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Start Over Coverage 103-111

1. A numerical investigation of a buoyancy driven flow in a semi-porous cavity: comparative effects of ramped and isothermal wall conditions

Creator:
Chandran, Pallath, Sacheti, Nirmal C., and Singh, Ashok K.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
rectangular cavity, free convection, brinkman model, coupled flow, ramped boundary condition, and numerical solution
Language:
Slovak
Description:
Steady two-dimensional natural convection taking place in a rectangular cavity, partially filled with an isotropic porous material, has been investigated numerically using an ADI method. It is assumed that one of the vertical walls of the cavity has a ramped temperature distribution. The vorticity-stream function formulation has been used to solve the set of nonlinear partial differential equations governing the flows in the clear region and the adjoining porous region. The effects of Darcy number and Rayleigh number have been discussed in detail.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2. Effects of mechanical ventilation versus apnea on bi-ventricular pressure-volume loop recording

Creator:
Dam Lyhne, Mads, Schmidt Mortensen, Christian, Valentin Hansen, Jacob, Juel Dragsbaek, Simone, Nielsen-Kudsk, Jens Erik, and Andersen, Asger
Format:
počítač and online zdroj
Type:
model:article and TEXT
Subject:
right ventricular function, left ventricular function, animal model, positive pressure ventilation, and respiration
Language:
English
Description:
Respiration changes intrathoracic pressure and lung volumes in a cyclic manner, which affect cardiac function. Invasive ventricular pressure-volume (PV) loops can be recorded during ongoing mechanical ventilation or in transient apnea. No consensus exists considering ventilatory mode during PV loop recording. The objective of this study was to investigate the magnitude of any systematic difference of bi-ventricular PV loop variables recorded during mechanical ventilation versus apnea. PV loops were recorded simultaneously from the right ventricle and left ventricle in a closed chest porcine model during mechanical ventilation and in transient apnea (n=72). Variables were compared by regression analyses. Mechanical ventilation versus apnea affected regression coefficients for important PV variables including right ventricular stroke volume (1.22, 95% CI [1.08-1.36], p=0.003), right ventricular ejection fraction (0.90, 95% CI [0.81-1.00], p=0.043) and right ventricular arterial elastance (0.61, 95%CI [0.55-0.68], p<0.0001). Right ventricular pressures and volumes were parallelly shifted with Y-intercepts different from 0. Few left ventricular variables were affected, mainly first derivatives of pressure (dP/dt(max): 0.96, 95% CI [0.92-0.99], p=0.016, and dP/dt(min): 0.92, 95% CI [0.86-0.99], p=0.026), which might be due to decreased heart rate in apnea (Y-intercept -6.88, 95% CI [-12.22; -1.54], p=0.012). We conclude, that right ventricular stroke volume, ejection fraction and arterial elastance were mostly affected by apnea compared to mechanical ventilation. The results motivate future standardization of respiratory modality when measuring PV relationships.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public