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A Markov-Chain Monte-Carlo Based Method for Flaw Detection in Beams

Description: A Bayesian inference methodology using a Markov Chain Monte Carlo (MCMC) sampling procedure is presented for estimating the parameters of computational structural models. This methodology combines prior information, measured data, and forward models to produce a posterior distribution for the system parameters of structural models that is most consistent with all available data. The MCMC procedure is based upon a Metropolis-Hastings algorithm that is shown to function effectively with noisy dat… more
Date: September 28, 2006
Creator: Glaser, R. E.; Lee, C. L.; Nitao, J. J.; Hickling, T. L. & Hanley, W. G.
Partner: UNT Libraries Government Documents Department
open access

An Incompressible Navier-Stokes with Particles Algorithm andParallel Implementation

Description: We present a variation of an adaptive projection method forcomputing solutions to the incompressible Navier-Stokes equations withsuspended particles. To compute the divergence-free component of themomentum forcing due to the particle drag, we employ an approach whichexploits the locality and smoothness of the Laplacian of the projectionoperator applied to the discretized particle drag force. We presentconvergence and performance results to demonstrate the effectiveness ofthis approach.
Date: November 28, 2006
Creator: Martin, Daniel F.; Colella, Phillip & Keen, Noel D.
Partner: UNT Libraries Government Documents Department
open access

Low Mach Number Modeling of Type Ia Supernovae. II. EnergyEvolution

Description: The convective period leading up to a Type Ia supernova (SNIa) explosion is characterized by very low Mach number flows, requiringhydrodynamical methods well-suited to long-time integration. We continuethe development of the low Mach number equation set for stellar scaleflows by incorporating the effects of heat release due to externalsources. Low Mach number hydrodynamics equations with a time-dependentbackground state are derived, and a numerical method based on theapproximate projection form… more
Date: March 28, 2006
Creator: Almgren, Ann S.; Bell, John B.; Rendleman, Charles A. & Zingale,Mike
Partner: UNT Libraries Government Documents Department
open access

Enhancement of T1 and T2 relaxation by paramagnetic silica-coated nanocrystals

Description: We present the first comprehensive investigation on water-soluble nanoparticles embedded into a paramagnetic shell and their properties as an MRI contrast agent. The nanoprobes are constructed with an inorganic core embedded into an ultra-thin silica shell covalently linked to chelated Gd{sup 3+} paramagnetic ions that act as an MRI contrast agent. The chelator contains the molecule DOTA and the inorganic core contains a fluorescent CdSe/ZnS qdots in Au nanoparticles. Optical properties of the … more
Date: August 28, 2006
Creator: Gerion, D; Herberg, J; Gjersing, E; Ramon, E; Maxwell, R; Gray, J W et al.
Partner: UNT Libraries Government Documents Department
open access

Three-dimensional architecture of hair-cell linkages as revealedby electron-microscopic tomography

Description: The senses of hearing and balance rest upon mechanoelectrical transduction by the hair bundles of hair cells in the inner ear. Located at the apical cellular surface, each hair bundle comprises several tens of stereocilia and a single kinocilium that are interconnected by extracellular proteinaceous links. Using electron-microscopic tomography of bullfrog saccular sensory epithelia, we examined the three-dimensional structures of ankle or basal links, kinociliary links, and tip links. We observ… more
Date: July 28, 2006
Creator: Auer, Manfred; Koster, Bram; Ziese, Ulrike; Bajaj, Chandrajit; Volkmann, Niels; Wang, Da Neng et al.
Partner: UNT Libraries Government Documents Department
open access

A grating-less, fiber-based oscillator that generates 25 nJ pulses

Description: We report a passively mode-locked fiber-based oscillator that has no internal dispersion-compensating gratings. This design, the first of its kind, produces 25 nJ pulses at 80 MHz with the pulses compressible to 150 fs. The pulses appear to be self-similar and initial data imply that their energy is further scalable.
Date: December 28, 2006
Creator: An, J; Kim, D; Dawson, J W; Messerly, M J & Barty, C J
Partner: UNT Libraries Government Documents Department
open access

Comment on "Methodology and results of calculating Central California surface temperature trends: evidence of human-induced climate change?" by Christy et al. (2006)

Description: Understanding the causes of observed regional temperature trends is essential to projecting the human influences on climate, and the societal impacts of these influences. In their recent study, Christy et al. (2006, hereinafter CRNG06) hypothesized that the presence of irrigated soils is responsible for rapid warming of summer nights occurring in California's Central Valley over the last century (1910-2003), an assumption that rules out any significant effect due to increased greenhouse gases, … more
Date: March 28, 2006
Creator: Bonfils, C; Duffy, P & Lobell, D
Partner: UNT Libraries Government Documents Department
open access

The Influence of Proposed Repository Thermal Load on MultiphaseFlow and Heat Transfer in the Unsaturated Zone of Yucca Mountain

Description: This paper investigates the impact of proposed repositorythermal-loading on mountain-scale flow and heat transfer in theunsaturated fractured rock of Yucca Mountain, Nevada. In this context, amodel has been developed to study the coupled thermal-hydrological (TH)processes at the scale of the entire Yucca Mountain. This mountain-scaleTH model implements the current geological framework and hydrogeologicalconceptual models, and incorporates the latest rock thermal andhydrological properties. The … more
Date: February 28, 2006
Creator: Wu, Y.-S.; Mukhopadhyay, Sumit; Zhang, Keni & Bodvarsson, G.S.
Partner: UNT Libraries Government Documents Department
open access

On the Initiation of High Explosives by Laser Radiation

Description: The problem of laser initiation of high explosives in munitions is considered. In this situation, the laser illuminates a small spot on the casing, and lateral thermal transport affects the initiation temperature. We use a variational method to calculate the critical temperature for explosive initiation as a function the laser spot size, for common high explosives. The effect of the dwelling time of the irradiation is then evaluated. We demonstrate that in typical situations the critical temper… more
Date: March 28, 2006
Creator: Rubenchik, A M
Partner: UNT Libraries Government Documents Department
open access

Metal inhibition of human alkylpurine-DNA-N-glycosylase activityin base excision repair

Description: Cadmium (Cd{sup 2+}), nickel (Ni{sup 2+}) and cobalt (Co{sup 2+}) are human and/or animal carcinogens. Zinc (Zn{sup 2+}) is not categorized as a carcinogen, and rather an essential element to humans. Metals were recently shown to inhibit DNA repair proteins that use metals for their function and/or structure. Here we report that the divalent ions Cd{sup 2+}, Ni{sup 2+}, and Zn{sup 2+} can inhibit the activity of a recombinant human N-methylpurine-DNA glycosylase (MPG) toward a deoxyoligonucleot… more
Date: February 28, 2006
Creator: Wang, Ping; Guliaev, Anton B. & Hang, Bo
Partner: UNT Libraries Government Documents Department
open access

Widespread Discordance of Gene Trees with Species Tree inDrosophila: Evidence for Incomplete Lineage Sorting

Description: The phylogenetic relationship of the now fully sequencedspecies Drosophila erecta and D. yakuba with respect to the D.melanogaster species complex has been a subject of controversy. All threepossible groupings of the species have been reported in the past, thoughrecent multi-gene studies suggest that D. erecta and D. yakuba are sisterspecies. Using the whole genomes of each of these species as well as thefour other fully sequenced species in the subgenus Sophophora, we set outto investigate the… more
Date: August 28, 2006
Creator: Pollard, Daniel A.; Iyer, Venky N.; Moses, Alan M. & Eisen,Michael B.
Partner: UNT Libraries Government Documents Department
open access

Characterization of Recompressed Spall in Copper Gas Gun Targets

Description: Complementary experiments and simulations are conducted to characterize the microstructure and mechanisms involved in recompression of spalled ductile metals. Soft capture experiments performed on copper targets in a gas gun include a dense secondary plate spaced behind the customary flyer to recompress the voids in the wake of the spall induced by the flyer. Control experiments are run without the secondary plate to obtain spall damage without recompression. The simulations feature explicit re… more
Date: August 28, 2006
Creator: Becker, R.; Cazamias, J. & LeBlanc, M.
Partner: UNT Libraries Government Documents Department
open access

Natural and industrial analogues for leakage of CO2 from storagereservoirs: identification of features, events, and processes and lessonslearned

Description: The injection and storage of anthropogenic CO2 in deepgeologic formations is a potentially feasible strategy to reduce CO2emissions and atmospheric concentrations. While the purpose of geologiccarbon storage is to trap CO2 underground, CO2 could migrate away fromthe storage site into the shallow subsurface and atmosphere if permeablepathways such as well bores or faults are present. Large-magnitudereleases of CO2 have occurred naturally from geologic reservoirs innumerous volcanic, geothermal, … more
Date: February 28, 2006
Creator: Lewicki, Jennifer L.; Birkholzer, Jens & Tsang, Chin-Fu
Partner: UNT Libraries Government Documents Department
open access

Urinary Metabolites of the Dietary Carcinogen PhIP are Predictive of Colon DNA Adducts After a Low Dose Exposure in Humans

Description: Epidemiologic evidence indicates that exposure to heterocyclic amines (HAs) in the diet is an important risk factor for the development of colon cancer. Well-done cooked meats contain significant levels of HAs which have been shown to cause cancer in laboratory animals. To better understand the mechanisms of HA bioactivation in humans, the most mass abundant HA, 2-amino-l-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), was used to assess the relationship between PhIP metabolism and DNA adduct for… more
Date: April 28, 2006
Creator: Malfatti, M.; Dingley, K.; Nowell, S.; Ubick, E.; Mulakken, N.; Nelson, D. et al.
Partner: UNT Libraries Government Documents Department
open access

Equation of state for high explosives detonation products with explicit polar and ionic species

Description: We introduce a new thermodynamic theory for detonation products that includes polar and ionic species. The new formalism extends the domain of validity of the previously developed EXP6 equation of state library and opens the possibility of new applications. We illustrate the scope of the new approach on PETN detonation properties and water ionization models.
Date: June 28, 2006
Creator: Bastea, S; Glaesemann, K R & Fried, L E
Partner: UNT Libraries Government Documents Department
open access

Magnetocentrifugal Winds in 3D: Nonaxisymmetric Steady State

Description: Outflows can be loaded and accelerated to high speeds along rapidly rotating, open magnetic field lines by centrifugal forces. Whether such magnetocentrifugally driven winds are stable is a longstanding theoretical problem. As a step towards addressing this problem, we perform the first large-scale 3D MHD simulations that extend to a distance {approx} 10{sup 2} times beyond the launching region, starting from steady 2D (axisymmetric) solutions. In an attempt to drive the wind unstable, we incre… more
Date: November 28, 2006
Creator: Anderson, Jeffrey M.; Li, Zhi-Yun; /Virginia U., Astron. Dept.; Krasnopolsky, Ruben; /Toronto U., Astron. Dept.; Blandford, Roger D. et al.
Partner: UNT Libraries Government Documents Department
open access

Magnetic Reconnection in the Spheromak: Physics and Consequences

Description: Magnetic reconnection in the spheromak changes magnetic topology by conversion of injected toroidal flux into poloidal flux and by magnetic surface closure (or opening) in a slowly decaying spheromak. Results from the Sustained Spheromak Physics Experiment, SSPX, are compared with resistive MHD simulations using the NIMROD code. Voltage spikes on the SSPX gun during spheromak formation are interpreted as reconnection across a negative-current layer close to the mean-field x-point. Field lines a… more
Date: February 28, 2006
Creator: Hooper, E. B.; Cohen, B. I.; Hill, D. N.; LoDestro, L. L.; McLean, H. S.; Romero-Talamas, C. A. et al.
Partner: UNT Libraries Government Documents Department
open access

Swift Detects a Remarkable Gamma-Ray Burst, GRB 060614, That Introduces a New Classification Scheme

Description: Gamma ray bursts (GRBs) are known to come in two duration classes, separated at {approx}2 s. Long bursts originate from star forming regions in galaxies, have accompanying supernovae (SNe) when near enough to observe and are likely caused by massive-star collapsars. Recent observations show that short bursts originate in regions within their host galaxies with lower star formation rates, consistent with binary neutron star (NS) or NS - black hole (BH) mergers. Moreover, although their hosts are… more
Date: November 28, 2006
Creator: Gehrels, Neil; Norris, J.P.; Mangano, V.; Barthelmy, S.D.; Burrows, D.N.; Granot, J. et al.
Partner: UNT Libraries Government Documents Department
open access

Size and habit evolution of PETN crystals - a lattice Monte Carlo study

Description: Starting from an accurate inter-atomic potential we develop a simple scheme of generating an ''on-lattice'' molecular potential of short range, which is then incorporated into a lattice Monte Carlo code for simulating size and shape evolution of nanocrystallites. As a specific example, we test such a procedure on the morphological evolution of a molecular crystal of interest to us, e.g., Pentaerythritol Tetranitrate, or PETN, and obtain realistic facetted structures in excellent agreement with … more
Date: February 28, 2006
Creator: Zepeda-Ruiz, L. A.; Maiti, A.; Gee, R.; Gilmer, G. H. & Weeks, B.
Partner: UNT Libraries Government Documents Department
open access

Vibration Stabilization of a Mechanical Model of a X-Band Linear Collider Final Focus Magnet

Description: The small beam sizes at the interaction point of a X-band linear collider require mechanical stabilization of the final focus magnets at the nanometer level. While passive systems provide adequate performance at many potential sites, active mechanical stabilization is useful if the natural or cultural ground vibration is higher than expected. A mechanical model of a room temperature linear collider final focus magnet has been constructed and actively stabilized with an accelerometer based syste… more
Date: September 28, 2006
Creator: Frisch, Josef; Chang, Allison; Decker, Valentin; Doyle, Eric; Eriksson, Leif; Hendrickson, Linda et al.
Partner: UNT Libraries Government Documents Department
open access

Current Driven Rotating Kink Mode in a Plasma Column with Non-Line-Tied Free End

Description: First experimental measurements are presented for the kink instability in a linear plasma column which is insulated from an axial boundary by finite sheath resistivity. Instability threshold below the classical Kruskal-Shafranov threshold, axially asymmetric mode structure and rotation are observed. These are accurately reproduced by a recent kink theory, which includes axial plasma flow and one end of the plasma column that is free to move due to a non-line-tied boundary condition.
Date: March 28, 2006
Creator: Furno, I.; Intrator, T. P.; Ryutov, D. D.; Abbate, S.; Madziwa-Nussinov, T.; Light, A. et al.
Partner: UNT Libraries Government Documents Department
open access

Recent tau Physics Studies at BaBar

Description: Recent results from {tau} physics studies at BABAR are presented with an emphasis on hadronic decays and lepton flavor violation studies.
Date: July 28, 2006
Creator: Wilson, F. F.
Partner: UNT Libraries Government Documents Department
open access

DEVELOPMENT OF A HYDROSTATIC JOURNAL BEARING WITH SLIT-STEP COMPENSATION

Description: This paper describes the mathematical modeling and initial testing of an oil-hydrostatic bearing that derives compensation from both a central radial slit where fluid enters and stepped clearances near each end. Bearings using either a radial slit or stepped clearances for compensation were well studied over forty years ago by Donaldson. These bearings have smooth bores uninterrupted with multiple recesses around the circumference. The present slit-step bearing achieves the best of both types w… more
Date: July 28, 2006
Creator: Hale, L C; Donaldson, R R; Castro, C; Chung, C A & Hopkins, D J
Partner: UNT Libraries Government Documents Department
open access

A Combined Saline Formation and Gas Reservoir CO2 Injection Pilotin Northern California

Description: A geologic sequestration pilot in the Thornton gas field in Northern California, USA involves injection of up to 4000 tons of CO{sub 2} into a stacked gas and saline formation reservoir. Lawrence Berkeley National Laboratory (LBNL) is leading the pilot test in collaboration with Rosetta Resources, Inc. and Calpine Corporation under the auspices of the U.S. Department of Energy and California Energy Commission's WESTCARB, Regional Carbon Sequestration Partnership. The goals of the pilot include:… more
Date: April 28, 2006
Creator: Trautz, Robert; Myer, Larry; Benson, Sally; Oldenburg, Curt; Daley, Thomas & Seeman, Ed
Partner: UNT Libraries Government Documents Department
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