999 resultados para Natural insecticides


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En este trabajo se estudia la influencia y el papel de un aspecto del contexto exterior producido por elecciones de tipo lingüístico. Cuando el lenguaje escogido es de tipo coloquial, las primeras preguntas son informales, sobre aspectos extraescolares, y la discusión numérica atañe a N, hablamos de contexto natural. Este contexto parece inducir, en el sujeto sometido a la prueba, la convicción implícita de que debería contestar según modelos intuitivos, que dependen de la competencia que adquirió en los primeros niveles de escolarización o de modelos ingenuos. También examinamos el problema de la conciencia de los alumnos en situaciones de dificultad.

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En esta comunicación presentamos parte de los resultados obtenidos en las investigaciones realizadas dentro de Planes Nacionales de Investigación Educativa del C.I.D.E. durante los cursos 1987-88 y 1988-89, que trataban de averiguar las dificultades del aprendizaje del álgebra en secundaria. El objetivo inicial de este trabajo era estudiar las dificultades planteadas en la resolución de problemas de enunciado verbal en los que se utiliza una ecuación de primer grado o un sistema lineal de dos ecuaciones con dos incógnitas, ya que considerabamos, como la mayoría de los profesores lo hace, que la mayor dificultad presentada en álgebra estaba en la resolución de estos problemas.

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A new general cell-centered solution procedure based upon the conventional control or finite volume (CV or FV) approach has been developed for numerical heat transfer and fluid flow which encompasses both structured and unstructured meshes for any kind of mixed polygon cell. Unlike conventional FV methods for structured and block structured meshes and both FV and FE methods for unstructured meshes, the irregular control volume (ICV) method does not require the shape of the element or cell to be predefined because it simply exploits the concept of fluxes across cell faces. That is, the ICV method enables meshes employing mixtures of triangular, quadrilateral, and any other higher order polygonal cells to be exploited using a single solution procedure. The ICV approach otherwise preserves all the desirable features of conventional FV procedures for a structured mesh; in the current implementation, collocation of variables at cell centers is used with a Rhie and Chow interpolation (to suppress pressure oscillation in the flow field) in the context of the SIMPLE pressure correction solution procedure. In fact all other FV structured mesh-based methods may be perceived as a subset of the ICV formulation. The new ICV formulation is benchmarked using two standard computational fluid dynamics (CFD) problems i.e., the moving lid cavity and the natural convection driven cavity. Both cases were solved with a variety of structured and unstructured meshes, the latter exploiting mixed polygonal cell meshes. The polygonal mesh experiments show a higher degree of accuracy for equivalent meshes (in nodal density terms) using triangular or quadrilateral cells; these results may be interpreted in a manner similar to the CUPID scheme used in structured meshes for reducing numerical diffusion for flows with changing direction.

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Review of: Noel Starkey (ed), Connectionist Natural Language Processing: Readings from 'Connection Science'

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The emergent behaviour of autonomic systems, together with the scale of their deployment, impedes prediction of the full range of configuration and failure scenarios; thus it is not possible to devise management and recovery strategies to cover all possible outcomes. One solution to this problem is to embed self-managing and self-healing abilities into such applications. Traditional design approaches favour determinism, even when unnecessary. This can lead to conflicts between the non-functional requirements. Natural systems such as ant colonies have evolved cooperative, finely tuned emergent behaviours which allow the colonies to function at very large scale and to be very robust, although non-deterministic. Simple pheromone-exchange communication systems are highly efficient and are a major contribution to their success. This paper proposes that we look to natural systems for inspiration when designing architecture and communications strategies, and presents an election algorithm which encapsulates non-deterministic behaviour to achieve high scalability, robustness and stability.

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Background: With the spread of pyrethroid resistance in mosquitoes, the combination of an insecticide (carbamate or organophosphate) with a repellent (DEET) is considered as a promising alternative strategy for the treatment of mosquito nets and other relevant materials. The efficacy of these mixtures comes from the fact that they reproduce pyrethroid features and that positive interactions occur between insecticides and repellent. To better understand the mechanisms involved and assess the impact of detoxifying enzymes (oxidases and esterases) in these interactions, bioassays were carried out in the laboratory against the main dengue vector Aedes aegypti. Methods: Topical applications of DEET and propoxur (carbamate), used alone or as a mixture, were carried out on female mosquitoes, using inhibitors of the two main detoxification pathways in the insect. PBO, an inhibitor of multi-function oxidases, and DEF, an inhibitor of esterases, were applied one hour prior to the main treatment. Results: Results showed that synergism between DEET and propoxur disappeared in the presence of PBO but not with DEF. This suggests that oxidases, contrary to esterases, play a key role in the interactions occurring between DEET and cholinesterase inhibitors in mosquitoes. Conclusion: These findings are of great interest for the implementation of "combination nets" in the field. They support the need to combine insecticide with repellent to overcome insecticide resistance in mosquitoes of public health importance.

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Article is available at: http://www.tandfonline.com/doi/full/10.1080/17439884.2015.1064953.

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Paper presented at the Cloud Forward Conference 2015, October 6th-8th, Pisa

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