Design of a fiber-phantom detector for quality assurance in Proton Therapy

Tese de mestrado, Engenharia Física , Universidade de Lisboa, Faculdade de Ciências, 2022The quality assurance of a beam is a key step in delivering a dose to a patient in a safe and accurate manner, with international recommendations for proton therapy being established by the American Association of Physicists in Medicine. This radiotherapy modality, in contrast to others, permits a greater accuracy by creating a high dose region, minimizing damage to the surrounding tissue. Depending on the delivery technique chosen there are several parameters that must be checked regularly, be it daily, weekly, monthly or annually. The detectors used in these procedures must be able to measure the in-depth energy distribution with very good spatial-resolution. In this project the prototype of a fiber-phantom for quality control in particle radiotherapy is to be designed using a detector currently constructed with scintillating plastic optical fibers juxtaposed in a frame. The dimensions of the fibers provide a high transversal spatial resolution and their composition allows them to be tissue equivalent. This phantom will be built with a modular structure consisting of a central module where the detector is embedded, to which additional volumes can be added to increase the size of the phantom, as well as changing the position of the detector, enabling it to measure the dose profile at different depths. Different designs will be tested in Monte Carlo simulations to ascertain the one most adequate one. As the fiber-phantom requires testing a 50 kV X-ray tube will be characterized through the use of other dosimeters (ionization chambers and radiochromic film) so it can be inserted into the simulations. A delay in the detector readout availability meant that practical results could not be achieved, nevertheless the photon source to be used was characterized and used in the study of the possible structures for the fiber-phantom through its inclusion in simulations. A proton source was also simulated to test the effectiveness of the detector setups, from which resulted the need to propose alternative configurations for the central module

Ocorrência de xenótimo em amostras aluvionares da região centro-leste de Portugal, Zona Centro Ibérica-Zona de Ossa Morena

Foi identificado, possivelmente pela primeira vez em Portugal, xenótimo aluvionar em concentrados de bateia colhidos numa campanha de prospecção de terras raras desenvolvida pelo ex-IGM no centro-leste deste país. O xenótimo ocorre em grãos sub-rolados de dimensão média =250um, em concentrações mais significativas em Nisa, Stº António das Areias e Marvão. A geologia regional e o cortejo mineral das amostras sugerem proveniência do xenótimo dos maciços graníticos de Penamacor e Nisa e ainda das Arcoses da Beira Baixa e níveis de cascalheiras plio-plistocénicas com intercalações argilo-arenosas

Nivelamento de dados para corrigir efeitos de bordadura, provenientes de diferentes levantamentos de prospeção geoquímica

ABSTRACT: The existence of a large number of chemical analyses resulting from decades of geochemical exploration campaigns, yields huge numbers of analytical results produced with different analytical methods, sampling protocols and sampling means. Therefore, it is necessary to level these analytical results to make them comparable and thus take advantage of the potential of geochemical information from contiguous areas. In this study, a levelling technique was used on geochemical datasets of tested bands between the 1:25 000 scale maps, 293/294 and 305/306 sheets, respectively, from the Beira Baixa region where stream sediments were sampled during a project for rare earth elements exploration. These samples were analysed for lanthanum by the same analytical methods and in the same laboratory, but in different periods and the border effects were observed. These levelling techniques must be adapted to the data to be compared and in the present case the disappearance of the border effect of the analytical results of 293/294 and 305/306 topographic sheets was observed.RESUMO: A existência de um grande número de análises químicas resultantes de décadas de campanhas de prospeção geoquímica produz um grande número de resultados analíticos com diferentes métodos analíticos, protocolos e meios de amostragem. Nesse sentido, é necessário nivelar estes resultados analíticos para torná-los comparáveis e assim aproveitar o potencial da informação geoquímica de áreas contíguas. Neste estudo foi utilizada uma técnica de nivelamento de dados de geoquímica baseada em bandas testadas com larguras variadas entre os mapas à escala 1:25 000, 293/294 e 305/306, respetivamente, da região da Beira Baixa. Nestes, foram amostrados sedimentos de corrente durante um projeto de prospeção de Elementos de Terras Raras. Essas amostras foram analisadas para lantânio pelos mesmos métodos analíticos e no mesmo laboratório, mas em períodos diferentes e foram observados efeitos de bordadura. As técnicas de nivelamento foram adaptadas aos dados a comparar e observou-se o desaparecimento do efeito bordadura dos resultados analíticos entre as cartas topográficas 293/294 e 305/306.info:eu-repo/semantics/publishedVersio

Widefield swept source optical coherence tomography for the monitoring of choroidal infiltrates

Publisher Copyright: © 2024Choroidal Infiltrates (Cis) detection is traditionally done using invasive imaging. We herein report the usage of topographic choroidal thickness maps (ChT maps) and en face swept-source Optical Coherence Tomography (OCT) as a rapid and non-invasive technique to monitor Cis in a patient with Chronic Lymphocytic Leukemia.publishersversionpublishe

Quasi-static Flow Model for Predicting the Extreme Values of Air Pocket Pressure in Draining and Filling Operations in Single Water Installations

[EN] Inertial models have been used by researchers to simulate the draining and filling processes in water pipelines, based on the evolution of the main hydraulic and thermodynamic variables. These models use complex differential equations, which are solved using advanced numerical codes. In this study, a quasi-static flow model is developed to study these operations in hydraulic installations. The quasi-static flow model represents a simplified formulation compared with inertial flow models, in which its numerical resolution is easier because only algebraic equations must be addressed. Experimental measurements of air pocket pressure patterns were conducted in a 4.36 m long single pipeline with an internal diameter of 42 mm. Comparisons between measured and computed air pocket pressure oscillations indicate how the quasi-static flow model can predict extreme values of air pocket pressure for experimental runs, demonstrating the possibility of selecting stiffness and pipe classes in actual pipelines using this model. Two case studies were analysed to determine the behaviour of the quasi-static flow model in large water pipelines.This research and the APC were funded by the Comision Nacional de Investigacion Cientifica y Tecnologica (Conicyt), grant number 1180660.Coronado-Hernández, ÓE.; Fuertes-Miquel, VS.; Mora-Meliá, D.; Salgueiro, Y. (2020). Quasi-static Flow Model for Predicting the Extreme Values of Air Pocket Pressure in Draining and Filling Operations in Single Water Installations. Water. 12(3):1-16. https://doi.org/10.3390/w12030664S116123Abreu, J., Cabrera, E., Izquierdo, J., & García-Serra, J. (1999). Flow Modeling in Pressurized Systems Revisited. Journal of Hydraulic Engineering, 125(11), 1154-1169. doi:10.1061/(asce)0733-9429(1999)125:11(1154)Izquierdo, J., Fuertes, V. S., Cabrera, E., Iglesias, P. L., & Garcia-Serra, J. (1999). Pipeline start-up with entrapped air. Journal of Hydraulic Research, 37(5), 579-590. doi:10.1080/00221689909498518Simpson, A. R., & Wylie, E. B. (1991). Large Water‐Hammer Pressures for Column Separation in Pipelines. Journal of Hydraulic Engineering, 117(10), 1310-1316. doi:10.1061/(asce)0733-9429(1991)117:10(1310)Zhou, L., Liu, D., Karney, B., & Wang, P. (2013). Phenomenon of White Mist in Pipelines Rapidly Filling with Water with Entrapped Air Pockets. Journal of Hydraulic Engineering, 139(10), 1041-1051. doi:10.1061/(asce)hy.1943-7900.0000765Zhou, L., & Liu, D. (2013). Experimental investigation of entrapped air pocket in a partially full water pipe. Journal of Hydraulic Research, 51(4), 469-474. doi:10.1080/00221686.2013.785985Coronado-Hernández, O., Fuertes-Miquel, V., Besharat, M., & Ramos, H. (2017). Experimental and Numerical Analysis of a Water Emptying Pipeline Using Different Air Valves. Water, 9(2), 98. doi:10.3390/w9020098Coronado-Hernández, Ó. E., Besharat, M., Fuertes-Miquel, V. S., & Ramos, H. M. (2019). Effect of a Commercial Air Valve on the Rapid Filling of a Single Pipeline: a Numerical and Experimental Analysis. Water, 11(9), 1814. doi:10.3390/w11091814Vasconcelos, J. G., & Wright, S. J. (2008). Rapid Flow Startup in Filled Horizontal Pipelines. Journal of Hydraulic Engineering, 134(7), 984-992. doi:10.1061/(asce)0733-9429(2008)134:7(984)Fuertes-Miquel, V. S., Coronado-Hernández, O. E., Iglesias-Rey, P. L., & Mora-Meliá, D. (2018). Transient phenomena during the emptying process of a single pipe with water–air interaction. Journal of Hydraulic Research, 57(3), 318-326. doi:10.1080/00221686.2018.1492465Fuertes-Miquel, V. S., Coronado-Hernández, O. E., Mora-Meliá, D., & Iglesias-Rey, P. L. (2019). Hydraulic modeling during filling and emptying processes in pressurized pipelines: a literature review. Urban Water Journal, 16(4), 299-311. doi:10.1080/1573062x.2019.1669188Besharat, M., Coronado-Hernández, O. E., Fuertes-Miquel, V. S., Viseu, M. T., & Ramos, H. M. (2018). Backflow air and pressure analysis in emptying a pipeline containing an entrapped air pocket. Urban Water Journal, 15(8), 769-779. doi:10.1080/1573062x.2018.1540711Besharat, M., Coronado-Hernández, O. E., Fuertes-Miquel, V. S., Viseu, M. T., & Ramos, H. M. (2019). Computational fluid dynamics for sub-atmospheric pressure analysis in pipe drainage. Journal of Hydraulic Research, 58(4), 553-565. doi:10.1080/00221686.2019.1625819Laanearu, J., Annus, I., Koppel, T., Bergant, A., Vučković, S., Hou, Q., … van’t Westende, J. M. C. (2012). Emptying of Large-Scale Pipeline by Pressurized Air. Journal of Hydraulic Engineering, 138(12), 1090-1100. doi:10.1061/(asce)hy.1943-7900.0000631Tijsseling, A. S., Hou, Q., Bozkuş, Z., & Laanearu, J. (2015). Improved One-Dimensional Models for Rapid Emptying and Filling of Pipelines. Journal of Pressure Vessel Technology, 138(3). doi:10.1115/1.4031508Malekpour, A., Karney, B. W., & Nault, J. (2016). Physical Understanding of Sudden Pressurization of Pipe Systems with Entrapped Air: Energy Auditing Approach. Journal of Hydraulic Engineering, 142(2), 04015044. doi:10.1061/(asce)hy.1943-7900.0001067Noto, L., & Tucciarelli, T. (2001). DORA Algorithm for Network Flow Models with Improved Stability and Convergence Properties. Journal of Hydraulic Engineering, 127(5), 380-391. doi:10.1061/(asce)0733-9429(2001)127:5(380)Zhou, L., Liu, D., & Ou, C. (2011). Simulation of Flow Transients in a Water Filling Pipe Containing Entrapped Air Pocket with VOF Model. Engineering Applications of Computational Fluid Mechanics, 5(1), 127-140. doi:10.1080/19942060.2011.11015357SaemI, S., Raisee, M., Cervantes, M. J., & Nourbakhsh, A. (2018). Computation of two- and three-dimensional water hammer flows. Journal of Hydraulic Research, 57(3), 386-404. doi:10.1080/00221686.2018.1459892Apollonio, C., Balacco, G., Fontana, N., Giugni, M., Marini, G., & Piccinni, A. (2016). Hydraulic Transients Caused by Air Expulsion During Rapid Filling of Undulating Pipelines. Water, 8(1), 25. doi:10.3390/w8010025Wang, L., Wang, F., Karney, B., & Malekpour, A. (2017). Numerical investigation of rapid filling in bypass pipelines. Journal of Hydraulic Research, 55(5), 647-656. doi:10.1080/00221686.2017.1300193Coronado-Hernández, O. E., Fuertes-Miquel, V. S., Besharat, M., & Ramos, H. M. (2018). Subatmospheric pressure in a water draining pipeline with an air pocket. Urban Water Journal, 15(4), 346-352. doi:10.1080/1573062x.2018.1475578Ramezani, L., Karney, B., & Malekpour, A. (2016). Encouraging Effective Air Management in Water Pipelines: A Critical Review. Journal of Water Resources Planning and Management, 142(12), 04016055. doi:10.1061/(asce)wr.1943-5452.0000695Martins, S. C., Ramos, H. M., & Almeida, A. B. (2015). Conceptual analogy for modelling entrapped air action in hydraulic systems. Journal of Hydraulic Research, 53(5), 678-686. doi:10.1080/00221686.2015.1077353Zhou, F., Hicks, F. E., & Steffler, P. M. (2002). Transient Flow in a Rapidly Filling Horizontal Pipe Containing Trapped Air. Journal of Hydraulic Engineering, 128(6), 625-634. doi:10.1061/(asce)0733-9429(2002)128:6(625)Cabrera, E., Abreu, J., Pérez, R., & Vela, A. (1992). Influence of Liquid Length Variation in Hydraulic Transients. Journal of Hydraulic Engineering, 118(12), 1639-1650. doi:10.1061/(asce)0733-9429(1992)118:12(1639

Pantóporos áporos: miseria y exuberancia de la discursividad en la Helena de Eurípides

El presente texto propone una lectura en clave filosófica y metateatral de la Helena de Eurípides. En primer lugar, destaca los problemas de carácter ontológico emplazados en el centro de la obra: la no correspondencia entre apariencia y realidad, y la falibilidad del lógos. En segunda instancia, desvela la reflexión enmascarada sobre su propio oficio que el trágico esconde en el texto. Su rol de creador y artífice de discursos verosímiles se ve reflejado en el personaje de Helena, que emula el papel del poeta omnisciente jugando a levantar ficciones en el aire. Puede decirse, pues, que la lacedemonia, consciente del poder de la palabra y la ambigüedad que ésta encierra, aparece en el texto como un alter ego del propio Eurípides a través del cual podemos acceder a la concepción que éste tenía sobre el teatro.Al margen de este análisis, añadimos también una reflexión propia al respecto de la tesis antibelicista que insiste en ver en la obra de Eurípides un canto a la paz. A nuestro entender, el trágico lamenta la guerra en tanto que a menudo constituye una consecuencia más de la pobre condición cognoscitiva humana y su percepción fragmentada de la realidad, y no porque ésta represente la desgracia humana de por sí.Al final del texto, comentamos también el difícil encaje que la obra de Eurípides tiene en la definición de tragedia aristotélica

Conocer, hablar y nombrar según Platón: una lectura cruzada del Fedro y del Crátilo

El presente artículo contiene una lectura cruzada del Fedro y el Crátilo en la que se aclaran algunos de sus ejes temáticos centrales con el fin de sacar a relucir las constantes del pensamiento platónico que ambos diálogos comparten. La descripción de la dialéctica presente en el Fedro encaja con una definición socrática del Crátilo que explicita que el nombre es un instrumento al servicio del dialéctico. Todo ello nos lleva a concluir que la técnica dialéctica, además de constituir el principal mecanismo regulador de la oratoria, se postula en los diálogos platónicos como un procedimiento de corrección que permite validar cualquier tipo de proposición y aproximar a la verdad los más variados discursos y representaciones de la realidad.AKTIBA-IT: Grupo de Investigación en Prácticas, Aprendizaje y Valores (IT1762-22), grupo reconocido por el Gobierno Vasco