Cetaceans have historically been object of heavy exploitation, and are still currently subject to different threats. For conservation and management purposes, most of the large cetacean populations have been categorized in stocks, considered as isolated and demographically independent management units. Many research techniques may contribute in the definition of these stocks, such as morphometric studies, mark recapture studies, genetics, satellite tracking. This thesis focuses on the development and application to cetacean populations of chemical markers of geographical origin and spatial movements. The main objective of the thesis is to evaluate the potentialities of chemical markers, such as stable isotopes and element concentrations, to investigate the patterns of distribution, the level of structuring and, when possible, the migration routes, of cetaceans populations. All these variables are essential to ensure the implementation of proper management measures and to guarantee the conservation of these animals. Three case studies were considered: the Eastern North Atlantic sperm whale (Physeter macrocephalus); the South Western Atlantic right whale (Eubalaena australis), and the North Atlantic fin whale (Balaenoptera physalus). δ15N, δ13C and δ18O values were analyzed in the dentinal growth layers of sperm whales from Denmark and NW Spain, in bone of right whales from Southern Brazil and Northern Argentina, and in bone of fin whales from W Iceland and NW Spain; concentrations of fluoride and selected metals (Zn, Pb, Ti, Sr, Cu) were analyzed in bone of fin whales from W Iceland and NW Spain. To establish the validity of each marker, the degree of compliance of each of the following four properties has been investigated: i) the basal levels of the chemical marker in the environment present significant gradients; ii) the chemical marker can be detected and measured in the tissues of whales; iii) the variability of the chemical marker within each population is moderate or, alternatively, it is predictable through measurable parameters, so that its effect can be taken into account; and iv) the values of the chemical marker in the body tissues reflect basal levels in a predictable and consistent manner. Each marker provided, at different levels, valuable information regarding the studied populations. Some difficulties emerged, connected with the complexity of the migratory cycles of whales, the possible intervention of homeostatic regulation mechanisms, and the characteristics of the tissues investigated. Nevertheless, results highlighted the occurrence of structuring within the North Atlantic sperm whale population, as well as within the South Western Atlantic right whale population, which are both currently considered as a single management unit. Moreover, results regarding the North Atlantic fin whale populations contributed to highlight the complexity of migration patterns and of the level of connectivity among the currently accepted stocks, challenging the proper definition of their limits and their degree of isolation within the basin. Some further research is recommended to deepen the knowledge about the North Atlantic fin whale population structure, as well as to investigate the levels of chemical markers in other tissues with different turnover characteristics, such as skin or baleen plates. Overall, the results obtained from the analyses performed in this thesis underline the power of chemical markers as a complementary tool to the traditional techniques used for investigating the structure and demography of cetaceans’ populations. / Los cetáceos han estado y están actualmente sujetos a diferentes tipos de amenazas. Para su correcta gestión y conservación, la mayoría de las poblaciones de grandes cetáceos han sido categorizadas en “stocks”, considerados como unidades de gestión aisladas y demográficamente independientes. Muchas técnicas de investigación pueden contribuir en la definición de estas unidades, como los estudios morfométricos, los estudios de marcaje y recaptura, la genética y el seguimiento por satélite. El objetivo principal de esta tesis es evaluar las potencialidades de los marcadores químicos, tales como los isótopos estables y las concentraciones de algunos elementos, como herramientas para la investigación de los patrones de distribución y del nivel de estructuración de las poblaciones de cetáceos. Para ello, se han considerado tres casos modelo: el cachalote del Atlántico Nororiental, la ballena franca del Atlántico Suroccidental, y el rorcual común del Atlántico Norte. Se analizaron las proporciones isotópicas de δ15N, δ13C y δ18O en muestras de dientes de cachalote y de hueso de ballena franca y rorcual común; y las concentraciones de flúor y de metales pesados (Zn, Pb, Ti, Sr, Cu) en muestras de hueso de rorcual común. Cada marcador proporcionó, a diferentes niveles, información valiosa sobre las poblaciones estudiadas. Al interpretar los resultados, surgieron algunas dificultades relacionadas con la complejidad de los ciclos migratorios de los cetáceos, la posible intervención de mecanismos de regulación homeostática, y las características de los tejidos investigados. Sin embargo, los resultados destacaron cierto nivel de estructuración dentro de las poblaciones de cachalotes del Atlántico Norte y de ballenas francas del Atlántico Suroccidental, que actualmente están ambas consideradas como unidades de gestión únicas. Por otra parte, los resultados obtenidos en las poblaciones de rorcual común del Atlántico Norte contribuyeron a evidenciar la complejidad de los patrones migratorios y del nivel de conectividad entre sus poblaciones, desafiando la adecuada definición de sus límites y de su grado de aislamiento. En general, los resultados de la tesis destacan las potencialidades de los marcadores químicos como herramienta complementaria a las técnicas utilizadas tradicionalmente para la investigación de la estructura y demografía de las poblaciones de cetáceos.

The use of renewable heat decreases the consumption of fossil resources, although its usage is intermittent and usually does not match the demand. A proper thermal energy storage system design can eliminate this problem by reducing the consumption of non-renewable resources and improving energy efficiency where used. In buildings, thermal energy storage using phase change materials (PCM) is a useful tool to achieve reduction in energy consumption. These can be incorporated into passive or/and active systems. Thus, a proper selection of materials and extensive characterization for its usage in thermal energy storage is critical for new construction systems and for those already constructed. This Thesis is divided in two blocks and presented as a compendium of published articles in scientific journals indexed in Materials, Engineering, and Energy areas. The emphasis is made in the chemical, physical, thermal, mechanical and environmental characterization of PCM, MPCM (microencapsulated phase change materials), and PCS (phase change slurries). The main purpose is to perform an exhaustive characterization of this kind of materials because several scientific studies have highlighted that PCM mixed with construction materials can suffer leakage. Polymeric encapsulation is an alternative for retaining PCM inside building materials, resulting in a system named MPCM. - Macroscopic samples: the nanoindentation tecnique has been used to characterize thermoplastics that, so far, have had few precedents. As mechanical properties of materials are an important criterion for their selection and nanoindentation allows their evaluation, we have studied the hardness and elastic modulus of different polymeric materials through Loubet and Oliver & Pharr methodologies, to discern which is the most suitable concerning the viscoelastic properties. The obtained values by Oliver & Pharr method are based on the unloading curve analysis; in case of Loubet methodology, these values are a function of the penetration depth of the indentation. Also, we have studied the mechanical changes that occur when a polymer that contains a flame retardant is immersed in PCM. It has been observed that using Mg(OH)2 increases rigidity and mechanical strength while reducing the degradation effect and improving the properties against fire. This block contains two scientific published papers. - Microscopic samples: This block is based on MPCM studies. A review of publications related to PCM, MPCM and slurries (PCS) (same shell and different PCM; different shell and same PCM; same shell and same PCM, but different encapsulation ratios) was prepared. Then, the evaluation of the chemical, physical, thermal, mechanical, and environmental properties of different MPCM and PCS samples was performed, concluding that AFM is a useful tool to characterize the stiffness and Young's modulus of MPCM. Because temperature is a key parameter in PCM systems, AFM experiments were carried out at different temperatures, in order to simulate the PCM in solid and/or liquid state. PCS samples were observed using SEM device coupled to a cryogenic system. Besides, environmental properties of PCS have been studied by gas chromatography (VOC’s). In addition, PCS were cycled for the evaluation of the polymeric shell durability after pumping the sample several cycles. Also, the chemical and thermophysical properties before and after pumping the sample were compared. Finally, due to the thermal behavior results of PCS in some performed studies, and depending on the liquid or dried PCS sample, the optimum conditions by means thermogravimetric analysis were evaluated. The second block contains five scientific published articles, one article under review after its first revision, one article finished without being submitted to a journal, and one unfinished research. Finally, the contribution in the state of the art of this PhD Thesis related with thermal energy storage in buildings using PCM, MPCM, and PCS is presented. / Un correcto diseño del sistema de almacenamiento de energía térmica (TES) puede eliminar un uso discontinuo y que habitualmente no coincide con la demanda. El TES mediante materiales de cambio de fase (PCM) en climatización pasiva y activa en edificios es un instrumento útil para alcanzar un descenso del consumo de energía. La Tesis se divide en dos bloques y se presenta como compendio de artículos publicados en revistas científicas indexadas en las áreas de Materiales, Ingeniería, y Energía, haciendo émfasis en la caracterización química, fisica, térmica, mecánica y ambiental de PCM, MPCM (materiales de cambio de fase microencapsulados) y PCS (pulpas con cambio de fase). - Caracterización de diferentes termoplásticos mediante nanoindentación. a través de los métodos de Loubet y Oliver & Pharr. También se han estudiado los cambios mecánicos que se producen cuando un polímero que contiene carga ignifugante en su formulación se sumerge en PCM. Este bloque contiene dos artículos científicos. - Estudio de MPCM. Se ha llevado a cabo una revisión de publicaciones por otros autores. Se han caracterizado con AFM diferentes MPCM y PCS, a diferentes temperaturas. Se han observado muestras de PCS mediante el uso de SEM acoplado a un sistema de crionizado, y se han estudiado las propiedades medioambientales por cromatogyafía de gases. Además, se han ciclado PCS para ver la durabilidad de la pared polimérica después de ciertos ciclos de bombeo. Se han investigado las condiciones óptimas mediante análisis termogravimétrico en PCS. Este segundo bloque contiene cinco artículos científicos publicados, un artículo aceptado en primera revisión, un artículo finalizado sin enviar a revista, y un estudio en investigación. Finalmente, se presentan las conclusiones principales de la contribución de esta Tesis Doctoral en el estado del arte de los PCM, MPCM, y PCS para almacenaje de energía en edificios.

In this thesis we apply a multidisciplinary approach, based on statistical physics and complex systems, to the study of neuronal dynamics. We focus on understanding, using theoretical and computational tools, how collective neuronal activity emerges in a controlled system, a neuronal culture. We show how the interplay between noise and network structure defines the emergent collective behavior of the system. We build, using theory and simulation, a framework that takes carefully describes spontaneous activity in neuronal cultures by taking into account the underlying network structure of neuronal cultures and use an accurate, yet simple, model for the individual neuronal dynamics. We show that the collective behavior of young cultures is dominated by the nucleation and propagations of activity fronts (bursts) throughout the system. These bursts nucleate at specific sites of the culture, called nucleation points, which result in a highly heterogeneous probability distribution of nucleation. We are able to explain the nucleation mechanism theoretically as a mechanism of noise propagation and amplification called noise focusing. We also explore the internal structure of activity avalanches by using well--defined regular networks, in which all the neurons have the same connectivity rules (motifs). Within these networks, we are able to associate to the avalanches an effective velocity and topological size and relate it to specific motifs. We also devise a continuum description of a neuronal culture at the mesoscale, i.e., we move away from the single neuron dynamics into a coarse--grained description that is able to capture most of the characteristic observables presented in previous chapters. This thesis also studies the spontaneous activity of neuronal cultures within the framework of quorum percolation. We study the effect of network structure within quorum percolation and propose a new model, called stochastic quorum percolation, that includes dynamics and the effect of internal noise. Finally, we use tools from information theory, namely transfer entropy, to show how to reliably infer the connectivity of a neuronal network from its activity, and how to distinguish between different excitatory and inhibitory connections purely from the activity, with no prior knowledge of the different neuronal types. The technique works directly on the fluorescence traces obtained in calcium imaging experiments, without the need to infer the underlying spike trains.

c-Src is the leading member of the Src family of non-receptor tyrosine kinases, which are involved in many signaling pathways. Its deregulation affects cell migration, proliferation and survival. c-Src is composed of the intrinsically disordered N-terminal SH4 and Unique domains, of the folded SH3, SH2, kinase domains and of a C-terminal tail. c-Src is myristoylated at its N-terminal region and anchored to membranes via cooperative electrostatic and hydrophobic interactions. Weak interactions with lipids in the Unique and SH3 domains and intramolecular interactions between them were recently found in the non-myristoylated form. These interactions involve the Unique Lipid Binding region (ULBR) in the Unique domain, and the RT and nSrc loops in the SH3 domain. Our objective consisted in obtaining and characterizing the myristoylated form of the Unique and SH3 domains (MyrUSH3). Protocols for the efficient production of myristoylated proteins were developed. The incorporation of shorter acyl chains was characterized as a general problem in the preparation of myristoylated proteins, and conditions enabling to minimize their formation were found, in particular in the case of expression in minimum media. A well-defined myristoylation-induced cleavage site was identified and characterized in the Unique Lipid Binding Region of the Unique Domain of c-Src. Conditions to obtain degradation-free samples for structural studies were established. The kinetics of MyrUSH3 binding to liposomes was followed using surface plasmon resonance (SPR) and revealed two MyrUSH3 populations, a dominant form binding with relatively fast association and dissociation, and a minor persistently bound (PB) population not described earlier. This PB form was studied in an assay involving detection by a secondary antibody and the model better explaining the experimental results described these PB species to be dimer forms of MyrUSH3. In a construct in which the SH3 domain was replaced by the GFP protein, single molecule photobleaching experiments of these PB species bound to supported lipid bilayers were conducted. A major population of dimers over the bilayer surface was detected. When binding of the myristoylated SH4 (MyrSH4) peptide to liposomes by SPR, a PB population was also observed. Monitoring of the surface activity of MyrSH4 revealed the micelar behavior of the peptide at low concentrations. Nuclear Magnetic Resonance (NMR) measurements permitted to study the effect of the myristoyl group on the intramolecular interactions between the Unique and SH3 domains, as well as on the binding of the ULBR and RT loops to liposomes when the protein was anchored in the bilayer. 1H-15N spectra of the myristoylated Unique domain (MyrUSrc) confirmed the propensity of the ULBR to bind liposomes, but in a different manner depending on the nature of the lipid in the bilayer. These measurements of MyrUSrc also pointed out some intermolecular propensities in the MyrSH4 domain. 1H-15N spectra of MyrUSH3 in solution revealed the presence of a myristoyl binding site has been found in the RT loop. Interaction of the myristoyl chain with lipids results in the loss of other lipid binding interactions in the Unique and SH3 domains that were observed in the non-myristoylated form. The interaction between the SH4 and the SH3 domains that restricts the conformational space of the Unique domain was preserved in the myristoylated forms and in the presence of lipids. The SPR and single molecule fluorescence studies revealed the formation of self-associated complexes of limited size upon binding of MyrUSH3 or MyrUGFP to liposomes, possibly driven by the presence of the MyrSH4 domain. The NMR data highlighted the interplay between the lipid binding regions of the Unique and SH3 domains, in presence or absence of liposomes. Therefore, the myristoylated intrinsically disordered Unique domain may act in c-Src regulation at the lipid bilayer interface. / c-Src es miembro de una importante familia de tirosina quinasas, que está involucrada en la transducción de señales en las células. c-Src está formada por una región N-terminal desordenada (compuesta de los dominios SH4 y Único), por los dominios plegados SH3, SH2, SH1 (el dominio quinasa), y por una cola C-terminal. c-Src es una proteína miristoilada en su extremo N-terminal, lo cual permite su unión a membranas, unión reforzada por la interacción del dominio SH4 polibásico con los lípidos cargados negativamente. En ausencia del grupo miristoilo, se encontraron zonas de unión a lípidos y de interacciones intramoleculares en los dominios Único y SH3. El objetivo de este trabajo es la obtención y la caracterización de la forma miristoilada de los dominios Único y SH3 (MyrUSH3). Se desarrollaron protocolos que permitieron la producción de proteínas miristoiladas. La cinética de unión de MyrUSH3 a liposomas se estudió con resonancia de plasmones superficiales. Se observó una población mayoritaria con una asociación y una disociación relativamente rápidas, y una población minoritaria con una unión persistente a liposomas. Esta segunda especie se estudió por detección secundaria via un anticuerpo y se dedujo que estaba posiblemente formada por dímeros. El dominio SH3 se remplazó por una proteína verde fluorescente (MyrUGFP) y se estudió la unión de MyrUGFP a liposomas, mediante su observación con microscopía confocal, usando la técnica de fotoblanqueo de moléculas individuales. Se observó una población mayoritaria de dímeros. A continuación, se estudió la proteína MyrUSH3 con resonancia magnética nuclear, en solución o unida a liposomas. En solución, se encontró un sitio de unión al grupo miristoil en el dominio SH3. Tras la inserción del grupo miristoil en la bicapa lipídica, se perdió la capacidad de unión a lípidos en los dominios Único y SH3 (excepto el dominio SH4), y algunas interacciones intramoleculares fueron afectadas.

The results presented in this thesis have shown the strong dependence of Audouin’s gull from the Ebro Delta on fisheries. Foraging movements of breeding birds showed a great association with fishing activities (specially trawling), determining the most of its at-sea distribution on work days. An increase in the use of rice field habitats was also detected in absence of fishing activities (during weekends) due to the opportunistic feeding on the American crayfish. However, a key aspect presented in this thesis was the significant sex-differences in their foraging behaviour in relation to fisheries. Female Audouin’s gull tended to perform longer at-sea foraging trips on weekends compared to males, probably due to the need of feeding on high quality resources after laying instead of the easily available but lower quality American crayfish. This great dependence on fishing activities was also reflected in the resource allocation into the clutch. An isotopic δ15N enrichment in the albumen of eggs synthesized during the weekends was observed, which is attributed to an increase in the consumption of rice field resources as well as to the mobilization of female reserves. However, rice field diets were associated to lower antioxidant capacity in the eggs. Also, rice field diets were related to smaller egg size. Finally, the limiting nature of calcium (in constraining egg synthesis) and antioxidant molecules (decreasing their concentration especially in the latter eggs of the clutch) were also revealed for females. / Los resultados presentados en esta tesis han mostrado la gran dependencia de las gaviotas de Audouin del Delta del Ebro sobre las pesquerías. Los movimientos de búsqueda de alimento de las aves durante la reproducción mostraron una gran asociación con las actividades pesqueras (especialmente el arrastre durante el día, aunque también es notable la influencia de la pesca de cerco durante noche), determinando la mayor parte de su distribución en el mar los días laborables. Un incremento en el uso de arrozales fue detectado en ausencia de actividades pesqueras (durante los fines de semana). Sin embargo, un aspecto clave presentado en esta tesis fue las diferencias significativas entre sexos para el comportamiento de alimentación en relación a las actividades pesqueras. Las hembras de gaviota de Audouin tendieron a realizar viajes de alimentación más largos que los machos durante los fines de semana. Esta gran dependencia sobre las actividades pesqueras fue también reflejada en la asignación de recursos sobre la puesta. Un enriquecimiento del δ15N fue detectado en el albumen de los huevos sintetizados durante los fines de semana, lo cual puede ser atribuido a un incremento en el uso de recursos de arrozal así como a la movilización de reservas de la hembra. Sin embargo, un mayor uso de dietas de arrozal se asoció con una menor capacidad antioxidante de los huevos. También, dietas de arrozal estaban relacionadas con tamaños del huevo más pequeños. Finalmente, se puso de manifiesto la naturaleza limitante del calcio (restringiendo la síntesis del huevo) y de las moléculas antioxidantes del huevo (decreciendo su concentración especialmente en los últimos huevos de la puesta).

Tesi realitzada conjuntament amb el Departament de Ciències Fisiològiques II / En la actualidad existe una gran evidencia científica sobre los múltiples beneficios que ofrecen la actividad física y el ejercicio físico en la promoción y mantenimiento de la salud. Los diferentes estudios han mostrado un abanico de resultados favorables en todas las poblaciones estudiadas. El correcto funcionamiento del endotelio vascular es de vital importancia en la salud cardiovascular y la incorporación de programas de ejercicio físico pueden representar un medio eficaz en la atención primaria y secundaria de la aterosclerosis y las enfermedades cardiovasculares. Las células madre hematopoyéticas CD34+, se originan fundamentalmente en la médula ósea y son trasportadas en la sangre periférica, a su vez, contribuyen a la hematopoyesis y pueden ser activadas mediante la actividad física contribuyendo en la formación de nuevos vasos sanguíneos y en la regeneración en los casos de existir lesión. Por otro lado, las diferentes investigaciones no son muy claras sobre los efectos de los diferentes programas de ejercicio físico (aeróbico, fuerza y mixto) en las concentraciones de sangre periférica de células madre CD 34+, tampoco sobre los tiempos de mayor concentración sanguínea pos-esfuerzo. Así mismo, existe poca información sobre los efectos sobre la presión arterial en reposo, en ejercicio submáximo y ejercicio máximo, después de los diferentes programas de ejercicio físico mencionados anteriormente. El objetivo principal ha sido examinar los efectos fisiológicos producidos en el organismo después de realizar diversas actividades y/o programas de ejercicio físico específico (aeróbico, de fuerza o mixto). En conclusión, la realización de una única actividad física aeróbica de muy larga duración produce aumentos en la concentración sanguínea de células madre hematopoyéticas CD34+ circulantes a los 5 días post-esfuerzo. La realización de 3 diferentes programas de ejercicio físico de 6 semanas de duración (aeróbico, fuerza o mixto) no produjo cambios significativos en la concentración sanguínea de células madre hematopoyéticas CD34+. Dado que se detectó una relación inversa entre los cambios observados en la concentración sanguínea de las células madre hematopoyéticas CD34+ y los valores de las mismas al inicio del estudio, deberán tenerse en cuenta los valores basales y su variabilidad siempre que se deban evaluar los cambios observados tras un estímulo de cualquier naturaleza. La realización de un programa de ejercicio físico aeróbico de 6 semanas de duración aumenta la potencia máxima y el VO2máx con respecto a los valores obtenidos inicialmente. La ejecución de un programa de entrenamiento mixto de 6 semanas produce mayor disminución de la presión arterial en reposo que el obtenido solo con ejercicio aeróbico o de fuerza. La presión arterial durante un ejercicio submáximo y máximo disminuye tras un programa de 6 semanas de duración ya sea de tipo aeróbico, de fuerza o mixto, manteniéndose el descenso de dichos valores tras 3 semanas de desentrenamiento. / In the actuality there is great scientific evidence about the multiple benefits offered by physical activity and exercise in promoting and maintaining health. The correct functioning of the vascular endothelium is vital for cardiovascular health, incorporating physical exercise programs is important in primary and secondary care of atherosclerosis and cardiovascular disease. The circulating CD34+ hematopoietic progenitor cells are bone marrow-derived cells that are mobilized into the circulation and incorporated at sites of injury where they are believed to participate in vascular repair through re-endothelization, but there are contradictory results regarding the increased levels and schedule of the cells after exercise. The circulating CD34+ hematopoietic progenitor cells levels in the days following a long-distance walking exercise have not been studied, neither after 3 different types of training programs: aerobic, resistance, and a combination of both. Also, it is important to know changes in blood pressure during submaximal and maximal exercise after physical training period. This study has provided initial evidence of important medium-term changes in the circulating CD34+ hematopoietic progenitor cells levels following to single session in long endurance exercise, on the other hand, no changes in the circulating CD34+ hematopoietic progenitor cells were detected after training programs: aerobic, resistance, and a combination of both. Moreover, it found clear differences in blood pressure changes among the three training groups, with exercise programmes clearly able to decrease the blood pressure during a submaximal and maximal exercise. These results indicate than we can no longer only consider how blood pressure is affected by exercise in general, but that we must also consider the effects of different training programmes on blood pressure.

Tesi realitzada a l'Institut de Ciència de Materials de Barcelona (ICMAB-CSIC) / Organic/inorganic interfaces play a key role in organic electronic devices such as organic light emitting diodes (OLED), organic field effect transistors (OFET) and organic solar cells (OSC). In these interfaces crucial processes such as charge injection or extraction take place. Improving the performance of these devices has the potential to result in more efficient sources of lighting, printable electronics, and highly scalable solar energy harvesting. With this aim, a solid understanding at atomic level of the structural and electronic properties of organic/inorganic interfaces is needed. The research presented in this thesis is based on scanning probe microscopies which are powerful techniques to probe and manipulate the electronic and structure at atomic scale. The structural and electronic properties of selected organic and inorganic 2D systems on metallic surfaces have been investigated by a combined scanning tunneling microscopy (STM) and frequency modulation atomic force microscopy (FM-AFM) in ultra-high vacuum conditions and at room temperature. The combination of these local probe techniques permits elucidating the interface structure at atomic level and disentangle electronic from topographic information. Particular attention has been dedicated to the measure and interpretation of the local work function. Cuprous oxide (Cu2O) is an intrinsic p-type semiconductor. Copper oxide ultrathin films have been suggested to be candidates as low resistance electrodes, catalysts, sensing materials and semiconductor materials for solar cell transformation. However the properties of ultrathin film may differ from those of the bulk material. With the aim of increasing the actual knowledge, an atomic thin film of copper oxide has been grown on Cu(111) by air-enriched argon sputtering plus annealing. Several structures have been found and the local work function has been evaluated by contact potential difference and distance spectroscopies. Its structural and electronic properties are presented in Chapters 5 and 6. Several organic molecules have been investigated on different surfaces: perylene-3,4,9,10-tetracarboxylic anhydride (PTCDA), diindenoperylene (DIP) and chloroaluminum phthalocyanine (ClAlPc). All of them are small pi-conjugated molecules that have been grown by molecular beam deposition and are served as model systems for a basic understanding of organic/inorganic interfaces. The choice of the selected molecules has been motivated by the distinct chemical and physical properties: PTCDA is a perylene derivate molecule with two anhydride end groups that has an electrical quadrupole moment and forms ordered films by hydrogen bonding, ClAlPc is a phthalocyanine that has a dipole moment perpendicular to the pi-plane of the molecule and DIP is another perylene derivate that is composed only by carbon and hydrogen atoms and forms films only by van der Waals interaction. The structural and electronic properties of a monolayer of PTCDA on Si(111)7x7 and AgSi(111) have been studied and are presented in Chapter 7. A monolayer of DIP on the Cu(111) surface and a monolayer and bilayer of ClAlPc on Au(111) are shown in Chapter 8 and Chapter 9, respectively. The final structure of these molecules on the surfaces is a competition between intermolecular and molecule-substrate forces. In the organic/metal interface many complex processes can occur such as charge transfer, charge rearrangement and push back effect, affecting the work function in a non trivial way what has been evaluated in all the mentioned systems. / En los dispositivos basados en semiconductores, las interfases entre material metálico y material semiconductor juegan un papel importante en el funcionamiento final de dichos dispositivos. Algunos ejemplos de dispositivos son las celdas solares, los diodos emisores de luz y los transistores de efecto campo. En las interfases metal/semiconductor se producen muchos de los procesos fundamentales para el correcto funcionamiento de éstos, como la inyección de carga o la separación de excitones. La optimización de dichos procesos requiere un sólido conocimiento a nivel atómico de las interfases desde un punto de vista estructural y electrónico. Por consiguiente, en esta tesis se han estudiado una serie de sistemas bidimensionales orgánicos e inorgánicos crecidos sobre diferentes superficies metálicas mediante microscopía de sonda próxima, una de las técnicas más potentes en el campo de la nanotecnología. Concretamente se ha utilizado un microscopio combinado de efecto túnel (STM) y de fuerzas atómicas (AFM), en condiciones de ultra alto vacío y a temperatura ambiente. Capas delgadas de óxido de cobre (Cu2O) han sido ampliamente utilizadas por sus óptimas propiedades en catálisis y como material semiconductor en celdas solares. Con el fin de estudiar las propiedades estructurales y electrónicas, se han crecido capas ultra delgadas (un átomo de grosor) de Cu2O sobre una superficie de cobre (111). Diferentes técnicas han sido utilizadas para su caracterización estructural y electrónica. Por otro lado, otro de los materiales semiconductores utilizados en el desarrollo de futuras celdas solares son capas finas formadas por moléculas orgánicas semiconductoras. A pesar de que se podrían utilizar muchas moléculas para la fabricación de dispositivos orgánicos, las moléculas pequeñas conjugadas son especialmente interesantes debido al bajo peso molecular, su estabilidad ante la polimerización y ante la descomposición térmica. Dichas moléculas pueden ser sublimadas en condiciones de ultra alto vacío mediante crecimiento epitaxial por haces de moléculas orgánicas. En el transcurso de esta tesis, varias moléculas orgánicas han sido crecidas sobre diferentes superficies metálicas: perileno tetracarboxílico dianhídrido (PTCDA), diindenoperileno (DIP) y ftalocianina de cloro y aluminio (ClAlPc). Su caracterización estructural y la medida e interpretación de la función de trabajo local se han presentado en esta tesis.

This thesis is devoted to prove the concept of the CO(2) reduction to CH(4) with a decreasing in the voltage requirements using a photocatalytic mechanism. Subsequently, part of the solar energy is transferred to the reaction, obtaining an improvement in the total energy balance. The work developed intends first, to take advantage of the know features of the photoactive nanostructured materials obtained by anodization and hydrothermal synthesis (allowing to obtain better surface areas and improving the photon collection, light photosynthetic reactions). Second investigate the copper and copper oxide cathodes for the CO(2) electroreduction activity to CH(4) (dark photosynthetic reactions) using a complete cell to understand the parameters involved in the process and the products selectivity for each cathodes. And third the implementation of the photoanode and cathode in a photoelectrochemical complete cell. Respect the photoactive materials we are going to talk about TiO(2) based nanostructured materials for water splitting. The first TiO(2) nanostructuration under study are nanotubes obtained by anodization of a Titanium foil using organic electrolytes. The TiO(2) crystal phase obtained by this technique was anatase. The next step in this material was the surface modification to improve the efficiency. To obtain this improvement the anodization process was done using two electrolytes in different steps. As sequence a porous surface with an increment in the surface area was obtained. After, the photoelectrochemical measurements were done in 1 M of sodium hydroxide (NaOH) under AM 1.5G illumination source to observe the photoactivity of these samples. The second nanostructured materials under study were TiO(2) nanorods obtained by hydrothermal synthesis over a conductive glass substrate, Fluorine Tin Oxide (FTO). The nanorods using this technique have rutile structure. An optimization of two parameters involved in the hydrothermal synthesis was studied: (1) initial titanium precursor concentration and (2) increasing the chlorine concentration to obtain larger and thinner rods. To enhance the photoactivity of TiO(2) we try to incorporate other materials inside the structure. The materials selected were: tin which improves the charge carriers, vanadium which allows the absorption in the visible range and nitrogen doping to enhance the efficiency in the photoactivity of the material. Concerning to methane production study, a discussion about the electrochemical CO(2) reduction activity over a copper based electrode using a hydrogen carbonate as supporting electrolyte was done, where the positive ions used are sodium and potassium. The first electrode selected is a pristine copper due to the interest of the methane production. The samples were characterized by scanning electronic microscopy (SEM) and X-Ray diffraction (XRD) to visualize the surface morphology and the crystal structure of the electrode. Afterwards, the electrochemical process is studied to understand the activity of these electrodes. Chronopotentiostatic (CP) experiments were done at different current densities to observe the activity as a function of the reached potential. The second electrode under study was a copper oxide cathode. In the electrochemical experiments an effect was studied related to the electrochemical reduction of the different copper oxide layers generated during the thermal synthesis, leading to a catalytically active copper that enables carbon dioxide reduction. With this type of electrodes a time- dependence test was done to carefully study these crystallographic changes. Finally, another important variable for CO(2) conversion was studied, the humidification of the CO(2) gas stream before the introduction in the electrochemical cell with the impact on the faradaic efficiency of the process. In the implementation in the PEC cell an evaluation of the photoanode and cathode was done. In this evaluation, the external potential requirements were studied concerning about the energy consumption and the benefit from the photoactivated process. / Esta tesis se ha desarrollado con el objetivo de probar el concepto de la reducción del dióxido de carbono a metano, mediante una reducción de los potenciales necesarios usando un mecanismo fotocatalítico. Parte de la energía solar es transferida a la reacción obteniendo una mejora en el balance energético total. El trabajo desarrollado se focaliza primero en el estudio de materiales nanoestructurados fotoactivos basados en dióxido de titanio obtenidos por anodización, generando nanotubos, y por síntesis hidrotermal obteniendo nanohilos sobre un sustrato conductor transparente, los cuales permiten obtener mayores superficies activas mejorando la colección de fotones, similar a las reacciones luminosas en la fotosíntesis. En segundo lugar, se ha estudiado la electroreducción del dióxido de carbono a metano usando cátodos de cobre y oxido de cobre (similar a las reacciones oscuras de la fotosíntesis). Usando el cobre como cátodo, se ha observado la obtención de metano a diferentes densidades de corriente aplicadas para poder observar la productividad respecto al potencial medido. Para el caso de los cátodos de óxido de cobre, no se ha encontrado producción de metano pero si de etileno. En estos cátodos se ha observado un efecto proveniente de la reducción de las capas de los diferentes óxidos de cobre, generados en la síntesis térmica, hacia un cobre catalíticamente activo para la reacción de reducción del dióxido de carbono. Este efecto se ha estudiado profundamente mediante un estudio de los cambios cristalográficos y superficiales a determinados tiempos. Finalmente, se ha estudiado el efecto de la humidificación del dióxido de carbono (gas) previa a la entrada a la celda electroquímica. Como parte final se ha realizado una evaluación energética de los fotoánodos generados por síntesis hidrotermal y de los cátodos basados en cobre estudiados, para poder implementar ambos en una celda fotoelectroquímica completa. En esta parte se ha estudiado los valores de los potenciales externos necesarios para que se pueda dar la reacción, asumiendo un 100% de eficiencia hacia la producción de metano para los cátodos de cobre y de etileno para los de óxido de cobre.

L'experiment d'Stern-Gerlach (SG) és considerat un dels més importants de la història de la teoria quàntica, i sovint s'utilitza en llibres de text de Mecànica Quàntica per il·lustrar el concepte d'espín i, fins i tot, els postulats de la teoria. Aquest ús didàctic tan estès ha fet que moltes vegades es confongui el rol que l'SG va jugar en el desenvolupament de la teoria quàntica: no és rar trobar fonts que afirmen que els resultats de l'SG es van rebre amb estupefacció o que van comportar el descobriment de l'espín. Si busquem estudis historiogràfics sobre aquest episodi tan important, ens trobarem davant d'una mancança completa de fonts especialitzades. La majoria de publicacions contenen poc més que algunes anècdotes entorn de l'experiment i algunes fins i tot perpetuen les interpretacions incorrectes que hem esmentat. Segurament l'únic estudi historiogràfic complet de l'experiment d'SG es pot trobar a la recent tesi de Wolfgang Trageser (“L'efecte Stern-Gerlach. Gènesi, desenvolupament i reconstrucció d'un dels experiments fonamentals de la teoria quàntica entre 1916 i 1926” —en alemany), presentada el 2011 a la Johann Wolfgang Goethe–Universität a Frankfurt am Main. L'autor tracta en detall el treball experimental d'Otto Stern i Walther Gerlach, però passa per sobre els comentaris sobre la motivació teòrica de l'experiment, així com les seves conseqüències teòriques. Analitzant en detall el context teòric que envoltava l'SG, intentarem recuperar la interpretació correcta del seu rol en el desenvolupament de la teoria quàntica; no ens ha de sorprendre trobar un relat completament nou amb importants conseqüències en l'àmbit didàctic. En aquesta tesi comencem revisant l'estat de la qüestió de la Teoria Quàntica Antiga (TQA) durant la dècada dels 1910, posant especial èmfasi en les teories de Niels Bohr i Arnold Sommerfeld. És important tenir clars els principis fonamentals d'aquesta teoria per interpretar correctament l'SG. Traçant les motivacions que van portar a l'experiment, estudiem l'efecte Zeeman i la quantització espacial. L'efecte Zeeman es pot considerar una de les principals guies dels desenvolupaments portats a terme per Bohr i Sommerfeld durant la construcció de les seves respectives teories. Precisament, una d'aquestes hipòtesis teòriques destinades a expilcar parcialment l'efecte Zeeman és la quantització espacial, proposada per Sommerfeld a mitjans 1916 i que ràpidament va ser adoptada per Bohr i incorporada a la teoria. La conveniència d'aquesta hipòtesi, però, va ser posada en dubte en repetides ocasions, i algunes de les seves prediccions experimentals no podien ser verificades. És per això que el 1921 Stern va proposar un dràstic experiment per confirmar-la (o falsar-la) d'una vegada per totes. Amb l'ajuda de Gerlach, els dos físics van trigar gairebé un any a obtenir el resultat buscat, confirmant la quantització espacial i aportant també un cert artibtratge a certs debats que s'havien establert entre Bohr i Sommerfeld sobre el nombre d'orientacions que podia atènyer un àtom immers en un camp magnètic. Malgrat aquest experiment, l'experiment d'Stern-Gerlach, sovint es postula com una pedra angular de la TQA, topem amb una contradicció històrica quan estudiem les seves conseqüències històriques. L'única reacció significativa és un article d'Einstein i Ehrenfest que posava de manifest les immenses contradiccions amb què topava la teoria si s'intentava fer un càlcul acurat de les observacions d'Stern i Gerlach. Malgrat el caire catastròfic d'aquest article, la seva publicació va obtenir una minsa resposta: breus discussions es van establir entre els dos autors i Bohr, Smekal, Born i Heisenberg. En cap es es pot considerar, però, que aquesta problemàtica s'incorporés a la naixent crisi que la TQA va patir durant el 1923–1924. / In an attempt to explain the Zeeman effect within the quantum framework, in mid 1916 Arnold Sommerfeld presented a new concept: Space Quantization, which introduced a new quantum number related to the discrete orientation of orbits inside the atom when immersed in an external magnetic field. The increasing explanatory success of Space Quantization made it necessary for Niels Bohr to also account for it in his quantum theoretical foundations of 1918, and even extend its uses. Thus Space Quantization became inherent to the genetic code of the Bohr-Sommerfeld theory. Four years later, an experimental endeavor by Otto Stern and Walther Gerlach confirmed for the first time a separation of an atomic beam in a magnetic field, in accordance to the predictions of Space Quantization. This result is usually taken as another success of the quantum theory. However, a closer look will reveal a much more intricate account of events, motivations and reactions. A further motivation for this research can be found in the vast contemporary bibliography that uses the Stern-Gerlach experiment as a cornerstone upon which to build a didactic approach to Quantum Mechanics (specially to illustrate the concept of spin) but usually at the price of introducing historical confusions or inconsistencies. With the aim to challenge incomplete and misleading accounts found elsewhere, we will relocate the Stern-Gerlach within the theoretical framework that both motivated the experiment and gathered its results.

Anaerobic digestion is a worldwide technology to treat organic waste streams, primarily due to its capacity to produce methane as renewable energy. However, there is an increasing interest on nutrient recovery (N and P), which from both environmental and economic reasons have been identified as key feature in anaerobic digestion plants. Controlled struvite formation has been attracting increasing attention as a near mature technology to recover nutrients from anaerobic digestion. However, struvite feasibility is generally limited by the high cost of chemical reagents. Because the economic feasibility of struvite is heavily influenced by reagent cost, several authors have trialled lower-cost magnesium sources. Studies to date on struvite precipitation with MgO have largely focused on the aqueous phase, with little attention given to the preceeding MgO dissolution. However, the observations noted above suggest that there may be opportunity to better understand, intervene and improve dissolution and access to MgO. The present study uses experiments and chemistry modelling to evaluate and better understand TAN removal from pig manure using MgO. Tests were performed with four industrial magnesium oxide (MgO) from natural magnesite calcination: a commercial high grade MgO (HGMgO) as well as a number of low-grade MgO (LGMgOs) by-products. All these MgO reagents were also pre-treated with phosphoric acid and tested separately after pre-treatment. The study focussed on the underlying chemistry to show how reactivity and dissolution of the various magnesium by-products influenced struvite precipitation and TAN removal performance. Moreover, another option to minimise struvite precipitation cost is to combine struvite precipitation and AD in the same reactor. Several authors have studied the addition of magnesium reagents (MgCl2 and Mg(OH)2) to precipitate struvite during anaerobic digestion, causing in some cases inhibition by pH or cation toxicity. However, to our knowledge, no references bave been found evaluating the utilization of magnesium by- products within the reactor to precipitate struvite during anaerobic digestion. In this study struvite precipitation and pig manure anaerobic digestion were coupled in the same reactor in order to mitigate the inhibitory effect of free ammonia and avoid precipitator costs. The stabilizing agent used to facilitate struvite precipitation was formulated with low-grade magnesium oxide by-product; an approach that would notably reduce struvite processing costs. Therefore, the feasibility of coupling anaerobic digestion and struvite precipitation in the same reactor was evaluated to enhance manure anaerobic digestion methane yields through ammonia inhibition mitigation. Five different magnesium sources were tested as struvite (ammonia sequestration agent) precursor, i.e. MgCl2, Mg(OH)2, two industrial by-products rich in MgO but with different reactivity, and a stabilizing agent. The latter was formulated in advance with the low reactivity industrial by-product and phosphoric acid. The effect of each magnesium source on anaerobic digestion as well as its struvite precipitation capacity was evaluated through a series biomethane potential test. However, a long term anaerobic digester operation was required to assess the feasibility of the process and to ensure that the stabilizing agent does not introduce any harmful compound for the anaerobic biomass. In this vein, the -3 addition of 5 and 30 kg m of the stabilizing agent in a pig manure continuous digester 3 -1 3 -1 resulted in a 25% (0.17 m kg ) and a 40% (0.19 m kg ) increase in methane production per mass of volatile solid, respectively, when compared with the reference digester (0.13 3 -1 m kg ). Moreover, the stability of the process during four hydraulic retention times guarantees that the stabilizing agent did not exert a negative effect on the consortium of microorganisms. / Diferentes esfuerzos han sido desarrollados para reducir la inhibición por nitrógeno amoniacal en la DA. Entre ellos, la adición de materiales con capacidad de intercambio catiónico (por ejemplo: bentonita, glauconita, fosforita y zeolitas) o materias con capacidad de adsorción (ej. arena, óxidos de magnesio, sepiolitas y zeolitas) han mostrado buenos resultados. Igualmente, en años recientes la posibilidad de acoplar la DA y la precipitación de estruvita (MgNH4PO4·6H2O) en el mismo reactor han llamado la atención. La precipitación de estruvita ocurre de manera natural cuando la concentración de 2+ + 3- Mg , NH4 y PO4 excede el producto de solubilidad de la estruvita. Con lo cual, la precipitación de estruvita en muchos sistemas de DA requiere la adición de compuestos 2+ 3- + químicos, ya que la concentración de Mg y PO4 es típicamente inferior a la del NH4 . El objetivo de este estudio es comparar el desempeño de cinco diferentes fuentes de magnesio (ej. MgCl2, Mg(OH)2, HG-MgO, LG-MgO y SA) en reactores, simultaneando los procesos de la DA y la precipitación de estruvita dentro del mismo reactor. La adición de agente estabilizante al purín de cerdo presento una máxima eficiencia de remoción de nitrógeno amoniacal total del 80%. La operación de los -1 digestores mostró que la adición de agente estabilizante de 5 y 30 g L al digestor resulta en un incremento del 25 y 40% en la producción de metano, respectivamente, comparado con el reactor de referencia. Este resultado puede estar relacionado con la reducción de la concentración de amonio y el incremento de la concentración de magnesio y concentración de partículas en el medio de digestión. Adicionalmente, los resultados de alcalinidad y ácidos grasos volátiles muestran que la adición de agente estabilizante no presenta un efecto negativo en los microorganismos anaeróbicos.