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Silicon-based nanostructures are essential building blocks for nanoelectronic devices and nano-electromechanical systems (NEMS). As the silicon device size continues to scale down, the surface to volume ratio becomes larger, rendering the properties of surfaces and interfaces more important for improving the properties of the nano-devices and systems. One of those properties is the friction, which is important in controlling the functionality and reliability of the nano-device and systems. The goal of this dissertation is to investigate the deformation and friction behaviors of single crystalline silicon nanolines (SiNLs) using nanoindentation techniques. Following an introduction and a summary of the theoretical background of contact friction in Chapters 1 and 2, the results of this thesis are presented in three chapters. In Chapter 3, the fabrication of the silicon nanolines is described. The fabrication method yielded high-quality single-crystals with line width ranging from 30nm to 90nm and height to width aspect ratio ranging from 10 to 25. These SiNL structures have properties and dimensions well suited for the study of the mechanical and friction behaviors at the nanoscale. In Chapter 4, we describe the study of the mechanical properties of SiNLs using the nanoindentation method. The loading-displacement curves show that the critical load to induce the buckling of the SiNLs can be correlated to the contact friction and geometry of SiNLs. A map was built as a guideline to describe the selection of buckling modes. The map was divided into three regions where different regions correlate to different buckling modes including Mode I, Mode II and slidingbending of SiNLs. In Chapter 5, we describe the study of the contact friction of the SiNL structures. The friction coefficient at the contact was extracted from the loaddisplacement curves. Subsequently, the frictional shear stress was evaluated. In addition, the effect of the interface between the indenter and SiNLs was investigated using SiNLs with surfaces coated by a thin silicon dioxide or chromium film. The material of the interface was found to influence significantly the contact friction and its behavior. Cyclic loading-unloading experiments showed the friction coefficient dramatically changed after only a few loading cycles, indicating the contact history is important in controlling the friction behaviors of SiNLs at nanoscales. This thesis is concluded with a summary of the results and proposed future studies. / text

The AsF6- anion, in the crystalline polymer electrolyte PEO6:LiAsF6, was replaced with the larger N(SO2CF3)2- anion. This produced an increase in the room temperature ionic conductivity of 1.5 orders of magnitude. It is believed that the enhancement is the result of the disruption of the electrostatic field around the lithium ions. The presence of the large and asymmetrical N(SO2CF3)2- ion creates a greater number of defects and thus enhances conductivity. These results demonstrate for the first time the enhancement lithium ion conductivity in a crystalline polymer electrolyte by isovalent doping. XF6- anions, in the crystalline polymer electrolyte system PEO6:LiXF6, were replaced by another anion of similar size and shape. A continuous solid solution was obtained for PEO6:(LiAsF6)1-x(LiSbF6)x. These results represent the first continuous solid solution demonstrated in the field of crystalline polymer electrolytes. They also show for the first time an enhancement of conductivity caused only by the size of the dopant anion. The enhancement is believed to originate from changes in the length of the crystal axis and changes in the potential landscape around the lithium ions. The structures of the glyme complexes monoglyme:LiAsF6, hexaglyme:LiAsF6, octaglyme:LiAsF6, undecaglyme:LiAsF6 and dodecaglyme:LiAsF6 have been solved. There structures are discussed and compared to that of PEO6:LiAsF6. The properties of these complexes together with those of diglyme:LiAsF6, triglyme:LiAsF6 and tetraglyme:LiAsF6 were investigated. Triglyme:LiAsF6 has been shown to demonstrate high ionic conductivity of 10-5.5 Scm-1 at 30oC as well as a high transport number of 0.8. These complexes demonstrate the control that crystal structure has over ionic conductivity. These complexes are neither ceramic nor polymeric. A number of the complexes show plastic crystal like solid-solid phase transitions.

This thesis focuses on the geochemistry of secondary minerals, mainly calcite but also others such as fluorite and Ca/Al silicates, precipitated throughout the last 1.5 billion years in fractures of crystalline rock, SE Sweden. The work was based on previous reconnaissance studies and has been possible thanks to access to high-quality drill cores and associated mapping data provided by the Swedish Nuclear Fuel and Waste Management Co (SKB). Concentrations of rare earth elements (REEs) and occasionally other metals were determined in a variety of secondary minerals from fractures (mainly open systems) and veins (mainly sealed systems) and in primary minerals from the bedrock. Stable-isotope composition was measured in the secondary minerals. The overall aim was to define the sources, uptake and fractionation of REEs in calcite, and a few other co-genetic minerals, precipitated throughout the geological history under conditions ranging from hydrothermal to low temperatures. Collectively, the findings of the individual studies show that there is no easy and straightforward control of REE abundance and fractionation in calcite and other minerals in fractures and veins in crystalline bedrock settings. For example, the REE features in calcite vary extensively within sub-generations of single vein-precipitating events, on micro scale in transects across individual veins, and unsystematically over the geological history characterised by successively decreasing temperatures of mineral formation. Although the REE content in, and release from, the crystalline bedrock can have an influence on REE distribution in calcite and other minerals, it is of overall minor importance within a given bedrock domain. The main advantage of determining REEs in secondary minerals in fractures and veins in crystalline rock is therefore, as revealed in this work, to assess the character and evolution of the conditions (including features of the paleofluids) during confined mineral-precipitating events.

The superior material properties of polymer/clay nanocomposites have attracted much research interests in the past years. The hypothesis of polymer stiffening in the vicinity of the nano-c1ay described using the "core-shell" model has not been fully investigated yet. The investigation of the interfacial region by atomic force microscopy (AFM) has provided us with details of the physical state of this region. It was found that the polymer stiffening region could extend as far as 200nm and 100nm from the face and the edge of a nano-clay respectively. Two different degrees of polymer stiffening have been observed from AFM micrographs with the help of amplitude and phase contrasting techniques. The temperature dependant property of the stiffened polymer has been studied using a heating stage, which showed the stiffened polymer was softened with increasing temperature between the studied range, 60°C and 91°C. The relative polymer crystallinity derived from the X-ray diffraction (XRD) data showed a general trend that increases with the clay content, regardless of the clay modification. However, an exception has been observed with the set of bi-axially drawn specimens, of which the highest polymer crystallinity was found to be the neat polymer when compared with the nanocomposites counterpart. It is believed that the presence of nano-c1ay particles restricted the reorientation of the polymer chains upon stress. From the in situ isothermal investigation of polymer crystal growth, it has been found the crystal grown from a nano-clay particle is larger than that from the bulk. This indicated that the crystallisation began at a lower temperature. The nano-clay and polymer crystal orientations have been further studied with X-ray texture analysis. It was found that the polymer chains were not completely aligned alone the extrusion direction as expected. Also, from the annealed specimens it was found that the orientation of the nano-clay particles had been influenced by the relaxation of the polymer chains.

O processo de interferência de RNA refere-se ao silenciamento pós transcricional seqüência-específico de genes em animais e plantas capaz de ser promovido por dsRNA homólogo à seqüência do gene silenciado. Este processo pode ser aplicado como terapia, que apresenta como vantagens a especificidade pelos alvos escolhidos, a possibilidade de tratar uma enorme gama de doenças genéticas, além do fato de ser muito potente e eficaz. Contudo, o principal desafio consiste em manter a estabilidade dos siRNAs nos fluidos biológicos, visto que estes são bastante susceptíveis à excreção renal e a degradação por RNAses. Com isso, reforça-se a necessidade de sistemas de liberação adequados, que sejam capazes de manter a estabilidade dos siRNAs por tempo suficiente para que atinjam os órgãos alvo da terapia e promover sua liberação sustentada. De particular interesse são determinadas proteínas e peptídeos de transdução (PTDs) que podem ser ligados a fármacos hidrofílicos e assim tornam possível com que estes atravessem membranas. Neste sentido, muitos sistemas carreadores não-virais tem sido estudados para a veiculação de siRNA, sendo de cunho inovador o desenvolvimento de sistemas de liberação nanoestruturados baseados em cristais líquidos funcionalizados com peptídeos de transdução de membrana para a veiculação tópica de siRNAs. Desta forma, nanopartículas de cristais líquidos de fase hexagonal contendo ou não os aditivos catiônicos polietileimina (PEI) e oleilamina (OAM) foram funcionalizadas com peptídeos de transdução de membranas TAT (TAT) ou penetratin (PNT). Os sistemas obtidos foram complexados com siRNA por interação eletrostática e caracterizados através de medidas de tamanho de partícula/ polidispersividade, potencial zeta e eficiência de complexação. A citotoxicidade dos sistemas foi avaliada em fibroblastos L929 pelo ensaio do MTT e por citometria de fluxo e a avaliação da transfecção in vitro foi realizada por citometria de fluxo e por microscopia de fluorescência. Os sistemas contendo PEI ou OAM apresentavam potencial zeta positivo e foram capazes de complexar o siRNA adicionado na concentração de 10 ?M. Os estudos em culturas celulares demonstraram que os sistemas contendo ácido oleico (AO) foram mais eficientes quanto à transfecção em células de fibroblastos L929 e esta eficiência de transfecção foi aumentada com a funcionalização com o peptídeo TAT. A partir daí, os sistemas selecionados foram avaliados quanto a penetração cutânea in vivo. Os sistemas nanodispersos formados por MO/AO/PEI proporcionaram uma maior liberação de siRNA na pele e a eficiência de supressão de TNF-alfa em modelo animal de inflamação cutânea foram maiores que formulações controle. Com isso, demonstrou-se que os sistemas desenvolvidos são promissores para a futura aplicação na terapia gênica tópica de doenças cutâneas inflamatórias. / The RNA interference process refers to the sequence-specific posttranscriptional silencing of genes in animals and plants capable of being promoted by dsRNA that are homologous to the sequence of the silenced gene. This process can be applied as therapy, which presents advantages such as the specificity to the chosen targets, the possibility to treat a variety of genetic diseases, besides being very potent and efficacious. However, the major hurdle consists in keeping the siRNAs stability in the biological fluids, because they are susceptible to renal clearance and degradation by RNAses. Thus, there is the need for suitable delivery systems, capable of maintaining the stability of siRNAs for sufficient time so they can reach the target organ in the therapy and promote sustained release. Of particular interest are certain proteins and peptides transduction domains (PTDs) that can be connected to hydrophilic drugs and thus make it possible to cross cell membranes. Within this context, many non-viral vectors have been studied for siRNA vehiculation which makes innovative the present study because it aims at the development of nanostructured delivery systems based on liquid crystals functionalyzed with membrane transduction peptides for the topical vehiculation of siRNAs. Thus, hexagonal phase liquid crystal nanoparticles containing or not the cationinc polyethylenimine (PEI) and oleylamine (OAM) were functionalyzed with membrane transduction peptides TAT (TAT) or penetratin (PNT). The obtained systems were complexed with siRNA by eletrostatic interaction and characterized for particle size, polidispersity, zeta potential and complexation efficiency. The cytotoxicity of the formulations was performed with L929 fibroblasts by MTT assay and flow cytometry and the in vitro transfection was evaluated by flow cytometry and fluorescence microscopy. The systems containing PEI or OAM presented positive zeta potential and could complex siRNA at the concentration of 10 ?M. The cell culture studies demonstrated that the systems containing oleic acid (OA) were the most efficient to transfect L929 cells and the transfection efficiency was enhanced with the functionalization with the TAT peptide. Thereafter, the selected systems were evaluated for the in vivo skin penetration. The nanosdispersed systems composed of MO/OA/PEI functionalyzed with TAT resulted in a higher siRNA penetration and release in the skin, promoting higher TNF alfa supression in animal model of cutaneous inflammation, compared to the control formulations. Hence, we demonstrated that the developed systems are promising for the treatment of inflammatory skin diseases.

O objetivo deste trabalho foi o estudo do íon Fe3+ em monocristais e fibras monocristalinas de LiNbO3, através da técnica espectroscópica da Ressonância Paramagnética Eletrônica (RPE), nas freqüências de 10 e 34GHz, à temperatura ambiente. O Hamiltoniano de Spin para o íon Fe3+ ocupando um sítio de simetria trigonal (C3v) é dado por: H = \'beta\' \'VET.H\' \'VET.g\' \'VET.S\' + \'B20O20+B40O40 . Foram analisadas três amostras de LiNbO3, com diferentes concentrações de Fe3+ e os parâmetros de campo cristalino e fator-g encontrados são: fibra (0.3 mol% de Fe3+) g = 1.9908 \'+OU-\' 0.0002, \'B. SUP. 0 INF. 2\' = 5.4\'+OU-\'0.2x10-2 cm-1 , \'B. SUP. 0 INF. 4\' = -7.7\'+OU-\'1.5x10-5cm-1, monocristal 90 (0.22 mol%) g = 2.0043\'+OU-\'0.0002, \'B. SUP. 0 INF. 2\' = 5.35\'+OU-\'0.25x10-2 cm-1, \'B. SUP. 0 INF. 4\'= - 4.03\'+OU-\'1.4x10-5cm-1, monocristal 99 (0.02 mol%) g = 2.0026\'+OU-\'0.0004, \'B. SUP. 0 INF. 2\' = 5.4\'+OU-\'0.3x10-2 cm-1, \'B. SUP. 0 INF. 4\' = - 8.33\'+OU-\'1.6x10-5cm-1. Foi medida e analisada a dependência angular da largura das linhas nas duas bandas de freqüências. Através de modelos teóricos (Watanabe, Orbach-Das-Sharma, Spinspin, Spin-spin Spin-órbita) calculamos o parâmetro de desdobramento a campo zero, \'B. SUP. 0 INF. 2\', do estado fundamental do íon Fe3+, para determinar qual o sítio que este íon ocupa no LiNbO3. / We report EPR measurements of Fe3+ ion in bulk LiNbO3 single crystals and in the form of fibers. Spin Hamiltonian for the Fe3+ ion in a trigonal symmetry (C3v) site is given by: H = \'beta\' \'VET.H\' \'VET.g\' \'VET.S\' + \'B20O20+B40O40. Measurements were performed at room temperature and two frequency bands, 10 and 34GHz, using three samples of LiNbO3 with different concentrations of Fe3+ g-factor and the crystal field parameters were found to be: for fiber (0.3 mol% of Fe3+) g = 1.9908 \'+OU-\' 0.0002, \'B. SUP. 0 INF. 2\' = 5.4\'+OU-\'0.2x10-2 cm-1 , \'B. SUP. 0 INF. 4\' = -7.7\'+OU-\'1.5x10-5cm-1, for the single crystal 90 (0.22 mol%) g = 2.0043\'+OU-\'0.0002, \'B. SUP. 0 INF. 2\' = 5.35\'+OU \'0.25x10-2 cm-1, \'B. SUP. 0 INF. 4\'= - 4.03\'+OU-\'1.4x10-5 cm-1, and for the single crystal 99 (0.02 mol%) g = 2.0026\'+OU-\'0.0004, \'B. SUP. 0 INF. 2\' = 5.4\'+OU-\'0.3x10-2 cm-1, \'B. SUP. 0 INF. 4\' = - 8.33\'+OU-\'1.6x10-5cm-1. The angular dependence of the line width were also measured and compared with theoretical model. To determine the substitutional site of Fe3+ ion in the LiNbO3 lattice, we calculated the zero field splitting parameter \'B. SUP. 0 INF. 2\' of the ground state, using many theoretical models (Watanabe, Orbach-Das-Sharma, Spin-spin, Spin-Spin Spinorbita).

The slightly water-soluble β-CD and its crystalline inclusion complexes with different molecular weights of poly( ethylene glycol), abbreviated as PEG, were prepared and characterized. The results show that the β -CD forms a crystalline inclusion complex with PEG (MW 600) and PEG (MW 1500) in the solid state. In the solution state, 2D NMR spectroscopy, shows that the PEG is present in the cavity of the P-CD. Coherent cross peaks were observed in both 2D NMR NOESY and ROESY showing correlation between the inner and outer protons of β -CD with the repeating unit of PEG. Scanning electron microscopy (SEM) shows the formation water soluble crystalline complexes between the β -CD with the amorphous PEG (MW 600) and PEG (MW 1500). Crystal formation was supported by wide angle X-Ray studies, W AXD. W AXD patterns for the β-CD/PEG crystalline complexes show new peaks indicative of formation of structures different from the crystalline β-CD.

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Total scattering can be used to study crystalline materials, whose structure presents a periodic arrangement of atoms, as well as disordered materials, such as liquids, glasses or nanomaterials. This thesis work reports three experimental case studies in which different analysis methods were chosen as appropriate on a case-by-case basis. This study demonstrates that total scattering combined with modelling and complementary experimental techniques can guide the understanding of the structure of complex nanostructures. X-ray and neutron total scattering data were collected on multi-walled carbon nanotubes continuously filled with iron and analysed using the program PDFgui for refinement of the pair distribution function and molecular dynamics simulations using the program DL_Poly_4. The analyses show that the iron core is mainly composed of ��-Fe and confirms the dependence of the local ordering on the orientation of the crystallographic axes of iron with respect to the nanowire axis. Prussian blue (Fe4[Fe(CN)6]3 · ��H2O) was synthesised in bulk and nanoparticulate phases using deuterated chemicals; the amount of D2O and H2O in the pores and vacancies, as well as polyvinylpyrrolidone remaining in the nanoparticle samples, were estimated, using an ad hoc modelling procedure of the first few peaks in the neutron PDF function. Models of the structure were refined using the programs PDFgui and RMCProfile. In the last case, a 50Å supercell of the bulk structure with randomly distributed stoichiometric vacancies and D2O and H2O molecules occupying both the pores and the vacancies was used as starting atomic configuration. The CaO/CaCO3 family of materials consists of a series of samples that have undergone carbonation and/or calcination. The X-ray and neutron pair distribution function data were compared to the theoretical PDF of the CaO and CaCO3 phase, generated using the program GULP, that produces PDF functions based on the spectrum of phonon frequencies of the material. The analysis shows that the carbonation is almost completed already after 2 minutes of carbonation and the structure remains stable under further carbonation.