DEPARTAMENTO SISTEMAS COMPLEJOS Y ALTAS ENERGÍAS
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Examinando DEPARTAMENTO SISTEMAS COMPLEJOS Y ALTAS ENERGÍAS por Materia "DINAMICA DE LA POBLACION"
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Ítem Acceso Abierto A corpus analysis of rubato in Bach's C major prelude, WTC I(Royal Northern College of Music, 2015) Benadon, Fernando; Zanette, Damian HoracioWe examined microtiming properties in a corpus of 48 recorded performances of J.S. Bach's C Major Prelude from The Well Tempered Clavier, Book I. Drawing on the results of a listening experiment and from wavelet analysis, we derived a quantitative measure of rubato 'depth' that was used to assess timing trends across performances. In addition to highlighting important structural moments in the Prelude, rubato was used to bring melodic elements into relief as well as to generate grouping segmentations that may contradict the Prelude's inherent phrase structure. We then applied the statistical method of principal components analysis (PCA) to examine timing contours specific to individual performers. Repetitively consistent microrhythmic patterns, which we qualified as groove-like, differed from non-consistent and non-repetitive timing inflections, which we qualified as rubatoSlike.Ítem Acceso Abierto Analysis of the role of the low threshold currents IT and Ih in intrinsic delta oscillations of thalamocortical neurons(Frontiers Media S.A., 2015-05-07) Amarillo Gomez, Yimy; Mato, German; Nadal, MarcelaThalamocortical neurons are involved in the generation and maintenance of brain rhythms associated with global functional states. The repetitive burst firing of TC neurons at delta frequencies (1-4 Hz) has been linked to the oscillations recorded during deep sleep and during episodes of absence seizures. To get insight into the biophysical properties that are the basis for intrinsic delta oscillations in these neurons, we performed a bifurcation analysis of a minimal conductance-based thalamocortical neuron model including only the IT channel and the sodium and potassium leak channels. This analysis unveils the dynamics of repetitive burst firing of TC neurons, and describes how the interplay between the amplifying variable mT and the recovering variable hT of the calcium channel IT is sufficient to generate low threshold oscillations in the delta band. We also explored the role of the hyperpolarization activated cationic current Ih in this reduced model and determine that, albeit not required, Ih amplifies and stabilizes the oscillation.Ítem Acceso Abierto Critical phenomena in the spreading of opinion consensus and disagreement(Papers in Physics, 2014-08-29) Chacoma, Andrés Alberto; Zanette, Damian HoracioWe consider a class of models of opinion formation where the dissemination of individual opinions occurs through the spreading of local consensus and disagreement. We study the emergence of full collective consensus or maximal disagreement in one- and two-dimensional arrays. In both cases, the probability of reaching full consensus exhibits well-defined scaling properties as a function of the system size. Two-dimensional systems, in particular, possess nontrivial exponents and critical points. The dynamical rules of our models, which emphasize the interaction between small groups of agents, should be considered as complementary to the imitation mechanisms of traditional opinion dynamics.Ítem Acceso Abierto Epidemic thresholds for bipartite networks(Amer Physical Soc, 2013-11) Hernandez, Damián G.; Risau Gusman, Sebastian LuisIt is well known that sexually transmitted diseases (STD) spread across a network of human sexual contacts. This network is most often bipartite, as most STD are transmitted between men and women. Even though network models in epidemiology have quite a long history now, there are few general results about bipartite networks. One of them is the simple dependence, predicted using the mean field approximation, between the epidemic threshold and the average and variance of the degree distribution of the network. Here we show that going beyond this
approximation can lead to qualitatively different results that are supported by numerical simulations. One of the new features, that can be relevant for applications, is the existence of a critical value for the infectivity of each population, below which no epidemics can arise, regardless of the value of the infectivity of the other population.Ítem Acceso Abierto Mathematical model of livestock and wildlife: Predation and competition under environmental disturbances(Elsevier Science, 2015-08-10) Laguna, Maria Fabiana; Abramson, Guillermo; Kuperman, Marcelo Nestor; Lanata, Jose Luis; Monjeau, Jorge AdrianInspired by real scenarios in Northern Patagonia, we analyze a mathematical model of a simple trophic web with two herbivores and one predator. The studied situations represent a common practice in the steppes of Argentine Patagonia, where livestock are raised in a semi-wild state, either on the open range or enclosed, coexisting with competitors and predators. In the present work, the competing herbivores represent sheep and guanacos, while the predator is associated with the puma. The proposed model combines the concepts of metapopulations and patches dynamics, and includes an explicit hierarchical competition between species, which affects their prospect to colonize an empty patch when having to compete with other species. We perform numerical simulations of spatially extended metapopulations assemblages of the system, which allow us to incorporate the effects of habitat heterogeneity and destruction. The numerical results are compared with those obtained from mean field calculations. We find that the model provides a good theoretical framework in several situations, including the control of the wild populations that the ranchers exert to different extent. Furthermore, the present formulation incorporates new terms in previously analyzed models that help to reveal the important effects due to the heterogeneous nature of the system.Ítem Acceso Abierto Random-walk model to study cycles emerging from the exploration-exploitation trade-off(American Physical Society, 2015-01-13) Kazimierski, Laila Daniela; Abramson, Guillermo; Kuperman, Marcelo NestorWe present a model for a random walk with memory, phenomenologically inspired in a biological system. The walker has the capacity to remember the time of the last visit to each site and the step taken from there. This memory affects the behavior of the walker each time it reaches an already visited site modulating the probability of repeating previous moves. This probability increases with the time elapsed from the last visit. A biological analog of the walker is a frugivore, with the lattice sites representing plants. The memory effect can be associated with the time needed by plants to recover its fruit load. We propose two different strategies, conservative and explorative, as well as intermediate cases, leading to nonintuitive interesting results, such as the emergence of cycles.Ítem Acceso Abierto Synchronization properties of self-sustained mechanical oscillators(Amer Physical Soc, 2013-05) Arroyo, Sebastián Ismael; Zanette, Damian HoracioWe study, both analytically and numerically, the dynamics of mechanical oscillators kept in motion by a feedback force, which is generated electronically from a signal produced by the oscillators themselves. This kind of self-sustained systems may become standard in the design of frequency-control devices at microscopic scales. Our analysis is thus focused on their synchronization properties under the action of external forces and on the joint dynamics of two to many coupled oscillators. Existence and stability of synchronized motion are assessed in terms of the mechanical properties of individual oscillators, namely, their natural frequencies and damping coefficients, and synchronization frequencies are determined. Similarities and differences with synchronization phenomena in other coupled oscillating systems are emphasized.Ítem Acceso Abierto The effect of synaptic plasticity on orientation selectivity in a balanced model of primary visual cortex(Frontiers Media S.A., 2015- 08-20) Gonzalo Cogno, Ximena Soledad; Mato, GermanOrientation selectivity is ubiquitous in the primary visual cortex (V1) of mammals. In cats and monkeys, V1 displays spatially ordered maps of orientation preference. Instead, in mice, squirrels, and rats, orientation selective neurons in V1 are not spatially organized, giving rise to a seemingly random pattern usually referred to as a salt-and-pepper layout. The fact that such different organizations can sharpen orientation tuning leads to question the structural role of the intracortical connections; specifically the influence of plasticity and the generation of functional connectivity. In this work, we analyze the effect of plasticity processes on orientation selectivity for both scenarios. We study a computational model of layer 2/3 and a reduced one-dimensional model of orientation selective neurons, both in the balanced state. We analyze two plasticity mechanisms. The first one involves spike-timing dependent plasticity (STDP), while the second one considers the reconnection of the interactions according to the preferred orientations of the neurons. We find that under certain conditions STDP can indeed improve selectivity but it works in a somehow unexpected way, that is, effectively decreasing the modulated part of the intracortical connectivity as compared to the non-modulated part of it. For the reconnection mechanism we find that increasing functional connectivity leads, in fact, to a decrease in orientation selectivity if the network is in a stable balanced state. Both counterintuitive results are a consequence of the dynamics of the balanced state. We also find that selectivity can increase due to a reconnection process if the resulting connections give rise to an unstable balanced state. We compare these findings with recent experimental results.