Orientador: Vânia Regina Nicoletti / Banca: Izabel Cristina Freitas Moraes / Banca: Poliana Moser / Resumo: Emulsões óleo em água (O/W) são sistemas formados por dois líquidos imiscíveis, envolvendo a presença de uma fase contínua (água), uma fase dispersa (óleo), um emulsificante e energia introduzida por meio de agitação ou cavitação. A energia transmitida é capaz de aumentar a área interfacial entre as fases dispersa e contínua, enquanto o emulsificante adsorve na interface, estabilizando o sistema. A emulsificação é uma etapa anterior e fundamental à microencapsulação de compostos lipofílicos por spray drying, em que gotas de emulsão são rapidamente desidratadas em uma câmara de secagem, possibilitando a microencapsulação da fase dispersa. Neste trabalho, objetivou-se produzir emulsões O/W utilizando microgéis de isolado proteico de soja (SPI) como estabilizantes, avaliar a estabilidade e o comportamento reológico das emulsões em diferentes concentrações de cloreto de sódio (NaCl) e, posteriormente, produzir microcápsulas por spray drying, avaliando o potencial dos microgéis de SPI como material de parede. Suspensões com 10% m/m de SPI foram preparadas em água deionizada e submetidas à desnaturação por aquecimento a 80 ºC por 30 minutos, seguido de resfriamento a 4 ºC por 12 h. Após a formação do gel, as suspensões foram diluídas para 6% m/m de SPI com água ou soluções de NaCl e homogeneizadas sob alta pressão ou sonicadas para produção dos microgéis, usados para estabilizar emulsões O/W com diferentes teores de óleo produzidas por homogeneização a alta pressão ou sonicação... / Abstract: Oil-in-water (O/W) emulsions are systems formed by two immiscible liquids, involving a continuous phase (water), a dispersed phase (oil), an emulsifier and energy input by homogenization or cavitation. The transmitted energy is able to increase the interfacial area between the dispersed and continuous phases, while the emulsifier adsorbs at the interface, stabilizing the system. The emulsification is an earlier and fundamental step to microencapsulation of lipophilic compounds by spray drying, wherein emulsion droplets are rapidly dehydrated in a drying chamber, enabling the microencapsulation of the dispersed phase. The objective of this work was to produce emulsions using soybean protein isolate (SPI) microgels as O/W emulsion stabilizers, to evaluate the stability and rheological behavior of the emulsions at different concentrations of sodium chloride (NaCl), and to produce microcapsules by spray drying of the emulsions, evaluating the potential of SPI microgels as wall material. Suspensions with 10 wt% SPI were prepared in deionized water and subjected to gelation by heating at 80 °C for 30 minutes, followed by cooling at 4 °C for 12 h. After gel formation, the suspensions were diluted to 6 wt% SPI with water or NaCl solutions and homogenized under high pressure or sonication to produce the microgels, which were used to stabilize O/W emulsions with different oil contents produced by high-pressure or ultrasound homogenization. The emulsions were then submitted to drying ... / Mestre

Tese de mestrado integrado. Engenharia Metalúrgica e de Materiais. Universidade do Porto. Faculdade de Engenharia. 2011

L’amélioration de la solubilité des principes actifs peu solubles est devenue l’un des principaux challenges de l’industrie pharmaceutique. Bien que présentant une structure chimique potentiellement idéale pour interagir avec la cible, elles échouent dans l’efficacité in vivo : après administration, elles ne peuvent se dissoudre dans les milieux aqueux biologiques et par conséquent ne peuvent être transportées sur leur site d’action pour atteindre la concentration efficace, amenant à un échec thérapeutique. De nombreuses stratégies très intéressantes ont été proposées pour surmonter ce sérieux obstacle.Les dispersions solides sont étudiées depuis plus de 40 ans et ont conduit à de très nombreuses publications mais jusqu’à aujourd’hui peu de produits ont été commercialisés principalement pour des raisons de stabilité physico-chimique. Celles-ci ont pour but de présenter le principe actif sous sa forme amorphe : cette dernière présentant un état d’énergie plus élevé et par conséquent une solubilisation facilitée. Dans le même temps, le système doit rester stable durant le stockage, ainsi la recristallisation ou tout autre changement entraînant une modification du profil de libération doivent être évités. Différentes techniques de production peuvent être utilisées pour préparer ce genre de systèmes polymériques tels que l’extrusion en phase chauffante ou l’atomisation-séchage. Le principal objectif de ce travail a été d’améliorer la solubilité des principes actifs peu solubles par formation de dispersions solides utilisant les deux techniques les plus utilisées : l’extrusion en phase chauffante et l’atomisation-séchage. Dans cette étude, le kétoprofène a été incorporé dans des matrices polymériques hydrophiles pour augmenter sa solubilité apparente. Les deux techniques ont été employées et l’Eudragit® E a été considéré comme une matrice intéressante pour plusieurs raisons : c’est un polymère thermoplastique, offrant une stabilité thermique suffisante pour l’extrusion en phase chauffante, il se dissout rapidement en milieu acide et peut interagir avec les groupements acides de par ses nombreux azotes ternaires. Des mélanges binaires « principe actif – Eudragit®E » ainsi que des mélanges ternaires « principe actif – Eudragit®E - PVP », « principe actif – Eudragit®E - PVPVA », « principe actif – Eudragit®E - HPMC » ont été étudiés et caractérisés Les systèmes obtenus ont été caractérisés par macro/microscopie optique, microscopie électronique à balayage, diffraction laser, analyse calorimétrique différentielle modulée, diffraction des rayons X et l’étude du profil de libération in vitro en milieu acide (HCl 0.1M). Les libérations ont été intentionnellement réalisées en condition « non sink » afin d'évaluer le potentiel des formulations à produire des solutions sur-saturées et la durée de ces dernières. Tous les systèmes présentent un profil de libération du kétoprofène beaucoup plus rapide comparé au produit commercial et à la dissolution du principe actif pur. De plus, des solutions sur-saturées peuvent être obtenues et restent stables au moins 2 h. Cependant, en fonction des polymères utilisés, différents profils de libération ont été obtenus indiquant que l’utilisation de matrices polymériques pour l’accélération de la libération de principes actifs peu solubles peut être très complexe puisqu’elle n’est pas seulement influencée par la composition du système mais aussi potentiellement par leur structure interne et notamment par l’homogénéité/hétérogénéité de la distribution des excipients.[...]. / Poor aqueous solubility has become a property of numerous new drug candidates causing major concern. Despite a potentially ideal chemical structure allowing for interaction with the target, these substances fail to be effective in vivo: upon administration, they cannot dissolve sufficiently in the aqueous fluids of the body and, thus, cannot be transported to their site of action to reach therapeutically effective concentrations. Various interesting strategies have been proposed to overcome this crucial hurdle.Solid dispersions have been studied for more than 40 years and lead to numerous interesting research articles. However, today, only a few products have reached the market principally due to problems with the physico-chemical stability. The idea is to transform the crystalline raw material into a physical state having a greater energy in order to increase the driving force for drug dissolution. At the same time, the system should be stable during long term storage, thus, re-crystallization or other system changes, resulting in altered drug release rates, must be avoided. Different manufacturing techniques can be used to prepare such polymeric drug delivery systems, including hot-melt extrusion and spray-drying.The main objective of this work has been to improve drug solubility by forming solid dispersions using the two most employed techniques: hot-melt extrusion and spray-drying. In this study ketoprofen has been incorporated into hydrophilic polymeric matrices to increase its apparent aqueous solubility. Both techniques have been applied and Eudragit® E has been considered to be an interesting matrix former in this case, as it is thermoplastic, provides sufficient thermal stability for hot-melt extrusion, rapidly dissolves at acidic pH and can interact with acidic drugs due to its multiple tertiary ammonium groups. Binary “drug-Eudragit®E” as well as ternary “drug-Eudragit®E-PVP”, “drug-Eudragit®E-PVPVA”, “drug-Eudragit®E-HPMC” combinations were investigated and characterized using X-ray diffraction, mDSC, SEM, optical macro/microscopy, and drug release measurements in 0.1 M HCl before and after storage. Drug release has been intentionally monitored under non-sink conditions, in order to evaluate the potential of the formulations to provide super-saturated solutions and the life-time of the latter. In all cases ketoprofen release was much faster compared to a commercially available product and the dissolution of the drug powder (as received). More important, super-saturated solutions could have been obtained, which were stable for at least 2 h. [...]

Tropical cyclone (TC) intensity change is governed by internal dynamics (e.g. eyewall contraction, eyewall replacement cycles, interactions of the inner-core with the rainbands) and environmental conditions (e.g. vertical wind shear, moisture distribution, and surface properties). This study aims to gain a better understanding of the physical mechanisms responsible for TC intensity changes with a particular focus to those related to the vertical wind shear and surface properties by using high resolution, full physics numerical simulations. First, the effects of the vertical wind shear on a rapidly intensifying storm and its subsequent weakening are examined. Second, a fully coupled atmosphere-wave-ocean model with a sea spray parameterization is used to study the impact of sea spray on the hurricane boundary layer. The coupled model consists of three components: the high resolution, non-hydrostatic, fifth generation Pennsylvania State University-NCAR mesoscale model (MM5), the NOAA/NCEPWAVEWATCH III (WW3) ocean surface wave model, and theWHOI threedimensional upper ocean circulation model (3DPWP). Sea spray parameterizations were developed at NOAA/ESRL and modified by the author to be introduced in uncoupled and coupled simulations. The model simulations are conducted in both uncoupled and coupled modes to isolate various physical processes influencing TC intensity. The very high-resolutionMM5 simulation of Hurricane Lili (at 0.5 km grid resolution) showed a rapid intensification associated with a contracting eyewall. Changes in both the magnitude and the direction of the vertical wind shear associated with an approaching upper-tropospheric trough were responsible for the weakening of the storm before landfall. Hurricane Lili weakened in a 5-10 m/s vertical wind shear environment. The simulated storm experienced wind shear direction normal to the storm motion, which produced a strong wavenumber one rainfall asymmetry in the downshear-left quadrant of the storm. The rainfall asymmetry was confirmed by various observations from the TRMM satellite and the WSR-88D ground radar in the coastal region. The increasing vertical wind shear induced a vertical tilt of the vortex with a time lag of about 5-6 hours after the wavenumber one rainfall asymmetry was first observed in the model simulation. Other key factors controlling intensity and intensity change in tropical cyclones are the air-sea fluxes. Accurate measurement and parameterization of air-sea fluxes under hurricane conditions are challenging. Although recent studies have shown that the momentum exchange coefficient levels off at high wind speed, little is known about the high wind behavior of the exchange coefficient for enthalpy flux. One of the largest uncertainties is the potential impact of sea spray. The current sea spray parameterizations are closely tied to wind speed and tend to overestimate the mediated heat fluxes by sea spray in the hurricane boundary layer. The sea spray generation depends not only on the wind speed but also on the variable wave state. A new spray parameterization based on the surface wave energy dissipation is introduced in the coupled model. In the coupled simulations, the wave energy dissipation is used to quantify the amount of wave breaking related to the generation of sea spray. The spray parameterization coupled to the waves may be an improvement compared to sea spray parameterizations that depends on wind speed only.

In this thesis, new empirical correlations that predict the behaviour of Cupric-Chloride droplets undergoing spraying and drying processes are developed. Cupric-Chloride is a chemical compound with the formula CuCl2 that is present as slurry or aqueous solution within the Copper-Chlorine (Cu-Cl) thermo-chemical cycle for generation of hydrogen. An experimental study examines the effects of inlet air and liquid temperatures, pressure, concentration, nozzle diameter, and liquid flow rate on the outlet air temperature, particle size, particle size distribution, morphology, moisture content, bulk density, and flowability. The analysis examines a single droplet of CuCl2 solution in a continuum drying media. The validation of the model involves comparisons with experimental data from previous studies of different fluids based on non-dimensional analysis. The study provides new information about the effects of different concentrations of water in the CuCl2 slurry drying at low to moderate air temperatures.Analytical correlations of heat and mass transfer are developed for the aqueous solution, subject to various drying conditions. The analysis is performed for moist air in contact with a sprayed aqueous solution of Copper (II) Chloride Dihydrate [CuCl2 ·(2H2O)]. Validation of the model is performed by comparisons with experimental results. / UOIT

With widespread use of pesticides in modern agriculture, the impacts of spray drift have become a topic of considerable interest. The drifting of sprays is a highly complex process influenced by many factors. Advances in aerial application technology and in our ability to measure drift, coupled with the adoption of new technologies for regulating pesticide application have necessitated further research in the pesticide application process. Experiments were conducted to quantify spray drift and describe its movement from aerial applications of pesticide. The effects of spray quality, atomizer type and ground cover were examined. Initial airborne drift amounts were greater than downwind deposits, thus not all of the drifting spray was deposited in the measuring area. Total off-target movement of spray was significantly greater for Fine compared to Coarse sprays. Rotary and hydraulic atomizers, both producing Fine sprays, produced statistically similar off-target movement of sprays. Similarly, no significant statistical differences in spray drift between applications to bare ground and applications to a headed barley crop canopy were not identified. Contrary to expectations, aerial application to bare ground seemed to result in less off-target movement than application to a crop canopy. The vertical spray cloud profiles were similar for all applications with the greatest amount of spray present at the height of release. Spray concentrations diminished from that height upward with diffusion and downward with deposition. The empirical data disagreed with the mechanistic model AgDISP which is currently used in the Canadian regulatory process. The model over-predicted drift deposition by a factor of two to five. Variability in spray deposit values could not be attributed to average differences in meteorological conditions at the time of application. Experiments with appropriate protocols for increased sensitivity may be required to more accurately report subtle differences in drift at distances greater than 200 m from the target area.

Pesticide use is an important component of the agricultural industry. Pesticides are typically applied to crops as a droplet spray, and these droplets are susceptible to off-target movement due to wind, which is called spray drift. It has recently been recognized that shelterbelts may protect vulnerable downwind areas from spray drift. There is a need to characterize the movement of spray drift past a shelterbelt to better understand the extent of this protection and the variables which affect it. The variables investigated in this research may be classified as meteorological conditions, spray application settings, and shelterbelt properties.<p>This research investigated the movement of spray drift past a 5 m tall carragana/chokecherry shelterbelt. Spray was applied using a conventional sprayer that travelled on a path that was upwind and parallel to the shelterbelt. A tracer substance was mixed into the spray solution, and the deposition and airborne concentration of drift was measured using a variety of collectors placed at perpendicular distances up- and downwind of a shelterbelt. The mass of drift deposit on the collectors was determined using spectrofluoremetry and standard solutions.<p>When the spray swath was a distance of 3H (where H is the height of the shelterbelt) upwind of the shelterbelt, it was found that the ground deposition of drift at a distance of 0.5H downwind of the shelterbelt was reduced by approximately 74%, compared to the drift deposit at 0.5H upwind. The reduction over the same downwind distances was 29% in the open field setting. The airborne drift cloud was attenuated by the shelterbelt and the airborne concentration of drift exiting the shelterbelt was reduced by approximately 85% of the entering drift. The airborne drift concentration profile indicated that there was a greater proportion of drift travelling over the top of the shelterbelt rather than passing through the shelterbelt, with the peak concentration occurring at approximately 1.2H.<p>Qualitative and multiple linear regression analyses were used to determine the significance of a number of meteorological and controlled variables on the deposition of drift. It was found that the mass of drift deposited downwind of the shelterbelt increased with a higher wind speed, higher temperature, and lower relative humidity. For the range of meteorological conditions sampled, the effect of wind direction and atmospheric stability were found to be insignificant. Finer spray qualities and higher shelterbelt optical porosity produced greater airborne drift and deposition downwind of the shelterbelt. With increasing upwind sprayer distance, the mass of drift deposited within the shelterbelt decreased.

Thermal spray coating was studied as one of the techniques used for coating graphite reinforced polymer composites, which are extensively used in the aviation industry. These coatings were studied for improvement of surface properties such as erosion resistance, UV protection, hardness and electro magnetic shielding. NiAl (65%Ni,35%Al) intermetallic, NiAl (95%Ni,5%Al), Aluminum and Zinc coating were thermal-spray deposited using different procedures (plasma, flame, electric wire arc) onto polymer composite substrate. Two categories of coating were evaluated: Coatings with bond coat and coatings without bond coat. Different levels of pre-surface preparation for thermal spray coatings were also studied. The microstructures, micro-hardness and electrical conductivity of these coatings were determined. Effect of different parameters on coating properties like micro-hardness and electrical conductivity were studied. / Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering / "December 2006."

As a logical extension of previous work conducted into viscoelastic atomization, initially motivated by the need to improve spray coating transfer efficiencies, an experimental investigation into the spray-surface interaction for a number of Newtonian and non-Newtonian substitute test liquids is presented. Three model elastic liquids of varying polymer molecular weight and three inelastic liquids of varying shear viscosity were sprayed upon a moving surface to isolate the effect of elasticity and shear viscosity, respectively, on spray impaction behavior. In addition, two liquids exhibiting shear thinning behavior and an industrial top of rail liquid friction modifier, KELTRACK, for use in the railroad industry, were included in the spray tests. High-speed photography was used to examine the impingement of these liquids on the surface. Ligaments, formed as a consequence of a liquid’s viscoelasticity, were observed impacting the surface for 300K PEO, 1000K PEO, and KELTRACK. These ligaments were broadly classified into four groups, based on their structure. Splashing of elastic liquid ligaments and droplets led to filamentary structures being expelled from the droplet periphery, which were then carried away by the atomizing air jet, leading to reductions in transfer efficiency. The effect of increasing elasticity amongst the three varying molecular weight elastic solutions was shown to increase the splash threshold; a similar effect was noted with increasing shear viscosity. Attempts were made at quantifying a critical splash-deposition limit for all test liquids however due to imaging system limitations, no quantitative conclusions could be made. For KELTRACK, both droplets and ligaments spread and deposited on the rail surface upon impact, with no observed splash or rebound. Splash was only noted when droplets impinged directly on a previously deposited liquid film and even then, splashing was well contained. Thus, KELTRACK’s current rheological formulation proved to be very effective in ensuring high coating transfer efficiencies.

As a logical extension of previous work conducted into viscoelastic atomization, initially motivated by the need to improve spray coating transfer efficiencies, an experimental investigation into the spray-surface interaction for a number of Newtonian and non-Newtonian substitute test liquids is presented. Three model elastic liquids of varying polymer molecular weight and three inelastic liquids of varying shear viscosity were sprayed upon a moving surface to isolate the effect of elasticity and shear viscosity, respectively, on spray impaction behavior. In addition, two liquids exhibiting shear thinning behavior and an industrial top of rail liquid friction modifier, KELTRACK, for use in the railroad industry, were included in the spray tests. High-speed photography was used to examine the impingement of these liquids on the surface. Ligaments, formed as a consequence of a liquids viscoelasticity, were observed impacting the surface for 300K PEO, 1000K PEO, and KELTRACK. These ligaments were broadly classified into four groups, based on their structure. Splashing of elastic liquid ligaments and droplets led to filamentary structures being expelled from the droplet periphery, which were then carried away by the atomizing air jet, leading to reductions in transfer efficiency. The effect of increasing elasticity amongst the three varying molecular weight elastic solutions was shown to increase the splash threshold; a similar effect was noted with increasing shear viscosity. Attempts were made at quantifying a critical splash-deposition limit for all test liquids however due to imaging system limitations, no quantitative conclusions could be made. For KELTRACK, both droplets and ligaments spread and deposited on the rail surface upon impact, with no observed splash or rebound. Splash was only noted when droplets impinged directly on a previously deposited liquid film and even then, splashing was well contained. Thus, KELTRACKs current rheological formulation proved to be very effective in ensuring high coating transfer efficiencies.