Papers by Luis Alejandro Vindas Bonilla
The tourist carrying capacity commands a growing interest given that it is closely linked with su... more The tourist carrying capacity commands a growing interest given that it is closely linked with sustainable tourist development. The justification of the utility of this concept is given by means of a simple and efficient methodological proposal, by analysing the social carrying capacity. To this end, an empirical application is carried out in the Western Andalusia. In some of the cases analysed, the satisfaction of the tourist is found to decline when the levels of the tourist use are higher with respect to those attributes of the tourist destination supply. This mechanism can constitute a useful alarm signal for tourism planners.
Fluctuation Phenomena: Disorder and Nonlinearity
ABSTRACT
Progress in Industrial Mathematics at ECMI 2006, 2008
A model for charge transport in photoexcited undoped semiconductor superlattices is proposed and ... more A model for charge transport in photoexcited undoped semiconductor superlattices is proposed and analyzed. Under dc voltage bias, self-sustained oscillations of the current due to repeated homogeneous nucleation of pairs of charge dipole waves inside the sample, followed by wave splitting and motion in opposite directions are among the numerical solutions of the model.
arXiv (Cornell University), Mar 12, 2006
Classical theory of nucleation based on Becker-Doering equations and coarsening for a binary alloy.
arXiv (Cornell University), Mar 12, 2006
Transient homogeneous nucleation is studied in the limit of large critical sizes. Starting from p... more Transient homogeneous nucleation is studied in the limit of large critical sizes. Starting from pure monomers, three eras of transient nucleation are characterized in the classic Becker-Döring kinetic equations with the Turnbull-Fisher discrete diffusivity. After an initial stage in which the number of monomers decreases, many clusters of small size are produced and a continuous size distribution is created. During the second era, nucleii are increasing steadily in size in such a way that their distribution appears as a wave front advancing towards the critical size for steady nucleation. The nucleation rate at critical size is negligible during this era. After the wave front reaches critical size, it ignites the creation of supercritical clusters at a rate that increases monotonically until its steady value is reached. Analytical formulas for the transient nucleation rate and the time lag are obtained that improve classical ones and compare very well with direct numerical solutions. In addition, we propose and solve numerically a modified Becker-Döring model having a discrete diffusivity proportional to the area of a spherical cluster with k monomers for small k (as in the Turnbull-Fisher case) and to the cluster radius for large k (as in the case of diffusive growth of clusters).
Circulation, 2002
Background Coronary anastomoses are currently primarily carried out with the use of running nonab... more Background Coronary anastomoses are currently primarily carried out with the use of running nonabsorbable sutures. Recently, a renewed interest has developed for facilitated mechanical anastomotic devices especially for minimal invasive techniques or limited access surgery. The initial experience with the first successful creation of mechanical vein-to-coronary artery anastomoses in humans is reported. Methods and Results Between November 2000 and June 2001, 14 patients scheduled for multivessel coronary artery bypass grafting (CABG) procedure were investigated. One vein graft-to-coronary artery anastomosis per patient was performed with the St. Jude Medical ATG Symmetry coronary connector system (stainless steel investigational device, not yet commercially available). We evaluated the overall performance of the device. Intraoperative flow measurements of the grafts using transit time methods were measured. A postoperative angiographic control was performed immediately after the pro...
arXiv (Cornell University), Jul 24, 2012
Strain and rotation fields of dislocations in monolayer graphene have been mapped in a recent exp... more Strain and rotation fields of dislocations in monolayer graphene have been mapped in a recent experiment. These fields are finite everywhere and differ from those given by linear elasticity which does not consider rotation explicitly and predicts infinite rotation and strains at the dislocation point. A derivative regularization of two-dimensional linear elasticity fixes these shortcomings. The theory adds rotation, dislocation and residual strain energies to the usual elastic energy. There are two extra material constants that determine the size of the dislocation core and are determined from experimental data. These findings are useful for studies of dislocations in graphene and for analyzing incipient plasticity in two dimensional crystals.
Las heteroestructuras de materiales semiconductores tienen unas propiedades ópticas peculiares de... more Las heteroestructuras de materiales semiconductores tienen unas propiedades ópticas peculiares debidas al fuerte acoplamiento entre los efectos ópticos con los efectos electrostáticos. Entre los posibles resultados se cuentan la aparición de biestabilidad óptica<br> intrínseca y sus consecuencias, tales como la formación de estructuras espaciales. Desde hace más de diez años, se ha desarrollado todo un campo de investigación de estos materiales y sus propiedades ópticas. Podemos destacar, entre los ejemplos recientes, heteroestructuras de pozos cuánticos fotoexcitados sujetos a la acción de un campo eléctrico externo, superredes de InAlAs/InGaAs encastradas en uniones p-i-n, dispositivos de efecto electro-óptico autosostenido (<em>SEEDs, Self-Electro--optical Effect Devices</em>), y efecto Stark bajo confinamiento cuántico en pozos cuánticos de nitruros-tipo III (GaN, AlN, InN, y todos sus compuestos derivados). En esta memoria analizamos en detalle los procesos de...
A harmonic oscillator linearly coupled with a linear chain of Ising spins is investigated. The N ... more A harmonic oscillator linearly coupled with a linear chain of Ising spins is investigated. The N spins in the chain interact with their nearest neighbours with a coupling constant proportional to the oscillator position and to N −1/2 , are in contact with a thermal bath at temperature T , and evolve under Glauber dynamics. The oscillator position is a stochastic process due to the oscillator-spin interaction which produces drastic changes in the equilibrium behaviour and the dynamics of the oscillator. Firstly, there is a second order phase transition at a critical temperature T c whose order parameter is the oscillator stable rest position: this position is zero above T c and different from zero below T c. This transition appears because the oscillator moves in an effective potential equal to the harmonic term plus the free energy of the spin system at fixed oscillator position. Secondly, assuming fast spin relaxation (compared to the oscillator natural period), the oscillator dynamical behaviour is described by an effective equation containing a nonlinear friction term that drives the oscillator towards the stable equilibrium state of the effective potential. The analytical results are compared with numerical simulation throughout the paper.
Homogeneous nucleation of dislocations as bifurcations in a periodized discrete elasticity model
Nanotechnology in the Security Systems, 2014
In this paper, a detailed analysis of anisotropic effects on the phonon induced spin relaxation r... more In this paper, a detailed analysis of anisotropic effects on the phonon induced spin relaxation rate in InAs semiconductor quantum dots (QDs) is carried out for possible implementation towards QDs in security devices, encrypted data and quantum information processing. We show that anisotropic gate potentials enhance the phonon mediated spin-flip rate and reduce the cusp-like structure to lower magnetic fields.
Progress in Industrial Mathematics at ECMI 2008, 2010
Puerto Rico health sciences journal, 2018
Phylogenetic studies suggest that ZIKV may have been introduced to Brazil, and therefore to the A... more Phylogenetic studies suggest that ZIKV may have been introduced to Brazil, and therefore to the Americas, in 2014 during the World Spring Canoe Championship held in the city of Rio de Janeiro. Since then the virus has spread across Latin America, Caribbean, and North America. It seems clear that Aedes aegypti and, to a lesser extent, Aedes albopictus are the main vectors of the pathogen. ZIKV infection symptoms are similar to other flaviviruses such as a dengue infection and therefore can be easily confounded. Currently, the ZIKV maintains two life cycles. The first, and the original one is the sylvatic/enzootic cycle that occurs in Africa. The second life cycle is the suburban-urban transmission cycle that emerged through natural evolution. ZIKV has gained the ability to maintain this human-endemic cycle in urban and suburban areas. ZIKV has never been isolated from non primates, so it is not clear whether other species can act as reservoir hosts. Several reports have been made of ...
Puerto Rico health sciences journal, 2018
On April 19, 2017, the 37th Medical Sciences Campus Annual Research and Education Forum opened wi... more On April 19, 2017, the 37th Medical Sciences Campus Annual Research and Education Forum opened with the discussion panel The role of research in policy and practice: The Zika phenomena in Puerto Rico, with Dr. Cruz M. Nazario Delgado, Dr. Carmen D. Zorrilla and Dr. Luis A. Bonilla Soto. In this article, we critically examine the public policy process of the Zika epidemic in Puerto Rico, as presented by authors Nazario and Bonilla. We argue that policymaking and the public health responses to confront the Zika epidemic in Puerto Rico took place in a political environment where different US and local actors operated to advance their goals and vision, undermining the role of knowledge, evidence and past experiences. We propose a bottom to top preventive and community empowerment approach to control the vector. This model must be built on successful policy implementation experiences with epidemics in the Island and strengthened by evidence, international guidelines and ethical principles.
European Consortium for Mathematics in Industry, 2014
We show that in a semiconductor superlattice with long scattering times, damping of Bloch oscilla... more We show that in a semiconductor superlattice with long scattering times, damping of Bloch oscillations due to scattering is so small that nonlinearities may compensate it and Bloch oscillations persist even in the hydrodynamic regime. In order to demonstrate this, we propose a Boltzmann-Poisson transport model of miniband superlattices with inelastic collisions and we derive by singular perturbation methods hydrodynamic equations for electron density, electric field, and the complex amplitude of the Bloch oscillations. Numerical solutions of these equations show stable Bloch oscillations with spatially inhomogeneous field, charge, current density, and energy density profiles. These Bloch oscillations disappear as scattering times become sufficiently short. For sufficiently low lattice temperatures (70 K), Bloch and Gunn type oscillations mediated by electric field, current, and energy domains coexist for a range of voltages. For larger lattice temperatures (300 K), there are only Bl...
arXiv: Statistical Mechanics, 2020
Ensemble averages of a stochastic model show that, after a formation stage, the tips of active bl... more Ensemble averages of a stochastic model show that, after a formation stage, the tips of active blood vessels in an angiogenic network form a moving two dimensional stable diffusive soliton, which advances toward sources of growth factor. Here we use methods of multiple scales to find the diffusive soliton as a solution of a deterministic equation for the mean density of active endothelial cells tips. We characterize the diffusive soliton shape in a general geometry, and find that its vector velocity and the trajectory of its center of mass along curvilinear coordinates solve appropriate collective coordinate equations. The vessel tip density predicted by the soliton compares well with that obtained by ensemble averages of simulations of the stochastic model.
espanolLos procesos de urbanizacion estan fuertemente vinculados con los mecanismos de acumulacio... more espanolLos procesos de urbanizacion estan fuertemente vinculados con los mecanismos de acumulacion de capital y la liberalizacion del mercado inmobiliario. En las ciudades, estos procesos se han convertido en algunos de los principales mecanismos de rentabilizacion del sector privado y han tenido efectos en la distribucion socioespacial de las ciudades y las desigualdades sociales. Dentro de esta dinamica, el fenomeno de la gentrificacion representa una tendencia urbana socioespacial de capitalizacion de las rentas potenciales del suelo. Este articulo analiza como en el Barrio Italia, en Santiago de Chile, esta aconteciendo un proceso de gentrificacion, en un contexto afectado por el fortalecimiento del mercado inmobiliario e influenciado por la constitucion de un enclave cultural, produciendose un aumento de las rentas inmobiliarias y de la produccion economica del sector. Como parte de este proceso de renovacion del espacio urbano del barrio, se observan tendencias que promueven e...
Soft Matter, 2021
Numerical simulations and linear stability analyses of expanding cellular monolayers suggest cell... more Numerical simulations and linear stability analyses of expanding cellular monolayers suggest cell–substrate friction is responsible for fingers at the edge. A critical contractile stress characterises wetting-dewetting; dewetting inhibits fingering.
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Papers by Luis Alejandro Vindas Bonilla