6,453 research outputs found
A gyrokinetic model for the plasma periphery of tokamak devices
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
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
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
The confined-deconfined interface tension, wetting, and the spectrum of the transfer matrix
The reduced tension of the interface between the confined and
the deconfined phase of pure gauge theory is determined from numerical
simulations of the first transfer matrix eigenvalues. At we find
for . 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 -symmetric 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
Analysis and correction of the magnetic field effects in the Hybrid Photo-Detectors of the RICH2 Ring Imaging Cherenkov detector of LHCb
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
Full-F Turbulent Simulation in a Linear Device using a Gyro-Moment Approach
Simulations of plasma turbulence in a linear plasma device configuration are
presented. These simulations are based on a simplified version of the
gyrokinetic (GK) model proposed by B. J. Frei et al. [J. Plasma Phys. 86,
905860205 (2020)] where the full-F distribution function is expanded on a
velocity-space polynomial basis allowing us to reduce its evolution to the
solution of an arbitrary number of fluid-like equations for the expansion
coefficients, denoted as the gyro-moments (GM). By focusing on the
electrostatic and neglecting finite Larmor radius effects, a full-F GM
hierarchy equation is derived to evolve the ion dynamics, which includes a
nonlinear Dougherty collision operator, localized sources, and Bohm sheath
boundary conditions. An electron fluid Braginskii model is used to evolve the
electron dynamics, coupled to the full-F ion GM hierarchy equation via a
vorticity equation where the Boussinesq approximation is used. A set of full-F
turbulent simulations are then performed using the parameters of the LArge
Plasma Device (LAPD) experiments with different numbers of ion GMs and
different values of collisionality. The ion distribution function is analyzed
illustrating the convergence properties of the GM approach. In particular, we
show that higher-order GMs are damped by collisions in the high-collisional
regime relevant to LAPD experiments. The GM results are then compared with
those from two-fluid Braginskii simulations, finding qualitative agreement in
the time-averaged profiles and statistical turbulent properties
Management der oberen Atemwege beim spontan atmenden Kind: Eine Herausforderung für den Anästhesisten
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
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
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