Nonlinear, nonlocal optical media has emerged as an ideal setting for experimentally observing and studying spatial optical solitary waves which otherwise cannot occur in Kerr media. Of particular interest is the eventual application to all-optical circuits. However, there is considerable work left to do on the theoretical end before this is a possibility. In this thesis we consider three problems. The first is how to solve the governing equations for optical beam propagation in the particular medium of the nematic liquid crystal (NLC), which is used as a prototypical example, exactly and approximately. In this respect we provide the first known, explicit solutions to the model as well as a comprehensive assessment on how to use variational, or modulation theory, in this context. This leads to the discovery of a novel form of bistability in the system, which shows there are two stable solitary wave solutions for a fixed power or L2 norm. We then consider how to approximate solutions for optical solitary waves propagating in a more general class of nonlocal nonlinear media using asymptotic methods. This is a long open problem and is resolved in the form of a simple to implement method with excellent accuracy and general applicability to previously intractable models. We conclude with the discovery and characterization of an instability mechanism in a coupled, defocussing nonlinear Schrodinger system. We show there is no stable, coupled, localized solution. This result is compared with the more well-studied bright solitary wave system and physical and mathematical explanations are offered.

As telas de cristal líquido (LCD) são usadas em TVs, calculadoras, telefones celulares, computadores (laptop e palm), vídeo games e agendas eletrônicas. O aumento e a rápida obsolescência tecnológica desses dispositivos eletrônicos causa o descarte excessivo de LCDs usados, diminuindo a vida útil de aterros. Por isso é necessário o desenvolvimento de uma metodologia de reciclagem de LCDs, que deve ser iniciada pela caracterização de LCDs, seguida do processamento das telas com objetivo de separar os materiais, utilizando algumas técnicas de Tratamento de Minérios. Os ensaios realizados para caracterização dos componentes da tela foram: solubilização em solvente; chama; infravermelho; DSC; MEV com EDS; difração de raios-X; e perda ao fogo. A seqüência identificada dos materiais de fora para dentro foi: triacetato de celulose, poli (álcool) vinil dopado com iodo, triacetato de celulose, cristal líquido, vidro com ITO, triacetato de celulose, poli (álcool) vinil dopado com iodo, triacetato de celulose, polímero não identificado com mica. Após a caracterização foi realizada a etapa de liberação de materiais, utilizando-se de moinhos de rolos, de disco, de martelos, de bolas, separação por álcool, imersão em nitrogênio líquido, e solubilização em água, para separação dos materiais recicláveis. A operação de Tratamento de Minérios que apresentou cerca de 98% de separação dos materiais foi com o moinho de martelos. Este material pode ser usado eventualmente como substituto da areia. Para viabilizar a separação dos materiais existe a necessidade de alteração no projeto das LCDs. / Liquid crystal displays (LCD) are used in TVs, calculators, mobiles, computers (laptop and palm), video games and electronic agendas. The increasing and fast technological obsolescence of these electronic devices causes their extreme discard, decreasing the landfills useful life. Therefore it is necessary the development of a LCD recycling methodology which must be started by the LCDs characterization, followed by the displays processing with the objective of separating materials, using some Ore Treatment techniques. The characterization tests of the LDC components: solvent solubilization, flame, infrarred, DSC, MEV with coupled EDS, X-ray diffraction and loss on fire. The sequence of the identified materials were: celulose triacetate, poly vinyl alcohol with iodine, cellulose triacetate, liquid cristal, ITO glass, cellulose triacetate, poly vinyl alcohol with iodine, cellulose triacetate, polymer with muscovite. Following the characterization, the materials releasing step was performed. Firstly the LCDs were grinded using different kinds of mills, then the grinded materials were passed through several separation tests: separation on alcohol, immersion in liquid nitrogen and solubilization in water. Hammer milling present the best results. The project of the LCDs should be improved in order to allow the materials separation.

Orientador: Rosiane Lopes da Cunha / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-25T04:10:36Z (GMT). No. of bitstreams: 1 Santana_RejanedeCastro_D.pdf: 3540578 bytes, checksum: 6ff1903cc61cd3c02a5bc21f49dbd351 (MD5) Previous issue date: 2014 / Resumo: Microemulsões (ME) e cristais líquidos (CL) são sistemas auto-organizáveis com potencial capacidade de solubilização de compostos lipofílicos e hidrofílicos. Microemulsões são formadas por gotas de tamanho reduzido e apresentam aspecto translúcido, enquanto os cristais líquidos apresentam estrutura mais complexa, com fases lamelares, hexagonais ou cúbicas. Entretanto, o estudo de ME e CL compostos por ingredientes biocompatíveis ainda é restrito, assim como a avaliação dos efeitos de cada componente e da temperatura na estrutura e reologia dos sistemas. Desta maneira, o objetivo deste trabalho foi avaliar a estrutura e reologia de ME e CL compostos por água, misturas de surfactantes (Tween 80, Tween 20, Span 80, Span 20 e lecitina), triacilglicerol de cadeia média (TCM) e etanol, em diferentes proporções de TCM:etanol (1:0, 2:1 e 1:2). Diferentes estruturas e comportamentos reológicos foram obtidos dependendo da concentração de água, etanol, tipo de surfactante e temperatura. Inicialmente, o estudo de sistemas contendo somente Tween 80 como surfactante mostrou que o incremento de etanol diminuiu a região de cristal líquido e aumentou a área de microemulsão no diagrama de fases, expandindo a região de micelas reversas para maiores concentrações de água. Além disso, maiores concentrações de etanol produziram sistemas com menor tamanho de partícula (DLS), menor distância (d) entre os planos das estruturas (SAXS) e baixa pseudoplasticidade. Já a avaliação de sistemas contendo inicialmente 70 % (m/m) de Tween 80 como surfactante único e diluídos em água (linha de diluição 7) mostrou que a baixas concentrações de água formaram-se microemulsões A/O com comportamento Newtoniano e tamanho de gota nanométrico. Em concentrações intermediárias de água, cristais líquidos com elevada distância (d) entre os planos das estruturas e de reologia complexa foram produzidos, incluindo fluidos viscoelásticos e com comportamento dependente do tempo de cisalhamento (tixotrópico e anti-tixotrópico). Sistemas com concentração intermediária de água com ausência ou baixa concentração de etanol apresentaram temperatura de transição próximo a 50 °C. Estruturas cúbicas e hexagonais com comportamento do tipo gel foram produzidas a 25 °C, enquanto sistemas desordenados com menor distância (d) entre os planos da estrutura e comportamento do tipo solução diluída foram observados a altas temperaturas. Na última etapa, sistemas compostos por diferentes misturas de surfactantes foram avaliados. Estruturas do tipo micelar e hexagonal prevaleceram em sistemas compostos por Tween, enquanto estruturas lamelares foram também observadas em sistemas de Tween/Span e Tween/Lecitina. Estruturas cúbicas foram observadas somente nos sistemas Tween 80/Lecitina. Uma relação entre os parâmetros estruturais, comportamento reológico e propriedades das misturas de surfactantes (parâmetro crítico de empacotamento - P, e balanço hidrofílico-lipofílico - BHL) foi observada. Misturas de surfactantes com menor BHL produziram cristais líquidos pseudoplásticos e viscoelásticos em elevadas concentrações de surfactante. A maior pseudoplasticidade foi associada à estrutura cristalina ordenada susceptível à quebra ou reorientação sob cisalhamento. Além disso, as propriedades das misturas de surfactantes influenciaram no fenômeno de partição do etanol, levando a maiores parâmetros de cela (a) em sistemas de menor BHL. Conhecendo os efeitos da temperatura, composição, concentração e interação entre componentes, as propriedades dos sistemas, como estrutura e reologia, podem ser preditas ou moduladas de acordo com o interesse tecnológico / Abstract: Microemulsions (ME) and liquid-crystals (LC) are self-assembly structures with potential ability to solubilise both lipophilic and hydrophilic components. Microemulsions are translucent systems formed by small swollen micelles, while liquid crystalline phases exhibit a more complex structure, as lamellar, hexagonal and cubic phases. However, the use of biocompatible ingredients in these systems was scarcely explored, as well as the effect of each component and temperature on the system structure and rheology. Thus, the aim of this work was to evaluate the structure and rheology of ME and LC systems formed by water, surfactant mixtures (Tween 80, Tween 20, Span 80, Span 20 and lecithin), medium-chain triacylglicerol (MCT) and ethanol, at different MCT:ethanol ratios (1:0, 2:1 and 1:2). Systems with different structures and rheology were produced according to water and ethanol concentration, surfactant type and temperature. In the first part of this work systems composed by Tween 80 as surfactant showed that the ethanol increment decreased the liquid crystalline area and increased microemulsion area in the pseudo-ternary diagram, expanding micelles production up to higher water content. Moreover, higher ethanol content produced systems with smaller particle size (DLS), smaller correlation distance (d) (SAXS) and lower pseudosplasticity. The evaluation of dilution line 7 of systems with only Tween 80 as surfactant showed that at W/O microemulsions with Newtonian behavior were produced at low water content. At intermediary water contents, liquid crystalline phases with larger correlation distance (d) and complex rheology were produced, including viscoelastic, thixotropic and anti-thixotropic behavior. Systems with intermediary water content and low water content (or absence) of ethanol showed temperature transition around 50 °C. Cubic and hexagonal structures with gel behavior were produced at 25°C, while disordered systems with smaller correlation distance and dilution solution behavior were produced at high temperatures. In the last part of this study, systems composed of different surfactant mixtures were evaluated. Micelle and hexagonal were the main phases observed on systems composed of Tween, while lamellar structures were also observed in Tween/Span and Tween/lecithin systems. Cubic structures were observed only in Tween 80/lecithin systems. A relationship between structural parameters, rheological behavior and surfactant mixture properties (critical packing parameter - CPP, and hydrophilic-lipophilic balance ¿ HLB) was observed. Surfactant mixtures with lower HLB produced pseudoplastic and viscoelastic liquid crystalline phases at high surfactant concentrations. The higher pseudoplasticity was associated with a structure susceptible to reorientation or to the structure broken under shear. In addition, characteristics of surfactant mixture affected the ethanol partition phenomenon, leading to higher lattice parameters (a) in systems with lower HLB. This discussion concerning the effects of temperature, composition, concentration and components interactions could be used to predict and design system properties, as structure and rheology, according to a variety of technological interest / Doutorado / Engenharia de Alimentos / Doutora em Engenharia de Alimentos

Abstract The indirect spin-spin coupling is a molecular internuclear interaction, which is observable by utilizing NMR spectroscopy. This coupling, denoted J, is a second-order tensorial property that consists of rank-0, 1, and 2 components. The present thesis deals with the experimental determination of the rank-0 and rank-2 components of J tensors for different pairs of interacting nuclei by utilizing liquid crystal NMR (LC NMR) method. The experimental information of the rank-2 component of the J tensor appears as Janiso, a combination of tensor elements. In LC NMR, Janiso is manifested as a contribution to the experimental anisotropic coupling (Dexp ) that contains also the corresponding internuclear dipolar coupling, D. The dipolar coupling is defined by the molecular geometry and average orientation, and affected by the molecular motions. Therefore, the molecular geometry and orientation have to be determined together with the studied Janiso couplings. The contributions to D couplings arising from the molecular vibrations and solvent-induced deformation of the molecular geometry are taken into account in the analysis of the experimental data; the contributions are presented briefly in this thesis. The LC NMR experiments are performed for C6H6, HCONH2, C2H2, C2H4, C2H6, 1,4-C6H4F2, CH3F, CH2F2, CHF3, and CSiH6 molecules, and some important aspects of the liquid crystal NMR method are discussed. The obtained information of J tensors is compared with the theoretical ab initio MCSCF results. Finally, the systematics of the J tensors in different structural surroundings is found and the significance of the indirect contribution to the corresponding Dexp coupling is discussed.

In order to meet the increasingly strict emissions targets required in modern civil aviation, lean burn combustors are being pursued as a means to reduce the environmental impact of gas-turbine engines. By adopting a lean air/fuel mixture NOx production may be reduced. The increase in proportional amount of high pressure air entering directly into the combustor reduces the amount available for cooling of the combustor liner tiles. A reduced mass of air places restrictions on the porosity of cooling arrays, requiring a departure from applications of pedestal and slotted film cooling typically used to cool double skin combustor liners. An alternative approach applied to lean burn combustors places impingement and effusion arrays on the cold and hot skins respectively for cooling of both sides of the hot liner skin. Although impingement cooling is well established as a means of promoting forced convection cooling, there are many areas on a liner tile where cooling behaviour is not well characterised. Additionally, film cooling reduces combustive efficiency and increases the production of NOx and CO, prompting interest in reducing its use in combustor cooling. The research for this thesis has focussed on investigations into current and proposed geometries to identify methods to enhance cold side cooling in lean burn applications. A fully modelled combustor liner tile has been used for investigation into the impact of structural and pressure blockages on cold side cooling performance of an impingementeffusion array using a transient liquid crystal technique to measure heat transfer performance. Research has found structural blockages can reduce heat transfer performance to ~60% of typical values, with crossflow development due to pressure blockage producing similar reductions in Nusselt values to ~70% of typical. A second investigation explored enhanced cooling geometries combining a distributed impingement feed over roughened channels of pedestals at variable height (H/D) and pitch (P/D). A newly proposed 'Shielded Impingement' concept combines full height pedestals, to protect impingement jets from developing crossflow, with quarter height pedestals for turbulence enhancement of crossflow cooling. The research has found that Shielded Impingement geometries displayed the strongest cooling performance of all tested designs due primarily to increased downstream Nusselt numbers. Pressure losses were comparable to short pedestal geometries, with little apparent effect of full height pedestals. Low pressure losses mean that application to extended channels in line with the full tile geometry is possible.

This thesis comprises an account of research carried out into the flexoelectro-optic effect, as observed in chiral nematic liquid crystals, and its potential for application in fibre optic communications components. The flexoelectro-optic effect provides a mechanism of fast, analogue rotation of the optic axis in chiral nematic materials via the application of an electric field to the sample. In particular, bimesogenic liquid crystal materials exhibit very large flexoelectro-optic tilt angles, and a large tilt angle per unit field in comparison to other mesogenic materials. In this work a new geometry for the flexoelectro-optic effect is developed in which the chiral nematic liquid crystal is aligned with its helical axis along the normal to the cell walls and the electric field is applied in the plane of the cell. It is shown that polymer stabilization of this device by the addition of a small percentage of reactive mesogen to mixture increases greatly the ability of the device to withstand high amplitude a.c. electric fields. Applied fields of up to 6.8 V/μm are shown to induce a maximum birefringence of ∆n=0.037, due to both flexoelectric and dielectric coupling, and ∆n=0.012 due to flexoelectric coupling only in a sample based on symmetric difluorinated bimesogens. This induced birefringence is shown to consistently respond to field application and removal on the sub millisecond timescale. Polymer stabilization of the same mixtures in the uniform lying helix texture is shown to affect the electro-optic response of the samples in a manner which is dependent on the concentration of reactive mesogen used, and the temperature at which the reactive mesogen is cured. A concentration of approximately 3% weight/weight, however, has little detrimental impact on the device characteristics, and curing of the sample at the lower end of the chiral nematic temperature range is shown to allow optimization of both tilt angle and response time of the samples. The effect is also employed to demonstrate a new method of fast electrical tuning of the output wavelength from chiral nematic photonic band edge lasers. An 8nm shift was induced in these devices by a 3.5 V/μm applied field.

In this work, we calculate the density of photon states (DOS) of the normal modes in dye-doped chiral nematic liquid crystal (LC) cells in the presence of various loss mechanisms. Losses and gain are incorporated into the transmission characteristics through the introduction of a small imaginary part in the dielectric constant perpendicular and along the director, for which we assume no frequency dispersion. Theoretical results are presented on the DOS in the region of the photonic band gap for a range of values of the loss coefficient and different values of the optical anisotropy. The obtained values of the DOS at the photonic band gap edges predict a reversal of the dominant modes in the structure. Our results are found to be in good agreement with the experimentally obtained excitation thresholds in chiral nematic LC lasers. The behaviour of the DOS is also discussed for amplifying LC cells providing an additional insight to the lasing mechanism of these structures. We subsequently investigate the spontaneous emission properties, under the assumption that the electronic transition frequency is close to the photonic edge mode of the structure (resonance). We take into account the transition broadening and the decay of electromagnetic field modes supported by the so-called 'mirror-less' cavity. We employ the Jaynes-Cummings Hamiltonian to describe the electron interaction with the electromagnetic field, focusing on the mode with the diffracting polarization in the chiral nematic layer. As known in these structures, the density of photon states, calculated via the Wigner method, has distinct peaks on either side of the photonic band gap, which manifests itself as a considerable modification of the emission spectrum. We demonstrate that, near resonance, there are notable differences between the behaviour of the density of states and the spontaneous emission profile of these structures. In addition, we examine in some detail the case of the logarithmic peak exhibited in the density of states in 2D photonic structures and obtain analytic relations for the Lamb shift and the broadening of the atomic transition in the emission spectrum. The dynamical behaviour of the atom-field system is described by a system of two first order differential equations, solved using the Green's function method and the Fourier transform. The emission spectra are then calculated and compared with experimental data. Finally, we detail a new technique for the pumping of dye lasers which requires no moving parts or flushing mechanisms and is applicable to both solid state and liquid based devices. A reconfigurable hologram is used to control the position of incidence of a pump beam onto a dye laser and significant increases in device lifetimes are achieved. The technique is also applied to wavelength tune a dye laser. This offers access to higher repetition rates and larger average output powers. With higher repetition rate pump lasers it is feasible that the approach could allow such organic lasers to reach operating frequencies on the order of MHz. The unique nature of the adaptive pumping method also allows precise control of the spatial wave-front and configuration of the pumping wave which allows greater versatility and functionality to be realised. It is possible to envisage that novel pump beam profiles that optimise propagation through the medium could also be demonstrated.

Polarized Raman Spectroscopy (PRS) is one of the experimental methods which can be employed to deduce orientational order parameters, e.g. 〈P_200 〉, 〈P_400 〉, in liquid crystals from the experimental depolarization ratio graph via fitting. However, it has long been known that the order parameters deduced from the different vibrational modes are found to be different within the same sample. As a result, only certain vibrational modes can be reliably selected for analysis, limiting the application of PRS. The possible explanations are discussed in this thesis. The first explanation is given by considering a dipole tilt β_0 which is defined as the tilt angle of the dipole vibrational direction and the molecular long axis. A second explanation comes from assuming different vibrational symmetries, i.e. cylindrical or elliptic cylindrical. Molecular biaxial order parameters are introduced in both explanations. A systematic check via calculation shows that a common set of order parameters (including molecular biaxial order parameters) can be obtained with different depolarization ratio graphs when the explanations are considered. Both depolarization ratio graphs can also agree well with that obtained from phenyl and cyano stretching modes experimentally. A supplementary discussion shows that by using the first explanation, 〈P_400 〉 which, in previous fitting, shown an excessive value by using cyano stretching mode is reduced (15% reduced at β_0=15°, 〈P_402 〉=0.0536). PRS is also employed to analyse the order parameters in a bent-core system using a molecular model with the bend angle Ω and tilt angle B_0. The effects of each of the uniaxial and phase biaxial order parameters are considered. With a total Raman tensor generated by the sum of Raman tensor from each arm, reasonable uniaxial order parameters fitting values can be obtained from PRS without considering biaxial order parameters. These results agree well with those deduced from the refractive index measurements, which shows a new approach to the investigation of bent-core systems. However, it is also shown that introducing phase biaxial order parameters can’t provide robust fitting, leading inaccurate fitting values in the end. Several different liquid crystals (5CB, E7, HAT-6 and SSY) have been examined on seeking graphene/graphene oxide dispersions in liquid crystal systems. Unfortunately, no stable dispersion was obtained by applying simple experimental techniques. However, a highlight comes from the test of a lyotropic liquid crystal formed by a discotic molecule in NMP suggesting a possible dispersion medium for graphene. Meanwhile, by using Raman spectroscopy, the interaction between liquid crystal molecules and graphene can be obtained from the peak shift of vibrational modes. The experimental results suggest a stronger interaction in E7 compared to 5CB. No shift in ZLI-1695 indicates the different effects from the rigid core. Further, the discotic liquid crystal (HAT-6) shows a strong interaction with graphene. These facts lead to a conclusion that the interaction still exists in the graphene/liquid crystal dispersion providing a guide on controlling and optimizing the dispersion quality for the future research.

Orientador: Denise Madalena Palomari Spolidorio / Resumo: Os sistemas precursores de cristal líquido associados aos extratos vegetais e compostos fitoquímicos abrem novas perspectivas para prevenção e controle eficiente de doenças infecciosas fúngicas. Os objetivos deste estudo foram: I) avaliar o efeito sinérgico da associação do terpinen-4-ol (t-4-ol) com a nistatina (nis); II) avaliar na forma de cristal líquido, a propriedade antifúngica do t-4-ol e possível sinergismo com a nis; III) avaliar a citotoxicidade do t-4-ol em células orais normais imortalizadas (NOK) e verificar se o t-4-ol interfere na adesão de Candida albicans sobre células orais. Assim, foi definida a Concentração Inibitória Mínima (CIM) e a Concentração Fungicida Mínima (CFM) do t-4-ol sobre isolados clínicos de C. albicans (Genotipagem A e B) e cepa SC 5314, empregando-se o método de microdiluição em caldo. Biofilmes foram preparados usando o modelo de placa de microtitulação estática e quantificados por metodologia colorimétrica do ensaio de redução de sal de tetrazólio (XTT). Os mesmos testes foram aplicados para avaliar o t-4-ol e nis na forma de cristal líquido. Adicionalmente, as células foram cultivadas em meio de cultura Dulbecco ́s Modified Eagle ́s Medium (DMEM) suplementado com 10% de soro fetal bovino e 1% de penicilina, estreptomicina e glutamina e mantidas em incubadora a 37o C em 5% de CO2. A citotoxicidade sobre linhagem de células NOK foi avaliada por citometria de fluxo e foi realizado o teste de co-cultura, para verificar a interferência do t... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The liquid crystal precursor systems associated with plant extracts and phytochemical compounds open new perspectives for efficient prevention and control of infectious fungal diseases. The objectives of this study were: I) to evaluate the synergistic effect of the combination of terpinen-4-ol (t-4-ol) with nystatin (nys); II) to evaluate in liquid crystal form the antifungal property of t-4-ol and possible synergism with nys; III) to evaluate the cytotoxic potential of t-4-ol in normal immortalized oral cells (NOK) and to verify whether t-4-ol interferes with the adhesion of Candida albicans to oral cells. Thus, the Minimum Inhibitory Concentration (MIC) and Minimum Fungicidal Concentration (CFM) of t-4-ol on clinical isolates of C. albicans (Genotype A and B) and strain SC 5314 were determined using the microdilution method in broth. Biofilms were prepared using the static microtiter plate model and quantified by colorimetric methodology of the tetrazolium salt reduction assay (XTT). The same tests were applied to evaluate t-4-ol and nys in liquid crystal form. In addition, the cells were cultured in Dulbecco's Modified Eagle's Medium (DMEM) medium supplemented with 10% fetal bovine serum and 1% penicillin, streptomycin and glutamine and maintained in an incubator at 37 ° C in 5% CO2 . Linear cytotoxicity of NOK cells was assessed by flow cytometry and the coculture test was performed to verify the interference of t-4-ol on Candida albicans adhesion on oral cells (NOK). Can... (Complete abstract click electronic access below) / Doutor

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