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The surface tension of liquid metals is an important and scientifically interesting parameter which affects many metallurgical processes such as casting, welding and melt spinning. Conventional methods for measuring surface tension are difficult to use for molten metals above temperatures of 1000 K. Containerless methods are can be used to measure the surface tension of molten metals above 1000 K. Oscillating drop method is one such method where a levitated droplet is allowed to undergo damped oscillations. Using the Rayleigh’s theory for the oscillation of force-free inviscid spherical droplets, surface tension and viscosity of the sample can be calculated from oscillation frequency and damping respectively. In this thesis, a numerical model is developed in ANSYS Fluent to simulate the oscillations of the molten metal droplet. The Volume of Fluid approach is used for multiphase modelling. The effect of numerical schemes, mesh size, and initialization boundary conditions on the frequency of oscillation and the surface tension of the liquid are studied. The single-phase model predicts the surface tension of zirconium within a range of 13% when compared to the experimental data. The validated single phase model is extended to predict the interfacial tension of a core-shell structured compound drop. We study the effect of the core and shell orientation at the time of flow initialization. The numerical model we developed predicts the interfacial tension between copper and cobalt within the range of 6.5% when compared to the experimental data. The multiphase model fails to provide any conclusive data for interfacial tension between molten iron and slag.

This research evaluated the influence of concentration and surface tension (γ) of aqueous solutions of a non-ionic surfactant on the barrier effectiveness of a fabric containing microporous polypropylene (PP) film that may be used in pesticide protective clothing (PPC). Aqueous solutions of Triton® X-100, a non-ionic surfactant, at various concentrations were prepared, and the γ of each solution was determined. The immediate advancing contact angles (θ), made by a 5-<i>μ</i>L drop of each test liquid on the test fabric, were measured. Barrier effectiveness was evaluated from the capillary penetration, wicking, and wetting characteristics of the fabric using the surfactant solutions at various concentrations. Wetting characteristics were evaluated from the drop absorbency test, a modified Draves test, the spreading coefficient (S_c) values and, by inference, from a Zisman plot. As surfactant concentration increased, γ decreased, and then remained relatively steady past the 0.0134 percent concentration level, the critical micelle concentration (CMC) of Triton® X-100. As Triton® X-100 concentration increased, θ decreased, even past the CMC. Results of the study indicate that, as surfactant concentration increases, the amount of capillary penetration and the wicking distance increase even past the CMC. The time for drop absorbency and the Draves wetting tests were very high (> 600 seconds) for all liquids below CMC. Beyond the CMC, drop absorbency times were significantly lower for solutions of 2.0 and 5.0 percent concentration, and the Draves wetting times were also significantly lower. The values of the cos θ and the γ were used to calculate the S_c for each liquid. The calculated spreading coefficients indicate that the liquids at all concentrations did not spread (wet) on the micro-porous PP test fabric for the advancing θ measured within 10 seconds of placing the drop. Results of the statistical analysis showed that surfactant concentration was a significant factor in determining the barrier effectiveness of the fabric tested. Even though γ remained relatively unchanged beyond the CMC of the surfactant, the inability of the test fabric to serve as an effective barrier against liquid penetration by capillary action, wicking, and wetting increased significantly. Surface energy terms, that are normally used to explain liquid transport and wetting phenomena, may not in themselves be sufficient to determine the effectiveness of a fabric for PPC, especially since concentration of the surfactant, a pesticide adjuvant, is a significant factor in determining the barrier effectiveness of PPC. Consideration must be made for the fact that very high concentrations of surfactants are routinely used in pesticide application. / Master of Science

The regulation of surface tension (ST) by surfactants plays an important role in the human respiratory system but is largely unexplored in brain homeostasis. The aim of this study was to evaluate changes in ST in relation to surfactant proteins (SPs) in children with intraventricular hemorrhage (IVH). CSF samples from 93 patients were analyzed for ST with a force tensiometer and SP-A-D and -G with ELISA assays. Patients belonged to six groups: (i) IVH before primary intervention (PI), (ii) IVH 4–28 days after PI, (iii) IVH 44–357 days after PI, (iv) hydrocephalus, (v) sepsis and (vi) controls. We found indirect correlations and significant differences in ST and SPs (all p < 0.001; except for SP-C, p = 0.007). Post hoc analyses showed significantly decreased ST in IVH patients before PI compared with patients with hydrocephalus, sepsis or controls (p < 0.001), but it increased in IVH patients over time. All SPs were significantly elevated when comparing IVH patients before PI with controls (all p < 0.001; except for SP-C, p = 0.003). Children suffering from IVH displayed an increase in SPs and a decrease in ST as coping mechanisms to preserve CSF flow. The increase in ST over time could serve as prognostic marker for the healing process.

Yes / Inhaled nanoparticles (NPs) are experienced by the first biological barrier inside the alveolus known as lung surfactant (LS), a surface tension reducing agent, consisting of phospholipids and proteins in the form of the monolayer at the air-water interface. The monolayer surface tension is continuously regulated by the alveolus compression and expansion and protects the alveoli from collapsing. Inhaled NPs can reach deep into the lungs and interfere with the biophysical properties of the lung components. The interaction mechanisms of bare gold nanoparticles (AuNPs) with the LS monolayer and the consequences of the interactions on lung function are not well understood. Coarse-grained molecular dynamics simulations were carried out to elucidate the interactions of AuNPs with simplified LS monolayers at the nanoscale. It was observed that the interactions of AuNPs and LS components deform the monolayer structure, change the biophysical properties of LS and create pores in the monolayer, which all interfere with the normal lungs function. The results also indicate that AuNP concentrations >0.1 mol% (of AuNPs/lipids) hinder the lowering of the LS surface tension, a prerequisite of the normal breathing process. Overall, these findings could help to identify the possible consequences of airborne NPs inhalation and their contribution to the potential development of various lung diseases. / University of Technology Sydney (UTS) FEIT Research Scholarship, UTS IRS (S.I.H.), 2018 Blue Sky scheme–Suvash Saha (Activity 2232368), N.S.G is supported by the Vice-Chancellor fellowship funded by QUT.

The regulation of surface tension (ST) by surfactants plays an important role in the human respiratory system but is largely unexplored in brain homeostasis. The aim of this study was to evaluate changes in ST in relation to surfactant proteins (SPs) in children with intraventricular hemorrhage (IVH). CSF samples from 93 patients were analyzed for ST with a force tensiometer and SP-A-D and -G with ELISA assays. Patients belonged to six groups: (i) IVH before primary intervention (PI), (ii) IVH 4–28 days after PI, (iii) IVH 44–357 days after PI, (iv) hydrocephalus, (v) sepsis and (vi) controls. We found indirect correlations and significant differences in ST and SPs (all p < 0.001; except for SP-C, p = 0.007). Post hoc analyses showed significantly decreased ST in IVH patients before PI compared with patients with hydrocephalus, sepsis or controls (p < 0.001), but it increased in IVH patients over time. All SPs were significantly elevated when comparing IVH patients before PI with controls (all p < 0.001; except for SP-C, p = 0.003). Children suffering from IVH displayed an increase in SPs and a decrease in ST as coping mechanisms to preserve CSF flow. The increase in ST over time could serve as prognostic marker for the healing process.:1. Einführung 3 1.1 Intraventrikuläre Hämorrhagie 3 1.1.1 Allgemeiner Überblick 3 1.1.2 Pathogenese 3 1.1.3 Risikofaktoren und Prävention 4 1.1.4 Klinik 5 1.1.5 Komplikationen 6 1.1.6 Behandlungsoptionen bei IVH und PHVD 7 1.1.6.1 Medikamente 7 1.1.6.2 Interventionen 7 1.2 Surfactant und Surfactant-Proteine 8 1.3 Zusammenfassung der IVH-Problematik und Fragestellungen der Dissertation 11 2. Publikationsmanuskript 13 3. Zusammenfassung der Arbeit 28 4. Literaturverzeichnis 32 5. Abkürzungsverzeichnis 39 6. Anlagen der Originalpublikation 41 7. Darstellung des eigenen Beitrags 48 8. Erklärung über die eigenständige Abfassung der Arbeit 49 9. Lebenslauf 50 10. Publikationen 51 11. Danksagung 52

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: See item for full text / AFRIKAANSE OPSOMMING: Sien item vir volteks

Le comportement (écoulement, adhésion,…) d'un fluide à seuil le long d'une surface solide est un problème récurrent dans de nombreux procédés industriels. Le caractère non newtonien de ce type de matériau rend difficile l'application des concepts établis dans le cas des écoulements similaires de liquides simples. Dans cette thèse, nous étudions expérimentalement ce problème en analysant l'écoulement généré le long d'une plaque solide en mouvement vertical (enfoncement et retrait) uniforme à travers un fluide à seuil simple. Nous déterminons d'abord le lien entre la force mesurée le long de l'objet et les propriétés rhéologiques du matériau. Nous en déduisons une nouvelle technique pour mesurer la contrainte seuil de ces matériaux. Nous décrivons, ensuite, les caractéristiques locales de l'écoulement généré lors de la pénétration de la plaque. Nous montrons que l'écoulement est localisé autour de l'objet, dans une couche d'épaisseur uniforme alors que le reste du fluide est déformé mais reste dans son état solide. Nous décrivons le processus par lequel cette couche limite se développe et nous déterminons la répartition des zones solides/ liquides autour de l'objet. Enfin, nous étudions les effets de mouillage et d'adhésion sur la plaque. En particulier, nous présentons une approche expérimentale permettant d'évaluer la tension de surface des fluides à seuil / The behavior (flow, adhesion,...) of a yield stress fluid along a solid surface is a recurrent problem in many industrial processes. The non-Newtonian character of this type of material makes it difficult to apply the concepts established in the case of similar flows of simple liquids. In this thesis, we study this problem experimentally by analyzing the flow generated along a solid plate moving vertically (penetration and withdrawal) through a simple yield stress fluid. We first determine the relationship between the measured force along the object and the rheological properties of the material. We derive a new technique for measuring the yield stress of the material. We describe then the local characteristics of the flow generated during the penetration of the plate. We show that the flow is located around the object in a layer of uniform thickness, while the rest of the fluid is deformed but remains in its solid state. We describe the process by which the boundary layer develops and determine the distribution of solid / liquid zones around the object. Finally, we study the effects of wetting and adhesion on the plate. In particular, we present an experimental approach to evaluate the surface tension of a yield stress fluid

Orientador: Carlos Gilberto Raetano / Banca: Ulisses Rocha Antuniassi / Banca: Cristina Gonçalves de Mendonça / Resumo: Este trabalho teve como objetivo avaliar o efeito de adjuvantes sobre algumas propriedades de soluções aquosas, como tamanho de gotas, tensão superficial dinâmica e ângulo de contato das gotas em diferentes superfícies, natural e artificial, bem como avaliar o efeito desses produtos sobre a deposição e a deriva utilizando como alvo três espécies de plantas daninhas (Euphorbia heterophylla, Ipomoea grandifolia e Brachiaria plantaginea). Seis formulações de adjuvantes (Antideriva®, Uno®, Pronto 3®, Li-700®, Supersil® e Silwet L-77®) foram avaliadas em soluções aquosas contendo a dose recomendada do produto comercial e o dobro dela. As avaliações de tamanho de gotas foram feitas com três diferentes pontas de pulverização (AXI 110 015, 110 02 e 110 03) por um equipamento a laser (Mastersizer, Malvern) na pressão de trabalho de 414 kPa. Os ângulos de contato formados pelas gotas em duas superfícies, uma hidrofílica (vidro) e outra hidrofóbica (óxido de alumínio), foram obtidos por análise de imagens capturadas por uma câmera digital. As avaliações de deposição e deriva das soluções aquosas associadas ou não aos adjuvantes e contendo o traçador azul brilhante (0,15% v/v), foram feitas sobre diferentes espécies vegetais, e com o auxílio de coletores laterais (placas de Petri). A quantificação do traçador foi por feita espectrofotometria. A tensão superficial dinâmica e o ângulo de contato formado sobre as superfícies adaxiais das folhas foram medidos por um tensiômetro. Em relação ao tamanho de gotas, o adjuvante Antideriva, com dobro da dose recomendada, foi o que apresentou os menores valores percentuais de volume de gotas com diâmetro menor que 100 µm e os maiores DMV, para todas as pontas em teste. As soluções que proporcionaram as maiores ...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The aim of this work is to evaluate the effect of adjuvants on droplet size, dynamic surface tension and contact angle formed by the water drops in different surfaces, as well as evaluating the adjuvants effect on the deposit and the spray drift using three species of plants (Euphorbia heterophylla, Ipomoea grandifolia e Brachiaria plantaginea). We studied six adjuvants formulations (Antideriva™, Uno™, Pronto 3™, Li- 700™, Supersil™ and Silwet L-77™) in water solution using the dosage recommended by the manufacturer and twice that dose. The droplet size of three different nozzles (AXI 110 015, 110 02 and 110 03), for a constant pressure of 414 kPa, were evaluated by a laser system. The contact angles of the drops in two surfaces (hydrophilic and hydrophobic) were obtained by the analysis of images captured by a digital camera. The evaluation of deposition and spray drift deposition of the solutions containing brilliant-blue dye (0.15 % v/v) were carried out in different plant species. The solutions were collected laterally using Petri dishes, and the brilliant-blue dye content quantified by absorption spectroscopy. The dynamic surface tension and the angle formed on the surfaces of the leaves were measured by a tensiometer. Regarding the droplet size, for all the nozzles tested the adjuvant Antideriva with twice the recommended dose presented the lowest percentage of spray volume in droplets with diameters smaller than 100µm, and highest VMD. The solutions that provided the highest reductions in the dynamic surface tension and the smallest contact angle were the ones with the adjuvants Silwet L-77 and Supersil for both appraised doses. The largest deposit average for I. grandifolia was obtained by using Uno with double of the dose; for B. ...(Complete abstract click electronic access below) / Mestre

Este trabalho apresenta um ambiente de simulação de escoamentos com simetria radial e superfícies livres, baseado no sistema Freeflow. O sistema é formado por três módulos: um modelador de moldes, um simulador e um visualizador de escoamentos. O simulador implementa o método GENSMAC para a solução das equações de Navier-Stokes em coordenadas cilíndricas, utilizando diferenças finitas em uma malha diferenciada. São introduzidos os efeitos da tensão superficial e do ângulo de contato nas simulações com simetria radial. Alguns resultados de simulações utilizando este sistema e uma validação do código são apresentados, comparando simulações com soluções analíticas e experimentais, e estudando a convergência do método. / This work presents an environment for the simulation of axisymmetric free surface flows, based on the Freeflow system. The system contains three modules: a geometric model modeller, a simulator and a visualizator. The simulator implements the GENSMAC method for the solution of the Navier-Stokes equations in cylindrical coordinates, using finite differences in a staggered grid. The effects of surface tension and contact angle are introduced in the axisymmetric simulations. Some results from simulations using this system and a validation of the code are presented, comparing the simulations with analytical and experimental solutions, and studying the convergence of the method.