Permeability parameter

BK Fritzinger, SK Bauman, DJ Lyman. Membrane characteristics, permeability parameters, and frictional coefficients for cupraphane. J Biomed Mater Res 5 3-16, 1971. 

As is the case with any experimental model it is important to make sure that PAMPA is used for the right type of experiments. Considering the properties of the system it is clear that the value of PAMPA is an early discovery to obtain approximate permeability parameters that can indicate the potential of the compound to permeate cell membranes. 

Most of the data is taken from earlier experimental work. The concentrations in the feed and reference values are taken from mouse and rat brain data for the sake of illustration. The membrane permeability parameters for S2 and S3 are assumed equal to the value for si. The normalized parameter > is taken equal to I>2, which was found earlier experimentally. The kinetic parameters 6m for m = 1,.., 8 of reaction (1) are chosen by using a known dissociation constant and by keeping the experimentally found proportion for reaction (2) on substrate-inhibition and hydrogen-ion effects. 

The samples without defensive film coat were studied by the method of concentration pulses (MCP) at pressure 0.2 Torr within the range of temperatures 370 -596 °C in order to determine the hydrogen permeability parameters of stainless steel (12X18H10T). The knowledge of these parameters allowed to simplify the problem of parameter identification for titanium nitride. The samples with titanium nitride covering were studied by method of permeability at pressures 0.5-249 Torr and the temperatures 380-670 °C. 

Table 9-3. Relative values of permeability parameters (van Krevelen, 1990).

The accuracy of the permeability method depends on the available relationship between the permeability parameters B0 and Kt and the structural parameters of porous media. When the pore texture is not sufficiently random and uniform, the accuracy of Equations 3.3 and 3.6 (and consequently of the method) becomes poor. This is a serious disadvantage of the permeability method, compared to the adsorption method, which does not depend on the pore texture. Nevertheless, permeability measurements are indicative of the porous structure and are useful for the determination of the parameters of the transport models. Various other experiments on flow and diffusion are also indicative of the texture of the porous particles. Some are discussed in Chapter 5. 

While the infinite dose technique has been invaluable in the determination of important skin permeability parameters such as dermal penetration coefficients and in the development of transdermal drug delivery concepts, to mimic in vivo conditions, the so-called finite dose technique was developed. This is essentially a modification of the traditional steady-state method. The important difference is that the skin preparation is supported over the receptor so that the epidermal surface is exposed in a manner that mimics the real-life exposure scenario, and the compound of interest is applied to the surface of the skin in a manner also similar to exposure in vivo. Although the results of such studies may give valuable information about the absorption of materials under specific exposure conditions, they are generally not amenable to extrapolation to other exposures since no invariant skin properties such as penetration coefficients can be readily calculated. 

Useful informetion regarding the characteristics of a particular separator aimngement often can be obtained through parametric studies. Separator specifications used in the following calculation are shown in Table 20.6-1 unless stated otherwise. Experimental permeability parameters, according to the dual-mode model, obtained from dense film-pure ges measurements34 36 are summerized in Table 20.6-2. For simplicity, only the results for a binaiy-component feed will he discussed. 

Fig. 9.19. A better correlation between observed bioavailability and predicted bioavailability when both aqueous solubility and permeability parameters of drugs are used to predict the fraction absorbed for three compounds. (From Burton P, Goodwin J, Vidamas T, et al. Predicting drug absorption how nature made it a difficult problem. J Pharm Exp Ther 2002 303 889-895and adapted from Hilgers AR, Smith DP, Biermacher JJ, et al. Predicting oral absorption of drugs a case study with novel class of antimicrobial agents. Pharm Res 2003 20 1149-1155 with permission.)...

Vapor permeability parameters of films from linear polymers are given in Table 3.1... 

Table 6.1 Models Using a Skin Compartment to Estimate Permeability Parameters...

Table 3 The Permeability Parameters of Pure S-Isomer and R-(from Racemic) Timolol Maleate (TM) Across Hairless Mouse Skin with and Without Chiral Enhancers... 

Malykh OV, Golub AY, Teplyakov W. Polymeric membrane materials New aspects of empirical approaches to prediction of gas permeability parameters in relation to permanent gases, linear lower hydrocarbons and some toxic gases. Adv Colloid Interface Sci 2011 164(l-2) 89-99. 

Cores No. 2 and 3 were from the same outcrop with the same approximate permeability. We assumed that the capillary effects in the 2 cc/min run from Core No. 2 which was the longer core in practically negligible. The production and pressure data from this experiment was used in the Buckley Leverett model to estimate the relative permeability parameters. Also the 0.2 cc/min run production data from Core No. 3 were analyzed. 

Zhou, Z.F., Huang, Y. Rapid field test technique and method for determining anisotropic permeable parameters of rock mass. 11th Congress of the International Association for Engineering Geology and the Environment, Geologically Active, 2010 2627-2632. 

Streaming potential measurements have been used extensively to eharaeterize surfaee properties of fibers (25), and this technique has been applied to analyze the effects of shampoos and conditioners on hair by a number of authors (26-28). Jachowicz and his coworkers developed new instrumentation for this purpose, which permits the simultaneous determination of electrokinetic and permeability parameters on hair fiber plugs. DEPA is... 

Note that the mathematical model developed for a curtain-wall-pile breakwater can be used for a pile breakwater just by setting d = 0. It can also be used for a curtain-wall breakwater by using the permeability parameter G = 1/6, which was derived from the energy dissipation formula for a curtain-wall breakwater of Kriebel.25... 

The permeability parameter based on Sollitt and Cross can be expressed as... 

Comut, R., and Lefrou, C. 2008. Studying permeable films with scanning electrochemical microscopy (SECM) quantitative determination of permeability parameter /. Electroand. Chem. 628 197-203. 

---