Size-dependent Si Nanowire Mechanics are Invariant to Changes in the Surface State (open access)

Size-dependent Si Nanowire Mechanics are Invariant to Changes in the Surface State

None
Date: December 29, 2010
Creator: Lee, B & Rudd, R E
System: The UNT Digital Library
Progress towards the Fielding of Ignition Targets on NIF (open access)

Progress towards the Fielding of Ignition Targets on NIF

None
Date: February 11, 2010
Creator: Mapoles, E R; Chernov, A A; Haid, B J; Kozioziemski, B J; Malsbury, T N; Mintz, J M et al.
System: The UNT Digital Library
A Parallel, High-Fidelity Radar Model (open access)

A Parallel, High-Fidelity Radar Model

None
Date: September 7, 2010
Creator: Horsley, M & Fasenfest, B
System: The UNT Digital Library
Reactive Blast Waves from Composite Charges (open access)

Reactive Blast Waves from Composite Charges

None
Date: March 12, 2010
Creator: Kuhl, A L; Reichenbach, H; Bell, J B & Beckner, V E
System: The UNT Digital Library
Simulations of divertor particle and heat loads in ohmic and L-mode plasmas in DIII-D, AUG, and JET using UEDGE (open access)

Simulations of divertor particle and heat loads in ohmic and L-mode plasmas in DIII-D, AUG, and JET using UEDGE

None
Date: May 17, 2010
Creator: Groth, M.; Porter, G. D.; Rensink, M. E.; Rognlien, T. D.; Wiesen, S.; Wischmeier, M. et al.
System: The UNT Digital Library
EUV spectroscopy of high-redshift x-ray objects (open access)

EUV spectroscopy of high-redshift x-ray objects

None
Date: June 8, 2010
Creator: Kowalski, M. P.; Wolff, M. T.; Wood, K. S.; Barbee, T. W. & Barstow, M. A.
System: The UNT Digital Library
Analysis of 14C and 13C in Teeth Provides Precise Birth Dating and Clues to Geographical Origin (open access)

Analysis of 14C and 13C in Teeth Provides Precise Birth Dating and Clues to Geographical Origin

None
Date: August 2, 2010
Creator: Alkass, K.; Buchholz, B. A.; Druid, H. & Spalding, K. L.
System: The UNT Digital Library
Optimization of azimuthal uniformity of thermal conductance between AI TMP and Si cooling arms (open access)

Optimization of azimuthal uniformity of thermal conductance between AI TMP and Si cooling arms

None
Date: February 17, 2010
Creator: Bhandarkar, S D; Mapoles, E A; Kroll, J J; Taylor, J S; Haid, B; Sater, J D et al.
System: The UNT Digital Library
Tungsten transport in the NSTX tokamak (open access)

Tungsten transport in the NSTX tokamak

None
Date: May 17, 2010
Creator: Clementson, J; Beiersdorfer, P; Roquemore, A L; Skinner, C H; Mansfield, D K; Hartzfeld, K et al.
System: The UNT Digital Library
Diffusive isotope fractionation in silicate liquids: Dependence on liquid composition, cation bonding, and isotopic exchange (open access)

Diffusive isotope fractionation in silicate liquids: Dependence on liquid composition, cation bonding, and isotopic exchange

None
Date: September 13, 2010
Creator: Watkins, J M; DePaolo, D J & Ryerson, F J
System: The UNT Digital Library
Time-Resolved Microscopic Imaging of Laser-Induced Material Modifications in Optical Materials (open access)

Time-Resolved Microscopic Imaging of Laser-Induced Material Modifications in Optical Materials

None
Date: May 10, 2010
Creator: Negres, R A
System: The UNT Digital Library
Directional Fast Neutron Detection using a Time Projection Chamber (open access)

Directional Fast Neutron Detection using a Time Projection Chamber

None
Date: April 13, 2010
Creator: Bowden, N.; Heffner, M.; Carosi, G.; Cater, D.; O'Malley, P.; Mintz, J. et al.
System: The UNT Digital Library
Laser-induced Ramp Compression of Tantalum and Iron to Over 300 GPa: EOS and X-ray Diffraction (open access)

Laser-induced Ramp Compression of Tantalum and Iron to Over 300 GPa: EOS and X-ray Diffraction

None
Date: January 26, 2010
Creator: Eggert, J. H.; Bastea, M.; Braun, D.; Fujino, D.; Rygg, R.; Smith, R. et al.
System: The UNT Digital Library
Betatron motion with coupling of horizontal and vertical degrees of freedom (open access)

Betatron motion with coupling of horizontal and vertical degrees of freedom

Presently, there are two most frequently used parameterizations of linear x-y coupled motion used in the accelerator physics. They are the Edwards-Teng and Mais-Ripken parameterizations. The article is devoted to an analysis of close relationship between the two representations, thus adding a clarity to their physical meaning. It also discusses the relationship between the eigen-vectors, the beta-functions, second order moments and the bilinear form representing the particle ellipsoid in the 4D phase space. Then, it consideres a further development of Mais-Ripken parameteresation where the particle motion is described by 10 parameters: four beta-functions, four alpha-functions and two betatron phase advances. In comparison with Edwards-Teng parameterization the chosen parametrization has an advantage that it works equally well for analysis of coupled betatron motion in circular accelerators and in transfer lines. Considered relationship between second order moments, eigen-vectors and beta-functions can be useful in interpreting tracking results and experimental data. As an example, the developed formalizm is applied to the FNAL electron cooler and Derbenev's vertex-to-plane adapter.
Date: September 1, 2010
Creator: Lebedev, V. A. & Bogacz, S. A.
System: The UNT Digital Library
Application of solution techniques to rapid growth of organic crystals (open access)

Application of solution techniques to rapid growth of organic crystals

None
Date: June 29, 2010
Creator: Zaitseva, N.; Carman, L.; Glenn, A.; Newby, J.; Faust, M.; Hamel, S. et al.
System: The UNT Digital Library
Fresh Water Generation from Aquifer-Pressured Carbon Storage (open access)

Fresh Water Generation from Aquifer-Pressured Carbon Storage

Can we use the pressure associated with sequestration to make brine into fresh water? This project is establishing the potential for using brine pressurized by Carbon Capture and Storage (CCS) operations in saline formations as the feedstock for desalination and water treatment technologies including reverse osmosis (RO) and nanofiltration (NF). Possible products are: Drinking water, Cooling water, and Extra aquifer space for CO{sub 2} storage. The conclusions are: (1) Many saline formation waters appear to be amenable to largely conventional RO treatment; (2) Thermodynamic modeling indicates that osmotic pressure is more limiting on water recovery than mineral scaling; (3) The use of thermodynamic modeling with Pitzer's equations (or Extended UNIQUAC) allows accurate estimation of osmotic pressure limits; (4) A general categorization of treatment feasibility is based on TDS has been proposed, in which brines with 10,000-85,000 mg/L are the most attractive targets; (5) Brines in this TDS range appear to be abundant (geographically and with depth) and could be targeted in planning future CCS operations (including site selection and choice of injection formation); and (6) The estimated cost of treating waters in the 10,000-85,000 mg/L TDS range is about half that for conventional seawater desalination, due to the anticipated pressure …
Date: February 19, 2010
Creator: Aines, R. D.; Wolery, T. J.; Bourcier, W. L.; Wolfe, T. & Haussmann, C.
System: The UNT Digital Library
Plasmon resonant cavities in vertical nanowire arrays (open access)

Plasmon resonant cavities in vertical nanowire arrays

We investigate tunable plasmon resonant cavity arrays in paired parallel nanowire waveguides. Resonances are observed when the waveguide length is an odd multiple of quarter plasmon wavelengths, consistent with boundary conditions of node and antinode at the ends. Two nanowire waveguides satisfy the dispersion relation of a planar metal-dielectric-metal waveguide of equivalent width equal to the square field average weighted gap. Confinement factors over 103 are possible due to plasmon focusing in the inter-wire space.
Date: February 23, 2010
Creator: Bora, Mihail; Fasenfest, Benjamin J.; Behymer, Elaine M.; Chang, Allan S-P & Bond, Tiziana C.
System: The UNT Digital Library
VERTICAL PILLAR ARRAYS FOR PLASMON NANOCAVITIES (open access)

VERTICAL PILLAR ARRAYS FOR PLASMON NANOCAVITIES

We investigate tunable plasmon resonant cavity arrays in paired parallel nanowire waveguides. Resonances are observed when the waveguide length is an odd multiple of quarter plasmon wavelengths, consistent with boundary conditions of node and antinode at the ends. Two nanowire waveguides satisfy the dispersion relation of a planar metal-dielectric-metal waveguide of equivalent width equal to the square field average weighted gap. Confinement factors over 10{sup 3} are possible due to plasmon focusing in the inter-wire space.
Date: April 2, 2010
Creator: Bora, M.; Fasenfest, B. J.; Behymer, E. M.; Chang, A. S.; Hguyen, H. T.; Britten, J. A. et al.
System: The UNT Digital Library
EXPERIMENTAL TESTS OF VANADIUM STRENGTH MODELS AT HIGH PRESSURES AND STRAIN RATES (open access)

EXPERIMENTAL TESTS OF VANADIUM STRENGTH MODELS AT HIGH PRESSURES AND STRAIN RATES

Experimental results showing significant reductions from classical in the Rayleigh-Taylor (RT) instability growth rate due to high pressure material strength or effective lattice viscosity in metal foils are presented. On the Omega Laser in the Laboratory for Laser Energetics, University of Rochester, target samples of polycrystalline vanadium are compressed and accelerated quasi-isentropically at {approx}1 Mbar pressures, while maintaining the samples in the solid-state. Comparison of the results with constitutive models for solid state strength under these conditions show that the measured RT growth is substantially lower than predictions using existing models that work well at low pressures and long time scales. High pressure, high strain rate data can be explained by the enhanced strength due to a phonon drag mechanism, creating a high effective lattice viscosity.
Date: March 2, 2010
Creator: Park, H.; Barton, N. R.; Becker, R. C.; Bernier, J. V.; Cavallo, R. M.; Lorenz, K. T. et al.
System: The UNT Digital Library
Application of a Multiscale Model of Tantalum Deformation at Megabar Pressures (open access)

Application of a Multiscale Model of Tantalum Deformation at Megabar Pressures

A new multiscale simulation tool has been developed to model the strength of tantalum under high-pressure dynamic compression. This new model combines simulations at multiple length scales to explain macroscopic properties of materials. Previously known continuum models of material response under load have built upon a mixture of theoretical physics and experimental phenomenology. Experimental data, typically measured at static pressures, are used as a means of calibration to construct models that parameterize the material properties; e.g., yield stress, work hardening, strain-rate dependence, etc. The pressure dependence for most models enters through the shear modulus, which is used to scale the flow stress. When these models are applied to data taken far outside the calibrated regions of phase space (e.g., strain rate or pressure) they often diverge in their predicted behavior of material deformation. The new multiscale model, developed at Lawrence Livermore National Laboratory, starts with interatomic quantum mechanical potential and is based on the motion and multiplication of dislocations. The basis for the macroscale model is plastic deformation by phonon drag and thermally activated dislocation motion and strain hardening resulting from elastic interactions among dislocations. The dislocation density, {rho}, and dislocation velocity, {nu}, are connected to the plastic strain rate …
Date: May 13, 2010
Creator: Cavallo, R. M.; Park, H.; Barton, N. R.; Remignton, B. A.; Pollaine, S. M.; Prisbrey, S. T. et al.
System: The UNT Digital Library
Mapping the Ionization State of Laser-Irradiated Ar Gas Jets With Multi-Wavelength Monochromatic X-Ray Imaging (open access)

Mapping the Ionization State of Laser-Irradiated Ar Gas Jets With Multi-Wavelength Monochromatic X-Ray Imaging

Two-dimensional monochromatic images of fast-electron stimulated Ar K{alpha} and He-{alpha} x-ray self-emission have recorded a time-integrated map of the extent of Ar{sup {approx}6+} and Ar{sup 16+} ions, respectively, within a high density (10{sup 20} cm{sup -3} atomic density) Ar plasma. This plasma was produced by irradiating a 2 mm wide clustering Ar gas jet with an ultra-high intensity (10{sup 19} W/cm{sup 2}, 200 fs) Ti:Sapphire laser operating at 800 nm. Spherically bent quartz crystals in the 200 (for K{alpha}) and 201 (for He-{alpha}) planes were used as near-normal incidence reflective x-ray optics. We see that a large (830 {micro}m long) region of plasma emits K{alpha} primarily along the laser axis, while the He-{alpha} emission is confined to smaller hot spot (230 {micro}m long) region that likely corresponds to the focal volume of the f/8 laser beam. X-ray spectra from a Bragg spectrometer operating in the von Hamos geometry, which images in one dimension, indicate that the centroids of the K{alpha} and He-{alpha} emission regions are separated by approximately 330 {micro}m along the laser axis.
Date: April 8, 2010
Creator: Kugland, N. L.; Doppner, T.; Kemp, A.; Schaeffer, D.; Glenzer, S. H. & Niemann, C.
System: The UNT Digital Library
Hydrogeology, chemical and microbial activity measurement through deep permafrost (open access)

Hydrogeology, chemical and microbial activity measurement through deep permafrost

Little is known about hydrogeochemical conditions beneath thick permafrost, particularly in fractured crystalline rock, due to difficulty in accessing this environment. The purpose of this investigation was to develop methods to obtain physical, chemical, and microbial information about the subpermafrost environment from a surface-drilled borehole. Using a U-tube, gas and water samples were collected, along with temperature, pressure, and hydraulic conductivity measurements, 420 m below ground surface, within a 535 m long, angled borehole at High Lake, Nunavut, Canada, in an area with 460-m-thick permafrost. Piezometric head was well above the base of the permafrost, near land surface. Initial water samples were contaminated with drill fluid, with later samples <40% drill fluid. The salinity of the non-drill fluid component was <20,000 mg/L, had a Ca/Na ratio above 1, with {delta}{sup 18}O values {approx}5{per_thousand} lower than the local surface water. The fluid isotopic composition was affected by the permafrost-formation process. Nonbacteriogenic CH{sub 4} was present and the sample location was within methane hydrate stability field. Sampling lines froze before uncontaminated samples from the subpermafrost environment could be obtained, yet the available time to obtain water samples was extended compared to previous studies. Temperature measurements collected from a distributed temperature sensor indicated …
Date: April 1, 2010
Creator: Stotler, Randy L.; Frape, Shaun K.; Freifeld, Barry M.; Holden, Brian; Onstott, Tullis C.; Ruskeeniemi, Timo et al.
System: The UNT Digital Library
Impact of elevated nitrate on sulfate-reducing bacteria: A comparative study of Desulfovibrio vulgaris (open access)

Impact of elevated nitrate on sulfate-reducing bacteria: A comparative study of Desulfovibrio vulgaris

Sulfate-reducing bacteria have been extensively studied for their potential in heavy-metal bioremediation. However, the occurrence of elevated nitrate in contaminated environments has been shown to inhibit sulfate reduction activity. Although the inhibition has been suggested to result from the competition with nitrate-reducing bacteria, the possibility of direct inhibition of sulfate reducers by elevated nitrate needs to be explored. Using Desulfovibrio vulgaris as a model sulfate-reducing bacterium, functional genomics analysis reveals that osmotic stress contributed to growth inhibition by nitrate as shown by the upregulation of the glycine/betaine transporter genes and the relief of nitrate inhibition by osmoprotectants. The observation that significant growth inhibition was effected by 70 mM NaNO{sub 3} but not by 70 mM NaCl suggests the presence of inhibitory mechanisms in addition to osmotic stress. The differential expression of genes characteristic of nitrite stress responses, such as the hybrid cluster protein gene, under nitrate stress condition further indicates that nitrate stress response by D. vulgaris was linked to components of both osmotic and nitrite stress responses. The involvement of the oxidative stress response pathway, however, might be the result of a more general stress response. Given the low similarities between the response profiles to nitrate and other stresses, …
Date: July 15, 2010
Creator: He, Q.; He, Z.; Joyner, D. C.; Joachimiak, M.; Price, M. N.; Yang, Z. K. et al.
System: The UNT Digital Library
Deep-sea oil plume enriches psychrophilic oil-degrading bacteria (open access)

Deep-sea oil plume enriches psychrophilic oil-degrading bacteria

The biological effects and expected fate of the vast amount of oil in the Gulf of Mexico from the Deepwater Horizon blowout are unknown owing to the depth and magnitude of this event. Here, we report that the dispersed hydrocarbon plume stimulated deep-sea indigenous {gamma}-Proteobacteria that are closely related to known petroleum degraders. Hydrocarbon-degrading genes coincided with the concentration of various oil contaminants. Changes in hydrocarbon composition with distance from the source and incubation experiments with environmental isolates demonstrated faster-than-expected hydrocarbon biodegradation rates at 5 C. Based on these results, the potential exists for intrinsic bioremediation of the oil plume in the deep-water column without substantial oxygen drawdown.
Date: September 1, 2010
Creator: Hazen, T. C.; Dubinsky, E. A.; DeSantis, T. Z.; Andersen, G. L.; Piceno, Y. M.; Singh, N. et al.
System: The UNT Digital Library