Algebraic algorithms for the analysis of mechanical trusses

Infinite periodic lattices can be used as models for analyzing and understanding various properties of mechanical truss constructions with periodic structures. For infinite lattices, the problems of connectivity and stability are nontrivial from the mathematical point of view and have not been addressed adequately in the literature. In this paper, we will present a set of algebraic algorithms, which are based on ideal theory, to solve such problems.

For the understanding of the notion ``complicated three-dimensional lattices', it is essential to have this paper with colored figures.

     

In vivo NMR in pharmaceutical research.

In vivo NMR techniques are currently well established in pharmaceutical research and will likely become increasingly important in the future, as they procure noninvasively morphological, physiological, and biochemical information. The status of magnetic resonance imaging (MRI) and spectroscopy (MRS) in drug development is discussed on the basis of the characterization and evaluation of a rat model of ischemic stroke and the development and profiling of drugs for cerebral ischemia in this model. It can be concluded that MRI is well suited for drug screening (quantitative determination of lesion size), while dynamic MRI and MRS techniques provide relevant information on the mechanism of drug actions. The possibility to follow changes, pathological and therapeutic, in the same individual is important from two points of view. First, variations due to interindividual differences may be eliminated, increasing the statistical power of the results. Second, dose and/or time dependence of a drug can be explored in the same individual. As a result, the number of animals required for a study will be reduced, which from both ethical and economic aspects is highly desirable.     

Synthesis and conformational studies of a new host system based on cholic acid

New synthetic hosts have been designed incorporating two molecules of cholic acid linked by a rigid diamine. Proton NMR studies indicate that the compounds exist in a rigid conformation with the steroid hydroxyl groups intramolecularly hydrogen-bonded. Heat or addition of methanol leads to conformational isomerism due to insertion of methanol into the cavity.A preliminary report of this work was presented at the 4th International Symposium on Inclusion Phenomena, July 20–25, 1986, Lancaster, U.K.     

Effects of the presence of pyrite and carbonate minerals on the kinetics of the uranium release from a natural rock

Summary The influence of calcite, dolomite, pyrite and vaterite on the kinetics of uranium release from a natural rock under relevant, i.e., field conditions has been investigated. The time dependence of the U release has been studied in two different experimental procedures (open and closed systems) at laboratory temperature (21±2 °C). Performing batch experiments in tap water, the U release efficiency of a natural U-bearing rock was characterized in the presence of varying amounts of three different carbonate bearing minerals for experimental durations of up to 782 days. Another experiment was conducted for a period of 14 days in the presence of a pyrite mineral. The results demonstrate that the presence of carbonate minerals does not have any significant influence on U release in closed systems where the U concentration at saturation was ca. 54 mg/l. In contrast, in open systems, the U concentration was ca. 8 mg/l at saturation and the effects of all additives both on kinetics and saturation concentration of U were apparent.     

Untersuchungen an reagenzien zur photometrischen zinnbestimmung

The formation of complexes between tin(IV) and o-diphenols, and o-hydroxyquinones, has been studied spectrophotometrically. Simple o-hydroxyquinones do not react with tin(IV), chloranilic acid gives an SnR₂ complex, and o-diphenols give SnR₃ complexes. The reactions of tin(IV) with hydroxyxanthene dyes to give coloured products were considered for their possible analytical utility: the pH range, absorption spectrum, solubility and composition of the complexes were investigated, and the stability constants determined. Analytical procedures have been developed for tin and checked for precision and sensitivity: gallein and hydroxyhydroquinonephthalein (dihydroxyfluorescein) are to be recommended.     

5,6-Dimethoxy- und [4,5,6-Trimethoxy-benzo[b]-thienyl-(3)]-acylamine

Zusammenfassung Umsetzung von 5,6-Dimethoxy- und [4,5,6-Trimethoxy-benzo[b]thienyl-(3)]-essigsäure mit PCl₅ lieferte die methoxysubstituierten [Benzo[b]thienyl-(3)]-essigsäurechloride, die mit sekundären Aminen zu den entsprechenden Amiden reagierten.Die homologen Verbindungen mit einer C₃-Brücke wurden durchArndt-Eistert-Reaktion des Diazomethylketons in Gegenwart der entsprechenden sekundären Amine erhalten.

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Reaction of 5.6-dimethoxy- and [4.5.6-trimethoxybenzo[b]-thienyl-(3)]-acetic acid with PCl₅ gave the methoxy-substituted [benzo[b]thienyl-(3)]-acetic acid chlorides, which reacted with secondary amines to the corresponding amides.The homologous compounds with a C₃-bridge were synthesized viaArndt-Eistert reaction of the diazomethyl ketone in presence of the corresponding secondary amines.

     

Synthese von Thieno[2,3—d]-1,2,3-triazin- und [1]Benzothieno [2,3—d]-1,2,3-triazin-Derivaten

The title substances, derivatives of two new heterocyclic ring systems, were synthesized by intramolecular cyclisations of diazonium compounds, prepared from derivatives of 2-amino-thiophene-3-carboxamide and of 2-amino-benzo[b]thiophene-3-carboxamide. By-reactions and substitution reactions are mentioned.     

A 50% n-octylmethyl, 50% diphenyl-polysiloxane as stationary phase with unique selectivity for gas chromatography

An n-octylmethyl, diphenyl-polysiloxane called SOP-50-Octyl was prepared by a condensation reaction of bis(dimethylamino) n-octylmethylsilane with diphenylsilanediol. The resulting copolymer was a gum with high molecular weight and was obtained with a yield of 80%. 1H and 29Si NMR spectroscopy revealed that the copolymer was a 52% octylmethyl, 48% diphenyl-polysiloxane with random microstructure. Small cyclic impurities could be almost quantitatively removed via a purification step. SOP-50-Octyl was used as stationary phase for the preparation of wall coated open tubular fused silica capillary columns for gas-liquid chromatography. The capillary columns exhibited high separation efficiency and high inertness. The stationary phase offered a unique selectivity due to its unique composition. The Rohrschneider-McReynolds constants indicated a low overall polarity in spite of the high phenyl content, as the polarity was distinctly decreased by the octyl substituent. Furthermore, the octyl substituent was responsible for a high column bleed, reducing the maximum allowable operating temperature to 280 degrees C. The elution temperatures of apolar compounds were increased due to increased interaction of the octyl substituent with the analytes. Some applications with volatile and semi-volatile organic compounds illustrate that SOP-50-Octyl is an excellent choice for confirmational analyses.