Global coupling

Cazenave A, Souriau A, Dominh K (1989) Global coupling of earth surface topography with hotspots, geoid, and mantle heterogeneities. Nature 340 54-57... 

Negative Global Coupling Close Distance Between the WE and the RE. 166... 

In some experiments the WE is grounded and the potential of the CE is controlled such that the potentiostatic or the galvanostatic constraint is fulfilled. This problem is completely equivalent, and thus everything we discuss here about the global coupling under potentiostatic or galvanostatic conditions holds also in that case. 

Kg. 7. Potential profiles perpendicular to the WE with corresponding potential drops for two different current densities (/ and I1) at the same value of the applied voltage U, demonstrating the origin of the global coupling. (The potential parallel to the cell is assumed to be uniform.)... 

Note that the local term depends through R uncomp = Rceii — RComp on the compensated and the cell resistance. Therefore, it is not possible to change the strength of the global coupling without also changing the local dynamics. 

When defining a global resistance Rg, with RG = Rcx - Rc0mp, we arrive at a more general formulation that incorporates both a close reference electrode and an additional external resistance. In this case the global coupling term becomes... 

Fig. 35. Simulations showing the influence of electrode geometry on front behavior (one-variable system) (a) short distance between the WE and the RE (strong negative global coupling) (b) intermediate distance between the RE and the WE, the CE far away from the WE (undercritical negative global coupling) ...

Fig. 47. Schematic of the growth rate X(n) (as defined in Eqs. (48) and (49)) of a perturbation of the homogeneous steady state versus the wave number of the perturbation in the case of negative global coupling.

Fig. 58. Calculated plot of the double layer potential as a function of position and time for a low value of the double layer capacitance. Model geometry ring-shaped WE and CE, symmetric RE close to the CE (weak negative global coupling). (Reproduced form A. Birzu, B. J. Green, N. I. Jaeger, J. L. Hudson, J. Electroanal. Chem. 504 (2001) 126, with permission of Elsevier Science.)...

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