Trapping quasiminimizing submanifolds in spaces of negative curvature

LetM be a Hadamard manifold with all sectional curvatures bounded above by some negative constant. A well-known lemma essentially due to M. Morse states that every quasigeodesic segment inM lies within an a priori bounded distance from the geodesic arc connecting its endpoints. In this paper we establish an analogue of this fact for quasiminimizing surfaces in all dimensions and codimensions; the only additional requirement is that the sectional curvatures ofM be bounded from below as well. We apply this estimate to obtain new solutions to the asymptotic Plateau problem in various settings. The second author was supported by the Swiss National Science Foundation and enjoyed the hospitality of the University of Bonn. The collaboration between the authors was facilitated by the program GADGET II.     

Eine Methode zur gleichzeitigen elementaranalytischen Bestimmung von Kohlenstoff, Wasserstoff und Stickstoff

Ohne Zusammenfassung     

Study of solid-state polymerization by positron lifetime measurements

The positron lifetime measurement technique was applied to analyze the structural changes occurring in solid-state polymerization of acrylamide and trioxane. Positronium (Ps) parameters, τ₂ and I₂, which show a marked change as a function of the γ-ray irradiation dose, signaled the presence of three clearly defined stages in the polymerization process: initiation, propagation, and saturation. The initial increase in τ₂, may very well be the result of efficient trapping of Ps in vacancies created around the polymer nuclei. The complicated behavior of I₂ may be explained as a chemical reaction between Ps precursors and the radiolysis products of this polymerization process.     

Synthesis of a new catechin-pyrylium derived pigment

A new catechin-pyrylium derived pigment compound was synthesised from the reaction of catechin with sinapaldehyde in acidic conditions and its structure has been characterised by UV-vis, MS and NMR spectroscopy. Similar compounds could be expected to be formed in wines and contribute to changes in colour and astringency during ageing.     

High-resolution synchrotron radiation core-level spectroscopy of semiconductor surfaces

Thanks to recent technical developments (optics and detection systems), at several synchrotron radiation facilities in the world, it is possible to perform photoemission spectroscopy studies with very high resolution. In the present report, we will review the new insights gained from high-resolution core-level spectroscopy on the structural and electronic properties of different semiconductor surfaces, such as InAs(110), Si and Ge (100) and (111), as well as clean and adsorbate covered Si and Ge(111) surfaces.