Environmental Energy Technologies Division Newsletter, Fall 2007,Vol.4, No. 4) (open access)

Environmental Energy Technologies Division Newsletter, Fall 2007,Vol.4, No. 4)

This issue's special focus is on advanced lithium ionbatteries for hybrid electric vehicle applications. The four articlesaddressing this area explore the modeling of lithium ion batterychemistries; the use of advanced diagnostic methods to study the physicsand chemistry of battery materials; a laboratory for advanced batterytesting; and approaches for improving battery safety. EETD's research isfunded by the Department of Energy's BATT (Batteries for AdvancedTransportation Technologies) program, FreedomCar and Vehicle TechnologiesProgram.
Date: December 14, 2007
Creator: Chen, Allan (Editor)
Object Type: Journal/Magazine/Newsletter
System: The UNT Digital Library
Erratum: High power impulse magnetron sputtering:Current-voltage-time characteristics indicate the onset of sustainedself-sputtering (open access)

Erratum: High power impulse magnetron sputtering:Current-voltage-time characteristics indicate the onset of sustainedself-sputtering

None
Date: December 14, 2007
Creator: Anders, Andre; Andersson, Joakim & Ehiasarian, Arutiun
Object Type: Article
System: The UNT Digital Library
Geology Data Package for the Single-Shell Tank Waste Management Areas at the Hanford Site (open access)

Geology Data Package for the Single-Shell Tank Waste Management Areas at the Hanford Site

This data package discusses the geology of the single-shell tank (SST) farms and the geologic history of the area. The purpose of this report is to provide the most recent geologic information available for the SST farms. This report builds upon previous reports on the tank farm geology and Integrated Disposal Facility geology with information available after those reports were published.
Date: December 14, 2007
Creator: Reidel, Stephen P. & Chamness, Mickie A.
Object Type: Report
System: The UNT Digital Library
ILC Reference Design Report: Accelerator Executive Summary (open access)

ILC Reference Design Report: Accelerator Executive Summary

The International Linear Collider (ILC) is a 200-500 GeV center-of-mass high-luminosity linear electron-positron collider, based on 1.3 GHz superconducting radiofrequency (SCRF) accelerating cavities. The use of the SCRF technology was recommended by the International Technology Recommendation Panel (ITRP) in August 2004 [1], and shortly thereafter endorsed by the International Committee for Future Accelerators (ICFA). In an unprecedented milestone in high-energy physics, the many institutes around the world involved in linear collider R&D united in a common effort to produce a global design for the ILC. In November 2004, the 1st International Linear Collider Workshop was held at KEK, Tsukuba, Japan. The workshop was attended by some 200 accelerator physicists from around the world, and paved the way for the 2nd ILC Workshop in August 2005, held at Snowmass, Colorado, USA, where the ILC Global Design Effort (GDE) was officially formed. The GDE membership reflects the global nature of the collaboration, with accelerator experts from all three regions (Americas, Asia and Europe). The first major goal of the GDE was to define the basic parameters and layout of the machine--the Baseline Configuration. This was achieved at the first GDE meeting held at INFN, Frascati, Italy in December 2005 with the creation …
Date: December 14, 2007
Creator: Phinney, Nan
Object Type: Article
System: The UNT Digital Library
Improved Radiation Dosimetry/Risk Estimates to Facilitate Environmental Management of Plutonium-Contaminated Sites (open access)

Improved Radiation Dosimetry/Risk Estimates to Facilitate Environmental Management of Plutonium-Contaminated Sites

This report summarizes 4 years of research achievements in this Office of Science (BER), U.S. Department of Energy (DOE) project. The research described was conducted by scientists and supporting staff at Lovelace Respiratory Research Institute (LRRI)/Lovelace Biomedical and Environmental Research Institute (LBERI) and the Southern Urals Biophysics Institute (SUBI). All project objectives and goals were achieved. A major focus was on obtaining improved cancer risk estimates for exposure via inhalation to plutonium (Pu) isotopes in the workplace (DOE radiation workers) and environment (public exposures to Pu-contaminated soil). A major finding was that low doses and dose rates of gamma rays can significantly suppress cancer induction by alpha radiation from inhaled Pu isotopes. The suppression relates to stimulation of the body's natural defenses, including immunity against cancer cells and selective apoptosis which removes precancerous and other aberrant cells.
Date: December 14, 2007
Creator: Scott, Bobby R.; Tokarskaya, Zoya B.; Zhuntova, Galina V.; Osovets, Sergey V. & Syrchikov, Victor A., Belyaeva, Zinaida D.
Object Type: Report
System: The UNT Digital Library
Investigating Inflation in Type IIA (open access)

Investigating Inflation in Type IIA

We prove that inflation is forbidden in the most well understood class of semi-realistic type IIA string compactifications: Calabi-Yau compactifications with only standard NS-NS 3-form flux, R-R fluxes, D6-branes and O6-planes at large volume and small string coupling. With these ingredients, the first slow-roll parameter satisfies {epsilon} {ge} 27/13 whenever V > 0, ruling out both inflation (including brane/anti-brane inflation) and de Sitter vacua in this limit. Our proof is based on the dependence of the 4-dimensional potential on the volume and dilaton moduli in the presence of fluxes and branes. We also describe broader classes of IIA models which may include cosmologies with inflation and/or de Sitter vacua. The inclusion of extra ingredients, such as NS 5-branes and geometric or non-geometric NS-NS fluxes, evades the assumptions used in deriving the no-go theorem. We focus on NS 5-branes and outline how such ingredients may prove fruitful for cosmology, but we do not provide an explicit model. We contrast the results of our IIA analysis with the rather different situation in IIB.
Date: December 14, 2007
Creator: Hertzberg, Mark P.; /MIT; Kachru, Shamit; /Stanford U., Phys. Dept. /SLAC; Taylor, Washington; Tegmark, Max et al.
Object Type: Article
System: The UNT Digital Library
Localized Pd Overgrowth on Cubic Pt Nanocrystals for Enhanced Electrocatalytic Oxidation of Formic Acid (open access)

Localized Pd Overgrowth on Cubic Pt Nanocrystals for Enhanced Electrocatalytic Oxidation of Formic Acid

Single crystalline surface such as (100), (111), (110) has been studied as an idealized platform for electrocatalytic reactions since the atomic arrangement affects a catalytic property. The secondary metal deposition on these surfaces also alters the catalytic property often showing improvement such as poisoning decrease. On the other hand, electrocatalysts used for practical purpose usually have a size on the order of nanometers. Therefore, linking the knowledge from single crystalline studies to nanoparticle catalysts is of enormous importance. Recently, the Pt nanoparticles which surface structure was preferentially oriented was synthesized and used as electrocatalysts. Here, we demonstrate a rational design of a binary metallic nanocatalyst based on the single crystalline study.
Date: December 14, 2007
Creator: Lee, Hyunjoo; Habas, Susan; Somorjai, Gabor & Yang, Peidong
Object Type: Article
System: The UNT Digital Library
Measurements and Phenomenological Modeling of Magnetic FluxBuildup in Spheromak Plasmas (open access)

Measurements and Phenomenological Modeling of Magnetic FluxBuildup in Spheromak Plasmas

Internal magnetic field measurements and high-speed imaging at the Sustained Spheromak Physics Experiment (SSPX) [E. B. Hooper, L. D. Pearlstein, R. H. Bulmer, Nucl. Fusion 39, 863 (1999)] are used to study spheromak formation and field buildup. The measurements are analyzed in the context of a phenomenological model of magnetic helicity based on the topological constraint of minimum helicity in the open flux before reconnecting and linking closed flux. Two stages are analyzed: (1) the initial spheromak formation, i. e. when all flux surfaces are initially open and reconnect to form open and closed flux surfaces, and (2) the stepwise increase of closed flux when operating the gun on a new mode that can apply a train of high-current pulses to the plasma. In the first stage, large kinks in the open flux surfaces are observed in the high-speed images taken shortly after plasma breakdown, and coincide with large magnetic asymmetries recorded in a fixed insertable magnetic probe that spans the flux conserver radius. Closed flux (in the toroidal average sense) appears shortly after this. This stage is also investigated using resistive magnetohydrodynamic simulations. In the second stage, a time lag in response between open and closed flux surfaces after …
Date: December 14, 2007
Creator: Romero-Talamas, C. A.; Hooper, E. B.; Jayakumar, R.; McLean, H. S.; Wood, R. D. & Moller, J. M.
Object Type: Article
System: The UNT Digital Library
New and Novel Nondestructive Neutron and Gamma-Ray Technologies Applied to Safeguards (open access)

New and Novel Nondestructive Neutron and Gamma-Ray Technologies Applied to Safeguards

None
Date: December 14, 2007
Creator: Dougan, A. D.; Snyderman, N. J.; Nakae, L. F.; Dietrich, D. D.; Kerr, P. L.; Wang, T. F. et al.
Object Type: Article
System: The UNT Digital Library
Non-Relativistic Superstring Theories (open access)

Non-Relativistic Superstring Theories

We construct a supersymmetric version of the 'critical' non-relativistic bosonic string theory [1] with its manifest global symmetry. We introduce the anticommuting bc CFT which is the super partner of the {beta}{gamma} CFT. The conformal weights of the b and c fields are both 1/2. The action of the fermionic sector can be transformed into that of the relativistic superstring theory. We explicitly quantize the theory with manifest SO(8) symmetry and find that the spectrum is similar to that of Type IIB superstring theory. There is one notable difference: the fermions are non-chiral. We further consider 'noncritical' generalizations of the supersymmetric theory using the superspace formulation. There is an infinite range of possible string theories similar to the supercritical string theories. We comment on the connection between the critical non-relativistic string theory and the lightlike Linear Dilaton theory.
Date: December 14, 2007
Creator: Kim, Bom Soo
Object Type: Article
System: The UNT Digital Library
Report Initial Work on Developing Plasma Modeling Capability in WARP for NDCX Experiments (open access)

Report Initial Work on Developing Plasma Modeling Capability in WARP for NDCX Experiments

This milestone has been accomplished. The Heavy Ion Fusion Science Virtual National Laboratory (HIFS-VNL) has developed and implemented an initial beam-in-plasma implicit modeling capability in Warp; has carried out tests validating the behavior of the models employed; has compared the results of electrostatic and electromagnetic models when applied to beam expansion in an NDCX-I relevant regime; has compared Warp and LSP results on a problem relevant to NDCX-I; has modeled wave excitation by a rigid beam propagating through plasma; and has implemented and begun testing a more advanced implicit method that correctly captures electron drift motion even when timesteps too large to resolve the electron gyro-period are employed. The HIFS-VNL is well on its way toward having a state-of-the-art source-to-target simulation capability that will enable more effective support of ongoing experiments in the NDCX series and allow more confident planning for future ones.
Date: December 14, 2007
Creator: Friedman, A; Cohen, R H; Grote, D P & Vay, J
Object Type: Report
System: The UNT Digital Library
Three-dimensional Dielectric Photonic Crystal Structures for Laser-driven Acceleration (open access)

Three-dimensional Dielectric Photonic Crystal Structures for Laser-driven Acceleration

We present the design and simulation of a three-dimensional photonic crystal waveguide for linear laser-driven acceleration in vacuum. The structure confines a synchronous speed-of-light accelerating mode in both transverse dimensions. We report the properties of this mode, including sustainable gradient and optical-to-beam efficiency. We present a novel method for confining a particle beam using optical fields as focusing elements. This technique, combined with careful structure design, is shown to have a large dynamic aperture and minimal emittance growth, even over millions of optical wavelengths.
Date: December 14, 2007
Creator: Cowan, Benjamin M. & /Tech-X, Boulder /SLAC
Object Type: Article
System: The UNT Digital Library
Unique Identification of Lee-Wick Gauge Bosons at Linear Colliders (open access)

Unique Identification of Lee-Wick Gauge Bosons at Linear Colliders

Grinstein, O'Connell and Wise have recently presented an extension of the Standard Model (SM), based on the ideas of Lee and Wick (LW), which demonstrates an interesting way to remove the quadratically divergent contributions to the Higgs mass induced by radiative corrections. This model predicts the existence of negative-norm copies of the usual SM fields at the TeV scale with ghost-like propagators and negative decay widths, but with otherwise SM-like couplings. In earlier work, it was demonstrated that the LW states in the gauge boson sector of these models, though easy to observe, cannot be uniquely identified as such at the LHC. In this paper, we address the issue of whether or not this problem can be resolved at an e{sup +}e{sup -} collider with a suitable center of mass energy range. We find that measurements of the cross section and the left-right polarization asymmetry associated with Bhabha scattering can lead to a unique identification of the neutral electroweak gauge bosons of the Lee-Wick type.
Date: December 14, 2007
Creator: Rizzo, Thomas G.
Object Type: Article
System: The UNT Digital Library
Use of ARM Data to address the Climate Change Further Development and Applications of A Multi-scale Modeling Framework (open access)

Use of ARM Data to address the Climate Change Further Development and Applications of A Multi-scale Modeling Framework

The Colorado State University (CSU) Multi-scale Modeling Framework (MMF) is a new type of general circulation model (GCM) that replaces the conventional parameterizations of convection, clouds and boundary layer with a cloud-resolving model (CRM) embedded into each grid column. The MMF that we have been working with is a “super-parameterized” version of the Community Atmosphere Model (CAM). As reported in the publications listed below, we have done extensive work with the model. We have explored the MMF’s performance in several studies, including an AMIP run and a CAPT test, and we have applied the MMF to an analysis of climate sensitivity.
Date: December 14, 2007
Creator: Randall, David A. & Khairoutdinov, Marat
Object Type: Report
System: The UNT Digital Library
Active Damping of the E-P Instability at the LANL PSR (open access)

Active Damping of the E-P Instability at the LANL PSR

A prototype of an analog, transverse (vertical) feedback system for active damping of the two-stream (e-p) instability has been developed and successfully tested at the Los Alamos National Laboratory Proton Storage Ring (PSR). This system was able to improve the instability threshold by approximately 30% (as measured by the change in RF buncher voltage at instability threshold). Evidence obtained from these tests suggests that further improvement in performance is limited by beam leakage into the gap at lower RF buncher voltage and the onset of instability in the horizontal plane, which had no feedback. Here we describe the present system configuration, system optimization, results of several recent experimental tests, and results from studies of factors limiting its performance.
Date: November 14, 2007
Creator: McCrady, R.; Macek, R.J.; Zaugg, T.; Alamos, /Los; Assadi, S.; Deibele, C. et al.
Object Type: Article
System: The UNT Digital Library
AGN-Induced Cavities in NGC 1399 And NGC 4649 (open access)

AGN-Induced Cavities in NGC 1399 And NGC 4649

We present an analysis of archival Chandra and VLA observations of the E0 galaxy NGC1399 and the E2 galaxy NGC4649 in which we investigate cavities in the surrounding X-ray emitting medium caused by the central AGN. We calculate the jet power required for the AGN to evacuate these cavities and find values of {approx} 8x10{sup 41} erg s-1 and {approx} 14x10{sup 41} erg s{sup -1} for the lobes of NGC1399 and {approx} 7x10{sup 41} erg s{sup -1} and {approx} 6x1041 erg s{sup -1} for those of NGC4649. We also calculate the k/f values for each cavity, where k is the ratio of the total particle energy to that of electrons radiating in the range of 10 MHz to 10 GHz, and f is the volume filling factor of the plasma in the cavity. We find that the values of k/f for the lobes of NGC1399 are {approx} 93 and {approx} 190, and those of the lobes of NGC4649 are {approx} 15000 and {approx} 12000. We conclude that the assumed spectrum describes the electron distribution in the lobes of NGC1399 reasonably well, and that there are few entrained particles. For NGC4649, either there are many entrained particles or the model spectrum …
Date: November 14, 2007
Creator: Shurkin, K.; U., /New Mexico; Dunn, R. J. H.; U., /Southampton; Gentile, G.; Taylor, G. B. et al.
Object Type: Article
System: The UNT Digital Library

Air Cooling Technology for Power Electronics Thermal Control

Assessing potential for air cooling in power electronics is a critical factor in power electronics equipment. NREL aims to assess effective air cooling techniques for power electronics technologies.
Date: November 14, 2007
Creator: Bharathan, D.
Object Type: Presentation
System: The UNT Digital Library
Direct Observation of Cosmic Strings Via Their Strong Gravitational Lensing Effect. 1. Predictions for High Resolution Imaging Surveys (open access)

Direct Observation of Cosmic Strings Via Their Strong Gravitational Lensing Effect. 1. Predictions for High Resolution Imaging Surveys

We use current theoretical estimates for the density of long cosmic strings to predict the number of strong gravitational lensing events in astronomical imaging surveys as a function of angular resolution and survey area. We show that angular resolution is the single most important factor, and that interesting limits on the dimensionless string tension G{mu}/c{sup 2} can be obtained by existing and planned surveys. At the resolution of the Hubble Space Telescope (0'.14), it is sufficient to survey of order a square degree -- well within reach of the current HST archive -- to probe the regime G{mu}/c{sup 2} {approx} 10{sup -8}. If lensing by cosmic strings is not detected, such a survey would improve the limit on the string tension by an order of magnitude on that available from the cosmic microwave background. At the resolution (0'.028) attainable with the next generation of large ground based instruments, both in the radio and the infra-red with adaptive optics, surveying a sky area of order ten square degrees will allow us to probe the G{mu}/c{sup 2} {approx} 10{sup -9} regime. These limits will not be improved significantly by increasing the solid angle of the survey.
Date: November 14, 2007
Creator: Gasparini, Maria Alice; Marshall, Phil; Treu, Tommaso; /UC, Santa Barbara; Morganson, Eric; /KIPAC, Menlo Park et al.
Object Type: Article
System: The UNT Digital Library
Discovery of a Jupiter/Saturn Analog With Gravitational Microlensing (open access)

Discovery of a Jupiter/Saturn Analog With Gravitational Microlensing

Searches for extrasolar planets have uncovered an astonishing diversity of planetary systems, yet the frequency of solar system analogs remains unknown. The gravitational microlensing planet search method is potentially sensitive to multiple-planet systems containing analogs of all the solar system planets except Mercury. We report the first detection of a multiple-planet system with microlensing. We identify two planets with masses of {approx} 0.71 and {approx} 0.27 times the mass of Jupiter and orbital separations of {approx} 2.3 and {approx} 4.6 astronomical units orbiting a primary of mass {approx} 0.50 solar masses. This system resembles a scaled version of our solar system in that the mass ratio, separation ratio, and equilibrium temperatures of the planets are similar to those of Jupiter and Saturn. These planets could not have been detected with other techniques; their discovery from only 6 confirmed microlensing planet detections suggests that solar system analogs may be common.
Date: November 14, 2007
Creator: Gaudi, B. S.; Bennett, D. P.; Udalski, A.; Gould, A.; Christie, G. W.; Maoz, D. et al.
Object Type: Article
System: The UNT Digital Library
ELECTROCHEMICAL CORROSION TESTS FOR TANK 241-AY-101 CORE 325 SEGMENTS 16R1 & 16R2 (open access)

ELECTROCHEMICAL CORROSION TESTS FOR TANK 241-AY-101 CORE 325 SEGMENTS 16R1 & 16R2

The interstitial liquid in the double-shell tank 241-AY-101 settled solids layer is below the hydroxide chemistry control limit required by HNF-SD-WM-TSR-006, Tank Farms Technical Safety Requirements, Administrative Control 5.16, 'Corrosion Mitigation Controls'. Operating tanks outside of the specification may increase the propensity corrosion of the carbon steel wall. This report is concerned with generalized electrochemical corrosion mechanism that may occur at specific loci. All cyclic potentiodynamic polarization scans exhibited a negative hysteresis, scan reversing at lower current density, indicating that there was no pitting propensity. The general electrochemical corrosion rates ranged from 4.4E-02 to 1.5E-03 mpy with the first round of coupons, while the second round yielded corrosion rates of 2.5E-03 to 2.9E-02 mpy.
Date: November 14, 2007
Creator: JB, DUNCAN & RB, WYRWAS
Object Type: Report
System: The UNT Digital Library
Electron Cloud Generation And Trapping in a Quadrupole Magnet at the Los Alamos PSR (open access)

Electron Cloud Generation And Trapping in a Quadrupole Magnet at the Los Alamos PSR

A diagnostic to measure electron cloud formation and trapping in a quadrupole magnet has been developed, installed, and successfully tested at PSR. Beam studies with this diagnostic show that the electron flux striking the wall in the quadrupole is comparable to or larger than in an adjacent drift. In addition, the trapped electron signal, obtained using the sweeping feature of diagnostic, was larger than expected and decayed very slowly with an exponential time constant of 50 to 100 {micro}s. Experimental results were also obtained which suggest that a significant fraction of the electrons observed in the adjacent drift space were seeded by electrons ejected from the quadrupole.
Date: November 14, 2007
Creator: Macek, R. J.; Browman, A. A.; Ledford, J. E.; Borden, M. J.; O'Hara, J. F.; McCrady, R. C. et al.
Object Type: Article
System: The UNT Digital Library
EXAMPLE OF A RISK BASED DISPOSAL APPROVAL SOLIDIFICATION OF HANFORD SITE TRANSURANIC (TRU) WASTE (open access)

EXAMPLE OF A RISK BASED DISPOSAL APPROVAL SOLIDIFICATION OF HANFORD SITE TRANSURANIC (TRU) WASTE

The Hanford Site requested, and the U.S. Environmental Protection Agency (EPA) Region 10 approved, a Toxic Substances Control Act of 1976 (TSCA) risk-based disposal approval (RBDA) for solidifying approximately four cubic meters of waste from a specific area of one of the K East Basin: the North Loadout Pit (NLOP). The NLOP waste is a highly radioactive sludge that contained polychlorinated biphenyls (PCBs) regulated under TSCA. The prescribed disposal method for liquid PCB waste under TSCA regulations is either thermal treatment or decontamination. Due to the radioactive nature of the waste, however, neither thermal treatment nor decontamination was a viable option. As a result, the proposed treatment consisted of solidifying the material to comply with waste acceptance criteria at the Waste Isolation Pilot Plant (WPP) in Carlsbad, New Mexico, or possibly the Environmental Restoration Disposal Facility at the Hanford Site, depending on the resulting transuranic (TRU) content of the stabilized waste. The RBDA evaluated environmental risks associated with potential airborne PCBs. In addition, the RBDA made use of waste management controls already in place at the treatment unit. The treatment unit, the T Plant Complex, is a Resource Conservation and Recovery Act of 1976 (RCRA)-permitted facility used for storing and …
Date: November 14, 2007
Creator: AL, PRIGNANO
Object Type: Article
System: The UNT Digital Library
Experiments to Understand HPC Time to Development (Final report for Department of Energy contract DE-FG02-04ER25633) Report DOE/ER/25633-1 (open access)

Experiments to Understand HPC Time to Development (Final report for Department of Energy contract DE-FG02-04ER25633) Report DOE/ER/25633-1

In order to understand how high performance computing (HPC) programs are developed, a series of experiments, using students in graduate level HPC classes and various research centers, were conducted at various locations in the US. In this report, we discuss this research, give some of the early results of those experiments, and describe a web-based Experiment Manager we are developing that allows us to run studies more easily and consistently at universities and laboratories, allowing us to generate results that more accurately reflect the process of building HPC programs.
Date: November 14, 2007
Creator: Basili, Victor, R. & Zelkowitz, Marvin, V.
Object Type: Report
System: The UNT Digital Library
Final-State Interactions and Single-Spin Asymmetries in Semi-inclusive Deep Inelastic Scattering (open access)

Final-State Interactions and Single-Spin Asymmetries in Semi-inclusive Deep Inelastic Scattering

Recent measurements from the HERMES and SMC collaborations show a remarkably large azimuthal single-spin asymmetries A{sub UL} and A{sub UT} of the proton in semi-inclusive pion leptoproduction {gamma}*(q)p {yields} {pi}X. We show that final-state interactions from gluon exchange between the outgoing quark and the target spectator system leads to single-spin asymmetries in deep inelastic lepton-proton scattering at leading twist in perturbative QCD; i.e., the rescattering corrections are not power-law suppressed at large photon virtuality q{sup 2} at fixed x{sub bj}. The existence of such single-spin asymmetries requires a phase difference between two amplitudes coupling the proton target with J{sup z}{sub p} = {+-}1/2 to the same final-state, the same amplitudes which are necessary to produce a nonzero proton anomalous magnetic moment. We show that the exchange of gauge particles between the outgoing quark and the proton spectators produces a Coulomb-like complex phase which depends on the angular momentum L{sup z} of the proton's constituents and thus is distinct for different proton spin amplitudes. The single-spin asymmetry which arises from such final-state interactions does not factorize into a product of structure function and fragmentation function, and it is not related to the transversity distribution {delta}q(x;Q) which correlates transversely polarized quarks with …
Date: November 14, 2007
Creator: Brodsky, Stanley J.; Hwang, Dae Sung & Schmidt, Ivan
Object Type: Article
System: The UNT Digital Library