Biomedical subjects

Hernán G Solari

Publications and source records attributed to Hernán G Solari.

5 recordsLinked to original sources

PubMed2006

A stochastic population dynamics model for Aedes aegypti: formulation and application to a city with temperate climate.

Aedes aegypti is the main vector for dengue and urban yellow fever. It is extended around the world not only in the tropical regions but also beyond them, reaching temperate climates. Because of its importance as a vector of deadly diseases, the significance of its distribution in urban areas and the possibility of breeding in laboratory facilities, Aedes aegypti is one of the best-known mosquitoes. In this work the biology of Aedes aegypti is incorporated into the framework of a stochastic population dynamics model able to handle seasonal and total extinction as well as endemic situations. The model incorporates explicitly the dependence with temperature. The ecological parameters of the model are tuned to the present populations of Aedes aegypti in Buenos Aires city, which is at the border of the present day geographical distribution in South America. Temperature thresholds for the mosquito survival are computed as a function of average yearly temperature and seasonal variation as well as breeding site availability. The stochastic analysis suggests that the southern limit of Aedes aegypti distribution in South America is close to the 15 degrees C average yearly isotherm, which accounts for the historical and current distribution better than the traditional criterion of the winter (July) 10 degrees C isotherm.

Aedes↗

PubMed2006

Modeling growth from the vapor and thermal annealing on micro- and nanopatterned substrates.

We propose a -dimensional mesoscopic model to describe the most relevant physical processes that take place while depositing and/or annealing micro- and nanopatterned solid substrates. The model assumes that a collimated incident beam impinges over the growing substrate; scattering effects in the vapor and reemission processes are introduced in a phenomenological way as an isotropic flow. Surface diffusion is included as the main relaxation process at the micro- or nanoscale. The stochastic model is built following population dynamics considerations; both stochastic simulations and the deterministic limit are analyzed. Numerical aspects regarding its implementation are also discussed. We study the shape-preserving growth mode, the coupling between shadowing effects and random fluctuations, and the spatial structure of noises using numerical simulations. We report important deviations from linear theories of surface diffusion when the interfaces are not compatible with the small slope approximation, including spontaneous formation of overhangs and nonexponential decay of pattern amplitudes. We discuss the dependence of stationary states with respect to the boundary conditions imposed on the system.

Journal Article↗

PubMed2004

Probing universality classes in solid-on-solid deposition.

We consider several stochastic processes corresponding to the same physical solid-on-solid deposition problem. Simplified models presenting the same (conditional) mean and variance for each process are also introduced as well as generalizations in terms of the deposition of blobs and probabilistic deposition rules. We compare the evolution of the roughness as a function of time for a three-parameter family that includes as limit cases the Family model and the Edwards-Wilkinson equation, showing that in all cases the derived models with the same mean and variance are indistinguishable from the originating models in terms of the evolution of the roughness. Finally, we show that although all the models studied belong to the same universality class, some relevant features such as the final surface roughness are reproduced only for models within a restricted class determined by sharing the same (conditional) mean and variance.

Journal Article↗

PubMed2003

Dynamics of solid growth under a gravitational field: influence of the formation of a diffusive layer.

We discuss the gravitational sedimentation of particles in terms of a stochastic model considering, in view of experimental evidence, that the aggregation to the growing surface (deposit) is mediated by the formation of a layer of suspended particles subject to gravitational forces, thermal agitation, as well as aggregation (contact) forces. The aggregation of such partially buoyant particles is ruled by the rates of occurrence of the different stochastic events: incorporation to the layer of suspended particles, sedimentation, and gravitationally biased diffusion. The model introduces bridges across different standard solid on solid deposition models which can be considered as limit cases of the present one. Analytical and numerical results show that for finite (realistic) deposits there are different regimes of aggregation including situations in which the deposit is grown completely during the transient time of the system.

Journal Article↗

PubMed2003

Stochastic population dynamics: the Poisson approximation.

We introduce an approximation to stochastic population dynamics based on almost independent Poisson processes whose parameters obey a set of coupled ordinary differential equations. The approximation applies to systems that evolve in terms of events such as death, birth, contagion, emission, absorption, etc., and we assume that the event-rates satisfy a generalized mass-action law. The dynamics of the populations is then the result of the projection from the space of events into the space of populations that determine the state of the system (phase space). The properties of the Poisson approximation are studied in detail. Especially, error bounds for the moment generating function and the generating function receive particular attention. The deterministic approximation for the population fractions and the Langevin-type approximation for the fluctuations around the mean value are recovered within the framework of the Poisson approximation as particular limit cases. However, the proposed framework allows to treat other limit cases and general situations with small populations that lie outside the scope of the standard approaches. The Poisson approximation can be viewed as a general (numerical) integration scheme for this family of problems in population dynamics.

Monte Carlo Method↗