A simple method for increasing the stable temperature range of the liquid crystalline blue phase is demonstrated, by mixing a non-mesogenic polymer of low molecular weight into the blue phase material. In a mixture of cholesteryl benzoate and cholesteryl nonanoate the addition of polystyrene increased the stable blue phase range from 0.5K to 12K. This was measured strictly on heating from the chiral nematic phase through the blue phase in order to minimise non-equilibrium effects, and is one of the largest ranges so measured. The stability range can be closely tuned by changing the polymer concentration and molecular weight. The maximum range found by adding a particular compound seems only to depend on its saturation point in the liquid crystal, and the dependence of the range on concentration is non-linear. These features were explained by a numerical model of a blue phase unit cell incorporating the mean field Flory-Huggins and Maier-Saupe theories where the polymer could fill the high energy defect regions. Two of the oligomers which are shown to stabilise the blue phase are fluorescent, at 450nm and 500nm respectively, and it is proposed that tests on these mixtures could reveal photonic effects caused by the concentration of the fluorophores in the blue phase defect regions. The twist-grain boundary (TGB) phase is present in mixtures of cholesteryl oleyl carbonate and cholesteryl nonanoate over a range of up to 0.3K. The addition of polystyrene has no effect on the stability of the TGB phase. Conventional, in situ UV-initiated polymer stabilisation does not appear to stabilise the TGB phase, but is capable of stabilising over at least 30K the micron-size filaments which appear in the TGB phase when it is heated from the smectic phase in a cell with homeotropic alignment. Some notes are made on the causes and structure of this filament texture, and it is observed that the filaments tend to grow with a characteristic curvature. It is shown theoretically that the correct material could stabilise the TGB phase similarly to the polymers in the blue phase, by extending the previous model to include the Kobayashi-McMillan theory of smectic ordering. A second theoretical model of chirality around the transition to the smectic phase is then presented which takes account of fluctuations, based on an analogy with the state of a smectic-forming material infiltrated into an aerogel. A phase resembling the TGB phase emerges from this model. The model gives two first order transitions in accordance with experiments on the TGB phase, and reflects other experimental pitch and calorimetry measurements too. The electrochemical polymerisation of an acrylate monomer in the nematic and smectic-C* phases is investigated. 30-100V is applied across a cell containing the liquid crystal-monomer mixture, with no additional initiating compound. In both phases, the texture during polymerisation is frozen in by the polymer formed. In a nematic phase in a cell with initially planar alignment, the director in the field off state can be observed to tilt toward the homeotropic over a number of hours. In the ferroelectric case, as well as the textural freezing there is a somewhat reversible agglomeration of polymer strands into micron-scale structures. Scanning electron microscopy reveals a range of structures on both electrode surfaces, including in the nematic case corrugations with a periodicity of 500-750nm. There is no evidence of a polymer network spanning the thickness of the cell - rather the liquid crystal seems to be realigned by a polymer film at the electrode surfaces.

Orientadores: Maria Alvina Krähenbühl, Mariana Conceição da Costa / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-18T18:50:59Z (GMT). No. of bitstreams: 1 Souza_JackineyAlfaia_M.pdf: 4286417 bytes, checksum: 4e844ea6eeef919244e2856b211b0a98 (MD5) Previous issue date: 2011 / Resumo: Os triacilgliceróis, oriundos da combinação de um glicerol com ácidos graxos, são os principais componentes dos óleos e gorduras de origem vegetal e animal. Os ácidos graxos e os triacilgliceróis presentes nos óleos e gorduras conferem-lhes propriedades que possibilitam ou não seu uso na formulação de muitos produtos das indústrias químicas, alimentícias e farmacêuticas. Nos últimos anos, o interesse por essas matérias-primas tem crescido e, junto com esse crescimento, a busca por novas tecnologias e pelo aprimoramento dos processos de separação que as envolvem. Para o desenvolvimento e aprimoramento destes processos de separação, é importante estar de posse de informações sobre as propriedades físico-químicas de tais componentes. Desse modo, a construção dos diagramas de fase destes compostos traz avanços na compreensão das transições de fases e podem levar a aplicações mais proveitosas de tais compostos. Para a construção dos diagramas dos triacilgliceróis pesquisados neste trabalho foram usados dados obtidos através da microscopia óptica, que possibilita a aquisição de filmes e imagens durante todo o processo de cristalização ou fusão de uma determinada amostra sendo possível visualizar as fronteiras entre as diferentes regiões de equilíbrio. A descrição do comportamento dos sistemas tripalmitina + triestearina e óleo de palma + triestearina no equilíbrio sólido-líquido é importante para a melhor compreensão do diagrama de fases destes / Abstract: Triacylglycerols, formed by a combination of glycerol with fatty acids, are the main components of vegetable and animal oils and fats. Fatty acids and triacylglycerols present in oil and fatty confers properties that can to allow or not their use in formulation of many chemical, food and in pharmaceutical products. In the last years the interest in these raw materials has grown and with this growth the search for new separation technologies and by the improvement of separation processes of such substances also increases. The development and improvement of separation processes requires the knowledge of physicochemical properties and of the equilibrium conditions of such components. In this way, the construction of phase diagrams of these compounds brings advances in the understanding of phase transitions and can lead to more useful applications of such compounds. The phase diagrams investigated in this study were constructed using data determined by optical microscopy, an experimental technique that allows capture movies and pictures throughout the crystallization or melting process of sample. This technique makes possible delimitate the boundaries between the different equilibrium regions of a system / Mestrado / Desenvolvimento de Processos Químicos / Mestre em Engenharia Química

Master thesis deals with the influence of polyvinylacetate, polycaprolactone, poly(butylene-adipate-co-terephtalate) and talc, ethylenevinylacetate, polyethylene glycol and monosodium citrate on the flow properties, mechanical properties and crystallization ability of PLA. The flow properties were studied using the melt flow index and mechanical properties were studied using a tensile test. The crystallinity was studied by differential scanning calorimetry and on a polarization optical microscope equipped with hot stage. Isothermal crystallization was performed at 95 and 105 °C for 3 h and non-isothermal crystallization was performed with a calorimeter at two cooling rates (1 and 10 °C/min). Upon the isothermal crystallization at 95 °C, the formation of denser crystalline structure was observed and the content of crystalline phase increased in most of the samples. The formation of spherulitic structure was observed at 105 °C in samples with 30 % PVAc, 30 % EVA and PEG. Reducing the cooling rate to 1 °C/min at non-isothermal crystallization had nearly no effect on the crystallization process of the most samples; the content of crystalline phase increased in the samples containing PBAT and PEG, which revealed double melting peak during subsequent heating. The crystalline fraction was the most significantly affected by the addition of PEG. All added polymers except PVAc affected the mechanical properties; PBAT, PCL, EVA and PEG increased the strain and decreased the strength and modulus of elasticity. The samples containing monosodium citrate showed unsatisfactory mechanical properties and could not be measured. The samples containing higher concentration of EVA copolymer showed the phase separation.

The aim of this work is to introduce the principle of scanning in optical microscopy. This thesis deals with problem of parameters of display process and their influence on the results and measurements of these parameters. In detail there is analyzed the depth of field of the optical system and there are established some possibilities of theoretical and experimental determination. Part of this thesis is the realization of the measurement work place and program providing experimental depth of field based on different measurement methods. The conclusion is devoted to the practical part, which has the task to monitor settings and optical systems and their impact on depth of field.

This diploma thesis is focused on encapsulation probiotics and co-encapsulation with some types of prebiotics. In theoretical part is aimed to probiotics, their general characteristics and application of probiotics in food industry. There are described prebiotics and their classification, there is described principles of encapsulation and encapsulation techniques. Methods, which are used for analysis of particles and encapsulation components were introduced too. The experimental part describes methods of prebiotics characterization by high performance liquid chromatography, thin layer chromatography and spectrophotometric methods. Cultivation of probiotics with prebiotics - hydrolyzed and non-hydrolyzed wad tested. Using flow cytometry cell viability was measured too. Finally probiotics and prebiotics were encapsulated, mainly by encapsulator machine. Long-term stability of particles during 6 week storage was observed. The particles were exposed to effect of artificial intestinal, gastric and bile juices.

Les sources de paires de photons corrélés sont des composants clés nécessaires aux réseaux de télécommunications quantiques. Réaliser directement ces sources à partir de fibres optiques permet de minimiser les pertes d'insertion. Nous proposons de concevoir une telle source à partir d'une fibre optique étirée. La fibre étirée possède un diamètre pouvant descendre à moins de 500 nm sur une longueur de quelques centimètres. Le faible diamètre de la section étirée favorise les effets non linéaires, tandis que les sections non étirées permettent de connecter avec de très faibles pertes cette fibre étirée avec les fibres des réseaux de télécommunication.Dans cette thèse, nous présentons donc une conception d’une nouvelle source de photons corrélés totalement fibrée à base de fibres standard de télécommunications (SMF28) étirées. Pour produire ces paires de photons nous utiliserons la fluorescence paramétrique due à la brisure de symétrie à la surface de la nanofibre en silice.Nous avons développé une technique de mesure par microscopie optique, qui permet de mesurer tout le profil de la fibre étirée avec une résolution nanométrique bien au-delà de la limite de diffraction.En parallèle, nous avons modélisé la susceptibilité non linéaire de surface de second ordre en prenant en compte l’aspect vectoriel de la propagation du champ optique dans une microfibre à deux ou trois couches. Dans un second temps, nous définissons les accords de phase modaux qui sont nécessaires pour l’obtention d’une forte fluorescence paramétrique. Nous dimensionnons cette nanofibre pour une bonne optimisation de l’efficacité de génération des paires. L'ensemble du processus de création de photons sera modélisé. / Sources of correlated photon pairs are key components required for quantum telecommunications networks. Implementing these sources directly with optical fibers minimizes the insertion losses. We propose to design such a source from a tapered optical fiber.The tapered fiber has a diameter lower than 500 nm over a length of a few centimeters. The small diameter of the tapered section favors the non-linear effects, while the unstretched sections make it possible to connect this tapered fiber with the fibers of the telecommunication networks with very low losses.In this thesis, we present a design of a new source, fully fibered of correlated photons based on standard telecommunications tapered fibers (SMF28). To produce these pairs of photons we will use the parametric fluorescence due to symmetry breaking at the surface of a silica nanofiber.We have developed an optical microscopy measurement technique to measure all the profile of tapered fibers with nanometer resolution far beyond the diffraction limit.In parallel, we modeled the second-order nonlinear surface susceptibility by taking into account the vector aspect of the propagation of the optical field in a two or three-layered microfiber. In a second step, we define modal phase matchings that are necessary to obtain a strong parametric fluorescence. We size this nanofiber for a good optimization of pairs generation efficiency. The entire process of photon creation will be modeled.

In this work, we use optical techniques to provide insight into how various components within electrochemical cells can impart apparent heterogeneity to single gold nanoparticle electrodes. Optical methods are advantageous in comparison to traditional electrochemical techniques due to their high sensitivity and spatial resolution, allowing us to study the impact of heterogeneity with single nanoparticle and single molecule sensitivity. Throughout the course of this dissertation, two optical techniques are discussed in detail, dark-field microscopy, and single molecule fluorescence imaging. We first began by studying the impact of the substrate using dark-field microscopy to monitor the electrodissolution kinetics of gold nanoparticles on thin films of tin-doped indium oxide (ITO), which is a commonly used supporting electrode for correlated optical and electrochemical studies. We found that ITO from two different suppliers showed marked differences in the gold electrodissolution kinetics, with ITO from one of the suppliers even showing poor sample-to-sample reproducibility across substrates within the same lot number. These results showed that the supporting electrode cannot be ignored when performing single nanoparticle structure-function studies. In the second work, we analyzed the electrodissolution of gold nanoparticles on well-behaved ITO substrates to investigate heterogeneity in their electrodissolution kinetics. The rate constants associated with the electrodissolution of Au NPs were extracted by fitting the intensity-time traces to a first-order kinetic model. We found that a non-negligible population of Au NPs didn’t fit the predictive kinetics model leading us to further probe whether surface effects play a role in the electrodissolution process. Super-localization imaging was used to track the center position of the Au NPs as they electrodissolved revealing three distinct electrodissolution behaviors, and a mechanism for the electrodissolution of Au NPs was proposed. Furthermore, calcite-assisted localization and kinetics (CLocK) microscopy was used to visualize changes in anisotropy and provide information as to how the shape of the Au NP changes as it electrodissolves. Lastly, in our third work, we provide insight as to how heterogeneity from all the different components of a single nanoparticle electrochemical sample impacts the apparent electrode performance. We proposed dark-field microscopy and single molecule fluorescence imaging as tools capable of detangling these effects. Moreover, we established Cresyl Violet as a reporter of single molecule electrochemistry and developed a two-working electrode optical system capable of visualizing single molecule activity. Lastly, we explored the relationships between Au NP size, Cresyl Violet activity and Au NP electrodissolution and found no clear trend between them suggesting the need for more studies to deconvolute these effects and provide meaningful insight into the structure-property relationships. Overall, this dissertation highlights the complexity of single nanoparticle studies and how heterogeneity can be induced from all the components of an electrochemical cell. / Chemistry

Block copolymers, long chain molecules of two distinct chemical species joined covalently to one another, have long been known to form organized structures on the nanoscopic level. For example, if the two chains are the same length a lamellar structure results . In this work we show how this internal structure causes distinct deviation from 'normal' fluid behavior. We begin with the observation of block copolymer droplets with atomic force microscopy. We note the droplets form nearly conical shapes in stark contrast to the usual spherical cap. These droplets are found t o spread at an incredibly slow speed, and to have interesting instabilities in their wetting layer. We move on to studies of completely wet substrates (i.e. thin films) near the order-disorder transition of the material. Here we directly observe, with optical microscopy, a change in the fundamental spacing of the diblock's internal structure. This represents a superior method of measurement of the Flory-Huggins interaction parameter, which we verify in several ways. We also use the change in lamellar thickness to drive diffusion from one layer to another, and by similar measurements we can determine the kinetics of diffusion between the lamellar layers. In the last study we measure the lamellar edges on a gradient thickness sample with optical microscopy. In so doing we can directly observe surface induced ordering, and for the first time, can precisely resolve the near surface ordering dynamics. / Thesis / Doctor of Philosophy (PhD)

No description available.

<p>This thesis explores the ablation and texturing of synthetic single crystal diamond under ultrashort laser pulse irradiation in rough vacuum ambient conditions. Experiments were performed with a 1 kHz repetition rate titanium sapphire laser system producing pulses at 800 nm central wavelength and 150 fs pulse duration. First, the production of ordered periodic nanostructures (ripples) on the diamond surface was characterized and the periodicity of these structures was analyzed against irradiation parameters. Ripples were usually found to fall into one of two categories: one with a spatial period near the irradiation wavelength and one with a spatial period near λ/2n, where λ is the central laser wavelength in air and n is the refractive index of diamond at λ. The spatial periods were plotted against irradiation conditions including the peak fluence, number of incident pulses, and the angle of incidence. Unique outcomes arising out of complex irradiation conditions were also explored. Second, the ablation thresholds for single pulse up to 1000 pulse irradiation were determined using the <em>D</em>² method at both the fundamental central wavelength (800 nm) and the second harmonic (400 nm). The single 800 nm pulse ablation threshold for synthetic single crystal diamond was determined to be 2.3 J/cm² with an incubation coefficient of 0.54. The single 400 nm pulse ablation threshold was determined to be 1.5 J/cm² with an incubation coefficient of 0.73.</p> / Master of Applied Science (MASc)