Diffusion constrained

High selectivity will result when the rate of the reactions involving the undesirable bulkier molecules is in the severely diffusion constrained regime. The observed selectivity depends on the relative rate of reaction to that of diffusion of these molecules. It is obvious that the degree of selectivity can be adjusted by varying the diffusion pathway and its acid site density (15). 

At constant focus size, it was shown that FCS cannot distinguish between diffusion constrained by elastic force, walking confined diffusion, and hop diffusion averaged over many measurements [44]. The simulations indicate that the mean square displacements of all these types of restricted diffusion can refiably be interpreted using one archetypal model presented by the following equation ... 

Thompson, M Compton R.G. (2006). Fickian Diffusion Constrained on Spherical Surfaces Voltammetiy. ChemPhysChem. Vol.7, No.9, (September 2006), pp. 1964-1970, ISSN 1439-7641... 

It appears that the complete model for both mass and heat transfer contains four adjustable constants, Dr, Er, K and Xr, but Er and Xr are constrained by the usual relationship between thermal diffusivity and thermal conductivity... 

A possible layered precursor to the layered nanoproduct conversion mechanism is thus proposed. The silver clusters formed at the initial heating stage by the partial decomposition of AgSR serve as nuclei at further reaction stages, and their distribution naturally inherits the layered pattern of the precursor. The following growth is mainly controlled by the atom concentration and atom diffusion path, which are both constrained by the crystal structure of the precursor [9]. 

Being a gas, NO can diffuse freely once produced, and so is not constrained by the usual mechanisms of release and uptake that confine most transmitters to the synapse. Likewise, the fact that it is not stored means that the criteria of presence and storage are... 

This is an extremely important equation since it tells us that, in the limit of very facile kinetics, the surface concentrations of O and R are constrained to satisfy the local Nernst equation. Under these conditions, the net current is always dictated by the diffusion of the electroactive species to the electrode i.e. the flux of O. 

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