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Environmental and Genetic Preconditioning for Long-Term Anoxia Responses Requires AMPK in Caenorhabditis elegans (open access)

Environmental and Genetic Preconditioning for Long-Term Anoxia Responses Requires AMPK in Caenorhabditis elegans

Article on environmental and genetic preconditioning for long-term anoxia responses requires AMPK in Caenorhabditis elegans.
Date: February 3, 2011
Creator: LaRue, Bobby L. & Padilla, Pamela A.
System: The UNT Digital Library
Iterative Algorithms for Ptychographic Phase Retrieval (open access)

Iterative Algorithms for Ptychographic Phase Retrieval

Ptychography promises diffraction limited resolution without the need for high resolution lenses. To achieve high resolution one has to solve the phase problem for many partially overlapping frames. Here we review some of the existing methods for solving ptychographic phase retrieval problem from a numerical analysis point of view, and propose alternative methods based on numerical optimization.
Date: May 3, 2011
Creator: Yang, Chao; Qian, Jianliang; Schirotzek, Andre; Maia, Filipe & Marchesini, Stefano
System: The UNT Digital Library
Measures of trajectory ensemble disparity in nonequilibrium statistical dynamics (open access)

Measures of trajectory ensemble disparity in nonequilibrium statistical dynamics

Many interesting divergence measures between conjugate ensembles of nonequilibrium trajectories can be experimentally determined from the work distribution of the process. Herein, we review the statistical and physical significance of several of these measures, in particular the relative entropy (dissipation), Jeffreys divergence (hysteresis), Jensen-Shannon divergence (time-asymmetry), Chernoff divergence (work cumulant generating function), and Renyi divergence.
Date: June 3, 2011
Creator: Crooks, Gavin & Sivak, David
System: The UNT Digital Library
Particle Suspension Mechanisms - Supplemental Material (open access)

Particle Suspension Mechanisms - Supplemental Material

This supplemental material provides a brief introduction to particle suspension mechanisms that cause exfoliated skin cells to become and remain airborne. The material presented here provides additional context to the primary manuscript and serves as background for designing possible future studies to assess the impact of skin cells as a source of infectious aerosols. This introduction is not intended to be comprehensive and interested readers are encouraged to consult the references cited.
Date: March 3, 2011
Creator: Dillon, M B
System: The UNT Digital Library
General-purpose event generators for LHC physics (open access)

General-purpose event generators for LHC physics

We review the physics basis, main features and use of general-purpose Monte Carlo event generators for the simulation of proton-proton collisions at the Large Hadron Collider. Topics included are: the generation of hard-scattering matrix elements for processes of interest, at both leading and next-to-leading QCD perturbative order; their matching to approximate treatments of higher orders based on the showering approximation; the parton and dipole shower formulations; parton distribution functions for event generators; non-perturbative aspects such as soft QCD collisions, the underlying event and diffractive processes; the string and cluster models for hadron formation; the treatment of hadron and tau decays; the inclusion of QED radiation and beyond-Standard-Model processes. We describe the principal features of the Ariadne, Herwig++, Pythia 8 and Sherpa generators, together with the Rivet and Professor validation and tuning tools, and discuss the physics philosophy behind the proper use of these generators and tools. This review is aimed at phenomenologists wishing to understand better how parton-level predictions are translated into hadron-level events as well as experimentalists wanting a deeper insight into the tools available for signal and background simulation at the LHC.
Date: March 3, 2011
Creator: Buckley, Andy; Butterworth, Jonathan; Gieseke, Stefan; Grellscheid, David; Hoche, Stefan; Hoeth, Hendrik et al.
System: The UNT Digital Library
Lensless x-ray imaging in reflection geometry (open access)

Lensless x-ray imaging in reflection geometry

Lensless X-ray imaging techniques such as coherent diffraction imaging and ptychography, and Fourier transform holography can provide time-resolved, diffraction-limited images. Nearly all examples of these techniques have focused on transmission geometry, restricting the samples and reciprocal spaces that can be investigated. We report a lensless X-ray technique developed for imaging in Bragg and small-angle scattering geometries, which may also find application in transmission geometries. We demonstrate this by imaging a nanofabricated pseudorandom binary structure in small-angle reflection geometry. The technique can be used with extended objects, places no restriction on sample size, and requires no additional sample masking. The realization of X-ray lensless imaging in reflection geometry opens up the possibility of single-shot imaging of surfaces in thin films, buried interfaces in magnetic multilayers, organic photovoltaic and field-effect transistor devices, or Bragg planes in a single crystal.
Date: February 3, 2011
Creator: Roy, S.; Parks, D. H.; Seu, K. A.; Turner, J. J.; Chao, W.; Anderson, E. H. et al.
System: The UNT Digital Library
RF system models for the CERN Large Hadron Collider with application to longitudinal dynamics (open access)

RF system models for the CERN Large Hadron Collider with application to longitudinal dynamics

The LHC RF station-beam interaction strongly influences the longitudinal beam dynamics, both single bunch and collective effects. Non-linearities and noise generated within the Radio Frequency (RF) accelerating system interact with the beam and contribute to beam motion and longitudinal emittance blowup. Thus, the noise power spectrum of the RF accelerating voltage strongly affects the longitudinal beam distribution. Furthermore, the coupled-bunch instabilities are also directly affected by the RF components and the configuration of the Low Level RF (LLRF) feedback loops. In this work we present a formalism relating the longitudinal beam dynamics with the RF system configurations, an estimation of collective effects stability margins, and an evaluation of longitudinal sensitivity to various LLRF parameters and configurations.
Date: March 3, 2011
Creator: Mastorides, T.; Rivetta, C.; Fox, J. D.; Winkle, D. Van & Baudrenghien, P.
System: The UNT Digital Library
Experience report with the Alignment Diagnostic System (open access)

Experience report with the Alignment Diagnostic System

Since 2009 an Alignment Diagnostic System (ADS) has been operating at the undulator of the new Linac Coherent Light Source at SLAC National Accelerator Laboratory. The undulator spans a distance of 132 meters and is structured into 33 segments. Each segment is equipped with four hydrostatic leveling sensors and four wire position monitors. This report describes the set up and reflects the experience gained with the ADS.
Date: March 3, 2011
Creator: Gassner, Georg
System: The UNT Digital Library
I/O Performance of Virtualized Cloud Environments (open access)

I/O Performance of Virtualized Cloud Environments

The scientific community is exploring the suitability of cloud infrastructure to handle High Performance Computing (HPC) applications. The goal of Magellan, a project funded through DOE ASCR, is to investigate the potential role of cloud computing to address the computing needs of the Department of Energy?s Office of Science, especially for mid-range computing and data-intensive applications which are not served through existing DOE centers today. Prior work has shown that applications with significant communication orI/O tend to perform poorly in virtualized cloud environments. However, there is a limited understanding of the I/O characteristics in virtualized cloud environments. This paper will present our results in benchmarking the I/O performance over different cloud and HPC platforms to identify the major bottlenecks in existing infrastructure. We compare the I/O performance using IOR benchmark on two cloud platforms - Amazon and Magellan. We analyze the performance of different storage options available, different instance types in multiple availability zones. Finally, we perform large-scale tests in order to analyze the variability in the I/O patterns over time and region. Our results highlight the overhead and variability in I/O performance on both public and private cloud solutions. Our results will help applications decide between the different storage …
Date: November 3, 2011
Creator: Ghoshal, Devarshi; Canon, Shane & Ramakrishnan, Lavanya
System: The UNT Digital Library
Nodal Quasiparticle Meltdown in Ultra-High Resolution Pump-Probe Angle-Resolved Photoemission (open access)

Nodal Quasiparticle Meltdown in Ultra-High Resolution Pump-Probe Angle-Resolved Photoemission

High-T{sub c} cuprate superconductors are characterized by a strong momentum-dependent anisotropy between the low energy excitations along the Brillouin zone diagonal (nodal direction) and those along the Brillouin zone face (antinodal direction). Most obvious is the d-wave superconducting gap, with the largest magnitude found in the antinodal direction and no gap in the nodal direction. Additionally, while antin- odal quasiparticle excitations appear only below T{sub c}, superconductivity is thought to be indifferent to nodal excitations as they are regarded robust and insensitive to T{sub c}. Here we reveal an unexpected tie between nodal quasiparticles and superconductivity using high resolution time- and angle-resolved photoemission on optimally doped Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}}#14;. We observe a suppression of the nodal quasiparticle spectral weight following pump laser excitation and measure its recovery dynamics. This suppression is dramatically enhanced in the superconducting state. These results reduce the nodal-antinodal dichotomy and challenge the conventional view of nodal excitation neutrality in superconductivity. The electronic structures of high-Tc cuprates are strongly momentum-dependent. This is one reason why the momentum-resolved technique of angle-resolved photoemission spectroscopy (ARPES) has been a central tool in the #12;field of high-temperature superconductivity. For example, coherent low energy excitations with momenta near the Brillouin …
Date: June 3, 2011
Creator: Graf, Jeff; Jozwiak, Chris; Smallwood, Chris L.; Eisaki, H.; Kaindl, Robert A.; Lee, Dung-Hai et al.
System: The UNT Digital Library
STUDY OF THERMAL SENSITIVITY AND THERMAL EXPLOSION VIOLENCE OF ENERGETIC MATERIALS IN THE LLNL ODTX SYSTEM (open access)

STUDY OF THERMAL SENSITIVITY AND THERMAL EXPLOSION VIOLENCE OF ENERGETIC MATERIALS IN THE LLNL ODTX SYSTEM

Some energetic materials may explode at fairly low temperatures and the violence from thermal explosion may cause a significant damage. Thus it is important to understand the response of energetic materials to thermal insults for safe handling and storage of energetic materials. The One Dimensional Time to Explosion (ODTX) system at the Lawrence Livermore National Laboratory can measure times to explosion, lowest explosion temperatures, and determine kinetic parameters of energetic materials. Samples of different configurations can be tested in the system. The ODTX testing can also generate useful data for determining thermal explosion violence of energetic materials. We also performed detonation experiments of LX-10 in aluminum anvils to determine the detonation violence and validated the Zerilli Armstrong aluminum model. Results of the detonation experiments agreed well with the model prediction.
Date: August 3, 2011
Creator: HSU, P C; Hust, G; May, C; Howard, M; Chidester, S K; Springer, H K et al.
System: The UNT Digital Library
Evaluation of the carbon content of aerosols from the burn- ing of biomass in the Brazilian Amazon using thermal, op- tical and thermal-optical analysis methods (open access)

Evaluation of the carbon content of aerosols from the burn- ing of biomass in the Brazilian Amazon using thermal, op- tical and thermal-optical analysis methods

Aerosol samples were collected at a pasture site in the Amazon Basin as part of the project LBA-SMOCC-2002 (Large-Scale Biosphere-Atmosphere Experiment in Amazonia - Smoke Aerosols, Clouds, Rainfall and Climate: Aerosols from Biomass Burning Perturb Global and Regional Climate). Sampling was conducted during the late dry season, when the aerosol composition was dominated by biomass burning emissions, especially in the submicron fraction. A 13-stage Dekati low-pressure impactor (DLPI) was used to collect particles with nominal aerodynamic diameters (D{sub p}) ranging from 0.03 to 0.10 m. Gravimetric analyses of the DLPI substrates and filters were performed to obtain aerosol mass concentrations. The concentrations of total, apparent elemental, and organic carbon (TC, EC{sub a}, and OC) were determined using thermal and thermal-optical analysis (TOA) methods. A light transmission method (LTM) was used to determine the concentration of equivalent black carbon (BC{sub e}) or the absorbing fraction at 880 nm for the size-resolved samples. During the dry period, due to the pervasive presence of fires in the region upwind of the sampling site, concentrations of fine aerosols (D{sub p} < 2.5 {mu}m: average 59.8 {mu}g m{sup -3}) were higher than coarse aerosols (D{sub p} > 2.5 {mu}m: 4.1 {mu}g m{sup -3}). Carbonaceous matter, …
Date: June 3, 2011
Creator: Soto-Garcia, Lydia L.; Andreae, Meinrat O.; Andreae, Tracey W.; taxo, Paulo Ar-; Maenhaut, Willy; Kirchstetter, Thomas et al.
System: The UNT Digital Library
The effect of microhydration on ionization energies of thymine (open access)

The effect of microhydration on ionization energies of thymine

A combined theoretical and experimental study of the effect of microhydration on ionization energies (IEs) of thymine is presented. The experimental IEs are derived from photoionization efficiency curves recorded using tunable synchrotron VUV radiation. The onsets of the PIE curves are 8.85+-0.05, 8.60+-0.05, 8.55+-0.05, and 8.40+-0.05 eV for thymine, thymine mono-, di-, and tri-hydrates, respectively. The computed (EOM-IP-CCSD/cc-pVTZ) AIEs are 8.90, 8.51, 8.52, and 8.35 eV for thymine and the lowest isomers of thymine mono-, di-, and tri-hydrates. Due to large structural relaxation, the Franck-Condon factors for the 0<-- 0 transitions are very small shifting the apparent PIE onsets to higher energies. Microsolvation strongly affects IEs of thymine -- addition of each water molecule reduces the first vertical IE by 0.10-0.15 eV. The adiabatic IE decreases even more (up to 0.4 eV). The magnitude of the effect varies for different ionized states and for different isomers. For the ionized states that are localized on thymine the dominant contribution to the IE reduction is the electrostatic interaction between the delocalized positive charge on thymine and the dipole moment of the water molecule.
Date: January 3, 2011
Creator: Khistyev, Kirill; Bravaya, Ksenia B.; Kamarchik, Eugene; Kostko, Oleg; Ahmed, Musahid & Krylov, Anna I.
System: The UNT Digital Library
Environmental Restoration of Corrective Action Unit 408: Bomblet Target Area, Tonopah Test Range, Nevada (Funded by the American Reinvestment and Recovery Act) (open access)

Environmental Restoration of Corrective Action Unit 408: Bomblet Target Area, Tonopah Test Range, Nevada (Funded by the American Reinvestment and Recovery Act)

The mission of the U.S. Department of Energy, National Nuclear Security Administration Nevada Site Office (NNSA/NSO) Environmental Restoration Program is to address the environmental impacts of weapons testing conducted on the Nevada National Security Site and the Nevada Test and Training Range. The large physical size of these sites, along with limits on funding and other resources available for remediation efforts, means that environmental restoration activities must be prioritized and accomplished incrementally over time. The remediation of a bomblet target area on the Tonopah Test Range (TTR), which is located within the Nevada Test and Training Range, was originally planned in 2007 but was not carried out until funding became available in the summer of 2009 through the American Reinvestment and Recovery Act. This activity was implemented in accordance with the Federal Facility Agreement and Consent Order established between NNSA/NSO and the Nevada Division of Environmental Protection. This activity which was complete by the end of Fiscal Year 2010, involved the excavation of disposal pits suspected of containing submunitions and the surface clearance of submunitions on seven target areas amounting to approximately 6.7 square kilometers of land at the TTR. The TTR was used by Sandia National Laboratories from the …
Date: March 3, 2011
Creator: Kevin Cabble (NSO), Mark Burmeister and Mark Krauss (N-I)
System: The UNT Digital Library
MODELING RESULTS FROM CESIUM ION EXCHANGE PROCESSING WITH SPHERICAL RESINS (open access)

MODELING RESULTS FROM CESIUM ION EXCHANGE PROCESSING WITH SPHERICAL RESINS

Ion exchange modeling was conducted at the Savannah River National Laboratory to compare the performance of two organic resins in support of Small Column Ion Exchange (SCIX). In-tank ion exchange (IX) columns are being considered for cesium removal at Hanford and the Savannah River Site (SRS). The spherical forms of resorcinol formaldehyde ion exchange resin (sRF) as well as a hypothetical spherical SuperLig{reg_sign} 644 (SL644) are evaluated for decontamination of dissolved saltcake wastes (supernates). Both SuperLig{reg_sign} and resorcinol formaldehyde resin beds can exhibit hydraulic problems in their granular (nonspherical) forms. SRS waste is generally lower in potassium and organic components than Hanford waste. Using VERSE-LC Version 7.8 along with the cesium Freundlich/Langmuir isotherms to simulate the waste decontamination in ion exchange columns, spherical SL644 was found to reduce column cycling by 50% for high-potassium supernates, but sRF performed equally well for the lowest-potassium feeds. Reduced cycling results in reduction of nitric acid (resin elution) and sodium addition (resin regeneration), therefore, significantly reducing life-cycle operational costs. These findings motivate the development of a spherical form of SL644. This work demonstrates the versatility of the ion exchange modeling to study the effects of resin characteristics on processing cycles, rates, and cold chemical …
Date: January 3, 2011
Creator: Nash, C.; Hang, T. & Aleman, S.
System: The UNT Digital Library
Nevada National Security Site Environmental Remediation Progress Toward Closure of Contaminated Sites (open access)

Nevada National Security Site Environmental Remediation Progress Toward Closure of Contaminated Sites

The Environmental Restoration activities at the U.S. Department of Energy (DOE), National Nuclear Security Administration Nevada Site Office assess the environmental impacts that resulted from atmospheric and underground nuclear tests conducted from 1951 to 1992 on the Nevada National Security Site and Nevada Test and Training Range (which includes the Tonopah Test Range). The goal is to protect public health and the environment through investigations and corrective actions. The Federal Facility Agreement and Consent Order (FFACO), established in 1996 between the State of Nevada Division of Environmental Protection (NDEP), DOE, and the U.S. Department of Defense, serves as the cleanup agreement for the Environmental Restoration activities and provides the framework for identifying, prioritizing, investigating, remediating, and monitoring contaminated sites. This agreement satisfies the corrective action requirements of the Resource Conservation and Recovery Act. To ensure efficiency in managing these corrective actions, the sites are grouped according to location, physical and geological characteristics, and/or contaminants. These groups, called corrective action units, are prioritized based on potential risk to workers and the public, available technology, future land use, agency and stakeholder concerns, and other criteria. Environmental Restoration activities include: Industrial Sites, Soils, and Underground Test Area. Nearly 15 years have passed since …
Date: March 3, 2011
Creator: Matthews, Patrick & Boehleke, Robert
System: The UNT Digital Library
Many-body interactions in quasi-freestanding graphene (open access)

Many-body interactions in quasi-freestanding graphene

The Landau-Fermi liquid picture for quasiparticles assumes that charge carriers are dressed by many-body interactions, forming one of the fundamental theories of solids. Whether this picture still holds for a semimetal such as graphene at the neutrality point, i.e., when the chemical potential coincides with the Dirac point energy, is one of the long-standing puzzles in this field. Here we present such a study in quasi-freestanding graphene by using high-resolution angle-resolved photoemission spectroscopy. We see the electron-electron and electron-phonon interactions go through substantial changes when the semimetallic regime is approached, including renormalizations due to strong electron-electron interactions with similarities to marginal Fermi liquid behavior. These findings set a new benchmark in our understanding of many-body physics in graphene and a variety of novel materials with Dirac fermions.
Date: June 3, 2011
Creator: Siegel, David; Park, Cheol-Hwan; Hwang, Choongyu; Deslippe, Jack; Fedorov, Alexei; Louie, Steven et al.
System: The UNT Digital Library
Local Structural Models of Complex Oxygen- and Hydroxyl-rich GaP/InP(001) Surfaces (open access)

Local Structural Models of Complex Oxygen- and Hydroxyl-rich GaP/InP(001) Surfaces

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Date: November 3, 2011
Creator: Wood, B; Ogitsu, T & Schwegler, E
System: The UNT Digital Library
Disentangling the Mn moments on different sublattices in the half-metallic ferrimagnet Mn3?xCoxGa (open access)

Disentangling the Mn moments on different sublattices in the half-metallic ferrimagnet Mn3?xCoxGa

Ferrimagnetic Mn{sub 3-x}Co{sub x}Ga compounds have been investigated by magnetic circular dichroism in x-ray absorption (XMCD). Compounds with x > 0.5 crystallize in the CuHg{sub 2}Ti structure. A tetragonal distortion of the cubic structure occurs for x {le} 0.5. For the cubic phase, magnetometry reveals a linearly increasing magnetization of 2x Bohr magnetons per formula unit obeying the generalized Slater-Pauling rule. XMCD confirms the ferrimagnetic character with Mn atoms occupying two different sublattices with antiparallel spin orientation and different degrees of spin localization and identifies the region 0.6 < x {le} 0.8 as most promising for a high spin polarization at the Fermi level. Individual Mn moments on inequivalent sites are compared to theoretical predictions.
Date: May 3, 2011
Creator: Klaer, P.; Jenkins, C. A.; Alijani, V.; Winterlik, J.; Balke, B.; Felser, C. et al.
System: The UNT Digital Library
Electronic structure and f-orbital occupancy in Yb-substituted CeCoIn5 (open access)

Electronic structure and f-orbital occupancy in Yb-substituted CeCoIn5

The local structure and 4f orbital occupancy have been investigated in Ce{sub 1−x}Yb{sub x}CoIn{sub 5} via Yb L{sub III}-edge extended x-ray absorption fine structure (EXAFS), Ce and Yb L{sub III}-edge x-ray absorption near-edge structure (XANES), and angle-resolved photoemission spectroscopy (ARPES) measurements. Yb(III) (4f{sup 13}) is the hole analog of Ce(III) (4f{sup 1}). Yb is found to be strongly intermediate-valent in Ce{sub 1−x}Yb{sub x}CoIn{sub 5} throughout the entire doping range, including pure YbCoIn{sub 5}, with an f-hole occupancy for Yb of n{sub f} ≃ 0.3 (i.e. Yb{sup 2.3+}), independent of Yb concentration and independent of temperature down to T = 20 K. In contrast, the f-electron orbital occupancy for Ce remains close to 1 for all Yb concentrations, suggesting that there is no mutual influence on n{sub f} between neighboring Ce and Yb sites. Likewise, ARPES measurements at 12 K have found that the electronic structure along {Gamma} − X is not sensitive to the Yb substitution, suggesting that the Kondo hybridization of Ce f electrons with the conduction band is not affected by the presence of Yb impurities in the lattice. The emerging picture is that in Ce{sub 1−x}Yb{sub x}CoIn{sub 5} there are two networks, interlaced but independent, that couple …
Date: May 3, 2011
Creator: Booth, C. H.; Durakiewicz, T.; Capan, C.; Hurt, D.; Bianchi, A. D.; Joyce, J.J. et al.
System: The UNT Digital Library
The Statistical Evolution of Multiple Generations of Oxidation Products in the Photochemical Aging of Chemically Reduced Organic Aerosol (open access)

The Statistical Evolution of Multiple Generations of Oxidation Products in the Photochemical Aging of Chemically Reduced Organic Aerosol

The heterogeneous reaction of hydroxyl radicals (OH) with squalane and bis(2-ethylhexyl) sebacate (BES) particles are used as model systems to examine how distributions of reactionproducts evolve during the oxidation of chemically reduced organic aerosol. A kinetic model of multigenerational chemistry, which is compared to previously measured (squalane) and new(BES) experimental data, reveals that it is the statistical mixtures of different generations of oxidation products that control the average particle mass and elemental composition during thereaction. The model suggests that more highly oxidized reaction products, although initially formed with low probability, play a large role in the production of gas phase reaction products.In general, these results highlight the importance of considering atmospheric oxidation as a statistical process, further suggesting that the underlying distribution of molecules could playimportant roles in aerosol formation as well as in the evolution of key physicochemical properties such as volatility and hygroscopicity.
Date: October 3, 2011
Creator: Wilson, Kevin R.; Smith, Jared D.; Kessler, Sean & Kroll, Jesse H.
System: The UNT Digital Library
Nuclear Operations Application to Environmental Restoration at Corrective Action Unit 547, Miscellaneous Contaminated Waste Sites, at the Nevada National Security Site (open access)

Nuclear Operations Application to Environmental Restoration at Corrective Action Unit 547, Miscellaneous Contaminated Waste Sites, at the Nevada National Security Site

The U.S. Department of Energy (DOE), National Nuclear Security Administration Nevada Site Office has responsibility for environmental restoration at the Nevada National Security Site (formerly the Nevada Test Site). This includes remediation at locations where past testing activities have resulted in the release of plutonium to the environment. One of the current remediation efforts involves a site where an underground subcritical nuclear safety test was conducted in 1964. The underground test was vented through a steel pipe to the surface in a closed system where gas samples were obtained. The piping downstream of the gas-sampling apparatus was routed belowground to a location where it was allowed to vent into an existing radioactively contaminated borehole. The length of the pipe above the ground surface is approximately 200 meters. This pipe remained in place until remediation efforts began in 2007, at which time internal plutonium contamination was discovered. Following this discovery, an assessment was conducted to determine the quantity of plutonium present in the pipe. This site has been identified as Corrective Action Unit (CAU) 547, Miscellaneous Contaminated Waste Sites. The quantity of plutonium identified at CAU 547 exceeded the Hazard Category 3 threshold but was below the Hazard Category 2 threshold …
Date: March 3, 2011
Creator: Kevin Cabble (NSO), Mark Krauss and Patrick Matthews (N-I)
System: The UNT Digital Library
Imaging Nonequilibrium Atomic Vibrations with X-ray Diffuse Scattering (open access)

Imaging Nonequilibrium Atomic Vibrations with X-ray Diffuse Scattering

We use picosecond x-ray diffuse scattering to image the nonequilibrium vibrations of the lattice following ultrafast laser excitation. We present images of nonequilibrium phonons in InP and InSb throughout the Brillouin-zone which remain out of equilibrium up to nanoseconds. The results are analyzed using a Born model that helps identify the phonon branches contributing to the observed features in the time-resolved diffuse scattering. In InP this analysis shows a delayed increase in the transverse acoustic (TA) phonon population along high-symmetry directions accompanied by a decrease in the longitudinal acoustic (LA) phonons. In InSb the increase in TA phonon population is less directional.
Date: March 3, 2011
Creator: Trigo, M.; Chen, J.; Vishwanath, V. H.; Sheu, Y. M.; Graber, T.; Henning, R. et al.
System: The UNT Digital Library
Land subsidence in the Cerro Prieto Geothermal Field, 1 Baja California, Mexico, from 1994 to 2005. An integrated analysis of DInSAR, levelingand geological data. (open access)

Land subsidence in the Cerro Prieto Geothermal Field, 1 Baja California, Mexico, from 1994 to 2005. An integrated analysis of DInSAR, levelingand geological data.

Cerro Prieto is the oldest and largest Mexican geothermal field in operation and has been producing electricity since 1973. The large amount of geothermal fluids extracted to supply steam to the power plants has resulted in considerable deformation in and around the field. The deformation includes land subsidence and related ground fissuring and faulting. These phenomena have produced severe damages to infrastructure such as roads, irrigation canals and other facilities. In this paper, the technique of Differential Synthetic Aperture Radar Interferometry (DInSAR) is applied using C-band ENVISAR ASAR data acquired between 2003 and 2006 to determine the extent and amount of land subsidence in the Mexicali Valley near Cerro Prieto Geothermal Field. The DInSAR results were compared with published data from precise leveling surveys (1994- 1997 and 1997-2006) and detailed geological information in order to improve the understanding of temporal and spatial distributions of anthropogenic subsidence in the Mexicali Valley. The leveling and DInSAR data were modeled to characterize the observed deformation in terms of fluid extraction. The results confirm that the tectonic faults control the spatial extent of the observed subsidence. These faults likely act as groundwater flow barriers for aquifers and reservoirs. The shape of the subsiding area …
Date: March 3, 2011
Creator: Sarychikhina, O; Glowacka, E; Mellors, R & Vidal, F S
System: The UNT Digital Library