Numerical Simulation of Tortuosity Effect on the Montmorillonite Permeability

AbstractThis study analyzed the association between the coefficient of permeability of clayey sealing materials and their tortuosity. Montmorillonite was selected because it is used as a barrier in geo-environmental projects and its sensitive structure results in wide variations in permeability when in contact with pore fluids. A DEM code was developed by considering mechanical force, diffuse double layer repulsion, and Van der Waals attraction as the inter-particle interaction. The coefficient of permeability was calculated by simulating a consolidation test and the DEM simulations were compared with experimental data. The results showed that the coefficient of permeability decreased as the void ratio decreased. At the same void ratio, there was a deviation between the coefficient of permeability for clay-electrolyte systems caused by the micro-fabric and variations in tortuosity. Micro-fabric evolution during loading showed that increasing the stress state caused reorientation of the particles perpendicular to the direction of loading and increased anisotropy of the particle orientation, increasing the tortuous flow path

True resistance to local anesthetics, a case report

Background: We report a case with apparent resistance to local anesthetics. While regional anesthetics failure are often attributed to technical failure, the clinical presentation and medical history of this patient suggests a true resistance to local anesthetics. Case report: A 28 years old man was scheduled for elective orthopedic surgery for right sided tibial bone fracture, and decision of spinal anesthesia was made. There was a questionable history of multiple prior episodes of local anesthetic unresponsiveness (Interscalan block, local infiltration for lipoma resection and dental surgery). Spinal anesthesia was performed and sensory or motor blockade was not obtained despite any evidence of technical problems. The surgical procedure performed under general anesthesia and skin analgesia (local infiltration of lidocaine 2% and bupivacaine 0.5% to forearm), did not achieve, the day after surgery. Conclusion: While the failure rate of spinal anesthesia has been shown range from 4 to 13% and is often attributed to technical failure, this particular case showed a true resistance to local anesthetics