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Otimização dinâmica de rotores com eixos em compósito

Mendonça, Willy Roger de Paula
Fonte: Universidade Estadual Paulista (UNESP) Publicador: Universidade Estadual Paulista (UNESP)
Tipo: Tese de Doutorado Formato: 166f. : il.
POR
Relevância na Pesquisa
27.52%
Pós-graduação em Engenharia Mecânica - FEG; Esta tese apresenta o desenvolvimento de uma metodologia de otimização dinâmica e estrutural para rotores com eixos em material compósito. A dinâmica destes rotores difere das análises convencionais devido à existência de amortecimento interno no eixo. As equações de movimento destes rotores apresentam a influencia do amortecimento interno sobre o comportamento dinâmico dos rotores. Materiais compósitos podem ser manufaturados em diferentes sequências de laminação. Para obter as melhores propriedades mecânicas, que possibilitem aos rotores operarem, em condições de estabilidade dinâmica e de esforços estruturais, foi necessário o desenvolvimento de uma metodologia de otimização para obter o melhor projeto. Para a aplicação desta metodologia foi desenvolvido um algoritmo de otimização. Para fundamentar este desenvolvimento foram revisados conceitos da teoria clássica de laminação, dos modelos de amortecimento estrutural, da dinâmica de rotores com amortecimento interno, de elementos finitos e dos métodos de otimização. O método de otimização escolhido foi o genético. Dentro do algoritmo de otimização foram inseridos módulos de análise para calcular as propriedades equivalentes...

Nonlinear Vibrations of Vertical Asymmetrically-Supported Rotors Under Fluid Confinement: Theoretical Results

Moreira, Miguel; Pina, H.; Antunes, J.
Fonte: Repositório Comum de Portugal Publicador: Repositório Comum de Portugal
Tipo: Conferência ou Objeto de Conferência
Publicado em //2001 ENG
Relevância na Pesquisa
27.43%
This paper is concerned about vertical rotors immersed in fluid annulus of moderate confinement. Such rotors are subjected to the dynamical effects of the fluctuating co-rotating flows. For high enough spinning velocities, the fluid-elastic forces become significant, and often lead to unstable dynamical regimes. These depend on the fluid gap and density, on the rotor eccentricity and spinning velocity, as well as structural properties. We developed an improved linear model for rotors under moderate fluid confinement as well as an exact model for the corresponding nonlinear rotordynamics. Recently a symbolic-numerical formulation based on a spectral/Galerkin approach was also developed by the authors. Numerical results showed a quite good agreement between exact solutions and these formulations and experimental validation of the theoretical model has been provided for symmetrically-supported rotors. Numerical simulations carried over immersed rotor configurations maintained by non-isotropic supports show that the rotor stability is affected by support stiffness-asymmetry. In this paper, we briefly summarize the theoretical approaches used in the numerical simulations and present an analysis of the linear rotor-dynamics, as a function of the support stiffness-asymmetry and of the rotor eccentricity. Theoretical stability domains are computed from the eigenvalues of the linearized model. Finally...

Bursting calcium rotors in cultured cardiac myocyte monolayers

Bub, Gil; Glass, Leon; Publicover, Nelson G.; Shrier, Alvin
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
Publicado em 18/08/1998 EN
Relevância na Pesquisa
27.32%
Rotating waves (rotors) of cellular activity were observed in nonconfluent cultures of embryonic chick heart cells by using a macroscopic imaging system that detected fluorescence from intracellular Ca2+. Unlike previous observations of rotors or spiral waves in other systems, the rotors did not persist but exhibited a repetitive pattern of spontaneous onset and offset leading to a bursting rhythm. Similar dynamics were observed in a cellular automaton model of excitable media that incorporates spontaneous initiation of activity, and a decrease of excitability as a consequence of rapid activity (fatigue). These results provide a mechanism for bursting dynamics in normal and pathological biological processes.

Imaging of Flow Patterns with Fluorescent Molecular Rotors

Mustafic, Adnan; Huang, Hsuan-Ming; Theodorakis, Emmanuel A.; Haidekker, Mark A.
Fonte: Springer US Publicador: Springer US
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.52%
Molecular rotors are a group of fluorescent molecules that form twisted intramolecular charge transfer states (TICT) upon photoexcitation. Some classes of molecular rotors, among them those that are built on the benzylidene malononitrile motif, return to the ground state either by nonradiative intramolecular rotation or by fluorescence emission. In low-viscosity solvents, intramolecular rotation dominates, and the fluorescence quantum yield is low. Higher solvent viscosities reduce the intramolecular rotation rate, thus increasing the quantum yield. We recently described a different mechanism whereby the fluorescence quantum yield of the molecular rotor also depends on the shear stress of the solvent. In this study, we examined a possible application for shear-sensitive molecular rotors for imaging flow patterns in fluidic chambers. Flow chambers with different geometries were constructed from polycarbonate or acrylic. Solutions of molecular rotors in ethylene glycol were injected into the chamber under controlled flow rates. LED-induced fluorescence (LIF) images of the flow chambers were taken with a digital camera, and the intensity difference between flow and no-flow images was visualized and compared to computed fluid dynamics (CFD) simulations. Intensity differences were detectable with average flow rates as low as 0.1 mm/s...

Detection of Liposome Membrane Viscosity Perturbations with Ratiometric Molecular Rotors

Nipper, Matthew E.; Dakanali, Marianna; Theodorakis, Emmanuel; Haidekker, Mark A.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.32%
Molecular rotors are a form of fluorescent intramolecular charge-transfer complexes that can undergo intramolecular twisting motion upon photoexcitation. Twisted-state formation leads to non-radiative relaxation that competes with fluorescence emission. In bulk solutions, these molecules exhibit a viscosity-dependent quantum yield. On the molecular scale, the fluorescence emission is a function of the local free volume, which in turn is related to the local microviscosity. Membrane viscosity, and the inverse; fluidity, are characteristic terms used to describe the ease of movement withing the membrane. Often, changes in membrane viscosity govern intracellular processes and are indicative of a disease state. Molecular rotors have been used to investigate viscosity changes in liposomes and cells, but accuracy is affected by local concentration gradients and sample optical properties. We have developed self-calibrating ratiometric molecular rotors to overcome this challenge and integrated the new molecules into a DLPC liposome model exposed to the membrane-fluidizing agent propanol. We show that the ratiometric emission intensity linearly decreases with the pentanol exposure and that the ratiometric intensity is widely independent of the total liposome concentration. Conversely...

Ionic and Substrate Mechanisms of Atrial Fibrillation: Rotors and the Excitation Frequency Approach

Berenfeld, Omer
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em //2010 EN
Relevância na Pesquisa
27.32%
Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia in humans however its mechanisms are poorly understood and its therapy is often sub-optimal. This article reviews recent experimental, numerical and clinical data on dynamics of wave propagation during AF and its mechanistic link to ionic and structural properties of the atria. At the onset, the article present numerical and optical mapping data suggesting that a presence of periodic source with increasingly high dominant frequency (DF) of excitation underlies observations of dispersion of local activation rate during AF. Further optical mapping studies in isolated normal sheep hearts in the presence of acetylcholine (ACh) reveals that rotors localized to the left atrium (LA) drive the arrhythmia and are faster than those in the right atrium (RA). Patch-clamp data from isolated cardiomycytes shows that the ACh-modulated potassium inward rectifier current is higher in the LA than in the RA which may explain the higher DFs and sensitivity of LA rotors to ACh compared with RA rotors. Following, the role of fibrosis in governing the propagation dynamics with a decrease in excitation frequency is presented in AF in failing sheep hearts and complex activation in cell cultures. Translation into the clinical setting is then discussed: DF distribution in patients with paroxysmal AF follows the LA-to-RA gradients found in the acute cholinergic AF of sheep hearts with highest DFs localized primarily to the posterior LA wall and pulmonary veins (PV) region; however in patients with persistent AF...

Rotors and the Dynamics of Cardiac Fibrillation

Pandit, Sandeep V.; Jalife, José
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/03/2013 EN
Relevância na Pesquisa
27.52%
The objective of this article is to present a broad review on the role of cardiac electrical rotors and their accompanying spiral waves in the mechanism of cardiac fibrillation. At the outset, we present a brief historical overview regarding reentry, and then discuss the basic concepts and terminologies pertaining to rotors and their initiation. Thereafter, the intrinsic properties of rotors and spiral waves, including phase singularities, wavefront curvature and dominant frequency maps are discussed. The implications of rotor dynamics for the spatio-temporal organization of fibrillation, independent of the species being studied are touched upon next. The knowledge gained regarding the role of cardiac structure in the initiation and/or maintenance of rotors and the ionic bases of spiral waves in the last two decades, and its significance for drug therapy is reviewed subsequently. We conclude by looking at recent evidence suggesting that rotors are critical in sustaining both atrial and ventricular fibrillation (AF, VF) in the human heart, and its implications for treatment with radio-frequency ablation.

Attraction of Rotors to the Pulmonary Veins in Paroxysmal Atrial Fibrillation: A Modeling Study

Calvo, Conrado J.; Deo, Makarand; Zlochiver, Sharon; Millet, José; Berenfeld, Omer
Fonte: The Biophysical Society Publicador: The Biophysical Society
Tipo: Artigo de Revista Científica
Publicado em 15/04/2014 EN
Relevância na Pesquisa
27.52%
Maintenance of paroxysmal atrial fibrillation (AF) by fast rotors in the left atrium (LA) or at the pulmonary veins (PVs) is not fully understood. To gain insight into this dynamic and complex process, we studied the role of the heterogeneous distribution of transmembrane currents in the PVs and LA junction (PV-LAJ) in the localization of rotors in the PVs. We also investigated whether simple pacing protocols could be used to predict rotor drift in the PV-LAJ. Experimentally observed heterogeneities in IK1, IKs, IKr, Ito, and ICaL in the PV-LAJ were incorporated into two- and pseudo three-dimensional models of Courtemanche-Ramirez-Nattel-Kneller human atrial kinetics to simulate various conditions and investigate rotor drifting mechanisms. Spatial gradients in the currents resulted in shorter action potential duration, minimum diastolic potential that was less negative, and slower upstroke and conduction velocity for rotors in the PV region than in the LA. Rotors under such conditions drifted toward the PV and stabilized at the shortest action potential duration and less-excitable region, consistent with drift direction under intercellular coupling heterogeneities and regardless of the geometrical constraint in the PVs. Simulations with various IK1 gradient conditions and current-voltage relationships substantiated its major role in the rotor drift. In our 1:1 pacing protocol...

Synchronization of Two Homodromy Rotors Installed on a Double Vibro-Body in a Coupling Vibration System

Fang, Pan; Hou, Yongjun; Nan, Yanghai
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 19/05/2015 EN
Relevância na Pesquisa
27.52%
A new mechanism is proposed to implement synchronization of the two unbalanced rotors in a vibration system, which consists of a double vibro-body, two induction motors and spring foundations. The coupling relationship between the vibro-bodies is ascertained with the Laplace transformation method for the dynamics equation of the system obtained with the Lagrange’s equation. An analytical approach, the average method of modified small parameters, is employed to study the synchronization characteristics between the two unbalanced rotors, which is converted into that of existence and the stability of zero solutions for the non-dimensional differential equations of the angular velocity disturbance parameters. By assuming the disturbance parameters that infinitely approach to zero, the synchronization condition for the two rotors is obtained. It indicated that the absolute value of the residual torque between the two motors should be equal to or less than the maximum of their coupling torques. Meanwhile, the stability criterion of synchronization is derived with the Routh-Hurwitz method, and the region of the stable phase difference is confirmed. At last, computer simulations are preformed to verify the correctness of the approximate solution of the theoretical computation for the stable phase difference between the two unbalanced rotors...

Contribuição ao estudo de máquinas rotativas na presença de não-linearidades; Contribution to the Study of Rotating Machines containing nonlinearities

Morais, Tobias Souza
Fonte: Universidade Federal de Uberlândia Publicador: Universidade Federal de Uberlândia
Tipo: Tese de Doutorado
POR
Relevância na Pesquisa
27.43%
Esta tese procura enfocar problemas relacionados a rotores inteligentes, ou seja, aqueles que são capazes de monitorar seu comportamento dinâmico, analisá-lo, propor soluções com certa autonomia e garantir seu funcionamento mesmo quando do aparecimento de falhas que podem comprometer seu comportamento seguro ou sua eficiência. Este trabalho, de maneira geral, está inserido no contexto da dinâmica de máquinas rotativas com características não-lineares. Mais especificamente, interessa-se a não-linearidades causadas por rotores que apresentam parâmetros variantes no tempo, como é o caso dos eixos trincados, e de sistemas com atuadores eletromagnéticos (AEM) que introduzem forças que são funções inversas do quadrado do deslocamento. Neste sentido, três assuntos mais significativos foram abordados, conforme abaixo especificado. O primeiro assunto está relacionado com a identificação de parâmetros variantes no tempo, através da expansão dos sinais de entrada e saída do sistema, além da expansão, também, dos parâmetros físicos do sistema em séries de funções ortogonais, permitindo, desta forma, a identificação dos parâmetros desconhecidos do sistema rotativo, tanto daqueles que são constantes como daqueles que variam com o tempo. Assim...

Controle de vibrações em máquinas rotativas utilizando atuadores eletromagnéticos; Vibration control of rotating machines using electromagnetic actuators

Koroishi, Edson Hideki
Fonte: Universidade Federal de Uberlândia Publicador: Universidade Federal de Uberlândia
Tipo: Tese de Doutorado
POR
Relevância na Pesquisa
27.43%
O presente trabalho tem por objetivo o estudo de controle ativo de vibrações em rotores flexíveis utilizando atuadores eletromagnéticos. Dentro deste contexto, foi estudado um rotor flexível que foi modelado empregando o Método dos Elementos Finitos. Como o modelo original do rotor possui um elevado número de graus de liberdade, foi necessário reduzir tal modelo, sendo utilizado para isto o Método Pseudo-Modal. O projeto dos controladores foi realizado utilizando duas diferentes abordagens. A primeira abordagem envolve controladores projetados via norma H∞ e Controle Ótimo, sendo que ambos os casos foram desenvolvidos utilizando desigualdades matriciais, técnica que facilita a inclusão de incertezas no projeto do controlador. Na segunda abordagem, os controladores foram desenvolvidos utilizando a Lógica Nebulosa (Fuzzy). Nestas duas abordagens os controladores foram projetados no domínio modal. A vantagem de se utilizar a metodologia de controle modal é que os controladores são projetados com base apenas em poucos modos de vibração do sistema, aspecto que, dentre suas vantagens, contribui para a redução do custo computacional. Neste tipo de controle, nem sempre os estados modais são acessíveis experimentalmente...

Étude expérimentale de l’écoulement et de l’interaction entre deux rotors contrarotatifs subsoniques

NOURI, Hussain; RAVELET, Florent; BAKIR, Farid
Fonte: Société Hydrotechnique de France Publicador: Société Hydrotechnique de France
FR
Relevância na Pesquisa
37.58%
Recently, the need for smaller axial‐flow fans with high specific speeds leads to the design of counter‐rotating axial fans. The design of this type of machines, which have promising aerodynamic performances, suffers from a lack of knowledge about their aerodynamics. Counter‐rotating rotors, widely studied in aeronautics, are an effective alternative to conventional machines and offer many advantages: rotation ratio and diameter reduction, and high flexibility in use. However, a better understanding of their working and of the rotors interaction is required to enhance their design and to make them widely integrated in current applications. This experimental research work investigates on a ducted counter‐rotating stage designed with a home code, MFT based on an inverse design method for rotors and rotor‐stator stages, and to which a rapid and simple method is implemented to design the rear rotor. The study focuses on the effects of the rotation ratio and on the axial spacing between rotors. It highlights several aspects of the rotors interaction through global performance and local unsteady measurements.

Lifetimes of Epicardial Rotors in Panoramic Optical Maps of Fibrillating Swine Ventricles

Kay, Matthew W.; Walcott, Gregory P.; Gladden, James D.; Melnick, Sharon B.; Rogers, Jack M.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.72%
During ventricular fibrillation (VF), electrical activation waves are fragmented and the heart cannot contract in synchrony. It has been proposed that VF waves emanate from stable periodic sources (often called “mother rotors”). The objective of the present study was to determine if stable rotors are consistently present on the epicardial surface of hearts comparable in size to human hearts. Using new optical mapping technology, we imaged VF from nearly the entire ventricular surface of 6 isolated swine hearts. Using newly developed pattern analysis algorithms, we identified and tracked VF wavefronts and phase singularities (PS: the pivot point of a reentrant wavefront). We introduce the notion of a compound rotor in which the rotor's central PS can change and describe an algorithm for automatically identifying such patterns. This prevents rotor lifetimes from being inappropriately abbreviated by wavefront fragmentation and collision events near the PS. We found that stable epicardial rotors were not consistently present during VF: only 1 of 17 VF episodes contained a compound rotor that lasted for the entire mapped interval of 4 s. However, shorter-lived rotors were common; 12.2±3.3 compound rotors with lifetime >200 ms were visible on the epicardium at any given instant. We conclude that epicardial mother rotors do not drive VF in this experimental model; if mother rotors do exist...

Complete control, direct observation and study of molecular super rotors

Korobenko, Aleksey; Milner, Alexander A.; Milner, Valery
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
27.52%
Extremely fast rotating molecules carrying significantly more energy in their rotation than in any other degree of freedom are known as "super rotors". It has been speculated that super rotors may exhibit a number of unique properties. Theoretical studies showed that ultrafast molecular rotation may change the character of molecular scattering from solid surfaces, alter molecular trajectories in external fields, make super rotors stable against collisions, and lead to the formation of gas vortices. New ways of molecular cooling and selective chemical bond breaking by ultrafast spinning have been suggested. Bringing a large number of molecules to fast, directional and synchronous rotation is rather challenging. An efficient method of accelerating molecular rotation with an "optical centrifuge" has been proposed and successfully implemented, yet only indirect evidence of super rotors has been reported to date. Here we demonstrate the first direct observation of molecular super rotors and study their spectroscopic, dynamical and magneto-optical properties. Using the centrifuge technique, we control the degree of rotational excitation and detect molecular rotation with high spectral and temporal resolution. Frequency-resolved detection enables us to map out the energy of extreme rotation levels...

Cooperative Self-Propulsion of Active and Passive Rotors

Fily, Yaouen; Baskaran, Aparna; Marchetti, M. Cristina
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
27.7%
Using minimal models for low Reynolds number passive and active rotors in a fluid, we characterize the hydrodynamic interactions among rotors and the resulting dynamics of a pair of interacting rotors. This allows us to treat in a common framework passive or externally driven rotors, such as magnetic colloids driven by a rotating magnetic field, and active or internally driven rotors, such as sperm cells confined at boundaries. The hydrodynamic interaction of passive rotors is known to contain an azimuthal component \sim 1/r^2 to dipolar order that can yield the recently discovered "cooperative self-propulsion" of a pair of rotors of opposite vorticity. While this interaction is identically zero for active rotors as a consequence of torque balance, we show that a \sim 1/r^4 azimuthal component of the interaction arises in active systems to octupolar order. Cooperative self-propulsion, although weaker, can therefore also occur for pairs of active rotors.; Comment: 9 pages, 5 figures

Non-equilibrium steady states for chains of four rotors

Cuneo, Noé; Eckmann, Jean-Pierre
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 20/04/2015
Relevância na Pesquisa
27.63%
We study a chain of four interacting rotors (rotators) connected at both ends to stochastic heat baths at different temperatures. We show that for non-degenerate interaction potentials the system relaxes, at a stretched exponential rate, to a non-equilibrium steady state (NESS). Rotors with high energy tend to decouple from their neighbors due to fast oscillation of the forces. Because of this, the energy of the central two rotors, which interact with the heat baths only through the external rotors, can take a very long time to dissipate. By appropriately averaging the oscillatory forces, we estimate the dissipation rate and construct a Lyapunov function. Compared to the chain of length three (considered previously by C. Poquet and the current authors), the new difficulty with four rotors is the apparition of resonances when both central rotors are fast. We deal with these resonances using the rapid thermalization of the two external rotors.

Dynamics and interactions of active rotors

Leoni, M.; Liverpool, T. B.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 13/12/2010
Relevância na Pesquisa
27.58%
We consider a simple model of an internally driven self-rotating object; a rotor, confined to two dimensions by a thin film of low Reynolds number fluid. We undertake a detailed study of the hydrodynamic interactions between a pair of rotors and find that their effect on the resulting dynamics is a combination of fast and slow motions. We analyse the slow dynamics using an averaging procedure to take account of the fast degrees of freedom. Analytical results are compared with numerical simulations. Hydrodynamic interactions mean that while isolated rotors do not translate, bringing together a pair of rotors leads to motion of their centres. Two rotors spinning in the same sense rotate with an approximately constant angular velocity around each other, while two rotors of opposite sense, both translate with the same constant velocity, which depends on the separation of the pair. As a result a pair of counter-rotating rotors are a promising model for controlled self-propulsion.; Comment: 6 pages, 6 figures

Orienting coupled quantum rotors by ultrashort laser pulses

Shima, Hiroyuki; Nakayama, Tsuneyoshi
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
27.58%
We point out that the non-adiabatic orientation of quantum rotors, produced by ultrashort laser pulses, is remarkably enhanced by introducing dipolar interaction between the rotors. This enhanced orientation of quantum rotors is in contrast with the behavior of classical paired rotors, in which dipolar interactions prevent the orientation of the rotors. We demonstrate also that a specially designed sequence of pulses can most efficiently enhances the orientation of quantum paired rotors.; Comment: 7 pages, 5 figures, to appear in Phys. Rev. A

Turbulence ingestion noise of open rotors

Robison, Rosalyn Aruna Venner
Fonte: University of Cambridge; Department of Applied Mathematics and Theoretical Physics Publicador: University of Cambridge; Department of Applied Mathematics and Theoretical Physics
Tipo: Thesis; doctoral; PhD
EN
Relevância na Pesquisa
27.43%
Renewed interest in open rotor aeroengines, due to their fuel efficiency, has driven renewed interest in all aspects of the noise they generate. Noise due to the ingestion of distorted atmospheric turbulence, known as Unsteady Distortion Noise (UDN), is likely to be higher for open rotors than for conventional turbofan engines since the rotors are fully exposed to oncoming turbulence and lack ducting to attenuate the radiated sound. However, UDN has received less attention to date, particularly in wind-tunnel and flight testing programmes. In this thesis a new prediction scheme for UDN is described, which allows inclusion of many key features of real open rotors which have not previously been investigated theoretically. Detailed features of the mean flow induced by the rotor, the form of atmospheric turbulence, asymmetries due to installation features, and the effect of rotor incidence are all considered. Parameter studies are conducted in each of these cases to investigate their effect upon UDN in typical static testing and flight conditions. A thorough review of the technological issues of most relevance and previous theoretical work on all types of turbulence-blade interaction noise is first undertaken. The prediction scheme is then developed for the case in which the mean flow into the rotor is axisymmetric. This shows excellent qualitative agreement with previous findings...

Ionic and substrate mechanisms of atrial fibrillation: rotors and the excitation frequency approach

Berenfeld,Omer
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2010 EN
Relevância na Pesquisa
37.43%
Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia in humans, however its mechanisms are poorly understood and its therapy is often sub-optimal. This article reviews recent experimental, numerical and clinical data on dynamics of wave propagation during AF and its mechanistic link to ionic and structural properties of the atria. At the onset, the article presents numerical and optical mapping data suggesting that a presence of periodic source with increasingly high dominant frequency (DF) of excitation underlies observations of dispersion of local activation rate during AF. Further optical mapping studies in isolated normal sheep hearts in the presence of acetylcholine (ACh) reveals that rotors localized to the left atrium (LA) drive the arrhythmia and are faster than those in the right atrium (RA). Patch-clamp data from isolated cardiomycytes shows that the ACh-modulated potassium inward rectifier current is higher in the LA than in the RA which may explain the higher DFs and sensitivity of LA rotors to ACh compared with RA rotors. Following, the role of fibrosis in governing the propagation dynamics with a decrease in excitation frequency is presented in AF in failing sheep hearts and complex activation in cell cultures. Translation into the clinical setting is then discussed: DF distribution in patients with paroxysmal AF follows the LA-to-RA gradients found in the acute cholinergic AF of sheep hearts with highest DFs localized primarily to the posterior LA wall and pulmonary veins (PV) region; however in patients with persistent AF...