To reduce the risk of pancreatic fistula after pancreatectomy, a satisfactory blood flow at the pancreatic stump is considered crucial. Our group has developed and validated a real-time computational imaging analysis of tissue perfusion, using fluorescence imaging, the fluorescence-based enhanced reality (FLER). Hyperspectral imaging (HSI) is another emerging technology, which provides tissue-specific spectral signatures, allowing for perfusion quantification. Both imaging modalities were employed to estimate perfusion in a porcine model of partial pancreatic ischemia. Perfusion quantification was assessed using the metrics of both imaging modalities (slope of the time to reach maximum fluorescence intensity and tissue oxygen saturation (StO2), for FLER and HSI, respectively). We found that the HSI-StO2 and the FLER slope were statistically correlated using the Spearman analysis (R = 0.697; p = 0.013). Local capillary lactate values were statistically correlated to the HSI-StO2 and to the FLER slope (R = −0.88; p < 0.001 and R = −0.608; p = 0.0074). HSI-based and FLER-based lactate prediction models had statistically similar predictive abilities (p = 0.112). Both modalities are promising to assess real-time pancreatic perfusion. Clinical translation in human pancreatic surgery is currently underway.

Advances in multiplex fluorescence imaging now allow the measurement of more than 50protein markers in whole tissue sections at single-cell resolution. This promises to reveal tumor biology at an unprecedented level of detail, both in undisturbed growth and in therapy. However, to quantitatively analyze these images, the images must be broken down into the basic units of tumor biology: single cells and their types. In this study, we applied a graph-based unsupervised clustering method, Leiden, to perform cell type identification in highly multiplexed fluorescence images, and based on the annotated images, we ran the tumor microenvironment niches analysis in order to resolve the recurring patterns of tumor microarchitecture. This thesis first introduces several potentially feasible clustering methods selected based on the structure of the datasets studied. The performance and stability of these clustering methods were compared. The project involved benchmarking different dimensionality reduction and clustering techniques on manually annotated reference datasets and healthy tissue with known cellular composition. It was ultimately determined that appropriate data transformations combined with Leiden clustering methods with proper parameters could automatically identify cells in a way coherent with established marker profiles. The results imply that Leiden clustering can also identify clusters of cells with novel marker combinations. Careful examination of the multiplex images shows that the markers are indeed found in the tumor, leading to new hypotheses regarding tumor biology. Tumor microenvironment niches analysis found several archetypal niches with specific cellular composition, indicating active accumulation of immune cells after radiotherapy, and the less vascularized feature of rebound glioblastomas after treatment. We hope to further validate our analysis to provide new insights into the pathological process of glioblastoma. In future research, the analysis pipeline is planned to be improved so that it can be robustly used to analyze the growing data of multiplexed tumor images, both in mouse cancer models or patient samples.

A técnica de fluorescência óptica tem sido aplicada em diversas áreas médicas, como no acompanhamento da degradação de drogas e na detecção de câncer, por apresentar alta sensibilidade, simplicidade e rapidez na obtenção de dados. A avaliação não-invasiva e não-destrutiva é um grande atrativo que esta técnica oferece para o diagnóstico clínico. Assim, o objetivo deste projeto consistiu no desenvolvimento de um sistema de fluorescência óptica por imagem de campo amplo e avaliação do sistema no monitoramento da fotodegradação da Protoporfirina XI, utilizada na Terapia Fotodinâmica (TFD), e na visualização da presença de microrganismos presentes na microbiota bucal. O sistema desenvolvido é constituído de um sistema óptico, mecânico, eletrônico e de detecção. O sistema óptico é composto por LEDs de alta intensidade, com emissão centrada em 405nm e 450nm e 3 filtros ópticos: 1. passa-banda: utilizado na excitação; 2. dicróico; e 3. passa-alta: utilizados para excitação e emissão da fluorescência. O sistema mecânico foi desenvolvido em alumínio, possuindo as funções de dissipação de calor do sistema de iluminação e estrutural. O sistema eletrônico possui a função de controle e fornecimento de energia ao sistema de iluminação. O sistema de detecção é composto por uma câmera CCD e fotográfica, acoplada ao sistema de fluorescência desenvolvido. Um dos principais fatores para obtenção de bons sinais de fluorescência é a potência óptica obtida no sistema de iluminação, que neste caso foi de 200 mW. Outro fator é o comprimento de onda da iluminação; neste sistema foi obtida uma banda de iluminação muito eficaz entre 390 nm e 460 nm. O sistema de filtros proporcionou um sinal de fluorescência bastante satisfatório, bem como um bom contraste na visualização das imagens de fluorescência. Com este sistema foi possível acompanhar a fotodegradação da Protoporfirina IX, em função do tempo de iluminação durante a TFD. Proporcionou-se, assim, uma nova ferramenta para o avanço na avaliação da dosimetria da TFD, podendo otimizar e personalizar a TFD para cada paciente, já que o sistema desenvolvido permite a visualização da presença do agente fotossensível na terapia. Outra contribuição relevante do trabalho alcançada foi a visualização da presença de microrganismos da microbiota bucal, já que estes são os grandes responsáveis pelas doenças bucais como é o caso da cárie dental. Desta forma, conclui-se que foi possível desenvolver um sistema para auxílio da dosimetria na TFD e na visualização de microrganismos presentes na microbiota bucal. O sistema desenvolvido se mostrou compacto, agregando iluminação e visualização, tornando-o num protótipo com interface para uso clínico. O protótipo foi testado em pacientes para a visualização da microbiota bucal, tratamento de pré-câncer de pele e de vulva. / Optical fluorescence has been applied to several medical areas, as to monitor drug degradation and cancer detection, due to its high sensitivity, simplicity and fast response. Non-invasive and non-destructive assessment of tissues using this technique is very attractive for clinical diagnosis. Hence, the aim of was the development of an optical fluorescence wide-field imaging system, and the evaluation of its performance on monitoring protoporphyrin IX (PpIX) during Photodynamic Therapy (PDT), and one visualization of microrganisms present in oral microbiota. The developed device is composed by optical, mechanical, electronic, and detection systems. Optical system is composed by high-intensity light-emitting diodes (LED), with emission centered at 405 nm and 450 nm, and 3 optical filters: a bandpass filter for excitation; and set of dichroic and long wave pass filter, for fluorescence excitation and emission. The mechanical system was built in aluminum for structural and ilumination systems heat dissipation. The electronic system provides the control of the illumination system. The detection system is composed by a CCD and a conventional didgital camera, coupled to the developed device. One of the main factors for good fluorescence signals is the achieved optical power - in our case, it was of 200 mW. Another factor is excitation wavelength; for this system, a very efficient illumination band was achieved between 390-460 nm. The optical filters allowed a very satisfying fluorescence signal, with good contrast for fluorescence images visualization. The developed system enabled the monitoring of PpIX photobleaching as a function of illumination time during PDT. Therefore, a new tool to improve PDT dosimetry is offered by the use this system, allowing a more customized dosimetry each patient, since the device allows visualization of the photosensitive agent during the therapy. Visualization of oral microrganisms was also achieved, which was another relevant contribution of the developed instrumentation because they are the main cause of oral diseases such as caries. Thus the development of a system to both improve PDT dosimetry and oral microrganisms visualization was achieved as a compact device, joining illumination and visualization. These characteristics shows a good interface for clinical use. The prototype was tested in patients for oral microbiota visualization, and skin/vulva pre-cancer lesions treatment.

O cancro cítrico é uma das doenças mais temidas da citricultura devido ao seu poder de proli-feração nas fazendas, aos danos causados às plantas e aos frutos e à forma de combate adota-da pelos órgãos responsáveis através da erradicação das plantas contaminadas e de outras em sua vizinhança. No Brasil, um dos principais motivos que minimiza a eficiência da erradicação do cancro cítrico é a confirmação do diagnóstico, que necessita ser realizada em alguns laboratórios credenciados. A análise de muitas amostras em conjunto com o tempo gasto com o transporte aumenta a chance de proliferação da doença no campo. Neste trabalho aplicamos técnicas de espectroscopia da fluorescência em folhas de culturas cítricas na intenção de pro-por um método de diagnóstico do cancro cítrico a ser realizado na fazenda e com resposta em tempo real. As amostras experimentais são folhas de variedades cítricas sadias e contaminadas com cancro ou outras doenças. Iniciamos o trabalho aplicando espectroscopia da fluorescência no laboratório. Os resultados provaram a viabilidade do método, mas revelou uma enorme sobreposição de dados ao tentar discriminar o cancro de outra doença. Análises com-plementares nos revelaram que os experimentos deveriam ser feitos no campo, identificando plantas contaminadas e tomando a fluorescência de folhas sadias como referência. A espec-troscopia da fluorescência no campo foi feita com um espectrômetro portátil. O resultado nos possibilitou propor critérios de discriminação do cancro baseado em figuras de mérito. O melhor critério apresentou 79% de acertos, com 88% de sensibilidade e 68% de especificidade. Concluímos que os valores poderiam ser melhores se a espectroscopia fosse realizada com imagens, pois as variações do espectro ocorrem devido ao posicionamento da fibra na lesão do cancro. Passamos a estudar a espectroscopia das imagens da fluorescência com um sistema baseado em um espectrógrafo. Os resultados provaram a viabilidade do estudo e revelaram particularidades espaciais e espectrais das doenças. Infelizmente essa instrumentação só pode ser usada no laboratório, por isso optamos por desenvolver outro sistema mais simples e robusto, a base de uma roda de filtros com filtros passa-banda. Os re-sultados revelaram novas particularidades espaciais e espectrais das amostras, porém nos revelou a necessidade de um processamento de imagem para obter análises quantitativas. O sistema de imagens com filtro ainda foi usado em outro experimento complementar onde as imagens forneceram resultados quantitativos, provando a funcionalidade da técnica. / Citrus canker is one of the most feared diseases of citrus due to its dissemination in the farms, the damage caused to plants and fruits and how to combat adopted by national government through the eradication of infected plants and others in your neighborhood. In Brazil, one of the main reasons that minimizes the effectiveness of citrus canker`s eradication is the confir-mation of the diagnosis by specialized laboratories. The time spent to transport and to analyses many samples increases the chance of canker spreading in the field. In our work we apply spectroscopic techniques of fluorescence in leaves of citrus crops with the aim to propose a method for diagnosis of citrus canker to be held on the farm and real-time response. The expe-rimental samples are leaves of healthy citrus varieties and contaminated with canker or other diseases. We began the work by applying fluorescence spectroscopy in the laboratory. The results proved the feasibility of the method, but showed a huge overlap of data to try to dis-criminate cancer from other diseases. Further analysis revealed that those experiments should be done in the field, focusing to identify infected plants and taking the fluorescence of healthy leaves as a reference. Fluorescence spectroscopy in the field was made with a portable spectrometer. The result allowed us to propose some criteria for canker discrimination based on figures of merit. The best criteria presents 79% correct tests, with 88% sensitivity and 68% specificity. We conclude that these values could be better if the spectroscopy was performed with images, because the variations of the spectrum are due to the positioning of the fiber over the canker lesion. We study the spectroscopy of fluorescence images with a system based on a spectrograph. The results proved its feasibility and revealed spatial and spectral particular features of the diseases. Unfortunately, this instrumentation can only be used in the laborato-ry, so we decided to develop another system more simple and robust. The new system is based on a filter wheel with band-pass filters. The results revealed new spatial and spectral characteristics of the samples, but revealed the need for an image processing for quantitative analysis. This imaging system was still used in another supplementary experiment where the images have provided quantitative results, proving the functionality of the technique.

A técnica de fluorescência óptica tem sido aplicada em diversas áreas médicas, como no acompanhamento da degradação de drogas e na detecção de câncer, por apresentar alta sensibilidade, simplicidade e rapidez na obtenção de dados. A avaliação não-invasiva e não-destrutiva é um grande atrativo que esta técnica oferece para o diagnóstico clínico. Assim, o objetivo deste projeto consistiu no desenvolvimento de um sistema de fluorescência óptica por imagem de campo amplo e avaliação do sistema no monitoramento da fotodegradação da Protoporfirina XI, utilizada na Terapia Fotodinâmica (TFD), e na visualização da presença de microrganismos presentes na microbiota bucal. O sistema desenvolvido é constituído de um sistema óptico, mecânico, eletrônico e de detecção. O sistema óptico é composto por LEDs de alta intensidade, com emissão centrada em 405nm e 450nm e 3 filtros ópticos: 1. passa-banda: utilizado na excitação; 2. dicróico; e 3. passa-alta: utilizados para excitação e emissão da fluorescência. O sistema mecânico foi desenvolvido em alumínio, possuindo as funções de dissipação de calor do sistema de iluminação e estrutural. O sistema eletrônico possui a função de controle e fornecimento de energia ao sistema de iluminação. O sistema de detecção é composto por uma câmera CCD e fotográfica, acoplada ao sistema de fluorescência desenvolvido. Um dos principais fatores para obtenção de bons sinais de fluorescência é a potência óptica obtida no sistema de iluminação, que neste caso foi de 200 mW. Outro fator é o comprimento de onda da iluminação; neste sistema foi obtida uma banda de iluminação muito eficaz entre 390 nm e 460 nm. O sistema de filtros proporcionou um sinal de fluorescência bastante satisfatório, bem como um bom contraste na visualização das imagens de fluorescência. Com este sistema foi possível acompanhar a fotodegradação da Protoporfirina IX, em função do tempo de iluminação durante a TFD. Proporcionou-se, assim, uma nova ferramenta para o avanço na avaliação da dosimetria da TFD, podendo otimizar e personalizar a TFD para cada paciente, já que o sistema desenvolvido permite a visualização da presença do agente fotossensível na terapia. Outra contribuição relevante do trabalho alcançada foi a visualização da presença de microrganismos da microbiota bucal, já que estes são os grandes responsáveis pelas doenças bucais como é o caso da cárie dental. Desta forma, conclui-se que foi possível desenvolver um sistema para auxílio da dosimetria na TFD e na visualização de microrganismos presentes na microbiota bucal. O sistema desenvolvido se mostrou compacto, agregando iluminação e visualização, tornando-o num protótipo com interface para uso clínico. O protótipo foi testado em pacientes para a visualização da microbiota bucal, tratamento de pré-câncer de pele e de vulva. / Optical fluorescence has been applied to several medical areas, as to monitor drug degradation and cancer detection, due to its high sensitivity, simplicity and fast response. Non-invasive and non-destructive assessment of tissues using this technique is very attractive for clinical diagnosis. Hence, the aim of was the development of an optical fluorescence wide-field imaging system, and the evaluation of its performance on monitoring protoporphyrin IX (PpIX) during Photodynamic Therapy (PDT), and one visualization of microrganisms present in oral microbiota. The developed device is composed by optical, mechanical, electronic, and detection systems. Optical system is composed by high-intensity light-emitting diodes (LED), with emission centered at 405 nm and 450 nm, and 3 optical filters: a bandpass filter for excitation; and set of dichroic and long wave pass filter, for fluorescence excitation and emission. The mechanical system was built in aluminum for structural and ilumination systems heat dissipation. The electronic system provides the control of the illumination system. The detection system is composed by a CCD and a conventional didgital camera, coupled to the developed device. One of the main factors for good fluorescence signals is the achieved optical power - in our case, it was of 200 mW. Another factor is excitation wavelength; for this system, a very efficient illumination band was achieved between 390-460 nm. The optical filters allowed a very satisfying fluorescence signal, with good contrast for fluorescence images visualization. The developed system enabled the monitoring of PpIX photobleaching as a function of illumination time during PDT. Therefore, a new tool to improve PDT dosimetry is offered by the use this system, allowing a more customized dosimetry each patient, since the device allows visualization of the photosensitive agent during the therapy. Visualization of oral microrganisms was also achieved, which was another relevant contribution of the developed instrumentation because they are the main cause of oral diseases such as caries. Thus the development of a system to both improve PDT dosimetry and oral microrganisms visualization was achieved as a compact device, joining illumination and visualization. These characteristics shows a good interface for clinical use. The prototype was tested in patients for oral microbiota visualization, and skin/vulva pre-cancer lesions treatment.

Articular cartilage is the connective tissue that lines joints and provides a smooth surface for articulation and shock absorption. Osteoarthritis, the progressive degeneration of cartilage, is a painful, debilitating, and widespread disease, affecting 70% of people over 65. Because cartilage is avascular, molecular transport occurs primarily via diffusion. The goal of these studies was to examine whether cartilage matrix structure and composition have a significant effect on diffusive transport. We hypothesized that diffusion is anisotropic in the surface zone of cartilage where collagen structure is aligned and densely packed. A theoretical model and experimental protocol for fluorescence imaging of continuous point photobleaching (FICOPP) were developed to measure diffusional anisotropy. Significant anisotropy was observed in ligament, a highly ordered collagenous tissue. In less ordered articular cartilage, diffusional anisotropy was dependent on site in the tissue and size of the diffusing molecule. These findings suggest that diffusional transport of macromolecules is anisotropic in collagenous tissues, with higher rates of diffusion along primary orientation of collagen fibers. We hypothesized that structural differences in the pericellular matrix of cartilage (PCM) would lead to differences in diffusive properties as compared to the surrounding extracellular matrix (ECM). We modified the scanning microphotolysis (SCAMP) technique to allow measurement of diffusion coefficients within the PCM. Diffusion coefficients in the PCM were lower than in the adjacent ECM in normal cartilage, but with early stage arthritis, the PCM diffusivity was not different from that of the ECM. These data suggest that breakdown of the PCM is an early step in arthritis development. We hypothesized that compression of cartilage would cause site‐specific diffusivity decreases and diffusional anisotropy increases. We utilized SCAMP and FICOPP to measure diffusion coefficients and diffusional anisotropy in cartilage as it was compressed. We found that diffusivity decreased and anisotropy increased with increasing strain in a site‐specific manner. These findings suggest that the high surface zone strains that lead to low diffusivity and high anisotropy will decrease transport between cartilage and synovial fluid in compressed cartilage. We have shown that matrix structure and composition have a significant effect on diffusive transport in cartilage. / Dissertation

abstract: Encapsulant is a key packaging component of photovoltaic (PV) modules, which protects the solar cell from physical, environmental and electrical damages. Ethylene-vinyl acetate (EVA) is one of the major encapsulant materials used in the PV industry. This work focuses on indoor accelerated ultraviolet (UV) stress testing and characterization to investigate the EVA discoloration and delamination in PV modules by using various non-destructive characterization techniques, including current-voltage (IV) measurements, UV fluorescence (UVf) and colorimetry measurements. Mini-modules with glass/EVA/cell/EVA/backsheet construction were fabricated in the laboratory with two types of EVA, UV-cut EVA (UVC) and UV-pass EVA (UVP). The accelerated UV testing was performed in a UV chamber equipped with UV lights at an ambient temperature of 50°C, little or no humidity and total UV dosage of 400 kWh/m2. The mini-modules were maintained at three different temperatures through UV light heating by placing different thickness of thermal insulation sheets over the backsheet. Also, prior to thermal insulation sheet placement, the backsheet and laminate edges were fully covered with aluminum tape to prevent oxygen diffusion into the module and hence the photobleaching reaction. The characterization results showed that mini-modules with UV-cut EVA suffered from discoloration while the modules with UV-pass EVA suffered from delamination. UVf imaging technique has the capability to identify the discoloration region in the UVC modules in the very early stage when the discoloration is not visible to the naked eyes, whereas Isc measurement is unable to measure the performance loss until the color becomes visibly darker. YI also provides the direct evidence of yellowing in the encapsulant. As expected, the extent of degradation due to discoloration increases with the increase in module temperature. The Isc loss is dictated by both the regions – discolored area at the center and non-discolored area at the cell edges, whereas the YI is only determined at the discolored region due to low probe area. This led to the limited correlation between Isc and YI in UVC modules. In case of UVP modules, UV radiation has caused an adverse impact on the interfacial adhesion between the EVA and solar cell, which was detected from UVf images and severe Isc loss. No change in YI confirms that the reason for Isc loss is not due to yellowing but the delamination. Further, the activation energy of encapsulant discoloration was estimated by using Arrhenius model on two types of data, %Isc drop and ΔYI. The Ea determined from the change in YI data for the EVA encapsulant discoloration reaction without the influence of oxygen and humidity is 0.61 eV. Based on the activation energy determined in this work and hourly weather data of any site, the degradation rate for the encaspulant browning mode can be estimated. / Dissertation/Thesis / Masters Thesis Chemical Engineering 2018

O cancro cítrico é uma das doenças mais temidas da citricultura devido ao seu poder de proli-feração nas fazendas, aos danos causados às plantas e aos frutos e à forma de combate adota-da pelos órgãos responsáveis através da erradicação das plantas contaminadas e de outras em sua vizinhança. No Brasil, um dos principais motivos que minimiza a eficiência da erradicação do cancro cítrico é a confirmação do diagnóstico, que necessita ser realizada em alguns laboratórios credenciados. A análise de muitas amostras em conjunto com o tempo gasto com o transporte aumenta a chance de proliferação da doença no campo. Neste trabalho aplicamos técnicas de espectroscopia da fluorescência em folhas de culturas cítricas na intenção de pro-por um método de diagnóstico do cancro cítrico a ser realizado na fazenda e com resposta em tempo real. As amostras experimentais são folhas de variedades cítricas sadias e contaminadas com cancro ou outras doenças. Iniciamos o trabalho aplicando espectroscopia da fluorescência no laboratório. Os resultados provaram a viabilidade do método, mas revelou uma enorme sobreposição de dados ao tentar discriminar o cancro de outra doença. Análises com-plementares nos revelaram que os experimentos deveriam ser feitos no campo, identificando plantas contaminadas e tomando a fluorescência de folhas sadias como referência. A espec-troscopia da fluorescência no campo foi feita com um espectrômetro portátil. O resultado nos possibilitou propor critérios de discriminação do cancro baseado em figuras de mérito. O melhor critério apresentou 79% de acertos, com 88% de sensibilidade e 68% de especificidade. Concluímos que os valores poderiam ser melhores se a espectroscopia fosse realizada com imagens, pois as variações do espectro ocorrem devido ao posicionamento da fibra na lesão do cancro. Passamos a estudar a espectroscopia das imagens da fluorescência com um sistema baseado em um espectrógrafo. Os resultados provaram a viabilidade do estudo e revelaram particularidades espaciais e espectrais das doenças. Infelizmente essa instrumentação só pode ser usada no laboratório, por isso optamos por desenvolver outro sistema mais simples e robusto, a base de uma roda de filtros com filtros passa-banda. Os re-sultados revelaram novas particularidades espaciais e espectrais das amostras, porém nos revelou a necessidade de um processamento de imagem para obter análises quantitativas. O sistema de imagens com filtro ainda foi usado em outro experimento complementar onde as imagens forneceram resultados quantitativos, provando a funcionalidade da técnica. / Citrus canker is one of the most feared diseases of citrus due to its dissemination in the farms, the damage caused to plants and fruits and how to combat adopted by national government through the eradication of infected plants and others in your neighborhood. In Brazil, one of the main reasons that minimizes the effectiveness of citrus canker`s eradication is the confir-mation of the diagnosis by specialized laboratories. The time spent to transport and to analyses many samples increases the chance of canker spreading in the field. In our work we apply spectroscopic techniques of fluorescence in leaves of citrus crops with the aim to propose a method for diagnosis of citrus canker to be held on the farm and real-time response. The expe-rimental samples are leaves of healthy citrus varieties and contaminated with canker or other diseases. We began the work by applying fluorescence spectroscopy in the laboratory. The results proved the feasibility of the method, but showed a huge overlap of data to try to dis-criminate cancer from other diseases. Further analysis revealed that those experiments should be done in the field, focusing to identify infected plants and taking the fluorescence of healthy leaves as a reference. Fluorescence spectroscopy in the field was made with a portable spectrometer. The result allowed us to propose some criteria for canker discrimination based on figures of merit. The best criteria presents 79% correct tests, with 88% sensitivity and 68% specificity. We conclude that these values could be better if the spectroscopy was performed with images, because the variations of the spectrum are due to the positioning of the fiber over the canker lesion. We study the spectroscopy of fluorescence images with a system based on a spectrograph. The results proved its feasibility and revealed spatial and spectral particular features of the diseases. Unfortunately, this instrumentation can only be used in the laborato-ry, so we decided to develop another system more simple and robust. The new system is based on a filter wheel with band-pass filters. The results revealed new spatial and spectral characteristics of the samples, but revealed the need for an image processing for quantitative analysis. This imaging system was still used in another supplementary experiment where the images have provided quantitative results, proving the functionality of the technique.

<p>To increase overall aircraft engine efficiency, the diameter of the high-pressure turbine is reduced, leading to low aspect ratio airfoils. Secondary flow dominates in these low aspect ratio turbines, and the small airfoil geometry inhibits flush-mounted, full-spatial dynamic pressure measurements with pressure transducers. Airfoil surface pressure measurements are vital to understanding the inherently unsteady flow phenomena in turbines. Additionally, aerodynamic performance data derived from high-resolution surface pressure measurements provide invaluable data for validating computational fluid dynamics codes used for prediction. Non-intrusive measurement techniques such as fast-responding Pressure Sensitive Paint (PSP) offer a potential solution of a full-field optical measurement of surface pressure fluctuation, with each camera pixel representing a sensor. The porous binder improves the dynamic response of PSP, making it suitable for unsteady flow environments such as turbomachinery applications. In this view, the overall objective of the current doctoral research is to develop a lifetime PSP method using laser-based excitation for surface pressure measurement on a new class of high-pressure turbines. </p> <p>The overall research goal was subdivided into three main strategies. (1) A pulse lifetime calibration procedure of a porous polymer/ceramic binder PSP was developed in a pressure-controlled chamber to assess the correlation between pressure and time-resolved luminescent lifetime, pressure sensitivity, and signal-to-noise ratio. (2) The lifetime technique was implemented for surface pressure measurements in a linear test section to measure high spatial pressure gradients and resolve unsteady flow features. A data reduction routine and an optimal binning bundle of pixels were proposed for calibration analysis to reduce the overall pressure uncertainty. Uncertainty quantification and sensitivity analysis were also completed to determine the parameters with a substantial effect on the pressure uncertainty. (3) The pulse lifetime method was demonstrated on a high-pressure turbine vane suction surface at engine representative conditions. The surface pressure data were corroborated with static pressure tappings and computational simulations. This research effort provided new insights into time-resolved luminescent lifetime PSP techniques. Steady and unsteady flow features from surface pressure measurements were identified using a precise calibration method. The lifetime pulse method was effective in a high-pressure turbine flow field, paving the way for back-to-back PSP experiments with different turbine geometries. </p>

Le caoutchouc naturel (NR pour Natural Rubber) est une matière première indispensable à la fabrication de milliers de produits !Le choix du latex naturel tient principalement à ses propriétés physico-chimiques intrinsèques bien supérieures à celles des latex synthétiques. Industriellement, le NR est cependant rarement utilisé seul mais associé à des particules de renfort, appelées charges, pour former un matériau composite aux propriétés mécaniques grandement améliorées en particulier la résistance à l’usure.Des études récentes ont mis en évidence que la méthode conventionnelle consistant à introduire les charges sous forme de poudres fines au sein d’un bloc de NR solide ou fondu n’est pas la plus efficace. Une nouvelle approche consistant à mélanger les deux entités, NR et charges, en phase liquide avant séchage s’annonce prometteuse industriellement, mais la littérature à ce sujet est encore très limitée. Ce travail de thèse a visé à parfaire la compréhension des processus gouvernant les interactions NR-charges renforçantes en phase liquide. Pour ce faire nous avons (i) décrit les propriétés physico-chimiques de surface des particules NR en phase liquide, (ii) étudier les effets de la charge renforçante (en termes de taille, composition, fonctionnalisation de surface, concentration) et de la solution (ions valence) sur l'interaction NR-charge et (iii) quantifier les propriétés mécaniques des particules NR.Nous avons été en mesure d’identifier les paramètres clés qui permettent en phase aqueuse diluée, non seulement d’influencer l’interaction particule de NR-charge mais aussi de réguler la dynamique d'interaction et de contrôler la structure des hétéro-agrégats formés.Cette approche originale de l’hétérocoagulation NR-charge en phase liquide ouvre de nombreuses perspectives en vue d’améliorer les propriétés des matériaux composites NR-particules de renfort. / Natural rubber (NR) is an indispensable raw material used in the manufacturing of more than 40,000 products primarily due to its excellent intrinsic physical properties. However, NR is seldom used in its raw state. Often, it needs to be reinforced with particulate fillers (nanoparticles) to further improve its physical strength required for most applications. The precise origin of this mechanical reinforcement effect remains unclear, however, optimal reinforcements appears to depend on the dispersion of filler in the NR matrix and the interaction of NR and filler.It was found that the conventional method of pouring fine powders in a solid block of rubber/melt is not the most efficient way to disperse the fillers. The new alternative approach in which the two components are first dispersed in liquid has shown promising results but available literature is still very limited. Furthermore, the microscopic mechanism involved in the interaction of NR and filler in liquid is still unknown. In this context, we (i) described the physico-chemical surface properties of NR particles in liquid, (ii) identified key filler (size, composition, surface activity, concentration) and solution (ion valence) related parameters to comprehend the structural, morphological, and dynamical evolution of the NR-filler interaction, and (iii) quantified the mechanical properties of the NR particles. With this approach we were able to provide the first reports on the physical processes involved in the interaction of NR and filler. More importantly, a recipe for the basic yet crucial parameters that controls and modulates NR-filler heteroaggregation was established. This could open the way to further understand the reinforcement effect.