The polarographic behavior of the five phenyl-substituted ethenes (styrene, stilbene, 1,1-diphenylethylene, triphenylethylene, and tetraphenylethylene) at the dropping mercury electrode has been examined in dimethylformamide (DMF) and DMF-water solution containing 0.2M tetra-n-butylammonium iodide as background electrolyte on the basis of the various criteria for reversibility based on direct current polarography. Heterogeneous rate constants and ana values have been calculated on the basis of the spherical expanding electrode theory.None of the reversibility criteria predictions for the various possible mechanisms are entirely in accord with the experimental results. Although polar0graphic reduction of the phenyl-substituted ethenes is indicated to occur by processes which involved a change of electron transfer mechanisms, a definite decision regarding the actual mechanisms cannot be reached because of the lack of adequate theoretical bases for such a mechanism change and for the effects of variation in double layer structure on any given mechanism.

The theoretically expected variations of the criteria of reversibility for electrochemical reduction, which have been proposed for inorganic systems on the basis of direct current polarography, have been developed for the various possible mechanisms, which might be expected for the reduction of the phenylsubstituted ethenes at the dropping mercury electrode. These criteria of reversibility include the beta function (ratio of mean current to instantaneous current), the dependence of the current on the drop-time (mercury column ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.210.126.199 Downloaded on 2015-05-29 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.210.126.199 Downloaded on 2015-05-29 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.210.126.199 Downloaded on 2015-05-29 to IP

A group of experiments was conducted by Apollo 14 astronaut Stuart A. Roosa during the lunar flyback on 7 Fehruary 1971 to obtain information on heat flow and convection in gases and liquids in an environment of less than 10-(6)g gravity. Flow observations and thermal data have shown that: (i) there are, as expected, convective motions caused by surface tension gradients in a plane liquid layer with a free upper surface; (ii) heat flow in enclosed liquids and gases occurs mainly by diffusive heat conduction; and (iii) some convective processes, whose characteristics are not fully known, add to the heat transfer.

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