Publications

The chlorine evolution reaction has been investigated on D.S.A. type electrodes in 5.13 M NaCl solution. A large amount of potentiostatic current-potential and impedance-potential data has been collected over a wide potential and frequency range. The current-potential and impedance-potential data has been reduced by curve fitting to a series of a parameter curves. The impedance-potential data were analysed by two methods: an equivalent circuit and the parameter curves CdlE, RctE, R$ømega$E reported, and a reaction mechanism and the parameter curves CdlE, kSHE, R$ømega$E reported. The two ways of analysing the impedance data are equivalent. However the analysis into a reaction parameter has the advantage that all the data, current-potential and impedance-potential, can be tested using a single set of parameters (kSH, R$ømega$, a, b, DA, DB, $δ$).In this work the data is compared to that expected for a redox reaction. Any deviation from the expected behaviour of a perfect redox reaction is ascribed to Cl2 bubble formation and to electrode structure effects. It is suggested that the parameter curves are related also to bubble formation characteristics and the real area of the electrode. © 1983.

It is often desirable to be able to predict the total current density at an electrode when multiple electrochemical reactions occur there under potentiostatic control. It is also sometimes desirable to include the effect of ionic migration within the diffusion layer upon the predicted total (1) and partial current densities (2). A procedure for doing this can be illustrated by considering the rotating disk electrode (RDE) system and the associated potential distribution near the RDE as shown in Fig. 1 and 2.

The question of protein dynamics and its relevance to function is currently a topic of great interest. Proteins are particularly dynamic at the side-chain level on the time scale of picoseconds to nanoseconds. Here, we present a comparison of NMR-monitored side-chain motion between three PDZ domains of approximately 30% sequence identity and show that the side-chain dynamics display nontrivial conservation. Methyl (2)H relaxation was carried out to determine side-chain order parameters (S(2)), which were found to be more similar than naively expected from sequence, local packing, or a combination of the two. Thus, the dynamics of a rather distant homologue appears to be an excellent predictor of a protein s side-chain dynamics and, on average, better than current structure-based methods. Fast side-chain dynamics therefore display a high level of organization associated with global fold. Beyond simple conservation, the analysis herein suggests that the pattern of side-chain flexibility has significant contributions from nonlocal elements of the PDZ fold, such as correlated motions, and that the conserved dynamics may directly support function.

A wide range of Au—Cu alloys was deposited from alkaline electroless solutions containing KAu(CN) sub 2 , cupric ions complexed with EDTA and formaldehyde as reducing agent. Using electrochemical measurements it was shown that in the presence of cyanide ions the oxidation of formaldehyde, which provides the electrons for the Au-ion reduction, can only occur on a Cu-containing surface. The kinetics of the electroless deposition reaction are described and discussed in terms of the electrochemical results. X-ray diffraction measurements showed that only homogeneous mixed crystals of Au and Cu are obtained with a single lattice constant for each composition. 10 ref.—AA

A finite difference technique for solving coupled, nonlinear parabolic or elliptic partial differential equations is presented. It consists of combining the implicit alternating direction technique with Newman s technique for solving coupled, nonlinear ordinary differential equations. The technique is direct, relatively simple, and easy to use. © 1980, American Chemical Society. All rights reserved.

Physical phenomena that interest chemical engineers can often be modeled mathematically as boundary value problems which consist of sets of nonlinear, coupled, second-order differential equations. Newman s (1968) technique for solving such problems is reviewed and extended slightly. © 1978, American Chemical Society. All rights reserved.

The hydrometallurgy of copper may involve leaching of the metal from its ore with an aqueous solution containing cupric and ferric chloride. The subsequent deposition of copper from such a process stream is modeled here in an idealized electrochemical cell with a rotating-disk electrode. The potential distribution and concentration profiles within the diffusion layer are predicted for given potential differences between the electrode and the solution. The cuprous ion, which is formed by the reduction of the complexed cupric ion at the electrode, is stabilized in the chloride solution and can react either at the electrode or with ferric species within the diffusion layer. The assumption is that this fast and irreversible homogeneous reaction generates a reaction plane, whose position is shown in the concentration and potential profiles. In addition, the position of the reaction plane is plotted as a function of the potential difference between the electrode and the adjacent solution. Predicted current-potential and current efficiency-potential curves are also reported. Finally, the iron contamination of the deposited copper is estimated to be less than 10-5 atom percent for some cases. Also, because some of the partial current densities are below their limiting values, the analysis is strictly valid only at the center of the disk. © 1977, The Electrochemical Society, Inc. All rights reserved.

Multiple reactions at a rotating-disk electrode are modeled. The governing equations are used to generate a parameter which characterizes the effect of a side reaction on the limiting-current curve of a main reaction. Various predicted current-potential curves illustrate the importance of this parameter for copper deposition with simultaneous formation of dissolved hydrogen at a disk electrode rotating in a copper sulfate solution containing sulfuric acid. Distributions of current, potential, and surface concentration on the disk indicate that in some cases the main reaction can be below its limiting rate at the center of the disk while hydrogen gas bubbles may be formed near the edge. In addition, predicted and measured limiting-current curves for this system are compared. © 1977 Elsevier Sequoia S.A.