Structure analysis and lesion detection from retinal fundus images

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Ocular pathology is one of the main health problems worldwide. The number of people with retinopathy symptoms has increased considerably in recent years. Early adequate treatment has demonstrated to be effective to avoid the loss of the vision. The analysis of fundus images is a non intrusive option for periodical retinal screening. Different models designed for the analysis of retinal images are based on supervised methods, which require of hand labelled images and processing time as part of the training stage. On the other hand most of the methods have been designed under the basis of specific characteristics of the retinal images (e.g. field of view, resolution). This compromises its performance to a reduce group of retinal image with similar features. For these reasons an unsupervised model for the analysis of retinal image is required, a model that can work without human supervision or interaction. And that is able to perform on retinal images with different characteristics. In this research, we have worked on the development of this type of model. The system locates the eye structures (e.g. optic disc and blood vessels) as first step. Later, these structures are masked out from the retinal image in order to create a clear field to perform the lesion detection. We have selected the Graph Cut technique as a base to design the retinal structures segmentation methods. This selection allows incorporating prior knowledge to constraint the searching for the optimal segmentation. Different link weight assignments were formulated in order to attend the specific needs of the retinal structures (e.g. shape). This research project has put to work together the fields of image processing and ophthalmology to create a novel system that contribute significantly to the state of the art in medical image analysis. This new knowledge provides a new alternative to address the analysis of medical images and opens a new panorama for researchers exploring this research area.Mexican National Council of Science and Technolog

Can Ecological Interactions be Inferred from Spatial Data?

The characterisation and quantication of ecological interactions, and the construction of species distributions and their associated ecological niches, is of fundamental theoretical and practical importance. In this paper we give an overview of a Bayesian inference framework, developed over the last 10 years, which, using spatial data, offers a general formalism within which ecological interactions may be characterised and quantied. Interactions are identied through deviations of the spatial distribution of co-occurrences of spatial variables relative to a benchmark for the non-interacting system, and based on a statistical ensemble of spatial cells. The formalism allows for the integration of both biotic and abiotic factors of arbitrary resolution. We concentrate on the conceptual and mathematical underpinnings of the formalism, showing how, using the Naive Bayes approximation, it can be used to not only compare and contrast the relative contribution from each variable, but also to construct species distributions and niches based on arbitrary variable type. We show how the formalism can be used to quantify confounding and therefore help disentangle the complex causal chains that are present in ecosystems. We also show species distributions and their associated niches can be used to infer standard "micro" ecological interactions, such as predation and parasitism. We present several representative use cases that validate our framework, both in terms of being consistent with present knowledge of a set of known interactions, as well as making and validating predictions about new, previously unknown interactions in the case of zoonoses

Epigenetic Factors Impacting Type 2 Diabetes in American Indians

American Indians have been found to be at higher risk of type 2 diabetes (T2D) than any other ethnic or racial groups in the United States, with an estimated prevalence rate of 33%. Given that T2D prevalence rates amongst the American Indian population are so high, studying the complex factors that contribute to T2D is crucial. Of particular importance to this study is identifying heritable effects involved in development of T2D. Epigenetic effects, heritable changes to DNA that affect gene expression such as DNA methylation (DNAm), have been shown to be associated with T2D phenotypes. Studies in other subpopulations have previously identified differential DNAm at the ABCG1 gene as being associated with T2D. ABCG1 plays a significant role in promoting cholesterol efflux, and it has been associated with T2D and related traits. As such, we sought to determine whether those results generalized to American Indians by assaying DNAm at ABCG1 within a sample population of 285 American Indian participants in the Strong Heart Study (SHS). In verifying whether there is a significant association between DNAm levels and T2D, we hypothesize that individuals diagnosed with T2D will have higher rates of DNAm at loci in ABCG1 than individuals who do not have T2D. Ultimately, we hope the results of this experiment can provide more insight on the role that differential DNAm has to play in the risk and development of T2D

Dihydropyridines as Calcium Channel Blockers: An Overview

Cardiovascular disease remains one of the leading causes of death in the United States. It is estimated that 1 in every 3 American adults suffer from high blood pressure. Hypertension, a precursor to most cardiovascular diseases, continues to grow at an alarming rate and is seldom managed carefully. Attempts have been made to manage hypertension and reduce the morbidity and mortality of the cardiovascular organ through methods including diets, increased amount of exercise, and medications. Many commercial drugs have been derived from dihydropyridine due to its antihypertensive property. Dihydropyridine derivatives work by acting as calcium channel blockers blocking the intake of calcium ions into the vascular smooth muscle and, to a lesser extent, cardiac muscles. Dihydropyridine moiety is well-known in pharmacology as L-type calcium channel blockers, which is extremely important since it treats hypertension in people who suffer from it. It is also highly important to understand the antagonists of calcium in the arterial hypertension. A brief overview is presented in this mini-review

Automatic graph cut based segmentation of retinal optic disc by incorporating blood vessel compensation.

Glaucoma is one of the main causes of blindness worldwide. Periodical retinal screening is highly recommended in order to detect any sign of the disease and apply the appropriated treatment. Different systems for the analysis of retinal images have been designed in order to assist this process. The segmentation of the optic disc is an important step in the development of a retinal screening system. In this paper we present an unsupervised method for the segmentation of the optic disc. The main obstruction in the optic disc segmentation process is the presence of blood vessels breaking the continuity of the object. While many other methods have addressed this problem trying to eliminate the vessels, we have incorporated the blood vessel information into our formulation. The blood vessels inside of the optic disc are used to give continuity to the object to segment. Our approach is based on the graph cut technique, where the graph is constructed by considering the relationship between neighbouring pixels and by the likelihood of them belonging to the foreground and background from prior information. Our method was tested on two public datasets, DIARETDB1 and DRIVE. The performance of our method was measured by calculating the overlapping ratio (Oratio), sensitivity and the mean absolute distance (MAD) with respect to the manually labeled images

Making use of the complementarity of hydropower and variable renewable energy in Latin America: A probabilistic analysis

Latin America is one of the regions most vulnerable to the effects of climate variability on hydropower generation. Hydropower is the backbone of the Latin-American power system and a key technology for ensuring low-carbon power generation in the region. Despite its importance, our understanding of the impact and likelihood of seasonal variability and of long-term phenomena such as the El Niño Southern Oscillation (ENSO) on hydropower is limited. There is an essential need to understand how likely these effects are and to identify measures to counterbalance them. A combination of wind, solar, and hydropower offers the potential to mitigate the impact of climate variability on renewable power generation and thus improve its reliability. Here we present a modeling framework to quantify the potential benefits of such combination. The modeling framework relies on a meteorological reanalysis dataset, large-scale renewable power generation models, and statistic models. We consider the countries with the largest hydropower capacity in the region, namely Argentina, Brazil, Colombia, Mexico, and Venezuela. We examine whether the probability of a production deficit is reduced when all renewable resources are combined compared to a scenario based solely on hydropower, especially during droughts. The approach presented allows for the first time an in-depth analysis of the benefits of a combined wind, solar, and hydropower-based power generation under different geographical conditions in altered ENSO phases. Our results suggest that—depending on the country and the percentile—the hydropower generated during drought ENSO phases could be up to 50% lower than that during neutral phases. The countries most affected are Colombia and Venezuela, while the reduction is somewhat less severe in Argentina, Brazil, and Mexico. Combining hydropower with variable renewable energy (VRE) offers the potential to reduce the risk of a power deficit during the 10th percentile of the driest months of the year, both in drought and neutral phases. Argentina is the country with the most effective combination of resources to mitigate a power deficit, as each MW of installed VRE generates 0.218 GWh of additional power. It is followed by Brazil and Mexico with 0.185 GWh per MW of VRE and by Venezuela and Colombia with 0.128–0.098 GWh/MW of VRE, respectively. These results can contribute to informing future decisions on capacity planning and regional transmission grids

Evaluación del Desarrollo Rural y Seguridad Alimentaría Nutricional a productores campesinos no asociados a la Cooperativa Flor de Pancasan, en las comunidades de Sitio Histórico y el Bálsamo, Pancasan- Matagalpa, durante el segundo semestre del 2008

En el siguiente documento se muestra un análisis sobre el impacto socio-económico de la no asociatividad campesina en el desarrollo rural y seguridad alimentaria desde las comunidades de “El Bálsamo” y “Sitio Histórico”, municipio de Matiguas, departamento de Matagalpa, durante el periodo del segundo semestre de 2008. Dicho estudio busca encontrar evidencias empíricas para descubrir que si la no asociatividad campesina produce desventajas para el desarrollo rural y la seguridad alimentaria, de los productores campesinos. Así mismo para determinar la situación del desarrollo rural y la seguridad alimentaria , se crearon índices para cada una de las variables: Los índices como el Índice Simple de dieta (IDD), Índice de Patrón Alimentario (IPA), Suficiencia Energética, se realizaron a partir de la metodología de la FAO. El índice Balance energético se realizo con los tres macro nutrientes: Proteínas, Carbohidratos y grasas, las cuales se obtienen a través del valor nutritivo que generan los alimentos consumidos divididos entre el total kilocalocalorias multiplicados por 100. En el caso del índice de vitaminas y minerales este se obtuvo a partir del procesamiento del procesamiento del patrón alimentario, es decir el valor nutritivo de los alimentos consumidos en el periodo de una semana. Las necesidades se obtienen a partir de una tabla de las necesidades nutricionales según estructura de población (FAO).Se utilizo la ecuación de la propuesta de Likert. Los índices de educación como el índice de disponibilidad de enseñanzas, índice de infraestructura escolar, índice interés de estudiar, Índice de Riesgo de la vivienda , Índice de higiene de la vivienda, Índice de Disponibilidad de alimentos Familiar, se calcularon a partir de la ecuación de Likert, su valoración es basada en una distribución de clases Índice general de educación (IEG) se calculo a través de la suma de tres los tres índices IIE (Índice de infraestructura Escolar), IDE (Índice de disponibilidad de enseñanza), Ies

An exact approach for the vehicle routing problem with two-dimensional loading constraints

We consider a special case of the symmetric capacitated vehicle routing problem, in which a fleet of K identical vehicles must serve n customers, each with a given demand consisting in a set of rectangular two-dimensional weighted items. The vehicles have a two-dimensional loading surface and a maximum weight capacity. The aim is to find a partition of the customers into routes of minimum total cost such that, for each vehicle, the weight capacity is taken into account and a feasible two-Dimensional allocation of the items into the loading surface exists. The problem has several practical applications in freight transportation, and it is -hard in the strong sense. We propose an exact approach, based on a branch-and-cut algorithm, for the minimization of the routing cost that iteratively calls a branch-and-bound algorithm for checking the feasibility of the loadings. Heuristics are also used to improve the overall performance of the algorithm. The effectiveness of the approach is shown by means of computational results

Selección de conexiones de acero para zonas sísmicas con base en criterios de confiabilidad

Los hallazgos encontrados a raíz del terremoto de Northridge en 1994 han atraído actualmente la atención de los especialistas, sobre todo en cuanto a los problemas de diseño y seguridad de las conexiones soldadas para estructuras ubicadas en zonas sísmicas. Para equilibrar la seguridad requerida deben tomarse decisiones en relación con los costos para prevenir la posibilidad de excederse algún estado límite de servicio. Las técnicas de confiabilidad estructural proporcionan el marco adecuado para incluir las incertidumbres inherentes en el proceso de diseño. La formulación propuesta permite apoyar a diseñadores y a constructores para la selección del tipo de conexión más conveniente para las zonas sísmicas.Los hallazgos encontrados a raíz del terremoto de Northridge en 1994 han atraído actualmente la atención de los especialistas, sobre todo en cuanto a los problemas de diseño y seguridad de las conexiones soldadas para estructuras ubicadas en zonas sísmicas. Para equilibrar la seguridad requerida deben tomarse decisiones en relación con los costos para prevenir la posibilidad de excederse algún estado límite de servicio. Las técnicas de conÀabilidad estructural proporcionan el marco adecuado para incluir las incertidumbres inherentes en el proceso de diseño. La formulación propuesta permite apoyar a diseñadores y a constructores para la selección del tipo de conexión más conveniente para las zonas sísmicas

DIAGNOSTICO Y ESTRATEGIAS SOCIOECONÓMICAS DEL MUNICIPIO DE XONACATLÁN ESTADO DE MÉXICO 2005-2015: UN ENFOQUE ECONÓMICO TERRITORIAL

En esta investigación se realiza un análisis de las principales acciones y estrategias que se han llevado a cabo en el municipio de Xonacatlán durante el periodo 2005- 2015 con el fin de elaborar un diagnóstico certero de la situación actual que pueda conducir a la elaboración de propuestas eficientes para generar desarrollo local. El motivo por el cual se realiza el análisis de este municipio es porque el Estado de México es una de las economía más importantes a nivel nacional y dada su cercanía con la ahora ciudad de México, el flujo turístico es de suma importancia para las economías locales. Xonacatlán se localiza al norte del Valle de Toluca y está adscrito en la parte central del Estado de México, pertenece a la Región Geopolítica VII Lerma, que es la región industrial del estado de México y por ser Xonacatlán un municipio de paso a Temoaya (que cuenta con un gran acervo cultural de atracción al turismo), enfatiza el interés de realizar un análisis de enfoque económico territorial. Es entonces que el objetivo general de esta investigación es: Analizar las características geográficas, económicas y sociales del municipio con la finalidad de construir las estrategias de desarrollo territorial para transformar la imagen-objeto del municipio. 7 Cuyos objetivos específicos desglosados en tres capítulos son: - Capítulo 1: Establecer el marco conceptual y jurídico de la Planeación municipal. En este capítulo se establecen las bases conceptuales que rigen la planeación en México y la forma en que pueden ser aplicables a nivel territorial en Xonacatlán. En este capítulo se tomó como fuentes de información a distintos autores expertos en el desarrollo del tema de análisis regional, así como documentos institucionales como la Constitución Política de los Estados Unidos Mexicanos, Ley de Planeación del Estado de México, la Ley de Planeación Federal, Código Administrativo del Estado de México, Plan de desarrollo Municipal, etc. - Capítulo 2: Elaborar y analizar el diagnóstico físico, económico y social del municipio. En este capítulo se hace un estudio profundo de la situación actual del municipio desde su medio físico, la estructura sociodemográfica y la situación económica. Este estudio es sin duda parte fundamental de la investigación, ya que con su análisis y la aplicación de herramientas como los modelos de curvas de localización, coeficiente de localización y modelo de cambio y participación (Shiff-Share), será posible definir aquellas áreas de oportunidad, a partir de las cuales se van a elaborar las propuestas de estrategias y llevaran a desencadenar el desarrollo local y regional. Los datos y fuentes de información que se utilizaron para realizar este análisis provienen principalmente del acervo municipal, Planes de Desarrollo anteriores, así como de instituciones oficiales encargadas de realizar estudios socio-demográficos como el Instituto Nacional de Estadística y Geografía, Concejo Nacional de Población, Concejo Estatal de Población, Comité de Planeación para el Desarrollo del Estado de México, Gobierno del Estado de México, Instituto de Geografía y Estadística Catastrál del Estado de México, etc