Structure-Transport Relationships

Clearly by working with typical spatial resolutions of approximately 30-50 pm, individual pores within the material are not resolved. However, a wealth of information can be obtained even at this lower resolution (53,54,55). Typical data are shown in Fig. 20, which includes images or maps of spin density, nuclear spin-lattice relaxation time (Ti), and self-diffusivity of water within a porous catalyst support pellet. In-plane spatial resolution is 45 pm x 45 pm, and the image slice thickness is 0.3 mm. The spin-density map is a quantitative measure of the amount of water present within the porous pellet (i.e., it is a spatially resolved map of void volume). Estimates of overall pellet void volume obtained from the MR data agree to within 5% with those obtained by gravimetric analysis. 

The spin-lattice relaxation time map (discussed in Section II.A.2) yields information about the spatial distribution of mean pore size within a given image pixel. Lighter shades in the image correspond to larger mean pore size. Even at this coarse 

The structure-transport relationship characteristic of the catalyst pellet is shown by comparison of Figs 20a-c the spatial heterogeneity in the values of the molecular diffusion coefficient is much more consistent with the heterogeneity in the intensity shown in the Ti map than that of the spin-density map. Thus, we conclude that it is the spatial variation of local pore size that has the dominant influence on molecular transport within the pellet. 

In an investigation of the spin-density (voidage) and spin-lattice relaxation time maps of many pellets, it was found that it was the heterogeneity in pore size, as characterized by the fractal dimension of the Ti map, that was consistent between images of pellets drawn from the same batch 58). The fractal dimensional of these images identifies a constant perimeter-area relationship for clusters of pixels of 

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Yoshida, N. H. and Roberts, M. S. Structure-transport relationships in transder-mal iontophoresis. Adv. Drug Deliv. Rev. 9 239, 1992. 

Structure-Transport Relationship of PepTI. Structural information on PepTl has been limited to its primary sequence and predicted structural membrane topology. Hydropathy analysis of the human, rabbit, and rat PepTl isoforms have predicted the presence of 12 transmembrane domains (TMD) in each isoform (212). This model has been partially proved by other investigators (144,213). 

STRUCTURE-TRANSPORT RELATIONSHIPS IN THE SURFACE DIFFUSION OF MOLECULES OVER HETEROGENEOUS SURFACES WITHIN POROUS CATALYSTS... 

Structure-transport relationships in the surface diffusion of molecules... 

Perkins, E.L., Lowe, J.R, Edler, K.J., and Rigby, S.R 2010. Studies of structure-transport relationships in biodegradable polymer microspheres for drug delivery using NMR cryodiffusometry. Chem. Eng. Sci. 

At present, the research on solid-state LE conductors is chiefly focused on ceramic materials, which seem to offer the most room for improvements. Here, in addition to the investigation of structure/transport relationships, many issues must be considered meso- and microstructure (particle dimensions, grain boundaries, thin films, etc.), chemical, electrochemical and mechanical stability. Glasses seem to have reached their maximum potential, having been explored as far as concerns composition, transport mechanisms, local and even medium range structure. Pol3uners (and composite) electrolytes may reserve some good news, chiefly in terms of chemical stability towards the electrodes, and electrochemical compliance with the recently proposed 5 V cathodes. 

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