Hydrodynamic and hydromagnetic stability

In rotating filtration, which is based on supercritical cylindrical Couette flow with a rotating porous inner cylinder, the motion of particles in the suspension depends on both centrifugal sedimentation and transport due to the vortical motion of Taylor vortices. We have simulated the motion of dilute, rigid, spherical particles in Taylor Couette flow using computational particle tracking in an analytic velocity field for flow just above the transition to supercritical Taylor vortex flow. Neutrally buoyant particles follow fluid streamlines closely, but not exactly due to the curvature of the velocity field very near the particle. The motion of particles with a density greater than the fluid is primarily determined by the competition between the centrifugal sedimentation related to the primary cylindrical Couette flow and the secondary radial and axial transport of the Taylor vortex flow. As a result, particles that start near the outer edge of a vortex spiral inward toward a limit cycle orbit. Likewise,...

Inertial particle motion in a Taylor Couette rotating filter

http://faculty.mccormick.northwestern.edu/richard-lueptow/docs/jms-wereley-particles-02.pdf

Particle-fluid velocities and fouling in rotating filtration of a suspension

Linear stability analysis predicts that a radial throughflow in a Taylor–Couette system will alter the stability of the flow, but the underlying physics for the stabilization of the flow is unclear. We investigate the impact of radial inflow and outflow on Taylor vortex flow and wavy vortex flow in a finite-length cavity via direct numerical simulation using a three-dimensional spectral method. The numerical simulations are consistent with linear stability predictions in that radial inflow and strong radial outflow have a stabilizing effect, while weak radial outflow destabilizes the system slightly. A small radial outflow velocity enhances the strength of the Taylor vortices resulting in destabilization of the base flow, whereas strong radial outflow and radial inflow reduce vortex strength, thus stabilizing the system. The transition to wavy vortex flow is unaffected by small radial outflow, but is stabilized for radial inflow. For strong radial outflow the wavy vortex flow includes localized dislocatio...

Stability of Taylor–Couette flow in a finite-length cavity with radial throughflow

Regional anaesthesia in the obese patient: lost landmarks and evolving ultrasound guidance.

A linear stability analysis was carried out for axial flow between a rotating porous inner cylinder and a concentric, stationary, porous outer cylinder when radial flow is present for several radius ratios. The radial Reynolds number, based on the radial velocity at the inner cylinder and the inner radius, was varied from −15 to 15, and the axial Reynolds number based on the mean axial velocity and the annular gap was varied from 0 to 10. Linear stability analysis for axisymmetric perturbations results in an eigenvalue problem that was solved using a numerical technique based on the Runge–Kutta method combined with a shooting procedure. At a given radius ratio, the critical Taylor number at which Taylor vortices first appear for radial outflow decreases slightly for small positive radial Reynolds numbers and then increases as the radial Reynolds number becomes more positive. For radial inflow, the critical Taylor number increases as the radial Reynolds number becomes more negative. For a given radial Reyn...

Hydrodynamic stability of flow between rotating porous cylinders with radial and axial flow

Purpose
To determine if the extent of sensory blockade after the intrathecal injection of hypobaric fentanyl (25 μg) and bupicavaine (2.5 mg) in the sitting position in term parturients is influenced by body habitus.

/pdf/body-habitus-does-not-influence-spread-of-sensory-blockade-3x95lstnb3.pdf

Body habitus does not influence spread of sensory blockade after the intrathecal injection of a hypobaric solution in term parturients.

Circadian transcriptional timekeepers in pacemaker neurons drive profound daily rhythms in sleep and wake. Here we reveal a molecular pathway that links core transcriptional oscillators to neuronal and behavioral rhythms. Using two independent genetic screens, we identified mutants of Transport and Golgi organization 10 (Tango10) with poor behavioral rhythmicity. Tango10 expression in pacemaker neurons expressing the neuropeptide PIGMENT-DISPERSING FACTOR (PDF) is required for robust rhythms. Loss of Tango10 results in elevated PDF accumulation in nerve terminals even in mutants lacking a functional core clock. TANGO10 protein itself is rhythmically expressed in PDF terminals. Mass spectrometry of TANGO10 complexes reveals interactions with the E3 ubiquitin ligase CULLIN 3 (CUL3). CUL3 depletion phenocopies Tango10 mutant effects on PDF even in the absence of the core clock gene timeless Patch clamp electrophysiology in Tango10 mutant neurons demonstrates elevated spontaneous firing potentially due to reduced voltage-gated Shaker-like potassium currents. We propose that Tango10/Cul3 transduces molecular oscillations from the core clock to neuropeptide release important for behavioral rhythms.

https://www.pnas.org/content/pnas/118/47/e2110767118.full.pdf

The E3 ubiquitin ligase adaptor Tango10 links the core circadian clock to neuropeptide and behavioral rhythms

Purpose: To determine if the extent of sensory blockade after the intrathecal injection of hypobaric fentanyl (25 µg) and bupicavaine (2.5 mg) in the sitting position in term parturients is influenced by body habitus. Methods: A prospective observational study in 245 term parturients who received intrathecal fentanyl and bupivacaine plus an epidural test dose to initiate labour analgesia at an academic university hospital. The highest sensory blockade to ice and pinprick was determined at 15 and 30 min after the intrathecal injection. Correlations between sensory blockade and parturient height, weight and body mass index (BMI) were determined. Results: There was no association between highest sensory blockade and parturients’ height. Increasing weight and BMI were associated with increased cephalad sensory blockade at 15 min, but not at 30 min. The estimated difference in sensory level between women at the extremes of BMI, based on our linear regression model, was less than one dermatome. Conclusion: Height did not influence the extent of sensory analgesia after initiation of intrathecal labour analgesia using a hypobaric solution injected with the parturient in the sitting position. Weight and BMI were associated with a non-clinically significant increase in the cephalic spread of analgesia, suggesting that dose adjustments based on body habitus in this population are not necessary. Objectif : Determiner si l’etendue du blocage sensitif, suivant l’injection intrathecale de fentanyl (25 µg) et de bupivacaine (2,5 mg) hypobares en position assise chez des parturientes a terme, est influencee par l’habitus corporel.

/pdf/obstetrical-and-pediatric-anesthesia-body-habitus-does-not-3d6us8nnz6.pdf

Obstetrical and Pediatric Anesthesia Body habitus does not influence spread of sensory blockade after the intrathecal injection of a hypobaric solution in term parturients (L'habitus corporel n'influence pas l'étendue du blocage sensitif qui suit l'injection intrathécale d'une solution hypobare chez des parturientes à terme)

Eric C. Johnson

Papers

Hydrodynamic stability of flow between rotating porous cylinders with radial and axial flow

Body habitus does not influence spread of sensory blockade after the intrathecal injection of a hypobaric solution in term parturients.

The E3 ubiquitin ligase adaptor Tango10 links the core circadian clock to neuropeptide and behavioral rhythms