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Measurement of the electroweak production of dijets in association with a Z-boson and distributions sensitive to vector boson fusion in proton-proton collisions at $ \sqrt{s} $ = 8 TeV using the ATLAS detector
Measurements of fiducial cross sections for the electroweak production of two jets in association with a Z-boson are presented. The measurements are performed using 20.3 fb -1 of proton-proton collision data collected at a centre-of-mass energy of √s = 8 TeV by the ATLAS experiment at the Large Hadron Collider. The electroweak component is extracted by a fit to the dijet invariant mass distribution in a fiducial region chosen to enhance the electroweak contribution over the dominant background in which the jets are produced via the strong interaction. The electroweak cross sections measured in two fiducial regions are in good agreement with the Standard Model expectations and the background-only hypothesis is rejected with significance above the 5σ level. The electroweak process includes the vector boson fusion production of a Z-boson and the data are used to place limits on anomalous triple gauge boson couplings. In addition, measurements of cross sections and differential distributions for inclusive Z-boson-plus-dijet production are performed in five fiducial regions, each with different sensitivity to the electroweak contribution. The results are corrected for detector effects and compared to predictions from the Sherpa and Powheg event generators.
Fe Vacancy Order and Domain Distribution in A{sub x}Fe{sub 2−y}Se{sub 2}
The Fe vacancy and its ordering pattern is a unique property of the A{sub x}Fe{sub 2−y}Se{sub 2} (A = K, Rb, Cs) superconductors. Below the structural transition temperature T{sub S} ∼ 550 K, the system phase separates into the I4/mmm phase with no Fe vacancy and the I4/m phase with the √5×√5×1 vacancy order. In this work, an Ising-like Hamiltonian defined on the Fe-sublattice is constructed and employed in a Metropolis Monte Carlo simulation to study the Fe vacancy order and the domain distribution under different thermal treatments. A third phase with randomly distributed Fe vacancies and space group I4/mmm is observed in the simulation. The response of the volume fraction of this simulated phase under thermal treatment shows a direct connection to the change of the superconducting shielding fraction under annealing and quenching processes, indicating a close relation between the vacancy disordered I4/mmm phase and the superconducting phase.
Transmission-distribution long-term volt-var planning considering reactive power support capability of distributed PV
High penetration of grid-edge, inverter-based photovoltaic (PV) can cause significant voltage fluctuations not only at the distribution but also at the sub-transmission levels due to PV output intermittency. Traditional reactive power planning approaches do not consider intermittency, nor the possibility of coordinating the control of existing and future volt-ampere reactive resources. This paper proposes a reactive power planning tool for sub-transmission systems to mitigate voltage violations and fluctuations caused by high PV penetration and intermittency with a minimum investment cost. The planning tool coordinates with an optimization-based volt-var operational tool for: a) modeling the coordination of all existing var assets in both sub-transmission and distribution systems to reduce the need of new equipment, and b)selecting a set of scenarios with voltage violations, derived from PV intermittency c) testing the final investment decision. The tool obtains an investment need for each intermittency scenario with a proposed optimal power-flow framework with efficient techniques to handle a high number of discrete variables. Two options are provided for final planning decision: i) a conservative direct combination of investment need solutions and ii) a machine learning-based selection of representative investment needs at most time steps. The final investment decision options are verified using a realistic large-scale sub-transmission system and 5-minute PV and load data. The results show a significant voltage performance improvement with a lower investment cost for additional var equipment compared to conventional approaches.
Effects of composition and canister centerline cooling on microstructure, phase distribution, and chemical durability of dehalogenated iron phosphate waste forms
This paper discusses the effects of composition and canister centerline cooling (CCC) on the microstructures, phase distribution, and chemical durability of dehalogenated iron phosphate waste forms starting from chloride-based salt simulants including KCl (Simple-1), NdCl3 (Simple-2), SrCl2 (Simple-3), LaCl3 (Simple-4), LiCl (Simple-5), CsCl (Simple-6), as well as a complex simulant containing LiCl, KCl, NaCl, CsI, SrCl2, CeCl3, and NdCl3 called ERV2. The simulants represent salt constituents present in salt wastes from electrorefiners used for electrochemical reprocessing. These salts are reacted with ammonium dihydrogen phosphate (ADP) resulting in a NH4Cl (dechlorination) byproduct that is captured and phosphate product containing oxides of the salt cations. This product is further stabilized using Fe2O3 through vitrification at higher temperatures. The results presented herein describe the properties of CCC-treated materials following dechlorination and vitrification including phase identification and quantification, elemental distributions, and chemical durabilities. The chemical durability in the CCC-cooled samples are lower durability than quenched materials for the ERV2 samples. The phases formed upon CCC cooling are very complex compositionally and microstructurally.
Synthesis and synchrotron characterisation of novel dual-template of hydroxyapatite scaffolds with controlled size porous distribution
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Generalized parton distributions obtained with CLAS and CLAS12
Recent promising results obtained with the Jefferson Lab CLAS detector on deeply virtual exclusive processes and their link to the generalized parton distributions, along with the experimental program for studying GPDs at the 12 GeV upgraded JLab using the CLAS12 detector, are discussed here. With its wide acceptance, high luminosity, good resolution and particle identification capabilities, as well as large Q2 and xB coverage (View the MathML source, 0.1 < xB < 0.8), CLAS12 will be the ideal facility to pursue the research on the three-dimensional structure of the nucleon in the valence region.
Simulating the Household Plug-in Hybrid Electric Vehicle Distribution and its Electric Distribution Network Impacts
This paper presents a multi agent-based simulation framework for modeling spatial distribution of plug-in hybrid electric vehicle ownership at local residential level, discovering plug-in hybrid electric vehicle hot zones where ownership may quickly increase in the near future, and estimating the impacts of the increasing plug-in hybrid electric vehicle ownership on the local electric distribution network with different charging strategies. We use Knox County, Tennessee as a case study to highlight the simulation results of the agent-based simulation framework.
Elucidating Electron Storage and Distribution within the Pentaheme Scaffold of Cytochrome c Nitrite Reductase (NrfA)
Cytochrome c nitrite reductases (CcNIR or NrfA) play important roles in the global nitrogen cycle by conserving the usable nitrogen in the soil. Here, the electron storage and distribution properties within the pentaheme scaffold of Geobacter lovleyi NrfA were investigated via EPR spectroscopy coupled with chemical titration experiments. Initially, a chemical reduction method was established to sequentially add electrons to the fully oxidized protein, one equivalent at a time. The step–by–step reduction of the hemes was then followed using UV–Vis and EPR spectroscopy. EPR–spectral simulations elucidate the sequence of heme reduction within the pentaheme scaffold, and identify the signals of all five hemes in the EPR spectra. Electrochemical experiments ascertain the reduction potentials for each heme, observed in a narrow +11 (Heme 5) to –212 mV (Heme 3) range (vs SHE). Based on quantitative analysis/simulation of the EPR data, we demonstrate that Hemes 4 and 5 are reduced first (before the active site Heme 1) and serve the purpose of an electron storage unit within the protein. To probe the role of the central Heme 3, a H108M NrfA variant was generated where the reduction potential of Heme 3 is shifted positively (from –212 mV to +29 mV). Here, the H108M mutation significantly impacts the distribution of electrons within the pentaheme scaffold and the reduction potentials of the hemes, reducing the catalytic activity of the enzyme to 3% compared to wild–type. We propose that this is due to Heme 3’s important role as an electron gateway in the wild–type enzyme.
Growth Kinetics and Size Distribution Dynamics of Viscous Secondary Organic Aerosol
Low bulk diffusivity inside viscous semisolid atmospheric secondary organic aerosol (SOA) can prolong equilibration time scale, but its broader impacts on aerosol growth and size distribution dynamics are poorly understood. In this article, we present quantitative insights into the effects of bulk diffusivity on the growth and evaporation kinetics of SOA formed under dry conditions from photooxidation of isoprene in the presence of a bimodal aerosol consisting of Aitken (ammonium sulfate) and accumulation (isoprene or α-pinene SOA) mode particles. Aerosol composition measurements and evaporation kinetics indicate that isoprene SOA is composed of several semivolatile organic compounds (SVOCs), with some reversibly reacting to form oligomers. Model analysis shows that liquid-like bulk diffusivities can be used to fit the observed evaporation kinetics of accumulation mode particles but fail to explain the growth kinetics of bimodal aerosol by significantly under-predicting the evolution of the Aitken mode. In contrast, the semisolid scenario successfully reproduces both evaporation and growth kinetics, with the interpretation that hindered partitioning of SVOCs into large viscous particles effectively promotes the growth of smaller particles that have shorter diffusion time scales. This effect has important implications for the growth of atmospheric ultrafine particles to climatically active sizes.
Impact of the Crystallite Orientation Distribution on Exciton Transport in Donor""Acceptor Conjugated Polymers
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Same Precursor, Two Different Products: Comparing the Structural Evolution of In–Ga–O “Gel-Derived” Powders and Solution-Cast Films Using Pair Distribution Function Analysis
Amorphous metal oxides are central to a variety of technological applications. In particular, indium gallium oxide has garnered attention as a thin-film transistor channel layer material. In this work we examine the structural evolution of indium gallium oxide gel-derived powders and thin films using infrared vibrational spectroscopy, X-ray diffraction, and pair distribution function (PDF) analysis of X-ray total scattering from standard and normal incidence thin-film geometries (tfPDF). We find that the gel-derived powders and films from the same aqueous precursor evolve differently with temperature, forming mixtures of Ga-substituted In2O3 and In-substituted β-Ga2O3 with different degrees of substitution. X-ray total scattering and PDF analysis indicate that the majority phase for both the powders and films is an amorphous/nanocrystalline β-Ga2O3 phase, with a minor constituent of In2O3 with significantly larger coherence lengths. This amorphous β-Ga2O3 phase could not be identified using the conventional Bragg diffraction techniques traditionally used to study crystalline metal oxide thin films. The combination of Bragg diffraction and tfPDF provides a much more complete description of film composition and structure, which can be used to detail the effect of processing conditions and structure–property relationships. This study also demonstrates how structural features of amorphous materials, traditionally difficult to characterize by standard diffraction, can be elucidated using tfPDF.
Delineating Facies Spatial Distribution by Integrating Ensemble Data Assimilation and Indicator Geostatistics with Level-Set Transformation
The facies-based approach has been widely adopted to delineate an aquifer into distinct geological units with unique distributions of hydraulic, physical, and/or chemical properties. The recent development in ensemble-based data assimilation methods allows both the direct and indirect data to be used to improve facies delineation. A major difficulty in those applications is to honor the spatial continuity and avoid overfitting after data assimilation. We introduce a new facies delineation framework to integrate ensemble data assimilation with traditional transition probability-based geostatistics. A level-set concept is used to parametrize discrete facies indicators and for updating facies shape. During the iterative data assimilation process, we impose spatial continuity by conditioning facies field generation on points selected adaptively based on their sensitivity to observation data. This reconditioning step is a key step to maintain spatial continuity and overcome over-fitting problems in inversion. We selected two examples to evaluate the performance of the new framework in estimating facies-based permeability field. The first example is a two-dimensional synthetic system with transient head data induced by pumping tests used for delineating two facies. The second example is a three-dimensional case with three facies, conceptualized from a field tracer experiment within the Columbia River corridor in Washington State, USA. Both examples demonstrate that the new method can adequately capture the spatial pattern of hydrofacies with reconditioning, which leads to the improved prediction of system behaviors.
Initial Land Use/Cover Distribution Substantially Affects Global Carbon and Local Temperature Projections in the Integrated Earth System Model
Initial land cover distribution varies among Earth system models, an uncertainty in initial conditions that can substantially affect carbon and climate projections. We use the integrated Earth System Model to show that a 3.9 M km2 difference in 2005 global forest area (9–14% of total forest area) generates uncertainties in initial atmospheric CO2 concentration, terrestrial carbon, and local temperature that propagate through a future simulation following the Representative Concentration Pathway 4.5. By 2095, the initial 6 ppmv uncertainty range increases to 9 ppmv and the initial 26 PgC uncertainty range in terrestrial carbon increases to 33 PgC. The initial uncertainty range in annual average local temperature of -0.74 to 0.96 °C persists throughout the future simulation, with a seasonal maximum in Dec-Jan-Feb. These results highlight the importance of accurately characterizing historical land use and land cover to reduce overall initial condition uncertainty.
Reconciling Contrasting Relationships Between Relative Dispersion and Volume-Mean Radius of Cloud Droplet Size Distributions
Cloud droplet spectral relative dispersion is critical to parameterizations of cloud radiative properties, warm-rain initiation, and aerosol-cloud interactions in models; however, there is no consistent relationship between relative dispersion and volume-mean radius in literature, which hinders improving relative dispersion parameterization and calls for physical explanation. Here we show, by analyzing aircraft observations of cumulus clouds during Routine AAF [Atmospheric Radiation Measurement (ARM) Aerial Facility] Clouds with Low Optical Water Depths (CLOWD) Optical Radiative Observations, that the correlation between relative dispersion and volume-mean radius changes from positive to negative as volume-mean radius increases. With the new observation, we postulate that the sign of the correlation is determined by whether or not condensation (evaporation) occurs simultaneously with significant new activation (deactivation). The hypothesis is validated by simulations of both an adiabatic cloud parcel model and a parcel model accounting for entrainment-mixing. A new quantity, first bin strength, is introduced to quantify this new observation. Theoretical analysis of truncated gamma and modified gamma size distributions further supports the hypothesis and reconciles the contrasting relationships between relative dispersion and volume-mean radius, including the results in polluted fog observations. The results could shed new light on the so-called “twilight zone” between cloudy and cloud-free air, which in turn affects evaluation of aerosol-cloud interactions and retrieval of aerosol optical depth.