Open Access. Powered by Scholars. Published by Universities.®

Engineering Commons™

Open Access. Powered by Scholars. Published by Universities.®

University of Nebraska - Lincoln

Discipline
Keyword
Publication Year
Publication
Publication Type
File Type

Articles 4831 - 4860 of 11222

Full-Text Articles in Engineering

Nebraska Summary: S806 New Holland T7.250, Nebraska Tractor Test Lab Jan 2011

Nebraska Summary: S806 New Holland T7.250, Nebraska Tractor Test Lab

Nebraska Tractor Tests

ABOUT THE TEST REPORT AND USE OF THE DATA The test data contained in this report are a tabulation of the results of a series of tests. Due to the restricted format of these pages, only a limited amount of data and not all of the tractor specifications are included. The full OECD report contains usually about 30 pages of data and specifications. The test data were obtained for each tractor under similar conditions and therefore, provide a means of comparison of performance based on a limited set of reported data. EXPLANATION OF THE TEST PROCEDURES Purpose The purpose of …

Go to article

Restoration Of Emergent Sandbar Habitat Complexes In The Missouri River, North Dakota Jan 2011

Restoration Of Emergent Sandbar Habitat Complexes In The Missouri River, North Dakota

United States Army Corps of Engineers, Omaha District

In 2003, the United States Fish and Wildlife Service (USFWS) issued an Amendment to the 2000 Biological Opinion (BiOp) with recommendations for the US Army Corps of Engineers’ (Corps) operations on the Missouri River Mainstem System (MRMS). The BiOp Amendment was the result of continuing consultation between the Corps and the USFWS under the Endangered Species Act (ESA) and supplemented the recommendations given in the previous BiOp (USFWS, 2000). The 2000 BiOp and amendments made in 2003 will be collectively referred to as “BiOp” hereafter. The document found that Corps operations on the Missouri River were not likely to jeopardize …

Go to article

Protective Immunity To Pre-Erythrocytic Stage Malaria, Robert J. Schwenk, Thomas L. Richie Jan 2011

Protective Immunity To Pre-Erythrocytic Stage Malaria, Robert J. Schwenk, Thomas L. Richie

United States Army: Publications

The development of a vaccine against malaria is a major research priority given the burden of disease, death and economic loss inflicted upon the tropical world by this parasite. Despite decades of effort, however, a vaccine remains elusive. The best candidate is a subunit vaccine termed RTS,S but this provides only partial protection against clinical disease. This review examines what is known about protective immunity against pre-erythrocytic stage malaria by considering the humoral and T cell-mediated immune responses that are induced by attenuated sporozoites and by the RTS,S vaccine. On the basis of these observations a set of research priorities …

Go to article

A New Explanation Of The Extinction Paradox, Matthew J. Berg, C. M. Sorensen, A. Chakrabarti Jan 2011

A New Explanation Of The Extinction Paradox, Matthew J. Berg, C. M. Sorensen, A. Chakrabarti

United States Army: Publications

This work presents a new explanation for the extinction paradox and shows that the canonical explanations are incorrect. This paradox refers to the large size limit of a particle’s extinction cross section. It is called a paradox because the geometrical optics approximation, which should be valid in this limit, predicts a cross section that is half of the true value. The new explanation is achieved by formulating the scattered wave in terms of an integral over the particle’s surface where the seemingly unrelated Ewald–Oseen theorem appears in the formulation. By expressing the cross section in terms of this surface integral, …

Go to article

Clostridium Difficile Infections In Patients With Severe Burns, Scott J. Crabtree, Janelle L. Robertson, Kevin K. Chung, Evan M. Renz, Steven E. Wolf, Duane R. Hospenthal, Clinton K. Murray Jan 2011

Clostridium Difficile Infections In Patients With Severe Burns, Scott J. Crabtree, Janelle L. Robertson, Kevin K. Chung, Evan M. Renz, Steven E. Wolf, Duane R. Hospenthal, Clinton K. Murray

United States Army: Publications

With improved survival in burn patients, Clostridium difficile infection (CDI) remains a significant potential complication. The incidence of, risk factors for, and outcomes of CDI in severely burned patients are poorly studied and remain unclear. This study involves retrospective case control and cohort studies using electronic medical records from February 1, 2002 to January 31, 2009 at the US Department of Defense’s only burn unit. Demographic, risk factor, and outcome data were collected for all C. difficile toxin positive patients in the burn, medical, and surgical intensive care units and the hospital’s step down unit along with an additional analysis …

Go to article

Determination Of Threshold Adverse Effect Doses Of Percutaneous Vx Exposure In African Green Monkeys, Raymond F. Genovese, Bernard J. Benton, John L. Oubre, Christopher E. Byers, E. Michael Jakubowski, Robert J. Mioduszewski, Timothy J. Settle, Thomas J. Steinbach Jan 2011

Determination Of Threshold Adverse Effect Doses Of Percutaneous Vx Exposure In African Green Monkeys, Raymond F. Genovese, Bernard J. Benton, John L. Oubre, Christopher E. Byers, E. Michael Jakubowski, Robert J. Mioduszewski, Timothy J. Settle, Thomas J. Steinbach

United States Army: Publications

Percutaneous exposure to the chemical warfare nerve agent VX was evaluated in African green monkeys (n = 9). Doses of VX (7.5–100 μg/kg) were applied to the skin for 60 min and residual agent was quantified (before decontamination) to estimate the absorbed dose. Monkeys were evaluated for the presence or absence of clinical signs of toxicity and blood was sampled periodically (30 min–12 weeks) following exposure to measure the degree of circulating acetylcholinesterase (AChE) inhibition. Monkeys were also evaluated for behavioral changes fromVXexposure using a serial probe recognition (SPR) task. The lowest observable adverse effect level (LOAEL) for the production …

Go to article

Mechanical Response Of Pig Skin Under Dynamic Tensile Loading, Jaeyoung Lim, Jihye Hong, Weinong W. Chen, Tusit Weerasooriya Jan 2011

Mechanical Response Of Pig Skin Under Dynamic Tensile Loading, Jaeyoung Lim, Jihye Hong, Weinong W. Chen, Tusit Weerasooriya

United States Army: Publications

Uniaxial tensile experiments were performed on pig skin to investigate the tensile stressestrain response at both quasi-static and dynamic rates of deformation. A Kolsky tension bar, also called a split Hopkinson tension bar (SHTB), was modified to conduct the dynamic experiments. Semiconductor strain gages were used to measure the low levels of the transmitted signal from pig skin. A pulse shaper technique was used for generating a suitable incident pulse to ensure stress equilibrium and approximate constant strain rate in the specimen of a thin skin sheet wrapped around the ends of the bars for minimizing radial inertia. In order …

Go to article

Detection Of Six Serotypes Of Botulinum Neurotoxin Using Fluorogenic Reporters, Daniel R. Ruge, F. Mark Dunning, Timothy M. Piazza, Brian E. Molles, Michael Adler, Füsûn N. Zeytin, Ward C. Tucker Jan 2011

Detection Of Six Serotypes Of Botulinum Neurotoxin Using Fluorogenic Reporters, Daniel R. Ruge, F. Mark Dunning, Timothy M. Piazza, Brian E. Molles, Michael Adler, Füsûn N. Zeytin, Ward C. Tucker

United States Army: Publications

Methods that do not require animal sacrifice to detect botulinum neurotoxins (BoNTs) are critical for BoNT antagonist discovery and the advancement of quantitative assays for biodefense and pharmaceutical applications. Here we describe the development and optimization of fluorogenic reporters that detect the proteolytic activity of BoNT/A, B, D, E, F, and G serotypes in real time with femtomolar to picomolar sensitivity. Notably, the reporters can detect femtomolar concentrations of BoNT/A in 4 h and BoNT/E in 20 h, sensitivity that equals that of animal-based methods. The reporters can be used to determine the specific activity of BoNT preparations with intra- …

Go to article

Prophylaxis With Human Serum Butyrylcholinesterase Protects Guinea Pigs Exposed To Multiple Lethal Doses Of Soman Or Vx, Ashima Saxena, Wei Sun, James M. Fedorko, Irwin Koplovitz, Bhupendra P. Doctor Jan 2011

Prophylaxis With Human Serum Butyrylcholinesterase Protects Guinea Pigs Exposed To Multiple Lethal Doses Of Soman Or Vx, Ashima Saxena, Wei Sun, James M. Fedorko, Irwin Koplovitz, Bhupendra P. Doctor

United States Army: Publications

Human serum butyrylcholinesterase (Hu BChE) is currently under advanced development as a bioscavenger for the prophylaxis of organophosphorus (OP) nerve agent toxicity in humans. It is estimated that a dose of 200 mg will be required to protect a human against 2 × LD50 of soman. To provide data for initiating an investigational new drug application for the use of this enzyme as a bioscavenger in humans, we purified enzyme from Cohn fraction IV-4 paste and initiated safety and efficacy evaluations in mice, guinea pigs, and non-human primates. In mice, we demonstrated that a single dose of enzyme that …

Go to article

Microstructure And Mechanical Properties At Different Length Scales And Strain Rates Of Nanocrystalline Tantalum Produced By High-Pressure Torsion, Q. Wei, Z. L. Pan, X. L. Wu, B. E. Schuster, L. J. Kecdkes, R. Z. Valiev Jan 2011

Microstructure And Mechanical Properties At Different Length Scales And Strain Rates Of Nanocrystalline Tantalum Produced By High-Pressure Torsion, Q. Wei, Z. L. Pan, X. L. Wu, B. E. Schuster, L. J. Kecdkes, R. Z. Valiev

United States Army: Publications

Fully dense, nanocrystalline tantalum (average grain size as small as ~40 nm) has been processed for the first time by high-pressure torsion. High-resolution transmission electron microscopy reveals non-equilibrium grain boundaries and grains decorated with high-density dislocations. Microhardness measurements and instrumented nanoindentation experiments indicate that the mechanical property is quite uniform except for the central area of the disks. Nanoindentation experiments at different strain rates suggest that the strain rate sensitivity of nanocrystalline tantalum is increased compared to the coarse- and ultrafine-grained counterparts and is accompanied by an activation energy of the order of a few ~b3 (b is the magnitude …

Go to article

Focusing Of Longitudinal Ultrasonic Waves In Air With An Aperiodic Flat Lens, John T. Welter, Shamachary Sathish, Daniel Christensen, Philip Brodrick, Jason D. Heebl, Matthew Cherry Jan 2011

Focusing Of Longitudinal Ultrasonic Waves In Air With An Aperiodic Flat Lens, John T. Welter, Shamachary Sathish, Daniel Christensen, Philip Brodrick, Jason D. Heebl, Matthew Cherry

United States Air Force: Publications

Modeling and experimental results of an ultrasonic aperiodic flat lens for use in air are presented. Predictive modeling of the lens is performed using a hybrid genetic-greedy algorithm constrained to a linear structure. The optimized design parameters are used to fabricate a lens. A method combining a fiber-disk arrangement and scanning laser vibrometer measurements is developed to characterize the acoustic field distribution generated by the lens. The focal spot size is determined to be 0.88 of the incident wavelength of 8090 kHz at a distance of 2.5 mm from the lens. Theoretically computed field distributions, optimized frequency of operation, and …

Go to article

Effects Of Damköhler Number On Flame Extinction And Reignition In Turbulent Non-Premixed Flames Using Dns, David Lignell, Jacqueline Chen, Hans Schmutz Jan 2011

Effects Of Damköhler Number On Flame Extinction And Reignition In Turbulent Non-Premixed Flames Using Dns, David Lignell, Jacqueline Chen, Hans Schmutz

United States Department of Energy: Publications

Results from a parametric study of flame extinction and reignition with varying Damköhler number using direct numerical simulation are presented. Three planar, non-premixed ethylene jet flames were simulated at a constant Reynolds number of 5120. The fuel and oxidizer stream compositions were varied to adjust the steady laminar extinction scalar dissipation rate, while maintaining constant flow and geometric conditions. Peak flame extinction varies from approximately 40% to nearly global blowout as the Damköhler number decreases. The degree of extinction significantly affects the development of the jets and the degree of mixing of fuel, oxidizer, and combustion products prior to reignition. …

Go to article

Variational Theory And Domain Decomposition For Nonlocal Problems, Burak Aksoylu, Michael L. Parks Jan 2011

Variational Theory And Domain Decomposition For Nonlocal Problems, Burak Aksoylu, Michael L. Parks

United States Department of Energy: Publications

In this article we present the first results on domain decomposition methods for nonlocal operators. We present a nonlocal variational formulation for these operators and establish the well-posedness of associated boundary value problems, proving a nonlocal Poincaré inequality. To determine the conditioning of the discretized operator, we prove a spectral equivalence which leads to a mesh size independent upper bound for the condition number of the stiffness matrix. We then introduce a nonlocal two-domain variational formulation utilizing nonlocal transmission conditions, and prove equivalence with the single-domain formulation. A nonlocal Schur complement is introduced. We establish condition number bounds for the …

Go to article

Automated Analysis Of Mouse Serum Peptidome Using Restricted Access Media And Nanoliquid Chromatography–Tandem Mass Spectrometry, Geun-Cheol Gil, Jim Brennan, Dan Throckmorton, Steven Branda, Gabriela Chirica Jan 2011

Automated Analysis Of Mouse Serum Peptidome Using Restricted Access Media And Nanoliquid Chromatography–Tandem Mass Spectrometry, Geun-Cheol Gil, Jim Brennan, Dan Throckmorton, Steven Branda, Gabriela Chirica

United States Department of Energy: Publications

We demonstrate use of restricted access media with reversed phase functionality (RAM-RP) for analysis of low molecular weight proteins and peptides in mouse serum (75ml) using a custom designed modular automated processing system (MAPS). RAM-RP fractionation with simultaneous removal of high molecular weight and high abundance proteins is integrated with a follow-on buffer exchange module (BE) to ensure compatibility with subsequent processing steps (trypsin digestion and intact peptide separation prior to mass spectrometric analysis). The high sample capacity afforded by chromatographic methods generates enough sample to achieve comprehensive serum peptidome identification (357 proteins) through tandem mass spectrometric analysis of both …

Go to article

An Experimental And Kinetic Modeling Study Of Methyl Formate Low-Pressure Flames, S. Dooley, F. L. Dryer, B. Yang, J. Wang, T. A. Cool, T. Kasper, N. Hansen Jan 2011

An Experimental And Kinetic Modeling Study Of Methyl Formate Low-Pressure Flames, S. Dooley, F. L. Dryer, B. Yang, J. Wang, T. A. Cool, T. Kasper, N. Hansen

United States Department of Energy: Publications

The oxidation of methyl formate (CH3OCHO), the simplest methyl ester, is studied in a series of burnerstabilized laminar flames at pressures of 22–30 Torr and equivalence ratios (Φ) from 1.0 to 1.8 for flame conditions of 25–35% fuel. Flame structures are determined by quantitative measurements of species mole fractions with flame-sampling molecular-beam synchrotron photoionization mass spectrometry (PIMS). Methyl formate is observed to be converted to methanol, formaldehyde and methane as major intermediate species of mechanistic relevance. Smaller amounts of ethylene and acetylene are also formed from methyl formate oxidation. Reactant, product and major intermediate species profiles …

Go to article

Reducing Error And Measurement Time In Impedance Spectroscopy Using Model Based Optimal Experimental Design, Francesco Ciucci, Thomas Carraro, William Chueh, Wei Lai Jan 2011

Reducing Error And Measurement Time In Impedance Spectroscopy Using Model Based Optimal Experimental Design, Francesco Ciucci, Thomas Carraro, William Chueh, Wei Lai

United States Department of Energy: Publications

In this work we introduce several novel tools for the reduction of errors in parameters estimated with electrochemical impedance spectroscopy experiments. An optimization strategy is developed that minimizes an estimate of the errors on the parameters while bounding the experimental time. The approach is also used to reduce experimental time while keeping a bound on the parameter errors. This feature is particularly critical in systems changing significantly within the experimental time. The paper uses a fuel cell electrode model to test this methodology and presents a real time algorithm for coupling experiment with the parameter estimation and experimental optimization.

Go to article

Real-Space Study Of The Growth Of Magnesium On Ruthenium, T. Herranz, B. Santos, K.F. Mccarty, J. De La Figuera Jan 2011

Real-Space Study Of The Growth Of Magnesium On Ruthenium, T. Herranz, B. Santos, K.F. Mccarty, J. De La Figuera

United States Department of Energy: Publications

The growth of magnesium on ruthenium has been studied by low-energy electron microscopy (LEEM) and scanning tunneling microscopy (STM). In LEEM, a layer-by-layer growth is observed except in the first monolayer, where the completion of the first layer in inferred by a clear peak in electron reflectivity. Desorption from the films is readily observable at 400 K. Real-space STM and low-energy electron diffraction confirm that sub-monolayer coverage presents a moiré pattern with a 12 Å periodicity, which evolves with further Mg deposition by compressing the Mg layer to a 22 Å periodicity. Layer-by-layer growth is followed in LEEM up to …

Go to article

Methods For Probabilistic Modeling Of Concentrating Solar Power Plants, Clifford Ho, Siri S. Khalsa, Gregory J. Kolb Jan 2011

Methods For Probabilistic Modeling Of Concentrating Solar Power Plants, Clifford Ho, Siri S. Khalsa, Gregory J. Kolb

United States Department of Energy: Publications

Probabilistic modeling of concentrating solar power technologies provides important information regarding uncertainties and sensitivities not available from deterministic models. Benefits of using probabilistic models include quantification of uncertainties inherent in the system and characterization of their impact on system performance and economics. This paper presents the tools necessary to conduct probabilistic modeling of concentrating solar technologies. The probabilistic method begins with the identification of uncertain variables and the assignment of appropriate distributions for those variables. Those parameters are then sampled using a stratified method (Latin Hypercube Sampling) to ensure complete and representative sampling from each distribution. Models of performance, reliability, …

Go to article

Magnetically Driven Hyper-Velocity Launch Capability At The Sandia Z Accelerator, R. W. Lemke, M. D. Knudson,, J. P. Davis Jan 2011

Magnetically Driven Hyper-Velocity Launch Capability At The Sandia Z Accelerator, R. W. Lemke, M. D. Knudson,, J. P. Davis

United States Department of Energy: Publications

The intense magnetic field generated by the Z accelerator at Sandia National Laboratories is used as a pressure source for material science studies. A current of ∼20 MA can be delivered to the loads used in experiments on a time scale of ∼100-600 ns. Magnetic fields (pressures) exceeding 1200 T (600 GPa) have been produced in planar configurations. In one application we have developed, the magnetic pressure launches a flyer plate to ultra-high velocity in a plate impact experiment; equation of state data is obtained on the Hugoniot of a material that is shock compressed to multi-megabar pressure. This capability …

Go to article

Multiple Benzene-Formation Paths In A Fuel-Rich Cyclohexane Flame, Wenjun Li, Matthew Law, Phillip Westmoreland, Tina Kasper, Nils Hansen, Katharina Kohse-Höinghaus Jan 2011

Multiple Benzene-Formation Paths In A Fuel-Rich Cyclohexane Flame, Wenjun Li, Matthew Law, Phillip Westmoreland, Tina Kasper, Nils Hansen, Katharina Kohse-Höinghaus

United States Department of Energy: Publications

Detailed data and modeling of cyclohexane flames establish that a mixture of pathways contributes to benzene formation and that this mixture changes with stoichiometry. Mole-fraction profiles are mapped for more than 40 species in a fuel-rich, premixed flat flame (Φ = 2.0, cyclohexane/O2/30% Ar, 30 Torr, 50.0 cm/s) using molecular-beam mass spectrometry with VUV-photoionization at the Advanced Light Source of the Lawrence Berkeley National Laboratory. The use of a newly constructed set of reactions leads to an excellent simulation of this flame and an earlier stoichiometric flame (M.E. Law et al., Proc. Combust. Inst. 31 (2007) 565–573), …

Go to article

Structure Of N-Heptane/Air Triple Flames In Partially-Premixed Mixing Layers, J. Prager, H. N. Najm, M. Valorani, D.A. Goussis Jan 2011

Structure Of N-Heptane/Air Triple Flames In Partially-Premixed Mixing Layers, J. Prager, H. N. Najm, M. Valorani, D.A. Goussis

United States Department of Energy: Publications

Results of a detailed numerical analysis of an n-heptane/air edge flame are presented. The equations of a low-Mach number reacting flow are solved in a two-dimensional domain using detailed models for species transport and chemical reactions. The reaction mechanism involves 560 species and 2538 reversible reactions. We consider an edge flame that is established in a mixing layer with a uniform velocity field. The mixing layer spans the equivalence ratios between pure air and 3.5. The detailed model enables us to analyze the chemical structure of the n-heptane edge flame. We identify major species profiles, discuss reactions causing the heat-release, …

Go to article

Roaming Radicals In The Thermal Decomposition Of Dimethyl Ether: Experiment And Theory, R. Sivaramakrishnan, J. Michael, A. Wagner, R. Dawes, A. Jasper, L. Harding, Y. Georgievskii, S. Klippenstein Jan 2011

Roaming Radicals In The Thermal Decomposition Of Dimethyl Ether: Experiment And Theory, R. Sivaramakrishnan, J. Michael, A. Wagner, R. Dawes, A. Jasper, L. Harding, Y. Georgievskii, S. Klippenstein

United States Department of Energy: Publications

The thermal dissociation of dimethyl ether has been studied with a combination of reflected shock tube experiments and ab initio dynamics simulations coupled with transition state theory based master equation calculations. The experiments use the extraordinary sensitivity provided by H-atom ARAS detection with an unreversed light source to measure both the total decomposition rate and the branching to radical products versus molecular products, with the molecular products arising predominantly through roaming according to the theoretical analysis. The experimental observations also provide a measure of the rate coefficient for H + CH3OCH3. An evaluation of the available experimental results for H …

Go to article

A Review Of Polymer Electrolyte Membrane Fuel Cells: Technology, Applications, And Needs On Fundamental Research, Yun Wang, Ken Chen, Jeffrey Mishler, Sung Chan Cho, Xavier Cordobes Adroher Jan 2011

A Review Of Polymer Electrolyte Membrane Fuel Cells: Technology, Applications, And Needs On Fundamental Research, Yun Wang, Ken Chen, Jeffrey Mishler, Sung Chan Cho, Xavier Cordobes Adroher

United States Department of Energy: Publications

Polymer electrolyte membrane (PEM) fuel cells, which convert the chemical energy stored in hydrogen fuel directly and efficiently to electrical energy with water as the only byproduct, have the potential to reduce our energy use, pollutant emissions, and dependence on fossil fuels. Great deal of efforts has been made in the past, particularly during the last couple of decades or so, to advance the PEM fuel cell technology and fundamental research. Factors such as durability and cost still remain as the major barriers to fuel cell commercialization. In the past two years, more than 35% cost reduction has been achieved …

Go to article

Direct Numerical Simulations Of Ignition Of A Lean N-Heptane/Air Mixture With Temperature Inhomogeneities At Constant Volume: Parametric Study, Chun Sang Yoo, Tianfeng Lu, Jacqueline Chen, Chung K. Law Jan 2011

Direct Numerical Simulations Of Ignition Of A Lean N-Heptane/Air Mixture With Temperature Inhomogeneities At Constant Volume: Parametric Study, Chun Sang Yoo, Tianfeng Lu, Jacqueline Chen, Chung K. Law

United States Department of Energy: Publications

The effect of thermal stratification on the ignition of a lean homogeneous n-heptane/air mixture at constant volume and high pressure is investigated by direct numerical simulations (DNS) with a new 58- species reduced kinetic mechanism developed for very lean mixtures from the detailed LLNL mechanism (H.J. Curran et al., Combust. Flame 129 (2002) 253–280). Two-dimensional DNS are performed in a fixed volume with a two-dimensional isotropic velocity spectrum and temperature fluctuations superimposed on the initial scalar fields. The influence of variations in the initial temperature field, imposed by changing the mean and variance of temperature, and the ratio of turbulence …

Go to article

Solution And Microbial Controls On The Formation Of Reduced U(Iv) Species, Maxim I. Boyanov, Kelly E. Fletcher, Man Jae Kwon, Xue Rui, Edward J. O’Loughlin, Frank E. Löffler, Kenneth M. Kemner Jan 2011

Solution And Microbial Controls On The Formation Of Reduced U(Iv) Species, Maxim I. Boyanov, Kelly E. Fletcher, Man Jae Kwon, Xue Rui, Edward J. O’Loughlin, Frank E. Löffler, Kenneth M. Kemner

United States Department of Energy: Publications

Reduction of UVI to UIV as the result of direct or indirect microbial activity is currently being explored for in situ remediation of subsurface U plumes, under the assumption that UIV solubility is controlled by the low solubility mineral uraninite (UIV-dioxide). However, recent characterizations of U in sediments from biostimulated field sites, as well as laboratory UVI bioreduction studies, report on the formation of UIV species that lack the U=O2=U coordination of uraninite, suggesting that phases other than uraninite may be controlling UIV solubility in environments with complexing surfaces and ligands. …

Go to article

Identification And Characterization Of Undahrcr-6, An Outer Membrane Endecaheme C-Type Cytochrome Of Shewanella Sp. Strain Hrcr-6, Liang Shi, Sara M. Belchik, Zheming Wang, David W. Kennedy, Alice C. Dohnalkova, Matthew J. Marshall, John M. Zachara, James K. Fredrickson Jan 2011

Identification And Characterization Of Undahrcr-6, An Outer Membrane Endecaheme C-Type Cytochrome Of Shewanella Sp. Strain Hrcr-6, Liang Shi, Sara M. Belchik, Zheming Wang, David W. Kennedy, Alice C. Dohnalkova, Matthew J. Marshall, John M. Zachara, James K. Fredrickson

United States Department of Energy: Publications

UndAHRCR-6 was identified from the metal-reducing bacterium Shewanella sp. strain HRCR-6. Both in vivo and in vitro characterization results indicate that UndAHRCR-6 is an outer membrane endecaheme c-type cytochrome and probably has a key functional role in the extracellular reduction of iron [Fe(III)] oxides and uranium [U(VI)] by Shewanella sp. HRCR-6.

Go to article

Purification And Characterization Of The [Nife]-Hydrogenase Of Shewanella Oneidensis Mr-1, Liang Shi, Sara M. Belchik, Andrew E. Plymale, Steve Heald, Alice C. Dohnalkova, Kateryna Sybirna, Herve Bottin, Thomas C. Squier, John M. Zachara, James K. Fredrickson Jan 2011

Purification And Characterization Of The [Nife]-Hydrogenase Of Shewanella Oneidensis Mr-1, Liang Shi, Sara M. Belchik, Andrew E. Plymale, Steve Heald, Alice C. Dohnalkova, Kateryna Sybirna, Herve Bottin, Thomas C. Squier, John M. Zachara, James K. Fredrickson

United States Department of Energy: Publications

Shewanella oneidensis MR-1 possesses a periplasmic [NiFe]-hydrogenase (MR-1 [NiFe]-H2ase) that has been implicated in H2 production and oxidation as well as technetium [Tc(VII)] reduction. To characterize the roles of MR-1 [NiFe]-H2ase in these proposed reactions, the genes encoding both subunits of MR-1 [NiFe]-H2ase were cloned and then expressed in an MR-1 mutant without hyaB and hydA genes. Expression of recombinant MR-1 [NiFe]-H2ase in trans restored the mutant’s ability to produce H2 at 37% of that for the wild type. Following purification, MR-1 [NiFe]-H2ase coupled H2 oxidation to …

Go to article

Microbial Reduction Of Chlorite And Uranium Followed By Air Oxidation, Gengxin Zhang, William D. Burgos, John M. Senko, Michael E. Bishop, Hailiang Dong, Maxim Boyanov, Kenneth M. Kemner Jan 2011

Microbial Reduction Of Chlorite And Uranium Followed By Air Oxidation, Gengxin Zhang, William D. Burgos, John M. Senko, Michael E. Bishop, Hailiang Dong, Maxim Boyanov, Kenneth M. Kemner

United States Department of Energy: Publications

To evaluate the stability of biogenic nanoparticulate U(IV) in the presence of an Fe(II)-rich iron-bearing phyllosilicate, we examined the reduction of structural Fe(III) in chlorite CCa-2 and uranium(VI) by Shewanella oneidensis MR-1, and the reoxidation of these minerals (after pasteurization) via the introduction of oxygen. Bioreduction experiments were conducted with combinations of chlorite, U(VI), and anthraquinone-2,6-disulfonate (AQDS). Abiotic experiments were conducted to quantify the reduction of U(VI) by chemically-reduced chlorite-associated Fe(II), the oxidation of nanoparticulate U(IV) by unaltered structural Fe(III) in chlorite, and the sorption of U(VI) to chlorite, to elucidate interactions between U(VI)/ U(IV) and Fe(II)/Fe(III)-chlorite. Solids were characterized …

Go to article

Competitive Reduction Of Pertechnetate (99tco4-) By Dissimilatory Metal Reducing Bacteria And Biogenic Fe(Ii), Andrew Plymale, James K. Fredrickson, John M. Zachara, Alice Dohnalkova, Steve Heald, Dean Moore, David Kennedy, Matthew Marshall, Chongmin Wang, Charles Resch, Ponnusamy Nachimuthu Jan 2011

Competitive Reduction Of Pertechnetate (99tco4-) By Dissimilatory Metal Reducing Bacteria And Biogenic Fe(Ii), Andrew Plymale, James K. Fredrickson, John M. Zachara, Alice Dohnalkova, Steve Heald, Dean Moore, David Kennedy, Matthew Marshall, Chongmin Wang, Charles Resch, Ponnusamy Nachimuthu

United States Department of Energy: Publications

The fate of pertechnetate (99Tc(VII)O4 -) during bioreduction was investigated in the presence of 2-line ferrihydrite (Fh) and various dissimilatory metal reducing bacteria (DMRB) (Geobacter, Anaeromyxobacter, Shewanella) in comparison with TcO4 - bioreduction in the absence of Fh. In the presence of Fh, Tc was present primarily as a fine-grained Tc(IV)/Fe precipitate that was distinct from the Tc(IV)O2 ·nH2O solids produced by direct biological Tc(VII) reduction. Aqueous Tc concentrations (<0.2 μm) in the bioreduced Fh suspensions (1.7 to 3.2 × 10-9 mol L-1) were over 1 order of magnitude lower than when TcO4 - …

Go to article

Effect Of Grain Size On Uranium(Vi) Surface Complexation Kinetics And Adsorption Additivity, Jianying Shang, Chongxuan Liu, Zheming Wang, John M. Zachara Jan 2011

Effect Of Grain Size On Uranium(Vi) Surface Complexation Kinetics And Adsorption Additivity, Jianying Shang, Chongxuan Liu, Zheming Wang, John M. Zachara

United States Department of Energy: Publications

The contribution of variable grain sizes to uranium adsorption/ desorption was studied using a sediment from the US DOE Hanford site. The sediment was wet sieved into four size fractions: coarse sand (1−2 mm), medium sand (0.2−1 mm), fine sand (0.053−0.2 mm), and clay/silt fraction (<0.053 mm). For each size fraction and their composite (sediment), batch and flow-cell experiments were performed to determine uranium adsorption isotherms and kinetic uranium adsorption and subsequent desorption. The results showed that uranium adsorption isotherms and adsorption/desorption kinetics were size specific, reflecting the effects of size-specific adsorption site concentration and kinetic rate constants. The larger-size fraction had a larger mass percentage in the sediment but with a smaller adsorption site concentration and generally a slower uranium adsorption/desorption rate. The same equilibrium surface complexation reaction and reaction constant could describe uranium adsorption isotherms for all size fractions and the composite after accounting for the effect of adsorption site concentration. Mass-weighted, linear additivity was observed for both uranium adsorption isotherms and adsorption/desorption kinetics in the composite. One important implication of this study is that grain-size distribution may be used to estimate uranium adsorption site and adsorption/desorption kinetic rates in heterogeneous sediments from a common location.

Go to article

First Prev Next Last