6,253 research outputs found

    A gyrokinetic model for the plasma periphery of tokamak devices

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    A gyrokinetic model is presented that can properly describe strong flows, large and small amplitude electromagnetic fluctuations occurring on scale lengths ranging from the electron Larmor radius to the equilibrium perpendicular pressure gradient scale length, and large deviations from thermal equilibrium. The formulation of the gyrokinetic model is based on a second order description of the single charged particle dynamics, derived from Lie perturbation theory, where the fast particle gyromotion is decoupled from the slow drifts, assuming that the ratio of the ion sound Larmor radius to the perpendicular equilibrium pressure scale length is small. The collective behavior of the plasma is obtained by a gyrokinetic Boltzmann equation that describes the evolution of the gyroaveraged distribution function and includes a non-linear gyrokinetic Dougherty collision operator. The gyrokinetic model is then developed into a set of coupled fluid equations referred to as the gyrokinetic moment hierarchy. To obtain this hierarchy, the gyroaveraged distribution function is expanded onto a velocity-space Hermite-Laguerre polynomial basis and the gyrokinetic equation is projected onto the same basis, obtaining the spatial and temporal evolution of the Hermite-Laguerre expansion coefficients. The Hermite-Laguerre projection is performed accurately at arbitrary perpendicular wavenumber values. Finally, the self-consistent evolution of the electromagnetic fields is described by a set of gyrokinetic Maxwell's equations derived from a variational principle, with the velocity integrals of the gyroaveraged distribution function explicitly evaluated

    Non-unique factorization of polynomials over residue class rings of the integers

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    We investigate non-unique factorization of polynomials in Z_{p^n}[x] into irreducibles. As a Noetherian ring whose zero-divisors are contained in the Jacobson radical, Z_{p^n}[x] is atomic. We reduce the question of factoring arbitrary non-zero polynomials into irreducibles to the problem of factoring monic polynomials into monic irreducibles. The multiplicative monoid of monic polynomials of Z_{p^n}[x] is a direct sum of monoids corresponding to irreducible polynomials in Z_p[x], and we show that each of these monoids has infinite elasticity. Moreover, for every positive integer m, there exists in each of these monoids a product of 2 irreducibles that can also be represented as a product of m irreducibles.Comment: 11 page

    Zapotec and Mixe use of Tropical Habitats for securing medicinal plants in MéXico

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    Medicinal plants are essential in the medical systems of the Mixe and Zapotec. In this study ethno-ecological strategies, employed by the two neighboring Indian groups in Mexico, for obtaining medicinal plants are analyzed. The indigenous classification of the environment is notably different from the Western one and distinguishes six dissimilar principal "zones” or land use types. Most ethnomedically important species are cultivated in the "house garden” or gathered in the community or its immediate surroundings. The house garden, for example, contributes 31.8% and 26.2% of all medical taxa for the Mixe and Zapotec, respectively. These ethnobotanical data on the indigenous uses indicate that anthropogenic types of vegetation yield the largest percentage of medicinal tax

    Analysis and correction of the magnetic field effects in the Hybrid Photo-Detectors of the RICH2 Ring Imaging Cherenkov detector of LHCb

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    The Ring Imaging Cherenkov detectors of the LHCb experiment at the Large Hadron Collider at CERN are equipped with Hybrid Photo-Detectors. These vacuum photo-detectors are affected by the stray magnetic field of the LHCb magnet, which degrades their imaging properties. This effect increases the error on the Cherenkov angle measurement and would reduce the particle identification capabilities of LHCb. A system has been developed for the RICH2 Ring Imaging Cherenkov detector to perform a detailed characterisation of the magnetic distortion effects. It is described, along with the methods implemented to correct for these effects, restoring the optimal resolution.Comment: 16 pages, 11 figure

    The confined-deconfined interface tension, wetting, and the spectrum of the transfer matrix

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    The reduced tension σcd\sigma_{cd} of the interface between the confined and the deconfined phase of SU(3)SU(3) pure gauge theory is determined from numerical simulations of the first transfer matrix eigenvalues. At Tc=1/LtT_c = 1/L_t we find σcd=0.139(4)Tc2\sigma_{cd} = 0.139(4) T_c^2 for Lt=2L_t = 2. The interfaces show universal behavior because the deconfined-deconfined interfaces are completely wet by the confined phase. The critical exponents of complete wetting follow from the analytic interface solutions of a Z(3)\Z(3)-symmetric Φ4\Phi^4 model in three dimensions. We find numerical evidence that the confined-deconfined interface is rough.Comment: Talk presented at the International Conference on Lattice Field Theory, Lattice 92, to be published in the proceedings, 4 pages, 4 figures, figures 2,3,4 appended as postscript files, figure 1 not available as a postscript file but identical with figure 2 of Nucl. Phys. B372 (1992) 703, special style file espcrc2.sty required (available from hep-lat), BUTP-92/4

    Management der oberen Atemwege beim spontan atmenden Kind: Eine Herausforderung für den Anästhesisten

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    Zusammenfassung: Partielle und totale Atemwegsobstruktionen treten bei spontan atmenden, bewusstlosen oder anästhesierten Kindern häufig auf und können eine adäquate Sauerstoffversorgung gefährden. Das Offenhalten der oberen Atemwege ist daher die wichtigste und effektivste Maßnahme in dieser Situation: Kinn hochheben ("chin lift"), Unterkiefer nach vorne verschieben ("jaw thrust", Esmarch-Handgriff) und kontinuierlich positiver Atemwegsdruck ("continuous positive airway pressure", CPAP) öffnen nachgewiesenermaßen den Atemweg. Neben diesen einfachen Atemwegsmanövern führen auch verschiedene Lagerungstechniken (Seitenlage oder Rückenlage unter Einnahme der "Schnüffelposition") zu einer besseren Öffnung und Stabilität des oberen Atemweg

    Improved serodiagnosis of alveolar echinococcosis of humans using an in vitro-produced Echinococcus multilocularis antigen

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    Serology is an important tool for the diagnosis of alveolar echinococcosis (AE) in humans. In order to improve serodiagnostic performance, we have developed an in vitro-produced Echinococcus mulilocularis metacestode vesicle fluid (EmVF) antigen for application in an immunoblot assay. Immunoblot analysis of EmVF revealed an abundant immunoreactive band triplet of 20-22kDa, achieving a sensitivity of 100% based on the testing of sera from 62 pre-operative and pre-treatment cases of active and inactive AE. Thus, the EmVF-immunoblotting allowed the specific detection of cases seronegative by the Em2- and/or EmII/3-10-ELISA, usually attributable to abortive, inactive cases of AE. The specificity of the EmVF-immunoblotting did not allow discrimination between AE and cystic echinococcosis (CE) but was 100% with respect to non-Echinococcus parasitic infections or cancer malignancies. Based on the findings of this study, it is recommended that the current ELISA test combination (Em2- and II/3-10-ELISA) be complemented with EmVF-immunoblotting, allowing an improved diagnosis of both clinical and subclinical forms of AE, including those associated with E. multilocularis-specific antibody reactivities not detectable by ELIS

    Accuracy of Estimating Highly Eccentric Binary Black Hole Parameters with Gravitational-wave Detections

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    Mergers of stellar-mass black holes on highly eccentric orbits are among the targets for ground-based gravitational-wave detectors, including LIGO, VIRGO, and KAGRA. These sources may commonly form through gravitational-wave emission in high-velocity dispersion systems or through the secular Kozai-Lidov mechanism in triple systems. Gravitational waves carry information about the binaries' orbital parameters and source location. Using the Fisher matrix technique, we determine the measurement accuracy with which the LIGO-VIRGO-KAGRA network could measure the source parameters of eccentric binaries using a matched filtering search of the repeated burst and eccentric inspiral phases of the waveform. We account for general relativistic precession and the evolution of the orbital eccentricity and frequency during the inspiral. We find that the signal-to-noise ratio and the parameter measurement accuracy may be significantly higher for eccentric sources than for circular sources. This increase is sensitive to the initial pericenter distance, the initial eccentricity, and the component masses. For instance, compared to a 30 M-circle dot-30 M-circle dot non-spinning circular binary, the chirp mass and sky-localization accuracy can improve by a factor of similar to 129 (38) and similar to 2 (11) for an initially highly eccentric binary assuming an initial pericenter distance of 20M(tot) (10M(tot))
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