O objetivo deste estudo foi avaliar a dissolução do tecido pulpar pelo NaOCl contendo em sua composição agentes redutores da tensão superfical (Chlor-Xtra) quando comparados ao NaOCl convencional. Com esta finalidade 44 dentes unirradiculares humanos com tecido pulpar preservado em solução de formol a 10% foram agrupados em 22 pares de acordo com a semelhança de sua anatomia interna previamente avaliada por radiografias. Os canais foram instrumentados com sistema Protaper Universal e todo o processo de irrigação teve, além do tempo, seu volume e fluxo controlado por meio automatizado por meio do sistema Vatea Endodontic Iirrigation Device. Após cada canal que compunha um par ter sido instrumentado empregando-se uma das diferentes soluções testadas, as quais foram previamente avaliadas quanto a sua tensão superficial, ambos foram devidamente preparados e enviados para processamento e análise histológica. Cortes a 0,5, 1,2,3 e 4mm do ápice foram realizados, corados e fotografados. As imagens foram analisadas por meio do programa AxioVision a fim de estabelecer o percentual de tecido remanescente em relação à área total do canal nos segmentos estudados. As análises referentes a tensão superficial revelaram que o Chlor-Xtra demonstrou possuir significativamente menor tensão superficial quando comparado ao NaOCL convencional (p>0,05). A análise estatística por meio do test T student das áreas dos canais, demonstrou que o pareamento das amostras foi eficiente entre os grupo NaOCl e Chlor-Xtra (p>0,05). Em relação ao Percentual de Tecido Remanescente (PTR), os resultados revelaram por meio de análise feita pelo teste Kruskal-Wallis e o teste de correlação de Spearman que o nível de corte influencia significantemente o PTR (P<0,05).Por fim, o teste de Mann-Whitney indicou que o PTR não é influenciado pela solução irrigadora utilizada (P>0,05). A partir da análise dos resultados foi possível concluir que quanto mais apicalmente foi o nível de corte histológico dos canais estudados, maior foi o percentual de tecido pulpar remanescente independentemente da solução utilizada, portanto.não houve diferença significativa na qualidade do debridamento produzido pelas duas soluções testadas, desta forma indicando que a presença de agentes modificadores da tensão adicionados ao NaOCl não foi capaz de superar os resultados obtidos por soluções de NaOCl convencionais. / Sodium hypochlorite solutions with added wetting agents are advertised to dissolve necrotic tissue in root canals faster than counterparts without lowered surface tension. This was tested in the current study using extracted, single-rooted teeth with oval canals that contained pulp tissue. Formerly vital extracted teeth (N = 44) with similar anatomy were radiographically paired and chemomechanically prepared. In one tooth, a 5.25% NaOCl solution with reduced surface tension was used, in the other a pure, technical-grade NaOCl solution of 5.25%. Percentage of remaining pulp tissue (PRPT) was histologically assessed in root cross-sections. The non-Gaussian raw data was subjected to Kruskal-Walis and Mann-Whitney U tests to verify the respective effect of level of cross-section and solution on the PRPT.The relationship between level of cross-section and PRPT was estimated by Spearman correlation test. Alpha-type error was set at 5%. The level of section significantly influenced the PRPT (P<0.05), whereas the PRPT was not influenced by the solution used (P>0.05). A significant inverse correlation was found between the level of section and PRPT (P<0.05, r = -0.330). The lower the distance to the apex, the higher the PRPT, regardless of the solution used.Contrary to the advertised statement, the dental solution with reduced surface tension did not dissolve vital pulp tissue in oval root canals any better than a conventional NaOCl solution of similar strength. Closer to the apex, pulp tissue dissolution is less efficient, irrespective of the solution.

Esta dissertação apresenta um novo modelo criado para a previsão do valor da tensão superficial de misturas de hidrocarbonetos. Pode ser utilizado na forma preditiva ou correlativa. Este modelo foi baseado no modelo preditivo para soluções ideais de HildebrandScott (1950) e no modelo correlativo de JouybanAcree (2004). Outras regras de mistura foram avaliadas e comparadas com o modelo proposto, incluindo abordagens clássicas como de Sprow e Prausnitz, parácoro e estados correspondentes. Foram avaliados os desempenhos dos modelos escolhidos na previsão e na correlação da tensão superficial de misturas de hidrocarbonetos em diferentes temperaturas que continham diferentes assimetrias na mistura, tanto em natureza química (e.g., parafínicos, naftênicos e aromáticos) quanto em tamanho de cadeia. No total foram empregados 773 dados experimentais. Dentre os modelos preditivos, o modelo proposto foi o de melhor desempenho. Para sistemas com comportamento próximo da idealidade, esse modelo apresentou desvios em relação aos dados experimentais compatíveis com o erro experimental. Todos os modelos correlativos estudados apresentaram desvios essencialmente da ordem do erro experimental. O modelo proposto é importante, pois é capaz de prever a tensão superficial de misturas binárias aproximadamente ideais de hidrocarbonetos com elevada acurácia, além de permitir a correlação eficiente dos dados de todas as misturas estudadas / This dissertation presents a new model created for the prediction of the value of the surface tension of hydrocarbons mixtures. It can be used in a predictive or correlative way. This model was based on the predictive model for ideal solutions of Hildebrand-Scott (1950) and on the correlative model of Jouyban-Acree (2004). Other mixing rules had been evaluated and compared with the proposed model, including classic approaches like Sprow and Prausnitz, parachor, and corresponding states. There was evaluated the performance of the chosen models in the prediction and the correlation of the surface tension of hydrocarbons mixtures at different temperatures that contained different asymmetries in the mixture, as in chemical nature (e.g., parafinics, naftenics and aromatics) as well as in chain size. The total of 773 experimental data had been used. The proposed model had the best performance among the predictive models. This model showed errors essentially of the order of the experimental error for approximately ideal systems. All of the correlative models studied have shown errors essentially of the order of the experimental error. The proposed model is important because it is capable of predicting the surface tension of approximately ideal binary mixtures of hydrocarbons with high accuracy, beyond permitting the efficient correlation of the data of all the studied mixtures

O objetivo do presente estudo foi determinar a capacidade de dissolução tecidual, tensão superficial, e capacidade de limpeza de soluções Ca(OCl)2 e compará-las ao NaOCl. A dissolução tecidual foi testada em fragmentos de polpas bovinas divididos em 18 grupos, metade deles utilizando as amostras livremente depositadas em poços de cultura de células e a outra metade utilizando as amostras fixadas em bases de dentina bovina. As soluções testadas foram o NaOCl a 0,5%, 1%, 2,5% e 5,25% e o Ca(OCl)2 a 0,5%, 1%, 2,5% e 5,25%. O grupo controle foi o soro fisiológico. Essas soluções foram empregadas sobre as amostras com dez irrigações/aspirações sucessivas de 1 minuto. A capacidade de dissolução foi mensurada pela percentagem de perda de peso. A tensão superficial do NaOCl a 0,5%, 1%, 2,5% e 5,25% e do Ca(OCl)2 a 0,5%, 1%, 2,5% e 5,25%, além de um grupo controle, água destilada, foi mensurada através da técnica do anel de platina com um tensiômetro de Du Noüy. Foram realizadas nove mensurações de cada solução e o resultado expresso em média e desvio padrão. Para a análise da capacidade de limpeza foram utilizados 50 dentes monorradiculares humanos, divididos em 5 grupos, que foram preparados com limas tipo K e irrigados com NaOCl a 2,5%, NaOCl 5,25%, Ca(OCl)2 2,5% ou Ca(OCl)2 5,25%. O grupo controle foi irrigado com soro fisiológico. Através da microscopia eletrônica de varredura foram analisados os diferentes terços dos canais quanto à remoção de debris e à presença de smear layer. Foram atribuídos escores de 1 a 4 e a frequência destes foi verificada para cada grupo. Os resultados mostraram que quanto à dissolução não houve diferença significante entre NaOCl e Ca(OCl)2 para iguais concentrações. As soluções mais concentradas foram mais eficazes na dissolução. Os valores de tensão superficial das soluções de Ca(OCl)2 variaram de 68,48 a 72,88 mJ/m. A remoção de debris do grupo do Ca(OCl)2 a 5,25% foi inferior ao grupo controle no terço cervical. Nos demais terços não houve diferença entre os grupos. Quanto à remoção de smear layer, não houve diferença entre os grupos. As soluções de hipoclorito de cálcio apresentam capacidade de dissolução tecidual, entretanto suas tensões superficiais foram superiores quando comparadas às soluções de hipoclorito de sódio. Além disso, não foram capazes de remover a smear layer e debris. / The aim of this study was to determine the tissue dissolution capacity, surface tension, and cleaning ability of Ca(OCl)2 solutions and compare to the NaOCl properties. The dissolution was tested on bovine pulps fragments divided into 18 groups, half of them was freely deposited samples in cell culture wells and the remaining samples were fixed on bovine dentin bases. The solutions tested were 0.5% NaOCl, 1.0% NaOCl, 2.5% NaOCl and 5.25% NaOCl, and 0.5% Ca(OCl)2, 1.0% Ca(OCl)2, 2.5% Ca(OCl)2, and 5.25% Ca(OCl)2. The control group was saline. These solutions were used on samples and were successively irrigated/aspirated 10 times, for 1 minute each. The dissolving capacity was measured by the percentual weight loss. The surface tension of all tested solutions and control was measured by the platinum ring technique with a Du Noüy tensiometer. Nine measurements were taken of each solution and the result expressed as mean and standard deviation. For the analysis of cleaning capacity, 50 monoradicular human teeth were divided into five groups. They were prepared with K files and irrigated with 2.5% NaOCl, 5.25% NaOCl, 2.5% Ca(OCl)2 or 5.25% Ca(OCl)2. The control group was irrigated with saline. The samples were analyzed by scanning electron microscopy. Each third of the root canals received a score regarding the removal of debris and the presence of smear layer. Scores were assigned from 1 to 4 and their frequency for each group was determined. There was no significant difference between NaOCl and Ca(OCl)2 with the same concentrations. The most concentrated solutions were more effectively in dissolution. The surface tension values of solutions for Ca(OCl)2 varied from 68.48 to 72.88 mJ/m. Debris removal for 5.25% Ca(OCl)2 was lower than the control group in the cervical third. In the other thirds there was no difference among groups. There was no difference for the smear layer removal among groups. Calcium hypochlorite solutions showed tissue dissolution ability, however their surface tensions were higher when compared with sodium hypochlorite solutions. Moreover, were not able to remove debris and smear layer.

O surfactante pulmonar é uma mistura complexa de fosfolipídios e proteínas, e encontra-se presente na interface ar-líquido dos alvéolos pulmonares. O seu papel principal é reduzir a tensão superficial para manter os alvéolos estáveis. A deficiência ou disfunção do surfactante leva ao colapso alveolar, provocando a falta de oxigenação que ocorre devido ao edema ou a resposta inflamatória nos pulmões. Em recém-nascidos, a imaturidade pulmonar, pela deficiência do surfactante, pode causar a Síndrome de Desconforto Respiratória (SDR). Nos adultos, a Síndrome de Desconforto Respiratório Agudo (SDRA) é a manifestação mais grave da Lesão Pulmonar Aguda (LPA), o tratamento para estas doenças inclui a utilização de surfactantes exógenos. Para entender a funcionalidade do surfactante é necessário caracterizá-lo biofisicamente. A principal característica observada neste estudo foi o espalhamento e recuperação do surfactante na subfase, para a interface ar-líquido. O espalhamento e recuperação foram quantificadas observando o trabalho feito em sucessivos ciclos de compressão e expansão na balança de Wilhelmy. Analisou-se o decaimento do trabalho ao longo dos ciclos até a sua estabilização. Os parâmetros obtidos neste ajuste do decaimento exponencial foram utilizados para a caracterização de dois surfactantes exógenos, o Curosurf® e o Survanta®. As comparações entre eles foram segundo a concentração, as subfases e das velocidades de barreira. O decaimento exponencial do trabalho nos ciclos só ocorreu para concentrações menores de surfactante. Quando em subfase de solução salina ocorreu a melhora na recuperação do surfactante para a interface ar-líquido, em comparação a subfase de água ultrapura. A melhor velocidade de barreira encontrada para otimização da recuperação do surfactante foi 120 mm/min. Foi observado nesse estudo que as propriedades de recuperação do Curosurf® foram melhores em relação ao Survanta®, os parâmetros se mostraram de acordo com os dados clínicos encontrados na literatura, a caracterização da dinâmica do surfactante foi feita de forma diferente de todos os métodos encontrados / Lung surfactant is a complex mixture of phospholipids and proteins, found at the airliquid interface of pulmonary alveoli. The main role is to reduce the surface tension to keep alveoli stable. Surfactant deficiency, or dysfunctional, leads to alveolar collapse, causes a lack of oxygen and it may be due to edema or inflammatory response in the lungs. In newborn babies, pulmonary immaturity, caused by surfactant deficiency, may cause Respiratory Distress Syndrome (RDS). In adults, the Acute Respiratory Distress Syndrome (ARDS) is the gravest manifestation of Acute Lung Injury (ALI), and the treatment includes Mechanical Ventilation (MV) and exogenous surfactants. To understand surfactant functionality, it is necessary to characterize them biophysically. The main characteristic observed in this work was the mobility and recovery of surfactant in the subphase to the air-liquid interface. The mobility and recover were quantified observing the work done in successive cycles of compression and expansion in a Wilhelmy plate tensiometer. The work decay was analyzed over cycles until its stabilization. The parameters obtained for the exponential fitting of decay were used for characterization of two exogenous surfactants, Curosurf® and Survanta®. The comparisons between them were done under concentration, subphases and barrier speeds. The exponential decay of the cycle work only happened for lower concentrations of surfactant. Saline solution subphase improved the surfactant recovery to the air-liquid interface over ultrapure water subphase. A suitable barrier speed founded to optimize surfactant recovery was 120 mm/min. In this study were observed that recovery properties of Curosurf® were better than Survanta®, the parameters agrees with clinical data from the literature, and the dynamic characterization of surfactant was done of different way than founded methods

Abstract The Eustachian tube (ET) connects the upper respiratory tract and the middle ear. It equilibrates the pressure in the middle ear and prevents the harmful impact of the airways. Middle ear infection, or otitis media, is one of the most common illnesses in childhood and affects nearly all children at least once. ET dysfunction is considered to be a major pathogenic factor in the development of otitis media. Surfactant proteins A (SP-A) and D (SP-D) have an important role in the pulmonary host defence system, and interactions with bacteria that also cause middle ear infections raised a question about the expression of surfactant proteins in ET. The local defence system could be significant in preventing ear infections. The purpose of the study was to increase our basic knowledge of the putative ET surfactant system. ET and lung epithelia are both of endodermal origin, and ET epithelium with its mucociliary system resembles that of the lower airways. The aim was to determine whether SP-A, SP-B and SP-D are expressed in ET. The expressions were characterized with reverse transcriptase polymerase chain reaction (RT-PCR), Northern hybridizations and in situ hybridizations. The surfactant proteins were localized using immunohistochemistry and immunoelectron microscopy. The proteins were characterized with Western analyses, and the properties of the ET surfactant were evaluated using electrospray ionization mass spectrometry and a pulsating bubble surfactometer. SP-A, SP-B and SP-D were found to be expressed in porcine ET epithelium, and the cDNA sequences were homologous to those detected in lung tissue. The proteins were localized to specific ET epithelial cells, and their sizes were characteristic of lung SP-A, SP-B and SP-D. ET lavage fluid contained the surfactant proteins and phospholipid. However, the phospholipid molecular species and surface tension measurements showed the structure and function of the surfactant in ET to be different from lung surfactant, suggesting that a very low surface tension is not a critical determinant of ET surfactant function. As a conclusion, surfactant proteins in ET are likely to be involved in the local host defence system and may contribute to the mucociliary function of the tube.

The goal of this work is to quantify the key design parameters such as the load capacity, actuation force, positioning repeatability, and reliability for droplet-based electrowetting actuators. Due to the fact that surface tension dominates gravity at both the mesoscale and microscale, droplet-based actuators can provide adequate force in manipulation tasks at those scales. Electrowetting, which uses an electric field to modulate the apparent surface tension of the liquid-ambient, provides a method to actuate droplets, which in turn transports the object carried by the droplet. Most previous electrowetting actuation efforts have concentrated on manipulating droplets in a closed two-plate configuration. In these configurations, a voltage potential is applied between a series of electrodes. The droplets can merge, split, and mix with only a voltage input, and without any external machinery. While some mechanical actuation demonstrations have been done, limited studies have been performed to investigate the key actuation performance characteristics of droplet-based actuators carrying solid objects. Design criteria for using droplets to carry solid components are still not well defined. The first part of this work provides fundamental understanding of the forces in electrowetting-based droplet actuation. The actuation force during electrowetting was experimentally validated according to the governing relation (Young–Lippmann equation) on a custom-designed testing apparatus. The results from the experiments show that the electrowetting actuation force is independent of surface tension below saturation, but the peak force is proportional to surface tension. Higher surface/interfacial tension would increase the actuation force in the horizontal direction, as well as the speed of the actuator. The second part of the dissertation demonstrates two actuation configurations based on electrowetting. The first actuator uses a droplet to carry a solid object and can be actuated in discrete steps to function as a micro-stepping linear motor. By implementing a leaky dielectric coating, the droplet/substrate contact area acts as an electrical diode. By varying the duty cycle of a square waveform, a range of droplet/part equilibrium position combinations are established. The underlying actuation mechanism was investigated and the position versus duty cycle relation was shown to be symmetrical but non–linear around the center of the electrodes. In contrast to the conventional electrowetting control scheme, the proposed actuation method required no feedback control loop while achieving a repeatability of less than 0.8% of the droplet diameter. Positioning matched a theoretical model based on idealized electrical elements to within 2.5% of the droplet diameter. The second type of electrowetting actuation uses metal-semiconductor diodes (Schottky diodes) in place of electrochemical diodes. This configuration uses only one pair of electrodes to actuate the droplet over a large distance (5X or more the droplet diameter). While the actuation concept had been previously demonstrated, the reliability of the diodes were shown to be insufficient. The new diodes actuated without degradation under repeated actuation (2000 cycles). Comparing this to electrochemical diodes, a 50% reduction in actuation voltage was also accomplished by Schottky diodes. The measured maximum speed also increased from 32 mm/s (electrochemical diodes) to 240 mm/s (Schottky), a 7.5 fold improvement. The last part of this dissertation used numerical simulations to investigate the load bearing capability and the stiffness variation of droplet-based actuators. The vertical force and stiffness - which are the primary figure of merit in designing droplet-based actuators are quantified. Three types of loading conditions were analyzed using simulation software and a simple analytical equation is shown to provide a useful approximation of the droplet force and stiffness. The results were further used in various case studies to demonstrate the optimal design strategy when using an electrowetting driven droplet as a fluidic bearing.

The existence of multiple hydrodynamic states (MHS) in trickle bed operation has been proved by hysteresis observed in flow loops, as well as variation between different prewetting modes. The most common theory presented as explanation for the existence of MHS, is the film vs. rivulet concept. Based on this concept, it was suspected that in-situ upsets might promote the formations of films, thereby providing a method through which the hydrodynamic states of the Dry and Levec modes can be manipulated to perform like the Kan Liquid and Super modes. Large performance enhancements can be obtained by altering the prewetting procedure, even for systems with a low surface tension. For the water system, the gas liquid mass transfer coefficient of the Kan Liquid and Super modes could be as much as 6 times greater than that of the Dry mode. For the low surface tension system, the gas liquid mass transfer of the Kan Liquid and Super modes could be up to 8 times greater than that of the Dry mode. Through a thorough investigation of various types of transient upsets and manipulation strategies, it was confirmed that prewetting is indeed the only way by which drastic variation in hydrodynamic states may be obtained. None of the investigated upsets (hysteresis, periodic operation or surface tension doping) resulted in changes in the liquid morphology that could compare to the significant variation that was observed by varying the prewetting mode. Two methods were identified by which the hydrodynamic gaps between the less uniform (Dry and Levec) modes and the more uniform modes (Kan Liquid and Super) could be bridged. The first is to reduce the Levec draining time, while the second method may be seen as an in-situ type of Kan Liquid prewetting. This type of prewetting was obtained during doping with a low surface tension liquid, at a flow rate associated with the high interaction regime for the low surface tension system. Though the hysteresis cycles did not drastically alter the predominant flow type, interesting trends were observed, some of which raised doubt about the application of the films vs. rivulet concept. One mode in particular displayed behaviour which contributed to this doubt, namely the Kan Gas mode; • Gas liquid mass transfer on this mode decreased with an increase in liquid flow rate • Relatively low pressure drops on this mode corresponded to relatively high liquid holdup • It was the only mode that exhibited no hysteresis with gas flow variation, on any of the hydrodynamic parameters The various trends and variations observed with the different types of upsets, leads to the conclusion that the concept of films vs. rivulets simply does not provide adequate explanation of the observed results. In general, two flow types may be distinguished. That which is caused by an initial increase in liquid flow rate as opposed to that which is caused by an initial increase in gas flow rate An investigation to determine the behaviour of each of the investigated parameters near the transition boundaries on all the modes, as well as a repetition of this study with non-intrusive visual techniques is recommended. / Dissertation (MEng (Chemical Engineering))--University of Pretoria, 2008. / Chemical Engineering / unrestricted

In extreme weather conditions and activity levels of human subjects evaporation of sweat is critical for maintaining the sensorial and thermal comfort. Fabrics, from which clothes worn next to the skin are made, play an important role in facilitating the transfer of body liquid perspiration away from the skin to the environment through the mechanisms of capillary flow and evaporation. This work is a theoretical and experimental investigation of water flow characteristics of plain knitted fabrics with relevance to their structure geometry and constituent fibre chemistry. Plain knitted fabrics were produced by systematically varying different production parameters including fibre type, fibre orientation, yarn folding, yarn twist, yarn linear density, and blend ratio. Cotton and polyester fibres were used. Some commercial fabrics were included in the study. The gravimetric absorbency test system (GATS) was adapted for testing the water areal flow and uptake rates through the fabrics. Yarns taken from the produced fabrics were also tested for horizontal linear flow of liquid water. A theoretical model to predict the capillary flow of liquid water through yarns was proposed. The model is based on the representation of the inter-fibre pores in terms of the hydraulic radius theory. It is established that the plain knitted fabric configuration as interlocking of loops plays an important role in facilitating the capillary flow of liquid water through the fabric. The yarn contact at the crossover points of the knitted loop enables a connected path for liquid flow which increases at higher contact pressure at the crossover points. If the contact pressure increases beyond a certain limit it starts to negatively affect the flow because the higher pressure reduces yarn porosity. When the number of yarns in contact with the liquid source per unit area of the fabric plane increases the capillary flow increases. Fabric compactness, which is controlled by yarn diameter and stitch length, is an important fabric parameter that determines these effects the fabric configuration have on the capillary flow. The experiments and the micro-structural analysis revealed that inter-fibre pores within the plain knitted fabric transfer the capillary driven liquid water through the structure at a faster rate. These pores hold the higher percentage of the fabric total air volume. It was also established that both fibre chemical nature and yarn fine structure geometry have critical effects on the apparent contact angle which is a critical factor controling capillary flow of liquid water. The smooth yarn surface made of filament polyester fibre gave a low apparent contact angle in contrast with the constituent filament which showed a high real contact angle. On the contrary, due to the more disorderly fibre arrangement on the yarn surface, yarns made of the staple polyester fibre showed a similar high contact angle to the constituent fibre. The experimental results of capillary flow of liquid water through yarns showed a strong correlation with the estimated results based on the theoretical model derived from the Kozeny-Carman equation. The model provides theoretical basis for understanding the effects of the geometric and material parameters on the capillary flow through the yarn. The model predicts that as the total fibre perimeter within the yarn cross section increases, or yarn porosity decreases, the velocity decreases, however, the eventual distance the water travels through the yarn increases.

The lack of significant buoyancy effects in zero-gravity conditions poses an issue with fluid transfer in a stagnant liquid. In this thesis, the movement of a bubble or droplet in both stagnant and rotating liquids is analysed and presented numerically using computational fluid dynamics (CFD). The governing continuum conservation equations for two-phase flow are solved using the commercial software package (2011). The Volume of Fluid (VOF) method is used to track the liquid/gas interface in 2D and 3D domains. User-Defined Functions (UDFs) are employed in order to include the effect of surface tension gradient and fluid properties as a function of temperature, with a view to efficiently investigating temperature effects on the properties of the two phases. The flow is driven via Marangoni influence induced by the surface tension gradient, which in turn drives the bubble/droplet from the cold to the hot region. For stationary liquid, the results indicate that the scaled velocity of the bubble decreases with an increase in the Marangoni number, which agrees with the results of previous space experiments. An expression for predicting the scaled velocity of a bubble has been regressed based on the obtained data from the present numerical study for thermal Marangoni numbers up to 10,721. An expression for predicting the scaled velocity of a Fluorinert droplet migrating in oil has also been presented for an MaT range from 24.05 to 2771. The interactions of two droplets in thermocapillary motion have also been studied and compared with the results obtained for the isolated droplet. The results have shown that the leading droplet will not move faster than if it were isolated, as the trailing droplet has no influence on the velocity of the leading droplet. Three-dimensional results show that no bubbles broke in any of the cases observed and agglomeration could occur during thermocapillary migration for bubbles placed side by side. The results of the motion of a singular and multiple bubbles incorporating thermocapillary forces in a rotating liquid in a zero-gravity environment have been presented for the first time. When the Rossby number is 1, the effects of rotation are important. Furthermore, the deflection of the gas bubble motion increases towards the axis of rotation with a decrease in the Rossby number (Ro). Bubble population balance modelling has been investigated in normal gravity using Luo kernels for breakage and agglomeration and two different laminar kernels for zero-gravity conditions. The simulations covered a wide range of scenarios and results are presented as a bell and histogram shapes for number density and particle percentage distribution, respectively.

The interfacial adsorption and bulk properties of a collagenous polypeptide derived from chicken eggshell membranes, the 40 KDa polypeptide, and its mixtures with common low molecular weight (LMW) surfactants, SDS, DTAB and C10E8, have been studied for the first time using surface tension, ζ-potential, foam observations and neutron scattering techniques. The biopolymer has been shown to act as an effective biosurfactant by lowering the surface tension of water below the values commonly achieved with conventional LMW surfactants, i.e. γ = 32 ± 1 mN/m. This capability is maximized at its isoelectric point, pH ~5, and addition of NaCl does not have a major impact upon adsorption. On its own, the 40 KDa polypeptide lacks the ability to foam. When mixed with cationic and anionic surfactants, a positive synergy is observed at low concentrations of both materials that exceeds the expectations from the individual components due to the formation of polypeptide/surfactant complexes with high surface activity and high ability to foam and foam stability. At these concentrations, maximum interfacial adsorption is achieved. The synergy is observed in spite of the type of charges present in the surfactant polar head. However, under the conditions studied, there is a difference in behaviour in regards to colloidal stability and surface film formation between the mixed solutions with the anionic SDS and the cationic DTAB. The non-existence of the synergy in the surface adsorption profile of the mixtures of the polypeptide with the non-ionic surfactant C10E8, as obtained via the plate method, suggests that electrostatic interactions are necessary for this strong synergy to act. ζ-potential has been used to prove the electrostatic nature of the synergy. Specular neutron reflection and SANS measurements offered an insight into the complex size and structure. The 40 KDa polypeptide thus offers a promising alternative to the use of high amounts of LMW surfactants in a range of products in which low surface tension and/or high and stable volumes of foams are needed, by combining small amounts of polypeptide and an ionic surfactant. This could be exploited by industries which have an interest in nanoparticle formation such as personal care or pharmaceutical companies. However, further work is needed to fully characterize these interactions.