Biomedical subjects
Publications and source records attributed to G B Mindlin.
In this Letter we extend the concept of stochastic resonance. We show that in forced excitable systems noise can be responsible for the appearance of recurrences presenting a robust topological organization inequivalent to the periodic orbits of the deterministic system. As in stochastic resonance, these new structures are most pronounced at an optimal noise intensity.
We present a biorthogonal decomposition of the temporal and latitudinal distribution of sunspots recorded since 1874. We show that the butterfly diagrams can be interpreted as the result of approximately constant amplitudes and phases of two oscillations with periods close to 22 years. Our analysis reveals clear evidence of the absence of low-dimensional chaos, at least for the time scales that can be analyzed with this database. This result suggests that the spatiotemporal irregularities observed in the solar cycle are due to the superposition of regular structures with a stochastic background.
We present a simple model that displays all classes of two-dimensional excitable regimes. One of the variables of the model displays the usual spikes observed in excitable systems. Since the model is written in terms of a "standard" vector field, it is always possible to fit it to experimental data displaying spikes in an algorithmic way. In fact, we use it to fit a series of membrane potential recordings obtained in the medicinal leech and time series generated with the FitzHugh-Nagumo equations and the excitability model of Eguía et al. [Phys. Rev. E 58, 2636 (1998)]. In each case, we determine the excitability class of the corresponding system.
In this work we show that excitable units with biologically inspired couplings are capable of performing any logic operation in a noisy environment without synchronization.
We present a model of sound production in a songbird's vocal organ and find that much of the complexity of the song of the canary (Serinus canaria) can be produced from simple time variations in forcing functions. The starts, stops, and pauses between syllables, as well as variation in pitch and timbre are inherent in the mechanics and can often be expressed through smooth and simple variations in the frequency and relative phase of two driving parameters
In this work we study the effects of delayed feedback on vocal fold dynamics. To perform this study, we work with a vocal fold model that is made as simple as possible while retaining the spectral content characteristic of human vocal production. Our results indicate that, even with the simplest explanation for vocal fold oscillation, delayed feedback due to reflected sound in the vocal tract can lead to extremely rich dynamics.
We report the analysis of branched manifolds through homologies, in order to extend the range of applicability of the topological approach to the analysis of chaotic data. Analytic and numerical cases are discussed.
Recently it was proposed that semiconductor lasers with optical feedback present a regime where they behave as noise driven excitable units. In this work we report on an experimental study in which we periodically force one of these lasers and we compare the results with the solutions of a simple model. The comparison is based on a topological analysis of experimental and theoretical solutions.
In this work we study a simple model of voiced sound production. We analyze contributions that the qualitative theory of dynamical systems can make to the analysis and synthesis of human speech.
We perform a detailed analysis of the sunspot number time series to reconstruct the phase space of the underlying dynamical system. The features of this phase space allow us to describe the behavior of the solar cycle in terms of a simple relaxation oscillator in two dimensions. The absence of systematic self-crossings suggests that the complexity of the sunspot time series does not arise as a consequence of chaos. Instead, we show that it can be adequately modeled through the introduction of a stochastic fluctuation in one of the parameters of the dynamic equations.
Semiconductor lasers with optical feedback present a regime in which power dropouts are observed. Although this regime has been extensively studied, there is no agreement about whether the dropouts are deterministically or stochastically generated. In this paper we will study the statistics of time intervals between dropouts assuming noise-driven simple excitable models. We explain the appearance of characteristic times in the first return maps.