Detecção automática de vasos sanguíneos em imagens da retina para determinação do coeficiente AVR

Dissertação para obtenção do Grau de Mestre em Engenharia Biomédica

Seroprevalence and sociocultural conditionants of Chagas disease in school aged children of marginal zones of Asunción

Chagas disease is becoming a public health problem in Latin America due to the wide distribution, the high prevalence, the magnitude of the damage caused and the difficulties to control it. In Paraguay, the disease is mainly distributed in the departments of Paraguari, Cordillera and Central. Prevalence in marginal zones, where migrations from rural populations and endemic areas make possible the urbanization of the disease, has no been studied yet. This is a descriptive study with a cross-sectional sampling and a probabilistic system recruitment carried out in school aged children from marginal zones of Asuncion to determine the prevalence of Chagas' disease. Serological methods, parasite isolation and questionnaires were used to achieve the goals. Nine hundred and fifty three children were studied to determine the prevalence of Chagas' disease in marginal zones which was 1.4%.

O provérbio: um género marginal(izado)?!

Enquanto o provérbio, numa cultura de tradição oral, representa tipicamente o tesouro do conhecimento e a colecção das regras sociais ou jurídicas, na transição para a cultura escrita e na formulação científica dos saberes, esse género da Literatura Tradicional perde a sua autoridade nos círculos dominantes da sociedade. Ressalve-se, porém, o facto de, ao longo desse processo, haver ciclos.

Automatic delimitation of the clinical region of interest in ultra-wide field of view images of the retina

Retinal ultra-wide field of view images (fundus images) provides the visu-alization of a large part of the retina though, artifacts may appear in those images. Eyelashes and eyelids often cover the clinical region of interest and worse, eye-lashes can be mistaken with arteries and/or veins when those images are put through automatic diagnosis or segmentation software creating, in those cases, the appearance of false positives results. Correcting this problem, the first step in the development of qualified auto-matic diseases diagnosis programs can be done and in that way the development of an objective tool to assess diseases eradicating the human error from those processes can also be achieved. In this work the development of a tool that automatically delimitates the clinical region of interest is proposed by retrieving features from the images that will be analyzed by an automatic classifier. This automatic classifier will evaluate the information and will decide which part of the image is of interest and which part contains artifacts. The results were validated by implementing a software in C# language and validated through a statistical analysis. From those results it was confirmed that the methodology presented is capable of detecting artifacts and selecting the clin-ical region of interest in fundus images of the retina.

Plataforma online de partilha e comparação de software para análise de imagens da retina

Nesta Tese foi desenvolvida uma plataforma online multiutilizador, que tem como objetivo principal comparar algoritmos de análise de imagens para de-terminar o seu grau de eficácia. Um exemplo de aplicação é a comparação de algoritmos de análise de imagens da retina para deteção de drusas. A compa-ração é feita considerando um dos algoritmos como referência padrão e sobre o este são avaliados os restantes. O funcionamento da plataforma é semelhante à de um fórum, onde é possível a um utilizador criar tópicos publicando imagens e seu descritivo. Após a cria-ção do tópico qualquer utilizador pode visualizar o mesmo, dando a hipótese de comentar ou de acrescentar imagens processadas com os seus próprios al-goritmos de análise. Com o aumento de imagens processadas, obtém-se uma base de dados de algoritmos de análise de imagens sobre a qual é possível avaliar o seu grau de eficácia. A plataforma pretende também criar comunidades onde os utilizadores pos-sam interagir uns com os outros comentando sobre os tópicos, contribuindo assim para o melhoramento dos algoritmos. Deste modo, além de uma base de dados que qualquer utilizador pode usar, obtém-se uma fonte de informação disponibilizada por outros profissionais da área.

Managing marginal capital requirements in solvency II: Analysis of a real insurance portfolio

This thesis provides a complete analysis of the Standard Capital Requirements given by Solvency II for a real insurance portfolio. We analyze the investment portfolio of BPI Vida e Pensões, an insurance company affiliated with a Portuguese bank BPI, both at security, sub-portfolio and asset class levels. By using the Standard Formula from EIOPA, Total SCR amounts to 239M€. This value is mostly explained by Market and Default Risk whereas the former is driven by Spread and Concentration Risks. Following the methodology of Leblanc (2011), we examine the Marginal Contribution of an asset to the SCR which allows for the evaluation of the risks of each security given its characteristics and interactions in the portfolio. The top contributors to the SCR are Corporate Bonds and Term Deposits. By exploring further the composition of the portfolio, our results show that slight changes in allocation of Term and Cash Deposits have severe impacts on the total Concentration and Default Risks, respectively. Also, diversification effects are very relevant by representing savings of 122M€. Finally, Solvency II represents an opportunity for the portfolio optimization. By constructing efficient frontiers, we find that as the target expected return increases, a shift from Term Deposits/ Commercial Papers to Eurozone/Peripheral and finally Equities occurs.

Development of a fundus camera for analysis of photoreceptor directionality in the healthy retina

The Stiles-Crawford effect (SCE) is the well-known phenomenon in which the brightness of light perceived by the human eye depends upon its entrance point in the pupil. This physiological characteristic is due to the directional sensitivity of the cone photoreceptors in the retina and it displays an approximately Gaussian dependency which is altered in a number of pathologies. Retinal imaging, a widely spread clinical practice, may be used to evaluate the SCE and thus serve as diagnostic tool. Nonetheless, its use for such a purpose is still underdeveloped and far from the clinical reality. In this project a fundus camera was built and used to assess the cone photoreceptor directionality by reflective imaging of the retina in healthy individuals. The physical and physiological implications of its development are addressed in detail in the text: the optical properties of the human eye, illumination issues, acquiring a retinal image formed by the eye, among others. A full description of the developmental process that led to the final measuring method and results is also given. The developed setup was successfully used to obtain high quality images of the eye fundus and in particular the parafoveal cone photoreceptors. The SCE was successfully observed and characterized. Even though considerable improvements could be done to the measurement method, the project showed the feasibility of using retinal imaging to evaluate the SCE thus motivating its usage in a clinical environment.

Persistence of the embryonic lateral marginal vein: report of two cases

PURPOSE: Congenital venous malformations of the lower limbs represent a particular challenge for the vascular surgeon. Persistence of fetal veins is a rare malformation, and the most common is the persistence of the lateral marginal vein usually observed in patients with Klippel-Trenaunnay Syndrome. The persistence of this embryonic vein as an isolated venous malformation without the other characteristics of the Klippel-Trenaunnay Syndrome has not yet been reported. This paper describes two cases. METHODS: Two patients, a 17-year-old male patient and a 16-year-old female, have had since their birth a large venous trunk in the lateral aspect of the right leg and thigh. The limbs underwent duplex scanning and phlebography. The surgical removal of the lateral marginal vein was performed. RESULTS: Surgical treatment resulted in very good functional and aesthetic results. Follow-up at 26 months showed no evidence of varicose vein recurrence. CONCLUSIONS: To achieve good results, surgical intervention may be indicated in cases of orthopedic deformity, hemorrhage, symptomatic, and unaesthetic lesions.

Creaciones fitogenéticas en Maíz con respuesta adaptativa a la zona marginal

La creación de una población mejorada de maíz, requiere al menos tres etapas: a) La conformación de una "población original" con variabilidad genética, b) La selección preliminar de plantas y/o progenies, y c) La "evaluación" en condiciones de campo de las mejores descendencias integradas en poblaciones experimentales. Precisamente, este proyecto está dirigido a la creación de variedades con estabilidad de rendimientos en las condiciones ambientales de la zona centro-norte de la Provincia de Córdoba, en donde el maíz es el único cereal que se cosecha y una de las mejores posibilidades como forrajera estival. Se ha inscripto el cv. "MPB-FCA 856", un maíz colorado duro creado para la producción de granos, que en marcado déficit hídrico produce rendimientos superiores a otros cultivares. Actualmente se dispone de una variedad sintética, próxima a ser inscripta como una nueva creación. Con orientación al desarrollo de otros cultivares, se plantean las líneas de trabajo que se enumeran seguidamente: Tema 1. Maíz Colorado Duro: Obtención de una variedad sintética. Se iniciará la caracterización varietal a fin de inscribir en el Instituto Nacional de Semillas el nuevo cv. sintético formado por 10 líneas S1, que presenta altos rendimientos de granos. Tema 2. Maíz Forrajero: Desarrollo de un cultivar con aptitud para ser utilizado como forraje en planta. En la zona marginal el pastoreo de lotes de maíz es común tanto en años con pocas precipitaciones pluviales como en ciclos favorables, por cuanto es una muy buena alternativa de forraje estival tanto en verdeo, silo o diferido. Se dispone de líneas propias con características de alto macollamiento y capacidad de rebrote; se plantea su mejoramiento por caracteres que hacen a la calidad forrajera, tales como porcentaje de materia seca, palatabilidad, fibra bruta, etc. Tema 3. Mejora en la eficiencia de selección para tolerancia a estrés hídrico en maíz ( Zea mays L.). Aportar evidencia experimental que mejore la eficiencia de la selección, cuando los genotipos se dispersarán en una gama de ambientes contrastantes por su disponibilidad hídrica. Se comenzará un esquema de selección recurrente en ambientes con diferente disponibilidad hídrica, empleando características que permitan identificar genotipos tolerantes. Paralelamente se implementarán metodologías de evaluación del germoplasma disponible mediante pruebas de laboratorio y campo, a fin de detectar fuentes de genes para tolerancia al estrés hídrico.

Mecanismos de Fotopercepción No-Visual y Control Circadiano en la Retina Interna de Vertebrados en Condiciones Fisiológicas y en un Modelo Animal de Ceguera. Mechanisms of Non-visual Perception and Circadian Control in the Vertebrate Inner Retina under Physiological Conditions and in Animal Model of Blindness.

La retina juega un rol esencial en el funcionamiento del sistema circadiano de los vertebrados al ser la encargada de sensar las condiciones de iluminación ambiental que ajustan el reloj interno con el fotoperíodo exterior a través de un circuito no-visual. Este circuito es independiente de la vía de formación de imágenes e involucra a las células ganglionares retinianas (CGRs) que proyectan a varias estructuras no-visuales del cerebro; esta vía es la encargada de regular el reflejo pupilar, la sincronización de los ritmos diarios de actividad, el sueño y la supresión de melatonina pineal. La retina contiene además un reloj autónomo que genera ritmos diarios autosostenidos en distintas funciones bioquímicas y fisiológicas, que le confiere la capacidad de predecir el tiempo y anticiparse en su fisiología a los cambios lumínicos a lo largo del ciclo día-noche. Este laboratorio ha demostrado por 1ra vez que las CGRs de pollo poseen osciladores endógenos que generan variaciones diarias en la biosíntesis de fosfolípidos (Guido et al, J Neurochem. 2001; Garbarino et al., J Neurosci Res. 2004a) y de la hormona melatonina con niveles máximos durante el día (Garbarino et al., J Biol Chem 2004b). Aún más, cultivos primarios de CGRs responden a la luz a través de una cascada bioquímica de fototransducción similar a la de invertebrados y que involucra la activación de la enzima fosfolipasa C (PLC) (Contin et al., FASEB J 2006). Estos cultivos fueron obtenidos a estadios embrionarios muy tempranos en dónde solo las CGRs son postmitóticas y mayoritariamente maduras. A estos estadios, los cultivos expresan marcadores de especificación de células ganglionares (pax6, brn3), la proteina Gq y los fotopigmentos melanopsina y criptocromos con gran homología con marcadores descriptos para fotorreceptores rabdoméricos de invertebrados (Contin et al, 2006). Recientemente comenzamos a investigar la percepción de luz en pollos GUCY1*, un modelo de ceguera, en animales que carecen de células fotorreceptoras-conos y bastones-funcionales. Resultados preliminares indicarían que la retina interna, y potencialmente las CGRs de estos animales conservarían la capacidad de responder a la luz regulando el reflejo pupilar y sincronizando los ritmos diarios de alimentación. La convergencia de osciladores y fotopigmentos en la población de CGRs podría contribuir al control temporal de la fisiología del organismo y regulación de funciones no-visuales. Son objetivos de este proyecto: a) Investigar el rol de las CGRs en el sistema circadiano estudiando: i- su habilidad para sintetizar melatonina y, su regulación por luz y dopamina; ii- su capacidad fotorreceptora intrínseca, investigando la presencia de fotopigmentos y componentes de la cascada de fototransducción fundamentalmente la vía de los fosfoinosítidos y la activación de PLC, mediante ensayos moleculares, bioquímicos y farmacológicos; b) Extender estos estudios a cultivos primarios de CGRs inmunopurificadas midiendo la respuesta a la luz sobre la síntesis de melatonina, y los niveles de los mensajeros 2rios Ca2+ y AMP cíclico, la inducción de genes tempranos y la regulación de la actividad NAT, enzima clave en la síntesis de melatonina; y c) Investigar la percepción de luz en pollos GUCY1*(ciegos), sobre distintas funciones no-visuales tales como el reflejo pupilar, la sincronización de los ritmos diarios de alimentación, la síntesis de melatonina y la expresión génica en animales expuestos a estimulación lumínica de distintas intensidades y longitudes de onda. Estos estudios permitirán construir el espectro de acción de la respuesta a la luz en los pollos ciegos a fin de identificar el/los fotopigmentos intervinientes en este fenómeno. Este proyecto profundizará el conocimiento sobre la capacidad fotorreceptora-no visual de la retina interna y particularmente de las CGRs, de la naturaleza de la cascada bioquímica que opera en las mismas y de los mecanismos de regeneración del cromóforo utilizado.

Einfluss von ZNS-Verletzung auf die m-RNA-Expression der Protease-Aktivierenden Rezeptoren (PARs) und Indentifizierung eines Interaktionspartners für PAR-2 in Retina

Protease-activated receptor, optic nerve crush, focal ischemia, protein-protein interaction, alpha crystallin A

Subsidizing extra jobs : the economics of marginal employment subsidies

Employment subsidies, wage subsidies, unemployment, displacement

Diet of the ichthyofauna associated with marginal vegetation of a mangrove forest in southeastern Brazil

The objective of this study was to analyze the diet of fish species that use the mangrove vegetation for shelter and feeding in a river southeastern Brazil. The fieldwork, including collecting and underwater observations, was carried out in the dry (July and August 2004) and in the rainy season (February and March 2005) in order to assess the existence of seasonal variation in the diets. Seven kinds of food items were consumed, two of plant origin and five of animal origin. Crustaceans predominated in the diet of most species, either in the form of unidentified fragments or discriminated in eight groups. The predominance of species using mainly a single food source (crustaceans, principally Ostracoda and Tanaidacea) and the existence of seasonal variation in the diets of some species became very evident in the analysis food niche breadth, with a predominance of dietary specialists. In the Rio da Fazenda mangrove, the submersed marginal vegetation was used by the ichthyofauna as a locale for foraging, and principally as cover by bottom-feeding species. These species may be using the vegetation for protection from aerial and aquatic predators, or even from the pull of the current during the turn of the tide. In the study area, the great diversity of crustaceans constitutes an important food source for most fish species which adjusted their diet according to seasonal changes in food availability and to interactions with other species.

Morphological and functional study of the marginal sphincter of the sea anemones Phymactis clematis and Aulactinia marplatensis from intertidal of Mar del Plata, Argentina

It was made the characterization of marginal sphincter to the species Phymactis clematis (Drayton in Dana, 1849) and Aulactinia marplatensis (Zamponi, 1977), from intertidal ecosystem through their morphogical and functional study. The species P. clematis has a circumscript sphincter of palmate type. This muscle is constituted by a mesogloeal axis and several mesogloeal subaxes. Axis as well as subaxes give a support to the endoderm which border is smooth. Aulactinia marplatensis has a circunscript sphincter pinnate type. The axis has a truncated cone shape while in P. clematis the shape is cylindrical on its origin and it is bifurcated at the end. Both species experiments were carried out using the isolated muscles. They were stimulated at increasing KCl concentrations ranging from 20 to 200 mM. The results were analysed in the form of dose-response curves expressed in tension in grams force vs concentration. Contractil force increases in a sigmoid form to increasing KCl concentrations. The correlation between morphology and function and the differences shown in both species would be related to their intertidal distribution.

Una estimación del coste marginal en bienestar del sistema impositivo en España

Actual tax systems do not follow the normative recommendations of yhe theory of optimal taxation. There are two reasons for this. Firstly, the informational difficulties of knowing or estimating all relevant elasticities and parameters. Secondly, the political complexities that would arise if a new tax implementation would depart too much from current systems that are perceived as somewhat egalitarians. Hence an ex-novo overhaul of the tax system might just be non-viable. In contrast, a small marginal tax reform could be politically more palatable to accept and economically more simple to implement. The goal of this paper is to evaluate, as a step previous to any tax reform, the marginal welfare cost of the current tax system in Spain. We do this by using a computational general equilibrium model calibrated to a point-in-time micro database. The simulations results show that the Spanish tax system gives rise to a considerable marginal excess burden. Its order of magnitude is of about 0.50 money units for each additional money unit collected through taxes.