Polystyrene-supported acid catalysis

The present state of polymer-supported acid catalysis is considered. Models describing the catalytic action of gel-like and macroporous resin catalysts are presented. By chemical modification of poly (styrene-co-divinylbenzene) matrices, e.g. different ways of sulphonation, nitration, chlorination, fluorination and sulphoalkylation, the activity/selectivity and thermal stability of sulphonic acid resin catalysts can be improved. The synthesis of polymer-supported Lewis acids is described. By comparison to AlCl₃ higher catalytic activities are obtained with the use of AlBr₃.     

Occurrence of Ti3+ and Fe2+ in Mullite

Electron paramagnetic studies showed that Ti³⁺ and Fe²⁺ occur in mullites taken from a refractory material which was fused-cast under a reducing atmosphere. Exposure of the mullite samples to temperatures >1600°C caused oxidation of Ti³⁺ and Fe²⁺ to Ti⁴⁺ and Fe³⁺, respectively.     

Charakterisierung niedermolekularer Zinkspezies in handelsüblichen pflanzlichen Lebensmitteln

In six different ordinary vegetables, namely kohlrabi, Chinese cabbage, chard, leek, spinach and Jerusalem artichoke, zinc was mainly found as low molecular weight species. In the present study, these important zinc compounds are further investigated. The determinations of the metal are performed by ET-AAS. The zinc complexes of all vegetables are anionic at pH 8.0 and show similar elution behaviour in gel permeation and anion exchange chromatography. Consequently, a great resemblance in structure between the low molecular weight zinc species from the different vegetables can be supposed. Exemplary, the zinc complexes of kohlrabi and Chinese cabbage are further examined. In more purified samples of these vegetables compared to zinc neither stoichiometric amounts of free protein amino acids nor nicotianamine, free malic acid, citric acid or phytic acid have been detected. Mainly glutamic acid is found in molar excess to zinc after acid hydrolysis in both cases. The cysteine contents of both zinc-binding fractions are very low. Conclusively, the wellknown γ-glutamylcysteinyl-glycines (phytochelatines) can not be responsible for the bonding of zinc in both ordinary vegetables. We suppose that zinc in kohlrabi and Chinese cabbage is bound to a glutamic acid derivative unknown as yet, possibly a malic acid ester.     

Comparison of different techniques for the observation of the lamellar texture of isotactic polypropylene: TEM of surface replicas,TEM after staining,and SFM

Summary In the present study three different techniques have been employed to observe the lamellar texture of isotactic polypropylene (iPP) crystallized from the melt under the influence of shearing: (a) Transmission electron microscopy (TEM) of surface replicas of permanganically etched samples (b) TEM of thin sections of Ruthenium-oxide stained samples and (c) Scanning force microscopy (SFM) in contact mode of permanganically etched samples. The aim was to assess their relative merits in terms of practicability, resolution and type of information.     

Coherent optical processing: Another approach

Demonstration of real-time coherent optical correlation for both vehicle tracking and identification has been demonstrated. A reference filter has been constructed that can recognize a vehicle from all orientations. A design of a coherent optical processor is presented using laser diode light sources and having a package size of 50 cm³.     

Organische und anorganische Ionenaustauscher zur heterogen katalysierten Alkylierung von Aromaten

Organic and inorganic ion exchangers as catalysts for the heterogeneous alkylation of aromatics . Ion exchangers has advantages over low molecular for use in industrial alkylation reactions. The reactivity and selectivity behaviour of the polymeric catalysts were found to be markedly influenced by the structure of the polymeric matrix as well as the type and number of the functional groups. In this connection many similarities between inorganic ion exchangers (zeolites) and organic ion exchange resins were detected.