Nitric oxide decomposition over BaRuxBi1?xO3 (X=0.33, 0.50, 0.67, 1.00) perovskite-like catalysts

The catalytic activity of Ba₂Ru_0.67Bi_1.33O₆, Ba₂RuBiO₆, Ba₃Ru₂BiO₉ and BaRuO₃ towards NO-decomposition prior to and after treatment with NH₃ has been studied. About 100% degree of conversion has been achieved at 400°C for samples with the highest percentage of hexagonal stacking in their crystal structures. It has been shown that the active sites are units of two or three face-sharing [RuO₆] octahedra in which a strong Ru−Ru interaction takes placevia the common faces.     

On the magnetic properties and the phase composition of the Cr2O3?MnOx-system (2 ≥ x ≥ 1.5)

The mixed oxide system Cr₂O₃? MnO_x (2 ≥ x ≥ 1.5) was investigated by X-ray diffraction, by measurements of magnetic susceptibility, and by chemical determination of excess oxygen (BUNSEN'S method). The Presence of the antiferromagnetic oxides Cr₂O₃, β-MnO₂, α-Mn₂O₃ and a ferromagnetic phase Cr_1?yMn_yO₂ was stated. The formation of the latter with fourvalent chromium is explained by a lattice induction effect of the MnO₂ (rutile type).     

Die multikomponenten Formen von Cellulase (EC 3.2.1.4) ausAspergillus oryzae

The enzyme cellulase fromAspergillus oryzae was resolved into four multiple forms, using anion exchange chromatography on DEAE Sephadex A-50 and gel filtration on Sephadex G-75. The stages of fractionation were followed by electrophoresis on cellulose acetate strips. These enzyme forms are characterized by different enzyme activities and isoelectric points.

Herrn Univ.-Prof. Dr.Hans Tuppy zum 65. Geburtstag herzlichst gewidmet.     

Ein Beitrag zur viskosimetrischen Verfolgung der Kinetik bestimmter Enzymreaktionen und Bestimmung der Enzymaktivität

Zusammenfassung Es wurde eine Theorie aufgestellt, die es gestattet, die Kinetik bestimmter enzymatischer Hydrolysen und die Aktivität des daran beteiligten Enzyms zu verfolgen. Die spezif. Aktivitätk des Enzyms ist durch diejenige Reaktionsgeschwindigkeit gegeben, die durch die Einheit der Enzymmasse in der Volumseinheit pro Zeiteinheit bewirkt wird. Nach der hier aufgestellten Theorie hängt die spezif. Aktivität des Enzyms nicht vom Molekulargewicht und der Konzentration des verwendeten Substrates ab.

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A theory has been set for tracing the kinetics of some hydrolysis enzymes, which allows to determine the activity of the enzyme participating in them. The specific activityk of the latter is determined through the reaction rate in a unit of volume by a unit of enzyme mass for a unit of time (cm³·g^–1·sec^–1). According to this theory, the specific activity of the enzyme does not depend on the molecular weight and the concentration of the substrate used.

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Herrn Prof. Dr.T. Trandafilov zum 60. Geburtstag gewidmet.     

Electrokinetic molecular separation in nanoscale fluidic channels

This report presents a study of electrokinetic transport in a series of integrated macro- to nano-fluidic chips that allow for controlled injection of molecular mixtures into high-density arrays of nanochannels. The high-aspect-ratio nanochannels were fabricated on a Si wafer using interferometric lithography and standard semiconductor industry processes, and are capped with a transparent Pyrex cover slip to allow for experimental observations. Confocal laser scanning microscopy was used to examine the electrokinetic transport of a negatively charged dye (Alexa 488) and a neutral dye (rhodamine B) within nanochannels that varied in width from 35 to 200 nm with electric field strengths equal to or below 2000 V m-1. In the negatively charged channels, nanoconfinement and interactions between the respective solutes and channel walls give rise to higher electroosmotic velocities for the negatively charged dye than for the neutral dye, towards the negative electrode, resulting in an anomalous separation that occurs over a relatively short distance (<1 mm). Increasing the channel widths leads to a switch in the electroosmotic transport behavior observed in microscale channels, where neutral molecules move faster because the negatively charged molecules are slowed by the electrophoretic drag. Thus a clear distinction between "nano-" and "microfluidic" regimes is established. We present an analytical model that accounts for the electrokinetic transport and adsorption (of the neutral dye) at the channel walls, and is in good agreement with the experimental data. The observed effects have potential for use in new nano-separation technologies.     

Chromatographic effect during the preparation of γ-Al2O3 supported Cu?Mn catalysts

A strong chromatographic effect has been established during copper-managenese formate impregnation of γ-Al₂O₃. The samples obtained have been characterized by adsorption, IR, X-ray and magnetochemistry methods.     

Theory of transport in nanofluidic channels with moderately thin electrical double layers: effect of the wall potential modulation on solutions of symmetric and asymmetric electrolytes

Electrokinetic phenomena play an important role for the transport in submicrometer-size channels since the electric double layers formed at the walls can occupy a substantial part of the channel volume. This presents a theoretical difficulty and specific problems are usually treated numerically or not comprehensively. In our work we present a theoretical model that allows one to obtain analytical expressions for the transport of fluid (electro-osmotic flow), ions (electric current), and dissolved charged molecules (analytes). The model is based on the weak double layer approximation and has a wide range of validity. An important feature of this theoretical approach is that it is applicable not only to symmetric but also to asymmetric 2:1 and 1:2 electrolytes which exhibit very interesting properties in nanoscale channels. The possibility of affecting the wall electrokinetic zeta potential by applying a transverse voltage bias is analyzed. This transverse bias is used in an attempt to control the transport in the channel and such devices are often called "fluidic field-effect transistors." Our model quantifies the effect of the voltage bias on the zeta potential of the channel wall and therefore can be used for prediction of transport and optimization of separations in such fluidic devices.     

Kinetics and mechanism of the hydrolysis of sodium carboxymethylcellulose (Na-CMC) by a cellulase complex

TheSomogyi-Nelson colorimetric method is applied in a new manner more suitable for evaluating the kinetics of the enzyme hydrolysis of sodium carboxymethylcellulose (Na-CMC) catalyzed by the cellulase complex. By means of selective inhibition of a chosen enzyme from the cellulase complex it became possible to trace the effect of the other enzymes included in its composition.

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Kinetik und Mechanismus der Hydrolyse von Natriumcarboxymethylcellulose (Na-CMC) durch einen Cellulase-Komplex

Zusammenfassung Die kolorimetrische Methode nachSomogyi undNelson wird nach einem neuen Verfahren zur Verfolgung der Kinetik der hydrolytischen Spaltung von Natriumcarboxymethylcellulose (Na-CMC), katalysiert durch den Cellulase-Komplex, angewandt. Durch selektive Inhibierung eines bestimmten Enzyms des Cellulase-Komplexes kann man die Wirkung der anderen zu seiner gesamten Zusammensetzung gehörenden Enzyme verfolgen.

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Symbols Used E enzyme (E—cellulase;E—exo-cellobiohydrolase;E—-glucosidase) - [E] _w weight concentration of enzymeE - S substrate (Na-CMC—sodium carboxymethylcellulose) - [S]₀ weight concentration of substrateS - I inhibitor (I—lactose;I—calcium chloride;I—condurrite-B-epoxide) - P product (P—oligosaccharides;P—cellobiose;P—D-glucose) - P end product (K , K , K ) - DP degree of polymerization - DS degree of substitution - ES enzyme-substrate complex (E S, E S, E S) - EP enzyme-product complex (E P, E P) - EI enzyme-inhibitor complex (E I, E I, E I) - M _s molecular mass of substrateS - K _s substrate constant (K _s , K _s , K _s ) - K _I inhibitor constant (K _I , K _I , K _I ) - K _m Michaelis-Menten constant - k ₊₁,k ₊₂ (k ₊₂ ,k ₊₂ ,k ₊₂ ) forward rate constants - k _–1 reverse rate constant - ₀ initial rate of reaction - V maximal reaction rate - A change in absorbance - molar absorption coefficient - wavelength Herrn Prof. Dr.Hans Tuppy zum 60. Geburtstag herzlichst gewidmet.     

Mechanism of the decomposition of cobaltous compounds in vacuo

The decomposition of cobaltous compounds (nitrate, hydroxide, carbonate, oxalate and oxyhydroxide) in vacuo has been investigated by magnetic methods and thermogravimetry. The mechanism is shown to be similar to that in air and begins with the formation of Co³⁺ ions in octahedral coordination. The formation of different final products (Co₃O₄, CoO and Co) has been attributed to the nature of the initial cobaltous compound. The results are in agreement with thermodynamic calculations.