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Publicación Acceso Abierto Primeros pasos hacia un modelo dinámico del comportamiento del fuego en incendios forestales para paisajes argentinos(Universidad Nacional de La Plata. Facultad de Informática, 2020) Laneri, Karina Fabiana; Waidelich, Sigfrido; Zimmerman, Viviana; Denham, MonicaEn este trabajo se presenta un modelo de Reacción-Difusión-Convección (RDC) para la propagación de incendios forestales implementado en un entorno desimulación y visualización. Dicho simulador posee amplias y útiles funcionalidades las cuales han sido planificadas junto a expertos combatientes del fuego denuestra región. El modelo presentado intenta comprender los mecanismos claves detrás de la propagación delfuego en la región Patagónica argentina. En este trabajo se exponen los primeros resultados del modelo enescenarios artificiales. Se generaron mapas sintéticos que fueron utilizados para probar nuestro modelo RDC, analizando paso a paso el efecto de cada una de las características del paisaje en la propagación del incendio. Los resultados de las simulaciones concuerdan con el comportamiento esperado del fuego en presenciade vegetación heterogénea, gradientes de viento y dependiente. El simulador, desarrollado en CUDA C/OpenGL, integra capas de información que incluyen topografía, meteorología y datos del combustible. Dicho simulador permite visualizar la propagación del fuego y que el usuario interactúe con el simulador en tiempode simulación. Además, en dicho simulador se implementó el índice Meteorológico de Peligro de Incendio (FWI: Fire Weather Index). Este índice es muy utilizado en Argentina para dar soporte al manejo yprevención del fuego. El cálculo de este índice en el simulador permite visualizar el peligro o riesgo de incendio para escenarios del noroeste de la Patagonia Argentina. Para la evaluación y uso del índice Meteorológico de Peligro de Incendio se han utilizado mapas reales de cobertura de vegetación, topografía ymeteorología. Dichos mapas se usaron para alimentar el simulador y mostrar en una forma visual amigable, el riesgo de incendio en diversos escenarios posibles.Publicación Acceso Abierto Functional integral approach to the transfer function of a stochastic scattering channel(Taylor & Francis, 2020) Cabrera, Octavio; Zanette, Damian HoracioWe apply the formalism of functional integration to the calculation of the transfer function of a stochastic scattering channel formed by stationary, non-interacting point scatterers. The channel is described through a scattering amplitude density, defined over space, whose random component is characterized by a functional probability distribution. This random component induces in turn a probability distribution for the scattering transfer function, which we compute by means of functional integration in the case of Gaussian distributions. Some geometric configurations relevant to radar operation are worked out, as well as the statistical properties of the transfer function in the large-frequency limit. Extensions of the formulation in order to include scattering phase shifts, i.e. complex scattering amplitudes, and to consider non-Gaussian probability distributions are outlined.Publicación Acceso Abierto Stochastic PDEs, random fields and exact mean-values(IOP science, 2020) Caceres, Manuel OsvaldoIntroducing projector-operator technique and algebra of Terwiel's cumulants we study stochastic linear partial differential equations with global and local disorder. We present the evolution equation for the mean-value of the field as a series in terms of Terwiel's cumulant operators. Then, we prove that if we use binary disorder with time exponential-correlated structure, as source of the stochastic perturbation, this series cuts leading to a treatable evolution equation. We apply this approach to find the exact mean-value solution of electromagnetic waves with stochastic absorption of energy in conducting media. This model shows the occurrence of novel time-scale separation phenomena. Local disorder in telegrapher's equation is also presented. Thus we show that strong disorder leads to anomalous behavior at short and long time regimes. In addition, other physical systems with global disorder are worked out to find exact mean-value solutions: finite-velocity diffusion in the presence of a deterministic force (Smoluchoswki-like process generalizing, in this way, Feynman–Kac's formula for its numerical solution); Lorentz' force on a fluctuating charge model (we calculate the diffusion coefficient transverse to the applied magnetic field); and a generalized non-Maxwellian velocity distribution (Ornstein–Uhlenbeck like process showing a noise-induced transition in the stationary distribution).Publicación Acceso Abierto Stochastic effects on the bistatic transfer function of a planar scatterer distribution(Taylor & Francis, 2020) Gavier, Ignacio; Zanette, Damián Horacio; Cabrera, OctavioWe evaluate the effects of several stochastic factors on signal transmission through a planar distribution of stationary scatterers, with non-collocated transmitter and receiver (bistatic configuration). The transmission channel is described by means of its transfer function, which –as a result of randomness in the scatterer distribution– fluctuates around its expectation value. Specifically, we consider randomness in the scatterer positions (both on the plane and in height), in their radar cross sections, and in the scattering phases. Our analytical results provide a quantitative relation between the parameters that characterize random components of each kind, and the fluctuations that alter the transfer function.Publicación Acceso Abierto Heaps’ Law and Heaps functions in tagged texts: evidences of their linguistic relevance(Royal Society, 2020) Chacoma, A.; Zanette, Damian HoracioWe study the relationship between vocabulary size and text length in a corpus of 75 literary works in English, authored by six writers, distinguishing between the contributions of three grammatical classes (or ‘tags,’ namely, nouns, verbs and others), and analyse the progressive appearance of new words of each tag along each individual text. We find that, as prescribed by Heaps’ Law, vocabulary sizes and text lengths follow a well-defined power-law relation. Meanwhile, the appearance of new words in each text does not obey a power law, and is on the whole well described by the average of random shufflings of the text. Deviations from this average, however, are statistically significant and show systematic trends across the corpus. Specifically, we find that the appearance of new words along each text is predominantly retarded with respect to the average of random shufflings. Moreover, different tags add systematically distinct contributions to this tendency, with verbs and others being respectively more and less retarded than the mean trend, and nouns following instead the overall mean. These statistical systematicities are likely to point to the existence of linguistically relevant information stored in the different variants of Heaps’ Law, a feature that is still in need of extensive assessment.Publicación Acceso Abierto Perturbation theory for operational quantum non-Markovianity(Taylor & Francis, 2020) Bonifacio, Mariano; Budini, Adrián AdolfoThe definition of memory in operational approaches to quantum non-Markovianity depends on the statistical properties of different sets of outcomes related to successive measurement processes performed over the system of interest. Using projector techniques we develop a perturbation theory that enable to expressing both joint probabilities and outcome correlations in terms of the unperturbed system density-matrix propagator. This object defines the open system dynamics in the absence of measurement processes. Successive series terms, which are scaled by the system-environment interaction strength, consist in a convolution structure involving system propagators weighted by higher-order bath correlations. The formalism is corroborated by studying different dynamics that admit an exact description. Using the perturbative approach, unusual memory effects induced by the interplay between the system-environment interaction and measurement processes are found in finite temperature reservoirs.Publicación Acceso Abierto Tell me where you live and I'll tell you who you are: Spatial segregation of southern species of Eligmodontia Cuvier in Patagonia, Argentina(Elsevier, 2020) Ruiz Barlett, Trinidad; Martin, Gabriel; Laguna, María Fabiana; Abramson, Guillermo; Monjeau, AdrianEligmodontia morgani y E. typus son dos pequeños (<25 g) roedores sigmodontinos que habitan los ambientes áridos del sur de Argentina. Debido a que las especies son difíciles de distinguir en el campo, su delimitiación geográfica siempre ha sido controvertida. En este trabajo usamos registros donde las especies fueron identificadas por su cariotipo y ADN mitocondrial, y modelamos su distribución potencial usando análisis de máxima entropía. Nuestros resultados muestran una segregación en el nicho entre las especies, mayormente impulsado por la temperatura. Los modelos ecológicos de nicho muestran que E. morgani es un habitante del oeste y centro patagónico correspondientes con la ecorregión de la Estepa Patagónica, mientras E. typus es un habitante de las regiones centrales y el este patagónico, correspondientes con la ecorregión del Monte. En áreas de ecotono, nuestros modelos predicen que E. morgani ocupa las zonas altas y frías de las mesetas, mientras que E. typus ocupa zonas bajas con una matriz de vegetación de la Ecorregión del Monte. Nuestros modelos matemáticos muestran una selección de hábitat de temperaturas medias mínimas de 1 °C y 5 °C para E. morgani y E. typus, respectivamente, y de temperaturas máximas medias de 22 °C y de 27 °C para cada especie.Publicación Acceso Abierto A spatially extended model to assess the role of landscape structure on the pollination service of Apis mellifera(Board, 2020) Joseph, Julien; Santibáñez, Fernanda; Laguna, María Fabiana; Abramson, Guillermo; Kuperman, Marcelo Néstor; Garibaldi, Lucas AlejandroApis mellifera plays a crucial role as pollinator of the majority of crops linked to food production and thus its presence is currently fundamental to our health and survival. The composition and configuration of the landscape in which Apis mellifera lives will likely determine the well-being of the hives and the pollination service that their members can provide to the crops. Here we present a spatially explicit model that predicts the spatial distribution of visits by Apis mellifera to crops, by simulating daily trips of honey bees, the demographical dynamic of each hive and their honey production. This model goes beyond existing approaches by including 1) a flower resource affected by the feedback interaction between nectar extraction, pollination, blossoming and repeated visits, 2) a pollinators dynamic that allows competition through short term resource depletion, 3) a probabilistic approach of the foraging behavior, modeling the fact that the pollinators have only partial knowledge of the resource on their surroundings, and 4) the specific and systematic foraging behavior and strategies of Apis mellifera at the moment of choosing foraging sites, as opposed to those adopted by solitary and wild pollinators. With a balance between simplicity and realism we show the importance of keeping a minimal fraction of natural habitat in an agricultural landscape. We also evaluate the effects of the landscape’s structure on pollination, and demonstrate that there exists an optimal size of natural habitat patches that maximizes the pollination service for a fixed fraction of natural habitat.Publicación Acceso Abierto The destructive effect of human stupidity: a revision of Cipolla’s fundamental laws(Springer, 2020) Barcenas, Donny R.; Kuperman, Joel; Kuperman, Marcelo NestorIn this work, we analyze an evolutionary game that incorporates the ideas presented by Carlo Cipolla in “The fundamental laws of human stupidity”. The game considers four strategies, three of them are inherent to the player behavior and can evolve via imitation dynamics, while the fourth one is associated with an eventual behavior that can be adopted by any player at any time with a certain probability. This fourth strategy corresponds to what Cipolla calls a stupid person. The probability of behaving stupidly acts as a parameter that induces a phase transition in the steady distribution of strategies among the population.Publicación Acceso Abierto Finite-Velocity Diffusion in Random Media(Board, 2020) Caceres, Manuel OsvaldoWe investigated a diffusion-like equation with a bounded speed of signal propagation (the so called telegrapher’s equation) in a random media. We discuss some properties of the mean-value solution in a well-defined perturbation theory. The frequency-dependent effective-velocity of propagation is studied in the long and short time regime. We show that due to the wave-like character of telegrapher’s equation the effective-velocity is a complex dispersive function in time. Exact results and asymptotic perturbative long-time behaviors (for an exponential space-correlated binary disorder) are presented, showing their agreement and corroborating the goodness of the effective medium approximation in continuous system.Publicación Acceso Abierto Assessing the growth rate of endangered Franciscana dolphin in Argentina, South America(Board, 2020) Caceres, Manuel Osvaldo; Cáceres-Saez, Iris; Secchi, Eduardo R.; Negri, María Fernanda; Panebianco, Maria Victoria; Cappozzo, Humberto LuisCetacean populations are vulnerable to decline due to anthropogenic threats and life history traits. The Franciscana dolphin (Pontoporia blainvillei) has been considered the most affected small dolphin in the Southwestern Atlantic Ocean. In this study a method is presented for estimating the growth rate of the Franciscana dolphin affected by incidental mortality (bycatch) in coastal marine areas of Argentina, South America. We used a general approach based on vital parameters information such as reproductive rates and survival probabilities for an age-structured population. The Franciscana’s growth rate was estimated using Leslie’s approach through an algorithm implemented in a 14 x 14 matrix model. Then, the population was characterized analysing the discrete-time evolution of the age–population vector. We found that the potential growth rate <1 indicates that Franciscanas in Argentina are susceptible to decline under current levels of incidental mortality.Publicación Acceso Abierto Digging the topology of rock art in northwestern Patagonia(Oxford University Press, 2020) Vargas, Fernando E.; Lanata, José L.; Abramson, Guillermo; Kuperman, Marcelo Nesto; Fiore, DáneaWe present a study on the rock art of northern Patagonia based on network analysis and communities detection. We unveil a significant aggregation of archaeological sites, linked by common rock art motifs that turn out to be consistent with their geographical distribution and archaeological background of hunter-gatherer stages of regional peopling and land use. This exploratory study will allow us to approach more accurately some social strategies of visual communication entailed by rock art motif distribution, in space and time.Publicación Acceso Abierto Detection of quantum non-Markovianity close to the Born-Markov approximation(American Physical Society, 2020) de Lima Silva, Thais; Walborn, Stephen P.; Santos, Marcelo F.; Aguilar, Gabriel H.; Budini, Adrián AdolfoWe calculate in an exact way the conditional past-future correlation for the decay dynamics of a two-level system in a bosonic bath. Different measurement processes are considered. In contrast to quantum memory measures based solely on system propagator properties, here memory effects are related to a convolution structure involving two system propagators and the environment correlation. This structure allows one to detect memory effects even close to the validity of the Born-Markov approximation. An alternative operational-based definition of environment-to-system backflow of information follows from this result. We provide experimental support to our results by implementing the dynamics and measurements in a photonic experiment.Publicación Acceso Abierto Energy exchange in globally coupled mechanical phase oscillators(American Physical Society, 2020) Sosa, Raúl I.; Zanette, Damian HoracioWe study the stationary dynamics of energy exchange in an ensemble of phase oscillators, coupled through a mean-field mechanical interaction and added with friction and an external periodic excitation. The degree of entrainment between different parts of the ensemble and the external forcing determines three dynamical regimes, each of them characterized by specific rates of energy exchange. Using suitable approximations, we are able to obtain analytical expressions for those rates, which are in satisfactory agreement with results from numerical integration of the equations of motion. In some of the dynamical regimes, the rates of energy exchange show nontrivial dependence on the friction coefficients—in particular, nonmonotonic behavior and sign switching. This suggests that, even in this kind of stylized model, power transfer between different parts of the ensemble and to the environment can be manipulated by a convenient choice of the individual oscillator parameters.Publicación Acceso Abierto Evolutionary game inspired by Cipolla's basic laws of human stupidity(American Physical Society, 2020) Kuperman, Joel; Barcenas, Donny R.; Kuperman, Marcelo NestorIn this work we present an evolutionary game inspired by the work of Carlo Cipolla entitled The Basic Laws of Human Stupidity. The game expands the classical scheme of two archetypical strategies, collaborators and defectors, by including two additional strategies. One of these strategies is associated with a stupid player that, according to Cipolla, is the most dangerous one as it undermines the global wealth of the population. By considering a spatial evolutionary game and imitation dynamics that go beyond the paradigm of a rational player we explore the impact of Cipolla's ideas and analyze the extent of the damage that stupid players inflict on the population.Publicación Acceso Abierto Emergence of stationary multimodality under two-timescaled dichotomic noise(American Physical Society, 2020) Budini, Adrián Adolfo; McHardy, Isaias; Caceres, Manuel Osvaldo; Nizama, MarcoWe study a linear Langevin dynamics driven by an additive non-Markovian symmetrical dichotomic noise. It is shown that when the statistics of the time intervals between noise transitions is characterized by two well differentiated timescales, the stationary distribution may develop multimodality (bi- and trimodality). The underlying effects that lead to a probability concentration in different points include intermittence and also a dynamical locking of realizations. Our results are supported by numerical simulations as well as by an exact treatment obtained from a Markovian embedding of the full dynamics, which leads to a third-order differential equation for the stationary distribution.Publicación Acceso Abierto Fat tails and black swans: Exact results for multiplicative processes with resets(AIP Publishing, 2020) Zanette, Damian Horacio; Manrubia, SusannaWe consider a class of multiplicative processes which, added with stochastic reset events, give origin to stationary distributions with power-law tails—ubiquitous in the statistics of social, economic, and ecological systems. Our main goal is to provide a series of exact results on the dynamics and asymptotic behavior of increasingly complex versions of a basic multiplicative process with resets, including discrete and continuous-time variants and several degrees of randomness in the parameters that control the process. In particular, we show how the power-law distributions are built up as time elapses, how their moments behave with time, and how their stationary profiles become quantitatively determined by those parameters. Our discussion emphasizes the connection with financial systems, but these stochastic processes are also expected to be fruitful in modeling a wide variety of social and biological phenomena.Publicación Acceso Abierto Thalamic neuron models encode stimulus information by burst-size modulation(Frontiers Media S.A., 2015-09-23) Elijah, Daniel H.; Samengo, Ines; Montemurro, Marcelo AlejandroThalamic neurons have been long assumed to fire in tonic mode during perceptive states, and in burst mode during sleep and unconsciousness. However, recent evidence suggests that bursts may also be relevant in the encoding of sensory information. Here, we explore the neural code of such thalamic bursts. In order to assess whether the burst code is generic or whether it depends on the detailed properties of each bursting neuron, we analyzed two neuron models incorporating different levels of biological detail. One of the models contained no information of the biophysical processes entailed in spike generation, and described neuron activity at a phenomenological level. The second model represented the evolution of the individual ionic conductances involved in spiking and bursting, and required a large number of parameters. We analyzed the models' input selectivity using reverse correlation methods and information theory. We found that n-spike bursts from both models transmit information by modulating their spike count in response to changes to instantaneous input features, such as slope, phase, amplitude, etc. The stimulus feature that is most efficiently encoded by bursts, however, need not coincide with one of such classical features. We therefore searched for the optimal feature among all those that could be expressed as a linear transformation of the time-dependent input current. We found that bursting neurons transmitted 6 times more information about such more general features. The relevant events in the stimulus were located in a time window spanning 〜100 ms before and 〜20 ms after burst onset. Most importantly, the neural code employed by the simple and the biologically realistic models was largely the same, implying that the simple thalamic neuron model contains the essential ingredients that account for the computational properties of the thalamic burst code. Thus, our results suggest the n-spike burst code is a general property of thalamic neurons.Publicación 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.Publicación 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.