International Symposium on Systems and Human Science - SSR2005 (open access)

International Symposium on Systems and Human Science - SSR2005

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Date: March 16, 2005
Creator: Addison, K J
System: The UNT Digital Library
Anomalies on orbifolds (open access)

Anomalies on orbifolds

We discuss the form of the chiral anomaly on an S1/Z2 orbifold with chiral boundary conditions. We find that the 4-divergence of the higher-dimensional current evaluated at a given point in the extra dimension is proportional to the probability of finding the chiral zero mode there. Nevertheless the anomaly, appropriately defined as the five dimensional divergence of the current, lives entirely on the orbifold fixed planes and is independent of the shape of the zero mode. Therefore long distance four dimensional anomaly cancellation ensures the consistency of the higher dimensional orbifold theory.
Date: March 16, 2001
Creator: Arkani-Hamed, Nima; Cohen, Andrew G. & Georgi, Howard
System: The UNT Digital Library
Search for the rare decay B to pi l+ l- (open access)

Search for the rare decay B to pi l+ l-

The authors have performed a search for the flavor-changing neutral-current decays B {yields} {pi}{ell}{sup +}{ell}{sup -}, where {ell}{sup +}{ell}{sup -} is either e{sup +}e{sup -} or {mu}{sup +}{mu}{sup -}, using a sample of 230 million {Upsilon}(4S) {yields} B{bar B} decays collected with the BABAR detector. They observe no evidence of a signal and measure the upper limit on the isospin-averaged branching fraction to be {Beta}(B {yields} {pi}{ell}{sup +}{ell}{sup -}) < 9.1 x 10{sup -8} at 90% confidence level. They also search for the lepton-flavor-violating decays B {yields} {pi}e{sup {+-}} {mu}{sup {-+}} and measure an upper limit on the isospin-averaged branching fraction of {Beta}(B {yields} {pi}e{sup {+-}} {mu}{sup {-+}}) < 9.2 x 10{sup -8} at 90% confidence level.
Date: March 16, 2007
Creator: Aubert, B.
System: The UNT Digital Library
Chromosome-specific DNA Repeat Probes (open access)

Chromosome-specific DNA Repeat Probes

In research as well as in clinical applications, fluorescence in situ hybridization (FISH) has gained increasing popularity as a highly sensitive technique to study cytogenetic changes. Today, hundreds of commercially available DNA probes serve the basic needs of the biomedical research community. Widespread applications, however, are often limited by the lack of appropriately labeled, specific nucleic acid probes. We describe two approaches for an expeditious preparation of chromosome-specific DNAs and the subsequent probe labeling with reporter molecules of choice. The described techniques allow the preparation of highly specific DNA repeat probes suitable for enumeration of chromosomes in interphase cell nuclei or tissue sections. In addition, there is no need for chromosome enrichment by flow cytometry and sorting or molecular cloning. Our PCR-based method uses either bacterial artificial chromosomes or human genomic DNA as templates with {alpha}-satellite-specific primers. Here we demonstrate the production of fluorochrome-labeled DNA repeat probes specific for human chromosomes 17 and 18 in just a few days without the need for highly specialized equipment and without the limitation to only a few fluorochrome labels.
Date: March 16, 2006
Creator: Baumgartner, Adolf; Weier, Jingly Fung & Weier, Heinz-Ulrich G.
System: The UNT Digital Library
Comparison of two up-scaling methods in poroelasticity and its generalizations (open access)

Comparison of two up-scaling methods in poroelasticity and its generalizations

Two methods of up-scaling coupled equations at the microscale to equations valid at the mesoscale and/or macroscale for fluid-saturated and partially saturated porous media are discussed, compared, and contrasted. The two methods are: (1) two-scale and multiscale homogenization, and (2) volume averaging. Both these methods have advantages for some applications and disadvantages for others. For example, homogenization methods can give formulas for coefficients in the up-scaled equations, whereas volume averaging methods give the form of the up-scaled equations but generally must be supplemented with physical arguments and/or data in order to determine the coefficients. Homogenization theory requires a great deal of mathematical insight from the user in order to choose appropriate scalings for use in the resulting power-law expansions, while volume averaging requires more physical insight to motivate the steps needed to find coefficients. Homogenization often is performed on periodic models, while volume averaging does not require any assumption of periodicity and can therefore be related very directly to laboratory and/or field measurements. Validity of the homogenization process is often limited to specific ranges of frequency - in order to justify the scaling hypotheses that must be made - and therefore cannot be used easily over wide ranges of frequency. …
Date: March 16, 2004
Creator: Berger, E. L.
System: The UNT Digital Library
Material properties limiting the performance of CZT gamma-ray detectors (open access)

Material properties limiting the performance of CZT gamma-ray detectors

CdZnTe (CZT) nuclear radiation detectors are advanced sensors that utilize innovative technologies developed for wide band-gap semiconductor industry and microelectronics. They open opportunities for new types of room-temperature operating, field deployable instruments that provide accurate identification of potential radiological threats and timely awareness for both the civilian and military communities. Room-temperature radiation detectors are an emerging technology that relies on the use of high-quality CZT crystals whose availability is currently limited by material non-uniformities and the presence of extended defects. To address these issues, which are most critical to CZT sensor developments, we developed X-ray mapping and IR transmission microscopy systems to characterize both CZT crystals and devices. Since a customized system is required for such X-ray measurements, we use synchrotron radiation beams available at BNL's National Synchrotron Light Source. A highly-collimated and high-intensity X-ray beam supports measurements of areas as small as 10 x 10 {micro}m{sup 2}, and allowed us to see fluctuations in collected charge over the entire area of the detector in a reasonable time. The IR microscopy system allows for 3D visualization of Te inclusions and other extended defects. In this paper, we describe the experimental techniques used in our measurements and typical results obtained from …
Date: March 16, 2009
Creator: Bolotnikov, A. E.; Babalola, S.; Camarda, G. S.; Cui, Y.; Egarievwe, S. U.; Hossain, A. et al.
System: The UNT Digital Library
Laboratory Evaluation of an Electrochemical Noise System for Detection of Localized and General Corrosion of Natural Gas Transmission Pipelines (open access)

Laboratory Evaluation of an Electrochemical Noise System for Detection of Localized and General Corrosion of Natural Gas Transmission Pipelines

Gas transmission pipelines are susceptible to both internal (gas side) and external (soil side) corrosion attack. Internal corrosion is caused by the presence of salt laden moisture, CO{sub 2}, H{sub 2}S, and perhaps O{sub 2} in the natural gas. Internal corrosion usually manifests itself as general corrosion. However, the presence of chlorides in entrained water also can lead to pitting corrosion damage. The electrochemical noise technique can differentiate general from localized corrosion and provide estimates of corrosion rates without external perturbation of the corroding system. It is increasingly being applied to field and industrial installations for in situ corrosion monitoring. It has been used here to determine its suitability for monitoring internal and external corrosion damage on gas transmission pipelines. Corrosion measurements were made in three types of environments: (1) aqueous solutions typical of those found within gas pipelines in equilibrium with th e corrosive components of natural gas; (2) biologically-active soils typical of wetlands; and (3) a simulated, unpressurized, internal gas/liquid gas pipeline environment. Multiple sensor designs were evaluated in the simulated pipe environment. Gravimetric measurements were conducted in parallel with the electrochemical noise measurements to validate the results.
Date: March 16, 2003
Creator: Bullard, S. J.; Covino, B. S., Jr.; Russell, J. H.; Holcomb, G. R.; Cramer, S. D.; Ziomek-Moroz, M. et al.
System: The UNT Digital Library
Estimation of fracture flow parameters through numerical analysis of hydromechanical pressure pulses (open access)

Estimation of fracture flow parameters through numerical analysis of hydromechanical pressure pulses

The flow parameters of a natural fracture were estimated by modeling in situ pressure pulses. The pulses were generated in two horizontal boreholes spaced 1 m apart vertically and intersecting a near-vertical highly permeable fracture located within a shallow fractured carbonate reservoir. Fracture hydromechanical response was monitored using specialized fiber-optic borehole equipment that could simultaneously measure fluid pressure and fracture displacements. Measurements indicated a significant time lag between the pressure peak at the injection point and the one at the second measuring point, located 1 m away. The pressure pulse dilated and contracted the fracture. Field data were analyzed through hydraulic and coupled hydromechanical simulations using different governing flow laws. In matching the time lag between the pressure peaks at the two measuring points, our hydraulic models indicated that (1) flow was channeled in the fracture, (2) the hydraulic conductivity tensor was highly anisotropic, and (3) the radius of pulse influence was asymmetric, in that the pulse travelled faster vertically than horizontally. Moreover, our parametric study demonstrated that the fluid pressure diffusion through the fracture was quite sensitive to the spacing and orientation of channels, hydraulic aperture, storativity and hydraulic conductivity. Comparison between hydraulic and hydromechanical models showed that the …
Date: March 16, 2008
Creator: Cappa, F.; Guglielmi, Y.; Rutqvist, J.; Tsang, C.-F. & Thoraval, A.
System: The UNT Digital Library
Design and testing of a control strategy for a large naturallyventilated office building (open access)

Design and testing of a control strategy for a large naturallyventilated office building

The design for the new Federal Building for San Franciscoincludes an office tower that is to be naturally ventilated. Each flooris designed to be cross-ventilated, through upper windows that arecontrolled by the building management system (BMS). Users have controlover lower windows, which can be as much as 50 percent of the totalopenable area. There are significant differences in the performance andthe control of the windward and leeward sides of the building, andseparate monitoring and control strategies are determined for each side.The performance and control of the building has been designed and testedusing a modified version of EnergyPlus. Results from studies withEnergyPlus and CFD are used in designing the control strategy. EnergyPluswas extended to model a simplified version of the airflow patterndetermined using CFD. Wind-driven cross-ventilation produces a main jetthrough the upper openings of the building, across the ceiling from thewindward to the leeward side. Below this jet, the occupied regions aresubject to a recirculating air flow. Results show that temperatureswithin the building are predicted to be satisfactory, provided a suitablecontrol strategy is implemented uses night cooling in periods of hotweather. The control strategy has 10 window opening modes. EnergyPlus wasextended to simulate the effects of these modes, and to assess …
Date: March 16, 2004
Creator: Carrilho da Graca, Guilherme; Linden, Paul F. & Haves, Philip
System: The UNT Digital Library
Overview of Light-Ion Beam Therapy (open access)

Overview of Light-Ion Beam Therapy

In 1930, Ernest Orlando Lawrence at the University of California at Berkeley invented the cyclotron. One of his students, M. Stanley Livingston, constructed a 13-cm diameter model that had all the features of early cyclotrons, accelerating protons to 80 keV using less than 1 kV on a semi-circular accelerating electrode, now called the ''dee''. Soon after, Lawrence constructed the first two-dee 27-Inch (69-cm) Cyclotron, which produced protons and deuterons of 4.8 MeV. In 1939, Lawrence constructed the 60-Inch (150-cm) Cyclotron, which accelerated deuterons to 19 MeV. Just before WWII, Lawrence designed a 184-inch cyclotron, but the war prevented the building of this machine. Immediately after the war ended, the Veksler-McMillan principle of phase stability was put forward, which enabled the transformation of conventional cyclotrons to successful synchrocyclotrons. When completed, the 184-Inch Synchrocyclotron produced 340-MeV protons. Following it, more modern synchrocyclotrons were built around the globe, and the synchrocyclotrons in Berkeley and Uppsala, together with the Harvard cyclotron, would perform pioneering work in treatment of human cancer using accelerated hadrons (protons and light ions). When the 184-Inch Synchrocyclotron was built, Lawrence asked Robert Wilson, one of his former graduate students, to look into the shielding requirements for of the new accelerator. …
Date: March 16, 2006
Creator: Chu, William T.
System: The UNT Digital Library
Role of Ash Deposits in the High Temperature Corrosion of Boiler Tubes (open access)

Role of Ash Deposits in the High Temperature Corrosion of Boiler Tubes

Ash deposits cause accelerated corrosion of waterwall boiler tubes in waste to energy (WTE) incinerators. To study this effect, a series of experiments were planned to determine the mechanism of corrosion of carbon steel boiler tubes under ash deposits. Results reported here were for carbon steel tubes exposed to an environment consisting of O{sub 2}, CO{sub 2}, N{sub 2}, and water vapor. Future experiments will include HCl and SO{sub 2}. Test procedures included both isothermal and thermal gradient tests. Temperatures ranged from 300 C to 510 C for the isothermal tests and a metal/gas temperature of 450/670 C for the thermal gradient test. Initial results indicated that increasing temperature caused the isothermal corrosion rates of ash-covered samples to increase. A shakedown test of a thermal gradient test apparatus was conducted at a metal/gas temperature of 450/670 C, a more severe environment than normally encountered in WTE waterwalls. Results showed that the corrosion rate under those conditions exceeds the isothermal corrosion rates at the same metal temperature by a factor of 2 or more.
Date: March 16, 2003
Creator: Covino, B. S., Jr.; Russell, J. H.; Cramer, S. D.; Holcomb, G. R.; Bullard, S. J.; Ziomek-Moroz, M. et al.
System: The UNT Digital Library
Laser beam shaping techniques (open access)

Laser beam shaping techniques

Industrial, military, medical, and research and development applications of lasers frequently require a beam with a specified irradiance distribution in some plane. A common requirement is a laser profile that is uniform over some cross-section. Such applications include laser/material processing, laser material interaction studies, fiber injection systems, optical data image processing, lithography, medical applications, and military applications. Laser beam shaping techniques can be divided into three areas: apertured beams, field mappers, and multi-aperture beam integrators. An uncertainty relation exists for laser beam shaping that puts constraints on system design. In this paper the authors review the basics of laser beam shaping and present applications and limitations of various techniques.
Date: March 16, 2000
Creator: Dicky, Fred M.; Weichman, Louis S. & Shagam, Richard N.
System: The UNT Digital Library
ADVANCES IN SE-79 ANALYSES ON SAVANNAH RIVER SITE RADIOACTIVE WASTE MATRICES (open access)

ADVANCES IN SE-79 ANALYSES ON SAVANNAH RIVER SITE RADIOACTIVE WASTE MATRICES

Waste cleanup efforts underway at the United States Department of Energy's (DOE) Savannah River Site (SRS) in South Carolina, as well as other DOE nuclear sites, have created a need to characterize {sup 79}Se in radioactive waste inventories. Successful analysis of {sup 79}Se in high activity waste matrices is challenging for a variety of reasons. As a result of these unique challenges, the successful quantification of {sup 79}Se in the types of matrices present at SRS requires an extremely efficient and selective separation of {sup 79}Se from high levels of interfering radionuclides. A robust {sup 79}Se radiochemical separation method has been developed at the Savannah River National Laboratory (SRNL) which is routinely capable of successfully purifying {sup 79}Se from a wide range of interfering radioactive species. In addition to a dramatic improvements in the Kd, ease, and reproducibility of the analysis, the laboratory time has been reduced from several days to only 6 hours.
Date: March 16, 2009
Creator: Diprete, D; C Diprete, C; Ned Bibler, N; Cj Bannochie, C & Michael Hay, M
System: The UNT Digital Library
Pion and photon production in heavy ion collisions (open access)

Pion and photon production in heavy ion collisions

Measurement of neutral pions and direct photons are closely connected experimentally, on the other hand they probe quite different aspects of relativistic heavy ion collisions. In this short review of the {pi}{sup 0} results from the PHENIX experiment at RHIC our focus is on the {phi}-integrated nuclear modification factor, its energy and system size dependence, and the impact of these results on parton energy loss models. We also discuss the current status of high p{sub T} and thermal direct photon measurements both in p+p and Au+Au collisions. Recognizing the advantages of measuring not only the 'signal', but also all the 'references' needed for proper interpretation in the same experiments (with same or similar systematics) we argue that RHIC should regularly include d+A and even d+d collisions into its system size and energy scan.
Date: March 16, 2008
Creator: Gabor,D.
System: The UNT Digital Library
EFFECT OF ELECTROLYZER CONFIGURATION AND PERFORMANCE ON HYBRID SULFUR PROCESS NET THERMAL EFFICIENCY (open access)

EFFECT OF ELECTROLYZER CONFIGURATION AND PERFORMANCE ON HYBRID SULFUR PROCESS NET THERMAL EFFICIENCY

Hybrid Sulfur cycle is gaining popularity as a possible means for massive production of hydrogen from nuclear energy. Several different ways of carrying out the SO{sub 2}-depolarized electrolysis step are being pursued by a number of researchers. These alternatives are evaluated with complete flowsheet simulations and on a common design basis using Aspen Plus{trademark}. Sensitivity analyses are performed to assess the performance potential of each configuration, and the flowsheets are optimized for energy recovery. Net thermal efficiencies are calculated for the best set of operating conditions for each flowsheet and the results compared. This will help focus attention on the most promising electrolysis alternatives. The sensitivity analyses should also help identify those features that offer the greatest potential for improvement.
Date: March 16, 2007
Creator: Gorensek, M
System: The UNT Digital Library
Searching for Double Beta Decay with the Enriched Xenon Observatory (open access)

Searching for Double Beta Decay with the Enriched Xenon Observatory

The Enriched Xenon Observatory (EXO) Collaboration is building a series of experiments to search for the neutrinoless double beta decay of {sup 136}Xe. The first experiment, known as EXO-200, will utilize 200 kg of xenon enriched to 80% in the isotope of interest, making it the largest double beta decay experiment to date by one order of magnitude. This experiment is rapidly being constructed, and will begin data taking in 2007. The EXO collaboration is also developing a technique to identify on an event-by-event basis the daughter barium ion of the double beta decay. If successful, this method would eliminate all conventional radioactive backgrounds to the decay, resulting in an ideal experiment. We summarize here the current status of EXO-200 construction and the barium tag R&D program.
Date: March 16, 2007
Creator: Hall, C.
System: The UNT Digital Library
THEORETICAL STUDY ON THE INTERACTION BETWEEN XENON AND POSITIVE SILVER CLUSTERS IN GAS PHASE AND ON THE (001) CHABAZITE SURFACE (open access)

THEORETICAL STUDY ON THE INTERACTION BETWEEN XENON AND POSITIVE SILVER CLUSTERS IN GAS PHASE AND ON THE (001) CHABAZITE SURFACE

A systematic study on the adsorption of xenon on silver clusters in the gas phase and on the (001) surface of silver-exchanged chabazite is reported. Density functional theory at the B3LYP level with the cluster model was employed. The results indicate that the dominant part of the binding is the {sigma} donation, which is the charge transfer from the 5p orbital of Xe to the 5s orbital of Ag and is not the previously suggested d{sub {pi}}-d{sub {pi}} back-donation. A correlation between the binding energy and the degree of {sigma} donation is found. Xenon was found to bind strongly to silver cluster cations and not to neutral ones. The binding strength decreases as the cluster size increases for both cases, clusters in the gas-phase and on the chabazite surface. The Ag{sup +} cation is the strongest binding site for xenon both in gas phase and on the chabazite surface with the binding energies of 73.9 and 14.5 kJ/mol, respectively. The results also suggest that the smaller silver clusters contribute to the negative chemical shifts observed in the {sup 129}Xe NMR spectra in experiments.
Date: March 16, 2009
Creator: Hunter, D.
System: The UNT Digital Library
The Role of Ledge Nucleation/Migration in ''Omega'' Plate Thickening Behavior in Al-Cu-Mg-Ag Alloys (open access)

The Role of Ledge Nucleation/Migration in ''Omega'' Plate Thickening Behavior in Al-Cu-Mg-Ag Alloys

The thickening kinetics of {Omega} plates in an Al-4Cu-0.3Mg-0.2Ag (wt. %) alloy have been measured at 200 C, 250 C and 300 C using conventional transmission electron microscopy techniques. At all temperatures examined the thickening showed a linear dependence on time. At 200 C the plates remained less than 6nm in thickness after 1000h exposure. At temperatures above 200 C the thickening kinetics are greatly increased. Atomic resolution Z-contrast microscopy has been used to examine the structure and chemistry of the (001){sub {Omega}} {parallel} (111){sub {alpha}} interphase boundary in samples treated at each temperature. In all cases, two atomic layers of Ag and Mg segregation were found at the broad face of the plate. The risers of the growth ledges and the ends of the plates were free of segregation. No significant levels of Ag or Mg were detected inside the plate at any time. The necessary redistribution of Ag and Mg accompanying a migrating thickening ledge occurs at all temperatures and is not considered to play a decisive role in the excellent coarsening resistance exhibited by the {Omega} plates at temperatures up to 200 C. Plates transformed at 200 C rarely contained ledges and usually exhibited a strong vacancy …
Date: March 16, 2001
Creator: Hutchinson, C.R.
System: The UNT Digital Library
Structural conformation in a poly (ethylene oxide) film obta inedfrom X-ray emission spectroscopy (XES) (open access)

Structural conformation in a poly (ethylene oxide) film obta inedfrom X-ray emission spectroscopy (XES)

The electronic structure of poly(ethylene oxide) (PEO) in a thin (< 1 {micro}) film sample was experimentally probed by X-ray emission spectroscopy. The emission spectra from this film were much sharper with more resolved fine structure than the spectra from the bulk polymer from which it was cast. Both non-resonant and resonant X-ray emission spectra were simulated using density functional theory (DFT) applied to four different models representing different conformations in the polymer. Calculated spectra were compared with experimental results for the PEO film. It was found that the best fit was obtained with the polymer conformation in PEO electrolytes from which the salt (LiMF6, M=P, As, or Sb) had been removed. This conformation is different from that in the crystalline bulk polymer and implies that film casting, commonly used to form electrolytes for Li polymer batteries, induces the same conformation in the polymer with or without the salt present.
Date: March 16, 2007
Creator: Kashtanov, S.; Zhuang, G.V.; Augustsson, A.; Guo, J.-H.; Nordgren, J.; Luo, Y. et al.
System: The UNT Digital Library
Electroweak Vector Boson Production in Joint Resummation (open access)

Electroweak Vector Boson Production in Joint Resummation

We study the application of the joint resummation to electroweak boson production at hadron colliders. The joint resummation formalism resumes both threshold and transverse momentum corrections to the transverse momentum distribution at, next-to-leading logarithmic accuracy. We obtain a good description of the transverse momentum distribution of Z bosons produced at the Tevatron collider.
Date: March 16, 2002
Creator: Kulesza, A.; Sterman, G. & Vogelsang, W.
System: The UNT Digital Library
Lifetime of the 1s2s 3S1 metastable level in He-like S14+ measured with an electron beam ion trap (open access)

Lifetime of the 1s2s 3S1 metastable level in He-like S14+ measured with an electron beam ion trap

A precision measurement of the lifetime of the lowest exited level of the He-like S{sup 14+} ion carried out at the Livermore EBIT-II electron beam ion trap yielded a value of (703 {+-} 4) ns. Our method extends the range of lifetime measurements accessible with electron beam ion traps into the nanosecond region and improves the accuracy of currently available data for this level by an order of magnitude.
Date: March 16, 2006
Creator: L?pez-Urrutia, J C; Beiersdorfer, P & Widmann, K
System: The UNT Digital Library
Data analysis and evaluation with SAMMY (open access)

Data analysis and evaluation with SAMMY

Various steps are required prior to the use of SAMMY to search for resonance parameters that best represent the experimental data. This lecture will focus on the common practice utilized to perform data evaluation, in particular, the evaluation procedure used for data analysis in the resolved-energy region using the reduced R-matrix formalism i.e., the Reich-Moore approximation. A similar approach can be used for data analysis and evaluation in other energy regions. The first step in the evaluation process consists of defining the energy range for which the evaluation will be carried out and making sure that all possible open reaction channels (i.e., inelastic channel, charged particle channels, etc.,) are identified.
Date: March 16, 2000
Creator: Leal, L.
System: The UNT Digital Library
Atmospheric Corrosion and Precipitation Runoff From Zinc and Zinc Alloys Surfaces (open access)

Atmospheric Corrosion and Precipitation Runoff From Zinc and Zinc Alloys Surfaces

The long-term atmospheric corrosion performance of rolled zinc and three thermal-sprayed (TS) zinc materials (Zn, Zn-15Al, and Al-12Zn-0.2In) was characterized by measuring corrosion product concentrations in precipitation runoff at coastal marine and inland sites. Corrosion rates and average zinc concentrations in the runoff were greater at the site having higher annual rainfall. Higher chloride concentrations did not seem to affect either the corrosion rates or the zinc concentrations in the runoff at the coastal site compared to those of the inland site. Zinc runoff concentrations were higher for TS Zn than rolled zinc due to the greater surface area of the thermal-sprayed surface. Average cumulative zinc runoff losses for the two sites were: 64 {micro}mol Zn/L for TS Zn, 37 {micro}mol Zn/L for rolled Zn, 24 {micro}mol Zn/L for TS Zn-15Al, and 1.8 {micro}mol Zn/L for TS Al-12Zn-0.2In. Cumulative zinc runoff losses were directly related both to the precipitation rate and to the availability of Zn in metal surfaces, a consequence of surface roughness and surface chemistry properties of the metal.
Date: March 16, 2003
Creator: Matthes, S. A.; Cramer, S. D.; Bullard, S. J.; Covino, B. S., Jr. & Holcomb, G. R.
System: The UNT Digital Library
A SERENDIPITOUS, LONG-TERM INFILTRATION EXPERIMENT: WATER AND RADIONUCLIDE CIRCULATION BENEATH THE CAMBRIC TRENCH AT THE NEVADA TEST SITE. (open access)

A SERENDIPITOUS, LONG-TERM INFILTRATION EXPERIMENT: WATER AND RADIONUCLIDE CIRCULATION BENEATH THE CAMBRIC TRENCH AT THE NEVADA TEST SITE.

Underground atomic weapons testing at the Nevada Test Site introduced numerous radionuclides that may be used to characterize subsurface hydrologic transport processes in arid climates. Beginning in 1975, groundwater adjacent to the CAMBRIC test, conducted beneath Frenchman Flat in 1965, was pumped steadily for 16 years to elicit experimental information on the migration of residual radioactivity through the saturated zone. Radionuclides in the pumping well effluent, including tritium, {sup 36}Cl and {sup 85}Kr, were extensively monitored prior to their discharge into an unlined ditch flowing toward a dry lake bed over a kilometer away. We have applied a large (6km x 6km x 1km) and highly resolved (4 m) variably saturated flow model to investigate infiltration into the 220-m vadose zone underlying the ditch as well as subsequent groundwater recharge and well recirculation processes. A Lagrangian particle-tracking model has been used to compute flow pathways and estimate radionuclide travel and residence times in various parts of the system based upon the flow model. Results are consistent with rising tritium levels observed in a monitoring well since 1991. They suggest that recirculation of the ditch effluent through the vadose zone, into groundwater, and back to the test cavity and pumping well …
Date: March 16, 2006
Creator: Maxwell, R; Tompson, A; Carle, S; Zavarin, M & Kollet, S
System: The UNT Digital Library