Application of chromatographic and spectroscopic techniques in the evaluation of the lipid fraction of animal products

Lipolysis and oxidation of lipids in foods are the major biochemical and chemical processes that cause food quality deterioration, leading to the characteristic, unpalatable odour and flavour called rancidity. In addition to unpalatability, rancidity may give rise to toxic levels of certain compounds like aldehydes, hydroperoxides, epoxides and cholesterol oxidation products. In this PhD study chromatographic and spectroscopic techniques were employed to determine the degree of rancidity in different animal products and its relationship with technological parameters like feeding fat sources, packaging, processing and storage conditions. To achieve this goal capillary gas chromatography (CGC) was employed not only to determine the fatty acids profile but also, after solid phase extraction, the amount of free fatty acids (FFA), diglycerides (DG), sterols (cholesterol and phytosterols) and cholesterol oxidation products (COPs). To determine hydroperoxides, primary products of oxidation and quantify secondary products UV/VIS absorbance spectroscopy was applied. Most of the foods analysed in this study were meat products. In actual fact, lipid oxidation is a major deterioration reaction in meat and meat products and results in adverse changes in the colour, flavour and texture of meat. The development of rancidity has long recognized as a serious problem during meat handling, storage and processing. On a dairy product, a vegetal cream, a study of lipid fraction and development of rancidity during storage was carried out to evaluate its shelf-life and some nutritional features life saturated/unsaturated fatty acids ratio and phytosterols content. Then, according to the interest that has been growing around functional food in the last years, a new electrophoretic method was optimized and compared with HPLC to check the quality of a beehive product like royal jelly. This manuscript reports the main results obtained in the five activities briefly summarized as follows: 1) comparison between HPLC and a new electrophoretic method in the evaluation of authenticity of royal jelly; 2) study of the lipid fraction of a vegetal cream under different storage conditions; 3) study of lipid oxidation in minced beef during storage under a modified atmosphere packaging, before and after cooking; 4) evaluation of the influence of dietary fat and processing on the lipid fraction of chicken patties; 5) study of the lipid fraction of typical Italian and Spanish pork dry sausages and cured hams.

Application of different instrumental techniques to the selective evaluation of bio-sensible compounds in foodstuff of animal and vegetable origin

This PhD thesis describes the application of some instrumental analytical techniques suitable to the study of fundamental food products for the human diet, such as: extra virgin olive oil and dairy products. These products, widely spread in the market and with high nutritional values, are increasingly recognized healthy properties although their lipid fraction might contain some unfavorable components to the human health. The research activity has been structured in the following investigations: ������Comparison of different techniques for trans fatty acids analysis��� ������Fatty acids analysis of outcrop milk cream samples, with particular emphasis on the content of Conjugated Linoleic Acid (CLA) and trans Fatty Acids (TFA), by using 100m high-polarity capillary column��� ������Evaluation of the oxidited fatty acids (OFA) content during the Parmigiano-Reggiano cheese seasoning��� ������Direct analysis of 4-desmethyl sterols and two dihydroxy triterpenes in saponified vegetal oils (olive oil and others) using liquid chromatography-mass spectrometry��� ������Quantitation of long chain poly-unsatured fatty acids (LC-PUFA) in base infant formulas by Gas Chromatography, and evaluation of the blending phases accuracy during their preparation��� ������Fatty acids composition of Parmigiano Reggiano cheese samples, with emphasis on trans isomers (TFA)���

Milk and dairy products: evaluation of bioactive components by analytical techniques

Milk and dairy products are important source of bioactive compounds useful to satisfy the nutritional and physiological needs of any newborns of mammalian species and useful to guarantee adequate growth and development of infants as well as provide a complete nourishment of adults. Physico-chemical, nutritional and organoleptic properties of the main constituents and the ���minor��� components have a crucial role in the quality of milk and milk products. Although in the past decades dietary milk fat was often regarded as harmful for the human health, recent researches suggest that milk contains specific fatty acids with nutritional and physiological health benefits. For these reasons, a major attention is given to the quantity and quality of total fat intake. In the recent years, as a result of the new concept of multifunctional agriculture and the changing behaviours about diet, consumer demands in favor of high-quality, security and safety dairy products are increased. Moreover, milk proteins and milk-derived bioactive peptides are recognized to have a high nutritive value, several health-promoting functional activities and excellent technological properties. Accordingly, growing interest in the development of functional dairy products and preparation of infant formulae for babies who cannot be breast-fed, has been give in order to meet the specific consumer���s requests. This manuscript presents the main results obtained during my PhD research aimed to evaluate the main bioactive lipids and proteins in milk and dairy products using innovative analytical techniques. The experimental section of this manuscript is divided in two sections where are reported the main results obtained during my research activities on dairy products and human milks in order to characterize their bioactive compounds for functional food applications.

Postoperative evaluation of surgery for craniosynostosis based on image registration techniques

Craniosynostosis consists of a premature fusion of the sutures in an infant skull, which restricts the skull and brain growth. During the last decades there has been a rapid increase of fundamentally diverse surgical treatment methods. At present, the surgical outcome has been assessed using global variables such as cephalic index, head circumerence and intracranial volume. However, the variables have failed in describing the local deformations and morphological changes, which are proposed to more likely induce neurological disorders.

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 3-dimensional superimposition techniques on various skeletal structures of the head using surface models.

OBJECTIVES To test the applicability, accuracy, precision, and reproducibility of various 3D superimposition techniques for radiographic data, transformed to triangulated surface data. METHODS Five superimposition techniques (3P: three-point registration; AC: anterior cranial base; AC + F: anterior cranial base + foramen magnum; BZ: both zygomatic arches; 1Z: one zygomatic arch) were tested using eight pairs of pre-existing CT data (pre- and post-treatment). These were obtained from non-growing orthodontic patients treated with rapid maxillary expansion. All datasets were superimposed by three operators independently, who repeated the whole procedure one month later. Accuracy was assessed by the distance (D) between superimposed datasets on three form-stable anatomical areas, located on the anterior cranial base and the foramen magnum. Precision and reproducibility were assessed using the distances between models at four specific landmarks. Non parametric multivariate models and Bland-Altman difference plots were used for analyses. RESULTS There was no difference among operators or between time points on the accuracy of each superimposition technique (p>0.05). The AC + F technique was the most accurate (D<0.17 mm), as expected, followed by AC and BZ superimpositions that presented similar level of accuracy (D<0.5 mm). 3P and 1Z were the least accurate superimpositions (0.79<D<1.76 mm, p<0.005). Although there was no difference among operators or between time points on the precision of each superimposition technique (p>0.05), the detected structural changes differed significantly between different techniques (p<0.05). Bland-Altman difference plots showed that BZ superimposition was comparable to AC, though it presented slightly higher random error. CONCLUSIONS Superimposition of 3D datasets using surface models created from voxel data can provide accurate, precise, and reproducible results, offering also high efficiency and increased post-processing capabilities. In the present study population, the BZ superimposition was comparable to AC, with the added advantage of being applicable to scans with a smaller field of view.

AN EVALUATION OF THE CONSISTENCY OF IMRT PATIENT-SPECIFIC QA TECHNIQUES

To ensure the integrity of an intensity modulated radiation therapy (IMRT) treatment, each plan must be validated through a measurement-based quality assurance (QA) procedure, known as patient specific IMRT QA. Many methods of measurement and analysis have evolved for this QA. There is not a standard among clinical institutions, and many devices and action levels are used. Since the acceptance criteria determines if the dosimetric tools��� output passes the patient plan, it is important to see how these parameters influence the performance of the QA device. While analyzing the results of IMRT QA, it is important to understand the variability in the measurements. Due to the different form factors of the many QA methods, this reproducibility can be device dependent. These questions of patient-specific IMRT QA reproducibility and performance were investigated across five dosimeter systems: a helical diode array, radiographic film, ion chamber, diode array (AP field-by-field, AP composite, and rotational composite), and an in-house designed multiple ion chamber phantom. The reproducibility was gauged for each device by comparing the coefficients of variation (CV) across six patient plans. The performance of each device was determined by comparing each one���s ability to accurately label a plan as acceptable or unacceptable compared to a gold standard. All methods demonstrated a CV of less than 4%. Film proved to have the highest variability in QA measurement, likely due to the high level of user involvement in the readout and analysis. This is further shown by how the setup contributed more variation than the readout and analysis for all of the methods, except film. When evaluated for ability to correctly label acceptable and unacceptable plans, two distinct performance groups emerged with the helical diode array, AP composite diode array, film, and ion chamber in the better group; and the rotational composite and AP field-by-field diode array in the poorer group. Additionally, optimal threshold cutoffs were determined for each of the dosimetry systems. These findings, combined with practical considerations for factors such as labor and cost, can aid a clinic in its choice of an effective and safe patient-specific IMRT QA implementation.

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: macrosc��pica y microsc��pica. Muchas propiedades de los alimentos, que son importantes para su procesamiento, calidad y tratamiento postcosecha, est��n relacionados con su microestructura. La presente tesis doctoral propone una metodolog��a completa para la determinaci��n de la estructura de alimentos desde un punto de vista multi-escala, bas��ndose en m��todos de Resonancia Magn��tica Nuclear (NMR). Las t��cnicas 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 Magn��tica (MRI) ha resultado ser muy ��til para la caracterizaci��n de alimentos. Para el estudio microestructural, la MRI requiere altos tiempos de adquisici��n, lo que hace muy dif��cil la transferencia de esta t��cnica a aplicaciones en industria. Por tanto, la optimizaci��n de procedimientos de NMR basados en secuencias relaxometr��a 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 magn��tico. 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). Adem��s, como primer paso para su posterior implementaci��n en la industria agroalimentaria, se ha mejorado una l��nea transportadora, especialmente dise��ada para trabajar bajo condiciones de NMR en trabajos anteriores del grupo LPF-TAGRALIA. Se han estudiado y seleccionado las secuencias m��s r��pidas y ��ptimas para la detecci��n de dos tipos de des��rdenes internos en manzanas: vitrescencia y roturas internas. La correcci��n de las im��genes en movimiento se realiza en tiempo real. Asimismo, se han utilizado protocolos de visi��n artificial para la clasificaci��n autom��tica de manzanas potencialmente afectadas por vitrescencia. El presente documento est�� dividido en diferentes cap��tulos: el Cap��tulo 2 explica los antecedentes de la presente tesis y el marco del proyecto en el que se ha desarrollado. El Cap��tulo 3 recoge el estado del arte. El Cap��tulo 4 establece los objetivos de esta tesis doctoral. Los resultados se dividen en cinco sub-secciones (dentro del Cap��tulo 5) que corresponden con los trabajos publicados bien en revistas revisadas por pares, bien en congresos internacionales o bien como cap��tulos de libros revisados por pares. La Secci��n 5.1. es un estudio del desarrollo de la vitrescencia en manzanas mediante MRI y lo relaciona con la posici��n de la fruta dentro de la copa del ��rbol. La Secci��n 5.2 presenta un trabajo sobre macro- y microestructura en modelos de alimentos. La Secci��n 5.3 es un art��culo en revisi��n en una revista revisada por pares, en el que se hace un estudio microestrcutural no destructivo mediante relaxometr��a 2D T1/T2. la Secci��n 5.4, hace una comparaci��n entre manzanas afectadas por vitrescencia mediante dos t��cnicas: tomograf��a de rayos X e MRI, en manzana. Por ��ltimo, en la Secci��n 5.5 se muestra un trabajo en el que se hace un estudio de secuencias de MRI en l��nea para la evaluaci��n de calidad interna en manzanas. Los siguientes cap��tulos ofrecen una discusi��n y conclusiones (Cap��tulo 6 y 7 respectivamente) de todos los cap��tulos de esta tesis doctoral. Finalmente, se han a��adido tres ap��ndices: el primero con una introducci��n de los principios b��sicos de resonancia magn��tica nuclear (NMR) y en los otros dos, se presentan sendos estudios sobre el efecto de las fibras en la rehidrataci��n de cereales de desayuno extrusionados, mediante diversas t��cnicas. Ambos trabajos se presentaron en un congreso internacional. Los resultados m��s relevantes de la presente tesis doctoral, se pueden dividir en tres grandes bloques: resultados sobre macroestructura, resultados sobre microestructura y resultados sobre MRI en l��nea. Resultados sobre macroestructura: - La imagen de resonancia magn��tica (MRI) se aplic�� satisfactoriamente para la caracterizaci��n de macroestructura. En particular, la reconstrucci��n 3D de im��genes de resonancia magn��tica permiti�� identificar y caracterizar dos tipos distintos de vitrescencia en manzanas: central y radial, que se caracterizan por el porcentaje de da��o y la conectividad (n��mero de Euler). - La MRI prove��a un mejor contraste para manzanas afectadas por vitrescencia que las im��genes de tomograf��a de rayos X (X-Ray CT), como se pudo verificar en muestras id��nticas de manzana. Adem��s, el tiempo de adquisici��n de la tomograf��a de rayos X fue alrededor de 12 veces mayor (25 minutos) que la adquisici��n de las im��genes de resonancia magn��tica (2 minutos 2 segundos). Resultados sobre microestructura: - Para el estudio de microestructura (nivel subcelular) se utilizaron con ��xito secuencias de relaxometr��a 2D T1/T2. Estas secuencias se usaron por primera vez en alto campo y sobre piezas de alimento completo, convirti��ndose en una forma no destructiva de llevar a cabo estudios de microestructura. - El uso de MRI junto con relaxometr��a 2D T1/T2 permite realizar estudios multiescala en alimentos de forma no destructiva. Resultados sobre MRI en l��nea: - El uso de imagen de resonancia magn��tica en l��nea fue factible para la identificaci��n de dos tipos de des��rdenes internos en manzanas: vitrescencia y podredumbre interna. ������Las secuencias de imagen tipo FLASH resultaron adecuadas para la identificaci��n en l��nea de vitrescencia en manzanas. Se realiz�� sin selecci��n de corte, debido a que la vitrescencia puede desarrollarse en cualquier punto del volumen de la manzana. Se consigui�� reducir el tiempo de adquisici��n, 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 detecci��n en l��nea de la podredumbre interna en manzanas. En este caso, se utiliz�� selecci��n de corte, ya que se trata de un desorden que se suele localizar en la parte central del volumen de la manzana. Se consigui�� reducir el tiempo de adquisic��n hasta 0.67 frutos por segundo (1475 ms por fruto). ������En ambos casos (FLASH y UFLARE) fueron necesarios algoritmos para la correcci��n del movimiento de las im��genes 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.

Modeling of dangerous phenomena and innovative techniques for hazard evaluation and risk mitigation

Society is frequently exposed to and threatened by dangerous phenomena in many parts of the world. Different types of such phenomena require specific actions for proper risk management, from the stages of hazard identification to those of mitigation (including monitoring and early-warning) and/or reduction. The understanding of both predisposing factors and triggering mechanisms of a given danger and the prediction of its evolution from the source to the overall affected zone are relevant issues that must be addressed to properly evaluate a given hazard.

Evaluation of reactivity monitoring techniques at the Yalina ��� Booster subcritical facility

La gesti��n de los residuos radiactivos de vida larga producidos en los reactores nucleares constituye uno de los principales desaf��os de la tecnolog��a nuclear en la actualidad. Una posible opci��n para su gesti��n es la transmutaci��n de los nucleidos de vida larga en otros de vida m��s corta. Los sistemas subcr��ticos guiados por acelerador (ADS por sus siglas en ingl��s) son una de las tecnolog��as en desarrollo para logar este objetivo. Un ADS consiste en un reactor nuclear subcr��tico mantenido en un estado estacionario mediante una fuente externa de neutrones guiada por un acelerador de part��culas. El inter��s de estos sistemas radica en su capacidad para ser cargados con combustibles que tengan contenidos de act��nidos minoritarios mayores que los reactores cr��ticos convencionales, y de esta manera, incrementar las tasas de trasmutaci��n de estos elementos, que son los principales responsables de la radiotoxicidad a largo plazo de los residuos nucleares. Uno de los puntos clave que han sido identificados para la operaci��n de un ADS a escala industrial es la necesidad de monitorizar continuamente la reactividad del sistema subcr��tico durante la operaci��n. Por esta raz��n, desde los a��os 1990 se han realizado varios experimentos en conjuntos subcr��ticos de potencia cero (MUSE, RACE, KUCA, Yalina, GUINEVERE/FREYA) con el fin de validar experimentalmente estas t��cnicas. En este contexto, la presente tesis se ocupa de la validaci��n de t��cnicas de monitorizaci��n de la reactividad en el conjunto subcr��tico Yalina-Booster. Este conjunto pertenece al Joint Institute for Power and Nuclear Research (JIPNR-Sosny) de la Academia Nacional de Ciencias de Bielorrusia. Dentro del proyecto EUROTRANS del 6�� Programa Marco de la UE, en el a��o 2008 se ha realizado una serie de experimentos en esta instalaci��n concernientes a la monitorizaci��n de la reactividad bajo la direcci��n del CIEMAT. Se han realizado dos tipos de experimentos: experimentos con una fuente de neutrones pulsada (PNS) y experimentos con una fuente continua con interrupciones cortas (beam trips). En el caso de los primeros, experimentos con fuente pulsada, existen dos t��cnicas fundamentales para medir la reactividad, conocidas como la t��cnica del ratio bajo las ��reas de los neutrones inmediatos y retardados (o t��cnica de Sj��strand) y la t��cnica de la constante de decaimiento de los neutrones inmediatos. Sin embargo, varios experimentos han mostrado la necesidad de aplicar t��cnicas de correcci��n para tener en cuenta los efectos espaciales y energ��ticos presentes en un sistema real y obtener valores precisos de la reactividad. En esta tesis, se han investigado estas correcciones mediante simulaciones del sistema con el c��digo de Montecarlo MCNPX. Esta investigaci��n ha servido tambi��n para proponer una versi��n generalizada de estas t��cnicas donde se buscan relaciones entre la reactividad el sistema y las cantidades medidas a trav��s de simulaciones de Monte Carlo. El segundo tipo de experimentos, experimentos con una fuente continua e interrupciones del haz, es m��s probable que sea empleado en un ADS industrial. La versi��n generalizada de las t��cnicas desarrolladas para los experimentos con fuente pulsada tambi��n ha sido aplicada a los resultados de estos experimentos. Adem��s, el trabajo presentado en esta tesis es la primera vez, en mi conocimiento, en que la reactividad de un sistema subcr��tico se monitoriza durante la operaci��n con tres t��cnicas simult��neas: la t��cnica de la relaci��n entre la corriente y el flujo (current-to-flux), la t��cnica de desconexi��n r��pida de la fuente (source-jerk) y la t��cnica del decaimiento de los neutrones inmediatos. Los casos analizados incluyen la variaci��n r��pida de la reactividad del sistema (inserci��n y extracci��n de las barras de control) y la variaci��n r��pida de la fuente de neutrones (interrupci��n larga del haz y posterior recuperaci��n). ABSTRACT The management of long-lived radioactive wastes produced by nuclear reactors constitutes one of the main challenges of nuclear technology nowadays. A possible option for its management consists in the transmutation of long lived nuclides into shorter lived ones. Accelerator Driven Subcritical Systems (ADS) are one of the technologies in development to achieve this goal. An ADS consists in a subcritical nuclear reactor maintained in a steady state by an external neutron source driven by a particle accelerator. The interest of these systems lays on its capacity to be loaded with fuels having larger contents of minor actinides than conventional critical reactors, and in this way, increasing the transmutation rates of these elements, that are the main responsible of the long-term radiotoxicity of nuclear waste. One of the key points that have been identified for the operation of an industrial-scale ADS is the need of continuously monitoring the reactivity of the subcritical system during operation. For this reason, since the 1990s a number of experiments have been conducted in zero-power subcritical assemblies (MUSE, RACE, KUCA, Yalina, GUINEVERE/FREYA) in order to experimentally validate these techniques. In this context, the present thesis is concerned with the validation of reactivity monitoring techniques at the Yalina-Booster subcritical assembly. This assembly belongs to the Joint Institute for Power and Nuclear Research (JIPNR-Sosny) of the National Academy of Sciences of Belarus. Experiments concerning reactivity monitoring have been performed in this facility under the EUROTRANS project of the 6th EU Framework Program in year 2008 under the direction of CIEMAT. Two types of experiments have been carried out: experiments with a pulsed neutron source (PNS) and experiments with a continuous source with short interruptions (beam trips). For the case of the first ones, PNS experiments, two fundamental techniques exist to measure the reactivity, known as the prompt-to-delayed neutron area-ratio technique (or Sj��strand technique) and the prompt neutron decay constant technique. However, previous experiments have shown the need to apply correction techniques to take into account the spatial and energy effects present in a real system and thus obtain accurate values for the reactivity. In this thesis, these corrections have been investigated through simulations of the system with the Monte Carlo code MCNPX. This research has also served to propose a generalized version of these techniques where relationships between the reactivity of the system and the measured quantities are obtained through Monte Carlo simulations. The second type of experiments, with a continuous source with beam trips, is more likely to be employed in an industrial ADS. The generalized version of the techniques developed for the PNS experiments has also been applied to the result of these experiments. Furthermore, the work presented in this thesis is the first time, to my knowledge, that the reactivity of a subcritical system has been monitored during operation simultaneously with three different techniques: the current-to-flux, the source-jerk and the prompt neutron decay techniques. The cases analyzed include the fast variation of the system reactivity (insertion and extraction of a control rod) and the fast variation of the neutron source (long beam interruption and subsequent recovery).

M��todos diferenciales e interferom��tricos para la evaluaci��n de deformaciones de la corteza terrestre mediante t��cnicas GNSS e InSAR = Differential and interferometric methods for evaluation of crustal deformation using GNSS and InSAR techniques

La actividad volc��nica interviene en multitud de facetas de la propia actividad humana, no siempre negativas. Sin embargo, son m��s los motivos de peligrosidad y riesgo que incitan al estudio de la actividad volc��nica. Existen razones de seguridad que inciden en el mantenimiento del seguimiento y monitorizaci��n de la actividad volc��nica para garantizar la vida y la seguridad de los asentamientos antr��picos en las proximidades de los edificios volc��nicos. En esta tesis se define e implementa un sistema de monitorizaci��n de movimientos de la corteza en las islas de Tenerife y La Palma, donde el impacto social que representa un aumento o variaci��n de la actividad volc��nica en las islas es muy severo. Aparte de la alta densidad demogr��fica del Archipi��lago, esta poblaci��n aumenta significativamente, en diferentes periodos a lo largo del a��o, debido a la actividad tur��stica que representa la mayor fuente de ingresos de las islas. La poblaci��n y los centros tur��sticos se diseminan predominantemente a lo largo de las costas y tambi��n a lo largo de los flancos de los edificios volc��nicos. Quiz�� el mantenimiento de estas estructuras sociales y socio-econ��micas son los motivos m��s importantes que justifican una monitorizaci��n de la actividad volc��nica en las Islas Canarias. Recientemente se ha venido trabajando cada vez m��s en el intento de predecir la actividad volc��nica utilizando los nuevos sistemas de monitorizaci��n geod��sica, puesto que la actividad volc��nica se manifiesta anteriormente por deformaci��n de la corteza terrestre y cambios en la fuerza de la gravedad en la zona donde m��s tarde se registran eventos volc��nicos. Los nuevos dispositivos y sensores que se han desarrollado en los ��ltimos a��os en materias como la geodesia, la observaci��n de la Tierra desde el espacio y el posicionamiento por sat��lite, han permitido observar y medir tanto la deformaci��n producida en el terreno como los cambios de la fuerza de la gravedad antes, durante y posteriormente a los eventos volc��nicos que se producen. Estos nuevos dispositivos y sensores han cambiado las t��cnicas o metodolog��as geod��sicas que se ven��an utilizando hasta la aparici��n de los mismos, renovando m��todos cl��sicos y desarrollando otros nuevos que ya se est��n afianzando como metodolog��as probadas y reconocidas para ser usadas en la monitorizaci��n volc��nica. Desde finales de la d��cada de los noventa del siglo pasado se han venido desarrollando en las Islas Canarias varios proyectos que han tenido como objetivos principales el desarrollo de nuevas t��cnicas de observaci��n y monitorizaci��n por un lado y el dise��o de una metodolog��a de monitorizaci��n volc��nica adecuada, por otro. Se presenta aqu�� el estudio y desarrollo de t��cnicas GNSS para la monitorizaci��n de deformaciones corticales y su campo de velocidades para las islas de Tenerife y La Palma. En su implementaci��n, se ha tenido en cuenta el uso de la infraestructura geod��sica y de monitorizaci��n existente en el archipi��lago a fin de optimizar costes, adem��s de complementarla con nuevas estaciones para dar una cobertura total a las dos islas. Los resultados obtenidos en los proyectos, que se describen en esta memoria, han dado nuevas perspectivas en la monitorizaci��n geod��sica de la actividad volc��nica y nuevas zonas de inter��s que anteriormente no se conoc��an en el entorno de las Islas Canarias. Se ha tenido especial cuidado en el tratamiento y propagaci��n de los errores durante todo el proceso de observaci��n, medida y proceso de los datos registrados, todo ello en aras de cuantificar el grado de fiabilidad de los resultados obtenidos. Tambi��n en este sentido, los resultados obtenidos han sido verificados con otros procedentes de sistemas de observaci��n radar de sat��lite, incorporando adem��s a este estudio las implicaciones que el uso conjunto de tecnolog��as radar y GNSS tendr��n en un futuro en la monitorizaci��n de deformaciones de la corteza terrestre. ABSTRACT Volcanic activity occurs in many aspects of human activity, and not always in a negative manner. Nonetheless, research into volcanic activity is more likely to be motivated by its danger and risk. There are security reasons that influence the monitoring of volcanic activity in order to guarantee the life and safety of human settlements near volcanic edifices. This thesis defines and implements a monitoring system of movements in the Earth���s crust in the islands of Tenerife and La Palma, where the social impact of an increase (or variation) of volcanic activity is very severe. Aside from the high demographic density of the archipelago, the population increases significantly in different periods throughout the year due to tourism, which represents a major source of revenue for the islands. The population and the tourist centres are mainly spread along the coasts and also along the flanks of the volcanic edifices. Perhaps the preservation of these social and socio-economic structures is the most important reason that justifies monitoring volcanic activity in the Canary Islands. Recently more and more work has been done with the intention of predicting volcanic activity, using new geodesic monitoring systems, since volcanic activity is evident prior to eruption because of a deformation of the Earth���s crust and changes in the force of gravity in the zone where volcanic events will later be recorded. The new devices and sensors that have been developed in recent years in areas such as geodesy, the observation of the Earth from space, and satellite positioning have allowed us to observe and measure the deformation produced in the Earth as well as the changes in the force of gravity before, during, and after the volcanic events occur. The new devices and sensors have changed the geodetic techniques and methodologies that were used previously. The classic methods have been renovated and other newer ones developed that are now vouched for as proven recognised methodologies to be used for volcanic monitoring. Since the end of the 1990s, in the Canary Islands various projects have been developed whose principal aim has been the development of new observation and monitoring techniques on the one hand, and the design of an appropriate volcanic monitoring methodology on the other. The study and development of GNSS techniques for the monitoring of crustal deformations and their velocity field is presented here. To carry out the study, the use of geodetic infrastructure and existing monitoring in the archipelago have been taken into account in order to optimise costs, besides complementing it with new stations for total coverage on both islands. The results obtained in the projects, which are described below, have produced new perspectives in the geodetic monitoring of volcanic activity and new zones of interest which previously were unknown in the environment of the Canary Islands. Special care has been taken with the treatment and propagation of errors during the entire process of observing, measuring, and processing the recorded data. All of this was done in order to quantify the degree of trustworthiness of the results obtained. Also in this sense, the results obtained have been verified with others from satellite radar observation systems, incorporating as well in this study the implications that the joint use of radar technologies and GNSS will have for the future of monitoring deformations in the Earth���s crust.