Zur Entstehung von Oberflächenladungen im Zusammenhang mit Ionentransport- und Sekundärelektronenemissionserscheinungen

Surface charges at the glassy or metallized but isolated inner walls of differently sized diodes are investigated as dependent upon different conditions (vacuum, inner geometry, electric operational conditions). For this purpose, a special condenser discharge method is used which gives the opportunity to study under well known conditions the temporal behaviour of those surface charges caused by electrical fields from outside the tube changing with time. One gets informations concerning the transport of positive ions and of electrons within such tubes in respect to the different kinds of wall material. The conditions are given for origin and maintenance of a stable positive wall potential above 150 V. In this case, the ratio of the electron current from the cathode to the wall and to the anode respectively comes out as ascending from 0.3 to 0.7 for a variation of the anode current from 200 to 900 μA, as one finds by comparing observations of a desorption effect stimulated by the electron current to the wall.     

Die Brüder Otto und Robert Margulies

It is difficult to understand that nearly no information can be found in encyclopedias and books about the history of the chemical industry about the Margulies family (father Benedikt and sons Otto and Robert), pioneers in industrial chemistry. The Margulies brothers realized the importance of catalysis and electrochemistry as a basis for industrial chemical processes. They initiated the fixation of N₂ from the air which resulted in the synthesis of Ammonia by Haber and Bosch and they also developed the first industrial process for the production of Hydrogen Peroxide and built the first industrial production unit in Austria. There is no monument to honor the pioneers, no price is named after them and they had very little benefit from what they initiated or made available on an industrial scale. This article is dedicated to their memories.     

The impact of structural biology on alkaloid biosynthesis research

Covering: 1997 to 2012In the recent past, macromolecular crystallography has gone through substantial methodological and technological development. The purpose of this review is to provide a general overview of structural biology and its impact on enzyme structure/function analysis and illustrate how it is modifying the focus of research relevant to alkaloid biosynthesis.     

Ein Kommutativitätskriterium für unendliche auflösbare Gruppen

Ohne Zusammenfassung     

Dielectric spectroscopy on aqueous solutions of some zwitterionic amino acids

The complex (electric) permittivity of aqueous solutions of dipolar solutes has been measured as a function of frequency between 1 MHz and 40 GHz. Solutes are the isomers DL-2-aminobutyric acid, DL-3-aminobutyric acid, and 4-aminobutyric acid, and also 6-aminohexanoic acid. The measured dielectric spectra show two dispersion/dielectric loss regions, one due to the orientational diffusion of the solute molecules the other one due to the dielectric relaxation of the solvent water. A relaxation spectral function based on a model of the solutions has been fitted to the measured frequency dependence of the complex permittivity. The values for the electric dipole moment and reorientation time of the zwitterionic part of the solute particles derived by this analysis from the measurements fairly agree with theoretical predictions. Quite remarkably, the dipole moment in solution of 4-aminobutyric acid and 6-aminohexanoic acid up to remarkably high solute concentrations is nearly constant. A noteworthy result for the hydration water of the amino acids is, that its relaxation time is almost independent of the solute dipole moment.