Emulsification in binary liquids containing colloidal particles: a structure-factor analysis

We present a quantitative confocal-microscopy study of the transient and final microstructure of particle-stabilised emulsions formed via demixing in a binary liquid. To this end, we have developed an image-analysis method that relies on structure factors obtained from discrete Fourier transforms of individual frames in confocal image sequences. Radially averaging the squared modulus of these Fourier transforms before peak fitting allows extraction of dominant length scales over the entire temperature range of the quench. Our procedure even yields information just after droplet nucleation, when the (fluorescence) contrast between the two separating phases is scarcely discernable in the images. We find that our emulsions are stabilised on experimental time scales by interfacial particles and that they are likely to have bimodal droplet-size distributions. We attribute the latter to coalescence together with creaming being the main coarsening mechanism during the late stages of emulsification and we support this claim with (direct) confocal-microscopy observations. In addition, our results imply that the observed droplets emerge from particle-promoted nucleation, possibly followed by a free-growth regime. Finally, we argue that creaming strongly affects droplet growth during the early stages of emulsification. Future investigations could clarify the link between quench conditions and resulting microstructure, paving the way for tailor-made particle-stabilised emulsions from binary liquids.Comment: http://iopscience.iop.org/0953-8984/22/45/455102

Selektive Hydroxylierung von Kohlenwasserstoffen mit Hilfe biologischer Verfahren am Beispiel der Herstellung von Phenol aus Benzol Abschlussbericht

A biotechnological process for selective hydroxylation of aromatic compounds was to be developed. Phenol production was used as an example. It can be produced in principle either from benzene or from toluene. The first phase of the project focused on toluene, which is tolerated better by bacteria, and the reaction of toluene into benzoic acid produces just as many reduction equivalents as required for oxidation of benzoic acid to benzoic acid-cis-1,2-dihydrodiol. Two strains of bacteria were developed specially for this purpose. The first was the toluene-tolerant strain Pseudomonas putida Idaho (Cruden et al., 1992) in which the benzoic acid-cis-1,2-dihydrodiol dehydrogenase genes were inactivated. The second was a derivative of the strain Pseudomonas putida U-JT103 (Rossiter et al., 1987; Jenkins eta al., 1995; Morawski et al., 1997) which is known to be capable of converting benzoic acid into benzoic acid-cis-1,2-dihydrodiol just like Ralstonia eutropha B9. Although both bacterial strains were capable of converting toluene into benzoic acid-cis-1,2-dihydrodiol, it was not possible so far to produce stoichiometric amounts of benzoic acid-cis-1,2-dihydrodiol from toluene or its metabolites.Ziel des Forschungsvorhabens war es, ein biotechnologisches Verfahren zur selektiven Hydroxylierung von aromatischen Verbindungen am Beispiel der Herstellung von Phenol zu entwickeln. Wie in der Zielsetzung ausgefuehrt gibt es prinzipiell die Moeglichkeit Benzol oder Toluol als Ausgangsverbindungen einzusetzen. Aufgrund der Tatsache, dass (i) Toluol von Bakterien besser toleriert wird als Benzol und dass (ii) der Umsatz von Toluol zur Benzoesaeure genauso viele Reduktionsaequivalente liefert wie fuer die Oxidation von Benzoesaeure zu Benzoesaeure-cis-1,2-dihydrodiol notwendig sind, wurde im Laufe der ersten Phase des Projektes beschlossen, ein Verfahren ausgehend von Toluol zu entwickeln. Hierfuer war es notwendig Produktionsstaemme zu konstruieren, die in der Lage sind, Toluol zu Benzoesaeure-cis-1,2-dihydrodiol umzusetzen. Es gelang zwei solche Produktionsstaemme mittels molekularbiolgogischer Methoden zu erhalten. Bei dem einen Konstrukt handelt es sich um den Toluol tolerierenden Bakterienstamm Pseudomonas putida Idaho (Cruden et al., 1992), bei dem die Benzoesaeure-cis-1,2-dihydrodiol-Dehydrogenase/Gene inaktiviert wurden. Bei dem zweiten Konstrukt handelt es sich um eine Derivat des Bakterienstammens Pseudomonas putida U-JT103 (Rossiter et al., 1987; Jenkins et al., 1995; Morawski et al., 1997), von dem bekannt war, dass er, entsprechend wie Ralstonia eutropha B9, Benzoesaeure in Benzoesaeure-cis-1,2-dihydrodiol umwandeln kann. Auf diesen Stamm wurde ein Modul mit den benoetigten Genen der Toluoloxidation uebertragen. Obwohl fuer beide Staemme gezeigt werden konnte, dass sie Toluol zu Benzoesaeure-cis-1,2-dihydrodiol umsetzen koennen, ist es bislang nicht gelungen, Benzoesaeure-cis-1,2-dihydrodiol in stoechiometrischen Mengen aus Toluol oder dessen Metaboliten herzustellen. (orig.)SIGLEAvailable from TIB Hannover: F02B1566 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung und Forschung, Berlin (Germany)DEGerman

Untersuchung ueber allergische Reaktionen bei Exposition gegen Platinverbindungen Schlussbericht

Available from TIB Hannover: F96B738+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Review Article: recent advances in metal-ceramic brazing Artigo Revisão: avanços recentes em brasagem metal-cerâmica

Metal-ceramic joining has slowly but steadily become an important manufacturing step. The evolution of joining processes has allowed ceramics to be used in combination with metals in a number of hybrid devices from traditional light bulbs and seals to improved cutting tools and modern monitoring and measuring electronic devices. New joining methods and newer approaches to conventional methods have been developed aiming at joints characterized by improved reliability, and interfaces capable of withstanding high-temperature resistance with minimum residual stresses. A summary of recent improvements on alternative approaches to ceramic-metal joining as well as new developments on brazing are presented herein. The present review also focuses on recent advances towards brazing metallized ceramics and the selection of filler alloys, since in a scenario that includes joining by laser and direct bonding with liquid transient phases, brazing continues to be by far the most widely used approach to joining as a result of its low-cost and possibility to join intricate geometries for large-scale production. Finally, methods to evaluate the mechanical strength and residual thermal stresses are presented in addition to alternative approaches to minimize residual stresses and, consequently, improve joint reliability.<br>O interesse no estudo de métodos de junção-cerâmica para aplicações industriais tem crescido gradativamente ao longo dos anos. A evolução dos processos de união tem permitido a utilização de cerâmicas em conjunto com metais na fabricação de diversos componentes híbridos incluindo lâmpadas tradicionais, juntas para vácuo, ferramentas de corte de alto desempenho e modernos dispositivos eletrônicos de medição e monitoramento. Novos métodos de união e aprimoramentos de métodos convencionais têm sido estudados com o intuito de produzir-se juntas com alta confiabilidade e interfaces capazes de suportar altas temperaturas de trabalho com o mínimo de tensões residuais. O presente trabalho apresenta um panorama dos recentes avanços em técnicas alternativas de união, incluindo união por laser e junção direta com fases líquidas transientes. Além disso, apresenta-se uma discussão sobre novas tendências em brasagem de cerâmicas metalizadas e seleção de ligas de adição, já que este processo continua sendo amplamente utilizado por seu baixo custo de fabricação de grandes lotes de peças. Por fim, métodos de análise de resistência mecânica e tensões residuais são apresentados juntamente com alternativas para melhoria de confiabilidade de juntas por meio da redução de tensões