Mechanismus der katalytischen Benzolhydrierung

Ohne Zusammenfassung     

Die Hemmwirkung von Spurenmengen Fe3+-Ionen im H2O2-Zerfall

Zusammenfassung In einer Lösung von basischem Magnesiumcarbonat rufen Fe³⁺-Ionen eine Hemmung des H₂O₂-Zerfalls hervor, was besonders deutlich in Gegenwart der in diesem System sonst aktiven Cu²⁺-Ionen zu erkennen war.     

Homogene Lösungskatalyse. Über die milieubedingte hemmende und aktivierende peroxidatische Wirkung von Zn2+−, Cr3+− und CrO −lonen in homogener Lösung

The title ions are in sodium acetate solution activators, and in sodium tartrate solution inhibitors, for the peroxidatic decolouration of indigocarmine by H₂O₂ at 37 °C.     

Zur Bildung von ferromagnetischen Ferriten aus bei Raumtemperatur gefällten Mischgelen durch wasserentziehende Mittel

Ohne Zusammenfassung     

Concentrating colloids with electric field gradients. I. Particle transport and growth mechanism of hard-sphere-like crystals in an electric bottle

This work concerns the use of electric field gradients to manipulate the local particle concentration in a hard-sphere-like suspension. Inside a specially designed "electric bottle," we observed our colloids to collect in the regions of lowest field strength ("negative dielectrophoresis"). This allows for the use of larger field gradients and stronger dielectrophoretic forces than in the original electric bottle design, which was based on positive dielectrophoresis [M. T. Sullivan et al., Phys. Rev. Lett. 96, 015703 (2006)]. We used confocal scanning laser microscopy to quantitatively follow the time-dependent change in the particle density and the suspension structure. Within a few days, the dielectrophoretic compression was seen to initiate a heterogeneouslike growth of large single crystals, which took place far out-of-equilibrium. The crystals had a random hexagonal close-packed structure and displayed an intriguing growth mechanism, during which the entire crystal was continuously transported, while growing both on the "high-field" and the "low-field" sides, although at different rates. After switching off the electric field, the compressed crystals were found to relax to a lower packing fraction and melt, at a much slower rate than the crystal growth. Besides revealing the particular (far out-of-equilibrium) crystal growth mechanism in these electric bottles, our observations also shed light on the role of the different particle transport processes in the cell and some of the relevant tuning parameters. This is useful for different types of experiments, for instance, focusing more on melting, homogeneous crystallization, or the glass transition.     

The shooting S-estimator for robust regression

To perform multiple regression, the least squares estimator is commonly used. However, this estimator is not robust to outliers. Therefore, robust methods such as S-estimation have been proposed. These estimators flag any observation with a large residual as an outlier and downweight it in the further procedure. However, a large residual may be caused by an outlier in only one single predictor variable, and downweighting the complete observation results in a loss of information. Therefore, we propose the shooting S-estimator, a regression estimator that is especially designed for situations where a large number of observations suffer from contamination in a small number of predictor variables. The shooting S-estimator combines the ideas of the coordinate descent algorithm with simple S-regression, which makes it robust against componentwise contamination, at the cost of failing the regression equivariance property.