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Control del punto de máxima potencia en paneles solares bajo variaciones de radiación y temperatura
Get PDF"El panel solar es un dispositivo con la capacidad de transformar la energía solar en energía eléctrica, esta transformación depende principalmente de dos factores externos, la radiación solar que reciben las celdas y la temperatura a la cual están sometidas; mientras mayor sea la radiación y menor la temperatura, la eficiencia de conversión de energía será mejor. Cabe mencionar que la radiación solar que reciben los paneles puede variar por diversos factores, uno de ellos, áreas sombreadas, generadas ya sea por suciedad o nubes que se interpongan en la superficie de panel. Este bloqueo a la radiación solar y los cambios de temperatura generan variaciones en las curvas características de los paneles solares, motivo por el cual el punto de máxima potencia varía, es por esto que se requieren sistemas de control donde el objetivo sea alcanzar o seguir el punto de máxima potencia que tiene el panel solar; el cual, algunas veces no es alcanzado por sistemas de control convencionales. En este trabajo, se presenta un sistema de control del punto de máxima potencia, con base en la proposición de una superficie de conmutación que utiliza valores medibles del panel solar, tales como, corriente, voltaje y temperatura para posicionar efectivamente el sistema en dicho punto, bajo condiciones variables de radiación y temperatura.""A solar panel is a device with the ability to transform solar energy into electrical energy; this transformation depends mainly on two external factors, the solar radiation received by the cells and the cells temperature, i.e., the higher radiation and the lower temperature, the higher energy conversion efficiency. It is worth mentioning, that the solar radiation can vary with several factors, one of them, shaded areas on the solar panel generated either by draff or clouds that block the surface of panel. This obstruction of the solar radiation along with temperature changes generates variations on the characteristic curves of the solar panels, leading to variations of the maximum power point that can be extracted from them. Control systems are used to track the maximum power of the solar panel; however, some conventional control systems, do not accomplish such objective. This work introduces a control system to track the maximum power point of a solar panel based on the use of a switching surface depending on the current, voltage and temperature of the panel, such a proposal allow us compensate temperature and radiation changes on-line.
Ultrastructural analysis of Candida albicans when exposed to silver nanoparticles
Get PDF"Candida albicans is the most common fungal pathogen in humans, and recently some studies have reported the antifungal activity of silver nanoparticles (AgNPs) against some Candida species. However, ultrastructural analyses on the interaction of AgNPs with these microorganisms have not been reported. In this work we evaluated the effect of AgNPs on C. albicans, and the minimum inhibitory concentration (MIC) was found to have a fungicidal effect. The IC50 was also determined, and the use of AgNPs with fluconazole (FLC), a fungistatic drug, reduced cell proliferation. In order to understand how AgNPs interact with living cells, the ultrastructural distribution of AgNPs in this fungus was determined. Transmission electron microscopy (TEM) analysis revealed a high accumulation of AgNPs outside the cells but also smaller nanoparticles (NPs) localized throughout the cytoplasm. Energy dispersive spectroscopy (EDS) analysis confirmed the presence of intracellular silver. From our results it is assumed that AgNPs used in this study do not penetrate the cell, but instead release silver ions that infiltrate into the cell leading to the formation of NPs through reduction by organic compounds present in the cell wall and cytoplasm.
A family of hyperchaotic multi-scroll attractors in Rn
Get PDF"In this work, we present a mechanism how to yield a family of hyperchaotic multi-scroll systems in based on unstable dissipative systems. This class of systems is constructed by a switching control law changing the equilibrium point of an unstable dissipative system. For each equilibrium point presented in the system a scroll emerges. The switching control law that governs the position of the equilibrium point varies according to the number of scrolls displayed in the attractor. Thus, if two systems display different numbers of scrolls, they have different switching control laws. This paper also presents a generalized theory that explains different approaches such as hysteresis and step functions from a unified viewpoint, extending the concept of chaos in to hyperchaotic multi-scroll systems in . An illustrative example of synchronizing a communication system is given based on the developed theory.
Bottom topography, recent sedimentation and water volume of the Cerro Prieto Dam, NE Mexico
Get PDF"The Cerro Prieto dam, a relatively small water reservoir in NE Mexico, is one of the main resources of potable water for Monterrey, a city with a population of about four million inhabitants. A high resolution seismic study using non-linear parametric sub-bottom echo-sounder SES-2000 was carried out in this water reservoir. High resolution acoustic data interpretation shows that the thickness of recent sediments due to siltation of the reservoir reaches 3.5-4.0 m. It shows a high recent sedimentation rate (1-2 up to 14 cm/year). Based on the echo-sounder data, the first bathymetric map and a digital model of recent sediment thickness were designed. A significant (5-12%) difference between the volume capacity value used by National Commission of Water (CNA) and acoustic survey results was revealed. Differences between the CNA and acoustic data indicate storage losses from 12-17 up to 30 million cubic meters. The results obtained through study such as this one, could be useful to improve a water resources management.""La presa Cerro Prieto, relativamente una pequeña reserva de agua en el noreste de México, es uno de los principales recursos de agua potable para Monterrey, ciudad con una población cerca de cuatro millones de habitantes. Se llevó a cabo un estudio de sísmica de alta resolución en esta reserva de agua con un equipo SES-2000 que utiliza un efecto acústico paramétrico no lineal. La interpretación de los datos de acústica de alta resolución muestra que el espesor de los sedimentos recientes alcanza 3.5-4.0 m debido a la sedimentación del embalse. Esto demuestra una alta velocidad de sedimentación reciente (de 1-2 hasta 14 cm por año). Con base a los resultados de este estudio, se ha preparado un mapa batimétrico y un modelo de espesores de sedimentos. Se reveló una diferencia significativa (5-12%) entre el valor de la capacidad de volumen calculado por la Comisión Nacional del Agua (CNA) y los resultados acústicos. La diferencia entre dichos datos indica pérdidas de almacenamiento de 12-17 hasta 30 millones de metros cúbicos. Los resultados obtenidos de un estudio como éste, son útiles para mejorar un sistema de gestión de los recursos hídricos.
Caracterización funcional del gen AtGRDP1 durante el crecimiento y desarrollo de Arabidopsis thaliana
Get PDF"AtGRDP1 es un gen que presenta un dominio de función desconocida DUF 1399 en el extremo N-terminal, un dominio putativo de unión a RNA en el centro de la proteína y un dominio rico en glicinas en el C-terminal. Se demostró que la sobreexpresión de este gen en plántulas de Arabidopsis thaliana les confiere tolerancia a estrés salino y osmótico. Además, se propone que podría estar participando en la señalización del ácido abscísico (ABA), esto debido al fenotipo de insensibilidad al ABA (ABI; ABA-insensitive) observado en las líneas sobre-expresoras y de hipersensibilidad para la línea mutante. En esta tesis reportamos la expresión del gen AtGRDP1 durante el desarrollo de Arabidopsis, observando una mayor expresión en raíz, roseta, hoja caulinar y silicuas. En estudios más específicos de la expresión de este gen, se utilizó una línea reportera que contiene el promotor de AtGRDP1 fusionado al gen reportero GUS, se identificó una expresión tejidoespecifica en tricomas de la hoja de roseta, en el receptáculo de la silicua y en los estambres. También se reportó, que las líneas sobreexpresantes (35S::AtGRDP1) presentan un crecimiento más acelerado cuando se compara con la mutante insercional (Atgrdp1) y parental Columbia-0 (Col-0), tanto en estadios tempranos como de planta adulta. Además se caracterizó la expresión de AtGRDP1 y su versión de splicing alternativo (saAtGRDP1) durante el desarrollo de Arabidopsis, en plantas de 18, 21, 26, 28 y 45 días, adicionalmente se evaluó el perfil transcripcional durante el desarrollo de la flor y la silicua, y se demostró que a ese nivel saAtGRDP1 está presente y muestra una expresión diferencial a AtGRDP1. En este estudio, presentamos datos interesantes sobre la expresión del gen AtGRDP1 en diferentes tejidos y etapas del desarrollo de la planta, y además demostramos que la versión de splicing alternativo saAtGRDP1 se expresa principalmente en la parte aérea de plantas adultas de Arabidopsis.""AtGRDP1 is a novel gene that contains a DUF1399 domain of unknown function at the N-terminal end, a putative RNA binding motif in the middle of the protein and a glycine rich motif in the C-terminal end. It has been demonstrated that overexpression of AtGRDP1 in plants provide tolerance to stress against salt and osmotic treatments. AtGRDP1 is proposed to be involved on ABA signaling pathway as overexpression lines showed an ABA-insensitive phenotype (ABI) while the mutant was hypersensitive. Here we show that AtGRDP1 gene is mainly expressed in roots, rosette leaves, cauline leaf and siliques. Expression studies with a reporter line that carry AtGRDP1 promoter fused to GUS showed a tissuespecific expression pattern on rosette leaf trichomes, silique receptacle and stamens. Furthermore, we characterized AtGRDP1 and its alternative spliced version (asAtGRDP1) expression during Arabidopsis development in plants of 18, 21, 26, 28 and 45 days, as well as during flower and silique development. These results showed that in a transcriptional level asAtGRDP1 is present and shows a differential expression that AtGRDP1. In this work, we present interesting information about AtGRDP1 gene expression in different tissues and different developmental stages. Also we show that the alternative splicing version of AtGRDP1 gene, asAtGRDP1, presents an expression in aerial part in Arabidopsis adult plants.
El silenciamiento local controla la respuesta al estrés oxidante y la resistencia multifarmacológica de Candida glabrata
Get PDFTesis (Doctorado en Ciencias en Biología Molecular)"En Candida glabrata las sirtuinas Sir2 y Hst1 regulan parcialmente la expresión de una gran cantidad de genes. Dentro de los genes regulados por estas sirtuinas destacan los que codifican para las adhesinas epiteliales y para los transportadores de niacina, que son requeridos para la colonización del hospedero y el crecimiento, respectivamente. Sin embargo, dado que las sirtuinas son susceptibles a inactivarse in vivo, nos preguntamos sí la inhibición de las sirtuinas podría modificar la respuesta de C. glabrata a las condiciones de estrés. En este trabajo encontramos que la deleción de HST1 disminuye la susceptibilidad de C. glabrata al fluconazol y al peróxido de hidrógeno. Nuestros experimentos indican que el factor Pdr1 y el transportador Cdr1 median el fenotipo resistente al fluconazol de la cepa hst1Δ. Por otra parte, el activador Msn4 y la catalasa (Cta1) son necesarios para proveer de resistencia al estrés oxidante. Además, demostramos que el factor de transcripción Sum1 interacciona físicamente con Hst1 y que participa en la regulación de los genes que confieren la resistencia. Finalmente, C. glabrata está relacionada filogenéticamente con la levadura Saccharomyces cerevisiae. Sin embargo, encontramos que la deleción de HST1 sólo modifica la susceptibilidad al fluconazol y al peróxido de hidrógeno en C. glabrata pero no en Saccharomyces cerevisiae, lo que sugiere un control distinto con sirtuinas similares. En conjunto, nuestros resultados sugieren que Hst1 funciona como un regulador de los genes asociados con la resistencia en el patógeno oportunista C. glabrata.""In Candida glabrata, the sirtuins Sir2 and Hst1 control the expression of a wide number of genes including adhesins required for host colonization and niacin transporters needed for growth. Given that these sirtuins can be inactivated during infection, we asked if their inhibition could modify the response of C. glabrata to other stressful conditions. Here, we found that deletion of HST1 decreases susceptibility of C. glabrata to fluconazole and hydrogen peroxide. The transcription factor Pdr1 and the ABC transporter Cdr1 mediated the fluconazole resistance phenotype of the hst1 cells, whereas the transcriptional activator Msn4 and the catalase Cta1 are necessary to provide oxidative stress resistance. We show that the transcription factor Sum1 interacts with Hst1 and participate in the regulation of these genes. Interestingly, even though C. glabrata and Saccharomyces cerevisiae are closely related phylogenetically, deletion of HST1 decreased susceptibility to fluconazole and hydrogen peroxide only in C. glabrata but not in S. cerevisiae, indicating a different transcriptional control by two similar sirtuins. Our findings suggest that Hst1 acts as a regulator of stress resistance associated-genes.
Patrones de distribución y reclutamiento de encinos (Quercus spp) en bosques fragmentados de la sierra de Álvarez, San Luis Potosi, México.
Get PDFTesis (Doctorado en Ciencias Ambientales)"Entre todos los cambios que pueden experimentar los bosques, el que mayores transformaciones produce en su estructura y funcionamiento es la deforestación. Esta actividad humana ha ocasionado la fragmentación de estos ecosistemas donde los fragmentos de bosque, así como los factores bióticos y abióticos asociados a ellos, se encuentran bajo la influencia ambiental proveniente de los campos deforestados aledaños. Uno de los procesos biológicos que pueden alterarse significativamente por la fragmentación es la reproducción de los árboles, ya que puede retrasar o disminuir la producción de semillas o su calidad. Estos cambios también pueden generar efectos negativos sobre procesos ecológicos que dependen directamente de las semillas, como la relación semilla-depredador-dispersor. Esto es importante cuando las semillas representan una fuente de alimento crítico para un grupo de consumidores, como ocurre con las bellotas en los bosques de encinos, que en su intento por transportarlas y acumularlas eventualmente las dispersan. Sin embargo, aún se desconoce cómo la aportación de semillas que tienen los árboles de un bosque fragmentado puede influir en estas interacciones con los organismos que las consumen y las dispersan, o de qué manera los diferentes tipos de hábitat que se pueden encontrar en un bosque fragmentado determinan dichas interacciones. La presente investigación se realizó en un bosque fragmentado de Quercus laeta en el centro de México. Allí se evaluó cómo se distribuyen de bellotas tras su dispersión primaria entre los diferentes tipos de hábitats del bosque fragmentado, y la manera en que esto se relaciona con su dispersión y consumo por parte de vertebrados, insectos y hongos parásitos. Los resultados indican que, después de su liberación del árbol parental, la mayor parte de las bellotas se encuentra al interior de los parches de bosque. Sin embargo, a medida que se reduce el área de los parches, mayores fueron las tasas de aborción y depredación por insectos parásitos y hongos. Los resultados también indicaron que la depredación por vertebrados ocurre principalmente en el centro de los parches. Esto muestra que los animales consumidores difícilmente estarían dispersando las bellotas hacia los claros que rodean los parches.""Among the changes that forest may experience, deforestation produces the major changes in their structure and functioning. This human activity causes the fragmentation of forests, where the remnant fragments that harbor the trees and their biotic and abiotic factors are subjected to the influence of the environment that predominates in the neighboring deforested fields. In this way, tree reproduction is perhaps the biotic process most deeply affected by fragmentation, causing reductions seed crops and seed quality. These effects on reproduction can also negatively impact on the ecological processes that directly depend on the seeds, such as the interaction between seeds and their predators and dispersers. The evaluation of the impacts of fragmentation on these processes is important when seeds are the critical source of food for a group of consumers, as occurs with acorns in oak forests, which in their attempt to transport and accumulate seeds they may eventually disperse them. However, it is still unknown how the impacts of fragmentation on seed production can influence on these interactions, or how the different habitat types from fragmented forest can also impact the distribution of seeds and their consumers. This research was conducted in a fragmented forest of Quercus laeta in central Mexico. We evaluated how acorns are distributed after primary dispersion across the different types of a fragmented forest, and how this relates to their dispersion and consumption by vertebrates, insects, parasitic fungi. The results indicate that, after their release from the parental tree, most the acorns are located within the forest patches. However, higher rates of abortion and predation by insects and fungi seem to occur as the area of the patches is reduced. The results also indicated that predation by vertebrates mainly occurs at the interior of the patches. Therefore, this indicates that consumers would hardly disperse acorns towards the open areas surrounding the patches. This first part of our research then suggests that forest fragmentation alters the production of acorns and, consequently, their interactions with other organisms. Therefore, fragmentation can negatively impact on forest regeneration.
Ermakov systems with multiplicative noise
Get PDF"Using the Euler-Maruyama numerical method, we present calculations of the Ermakov-Lewis invariant and the dynamic, geometric, and total phases for several cases of stochastic parametric oscillators, including the simplest case of the stochas-tic harmonic oscillator. The results are compared with the corresponding numerical noiseless cases to evaluate the effect of the noise. Besides, the noiseless cases are analytic and their analytic solutions are briefly presented. The Ermakov-Lewis in-variant is not affected by the multiplicative noise in the three particular examples presented in this work, whereas there is a shift effect in the case of the phases.
Expanded use of a fast photography technique to characterize laser-induced plasma plumes
Get PDF"Expanded use of fast photography is proposed to characterize laser ablation plasma plumes by the analysis of a set of photographs by means of appropriate mathematical algorithms. The laser ablation plasma plumes studied were generated by ablation of both a multicomponent target of the nominal composition Ni50Mn37Sn13 and a highly pure Cu target (Cu) using a Q-switched Nd-YAG laser system. The experiments were conducted under different background argon pressures. Several photograph parameters such as intensity per unit time of exposure for a pixel, mean intensity per pixel per unit time of exposure, integrated intensity and cross correlation were studied. The intensity per unit time of exposure allowed for identification of the fast component of the triple structure of the expanding plasma into the background gas (that travels at a speed close to the one measured in vacuum). This parameter together with the use of cross correlation enabled the identification of regions of the expanded plasma plume with higher and lower similarities in their optical emission behavior. The mean intensity per pixel per unit time of exposure can be used as a measurement of the amount of light emitted by the plume as a function of time.
Physiological and molecular implications of plant polyamine metabolism during biotic interactions
Get PDF"During ontogeny, plants interact with a wide variety of microorganisms. The association with mutualistic microbes results in benefits for the plant. By contrast, pathogens may cause a remarkable impairment of plant growth and development. Both types of plant microbe interactions provoke notable changes in the polyamine (PA) metabolism of the host and/or the microbe, being each interaction a complex and dynamic process. It has been well documented that the levels of free and conjugated PAs undergo profound changes in plant tissues during the interaction with microorganisms. In general, this is correlated with a precise and coordinated regulation of PA biosynthetic and catabolic enzymes. Interestingly, some evidence suggests that the relative importance of these metabolic pathways may depend on the nature of the microorganism, a concept that stems from the fact that these amines mediate the activation of plant defense mechanisms. This effect is mediated mostly through PA oxidation, even though part of the response is activated by non-oxidized PAs. In the last years, a great deal of effort has been devoted to profile plant gene expression following microorganism recognition. In addition, the phenotypes of transgenic and mutant plants in PA metabolism genes have been assessed. In this review, we integrate the current knowledge on this field and analyze the possible roles of these amines during the interaction of plants with microbes.