Analytical Study of Light Propagation in Highly Nonlinear Media

The present dissertation is devoted to the construction of exact and approximate analytical solutions of the problem of light propagation in highly nonlinear media. It is demonstrated that for many experimental conditions, the problem can be studied under the geometrical optics approximation with a sufficient accuracy. Based on the renormalization group symmetry analysis, exact analytical solutions of the eikonal equations with a higher order refractive index are constructed. A new analytical approach to the construction of approximate solutions is suggested. Based on it, approximate solutions for various boundary conditions, nonlinear refractive indices and dimensions are constructed. Exact analytical expressions for the nonlinear self-focusing positions are deduced. On the basis of the obtained solutions a general rule for the single filament intensity is derived; it is demonstrated that the scaling law (the functional dependence of the self-focusing position on the peak beam intensity) is defined by a form of the nonlinear refractive index but not the beam shape at the boundary. Comparisons of the obtained solutions with results of experiments and numerical simulations are discussed.

The Media is the Message?!

Diese Arbeit beschäftigt sich mit der grafischen Gestaltung von Mathematiklehrwerken und der damit verbundenen Wirkungen auf die SchülerInnen. Es wurde untersucht, welche Art von Gestaltungsaspekten in Schulbüchern eine positive Auswirkung auf die Lernmotivation hat. Im theoretischen Teil dieser Arbeit wird zunächst erläutert, wie der menschliche Wahrnehmungsapparat nach theoretischen Erkenntnissen aus der Wahrnehmungspsychologie visuelle Elemente wie Farbe und Form verarbeitet. Anhand gestaltpsychologischer und motivationspsychologischer Theorien werden mögliche Einflüsse und in diesem Zusammenhang bedeutungsvolle Aspekte aufgezeigt. Einzelne Funktionen und Wirkungsaspekte der einzelnen Medienbausteine wie Bild, Typografie und Bild-Text-Kombinationen werden anhand von Beispielen aus Mathematiklehrwerken dargestellt. Ein Exkurs über den vermehrten Einfluss der neuen Medien bei Kindern und Jugendlichen verdeutlicht, welche visuellen Medienerfahrungen Kinder und Jugendliche bei der Betrachtung eines Schulbuches mitbringen. Anschließend werden die erarbeiteten theoretischen Grundlagen in einer praktischen Arbeit genutzt. Eine exemplarisch ausgewählte Seite eines Mathematiklehrwerks werde unter verschiedenen gestalterischen Gesichtspunkten umgestaltet, so dass mehreren Varianten entstehen. Diese Entwürfe werden in einer qualitativen Studie mit einzelnen SchülerInnen diskutiert. Die Ergebnisse der aufgezeichneten Interviews wurden durch die Auswertungsmethode des zirkulären Dekonstruierens auf die aufgeworfenen Forschungsfragen untersucht und ausgewertet.

Re-Framing Trade

Given the substantial and increasing encroachment of trade agreements into almost every aspect of economic and social life, there is a pressing need for research that provides a more coherent framework for understanding the source and effectiveness of organised labour ’s power and capacity to influence international trade policy. Taking the union protests against the General Agreement on Trade in Services (GATS) as a case study, this research uses core concepts derived from social movement theory to analyse the opportunities that existed for unions to influence these trade negotiations and their capacity to identify and take advantage of such opportunities. Importantly, it adds a power analysis designed to reveal the sources of power that unions draw on to take action. The research demonstrates that even where unions faced considerable constraints they were able to re-frame trade issues in a way that built broad support for their position and to utilise opportunities in the trade negotiation process to mobilise resistance against the GATS and further liberalisation of services. The theoretical framework developed for the research provides conceptual tools that can be developed for improving strategic campaign planning and for analytical assessment of past campaigns. The theoretical framework developed for this research has potential for further application as an analytical and strategic planning tool for unions.

Detecting ultrafast interatomic electronic processes in media by fluorescence

Interatomic coulombic decay (ICD), a radiationless transition in weakly bonded systems, such as solutes or van der Waals bound aggregates, is an effective source for electrons of low kinetic energy. So far, the ICD processes could only be probed in ultra-high vacuum by using electron and/or ion spectroscopy. Here we show that resonant ICD processes can also be detected by measuring the subsequently emitted characteristic fluorescence radiation, which makes their study in dense media possible.