Feasibility of T2* mapping for the evaluation of hip joint cartilage at 1.5T using a three-dimensional (3D), gradient-echo (GRE) sequence: a prospective study

This study defines the feasibility of utilizing three-dimensional (3D) gradient-echo (GRE) MRI at 1.5T for T(2)* mapping to assess hip joint cartilage degenerative changes using standard morphological MR grading while comparing it to delayed gadolinium-enhanced MRI of cartilage (dGEMRIC). MRI was obtained from 10 asymptomatic young adult volunteers and 33 patients with symptomatic femoroacetabular impingement (FAI). The protocol included T(2)* mapping without gadolinium-enhancement utilizing a 3D-GRE sequence with six echoes, and after gadolinium injection, routine hip sequences, and a dual-flip-angle 3D-GRE sequence for dGEMRIC T(1) mapping. Cartilage was classified as normal, with mild changes, or with severe degenerative changes based on morphological MRI. T(1) and T(2)* findings were subsequently correlated. There were significant differences between volunteers and patients in normally-rated cartilage only for T(1) values. Both T(1) and T(2)* values decreased significantly with the various grades of cartilage damage. There was a statistically significant correlation between standard MRI and T(2)* (T(1)) (P < 0.05). High intraclass correlation was noted for both T(1) and T(2)*. Correlation factor was 0.860 to 0.954 (T(2)*-T(1) intraobserver) and 0.826 to 0.867 (T(2)*-T(1) interobserver). It is feasible to gather further information about cartilage status within the hip joint using GRE T(2)* mapping at 1.5T.

The role of the sinuses of Valsalva in aortic root flow dynamics and aortic root surgery: evaluation by magnetic resonance imaging

BACKGROUND AND AIM OF THE STUDY: Combined replacement of the aortic valve and ascending aorta using a composite graft represents the standard treatment for dilated aortic root with concomitant structural damage of the aortic valve, especially when the aortic valve cannot be preserved. Unfortunately, hemodynamic changes associated with prosthetic replacement of the aortic root have not been fully elucidated. The study aim was to compare hemodynamics within the replaced aortic root using either a prosthetic vascular graft with bulges mimicking the sinuses of Valsalva and including a stented pericardial valve, or a straight xenopericardial conduit and a stentless porcine valve. METHODS: Between July 2004 and March 2006, a total of 35 patients (mean age 65.2 years: range: 32-80 years) was enrolled into the present study. Aortic root replacement was performed in nine patients with a Valsalva graft (Gelweave Valsalva; Vascutek, Renfrewshire, UK) including a stented pericardial valve, and in 19 patients with a xenopericardial conduit containing a stentless porcine valve. All patients underwent postoperative magnetic resonance imaging (MRI). A control group of seven patients allowed for comparison with native aortic root hemodynamics. RESULTS: Maximum flow-velocity above the aortic valve as one marker of compliance of the aortic root was slightly higher in patients with a Valsalva graft compared to native aortic roots (1.9 m/s versus 1.3 m/s, p = 0.001), but was significantly lower than in patients with the xenopericardial graft without neo-sinuses (1.3 m/s versus 2.4 m/s, p < 0.001). CONCLUSION: The pre-shaped bulges in the prosthetic Valsalva graft effectively mimic the native sinuses of Valsalva, improve compliance of the aortic root, and result in a more physiologic flow pattern, as demonstrated by postoperative MRI.

Evaluation of control and surveillance strategies for classical swine fever using a simulation model

Classical swine fever (CSF) outbreaks can cause enormous losses in naïve pig populations. How to best minimize the economic damage and number of culled animals caused by CSF is therefore an important research area. The baseline CSF control strategy in the European Union and Switzerland consists of culling all animals in infected herds, movement restrictions for animals, material and people within a given distance to the infected herd and epidemiological tracing of transmission contacts. Additional disease control measures such as pre-emptive culling or vaccination have been recommended based on the results from several simulation models; however, these models were parameterized for areas with high animal densities. The objective of this study was to explore whether pre-emptive culling and emergency vaccination should also be recommended in low- to moderate-density areas such as Switzerland. Additionally, we studied the influence of initial outbreak conditions on outbreak severity to improve the efficiency of disease prevention and surveillance. A spatial, stochastic, individual-animal-based simulation model using all registered Swiss pig premises in 2009 (n=9770) was implemented to quantify these relationships. The model simulates within-herd and between-herd transmission (direct and indirect contacts and local area spread). By varying the four parameters (a) control measures, (b) index herd type (breeding, fattening, weaning or mixed herd), (c) detection delay for secondary cases during an outbreak and (d) contact tracing probability, 112 distinct scenarios were simulated. To assess the impact of scenarios on outbreak severity, daily transmission rates were compared between scenarios. Compared with the baseline strategy (stamping out and movement restrictions) vaccination and pre-emptive culling neither reduced outbreak size nor duration. Outbreaks starting in a herd with weaning piglets or fattening pigs caused higher losses regarding to the number of culled premises and were longer lasting than those starting in the two other index herd types. Similarly, larger transmission rates were estimated for these index herd type outbreaks. A longer detection delay resulted in more culled premises and longer duration and better transmission tracing increased the number of short outbreaks. Based on the simulation results, baseline control strategies seem sufficient to control CSF in low-medium animal-dense areas. Early detection of outbreaks is crucial and risk-based surveillance should be focused on weaning piglet and fattening pig premises.

Bacterial meningitis: insights into pathogenesis and evaluation of new treatment options: a perspective from experimental studies.

ABSTRACT  Bacterial meningitis is associated with high mortality and morbidity rates. Bacterial components induce an overshooting inflammatory reaction, eventually leading to brain damage. Pathological correlates of neurofunctional deficits include cortical necrosis, damage of the inner ear and hippocampal apoptosis. The hippocampal dentate gyrus is important for memory acquisition and harbors a neuronal stem cell niche, thus being potentially well equipped for regeneration. Adjuvant therapies aimed at decreasing the inflammatory reaction, for example, dexamethasone, and those protecting the brain from injury have been evaluated in animal models of the disease. They include nonbacteriolytic antibiotics (e.g., daptomycin), metalloproteinase inhibitors and modulators of the immunological response, for example, granulocyte colony-stimulating factor. Increasing research interest has recently been focused on interventions aimed at supporting regenerative processes.

Development and Evaluation of a New Tablet Computer Application for the Therapy of Brain-Injured Patients with Aphasia

Introduction Language is the most important mean of communication and plays a central role in our everyday life. Brain damage (e.g. stroke) can lead to acquired disorders of lan- guage affecting the four linguistic modalities (i.e. reading, writing, speech production and comprehension) in different combinations and levels of severity. Every year, more than 5000 people (Aphasie Suisse) are affected by aphasia in Switzerland alone. Since aphasia is highly individual, the level of difficulty and the content of tasks have to be adapted continuously by the speech therapists. Computer-based assignments allow patients to train independently at home and thus increasing the frequency of ther- apy. Recent developments in tablet computers have opened new opportunities to use these devices for rehabilitation purposes. Especially older people, who have no prior experience with computers, can benefit from the new technologies. Methods The aim of this project was to develop an application that enables patients to train language related tasks autonomously and, on the other hand, allows speech therapists to assign exercises to the patients and to track their results online. Seven categories with various types of assignments were implemented. The application has two parts which are separated by a user management system into a patient interface and a therapist interface. Both interfaces were evaluated using the SUS (Subject Usability Scale). The patient interface was tested by 15 healthy controls and 5 patients. For the patients, we also collected tracking data for further analysis. The therapist interface was evaluated by 5 speech therapists. Results The SUS score are xpatients = 98 and xhealthy = 92.7 (median = 95, SD = 7, 95% CI [88.8, 96.6]) in case of the patient interface and xtherapists = 68 in case of the therapist interface. Conclusion Both, the patients and the healthy subjects, attested high SUS scores to the patient interface. These scores are considered as "best imaginable". The therapist interface got a lower SUS score compared to the patient interface, but is still considered as "good" and "usable". The user tracking system and the interviews revealed that there is room for improvements and inspired new ideas for future versions.

Sensitivity of the WRF model to PBL parametrisations and nesting techniques: evaluation of wind storms over complex terrain

Simulating surface wind over complex terrain is a challenge in regional climate modelling. Therefore, this study aims at identifying a set-up of the Weather Research and Forecasting Model (WRF) model that minimises system- atic errors of surface winds in hindcast simulations. Major factors of the model configuration are tested to find a suitable set-up: the horizontal resolution, the planetary boundary layer (PBL) parameterisation scheme and the way the WRF is nested to the driving data set. Hence, a number of sensitivity simulations at a spatial resolution of 2 km are carried out and compared to observations. Given the importance of wind storms, the analysis is based on case studies of 24 historical wind storms that caused great economic damage in Switzerland. Each of these events is downscaled using eight different model set-ups, but sharing the same driving data set. The results show that the lack of representation of the unresolved topography leads to a general overestimation of wind speed in WRF. However, this bias can be substantially reduced by using a PBL scheme that explicitly considers the effects of non-resolved topography, which also improves the spatial structure of wind speed over Switzerland. The wind direction, although generally well reproduced, is not very sensitive to the PBL scheme. Further sensitivity tests include four types of nesting methods: nesting only at the boundaries of the outermost domain, analysis nudging, spectral nudging, and the so-called re-forecast method, where the simulation is frequently restarted. These simulations show that restricting the freedom of the model to develop large-scale disturbances slightly increases the temporal agreement with the observations, at the same time that it further reduces the overestimation of wind speed, especially for maximum wind peaks. The model performance is also evaluated in the outermost domains, where the resolution is coarser. The results demonstrate the important role of horizontal resolution, where the step from 6 to 2 km significantly improves model performance. In summary, the combination of a grid size of 2 km, the non-local PBL scheme modified to explicitly account for non-resolved orography, as well as analysis or spectral nudging, is a superior combination when dynamical downscaling is aimed at reproducing real wind fields.

Evaluation of the Morphological Characteristics of Laser-Irradiated Dentin

OBJECTIVE The aim of this study was to investigate the effect of different energy settings of Er:YAG laser irradiation on dentin surface morphology with respect to the number of opened dentinal tubules. BACKGROUND DATA An ideally prepared dentin surface with opened dentinal tubules is a prerequisite for adhesive fixation. No study, however, has yet compared the numbers of opened dentinal tubules with regard to statistical differences. METHODS Conventional preparations using a bur with or without additional acid etching acted as control groups. Dentin specimens were prepared from human third molars and randomly divided into eight groups according to the energy settings of the laser (1, 1.5, 4, 6, 7.5, and 8 W) and two controls (bur and bur plus acid etching). After surface preparation, dentin surfaces were analyzed with a scanning electron microscope, and the number of opened dentinal tubules in a defined area was counted. RESULTS The control groups showed smooth surfaces with (bur plus acid etching) and without opened dentinal tubules (bur), whereas all laser-irradiated surfaces showed rough surfaces. Using the energy setting of 4 W resulted in significantly more opened dentinal tubules than the conventional preparation technique using the bur with additional acid etching. In contrast, the energy setting of 8 W showed significantly fewer opened dentinal tubules, and also exhibited signs of thermal damage. CONCLUSIONS The Er:YAG laser with an energy setting of 4 W generates a dentin surface with opened dentinal tubules, a prerequisite for adhesive fixation.

BRONCHOALVEOLAR LAVAGE AND GALLIUM-67 LUNG SCANNING IN THE EVALUATION OF ASBESTOS-EXPOSED INDIVIDUALS

In this study, an attempt is made to evaluate certain parameters that might indicate the beginning of a certain fibrogenic activity in the lung parenchyma, even before such changes become visible on the chest x-ray. The hypothesis is that studies such as certain bronchoalveolar immunological characteristics and Gallium-67 lung scans may be more sensitive indicators of parenchymal lung damage in response to asbestos inhalation than conventional radiographic criteria. If so, then in those cases where the criteria for the diagnosis of asbestosis lack the presence of parenchymal changes, it would be unwise to deny the diagnosis unless further investigations, such as the bronchoalveolar lavage fluid analysis and the Gallium-67 lung scan techniques, are made available.^ Four groups of individuals have been included in this study. The volunteer group showing no history of asbestos exposure with normal chest x-rays has been used as a normal healthy comparison group. The other three groups are all asbestos-exposed but differ as to their findings in the chest radiographs. One has parenchymal changes (0/1 or more, ILO Classification), the second has no parenchymal but pleural changes, and the third has neither.^ The most significant laboratory parameter for bronchoalveolar lavage, in this study, is that of Neutrophils (PMNs). All three asbestos-exposed groups showed no differences when compared with each other, while such differences were statistically significant when such groups were separately compared with the normal comparison group. A similar finding existed also when the Helper: Suppressor T-Cell ratios were compared, and found to be higher in all the asbestos-exposed groups.^ Another sensitive test is that of Gallium-67 lung scan. This was found to be positive in some patients where parenchymal changes were absent. Even in some of those who showed neither parenchymal nor pleural changes in their chest x-ray showed positive test results. Such changes indicate a state of an underlying pathogenic process that is still undetectable by conventional radiography. This highly recommends the future application of such tests for the early detection of active pulmonary disease, especially in those who show no parenchymal changes in their chest x-rays. (Abstract shortened with permission of author.) ^

Evaluation of the attack rates and level of damages by the fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), affecting corn-crops in the northeast of Argentina

The fall armyworm (FAW) is the most important threat to corn crops in Argentina, and there exists very little up-to-date information on its actual pest status because the available literature was published more than 20 years ago. Therefore, field surveys were carried out in the northeast of Argentina, in order to establish the attack rates and injury levels of the pest in relation to the crop phenology. The study was carried out at two localities: Colonia Benítez, an agricultural region, and Tapenagá, a cattle-raising area. At each site two 1-ha plots were sown either with a Bt-corn expressing Cry 1F protein or with an untransformed corn germplasm. Optimal and late sowing was assayed and FAW larval abundance, relative age composition, attack rates and level of damage to corn were recorded. At the moment of the field experiments, Bt-corn was not affected by FAW larvae. However, untransformed germplasms were severely affected by FAW larvae, with an average of attacked plants of 18% or more. In contrast to data obtained 30 years ago, higher values of FAW density were registered. Levels of damage to corn plants were higher after the V4 stage. It was found that the sowing date affected the infestation levels and early seeding avoided high armyworm densities that develop later in the season; in northern Argentina, this was only relevant in agricultural areas.

Implementation of a module for risk of ozone impacts assessment to vegetation in the integrated assessment modelling system for the Iberian peninsula. Evaluation for wheat and holm oak

A module to estimate risks of ozone damage to vegetation has been implemented in the Integrated Assessment Modelling system for the Iberian Peninsula. It was applied to compute three different indexes for wheat and Holm oak; daylight AOT40 (cumulative ozone concentration over 40 ppb), cumulative ozone exposure index according to the Directive 2008/50/EC (AOT40-D) and PODY (Phytotoxic Ozone Dose over a given threshold of Y nmol m−2 s−1). The use of these indexes led to remarkable differences in spatial patterns of relative ozone risks on vegetation. Ozone critical levels were exceeded in most of the modelling domain and soil moisture content was found to have a significant impact on the results. According to the outputs of the model, daylight AOT40 constitutes a more conservative index than the AOT40-D. Additionally, flux-based estimations indicate high risk areas in Portugal for both wheat and Holm oak that are not identified by AOT-based methods.

Detailed damage mechanisms assessment in composite materials by means of X-ray tomography

This research focused on the evaluation of damage formation on ±45º carbon fiber laminates subjected to tensile tests. The damage was evaluated by means of X-ray tomography. A high density of cracks developed during the plateau of the stress-strain curve and were qualitatively analyzed, showing that the inner plies eventually developed a higher crack concentration than the outer plies. Delamination started to occur in the outermost ply interface when the slope after the plateau of the stress-strain curve began to increase.

Computational model for local damage assesment of structures

In the last years many studies have been developed to analyze the seismic behavior throug the damage concept. In fact, the evaluation of the structural damage is important in order to quantify the safety of new and existing structures and, also, to establish a framework for seismic retrofitting decision making of structures. Most proposed models are based on a post-earthquake evaluation in such a way they uncouple the computation of the structural response from that of damage. However, there are other models which include explicity the existing coupling between the degradation and the structural mechanical beaviour. Those models are closer to the physical reality and its formulation is based on the principles of Continuum Damage Mechanics. In the present work, a coupled model is formulated using a simplified application of the Continuum Damage Mechanics to the analysis of frames and allows its representation in standard finite element programs. This work is part of the activities developed by the Structural Mechanics Department (UPM) within ICONS (European Research Project on Innovative Seismic Design Concepts for New and Existing Structures).

Application of NMR techniques for the evaluation of fruit internal quality and physical properties of food

Los alimentos son sistemas complejos, formados por diversas estructuras a diferentes escalas: macroscópica y microscópica. Muchas propiedades de los alimentos, que son importantes para su procesamiento, calidad y tratamiento postcosecha, están relacionados con su microestructura. La presente tesis doctoral propone una metodología completa para la determinación de la estructura de alimentos desde un punto de vista multi-escala, basándose en métodos de Resonancia Magnética Nuclear (NMR). Las técnicas de NMR son no invasivas y no destructivas y permiten el estudio tanto de macro- como de microestructura. Se han utilizado distintos procedimientos de NMR dependiendo del nivel que se desea estudiar. Para el nivel macroestructural, la Imagen de Resonancia Magnética (MRI) ha resultado ser muy útil para la caracterización de alimentos. Para el estudio microestructural, la MRI requiere altos tiempos de adquisición, lo que hace muy difícil la transferencia de esta técnica a aplicaciones en industria. Por tanto, la optimización de procedimientos de NMR basados en secuencias relaxometría 2D T1/T2 ha resultado ser una estrategia primordial en esta tesis. Estos protocolos de NMR se han implementado satisfactoriamente por primera vez en alto campo magnético. Se ha caracterizado la microestructura de productos alimentarios enteros por primera vez utilizando este tipo de protocolos. Como muestras, se han utilizado dos tipos de productos: modelos de alimentos y alimentos reales (manzanas). Además, como primer paso para su posterior implementación en la industria agroalimentaria, se ha mejorado una línea transportadora, especialmente diseñada para trabajar bajo condiciones de NMR en trabajos anteriores del grupo LPF-TAGRALIA. Se han estudiado y seleccionado las secuencias más rápidas y óptimas para la detección de dos tipos de desórdenes internos en manzanas: vitrescencia y roturas internas. La corrección de las imágenes en movimiento se realiza en tiempo real. Asimismo, se han utilizado protocolos de visión artificial para la clasificación automática de manzanas potencialmente afectadas por vitrescencia. El presente documento está dividido en diferentes capítulos: el Capítulo 2 explica los antecedentes de la presente tesis y el marco del proyecto en el que se ha desarrollado. El Capítulo 3 recoge el estado del arte. El Capítulo 4 establece los objetivos de esta tesis doctoral. Los resultados se dividen en cinco sub-secciones (dentro del Capítulo 5) que corresponden con los trabajos publicados bien en revistas revisadas por pares, bien en congresos internacionales o bien como capítulos de libros revisados por pares. La Sección 5.1. es un estudio del desarrollo de la vitrescencia en manzanas mediante MRI y lo relaciona con la posición de la fruta dentro de la copa del árbol. La Sección 5.2 presenta un trabajo sobre macro- y microestructura en modelos de alimentos. La Sección 5.3 es un artículo en revisión en una revista revisada por pares, en el que se hace un estudio microestrcutural no destructivo mediante relaxometría 2D T1/T2. la Sección 5.4, hace una comparación entre manzanas afectadas por vitrescencia mediante dos técnicas: tomografía de rayos X e MRI, en manzana. Por último, en la Sección 5.5 se muestra un trabajo en el que se hace un estudio de secuencias de MRI en línea para la evaluación de calidad interna en manzanas. Los siguientes capítulos ofrecen una discusión y conclusiones (Capítulo 6 y 7 respectivamente) de todos los capítulos de esta tesis doctoral. Finalmente, se han añadido tres apéndices: el primero con una introducción de los principios básicos de resonancia magnética nuclear (NMR) y en los otros dos, se presentan sendos estudios sobre el efecto de las fibras en la rehidratación de cereales de desayuno extrusionados, mediante diversas técnicas. Ambos trabajos se presentaron en un congreso internacional. Los resultados más relevantes de la presente tesis doctoral, se pueden dividir en tres grandes bloques: resultados sobre macroestructura, resultados sobre microestructura y resultados sobre MRI en línea. Resultados sobre macroestructura: - La imagen de resonancia magnética (MRI) se aplicó satisfactoriamente para la caracterización de macroestructura. En particular, la reconstrucción 3D de imágenes de resonancia magnética permitió identificar y caracterizar dos tipos distintos de vitrescencia en manzanas: central y radial, que se caracterizan por el porcentaje de daño y la conectividad (número de Euler). - La MRI proveía un mejor contraste para manzanas afectadas por vitrescencia que las imágenes de tomografía de rayos X (X-Ray CT), como se pudo verificar en muestras idénticas de manzana. Además, el tiempo de adquisición de la tomografía de rayos X fue alrededor de 12 veces mayor (25 minutos) que la adquisición de las imágenes de resonancia magnética (2 minutos 2 segundos). Resultados sobre microestructura: - Para el estudio de microestructura (nivel subcelular) se utilizaron con éxito secuencias de relaxometría 2D T1/T2. Estas secuencias se usaron por primera vez en alto campo y sobre piezas de alimento completo, convirtiéndose en una forma no destructiva de llevar a cabo estudios de microestructura. - El uso de MRI junto con relaxometría 2D T1/T2 permite realizar estudios multiescala en alimentos de forma no destructiva. Resultados sobre MRI en línea: - El uso de imagen de resonancia magnética en línea fue factible para la identificación de dos tipos de desórdenes internos en manzanas: vitrescencia y podredumbre interna. Las secuencias de imagen tipo FLASH resultaron adecuadas para la identificación en línea de vitrescencia en manzanas. Se realizó sin selección de corte, debido a que la vitrescencia puede desarrollarse en cualquier punto del volumen de la manzana. Se consiguió reducir el tiempo de adquisición, de modo que se llegaron a adquirir 1.3 frutos por segundos (758 ms por fruto). Las secuencias de imagen tipo UFLARE fueron adecuadas para la detección en línea de la podredumbre interna en manzanas. En este caso, se utilizó selección de corte, ya que se trata de un desorden que se suele localizar en la parte central del volumen de la manzana. Se consiguió reducir el tiempo de adquisicón hasta 0.67 frutos por segundo (1475 ms por fruto). En ambos casos (FLASH y UFLARE) fueron necesarios algoritmos para la corrección del movimiento de las imágenes en tiempo real. ABSTRACT Food is a complex system formed by several structures at different scales: macroscopic and microscopic. Many properties of foods that are relevant to process engineering or quality and postharvest treatments are related to their microstructure. This Ph.D Thesis proposes a complete methodology for food structure determination, in a multiscale way, based on the Nuclear Magnetic Resonance (NMR) phenomenon since NMR techniques are non-invasive and non-destructive, and allow both, macro- and micro-structure study. Different NMR procedures are used depending on the structure level under study. For the macrostructure level, Magnetic Resonance Imaging (MRI) revealed its usefulness for food characterization. For microstructure insight, MRI required high acquisition times, which is a hindrance for transference to industry applications. Therefore, optimization of NMR procedures based on T1/T2 relaxometry sequences was a key strategy in this Thesis. These NMR relaxometry protocols, are successfully implemented in high magnetic field. Microstructure of entire food products have been characterized for the first time using these protocols. Two different types of food products have been studied: food models and actual food (apples). Furthermore, as a first step for the food industry implementation, a grading line system, specially designed for working under NMR conditions in previous works of the LPF-TAGRALIA group, is improved. The study and selection of the most suitable rapid sequence to detect two different types of disorders in apples (watercore and internal breakdown) is performed and the real time image motion correction is applied. In addition, artificial vision protocols for the automatic classification of apples potentially affected by watercore are applied. This document is divided into seven different chapters: Chapter 2 explains the thesis background and the framework of the project in which it has been worked. Chapter 3 comprises the state of the art. Chapter 4 establishes de objectives of this Ph.D thesis. The results are divided into five different sections (in Chapter 5) that correspond to published peered reviewed works. Section 5.1 assesses the watercore development in apples with MRI and studies the effect of fruit location in the canopy. Section 5.2 is an MRI and 2D relaxometry study for macro- and microstructure assessment in food models. Section 5.3 is a non-destructive microstructural study using 2D T1/T2 relaxometry on watercore affected apples. Section 5.4 makes a comparison of X-ray CT and MRI on watercore disorder of different apple cultivars. Section 5.5, that is a study of online MRI sequences for the evaluation of apple internal quality. The subsequent chapters offer a general discussion and conclusions (Chapter 6 and Chapter 7 respectively) of all the works performed in the frame of this Ph.D thesis (two peer reviewed journals, one book chapter and one international congress).Finally, three appendices are included in which an introduction to NMR principles is offered and two published proceedings regarding the effect of fiber on the rehydration of extruded breakfast cereal are displayed. The most relevant results can be summarized into three sections: results on macrostructure, results on microstructure and results on on-line MRI. Results on macrostructure: - MRI was successfully used for macrostructure characterization. Indeed, 3D reconstruction of MRI in apples allows to identify two different types of watercore (radial and block), which are characterized by the percentage of damage and the connectivity (Euler number). - MRI provides better contrast for watercore than X-Ray CT as verified on identical samples. Furthermore, X-Ray CT images acquisition time was around 12 times higher (25 minutes) than MRI acquisition time (2 minutes 2 seconds). Results on microstructure: - 2D T1/T2 relaxometry were successfully applied for microstructure (subcellular level) characterization. 2D T1/T2 relaxometry sequences have been applied for the first time on high field for entire food pieces, being a non-destructive way to achieve microstructure study. - The use of MRI together with 2D T1/T2 relaxometry sequences allows a non-destructive multiscale study of food. Results on on-line MRI: - The use of on-line MRI was successful for the identification of two different internal disorders in apples: watercore and internal breakdown. FLASH imaging was a suitable technique for the on-line detection of watercore disorder in apples, with no slice selection, since watercore is a physiological disorder that may be developed anywhere in the apple volume. 1.3 fruits were imaged per second (768 ms per fruit). UFLARE imaging is a suitable sequence for the on-line detection of internal breakdown disorder in apples. Slice selection was used, as internal breakdown is usually located in the central slice of the apple volume. 0.67 fruits were imaged per second (1475 ms per fruit). In both cases (FLASH and UFLARE) motion correction was performed in real time, during the acquisition of the images.

Identification of intermediate debonding damage in FRP-plated RC beams based on multi-objective particle swarm optimization without updated baseline model

Fiber reinforced polymer composites (FRP) have found widespread usage in the repair and strengthening of concrete structures. FRP composites exhibit high strength-to-weight ratio, corrosion resistance, and are convenient to use in repair applications. Externally bonded FRP flexural strengthening of concrete beams is the most extended application of this technique. A common cause of failure in such members is associated with intermediate crack-induced debonding (IC debonding) of the FRP substrate from the concrete in an abrupt manner. Continuous monitoring of the concrete?FRP interface is essential to pre- vent IC debonding. Objective condition assessment and performance evaluation are challenging activities since they require some type of monitoring to track the response over a period of time. In this paper, a multi-objective model updating method integrated in the context of structural health monitoring is demonstrated as promising technology for the safety and reliability of this kind of strengthening technique. The proposed method, solved by a multi-objective extension of the particle swarm optimization method, is based on strain measurements under controlled loading. The use of permanently installed fiber Bragg grating (FBG) sensors embedded into the FRP-concrete interface or bonded onto the FRP strip together with the proposed methodology results in an automated method able to operate in an unsupervised mode.

Using damage from 2010 Haiti earthquake for vulnerability estimation of typical structures in Port-au-Prince (Haiti).

After the 2010 Haiti earthquake, that hits the city of Port-au-Prince, capital city of Haiti, a multidisciplinary working group of specialists (seismologist, geologists, engineers and architects) from different Spanish Universities and also from Haiti, joined effort under the SISMO-HAITI project (financed by the Universidad Politecnica de Madrid), with an objective: Evaluation of seismic hazard and risk in Haiti and its application to the seismic design, urban planning, emergency and resource management. In this paper, as a first step for a structural damage estimation of future earthquakes in the country, a calibration of damage functions has been carried out by means of a two-stage procedure. After compiling a database with observed damage in the city after the earthquake, the exposure model (building stock) has been classified and through an iteratively two-step calibration process, a specific set of damage functions for the country has been proposed. Additionally, Next Generation Attenuation Models (NGA) and Vs30 models have been analysed to choose the most appropriate for the seismic risk estimation in the city. Finally in a next paper, these functions will be used to estimate a seismic risk scenario for a future earthquake.