Gels, diffusion measurements

Perrin model and the Johansson and Elvingston model fall above the experimental data. Also shown in this figure is the prediction from the Stokes-Einstein-Smoluchowski expression, whereby the Stokes-Einstein expression is modified with the inclusion of the Ein-stein-Smoluchowski expression for the effect of solute on viscosity. Penke et al. [290] found that the Mackie-Meares equation fit the water diffusion data however, upon consideration of water interactions with the polymer gel, through measurements of longitudinal relaxation, adsorption interactions incorporated within the volume averaging theory also well described the experimental results. The volume averaging theory had the advantage that it could describe the effect of Bis on the relaxation within the same framework as the description of the diffusion coefficient. 

E Schantz, M Lauffer. Diffusion measurements in agar gel. Biochemistry 1 658, 1962. 

Westrin BA, Axelsson A, and Zacchi G. Diffusion measurement in gels. J. Control. Rel. 1994 30 189-199. 

Botto and coworkers combined high-pressure xenon (30 atm) and chemical shift imaging to investigate aero gel samples. The authors characterized the average pore structure and steady-state spatial distributions of xenon atoms in the various parts of the sample. Xenon-exchange rate constants were measured to be of the order of 1 s , while PFG diffusion measurements yielded self-diffusivity coefficients of the order of D = 10 cm s ... 

Krajeswska, B. and Olech, A. (1996). Pore structure of gel chitosan membranes. I. solute diffusion measurements. Polymer Gels and Network 4, 33 3. 

Most of the measurements on diffusivities of compounds in the liquid phase, in catalyst pores, have been made with small molecules. Recently Chantong and Massoth [26] measured diffusivities of non-metallic porphyrin molecules. Baltus and Anderson [27] made diffusivity measurements using narrow molecular weight fractions of a petroleum residuum. In their work tetrahydrofuran asphaltenes were separated into five fractions by gel permeation chromatography. The polystyrene equivalent average molecular weights they reported were 3000, 6000, 12000, 24000, and 48000. 

Wayne LG, Brenner DJ, Colwell RR, Grimont PAD, Kandler O, Krichevsky MI, Moore C, Moore WEC, Murray RGB, Stackebrandt E, Starr MP, Trtiper HG (1987) Report of the ad hoc committee on reconciliation of approaches to bacterial systematics. Int J Syst Bacteriol 37 463-464 Westrin BA (1991) Diffusion measurements in gels. University of Lund, Lund Whiteley M, Brown E, McLean RJC (1997) An inexpensive chemostat apparatus for the study of microbial biofilms. J Microbiol Meth 30(2) 125-132 Widdel F (1988) Microbiology and ecology of sulfate and sulfur reducing bacteria. In Zehnder ADJ (ed) Biology of anaerobic microorganisms. Wiley, New York, pp 469-585... 

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