Optical coherence tomography in patients undergoing cataract surgery

ABSTRACTPurpose:To assess the ability of spectral domain optical coherence tomography (SD-OCT) to diagnose macular changes pre- and post-cataract surgery and to identify changes in central foveal thickness (CFT) relative to age, sex, and presence of concomitant ophthalmic pathologies, for a period of 6 months post-surgery.Methods:A prospective study of patients evaluated by SD-OCT within 5 h before surgery at 7, 30, 60, 90, and 180 days post-op, with respect to CFT and presence of maculopathy.Results:Ninety-eight eyes of 98 patients were evaluated, with the following mean results: age = 71.4 years, pre-op VA = 0.27 logMAR, and final VA = 0.73 logMAR. There were 21 eyes in patients with diabetes mellitus (DM) and 10 eyes with age-related macular degeneration (AMD), three with epiretinal membrane, and four with glaucoma. Sixty eyes had no other ophthalmic-related pathologies (NOO), and had a mean pre-op CFT of 222 μm, which progressively increased up to the 60thday post-op, reaching a mean of 227.2 μm. No pseudophakic cystoid macular edema was observed. The mean CFT was statistically significantly different (p<0.001) between NOO and diabetic patients from 30 days post-op. Four eyes presented with preoperative diagnosis of AMD as measured by ophthalmoscopy. After completion of the OCT, which was performed within 5 h before surgery, six additional patients were found to have AMD. Of the 98 total eyes, 10 were diagnosed with maculopathy only by OCT exam. Binocular indirect ophthalmoscopy (BIO) was unable to detect such changes.Conclusion:OCT diagnosed preoperative maculopathies in 21.4% of the patients, and was more effective than BIO (11.2%). OCT showed a progressive increase in CFT in diabetics up to 180 days post-operatively, as well as greater CFT in male patients and patients older than 70 years

Generalized linear mixing model accounting for endmember variability

Endmember variability is an important factor for accurately unveiling vital information relating the pure materials and their distribution in hyperspectral images. Recently, the extended linear mixing model (ELMM) has been proposed as a modification of the linear mixing model (LMM) to consider endmember variability effects resulting mainly from illumination changes. In this paper, we further generalize the ELMM leading to a new model (GLMM) to account for more complex spectral distortions where different wavelength intervals can be affected unevenly. We also extend the existing methodology to jointly estimate the variability and the abundances for the GLMM. Simulations with real and synthetic data show that the unmixing process can benefit from the extra flexibility introduced by the GLMM

Study of design issues in a prototype lower-limb prosthesis - proof-of-concept in a 3D printed model

Dissertação de Mestrado Integrado em Engenharia Biomédica Ramo de Biomateriais, Reabilitação e BiomecânicaThe amputation of one or both lower limbs, which can be brought on by trauma, diabetes, or other vascular diseases, is an increasingly common occurrence, especially due to the increase in the number of cases of diabetes in the developed world. In Portugal alone 1300 amputations each year are attributed to diabetes. These amputations severely impact the mobility, self-esteem, and quality of life of the patients, a situation that can be alleviated via the installation of a lower limb prosthesis. Sadly, these prostheses are not yet capable of completely emulating a sound limb in an affordable fashion. In this dissertation, state-of-the-art research was carried out regarding the mechanics of human gait, both healthy and prosthetic. An investigation regarding the state-of-the-art research was also carried out regarding lower-limb prostheses, their evolution, mechanics, and prospects, as well as additive manufacturing techniques, and how they can be crucial to the development of affordable prostheses. Special attention was provided to the study of the leading edge of prostheses research, namely active prostheses, capable of generating and introducing energy into the human gait, rather than simply acting as passive devices. This dissertation follows up on previous work carried out in the BioWalk Project of Universidade do Minho’s BiRDLab: “Prosthetic Devices and Rehabilitation Solutions for the Lower Limbs Amputees”. This work consisted of the development of an active lower-limb prosthesis prototype, with the goal of providing an affordable, but functional, prosthesis for future testing with patients. However, the resulting prototype was laden with issues, such as excessive weight and an underpowered motor. As such, this work set out to identify these issues, design, implement and test modifications to the prosthesis to produce a satisfying prototype. Given the limited resources and facilities available, it was decided to work on a smaller model prosthesis installed in a bipedal robot, the DARwIn-OP, using it as proof-of-concept for modifications to be implemented in the BiRDLab prosthesis. Modifications were successfully implemented, chiefly among them a planetary gear-based reductor and a novel attachment mechanism built using additive manufacturing techniques. It is possible to conclude that there is a great potential in the implementation of additive manufacturing techniques in the development of affordable prosthesis.A amputação de um ou ambos os membros inferiores, que pode ser causada por trauma, diabetes, ou outras doenças vasculares, é um evento cada vez mais frequente, especialmente devido ao aumento do número de casos de diabetes no mundo desenvolvido. Em Portugal, 1300 amputações são atribuídas aos diabetes todos os anos. Estas amputações influenciam negativamente a mobilidade, autoestima e qualidade de vida dos pacientes, mas estes efeitos podem ser minimizados através da instalação de uma prótese de membro inferior. Infelizmente, estas próteses ainda não são capazes de emular completamente um membro saudável de forma económica. Nesta dissertação, um estado da arte do caminhar humano foi realizado, tendo em atenção o funcionamento deste, quer em sujeitos saudáveis ou amputados. Um estado da arte também foi realizado relativamente às próteses de membros inferiores, a sua evolução, funcionamento, e perspetivas futuras, e também relativamente a técnicas de fabrico aditivas e a forma como estas podem ser aplicadas em próteses acessíveis. Tomou-se atenção especial ao estudo das próteses ativas, capazes de gerar e introduzir energia no caminhar, ao invés das próteses passivas tradicionais. Esta dissertação baseia-se em trabalho prévio ao abrigo do projeto BioWalk do laboratório BiRDLab da Universidade do Minho: “Dispositivos prostéticos e soluções de reabilitação para amputados dos membros inferiores”. Este trabalho consistiu no desenvolvimento de um protótipo de prótese de membro inferior ativa, com o objetivo de criar uma prótese de baixo custo para testes em pacientes. No entanto, o protótipo produzido possuí vários problemas, tais como peso excessivo e um motor subdimensionado. Assim sendo, este trabalho propôs-se a identificar estes problemas e a desenhar, implementar, e testar modificações. Tendo em conta os limitados recursos disponíveis, decidiu-se trabalhar numa prótese modelo mais pequena, instalada num robô bipedal, o DARwIN-OP, e a usá-la para testar modificações a implementar na prótese do BiRDLab. As modificações foram implementadas com sucesso, especialmente um redutor de engrenagens planetárias e um novo método de conectar a prótese, usando técnicas de fabrico aditivas

On the Lagrange and Markov Dynamical Spectra for Geodesic Flows in Surfaces with Negative Curvature

We consider the Lagrange and the Markov dynamical spectra associated to a geodesic flow on a surface of negative curvature. We show that for a large set of real functions on the unit tangent bundle and for typical metrics with negative curvature and finite volume, both the Lagrange and the Markov dynamical spectra have non-empty interior

Finite element simulation of additive manufacturing with enhanced accuracy

Tesi en modalitat de compendi de publicacionsThis thesis develops numerical methods to improve the accuracy and computational efficiency of the part-scale simulation of Additive Manufacturing (AM) (or 3D printing) metal processes. AM is characterized by multiple scales in space and time, as well as multiple complex physics that occur in three-dimensional growing-in-time geometries, making its simulation a remarkable computational challenge. To this end, the computational framework is built by addressing four key topics: (1) a Finite Element technology with enhanced stress/strain accuracy including the incompressible limit; (2) an Adaptive Mesh Refinement (AMR) strategy accounting for geometric and solution accuracies; (3) a coarsening correction strategy to avoid loss of information in the coarsening AMR procedure, and (4) a GCodebased simulation tool that uses the exact geometric and process parameters data provided to the actual AM machinery. In this context, the mixed displacement/deviatoric-strain/pressure u/e/p FE formulation in (1) is adopted to solve incompressible problems resulting from the isochoric plastic flow in the Von Mises criterion typical of metals. The enhanced stress/strain accuracy of the u/e/p over the standard and u/p FE formulations is verified in a set of numerical benchmarks in iso-thermal and non-isothermal conditions. A multi-criteria AMR strategy in (2) is used to improve computational efficiency while keeping the number of FEs controlled and without the strictness of imposing the commonly adopted 2:1 balance scheme. Avoiding this enables to use high jumps on the refinement level between adjacent FEs; this improves the mesh resolution on the region of interest and keeps the mesh coarse elsewhere. Moving the FE solution from a fine mesh to a coarse mesh introduces loss of information. To prevent this, a coarsening correction strategy presented in (3) restores the fine solution in the coarse mesh, providing computational cost reduction and keeping the accuracy of the fine mesh solution accuracy. Lastly, design flexibility is one of the main advantages of AM over traditional manufacturing processes. This flexibility is observed in the design of complex components and the possibility to change the process parameters, i.e. power input, speed, waiting pauses, among others, throughout the process. In (4) a GCode-based simulation tool that replicates the exact path travelled and process parameters delivered to the AM machiney is developed. Furthermore, the GCode-based tool together with the AMR strategy allows to automatically generate an embedded fitted cartesian FE mesh for the evolving domain and removes the challenging task of mesh manipulation by the end-user. The FE framework is built on a high-performance computing environment. This framework enables to accelerate the process-to-performance understanding and to minimize the number of trial-and-error experiments, two key aspects to exploit the technology in the industrial environment.Esta tesis tiene como objetivo desarrollar métodos numéricos para mejorar la precisión y eficiencia computacionales en simulaciones de piezas fabricadas mediante Manufactura Aditiva (MA), también conocida como Impresión 3D. La manufactura aditiva es un problema complejo que involucra múltiples fenómenos físicos, que se desarolla en múltiples escalas, y cuya geometría evoluciona en el tiempo. Para tal fin, se plantean cuatro objetivos: (1) Desarrollo de una tecnología de elementos finitos para capturar con mayor precisión tanto tensiones como deformaciones en casos en el que el material tiene comportamiento isocórico; (2) Una estrategia de adaptividad de malla (AMR), que busca modificar la malla teniendo en cuenta la geometría y los errores en la solución numérica; (3) Una estrategia para minimizar la aproximación numérica durante el engrosamiento (coarsening) de la malla, crucial en la reducción de tiempos de cómputo en casos de piezas de grandes dimensiones; y (4) Un marco de simulación basado en la lectura de ficheros GCode, ampliamente usado por maquinaria de impresión en procesos de manufactura aditiva, un formato que no sólo proporciona los datos asociados a la geometría, sino también los parámetros de proceso. Con respecto a (1), esta tesis propone el uso de una formulación mixta en desplazamientos /deformación-desviadora / presión (u/e/p), para simular la deposición de materiales con deformación inelástica isocórica, como ocurre en los metales. En cuanto a la medición de la precisión en el cálculo de las tensiones y las deformaciones, en esta tesis se realiza un amplio número de experimentos tanto en condiciones isotérmicas como no isotérmicas para establecer una comparativa entre las dos formulaciones mixtas, u/e/p y u/p. Con respecto a (2), para mejorar la eficiencia computacional manteniendo acotado el número total de elementos finitos, se desarrolla una novedosa estrategia multicriterio de refinamiento adaptativo. Esta estrategia no se restringe a mallas con balance 2:1, permitiendo así tener saltos de nivel mayores entre elementos adyacentes. Por otra parte, para evitar la pérdida de información al proyectar la solución a mallas más gruesas, se plantee una corrección en (3), que tiene como objetivo recuperar la solución de la malla fina, garantizando así que la malla gruesa conserve la precisión obtenida en la malla fina. El proceso de manufactura aditiva se distingue por su gran flexibilidad comparándolo con otros métodos tradicionales de manufactura. Esta flexibilidad se observa en la posibilidad de construir piezas de gran complejidad geométrica, optimizando propiedades mecánicas durante el proceso de deposición. Por ese motivo, (4) se propone la lectura de ficheros en formato GCode que replica la ruta exacta del recorrido del láser que realiza la deposición del material. Los ingredientes lectura de comandos escritos en lenguaje Gcode, multicriterio de adaptividad de malla y el uso de mallas estructuradas basadas en octrees, permiten capturar con gran precisión el dominio discreto eliminando así la engorrosa tarea de generar un dominio discreto ad-hoc para la pieza a modelar. Los desarrollos de esta tesis se realizan en un entorno de computación de altas prestaciones (HPC) que permite acelerar el estudio de la ejecución del proceso de impresión y por ende reducir el número de experimentos destructivos, dos aspectos clave que permiten explorar y desarrollar nuevas técnicas en manufactura aditiva de piezas industriales.Postprint (published version

Art and Technology: coherence, connectedness, and the integrative field

Merged with duplicate record 10026.1/690 on 03.04.2017 by CS (TIS)This thesis is a theoretical and practical intervention in the field of art and technology. It proceeds from the re-examination of four specific domains that in the past 40 years have considerably informed the invention of new aesthetic forms. They are: art, science, nature and technology. We have identified that each one of these domains and the way they inform one another reflects the influence of a Western analytical tradition based on fragmentation, dichotomies and dualities. In consequence of this, art of the last decades has suffered from a sort of mechanistic thought which results from a predominantly weary aesthetic model, founded in dualities such as: object/process, form/behaviour, meaning/information. The main question that the present study addresses is how to overcome this predominantly reductionist inheritance and to develop an aesthetic model able to interconnect in an integrative fashion those disparate domains, respective discourses and practices? The answer to this question, developed throughout this thesis, is an aesthetic principle built upon the notions of resonance, coherence and field models, rooted in an integrative view of living organisms based on the theory of biophotons. This constitutes the main contribution of the thesis to new knowledge. The theoretical approach of this thesis is developed upon the revision of the concept of form, supported by a Gestalt analysis as provided by Rudolf Arnheim, and has involved the consideration of the ideas of Gilbert Simondon (the concept of "concretisation") and Vilem Flusser (the concept of "apparatus"), in order to gain a deeper insight into the nature of technology. In conclusion, the practice-based methodology of this thesis has been to develop artworks based on the confluence of living organisms (plants) and artificial systems in order to permit empirical observation and reflection on the proposed theory. The major outcome of the practice is the artwork "Breathing", a hybrid creature made of a living organism (a plant) and an artificial system. The creature responds to its environment through movement, light and the noise of its mechanical parts and interacts with the observer through his/her act of breathing. This work is the result of an investigation into plants as sensitive agents for the creation of art. The intention was to explore new forms of artistic experience through the dialogue of natural and artificial processes

Family income, food prices, and household purchases of fruits and vegetables in Brazil

OBJETIVO: Analisar a influência da renda familiar e do preço de alimentos sobre a participação de frutas e hortaliças dentre os alimentos adquiridos pelas famílias brasileiras. MÉTODOS: Foram utilizados dados da Pesquisa de Orçamentos Familiares realizada pelo Instituto Brasileiro de Geografia e Estatística, com amostra probabilística de 48.470 domicílios brasileiros entre 2002 e 2003. A participação de frutas e hortaliças no total de aquisições de alimentos foi expressa como percentual do total de calorias adquiridas e como calorias provenientes desses alimentos ajustadas para o total de calorias adquirido. Empregaram-se técnicas de análise de regressão múltipla para estimação de coeficientes de elasticidade, controlando-se variáveis sociodemográficas e preço dos demais alimentos. RESULTADOS: Observou-se aumento da participação de frutas e hortaliças no total de aquisições de alimentos com a diminuição de seu próprio preço ou com o aumento da renda. A diminuição do preço de frutas e hortaliças em 1 por cento aumentaria sua participação em 0,79 por cento do total calórico; o aumento de 1 por cento na renda familiar aumentaria essa participação no total calórico em 0,27 por cento. O efeito da renda tendeu a ser menor nos estratos de maior renda. CONCLUSÕES: A redução do preço de frutas e hortaliças, tanto pelo apoio à cadeia de produção dos alimentos quanto por medidas fiscais, é um promissor instrumento de política pública capaz de aumentar a participação desses alimentos na dieta brasileiraOBJECTIVE: To analyze the influence of family income and food prices on the participation of fruits and vegetables in the food purchases of Brazilian households. METHODS: Data analyzed refers to the Household Budget Survey conducted by the Instituto Brasileiro de Geografia e Estatística on a probabilistic sample of 48,470 Brazilian households between 2002 and 2003. Fruit and vegetable participation in total food purchases was expressed as a percentage of total calories purchased and as calories from fruit and vegetables adjusted for total calories purchased. A multiple regression analysis was employed to estimate elasticity coefficients, controlling for sociodemographic variables and price of other foods. RESULTS: Fruit and vegetable participation in total food purchases increased as the price of these foods decreased, or as income increased. A 1 per cent decrease in the price of fruit and vegetables would increase their participation by 0.79 per cent, whereas a 1 per cent increase in family income would increase participation by 0.27 per cent. The effect of income tended to be smaller among higher income strata. CONCLUSIONS: Reducing the price of fruit and vegetables, either by supporting their production or through fiscal measures, is a promising public policy instrument, capable of increasing the participation of these foods in the diet of the Brazilian populationFAPESP nº 2007/00064-