The Experts below are selected from a list of 46041 Experts worldwide ranked by ideXlab platform
Hans Lennernas - One of the best experts on this subject based on the ideXlab platform.
-
human jejunal Effective Permeability and its correlation with preclinical drug absorption models
Journal of Pharmacy and Pharmacology, 2011Co-Authors: Hans LennernasAbstract:This review focuses on intestinal Permeability measurements in humans and various aspects of in-vivo transport mechanisms. In addition, comparisons of human data with preclinical models and the blood-brain barrier is discussed. The regional human jejunal perfusion technique has been validated by several crucial points. One of the most important findings is that there is a good correlation between the measured human Effective Permeability values and the extent of absorption of drugs in humans determined by pharmacokinetic studies. We have also shown that it is possible to determine the Effective Permeability (Peff) for carrier-mediated transported compounds, and to classify them according to the proposed Biopharmaceutical Classification System (BCS). Furthermore, it is possible to predict human in-vivo Permeability using preclinical Permeability models, such as in-situ perfusion of rat jejunum, the Caco-2 model and excized intestinal segments in the Ussing chamber. The Permeability of passively transported compounds can be predicted with a particularly high degree of accuracy. However, special care must be taken for drugs with a carrier-mediated transport mechanism, and a scaling factor has to be used. It is also suggested that it is possible to roughly estimate the Permeability of the blood-brain barrier using measurements of intestinal Permeability, even if the quantitative role of efflux of P-glycoprotein(s) in-vivo still remains to be clarified. Finally, the data obtained in-vivo in humans emphasize the need for more clinical studies investigating the effect of physiological in-vivo factors and molecular mechanisms influencing the transport of drugs across the intestinal and as well as other membrane barriers. It is also important to study the effect of anti-transport mechanisms, such as efflux by P-glycoprotein(s), and gut wall metabolism, for example CYP 3A4, on the bioavailability.
-
human jejunal Effective Permeability and its correlation with preclinical drug absorption models
Journal of Pharmacy and Pharmacology, 1997Co-Authors: Hans LennernasAbstract:This review focuses on intestinal Permeability measurements in humans and various aspects of in-vivo transport mechanisms. In addition, comparisons of human data with preclinical models and the blood-brain barrier is discussed. The regional human jejunal perfusion technique has been validated by several crucial points. One of the most important findings is that there is a good correlation between the measured human Effective Permeability values and the extent of absorption of drugs in humans determined by pharmacokinetic studies. We have also shown that it is possible to determine the Effective Permeability (Peff) for carrier-mediated transported compounds, and to classify them according to the proposed Biopharmaceutical Classification System (BCS). Furthermore, it is possible to predict human in-vivo Permeability using precuneal Permeability models, such as in-situ perfusion of rat jejunum, the Caco-2 model and excized intestinal segments in the Ussing chamber. The Permeability of passively transported compounds can be predicted with a particularly high degree of accuracy. However, special care must be taken for drugs with a carrier-mediated transport mechanism, and a scaling factor has to be used. It is also suggested that it is possible to roughly estimate the Permeability of the blood-brain barrier using measurements of intestinal Permeability, even if the quantitative role of efflux of P-glycoprotein(s) in-vivo still remains to be clarified. Finally, the data obtained in-vivo in humans emphasize the need for more clinical studies investigating the effect of physiological in-vivo factors and molecular mechanisms influencing the transport of drugs across the intestinal and as well as other membrane barriers. It is also important to study the effect of anti-transport mechanisms, such as efflux by P-glycoprotein(s), and gut wall metabolism, for example CYP 3A4, on the bioavailabaility.
Shu Tao - One of the best experts on this subject based on the ideXlab platform.
-
a dynamic prediction model for gas water Effective Permeability in unsaturated coalbed methane reservoirs based on production data
Journal of Natural Gas Science and Engineering, 2014Co-Authors: Junlong Zhao, Dazhen Tang, Yanjun Meng, Shu TaoAbstract:Abstract Effective Permeability of gas and water in coalbed methane (CBM) reservoirs is vital during CBM development. However, few studies have investigated it for unsaturated CBM reservoirs rather than saturated CBM reservoirs. In this work, the dynamic prediction model (PM-Corey model) for average gas-water Effective Permeability in two-phase flow in saturated CBM reservoirs was improved to describe unsaturated CBM reservoirs. In the improved Effective Permeability model, Palmer et al. absolute Permeability model segmented based on critical desorption pressure and Chen et al. relative Permeability model segmented based on critical water saturation were introduced and coupled comprehensively under conditions with the identical reservoir pressures and the identical water saturations through production data and the material balance equations (MBEs) in unsaturated CBM reservoirs. Taking the Hancheng CBM field as an example, the differences between the saturated and unsaturated Effective Permeability curves were compared. The results illustrate that the new dynamic prediction model could characterize not only the stage of two-phase flow but also the stage of single-phase water drainage. Also, the new model can accurately reflect the comprehensive effects of the positive and negative effects (the matrix shrinking effect and the Effective stress effect) and the gas Klinkenberg effect of coal reservoirs, especially for the matrix shrinkage effect and the gas Klinkenberg effect, which can improve the Effective Permeability of gas production and render the process more economically. The new improved model is more realistic and practical than previous models.
-
a dynamic prediction model for gas water Effective Permeability based on coalbed methane production data
International Journal of Coal Geology, 2014Co-Authors: Dazhen Tang, Junlong Zhao, Shuling Tang, Yanjun Meng, Shu TaoAbstract:Abstract An understanding of the relative Permeability of gas and water in coal reservoirs is vital for coalbed methane (CBM) development. In this work, a prediction model for gas–water Effective Permeability is established to describe the Permeability variation within coal reservoirs during production. The Effective stress and matrix shrinkage effects are taken into account by introducing the Palmer and Mansoori (PM) absolute Permeability model. The endpoint relative Permeability is calibrated through experimentation instead of through the conventional Corey relative Permeability model, which is traditionally employed for the simulation of petroleum reservoirs. In this framework, the absolute Permeability model and the relative Permeability model are comprehensively coupled under the same reservoir pressure and water saturation conditions through the material balance equation. Using the Qinshui Basin as an example, the differences between the actual curve that is measured with the steady-state method and the simulation curve are compared. The model indicates that the Effective Permeability is expressed as a function of reservoir pressure and that the curve shape is controlled by the production data. The results illustrate that the PM–Corey dynamic prediction model can accurately reflect the positive and negative effects of coal reservoirs. In particular, the model predicts the matrix shrinkage effect, which is important because it can improve the Effective Permeability of gas production and render the process more economically feasible.
Xinmin Wang - One of the best experts on this subject based on the ideXlab platform.
-
surface crystallization and magnetic properties of fecusibnbmo melt spun nanocrystalline alloys
Materials Research Bulletin, 2017Co-Authors: Fangpei Wan, Jianhua Zhang, Jiancheng Song, Anding Wang, Chuntao Chang, Tao Liu, Fengyu Kong, Muqin Tian, Xinmin WangAbstract:Abstract Fe 82 Cu 1 Si 4 B 11.5 Nb 1.5 −x Mo x ( x = 0, 0.75 and 1.5 at. %) nanocrystalline alloys were prepared using a melt-spinning technique and the effects of Mo content on thermal stability, soft magnetic properties and microstructure evolution were investigated. It was found that the Mo addition can improve the amorphous-forming ability and inhibit surface crystallization in a low vacuum atmosphere which may be due to better oxidative resistance. All the alloys exhibited excellent soft-magnetic properties with low coercivity of 8.9–10.8 A/m, high Effective Permeability of 11,500–11,900 at 1 kHz and high saturation magnetic flux density of 1.67–1.72 T after annealing at optimal annealing conditions. In addition, the alloys containing Mo have better transient Effective Permeability stability with increase in frequency. Decreasing the melt-spinning wheel speed can widen the annealing temperature range for Fe 82 Cu 1 Si 4 B 11.5 Nb 1.5 ribbon. Results indicate that these soft-magnetic nanocrystalline materials have good manufacturability for industrial production.
-
effect of p on glass forming ability magnetic properties and oxidation behavior of fesibp amorphous alloys
Intermetallics, 2017Co-Authors: Anding Wang, Chuntao Chang, Chengjuan Wang, Jing Pang, Xiaofeng Liang, Keqiang Qiu, Xinmin WangAbstract:Abstract The effect of P on the glass forming ability, soft magnetic properties and oxidation behavior of Fe 78 B 13 Si 9- x P x ( x = 0–7) amorphous alloys were investigated. It is found that the proper introduction of P, can Effectively improve the glass forming ability and stability of supercooled liquid region. Fe 78 Si 4 B 13 P 5 BMG, which exhibits high saturation flux density of 1.56 T, was readily made into rod sample with a diameter of 1.5 mm under air casting atmosphere. P bearing alloys also exhibit excellent soft magnetic properties containing low coercivity of 1.7–2.7 A/m, and high Effective Permeability of 8200–12,200. Slight oxidation can further improve the coercivity to a lower value of 1.1 A/m and the higher Effective Permeability to 11,900 for the alloys with P content no more than 3 at. %. Excessive addition of P may deteriorate the glass forming ability, soft magnetic properties and oxidation behavior. Magnetic domain revealing the magnetization process of the amorphous ribbons were characterized to explain the effect of P on magnetic properties and oxidation behavior.
Shuxia Qiu - One of the best experts on this subject based on the ideXlab platform.
-
Effective Permeability of fractured porous media with fractal dual porosity model
Fractals, 2017Co-Authors: Haicheng Liu, Agus P Sasmito, Shuxia QiuAbstract:As natural fractures show statistically fractal scaling laws, fractal geometry has been proposed and applied to model the fracture geometry and to study the hydraulic properties of fractured porous media. In this paper, a fractal dual-porosity model is developed to study the single-phase fluid flow through fractured porous media. An analytical expression for Effective Permeability of fractured porous media is derived, which depends on the fractal dimension and fracture aperture. The effect of fractal dimensions for fracture aperture distribution and tortuosity, the ratio of minimum to maximum fracture apertures and fracture fraction on the Effective Permeability have been discussed. In addition, a power law relationship between the Effective Permeability and fracture fraction is proposed to predict the equivalent hydraulic properties of fractured porous media. Compared with empirical formulas for Effective Permeability, the present fractal dual-porosity model can capture the statistical characteristics of...
-
the gas Effective Permeability of porous media with klinkenberg effect
Journal of Natural Gas Science and Engineering, 2016Co-Authors: Shuxia Qiu, Yan ZhouAbstract:Abstract Gas transport properties in micro and nano-scale porous media are of significance for low-Permeability reservoirs. Gas slippage and gas molecular diffusion in micro- and nano-pores take important effect on the gas Permeability of porous media. Therefore, gas Effective Permeability of micro and nano-scale porous media over the entire Knudsen regime is presented by a fractal model. The analytical expression for gas Effective Permeability with Klinkenberg effect which is a function of structural parameters of porous media (porosity, fractal dimensions and pore diameter) and gas property (mean free path of gas molecule) is derived based on the microflow model and fractal capillary model. In order to further address the local flow field characteristics, numerical simulations are also performed on a fractal Sierpinski carpet. The fractal model is validated by comparison with available experimental results, and the effect of gas slippage on the gas Permeability is discussed also. The present results indicate that gas Effective Permeability with slippage effect increases with the increase of fractal dimension for pore size distribution and decreases as the fractal dimension for tortuosity increases. And the gas slip factor increases with the decrease of pore size, it can be also increased by increased fractal dimension for pore size distribution under fixed maximum pore size and porosity. The current fractal model can characterize the multi-scale microstructures in porous media, and every parameter in the proposed gas Effective Permeability model has specific physical meaning.
Dazhen Tang - One of the best experts on this subject based on the ideXlab platform.
-
a dynamic prediction model for gas water Effective Permeability in unsaturated coalbed methane reservoirs based on production data
Journal of Natural Gas Science and Engineering, 2014Co-Authors: Junlong Zhao, Dazhen Tang, Yanjun Meng, Shu TaoAbstract:Abstract Effective Permeability of gas and water in coalbed methane (CBM) reservoirs is vital during CBM development. However, few studies have investigated it for unsaturated CBM reservoirs rather than saturated CBM reservoirs. In this work, the dynamic prediction model (PM-Corey model) for average gas-water Effective Permeability in two-phase flow in saturated CBM reservoirs was improved to describe unsaturated CBM reservoirs. In the improved Effective Permeability model, Palmer et al. absolute Permeability model segmented based on critical desorption pressure and Chen et al. relative Permeability model segmented based on critical water saturation were introduced and coupled comprehensively under conditions with the identical reservoir pressures and the identical water saturations through production data and the material balance equations (MBEs) in unsaturated CBM reservoirs. Taking the Hancheng CBM field as an example, the differences between the saturated and unsaturated Effective Permeability curves were compared. The results illustrate that the new dynamic prediction model could characterize not only the stage of two-phase flow but also the stage of single-phase water drainage. Also, the new model can accurately reflect the comprehensive effects of the positive and negative effects (the matrix shrinking effect and the Effective stress effect) and the gas Klinkenberg effect of coal reservoirs, especially for the matrix shrinkage effect and the gas Klinkenberg effect, which can improve the Effective Permeability of gas production and render the process more economically. The new improved model is more realistic and practical than previous models.
-
a dynamic prediction model for gas water Effective Permeability based on coalbed methane production data
International Journal of Coal Geology, 2014Co-Authors: Dazhen Tang, Junlong Zhao, Shuling Tang, Yanjun Meng, Shu TaoAbstract:Abstract An understanding of the relative Permeability of gas and water in coal reservoirs is vital for coalbed methane (CBM) development. In this work, a prediction model for gas–water Effective Permeability is established to describe the Permeability variation within coal reservoirs during production. The Effective stress and matrix shrinkage effects are taken into account by introducing the Palmer and Mansoori (PM) absolute Permeability model. The endpoint relative Permeability is calibrated through experimentation instead of through the conventional Corey relative Permeability model, which is traditionally employed for the simulation of petroleum reservoirs. In this framework, the absolute Permeability model and the relative Permeability model are comprehensively coupled under the same reservoir pressure and water saturation conditions through the material balance equation. Using the Qinshui Basin as an example, the differences between the actual curve that is measured with the steady-state method and the simulation curve are compared. The model indicates that the Effective Permeability is expressed as a function of reservoir pressure and that the curve shape is controlled by the production data. The results illustrate that the PM–Corey dynamic prediction model can accurately reflect the positive and negative effects of coal reservoirs. In particular, the model predicts the matrix shrinkage effect, which is important because it can improve the Effective Permeability of gas production and render the process more economically feasible.
