Permeability ratio

Intestinal infections that cause persistent diarrhea normally result in histopathological changes to the intestine including villus blunting, crypt hypertrophy and inflammatory infiltrate in the lamina propria. These histopathological disarrangements are seen in Cryptosporidium, Cy-clospora and microsporidial infections [28], Furthermore, it has been documented that there are substantial disruptions of intestinal barrier function as measured by lactu-lose mannitol permeability ratios in patients with AIDS... 

Figure 3.3 Impact of passive permeability on the efflux ratio (ER). Passive permeability (x-axis) was measured in a PAMPA assay [19]. Efflux ratios were derived from permeability measurements in a Caco-2 monolayer assay [44] and are expressed as the basolateral to apical/ apical to basolateral permeability ratios. The loading concentration was 5 XM in the PAMPA assay and 10 xM in the Caco assay. LC-MS/MS readout was used for both assays. The y-axis...

Fig. 2. Comparison of the selectivities of neutral-carrier-modified solvent polymeric- [43] and bilayer membranes. The permeability ratios PJP (at equilibrium" (Ref. 18) as far as available) fulfilled for the glyceryl dioleate BLM s are taken from Figs. 10 and 11 in Ref. 18. Values on the SPM s were obtained using 0.1 M solutions of the aqueous chlorides and membranes of the composition 33.1 wt.% polyvinyl chloride, 66.2 wt.% dioctyl adipate, 0.7 wt.% carrier. For the macrotetrolides I2 NH( for valinomycin IZ K. ...

Figure 4. Dependence of the permeability ratio (PcoJ hb) at 50°C on the blend composition for physical blends of FVC/EVA...

Table II. Effect of Grafting on Permeability Coefficient (P) and Permeability Ratio in PVC/EVA Blends at 50°C...

For a defect-free ideal membrane, the selectivity is independent of thickness, and either permeability ratios or permeance ratios can be used for comparison of selectivi-ties of different materials. Nonideal module flow patterns, defective separating layers, impurities in feeds, and other factors can lower the actual selectivity of a membrane compared to tabulated values based on ideal conditions (Koros and Pinnau, 1994). 

The permeabilities of the stereocomplex membranes to water and NaCl are shown in Fig. 38 as a function of the water content or the composition (isotactic mol%). The permeability ratios of urea to NaCl are summarized in Table 20315). The dependence of water permeability on the water content is very strong whereas that of the permeability to solutes (in this case NaCl) is weak. The water permeability of the PMMA membrane is extremely high compared to that of cuprophan whereas its permeability to solute is almost the same. This characteristic permeability accounts for the effect of the hyd-... 

The transport flux across a membrane per unit thickness, which is expressed by permeability coefficient, P, and its dependence on the nature of permeant, which could be represented by the permeability ratio for different permeant A and B, a = P jP, are two important parameters for dealing with membranes. In most cases, the smaller value of P is used in the denominator so that the value of a is greater than unity. 

The deviation from the near-constant rule also occurs if the gas interacts specifically with polymer molecules. This is seen in the case of water vapor permeability. The molecular size of H2O is approximately the same as that of O2 however, the solubility of H2O is much greater than that of O2 in orders of magnitudes and varies greatly depending on the nature of polymers. Consequently, there is no near-constant value of oc that is found for many gas pairs, and the permeability ratio of H2O/O2 for polymers spreads in orders of magnitude. 

Plasma polymer films from cyanogen bromide and benzonitrile were also deposited on PPO films. The composite films gave hydrogen-to-methane permeability ratios of 297 and 68 for cyanogen bromide and benzonitrile plasma-polymerized composites, respectively. The PPO substrate film itself has a higher permeability ratio (23.5) than the SC substrate (0.87), although lower hydrogen (6.42 X 10 ) and methane (2.73-10 ) permeability than the SC substrate. 

Tables 34.1 and 34.2 show the gas permeability results pertaining to plasma polymers prepared from various nitrile-type monomers that were deposited onto 1-mil thick silicone and silicone-carbonate copolymer sheets [7]. Shown also are the results obtained from the uncoated polymer sheets for comparisons. Both silicone and silicone-carbonate polymer films prior to the plasma polymer deposition show H2/CH4 permeability ratios of 0.79 and 0.97, respectively. After being coated with a...

Table 34.1 H2 Permeation Rates and the Permeability Ratio of H2/CH4 for Plasma Pol5miers of Nitrile-Type Monomers Deposited on Silicone Sheet...

Monomer Flow rate (seem) Power (W) Pressure (mtorr) Thickness (A) Pjl X 10 H2 Permeability ratio a (H2/CH4)... 

The values in the parentheses are the permeability ratios for the uncoated composite membrane. The location of substrate within a reactor is not the same. 

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