A cold atomic cloud is a versatile object, because it offers many handles to control and tune its properties. This facilitates studies of its behavior in various circumstances, such as sample temperature, size and density, composition, dimensionality and coherence time. The range of possible experiments is constrained by the specifications of the atomic species used. In this thesis presents the work done in the experiment for laser cooling of strontium atoms, focusing on its stability, which should provide cold and ultracold samples for the study of collective effects in light scattering. From the initial apparatus, innumerous changes were performed. The vacuum system got improved and now reached lower ultra high vacuum due to the pre-baking done to its parts and adding a titanium-sublimation stage. The quadrupole trap were improved by the design and construction of a new pair of coils. The stability of the blue, green and red laser systems and the loss prevention of laser light were improved, giving rise to a robust apparatus. Another important point is the development of homemade devices to reduce the costs and to be used as a monitor of different parts of an cold atoms experiment. From this homemade devices, we could demonstrate a dramatic linewidth narrowing by injection lock of an low cost 461 nm diode laser and its application to our strontium experiment. In the end, this improved experimental apparatus made possible the study of a new scattering effect, the mirror assisted coherent back-scattering (mCBS). / Uma nuvem atômica fria é um objeto versátil porque oferece muitas formas de controlar e ajustar suas propriedades. Isso facilita o estudo de seu comportamento em várias circunstâncias, tais como temperatura da amostra, tamanho e densidade, composição, dimensionalidade e tempo de coerência. A extensão de experimentos possíveis é limitada pelas especificações da espécie atômica utilizada. Nessa tese, eu apresento o trabalho feito em um experimento para resfriamento de átomos de estrôncio, focando em sua estabilidade, que deve gerar amostras frias e ultras-frias para o estudo de efeitos coletivos em espalhamento de luz. Do aparato inicial, inúmeras mudanças foram feitas. O sistema de vácuo foi melhorado e agora atinge vácuos ultra altos mais baixos, devido ao pré-cozimento feito em suas partes e a adição de um estágio de sublimação de titânio. A estabilidade e a prevenção de perdas de luz dos sistemas de laser azul, verde e vermelho foram melhorados, levando a um sistema mais robusto. Outro ponto importante é o desenvolvimento de dispositivos caseiros para reduzir os custos e para ser usado como monitor de diferentes partes de um experimento de átomos frios. Destes dispositivos, pudemos demonstrar a redução dramática da largura de linha de um diodo laser de 461 nm de baixo custo devido a estabilização por injeção. No fim, esse aparato experimental melhorado fez possível o estudo de um novo efeito de espalhamento, o retro espalhamento coerente da luz assistido por espelho.

Orientador: Maria Regina Wolf Maciel / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-15T01:50:27Z (GMT). No. of bitstreams: 1 RoccaRivarola_FlorenciaWisnivesky_M.pdf: 9147569 bytes, checksum: 2744b00d9edfcd31f6704d23a6fa772d (MD5) Previous issue date: 2009 / Resumo: Os asfaltenos são macromoleculas aromáticas complexas, que apresentam estrutura que varia de acordo com o local de extração do óleo. Esta fração tem sido muito estudada pela indústria de petróleo, não apenas por sua contribuição às propriedades do óleo cru, mas também pelos problemas associados a sua agregação e precipitação. Com isso, foram desenvolvidos novos processos para valoração de petróleos pesados, que recuperam os asfaltenos, obtendo também óleo lubrificante. Neste trabalho foi estudado um dos processos para valoração de petróleos pesados, que utiliza fluidos supercríticos para a desasfaltação e produção de óleo lubrificante. Este processo foi estudado a partir de duas abordagens. A primeira abordagem foi o desenvolvimento de uma planta piloto de desasfaltação supercrítica, no qual o projeto de uma planta piloto construída foi adequado para o uso com petróleo. Este comissionamento foi assistido por simulações do processo realizadas em um software de simulação, no qual as variáveis de processo foram avaliadas em termos de sua influência no desempenho. Diversos testes foram feitos na planta piloto com frações pesadas de petróleos brasileiros, onde as condições operacionais foram avaliadas para a constatação das modificações de projeto necessárias. Uma vez concluída a primeira etapa, foi feita uma segunda abordagem para o processo, que representou o estudo do mecanismo de agregação e precipitação dos asfaltenos, que corresponde à primeira etapa do processo de desasfaltação. Este mecanismo foi avaliado com experimentos utilizando espalhamento de luz dinâmica, para quantificar a variação do tamanho das partículas de asfalteno com o tempo, em amostras preparadas com solventes orgânicos. Como complementação para este estudo, foi utilizada a Espectroscopia Raman Anti-Stokes Coerente para obter imagens das partículas de asfalteno no processo de agregação. Estes dados são de extrema importância, uma vez que ajudam a entender melhor o mecanismo de agregação dos asfaltenos, que ainda permanece como um grande problema sem solução na industria de petróleo e permitem o estudo e avaliação do processo de extração supercrítica para o melhor aproveitamento dos petróleos brasileiros na indústria. / Abstract: Alphaltenes are complex aromatic macro-cycle molecules, with a molecular structure that varies depending on the origin of the crude oil. Apart from heir contribution to the properties of petroleum, the study of the asphaltic fraction asbecome more important, due to the problems encountered during petroleum Pro cessing caused by asphaltene precipitation, which causes pipe clogging and catalyst deactivation. Associated with the problems related to the presence of asphalthenes, the petroleum industry developed new processes for upgrading of heavy oils and residues, designed for recovering asphaltenes and lube oil from that mixture. The Residuum Oil Supercritical Extraction (ROSE¿) process is the premier deasphalting technology available in industry. This process extracts high-quality deasphalted oil (DAO) and asphaltenes from atmospheric or vacuum residues and other heavier feedstocks. In this work the extraction of asphaltenes from oil was assessed using two different approaches. The first one was the installation and commissioning of a supercritical deasphalting pilot plant, assisted by simulations using a process simulation software and a thermodynamic study of the system comprised of deasphalted oil, asphaltenes and the solvent. The second approach was the use optical strategies to analyze and model asphaltene aggregation, which is the first step of the supercritical dealphalting process. The first optical technique used was dynamic light scattering (DLS), which gave information such as to study and describe the kinetics of asphaltene aggregation in aromatic solvents, at different temperatures. Associated with the DLS results, CARS (Coherent Anti-Stokes Raman Scattering) images were acquired with different solvents, and allowed an evaluation of the behavior of asphaltenes while they aggregate. These results are very important, once they provide insightful information on the asphaltene aggregation mechanism that still remains as a great unsolved problem in the petroleum industry, allowing it to be controlled in order to reduce problems related with asphaltene precipitation in oil transport and processing and improving the performance of heavy oils upgrading processes. / Mestrado / Desenvolvimento de Processos Químicos / Mestre em Engenharia Química

Orientador: Fernando Galembeck / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-15T06:51:39Z (GMT). No. of bitstreams: 1 SilvaeSouza_CristianeAparecida_D.pdf: 8520514 bytes, checksum: 17e73481eda5f744b4ec360be3455823 (MD5) Previous issue date: 2009 / Resumo: A morfologia de filmes compósitos preparados com fosfato de alumínio e látexes de poli(metacrilato de metila-co-acrilato de butila) e de poli(estireno-co-acrilato de butila) foi caracterizada por técnicas de microscopia eletrônica de transmissão e de varredura (TEM, SEM) e por técnicas de microscopia de varredura por sonda (AFM, DPFM). O grau de opacidade (razão de contraste) e os cálculos de coeficiente de espalhamento das partículas de fosfato de alumínio nos filmes compósitos foram obtidos através dos espectros de refletância. As micrografias das superfícies de desbaste dos filmes compósitos mostraram espaços vazios entre os agregados de partículas de fosfato de alumínio dispersos pela matriz polimérica. A adesão entre os agregados de partículas de fosfato de alumínio e polímero é muito boa nas interfaces de contato. A refletância dos filmes compósitos varia amplamente, dependendo da concentração das partículas de fosfato de alumínio, assim como da sua forma de uso em pó ou em dispersão e da dimensão dos espaços vazios entre os agregados de partículas. Os resultados das medidas óticas de opacidade mostraram que os filmes compósitos mais opacos foram os obtidos com fosfato de alumínio na forma de pó e com a dimensão dos vazios entre os agregados de partículas na mesma ordem de grandeza que o comprimento de onda da luz na região do visível (400 a 700 nm). Os coeficientes de espalhamento dos filmes de fosfato de alumínio/poli(estireno-co-acrilato de butila) foram calculados empiricamente usando o modelo de Kubelka-Munk e os resultados mostraram que os vazios contidos nos agregados de partículas de fosfato de alumínio justificam a opacidade dos filmes. O filme mais opaco, com razão de contraste de 88 %, apresentou ampla distribuição de dimensão dos vazios com média numérica igual a 650 nm. Além disso, os valores obtidos dos coeficientes de espalhamento experimentais são muito próximos dos coeficientes de espalhamento estimados pela teoria de Mie. A eficiência de espalhamento, predita pela teoria de Mie, de uma bolha de ar rodeada por fosfato de alumínio com diâmetro médio de 650 nm é apenas 12 % menor que a eficiência de espalhamento de uma partícula de dióxido de titânio, no seu diâmetro ótimo de 350 nm, dispersa no mesmo meio / Abstract: Composite films prepared with aluminum phosphate and latex of poly(methyl methacrylate-co-butyl acrylate) and poly(styrene-co-butyl acrylate) were characterized by electronic microscopy (TEM, SEM) and by different techniques of scanning probe microscopy (AFM, DPFM). Opacity (contrast ratio) and light scattering coefficients of composite films were obtained from reflectance spectra. SEM and TEM micrographs from composite films trimmed surfaces or thin cuts showed voids within aluminum phosphate particle aggregates. The adhesion between aluminum phosphate particle aggregates and polymer is very good at contact interfaces. Composite films reflectance changes widely, depending on void diameters, on aluminum phosphate particle concentration, as well as its use in the form of powder or dispersion. Opacity results showed that the most opaque composite films were obtained with aluminum phosphate powder and with void diameters in the same order of magnitude as the wavelength of light in the visible region (400 to 700 nm). Scattering coefficients of aluminum phosphate/poly(styrene-co-butyl acrylate) films were calculated empirically using the Kubelka-Munk model and the results showed that the observed voids account for films opacity. The most opaque composite film shows contrast ratio equal to 88 % and a broad distribution of void diameters, peaking at ca. 650 nm. Film scattering coefficient of the observed voids was calculated using Mie theory to evaluate their contribution to film opacity showing that the measured and estimated values are in reasonable agreement. The Mie calculations show that scattering efficiency for air trapped within the phosphate particles dispersed in polymer latex is in excess of 4 units in the 650 nm diameter range, which is only 12 % lower than the calculated values for optimum size TiO2 particles (350 nm) dispersed in the same polymer / Doutorado / Físico-Química / Doutor em Ciências

Light scattering by small particles is the physical phenomenon that produces the natural rainbow in the sky. The same phenomenon can be reproduced in laboratory with monochromatic light giving rise to non-intrusive laser based techniques for the measurement of size and refractive index of particles suspended in a medium possessing lower refractive index. These techniques are commonly called "Rainbow Thermometry" techniques and appear at the beginning of the nineties. The measurement of size and refractive index of the particles is obtained through the analysis of the interference fringe image generated in the far field by means of the interaction between the laser light and the particles themselves. The work presented in this thesis has as objective the improvement of the Rainbow Techniques both on the theoretical aspects and the application.<p>In this thesis the Airy theory, which is used as theoretical model for the Standard Rainbow Thermometry, has been improved to minimize the discrepancies it was presenting respect to more complex and complete theories and it has been generalized to spherical particles presenting a spherically symmetric refractive index gradient. This generalized model has been used to evaluate the size and temperature of a n-octane burning droplet in standard atmosphere with good results. The generalization of the Standard Rainbow Thermometry to multiple particles, Global Rainbow Thermometry, is presented both theoretically and experimentally and the role of the particle asphericity in the light scattered intensity is evaluated.<p>Two experimental application of the Global Rainbow Thermometry are reported. The first one concerns the measurement of size and refractive index of silicon oil droplets suspended in an aqueous bulk. This experiment allows the Global Rainbow Thermometry validation through the comparison with measurements simultaneously obtained with well known experimental techniques as Back-Light scattering and thermocouple measurement with satisfactory results.<p>The second experiment concerns Global Rainbow Thermometry measurement performed on an evaporating flat-fan water spray. The results obtained, both for temperature and for size, are in satisfactory agreement with predictions already done by other authors and with numerical simulations performed by the engineering code CASIMIRE.<p> / Doctorat en sciences appliquées / info:eu-repo/semantics/nonPublished

Abstract The development of a non-invasive glucose monitoring technique is very important because it would tremendously diminish the need to puncture the skin when taking blood samples and help diabetic patients in controlling their blood glucose levels and in treating Diabetes Mellitus. The focus of this thesis is on measuring the effect of glucose on the light scattering properties of a tissue-simulating phantom and biological tissues in vitro. Optical coherence tomography (OCT), the pulsed photoacoustic (PA) technique, and the time-of-flight (TOF) technique are used in the measurements and their capabilities for detecting changes in the scattering properties are evaluated and compared with each other. The theoretical background of the techniques, light propagation and PA wave generation are briefly explained. The glucose-induced changes in light scattering are also reviewed. The measurement results with the OCT and the PA technique from Intralipid, pig whole blood, and mouse skin tissue samples show that the glucose-induced changes are larger in the biological tissues than in the Intralipid phantom. The PA measurements show that although the PA signals are stronger at a wavelength of 532 nm than at 1064 nm, the glucose-induced change in the peak-to-peak value of the PA signal measured from pig whole blood is larger at a wavelength of 1064 nm than at 532 nm. The TOF measurements with a streak camera show that the scattering-related changes in the registered pulse shapes occur mainly in the rising part of the pulses. The utilization of fiber-optic measurement heads enabled the detection of back-scattered photons at different distances from the emitting fiber. Although all the techniques are able to detect changes induced by large glucose concentrations (0–5000 mg/dl) in Intralipid, the effect of glucose on the scattering properties of Intralipid is so weak that the techniques failed to detect changes with lower (50–500 mg/dl) concentrations. The measurements of biological samples with the PA technique and with the OCT also demonstrate capabilities to measure glucose concentrations in the physiologically relevant range (18–450 mg/dl) as well. The results compare well with earlier literature and also confirm some earlier findings.

Abstract Optical coherence tomography (OCT) is a modern rapidly developing technique for non-invasive imaging of the internal structure of optically non-uniform objects based on the principles of low-coherent interferometry. However, multiple scattering of light in the objects under study brings distortions to the images obtained by OCT. The analysis of formation of the OCT signals is required for understanding the role of multiple scattering in this formation and providing recommendations for optimal configuration of a measuring setup. In the present thesis formation of the OCT signals and images is analyzed implementing Monte Carlo simulations of light propagation in scattering media. Blood, intralipid solution, human skin and paper samples are chosen as the objects under study due to the interest in the diagnostics of these objects in biomedicine and paper industry. Multilayer models of skin phantoms, skin and paper were developed in the frames of the present study for simulation of OCT signals and two-dimensional OCT images of these objects. The contribution of different scattering orders as well as different fractions of photons (least and multiply scattered, diffusive and non-diffusive) to these images was found allowing to evaluate the maximal depth of non-distorted imaging in each particular case. The simulated OCT images were compared to the experimental ones demonstrating qualitative similarity. This fact allowed the author to analyze qualitatively the influence of parameters of the OCT setup on the images which have also been acquired in this work. The formation of the OCT images of paper samples with various refractive index matching liquids was also studied.

Title: Dust trap for light scattering study Author: Petr Bartoň Department: Department of Surface and Plasma Science Supervisor: doc. RNDr. Jiří Pavlů, Ph.D., Department of Surface and Plasma Science Abstract: Light scattering on small grains is common interaction occurring wi- dely in space environments, including Moon surface, dusty nebulas or even the upper atmosphere of the Earth. For experimental measurements of light scatte- ring intensity profiles, we designed and constructed a unique experiment. Using so called acoustic trapping, we are able to capture a single dust grain (or small water droplet) in midair, to irradiate it with the laser beam, and to observe scattered light directly with the photodiode mounted on a precise goniometer. In the thesis, we present not only construction details, but also the first results, which help us to evaluate abilities of the experiment, and provide useful recommendations for further development of all dust-related experiments. Keywords: light scattering, acoustic trap, dust grain, scattering measurement 1

This master thesis analyses light scattering on atmospheric aerosols, which has been measured at Košetice observatory in Pelhřimov region since 2012. In the thesis, data are processed for period from 1. 1. 2014 to 31. 12. 2015 which provide representative values of scattering and backscattering light measurement. Angstroem exponent was calculated based on which data corrections were performed. Data were processed using hour steps and compared with meteorological and emissions concentrations data. Correlations were calculated and regressions models estimated in order to verify correctness of measurement and to explore impact of meteorological conditions and emissions concentrations PM2,5 and PM10 on scattering coefficients. Performed analyses imply, that light scattering is higher for higher concentrations of PM2,5 and PM10 and for higher relative air humidity and lower for higher outdoor temperature, total precipitations, and wind speed. In addition, it was showed that light scattering is influenced by wind direction, which determines compositions of aerosols in the sample. Key words: atmospheric aerosol, light scattering, time series evaluation

Growth and deposition of amyloid fibrils, polymers of proteins with a cross beta-sheet structure, are associated with a significant number of human pathologies including Alzheimer’s disease, Parkinson’s disease, prion diseases, type II diabetes, and senile systematic or dialysis-related amyloidoses. The broader objective of my research is to identify the basic mechanisms regulating nucleation and growth of amyloid fibrils. There is increasing evidence that amyloid formation may proceed along at least two distinct assembly pathways for the formation of rigid fibrils. One pathway involves the nucleated polymerization of the characteristic rigid fibrils from partially denatured monomers and the other proceeds via the growth of globular oligomers and their associated curvilinear fibrils (also known as protofibrils) which, in ways yet to be determined, transform into late-stage rigid fibrils. These oligomeric intermediates of fibril assembly, in particular, have been implicated as the predominant aggregate species causing cellular toxicity in amyloid diseases. Yet, amyloid oligomers and curvilinear fibrils are considered transient, metastable aggregates. This raises the question whether and how such transient aggregate species can be responsible for most of the cell/tissue toxicity? In this dissertation, I report on my investigation of several basic questions related to the mechanisms of amyloid formation. Using the model amyloid hen egg-white lysozyme, I participated in research to characterize the distinct kinetics of amyloid formation along distinct assembly pathways, to determine the morphological features of the various aggregate species emerging along either pathway, and to investigate the structural evolution of the monomers from their native state to the amyloid cross- sheet structure (chapter 3). Chapters 4-6 represent the core of my dissertation work. There I investigated whether amyloid aggregates from three different amyloid proteins, formed under denaturing condition, could undergo prion-like proliferation upon return to physiological solution conditions. I was also intimately involved in a project on the conditions inducing amyloid spherulites formation by polyglutamic acid and the mechanisms resulting in the formation of this often-overlooked amyloid aggregate structure (chapter 7). In the appendix I provide a short summary of the various experimental techniques I have used in the above experiments.

Dans ce travail, nous avons étudié la relation entre la viscosité et la dynamique microscopique (caractérisée par le temps de relaxation structurale) d'une suspension colloïdale en fonction de la fraction volumique. Nous avons mis au point une expérience originale nous permettant de mesurer la viscosité et le temps de relaxation simultanément sur le même échantillon. La dynamique microscopique est mesurée à l'aide de techniques conventionnelles de diffusion dynamique de la lumière "multi-speckles" ; la viscosité est quant à elle obtenue en mesurant la vitesse de sédimentation de particules-sondes micrométriques. Ces mesures nous ont permis d'étendre d'au moins deux décades la gamme de viscosités à taux de cisaillement nul préalablement explorée. Nous montrons que la viscosité et le temps de relaxation structurale mesuré au pic du facteur de structure statique, sont couplés jusqu'à des fractions volumiques situées bien au-delà de la transition vers un régime surfondu. Par ailleurs, nous avons constaté que le fort accroissement du temps de relaxation à l'approche de la transition vitreuse était bien décrit par une divergence exponentielle, plutôt que par une loi de puissance critique prévue par la Théorie de Couplage des Modes (MCT). / In this work, we have investigated the relation between the viscosity and the microscopic dynamics (structural relaxation time) of colloidal suspensions, as a function of volume fraction. We have designed and implemented an original setup which allows us to measure the viscosity and the relaxation time simultaneously on the very same sample. The dynamics are measured by conventional multispeckle dynamic light scattering, while the viscosity is obtained by measuring the sedimentation velocity of micron-sized tracer particles. Our measurements extend the range of previous measurements of the zero-shear viscosity by two decades. We find that the viscosity and the relaxation time measured at the peak of the static structure factor are coupled up to deep in the supercooled regime, thereby extending previous observations that were limited to the onset of supercooling. Furthermore, we show that the steep growth of the relaxation time on approaching the glass transition is well described by an exponential divergence, rather than by a critical power law as predicted by Mode Coupling Theory (MCT).