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Peter Jones' theorem on the factorization of Ap weights is sharpened for weights with bounds near 1, allowing the factorization to be performed continuously near the limiting, unweighted case. When 1 < p < infinite and omega is an Ap weight with bound Ap(omega) = 1 + epsilon, it is shown that there exist Asub1 weights u, v such that both the formula omega = uv(1-p) and the estimates A1 (u), A1 (v) = 1 + Omikron (√epsilon) hold. The square root in these estimates is also proven to be the correct asymptotic power as epsilon -> 0.
The quantization of contact transformations of the cosphere bundle over a manifold with conical singularities is described. The index of Fredholm operators given by this quantization is calculated. The answer is given in terms of the Epstein-Melrose contact degree and the conormal symbol of the corresponding operator.
In the paper we study the possibility to represent the index formula for spectral boundary value problems as a sum of two terms, the first one being homotopy invariant of the principal symbol, while the second depends on the conormal symbol of the problem only. The answer is given in analytical, as well as in topological terms.
The paper deals with a non-linear singular partial differential equation: (E) t∂/∂t = F(t, x, u, ∂u/∂x) in the holomorphic category. When (E) is of Fuchsian type, the existence of the unique holomorphic solution was established by Gérard-Tahara [2]. In this paper, under the assumption that (E) is of totally characteristic type, the authors give a sufficient condition for (E) to have a unique holomorphic solution. The result is extended to higher order case.
The paper is devoted to pseudodifferential boundary value problems in domains with cuspidal wedges. Concerning the geometry we even admit a more general behaviour, namely oscillating cuspidal wedges. We show a criterion for the Fredholm property of a boundary value problem and derive estimates of solutions close to edges.
Inhalt: Leitartikel Kongreß für Jüdische Studien - Sektion beim Deutschen Orientalistentag / Selbstkritik, Selbstverpflichtung oder Selbstzweck? / 16. DGfE-Kongreß, Der osteuropäische Chassidismus - neuere Forschungen / Schließung der Israelwissenschaft in der Humboldt-Universität / Einführung in das Fach Jüdische Studien / Notizen / Aus der jüdischen Welt / Veröffentlichungen unserer Mitglieder / Verbandsnachrichten
The nonlinear interaction of waves excited by the modified two-stream instability (Farley-Buneman instability) is considered. It is found that, during the linear stage of wave growth, the enhanced pressure of the high-frequency part of the waves locally generates a ponderomotive force. This force acts on the plasma particles and redistributes them. Thus an additional electrostatic polarization field occurs, which influences the low-frequency part of the waves. Then, the low-frequency waves also cause a redistribution of the high-frequency waves. In the paper, a self-consistent system of equations is obtained, which describes the nonlinear interaction of the waves. It is shown that the considered mechanism of wave interaction causes a nonlinear stabilization of the high-frequency waves’ growth and a formation of local density structures of the charged particles. The density modifications of the charged particles during the non-linear stage of wave growth and the possible interval of aspect angles of the high-frequency waves are estimated.
We have numerically studied the bifurcations and transition to chaos in a two-dimensional fluid for varying values of the Reynolds number. These investigations have been motivated by experiments in fluids, where an array of vortices was driven by an electromotive force. In these experiments, successive changes leading to a complex motion of the vortices, due to increased forcing, have been explored [Tabeling, Perrin, and Fauve, J. Fluid Mech. 213, 511 (1990)]. We model this experiment by means of two-dimensional Navier-Stokes equations with a special external forcing, driving a linear chain of eight counter-rotating vortices, imposing stress-free boundary conditions in the vertical direction and periodic boundary conditions in the horizontal direction. As the strength of the forcing or the Reynolds number is raised, the original stationary vortex array becomes unstable and a complex sequence of bifurcations is observed. Several steady states and periodic branches and a period doubling cascade appear on the route to chaos. For increasing values of the Reynolds number, shear flow develops, for which the spatial scale is large compared to the scale of the forcing. Furthermore, we have investigated the influence of the aspect ratio of the container as well as the effect of no-slip boundary conditions at the top and bottom, on the bifurcation scenario.
This paper deals with the electrical conductivity problem in geophysics. It is formulated as an elliptic boundary value problem of second order for a large class of bounded and unbounded domains. A special boundary condition, the so called "Complete Electrode Model", is used. Poincaré inequalities are formulated and proved in the context of weighted Sobolev spaces, leading to existence and uniqueness statements for the boundary value problem. In addition, a parameter-to-solution operator arising from the inverse conductivity problem in medicine (EIT) and geophysics is investigated mathematically and is shown to be smooth and analytic.
The determination of the atmospheric aerosol size distribution is an inverse illposed problem. The shape and the material composition of the air-carried particles are two substantial model parameters. Present evaluation algorithms only used an approximation with spherical homogeneous particles. In this paper we propose a new numerically efficient recursive algorithm for inhomogeneous multilayered coated and absorbing particles. Numerical results of real existing particles show that the influence of the two parameters on the model is very important and therefore cannot be ignored.
Contents: 1 Introduction 2 Formation and destruction of sporadic E-layers 3 Temporal variations of parameters of sporadic E-layers during earthquake preparation 3.1 Temporal variations of fbEs with time-scales of a few hours 3.2 Study of fbEs variations with characteristic time-scales of 0.5-3 hours 3.3 Variations of the parameters of sporadic E-layers with characteristic time-scales of 15-45 minutes 3.4 Sporadic E-layer variations with characteristic time-scales of 2-15 minutes 4 On the spatial scales of sporadic E-layer disturbances related to seismic activity 5 Complex experimental researches of the ionosphere, electromagnetic noise and the geomagnetic field 5.1 Ionospheric and electromagnetic phenomena of the Kayraccum earthquake in 1985 5.2 Comparison of anomalies with characteristic time-scales of 2-3 hours for ionospheric E- and F-layers, and temporal behaviour of electromagnetic noise emission intensity 5.3 Night airglow emissions in the E-region before earthquakes and sporadic E-layer variations 6 Physical models of lithosphere-ionosphere links 6.1 Lithosphere-ionosphere links due to AGW 6.2 Electromagnetic models for the lithosphere-ionosphere coupling 6.3 Sporadic E-layers as current generators 7 Discussion and conclusion
In single photon emission computed tomography (SPECT) one is interested in reconstructing the activity distribution f of some radiopharmaceutical. The data gathered suffer from attenuation due to the tissue density µ. Each imaged slice incorporates noisy sample values of the nonlinear attenuated Radon transform (formular at this place in the original abstract) Traditional theory for SPECT reconstruction treats µ as a known parameter. In practical applications, however, µ is not known, but either crudely estimated, determined in costly additional measurements or plainly neglected. We demonstrate that an approximation of both f and µ from SPECT data alone is feasible, leading to quantitatively more accurate SPECT images. The result is based on nonlinear Tikhonov regularization techniques for parameter estimation problems in differential equations combined with Gauss-Newton-CG minimization.
The aim of this paper is to describe an efficient strategy for descritizing ill-posed linear operator equations of the first kind: we consider Tikhonov-Phillips-regularization χ^δ α = (a * a + α I)^-1 A * y ^δ with a finite dimensional approximation A n instead of A. We propose a sparse matrix structure which still leads to optimal convergences rates but requires substantially less scalar products for computing A n compared with standard methods.
Inhalt: Wolfgang Thiem Lehrerbildung in Ländern gesellschaftlicher Transformation auf dem Prüfstand vergleichender Betrachtung : Resümee einer Tagung Wladimir I. Andreev Zum Problem der pädagogischen Ausbildung von Lehrern in der Republik Belarus : Konzeptionen und Realität Wassili A. Bondar; Adam A. Grimot Tendenzen der Entwicklung pädagogischer Bildung in der Republik Belarus Maria Jakowicka; Kazimierz Uzdzicki Standards der Ausbildung von Fachlehrern in Polen Zenon Jasinski Berufskompetenzen der Lehrer Maria Molnar Reform der Lehrerbildung in der Folge der politischen und gesellschaftlichen Transformationen in Ungarn Magdalena Piorunek Qualitative Aspekte der Änderungen in der Lehrerbildung in Polen Ludmilla Regusch Thesen zur psychologischen Ausbildung des Lohrers an der Pädagogischen Universität A. I. Herzen in St. Petersburg (Rußland) Lech Salacinski Stereotype bei der pädagogischen Ausbildung von Lehrern in Polen : Versuche zu ihrer Überwindung Eleonora Sapia-Drewniak Der Lehrer im Antlitz gesellschaftlicher Veränderungen in Polen Andreas Seidel Zum Stellenwert praktischer Ausbildung Wolfgang Thiem Aktuelle Materialien und Diskussionen zur Weiterentwicklung der Lehrerbildung in Deutschland Frank Tosch: Lehrerbildung in Potsdam Ein Modell auf dem Prüfstand zwischen Hoffen und Realität Krystina Zielinska Strukturelle und bildungspolitische Aspekte der Lehrerbildung in Polen
Antike Epik : zur Geschichte narrativer metrischer Großtexte in oralen und semioralen Gesellschaften
(1998)
Inhalt: 0 Einführung 0.1 Literatur 0.2 Epos 0.3 Gattung 0.4 Aufgabe der Vorlesung 1 Anfänge griechischer Epik 1.1 Homer 1.2 Das Problem 1.3 Der Text 1.4 Medienwechsel 1.4.1 Oralpoetry 1.4.2 Schriftlichkeit 1.4.3 Leistungen der Verschriftlichung 1.5 Das Publikum 1.6 Die ersten Epen 1.7 Ilias 1.7.1 Inhalt 1.7.2 Struktur 1.7.3 Charakteristika 1.7.4 Troia und die Quellenfrage 1.8 Odyssee 1.8.1 Inhalt 1.8.2 Struktur 1.9 Wirkungsgeschichte 2 Anfänge römischer Epik 2.0 Griechische Einflüsse in der vorliterarischen Epoche 2.1 Der Befund 2.2 Das Problem 2.3 Methodisches Vorgehen 2.4 Inventar und Verortung mündlicher Literatur 2.5 Ergänzungen zum Sitz im Leben 2.6 Kristallisationskerne des Verschriftlichungsprozesses 2.7 Epos 2.8 Veränderungen im Gesamtsystem literarischer Kommunikation 2.9 Die Leistung des verschriftlichten Epos 3 Entwicklungen des zweiten und ersten Jahrhunderts v. Chr 3.1 Ennius 3.1.1 Zu Person und Werk 3.1.2 Die Annales 3.1.3 Kontext 3.2 Die weitere römische Entwicklung 3.3 Hellenistische griechische Epik 3.4 Rom 4 Vergils Aeneis 4.1 Biographie 4.2 Grundentscheidungen 4.3 Inhalt 4.4 Rezeption 4.4.1 Vergil und die europäische Literaturgeschichte 4.4.2 Zeitgenössische Rezeption 4.5 Leistung 4.5.1 Hauptperson der Aeneis ist Vergil 4.5.2 Gegenstand der Aeneis ist das zeitgenössische Rom 4.5.3 Kein Götter-, sondern ein Menschenapparat in der Aeneis 4.5.4 Die Aeneis nicht Helden-, sondern Proletarierepos 5 Das antike Lehrgedicht: Lukrez 5.1 Expositorische Dichtung 5.2 Der Epikureer Lukrez 5.3 Werkübersicht 5.4 Aussage 6 Ovid 6.1 Einführung: Ovidrezeption 6.2 Zur Person 6.3 Metamorphosen: Ein erster Zugang 6.4 Augusteische Epik 6.5 Die Metamorphosen als Epos-Parodie 6.5.1 Metamorphosen 6.5.2 Großepos 6.5.3 Systematisierung 6.5.4 Handlungsführung 6.5.5 Ovid und seine Vorgänger 6.5.6 Erzählen im Epos 6.5.7 Einzelmotive 6.5.8 Gelebte Parodie 7 Historische Epik der Prinzipatszeit 7.1 Allgemeines 7.2 Lukan 7.3 Die Pharsalia 7.3.1 Titel und Quellen 7.3.2 Inhalt 7.3.3 Gehalt 7.4 Silius Italicus 7.5 Ausblick 8 Mythologische Epik 8.1 Einführung 8.2 Valerius Flaccus 8.3 Statius 8.3.1 Zur Person 8.3.2 Thebais: Inhalt 8.3.3 Komposition 8.3.4 Einheitlichkeit 8.4 Manierismus 9 Die spätantike Epik 9.1 Überblick 9.1.1 Historischer Überblick 9.1.2 Der literaturgeschichtliche Einschnitt 9.1.3 Präzisierung 1: Christentum 9.1.4 Präzisierung 2: Ausnahmen 9.1.5 Präzisierung 3: Griechische Epik 9.1.6 Entwicklungsstränge 9.2 Panegyrisch-historische Dichtung 9.2.1 Allgemeines 9.2.2 Claudius Claudianus 9.3 Christliche Dichtung 9.3.1 Anfangsphase 9.3.2 Hauptphase 10 Epilog
Der dritte Band der Potsdamer Textbücher befasst sich mit gesellschaftlichen Entwicklungen im konfliktreichen Nahen Osten. Die Zusammenstellung der Texte erfolgte sowohl mit Blick auf die anhaltende Kulturkreisdiskussion als auch hinsichtlich der Bemühungen um Stabilität in dieser Region. Hinzu kommen Analysen zur wirtschaftlichen Entwicklung und den politischen Regimes in Israel, Palästina, Ägypten, im Jemen und Iran. Auszüge aus Verfassungen arabischer Staaten, statistische Angaben und eine Bibliographie vervollständigen das Textbuch.
Die Anwendung von optischen Parametern zur Stoffcharakterisierung wird diskutiert. Dabei ist der Schwerpunkt der Diskussion auf absorptions- und fluoreszenzspektroskopische Methoden gesetzt. Beide Methoden können schnell und zuverlässig – auch im on-line Betrieb – eingesetzt werden. Der Beitrag soll einen Überblick über die grundlegenden Möglichkeiten der Anwendung beider Methoden geben.