Molecular and crystal structure of 1-methyl-3-[(3-methylthio-4-quinolyl)thio]-1,4-dihydro-4-oxo-quinoline

The crystal structure of 1-methyl-3-[(3-methylthio-4-quinolyl)thio]-1,4-dihydro-4-oxo-quinoline has been determined. The molecule of the title compound adopts a conformation that is skew, but with a tendency to a twist. Both ortho-substituents, the carbonyl and methylthio groups, are in a cis orientation to the central C_ar-S-C_ar bridge. This mutual orientation of substituents follows from the SO and SS attractive interactions. Several short intramolecular contacts between N-methyl and neighboring protons as well as between S-methyl and neighboring protons explain the presence of the strong NOE enhancement in the NMR spectrum.Part XVII in the Series of Azinyl Sulfides.     

The isoxazole heterocyclic system: synthesis of a new model structure in immunosuppressing agents

A new lead structure in the isoxazole heterocyclic system showing immunosuppressing activity is described. Synthesis, spectral and X-ray data giving evidence of the structures of these compounds are presented. X-ray studies were carried out on compounds I C₁₈H₂₂N₄O₄ with a = 9.606(3), b = 9.813(3), c = 9.849(3)Å, = 87.28(3), = 79.06(3). = 80.89(3)° Z = 2, and space group ; and II C₁₄H₁₅N₄O₃Cl with a = 7.090(3), b = 16.807(3), c = 12.925(3)Å, = 104.41(3)°, Z = 4 and space group P2₁/n.     

The kinetics of gasification of char derived from sewage sludge

Gasification of char derived from sewage sludge was studied under different oxidizing atmospheres containing CO₂, O₂ or H₂O. The gasification tests were carried out in thermobalance at different temperatures and oxidizing reagent concentrations. The most efficient were the gaseous mixtures containing oxygen. The reaction took place at temperature 400–500 °C, whilst in the case of CO₂ and steam much higher temperatures (700–900 °C) were necessary to complete the conversion. Two rate models for gas–solid reaction were applied to describe the effect of char conversion on reaction rate. The shrinking core model for reaction-controlled regime was found to be the best for predicting the rate of char gasification in CO₂ and O₂ atmosphere. The experimental data for steam gasification of the char were fitted best by the first-order kinetics. The kinetic parameters estimated from the experimental data are in accordance with the literature for lignocellulosic char gasification and are the first published for sewage sludge char gasification.     

Electrical conductivity in solid solutions and in two-phase regions of the silver halide-bivalent metal (cadmium,cobalt, zinc) halide systems

Electrical conductivity of solid systems AgX-MX₂ (where M=Cd, Co, Zn and X=Cl, Br) were measured in a large range of temperature and compositions. Activation energies and conductivity values vs. composition are presented and discussed in relation to phase equilibria in the respective systems. Maximum of the conductivity value and stabilization of the activation energy have been found for silver halides doped heavily with divalent cation e.g. in the systems forming solid solutions on the silver halide side. Disorder in AgBr on the approach to melting, expected to be higher than in AgCl, has been shown by means of original DSC curves presented for both halides.     

Determination of elemental sulfur in coal by gas chromatography – mass spectrometry

A method for the determination of S⁰ in coal based on the extraction with cyclohexane with subsequent quantitative analysis of elemental sulfur in the extract by GC/MS is described. The quantity of elemental sulfur was determined in four coal samples with different distribution of sulfur forms. The effect of solvent and extraction time on the efficiency of sulfur removal was studied. The elemental sulfur extracted from coal occurred in the form of S₆, S₇ and S₈. Calibration solutions were prepared from freshly recrystalized elemental sulfur. It was found that the injection temperature has a crucial influence on the m/z 64 ion chromatogram.     

Study on Influence of Gelatin-Alginate Matrixes on the Coagulation System and Morphotic Blood Elements

Summary: The paper presents evaluation hemolytic and hemostatic activity of gelatin-alginate matrixes in contact with human blood in vitro studies. The percentage of hemolysis and free hemoglobin concentration were normal. The blood recalcyfication time (CT) was shortened and activated partial thromboplastin time (APTT) was prolonged. That sugested that coagulation processes were activated. Discrabed changes were depended an component composition of sponge.     

Progress in Polymerization of Cyclic Esters: Mechanisms and Synthetic Applications

Recent advances in the controlled ring-opening polymerization of aliphatic cyclic esters are briefly reviewed. Particular attention is paid to the high molecular weight linear, branched, and star-shaped poly(lactide)s and poly(ε-caprolactone) synthesis. It is concluded that despite the plethora of initiating and/or catalytic systems applied for this purpose the best results so far were achieved with Al- and Sn(II) derivatives. Analytical methods employed for aliphatic polyesters of various architectures characterization, including SEC-MALLS, LC-CC, and fluorescence spectroscopy, are also discussed.     

Screen-printed copper ion-selective electrodes

A simple, low-cost and reproducible method for the mass production of potentiometric ion-selective electrodes for copper ions is presented. These planar, strip sensors were obtained by screen-printing. The application of pastes cured at low temperature allows printing of the sensors on low-cost, plastic substrates. The pastes for printing of ion-sensitive thick-film membranes were based on copper (I) and copper (II) sulfides. The analytical characteristics of the thick-film electrodes were compared. The analytical properties (range of determination, sensitivity, selectivity, response time) of the copper (I) sulfide-based sensors were comparable with those for conventional ion-selective electrodes. Received: 12 January 2000 / Revised: 13 March 2000 / Accepted: 16 March 2000     

A Note on the Integrability of Hamiltonian Systems

We consider a family of Hamiltonian systems

Singularities of Lagrangian varieties and related topics

We study the classification problem for generic projections of Lagrangian submanifolds. A classification list for symmetric Lagrangian submanifolds is obtained and the generic evolutions of symmetric caustics are illustrated. We show how the singular Lagrangian varieties appear in the invariant theory of binary forms and we introduce the basic concepts of the desingularization procedure. Applications to differential geometry, geometrical optics, and mechanics are presented.