Computational hemodynamic analysis of the offending vertebral artery at the site of neurovascular contact in a case of hemifacial spasm associated with subclavian steal syndrome: illustrative case

BACKGROUND Hemifacial spasm (HFS) is caused by neurovascular contact along the facial nerve’s root exit zone (REZ). The authors report a rare HFS case that was associated with ipsilateral subclavian steal syndrome (SSS). OBSERVATIONS A 42-year-old man with right-sided aortic arch presented with progressing left HFS, which was associated with ipsilateral SSS due to severe stenosis of the left brachiocephalic trunk. Magnetic resonance imaging showed contact between the left REZ and vertebral artery (VA), which had shifted to the left. The authors speculated that the severe stenosis at the left brachiocephalic trunk resulted in the left VA’s deviation, which was the underlying cause of the HFS. The authors performed percutaneous angioplasty (PTA) to dilate the left brachiocephalic trunk. Ischemic symptoms of the left arm improved after PTA, but the HFS remained unchanged. A computational fluid dynamics study showed that the high wall shear stress (WSS) around the site of neurovascular contact decreased after PTA. In contrast, pressure at the point of neurovascular contact increased after PTA. LESSONS SSS is rarely associated with HFS. Endovascular treatment for SSS reduced WSS of the neurovascular contact but increased theoretical pressure of the neurovascular contact. Physical release of the neurovascular contact is the best treatment option for HFS.

Numerical study on key parameters of a Magnetorheological Fluid reciprocating seal with increasing width of pole teeth and pole piece

In order to solve the problem of reciprocating seal for hydraulic cylinder, a new structure of Magnetorheological fluid (MRF) reciprocating seal with increasing width of pole teeth and pole piece was designed. The theoretical analysis of MRF reciprocating seal is carried out. The magnetic field intensity distribution in the sealing gap of MRF reciprocating seal was analyzed by finite element method. According to the pressure capability formula of MRF, the theoretical pressure capability is calculated. The influences of structure parameters such as the number of magnetic sources, sealing gap height, pole teeth length, the ratio of permanent magnet height to its length, the ratio of pole piece height to shaft radius on the sealing capabilities were studied. The results showed that the pressure capability of MRF reciprocating seal increases with the increase of the number of magnetic sources and with the decrease of the sealing gap height. With the increase of the pole tooth length, the pressure capability of the reciprocating seal increases. With the increase of the ratio of permanent magnet height to its length, the pressure capability of the reciprocating seal increases first and then decreases. With the increase of the ratio of the pole piece height to shaft radius, the pressure capability of the MRF reciprocating seal increases first and then decreases.

Massive Pressure Amplification by Stimulated Contraction of Mesoporous Frameworks

Negative Gas Adsorption (NGA), discovered in a series of mesoporous switchable MOFs, was hitherto regarded as a curios phenomenon occurring only at pressures well below or close to atmospheric merit. Herein we demonstrate mesoporous frameworks interacting with carbon dioxide, to show stimulated breathing transitions well above 100 kPa. Reversible CO₂ adsorption-induced switching was observed in DUT-46 (DUT = Dresden University of Technology), in contrast to irreversible transitions for DUT-49 and DUT-50, as demonstrated via synchrotron in situ PXRD/adsorption experiments. Systematic physisorption experiments reveal the best conditions for high pressure NGA transitions in the pressure range of 350 - 680 kPa. The stimulated framework contraction expells CO₂ in the range of 1.1 to 2.4 mmol g^-1 leading to autonomous pressure amplification in a closed system. In a pneumatic demonstrator system we achieved pressure amplification of 90 kPa at a high operating pressure of 340 kPa. According to system level estimations even higher theoretical pressure amplification may be achieved between 535 kPa and 1011 kPa for DUT-49 using CO₂ as a non-toxic and non-flammable working gas. Operable pressure ranges exceeding 100 kPa render pressure amplifying framework materials as realistic candidates for the integration into energy autonomous responsive pneumatic systems.

High-Sensitivity Cuboid Interferometric Fiber-Optic Hydrophone Based on Planar Rectangular Film Sensing

Interferometric fiber-optic hydrophones are an important means in the field of underwater acoustic detection. The design of the hydrophone sensor head is the key technology related to its detection sensitivity. In this paper, a high-sensitivity cuboid interferometric fiber-optic hydrophone based on planar rectangular film sensing is proposed, and the sensitivity of the sensor is compared with that of the widely used air-backed mandrel hydrophone under the same conditions. The acoustic characteristic models of the two types of sensors were established by theoretical calculation and simulation analysis to obtain the theoretical pressure sensitivity. Some experiments were performed to examine the theory and design. According to the experiment results, the mean phase sensitivity of the mandrel type was −112.85 dB re 1 rad/μPa in the operating frequency range of 10–300 Hz, and that of the cuboid type was −84.50 dB re 1 rad/μPa. The latter was 28.35 dB higher than the former was. These results are useful for improving hydrophone sensitivity.

High Pressure Amplifying Framework Materials for Programmable Pneumatics Systems

Negative Gas Adsorption (NGA), discovered in a series of mesoporous switchable MOFs, was hitherto regarded as a curios phenomenon occurring only at pressures well below or close to atmospheric merit. Herein we demonstrate mesoporous frameworks interacting with carbon dioxide, to show stimulated breathing transitions well above 100 kPa. Reversible CO₂ adsorption-induced switching was observed in DUT-46 (DUT = Dresden University of Technology), in contrast to irreversible transitions for DUT-49 and DUT-50, as demonstrated via synchrotron in situ PXRD/adsorption experiments. Systematic physisorption experiments reveal the best conditions for high pressure NGA transitions in the pressure range of 350 - 680 kPa. The stimulated framework contraction expells CO₂ in the range of 1.1 to 2.4 mmol g^-1 leading to autonomous pressure amplification in a closed system. In a pneumatic demonstrator system we achieved pressure amplification of 90 kPa at a high operating pressure of 340 kPa. According to system level estimations even higher theoretical pressure amplification may be achieved between 535 kPa and 1011 kPa for DUT-49 using CO₂ as a non-toxic and non-flammable working gas. Operable pressure ranges exceeding 100 kPa render pressure amplifying framework materials as realistic candidates for the integration into energy autonomous responsive pneumatic systems.

High Pressure Amplifying Framework Materials for Programmable Pneumatics Systems

Negative Gas Adsorption (NGA), discovered in a series of mesoporous switchable MOFs, was hitherto regarded as a curios phenomenon occurring only at pressures well below or close to atmospheric merit. Herein we demonstrate mesoporous frameworks interacting with carbon dioxide, to show stimulated breathing transitions well above 100 kPa. Reversible CO₂ adsorption-induced switching was observed in DUT-46 (DUT = Dresden University of Technology), in contrast to irreversible transitions for DUT-49 and DUT-50, as demonstrated via synchrotron in situ PXRD/adsorption experiments. Systematic physisorption experiments reveal the best conditions for high pressure NGA transitions in the pressure range of 350 - 680 kPa. The stimulated framework contraction expells CO₂ in the range of 1.1 to 2.4 mmol g^-1 leading to autonomous pressure amplification in a closed system. In a pneumatic demonstrator system we achieved pressure amplification of 90 kPa at a high operating pressure of 340 kPa. According to system level estimations even higher theoretical pressure amplification may be achieved between 535 kPa and 1011 kPa for DUT-49 using CO₂ as a non-toxic and non-flammable working gas. Operable pressure ranges exceeding 100 kPa render pressure amplifying framework materials as realistic candidates for the integration into energy autonomous responsive pneumatic systems.

High Pressure Amplifying Framework Materials for Programmable Pneumatics Systems

Negative Gas Adsorption (NGA), discovered in a series of mesoporous switchable MOFs, was hitherto regarded as a curios phenomenon occurring only at pressures well below or close to atmospheric merit. Herein we demonstrate mesoporous frameworks interacting with carbon dioxide, to show stimulated breathing transitions well above 100 kPa. Reversible CO₂ adsorption-induced switching was observed in DUT-46 (DUT = Dresden University of Technology), in contrast to irreversible transitions for DUT-49 and DUT-50, as demonstrated via synchrotron in situ PXRD/adsorption experiments. Systematic physisorption experiments reveal the best conditions for high pressure NGA transitions in the pressure range of 350 - 680 kPa. The stimulated framework contraction expells CO₂ in the range of 1.1 to 2.4 mmol g^-1 leading to autonomous pressure amplification in a closed system. In a pneumatic demonstrator system we achieved pressure amplification of 90 kPa at a high operating pressure of 340 kPa. According to system level estimations even higher theoretical pressure amplification may be achieved between 535 kPa and 1011 kPa for DUT-49 using CO₂ as a non-toxic and non-flammable working gas. Operable pressure ranges exceeding 100 kPa render pressure amplifying framework materials as realistic candidates for the integration into energy autonomous responsive pneumatic systems.

Magnetic Circuit Design and Magnetic Field Finite Element Analysis of Converging Stepped Magnetofluid Seal with Small Clearance

The stepped magnetofluid seal is an effective method for improving the pressure ability of ordinary magnetofluid seals (OMS) with large clearance. At present, the research on stepped magnetofluid seal with less than 0.4 mm small clearance has not been carried out yet. The equivalent magnetic circuit design of converging stepped magnetofluid seal (CSMS) with small clearance has been carried out and verified by magnetic field finite element method based on the CSMS theory and magnetic circuit theory. The effects of the width of the axial seal position, the height of the radial seal position, the number of the pole tooth in the axial seal position, and the number of the pole tooth in the radial seal position on the theoretical pressure ability of the CSMS are investigated by numerical simulation. The calculation results are analyzed and discussed. The results show that the magnetic flux leakage at the junction of the permanent magnet and pole piece causes the higher pressure ability of the CSMS structure designed by the equivalent magnetic circuit method than that calculated by the magnetic field finite element method. When the width of the axial seal position is greater than the height of the radial seal position and the number of pole teeth in the axial seal position is less than the number of pole teeth in the radial seal position, the CSMS has the best effect. Compared with OMS with small clearance, CSMS has greater advantages.

Pressure Drop in Circular Two-Phase Pipe Flow As Influenced by the Angle of Inclination

A variety of models exist to describe the frictional pressure drop for two-phase flow in a pipe. These models all are based on assumptions and simplifications of the flow regime and can experience difficulty when modeling flow through non-horizontal pipes due to the buoyant effects as the bubbles grow in size. Using computational fluid dynamics, it is possible to model the interaction between the two phases and determine an expected pressure drop. In order to evaluate the effect of the inclination angle of a channel, a parametric study will be conducted using ANSYS Fluent; these predicted pressure drops will then be compared to those found in literature for validation and then to other theoretical pressure drop calculations. Through this study, the benefits of both the theoretical framework and the numerical simulation will be identified.