Spatial spread of the Hantavirus infection.

The spatial propagation of Hantavirus-infected mice is considered a serious threat for public health. We analyze the spatial spread of the infected mice by including diffusion in the stage-dependent model for Hantavirus infection recently proposed by Reinoso and de la Rubia [Phys. Rev.

Stage-dependent model for Hantavirus infection: the effect of the initial infection-free period.

We propose a stage-dependent model with constant delay to study the effect of the initial infection-free period on the spread of Hantavirus infection in rodents. We analyze the model under various extreme weather conditions, in the context of the El Niño-La Niña Southern Oscillation phenomenon, and show how these variations determine the evolution of the system significantly. When the scenario corresponds to El Niño, the system presents a demographic explosion and a delayed outbreak of Hantavirus infection, whereas if the scenario is the opposite there is a rapid decline of the population, but with a possible persistence period that may imply a considerable risk for public health, a fact that is in agreement with available field data.

Patterns of phase-dependent spiral wave attenuation in excitable media.

We show that introducing periodic planar fronts with long excitation duration can lead to spiral attenuation. The attenuation occurs periodically over cycles of several planar fronts, forming a variety of complex spatiotemporal patterns. We find that these attenuation patterns occur only at specific phases of the descending fronts relative to the rotational phase of the spiral.

Patterns of spiral wave attenuation by low-frequency periodic planar fronts.

There is evidence that spiral waves and their breakup underlie mechanisms related to a wide spectrum of phenomena ranging from spatially extended chemical reactions to fatal cardiac arrhythmias [A. T. Winfree, The Geometry of Biological Time (Springer-Verlag, New York, 2001); J.

System-size resonance in a binary attractor neural network.

System size resonance (SSR) is a phenomenon in which the response of a system is optimal for a certain finite size, but poorer as the size goes to zero or infinity. In order to show SSR effects in binary attractor neural networks, we study the response of a network, in the ferromagnetic phase, to an external, time-dependent stimulus. Under the presence of such a stimulus, the network shows SSR, as is demonstrated by the measure of the signal amplification both analytically and by simulation.

Effects of internal fluctuations on the spreading of Hantavirus.

We study the spread of Hantavirus over a host population of deer mice using a population dynamics model. We show that taking into account the internal fluctuations in the mouse population due to its discrete character strongly alters the behavior of the system. In addition to the familiar transition present in the deterministic model, the inclusion of internal fluctuations leads to the emergence of an additional deterministically hidden transition.

Extinction in population dynamics.

We study a generic reaction-diffusion model for single-species population dynamics that includes reproduction, death, and competition. The population is assumed to be confined in a refuge beyond which conditions are so harsh that they lead to certain extinction. Standard continuum mean field models in one dimension yield a critical refuge length L(c) such that a population in a refuge larger than this is assured survival.

Outbreaks of Hantavirus induced by seasonality.

Using a model for rodent population dynamics, we study outbreaks of Hantavirus infection induced by the alternation of seasons. Neither season by itself satisfies the environmental requirements for propagation of the disease. This result can be explained in terms of the seasonal interruption of the relaxation process of the mouse population toward equilibrium, and may shed light on the reported connection between climate variations and outbreaks of the disease.

Coherence enhancement in nonlinear systems subject to multiplicative Ornstein-Uhlenbeck noise.

We show that for two biologically relevant models with self-sustained oscillations under the action of a multiplicative Ornstein-Uhlenbeck process, their coherence response behaves nonmonotonically with the process correlation time. There is a correlation time for which the quality factor is optimized. This phenomenon is a consequence of the interplay between the correlation time and the system's periodicity.

Random Ginzburg-Landau model revisited: reentrant phase transitions.

We analyze the phase diagram of the random Ginzburg-Landau model, where a quenched dichotomous noise affects the control parameter. We show that the system exhibits two types of counterintuitive reentrant second-order phase transitions. In the first case, increasing the coupling drives the system from a disordered to an ordered state and then back to a disordered state.

Negative resistance and anomalous hysteresis in a collective molecular motor.

A spatially extended model for a collective molecular motor is presented. The system is driven far from equilibrium by a quenched additive noise. As a result, it exhibits anomalous transport properties, namely, negative resistance and a clockwise hysteresis cycle.

Finite resolution effects in the analysis of the scaling behavior of rough surfaces.

We investigate the influence of finite spatial resolution in the analysis of the scaling behavior of rough surfaces. We analyze such an effect for two usual measurement methods: the local width and the height-height correlation function. We show that while the correlation function is insensitive to finite resolution effects for practical purposes, the local width presents correction terms to the scaling law, leading to an effective value of the local roughness exponent smaller than the theoretically expected.