429 research outputs found

    Role of graphene on hierarchical flower-like NiAl layered double hydroxide-nickel foam-graphene as binder-free electrode for high-rate hybrid supercapacitor

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    In this work, a facile two-step hydrothermal method was reported to grow hierarchical flower-like NiAl layered double hydroxide (LDH) directly on 3D nickel foam (NF) which was further coated with 2D graphene nanosheets (GNS) layers as binder-free supercapacitor electrode. The positive and negative effects of GNS on the electrochemical performance of LDH-NF electrode were investigated in detail. The prepared LDH-NF/GNS electrode maintained an enhanced specific capacity of 165.6 C g-1 after 4000 cycles at a high current density of 40 A g-1. Furthermore, a hybrid supercapacitor, with LDH-NF/GNS and GNS-NF as the positive and negative electrodes, achieved an energy density (31.5 Wh kg-1 at a power density of 400 W kg-1) and super long-term cycle stability (a specific capacity of 67.2 C g-1 at 5 A g-1 after 5000 cycles with 80% retention). This study not only opens up the possibility of engineering LDH-NF/GNS into a promising electrode, but also highlights the positive and negative roles of GNS on LDH-NF as binder-free electrodes for further development of high-performance supercapacitors

    Thermal performance of loop heat pipes with smooth and rough porous copper fiber sintered sheets

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    Smooth and rough porous copper fiber sintered sheets, employed here as wicks for loop heat pipes for the first time, were fabricated using a low-temperature solid-phase sintering method. The capillary performance of these porous copper fiber sintered sheets were analyzed and discussed. The influence of the surface morphology, filling ratio, and working fluid on the thermal resistance, evaporator wall temperature, and start-up time of the loop heat pipes were investigated. The results showed that the capillary pumping amount of working fluid for both smooth and rough porous copper fiber sintered sheets initially increases rapidly, and then gradually attains a stable state. The curve of the capillary pumping amount of working fluid can be described as a function that increases exponentially over time. When rough porous copper fiber sintered sheets are used as wicks and deionized water is used as the working fluid, the capillary pumping amount is maximized. Compared to smooth porous copper fiber sintered sheets, loop heat pipes with rough porous copper fiber sintered sheets exhibit a shorter start-up time, lower thermal resistance, and lower evaporator wall temperature. For a filling ratio in the range of 15–45%, loop heat pipes with rough porous copper fiber sintered sheets and a 30% filling ratio show lower thermal resistance and a lower evaporator wall temperature. Ultimately, the use of deionized water as the working fluid with a 30% filling ratio enables loop heat pipes with rough porous copper fiber sintered sheets to be stably operated at a heat load of 200 W

    Solution Atomic Layer Deposition of Smooth, Continuous, Crystalline Metal-Organic Framework Thin Films

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    For the first time, a procedure has been established for the growth of surface-anchored metal–organic framework (SURMOF) copper(II) benzene-1,4-dicarboxylate (Cu-BDC) thin films of thickness control with single molecule accuracy. For this, we exploit the novel method solution atomic layer deposition (sALD). The sALD growth rate has been determined at 4.5 Å per cycle. The compact and dense SURMOF films grown at room temperature by sALD possess a vastly superior film thickness uniformity than those deposited by conventional solution-based techniques, such as dipping and spraying while featuring clear crystallinity from 100 nm thickness. The highly controlled layer-by-layer growth mechanism of sALD proves crucial to prevent unwanted side reactions such as Ostwald ripening or detrimental island growth, ensuring continuous Cu-BDC film coverage. This successful demonstration of sALD-grown compact continuous Cu-BDC SURMOF films is a paradigm change and provides a key advancement enabling a multitude of applications that require continuous and ultrathin coatings while maintaining tight film thickness specifications, which were previously unattainable with conventional solution-based growth methods

    Sustainable composite super absorbents made from polysaccharides

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    Compared to traditional super absorbent polymers using raw materials from petrochemical industry, natural polymer absorbents are more favorable because they are sustainable and biodegradable. In this study, composite absorbents were developed by crosslinking carrageenan with sodium alginate using calcium chloride. Effect of composition on absorption was tested. Absorption was improved by increasing carrageenan content. The super absorbent exhibited the maximal swelling ratio of 13.1 g/g in 0.9% saline water in just 5 min. The maximal tensile strength was reached with a value of 12.8 MPa. Water contact angle revealed that carrageenan is more hydrophobic than sodium alginate. Presence of sulfate groups might be a key factor promoting absorption. The scanning electron microscopic images showed that the composite material had a structure with alginate arranged at the outside surface. These results demonstrate that a sustainable and biodegradable absorbent was successfully developed with a matrix of properties for potential application in diapers

    Acute Encephalopathy Associated with Influenza A Infection in Adults

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    We report acute encephalopathy associated with influenza A infection in 3 adults. We detected high cerebrospinal fluid (CSF) and plasma concentrations of CXCL8/IL-8 and CCL2/MCP-1 (CSF/plasma ratios >3), and interleukin-6, CXCL10/IP-10, but no evidence of viral neuroinvasion. Patients recovered without sequelae. Hyperactivated cytokine response may play a role in pathogenesis

    Pair production of neutralinos via gluon-gluon collisions

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    The production of a neutralino pair via gluon-gluon fusion is studied in the minimal supersymmetric model(MSSM) at proton-proton colliders. The numerical analysis of their production rates are carried out in the mSUGRA scenario. The results show that this cross section may reach about 80 femto barn for χ~10χ~20\tilde{\chi}^{0}_{1}\tilde{\chi}^{0}_{2} pair production and 23 femto barn for χ~20χ~20\tilde{\chi}^{0}_{2}\tilde{\chi}^{0}_{2} pair production with suitable input parameters at the future LHC collider. It shows that this loop mediated process can be competitive with the quark-antiquark annihilation process at the LHC.Comment: LaTex file, l4 pages, 5 EPS figure

    Mirror Matter as Self Interacting Dark Matter

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    It has been argued that the observed core density profile of galaxies is inconsistent with having a dark matter particle that is collisionless and alternative dark matter candidates which are self interacting may explain observations better. One new class of self interacting dark matter that has been proposed in the context mirror universe models of particle physics is the mirror hydrogen atom whose stability is guaranteed by the conservation of mirror baryon number. We show that the effective transport cross section for mirror hydrogen atoms, has the right order of magnitude for solving the ``cuspy'' halo problem. Furthermore, the suppression of dissipation effects for mirror atoms due to higher mirror mass scale prevents the mirror halo matter from collapsing into a disk strengthening the argument for mirror matter as galactic dark matter.Comment: 6 pages; some references adde

    Novel mechanistic view of catalytic ozonation of gaseous toluene by dual-site kinetic modelling

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    The catalytic ozonation of VOCs is a promising approach for degradation of indoor VOCs, such as gaseous toluene. However, the mechanism and relevant kinetic steps involved in this reaction remain unclear. In this study, the catalytic ozonation of toluene over MnO2/graphene was investigated using the empirical power law model and classic Langmuir-Hinshelwood single-site (denoted as L-Hs) mechanism. The apparent activation energy determined using the power law model was 29.3±2.5 kJ mol−1. This finding indicated that the catalytic ozonation of toluene over MnO2/graphene was a heterogeneous reaction, and the Langmuir-Hinshelwood mechanism was applicable. However, the L-Hs mechanism did not fit the experimental data, suggesting that the reaction was non-single-site governed. A novel Langmuir-Hinshelwood dual-site (denoted as L-Hd) mechanism was then proposed to explain the experimental observations of the catalytic ozonation of toluene over MnO2/graphene through a steady-state kinetic study. This mechanism was based on the hypothesis that MnO2 was responsible for ozone decomposition and toluene adsorption on graphene; these two types of adsorption were coupled by an adjacent attack. Furthermore, XPS results confirmed the presence of a strong connection between MnO2 and graphene sites on the surface of MnO2/graphene. This connection allowed the adjacent attack and validated the dual-site mechanism. The L-Hd model was consistent with the predicted reaction rate of toluene removal with a correlation coefficient near unity (r2 = 0.9165). Moreover, the physical criterion was in accordance with both enthalpy and entropy of toluene adsorption constraints. Fulfillment of mathematical and physical criteria indicated the catalytic ozonation of toluene over MnO2/graphene can be well described by the L-Hd mechanism. This study helps understand the catalytic ozonation of toluene over MnO2/graphene in a closely mechanistic view

    Gamma-rays from millisecond pulsars in Globular Clusters

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    Globular clusters (GCs) with their ages of the order of several billion years contain many final products of evolution of stars such as: neutron stars, white dwarfs and probably also black holes. These compact objects can be at present responsible for the acceleration of particles to relativistic energies. Therefore, gamma-ray emission is expected from GCs as a result of radiation processes occurring either in the inner magnetosperes of millisecond pulsars or in the vicinity of accreting neutron stars and white dwarfs or as a result of interaction of particles leaving the compact objects with the strong radiation field within the GC. Recently, GeV gamma-ray emission has been detected from several GCs by the new satellite observatory Fermi. Also Cherenkov telescopes reported interesting upper limits at the TeV energies which start to constrain the content of GCs. We review the results of these gamma-ray observations in the context of recent scenarios for their origin.Comment: 20 pages, 9 figures, will be published in Astrophysics and Space Science Series (Springer), eds. N. Rea and D.F. Torre
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