Serial/Series Title
Fiscal Year 2000
5
ARM Facilities Newsletter
4
OIT Best Practices
4
Reducing Ultra-Clean Transportation Fuel Costs with HyMelt Hydrogen Quarterly Report
4
Advanced Cuttings Transport Study Quarterly Report
3
Dilute Surfactant Methods for Carbonate Formations Quarterly Report
3
Evaluation of Roof Bolting Requirements Based on In-Mine Bolter Drilling Progress Report
3
Fiber Optical Micro-Detectors for Oxygen Sensing in Power Plants Progress Report
3
Fiscal Year 2001
3
MUSC Environmental Biosciences Progress Report
3
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Environmentally Benign Stab Detonators
The coupling of energetic metallic multilayers (a.k.a. flash metal) with energetic sol-gel synthesis and processing is an entirely new approach to forming energetic devices for several DoD and DOE needs. They are also practical and commercially viable manufacturing techniques. Improved occupational safety and health, performance, reliability, reproducibility, and environmentally acceptable processing can be achieved using these methodologies and materials. The development and fielding of this technology will enhance mission readiness and reduce the costs, environmental risks and the necessity of resolving environmental concerns related to maintaining military readiness while simultaneously enhancing safety and health. Without sacrificing current performance, we will formulate new impact initiated device (IID) compositions to replace materials from the current composition that pose significant environmental, health, and safety problems associated with functions such as synthesis, material receipt, storage, handling, processing into the composition, reaction products from testing, and safe disposal. To do this, we will advance the use of nanocomposite preparation via the use of multilayer flash metal and sol-gel technologies and apply it to new small IIDs. This work will also serve to demonstrate that these technologies and resultant materials are relevant and practical to a variety of energetic needs of DoD and DOE. The goal …
Date:
July 7, 2006
Creator:
Gash, A. E.
Object Type:
Report
System:
The UNT Digital Library
New experimental capabilities and theoretical insights of high pressure compression waves
Currently there are three platforms that offer quasi-isentropic compression or ramp-wave compression (RWC): light-gas gun, magnetic flux (Z-pinch), and laser. We focus here on the light-gas gun technique and on some current theoretical insights from experimental data. A gradient impedance through the length of the impactor provides the pressure pulse upon impactor to the subject material. Applications and results are given concerning high-pressure strength and liquid to solid, phase transition of water plus its associated phase fraction history. We also introduce the Korteweg-deVries-Burgers equation as a means to understand the evolution these RWC waves that propagate through the thickness of the subject material. This equation has the necessary competition between non-linear, dispersion, and dissipation processes, which is shown through observed structures that are manifested in the experimental particle velocity histories. Such methodology points towards a possible quantifiable dissipation, through which RWC experiments may be analyzed.
Date:
July 20, 2007
Creator:
Orlikowski, D.; Nguyen, J.; Patterson, J. R.; Minich, R.; Martin, L. P. & Holmes, N.
Object Type:
Article
System:
The UNT Digital Library
Loss Factor of the PEP-II Rings
An RF power balance method is used to measure the synchrotron radiation losses and the wake field losses. We present the history of the losses in the Low Energy Ring (LER) and the High Energy Ring (HER) during the last several runs of PEP-II.
Date:
July 11, 2008
Creator:
Novokhatski, A. & Sullivan, M.
Object Type:
Article
System:
The UNT Digital Library
Elastic electron scattering from formic acid
Following our earlier study on the dynamics of low energy electron attachment to formic acid, we report the results of elastic low-energy electron collisions with formic acid. Momentum transfer and angular differential cross sections were obtained by performing fixed-nuclei calculations employing the complex Kohn variational method. We make a brief description of the technique used to account for the polar nature of this polyatomic target and compare our results with available experimental data.
Date:
July 31, 2006
Creator:
Trevisan, Cynthia S.; Orel, Ann E. & Rescigno, Thomas N.
Object Type:
Article
System:
The UNT Digital Library
Certifying Industrial Energy Efficiency Performance: AligningManagement, Measurement, and Practice to Create Market Value
More than fifteen years after the launch of programs in theU.K. and U.S., industry still offers one of the largest opportunities forenergy savings worldwide. The International Energy Agency (IEA) estimatesthe savings potential from cost-optimization of industrial motor-drivensystems alone at 7 percent of global electricity use. The U.S. Departmentof Energy (USDOE) Industrial Technologies Program estimates 7 percentsavings potential in total US industrial energy use through theapplication of proven best practice. Simple paybacks for these types ofprojects are frequently two years or less. The technology required toachieve these savings is widely available; the technical skills requiredto identify energy saving opportunities are known and transferable.Although programs like USDOE's Best Practices have been highlysuccessful, most plants, as supported by 2002 MECS data, remain eitherunaware or unmotivated to improve their energy efficiency--as evidencedby the 98 percent of US industrial facilities reporting to MECS say thatthey lack a full-time energy manager. With the renewed interest in energyefficiency worldwide and the emergence of carbon trading and newfinancial instruments such as white certificates1, there is a need tointroduce greater transparency into the way that industrial facilitiesidentify, develop, and document energy efficiency projects. Historically,industrial energy efficiency projects have been developed by plantengineers, frequently with assistance from consultants and/or supplierswith …
Date:
July 1, 2007
Creator:
McKane, Aimee; Scheihing, Paul & Williams, Robert
Object Type:
Article
System:
The UNT Digital Library
Database and Analytical Tool Development for the Management of Data Derived from US DOE (NETL) Funded Fine Particulate (PM2.5) Research
Advanced Technology Systems, Inc. (ATS) was contracted by the U. S. Department of Energy's National Energy Technology Laboratory (DOE-NETL) to develop a state-of-the-art, scalable and robust web-accessible database application to manage the extensive data sets resulting from the DOE-NETL-sponsored ambient air monitoring programs in the upper Ohio River valley region. The data management system was designed to include a web-based user interface that will allow easy access to the data by the scientific community, policy- and decision-makers, and other interested stakeholders, while providing detailed information on sampling, analytical and quality control parameters. In addition, the system will provide graphical analytical tools for displaying, analyzing and interpreting the air quality data. The system will also provide multiple report generation capabilities and easy-to-understand visualization formats that can be utilized by the media and public outreach/educational institutions. The project was conducted in two phases. Phase One included the following tasks: (1) data inventory/benchmarking, including the establishment of an external stakeholder group; (2) development of a data management system; (3) population of the database; (4) development of a web-based data retrieval system, and (5) establishment of an internal quality assurance/quality control system on data management. Phase Two involved the development of a platform for …
Date:
July 31, 2007
Creator:
Khosah, Robinson
Object Type:
Report
System:
The UNT Digital Library
First Principles Study of Double Photoionization of H2 UsingExterior Complex Scaling
Exterior complex scaling provides a practical path forfirst-principles studies of atomic and molecular ionizationproblemssince it avoids explicit enforcement of asymptotic boundary conditionsfor 3-body Coulomb breakup. We have used the method of exterior complexscaling, implemented with both the discrete variable representation andB-splines, to obtain the first-order wave function for molecular hydrogencorresponding to a single photon having been absorbed by a correlatedinitial state. These wave functions are used to construct convergedtriple differential cross sections for double photoionization of alignedH2 molecules.
Date:
July 21, 2006
Creator:
Rescigno, Thomas N.; Vanroose, Wim; Horner, Daniel A.; Martin,Fernando & McCurdy, C. William
Object Type:
Article
System:
The UNT Digital Library
Quench performance of Nb3Sn cos-theta coils made of 108/127 RRP strands
A series of 1-m long Nb{sub 3}Sn dipole models has been built at Fermilab in an attempt to refine the wind-and-react technology for Nb3Sn accelerator magnets. Three models made with Powder-in-Tube Nb{sub 3}Sn strand reached their design field of 10 T demonstrating a good reproducibility of magnet quench performance and field quality. Recently a new dipole 'mirror' model based on Nb{sub 3}Sn coil made of improved Restack Rod Process strand was constructed and tested reaching the maximum field above 11 T. This paper describes the parameters of the RRP strand and cable used as well as the design, fabrication and test results of this magnet.
Date:
July 1, 2007
Creator:
Zlobin, A.V.; Ambrosio, G.; Andreev, N.; Barzi, E.; Bossert, R.; Carcagno, R. et al.
Object Type:
Article
System:
The UNT Digital Library
Radio-loud high-redshift protogalaxy canidates in Bootes
We used the Near Infrared Camera (NIRC) on Keck I to obtain K{sub s}-band images of four candidate high-redshift radio galaxies selected using optical and radio data in the NOAO Deep Wide-Field Survey in Bootes. Our targets have 1.4 GHz radio flux densities greater than 1 mJy, but are undetected in the optical. Spectral energy distribution fitting suggests that three of these objects are at z > 3, with radio luminosities near the FR-I/FR-II break. The other has photometric redshift z{sub phot} = 1.2, but may in fact be at higher redshift. Two of the four objects exhibit diffuse morphologies in K{sub s}-band, suggesting that they are still in the process of forming.
Date:
July 20, 2007
Creator:
Croft, S.; van Breugel, W.; Brown, M. J.; de Vries, W.; Dey, A.; Eisenhardt, P. et al.
Object Type:
Article
System:
The UNT Digital Library
A fast contour descriptor algorithm for supernova imageclassification
We describe a fast contour descriptor algorithm and its application to a distributed supernova detection system (the Nearby Supernova Factory) that processes 600,000 candidate objects in 80 GB of image data per night. Our shape-detection algorithm reduced the number of false positives generated by the supernova search pipeline by 41% while producing no measurable impact on running time. Fourier descriptors are an established method of numerically describing the shapes of object contours, but transform-based techniques are ordinarily avoided in this type of application due to their computational cost. We devised a fast contour descriptor implementation for supernova candidates that meets the tight processing budget of the application. Using the lowest-order descriptors (F{sub 1} and F{sub -1}) and the total variance in the contour, we obtain one feature representing the eccentricity of the object and another denoting its irregularity. Because the number of Fourier terms to be calculated is fixed and small, the algorithm runs in linear time, rather than the O(n log n) time of an FFT. Constraints on object size allow further optimizations so that the total cost of producing the required contour descriptors is about 4n addition/subtraction operations, where n is the length of the contour.
Date:
July 16, 2006
Creator:
Aragon, Cecilia R. & Aragon, David Bradburn
Object Type:
Article
System:
The UNT Digital Library
Searches for Large Extra Dimensions at the Tevatron
None
Date:
July 1, 2008
Creator:
Krutelyov, Vyacheslav
Object Type:
Article
System:
The UNT Digital Library
Mg-induced increase of bandgap in Zn1-xMgxO nanorods revealed by x-ray absorption and emission spectroscopy
X-ray absorption near-edge structure (XANES) and x-ray emission spectroscopy (XES) measurements were used to investigate the effect of Mg doping in ZnO nanorods. The intensities of the features in the O K-edge XANES spectra of Zn{sub 1-x}Mg{sub x}O nanorods are lower than those of pure ZnO nanorods, suggesting that Mg doping increases the negative effective charge of O ions. XES and XANES spectra of O 2p states indicate that Mg doping raises (lowers) the conduction-band-minimum (valence-band-maximum) and increases the bandgap. The bandgap is found to increase linearly with the Mg content, as revealed by photoluminescence and combined XANES and XES measurements.
Date:
July 10, 2008
Creator:
Pong, Way-Faung; Chiou, J. W.; Tsai, H. M.; Pao, C. W.; Chien, F. Z.; Pong, W. F. et al.
Object Type:
Article
System:
The UNT Digital Library
Multiple Valley Couplings in Nanometer Si MOSFETs
We investigate the couplings between different energy band valleys in a MOSFET device using self-consistent calculations of million-atom Schroedinger-Poisson Equations. Atomistic empirical pseudopotentials are used to describe the device Hamiltonian and the underlying bulk band structure. The MOSFET device is under nonequilibrium condition with a source-drain bias up to 2V, and a gate potential close to the threshold potential. We find that all the intervalley couplings are small, with the coupling constants less than 3 meV. As a result, the system eigenstates derived from different bulk valleys can be calculated separately. This will significantly reduce the simulation time, because the diagonalization of the Hamiltonian matrix scales as the third power of the total number of basis functions.
Date:
July 11, 2008
Creator:
Wang, Lin-Wang; Deng, Hui-Xiong; Jiang, Xiang-Wei; Luo, Jun-Wei; Li, Shu-Shen; Xia, Jian-Bai et al.
Object Type:
Article
System:
The UNT Digital Library
Third millenium ideal gas and condensed phase thermochemical database for combustion (with update from active thermochemical tables).
The thermochemical database of species involved in combustion processes is and has been available for free use for over 25 years. It was first published in print in 1984, approximately 8 years after it was first assembled, and contained 215 species at the time. This is the 7th printed edition and most likely will be the last one in print in the present format, which involves substantial manual labor. The database currently contains more than 1300 species, specifically organic molecules and radicals, but also inorganic species connected to combustion and air pollution. Since 1991 this database is freely available on the internet, at the Technion-IIT ftp server, and it is continuously expanded and corrected. The database is mirrored daily at an official mirror site, and at random at about a dozen unofficial mirror and 'finger' sites. The present edition contains numerous corrections and many recalculations of data of provisory type by the G3//B3LYP method, a high-accuracy composite ab initio calculation. About 300 species are newly calculated and are not yet published elsewhere. In anticipation of the full coupling, which is under development, the database started incorporating the available (as yet unpublished) values from Active Thermochemical Tables. The electronic version now …
Date:
July 29, 2005
Creator:
Burcat, A.; Ruscic, B.; Chemistry & Tech., Technion - Israel Inst. of
Object Type:
Report
System:
The UNT Digital Library
300 Area Building Retention Evaluation Mitigation Plan
Evaluate the long-term retention of several facilities associated with the PNNL Capability Replacement Laboratory and other Hanfor mission needs. WCH prepared a mitigation plan for three scenarios with different release dates for specific buildings. The evaluations present a proposed plan for providing utility services to retained facilities in support of a long-term (+20 year) lifespan in addition to temporary services to buildings with specified delayed release dates.
Date:
July 3, 2007
Creator:
McBride, D. J.
Object Type:
Report
System:
The UNT Digital Library
Fine-scale Horizontal Structure of Arctic Mixed-Phase Clouds.
Recent in situ observations in stratiform clouds suggest that mixed phase regimes, here defined as limited cloud volumes containing both liquid and solid water, are constrained to narrow layers (order 100 m) separating all-liquid and fully glaciated volumes (Hallett and Viddaurre, 2005). The Department of Energy Atmospheric Radiation Measurement Program's (DOE-ARM, Ackerman and Stokes, 2003) North Slope of Alaska (NSA) ARM Climate Research Facility (ACRF) recently started collecting routine measurement of radar Doppler velocity power spectra from the Millimeter Cloud Radar (MMCR). Shupe et al. (2004) showed that Doppler spectra has potential to separate the contributions to the total reflectivity of the liquid and solid water in the radar volume, and thus to investigate further Hallett and Viddaurre's findings. The Mixed-Phase Arctic Cloud Experiment (MPACE) was conducted along the NSA to investigate the properties of Arctic mixed phase clouds (Verlinde et al., 2006). We present surface based remote sensing data from MPACE to discuss the fine-scale structure of the mixed-phase clouds observed during this experiment.
Date:
July 10, 2006
Creator:
Rambukkange,M.; Verlinde, J.; Elorante, E.; Luke, E.; Kollias, P. & Shupe, M.
Object Type:
Article
System:
The UNT Digital Library
ISOPAR L RELEASE RATES FROM SALTSTONE USING SIMULATED SALT SOLUTIONS
The Modular Caustic-Side Solvent Extraction (CSSX) Unit (MCU) and the Salt Waste Processing Facility (SWPF) will produce a Decontaminated Salt Solution (DSS) that will go to the Saltstone Production Facility (SPF). Recent information indicates that solvent entrainment in the DSS is larger than expected. The main concern is with Isopar{reg_sign} L, the diluent in the solvent mixture, and its flammability in the saltstone vault. If it is assumed that all the Isopar{reg_sign} L is released instantaneously into the vault from the curing grout before each subsequent pour, the Isopar{reg_sign} L in the vault headspace is well mixed, and each pour displaces an equivalent volume of headspace, the maximum concentration of Isopar{reg_sign} L in the DSS to assure 25% of the lower flammable limit is not exceeded has been determined to be about 4 ppm. The amount allowed would be higher if the release from grout were significantly less. The Savannah River National Laboratory was tasked with determining the release of Isopar{reg_sign} L from saltstone prepared with a simulated DSS with Isopar{reg_sign} L concentrations ranging from 50 to 200 mg/L in the salt fraction and with test temperatures ranging from ambient to 95 C. The results from the curing of the …
Date:
July 31, 2008
Creator:
Zamecnik, J; Michael Bronikowski, M; Alex Cozzi, A; Russell Eibling, R & Charles Nash, C
Object Type:
Report
System:
The UNT Digital Library
Pathway confirmation and flux analysis of central metabolicpathways in Desulfovibrio vulgaris Hildenborough using gaschromatography-mass spectrometry and fourier transform-ion cyclotronresonance mass spectrometry
It has been proposed that during growth under anaerobic oroxygen-limited conditions Shewanella oneidensis MR-1 uses theserine-isocitrate lyase pathway common to many methylotrophic anaerobes,in which formaldehyde produced from pyruvate is condensed with glycine toform serine. The serine is then transformed through hydroxypyruvate andglycerate to enter central metabolism at phosphoglycerate. To examine itsuse of the serine-isocitrate lyase pathway under anaerobic conditions, wegrew S. oneidensis MR-1 on [1-13C]lactate as the sole carbon source witheither trimethylamine N-oxide (TMAO) or fumarate as an electron acceptor.Analysis of cellular metabolites indicates that a large percentage(>75 percent) of lactate was partially oxidized to either acetate orpyruvate. The 13C isotope distributions in amino acids and other keymetabolites indicate that, under anaerobic conditions, a complete serinepathway is not present, and lactate is oxidized via a highly reversibleserine degradation pathway. The labeling data also suggest significantactivity in the anaplerotic (malic enzyme and phosphoenolpyruvatecarboxylase) and glyoxylate shunt (isocitrate lyase and malate synthase)reactions. Although the tricarboxylic acid (TCA) cycle is often observedto be incomplete in many other anaerobes (absence of 2-oxoglutaratedehydrogenase activity), isotopic labeling supports the existence of acomplete TCA cycle in S. oneidensis MR-1 under TMAO reductioncondition.
Date:
July 11, 2006
Creator:
Tang, Yinjie; Pingitore, Francesco; Mukhopadhyay, Aindrila; Phan,Richard; Hazen, Terry C. & Keasling, Jay D.
Object Type:
Article
System:
The UNT Digital Library
MODEL-BASED HYDROACOUSTIC BLOCKAGE ASSESSMENT AND DEVELOPMENT OF AN EXPLOSIVE SOURCE DATABASE
We are continuing the development of the Hydroacoustic Blockage Assessment Tool (HABAT) which is designed for use by analysts to predict which hydroacoustic monitoring stations can be used in discrimination analysis for any particular event. The research involves two approaches (1) model-based assessment of blockage, and (2) ground-truth data-based assessment of blockage. The tool presents the analyst with a map of the world, and plots raypath blockages from stations to sources. The analyst inputs source locations and blockage criteria, and the tool returns a list of blockage status from all source locations to all hydroacoustic stations. We are currently using the tool in an assessment of blockage criteria for simple direct-path arrivals. Hydroacoustic data, predominantly from earthquake sources, are read in and assessed for blockage at all available stations. Several measures are taken. First, can the event be observed at a station above background noise? Second, can we establish backazimuth from the station to the source. Third, how large is the decibel drop at one station relative to other stations. These observational results are then compared with model estimates to identify the best set of blockage criteria and used to create a set of blockage maps for each station. The …
Date:
July 11, 2005
Creator:
Matzel, E; Ramirez, A & Harben, P
Object Type:
Article
System:
The UNT Digital Library
Linearly Scaling 3D Fragment Method for Large-Scale Electronic Structure Calculations
We present a new linearly scaling three-dimensional fragment (LS3DF) method for large scale ab initio electronic structure calculations. LS3DF is based on a divide-and-conquer approach, which incorporates a novel patching scheme that effectively cancels out the artificial boundary effects due to the subdivision of the system. As a consequence, the LS3DF program yields essentially the same results as direct density functional theory (DFT) calculations. The fragments of the LS3DF algorithm can be calculated separately with different groups of processors. This leads to almost perfect parallelization on tens of thousands of processors. After code optimization, we were able to achieve 35.1 Tflop/s, which is 39percent of the theoretical speed on 17,280 Cray XT4 processor cores. Our 13,824-atom ZnTeO alloy calculation runs 400 times faster than a direct DFTcalculation, even presuming that the direct DFT calculation can scale well up to 17,280 processor cores. These results demonstrate the applicability of the LS3DF method to material simulations, the advantage of using linearly scaling algorithms over conventional O(N3) methods, and the potential for petascale computation using the LS3DF method.
Date:
July 1, 2008
Creator:
Wang, Lin-Wang; Lee, Byounghak; Shan, Hongzhang; Zhao, Zhengji; Meza, Juan; Strohmaier, Erich et al.
Object Type:
Article
System:
The UNT Digital Library
DHS Student Report
Throughout this project I have been involved in every step of the protocol. After proper training, I was introduced to the necessary lab techniques for the project. From then on it has been my responsibility to perform the necessary tasks to identify and isolate the mutants. This includes carrying out a detailed protocol of mixing reagents, streaking and incubating plates, inoculating cultures and evaluating any results in order to guide my actions for the next antibiotic concentration level. Simultaneously, I have been running PCR and sequencing reactions on all mutants in order to obtain the genetic sequence of the genes of interest for comparison. Once I have the gene sequences of interest I am able, with the aid of a sequencing program (Sequencher 4.2.2), to analyze the sequences of the mutants against that of a wild type strain. This entails aligning the DNA sequences of a given gene for each of the mutants and locating any base changes from the wild types bacteria's genes. These polymorphisms allow me to identify the QRDR for that particular gene. Depending on whether the polymorphism occurred at a low antibiotic concentration level or high concentration level, we can evaluate whether that change is necessary …
Date:
July 23, 2007
Creator:
Wynne, Elizabeth K.
Object Type:
Report
System:
The UNT Digital Library
Light-Front Holography and Hadronization at the Amplitude Level
The correspondence between theories in anti-de Sitter space and conformal field theories in physical space-time leads to an analytic, semiclassical model for strongly-coupled QCD which has scale invariance at short distances and color confinement at large distances. Light-front holography is a remarkable feature of AdS/CFT: it allows hadronic amplitudes in the AdS fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time, thus providing a relativistic description of hadrons at the amplitude level. Some novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates and the behavior of the QCD coupling in the infrared. We suggest that the spatial support of QCD condensates is restricted to the interior of hadrons, since they arise due to the interactions of confined quarks and gluons. Chiral symmetry is thus broken in a limited domain of size 1=m{sub {pi}} in analogy to the limited physical extent of superconductor phases. A new method for computing the hadronization of quark and gluon jets at the amplitude level, an event amplitude generator, is outlined.
Date:
July 25, 2008
Creator:
Brodsky, Stanley J.; de Teramond, Guy & Shrock, Robert
Object Type:
Article
System:
The UNT Digital Library
The Reactivity and Structural Dynamics of Supported Metal Nanoclusters Using Electron Microscopy, in situ X-Ray Spectroscopy, Electronic Structure Theories, and Molecular Dynamics Simulations.
The distinguishing feature of our collaborative program of study is the focus it brings to emergent phenomena originating from the unique structural/electronic environments found in nanoscale materials. We exploit and develop frontier methods of atomic-scale materials characterization based on electron microscopy (Yang) and synchrotron X-ray absorption spectroscopy (Frenkel) that are in turn coupled innately with advanced first principles theory and methods of computational modeling (Johnson). In the past year we have made significant experimental advances that have led to important new understandings of the structural dynamics of what are unquestionably the most important classes of heterogeneous catalysts—the materials used to both produce and mitigate the consequences of the use of liquid hydrocarbon fuels.
Date:
July 1, 2008
Creator:
Yang, Judith C. & Ralph G. Nuzzo, Duane Johnson, Anatoly Frenkel
Object Type:
Report
System:
The UNT Digital Library
Cold Fusion Production and Decay of Neutron-Deficient Isotopes of Dubnium and Development of Extraction Systems for Group V Elements
Excitation functions for the 1n and 2n exit channels of the 208Pb(51V,xn)259-xDb reaction were measured. A maximum cross section of the 1n exit channel of 2070+1100/-760 pb was measured at an excitation energy of 16.0 +- 1.8 MeV. For the 2n exit channel, a maximum cross section of 1660+450/-370 pb was measured at 22.0 +- 1.8 MeV excitation energy. The 1n excitation function for the 209Bi(50Ti,n)258Db reaction was remeasured, resulting in a cross section of 5480+1730/1370 pb at an excitation energy of 16.0 +- 1.6 MeV. Differences in cross section maxima are discussed in terms of the fusion probability below the barrier. The extraction of niobium (Nb) and tantalum (Ta) from hydrochloric acid and mixed hydrochloric acid/lithium chloride media by bis(2-ethylhexyl) hydrogen phosphate (HDEHP) and bis(2-ethylhexyl) hydrogen phosphite (BEHP) was studied. The goal of the experiments was to find a system that demonstrates selectivity among the members of group five of the Periodic Table and is also suitable for the study of dubnium (Db, Z = 105). Experiments with niobium and tantalum were performed with carrier (10-6 M), carrier free (10-10 M) and trace (10-16 M) concentrations of metal using hydrochloric acid solution with concentrations ranging from 1 - 11 …
Date:
July 31, 2008
Creator:
Gates, Jacklyn M.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library