Pulsatile nanofluid flow with variable pressure gradient and heat transfer in wavy channel.

This research contributes to the comprehension of nanofluid behaviour through a wavy channel, emphasizing the significance of considering diverse influences in the modelling process. The study explores the collective influence of pressure gradient variation, magnetic field, porosity, channel waviness, nanoparticle concentration, and heat transfer on nano-blood flow in a two-dimensional wavy channel. In contrast to prior research assuming a constant pulsatile pressure gradient during channel waviness, this innovative study introduces a variable pressure gradient, significantly influencing several associated parameters. The mathematical model characterizing nano-blood flow in a horizontally wavy channel is solved using the perturbation technique. Analytical solutions for fundamental variables such as stream function, velocity, wall shear stress, pressure gradient, and temperature are visually depicted across different physical parameters values. The findings obtained for differing parameter values in the given problem demonstrate a significant influence of the amplitude ratio parameter of channel waviness, Hartmann number of the magnetic field, permeability parameter of the porous medium, volume fraction of nanoparticles, radiation parameter, Prandtl number, and the suction/injection parameter on the flow dynamics. The simulations provide valuable insights into the decrease in velocity with increasing magnetic field and its increase with higher permeability. Additionally, the temperature is observed to escalate with a rising nanoparticle volume fraction and radiation parameter, while it declines with increasing Prandtl number.

Dexmedetomidine as a part of general anaesthesia for caesarean delivery in patients with pre-eclampsia: A randomised double-blinded trial.

BACKGROUND: During general anaesthesia, endotracheal intubation of patients with pre-eclampsia causes stimulation of the sympathetic nervous system and catecholamine release, which may lead to maternal and neonatal complications. OBJECTIVE: To attenuate both the stress response and the haemodynamic response to tracheal intubation in patients with pre-eclampsia. DESIGN: A randomised, double-blind, controlled study. SETTING: Single University Hospital. PATIENTS: Sixty patients aged 18 to 45 years with pre-eclampsia receiving general anaesthesia for caesarean section. INTERVENTIONS: The patients were randomly allocated to three groups. Groups D1and D2 received an infusion of dexmedetomidine 1 µg kg over the 10 min before induction of general anaesthesia, then 0.4 and 0.6 µg kg h dexmedetomidine, respectively. Group C received equivalent volumes of 0.9% saline. MAIN OUTCOME MEASURES: The primary outcome was the effect of dexmedetomidine on mean arterial blood pressure measured before induction of general anaesthesia at 1 and 5 min after intubation, and then every 5 min until 10 min after extubation. The secondary outcomes were blood glucose and serum cortisol (measured before induction of general anaesthesia, and at 1 and 5 min after intubation), postoperative visual analogue pain scores, time to first request for analgesia, the total consumption of analgesia, Ramsay sedation score, maternal and placental vein blood serum levels of dexmedetomidine and neonatal Apgar score at 1 and 5 min. RESULTS: At all assessment times, the mean arterial pressures were significantly lower in the dexmedetomidine groups than in the control group. Compared with group C, the heart rate was significantly lower in both groups D1 and D2. In group D2, the heart rate was lower than in group D1. Serum glucose and cortisol were significantly higher in the controls than in either group D1 or D2. Group D2 patients were significantly more sedated on arrival in the recovery room followed by D1. Time to first analgesia was significantly longer in groups D2 and D1 than in group C, and the visual analogue pain scores were significantly lower in groups D1 and D2 than in group C at 1, 2, 3 and 5 h. Total morphine consumption was significantly lower in groups D1 and D2 than in the control group. There was no difference in Apgar scores across the three groups despite significantly higher dexmedetomidine concentrations in group D2 (both maternal and placental vein) than in group D1. CONCLUSION: Administration of dexmedetomidine in doses 0.4 and 0.6 µg kg h was associated with haemodynamic and hormonal stability, without causing significant adverse neonatal outcome. TRIAL REGISTRATION: Pan African Clinical Trial Registry (PACTR201706002303170), (www.pactr.org).

Slip Effects on Peristaltic Transport of a Particle-Fluid Suspension in a Planar Channel.

Peristaltic pumping induced by a sinusoidal traveling wave in the walls of a two-dimensional channel filled with a viscous incompressible fluid mixed with rigid spherical particles is investigated theoretically taking the slip effect on the wall into account. A perturbation solution is obtained which satisfies the momentum equations for the case in which amplitude ratio (wave amplitude/channel half width) is small. The analysis has been carried out by duly accounting for the nonlinear convective acceleration terms and the slip condition for the fluid part on the wavy wall. The governing equations are developed up to the second order of the amplitude ratio. The zeroth-order terms yield the Poiseuille flow and the first-order terms give the Orr-Sommerfeld equation. The results show that the slip conditions have significant effect within certain range of concentration. The phenomenon of reflux (the mean flow reversal) is discussed under slip conditions. It is found that the critical reflux pressure is lower for the particle-fluid suspension than for the particle-free fluid and is affected by slip condition. A motivation of the present analysis has been the hope that such theory of two-phase flow process under slip condition is very useful in understanding the role of peristaltic muscular contraction in transporting biofluid behaving like a particle-fluid mixture. Also the theory is important to the engineering applications of pumping solid-fluid mixture by peristalsis.