A quartz crystal microbalance study of the adsorption of asphaltenes and resins onto a hydrophilic surface

The adsorption of extracted and purified samples of asphaltenes and resins onto gold surfaces has been studied as a function of bulk concentration using a quartz crystal microbalance with dissipation measurements (QCM-D). With this device, which works equally well in transparent, opaque, and nontransparent samples, the adsorbed amount is measured through a change in resonant frequency of the quartz oscillator. The measured change in dissipation reports on changes in layer viscoelasticity and slip of the solvent at the surface. The results show that the adsorbed amount for resins from heptane corresponds to a rigidly attached monolayer. The adsorbed amount decreases with increasing amount of toluene in the solvent and is virtually zero in pure toluene. Asphaltenes, on the other hand, adsorb in large quantities and the mass and dissipation data demonstrate the presence of aggregates on the surface. The aggregates are firmly attached and cannot be removed by addition of resins. On the other hand, resins and asphaltenes associate in bulk liquid and the adsorption from mixtures containing both resins and asphaltenes is markedly different from that obtained from the pure components. Hence, we conclude that preformed resin aggregates adsorb to the surface. These results are compared and discussed in relation to adsorption from crude oil diluted in heptane/toluene mixtures.     

Enzymatic One-Step Reduction of Carboxylates to Aldehydes with Cell-Free Regeneration of ATP and NADPH

The direct generation of aldehydes from carboxylic acids is often a challenging synthetic task but undoubtedly attractive in view of abundant supply of such feedstocks from nature. Though long known, biocatalytic carboxylate reductions are at an early stage of development, presumably because of their co-factor requirement. To establish an alternative to whole-cell-based carboxylate reductions which are limited by side reactions, we developed an in vitro multi-enzyme system that allows for quantitative reductions of various carboxylic acids with full recycling of all cofactors and prevention of undesired over-reductions. Regeneration of adenosine 5′-triphosphate is achieved through the simultaneous action of polyphosphate kinases from Meiothermus ruber and Sinorhizobium meliloti and β-nicotinamide adenine dinucleotide 2′-phosphate is reduced by a glucose dehydrogenase. Under these conditions and in the presence of the carboxylate reductases from Neurospora crassa or Nocardia iowensis, various aromatic, heterocyclic and aliphatic carboxylic acids were quantitatively reduced to the respective aldehydes.     

Ueber die Differentialgleichung der Functionen des elliptischen Cylinders

Ohne Zusammenfassung     

Versuche über die Elektrolyse von Bronzen mit Silberzusätzen

Ohne Zusammenfassung     

Quantum Mechanics from Focusing and Symmetry

A foundation of quantum mechanics based on the concepts of focusing and symmetry is proposed. Focusing is connected to c-variables—inaccessible conceptually derived variables; several examples of such variables are given. The focus is then on a maximal accessible parameter, a function of the common c-variable. Symmetry is introduced via a group acting on the c-variable. From this, the Hilbert space is constructed and state vectors and operators are given a definite interpretation. The Born formula is proved from weak assumptions, and from this the usual rules of quantum mechanics are derived. Several paradoxes and other issues of quantum theory are discussed.     

Die colorimetrische Bestimmung der Komponenten einer 3,4-Dioxyphenylalanin-Tyrosinmischung

Ohne Zusammenfassung     

Die Bindung von Zink durch Zellwände von Chlorella

Zusammenfassung Aus Chlorella pyrenoidosa präparierte Zellwände wurden durch Analyse und pH-Titration gekennzeichnet. Die Bindung von markiertem Zink durch die Zellwände, die reversibel ist, erfolgt an 2 Arten aktiver Stellen, die sich durch Affinität und Kapazität unterscheiden. Die Zahlenwerte dieser Größen wurden durch Aufnahme einer aus den beiden Komponenten zusammengesetztenLangmuir-Isotherme bestimmt. Die Verdrängung des Zinks von den Zellwänden durch mehrere Arten zweiwertiger Kationen wurde durch Gleichgewichtsdialyse gemessen und auf Grund der erhaltenen Affinitätsreihe die Natur der bindenden Gruppen diskutiert.

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Binding ofZn by cell walls of Chlorella

Cell wall material prepared from Chlorella pyrenoidosa was characterized by analysis and pH titration. Labelled zinc is found to be bound, reversibly, by 2 kinds of active sites. They differ in affinities and capacities, and these were determined from a 2-componentLangmuir isotherm. The displacement of zinc from the cell walls by several kinds of 2-valent cations was measured by equilibrium dialysis. The nature of the sites was discussed on the basis of the affinity series obtained.

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