2,441 research outputs found

    A general model for collaboration networks

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    In this paper, we propose a general model for collaboration networks. Depending on a single free parameter "{\bf preferential exponent}", this model interpolates between networks with a scale-free and an exponential degree distribution. The degree distribution in the present networks can be roughly classified into four patterns, all of which are observed in empirical data. And this model exhibits small-world effect, which means the corresponding networks are of very short average distance and highly large clustering coefficient. More interesting, we find a peak distribution of act-size from empirical data which has not been emphasized before of some collaboration networks. Our model can produce the peak act-size distribution naturally that agrees with the empirical data well.Comment: 10 pages, 10 figure

    Photocatalytic performances of ZnO nanoparticle film and vertically aligned nanorods in chamber-based microfluidic reactors: Reaction kinetics and flow effects

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    The final publication is available at Elsevier via https://doi.org/10.1016/j.apcatb.2017.03.020 © 2017. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/The nanoparticle seed layer (a film) and vertically aligned nanorods of zinc oxide (ZnO) with different lengths were fabricated within a novel chamber-based microfluidic (microchamber) reactor with a varying height of 0.127-5 mm and characterized with their microstructures, photocatalytic performances as well as qualitative reaction kinetics. The ZnO seed layer was produced by a sol-gel procedure and the nanorods were hydrothermally grown on seed layer coated glass substrates. These ZnO samples were integrated into the microchamber reactor through a seven-layer sandwiched configuration. The aqueous methyl orange (MO) solution was chosen as a model polluted water. By comparing the ultraviolet-visible (UV-vis) absorbance of the original MO solution and the post-treatment sample, the reaction constants were calculated, representing the efficiencies of the reactors. The ZnO samples, usually possessing a large amount of defects, with a higher crystal quality showed an enhanced activity. The reaction constant was featured of a plateau with accelerating flow rates, exhibited an exponentially decreasing function of the chamber height, and declined with increasing the initial concentration of the MO solution. The efficiency of the microchamber reactor was found to be one to two orders of magnitude higher than that of a batch reactor. The rate determining step was suggested to be the mass transport related adsorption of MO on ZnO. The measured reaction properties and the reactor design should be of considerable significance to the scaling-up and optimization of microchamber catalytic reactors dedicated to water purification and other applications. (C) 2017 Elsevier B.V. All rights reserved

    Polyamide 6.6 separates oil/water due to its dual underwater oleophobicity/underoil hydrophobicity: Role of 2D and 3D porous structures

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    The final publication is available at Elsevier via https://dx.doi.org/10.1016/j.apsusc.2018.10.041 © 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/Porous polyamide functionalized by plasma or various coatings has been investigated for oil/water separation. In literature, polyamide has rarely been studied for oil removal, and this work investigated the performance of bare polyamide 6.6 (nylon 6.6) in terms of the oil/water separation efficiency and the intrusion pressure, inspiring cost-effective solutions for large-scale oil removal in the industry. Both polyamide meshes possessing two-dimensional (2D) one-layer pores and nonwoven fabrics with three-dimensional (3D) irregular pores were found to be able to separate oil/water with a high efficiency above 98.5%. This finding was attributed to the dual underwater oleophobicity and underoil hydrophobicity of these polyamide samples. The roles of 2D and 3D structures in oil/water separation were illustrated, to provide a new insight into filter designing. Due to its greater intrusion pressure, the 3D netting structure was suggested as being more beneficial for oil/water separation than the 2D structure.Natural Sciences and Engineering Research Council of Canad

    Linear-Optical Implementation of Perfect Discrimination between Single-bit Unitary Operations

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    Discrimination of unitary operations is a fundamental quantum information processing task. Assisted with linear optical elements, we experimentally demonstrate perfect discrimination between single-bit unitary operations using two methods--sequential scheme and parallel scheme. The complexity and resource consumed in these two schemes are analyzed and compared.Comment: 10 pages, 3 figure

    Topological crystalline insulator states in Pb(1-x)Sn(x)Se

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    Topological insulators are a novel class of quantum materials in which time-reversal symmetry, relativistic (spin-orbit) effects and an inverted band structure result in electronic metallic states on the surfaces of bulk crystals. These helical states exhibit a Dirac-like energy dispersion across the bulk bandgap, and they are topologically protected. Recent theoretical proposals have suggested the existence of topological crystalline insulators, a novel class of topological insulators in which crystalline symmetry replaces the role of time-reversal symmetry in topological protection [1,2]. In this study, we show that the narrow-gap semiconductor Pb(1-x)Sn(x)Se is a topological crystalline insulator for x=0.23. Temperature-dependent magnetotransport measurements and angle-resolved photoelectron spectroscopy demonstrate that the material undergoes a temperature-driven topological phase transition from a trivial insulator to a topological crystalline insulator. These experimental findings add a new class to the family of topological insulators. We expect these results to be the beginning of both a considerable body of additional research on topological crystalline insulators as well as detailed studies of topological phase transitions.Comment: v2: published revised manuscript (6 pages, 3 figures) and supplementary information (5 pages, 8 figures

    Formation of the ηc\eta_c in Two-Photon Collisions at LEP

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    The two-photon width Γγγ\Gamma_{\gamma\gamma} of the ηc\eta_c meson has been measured with the L3 detector at LEP. The ηc\eta_c is studied in the decay modes π+ππ+π\pi^+\pi^-\pi^+\pi^-, π+π\pi^+\pi^-K+^+K^-, Ks0_s^0K±π^\pm\pi^\mp, K+^+Kπ0^-\pi^{0}, π+πη\pi^+\pi^-\eta, π+πη\pi^+\pi^-\eta', and ρ+ρ\rho^+\rho^- using an integrated luminosity of 140 pb1^{-1} at s91\sqrt{s} \simeq 91 GeV and of 52 pb1^{-1} at s183\sqrt{s} \simeq 183 GeV. The result is Γγγ(ηc)=6.9±1.7(stat.)±0.8(sys.)±2.0\Gamma_{\gamma\gamma}(\eta_c) = 6.9 \pm 1.7 (stat.) \pm 0.8 (sys.) \pm 2.0(BR) keV. The Q2Q^2 dependence of the ηc\eta_c cross section is studied for Q2<9Q^2 < 9 GeV2^{2}. It is found to be better described by a Vector Meson Dominance model form factor with a J-pole than with a ρ\rho-pole. In addition, a signal of 29±1129 \pm 11 events is observed at the χc0\chi_c0 mass. Upper limits for the two-photon widths of the χc0\chi_c0, χc2\chi_c2, and ηc\eta_c' are also given

    Identification of Giardia lamblia DHHC Proteins and the Role of Protein S-palmitoylation in the Encystation Process

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    Protein S-palmitoylation, a hydrophobic post-translational modification, is performed by protein acyltransferases that have a common DHHC Cys-rich domain (DHHC proteins), and provides a regulatory switch for protein membrane association. In this work, we analyzed the presence of DHHC proteins in the protozoa parasite Giardia lamblia and the function of the reversible S-palmitoylation of proteins during parasite differentiation into cyst. Two specific events were observed: encysting cells displayed a larger amount of palmitoylated proteins, and parasites treated with palmitoylation inhibitors produced a reduced number of mature cysts. With bioinformatics tools, we found nine DHHC proteins, potential protein acyltransferases, in the Giardia proteome. These proteins displayed a conserved structure when compared to different organisms and are distributed in different monophyletic clades. Although all Giardia DHHC proteins were found to be present in trophozoites and encysting cells, these proteins showed a different intracellular localization in trophozoites and seemed to be differently involved in the encystation process when they were overexpressed. dhhc transgenic parasites showed a different pattern of cyst wall protein expression and yielded different amounts of mature cysts when they were induced to encyst. Our findings disclosed some important issues regarding the role of DHHC proteins and palmitoylation during Giardia encystation.Fil: Merino, Maria Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra. Universidad Nacional de Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra; ArgentinaFil: Zamponi, Nahuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra. Universidad Nacional de Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra; ArgentinaFil: Vranych, Cecilia Verónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra. Universidad Nacional de Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra; ArgentinaFil: Touz, Maria Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra. Universidad Nacional de Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra; ArgentinaFil: Ropolo, Andrea Silvana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra. Universidad Nacional de Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra; Argentin
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