Platinum group element concentrations and osmium isotopic composition in urban airborne particles from Boston, Massachusetts

Platinum, Pd, Rh, and Os were found to occur at elevated concentrations in airborne particles (PM10) collected at urban sites in Boston, MA. Average Pt, Pd, Rh, and Os concentrations were 6.9 +/- 1.9, 8.1 +/- 1.8, 1.50 +/- 0.50, and 0.068 (-0.068 + 0.070) pg m(-3), respectively. Elevated Pt, Pd, and Rh concentrations are attributed to automobile catalysts, which use Pt, Pd, and Rh for the removal of pollutants from engine exhaust gas. An automobile catalyst source is supported by significant correlations between these elements and by a Pt/Rh similar to that in catalysts. Elevated Os concentrations are also believed to be the result of emission from automobile catalysts in which Os occurs as an impurity. The isotopic composition of Os (187Os/ 188Os) ranged from 0.30 to 2.90, indicating large variations in Os sources. Osmium has a predominantly anthropogenic origin at concentrations > 0.1 pg m(-3), whereas natural sources are more important at lower Os concentrations. Osmium isotopic composition also indicates that Pt, Pd, and Rh in Boston air are of almost exclusive anthropogenic origin, with a relatively small natural contribution. Our results indicate that scavenging by rain plays a major role in the atmospheric residence time and environmental fate of PGE.     

The KeY tool

KeY is a tool that provides facilities for formal specification and verification of programs within a commercial platform for UML based software development. Using the KeY tool, formal methods and object-oriented development techniques are applied in an integrated manner. Formal specification is performed using the Object Constraint Language (OCL), which is part of the UML standard. KeY provides support for the authoring and formal analysis of OCL constraints. The target language of KeY based development is Java Card DL, a proper subset of Java for smart card applications and embedded systems. KeY uses a dynamic logic for Java Card DL to express proof obligations, and provides a state-of-the-art theorem prover for interactive and automated verification. Apart from its integration into UML based software development, a characteristic feature of KeY is that formal specification and verification can be introduced incrementally.     

Beitrag zum Messen von Reibtemperaturen an Folien

Zusammenfassung Die technisch bedeutungsvollen Reibtemperaturen lassen sich schwer messen. Deshalb wurde die me?technisch günstige Kombination von umlaufender Welle und ruhender Folie gew?hlt. Aus einer Absch?tzung geht n?mlich hervor, da? die an der Reibstelle entstehende maximale Reibtemperatur nahezu mit der an der Folienrückseite zu messenden Temperatur übereinstimmt. Zum Messen der Temperatur an der Folienrückseite diente eine Ultrarotkamera, weil bei den kleinen umgesetzten Reibenergien nur eine berührungslose Messung der Temperatur Aussicht auf Erfolg verspricht. Die so gemessenen „Reibtemperaturen” wurden mit Berechnungen sowohl nach J. C. Jaeger als auch nach R. Holm verglichen; dabei war die übereinstimmung zwischen experimentellen und theoretischen Werten mangelhaft. Ein nach eigenen Vorstellungen der Verfasser entwickeltes Berechnungsverfahren liefert Ergebnisse, die mit den experimentellen Befunden besser übereinstimmen. Für den hier experimentell nicht untersuchten Fall der bewegten Folie bei ruhender Welle dürften die Berechnungen nach J. C. Jaeger oder H. Blok die auftretenden Reibtemperaturen richtig beschreiben. Mitteilung aus der Bundesanstalt für Materialprüfung, Berlin. Die Verfasser danken Herrn Prof. Dr.-Ing.K. Kirschke, Herrn Dr.-Ing.H. Czichos und Herrn Dipl.-Phys.H. Mewes für das Bereitstellen finanzieller Mittel und das überlassen von Me?ger?ten sowie Herrn Prof. Dr.-Ing.E. Mundry für Diskussionsbeitr?ge zum theoretischen Teil dieser Untersuchung.     

Effect of diet composition and fasting on lipogenesis in lean and polygenic obese mice

A line of mice was developed which exhibited spontaneous obesity when fed commercial laboratory ration low in fat content. Obese mice were compared to a nonobese related line to determine whether energy source in the diet would affect onset of obesity. Experimental diets-beef tallow (38% of calories as beef fat and 2% as corn oil), corn oil (40% corn oil) or low-fat (2% corn oil)-were instituted ad libitum at the time of weaning. When the mice reached 6 months of age, lipogenesis was investigated by injecting intravenously³H₂O and glucose-U-¹⁴C.³H₂O and glucose-U-¹⁴C incorporation into fatty acids of fed mice was greater for obese than for lean mice. Fatty acid synthesis was inhibited by high-fat diets compared to low-fat diet in both lines. Of the 2 high-fat diets, the corn oil diet inhibited fatty acid synthesis about twice as much as beef tallow diet. There was no line effect on tritium incorporation into cholesterol. Cholesterol synthesis from glucose-U-¹⁴C was greater in obese than lean mice. Diets had no effect on tritium and glucose-U-¹⁴C incorporation into cholesterol. Fasting reduced fatty acid synthesis in all mice, but total body fatty acid synthesis was not affected by lines or dietary treatment under fasted conditions. These data suggest that degree of lipogenesis, in part, explains obesity. A failure of inhibition of lipogenesis or an enhanced efficiency in fat deposition by feeding beef tallow compared to corn oil diet may explain the fact that lean mice fed the beef tallow diet tended to be more obese that lean mice fed corn oil or low-fat diets.     

Zur Deformation eines frei aufliegenden Biegebalkens bei Lasteinleitung über ein starres,kreisförmiges Werkzeug

Beim Hochkantbiegen eines Rechteckbalkens über ein starres, kreisförmiges Werkzeug kann eine Umformung nur mit einem Werkzeughalbmesser unterhalb eines kritischen Wertes erreicht werden. Es wird gezeigt, daß eine kreisförmige Formgebung in nur einem Arbeitsgang nicht erzielt werden kann.     

Effect of the position of Cl-substituents on the nitrile formation during the ammoxidation of chlorotoluenes

The conversion of isomeric chlorotoluenes to the corresponding benzonitriles by heterogeneous catalytic ammoxidation was studied. The reaction was carried out over (NH₄)₂[(VO)₃(P₃O₇)₂] as catalyst generated under the applied ammoxidation conditions by a solid-state reaction of the precursor compound VOHPO₄· 0.5H₂O. Activity and selectivity of the ammoxidation of chlorotoluenes are shown to depend on the position of the Cl-substituents causing a changed accessibility of the methyl group and a possible different electronic stabilization of the reaction intermediates.     

In situ-electron spin resonance: a useful tool for the investigation of vanadium phosphate catalysts (VPO) under working conditions

Differently prepared (VO)₂P₂O₇ phases and an amorphous V³⁺PO catalyst were investigated under conditions of the selective n-butane oxidation and the toluene ammoxidation, respectively, using a self-constructed in situ-ESR flow reactor in the X-band. By examining the temperature dependence and the line shape of the ESR signals exchange integrals as well as the 2nd and the 4th moment were obtained. These parameters characterize the spin—spin exchange behaviour and, thus, structural and electronic disorder of the catalysts. Increasing structural disorder was found to improve the catalytic performance in the n-butane oxidation. For both catalytic processes a significant reversible alteration of the ESR line shape was observed under working conditions which is discussed in terms of a perturbation of exchange interactions between neighbouring vanadyl centres near the surface the oxidation state of which is assumed to fluctuate between +4 and +5 during the catalytic reaction.