Moreover, in the small τex limit the results provided are indepen

Moreover, in the small τex limit the results provided are independent of the Kärger model. As an alternative to

the correction method, one could instead measure the variation of the diffusional decay by the diffusion time and CYC202 cell line extract, within the Kärger model, the site specific diffusion coefficient [24] and [25]. However, the same limitations as above would apply because of model dependence. In addition, if the system exhibited restricted diffusion [3] the variation with the diffusion time would certainly lead to artifacts in the extracted diffusion coefficients. The other issue besides accuracy is precision. It would seem that the method presented here has a clear disadvantage in this respect since it suppresses the effects of exchange at the cost of a large intensity loss (recall Eq. (10)). One should note, however, that the signal loss per unit experimental time is far less severe since the correction method requires an accurate estimate of the magnetization

exchange rate that in turn requires a series of Goldman–Shen-type experiments. Performing experiments with several different diffusion times similarly carries a time penalty. In the limit of fast exchange 1/kb ≪ Δ, none of the methods work well, albeit for different reasons. The T2-filter method PD-0332991 order would suffer from excessive signal loss. On the other hand, the diffusional signal decay from conventional experiments would approach the functional form given in Eq. (1) with D set to the

population- and relaxation-weighted average of the two involved diffusion coefficients. While that average certainly depends on Df the actual value of Df could not be extracted by the correction method alone. In that case, one should resort to experiments performed at different compositions and one could obtain Df from the variation of D with composition. However, this is not only tedious but is not always permitted since it may lead to structural changes. As is well known, exchange of magnetization between different molecular pools Etofibrate has a strong influence on stimulated-echo-type NMR diffusion measurements [4], [6], [7], [10], [11], [12], [13], [24], [25] and [26]. Often, this effect is unwanted and acts as a source of error. We proposed and presented a detailed analysis of a new stimulated-echo-type experiment where we introduced T2-filters in the longitudinal evolution period. The purpose of this modification was to suppress the deleterious effects of magnetization exchange on the obtained diffusion coefficient data. Indeed, as demonstrated by experiments made on water in agarose gel, the method performs well and yields the water diffusion coefficient free of artifacts that, in a conventional stimulated-echo experiment, would arise due to magnetization exchange between water and agarose either because of proton exchange or because of cross-relaxation.

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