scholarly journals Cardiac Spiral Wave Drifting Due to Spatial Temperature Gradients – a Numerical Study

2018 ◽  
Author(s):  
Guy Malki ◽  
Sharon Zlochiver
Keyword(s):  
Numerical Simulations ◽  
Single Cell ◽  
Numerical Study ◽  
Spiral Wave ◽  
Spiral Waves ◽  
Temperature Gradients ◽  
Effect Of Temperature ◽  
Local Perturbation ◽  
Marginal Effect ◽  
Spatial Temperature

ABSTRACTCardiac rotors are believed to be a major driver source of persistent atrial fibrillation (AF), and their spatiotemporal characterization is essential for successful ablation procedures. However, electrograms guided ablation have not been proven to have benefit over empirical ablation thus far, and there is a strong need of improving the localization of cardiac arrhythmogenic targets for ablation. A new approach for characterize rotors is proposed that is based on induced spatial temperature gradients (STGs), and investigated by theoretical study using numerical simulations. We hypothesize that such gradients will cause rotor drifting due to induced spatial heterogeneity in excitability, so that rotors could be driven towards the ablating probe. Numerical simulations were conducted in single cell and 2D atrial models using AF remodeled kinetics. STGs were applied either linearly on the entire tissue or as a small local perturbation, and the major ion channel rate constants were adjusted following Arrhenius equation. In the AF-remodeled single cell, recovery time increased exponentially with decreasing temperatures, despite the marginal effect of temperature on the action potential duration. In 2D models, spiral waves drifted with drifting velocity components affected by both temperature gradient direction and the spiral wave rotation direction. Overall, spiral waves drifted towards the colder tissue region associated with global minimum of excitability. A local perturbation with a temperature of T=28°C was found optimal for spiral wave attraction for the studied conditions. This work provides a preliminary proof-of-concept for a potential prospective technique for rotor attraction. We envision that the insights from this study will be utilize in the future in the design of a new methodology for AF characterization and termination during ablation procedures.

SPIRAL WAVE MAINTAINED BY NOISE

2004 ◽  
Vol 04 (03) ◽  
pp. L447-452 ◽  
Author(s):  
AI ZHONG LEI ◽  
QIAN SHU LI ◽  
WEIGUO XU ◽  
DAIPING HU
Keyword(s):  
White Noise ◽  
Numerical Simulations ◽  
Noise Level ◽  
Gaussian White Noise ◽  
Spiral Wave ◽  
Reaction Diffusion ◽  
Spiral Waves ◽  
Reaction Diffusion System ◽  
Diffusion System ◽  
Zero Level

The effect of Gaussian white noise on a chemical wavefront is studied in a modified FitzHugn–Nagumo model by applying numerical simulations. A rotating spiral waves can be formed if the medium is excitable enough and the fronts has a free end, when the reaction diffusion system is disturbed by a certain non-zero level noise. It is counterintuitive that noise plays a constructive role in the product and propagation of single spiral waves in this letter. Weak or strong noise will make against the product and propagation of spiral waves. In a certain noise level, spiral wave can be maintained in a medium, where such spiral waves cannot be observed in the absence of the noise.

Experimental and Numerical Study of Solidification in Constant and Oscillating Temperature Gradients

2003 ◽  
Author(s):  
Y. Shu ◽  
B. Q. Li
Keyword(s):  
Numerical Simulations ◽  
Numerical Study ◽  
Numerical Models ◽  
Experimental System ◽  
Temperature Gradients ◽  
Working Fluid ◽  
Set Up ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Planar Solidification

Transient finite element models are developed to describe solidification of materials in constant and oscillating temperature gradients. Both moving grids and fixed methods are applied, with the former intended to model the near-planar solidification front, while the latter for complex solid-liquid interface morphology. Extensive numerical simulations are conducted for various configurations. To validate the model predictions, an experimental system has been set up with Succinonitrile (SCN) as a working fluid. The melt flows and solidification are measured using a laser PIV system. The measurements are compared well with numerical results obtained from the numerical models. Reasonably good agreement between the experimental measurements and numerical simulations is obtained.

Using Ansys for Design and Numerical Study of a Specific Fixed Wing UAV

2018 ◽  
Vol 55 (4) ◽  
pp. 652-657 ◽  
Author(s):  
Gabriel Murariu ◽  
Razvan Adrian Mahu ◽  
Adrian Gabriel Murariu ◽  
Mihai Daniel Dragu ◽  
Lucian P. Georgescu ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Unmanned Aerial Vehicle ◽  
Numerical Study ◽  
Flight Time ◽  
Cluster System ◽  
Numerical Results ◽  
Operational Performance ◽  
Gliding Flight ◽  
Aerial Vehicle ◽  
Constant Altitude

This article presents the design of a specific unmanned aerial vehicle UAV prototype own building. Our UAV is a flying wing type and is able to take off with a little boost. This system happily combines some major advantages taken from planes namely the ability to fly horizontal, at a constant altitude and of course, the great advantage of a long flight-time. The aerodynamic models presented in this paper are optimized to improve the operational performance of this aerial vehicle, especially in terms of stability and the possibility of a long gliding flight-time. Both aspects are very important for the increasing of the goals� efficiency and for the getting work jobs. The presented simulations were obtained using ANSYS 13 installed on our university� cluster system. In a next step the numerical results will be compared with those during experimental flights. This paper presents the main results obtained from numerical simulations and the obtained magnitudes of the main flight coefficients.

Effect of Temperature Gradients on Anammox Activity- A Genome Wide Approach

2018 ◽  
Vol 2018 (7) ◽  
pp. 5219-5228
Author(s):  
Ananda Shankar Bhattacharjee ◽  
Sha Wu ◽  
Ramesh Goel
Keyword(s):  
Temperature Gradients ◽  
Effect Of Temperature ◽  
Genome Wide ◽  
A Genome ◽  
Anammox Activity

Vortex-Induced Vibrations of a Cylinder at Subcritical Reynolds Number

2011 ◽  
Author(s):  
Yoann Jus ◽  
Elisabeth Longatte ◽  
Jean-Camille Chassaing ◽  
Pierre Sagaut
Keyword(s):  
Reynolds Number ◽  
Numerical Simulations ◽  
Numerical Study ◽  
Damping Ratio ◽  
Experimental Studies ◽  
Cross Flow ◽  
Physical Analysis ◽  
Arbitrary Lagrangian Eulerian ◽  
Vortex Induced Vibrations ◽  
Low Mass

The present work focusses on the numerical study of Vortex-Induced Vibrations (VIV) of an elastically mounted cylinder in a cross flow at moderate Reynolds numbers. Low mass-damping experimental studies show that the dynamic behavior of the cylinder exhibits a three-branch response model, depending on the range of the reduced velocity. However, few numerical simulations deal with accurate computations of the VIV amplitudes at the lock-in upper branch of the bifurcation diagram. In this work, the dynamic response of the cylinder is investigated by means of three-dimensional Large Eddy Simulation (LES). An Arbitrary Lagrangian Eulerian framework is employed to account for fluid solid interface boundary motion and grid deformation. Numerous numerical simulations are performed at a Reynolds number of 3900 for both no damping and low-mass damping ratio and various reduced velocities. A detailed physical analysis is conducted to show how the present methodology is able to capture the different VIV responses.

scholarly journals Effect of temperature gradients in (reverse) electrodialysis in the Ohmic regime

2018 ◽  
Vol 548 ◽  
pp. 421-428 ◽  
Author(s):  
Anne M. Benneker ◽  
Timon Rijnaarts ◽  
Rob G.H. Lammertink ◽  
Jeffery A. Wood
Keyword(s):  
Temperature Gradients ◽  
Effect Of Temperature ◽  
Reverse Electrodialysis
Sign in / Sign up

Export Citation Format

Share Document