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Extraction of niobium and tantalum isotopes using organophosphorus compounds -- Part II -- Extraction of 'carrier-free' concentrations from HCl/LiCl solutions
We have studied the extraction of niobium and tantalum from mixed hydrochloric acid/lithium chloride media by bis(2-ethylhexyl) hydrogen phosphate (HDEHP) and bis(2-ethylhexyl) hydrogen phosphite (BEHP) as a function of hydrogen ion (H+) concentration. The amount of niobium extracted by both HDEHP and BEHP decreased with increasing hydrogen ion concentration. Equilibrium with niobium occurred within 10 s at all hydrogen ion concentrations for both systems. For tantalum, the amount extracted increased until 6 - 9 M H+, before decreasing at higher H+ concentrations when extracted by both HDEHP and BEHP. Equilibrium occurred within 10 s at two H+ concentrations when extracted by HDEHP. The data obtained are used as the basis to discuss the speciation of Nb and Ta under the conditions studied and to evaluate possible extraction mechanisms.
Date:
December 1, 2008
Creator:
Gates, J. M.; Stavsetra, L.; Sudowe, R.; Ali, M. N.; Calvert, M. G.; Dragojevic, I. et al.
Object Type:
Article
System:
The UNT Digital Library
Fast marching methods for the continuous traveling salesman problem
We consider a problem in which we are given a domain, a cost function which depends on position at each point in the domain, and a subset of points ('cities') in the domain. The goal is to determine the cheapest closed path that visits each city in the domain once. This can be thought of as a version of the Traveling Salesman Problem, in which an underlying known metric determines the cost of moving through each point of the domain, but in which the actual shortest path between cities is unknown at the outset. We describe algorithms for both a heuristic and an optimal solution to this problem. The order of the heuristic algorithm is at worst case M * N logN, where M is the number of cities, and N the size of the computational mesh used to approximate the solutions to the shortest paths problems. The average runtime of the heuristic algorithm is linear in the number of cities and O(N log N) in the size N of the mesh.
Date:
December 1, 2008
Creator:
Andrews, J. & Sethian, J. A.
Object Type:
Article
System:
The UNT Digital Library
Fast six-channel pyrometer for warm-dense-matter experiments with intense heavy-ion beams
This paper describes a fast multi-channel radiation pyrometer that was developed for warmdense-matter experiments with intense heavy ion beams at Gesellschaft fur Schwerionenforschung mbH (GSI). The pyrometer is capable of measuring of brightness temperatures from 2000 K to 50000 K, at 6 wavelengths in visible and near-infrared parts of spectrum, with 5 nanosecond temporal resolution and several micrometers spatial resolution. The pyrometer's spectral discrimination technique is based on interference filters, which act as filters and mirrors to allow for simultaneous spectral discrimination of the same ray at multiple wavelengths.
Date:
December 1, 2008
Creator:
Ni, P.A.; Kulish, M.I.; Mintsev, V.; Nikolaev, D.N.; Ternovoi, V.Ya.; Hoffmann, D.H.H. et al.
Object Type:
Article
System:
The UNT Digital Library
Final Scientific/Technical Report GRANT NO. DE-FG02-06ER41450
Remarkable progress towards understanding of the behavior of Nb grain boundaries in high purity cavity sheet has been accomplished. An excellent graduate student has been trained in superconductor characterization and he has developed new techniques for the preparation of high quality electron transparent samples for transmission electron microscopy so that electrical and magneto optical measurements can be made on the same local areas. Nb grain boundaries have been characterized for surface topography, superconducting flux penetration, transport current measurement and microstructure. An excellent framework for continued studies in this area has been established. The work has been well received in the SRF community and has been presented at international workshops.
Date:
December 1, 2008
Creator:
Lee, Peter J. & Larbalestier, David C.
Object Type:
Report
System:
The UNT Digital Library
Finite element analysis of the Arquin-designed CMU wall under a dynamic (blast) load.
The Arquin Corporation designed a CMU (concrete masonry unit) wall construction and reinforcement technique that includes steel wire and polymer spacers that is intended to facilitate a faster and stronger wall construction. Since the construction method for an Arquin-designed wall is different from current wall construction practices, finite element computer analyses were performed to estimate the ability of the wall to withstand a hypothetical dynamic load, similar to that of a blast from a nearby explosion. The response of the Arquin wall was compared to the response of an idealized standard masonry wall exposed to the same dynamic load. Results from the simulations show that the Arquin wall deformed less than the idealized standard wall under such loading conditions. As part of a different effort, Sandia National Laboratories also looked at the relative static response of the Arquin wall, results that are summarized in a separate SAND Report.
Date:
December 1, 2008
Creator:
Lopez, Carlos & Petti, Jason P.
Object Type:
Report
System:
The UNT Digital Library
Foreign Investment and National Security: Economic Considerations
This report assesses recent international developments as the leaders from a number of nations work to reach a consensus on an informal set of best practices regarding national restrictions on foreign investment for national security purposes.
Date:
December 1, 2008
Creator:
Jackson, James K.
Object Type:
Report
System:
The UNT Digital Library
Forrest Conservation Area : Management & Implementation FY 2004 Annual Report.
The Confederated Tribes of Warm Springs Reservation of Oregon (Tribes) acquired the Forrest Conservation Area during July of 2002. The property is located in the Upper John Day subbasin within the Columbia basin. The property consists of two parcels comprising 4,232 acres. The Mainstem parcel consists of 3,445 acres and is located 1/2 mile to the east of Prairie City, Oregon on the mainstem John Day River. The Middle Fork parcel consists of 786 acres and is located one mile to the west of the town of Austin, OR on the Middle Fork John Day River. The Forrest Conservation Area is under a memorandum of agreement with the Bonneville Power Administration (BPA) to provide an annual written report generally describing the real property interests of the project and management activities undertaken or in progress. Acquisition of the Forrest Conservation Area was funded by BPA as part of their program to protect, mitigate, and enhance fish and wildlife habitat affected by hydroelectric facilities on the Columbia River and its tributaries. The intent of the Conservation Area is to partially mitigate fish and wildlife impacts for the John Day Dam on the Columbia River as outlined in the Northwest Power Planning Council's …
Date:
December 1, 2008
Creator:
Smith, Brent
Object Type:
Report
System:
The UNT Digital Library
Fuel Cell Buses in U.S. Transit Fleets: Current Status 2008
This report provides results from fuel cell bus evaluations at Alameda-Contra Costa Transit District, SunLine Transit Agency, and Santa Clara Valley Transportation Authority.
Date:
December 1, 2008
Creator:
Eudy, L.; Chandler, K. & Gikakis, C.
Object Type:
Report
System:
The UNT Digital Library
Function and dynamics of aptamers: A case study on the malachite green aptamer
Aptamers are short single-stranded nucleic acids that can bind to their targets with high specificity and high affinity. To study aptamer function and dynamics, the malachite green aptamer was chosen as a model. Malachite green (MG) bleaching, in which an OH- attacks the central carbon (C1) of MG, was inhibited in the presence of the malachite green aptamer (MGA). The inhibition of MG bleaching by MGA could be reversed by an antisense oligonucleotide (AS) complementary to the MGA binding pocket. Computational cavity analysis of the NMR structure of the MGA-MG complex predicted that the OH{sup -} is sterically excluded from the C1 of MG. The prediction was confirmed experimentally using variants of the MGA with changes in the MG binding pocket. This work shows that molecular reactivity can be reversibly regulated by an aptamer-AS pair based on steric hindrance. In addition to demonstrate that aptamers could control molecular reactivity, aptamer dynamics was studied with a strategy combining molecular dynamics (MD) simulation and experimental verification. MD simulation predicted that the MG binding pocket of the MGA is largely pre-organized and that binding of MG involves reorganization of the pocket and a simultaneous twisting of the MGA terminal stems around the pocket. …
Date:
December 1, 2008
Creator:
Wang, Tianjiao
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
FY 2008 Infrared Photonics Final Report
Through the duration of the NNSA Office of Nuclear Nonproliferation Research and development (NA-22) ITAS lifecycle project, the Infrared Photonics research has been focused on developing integrated quantum cascade (QC) laser technology to enable next-generation remote sensing designs. Our team developed the concept of the integrated QC laser transmitter and originated and promoted the vision of mid-infrared (3–12 μm) wavelength photonics. Sustained NA-22 project funding produced the QC laser transmitter that is now deployed in follow-on projects. Our team produced nationally recognized cutting-edge research in the area of infrared transparent chalcogenide photonics. Three technical staff were recruited from outside PNNL and hired to support this research. This project also supported student research at the national laboratory, including high school, undergraduate, and graduate students. This provided a derivative benefit to NA-22, PNNL, and the educational institutions through training and mentoring next-generation students in science and technology. The student support was also the catalyst to develop research collaborations with two universities that are internationally recognized for their chalcogenide glass research.
Date:
December 1, 2008
Creator:
Anheier, Norman C.; Bernacki, Bruce E.; Carlie, Nathan A.; Gervais, Kevin L.; Hatchell, Brian K.; Johnson, Bradley R. et al.
Object Type:
Report
System:
The UNT Digital Library
Gender Equity in Materials Science and Engineering
At the request of the University Materials Council, a national workshop was convened to examine 'Gender Equity Issues in Materials Science and Engineering.' The workshop considered causes of the historic underrepresentation of women in materials science and engineering (MSE), with a goal of developing strategies to increase the gender diversity of the discipline in universities and national laboratories. Specific workshop objectives were to examine efforts to level the playing field, understand implicit biases, develop methods to minimize bias in all aspects of training and employment, and create the means to implement a broadly inclusive, family-friendly work environment in MSE departments. Held May 18-20, 2008, at the Conference Center at the University of Maryland, the workshop included heads and chairs of university MSE departments and representatives of the National Science Foundation (NSF), the Office of Basic Energy Sciences of the Department of Energy (DOE-BES), and the national laboratories. The following recommendations are made based on the outcomes of the discussions at the workshop. Many or all of these apply equally well to universities and national laboratories and should be considered in context of industrial environments as well. First, there should be a follow-up process by which the University Materials Council (UMC) …
Date:
December 1, 2008
Creator:
Rockett, Angus
Object Type:
Text
System:
The UNT Digital Library
The genome sequence of Geobacter metallireducens: features of metabolism, physiology and regulation common and dissimilar to Geobacter sulfurreducens
Background: The genome sequence of Geobacter metallireducens is the second to be completed from the metal-respiring genus Geobacter, and is compared in this report to that of Geobacter sulfurreducens in order to understand their metabolic, physiological and regulatory similarities and differences. Results: The experimentally observed greater metabolic versatility of G. metallireducens versus G. sulfurreducens is borne out by the presence of more numerous genes for metabolism of organic acids including acetate, propionate, and pyruvate. Although G. metallireducens lacks a dicarboxylic acid transporter, it has acquired a second succinate dehydrogenase/fumarate reductase complex, suggesting that respiration of fumarate was important until recently in its evolutionary history. Vestiges of the molybdate (ModE) regulon of G. sulfurreducens can be detected in G. metallireducens, which has lost the global regulatory protein ModE but retained some putative ModE-binding sites and multiplied certain genes of molybdenum cofactor biosynthesis. Several enzymes of amino acid metabolism are of different origin in the two species, but significant patterns of gene organization are conserved. Whereas most Geobacteraceae are predicted to obtain biosynthetic reducing equivalents from electron transfer pathways via a ferredoxin oxidoreductase, G. metallireducens can derive them from the oxidative pentose phosphate pathway. In addition to the evidence of greater metabolic …
Date:
December 1, 2008
Creator:
Aklujkar, Muktak; Krushkal, Julia; DiBartolo, Genevieve; Lapidus, Alla; Land, Miriam L. & Lovley, Derek R.
Object Type:
Article
System:
The UNT Digital Library
The Geochemistry of Technetium: A Summary of the Behavior of an Artificial Element in the Natural Environment
Interest in the chemistry of technetium has only increased since its discovery in 1937, mainly because of the large and growing inventory of 99Tc generated during fission of 235U, its environmental mobility in oxidizing conditions, and its potential radiotoxicity. For every ton of enriched uranium fuel (3% 235U) that is consumed at a typical burn-up rate, nearly 1 kg of 99Tc is generated. Thus, the mass of 99Tc produced since 1993 has nearly quadrupled, and will likely to continue to increase if more emphasis is placed on nuclear power to slow the accumulation of atmospheric greenhouse gases. In order to gain a comprehensive understanding of the interaction of 99Tc and the natural environment, we review the sources of 99Tc in the nuclear fuel cycle, its chemical properties, radiochemistry, and biogeochemical behavior. We include an evaluation of the use of Re as a chemical analog of Tc, as well as a summary of the redox potential, thermodynamics, sorption, colloidal behavior, and interaction of humic substances with Tc, and the potential for re-oxidation and remobilization of Tc(IV). What emerges is a more complicated picture of Tc behavior than that of an easily tractable transition of Tc(VII) to Tc(IV) with consequent immobilization. Reducing …
Date:
December 1, 2008
Creator:
Icenhower, Jonathan P.; Qafoku, Nikolla; Martin, Wayne J. & Zachara, John M.
Object Type:
Report
System:
The UNT Digital Library
Geothermal(Ground-Source)Heat Pumps: Market Status, Barriers to Adoption, and Actions to Overcome Barriers
More effective stewardship of our resources contributes to the security, environmental sustainability, and economic well-being of the nation. Buildings present one of the best opportunities to economically reduce energy consumption and limit greenhouse gas emissions. Geothermal heat pumps (GHPs), sometimes called ground-source heat pumps, have been proven capable of producing large reductions in energy use and peak demand in buildings. However, GHPs have received little attention at the policy level as an important component of a national strategy. Have policymakers mistakenly overlooked GHPs, or are GHPs simply unable to make a major contribution to the national goals for various reasons? This brief study was undertaken at DOE's request to address this conundrum. The scope of the study includes determining the status of global GHP markets and the status of the GHP industry and technology in the United States, assembling previous estimates of GHP energy savings potential, identifying key barriers to application of GHPs, and identifying actions that could accelerate market adoption of GHPs. The findings are documented in this report along with conclusions and recommendations.
Date:
December 1, 2008
Creator:
Hughes, Patrick
Object Type:
Report
System:
The UNT Digital Library
Getting the Word Out: Diesel Exhaust Fluid (DEF) Locator, Mapping Tools, and Outreach Activities
Presentation covers diesel exhaust fluid resources on the Alternative Fuels and Advanced Vehicles Data Center.
Date:
December 1, 2008
Creator:
Brodt-Giles, Debbie
Object Type:
Presentation
System:
The UNT Digital Library
The Global Financial Crisis: The Role of the International Monetary Fund (IMF)
This report discusses two potential roles the International Monetary Fund (IMF) may have in helping to resolve the current global financal crisis
Date:
December 1, 2008
Creator:
Weiss, Martin A.
Object Type:
Report
System:
The UNT Digital Library
E-Government and Libraries Helpful Resources
Article on e-government services and how libraries can provide helpful online government resources.
Date:
December 1, 2008
Creator:
Sears, Suzanne
Object Type:
Article
System:
The UNT Digital Library
GUTs on Compact Type IIB Orientifolds
We systematically analyze globally consistent SU(5) GUT models on intersecting D7-branes in genuine Calabi-Yau orientifolds with O3- and O7-planes. Beyond the well-known tadpole and K-theory cancellation conditions there exist a number of additional subtle but quite restrictive constraints. For the realization of SU(5) GUTs with gauge symmetry breaking via U(1)Y flux we present two classes of suitable Calabi-Yau manifolds defined via del Pezzo transitions of the elliptically fibred hypersurface P{sub 1,1,1,6,9}[18] and of the Quintic P{sub 1,1,1,1,1}[5], respectively. To define an orientifold projection we classify all involutions on del Pezzo surfaces. We work out the model building prospects of these geometries and present five globally consistent string GUT models in detail, including a 3-generation SU(5) model with no exotics whatsoever. We also realize other phenomenological features such as the 10 10 5{sub H} Yukawa coupling and comment on the possibility of moduli stabilization, where we find an entire new set of so-called swiss-cheese type Calabi-Yau manifolds. It is expected that both the general constrained structure and the concrete models lift to F-theory vacua on compact Calabi-Yau fourfolds.
Date:
December 1, 2008
Creator:
Blumenhagen, Ralph; Braun, Volker; Grimm, Thomas W. & Weigand, Timo
Object Type:
Report
System:
The UNT Digital Library
Head-Tail Modes for Strong Space Charge
Head-tail modes are described here for the space charge tune shift significantly exceeding the synchrotron tune. General equation for the modes is derived. Spatial shapes of the modes, their frequencies, and coherent growth rates are explored. The Landau damping rates are also found. Suppression of the transverse mode coupling instability by the space charge is explained.
Date:
December 1, 2008
Creator:
Burov, Alexey
Object Type:
Article
System:
The UNT Digital Library
Higgs Searches at the Fermilab Tevatron p anti-p Collider
Searching for and potential discovery of Higgs boson(s) both within and beyond the standard model is perhaps the most visible physics goal of the current Fermilab Tevatron program. In this proceeding, recent results from both the CDF and D0 experiments based on analyses of datasets with integrated luminosities between 1.7 and 3.0 fb{sup -1} are summarized. The combined Tevatron cross section upper limits on the production of a standard model Higgs boson are fast approaching the expected standard model values for a wide mass range. Particularly, the Tevatron has now excluded a standard model Higgs boson with a mass of 170 GeV at 95% C.L.
Date:
December 1, 2008
Creator:
Qian, Jianming
Object Type:
Article
System:
The UNT Digital Library
High-precision gamma-ray total cross-section measurements between 3.45 and 12 MeV
A Compton-backscatter capability has recently become available at the Duke University Free Electron Laser Laboratory. This capability allows one to produce high fluxes of tunable, nearly monoenergetic gamma rays. Using these gamma-ray beams, we have made high-precision (~0.5%) measurements of the gamma-ray total cross section at 3.45, 4, 5, 6, 8, 10, and 12 MeV. The nuclei measured were Be, C, Cu, Ta, W, Pb, and U
Date:
December 1, 2008
Creator:
Frankle, Christen M. & Moss, Calvin E.
Object Type:
Report
System:
The UNT Digital Library
High Repetition Rate, LINAC-Based Nuclear Resonance Fluorescence FY 2008 Final Report
This summarizes the first year of a multi-laboratory/university, multi-year effort focusing on high repetition rate, pulsed LINAC-based nuclear resonance fluorescence (NRF) measurements. Specifically, this FY2008 effort centered on experimentally assessing NRF measurements using pulsed linear electron accelerators, operated at various repetition rates, and identifying specific detection requirements to optimize such measurements. Traditionally, interest in NRF as a detection technology, which continues to receive funding from DHS and DOE/NA-22, has been driven by continuous-wave (CW), Van de Graff-based bremsstrahlung sources. However, in addition to the relatively sparse present-day use of Van de Graff sources, only limited NRF data from special nuclear materials has been presented; there is even less data available regarding shielding effects and photon source optimization for NRF measurements on selected nuclear materials.
Date:
December 1, 2008
Creator:
Watson, Scott M; Kinlaw, Mathew T; Jones, James L; Hunt, Alan W. & Warren, Glen A.
Object Type:
Report
System:
The UNT Digital Library
[Historic Marker Application: Gugger Homestead]
Application materials submitted to the Texas Historical Commission requesting a historic marker for the Gugger Homestead, in Helotes, Texas. The materials include the inscription text of the marker, original application, narrative, floor plans, and photographs.
Date:
December 1, 2008
Creator:
Texas Historical Commission
Object Type:
Text
System:
The Portal to Texas History
[Historic Marker Application: Hicks-Gregg House]
Application materials submitted to the Texas Historical Commission requesting a historic marker for the Hicks-Gregg House, in Brownsville, Texas. The materials include the inscription text of the marker, original application, narrative, floor plans, and photographs.
Date:
December 1, 2008
Creator:
Texas Historical Commission
Object Type:
Text
System:
The Portal to Texas History