Les émulsions de Pickering ont suscité un intérêt croissant dans de nombreux domaines de la recherche en raison de leur grande stabilité et versatilité. Une attention particulière a été accordée à la fabrication des systèmes complexes et originaux qui peuvent être obtenus avec différentes particules. Cette étude a consisté dans l'analyse des différents paramètres physico-chimiques des particules, des milieux liquides et des systèmes dispersées, et leur relation avec le comportement mécanique et la structure des émulsions afin de prédire et de moduler les caractéristiques de ces dernières. Nous avons étudié plus particulièrement pour la première fois, le diagramme de phase concernant les inversions de phase du type catastrophique et transitionnelle des émulsions de Pickering. Nous avons utilisé des particules de silice avec des structures et hydrophobicités différentes. En particulier, nous avons montré que le mélange de particules de différente hydrophobicités peut moduler finement l'inversion de phase aussi bien que les propriétés rhéologiques et structurales des émulsions. La fabrication de membranes à partir des émulsions de Pickering précédentes a été proposée comme un exemple de l'utilisation de ces systèmes modèles pour la conception de matériaux complexes. / Pickering emulsions have gained interest in many fields of research due their properties like higher stability and versatility. Special attention has been given to the processing of complex and original systems which can be obtained by using different particles. This study consists in the analysis of the different physicochemical parameters of particles, liquid media as well dispersion systems, and their relationship with emulsions structural and mechanical behavior in order to predict and modulate the emulsions characteristics. We studied extensively for the first time the phase diagram of catastrophic and transitional phase inversion of Pickering emulsions. We used silica particles with different structure and hydrophobicity. In particular we showed that mixing particles with different hydrophobicity can finely modulate the phase inversion as well the rheological and structural properties of the emulsions. The manufacturing of emulsified membranes based on previous Pickering emulsions was proposed as an example of the use of these systems as templates for the design of complex materials.

In this letter, we propose all-dielectric Huygens' metasurface structures to construct high numerical aperture flat lenses and beam deflecting devices. The designed metasurface consists of two-dimensional array of all dielectric nanodisk resonators with spatially varying radii, thereby introducing judiciously designed phase shift to the propagating light. Owing to the overlap of Mie-type magnetic and electric resonances, high transmission was achieved with rigorous design analysis. The designed flat lenses have numerical aperture value of 0.85 and transmission values around 80%. It also offers easy fabrication and compatibility with available semiconductor technology. This spectrally and physically scalable, versatile design could implement efficient wavefront manipulation or beam shaping for high power laser beams, as well as various optical microscopy applications without requiring plasmonic structures that are susceptible to ohmic loss of metals and sensitive to the polarization of light.

Abstract The effects of perioperative filgrastim (rhG-CSF) and surgery per se on the postoperative acute phase reaction were studied by assessing leukocyte functions, cytokine levels and tenascin-C (Tn-C) and procollagen propeptide (PINP, PIIINP) concentrations in different body fluid compartments in patients undergoing gastrointestinal surgery. Thirty consecutive patients were randomized to receive either filgrastim or placebo for five days, starting 12 hours before colorectal surgery. Filgrastim treatment led to marked neutrophilia with decreased neutrophil migration in peripheral blood but not in peritoneal fluid 48 hours postoperatively. Neutrophil phagocytosis and bacterial killing did not differ between the groups. Filgrastim caused increased postoperative expression of neutrophil CD11b/CD18 in blood but not in peritoneal fluid or wound fluid. CD11b/CD18 expression was higher in both wound fluid and peritoneal fluid than in blood in the placebo group. The expression of neutrophil CD62L was higher in blood than in peritoneal fluid or wound fluid in both groups. The serum concentration of interleukin (IL)-8 was lower in the filgrastim group 5 hours postoperatively. The concentrations of IL-1β, IL-6, transforming growth factor (TGF)-β and IL-10 did not differ between the groups. The cytokine levels were markedly higher locally in the wound and in the peritoneal cavity compared to circulating blood. No adverse events attributable to filgrastim were seen. Leukocyte counts, neutrophil and monocyte functions and the levels of IL-6, IL-8 and granulocyte colony-stimulating factor (G-CSF) were measured from 18 patients before and after colorectal surgery. Surgery caused an increase in neutrophil and monocyte counts along with lymphocytopenia. Neutrophil phagocytosis was decreased 4 and 24 hours postoperatively, but normalized after that. A distinct systemic cytokine response was seen postoperatively. In a study with 24 patients, Tn-C concentration increased in wound fluid during the first postoperative week after abdominal surgery. The Tn-C level was markedly higher in wound fluid than in serum.

The project contributes to the general theme of complex chemical systems and strengthens ties with Innospec, a multi-national chemical company. Sodium lauroyl methyl isethionate (SLMI. Trade name “Iselux”) is a newly developed surfactant with attractive product properties for personal care applications. Little is known about the fundamental surface and solution properties of SLMI, and it is not currently possible to use information on available surfactants to predict phase behaviour. We characterise the solution and liquid crystalline phase behaviour of the SLMI/water system using a combination of optical microscopy, X-ray scattering and differential scanning calorimetry techniques. SLMI is synthesised using a batch process that leads to variable component concentrations. Preliminary studies conducted by Innospec indicate that the presence of particular process components has a significant influence on SLMI formulation rheological properties. We investigate the effects of synthesis-derived components on the rheological properties of the SLMI/sodium {(3-(dodecanoylamino)propyl)(dimethyl)ammonio)}acetate/water system using rheology and light scattering (static and dynamic) techniques. SLMI is often formulated into personal care products on mixing aqueous formulation components. Micelle growth occurs via a mechanistic process that is not understood and the equilibrium viscosity is attained at a time after mixing that ranges from seconds to weeks. Developing an improved understanding of the micelle growth mechanism is of both academic and industrial value. We utilise static light scattering and nuclear magnetic resonance techniques to probe a range of samples in the viscoelastic region of the SLMI/(carboxymethyl)hexadecyldimethyl ammonium hydroxide/water system. Experimental findings improve our current understanding of micelle growth process and provide a platform for future research on non-equilibrium mixing kinetics. In the final section we investigate salt-induced cloud point and precipitation phenomena in the SLMI/salt/water system. The cloud point is commonly observed in surfactant and protein systems by increasing the solution temperature above a critical value, resulting in phase separation of solute-rich and solute-depleted layers. Cloud point induced phase separation may also be prompted by addition of salt. The mechanistic process driving electrolyte-induced cloud point phenomena is not understood. We use a combination of turbidimetry measurements and lightscattering (static and dynamic) techniques to measure cloud point curves andcharacterise micellar behaviour prior to clouding.

In this research study, the feasibility of using one of the Hybrid Permanent Magnet (HPM) machine topologies acting as a generator with a passive rectification stage is considered. The primary application area is in the power-train of a series hybrid electric vehicle where the concept will be considered as an alternative to brushless PM machines interfacing to the vehicle power-train via active power electronic converters. The electro-magnetic design of the two main parts in the selected HPM generator topology and their individual system behaviour at normal and rated conditions will be studied. Prediction of the transient and steady state temperature in some of the HPM machine parts will be conducted based on commercial thermal analysis software. Two HPM machine stator winding configurations; 3-phase and 9-phase, with their relevant passive rectification stages will be analysed in terms of their terminal and DC-link output power along with the quality of the generated DC output voltage. An investigation of the operational characteristic of the HPM generator when delivering a fixed power at a fixed speed into a dynamic DC voltage source typical of a hybrid electric vehicle power-train subject to urban driving regimes will be presented. The research work will be a mixture of simulation studies using electro-magnetic finite element analysis (FEA), transient machine and system analysis via SimPower, a Matlab/Simulink toolbox set, along with test validation via a representative prototype HPM generator configuration and its interface to an experimental electrical system evaluation platform.

Polynomial phase modulated (PPM) signals have been shown to provide improved error rate performance with respect to conventional modulation formats under additive white Gaussian noise and fading channels in single-input single-output (SISO) communication systems. In this dissertation, systems with two and four transmit antennas using PPM signals were presented. In both cases we employed full-rate space-time block codes in order to take advantage of the multipath channel. For two transmit antennas, we used the orthogonal space-time block code (OSTBC) proposed by Alamouti and performed symbol-wise decoding by estimating the phase coefficients of the PPM signal using three different methods: maximum-likelihood (ML), sub-optimal ML (S-ML) and the high-order ambiguity function (HAF). In the case of four transmit antennas, we used the full-rate quasi-OSTBC (QOSTBC) proposed by Jafarkhani. However, in order to ensure the best error rate performance, PPM signals were selected such as to maximize the QOSTBC’s minimum coding gain distance (CGD). Since this method does not always provide a unique solution, an additional criterion known as maximum channel interference coefficient (CIC) was proposed. Through Monte Carlo simulations it was shown that by using QOSTBCs along with the properly selected PPM constellations based on the CGD and CIC criteria, full diversity in flat fading channels and thus, low BER at high signal-to-noise ratios (SNR) can be ensured. Lastly, the performance of symbol-wise decoding for QOSTBCs was evaluated. In this case a quasi zero-forcing method was used to decouple the received signal and it was shown that although this technique reduces the decoding complexity of the system, there is a penalty to be paid in terms of error rate performance at high SNRs.

Le but de ce travail était de contribuer à une meilleure compréhension des mécanismes complexes qui sous-tendent la formation et l’évolution des hydrures dans le zirconium α et ses alliages. Dans ce contexte, des approches multi-échelles, mêlant simulations atomiques et par champ de phase, ont été employées pour aborder les propriétés structurales et énergétiques des interfaces hétérophases α|hydrures. Un intérêt particulier a été porté à l'hydrure γ-ZrH, en raison de sa stabilité et ses relations avec les chemins de précipitation controversés, via l’étude des interfaces basales et prismatiques complétée par une étude soignée des plans d’habitat. Une méthodologie originale transposable à d’autres systèmes, fondée sur la théorie microélastique combinée à des calculs ab initio, a été proposée pour estimer les énergies relatives à ces interfaces. Les résultats montrent une forte anisotropie jusque-là négligée dans la littérature. Du fait du caractère semi-cohérent des interfaces prismatiques, une évaluation correcte de leur énergie s'est révélée difficile. Une approche alternative a donc été suggérée, fondée sur un formalisme de champ de phase à même de décrire la structure de cœur des dislocations inhérentes à des interfaces prismatiques hc|cfc. Elle s’est avérée utile pour estimer la stabilité interfaciale de divers systèmes et pour prédire la perte de cohérence d’un germe croissant. Il a été montré que l'hydrure ζ-Zr2H cohérent constituerait un bon précurseur de γ. Enfin, l'emploi de la théorie microélastique aux interfaces α|hydrures a clairement indiqué la préférence pour des plans d'habitat pyramidaux πI. Un effet notable de la teneur en hydrogène a aussi été observé. / The goal of this work was to contribute to a better understanding of the complex mechanisms underpinning the formation and evolution of hydrides in α zirconium and its alloys. In this context, multi-scale approaches combining atomic and phase-field simulations were employed to address the structural and energetic properties of heterophase α|hydrides interfaces. A peculiar attention was focused on the γ-ZrH hydride due to its controversed stability and to its supposed role one many sequences of precipitation. In particular, the study was concentrated on the basal and prismatic interfaces complemented by a meticulous study of the habit planes. An original methodology, transferable to other systems and based on the microelasticity theory combined with ab initio calculations, was proposed to estimate the energies related to these interfaces. The results show a strong anisotropy hitherto neglected in the literature. Due to the semi-coherent nature of prismatic interfaces, a correct evaluation of its energy was proven to be difficult. Thus, an alternative approach, grounded in a phase-field formalism and able to describe the core structure of inherent dislocations in prismatic interfaces, has been suggested. This approach turned out useful to estimate the interfacial stability of various systems as well as to predict the coherency loss of a growing seed. It has been showed that the coherent ζ-Zr2H hydride could constitute a good precursor of γ-hydride. Finally, the application of the microelasticity theory to α|hydrides interfaces has clearly showed a preference for πI pyramidal habit planes where a significant effect of hydrogen content in the hydride has also been observed.

No description available.

No description available.

The phase behaviour of methane at temperatures below 20°K is still not understood. There is recent evidence for a second phase transition at 8°K, in addition to the well known transition at 20.4°K. This second transition requires a long time to reach equilibrium. In our experiment, the nuclear magnetic resonance signal of the methane protons was monitored for a period of many hours at 1.2°K, in order to; determine whether a slow phase change occurred in the approach to equilibrium. This change would manifest itself in the width of the resonance line, which is sensitive to the local environment of the proton, and thus able to provide information about the crystal structure. No definite time variation of line width was observed. The line width increased by 15% from 4.2°K to 1.2°K. The second moment of the line also rose sharply as the temperature increased, indicating an increasing contribution to the spin-spin interaction from intra-molecular broadening. An approximate model yielded a correlation time for the intra-molecular term of the order of a microsecond. Significant differences between different methane samples indicate that sample preparation is important, and that the above results were for samples in some sort of metastable phase. / Science, Faculty of / Physics and Astronomy, Department of / Graduate