60 research outputs found

    Magnetic Field Effect in a Two-dimensional Array of Short Josephson Junctions

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    We study analytically the effect of a constant magnetic field on the dynamics of a two dimensional Josephson array. The magnetic field induces spatially dependent states and coupling between rows, even in the absence of an external load. Numerical simulations support these conclusions

    Improving permafrost physics in the coupled Canadian Land Surface Scheme (v.3.6.2) and Canadian Terrestrial Ecosystem Model (v.2.1) (CLASS-CTEM)

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    The Canadian Land Surface Scheme and Canadian Terrestrial Ecosystem Model (CLASS-CTEM) together form the land surface component of the Canadian Earth System Model (CanESM). Here, we investigate the impact of changes to CLASS-CTEM that are designed to improve the simulation of permafrost physics. Overall, 18 tests were performed, including changing the model configuration (number and depth of ground layers, different soil permeable depth datasets, adding a surface moss layer), and investigating alternative parameterizations of soil hydrology, soil thermal conductivity, and snow properties. To evaluate these changes, CLASS-CTEM outputs were compared to 1570 active layer thickness (ALT) measurements from 97 observation sites that are part of the Global Terrestrial Network fo

    Uniqueness of the compactly supported weak solutions of the relativistic Vlasov-Darwin system

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    We use optimal transportation techniques to show uniqueness of the compactly supported weak solutions of the relativistic Vlasov-Darwin system. Our proof extends the method used by Loeper in J. Math. Pures Appl. 86, 68-79 (2006) to obtain uniqueness results for the Vlasov-Poisson system.Comment: AMS-LaTeX, 21 page

    Screening current effects in Josephson junction arrays

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    The purpose of this work is to compare the dynamics of arrays of Josephson junctions in presence of magnetic field in two different frameworks: the so called XY frustrated model with no self inductance and an approach that takes into account the screening currents (considering self inductances only). We show that while for a range of parameters the simpler model is sufficiently accurate, in a region of the parameter space solutions arise that are not contained in the XY model equations.Comment: Figures available from the author

    Lattice density-functional theory of surface melting: the effect of a square-gradient correction

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    I use the method of classical density-functional theory in the weighted-density approximation of Tarazona to investigate the phase diagram and the interface structure of a two-dimensional lattice-gas model with three phases -- vapour, liquid, and triangular solid. While a straightforward mean-field treatment of the interparticle attraction is unable to give a stable liquid phase, the correct phase diagram is obtained when including a suitably chosen square-gradient term in the system grand potential. Taken this theory for granted, I further examine the structure of the solid-vapour interface as the triple point is approached from low temperature. Surprisingly, a novel phase (rather than the liquid) is found to grow at the interface, exhibiting an unusually long modulation along the interface normal. The conventional surface-melting behaviour is recovered only by artificially restricting the symmetries being available to the density field.Comment: 16 pages, 6 figure

    Superconducting states and depinning transitions of Josephson ladders

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    We present analytical and numerical studies of pinned superconducting states of open-ended Josephson ladder arrays, neglecting inductances but taking edge effects into account. Treating the edge effects perturbatively, we find analytical approximations for three of these superconducting states -- the no-vortex, fully-frustrated and single-vortex states -- as functions of the dc bias current II and the frustration ff. Bifurcation theory is used to derive formulas for the depinning currents and critical frustrations at which the superconducting states disappear or lose dynamical stability as II and ff are varied. These results are combined to yield a zero-temperature stability diagram of the system with respect to II and ff. To highlight the effects of the edges, we compare this dynamical stability diagram to the thermodynamic phase diagram for the infinite system where edges have been neglected. We briefly indicate how to extend our methods to include self-inductances.Comment: RevTeX, 22 pages, 17 figures included; Errata added, 1 page, 1 corrected figur

    Molecular characterization of Cryptococcus neoformans recovered from pigeon droppings in Rivera and Neiva, Colombia

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    Objective. Characterize phenotypically and genotypically isolates of Cryptococcus neoformans and Cryptococcus gattii that can be found in feces of pigeons (Columba livia) and in soil, leaves and detritus of almond trees (Terminalia catappa) in the municipalities of Neiva and Rivera, Colombia. Materials and methods. One hundred and eighteen samples were collected in 13 specific areas, characterized by the presence of almond trees and high density of birds, between January and June 2016. Incubation of the processed samples was done at 27°C for two weeks using Guizottia abyssinica agar. The phenotypic characterization, the species determination and the subsequent molecular typing was done using PCR fingerprinting with (GTG)5 primer and Restriction Fragment Length Polymorphism with URA5 and SJ01 primers. Results. A 5,9% of the samples from pigeon feces were positive for C neoformans var. grubii (VNI molecular pattern). Samples collected from almond tree detritus were not positive for any of the species studied. Conclusions. The isolation of C. neoformans from pigeon droppings in the municipalities of Rivera and Neiva adds to the scarce knowledge about this pathogen in the department of Huila, revealing the importance of continuing with these type of studies, not only in the environment but in the exposed population

    Row-switched states in two-dimensional underdamped Josephson junction arrays

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    When magnetic flux moves across layered or granular superconductor structures, the passage of vortices can take place along channels which develop finite voltage, while the rest of the material remains in the zero-voltage state. We present analytical studies of an example of such mixed dynamics: the row-switched (RS) states in underdamped two-dimensional Josephson arrays, driven by a uniform DC current under external magnetic field but neglecting self-fields. The governing equations are cast into a compact differential-algebraic system which describes the dynamics of an assembly of Josephson oscillators coupled through the mesh current. We carry out a formal perturbation expansion, and obtain the DC and AC spatial distributions of the junction phases and induced circulating currents. We also estimate the interval of the driving current in which a given RS state is stable. All these analytical predictions compare well with our numerics. We then combine these results to deduce the parameter region (in the damping coefficient versus magnetic field plane) where RS states can exist.Comment: latex, 48 pages, 15 figs using psfi

    Therapy and prophylaxis of opportunistic infections in HIV-infected patients: a guideline by the German and Austrian AIDS societies (DAIG/Ă–AG) (AWMF 055/066)

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    Del tratamiento realizado en la ClĂ­nica Integral

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