Journal articles on the topic 'Turn permeability'
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Fujita, Shogo, and Hajime Igarashi. "Homogenization of multi-turn coil with elliptic cross-section using complex permeability." COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 38, no. 3 (May 7, 2019): 999–1008. http://dx.doi.org/10.1108/compel-09-2018-0356.
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Purpose The tensor complex permeability of a multi-turn coil with elliptic cross-section is analytically expressed. In field analysis, a multi-turn coil can be modeled by the uniform material that has the present tensor complex permeability. It is shown that the frequency characteristic of the present tensor complex permeability is in good agreement with that evaluated by finite element method applied to a unit cell of the multi-turn coil region. Design/methodology/approach The authors introduce a new method to evaluate the complex permeability of a multi-turn rectangular coil. To obtain the complex permeability of a rectangular coil in a closed form, it is approximated as an elliptic coil. Because the rectangular coil has different complex permeabilities in the vertical and horizontal directions, the complex permeability have to be defined in a tensor form. It suffices to discretize the coil region into rather coarse finite elements without considering the skin depth in contrast to the conventional finite element method. Findings The proposed method is shown to give the impedance of multi-turn coils which is in good agreement with results obtained by the conventional finite element (FE) analysis. By extending the proposed approach, the authors can easily perform 3D FE analysis without difficulty in discretization of the coil region with fairly fine finite elements. Moreover, they found that the approximation of rectangular coils as the elliptic coils is valid for analysis of quasi-static fields using this homogenization method. Originality/value The novelty of this study is in the approximation of the rectangular coils with elliptic coils, and the complex permeability for them is formulated here in a closed form. The proposed formula includes that for the round coils. Using the present method, the authors analyze the rectangular coils without fine discretization.
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Xu, Rou-Di, Kensuke Watanabe, and Atsushi Komatsuzaki. "Permeability for Horseradish Peroxidase in Strial Capillaries in Each Turn of Cochlea." ORL 56, no. 4 (1994): 183–89. http://dx.doi.org/10.1159/000276653.
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Maksimova, O. V. "Erythrocyte membrane permeability in diabetic patients." Kazan medical journal 69, no. 4 (August 15, 1988): 295. http://dx.doi.org/10.17816/kazmj99686.
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The state of cellular homeostasis in diabetic patients was assessed by the permeability of erythrocyte membranes, which can serve as an indicator of functional disorders of the vascular wall. It was found that the value of cytoplasmic membrane permeability depends largely on the variations in the ratio of cholesterol and phospholipids. An absolute or relative increase in membrane cholesterol content is accompanied by stabilization of cellular structures, which, in turn, leads to a decrease in permeability to non-electrolytes and ions and changes in the activity of membrane-bound enzymes.
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Kuwahara, Michio, and A. S. Verkman. "Pre-steady-state analysis of the turn-on and turn-off of water permeability in the kidney collecting tubule." Journal of Membrane Biology 110, no. 1 (August 1989): 57–65. http://dx.doi.org/10.1007/bf01870993.
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Sugita, Kazuya, Noriyuki Takata, and Etsuo Yonemochi. "Non-Effective Improvement of Absorption for Some Nanoparticle Formulations Explained by Permeability under Non-Sink Conditions." Pharmaceutics 14, no. 4 (April 7, 2022): 816. http://dx.doi.org/10.3390/pharmaceutics14040816.
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We evaluated the in vitro permeability of nanoparticle formulations of high and low lipophilic compounds under non-sink conditions, wherein compounds are not completely dissolved. The permeability of the highly lipophilic compound, griseofulvin, was improved by about 30% due to nanonization under non-sink conditions. Moreover, this permeability was about 50% higher than that under sink conditions. On the other hand, for the low lipophilic compound, hydrocortisone, there was no difference in permeability between micro-and nano-sized compounds under non-sink conditions. The nanonization of highly lipophilic compounds improves the permeability of the unstirred water layer (UWL), which in turn improves overall permeability. On the other hand, because the rate-limiting step in permeation for the low lipophilic compounds is the diffusion of the compounds in the membrane, the improvement of UWL permeability by nanonization does not improve the overall permeability. Based on this mechanism, nanoparticle formulations are not effective for low lipophilic compounds. To accurately predict the absorption of nanoparticle formulations, it is necessary to consider their permeability under non-sink conditions which reflect in vivo conditions.
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Che Norazman, Che Wan, Ramadhansyah Putra Jaya, and Meor Othman Hamzah. "Properties of Porous Asphalt Mixture Made with Styrene Butadiene Styrene under Long Term Oven Ageing." Advanced Materials Research 486 (March 2012): 378–83. http://dx.doi.org/10.4028/www.scientific.net/amr.486.378.
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Oven ageing is a set of procedure to simulate the accelerated effects of ageing on pavements structures. In this study, the effect of long-term oven ageing on porous asphalt mixture made with SBS modified binder was investigated. The resilient modulus, water permeability and air voids test results were the performance indicators used to evaluate the effects of ageing. The test results showed that, the resilient modulus of long term aged specimens was higher than those of unaged specimens. From the permeability test results, unaged SBS mixes exhibit lower coefficient permeability compared to the corresponding long-term oven age specimens. Most likely, ageing caused binder hardening, making the mix more difficult to compact and hence exhibited more continuous voids which in turn lead to higher permeability. In addition, the coefficient of permeability decreases as the binder content increased.
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Feng, Naichao, Shiqing Cheng, Weixing Lan, Guoquan Mu, Yao Peng, and Haiyang Yu. "Variable-Permeability Well-Testing Models and Pressure Response in Low-Permeability Reservoirs with non-Darcy Flow." Earth Sciences Research Journal 20, no. 1 (April 30, 2016): 1–6. http://dx.doi.org/10.15446/esrj.v20n1.54144.
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<p>This paper proposes the concept of variable-permeability effect and sets up the one-dimensional and two-dimensional non-Darcy well testing models. The finite difference algorithm is employed to solve the differential equations of the variable-permeability model, and the non-convergence of the numerical solutions is solved by using the geometric mean of permeability. The type curves of pressure and pressure derivative with variable-permeability effect are obtained, and sensitivity analysis is conducted. The results show that the type curves upturn in the middle and late sections, and the curves turn more upward with the severer of the variable-permeability effect. The severer the non-Darcy effect is, the less obviously the curve upturns caused by boundary effect. Furthermore, the boundary effect is increased by increasing the number of impermeable boundaries or decreasing the distance between the well and boundary.</p>
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Denda, Mitsuhiro, Toru Tsuchiya, Peter M. Elias, and Kenneth R. Feingold. "Stress alters cutaneous permeability barrier homeostasis." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 278, no. 2 (February 1, 2000): R367—R372. http://dx.doi.org/10.1152/ajpregu.2000.278.2.r367.
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Recent studies have shown that psychological stress can influence cutaneous barrier function, suggesting that this form of stress could trigger or aggravate skin disease. In the present study, we demonstrate that transfer of hairless mice to a different cage delays barrier recovery rates. Pretreatment with a phenothiazine sedative, chlorpromazine, before transfer of animals restored the kinetics of barrier recovery toward normal, suggesting that psychological stress is the basis for this alteration in barrier homeostasis. To determine the mechanism linking psychological stress to altered barrier recovery, we first demonstrated that plasma corticosterone levels increase markedly after transfer of animals to new cages and that pretreatment with chlorpromazine blocks this increase. Second, we demonstrated that the systemic administration of corticosterone delays barrier recovery. Finally, we demonstrated that pretreatment with the glucocorticoid receptor antagonist RU-486 blocks the delay in barrier recovery produced by systemic corticosterone, change of cage, or immobilization. These results suggest that psychological stress stimulates increased production of glucocorticoids, which, in turn, adversely affects permeability barrier homeostasis.
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Li, Guangquan, Yifang Miao, and Ruoyu Li. "Ultrasonic S-Wave to Obtain Shear Modulus and Matrix Permeability of D’Euville Limestone." Geofluids 2022 (May 6, 2022): 1–9. http://dx.doi.org/10.1155/2022/5126760.
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In this paper, velocity and attenuation of ultrasonic S-wave in a water-saturated rock are used for calculating shear modulus and matrix permeability of the rock, via a model improved from Biot theory. The model requires two inputs, i.e., the dry velocity of S-wave and the average distance of aperture representing pores, to yield phase velocity and the quality factor as functions of frequency. By fitting the predicted velocity and quality factor against the ultrasonically measured counterparts, the dry velocity of S-wave and the average distance of aperture are ascertained, which in turn yield shear modulus and matrix permeability, respectively. The modeling results on D’Euville limestone from France show that the specimen has shear modulus of 11.35 and 11.55 GPa (under differential pressures of 3 and 5 MPa, respectively) and matrix permeability of 0.0486 Darcy (under both differential pressures). The matrix permeability appears to be approximately one half of Darcy permeability.
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Zijlstra, Freek J., Marieke E. van Meeteren, Ingrid M. Garrelds, and Maarten A. C. Meijssen. "Effect of pharmacologically induced smooth muscle activation on permeability in murine colitis." Mediators of Inflammation 12, no. 1 (2003): 21–27. http://dx.doi.org/10.1080/0962935031000096944.
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Background:Both intestinal permeability and contractility are altered in inflammatory bowel disease. Little is known about their mutual relation. Therefore, anin vitroorgan bath technique was developed to investigate the simultaneous effects of inflammation on permeability and smooth muscle contractility in different segments of the colon.Methods and materials:BALB/c mice were exposed to a 10% dextran sulphate sodium drinking water solution for 7 days to induce a mild colitis, while control mice received normal tap water. Intestinal segments were placed in an oxygenated organ bath containing Krebs buffer. Permeability was measured by the transport of the marker molecules3H-mannitol and14C-polyethyleneglycol 4000. Contractility was measured through a pressure sensor. Smooth muscle relaxation was obtained by salbutamol and l-phenylephrine, whereas contraction was achieved by carbachol and 1-(3-chlorophenyl)-biguanide.Results:The intensity of mucosal inflammation increased throughout the colon. Also, regional differences were observed in intestinal permeability. In both normal and inflamed distal colon segments, permeability was diminished compared with proximal colon segments and the non-inflamed ileum. Permeability in inflamed distal colon segments was significantly decreased compared with normal distal segments. Pharmacologically induced relaxation of smooth muscles did not affect this diminished permeability, although an increased motility positively affected permeability in inflamed and non-inflamed distal colon.Conclusions:Inflammation and permeability is inversely related. The use of pro-kinetics could counteract this disturbed permeability and, in turn, could regulate the disturbed production of inflammatory mediators.
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Iffat, Shohana, Abul Bashar Emon, Tanvir Manzur, and Syed Ishtiaq Ahmad. "An Experiment on Durability Test (RCPT) of Concrete According to ASTM Standard Method Using Low-Cost Equipments." Advanced Materials Research 974 (June 2014): 335–40. http://dx.doi.org/10.4028/www.scientific.net/amr.974.335.
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Durability means the resistance to physical or chemical deterioration of concrete resulting from interaction with environment (physical deterioration) or interaction between constituents (chemical deterioration) of concrete. A durable concrete ensures corrosion resistance of embedded steel which in turn ensures a better longevity of the structure as a whole. Concrete in structures in the coastal areas are the most susceptible to chemical deterioration as sea water, with high concentration of chloride ions, has quite a detrimental effect on durability of concrete. In these cases, the lower the chloride permeability, the better the durability of concrete. As instruments for standard chloride permeability test is very expensive, an experiment has been conducted to carry out Rapid Chloride Permeability Test (RCPT) using improvised apparatus made of readily available low-cost materials. Several RCPT tests were performed using this simple method and results showed marked variation in chloride permeability for concrete with different quality.
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Wong, Ron CK. "A model for strain-induced permeability anisotropy in deformable granular media." Canadian Geotechnical Journal 40, no. 1 (February 1, 2003): 95–106. http://dx.doi.org/10.1139/t02-088.
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In a deformable granular medium, shear deformation results in a change in pore volume, thereby causing a change in permeability. In previous studies, it is assumed that the change in absolute permeability is a function of porosity or volumetric strain, which in turn is a function of the mean or minimum effective stress. In such semi-empirical correlations, the changes in permeability are equal in all directions, even though the changes in strains are different in each direction. This paper proposes a new model accounting for permeability anisotropy induced by strains in deformable porous media. This model is derived from the well-known phenomenological KozenyCarman equation with some modifications. It was proven that tensor parameters embedded in the KozenyCarman equation (hydraulic radius and tortuosity of flow channels) can be expressed in terms of principal strains for granular assemblies of idealized packings. This approach allows one to formulate the evolution of changes in permeability in three directions under continuous shearing. The model explicitly states that the permeability changes are anisotropic, dependent on the induced strains. A comparison between experimental data and predicted results is presented to show the validity of the proposed model.Key words: strain-induced anisotropy, permeability, shear dilation, principal strain, tortuosity, tensor.
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de Jong, Arjan S., Willem J. G. Melchers, Dirk H. R. F. Glaudemans, Peter H. G. M. Willems, and Frank J. M. van Kuppeveld. "Mutational Analysis of Different Regions in the Coxsackievirus 2B Protein." Journal of Biological Chemistry 279, no. 19 (February 18, 2004): 19924–35. http://dx.doi.org/10.1074/jbc.m314094200.
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The coxsackievirus 2B protein is a small hydrophobic protein (99 amino acids) that increases host cell membrane permeability, possibly by forming homo-multimers that build membrane-integral pores. Previously, we defined the functional role of the two hydrophobic regions HR1 and HR2. Here, we investigated the importance of regions outside HR1 and HR2 for multimerization, increasing membrane permeability, subcellular localization, and virus replication through analysis of linker insertion and substitution mutants. From these studies, the following conclusions could be drawn. (i) The hydrophilic region (58RNHDD62) between HR1 and HR2 is critical for multimerization and increasing membrane permeability. Substitution analysis of Asn61and Asn62demonstrated the preference for short polar side chains (Asp, Asn), residues that are often present in turns, over long polar side chains (Glu, Gln). This finding supports the idea that the hydrophilic region is involved in pore formation by facilitating a turn between HR1 and HR2 to reverse chain direction. (ii) Studies undertaken to define the downstream boundary of HR2 demonstrated that the aromatic residues Trp80and Trp82, but not the positively charged residues Arg81, Lys84, and Lys86are important for increasing membrane permeability. (iii) The N terminus is not required for multimerization but does contribute to the membraneactive character of 2B. (iv) The subcellular localization of 2B does not rely on regions outside HR1 and HR2 and does not require multimerization. (v) Virus replication requires both the membrane-active character and an additional function of 2B that is not connected to this activity.
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Watanabe, Kensuke, and Yasuo Tanaka. "Horseradish Peroxidase Permeation from the Capillaries of the Stria Vascularis after Inoculation of Endotoxin into the Middle Ear." Annals of Otology, Rhinology & Laryngology 106, no. 5 (May 1997): 394–98. http://dx.doi.org/10.1177/000348949710600507.
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Escherichia coli-derived endotoxin was inoculated in the middle ear of guinea pigs 24 hours after being injected intraperitoneally. Twenty-four hours after the middle ear inoculation, horseradish peroxidase (HRP) was injected via the femoral vein and the permeability of HRP through the capillaries of the stria vascularis and the destination of the leaked HRP were examined. A large amount of HRP leaked out of the capillary through the opened endothelial cell junctions and penetrated the enlarged intercellular spaces. Leaked HRP entered the pinocytotic vesicles of the intermediate cells. Even slightly degenerated intermediate cells retained this function. The HRP penetrated the spongelike structure of the marginal cells leading to the intercellular space. This structure was not observed without endotoxin. The HRP could not pass to the cochlear duct through the tight junctions between marginal cells. Blood sludging was observed in the strial capillaries. It appeared more frequently in the upper three turns than in the basal turn. The HRP leakage out of the capillaries was observed not only in the upper three turns but also in the basal turn.
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Xu, Tao, and Chun An Tang. "Modeling of Stress-Induced Permeability Evolution and Damage of Rock." Advanced Materials Research 33-37 (March 2008): 609–16. http://dx.doi.org/10.4028/www.scientific.net/amr.33-37.609.
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Rock permeability is important in civil and geo-hydraulic engineering, the mining and petroleum industries, and in environmental and engineering geology. In this paper, considering the mutual hydro-mechanical response between stress-induced permeability and damage, a coupled mathematical model for solid deformation and gas flow in the coal or rock was established and an attempt is made to investigate the rock permeability evolution, fracture patterns, and flow vectors in rock samples at the scale of usual laboratory samples as well as the relation between permeability and stress induced damage in connection with the complete strain-stress process of loaded rocks. Numerical simulations show that the permeability of rock was not constant, closely related to the state of stress, but varied with the stress and strain states in the rocks. Microcracking, resulting from the concentration of stress on relatively weak rock elements, triggers successive crack initiation and propagation that in turn leads to permeability enhancement. Prior to the peak strength, the permeability decreases with increasing load. A dramatic increase in permeability occurs in the post-peak stress-strain region due to the catastrophic collapse of microstructure in rock. Moreover, the permeability of rock in post-peak stress-strain region is much higher that that of in pre-peak region. Such intensive studies of gas flow in stressed heterogeneous rocks are useful as initial approaches to many engineering problems in mining and petroleum industries.
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MOUSA, H. M., and M. M. SHABAT. "NONLINEAR TE SURFACE WAVES IN A LEFT-HANDED MATERIAL AND SUPER LATTICES WAVE-GUIDE STRUCTURE." International Journal of Modern Physics B 21, no. 06 (March 10, 2007): 895–906. http://dx.doi.org/10.1142/s0217979207036746.
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The paper is concerned with the propagation characteristics of TE surface waves in a planar wave-guide structure of a lateral antiferromagnetic-non magnetic super lattices (LANS) film bounded by a nonlinear dielectric cover and a left-handed substrate (LHM). In LHM substrate both permittivity and magnetic permeability are negative in definite frequency range. We study nonlinear dispersion properties of the TE surface waves and illustrate the power flow variation with the wave index in three different cases, i.e., when both permittivity and magnetic permeability are negative, when permittivity is negative and permeability is positive, and when both permittivity and magnetic permeability are positive. In the first case, we found that surface waves are backward traveling and the wave power variation with the wave index shows bistability behavior. We also found that by increasing the film thickness the waves turn from forward to backward traveling in the second case. In the third case, surface waves are always forward traveling.
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Rajni, Rajni, and Anupma Marwaha. "Resonance Characteristics and Effective Parameters of New Left Hand Metamaterial." TELKOMNIKA Indonesian Journal of Electrical Engineering 15, no. 3 (September 1, 2015): 497. http://dx.doi.org/10.11591/tijee.v15i3.1567.
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It is essential to alter effective electromagnetic parameters of a material to enhance its response. In the present work, we propose a novel Left Hand Metamaterial (LHM) structure comprising dual turn spiral resonator (DTSR) and capacitance loaded strips (CLS). This structure is numerically explored to examine the resonance and effective material parameters i.e. permeability and permittivity. The negative refraction in the unit cell is confirmed with identification of double negative region (negative permittivity, ε and negative permeability, µ ) on placing the unit cell in a waveguide with well defined Perfect Electric Conduction/Perfect Magnetic Conduction boundary conditions.
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Chen, Liang, Dongsheng Zhang, Wei Zhang, Jingna Guo, Nan Yao, Gangwei Fan, Shizhong Zhang, Xufeng Wang, and Peng Wu. "Experimental Investigation on Post-Peak Permeability Evolution Law of Saturated Sandstone under Various Cyclic Loading–Unloading and Confining Pressure." Water 14, no. 11 (May 31, 2022): 1773. http://dx.doi.org/10.3390/w14111773.
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The permeability evolution law of saturated rock under cyclic loading–unloading after shear yield is an important basis for revealing the water resistance performance and water inrush risk of overlying rock under multiple mining conditions. In this paper, the influence of the confining pressure, the cyclic loading–unloading times (CLT), and the volumetric strain on the post-peak permeability of saturated sandstone was studied by carrying out a post-peak permeability experiment. Based on SEM images and an improved simulated annealing algorithm, the 3D internal structure characteristics of sandstone samples before and after the experiment were reconstructed. The influences of the confining pressure on pore diameter, effective porosity, connectivity, seepage path length, and tortuosity of the sandstone before and after the experiment are discussed. Research results indicated that (1) In the post-peak cyclic loading–unloading stage, the volumetric strain is negatively correlated with permeability. At the unloading and initial loading stage, the volumetric strain showed a gradually decreasing trend as the specimen was slowly compressed. However, at the middle and final loading stages, the volumetric strain curve shifted to the left and showed a decreasing trend, resulting in an obvious increase in permeability. (2) The influence of CLT on k is closely related to the confining pressure level. When the confining pressure changed from 4 MPa to 12 MPa, the volumetric strain–average stress hysteretic curve shifted to the left in turn and the corresponding permeability gradually increased. When the confining pressure increased to 16 MPa and 20 MPa, the volumetric strain–average stress hysteretic curve shifted to the right in turn and the corresponding permeability showed a decreasing trend. No matter what the value of CLT, the magnitude of sandstone permeability gradually decreased and the decreasing trend became flat as the confining pressure increased, especially for σ3 = 16 MPa and 20 MPa. (3) No matter what value of the confining pressure, the hysteresis area of the first cycle was larger than that of last three cycles, indicating that the plastic deformation generated in the first cycle was larger than that generated in the last three cycles and the recovery rate of the permeability increased with an increase of CLT. (4) As the confining pressure gradually increased, the pore diameter, effective porosity, and connectivity all approximately showed a linear decrease due to more easily compacted pores and cracks under high confining pressure, lower connectivity, and permeability, while the length and tortuosity of the seepage path increased nonlinearly, roughly due to a more significant shear failure phenomenon where the seepage path became more tortuous, that is, the greater the tortuosity, the longer the seepage path. The research results can provide an important theoretical basis for water resistance performance and water inrush risk assessment of overlying aquifer under the influence of mining stress.
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Hurst, A., and J. S. Archer. "Some applications of clay mineralogy to reservoir description." Clay Minerals 21, no. 4 (October 1986): 811–26. http://dx.doi.org/10.1180/claymin.1986.021.4.22.
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AbstractStudy of sandstone diagenesis provides information about the origin, texture, distribution and composition of clay minerals, which in turn is used in reservoir description. Three examples of the use of clay mineralogy in reservoir description are given. (1) Kaolinite commonly forms pore-filling cements which are pervasive in specific sandstone intervals. It is shown that water-zone kaolinization homogenizes and lowers the porosity and permeability relative to the oil zone; in a reservoir model different Ø/Krelationships are defined above and below the oil-water contact. (2) An occurrence of chlorite in dish-structured horizons is shown to increase horizontal permeability and decrease formation resistivity. The sensitivity of the neutron porosity log to the chlorite cement reduces the usefulness of the log for porosity evaluation. Uncritical application of wireline logs to define reservoir parameters can give pessimistic reservoir evaluation. (3) Sand production can be related to wettability, which in turn is strongly influenced by clay mineralogy. A perforation strategy to minimize sand production may then be based on knowledge of the clay mineralogy of a reservoir.
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Hordijk, P. L., E. Anthony, F. P. Mul, R. Rientsma, L. C. Oomen, and D. Roos. "Vascular-endothelial-cadherin modulates endothelial monolayer permeability." Journal of Cell Science 112, no. 12 (June 15, 1999): 1915–23. http://dx.doi.org/10.1242/jcs.112.12.1915.
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Vascular endothelial (VE)-cadherin is the endothelium-specific member of the cadherin family of homotypic cell adhesion molecules. VE-cadherin, but not the cell adhesion molecule platelet/endothelial cell adhesion molecule (PECAM-1), markedly colocalizes with actin stress fibers at cell-cell junctions between human umbilical vein endothelial cells. Inhibition of VE-cadherin-mediated, but not PECAM-1-mediated, adhesion induced reorganization of the actin cytoskeleton, loss of junctional VE-cadherin staining and loss of cell-cell adhesion. In functional assays, inhibition of VE-cadherin caused increased monolayer permeability and enhanced neutrophil transendothelial migration. In a complementary set of experiments, modulation of the actin cytoskeleton was found to strongly affect VE-cadherin distribution. Brief stimulation of the beta2-adrenergic receptor with isoproterenol induced a loss of actin stress fibers resulting in a linear, rather than ‘jagged’, VE-cadherin distribution. The concomitant, isoproterenol-induced, reduction in monolayer permeability was alleviated by a VE-cadherin-blocking antibody. Finally, cytoskeletal reorganization resulting from the inactivation of p21Rho caused a diffuse localization of VE-cadherin, which was accompanied by reduced cell-cell adhesion. Together, these data show that monolayer permeability and neutrophil transendothelial migration are modulated by VE-cadherin-mediated cell-cell adhesion, which is in turn controlled by the dynamics of the actin cytoskeleton.
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Mortezaei, Hanane, and Mehran Karimpour Fard. "Variation of the Hydraulic Conductivity of Clayey Soils in Exposure to Organic Permeants." Civil Engineering Journal 3, no. 11 (December 10, 2017): 1036. http://dx.doi.org/10.28991/cej-030936.
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Clayey soils are the most common material used in waterproofing and play an essential role in waste and contamination control. Permeability is a key parameter in such problems and its determination is needed in ensuring the satisfactory performance of the soil. Research has shown that a permeant fluid with a low dielectric constant can shrink the double layer around the clay particles which will, in turn, increase the permeability of the soil. In this paper, the permeability of two types of clay with different plasticity, exposed to the flow of water and methanol as polar and miscible solvents and gasoline and car oil as non-polar and immiscible solvents is investigated. In addition, the effect of soil properties such as plasticity and compaction water content on permeability of the samples is examined. To this end, soil samples are prepared and compacted at various water contents. Then, permeability tests are conducted according to the modified constant head method and the effects of parameters such as the fluid dielectric constant, water content of the samples and soil plasticity are examined. The results demonstrate that the lower dielectric constant of the organic fluid decreases the thickness of the double layer, providing more space for the flow of the permeant and as a result, the permeability of the clay increases. The reduction of the permeant dielectric constant from 80.4 to 2.28 led to a remarkable increase in soil permeability.
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Roma, Fábia, Karla Penha, Carlos Torres, Etevaldo Maia-Filho, and Leily Firoozmand. "Assessment of permeability of eroded dentin after the use of universal, self-etch, and conventional systems." Acta Odontológica Latinoamericana 34, no. 1 (April 2021): 10–17. http://dx.doi.org/10.54589/aol.34/1/010.
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Dentin hypersensitivity is caused by increased dentinal permeability due to total or partial exposure of dentinal tubules, which in turn can be produced by alterations of dental structures or failure of restorative procedures. The purpose of this in vitro study was to evaluate the efficacy of the application of different kinds of adhesive systems to prevent dentin permeability before and after an erosive challenge. Fifty bovine dentin discs (6x1 mm) were prepared and the specimens were divided into 5 groups (n=10): (SB2) Single Bond 2, (SBU) Universal Single Bond, (CSB) Clearfil SE Bond, (SM) Scotchbond Multipurpose and (C) Control. Hydraulic conductance of dentin was recorded after adhesive application (HC-1) and after erosive challenge (HC-2). Dentin surface images of post-treatment and post-erosive challenge were obtained by scanning electron microscopy (SEM). Data were analyzed using Kruskal Wallis, Mann-Whitney with Bonferroni correction and Wilcoxon tests (p<0.05). Reduction in dentin permeability was observed with the application of adhesive systems (p<0.05). After the erosive challenge, dentin permeability increased for SBU and CSB (p<0.05), while SB2 and SM did not differ in HC-1 or HC-2 (p>0.05). The conventional, self-etching and universal adhesive systems reduce dentinal permeability by more than 80%, and dentin demineralization may contribute to the increased permeability of universal and self-etching systems.
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Kudasik, Mateusz. "Investigating Permeability of Coal Samples of Various Porosities under Stress Conditions." Energies 12, no. 4 (February 25, 2019): 762. http://dx.doi.org/10.3390/en12040762.
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Among the numerous factors that have an impact on coal permeability, coal porosity is one of the main parameters. A change in the mechanical stress applied to coal results in a change of porosity. The main objective of the conducted research was to answer the following question: is a decline in coal permeability a direct effect of a decrease in coal porosity, and does mechanical stress result solely in a porosity change? A study of coal porosity under mechanical stress conditions was conducted using a uniquely constructed measurement stand. The coal samples used were briquettes prepared from a granular coal material (middle-rank coal of type B—meta bituminous, upper carboniferous formation) from the “Zofiówka” coal mine, in Poland. In order to describe coal permeability, the Klinkenberg equation was used, as it takes into consideration the slippage effect, typical of porous media characterized by low permeability. On the basis of the obtained results, it was established that the values of the Klinkenberg permeability coefficient decrease as the mechanical stress and the corresponding reduction in porosity become greater. As the briquette porosity increased, the Klinkenberg slippage effect: (i) disappeared in the case of nitrogen, (ii) and was minor for methane. The briquettes used were characterized by various porosities and showed that mechanical stress results mainly in a change in coal porosity, which, in turn, reduces coal permeability.
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Goldsmith, D. I., R. A. Jodorkovsky, J. Sherwinter, S. R. Kleeman, and A. Spitzer. "Glomerular capillary permeability in developing canines." American Journal of Physiology-Renal Physiology 251, no. 3 (September 1, 1986): F528—F531. http://dx.doi.org/10.1152/ajprenal.1986.251.3.f528.
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The changes in glomerular permeability that occur during development were assessed in 1- and 6-wk-old canines by analyzing dextran-sieving curves obtained in six animals at each age. The fractional clearance of the smallest dextran molecules (18 A) was 0.97 +/- 0.02 (+/- SE) in both 1- and 6-wk-old animals, and it became progressively less at larger molecular sizes. The sieving curves were consistent with an isosporous model of a glomerular capillary. When axial changes in protein concentration were included in the mathematical model, the apparent pore radius was 62.7 +/- 1.7 and 61.7 +/- 1.69 A in 1- and 6-wk-old puppies, respectively (P greater than 0.7). The effects of developmental changes in hydrostatic pressure and renal blood flow were balanced by the increases in serum protein concentration and filtration fraction leaving the fractional clearances of macromolecules unchanged. In contrast, the total cross-sectional pore area per unit path length (Aw/delta x) increased during this 6-wk period by approximately 7.5-fold (from 1.39 +/- 0.2 to 10.55 +/- 3.0 10(-5) cm, P less than 0.0001), and the ultrafiltration coefficient rose from 0.012 +/- 0.002 to 0.093 +/- 0.012 ml X s-1 X mmHg-1 (P less than 0.0001). The findings reveal constancy of pore size and an increase in total pore area as a function of age. Analysis by classical pore theory yielded similar findings. We conclude that the predominant factor determining the rise in glomerular filtration rate during development is the large increment in Aw/delta x, which in turn is due to increases in the surface area and pore density of the glomerular capillaries.
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Gao, Yanfang, Huiwen Pang, Yan Jin, and Mian Chen. "Evaluation of Shear Dilation Capability/Potential and Permeability Changes in Karamay Oil Sands under Water Injection." Geofluids 2019 (November 25, 2019): 1–21. http://dx.doi.org/10.1155/2019/7245081.
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Water injection can effectively improve the reservoir porosity and permeability by shear dilation in the vicinity of wellbores. In this paper, shear dilation and permeability improvement capability/potential are proposed to describe the evolutions of porosity and permeability under water injection-induced shear. The mathematical models based on Karamay oil sand microstructures derived from ESEM (environmental scanning electron microscope) are established to predict the shear dilation effects based on the particle packing theory. Triaxial compression and permeability experiments are conducted to validate the theoretical models, and the experimental data is consistent with model results. Also, the study compares shear dilation capabilities evaluated from three scales: ESEM (μm), laboratory triaxial compression tests (cm), and field injection tests (m). Major conclusions through an application on the wellpair A-2 in area A of the Karamay oil field showed that the oil sands have an excellent shear dilation potential. The larger arrangement angle results in stronger shear dilation and permeability, which means a lower arrangement angle provides a higher potential for improvement. The shear dilation capabilities predicted by ESEM, triaxial compression experiments, and field injection data descend in turn, which indicates that the actual shear dilation capability is difficult to be utilized by present field operations.
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Sarraguça, Mafalda C., Paulo R. S. Ribeiro, Cláudia Nunes, and Catarina Leal Seabra. "Solids Turn into Liquids—Liquid Eutectic Systems of Pharmaceutics to Improve Drug Solubility." Pharmaceuticals 15, no. 3 (February 23, 2022): 279. http://dx.doi.org/10.3390/ph15030279.
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The low solubility of active pharmaceutical ingredients (APIs) is a problem in pharmaceutical development. Several methodologies can be used to improve API solubility, including the use of eutectic systems in which one of the constituents is the API. This class of compounds is commonly called Therapeutic Deep Eutectic Systems (THEDES). THEDES has been gaining attention due to their properties such as non-toxicity, biodegradability, and being non-expensive and easy to prepare. Since the knowledge of the solid liquid diagram of the mixture and the ideal eutectic point is necessary to ascertain if a mixture is a deep eutectic or just a eutectic mixture that is liquid at ambient temperature, the systems studied in this work are called Therapeutic Liquid Eutectic Systems (THELES). Therefore, the strategy proposed in this work is to improve the solubility of chlorpropamide and tolbutamide by preparing THELES. Both APIs are sulfonylurea compounds used for the treatment of type 2 diabetes mellitus and have low solubility in water. To prepare the THELES, several coformers were tested, namely, tromethamine, L(+)-arginine, L-tryptophan, citric acid, malic acid, ascorbic acid, and p-aminobenzoic acid, in molar ratios of 1:1 and 1:2. To improve viscosity, water was added in different molar ratios to all systems. THELES were characterized by mid-infrared spectroscopy (MIR), and differential scanning calorimetry. Their viscosity, solubility, and permeability were also determined. Their stability at room temperature and 40 °C was accessed by MIR. Cytocompatibility was performed by metabolic activity and cell lysis evaluation, according to ISO10993-5:2009, and compared with the crystalline APIs. THELES with TRIS were successfully synthesized for both APIs. Results showed an increased solubility without a decrease in the permeability of the APIs in the THELES when compared with the pure APIs. The THELES were also considered stable for 8 weeks at ambient temperature. The cells studied showed that the THELES were not toxic for the cell lines used.
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Boudry, Gaëlle, Jennifer Jury, Ping Chang Yang, and Mary H. Perdue. "Chronic psychological stress alters epithelial cell turn-over in rat ileum." American Journal of Physiology-Gastrointestinal and Liver Physiology 292, no. 5 (May 2007): G1228—G1232. http://dx.doi.org/10.1152/ajpgi.00358.2006.
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Dysregulated epithelial cell kinetics associated with mucosal barrier dysfunction may be involved in certain intestinal disorders. We previously showed that chronic psychological stress, in the form of repetitive sessions of water avoidance stress (WAS), has a major detrimental impact on ileal barrier function. We hypothesized that these changes were related to a disturbance in enterocyte kinetics. Rats were submitted to WAS (1 h/day) for 5 or 10 days. As previously shown, permeability to macromolecules was enhanced in rats stressed for 5 and 10 days compared with controls. WAS induced a decrease in crypt depth at day 5 associated with an increased number of apoptotic cells. Cell proliferation was significantly increased at days 5 and 10. Villus height and the specific activity of sucrase were significantly reduced at day 10. We concluded that WAS induces a disturbance of epithelial cell kinetics, with the pattern depending on the duration of the stress period. These findings help to explain the mechanism underlying altered epithelial barrier function resulting from exposure to chronic psychological stress.
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Vorobyeva, Natalia M., and Olga N. Tkacheva. "Syndrome of increased epithelial permeability, non-alcoholic fatty liver disease and cardiovascular diseases: what is the association and what can be done about it?" Clinical review for general practice 2, no. 8 (October 2, 2021): 12–19. http://dx.doi.org/10.47407/kr2021.2.8.00093.
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Syndrome of increased epithelial permeability occurs due to a decrease in the barrier function of the gastrointestinal mucosa due to impaired intercellular interactions, resulting in bacterial translocation (i. e. penetration of bacteria and toxins from the gastrointestinal lumen into the bloodstream), which can initiate an inflammatory process in various diseases. Syndrome of increased epithelial permeability plays an important role in the pathogenesis of many chronic diseases, including cardiovascular and non-alcoholic fatty liver disease (NAFLD). In turn, the presence of NAFLD is associated with an increase in cardiovascular morbidity and mortality. The use of ursodeoxycholic acid in NAFLD allows reducing both hepatological and cardiovascular risks. Gastro- and enteroprotector rebamipide not only eliminates increased epithelial permeability and acts at all three levels of protection of the mucosepithelial barrier, but also has multiple pleiotropic effects, which opens up wide prospects for its use in cardiovascular diseases and NAFLD. The hepatoprotective and anti-sclerotic effects of rebamipide identified in experimental studies need further study in clinical trials in NAFLD patients.
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Blom, Saskia M. P., and Jacques Hagoort. "The Combined Effect of Near-Critical Relative Permeability and Non-Darcy Flow on Well Impairment by Condensate Drop Out." SPE Reservoir Evaluation & Engineering 1, no. 05 (October 1, 1998): 421–29. http://dx.doi.org/10.2118/51367-pa.
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This paper (SPE 51367) was revised for publication from paper SPE 39976, first presented at the 1998 SPE Gas Technology Symposium, Calgary, 15-18 March. Original manuscript received for review 19 March 1998. Revised manuscript received 8 July 1998. Paper peer approved 13 July 1998. Summary We present a comprehensive numerical method to calculate well impairment based on steady-state radial flow. The method incorporate near-critical relative permeability and saturation-dependent inertial resistance. Example calculations show that near-critical relative permeability, which depends on the capillary number, and non-Darcy flow are strongly coupled. Inertial resistance gives rise to a higher capillary number. In its turn, the improved mobility of the gas phase caused by a higher capillary number enhances the importance of the inertial resistance. The effect of non-Darcy flow is much more pronounced in gas condensate reservoirs than in dry gas reservoirs. Well impairment may be grossly overestimated if the dependence of relative permeability on the capillary number is ignored. P. 421
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Eggena, P., C. L. Ma, F. Fahrenholz, and I. L. Schwartz. "Persistent stimulation of adenylate cyclase and urea transport by an AVP photolabel." American Journal of Physiology-Cell Physiology 249, no. 1 (July 1, 1985): C84—C88. http://dx.doi.org/10.1152/ajpcell.1985.249.1.c84.
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The effects of a photoaffinity label for arginine vasopressin receptors, [Phe2, Phe(p-N3)3]AVP (N3-AVP), on urea permeability and adenylate cyclase activity have been investigated in the toad urinary bladder. This compound, when activated by ultraviolet light, induced a maximal and persistent increase in the urea permeability of the intact bladder and a persistent increase in the adenylate cyclase activity of toad bladder epithelial cell homogenates. Covalent attachment of the analogue to target tissue during photolysis was equivalent at 4 and 20 degrees C. Bladders exposed to N3-AVP in the presence of AVP during photolysis were substantially less permeable to urea than controls that had been exposed to N3-AVP alone. These findings constitute further evidence in support of our previous suggestion that N3-AVP binds covalently to AVP receptors and, in addition, demonstrates that N3-AVP evokes a persistent increase in adenylate cyclase activity which, in turn, triggers a persistent increase in bladder permeability to urea.
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Savarina, V. A., and V. M. Mitsura. "THE ROLE OF THE GUT-LIVER AXIS IN LIVER CIRRHOSIS PATHOGENESIS AND COMPLICATIONS." Hepatology and Gastroenterology 4, no. 2 (2020): 151–54. http://dx.doi.org/10.25298/2616-5546-2020-4-2-151-154.
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Background. Liver cirrhosis is a severe disease that can provoke hepatocellular carcinoma. It is known that such patients have increased intestinal permeability causing the translocation of living bacteria and bacterial products through the inferior vena cava system into the liver, that leads to a cascade of immune and molecular events. Objective – to establish the role of the gut-liver axis in the pathogenesis and outcomes of liver cirrhosis. Material and methods. We performed a PubMed search of publications over the last 10 years, using the keywords ‘intestinal permeability’, ‘cirrhosis’. Results. Increased intestinal permeability and bacterial translocation are of great importance in the development of liver cirrhosis. In turn, the progression of the disease further enhances the transfer of bacteria from the intestine into the inferior vena cava system. The severity of this process is proportional to the stage of cirrhosis and correlates with the prognosis of the disease. Conclusion. Increased intestinal permeability, altered gut microbiota and bacterial translocation contribute to liver damage and fbrosis up to the development of liver cirrhosis and its complications. Further research is required to determine if modulation of the gut microbiota can affect the course of liver disease.
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Mósca, Andreia, Andreia de Almeida, Darren Wragg, Ana Martins, Farzana Sabir, Stefano Leoni, Teresa Moura, Catarina Prista, Angela Casini, and Graça Soveral. "Molecular Basis of Aquaporin-7 Permeability Regulation by pH." Cells 7, no. 11 (November 10, 2018): 207. http://dx.doi.org/10.3390/cells7110207.
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The aquaglyceroporin AQP7, a family member of aquaporin membrane channels, facilitates the permeation of water and glycerol through cell membranes and is crucial for body lipid and energy homeostasis. Regulation of glycerol permeability via AQP7 is considered a promising therapeutic strategy towards fat-related metabolic complications. Here, we used a yeast aqy-null strain for heterologous expression and functional analysis of human AQP7 and investigated its regulation by pH. Using a combination of in vitro and in silico approaches, we found that AQP7 changes from fully permeable to virtually closed at acidic pH, and that Tyr135 and His165 facing the extracellular environment are crucial residues for channel permeability. Moreover, instead of reducing the pore size, the protonation of key residues changes AQP7’s protein surface electrostatic charges, which, in turn, may decrease glycerol’s binding affinity to the pore, resulting in decreased permeability. In addition, since some pH-sensitive residues are located at the monomer-monomer interface, decreased permeability may result from cooperativity between AQP7’s monomers. Considering the importance of glycerol permeation via AQP7 in multiple pathophysiological conditions, this mechanism of hAQP7 pH-regulation may help the design of selective modulators targeting aquaglyceroporin-related disorders.
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Yuan, Ran, Dan Ma, and Hongwei Zhang. "Flow Characteristics and Grain Size Distribution of Granular Gangue Mineral by Compaction Treatment." Advances in Materials Science and Engineering 2017 (2017): 1–7. http://dx.doi.org/10.1155/2017/2509286.
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A test system for water flow in granular gangue mineral was designed to study the flow characteristics by compaction treatment. With the increase of the compaction displacement, the porosity decreases and void in granular gangue becomes less. The main reason causing initial porosity decrease is that the void of larger size is filled with small particles. Permeability tends to decrease and non-Darcy flow factor increases under the compaction treatment. The change trend of flow characteristics shows twists and turns, which indicate that flow characteristics of granular gangue mineral are related to compaction level, grain size distribution, crushing, and fracture structure. During compaction, larger particles are crushed, which in turn causes the weight of smaller particles to increase, and water flow induces fine particles to migrate (weight loss); meanwhile, a sample with more weight of size (0–2.5 mm) has a higher amount of weight loss. Water seepage will cause the decrease of some chemical components, where SiO2 decreased the highest in these components; the components decreased are more likely locked at fragments rather than the defect of the minerals. The variation of the chemical components has an opposite trend when compared with permeability.
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Mori, Hisatake, Muhammad Aminul Huq, Md Monirul Islam, and Naoshi Takeyama. "Neutrophil extracellular traps are associated with altered human pulmonary artery endothelial barrier function." European Journal of Inflammation 19 (January 2021): 205873922110623. http://dx.doi.org/10.1177/20587392211062386.
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Introduction: Acute respiratory response syndrome (ARDS) leads to increased permeability of the endothelial-epithelial barrier, which in turn promotes edema formation and hypoxemic respiratory failure. Although activated neutrophils are thought to play a significant role in mediating ARDS, at present the contribution of neutrophil extracellular traps (NETs) to lung endothelial barrier function is unclear. Methods: To clarify their role, we co-cultured in vitro NETs induced by phorbol myristate acetate (PMA)–activated neutrophils with lung endothelial cell monolayers and examined the barrier function of lung endothelial cells by immunofluorescence microscopy and albumin permeability in a double-chamber culture method. Results: Co-culture with stimulated neutrophils increased the albumin permeability of the human pulmonary artery endothelial cell (HPAEC) monolayer and altered cytoskeleton F-actin and vascular endothelial-cadherin in cell-cell junctions. Hyperpermeability to albumin and histological alterations were prevented by inhibition of NET formation with peptidyl arginine deiminase inhibitor or a neutrophil elastase inhibitor and were also prevented by increased degradation of NET structure with DNase. Conclusion: This in vitro experiment shows that altered HPAEC barrier function and increased albumin permeability are caused by the direct effect of PMA-induced NETs and their components. NET formation may be involved in the increased vascular permeability of the lung, which is a common feature in ARDS of various etiologies. These insights may help generate novel approaches for medical interventions.
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Soni, Dheeraj, Sushil C. Regmi, Dong-Mei Wang, Auditi DebRoy, You-Yang Zhao, Stephen M. Vogel, Asrar B. Malik, and Chinnaswamy Tiruppathi. "Pyk2 phosphorylation of VE-PTP downstream of STIM1-induced Ca2+ entry regulates disassembly of adherens junctions." American Journal of Physiology-Lung Cellular and Molecular Physiology 312, no. 6 (June 1, 2017): L1003—L1017. http://dx.doi.org/10.1152/ajplung.00008.2017.
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Vascular endothelial protein tyrosine phosphatase (VE-PTP) stabilizes endothelial adherens junctions (AJs) through constitutive dephosphorylation of VE-cadherin. Here we investigated the role of stromal interaction molecule 1 (STIM1) activation of store-operated Ca2+ entry (SOCE) in regulating AJ assembly. We observed that SOCE induced by STIM1 activated Pyk2 in human lung microvascular endothelial cells (ECs) and induced tyrosine phosphorylation of VE-PTP at Y1981. Pyk2-induced tyrosine phosphorylation of VE-PTP promoted Src binding to VE-PTP, Src activation, and subsequent VE-cadherin phosphorylation and thereby increased the endothelial permeability response. The increase in permeability was secondary to disassembly of AJs. Pyk2-mediated responses were blocked in EC-restricted Stim1 knockout mice, indicating the requirement for STIM1 in initiating the signaling cascade. A peptide derived from the Pyk2 phosphorylation site on VE-PTP abolished the STIM1/SOCE-activated permeability response. Thus Pyk2 activation secondary to STIM1-induced SOCE causes tyrosine phosphorylation of VE-PTP, and VE-PTP, in turn, binds to and activates Src, thereby phosphorylating VE-cadherin to increase endothelial permeability through disassembly of AJs. Our results thus identify a novel signaling mechanism by which STIM1-induced Ca2+ signaling activates Pyk2 to inhibit the interaction of VE-PTP and VE-cadherin and hence increase endothelial permeability. Therefore, targeting the Pyk2 activation pathway may be a potentially important anti-inflammatory strategy.
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Zhang, Hongwei, Zhijun Wan, Zijun Feng, and Jinwen Wu. "Shear-induced Permeability Evolution of Sandstone Fractures." Geofluids 2018 (December 23, 2018): 1–11. http://dx.doi.org/10.1155/2018/2416481.
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In underground coal mines, shear-induced changes in regional fluid flow are a major factor causing water inrushes from faults into working faces. Shear slip along preexisting fractures tends to be activated during hydraulic fracturing, and this movement can either enhance or diminish hydraulic fracturing efficiency. To prevent water inrush disasters and further hydraulic fracturing, understanding the evolution of shear-induced permeability in fractures in sedimentary rock is very important. In this study, the evolution of shear-induced permeability in saw-cut sandstone fractures with three different types of surface roughness was investigated by conducting triaxial shear tests and examining the 3-D topography of the unsheared and sheared fracture surfaces. The results allow several important conclusions to be drawn. (1) The permeability of fractures follows a three-stage shear-displacement-dependent evolution. The permeability remains unchanged in the first stable stage. After that, permeability decreases sharply with increasing shear displacement. Finally, the permeability enters a second stable stage. (2) The shear stress versus shear-displacement curves can also be divided into three stages, namely, a stress adjustment stage, a stage of increasing stress, and a stable stage. During the experiments, the fractures always experienced stick-slip shear in the stable stage. The oscillations of the shear stress in the stick-slip stage had a higher frequency for fractures with rougher surfaces. In addition, the rougher surfaces exhibited a greater permeability drop after shearing than that shown by smoother fracture surfaces. (3) The 3-D scanning results imply that the coupled effects of grinding (plus scraping) and sealing lead to decreased permeability. During shearing, the fracture walls grind and scrape against each other resulting in partial flattening of the fracture surface and the production of fault gouge in the fracture. This leads in turn to the flow pathways being partially sealed by crushed mineral grains.
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Huidobro, Paloma A., Emanuele Galiffi, Sébastien Guenneau, Richard V. Craster, and J. B. Pendry. "Fresnel drag in space–time-modulated metamaterials." Proceedings of the National Academy of Sciences 116, no. 50 (November 25, 2019): 24943–48. http://dx.doi.org/10.1073/pnas.1915027116.
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A moving medium drags light along with it as measured by Fizeau and explained by Einstein’s theory of special relativity. Here we show that the same effect can be obtained in a situation where there is no physical motion of the medium. Modulations of both the permittivity and permeability, phased in space and time in the form of traveling waves, are the basis of our model. Space–time metamaterials are represented by effective bianisotropic parameters, which can in turn be mapped to a moving homogeneous medium. Hence these metamaterials mimic a relativistic effect without the need for any actual material motion. We discuss how both the permittivity and permeability need to be modulated to achieve these effects, and we present an equivalent transmission line model.
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Jankovskis, Janis, Nikolajs Ponomarenko, and Deniss Stepins. "Frequency Dependence of Complex Permeability of Polycrystalline Ferrites Based on the Realities of Microstructure." Key Engineering Materials 543 (March 2013): 507–10. http://dx.doi.org/10.4028/www.scientific.net/kem.543.507.
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Complex permeability spectra of polycrystalline ferrites are analyzed on the basis of the model accounting for the effects of their grain size distribution (GSD). The model allows for explicit relation for absorption component. It shows, that by change of only one parameter (related with GSD) it is possible to turn from the relaxation to resonance character of spectrum, that spectra of ferrites, sintered at low temperature, tend to the most theoretical type - symmetrical one.
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Martínez, Francisco. "Introduction." Anthropological Journal of European Cultures 29, no. 2 (September 1, 2020): 1–10. http://dx.doi.org/10.3167/ajec.2020.290201.
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Boundaries influence how we live, the way we do and see things – but how? What role do boundaries play in effecting disciplinary shifts or stability in turn? And who is excluded when tracing epistemic frontiers and hard notions of relevance? This theme issue discusses the porosity of anthropology’s borders and the difficulty of establishing scholarly authority. We set out to reopen the conversation about the permeability of academic boundaries, exploring different conceptual, methodological and historical reconfigurations with and within European anthropologies. We also discuss how the epistemic and institutional boundaries of our discipline are changing, affecting in turn what people can know and with whom, as well as our sense of professional strength and vulnerability.
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Ranjous, Yasmin, Dóra Kósa, Zoltán Ujhelyi, Géza Regdon, Krisztina Anita Nagy, Imre Szenti, Zoltán Kónya, Ildikó Bácskay, and Tamás Sovány. "Evaluation of the permeability and in vitro cytotoxicity of functionalized titanate nanotubes on Caco-2 cell line." Acta Pharmaceutica Hungarica 91, no. 1 (June 15, 2021): 31–39. http://dx.doi.org/10.33892/aph.2021.91.31-39.
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Titanate nanotubes (TNTs) are promising vectors for drug delivery due to their unique physicochemical properties such as biocompatibility, mechanical strength, and chemical resistivity. However, considering their strong hydrophilicity, pristine TNTs exert very limited permeability through the intestinal cell layer. The aim of this study was to turn the surface characteristics and thus enhance the permeability of TNTs by functionalization. TNTs were functionalized with trichloro(octyl)silane (TCOS) and magnesium stearate (MgSt). Carbon content and surface free energy of the functionalized TNTs were detected to evaluate the effectiveness of functionalization, by using CHNS analytical and optical contact angle (OCA) measurements, respectively. Caco-2 cell line was applied to test the permeability and the cytotoxicity of the samples. Cytotoxicity was evaluated by using MTT assay. The results revealed that the surface characteristics of TNTs may be adjusted in a wider range with TCOS-TNT than with St, but the samples show higher toxicity. Silane functionalized TNTs may be safe up to 1 mg/ml, while St functionalized TNTs up to 2 mg/ml concentration. The preparation method of MgSt-TNT was also superior from the aspect of environmental safety. The permeability was suitable for samples with moderate hydrophobicity (aqueous contact angle 60-90°).
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Sun, Zuyue, Xiujuan Li, Sara Massena, Simone Kutschera, Narendra Padhan, Laura Gualandi, Vibeke Sundvold-Gjerstad, et al. "VEGFR2 induces c-Src signaling and vascular permeability in vivo via the adaptor protein TSAd." Journal of Experimental Medicine 209, no. 7 (June 11, 2012): 1363–77. http://dx.doi.org/10.1084/jem.20111343.
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Regulation of vascular endothelial (VE) growth factor (VEGF)–induced permeability is critical in physiological and pathological processes. We show that tyrosine phosphorylation of VEGF receptor 2 (VEGFR2) at Y951 facilitates binding of VEGFR2 to the Rous sarcoma (Src) homology 2-domain of T cell–specific adaptor (TSAd), which in turn regulates VEGF-induced activation of the c-Src tyrosine kinase and vascular permeability. c-Src was activated in vivo and in vitro in a VEGF/TSAd-dependent manner, and was regulated via increased phosphorylation at pY418 and reduced phosphorylation at pY527. Tsad silencing blocked VEGF-induced c-Src activation, but did not affect pathways involving phospholipase Cγ, extracellular regulated kinase, and endothelial nitric oxide. VEGF-induced rearrangement of VE–cadherin–positive junctions in endothelial cells isolated from mouse lungs, or in mouse cremaster vessels, was dependent on TSAd expression, and TSAd formed a complex with VE-cadherin, VEGFR2, and c-Src at endothelial junctions. Vessels in tsad−/− mice showed undisturbed flow and pressure, but impaired VEGF-induced permeability, as measured by extravasation of Evans blue, dextran, and microspheres in the skin and the trachea. Histamine-induced extravasation was not affected by TSAd deficiency. We conclude that TSAd is required for VEGF-induced, c-Src-mediated regulation of endothelial cell junctions and for vascular permeability.
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Allison, R. C., E. M. Hernandez, V. R. Prasad, M. B. Grisham, and A. E. Taylor. "Protective effects of O2 radical scavengers and adenosine in PMA-induced lung injury." Journal of Applied Physiology 64, no. 5 (May 1, 1988): 2175–82. http://dx.doi.org/10.1152/jappl.1988.64.5.2175.
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We have previously shown that phorbol myristate acetate (PMA) produces acute lung injury in blood-perfused lungs but not in plasma-dextran-perfused lungs. This is compatible with the concept that its major mechanism of injury is the stimulation of O2 radicals by neutrophils, which in turn increase permeability by damaging the endothelial cells. In this study we measured vascular permeability and resistance before and 1 h after PMA in five groups of blood-perfused dog lungs: PMA alone in one group and pretreatment with catalase, superoxide dismutase, deferoxamine, and adenosine each in four other groups. By the use of two indexes of permeability, the filtration coefficient and the isogravimetric capillary pressure, we found that, compared with PMA alone, catalase, deferoxamine, and adenosine provided significant protection, whereas the results with superoxide dismutase were variable. These four drugs also significantly attenuated the marked increased resistance seen with PMA alone. Although the effects seen with the first three can be explained by their scavenging of O2 radicals, adenosine appears to provide protection through a separate mechanism.
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Farquharson, Jamie I., Patrick Baud, and Michael J. Heap. "Inelastic compaction and permeability evolution in volcanic rock." Solid Earth 8, no. 2 (April 27, 2017): 561–81. http://dx.doi.org/10.5194/se-8-561-2017.
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Abstract. Active volcanoes are mechanically dynamic environments, and edifice-forming material may often be subjected to significant amounts of stress and strain. It is understood that porous volcanic rock can compact inelastically under a wide range of in situ conditions. In this contribution, we explore the evolution of porosity and permeability – critical properties influencing the style and magnitude of volcanic activity – as a function of inelastic compaction of porous andesite under triaxial conditions. Progressive axial strain accumulation is associated with progressive porosity loss. The efficiency of compaction was found to be related to the effective confining pressure under which deformation occurred: at higher effective pressure, more porosity was lost for any given amount of axial strain. Permeability evolution is more complex, with small amounts of stress-induced compaction ( < 0.05, i.e. less than 5 % reduction in sample length) yielding an increase in permeability under all effective pressures tested, occasionally by almost 1 order of magnitude. This phenomenon is considered here to be the result of improved connectivity of formerly isolated porosity during triaxial loading. This effect is then overshadowed by a decrease in permeability with further inelastic strain accumulation, especially notable at high axial strains ( > 0.20) where samples may undergo a reduction in permeability by 2 orders of magnitude relative to their initial values. A physical limit to compaction is discussed, which we suggest is echoed in a limit to the potential for permeability reduction in compacting volcanic rock. Compiled literature data illustrate that at high axial strain (both in the brittle and ductile regimes), porosity ϕ and permeability k tend to converge towards intermediate values (i.e. 0.10 ≤ ϕ ≤ 0.20; 10−14 ≤ k ≤ 10−13 m2). These results are discussed in light of their potential ramifications for impacting edifice outgassing – and in turn, eruptive activity – in active volcanoes.
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Bauer, Johanna F., Michael Krumbholz, Elco Luijendijk, and David C. Tanner. "A numerical sensitivity study of how permeability, porosity, geological structure, and hydraulic gradient control the lifetime of a geothermal reservoir." Solid Earth 10, no. 6 (December 18, 2019): 2115–35. http://dx.doi.org/10.5194/se-10-2115-2019.
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Abstract. Geothermal energy is an important and sustainable resource that has more potential than is currently utilized. Whether or not a deep geothermal resource can be exploited, mostly depends on, besides temperature, the utilizable reservoir volume over time, which in turn largely depends on petrophysical parameters. We show, using over 1000 (n=1027) 4-D finite-element models of a simple geothermal doublet, that the lifetime of a reservoir is a complex function of its geological parameters, their heterogeneity, and the background hydraulic gradient (BHG). In our models, we test the effects of porosity, permeability, and BHG in an isotropic medium. Furthermore, we simulate the effect of permeability contrast and anisotropy induced by layering, fractures, and a fault. We quantify the lifetime of the reservoir by measuring the time to thermal breakthrough, i.e. how many years pass before the temperature of the produced fluid falls below the 100 ∘C threshold. The results of our sensitivity study attest to the positive effect of high porosity; however, high permeability and BHG can combine to outperform the former. Particular configurations of all the parameters can cause either early thermal breakthrough or extreme longevity of the reservoir. For example, the presence of high-permeability fractures, e.g. in a fault damage zone, can provide initially high yields, but it channels fluid flow and therefore dramatically restricts the exploitable reservoir volume. We demonstrate that the magnitude and orientation of the BHG, provided permeability is sufficiently high, are the prime parameters that affect the lifetime of a reservoir. Our numerical experiments show also that BHGs (low and high) can be outperformed by comparatively small variations in permeability contrast (103) and fracture-induced permeability anisotropy (101) that thus strongly affect the performance of geothermal reservoirs.
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Kim, Jihoon, and George J. Moridis. "Gas Flow Tightly Coupled to Elastoplastic Geomechanics for Tight- and Shale-Gas Reservoirs: Material Failure and Enhanced Permeability." SPE Journal 19, no. 06 (June 18, 2014): 1110–25. http://dx.doi.org/10.2118/155640-pa.
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Summary We investigate coupled flow and geomechanics in gas production from extremely low-permeability reservoirs such as tight- and shale-gas reservoirs, using dynamic porosity and permeability during numerical simulation. In particular, we take the intrinsic permeability as a step function of the status of material failure, and the permeability is updated every timestep. We consider gas reservoirs with the vertical and horizontal primary fractures, using the single- and dynamic double-porosity (dual-continuum) models. We modify the multiple-porosity constitutive relations for modeling the double porous continua for flow and geomechanics. The numerical results indicate that the production of gas causes redistribution of the effective-stress fields, increasing the effective shear stress and resulting in plasticity. Shear failure occurs not only near the fracture tips but also away from the primary fractures, which indicates the generation of secondary fractures. These secondary fractures increase the permeability significantly, and change the flow pattern, which, in turn, causes a change in the distribution of geomechanical variables. From various numerical tests, we find that shear failure is enhanced by a large pressure drop at the production well, a high Biot's coefficient, and low frictional and dilation angles. Smaller spacing between the horizontal wells also contributes to faster secondary fracturing. When the dynamic double-porosity model is used, we observe a faster evolution of the enhanced-permeability areas than that obtained from the single-porosity model, mainly because of a higher permeability of the fractures in the double-porosity model. These complicated physics for stress-sensitive reservoirs cannot properly be captured by the uncoupled or flow-only simulation, and, thus, tightly coupled flow and geomechanical models are highly recommended to describe accurately the reservoir behavior during gas production in tight- and shale-gas reservoirs and to design production scenarios smartly.
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Fogliatto, Aloysio Arthur Becker, Carlos Henrique Ahrens, Paulo Antônio Pereira Wendhausen, Edson Costa Santos, and Daniel Rodrigues. "Correlation between porosity and permeability of stainless steel filters with gradient porosity produced by SLS/SLM." Rapid Prototyping Journal 26, no. 1 (January 6, 2020): 73–81. http://dx.doi.org/10.1108/rpj-09-2018-0224.
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Purpose Porous structures have been widely used in filtration, medical implants and aerospace field. In the filtration field, the study of permeability of the porous structures is of great importance. This paper aims to study the influence of selective laser sintering/melting (SLS/SLM) process parameters on porosity and permeability of stainless steels filters with gradient porosity (FGM). Design/methodology/approach AISI 316L stainless steel powder was used to manufacture FGM filters by varying the hatch distance while other process parameters were fixed. The relationship between porosity and permeability of such FGM filters was investigated by means of Archimedes’ and Forchheimer’s laws. The gradient of porosity was also analyzed by means of micro-computed tomography. Findings The results have confirmed the ability of SLS/SLM in controlling porosity of the final product by varying the hatch distance. Further, the results allow to assume that FGM filters will have particle retention capacity related to lowest porosity value (which in turn is associated with the lowest hatch distance value used), while it will work at lower pressure drops – or at higher flow rates for equal pressure drop – when compared to a filter without gradient porosity. Originality/value Some research found in recent literature has showed the relationship between SLS/SLM process parameters and permeability of stainless steel porous structures. However, this paper fulfils the need to understand the relationship between SLS/SLM process parameters, porosity and permeability behavior of functionally graded porous structures (FGM filters).
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Kim, Jungsik, Eugene Song, and Seongsoo Lee. "Organizational change and employee organizational identification: Mediation of perceived uncertainty." Social Behavior and Personality: an international journal 41, no. 6 (July 1, 2013): 1019–34. http://dx.doi.org/10.2224/sbp.2013.41.6.1019.
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In this study we explored the relationship between organizational change and employee organizational identification by examining the mediating effects of perception of uncertainty. Considering the importance of an individual's subjective perception, we hypothesized that perceived pace and scope of organizational change would increase an employee's feelings of uncertainty, which would, in turn, result in stronger organizational identification. We also predicted that employee perceptions of boundary permeability between organizations would moderate the proposed relationships. Employees working in Korean firms participated in a survey to report on their experience of major organizational changes, their feelings of uncertainty, and organizational identification. The results of the analyses supported the proposed hypotheses: both the mediating effect of uncertainty and the moderating effect of boundary permeability. The managerial and theoretical implications of the findings are discussed.
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Quinn, Hubert M. "A Reconciliation of Packed Column Permeability Data: Deconvoluting the Ergun Papers." Journal of Materials 2014 (September 22, 2014): 1–24. http://dx.doi.org/10.1155/2014/548482.
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In his 1952 publication, Ergun made the following proclamation: “Data of the present investigation and those presented earlier have been treated accordingly, and the coefficients k1 and k2 have been determined by the method of least squares. The values obtained are k1 = 150 and, k2 = 1.75, representing 640 experiments.” In this paper, we demonstrate that because his experimental methodology was flawed, the corrected values, which his experimental results would otherwise have established for these coefficients, are significantly higher. This is, in part, because Ergun’s reporting of his measured data was ambiguous with respect to the embedded coefficients k1 and k2. In addition, this ambiguity made it difficult for any subsequent researcher to figure out the true meaning of his empirical results which, in turn, resulted in his choice of the values for these coefficients being accepted by default in the scientific community.
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Launay, Gaëtan, Stanislas Sizaret, Laurent Guillou-Frottier, Colin Fauguerolles, Rémi Champallier, and Eric Gloaguen. "Dynamic Permeability Related to Greisenization Reactions in Sn-W Ore Deposits: Quantitative Petrophysical and Experimental Evidence." Geofluids 2019 (February 27, 2019): 1–23. http://dx.doi.org/10.1155/2019/5976545.
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Massive greisens are commonly associated with Sn-W mineralization and constitute low-grade high-tonnage deposits. The formation of this type of deposit results from an intense pervasive metasomatic alteration involving a major fluid and mass transfer through a nominally impermeable parental granite. A decrease in the volume of the solid phases associated with the mineral replacement reactions may be a potential process for creating pathways to enhance fluid flow. Here, we explore the effects of the replacement reactions related to greisenization on the granite’s mineralogy and petrophysical properties (density, porosity, and permeability), as well as their potential implications for fluid flow in the case of the world-class Panasqueira W-Sn-(Cu) deposit, Portugal. Mineralogical and microtextural analyses of greisenized facies show that the total replacement of feldspars by muscovite is associated with a volume decrease of the solid phases that induces a significant porosity generation in greisen (~8.5%). Greisenization experiments coupled with permeability measurements show that the replacement of feldspars by muscovite permits new pathways at the crystal scale that significantly enhance the transient permeability. Moreover, permeability measurements performed on representative samples with different degrees of greisenization show that permeability increases progressively with the level of alteration from 10-20 m2 in least granite to 10-17 m2 in greisen. The correlation between the permeability and porosity evolutions demonstrates that the porous texture developed during replacement reactions creates new pathways that enhance significantly the permeability in greisen systems. The occurrences of mineral-bearing metals such as cassiterite in the newly formed porosity of greisen provide evidence that greisenization can be a decisive process for enhancing fluid flow and promoting transport of metals in Sn-W deposits. Finally, we present a model involving a positive feedback between greisenization and permeability, in which mineralizing fluids are able to generate their own pathways in initially impermeable granite via replacement reactions, which in turn promote further hydrothermal alteration and mass transport.
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Ostretsov, A. V., A. E. Esakov, and V. M. Sharipov. "Comparative evaluation of automobiles KAMAZ-4350, KAMAZ-43114 and Ural-4320-31 flotation on loose sand." Izvestiya MGTU MAMI 8, no. 1-1 (January 10, 2014): 50–54. http://dx.doi.org/10.17816/2074-0530-67709.
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The article contains the results of experimental studies of automobiles KAMAZ-4350, KAMAZ-43114 and Ural-4320-31 flotation on dry loose sand. Comparative evaluation of flotation was made through the main indicators: the specific thrust force on the hook, specific resisting force to vehicle towing, the greatest speed of rectilinear uniform motion with no load on the hook and the least radius of turn of the vehicle without loss of permeability.