Does Age Matter? Semantic Memory in Healthy Young and Elderly Adults

Background: Semantic memory processes have been well described in literature. However, the available findings are mostly based on relatively young subjects and concrete word material (e.g. tree). Comparatively little information exists about semantic memory for abstract words (e.g. mind) and possible age related changes in semantic retrieval. In this respect, we developed a paradigm that is useful to investigate the implicit (i.e. attentionindependent) access to concrete and abstract semantic memory. These processes were then compared between young and elderly healthy subjects. Methods: A well established tool for investigating semantic memory processes is the semantic priming paradigm, which consists both of semantically unrelated and related word pairs. In our behavioral task these noun-noun word pairs were further divided into concrete, abstract and matched pronounceable non-word conditions. With this premise, the young and elderly participants performed a lexical decision task: they were asked to press a choice of two buttons as an indication for whether the word pair contained a non-word or not. In order to minimize controlled (i.e. attention-dependent) retrieval strategies, a short stimulus onset asynchrony (SOA) of 150ms was set. Reaction time (RT) changes and accuracy to related and unrelated words (priming effect) in the abstract vs. concrete condition (concreteness effect) were the dependent variables of interest. Results and Discussion: Statistical analysis confirmed both a significant priming effect (i.e. shorter RTs in semantically related compared to unrelated words) and a concreteness effect (i.e. RT decrease for concrete compared to abstract words) in the young and elderly subjects. There was no age difference in accuracy. The only age effect was a commonly known general slowing in RT over all conditions. In conclusion, age is not a critical factor in the implicit access to abstract and concrete semantic memory.

The legacy of Israel : essays

by Sir George Adam Smith ... ; planned by ... Israel Abrahams and ed. by Edwyn R. Bevan ... With an introduction by the master of Balliol

The stable carbon isotopic composition of Daphnia ephippia in small, temperate lakes reflects in-lake methane availability

Daphnia can ingest methane-oxidizing bacteria and incorporate methanogenic carbon into their biomass, leading to low stable carbon isotope ratios (expressed as δ13C values) of their tissue. Therefore, δ13C analysis of Daphnia resting eggs (ephippia) in lake sediment records can potentially be used to reconstruct past in-lake availability of methane (CH4). However, detailed multilake studies demonstrating that δ13C values of recently deposited Daphnia ephippia (δ13Cephippia) are systematically related to in-lake CH4 concentrations (CH4aq) are still missing. We measured δ13Cephippia from surface sediments of 15 small lakes in Europe, and compared these values with late-summer CH4aq. δ13Cephippia ranged from −51.6‰ to −25.9‰, and was strongly correlated with CH4aq in the surface water and above the sediment (r −0.73 and −0.77, respectively), whereas a negative rather than the expected positive correlation was found with δ13C values of carbon dioxide (CO2) (r −0.54), and no correlation was observed with CO2aq. At eight sites, offsets between δ13 CCO2 and δ13Cephippia exceeded offsets between δ13 CCO2 and δ13Calgae reported in literature. δ13Cephippia was positively correlated with δ13C values of sedimentary organic matter (r 0.54), but up to 20.7‰ lower in all except one of the lakes (average −6.1‰). We conclude that incorporation of methanogenic carbon prior to ephippia formation must have been widespread by Daphnia in our study lakes, especially those with high CH4aq. Our results suggest a systematic relationship between δ13Cephippia values and CH4aq in small temperate lakes, and that δ13Cephippia analysis on sediment records may provide insights into past changes in in-lake CH4aq.

Fatal steamer accident; blunt force injuries and drowning in post-mortem MSCT and MRI.

Steamer accidents, through contact with the bucket wheel, are very seldom today. No publication of such a kind of fatal accident could be found in literature. We present the case of a fatal steamer accident, in which the findings of a blunt traumatization of a person by the ship was completely documented by post-mortem combined multi-slice computed tomography (MSCT) and magnetic resonance imaging (MRI) examinations. A rupture of the aorta was detected using both radiological methods without use of radiopaque material. Radiological examination revealed a comminuted fracture of the thorax vertebrae at the same level as the aortic rupture. Injuries of the soft tissues of the back, caused by the bucket wheel of the steamer, were also diagnosed. In addition to the signs of blunt force trauma the findings of drowning such as an over inflation of the lungs, fluid in the stomach and duodenum were revealed. Furthermore, algological analysis detected diatoms in the lung tissue and blood from the left heart. Therefore, the cause of death was considered being a combination of fatal hemorrhage, caused by the aortic rupture, and drowning. We conclude that virtual autopsy using combined post-mortem MSCT and MRI is a useful tool for documentation, visualisation and analysis of the findings of blunt force trauma and drowning with a large potential in forensic medicine.

129I/127I ratios and 129I concentrations in a recent sea sediment core and in rainwater from Sevilla (Spain) by AMS

In spite of the environmental relevance of 129I, there is still a scarcity of data about its presence in the different natural compartments. In this work, results are presented on the concentration of 129I in rainwater samples taken in Sevilla (southwestern Spain) and in a sediment core taken near the Ringhals coast (Sweden). Typical concentrations of 108 and 109129I at/l are found in rainwater samples, similar to other values in literature. In the case of the sediment core, our results clearly show the impact of anthropogenic sources, with concentrations in the order of 1013129I at./kg and isotopic ratios 129I/127I in the order of 10−8 in the higher layers.

New Clinical Indications for (18)F/(11)C-choline, New Tracers for Positron Emission Tomography and a Promising Hybrid Device for Prostate Cancer Staging: A Systematic Review of the Literature

CONTEXT Radiolabelled choline positron emission tomography has changed the management of prostate cancer patients. However, new emerging radiopharmaceutical agents, like radiolabelled prostate specific membrane antigen, and new promising hybrid imaging will begin new challenges in the diagnostic field. OBJECTIVE The continuous evolution in nuclear medicine has led to the improvement in the detection of recurrent prostate cancer (PCa), particularly distant metastases. New horizons have been opened for radiolabelled choline positron emission tomography (PET)/computed tomography (CT) as a guide for salvage therapy or for the assessment of systemic therapies. In addition, new tracers and imaging tools have been recently tested, providing important information for the management of PCa patients. Herein we discuss: (1) the available evidence in literature on radiolabelled choline PET and their recent indications, (2) the role of alternative radiopharmaceutical agents, and (3) the advantages of a recent hybrid imaging device (PET/magnetic resonance imaging) in PCa. EVIDENCE ACQUISITION Data from recently published (2010-2015), original articles concerning the role of choline PET/CT, new emerging radiotracers, and a new imaging device are analysed. This review is reported according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. EVIDENCE SYNTHESIS In the restaging phase, the detection rate of choline PET varies between 4% and 97%, mainly depending on the site of recurrence and prostate-specific antigen levels. Both 68gallium (68Ga)-prostate specific membrane antigen and 18F-fluciclovine are shown to be more accurate in the detection of recurrent disease as compared with radiolabelled choline PET/CT. Particularly, Ga68-PSMA has a detection rate of 50% and 68%, respectively for prostate-specific antigen levels < 0.5ng/ml and 0.5-2ng/ml. Moreover, 68Ga- PSMA PET/magnetic resonance imaging demonstrated a particularly higher accuracy in detecting PCa than PET/CT. New tracers, such as radiolabelled bombesin or urokinase-type plasminogen activator receptor, are promising, but few data in clinical practice are available today. CONCLUSIONS Some limitations emerge from the published papers, both for radiolabelled choline PET/CT and also for new radiopharmaceutical agents. Efforts are still needed to enhance the impact of published data in the world of oncology, in particular when new radiopharmaceuticals are introduced into the clinical arena. PATIENT SUMMARY In the present review, the authors summarise the last evidences in clinical practice for the assessment of prostate cancer, by using nuclear medicine modalities, like positron emission tomography/computed tomography and positron emission tomography/magnetic resonance imaging.

Effectiveness of healthcare waste management interventions in developing countries

Inefficiencies during the management of healthcare waste can give rise to undesirable health effects such as transmission of infections and environmental pollution within and beyond the health facilities generating these wastes. Factors such as prevalence of diseases, conflicts, and the efflux of intellectual capacity make low income countries more susceptible to these adverse health effects. The purpose of this systematic review was to describe the effectiveness of interventions geared towards better managing the generation, collection, transport, treatment and disposal of medical waste, as they have been applied in lower and middle income countries.^ Using a systematic search strategy and evaluation of study quality, this study reviewed the literature for published studies on healthcare waste management interventions carried out in developing countries, specifically the low and lower middle income countries from year 2000 to the current year. From an initially identified set of 829 studies, only three studies ultimately met all inclusion, exclusion and high quality criteria. A multi component intervention in Syrian Arab Republic, conducted in 2007 was aimed at improving waste segregation practice in a hospital setting. There was an increased use of segregation boxes and reduced rates of sharps injury among staff as a result of the intervention. Another study, conducted in 2008, trained medical students as monitors of waste segregation practice in an Indian teaching hospital. There was improved practice in wards and laboratories but not in the intensive care units. The third study, performed in 2008 in China, consisted of modification of the components of a medical waste incinerator to improve efficiency and reduce stack emissions. Gaseous pollutants emitted, except polychlorodibenzofurans (PCDF) were below US EPA permissible exposure limits. Heavy metal residues in the fly ash remained unchanged.^ Due to the paucity of well-designed studies, there is insufficient evidence in literature to conclude on the effectiveness of interventions in low income settings. There is suggestive but insufficient evident that multi-component interventions aimed at improving waste segregation through behavior modification, provision of segregation tools and training of monitors are effective in low income settings.^

2005 ACIP recommendations effect on newborn hepatitis B vaccination rates and the factors affecting the successful implementation of the recommendations in the US

Background. Hepatitis B virus infection is one of major causes of acute and chronic hepatitis, cirrhosis of the liver, and primary hepatocellular carcinoma. Hepatitis B and its long term consequences are major health problems in the United States. Hepatitis B virus can be vertically transmitted from mother to infant during birth. Hepatitis B vaccination at birth is the most effective measure to prevent the newborn from HBV infection and its consequences, and is part of any robust perinatal hepatitis B prevention program following ACIP recommendations. Universal vaccination of the new born will prevent HBV infection during early childhood and, assuming that children receive the three dosages of the vaccine, it will also prevent adolescent and adult infections. Hepatitis B vaccination is now recommended as part of a comprehensive strategy to eliminate HBV transmission in the United States. ^ Objective. (1)To assess if the hepatitis B vaccination rates of newborn babies have improved after the 2005 ACIP recommendations. (2) To identify factors that affects the implementation of ACIP recommendation for hepatitis B vaccination in newborn babies. These factors will encourage ongoing improvement by identifying successful efforts and pinpointing areas that fall short and need attention. Additional focus areas may be identified to accelerate progress in eliminating perinatal HBV transmission.^ Methods. This review includes information from all pertinent articles, reviews, National immunization survey (NIS) surveys, reports, peer reviewed literature and web sources that were published after 1991.The key words to be used for selecting the articles are: "Perinatal Hepatitis B Prevention program", "Universal Hepatitis B vaccination of newborn babies", "ACIP Recommendations." The data gathered will be supplemented with an analysis of vaccination rates using the National Immunization Survey (NIS) birth dose coverage data.^ Results. The data collected in the NIS of 2009 reveals that the national coverage for birth dose of HepB increased to 60.8% from 50.1% in 2006. The largest increase observed for the birth dose in the past 5 years is from 2008 which increased from 55.3 % to 60.8% in 2009. By state, coverage ranged from 22.8% in Vermont to 80.7% in Michigan. %. Overall, in 2009 the estimated vaccination rates are in higher ranges for most states compared to the estimated vaccination rates in 2006. States vary widely in hepatitis B vaccination rates and in their compliance with the 2005 ACIP recommendation. There are many factors at various stages that might affect the successful implementation of the new ACIP recommendation as revealed in literature review. ^ Conclusions. HBV perinatal transmission can be eliminated, but it requires identifying the gaps and measures taken to increase the current vaccination coverage, ensuring timely administration of post exposure immunoprophylaxis and continued evaluations of the impact of immunization recommendations.^

Gaussian Multiscale Aggregation oriented to Hand Biometric Segmentation in Mobile Devices

New trends in biometrics are oriented to mobile devices in order to increase the overall security in daily actions like bank account access, e-commerce or even document protection within the mobile. However, applying biometrics to mobile devices imply challenging aspects in biometric data acquisition, feature extraction or private data storage. Concretely, this paper attempts to deal with the problem of hand segmentation given a picture of the hand in an unknown background, requiring an accurate result in terms of hand isolation. For the sake of user acceptability, no restrictions are done on background, and therefore, hand images can be taken without any constraint, resulting segmentation in an exigent task. Multiscale aggregation strategies are proposed in order to solve this problem due to their accurate results in unconstrained and complicated scenarios, together with their properties in time performance. This method is evaluated with a public synthetic database with 480000 images considering different backgrounds and illumination environments. The results obtained in terms of accuracy and time performance highlight their capability of being a suitable solution for the problem of hand segmentation in contact-less environments, outperforming competitive methods in literature like Lossy Data Compression image segmentation (LDC).

Gaussian Multiscale Aggregation Applied to Segmentation in Hand Biometrics

This paper presents an image segmentation algorithm based on Gaussian multiscale aggregation oriented to hand biometric applications. The method is able to isolate the hand from a wide variety of background textures such as carpets, fabric, glass, grass, soil or stones. The evaluation was carried out by using a publicly available synthetic database with 408,000 hand images in different backgrounds, comparing the performance in terms of accuracy and computational cost to two competitive segmentation methods existing in literature, namely Lossy Data Compression (LDC) and Normalized Cuts (NCuts). The results highlight that the proposed method outperforms current competitive segmentation methods with regard to computational cost, time performance, accuracy and memory usage.

Automatic physical activity pattern recognition and meal intake modelling in type 1 diabetes for their inclusion in artificial pancreas systems

La diabetes comprende un conjunto de enfermedades metabólicas que se caracterizan por concentraciones de glucosa en sangre anormalmente altas. En el caso de la diabetes tipo 1 (T1D, por sus siglas en inglés), esta situación es debida a una ausencia total de secreción endógena de insulina, lo que impide a la mayoría de tejidos usar la glucosa. En tales circunstancias, se hace necesario el suministro exógeno de insulina para preservar la vida del paciente; no obstante, siempre con la precaución de evitar caídas agudas de la glucemia por debajo de los niveles recomendados de seguridad. Además de la administración de insulina, las ingestas y la actividad física son factores fundamentales que influyen en la homeostasis de la glucosa. En consecuencia, una gestión apropiada de la T1D debería incorporar estos dos fenómenos fisiológicos, en base a una identificación y un modelado apropiado de los mismos y de sus sorrespondientes efectos en el balance glucosa-insulina. En particular, los sistemas de páncreas artificial –ideados para llevar a cabo un control automático de los niveles de glucemia del paciente– podrían beneficiarse de la integración de esta clase de información. La primera parte de esta tesis doctoral cubre la caracterización del efecto agudo de la actividad física en los perfiles de glucosa. Con este objetivo se ha llevado a cabo una revisión sistemática de la literatura y meta-análisis que determinen las respuestas ante varias modalidades de ejercicio para pacientes con T1D, abordando esta caracterización mediante unas magnitudes que cuantifican las tasas de cambio en la glucemia a lo largo del tiempo. Por otro lado, una identificación fiable de los periodos con actividad física es un requisito imprescindible para poder proveer de esa información a los sistemas de páncreas artificial en condiciones libres y ambulatorias. Por esta razón, la segunda parte de esta tesis está enfocada a la propuesta y evaluación de un sistema automático diseñado para reconocer periodos de actividad física, clasificando su nivel de intensidad (ligera, moderada o vigorosa); así como, en el caso de periodos vigorosos, identificando también la modalidad de ejercicio (aeróbica, mixta o de fuerza). En este sentido, ambos aspectos tienen una influencia específica en el mecanismo metabólico que suministra la energía para llevar a cabo el ejercicio y, por tanto, en las respuestas glucémicas en T1D. En este trabajo se aplican varias combinaciones de técnicas de aprendizaje máquina y reconocimiento de patrones sobre la fusión multimodal de señales de acelerometría y ritmo cardíaco, las cuales describen tanto aspectos mecánicos del movimiento como la respuesta fisiológica del sistema cardiovascular ante el ejercicio. Después del reconocimiento de patrones se incorpora también un módulo de filtrado temporal para sacar partido a la considerable coherencia temporal presente en los datos, una redundancia que se origina en el hecho de que en la práctica, las tendencias en cuanto a actividad física suelen mantenerse estables a lo largo de cierto tiempo, sin fluctuaciones rápidas y repetitivas. El tercer bloque de esta tesis doctoral aborda el tema de las ingestas en el ámbito de la T1D. En concreto, se propone una serie de modelos compartimentales y se evalúan éstos en función de su capacidad para describir matemáticamente el efecto remoto de las concetraciones plasmáticas de insulina exógena sobre las tasas de eleiminación de la glucosa atribuible a la ingesta; un aspecto hasta ahora no incorporado en los principales modelos de paciente para T1D existentes en la literatura. Los datos aquí utilizados se obtuvieron gracias a un experimento realizado por el Institute of Metabolic Science (Universidad de Cambridge, Reino Unido) con 16 pacientes jóvenes. En el experimento, de tipo ‘clamp’ con objetivo variable, se replicaron los perfiles individuales de glucosa, según lo observado durante una visita preliminar tras la ingesta de una cena con o bien alta carga glucémica, o bien baja. Los seis modelos mecanísticos evaluados constaban de: a) submodelos de doble compartimento para las masas de trazadores de glucosa, b) un submodelo de único compartimento para reflejar el efecto remoto de la insulina, c) dos tipos de activación de este mismo efecto remoto (bien lineal, bien con un punto de corte), y d) diversas condiciones iniciales. ABSTRACT Diabetes encompasses a series of metabolic diseases characterized by abnormally high blood glucose concentrations. In the case of type 1 diabetes (T1D), this situation is caused by a total absence of endogenous insulin secretion, which impedes the use of glucose by most tissues. In these circumstances, exogenous insulin supplies are necessary to maintain patient’s life; although caution is always needed to avoid acute decays in glycaemia below safe levels. In addition to insulin administrations, meal intakes and physical activity are fundamental factors influencing glucose homoeostasis. Consequently, a successful management of T1D should incorporate these two physiological phenomena, based on an appropriate identification and modelling of these events and their corresponding effect on the glucose-insulin balance. In particular, artificial pancreas systems –designed to perform an automated control of patient’s glycaemia levels– may benefit from the integration of this type of information. The first part of this PhD thesis covers the characterization of the acute effect of physical activity on glucose profiles. With this aim, a systematic review of literature and metaanalyses are conduced to determine responses to various exercise modalities in patients with T1D, assessed via rates-of-change magnitudes to quantify temporal variations in glycaemia. On the other hand, a reliable identification of physical activity periods is an essential prerequisite to feed artificial pancreas systems with information concerning exercise in ambulatory, free-living conditions. For this reason, the second part of this thesis focuses on the proposal and evaluation of an automatic system devised to recognize physical activity, classifying its intensity level (light, moderate or vigorous) and for vigorous periods, identifying also its exercise modality (aerobic, mixed or resistance); since both aspects have a distinctive influence on the predominant metabolic pathway involved in fuelling exercise, and therefore, in the glycaemic responses in T1D. Various combinations of machine learning and pattern recognition techniques are applied on the fusion of multi-modal signal sources, namely: accelerometry and heart rate measurements, which describe both mechanical aspects of movement and the physiological response of the cardiovascular system to exercise. An additional temporal filtering module is incorporated after recognition in order to exploit the considerable temporal coherence (i.e. redundancy) present in data, which stems from the fact that in practice, physical activity trends are often maintained stable along time, instead of fluctuating rapid and repeatedly. The third block of this PhD thesis addresses meal intakes in the context of T1D. In particular, a number of compartmental models are proposed and compared in terms of their ability to describe mathematically the remote effect of exogenous plasma insulin concentrations on the disposal rates of meal-attributable glucose, an aspect which had not yet been incorporated to the prevailing T1D patient models in literature. Data were acquired in an experiment conduced at the Institute of Metabolic Science (University of Cambridge, UK) on 16 young patients. A variable-target glucose clamp replicated their individual glucose profiles, observed during a preliminary visit after ingesting either a high glycaemic-load or a low glycaemic-load evening meal. The six mechanistic models under evaluation here comprised: a) two-compartmental submodels for glucose tracer masses, b) a single-compartmental submodel for insulin’s remote effect, c) two types of activations for this remote effect (either linear or with a ‘cut-off’ point), and d) diverse forms of initial conditions.

Selected topics in the Hydrodynamics of floating offshore wind turbines: heave damping and second order surge motions

La Energía eléctrica producida mediante tecnología eólica flotante es uno de los recursos más prometedores para reducir la dependencia de energía proveniente de combustibles fósiles. Esta tecnología es de especial interés en países como España, donde la plataforma continental es estrecha y existen pocas áreas para el desarrollo de estructuras fijas. Entre los diferentes conceptos flotantes, esta tesis se ha ocupado de la tipología semisumergible. Estas plataformas pueden experimentar movimientos resonantes en largada y arfada. En largada, dado que el periodo de resonancia es largo estos puede ser inducidos por efectos de segundo orden de deriva lenta que pueden tener una influencia muy significativa en las cargas en los fondeos. En arfada las fuerzas de primer orden pueden inducir grandes movimientos y por tanto la correcta determinación del amortiguamiento es esencial para la analizar la operatividad de la plataforma. Esta tesis ha investigado estos dos efectos, para ello se ha usado como caso base el diseño de una plataforma desarrollada en el proyecto Europeo Hiprwind. La plataforma se compone de 3 columnas cilíndricas unidas mediante montantes estructurales horizontales y diagonales, Los cilindros proporcionan flotabilidad y momentos adrizante. A la base de cada columna se le ha añadido un gran “Heave Plate” o placa de cierre. El diseño es similar a otros diseños previos (Windfloat). Se ha fabricado un modelo a escala de una de las columnas para el estudio detallado del amortiguamiento mediante oscilaciones forzadas. Las dimensiones del modelo (1m diámetro en la placa de cierre) lo hacen, de los conocidos por el candidato, el mayor para el que se han publicado datos. El diseño del cilindro se ha realizado de tal manera que permite la fijación de placas de cierre planas o con refuerzo, ambos modelos se han fabricado y analizado. El modelo con refuerzos es una reproducción exacta del diseño a escala real incluyendo detalles distintivos del mismo, siendo el más importante la placa vertical perimetral. Los ensayos de oscilaciones forzadas se han realizado para un rango de frecuencias, tanto para el disco plano como el reforzado. Se han medido las fuerzas durante los ensayos y se han calculado los coeficientes de amortiguamiento y de masa añadida. Estos coeficientes son necesarios para el cálculo del fondeo mediante simulaciones en el dominio del tiempo. Los coeficientes calculados se han comparado con la literatura existente, con cálculos potenciales y por ultimo con cálculos CFD. Para disponer de información relevante para el diseño estructural de la plataforma se han medido y analizado experimentalmente las presiones en la parte superior e inferior de cada placa de cierre. Para la correcta estimación numérica de las fuerzas de deriva lenta en la plataforma se ha realizado una campaña experimental que incluye ensayos con modelo cautivo de la plataforma completa en olas bicromaticas. Pese a que estos experimentos no reproducen un escenario de oleaje realista, los mismos permiten una verificación del modelo numérico mediante la comparación de fuerzas medidas en el modelo físico y el numérico. Como resultados de esta tesis podemos enumerar las siguientes conclusiones. 1. El amortiguamiento y la masa añadida muestran una pequeña dependencia con la frecuencia pero una gran dependencia con la amplitud del movimiento. siendo coherente con investigaciones existentes. 2. Las medidas con la placa de cierre reforzada con cierre vertical en el borde, muestra un amortiguamiento significativamente menor comparada con la placa plana. Esto implica que para ensayos de canal es necesario incluir estos detalles en el modelo. 3. La masa añadida no muestra grandes variaciones comparando placa plana y placa con refuerzos. 4. Un coeficiente de amortiguamiento del 6% del crítico se puede considerar conservador para el cálculo en el dominio de la frecuencia. Este amortiguamiento es equivalente a un coeficiente de “drag” de 4 en elementos de Morison cuadráticos en las placas de cierre usadas en simulaciones en el dominio del tiempo. 5. Se han encontrado discrepancias en algunos valores de masa añadida y amortiguamiento de la placa plana al comparar con datos publicados. Se han propuesto algunas explicaciones basadas en las diferencias en la relación de espesores, en la distancia a la superficie libre y también relacionadas con efectos de escala. 6. La presión en la placa con refuerzos son similares a las de la placa plana, excepto en la zona del borde donde la placa con refuerzo vertical induce una gran diferencias de presiones entre la cara superior e inferior. 7. La máxima diferencia de presión escala coherentemente con la fuerza equivalente a la aceleración de la masa añadida distribuida sobre la placa. 8. Las masas añadidas calculadas con el código potencial (WADAM) no son suficientemente precisas, Este software no contempla el modelado de placas de pequeño espesor con dipolos, la poca precisión de los resultados aumenta la importancia de este tipo de elementos al realizar simulaciones con códigos potenciales para este tipo de plataformas que incluyen elementos de poco espesor. 9. Respecto al código CFD (Ansys CFX) la precisión de los cálculos es razonable para la placa plana, esta precisión disminuye para la placa con refuerzo vertical en el borde, como era de esperar dado la mayor complejidad del flujo. 10. Respecto al segundo orden, los resultados, en general, muestran que, aunque la tendencia en las fuerzas de segundo orden se captura bien con los códigos numéricos, se observan algunas reducciones en comparación con los datos experimentales. Las diferencias entre simulaciones y datos experimentales son mayores al usar la aproximación de Newman, que usa únicamente resultados de primer orden para el cálculo de las fuerzas de deriva media. 11. Es importante remarcar que las tendencias observadas en los resultados con modelo fijo cambiarn cuando el modelo este libre, el impacto que los errores en las estimaciones de fuerzas segundo orden tienen en el sistema de fondeo dependen de las condiciones ambientales que imponen las cargas ultimas en dichas líneas. En cualquier caso los resultados que se han obtenido en esta investigación confirman que es necesaria y deseable una detallada investigación de los métodos usados en la estimación de las fuerzas no lineales en las turbinas flotantes para que pueda servir de guía en futuros diseños de estos sistemas. Finalmente, el candidato espera que esta investigación pueda beneficiar a la industria eólica offshore en mejorar el diseño hidrodinámico del concepto semisumergible. ABSTRACT Electrical power obtained from floating offshore wind turbines is one of the promising resources which can reduce the fossil fuel energy consumption and cover worldwide energy demands. The concept is the most competitive in countries, such as Spain, where the continental shelf is narrow and does not provide space for fixed structures. Among the different floating structures concepts, this thesis has dealt with the semisubmersible one. Platforms of this kind may experience resonant motions both in surge and heave directions. In surge, since the platform natural period is long, such resonance can be excited with second order slow drift forces and may have substantial influence on mooring loads. In heave, first order forces can induce significant motion, whose damping is a crucial factor for the platform downtime. These two topics have been investigated in this thesis. To this aim, a design developed during HiPRWind EU project, has been selected as reference case study. The platform is composed of three cylindrical legs, linked together by a set of structural braces. The cylinders provide buoyancy and restoring forces and moments. Large circular heave plates have been attached to their bases. The design is similar to other documented in literature (e.g. Windfloat), which implies outcomes could have a general value. A large scale model of one of the legs has been built in order to study heave damping through forced oscillations. The final dimensions of the specimen (one meter diameter discs) make it, to the candidate’s knowledge, the largest for which data has been published. The model design allows for the fitting of either a plain solid heave plate or a flapped reinforced one; both have been built. The latter is a model scale reproduction of the prototype heave plate and includes some distinctive features, the most important being the inclusion of a vertical flap on its perimeter. The forced oscillation tests have been conducted for a range of frequencies and amplitudes, with both the solid plain model and the vertical flap one. Forces have been measured, from which added mass and damping coefficients have been obtained. These are necessary to accurately compute time-domain simulations of mooring design. The coefficients have been compared with literature, and potential flow and CFD predictions. In order to provide information for the structural design of the platform, pressure measurements on the top and bottom side of the heave discs have been recorded and pressure differences analyzed. In addition, in order to conduct a detailed investigation on the numerical estimations of the slow-drift forces of the HiPRWind platform, an experimental campaign involving captive (fixed) model tests of a model of the whole platform in bichromatic waves has been carried out. Although not reproducing the more realistic scenario, these tests allowed a preliminary verification of the numerical model based directly on the forces measured on the structure. The following outcomes can be enumerated: 1. Damping and added mass coefficients show, on one hand, a small dependence with frequency and, on the other hand, a large dependence with the motion amplitude, which is coherent with previously published research. 2. Measurements with the prototype plate, equipped with the vertical flap, show that damping drops significantly when comparing this to the plain one. This implies that, for tank tests of the whole floater and turbine, the prototype plate, equipped with the flap, should be incorporated to the model. 3. Added mass values do not suffer large alterations when comparing the plain plate and the one equipped with a vertical flap. 4. A conservative damping coefficient equal to 6% of the critical damping can be considered adequate for the prototype heave plate for frequency domain analysis. A corresponding drag coefficient equal to 4.0 can be used in time domain simulations to define Morison elements. 5. When comparing to published data, some discrepancies in added mass and damping coefficients for the solid plain plate have been found. Explanations have been suggested, focusing mainly on differences in thickness ratio and distance to the free surface, and eventual scale effects. 6. Pressures on the plate equipped with the vertical flap are similar in magnitude to those of the plain plate, even though substantial differences are present close to the edge, where the flap induces a larger pressure difference in the reinforced case. 7. The maximum pressure difference scales coherently with the force equivalent to the acceleration of the added mass, distributed over the disc surface. 8. Added mass coefficient values predicted with the potential solver (WADAM) are not accurate enough. The used solver does not contemplate modeling thin plates with doublets. The relatively low accuracy of the results highlights the importance of these elements when performing potential flow simulations of offshore platforms which include thin plates. 9. For the full CFD solver (Ansys CFX), the accuracy of the computations is found reasonable for the plain plate. Such accuracy diminishes for the disc equipped with a vertical flap, an expected result considering the greater complexity of the flow. 10. In regards to second order effects, in general, the results showed that, although the main trend in the behavior of the second-order forces is well captured by the numerical predictions, some under prediction of the experimental values is visible. The gap between experimental and numerical results is more pronounced when Newman’s approximation is considered, making use exclusively of the mean drift forces calculated in the first-order solution. 11. It should be observed that the trends observed in the fixed model test may change when the body is free to float, and the impact that eventual errors in the estimation of the second-order forces may have on the mooring system depends on the characteristics of the sea conditions that will ultimately impose the maximum loads on the mooring lines. Nevertheless, the preliminary results obtained in this research do confirm that a more detailed investigation of the methods adopted for the estimation of the nonlinear wave forces on the FOWT would be welcome and may provide some further guidance for the design of such systems. As a final remark, the candidate hopes this research can benefit the offshore wind industry in improving the hydrodynamic design of the semi-submersible concept.

(+)-Germacrene A Biosynthesis : The Committed Step in the Biosynthesis of Bitter Sesquiterpene Lactones in Chicory

The leaves and especially the roots of chicory (Cichorium intybus L.) contain high concentrations of bitter sesquiterpene lactones such as the guianolides lactupicrin, lactucin, and 8-deoxylactucin. Eudesmanolides and germacranolides are present in smaller amounts. Their postulated biosynthesis through the mevalonate-farnesyl diphosphate-germacradiene pathway has now been confirmed by the isolation of a (+)-germacrene A synthase from chicory roots. This sesquiterpene cyclase was purified 200-fold using a combination of anion-exchange and dye-ligand chromatography. It has a Km value of 6.6 μm, an estimated molecular mass of 54 kD, and a (broad) pH optimum around 6.7. Germacrene A, the enzymatic product, proved to be much more stable than reported in literature. Its heat-induced Cope rearrangement into (−)-β-elemene was utilized to determine its absolute configuration on an enantioselective gas chromatography column. To our knowledge, until now in sesquiterpene biosynthesis, germacrene A has only been reported as an (postulated) enzyme-bound intermediate, which, instead of being released, is subjected to additional cyclization(s) by the same enzyme that generated it from farnesyl diphosphate. However, in chicory germacrene A is released from the sesquiterpene cyclase. Apparently, subsequent oxidations and/or glucosylation of the germacrane skeleton, together with a germacrene cyclase, determine whether guaiane- or eudesmane-type sesquiterpene lactones are produced.