Optimizing the structure of acene clusters.

We present a study of the potential energy surface of anthracene, tetracene, and pentacene clusters with up to 30 molecules. We have applied the basin-hopping Monte Carlo algorithm to clusters of acene molecules in order to find their lowest energy states. The acene molecules are described by the polymer-consistent force field-interface force field. We present the structures with the lowest observed energy, and we discuss the relative stability and accessibility of structures corresponding to local energy minima.

Phase behavior of the generalized chiral Lebwohl-Lasher model in bulk and confinement.

One of the simplest models that is used to study the isotropic-nematic tranition in liquid crystalline systems is the Lebwohl-Lasher model. Several extensions of this model further enhanced its applicability. We combine two of these extensions (a generalization and the inclusion of a chiral term) and study the phase behavior and the nature of phase transitions of the resulting generalized chiral Lebwohl-Lasher model using Monte Carlo simulations. We find that the type (and even the existence) of the transition depends on the combination of the width of the interaction potential, the strength of the chiral part of the interaction, and the geometry of the system. As well, the pitch of the cholesteric bulk phase changes on approaching the phase transition if the interaction width differs from the one of the original Lebwohl-Lasher model. Thus, we identify parameter combinations that allow one to tune the properties of the ordered phase and the nature of the order-disorder transition.

Double suicide and homicide-suicide in Switzerland.

Double suicide and homicide-suicide are infrequent and are different in psychopathology from that of a single suicide. However, precipitating factors for double suicide and homicide-suicide are similar to these found in single suicide. Depression, borderline disturbances, and narcissistic neuroses in combination with stressors such as physical illness, isolation, and social losses can lead to homicide-suicide. Epidemiological studies indicate that double suicide and homicide-suicide are influenced by ethnicity and cultural and social background. This study explores the situation in Switzerland between 1928-48 and 1971-1990.

Cytotoxicity of lectins on rat intestinal mucosa enhanced by neuraminidase.

The lectins wheat germ agglutinin (WGA) and Concanavalin A (ConA) were perfused into an isolated small intestinal segment alone or after prior perfusion with neuraminidase for a 10 day period in the rat. Intestinal morphometry, intraepithelial Lymphocyte (IEL) and round cell content as well as digestive capacity was measured in the loop and in the adjacent segments. Both lectins induce a mucosal transformation in all segments but ConA is more effective than WGA. Pre-incubation with neuraminidase enhances the action of ConA throughout, whereas only a partial enhancement of the effect of WGA is observed. The mucosal transformation after long term perfusion with the lectins resembles the hyperregenerative adaptation of the mucosa due to gluten in coeliac disease and may thus serve as an animal model for this disease.