Application of a pilot control banding tool for risk level assessment and control of nanoparticle exposures (open access)

Application of a pilot control banding tool for risk level assessment and control of nanoparticle exposures

Control Banding (CB) strategies offer simplified solutions for controlling worker exposures to constituents that are found in the workplace in the absence of firm toxicological and exposure data. These strategies may be particularly useful in nanotechnology applications, considering the overwhelming level of uncertainty over what nanomaterials and nanotechnologies present as potential work-related health risks, what about these materials might lead to adverse toxicological activity, how risk related to these might be assessed, and how to manage these issues in the absence of this information. This study introduces a pilot CB tool or 'CB Nanotool' that was developed specifically for characterizing the health aspects of working with engineered nanoparticles and determining the level of risk and associated controls for five ongoing nanotechnology-related operations being conducted at two Department of Energy (DOE) research laboratories. Based on the application of the CB Nanotool, four of the five operations evaluated in this study were found to have implemented controls consistent with what was recommended by the CB Nanotool, with one operation even exceeding the required controls for that activity. The one remaining operation was determined to require an upgrade in controls. By developing this dynamic CB Nanotool within the realm of the scientific information …
Date: March 3, 2008
Creator: Paik, S Y; Zalk, D M & Swuste, P
System: The UNT Digital Library
Cfd Modeling Analysis of Mechanical Draft Cooling Tower (open access)

Cfd Modeling Analysis of Mechanical Draft Cooling Tower

Industrial processes use mechanical draft cooling towers (MDCT's) to dissipate waste heat by transferring heat from water to air via evaporative cooling, which causes air humidification. The Savannah River Site (SRS) has a MDCT consisting of four independent compartments called cells. Each cell has its own fan to help maximize heat transfer between ambient air and circulated water. The primary objective of the work is to conduct a parametric study for cooling tower performance under different fan speeds and ambient air conditions. The Savannah River National Laboratory (SRNL) developed a computational fluid dynamics (CFD) model to achieve the objective. The model uses three-dimensional steady-state momentum, continuity equations, air-vapor species balance equation, and two-equation turbulence as the basic governing equations. It was assumed that vapor phase is always transported by the continuous air phase with no slip velocity. In this case, water droplet component was considered as discrete phase for the interfacial heat and mass transfer via Lagrangian approach. Thus, the air-vapor mixture model with discrete water droplet phase is used for the analysis. A series of the modeling calculations was performed to investigate the impact of ambient and operating conditions on the thermal performance of the cooling tower when fans …
Date: March 3, 2008
Creator: Lee, S.; Alfred Garrett, A.; James02 Bollinger, J. & Larry Koffman, L.
System: The UNT Digital Library
PREDICTION OF SURFACE SETTLEMENT DUE TO THE DISPLACEMENT OF SOFT ZONES (open access)

PREDICTION OF SURFACE SETTLEMENT DUE TO THE DISPLACEMENT OF SOFT ZONES

In areas composed of coastal plain sediments, soft zones subjected to partial overburden may be present in the subsurface. During or after a seismic event, these soft zones may be compressed. The resulting displacement due to the deformation of the soft zones will propagate to the ground surface and cause the surface to settle. This paper presents a method to predict the settlement at the surface due to the propagation of the displacement from the soft zones. This method is performed by discretizing the soft zones into multiple clusters of finite sub-areas or subspaces. Settlement profile at the ground surface due to the displacement of each sub-area or subspace is computed assuming the shape is a normal distribution function. Settlement due to the displacement of the soft zones can then be approximated by adding the settlements computed for all the sub-areas or subspaces. This method provides a simple and useful tool for the prediction of the settlement profile and the results are consistent with those obtained from the finite difference analysis.
Date: March 3, 2008
Creator: Li, W
System: The UNT Digital Library
Estimating solar access of typical residential rooftops: A case study in San Jose, CA (open access)

Estimating solar access of typical residential rooftops: A case study in San Jose, CA

Shadows cast by trees and buildings can limit the solar access of rooftop solar-energy systems, including photovoltaic panels and thermal collectors. This study characterizes rooftop shading in a residential neighborhood of San Jose, CA, one of four regions analyzed in a wider study of the solar access of California homes.High-resolution orthophotos and LiDAR (Light Detection And Ranging) measurements of surface height were used to create a digital elevation model of all trees and buildings in a 4 km2 residential neighborhood. Hourly shading of roofing planes (the flat elements of roofs) was computed geometrically from the digital elevation model. Parcel boundaries were used to determine the extent to which roofing planes were shaded by trees and buildings in neighboring parcels.In the year in which surface heights were measured (2005), shadows from all sources ("total shading") reduced the insolation received by S-, SW-, and W-facing residential roofing planes in the study area by 13 - 16percent. Shadows cast by trees and buildings in neighboring parcels reduced insolation by no more than 2percent. After 30 years of simulated maximal tree growth, annual total shading increased to 19 - 22percent, and annual extraparcel shading increased to 3 - 4percent.
Date: March 3, 2008
Creator: Levinson, Ronnen M.; Gupta, Smita; Akbari, Hashem & Pomerantz, Melvin
System: The UNT Digital Library
An Investigation of the Effect of Graphite Degradation on the Irreversible Capacity in Lithium-ion Cells (open access)

An Investigation of the Effect of Graphite Degradation on the Irreversible Capacity in Lithium-ion Cells

The effect of surface structural damage on graphitic anodes, commonly observed in tested Li-ion cells, was investigated. Similar surface structural disorder was artificially induced in Mag-10 synthetic graphite anodes using argon-ion sputtering. Raman microscopy, scanning electron microscopy (SEM) and Brunauer Emmett Teller (BET) measurements confirmed that Ar-ion sputtered Mag-10 electrodes display similar degree of surface degradation as the anodes from tested Li-ion cells. Artificially modified Mag-10 anodes showed double the irreversible charge capacity during the first formation cycle, compared to fresh un-altered anodes. Impedance spectroscopy and Fourier transform infrared (FTIR) spectroscopy on surface modified graphite anodes indicated the formation of a thicker and slightly more resistive SEI layer. Gas chromatography/mass spectroscopy (GC/MS) analysis of solvent extracts from the electrodes detected the presence of new compounds with M{sub w} on the order of 1600 g mol{sup -1} for the surface modified electrode with no evidence of elevated M{sub w} species for the unmodified electrode. The structural disorder induced in the graphite during long-term cycling maybe responsible for the slow and continuous SEI layer reformation, and consequently, the loss of reversible capacity due to the shift of lithium inventory in cycled Li-ion cells.
Date: March 3, 2008
Creator: Stevenson, Cynthia; Hardwick, Laurence J.; Marcinek, Marek; Beer, Leanne; Kerr, John B. & Kostecki, Robert
System: The UNT Digital Library
Unraveling duality violations in hadronic tau decays (open access)

Unraveling duality violations in hadronic tau decays

There are some indications from recent determinations of the strong coupling constant alpha_s and the gluon condensate that the Operator Product Expansion may not be accurate enough to describe non-perturbative effects in hadronic tau decays. This breakdown of the Operator Product Expansion is usually referred to as being due to"Duality Violations." With the help of a physically motivated model, we investigate these duality violations. Based on this model, we argue how they may introduce a non-negligible systematic error in the current analysis, which employs finite-energy sum rules with pinched weights. In particular, this systematic effect might affect the precision determination of alpha_s from tau decays. With a view to a possible future application to real data, we present an alternative method for determining the OPE coefficients that might help estimating, and possibly even reducing, this systematic error.
Date: March 3, 2008
Creator: Cata, Oscar; Cata, Oscar; Golterman, Maarten & Peris, Santiago
System: The UNT Digital Library
Revisiting the U-238 thermal capture cross section and gamma-raymission probabilities from Np-239 decay (open access)

Revisiting the U-238 thermal capture cross section and gamma-raymission probabilities from Np-239 decay

The precise value of the thermal capture cross section of238U is uncertain, and evaluated cross sections from various sourcesdiffer by more than their assigned uncertainties. A number of theoriginal publications have been reviewed to assess the discrepant data,corrections were made for more recent standard cross sections andotherconstants, and one new measurement was analyzed. Due to the strongcorrelations in activation measurements, the gamma-ray emissionprobabilities from the beta decay of 239Np were also analyzed. As aresult of the analysis, a value of 2.683 +- 0.012 barns was derived forthe thermal capture cross section of 238U. A new evaluation of thegamma-ray emission probabilities from 239Np decay was alsoundertaken.
Date: March 3, 2005
Creator: Trkov, A.; Molnar, G. L.; Revay, Z. S.; Mughabghab, S. F.; Firestone, R. B.; Pronyaev, V. G. et al.
System: The UNT Digital Library
The effect of problem perturbations on nonlinear dynamical systems and their reduced order models (open access)

The effect of problem perturbations on nonlinear dynamical systems and their reduced order models

Reduced order models are used extensively in many areas of science and engineering for simulation, design, and control. Reduction techniques for nonlinear dynamical systems produce models that depend strongly on the nominal set of parameters for which the reduction is carried out. In this paper we address the following two questions: 'What is the effect of perturbations in the problem parameters on the output functional of a nonlinear dynamical system?' and 'To what extent does the reduced order model capture this effect?'
Date: March 3, 2005
Creator: Serban, R; Homescu, C & Petzold, L
System: The UNT Digital Library
Accelerator mass spectrometry of Strontium-90 for homeland security, environmental monitoring, and human health (open access)

Accelerator mass spectrometry of Strontium-90 for homeland security, environmental monitoring, and human health

Strontium-90 is one of the most hazardous materials managed by agencies charged with protecting the public from radiation. Traditional radiometric methods have been limited by low sample throughput and slow turnaround times. Mass spectrometry offers the advantage of shorter analysis times and the ability to measure samples immediately after processing, however conventional mass spectrometric techniques are susceptible to molecular isobaric interferences that limit their overall sensitivity. In contrast, accelerator mass spectrometry is insensitive to molecular interferences and we have therefore begun developing a method for determination of {sup 90}Sr by accelerator mass spectrometry. Despite a pervasive interference from {sup 90}Zr, our initial development has yielded an instrumental background of {approx} 10{sup 8} atoms (75 mBq) per sample. Further refinement of our system (e.g., redesign of our detector, use of alternative target materials) is expected to push the background below 10{sup 6} atoms, close to the theoretical limit for AMS. Once we have refined our system and developed suitable sample preparation protocols, we will utilize our capability in applications to homeland security, environmental monitoring, and human health.
Date: March 3, 2008
Creator: Tumey, S J; Brown, T A; Hamilton, T F & Hillegonds, D J
System: The UNT Digital Library
Direct CP, Lepton Flavor and Isospin Asymmetries in the Decays B->K(*)l+l- (open access)

Direct CP, Lepton Flavor and Isospin Asymmetries in the Decays B->K(*)l+l-

We measure rate asymmetries for the rare decays B {yields} K{sup (*)}{ell}{sup +}{ell}{sup -}, where {ell}{sup +}{ell}{sup -} is either e{sup +}e{sup -} or {mu}{sup +}{mu}{sup -}, using a sample of 384 million B{bar B} events collected with the BABAR detector at the PEP-II e{sup +}e{sup -} collider. We find no evidence for direct CP or lepton-flavor asymmetries. For dilepton masses below the J/{psi} resonance, we find evidence for unexpectedly large isospin asymmetries in both B {yields} K{ell}{sup +}{ell}{sup -} and B {yields} K*{ell}{sup +}{ell}{sup -} which differ respectively by 3.2{sigma} and 2.7{sigma}, including systematic uncertainties, from the Standard Model expectations.
Date: March 3, 2009
Creator: Aubert, B.; Bona, M.; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Prencipe, E. et al.
System: The UNT Digital Library
Hyperspectral Mineral Mapping in Support of Geothermal Exploration: Examples from Long Valley Caldera, CA and Dixie Valley, NV, USA (open access)

Hyperspectral Mineral Mapping in Support of Geothermal Exploration: Examples from Long Valley Caldera, CA and Dixie Valley, NV, USA

Growing interest and exploration dollars within the geothermal sector have paved the way for increasingly sophisticated suites of geophysical and geochemical tools and methodologies. The efforts to characterize and assess known geothermal fields and find new, previously unknown resources has been aided by the advent of higher spatial resolution airborne geophysics (e.g. aeromagnetics), development of new seismic processing techniques, and the genesis of modern multi-dimensional fluid flow and structural modeling algorithms, just to name a few. One of the newest techniques on the scene, is hyperspectral imaging. Really an optical analytical geochemical tool, hyperspectral imagers (or imaging spectrometers as they are also called), are generally flown at medium to high altitudes aboard mid-sized aircraft and much in the same way more familiar geophysics are flown. The hyperspectral data records a continuous spatial record of the earth's surface, as well as measuring a continuous spectral record of reflected sunlight or emitted thermal radiation. This high fidelity, uninterrupted spatial and spectral record allows for accurate material distribution mapping and quantitative identification at the pixel to sub-pixel level. In volcanic/geothermal regions, this capability translates to synoptic, high spatial resolution, large-area mineral maps generated at time scales conducive to both the faster pace of …
Date: March 3, 2004
Creator: Pickles, W. L.; Martini, B. A.; Silver, E. A. & Cocks, P. A.
System: The UNT Digital Library
Passive Seismic Monitoring for Rockfall at Yucca Mountain: Concept Tests (open access)

Passive Seismic Monitoring for Rockfall at Yucca Mountain: Concept Tests

For the purpose of proof-testing a system intended to remotely monitor rockfall inside a potential radioactive waste repository at Yucca Mountain, a system of seismic sub-arrays will be deployed and tested on the surface of the mountain. The goal is to identify and locate rockfall events remotely using automated data collecting and processing techniques. We install seismometers on the ground surface, generate seismic energy to simulate rockfall in underground space beneath the array, and interpret the surface response to discriminate and locate the event. Data will be analyzed using matched-field processing, a generalized beam forming method for localizing discrete signals. Software is being developed to facilitate the processing. To date, a three-component sub-array has been installed and successfully tested.
Date: March 3, 2003
Creator: Cheng, J.; Twilley, K.; Murvosh, H.; Tu, Y.; Luke, B.; Yfantis, A. et al.
System: The UNT Digital Library
A primer on regression methods for decoding cis-regulatory logic (open access)

A primer on regression methods for decoding cis-regulatory logic

The rapidly emerging field of systems biology is helping us to understand the molecular determinants of phenotype on a genomic scale [1]. Cis-regulatory elements are major sequence-based determinants of biological processes in cells and tissues [2]. For instance, during transcriptional regulation, transcription factors (TFs) bind to very specific regions on the promoter DNA [2,3] and recruit the basal transcriptional machinery, which ultimately initiates mRNA transcription (Figure 1A). Learning cis-Regulatory Elements from Omics Data A vast amount of work over the past decade has shown that omics data can be used to learn cis-regulatory logic on a genome-wide scale [4-6]--in particular, by integrating sequence data with mRNA expression profiles. The most popular approach has been to identify over-represented motifs in promoters of genes that are coexpressed [4,7,8]. Though widely used, such an approach can be limiting for a variety of reasons. First, the combinatorial nature of gene regulation is difficult to explicitly model in this framework. Moreover, in many applications of this approach, expression data from multiple conditions are necessary to obtain reliable predictions. This can potentially limit the use of this method to only large data sets [9]. Although these methods can be adapted to analyze mRNA expression data from …
Date: March 3, 2009
Creator: Das, Debopriya; Pellegrini, Matteo & Gray, Joe W.
System: The UNT Digital Library
Molecular stress response in the CNS of mice after systemic exposureto interferon-alpha, ionizing radiation and ketamine (open access)

Molecular stress response in the CNS of mice after systemic exposureto interferon-alpha, ionizing radiation and ketamine

We previously showed that the expression of troponin T1 (Tnnt 1) was induced in the central nervous system (CNS) of adultmice 30 min after treatment with ketamine, a glutamate N-methyl-D-aspartic acid (NMDA) receptor antagonist. We hypothesized that Tnnt 1 expression may be an early molecular biomarker of stress response in the CNS of mice. To further evaluate this hypothesis, we investigated the regional expression of Tnnt 1 in the mouse brain using RNA in situ hybridization 4 h after systemic exposure to interferon-a (IFN-a) and gamma ionizing radiation, both of which have be associated with wide ranges of neuropsychiatric complications. Adult B6C3F1 male mice were treated with either human IFN-a (a single i.p. injection at 1 x 105 IU/kg) or whole body gamma-radiation (10 cGy or 2 Gy). Patterns of Tnnt 1 transcript expression were compared in various CNS regions after IFN-a, radiation and ketamine treatments (previous study). Tnnt 1 expression was consistently induced in pyramidal neurons of cerebral cortex and hippocampus after all treatment regimens including 10 cGy of ionizing radiation. Regional expression of Tnnt 1 was induced in Purkinje cells of cerebellum after ionizing radiation and ketamine treatment; but not after IFN-a treatment. None of the three treatments …
Date: March 3, 2009
Creator: Lowe, Xiu R.; Marchetti, Francesco; Lu, Xiaochen & Wyrobek, Andrew J.
System: The UNT Digital Library
Z' Bosons, the NuTeV Anomaly, and the Higgs Boson Mass (open access)

Z' Bosons, the NuTeV Anomaly, and the Higgs Boson Mass

Fits to the precision electroweak data that include the NuTeV measurement are considered in family universal, anomaly free U(1) extensions of the Standard Model. In data sets from which the hadronic asymmetries are excluded, some of the Z{prime} models can double the predicted value of the Higgs boson mass, from {approx} 60 to {approx} 120 GeV, removing the tension with the LEP II lower bound, while also modestly improving the {chi}{sup 2} confidence level. The effect of the Z{prime} models on both m{sub H} and the {chi}{sup 2} confidence level is increased when the NuTeV measurement is included in the fit. Both the original NuTeV data and a revised estimate by the PDG are considered.
Date: March 3, 2009
Creator: Chanowitz, Michael S
System: The UNT Digital Library
IMPACT OF NOBLE METALS AND MERCURY ON HYDROGEN GENERATION DURING HIGH LEVEL WASTE PRETREATMENT AT THE SAVANNAH RIVER SITE (open access)

IMPACT OF NOBLE METALS AND MERCURY ON HYDROGEN GENERATION DURING HIGH LEVEL WASTE PRETREATMENT AT THE SAVANNAH RIVER SITE

The Defense Waste Processing Facility (DWPF) at the Savannah River Site vitrifies radioactive High Level Waste (HLW) for repository internment. The process consists of three major steps: waste pretreatment, vitrification, and canister decontamination/sealing. HLW consists of insoluble metal hydroxides (primarily iron, aluminum, calcium, magnesium, manganese, and uranium) and soluble sodium salts (carbonate, hydroxide, nitrite, nitrate, and sulfate). The pretreatment process in the Chemical Processing Cell (CPC) consists of two process tanks, the Sludge Receipt and Adjustment Tank (SRAT) and the Slurry Mix Evaporator (SME) as well as a melter feed tank. During SRAT processing, nitric and formic acids are added to the sludge to lower pH, destroy nitrite and carbonate ions, and reduce mercury and manganese. During the SME cycle, glass formers are added, and the batch is concentrated to the final solids target prior to vitrification. During these processes, hydrogen can be produced by catalytic decomposition of excess formic acid. The waste contains silver, palladium, rhodium, ruthenium, and mercury, but silver and palladium have been shown to be insignificant factors in catalytic hydrogen generation during the DWPF process. A full factorial experimental design was developed to ensure that the existence of statistically significant two-way interactions could be determined without …
Date: March 3, 2009
Creator: Stone, M; Tommy Edwards, T & David Koopman, D
System: The UNT Digital Library
PACKAGING AND TRANSPORTATION OF NEPTUNIUM OXIDE (open access)

PACKAGING AND TRANSPORTATION OF NEPTUNIUM OXIDE

The Savannah River Site's HB-Line Facility completed a campaign in which fifty (50) cans of neptunium oxide were produced and shipped to the Idaho National Laboratory in the 9975 shipping container. This shipping campaign involved the addition of neptunium oxide to the 9975 Safety Analysis Report for Packaging (SARP) as a new content and subsequently a Letter of Amendment to the SARP content table. This paper will address the proper steps which should be taken to add a new content table to a SARP. It will also address the importance of product sampling and understanding the material shipping requirements of a SARP.
Date: March 3, 2009
Creator: Watkins, R; Steve Hensel, S & Jeffrey Jordan, J
System: The UNT Digital Library
Subject Responses to Electrochromic Windows (open access)

Subject Responses to Electrochromic Windows

Forty-three subjects worked in a private office with switchable electrochromic windows, manually-operated Venetian blinds, and dimmable fluorescent lights. The electrochromic window had a visible transmittance range of approximately 3-60%. Analysis of subject responses and physical data collected during the work sessions showed that the electrochromic windows reduced the incidence of glare compared to working under a fixed transmittance (60%) condition. Subjects used the Venetian blinds less often and preferred the variable transmittance condition, but used slightly more electric lighting with it than they did when window transmittance was fixed.
Date: March 3, 2006
Creator: Clear, Robert; Inkarojrit, Vorapat & Lee, Eleanor
System: The UNT Digital Library
Improving the Performance of Lithium Manganese Phosphate Through Divalent Cation Substitution (open access)

Improving the Performance of Lithium Manganese Phosphate Through Divalent Cation Substitution

Highly crystalline samples of LiMnPO{sub 4} and its analogs with partial substitution of Mn by divalent Mg, Cu, Zn, and Ni were prepared by hydrothermal synthesis and characterized by x-ray diffraction and infrared spectroscopy. Chemical oxidation produced two-phase mixtures of the initial phases LiMn{sub (1-y)}M{sub y}PO{sub 4} and the delithiated forms, Li{sub y}Mn{sub (1-y)}M{sub y}PO{sub 4}, all with the olivine structure. The extent of oxidation depended upon the quantity of oxidizing agent used and on the identity of the substituent ions. Mg, Ni and Cu were found to increase the level of delithation relative to that in pure LiMnPO{sub 4}. Mg was also shown to reduce the tendency of the oxidized phase to absorb water.
Date: March 3, 2008
Creator: Chen, Guoying & Richardson, Thomas J.
System: The UNT Digital Library
Automated Tamper Indicating Device (TID) Issuance System (open access)

Automated Tamper Indicating Device (TID) Issuance System

The Material Control and Accountability (MC and A) Group has developed an electronic scan system to acknowledge issuance and returns of Tamper Indicating Device (TID) seals. Important MC and A features of the system are: 1. The system requires the issuer identification and the identification of applicators to be entered, thereby ensuring that at least two qualified issuers and applicators possess the seals. Also, Operations is prompted to ensure the Two Person Rule is met during issuance and application of the seals. 2. All input is date and time stamped to ease resolution of anomalies. 3. The system requires all information to be input before allowing the user to logoff, thereby eliminating the problem of incomplete information in the records. 4. The input is immediately available to FBL MC and A personnel outside the facility who then know to expect completed procedures and forms regarding these transactions. The paper will describe the application of these features in routine operations as well as the development effort and final configuration of the system.
Date: March 3, 2004
Creator: WILSON, LEE
System: The UNT Digital Library
Vadose Zone Remediation of CO2 Leakage from Geologic CO2 Storage Sites (open access)

Vadose Zone Remediation of CO2 Leakage from Geologic CO2 Storage Sites

In the unlikely event that CO2 leakage from deep geologic CO2 sequestration sites reaches the vadose zone, remediation measures for removing the CO2 gas plume may have to be undertaken. Carbon dioxide leakage plumes are similar in many ways to volatile organic compound (VOC) vapor plumes, and the same remediation approaches are applicable. We present here numerical simulation results of passive and active remediation strategies for CO2 leakage plumes in the vadose zone. The starting time for the remediation scenarios is assumed to be after a steady-state CO2 leakage plume is established in the vadose zone, and the source of this plume has been cut off. We consider first passive remediation, both with and without barometric pumping. Next, we consider active methods involving extraction wells in both vertical and horizontal configurations. To compare the effectiveness of the various remediation strategies, we define a half-life of the CO2 plume as a convenient measure of the CO2 removal rate. For CO2 removal by passive remediation approaches such as barometric pumping, thicker vadose zones generally require longer remediation times. However, for the case of a thin vadose zone where a significant fraction of the CO2 plume mass resides within the high liquid saturation …
Date: March 3, 2004
Creator: Zhang, Yingqi; Oldenburg, Curtis M. & Benson, Sally M.
System: The UNT Digital Library
NMR Chemical Shifts in Amino Acids: Effects of Environments, Electric Field, and Amine Group Rotation (open access)

NMR Chemical Shifts in Amino Acids: Effects of Environments, Electric Field, and Amine Group Rotation

The authors present calculations of NMR chemical shifts in crystalline phases of some representative amino acids such as glycine, alanine, and alanyl-alanine. To get an insight on how different environments affect the chemical shifts, they study the transition from the crystalline phase to completely isolated molecules of glycine. In the crystalline limit, the shifts are dominated by intermolecular hydrogen-bonds. In the molecular limit, however, dipole electric field effects dominate the behavior of the chemical shifts. They show that it is necessary to average the chemical shifts in glycine over geometries. Tensor components are analyzed to get the angle dependent proton chemical shifts, which is a more refined characterization method.
Date: March 3, 2002
Creator: Yoon, Young-Gui; Pfrommer, Bernd G.; Louie, Steven G. & Canning, Andrew
System: The UNT Digital Library
Hydrogen Storage: The Key Challenge Facing a Hydrogen Economy (open access)

Hydrogen Storage: The Key Challenge Facing a Hydrogen Economy

The development of a viable hydrogen storage system is one of the key challenges that must be met prior to the establishment of a true hydrogen economy. Current hydrogen storage options, such as compressed gas and liquid hydrogen, fall short of meeting vehicle manufacturers' goals for safe and efficient energy storage. The most viable long-term alternative to these options is solid-state storage, which has been proven both safe and efficient. The Savannah River Technology Center (SRTC), with over 50 years of hydrogen storage expertise and over 25 years of expertise in solid-state storage, has assembled a world-class team to meet this key challenge. The SRTC team is comprised of distinguished scientists and engineers from national laboratories, leading universities, and major corporate research centers that are actively performing research in hydrogen storage on complex hydrides. Their collective expertise in materials development combined with fundamental science and systems engineering, will provide the synergy to meet the hydrogen storage goals. The team's goal is to develop a hydrogen storage system that meets the 2010 U.S. DOE targets, which includes a system with greater than 6 wt per cent hydrogen.
Date: March 3, 2004
Creator: MOTYKA, THEODORE
System: The UNT Digital Library
Cesium Removal from Savannah River Site Radioactive Waste Using the Caustic Side Solvent Extraction (CSSX) Process (open access)

Cesium Removal from Savannah River Site Radioactive Waste Using the Caustic Side Solvent Extraction (CSSX) Process

Researchers at the Savannah River Technology Center (SRTC) successfully demonstrated the Caustic-Side Solvent Extraction (CSSX) process flow sheet using a 33-stage, 2-cm centrifugal contactor apparatus in two 24-hour tests using actual high level waste. Previously, we demonstrated the solvent extraction process with actual SRS HLW supernatant solution using a non-optimized solvent formulation. Following that test, the solvent system was optimized to enhance extractant solubility in the diluent by increasing the modifier concentration. We now report results of two tests with the new and optimized solvent.
Date: March 3, 2004
Creator: WALKER, DARREL
System: The UNT Digital Library