Biomedical subjects

Diego Pazó

Publications and source records attributed to Diego Pazó.

7 recordsLinked to original sources

PubMed2006

Universal behavior in populations composed of excitable and self-oscillatory elements.

We study the robustness of self-sustained oscillatory activity in a globally coupled ensemble of excitable and oscillatory units. The critical balance to achieve collective self-sustained oscillations is analytically established. We also report a universal scaling function for the ensemble's mean frequency. Our results extend the framework of the "aging transition" [Phys. Rev. Lett. 93, 104101 (2004)] including a broad class of dynamical systems potentially relevant in biology.

Journal Article↗

PubMed2006

Comment on "Periodic phase synchronization in coupled chaotic oscillators".

Kye [Phys. Rev. E 68, 025201 (2003)] have recently claimed that, before the onset of chaotic phase synchronization in coupled phase coherent oscillators, there exists a temporally coherent state called periodic phase synchronization (PPS). Here we give evidence that some of their numerical calculations are flawed, while we provide theoretical arguments that indicate that PPS is not to be expected generically in this type of systems.

Comment↗

PubMed2006

Experimental study of the transitions between synchronous chaos and a periodic rotating wave.

In this work we characterize experimentally the transition between periodic rotating waves and synchronized chaos in a ring of unidirectionally coupled Lorenz oscillators by means of electronic circuits. The study is complemented by numerical and theoretical analysis, and the intermediate states and their transitions are identified. The route linking periodic behavior with synchronous chaos involves quasiperiodic behavior and a type of high-dimensional chaos known as chaotic rotating wave. The high-dimensional chaotic behavior is characterized, and is shown to be composed actually by three different behaviors. The experimental study confirms the robustness of this route.

Mathematics↗

PubMed2005

Anomalous nonequilibrium Ising-Bloch bifurcation in discrete systems.

We investigate the self-organization of two-dimensional activator-inhibitor discrete bistable systems in the neighborhood of a nonequilibrium Ising-Bloch bifurcation. The system exhibits an anomalous transition--induced by discretization--whose signature is the coexistence of Ising and Bloch walls for selected values of the spatial coupling. After curvature reduction of Bloch walls, coexistence gives rise to a unique and striking spatiotemporal dynamics: Bloch walls drive the motion and Ising walls play the role of "extended defects" oriented along the background grid directions. Strong enough external noise asymptotically restores the scenario found in the continuum limit.

Journal Article↗

PubMed2005

Thermodynamic limit of the first-order phase transition in the Kuramoto model.

In the Kuramoto model, a uniform distribution of the natural frequencies leads to a first-order (i.e., discontinuous) phase transition from incoherence to synchronization, at the critical coupling parameter K(c). We obtain the asymptotic dependence of the order parameter above criticality: r-r(c)alpha(K - K(c))(2/3). For a finite population, we demonstrate that the population size N may be included into a self-consistency equation relating r and K in the synchronized state. We analyze the convergence to the thermodynamic limit of two alternative schemes to set the natural frequencies. Other frequency distributions different from the uniform one are also considered.

Journal Article↗

PubMed2003

Role of unstable periodic orbits in phase and lag synchronization between coupled chaotic oscillators.

An increase of the coupling strength in the system of two coupled Rössler oscillators leads from a nonsynchronized state through phase synchronization to the regime of lag synchronization. The role of unstable periodic orbits in these transitions is investigated. Changes in the structure of attracting sets are discussed. We demonstrate that the onset of phase synchronization is related to phase-lockings on the surfaces of unstable tori, whereas transition from phase to lag synchronization is preceded by a decrease in the number of unstable periodic orbits.

Models, Theoretical↗

PubMed2003

Traveling fronts in an array of coupled symmetric bistable units.

Traveling fronts are shown to occur in an array of nearest-neighbor coupled symmetric bistable units. When the local dynamics is given by the Lorenz equations we observe the route: standing-->oscillating-->traveling front, as the coupling is increased. A key step in this route is a gluing bifurcation of two cycles in cylindrical coordinates. When this is mediated by a saddle with real leading eigenvalues, the asymptotic behavior of the front velocity is found straightforwardly. If the saddle is focus-type instead, the front's dynamics may become quite complex, displaying several oscillating and propagating regimes and including (Shil'nikov-type) chaotic front propagation. These results stand as well for other nearest-neighbor coupling schemes and local dynamics.

Journal Article↗