Le La2CuO4 est un isolant antiferromagnétique qui devient supraconducteur lorsqu'il est suffisamment oxydé. Cette étude qui porte sur la faisabilité de la synthèse de films de La2CuO4 par pulvérisation magnétron sur des substrats à moindre coût a été développée selon trois axes : l'élaboration des films, l'étude de leur cristallisation et l'influence de la nature du substrat sur leur tenue mécanique. Sous l'aspect élaboration ont été regroupés la présentation et la comparaison de quatre procédés d'élaboration. Nous avons ainsi déterminé que le procédé utilisant une cible céramique est le procédé permettant d'obtenir la zone homogène la plus étendue. La structure des films après recuit dans l'air a été déterminée par diffraction des rayons X et par microscopie électronique en transmission. Ces techniques ont permis de démontrer que les films cristallisent majoritairement dans une structure quadratique métastable et dans une moindre mesure dans une structure orthorhombique. L'effet de la composition chimique des films, de la nature du substrat et sur la cristallisation des films ont été étudiés. Il apparaît que l'utilisation de substrats en acier constitue une voie prometteuse pour la synthèse de films de La2CuO4. En utilisant des techniques de microscopie in situ, nous avons démontré que le recuit induit la formation de défauts en surface des films. La nature de ces défauts dépend des propriétés thermiques des substrats. Pour expliquer ces résultats, nous avons estimé les coefficients de dilatation thermique apparents de nos films à partir d'analyses par diffraction des rayons X. Ceci nous a permis de proposer un modèle d'initiation de la délamination des films / Lanthanum cuprate is an antiferromagnetique insulator that becomes superconducting when sufficiently oxidized. The aim of this study is to show the feasibility of the lanthanum cuprate thin film deposition by magnetron sputtering on low cost substrates. This work is developed around three points: the synthesis of the films, a study of their crystallization and the influence of the substrate nature on the films delamination. The synthesis aspect includes the presentation of the four different synthesis processes and a comparison of these processes in terms of reproducibility, chemical composition and thickness homogeneous zones. The process using a ceramic target was determined to have the larger homogeneous zone but does not allow obtaining stoichiometric films. The films structure after annealing in air has been determined by X-ray diffraction and Transmission Electronic Microscopy. This technique allowed us to demonstrate that the films mostly crystallize in a metastable tetragonal structure and in a lesser extend in orthorhombic structure. The effects of the chemical composition of the film, the substrate nature, and the annealing atmosphere on the films crystallization were studied. The use of steel as a substrate is promising way to the elaboration of La2CuO4 thin films. By using in situ microscope techniques, we showed that the thermal treatment induces defaults formation on the film surface. The natures of these defaults strongly depend on the substrate nature. To explain these results, the apparent thermal expansion coefficients of the films were calculated from x-ray diffraction analyses. These results allowed us to suggest a film delamination initiation model

La compréhension des propriétés électroniques, électriques et mécaniques de nanostructures est une question clé en nanosciences et nanotechnologies. Pour sonder et comprendre ces propriétés à l’échelle nanométrique, une technique expérimentale essentielle est la microscopie champ proche. L’objectif de cette thèse a été de comprendre les propriétés électroniques et électromécaniques de nanostructures colloïdales individuelles ou assemblées par microscopie à force atomique en environnement ultra vide.La première partie du travail concerne les propriétés de transport à travers des assemblées de nanoparticules colloïdales métalliques d’or et transparentes d’oxyde d’indium (ITO) formant les zones actives de jauges de contraintes résistives. L’étude par conducting AFM a permis de mesurer les spectroscopies courant-tension I(V) en fonction de la force d’appui du levier et de la température. Le transport tunnel a été étudié du régime linéaire au régime Fowler Nordheim, permettant une mesure du module de Young effectif des ligands des nanoparticules.La deuxième partie du travail correspond en premier lieu la caractérisation des nanocristaux semiconducteurs colloïdaux individuels d’Arséniure d’Indium (InAs) dopés ou non-intentionnellement dopés, de tailles inférieures dans la gamme 2-8 nm. Cette étude visait à comprendre les processus de transfert de charges entre les nanocristaux et leur environnement dans un régime physique de fort confinement quantique et coulombien. Les résultats expérimentaux ont fourni une estimation du taux de dopage actif de l’ordre de avec une densité de défauts de l’ordre de . Ensuite, une caractérisation par KPFM couplée au nc-AFM sous ultra vide a été menée sur les nanocristaux semi-conducteur colloïdaux de pérovskites (CsPbBr3). Les expériences ont été réalisées dans le noir puis sous illumination laser avec différentes longueurs d’onde afin d’explorer les mécanismes de photo-génération de porteurs au sein des nanocristaux. / Understanding the electronic, electrical and mechanical properties of nanostructures is a key issue in nanoscience and nanotechnology. Scanning probe microscopy is an essential tool to probe and understand these properties at the nanoscale. The objective of this thesis was to characterize the electromechanical and electrostatic properties of individual or assembled colloidal nanocrystals using atomic force microscopy in ultra-high vacuum environment.The first part of the manuscript deals with the transport properties of assemblies of gold and indium tin oxide nanoparticles, forming the active areas of resistive strain gauges. Current-bias spectroscopies are measured as a function of the force applied on the cantilever and as a function of temperature. Tunneling transport is evidenced and measured from the linear regime to the Fowler Nordheim regime. The mechanical characteristic (effective Young modulus) of ligands is extracted.The second part of the thesis is devoted to the characterization of the electrostatic properties of individual indium arsenide (InAs) colloidal doped nanocrystals with sizes in the 2-8 nm range, using non-contact atomic force microscopy coupled to Kelvin probe force microscopy. This aim was to understand the charge transfer mechanisms between doped or undoped nanocrystals and their environment, in a physical regime of strong quantum and Coulomb confinement. Experimental results enable to measure a doping level of and a defect density of about . Kelvin probe force microscopy measurements were in addition performed on colloidal perovskite (CsPbBr3) semiconductor nanocrystals in order to explore the photo-generation mechanisms of carriers.

The region GGD 27, located in Sagittarius at a distance of 1.7 kpc, is an active star forming region. The most well-known observational signature of this region, the HH 80/81/80N jet, is one of the largest collimated jet system known so far, spanning over a total length of about 5 pc. Ahead of the Herbig-Haro object HH 80N, assumed to be the northern head of the jet, there is a dense core of 0.3 pc in size and mass of 20 M (HH 80N core) that exhibits peculiar chemistry, possibly induced by the UV radiation incoming from the HH object. In addition, the HH 80N core has star forming signatures, namely a bipolar molecular outflow and supersonic infall velocity (0.6 km s(-1)), which differs from what standard contracting core models predict. This rises the question whether the HH 80/81/80N jet has triggered or sped up the star formation process in this core. VLA cm continuum observations carried out as a preliminary part of this thesis show that the jet could expand further away than HH 80N. This makes possible the cause-and-effect relationship between the jet and the star forming signatures of the core. In this thesis we study the possible influence of the HH 80/81/80N jet on the properties of the HH 80N core in several approaches. We first derive the physical and chemical properties of the large envelope of the HH 80N core using data obtained with the BIMA and IRAM 30m telescopes. All the detected BIMA molecular species arise in a ring-like structure contracting at 0.6 km s(-1). This morphology is likely the result of strong molecular depletion occurring at the inner part of the core (r < 0.1 pc), when the gas reaches densities > 10(5) cm(-3), as derived from a multi-transition analysis of CS and SO lines observed with IRAM 30m. Despite the overall morphology and kinematic similarity between the different species, there is significant molecular differentiation along the ring-like structure. Part of this differentiation may be caused by the UV irradiation of the nearby HH 80N object that illuminates the part of the core facing HH 80N, which results in an abundance enhancement of some species. Given the peculiar kinematic properties of the HH 80N core, we analyze the continuum emission of the core using self-consistent standard models of protostellar collapse to see if the dynamical evolution of this core departs from the predictions of classic models of star formation. We find that a young protostar (IRS1) surrounded by a slowly rotating collapsing envelope plus a circumstellar disk provide a good fit to our data observed at several bands. However, this model implies that the core has a static envelope at radii > 1.5 x10(4) AU, apparently in contradiction with the contracting ring-like structure that has 10(6) AU of radius. Besides, the continuum maps at 350 m and 3.5 mm reveal additional clumps independent from the main continuum peak at IRS 1. Therefore, we propose a scenario where IRS1 has infall motions with no connection with the kinematics of the large envelope of the HH 80N core. The later is possibly affected by the HH 80/81/80N jet and exhibits fragmentation that may lead to the formation of several protostars. In order to disentangle the gas motions belonging to the protostellar collapse of IRS1 from those associated to large scale kinematics we analyze high-density tracers (NH(3), HN(13)C, NH(2)D), observed at high angular resolution with VLA and PdBI, aiming to recover kinematic information in parts of the HH 80N core where other molecules are depleted. The results question the scenario of the contracting molecular ring. Instead, the velocity gradients seen with high density tracers suggest that part of the core is being swept by the HH 80/81/80N jet in the process of dissipating energy (e.g. though generation of magneto hydrodynamic waves in the medium). Future simulations of the events occurring in the HH 80N region are paramount to confirm whether the formation of IRS1 was caused by the interaction of the HH 80N core with the HH 80/81/80N outflow. / La font amb formació estel_lar per davant d'HH 80N: estudi de la seva interacció amb un jet a escala de parsecs Josep-Maria Masqué Saumell - Universitat de Barcelona L'objecte Herbig-Haro HH 80N representa l'extrem nord del sistema HH 80/81/80N, el jet estel.lar més llarg i col.limat conegut fins ara, que es troba a 1.7 kpc de distància a la regió de Sagitari. Observacions al voltant d'HH 80N revelen que a 0.3 pc de l'objecte HH hi ha un nucli dens (font d'HH 80N) de 0.3 pc de grandària i de massa 20 M, que mostra una química i cinemàtica peculiars i, a més, té un protoestel embegut al seu interior (IRS1). Donades aquestes característiques existeix la possibilitat de que les propietats de la font d'HH 80N hagin estat alterades pel jet d'HH 80/81/80N. L'objectiu d'aquesta tesi és l'estudi de la influència dels jets protoestel_lars centrant-nos en el cas particular de la regió d'HH 80N. Primer, trobem que la radiació ultraviolada provinent d'HH 80N és capaç d'alterar la química de la part de la font més exposada a l'objecte HH. Segon, malgrat una possible influència dinàmica del jet a la font d'HH 80N, el procés de col.lapse d'IRS1 es pot explicar dins el marc clàssic de formació estel.lar. No obstant, trobem que gran part del material de la font d'HH 80N constitueix un embolcall independent d'IRS1, el qual es fragmenta en vàries condensacions de gas. Possiblement, el gas d'aquest embolcall extens ha estat parcialment escombrat per ones magneto-hidrodinàmiques produïdes pel pas del jet. Aquest tipus d'interacció podria provocar inestabilitats a la font d'HH 80N donant lloc al naixement induït d'estels. Concloem que futures simulacions magneto-hidrodinàmiques són necessàries per confirmar que la formació d'IRS1 ha estat provocada per la interacció del jet HH 80/81/80N amb la font d'HH

Òrbites de segona espècie del problema espacial de 3 cossosEl problema general de tres cossos consisteix en l'estudi del moviment de tres cossos subjectes a les atraccions gravitacionals mútues. Una simplificació d'aquest problema s'obté en considerar que un dels cossos té massa menyspreable (P), de manera que la seva presència no afecta el moviment dels altres dos (anomenats primaris, E i M), els quals es mouen en òrbites circulars al voltant del seu centre de masses. L'estudi del moviment del tercer cos degut a l'atracció dels dos primaris és el que es coneix com a problema restringit de tres cossos, pla o espacial segons que aquest moviment es mantingui en el pla orbital dels primaris o no.En aquest context, es situa l'origen de coordenades en el centre de masses dels dos primaris i es pren un sistema d'eixos giratori (sinòdic) de manera que aquests es trobin fixos sobre un dels eixos. Prenent les unitats adequades, els cossos E i M tenen masses 1-m i m respectivament, on m [0,1]. Poincaré en els Méthodes Nouvelles de la Mechanique Celeste defineix dos tipus de solucions periòdiques del problema restringit: les de primera espècie, que són solucions properes a òrbites keplerianes per valors de m petits, i les de segona espècie, que són properes a arcs d'el·lipse connectats per punts angulosos. Aquestes últimes són òrbites que passen molt a prop del primari de massa petita.Ens centrem en l'estudi de les òrbites p-q ressonants. Són òrbites que surten d'un entorn de centre M i radi ma i que, després d'allunyar-se, tornen a ell al cap d'un cert temps, durant el qual el primari petit a fet aproximadament q voltes al voltant de E i el cos infinitesimal n'ha fet p. Mentre P està fora de l'entorn de M, es veu que la solució del problema restringit (solució exterior) es pot aproximar per la d'un problema de dos cossos i es calcula de quin ordre és l'error que es comet en l'aproximació. Aquesta aproximació ens permetrà calcular la posició i velocitat del tercer cos en l'instant de retorn a l'entorn de M i estudiar quines condicions inicials asseguren que l'òrbita és p-q ressonant.S'estudia també la solució del problema restringit amb les mateixes condicions inicials sobre l'entorn de M de radi ma, però fent anar el temps enrera i passant per dins l'entorn (solució interior). En aquest cas es veu que l'òrbita del tercer cos s'aproxima per una d'hiperbòlica i es calcula l'error que es comet en l'aproximació, la qual ens permetrà donar la posició i velocitat de P en el moment de sortir de l'entorn de M i després d'haver-hi passat per dins. Finalment, s'estudia quines condicions inicials asseguren que les posicions i velocitats de retorn a l'entorn exteriors i interiors coincideixen fins a ordre ma i a més asseguren que l'òrbita és p-q ressonant. La memòria finalitza amb algunes exploracions numèriques que mostren famílies d'òrbites periòdiques espacials trobades a partir d'òrbites crítiques, periòdiques i simètriques de segona espècie planes. / Second Species Orbits of the Spatial Three Body ProblemThe three-body problem consists of studying the movement of three bodies subjected to their mutual gravitational attraction. This problem can be simplified considering that the mass of one of the bodies (P) is negligible and has no effect on the movement of the other two bodies (E and M, called primaries), which are moving in circular orbits around their centre of mass. The study of the movement of the massless body is known as the Restricted Three-Body Problem (RTBP). It is called Plane RTBP if the third body keeps within the orbital plane of the primaries and, if not, spatial. The later will be our case.In this context, we take a synodical system, in which the origin of coordinates is at the centre of the masses and the primaries are fixed on the x-axis. The units can be chosen in such a way that E and M have respectively mass 1-m and m, where m [0,1]. Poincaré in Méthodes Nouvelles de la Mechanique Celeste defines two classes of periodic solutions in the restricted problem: first species and second species. The first ones are close to Keplerian circles or ellipses for values of m near zero, and the second ones are closed to arcs of Keplerian ellipses joined by corners. These are orbits which several passages near the small primary.Our study is focused on the p-q resonant orbits. These orbits leave the neighbourhood of centre M and radius ma and return to it, while the small and the infinitesimal bodies do p and q revolutions respectively around the main primary. While the third body is far from the small body, the solution of the restricted problem (called outer solution) can be approximated by a two-body solution (an elliptic orbit) and the error involved in the approximation is calculated. This approximated orbit allows us to calculate the position and the velocity of the third body at the time of its return to the neighbourhood of M and to study which initial conditions ensure that the orbit is p-q resonant. The solution to the restricted problem with the same initial conditions on the ball of centre M and radius ma, but moving back inside the ball (called inner solution) is also studied. In that case the orbit of the third body can be approximated by a hyperbola and the error involved in the approximation can also be calculated. This approximation gives us the position and the velocity at the time the orbit leaves the ball after passing through it. In order to obtain periodic orbits it is necessary that the outer and inner applications match. To give an approximation, the set of initial conditions which ensure that the return positions and the velocities match up to order of ma and the orbit is p-q resonant is studied.Finally there are several numerical explorations that show families of spatial, periodic orbits originating from plane, critical, symmetric, periodic second species orbits.

La historia de la astronomía de los rayos gammas en los últimos veinte años está marcada por el éxito que los telescopios Cherenkov han tenido en la exploración de la banda de muy altas energías. La ultima generación de telescopios Cherenkov, que incluye los telescopios HESS, VERITAS y MAGIC, ha logrado, en sólo siete años, aumentar el número total de fuentes conocidas de muy altas energías, desde unas pocas hasta más de un centenar. Esta populación de fuentes incluye objetos galácticos y extragalácticos. Los telescopios Cherenkov se han demostrado muy eficientes en el descubrimiento de nuevas emisoras de rayos gammas y también en el estudio detallado de la propiedades físicas de las fuentes bien conocidas, como por ejemplo, la Nebulosa del Cangrejo, el prototipo de los pleriones o Nebulosas de Viento de Púlsar ("pulsar wind nebulae"). Gracias a su brillo a todas las longitudes de onda, el Cangrejo es una fuente astrofísica de referencia. Su espectro ha sido medido en veinte ordenes de magnitud en energía, desde las frecuencias radio hasta las muy altas energías, pero nuevas medidas resultan aún esenciales para entender las contradicciones que surgen cuando se combinan los resultados de diferentes longitudes de onda. Finalizado del commissioning del segundo telescopio en el Otoño del 2009, y tras el comienzo de la toma de datos en modalidad estereoscopica, MAGIC ha mejorado significantivamente su rendimiento y alcanza el umbral en energía más bajo de todos los telescopios Cherenkov. Por lo tanto MAGIC es un instrumento ideal para medir el espectro de la Nebulosa del Cangrejo con una precisión sin precedentes a partir de 50 GeV. Este logro tiene una importancia extraordinaria para el astrofísica de muy altas energías y tiene el potencial de solucionar unos de los misterios aun no resueltos de esta fuente. Este es uno de los asuntos centrales de este trabajo de tesis. Por otro lado, MAGIC ha tenido también un impacto fundamental en el descubrimiento de nuevos objetos astrofísicos, y, con la mejora en sensibilidad del nuevo sistema de dos telescopios , este impacto será aún mas significativo. Entre las fuentes galacticas, los microcuásares constituyen unos de los mejores candidatos a emisores de rayos gammas. Su caracterización a muy alta energía aportaría información muy útil para entender la formación de chorros de partículas en objetos astronomicos. Aunque muchos modelos teóricos predicen esta emisión, aún no ha sido detectada. De hecho hay evidencias de que los tres sistemas binarios que se han detectado hasta la fecha por encima de 300 GeV son binarias de púlsares más que microcuásares. Sin embargo, el hecho que el microcuásar Cygnus X-3 haya sido detectado por encima de 100 MeV por los satélites AGILE y Fermi/LAT confirma que esta clase de objetos sigue siendo un objetivo interesente por la astrofísica de muy alta energía. En los últimos años, MAGIC ha dedicado un esfuerzo muy importante búsqueda de señales desde los microcuásares. Esta tesis presenta los resultados de las observaciones de dos de ellos: Cygnus X-3 y Scorpius X-1. Se han logrado extraer los limites superiores al flujo integral de estas dos fuentes más restrictivos hasta la fecha por encima de unos centenares de GeV. Para Cygnus X-3 en particular, se presentan además las primeras observaciones a estas energías totalmente simultáneas con la emisión detectada por los satélites. / of the Imaging Atmospheric Cherenkov Telescopes (IACTs) in the exploration of the Very- High-Energy (VHE) band. The last generation of IACTs have been capable to increase the total number of known VHE emitting sources from a few to almost one hundred in just seven years of operation. This population comprises galactic and extragalactic objects. IACTs have proved to be very effective in both the discovery of new emitters, as well as in the fine analysis of the physics properties of well established sources. Among them, the Crab Pulsar Wind Nebula is probably the best studied astrophysical object and the archetypal PWN. Due to its brightness at almost all wavelenghts, it is considered as an astrophysical candle. Despite the Crab Nebula broad-band spectrum has been thoroughly studied across twenty orders of magnitudes, from radio frequencies to VHE, further effort is needed to resolve the contradictions in the combination of all the multiwavelenght results. With the commissioning of the second MAGIC telescope in 2009 and the beginning of the operations in stereoscopic mode, the performance of the instrument improved dramatically, allowing MAGIC to reach the lowest ever energy threshold among all the existing IACTs, and describe the Crab Nebula spectrum with unprecedented precision down to 50 GeV. This achievement is of crucial importance for the VHE !-ray astrophysics in the pre-CTA era, since it can cast new light on some of the unsolved mysteries of one of its most established sources. On the other hand, MAGIC made a strong impact in the discovery of new VHE sources and, with the improved sensitivity of the stereoscopic mode, this will be even more so in the future. Among the galactic objects, Microquasars (MQs) constitute some of the best candidates for VHE emission, but despite several well accepted models predict such signal, it has not been detected. There are, in fact, evidences that the three binary systems which have been unambiguously detected at energies above few hundreds of GeV are binary pulsars rather than accreting microquasars. Nevertheless, the recent detection of the microquasar Cygnus X-3 above 100 MeV by both Agile and Fermi satellites, and the claim of short oneday flares from Cygnus X-1 reported by Agile confirmed that microquasars remain interesting targets for VHE telescopes. MAGIC made a strong effort in searching for VHE signals from microquasars, but found only a non-significant evidence of signal from Cygnus X-1 in 80 minutes of observation on September 24, 2006. MAGIC tried to detect similar flares in the following four years but the subsequent hundred more hours of observations were unsuccessful. Besides Cygnus X-1, MAGIC pointed at two other microquasar candidates, whose results are presented in this thesis: Cygnus X-3 and Scorpius X-1. The most constraining UL to the integral flux of these sources at the energy above few hundred GeV are provided. Further investigations are being planned to discover these sources at VHE in the next years.

Esta Memoria aborda el estudio de la dinámica de actitud de un sólido rígido triaxial (parte integrable) bajo la acción de lo que se conoce como gravity-gradient torque (perturbación). El sistema así constituido resulta ser uno de los modelos básicos no integrables válidos para analizar el movimiento tanto de satélites artificiales como de otros cuerpos naturales. Una forma muy común de abordar este tipo de problemas es llevar a cabo lo que se conoce como la reducción completa de la parte integrable considerada como orden cero. En ese sentido se han propuesto en la literatura distintos conjuntos de variables tomando como base las variables de Andoyer. Así, el principal objetivo de este trabajo es mostrar el comportamiento de dos conjuntos diferentes de estas variables que pueden presentar ciertas propiedades que las hacen más o menos adecuadas para el estudio de una perturbación. El primer conjunto, conocido como variables de ángulo-acción, fue introducido por Sadov, el cual será comparado con un nuevo conjunto propuesto recientemente por Ferrer y Lara. Además del capítulo introductorio, en el Capítulo 2 se realiza una revisión del sólido libre. La integración del problema no perturbado se da en variables de Andoyer, las cuales se emplearán para llevar a cabo la reducción completa del problema. Por otra parte, este Capítulo 2 recoge en detalle la idea de llevar a cabo la integración del problema realizando una regularización consistente en un cambio de la variable independiente (el tiempo). En ambas integraciones se ofrecen detalles sobre la manipulación de las funciones elípticas involucradas. El capítulo finaliza con una sección donde se recoge el estudio de las fases del problema. El Capítulo 3 muestra cómo se lleva a cabo la reducción completa del problema resolviendo la ecuación de Hamilton-Jacobi a la Poincaré. Dado que existen distintas variables intermedias que permiten resolver las cuadraturas existentes, utilizamos una diferente a la propuesta por Sadov para deducir un conjunto alternativo de variables de ángulo-acción cuya bondad dependerá del tipo de perturbación que se esté manejando. Finalmente se presentan las ecuaciones de transformación expresadas en términos de funciones Theta de Jacobi. En el Capítulo 4 se realiza una aproximación en forma cerrada de primer orden del problema perturbado donde se muestra, no sólo el modo en que se manejan las funciones elípticas bajo el método de perturbación, sino también las diferencias existentes cuando éstas se analizan empleando los dos conjuntos diferentes de variables estudiados en esta Memoria. A su vez, el Capítulo 5 emula al Capítulo 4 con el objetivo de comparar las soluciones analíticas y numéricas dadas por un desarrollo en serie de la función perturbación. En este sentido, dado que anteriores trabajos han llevado a cabo desarrollos en serie de Fourier, en esta Memoria exploramos la posibilidad de llevar a cabo series de Taylor de funciones elípticas previamente expresadas en términos de funciones Theta de Jacobi. Los resultados muestran que la aplicación de ambos conjuntos de variables a la perturbación tratada difiere esencialmente en el hecho de que la derivada de la función Zeta de Jacobi con respecto al módulo elíptico, presente en las ecuaciones de transformación, no es periódica en variables Ferrer-Lara, lo cual produce un efecto rizado creciente en la evolución temporal de las variables del problema que no se observa en las variables de ángulo-acción. / This Memoir focuses on the attitude dynamics of a triaxial rigid body (integrable part) under gravity-gradient torque (perturbation), which is considered one of the basic nonintegrable models to analyze the attitude propagation of artificial satellites, although this approximation is also valid to describe the motion of natural bodies. A common way to tackle such approximations is to accomplish the complete reduction of the integrable part considered as the zero order. Different sets of variables have been proposed in the literature in order to address such analytical approximation, most of them starting from Andoyer variables. Thus, the main goal of this work is to show the behaviour of two different sets of these variables which may present a number of properties which can make them more or less suitable for the study of a perturbation. The first set, well known as action-angle variables, was introduced by Sadov and we will compare it with a new set recently proposed by Ferrer and Lara. Apart from the Introduction, in Chapter 2 the free rigid body dynamics is revisited. The integration of the torque-free motion is given in Andoyer variables, which will be used to accomplish the complete reduction of the torque-free motion. Some details on the manipulation of the involved elliptic functions are also given. Furthermore, a different way to address the integration of the free rigid body problem is carried out by a regularization of time. Finally, due to a renewal of interest in geometric aspects of the rigid body dynamics, a study of the phases of the problem is also included. Chapter 3 shows how the complete reduction is carried out by solving the Hamilton-Jacobi-Poincaé equation. Moreover, an alternative intermediary variable is used to build up a new set of action-angle variables which may be utilized for the study of a number of perturbations.\par Next, a first-order closed form solution of the perturbed problem is presented in Chapter 4 where it is shown not only the way to handle the elliptic functions under a perturbation method but also the existing differences when analyzing them using the two different sets of variables given by Sadov and Ferrer-Lara. In turn, Chapter 5 emulates Chapter 4 in order to compare the analytical and numerical solutions given by a series expansion of the perturbing function. In this sense, since other previous works have carried out expansions as Fourier Series, in this work we explore the possibility of developing Taylor expansions of the elliptic functions previously expressed in terms of Jacobi Theta functions. The results show that the application of both sets of variables to the perturbing function differs in the fact that the partial derivative of the Jacobi Zeta function with respect to the elliptic modulus, which is present in the transformation equations, is not periodic in Ferrer-Lara variables. This fact produces an increasing curly effect along the evolution of the variables of the problem which is not observed when action-angle variables are used.

The aim of this thesis is the study of the total and spectral solar irradiance variability induced by the presence of small magnetic elements that emerge into the solar photosphere. It is important to study changes in the solar energy output because they reflect the existence of several physical processes in the solar interior, their interpretation helps to understand the solar cycle and because of their influence on the terrestrial climate. The work presented in this thesis is exclusively based on data provided by the SOHO spacecraft, specifically by the VIRGO and MDI instruments.Irradiance variations produced on the solar rotation time-scale are due to the passage of active regions across the solar disk. However, the origin of variations on the solar cycle time-scale is under debate. One of the most controversial aspects is the long-term contribution of the small magnetic elements conforming faculae and the network. Their identification and contrast measurement is difficult and, consequently, their contrast center-to-limb variation (CLV) remains poorly defined in spite of the fact that its knowledge is essential to determine their contribution to variability.In this work we have studied the contribution of small photospheric magnetic elements (those with a positive contribution to variability), both on short, i.e. solar rotation, and long, i.e. solar cycle, time-scales. By analyzing the evolution of an isolated active region (NOAA AR 7978) during several Carrington rotations, we have evaluated the variations in luminosity induced by this facular region during the 1996 minimum of activity. Simultaneous photometric and magnetic data from the MDI instrument have been combined in order to study the contrast of small scale magnetic features and its dependence both on position and magnetic field, as well as its evolution along the rising phase of solar cycle 23.The study of the solar variability has required reduction and analysis of the employed MDI and VIRGO data. These data had to be converted from level 0 (raw data) to level 2 (scientifically useful data), since solar variations were hidden by instrumental effects. We developed original algorithms to correct instrument-related effects from the data, such as filter degradation and the variation of the limb darkening with distance. The determination of the contrast of magnetic features also required the development of an algorithm in order to identify the surface distribution of those small features present over the solar disk.By analyzing irradiance variations induced by the small magnetic features that emerge into the solar photosphere we have concluded that:· active region faculae and the magnetic network present very different contrast CLV's, therefore, their contributions to irradiance variability are distinct; as a consequence, both contributions need to be taken into account separately when reconstructing variations of the solar irradiance.· the functional dependence on position and magnetic signal of the facular contrast is time independent; this suggests that the physical properties of the underlying flux tubes do not vary with time.· network elements are bright over the whole solar disk and have proved to be the dominant population along the solar cycle; this implies that their contribution to long-term irradiance variations is significant and needs to be taken into account.

This thesis is focused on the implication of de dynamics of clusters on the HI content of galaxies. Target of this study has been the Virgo cluster region.We have first inferred the three-dimensional galaxy distribution of the Virgo cluster using Tully-Fisher distance estimates from eight published datasets. The spiral distribution is found to be very elongated along the line of sight. This filamentary structure is also reflected by the HI-deficient objects. We found a central enhancement in the HI distribution, arising from galaxies that belong to the Virgo cluster proper. However, significant gas deficiencies were also detected outside the main body of the cluster in a probable group of galaxies at distances circa 25 to 30 Mpc, as well as in various foreground galaxies. The presence on the Virgo cluster outskirts of spiral galaxies with gas deficiencies as strong as those of the inner galaxies likely stripped by the intracluster medium (ICM) has led us to explore the possibility that some of these peripheral objects were not newcomers. A dynamical model for the collapse and rebound of spherical shells was developed. According to our analysis, it is not unfeasible that galaxies far from the cluster went through its core a few Gyr ago. In order to further investigate this possibility, we have estimated the maximum radius out to which galaxies can bounce out of a virialized system, using both cosmological N-body simulations and analytical arguments. We have shown that material that falls into a cosmological structure cannot bounce out beyond circa2.5 virial radii. This would explain the presence of stripped galaxies up to circa2 virial radii, which is more than twice the extension of the ICM revealed by the X-ray maps. After estimating the virial radius and mass of the Virgo cluster from X-ray observations, the peripheral HI-deficient galaxies appear to lie significantly farther away from the cluster centre. Therefore, it does not seen plausible that these galaxies have crossed the cluster core if their distance estimates are accurate. The velocity field drawn by the Virgo cluster has been further studied by comparing the positions of both spiral and elliptical galaxies in velocity-distance plots with simulated diagrams obtained from cosmological N-body simulations. We have found that circa20% relative Tully-Fisher distance error is consistent with the great majority of the galaxies. We have shown, moreover, that distance errors may lead to an incorrect fitting of infall models that can generate significant errors in the distance and, specially, in the mass estimates of clusters. In addition, we have investigated in detail the feasibility of four possibilities for the origin of the dearth of neutral gas in the outlying HI-deficient Virgo spirals: 1) large relative distance errors so these galaxies have passed through its core and seen their gas removed by ram pressure stripping; 2) tidal interactions with other galaxies; 3) recent mergers with smaller galaxies; and 4) an erroneous determination of their gas content (e.g. S0/a's misclassified as Sa's).Finally, the cosmological N-body simulations of dark matter halos have also been used to study the effects of non-sphericity, substructure and streaming motions on the structure and internal kinematics of clusters recovered from the Jeans analysis. We found that the virial mass, concentration parameter and velocity anisotropy of the halos can be reproduced satisfactory independently of the halo shape, although the viral mass tends to be underestimated, the concentration parameter overestimated, while the recovered anisotropy is typically more tangential that the true one. The mass, concentration and velocity anisotropy of halos are recovered with better precision when their mean velocity profiles are near zero.

EN CASTELLANO:En este trabajo se ha realizado un estudio de la estructura espacial y cinemática de la componente estelar joven de la Galaxia en el entorno solar en tres escalas diferentes, que han permitido estudiar la estructura espiral galáctica, el Cinturón de Gould y la componente estelar joven en el entorno solar más cercano.Se han construido tres muestras de estrellas con datos procedentes del catálogo Hipparcos. La primera de ellas está formada por estrellas de los tipos espectrales O y B, y contiene información astrométrica, fotométrica, velocidades radiales y diversos parámetros físicos de las estrellas, incluyendo la edad. La segunda muestra contiene todas las estrellas variables cefeidas del catálogo Hipparcos, con información astrométrica, distancias calculadas a partir de dos calibraciones periodo-luminosidad y velocidades radiales. Finalmente, se ha recopilado toda la información existente hasta la fecha en la bibliografía referente a las asociaciones locales jóvenes que han sido descubiertas en el entorno solar más cercano durante los últimos años.A partir de las muestras de estrellas que se han construido se ha estudiado, en primer lugar, la estructura espiral de la Galaxia. Los resultados más destacados en este apartado son que el Sol se encuentra situado en la parte externa del brazo espiral más cercano y fuera del círculo de corrotación. Ambos resultados pueden tener una gran importancia en la historia de la formación estelar reciente en el entorno solar. También se ha obtenido un valor negativo (y significativo) para la divergencia del campo de velocidades (término K). Los resultados obtenidos han sido validados a través de unas simulaciones, que han permitido obtener una estimación externa de los errores y una evaluación de los sesgos que afectan a los diferentes parámetros obtenidos.A una escala a 1 kpc de distancia heliocéntrica, la estructura dominante en el entorno solar es el denominado Cinturón de Gould, que contiene la mayor parte de las estrellas jóvenes y nubes de polvo y gas de esta región. En nuestro trabajo hemos obtenido los parámetros de orientación del Cinturón y se ha estudiado su peculiar cinemática, tras la realización de unas simulaciones con los mismos objetivos que las mencionadas anteriormente. Se ha obtenido que las estrellas del complejo de Scorpio-Centaurus (Sco-Cen) presentan una cinemática que no se ajusta a la prevista por los diversos modelos que intentan explicar la evolución cinemática del Cinturón. También se ha obtenido que el movimiento de expansión de esta estructura no parece ser un efecto global, ya que se restringe a los primeros ~250 pc de distancia heliocéntrica.Finalmente, el estudio de la integración de las órbitas hacia atrás en el tiempo de las asociaciones locales jóvenes y de los miembros del complejo de Sco-Cen nos ha permitido inferir que las primeras no se formaron en el interior de este complejo, sino en pequeñas nubes moleculares situadas en sus alrededores, y que previamente habían sido expulsadas. Por otro lado, se ha visto que alguna supernova de estas asociaciones locales jóvenes fue probablemente la responsable del recalentamiento de la Burbuja Local hace unos pocos millones de años. Finalmente, teniendo en cuenta los resultados obtenidos en diversos apartados de este trabajo, se ha propuesto un escenario para la formación estelar reciente en el entorno solar a partir del impacto de una gran nube molecular con el brazo espiral interno, que dio lugar, en diferentes fases, al complejo de Sco-Cen y a las asociaciones locales jóvenes. / Title: "On the spatial and kinematic structure of the young stellar component in the solar neighbourhood" Text: The spatial and kinematic structure of the young stellar component in the solar neighbourhood has been analysed on three different scales, which have allowed the study of the galactic spiral structure, the Gould Belt, and the young stellar component in the solar neighbourhood.Three stellar samples have been constructed with data coming from the Hipparcos catalogue. The first one is composed of O- and B-type stars, and contains not only the astrometric data from Hipparcos but also other relevant astrophysical data. The second sample contains all the Hipparcos Cepheid stars with astrometry, distances and radial velocities. Finally, the third sample compiles all the information published in the literature on the young local associations that have been discovered in the solar neighbourhood over the last years.From these stellar samples we have studied, firstly, the galactic spiral structure. The most important results in this section are the location of the Sun at the external side of the nearest spiral arm and outside the corotation circle. We have also obtained a negative (and significant) value for the divergence of the velocity field (K term). Our results have been checked through a set of simulations that have made possible an external estimation of the errors and an evaluation of the biases affecting the obtained parameters. The most important structure present in the solar neighbourhood at a 1-kpc scale is the so-called Gould Belt. We have derived the orientation parameters of the Gould Belt and studied its peculiar kinematics, after carrying out a set of simulations. We have found that the stars belonging to the Scorpio-Centaurus (Sco-Cen) complex present a kinematic behaviour that is not well explained in the frame of the several models proposed for the kinematic evolution of the Belt. We have also found that the expansion motion of this structure does not seem to be a large-scale effect, since it is only observed in the first ~250 pc from the Sun.The integration of the orbits back in time for the young local associations and the members of the Sco-Cen complex has led to the conclusion that the former were not born inside this complex, but in previously-ejected small molecular clouds. Also, we presume that some supernovae from these associations could be responsible for the heating of the Local Bubble a few million years ago. Finally, the scenario for the recent star formation in the solar neighbourhood proposed is the impact of a large molecular cloud with the internal spiral arm, which produced, on different phases, the birth of the Sco-Cen complex and the young local associations.

We have developed a Monte Carlo model to simulate the transport of solar near-relativistic (NR; 30-300 keV) electrons along the interplanetary magnetic field (IMF), including adiabatic focusing, pitch-angle dependent scattering, and solar wind effects. By taking into account the angular response of the LEFS60 telescope of the EPAM experiment on board the "Advanced Composition Explorer" spacecraft, we have been able to transform simulated pitch-angle distributions into sectored intensities measured by the telescope. We have developed an algorithm that allows us, for the first time, to infer the best-fit transport conditions and the underlying solar injection profile of NR electrons from the deconvolution of the effects of interplanetary transport on observational sectored intensities. We have studied seven NR electron events observed by the LEFS60 telescope between 1998 and 2004 with the aim of estimating the roles that solar flares and CME-driven shocks play in the acceleration and injection of NR electrons, as well as the conditions of the electron transport along the IMF.In this set of seven NR electron events, we have identified two types of injection episodes in the derived injection profiles: short (< 20 min) and time-extended (> 1 h). The injection profile of three events shows both components; an initial injection episode of short duration, followed by a second much longer lasting episode; two events only show a time-extended injection episode; while the others show an injection profile composed by several short injection episodes. We have found that the timing of the prompt short injection episodes agrees with the timing of the hard X-rays and radio type III bursts. On the other hand, time-extended injection episodes seem to be related to intermittent radio emissions at the height of the CME leading edge or below, and sometimes to type II radio bursts. Thus, we conclude that short injection episodes are preferentially associated with the injection of flare-accelerated particles, while longer lasting episodes are provided by CME-driven shocks or post-eruptive reconnection phenomena at coronal heights lower than those of the CME-driven shocks.From the fit of the events, we have derived the transport conditions of the electrons. We have found that the electron propagation was almost scatter-free (the radial mean free path of the electrons was ~0.9 AU) during two of the events, whereas during five of the events the propagation occurred under strong scattering conditions (the radial mean free path of the electrons was smaller than 0.2 AU). Those events showing a long radial mean free path reached the maximum intensity shortly (< 15 min) after the onset of the event; whereas those events showing a small radial mean free path reached the maximum intensity more than one hour after the onset. The overall conclusion from this study is that there is a continuous spectrum of scenarios that allow for either flare or CME-driven shock NR electron injection, or for both, and that this can occur both under strong scattering and under almost "scatter-free" propagation conditions.SUBJECT HEADINGS: Sun: coronal mass ejections (CMEs) Sun: flares Sun: particle emission / Hemos desarrollado un modelo Monte Carlo para simular el transporte de electrones solares casi-relativistas (30-300 keV) en el medio interplanetario que tiene en cuenta los efectos de la focalización adiabática, la dispersión en ángulo de batida y los efectos del viento solar. Teniendo en cuenta la respuesta angular del telescopio, hemos desarrollado un método que permite transformar las distribuciones angulares de partículas simuladas en intensidades sectoritzadas observadas por el telescopio LEFS60 a bordo de la sonda interplanetaria ACE. Esto nos ha permitido desarrollar un algoritmo que permite, por primera vez, deconvolucionar los efectos del transporte interplanetario en las intensidades sectoritzadas observadas, con el objetivo de determinar el perfil de inyección solar de electrones y las características del transporte. Hemos aplicado el modelo al estudio de siete sucesos de electrones observados por la sonda ACE. Los resultados ponen de manifiesto que la inyección de electrones casi-relativistas está asociada con procesos fulgurativos, choques conducidos por eyecciones de masa coronal o con ambos, y que el transporte se puede producir tanto en condiciones muy dispersivas como en condiciones muy poco dispersivas. / RESUM:Hem desenvolupat un model Monte Carlo per simular el transport d'electrons solars quasi-relativistes (30-300 keV) en el medi interplanetari que té en compte els efectes de la focalització adiabàtica, la dispersió en angle de batuda i els efectes del vent solar. Hem desenvolupat un mètode per transformar les distribucions angulars de partícules simulades en intensitats sectoritzades observades pel telescopi LEFS60 a bord de la sonda interplanetària ACE, tenint en compte la resposta angular del telescopi. Això ens ha permès desenvolupar un algoritme que permet, per primera vegada, deconvolucionar els efectes del transport interplanetari en les intensitats sectoritzades observades, amb l'objectiu de determinar el perfil d'injecció solar d'electrons observats per la sonda ACE. Els resultats posen de manifest que la injecció d'electrons quasi-relativistes pot produir-se en processos fulguratius, en xocs conduïts per ejeccions de massa coronal o en ambdós, i que el transport es pot produir tant en condicions molt dispersives com en condicions molt poc dispersives.