89 Matching Results

Results open in a new window/tab.

2005 Plant Metabolic Engineering Gordon Conference - July 10-15, 2005 (open access)

2005 Plant Metabolic Engineering Gordon Conference - July 10-15, 2005

The post-genomic era presents new opportunities for manipulating plant chemistry for improvement of plant traits such as disease and stress resistance and nutritional qualities. This conference will provide a setting for developing multidisciplinary collaborations needed to unravel the dynamic complexity of plant metabolic networks and advance basic and applied research in plant metabolic engineering. The conference will integrate recent advances in genomics, with metabolite and gene expression analyses. Research discussions will explore how biosynthetic pathways interact with regard to substrate competition and channeling, plasticity of biosynthetic enzymes, and investigate the localization, structure, and assembly of biosynthetic metabolons in native and nonnative environments. The meeting will develop new perspectives for plant transgenic research with regard to how transgene expression may influence cellular metabolism. Incorporation of spectroscopic approaches for metabolic profiling and flux analysis combined with mathematical modeling will contribute to the development of rational metabolic engineering strategies and lead to the development of new tools to assess temporal and subcellular changes in metabolite pools. The conference will also highlight new technologies for pathway engineering, including use of heterologous systems, directed enzyme evolution, engineering of transcription factors and application of molecular/genetic techniques for controlling biosynthetic pathways.
Date: June 30, 2006
Creator: Wurtzel, Eleanore T.
System: The UNT Digital Library
Accelerator and Ion Beam Tradeoffs for Studies of Warm DenseMatter (open access)

Accelerator and Ion Beam Tradeoffs for Studies of Warm DenseMatter

One approach for heating a target to ''Warm Dense Matter'' conditions (similar, for example, to the interiors of giant planets or certain stages in inertial confinement fusion targets), is to use intense ion beams as the heating source (see refs.[6] and [7] and references therein for motivation and accelerator concepts). By consideration of ion beam phase-space constraints, both at the injector, and at the final focus, and consideration of simple equations of state and relations for ion stopping, approximate conditions at the target foil may be calculated. Thus, target temperature and pressure may be calculated as a function of ion mass, ion energy, pulse duration, velocity tilt, and other accelerator parameters. We connect some of these basic parameters to help search the extensive parameter space including ion mass, ion energy, total charge in beam pulse, beam emittance, target thickness and density.
Date: January 30, 2006
Creator: Barnard, J. J.; Briggs, R. J.; Callahan, D. A.; Davidson, R. C.; Friedman, A.; Grisham, L. et al.
System: The UNT Digital Library
Algebraic Sub-Structuring for Electromagnetic Applications (open access)

Algebraic Sub-Structuring for Electromagnetic Applications

Algebraic sub-structuring refers to the process of applying matrix reordering and partitioning algorithms to divide a large sparse matrix into smaller submatrices from which a subset of spectral components are extracted and combined to form approximate solutions to the original problem. In this paper, they show that algebraic sub-structuring can be effectively used to solve generalized eigenvalue problems arising from the finite element analysis of an accelerator structure.
Date: June 30, 2006
Creator: Yang, C.; Gao, W.G.; Bai, Z.J.; Li, X.Y.S.; Lee, L.Q.; Husbands, P. et al.
System: The UNT Digital Library
Amplitude Dependence of Time of Flight. (open access)

Amplitude Dependence of Time of Flight.

Machida found in tracking studies [Shinji Machida, presentation at the FFAG05 Workshop, Kyoto University Research Reactor Institute, Osaka, Japan, 5-9 December 2005] that the time of flight in a linear non-scaling FFAG depended on the transverse amplitude of the particles. I compute a relationship between the transverse amplitude dependence of the time of flight and the variation of tune with energy and explain its physical origin.
Date: January 30, 2006
Creator: Berg, J. S.
System: The UNT Digital Library
Analysis of Carrier Recombination Processes in 0.6 eV InGaAs Epitaxial Materials for Thermophotovoltaic Devices (open access)

Analysis of Carrier Recombination Processes in 0.6 eV InGaAs Epitaxial Materials for Thermophotovoltaic Devices

Minority carrier lifetime was measured by time-resolved photoluminescence (TRPL) method in sets of p-type and n-type InGaAs double heterostructures (DH) moderately doped with Zn and Te, respectively. Contributions of the radiative and non-radiative recombination terms were separated by fitting experimental data to temperature dependences of the radiative term. The latter was modeled with measured fundamental absorption spectrum and the temperature dependence of the photon recycling effect was taken into account. Different temperature dependences of radiative terms for electron and hole materials were obtained. It was concluded that in 0.6 eV Te-doped InGaAs structures the radiative recombination controls the hole lifetime at liquid nitrogen temperatures, while Auger recombination dominates at room and above room temperatures. In similar 0.6 eV InGaAs with Zn-doped active regions Shockley-Read-Hall (SRH) recombination was found dominant in a wide temperature range from liquid nitrogen to above-room temperatures. Rapid decrease of electron lifetime with decrease of excess carrier concentration was observed and attributed to recombination through partially-ionized deep donor centers. The obtained data allows for more adequate modeling of the performance and design optimization of narrow-gap photonic devices based on InGaAs Indium-rich compounds.
Date: October 30, 2006
Creator: Donetsky, D.; Newman, F. & Dashiell, M.
System: The UNT Digital Library
An analysis of model tropospheric response to various forcings (open access)

An analysis of model tropospheric response to various forcings

None
Date: January 30, 2006
Creator: Hnilo, J J & Christy, J R
System: The UNT Digital Library
Anisotropic x-ray magnetic linear dichroism at the Fe L2,3 edgesin Fe3O4 (open access)

Anisotropic x-ray magnetic linear dichroism at the Fe L2,3 edgesin Fe3O4

X-ray magnetic linear dichroism at the Fe L{sub 2,3} edges of the ferrimagnet Fe{sub 3}O{sub 4} was found to exhibit a strong dependence on the relative orientation of external magnetic field, x-ray polarization, and crystalline axes. Spectral shape and magnitude of the effect were determined for Fe{sub 3}O{sub 4}(011) and Fe{sub 3}O{sub 4}(001) thin films varying the in-plane orientation of field and polarization. All dichroism spectra can be described as a linear combination of three fundamental spectra which in turn give a good agreement with calculated spectra using atomic multiplet theory. The angular dependence of the magnetic dichroism reflects the crystal field symmetry. It can be used to estimate the crystal field splitting and allows determining the spin quantization axis.
Date: April 30, 2006
Creator: Arenholz, Elke; van der Laan, Gerrit; Chopdekar, Rajesh V. & Suzuki, Yuri
System: The UNT Digital Library
CHARGED PARTICLE PRODUCTION AT HIGH RAPIDITY IN p+p COLLISIONS AT RHIC. (open access)

CHARGED PARTICLE PRODUCTION AT HIGH RAPIDITY IN p+p COLLISIONS AT RHIC.

This report describes the recent analysis of identified charged particle production at high rapidity performed on data collected from p+p collisions at RHIC ({radical}s = 200 GeV). The extracted invariant cross-sections compare well to NLO pQCD calculations. However, a puzzling high yield of protons at high rapidity and p{sub T} has been found.
Date: May 30, 2006
Creator: DEBBE,R.
System: The UNT Digital Library
Clustering of High Redshift (z>2.9) Quasars from the Sloan Digital Sky Survey (open access)

Clustering of High Redshift (z>2.9) Quasars from the Sloan Digital Sky Survey

We study the two-point correlation function of a uniformly selected sample of 4,428 optically selected luminous quasars with redshift 2.9 {le} z {le} 5.4 selected over 4041 deg{sup 2} from the Fifth Data Release of the Sloan Digital Sky Survey. We fit a power-law to the projected correlation function w{sub p}(r{sub p}) to marginalize over redshift space distortions and redshift errors. For a real-space correlation function of the form {zeta}(r) = (r/r{sub 0}){sup -{gamma}}, the fitted parameters in comoving coordinates are r{sub 0} = 15.2 {+-} 2.7 h{sup -1} Mpc and {gamma} = 2.0 {+-} 0.3, over a scale range 4 {le} r{sub p} {le} 150 h{sup -1} Mpc. Thus high-redshift quasars are appreciably more strongly clustered than their z {approx} 1.5 counterparts, which have a comoving clustering length r{sub 0} {approx} 6.5 h{sup -1} Mpc. Dividing our sample into two redshift bins: 2.9 {le} z {le} 3.5 and z {ge} 3.5, and assuming a power-law index {gamma} = 2.0, we find a correlation length of r{sub 0} = 16.9 {+-} 1.7 h{sup -1} Mpc for the former, and r{sub 0} = 24.3 {+-} 2.4 h{sup -1} Mpc for the latter. Strong clustering at high redshift indicates that quasars are …
Date: November 30, 2006
Creator: Shen, Yue; Strauss, Michael A.; Oguri, Masamune; Hennawi, Joseph F.; Fan, Xiaohui; Richards, Gordon T. et al.
System: The UNT Digital Library
CONTACT ANGLE OF YUCCA MOUNTAIN WELDED TUFF WITH WATER AND BRINES (open access)

CONTACT ANGLE OF YUCCA MOUNTAIN WELDED TUFF WITH WATER AND BRINES

A number of tests were performed to acquire contact angles between Yucca Mountain welded tuff from Topopah Springs Lower Lithophysal geologic unit and various brine solutions. The tests were performed on core disks received from Sample Management Facility (SMF), oven dried to a constant weight and the core disks vacuum saturated in: distilled water, J-13 water, calcium chloride brine and sodium chloride brine to constant weight. The contact angles were acquired from eight points on the surface of the core disks, four on rough surface, and four on polished surface. The contact angle was measured by placing a droplet of the test fluid, distilled water, J-13 water, calcium chloride brine and sodium chloride brine on the core disks. The objective of this test was to acquire contact angles as a potential input to estimating capillary forces in accumulated dust on the waste packages and drip shields slated for the proposed High-Level Radioactive Waste Repository at Yucca Mountain, Nevada. It was noted that once the droplet contacts the test surface, it continues to spread hence the contact angle continues to decrease with elapsed time. The maximum observed angle was at time 0 or when the drop contacted the rock surface. The …
Date: April 30, 2006
Creator: Kalia, H.
System: The UNT Digital Library
Correct Tracking in FFAGS (open access)

Correct Tracking in FFAGS

Fixed field alternating gradient accelerators have many features which require careful modeling in simulation. They accept beams over an extremely large momentum range, generally at least a factor of 2. They often use magnets whose lengths are comparable to their apertures. The beam often makes large angles with respect to the magnet axis and pole face normal. In some applications (muons in particular), the beam occupies a substantial fraction of the magnet aperture. The longitudinal dynamics in these machines often differ significantly from what one finds in more conventional machines such as synchrotrons. These characteristics require that simulation codes be careful to avoid inappropriate approximations in describing particle motion in FFAGs. One must properly treat the coordinate system geometry independently from the magnetic fields. One cannot blindly assume that phase space variables are small. One must take magnet end fields properly into account. Finally, one must carefully consider what it means to have a ''matched'' distribution that is injected into these machines.
Date: January 30, 2006
Creator: Berg, J. S.
System: The UNT Digital Library
COUPLED MULTI-ELECTRODE INVESTIGATION OF CREVICE CORROSION OF 316 STAINLESS STEEL (open access)

COUPLED MULTI-ELECTRODE INVESTIGATION OF CREVICE CORROSION OF 316 STAINLESS STEEL

Crevice corrosion is currently studied using either one of two techniques depending on the data needed. The first method is a multi-crevice former over a metallic sample; this provides information on the severity of crevice corrosion (depth, position, frequency) but delivers little to no electrochemical information [1]. The second method involves the potentiodynamic or potentiostatic study of an uncreviced sample in model crevice solution or under a crevice former in aggressive solution [2]. Crevice corrosion is highly dependent on the position in the crevice. The distance from the crevice mouth will affect the depth of attack, the solution composition and pH, and the ohmic drop and the true potential in the crevice [3-6]. These in turn affect the current density as a function of potential and position. A Multi-Channel Micro-Electrode Analyzer (MMA) has been recently used to demonstrate the interaction between localized corrosion sites (pitting corrosion and intergranular corrosion) [7]. MMA can provide spatial resolution of electrochemical properties in the crevice. By coupling such a tool with scaling laws derived from experimental data (a simple equation linking the depth of crevice corrosion initiation to the crevice gap), it is possible to produce highly instrumented crevices, rescaled to enable spatial resolution …
Date: January 30, 2006
Creator: Scully, F. Bocher and J. R.
System: The UNT Digital Library
COUPLED MULTI-ELECTRODE INVESTIGATION OF CREVICE CORROSION OF 316 STAINLESS STEEL (open access)

COUPLED MULTI-ELECTRODE INVESTIGATION OF CREVICE CORROSION OF 316 STAINLESS STEEL

Crevice corrosion is currently studied using either one of two techniques depending on the data needed. The first method is a multi-crevice former over a metallic sample; this provides information on the severity of crevice corrosion (depth, position, frequency) but delivers little to no electrochemical information [1]. The second method involves the potentiodynamic or potentiostatic study of an uncreviced sample in model crevice solution or under a crevice former in aggressive solution [2]. Crevice corrosion is highly dependent on the position in the crevice. The distance from the crevice mouth will affect the depth of attack, the solution composition and pH, and the ohmic drop and the true potential in the crevice [3-6]. These in turn affect the current density as a function of potential and position. An Multi-Channel Micro-Electrode Analyzer' (MMA) has been recently used to demonstrate the interaction between localized corrosion sites (pitting corrosion and intergranular corrosion) [7]. MMA can provide spatial resolution of electrochemical properties in the crevice. By coupling such a tool with scaling laws derived from experimental data (a simple equation linking the depth of crevice corrosion initiation to the crevice gap), it is possible to produce highly instrumented crevices, rescaled to enable spatial resolution …
Date: January 30, 2006
Creator: F. Bocher, J. R. Scully
System: The UNT Digital Library
D0-Anti-D0 Mixing Results From BaBar By Analysis of D0 ---> K+ Pi- Pi0 Dalitz-Plot Regions (open access)

D0-Anti-D0 Mixing Results From BaBar By Analysis of D0 ---> K+ Pi- Pi0 Dalitz-Plot Regions

We present a preliminary search for D{sup 0}-{bar D}{sup 0} mixing using the decays D{sup 0} {yields} K{sup +}{pi}{sup -}{pi}{sup 0}, additionally presenting Dalitz-plot distributions and a measurement of the branching ratio for this mode. A new tagging technique is used to produce the doubly Cabibbo-suppressed Dalitz plot, which in turn is used to motivate the method used for the D-mixing search. We analyze 230.4 fb{sup -1} of data collected from the BABAR detector at the PEP-II collider. Assuming CP conservation, we find R{sub M} < 0.054% with 95% confidence, and we estimate that the data are consistent with no mixing at a 4.5% confidence level. We present D-mixing results both with and without the assumption of CP conservation.
Date: June 30, 2006
Creator: Wilson, Michael G.
System: The UNT Digital Library
Design and implementation of an emergency environmental responsesystem to protect migrating salmon in the lower San Joaquin River,California (open access)

Design and implementation of an emergency environmental responsesystem to protect migrating salmon in the lower San Joaquin River,California

In the past decade tens of millions of dollars have beenspent by water resource agencies in California to restore the nativesalmon fishery in the San Joaquin River and its major tributaries. Anexcavated deep water ship channel (DWSC), through which the river runs onits way to the Bay/Delta and Pacific Ocean, experiences episodes of lowdissolved oxygen which acts as a barrier to anadromous fish migration anda threat to the long-term survival of the salmon run. An emergencyresponse management system is under development to forecast theseepisodes of low dissolved oxygen and to deploy measures that will raisedissolved oxygen concentrations to prevent damage to the fisheryresource. The emergency response management system has been designed tointeract with a real-time water quality monitoring network and is servedby a comprehensive data management and forecasting model toolbox. TheBay/Delta and Tributaries (BDAT) Cooperative Data Management System is adistributed, web accessible database that contains terabytes ofinformation on all aspects of the ecology of the Bay/Delta and upperwatersheds. The complexity of the problem dictates data integration froma variety of monitoring programs. A unique data templating system hasbeen constructed to serve the needs of cooperating scientists who wish toshare their data and to simplify and streamline data uploading into themaster database. …
Date: January 30, 2006
Creator: Quinn, Nigel W.T. & Jacobs, Karl C.
System: The UNT Digital Library
Dosimetry Modeling for Predicting Radiolytic Production at the Spent Fuel - Water Interface (open access)

Dosimetry Modeling for Predicting Radiolytic Production at the Spent Fuel - Water Interface

Modeling of the alpha, beta, and gamma dose from spent fuel as a function of particle size and fuel to water ratio was examined. These doses will be combined with modeling of G values and interactions to determine the concentration of various species formed at the fuel water interface and their affect on dissolution rates.
Date: April 30, 2006
Creator: Miller, William H.; Kline, Amanda J. & Hanson, Brady D.
System: The UNT Digital Library
Effect of Crevice Former on Corrosion Damage Propagation (open access)

Effect of Crevice Former on Corrosion Damage Propagation

None
Date: January 30, 2006
Creator: J. H. Payer, U. Landau, X. Shan, A. S. Agarwal
System: The UNT Digital Library
Estimation of Failure Rates of Digital Components Using a Hierarchical Bayesian Method. (open access)

Estimation of Failure Rates of Digital Components Using a Hierarchical Bayesian Method.

One of the greatest challenges in evaluating reliability of digital I&C systems is how to obtain better failure rate estimates of digital components. A common practice of the digital component failure rate estimation is attempting to use empirical formulae to capture the impacts of various factors on the failure rates. The applicability of an empirical formula is questionable because it is not based on laws of physics and requires good data, which is scarce in general. In this study, the concept of population variability of the Hierarchical Bayesian Method (HBM) is applied to estimating the failure rate of a digital component using available data. Markov Chain Monte Carlo (MCMC) simulation is used to implement the HBM. Results are analyzed and compared by selecting different distribution types and priors distributions. Inspired by the sensitivity calculations and based on review of analytic derivations, it seems reasonable to suggest avoiding the use of gamma distribution in two-stage Bayesian analysis and HBM analysis.
Date: January 30, 2006
Creator: Yue, M. & Chu, T. L.
System: The UNT Digital Library
EXPERIENCE USING PHENOMENA IDENTIFICATION AND RANKING TECHNIQUE (PIRT) FOR NUCLEAR ANALYSIS. (open access)

EXPERIENCE USING PHENOMENA IDENTIFICATION AND RANKING TECHNIQUE (PIRT) FOR NUCLEAR ANALYSIS.

THE PHENOMENA IDENTIFICATION AND RANKING TECHNIQUE (PIRT) IS A SYSTEMATIC WAY OF GATHERING INFORMATION FROM EXPERTS ON A SPECIFIC SUBJECT, AND RANKING THE IMPORTANCE OF THE INFORMATION, IN ORDER TO MEET SOME DECISION MAKING OBJECTIVE. IT HAS BEEN APPLIED TO MANY NUCLEAR TECHONLOGY ISSUES INCLUDING NUCLEAR ANALYSIS IN ORDER TO HELP GUIDE RESEARCH OR DEVELOP REGULATORY REQUIREMENTS.
Date: June 30, 2006
Creator: DIAMOND, DAVID J.
System: The UNT Digital Library
Exploring nanomagnetism with soft x-ray microscopy (open access)

Exploring nanomagnetism with soft x-ray microscopy

Magnetic soft X-ray microscopy images magnetism in nanoscale systems with a spatial resolution down to 15nm provided by state-of-the-art Fresnel zone plate optics. X-ray magnetic circular dichroism (X-MCD) is used as element-specific magnetic contrast mechanism similar to photoemission electron microscopy (PEEM), however, with volume sensitivity and the ability to record the images in varying applied magnetic fields which allows to study magnetization reversal processes at fundamental length scales. Utilizing a stroboscopic pump-probe scheme one can investigate fast spin dynamics with a time resolution down to 70 ps which gives access to precessional and relaxation phenomena as well as spin torque driven domain wall dynamics in nanoscale systems. Current developments in zone plate optics aim for a spatial resolution towards 10nm and at next generation X-ray sources a time resolution in the fsec regime can be envisioned.
Date: October 30, 2006
Creator: Fischer, P.; Kim, D. H.; Mesler, B. L.; Chao, W.; Sakdinawat,A. E. & Anderson, E. H.
System: The UNT Digital Library
Fabrication and Characterization of Suspended Carbon Nanotube Devices in Liquid (open access)

Fabrication and Characterization of Suspended Carbon Nanotube Devices in Liquid

Suspended carbon nanotube devices are a promising platform for future bio-electronic applications. Suspended carbon nanotube transistors have been previously fabricated in air; however all previous attempts to bring them into liquid failed. We analyze forces acting on the suspended nanotube devices during immersion into liquids and during device operation and show that surface tension forces acting on the suspended nanotubes during transfer into the liquid phase are responsible for the nanotube damage. We have developed a new strategy that circumvents these limitations by coating suspended nanotubes with a rigid inorganic shell in the gas phase. The coating reinforces the nanotubes and allows them to survive transfer through the interface. Subsequent removal of the coating in the solution phase restores pristine suspended nanotubes. We demonstrate that devices fabricated using this technique preserve their original electrical characteristics.
Date: October 30, 2006
Creator: Artyukhin, A.; Stadermann, M.; Stroeve, P.; Bakajin, O. & Noy, A.
System: The UNT Digital Library
Field Ionization of Neutral Litium Vapor Using a 28.5 GeV Electron Beam (open access)

Field Ionization of Neutral Litium Vapor Using a 28.5 GeV Electron Beam

The E164/E164X plasma wakefield experiment studies beam-plasma interactions at the Stanford Linear Acceleration Center (SLAC). Due to SLAC's recent ability to variably compress bunches longitudinally from 650 {micro}m down to 20 {micro}m, the incoming beam is sufficiently dense to field ionize the neutral lithium (Li) vapor. The field ionization effects are characterized by the beams energy loss through the Li vapor column. Experiment results are presented.
Date: January 30, 2006
Creator: O'Connell, C. L.; Barnes, C. D.; Decker, F. J.; Hogan, M. J.; Iverson, R.; Krejcik, P. et al.
System: The UNT Digital Library
Frequency-Domain Multiplexed Readout for Superconducting Gamma-Ray Detectors (open access)

Frequency-Domain Multiplexed Readout for Superconducting Gamma-Ray Detectors

We are developing a frequency-multiplexed readout for arrays of high-resolution Gamma detectors based on superconducting transition edge sensors (TESs). Each sensor is part of an LCR resonant circuit and is biased at an identifying carrier frequency. Several carrier signals are added and amplified with a single SQUID preamplifier at 4 K. Gamma absorption modulates the amplitude of the carrier, and demodulation at room temperature retrieves the initial temperature evolution of the sensor. This multiplexing system has originally been developed to read out large arrays of bolometers for cosmic microwave background studies. To accommodate the faster Gamma-ray signals, its demodulator bandwidth is being extended to 20 kHz to allow reading out up to eight TESs with a detector bandwidth of 10 kHz. Here we characterize the system noise performance and show how this multiplexing scheme can be adapted to read out arrays of superconducting Gamma-ray detectors.
Date: August 30, 2006
Creator: Dreyer, Jonathan G.; Arnold, Kam; Lanting, Trevor M.; Dobbs, Matt A.; Friedrich, Stephan; Lee, Adrian T. et al.
System: The UNT Digital Library
GAS PHASE MOLECULAR DYNAMICS: HIGH-RESOLUTION SPECTROSCOPIC PROBES OF CHEMICAL DYNAMICS. (open access)

GAS PHASE MOLECULAR DYNAMICS: HIGH-RESOLUTION SPECTROSCOPIC PROBES OF CHEMICAL DYNAMICS.

This research is carried out as part of the Gas Phase Molecular Dynamics group program in the Chemistry Department at Brookhaven National Laboratory. High-resolution spectroscopic tools are developed and applied to problems in chemical dynamics. Recent topics have included the state-resolved studies of collision-induced electronic energy transfer, dynamics of barrierless unimolecular reactions, and the kinetics and spectroscopy of transient species.
Date: May 30, 2006
Creator: Hall, G. E.
System: The UNT Digital Library