Photopolymers for Rapid Prototyping of Soluble Mold Materials and Molding of Cellular Biomaterials

Summary. To substitute cross-linked photopolymers in rapid prototyping of mold materials and therefore extend the range of materials which can be casted, organo-soluble photopolymers were developed. Branched bisalkylacrylamides were suitable as base component for such formulations, due to their high reactivity, good mechanical properties, and excellent solubility of the formed polymers. These molding materials were used to prepare cellular biocompatible materials which could be used as bone replacement materials. Biocompatible crosslinkers based on methacrylates from hydrolyzed gelatine or lactic acid ethyleneglycol blockcopolymers and commercially available reactive diluents are the base components of such a formulation. Biocompatibility was investigated by osteoblast-like cells. Cellular biocompatible parts were obtained by thermal polymerization in soluble mould materials prepared by 3D-photoshaping.     

Study of silica supported PtxNi1-x catalysts by ion scattering spectroscopy

As supported Pt_xNi_1–x catalysts are used for hydrogenation reactions, it seemed necessary to assess the surface composition of the reduced samples. To approach the usual reduction conditions we applied in situ reduction in a reaction chamber (1 mbar H₂ up to 500 °C) placed in ultra high vacuum recipient (UHV: 10^–9 to 2.10^–10mbar). All ion scattering spectroscopy measurements were performed in UHV. Charging of the samples was avoided by electron bombardment (5 eV). The variation of the surface composition was determined after subsequent sputtering, thermal treatment at 500 °C and during oxygen adsorption. A comparison with previous results of surface compositions of binary alloys (polycrystalline foils [1, 2] and single crystals Pt_xNi_1–x [3]) is given.Dedicated to Professor Dr. rer. nat. Dr. h. c. Hubertus Nickel on the occasion of his 65th birthday     

Correlation of unified retention indices for OV-101 and squalane

Summary Gas chromatographic unified retention indices for 43 hydrocarbons (alkanes and cycloalkanes) are given for squalane and OV-101. Comparison of these values and unified retention index increments are presented as linear regression equations with high correlation coefficients and acceptable standard deviations.     

Solvent extraction and radiometric determination of3H-stobadine in biological material

A simple and rapid radiochemical method for the efficient and selective isolation of³H-stobadine from plasma, urine and organ homogenates has been developed. The method comprises the extraction of³H-stobadine from the biological matrix containing 2M Na₂CO₃ into n-hexane followed by scrubbing of partly coextracted metabolites into an equal volume of 2M Na₂CO₃. The specificity of the procedure presented is demonstrated by TLC and the comparison of distribution coefficients of authentic and apparent (isolated) substances.     

Preparation and practical application of spinel pigment Co0.46Zn0.55(Ti0.064Cr0.91)2O4

Synthesis of the green spinel pigment Co_0.46Zn_0.55(Ti_0.064Cr_0.91)₂O₄ by a novel two-step method of preparation have been investigated. Inorganic pigments are almost always prepared by a solid state reaction. It is classical ceramic method which used oxides, hydroxides or carbonates as precursors. The reaction is performed at temperature higher than 1300°C and an agent of mineralization is usually present. The presented novel method of preparation decreases the calcining temperature necessary for reaching of bright and clear hue of the pigments prepared. Main attention was focused on the influence of two types of titanium raw materials on the temperature region of the spinel structure formation and on the colour properties of the pigments. The mixture of precursors with TiO₂ gives a one-phase system when calcining at 1100°C but the colour properties are more interesting at 1150°C. Thermal stability of this pigment is limited by temperature 1300°C. This temperature is connected with partial oxidation of Cr(III) to Cr(VI). Thermal analysis provided the first information about the temperature region of the pigment formation and determined the thermal stability of pigment.     

A test for monitoring traces of cholinesterase inhibitors in surface waters

Summary The inhibitory effect on cholinesterase activity is the only common attribute of organophosphorus pesticides and carbamates. Therefore a screening test based on cholinesterase assay is suitable for detection of total pesticides in the pollution control of surface waters. The reaction-rate cholinesterase assay in which acetylthiocholine iodide is used as substrate and 5,5-dithio-bis (2-nitrobenzoic acid) (Ellman's reagent) as indicator, with spectrophotometric monitoring at 412 nm for 2 min is applied. The detection limits for various pesticides in aqueous solutions have been determined. The results are comparable to those of gas Chromatographic analyses and for carbamates are even better. The sensitivity can be improved by two orders of magnitude by preconcentration on Amberlite XAD-4 column. The collection efficiency of about 80% for all the pesticides tested has been confirmed by gas chromatography. A rapid and simple field test is based on the same assay system. The reaction is stopped by complete inhibition of the enzyme and the colour is compared visually with that of standards prepared by dilution of the initial enzyme solution, and the comparison is facilitated by use of a red filter (_max 555 nm). A relative standard deviation of 5.5% was obtained for 3 series of sample covering the range 0–100% inhibition, 9 experiments done by 6 persons.

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Nachweis von Spuren Cholinesterase hemmender Faktoren in Oberflächenwässern

Zusammenfassung Der hemmende Effekt gegenüber Cholinesterase ist das einzige gemeinsame Kennzeichen phosphor-organischer Pestizide und Carbamate. Der Nachweis mit Cholinesterase eignet sich daher für den Nachweis von Pestiziden bei der Reinheitskontrolle von Oberflächengewässern. Der Nachweis mit Acetylthiocholinjodid als Substrat und 5,5-Dithio-bis(2-nitrobenzoe-säure) (Ellmans Reagens) als Indikator durch spektrophotometrische Bestimmung bei 412 nm wurde angewendet. Die Erfassungsgrenzen für verschiedene Pestizide in wäßriger Lösung wurden bestimmt. Die Ergebnisse sind mit denen gaschromatographischer Analysen vergleichbar, für Carbamate sogar besser. Die Empfindlichkeit kann durch Anreicherung mit Amberlit XAD-4 um zwei Größenordnungen verbessert werden. Die Anreicherung um ungefähr 80% wurde gaschromatographisch für alle untersuchten Pestizide bestätigt. Ein schneller und einfacher Feldversuch beruht auf demselben Reaktionsvorgang. Die Reaktion wird durch vollständige Hemmung des Enzyms abgebrochen und die Farbe visuell verglichen mit verdünnten Standardlösungen der ursprünglichen Enzymlösung. Dieser Vergleich wird durch ein Rotfilter (_max 555 nm) erleichtert. Eine relative Standardabweichung von 5,5% wurde für 3 Probenreihen mit einem Hemmungseffekt von 0–100% erhalten, wobei 6 Personen 9 Versuche durchführten.

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Presented at the 8th International Microchemical Symposium, Graz, August 25–30, 1980.     

Thermal Analysis of the System Na3AlF6–NaVO3

Summary. The phase diagram of the system Na₃AlF₆–NaVO₃ was determined by means of thermal analysis. The system is a simple binary eutectic one. The eutectic point was estimated at x(NaVO₃) = 0.975 and t _eut = 617°C. The XRD patterns of samples after thermal analysis revealed the presence of cryolite and NaVO₃ only supporting the above assumption of a simple eutectic binary system.     

Novel method for the preparation of anionic surfactant-selective electrodes

A simple one-step synthesis is described for the functionalization of poly(vinyl chloride) used for the preparation of anionic surfactant-selective membrane electrodes. The method is based on the nucleophilic substitution of a fraction of the chlorine atoms bound to the poly(vinyl chloride) backbone by trimethylamine. The prepared slightly charged polymer gave rise to high-quality surfactant-selective electrode membranes, which had a Nernstian response, short response time, and appropriate stability.     

Book review

S. E. J_rgensen and Yu. M. Svirezhev Towards a Thermodynamic Theory for Ecological Systems Elsevier, Amsterdam 2004, Price: paperback 85€; hardbound 140€, 350 (A4 size) pages     

A new photoionization detector for gas chromatography

Summary A new photoionization detector for gas chromatography is discribed. The source of vacuum ultra-violet (VUV) radiation is separated from the ionization chamber by a window and thus the ionization chamber may be run at atmospheric pressure using an intense source of ionizing radiation. The operation consequently is improved and considerably simplified. Except for a ten times reduction in linearity, the performance characteristics of the detector are comparable to those of the flame ionization detector. Filtration of the VUV radiation allows the selectivity to be varied without affecting the dynamic properties of the detector.Z. ternberg, N. Ostoji, Yug. Pat. Appl.