BMED+3300+Lecture+2+Slides+082411

BMED+3300+Lecture+2+Slides+082411 - BMED 3300 Biotransport...

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MED 3300 Biotransport BMED 3300 Biotransport Lecture 2 August 24, 2011. Professor Julie Babensee
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Fick’s First Law of Diffusion A C AB D A J = v z (For diffusion in the z-direction only) dz A dC AB D z A J = , Diffusion z=0 For dilute biological solutions, N A,z = J A,z J A = molar flux in the z-direction relative to the molar average velocity, [mol/cm 2 s] dC = the concentration gradient in the z direction [mol/cm 3 /cm] D AB = mass diffusivity or diffusion coefficient for component A iffusing through component B [cm ] dz A diffusing through component B [cm 2 /s]
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iffusivity Units for diffusivity Diffusivity t L L L M t L M dz A dC z A J AB D 2 / 1 3 / 1 2 / , = = = D = f (P, T, composition) For gases, D = 5x10 -6 –1 ±x ±10 -5 m 2 /s For liquids, D = 10 -10 –10 -9 m 2 /s or solids D = 10 -14 0 -10 2 For solids, D = 10 10 m /s
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iquid ass Diffusivity Liquid-Mass Diffusivity 6 . 0 2 / 1 ) ( 8 10 4 . 7 A V B M B T B AB D Φ × = μ For nonelectrolytes in an dilute solutions Where, D AB is the mass diffusivity of A diffusing through liquid solvent B in cm 2 /s μ B is the viscosity of the solution in centipoises is the absolute temperature in Kelvin T is the absolute temperature in Kelvin M B is the molecular weight of the solvent V A is the molal (or molecular) volume of solute at normal boiling point in cm 3 /g mol (See Table 24.4, 24.5, WWWR p. 439-440) (Wilke and Chang, 1955) Φ B is the “association” parameter for solvent B (see WWWR p. 440) Other empirical relationships for diffusivity as a function of molecular weight for pp y g biological systems exist
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Vast Differences in Extracellular and Intracellular Fluid Composition D. O. Cooney, Biomedical Engineering Principles An Introduction to Fluid, Heat and Mass Transport Processes, Marcel Dekker, Inc., 1976.
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Transport of Species Through the Cell Membrane Occur by: • Ordinary “passive” diffusion
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This note was uploaded on 09/07/2011 for the course BME 3300 taught by Professor Babensee during the Spring '11 term at Georgia Institute of Technology.

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BMED+3300+Lecture+2+Slides+082411 - BMED 3300 Biotransport...

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