Gene transfer represents an important advance in the treatment of both genetic and acquired diseases. Topical gene therapy involves administration of the genetic material onto the surface of skin and mucosal membranes. Cationic gemini surfactants (m-s-m, where m represents the carbon atoms in the alkyl tail and s represents the carbon atoms in the spacer) are a novel category of delivery agents with especially high potential for polynucleotides. This is due to their structural versatility, ability to bind and condense DNA, and relatively low toxicity. <p>The objectives were to design, construct and characterize a cationic, non-viral gemini surfactant-based delivery system for an IFN-ã coding plasmid suitable for cutaneous gene therapy and to evaluate this novel therapeutic approach in a Tsk (tight-skin scleroderma) mouse model to determine its clinical feasibility. <p>The delivery systems were characterized by microscopy, dynamic light scattering (DLS), circular dichroism (CD) and small angle X-ray scattering (SAXS). <i>In vitro</i> gene expression was evaluated in PAM 212 keratinocyte culture. The extent of topical delivery of the plasmid using nanoparticle and nanoemulsion formulations was evaluated by measuring IFN-ã levels in CD1, IFN-ã-deficient and Tsk mice. The effect of transgene expression on collagen synthesis was evaluated in Tsk animals by real-time PCR.<p>The <i>in vitro</i> plasmidgeminilipid (PGL) system showed heterogeneous particle size (100-200 nm small particles and 300-600 nm aggregates). Electrostatic interactions between the DNA and PGL systems shifted the negative æ-potential of the DNA (-47 mV) to positive values (30-50 mV). At the same time, condensation of the DNA, and formation of Ø DNA was indicated by the increase of the overall negative signal in the CD spectra, due to the flattening of the 290 nm peak and shift of the 260 nm peak into the negative region in a structure-dependent manner. Lipid organization of the DNADOPE system, in the absence of gemini surfactants, shows hexagonal structure, while addition of gemini surfactant at +/- charge ratio of 10 caused lamellar phase organization. For short spacers (n=3-6), additional Pn3m cubic phase also appear to be present. <p><i> In vitro</i> transfection efficiency in the 12-n-12 series was found to be dependent on the length of the spacer between the two positively charged head groups, with the n=3 spacer showing the highest activity. The PGL systems with 12-3-12 and 12-4-12 led to significantly higher transgene expression compared to the other surfactants of the series. The transfection efficiency significantly correlated with the surface area occupied by one molecule (a). The effect of the tail length influenced the transfection efficiency, with longer tails being associated with higher protein expression. The highest <i>in vitro</i> transfection efficiency was recorded with the 18:1-3-18:1 surfactant (1.4±0.3 ng/5x10E4 cells). <p><i>In vivo</i>, high levels of IFN-ã expression were detected in the skin of animals treated with both nanoparticle (359±239 pg/cm2) and nanoemulsion (607±411 pg/cm2) formulations compared to topical naked DNA (136±125 pg/cm2). IFN-ã levels in the skin of animals injected with 5 ìg DNA were 256±130 pg/cm2. IFN-ã levels in the lymph nodes were higher for the nanoparticle formulation (433±456 pg/animal) compared to nanoemulsion (131±136 pg/animal) suggesting different delivery pathway of the two formulations.<p>IFN-ã expression was at high levels in the skin of Tsk mice after 4-day and 20-day treatments (472±171 and 345±276 pg/cm2). Both 4-day and 20-day treatments reduced the procollagen type I á1 mRNA levels for the topical treatment (64 and 70% reduction) and intradermal injection (58 and 72% reduction). Intercellular adhesion molecule-1 (ICAM-1) was upregulated by 50% in both topically treated and injected animals after 20-day treatment. <p>Here, it has been demonstrated that cationic gemini surfactant-based delivery systems are able to transfect epidermal cells <i>in vivo</i>, and the transgene IFN-ã expression is sufficient to cause significant reduction of collagen in an animal model of scleroderma. It has been shown for the first time that topical gene therapy is a feasible approach for the modulation of excessive collagen synthesis in scleroderma-affected skin.

Gene transfer represents an important advance in the treatment of both genetic and acquired diseases. Topical gene therapy involves administration of the genetic material onto the surface of skin and mucosal membranes. Cationic gemini surfactants (m-s-m, where m represents the carbon atoms in the alkyl tail and s represents the carbon atoms in the spacer) are a novel category of delivery agents with especially high potential for polynucleotides. This is due to their structural versatility, ability to bind and condense DNA, and relatively low toxicity. <p>The objectives were to design, construct and characterize a cationic, non-viral gemini surfactant-based delivery system for an IFN-ã coding plasmid suitable for cutaneous gene therapy and to evaluate this novel therapeutic approach in a Tsk (tight-skin scleroderma) mouse model to determine its clinical feasibility. <p>The delivery systems were characterized by microscopy, dynamic light scattering (DLS), circular dichroism (CD) and small angle X-ray scattering (SAXS). <i>In vitro</i> gene expression was evaluated in PAM 212 keratinocyte culture. The extent of topical delivery of the plasmid using nanoparticle and nanoemulsion formulations was evaluated by measuring IFN-ã levels in CD1, IFN-ã-deficient and Tsk mice. The effect of transgene expression on collagen synthesis was evaluated in Tsk animals by real-time PCR.<p>The <i>in vitro</i> plasmidgeminilipid (PGL) system showed heterogeneous particle size (100-200 nm small particles and 300-600 nm aggregates). Electrostatic interactions between the DNA and PGL systems shifted the negative æ-potential of the DNA (-47 mV) to positive values (30-50 mV). At the same time, condensation of the DNA, and formation of Ø DNA was indicated by the increase of the overall negative signal in the CD spectra, due to the flattening of the 290 nm peak and shift of the 260 nm peak into the negative region in a structure-dependent manner. Lipid organization of the DNADOPE system, in the absence of gemini surfactants, shows hexagonal structure, while addition of gemini surfactant at +/- charge ratio of 10 caused lamellar phase organization. For short spacers (n=3-6), additional Pn3m cubic phase also appear to be present. <p><i> In vitro</i> transfection efficiency in the 12-n-12 series was found to be dependent on the length of the spacer between the two positively charged head groups, with the n=3 spacer showing the highest activity. The PGL systems with 12-3-12 and 12-4-12 led to significantly higher transgene expression compared to the other surfactants of the series. The transfection efficiency significantly correlated with the surface area occupied by one molecule (a). The effect of the tail length influenced the transfection efficiency, with longer tails being associated with higher protein expression. The highest <i>in vitro</i> transfection efficiency was recorded with the 18:1-3-18:1 surfactant (1.4±0.3 ng/5x10E4 cells). <p><i>In vivo</i>, high levels of IFN-ã expression were detected in the skin of animals treated with both nanoparticle (359±239 pg/cm2) and nanoemulsion (607±411 pg/cm2) formulations compared to topical naked DNA (136±125 pg/cm2). IFN-ã levels in the skin of animals injected with 5 ìg DNA were 256±130 pg/cm2. IFN-ã levels in the lymph nodes were higher for the nanoparticle formulation (433±456 pg/animal) compared to nanoemulsion (131±136 pg/animal) suggesting different delivery pathway of the two formulations.<p>IFN-ã expression was at high levels in the skin of Tsk mice after 4-day and 20-day treatments (472±171 and 345±276 pg/cm2). Both 4-day and 20-day treatments reduced the procollagen type I á1 mRNA levels for the topical treatment (64 and 70% reduction) and intradermal injection (58 and 72% reduction). Intercellular adhesion molecule-1 (ICAM-1) was upregulated by 50% in both topically treated and injected animals after 20-day treatment. <p>Here, it has been demonstrated that cationic gemini surfactant-based delivery systems are able to transfect epidermal cells <i>in vivo</i>, and the transgene IFN-ã expression is sufficient to cause significant reduction of collagen in an animal model of scleroderma. It has been shown for the first time that topical gene therapy is a feasible approach for the modulation of excessive collagen synthesis in scleroderma-affected skin.

The main focus of this thesis is ab initio modeling of core level spectra with a high-level quantum chemical description both of the chemical interactions and of local atomic multiplet effects. In particular, the combination of calculations and synchrotron-based core-level spectroscopy aims at understanding the local structure of the electronic valence in transition metal complexes, and the details of the solvation mechanisms of electrolyte solutions, systems relevant for the dye-sensitized solar cell. Configurational sampling in solution is included through molecular dynamics simulations. Transition metal complexes are studied with x-ray absorption (XA) and resonant inelastic scattering (RIXS) spectroscopy, characterizing excited states with atomic site specificity. The theoretical multiconfigurational method, applying an active-space partitioning of the molecular orbitals (RASSCF), is used to assign the transitions observed in spectra of hydrated Ni2+ explicitly, including charge transfer and multiplet effects. Furthermore, the solvent-induced binding energy properties of the I- and I3- anions in aqueous, ethanol, and acetonitrile solutions are analyzed using photoelectron spectroscopy (XPS). The study shows that specific ion–solvent interactions are important for the core-level binding energy shifts in solution. The special case with I3- dissolved in water, where hydrogen bonding causes breaking of the molecular symmetry, is treated and proves that the geometry changes influence the photoelectron spectrum of aqueous I3- directly.

In the present work, we have undertaken a structural study of PS-b-PEO single crystals to elucidate the influence of the state of the PS block on crystallization from dilute solution and on subsequent thermal annealing at elevated temperature. It is noteworthy that the interest in these systems has been recently renewed in the perspective of using them as a model of grafted amorphous brushes with variable grafting density. Indeed, during crystallization of PEO, the amorphous block, i.e. PS, is rejected from the crystal accumulating on its basal surfaces. Since the crystal thickness formed during isothermal crystallization is a sharply selected value, the grafting density of the resulting PS brush is also well defined. Therefore by varying the crystal thickness one can obtain the PS brushes with grafting density varying in a broad range.In our study, a combination of reciprocal and direct-space techniques such as SAXS/WAXS and AFM was employed. While AFM experiments were performed on isolated single crystals, the SAXS investigation was carried out on oriented mats of single crystals slowly sedimented from the "mother" solution. In this case, the one-dimensional two-phase system model was used for the data interpretation where the thickness of the amorphous (La) and crystalline (Lc) layers are conventionally determined following the correlation fonction and interface distribution fonction approaches.

Controlling the micro-structure of organic materials is crucial for a variety of practical applications such as photonics, biomedicine or the rapidly growing field of organic electronics. Recent studies have shown a possibility of tailoring the polymer structure on the nanoscale using supramolecular self-assembly under spatial confinement. Despite extensive studies already performed in this field, many questions remain open. In particular, it will be important to understand how different structure formation processes such as crystallization, LC-phase formation, microphase separation, and others occur under confinement. In the present work, we address the effect of 1D- and 2D-confinement on the structure formation for a variety of systems including segmented poly(ether-ester-amide) (PEEA) copolymers, main-chain liquid-crystalline (LC) polymers belonging to the family of poly(di-n-alkylsiloxane)s and liquid-crystalline/semicrystalline block copolymers formed through complexation of poly (2-vinylpyridine-b-ethylene oxide) (P2VP-PEO) with a wedge-shaped ligand, 4'-(3'',4'',5''-tris(octyloxy) benzamido) propanoic acid. In order to reveal the morphological diversity of the studied systems under confinement, the work was carried out on bulk materials and on thin films employing a battery of experimental methods. The main experimental techniques operational in direct and reciprocal space applied in my work are described in chapter 2. [...]

Ferritic superalloys strengthened by coherent ordered NiAl B2-type precipitates are promising candidates for ultra-supercritical steam-turbine applications, due to their superior resistance to creep, coarsening, oxidation, and steam corrosion as compared to Cr ferritic steels at high temperatures. Combined computational and experimental tools have been employed to investigate the interrelationships among the composition, microstructure, and mechanical behavior, and provide insight into deformation micromechanisms at elevated temperatures. Self and impurity diffusivities in a body-centered-cubic (bcc) iron are calculated using first-principles methods. Calculated self and impurity diffusivities compare favorably with experimental measurements in both ferromagnetic and paramagnetic states of bcc Fe. The calculated impurity diffusivities of W and Mo are larger than the self diffusivity of Fe, mainly owing to the lower activation energies. The microstructural attributes of NiAl-type B2 precipitates are investigated in several designed ferritic superalloys. Ultra-small-angle X-ray scattering in conjunction with transmission electron microscopy is employed to quantify the average size, size distribution, inter-particle spacing, and volume fraction of the primary precipitates. It is observed that as the Al amount increases from 4 to 10 mass%, there is a decrease in the average inter-particle spacing and average particle diameter. An alloy with 6.5 weight percent Al exhibits the optimal creep resistance and an associated maximum Orowan stress at 973 K. The dislocations-particle interaction mode during the secondary creep regime is identified as a combination of Orowan looping and dislocation climb. In-situ neutron diffraction experiments during tensile and creep deformations reveal the intergranular and interphase load-sharing mechanisms during plastic deformation at elevated temperatures. The change of deformation mechanisms from dislocation slip below 773 K to power-law creep above 873 K is well captured by the evolution of the different lattice strains. High-temperature deformation above 873 K is possibly assisted by the relaxation processes, e.g., grain-boundary sliding and/or diffusional flow along grain boundaries and matrixparticle interfaces. The evolution of lattice strains during high-temperature deformation is further verified by crystal-plasticity finite-element simulations. The significant findings in the present work provide the crucial baseline information for further alloy optimization and improvement in high-temperature creep resistance of ferritic superalloys.

Ce rapport de thèse présente une étude de la dynamique transitoire de molécules de taille réduite en solution induite par photoexcitation. Celle-ci est réalisée au travers d'une expérience de mesure de diffusion de rayons X aux grands angles (TR-WAXS). La partie principale de ce rapport s'articule autour de la dertermination des structures transitoires avec l'utilisation de plusieurs schémas structurelles d'optimisation. Certains résultats obtenus par TR-WAXS sont complétés avec ceux obtenus par spectroscopie optique résolue dans le temps (TOAS) ainsi que par spectroscopie d'émission de rayons X de ces molécules (TR-XES) permettant une plus complète description de ces systèmes.Ce travail est composé de 4 differents projets lesquelles peuvent être regroupé en 2 groupes selon le type de réaction declenchées par photoexcitation: dissociation et transfert d'électron. Le premier groupe comprends la molécule triatomique de mercure, halogénure métallique et le triiodide où nous étudions la dynamique de recombinaison des photofragments libres. Cette partie démontre la possibilité de développer de nouvelles connaissances concernant la dynamique de ces modèles, comme par exemple, la découverte de la recombinaison par canaux ou bien par l'apparition de réactions intermédiaires en moins de 100 ps, correspondant à la longueur de l'impulsion de rayons X générée par le synchrotron, mise en évidence en utilisant la technique de découpage temporelle. Le deuxième groupe de systèmes est composé de complexes de métaux de transition, très pertinents pour les applications liées à la récolte de lumière, [Fe(NHC)2]2+ et Ru=Co, où le spin et les structures dynamiques sont étudiées. Ces projets prolongent de précedents travaux à une famille de systèmes plus complexes avec un numéro atomique bas (première colonne de transition metallique) et fait la lumière sur de nouveaux composés en photochimie. / This thesis investigates photoinduced transient dynamics of small molecules in solution with the use of time-resolved wide angle x-ray scattering (TR-WAXS). The core of the thesis is the precise determination of transient structures with the use of various structural optimization schemes. Some of the TR-WAXS results are supplemented with transient absorption optical spectroscopy (TOAS) and time-resolved x-ray emission spectroscopy (TR-XES) measurements allowing for a more complete description of the systems.par The work includes four different projects which can be grouped into two classes according to the type of reaction appearing upon photoexcitation: dissociation and electron transfer. The first class includes the simple triatomic molecules mercury halides and triiodide where we study the recombination dynamics of the free photofragments. This part of the thesis demonstrates the possibility to gain new knowledge about the dynamics of these model systems such as new recombination channels and reaction intermediates appearing in less than 100 ps, the xray pulse length from the synchrotron, by the use of time-slicing technique. The second class of systems includes transition metal complexes that are highly relevant for light harvesting applications, [Fe(NHC)2]2+ and Ru=Co, where the spin and structural dynamics are investigated. These projects extend previous work to a family of more complex systems constituted of relatively low-Z atoms (first row transition metals) and bring new insights into the photochemistry of the compounds.

Les composés intermétalliques à base de cérium présentent à basse température des propriétés magnétiques, électroniques et thermodynamiques tout à fait fascinantes. Deux interactions majeures entre la bande de conduction et les électrons localisés de la couche 4f entrent en compétition et régissent la physique de ces composés: l'effet Kondo tend à écranter les moments magnétiques 4f alors que les interactions RKKY favorisent plutôt des moments localisés et ordonnés. Un diagramme de phase complexe naît de cette compétition et le comprendre exige une caractérisation complète des niveaux 4f. La dégénérescence des multiplets liés au couplage spin-orbit est levée par les effets de champ cristallin, et les écarts entre les niveaux d'énergie qui en résultent ainsi que les symétries des états fondamentaux et excités doivent être déterminés expérimentalement. Les effets de champ cristallin dans les lanthanides peuvent être sondés par diverses techniques expérimentales dont la susceptibilité magnétique, la diffusion inélastique de neutrons, la spectroscopie par absorption de rayons X ou de photoémission. Cependant, chacune de ces techniques présente des limitations propres qui empêchent une caractérisation précise de ces effets. Nous présentons dans cette thèse les capacités de la technique de diffusion résonante inélastique des rayons X mous (soft-RIXS) à sonder les effets de champ cristallin dans les composés à base de cérium. Les dernières avancées en instrumentation ont permis de repousser les limites de la résolution en énergie jusqu'à 30 meV au seuil M5 du Cérium, suffisant pour séparer les transitions électroniques des plus bas des niveaux 4f. Le composé CeRh2Si2 a été étudié à titre d'exemple. Les énergies des excitations de couplage spin-orbit et de champ cristallin observées expérimentalement fournissent une mesure directe des écarts des niveaux 4f, tandis que la comparaison entre les spectres expérimentaux et des calculs basés sur le multiplet complet dans l'approximation à un ion permet d'identifier sans ambiguïté la symétrie des états de plus basse énergie du champ cristallin. L'orientation des fonctions d'ondes dans les plans ab du cristal peut aussi être déterminée de manière très simple en mesurant la polarisation des photons diffusés de manière inélastique. L'interaction avec les états itinérants peut introduire une variation de l'énergie des niveaux 4f en fonction du vecteur de diffusion q, qui se traduit par des signatures observables dans les spectres de diffusion inélastique résonante de rayons X. Un modèle simple est proposé pour expliquer la variation observée en fonction de q, mais des calculs théoriques plus poussés apparaissent nécessaires pour rendre compte de manière plus exacte de ces variations. L'étude des composés CeCu2Si2 et CeCo2Ge2 montre que la diffusion inélastique des rayons X peut sonder des effets de champ cristallin bien plus faibles ou bien plus importants que ceux observés dans CeRh2Si2. Dans le futur, une meilleure résolution en énergie et des modélisations plus poussées devraient encore améliorer la précision des études des effets de champ cristallin dans les composés de Cérium et autres lanthanides par diffusion inélastique de rayons X. / Cerium intermetallic compounds exhibit fascinating magnetic, electronic and thermodynamic properties at low temperatures. Their physics is governed by two competing interactions between the conduction band and localised 4f electrons: the Kondo effect tends to screen the 4f magnetic moments while RKKY exchange favours ordered local moments. From this competition, a complex phase diagram arises and its understanding requires a full characterisation the 4f levels. The crystal electric field (CEF) effects lift the degeneracy of the spin-orbit multiplets and the resulting energy splittings (tens of meV) as well as the symmetry of the ground and excited states must be determined experimentally. CEF effects in the lanthanides can be studied with a number of experimental probes including magnetic susceptibility, inelastic neutron scattering, X-ray absorption spectroscopy or photoemission spectroscopy. However, each of these techniques has limitations which can prevent an accurate characterisation. This thesis discusses the potential of Resonant Inelastic soft X-ray Scattering (soft-RIXS) to become a new probe of the CEF in cerium compounds. The latest advances in instrumentation have pushed the energy resolution in soft RIXS down to 30 meV at the Ce M5 edge, good enough to resolve the electronic transitions between the lowest lying 4f levels. This is demonstrated using the example of CeRh2Si2 spectra. The observed energies of the spin-orbit and CEF excitations provide a direct measurement of the 4f splittings and the comparison of the experimental spectra with full-multiplet single-ion calculations unambiguously identifies the symmetry of the lowest CEF levels. The orientation of the wave-functions in the crystal ab plane can also be determined in a straightforward manner by measuring the polarisation of the inelastically scattered photons. The interaction with itinerant states can lead to a momentum dependence of the 4f levels' energy and this leaves signatures in the excitation spectra that can be observed in RIXS. A simple model is proposed to explain the observed q dependence but further theoretical work is needed to properly account for the momentum dependence of the 4f excitations. Using the examples of CeCu2Si2 and CeCo2Ge2 it is demonstrated that RIXS can probe CEF splittings that are significantly smaller or much larger than those in CeRh2Si2. With better energy resolution and more advanced modelling RIXS studies of the CEF in cerium and other lanthanide ions will become even more accurate in the future.

Les oxydes d’iridium (iridates) ont attiré particulière attention au cours de la dernière décennie grâce à l’identification d’un état isolant de Mott induit par l’action conjointe du champ cristallin, de la corrélation électronique et du couplage spin-orbite. Cet état a été intensément investigué et des phases et excitations nouvelles ont été prédites théoriquement et aussi individuées expérimentalement. Sans doute, la diffusion inélastique résonante de rayons X (RIXS) est l’une des techniques les plus adoptée pour mesurer les excitations à basse énergie des iridates. En effet, la section efficace relativement large de la spectroscopie RIXS au seuil L3 de l’iridium et la bonne résolution en énergie ont encouragé l’emploi de cette technique. Cette thèse se pose un double objectif : concevoir des développements instrumentaux ayant pour but d’améliorer les possibilités offertes par la spectroscopie RIXS, et appliquer le RIXS afin d’étudier la physique à basse énergie de certains iridates.Le principal projet de développement instrumental est un nouveau spectromètre RIXS avec résolution en polarisation. L’analyse de la polarisation des rayons X diffusés permet d’obtenir des informations sur la symétrie et donc la nature des excitations. Cependant, elle est peu employée à cause de problèmes techniques qui naissent quand l’on veut préserver aussi la résolution en énergie et l’efficience du spectromètre. Même si le polarimètre RIXS projeté n’est pas encore disponible, le schéma optique a été vérifié et validé. Le polarimètre aura une résolution en énergie et une efficience équivalentes à celles des spectromètres RIXS courants. Le second développement technique comprend l’équipement permettant de réaliser des mesures RIXS à basse température et haute pression. Ces équipements ont permis d’investiguer l’évolution en pression des excitations magnétique du composé Sr3Ir2O7 en dessous de la température de Néel et jusqu’au 12 GPa. Les mesures peuvent aider l’affinage des modèles magnétiques courants pour ce système. Ces mesures démontrent que les excitations magnétiques peuvent être acquises en haute pression par la spectroscopie RIXS, démontrant ainsi la possible utilisation de cette technique dans ce nouveau domaine.Cette thèse comprend aussi des ultérieurs travails expérimentaux. Le premier considère le composé CaIrO3, dont la structure cristalline est constituée par des octaèdres partageant un sommet et une arête dans deux directions orthogonales. Du coup, les interactions magnétiques sont très différentes selon la direction cristallographique. Spécifiquement, la suppression du couplage de type Heisenberg dans la direction où les octaèdres partagent une arête produit des interactions magnétiques principalement unidimensionnelles. La caractéristique de ceux-ci est la présence d’un continuum d’excitations avec une dépendance en énergie et quantité de mouvement typique, qui a été révélé par la spectroscopie RIXS. Les excitations électroniques de CaIrO3 ont aussi des caractéristiques propres. Enfin, j’ai étudié les propriétés électroniques du composé Rb2[IrF6]. Des calculs récents proposaient que ce système possède un état d’isolant de Mott similairement aux oxydes d’iridium. Les mesures RIXS ont aidé à éclairer les propriétés électroniques de ce composé. La solidité des propriétés électroniques a été vérifiée par rapport à la substitution du métal alcalin ou de l’halogène, et à l’application de pression.Cette thèse accroit l’importance de l’utilisation de la spectroscopie RIXS dans des domaines qui étaient précédemment inexplorés. L’analyse de la polarisation des rayons X diffusés sera avantageuse dans les cas où la nature des excitations ne peut être établie sans ambiguïté. L’équipement développé pour réaliser les mesures RIXS en conditions extrêmes permet d’étudier la dynamique électronique et magnétique dans des phases de la matière inaccessibles jusqu’à aujourd’hui. / Iridium oxides (iridates) have raised notable attention in the last decade due to the identification of a Mott insulating state realized by the joint action of crystal field, electron correlation, and spin-orbit coupling. Such state has been intensively investigated and novel quantum phases and excitations have been theoretically predicted and experimentally found. Undoubtedly, one of the most employed techniques to elucidate the low-energy physics of iridates is resonant inelastic X-ray scattering (RIXS). At the iridium L3 edge, it benefits from a particularly good energy resolution, which matches the energy scales of the relevant excitations, and from a favorable inelastic cross-section. The aim of the present thesis is twofold: conceive challenging instrumental upgrades that contribute to the advancement of the technique itself, and apply RIXS to inspect the magnetic and electronic properties of selected iridates.The main instrumental development concerns the design of a new RIXS spectrometer with polarization resolution. Polarization analysis of the scattered X-rays provides useful information about the symmetry and thus the nature of an excitation. However, it is rather unexploited because of severe technical challenges when energy resolution and efficiency must be preserved. The designed RIXS spectrometer with polarization analysis capabilities is still under construction, however the optical scheme has been validated by preliminary tests. Full polarization analysis is expected without degradation of energy resolution or efficiency with respect to current state-of-the-art RIXS spectrometers. Additional technical developments include sample-environment equipment to perform RIXS experiments in low-temperature and high-pressure conditions. The equipment has been successfully utilized to investigate the magnetic dynamics of the bilayer-perovskite Sr3Ir2O7 below its Néel temperature and up to 12 GPa. Our measurements provide additional observations that may sharpen the challenge to theoretical understanding of the magnetic dynamics of this material. Moreover, we demonstrate for the first time that RIXS experiments of the magnetic dynamics can be extended to unexplored thermodynamic conditions.Besides instrumental advances, additional experimental work has been carried out in order to study the magnetic and electronic excitations of the post-perovskite CaIrO3. Owing to its peculiar crystal structure, featuring both edge- and corner-sharing octahedra, the magnetic interactions of CaIrO3 are very different along orthogonal directions. In particular, the inhibition of the Heisenberg coupling along the edge-sharing direction induces one-dimensional magnetic behavior with characteristic fractional spinon-like excitations, which have been detected by RIXS. Electronic excitations are also found to have particular properties. Finally, I have focused on the electronic structure of Rb2[IrF6], which was theoretically predicted to realize a Mott insulating state similar to the one of iridium oxides. RIXS measurements helped to elucidate the electronic properties of this compound. The robustness of the electronic state has been tested against substitutions of the alkali metal and halogen, and application of physical pressure.The present work extends the potential of the RIXS technique to domains previously unexplored, i.e. polarization analysis of the scattered X-rays and high-pressure low-temperature experiments. I hope that the instrumental upgrades and applications of RIXS discussed in this thesis will further promote the technique as a powerful and reliable tool to characterize elementary excitations in correlated-electron systems.

Cette thèse présente des travaux de recherche de métrologie en ligne de faisceaux de rayons X dans les installations synchrotrons. Deux approches principales ont été étudiées pour extraire la phase d'un front d'onde X : les méthodes utilisant des réseaux optiques et celles utilisant l'effet speckle dans le domaine X. L'interféromètre à réseaux X est l'outil le plus répandu résentatif de la première catégorie. Ses performances et son potentiel furent étudiés dans diverses situations de métrologie en ligne. Les méthodes utilisant le speckle X sont des techniques originales développées au cours de ce projet. Elles utilisent des membranes faites de petits grains diffusants, dont seule la distribution statistique est connue, pour permettre la modulation du front d'onde. Les différentes techniques furent déployées expérimentalement sur les lignes de lumière BM05 de l'ESRF et B16 de Diamond Light Source. Leurs implémentations servirent à la caractérisation de différents composants optiques utilisés pour manipuler les faisceaux synchrotron X et à l'étude de la faisabilité de micro imagerie par contraste de phase avec les sus citées techniques. / This thesis presents research and development work on synchrotron X-ray at-wavelength metrology methods. Two approaches for measuring the phase of an X-ray wavefront were studied: the grating-based and the speckle-based methods. The X-ray grating interferometer is the most widespread technique representative of the first category. Its performance and potential in various situations encountered in at-wavelength metrology was investigated. Speckle methods are X-ray phase sensing techniques newly developed during this thesis project. They make use of membranes with small statistical features to modulate the beam wavefront. The different methods were deployed experimentally at the beamlines BM05 of the ESRF and B16 of the Diamond Light Source. Their implementation permitted the characterization of various kinds of optical elements used to manipulate synchrotron X-ray beamsas well as the feasibility study of micro phase contrast imaging using the two methods described above.