Contrast gain

M. D Zmura and B. Singer, Contrast Gain Control, in L. T. Sharpe and K. R. Gegenfurtner, Eds., Color Vision From Genes to Perception, Cambridge University Press, Cambridge, pp. 369-385 (1999). 

M. D Zmura, Color Contrast Gain Control, in W. Backhaus, R. Kliegl, and J. Werner, Eds., Color Vision, Walter de Gruyter, New York 251-266 (1997). 

Figure 12. Principle of video-enhanced conlrast microscopy A) Original image B) Offset (brightness) C) Contrast gain...

The term nucleophilicity refers to the effect of a Lewis base on the rate of a nucleophilic substitution reaction and may be contrasted with basicity, which is defined in terms of the position of an equilibrium reaction with a proton or some other acid. Nucleophilicity is used to describe trends in the kinetic aspects of substitution reactions. The relative nucleophilicity of a given species may be different toward various reactants, and it has not been possible to devise an absolute scale of nucleophilicity. We need to gain some impression of the structural features that govern nucleophilicity and to understand the relationship between nucleophilicity and basicity. ... 

The conclusions are evidently relevant to the amount of entropy lost by ions in methanol solution—see Table 29. If, however, the expression (170) is used for an atomic ion, we know that it is applicable only for values of R that are large compared with the ionic radius—that is to say, it will give quantitative results only when applied to the solvent dipoles in the outer parts of the co-sphere. The extent to which it applies also to the dipoles in the inner parts of the co-sphere must depend on the degree to which the behavior of these molecules simulates that of the more distant molecules. This can be determined only by experiment. In Table 29 we have seen that for the ion pair (K+ + Br ) and for the ion pair (K+ + Cl-) in methanol the unitary part of ASa amounts to a loss of 26.8 e.u. and 30.5 e.u., respectively, in contrast to the values for the same ions in aqueous solution, where the loss of entropy in the outer parts of the co-sphere is more than counterbalanced by a gain in entropy that has been attributed to the disorder produced by the ionic field. 

This time, copper ion gains electrons from the zinc, in contrast to the behavior in Experiment 7, where copper metal lost electrons to silver. 

In 1979, Diaz et al. produced the first flexible, stable polypyrrole (PPy) film with high conductivity (1(X) Scm ). The substance was polymerized on a Pt-electrode by anodic oxidation in acetonitrile. The then known chemical methods of synthesis " usually produced low conductivity powders from the monomers. By contrast, electropolymerization in organic solvents formed smooth and manageable films of good conductivity. Thus, this technique soon gained general currency, stimulating further electropolymerization experiments with other monomers. In 1982, Tourillon... 

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