Regenerative medicine takes multifaceted approaches towards healing complex injury and restoring normal tissue function by combining biomaterials with cells and drugs. Recently, naturally occurring polymers found in the human body have inspired biomaterials that play active roles in the regenerative process. One polymer, hyaluronic acid, has ubiquitous roles in the human body, and is an important component to tissue development and healing. These materials are proving to be more capable to the complex tasks of guiding tissue regeneration; however, the search continues for laboratory inspired solutions to help guide the regeneration process. We need to be able to control the presentation of bioactive agents in the microenvironment which is the level at which cells operate. Some researchers have attempted to augment the scaffold biochemistry by controlling the spatial presentation of bioactive molecules by playing with clustering peptide sequences, but they do not have a high control over the nanoscale aspect. For the problem of controlling the molecular architecture of the biomaterial microenvironment, nanotechnology has a solution. Dendrimers are synthetic branched macromolecules which are symmetric, monodisperse, and globular in shape. Most importantly however, is that their inherent structure maintains strict presentation of terminal groups. Up to this point, never before have dendrimers been covalently mixed with biomaterials to provide strict control over the presentation of biomolecules in the scaffold microenvironment. This novel technology poses a new biomaterials niche for guiding bone regeneration. The motivation of the thesis is to contribute to the development of intelligent biomaterial platforms by combining peptide epitope binding dendrimers with a thermoreversible biomaterial platform based on hyaluronic acid in the hope to advance bone regeneration. / La medicina regenerativa utiliza distintos enfoques hacia procesos complejos de curación de lesiones: uno de ellos es la restauración de la función normal de tejidos mediante la combinación de biomateriales con células y fármacos. Pero si nos centramos en lo que ahora pueden hacer los biomateriales sabemos que son un material capaz de guiar tareas complejas en procesos de regeneración tisular. No obstante, la investigación en los laboratorios continua explorando este mundo inspirada por la búsqueda de soluciones para mejorar, todavía más, esta función de guía en el proceso de regeneración tisular. Hemos de ser capaces de controlar la entrega de agentes bioactivos en los microambientes que se encuentran a niveles en los que las células operan. Algunos investigadores han intentado aumentar la funcionalidad bioquímica de las estructuras de los polímeros, o “andamios” (en la literatura inglesa scaffold), mediante el control de la presentación espacial de moléculas bioactivas jugando con clústeres de secuencias de péptidos, pero sin tener un alto control a escala nanoscópica. Ahora, para el problema sobre el control de la arquitectura molecular del microambiente de un biomaterial la nanotecnología tiene una solución. Se trata de los dendrímeros, moléculas sintéticas ramificadas, simétricas, monodispersas y con forma globular. Más importante todavía, su estructura inherente mantiene una presentación estricta de los grupos terminales. Hasta este momento, nunca antes se habían mezclado covalentemente dendrímeros con biomateriales para proporcionar un control estricto de la presentación de biomoléculas en el microambiente de “andamio”. Esta nueva tecnología (la de los dendrímeros) coloca a los biomateriales en el nicho para la guía de la regeneración ósea. El objetivo de estas tesis es contribuir al desarrollo de biomateriales inteligentes mediante la combinación de dendrímeros con afinidad por proteínas específicas en una plataforma de biomaterial termorreversible a base de ácido hialurónico. La meta: avanzar en el campo de la regeneración ósea.

La introducció dels feixos amb polaritzacions no uniformes ha aportat grans avenços en multitud d'àrees. En un nivell més fonamental, ha permès entendre la naturalesa de la llum d'una manera més amplia, estenent les teories òptiques conegudes, com ('escalar, a d'altres més precises com la vectorial. La síntesi de feixos amb una distribució no uniforme de la polarització segueix sent una tasca desafiant. Mentre que algunes tècniques utilitzen sistemes totalment òptics, en aquesta tesi, s'ha optat per incorporar dispositius optoelectrònics per modular la llum, obtenint així una major flexibilitat a la hora de dissenyar el feix. Per altra banda, el muntatge òptic utilitzat està basat en un interferòmetre de Mach-Zehnder per tal de manipular les dues components del feix, d'una manera independent, en cada braç de l'interferòmetre. D'aquesta manera, utilitzant en cada braç de l'interferòmetre un modulador de cristall líquid, tenim la capacitat de modular ambdues components del feix incident. Aquests moduladors són els proporcionats per Holoeye, concretament el model HEO 0017, els quals treballen en transmissió. Compten amb una configuració pixelada, dotant-nos d'una capacitat de modulació espacial amb una resolució de 32gm. Complementant aquesta modulació amb una tècnica d'holografia digital, som capaços de modular tant l'amplitud com la fase d'ambdues components del camp i, per tant, d'esculpir qualsevol forma amb qualsevol distribució de la polarització. Per tal de mostrar aquesta flexibilitat, s'ha sintetitzat un conjunt de feixos amb diversos perfils i diverses distribucions de la polarització. Els feixos generats s’han avaluat mitjançant un analitzador, compost d’una làmina retardadora λ/4 i un polaritzador lineal, enfront d’una càmera CCD de 14 bits de rang dinàmic del model Stingray F080B A5G. D’aquesta manera, s’han obtingut les distribucions dels paràmetres d’Stokes en el pla de la càmera. Aprofitant aquesta capacitat de modulació, s’ha dissenyat una tècnica d’encriptació hologràfica utilitzant el mateix sistema òptic amb lleugeres modificacions. Les claus secretes, que garanteixen la seguretat en la codificació, són màscares de polarització. Per incrementar el nivell de seguretat del sistema, s’han afegit dos paràmetres físics necessaris per poder desencriptar la informació. A més, s’ha simulat, sobre els resultats experimentals obtinguts, la resposta del sistema sota condicions de molt baixa il·luminació. Aquestes condicions, sovint utilitzades en treballs previs, augmenten significativament la robustesa del mètode d’encriptació. Un cop garantida la correcta manipulació d’ambdues components d’un feix paraxial, s’ha procedit a desenvolupar un marc teòric per sintetitzar feixos altament focalitzats amb una polarització tridimensional arbitrària. Per tal d’obtenir aquests feixos, s’ha utilitzat un objectiu de microscopi amb una obertura numèrica de NA=0.85, on s’ha modulat el camp en la pupil·la d’entrada mitjançant el mètode hologràfic anterior. El disseny del camp en la zona focal, en funció de la distribució de la polarització en la pupil·la d’entrada, s’ha realitzat en el marc de la teoria vectorial desenvolupada per B. Richards i E. Wolf. Per avaluar el funcionament del sistema, s’ha sintetitzat un feix altament focalitzat amb polarització circular en qualsevol pla, i s’ha comparat els resultats obtinguts experimentalment amb els extrets numèricament. La definició del grau de polarització en feixos altament focalitzats, encara ara, genera certs debats degut a que no es pot expandir d’una manera inequívoca com una suma directa del camp totalment polaritzat i del camp totalment despolaritzat. En aquesta tesi, hem fet l’estudi en el marc dels paràmetres d’Stokes generalitzats, obtenint una correspondència entre la distribució del paràmetres d’Stokes en la pupil·la d’entrada i la distribució del paràmetres d’Stokes de la contribució transversal del camp focalitzat. S’ha proposat un feix paraxial, que, un cop focalitzat, genera un camp amb les components transversals despolaritzades i que compta amb una component longitudinal no nul·la. Aquests tipus de feixos són de gran utilitat, entre d’altres camps, en la confecció de capes de invisibilitat. / Non uniformly polarized beams have provided great strides in many areas. The synthesis of arbitrary polarized beams remains a challenging task. While some techniques use full optics systems, in this dissertation we introduce a system where optoelectronic devices modulate the light, providing more flexibility in the beam design. Complementing this modulation with a digital holography method, we modulate both amplitude and phase of the field. Moreover, the optical assembly is based on a Mach-Zehnder interferometer where the two components of the field can be independently manipulated in each arm of the interferometer. Applying an arbitrary modulation in both compontents, we can sculpt any profile with any distribution of polarization. To show this flexibility, a set of beams with multiple profiles and polarization distribution have been presented. In addition, taking this modulation capability, we introduce an holographic encryption technique where the secret keys are polarization masks. Two physical parameters are necessary to decrypt the information, increasing the security of the system. We have simulated the system response under very low illumination. Once guaranteed the flexibility in the design of paraxial beams with arbitrary polarization distribution, a theoretical framework to synthesize highly focused beams with an arbitrary three-dimensional polarization has been developed. The B. Richards y E. Wolf theory relates the polarization distribution on the entrance pupil of a microscope objective with the vectorial structure of the field in the focal region. To evaluate the performance of the system we have implemented a highly focused beam (NA=0.85) with circular polarization in any plane. The definition of the degree of polarization in highly focused beams even now generates some discussion because it can not be expanded unequivocally as a direct sum of completely polarized fields and completely depolarized fields. In this thesis, we have made the study within the frame of generalized Stokes parameters. We have obtained a correspondence between the distribution of the Stokes parameters in the entrance pupil and the distribution of the transverse Stokes parameters in the focused field. We have proposed a paraxial beam, which once focused, it generates a field with the transverse components depolarized and a non-zero longitudinal component.

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.

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.

Tesi realitzada a l'Institut de Recerca de l'Energia de Catalunya (IREC) / In the last decades, energy requirements of portable devices are exponentially increasing while the capacity of the current battery technology is not progressing accordingly. This energy gap claims for the development of new technologies beyond Li-ion. Novel miniaturized devices able to efficiently operate on the low power regime (1 — 20 W) in continuous mode by using a fuel are receiving increased attention. Due to their long lifetime, high power density and integrability, probably the most promising alternative is the development of micro fuel cells. Amongst them, micro Solid Oxide Fuel Cells mi-SOFCs) present the highest values of specific energy densities (by unit mass and volume), mainly due to their higher operating temperature and their capability of operating directly on hydrocarbon fuels. One of the most promising approaches for the mi-SOFCs is based on the monolithic integration of functional free-standing electrolyte membranes in silicon technology. This approach ensures high reproducibility and reliability, cheap mass production and easy integration to mainstream technology. This thesis encompasses the design, fabrication and test of the main components of a novel mi-SOFC power generator as a first step to develop a complete device in the near future. The adopted approach is based on the use of MEMS fabrication methods to miniaturize mi-SOFCs in silicon technology and high energy density hydrocarbons as fuels. The mi-SOFC power generator is designed to supply 1W of electrical energy in a small volume (10-20 cm3). The work developed is divided into six chapters. The first chapter introduces the basics and challenges of a mi-SOFC power generator. The second chapter focuses on the experimental procedures and characterization techniques used. In the third chapter, the thermal analysis of a new mi-SOFC power generator with finite-volume simulations is presented. The fourth chapter shows the fabrication and characterization of a fuel processing unit capable to produce hydrogen from ethanol steam reforming and methane dry reforming. The next chapter is related to a catalytic micro-machined combustor. Finally, chapter six presents the development of a full ceramic mi-SOFC. / La demanda d'energia dels dispositius electrònics portàtils augmenta exponencialment any rere any, però la tecnologia actual amb les bateries d'ió liti no progressa suficientment. Aquesta divergència energètica és una oportunitat per poder desenvolupar noves tecnologies. En aquest sentit, micro dispositius que operin de forma contínua mitjançant l'ús d'un combustible i que proporcionin una potència compresa entre 1 i 20 W reben una especial atenció per part de la comunitat científica. Probablement, l'alternativa més prometedora són les micro piles de combustible, ja que tenen una llarga vida útil, una alta densitat de potència i són fàcils d'integrar. Dels diferents tipus, les piles de combustible d'òxid sòlid (mi-SOFCs) són les que tenen una major densitat específica d'energia (per unitat de massa i de volum). A més a més, treballen a una temperatura més alta i aquesta característica permet utilitzar hidrocarburs com a combustible. Una de les configuracions més esteses de les mi-SOFCs és la que es basa en membranes electrolítiques en suspensió, integrades amb la tecnologia de silici. Aquesta configuració permet una producció elevada, barata i fiable. La present tesi té com a objectiu dissenyar, fabricar i validar experimentalment els principals components d'un nou dispositiu generador. Els resultats obtinguts són un primer pas per desenvolupar en un futur proper un dispositiu complet basat en l'ús de MEMS (sistemes micro electromecànics) i hidrocarburs d' alta densitat d'energia. El dispositiu mi-SOFC ha estat ideat per subministrar 1W de potència elèctrica i ocupar un volum entre 10 i 20 cm3. La tesi consta de sis capítols. En el primer es descriuen els conceptes generals relacionats amb un dispositiu mi-SOFC i els principals reptes associats que presenta el seu desenvolupament. El segon es centra en els procediments experimentals i les tècniques de caracterització utilitzades al llarg de la tesi. El tercer capítol presenta l'anàlisi tèrmica del sistema proposat mitjançant simulacions termofluídiques. El quart mostra la fabricació i caracterització d'una unitat de processament de combustible capaç de produir hidrogen a partir del reformat d'etanol i metà. El cinquè descriu una unitat catalítica de combustió. I l'últim capítol, es centra en les capes funcionals d'una pila de combustible mi-SOFC completament ceràmica.

There are several applications where the measurement of VOC results to be useful, such as: toxic leaks, air quality measurements, explosive detection, monitoring of food and beverages quality, diagnosis of diseases, etc. Some of this applications claim for fast responses or even real time responses. In this context, there are few analytical techniques for performing gas phase analysis, among of them Ion Mobility Spectrometry (IMS). IMS is a fast analytical device based on the time of flight of ions in a drift tube. The response of IMS lasts typically few seconds, but it can be even less than a second. This fast response has drifted its use towards novel applications, such as biomedical and food applications (bio-related applications). Nonetheless, it has also brought the need to analyze complex spectra with hundreds of compounds. In fact, tackling this disadvantage is the main focus of this thesis, where new algorithms for enhancing the IMS performance are investigated when are applied to bio-related applications. Nonlinear behavior and charge competitions of IMS responses are important issues that need to be addressed. Both effects have a direct impact in the IMS spectra interpretation —especially when real dataset are studied. Additionally, the use of univariate spectra analysis, where peaks information is extracted manually, becomes unfeasible in bio-related applications. In this context, this work introduces multivariate methodologies focused on quantitative and qualitative analysis. In the case of quantitative analysis, calibration models were built using univariate methodology, Partial Leas Squares (PLS) and Multivariate Curve Resolution techniques (MCR). The quantitative analysis aims tackling the main issues of IMS such as non linearities and mixture effect. Definitely, univariate techniques provides poor or overoptimistic results that minimize the impact of the IMS use. The results show a really improvement on the performance when multivariate techniques were used. Regarding the results between MCR and PLS, the main difference is the interpretability that offers MCR. In the case of qualitative analysis, two different approaches were planned for building models for classes' discrimination. The first approach consisted on building a model through principal component analysis and linear discriminant analysis, besides of using robust cross validation methodology for obtaining reliable results. This methodology were implemented in samples of wine, where main motivation was found discrimination regarding to their origin. The results were fully satisfactory because the model was able to separate four groups with a high accuracy rate. The second approach involves the use of Multivarite Curve Resolution — Lasso algorithm for extracting pure components of samples from rats' breath and then use a feature selection technique for obtaining the most representative features subset. In this case, the objective of the application was to find a model that discriminate rats with sepsis from control rats. The results shows there were few pure components of IMS that generate a discriminatory model that means there are specific compounds in the breath linked with the disease. Summarizing, the following proposal has as main objective resolving open issues in stand-alone IMS that are applied to the analysis of bio-related applications. Two major investigation lines were proposed in this thesis: (i) qualitative analysis and (ii) quantitative analysis. The qualitative analysis covers pre-processing algorithms and the developing of new methodologies for building models in bio-related applications. The quantitative analysis are focused on highlighting the importance of the use of multivariate techniques instead of univariate techniques. In order to reach the objectives of this thesis, a set of datasets were created, which are detailed on the content of this thesis. The results and main conclusions are deeply explained in the extended proposal. / El objetivo de esta tesis es el desarrollo de nuevas metodologías en el procesado de señal multivariante en espectros IMS. En este trabajo se ha realizado una comparación entre tres espectrómetros IMS. Esta labor comparativa, mediante procesado multivariante, es prácticamente inédita en este ámbito. En este caso se realizó un estudio con 3 aminas y se determinó el límite de detección. Los resultados mostraron que los 3 espectrómetros tuvieron un rendimiento similar, a pesar de que sus condiciones de operación son distintas. Se propuso una técnica específica para eliminar ruido de baja frecuencia acoplado al espectro de IMS. Se observó que utilizar PCA o ICA (métodos multivariantes) mejora notablemente la relación señal ruido si se compara con las técnicas convencionales. Se ha estudiado el alineamiento de los espectros y se han propuesto soluciones basadas en los diferentes métodos del estado del arte. Se ha evidenciado que incluir compuestos de referencia para garantizar que el proceso de alineamiento es el adecuado es ventajoso. En el caso de que esto no fuese posible se aconseja realizar el alineamiento por etapas, primero un alineamiento en una misma muestra, y luego entre muestras. Se realizaron modelos cualitativos para diferenciar o discriminar clases a partir de medidas de IMS. Se propusieron dos modelos multivariantes con técnicas de validación cruzada. Los resultados obtenidos muestran el gran potencial de IMS en este sentido. Se evaluó el rendimiento cuantitativo de los IMS al utilizar métodos multivariantes y fueron comparados con métodos univariantes habituales en el ámbito de IMS. De los resultados obtenidos se observó que los modelos univariantes no son capaces de resolver comportamientos típicos de IMS como son el comportamiento no lineal y el efecto en mezclas. En este sentido las técnicas multivariantes mostraron mejores prestaciones. Se comparó la utilización de técnicas multivariantes que proyectan los datos en un nuevo subespacio como lo es PLS con técnicas de deconvolución como lo es MCR en sus dos versiones ALS y Lasso. Los resultados obtenidos fueron bastante similares, sin embargo MCR ofrece una ventaja importante ya que permite interpretar de mejor manera los resultados.

The ability of detecting farces and torques at the micro-and nano-scale is fundamental. When this Thesis started, various scanning probe techniques had already been developed to probe the mechanical properties of microsystems. In 1993 Ghislain and coworkers devised a new scanning force microscopy using an optically trapped microsphere as a probe. This technique was later called Photonic Force Microscope (PFM).A typical PFM comprises an optical trap that holds a probe - a dielectric or metallic particle of micrometer size, which randomly moves due to Brownian motion In the potential well formed by the optical trap - and a position sensing system. The analysis of the thermal motion provides information about the local forces acting on the particle. The three-dimensional probe position can be recorded through different devices, which detect the forward or backward scattered light from the particle.The PFM had been applied to measure forces in the range of femto- to pico-Newton - well below the limits of what can be achieved with techniques based an micro-fabricated mechanical cantilevers, such as AFM - in many different fields with exciting applications, for example, in biophysics, equilibrium and nonequilibrium thermodynamics of small systems, and colloidal physics.We defined various problems that deserved our attention. All of them concerned the enhancement of the possibilities of the PFM, either by applying the PFM to new fields or by making it more powerful.These are the main results:1. Brownian motion in an nonhomegeneous force field and Photonic Torque MicroscopeWe reported how to expand the PFM technique to deal with force fields varying on the scale of the Brownian motion. We also proposed a concrete analysis workflow to reconstruct the force field from the experimental time series of the probe position. In particular, we analyzed the PFM probe movement in the presence of a torque. The value of the torque is found from the auto- and cross-correlation functions of the particles coordinates. We experimentally detected the torque exerted onto an optically trapped particle by an optical beam with orbital angular momentum.2. Backscattering position detectionWe studied theoretically the probe displacement sensitivity in back-scattering and forward-scattering geometry. To achieve this aim an original calculation procedure based on Mie scattering theory was developed and realized on MatLab platform. The calculation results were compared with known experimental data.3. Surface Plasmon (SP) Radiation FarcesWe reported the first experimental observation of the momentum transfer from a SP to a single dielectric sphere. We showed that the force at resonance conditions resulted enhanced 40 times compared to nonresonant illumination. We also reported a quantitative analysis of 20 surface-plasmon-based optical tweezers at a patterned metal surface.4. Characterization of microscopic flowsWe suggested an approach to microrheology based on optical traps capable of measuring fluid fluxes around singular points. The concept was to monitor the position of an optically trapped probe in order to locally characterize the drag torte field as a generic function of the space coordinates up to the first order in its Taylor expansion around the probe position. We experimentally demonstrated this technique, applying it to the charactedeation of controlled flows.5. Cell dynamics in an optical trapWe reported the analysis of the forward scattered light from a single optically trapped cell during its growth. We showed that the cell continued adjusting itself to the applied optical force because of the growth processes, and hence it kept changing its orientation in the trap. We pointed out the relevance of these findings for single optically trapped cell spectroscopic measurements. We also demonstrated the possibility of monitoring the cytoskeleton structural transformations in optically trapped yeast cells (S. cerevisiae ) using this technique.

The aim of this thesis was to study quantum phenomena and excitation modes in type-I superconductors and magnetic vortices. The intermediate state in type-I superconductors is characterized by the gradual penetration of magnetic flux and the coexistence of normal and superconducting domains. This thermodynamic phase shows a magnetic irreversibility of topological origin, even in the case of defect-free samples. This irreversibility has been explored in disk-shaped samples made of lead (the prototype of a type-I superconductor) using a magnetic field applied perpendicularly to the disk plane, by means of the measurement of hysteresis cycles at different temperatures, zero-field-cooled and field-cooled magnetization curves at different magnetic fields and magnetic relaxations along the descending branch of the hysteresis cycles. Non-thermal magnetic relaxations have been observed in these samples at low temperatures, which have been attributed to the tunnel effect of normal-superconductor interfaces through pinning energy barriers. A quantum model based on the Caldeira-Leggett theory for dissipative systems have been developed to explain these experimental observations. The interface is described as a 2D elastic manifold that is pinned by a planar defect. The pinning barrier can be controlled by a supercurrent that exerts a force on the interface. The vortex state turns out to be the ground state of magnetic disks for a wide variety of thicknesses and radii. It is characterized by the curling of the magnetization in the plane of the disk, leaving virtually no magnetic ‘charges’. The very weak uncompensated magnetic moment of the disk sticks out of a small area confined to the vortex core. The low-frequency dynamics of the vortex state is characterized by the spiral-like precessional motion of the vortex core as a whole (gyrotropic mode), which can be induced by the application of an in-plane magnetic field. The presence of structural defects in these magnetic disks affects the dynamics of the vortex state, which is indicative of the elastic nature of the vortex core along the axial direction of the disk. It has been studied whether the gyrotropic mode allows spatial dispersion similar to spin waves of a finite wavelength in ferromagnets. The excitation spectrum splits into two branches, one related to the gyrotropic mode with a gap given by the gyrofrequency of the disk and the other related to the existence of an effective mass associated to the vortex core. The magnetic irreversibility of the vortex state has been also explored by means of an experimental protocol analogous to that used in the case of type-I superconductors. Non-thermal magnetic relaxations have been observed again at low temperatures, which is attributed to the tunnel effect of a segment of the vortex core line through pinning barriers. A quantum model based on the Caldeira-Leggett theory for dissipative systems have been developed to explain these experimental observations. The interface is described as a 1D elastic manifold that is pinned by a linear defect. To conclude, the effect of the vortex state on the supercurrent of a Josephson junction has been studied in the case where the non-superconducting layer consists of a magnetic disk with the vortex as the ground state. It has been concluded that the variation of the Josephson current with tiny displacements of the vortex core can be detected experimentally. / El objetivo de esta tesis ha sido estudiar fenómenos cuánticos y modos de excitación en superconductores tipo-I y vórtices magnéticos. La irreversibilidad magnética en muestras de plomo con forma de disco en el estado intermedio ha sido explorada mediante medidas de ciclos de histéresis a diferentes temperaturas, medidas de las curvas de magnetización zero-field-cooled y field-cooled a diferentes campos y relajaciones magnéticas a lo largo de la rama descendiente de los ciclos de histéresis. Se han observado relajaciones magnéticas independientes de la temperatura en estas muestras, las cuales se atribuyen al efecto túnel de las interficies normal-superconductor a través de barreras de anclaje. Un modelo de efecto túnel basado en la teoría de Caldeira-Leggett para sistemas disipativos se ha construido para explicar estas observaciones experimentales, donde la interfície se trata como una variedad 2D elástica que se ancla a defectos planares. La barrera de anclaje se puede controlar mediante la inyección de supercorriente en el sistema. El núcleo del estado vórtice muestra una naturaleza elástica a lo largo de la dirección axial de los discos magnéticos que lo presentan como estado fundamental. Se ha estudiado bajo qué condiciones el modo girótropo es compatible con una dispersión espacial semejante a las ondas de espín de longitud de onda finita presentes en un ferromagneto. El espectro de excitaciones axiales presenta dos ramas bien definidas, una asociada al modo girótropo y la otra originada por la existencia de una masa efectiva asociada al núcleo. También se ha explorado la irreversibilidad magnética del estado vórtice mediante un protocolo análogo al de los superconductores tipo-I. De nuevo se ha observado un comportamiento no térmico a bajas temperaturas en las relajaciones magnéticas, el cual es atribuido al efecto túnel de un segmento del núcleo vorticial a través de las barreras de anclaje. Un modelo de efecto túnel basado en la teoría de Caldeira-Leggett para sistemas disipativos se ha construido para explicar estas observaciones experimentales, donde el núcleo vorticial se trata como una variedad 1D elástica anclada a un defecto lineal. Por último, se ha estudiado cuál sería el efecto del estado vórtice sobre la supercorriente de una unión Josephson si como capa no superconductora se escogiera un disco magnético con este estado fundamental. Se ha concluido que la variación de la corriente Josephson con desplazamientos pequeños del núcleo vorticial es detectable experimentalmente.