Modern Modelling Methods in Drying

Several modern modelling techniques are presented as tools for drying science and technology, namely pore networks, discrete element method and population balances. After first presenting results from their own research, the authors indicate what future contributions to a better understanding of the drying process at different levels—single porous particles, agitated and fluidised beds—may be expected.     

Umweltanalytische Antimon-Bestimmung durch inverse Wechselstromvoltammetrie mit der Quecksilberfilmelektrode

Zusammenfassung Die Ergebnisse neuerer Untersuchungen deuten auf eine bisher weitgehend unterschätzte Toxizität verschiedener Antimonverbindungen hin, weshalb diese auch aus ökotoxikologischer Sicht eine weitaus größere Beachtung verdienen sollten. Hierzu ist eine leistungsstarke Analytik Voraussetzung.Unter Anwendung der inversen Wechselstromvoltammetrie läßt sich Antimon nach vorausgegangener Probenvorbereitung aus einer salz-perchlorsauren Lösung an einer rotierenden Glas-Kohlenstoffelektrode, auf der elektrolytisch ein dünner Quecksilberfilm abgeschieden wurde, auch noch im Spurenbereich mit einer reagentienblindwertbedingten Nachweisgrenze von 40 ng/l bestimmen. Der Einfluß verschiedener Abscheideparameter auf den Bestimmungsvorgang wird untersucht und die Anwendbarkeit des Verfahrens anhand einiger umweltrelevanter Matrices gezeigt.

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Antimony determination in environmental material by inverse ac voltammetry with the mercury film electrode

Summary The results of recent investigations suggest a toxicity of various antimony compounds which has been greatly underestimated so far. This is the reason why much more attention should be paid to it also from the ecotoxicological point of view. The prerequisite is an efficient analysis.By use of the inverse alternating current voltammetry even traces of antimony can be determined after appropriate sample conditioning from a hydrochloric-perchloric solution on a rotating glass-carbon electrode on which a thin mercury film has been separated electrolytically. The detection limit is 40 ng/l, a value fixed by the reagent blank test. The influence of various separation parameters on the analytical procedure is studied and the applicability of the technique is demonstrated by the example of some environmentally relevant matrices.

     

Photonic integrated transceiver for the access network

To reduce fabrication costs of fibre-optic terminal modules for interactive services, an InGaAsP/InP chip fabrication process has been developed for monolithic integration of a strained-layer multiple quantum well laser, a monitor diode and a photoreceiver with a 1300/1530nm filter. Reception responsivity and output power of the chips are 0.1 AW^-1 at 1300nm wavelength and 4.5mW at 1530nm wavelength, respectively. At present, complete modules with fibre pigtail exhibit 0.7mW launch power, but 1.4 mW is expected with the latest chips.     

Etudes photochimiques en série hétérocyclique. V. Mise en évidence d'oxazoles par photooxydation de thiazoles

Formation of oxazoles as by-products of photooxydation of thiazoles In the presence of air, light (high pressure mercury lamp) and iodine as sensitizer, benzene solution of arylthiazoles 2 , 3 and 13 (see scheme 1) were converted into a mixture of photoisomers and aryloxazoles (see scheme 2). Upon shorter times of irradiation under oxygen in chloroform containing methylene blue as a sensitizer 2,4,5-triphenylthiazole (7) is converted in 2,4,5-triphenyloxazole. Under usual photooxidation conditions, in methanol as solvent, most of arylthiazoles studied gave a mixture of nitriles, amides, acids esters and diketones. In the case of thiazole 7 , the corresponding oxazole was also found. A possible mechanism for the photochemical oxidation of arylthiazoles to aryloxazoles, via 2,5- and 4,5-endo-peroxides, may be proposed (see schemes 5 and 6).     

Static properties of end-tethered polymers in good solution: a comparison between different models

We present a comparison between results, obtained from different simulation models, for the static properties of end-tethered polymer layers in good solvent. Our analysis includes data from two previous studies--the bond fluctuation model of Wittmer et al. [J. Chem. Phys. 101, 4379 (1994)] and the off-lattice bead-spring model of Grest and Murat [Macromolecules 26, 3108 (1993)]. Additionally, we explore the properties of a similar off-lattice model simulated close to the Theta temperature. We show that the data for the bond fluctuation and the Grest-Murat model can be analyzed in terms of scaling theory because chains are swollen inside the Pincus blob. In the vicinity of the Theta point the structure of the chains is essentially Gaussian in the Pincus blob. Therefore, the data for the second off-lattice model can be compared quantitatively to the self-consistent field theory. Different ways to determine the parameters of the self-consistent field theory are discussed.