Estudios de salinidad en la provincia de Guanacaste (Costa Rica) y caracterización de algunos suelos con influencia salina.

Los suelos afectados por sales se desarrollan preferentemente en regiones donde la precipitación es limitada, la temperatura es alta y las condiciones de avenamiento son restringidas como sucede en algunos suelos del área de Guanacaste, Costa Rica. Con el objetivo de caracterizar algunos suelos con contenidos salinas altos se realizó una revisión bibliográfica sobre estudios de salinidad en Guanacaste, Costa Rica, se muestrearon dos suelos provenientes del Ingenio Taboga en Cañas clasificados como: Typic Haplustert y Fluventic Ustropept; los culaes son analizados mediante métodos que caracterizan la salinidad en los suelos junto con las técnicas de análisis rutinarios

Computational results for an automatically tuned CMA-ES with increasing population size on the CEC'05 benchmark set

Abstract In this article, we apply an automatic algorithm configuration tool to improve the performance of the CMA-ES algorithm with increasing population size (iCMA-ES), the best performing algorithm on the CEC'05 benchmark set for continuous function optimization. In particular, we consider a separation between tuning and test sets and, thus, tune iCMA-ES on a different set of functions than the ones of the CEC'05 benchmark set. Our experimental results show that the tuned iCMA-ES improves significantly over the default version of iCMA-ES. Furthermore, we provide some further analyses on the impact of the modified parameter settings on iCMA-ES performance and a comparison with recent results of algorithms that use CMA-ES as a subordinate local search

An analysis of post-selection in automatic configuration

info:eu-repo/semantics/publishe

A Note on Bound Constraints Handling for the IEEE CEC’05 Benchmark Function Suite

The benchmark functions and some of the algorithms proposed for the special session on real parameter optimization of the 2005 IEEE Congress on Evolutionary Computation (CEC'05) have played and still play an important role in the assessment of the state of the art in continuous optimization. In this article, we show that if bound constraints are not enforced for the final reported solutions, state-of-the-art algorithms produce infeasible best candidate solutions for the majority of functions of the IEEE CEC'05 benchmark function suite. This occurs even though the optima of the CEC'05 functions are within the specified bounds. This phenomenon has important implications on algorithm comparisons, and therefore on algorithm designs. This article's goal is to draw the attention of the community to the fact that some authors might have drawn wrong conclusions from experiments using the CEC'05 problems. © 2014 by the Massachusetts Institute of Technology.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Genomic epidemiology of third-generation cephalosporin-resistant Escherichia coli from Argentinian pig and dairy farms reveals animal-specific patterns of co-resistance and resistance mechanisms

Control measures are being introduced globally to reduce the prevalence of antibiotic resistance (ABR) in bacteria on farms. However, little is known about the current prevalence and molecular ecology of ABR in bacterial species with the potential to be key opportunistic human pathogens, such as Escherichia coli, on South American farms. Working with 30 dairy cattle farms and 40 pig farms across two provinces in central-eastern Argentina, we report a comprehensive genomic analysis of third-generation cephalosporin-resistant (3GC-R) E. coli, which were recovered from 34.8% (cattle) and 47.8% (pigs) of samples from fecally contaminated sites. Phylogenetic analysis revealed substantial diversity suggestive of long-term horizontal and vertical transmission of 3GC-R mechanisms. CTX-M-15 and CTX-M-2 were more often produced by isolates from dairy farms, while CTX-M-8 and CMY-2 and co-carriage of amoxicillin/clavulanate resistance and florfenicol resistance were more common in isolates from pig farms. This suggests different selective pressures for antibiotic use in these two animal types. We identified the β-lactamase gene blaROB, which has previously only been reported in the family Pasteurellaceae, in 3GC-R E. coli. blaROB was found alongside a novel florfenicol resistance gene, ydhC, also mobilized from a pig pathogen as part of a new composite transposon. As the first comprehensive genomic survey of 3GC-R E. coli in Argentina, these data set a baseline from which to measure the effects of interventions aimed at reducing on-farm ABR and provide an opportunity to investigate the zoonotic transmission of resistant bacteria in this region

Effects on Clustering Quality of Direct and Indirect Communication Among Agent in Ant-based Clustering Algorithms

Ant-based clustering algorithms are knowledge discovery tools inspired by the collective behavior of social insect colonies. In these algorithms, insects are modeled as software agents that communicate with each other indirectly through the environment. This particular kind of communication is known as stigmergic communication. In the classic ant-based clustering algorithm, a group of agents that exhibit the same behavior move randomly over a toroidal square grid. In the environment there are data objects that were initially scattered in a random fashion. The objects can be picked up, moved or dropped in any free location on the grid. An object is picked up with high probability if it is not surrounded by similar objects and is dropped with high probability if an agent's neighborhood is densely populated by other similar objects and its location is free. Here, stigmergy occurs when an object is placed next to another. The resultant structure is much more attractive to agents to drop other similar objects nearby. However, stigmergy is not the only way social insects interact with each other. In most species, trophallaxis or liquid food exchange among members of the same colony, plays a key role in their social organization. Consider the case of some termite species which require intestinal protozoa to derive benefits from cellulose. Their early instar nymphs are fed either by oral or anal trophallaxis. The latter infects them with symbiotic protozoa or bacteria contained in the proctodeal liquid. The subsocial association result of this codependence have evolved into a complex social and morphological structure. Inspired by the trophallaxis phenomenon observed in some ant and termite species, two different communication strategies among agents in ant-based clustering algorithms are investigated: (i) direct and (ii) indirect communication. The impact on the final clustering quality is evaluated by comparing the development of the clustering process generated by each strategy. It is shown that benefits on the final clustering are directly related to the usefulness of the exchanged information, its use, and on the number of participating agents

On the Performance of Particle Swarm Optimizers

Since the introduction of the first Particle Swarm Optimization algorithm by James Kennedy and Russell Eberhart in the mid-90’s, many variants of the original algorithm have been proposed. However, there is no general agreement on which variant(s) could be considered the state-of-the-art in the field. This is, in part, due to a general lack of cross-comparisons among variants in the literature. The work reported in this document was carried out with the goal of identifying the best-performing particle swarm optimization algorithms. For practical reasons, we could not compare all the available algorithmic variants. Instead, we focused on those that have been the most widely used variants. We also considered algorithms that incorporate some of the latest developments in field. The comparison of the chosen particle swarm optimization algorithms was based on run-length and solution-quality distributions. These analytical tools allow the comparison of stochastic optimization algorithms in terms of the probabilit