Effect of noble metals in the decomposition of nitrous oxide over Fe-ferrierites

The decomposition of nitrous oxide was studied over Fe-ferrierite, Me-ferrierites and Fe/Me-ferrierites (Me: Pt, Rh and Ru). Flow as well as batch experiments were carried out and showed a synergy between Fe and Me ions. Ions of noble metals in Fe-ferrierite increased the catalytic activity in the sequence Pt < Rh ≅ Ru. Addition of NO substantially decreased the decomposition of N₂O over Rh/ferrierite and Ru/ferrierite, but not over bimetallic ferrierites. NO _x species created during the decomposition of nitrous oxide alone as well as with addition of NO, and employment of nitrous oxide labeled with ¹⁸O allowed us to assume a changing decomposition mechanism in the presence of Me ions in Fe-ferrierites.     

Holz im italienischen Flugzeugbau

Zusammenfassung Grunds?tzliche Betrachtungen über die Verwendung von Holz im Flugzeugbau. Der Holzflugzeugbau in Italien. Werkstoffe, Fertigungsweisen und Erfahrungen. Vgl. A. Guglielmetti, Entwicklungsrichtlinien der italienischen Luftfahrttechnik. Z. Luftwissen Bd. 8 (1941) S. 209 bis 215.     

Berechnung der magnetischen Kreise mit Hilfe der fiktiven Durchflutungen

Übersicht Es wird gezeigt, daß man magnetische Spannungen in einzelnen Teilen von magnetischen Kreisen als Durchflutungen von zusätzlichen fiktiven Wicklungen in das Gleichungssystem zur Berechnung der Wicklungsströme einführen kann. Diese Lösungsmethode hat den Vorteil, daß geometrisch komplizierte oder nichtlineare Teile von magnetischen Kreisen auf geometrisch einfachere bzw. lineare Modelle zurückgeführt werden, deren Berechnung bereits bekannt oder mit modernen Rechnern problemlos ist. Die sich ergebenden Transformationen haben einen klaren physikalischen Hintergrund, so daß auch die Rechenergebnisse überschaubar bleiben.

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Calculation of magnetic circuits by means of fictitious ampere-turns

It is shown that magnetic potential differences in the individual parts of magnetic circuits can be considered as ampere-turns of fictitious additional windings and introduced in the equation system for winding currents in this form. This method has the advantage that geometrically complicated and nonlinear parts of magnetic circuits can be transformed into simpler and linear elements respectively, the calculation of which is already known or simply feasible with the help of modern computers. The transformations used in the approach have a solid physical significance so that also the results are intuitive.

     

Trees,grids, and MSO decidability: From graphs to matroids

Monadic second order (MSO) logic has proved to be a useful tool in many areas of application, reaching from decidability and complexity to picture processing, correctness of programs and parallel processes. To characterize the structural borderline between decidability and undecidability is a classical research problem here. This problem is related to questions in computational complexity, especially to the model checking problem, for which many tools developed in the area of decidability have proved to be useful. For more than two decades it was conjectured in [D. Seese, The structure of the models of decidable monadic theories of graphs, Ann. Pure Appl. Logic 53 (1991) 169–195] that decidability of monadic theories of countable structures implies that the theory can be reduced via interpretability to a theory of trees.     

Super/subcritical fluid extractions for preparation of the crystalline titania

Various extraction techniques which use fluids in super/subcritical state (CO₂, H₂O, CH₃OH) were used for the preparation of crystalline TiO₂ from surfactant-mediated titania organogels (the amorphous reaction intermediate products of surfactant-mediated sol-gel synthesis). Crystallinity, purity and texture of TiO₂ powders (titania aerogels) were studied in detail for different treatment modes of titania organogels. Suitable combinations of extraction solvents and extraction temperature and pressure were considered for synthesis of TiO₂ powder crystalline phase (anatase) with high specific surface area and purity (carbon content < 0.1 wt.%). Optimum results were achieved by combined extraction procedures—subcritical water extraction and supercritical fluid extraction or pressurised liquid extraction. Moreover, the possible tuning of the TiO₂ powder pore-size distribution by regulation of temperature at constant pressure for the combined subcritical water extraction and pressurised liquid extraction was found.     

μ‐Consortium: Aufbau einer mobilen Anlage für die Aus‐ und Weiterbildung in der Mikroverfahrenstechnik

A mobile plant for practical training was developed as part of the project μ‐Consortium to integrate micro process engineering into teaching. Lab experiments in the fields of mixing and homogenous reactions, heterogeneous reactions, heat transfer and particle synthesis were worked out to impart knowledge of different process‐engineering operations.     

Furanocoumarins in vegetables: influence of farming system and other factors on levels of toxicants

Furanocoumarins are toxic chemicals that occur naturally in edible food plants such as celery, parsnip, carrot, etc. belonging to the Apiaceae family. Lower levels of these phytochemicals are also found in citrus fruits and other crops representing the Rutaceae family. Since their presence in the human diet represents a food safety issue of concern, more knowledge is needed to reduce consumer exposure. This paper provides an overview of various factors influencing the levels of furanocoumarins in vegetables and processed commodities. Special attention is paid to the comparison of crops from organic and conventional farming systems with regard to levels of furanocoumarins and their changes during storage and processing. Copyright © 2007 Society of Chemical Industry