Showing papers by "United States Department of Energy published in 2013"
University of Illinois at Urbana–Champaign1, Joint Institute for the Study of the Atmosphere and Ocean2, Cooperative Institute for Research in Environmental Sciences3, University of Leeds4, University of Oslo5, United States Environmental Protection Agency6, University of Michigan7, Pacific Northwest National Laboratory8, German Aerospace Center9, United States Department of Energy10, Max Planck Society11, University of Tokyo12, National Oceanic and Atmospheric Administration13, Forschungszentrum Jülich14, Norwegian Meteorological Institute15, Indian Institute of Technology Bombay16, China Meteorological Administration17, Peking University18, Met Office19, Desert Research Institute20, Clarkson University21, Stanford University22, European Centre for Medium-Range Weather Forecasts23, International Institute of Minnesota24, Goddard Institute for Space Studies25, Yale University26, University of Washington27, University of California, Irvine28
TL;DR: In this paper, the authors provided an assessment of black-carbon climate forcing that is comprehensive in its inclusion of all known and relevant processes and that is quantitative in providing best estimates and uncertainties of the main forcing terms: direct solar absorption; influence on liquid, mixed phase, and ice clouds; and deposition on snow and ice.
Abstract: Black carbon aerosol plays a unique and important role in Earth's climate system. Black carbon is a type of carbonaceous material with a unique combination of physical properties. This assessment provides an evaluation of black-carbon climate forcing that is comprehensive in its inclusion of all known and relevant processes and that is quantitative in providing best estimates and uncertainties of the main forcing terms: direct solar absorption; influence on liquid, mixed phase, and ice clouds; and deposition on snow and ice. These effects are calculated with climate models, but when possible, they are evaluated with both microphysical measurements and field observations. Predominant sources are combustion related, namely, fossil fuels for transportation, solid fuels for industrial and residential uses, and open burning of biomass. Total global emissions of black carbon using bottom-up inventory methods are 7500 Gg yr−1 in the year 2000 with an uncertainty range of 2000 to 29000. However, global atmospheric absorption attributable to black carbon is too low in many models and should be increased by a factor of almost 3. After this scaling, the best estimate for the industrial-era (1750 to 2005) direct radiative forcing of atmospheric black carbon is +0.71 W m−2 with 90% uncertainty bounds of (+0.08, +1.27) W m−2. Total direct forcing by all black carbon sources, without subtracting the preindustrial background, is estimated as +0.88 (+0.17, +1.48) W m−2. Direct radiative forcing alone does not capture important rapid adjustment mechanisms. A framework is described and used for quantifying climate forcings, including rapid adjustments. The best estimate of industrial-era climate forcing of black carbon through all forcing mechanisms, including clouds and cryosphere forcing, is +1.1 W m−2 with 90% uncertainty bounds of +0.17 to +2.1 W m−2. Thus, there is a very high probability that black carbon emissions, independent of co-emitted species, have a positive forcing and warm the climate. We estimate that black carbon, with a total climate forcing of +1.1 W m−2, is the second most important human emission in terms of its climate forcing in the present-day atmosphere; only carbon dioxide is estimated to have a greater forcing. Sources that emit black carbon also emit other short-lived species that may either cool or warm climate. Climate forcings from co-emitted species are estimated and used in the framework described herein. When the principal effects of short-lived co-emissions, including cooling agents such as sulfur dioxide, are included in net forcing, energy-related sources (fossil fuel and biofuel) have an industrial-era climate forcing of +0.22 (−0.50 to +1.08) W m−2 during the first year after emission. For a few of these sources, such as diesel engines and possibly residential biofuels, warming is strong enough that eliminating all short-lived emissions from these sources would reduce net climate forcing (i.e., produce cooling). When open burning emissions, which emit high levels of organic matter, are included in the total, the best estimate of net industrial-era climate forcing by all short-lived species from black-carbon-rich sources becomes slightly negative (−0.06 W m−2 with 90% uncertainty bounds of −1.45 to +1.29 W m−2). The uncertainties in net climate forcing from black-carbon-rich sources are substantial, largely due to lack of knowledge about cloud interactions with both black carbon and co-emitted organic carbon. In prioritizing potential black-carbon mitigation actions, non-science factors, such as technical feasibility, costs, policy design, and implementation feasibility play important roles. The major sources of black carbon are presently in different stages with regard to the feasibility for near-term mitigation. This assessment, by evaluating the large number and complexity of the associated physical and radiative processes in black-carbon climate forcing, sets a baseline from which to improve future climate forcing estimates.
4,591 citations
Centre national de la recherche scientifique1, Commonwealth Scientific and Industrial Research Organisation2, National Oceanic and Atmospheric Administration3, United States Department of Energy4, University of California, Irvine5, Central Maine Community College6, Seconda Università degli Studi di Napoli7, Max Planck Society8, Swiss Federal Institute for Forest, Snow and Landscape Research9, Utrecht University10, Carma11, National Center for Atmospheric Research12, University of East Anglia13, Massachusetts Institute of Technology14, VU University Amsterdam15, Goddard Space Flight Center16, University of Bern17, Nagoya University18, Imperial College London19, Royal Netherlands Meteorological Institute20, University of California, San Diego21, National Institute of Water and Atmospheric Research22
TL;DR: In this paper, the authors construct decadal budgets for methane sources and sinks between 1980 and 2010, using a combination of atmospheric measurements and results from chemical transport models, ecosystem models, climate chemistry models and inventories of anthropogenic emissions.
Abstract: Methane is an important greenhouse gas, responsible for about 20% of the warming induced by long-lived greenhouse gases since pre-industrial times. By reacting with hydroxyl radicals, methane reduces the oxidizing capacity of the atmosphere and generates ozone in the troposphere. Although most sources and sinks of methane have been identified, their relative contributions to atmospheric methane levels are highly uncertain. As such, the factors responsible for the observed stabilization of atmospheric methane levels in the early 2000s, and the renewed rise after 2006, remain unclear. Here, we construct decadal budgets for methane sources and sinks between 1980 and 2010, using a combination of atmospheric measurements and results from chemical transport models, ecosystem models, climate chemistry models and inventories of anthropogenic emissions. The resultant budgets suggest that data-driven approaches and ecosystem models overestimate total natural emissions. We build three contrasting emission scenarios-which differ in fossil fuel and microbial emissions-to explain the decadal variability in atmospheric methane levels detected, here and in previous studies, since 1985. Although uncertainties in emission trends do not allow definitive conclusions to be drawn, we show that the observed stabilization of methane levels between 1999 and 2006 can potentially be explained by decreasing-to-stable fossil fuel emissions, combined with stable-to-increasing microbial emissions. We show that a rise in natural wetland emissions and fossil fuel emissions probably accounts for the renewed increase in global methane levels after 2006, although the relative contribution of these two sources remains uncertain. © 2013 Macmillan Publishers Limited.
1,668 citations
Pacific Northwest National Laboratory1, California Institute of Technology2, Princeton University3, Humboldt University of Berlin4, Pennsylvania State University5, Brookhaven National Laboratory6, University of California, Riverside7, University of Illinois at Urbana–Champaign8, University of California, Berkeley9, United States Department of Energy10, University of Toronto11, University of Michigan12, University of Amsterdam13, Utah State University14, Max Planck Society15, Louisiana State University16
TL;DR: Providing a future energy supply that is secure and CO_2-neutral will require switching to nonfossil energy sources such as wind, solar, nuclear, and geothermal energy and developing methods for transforming the energy produced by these new sources into forms that can be stored, transported, and used upon demand.
Abstract: Two major energy-related problems confront the world in the
next 50 years. First, increased worldwide competition for
gradually depleting fossil fuel reserves (derived from past
photosynthesis) will lead to higher costs, both monetarily and politically. Second, atmospheric CO_2 levels are at their highest recorded level since records began. Further increases are predicted to produce large and uncontrollable impacts on the world climate. These projected impacts extend beyond climate to ocean acidification, because the ocean is a major sink for atmospheric CO2.1 Providing a future energy supply that is secure and CO_2-neutral will require switching to nonfossil energy sources such as wind, solar, nuclear, and geothermal energy and developing methods for transforming the energy produced by these new sources into forms that can be stored, transported, and used upon demand.
1,651 citations
TL;DR: In this article, the authors present the results of a technical and economic feasibility analysis conducted for four hypothetical, centralized, large-scale hydrogen production plants based on this technology, including a single bed particle suspension system, a dual-bed particle suspension systems, a fixed panel array, and a tracking concentrator array.
Abstract: Photoelectrochemical water splitting is a promising route for the renewable production of hydrogen fuel. This work presents the results of a technical and economic feasibility analysis conducted for four hypothetical, centralized, large-scale hydrogen production plants based on this technology. The four reactor types considered were a single bed particle suspension system, a dual bed particle suspension system, a fixed panel array, and a tracking concentrator array. The current performance of semiconductor absorbers and electrocatalysts were considered to compute reasonable solar-to-hydrogen conversion efficiencies for each of the four systems. The U.S. Department of Energy H2A model was employed to calculate the levelized cost of hydrogen output at the plant gate at 300 psi for a 10 tonne per day production scale. All capital expenditures and operating costs for the reactors and auxiliaries (compressors, control systems, etc.) were considered. The final cost varied from $1.60–$10.40 per kg H2 with the particle bed systems having lower costs than the panel-based systems. However, safety concerns due to the cogeneration of O2 and H2 in a single bed system and long molecular transport lengths in the dual bed system lead to greater uncertainty in their operation. A sensitivity analysis revealed that improvement in the solar-to-hydrogen efficiency of the panel-based systems could substantially drive down their costs. A key finding is that the production costs are consistent with the Department of Energy's targeted threshold cost of $2.00–$4.00 per kg H2 for dispensed hydrogen, demonstrating that photoelectrochemical water splitting could be a viable route for hydrogen production in the future if material performance targets can be met.
1,058 citations
Centra1, Clemson University2, Washington State University3, United States Department of Energy4, Parco Tecnologico Padano5, University of Chile6, North Carolina State University7, University of California, Berkeley8, University of Bologna9, Andrés Bello National University10, University of Milan11, University of Udine12, University of Barcelona13
TL;DR: Comparisons showed that peach has not undergone recent whole-genome duplication, and even though the ancestral triplicated blocks in peach are fragmentary compared to those in grape, all seven paleosets of paralogs from the putative paleoancestor are detectable.
Abstract: Rosaceae is the most important fruit-producing clade, and its key commercially relevant genera (Fragaria, Rosa, Rubus and Prunus) show broadly diverse growth habits, fruit types and compact diploid genomes. Peach, a diploid Prunus species, is one of the best genetically characterized deciduous trees. Here we describe the high-quality genome sequence of peach obtained from a completely homozygous genotype. We obtained a complete chromosome-scale assembly using Sanger whole-genome shotgun methods. We predicted 27,852 protein-coding genes, as well as noncoding RNAs. We investigated the path of peach domestication through whole-genome resequencing of 14 Prunus accessions. The analyses suggest major genetic bottlenecks that have substantially shaped peach genome diversity. Furthermore, comparative analyses showed that peach has not undergone recent whole-genome duplication, and even though the ancestral triplicated blocks in peach are fragmentary compared to those in grape, all seven paleosets of paralogs from the putative paleoancestor are detectable.
935 citations
Environment Canada1, École Polytechnique Fédérale de Lausanne2, University of Montpellier3, United States Department of Energy4, Centre national de la recherche scientifique5, University of Bristol6, VU University Amsterdam7, Oeschger Centre for Climate Change Research8, University of Washington9, University of Victoria10, University of Sheffield11, Auburn University12, Kazan Federal University13, Russian Academy of Sciences14, Lawrence Berkeley National Laboratory15, Max Planck Society16, Lehigh University17
TL;DR: The Wetland and Wetland CH4 Inter-comparison of Models Project (WETCHIMP) as mentioned in this paper investigated the ability to simulate large-scale wetland characteristics and corresponding CH4 emissions.
Abstract: . Global wetlands are believed to be climate sensitive, and are the largest natural emitters of methane (CH4). Increased wetland CH4 emissions could act as a positive feedback to future warming. The Wetland and Wetland CH4 Inter-comparison of Models Project (WETCHIMP) investigated our present ability to simulate large-scale wetland characteristics and corresponding CH4 emissions. To ensure inter-comparability, we used a common experimental protocol driving all models with the same climate and carbon dioxide (CO2) forcing datasets. The WETCHIMP experiments were conducted for model equilibrium states as well as transient simulations covering the last century. Sensitivity experiments investigated model response to changes in selected forcing inputs (precipitation, temperature, and atmospheric CO2 concentration). Ten models participated, covering the spectrum from simple to relatively complex, including models tailored either for regional or global simulations. The models also varied in methods to calculate wetland size and location, with some models simulating wetland area prognostically, while other models relied on remotely sensed inundation datasets, or an approach intermediate between the two. Four major conclusions emerged from the project. First, the suite of models demonstrate extensive disagreement in their simulations of wetland areal extent and CH4 emissions, in both space and time. Simple metrics of wetland area, such as the latitudinal gradient, show large variability, principally between models that use inundation dataset information and those that independently determine wetland area. Agreement between the models improves for zonally summed CH4 emissions, but large variation between the models remains. For annual global CH4 emissions, the models vary by ±40% of the all-model mean (190 Tg CH4 yr−1). Second, all models show a strong positive response to increased atmospheric CO2 concentrations (857 ppm) in both CH4 emissions and wetland area. In response to increasing global temperatures (+3.4 °C globally spatially uniform), on average, the models decreased wetland area and CH4 fluxes, primarily in the tropics, but the magnitude and sign of the response varied greatly. Models were least sensitive to increased global precipitation (+3.9 % globally spatially uniform) with a consistent small positive response in CH4 fluxes and wetland area. Results from the 20th century transient simulation show that interactions between climate forcings could have strong non-linear effects. Third, we presently do not have sufficient wetland methane observation datasets adequate to evaluate model fluxes at a spatial scale comparable to model grid cells (commonly 0.5°). This limitation severely restricts our ability to model global wetland CH4 emissions with confidence. Our simulated wetland extents are also difficult to evaluate due to extensive disagreements between wetland mapping and remotely sensed inundation datasets. Fourth, the large range in predicted CH4 emission rates leads to the conclusion that there is both substantial parameter and structural uncertainty in large-scale CH4 emission models, even after uncertainties in wetland areas are accounted for.
508 citations
TL;DR: In this article, a Co{sub 3}O{sub 4} nanoparticles are in-situ grown on the chemically reduced graphene oxide (rGO) sheets to form a rGO-Co-sub 3,O-sub 4,sub 4 composite during hydrothermal processing.
463 citations
California State University San Marcos1, Alfred Wegener Institute for Polar and Marine Research2, University of Alberta3, United States Department of Energy4, J. Craig Venter Institute5, Institut national de la recherche agronomique6, Ruhr University Bochum7, University of Maryland, College Park8, Monterey Bay Aquarium Research Institute9, University College London10, Centre national de la recherche scientifique11, Harvard University12, Ghent University13, Rothamsted Research14, Pierre-and-Marie-Curie University15, University of Essex16, Pontifical Catholic University of Chile17, Plymouth Marine Laboratory18, Woods Hole Oceanographic Institution19, Columbia University20, University of Cologne21, Natural History Museum22, Rutgers University23, Georgia Institute of Technology24, Moscow Institute of Physics and Technology25, University of Ostrava26, National Institutes of Health27, University of Nebraska Medical Center28, University of Southampton29, Oregon State University30, Dalhousie University31, University of Texas Health Science Center at Houston32, University of East Anglia33, University of Potsdam34, University of Bergen35, University of Washington36, University of Freiburg37, University of Marburg38, University of Los Andes39, Bigelow Laboratory For Ocean Sciences40, University of Exeter41, Oak Ridge National Laboratory42, California State University, Chico43, University of Tsukuba44
TL;DR: Comparisons across strains demonstrate that E. huxleyi, which has long been considered a single species, harbours extensive genome variability reflected in different metabolic repertoires, and reveals a pan genome (core genes plus genes distributed variably between strains) probably supported by an atypical complement of repetitive sequence in the genome.
Abstract: Coccolithophores have influenced the global climate for over 200 million years(1). These marine phytoplankton can account for 20 per cent of total carbon fixation in some systems(2). They form blooms that can occupy hundreds of thousands of square kilometres and are distinguished by their elegantly sculpted calcium carbonate exoskeletons (coccoliths), rendering them visible from space(3). Although coccolithophores export carbon in the form of organic matter and calcite to the sea floor, they also release CO2 in the calcification process. Hence, they have a complex influence on the carbon cycle, driving either CO2 production or uptake, sequestration and export to the deep ocean(4). Here we report the first haptophyte reference genome, from the coccolithophore Emiliania huxleyi strain CCMP1516, and sequences from 13 additional isolates. Our analyses reveal a pan genome (core genes plus genes distributed variably between strains) probably supported by an atypical complement of repetitive sequence in the genome. Comparisons across strains demonstrate that E. huxleyi, which has long been considered a single species, harbours extensive genome variability reflected in different metabolic repertoires. Genome variability within this species complex seems to underpin its capacity both to thrive in habitats ranging from the equator to the subarctic and to form large-scale episodic blooms under a wide variety of environmental conditions.
430 citations
University of Toronto1, Uppsala University2, New York University Abu Dhabi3, Max Planck Society4, Institut national de la recherche agronomique5, Chinese Academy of Sciences6, McGill University7, Masaryk University8, University of Utah9, Colby–Sawyer College10, University of California, Davis11, University of California, Irvine12, Princeton University13, Gregor Mendel Institute14, United States Department of Energy15, University of California, Berkeley16
TL;DR: The transition to selfing may be typified by parallel shifts in gene expression, along with a measurable reduction of purifying selection, similar to that seen in Arabidopsis, which self fertilization evolved about 1 million years ago.
Abstract: The shift from outcrossing to selfing is common in flowering plants(1,2), but the genomic consequences and the speed at which they emerge remain poorly understood. An excellent model for understanding the evolution of self fertilization is provided by Capsella rubella, which became self compatible <200,000 years ago. We report a C. rubella reference genome sequence and compare RNA expression and polymorphism patterns between C. rubella and its outcrossing progenitor Capsella grandiflora. We found a clear shift in the expression of genes associated with flowering phenotypes, similar to that seen in Arabidopsis, in which self fertilization evolved about 1 million years ago. Comparisons of the two Capsella species showed evidence of rapid genome-wide relaxation of purifying selection in C. rubella without a concomitant change in transposable element abundance. Overall we document that the transition to selfing may be typified by parallel shifts in gene expression, along with a measurable reduction of purifying selection.
404 citations
TL;DR: Fluorescence thermometry techniques with sensitivities approaching 10 mK⋅Hz−1/2 based on the spin-dependent photoluminescence of nitrogen vacancy (NV) centers in diamond are demonstrated, suggesting that the quantum coherence of single spins could be practically leveraged for sensitive thermometry in a wide variety of biological and microscale systems.
Abstract: We demonstrate fluorescence thermometry techniques with sensitivities approaching 10 mK · Hz(-1/2) based on the spin-dependent photoluminescence of nitrogen vacancy (NV) centers in diamond. These techniques use dynamical decoupling protocols to convert thermally induced shifts in the NV center's spin resonance frequencies into large changes in its fluorescence. By mitigating interactions with nearby nuclear spins and facilitating selective thermal measurements, these protocols enhance the spin coherence times accessible for thermometry by 45-fold, corresponding to a 7-fold improvement in the NV center's temperature sensitivity. Moreover, we demonstrate these techniques can be applied over a broad temperature range and in both finite and near-zero magnetic field environments. This versatility suggests that the quantum coherence of single spins could be practically leveraged for sensitive thermometry in a wide variety of biological and microscale systems.
380 citations
TL;DR: The dynamic enhancer activities uncovered in this study illuminate rapid and pervasive temporal in vivo changes in enhancer usage that underlie processes central to development and disease.
TL;DR: In this paper, the authors report sequencing of genomes from three Brassicaceae species (Leavenworthia alabamica, Sisymbrium irio and Aethionema arabicum) and their joint analysis with six previously sequenced crucifer genomes.
Abstract: Despite the central importance of noncoding DNA to gene regulation and evolution, understanding of the extent of selection on plant noncoding DNA remains limited compared to that of other organisms. Here we report sequencing of genomes from three Brassicaceae species (Leavenworthia alabamica, Sisymbrium irio and Aethionema arabicum) and their joint analysis with six previously sequenced crucifer genomes. Conservation across orthologous bases suggests that at least 17% of the Arabidopsis thaliana genome is under selection, with nearly one-quarter of the sequence under selection lying outside of coding regions. Much of this sequence can be localized to approximately 90,000 conserved noncoding sequences (CNSs) that show evidence of transcriptional and post-transcriptional regulation. Population genomics analyses of two crucifer species, A. thaliana and Capsella grandiflora, confirm that most of the identified CNSs are evolving under medium to strong purifying selection. Overall, these CNSs highlight both similarities and several key differences between the regulatory DNA of plants and other species.
TL;DR: This work describes and implements a methodology to construct detailed temporal and spatial representations of demand response resources and to incorporate those resources into power system models and demonstrates how the combination of these three analyses can be used to assess economic value of the realizable potential ofDemand response for ancillary services.
Abstract: Many demand response resources are technically capable of providing ancillary services. In some cases, they can provide superior response to generators, as the curtailment of load is typically much faster than ramping thermal and hydropower plants. Analysis and quantification of demand response resources providing ancillary services is necessary to understand the resources' economic value and impact on the power system. Methodologies used to study grid integration of variable generation can be adapted to the study of demand response. In the present work, we describe and implement a methodology to construct detailed temporal and spatial representations of demand response resources and to incorporate those resources into power system models. In addition, the paper outlines ways to evaluate barriers to implementation. We demonstrate how the combination of these three analyses can be used to assess economic value of the realizable potential of demand response for ancillary services.
TL;DR: In this article, a comprehensive review on the production of bio-fuels from lignocellulosic agricultural products and promising energy crops is presented, including non-staple miscanthus and sorghum.
Abstract: Energy crops constitute significant potential for meeting the future energy need worldwide. In addition, agricultural lands offer an alternative to the agriculture which is referred to as energy farming. The studies on energy crops in biofuel production show that they are quite an economical and environmentally beneficial way of sustainable energy production. Today most of the developed countries use staples such as corn, sugar beet, soybean, rapeseed, and wheat in order to obtain energy. Moreover, bioethanol is mostly produced from sugarcane and corn and biodiesel from oilseed plants. Therefore, these produced raw materials compete with food and feed production. Consequently, the use of those energy crops which are used as food products for biofuel production is an important issue which must be considered in terms of the current food safety. Some energy crops, such as miscanthus, switchgrass and sweet sorghum, that are called C4 crops, can grow with high biomass yield even in infertile land. Thus, these crops are used in energy farming – a new type of agriculture. Furthermore, C4-type crops possess the features of resistance to aridity, high photosynthetic yield and a high rate of CO2 capture when compared with C3 crops. In conclusion, C4 crops tend to produce more biomass than C3 crops. Therefore, these crops are investigated, focused on, and elaborated on in this paper.
This study aims to present a comprehensive review on the production of biofuels from lignocellulosic agricultural products and promising energy crops. Thus, the energy crops to be used as raw materials for biofuels today and in the future are investigated. In addition, it is intended to highlight the energy crops used as staples by discussing them in detail for biofuel production. The energy crops which are promising in biofuel production, particularly non-staple miscanthus and sorghum, are presented in detail as they are non-food crops and have a high yield. Furthermore, the energy crops used as raw materials for bioenergy today and their potential are compared both worldwide and in Turkey.
TL;DR: A regulation strategy capable of controlling the energy stored in the modular multilevel converter (MMC) in an HVDC configuration by regulating the positive, negative, and zero sequences in dqo coordinates of the differential current using two rotating reference frames.
Abstract: This paper consists of the presentation of a regulation strategy capable of controlling the energy stored in the modular multilevel converter (MMC) in an HVDC configuration. This is achieved by regulating the positive, negative, and zero sequences in dqo coordinates of the differential current using two rotating reference frames: at once and at twice the fundamental grid frequency value. The active and reactive negative sequence components of the differential current at twice the fundamental frequency are used to eliminate the oscillations of the three-phased leg energy, reducing significantly the capacitor voltage oscillations, while the zero-sequence component is used to regulate the total energy stored at a given reference. Meanwhile, active and reactive positive sequence components of the circulating current are used for eliminating the average energy difference between the upper and lower arms in a three-phase MMC. In order to decouple efficiently the differential current components, the decoupled-double-synchronous-reference-frame current control strategy is used. Finally, simulation results validate the performance of the MMC in an HVDC configuration with the proposed control. Control equations are demonstrated, and cross-coupled leg-energy terms are introduced.
TL;DR: Using methanol decomposition and oxidative dehydrogenation of ethane as probe reactions, it is demonstrated that selectively blocking low coordination metal sites by oxide overcoats can provide another strategy to enhance both the durability and selectivity of metal catalysts.
Abstract: Supported metal nanoparticles are among the most important cata-lysts for many practical reactions, including petroleum refining, automobile exhaust treatment, and Fischer–Tropsch synthesis. The catalytic performance strongly depends on the size, composition, and structure of the metal nanoparticles, as well as the underlying support. Scientists have used conventional synthesis methods including impregnation, ion exchange, and deposition–precipitation to control and tune these factors, to establish structure–performance relationships, and to develop better catalysts. Meanwhile, chemists have improved the stability of metal nanoparticles against sintering by the application of protective layers, such as polymers and oxides that encapsulate the metal particle. This often leads to decreased catalytic activity due to a lack of precise control over the thickness of the protective layer.A promising method of catalyst synthesis is atomic layer deposition (ALD). ALD is a variation on chemical vapor deposition in ...
TL;DR: This report shows that the chemical interactions and atomic diffusivities predicted from ab initio molecular dynamics simulations which are closely related to primary crystallization during solidification can be used to assist in identifying single phase high-entropy solid solution compositions.
Abstract: There has been considerable technological interest in high-entropy alloys (HEAs) since the initial publications on the topic appeared in 2004. However, only several of the alloys investigated are truly single-phase solid solution compositions. These include the FCC alloys CoCrFeNi and CoCrFeMnNi based on 3d transition metals elements and BCC alloys NbMoTaW, NbMoTaVW, and HfNbTaTiZr based on refractory metals. The search for new single-phase HEAs compositions has been hindered by a lack of an effective scientific strategy for alloy design. This report shows that the chemical interactions and atomic diffusivities predicted from ab initio molecular dynamics simulations which are closely related to primary crystallization during solidification can be used to assist in identifying single phase high-entropy solid solution compositions. Further, combining these simulations with phase diagram calculations via the CALPHAD method and inspection of existing phase diagrams is an effective strategy to accelerate the discovery of new single-phase HEAs. This methodology was used to predict new single-phase HEA compositions. These are FCC alloys comprised of CoFeMnNi, CuNiPdPt and CuNiPdPtRh, and HCP alloys of CoOsReRu.
TL;DR: Results show that the proposed three-step approach is able to charge PHEVs with comparable quality to optimal, centrally computed charging plans, while significantly improving scalability.
Abstract: In this paper, we present a scalable approach for DSM (demand side management) of PHEVs (plug-in hybrid electric vehicles). Essentially, our approach consists of three steps: aggregation, optimization, and control. In the aggregation step, individual PHEV charging constraints are aggregated upwards in a tree structure. In the optimization step, the aggregated constraints are used for scalable computation of a collective charging plan, which minimizes costs for electricity supply. In the real-time control step, this charging plan is used to create an incentive signal for all PHEVs, determined by a market-based priority scheme. These three steps are executed iteratively to cope with uncertainty and dynamism. In simulation experiments, the proposed three-step approach is benchmarked against classic, fully centralized approaches. Results show that our approach is able to charge PHEVs with comparable quality to optimal, centrally computed charging plans, while significantly improving scalability.
TL;DR: A digital atlas of in vivo enhancers active in subregions of the developing telencephalon, identifying more than 4,600 candidate embryonic forebrain enhancers and studying the in vivo activity of 329 of these sequences in transgenic mouse embryos is described.
TL;DR: A review of the key advances that have occurred in the past several years in the field of single cell optical imaging to highlight the types of findings that are possible at the nexus of microscopy, nanoprobes, and live cells.
Abstract: In his 1665 treatise, Micrographia, Robert Hooke described the many observations he had made using a microscope, including compartment-like structures in cork samples that he termed ‘cells’.1 In the three and a half centuries since Hooke’s day, both the microscope and our understanding of the cell have been vastly improved upon, and the current outlook suggests that the symbiotic relationship between the microscope and the cell will continue to flourish into the foreseeable future. The cell is a basic yet complicated ‘unit’ of interest to biology, just as the atom is to chemists. Ultimately, scientists want to ‘see to believe’ when it comes to an explanation of the complex inner workings of cells, but therein lies a complication. Seeing is not always a possibility in biological systems. Size, speed, sensitivity, and additional concerns plague the microscopist who wants to peek inside of a cell. Enter a variety of molecular and nanoparticle probes that are capable of tagging and pinpointing the location of biological components that would otherwise be invisible under the microscope. Advances in laser, camera, and imaging processing technologies have also played a crucial role in the burgeoning field of single cell imaging, because they have brought into view the fast processes that would normally escape the human eye.
The purpose of this review is to highlight the key advances that have occurred in the past several years in the field of single cell optical imaging. It is not our intent to provide a comprehensive review of the types of experiments or the areas of cell research that are ongoing. Reviews with a distinctly biological flavor have been published recently, and these alternative reviews focus on specific details of the cell and the processes that occur within.2-7 Likewise, exceptional review papers that have discussed the full spectrum of nanoparticle probes and their properties have appeared recently.6-12 This review is designed to give an overview of the tools that are being specifically used to accomplish single cell imaging. As such, much of our emphasis in the first several sections of this paper is on imaging platforms, with a focus on design details that are important to single cell imaging experiments. Next we emphasize specific imaging experiments that highlight the types of findings that are possible at the nexus of microscopy, nanoprobes, and live cells. Particular attention is paid to the emerging orientation and rotational tracking of single probes linked to mechanistic functions and differentiated structures of biological interest. Finally, we provide a brief, yet rather complete, summary of single cell manipulation techniques.
TL;DR: The results demonstrate that, unlike membrane-bound organelles of eukaryotes, in carboxysomes the interior of the compartment forms first, at a distinct site within the cell, and it is proposed that the principles of car boxysome assembly that are uncovered extend to diverse bacterial microcompartments.
TL;DR: In this article, the photocatalytic water oxidation activity of hematite (α-Fe2O3) has been greatly enhanced by incorporating hematitic nanoparticles on the reduced graphene oxide (rGO) nanosheets.
Abstract: The photocatalytic water oxidation activity of hematite (α-Fe2O3) has been greatly enhanced by incorporating hematite nanoparticles on the reduced graphene oxide (rGO) nanosheets. Photoelectrochemical measurement results show that coupling the hematite nanoparticles with the rGO greatly increases the photocurrent and reduces the charge recombination rate. Transient absorption spectroscopy and time-domain terahertz spectroscopy have provided the direct evidence that the photogenerated electrons have transferred as the mobile carriers from α-Fe2O3 to rGO, which enhances the charge separation and suppresses the charge recombination. This work has provided new insight into the mechanism of photocatalysis enhancement by reduced graphene oxide, which has implications in the design of semiconductor/graphene heterojunction photocatalysts.
TL;DR: The results support that variation in the sequence or copy number of craniofacial enhancers may contribute to the spectrum of facial variation the authors find in human populations.
Abstract: The shape of the human face and skull is largely genetically determined. However, the genomic basis of craniofacial morphology is incompletely understood and hypothesized to involve protein-coding genes, as well as gene regulatory sequences. We used a combination of epigenomic profiling, in vivo characterization of candidate enhancer sequences in transgenic mice, and targeted deletion experiments to examine the role of distant-acting enhancers in craniofacial development. We identified complex regulatory landscapes consisting of enhancers that drive spatially complex developmental expression patterns. Analysis of mouse lines in which individual craniofacial enhancers had been deleted revealed significant alterations of craniofacial shape, demonstrating the functional importance of enhancers in defining face and skull morphology. These results demonstrate that enhancers are involved in craniofacial development and suggest that enhancer sequence variation contributes to the diversity of human facial morphology.
TL;DR: The electrical behavior of a conducting-polymer/inorganic-nanowire composite is explained with a model in which carrier transport occurs predominantly through a highly conductive volume of polymer that exists at the polymer- nanowire interface.
Abstract: The electrical behavior of a conducting-polymer/inorganic-nanowire composite is explained with a model in which carrier transport occurs predominantly through a highly conductive volume of polymer that exists at the polymer-nanowire interface. This result highlights the importance of controlling nanoscale interfaces for thermoelectric materials, and provides a general route for improving carrier transport in organic/inorganic composites.
TL;DR: A number of special qualities of graphene that also make it desirable for devices manipulating terahertz waves are discussed that may be useful for plasmonics and metamaterials at terAhertz frequencies.
Abstract: The optoelectronic properties of graphene are being explored for possible use in plasmonics and metamaterials at terahertz frequencies.
TL;DR: The genomes of five C. heterostrophus strains, two C. sativus strains and three additional C. species were sequenced at the Joint Genome Institute (JGI) to identify SNPs between strains and species, unique genomic regions, core secondary metabolism genes, and small secreted protein (SSP) candidate effector encoding genes as discussed by the authors.
Abstract: The genomes of five Cochliobolus heterostrophus strains, two Cochliobolus sativus strains, three additional Cochliobolus species (Cochliobolus victoriae, Cochliobolus carbonum, Cochliobolus miyabeanus), and closely related Setosphaeria turcica were sequenced at the Joint Genome Institute (JGI). The datasets were used to identify SNPs between strains and species, unique genomic regions, core secondary metabolism genes, and small secreted protein (SSP) candidate effector encoding genes with a view towards pinpointing structural elements and gene content associated with specificity of these closely related fungi to different cereal hosts. Whole-genome alignment shows that three to five percent of each genome differs between strains of the same species, while a quarter of each genome differs between species. On average, SNP counts among field isolates of the same C. heterostrophus species are more than 25× higher than those between inbred lines and 50× lower than SNPs between Cochliobolus species. The suites of nonribosomal peptide synthetase (NRPS), polyketide synthase (PKS), and SSP–encoding genes are astoundingly diverse among species but remarkably conserved among isolates of the same species, whether inbred or field strains, except for defining examples that map to unique genomic regions. Functional analysis of several strain-unique PKSs and NRPSs reveal a strong correlation with a role in virulence.
TL;DR: An analysis was conducted that predicts human exposure potential for chemicals and estimates uncertainty in these predictions by comparison to biomonitoring data, and a framework for high-throughput exposure assessment is proposed.
Abstract: The United States Environmental Protection Agency (U.S. EPA) must characterize potential risks to human health and the environment associated with manufacture and use of thousands of chemicals. High-throughput screening (HTS) for biological activity allows the ToxCast research program to prioritize chemical inventories for potential hazard. Similar capabilities for estimating exposure potential would support rapid risk-based prioritization for chemicals with limited information; here, we propose a framework for high-throughput exposure assessment. To demonstrate application, an analysis was conducted that predicts human exposure potential for chemicals and estimates uncertainty in these predictions by comparison to biomonitoring data. We evaluated 1936 chemicals using far-field mass balance human exposure models (USEtox and RAIDAR) and an indicator for indoor and/or consumer use. These predictions were compared to exposures inferred by Bayesian analysis from urine concentrations for 82 chemicals reported ...
TL;DR: In this paper, a search for squarks and gluinos in final states containing jets, missing transverse momentum and no high-p(T) electrons or muons is presented.
Abstract: A search for squarks and gluinos in final states containing jets, missing transverse momentum and no high-p(T) electrons or muons is presented. The data represent the complete sample recorded in 2011 by the ATLAS experiment in 7 TeV proton-proton collisions at the Large Hadron Collider, with a total integrated luminosity of 4.7 fb(-1). No excess above the Standard Model background expectation is observed. Gluino masses below 860 GeV and squark masses below 1320 GeV are excluded at the 95% confidence level in simplified models containing only squarks of the first two generations, a gluino octet and a massless neutralino, for squark or gluino masses below 2 TeV, respectively. Squarks and gluinos with equal masses below 1410 GeV are excluded. In minimal supergravity/constrained minimal supersymmetric Standard Model models with tan beta = 10, A(0) = 0 and mu > 0, squarks and gluinos of equal mass are excluded for masses below 1360 GeV. Constraints are also placed on the parameter space of supersymmetric models with compressed spectra. These limits considerably extend the region of supersymmetric parameter space excluded by previous measurements with the ATLAS detector.
TL;DR: In this paper, a new gas hydrate-based desalination process using water-immiscible hydrate formers; cyclopentane (CP) and cyclohexane (CH) as secondary hydrate guests to alleviate temperature requirements for hydrate formation.
Abstract: We suggest a new gas hydrate-based desalination process using water-immiscible hydrate formers; cyclopentane (CP) and cyclohexane (CH) as secondary hydrate guests to alleviate temperature requirements for hydrate formation. The hydrate formation reactions were carried out in an isobaric condition of 3.1 MPa to find the upper temperature limit of CO2 hydrate formation. Simulated produced water (8.95 wt % salinity) mixed with the hydrate formers shows an increased upper temperature limit from −2 °C for simple CO2 hydrate to 16 and 7 °C for double (CO2 + CP) and (CO2 + CH) hydrates, respectively. The resulting conversion rate to double hydrate turned out to be similar to that with simple CO2 hydrate at the upper temperature limit. Hydrate formation rates (Rf) for the double hydrates with CP and CH are shown to be 22 and 16 times higher, respectively, than that of the simple CO2 hydrate at the upper temperature limit. Such mild hydrate formation temperature and fast formation kinetics indicate increased energ...
University of Montpellier1, Environment Canada2, École Polytechnique Fédérale de Lausanne3, United States Department of Energy4, Centre national de la recherche scientifique5, University of Bristol6, VU University Amsterdam7, Oeschger Centre for Climate Change Research8, University of Washington9, University of Victoria10, Camosun College11, Auburn University12, Russian Academy of Sciences13, Kazan Federal University14, Lawrence Berkeley National Laboratory15, Princeton University16, Max Planck Society17, Lehigh University18, University of Sheffield19
TL;DR: The Wetland and Wetland CH4 Intercomparison of Models Project (WETCHIMP) was created to evaluate the present ability to simulate large-scale wetland characteristics and corresponding methane (CH4) emissions as discussed by the authors.
Abstract: The Wetland and Wetland CH4 Intercomparison of Models Project (WETCHIMP) was created to evaluate our present ability to simulate large-scale wetland characteristics and corresponding methane (CH4) emissions. A multi-model comparison is essential to evaluate the key uncertainties in the mechanisms and parameters leading to methane emissions. Ten modelling groups joined WETCHIMP to run eight global and two regional models with a common experimental protocol using the same climate and atmospheric carbon dioxide (CO2) forcing datasets. We reported the main conclusions from the intercomparison effort in a companion paper (Melton et al., 2013). Here we provide technical details for the six experiments, which included an equilibrium, a transient, and an optimized run plus three sensitivity experiments (temperature, precipitation, and atmospheric CO2 concentration). The diversity of approaches used by the models is summarized through a series of conceptual figures, and is used to evaluate the wide range of wetland extent and CH4 fluxes predicted by the models in the equilibrium run. We discuss relationships among the various approaches and patterns in consistencies of these model predictions. Within this group of models, there are three broad classes of methods used to estimate wetland extent: prescribed based on wetland distribution maps, prognostic relationships between hydrological states based on satellite observations, and explicit hydrological mass balances. A larger variety of approaches was used to estimate the net CH4 fluxes from wetland systems. Even though modelling of wetland extent and CH4 emissions has progressed significantly over recent decades, large uncertainties still exist when estimating CH4 emissions: there is little consensus on model structure or complexity due to knowledge gaps, different aims of the models, and the range of temporal and spatial resolutions of the models.