A constitutive model of human esophagus tissue with application for the treatment of stenosis

This dissertation is a research about the mechanical behavior of the human esophagus. This work is intended to be applied in the treatment of stenosis and other esophageal diseases that frequently require a procedure of forced dilation, that involves high pressures on the esophagus wall. This study proposes a constitutive model to simulate forced dilatations. This study includes the experimental characterization of the mechanical behavior of human esophagus. In addition, some theoretical questions and experimental issues were addressed and solved. This dissertation summarizes the previous work on esophageal tissues by other authors. Additionally, a short explanation about the microcontinuum theory developed in the last decades is given, as well as a summary of the general theory of nonlinear hyperelastic constitutive models (with large deformation). This study required extensive testing of esophageal tissue in order to characterize the in vitro mechanical behavior. The testing included mainly tensile tests and complementary inflation tests. Optical motion track analysis was used for accurate computation of the strains in the tissue. The results of the tests were used for adjusting the mechanical properties that characterize the mechanical behavior of esophagus in the proposed models of the literature. The statistical analysis of the data revealed, some significant correlations between anthropometric factors, such as the body mass index, and some mechanical properties were found in the analysis of the data. The typical values of the mechanical properties were used to perform some numerical finite element simulations based on the proposed models. In addition, a number of theoretical results were obtained concerning the residual stress and the predictions of statistical mechanics for a system of collagenous fibers inside a soft tissue. The main result is a constitutive non-linear microstretch anisotropic hyperelastic constitutive model with large deformations (and with residual stresses) to characterize the multi-layered tissue of human esophagus. This model is suitable for numerical simulation.Esta tesis es una investigación sobre el comportamiento mecánico del esófago humano. Este trabajo se pensó para ser aplicado al tratamiento de la estenosis y otras afecciones esofágicas que, con frecuencia, requieren dilatación forzada, lo que supone altas presiones sobre la pared esofágica. Este estudio propone un modelo constitutivo para simular estas dilataciones forzadas. Este estudio incluye la caracterización experimental del comportamiento mecánico del esófago. Además, se han planteado algunas cuestiones teóricas y experimentales que han sido resueltas. Esta tesis resume el trabajo previo sobre tejido esofágico de otros investigadores. Además, se da una pequeña explicación sobre la teoría del medio microntinuo desarrollada en las últimas décadas y un breve resumen de la teoría general de modelos constitutivos hiperelásticos no-lineales (con grandes deformaciones). El estudio requirió experimentación de tejido para caracterizar el comportamiento in vitro. Los test incluyeron test de tracción y test de inflado. Se empleó rastreo óptico para un cálculo adecuado de la deformación. Los resultados de los test permitieron encontrar las propiedades mecánicas según dos modelos de esófago de la literatura. El análisis de los datos rebeló, algunas correlaciones significativas entre factores como el índice de masa corporal y algunas propiedades mecánicas. Los valores típicos de las propiedades fueron usados para algunas simulaciones numéricas basadas en los modelos propuestos. Además se han obtenido algunos resultados teóricos sobre la tensión residual y las predicciones de la mecánica estadística para un sistema de fibras de colágeno del tejido. El principal resultado es un modelo constitutivo de microestiramiento anisótropo no-lineal e hiperelástico para caracterizar el esófago Este modelo es adecuado para la computación numérica.Postprint (published version

Constitutive relationships for osteonal microcracking in human cortical bone using statistical mechanics

The post-elastic mechanical behavior of cortical bone, which is represented by extensive microcracking once the elastic regime is exceeded, has been characterized by a nonlinear constitutive relationship for osteonal microcracking. The relationship/model is based on the formalism of Statistical Mechanics, allowing the degree of irreversibility to be calculated using the increase in entropy associated with the progression of microcracking. Specific tensile and bending tests were conducted to compare theoretical predictions of constitutive relationships to empirical curves. In addition, the tests were utilized to determine the model’s parameters, whose values were used to explicitly calculate the entropy increase. A large sample was used: 51 cortical bone coupons (dog-bone-shaped specimens) were extracted from the 4th ribs of numerous individuals and subjected to uniaxial tensile testing. Additionally, fifteen complete 4th ribs were used for bending tests. Displacement and strain fields were measured for both types of tests using digital image correlation or video recordings of the tests. All experimental specimen data were successfully fitted to the model, and all constitutive parameter values were found to be correlated with anthropometric variables. Explicit entropy calculations indicate that microcracking is minimal for low strain and, initially, stress is nearly proportional to strain. After a certain point, significant microcracking occurs, and the relationship between stress and strain becomes invalid. Several significant associations between constitutive parameters and age have also been identified.Peer ReviewedPostprint (published version

Cálculo de elementos estructurales

Descripció del recurs: el 21 de setembre de 2011El presente libro ha sido concebido como una introducción al cálculo de estructuras complejas y se dirige a estudiantes que ya han superado un primer curso de resistencia de materiales. Los capítulos 1 y 2 explican el cálculo de estructuras modelizables como elementos estructurales 1D (barras esbeltas). El capítulo 3 explica el cálculo de elementos estructurales bidimensionales (2D), como placas y paredes delgadas de depósitos para fluidos a presión. Los capítulos 4 y 5 estudian los elementos de cimentación que han de ser tratados como elementos estructurales 3D. Finalmente, en el capítulo 6 se introduce el cálculo dinámico aplicado al cálculo sísmico de edificios simples

La Gira de Campo como estrategia motivadora en la fase de planificación del proceso de redacción de textos expositivos-argumentativos en los estudiantes del séptimo grado F del colegio público La Salle, del municipio de Diriamba del departamento de Carazo, durante el II semestre del año 2016

El presente trabajo investigativo se realizó en la asignatura de seminario de Graduación, para proponer la gira de campo como estrategia motivadora en la fase de planificación en el proceso de la redacción de textos expositivos-argumentativos en los estudiantes de séptimo grado “f” del colegio público La Salle, en el segundo semestre del año 2016. Lo esencial de este trabajo es de enriquecer la labor docente en cuanto a estrategias motivadoras e innovadoras dentro del proceso de enseñanza-aprendizaje, de acuerdo a la relevancia de éstas, así será la motivación para los aprendizajes significativos de los estudiantes. Por tal razón, se procuró realizar la gira de campo de forma vivencial a la realidad de los estudiantes, para que recolectaran información en la fase de planificación del proceso de redacción, facilitándole la producción de textos expositivos-argumentativos. Para la selección de la población de estudiantes, primeramente se observó una clase en la sección “f” donde se constató la necesidad de estrategias de enseñanzas innovadoras dirigida a 36 estudiantes, luego se propuso elaborar y ejecutar una unidad didáctica con dinámicas, técnicas y estrategias de enseñanzas motivadoras, aplicándola a esta misma sección. A los estudiantes se les realizó rúbricas de autoevaluación, coevaluación y heteroevaluación, con la finalidad de hacerlos reflexionar sobre su propio desempeño con la misión de mejorar, identificando fortalezas y debilidades para ser superadas, en función de su formación integral priorizando lo conceptual, procedimental y actitudinal retomando el contenido de los textos expositivos-argumentativos y la gira de campo como estrategia motivadora e innovadora de este trabajo contribuyendo así al aprendizaje significativo en cuanto al proceso de redacción de textos expositivos-argumentativos. El resultado que se obtuvo permite destacar que las estrategias de enseñanzas innovadoras contribuyen a la adquisición de aprendizajes significativos y más cuando éste es contextualizado a la realidad, fomentando la participación activa, el desarrollo de la expresión oral, desarrollo de habilidades comunicativas escritas, pensamiento lógico y la observación. Es necesario aplicar dinámicas para motivar a los estudiantes y técnicas de enseñanzas para retroalimentar el aprendizaje que en conjunto con la gira de campo en la fase de planificación ofrecen resultados satisfactorios y aprendizajes significativos

Traumatic brain injury in pedestrian–vehicle collisions: Convexity and suitability of some functionals used as injury metrics

Background and Objective: Abrupt accelerations or decelerations can cause large strain in brain tissues and, consequently, different forms of Traumatic Brain Injury (TBI). In order to predict the effect of the accelerations upon the soft tissues of the brain, many different injury metrics have been proposed (typically, an injury metric is a real valued functional of the accelerations). The objective of this article is to make a formal and empirical comparison, in order to identify general criteria for reasonable injury metrics, and propose a general guideline to avoid ill-proposed injury metrics. Methods: A medium-size sample of vehicle-pedestrian collisions, from Post Mortem Human Subject (PMHS) tests, is analyzed. A statistical study has been conducted in order to determine the discriminant power of the usual metrics. We use Principal Component Analysis to reduce dimensionality and to check consistency among the different metrics. In addition, this article compares the mathematical properties of some of these functionals, trying to identify the desirable properties that any of those functionals needs to fulfill in order to be useful for optimization. Results: We have found a pair-wise consistency of all the currently used metrics (any two injury metrics are always positively related). In addition, we observed that two independent principal factors explain about 72.5% of the observed variance among all collision tests. This is remarkable because it indicates that despite high number of different injury metrics, a reduced number of variables can explain the results of all these metrics. With regard to the formal properties, we found that essentially all injury mechanisms can be accounted by means of scalable, differentiable and convex functionals (we propose to call minimization suitable injury metric to any metric having these three formal properties). In addition three useful functionals, usable as injury metrics, are identified on the basis of the empirical comparisons. Conclusions: The commonly used metrics are highly consistent, but also highly redundant. Formal minimal conditions of a reasonable injury metric have been identified. Future proposals of injury metrics can benefit from the results of this study.Peer ReviewedPostprint (author's final draft

Development of carbon fiber acrylonitrile styrene acrylate composite for large format additive manufacturing

The increasing interest of Large Format Additive Manufacturing (LFAM) technologies in various industrial sectors mainly lies on the attainable production of pieces reaching several cubic meters. These new technologies require the development of optimized materials with two-folded capabilities, able to satisfy functional in-service requirements but also showing a proper printability. Acrylonitrile Styrene Acrylate (ASA) is among the most interesting thermoplastic materials to be implemented in a LFAM device due to its excellent wettability and mechanical properties. This research focuses on the development and characterization of ASA and carbon fiber (CF) ASA composites suitable for LFAM. The rheological, thermal and mechanical properties of neat ASA and ASA containing 20 wt% CF are addressed. The results evidence the higher performance of the CF loaded composite compared to the raw ASA polymer (i.e., the 20 wt% CF composite shows a 350% increase in flexural Young's Modulus and a 500% increment in thermal conductivity compared with neat ASA). Additionally, both materials were successfully printed along perpendicular directions (X and Z), showing the maximum tensile strain for the composite printed along the X orientation as was expected. The results of the flexural tests are comparable or slightly higher than those of injected parts. Finally, the fracture surface was analysed, identifying different types of porosity

The influence of the parents and equals in the realization of physical sports-activity of the students of primary education

El presente trabajo de investigación se centró en conocer la cantidad de actividad física y la intencionalidad de ser físicamente activos en el futuro que tiene el alumnado de sexto de Educación Primaria. Se realizó un estudio de tipo transversal con una estrategia descriptiva y asociativa. La muestra estaba formada por alumnos de centros educativos de la provincia de Badajoz (n=542), el 50.2% eran chicos y el 49.8% chicas, con edades comprendidas entre 11-13 años. Como instrumentos de medida se utilizaron el cuestionario de actividad física para niños (Physical activity questionnaire for children(PAQ-C)) y la Medida de la Intencionalidad para ser Físicamente Activo (MIFA). Se encontraron diferencias en el nivel de actividad física de los escolares (p<.05) en función de las variables género, nivel de actividad física de los progenitores y nivel de actividad física de los amigos. Con respecto a la intencionalidad de practicar actividad física en el futuro se han encontrado diferencias significativas (p<.01) en función del género, la influencia que reciben de los padres cuando se ven obligados a realizar actividad física, el nivel de actividad física de los progenitores y el nivel de actividad física de los amigos. El alumnado que tiene una intención mayor de practicar actividad física en un futuro son aquellos que se consideran bastante activos.The present research work is focused on knowing the amount of physical activity and the intentionality of being physically active in the future that the students of sixth grade from Primary Education. A study was done of transversal type with a descriptive and associative strategy. The sample consisted of students from educational centers in the province of Badajoz (n=542), 50.2% were boys and 49.8% were girls, with ages between 11-13 years. As a measuring instrument, the physical activity questionnaire for children was used (Physical activity questionnaire for children) and the Measure of Intentionality to be Physically Active (MIFA). Differences were found in the physical activity level of the students (p <.05), in function, the variables gender, level of physical activity of the parents and level of physical activity of the friends. With respect to the intentionality of practicing physical activity in the future, significant differences (p <.01) according to gender, the influence they receive from the parents when they are compelled to perform physical activity, level of physical activity of the parents and level of physical activity of the friends. The students that have a greater intention of practicing physical activity in the future are those that are considered quite active.peerReviewe

MELOMICS: Contributions of computer science and biology to receptive music therapy

It is surprising the fact that while the personalized medicine model is more and more accepted, receptive music therapy is still applied collectively. Although, in some hospitals the subject (patient or health-medical staff) is allowed to select the genre or artist, with most published clinical studies reporting on concrete types of music (eg, relaxing or classical) that are applied to groups of patients. Customizing songs to patient characteristics would make the study much more complex: on the one hand, a higher variability demands a larger sample and, on the other hand, it significantly increases the time and care dedicated to each patient. In any case, customization is a subjective element which strongly depends on individual preferences. MELOMICS integrates computer technology that adapts music to the condition of the patient, in an automatic and objective way. This enables the future design of biofeedback devices, which in the long run results in being favorable for the therapeutic response of the patient.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Aportaciones de la informática y la biología a la musicoterapia receptiva

Contrasta que mientras la medicina personalizada toma un mayor protagonismo, la terapia musical receptiva siga seleccionando la música de manera colectiva. Si bien la praxis en algunos hospitales permite al sujeto (paciente o personal médico-sanitario) seleccionar el género o el artista, la mayoría de los estudios publicados hablan de un tipo de música (por ejemplo, relajante o clásica) que se aplica a todos los pacientes que van a ser estimulados. Personalizar los temas a las características del paciente complicaría extraordinariamente la realización del estudio: por un lado, la variabilidad introducida exige un mayor número de probandos y, por otro, incrementa considerablemente el tiempo y la dedicación por paciente. Y en última instancia la personalización sería un elemento subjetivo, dependiente de las preferencias del sujeto. MELOMICS aglutina la tecnología informática necesaria para adecuar la reproducción de los temas al estado particular del paciente y a su evolución temporal, de manera automática y objetiva; permitiendo el diseño de dispositivos de biofeedback que optimizan la respuesta terapéutica.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

A new predictive neural architecture for solving temperature inverse problems in microwave-assisted drying processes

In this paper, a novel learning architecture based on neural networks is used for temperature inverse modeling in microwave-assisted drying processes. The proposed design combines the accuracy of the radial basis functions (RBF) and the algebraic capabilities of the matrix polynomial structures by using a two-level structure. This architecture is trained by temperature curves, TcðtÞ; previously generated by a validated drying model. The interconnection of the learning-based networks has enabled the finding of electric field (E) optimal values which provide the TcðtÞ curve that best fits a desired temperature target in a specific time slo