UA Open Access Publishing Fund / Molecular diagnostics offers quick access to information but fails to operate at a speed required for clinical decision-making. Our novel methodology, droplet-on-thermocouple silhouette real-time polymerase chain reaction (DOTS qPCR), uses interfacial effects for droplet actuation, inhibition relief, and amplification sensing. DOTS qPCR has sample-to-answer times as short as 3 min 30 s. In infective endocarditis diagnosis, DOTS qPCR demonstrates reproducibility, differentiation of antibiotic susceptibility, subpicogram limit of detection, and thermocycling speeds of up to 28 s/cycle in the presence of tissue contaminants. Langmuir and Gibbs adsorption isotherms are used to describe the decreasing interfacial tension upon amplification. Moreover, a log-linear relationship with low threshold cycles is presented for real-time quantification by imaging the droplet-on-thermocouple silhouette with a smartphone. DOTS qPCR resolves several limitations of commercially available real-time PCR systems, which rely on fluorescence detection, have substantially higher threshold cycles, and require expensive optical components and extensive sample preparation. Due to the advantages of low threshold cycle detection, we anticipate extending this technology to biological research applications such as single cell, single nucleus, and single DNA molecule analyses. Our work is the first demonstrated use of interfacial effects for sensing reaction progress, and it will enable point-of-care molecular diagnosis of infections.

Dióxido de carbono supercrítico (scCO2) é um solvente pouco eficiente para substâncias polares em geral. Uma maneira interessante de superar esta limitação e explorar todo o seu potencial como solvente verde, possível substituto para os solventes orgânicos voláteis comuns, é a introdução de tensoativos específicos para scCO2 no sistema. No presente trabalho, foram sintetizadas três novas séries de tensoativos oxigenados para scCO2. As moléculas possuem cabeças CO2-fóbicas mono e poli-hidroxiladas, em sua maioria à base de açúcares, e três tipos de cadeias CO2-fílicas, duas delas perfluoradas (-C7F15 e -C9F19) e uma peracetilada (derivada do ácido D-glucônico). Foram investigadas as suas solubilidades e comportamentos de fase em CO2 e em sistemas ternários (água-CO2-tensoativo), bem como a atividade na interface CO2-água. Todos eles dispersaram água em scCO2 com [água] / [tensoativo] (W) igual a 10, exibindo pressões de névoa comparáveis àquelas do sistema \"a seco\". Adicionalmente, os tensoativos reduziram a tensão interfacial CO2-água. O efeito das cabeças CO2-fóbicas e cadeias CO2-fílicas nessa redução pôde ser analisado separadamente. Os resultados dos experimentos de tensão interfacial dinâmica sugerem que tanto a difusão das moléculas da fase contínua para a subinterface, quanto a sua inserção e migração na interface contribuem para o decaimento das tensões interfaciais. / Supercritical carbon dioxide (scCO2) is a poor solvent for polar substances in general. An interesting way to overcome this limitation and fulfill its potential as a green solvent, a possible substitute for common volatile organic solvents, is the introduction of scCO2-suitable surfactants in the system. In the present work, three series of novel oxygenated surfactants for scCO2 were synthesized. The amphiphiles contain mono and poly-hydroxylated CO2-phobic heads, most of them sugar-based, as well as three types of CO2-philic tails, two of them perfluorinated (-C7F15 and -C9F19) and one peracetylated (D-gluconic acid derivative). Their solubilities and phase behaviors in CO2 and in ternary systems (water-CO2-surfactant), as well as their activities at the CO2-water interface, were investigated. All of them dispersed water in scCO2- with water-to-surfactant ratio (W) of 10, exhibiting cloud pressures comparable to those of \"dry\" systems. Also, the surfactants reduced the CO2-water interfacial tension. The effect of both the CO2-phobic heads and the CO2-philic tails could be analyzed separately. Dynamic interfacial tension results suggest that both diffusion from bulk CO2 to subinterface and insertion and migration of molecules within the interface contribute to the time-dependent decay of the interfacial tensions.

Dióxido de carbono supercrítico (scCO2) é um solvente pouco eficiente para substâncias polares em geral. Uma maneira interessante de superar esta limitação e explorar todo o seu potencial como solvente verde, possível substituto para os solventes orgânicos voláteis comuns, é a introdução de tensoativos específicos para scCO2 no sistema. No presente trabalho, foram sintetizadas três novas séries de tensoativos oxigenados para scCO2. As moléculas possuem cabeças CO2-fóbicas mono e poli-hidroxiladas, em sua maioria à base de açúcares, e três tipos de cadeias CO2-fílicas, duas delas perfluoradas (-C7F15 e -C9F19) e uma peracetilada (derivada do ácido D-glucônico). Foram investigadas as suas solubilidades e comportamentos de fase em CO2 e em sistemas ternários (água-CO2-tensoativo), bem como a atividade na interface CO2-água. Todos eles dispersaram água em scCO2 com [água] / [tensoativo] (W) igual a 10, exibindo pressões de névoa comparáveis àquelas do sistema \"a seco\". Adicionalmente, os tensoativos reduziram a tensão interfacial CO2-água. O efeito das cabeças CO2-fóbicas e cadeias CO2-fílicas nessa redução pôde ser analisado separadamente. Os resultados dos experimentos de tensão interfacial dinâmica sugerem que tanto a difusão das moléculas da fase contínua para a subinterface, quanto a sua inserção e migração na interface contribuem para o decaimento das tensões interfaciais. / Supercritical carbon dioxide (scCO2) is a poor solvent for polar substances in general. An interesting way to overcome this limitation and fulfill its potential as a green solvent, a possible substitute for common volatile organic solvents, is the introduction of scCO2-suitable surfactants in the system. In the present work, three series of novel oxygenated surfactants for scCO2 were synthesized. The amphiphiles contain mono and poly-hydroxylated CO2-phobic heads, most of them sugar-based, as well as three types of CO2-philic tails, two of them perfluorinated (-C7F15 and -C9F19) and one peracetylated (D-gluconic acid derivative). Their solubilities and phase behaviors in CO2 and in ternary systems (water-CO2-surfactant), as well as their activities at the CO2-water interface, were investigated. All of them dispersed water in scCO2- with water-to-surfactant ratio (W) of 10, exhibiting cloud pressures comparable to those of \"dry\" systems. Also, the surfactants reduced the CO2-water interfacial tension. The effect of both the CO2-phobic heads and the CO2-philic tails could be analyzed separately. Dynamic interfacial tension results suggest that both diffusion from bulk CO2 to subinterface and insertion and migration of molecules within the interface contribute to the time-dependent decay of the interfacial tensions.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O estudo da estabilidade de emulsões de biocombustíveis destaca-se, dentre outros aspectos, pela necessidade de identificação das características destas. Esta necessidade reforça-se pela dificuldade de detecção de biodiesel e suas misturas quando estão fora de especificação, além de se aplicar aos processos de separação e purificação do biodiesel após a transesterificação. O entendimento deste problema poderá ser alcançado a partir de estudos de estabilidade associados aos modelos termodinâmicos de equilíbrio líquido-líquido (modelo NRTL) em sistemas ternários, que serão a base da modelagem proposta neste trabalho. O levantamento de dados envolve técnicas de observação direta em titulação, e ensaios de estabilidade e tensiometria, com algumas alterações das técnicas clássicas. Desta forma, o objetivo principal do trabalho é propor uma maneira de identificar e caracterizar as interfaces das emulsões formadas e estudar a estabilidade das fases envolvidas. Além disso, estuda-se a introdução de alcoóis como agentes tensoativos para viabilizar a utilização de misturas de combustíveis, mesmo na região de mais de uma fase. Para o desenvolvimento do trabalho, emulsões envolvendo os constituintes básicos serão combinadas entre si em diferentes proporções. A etapa inicial constitui-se de um mapeamento das misturas e proporções que formam as emulsões, baseadas nas curvas de equilíbrio. Em seguida, faz-se o estudo de caracterização e estabilidade destes sistemas. Com estas informações é possível mapear o sentido de incremento de tensão na interface e instabilidade da separação de fases das emulsões em relação aos diagramas ternários correspondentes. Por fim, propõe-se uma estratégia para estimar os parâmetros termodinâmicos do NRTL para as espécies presentes nos sistemas estudados e prever o comportamento dos mesmos e de sistemas similares. Este modelo matemático proposto tem como objetivo complementar a técnica experimental adotada para construção das curvas de equilíbrio, sendo bem sucedido / The study of the stability of biofuels emulsions calls attention, among other things, to the need to identify their characteristics. This need is reinforced by the difficulty of detecting biodiesel and its blends when they are out of specification, and apply the processes of biodiesel separation and purification after transesterification. The understanding of this issue could be reach from stability studies associated with thermodynamic models of liquid-liquid equilibrium (NRTL) in ternary systems, which will be the basis for modeling proposed in this paper. The research involves direct observation techniques for titration, and stability tests and tensiometry, with some changes of classical techniques. Thus, the main objective is to propose a way to identify and characterize the interfaces of emulsions formed and study the stability of the phases involved. Furthermore, it studies the introduction of alcohols as surfactants to enable the use of mixtures of fuel, even in the region of more than one phase. For development work, emulsions involving basic constituents will be combined in different proportions. The first step consists of mapping the mixtures and proportions which form emulsions, based on the equilibrium curves. Then, it is done the study of characterization and stability of these systems. With this information it is possible to map the direction of an increase in the interface tension and phase separation instability of emulsions in relation to the corresponding ternary diagrams. Finally, it proposes a strategy to estimate the thermodynamic parameters of the NRTL for the species present in the systems studied and predict the behavior of these and similar systems. This mathematical model aims to complement the experimental technique adopted for construction of the equilibrium curves, being successful

Successful field waterflood is a crucial prerequisite for improving the performance before EOR methods, such as ASP, SP, and P flooding, are applied in the field. Excess water production is a major problem in mature waterflooded oil fields that leads to early well abandonment and unrecoverable hydrocarbon. Gel treatments at the injection and production wells to preferentially plug the thief zones are cost-effective methods to improve sweep efficiency in reservoirs and reduce excess water production during hydrocarbon recovery. There are extensive experimental studies performed by some researchers in the past to investigate the performance of gels in conformance control and decreasing water production in mature waterflooded reservoirs, but no substantial modeling work has been done to simulate these experiments and predict the results for large field cases. We developed a novel, 3-dimensional chemical compositional and robust general reservoir simulator (UTGEL) to model gel treatment processes. The simulator has the capability to model different types of microgels, such as preformed particle gels (PPG), thermally active polymers (TAP), pH-sensitive microgels, and colloidal dispersion gels (CDG). The simulator has been validated for gel flooding using laboratory and field scale data. The simulator helps to design and optimize the flowing gel injection for conformance control processes in larger field cases. The gel rheology, adsorption, resistance factor and residual resistance factor with salinity effect, gel viscosity, gel kinetics, and swelling ratio were implemented in UTGEL. Several simulation case studies in fractured and heterogeneous reservoirs were performed to illustrate the effect of gel on production behavior and water control. Laboratory results of homogeneous and heterogeneous sandpacks, and Berea sandstone corefloods were used to validate the PPG transport models. Simulations of different heterogeneous field cases were performed and the results showed that PPG can improve the oil recovery by 5-10% OOIP compared to waterflood. For recovery from fractured reservoirs by waterflooding, injected water will flow easily through fractures and most part of reservoir oil will remain in matrix blocks unrecovered. Recovery from these reservoirs depends on matrix permeability, wettability, fracture intensity, temperature, pressure, and fluid properties. Chemical processes such as polymer flooding (P), surfactant/polymer (SP) flooding and alkali/surfactant/polymer (ASP) flooding are being used to enhance reservoir energy and increase the recovery. Chemical flooding has much broader range of applicability than in the past. These include high temperature reservoirs, formations with extreme salinity and hardness, naturally fractured carbonates, and sandstone reservoirs with heavy and viscous crude oils. The recovery from fractured carbonate reservoirs is frequently considered to be dominated by spontaneous imbibition. Therefore, any chemical process which can enhance the rate of imbibition has to be studied carefully. Wettability alteration using chemicals such as surfactant and alkali has been studied by many researchers in the past years and is recognized as one of the most effective recovery methods in fractured carbonate reservoirs. Injected surfactant will alter the wettability of matrix blocks from oil-wet to water-wet and also reduce the interfacial tension to ultra-low values and consequently more oil will be recovered by spontaneous co-current or counter-current imbibition depending on the dominant recovery mechanism. Accurate and reliable up-scaling of chemical enhanced oil recovery processes (CEOR) are among the most important issues in reservoir simulation. The important challenges in up-scaling CEOR processes are predictability of developed dimensionless numbers and also considering all the required mechanisms including wettability alteration and interfacial tension reduction. Thus, developing new dimensionless numbers with improved predictability at larger scales is of utmost importance in CEOR processes. There are some scaling groups developed in the past for either imbibition or coreflood experiments but none of them were predictive because all the physics related to chemical EOR processes (interfacial tension reduction and wettability alteration) were not included. Furthermore, most of commercial reservoir simulators do not have the capability to model imbibition tests due to lack of some physics, such as surfactant molecular diffusion. The modeling of imbibition cell tests can aid to understand the mechanisms behind wettability alteration and consequently aid in up-scaling the process. Also, modeling coreflood experiments for fractured vuggy carbonates is challenging. Different approaches of random permeability distribution and explicit fractures were used to model the experiments which demonstrate the validity and ranges of applicability of upscaled procedures, and also indicate the importance of viscous and capillary forces in larger scales. The simulation models were then used to predict the recovery response times for larger cores.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O estudo da estabilidade de emulsões de biocombustíveis destaca-se, dentre outros aspectos, pela necessidade de identificação das características destas. Esta necessidade reforça-se pela dificuldade de detecção de biodiesel e suas misturas quando estão fora de especificação, além de se aplicar aos processos de separação e purificação do biodiesel após a transesterificação. O entendimento deste problema poderá ser alcançado a partir de estudos de estabilidade associados aos modelos termodinâmicos de equilíbrio líquido-líquido (modelo NRTL) em sistemas ternários, que serão a base da modelagem proposta neste trabalho. O levantamento de dados envolve técnicas de observação direta em titulação, e ensaios de estabilidade e tensiometria, com algumas alterações das técnicas clássicas. Desta forma, o objetivo principal do trabalho é propor uma maneira de identificar e caracterizar as interfaces das emulsões formadas e estudar a estabilidade das fases envolvidas. Além disso, estuda-se a introdução de alcoóis como agentes tensoativos para viabilizar a utilização de misturas de combustíveis, mesmo na região de mais de uma fase. Para o desenvolvimento do trabalho, emulsões envolvendo os constituintes básicos serão combinadas entre si em diferentes proporções. A etapa inicial constitui-se de um mapeamento das misturas e proporções que formam as emulsões, baseadas nas curvas de equilíbrio. Em seguida, faz-se o estudo de caracterização e estabilidade destes sistemas. Com estas informações é possível mapear o sentido de incremento de tensão na interface e instabilidade da separação de fases das emulsões em relação aos diagramas ternários correspondentes. Por fim, propõe-se uma estratégia para estimar os parâmetros termodinâmicos do NRTL para as espécies presentes nos sistemas estudados e prever o comportamento dos mesmos e de sistemas similares. Este modelo matemático proposto tem como objetivo complementar a técnica experimental adotada para construção das curvas de equilíbrio, sendo bem sucedido / The study of the stability of biofuels emulsions calls attention, among other things, to the need to identify their characteristics. This need is reinforced by the difficulty of detecting biodiesel and its blends when they are out of specification, and apply the processes of biodiesel separation and purification after transesterification. The understanding of this issue could be reach from stability studies associated with thermodynamic models of liquid-liquid equilibrium (NRTL) in ternary systems, which will be the basis for modeling proposed in this paper. The research involves direct observation techniques for titration, and stability tests and tensiometry, with some changes of classical techniques. Thus, the main objective is to propose a way to identify and characterize the interfaces of emulsions formed and study the stability of the phases involved. Furthermore, it studies the introduction of alcohols as surfactants to enable the use of mixtures of fuel, even in the region of more than one phase. For development work, emulsions involving basic constituents will be combined in different proportions. The first step consists of mapping the mixtures and proportions which form emulsions, based on the equilibrium curves. Then, it is done the study of characterization and stability of these systems. With this information it is possible to map the direction of an increase in the interface tension and phase separation instability of emulsions in relation to the corresponding ternary diagrams. Finally, it proposes a strategy to estimate the thermodynamic parameters of the NRTL for the species present in the systems studied and predict the behavior of these and similar systems. This mathematical model aims to complement the experimental technique adopted for construction of the equilibrium curves, being successful

No description available.

Sewage exfiltration from a sanitary and combined sewer systems and its percolation into porous medium results in a clogged or colmation layer in the nearby soil. In order to develop a comprehensive understanding of raw sewage transport mechanisms in porous media, investigations were carried out on the micro-scale properties of the multiphase system. In our laboratory experiments, the role of surfactants as a major organic chemical compound in wastewater was evaluated by using a surfactant solution as an artificial wastewater percolating into a porous media, represented by using columns and Plexiglas model. We studied flows of water and surfactants solution in saturated porous medium to detect the dynamic effects by means of measuring pressure and permeability as well as by visualization of flow regions and consequence for porosity along interfaces between water and surfactants solution. The tests revealed that mechanisms at interfaces between fluids and solids as well as between water and surfactants solution (i.e. wastewater) are significantly influencing the flow behavior. At the interfaces surfactant molecules are adsorbed or accumulate, respectively, and subsequently inducing electrical charges to those layers, altering the properties of fluids and these interfaces. Depending on the conditions, channels might be narrowed and thus decreasing the flow rate with a later erosion and increase of flow rates, or the flow and thus the erosive capacity might become intensified along the interface between surfactants solution and neighbouring water. In conclusion, the results of tests proved the surfactants to be an important controlling factor in the hydraulic properties of wastewater percolating into soil.

La tension interfaciale est une grandeur physico-chimique d'intérêt pour de nombreuses industries et notamment l'industrie pétrolière. Cette grandeur est l'un des paramètres qui permet d'optimiser le rendement d'un puits de pétrole. La difficulté liée à sa mesure dans les conditions réservoirs a amené à étudier les systèmes eau/tensioactif/huile par simulation moléculaire. Ce travail a permis de montrer que la Dynamique Particulaire Dissipative (DPD) était un outil adapté pour l’étude de systèmes eau/tensioactif/huile sous différents aspects, de la caractérisation de la structure des interfaces au calcul de la tension interfaciale. Cette thèse a permis la démonstration de l’influence non-négligeable de la variation des paramètres de la force harmonique, l’amplitude K et la distance d’équilibre r0 , sur le calcul de la tension interfaciale et sur la structure des interfaces à forte concentration en tensioactif. En effet, la structure des tensioactifs aux interfaces est le résultat d’une balance subtile entre les forces intra et inter moléculaire. L’étude d’une population modèle de tensioactifs non chargés a permis de montrer que la DPD reproduit bien l'évolution de la tension interfaciale en fonction de la concentration en tensioactif en solution et en fonction du coefficient de partage de tensioactifs modèles non chargés. Une méthodologie est proposée pour caractériser les systèmes contenant des interfaces et où la tension interfaciale est calculée.Des travaux prospectifs ont permis de montrer que la DPD permettait d'étudier des phénomènes liés à la tension interfaciale comme le mûrissement d'Ostwald dans les émulsions d'huile dans l'eau. Ces derniers travaux ouvrent la voie à l’étude d’autres systèmes d’intérêt pour le milieu pétrolier comme le décollement de gouttes de pétroles adsorbées sur des parois ou l’étude d’émulsions pétrolières. / The interfacial tension is a physical-chemical property that numerous industrial areas have an interest of especially the petroleum industry. This property is one of the many which helps to optimize production wells' rate of return. Measuring that property in reservoir's conditions (high pressure and temperature) is highly difficult and led to study water/surfactant/oil systems using molecular modeling. The difficulty to measure that specific physical-chemical property linked to the pressure and temperature conditions in the reservoirs led the scientists to study water/surfactant/oil systems using molecular modeling. This thesis establishes that the Dissipative Particle Dynamics (DPD) is able to study water/surfactant/oil systems. The study of the effect of the variation of the harmonic force's parameters, namely the force constant K and the equilibrium distance r0, demonstrated that their variation can heavily influence the interfacial tension computation. Actually, a subtle balance exists between the intra and inter-molecular interactions, which influences the local structure of the surfactants at the oil-water interface, modifies the interfacial tension and influences the interface stability. It was demonstrated that DPD reproduces the variation of interfacial tension with the bulk surfactant concentration and the effect of the variation of hydrophobicity of models of un-charged surfactants on interfacial tension by mean of their coefficient partition. We established a method to properly study systems containing interfaces where interfacial tension is computed. Prospective work showed that DPD was a good tool to study microscopic phenomenon which can be observed macroscopically like the Ostwald ripening in oil in water emulsions. This is a first step before studying others systems of interest for the petroleum industry such as oil/water emulsion or the adsorption of oil droplets on rock wall.

Ce travail vise à obtenir une morphologie cœur-peau directement lors du mélangeage à l’état fondu de polymères ternaires PLA/PBAT/PA. Le but final est d'améliorer la ténacité de l'acide polylactique (PLA). La morphologie des mélanges de polymères multi-phases est contrôlée par la thermodynamique du système. La morphologie des mélanges ternaires peut être prédite à partir des valeurs relatives des trois coefficients d'étalement caractérisant le triplet de polymères. Les coefficients d'étalement sont calculés à partir des valeurs des tensions interfaciales entre les composants binaires. La détermination des tensions interfaciales entre PLA, poly (butylène adipate-co-téréphtalate) (PBAT) et un copolyamide (PA) prédit une morphologie dispersée complexe dans la matrice PLA où les sous-inclusions PA sont partiellement encapsulées dans la phase PBAT. Cette morphologie a été obtenue par mélange à l'état fondu des trois composants, comme observé par les observations en microscopie électronique à balayage. Dans une seconde étape, une compatibilisation sélective a été utilisée pour modifier l'emplacement des sous-inclusions de PA. A cette fin, deux copolymères diblocs PBAT-b-PLA, PA-b-PBAT ont été synthétisés. La présence des copolymères diblocs nous permet de modifier la tension interfaciale des couples PLA/PBAT, PA/PBAT. Cette modification de l'équilibre de tension interfaciale modifie avec succès la morphologie, passant d’une semi-encapsulation à une encapsulation complète des sous-inclusions de PA dans les gouttes de PBAT. La performance mécanique de ce mélange ternaire a été évaluée. / This work aims at achieving direct core-shell morphologies in ternary PLA/PBAT/PA polymer blends by melt mixing. The final goal is to improve the toughness of polylactic acid (PLA). The morphology of multi-phase polymer blends is controlled by the thermodynamics of the system. The morphology of ternary blends can be predicted from the relative values of the three spreading coefficients characterizing the triplet of polymers. Spreading coefficients are calculated from the values of interfacial tensions between binary components. The determination of interfacial tensions between a PLA, a poly(butylene adipate-co-terephthalate) (PBAT) and a copolyamide (PA) predicts a complex dispersed morphology in the PLA matrix where PA subinclusions are partly encapsulated in the PBAT phase. This morphology was obtained by melt mixing the three components, as observed by scanning electron microscopy. In a second step, selective compatibilization was used to modify the PA sub-inclusion location. To this end, PBAT-b-PLA and PA-b-PBAT di-block copolymers were synthesized. The presence of the di-block copolymers enabled to modify the interfacial tension in PLA/PBAT and PA/PBAT. The modification of the interfacial tension balance was shown to successfully change the morphology from semi-encapsulation to full encapsulation of PA sub-inclusions in the PBAT drops. The mechanical performance of this ternary blend was evaluated.