2007 Plant Metabolic Engineering Gordon Conference and Graduate Research Seminar (open access)

2007 Plant Metabolic Engineering Gordon Conference and Graduate Research Seminar

Plant Metabolic Engineering is an emerging field that integrates a diverse range of disciplines including plant genetics, genomics, biochemistry, chemistry and cell biology. The Gordon-Kenan Graduate Research Seminar (GRS) in Plant Metabolic Engineering was initiated to provide a unique opportunity for future researcher leaders to present their work in this field. It also creates an environment allowing for peer-review and critical assessment of work without the intimidation usually associated with the presence of senior investigators. The GRS immediately precedes the Plant Metabolic Engineering Gordon Research Conference and will be for and by graduate students and post-docs, with the assistance of the organizers listed.
Date: September 15, 2008
Creator: Grotewold, Erich
System: The UNT Digital Library
ABSTRACT: Design of Groundwater Monitoring Networks Considering Conceptual Model and Parametric Uncertainty (open access)

ABSTRACT: Design of Groundwater Monitoring Networks Considering Conceptual Model and Parametric Uncertainty

Uncertainty built into conceptual groundwater flow and transport models and associated parametric uncertainty should be appropriately included when such models are used to develop detection monitoring networks for contaminated sites. We compare alternative approaches of propagating such uncertainty from the flow and transport model into the network design. The focus is on detection monitoring networks where the primary objective is to intercept the contaminant before it reaches a boundary of interest (e.g., compliance boundary). Different uncertainty propagation approaches identify different well locations and different well combinations (networks) as having the highest detection efficiency. It is thus recommended that multiple uncertainty propagation approaches are considered. If several approaches yield consistent results in terms of identifying the best performing candidate wells and the best performing well network for detecting a contaminant plume, this would provide confidence in the suitability of the selected well locations.
Date: September 15, 2008
Creator: Hassan, A.; Bekhit, H.; Zhang, Y. & Chapman, J.
System: The UNT Digital Library
ABSTRACT: Upscaling Fracture Properties in Support of Dual-permeability Simulations (open access)

ABSTRACT: Upscaling Fracture Properties in Support of Dual-permeability Simulations

Rainier Mesa (RM) is a tuffaceous, high-elevation plateau on the Nevada Test Site (NTS) that has been subjected to numerous nuclear tests between 1957 and 1992. Unlike other tests on the NTS located within or just above the saturated zone, tests at the RM T-tunnel complex were conducted within a variably saturated sequence of bedded and non-welded vitric and zeolitized tuff units, located approximately 500 m above the regional groundwater flow system. The low permeability and high porosity of the underlying zeolitized tuff units suggest the downward transport of radionuclides released from these tests are minimal through the tuff matrix. However, numerous faults observed to discharge water into tunnel drifts may serve as preferential pathways for radionuclide migration. Data collected from tunnel drifts indicate that faulting within the zeolitized tuff units is sparse with fractal clustering, and that connectivity between adjacent fault clusters is often weak to non-existent. The sparse fault density at RM, in conjunction with the extreme variability in the spatial distribution of faults, poses challenges not readily addressed by existing upscaling methods that upscale fracture properties as equivalent grid tensors. The unique fault statistics at RM has led to the development of a fracture continuum method designed …
Date: September 15, 2008
Creator: Parashar, Rishi & Reeves, Donald M.
System: The UNT Digital Library
Concentration of Actinides in Plant Mounds at Safety Test Nuclear Sites in Nevada (open access)

Concentration of Actinides in Plant Mounds at Safety Test Nuclear Sites in Nevada

Plant mounds or blow-sand mounds are accumulations of soil particles and plant debris around large shrubs and are common features in deserts in the southwestern United States. Believed to be an important factor in their formation, the shrubs create surface roughness that causes wind-suspended particles to be deposited and resist further suspension. Shrub mounds occur in some plant communities on the Nevada Test Site, the Nevada Test and Training Range (NTTR), and Tonopah Test Range (TTR), including areas of surface soil contamination from past nuclear testing. In the 1970s as part of early studies to understand properties of actinides in the environment, the Nevada Applied Ecology Group (NAEG) examined the accumulation of isotopes of Pu, {sup 241}Am, and U in plant mounds at safety test sites. The NAEG studies found concentrations of these contaminants to be greater in shrub mounds than in the surrounding areas of desert pavement. For example, at Project 57 on the NTTR, it was estimated that 15 percent of the radionuclide inventory of the site was associated with shrub mounds, which accounted for 17 percent of the surface area of the site, a ratio of inventory to area of 0.85. At Clean Slate III at the …
Date: September 15, 2008
Creator: Shafer, David S. & Gommes, Jenna
System: The UNT Digital Library
Recent Advances in Developing Platinum Monolayer Electrocatalysts for the O2 Reduction Reaction (open access)

Recent Advances in Developing Platinum Monolayer Electrocatalysts for the O2 Reduction Reaction

For Pt, the best single-element catalyst for many reactions, the question of content and loading is exceedingly important because of its price and availability. Using platinum as a fuel-cell catalyst in automotive applications will cause an unquantifiable increase in the demand for this metal. This big obstacle for using fuel cells in electric cars must be solved by decreasing the content of Pt, which is a great challenge of electrocatalysis Over the last several years we inaugurated a new class of electrocatalysts for the oxygen reduction reaction (ORR) based on a monolayer of Pt deposited on metal or alloy carbon-supported nanoparticles. The possibility of decreasing the Pt content in the ORR catalysts down to a monolayer level has a considerable importance because this reaction requires high loadings due to its slow kinetics. The Pt-monolayer approach has several unique features and some of them are: high Pt utilization, enhanced (or decreased) activity, enhanced stability, and direct activity correlations. The synthesis of Pt monolayer (ML) electrocatalysts was facilitated by our new synthesis method which allowed us to deposit a monolayer of Pt on various metals, or alloy nanoparticles [1, 2] for the cathode electrocatalyst. In this synthesis approach Pt is laid down …
Date: September 15, 2008
Creator: Vukmirovic, M. B.; Sasaki, K.; Zhou, W. P.; Li, M.; Liu, P.; Wang, J. X. et al.
System: The UNT Digital Library
Heavy-Ion Irradiation of Thulium(III) Oxide Targets Prepared by Polymer-Assisted Deposition (open access)

Heavy-Ion Irradiation of Thulium(III) Oxide Targets Prepared by Polymer-Assisted Deposition

Thulium(III) oxide (Tm{sub 2}O{sub 3}) targets prepared by the polymer-assisted deposition (PAD) method were irradiated by heavy-ion beams to test the method's feasibility for nuclear science applications. Targets were prepared on silicon nitride backings (thickness of 1000 nm, 344 {micro}g/cm{sup 2}) and were irradiated with an {sup 40}Ar beam at laboratory frame energy of {approx}210 MeV (50 particle nA). The root mean squared (RMS) roughness prior to irradiation is 1.1 nm for a {approx}250 nm ({approx}220 {micro}g/cm{sup 2}) Tm{sub 2}O{sub 3} target, and an RMS roughness of 2.0 nm after irradiation was measured by atomic force microscopy (AFM). Scanning electron microscopy of the irradiated target reveals no significant differences in surface homogeneity when compared to imaging prior to irradiation. Target flaking was not observed from monitoring Rutherford scattered particles as a function of time.
Date: September 15, 2008
Creator: Garcia, Mitch A.; Ali, Mazhar N.; Chang, Noel N.; Parsons-Moss, Tashi; Ashby, Paul D.; Gates, Jacklyn M. et al.
System: The UNT Digital Library
Energy Efficiency as a Preferred Resource: Evidence from Utility Resource Plans in the Western United States and Canada (open access)

Energy Efficiency as a Preferred Resource: Evidence from Utility Resource Plans in the Western United States and Canada

This article examines the future role of energy efficiency as a resource in the Western United States and Canada, as envisioned in the most recent resource plans issued by 16 utilities, representing about 60percent of the region's load. Utility and third-party administered energy efficiency programs proposed by 15 utilities over a ten-year horizon would save almost 19,000 GWh annually, about 5.2percent of forecast load. There are clear regional trends in the aggressiveness of proposed energy savings. California's investor-owned utilities (IOUs) had the most aggressive savings targets, followed by IOUs in the Pacific Northwest, and the lowest savings were proposed by utilities in Inland West states and by two public utilities on the West coast. The adoption of multiple, aggressive policies targeting energy efficiency and climate change appear to produce sizeable energy efficiency commitments. Certain specific policies, such as mandated energy savings goals for California's IOUs and energy efficiency provisions in Nevada's Renewable Portfolio Standard had a direct impact on the level of energy savings included in the resource plans. Other policies, such as revenue decoupling and shareholder incentives, and voluntary or legislatively mandated greenhouse gas emission reduction policies, may have also impacted utilities' energy efficiency commitments, though the effects of …
Date: September 15, 2008
Creator: Hopper, Nichole; Barbose, Galen; Goldman, Charles & Schlegel, Jeff
System: The UNT Digital Library
The Ridge, the Glasma and Flow (open access)

The Ridge, the Glasma and Flow

I discuss the ridge phenomena observed in heavy ion collisions at RHIC. I argue that the ridge may be due to flux tubes formed from the Color Glass Condensate in the early Glasma phase of matter produced in such collisions.
Date: September 15, 2008
Creator: McLerran, L.
System: The UNT Digital Library
The role of optimality in characterizing CO2 seepage from geological carbon sequestration sites (open access)

The role of optimality in characterizing CO2 seepage from geological carbon sequestration sites

Storage of large amounts of carbon dioxide (CO{sub 2}) in deep geological formations for greenhouse gas mitigation is gaining momentum and moving from its conceptual and testing stages towards widespread application. In this work we explore various optimization strategies for characterizing surface leakage (seepage) using near-surface measurement approaches such as accumulation chambers and eddy covariance towers. Seepage characterization objectives and limitations need to be defined carefully from the outset especially in light of large natural background variations that can mask seepage. The cost and sensitivity of seepage detection are related to four critical length scales pertaining to the size of the: (1) region that needs to be monitored; (2) footprint of the measurement approach, and (3) main seepage zone; and (4) region in which concentrations or fluxes are influenced by seepage. Seepage characterization objectives may include one or all of the tasks of detecting, locating, and quantifying seepage. Each of these tasks has its own optimal strategy. Detecting and locating seepage in a region in which there is no expected or preferred location for seepage nor existing evidence for seepage requires monitoring on a fixed grid, e.g., using eddy covariance towers. The fixed-grid approaches needed to detect seepage are expected …
Date: September 15, 2008
Creator: Cortis, Andrea; Oldenburg, Curtis M. & Benson, Sally M.
System: The UNT Digital Library
FAILURE ANALYSIS: WASTEWATER DRUM BULGING (open access)

FAILURE ANALYSIS: WASTEWATER DRUM BULGING

A 55 gallon wastewater drum lid was found to be bulged during storage in a remote area. Drum samples were obtained for analysis. The interior surface of these samples revealed blistering and holes in the epoxy phenolic drum liner and corrosion of the carbon steel drum. It is suspected that osmotic pressure drove permeation of the water through the epoxy phenolic coating which was weakened from exposure to low pH water. The coating failed at locations throughout the drum interior. Subsequent corrosion of the carbon steel released hydrogen which pressurized the drum causing deformation of the drum lid. Additional samples from other wastewater drums on the same pallet were also evaluated and limited corrosion was visible on the interior surfaces. It is suspected that, with time, the corrosion would have advanced to cause pressurization of these sealed drums.
Date: September 15, 2008
Creator: Vormelker, P
System: The UNT Digital Library
A Reactive Oxide Overlayer on Rh Nanoparticles during CO Oxidation and Its Size Dependence Studied by in Situ Ambient Pressure XPS (open access)

A Reactive Oxide Overlayer on Rh Nanoparticles during CO Oxidation and Its Size Dependence Studied by in Situ Ambient Pressure XPS

None
Date: September 15, 2008
Creator: Grass, Michael E.; Zhang, Yawen; Butcher, Derek R.; Park, Jeong Y.; Li, Yimin; Bluhm, Hendrik et al.
System: The UNT Digital Library
A Reactive Oxide Overlayer on Rh Nanoparticles during CO Oxidation and Its Size Dependence Studied by in Situ Ambient Pressure XPS (open access)

A Reactive Oxide Overlayer on Rh Nanoparticles during CO Oxidation and Its Size Dependence Studied by in Situ Ambient Pressure XPS

CO oxidation is one of the most studied heterogeneous reactions, being scientifically and industrially important, particularly for removal of CO from exhaust streams and preferential oxidation for hydrogen purification in fuel cell applications. The precious metals Ru, Rh, Pd, Pt, and Au are most commonly used for this reaction because of their high activity and stability. Despite the wealth of experimental and theoretical data, it remains unclear what is the active surface for CO oxidation under catalytic conditions for these metals. In this communication, we utilize in situ synchrotron ambient pressure X-ray photoelectron spectroscopy (APXPS) to monitor the oxidation state at the surface of Rh nanoparticles during CO oxidation and demonstrate that the active catalyst is a surface oxide, the formation of which is dependent on particle size. The amount of oxide formed and the reaction rate both increase with decreasing particle size.
Date: September 15, 2008
Creator: Grass, Michael E.; Zhang, Yawen; Butcher, Derek R.; Park, Jeong Y.; Li, Yimin; Bluhm, Hendrik et al.
System: The UNT Digital Library
Stripping foils at RHIC (open access)

Stripping foils at RHIC

There are two major science programs at the Relativistic Heavy Ion Collider (RHIC). These are the heavy ion program, which collides beams of fully stripped ions, and the polarized proton program. A wide variety of stripper foils and carbon targets are used throughout the RHIC accelerator chain to facilitate these collisions. Each stripper and target has unique properties and functions. Those characteristics will be discussed, as well as recent efforts to improve their performance.
Date: September 15, 2008
Creator: Steski,D.B. & Thieberger, P.
System: The UNT Digital Library
A Reactive Oxide Overlayer on Rh Nanoparticles during CO Oxidation and Its Size Dependence Studied by in Situ Ambient Pressure XPS (open access)

A Reactive Oxide Overlayer on Rh Nanoparticles during CO Oxidation and Its Size Dependence Studied by in Situ Ambient Pressure XPS

None
Date: September 15, 2008
Creator: Grass, Michael E.; Zhang, Yawen; Butcher, Derek R.; Park, Jeong Y.; Li, Yimin; Bluhm, Hendrik et al.
System: The UNT Digital Library