Resource Type

875 Matching Results

Results open in a new window/tab.

Electronic and Transport Properties of Artificial Gold Chains (open access)

Electronic and Transport Properties of Artificial Gold Chains

Article on electronic and transport properties of artificial gold chains.
Date: August 27, 2004
Creator: Calzolari, Arrigo; Cavazzoni, Carlo & Buongiorno Nardelli, Marco
System: The UNT Digital Library
Phase Equilibria in High Energy Density PVDF-Based Polymers (open access)

Phase Equilibria in High Energy Density PVDF-Based Polymers

Article on phase equilibria in high energy density PVDF-based polymers.
Date: July 27, 2007
Creator: Ranjan, Vivek; Yu, Liping; Buongiorno Nardelli, Marco & Bernholc, Jerry
System: The UNT Digital Library
Dynamic Conductance of Carbon Nanotubes (open access)

Dynamic Conductance of Carbon Nanotubes

Article on dynamic conductance of carbon nanotubes.
Date: March 27, 2000
Creator: Roland, Christopher; Buongiorno Nardelli, Marco; Wang, Jian & Guo, Hong
System: The UNT Digital Library
Ultimate strength of carbon nanotubes: A theoretical study (open access)

Ultimate strength of carbon nanotubes: A theoretical study

Article on a theoretical study of the ultimate strength of carbon nanotubes.
Date: March 27, 2002
Creator: Zhao, Qingzhong; Buongiorno Nardelli, Marco & Bernholc, Jerry
System: The UNT Digital Library
Switchgrass (Panicum virgatum) possesses a divergent family of cinnamoyl CoA reductases with distinct biochemical properties (open access)

Switchgrass (Panicum virgatum) possesses a divergent family of cinnamoyl CoA reductases with distinct biochemical properties

Article on switchgrass (Panicum virgatum) possessing a divergent family of cinnamoyl CoA reductases with distinct biochemical properties.
Date: July 27, 2009
Creator: Escamilla-Treviño, Luis; Shen, Hui; Uppalapati, Srinivasa Rao; Ray, Tui; Tang, Yuhong; Hernandez, Timothy et al.
System: The UNT Digital Library
Renewal, Modulation, and Superstatistics in Times Series (open access)

Renewal, Modulation, and Superstatistics in Times Series

Article discussing two different approaches, referred to as renewal and modulation, to generate time series with a nonexponential distribution of waiting times.
Date: April 27, 2006
Creator: Allegrini, Paolo; Barbi, Francesco; Grigolini, Paolo & Paradisi, Paolo
System: The UNT Digital Library
Environmental Challenges for the Nuclear Diagnostics on the NIF and LMJ (open access)

Environmental Challenges for the Nuclear Diagnostics on the NIF and LMJ

The National Ignition Facility (NIF) and Laser Mega Joule (LMJ) facilities are currently under construction in the United States and France. Ignited targets at these facilities are anticipated to produce up to 1019 deuterium-tritium fusion neutrons. This will provide unprecedented opportunities and challenges for the use of nuclear diagnostics in inertial confinement fusion experiments. The NIF and LMJ nuclear diagnostics will work in a harsh radiation environment that includes neutron, hard x-ray, and gamma backgrounds, neutron induced signals in coaxial cables, and electromagnetic pulse (EMP) generated signals. Recent results of different background measurements on OMEGA laser facility will be reported. Based on these results, specific design concepts have been identified to mitigate much of the radiation and EMP-induced backgrounds. An overview of the background mitigation techniques in the NIF nuclear diagnostics conceptual designs will be presented.
Date: June 27, 2007
Creator: al., K. Miller et
System: The UNT Digital Library
Time Reversal Violation (open access)

Time Reversal Violation

This talk briefly reviews three types of time-asymmetry in physics, which I classify as universal, macroscopic and microscopic. Most of the talk is focused on the latter, namely the violation of T-reversal invariance in particle physics theories. In sum tests of microscopic T-invariance, or observations of its violation, are limited by the fact that, while we can measure many processes, only in very few cases can we construct a matched pair of process and inverse process and observe it with sufficient sensitivity to make a test. In both the cases discussed here we can achieve an observable T violation making use of flavor tagging, and in the second case also using the quantum properties of an antisymmetric coherent state of two B mesons to construct a CP-tag. Both these tagging properties depend only on very general properties of the flavor and/or CP quantum numbers and so provide model independent tests for T-invariance violations. The microscopic laws of physics are very close to T-symmetric. There are small effects that give CP- and T-violating processes in three-generation-probing weak decays. Where a T-violating observable can be constructed we see the relationships between T-violation and CP-violation expected in a CPT conserving theory. These microscopic …
Date: January 27, 2009
Creator: Quinn, H.
System: The UNT Digital Library
Hyperon Polarization in Unpolarized Scattering Processes (open access)

Hyperon Polarization in Unpolarized Scattering Processes

Transverse polarization in the Hyperon (\Lambda) production in the unpolarizeddeep inelastic scattering and pp collisions is studied in the twist-three approach, considering the contribution from the quark-gluon-antiquark correlation distribution in nucleon. We further compare our results for deep inelastic scattering to a transverse momentum dependent factorization approach, and find consistency between the two approaches in the intermediate transverse momentum region. We also find that in pp collisions, there are only derivative terms contributions, and the non-derivative terms vanish.
Date: August 27, 2008
Creator: Zhou, Jian; Yuan, Feng & Liang, Zuo-Tang
System: The UNT Digital Library
Separation of Yeast Cells from MS2 Viruses Using Acoustic Radiation Force (open access)

Separation of Yeast Cells from MS2 Viruses Using Acoustic Radiation Force

We report a rapid and robust separation of Saccharomyces cerevisiae and MS2 bacteriophage using acoustic focusing in a microfluidic device. A piezoelectric transducer (PZT) generates acoustic standing waves in the microchannel. These standing waves induce acoustic radiation force fields that direct microparticles towards the nodes (i.e., pressure minima) or the anti-nodes (i.e., pressure maxima) of the standing waves depending on the relative compressidensity between the particle and the suspending liquid.[1] For particles larger than 2 {micro}m, the transverse velocities generated by these force fields enable continuous, high throughput separation. Extensive work in the last decade [2-4] has demonstrated acoustic focusing for manipulating microparticles or biological samples in microfluidic devices. This prior work has primarily focused on experimental realization of acoustic focusing without modeling or with limited one-dimensional modeling estimates. We recently developed a finite element modeling tool to predict the two-dimensional acoustic radiation force field perpendicular to the flow direction in microfluidic devices.[1] Here we compare results from this model with experimental parametric studies including variations of the PZT driving frequencies and voltages as well as various particle sizes and compressidensities. These experimental parametric studies also provide insight into the development of an adjustable 'virtual' pore-size filter as well as …
Date: March 27, 2008
Creator: Jung, B.; Fisher, K.; Ness, K.; Rose, K. A. & Mariella, R. P., Jr.
System: The UNT Digital Library
Isotopomer distributions in amino acids from a highly expressed protein as a proxy for those from total protein (open access)

Isotopomer distributions in amino acids from a highly expressed protein as a proxy for those from total protein

{sup 13}C-based metabolic flux analysis provides valuable information about bacterial physiology. Though many biological processes rely on the synergistic functions of microbial communities, study of individual organisms in a mixed culture using existing flux analysis methods is difficult. Isotopomer-based flux analysis typically relies on hydrolyzed amino acids from a homogeneous biomass. Thus metabolic flux analysis of a given organism in a mixed culture requires its separation from the mixed culture. Swift and efficient cell separation is difficult and a major hurdle for isotopomer-based flux analysis of mixed cultures. Here we demonstrate the use of a single highly-expressed protein to analyze the isotopomer distribution of amino acids from one organism. Using the model organism E. coli expressing a plasmid-borne, his-tagged Green Fluorescent Protein (GFP), we show that induction of GFP does not affect E. coli growth kinetics or the isotopomer distribution in nine key metabolites. Further, the isotopomer labeling patterns of amino acids derived from purified GFP and total cell protein are indistinguishable, indicating that amino acids from a purified protein can be used to infer metabolic fluxes of targeted organisms in a mixed culture. This study provides the foundation to extend isotopomer-based flux analysis to study metabolism of individual strains …
Date: June 27, 2008
Creator: Shaikh, Afshan; Shaikh, Afshan S.; Tang, Yinjie; Mukhopadhyay, Aindrila & Keasling, Jay D.
System: The UNT Digital Library
Initial Study Comparing the Radiating Divertor Behavior in Single-Null and Double-Null Plasmas in DIII-D (open access)

Initial Study Comparing the Radiating Divertor Behavior in Single-Null and Double-Null Plasmas in DIII-D

'Puff and pump' radiating divertor scenarios [1,2] were applied to upper SN and DN H-mode plasmas. Under similar operating conditions, argon (Ar) accumulated in the main plasma of single-null (SN) plasmas more rapidly and reached a higher steady-state concentration when the B x {del}B ion drift direction was toward the divertor than when the B x {del}B ion drift direction was out of the divertor. The initial rate that Ar accumulated inside double-null (DN) plasmas was more than twice that of comparably-prepared SNs with the same B x {del}B direction. One way to reduce power loading at the divertor targets is to 'seed' the divertor plasma with impurities that radiatively reduce the conducted power. Studies have shown that the concentration of impurities in the divertor are increased by raising the flow of deuterium ions (D{sup +}) into the divertor by a combination of upstream deuterium gas puffing and active particle exhaust at the divertor targets, i.e., puff-and-pump. An enhanced D{sup +} particle flow toward the divertor targets exerts a frictional drag on impurities, and inhibits their escape from the divertor. A puff-and-pump approach using Ar as the impurity was successfully applied in recent DIII-D experiments to SN plasmas [3] while …
Date: June 27, 2007
Creator: Petrie, T; Brooks, N; Fenstermacher, M; Groth, M; Hyatt, A; Isler, R et al.
System: The UNT Digital Library
Strangelet Search at the BNL Relativistic Heavy Ion Collider (open access)

Strangelet Search at the BNL Relativistic Heavy Ion Collider

We have searched for strangelets in a triggered sample of 61 million central (top 4percent) Au+Au collisions at sqrt sNN = 200 GeV near beam rapidities at the STAR solenoidal tracker detector at the BNL Relativistic Heavy Ion Collider. We have sensitivity to metastable strangelets with lifetimes of order>_0.1 ns, in contrast to limits over ten times longer in BNL Alternating Gradient Synchrotron (AGS) studies and longer still at the CERN Super Proton Synchrotron (SPS). Upper limits of a few 10-6 to 10-7 per central Au+Au collision are set for strangelets with mass>~;;30 GeV/c2.
Date: November 27, 2005
Creator: Ritter, Ha
System: The UNT Digital Library
A THERMAL MODEL OF THE IMMOBILIZATION OF LOW-LEVEL RADIOACTIVE WASTE AS GROUT IN CONCRETE VAULTS (open access)

A THERMAL MODEL OF THE IMMOBILIZATION OF LOW-LEVEL RADIOACTIVE WASTE AS GROUT IN CONCRETE VAULTS

Salt solution will be mixed with cement and flyash/slag to form a grout which will be immobilized in above ground concrete vaults. The curing process is exothermic, and a transient thermal model of the pouring and curing process is herein described. A peak temperature limit of 85 C for the curing grout restricts the rate at which it can be poured into a vault. The model is used to optimize the pouring.
Date: October 27, 2008
Creator: Shadday, M
System: The UNT Digital Library
Coupled Reservoir-Geomechanical Analysis of the Potential for Tensile and Shear Failure Associated With CO2 Injection in Multilayered Reservoir-Caprock Systems (open access)

Coupled Reservoir-Geomechanical Analysis of the Potential for Tensile and Shear Failure Associated With CO2 Injection in Multilayered Reservoir-Caprock Systems

Coupled reservoir-geomechanical simulations were conductedto study the potential for tensile and shear failure e.g., tensilefracturing and shear slip along pre-existing fractures associated withunderground CO2 injection in a multilayered geological system. Thisfailure analysis aimed to study factors affecting the potential forbreaching a geological CO2 storage system and to study methods forestimating the maximum CO2 injection pressure that could be sustainedwithout causing such a breach. We pay special attention to geomechanicalstress changes resulting from upward migration of the CO2 and how theinitial stress regime affects the potential for inducing failure. Weconclude that it is essential to have an accurate estimate of thethree-dimensional in situ stress field to support the design andperformance assessment of a geological CO2 injection operation. Moreover,we also conclude that it is important to consider mechanical stresschanges that might occur outside the region of increased reservoir fluidpressure (e.g., in the overburden rock) between the CO2-injectionreservoir and the ground surface.
Date: March 27, 2007
Creator: Rutqvist, J.; Birkholzer, J. T. & Tsang, C.-F.
System: The UNT Digital Library
Plasma Electrode Pockels Cell Subsystem Performance in the National Ignition Facility (open access)

Plasma Electrode Pockels Cell Subsystem Performance in the National Ignition Facility

The Plasma Electrode Pockels Cell (PEPC) subsystem is a key component of the National Ignition Facility, enabling the laser to employ an efficient four-pass main amplifier architecture. PEPC relies on a pulsed power technology to initiate and maintain plasma within the cells and to provide the necessary high voltage bias to the cells nonlinear crystals. Ultimately, nearly 300 high-voltage, high-current pulse generators will be deployed in the NIF in support of PEPC. Production of solid-state plasma pulse generators and thyratron-switched pulse generators is now complete, with the majority of the hardware deployed in the facility. An entire cluster (one-fourth of a complete NIF) has been commissioned and is operating on a routine basis, supporting laser shot operations. Another cluster has been deployed, awaiting final commissioning. Activation and commissioning of new hardware continues to progress in parallel, driving toward a goal of completing the PEPC subsystem in late 2007.
Date: July 27, 2007
Creator: Barbosa, F.; Arnold, P.; Hinz, A.; Zacharias, R.; Ollis, C.; Fulkerson, E. et al.
System: The UNT Digital Library
Electron Density Measurements in the National Spherical Torus Experiment Detached Divertor Region Using Stark Broadening of Deuterium Infrared Paschen Emission Lines (open access)

Electron Density Measurements in the National Spherical Torus Experiment Detached Divertor Region Using Stark Broadening of Deuterium Infrared Paschen Emission Lines

Spatially resolved measurements of deuterium Balmer and Paschen line emission have been performed in the divertor region of the National Spherical Torus Experiment using a commercial 0.5 m Czerny-Turner spectrometer. While the Balmer emission lines, Balmer and Paschen continua in the ultraviolet and visible regions have been extensively used for tokamak divertor plasma temperature and density measurements, the diagnostic potential of infrared Paschen lines has been largely overlooked. We analyze Stark broadening of the lines corresponding to 2-n and 3-m transitions with principle quantum numbers n = 7-12 and m = 10-12 using recent Model Microfield Method calculations (C. Stehle and R. Hutcheon, Astron. Astrophys. Supl. Ser. 140, 93 (1999)). Densities in the range (5-50) x 10{sup 19} m{sup -3} are obtained in the recombining inner divertor plasma in 2-6 MW NBI H-mode discharges. The measured Paschen line profiles show good sensitivity to Stark effects, and low sensitivity to instrumental and Doppler broadening. The lines are situated in the near-infrared wavelength domain, where optical signal extraction schemes for harsh nuclear environments are practically realizable, and where a recombining divertor plasma is optically thin. These properties make them an attractive recombining divertor density diagnostic for a burning plasma experiment.
Date: April 27, 2007
Creator: Soukhanovskii, V A; Johnson, D W; Kaita, R & Roquemore, A L
System: The UNT Digital Library
Seismic imaging of reservoir flow properties: Resolving waterinflux and reservoir permeability (open access)

Seismic imaging of reservoir flow properties: Resolving waterinflux and reservoir permeability

Methods for geophysical model assessment, in particuale thecomputation of model parameter resolution, indicate the value and thelimitations of time-lapse data in estimating reservoir flow properties. Atrajectory-based method for computing sensitivities provides an effectivemeans to compute model parameter resolutions. We examine the commonsituation in which water encroaches into a resrvoir from below, as due tothe upward movement of an oil-water contact. Using straight-forwardtechniques we find that, by inclusing reflections off the top and bottomof a reservoir tens of meters thick, we can infer reservoir permeabilitybased upon time-lapse data. We find that, for the caseof water influxfrom below, using multiple time-lapse 'snapshots' does not necessarilyimprove the resolution of reservoir permeability. An application totime-lapse data from the Norne field illustrates that we can resolve thepermeability near a producing well using reflections from threeinterfaces associated with the reservoir.
Date: November 27, 2006
Creator: Vasco, D.W. & Keers, Henk
System: The UNT Digital Library
FRONT-END ASIC FOR A SILICON COMPTON TELESCOPE. (open access)

FRONT-END ASIC FOR A SILICON COMPTON TELESCOPE.

We describe a front-end application specific integrated circuit (ASIC) developed for a silicon Compton telescope. Composed of 32 channels, it reads out signals in both polarities from each side of a Silicon strip sensor, 2 mm thick 27 cm long, characterized by a strip capacitance of 30 pF. Each front-end channel provides low-noise charge amplification, shaping with a stabilized baseline, discrimination, and peak detection with an analog memory. The channels can process events simultaneously, and the read out is sparsified. The charge amplifier makes uses a dual-cascode configuration and dual-polarity adaptive reset, The low-hysteresis discriminator and the multi-phase peak detector process signals with a dynamic range in excess of four hundred. An equivalent noise charge (ENC) below 200 electrons was measured at 30 pF, with a slope of about 4.5 electrons/pF at a peaking time of 4 {micro}s. With a total dissipated power of 5 mW the channel covers an energy range up to 3.2 MeV.
Date: October 27, 2007
Creator: DE GERONIMO,G.; FRIED, J.; FROST, E.; PHLIPS, B.; VERNON, E. & WULF, E.A.
System: The UNT Digital Library
Do grain boundaries in nanophase metals slide? (open access)

Do grain boundaries in nanophase metals slide?

Nanophase metallic materials show a maximum in strength as grain size decreases to the nano scale, indicating a break down of the Hall-Petch relation. Grain boundary sliding, as a possible accommodation mechanisms, is often the picture that explain computer simulations results and real experiments. In a recent paper, Bringa et al. Science 309, 1838 (2005), we report on the observation of an ultra-hard behavior in nanophase Cu under shock loading, explained in terms of a reduction of grain boundary sliding under the influence of the shock pressure. In this work we perform a detailed study of the effects of hydrostatic pressure on nanophase Cu plasticity and find that it can be understood in terms of pressure dependent grain boundary sliding controlled by a Mohr-Coulomb law.
Date: October 27, 2006
Creator: Bringa, E M; Leveugle, E & Caro, A
System: The UNT Digital Library
Monitoring the Thermal Power of Nuclear Reactors with a Prototype Cubic Meter Antineutrino Detector (open access)

Monitoring the Thermal Power of Nuclear Reactors with a Prototype Cubic Meter Antineutrino Detector

In this paper, we estimate how quickly and how precisely a reactor's operational status and thermal power can be monitored over hour to month time scales, using the antineutrino rate as measured by a cubic meter scale detector. Our results are obtained from a detector we have deployed and operated at 25 meter standoff from a reactor core. This prototype can detect a prompt reactor shutdown within five hours, and monitor relative thermal power to 3.5% within 7 days. Monitoring of short-term power changes in this way may be useful in the context of International Atomic Energy Agency's (IAEA) Reactor Safeguards Regime, or other cooperative monitoring regimes.
Date: June 27, 2007
Creator: Bernstein, A; Bowden, N; Misner, A & Palmer, T
System: The UNT Digital Library
Investigations of the Wideband Spectrum of Higher Order Modes Measured on TESLA-style Cavities at the FLASH Linac (open access)

Investigations of the Wideband Spectrum of Higher Order Modes Measured on TESLA-style Cavities at the FLASH Linac

None
Date: June 27, 2007
Creator: Molloy, S.; Adolphsen, C.; Bane, K.; Frisch, J.; Li, Z.; May, J. et al.
System: The UNT Digital Library
BIOTIGER, A NATURAL MICROBIAL PRODUCT FOR ENHANCED HYDROCARBON RECOVERY FROM OIL SANDS. (open access)

BIOTIGER, A NATURAL MICROBIAL PRODUCT FOR ENHANCED HYDROCARBON RECOVERY FROM OIL SANDS.

BioTiger{trademark} is a unique microbial consortia that resulted from over 8 years of extensive microbiology screening and characterization of samples collected from a century-old Polish waste lagoon. BioTiger{trademark} shows rapid and complete degradation of aliphatic and aromatic hydrocarbons, produces novel surfactants, is tolerant of both chemical and metal toxicity and shows good activity at temperature and pH extremes. Although originally developed and used by the U.S. Department of Energy for bioremediation of oil-contaminated soils, recent efforts have proven that BioTiger{trademark} can also be used to increase hydrocarbon recovery from oil sands. This enhanced ex situ oil recovery process utilizes BioTiger{trademark} to optimize bitumen separation. A floatation test protocol with oil sands from Ft. McMurray, Canada was used for the BioTiger{trademark} evaluation. A comparison of hot water extraction/floatation test of the oil sands performed with BioTiger{trademark} demonstrated a 50% improvement in separation as measured by gravimetric analysis in 4 h and a five-fold increase at 25 hr. Since BioTiger{trademark} performs well at high temperatures and process engineering can enhance and sustain metabolic activity, it can be applied to enhance recovery of hydrocarbons from oil sands or other complex recalcitrant matrices.
Date: May 27, 2008
Creator: Brigmon, R; Topher Berry, T; Whitney Jones, W & Charles Milliken, C
System: The UNT Digital Library
Radiation damage to BSCCO-2223 from 50 MEV protons. (open access)

Radiation damage to BSCCO-2223 from 50 MEV protons.

The use of HTS materials in high radiation environmentsrequires that the superconducting properties remain constant up to aradiation high dose. BSCCO-2223 samples from two manufacturers wereirradiated with 50 MeV protons at fluences of up to 5 x 1017 protons/cm2.The samples lost approximately 75 percent of their pre-irradiation Ic.This compares with Nb3Sn, which loses about 50 percent at the samedisplacements per atom.
Date: November 27, 2007
Creator: Zeller, A. F.; Ronningen, R. M.; Godeke, A.; Heilbronn, L. H.; McMahan-Norris, P. & Gupta, R.
System: The UNT Digital Library