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  • Articles: DFG German National Licenses  (18)
  • 1985-1989  (11)
  • 1980-1984  (7)
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  • Articles: DFG German National Licenses  (18)
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Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 879-881 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Within the framework of the sine-Gordon model of a long Josephson junction, we have calculated a threshold value of bias current density which admits capture of a fluxon by an effective potential well generated by a step of inductance in the junction. Along with a kinematic approximation, a nontrivial dynamical correction is found. We have also calculated analytically energy emitted by a fast fluxon moving past the step.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 986-991 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper: (1) provides the Hamiltonian formulation of the hyperbolic system of two-phase flow equations for separated flows including surface tension; (2) shows that equilibrium solutions of this system are critical states of a certain sum of conserved functionals; and (3) determines sufficient conditions for Lyapunov stability of the equilibrium solutions in two dimensions. The method used to establish the Lyapunov stability conditions incorporates recent advances in the Hamiltonian theory of continuum systems.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 49-68 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Lyapunov stability of relativistic ideal fluid and plasma equilibria is studied analytically using the energy-Casimir method. Two- and three-dimensional relativistic equilibria in a fixed bounded domain are investigated within the framework of the macroscopic multifluid plasma model. Linearized Lyapunov stability conditions and stability norms are given, accounting for warm-plasma effects as well as relativistic and electromagnetic effects. The resulting Lyapunov stability conditions are compared to spectral stability analyses for relativistic cold plasmas in various examples and special cases, including (1) non-neutral electron flow in a planar diode and (2) circularly symmetric plasma flow enclosed in a coaxial waveguide. These linearized stability results can be extended readily to nonlinear Lyapunov stability conditions for finite-amplitude perturbations by employing standard convexity arguments for the Lyapunov functions given here. The relativistic stability conditions are shown to reduce either to their nonrelativistic counterparts or to trivial identities in the nonrelativistic limit.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 3889-3891 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This Brief Communication introduces a special relativistic extension of ideal magnetohydrodynamics having anisotropic pressure, and provides its Hamiltonian formulation in a fixed inertial frame. The nonrelativistic limit of this theory recovers the "double adiabatic'' hydromagnetic equations of Chew, Goldberger, and Low [Proc. R. Soc. London Ser. A 236, 112 (1956)]. For isotropic pressure distribution the equations and Hamiltonian structure reduce to the usual theory of relativistic magnetohydrodynamics. The Poisson bracket for the system is not symplectic. Rather, it is dual to a Lie algebra of semidirect-product type.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 29 (1988), S. 21-30 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: A dictionary of correspondence is established between the dynamical variables for spin-glass fluid and Yang-Mills plasma. The Lie-algebraic interpretation of these variables is presented for the two theories. The noncanonical Poisson bracket for the Hamiltonian dynamics of an ideal spin glass is shown to be identical to that for the dynamics of a Yang–Mills fluid plasma, although the Hamiltonians differ for the two theories. This Poisson bracket is associated to the dual space of an infinite-dimensional Lie algebra of semidirect-product type.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Letters in mathematical physics 15 (1988), S. 281-287 
    ISSN: 1573-0530
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract The hydrodynamical approximation to an infinite system of one-dimensional identical hard rods interacting through elastic collisions, is shown to be an integrable system possessing a one-parameter family of nonlinear Hamiltonian structures.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Archives of dermatological research 280 (1988), S. 246-251 
    ISSN: 1432-069X
    Keywords: Retinoids ; Sebum ; Arotinoid ; Hypervitaminosis A
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Retinoids are known to modulate sebaceous gland activity in humans and animals. The nonpolar arotinoid Ro 15-0778 [(E)-1,2,3,4-tetrahydro-1,1,4,4-tetramethyl-6-(1-methyl-2-phenylethenyl) naphthalene] does not contain a polar end group and is devoid of the classical retinoid side effects of hypervitaminosis A. The favorable toxicological profile stimulated the evaluation of this arotinoid in animal models of sebum production. In castrated, testosterone-stimulated male rats, Ro 15-0778 is 50 times more potent than 13-cis-retinoic acid in inhibiting the production and subsequent secretion of sebum. The oral ED50 value of Ro 15-0778 is 30μg/kg, while an oral dose of 0.5 mg/kg inhibited sebum secretion nearly 1005. In testosterone-stimulated female rats, Ro 15-0778 inhibits sebum secretion significantly with an oral ED50 of 140 μg/kg and an s.c. ED50 of 75μg/kg. Ro 15-0778 was also evaluated for its ability to prevent testosterone induction of the immature hamster flank organ. The topical ED50 is 0.53 mg/kg and the oral ED50 is 38 mg/kg. This arotinoid is similarly active in mature male hamsters without testosterone treatment. In addition, the retinoid is active topically and orally in reducing the size of the gerbil abdominal sebaceous gland. The compound exhibits no antiandrogenic activity when tested in ventral prostrate and seminal vesicle assays in rats. Additionally, the compound does not have estrogenic activity when tested in the rat uterine weight assay. High doses of Ro 15-0778 in humans did not demonstrate significant sebumsuppressing activity. This study indicates that extra-polation of retinoid data from rodent animal models to activity in human sebaceous glands can not be made with a high degree of certainty. There is a need to develop new, more predictive models for retinoid activity.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Communications in mathematical physics 90 (1983), S. 235-250 
    ISSN: 1432-0916
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract It is shown that two canonical maps arising in the Poisson bracket formulations of elasticity and superfluids are particular instances of general canonical maps between duals of semidirect product Lie algebras.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Ocean dynamics 34 (1981), S. 273-283 
    ISSN: 1616-7228
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Description / Table of Contents: Zusammenfassung Es werden zwei Methoden der Parametrisierung von Schelfeffekten vorgeschlagen: eine vom lokalen Typ, die andere vom integralen. Die Versuchsergebnisse dieser Typen werden am Beispiel der Gezeitenberechnung nach den Ozeanmodellen von Webb [1976] und von von Trepka [1967] vorgelegt. Es ist gezeigt, daß die hier vorgeschlagenen Parametrisierungsmethoden von Schelfeffekten eine vollkommen ausreichende Genauigkeit bei der Wiedergabe der halbtägigen Gezeiten im freien Ozean bieten, jedoch in einigen Fällen wird die Dissipation der Gezeitenenergie am Schelf unterschätzt. Dieses wird durch den vernachlässigten Einfluß der Randwellen mit einem Längsmaßstab von der Größenordnung der Schelfbreite hervorgerufen.
    Abstract: Résumé On propose deux méthodes de paramétrisation du plateau: l'une de type local, l'autre de type intégral. Cet article décrit les résultats des essais de ces deux méthodes dans un calcul de marées à l'aide des modèles d'océan de Webb [1976] et de von Trepka [1967]. Les méthodes de paramétrisation des effets du plateau proposées ici fournissent une précision de simulation tout à fait suffisante pour la marée semi-diurne océanique, mais, dans certains cas, elles sous-estiment la dissipation d'énergie sur le plateau. Ceci est dû au fait qu'elles négligent l'influence des ondes de bord dont la longueur d'onde est de l'ordre de la largeur du plateau.
    Notes: Summary Two methods of shelf parameterization are proposed: one of the local and the other of the integral type. The paper gives the results of testing these methods using a calculation of tides according to Webb's [1976] and von Trepka's [1967] model oceans as an example. The proposed methods of shelf effect parameterization provide a quite acceptable accuracy of simulation of semi-diurnal tides in the open ocean, but in some cases they underestimate the tidal energy dissipation on the shelf. The latter circumstance is caused by the ignored effect of edge waves with a longitudinal scale of the order of the shelf width.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1616-7228
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Description / Table of Contents: Zusammenfassung Numerische Lösungen für ein Gezeitenmodell des Weltozeans unter Berücksichtigung von Schelfeffekten werden beschrieben. Die Ergebnisse der numerischen Experimente zeigen, daß die räumliche Struktur und die Energetik der globalen halbtägigen Gezeiten höchst empfindlich auf die Wahl der Parametrisierungsmethode der Schelfeffekte und auf deren Parameter reagieren. Dieser Umstand kann als indirekte Bestätigung des Resonanzcharakters der halbtägigen Gezeiten im Weltozean dienen.
    Abstract: Résumé On décrit une solution numérique au problème de la marée dans l'Océan Mondial en tenant compte des effets du plateau. Les résultats des essais numériques montrent que la structure spatiale et le bilan d'énergie de la marée semi-diurne globale sont très sensibles au choix de méthode de paramétrisation des effets du plateau et aux variations des paramètres du plateau. Ce fait peut être considéré comme une preuve indirecte de la résonance de la marée semi-diurne dans l'Océan Mondial.
    Notes: Summary A numerical solution to the problem of tides in the World Ocean taking into account the shelf effects is described. Results of the numerical experiments show that the spatial structure and energetics of global semi-diurnal tides are quite sensitive to the choice of the shelf effect parameterization and to the variations in shelf parameters. This fact can be regarded as indirect evidence of the resonant nature of semi-diurnal tides in the World Ocean.
    Type of Medium: Electronic Resource
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