Osmotic permeability coefficient

In this equation, n is the porosity and A is the cross-sectional area of the soil. Furthermore, it should be noted that the use of the effective porosity (n ) or the porosity (n) divided by the tortuosity squared (n/r) may be more accurate than using the porosity (n). For civil engineering apphcations, the electro-osmotic permeability coefficient (k ) is computed as follows ... 

In many cases, the difference between Pf and P can be attributed to the presence of an unstirred layer. On the other hand, in the case of human red cell membrane the difference cannot be accounted for by the presence of an unstirred layer [14]. Additional support for this difference between Pf and Pdealing with the effect of antidiuretic hormone (ADH) on water movement across epithelia. It was found that in the presence of ADH, the osmotic permeability coefficient of this tissue to water is 120 times greater than the diffusional coefficient (see Table 9.5 in [23]). 

TABLE 1. Biophysical characteristics of human fetal liver CD34 CD38 cells. Legends Vo - cell volume in isoosmotic solutions, Vb - osmotically inactive volume, Lp - permeability coefficient of membranes for water, p - permeability coefficient of membranes for DMSO cryoprotectant, a - reflection coefficient. 

The release rate (dM/dt) of a dmg from an osmotic pump can be described as Cd (dV/dt) where Cd is the dmg solubility in its reservoir compartment. The effective surface area, permeability coefficient, thickness, and osmotic reflection coefficient of the semi-permeable membrane used for the pump are 3.0 cm2, 0.7 10-4 cm2/day, 500 pm, and 0.8, respectively. Initially, the pump has a reservoir compartment with a dmg having Cd of 100 mg/ml, and the observed Ax is 100 atm. If we change the reservoir medium and osmotic agent to increase Cd of the dmg from 100 to 300 mg/ml and to increase Ax from 100 to 300 atm, by how much will the release rate of the dmg increase ... 

If we consider a membrane having the same solute concentration on both sides, we have All 0 However, a hydrostatic pressure difference AP exists between the two sides, and we have a flow Jv that is a linear function of AP. The term Lp is called the mechanical filtration coefficient, which represents the velocity of the fluid per unit pressure difference between the two sides of the membrane. The cross-phenomenological coefficient Ldp is called the ultrafiltration coefficient, which is related to the coupled diffusion induced by a mechanical pressure of the solute with respect to the solvent. Osmotic pressure difference produces a diffusion flow characterized by the permeability coefficient, which indicates the movement of the solute with respect to the solvent due to the inequality of concentrations on both sides of the membrane. 

A reverse osmosis unit is to demineralize 750,000 L/day treated effluent. Pertinent data are permeability coefficient = 0.2 L/(m day kPa) at 25 °C, pressure difference between the feed and product water = 2500 kPa, osmotic pressure difference between the feed and product water = 300 kPa, lowest operating temperature = 10 °C. 

The reflection coefficient (a,-) and osmotic pressure coefficient (Op) would only be the same for either a fully permeable membrane or an ideal semi-permeable membrane. The reflection coefficient (Op) can be determined from either empirical relationships with osmotic pressure coefficient based on back-analyses of the experimental results obtained for a given drilling fluid-shale system or theoretical equations based on thermodynamics (van Oort et al., 1995 Zeynaly-Andabily et al., 1996). 

Again the same convention as described earlier is used, and flow into the cell is considered to be in the positive direction. The osmotic pressure due to the permeant solute is denoted by which is defined as = RT(Cf - Att has units of dyne/cm. In these equations we speak of differences in concentrations in bulk phases since the partition coefficient which relates the concentration in the membrane phase to that of the bulk phase is incorporated in the permeability coefficients. The subscripts i and s refer to impermeant and permeant solute respectively. Lpj is the cross-coefficient for the volume flow arising from differences in the osmotic pressure of the permeant solute, Aw, when there is no difference of either hydrostatic or osmotic pressure produced by impermeant solutes ( Attj = 0). L p is the relative diffusional solute mobility per unit hydrostatic (or impermeant solute) pressure difference when Asr = 0. Although is always positive, and L p are both negative and have the same units as L. If the Onsager reciprocal relation holds, then is the diffusional flow and is a measure of the relative... 

Permeability coefficients of representative membranes and tissues to water under both osmotic and diffusional flows ... 

L is the water permeability coefficient Ap is the transmembrane pressure difference Ax is the difference in osmotic pressure between the upstream and downstream sides of the membrane... 

In the formulation of Bernardi and Verbrugge, the membrane is assumed fully hydrated, and the gases are taken to be dissolved in the pore fluid [42]. A more general variant of this hydraulic model was proposed by Eikerling et al. [44] and allows water content variation, and dependence of conductivity, permeability, and electro-osmotic drag coefficient on the local water content. 

According to Eq. 6.11, the DMFC determination of the methanol permeability requires the knowledge of the methanol drag factor, because the electro-osmotic flux could afford for a considerable fraction of the methanol flow, particularly at high methanol concentrations. An important drawback of this method is that the methanol drag coefficient is not well known, so Ren et al. [299] assumed that it was similar to the water drag coefficient ( =2.5). However, some recent NMR [300] and electro-osmosis [301] studies would indicate that this assumption is not valid, leading to considerable uncertainties in the methanol permeability coefficients determined by this method. 

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