StralSV: assessment of sequence variability within similar 3D structures and application to polio RNA-dependent RNA polymerase (open access)

StralSV: assessment of sequence variability within similar 3D structures and application to polio RNA-dependent RNA polymerase

Most of the currently used methods for protein function prediction rely on sequence-based comparisons between a query protein and those for which a functional annotation is provided. A serious limitation of sequence similarity-based approaches for identifying residue conservation among proteins is the low confidence in assigning residue-residue correspondences among proteins when the level of sequence identity between the compared proteins is poor. Multiple sequence alignment methods are more satisfactory - still, they cannot provide reliable results at low levels of sequence identity. Our goal in the current work was to develop an algorithm that could overcome these difficulties and facilitate the identification of structurally (and possibly functionally) relevant residue-residue correspondences between compared protein structures. Here we present StralSV, a new algorithm for detecting closely related structure fragments and quantifying residue frequency from tight local structure alignments. We apply StralSV in a study of the RNA-dependent RNA polymerase of poliovirus and demonstrate that the algorithm can be used to determine regions of the protein that are relatively unique or that shared structural similarity with structures that are distantly related. By quantifying residue frequencies among many residue-residue pairs extracted from local alignments, one can infer potential structural or functional importance of specific …
Date: November 29, 2010
Creator: Zemla, A; Lang, D; Kostova, T; Andino, R & Zhou, C
Object Type: Article
System: The UNT Digital Library
HYDROGEN PRODUCTION AND DELIVERY INFRASTRUCTURE AS A COMPLEX ADAPTIVE SYSTEM (open access)

HYDROGEN PRODUCTION AND DELIVERY INFRASTRUCTURE AS A COMPLEX ADAPTIVE SYSTEM

An agent-based model of the transition to a hydrogen transportation economy explores influences on adoption of hydrogen vehicles and fueling infrastructure. Attention is given to whether significant penetration occurs and, if so, to the length of time required for it to occur. Estimates are provided of sensitivity to numerical values of model parameters and to effects of alternative market and policy scenarios. The model is applied to the Los Angeles metropolitan area In the benchmark simulation, the prices of hydrogen and non-hydrogen vehicles are comparable. Due to fuel efficiency, hydrogen vehicles have a fuel savings advantage of 9.8 cents per mile over non-hydrogen vehicles. Hydrogen vehicles account for 60% of new vehicle sales in 20 years from the initial entry of hydrogen vehicles into show rooms, going on to 86% in 40 years and reaching still higher values after that. If the fuel savings is 20.7 cents per mile for a hydrogen vehicle, penetration reaches 86% of new car sales by the 20th year. If the fuel savings is 0.5 cents per mile, market penetration reaches only 10% by the 20th year. To turn to vehicle price difference, if a hydrogen vehicle costs $2,000 less than a non-hydrogen vehicle, new …
Date: June 29, 2010
Creator: Tolley, George S
Object Type: Report
System: The UNT Digital Library
Subduction Controls of Hf and Nd Isotopes in Lavas of the Aleutian Island Arc (open access)

Subduction Controls of Hf and Nd Isotopes in Lavas of the Aleutian Island Arc

The Hf and Nd isotopic compositions of 71 Quaternary lavas collected from locations along the full length of the Aleutian island arc are used to constrain the sources of Aleutian magmas and to provide insight into the geochemical behavior of Nd and Hf and related elements in the Aleutian subduction-magmatic system. Isotopic compositions of Aleutian lavas fall approximately at the center of, and form a trend parallel to, the terrestrial Hf-Nd isotopic array with {var_epsilon}{sub Hf} of +12.0 to +15.5 and {var_epsilon}{sub Nd} of +6.5 to +10.5. Basalts, andesites, and dacites within volcanic centers or in nearby volcanoes generally all have similar isotopic compositions, indicating that there is little measurable effect of crustal or other lithospheric assimilation within the volcanic plumbing systems of Aleutian volcanoes. Hafnium isotopic compositions have a clear pattern of along-arc increase that is continuous from the eastern-most locations near Cold Bay to Piip Seamount in the western-most part of the arc. This pattern is interpreted to reflect a westward decrease in the subducted sediment component present in Aleutian lavas, reflecting progressively lower rates of subduction westward as well as decreasing availability of trench sediment. Binary bulk mixing models (sediment + peridotite) demonstrate that 1-2% of the …
Date: August 29, 2010
Creator: Yogodzinski, Gene; Vervoort, Jeffery; Brown, Shaun Tyler & Gerseny, Megan
Object Type: Article
System: The UNT Digital Library
Demonstration Assessment of Light-Emitting Diode (LED) Parking Lot Lighting at T.J.Maxx in Manchester, NH Phase I (open access)

Demonstration Assessment of Light-Emitting Diode (LED) Parking Lot Lighting at T.J.Maxx in Manchester, NH Phase I

A report describing the process and results of replacing existing parking lot lighting, looking at a LED option with occupancy sensors, and conventional alternates. Criteria include payback, light levels, occupant satisfaction. This report is Phase I of II. Phase I deals with initial installation.
Date: June 29, 2010
Creator: Myer, Michael & Goettel, Russell T.
Object Type: Report
System: The UNT Digital Library
In situ spectroscopic detection of SMSI effect in a Ni/CeO2 system: hydrogen-induced burial and dig out of metallic nickel (open access)

In situ spectroscopic detection of SMSI effect in a Ni/CeO2 system: hydrogen-induced burial and dig out of metallic nickel

In situ APPES technique demonstrates that the strong metal support interaction effect (SMSI) in the Ni-ceria system is associated with the decoration and burial of metallic particles by the partially reduced support, a phenomenon reversible by evacuation at high temperature of the previously absorbed hydrogen.
Date: June 29, 2010
Creator: Caballero, Alfonso; Holgado, Juan P.; Gonzalez-delaCruz, Victor M.; Habas, Susan e.; Herranz, Tirma & Salmeron, Miquel
Object Type: Article
System: The UNT Digital Library
Science and Technology Review December 2010 (open access)

Science and Technology Review December 2010

This month's issue has the following articles: (1) More Insight to Better Understand Climate Change - Commentary by Tomas Diaz de la Rubia; (2) Strengthening Our Understanding of Climate Change - Researchers at the Center for Accelerator Mass Spectrometry are working to better understand climate variation and sharpen the accuracy of predictive models; (3) Precision Diagnostics Tell All - The National Ignition Facility relies on sophisticated diagnostic instruments for measuring the key physical processes that occur in high-energy-density experiments; (4) Quick Detection of Pathogens by the Thousands - Livermore scientists have developed a device that can simultaneously identify thousands of viruses and bacteria within 24 hours; and (5) Carbon Dioxide into the Briny Deep - A proposed technique for burying carbon dioxide underground could help mitigate the effects of this greenhouse gas while producing freshwater.
Date: October 29, 2010
Creator: Blobaum, K M
Object Type: Report
System: The UNT Digital Library
Post-Shot Radiation Environment Following Low-Yield Shots Inside the National Ignition Facility (open access)

Post-Shot Radiation Environment Following Low-Yield Shots Inside the National Ignition Facility

A detailed model of the Target Bay (TB) at the National Ignition Facility (NIF) has been developed to estimate the post-shot radiation environment inside the facility. The model includes large number of structures and diagnostic instruments present inside the TB. These structures and instruments are activated by the few nanosecond pulse of neutrons generated during a shot and the resultant gamma dose rates are estimated at various decay times following the shot. The results presented in this paper are based on a low-yield D-T shot of 10{sup 16} neutrons. General environment dose rates drop to below 3 mrem/h within three hours following a shot with higher dose rates observed at contact with some of the components. Dose rate maps of the different TB levels were generated to aid in estimating worker stay-out times following a shot before entry is permitted into the TB.
Date: October 29, 2010
Creator: Sitaraman, S.; Brereton, S.; Dauffy, L.; Hall, J.; Hansen, L.; Khater, H. et al.
Object Type: Article
System: The UNT Digital Library
Kalman filtering to suppress spurious signals in Adaptive Optics control (open access)

Kalman filtering to suppress spurious signals in Adaptive Optics control

In many scenarios, an Adaptive Optics (AO) control system operates in the presence of temporally non-white noise. We use a Kalman filter with a state space formulation that allows suppression of this colored noise, hence improving residual error over the case where the noise is assumed to be white. We demonstrate the effectiveness of this new filter in the case of the estimated Gemini Planet Imager tip-tilt environment, where there are both common-path and non-common path vibrations. We discuss how this same framework can also be used to suppress spatial aliasing during predictive wavefront control assuming frozen flow in a low-order AO system without a spatially filtered wavefront sensor, and present experimental measurements from Altair that clearly reveal these aliased components.
Date: March 29, 2010
Creator: Poyneer, L & Veran, J P
Object Type: Article
System: The UNT Digital Library
Oxidative cleavage of erucic acid for the synthesis of brassylic acid (open access)

Oxidative cleavage of erucic acid for the synthesis of brassylic acid

The main focus of this work is to synthesize Brassylic Acid (BA) using oxidative cleavage of Erucic Acid (EA). Crambe (Crambe abyssinica) is an industrial oilseed grown in North Dakota. Crambe has potential as an industrial fatty acid feedstock as a source of Erucic acid (EA). It has approximately 50-60 % of EA, a C{sub 22} monounsaturated fatty acid. Oxidative cleavage of unsaturated fatty acids derived from oilseeds produces long chain (9, 11, and 13 carbon atoms) dibasic and monobasic acids. These acids are known commercial feedstocks for the preparation of nylons, polyesters, waxes, surfactants, and perfumes. Other sources of EA are Rapeseed seed oil which 50-60 % of EA. Rapeseed is grown outside USA. The oxidative cleavage of EA was done using a high throughput parallel pressure reactor system. Kinetics of the reaction shows that BA yields reach a saturation at 12 hours. H{sub 2}WO{sub 4} was found to be the best catalyst for the oxidative cleavage of EA. High yields of BA were obtained at 80 C with bubbling of O{sub 2} or 10 bar of O{sub 2} for 12 hours.
Date: October 29, 2010
Creator: Nasrullah, Mohammed J.; Thapliyal, Pooja; Pfarr, Erica N.; Dusek, Nicholas S.; Schiele, Kristofer L. & Bahr, James A.
Object Type: Article
System: The UNT Digital Library
Development of a Future Representative Concentration Pathway for Use in the IPCC 5th Assessment Earth System Model Simulations (open access)

Development of a Future Representative Concentration Pathway for Use in the IPCC 5th Assessment Earth System Model Simulations

The representative concentration pathway to be delivered is a scenario of atmospheric concentrations of greenhouse gases and other radiatively important atmospheric species, along with land-use changes, derived from the Global Change Assessment Model (GCAM). The particular representative concentration pathway (RCP) that the Joint Global Change Research Institute (JGCRI) has been responsible for is a not-to-exceed pathway that stabilizes at a radiative forcing of 4.5Wm-2 in the year 2100.
Date: December 29, 2010
Creator: unknown
Object Type: Text
System: The UNT Digital Library
INDEPENDENT TECHNICAL REVIEW OF THE C-400 INTERIM REMEDIAL PROJECT PHASE I RESULTS, PADUCAH, KENTUCKY (open access)

INDEPENDENT TECHNICAL REVIEW OF THE C-400 INTERIM REMEDIAL PROJECT PHASE I RESULTS, PADUCAH, KENTUCKY

The groundwater and soil in the vicinity of the C-400 Building at the Paducah Gaseous Diffusion Plant (PGDP), is contaminated with substantial quantities of industrial solvents, primarily trichoroethene (TCE). This solvent 'source' is recognized as a significant challenge and an important remediation target in the overall environmental cleanup strategy for PGDP. Thus, the cleanup of the C-400 TCE Source is a principal focus for the Department of Energy (DOE) and its contractors, and for PGDP regulators and stakeholders. Using a formal investigation, feasibility study and decision process, Electrical Resistance Heating (ERH) was selected for the treatment of the soil and groundwater in the vicinity of C-400. ERH was selected as an interim action to remove 'a significant portion of the contaminant mass of TCE at the C-400 Cleaning Building area through treatment' with the longer term goal of reducing 'the period the TCE concentration in groundwater remains above its Maximum Contaminant Level (MCL).' ERH is a thermal treatment that enhances the removal of TCE and related solvents from soil and groundwater. The heterogeneous conditions at PGDP, particularly the high permeability regional gravel aquifer (RGA), are challenging to ERH. Thus, a phased approach is being followed to implement this relatively expensive …
Date: October 29, 2010
Creator: Looney, B.; Rossabi, J.; Stewart,L. & Richards, W.
Object Type: Report
System: The UNT Digital Library
Enzyme-Like Catalysis of the Nazarov Cyclization by Supramolecular Encapsulation (open access)

Enzyme-Like Catalysis of the Nazarov Cyclization by Supramolecular Encapsulation

A primary goal in the design and synthesis of molecular hosts has been the selective recognition and binding of a variety of guests using non-covalent interactions. Supramolecular catalysis, which is the application of such hosts towards catalysis, has much in common with many enzymatic reactions, chiefly the use of both spatially appropriate binding pockets and precisely oriented functional groups to recognize and activate specific substrate molecules. Although there are now many examples which demonstrate how selective encapsulation in a host cavity can enhance the reactivity of a bound guest, all have failed to reach the degree of increased reactivity typical of enzymes. We now report the catalysis of the Nazarov cyclization by a self-assembled coordination cage, a carbon-carbon bond-forming reaction which proceeds under mild, aqueous conditions. The acceleration in this system is over a million-fold, and represents the first example of supramolecular catalysis that achieves the level of rate enhancement comparable to that observed in several enzymes. We explain the unprecedented degree of rate increase as due to the combination of (a) preorganization of the encapsulated substrate molecule, (b) stabilization of the transition state of the cyclization by constrictive binding, and (c) increase in the basicity of the complexed alcohol …
Date: March 29, 2010
Creator: Hastings, Courtney; Pluth, Michael; Bergman, Robert & Raymond, Kenneth
Object Type: Article
System: The UNT Digital Library
Systematic reduction of sign errors in many-body calculations of atoms and molecules (open access)

Systematic reduction of sign errors in many-body calculations of atoms and molecules

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Date: March 29, 2010
Creator: Bajdich, M.; Tiago, M. L.; Hood, R. Q.; Kent, P. R. & Reboredo, F. A.
Object Type: Article
System: The UNT Digital Library
Metal-Organic Frameworks: Literature Survey and Recommendation of Potential Sorbent Materials (open access)

Metal-Organic Frameworks: Literature Survey and Recommendation of Potential Sorbent Materials

Metal-organic frameworks (MOFs) are a special type of porous material with a number of unique properties, including exceptionally high surface areas, large internal pore volumes (void space) and tunable pore sizes. These materials are prepared through the assembly of molecular building blocks into ordered three-dimensional structures. The bulk properties of the MOF are determined by the nature of the building blocks and, as such, these materials can be designed with special characteristics that cannot be realized in other sorbent materials, like activated carbons. For example, MOFs can be constructed with binding sites or pockets that can exhibit selectivity for specific analytes. Alternatively, the framework can be engineered to undergo reversible dimensional changes (or 'breathing') upon interaction with an analyte, effectively trapping the molecule of interest in the lattice structure. In this report, we have surveyed the 4000 different MOF structures reported in the open literature and provided recommendations for specific MOF materials that should be investigated as sorbents for this project.
Date: April 29, 2010
Creator: Baumann, T F
Object Type: Report
System: The UNT Digital Library
Analysis Efforts Supporting NSTX Upgrades (open access)

Analysis Efforts Supporting NSTX Upgrades

The National Spherical Torus Experiment (NSTX) is a low aspect ratio, spherical torus (ST) configuration device which is located at Princeton Plasma Physics Laboratory (PPPL) This device is presently being updated to enhance its physics by doubling the TF field to 1 Tesla and increasing the plasma current to 2 Mega-amperes. The upgrades include a replacement of the centerstack and addition of a second neutral beam. The upgrade analyses have two missions. The first is to support design of new components, principally the centerstack, the second is to qualify existing NSTX components for higher loads, which will increase by a factor of four. Cost efficiency was a design goal for new equipment qualification, and reanalysis of the existing components. Showing that older components can sustain the increased loads has been a challenging effort in which designs had to be developed that would limit loading on weaker components, and would minimize the extent of modifications needed. Two areas representing this effort have been chosen to describe in more details: analysis of the current distribution in the new TF inner legs, and, second, analysis of the out-of-plane support of the existing TF outer legs.
Date: November 29, 2010
Creator: H.Zhang, P. Titus, P. Rogoff, A.Zolfaghari, D. Mangra, M. Smith
Object Type: Article
System: The UNT Digital Library
Summary of Previous Chamber or Controlled Anthrax Studies and Recommendations for Possible Additional Studies (open access)

Summary of Previous Chamber or Controlled Anthrax Studies and Recommendations for Possible Additional Studies

This report and an associated Excel file(a) summarizes the investigations and results of previous chamber and controlled studies(b) to characterize the performance of methods for collecting, storing and/or transporting, extracting, and analyzing samples from surfaces contaminated by Bacillus anthracis (BA) or related simulants. This report and the Excel are the joint work of the Pacific Northwest National Laboratory (PNNL) and the National Institute of Standards and Technology (NIST) for the Department of Homeland Security, Science and Technology Directorate. The report was originally released as PNNL-SA-69338, Rev. 0 in November 2009 with limited distribution, but was subsequently cleared for release with unlimited distribution in this Rev. 1. Only minor changes were made to Rev. 0 to yield Rev. 1. A more substantial update (including summarizing data from other studies and more condensed summary tables of data) is underway
Date: December 29, 2010
Creator: Piepel, Gregory F.; Amidan, Brett G. & Morrow, Jayne B.
Object Type: Report
System: The UNT Digital Library
Background and Derivation of ANS-5.4 Standard Fission Product Release Model (open access)

Background and Derivation of ANS-5.4 Standard Fission Product Release Model

This background report describes the technical basis for the newly proposed American Nuclear Society (ANS) 5.4 standard, Methods for Calculating the Fractional Release of Volatile Fission Products from Oxide Fuels. The proposed ANS 5.4 standard provides a methodology for determining the radioactive fission product releases from the fuel for use in assessing radiological consequences of postulated accidents that do not involve abrupt power transients. When coupled with isotopic yields, this method establishes the 'gap activity,' which is the inventory of volatile fission products that are released from the fuel rod if the cladding are breached.
Date: January 29, 2010
Creator: Beyer, Carl E. & Turnbull, Andrew J.
Object Type: Report
System: The UNT Digital Library
Natural Gas Vehicles : Status, Barriers, and Opportunities. (open access)

Natural Gas Vehicles : Status, Barriers, and Opportunities.

In the United States, recent shale gas discoveries have generated renewed interest in using natural gas as a vehicular fuel, primarily in fleet applications, while outside the United States, natural gas vehicle use has expanded significantly in the past decade. In this report for the U.S. Department of Energy's Clean Cities Program - a public-private partnership that advances the energy, economic, and environmental security of the U.S. by supporting local decisions that reduce petroleum use in the transportation sector - we have examined the state of natural gas vehicle technology, current market status, energy and environmental benefits, implications regarding advancements in European natural gas vehicle technologies, research and development efforts, and current market barriers and opportunities for greater market penetration. The authors contend that commercial intracity trucks are a prime area for advancement of this fuel. Therefore, we examined an aggressive future market penetration of natural gas heavy-duty vehicles that could be seen as a long-term goal. Under this scenario using Energy Information Administration projections and GREET life-cycle modeling of U.S. on-road heavy-duty use, natural gas vehicles would reduce petroleum consumption by approximately 1.2 million barrels of oil per day, while another 400,000 barrels of oil per day reduction could …
Date: November 29, 2010
Creator: Rood Werpy, M.; Santini, D.; Burnham, A.; Mintz, M. & Systems, Energy
Object Type: Report
System: The UNT Digital Library
On the Performance of an Algebraic MultigridSolver on Multicore Clusters (open access)

On the Performance of an Algebraic MultigridSolver on Multicore Clusters

Algebraic multigrid (AMG) solvers have proven to be extremely efficient on distributed-memory architectures. However, when executed on modern multicore cluster architectures, we face new challenges that can significantly harm AMG's performance. We discuss our experiences on such an architecture and present a set of techniques that help users to overcome the associated problems, including thread and process pinning and correct memory associations. We have implemented most of the techniques in a MultiCore SUPport library (MCSup), which helps to map OpenMP applications to multicore machines. We present results using both an MPI-only and a hybrid MPI/OpenMP model.
Date: April 29, 2010
Creator: Baker, A H; Schulz, M & Yang, U M
Object Type: Article
System: The UNT Digital Library
STP-ECRTS - THERMAL AND GAS ANALYSES FOR SLUDGE TRANSPORT AND STORAGE CONTAINER (STSC) STORAGE AT T PLANT (open access)

STP-ECRTS - THERMAL AND GAS ANALYSES FOR SLUDGE TRANSPORT AND STORAGE CONTAINER (STSC) STORAGE AT T PLANT

The Sludge Treatment Project (STP) is responsible for the disposition of sludge contained in the six engineered containers and Settler tank within the 105-K West (KW) Basin. The STP is retrieving and transferring sludge from the Settler tank into engineered container SCS-CON-230. Then, the STP will retrieve and transfer sludge from the six engineered containers in the KW Basin directly into a Sludge Transport and Storage Containers (STSC) contained in a Sludge Transport System (STS) cask. The STSC/STS cask will be transported to T Plant for interim storage of the STSC. The STS cask will be loaded with an empty STSC and returned to the KW Basin for loading of additional sludge for transportation and interim storage at T Plant. CH2MHILL Plateau Remediation Company (CHPRC) contracted with Fauske & Associates, LLC (FAI) to perform thermal and gas generation analyses for interim storage of STP sludge in the Sludge Transport and Storage Container (STSCs) at T Plant. The sludge types considered are settler sludge and sludge originating from the floor of the KW Basin and stored in containers 210 and 220, which are bounding compositions. The conditions specified by CHPRC for analysis are provided in Section 5. The FAI report (FAI/10-83, …
Date: April 29, 2010
Creator: RD, CROWE; R, APTHORPE; SJ, LEE & MG, PLYS
Object Type: Report
System: The UNT Digital Library
Finite temperature spin-dynamics and phase transitions in spin-orbital models (open access)

Finite temperature spin-dynamics and phase transitions in spin-orbital models

We study finite temperature properties of a generic spin-orbital model relevant to transition metal compounds, having coupled quantum Heisenberg-spin and Ising-orbital degrees of freedom. The model system undergoes a phase transition, consistent with that of a 2D Ising model, to an orbitally ordered state at a temperature set by short-range magnetic order. At low temperatures the orbital degrees of freedom freeze-out and the model maps onto a quantum Heisenberg model. The onset of orbital excitations causes a rapid scrambling of the spin spectral weight away from coherent spin-waves, which leads to a sharp increase in uniform magnetic susceptibility just below the phase transition, reminiscent of the observed behavior in the Fe-pnictide materials.
Date: April 29, 2010
Creator: Chen, C. C.
Object Type: Article
System: The UNT Digital Library
Tunneling density of states as a function of thickness in superconductor/ strong ferromagnet bilayers (open access)

Tunneling density of states as a function of thickness in superconductor/ strong ferromagnet bilayers

We have made an experimental study of the tunneling density of states (DOS) in strong ferromagnetic thin films (CoFe) in proximity with a thick superconducting film (Nb) as a function of d{sub F}, the ferromagnetic thickness. Remarkably, we find that as d{sub F} increases, the superconducting DOS exhibits a scaling behavior in which the deviations from the normal-state conductance have a universal shape that decreases exponentially in amplitude with characteristic length d* {approx} 0.4 nm. We do not see oscillations in the DOS as a function of d{sub F}, as expected from predictions based on the Usadel equations, although an oscillation in T{sub c}(d{sub F}) has been seen in the same materials.
Date: April 29, 2010
Creator: Reymond, S.
Object Type: Article
System: The UNT Digital Library
A Southern Sky Survey with Fermi LAT and ASKAP (open access)

A Southern Sky Survey with Fermi LAT and ASKAP

We present the prospects for a future joint gamma-ray and radio survey of southern hemisphere sources using the Fermi Large Area Telescope (LAT) and the upcoming Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope. ASKAP is a next generation radio telescope designed to perform surveys at GHz frequencies at a much higher survey speed than previous radio telescopes, and is scheduled to start engineering observations in 2011. The survey capabilities of both Fermi LAT and ASKAP are described, and the planned science surveys for ASKAP are summarized. We give some expected details of the Variable and Slow Transient (VAST) survey using ASKAP, which will search for transients on timescales from 5 seconds to years. Some observational properties of faint and transient sources seen at gamma-ray and radio wavelengths are summarized, and prospects and strategies for using ASKAP survey data for LAT source counterpart identification are summarized.
Date: April 29, 2010
Creator: Cameron, Robert A. & /SLAC /KIPAC, Menlo Park
Object Type: Article
System: The UNT Digital Library
Origin of charge density at LaAlO3-on-SrTiO3 heterointerfacespossibility of intrinsic doping (open access)

Origin of charge density at LaAlO3-on-SrTiO3 heterointerfacespossibility of intrinsic doping

As discovered by Ohtomo et al., a large sheet charge density with high mobility exists at the interface between SrTiO{sub 3} and LaAlO{sub 3}. Based on transport, spectroscopic and oxygen-annealing experiments, we conclude that extrinsic defects in the form of oxygen vacancies introduced by the pulsed laser deposition process used by all researchers to date to make these samples is the source of the large carrier densities. Annealing experiments show a limiting carrier density. We also present a model that explains the high mobility based on carrier redistribution due to an increased dielectric constant.
Date: April 29, 2010
Creator: Siemons, W.
Object Type: Article
System: The UNT Digital Library