Selective nucleophilic replacement of the benzylsulfanyl group in 2,4‐disulfanyl‐substituted thieno[2,3‐d]pyrimidin‐6‐carboxylic acid derivatives by secondary amines

Thieno[2,3‐d]pyrimidines with benzylsulfanyl and allylsulfanyl group in the presence of other alkylsul‐fanyl substituents react selectively under mild conditions with secondary amines under replacement of the benzyl or allyl residue whereas the other substituents remain intact. This enables the synthesis of different basic substituted derivatives with potentially biologically activity.     

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Ohne Zusammenfassung     

Electrochemical reactions of YBaCuO-superconductors and their relations to stoichiometry and structure

Summary Electrochemical signals of YBaCuO superconducting compounds are detected using a voltammetric procedure and a carbon paste electrode in alkaline medium. Their intensity depends on the annealing temperature and correlates with the oxidizing power. The latter is determined by the reaction of the compounds with iodide and subsequent iodometric titration and is expressed in a general form as oxidation equivalent. The oxidation equivalent can easily be transferred to the usual expressions as Cu(III) or defect spots. The iodometric titration offers a calibration possibility for the direct electrochemical method as a helpful tool in the process control of superconducting compounds.

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Elektrochemische Reaktionen von YBaCuO-Supraleitern und ihre Beziehungen zu Stöchiometrie und Struktur

     

Direct measurement of the flow field around swimming microorganisms

Swimming microorganisms create flows that influence their mutual interactions and modify the rheology of their suspensions. While extensively studied theoretically, these flows have not been measured in detail around any freely-swimming microorganism. We report such measurements for the microphytes Volvox carteri and Chlamydomonas reinhardtii. The minute (～0.3%) density excess of V. carteri over water leads to a strongly dominant Stokeslet contribution, with the widely-assumed stresslet flow only a correction to the subleading source dipole term. This implies that suspensions of V. carteri have features similar to suspensions of sedimenting particles. The flow in the region around C. reinhardtii where significant hydrodynamic interaction is likely to occur differs qualitatively from a puller stresslet, and can be described by a simple three-Stokeslet model.     

Solving symmetric mixed-model multi-level just-in-time scheduling problems

The generation of leveled production schedules is of high importance for mixed-model assembly lines whose parts and materials are supplied just-in-time by multi-level production processes. The Output Rate Variation problem is the standard mathematical representation of this complex level scheduling problem and has been extensively studied by research thus far. This work identifies novel symmetries in solution sequences of this problem class and shows how these insights can be used to improve exact solution procedures presented in the literature. The effectiveness of the modifications is evaluated by a computational study.