Ultrahigh dielectric constant of thin films obtained by electrostatic force microscopy and artificial neural networks

Copyright 2012 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.A detailed analysis of the electrostatic interaction between an electrostatic force microscope tip and a thin film is presented. By using artificial neural networks, an equivalent semiinfinite sample has been described as an excellent approximation to characterize the whole thin film sample. A useful analytical expression has been also developed. In the case of very small thin film thicknesses (around 1 nm), the electric response of the material differs even for very high dielectric constants. This effect can be very important for thin materials where the finite size effect can be described by an ultrahigh thin filmdielectric constant.This work was supported by TIN2010-196079. G.M.S. acknowledges support from the Spanish Ramón y Cajal Program

Finite Conductivity Effects in Electrostatic Force Microscopy on Thin Dielectric Films: A Theoretical Model

A study of the electrostatic force between an Electrostatic Force Microscope tip and a dielectric thin film with finite conductivity is presented. By using the Thomas-Fermi approximation and the method of image charges, we calculate the electrostatic potential and force as a function of the thin film screening length, which is a magnitude related to the amount of free charge in the thin film and is defined as the maximum length that the electric field is able to penetrate in the sample. We show the microscope's signal on dielectric films can change significantly in the presence of a finite conductivity even in the limit of large screening lengths. This is particularly relevant in determining the effective dielectric constant of thin films from Electrostatic Force Microscopy measurements. According to our model, for example, a small conductivity can induce an error of more than two orders of magnitude in the determination of the dielectric constant of a material. Finally, we suggest a method to discriminate between permittivity and conductivity effects by analyzing the dependence of the signal with the tip-sample distance.The authors acknowledge J. J. Saenz, C. Gomez-Navarro, and J. Gomez-Herrero for insightful discussions. This work has been partially funded by the Banco Santander-UAM Research Program. G. M. Sacha acknowledges support from the Spanish Ramon y Cajal Program

Distinct macroinvertebrate soil food webs at one-meter scale in a Mediterranean agroecosystem

Altres ajuts: Acord transformatiu CRUE-CSICSoil macroinvertebrates play a central role in ecosystem processes such as decomposition and nutrient cycling, but the extent to which macroinvertebrate food web structure varies within ecosystems is basically unknown. Here, we examined changes in plant and macroinvertebrate community composition at increasing distances from trees within a citrus grove, following a gradient in organic matter and water availability created by the localized fertilization and irrigation of citrus trees. In addition, we analysed stable isotope signatures (δC and δN) of soil, plants, and macroinvertebrates to investigate changes in trophic structure within the grove. The macroinvertebrate community near the tree trunks had a higher number of detritivores and predators than the community located farther away. After correcting the isotope values of macroinvertebrates by their isotopic baseline, a spatial shift in trophic structure emerged: macroinvertebrates near the trunks had lower δC-values than those located farther away (i.e., they apparently relied more on plant- based resources). This pattern is attributable to species only found near the trunks. In contrast, species distributed across the studied area showed no differences in their isotopic signatures across space, suggesting that they are connecting otherwise two compartmentalized food webs. A reduction in organic matter and water availability at increasing distances from trees is the most parsimonious explanation of the observed isotopic gradient in soil and plants, and this may, in turn, be responsible for the observed changes in food web composition and structure. This study shows that spatial variability in macroinvertebrate soil food webs can be present at scales as small as one meter if spatial variability in environmental factors is high enough

Formulación del M.E.C. en elasticidad tridimensional mediante macroelementos y colocación no nodal

Se presenta en este trabajo un nuevo enfoque del Método de los Elementos de Contorno en Elasticidad tridimensional basado en una aproximación global de la geometría en el interior de macroelementos junto con una estrategia de colocación no nodal, que permite obviar el tema de los nodos esquina, elimina la necesidad de evaluación del término libre que ahora es fijo y de valor 0.5 Sij y simplifica el tratamiento de subregiones con las ventajas que ello supone desde el punto de vista computacional.Peer Reviewe

Manual de obras de bioingeniería en zonas de laderas con procesos de remoción de masas para altitudes superiores a 3000 m.s.n.m. El caso de la localidad de Sumapaz-Bogotá D.C

Trabajo de InvestigaciónSe realizaron estudios de estabilidad geotécnica y las características físicas de los sectores identificados anteriormente por la funcionarios de planeación quienes tomaron las estrategias, medidas y alternativas de mitigación del riesgo más favorable, se verifico que estos presentaran procesos de erosión y tuvieran zonas potencialmente inestables del talud o el borde de la ladera; para de tal forma se poder identificar la condición de amenaza a corto y largo plazo. A partir de la información adquirida, recopilada se analizaron los resultados del estudio. Se evaluaron los resultados de la investigación del subsuelo efectuado y determinando en estos la capacidad portante del suelo y el análisis de estabilidad de los taludes en la zona. Finalmente se elaboró un Manual de Obras de bioingeniería de fácil comprensión para la comunidad, describiendo en este cada uno de los pasos a seguir para llevara a cabo con la construcción de los sistemas de estabilización.INTRODUCCIÓN 1. GENERALIDADES 2. GENERALIDADES GEOLÓGICAS 3. CARACTERIZACIÓN PUNTOS INTERVENIDOS EN LA LOCALIDAD DE SUMAPAZ 4. SISTEMATIZACION EXPERIENCIAS CON BIOINGENIERIA 5. CONCLUSIONES 6. ANALISIS DE RESULTADOS Y RECOMENDACIONES GENERALES BIBLIOGRAFIA ANEXOSPregradoIngeniero Civi

Análisis de cuatro propuestas y presentación de una nueva para la modificación del régimen impositivo a los licores en Colombia

123 páginas y anexos.The analysis of the regime to liquors in Colombia is carried out, for which we explored how the tax regime and the monopoly of the departmental liquors are today. The importance of the liquor monopoly and the tax on the consumption of liquors is analyzed, not only from the economic point of view, but also from the implications they have of decentralization and territorial autonomy. In tum, a review of the behavior of the liquor market in Colombia is carried out in three dimensions: its historical aspect, its current situation and the challenges it faces both economically and legally.Se realiza el análisis del régimen a los licores en Colombia, para lo cual se explora cómo se encuentra el régimen impositivo y el monopolio de los licores departamentales en la actualidad. Se analiza la importancia que tiene el monopolio de licores y el impuesto al consumo de licores, no solo desde el punto de vista económico, sino desde las implicaciones que estos tienen a nivel de la descentralización y autonomía territorial. A su vez se realiza la revisión del comportamiento del mercado de licores en Colombia en tres dimensiones: su aspecto histórico, su situación actual y los desafíos por los que atraviesa tanto a nivel económico coma legal.Magíster en Gobierno y Políticas PúblicasMaestrí

Hervás, an academic route through its past

[ES] En la actualidad, la enseñanza del tiempo histórico en Educación Primaria afronta un gran reto: la adaptación de la enseñanza de sus contenidos a los cambios tecnológicos y la inteligencia artificial. Existen muy pocos estudios que aborden cuáles son las metodologías y recursos educativos óptimos para ofrecer resultados significativos este campo. No obstante, cada vez son más los estudios que se suman a innovar en la enseñanza del tiempo histórico a través de metodologías constructivistas que parten de elementos cercanos a los estudiantes como el patrimonio de su localidad, enlazando, después, con los diferentes acontecimientos históricos nacionales. Así, con su puesta en marcha se fomentan valores de respeto, cuidado, preservación y puesta en valor de la cultura autóctona, impidiendo que esta caiga en el olvido. Partiendo de esta problemática, este Trabajo de Fin de Grado, pretende conocer cuál es y ha sido la realidad educativa en las aulas del colegio Hervás con respecto a la enseñanza del tiempo histórico. Para ello, se han realizado varias entrevistas semiestructuradas a docentes del Colegio de Educación Infantil y Primaria Santísimo Cristo de la Salud, cuyas respuestas han sido analizadas a partir de un sistema de categorías de tipo deductivo. Posteriormente, y atendiendo a los resultados obtenidos, se plantea una propuesta de aprendizaje personalizada para el curso de sexto de Primaria del colegio de Hervás. Esta propuesta, basada en un itinerario didáctico que recorre el pueblo de Hervás, pretende innovar en las formas de enseñanza del tiempo histórico local. De esta forma, se utilizan recursos como las nuevas tecnologías o las inteligencias artificiales para crear un aprendizaje significativo entre el alumnado, aspirando a mejorar la calidad de la enseñanza del tiempo histórico local, incrementando la valoración del patrimonio histórico-cultural y despertando interés por la historia de la localidad.[EN] Currently, teaching historical time in Primary Education faces a great challenge: the adaptation of its content to technological changes and artificial intelligence. There are few studies that investigate the optimal educational methodologies and resources to offer significant results in this area. However, some new studies are in the process of being developed to innovate in the teaching of historical time through constructivist methodologies that start from elements close to the students such as the heritage of their locality, to later, link them with different national historical events. Therefore, the implementation of this methodologies and resources, values of respect, care, preservation and enhancement of the native culture are promoted, preventing it from being forgotten. Taking these facts into account, this Final Degree Project aims to explore the present and the past educational reality in the classrooms of the Hervás school according to the teaching of historical time. To achieve it, several semi-structured interviews have been carried out with teachers from the Santísimo Cristo de la Salud School of Early Childhood and Primary Education, whose responses have been analysed based on a system of deductive categories. Subsequently, this Final Degree Project, tries to create a personalized learning proposal for the sixth year of Primary at the Hervás school based on the results obtained in the results of the different interviews. This learning proposal, based on a didactic itinerary that tours the town of Hervás, aims to innovate in the ways of teaching local historical time. On this way, resources such as new technologies or artificial intelligence are used to create meaningful learning among students, trying to improve the quality of teaching about local historical time, increasing the appreciation of historical-cultural heritage and the interest in the local history of Hervás