Uber eine Beziehung zwischen Zentrum und Kern endlicher Fastkörper

Ohne ZusammenfassungHebmann Schmidt zum 60. Geburtstag gewidmet     

Novel synthesis of aza-heterocycles

N-formyl aza-heterocycles $\text{15}$ – $\text{24}$ can be prepared by RaNi desulfirization of thiazolidine derived polycyclics $\text{5}$ – $\text{14}$ which in turn are obtained by intramolecular thiono α-acyliminium cyclisations of π-nucleophiles.     

Effective conductivity and skew Brownian motion

We consider heat conduction in a periodic body which is composed of finitely many different components. The effective conductivity is represented in terms of skew Brownian motion. The representation formula is a fluctuation-dissipation relation. The dissipation term in this formula is related to the transmission of heat through the surface separating the different components of the body; it is described by the skew reflections of Brownian motion at these surfaces. The problems caused by the discontinuity of the microscopic conductivity are handled in the framework of Dirichlet forms.     

ERYTHEMAL UV-B IRRADIANCE (ROBERTSON-BERGER SUNBURN METER DATA) UNDER OZONE DEFICIENCIES IN WINTER/SPRING 1993

Abstract –Robertson-Berger sunburn meter data recorded from August 1992 to May 1993 (Innsbruck, 577 m above sea level, Austria) were compared with measurements taken in previous years. In February and March 1993 instantaneous values on clear days were found to be higher by up to 37% than those registered in previous years (1986–1988). However, in winter/spring 1993 daily totals for all days, averaged over 7 days, were within the range of standard deviation of the previous years (1981–1988). Therefore the cumulative UV-B exposure of the ecosystem is within the general range of variability even under the record low ozone values in winter/spring 1993, while single peak doses were enhanced significantly.     

Phospha-alkene durch thermische,basen- oder metall-induzierte eliminierung

Thermal, base- and metal- induced 1,2-elimination reactions at P-halogen phosphanes of the type RP(Hal)-C(X)R¹R² were used for the preparation of phospha-alkenes with a new-type pattern of substitution at the (PC)-double-bond. The different methods are discussed in more detail.     

Synthesis of Alkenyl-Substituted Allenecarboxylates

The Wittig olefination of decanoyl chloride by using the phosphonium salt 1 in the presence of two equivalents of Et₃N represents a one-step synthesis of the racemic form of the naturally occurring pheromone (–)- 2 which contains an alkenyl-substituted allenic moiety (ef. Scheme 1). It is also shown, that unsaturated acyl chlorides which contain at least one γ-H-atom undergo the Wittig reaction with an appropriate phosphorane yielding γ-alkenyl-substituted α-allenic esters and α-allenic γ-lactones, respectively (ef. Schemes 2 and 3).     

Condensed phases in flame spectrometry: an equilibrium model of the acetylene flame

An equilibrium model for a wet acetylene flame has been used for the calculation of the distribution of carbon, aluminium and silicon between gaseous and condensed phases. Calculated values of free atom vapour fractions are in agreement with published experimental data. It is thermodynamically probable that the formation of condensed phases limits atom vapour formation. There is a relationship between the position of an element in the Periodic Table and the nature of the condensed phase.     

Oxygen-related band gap state in single crystal rubrene

A molecular exciton signature is established and investigated under different ambient conditions in rubrene single crystals. An oxygen-related band gap state is found to form in the ambient atmosphere. This state acts as an acceptor center and assists in the fast dissociation of excitons, resulting in a higher dark and photoconductivity of oxidized rubrene. The band gap state produces a well-defined photoluminescence band at an energy 0.25 eV below the energy of the 0-0 molecular exciton transition. Two-photon excitation spectroscopy shows that the states are concentrated near the surface of naturally oxidized rubrene.     

Freezing and melting of a colloidal adsorbate on a 1D quasicrystalline substrate

Using Monte Carlo simulations and an extended Landau-Alexander-McTague theory, we demonstrate that colloids in a one-dimensional quasicrystalline potential order in triangular and rhombic-alpha crystalline phases. Increasing the strength of the potential further, a new type of light-induced melting is discovered that has its origin in the nonperiodicity of the potential. In contrast to reentrant melting in periodic potentials, the quasicrystalline potential melts the crystalline phases even when they already exist at zero potential.