Resonant frequency measurements as an alternative to phase-selective A.C. polarography in tensammetry and pseudocapacitance determinations

A new method is proposed for the determination of the double-layer capacitance and pseudocapacitance of electrochemical cells. The method is based on the measurement of the resonant frequency of the circuit consisting of the electrochemical cell connected in series with a standard inductor. The performance of the method is demonstrated with double-layer capacitance measurements at the dropping mercury electrode in 1 M KCl and butanol-1/1 M KCl mixtures and with the determination of heterogeneous charge-transfer rate constants ranging from 10−2 to 10−5 m s−1

Selective oxidation of n-butane to maleic anhydride under oxygen-deficient conditions over V-P-O mixed oxides

The selective oxidation of n-butane to maleic anhydride over V-P-O mixed oxides was studied under oxygen deficient conditions. The mixed oxides were prepared with P/V atomic ratios ranging from 0.7 to 1.0. Catalysts with P/V <1.0 did not show any selectivity to maleic anhydride formation, regardless of whether or not (VO)2P2O7 was present. For catalysts with P/V = 1.0, containing (VO)2P2O7 and/or the so-called. β-phase, the selectivity was strongly influenced by the actual surface V5+/V4+ ratio. This ratio is determined by the temperature, the crystal phases present in the catalyst and the composition of the gas mixture. Optimal selectivity was obtained at 425°C with 15% butane in air and a butane/oxygen ratio of 0.9

Biocatalysis and process integration in the synthesis of semi-synthetic antibiotics

Contains fulltext : 28996.pdf (publisher's version ) (Open Access

Proving Termination of Graph Transformation Systems using Weighted Type Graphs over Semirings

We introduce techniques for proving uniform termination of graph transformation systems, based on matrix interpretations for string rewriting. We generalize this technique by adapting it to graph rewriting instead of string rewriting and by generalizing to ordered semirings. In this way we obtain a framework which includes the tropical and arctic type graphs introduced in a previous paper and a new variant of arithmetic type graphs. These type graphs can be used to assign weights to graphs and to show that these weights decrease in every rewriting step in order to prove termination. We present an example involving counters and discuss the implementation in the tool Grez