1/ Homogeneous materials have greater diffusivity than heterogeneous.
2/Dab> Dplasma > D0 > Dpore > Dm> De > Dt
3/ The tissue and the blood almost have the same diffusivity ( Dt)
4/Porous membranes have smaller diffusivity than capillary walls ( the differences are the tortuous path, and the area available for diffusion).
5/Lporous membrane >>> L capillary
6/ The epsilon is useless if the solute is soluble in the continuous nonporous phase.
7/pores reduce the diffusivity due to : steric exclusion + hydrodynamic drag
8/ as the radius of the solute increases, the hydrodynamic drag and the steric exclusion increase and then the diffusivity decreases.
9/It is better to measure the partition coefficient experimentally because theoretically we neglect the effect of any force between the wall of the membrane and solute molecules.
10/Straight cylindrical pores mean t=1
11/ The solute concentration is a linear function depends on x (thickness of the wall ).
12/It is difficult to measure the concentration of the solute within the pore, therefore, we usually relate that concentration to the concentration of the bulk by *K
13/ The diffusivity depends on : size, concentration, T, P, physical properties like the viscosity.
14/ D gas> Dliquid-small > D liquid-big > D solid
15/ The permeability is used to describe solute transport across a membrane. ( It is the controlling resistance and usually we consider the overall conductance = Pm)
16/Why the diffusivity of tumor cell is not affected by the change in the radius of the solute? due to the random division ( the amount we need for one cell, here it is needed for 10 or more) more number of cells required higher amount of O2, and nutrients.
17/ Diffusion and Convection are interdependent.
18/ ultrafiltration: separation between solvent and solute when Selma = 0 or 1.
19/ Sieving coefficient = the complement of the reflection coefficient
20/We neglect any forces when we consider Sa
21/Peclet number : >>>1 convection is higher ( we need this to happen in case of plasmapheresis and selective filtration)
<<<1 Diffusion is higher
22/ We have three different categories of solutes inside the body
Category 1: water- soluble lipid-insoluble like ions and many drugs
Category 2: Lipid- soluble like O2
Category 3: Large lipid-insoluble like proteins
23/Concentration polarization: selective membrane where small molecules will pass and larger molecules will accumulate in the fed side and then there will be a backward diffusion.
24/ There will be new sieving coefficient called observed sieving coefficient usually > Sa and =Sa when q is very low compared with Km
and = 1 when q is very high compared with Km
25/ convection + diffusion make the transport more efficient.