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Oxidation of alloys targeted for advanced steam turbines (open access)

Oxidation of alloys targeted for advanced steam turbines

Ultra supercritical (USC) power plants offer the promise of higher efficiencies and lower emissions. Current goals of the U.S. Department of Energy’s Advanced Power Systems Initiatives include coal generation at 60% efficiency, which would require steam temperatures of up to 760°C. This research examines the steamside oxidation of alloys for use in USC systems, with emphasis placed on applications in high- and intermediate-pressure turbines.
Date: March 12, 2006
Creator: Holcomb, G. R.; Covino, B. S., Jr.; Bullard, S. J.; Ziomek-Moroz, M. & Alman, D. E.
Object Type: Article
System: The UNT Digital Library
Vibrational Spectroscopy and X-ray Diffraction of Cd(OH)2 to 28GPa at 300 K (open access)

Vibrational Spectroscopy and X-ray Diffraction of Cd(OH)2 to 28GPa at 300 K

We report Raman and infrared absorption spectroscopy alongwith X-ray diffraction for brucite-type beta-Cd(OH)2 to 28 GPa at 300 K.The OH-stretching modes soften with pressure and disappear at 21 GPa withtheir widths increasing rapidly above 5 GPa, consistent with a gradualdisordering of the H sublattice at 5 20 GPa similar to that previouslyobserved for Co(OH)2.Asymmetry in the peak shapes of the OH-stretchingmodes suggests the existence of diverse disordered sitesfor H atoms inCd(OH)2 under pressure. Above 15 GPa, the A1g(T) lattice mode showsnon-linear behavior and softens to 21 GPa, at which pressure significantchanges are observed: new Raman modes appear, two Raman-active latticemodes and the OH-stretching modes of the low-pressure phase disappears,and the positions of some X-ray diffraction lines change abruptly withthe appearance of weak new diffraction features. These observationssuggest that amorphization of the H sublattice is accompanied by acrystalline-to-crystalline transition at 21 GPa in Cd(OH)2, which has notbeen previously observed in the brucite-type hydroxides. The Ramanspectra of the high-pressure phase of Cd(OH)2 is similar to those of thehigh-pressure phase of single-crystal Ca(OH)2 of which structure has beententatively assigned to the Sr(OH)2 type.
Date: March 20, 2006
Creator: Shim, Sang-Heon; Rekhi, Sandeep; Martin, Michael C. & Jeanloz,Raymond
Object Type: Article
System: The UNT Digital Library
Comparative Genome Analysis in the Integrated Microbial Genomes (IMG) System (open access)

Comparative Genome Analysis in the Integrated Microbial Genomes (IMG) System

Comparative genome analysis is critical for the effectiveexploration of a rapidly growing number of complete and draft sequencesfor microbial genomes. The Integrated Microbial Genomes (IMG) system(img.jgi.doe.gov) has been developed as a community resource thatprovides support for comparative analysis of microbial genomes in anintegrated context. IMG allows users to navigate the multidimensionalmicrobial genome data space and focus their analysis on a subset ofgenes, genomes, and functions of interest. IMG provides graphicalviewers, summaries and occurrence profile tools for comparing genes,pathways and functions (terms) across specific genomes. Genes can befurther examined using gene neighborhoods and compared with sequencealignment tools.
Date: March 1, 2006
Creator: Kyrpides, Nikos C. & Markowitz, Victor M.
Object Type: Article
System: The UNT Digital Library
MICROFLUIDIC MIXERS FOR THE INVESTIGATION OF PROTEIN FOLDING USING SYNCHROTRON RADIATION CIRCULAR DICHROISM SPECTROSCOPY (open access)

MICROFLUIDIC MIXERS FOR THE INVESTIGATION OF PROTEIN FOLDING USING SYNCHROTRON RADIATION CIRCULAR DICHROISM SPECTROSCOPY

The purpose of this study is to design, fabricate and optimize microfluidic mixers to investigate the kinetics of protein secondary structure formation with Synchrotron Radiation Circular Dichroism (SRCD) spectroscopy. The mixers are designed to rapidly initiate protein folding reaction through the dilution of denaturant. The devices are fabricated out of fused silica, so that they are transparent in the UV. We present characterization of mixing in the fabricated devices, as well as the initial SRCD data on proteins inside the mixers.
Date: March 20, 2006
Creator: Kane, A; Hertzog, D; Baumgartel, P; Lengefeld, J; Horsley, D; Schuler, B et al.
Object Type: Article
System: The UNT Digital Library
QUESTIONNAIRE ON THE CAPABILITIES OF MEMBER STATES REGARDING THE ANALYSIS OF BIOMEDICAL SAMPLES (open access)

QUESTIONNAIRE ON THE CAPABILITIES OF MEMBER STATES REGARDING THE ANALYSIS OF BIOMEDICAL SAMPLES

None
Date: March 27, 2006
Creator: Alcaraz, A. & Gregg, H.
Object Type: Report
System: The UNT Digital Library
Numerical Modeling of CO2 Sequestration in Geologic Formations - Recent Results and Open Challenges (open access)

Numerical Modeling of CO2 Sequestration in Geologic Formations - Recent Results and Open Challenges

Rising atmospheric concentrations of CO2, and their role inglobal warming, have prompted efforts to reduce emissions of CO2 fromburning of fossil fuels. An attractive mitigation option underconsideration in many countries is the injection of CO2 from stationarysources, such as fossil-fueled power plants, into deep, stable geologicformations, where it would be stored and kept out of the atmosphere fortime periods of hundreds to thousands of years or more. Potentialgeologic storage reservoirs include depleted or depleting oil and gasreservoirs, unmineable coal seams, and saline formations. While oil andgas reservoirs may provide some attractive early targets for CO2 storage,estimates for geographic regions worldwide have suggested that onlysaline formations would provide sufficient storage capacity tosubstantially impact atmospheric releases. This paper will focus on CO2storage in saline formations.Injection of CO2 into a saline aquifer willgive rise to immiscible displacement of brine by the advancing CO2. Thelower viscosity of CO2 relative to aqueous fluids provides a potentialfor hydrodynamic instabilities during the displacement process. Attypical subsurface conditions of temperature and pressure, CO2 is lessdense than aqueous fluids and is subject to upward buoyancy force inenvironments where pressures are controlled by an ambient aqueous phase.Thus CO2 would tend to rise towards the top of a permeable formation andaccumulate …
Date: March 8, 2006
Creator: Pruess, Karsten
Object Type: Article
System: The UNT Digital Library
Membrane composition analysis by imaging mass spectrometry (open access)

Membrane composition analysis by imaging mass spectrometry

Membranes on solid supports offer an ideal format for imaging. Secondary ion mass spectrometry (SIMS) can be used to obtain composition information on membrane-associated components. Using the NanoSIMS50, images of composition variations in membrane domains can be obtained with a lateral resolution better than 100 nm. By suitable calibration, these variations in composition can be translated into a quantitative analysis of the membrane composition. Progress towards imaging small phase-separated lipid domains, membrane-associated proteins and natural biological membranes will be described.
Date: March 29, 2006
Creator: Boxer, S G; Kraft, M L; Longo, M; Hutcheon, I D & Weber, P K
Object Type: Article
System: The UNT Digital Library
Public Health-Related Impacts of Climate Change in California (open access)

Public Health-Related Impacts of Climate Change in California

In June 2005 Governor Arnold Schwarzenegger issued Executive Order S-3-05 that set greenhouse gas emission reduction targets for California, and directed the Secretary of the California Environmental Protection Agency to report to the governor and the State legislature by January 2006 and biannually thereafter on the impacts to California of global warming, including impacts to water supply, public health, agriculture, the coastline, and forestry, and to prepare and report on mitigation and adaptation plans to combat these impacts. This report is a part of the report to the governor and legislature, and focuses on public health impacts that have been associated with climate change. Considerable evidence suggests that average ambient temperature is increasing worldwide, that temperatures will continue to increase into the future, and that global warming will result in changes to many aspects of climate, including temperature, humidity, and precipitation (McMichael and Githeko, 2001). It is expected that California will experience changes in both temperature and precipitation under current trends. Many of the changes in climate projected for California could have ramifications for public health (McMichael and Githeko, 2001), and this document summarizes the impacts judged most likely to occur in California, based on a review of available peer-reviewed …
Date: March 2006
Creator: Drechsler, Deborah M.; Motallebi, Nehzat; Kleeman, Michael; Cayan, Dan; Hayhoe, Katherine; Kalkstein, Laurence S. et al.
Object Type: Report
System: The UNT Digital Library
Downregulation of Protein 4.1R impairs centrosome function,bipolar spindle organization and anaphase (open access)

Downregulation of Protein 4.1R impairs centrosome function,bipolar spindle organization and anaphase

Centrosomes nucleate and organize interphase MTs and areinstrumental in the assembly of the mitotic bipolar spindle. Here wereport that two members of the multifunctional protein 4.1 family havedistinct distributions at centrosomes. Protein 4.1R localizes to maturecentrioles whereas 4.1G is a component of the pericentriolar matrixsurrounding centrioles. To selectively probe 4.1R function, we used RNAinterference-mediated depletion of 4.1R without decreasing 4.1Gexpression. 4.1R downregulation reduces MT anchoring and organization atinterphase and impairs centrosome separation during prometaphase.Metaphase chromosomes fail to properly condense/align and spindleorganization is aberrant. Notably 4.1R depletion causes mislocalizationof its binding partner NuMA (Nuclear Mitotic Apparatus Protein),essential for spindle pole focusing, and disrupts ninein. Duringanaphase/telophase, 4.1R-depleted cells have lagging chromosomes andaberrant MT bridges. Our data provide functional evidence that 4.1R makescrucial contributions to centrosome integrity and to mitotic spindlestructure enabling mitosis and anaphase to proceed with the coordinatedprecision required to avoid pathological events.
Date: March 17, 2006
Creator: Spence, Jeffrey R.; Go, Minjoung M.; Bahmanyar, S.; Barth,A.I.M. & Krauss, Sharon Wald
Object Type: Article
System: The UNT Digital Library
Low Mach Number Modeling of Type Ia Supernovae. II. EnergyEvolution (open access)

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

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 formalism is presented. We demonstrate throughvalidation with a fully compressible hydrodynamics code that this lowMach number model accurately captures the expansion of the stellaratmosphere as well as the local dynamics due to external heat sources.This algorithm provides the basis for an efficient simulation tool forstudying the ignition of SNe Ia.
Date: March 28, 2006
Creator: Almgren, Ann S.; Bell, John B.; Rendleman, Charles A. & Zingale,Mike
Object Type: Article
System: The UNT Digital Library
Fox-2 Splicing Factor Binds to a Conserved Intron Motif to PromoteInclusion of Protein 4.1R Alternative Exon 16 (open access)

Fox-2 Splicing Factor Binds to a Conserved Intron Motif to PromoteInclusion of Protein 4.1R Alternative Exon 16

Activation of protein 4.1R exon 16 (E16) inclusion during erythropoiesis represents a physiologically important splicing switch that increases 4.1R affinity for spectrin and actin. Previous studies showed that negative regulation of E16 splicing is mediated by the binding of hnRNP A/B proteins to silencer elements in the exon and that downregulation of hnRNP A/B proteins in erythroblasts leads to activation of E16 inclusion. This paper demonstrates that positive regulation of E16 splicing can be mediated by Fox-2 or Fox-1, two closely related splicing factors that possess identical RNA recognition motifs. SELEX experiments with human Fox-1 revealed highly selective binding to the hexamer UGCAUG. Both Fox-1 and Fox-2 were able to bind the conserved UGCAUG elements in the proximal intron downstream of E16, and both could activate E16 splicing in HeLa cell co-transfection assays in a UGCAUG-dependent manner. Conversely, knockdown of Fox-2 expression, achieved with two different siRNA sequences resulted in decreased E16 splicing. Moreover, immunoblot experiments demonstrate mouse erythroblasts express Fox-2, but not Fox-1. These findings suggest that Fox-2 is a physiological activator of E16 splicing in differentiating erythroid cells in vivo. Recent experiments show that UGCAUG is present in the proximal intron sequence of many tissue-specific alternative exons, and …
Date: March 1, 2006
Creator: Ponthier, Julie L.; Schluepen, Christina; Chen, Weiguo; Lersch,Robert A.; Gee, Sherry L.; Hou, Victor C. et al.
Object Type: Article
System: The UNT Digital Library
Materials Evaluation Test Series (METS) 04, 05, and 06 (open access)

Materials Evaluation Test Series (METS) 04, 05, and 06

The purpose of this work is to examine the environmental, safety, health and operational aspects of detonating a confined explosive test apparatus that has been designed to maximize the dynamics of impact on beryllium metal components for Contained Firing Facility (CFF) applications. A combination of experimental collection and evaluation methods were designed and implemented to provide an evaluation of immediately postdetonation by-products reflecting a potential worst-case scenario beryllium aerosolization explosive event. The collective Material Evaluation Test Series (METS) 04 - 06 provided explosive devices designed to scale for the dedicated METS firing tank that would provide a post-detonation internal environment comparable to the CFF. The experimental results provided appropriate information to develop operational parameters to be considered for conducting full-scale beryllium-containing experimental tests with similar designs within CFF and B801A. These operational procedures include the inclusion of chelating agents in pre-shot CFF cardboard containers with a minimum of 600 gallons content, an extended time period post-test before purging the CFF chamber, and an adaptation of approaches toward applications of the scrubber and HEPA systems during the post-shot sequence for an integrated environmental, safety, and health approach. In addition, re-entry and film retrieval procedures will be adapted, in line with abatement …
Date: March 23, 2006
Creator: Zalk, D.; Ingram, C.; Simmons, L.; Arganbright, R.; Lyle, J. & Wong, K.
Object Type: Report
System: The UNT Digital Library
Stark Tuning of Donor Electron Spins of Silicon (open access)

Stark Tuning of Donor Electron Spins of Silicon

We report Stark shift measurements for {sup 121}Sb donor electron spins in silicon using pulsed electron spin resonance. Interdigitated metal gates on top of a Sb-implanted {sup 28}Si epi-layer are used to apply electric fields. Two Stark effects are resolved: a decrease of the hyperfine coupling between electron and nuclear spins of the donor and a decrease in electron Zeeman g-factor. The hyperfine term prevails at X-band magnetic fields of 0.35T, while the g-factor term is expected to dominate at higher magnetic fields. A significant linear Stark effect is also resolved presumably arising from strain.
Date: March 23, 2006
Creator: Bradbury, Forrest R.; Tyryshkin, Alexei M.; Sabouret, Guillaume; Bokor, Jeff; Schenkel, Thomas & Lyon, Stephen A.
Object Type: Article
System: The UNT Digital Library
Cleanup Verification Package for the 300 VTS Waste Site (open access)

Cleanup Verification Package for the 300 VTS Waste Site

This cleanup verification package documents completion of remedial action for the 300 Area Vitrification Test Site, also known as the 300 VTS site. The site was used by Pacific Northwest National Laboratory as a field demonstration site for in situ vitrification of soils containing simulated waste.
Date: March 13, 2006
Creator: Mitchell, S. W. Clark and T. H.
Object Type: Report
System: The UNT Digital Library
SOLVING THE STAND-OFF PROBLEM FOR MAGNETIZED TARGET FUSION: PLASMA STREAMS AS DISPOSABLE ELECTRODES, PLUS A LOCAL SPHERICAL BLANKET (open access)

SOLVING THE STAND-OFF PROBLEM FOR MAGNETIZED TARGET FUSION: PLASMA STREAMS AS DISPOSABLE ELECTRODES, PLUS A LOCAL SPHERICAL BLANKET

In a fusion reactor based on the Magnetized Target Fusion approach, the permanent power supply has to deliver currents up to a few mega-amperes to the target dropped into the reaction chamber. All the structures situated around the target will be destroyed after every pulse and have to be replaced at a frequency of 1 to 10 Hz. In this paper, an approach based on the use of spherical blanket surrounding the target, and pulsed plasma electrodes connecting the target to the power supply, is discussed. A brief physic analysis of the processes associated with creation of plasma electrodes is discussed.
Date: March 21, 2006
Creator: Ryutov, D. D. & Thio, Y. F.
Object Type: Article
System: The UNT Digital Library
A method for obtaining three-dimensional computation equilibrium of non-neutral plasmas using WARP (open access)

A method for obtaining three-dimensional computation equilibrium of non-neutral plasmas using WARP

Computer simulation studies of the stability and transport properties of trapped non-neutral plasmas require the numerical realization of a three-dimensional plasma distribution. This paper presents a new numerical method for obtaining, without an explicit model for physical collisions in the code, a low noise three-dimensional computational equilibrium distribution. This requires both the loading of particles into an idealized distribution and the relaxation from that distribution toward an approximate numerical equilibrium. The equilibrium can then be modified through a slow change of system parameters, to generate other equilibria. In the present work we apply this method to a UC Berkeley experiment on electron confinement in magnetic geometries appropriate for the ALPHA anti-hydrogen experiment, using the three-dimensional Particle-In-Cell code WARP. WARP's guiding center mover and its option to switch between different solvers during a simulation are highly valuable because they speed up the simulations; they enable the practical use of the new technique for generating numerical equilibrium states of trapped nonneutral plasmas.
Date: March 25, 2006
Creator: Wurtele, J.; Wurtele, J.; Friedman, A.; Grote, D. P.; Vay, J. L. & Gomberoff, K.
Object Type: Article
System: The UNT Digital Library
Health, Safety, and Environmental Screening and Ranking Frameworkfor Geologic CO2 Storage Site Selection (open access)

Health, Safety, and Environmental Screening and Ranking Frameworkfor Geologic CO2 Storage Site Selection

This report describes a screening and ranking framework(SRF) developed to evaluate potential geologic carbon dioxide (CO2)storage sites on the basis of health, safety, and environmental (HSE)risk arising from possible CO2 leakage. The approach is based on theassumption that HSE risk due to CO2 leakage is dependent on three basiccharacteristics of a geologic CO2 storage site: (1) the potential forprimary containment by the target formation, (2) the potential forsecondary containment if the primary formation leaks, and (3) thepotential for attenuation and dispersion of leaking CO2 if the primaryformation leaks and secondary containment fails. The framework isimplemented in a spreadsheet in which users enter numerical scoresrepresenting expert opinions or general information available frompublished materials along with estimates of uncertainty to evaluate thethree basic characteristics in order to screen and rank candidate sites.Application of the framework to the Rio Vista Gas Field, Ventura OilField, and Mammoth Mountain demonstrates the approach. Refinements andextensions are possible through the use of more detailed data or modelresults in place of property proxies. Revisions and extensions to improvethe approach are anticipated in the near future as it is used and testedby colleagues and collaborators.
Date: March 15, 2006
Creator: Oldenburg, Curtis M.
Object Type: Article
System: The UNT Digital Library
Sonoma Persistent Surveillance System (open access)

Sonoma Persistent Surveillance System

Sonoma offers the first cost-effective, broad-area, high-resolution, real-time motion imagery system for surveillance applications. Sonoma is unique in its ability to provide continuous, real-time video imagery of an area the size of a small city with resolutions sufficient to track 8,000 moving objects in the field of view. At higher resolutions and over smaller areas, Sonoma can even track the movement of individual people. The visual impact of the data available from Sonoma is already causing a paradigm shift in the architecture and operation of other surveillance systems. Sonoma is expected to cost just one-tenth the price of comparably sized sensor systems. Cameras mounted on an airborne platform constantly monitor an area, feeding data to the ground for real-time analysis. Sonoma was designed to provide real-time data for actionable intelligence in situations such as monitoring traffic, special events, border security, and harbors. If a Sonoma system had been available in the aftermath of the Katrina and Rita hurricanes, emergency responders would have had real-time information on roads, water levels, and traffic conditions, perhaps saving many lives.
Date: March 24, 2006
Creator: Pennington, D M
Object Type: Report
System: The UNT Digital Library
FY05 LDRD Final Report Spectroscopy of Shocked Deuterium (open access)

FY05 LDRD Final Report Spectroscopy of Shocked Deuterium

We summarize the observations of unusual optical properties of shocked liquid deuterium (D{sub 2}) that led to proposing spectroscopic measurements. The apparatus built for the measurements is briefly described, along with some representative results in a test material. Unfortunately, spectroscopic measurements were not performed in shocked D{sub 2} during the course of the project. Some reasons are noted.
Date: March 27, 2006
Creator: Holmes, N. C.
Object Type: Report
System: The UNT Digital Library
Protect and Restore Lolo Creek Watershed : Annual Report CY 2005. (open access)

Protect and Restore Lolo Creek Watershed : Annual Report CY 2005.

The Nez Perce Tribe Department of Fisheries Resource Management, Watershed Division approaches watershed restoration with a ridge-top to ridge-top approach. Watershed restoration projects within the Lolo Creek watershed are coordinated with the Clearwater National Forest and Potlatch Corporation. The Nez Perce Tribe began watershed restoration projects within the Lolo Creek watershed of the Clearwater River in 1996. Fencing to exclude cattle for stream banks, stream bank stabilization, decommissioning roads, and upgrading culverts are the primary focuses of this effort. The successful completion of the replacement and removal of several passage blocking culverts represent a major improvement to the watershed. These projects, coupled with other recently completed projects and those anticipated in the future, are a significant step in improving habitat conditions in Lolo Creek.
Date: March 1, 2006
Creator: McRoberts, Heidi
Object Type: Report
System: The UNT Digital Library
Corrosion behavior of iron and nickel base alloys under solid oxide fuel cell exposure conditions (open access)

Corrosion behavior of iron and nickel base alloys under solid oxide fuel cell exposure conditions

Topography and phase composition of the scales formed on commercial ferritic stainless steels and experimental low CTE nickel-based alloys were studied in atmospheres simulating solid oxide fuel cell (SOFC) environments. The materials were studied under dual environment conditions with air on one side of the sample and carbon monoxide on the other side at 750°C. Surface characterization techniques, such as scanning electron microscopy and X-ray diffraction analysis were used in this study.
Date: March 1, 2006
Creator: Ziomek-Moroz, M.; Holcomb, G. R.; Covino, B. S., Jr. & Bullard, S. J.
Object Type: Article
System: The UNT Digital Library
Probabilistic aspects of meteorological and ozone regional ensemble forecasts (open access)

Probabilistic aspects of meteorological and ozone regional ensemble forecasts

This study investigates whether probabilistic ozone forecasts from an ensemble can be made with skill; i.e., high verification resolution and reliability. Twenty-eight ozone forecasts were generated over the Lower Fraser Valley, British Columbia, Canada, for the 5-day period 11-15 August 2004, and compared with 1-hour averaged measurements of ozone concentrations at five stations. The forecasts were obtained by driving the CMAQ model with four meteorological forecasts and seven emission scenarios: a control run, {+-} 50% NO{sub x}, {+-} 50% VOC, and {+-} 50% NO{sub x} combined with VOC. Probabilistic forecast quality is verified using relative operating characteristic curves, Talagrand diagrams, and a new reliability index. Results show that both meteorology and emission perturbations are needed to have a skillful probabilistic forecast system--the meteorology perturbation is important to capture the ozone temporal and spatial distribution, and the emission perturbation is needed to span the range of ozone-concentration magnitudes. Emission perturbations are more important than meteorology perturbations for capturing the likelihood of high ozone concentrations. Perturbations involving NO{sub x} resulted in a more skillful probabilistic forecast for the episode analyzed, and therefore the 50% perturbation values appears to span much of the emission uncertainty for this case. All of the ensembles analyzed …
Date: March 20, 2006
Creator: Monache, L D; Hacker, J; Zhou, Y; Deng, X & Stull, R
Object Type: Article
System: The UNT Digital Library
The Shewanella oneidensis MR-1 Fluxome under Various OxygenConditions (open access)

The Shewanella oneidensis MR-1 Fluxome under Various OxygenConditions

The central metabolic fluxes of Shewanella oneidensis MR-1were examined under carbon-limited (aerobic) and oxygen-limited(micro-aerobic) chemostat conditions using 13C labeled lactate as thesole carbon source. The carbon labeling patterns of key amino acids inbiomass were probed using both GC-MS and 13C-NMR. Based on the genomeannotation, a metabolic pathway model was constructed to quantify thecentral metabolic flux distributions. The model showed that thetricarboxylic acid (TCA) cycle is the major carbon metabolism route underboth conditions. The Entner-Doudoroff and pentose phosphate pathways weremainly utilized for biomass synthesis (flux below 5 percent of thelactate uptake rate). The anapleurotic reactions (pyruvate to malate andoxaloacetate to phosphoenolpyruvate) and the glyoxylate shunt wereactive. Under carbon-limited conditions, a substantial amount of carbonwas oxidized via the highly reversible serine metabolic pathway. Fluxesthrough the TCA cycle were less whereas acetate production was more underoxygen limitation than under carbon limitation. Although fluxdistributions under aerobic, micro-aerobic, and shake-flask cultureconditions were dramatically different, the relative flux ratios of thecentral metabolic reactions did not vary significantly. Hence, S.oneidensis metabolism appears to be quite robust to environmentalchanges. Our study also demonstrates the merit of coupling GC-MS with 13CNMR for metabolic flux analysis to reduce the use of 13C labeledsubstrates and to obtain more accurate flux values.
Date: March 17, 2006
Creator: Tang, Yinjie J.; Hwang, Judy S.; Wemmer, David E. & Keasling, Jay D.
Object Type: Article
System: The UNT Digital Library
Analysis of the causes of failure in high chrome oxide refractory materials from slagging gasifiers (open access)

Analysis of the causes of failure in high chrome oxide refractory materials from slagging gasifiers

High Cr2O3 refractory materials are used to line the hot face of slagging gasifiers. Gasifiers are reaction chambers that convert water, oxygen, and a carbon feedstock into CO, H2, and methane at temperatures as high as 1575oC and pressures up to 1000 psi. Ash in the carbon feedstock liquefies, erodes and corrodes the gasifier’s refractory liner, contributing to liner failure within a few months to two years. The failure of a refractory liner decreases a gasifier’s on-line availability and causes costly system downtime and repairs. Many factors contribute to refractory lining failure, including slag penetration and corrosion, thermal cycling, gasifier environment, and mechanical loads. The results of refractory post-mortem failure analysis and how observations relate to gasifier service life will be discussed.
Date: March 1, 2006
Creator: Bennett, J. P.; Kwong, K. -S.; Powell, C. A.; Thomas, H. & Krabbe, R. A.
Object Type: Article
System: The UNT Digital Library