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Meduri P.,Pacific Northwest National Laboratory | Clark E.,University of Louisville | Dayalan E.,ENSER Corporation | Sumanasekera G.U.,University of Louisville | Sunkara M.K.,University of Louisville
Energy and Environmental Science | Year: 2011

In this paper, we report that Sn-nanocluster-covered SnO2 nanowire ("hybrid architectures") electrodes exhibited stage-wise de-lithiation suggesting complete lithium extraction. The lithiation and de-lithiation behavior explains that the high capacity retention of 814 mAh g-1 and durability over hundred cycles is because of low irreversible capacity loss. Mono-layers of un-agglomerated, sub 60 nm size Sn clusters supported on metallic electrodes also exhibited similar stage-wise de-lithiation while the microscale Sn clusters exhibited single-phase lithium extraction. This can be attributed to shorter lithium ion diffusion lengths and high surface area of the nanomaterials. The cyclic voltammetric studies of Sn nanoclusters (sub 60 nm size) confirm the reaction kinetics limited behavior of lithiation and de-lithiation characteristics. The Sn-nanocluster-covered SnO2 nanowires showed a capacity retention of 458 mAh g-1 at 500 mAg-1 current density indicating an excellent rate capability. © The Royal Society of Chemistry 2011.


Pinchuk G.E.,Pacific Northwest National Laboratory
PLoS computational biology | Year: 2010

Shewanellae are gram-negative facultatively anaerobic metal-reducing bacteria commonly found in chemically (i.e., redox) stratified environments. Occupying such niches requires the ability to rapidly acclimate to changes in electron donor/acceptor type and availability; hence, the ability to compete and thrive in such environments must ultimately be reflected in the organization and utilization of electron transfer networks, as well as central and peripheral carbon metabolism. To understand how Shewanella oneidensis MR-1 utilizes its resources, the metabolic network was reconstructed. The resulting network consists of 774 reactions, 783 genes, and 634 unique metabolites and contains biosynthesis pathways for all cell constituents. Using constraint-based modeling, we investigated aerobic growth of S. oneidensis MR-1 on numerous carbon sources. To achieve this, we (i) used experimental data to formulate a biomass equation and estimate cellular ATP requirements, (ii) developed an approach to identify cycles (such as futile cycles and circulations), (iii) classified how reaction usage affects cellular growth, (iv) predicted cellular biomass yields on different carbon sources and compared model predictions to experimental measurements, and (v) used experimental results to refine metabolic fluxes for growth on lactate. The results revealed that aerobic lactate-grown cells of S. oneidensis MR-1 used less efficient enzymes to couple electron transport to proton motive force generation, and possibly operated at least one futile cycle involving malic enzymes. Several examples are provided whereby model predictions were validated by experimental data, in particular the role of serine hydroxymethyltransferase and glycine cleavage system in the metabolism of one-carbon units, and growth on different sources of carbon and energy. This work illustrates how integration of computational and experimental efforts facilitates the understanding of microbial metabolism at a systems level.


McDowell M.T.,Stanford University | Lee S.W.,Stanford University | Harris J.T.,University of Texas at Austin | Korgel B.A.,University of Texas at Austin | And 4 more authors.
Nano Letters | Year: 2013

To utilize high-capacity Si anodes in next-generation Li-ion batteries, the physical and chemical transformations during the Li-Si reaction must be better understood. Here, in situ transmission electron microscopy is used to observe the lithiation/delithiation of amorphous Si nanospheres; amorphous Si is an important anode material that has been less studied than crystalline Si. Unexpectedly, the experiments reveal that the first lithiation occurs via a two-phase mechanism, which is contrary to previous understanding and has important consequences for mechanical stress evolution during lithiation. On the basis of kinetics measurements, this behavior is suggested to be due to the rate-limiting effect of Si-Si bond breaking. In addition, the results show that amorphous Si has more favorable kinetics and fracture behavior when reacting with Li than does crystalline Si, making it advantageous to use in battery electrodes. Amorphous spheres up to 870 nm in diameter do not fracture upon lithiation; this is much larger than the 150 nm critical fracture diameter previously identified for crystalline Si spheres. © 2013 American Chemical Society.


Harmon M.E.,Oregon State University | Bond-Lamberty B.,Pacific Northwest National Laboratory | Tang J.,Ecosystems Center | Vargas R.,Research Center Cientifica Educacion Superior Of Ensenada
Journal of Geophysical Research: Biogeosciences | Year: 2011

Heterotrophic respiration (RH) is a major process releasing carbon to the atmosphere and is essential to understanding carbon dynamics in terrestrial ecosystems. Here we review what is known about this flux as related to forest disturbance using examples from North America. The global R H flux from soils has been estimated at 53-57 Pg C yr-1, but this does not include contributions from other sources (i.e., dead wood, heart-rots). Disturbance-related inputs likely account for 20-50% of all R H losses in forests, and disturbances lead to a reorganization of ecosystem carbon pools that influences how RH changes over succession. Multiple controls on RH related to climate, the material being decomposed, and the decomposers involved have been identified, but how each potentially interacts with disturbance remains an open question. An emerging paradigm of carbon dynamics suggests the possibility of multiple periods of carbon sinks and sources following disturbance; a large contributing factor is the possibility that postdisturbance RH does not always follow the monotonic decline assumed in the classic theory. Without a better understanding and modeling of RH and its controlling factors, it will be difficult to estimate, forecast, understand, and manage carbon balances of regions in which disturbance frequency and severity are changing. Meeting this challenge will require (1) improved field data on processes and stores, (2) an improved understanding of the physiological and environmental controls of R H, and (3) a more formal analysis of how model structure influences the RH responses that can be predicted. Copyright 2011 by the American Geophysical Union.


Zhang H.,University of California at Berkeley | De Yoreo J.J.,Pacific Northwest National Laboratory | Banfield J.F.,University of California at Berkeley
ACS Nano | Year: 2014

Crystal growth is one of the most fundamental processes in nature. Understanding of crystal growth mechanisms has changed dramatically over the past two decades. One significant advance has been the recognition that growth does not only occur atom by atom, but often proceeds via attachment and fusion of either amorphous or crystalline particles. Results from recent experiments and calculations can be integrated to develop a simple, unified conceptual description of attachment-based crystal growth. This enables us to address three important questions: What are the driving forces for attachment-based growth? For crystalline particles, what enables the particles to achieve crystallographic coalignment? What determines the surface on which attachment occurs? We conclude that the extent of internal nanoparticle order controls the degree of periodicity and anisotropy in the surrounding electrostatic field. For crystalline particles, the orienting force stemming from the electrostatic field can promote oriented attachment events, although solvent-surface interactions modulate this control. In cases where perfect crystallographic alignment is not achieved, misorientation gives rise to structural defects that can fundamentally modify nanomaterial properties. © 2014 American Chemical Society.


Daily J.,Pacific Northwest National Laboratory
BMC Bioinformatics | Year: 2016

Background: Sequence alignment algorithms are a key component of many bioinformatics applications. Though various fast Smith-Waterman local sequence alignment implementations have been developed for x86 CPUs, most are embedded into larger database search tools. In addition, fast implementations of Needleman-Wunsch global sequence alignment and its semi-global variants are not as widespread. This article presents the first software library for local, global, and semi-global pairwise intra-sequence alignments and improves the performance of previous intra-sequence implementations. Results: A faster intra-sequence local pairwise alignment implementation is described and benchmarked, including new global and semi-global variants. Using a 375 residue query sequence a speed of 136 billion cell updates per second (GCUPS) was achieved on a dual Intel Xeon E5-2670 24-core processor system, the highest reported for an implementation based on Farrar's 'striped' approach. Rognes's SWIPE optimal database search application is still generally the fastest available at 1.2 to at best 2.4 times faster than Parasail for sequences shorter than 500 amino acids. However, Parasail was faster for longer sequences. For global alignments, Parasail's prefix scan implementation is generally the fastest, faster even than Farrar's 'striped' approach, however the opal library is faster for single-threaded applications. The software library is designed for 64 bit Linux, OS X, or Windows on processors with SSE2, SSE41, or AVX2. Source code is available from https://github.com/jeffdaily/parasail under the Battelle BSD-style license. Conclusions: Applications that require optimal alignment scores could benefit from the improved performance. For the first time, SIMD global, semi-global, and local alignments are available in a stand-alone C library. © 2016 Daily.


Khan A.S.,University of Maryland Baltimore County | Baig M.,King Saud University | Choi S.-H.,Sunchon National University | Yang H.-S.,Sunchon National University | Sun X.,Pacific Northwest National Laboratory
International Journal of Plasticity | Year: 2012

Measured responses of advanced high strength steels (AHSS) and their tailor welded blanks (TWBs), over a wide range of strain-rates (10 -4 to 10 3 s -1) are presented. The steels investigated include transformation induced plasticity (TRIP), dual phase (DP), and drawing quality (DQ) steels. The TWBs include DQ-DQ and DP-DP laser welds. A tensile split Hopkinson pressure bar (SHPB) was used for the dynamic experiments. AHSS and their TWB's were found to exhibit positive strain-rate sensitivity. The Khan-Huang-Liang (KHL) constitutive model is shown to correlate and predict the observed responses reasonably well. Micro-texture characterization of DQ steels, DQ-DQ and DP-DP laser welds were performed to investigate the effect of strain-rate on texture evolution of these materials. Electron backscatter diffraction (EBSD) technique was used to analyze the micro-texture evolution and kernel average misorientation (KAM) map. Measurement of micro-hardness profile across the cross section of tensile samples was conducted to understand the effect of initial microstructure on ductility of laser weld samples. © 2011 Elsevier Ltd. All rights reserved.


De Yoreo J.J.,Lawrence Berkeley National Laboratory | De Yoreo J.J.,Pacific Northwest National Laboratory | Chung S.,Lawrence Berkeley National Laboratory | Friddle R.W.,Sandia National Laboratories
Advanced Functional Materials | Year: 2013

Atomic force imaging and spectroscopy provide unique tools for investigating molecular interactions and dynamics in biomolecular and biomineral systems in situ. Herein, three recent examples of methods used to gain mechanistic insights into the self-assembly of protein matrices and biomolecular controls over mineral formation are reviewed. Studies of S-layer protein assembly reveal the complex nature of the nucleation and growth pathway, demonstrate the importance of kinetic traps in determining that pathway and provide quantification of the energy barriers controlling formation rates. Investigations of citrate and polypeptide modification of calcium oxalate monohydrate growth combined with molecular dynamics simulations (MD) demonstrate the importance of stereochemical matching at atomic steps on the crystal surface and establish a direct relationship between the step edge binding energies and shape modification. Measurements of step kinetics lead to detailed atomic-scale models that include both thermodynamic and kinetic effects, including time-dependent phenomena related to the multi-stage binding dynamics of polypeptide chains. Dynamic force spectroscopy measurements of binding between amelogenin peptide segments and hydroxyapatite (HAP) crystal faces, again combined with MD simulations, establish an energetic rationale for the observed c-axis elongation characteristic of HAP in tooth enamel, based on determinations of the peptide-HAP binding free energy. These examples demonstrate the deep level of understanding that can be obtained by applying in situ AFM imaging and force spectroscopy to biomolecular and biomineral systems. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Roehling J.D.,University of California at Davis | Batenburg K.J.,Centrum Wiskunde and Informatica | Batenburg K.J.,University of Antwerp | Swain F.B.,Luna Innovations, Inc. | And 2 more authors.
Advanced Functional Materials | Year: 2013

The three-dimensional morphology of mixed organic layers are quantitatively measured using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) with electron tomography for the first time. The mixed organic layers used for organic photovoltaic applications have not been previously imaged using STEM tomography as there is insufficient contrast between donor and acceptor components. Contrast is generated by substituting fullerenes with endohedral fullerenes that contain a Lu3N cluster within the fullerene cage. The high contrast and signal-to-noise ratio, in combination with use of the discrete algebraic reconstruction technique (DART), allows generation of the most detailed and accurate three-dimensional map of BHJ morphology to date. From the STEM-tomography reconstructions it is determined that three distinct material phases are present within the BHJs. By observing changes to morphology and mixing ratio during thermal and solvent annealing, the effects of mutual solubility and fullerene crystallization on morphology and long term stability are determined. This material/technique combination shows itself as a powerful tool for examining morphology in detail and allows for observation of nanoscopic changes in local concentration. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Henderson M.A.,Pacific Northwest National Laboratory
Journal of Physical Chemistry C | Year: 2015

A mixed Fe + Cr oxide surface was used to explore the photochemical fate of adsorbed O2 under ultra-high-vacuum conditions. The mixed oxide surface possessed a magnetite-like (111) structure based on low-energy electron diffraction, with its chemical behavior resembling that of Fe3O4(111). Oxygen adsorption at 40 K resulted in two chemisorption states, a strongly bound form desorbing in temperature-programmed desorption (TPD) at 230 K and a weakly bound form evolving at 100 K. The former was assigned to charge transfer adsorption at Fe2+ sites and the latter to electrostatic binding at Fe3+ sites. A minority state was also detected at ∼160 K and tentatively assigned to adsorption at Cr3+ sites. The 230 K O2 state was the focus of photochemical studies employing four wavelengths of light from the red to the UV. Irrespective of wavelength, O2 molecules in the 230 K state preferentially photodesorbed when irradiated, with comparable rates across the visible and an order of magnitude higher in the UV. Approximately 10% of adsorbed O2 irreversibly photodissociated, irrespective of wavelength, with the resulting fragments blocking access to both Fe3+ and Fe2+ sites for subsequent O2 adsorption. Preadsorbed water also blocked O2 adsorption, but postadsorbed water stabilized O2 at Fe2+ sites in TPD to 285 K. The water-stabilized O2 molecules were insensitive to photodesorption. O2 photodissociation and photopassivation both represent potentially adverse outcomes in the release of O2 during the heterogeneous water photooxidation reaction. © 2015 American Chemical Society.


Zhang Z.F.,Pacific Northwest National Laboratory
Soil Science Society of America Journal | Year: 2010

Accurate simulation and prediction of flow and transport of solutes in a heterogeneous vadose zone requires the appropriate hydraulic properties corresponding to the spatial scale of interest Upscaling techniques are needed to provide effective properties for describing the vadose zone system's behavior with information collected at a much smaller scale. Numerical experiments were performed to investigate the efective unsaturated hydraulic conductivity of soils with different degrees and dimensionalities of heterogeneity. Researchers have extended Marheron's method for determining the hydraulic conductivity of soils with one-dimensional heterogeneity under a saturated condition to unsaturated conditions. In this work, Marheron's method was further extended to the unsaturated soils with two- and three-dimensional heterogeneity. It was found that the first-order approximation of the extended formula is similar to those based on the small-perturbation approach. The extended Matheron's method was verified using multistep numerical experiments of gravity-induced flow into synthetic soils with different degrees of heterogeneity. Results showed that the dimensionality of soil heterogeneity has a significant impact on the effective unsaturated hydraulic conductivity, and the extended Marheron's method can well estimate the effective conductivity of the soils with multidimensional heterogeneity. © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA All rights reserved.


Laskin J.,Pacific Northwest National Laboratory
International Journal of Mass Spectrometry | Year: 2015

This article presents a personal perspective regarding the development of key concepts in understanding hyperthermal collisions of polyatomic ions with surfaces as a unique tool for mass spectrometry applications. In particular, this article provides a historic overview of studies focused on understanding the phenomena underlying surface-induced dissociation (SID) and mass-selected deposition of complex ions on surfaces. Fast energy transfer in ion-surface collisions makes SID especially advantageous for structural characterization of large complex molecules, such as peptides, proteins, and protein complexes. Soft, dissociative, and reactive landing of mass-selected ions provide the basis for preparatory mass spectrometry. These techniques enable precisely controlled deposition of ions on surfaces for a variety of applications. This perspective article shows how basic concepts developed in the 1920s and 1970s have evolved to advance promising mass-spectrometry-based applications. © 2014 Elsevier B.V. All rights reserved.


Oxford G.A.E.,U.S. National Institute of Standards and Technology | Chaka A.M.,U.S. National Institute of Standards and Technology | Chaka A.M.,Pacific Northwest National Laboratory
Journal of Physical Chemistry C | Year: 2012

Hydration of the β-MnO 2 (110), (100), and (101) surfaces is investigated using a combination of periodic density functional theory and ab initio thermodynamics. Fully hydrated surfaces are found to be significantly more stable than the stoichiometric ones up to temperatures in the range of 650 to 730 K at ambient oxygen and water partial pressures. A mixture of molecular and dissociative water adsorption is predicted to occur on the (110) and (101) surfaces, while the (100) surface does not dissociate water. Changes in surface reactivity upon water adsorption are explored via partial density of states analysis. Differences in surface relaxations and vibrational spectra are discussed and can be used to identify the type of adsorption mode. © This article not subject to U.S. © 2012 American Chemical Society.


Singhal S.C.,Pacific Northwest National Laboratory
Green Energy and Technology | Year: 2013

Although fuel cells have been known for over 150 years, research on solid oxide fuel cells (SOFCs) based on an oxide ion conducting electrolyte only accelerated in the last 30 years. This chapter, after a brief history of SOFCs, reviews the materials for different cell components (electrolyte and the two electrodes) and cell stacks (seals and interconnects); novel materials and their structures have been investigated and developed to improve electrochemical performance. Different SOFC designs and their relative advantages and disadvantages are then discussed. Finally, various applications of SOFC power systems and the status of their demonstration and commercialization are reviewed. © Springer-Verlag London 2013.


Renslow R.S.,Washington State University | Babauta J.T.,Washington State University | Majors P.D.,Pacific Northwest National Laboratory | Beyenal H.,Washington State University
Energy and Environmental Science | Year: 2013

The goal of this study was to measure spatially and temporally resolved effective diffusion coefficients (De) in biofilms respiring on electrodes. Two model electrochemically active biofilms, Geobacter sulfurreducens PCA and Shewanella oneidensis MR-1, were investigated. A novel nuclear magnetic resonance microimaging perfusion probe capable of simultaneous electrochemical and pulsed-field gradient nuclear magnetic resonance (PFG-NMR) techniques was used. PFG-NMR allowed for noninvasive, nondestructive, high spatial resolution in situ De measurements in living biofilms respiring on electrodes. The electrodes were polarized so that they would act as the sole terminal electron acceptor for microbial metabolism. We present our results as both two-dimensional De heat maps and surface-averaged relative effective diffusion coefficient (Drs) depth profiles. We found that (1) Drs decreases with depth in G. sulfurreducens biofilms, following a sigmoid shape; (2) Drs at a given location decreases with G. sulfurreducens biofilm age; (3) average De and Drs profiles in G. sulfurreducens biofilms are lower than those in S. oneidensis biofilms - the G. sulfurreducens biofilms studied here were on average 10 times denser than the S. oneidensis biofilms; and (4) halting the respiration of a G. sulfurreducens biofilm decreases the De values. Density, reflected by De, plays a major role in the extracellular electron transfer strategies of electrochemically active biofilms. This journal is © The Royal Society of Chemistry 2013.


Runkle R.C.,Pacific Northwest National Laboratory | Chichester D.L.,Idaho National Laboratory | Thompson S.J.,Idaho National Laboratory
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2012

Active interrogation is a vigorous area of research and development due to its promise of offering detection and characterization capabilities of special nuclear material in environments where passive detection fails. The primary value added by active methods is the capability to penetrate shielding - special nuclear material itself, incidental materials, or intentional shielding - and advocates hope that active interrogation will provide a solution to the problem of detecting shielded uranium, which is at present the greatest obstacle to interdiction efforts. The technique also provides a unique benefit for quantifying nuclear material in high background-radiation environments, an area important for nuclear material safeguards and material accountancy. Progress has been made in the field of active interrogation on several fronts, most notably in the arenas of source development, systems integration, and the integration and exploitation of multiple fission and non-fission signatures. But penetration of interrogating radiation often comes at a cost, not only in terms of finance and dose but also in terms of induced backgrounds, system complexity, and extended measurement times (including set up and acquisition). These costs make the calculus for deciding to implement active interrogation more subtle than may be apparent. The purpose of this review is thus to examine existing interrogation methods, compare and contrast their attributes and limitations, and identify missions where active interrogation may hold the most promise. © 2011 Elsevier B.V. All rights reserved.


Pokorny R.,Institute of Chemical Technology Prague | Hrma P.,Pacific Northwest National Laboratory | Hrma P.,Pohang University of Science and Technology
Journal of Nuclear Materials | Year: 2012

The ultimate goal of studies of cold cap behavior in glass melters is to increase the rate of glass processing in an energy-efficient manner. Regrettably, mathematical models, which are ideal tools for assessing the responses of melters to process parameters, have not paid adequate attention to the cold cap. In this study, we consider a cold cap resting on a pool of molten glass from which it receives a steady heat flux while temperature, velocity, and extent of conversion are functions of the position along the vertical coordinate. A one-dimensional mathematical model simulates this process by solving the differential equations for mass and energy balances with appropriate boundary conditions and constitutive relationships for material properties. The sensitivity analyses on the effects of incoming heat fluxes to the cold cap through its lower and upper boundaries show that the cold cap thickness increases as the heat flux from above increases, and decreases as the total heat flux increases. We also discuss the effects of foam, originating from batch reactions and from redox reactions in molten glass, and argue that models must represent the foam layer to achieve a reliable prediction of the melting rate as a function of feed properties and melter conditions. © 2012 Elsevier B.V. All rights reserved.


Wu D.,Pacific Northwest National Laboratory | Aliprantis D.C.,Purdue University
Energy Policy | Year: 2013

This paper sets forth a family of models of light-duty plug-in electric vehicle (PEV) fleets, appropriate for conducting long-term national-level planning studies of the energy and transportation sectors in an integrated manner. Using one of the proposed models, three case studies on the evolution of the U.S. energy and transportation infrastructures are performed, where portfolios of optimum investments over a 40-year horizon are identified, and interdependencies between the two sectors are highlighted. The results indicate that with a gradual but aggressive introduction of PEVs coupled with investments in renewable energy, the total cost from the energy and transportation systems can be reduced by 5%, and that overall emissions from electricity generation and light-duty vehicle (LDV) tailpipes can be reduced by 10% over the 40-year horizon. The annual gasoline consumption from LDVs can be reduced by 66% by the end of the planning horizon, but an additional 800. TWh of annual electricity demand will be introduced. In addition, various scenarios of greenhouse gas (GHG) emissions reductions are investigated. It is found that GHG emissions can be significantly reduced with only a marginal cost increment, by shifting electricity generation from coal to renewable sources. © 2013 Elsevier Ltd.


Ewing R.P.,Iowa State University | Liu C.,Pacific Northwest National Laboratory | Hu Q.,University of Texas at Arlington
Water Resources Research | Year: 2012

Characterizing the diffusive exchange of solutes between bulk water in an aquifer and water in the intragranular pores of the solid phase is still challenging despite decades of study. Many disparities between observation and theory could be attributed to low connectivity of the intragranular pores. The presence of low connectivity indicates that a useful conceptual framework is percolation theory. The present study was initiated to develop a percolation-based finite difference (FD) model, and to test it rigorously against both random walk (RW) simulations of diffusion starting from nonequilibrium, and data on Borden sand published by Ball and Roberts (1991a,b) and subsequently reanalyzed by Haggerty and Gorelick (1995) using a multirate mass transfer (MRMT) approach. The percolation-theoretical model is simple and readily incorporated into existing FD models. The FD model closely matches the RW results using only a single fitting parameter, across a wide range of pore connectivities. Simulation of the Borden sand experiment without pore connectivity effects reproduced the MRMT analysis, but including low pore connectivity effects improved the fit. Overall, the theory and simulation results show that low intragranular pore connectivity can produce diffusive behavior that appears as if the solute had undergone slow sorption, despite the absence of any sorption process, thereby explaining some hitherto confusing aspects of intragranular diffusion. Copyright 2012 by the American Geophysical Union.


Oasmaa A.,VTT Technical Research Center of Finland | Kuoppala E.,VTT Technical Research Center of Finland | Elliott D.C.,Pacific Northwest National Laboratory
Energy and Fuels | Year: 2012

Methods for easily following the main changes in the composition, stability, and acidity of bio-oil as a result of hydrotreatment are presented in this paper. The methods provide the basis for the development of an analytical protocol, which can be used for bio-oil, as well as the hydrotreated products from bio-oil. The correlation to more conventional methods is provided; however, the use of these methods for the upgrading products is different than previously recognized. The differences in the properties of bio-oil and the hydrotreated products will also create challenges for the analytical protocol. Polar pyrolysis liquids and their hydrotreated products can be divided into five main groups with solvent fractionation, and the change in the proportions of the groups as a result of handling or processing is easy to follow. Over the past 10 years, this method has been successfully used for comparison of fast pyrolysis bio-oil quality and the changes during handling and storage and provides the basis of the analytical protocol presented in this paper. This paper describes the use of the method for characterization of bio-oil hydrotreatment products. A discussion of the use of gas chromatographic and spectroscopic methods is also included. In addition, fuel oil analyses suitable for fast pyrolysis bio-oils and hydrotreatment products are discussed. © 2012 American Chemical Society.


Srinivasan R.,Texas A&M University | Zhang X.,Pacific Northwest National Laboratory | Arnold J.,U.S. Department of Agriculture
Transactions of the ASABE | Year: 2010

Physically based, distributed hydrologic models are increasingly used in assessments of water resources, best management practices, and climate and land use changes. Model performance evaluation in ungauged basins is an important research topic. In this study, we propose a framework for developing Soil and Water Assessment Tool (SWAT) input data, including hydrography, terrain, land use, soil, tile, weather, and management practices, for the Upper Mississippi River basin (UMRB). We also present a performance evaluation of SWAT hydrologic budget and crop yield simulations in the UMRB without calibration. The uncalibrated SWAT model ably predicts annual streamflow at 11 USGS gauges and crop yield at a four-digit hydrologic unit code (HUC) scale. For monthly streamflow simulation, the performance of SWAT is marginally poor compared with that of annual flow, which may be due to incomplete information about reservoirs and dams within the UMRB. Further validation shows that SWAT can predict base flow contribution ratio reasonably well. Compared with three calibrated SWAT models developed in previous studies of the entire UMRB, the uncalibrated SWAT model presented here can provide similar results. Overall, the SWAT model can provide satisfactory predictions on hydrologic budget and crop yield in the UMRB without calibration. The results emphasize the importance and prospects of using accurate spatial input data for the physically based SWAT model. This study also examines biofuel-biomass production by simulating all agricultural lands with switchgrass, producing satisfactory results in estimating biomass availability for biofuel production. © 2010 American Society of Agricultural and Biological Engineers.


Shvartsburg A.A.,Pacific Northwest National Laboratory
Analytical Chemistry | Year: 2014

Biomacromolecules tend to assume numerous structures in solution or the gas phase. It has been possible to resolve disparate conformational families but not unique geometries within each, and drastic peak broadening has been the bane of protein analyses by chromatography, electrophoresis, and ion mobility spectrometry (IMS). The new differential or field asymmetric waveform IMS (FAIMS) approach using hydrogen-rich gases was recently found to separate conformers of a small protein ubiquitin with the same peak width and resolving power up to ∼400 as for peptides. The present work explores the reach of this approach for larger proteins, exemplified by cytochrome c and myoglobin. Resolution similar to that for ubiquitin was largely achieved with longer separations, while the onset of peak broadening and coalescence with shorter separations suggests the limitation of the present technique to proteins under ∼20 kDa. This capability may enable one to distinguish whole proteins with differing residue sequences or localizations of post-translational modifications. Small features at negative compensation voltages that markedly grow from cytochrome c to myoglobin indicate the dipole alignment of rare conformers in accord with theory, further supporting the concept of pendular macroions in FAIMS. © 2014 American Chemical Society.


Devaraj A.,Pacific Northwest National Laboratory | Devaraj A.,University of North Texas | Nag S.,University of North Texas | Banerjee R.,University of North Texas
Scripta Materialia | Year: 2013

Nucleation and growth of alpha precipitates during low-temperature annealing of Ti-10 at.% Mo-10 at.% Al alloy was investigated using direct coupling of transmission electron microscopy and atom probe tomography. The initial stages of annealing at 400 C showed structurally well-defined alpha precipitates that were depleted in Mo as well as Al, and were confined within the Ti-rich beta phase separated pockets. The Al-enriched alpha phase was only observed after further annealing at 600°C. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.


Zhang Z.F.,Pacific Northwest National Laboratory
Water Resources Research | Year: 2016

A surface barrier is a commonly used technology for isolation of subsurface contaminants. Surface barriers for isolating radioactive waste are expected to perform for centuries to millennia, yet there are very few data for field-scale surface barriers for periods approaching a decade or longer. The Prototype Hanford Barrier (PHB) with a design life of 1000 years was constructed over an existing radioactive waste site in 1994 to demonstrate its long-term performance. The primary element of the PHB is an evapotranspiration-capillary (ETC) barrier in which precipitation water is stored in a fine-textured soil layer and later released to the atmosphere via evapotranspiration. To address the barrier performance under extreme conditions, this study included an enhanced precipitation stress test from 1995 to 1997 to determine barrier response to extreme precipitation events. During this period a 1000 year 24 h return rainstorm was simulated in March every year. The loss of vegetation on barrier hydrology was tested with a controlled fire test in 2008. The 19 year monitoring record shows that the store-and-release mechanism worked as well as or better than the design criterion. Average drainage from the ETC barrier amounted to an average of 0.005 mm yr−1, which is well below the design criterion of 0.5 mm yr−1. After a simulated wildfire, the naturally reestablished vegetation and increased evaporation combined to release the stored water and summer precipitation to the atmosphere such that drainage did not occur in the 5 years subsequent to the fire. © 2016. American Geophysical Union. All Rights Reserved.


Greenwood M.S.,Pacific Northwest National Laboratory
Review of Scientific Instruments | Year: 2012

The pivotal experiment was performed with a setup in which a plastic cylinder was mounted on the top of a horizontal Rexolite plate and a transducer mounted directly below the cylinder; a single layer of stationary 1588-μm acrylic spheres was placed in the cylinder filled with water. Two well-separated signals were received by the transducer operating in the pulse-echo mode: (1) a signal due to the reflection from water at the interface and (2) a time-delayed signal resulting from the backscattering from the spheres of diameter D. The important observation was that the time delay was equal to 2 D/c using standard notation. A method was developed to use the FFT phase difference between the incident and scattered signals at the interface to determine the time-delay as a function of frequency, the backscattering coefficient M versus frequency, a particle size distribution, and an average value of the diameter. Experimental average diameter results are shown in the square brackets for nominal particle sizes: (1) 1588-μm acrylic spheres [1564 μm], (2) polystyrene spheres for diameters from 200 μm to 500 μm [260 μm-536 μm], (3) suspended slurry of 250-300 μm polystyrene spheres at 2.25 MHz [253 μm], (4) 794 μm [759 μm] and 1588-μm [1623 μm] Teflon spheres, (5) 1588-μm stainless steel spheres [1674 μm], and (6) suspended slurry of 250-300 μm polystyrene spheres [275 μm] at 3.5 MHz for seven volume fractions. Density and particle size measurements were obtained for the latter. For the density measurement, the FFT amplitude of the scattered signal was summed from 2 to 4 MHz for each slurry. A plot of the square root of the FFT-amplitude-sum versus the volume fraction yields a straight line, passing through the origin. A calibration of the experimental setup is obtained by fitting a straight line through the data with error bars. Thus, the volume fraction for a slurry of unknown concentration can be determined by measuring the FFT-amplitude-sum. The density of the slurry is obtained from the volume fraction. These results make it feasible to develop an online and real-time pipeline sensor to measure particle size and slurry density. © 2012 American Institute of Physics.


Coble J.B.,University of Tennessee at Knoxville | Fraga C.G.,Pacific Northwest National Laboratory
Journal of Chromatography A | Year: 2014

Preprocessing software, which converts large instrumental data sets into a manageable format for data analysis, is crucial for the discovery of chemical signatures in metabolomics, chemical forensics, and other signature-focused disciplines. Here, four freely available and published preprocessing tools known as MetAlign, MZmine, SpectConnect, and XCMS were evaluated for impurity profiling using nominal mass GC/MS data and accurate mass LC/MS data. Both data sets were previously collected from the analysis of replicate samples from multiple stocks of a nerve-agent precursor and method blanks. Parameters were optimized for each of the four tools for the untargeted detection, matching, and cataloging of chromatographic peaks from impurities present in the stock samples. The peak table generated by each preprocessing tool was analyzed to determine the number of impurity components detected in all replicate samples per stock and absent in the method blanks. A cumulative set of impurity components was then generated using all available peak tables and used as a reference to calculate the percent of component detections for each tool, in which 100% indicated the detection of every known component present in a stock. For the nominal mass GC/MS data, MetAlign had the most component detections followed by MZmine, SpectConnect, and XCMS with detection percentages of 83, 60, 47, and 41%, respectively. For the accurate mass LC/MS data, the order was MetAlign, XCMS, and MZmine with detection percentages of 80, 45, and 35%, respectively. SpectConnect did not function for the accurate mass LC/MS data. Larger detection percentages were obtained by combining the top performer with at least one of the other tools such as 96% by combining MetAlign with MZmine for the GC/MS data and 93% by combining MetAlign with XCMS for the LC/MS data. In terms of quantitative performance, the reported peak intensities from each tool had averaged absolute biases (relative to peak intensities obtained using instrument software) of 41, 4.4, 1.3 and 1.3% for SpectConnect, MetAlign, XCMS, and MZmine, respectively, for the GC/MS data. For the LC/MS data, the averaged absolute biases were 22, 4.5, and 3.1% for MetAlign, MZmine, and XCMS, respectively. In summary, MetAlign performed the best in terms of the number of component detections; however, more than one preprocessing tool should be considered to avoid missing impurities or other trace components as potential chemical signatures. © 2014 Elsevier B.V.


Choi D.,Pacific Northwest National Laboratory | Kumta P.N.,University of Pittsburgh
Journal of the American Ceramic Society | Year: 2011

Nanosized NbNx (1.64>x>1.33) and MoNx (1.32>x>0.77) crystallites were synthesized at a relatively low temperature (≥yen;600°C) through ammonolysis and nitridation of the corresponding metal chlorides. The ammonolysis reaction in anhydrous chloroform at room temperature and the nitridation mechanism during subsequent heat treatment was investigated using Fourier transform infrared spectroscopy, X-ray diffraction (XRD), thermogravimetric (TG), and mass spectroscopy analysis. The effects of the synthesis parameters on the stoichiometry, structure, specific surface area, density, and electronic conductivity of the final nitrides were studied using TGA, XRD, N2 adsorption, high-resolution transmission microscopy, helium pycnometry, and four-point probe technique. Preliminary electrochemical responses of the obtained nitrides were studied using cyclic voltammetry to explore their possible use as electrochemical capacitors. © 2011 The American Ceramic Society.


Lindemann S.R.,Pacific Northwest National Laboratory
ISME Journal | Year: 2016

Much research has been invested into engineering microorganisms to perform desired biotransformations; nonetheless, these efforts frequently fall short of expected results due to the unforeseen effects of biofeedback regulation and functional incompatibility. In nature, metabolic function is compartmentalized into diverse organisms assembled into robust consortia, in which the division of labor is thought to lead to increased community efficiency and productivity. Here we consider whether and how consortia can be designed to perform bioprocesses of interest beyond the metabolic flexibility limitations of a single organism. Advances in post-genomic analysis of microbial consortia and application of high-resolution global measurements now offer the promise of systems-level understanding of how microbial consortia adapt to changes in environmental variables and inputs of carbon and energy. We argue that, when combined with appropriate modeling frameworks, systems-level knowledge can markedly improve our ability to predict the fate and functioning of consortia. Here we articulate our collective perspective on the current and future state of microbial community engineering and control while placing specific emphasis on ecological principles that promote control over community function and emergent properties.The ISME Journal advance online publication, 11 March 2016; doi:10.1038/ismej.2016.26. © 2016 International Society for Microbial Ecology


Aquino F.,State University of New York at Buffalo | Govind N.,Pacific Northwest National Laboratory | Autschbach J.,State University of New York at Buffalo
Journal of Chemical Theory and Computation | Year: 2011

Density functional theory (DFT) calculations of NMR chemical shifts and molecular g tensors with Gaussian-type orbitals are implemented via second-order energy derivatives within the scalar relativistic zeroth order regular approximation (ZORA) framework. Nonhybrid functionals, standard (global) hybrids, and range-separated (Coulomb-attenuated, long-range corrected) hybrid functionals are tested. Origin invariance of the results is ensured by use of gauge-including atomic orbital (GIAO) basis functions. The new implementation in the NWChem quantum chemistry package is verified by calculations of nuclear shielding constants for the heavy atoms in HX (X = F, Cl, Br, I, At) and H 2X (X = O, S, Se, Te, Po) and 125Te chemical shifts in a number of tellurium compounds. The basis set and functional dependence of g-shifts is investigated for 14 radicals with light and heavy atoms. The problem of accurately predicting 19F NMR shielding in UF 6-nCln, n = 1-6, is revisited. The results are sensitive to approximations in the density functionals, indicating a delicate balance of DFT self-interaction vs correlation. For the uranium halides, the range-separated functionals are not clearly superior to global hybrids. © 2011 American Chemical Society.


Adams S.M.,Oak Ridge National Laboratory | Ham K.D.,Pacific Northwest National Laboratory
Environmental Management | Year: 2011

Recovery dynamics in a previously disturbed stream were investigated to determine the influence of a series of remedial actions on stream recovery and to evaluate the potential application of bioindicators as an environmental management tool. A suite of bioindicators, representing five different functional response groups, were measured annually for a sentinel fish species over a 15 year period during which a variety of remedial and pollution abatement actions were implemented. Trends in biochemical, physiological, condition, growth, bioenergetic, and nutritional responses demonstrated that the health status of a sentinel fish species in the disturbed stream approached that of fish in the reference stream by the end of the study. Two major remedial actions, dechlorination and water flow management, had large effects on stream recovery resulting in an improvement in the bioenergetic, disease, nutritional, and organ condition status of the sentinel fish species. A subset of bioindicators responded rather dramatically to temporal trends affecting all sites, but some indicators showed little response to disturbance or to restoration activities. In assessing recovery of aquatic systems, application of appropriate integrative structural indices along with a variety of sensitive functional bioindicators should be used to understand the mechanistic basis of stress and recovery and to reduce the risk of false positives. Understanding the mechanistic processes involved between stressors, stress responses of biota, and the recovery dynamics of aquatic systems reduces the uncertainty involved in environmental management and regulatory decisions resulting in an increased ability to predict the consequences of restoration and remedial actions for aquatic systems. © 2011 Springer Science+Business Media, LLC.


Croy J.R.,Argonne National Laboratory | Abouimrane A.,Argonne National Laboratory | Zhang Z.,Pacific Northwest National Laboratory
MRS Bulletin | Year: 2014

The commercialization of lithium-ion batteries has intimately changed our lives and enabled portable electronic devices, which has revolutionized communications, entertainment, medicine, and more. After three decades of commercial development, researchers around the world are now pursuing major advances that would allow this technology to power the next generation of light-duty, electric, and hybrid-electric vehicles. If this goal is to be met, concerted advances in safety and cost, as well as cycle-life and energy densities, must be realized through advances in the properties of the highly correlated, but separate, components of lithium-ion energy-storage systems. © 2014 Materials Research Society.


Vaughey J.T.,Argonne National Laboratory | Liu G.,Lawrence Berkeley National Laboratory | Zhang J.-G.,Pacific Northwest National Laboratory
MRS Bulletin | Year: 2014

The success of high capacity energy storage systems based on lithium (Li) batteries relies on the realization of the promise of Li-metal anodes. Li metal has many advantageous properties, including an extremely high theoretical specific capacity (3860 mAh g-1), the lowest electrochemical potential (-3.040 V versus standard hydrogen electrode), and low density (0.59 g cm-3), which, all together, make it a very desirable electrode for energy storage devices. However, while primary Li batteries are used for numerous commercial applications, rechargeable Li-metal batteries that utilize Li-metal anodes have not been as successful. This article discusses the properties of Li metal in the absence of surface stabilization, as well as three different approaches currently under investigation for stabilizing the surface of Li metal to control its reactivity within the electrochemical environment of a Li-based battery. © 2014 Materials Research Society.


We rely on a hierarchical approach to identify the low-lying isomers and corresponding global minima of the pentagonal dodecahedron (H 2O) 20 and the H 3O +(H 2O) 20 nanoclusters. Initial screening of the isomers is performed using classical interaction potentials, namely the Transferable Interaction 4-site Potential (TIP4P), the Thole-Type Flexible Model, versions 2.0 (TTM2-F) and 2.1 (TTM2.1-F) for (H 2O) 20 and the Anisotropic Site Potential (ASP) for H 3O +(H 2O) 20. The nano-networks obtained with those potentials were subsequently refined at the density functional theory (DFT) with the Becke-3-parameter Lee-Yang-Parr (B3LYP) functional and at the second order Møller-Plesset perturbation (MP2) levels of theory. For the pentagonal dodecahedron (H 2O) 20 it was found that DFT (B3LYP) and MP2 produced the same global minimum. However, this was not the case for the H 3O +(H 2O) 20 cluster, for which MP2 produced a different network for the global minimum when compared to DFT (B3LYP). The low-lying networks of H 3O +(H 2O) 20 correspond to structures having 9 'free' OH bonds and the hydronium ion on the surface of the nanocluster. The IR spectra of the various networks are further analysed in the OH stretching ('fingerprint') region and the various bands are assigned to structural arrangements of the underlying hydrogen bonding network. © 2012 Canadian Society for Chemical Engineering.


Geelhood K.,Pacific Northwest National Laboratory
Nuclear Engineering and Technology | Year: 2011

FRAPCON-3.4a and FRAPTRAN 1.4 are the most recent versions of the U.S. Nuclear Regulatory Commission (NRC) steady-state and transient fuel performance codes, respectively. These codes have been assessed against separate effects data and integral assessment data and have been determined to provide a best estimate calculation of fuel performance. Recent updates included in FRAPCON-3.4a include updated material properties models, models for new fuel and cladding types, cladding finite element analysis capability, and capability to perform uncertainty analyses and calculate upper tolerance limits for important outputs. Recent updates included in FRAPTRAN 1.4 include: material properties models that are consistent with FRAPCON-3.4a, cladding failure models that are applicable for loss-of coolant-accident and reactivity initiated accident modeling, and updated heat transfer models. This paper briefly describes these code updates and data assessments, highlighting the particularly important improvements and data assessments. This paper also discusses areas of improvements that will be addressed in upcoming code versions.


Henderson M.A.,Pacific Northwest National Laboratory
Journal of Physical Chemistry C | Year: 2011

The chemistry of trimethyl phosphate (TMP) was examined on the (012) crystallographic face of hematite (α-Fe 2O 3) using temperature-programmed desorption (TPD), high resolution electron energy loss spectroscopy (HREELS), static secondary ion mass spectrometry (SSIMS), and Auger electron spectroscopy (AES). TMP adsorbed at Fe 3+ sites on the clean α-Fe 2O 3(012) surface through lone pair electrons on the P=O oxygen atom. A small portion of adsorbed TMP desorbed without decomposition; however, the majority of adsorbed TMP decomposed on the clean surface in a two-step process. The first step, occurring at or below room temperature, involved displacement of one methoxy group of TMP to form a surface methoxy and adsorbed dimethyl phosphate (DMP). In the second step, adsorbed DMP decomposed above 500 K to a 1:1 ratio of gaseous methanol and formaldehyde leaving phosphate on the surface. The phosphate was stable on the α-Fe 2O 3(012) surface to 950 K. Identification of these steps was assisted by using the chemistry of methanol on the clean surface. Coadsorption of TMP and water led to a small degree of hydrolysis between these two molecules in the multilayer but no significant changes in the chemistry of TMP molecules adsorbed on the surface. © 2011 American Chemical Society.


Wick C.D.,Louisiana Tech University | Dang L.X.,Pacific Northwest National Laboratory
Journal of Chemical Physics | Year: 2010

Molecular dynamics simulations with a polarizable multistate empirical valence-bond model were carried out to investigate NaOH dissociation and pairing in water bulk and at the air-water interface. It was found that NaOH readily dissociates in the bulk and the effect of the air-water interface on NaOH dissociation is fairly minor. Also, NaOH complexes were found to be strongly repelled from the air-water interface, which is consistent with surface tension measurements. At the same time, a very strong preference for the hydroxide anion to be oriented toward the air was found that persisted a few angstroms toward the liquid from the Gibbs dividing surface of the air-water interface. This was due to a preference for the hydroxide anion to have its hydrogen pointing toward the air and the fact that the sodium ion was more likely to be found near the hydroxide oxygen than hydrogen. As a consequence, the simulation results show that surfaces of NaOH solutions should be negatively charged, in agreement with experimental observations, but also that the hydroxide has little surface affinity. This provides the possibility that the surface of water can be devoid of hydroxide anions, but still have a strong negative charge. © 2010 American Institute of Physics.


Tierny J.,Telecom ParisTech | Pascucci V.,Pacific Northwest National Laboratory
IEEE Transactions on Visualization and Computer Graphics | Year: 2012

We present a combinatorial algorithm for the general topological simplification of scalar fields on surfaces. Given a scalar field ƒ, our algorithm generates a simplified field g that provably admits only critical points from a constrained subset of the singularities of ƒ, while guaranteeing a small distance ||ƒ- g||∞ for data-fitting purpose. In contrast to previous algorithms, our approach is oblivious to the strategy used for selecting features of interest and allows critical points to be removed arbitrarily. When topological persistence is used to select the features of interest, our algorithm produces a standard ∊-simplification. Our approach is based on a new iterative algorithm for the constrained reconstruction of sub-and sur-level sets. Extensive experiments show that the number of iterations required for our algorithm to converge is rarely greater than 2 and never greater than 5, yielding O(n log(n)) practical time performances. The algorithm handles triangulated surfaces with or without boundary and is robust to the presence of multi-saddles in the input. It is simple to implement, fast in practice and more general than previous techniques. Practically, our approach allows a user to arbitrarily simplify the topology of an input function and robustly generate the corresponding simplified function. An appealing application area of our algorithm is in scalar field design since it enables, without any threshold parameter, the robust pruning of topological noise as selected by the user. This is needed for example to get rid of inaccuracies introduced by numerical solvers, thereby providing topological guarantees needed for certified geometry processing. Experiments show this ability to eliminate numerical noise as well as validate the time efficiency and accuracy of our algorithm. We provide a lightweight C++ implementation as supplemental material that can be used for topological cleaning on surface meshes. © 2012 IEEE.


Burrows S.M.,Max Planck Institute for Chemistry | Burrows S.M.,Pacific Northwest National Laboratory | Hoose C.,Karlsruhe Institute of Technology | Poschl U.,Max Planck Institute for Chemistry | And 2 more authors.
Atmospheric Chemistry and Physics | Year: 2013

Ice nuclei impact clouds, but their sources and distribution in the atmosphere are still not well known. Particularly little attention has been paid to IN sources in marine environments, although evidence from field studies suggests that IN populations in remote marine regions may be dominated by primary biogenic particles associated with sea spray. In this exploratory model study, we aim to bring attention to this long-neglected topic and identify promising target regions for future field campaigns. We assess the likely global distribution of marine biogenic ice nuclei using a combination of historical observations, satellite data and model output. By comparing simulated marine biogenic immersion IN distributions and dust immersion IN distributions, we predict strong regional differences in the importance of marine biogenic IN relative to dust IN. Our analysis suggests that marine biogenic IN are most likely to play a dominant role in determining IN concentrations in near-surface-air over the Southern Ocean, so future field campaigns aimed at investigating marine biogenic IN should target that region. Climate-related changes in the abundance and emission of biogenic marine IN could affect marine cloud properties, thereby introducing previously unconsidered feedbacks that influence the hydrological cycle and the Earth's energy balance. Furthermore, marine biogenic IN may be an important aspect to consider in proposals for marine cloud brightening by artificial sea spray production. © 2013 Author(s).


Chambers S.A.,Pacific Northwest National Laboratory
Surface Science | Year: 2011

The observation of conductivity at (001)-oriented interfaces of the 2 band insulators LaAlO3 and SrTiO3 is both fascinating and potentially useful for next-generation electronics. The paradigm commonly used to explain this phenomenon is an electronic reconstruction resulting from the instability created by forming an interface of polar and nonpolar perovskites, leading to the formation of a two-dimensional electron gas. This explanation has typically been conceptualized within the framework of an atomically abrupt interface. However, a significant and growing body of data now exists which reveals that the interface is not abrupt, and that all four cations diffuse across the interface. Yet, the potential roles of the resulting defects and dopants in alleviating the polar catastrophe and promoting conductivity are rarely considered. The purpose of this prospective is to take an overview of the field from outside the reigning paradigm and consider ways in which dopants and defects might affect the electronic structure. © 2011 Elsevier B.V.


Refaely-Abramson S.,Weizmann Institute of Science | Sharifzadeh S.,Lawrence Berkeley National Laboratory | Govind N.,Pacific Northwest National Laboratory | Autschbach J.,State University of New York at Buffalo | And 3 more authors.
Physical Review Letters | Year: 2012

We present a method for obtaining outer-valence quasiparticle excitation energies from a density-functional-theory-based calculation, with an accuracy that is comparable to that of many-body perturbation theory within the GW approximation. The approach uses a range-separated hybrid density functional, with an asymptotically exact and short-range fractional Fock exchange. The functional contains two parameters, the range separation and the short-range Fock fraction. Both are determined nonempirically, per system, on the basis of the satisfaction of exact physical constraints for the ionization potential and frontier-orbital many-electron self-interaction, respectively. The accuracy of the method is demonstrated on four important benchmark organic molecules: perylene, pentacene, 3,4,9,10-perylene-tetracarboxylic-dianydride (PTCDA), and 1,4,5,8-naphthalene-tetracarboxylic-dianhydride (NTCDA). We envision that for the outer-valence excitation spectra of finite systems the approach could provide an inexpensive alternative to GW, opening the door to the study of presently out of reach large-scale systems. © 2012 American Physical Society.


Lu N.,Pacific Northwest National Laboratory
IEEE Transactions on Smart Grid | Year: 2012

This paper investigates the potential of providing intra-hour load balancing services using aggregated heating, ventilating, and air-conditioning (HVAC) loads. A directload control algorithm is presented. A temperature-priority-list method is used to dispatch the HVAC loads optimally to maintain customer-desired indoor temperatures and load diversity. Realistic intra-hour load balancing signals are used to evaluate the operational characteristics of the HVAC load under different outdoor temperature profiles and different indoor temperature settings. The number of HVAC units needed is also investigated. Modeling results suggest that the number of HVAC units needed to provide a ±1-MW load balancing service 24 hours a day varies significantly with baseline settings, high and low temperature settings, and outdoor temperatures. The results demonstrate that the intra-hour load balancing service provided by HVAC loads meets the performance requirements and can become a major source of revenue for load-serving entities where the two-way communication smart grid infrastructure enables direct load control over the HVAC loads. © 2010-2012 IEEE.


De Anna P.,CNRS Geosciences Laboratory of Rennes | De Anna P.,Massachusetts Institute of Technology | Le Borgne T.,CNRS Geosciences Laboratory of Rennes | Dentz M.,Spanish National Research Council IDAeA CSIC | And 3 more authors.
Physical Review Letters | Year: 2013

We study the intermittency of fluid velocities in porous media and its relation to anomalous dispersion. Lagrangian velocities measured at equidistant points along streamlines are shown to form a spatial Markov process. As a consequence of this remarkable property, the dispersion of fluid particles can be described by a continuous time random walk with correlated temporal increments. This new dynamical picture of intermittency provides a direct link between the microscale flow, its intermittent properties, and non-Fickian dispersion. © 2013 American Physical Society.


Yang F.,Michigan Technological University | Ovchinnikov M.,Pacific Northwest National Laboratory | Shaw R.A.,Michigan Technological University
Geophysical Research Letters | Year: 2013

The question of whether persistent ice crystal precipitation from supercooled layer clouds can be explained by time-dependent, stochastic ice nucleation is explored using an approximate, analytical model and a large-eddy simulation (LES) cloud model. The updraft velocity in the cloud defines an accumulation zone, where small ice particles cannot fall out until they are large enough, which will increase the residence time of ice particles in the cloud. Ice particles reach a quasi-steady state between growth by vapor deposition and fall speed at cloud base. The analytical model predicts that ice water content (wi) has a 2.5 power-law relationship with ice number concentration (ni). wi and ni from a LES cloud model with stochastic ice nucleation confirm the 2.5 power-law relationship, and initial indications of the scaling law are observed in data from the Indirect and Semi-Direct Aerosol Campaign. The prefactor of the power law is proportional to the ice nucleation rate and therefore provides a quantitative link to observations of ice microphysical properties. © 2013. American Geophysical Union. All Rights Reserved.


Gao Y.,University of Tennessee at Knoxville | Gao Y.,Pacific Northwest National Laboratory | Fu J.S.,University of Tennessee at Knoxville | Drake J.B.,University of Tennessee at Knoxville | And 2 more authors.
Atmospheric Chemistry and Physics | Year: 2013

Dynamical downscaling was applied in this study to link the global climate-chemistry model Community Atmosphere Model (CAM-Chem) with the regional models Weather Research and Forecasting (WRF) Model and Community Multi-scale Air Quality (CMAQ). Two representative concentration pathway (RCP) scenarios (RCP 4.5 and RCP 8.5) were used to evaluate the climate impact on ozone concentrations in the 2050s.

From the CAM-Chem global simulation results, ozone concentrations in the lower to mid-troposphere (surface to ∼300 hPa), from mid-to high latitudes in the Northern Hemisphere, decreases by the end of the 2050s (2057-2059) in RCP 4.5 compared to present (2001-2004), with the largest decrease of 4-10 ppbv occurring in the summer and the fall; and an increase as high as 10 ppbv in RCP 8.5 resulting from the increased methane emissions.

From the regional model CMAQ simulation results, under the RCP 4.5 scenario (2057-2059), in the summer when photochemical reactions are the most active, the large ozone precursor emissions reduction leads to the greatest decrease of downscaled surface ozone concentrations compared to present (2001-2004), ranging from 6 to 10 ppbv. However, a few major cities show ozone increases of 3 to 7 ppbv due to weakened NO titration. Under the RCP 8.5 scenario, in winter, downscaled ozone concentrations increase across nearly the entire continental US in winter, ranging from 3 to 10 ppbv due to increased methane emissions. More intense heat waves are projected to occur by the end of the 2050s in RCP 8.5, leading to a 0.3 ppbv to 2.0 ppbv increase (statistically significant except in the Southeast) of the mean maximum daily 8 h daily average (MDA8) ozone in nine climate regions in the US. Moreover, the upper 95% limit of MDA8 increase reaches 0.4 ppbv to 1.5 ppbv in RCP 4.5 and 0.6 ppbv to 3.2 ppbv in RCP 8.5. The magnitude differences of increase between RCP 4.5 and 8.5 also reflect that the increase of methane emissions may favor or strengthen the effect of heat waves. © Author(s) 2013.


Shao S.,Washington State University | Abdolrahim N.,Washington State University | Bahr D.F.,Purdue University | Lin G.,Pacific Northwest National Laboratory | Zbib H.M.,Washington State University
International Journal of Plasticity | Year: 2014

Recent studies of micro- and nano-scale metallic structures have exposed considerable statistical distribution, in addition to significant size dependencies, in the yield strength. This intrinsic statistical variation is particularly evident in the micro-compression and microtension thin film tests. This work investigates the relationship between the initial dislocation density, the heterogeneous initial spatial dislocation distribution, and the resulting localized deformation with multiscale discrete dislocation dynamics simulations. This relationship is examined separately from commonly reported external factors affecting observed strength, such as variations in specimen geometry and base support. Towards this end, we performed multiscale dislocation dynamics simulations of geometries commonly employed in micro-scale testing techniques, including micro-pillar compression, microtensile thin film, and microbulge tests. The statistical variation of yield strengths from all three simulation geometries is in agreement with experimental data from the corresponding loading techniques. We show that the onset of plasticity is stochastic in small volumes containing a small density of dislocations: a contrast to classical deterministic plasticity theory. The yield stress in these small volumes is stochastic, not deterministic, because of statistical variation of the initial dislocation content. The numerical results exhibit a localized deformation process and demonstrate a strong dependence of the yield stress on the initial dislocation density, the initial dislocation spatial distribution, and the specimen geometry size. Leveraging nucleation theory, a stochastic model for the onset of plasticity in micro- and nano-scale structures is developed based on these results. © 2013 Elsevier Ltd. All rights reserved.


Wang Y.,University of Nebraska - Lincoln | Wang Y.,Pacific Northwest National Laboratory | Liu X.,University of Nebraska - Lincoln | Burton J.D.,University of Nebraska - Lincoln | And 2 more authors.
Physical Review Letters | Year: 2012

We explore the effect of charge carrier doping on ferroelectricity using density functional calculations and phenomenological modeling. By considering a prototypical ferroelectric material, BaTiO3, we demonstrate that ferroelectric displacements are sustained up to the critical concentration of 0.11 electron per unit cell volume. This result is consistent with experimental observations and reveals that the ferroelectric phase and conductivity can coexist. Our investigations show that the ferroelectric instability requires only a short-range portion of the Coulomb force with an interaction range of the order of the lattice constant. These results provide a new insight into the origin of ferroelectricity in displacive ferroelectrics and open opportunities for using doped ferroelectrics in novel electronic devices. © 2012 American Physical Society.


Whalen S.A.,Pacific Northwest National Laboratory | Dykhuizen R.C.,Sandia National Laboratories
Energy Conversion and Management | Year: 2012

We built and tested a subterranean thermoelectric power source that converts diurnal heat flow through the upper soil layer into electricity. This paper describes the operation, design, and performance of the device. Key features of the power source include the use of bismuth-telluride thermopiles optimized for small ΔT and aerogel insulation to minimize thermal losses. The device weighs 0.24 kg and was designed with a flat form factor measuring 12 × 12 × 1.7 cm to facilitate modularity, packing, and assembly into larger arrays. One full year of field testing was performed between June 2009 and May 2010 in Albuquerque, New Mexico where the device generated an average power output of 1.1 mW. The season with the highest performance was spring (March-May) while the season of lowest performance was winter (November-January). During May 2010, the device generated an average power of 1.5 mW and a peak power of 9.8 mW at 9.3 V. Ten years of continuous operation at 1.1 mW would yield an energy density and specific energy of 1384 W h/L and 1430 W h/kg respectively, which is competitive with chemical batteries and is orders of magnitude greater than published subterranean and ambient thermoelectric harvesters. Numerical simulations show that performance is sensitive to the thermal properties of the soil and environmental conditions. This class of energy harvester may provide an option for supplemental power, or possibly primary power, for low power remote sensing applications. © 2012 Elsevier Ltd. All rights reserved.


Werhahn J.C.,TU Munich | Pandelov S.,TU Munich | Xantheas S.S.,Pacific Northwest National Laboratory | Iglev H.,TU Munich
Journal of Physical Chemistry Letters | Year: 2011

The properties of three distinct types of hydrogen bonds, namely a weak, a bifurcated, and a strong one, all present in the LiNO3·(HDO) (D2O)2 hydrate lattice unit cell are studied using steady-state and time-resolved spectroscopy. The lifetimes of the OH stretching vibrations for the three individual bonds are 2.2 ps (weak), 1.7 ps (bifurcated), and 1.2 ps (strong). For the first time, the properties of bifurcated H bonds can thus be unambiguously directly compared to those of weak and strong H bonds in the same system. The values of their OH stretching vibration lifetime, anharmonicity, red shift, and bond strength lie between those for the strong and weak H bonds. The experimentally observed inhomogeneous broadening of their spectral signature can be partly attributed to the coupling with a low frequency intermolecular wagging vibration. © 2011 American Chemical Society.


Pryor K.H.,Pacific Northwest National Laboratory
Health Physics | Year: 2015

Sealed radioactive sources are used in a wide variety of occupational settings and under differing regulatory/licensing structures. The definition of a sealed radioactive source varies between U.S. regulatory authorities and standard-setting organizations. Potential problems with sealed sources cover a range of risks and impacts. The loss of control of high activity sealed sources can result in very high or even fatal doses to members of the public who come in contact with them. Sources that are not adequately sealed and that fail can cause spread of contamination and potential intake of radioactive material. There is also the possibility that sealed sources may be (or threaten to be) used for terrorist purposes and disruptive opportunities. Until fairly recently, generally licensed sealed sources and devices received little, if any, regulatory oversight and were often forgotten, lost or unaccounted for. Nonetheless, generally licensed devices can contain fairly significant quantities of radioactive material, and there is some potential for exposure if a device is treated in a way for which it was never designed. Industrial radiographers use and handle high activity and/or high dose-rate sealed sources in the field with a high degree of independence and minimal regulatory oversight. Failure to follow operational procedures and properly handle radiography sources can and has resulted in serious injuries and death. Industrial radiographers have experienced a disproportionately large fraction of incidents that have resulted in unintended exposure to radiation. Sources do not have to contain significant quantities of radioactive material to cause problems in the event of their failure. A loss of integrity can cause the spread of contamination and potential exposure to workers and members of the public. The National Council on Radiation Protection and Measurements has previously provided recommendations on select aspects of sealed source programs. Future efforts to provide recommendations for sealed source programs are discussed. © 2014 Health Physics Society.


Bulgac A.,University of Washington | Luo Y.-L.,University of Washington | Roche K.J.,University of Washington | Roche K.J.,Pacific Northwest National Laboratory
Physical Review Letters | Year: 2012

We show that in the collision of two superfluid fermionic atomic clouds one observes the formation of quantum shock waves as discontinuities in the number density and collective flow velocity. Domain walls, which are topological excitations of the superfluid order parameter, are also generated and exhibit abrupt phase changes by π and slower motion than the shock waves. The domain walls are distinct from the gray soliton train or number density ripples formed in the wake of the shock waves and observed in the collisions of superfluid bosonic atomic clouds. Domain walls with opposite phase jumps appear to collide elastically. © 2012 American Physical Society.


Mardirossian N.,University of California at Berkeley | Lambrecht D.S.,University of Pittsburgh | McCaslin L.,University of Texas at Austin | Xantheas S.S.,Pacific Northwest National Laboratory | Head-Gordon M.,University of California at Berkeley
Journal of Chemical Theory and Computation | Year: 2013

The performance of 24 density functionals, Hartree-Fock, and MP2 is assessed with respect to the CCSD(T)/CBS* energetics of 49 sulfate-water clusters with three to six water molecules. Included among the density functionals are GGA, meta-GGA, hybrid GGA, hybrid meta-GGA, and double hybrid density functionals, as well as the LDA. Three types of dispersion corrections (VV10, XDM, and -D) are tested in conjunction with these functionals. The 26 methods are compared using the relative and binding energies of the sulfate-water clusters as the main criteria. It was discovered that a majority of the tested density functionals are unable to simultaneously capture the physics necessary to describe both the relative and binding energies of the anionic solvation clusters. The three density functionals with the best overall performance are XYG3, ωB97X-2, and XYGJ-OS. The only other density functional that performs comparably to these three double hybrids is M11. A majority of the density functionals that contain a fraction of exact exchange tend to perform well only for the relative energies, while functionals lacking exact exchange generally perform poorly with respect to both criteria. However, the meta-GGA functional, M11-L, stands out due to its superior performance for the relative energies. While dispersion correction functionals cannot replace the accuracy provided by MP2 correlation, it is shown that the proper combination of a hybrid GGA functional (LC-ωPBE) with a dispersion correction functional (VV10) can lead to drastic improvements in the binding energies of the parent functional, while preserving its performance with respect to the relative energies. Ultimately, however, MP2 has the best overall performance out of the 26 benchmarked methods. © 2013 American Chemical Society.


Nielsen L.C.,Stanford University | De Yoreo J.J.,Pacific Northwest National Laboratory | DePaolo D.J.,Lawrence Berkeley National Laboratory | DePaolo D.J.,University of California at Berkeley
Geochimica et Cosmochimica Acta | Year: 2013

The concentrations of Sr, Mg and other elements in calcite are widely used to infer the conditions of mineral growth. However, such inferences are dependent on the mechanisms that govern the incorporation of minor constituents into the calcite lattice during growth. A particularly confusing observation is that both Sr and Mg are readily incorporated into growing calcite crystals at low concentrations but inhibit calcite growth at higher concentrations. Here we show that the growth rate dependence of Sr and Mg incorporation into calcite, as well the inhibitory effects on calcite growth of both incorporating and non-incorporating ions, can be predicted with an ion-by-ion crystal growth model where ion attachment is confined to kink sites on the crystal surface.The exchange of ions between active growth (kink) sites on the mineral surface and aqueous solution governs both the efficiency of incorporation of minor constituents and the kinetics of mineral precipitation. Ions such as Sr and Mg in calcite, that are not stoichiometric constituents, may attach to kink sites and impede crystal growth by either blocking propagation of the kink (kink blocking), or if incorporated into the growing mineral, straining the local crystal lattice, and hence increasing the mineral solubility (incorporation inhibition). Here we investigate the effects of including these growth inhibition mechanisms into a microscopic model for crystal growth based on kink creation, propagation and collision (CPC) theory. This model predicts that kink blocking by either incorporated or non-incorporated ions causes an exponential decrease in mineral growth rate with increasing impurity concentration, while incorporation inhibition results in more complicated functional forms of the growth rate effect depending on the thermodynamics of the solid solution. Applying this model to existing data on the partitioning of strontium and magnesium into calcite and the simultaneous effects on growth kinetics and mineral composition, we find that strontium uptake inhibits growth by enhancing mineral solubility while magnesium inhibits growth primarily by kink blocking. Our model should be widely applicable to understanding the impurity content of a large range of sparingly soluble minerals that form by precipitation from aqueous solutions. © 2013 Elsevier Ltd.


Severa G.,University of Hawaii at Manoa | Ronnebro E.,Sandia National Laboratories | Ronnebro E.,Pacific Northwest National Laboratory | Jensen C.M.,University of Hawaii at Manoa
Chemical Communications | Year: 2010

Conditions have been found whereby it is possible to reversibly store >11 wt% hydrogen through the direct hydrogenation of MgB2 to Mg(BH4)2. © 2010 The Royal Society of Chemistry.


Wang S.-Y.,Utah State University | L'heureux M.,National Oceanic and Atmospheric Administration | Yoon J.-H.,Pacific Northwest National Laboratory
Journal of Climate | Year: 2013

Using multiple observational and model datasets, the authors document a strengthening relationship between boreal winter sea surface temperature anomalies (SSTAs) in the western North Pacific (WNP) and the development of the El Ni~no-Southern Oscillation (ENSO) in the following year. The increased WNP-ENSO association emerged in the mid-twentieth century and has grown through the present, reaching correlation coefficients as high as ;0.70 in recent decades. Fully coupled climate experiments with the Community Earth System Model, version 1 (CESM1), replicate the WNP-ENSO association and indicate that greenhouse gases (GHGs) are largely responsible for this observed increase. The authors speculate that shifts in the location of the largest positive SST trends between the subtropical and tropical western Pacific impact the low-level circulation in a manner that reinforces the link between the WNP and the development of ENSO. A strengthened GHG-driven relationship with the WNP provides an example of how anthropogenic climate change may directly influence one of the most prominent patterns of natural climate variability, ENSO, and potentially improve the skill of intraseasonal-to-interannual climate prediction .© 2013 American Meteorological Society.


Sun J.,Washington State University | Wang Y.,Washington State University | Wang Y.,Pacific Northwest National Laboratory
ACS Catalysis | Year: 2014

With increased availability and decreased cost, ethanol is potentially a promising platform molecule for the production of a variety of value-added chemicals. In this review, we provide a detailed summary of recent advances in catalytic conversion of ethanol to a wide range of chemicals and fuels. We particularly focus on catalyst advances and fundamental understanding of reaction mechanisms involved in ethanol steam reforming (ESR) to produce hydrogen, ethanol conversion to hydrocarbons ranging from light olefins to longer chain alkenes/alkanes and aromatics, and ethanol conversion to other oxygenates including 1-butanol, acetaldehyde, acetone, diethyl ether, and ethyl acetate. © 2014 American Chemical Society.


Ferguson R.M.,University of Washington | Minard K.R.,Pacific Northwest National Laboratory | Khandhar A.P.,University of Washington | Krishnan K.M.,University of Washington
Medical Physics | Year: 2011

Purpose: Magnetic particle imaging (MPI), using magnetite nanoparticles (MNPs) as tracer material, shows great promise as a platform for fast tomographic imaging. To date, the magnetic properties of MNPs used in imaging have not been optimized. As nanoparticle magnetism shows strong size dependence, the authors explore how varying MNP size impacts imaging performance in order to determine optimal MNP characteristics for MPI at any driving field frequency f 0. Methods: Monodisperse MNPs of varying size were synthesized and their magnetic properties characterized. Their MPI response was measured experimentally using a custom-built MPI transceiver designed to detect the third harmonic of MNP magnetization. The driving field amplitude H 0 =6 mT μ 0 -1 and frequency f 0 =250 kHz were chosen to be suitable for imaging small animals. Experimental results were interpreted using a model of dynamic MNP magnetization that is based on the Langevin theory of superparamagnetism and accounts for sample size distribution and size-dependent magnetic relaxation. Results: The experimental results show a clear variation in the MPI signal intensity as a function of MNP diameter that is in agreement with simulated results. A maximum in the plot of MPI signal vs MNP size indicates there is a particular size that is optimal for the chosen f 0. Conclusions: The authors observed that MNPs 15 nm in diameter generate maximum signal amplitude in MPI experiments at 250 kHz. The authors expect the physical basis for this result, the change in magnetic relaxation with MNP size, will impact MPI under other experimental conditions. © 2011 American Association of Physicists in Medicine.


Schneider K.P.,Pacific Northwest National Laboratory | Weaver T.F.,American Electric Power
IEEE Transactions on Smart Grid | Year: 2014

In a regulated business environment, a utility must be able to validate that deployed technologies provide quantifiable benefits to the end-use customers. While there are well established procedures for determining the benefits derived from the deployment of traditional technologies, the same procedures do not exist for many emerging technologies. Volt-VAR Optimization is an example of an emerging technology that is being deployed across the nation without a standardized method for determining system performance and benefits. This paper will present a method for the evaluation, and quantification of benefits, for field deployments of Volt-VAR Optimization technologies. In addition to presenting the methodology, the paper will present a summary of results, and observations, from two separate Volt-VAR Optimization field evaluations using the presented method. © 2014 IEEE.


Rucker D.F.,HydroGEOPHYSICS Inc. | Noonan G.E.,HydroGEOPHYSICS Inc. | Greenwood W.J.,Pacific Northwest National Laboratory
Engineering Geology | Year: 2011

Dredging and widening of the Panama Canal is currently being conducted to allow larger vessels to transit to and from the Americas, Asia, and Europe. Dredging efficiency relies heavily on knowledge of the types and volumes of sediments and rocks beneath the waterway to ensure the right equipment is used for their removal. To aid this process, a waterborne streaming electrical resistivity survey was conducted along the entire length of the canal to provide information on its geology. Within the confines of the canal, a total of 663 line-kilometers of electrical resistivity data were acquired using the dipole-dipole array. The support of the survey data for dredging activities was realized by calibrating and qualitatively correlating the resistivity data with information obtained from nearby logged boreholes and geological maps. The continuity of specific strata was determined in the resistivity sections by evaluating the continuity of similar ranges of resistivity values between boreholes. It was evident that differing geological units and successions can have similar ranges of resistivity values. For example, Quaternary sandy and gravelly alluvial fill from the former river channel of the Chagres River had similar resistivity ranges (generally from 40 to 250. Ω m) to those characteristic of late Miocene basalt dikes (from 100 to 400 Ω m), but for quite different reasons. Similarly, competent marine-based sedimentary rocks of the Caimito Formation were similar in resistivity values (ranging from 0.7 to 10 Ω m) to sandstone conglomerate of the Bohio Formation. Consequently, it would be difficult to use the resistivity data alone to extrapolate more complex geotechnical parameters, such as the hardness or strength of the substrate. A necessary component for such analyses requires detailed objective information regarding the specific context from which the geotechnical parameters were derived. If these data from cored boreholes and detailed geological surveys are taken into account, however, then waterborne streaming resistivity surveying can be a powerful tool. In this case, it provided inexpensive and highly resolved quantitative information on the potential volume of loose suctionable material along the Gamboa Sub-reach, which could enable large cost savings to be made on a major engineering project involving modification of one of the most important navigable waterways in the world. © 2010 Elsevier B.V.


Kirsch J.,Siemens AG | Goose S.,Siemens AG | Amir Y.,Johns Hopkins University | Wei D.,Siemens AG | Skare P.,Pacific Northwest National Laboratory
IEEE Transactions on Smart Grid | Year: 2014

Providers of critical infrastructure services strive to maintain the high availability of their SCADA systems. This paper reports on our experience designing, architecting, and evaluating the first survivable SCADA system-one that is able to ensure correct behavior with minimal performance degradation even during cyber attacks that compromise part of the system. We describe the challenges we faced when integrating modern intrusion-tolerant protocols with a conventional SCADA architecture and present the techniques we developed to overcome these challenges. The results illustrate that our survivable SCADA system not only functions correctly in the face of a cyber attack, but that it also processes in excess of 20 000 messages per second with a latency of less than 30 ms, making it suitable for even large-scale deployments managing thousands of remote terminal units. © 2010-2012 IEEE.


Park S.,University of South Carolina | Park S.,Pacific Northwest National Laboratory | Popov B.N.,University of South Carolina
Fuel | Year: 2011

A commercially available GDL based on carbon paper or carbon cloth as a macroporous substrate was characterized by various physical and electrochemical measurements: mercury porosimetry, surface morphology analysis, contact angle measurement, water permeation measurement, polarization techniques, and ac-impedance spectroscopy. SGL 10BB based on carbon paper demonstrated dual pore size distribution and high water flow resistance owing to less permeable macroporous substrate, and more hydrophobic and compact microporous layer, as compared to ELAT-LT-1400 W based on carbon cloth. The membrane-electrode- assembly fabricated using SGL 10BB showed an improved fuel cell performance when air was used as an oxidant. The ac-impedance response indicated that a microporous layer which has high volume of micropores and more hydrophobic property allows oxygen to readily diffuse towards the catalyst layer due to effective water removal from the catalyst layer to the gas flow channel. © 2010 Elsevier Ltd. All rights reserved.


Singhal S.C.,Pacific Northwest National Laboratory
Wiley Interdisciplinary Reviews: Energy and Environment | Year: 2014

Solid oxide fuel cells (SOFCs), based on an oxide ion conducting electrolyte, offer a clean, low-pollution technology to electrochemically generate electricity at high efficiencies. These fuel cells provide many advantages over traditional energy conversion systems including high efficiency, reliability, modularity, fuel adaptability, and very low levels of SOx and NOx emissions. Quiet, vibration-free operation of SOFCs also eliminates noise usually associated with conventional power generation systems. Furthermore, because of their high operation temperature (600-1000°C), some hydrocarbon fuels such as natural gas can be reformed within the cell stack eliminating the need for an expensive, external reformer. In spite of these advantages, the degree and extent of their market penetration really depends on the ability to reduce the cost of SOFC-based power systems while ensuring their long-term durability. This article reviews the cell and stack materials, cell designs, and present commercial status of power systems built using SOFCs. © 2013 John Wiley & Sons, Ltd.


Henderson M.A.,Pacific Northwest National Laboratory
Surface Science Reports | Year: 2011

The field of surface science provides a unique approach to understanding bulk, surface and interfacial phenomena occurring during TiO2 photocatalysis. This review highlights, from a surface science perspective, recent literature that provides molecular-level insights into photon-initiated events occurring at TiO2 surfaces. Seven key scientific issues are identified in the organization of this review. These are: (1) photon absorption, (2) charge transport and trapping, (3) electron transfer dynamics, (4) the adsorbed state, (5) mechanisms, (6) poisons and promoters, and (7) phase and form. This review ends with a brief examination of several chemical processes (such as water splitting) in which TiO2 photocatalysis has made significant contributions in the literature. © 2011 Elsevier B.V. All rights reserved.


Shokri A.,University of Minnesota | Schmidt J.,University of Minnesota | Wang X.-B.,Pacific Northwest National Laboratory | Kass S.R.,University of Minnesota
Journal of the American Chemical Society | Year: 2012

Nature employs flexible molecules to bind anions in a variety of physiologically important processes whereas supramolecular chemists have been designing rigid substrates that minimize or eliminate intramolecular hydrogen bond interactions to carry out anion recognition. Herein, the association of a flexible polyhydroxy alkane with chloride ion is described and the bound receptor is characterized by infrared and photoelectron spectroscopy in the gas phase, computations, and its binding constant as a function of temperature in acetonitrile. © 2012 American Chemical Society.


Hou J.,Virginia Polytechnic Institute and State University | Shao Y.,Pacific Northwest National Laboratory | Ellis M.W.,Virginia Polytechnic Institute and State University | Moore R.B.,Virginia Polytechnic Institute and State University | Yi B.,CAS Dalian Institute of Chemical Physics
Physical Chemistry Chemical Physics | Year: 2011

Graphene has attracted extensive research interest due to its strictly 2-dimensional (2D) structure, which results in its unique electronic, thermal, mechanical, and chemical properties and potential technical applications. These remarkable characteristics of graphene, along with the inherent benefits of a carbon material, make it a promising candidate for application in electrochemical energy devices. This article reviews the methods of graphene preparation, introduces the unique electrochemical behavior of graphene, and summarizes the recent research and development on graphene-based fuel cells, supercapacitors and lithium ion batteries. In addition, promising areas are identified for the future development of graphene-based materials in electrochemical energy conversion and storage systems. This journal is © the Owner Societies.


Wick C.D.,Louisiana Tech University | Dang L.X.,Pacific Northwest National Laboratory
Journal of Chemical Physics | Year: 2010

NaCl pairing and dissociation was investigated at the CCl4 -water and 1,2-dichloroethane (DCE)-water interfaces, and compared with dissociation results in the bulk and at the air-water interface utilizing polarizable potentials. The transition path sampling methodology was used to calculate the rate constant for dissociation, while umbrella sampling was used to map out a free energy profile for NaCl dissociation. The results found that ion pairing was weakest at the organic-water interfaces, even weaker than in the water bulk. This is in contrast to what has been observed previously for the air-water interface, in which NaCl ion paring is stronger than in the bulk [C. D. Wick, J. Phys. Chem. C 113, 6356 (2009)]. A consequence of the weaker binding at the organic-water interfaces was that ion dissociation was faster than in the other systems studied. Interactions of the organic phase with the ions influenced the magnitude of the Cl- induced dipole moment, and at the organic-water interfaces, the average Cl- induced dipole was found to be lower than at the air-water interface, weakening interactions with Na +. These weaker interactions were found to be responsible for the weaker ion pairing found at the organic-water interfaces. © 2010 American Institute of Physics.


Hurlbert A.H.,University of North Carolina at Chapel Hill | Stegen J.C.,Pacific Northwest National Laboratory
Frontiers in Genetics | Year: 2014

We use a simulation model to examine four of the most common hypotheses for the latitudinal richness gradient and identify patterns that might be diagnostic of those four hypotheses. The hypotheses examined include (1) tropical niche conservatism, or the idea that the tropics are more diverse because a tropical clade origin has allowed more time for diversification in the tropics and has resulted in few species adapted to extra-tropical climates. (2) The ecological limits hypothesis suggests that species richness is limited by the amount of biologically available energy in a region. (3) The speciation rates hypothesis suggests that the latitudinal gradient arises from a gradient in speciation rates. (4) Finally, the tropical stability hypothesis argues that climatic fluctuations and glacial cycles in extratropical regions have led to greater extinction rates and less opportunity for specialization relative to the tropics. We found that tropical niche conservatism can be distinguished from the other three scenarios by phylogenies which are more balanced than expected, no relationship between mean root distance (MRD) and richness across regions, and a homogeneous rate of speciation across clades and through time. The energy gradient, speciation gradient, and disturbance gradient scenarios all produced phylogenies which were more imbalanced than expected, showed a negative relationship between MRD and richness, and diversity-dependence of speciation rate estimates through time. We found that the relationship between speciation rates and latitude could distinguish among these three scenarios, with no relation expected under the ecological limits hypothesis, a negative relationship expected under the speciation rates hypothesis, and a positive relationship expected under the tropical stability hypothesis. We emphasize the importance of considering multiple hypotheses and focusing on diagnostic predictions instead of predictions that are consistent with multiple hypotheses. © 2014 Hurlbert and Stegen.


Bond L.J.,Pacific Northwest National Laboratory
Journal of Pressure Vessel Technology, Transactions of the ASME | Year: 2012

There is growing interest in life extensions to enable longer term operation (LTO) for both existing nuclear power plants (NPPs) and proposed new NPPs. In order to justify an initial license extension for the 40-60 yr period, new nondestructive examination (NDE) approaches have been developed and deployed by NPP operators in their aging management programs. However, to achieve the goals of even longer term operation, and specifically for the United States in looking at methodologies to support subsequent license renewal periods (i.e., 60-80 yr and beyond), it is necessary to understand the capabilities of current NDE methods to detect, monitor, and trend degradation and hence enable timely implementation of appropriate mitigation and corrective actions. This paper discusses insights from past experience, the state-of-the-art, and current activities in the move toward providing a capacity for proactive management of materials degradation to support NPP LTO.


Guo C.-J.,University of Southern California | Sun W.-W.,University of Southern California | Bruno K.S.,Pacific Northwest National Laboratory | Wang C.C.C.,University of Southern California
Organic Letters | Year: 2014

Terreic acid is a natural product derived from 6-methylsalicylic acid (6-MSA). A compact gene cluster for its biosynthesis was characterized. Isolation of the intermediates and shunt products from the mutant strains, combined with bioinformatic analyses, allowed for the proposition of a biosynthetic pathway for terreic acid. (Chemical Equation Presented). © 2014 American Chemical Society.


Thrall K.D.,Pacific Northwest National Laboratory
Health Physics | Year: 2010

Although four stable isotopes of strontium occur naturally, Sr is produced by nuclear fission and is present in surface soil around the world as a result of fallout from atmospheric nuclear weapons tests. It can easily transfer to humans in the event of a nuclear/radiological emergency or through the plant-animal-human food chain causing long-term exposures. Strontium is chemically and biologically similar to calcium, and is incorporated primarily into bone following internal deposition. Alginic acid (alginate) obtained from seaweed (kelp) extract selectively binds ingested strontium in the gastrointestinal tract blocking its systemic uptake and reducing distribution to bone in rats, while other natural polysaccharides including chitosan and hyaluronic acid had little in vivo affinity for strontium. Alginate exhibits the unique ability to discriminate between strontium and calcium and has been previously shown to reduce intestinal absorption and skeletal retention of strontium without changing calcium metabolism. In our studies, the effect of commercially available alginate on intestinal absorption of strontium was examined. One problem associated with alginate treatment is its limited solubility and gel formation in water. The aqueous solubility of sodium alginate was improved in a sodium chloride/sodium bicarbonate electrolyte solution containing low molecular weight polyethylene glycol (PEG). Furthermore, oral administration of the combined alginate/electrolyte/PEG solution accelerated removal of internal strontium in rats when compared to treatment with individual sodium alginate/electrolyte or electrolyte/PEG solutions. Importantly, both alginate and PEG are nontoxic, readily available materials that can be easily administered orally in case of a national emergency when potentially large numbers of the population may require medical treatment for internal depositions. Our results suggest further studies to optimize in vivo decorporation performance of engineered alginate material via modification of its chemical and physicochemical properties are warranted. Copyright © 2010 Health Physics Society.


Summa B.,VISUS Inc | Tierny J.,Telecom ParisTech | Pascucci V.,Pacific Northwest National Laboratory
ACM Transactions on Graphics | Year: 2012

A fundamental step in stitching several pictures to form a larger mosaic is the computation of boundary seams that minimize the visual artifacts in the transition between images. Current seam computation algorithms use optimization methods that may be slow, sequential, memory intensive, and prone to finding suboptimal solutions related to local minima of the chosen energy function. Moreover, even when these techniques perform well, their solution may not be perceptually ideal (or even good). Such an inflexible approach does not allow the possibility of user-based improvement. This paper introduces the Panorama Weaving technique for seam creation and editing in an image mosaic. First, Panorama Weaving provides a procedure to create boundaries for panoramas that is fast, has low memory requirements and is easy to parallelize. This technique often produces seams with lower energy than the competing global technique. Second, it provides the first interactive technique for the exploration of the seam solution space. This powerful editing capability allows the user to automatically extract energy minimizing seams given a sparse set of constraints. With a variety of empirical results, we show how Panorama Weaving allows the computation and editing of a wide range of digital panoramas including unstructured configurations. © 2012 ACM 0730-0301/2012/08-ART83.


Ilton E.S.,Pacific Northwest National Laboratory | Bagus P.S.,University of North Texas
Surface and Interface Analysis | Year: 2011

This contribution is both a review of different aspects of X-ray photoelectron spectroscopy that can help one determine U oxidation states and a personal perspective on how to effectively model the X-ray photoelectron spectroscopy of complicated mixed-valence U phases. After a discussion of the valence band, the focus lingers on the U4f region, where the use of binding energies, satellite structures, and peak shapes is discussed in some detail. Binding energies were shown to be very dependent on composition/structure and consequently unreliable guides to oxidation state, particularly where assignment of composition is difficult. Likewise, the spin orbit split 4f 7/2 and 4f 5/2 peak shapes do not carry significant information on oxidation states. In contrast, both satellite-primary peak binding energy separations, as well as intensities to a lesser extent, are relatively insensitive to composition/structure within the oxide-hydroxide-hydrate system and can be used to both identify and help quantify U oxidation states in mixed valence phases. An example of the usefulness of the satellite structure in constraining the interpretation of a complex multivalence U compound is given. © 2011 John Wiley & Sons, Ltd.


Anderson N.L.,Purdue University | Vedula R.P.,Purdue University | Schultz P.A.,Sandia National Laboratories | Van Ginhoven R.M.,Pacific Northwest National Laboratory | Strachan A.,Purdue University
Physical Review Letters | Year: 2011

We show that oxygen vacancies are not necessary for the formation of E ′ centers in amorphous SiO2 and that a single O deficiency can lead to two charge traps. Employing molecular dynamics with a reactive potential and density functional theory, we generate an ensemble of stoichiometric and oxygen-deficient amorphous SiO2 atomic structures and identify low-energy network defects. Three-coordinated Si atoms appear in several low-energy defects both in stoichiometric and O-deficient samples where, in addition to the neutral oxygen vacancy, they appear as isolated defects. © 2011 American Physical Society.


Yoon J.-H.,Pacific Northwest National Laboratory
Atmospheric Science Letters | Year: 2016

Amazon rainfall is subject to year-to-year fluctuation resulting in drought and flood in various intensities. A major climatic driver of the interannual variation of the Amazon rainfall is El Niño/Southern Oscillation. Also, the sea surface temperature over the Atlantic Ocean is identified as an important climatic driver on the Amazon water cycle. Previously, observational data sets were used to support the Atlantic influence on Amazon rainfall. Here, it is found that multiple global climate models do reproduce the Atlantic-Amazon link robustly. However, there exist differences in rainfall response, which primarily depends on the climatological rainfall amount. © 2016 Royal Meteorological Society.


Masica D.L.,Johns Hopkins University | Gray J.J.,Johns Hopkins University | Shaw W.J.,Pacific Northwest National Laboratory
Journal of Physical Chemistry C | Year: 2011

The formation of biogenic materials requires the interaction of organic molecules with the mineral phase. In forming enamel, the amelogenin proteins contribute to the mineralization of hydroxyapatite (HAp). Leucine-rich amelogenin protein (LRAP) is a naturally occurring splice variant of amelogenin that comprises amelogenins predicted HAp binding domains. We determined the partial structure of phosphorylated and non-phosphorylated LRAP variants bound to HAp using combined solid-state NMR (ssNMR) and ssNMR-biased computational structure prediction. New ssNMR measurements in the N-terminus indicate a largely extended structure for both variants, though some measurements are consistent with a partially helical N-terminal segment. The N-terminus of the phosphorylated variant is found to be consistently closer to the HAp surface than the non-phosphorylated variant. Structure prediction was biased using 21 ssNMR measurements in the N-and C-terminus at five HAp crystal faces. The predicted fold of LRAP is similar at all HAp faces studied, regardless of phosphorylation. Largely consistent with experimental observations, LRAPs predicted structure is relatively extended with a helix-turn-helix motif in the N-terminal domain and some helix in the C-terminal domain, and the N-terminal domain of the phosphorylated variant binds HAp more closely than the N-terminal domain of the non-phosphorylated variant. Both predictions and experiments are consistent with structural heterogeneity of the surface adsorbed protein. Predictions for both variants show some potential binding specificity for the {010} HAp crystal face, providing further support that amelogenins block crystal growth on the a and b faces to allow elongated crystals in the c-axis. © 2011 American Chemical Society.


He J.,TU Munich | Zhao C.,TU Munich | Lercher J.A.,TU Munich | Lercher J.A.,Pacific Northwest National Laboratory
Journal of Catalysis | Year: 2014

Impacts of water, methanol, and hexadecane solvents on the individual steps of phenol hydrodeoxygenation are investigated over Pd/C and HZSM-5 catalyst components at 473 K in presence of H2. Hydrodeoxygenation of phenol to cyclohexane includes four individual steps of phenol hydrogenation to cyclohexanone on Pd/C, cyclohexanone hydrogenation to cyclohexanol on Pd/C, cyclohexanol dehydration to cyclohexene on HZSM-5, and cyclohexene hydrogenation to cyclohexane on Pd/C. Individual phenol and cyclohexanone hydrogenation rates are much lower in methanol and hexadecane than in water, while rates of cyclohexanol dehydration and cyclohexene hydrogenation are similar in three solvents. The slow rate in methanol is due to the strong solvation of reactants and the adsorption of methanol on Pd, as well as to the reaction between methanol and the cyclohexanone intermediate. The low solubility of phenol and strong interaction of hexadecane with Pd lead to the slow rate in hexadecane. The apparent activation energies for hydrogenation follow the order E a phenol > Ea cyclohexanone > E a cyclohexene, and the sequences of individual reaction rates are reverse in three solvents. The dehydration rates 1.1-1.8×10 3molmolBAS-1h-1 and apparent activation energies (115-124 kJ mol-1) are comparable in three solvents. In situ liquid-phase IR spectroscopy shows the rates consistent with kinetics derived from chromatographic evidence in the aqueous phase and verifies that hydrogenation of phenol and cyclohexanone follows reaction orders of 1.0 and 0.55 over Pd/C, respectively. Conversion of cyclohexanol with HZSM-5 shows first-order dependence in approaching the dehydration-hydration equilibrium in the aqueous phase. © Published by Elsevier Inc.


Santelli C.M.,Harvard University | Webb S.M.,SLAC | Dohnalkova A.C.,Pacific Northwest National Laboratory | Hansel C.M.,Harvard University
Geochimica et Cosmochimica Acta | Year: 2011

Manganese (Mn) oxides are environmentally abundant, highly reactive mineral phases that mediate the biogeochemical cycling of nutrients, contaminants, carbon, and numerous other elements. Despite the belief that microorganisms (specifically bacteria and fungi) are responsible for the majority of Mn oxide formation in the environment, the impact of microbial species, physiology, and growth stage on Mn oxide formation is largely unresolved. Here, we couple microscopic and spectroscopic techniques to characterize the Mn oxides produced by four different species of Mn(II)-oxidizing Ascomycete fungi (Plectosphaerella cucumerina strain DS2psM2a2, Pyrenochaeta sp. DS3sAY3a, Stagonospora sp. SRC1lsM3a, and Acremonium strictum strain DS1bioAY4a) isolated from acid mine drainage treatment systems in central Pennsylvania. The site of Mn oxide formation varies greatly among the fungi, including deposition on hyphal surfaces, at the base of reproductive structures (e.g., fruiting bodies), and on envisaged extracellular polymers adjacent to the cell. The primary product of Mn(II) oxidation for all species growing under the same chemical and physical conditions is a nanoparticulate, poorly-crystalline hexagonal birnessite-like phase resembling synthetic δ-MnO2. The phylogeny and growth conditions (planktonic versus surface-attached) of the fungi, however, impact the conversion of the initial phyllomanganate to more ordered phases, such as todorokite (A. strictum strain DS1bioAY4a) and triclinic birnessite (Stagonospora sp. SRC1lsM3a). Our findings reveal that the species of Mn(II)-oxidizing fungi impacts the size, morphology, and structure of Mn biooxides, which will likely translate to large differences in the reactivity of the Mn oxide phases. © 2011 Elsevier Ltd.


Weiner S.C.,Pacific Northwest National Laboratory
International Journal of Hydrogen Energy | Year: 2014

The International Energy Agency's Hydrogen Implementing Agreement (IEA HIA) was established in 1977 to pursue collaborative hydrogen research and development and information exchange among its member countries. Information and knowledge dissemination is a key aspect of the work within IEA HIA tasks, and case studies, technical reports and presentations/publications often result from the collaborative efforts. The work conducted in hydrogen safety under Task 31 and its predecessor, Task 19, can positively impact the objectives of national programs even in cases for which a specific task report is not published. The interactions within Task 31 illustrate how technology information and knowledge exchange among participating hydrogen safety experts serve the objectives intended by the IEA HIA. © 2014 Hydrogen Energy Publications, LLC. All rights reserved.


Klimont Z.,International Institute For Applied Systems Analysis | Smith S.J.,Pacific Northwest National Laboratory | Cofala J.,International Institute For Applied Systems Analysis
Environmental Research Letters | Year: 2013

The evolution of global and regional anthropogenic SO2 emissions in the last decade has been estimated through a bottom-up calculation. After increasing until about 2006, we estimate a declining trend continuing until 2011. However, there is strong spatial variability, with North America and Europe continuing to reduce emissions, with an increasing role of Asia and international shipping. China remains a key contributor, but the introduction of stricter emission limits followed by an ambitious program of installing flue gas desulfurization on power plants resulted in a significant decline in emissions from the energy sector and stabilization of total Chinese SO 2 emissions. Comparable mitigation strategies are not yet present in several other Asian countries and industrial sectors in general, while emissions from international shipping are expected to start declining soon following an international agreement to reduce the sulfur content of fuel oil. The estimated trends in global SO2 emissions are within the range of representative concentration pathway (RCP) projections and the uncertainty previously estimated for the year 2005. © 2013 IOP Publishing Ltd.


Shi X.,Oak Ridge National Laboratory | Mao J.,Oak Ridge National Laboratory | Thornton P.E.,Oak Ridge National Laboratory | Huang M.,Pacific Northwest National Laboratory
Environmental Research Letters | Year: 2013

Spatiotemporal patterns of evapotranspiration (ET) over the period from 1982 to 2008 are investigated and attributed to multiple environmental factors using the Community Land Model version 4 (CLM4). Our results show that CLM4 captures the spatial distribution and interannual variability of ET well when compared to observation-based estimates. We find that climate dominates the predicted variability in ET. Elevated atmospheric CO2 concentration also plays an important role in modulating the trend of predicted ET over most land areas, and replaces climate to function as the dominant factor controlling ET changes over the North America, South America and Asia regions. Compared to the effect of climate and CO2 concentration, the roles of other factors such as nitrogen deposition, land use change and aerosol deposition are less pronounced and regionally dependent. The aerosol deposition contribution is the third most important factor for trends of ET over Europe, while it has the smallest impact over other regions. As ET is a dominant component of the terrestrial water cycle, our results suggest that environmental factors like elevated CO2, nitrogen and aerosol depositions, and land use change, in addition to climate, could have significant impact on future projections of water resources and water cycle dynamics at global and regional scales. © 2013 IOP Publishing Ltd.


Runkle R.C.,Office of Non proliferation and Verification Research and Development | Runkle R.C.,Pacific Northwest National Laboratory
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2011

Perhaps the most familiar application of neutron detection technology to nonproliferation resides in materials accounting, where the quantification of plutonium has a rich history. With a changing dynamic in nuclear security, the application of sensor technology to further other nonproliferation objectives has received considerable attention. This fact, amplified by a dwindling supply of 3He, has stimulated considerable interest in neutron detection technology development for applications ranging from interdicting smuggled nuclear material to the verification of stockpile reductions. This manuscript briefly overviews the application of neutron sensors to nonproliferation and examines three specific examples that highlight the constraints applied to field-deployed technology. © 2011 Elsevier B.V.


Spurgeon S.R.,Pacific Northwest National Laboratory
MRS Bulletin | Year: 2014

The University of Cincinnati develops many paper-based projects as part of an innovative laboratory class that bridges the gap between science and engineering education. Andrew Steckl, Gieringer Professor and Ohio Eminent Scholar at the University of Cincinnati's Nanoelectronics Laboratory have developed a special topics class for incoming graduate students to design. The students were offered project suggestions, but would otherwise are free to choose their own ideas, vetted by in-class discussions. One group studied the design of smart diapers that can characterize waste products and record biometrics. Prajokta Ray, a PhD student, designed a flexible, urine powered electrochemical battery to provide power for various sensors in the diaper. In one case, a student attempted to design an adhesive-backed portable weather sensor to detect local temperature and humidity. Steckl believes that a course in which students are required to set goals, adhere to a strict budget, and deliver a final product can prepare them for the demands imposed on scientists today.


Xu Y.,Oak Ridge National Laboratory | Shelton W.A.,Oak Ridge National Laboratory | Shelton W.A.,Pacific Northwest National Laboratory
Journal of the Electrochemical Society | Year: 2011

Li-air batteries have attracted substantial interest for their high theoretical specific energies, but the oxygen reduction reaction by Li (Li-ORR) that occurs at the carbon cathode remains poorly understood. Periodic density functional theory calculations have been performed to examine the Li-ORR on several model carbon structures, including the graphite(0001) basal plane, the (8,0) single-wall nanotube, the armchair-type edge, and a di-vacancy in the basal plane. The inertness of the basal plane limits the reversible potential of O 2 reduction to 1.1 V, and slightly higher to 1.2 V on the curved nanotube. The armchair edge and di-vacancy are highly reactive and significantly oxidized at ambient conditions to various CO x groups, which are reduced by Li via redox mechanisms at 1.2-1.4 V. These CO x groups can also catalyze O 2 reduction at up to 2.3 V (an overpotential of 0.4 V vs. the calculated equilibrium potential for bulk Li 2O 2 formation) by chelating and stabilizing the LiO 2 intermediate. The Li-ORR on graphitic carbon, if via concerted Li/e - transfer and involving carbon, lithium, and oxygen only, is therefore expected to initiate with the smallest overpotential at under-coordinated carbon centers that are oxidized at ambient conditions. © 2011 The Electrochemical Society.


McClain C.R.,National Evolutionary Synthesis Center | Stegen J.C.,University of North Carolina at Chapel Hill | Stegen J.C.,Pacific Northwest National Laboratory | Hurlbert A.H.,University of North Carolina at Chapel Hill
Proceedings of the Royal Society B: Biological Sciences | Year: 2012

Patterns of beta-diversity or distance decay at oceanic scales are completely unknown for deep-sea communities. Even when appropriate data exist, methodological problems have made it difficult to discern the relative roles of environmental filtering and dispersal limitation for generating faunal turnover patterns. Here, we combine a spatially extensive dataset on deep-sea bivalves with a model incorporating ecological dynamics and shared evolutionary history to quantify the effects of environmental filtering and dispersal limitation. Both the model and empirical data are used to relate functional, taxonomic and phylogenetic similarity between communities to environmental and spatial distances separating them for 270 sites across the Atlantic Ocean. This study represents the first ocean-wide analysis examining distance decay as a function of a broad suite of explanatory variables.We find that both strong environmental filtering and dispersal limitation drive turnover in taxonomic, functional and phylogenetic composition in deep-sea bivalves, explaining 26 per cent, 34 per cent and 9 per cent of the variation, respectively. This contrasts with previous suggestions that dispersal is not limiting in broad-scale biogeographic and biodiversity patterning in marine systems. However, rates of decay in similarity with environmental distance were eightfold to 44-fold steeper than with spatial distance. Energy availability is the most influential environmental variable evaluated, accounting for 3.9 per cent, 9.4 per cent and 22.3 per cent of the variation in functional, phylogenetic and taxonomic similarity, respectively. Comparing empirical patterns with process-based theoretical predictions provided quantitative estimates of dispersal limitation and niche breadth, indicating that 95 per cent of deep-sea bivalve propagules will be able to persist in environments that deviate from their optimum by up to 2.1 g m -2 yr -1 and typically disperse 749 km from their natal site. © 2011 The Royal Society.


Booker B.M.,University of Alabama at Birmingham | Deng S.,University of Alabama at Birmingham | Deng S.,Pacific Northwest National Laboratory | Higgins N.P.,University of Alabama at Birmingham
Molecular Microbiology | Year: 2010

Bacteria differ from eukaryotes by having the enzyme DNA gyrase, which catalyses the ATP-dependent negative supercoiling of DNA. Negative supercoils are essential for condensing chromosomes into an interwound (plectonemic) and branched structure known as the nucleoid. Topo-1 removes excess supercoiling in an ATP-independent reaction and works with gyrase to establish a topological equilibrium where supercoils move within 10 kb domains bounded by stochastic barriers along the sequence. However, transcription changes the stochastic pattern by generating supercoil diffusion barriers near the sites of gene expression. Using supercoil-dependent Tn3 and γδ resolution assays, we studied DNA topology upstream, downstream and across highly transcribed operons. Whenever two Res sites flanked efficiently transcribed genes, resolution was inhibited and the loss in recombination efficiency was proportional to transcription level. Ribosomal RNA operons have the highest transcription rates, and resolution assays at the rrnG and rrnH operons showed inhibitory levels 40-100 times those measured in low-transcription zones. Yet, immediately upstream and downstream of RNA polymerase (RNAP) initiation and termination sites, supercoiling characteristics were similar to poorly transcribed zones. We present a model that explains why RNAP blocks plectonemic supercoil movement in the transcribed track and suggests how gyrase and TopA control upstream and downstream transcription-driven supercoiling. © 2010 Blackwell Publishing Ltd.


Lemoine D.,University of Arizona | McJeon H.C.,Pacific Northwest National Laboratory
Environmental Research Letters | Year: 2013

Climate change policies must trade off uncertainties about future warming, about the social and ecological impacts of warming, and about the cost of reducing greenhouse gas emissions. We show that laxer carbon targets produce broader distributions for climate damages, skewed towards severe outcomes. However, if potential low-carbon technologies fill overlapping niches, then more stringent carbon targets produce broader distributions for the cost of reducing emissions, skewed towards high-cost outcomes. We use the technology-rich GCAM integrated assessment model to assess the robustness of 450 and 500 ppm carbon targets to each uncertain factor. The 500 ppm target provides net benefits across a broad range of futures. The 450 ppm target provides net benefits only when impacts are greater than conventionally assumed, when multiple technological breakthroughs lower the cost of abatement, or when evaluated with a low discount rate. Policy evaluations are more sensitive to uncertainty about abatement technology and impacts than to uncertainty about warming. © 2013 IOP Publishing Ltd.


Du D.,Central China Normal University | Liu J.,Central China Normal University | Zhang X.,Fudan University | Cui X.,Fudan University | Lin Y.,Pacific Northwest National Laboratory
Journal of Materials Chemistry | Year: 2011

This paper described the preparation, characterization, and electrochemical properties of a graphene-ZrO2 nanocomposite (GZN) and its application for both the enrichment and detection of methyl parathion (MP). GZN was fabricated using electrochemical deposition and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), which showed the successful formation of nanocomposites. Due to the strong affinity to the phosphoric group and the fast electron-transfer kinetics of GZN, both the extraction and electrochemical detection of organophosphorus (OP) agents at the same GZN modified electrochemical sensor was possible. The combination of solid-phase extraction and stripping voltammetric analysis allowed fast, sensitive, and selective determination of MP in garlic samples. The stripping response was highly linear over the MP concentrations ranging from 0.5 ng mL-1 to 100 ng mL-1, with a detection limit of 0.1 ng mL-1. This new nanocomposite-based electrochemical sensor provides an opportunity to develop a field-deployable, sensitive, and quantitative method for monitoring exposure to OPs. © 2011 The Royal Society of Chemistry.


Grell G.,National Oceanic and Atmospheric Administration | Freitas S.R.,National Institute for Space Research | Stuefer M.,University of Alaska Fairbanks | Fast J.,Pacific Northwest National Laboratory
Atmospheric Chemistry and Physics | Year: 2011

A plume rise algorithm for wildfires was included in WRF-Chem, and applied to look at the impact of intense wildfires during the 2004 Alaska wildfire season on weather simulations using model resolutions of 10 km and 2 km. Biomass burning emissions were estimated using a biomass burning emissions model. In addition, a 1-D, time-dependent cloud model was used online in WRF-Chem to estimate injection heights as well as the vertical distribution of the emission rates. It was shown that with the inclusion of the intense wildfires of the 2004 fire season in the model simulations, the interaction of the aerosols with the atmospheric radiation led to significant modifications of vertical profiles of temperature and moisture in cloud-free areas. On the other hand, when clouds were present, the high concentrations of fine aerosol (PM2.5) and the resulting large numbers of Cloud Condensation Nuclei (CCN) had a strong impact on clouds and cloud microphysics, with decreased precipitation coverage and precipitation amounts during the first 12 h of the integration. During the afternoon, storms were of convective nature and appeared significantly stronger, probably as a result of both the interaction of aerosols with radiation (through an increase in CAPE) as well as the interaction with cloud microphysics. © 2011 Author(s).


Dooley J.J.,Pacific Northwest National Laboratory
International Journal of Greenhouse Gas Control | Year: 2011

By their very nature, early national and basin scale assessments of geologic carbon dioxide (CO2) storage capacity must rely on simplifying assumptions and generalizations across a broad range of deep geologic structures. Key aspects of the technical literature and much of the public policy dialogue surrounding these assessments tend to emphasize the lack of detailed data and uncertainties at these scales. However, looking beyond the imperfections of data and methodology, the results of such assessments offer significant value in helping us to understand the potential for carbon dioxide capture and storage (CCS) technologies to deploy across various regions of the world. © 2010.


Wang M.,University of Michigan | Wang M.,Pacific Northwest National Laboratory | Penner J.E.,University of Michigan
Atmospheric Chemistry and Physics | Year: 2010

A statistical cirrus cloud scheme that accounts for mesoscale temperature perturbations is implemented in a coupled aerosol and atmospheric circulation model to better represent both subgrid-scale supersaturation and cloud formation. This new scheme treats the effects of aerosol on cloud formation and ice freezing in an improved manner, and both homogeneous freezing and heterogeneous freezing are included. The scheme is able to better simulate the observed probability distribution of relative humidity compared to the scheme that was implemented in an older version of the model. Heterogeneous ice nuclei (IN) are shown to decrease the frequency of occurrence of supersaturation, and improve the comparison with observations at 192 hPa. Homogeneous freezing alone can not reproduce observed ice crystal number concentrations at low temperatures (<205 K), but the addition of heterogeneous IN improves the comparison somewhat. Increases in heterogeneous IN affect both high level cirrus clouds and low level liquid clouds. Increases in cirrus clouds lead to a more cloudy and moist lower troposphere with less precipitation, effects which we associate with the decreased convective activity. The change in the net cloud forcing is not very sensitive to the change in ice crystal concentrations, but the change in the net radiative flux at the top of the atmosphere is still large because of changes in water vapor. Changes in the magnitude of the assumed mesoscale temperature perturbations by 25% alter the ice crystal number concentrations and the net radiative fluxes by an amount that is comparable to that from a factor of 10 change in the heterogeneous IN number concentrations. Further improvements on the representation of mesoscale temperature perturbations, heterogeneous IN and the competition between homogeneous freezing and heterogeneous freezing are needed. © 2010 Author(s).


Ghan S.J.,Pacific Northwest National Laboratory
Atmospheric Chemistry and Physics | Year: 2013

Estimating anthropogenic aerosol effects on the planetary energy balance through the aerosol influence on clouds using the difference in cloud radiative forcing from simulations with and without anthropogenic emissions produces estimates that are positively biased. A more representative method is suggested using the difference in cloud radiative forcing calculated as a diagnostic with aerosol scattering and absorption neglected. The method also yields an aerosol radiative forcing decomposition that includes a term quantifying the impact of changes in surface albedo. The method requires only two additional diagnostic calculations: the whole-sky and clear-sky top-of-atmosphere radiative flux with aerosol scattering and absorption neglected. © Author(s) 2013.


Walcarius A.,CNRS Laboratory of Physical Chemistry and Microbiology for the Environment | Minteer S.D.,University of Utah | Wang J.,University of California at San Diego | Lin Y.,Washington State University | And 2 more authors.
Journal of Materials Chemistry B | Year: 2013

Recent years have faced stimulating developments in the functionalization of electrode surfaces with biological materials, notably due to the significant input of nanosciences and nanotechnology. In this review (over 450 references), we are discussing the interest of both nano-objects (metal nanoparticles and quantum dots, carbon nanotubes and graphene) and nano-engineered and/or nanostructured materials (template-based materials, advanced organic polymers) for the rational design of bio-functionalized electrodes and related (bio)sensing systems. The attractiveness of such nanomaterials relies not only on their ability to act as effective immobilization matrices, which are, e.g., likely to enhance the long-term stability of bioelectrochemical devices, but also on their intrinsic and unique features (large surface areas, electrocatalytic properties, controlled morphology and structure, possible use as labels) that can be advantageously combined with the functioning of biomolecules, thus contributing to improved bioelectrode performance in terms of sensitivity and selectivity (enzymatic biosensors, DNA sensors, immunosensors and cell sensors) or power (biofuel cells). © 2013 The Royal Society of Chemistry.


Isaac G.,Pacific Northwest National Laboratory
Methods in molecular biology (Clifton, N.J.) | Year: 2011

In the past decade, many new strategies for mass spectrometry (MS)-based analyses of lipids have been developed. Lipidomics is one of the most promising research fields to emerge as a result of these advances in MS. Currently, mass spectrometric analysis of lipids involves two complementary approaches: direct infusion (shotgun lipidomics) and liquid chromatography coupled to MS. In this chapter, I will demonstrate the approach of shotgun lipidomics using electrospray ionization tandem MS for the analysis of lipid molecular species directly from crude biological extracts of tissue or fluids.


Wu S.,Pacific Northwest National Laboratory
Methods in molecular biology (Clifton, N.J.) | Year: 2011

Bottom-up and top-down strategies are two commonly used methods for mass spectrometry (MS) based protein identification; each method has its own advantages and disadvantages. In this chapter, we describe an integrated top-down and bottom-up approach facilitated by concurrent liquid chromatography-mass spectrometry (LC-MS) analysis and fraction collection for comprehensive high-throughput intact protein profiling. The approach employs a high resolution reversed phase (RP) LC separation coupled with LC eluent fraction collection and concurrent on-line MS with a high field (12 T) Fourier-transform ion cyclotron resonance (FTICR) mass spectrometer. Protein elusion profiles and tentative modified protein identification are made using detected intact protein mass in conjunction with bottom-up protein identifications from the enzymatic digestion and analysis of corresponding LC fractions. Specific proteins of biological interest are incorporated into a target ion list for subsequent off-line gas-phase fragmentation that uses an aliquot of the original collected LC fraction, an aliquot of which was also used for bottom-up analysis.


Majzoub E.H.,University of Missouri-St. Louis | Ronnebro E.C.E.,Pacific Northwest National Laboratory
Materials Science and Engineering R: Reports | Year: 2012

We present a review of the experimental and theoretical methods used in the discovery of new metal-hydrogen materials systems for hydrogen storage applications. Rather than a comprehensive review of all new materials and methods used in the metal hydride community, we focus on a specific subset of successful methods utilizing theoretical crystal structure prediction methods, computational approaches for screening large numbers of compound classes, and medium-throughput experimental methods for the preparation of such materials. Monte Carlo techniques paired with a simplified empirical Hamiltonian provide crystal structure candidates that are refined using density functional theory. First-principle methods using high-quality structural candidates are further screened for an estimate of reaction energetics, decomposition enthalpies, and determination of reaction pathways. Experimental synthesis utilizes a compacted-pellet sintering technique under high-pressure hydrogen at elevated temperatures. Crystal structure determination follows from a combination of Rietveld refinements of diffraction patterns and first-principles computation of total energies and dynamical stability of competing structures. The methods presented within are general and applicable to a wide class of materials for energy storage. © 2012 Published by Elsevier B.V.


Henderson M.A.,Pacific Northwest National Laboratory
Surface Science | Year: 2012

Nitric oxide chemistry and photochemistry on the Cr-terminated surface of α-Cr 2O 3(0001) were examined using temperature programmed desorption (TPD), sticking coefficient measurements and photodesorption. NO exposed to α-Cr 2O 3(0001) at 100 K binds at surface Cr cation sites forming a strongly bound surface species that thermally desorbs at 320-340 K, depending on coverage. No thermal decomposition was detected in TPD in agreement with previous results in the literature. Sticking probability measurements at 100 K indicated near unity sticking for NO up to coverages of ∼ 1.3 ML, with additional adsorption with higher exposures at decreased sticking probability. These results suggest that some Cr cation sites on the α-Cr 2O 3(0001) surface were capable of binding more than one NO molecule, although it is unclear whether this was as separate NO molecules or as dimers. Photodesorption of adsorbed NO was examined for surface coverages below the 1 ML point. Both visible and UV light were shown to photodesorb NO without detectable NO photodecomposition. Visible light photodesorption of NO occurred with a greater cross section than estimated using UV light. The visible light photodesorption event was not associated with bandgap excitation in α-Cr 2O 3(0001), but instead was linked to excitation of a surface Cr 3 +-NO - charge transfer complex. These results illustrate that localized photoabsorption events at surface sites with unique optical properties (relative to the bulk) can result in unexpected surface photochemistry. © 2011 Elsevier B.V. All rights reserved.


Aypar U.,University of Maryland Baltimore County | Morgan W.F.,Pacific Northwest National Laboratory | Baulch J.E.,University of Maryland Baltimore County
International Journal of Radiation Biology | Year: 2011

Purpose: This review examines the evidence for the hypothesis that epigenetics are involved in the initiation and perpetuation of radiation-induced genomic instability (RIGI). Conclusion: In addition to the extensively studied targeted effects of radiation, it is now apparent that non-targeted delayed effects such as RIGI are also important post-irradiation outcomes. In RIGI, unirradiated progeny cells display phenotypic changes at delayed times after radiation of the parental cell. RIGI is thought to be important in the process of carcinogenesis; however, the mechanism by which this occurs remains to be elucidated. In the genomically unstable clones developed by Morgan and colleagues, radiation-induced mutations, double-strand breaks, or changes in messenger RNA (mRNA) levels alone could not account for the initiation or perpetuation of RIGI. Since changes in the DNA sequence could not fully explain the mechanism of RIGI, inherited epigenetic changes may be involved. Epigenetics are known to play an important role in many cellular processes and epigenetic aberrations can lead to carcinogenesis. Recent studies in the field of radiation biology suggest that the changes in methylation patterns may be involved in RIGI. Together these clues have led us to hypothesise that epigenetics may be the missing link in understanding the mechanism behind RIGI. © 2011 Informa UK, Ltd.


Huang M.,Pacific Northwest National Laboratory | Huang M.,Carnegie Institution | Asner G.P.,Carnegie Institution
Global Biogeochemical Cycles | Year: 2010

Amazon deforestation contributes significantly to global carbon (C) emissions. In comparison, the contribution from selective logging to atmospheric CO2 emissions, and its impact on regional C dynamics, is highly uncertain. Using a new geographically based modeling approach in combination with high resolution remote sensing data from 1999 to 2002, we estimate that C emissions were 0.04-0.05 Pg C yr-1 due to selective logging from a ∼2,664,960 km2 region of the Brazilian Amazon. Selective logging was responsible for 15-19% higher carbon emissions than reported from deforestation (clear-cutting) alone. Our simulations indicated that forest carbon lost via selective logging lasts two to three decades following harvest, and that the original live biomass takes up to a century to recover, if the forests are not subsequently cleared. The two-to three-decade loss of carbon results from the biomass damaged by logging activities, including leaves, wood, and roots, estimated to be 89.1 Tg C yr-1 from 1999 to 2002 over the study region, leaving 70.0 Tg C yr-1 and 7.9 Tg C yr-1 to accumulate as coarse woody debris and soil C, respectively. While avoided deforestation is central to crediting rain forest nations for reduced carbon emissions, the extent and intensity of selective logging are also critical to determining carbon emissions in the context of Reduced Emissions from Deforestation and Forest Degradation (REDD). We show that a combination of automated high-resolution satellite monitoring and detailed forest C modeling can yield spatially explicit estimates of harvest-related C losses and subsequent recovery in support of REDD and other international carbon market mechanisms. © 2010 by the American Geophysical Union.


Ryan E.M.,Boston University | Sanquist T.F.,Pacific Northwest National Laboratory
Energy and Buildings | Year: 2012

Building energy models provide valuable insight into energy use in commercial and residential buildings based on architecture, materials and thermal loads. They are used in the design of new buildings and retrofitting to increase the efficiency of older buildings. The accuracy of these models is crucial to reducing energy use in the US and building a sustainable energy future. In addition to the architecture and thermal loads, building energy models also must account for the effects of the building's occupants on energy use. Traditionally simple schedule based methods have been used to account for the effects of occupants. However, newer research has shown that these methods often result in large differences between the modeled and actual energy use of buildings. In this paper we discuss building energy models and their accuracy in predicting energy use. In particular we focus on the different types of validation methods which have been used to investigate the accuracy of building energy models and how they account for (or do not) the effects of occupants. We also review newer work on stochastic methods for estimating the effects of occupants on energy use and discuss the improvements necessary to increase the accuracy of building energy models. © 2012 Elsevier B.V.


Spichtinger P.,ETH Zurich | Cziczo D.J.,ETH Zurich | Cziczo D.J.,Pacific Northwest National Laboratory
Journal of Geophysical Research: Atmospheres | Year: 2010

The influence of initial heterogeneous nucleation on subsequent homogeneous nucleation events in cirrus clouds is investigated using a box model which includes the explicit impact of aerosols on the nucleation of ice crystals and a new sedimentation scheme. Different effects are discussed, namely the impact of external versus internal mixtures of heterogeneous ice nuclei and the influence of size-dependent freezing thresholds. Several idealized experiments are carried out, which show that the treatment of external mixtures of ice nuclei can strongly change subsequent homogeneous nucleation events (i.e., the ice crystal number densities) over a large variety of environmental conditions relevant for the upper troposphere. In most cases a strong reduction in ice crystal number concentrations formed in subsequent homogeneous freezing events is observed. The use of size-dependent freezing thresholds can change cloud properties when compared to more simple parameterizations and is most important at largest ice nuclei concentrations. Copyright 2010 by the American Geophysical Union.


Jaisi D.P.,Yale University | Blake R.E.,Yale University | Kukkadapu R.K.,Pacific Northwest National Laboratory
Geochimica et Cosmochimica Acta | Year: 2010

Iron (III) oxides are ubiquitous in near-surface soils and sediments and interact strongly with dissolved phosphates via sorption, co-precipitation, mineral transformation and redox-cycling reactions. Iron oxide phases are thus, an important reservoir for dissolved phosphate, and phosphate bound to iron oxides may reflect dissolved phosphate sources as well as carry a history of the biogeochemical cycling of phosphorus (P). It has recently been demonstrated that dissolved inorganic phosphate (DIP) in rivers, lakes, estuaries and the open ocean can be used to distinguish different P sources and biological reaction pathways in the ratio of 18O/ 16O (δ 18O P) in PO 4 3-. Here we present results of experimental studies aimed at determining whether non-biological interactions between dissolved inorganic phosphate and solid iron oxides involve fractionation of oxygen isotopes in PO 4. Determination of such fractionations is critical to any interpretation of δ 18O P values of modern (e.g., hydrothermal iron oxide deposits, marine sediments, soils, groundwater systems) to ancient and extraterrestrial samples (e.g., BIF's, Martian soils). Batch sorption experiments were performed using varied concentrations of synthetic ferrihydrite and isotopically-labeled dissolved ortho-phosphate at temperatures ranging from 4 to 95 °C. Mineral transformations and morphological changes were determined by X-Ray, Mössbauer spectroscopy and SEM image analyses. Our results show that isotopic fractionation between sorbed and aqueous phosphate occurs during the early phase of sorption with isotopically-light phosphate (P 16O 4) preferentially incorporated into sorbed/solid phases. This fractionation showed negligible temperature-dependence and gradually decreased as a result of O-isotope exchange between sorbed and aqueous-phase phosphate, to become insignificant at greater than ∼100 h of reaction. In high-temperature experiments, this exchange was very rapid resulting in negligible fractionation between sorbed and aqueous-phase phosphate at much shorter reaction times. Mineral transformation resulted in initial preferential desorption/loss of light phosphate (P 16O 4) to solution. However, the continual exchange between sorbed and aqueous PO 4, concomitant with this mineralogical transformation resulted again in negligible fractionation between aqueous and sorbed PO 4 at long reaction times (>2000 h). This finding is consistent with results obtained from natural marine samples. Therefore, 18O values of dissolved phosphate (DIP) in sea water may be preserved during its sorption to iron-oxide minerals such as hydrothermal plume particles, making marine iron oxides a potential new proxy for dissolved phosphate in the oceans. © 2009 Elsevier Ltd.


Braley J.C.,Washington State University | Braley J.C.,Pacific Northwest National Laboratory | Grimes T.S.,Washington State University | Nash K.L.,Washington State University
Industrial and Engineering Chemistry Research | Year: 2012

The TALSPEAK process is an established option for lanthanide/minor actinide separations using solvent extraction. In this process, selective extraction of lanthanides is achieved by contacting a water-soluble aminopolycarboxylate complexant in a concentrated carboxylic acid buffer with a liquid cation exchanging extractant in an immiscible organic diluent. Although TALSPEAK process development has been successful on several levels, studies of the detailed fundamental chemistry have revealed undesirable complex interactions between aqueous and organic solute species. These complications threaten to impair process modeling and could impact engineered operations. In the present work, results are reported describing equilibrium partitioning and phase transfer kinetics trends for trivalent lanthanide ions and americium into bis-2-ethyl(hexyl) phosphoric acid (HDEHP) or structural analog 2-ethyl(hexyl) phosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) organic phases from aqueous lactate solutions containing diethylenetriamine-N,N,N′,N″,N″- pentaacetic acid (DTPA), triethylenetetramine-N,N,N′,N″,N″, N″-hexaacetic acid (TTHA), or N-(2-hydroxyethyl)ethylenediamine-N, N′,N′-triacetic acid (HEDTA). The undesirable partitioning of Na +, lactic acid, and water into the organic phase is greatly reduced when HEH[EHP] replaces HDEHP as the extractant. TTHA appears to offer little advantage over DTPA in conventional TALSPEAK, but both DTPA and TTHA are too strong for use in combination with HEH[EHP]. The combination of HEDTA with HEH[EHP] achieves good balance and exhibits a nearly flat pH dependence between 2.5 and 4.5, in contrast with conventional TALSPEAK. The latter combination demonstrates more predictable performance than is seen in conventional TALSPEAK, while providing acceptable americium/lanthanide separation factors. The HEDTA/HEH[EHP] combination offers the additional advantage of more rapid phase transfer kinetics for the heavier lanthanides without the need for high concentrations of a lactate buffer. © 2011 American Chemical Society.


Wogman N.A.,Pacific Northwest National Laboratory
Journal of Radioanalytical and Nuclear Chemistry | Year: 2013

The International Atomic Energy Agency (IAEA) is committed to strengthening and streamlining the overall effectiveness of the IAEA safeguards system within the context of the Non-Proliferation Treaty (NPT). The IAEA has investigated the use of environmental monitoring techniques and a variety of techniques were studied as part of extensive field trials. The efficacy of long-range monitoring depends on the availability of mobile signature isotopes or compounds and on the ability to distinguish the nuclear signatures from background signals and attribute them to a source. The Comprehensive Nuclear Test Ban Treaty (CTBT) also requires a variety of environmental sampling and analysis techniques. This paper serves as a scientific basis to start discussions of environmental sampling techniques that could be considered for wide-area monitoring for the detection of undeclared nuclear activities within the NPT or for the possible future use within the CTBT. © Akadémiai Kiadó, Budapest, Hungary 2012.


Xiao J.,Pacific Northwest National Laboratory | Chernova N.A.,Binghamton University State University of New York | Stanley Whittingham M.,Binghamton University State University of New York
Chemistry of Materials | Year: 2010

The layered oxide cathode material LiMO2, where M = Ni 0.9.yMnyCo0.1 and 0.45 ≤ y ≤ 0.60, was synthesized by a coprecipitation method. X-ray diffraction analysis shows that the maximum manganese content in the stoichiometric material, i.e. with Li:M = 1. cannot exceed 50%; otherwise, a second phase is formed. Rietveld refinement reveals that increasing manganese content suppresses the disorder between the lithium and nickel ions. Magnetic measurements show that part of the Mn 4+ ions in the manganese rich compounds is reduced to Mn 3+; this results in a larger hysteresis loop due to the increased magnetic moment of the resulting ferrimagnctically ordered clusters. LiNi 0.4Mn0.5Co0.1O2 and LiNi 0.45Mn0.45 Co0.1O2 show similar electrochemical capacities of around 180 mAh/'g (between 2.5 and 4.6 V at 0.5 mA/cm2) for the first discharge. However, subsequent cycling of LiNi0.4Mn0.5Co0.1O2 results in faster capacity loss and poorer rate capability indicating that manganese rich compounds, with Li:M = 1:1, are probably not suitable candidates for lithium batteries. © 2009 American Chemical Society.


Lv D.,Pennsylvania State University | Gordin M.L.,Pennsylvania State University | Yi R.,Pennsylvania State University | Xu T.,Pennsylvania State University | And 4 more authors.
Advanced Functional Materials | Year: 2014

A self-assembled GeOx/reduced graphene oxide (GeO x/RGO) composite, where GeOx nanoparticles are grown directly on reduced graphene oxide sheets, is synthesized via a facile one-step reduction approach and studied by X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy, electron energy loss spectroscopy elemental mapping, and other techniques. Electrochemical evaluation indicates that incorporation of reduced graphene oxide enhances both the rate capability and reversible capacity of GeOx, with the latter being due to the RGO enabling reversible utilization of Li2O. The composite delivers a high reversible capacity of 1600 mAh g-1 at a current density of 100 mA g-1, and still maintains a capacity of 410 mAh g-1 at a high current density of 20 A g-1. Owing to the flexible reduced graphene oxide sheets enwrapping the GeOx particles, the cycling stability of the composite is also improved significantly. To further demonstrate its feasibility in practical applications, the synthesized GeOx/RGO composite anode is successfully paired with a high voltage LiNi0.5Mn1.5O4 cathode to form a full cell, which shows good cycling and rate performance. A GeOx/reduced graphene oxide (RGO) composite, where amorphous GeOx (1.01 < x < 1.07) nanoparticles are in intimate contact with well-dispersed RGO sheets, is successfully synthesized via a facile one-step reduction approach. The introduction of conductive RGO sheets into germanium oxide is a simple but effective strategy for enhancing the reversible utilization of Li2O and improving rate capability for Li+ storage in germanium oxides. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Rustad J.R.,University of California at Davis | Bylaska E.J.,Pacific Northwest National Laboratory | Jackson V.E.,University of Alabama | Dixon D.A.,University of Alabama
Geochimica et Cosmochimica Acta | Year: 2010

Density functional and correlated molecular orbital calculations (MP2) are carried out on B(OH)3·nH2O clusters (n=0, 6, 32), and B(OH)4 -·nH2O (n=0, 8, 11, 32) to estimate the equilibrium distribution of 10B and 11B isotopes between boric acid and borate in aqueous solution. For the large 32-water clusters, multiple conformations are generated from ab initio molecular dynamics simulations to account for the effect of solvent fluctuations on the isotopic fractionation. We provide an extrapolated value of the equilibrium constant α34 for the isotope exchange reaction 10B(OH)3(aq)+11B(OH)4 - (aq)=11B(OH)3(aq)+11B(OH)4 - (aq) of 1.026-1.028 near the MP2 complete basis set limit with 32 explicit waters of solvation. With some exchange-correlation functionals we find potentially important contributions from a tetrahedral neutral B(OH)3·H2O Lewis acid-base complex. The extrapolations presented here suggest that DFT calculations give a value for 103lnα34 about 15% higher than the MP2 calculations. © 2010 Elsevier Ltd.


Lichtner P.C.,Los Alamos National Laboratory | Hammond G.E.,Pacific Northwest National Laboratory
Vadose Zone Journal | Year: 2012

Evolution of a hexavalent uranium [U(VI)] plume at the Hanford 300 Area bordering the Columbia River was investigated to evaluate the roles of labile and nonlabile forms of U(VI) on the longevity of the plume. A high fidelity, three-dimensional, field-scale, reactive flow and transport model was used to represent the system. Richards' equation coupled to multicomponent reactive transport equations were solved for times up to 100 yr, taking into account rapid fluctuations in the Columbia River stage resulting in pulse releases of U(VI) into the river. The petascale computer code PFLOTRAN developed under a Department of Energy Scientific Discovery through Advanced Computing (SciDAC-2) project was used in the simulations and executed on Oak Ridge National Laboratory's Jaguar XT5 Cray supercomputer. Labile U(VI) was represented in the model through surface complexation reactions and its nonlabile form through dissolution of metatorbernite used as a surrogate mineral. Initial conditions were constructed corresponding to the U(VI) plume already in place to avoid uncertainties associated with the lack of historical data for the waste stream. The cumulative U(VI) flux into the river was compared for cases of equilibrium and multirate sorption models and for no sorption, and its sensitivity on the initial plume configuration was investigated. The presence of nonlabile U(VI) was found to be essential in explaining the longevity of the U(VI) plume and the prolonged high U(VI) concentrations at the site exceeding the USEPA maximum contaminant level for U(VI). © Soil Science Society of America.


Ronnebro E.,Pacific Northwest National Laboratory
Current Opinion in Solid State and Materials Science | Year: 2011

The group II alkaline-earth metal borohydrides, Mg(BH4) 2 and Ca(BH4)2 are among the most promising materials for light-weight, high-capacity hydrogen storage. Five years ago, little were known about the potential of these materials for reversible hydrogen storage, except for their high hydrogen content of 14.9 wt% and 11.6 wt% respectively. Theory predicted nearly ideal thermodynamics, but finding competing decomposition pathways with formation of very stable phases which limits cycle life. Solid-state synthesis routes have been developed and crystal structures and decomposition products have been identified as well as methods to improve hydrogen sorption performance including catalysis and nanoscience. Reversibility was demonstrated for both materials at high pressures and temperatures. We will here review recent progress and discuss challenges and future pathways towards applications. © 2010 Elsevier Ltd. All rights reserved.


Murray C.J.,Pacific Northwest National Laboratory
Journal of contaminant hydrology | Year: 2013

A large set of sediment samples from a 1600 m2 experimental plot within a 2.2 km2 vadose zone and groundwater uranium (VI) plume was subject to physical, chemical, and mineralogic characterization. The plot is being used for field experimentation on U(VI) recharge and transport processes within a persistent groundwater plume that exists in the groundwater-river interaction zone of the Columbia River at the U.S. DOE Hanford site. The samples were obtained during the installation of 35 tightly spaced (10 m separation) groundwater monitoring wells. The characterization measurements for each sample included total contaminant concentrations (U and Cu primarily), bicarbonate extractable U(VI), sequential 238U(VI) contaminant desorption Kd, 233U(VI) adsorption K(d), grain size distribution, surface area, extractable poorly crystalline Fe(III) oxides, and mineralogy. The characterization objective was to inform a conceptual model of coupled processes controlling the anomalous longevity of the plume, and to quantify the spatial heterogeneity of the contaminant inventory and the primary properties effecting reactive transport. Correlations were drawn between chemical, physical, and reaction properties, and Gaussian simulation was used to compute multiple 3-D realizations of extractable U(VI), the 233U(VI) adsorption K(d), and the distribution of the reactive <2 mm fraction. Adsorbed contaminant U(VI) was highest in the vadose zone and the zone of seasonal water table fluctuation lying at its base. Adsorbed U(VI) was measureable, but low, in the groundwater plume region where very high hydraulic conductivities existed. The distribution of adsorbed U(VI) displayed no apparent correlation with sediment physical or chemical properties. Desorption [238U(IV)] and adsorption [233U(VI)] K(d) values showed appreciable differences due to mass transfer controlled surface complexation and the effects of long subsurface residence times. The 233U(VI) adsorption K(d), a combined measure of surface complexation strength and site concentration, was relatively uniform throughout the domain, displaying correlation with fines distribution and surface area. The characterization results revealed U(VI) supplied to the groundwater plume through spatially heterogeneous recharge from residual contamination in the zone of seasonal water table fluctuation, and transport of U(VI) controlled by weak, kinetically-controlled surface complexation in the coarse-textured saturated zone. Geostatistical relationships for the adsorbed contaminant U distribution in the characterization domain allow an extrapolation to inventory at the plume scale, a critical unknown for remedial action. Copyright © 2012 Elsevier B.V. All rights reserved.


Wlazlowski G.,Warsaw University of Technology | Wlazlowski G.,University of Washington | Holt J.W.,University of Washington | Moroz S.,University of Washington | And 3 more authors.
Physical Review Letters | Year: 2014

We present variational Monte Carlo calculations of the neutron matter equation of state using chiral nuclear forces. The ground-state wave function of neutron matter, containing nonperturbative many-body correlations, is obtained from auxiliary-field quantum Monte Carlo simulations of up to about 340 neutrons interacting on a 103 discretized lattice. The evolution Hamiltonian is chosen to be attractive and spin independent in order to avoid the fermion sign problem and is constructed to best reproduce broad features of the chiral nuclear force. This is facilitated by choosing a lattice spacing of 1.5 fm, corresponding to a momentum-space cutoff of Λ=414MeV/c, a resolution scale at which strongly repulsive features of nuclear two-body forces are suppressed. Differences between the evolution potential and the full chiral nuclear interaction (Entem and Machleidt Λ=414MeV [L. Coraggio et al., Phys. Rev. C 87, 014322 (2013)]) are then treated perturbatively. Our results for the equation of state are compared to previous quantum Monte Carlo simulations that employed chiral two-body forces at next-to-next-to-leading order (N2LO). In addition, we include the effects of three-body forces at N2LO, which provide important repulsion at densities higher than 0.02fm-3 as well as two-body forces at next-to-next-to-next-to-leading order. © 2014 American Physical Society.


Laskin J.,Pacific Northwest National Laboratory
International Journal of Mass Spectrometry | Year: 2015

In this work, resonant ejection coupled with surface-induced dissociation (SID) in a Fourier transform ion cyclotron resonance mass spectrometer is used to examine fragmentation kinetics of two singly protonated hexapeptides, RYGGFL and KYGGFL, containing the basic arginine residue and less basic lysine residue at the N-terminus. The kinetics of individual reaction channels at different collision energies are probed by applying a short ejection pulse (1 ms) in resonance with the cyclotron frequency of a selected fragment ion and varying the delay time between ion-surface collision and resonant ejection while keeping total reaction delay time constant. Rice-Ramsperger-Kassel-Marcus (RRKM) modeling of the experimental data provides accurate threshold energies and activation entropies of individual reaction channels. Substitution of arginine with less basic lysine has a pronounced effect on the observed fragmentation kinetics of several pathways, including the b2 ion formation, but has little or no effect on formation of the b5+H2O fragment ion. The combination of resonant ejection SID, time- and collision energy-resolved SID, and RRKM modeling of both types of experimental data provides a detailed mechanistic understanding of the primary dissociation pathways of complex gaseous ions. © 2015 Elsevier B.V. All rights reserved.


Bi Y.,University of Michigan | Hyun S.P.,University of Michigan | Hyun S.P.,Korea Institute of Geoscience and Mineral Resources | Kukkadapu R.,Pacific Northwest National Laboratory | Hayes K.F.,University of Michigan
Geochimica et Cosmochimica Acta | Year: 2013

The long-term success of in situ reductive immobilization of uranium (U) depends on the stability of U(IV) precipitates (e.g., uraninite) in the presence of natural oxidants, such as oxygen, Fe(III) hydroxides, or nitrite. Field and laboratory studies have implicated iron sulfide minerals as redox buffers or oxidant scavengers that may slow oxidation of reduced U(VI) solid phases. Yet, the inhibition mechanism(s) and reaction rates of uraninite (UO2) oxidative dissolution by oxic species such as oxygen in FeS-bearing systems remain largely unresolved. To address this knowledge gap, abiotic batch experiments were conducted with synthetic UO2 in the presence and absence of synthetic mackinawite (FeS) under simulated groundwater conditions of pH=7, PO2=0.02atm, and PCO2=0.05atm. The kinetic profiles of dissolved uranium indicate that FeS inhibited UO2 dissolution for about 51h by effectively scavenging oxygen and keeping dissolved oxygen (DO) low. During this time period, oxidation of structural Fe(II) and S(-II) of FeS were found to control the DO levels, leading to the formation of iron oxyhydroxides and elemental sulfur, respectively, as verified by X-ray diffraction (XRD), Mössbauer and X-ray absorption spectroscopy (XAS). After FeS was depleted due to oxidation, DO levels increased and UO2 oxidative dissolution occurred at an initial rate of rm=1.2±0.4×10-8molg-1s-1, higher than rm=5.4±0.3×10-9molg-1s-1 in the control experiment where FeS was absent. XAS analysis confirmed that soluble U(VI)-carbonato complexes were adsorbed by iron oxyhydroxides (i.e., nanogoethite and lepidocrocite) formed from FeS oxidation, which provided a sink for U(VI) retention. This work reveals that both the oxygen scavenging by FeS and the adsorption of U(VI) to FeS oxidation products may be important in U reductive immobilization systems subject to redox cycling events. © 2012 Elsevier Ltd.


Hammond G.E.,Pacific Northwest National Laboratory | Lichtner P.C.,Los Alamos National Laboratory
Water Resources Research | Year: 2010

High-resolution, three-dimensional, reactive flow and transport simulations are carried out to describe the migration of hexavalent uranium [U(VI)] at the Hanford 300 Area bordering the Columbia River and to better understand the persistence of the uranium plume at the site. The computer code PFLOTRAN developed under a DOE SciDAC-2 project is employed in the simulations that are executed on ORNL's Cray XT4/XT5 supercomputer Jaguar. The conceptual model used in the simulations is based on the recognition of three distinct phases or time periods in the evolution of the U(VI) plume. These correspond to (1) initial waste emplacement; (2) initial presence of both labile and nonlabile U(VI) with an evolved U(VI) plume extending from the source region to the river boundary, representing present-day conditions; and (3) the complete removal of all nonlabile U(VI) and labile U(VI) in the vadose zone. This work focuses primarily on modeling Phase II using equilibrium and multirate sorption models for labile U(VI) and a continuous source release of nonlabile U(VI) in the South Process Pond through dissolution of metatorbernite as a surrogate mineral. For this case, rapid fluctuations in the Columbia River stage combined with the slow release of nonlabile U(VI) from contaminated sediment are found to play a predominant role in determining the migration behavior of U(VI) with sorption only a second-order effect. Nevertheless, a multirate model was essential in explaining breakthrough curves obtained from laboratory column experiments using the same sediment and is demonstrated to be important in Phase III. The calculations demonstrate that U(VI) is discharged to the river at a highly fluctuating rate in a ratchet-like behavior as the river stage rises and falls. The high-frequency fluctuations must be resolved in the model to calculate the flux of U(VI) at the river boundary. By time averaging the instantaneous flux to average out noise superimposed on the river stage fluctuations, the cumulative U(VI) flux to the river is found to increase approximately linearly with time. The flow rate and U(VI) flux are highly sensitive to the conductance boundary condition that describes the river-sediment interface. By adjusting the conductance coefficient to give a better match to the measured piezometric head, good agreement was obtained with field studies for both the mean flux of water of 109 kg/yr and U(VI) of 25 kg/yr at the river-aquifer boundary for a computational domain encompassing the South Process Pond. Finally, it is demonstrated that, through global mass conservation, the U(VI) leach rate from the source region is related to the U(VI) flux at the river boundary. Copyright 2010 by the American Geophysical Union.


Kalenderski S.,King Abdullah University of Science and Technology | Stenchikov G.,King Abdullah University of Science and Technology | Zhao C.,Pacific Northwest National Laboratory
Atmospheric Chemistry and Physics | Year: 2013

We used WRF-Chem, a regional meteorological model coupled with an aerosol-chemistry component, to simulate various aspects of the dust phenomena over the Arabian Peninsula and Red Sea during a typical winter-time dust event that occurred in January 2009. The model predicted that the total amount of emitted dust was 18.3 Tg for the entire dust outburst period and that the two maximum daily rates were ∼2.4 Tg day-1 and ∼1.5 Tg day-1, corresponding to two periods with the highest aerosol optical depth that were well captured by ground-and satellite-based observations. The model predicted that the dust plume was thick, extensive, and mixed in a deep boundary layer at an altitude of 3-4 km. Its spatial distribution was modeled to be consistent with typical spatial patterns of dust emissions. We utilized MODIS-Aqua and Solar Village AERONET measurements of the aerosol optical depth (AOD) to evaluate the radiative impact of aerosols. Our results clearly indicated that the presence of dust particles in the atmosphere caused a significant reduction in the amount of solar radiation reaching the surface during the dust event. We also found that dust aerosols have significant impact on the energy and nutrient balances of the Red Sea. Our results showed that the simulated cooling under the dust plume reached 100 W m-2, which could have profound effects on both the sea surface temperature and circulation. Further analysis of dust generation and its spatial and temporal variability is extremely important for future projections and for better understanding of the climate and ecological history of the Red Sea. © 2013 Author(s).


Neale R.B.,U.S. National Center for Atmospheric Research | Richter J.,U.S. National Center for Atmospheric Research | Park S.,U.S. National Center for Atmospheric Research | Lauritzen P.H.,U.S. National Center for Atmospheric Research | And 3 more authors.
Journal of Climate | Year: 2013

The Community Atmosphere Model, version 4 (CAM4), was released as part of the Community Climate System Model, version 4 (CCSM4). The finite volume (FV) dynamical core is now the default because of its superior transport and conservation properties. Deep convection parameterization changes include a dilute plume calculation of convective available potential energy (CAPE) and the introduction of convective momentum transport (CMT). An additional cloud fraction calculation is now performed following macrophysical state updates to provide improved thermodynamic consistency. A freeze-drying modification is further made to the cloud fraction calculation in very dry environments (e.g., the Arctic), where cloud fraction and cloud water values were often inconsistent in CAM3. In CAM4 the FV dynamical core further degrades the excessive trade-wind simulation, but reduces zonal stress errors at higher latitudes. Plume dilution alleviates much of the midtropospheric tropical dry biases and reduces the persistent monsoon precipitation biases over the Arabian Peninsula and the southern Indian Ocean. CMT reduces much of the excessive tradewind biases in eastern ocean basins. CAM4 shows a global reduction in cloud fraction compared to CAM3, primarily as a result of the freeze-drying and improved cloud fraction equilibrium modifications. Regional climate feature improvements include the propagation of stationary waves from the Pacific into midlatitudes and the seasonal frequency of Northern Hemisphere blocking events. A 18 versus 28 horizontal resolution of the FV dynamical core exhibits superior improvements in regional climate features of precipitation and surface stress. Improvements in the fully coupled mean climate between CAM3 and CAM4 are also more substantial than in forced sea surface temperature (SST) simulations.©2013 American Meteorological Society.


Yoneyama K.,Japan Agency for Marine - Earth Science and Technology | Zhang C.,University of Miami | Long C.N.,Pacific Northwest National Laboratory
Bulletin of the American Meteorological Society | Year: 2013

A field campaign in the Indian Ocean region collected unprecedented observations during October 2011'March 2012 to help advance knowledge of physical processes of the Madden-Julian oscillation (MJO). Studies on the MJO mean seasonal cycle indicated that main MJO initiation activity takes place in the central IO from October to March, with the highest occurrence probability near the equator in October-January. The special observing period (SOP) was designed to obtain high-resolution data to capture the diurnal cycle of convective activity with the maximum observing capacity. All other instruments continued to operate after the SOP until the end of the intensive observing period (IOP). Accompanying the sounding arrays and equally essential to the field campaign was a radar network. The 2011-12 MJO field campaign provided observations that are unique in several aspects in comparison to previous tropical field campaigns that aimed at interactions between atmospheric convection and its large-scale environment and between the atmosphere and ocean.


Zhang X.,Pacific Northwest National Laboratory | Srinivasan R.,Texas A&M University
Environmental Modelling and Software | Year: 2010

Precipitation is one important input variable for land surface hydrologic and ecological models. Next Generation Radar (NEXRAD) can provide precipitation products that cover most of the conterminous United States at high resolution (approximately 4 km × 4 km). There are two major issues concerning the application of NEXRAD data: 1) the lack of a NEXRAD geo-processing and geo-referring program and 2) bias correction of NEXRAD estimates. However, in public domain, there is no Geographic Information System (GIS) software that can use geostatistical approaches to calibrate NEXRAD data using raingauge data, and automatically process NEXRAD data for hydrologic and ecological models. In this study, we developed new GIS software for NEXRAD validation and calibration (NEXRAD-VC) using raingauge data. NEXRAD-VC can automatically read in NEXRAD data in NetCDF or XMRG format, transform projection of NEXRAD data to match with raingauge data, apply different geostatistical approaches to calibrate NEXRAD data using raingauge data, evaluate performance of different calibration methods using leave-one-out cross-validation scheme, output spatial precipitation maps in ArcGIS grid format, calculate spatial average precipitation for each spatial modeling unit used by hydrologic and ecological models. The major functions of NEXRAD-VC are illustrated in the Little River Experimental Watershed (LREW) in Georgia using daily precipitation records of fifteen raingauges and NEXRAD products of five years. The validation results show that NEXRAD has a high success rate for detecting rain and no-rain events: 82.8% and 95.6%, respectively. NEXRAD estimates have high correlation with raingauge observations (correlation coefficient of 0.91), but relatively larger relative mean absolute error value of 36%. It is also worth noting that the performance of NEXRAD increases with the decreasing of rainfall variability. Three methods (Bias Adjustment method (BA), Regressing Kriging (RK), and Simple Kriging with varying local means (SKlm)) were employed to calibrate NEXRAD using raingauge data. Overall, SKlm performed the best among these methods. Compared with NEXRAD, SKlm improved the correlation coefficient to 0.96 and the relative mean absolute error to 22.8%, respectively. SKlm also increased the success rate of detection of rain and no-rain events to 87.47% and 96.05%, respectively. Further analysis of the performance of the three calibration methods and NEXRAD for daily spatial precipitation estimation shows that no one method can consistently provide better results than the other methods for each evaluation coefficient for each day. It is suggested that multiple methods be implemented to predict spatial precipitation. The NEXRAD-VC developed in this study can serve as an effective and efficient tool to batch process large amounts of NEXRAD data for hydrologic and ecological modeling. © 2010 Elsevier Ltd.


Dang L.X.,Pacific Northwest National Laboratory | Wick C.D.,Louisiana Tech University
Journal of Physical Chemistry B | Year: 2011

Molecular dynamics simulations with many-body interactions were carried out to systematically study the effect of anion type, tetrafluoroborate [BF 4] or hexafluorophosphate [PF6], paired with the cation 1-butyl-3-methylimidazolium [bmim], on the interfacial absorption of gases in room temperature ionic liquids (RTILs). The potentials of mean force (PMF) of CO2 and H2O at 350 K were calculated across the air-liquid interfaces of [bmim][BF4] and [bmim][PF6]. We found that the PMFs for H2O exhibited no interfacial minima at both interfaces, while the corresponding PMFs for CO2 had significant free energy minima there. However, the PMFs for H2O showed a much higher interfacial free energy than in the bulk for [bmim][BF4], but only a slightly higher interfacial free energy for [bmim][PF6] than in bulk. The reason for this was due to the more hydrophilic nature of the [BF 4] anion, and the fact that [BF4] was found to have little propensity for the interface. Our results show that H2O is much more likely to be found at the air-[bmim][PF6] interface than at the air-[bmim][BF4] interface. The free energies of solvation were found to be more negative for [bmim][BF4] than [bmim][PF6] for water and similar for CO2. This observation is consistent with experimental Henry's law coefficients. Our results show that anion type, in addition to affecting the free energy of solvation into RTILs, should also significantly influence the uptake mechanism. © 2011 American Chemical Society.


Zheng J.,Pacific Northwest National Laboratory
Electrochimica Acta | Year: 2013

High capacity cathode materials Li[Li0.2Mn0.54Ni 0.13Co0.13]O2-xFx (x = 0, 0.05 and 0.10) have been synthesized by a sol-gel method using NH4F as F source. The effects of fluorine content on the structure, morphology and electrochemical performance of the Li[Li0.2Mn0.54Ni 0.13Co0.13]O2-xFx have been extensively studied. With fluorine doping, cycling stability of Li[Li 0.2Mn0.54Ni0.13Co0.13]O 2-xFx is significantly improved because of the stabilization of the host structure. Li[Li0.2Mn0.54Ni 0.13Co0.13]O1.95F0.05 shows a capacity retention of 88.1% after 50 cycles at 0.2 C at room temperature, much higher than that of 72.4% for pristine one. The improvement mechanism of fluorine doping has been investigated by electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). The results demonstrate that fluorine incorporation stabilizes the electrode/electrolyte interface by suppressing the formation of poorly conducting LiF in the SEI layer and thus maintains stable interfacial resistances. As compared to the enhanced material structure, the stabilized electrode/electrolyte interface is the primary factor contributing to the improved electrochemical performance. In addition, the thermal stability of fully delithiated electrode is also greatly improved by fluorine doping. © 2013 Elsevier Ltd. All rights reserved.


Malone E.L.,Pacific Northwest National Laboratory
Weather, Climate, and Society | Year: 2013

Climate change is increasingly recognized as having national security implications, which has prompted dialogue between the climate change and national security communities-with resultant advantages and differences. Climate change research has proven useful to the national security community sponsors in several ways. It has opened security discussions to consider climate as well as political factors in studies of the future. It has encouraged factoring in the stresses placed on societies by climate changes (of any kind) to help assess the potential for state stability. And it has shown that changes such as increased heat, more intense storms, longer periods without rain, and earlier spring onset call for building climate resilience as part of building stability. For the climate change research community, studies from a national security point of view have revealed research lacunae, such as the lack of usable migration studies. This has also pushed the research community to consider second- and third-order impacts of climate change, such as migration and state stability, which broadens discussion of future impacts beyond temperature increases, severe storms, and sea level rise and affirms the importance of governance in responding to these changes. The increasing emphasis in climate change science toward research in vulnerability, resilience, and adaptation also frames what the intelligence and defense communities need to know, including where there are dependencies and weaknesses that may allow climate change impacts to result in security threats and where social and economic interventions can prevent climate change impacts and other stressors from resulting in social and political instability or collapse. © 2013 American Meteorological Society.


Vasdekis A.E.,Ecole Polytechnique Federale de Lausanne | Vasdekis A.E.,Pacific Northwest National Laboratory
RSC Advances | Year: 2013

Life on Earth is comprised mostly of microbes with significant implications in disease and carbon cycling. However, their dimensions and mobility make microbes challenging to analyse on-chip. A sub-micron resolution microfluidic system (sub-microfluidics) capable of trapping and releasing single Escherichia coli bacteria is presented. The fabrication method based on electron-beam and cast molding lithography is described, as well as the trap and release of single E. coli. The release time from the trap is found to depend on cell morphology. © 2013 The Royal Society of Chemistry.


Zhang J.,University of North Carolina at Chapel Hill | Welch G.,University of Central Florida | Bishop G.,University of North Carolina at Chapel Hill | Huang Z.,Pacific Northwest National Laboratory
IEEE Transactions on Sustainable Energy | Year: 2014

As electricity demand continues to grow and renewable energy increases its penetration in the power grid, real-time state estimation becomes essential for system monitoring and control. Recent development in phasor technology makes it possible with high-speed time-synchronized data provided by phasor measurement units (PMUs). In this paper, we present a two-stage Kalman filter approach to estimate the static state of voltage magnitudes and phase angles, as well as the dynamic state of generator rotor angles and speeds. Kalman filters achieve optimal performance only when the system noise characteristics have known statistical properties (zero-mean, Gaussian, and spectrally white). However, in practice, the process and measurement noise models are usually difficult to obtain. Thus, we have developed the adaptive Kalman filter with inflatable noise variances (AKF with InNoVa), an algorithm that can efficiently identify and reduce the impact of incorrect system modeling and/or erroneous measurements. In stage one, we estimate the static state from raw PMU measurements using the AKF with InNoVa; then in stage two, the estimated static state is fed into an extended Kalman filter to estimate the dynamic state. The simulations demonstrate its robustness to sudden changes of system dynamics and erroneous measurements. © 2010-2012 IEEE.


Chen G.,CAS Shanghai Institute of Applied Physics | Chen G.,Lawrence Berkeley National Laboratory | Zwart P.H.,Lawrence Berkeley National Laboratory | Li D.,Pacific Northwest National Laboratory
Physical Review Letters | Year: 2013

The ring angular correlation function is a characteristic feature determined by the particle structure. Averaging over a large number of ring angular correlation functions calculated from x-ray diffraction patterns will cancel out the cross correlations between different particles and converge to the autocorrelation functions of single particles. Applied on heterogeneous disordered ensembles, the retrieved function is a linear combination of a single-particle autocorrelation function multiplied by the molar ratios in a heterogeneous system. Using this relation, the ring angular correlation functions of the individual component particles in the heterogeneous system can be retrieved through the high throughput fluctuation x-ray scattering technique. This method is demonstrated with a simulated heterogeneous system composed of nanorods, nanoprism, and nanorice. © 2013 American Physical Society.


Ewbank J.L.,Georgia Institute of Technology | Kovarik L.,Pacific Northwest National Laboratory | Kenvin C.C.,Georgia Institute of Technology | Sievers C.,Georgia Institute of Technology
Green Chemistry | Year: 2014

Two methods, dry impregnation (DI) and controlled adsorption (CA), are used for the preparation of Co/Al2O3 catalysts for methane dry reforming reactions. Point of zero charge (PZC) measurements, pH-precipitation studies, and adsorption isotherms are used to develop a synthesis procedure in which deposition of Co2+ takes place in a more controlled manner than metal deposition during drying in synthesis by dry impregnation. The possible adsorption phenomena that occur during preparation of Co/Al2O 3 catalysts by controlled adsorption are discussed. H2 chemisorption and TEM show that catalysts prepared by CA have smaller average particle sizes and higher dispersions. TPR studies show that for the sample prepared by CA a higher amount of cobalt is reduced to its metallic state and that more CoAl2O4 spinel species are present relative to DI samples. The catalyst prepared by CA shows higher activity and slower deactivation for methane dry reforming than the catalyst prepared by DI. XPS and C, H, N analysis on spent catalysts confirm two types of carbonaceous deposits are formed depending on the preparation method. © 2014 The Royal Society of Chemistry.


Hrma P.,Pacific Northwest National Laboratory
Journal of Non-Crystalline Solids | Year: 2010

Under typical glass-processing conditions, crystals nucleate, grow, and dissolve in a nonuniform temperature field in a melt subjected to deformation and flow. Using examples of the results obtained on nuclear waste glasses, this paper describes various phenomena associated with crystallization under non-static conditions, such as crystal formation during batch melting, crystal settling at the melter bottom, and crystal precipitation during glass cooling, including its impact on glass corrosion resistance. © 2010 Elsevier B.V. All rights reserved.


De Anna P.,Massachusetts Institute of Technology | Dentz M.,CSIC - Institute of Environmental Assessment And Water Research | Tartakovsky A.,University of South Florida | Tartakovsky A.,Pacific Northwest National Laboratory | Le Borgne T.,CNRS Geosciences Laboratory of Rennes
Geophysical Research Letters | Year: 2014

The mixing dynamics resulting from the combined action of diffusion, dispersion, and advective stretching of a reaction front in heterogeneous flows leads to reaction kinetics that can differ by orders of magnitude from those measured in well-mixed batch reactors. The reactive fluid invading a porous medium develops a filamentary or lamellar front structure. Fluid deformation leads to an increase of the front length by stretching and consequently a decrease of its width by compression. This advective front deformation, which sharpens concentration gradients across the interface, is in competition with diffusion, which tends to increase the interface width and thus smooth concentration gradients. The lamella scale dynamics eventually develop into a collective behavior through diffusive coalescence, which leads to a disperse interface whose width is controlled by advective dispersion. We derive a new approach that quantifies the impact of these filament scale processes on the global mixing and reaction kinetics. The proposed reactive filament model, based on the elementary processes of stretching, coalescence, and fluid particle dispersion, provides a new framework for predicting reaction front kinetics in heterogeneous flows. Key Points We propose a new model based on stretching, coalescence, and dispersion The coalescence of filament-like structures impact the global reaction kinetics Our model provides a framework for predicting heterogeneous front kinetics ©2014. American Geophysical Union. All Rights Reserved.


Devanathan R.,Pacific Northwest National Laboratory | Weber W.J.,University of Tennessee at Knoxville | Weber W.J.,Oak Ridge National Laboratory | Gale J.D.,Curtin University Australia
Energy and Environmental Science | Year: 2010

We have used molecular dynamics simulations to investigate the effects of radiation damage accumulation in two pyrochlore-structured ceramics, namely Gd2Ti2O7 and Gd2Zr2O 7. It is well known from experiment that the titanate is susceptible to radiation-induced amorphization, while the zirconate does not go amorphous under prolonged irradiation. Our simulations show that cation Frenkel pair accumulation eventually leads to amorphization of Gd2Ti 2O7, and both anion disorder and cation disorder occur during damage accumulation. Amorphization in Gd2Ti2O 7 is accompanied by a density decrease of about 12.7% and a decrease of about 50% in the elastic modulus. In Gd2Zr2O 7, amorphization does not occur, because the residual damage introduced by radiation is not sufficiently energetic to destabilize the crystal structure and drive the material amorphous. Subtle differences in damage accumulation and annealing between the two pyrochlores lead to drastically different radiation response as the damage accumulates. © 2010 The Royal Society of Chemistry.


Goulden M.L.,University of California at Irvine | Mcmillan A.M.S.,University of California at Irvine | Winston G.C.,University of California at Irvine | Rocha A.V.,University of California at Irvine | And 3 more authors.
Global Change Biology | Year: 2011

We combined year-round eddy covariance with biometry and biomass harvests along a chronosequence of boreal forest stands that were 1, 6, 15, 23, 40, 74, and 154 years old to understand how ecosystem production and carbon stocks change during recovery from stand-replacing crown fire. Live biomass (Clive) was low in the 1 and 6 year old stands, and increased following a logistic pattern to high levels in the 74 and 154year old stands. Carbon stocks in the forest floor (Cforest floor) and coarse woody debris (CCWD) were comparatively high in the 1year old stand, reduced in the 6 through 40year old stands, and highest in the 74 and 154year old stands. Total net primary production (TNPP) was reduced in the 1 and 6year old stands, highest in the 23 through 74year old stands and somewhat reduced in the 154year old stand. The NPP decline at the 154year old stand was related to increased autotrophic respiration rather than decreased gross primary production (GPP). Net ecosystem production (NEP), calculated by integrated eddy covariance, indicated the 1 and 6 year old stands were losing carbon, the 15year old stand was gaining a small amount of carbon, the 23 and 74year old stands were gaining considerable carbon, and the 40 and 154year old stands were gaining modest amounts of carbon. The recovery from fire was rapid; a linear fit through the NEP observations at the 6 and 15year old stands indicated the transition from carbon source to sink occurred within 11-12 years. The NEP decline at the 154year old stand appears related to increased losses from Clive by tree mortality and possibly from Cforest floor by decomposition. Our findings support the idea that NPP, carbon production efficiency (NPP/GPP), NEP, and carbon storage efficiency (NEP/TNPP) all decrease in old boreal stands. © 2010 Blackwell Publishing Ltd.


Zhang L.,Central China Normal University | Zhang A.,Central China Normal University | Du D.,Central China Normal University | Lin Y.,Pacific Northwest National Laboratory
Nanoscale | Year: 2012

We demonstrate a facile procedure to efficiently prepare Prussian blue nanocubes/reduced graphene oxide (PBNCs/rGO) nanocomposite by directly mixing Fe 3+ and [Fe(CN) 6] 3- in the presence of GO in polyethyleneimine aqueous solution, resulting in a novel acetylcholinesterase (AChE) biosensor for detection of organophosphorus pesticides (OPs). The obtained nanocomposite was characterized by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and energy-dispersive X-ray (EDX) microanalysis. It was clearly observed that the nanosheet has been decorated with cubic PB nanoparticles and nearly all the nanoparticles are distributed uniformly only on the surface of the reduced GO. No isolated PB nanoparticles were observed, indicating the strong interaction between PB nanocubes and the reduced GO and the formation of PBNCs/rGO nanocomposite. The obtained PBNCs/rGO based AChE biosensor make the peak potential shift negatively to 220 mV. The over-potential decreases ∼460 mV compared to that on a bare electrode, suggesting that PBNCs/rGO has a high electrocatalytic activity towards the oxidation of thiocholine. The AChE biosensor shows rapid response and high sensitivity for detection of monocrotophos with a linear range from 1.0 to 600 ng mL -1 and a detection limit of 0.1 ng mL -1. These results suggest that the PBNCs/rGO hybrids nanocomposite exhibited high electrocatalytic activity towards the oxidation of thiocholine, which lead to the sensitive detection of OP pesticides. This journal is © 2012 The Royal Society of Chemistry.


Kerisit S.,Pacific Northwest National Laboratory | Pierce E.M.,Oak Ridge National Laboratory
Journal of Non-Crystalline Solids | Year: 2012

Monte Carlo simulations were performed to investigate the mechanisms of glass dissolution as equilibrium conditions are approached in both static and flow-through conditions. The glasses studied are borosilicate glasses in the compositional range (80 - x)% SiO 2 (10 + x / 2)% B 2O 3 (10 + x / 2)% Na 2O, where 5 < x < 30%. In static conditions, dissolution/condensation reactions lead to the formation, for all compositions studied, of a blocking layer composed of polymerized Si sites with principally 4 connections to nearest Si sites. This layer forms atop the altered glass layer and shows similar composition and density for all glass compositions considered. In flow-through conditions, three main dissolution regimes are observed: at high flow rates, the dissolving glass exhibits a thin alteration layer and congruent dissolution; at low flow rates, a blocking layer is formed as in static conditions but the simulations show that water can occasionally break through the blocking layer causing the corrosion process to resume; and, at intermediate flow rates, the glasses dissolve incongruently with an increasingly deepening altered layer. The simulation results suggest that, in geological disposal environments, small perturbations or slow flows could be enough to prevent the formation of a permanent blocking layer. Finally, a comparison between predictions of the linear rate law and the Monte Carlo simulation results indicates that, in flow-through conditions, the linear rate law is applicable at high flow rates and deviations from the linear rate law occur under low flow rates (e.g., at near-saturated conditions with respect to amorphous silica). This effect is associated with the complex dynamics of Si dissolution/condensation processes at the glass-water interface. © 2012 Elsevier Ltd. All rights reserved.


Muhlbauer A.,University of Washington | Berry E.,University of Utah | Comstock J.M.,Pacific Northwest National Laboratory | MacE G.G.,University of Utah
Journal of Geophysical Research: Atmospheres | Year: 2014

In this study, the effect of uncertainties in the parameterization of ice microphysical processes and initial conditions on the variability of cirrus microphysical and radiative properties are investigated in a series of cloud system-resolving perturbed physics ensemble (PPE) and initial condition ensemble (ICE) simulations. Three cirrus cases representative of midlatitude, subtropical, and tropical anvil cirrus are examined. The variability in cirrus properties induced by perturbing uncertain parameters in ice microphysics parameterizations outweighs the variability induced by perturbing the initial conditions in midlatitude and subtropical cirrus. However, in tropical anvil cirrus the variability spanned by the PPE and ICE simulations is on the same order of magnitude. Uncertainties in the parameterization of ice microphysical processes affect the vertical distribution of cloud fraction, ice water content, and cloud thickness, whereas cirrus cloud cover is only marginally affected. The top three uncertainties controlling the microphysical variability and radiative impact of cirrus clouds are the mode of ice nucleation, the number concentrations of ice nuclei available for heterogeneous freezing, and the threshold size of the parameterized ice autoconversion process. Uncertainties in ice fall speeds are of minor importance. Changes in the ice deposition coefficient induce only transient effects on the microphysical properties and radiative impacts of cirrus except in cases of very low ice deposition coefficients of about 0.05. Changes in the sulfate aerosol number concentration available for homogeneous freezing have virtually no effect on the microphysical properties and radiative impact of midlatitude and subtropical cirrus but a minor effect on tropical anvil cirrus. Key Points Uncertainties in ice microphysics outweigh uncertainties in initial conditions Ice fall speeds are the leading uncertainty affecting cirrus radiative impact Sensitivity of cirrus properties and radiative impact is largest at midlatitudes. © 2014. American Geophysical Union. All Rights Reserved.


Ronnebro E.,Pacific Northwest National Laboratory
Journal of Physics and Chemistry of Solids | Year: 2010

This overview will highlight features of the main classes of hydrogen storage materials based on their crystal structures. High-pressure techniques have proven to be a useful approach to rapidly discover light-weight, high-capacity hydrogen storage materials in the solid state. Focus will be on three different materials systems; magnesium-based transition metal hydrides, alanates and borohydrides, their crystal structures and properties, prepared by high-pressure sintering, high-energy ball milling or in a cubic anvil. © 2010 Elsevier Ltd.


Elliott D.C.,Pacific Northwest National Laboratory
Current Opinion in Chemical Engineering | Year: 2015

This review addresses recent developments in biomass fast pyrolysis bio-oil upgrading by catalytic hydrotreating. The research in the field has expanded dramatically in the past few years with numerous new research groups entering the field while existing efforts from others grow. The issues revolve around the catalyst formulation and operating conditions. Much work in batch reactor tests with precious metal catalysts needs further validation to verify long-term operability in continuous flow systems. The effect of the low level of sulfur in bio-oil needs more study to be better understood. Utilization of the upgraded bio-oil for feedstock to finished fuels is still in an early stage of understanding. © 2015 Published by Elsevier Ltd.


Traub R.J.,Pacific Northwest National Laboratory
Health Physics | Year: 2010

In vivo monitoring facilities determine the absence or presence of internally entrained radionuclides. To be of greatest utility, the detection systems must detect and quantify the nuclides of interest at levels of interest. Phantoms have been developed to improve measurements at in vivo monitoring facilities. Since the 1970's, the torso phantom originally developed at Lawrence Livermore National Laboratory (LLNL, or simply "Livermore") continues to be a well-used tool at lung monitoring facilities, especially for the detection of low-energy photons from transuranics. The history of its development from need through design development and current availability is summarized. The authors have taken the LLNL phantom one step further by scanning the phantom surface and announce the availability of the scan files on the Internet. Copyright © 2010 Health Physics Society.


Zhang F.,The Broad Institute of MIT and Harvard | Zhang F.,Massachusetts Institute of Technology | Vierock J.,Humboldt University of Berlin | Yizhar O.,Weizmann Institute of Science | And 10 more authors.
Cell | Year: 2011

The capture and utilization of light is an exquisitely evolved process. The single-component microbial opsins, although more limited than multicomponent cascades in processing, display unparalleled compactness and speed. Recent advances in understanding microbial opsins have been driven by molecular engineering for optogenetics and by comparative genomics. Here we provide a Primer on these light-activated ion channels and pumps, describe a group of opsins bridging prior categories, and explore the convergence of molecular engineering and genomic discovery for the utilization and understanding of these remarkable molecular machines. © 2011 Elsevier Inc.


The oxidation of NO was explored on a mixed Fe + Cr oxide surface using temperature-programmed desorption (TPD). NO desorbs from (Fe,Cr) 3O4(1 1 1) in two main peaks at 220 and 370 K, with a third minor peak at ∼315 K. O2 TPD shows similar behavior. The strongly and weakly bound molecules are due to adsorption at Fe2+ and Fe3+ sites, respectively, and the minor states are assigned to Cr3+ sites. No thermal decomposition was detected for adsorbed NO, whereas ∼10% of the adsorbed O2 dissociated at Fe2+ sites. NO reacts with preadsorbed O2 to produce surface nitrate, as confirmed by isotopic labeling, which decomposes in TPD at 425 K. Atomically adsorbed O does not react with NO. Fe3+ and Cr3+ sites do not appear to participate in NO oxidation. Irradiation of adsorbed NO or NO + O2 with 460 nm light results predominantly in photodesorption, which limits the extent of possible surface photoreactions. © 2014 Elsevier Inc. All rights reserved.


Tartakovsky A.M.,Pacific Northwest National Laboratory
Stochastic Environmental Research and Risk Assessment | Year: 2010

A new Lagrangian particle model based on smoothed particle hydrodynamics (SPH) is developed and used to simulate Darcy scale flow and transport in porous media. The method has excellent conservation properties and treats advection exactly. The Lagrangian method is used in stochastic analysis of miscible density-driven fluid flows. Results show that heterogeneity significantly increases dispersion and slows development of Rayleigh-Taylor instability. The presented numerical examples illustrate the advantages of Lagrangian methods for stochastic transport simulations. © 2010 Springer-Verlag.


Aydin C.,University of California at Davis | Lu J.,University of California at Davis | Browning N.D.,University of California at Davis | Browning N.D.,Pacific Northwest National Laboratory | Gates B.C.,University of California at Davis
Angewandte Chemie - International Edition | Year: 2012

Like billiard balls: Atomic-scale observations by electron microscopy of supported iridium nanoclusters show that the nanoclusters aggregate to reach a critical diameter of approximately 1nm and then resist further aggregation (see picture). The observations highlight the potential for this catalyst to assemble into clusters that may be nearly optimum for catalytic activity. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Lu J.,University of California at Davis | Aydin C.,University of California at Davis | Browning N.D.,University of California at Davis | Browning N.D.,Pacific Northwest National Laboratory | Gates B.C.,University of California at Davis
Angewandte Chemie - International Edition | Year: 2012

As good as atomic gold: Aberration-corrected scanning transmission electron microscopy images of zeolite NaY-supported mononuclear gold complexes, obtained with atomic resolution of the gold atoms, showed the locations of the gold complexes in the zeolite framework (see picture) and identified them as the catalytically active species for CO oxidation at 298K and 1bar. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Wang S.-Y.,Utah State University | Hipps L.,Utah State University | Gillies R.R.,Utah State University | Yoon J.-H.,Pacific Northwest National Laboratory
Geophysical Research Letters | Year: 2014

The 2013-2014 California drought was initiated by an anomalous high-amplitude ridge system. The anomalous ridge was investigated using reanalysis data and the Community Earth System Model (CESM). It was found that the ridge emerged from continual sources of Rossby wave energy in the western North Pacific starting in late summer and subsequently intensified into winter. The ridge generated a surge of wave energy downwind and deepened further the trough over the northeast U.S., forming a dipole. The dipole and associated circulation pattern is not linked directly with either El Niño-Southern Oscillation (ENSO) or Pacific Decadal Oscillation; instead, it is correlated with a type of ENSO precursor. The connection between the dipole and ENSO precursor has become stronger since the 1970s, and this is attributed to increased greenhouse gas loading as simulated by the CESM. Therefore, there is a traceable anthropogenic warming footprint in the enormous intensity of the anomalous ridge during winter 2013-2014 and the associated drought. Key Points The drought-inducing ridge is recurrent The ridge is linked to an ENSO precursor The link of the ridge with ENSO precursor has grown © 2014. American Geophysical Union. All Rights Reserved.


Qafoku N.P.,Pacific Northwest National Laboratory
Advances in Agronomy | Year: 2015

Climate change (i.e., high atmospheric carbon dioxide (CO2) concentrations (≥400ppm); increasing air temperatures (2-4°C or greater); significant and/or abrupt changes in daily, seasonal, and interannual temperature; changes in the wet/dry cycles; intensive rainfall and/or heavy storms; extended periods of drought; extreme frost; heat waves and increased fire frequency) is and will significantly affect soil properties and fertility, water resources, food quantity and quality, and environmental quality. Biotic processes that consume atmospheric CO2 and create organic carbon (C) that is either reprocessed to CO2 or stored in soils, are the subject of active current investigations with great concern over the influence of climate change. In addition, abiotic C cycling and its influence on the inorganic C pool in soils is a fundamental global process in which acidic atmospheric CO2 participates in the weathering of carbonate and silicate minerals, ultimately delivering bicarbonate and Ca2+ or other cations that precipitate in the form of carbonates in soils or are transported to the rivers, lakes, and oceans. Soil responses to climate change will be complex, and there are many uncertainties and unresolved issues. The objective of the review is to initiate and further stimulate a discussion about some important and challenging aspects of climate-change effects on soils, such as accelerated weathering of soil minerals and resulting C and elemental fluxes in and out of soils, soil/geo-engineering methods used to increase C sequestration in soils, soil organic matter (SOM) protection, transformation and mineralization, and SOM temperature sensitivity. This review reports recent discoveries and identifies key research needs required to understand the effects of climate change on soils. © 2015 Battelle Memorial Institute.


Xu X.G.,University of Colorado at Boulder | Rang M.,Forschungsinstitut Am Goetheanum | Craig I.M.,Pacific Northwest National Laboratory | Raschke M.B.,University of Colorado at Boulder
Journal of Physical Chemistry Letters | Year: 2012

While scattering-scanning near-field optical microscopy (s-SNOM) has demonstrated its potential to extend infrared (IR) spectroscopy into the nanometer scale, it has not yet reached its full potential in terms of spectroscopic sensitivity. We combine broadband femtosecond mid-IR excitation with an optimized spectral irradiance of ∼2 W/cm2/ cm -1 (power/area/bandwidth) and a combination of tip- and substrate enhancement to demonstrate single-monolayer sensitivity with exceptional signal-to-noise ratio. Using interferometric time domain detection, the near-field IR s-SNOM spectral phase directly reflects the molecular vibrational resonances and their intrinsic line shapes. We probe the stretching resonance of ∼1000 carbonyl groups at 1700 cm-1 in a self-assembled monolayer of 16-mercaptohexadecanoic acid (MHDA) on an evaporated gold substrate with spectroscopic contrast and sensitivity of ≤100 vibrational oscillators. From these results we provide a roadmap for achieving true single-molecule IR vibrational spectroscopy in s-SNOM by implementing optical antenna resonant enhancement, increased spectral pump power, and improved detection schemes. © 2012 American Chemical Society.


Vorontsov V.A.,Imperial College London | Kovarik L.,Pacific Northwest National Laboratory | Mills M.J.,Ohio State University | Rae C.M.F.,University of Cambridge
Acta Materialia | Year: 2012

High-resolution scanning transmission electron microscopy (STEM) has been used to study the structure of dislocations in single crystal superalloy samples that have been subjected to conditions that favour the primary creep regime. The study has revealed the detailed structure of extended a2〈112〉 dislocations as they shear the γ′ precipitates during creep. These dislocations dissociate in a manner that is consistent with predictions made using the phase-field model of dislocations and also suggests the importance of the reordering process during their movement. The shearing done by the a〈1 1 2〉 dislocations was also found to distort the γ/γ′ interface, changing its appearance from linear to a "saw tooth" pattern. Another important observation was the segregation of alloying elements with a high atomic mass to the stacking faults, presumably to reduce their energies during shear. Numerous a2〈110〉 dissociated dislocations were also observed in the γ channels of the superalloy. The high resolution provided by the STEM imaging enables one to study the high-energy faults that are usually difficult to observe in conventional weak-beam TEM, such as complex intrinsic and extrinsic stacking faults in the γ′ and intrinsic stacking faults in the γ, and to make estimates of their energies. © 2012 Acta Materialia Inc. Published by Elsevier Ltd.


Wiley H.S.,Pacific Northwest National Laboratory
Science Signaling | Year: 2011

New technologies promise to provide unprecedented amounts of information that can build a foundation for creating predictive models of cell signaling pathways. To be useful, however, this information must be integrated into a coherent framework. In addition, the sheer volume of data gathered from the new technologies requires computational approaches for its analysis. Unfortunately, there are many barriers to data integration and analysis, mostly because of a lack of adequate data standards and their inconsistent use by scientists. However, solving the fundamental issues of data sharing will enable the investigation of entirely new areas of cell signaling research.


Liu X.,Pacific Northwest National Laboratory | Wang J.,Brookhaven National Laboratory
Environmental Research Letters | Year: 2010

Organics are among the most abundant aerosol components in the atmosphere. However, there are still large uncertainties with emissions of primary organic aerosol (POA) and volatile organic compounds (VOCs) (precursor gases of secondary organic aerosol, SOA), formation of SOA, and chemical and physical properties (e.g., hygroscopicity) of POA and SOA. All these may have significant impacts on aerosol direct and indirect forcing estimated from global models. In this study a modal aerosol module (MAM) in the NCAR community atmospheric model (CAM) is used to examine sensitivities of aerosol indirect forcing to hygroscopicity (represented by a single parameter 'κ') of POA and SOA. Our model simulation indicates that in the present-day (PD) condition changing the 'κ' value of POA from 0 to 0.1 increases the number concentration of cloud condensational nuclei (CCN) at supersaturation S = 0.1% by 40-80% over the POA source regions, while changing the 'κ' value of SOA by ±50% (from 0.14 to 0.07 and 0.21) changes the CCN concentration within 40%. There are disproportionally larger changes in CCN concentration in the pre-industrial (PI) condition. Due to the stronger impact of organics hygroscopicity on CCN and cloud droplet number concentration at PI condition, global annual mean anthropogenic aerosol indirect forcing (AIF) between PD and PI conditions reduces with the increase of the hygroscopicity of organics. Global annual mean AIF varies by 0.4 W m-2 in the sensitivity runs with the control run of -1.3 W m-2, highlighting the need for improved understanding of organics hygroscopicity and its representation in global models. © 2010 IOP Publishing Ltd.


Mei D.,Pacific Northwest National Laboratory
Journal of Physical Chemistry C | Year: 2010

Periodic density functional theory calculations were used to study the formation and stability of surface carbonate on BaO(001) at CO2 exposure. CO2 adsorbs at Lewis basic Os sites, forming anionic surface carbonate (CO3-δ) species. Upon adsorption, a portion of electrons is transferred from the surface to CO 2. Although the adsorption strength of CO2 decreases with the increasing coverage (θCO2), the surface carbonate overlayer in the perpendicular pattern is stable up to one monolayer (1 ML). Dramatic surface reconstruction is found for the surface carbonate overlayer in the parallel pattern at θCO2 > 0.75 ML. The BaO(001) surface is reconstructed such that the surface Ba atoms are actually pulled out of the surface plane into the carbonate overlayer, suggesting a possible onset of phase transition from surface carbonate to crystalline bulklike carbonate when the coverage is higher than 0.75 ML. At ambient CO2 pressure, the calculated surface free energies indicate that the surface carbonate monolayer becomes unstable at 600 K, while the isolated surface carbonate is still stable at 800 K. This is in good agreement with previous experimental observations. The effect of surface hydroxyl on the stability of surface carbonate was also investigated in this work. At low hydroxyl coverage, the neighboring hydroxyls stabilize the surface carbonate. On the fully hydroxylated BaO(001) surface, chelating bicarbonate, instead of surface carbonate, is formed upon CO2 adsorption. © 2010 American Chemical Society.


Stein T.,Hebrew University of Jerusalem | Autschbach J.,State University of New York at Buffalo | Govind N.,Pacific Northwest National Laboratory | Kronik L.,Weizmann Institute of Science | Baer R.,Hebrew University of Jerusalem
Journal of Physical Chemistry Letters | Year: 2012

Perdew et al. discovered two different properties of exact Kohn-Sham density functional theory (DFT): (i) The exact total energy versus particle number is a series of linear segments between integer electron points. (ii) Across an integer number of electrons, the exchange-correlation potential "jumps" by a constant, known as the derivative discontinuity (DD). Here we show analytically that in both the original and the generalized Kohn-Sham formulation of DFT the two properties are two sides of the same coin. The absence of a DD dictates deviation from piecewise linearity, but the latter, appearing as curvature, can be used to correct for the former, thereby restoring the physical meaning of orbital energies. A simple correction scheme for any semilocal and hybrid functional, even Hartree-Fock theory, is shown to be effective on a set of small molecules, suggesting a practical correction for the infamous DFT gap problem. We show that optimally tuned range-separated hybrid functionals can inherently minimize both DD and curvature, thus requiring no correction, and that this can be used as a sound theoretical basis for novel tuning strategies. © 2012 American Chemical Society.


Kovarik L.,Pacific Northwest National Laboratory | Mills M.J.,Ohio State University
Acta Materialia | Year: 2012

Due to the inherit difficulties associated with microstructure characterization in the early stages of aging, the origin of rapid hardening in Al-Cu-Mg alloys remains a poorly understood and controversial issue. This work addresses the precipitation processes in the early stages by ab initio modeling of Guinier-Preston-Bagaryatsky (GPB) zone nucleation. We derive the structural nature of GPB zone nuclei and establish that the nucleation starts with 1D-GPB 1 crystals, which represent thermodynamically stable configurations at the size scale previously associated only with solute clusters. It is also established that the 1D-GPB 1 can form very rapidly due a simple structural transition from face-centered-cubic-based configurations (clusters). The formation of GPB zones in the early stages of aging is validated by comparison with previous experimental measurements. Based on previous experimental evidence, it is postulated that GPB zones rather than solute clusters may be able to rationalize the rapid hardening in the Al-Cu-Mg alloys. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.


Gorton I.,Pacific Northwest National Laboratory
IEEE Software | Year: 2013

This is the first article we're fortunate to have from the SATURN 2012 conference. This issue highlights a compelling story of crisis, larceny, and, of course, Fortran—the first programming language I learned, which I did by teaching it to undergrad engineering students. Because I never saw those engineers after they left my class, it's heartening to see that others like them learned some good lessons and developed useful insights. I'm sure you will enjoy reading this architectural tale. © 1984-2012 IEEE.


Henderson M.A.,Pacific Northwest National Laboratory
Journal of Physical Chemistry C | Year: 2014

The chemical and photochemical properties of a mixed oxide single crystal surface were examined in ultrahigh vacuum (UHV) with temperature-programmed desorption (TPD), photon stimulated desorption (PSD), and low energy electron diffraction (LEED) using nitric oxide as a probe molecule. A mixed Fe and Cr corundum oxide film with a (0001) orientation prepared on an α-Al2O3(0001) crystal was employed. After sputter/anneal cleaning, the films surface was transformed into a magnetite-like (111) termination based on LEED images which revealed a (2 × 2) surface periodicity. The sputter/anneal surface, designated as (Fe,Cr)3O4(111), also showed faint (√3 × √3)R30° LEED spots suggestive of the presence of a minority termination or of a poorly order surface structure within the (2 × 2) surface phase. TPD of NO from the (Fe,Cr)3O4(111) surface revealed three chemisorbed states at 220, ∼315, and 370 K tentatively assigned to NO binding at Fe3+, Cr3+, and Fe2+ sites, respectively. The relative populations of these sites followed the trend: Fe2+ > Fe3+ 蠑 Cr3+. No significant thermal chemistry of NO was detected. Photodesorption was the primary photochemical pathway for NO on the (Fe,Cr)3O4(111) surface in UHV. The NO photodesorption rate was sensitive to the adsorption site, following the trend: Fe3+ > Fe2+ > Cr3+. Multiexponential rate behavior seen in the overall NO PSD spectra was shown to be due to site heterogeneity (i.e., a convolution of the individual rates at the three types of surface sites) and not due to carrier-dependent or charge trapping effects. The photodesorption rate with UV light (365 nm) was ∼10× greater than that in the visible, and the per photon rates in the visible (between 460 and 630 nm) were essentially independent of the wavelength. Results in this study illustrate the importance of identifying adsorption sites in interpreting photochemical events on the surfaces of mixed oxide photocatalysts. © 2014 American Chemical Society.


Zhang X.,Pacific Northwest National Laboratory | Srinivasan R.,Texas A&M University
Hydrological Processes | Year: 2010

With the availability of spatially distributed data, distributed hydrologic models are increasingly used for simulation of spatially varied hydrologic processes to understand and manage natural and human activities that affect watershed systems. Multi-objective optimization methods have been applied to calibrate distributed hydrologic models using observed data from multiple sites. As the time consumed by running these complex models is increasing substantially, selecting efficient and effective multi-objective optimization algorithms is becoming a nontrivial issue. In this study, we evaluated a multi-algorithm, genetically adaptive multi-objective method (AMALGAM) for multi-site calibration of a distributed hydrologic model-Soil and Water Assessment Tool (SWAT), and compared its performance with two widely used evolutionary multi-objective optimization (EMO) algorithms (i.e. Strength Pareto Evolutionary Algorithm 2 (SPEA2) and Non-dominated Sorted Genetic Algorithm II (NSGA-II)). In order to provide insights into each method's overall performance, these three methods were tested in four watersheds with various characteristics. The test results indicate that the AMALGAM can consistently provide competitive or superior results compared with the other two methods. The multi-method search framework of AMALGAM, which can flexibly and adaptively utilize multiple optimization algorithms, makes it a promising tool for multi-site calibration of the distributed SWAT. For practical use of AMALGAM, it is suggested to implement this method in multiple trials with relatively small number of model runs rather than run it once with long iterations. In addition, incorporating different multi-objective optimization algorithms and multi-mode search operators into AMALGAM deserves further research. Copyright © 2009 John Wiley & Sons, Ltd.


Tian J.,University of Missouri | Tian J.,Pacific Northwest National Laboratory | Dalgarno S.J.,University of Missouri | Dalgarno S.J.,Heriot - Watt University | Atwood J.L.,University of Missouri
Journal of the American Chemical Society | Year: 2011

The robust nature of network materials allows them to (for example) respond to external stimuli such as pressure, temperature, light, or gas/solvent adsorption and desorption. There is difficulty in retaining long-range order in purely molecular organic solids, due to weak intermolecular interactions such as van der Waals forces. Here, we show gas-induced transformations of the well-known pharmaceuticals clarithromycin and lansoprazole. For clarithromycin, the stimulus is capable of converting the kinetic solvate and guest-free crystal forms to the commercial thermodynamically stable polymorph with a huge saving in energy cost relative to industrially employed methods. The synthesis of the marketing form of lansoprazole involves a solvate that readily decomposes and that is stirred in water, filtered, and dried intensively. Our method readily circumvents such synthetic problems and transforms the sensitive solvate to the marketed drug substance with ease. Such expedient transformations hold great implications for the pharmaceutical industry in general when considering the ease of transformation and mild conditions employed. © 2011 American Chemical Society.


Mei D.,Pacific Northwest National Laboratory
Journal of Energy Chemistry | Year: 2013

Molecular adsorption of formate and carboxyl on stoichiometric CeO 2(111) and CeO2(110) surfaces was studied using periodic density functional theory (DFT+U) calculations. Two distinguishable adsorption modes (strong and weak) of formate are identified. The bidentate configuration is more stable than the monodentate adsorption configuration. Both formate and carboxyl bind at the more open CeO2(110) surface are stronger. The calculated vibrational frequencies of two adsorbed species are consistent with the experimental measurements. Finally, the effects of U parameters on the adsorption of formate and carboxyl over both CeO2 surfaces were investigated. We found that the geometrical configurations of two adsorbed species are not affected by different U parameters (U = 0, 5, and 7). However, the calculated adsorption energy of carboxyl pronouncedly increases with the U value while the adsorption energy of formate only slightly changes (<0.2 eV). The Bader charge analysis shows the opposite charge transfer occurs for formate and carboxyl adsorption where the adsorbed formate is negatively charge while the adsorbed carboxyl is positively charged. Interestingly, with the increasing U parameter, the amount of charge is also increased. Copyright © 2013, Dalian Institute of Chemical Physics, Chinese Academy of Sciences.


Neacsu C.C.,University of Washington | Berweger S.,University of Washington | Olmon R.L.,University of Washington | Saraf L.V.,Pacific Northwest National Laboratory | And 2 more authors.
Nano Letters | Year: 2010

Focusing light to subwavelength dimensions has been a long-standing desire in optics but has remained challenging, even with new strategies based on near-field effects, polaritons, and metamaterials. The adiabatic propagation of surface plasmon polaritons (SPP) on a conical taper as proposed theoretically has recently emerged as particularly promising to obtain a nanoconfined light source at the tip. Employing grating-coupling of SPPs onto gold tips, we demonstrate plasmonic nanofocuslng into a localized excitation of ∼20 nm in size and investigate its near- and far-field behavior. Por cone angles of ∼10-20°, the breakdown of the adiabatic propagation conditions is found to be localized at or near the apex region with ∼10 nm radius. Despite an asymmetric side-on SPP excitation, the apex far-field emission with axial polarization characteristics representing a radially symmetric SPP mode in the nanofocus confirms that the conical tip acts as an effective mode filter with only the fundamental radially symmetric TM mode (m = 0) propagating to the apex. We demonstrate the use of these tips as a source for nearly background-free scattering-type scanning near-field optical microscopy (s-SNOM). © 2010 American Chemical Society.


Fred Zhang Z.,Pacific Northwest National Laboratory
Vadose Zone Journal | Year: 2015

Engineered surface barriers (or covers) are used to isolate underlying contaminants from water, plants, animals, and humans. To understand the flow processes within a barrier and the barrier's ability to store and release water, the field hydraulic properties of the barrier need to be known. A multiyear test of the evapotranspiration (ET) barrier at the US Department of Energy's Hanford Site in the southeast of the state of Washington has yielded in situ soil water content and pressure data from multiple locations for a 9-yr period, offering the opportunity to estimate soil water retention properties at different locations and times. The upper 2-m layer of the ET barrier is a silt loam, and the top 1 m also contains 15% (w/w) pea gravel. Within this layer, valid monitoring data from 1995 to 2003 for four depths at 12 monitoring stations were used to determine the field water retention of the silt loam, with and without gravel. The data covered a wide range of wetness, from near saturation to the permanent wilting point, and each retention curve contained 51 to 96 data points. The data were described well with the commonly used van Genuchten water retention model. It was found that the spatial variation of the saturated and residual water content and the pore size distribution parameter was relatively small, while that of the van Genuchten a was relatively large. The effects of spatial variability of the retention properties appeared to be larger than the combined effects of added pea gravel and plant roots on the properties. Neither the primary wetting process in the winter season nor the drying process in the summer season nor time had a detectable effect on the water retention of the silt loam barrier. © Soil Science Society of America.


Yao M.,University of Texas at Arlington | Joly A.G.,Pacific Northwest National Laboratory | Chen W.,University of Texas at Arlington
Journal of Physical Chemistry C | Year: 2010

LaF3:Ce3+-doped nanoparticles were synthesized at different temperatures in dimethyl sulfoxide (DMSO) by the chemical reaction of lanthanum nitrate hydrate and cerium nitrate hexahydrate with ammonium fluoride. The formation of Ce3+-doped LaF3 nanoparticles is confirmed by X-ray diffraction and high-resolution transmission electron microscopy. An intense emission at around 310 nm from the d-f transition of Ce3+ was observed from the LaF3:Ce3+ powder samples. However, in solution samples, the ultraviolet emission from Ce 3+ is mostly absent, but intense luminescence is observed in the visible range from blue to red. The emission wavelength of the solution samples is dependent on the reaction time and temperature. More interestingly, the emission wavelength varies with the excitation wavelength. Most likely, this emission is from metal organic compounds of Ce3+ or La3+ and DMSO as similar phenomena are also observed when lanthanum nitrate hydrate or cerium nitrate hexahydrate are heated in DMSO. © 2010 American Chemical Society.


Shokri A.,University of Minnesota | Schmidt J.,University of Minnesota | Wang X.-B.,Pacific Northwest National Laboratory | Wang X.-B.,Washington State University | Kass S.R.,University of Minnesota
Journal of the American Chemical Society | Year: 2012

Hydrogen bond interactions in small covalent model compounds (i.e., deprotonated polyhydroxy alcohols) were measured by negative ion photoelectron spectroscopy. The experimentally determined vertical and adiabatic electron detachment energies for (HOCH 2CH 2) 2CHO -(2a), (HOCH 2CH 2) 3CO - (3a), and (HOCH 2CH 2CH(OH)CH 2) 3CO - (4a)reveal that hydrogen-bonded networks can provide enormous stabilizations and that a single charge center not only can be stabilized by up to three hydrogen bonds but also can increase the interaction energy between noncharged OH groups by 5.8 kcal mol -1 or more per hydrogen bond. This can lead to pK a values that are very different from those in water and can provide some of the impetus for catalytic processes. © 2011 American Chemical Society.


Bagus P.S.,University of North Texas | Ilton E.S.,Pacific Northwest National Laboratory
Topics in Catalysis | Year: 2013

Two aspects of the electronic structure of actinide oxides that significantly affect the X-ray photoelectron spectroscopy (XPS) spectra are described; these aspects are also important for the materials properties of the oxides. The two aspects considered are: (1) The spin-orbit coupling of the open 5f shell electrons in actinide cations and how this coupling affects the electronic structure. And, (2) the covalent character of the metal oxygen interaction in actinide compounds. Because of this covalent character, there are strong departures from the nominal oxidation states that are significantly larger in core-hole states than in the ground state. The consequences of this covalent character for the XPS are examined. A proper understanding of the way in which they influence the XPS makes it possible to use the XPS to correctly characterize the electronic structure of the oxides. © 2013 Springer Science+Business Media New York.


Kleidon A.,Max Planck Institute for Biogeochemistry | Kravitz B.,Pacific Northwest National Laboratory | Renner M.,Max Planck Institute for Biogeochemistry
Geophysical Research Letters | Year: 2015

We derive analytic expressions of the response of the hydrological cycle to surface warming from the surface energy balance in which turbulent heat fluxes are constrained by the thermodynamic limit of maximum power. For a given steady state temperature change, this approach predicts the transient and steady state response of surface energy partitioning and the hydrologic cycle. We show that the predicted hydrological sensitivities to greenhouse warming and solar geoengineering are comparable to the results from climate model simulations of the Geoengineering Model Intercomparison Project. Although not all effects can be explained, our approach nevertheless predicts the general trend as well as the magnitude of the changes in the global-scale hydrological cycle surprisingly well. This implies that much of the global-scale changes in the hydrologic cycle can be robustly predicted by the response of the thermodynamically constrained surface energy balance to altered radiative forcing. Key Points Thermodynamic constraints predict hydrologic sensitivity to climate change Analytic derivation for rapid and steady state changes of the hydrologic cycle Analytical derivations mostly match climate model predictions ©2014. American Geophysical Union. All Rights Reserved.


Zhang Z.F.,Pacific Northwest National Laboratory
Vadose Zone Journal | Year: 2011

Common conceptual models for unsaturated flow assume that the matric potential is attributed to the capillary force only. These models are successful at high and medium water contents but often give poor results at low water contents. The lower bound of existing water retention functions and conductivity models was extended from residual water content to the oven-dry condition (i.e., zero water content) by defining a state-dependent residual water content for a soil drier than a critical value. The advantages of the extended water retention functions include not refitting the retention parameters from the unextended model, its reduction to the unextended form when the soil is wetter than the critical value, and its compatibility with existing relative permeability models. In addition, a hydraulic conductivity model for film flow in a medium of smooth uniform spheres was modified by introducing a correction factor to describe the film flow-induced hydraulic conductivity for natural porous media. The total unsaturated hydraulic conductivity is the sum of those due to capillary and film flow; it smoothly transits between capillary-dominated flow and film-dominated flow over the full range of water content. The film flow is insignificant when the soil is wetter than the critical water content, and, vice versa, the capillary flow is insignificant when the soil is drier than the critical water content. The extended retention and conductivity models were tested with measurements. Results show that, when the soil is at high and intermediate water content, there is no difference between the unextended and the extended models as defined by the theory. When the soil is at low water content, the unextended models overestimate the water content but underestimate the conductivity. The extended models match the retention and conductivity measurements well. © Soil Science Society of America.


Zhou N.,Pacific Northwest National Laboratory | Pierre J.W.,University of Wyoming | Trudnowski D.,Montana Tech of the University of Montana
IEEE Transactions on Power Systems | Year: 2012

Prony analysis has been applied to estimate inter-area oscillation modes using phasor measurement unit (PMU) measurements. To suppress noise and signal offset effects, a high-order Prony model usually is used to over-fit the data. As such, some trivial modes are intentionally added to improve the estimation accuracy of the dominant modes. Therefore, to reduce the rate of false alarms, it is important to distinguish between the dominant modes that reflect the dynamic features of a power system and the trivial modes that are artificially introduced to improve the estimation accuracy. In this paper, a stepwise-regression method is applied to automatically identify the dominant modes from Prony analysis. A Monte Carlo method is applied to evaluate the performance of the proposed method using data obtained from simulations. Field-measured PMU data are used to verify the applicability of the proposed method. A comparison of results obtained using the proposed approach with results from a traditional energy-sorting method shows the improved performance of the proposed method. © 2012 IEEE.


Cheng D.,Beijing University of Chemical Technology | Negreiros F.R.,CNR Institute for Chemical and Physical Processes | Apra E.,Pacific Northwest National Laboratory | Fortunelli A.,CNR Institute for Chemical and Physical Processes
ChemSusChem | Year: 2013

The conversion of CO2 into fuels and chemicals is viewed as an attractive route for controlling the atmospheric concentration and recycling of this greenhouse gas, but its industrial application is limited by the low selectivity and activity of the current catalysts. Theoretical modeling, in particular density functional theory (DFT) simulations, provides a powerful and effective tool to discover chemical reaction mechanisms and design new catalysts for the chemical conversion of CO2, overcoming the repetitious and time/labor consuming trial-and-error experimental processes. In this article we give a comprehensive survey of recent advances on mechanism determination by DFT calculations for the catalytic hydrogenation of CO2 into CO, CH 4, CH3OH, and HCOOH, and CO2 methanation, as well as the photo- and electrochemical reduction of CO2. DFT-guided design procedures of new catalytic systems are also reviewed, and challenges and perspectives in this field are outlined. Calculating transformations: A comprehensive and critical review of the status of research in the field of the chemical conversion of CO2 into carbon forms in a lower oxidation state is presented. Particular attention is devoted to the description of reaction mechanism of CO2 transformation catalyzed by various types of systems (heterogeneous, homogeneous, and electro- and photocatalysts) and to the possible essential role that theoretical and computational approaches can play in this field. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Huang Z.,University of Wollongong | Autrey T.,Pacific Northwest National Laboratory
Energy and Environmental Science | Year: 2012

The strong efforts devoted to the exploration of BNH compounds for hydrogen storage have led to impressive advances in the field of boron chemistry. This review summarizes progress in this field from three aspects. It starts with the most recent developments in using BNH compounds for hydrogen storage, covering NH 3BH 3, B 3H 8 - containing compounds, and CBN compounds. The following section then highlights interesting applications of BNH compounds in hydrogenation and catalysis. The last part is focused on breakthroughs in the syntheses and discovery of new BNH organic analogues. The role of N-H δ+⋯H δ--B dihydrogen interactions in molecule packing, thermal hydrogen evolution, and syntheses is also discussed within the review. © 2012 The Royal Society of Chemistry.


Bond-Lamberty B.,Pacific Northwest National Laboratory
Environmental Research Letters | Year: 2013

Climate change is modifying global biogeochemical cycles, and is expected to exert increasingly large effects in the future. How these changes will affect and interact with the structure and function of particular ecosystems is unclear, both because of scientific uncertainties and the very diversity of global vegetation models in use. Writing in ERL, Warszawski et al (2013 Environ. Res. Lett. 8 044018) aggregate results from a group of models, across a range of emissions scenarios and climate data, to investigate these risks. Although the models frequently disagree about which specific regions are at risk, they consistently predict a greater chance of ecosystem restructuring with more warming; this risk roughly doubles between a 2 and 3 ° C increase in global mean temperature. The innovative work of Warszawski et al represents an important first step towards fully consistent multi-model, multi-scenario assessments of the future risks to global ecosystems. © 2013 IOP Publishing Ltd.


Laskin A.,Environmental Molecular science Laboratory | Laskin J.,Pacific Northwest National Laboratory | Nizkorodov S.A.,University of California at Irvine
Chemical Reviews | Year: 2015

The chemistry of atmospheric brown carbon (BrC) is reviewed. BrC is now recognized as an important component in the atmosphere that affects climate forcing through a combination of direct effects on the transmission of solar and terrestrial radiation and indirect effects resulting from changes in cloud formation and microphysics. In addition, long-range transport and deposition of BrC most likely play a role in carbon and nitrogen cycling between atmosphere, land, and water and contribute to the formation of colored dissolved organic matter (CDOM). The existing evidence suggests that even a very small weight fraction of strongly absorbing BrC chromophores may have a distinct effect on organic aerosols (OA) optical properties. Because of the low concentrations of light-absorbing molecules in complex organic mixtures composing both laboratory-generated and ambient OA, identification of BrC chromophores is a very challenging task. Despite the analytical difficulties, several classes of compounds have been identified as potential contributors to light absorption by BrC. These include nitroaromatic compounds, such as nitrophenols, imidazole-based and other N-heterocyclic compounds, and quinines. The identification and structural characterization of BrC chromophores clearly require highly sensitive molecular characterization approaches capable of detecting both strongly and weakly absorbing species.


Tao J.,Pacific Northwest National Laboratory
Methods in Enzymology | Year: 2013

Spectroscopy techniques, such as Fourier transform infrared (FTIR) and Raman, offer methodologies that overlap and expand X-ray diffraction and transmission electron microscopy (TEM) analyses and help gain new insight into mechanisms of biomineralization. FTIR and Raman spectroscopy techniques measure the molecular environment of asymmetrically and symmetrically vibrating bonds, respectively. As such, these techniques have widely been used to gain information on mineral content, phase, and orientation as well as chemical composition of associated organic matrices like collagen, chitin, or lipids. The traditional coupling of optical microscopes to the newer generation FTIR and Raman spectrometers has enabled these analyses to be performed on samples with 0.1-20 μm spatial resolution. Herein, we briefly discuss the basis and protocol for effective measurements using vibrational spectroscopy by taking two systems from our own research as examples. © 2013 Elsevier Inc.


Spagnolo V.,Polytechnic of Bari | Patimisco P.,Polytechnic of Bari | Borri S.,Polytechnic of Bari | Scamarcio G.,Polytechnic of Bari | And 2 more authors.
Optics Letters | Year: 2012

A sensitive spectroscopic sensor based on a hollow-core fiber-coupled quantum cascade laser (QCL) emitting at 10.54 μm and quartz enhanced photoacoustic spectroscopy (QEPAS) technique is reported. The design and realization of mid-IR fiber and coupler optics has ensured single-mode QCL beam delivery to the QEPAS sensor. The collimation optics was designed to produce a laser beam of significantly reduced beam size and waist so as to prevent illumination of the quartz tuning fork and microresonator tubes. SF6 was selected as the target gas. A minimum detection sensitivity of 50 parts per trillion in 1 s was achieved with a QCL power of 18 mW, corresponding to a normalized noise-equivalent absorption of 2.7 × 10-10 W · cm-1/Hz1/2. © 2012 Optical Society of America.


Li W.,University of Pennsylvania | Schumacher C.,Texas A&M University | Mcfarlane S.A.,Pacific Northwest National Laboratory
Journal of Geophysical Research: Atmospheres | Year: 2013

Radiative heating profiles of the International Satellite Cloud Climatology Project (ISCCP) cloud regimes (or weather states) were estimated by matching ISCCP observations with radiative properties derived from cloud radar and lidar measurements from the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) sites at Manus, Papua New Guinea, and Darwin, Australia. Focus was placed on the ISCCP cloud regimes containing the majority of upper level clouds in the tropics, i.e., mesoscale convective systems (MCSs), deep cumulonimbus with cirrus, mixed shallow and deep convection, and thin cirrus. At upper levels, these regimes have average maximum cloud occurrences ranging from 30% to 55% near 12 km with variations depending on the location and cloud regime. The resulting radiative heating profiles have maxima of approximately 1 K/day near 12 km, with equal heating contributions from the longwave and shortwave components. Upper level minima occur near 15 km, with the MCS regime showing the strongest cooling of 0.2 K/day and the thin cirrus showing no cooling. The gradient of upper level heating ranges from 0.2 to 0.4 K/(daykm), with the most convectively active regimes (i.e., MCSs and deep cumulonimbus with cirrus) having the largest gradient. When the above heating profiles were applied to the 25-year ISCCP data set, the tropics-wide average profile has a radiative heating maximum of 0.45Kday-1 near 250 hPa. Column-integrated radiative heating of upper level cloud accounts for about 20% of the latent heating estimated by the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR). The ISCCP radiative heating of tropical upper level cloud only slightly modifies the response of an idealized primitive equation model forced with the tropics-wide TRMM PR latent heating, which suggests that the impact of upper level cloud is more important to large-scale tropical circulation variations because of convective feedbacks rather than direct forcing by the cloud radiative heating profiles. However, the height of the radiative heating maxima and gradient of the heating profiles are important to determine the sign and patterns of the horizontal circulation anomaly driven by radiative heating at upper levels. © 2012. American Geophysical Union.


Nadeau J.S.,University of Washington | Wright B.W.,Pacific Northwest National Laboratory | Synovec R.E.,University of Washington
Talanta | Year: 2010

A critical comparison of methods for correcting severely retention time shifted gas chromatography-mass spectrometry (GC-MS) data is presented. The method reported herein is an adaptation to the piecewise alignment algorithm to quickly align severely shifted one-dimensional (1D) total ion current (TIC) data, then applying these shifts to broadly align all mass channels throughout the separation, referred to as a TIC shift function (SF). The maximum shift varied from (-) 5 s in the beginning of the chromatographic separation to (+) 20 s toward the end of the separation, equivalent to a maximum shift of over 5 peak widths. Implementing the TIC shift function (TIC SF) prior to Fisher Ratio (F-Ratio) feature selection and then principal component analysis (PCA) was found to be a viable approach to classify complex chromatograms, that in this study were obtained from GC-MS separations of three gasoline samples serving as complex test mixtures, referred to as types C, M and S. The reported alignment algorithm via the TIC SF approach corrects for large dynamic shifting in the data as well as subtle peak-to-peak shifts. The benefits of the overall TIC SF alignment and feature selection approach were quantified using the degree-of-class separation (DCS) metric of the PCA scores plots using the type C and M samples, since they were the most similar, and thus the most challenging samples to properly classify. The DCS values showed an increase from an initial value of essentially zero for the unaligned GC-TIC data to a value of 7.9 following alignment; however, the DCS was unchanged by feature selection using F-Ratios for the GC-TIC data. The full mass spectral data provided an increase to a final DCS of 13.7 after alignment and two-dimensional (2D) F-Ratio feature selection. © 2009 Elsevier B.V.


Carpita J.B.,Pacific Northwest National Laboratory
Geosynthetics | Year: 2016

The Pioneer Mountains Scenic Byway, located about 30 miles (48km) west of Dillon, Mont., seasonally experiences frost heave problems over a 20-mile (30-km) stretch of road. The road is closed to winter traffic and typically re-opens in May. Longitudinal full-section depth cracks form during the spring thaw. One location, in the high alpine meadows of Moose Park, experiences the largest of these frost heaves, requiring annual maintenance and scheduled repairs. Past repair efforts in 2004 were not successful, so the Federal Highway Administration (FHWA) and Beaverhead County tried a new design using wicking technology to address frost heaves at the worst location on the byway, stretching 375 yards (340m).


Du D.,Central China Normal University | Yang Y.,Central China Normal University | Lin Y.,Pacific Northwest National Laboratory
MRS Bulletin | Year: 2012

Graphene, a free-standing two-dimensional crystal with one-atom thickness, exhibits distinct properties that are highly attractive for biosensing and bioimaging, such as a high electrical conductivity, a large planar area, and an excellent ability to quench fluorescence. This article selectively reviews recent advances in the field of graphene-based materials for biosensing and bioimaging. In particular, graphene-based enzyme biosensors, DNA biosensors, and immunosensors are summarized in detail. Graphene-based biotechnology for cell imaging is also described. Future perspectives and possible challenges in this rapidly developing area are also discussed. © Copyright 2012 Materials Research Society.


The ISO technical report 14187 provides an introduction to (and examples of) the information that can be obtained about nanostructured materials by using surface analysis tools. In addition, both general issues and challenges associated with characterizing nanostructured materials and the specific opportunities and challenges associated with individual analytical methods are identified. As the size of objects or components of materials approaches a few nanometers, the distinctions among 'bulk', 'surface', and 'particle' analysis blur. This technical report focuses on issues specifically relevant to surface chemical analysis of nanostructured materials. The report considers a variety of analysis methods but focuses on techniques that are in the domain of ISO/TC 201 including Auger electron spectroscopy, X-ray photoelectron spectroscopy, secondary ion mass spectrometry, and scanning probe microscopy. Measurements of nanoparticle surface properties such as surface potential that are often made in a solution are not discussed. Copyright © 2012 John Wiley & Sons, Ltd. Copyright © 2012 John Wiley & Sons, Ltd.


Whether there is sufficient geologic CO2 storage capacity to allow CCS to play a significant role in mitigating climate change has been the subject of debate since the 1990s. This paper presents a meta- Analysis of a large body of recently published literature to derive updated estimates of the global deep geologic storage resource as well as the potential demand for this geologic CO2 storage resource over the course of this century. This analysis reveals that, for greenhouse gas emissions mitigation scenarios that have end-of-century atmospheric CO2 concentrations of between 350 ppmv and 725 ppmv, the average demand for deep geologic CO2 storage over the course of this century is between 410 GtCO2 and 1,670 GtCO2. The literature summarized here suggests that - depending on the stringency of criteria applied to calculate storage capacity - global geologic CO2 storage capacity could be: 35,300 GtCO2 of "theoretical" capacity; 13,500 GtCO2 of "effective" capacity; 3,900 GtCO2, of "practical" capacity; and 290 GtCO2 of "matched" capacity for the few regions where this narrow definition of capacity has been calculated. The cumulative demand for geologic CO2 storage is likely quite small compared to global estimates of the deep geologic CO2 storage capacity, and therefore, a "lack" of deep geologic CO2 storage capacity is unlikely to be an impediment for the commercial adoption of CCS technologies in this century.


Liu J.,Pacific Northwest National Laboratory
Advanced Functional Materials | Year: 2013

The Special Issue of Advanced Functional Material 2013 on Energy Storage provides a comprehensive and balanced view of materials chemistry and materials challenges for a wide range of technologies and applications from transportation electrification to the utility grid. The paper by Liu and co-researchers gives a detailed analysis of the energy storage landscape and status of the materials and technologies, which is followed by review articles on important technologies and featured research articles that include the latest advances in leading groups from the international community. Papers by Perez and colleagues and Byon and colleagues report new results on methods to produce novel carbon architectures which have good potential for anodes in Li-ion batteries and electrodes for supercapacitors. This Special Issue also includes one paper by Lee and researchers on composite gel electrolytes with Li powders as the anode.


Bhattacharya P.,Pacific Northwest National Laboratory | Geitner N.K.,Clemson University | Sarupria S.,Clemson University | Ke P.C.,Clemson University
Physical Chemistry Chemical Physics | Year: 2013

In this perspective we first examine the rich physicochemical properties of dendritic polymers for hosting cations, anions, and polyaromatic hydrocarbons. We then extrapolate these conceptual discussions to the use of dendritic polymers in humic acid antifouling, oil dispersion, copper sensing, and fullerenol remediation. In addition, we review the state-of-the-art of dendrimer research and elaborate on its implications for water purification, environmental remediation, nanomedicine, and energy harvesting. © 2013 the Owner Societies.


Yang K.,Duke University | Setyawan W.,Pacific Northwest National Laboratory | Wang S.,Duke University | Buongiorno Nardelli M.,University of North Texas | And 3 more authors.
Nature Materials | Year: 2012

Topological insulators (TI) are becoming one of the most studied classes of novel materials because of their great potential for applications ranging from spintronics to quantum computers. To fully integrate TI materials in electronic devices, high-quality epitaxial single-crystalline phases with sufficiently large bulk bandgaps are necessary. Current efforts have relied mostly on costly and time-consuming trial-and-error procedures. Here we show that by defining a reliable and accessible descriptor, which represents the topological robustness or feasibility of the candidate, and by searching the quantum materials repository aflowlib.org, we have automatically discovered 28 TIs (some of them already known) in five different symmetry families. These include peculiar ternary halides, Cs{Sn,Pb,Ge}{Cl,Br,I} 3, which could have been hardly anticipated without high-throughput means. Our search model, by relying on the significance of repositories in materials development, opens new avenues for the discovery of more TIs in different and unexplored classes of systems. © 2012 Macmillan Publishers Limited. All rights reserved.


Le S.T.,Brown University | Jannaty P.,Brown University | Luo X.,Brown University | Zaslavsky A.,Brown University | And 4 more authors.
Nano Letters | Year: 2012

We present silicon-compatible trigated p-Ge/i-Si/n-Si axial heteronanowire tunneling field-effect transistors (TFETs), where on-state tunneling occurs in the Ge drain section, while off-state leakage is dominated by the Si junction in the source. Our TFETs have high ION ∼ 2 μA/μm, fully suppressed ambipolarity, and a subthreshold slope SS ∼ 140 mV/decade over 4 decades of current with lowest SS ∼ 50 mV/decade. Device operation in the tunneling mode is confirmed by three-dimensional TCAD simulation. Interestingly, in addition to the TFET mode, our devices work as standard nanowire FETs with a good ION/IOFF ratio when the source-drain junction is forward-biased. The improved transport in both biasing modes confirms the benefits of utilizing bandgap engineered axial nanowires for enhancing device performance. © 2012 American Chemical Society.


Salice C.J.,Texas Tech University | Anderson T.A.,Texas Tech University | Roesijadi G.,Pacific Northwest National Laboratory
Ecotoxicology | Year: 2010

Population response to anthropogenic activities will be influenced by prior adaptation to environmental conditions. We tested how parasite-resistant and -susceptible strains of the freshwater snail, Biomphalaria glabrata, responded to cadmium and elevated temperature challenges after having been exposed to low-level cadmium continuously for multiple generations. Snails exposed to cadmium for three generations were removed for the fourth generation, and challenged in the fifth generation with (1) chronic cadmium exposure over the entire life cycle; (2) lethal cadmium exposure of adults; and (3) elevated temperature challenge of adults. The parasite susceptible NMRI strain is more cadmium tolerant than the parasite resistant BS90 strain and remained more tolerant than BS90 throughout this study. Additionally, NMRI exhibited greater adaptive capacity for cadmium than BS90 and became more tolerant of both chronic and lethal cadmium challenges, while BS90 became more tolerant of lethal cadmium challenge only. Fitness costs, reflected in population growth rate, were not apparent in fifth generation snails maintained in control conditions. However, costs were latent and expressed as decreased tolerance to a secondarily imposed temperature stress. Adaptation to prior selection pressures can influence subsequent adaptation to anthropogenic stresses and may have associated costs that reduce fitness in novel environments. © Springer Science+Business Media, LLC 2010.


Zhang B.,Vanderbilt University | Huang Y.,University of Texas at San Antonio | McDermott J.E.,Pacific Northwest National Laboratory | Posey R.H.,Vanderbilt University | And 2 more authors.
BMC Genomics | Year: 2013

The 2013 International Conference on Intelligent Biology and Medicine (ICIBM 2013) was held on August 11-13, 2013 in Nashville, Tennessee, USA. The conference included six scientific sessions, two tutorial sessions, one workshop, two poster sessions, and four keynote presentations that covered cutting-edge research topics in bioinformatics, systems biology, computational medicine, and intelligent computing. Here, we present a summary of the conference and an editorial report of the supplements to BMC Genomics and BMC Systems Biology that include 19 research papers selected from ICIBM 2013. © 2013 Zhang et al.; licensee BioMed Central Ltd.


McDowell M.T.,Stanford University | Ryu I.,Stanford University | Lee S.W.,Stanford University | Wang C.,Pacific Northwest National Laboratory | And 3 more authors.
Advanced Materials | Year: 2012

In situ transmission electron microscopy (TEM) is used to study the electrochemical lithiation of high-capacity crystalline Si nanoparticles for use in Li-ion battery anodes. The lithiation reaction slows down as it progresses into the particle interior, and analysis suggests that this behavior is due not to diffusion limitation but instead to the influence of mechanical stress on the driving force for reaction. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Wu X.,Nanjing University of Information Science and Technology | Wu X.,Iowa State University | Deng L.,Pacific Northwest National Laboratory
Journal of Climate | Year: 2013

The moist static energy (MSE) anomalies and MSE budget associated with the Madden-Julian oscillation (MJO) simulated in the Iowa State University General Circulation Model (ISUGCM) over the Indian and Pacific Oceans are compared with observations. Different phase relationships between MJO 850-hPa zonal wind, precipitation, and surface latent heat flux are simulated over the Indian Ocean and western Pacific, which are greatly influenced by the convection closure, trigger conditions, and convective momentum transport (CMT). The moist static energy builds up from the lower troposphere 15-20 days before the peak of MJOprecipitation, and reaches the maximum in the middle troposphere (500-600 hPa) near the peak ofMJO precipitation. The gradual lower-tropospheric heating and moistening and the upward transport of moist static energy are important aspects of MJO events, which are documented in observational studies but poorly simulated in most GCMs. The trigger conditions for deep convection, obtained from the year-long cloudresolving model (CRM) simulations, contribute to the striking difference between ISUGCM simulations with the original and modified convection schemes and play the major role in the improved MJO simulation in ISUGCM. Additionally, the budget analysis with the ISUGCM simulations shows the increase in MJO MSE is in phase with the horizontal advection of MSE over the western Pacific, while out of phase with the horizontal advection of MSE over the Indian Ocean. However, the NCEP analysis shows that the tendency of MJO MSE is in phase with the horizontal advection of MSE over both oceans. ©2013 American Meteorological Society.


Jessop P.G.,Queens University | Mercer S.M.,Queens University | Heldebrant D.J.,Pacific Northwest National Laboratory
Energy and Environmental Science | Year: 2012

Waste CO2 at atmospheric pressure can be used to trigger dramatic changes in the properties of certain switchable materials. Compared to other triggers such as light, acids and oxidants, CO2 has the advantages that it is inexpensive, nonhazardous, non-accumulating in the system, easily removed, and it does not require the material to be transparent. Known CO2-triggered switchable materials now include solvents, surfactants, solutes, catalysts, particles, polymers, and gels. These have also been described as "smart" materials or, for some of the switchable solvents, "reversible ionic liquids". The added flexibility of switchable materials represents a new strategy for minimizing energy and material consumption in process and product design. This journal is © 2012 The Royal Society of Chemistry.


Dathar G.K.P.,Oak Ridge National Laboratory | Shelton W.A.,Oak Ridge National Laboratory | Shelton W.A.,Pacific Northwest National Laboratory | Xu Y.,Oak Ridge National Laboratory
Journal of Physical Chemistry Letters | Year: 2012

Periodic density functional theory (DFT) calculations indicate that the intrinsic activity of Au, Ag, Pt, Pd, Ir, and Ru for the oxygen reduction reaction by Li (Li-ORR) forms a volcano-like trend with respect to the adsorption energy of oxygen, with Pt and Pd being the most active. The trend is based on two mechanisms: the reduction of molecular O 2 on Au and Ag and of atomic O on the remaining metals. Step edges are found to be more active for catalyzing the Li-ORR than close-packed surfaces. Our findings identify important considerations in the design of catalyst-promoted air cathodes for nonaqueous Li-air batteries. © 2012 American Chemical Society.


Widder S.,Pacific Northwest National Laboratory
Journal of Renewable and Sustainable Energy | Year: 2010

Nuclear power can play an important role in our energy future, helping to meet increasing electricity demand while at the same time decreasing carbon dioxide emissions. However, the nuclear fuel cycle in the United States today is unsustainable. The 1982 Nuclear Waste Policy Act establishes the U.S. Department of Energy as responsible for disposing of spent nuclear fuel (SNF) generated by commercial nuclear power plants operating in a "once- through" fuel cycle in a deep geologic repository located at Yucca Mountain, NV. However, unyielding political opposition to the Yucca Mountain site has hindered the commissioning process to the extent that the current administration has recently declared the site unsuitable. In light of this, the DOE is exploring other options, including closing the fuel cycle through reprocessing and recycling of spent nuclear fuel. The possibility of closing the fuel cycle is receiving special attention because of its ability to minimize the final high level waste package by separating and isolating the most long-lived components, as well as recovering additional energy value from the original fuel. Reprocessing and recycling of SNF can decrease the volume of waste stored by a factor of 4 and reduce the timeframe of storage from hundreds of thousands of years to thousands of years. Reprocessing and recycling technologies are, however, still very controversial because of the increased cost and proliferation risk reprocessing can present. Estimates of increases in the levelized cost of electricity with reprocessing range from about 10% to 50% due to large uncertainties in the financing, construction, and licensing of a new plant. Ultimately, the U.S. will need to compare each of these fuel cycle options with respect to sustainability, proliferation risk, commercial viability, waste management, and energy security to define the future of nuclear power. © 2010 American Institute of Physics.


Sakaeda N.,University of Washington | Wood R.,University of Washington | Rasch P.J.,Pacific Northwest National Laboratory
Journal of Geophysical Research: Atmospheres | Year: 2011

Direct and semidirect radiative effects of biomass burning aerosols from southern African fires during July-October are investigated using 20 year runs of the Community Atmospheric Model (CAM) coupled to a slab ocean model. Aerosol optical depth is constrained using observations in clear skies from Moderate Resolution Imaging Spectroradiometer (MODIS) and for aerosol layers above clouds from Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO). Over the ocean, where the aerosol layers are primarily located above cloud, negative top of atmosphere (TOA) semidirect radiative effects associated with increased low cloud cover dominate over a weaker positive all-sky direct radiative effect (DRE). In contrast, over the land where the aerosols are often below or within cloud layers, reductions in cloud liquid water path (LWP) lead to a positive semidirect radiative effect that dominates over a near-zero DRE. Over the ocean, the cloud response can be understood as a response to increased lower tropospheric stability (LTS) which is caused both by radiative heating in overlying layers and surface cooling in response to direct aerosol forcing. The marine cloud changes are robust to changes in the cloud parameterization (removal of the hard-wired dependence of clouds on LTS), suggesting that they are physically realistic. Over land, decreased LWP is consistent with weaker convection driven by increased static stability. Over the entire region the overall TOA radiative effect from the biomass burning aerosols is almost zero due to opposing effects over the land and ocean. However, the surface forcing is strongly negative, which leads to a reduction in precipitation and also a reduction in sensible heat flux. The former is primarily realized through reductions in convective precipitation on both the southern and northern flanks of the convective precipitation region spanning the equatorial rain forest and the Intertropical Convergence Zone (ITCZ) in the southern Sahel. The changes are consistent with the low-level aerosol-forced cooling pattern. The results highlight the importance of semidirect radiative effects and precipitation responses for determining the climatic effects of aerosols in the African region. Copyright 2011 by the American Geophysical Union.


Kerisit S.,Pacific Northwest National Laboratory
Geochimica et Cosmochimica Acta | Year: 2011

The atomic-level structure of water at mineral surfaces is an important controlling factor in interfacial reactions such as foreign ion incorporation, crystal growth and dissolution, and redox reactions. Molecular dynamics simulations with four different models based on interatomic potentials have been carried out to determine the atomic-level structure of three hematite-water interfaces. In addition, for each of the three surfaces, different terminations or protonation schemes were considered. The availability of surface X-ray scattering data for the surfaces considered here allowed for an extensive comparison with experimental data. Qualitatively, with the exception of one termination with one model, all models predict the correct arrangement of water molecules at the interface. Quantitatively, the agreement with experimental positions, distances, and layer occupancies is good to excellent, especially given the range of values reported in published experimental studies. Therefore, this study provides further evidence that interatomic potential models can be used to reliably predict the structure of mineral-water interfaces. In addition, molecular simulations are a valuable source of information to complement surface X-ray scattering experiments owing to their ability to directly determine the position of hydrogen atoms and to yield three-dimensional predicted structures at no added cost, as demonstrated in this work. Indeed, the molecular dynamics trajectories were analyzed to determine the surface structural controls on the interfacial water structure. Each of the three surface functional groups present at the surfaces considered in this work, namely, triply-coordinated oxo, doubly-coordinated hydroxo, and singly-coordinated aquo groups, was found to form similar hydrogen bond configurations with adsorbed water molecules at all surfaces. Oxo groups accept long-lasting and linear hydrogen bonds from adsorbed water molecules; hydroxo groups can form hydrogen bonds with other surface functional groups as well as with adsorbed water molecules; and aquo groups normally only donate hydrogen bonds to other surface groups or adsorbed water molecules. Additionally, the majority of adsorbed water molecules were found to adopt multiple configurations and orientations. This information was used to evaluate three-dimensional structural models of the interfaces, which were previously derived experimentally from one-dimensional electron density profiles and steric considerations. © 2011 Elsevier Ltd.


Lumetta G.J.,Pacific Northwest National Laboratory | Gelis A.V.,Argonne National Laboratory | Vandegrift G.F.,Argonne National Laboratory
Solvent Extraction and Ion Exchange | Year: 2010

This paper is a review of recent publications that have focused on combined extractant systems for separating trivalent actinides from the lanthanides. These mixed solvent systems combine an acidic extractant with a neutral extractant to achieve the actinide/lanthanide separation. Depending on the neutral extractant used, three categorizations of systems can be considered, including combinations of acidic extractants with 1) diamides, 2) carbamoylmethylphosphine oxides, and 3) polydentate nitrogen-donor ligands. This review of relevant publications indicates that, although there is significant potential for practical exploitation of mixed neutral/acidic extractant systems to achieve a single-step separation of trivalent actinides from acidic high-level waste solutions, the fundamental chemistry underlying these combined systems is not yet well understood. For example, although there is strong evidence suggesting that adducts form between the neutral and acidic extractants, the nature of these adducts generally is not known. Likewise, the structures of the mixed complexes formed between the metal ions and the two different extractants are not fully understood. Research into these basic phenomena likely will provide clues about how to design practical mixed-extractant systems that can be used to efficiently separate the transuranic elements from the lanthanides and other components of irradiated fuel. © 2010 Battelle Memorial Institute.


Martinez I.,University of Alberta | Martinez I.,University of Nebraska - Lincoln | Stegen J.C.,Pacific Northwest National Laboratory | Maldonado-Gomez M.X.,University of Nebraska - Lincoln | And 6 more authors.
Cell Reports | Year: 2015

Although recent research revealed an impact of westernization on diversity and composition of the human gut microbiota, the exact consequences on metacommunity characteristics are insufficiently understood, and the underlying ecological mechanisms have not been elucidated. Here, we have compared the fecal microbiota of adults from two non-industrialized regions in Papua New Guinea (PNG) with that of United States (US) residents. Papua New Guineans harbor communities with greater bacterial diversity, lower inter-individual variation, vastly different abundance profiles, and bacterial lineages undetectable in US residents. A quantification of the ecological processes that govern community assembly identified bacterial dispersal as the dominant process that shapes the microbiome in PNG but not in the US. These findings suggest that the microbiome alterations detected in industrialized societies might arise from modern lifestyle factors limiting bacterial dispersal, which has implications for human health and the development of strategies aimed to redress the impact of westernization. © 2015 The Authors.


Napier B.A.,Pacific Northwest National Laboratory
Health Physics | Year: 2014

Beginning in 1948, the Soviet Union initiated a program for production of nuclear materials for a weapons program. The first facility for production of plutonium was constructed in the central portion of the country east of the southern Ural Mountains, about halfway between the major industrial cities of Ekaterinburg and Chelyabinsk. The facility, now known as the Mayak Production Association, and its associated town, now known as Ozersk, were built to irradiate uranium in reactors, separate the resulting plutonium in reprocessing plants, and prepare plutonium metal in the metallurgical plant. The rush to production, coupled with inexperience in handling radioactive materials, led to large radiation exposures, not only to the workers in the facilities, but also to the surrounding public. Fuel processing started with no controls on releases, and fuel dissolution and accidents in reactors resulted in release of ∼37 PBq of I between 1948 and 1967. Designed disposals of low- and intermediate-level liquid radioactive wastes, and accidental releases via cooling water from tank farms of high-level liquid radioactive wastes into the small Techa River, caused significant contamination and exposures to residents of numerous small riverside villages downstream of the site. Discovery of the magnitude of the aquatic contamination in late 1951 caused revisions to the waste handling regimes, but not before over 200 PBq of radionuclides (with large contributions of Sr and Cs) were released. Liquid wastes were diverted to tiny Lake Karachay (which today holds over 4 EBq); cooling water was stopped in the tank farms. In 1957, one of the tanks in the tank farm overheated and exploded; over 70 PBq, disproportionately Sr, was blown over a large area to the northeast of the site. A large area was contaminated and many villages evacuated. This area today is known as the East Urals Radioactive Trace (EURT). Each of these releases was significant; together they have created a unique group of cohorts with their chronic, low dose-rate radiation exposure. The 26,000 workers at Mayak were highly exposed to external gamma and inhaled plutonium. A cohort of individuals raised as children in Ozersk is under evaluation for their exposures to radioiodine. The Techa River Cohort consists of over 30,000 people who were born before the start of exposure in 1949 and lived along the Techa River. The Techa River Offspring Cohort consists of ∼21,000 persons born to one or more exposed parents of this group, many who also lived along the contaminated river. The EURT Cohort consists of ∼18,000 people who were evacuated from the EURT soon after the 1957 explosion and another 8,000 who remained. These groups together are the focus of dose reconstruction and epidemiological studies funded by the United States, Russia, and the European Union to address the question, "Are doses delivered at low dose rates as effective in producing health effects as the same doses delivered at high dose rates?". © 2014 Health Physics Society.


Song F.,CAS Institute of Atmospheric Physics | Song F.,University of Chinese Academy of Sciences | Zhou T.,CAS Institute of Atmospheric Physics | Zhou T.,Chinese Academy of Sciences | Qian Y.,Pacific Northwest National Laboratory
Geophysical Research Letters | Year: 2014

In this study, we examined the responses of East Asian summer monsoon (EASM) to natural (solar variability and volcanic aerosols) and anthropogenic (greenhouse gasses and aerosols) forcings simulated in the 17 latest Coupled Model Intercomparison Program phase 5 models with 105 realizations. The observed weakening trend of low-level EASM circulation during 1958-2001 is partly reproduced under all-forcing runs. A comparison of separate forcing experiments reveals that the aerosol forcing plays a primary role in driving the weakened low-level monsoon circulation. The preferential cooling over continental East Asia caused by aerosol affects the monsoon circulation through reducing the land-sea thermal contrast and results in higher sea level pressure over northern China. In the upper level, both natural forcing and aerosol forcing contribute to the observed southward shift of East Asian subtropical jet through changing the meridional temperature gradient. ©2013. American Geophysical Union. All Rights Reserved.


This paper is Part 2 of a three-part series investigating effective dose rates to residents of the United States from intakes of ubiquitous radionuclides, including radionuclides occurring naturally, radionuclides whose concentrations are technologically enhanced, and anthropogenic radionuclides. This series of papers explicitly excludes intakes from inhaling 222Rn, 220Rn, and their short-lived decay products; it also excludes intakes of radionuclides in occupational and medical settings. In this work, it is assumed that instantaneous dose rates in target organs are proportional to steady-state radionuclide concentrations in source regions. Part 1 reviewed, summarized, characterized, and grouped all published and some unpublished data for U.S. residents on ubiquitous radionuclide concentrations in tissues and organs. Assumptions about equilibrium with long-lived parents are made for the 28 other radionuclides in these series lacking data. This paper describes the methods developed to group the collected data into source regions described in the Radiation Dose Assessment Resource (RADAR) dosimetric methodology. Methods for converting the various units of data published over 50 y into a standard form are developed and described. Often, meaningful values of uncertainty of measurements were not published, so that variability in data sets is confounded with measurement uncertainty. A description of the methods developed to estimate variability is included in this paper. The data described in Part 1 are grouped by gender and age to match the RADAR dosimetric phantoms. Within these phantoms, concentration values are grouped into source tissue regions by radionuclide, and they are imputed for source regions lacking tissue data. Radionuclide concentrations are then imputed for the source regions of other phantoms with missing concentration values, and the uncertainties of the imputed values are increased. The concentrations of hollow organs' contents are calculated, and activities are apportioned to the bone source regions using assumptions about each radionuclide's bone-seeking behavior. The data sets are then ready to be used to estimate equivalent dose rates to target tissues from these source regions. The target tissues are then mapped to lists of tissues with International Commission on Radiation Protection (ICRP) tissue weighting factors, or they are mapped to surrogate tissue regions when there is no direct match. Effective dose rates, using ICRP tissue weighting factors recommended in 1977, 1990, and 2007, can be calculated from the tissue and organ equivalent dose rates. These effective dose rates are reported in Part 3 of this series. Copyright © 2011 Health Physics Society.


Chassin D.P.,Pacific Northwest National Laboratory
Electricity Journal | Year: 2010

The intersection of technology and economics is where all the Smart Grid benefits arise. If we do one without the other, then utilities and consumers hardly see any enduring benefit at all and the investment made in the underlying infrastructure justified on the basis of those benefits is wasted. © 2010 Elsevier Inc.


Buchko G.W.,Pacific Northwest National Laboratory
Protein and Peptide Letters | Year: 2010

The crystal structure for the Deinococcus radiodurans Nudix protein DR_0079 was recently determined in the metal-free form at 1.9 Å resolution (2O5F). The protein adopts the fundamental fold common to the Nudix family of proteins, a large mixed β-sheet sandwiched between the α-helix of the "Nudix box" and a second α-helix. The protein's physical properties were further characterized by circular dichroism (CD) spectroscopy. A CD thermal melt at 220 nm indentifies an inflection point at ~52°C. However, unlike typical CD thermal melts, the negative ellipticity at 220 nm becomes more negative upon passing through the inflection point. Both NMR spectroscopy and size exclusion chromatography indicate that heating effects the irreversible formation of a large molecular weight complex. After cooling, the negative ellipiticity at 220 nm increases further, and overall, the CD spectrum at 25°C suggests that heat-treated DR_0079 has more α-helical and β-sheet structure than non-heat treated DR_0079. © 2010 Bentham Science Publishers Ltd.


Wang D.,University of Central Florida | Hejazi M.,Pacific Northwest National Laboratory
Water Resources Research | Year: 2011

Both climate change and human activities are known to have induced changes to hydrology. Consequently, quantifying the net impact of human contribution to the streamflow change is a challenge. In this paper, a decomposition method based on the Budyko hypothesis is used to quantify the climate (i.e., precipitation and potential evaporation change) and direct human impact on mean annual streamflow (MAS) for 413 watersheds in the contiguous United States. The data for annual precipitation, runoff, and potential evaporation are obtained from the international Model Parameter Estimation Experiment (MOPEX), which is often assumed to only include gauges unaffected by human interferences. The data are split into two periods (1948-1970 and 1971-2003) to quantify the change over time. Although climate is found to affect MAS more than direct human impact, the results show that assuming the MOPEX data set to be unaffected by human activities is far from realistic. Climate change causes increasing MAS in most watersheds, while the direct human-induced change is spatially heterogeneous in the contiguous United States, with strong regional patterns, e.g., human activities causing increased MAS in the Midwest and significantly decreased MAS in the High Plains. The climate- and human-induced changes are found to be more severe in arid regions, where water is limited. Comparing the results to a collection of independent data sets indicates that the estimated direct human impacts on MAS in this largely nonurban set of watersheds might be attributed to several human activities, such as cropland expansion, irrigation, and the construction of reservoirs. © Copyright 2011 by the American Geophysical Union.


Lin R.,University of Chinese Academy of Sciences | Zhou T.,University of Chinese Academy of Sciences | Qian Y.,Pacific Northwest National Laboratory
Journal of Climate | Year: 2014

With the motivation to identify whether a reasonably simulated atmospheric circulation would necessarily lead to a successful reproduction of monsoon precipitation, the performances of five sets of reanalysis data [NCEP-U.S. Department of Energy (DOE) Atmospheric Model Intercomparison Project II (AMIP-II) reanalysis (NCEP-2), 40-yr ECMWF Re-Analysis (ERA-40), Japanese 25-yr Reanalysis Project (JRA-25), Interim ECMWF Re-Analysis (ERA-Interim), and Modern-Era Retrospective Analysis for Research and Applications(MERRA)] in reproducing the climatology, interannual variation, and long-term trend of global monsoon (GM) precipitation are comprehensively evaluated. To better understand the variability and longterm trend of GM precipitation, the authors also examined the major components of water budget, including evaporation, water vapor convergence, and the change in local column water vapor, based on the five reanalysis datasets. Results show that all five reanalysis datasets reasonably reproduce the climatology of GM precipitation. ERA-Interim (NCEP-2) shows the highest (lowest) skill among the five datasets. The observed GMprecipitation shows an increasing tendency during 1979-2011 along with a strong interannual variability, which is reasonably reproduced by five reanalysis datasets. The observed increasing trend ofGMprecipitation is dominated by contributions from the Asian, North American, Southern African, and Australian monsoons. All five datasets fail in reproducing the increasing tendency of the North African monsoon precipitation. The wind convergence term in the water budget equation dominates the GM precipitation variation, indicating a consistency between the GM precipitation and the seasonal change of prevailing wind. © 2014 American Meteorological Society.


King A.W.,Oak Ridge National Laboratory | Hayes D.J.,Oak Ridge National Laboratory | Huntzinger D.N.,Northern Arizona University | West T.O.,Pacific Northwest National Laboratory | Post W.M.,Oak Ridge National Laboratory
Frontiers in Ecology and the Environment | Year: 2012

North America is both a source and sink of atmospheric carbon dioxide CO2. Continental sources - such Abstract: fossil-fuel combustion in the US and deforestation in Mexico - and sinks - including most ecosystems, and particularly secondary forests - add and remove CO2 from the atmosphere, respectively. Photosynthesis converts CO2 into carbon as biomass, which is stored in vegetation, soils, and wood products. However, ecosystem sinks compensate for only ∼35% of the continent's fossil-fuel-based CO2 emissions; North America therefore represents a net CO2 source. Estimating the magnitude of ecosystem sinks, even though the calculation is confounded by uncertainty as a result of individual inventory- and model-based alternatives, has improved through the use of a combined approach. © The Ecological Society of America.


Hengel S.M.,University of Washington | Hengel S.M.,Pacific Northwest National Laboratory | Goodlett D.R.,University of Washington
International Journal of Mass Spectrometry | Year: 2012

The use of tandem mass spectrometry to identify and characterize sites of protein adenosine diphosphate (ADP) ribosylation will be reviewed. Specifically, we will focus on data acquisition schemes and fragmentation techniques that provide peptide sequence and modification site information. Also discussed are uses of synthetic standards to aid characterization, and an enzymatic method that converts ADP-ribosylated peptides into ribosyl mono phosphorylated peptides making identification amenable to traditional phosphopeptide characterization methods. Finally the potential uses of these techniques to characterize poly ADP-ribosylation sites, and inherent challenges, are addressed. © 2011 Elsevier B.V.


Ju X.,Washington State University | Engelhard M.,Pacific Northwest National Laboratory | Zhang X.,Washington State University
Bioresource Technology | Year: 2013

In this study, chemical pulping techniques were applied to create a set of biomass substrates with intact lignocellulosic fibers and controlled morphological and chemical properties to allow the investigation of the individual effects of xylan and surface lignin content on enzymatic hydrolysis. A high resolution X-ray photoelectron spectroscopy technique was established for quantifying surface lignin content on lignocellulosic biomass substrates. The results from this study show that, apart from its hindrance effect, xylan can facilitate cellulose fibril swelling and thus create more accessible surface area, which improves enzyme and substrate interactions. Surface lignin has a direct impact on enzyme adsorption kinetics and hydrolysis rate. Advanced understanding of xylan and surface lignin effects provides critical information for developing more effective biomass conversion process. © 2013 .


Chambers S.A.,Pacific Northwest National Laboratory
Advanced Materials | Year: 2010

The detailed science and technology of crystalline oxide film growth using vacuum methods is reviewed and discussed with an eye toward gaining fundamental insights into the relationships between growth process and parameters, film and interface structure and composition, and electronic, magnetic and photochemical properties. The topic is approached first from a comparative point of view based on the most widely used growth methods, and then on the basis of specific material systems that have generated very high levels of interest. Emphasis is placed on the wide diversity of structural, electronic, optical and magnetic properties exhibited by oxides, and the fascinating results that this diversity of properties can produce when combined with the degrees of freedom afforded by heteroepitaxy. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA.


Brown E.E.,Washington State University | Hu D.,Pacific Northwest National Laboratory | Abu Lail N.,Washington State University | Zhang X.,Washington State University
Biomacromolecules | Year: 2013

The potential of synthesizing new nanocomposites from nanocrystalline cellulose (NCC) and fibrin for small-diameter replacement vascular graft (SDRVG) application was demonstrated. Periodate oxidation of NCC can augment reactive carbonyl groups on NCC and facilitate its cross-linking with fibrin. NCC-fibrin nanocomposites were synthesized, composed of homogeneously dispersed oxidized NCC (ONCC) in a fibrin matrix, with fibrin providing elasticity and ONCC providing strength. The maximum strength and elongation of the nanocomposites were determined by Atomic Force Microscopy (AFM) and compared with a native blood vessel. The manipulation of degree of oxidation of NCC and the NCC-to-fibrin ratio resulted in the variation of strength and elongation of the nanocomposites, indicating that the nanocomposites can be tailored to conform to the diverse mechanical properties of native blood vessels. A mechanistic understanding of the molecular interactions of ONCC and fibrin was illustrated. This study established fundamental information to utilizing NCC for SDRVG applications. © 2013 American Chemical Society.