Optimal Control of a Fractional Diffusion Equation with Delay

We study a homogeneous Dirichlet boundary fractional diffusion equation with delay in a bounded domain. The fractional time derivative is considered in the left Caputo sense. By means of a linear continuous operator, we first transform the fractional diffusion equation with delay into a an equivalent equation without delay. Then we show that the optimal control problem associate to the controlled equivalent fractional diffusion equation has a unique solution. Interpreting the Euler-Lagrange first order optimality condition with an adjoint problem defined by means of right fractional Caputo derivative, we obtain an optimality system

Andean Pastures in the Fourth Region of Chile: Marginal Lands and Vital Spaces for a Transhumance System

In the fourth region of Chile, the high Andean pastures between Chile and Argentina are the summer destination for transhumant shepherds and sustain a part of the regional livestock. Since 2000, Chile has prohibited the passage of livestock to Argentina for animal health reasons in spite of official registers indicating that 60 to 75% of the summer transhumance livestock had an Argentine destination. Under those conditions it is questionable whether the Andean Chilean grasslands can absorb the increased pastoral demand without suffering damage. The objective is to provide elements of an answer to this question regarding the distribution and availability of the Andean forage resource and its modalities of explotation in the local transhumance system

Un modèle intégré pour explorer les trajectoires d’utilisation de l’espace

International audienceDynamic spatial models are important tools for the study of complex systems like environmental systems. This paper presents an integrated model that has been designed to explore land use trajectories in a small region around Maroua, located in the far north of Cameroon. The model simulates competition between land use types taking into account a set of biophysical, socio-demographic and geo-economics driving factors. The model includes three modules. The dynamic simulation module combines results of the spatial analysis and prediction modules. Simulation results for each scenario can help to identify where changes occur. The model developed constitutes an efficient knowledge support system for exploratory research and land use planning.Les modèles spatiaux dynamiques sont des outils de très grande importance pour l'étude des systèmes complexes comme les systèmes environnementaux. De plus, une approche intégrée est indispensable lorsqu'on veut avoir une compréhension plus complète du comportement de ces systèmes. Cet article décrit les bases d'un modèle intégré développé pour explorer les trajectoires d'utilisation de l'espace dans la région autour de Maroua, à l'Extrême Nord du Cameroun. Le modèle simule la compétition entre différentes catégories d'utilisation de l'espace en prenant en compte l'influence d'un ensemble de facteurs biophysiques, sociodémographiques et géoéconomiques. On distingue trois principaux modules. Le module de simulation dynamique combine les résultats des modules d'analyse spatiale et de prédiction. La calibration et la validation du modèle ont été effectuées pour la période entre 1987 et 1999, et la simulation des changements entre 1999 et 2010. Trois scénarios ont été formulés en s'appuyant sur l'analyse des tendances observées et les hypothèses de transition du système d'utilisation de l'espace. Les principales dynamiques observées concernent le développement de la culture maraîchère et l'extension de la culture du sorgho de contre saison qui induisent une compétition plus importante et des conflits. Les résultats de simulation pour chaque scénario permettent d'identifier des zones prioritaires pour toute intervention allant dans le sens de l'intensification ou d'une gestion intégrée et plus durable de l'espace. Le modèle développé constitue ainsi un outil de recherche exploratoire et un support de connaissances utilisable pour la planification de l'utilisation de l'espace. Une utilisation est envisageable pour initier toute concertation ou négociation entre les acteurs concernés par la gestion de l'espace

Laser modulated optical reflectance of thin semiconductor films on glass

Semiconductor films, deposited by reactive magnetron sputtering on glass substrates have been analyzed with the help of laser-modulated optical reflectance. The results are discussed with respect to the thermal and charge carrier transport properties. Semiconductor properties have been identified both for micro-crystalline and amorphous film

Living at the edge: biogeographic patterns of habitat segregation conform to speciation by niche expansion in Anopheles gambiae

<p>Abstract</p> <p>Background</p> <p>Ongoing lineage splitting within the African malaria mosquito <it>Anopheles gambiae </it>is compatible with ecological speciation, the evolution of reproductive isolation by divergent natural selection acting on two populations exploiting alternative resources. Divergence between two molecular forms (M and S) identified by fixed differences in rDNA, and characterized by marked, although incomplete, reproductive isolation is occurring in West and Central Africa. To elucidate the role that ecology and geography play in speciation, we carried out a countrywide analysis of <it>An. gambiae </it>M and S habitat requirements, and that of their chromosomal variants, across Burkina Faso.</p> <p>Results</p> <p>Maps of relative abundance by geostatistical interpolators produced a distinct pattern of distribution: the M-form dominated in the northernmost arid zones, the S-form in the more humid southern regions. Maps of habitat suitability, quantified by Ecological Niche Factor Analysis based on 15 eco-geographical variables revealed less contrast among forms. M was peculiar as it occurred proportionally more in habitat of marginal quality. Measures of ecological niche breadth and overlap confirmed the mismatch between the fundamental and realized patterns of habitat occupation: forms segregated more than expected from the extent of divergence of their environmental envelope – a signature of niche expansion. Classification of chromosomal arm 2R karyotypes by multilocus genetic clustering identified two clusters loosely corresponding to molecular forms, with 'mismatches' representing admixed individuals due to shared ancestral polymorphism and/or residual hybridization. In multivariate ordination space, these karyotypes plotted in habitat of more marginal quality compared to non-admixed, 'typical', karyotypes. The distribution of 'typical' karyotypes along the main eco-climatic gradient followed a consistent pattern within and between forms, indicating an adaptive role of inversions at this geographical scale.</p> <p>Conclusion</p> <p>Ecological segregation between M and S is consistent with niche expansion into marginal habitats by chromosomal inversion variants during early lineage divergence; presumably, this process is promoted by inter-karyotype competition in the higher-quality core habitat. We propose that the appearance of favourable allelic combinations in other regions of suppressed recombination (e.g. pericentromeric portions defining speciation islands in <it>An. gambiae</it>) fosters development of reproductive isolation to protect linkage between separate chromosomal regions.</p

Enteroaggregative Escherichia coli: a public health hazard in Yaoundé, Cameroon?

The prevalence of various pathotypes of Escherichia coli was investigated during a case-control study conducted in children diarrhoea in Yaoundé. Isolates obtained from the stools samples of children aged 6 months to 5 years were selected on phenotypic basis, and identified by virulence genes detection using polymerase chain reactions. The most prevalent pathotype was enteroaggregative Escherichia coli (25.8%). Enteropathogenic Escherichia coli (3.6%), enterotoxigenic Escherichia coli (1%), and enteroinvasive Escherichia coli (0.2%) followed. No shiga toxin-producing Escherichia coli were identified. Enteroaggregative Escherichia coli was not associated with diarrhoea (cases 26.1%, controls 25.5%; P=0,887), unlike enteropathogenic Escherichia coli (cases 6.7%, controls 1%; P=0.003). Investigations into documented potentials of enteroaggregative Escherichia coli in causing diarrhoea and other related pathologies indicated that it could be a major public health threat in Cameroon despite the fact that it was not found associated with clinical diarrhoeal cases in this study. Keywords: Cameroon, diarrhoeagenic Escherichia coli, public health. Int. J. Biol. Chem. Sci. Vol. 2 (3) 2008: pp. 272-28

Investigations on PrP and PrPres in porcine brain and in stimufol preparations

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