An improved sonochemical reactor

The design and optimization of sonochemical apparatus are still open to advancement. Under high-intensity ultrasound reaction rates and yields are mainly influenced by the characteristics of transducer and reactor. Several useful improvements are introduced and described. In order to achieve uniformity of the acoustic field and optimal acoustic streaming in every part of the reaction vessel (a Teflon tube), the reactor can be made to rotate eccentrically around the horn axis and the probe to move alternatively up and down by a pre-determined excursion at a chosen speed. Continuous high-power irradiation is feasible without any time limit because the whole probe system is refrigerated by an oil forced-circulation circuit connected to a chiller. The apparatus can control a number of important reaction parameters: modified atmosphere, reaction temperature, tunable frequency and constant amplitude. Excellent performance was observed on several reactions, such as the chemical modification of chitosan, a poorly soluble biopolymer.     

Synthesis and Antiproliferative Activity of Cyano and Amidino Substituted 2-Phenylbenzothiazoles

Summary. Series of cyano, dicyano, amidino, and diamidino substituted 2-phenylbenzothiazoles were prepared. Mono- and dicyano substituted benzothiazoles were obtained by condensation of appropriate substituted benzaldehydes with 2-aminothiophenol or 4-amino-3-mercaptobenzonitrile. The appropriate amidines or diamidines were prepared by Pinner reaction. The compounds were tested against breast, prostate, and lung cancer cell lines in a 72 h cytotoxicity assay. Many of the compounds had at 10 μM activity equivalent to 2-(4-aminophenyl)benzothiazole, while four compounds had significantly better activity, particularly in the breast cancer model.     

A computer method to determine the kinetic law of solid-state reactions from DSC curves

A computer program has been worked out to evaluate the activation energy, the Arrhenius pre-exponential factor and the mechanism of solid-state reactions from non-isothermal measurements. A univocal determination of the reaction mechanism is obtained by the simultaneous application of two selection criteria: (a) activation energy value by the Ozawa method; (b) degree of linearity in the <Satava method.A modification of the Rogers and Smith method was then used to obtain empirically complete agreement between kinetic expression and experimental results when the kinetic law has to be improved to account for a whole experimental curve.The accuracy of the computer method has been checked through a calibration of the program by means of 16 theoretical functions proposed by <Sesták.     

On the averaging principle for one-frequency systems. Seminorm estimates for the error

We extend some previous results of our work (Morosi and Pizzocchero in J. Phys. A: Math. Gen. 39:3673–3702, 2006) on the error of the averaging method, in the one-frequency case. The new error estimates apply to any separating family of seminorms on the space of the actions; they generalize our previous estimates in terms of the Euclidean norm. For example, one can use the new approach to get separate error estimates for each action coordinate. An application to rigid body under damping is presented. In a companion paper (Morosi and Pizzocchero, 2006), the same method will be applied to the motion of a satellite around an oblate planet.     

Absence of turbulence in a unidimensional model of fluid motion (Burgers model)

Summary We study a quasilinear partial differential equation which is a classical unidimensional model of fluid motion (Burgers equation). We consider the problem in a finite interval with stationary boundary conditions. The aim is to see whether the model shows transitions in the asymptotic behaviour as viscosity varies. We show that there is always a unique stationary solution, which is explicitely exhibited, and, by using the Hopf-Cole transformation, that it is globally attractive for any value of the viscosity, both in the homogeneous and inhomogeneous case.

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Sommario In questo lavoro si considera un classico modello unidimensionale della fluidodinamica, consistente in un'equazione alle derivate parziali parabolica quasilineare (equazione di Burgers). Si considera il problema in un intervallo con condizioni al contorno stazionarie. L'intento è quello di indagare se il modello presenta transizioni nel comportamento asintotico al variare della viscosità. Facendo uso della trasformazione di Hopf-Cole si trova che la soluzione stazionaria (che viene calcolata esplicitamente) è globalmente attrattiva per ogni valore della viscosità, sia nel caso omogeneo che in presenza di una forza.

     

Preparation and characterization of some pyridine-2,6-dicarboxylato thorium(IV) complexes

Summary The preparation of complexes of pyridine-2,6-dicarboxylic acid (H₂PDC) with thorium(IV) is reported and discussed. The reactivity of Th(PDC)₂ (H₂O)₄ (1) was tested by preparing adducts with some neutral ligands. The complexes were characterized by i.r. spectroscopy, elemental analysis and thermal behaviour. Preliminary information on the structure of(1) obtained by x-ray analysis, are also reported.Author to whom all correspondence should be directed.     

The application of microchemistry in forensic chemistry

Summary The application, then, of microchemistry in the field of forensic chemistry is unlimited. The identification of blood and body fluids, paint, hairs and fibers, narcotics and drugs, glass fragments, soil, the examination of dust, stains, explosives, metals, chemical accelerants used in arson cases, the examination of powder for firearms, the search for powder residues remaining on clothing or in the barrel of a firearm, the identification of poisonous mixtures, the analysis of tobacco, liquor, and innumerable other objects should convince any skeptic of the tremendous importance of microchemistry in the field of forensic chemistry.Though instrumental analysis may be rapid, modern, and accurate the techniques of microchemistry and instrumental analysis should supplement rather than try to replace one another.

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Zusammenfassung Die Identifizierung von Bodenproben, Glasstücken, die Untersuchung von Staub, Flecken, Explosivstoffen, Metallen, chemischen Brandsätzen, Schießpulver, Pulverrückständen auf Kleidern oder in Gewehrläufen, die Identifizierung von Giften, die Analyse von Tabak, Getränken und zahlreichen anderen Objekten erweisen die Mikrochemie als wesentlich für die Aufgaben der forensischen Chemie. Wenn auch die instrumentelle Analyse rasch, modern und genau arbeitet, so sollen die Verfahren der Mikrochemie und der instrumentellen Analyse einander ergänzen, statt sich gegenseitig den Rang streitig zu machen.

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Résumé Dans le domaine de la chimie légale, le champ d'applications de la microchimie est illimité. Tout sceptique doit être convaincu de l'importance considérable de ces applications de la microchimie s'il considère qu'elle permet l'identification du sang et des liquides du corps, des peintures, des poils et des fibres, des narcotiques et des drogues, des fragments de verre, des sols, l'examen des poussières, des souillures, des explosifs, des métaux, des accélérateurs chimiques employés lors d'incendies criminels, l'examen des poudres d'armes à feu, la recherche des résidus de poudre subsistant sur des vêtements ou dans le barillet d'une arme à feu, l'identification de mélanges toxiques, l'analyse du tabac, des liqueurs ainsi que d'innombrables autres investigations. Bien que l'analyse instrumentale puisse être rapide, moderne et précise, elle doit compléter les techniques de la microchimie plutôt que de se substituer à elles.