Definitizable extensions of positive symmetric operators in a Krein space

The Friedrichs extension and the Krein extension of a positive operator in a Krein space are characterized in terms of their spectral functions in a Krein space.     

Kinetics and mechanism of the formation of poly[(1,1,3,3-tetramethyldisiloxanyl)ethylene] and poly(methyldecylsiloxane) by hydrosilylation

The kinetics of the formation of poly(carbosiloxane), as well as of alkyl-substituted poly(siloxane), by Karstedt's catalyst catalyzed hydrosilylation were investigated. Linear poly(carbosiloxane), poly[(1,1,3,3-tetramethyldisiloxanyl)ethylene], (PTMDSE), was obtained by hydrosilylation of 1,3-divinyltetramethyldisiloxane (DVTMDS) and 1,1,3,3-tetramethyldisiloxane (TMDS), while alkyl-substituted poly(siloxane), poly(methyldecylsiloxane), (PMDS), was synthesized by hydrosilylation of poly(methylhydrosiloxane) (PMHS) and 1-decene. To investigate the kinetics of PTMDSE formation, two series of experiments were performed at reaction temperatures ranging from 25 to 56 °C and with catalyst concentrations ranging from 7.0 × 10⁻⁶ to 3.1 × 10⁻⁵ mol Pt/mol CHCH₂. A series of experiments was performed at reaction temperatures ranging from 28 to 48 °C, with catalyst concentrations of 7.0 ×10⁻⁶ mol of Pt per mol of CHCH₂, when kinetics of PMDS formation was investigated. All reactions were carried out in bulk, with equimolar amounts of the reacting Si H and CHCH₂ groups. The course of the reactions was monitored by following the disappearance of the Si H bands using quantitative infrared spectroscopy. The results obtained showed typical first order kinetics for the PTMDSE formation, consistent with the proposed reaction mechanism. In the case of PMDS an induction period occurred at lower reaction temperatures, but disappeared at 44 °C and the rate of Si H conversion also started to follow the first-order kinetics. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2246–2258, 2007     

A new approach to predict the biological activity of molecules based on similarity of their interaction fields and the logP and logD values: application to auxins

The activity of a biological compound is dependent both on specific binding to a target receptor and its ADME (Absorption, Distribution, Metabolism, Excretion) properties. A challenge to predict biological activity is to consider both contributions simultaneously in deriving quantitative models. We present a novel approach to derive QSAR models combining similarity analysis of molecular interaction fields (MIFs) with prediction of logP and/or logD. This new classification method is applied to a set of about 100 compounds related to the auxin plant hormone. The classification based on similarity of their interaction fields is more successful for the indole than the phenoxy compounds. The classification of the phenoxy compounds is however improved by taking into account the influence of the logP and/or the logD values on biological activity. With the new combined method, the majority (8 out of 10) of the previously misclassified derivatives of phenoxy acetic acid are classified in accord with their bioassays. The recently determined crystal structure of the auxin-binding protein 1 (ABP1) enabled validation of our approach. The results of docking a few auxin related compounds with different biological activity to ABP1 correlate well with the classification based on similarity of MIFs only. Biological activity is, however, better predicted by a combined similarity of MIFs + logP/logD approach.     

Application of the ring oven method to the determination of dyestuffs

Summary The Weisz ring oven method has been applied to the semiquantitative determination of indigo carmine, erythrosin A, amaranth O, new coccine, Victoria blau B, tartrazine, azorubin S, alizarin S, eosin, light green SF, Guinea green B, fuchsin, eriochrome black T, saphranine, ponceau 3 R, cyanine, gelborange S, and methyl violet 6 B. The amount of dye needed ranges from 0.5 to 20g, and the error is generally less than 5%. The method has been used for the determination of azorubin S, methyl violet 6 B, tartrazine, and amaranth O in various materials.

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Zusammenfassung Die Ringofenmethode vonWeisz wurde für die semiquantitative Bestimmung folgender Farbstoffe angewendet: Indigocarmin, Erythrosin A, Amaranth O, Neucoccin, Viktoria blau B, Tartrazin, Azorubin S, Alizarin S, Eosin, Lichtgrün SF, Guineagrün B, Fuchsin, Eriochromschwarz T, Saphranin, Ponceau 3 R, Cyanin, Gelborange S und Methylviolett 6 B. Die dazu nötige Farbstoffmenge beträgt 0,5 bis 20g, der Fehler ist im allgemeinen geringer als 5%. Die Methode wurde für die Bestimmung von Azorubin S, Methylviolett 6 B, Tartrazin und Amaranth O in verschiedenen Materialien angewendet.

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Résumé On a appliqué la méthode du four annulaire deWeisz au dosage semi-quantitatif du carmin d'indigo, de l'érythrosine A, de l'amaranthe O, de la coccine nouvelle, du bleu Victoria B, de la tartrazine, de l'azorubine S, de l'alizarine S, de l'éosine, du vert lumière SF, du vert Guinée B, de la fuchsine, du noir ériochrome T, de la safranine, du ponceau 3 R, de l'orangé jaune, de la cyanine S et du violet de méthyle 6 B. La quantité de colorant nécessaire va de 0,5 à 20g et l'erreur est généralement inférieure à 5%. On a appliqué la méthode au dosage de l'azorubine S, du violet de méthyle 6 B, de la tartrazine et de l'amaranthe O dans diverses substances.

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We wish to thank Mrs.Lidija Pfendt of the Faculty of Sciences in the University of Belgrade for doing the spectrophotometric analyses.     

The application of levulinic acid and 5-nitro-2-furylmethylene diacetate in the total synthesis of some novel biologically active (5-nitro-2-furyl)azomethines

Summary The syntheses andin vitro antibacterial and antifungal evaluation of certain (5-nitro-2-furyl)azomethines with different heterocyclic nuclei are described.

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Die Anwendung von Lävulinsäure und 5-Nitro-2-furylmethylendiacetat in der Totalsynthese einiger neuer biologisch aktiver (5-Nitro-2-furyl)azomethine

Zusammenfassung Es wird die Synthese und diein-vitro-antibakterielle und antifungale Wirksamkeit für bestimmte (5-Nitro-2-furyl)azomethine mit verschiedenen heterocyclischen Kernen beschrieben.

     

Semiquantitative determination of micro amounts of phenols using the ring colorimetry method

Summary The semiquantitative determination of micro amounts of pyrocatechol, resorcinol, hydroquinone, pyrogallol, phloroglucinol, andp-nitrophenol using the Weisz ring colorimetry method has been described. The results obtained deviated, on an average, from those calculated by about 4% and the amount of phenol required for one determination was about 4 g.

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Zusammenfassung Die halbquantitative Bestimmung von Mikromengen Brenzcatechin, Resorcin, Hydrochinon, Pyrogallol, Phloroglucin und p-Nitrophenol mit Hilfe der vonWeisz angegebenen Ringkolorimetrie wurde beschrieben. Die Resultate weichen von den berechneten Werten durchschnittlich um etwa 4% ab, wobei für eine Bestimmung etwa 4 g benötigt werden.

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Résumé On décrit le dosage semiquantitatif de microquantités de pyrocatéchol, résorcinol, hydroquinone, pyrogallol, phloroglucinol etp-nitrophénol, à l'aide de la méthode colorimétrique annulaire deWeisz. Les résultats obtenus se sont écartés, en moyenne, d'environ 4% d'avec ceux calculés et la quantité de phénol nécessaire pour un dosage s'élevait à 4 g environ.

     

Electrochemical generation of manganese(III) and behaviour of the generated oxidant in acetic acid in the presence of perchlorate ions

Summary Research was carried out to determine conditions for the anodic generation of manganese(III) with high current efficiency in solutions of sodium perchlorate in acetic acid, and to examine the behaviour of the oxidant thus generated. The effects of water and acetic anhydride on current efficiency in the generation of the oxidant was also examined. The formal redox potential of the Mn(III)/ Mn(II) system is decreased with increasing concentrations of sodium acetate in the solution. The effect of sodium perchlorate and perchloric acid concentrations is the reverse. Procedures for coulometric titrations of a number of substances with the generated oxidant were developed, end point being detected using biamperometric and potentiometric methods. Perchloric acid accelerates the oxidation of certain substances with manganese(III) in acetic acid and increases the sensitivity of end-point detection using the potentiometric method.

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Elektrochemische Erzeugung von Mangan(III) und das Verhalten dieses Oxydationsmittels in Essigsäure bei Gegenwart von Perchlorat

Zusammenfassung Die Bedingungen der anodischen Erzeugung von Mangan(III) mit hoher Stromausbeute in Essigsäure, nach Zugabe von Natriumperchlorat wurden untersucht; das elektrochemische Verhalten des so dargestellten Oxydationsmittels wurde ebenfalls untersucht. Der Einfluß von Wasser und Essigsäureanhydrid auf die prozentuelle Stromausbeute des erwähnten Oxydationsmittels wurde verfolgt. Das Formalredoxpotential des Systems Mn(III)/ Mn(II) sinkt bei Erhöhung der Konzentration an Natriumacetat in der Lösung. Perchlorsäure wie auch Natriumperchlorat üben eine entgegengesetzte Wirkung aus und führen zur Steigerung des Formalredoxpotentials bei Erhöhung ihrer Konzentration. Verfahren zur coulometrischen Titration verschiedener Substanzen mittels biamperometrischer oder potentiometrischer Erfassung des Titrationsendpunktes wurden ausgearbeitet. In Gegenwart von Perchlorsäure wächst die Geschwindigkeit der Oxydation einiger Substanzen in Essigsäure in Gegenwart von Mn(III) und auch die Empfindlichkeit der Endpunktbestimmung verbessert sich.

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Presented at the 9th International Symposium on Microchemical Techniques, Amsterdam, August 28–September 2, 1983.     

Thermal study and mechanism of Ag2S oxidation in air

The results of thermal study and mechanism of the oxidation process of synthetic Ag₂S in air are presented in this article based on the comparative analysis of DTA and XRD results, as well as by constructed phase stability diagrams (PSD) for the Ag–S–O system.     

“You have to get wet to learn how to swim” applied to bridging the gap between research into personnel scheduling and its implementation in practice

Personnel scheduling problems have attracted research interests for several decades. They have been considerably changed over time, accommodating a variety of constraints related to legal and organisation requirements, part-time staff, flexible hours of staff, staff preferences, etc. This led to a myriad of approaches developed for solving personnel scheduling problems including optimisation, meta-heuristics, artificial intelligence, decision-support, and also hybrids of these approaches. However, this still does not imply that this research has a large impact on practice and that state-of-the art models and algorithms are widely in use in organisations. One can find a reasonably large number of software packages that aim to assist in personnel scheduling. A classification of this software based on its purpose will be proposed, accompanied with a discussion about the level of support that this software offers to schedulers. A general conclusion is that the available software, with some exceptions, does not benefit from the wealth of developed models and methods. The remaining of the paper will provide insights into some characteristics of real-world scheduling problems that, in the author’s opinion, have not been given a due attention in the personnel scheduling research community yet and which could contribute to the enhancement of the implementation of research results in practice. Concluding remarks are that in order to bridge the gap that still exists between research into personnel scheduling and practice, we need to engage more with schedulers in practice and also with software developers; one may say we need to get wet if we want to learn how to swim.