordinatively unsaturated Ruthenium(II) parent amido complex and studies of X-H activation (X = H or C).
Date: April 27, 2004
Creator: Conner, David; Jayaprakash, K. N.; Cundari, Thomas R., 1964- & Gunnoe, T. Brent
System: The UNT Digital Library
Electronic and Transport Properties of Artificial Gold Chains (open access)

Electronic and Transport Properties of Artificial Gold Chains

Article on electronic and transport properties of artificial gold chains.
Date: August 27, 2004
Creator: Calzolari, Arrigo; Cavazzoni, Carlo & Buongiorno Nardelli, Marco
System: The UNT Digital Library
Kinetic studies of the Cl + HI reaction using three techniques (open access)

Kinetic studies of the Cl + HI reaction using three techniques

Article on kinetic studies of the Cl + HI reaction using three techniques.
Date: July 27, 2004
Creator: Yuan, Jessie; Misra, Ashutosh; Goumri, Abdellatif; Shao, Diane D. & Marshall, Paul
System: The UNT Digital Library
Hadron calorimeters for future hadron colliders (open access)

Hadron calorimeters for future hadron colliders

Hadron calorimeters are essential for jet and neutrino physics at collider experiments. Current hadron calorimeters for the ATLAS and CMS detectors are described. Increased energy and luminosity of future hadron colliders place constraints on detector technology. Difficulties for operation of the current detectors in future hadron collider environments are discussed. New experiments for future colliders should take notice of physics processes during jet evolution that place fundamental limits on performance of the calorimeter to reconstruct jets. A technique of incorporating tracking information to improve jet resolution is described. Future detectors should be designed with these constraints in mind. Possible avenues of exploration for future technology are described.
Date: January 27, 2004
Creator: Freeman, Jim
System: The UNT Digital Library
Computational Accelerator Physics Working Group Summary (open access)

Computational Accelerator Physics Working Group Summary

The working group on computational accelerator physics at the 11th Advanced Accelerator Concepts Workshop held a series of meetings during the Workshop. Verification, i.e., showing that a computational application correctly solves the assumed model, and validation, i.e., showing that the model correctly describes the modeled system, were discussed for a number of systems. In particular, the predictions of the massively parallel codes, OSIRIS and VORPAL, used for modeling advanced accelerator concepts, were compared and shown to agree, thereby establishing some verification of both codes. In addition, a number of talks on the status and frontiers of computational accelerator physics were presented, to include the modeling of ultrahigh-brightness electron photoinjectors and the physics of beam halo production. Finally, talks discussing computational needs were presented.
Date: August 27, 2004
Creator: Cary, John R. & Bohn, Courtlandt L.
System: The UNT Digital Library
Savannah River Site Levels of Control Implementation (open access)

Savannah River Site Levels of Control Implementation

The Savannah River Site (SRS) established a prescriptive approach to defining and protecting major contributors to defense in depth in the mid '90s. This approach came in partial response to the Defense Nuclear Facility Safety Board (DNFSB) criticism at the time of inconsistent classifications between similar facilities at the site. This basic approach of a rigorous and prescriptive minimum definition of levels of control has been in place since that time. Recently SRS has changed its policy of defining major contributors to defense in depth to be a more qualitative approach, with no prescribed minimum number of levels of control. However, to assure that consistency is maintained, guidance has been developed to identify areas of attention when identifying the major contributors to defense in depth that receive the Safety Significant functional classification label or that are protected within the technical safety requirements. This paper discusses this guidance and its implementation within the overall hazard analysis and functional classification process. Based on the experience with selecting safety structures, systems and components (SSCs) and Administrative Controls, the Savannah River Site has moved from a prescriptive process of control selection based on numbers of levels of control (LOCs) and moved to an informed …
Date: April 27, 2004
Creator: VINCENT, AM
System: The UNT Digital Library
Multiple Ion Exchange Column Tests for Technetium Removal from Hanford Tank Waste Supernate (open access)

Multiple Ion Exchange Column Tests for Technetium Removal from Hanford Tank Waste Supernate

Five cycles of loading, elution, and regeneration were performed to remove technetium from a Hanford waste sample retrieved from Tank 241-AW-101 using SuperLig 639 resin. The waste sample was diluted to 4.95 M Na plus and then was processed to remove 137Cs through dual ion exchange columns each containing 15 mL of SuperLig 644. To remove 99Tc, the cesium decontaminated solution was processed downwards through two ion exchange columns, each containing 12 mL of SuperLig 639 resin. The columns, designated as lead and lag, each had an inside diameter of 1.45 cm and a height of 30 cm. The columns were loaded in series, but were eluted and then regenerated separately. The average technetium loading for the cycles was 250 BV at 10 percent breakthrough. There was no significant difference in the loading performances among the five cycles. The percent removal of 99Tc was greater than 99.94 percent and the average decontamination factor (DF) was approximately 1.7 x 103. Approximately 99 percent of the 99Tc loaded on the resin was eluted with less than 15 BV of de-ionized water at 65 degrees C.
Date: February 27, 2004
Creator: Hassan, N. M.
System: The UNT Digital Library
How might a statistical cloud scheme be coupled to a mass-flux convection scheme? (open access)

How might a statistical cloud scheme be coupled to a mass-flux convection scheme?

The coupling of statistical cloud schemes with mass-flux convection schemes is addressed. Source terms representing the impact of convection are derived within the framework of prognostic equations for the width and asymmetry of the probability distribution function of total water mixing ratio. The accuracy of these source terms is quantified by examining output from a cloud resolving model simulation of deep convection. Practical suggestions for inclusion of these source terms in large-scale models are offered.
Date: September 27, 2004
Creator: Klein, Stephen A.; Pincus, Robert; Hannay, Cecile & Xu, Kuan-man
System: The UNT Digital Library
Laboratory evaluation of fan/filter units' aerodynamic and energy performance (open access)

Laboratory evaluation of fan/filter units' aerodynamic and energy performance

The paper discusses the benefits of having a consistent testing method to characterize aerodynamic and energy performance of FFUs. It presents evaluation methods of laboratory-measured performance of ten relatively new, 1220 mm x 610 mm (or 4 ft x 2 ft) fan-filter units (FFUs), and includes results of a set of relevant metrics such as energy performance indices (EPI) based upon the sample FFUs tested. This paper concludes that there are variations in FFUs' performance, and that using a consistent testing and evaluation method can generate compatible and comparable FFU performance information. The paper also suggests that benefits and opportunities exist for our method of testing FFU energy performance to be integrated in future recommended practices.
Date: July 27, 2004
Creator: Xu, Tengfang & Jeng, Ming-Shan
System: The UNT Digital Library
Development and test of single-layer common coil dipole wound with reacted Nb3Sn cable (open access)

Development and test of single-layer common coil dipole wound with reacted Nb3Sn cable

The first one-meter long common coil dipole model (HFDC-01) has been fabricated and is being tested at Fermilab. This magnet has several innovative features such as: single-layer racetrack coils, a 22-mm wide 59-strand Rutherford-type cable made of 0.7-mm Nb{sub 3}Sn strands, and a stainless steel coil-support structure reinforced by horizontal bridges inserted between coil blocks. The model was instrumented with voltage taps, quench heaters, temperature sensors and strain gauges in order to monitor the quench origin and propagation, and to study mechanical and quench protection issues. This paper summarizes the model design parameters, the fabrication procedures and the test results.
Date: April 27, 2004
Creator: al., Vladimir Kashikhin et
System: The UNT Digital Library
Uranium Age Determination by Measuring the 230Th / 234U Ratio (open access)

Uranium Age Determination by Measuring the 230Th / 234U Ratio

A radiochemical isotope dilution mass spectrometry method has been developed to determine the age of uranium materials. The amount of 230Th activity, the first progeny of 234U, that had grown into a small uranium metal sample was used to determine the elapsed time since the material was last radiochemically purified. To preserve the sample, only a small amount of oxidized uranium was removed from the surface of the sample and dissolved. Aliquots of the dissolved sample were spiked with 233U tracer and radiochemically purified by anion-exchange chromatography. The 234U isotopic concentration was then determined by thermal ionization mass spectrometry. Additional aliquots of the sample were spiked with 229Th tracer, and the thorium was purified using two sequential anion-exchange chromatography separations. The isotopic concentrations of 230Th and 232Th were determined by TIMS. The lack of any 232Th confirmed the assumption that all thorium was removed from the uranium sample at the time of purification. The 230Th and 234U mass concentrations were converted to activities and the 230Th/234U ratio for the sample was calculated. The experimental 230Th/234U ratio showed the uranium in this sample was radiochemically purified in about 1945. Isotope dilution thermal ionization mass spectrometry has sufficient sensitivity to determine the …
Date: July 27, 2004
Creator: LAMONT, STEPHENP.
System: The UNT Digital Library
A Combined Experimental and Computational Approach for the Design of Mold Topography that Leads to Desired Ingot Surface and Microstructure in Aluminum Casting. (open access)

A Combined Experimental and Computational Approach for the Design of Mold Topography that Leads to Desired Ingot Surface and Microstructure in Aluminum Casting.

A stabilized equal-order velocity-pressure finite element algorithm is presented for the analysis of flow in porous media and in the solidification of binary alloys. The adopted governing macroscopic conservation equations of momentum, energy and species transport are derived from their microscopic counterparts using the volume-averaging method. The analysis is performed in a single domain with a fixed numerical grid. The fluid flow scheme developed includes SUPG (streamline-upwind/Petrov-Galerkin), PSPG (pressure stabilizing/Petrov-Galerkin) and DSPG (Darcy stabilizing/Petrov-Galerkin) stabilization terms in a variable porosity medium. For the energy and species equations a classical SUPG-based finite element method is employed. The developed algorithms were tested extensively with bilinear elements and were shown to perform stably and with nearly quadratic convergence in high Rayleigh number flows in varying porosity media. Examples are shown in natural and double diffusive convection in porous media and in the directional solidification of a binary-alloy.
Date: May 27, 2004
Creator: Dr. Zabaras, N. & Samanta, D.
System: The UNT Digital Library
Mineralization of Synthetic Polymer Scaffolds: A Bottom-upApproach for the Development of Artificial Bone (open access)

Mineralization of Synthetic Polymer Scaffolds: A Bottom-upApproach for the Development of Artificial Bone

The controlled integration of organic and inorganic components confers natural bone with superior mechanical properties. Bone biogenesis is thought to occur by templated mineralization of hard apatite crystals by an elastic protein scaffold, a process we sought to emulate with synthetic biomimetic hydrogel polymers. Crosslinked polymethacrylamide and polymethacrylate hydrogels were functionalized with mineral-binding ligands and used to template the formation of hydroxyapatite. Strong adhesion between the organic and inorganic materials was achieved for hydrogels functionalized with either carboxylate or hydroxy ligands. The mineral-nucleating potential of hydroxyl groups identified here broadens the design parameters for synthetic bone-like composites and suggests a potential role for hydroxylated collagen proteins in bone mineralization.
Date: September 27, 2004
Creator: Song, Jie; Viengkham, Malathong & Bertozzi, Carolyn R.
System: The UNT Digital Library
Development of superconducting magnet systems for HIFExperiments (open access)

Development of superconducting magnet systems for HIFExperiments

The U.S. Heavy Ion Fusion program is developing superconducting focusing quadrupoles for near-term experiments and future driver accelerators. Following the fabrication and testing of several models, a baseline quadrupole design was selected and further optimized. The first prototype of the optimized design achieved a conductor-limited gradient of 132 T/m in a 70 mm bore, with measured field harmonics within 10 parts in 10{sup 4}. In parallel, a compact focusing doublet was fabricated and tested using two of the first-generation quadrupoles. After assembly in the cryostat, both magnets reached their conductor-limited quench current. Further optimization steps are currently underway to improve the performance of the magnet system and reduce its cost. They include the fabrication and testing of a new prototype quadrupole with reduced field errors as well as improvements of the cryostat design for the focusing doublet. The prototype units will be installed in the HCX beamline at LBNL, to perform accelerator physics experiments and gain operational experience. Successful results in the present phase will make superconducting magnets a viable option for the next generation of integrated beam experiments.
Date: July 27, 2004
Creator: Sabbi, Gian Luca; Faltens, A.; Leitzke, A.; Seidl, P.; Lund, S.; Martovets ky, N. et al.
System: The UNT Digital Library
Time-dependence ion charge state distributions of vacuum arcs: An interpretation involving atoms and charge exchange collisions (open access)

Time-dependence ion charge state distributions of vacuum arcs: An interpretation involving atoms and charge exchange collisions

Experimentally observed charge state distributions are known to be higher at the beginning of each arc discharge. Up to know, this has been attributed to cathode surface effects in terms of changes of temperature, chemical composition and spot mode. Here it is shown that the initial decay of charge states of cathodic arc plasmas may at least in part due to charge exchange collisions of ions with neutrals that gradually fill the discharge volume. Sources of neutrals may include evaporated atoms from macroparticles and still-hot craters of previously active arc spots. More importantly, atoms are also produced by energetic condensation of the cathodic arc plasma. Self-sputtering is significant when ions impact with near-normal angle of incidence, and ions have low sticking probability when impacting at oblique angle of incidence. Estimates show that the characteristic time for filling the near-cathode discharge volume agrees well with the charge state decay time, and the likelihood of charge exchange is reasonably large to be taken into account.
Date: August 27, 2004
Creator: Anders, Andre
System: The UNT Digital Library
A localized basis that allows fast and accurate second order Moller-Plesset calculations (open access)

A localized basis that allows fast and accurate second order Moller-Plesset calculations

We present a method for computing a basis of localized orthonormal orbitals (both occupied and virtual), in whose representation the Fock matrix is extremely diagonal-dominant. The existence of these orbitals is shown empirically to be sufficient for achieving highly accurate MP@ energies, calculated according to Kapuy's method. This method (which we abbreviate KMP2), which involves a different partitioning of the n-electron Hamiltonian, scales at most quadratically with potential for linearity in the number of electrons. As such, we believe the KMP2 algorithm presented here could be the basis of a viable approach to local correlation calculations.
Date: October 27, 2004
Creator: Subotnik, Joseph E. & Head-Gordon, Martin
System: The UNT Digital Library
Studies of W + jets and prompt diphoton production with the CDF Detector (open access)

Studies of W + jets and prompt diphoton production with the CDF Detector

The authors have studied the W + {ge} n jets process in Tevatron Run II experiment. This is the first result for the CDF Run II experiment. The data used corresponds to a total integrated luminosity of 72 pb{sup -1} taken from March 2002 through January 2003. The lowest order QCD predictions have been tested with a new prescription of the parton-jet matching, which allows to construct the enhanced LO phase space. They found a good agreement between data and theory in the typical kinematics distributions. Number of events for each inclusive samples up to 3 jets are compared with Monte Carlo calculations. The comparison with Run I results is also presented.
Date: April 27, 2004
Creator: Tsuno, S.
System: The UNT Digital Library
Summary of workshop session F on electron-cloud instabilities (open access)

Summary of workshop session F on electron-cloud instabilities

We summarize Session F of the ECLOUD 04 workshop. This session was dedicated to beam instabilities driven by electron cloud. Specifically, we discuss the principal observations of electron-cloud instabilities, analytical models, simulation codes and the next steps that need to be taken to arrive at a predictive theory.
Date: May 27, 2004
Creator: Zimmermann, Frank & Wolski, Andrzej
System: The UNT Digital Library
Helium Release Behavior of Aged Titanium Tritides (open access)

Helium Release Behavior of Aged Titanium Tritides

One sample of bulk Ti has been loaded with a 50 per cent / 50 per cent deuterium/tritium mixture and statically aged for 6.5 years. Thermal desorption of the sample shows an initial release of hydrogen isotopes followed by 3He release. Subsequent D2 loading/desorption was used to quantify the trapped tritium heel. The sample shows an excess hydrogen capacity as a second thermal desorption peak that partially disappears and shifts with annealing at 923-973K. The main hydrogen desorption peak also shifts to higher temperature, indicating a partial reversal of the tritium-decay induced damage by annealing.
Date: July 27, 2004
Creator: SHANAHAN, KIRKL.
System: The UNT Digital Library
V-shaped inversion domains in InN grown on c-plane sapphire (open access)

V-shaped inversion domains in InN grown on c-plane sapphire

Inversion domains with a V-shape were found to nucleate inside a Mg-doped InN heteroepitaxial layer. They resemble Al-polarity domains, observed recently, in N-polarity AlN films. However, the angle between the side-walls of the V-shaped domain and the c-axis differs in these two cases. In InN, this angle is almost two times bigger than that reported for AlN. The origin of V-shaped inversion domains in InN film is not yet clear.
Date: April 27, 2004
Creator: Jasinski, J.; Liliental-Weber, Z.; Lu, H. & Schaff, W.J.
System: The UNT Digital Library
Selective molecular recognition, C-H bond activation, and catalysis in nanoscale reaction vessels (open access)

Selective molecular recognition, C-H bond activation, and catalysis in nanoscale reaction vessels

Supramolecular chemistry represents a way to mimic enzyme reactivity by using specially designed container molecules. We have shown that a chiral self-assembled M{sub 4}L{sub 6} supramolecular tetrahedron can encapsulate a variety of cationic guests, with varying degrees of stereoselectivity. Reactive iridium guests can be encapsulated and the C-H bond activation of aldehydes occurs, with the host cavity controlling the ability of substrates to interact with the metal center based upon size and shape. In addition, the host container can act as a catalyst by itself. By restricting reaction space and preorganizing the substrates into reactive conformations, it accelerates the sigmatropic rearrangement of enammonium cations.
Date: November 27, 2004
Creator: Fiedler, Dorothea; Leung, Dennis H.; Raymond, Kenneth N. & Bergman, Robert G.
System: The UNT Digital Library
Metals Retention in Constructed Wetland Sediments (open access)

Metals Retention in Constructed Wetland Sediments

The A-01 wetland treatment system (WTS) was designed to remove metals from the effluent at the A-01 NPDES outfall at the Savannah River Site, Aiken, SC. Sequential extraction data was used to evaluate remobilization and retention of Cu, Pb, Zn, Mn, and Fe in the wetland sediment. Remobilization of metals was determined by the Potentially Mobile Fraction (PMF) and metal retention by the Recalcitrant Factor (RF). The PMF, which includes water soluble, exchangeable, and oxides fractions, is the contaminant fraction that has the potential to enter into the mobile aqueous phase under changeable environmental conditions. PMF values were low for Cu, Zn and Pb (about 20 percent) and high for Fe and Mn (about 60 to 70 percent). The RF, which includes crystalline oxides, sulfides or silicates and aluminosilicates, is the ratio of strongly bound fractions to the total concentration of elements in sediment. RF values were about 80 percent for Cu, Zn and Pb, indicating high retention in the sediment and 30 percent to above 40 percent for Fe and Mn indication low retention.
Date: October 27, 2004
Creator: KNOX, ANNA
System: The UNT Digital Library
Systems analysis for modular versus multi-beam HIF drivers (open access)

Systems analysis for modular versus multi-beam HIF drivers

None
Date: July 27, 2004
Creator: Meier, W. R. & Logan, B. G.
System: The UNT Digital Library