Permeability adjustment

Dovan, H.T. Hutchins, R.D. "Development of a New Aluminum-Polymer Gel System for Permeability Adjustment," SPE/DOE Paper 12641, 1984 SPE/DOE Fourth Symposium on Enhanced Oil Recovery, Tulsa, April 15-18. 

Near the end of the planned operational period, soil samples were collected from the treatment area to determine if the soil concentrations were reduced to less than 5.6mg/kg. These samples, taken only in areas of known high-preoperation TCE concentrations, were collected to get a conservative estimate of the concentration reductions. This preliminary soil sampling showed that the process had worked and that the ROD limit would be met. The unit was then operated until the end of the contract period. Based on the laboratory-determined electroosmotic permeability (adjusted for temperature), applied voltage, and operational time, a total of 1.6 pore volumes of treatment occurred. No groundwater (or pore water) samples were collected during the operation of Phase Ilb. 

Isothermal-isobaric single-component diffusion. Now consider both phases to contain samples of the same pure component, and let the interface between them be thermally conducting, movable, and permeable. Adjust the reservoirs so the phases have the same T and P then we have T = TP = constant and P = pP = constant. The process is diffusion of the pure component across the interface. Under these restrictions, the combined laws (7.2.13) reduce to... 

Co-administration of ofloxacin and chitosan in eyedrops increased the bioavailabUity of the antibiotic [290]. Trimethyl chitosan was more effective because of its solubility (plain chitosan precipitates at the pH of the tear fluid). On the other hand, N-carboxymethyl chitosan did not enhance the corneal permeability nevertheless it mediated zero-order ofloxacin absorption, leading to a time-constant effective antibiotic concentration [291]. Also W,0-carboxymethyl chitosan is suitable as an excipient in ophthalmic formulations to improve the retention and the bioavailability of drugs such as pilocarpine, timolol maleate, neomycin sulfate, and ephedrine. Most of the drugs are sensitive to pH, and the composition should have an acidic pH, to enhance stability of the drug. The delivery should be made through an anion exchange resin that adjusts the pH at around 7 [292]. Chitosan solutions do not lend themselves to thermal sterilization. A chitosan suspension, however. 

Hydroxyethylcellulose with a degree of substitution of 1.1 to 1.6 has been described for fluid loss control in water-based drilling fluids [1473]. An apparent viscosity in water of at least 15 cP should be adjusted to achieve an API fluid loss of less than 50 ml/30 min. Crosslinked hydroxyethylcellulose is suitable for high-permeability formations [344,346]. 

Cationic polyacrylamide may be used in the initial treatment stages to promote rapid polymer adsorption (201). Adjustment of the pH may allow deeper penetration of the fluids in an aluminate crosslinking system prior to gelation (202). A process involving injection of alternate slugs of stoichiometrically equivalent amounts of partially hydrolyzed polyacrylamide and Al O ) has been evaluated in the laboratory permeability of sana packs were reduced by more than 96% (203). Mixtures of Al(IIl) and Zr(IV) have also been evaluated as partially hydrolyzed polyacrylamide crosslinkers (204). 

The benefit of the LbL technique is that the properties of the assemblies, such as thickness, composition, and function, can be tuned by varying the layer number, the species deposited, and the assembly conditions. Further, this technique can be readily transferred from planar substrates (e.g., silicon and quartz slides) [53,54] to three-dimensional substrates with various morphologies and structures, such as colloids [55] and biological cells [56]. Application of the LbL technique to colloids provides a simple and effective method to prepare core-shell particles, and hollow capsules, after removal of the sacrificial core template particles. The properties of the capsules prepared by the LbL procedure, such as diameter, shell thickness and permeability, can be readily adjusted through selection of the core size, the layer number, and the nature of the species deposited [57]. Such capsules are ideal candidates for applications in the areas of drug delivery, sensing, and catalysis [48-51,57]. 

Recently, we proposed an alternative process for encapsulating biomacromolecules within PE microcapsules. This approach involves using nanoporous particles as sacrificial templates for both enzyme immobilization and PE multilayer capsule formation (Figure 7.2, route (I)) [66,67]. Unlike previous LbL encapsulation strategies, this approach is not limited to species that undergo crystallization, and is not dependent upon adjustments in electrostatic interactions within PE microcapsules to alter shell permeability characteristics. The salient feature of this method is that it is applicable to a wide range of materials for encapsulation. 

The device for examination of gas permeability of samples of constructive materials has been constructed. The device consists of compressor 1, receiver 2 with manometer 3, gates 4,5, holder 6 of concrete samples 7, flow meter of air 8 and vessel with gas 9 (Fig.l). The gate 5 adjusted the value of the gas pressure. In all experiments the pressure of gases in the receiver was 110 kPa. Air, Ar and 222Rn with concentration of 100 pCu/L in air were used as the gases. 

Confining their study to monofunctional molecules, Roberts et al. [38] compared seven different models for predicting human stratum corneum permeability coefficients. The performance of the models was assessed by the adjusted coefficient of determination r2dj and the Akaike Information Criterion (AIC) [39], Both r2dj and AIC allow for comparing models with different numbers of variables (degrees of freedom). Exclusion of polyfunctional molecules led to a comparatively small set of only 24 molecules. The previously reported... 

P. Koschany. Electrodes with adjustable gas permeability, and method of producing such electrodes. US Patent 2003138689 (2003). 

At the beginning of the project, it is often difficult to have a precise idea of the projected therapeutic dose. Projects usually start with an estimated average potency of 1 mg/kg, once daily dose as an optimal approach. When initial pharmacokinetic/ pharmacodynamic (PK/PD) data becomes available one can better refine the TCP. Table 3.1 gives some guidelines on how to adjust the solubility requirement depending on the therapeutic dose and compound permeability. 

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