Change Of Permeability Coefficient Research Articles

The Analysis of Soil Slope Transient Seepage Consider the Change of Permeability Coefficient in Rainfall Condition

In order to study the transient seepage field of soil slope when the saturated permeability coefficient changes under rainfall infiltration condition, the finite element software is used to build the numerical analysis model, the influence of slope seepage field and pore water pressure caused by the change of saturated permeability coefficient are emphatically discussed. The results show, under the condition of the certain sustained rainfall strength and rainfall duration, the rain water infiltration rate and infiltration depth are proportional to slope soil saturation permeability coefficient; Pore water pressure along the elevation direction shows the characteristic of “two big heads, among small” under the influence of rainfall infiltration.

The Analysis of Soil Slope Transient Seepage Consider the Change of Permeability Coefficient in Rainfall Condition

In order to study the transient seepage field of soil slope when the saturated permeability coefficient changes under rainfall infiltration condition, the finite element software is used to build the numerical analysis model, the influence of slope seepage field and pore water pressure caused by the change of saturated permeability coefficient are emphatically discussed. The results show, under the condition of the certain sustained rainfall strength and rainfall duration, the rain water infiltration rate and infiltration depth are proportional to slope soil saturation permeability coefficient; Pore water pressure along the elevation direction shows the characteristic of “two big heads, among small” under the influence of rainfall infiltration.

Study on coupled seepage and stress fields in the concrete lining of the underground pipe with high water pressure

When an underground pipe works in high water pressure, cracks often occur in the concrete lining and cause the inner water flowing out to the rock mass. For simulating the hydraulic–mechanical interaction in the process of cracking, a coupling method which based on the three-dimension elasto-plastic finite element method (FEM) is proposed in this paper. The coupling principle can be described as follows: the change of stress field leads to the change of permeability coefficient and the redistribution of the seepage field; the new seepage field will produce new seepage force and lead to the change of stress field. The crack expansion and its influence on the seepage and stress fields are studied in paper. As an engineering example, the coupling model is applied in the structural analysis of the lower bifurcated pipes and the surge chamber of Xiaowan Hydropower Station in China, and the computation results show the coupling method is reasonable.

Cell Volume Kinetics of Adherent Epithelial Cells Measured by Laser Scanning Reflection Microscopy: Determination of Water Permeability Changes of Renal Principal Cells

The water channel aquaporin-2 (AQP2), a key component of the antidiuretic machinery in the kidney, is rapidly regulated by the antidiuretic hormone vasopressin. The hormone exerts its action by inducing a translocation of AQP2 from intracellular vesicles to the cell membrane. This step requires the elevation of intracellular cyclic AMP. We describe here a new method, laser scanning reflection microscopy (LSRM), suitable for determining cellular osmotic water permeability coefficient changes in primary cultured inner medullary collecting duct (IMCD) cells. The recording of vertical-reflection-mode x- z-scan section areas of unstained, living IMCD cells proved useful and valid for the investigation of osmotic water permeability changes. The time-dependent increases of reflection-mode x- z-scan section areas of swelling cells were fitted to a single-exponential equation. The analysis of the time constants of these processes indicates a twofold increase in osmotic water permeability of IMCD cells after treatment of the cells both with forskolin, a cyclic AMP-elevating agent, and with Clostridium difficile toxin B, an inhibitor of Rho proteins that leads to depolymerization of F-actin-containing stress fibers. This indicates that both agents lead to the functional insertion of AQP2 into the cell membrane. Thus, we have established a new functional assay for the study of the regulation of the water permeability at the cellular level.

Permselectivity of a PA6 membrane for the separation of a compressed CO 2/H 2 gas mixture at elevated pressures

Since recently, compressed gases can substitute for hazardous solvents in the chemical industry. To meet economic and ecological demands, the reuse of compressed gas has become very desirable. This creates the need to remove, in advance, unwanted components (e.g. unconverted H 2 from hydrogenation reactions). This study examines a gas permeation process to achieve the separation of CO 2/H 2 mixture under high pressure. For hydrogen separation from the mixture, a homogeneous PA6 membrane is applied at a temperature of 35°C and at a pressure range between 20 and 380 bar. Due to the competitive impact of membrane compaction and swelling on the transport properties, significant changes in permeability coefficients and selectivity with feed gas composition and pressure can be observed. As reported in this paper, a substantial increase in selectivity can be gained at elevated pressures.

Evaluation of viability of excised rat intestinal segments in the Ussing chamber: investigation of morphology, electrical parameters, and permeability characteristics.

To clarify relations between alterations in electrical and permeability data with time and to elaborate accompanying structural changes of intestinal segments in Ussing chamber experiments. Excised intestinal segments from the rat were studied in a modified Ussing chamber. Experiments were run up to 180 minutes during which the electrical parameters, PD, SCC, and R, were measured and the permeability coefficients (Papp) of mannitol and propranolol were determined. Each segment was observed under the light microscope for morphological evaluation. PD and SCC values showed a decrease for most segments while the R values remained steady throughout the experiment. The Papp for propranolol increased aborally to the small intestine. For mannitol, the reversed was observed. In some cases, there was a time-dependent change in permeability for these marker molecules. The main morphological changes observed were a decreased nucleo-apical distance, decreased villi amplification factor, initial edema, cell sloughing, and epithelial restitution. The time-dependent changes in permeability coefficients of mannitol and propranolol are suggested to be related to changes in electrical parameters and morphological alterations. Presented data illustrates the importance of information regarding time-dependent structural changes for correct interpretation of permeability data.

The effects of pH and chemical enhancers on the percutaneous absorption of indomethacin

AbstractThe absorption of indomethacin through excised hairless mouse skin from aqueous solution was determined at different pH values. We found that the rate of its absorption increased with decreasing pH. Its distribution coefficient in octanol-phosphate buffer was also pH dependent. Furthermore, the change of permeability coefficient with pH correlated well with the distribution coefficient by a two-degree polynominal equation. The individual incorporation of five chemical enhancers into a polymeric patch at optimal pH resulted in an increase or decrease in the in vitro absorption rate and in the amount absorbed during the first 24 hours depending on the enhancer and its concentration used. Both sodium cholate at 4 and 6 %, and sodium lauryl sulfate at 4 % increased the absorption rate about four to seven times compared to the control. The in vivo absorption using rabbits from patch containing 6% sodium cholate also showed an increase in rate and the AUC compared to that from the control; however, the ...

Studies on membrane potentials of excitable membranes using a sublayer model.

Excitation of membranes is usually interpreted by two kinds of theory. One of them is the change of permeability coefficient of Hodgkin & Katz. The other is the opening and closing of ionic channels. If these two theories are to be compatible, the permeability coefficient of Hodgkin & Katz ought to be correlated with the opening and closing of ionic channels. In this paper, the correlation between them are theoretically discussed and a study of the excitation of membrane is developed.As the result, it is pointed out that the Goldman-Hodgkin-Katz equation fails to explain the experimental results on the excitation of membrane (for example, excitation of squid giant axon), if the membrane model which is usually used as the theoretical model since Teorell and Meyer & Sievers, bulk soln. //membrane// bulk soln., is used as the theoretical model. We, therefore, propose a sublayer model of membrane, bulk soln. /sublayer//membrane//sublayer/bulk soln., together with the following assumptions : i) The membrane has ionic channels. ii) The membrane has electric charge and its density is θM (algebraic). iii) A Donnan equilibrium condition is set up between the sublayer and the bulk solution. iV) Ions in the sublayer are adsorbed on the surface of specific ionic channels and permeate through these channels. V) The electric potential in the sublayer is equal to that at the membrane surface.On the basis of this sublayer model, we conclude that the permeability coefficient of Hodgkin & Katz is related to the number of open ionic channels, so that the permeability coefficient changes with opening and closing of the ionic channel.