Enhanced structural correlations accelerate diffusion in charge-stabilized colloidal suspensions

Theoretical calculations for colloidal charge-stabilized and hard sphere suspensions show that hydrodynamic interactions yield a qualitatively different particle concentration dependence of the short-time self-diffusion coefficient. The effect, however, is numerically small and hardly accessible by conventional light scattering experiments. Applying multiple-scattering decorrelation equipment and a careful data analysis we show that the theoretical prediction for charged particles is in agreement with our experimental results from aqueous polystyrene latex suspensions.Comment: 1 ps-file (MS-Word), 14 page

Tendenzen, Triebkräfte und Steuerungsmöglichkeiten der Entwicklung der Kulturlandschaft ländlicher Räume Baden-Württembergs

Die wesentlichen bei der Erarbeitung von Überblicken und Fallstudien sowie in der Diskussion gewonnenen Ergebnisse werden in vierzehn Punkten zusammengefasst, um die Bedeutung der Kulturlandschaft für die Entwicklung ländlicher Räume in Baden-Württemberg zu unterstreichen. Daraus ergeben sich Schlussfolgerungen für die räumliche Planung, aber auch neue Fragen und Aufgaben für die Forschung.The most important results derived from the work on the overviews, case studies and discussions are summarised in 14 points, underlining the significance of the cultural landscape for the development of rural spaces in Baden-Württemberg. This reveals consequences for spatial planning, but also new research questions and tasks

Silicon avalanche photodiodes as detectors for photon correlation experiments

In view of time correlated photon-counting experiments using wavelengths at the red end of the electromagnetic spectrum, we developed a simple electronic circuit for periodical gated quenching of silicon avalanche photodiodes. We compare the performance of this device with commercially available passive and active quenching modules and a reference photomultiplier. The detection system's nonlinearities, i.e., dead time and afterpulsing, lead to direct and indirect distortions of photocount correlation functions. We characterize this nonlinear behavior by measuring intensity auto-and cross-correlation functions and supply nonlinearity parameters for each of the four detection systems. In addition, transfer functions are given which allow an estimate for the highest count rates accessible for each detection system