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Average Permeability (average + permeability)
Selected AbstractsDevelopment of an in vitro blood,brain barrier model to study the effects of endosulfan on the permeability of tight junctions and a comparative study of the cytotoxic effects of endosulfan on rat and human glial and neuronal cell culturesENVIRONMENTAL TOXICOLOGY, Issue 3 2006Melissa P. L. Chan Abstract Endosulfan, an organochlorine (OC) insecticide that belongs to the cyclodiene group, is one of the most commonly used pesticides to control pests in vegetables, cotton, and fruits. Porcine brain microvascular endothelial cells were used to develop a model to study the effects of endosulfan on the permeability of tight junctions in the blood,brain barrier (BBB). BBB permeability, measured as transendothelial electrical resistance, decreased in a dose- and time-dependent manner when treated with ,-endosulfan, ,-endosulfan, or endosulfan sulfate. Cytotoxicity testing revealed that the three endosulfans did not cause cell death at concentrations of 10 ,M and below. The ratio of the average permeability of the filter-grown endothelial cell monolayer to 14C-endosulfan (Pe) going from the outer to the inner compartments with that going from the inner to the outer compartments was approximately 1:1.2,2.1 after exposure to concentrations of 0.01,10 ,M. ,-Endosulfan, ,-endosulfan, and endosulfan sulfate had cytotoxic effects on rat glial (C6) and neuronal (PC12) cell cultures as well as on human glial (CCF-STTG1) and neuronal (NT2) cell cultures. The effects of ,-endosulfan were highly selective, with a wide range of LC50 values found in the different cultures, ranging from 11.2 ,M for CCF-STTG1 cells to 48.0 ,M for PC12 cells. In contrast, selective neurotoxicity was not so manifest in glial and neuronal cell cultures after exposure to endosulfan sulfate, as LC50 values were in the range of 10.4,21.6 ,M. CCF-STTG1 cells were more sensitive to ,-endosulfan and endosulfan sulfate, whereas NT2 cells were more sensitive to ,-endosulfan. © 2006 Wiley Periodicals, Inc. Environ Toxicol 21: 223,235, 2006. [source] Effect of compressibility on performance of hydraulic wash columnsAICHE JOURNAL, Issue 7 2002L. van Oord-Knol In a hydraulic wash column the solid crystals are separated from the mother liquor by filtration in the top section of the column. Remaining impurities are removed via countercurrent washing of the crystals in the bottom section. Since compressibility limits the capacity of a wash column, this phenomenon needs to be quantified and modeled rigorously. The compressibility of the bed was determined from the porosity profile and the liquid-pressure profile inside the wash column. The porosity of the bed decreases from 0.65 to 0.3 during transport of the bed. This is associated with a decrease in local bed permeability by a factor of 10. The compressibility of the bed, therefore, partly explains the large ratio between the average permeability above and below the wash front. Compressibility coefficients make it possible to relate the compressive stress to the porosity and permeability in the top section of the bed. These coefficients are, therefore, incorporated in a model to successfully predict the capacity of a wash column with a compressible bed. [source] GEOLOGICAL MODEL EVALUATION THROUGH WELL TEST SIMULATION: A CASE STUDY FROM THE WYTCH FARM OILFIELD, SOUTHERN ENGLANDJOURNAL OF PETROLEUM GEOLOGY, Issue 1 2007S.Y. Zheng This paper presents an approach to the evaluation of reservoir models using transient pressure data. Braided fluvial sandstones exposed in cliffs in SW England were studied as the surface equivalent of the Triassic Sherwood Sandstone, a reservoir unit at the nearby Wytch Farm oilfield. Three reservoir models were built; each used a different modelling approach ranging in complexity from stochastic pixel-based modelling using commercially available software, to a spreadsheet random number generator. In order to test these models, numerical well test simulations were conducted using sector models extracted from the geological models constructed. The simulation results were then evaluated against the actual well test data in order to find the model which best represented the field geology. Two wells at Wytch Farm field were studied. The results suggested that for one of the sampled wells, the model built using the spreadsheet random number generator gave the best match to the well test data. In the well, the permeability from the test interpretation matched the geometric average permeability. This average is the "correct" upscaled permeability for a random system, and this was consistent with the random nature of the geological model. For the second well investigated, a more complex "channel object" model appeared to fit the dynamic data better. All the models were built with stationary properties. However, the well test data suggested that some parts of the field have different statistical properties and hence show non-stationarity. These differences would have to be built into the model representing the local geology. This study presents a workflow that is not yet considered standard in the oil industry, and the use of dynamic data to evaluate geological models requires further development. The study highlights the fact that the comparison or matching of results from reservoir models and well-test analyses is not always straightforward in that different models may match different wells. The study emphasises the need for integrated analyses of geological and engineering data. The methods and procedures presented are intended to form a feedback loop which can be used to evaluate the representivity of a geological model. [source] THE LACUSTRINE LIANGJIALOU FAN IN THE DONGYING DEPRESSION, EASTERN CHINA: DEEP-WATER RESERVOIR SANDSTONES IN A NON-MARINE RIFT BASINJOURNAL OF PETROLEUM GEOLOGY, Issue 4 2005Jin Qiang A lacustrine fan covering an area of about 175sq. km has been identified in the Liangjialou area in the SW of the Dongying Depression, a Tertiary non-marine rift basin in eastern China. Fluvial and deltaic sandstones are established reservoir rocks in the basin, and the deep-water sandstones of the fan succession, which are assigned to Member 3 of the lower Tertiary Shahejie Formation, are also thought to have important reservoir potential. Available data for this study included some 800m of core from 16 wells, well-log data from 426 wells, and 220 sq.km of 3D surveys together with well-test and other production data. From geomorphological reconstructions of the fan, we distinguish first-order (major) fan channels from second-order branched and more distal tip channels. Crevasse splays and overbank shales occur between channels, and sandstone lobes were deposited at channel mouths. Conglomeratic sandstones deposited in major channels are probably the most promising reservoir facies (average porosity c. 20%; average permeability > 1D). Fan construction took place during a single complete cycle of lake level variation which was composed of several sub-cycles. During initial highstand conditions, the fan was dominated by small-scale branched and tip channels and intervening sandy lobes. Fan size increased rapidly during the following lowstand, and then decreased during the ensuing highstand. [source] Simplified description of asymmetric right-handed composite right/left-handed coupler in microstrip chip technologyMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2007Youzhen Wang Abstract The coupling frequency range of the asymmetric coupler composed of a conventional microstrip right-handed (RH) transmission line and a composite right/left-handed (CRLH) transmission line with lumped-elements is investigated. It shows theoretically that the coupling frequency range can be explicitly determined by the given formulas. In the coupling frequency range, the effective permittivity and permeability of the CRLH transmission lines are both negative, at the same time the product of the average permittivity and the average permeability is negative, i.e., ,L < 0, ,L < 0, and · < 0. Two types of RH-CRLH couplers are designed, simulated, and measured. The coupling frequency range obtained from the simulated and the experimental results confirms the theoretical results. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2063,2068, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22643 [source] | ||||||||||