Magister Pharmaceuticae - MPharm / The aim of this study was to investigate the mechanism of fenfluramine-induced pulmonary phospholipidosis, by comparing the profile and levels of induced phospholipids in the rat and the mode of phospholipase inactivation, both relative to that produced by chlorphentermine. Wistar and BD9 rats were injected with fenfluramine (FF) and chlorphentermine (CP) intra-peritoneally daily over a six week period to induce phospholipidosis. The lungs isolated from such treated and untreated animals, were grouped into unlavaged lungs and lungs to be lavaged and from the latter group the alveolar macrophages were isolated. Small sections of the unlavaged lungs were microscopically examined to verify the induction of phospholipidosis. Further the levels of phosphatidyl choline (PC), spingomyelin (SPM), phosphatidyl ethanolamine (PE), phosphatidyl glycerol (PG), phosphatidyl inositol (PI), phosphatidyl serine (PS) and phosphatidic acid (PA) were determined in both groups of lungs using a TLC method. To assess whether the drug-mediated inactivation of the phospholipases (PL) occurred via direct inhibition of the enzymes or via the drug-phospholipid complex, the hydrolysis of the above phospholipids by PL-A or PL-C were monitored using colorimetric methods. The feasibility of the phospholipid-drug complex-mediated mechanism was further explored, by assessing the effect the two drugs had on the phase transition temperature of the phospholipids. Electron microscopy revealed the presence of hypertrophied and elevated counts of alveolar macrophages in the treated-Wistar and -BD9 rats. In the FF- and CP treated Wistar and BD9 rats there were, compared to the saline-treated rats, a 200 % and 235 % increase in macrophage counts, respectively, for the FF-treated rats and a 700 % and 965 % increase in macrophage counts, respectively, for the CP treated rats. The levels of all the phospholipids in the unlavaged lungs of both rat strains were elevated, except that for PG, PS and PA. In both rat strains following the treatment with both drugs the PG levels were not elevated and the PS levels were not elevated following CP treatment. Following the treatment for both drugs, the PA levels were also not elevated in the BD9 rats. Relative to the levels found in the unlavaged lungs of the control rats, the increases ranged from a minimum of 9 to a maximum of 216 %. In general, Wistar rats appeared to be more susceptible to both FF and CP treatment. In both rat strains, lavaging of the lungs considerably reduced the levels of phospholipids remaining in the lung and the differences between the treated and untreated animals became less striking. The addition of FF or CP, whether directly to the enzyme, or in the form of the drug phospholipid complex, resulted in significant decreases in the PL-A-mediated or PL-C-mediated hydrolysis of virtualy all the test phospholipids. The average decrease ranged from 0.811 to 4.04 ,.,.FFAbbb ,.,.1-1sample min-I, for the PL-A activity and 0.023 to 0.827 ,.,.gIp'CC100 ,.,.1-1 sample min-I, for the PL-C activity. In the case of FF, the inhibition of PL-A activity could not be ascribed exclusively to either direct inhibition of the enzyme or reduced susceptibility of the phospholipid substrate-drug complex. The PL-C activity appeared to be inhibited to a greater extent via the phospholipid substrate-drug complex rather than by direct inhibition. On the other hand, CP induced a small, but significantly greater degree of inhibition of PL-A activity, more via direct inhibition, rather than by the phospholipid substrate-drug complex. The PL-C activity appeared to be inhibited to a greater extent via phospholipid substrate-drug complexation than by direct inhibition. From the above data, considered collectively, it was not possible to declare either of the two possible mechanisms as the more likely one for FF or CP-induced inhibition of the phospholipases. The feasibility of the indirect mode was further explored, by determining the phase transition temperatures for the phospholipid-drug complexes of each drug. The addition of each drug caused a depression of the phase transition temperature of all the phospholipids with a .1T'dd ranging from 0.52 to 15.73 °C. This appears to support the notion that both drugs bind to the phospholipids and the differences in the extent of the phase transition temperature depression of the individual phospholipids may indicate differences in the binding capacities of these drugs. The following major conclusions may be drawn from the results of this investigation. Fenfluramine induces a phospholipidosis syndrome in the lungs of Wistar and BD9 rats that are histologically similar to that induced by CP. It induces the elevation of essentially the same phospholipids as CP, primarily in the alveolar spaces and macrophages, and by implication, most likely via similar mechanisms. For both FF and CP, both direct inhibition and phospholipid-drug complex-mediated inhibition of phospholipases were found to be a viable mechanism for this syndrome. The mechanism for FF-induced pulmonary phospholipidosis thus appears to be similar to that of CP; small quantitative differences in essentially similar mechanisms, may explain the differences in the levels of induced phospholipidosis found in this study.

Le travail présenté dans ce manuscrit concerne les mesures de taille de particule et de fraction volumique de suies dans des conditions moteur Diesel. Les techniques utilisées sont la laser-Induced incandescence (LII), la méthode d’extinction laser (LEM), la pyrométrie, et l’analyse d’images de microscopie électronique par transmission (TEM) d’échantillons prélevés in-Situ. Des stratégies de mesure de tailles de particules sont développées en se basant sur l’utilisation d’un modèle LII et en analysant la poly-Dispersion des tailles de particules, aussi bien à partir de signaux de LII résolu en temps (mesures ponctuelles) à pression atmosphérique, que d’informations résolues spatialement provenant d’images acquises a deux instants différents. Des mesures sont effectuées avec ces stratégies sur une flamme à pression atmosphérique et dans des conditions représentatives des conditions moteur Diesel pour évaluer leur applicabilité. Des mesures supplémentaires de température et de fraction volumique de suies sont aussi réalisés.Une nouvelle méthode, appelée two-Exponential reverse fitting (TERF) est introduite. Elle vise à extraire des informations sur la distribution de tailles de particules. Cette méthode est basée sur l’utilisation de fits mono-Exponentiel du signal de décroissance de LII à différents intervalles de temps. La distribution de tailles de particules est approximée par la combinaison de deux distributions de tailles de particules mono-Disperses : une petite et une large. Aucune hypothèse sur la forme de la distribution n’est nécessaire. La méthode permet aussi de fournir le ratio de la proportion respective des deux classes de particules. L’erreur systématique induite par la description mono-Exponentielle de la décroissance du signal de LII a été calculée et est inférieure à 2% pour des décroissances de signal de LII d’aggregats mono-Disperses avec des températures de chauffe pour lesquels la sublimation des suies est négligeable. La méthode a été appliquée à des données de LII obtenus sur une flamme laminaire atmosphérique éthylene/air à différentes hauteurs. Les résultats obtenus montrent un bon accord entre les tailles des grosses particules évaluées avec la méthode TERF et celle obtenue par analyse des images TEM. En revanche l’accord n’est pas obtenu pour les petites particules, ce qui est attribué à un manque d’information sur cette classe de particule dans l’analyse TEM.Des champs de fraction volumique de suies sont ensuite obtenus dans une cellule haute pression haute température dans les conditions opératoires du réseau ECN (Engine Combustion Network) par technique combinée de LEM et LII simultanées. Les mesures sont réalisées dans les conditions du spray A et incluent des variations paramétriques (température et dilution). La distance de Lift Off de la flamme est déterminée en parallèle par visualisation directe de la chimiluminescence OH. Des niveaux de fraction volumique maximale de 2-3ppm sont obtenus dans les conditions nominales du spray A (i.e. 900K), et peuvent atteindre 12 pmm à haute température (1030K). L’effet des variations de température et de concentration d’oxygène sur la formation et l’oxydation des suies et cohérente avec les résultats issus de la littérature.Une méthode d’imagerie de taille de particules est développée. Elle est basée sur l’acquisition de deux images de LII obtenues à deux instants différents après le pulse laser et l’analyse de ces images à l’aide de la simulation du signal LII pour déduire les tailles des particules à partir du rapport des images. Une stratégie basée sur une analyse par modèle LII est développée pour évaluer les incertitudes de mesure. La dépendance aux conditions limites de l’imagerie de taille de particule par LII est ainsi évaluée. [...] / This work focuses on measurements of soot particle size and volume fraction at Diesel engine conditions. A combination of laser-Induced incandescence (LII) imaging, line-Of-Sight laser extinction, soot pyrometry, and transmission electron microscopy (TEM) measurements of thermophoretically-Sampled soot was used. Particle sizing strategies were developed with LII model for the analysis of particle-Size poly-Dispersity with time-Resolved LII signal that is suitable for point-Wise measurements at atmospheric pressure, and for spatially-Resolved characterization with two-Time-Step LII imaging. Measurements were performed with these strategies in a flame at atmospheric pressure and in Diesel engine combustion to investigate their applicability. Additional measurements were performed for temperature and soot volume fraction.A novel method, called two-Exponential reverse fitting (TERF), is introduced to extract information about the size distribution. The method is based on mono-Exponential fits to the LII signal decay at a delayed time. It approximates the particle-Size distribution as a combination of one large and one small mono-Disperse equivalent mean particle size and does not require a distribution assumption. It also provides a ratio of the contribution of both size classes. The systematic error caused by de-Scribing LII signals by mono-Exponential decays was calculated as less than 2% for LII signals simulated for mono-Disperse aggregated soot with heat-Up temperatures for which evaporation is negligible. The method was applied to LII data acquired in a laminar non-Premixed ethylene/air flame at various heights above the burner. The particle size of the large particle-Size class evaluated with the method showed good consistency with TEM results, however the size of the small particle-Size class and its relative contribution could not be compared due to insufficient information in the TEM results for small particles. Simultaneous line-Of-Sight laser extinction measurements and LII imaging were performed to de-Rive the soot volume fraction in a high-Temperature high-Pressure constant-Volume pre-Combustion vessel under the Engine Combustion Network’s (ECN) "Spray A" conditions with parametric variations of gas temperature and composition. Extinction measurements were used to calibrate LII images for quantitative soot distribution measurements. OH-Chemiluminescence imaging was used to determine the lift-Off length, and used to interpret the soot measurements. Maximum soot volume fractions around 2–3 ppm were obtained at the nominal ambient temperature defined for Spray A (i.e. 900 K) that rise to 12 ppm at elevated temperature (1030 K). Variations of ambient temperature and oxygen concentration were carried out showing effects on soot formation and oxidation that are consistent with the literature.The method for particle-Size imaging is based on evaluating gated LII signals acquired with two cameras consecutively after the laser pulse and using LII modeling to deduce particle size from the ratio of local signals. A strategy was developed with a model-Based analysis: the dependence of LII particle-Size imaging on the assumed boundary conditions was identified such as bathgas temperature, pressure, particle heat-Up temperature, thermal accommodation coefficients, and soot morphology. Various laser-Fluence regimes and gas pressures were considered. Effects of laser attenuation were evaluated. A combination of one detection gate starting with the particle-Heating and the other starting with 11 ns delay with twice as long gate width was found to provide the highest sensitivity for particle sizing at 60 bar. The optimum gate delays for different pressures were calculated. The effects of timing jitter for laser pulse and poly-Dispersity were investigated. Systematic errors in pyrometry imaging at 60 bar was evaluated. [...]

Nanocrystalline metals exhibit a high strength/hardness but generally poor ductility during deformation regardless of their crystal structure which is often called the strength-ductility trade-off relationship and generally appears in most ultrafine-grained metals. The ultrafine-grained (UFG) high manganese austenitic twinning-induced plasticity (TWIP) steels have been found to overcome the strength-ductility trade-off but their underlying mechanism of discontinuous yielding behavior has not been well understood. In this study, our systematic TEM characterization suggests that the plastic deformation mechanisms in the early stage of deformation, around the macroscopic yield point, show an obvious association with grain size and nucleation of deformation twin was promoted rather than suppressed in UFG. More specifically, the main mechanism shifts from the conventional slip in grain interior to twinning nucleated from grain boundaries with decreasing the grain size down to less than 1 m. We also provide insights into the atomistic process of deformation twin nucleation at 3{111} twin boundaries, the dominant type of grain boundary in the UFG-TWIP steel of interest. In response to the external tensile stresses, the structure of coherent 3{111} twin boundary changes from atomistically smooth to partly defective by the grain boundary migration mechanism thus the "kink-like" defective step can act as a nucleation site for deformation twin, which deformation process is different from the one induced by dislocation pile-ups in coarse-grained counterparts and explain why UFG TWIP steel can retain the moderate ductility. In addition to the effect of grain size on deformation twin nucleation, grain boundary character was also taken into account. In coarse-grained TWIP steel, we experimentally reveal that deformation twin nucleation occurs at an annealing twin () boundary in a high-Mn austenitic steel when dislocation pile-up at boundary produced a local stress exceeding the twining stress, while no obvious local stress concentration was required at relatively high-energy grain boundaries such as or  A periodic contrast reversal associated with a sequential stacking faults emission from boundary was observed by in-situ transmission electron microscopy (TEM) deformation experiments, proving the successive layer-by-layer stacking fault emission was the deformation twin nucleation mechanism. The correlation between grain boundary character and deformation behavior was discussed both in low- and high-sigma value grain boundaries. On the other hand, localized strain concentration causes the nucleation of deformation twins at grain boundaries regardless of the grain boundary misorientation character in UFG TWIP steel. The invisibility of stacking fault (zero contrast) was also observed to be emitted at 3{111} boundaries in the coarse-grained TWIP steel, which deformation twin nucleation mechanism is found to be identical to UFG Fe-31Mn-3Si-3Al TWIP steel. / Doctor of Philosophy / High manganese (Mn) twin-induced plasticity (TWIP) steel is a new type of steels which exhibit pronounced strain hardening rate so that offering an extraordinary potential to adjust the strength-ductility relationship. This key advantage will help implement the current development of lightweighting components in automobile industry due to a considerable reduction of material use and an improved press formability. Such outstanding ductility can be contributed by the pronounced strain hardening rate during every such deformation processes, which is highly associated with several different controlling parameters, i.e., SFE, grain orientation, grain size, and grain boundary characters. In this study, we take particular attention to the effect of grain size and grain boundary characters on deformation twinning behavior besides well-known parameters such as SFE and grain orientation. The effect of grain size on deformation twinning behavior was found to be deeply associated with the yielding behavior in TWIP steel, i.e., a discontinuous yielding behavior with a unique yield drop was observed in ultrafine-grained TWIP while a continuous yielding behavior was observed in coarse-grained counterpart. Our TEM characterization indicates that the microstructural features of grains >10 m are different from the microstructural features in grains < 1 m. In over-10 m grains, normal dislocation slips and the formation of in-grain stacking faults are the main deformed microstructure. However, in the under-1 m grains, the in-grain dislocation slip is inhibited, but the deformation twinning is promoted at grain boundaries. This deformation transition from in-grain slip to twinning at grain boundary appears to be responsible for the discontinuous yielding behavior observed in stress-strain curve. The effect of grain boundary character on deformation twinning was examined in both coarse- and ultrafine-grained TWIP steels. In coarse-grained TWIP steel, we found that deformation twinning behavior varies as the function of boundary structure, i.e., different atomic configuration. Coherent twin boundary can act as a nucleation site for deformation twin as a localized strain concentration was introduced by dislocation pile-ups. On the other hand, incoherent boundaries can act as a deformation twin nucleation site by a boundary relaxation mechanism, i.e., grain-boundary dislocations can dissociate into partial dislocations to both side of boundary to accommodate the misfit between grains. In UFG TWIP steel, we found that the coherent twin boundary can act as a deformation twin nucleation site without presence of dislocation pile-ups. Alternatively, twin boundary becomes defective with a "kink-like" step by boundary migration. As a result, this defective step would progressively accumulate localized strain field thus stimulate the nucleation of deformation twin. Such study provides a novel insight into the UFG TWIP steel and a roadmap toward controlling TWIP effect.

Organic semiconductors functionalized nanostructures are becoming as promising materials for electronic device applications including organic photovoltaics (OPVs). Perylenediimide (PDI) derivatives have also been known as one of the best n-type organic semiconductors. PDI derivatives can form bulk materials, which are both photochemically and thermally stable and have been widely used in various optoelectronic devices. Due to the formation of high electron mobility of crystalline domains, they prefer to incorporate into a silsesquioxane network. Here, we describe the potential applicability of perylenediimide functionalized silsesquioxane nanoribbons (PDI-dimethyl nanoribbons) as an acceptor for optoelectronic devices. We have developed synthetic procedures to make the PDI-dimethyl nanoribbons by the substitution reaction and the modified Stöber method. The PDI-dimethylethoxy silane precursor was produced in high yield by substituting 3-aminopropyldimethylethoxysilane on perylene-3,4,9,10-tetracarboxylicdianhydride as side chains. The optically active PDI-dimethyl nanoribbons were then formed upon hydrolysis with the certain concentration of ammonium hydroxide as a base. These nanoribbons were characterized using transmission electron microscopy (TEM), elemental analysis, and polarized optical microscopy. The photophysical properties in solution phase were also studied. The synthesis procedure developed here will have a great promise in large-scale manufacturing. Different shapes of PDI-dimethyl nanostructures, such as nanorods, nanochains, and nanoparticles, were discovered while varying the base concentrations. Also the morphologies of these PDI nanostructures were studied using TEM. Future studies will focus on optimizing procedures of PDI-dimethyl nanostructures and exploring new derivatives like perylenediimide dimer functionalized silsesquioxane polymers.

Sodium borohydride is stable in alkaline solution, however, it hydrolyses and generates hydrogen gas in the presence of suitable catalyst. By this way hydrogen can be generated safely for the fuel cells. All of the catalyst having been used in the hydrolysis of sodium borohydride, with one exception, are heterogeneous. The limited surface area of the heterogeneous and therefore, have limited activity because of the surface area. Thus, the use of metal nanoclusters as catalyst with large surface area is expected to provide a potential route to increase the catalytic activity. In this dissertation we report for the first time the use of ruthenium(0) nanoparticles as catalyst in the hydrolysis of sodium borohydride. The water dispersible ruthenium(0) nanoparticles were prepared by the reduction of RuCl3.xH2O with sodium borohydride and were stabilized by three different ligands dodecanethiol, ethylenediamine and acetate. Among these three colloidal materials the acetate stabilized ruthenium(0) nanoparticles were found to have the highest catalytic activity in catalyzing the hydrolysis of sodium borohydride. The acetate stabilized ruthenium(0) nanoparticles were characterized by tranmission electron microscopy (TEM), X-ray photoelectron spectroscopy and FT-IR spectroscopy. The particle size of the acetate stabilized ruthenium(0) nanoparticles was determined to be 2.62&plusmn / 1.18 nm from the TEM analysis. The kinetic of the ruthenium(0) nanoparticles catalyzed hydrolysis of sodium borohydride was studied depending on the catalyst concentration, substrate concentration and temperature. The activation parameters of this reaction were also determined from the evaluation of the kinetic data. This catalyst provides the lowest activation energy ever found for the hydrolysis of sodium borohydride.

Dans cette thèse, nous proposons une étude détaillée des mécanismes responsables de la perte de données dans les mémoires à changement de phase enrichies en germanium (Ge-rich PRAMs), à savoir la dérive de la résistance au cours du temps et la recristallisation de la phase amorphe. Nous commençons par une présentation du contexte dans lequel s'inscrit cette étude an donnant un aperçu rapide du marché des mémoires à semiconducteur et une comparaison des mémoires non volatiles émergentes. Les principes de fonctionnement de la technologie PRAM sont introduits, avec ses avantages, ses inconvénients, ainsi que la physique régissant le processus de cristallisation dans les matériaux à changement de phase, avant de décrire les problèmes de fiabilité qui nous intéressent.Une caractérisation électrique complète de dispositifs intégrant des alliages de GST enrichi en germanium est ensuite proposée, en commençant par la caractérisation des matériaux utilisés dans nos cellules, introduisant alors les avantages des alliages enrichis en Ge sur le GST standard. Les performances électriques des dispositifs intégrant ces matériaux sont analysées, avec une étude statistique des caractéristiques SET & RESET, de la fenêtre de programmation, de l'endurance et de la vitesse de cristallisation. Nous nous concentrons ensuite sur le thème principal de cette thèse en analysant la dérive en résistance de l'état SET de nos dispositifs Ge-rich, ainsi que les performances de rétention de l'état RESET.Dans la dernière partie, nous étudions les mécanismes physiques impliqués dans ces phénomènes en fournissant une étude détaillée de la structure des cellules, grâce à l'utilisation de la Microscopie Électronique en Transmission (MET). Les conditions et configurations expérimentales sont décrites, avant de présenter les résultats qui nous ont permis d'aller plus loin dans la compréhension de la dérive en résistance et de la recristallisation de la phase amorphe dans les dispositifs Ge-rich. Une discussion est finalement proposée, reliant les résultats des caractérisations électriques avec ceux des analyses TEM, conduisant à de nouvelles perspectives pour l'optimisation des dispositifs PRAMs. / In this thesis we provide a detailed study of the mechanisms responsible for data loss in Ge-rich Ge2Sb2Te5 Phase-Change Memories, namely resistance drift over time and recrystallization of the amorphous phase. The context of this work is first presented with a rapid overview of the semiconductor memory market and a comparison of emerging non-volatile memories. The working principles of PRAM technology are introduced, together with its advantages, its drawbacks, and the physics governing the crystallization process in phase-change materials, before describing the reliability issues in which we are interested.A full electrical characterization of devices integrating germanium-enriched GST alloys is then proposed, starting with the characterization of the materials used in our PCM cells and introducing the benefits of Ge-rich GST alloys over standard GST. The electrical performances of devices integrating those materials are analyzed, with a statistical study of the SET & RESET characteristics, programming window, endurance and crystallization speed. We then focus on the main topic of this thesis by analyzing the resistance drift of the SET state of our Ge-rich devices, as well as the retention performances of the RESET state.In the last part, we investigate on the physical mechanisms involved in these phenomena by providing a detailed study of the cells' structure, thanks to Transmission Electron Microscopy (TEM). The experimental conditions and setups are described before presenting the results which allowed us to go deeper into the comprehension of the resistance drift and the recrystallization of the amorphous phase in Ge-rich devices. A discussion is finally proposed, linking the results of the electrical characterizations with the TEM analyses, leading to new perspectives for the optimization of PRAM devices.

De par leurs propriétés physico-chimiques spécifiques, les nanomatériaux attirent de plus en plus la communauté scientifique. Dans ce contexte, il est important d'améliorer les techniques de caractérisation à l'échelle nanométrique. Ce travail de thèse est basé sur le développement de techniques de diffraction électronique pour l'étude de matériaux bi-dimensionnels et tri-dimensionnels.La diffraction électronique en faisceau convergent contient de nombreuses informations sur la structure l'échantillon. Ces informations, portées par les lignes de HOLZ, permettent de déterminer l'épaisseur de l'échantillon, le facteur de structure, la direction d'observation, la tension d'accélération des électrons, ainsi que la longueur de caméra. Des ambiguïtés existent dans la détermination de l'état de contraintes car un cliché expérimental est une projection bi-dimensionnelle d'une information tri-dimensionnelle. Il a été possible au cours de cette thèse de réduire ces ambiguïtés et de déterminer ainsi les composantes diagonales du tenseur de déformation à partir d'une seule direction d'observation. En étudiant l'élargissement des lignes de HOLZ, dû à une déformation non uniforme dans le sens de propagation des électrons, il a été possible de remonter au champ de déplacement suivant l'axe du faisceau d'électrons.La seconde partie de cette thèse s'intéresse aux matériaux bi-dimensionnels comme le Graphène, le Nitrure de Bore (BN) et le disulfure de Molybdène (MoS2). L'interprétation du contraste d'une image de microscopie électronique en transmission haute résolution est discutée, notamment sur l'importance de l'orientation de l'échantillon et des aberrations. Une méthode de mesure de l'orientation d'un échantillon bi-dimensionnel basée sur la projection des tâches de diffraction est présentée. Enfin, trois techniques de mesure d'épaisseur sont comparées en les appliquant à quelques couches atomique de MoS2 et BN. / The small dimensions of nanomaterials give them remarkable properties attracting the scientific community. In order to understand and control these properties, it is essential to characterize them at the nanometer scale. This thesis work is based on the development of electron microscopy diffraction techniques for the study of two and three dimensional materials.Convergent Beam Electron Diffraction patterns contain large amount of information on the sample geometry. This information, carried by HOLZ lines, allows to determine the sample thickness, the structure factor, the direction of observation, the electron acceleration voltage and the camera length. Ambiguities in strain measurement arise from the experimental two-dimensional projection of three-dimensional information. During this thesis, it has been possible to reduce these ambiguities and therefore to measure the diagonal components of the deformation gradient tensor from one direction of observation only. By studying the HOLZ lines broadening, due to a non-uniform strain along the electron beam direction, it has been possible to retrieve the displacement field along the beam direction.The second part of this thesis is focused on the study of two-dimensional materials such as Graphene, Boron Nitride (BN) or Molybdenum disulfide (MoS2). The delicate interpretation of the contrast of high-resolution transmission electron microscopy images and especially the importance of aberrations and sample tilt on this contrast is discussed. A method to quantify two-dimensional sample orientation using diffraction spots projection effect is presented. Finally, three thickness measurement techniques are compared by applying them to few-layered MoS2 et BN.

The Gram-negative bacterium Pseudomonas aeruginosa is a life-threatening nosocomial pathogen due to its generally low susceptibility toward antibiotics. Furthermore, many strains have acquired resistance mechanisms requiring new antimicrobials with novel mechanisms to enhance treatment options. Proline-rich antimicrobial peptides, such as the apidaecin analog Api137, are highly efficient against various Enterobacteriaceae infections in mice, but less active against P. aeruginosa in vitro. Here, we extended our recent work by optimizing lead peptides Api755 (gu-OIORPVYOPRPRPPHPRL-OH; gu = N,N,N′,N′-tetramethylguanidino, O = L-ornithine) and Api760 (gu-OWORPVYOPRPRPPHPRL-OH) by incorporation of Ile-Orn- and Trp-Orn-motifs, respectively. Api795 (gu-O(IO)2RPVYOPRPRPPHPRL-OH) and Api794 (gu-O(WO)3RPVYOPRPRPPHPRL-OH) were highly active against P. aeruginosa with minimal inhibitory concentrations of 8–16 and 8–32 μg/mL against Escherichia coli and Klebsiella pneumoniae. Assessed using a quartz crystal microbalance, these peptides inserted into a membrane layer and the surface activity increased gradually from Api137, over Api795, to Api794. This mode of action was confirmed by transmission electron microscopy indicating some membrane damage only at the high peptide concentrations. Api794 and Api795 were highly stable against serum proteases (half-life times >5 h) and non-hemolytic to human erythrocytes at peptide concentrations of 0.6 g/L. At this concentration, Api795 reduced the cell viability of HeLa cells only slightly, whereas the IC50 of Api794 was 0.23 ± 0.09 g/L. Confocal fluorescence microscopy revealed no colocalization of 5(6)-carboxyfluorescein-labeled Api794 or Api795 with the mitochondria, excluding interactions with the mitochondrial membrane. Interestingly, Api795 was localized in endosomes, whereas Api794 was present in endosomes and the cytosol. This was verified using flow cytometry showing a 50% higher uptake of Api794 in HeLa cells compared with Api795. The uptake was reduced for both peptides by 50 and 80%, respectively, after inhibiting endocytotic uptake with dynasore. In summary, Api794 and Api795 were highly active against P. aeruginosa in vitro. Both peptides passed across the bacterial membrane efficiently, most likely then disturbing the ribosome assembly, and resulting in further intracellular damage. Api795 with its IOIO-motif, which was particularly active and only slightly toxic in vitro, appears to represent a promising third generation lead compound for the development of novel antibiotics against P. aeruginosa.

Three-dimensional porous single crystals (PSCs) are a recent development in the growing world of mesoporous material. The mesoporosity allows for the material to retain their nanoproperties whilst being bulk in size. The current work concentrates on chromium oxide and cobalt oxide PSCs formed in the templates SBA-15 and KIT-6. HRTEM is the main technique used in this investigation, looking at the morphology and single crystallinity of these materials. A growth mechanism for the PSC material is proposed based on HRTEM observations. XRD studies revealed that the confinement effect, caused by the mesopores, reduces the temperature for both cobalt and chromium oxide crystallisation, as well as a different intermediate route from the metal nitrates. The properties of chromium oxide PSC are also investigated magnetically and catalytically. Some metal oxides in different templates are also presented, despite no PSC forming. HRTEM work on other nanomaterials, based on collaboration, is also presented.

In-situ polymerization is one of the most efficient methods for production of polymer clay nanocomposites. In-situ polymerization of olefins using coordination catalysts is a type of heterogeneous polymerization. In order to achieve acceptable clay nanolayer dispersion in the polyolefin matrix, the clay layer exfoliation and particle break up during the polymerization are essential requirements. A literature review on polyolefin/clay nanocomposite is given in Chapter 2. In Chapter 3, we present a new mathematical model, which is as an extension of the multigrain model (MGM), to describe the intercalative polymerization and expansion of clay interlayer spaces during polymerization using clay-supported metallocenes. The results from the model show that, under the studied conditions, mass transfer is not a strong factor controlling clay exfoliation and particle break up. If the polymerization active sites are supported uniformly on all clay surfaces, effective exfoliation will be achieved after a relative short polymerization time. In practice, obtaining good dispersion of clay nanolayers with uniform properties requires that the active sites be exclusively located on the clay nanolayer surfaces, and not extracted by the solvent to form a homogeneous solution. Factors favouring active site extraction would result in nanocomposites with poor properties. In addition, high polymerization activities, stable polymerization runs, and ease of supporting are other criteria for a successful in-situ polymerization. For this purpose we established a catalyst supporting method by which most of these requirements were met. In this method, the water content on the clay surface, which is considered as poison for the metallocene catalyst, was used to produce MAO upon reaction with trimethylaluminum (TMA). Using this method, polymerization was highly active in absence of MAO cocatalyst, knowing that MAO cocatalyst promotes active site extraction from the clay surface and results in poor powder morphology. Chapter 4 describes the development of this supporting methodology. Chapter 4 also investigates the effect of the organic modification type existing on the clay surface on the success of catalyst supporting and in-situ polymerization. We found that using the proposed supporting procedure, only tertiary ammonium type modification enhanced the in-situ polymerization, whereas the quaternary ammonium worsened the catalyst supporting efficiency and led to catalyst with poor or no polymerization activity. It is suggested that, in addition to enhancing clay surface-organic solvent compatibility (which facilitates catalyst supporting), the tertiary ammonium cation reacts with the in-situ produced MAO and increases the stability of the cocatalyst bonded to the clay surface. The effect of different polymerization conditions on the polymerization behavior and nanocomposite structural properties, such as catalyst loading during supporting, polymerization temperature and triisobutylaluminum (TIBA) concentration, were studied in Chapter 5. It was found that TIBA acts merely as scavenger. High polymerization activities were obtained with low Al/Zr ratios (Al from TIBA) and increased Al concentration decreased the polymerization activity and also the quality of powder morphology. Catalyst loading in the supporting step showed to have an important role in determining the final properties. The clay particles with higher catalyst loading resulted in better exfoliation and powder morphologies The effect of solvent type during catalyst supporting and polymerization was studied in Chapter 6. It was shown that catalyst supporting in n-hexane resulted in polymerizations with higher activities and polymers with higher molecular weight were produced. Polymerization with catalyst supported in hexane showed different ethylene uptake profiles, suggesting different mechanism of exfoliation. It is suggested that using this catalyst, the clay is mostly exfoliated before polymerization started. Similar to the original clay, the catalyst supporting efficiency on the organically modified clay was close to 100 percent. However, comparing the polymerization activities of these catalysts to those that were supported directly in the reactor just before the polymerization (in-reactor, or in-situ, supported catalysts) shows that a considerable fraction of the active sites are deactivated during the prolonged contact between catalyst and clay support surface. In Chapter 5, it was shown that the in-reactor supported catalyst had considerably higher polymerization activities, up to 40 percent of that of the homogeneous catalyst. Nanocomposites made with in-reactor supported catalysts had powder morphology and nanaolayer dispersion comparable to those made with clay-supported catalysts.