Bioresource and Agricultural Engineering Commons^™

Enhancement Of Thermopower Of Tags-85 High-Performance Thermoelectric Material By Doping With The Rare Earth Dy, E. M. Levin, S. L. Bud’Ko, K. Schmidt-Rohr

US Department of Energy Publications

Enhancement of thermopower is achieved by doping the narrow-band semiconductor Ag_6.52Sb_6.52Ge_36.96Te₅₀ (acronym TAGS-85), one of the best p -type thermoelectric materials, with 1 or 2% of the rare earth dysprosium (Dy). Evidence for the incorporation of Dy into the lattice is provided by X-ray diffraction and increased orientation-dependent local fields detected by ¹²⁵Te NMR spectroscopy. Since Dy has a stable electronic configuration, the enhancement cannot be attributed to 4f -electron states formed near the Fermi level. It is likely that the enhancement is due to a small reduction in the carrier …

Incorporating A Completely Renormalized Coupled Cluster Approach Into A Composite Method For Thermodynamic Properties And Reaction Paths, Sean A. Nedd, Nathan J. Deyonker, Angela K. Wilson, Mark S. Gordon, Piotr Piecuch

US Department of Energy Publications

The correlation consistent composite approach (ccCA), using the S4 complete basis set two-point extrapolation scheme (ccCA-S4), has been modified to incorporate the left-eigenstate completely renormalized coupled cluster method, including singles, doubles, and non-iterative triples (CR-CC(2,3)) as the highest level component. The new ccCA-CC(2,3) method predicts thermodynamic properties with an accuracy that is similar to that of the original ccCA-S4 method. At the same time, the inclusion of the single-reference CR-CC(2,3) approach provides a ccCA scheme that can correctly treat reaction pathways that contain certain classes of multi-reference species such as diradicals, which would normally need to be treated by more …

Experimental And Theoretical Electronic Structure Of Eurh2as2, A. D. Palczewski, R. S. Dhaka, Y. Lee, Yogesh Singh, D. C. Johnston, B. N. Harmon, Adam Kaminski

US Department of Energy Publications

The Fermi surfaces (FS’s) and band dispersions of EuRh₂As₂ have been investigated using angle-resolved photoemission spectroscopy. The results in the high-temperature paramagnetic state are in good agreement with the full-potential linearized augmented-plane-wave calculations, especially in the context of the shape of the two-dimensional FS’s and band dispersion around the Γ (0,0) and X (π,π) points. Interesting changes in band folding are predicted by the theoretical calculations below the magnetic transition temperature T_N ≈ 47 K. However, by comparing the FS’s measured at 60 and 40 K, we did not observe any signature of this transition at …

Magnetic And Structural Transitions In The Iron-Chalcogenide High-Tc Superconductor: K0.8fe1.76se2.00, W. N. Rowan-Weetaluktuk, D. H. Ryan, J. M. Cadogan, R. Hu, S. L. Bud’Ko, Paul C. Canfield

US Department of Energy Publications

⁵⁷Fe Mössbauer spectroscopy was used to study single-crystals of K_0.8Fe_1.76Se_2.00 from 6K to 673 K. At 6 K, the hyperfine field (B_hf) is canted away from the c-axis by 18±3°. The temperature dependence of B_hf follows a spin wave model with a spin excitation gap of 9±1 meV. A sudden increase in the line width and a corresponding drop in (1/2)eQV_zz at T_N = 532 K are indications of strong coupling between the magnetic and structural transitions.

Evaluation Of Niobium As Candidate Electrode Material For Dc High Voltage Photoelectron Guns, M. Bastaninejad, Md. Abdullah Mohamed, A. A. Elmustafa, P. Adderley, J. Clark, S. Covert, J. Hansknecht, C. Hernandez-Garcia, M. Poelker, R. Mammei, K. Surles-Law, P. Williams

US Department of Energy Publications

The field emission characteristics of niobium electrodes were compared to those of stainless steel electrodes using a DC high voltage field emission test apparatus. A total of eight electrodes were evaluated: two 304 stainless steel electrodes polished to mirror like finish with diamond grit and six niobium electrodes (two single-crystal, two large-grain, and two fine-grain) that were chemically polished using a buffered-chemical acid solution. Upon the first application of high voltage, the best large-grain and single-crystal niobium electrodes performed better than the best stainless steel electrodes, exhibiting less field emission at comparable voltage and field strength. In all cases, field …

The Genome Portal Of The Department Of Energy Joint Genome Institute, Igor V. Grigoriev, Henrik Nordberg, Igor Shabalov, Andrea Aerts, Mike Cantor, David Goodstein, Alan Kuo, Simon Minovitsky, Roman Nikitin, Robin A. Ohm, Robert Otillar, Alex Poliakov, Igor Ratnere, Robert Riley, Tatyana Smirnova, Daniel Rokhsar, Inna Dubchak

US Department of Energy Publications

The Department of Energy (DOE) Joint Genome Institute (JGI) is a national user facility with massive-scale DNA sequencing and analysis capabilities dedicated to advancing genomics for bioenergy and environmental applications. Beyond generating tens of trillions of DNA bases annually, the Institute develops and maintains data management systems and specialized analytical capabilities to manage and interpret complex genomic data sets, and to enable an expanding community of users around the world to analyze these data in different contexts over the web. The JGI Genome Portal (http://genome.jgi.doe.gov) provides a unified access point to all JGI genomic databases and analytical tools. A user …

Bioenergy Feedstock-Specific Enrichment Of Microbial Populations During High-Solids Thermophilic Deconstruction, Amitha P. Reddy, Martin Allgaier, Steven W. Singer, Terry C. Hazen, Blake A. Simmons, Philip Hugenholtz, Jean S. Vandergheynst

US Department of Energy Publications

Thermophilic microbial communities that are active in a high-solids environment offer great potential for the discovery of industrially relevant enzymes that efficiently deconstruct bioenergy feedstocks. In this study, finished green waste compost was used as an inoculum source to enrich microbial communities and associated enzymes that hydrolyze cellulose and hemicellulose during thermophilic high-solids fermentation of the bioenergy feedstocks switchgrass and corn stover. Methods involving the disruption of enzyme and plant cell wall polysaccharide interactions were developed to recover xylanase and endoglucanase activity from deconstructed solids. Xylanase and endoglucanase activity increased by more than a factor of 5, upon four successive …

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

US 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 …

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

US 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 …

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

US 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.

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

US 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 …

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

US 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 …

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

US 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 …

Error Analysis Of Large-Eddy Simulation Of The Turbulent Non-Premixed Sydney Bluff-Body Flame, A. M. Kempf, B. J. Geurts, J. C, Oefelein

US Department of Energy Publications

A computational error analysis is applied to the large-eddy simulation of the turbulent non-premixed Sydney bluff-body flame, where the error is defined with respect to experimental data. The errorlandscape approach is extended to heterogeneous compressible turbulence, which is coupled to combustion as described by a flamelet model. The Smagorinsky model formulation is used to model the unknown turbulent stresses. We introduce several measures to quantify the total simulation error and observe a striking ‘valley-structure’ in the error that arises as function of the spatial resolution and the Smagorinsky length parameter. The optimal refinement strategy that can be extracted from this …

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

US 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, …

Comparison Of Dynamic Compression Behavior Of Single Crystal Sapphire To Polycrystalline Alumina, G. J. Kleiser, L.C. Chhabildas, W.D. Reinhart

US Department of Energy Publications

Due to the considerable interest in the shock loading behavior of aluminum oxide whether it is in the polycrystalline phase or in the single crystal phase well-controlled experiments were conducted to probe differences in shock loading behavior between these two materials. Previous studies concluded that the behavior was similar but careful examination of well-controlled experiments has revealed the two materials are different.Although the experimental results appear to have the same behavior in the shock velocity vs. particle velocity plane, they are considerably different in the stressevolume compression plane and evidence is provided that indicates the single crystal remains crystalline up …

Combining Power Plant Water Needs And Carbon Dioxide Storage Using Saline Formations: Implications For Carbon Dioxide And Water Management Policies, Peter Kobos, Malynda Cappelle, Jim Krumhansl, Thomas Dewers, Andrea Mcnemar, David Borns

US Department of Energy Publications

Research involving management of carbon dioxide has increased markedly over the last decade as it relates to concerns over climate change. Capturing and storing carbon dioxide (CO₂) in geological formations is one of many proposed methods to manage, and likely reduce, CO₂ emissions from burning fossil fuels in the electricity sector. Saline formations represent a vast storage resource, and the waters they contain could be managed for beneficial use. To address this issue, a methodology was developed to test the feasibility of linking coal-fired power plants, deep saline formations for CO₂ storage, and extracting and treating …

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

US 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 …

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

US 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), …

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

US 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. …

Solubility Of Fe2(Oh)3cl (Pure-Iron End-Member Of Hibbingite) In Nacl And Na2so4 Brines, Martin Nemer, Yongliang Xiong, Ahmed Ismail, Je-Hun Jang

US Department of Energy Publications

Pure-iron end-member hibbingite, Fe₂(OH)₃Cl(s), may be important to geological repositories in salt formations, as it may be a dominant corrosion product of steel waste canisters in an anoxic environment in Na–Cl- and Na–Mg–Cl-dominated brines. In this study, the solubility of Fe₂(OH)₃Cl(s), the pure-iron endmember of hibbingite (Fe^II, Mg)₂(OH)₃Cl(s), and Fe(OH)₂(s) in 0.04 m to 6 m NaCl brines has been determined. For the reaction

Fe₂ (OH)₃Cl(s) + 3H⁺↔ 3H₂O + 2Fe²⁺ + Cl⁻,

the …

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

US 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, …

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

US 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 …

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

US 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 …

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

US 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 …

Nonlocal Instability Analysis Of Fcc Bulk And (100) Surfaces Under Uniaxial Stretching, Geng Yun, Penghui Cao, Jonathan Zimmerman, Terry Delph, Harold Park

US Department of Energy Publications

The objective of this paper is to examine the instability characteristics of both a bulk FCC crystal and a (100) surface of an FCC crystal under uniaxial stretching along a h100i direction using an atomisticbased nonlocal instability criterion. By comparison to benchmark atomistic simulations, we demonstrate that for both the FCC bulk and (100) surface, about 5000–10,000 atoms are required in order to obtain an accurate converged value for the instability strain and a converged instability mode. The instability modes are fundamentally different at the surface as compared to the bulk, but in both cases a strong dependence of the …

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

US Department of Energy Publications

Reduction of U^VI to U^IV 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 (U^IV-dioxide). However, recent characterizations of U in sediments from biostimulated field sites, as well as laboratory U^VI bioreduction studies, report on the formation of U^IV species that lack the U=O₂=U coordination of uraninite, suggesting that phases other than uraninite may be controlling U^IV solubility in environments with complexing surfaces and ligands. …

Evidence For Multiple Modes Of Uranium Immobilization By An Anaerobic Bacterium, Allison E. Ray, John R. Bargar, Vaideeswaran Sivaswamy, Alice C. Dohnalkova, Yoshiko Fujita, Brent M. Peyton, Timothy S. Magnuson

US Department of Energy Publications

Microbial reduction of hexavalent uranium has been studied widely for its potential role in bioremediation and immobilization of soluble U(VI) in contaminated groundwater. More recently, some microorganisms have been examined for their role in immobilization of U(VI) via precipitation of uranyl phosphate minerals mediated by microbial phosphate release, alleviating the requirement for long-term redox control. Here, we investigated the mechanism of U(VI) removal mediated by an environmental isolate, strain UFO1, that is indigenous to the Field Research Center (FRC) in Oak Ridge, TN and has been detected in U(VI)- contaminated sediments. Changes in U(VI) speciation were examined in the presence …

Persistence Of Uranium Groundwater Plumes: Contrasting Mechanisms At Two Contaminated Doe Sites, John M. Zachara, James A. Davis, Philip E. Long, Kenneth H. Williams, Mark Freshley, James P. Mckinley

US Department of Energy Publications

We examine subsurface uranium (U) plumes at two U.S. Department of Energy sites located near large river systems. Following excavation of contaminated materials, both sites were projected to naturally flush remnant uranium contamination to levels below regulatory limits (e.g., 30 μg/L), within 10 years at the Hanford 300 Area (Columbia River) and 12 years at the Rifle site (Colorado River). The observed rate of attenuation was much lower than expected at both sites. Current understanding suggests that the two sites have common, but also differing mechanisms controlling plume persistence. At Hanford, the persistent source is adsorbed U(VI) in the deep …

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

US Department of Energy Publications

UndA_HRCR-6 was identified from the metal-reducing bacterium Shewanella sp. strain HRCR-6. Both in vivo and in vitro characterization results indicate that UndA_HRCR-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.